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Fundamental Concepts of Periodontal Tissues

Robert M. London | Sul-Ki Hong | Ariel J. Raigrodski

Periodontal tissues are vital and responsive to their environment. They develop and differentiate as teeth erupt into the oral cavity, and once in function, they change and adapt to environmental stimuli. Restorative dentistry is a major source of environmental stimuli. By developing a strong understanding of the underlying tissues and how they are impacted by our clinical procedures, clinicians can execute a restorative plan that maximizes health and esthetics at the soft tissue–restorative interface.

Periodontal tissues can be defined in simple terms: epithelium, connective tissue, and bone. Of course, there is a vascular component and a component comprised of immune cells—neutrophils, macrophages, T and B lymphocytes, and plasma cells. From a clinical perspective, an understanding of the epithelium and connective tissues, together with their health parameters, gives a good foundation for facilitating and optimizing patient care.

Epithelium is the fast-moving tissue responsible for maintaining a seal between the body and the oral cavity, and it is quick to repair when injured.¹ When a tooth first erupts, the epithelium remains attached to the enamel coronal to the cementoenamel junction (CEJ). As the patient matures into adulthood and the tooth continues to function, the junctional epithelium (the epithelium actually forming the attachment to the tooth) moves apically. Initially adhering to the enamel, the junctional epithelium will eventually lie on the most coronal portion of the tooth root. It adheres via a hemidesmosomal attachment²; the epithelial cells adhere directly to the root structure at a strength similar to that of cell-cell connections.

Gingival connective tissue forms the durable attachment around teeth. During the time of development and calcification of the cementum and bone, gingival fibers become embedded, suspending the tooth in its socket. These fibers, known as Sharpey’s fibers, are functionally oriented and form the periodontal ligament of the socket. Above the bone crest, the Sharpey’s fibers extend from the cementum perpendicularly outward into the surrounding gingival connective tissue, anchoring it to the tooth.³ This fibrous attachment is deemed stronger and more resistant to trauma than epithelial attachment.

Biologic Width and Teeth

In order to maintain appropriate function, the tooth requires a minimal distance from the crest of bone moving coronally to the base of the gingival sulcus. This allows for supracrestal connective tissue attachment and epithelial attachment to the tooth above the bone. The sum of these attachments is defined as the biologic width.⁴ Biologic width can vary significantly from patient to patient and even from tooth to tooth in the same patient.^5,6 In areas where the root is prominent and the bone is dehisced, the width of the soft tissue attachment can be many millimeters greater than the mean values. In other situations, particularly if a tooth has not completely erupted, this width can be quite narrow.

In a classic cadaver study, Gargiulo et al⁵ demonstrated an average sulcus depth of 0.69 mm, an average epithelial attachment width of 0.97 mm, and an average connective tissue attachment width of 1.07 mm. While these numbers are often quoted, the article demonstrated significant variability within these three different components. In a later study by Vacek et al,⁶ very similar averages were seen with a somewhat narrower but still highly variable range. From a clinical perspective, most practitioners have accepted an average distance of about 3 mm between the free gingival margin and the crest of the facial bone. This distance consists of 1 mm of sulcular depth followed by an attachment consisting of 1 mm of junctional epithelium and 1 mm of connective tissue attachment.

Biologic width and finish line placement for complete-coverage restorations

Periodontal tissue response and the esthetic outcome may be affected by several factors, including location of the crown margin, type of restorative material, selection of implant abutment and/or restorative implant components, presence of bone and keratinized gingiva, the implant-abutment interface (microgap), and oral hygiene.^7–15 The finish line of a tooth preparation for a complete-coverage restoration can be placed supragingivally, equigingivally, or subgingivally. In clinical practice, subgingival placement of the finish line may be required to hide the tooth-restorative interface for esthetics, to address dental caries or a preexisting restoration, to manage a coronal endodontic perforation, to manage crown or coronal root fracture, and for retention and resistance purposes. Ideally, in such clinical scenarios, the finish line is placed 0.5 to 1.0 mm below the free gingival margin (Fig 1-1). Theoretically, any level above the base of the sulcus is acceptable. Consequently, the finish line must not intrude further into the periodontal attachment apparatus, because this can lead to violation of the biologic width.¹⁶

Fig 1-1 (a and b) A crown preparation for a ceramic crown with the finish line placed 0.5 to 1.0 mm below the free gingival margins on the facial and interproximal aspects. Note the equigingival and supragingival finish line placement on the palatal aspect and the general gingival health.

Subgingival finish line placement may, however, result in more gingival inflammation, loss of attachment, and gingival recession compared with equigingival or supragingival finish line placement.^7,8,17,18 This is more evident in patients with poor plaque control.¹⁹ The tissue is certainly the healthiest when the margins of the restoration are kept away from it (Fig 1-2). Similarly, when esthetics dictates that restorative materials must be hidden below the free gingival margin, the likelihood of inflammation is increased. In addition to bacterially induced inflammation, physical encroachment on the epithelial or even connective tissue attachment may occur. This mechanical invasion may initiate its own inflammatory remodeling of soft tissue and bone. Additionally, because luting cements flow initially as liquids²⁰ away from the crown margin, inaccessible restoration margins may increase the challenge of removing excess cement. This can occur around tooth-borne restorations and particularly around cement-retained implant-supported restorations. The resultant tissue inflammation in response to the cement can subsequently lead to inflammatory bone loss.^21,22

Fig 1-2 Facial view of a tooth preparation for a ceramic veneer with supragingival finish line placement on the facial aspect. Note the excellent gingival health.

If the zone of biologic width is invaded, this biologic seal (ie, the periodontal tissues) must adapt and reconstruct itself. Thus, if a tooth preparation finish line is placed into the attachment, the inflammatory response may resorb bone until there is adequate distance for the various attachment layers. Sometimes this resorption can go undetected, such as on the facial aspect of a restoration, where bone loss cannot be detected radiographically. In other circumstances, the inflammatory process may occur with slow remodeling, resulting in erythematous tissue color changes.

Clinicians must be prudent during patient evaluation prior to surgical and restorative procedures and must ensure that adequate periodontal health is achieved prior to a definitive assessment of the dentogingival complex. Periodontal probing may overestimate the available sulcus depth when the gingiva is not healthy. In a series of studies summarized in 1980,^23–25 Listgarten evaluated where a probe stops in the sulcus. In healthy tissues, the probe penetrated partially through the junctional epithelium. In inflamed and diseased tissue, the probe penetrated through the epithelium into the underlying connective tissue.²⁶ These measurement inaccuracies worsened with disease.²⁷ Thus, prior to commencing restorative procedures, one might think that there is adequate sulcus to avoid impinging on the attachment when, in reality, the sulcus may be overestimated by over 1 mm.

The zone of keratinized gingival tissue can also influence the extent and severity of gingival inflammation around restorations with subgingival margins. Sites with a narrow zone of keratinization (≤ 2 mm) showed more noticeable gingival inflammation when compared with sites with a wide band of gingiva. A total of 5 mm of keratinized gingiva—2 mm of free gingiva and 3 mm of attached gingiva—is recommended for gingival health around teeth with subgingival finish line placement.^16,28 Furthermore, ill-fitting margins can contribute to the progression of periodontal disease by facilitating plaque accumulation and shift of the subgingival flora to a more pathogenic one.^29,30

Kois³¹ has coined three categories of biologic width based on sulcus depth and total attachment width. Referring to the bone level, he called these normal crest, high crest, and low crest. Crest refers to the facial height of bone as detected by a periodontal probe sounding to the bone through the sulcus. A normal crest is defined as 3 mm from the free gingival margin to the bone crest on the facial aspect of the tooth and 3.0 to 4.5 mm at the interproximal areas. A lesser number indicates a high crest, suggesting that bone is closer to the CEJ than normal. A low crest is farther away from the free gingival margin, indicating a larger total width of the dentogingival complex and the possibility of resecting gingiva without encroaching on a normal biologic width. Later Kois³² described preparation guidelines related to respecting the biologic width. For the normal crest dentogingival complex, the finish line on the facial aspect should be placed 0.5 to 1.0 mm below the free gingival margin.

When bone is lost in an uncontrolled fashion, the periodontal damage may result in either increased pocket depth or gingival recession. Because satisfactory esthetics requires a healthy and adequately contoured gingival frame surrounding the restoration, the stability of bone and attachment levels is essential. Just as bone supports the soft tissue to create the attractive, scalloped appearance of healthy gingiva, lost bone will typically translate to negative esthetic gingival changes.

Biologic width management and correction

If the restoration margin infringes on the biologic width, the natural width can be reestablished only by creating adequate distance between the free gingival margin and the bone crest. Such an infringement may be prevented by keeping the finish line of the tooth preparation and subsequently the margin of the restoration more coronal during tooth preparation. However, when it is necessary to extend the finish line apically, one of two courses of treatment may be selected. The first and most common choice is crown lengthening osseous surgery—resecting bone to restore a proper biologic width and positioning tissue in a manner that will maintain health and viable esthetics. The alternative is to consider orthodontic extrusion of the tooth, thus moving the margin in a coronal direction. Bone tends to follow the tooth movement, resulting in no net change in the attachment width; to prevent bone from following, fiberotomy is used during orthodontics,^33–35 or limited crown lengthening surgery can be performed once orthodontics is complete. The authors concur with Berglundh et al³⁶ that fiberotomy may not yield the complete desired lengthening, because the tissue continues to follow the tooth movement but to a lesser degree than without fiberotomy. In such cases, extrusion should be followed by additional surgery to establish biologic width and balance the esthetics.

The gingival attachment repairs itself after injury. With a clean injury, as in surgery, if all the tissue components remain, the connective tissue will reattach, and the epithelium will re-form its hemidesmosomal junction coronal to that connective tissue attachment. In primate models, this repair takes over 6 weeks.³⁷ In humans, repair and remodeling can go on for much longer, ranging from 6 to 12 months.³⁸ Lanning et al³⁹ found that a normal biologic width and gingival dimension was restored after 6 months of healing. This was referenced to the new, more apical bone crest. Ganji et al⁴⁰ found that biologic width is reestablished by 3 months after either osseous resective surgery or gingivectomy, although the osseous procedure was more effective for stability of clinical crown lengthening. To avoid confusion, the term osseous resective crown lengthening should be used.⁴¹

Gingivectomy addresses only the soft tissue component of the dentogingival complex. Because it does not change the level of bone and thus cannot relocate the level of the biologic attachment, gingivectomy risks encroachment on the healthy biologic width. As mentioned above, the periodontal probe extends partially into the attachment, resulting in a perception that the sulcus is deeper than it is biologically.²⁴ Gingivectomy should only be considered if the tissue depth from the proposed free gingival margin to the level of the attachment is at least 3.0 mm, allowing for biologic width without bone resection. Regardless of choice of instrumentation, a residual sulcus of at least 1.5 mm should remain after soft tissue resection, or an osseous resective crown lengthening surgery should be performed.

When the soft tissue is placed apically to expose more coronal tooth structure, the tissue may remain stable where apically positioned, or it may rebound coronally, covering some of the previously exposed tooth structure and increasing the subgingival location of the crown margin. This too can be explained by the concept of biologic width. Flaps placed at the bone crest may not have room apically for a normal width. They may proliferate coronally until a normal width has occurred, as evidenced from greater rebound when positioned at the crest.⁴² This coronal migration is also more prevalent in patients with a thicker tissue type.⁴¹ Six months would be prudent to allow stable healing after osseous resective crown lengthening surgery, recognizing that minor further changes may occur for up to 12 months.⁴³ Prior to commencing or continuing with definitive restorative procedures, clinicians should wait at least 3 months for healing after minor gingivectomy procedures and 6 to 12 months after osseous resective crown lengthening surgery.

Impact of restorations on gingival attachment

Both the restorative process and the resulting restorations have an impact on the gingival tissues. Preparation, provisionalization procedures, retraction and impression procedures, and delivery (conventional luting and adhesive cementation) procedures all irritate the tissue. Epithelium is typically disrupted or even removed by the aforementioned routine procedures. Emphasis should be placed on trying to accomplish the treatment with minimal irritation to the tissue and then allowing repair to begin (Fig 1-3). Cumulative irritation from repeated attempts to perform such procedures may result in longer duration of inflammation and greater remodeling of the attachment level.

Fig 1-3 (a and b) Facial views of teeth prepared for zirconia-based ceramic crowns with minimal trauma to the soft tissue. (c and d) Facial views of the zirconia-based ceramic crowns 1 year after delivery, demonstrating that the trauma to the soft tissue has been reversible. (e) Facial view of the crowns 4 years after delivery, demonstrating soft tissue stability around the crowns. (Ceramics: Andreas Saltzer.)

Marginal adaptation, cement line exposure, and restorative contours all influence future tissue health. Any contours or gaps that foster plaque accumulation increase the likelihood of inflammation. Inadequate preparation design in terms of axial reduction and finish line width may result in an overcontoured restoration. This is especially true at the facial aspect, where adequate thickness of restorative materials is necessary to provide adequate translucency and esthetics (Fig 1-4). Such overcontoured restorations may mechanically encourage tissue change, such as recession, as well as trap plaque. In animal model studies, overcontouring was found to increase plaque retention and contributed to higher loss of clinical attachment levels compared with normally contoured controls. Crowns that are comparably contoured to the original tooth form provided the highest levels of periodontal health. Despite greater attachment loss in overcontoured groups, carefully instituted hygiene procedures mitigated the damage to only slightly worse conditions than the controls.⁴⁴

Fig 1-4 Facial view of failing metal-ceramic crowns. Note the questionable marginal adaptation that fosters plaque accumulation, resulting in increased inflammation as compared with the adjacent teeth.

Many studying the effects of crown contour on tissue health have concluded that undercontouring is equal to a natural contour or an improvement in terms of gingival health. This has been evaluated in animal models and in humans, discrediting the idea of a protective function of a supragingival bulge. In fact, more plaque accumulates with a larger contour, whereas flatter contours favor gingival health.^45–48

Ovate Pontic Sites

Ovate pontics are considered optimal for esthetics and for cleansability. Being smooth and convex, such pontics support the edentulous space while providing appropriate facial and interproximal contours (Figs 1-5 to 1-7). Procedures to enhance the tissue ridge to accommodate such pontics have been proposed.⁴⁹ The design and fabrication for close adaptation of the pontic to the pontic site require special techniques,⁵⁰ which are discussed in the following chapters.

Fig 1-5 Removed restoration with a pontic that is inadequately designed. Note the concave ridge lap design and the rough intaglio surface, which may adversely affect the ability of the patient to clean as well as subsequently compromise the health of the pontic site.

Fig 1-6 (a) View of the intaglio surface of an ovate pontic. (b) Being smooth and convex, such pontics support the edentulous space while providing appropriate facial and interproximal contours and allowing the patient to maintain adequate oral hygiene. (Ceramics: Masayuki Saito.)

Fig 1-7 Facial view of the try-in of a ceramic zirconia-based fixed dental prosthesis with an ovate pontic. A cautious and delicate approach is applied during the provisional phase to facilitate an adequate design and a close adaptation of the pontic to the pontic site.

The question arises as to tissue response to materials intimately adapted to these structures. There are many materials that can be used for restorations in contact with tissue. Ovate pontics provide an opportunity to assess tissue response to various metal alloys, polymers (ie, acrylic resins and composite resins), and ceramics. With proper home care and a daily flossing regimen, no real differences are seen among a wide variety of materials.¹⁴ This can perhaps be explained by the repeated and frequent separation of the epithelial interface from the restorative material. Flossing this area completely is principally possible under such convex pontics. During initial healing following placement of the pontics, tissue responses may indeed vary. Low-fusing ceramic may be favored over acrylic resins.⁵¹ Edentulous spaces in contact with ovate pontics do not show clinical and histologic signs of inflammation in the presence of adequate oral hygiene measures (Fig 1-8). Histologically, this style of pontic is associated with a thinner keratin layer and mild changes in the composition of the adjacent connective tissue, in comparison with tissues not in contact with the pontic.⁵² Despite a lack of specific research, the tissue is presumed healed by 6 weeks and mature by 12 weeks.

Fig 1-8 Occlusal view of an ovate pontic site demonstrating no clinical signs of inflammation.

When plaque accumulation and severity of gingival inflammation were evaluated underneath pontic sites fabricated with different dental materials (gold alloys, silver-palladium, cobalt-chromium, nickel-chromium, feldspathic porcelain, and composite resin), high levels of plaque control were associated with healthy gingival tissue irrespective of the pontic material used. Inadequate plaque control was associated with the development of gingival inflammation and increases in the amount of bacterial plaque underneath and around the pontic site.^14,15

Biologic Width and Implants

General concepts

Lessons learned from the biologic width of natural teeth have parallels when working with dental implants. Like teeth, implants also display a zone of epithelial attachment and a zone of connective tissue apical to that. The connective tissue has different characteristics but occupies the same location as around natural teeth. Unlike teeth with perpendicularly oriented Sharpey’s fibers, with implants, connective tissue fibers display an orientation mostly parallel or oblique to the implant surface.^53,54 When titanium abutments are placed at the time of surgery and are never removed, epithelium and connective tissue can attach themselves to the abutment itself.⁵⁵ This has been evidenced in human cadavers.⁵⁶ The result is a wider band of total attachment than that seen on natural teeth or when implant components are removed and replaced. In a dog model, when similar abutments were removed and replaced repeatedly, epithelial attachment was found to be positioned more apically on the abutment. More bone resorption was also observed when the zone of connective tissue was more apically positioned. It would appear that bone resorbs to allow for an appropriate reestablishment of biologic width even around implants.⁵⁷ The degree of resorption was similar in a human study comparing abutments placed at the time of surgery with abutments removed and replaced twice.⁵⁸

Similarly to what is seen with crown lengthening procedures when the tissue is positioned very close to the bone crest, implants also appear to need enough tissue height to form the biologic width to avoid bone resorption. When implants are placed with excessively thinned flap tissues, biologic width has to be re-formed. Loss of crestal bone height is seen in both animal⁵⁹ and human⁶⁰ models. It is recommended that flaps placed around implants be coronally positioned adequately to allow for over 2 mm of vertical tissue thickness in order to ensure that biologic width is established without bone resorption.

From a structural point of view, Moon et al⁶¹ described the nature of the biologic attachment around dental implants in a beagle dog model. In evaluating the connective tissue zone, they observed one zone of 40 µm close to the implant surface and one more distant zone of 160 µm. While the zones were continuous with one another, they had different characteristics. The zone against the implant was characterized by an absence of blood vessels and an abundance of fibroblasts. The fibroblasts were interposed between thin collagen fibers. The zone farther from the implant contained fewer fibroblasts but more collagen fibers and blood vessels. They speculated that the more fibroblast-rich region plays a role in maintenance of a proper seal to the titanium between the oral environment and the peri-implant bone.

In another beagle dog study, Abrahamsson et al⁶² examined the nature of attachment to different dental materials used on implant abutments. In observations on titanium, densely sintered high-purity alumina, gold alloy, and feldspathic porcelain (for metal-ceramic restorations), they found that titanium and alumina allowed formation of attachment that included a normal epithelial and connective tissue band totaling approximately 3.5 mm. In contrast, when gold alloy or feldspathic porcelain was used, no attachment was formed on the abutments. The free gingival margin receded and bone resorption occurred, causing the biologic width to reform apical to the materials. This pattern has been repeated in a dog model in which zirconia and titanium maintained attachment while gold alloy lost attachment and adjacent bone over 5 months.⁶³

Biologic width and implant platform switching

A proposed way to preserve marginal bone around implants is to utilize an implant abutment that is smaller in diameter than the head/platform of the implant, a technique called platform switching. In this manner, an inward horizontal offset at the top of the implant is accomplished (Fig 1-9). Because this moves the implant-abutment interface away from bone, it increases the distance available for biologic width. Much has been made of this phenomenon, with designs that incorporate an offset considered superior by the manufacturers.

Fig 1-9 Periapical radiograph demonstrating the platform switching approach. Note that the implant abutment is smaller in diameter at the platform level.

Two-piece implants are designed for placement of the implant at the level of the bone crest, followed by connection of the implant abutment. The microscopic space between the parts is known as the microgap or the implant-abutment interface. Proximity to the alveolar bone crest implicates this interface as being responsible for remodeling of bone at the time of abutment connection, inflammation of peri-implant mucosa, and peri-implantitis.^12,13,64,65 The implant-abutment interface may favor bacterial colonization. The dimension of the interface space is about 10 µm, while the mean diameter of bacteria is less than 2.0 µm.^66,67 This microbial leakage may be the main culprit for the presence of chronic inflammatory infiltrate and crestal bone resorption. Occlusal loading of the abutment may result in additional opening of the interface, increasing the level of bacterial penetration.^{12,66,68–75} The mere presence and contamination of the microgap by periodontal pathogens, however, may not necessarily result in inflammation of the peri-implant mucosa or peri-implantitis.^66,75

Many studies have evaluated the effect of platform switching. Some take place in the form of cohort clinical studies (without controls), while others are in the form of randomized controlled trials. Results of such trials have been inconsistent. Generally speaking, platform switching results in a small but statistically significant difference at 1 year after the restoration delivery compared with implants restored with abutments matching the implant platform diameter. Studies demonstrate a difference ranging from 0.25 to 0.37 mm of bone preserved by platform switching.^76,77 However, some studies showed no difference at 1 year.⁷⁸ In a systematic review, the authors concluded that there may be about 0.5 mm of bone preservation with platform-switched implants.⁷⁹ In the same review, however, caution was emphasized because heterogeneity of data and publication bias were noted. No systematic reviews showed a difference in implant survival rates between the two types of restorative design.^77,79 Enkling et al⁸⁰ performed a randomized clinical trial and concluded that at the 3-year follow-up there was no significant difference in bone height, with a mean intra-individual difference of 0.05 mm between the platform switching and the traditional implant/abutment approaches. In a 5-year follow-up study, Vigolo and Givani⁸¹ showed a similar 1-year difference of 0.3 mm, favoring bone levels on platform-switched abutments. No changes were noted from that point out to 5 years.

The smaller abutment diameter would seem to be unfavorable to load, but this may depend on the design of the implant-abutment interface. In an in vitro study, Leutert et al⁸² found that internally connected abutments with a smaller diameter than the implant platform showed significantly higher bending moments compared with abutments of the same diameter. The small offset does present an obstacle to probing and periodontal maintenance curetting in cases where there is implant disease. In larger teeth, it may also create a larger size mismatch, negatively affecting tissue emergence profile angle.

Based on the available research evidence, it seems reasonable to conclude that platform switching results in a slightly (approximately 0.4 mm) better maintenance of crestal bone height around the implant at 1 year. This does not appear to make a clinically significant difference in patient outcomes; thus, at present, it seems reasonable to choose either a platform-switched or conventional equal-diameter restorative solution based on other parameters. Such parameters might include contour matched to the proposed restoration, availability of a specific custom abutment modality, and desired placement of restorative margins.⁸³ The exception to this may be when adjacent implants must be placed in close proximity.^84,85 It remains to be seen in longer-term studies if there is a difference in incidence of peri-implant disease based on abutment diameter at the implant platform.

Tissue Phenotype

General concepts

In 1969, Ochsenbein and Ross⁸⁶ reported two main types of gingival morphology: flat and scalloped. The flat gingival morphology was closely related to a square tooth form with a minimal distance between the buccal gingival margin and interdental gingival levels. The scalloped gingival morphology was associated with a tapered tooth form and considerable height—about 5 to 6 mm—between the buccal gingival margin and interdental gingival levels. They also indicated that the gingival contours mimic and follow the contours of the underlying bone. Later, the term periodontal biotype was proposed by Seibert and Lindhe,⁸⁷ classifying the gingiva into two distinct types of gingival morphology: thin (less than 1 mm) and scalloped, or thick (more than 1 mm) and flat. This term has been frequently used clinically to describe the faciolingual thickness of the facial gingiva around teeth (synonymous with gingival thickness), relating it to papilla height. The thin and scalloped gingival type is associated with a tooth with tapered crown form, subtle cervical convexity, small proximal contact areas located near the incisal edge of the tooth, shallow probing depths, a narrow zone of keratinized gingiva, and thin alveolar bone. The thick and flat type corresponds to a tooth with squared facial form, distinct cervical convexity, relatively large and more apically located contact areas, a wide zone of keratinized gingiva, and thicker alveolar bone⁸⁸ (Table 1-1). In a study assessing different morphologic characteristics of the gingiva, Müller and Eger⁹⁴ proposed the use of the term phenotype instead of biotype as the correct term in describing features of the marginal periodontium that are influenced by both genetic and environmental factors.

Table 1-1 Features of thin and thick gingival phenotypes*

	Thin phenotype	Thick phenotype
Gingival thickness	< 1 mm	≥ 1 mm
Gingival tissue	Delicate and friable	Dense and fibrotic
Keratinized gingiva	Narrow band	Wide band
Soft tissue architecture	Scalloped	Flat
Underlying bony architecture	Thin or minimal	Thick
Crown form	Tapered	Square
Cervical convexity	Subtle	Distinct
Proximal contact area	Located near the incisal edge	Located more apically

*Data compiled from multiple studies.^86–93

However, not all patients will fit the molds of thin scalloped or thick flat gingival morphology. There are certainly variations and combinations of the morphologic characteristics from the basic two gingival phenotypes. De Rouck et al⁸⁹ identified and confirmed through a cluster analysis the existence of three different gingival types around the maxillary central incisors in a sample of 100 participants: cluster A1, slender tooth form and thin gingiva; cluster A2, slender tooth form and thick gingiva; and cluster B, quadratic tooth form with thick gingiva. Cluster A1 corresponds to the thin scalloped phenotype, while cluster B represents the thick flat phenotype. The participants from cluster A2 differed significantly from the other clusters, showing a definitive thick gingiva but slender teeth. Thin gingiva was found in one-third, mainly female participants, while thick gingiva was found in two-thirds of the participants and was predominantly a male trait.

Patients will frequently present with both thick and thin periodontium in the same dentition. Canines and mesiobuccal roots of maxillary molars tend to have a thin periodontium due to their position in the dental arch. Central incisors are usually associated with thick periodontium. As a general rule, the prevalence of thick periodontium is more common in males than in females, in younger patients than in older patients, in the maxilla than in the mandible, and in white patients (72% to 88%) than in patients of Asian descent (< 40%). These differences are due to intra- and interindividual variations in conjunction with tooth type, tooth shape, tooth position, and genetic determinants.^90,94–99

The thick phenotype is commonly associated with periodontal durability and health. It is characterized by dense fibrotic gingival tissue, a wide band of keratinized tissue, and flat soft tissue with thick underlying bony architecture. The thin phenotype is usually associated with delicate and friable gingiva that is almost translucent in appearance, a narrow band of keratinized tissue, and highly scalloped soft tissue with thin or minimal underlying buccal bony thickness^86–93 (see Table 1-1).

Clinical implications of tissue phenotype

The clinician should be able to correctly identify and categorize these two distinct gingival phenotypes. Differences in gingival and osseous architecture have been shown to have a significant impact on treatment outcomes. Accordingly, thin and thick phenotypes behave differently when subjected to inflammation, tooth extraction, and surgical trauma⁹³ (Table 1-2). They also respond differently to restorative, periodontal, implant, and orthodontic therapy.^{41,60,86,89,90,92,93,97,100–107}

Table 1-2 Clinical implications of gingival phenotype*

	Thin phenotype	Thick phenotype
Inflammation
Soft tissue	Gingival recession without pocket formation	Marginal inflammation with pocket formation, bleeding on probing, and edema
Hard tissue	Loss of the thin vestibular bone plate	Formation of intrabony defects
Surgical procedures
Osseous surgery	More susceptible to gingival recession	Marginal periodontal tissue shows a tendency to grow in a coronal direction
Mucogingival surgeries	Associated with partial root coverage	Associated with complete root coverage
Guided tissue regeneration	Greater postoperative recession	Less postoperative recession
Orthodontic treatment	Greater risk of developing soft tissue recession	Prevents or minimizes soft tissue recession
Implant therapy	More susceptible to marginal bone loss, angular bone defects, and recession	Maintains stable crestal bone and is less prone to recession
Restorative procedures	Restoration may be slightly visible through the thin soft tissue	May mask discoloration from metal-ceramic restorations with metal collars and disappearing margins, metal implant abutments, and discolored roots
Extractions	Extensive ridge resorption	Minimal ridge resorption

*Data compiled from multiple studies.^{41,59,90,92,93,100–107}

Gingival recession

A major clinical challenge is gingival recession around ceramic veneers and complete-coverage restorations when the finish line is placed subgingivally. Many etiologic factors have been proposed as the cause for recession. Faulty restorative margins, mechanical and chemical irritants from impression procedures, overcontoured restorations, incomplete removal of excess cement, violation of biologic width, or adverse gingival reactions to alloys used in the oral cavity have all been implicated.⁹² Patients with thin gingival phenotype are more susceptible to such recession. Gingival grafting should be considered prior to restoration to modify the phenotype to a thicker state.

Gingival inflammation

The thin phenotype reacts to insult by initial gingival inflammation followed by gingival recession, while the thick phenotype responds by tissue proliferation and eventual formation of a periodontal pocket. This is probably due to the fact that a thick periodontium has a greater volume of soft tissue than the thin periodontium, with attachment loss leading to development of a periodontal pocket instead of recession.⁹²

Surgical periodontal therapy

During the healing stages following osseous resective crown lengthening surgery, the marginal periodontal tissue shows a tendency to grow in a coronal direction. This pattern of coronal displacement of the gingival margin is more pronounced in patients with a thick periodontium compared with those with a thin periodontium phenotype.⁴¹ In the context of osseous surgery, it is extremely important to make a distinction presurgically between flat and scalloped gingival architecture. Usually, markedly scalloped soft tissue architecture would be more challenging in terms of pocket recurrence than flat architecture in the interproximal area. This is especially true if the gingiva takes on a scalloped architecture while the underlying osseous tissue does not follow the same scalloped pattern, resulting in greater distance between the tip of the papilla and the crest of the bone, leading to the formation of interproximal pocket depth.⁸⁶

For mucogingival surgery such as the coronally positioned flap, it has been shown that greater initial thickness of gingival tissues (> 0.8 to 1.1 mm) is positively associated with complete root coverage. The probabilities of obtaining better root coverage outcomes are strongly related to the marginal tissue thickness.^108,109 Tissue thickness is also an important factor to be considered during regenerative procedures around teeth. Tissue thickness greater than 1 mm led to less postoperative recession at 6 months compared with thin tissue (0.6 vs 2.1 mm).¹⁰²

Orthodontic therapy

The development of gingival recession during orthodontic treatment is a major concern as well. Alterations of the mucogingival complex are inevitable during orthodontic therapy, but the important factors to consider are the direction of the tooth movement and the thickness of the buccal gingival tissue. Movement of the tooth in the lingual direction will result in increased thickness of the gingival tissue on the facial aspect. It will also result in coronal migration of the free gingival margin. Movement of the tooth in the facial direction will result in reduced tissue thickness and migration of tissue apically, resulting in increased crown height. The thickness of the soft tissue correlates to the prevention of soft tissue recession. The risk of developing recession is increased in the presence of thin tissue when the tooth is being moved out of the alveolar bone housing. If mucogingival surgery is considered in order to prevent or reduce the risk of developing recession, it should be aimed at increasing the thickness of marginal soft tissue rather than only the width of keratinized gingiva.¹⁰³

Implant therapy

In the case of dental implants, there is evidence indicating that the tissue phenotype is a key element for predictable and successful esthetic outcomes. Thin gingival tissues are more susceptible to marginal bone loss, angular bone defects, and recession, while thick gingival tissue results in the maintenance of stable crestal bone and is less prone to recession around dental implants.^59,104,105

Restorative procedures

A thick periodontium reduces the risk of gingival recession when the finish line of the crown preparation for a ceramic crown or a porcelain laminate veneer is placed subgingivally for esthetics. It can mask and eliminate the grayish discoloration from metal-ceramic restorations with metal collars or disappearing margins. The placement of retraction cord can be accomplished with a reduced risk of inducing recession, which may lead to disparate gingival levels and compromise the esthetic outcome.¹⁰⁶ With thin tissue phenotypes, the risk of inducing recession is increased, mainly during impression procedures. Clinicians may opt to use metal-free restorations such as ceramic crowns and fixed dental prostheses. When the finish line is placed subgingivally, it is placed more conservatively than with metal-ceramic restorations. Therefore, the likelihood of trauma to the tissue is diminished, and the color of the soft tissue, mainly in terms of brightness, will be uncompromised even though the restoration may be slightly visible through the thin soft tissue.¹⁰⁷

In summary, an accurate evaluation of the soft tissue morphology and phenotype not only helps clinicians predict therapeutic outcomes but also helps them determine the most appropriate periodontal and restorative management, leading to more favorable and predictable treatment outcomes.^97,100

Gingival phenotype assessment

Many different methods are available for gingival phenotype assessment. An ideal method should be simple to use, accurate, reproducible, and noninvasive. It should allow clinicians to predict risks in terms of soft tissue treatment complications and enhance the customization of therapy for each patient. The gingival thickness can be evaluated by invasive methods such as transgingival probing as well as by noninvasive methods such as visual evaluation of the gingiva, periodontal probing, direct measurement with a caliper immediately postextraction, and cone beam computed tomography (CBCT), if indicated.^{91,95–97,110}

Visual evaluation of the gingiva

Visual evaluation was one of the first methods used to evaluate tissue phenotype.^86,87 Because of its simplicity, it is widely used in clinical practice settings to identify high-risk patients. While simple, this method may lack accuracy.

Accuracy of a visual inspection method for identification of three different groups of patients (thin scalloped, thick flat, thick scalloped) was evaluated based on clinical photographic slides.¹¹¹ The thick flat phenotype was relatively easily identified, but about half of the thin scalloped cases were misidentified. Precise identification of different phenotypes by means of visual evaluation was not reliable, as half of the patients at high risk were overlooked. In a similar study, 124 clinicians were asked to assign each of 53 patients to one of three phenotypes: thin scalloped, thick flat, or thick scalloped.⁹⁷ The results showed that visual evaluation was not very effective in identifying different phenotypes, with less than 50% probability of identifying the correct cluster.

Periodontal probing

The gingival tissue around teeth and implants can be classified as thick or thin by assessing tissue translucency. A periodontal probe is positioned into the sulcus, and the clinician assesses whether or not the underlying periodontal probe can be seen through the tissue. If the outline of the probe is visible through the gingiva, the tissue is considered to be thin.^91,112 This method is extremely simple, minimally invasive, reliable, objective, and reproducible^{89,97,112,113} (Figs 1-10 and 1-11).

Fig 1-10 (a) Facial view of a tooth prepared for a zirconia-based ceramic crown. (b) Crown at the 4-year recall. Note the visual appearance of the tissue, looking relatively flat and thick. (c) The outline of a periodontal probe positioned into the sulcus is visible through the gingiva, demonstrating that the tissue is thin and translucent. (Ceramics: Andreas Saltzer.)

Fig 1-11 Facial view of a failing tooth planned to be restored with an implant-supported restoration. The outline of a periodontal probe positioned into the sulcus is not visible through the gingiva, demonstrating that the tissue is thick and opaque.

Transgingival probing

This is a very simple method in which a periodontal probe or endodontic file is used to measure the gingival thickness, usually at a point 2 mm apical to the gingival margin. However, this method is limited by the precision of the probe, which is usually rounded to the nearest 0.5 mm; the angulation of the probe penetration through the soft tissue; distortion of the tissue during the probing; a need for anesthesia; and the invasive nature of this tissue-penetrating procedure^112–114 (Figs 1-12 and 1-13). Alternatively, the use of an endodontic file with a stop has been advocated as well.

Fig 1-12 Transgingival probing of less than 1 mm at a point 2 mm apical to the facial free gingival margins confirms that the tissue is thin, as demonstrated in Fig 1-10c. (Ceramics: Andreas Saltzer.)

Fig 1-13 Transgingival probing of just less than 2 mm at a point 2 mm apical to the facial free gingival margins confirms that the tissue is thick, as demonstrated in Fig 1-11.

Direct measurement with a caliper

This method is limited for tissue assessment prior to immediate implant placement. A comparison was made among three different methods of evaluation of gingival phenotype around maxillary anterior teeth scheduled for extraction and immediate implant placement. A statistically significant difference was noted between visual inspection and both periodontal probing and the direct caliper measurement method. However, no significant difference was noted between periodontal probing and direct caliper measurement.⁹¹ The only drawback of the caliper method is that it cannot be used for presurgical evaluation, because it can only be used at the time of tooth extraction.^112,115,116

CBCT scans of tissue thickness

CBCT scans are used extensively for three-dimensional imaging of hard tissue for orthodontics, endodontics, extractions, and especially for implant-related procedures.¹¹⁷ Another useful novel application of CBCT scans is to measure the thickness of soft tissues.^{97,110,111,118} One study used a caliper for clinical measurement of facial gingival thickness and compared this to CBCT measurements.¹¹⁹ There was no significant difference between the clinical and CBCT measurements. Due to radiation concerns, this method can only be applied to patients requiring a diagnostic evaluation and visualization of the anatomical structures and/or underlying bone prior to treatment.

Strategies for Managing Soft Tissue Phenotype with Implant-Supported Restorations

Management strategies to maintain or improve existing soft and hard tissue architecture revolve around a goal of thick bone and thick soft tissue. A thick periodontium can optimize esthetics around implant-supported restorations. It can reduce the amount of gingival recession and create a better, more stable restorative environment^93,120,121 (Fig 1-14). Periodontal plastic surgery and osseous regenerative procedures are available to convert a thin phenotype into a thick phenotype, which is easier and more predictable to manage for the restorative dentist.^93,120,121 This has been examined with immediate and delayed implant placement protocols.

Fig 1-14 Occlusal view of an implant prior to impression making, demonstrating thick tissue on the facial aspect.

Immediate implant placement

Esthetic advantages of using subepithelial connective tissue grafts around dental implants have been reported. The change in the buccolingual width of the ridge around immediate implants has been evaluated with and without connective tissue grafts. After 6 months of healing, a loss of 1.063 mm of labial tissue was noted in a horizontal dimension in the nongrafted sites, while the grafted sites had a gain of

0.34 mm of labial tissue. Nine out of 12 nongrafted sites were considered to have compromised esthetics, with a “disturbing shadow” appearance, while no compromised esthetics were seen in the grafted sites.¹²⁰

A successful conversion of a thin to a thick phenotype around immediate implants was demonstrated by subepithelial connective tissue graft placement in 20 patients. A thick phenotype was presented by 8 patients and thin phenotype by 12 patients prior to surgery. After a mean followup of 2 years, the mean facial free gingival margin change for the thick phenotype patients was +0.23 mm, whereas for the thin phenotype patients it was +0.06 mm. All the treated implant sites exhibited a thick phenotype.¹²² Thus, the enhanced facial free gingival margins can be maintained at appropriate levels regardless of the initial gingival phenotype presented by the patient.

Subepithelial connective tissue grafts should have large dimensions with a vertical height of 9 mm and a horizontal width equal to the mesiodistal extent of the recipient site. A minimal thickness of 1.5 mm is used to prevent shrinkage following surgery.¹²³ Evaluation of long-term efficacy reveals a very predictable approach for achieving favorable functional and esthetic results around implant-supported crowns.¹²⁴ Therefore, additional soft tissue volume needed in esthetically demanding areas must be established surgically.¹²¹

Delayed implant placement

Bone regeneration and soft tissue grafting procedures in conjunction with delayed implant placement has also been described.^121,125,126 One clinical study reported on dimensional changes of peri-implant tissues by comparing pre- and posttreatment soft tissue dimensions. Placement of implants with simultaneous bone regenerative efforts and connective tissue grafting was successful in increasing the tissue volume. A 1.3-mm gain of buccal thickness and only 0.2 mm of recession (from crown delivery to 1 year postfunction) indicated stability of peri-implant tissues at 1 year.¹²⁵

Successful esthetic outcomes can be achieved utilizing guided bone regeneration and soft tissue grafting in sites with missing facial bone. In one clinical study, implants were positioned in deficient sites followed by simultaneous horizontal and vertical augmentation. Six months later, at the time of membrane removal, connective tissue grafts were placed. The average bone gain was 3.75 ± 0.47 mm horizontally and 6.5 ± 0.81 mm vertically. The surgical procedure was able to provide predictable esthetic outcomes in deficient sites with favorable long-term soft tissue contour.¹²⁶

Enhancing Existing Peri-implant Soft Tissues

Malpositioned implants may cause esthetic and maintenance complications (Fig 1-15). Improper soft tissue management may create a defect complicated by the malposition, and inadequate initial hard and soft tissue volume prior to implant placement can be extremely difficult to correct once the implant is positioned. There may be a need to repair an unesthetic situation and/or regain pre-extraction ridge contours.⁹³ Treatment options such as implant removal, recontouring of the abutment, and soft tissue grafting should be considered. Several studies have shown improvement in cases of adverse esthetics around dental implants by means of connective tissue grafting and/or use of allogeneic bone grafts.^127–130

Fig 1-15 Facial view of a failing implant-supported restoration, which may be the result of multiple factors including less than ideal implant positioning in every dimension.

Gingival phenotype again contributes to the amount and prevalence of gingival recession. One clinical study analyzing the esthetic outcomes of 42 single implant-supported restorations (mean time in function, 18.9 months) reported a mean recession of 0.9 mm. Patients with the thin phenotype had slightly greater recession compared with patients with the thick phenotype. That finding was further supported by another similar study reporting that recession was more prevalent in thin phenotype sites. Recession was present at 6 of 25 thin phenotype sites compared with 2 of 19 thick phenotype sites.^105,131

Recession around implant-supported restorations

A dental prosthesis with soft tissue that truly mimics the soft tissue of the adjacent dentition and blends with the natural adjacent teeth is a challenging goal.^132,133 Various studies report the apparently inevitable occurrence of marginal gingival recession around dental implants leading to adverse esthetic outcomes. Long clinical crowns, grayish appearance through the thin peri-implant tissue, and exposure of crown margins, abutments, or even implant threads are not uncommon.^{105,121,131,134–136}

Several factors have been implicated in the etiology of marginal gingival recession. These include implant position,^{105,131,137–141} tissue phenotype,^{104,105,131,136,139} integrity and thickness of the facial bone,^{60,136,140,142,143} surgical approach (conventional vs flapless),^136,144 and presence or lack of immediate provisionalization.^144–146

Implant position within the alveolar bony housing is considered to be one of the most important contributing factors for gingival recession. Recession is more pronounced for implants placed facially compared with those implants placed lingually within the extraction socket. In addition, facially positioned implants showed three times more recession than implants positioned lingually (1.8 vs 0.6 mm).^105,131 Undoubtedly, excessive lingual positioning may create unnatural buccal emergence angles or unmaintainable contours. Optimal placement is a balance of these issues.

Peri-implant soft tissue recession can be improved by employing a combination of coronally advanced flaps and connective tissue grafts. In one study,¹²⁹ significant improvement was achieved in 10 patients from baseline, but complete coverage could not be achieved. Significant shrinkage (66%) at 6 months followed coronal advancement of the flap. Alternatively, a prosthetic-surgical method has been proposed to correct the peri-implant soft tissue dehiscence around single implants. After the existing crown is removed, the abutment is modified, and a coronally advanced flap in conjunction with a connective tissue graft is performed. A year after delivery of the definitive restoration, the mean coverage of the dehiscence was about 96%, with complete coverage in 75% of the cases. Facial tissue thickness was increased an average of 1.54 ± 0.21 mm with a significant esthetic improvement.¹³⁰

Esthetic improvement in clinical scenarios of suboptimal implant placement can also be achieved by means of a pediculated connective tissue graft. The existing crown and abutment are removed, and the soft tissue is allowed to naturally “self-cover.” Approximately 3 months later, the implant is exposed, followed by placement of a 2-mm-tall healing abutment. A pediculated connective tissue graft is rotated from the palate, then flipped over the implant/healing abutment and secured with sutures. The second-stage surgery is performed in 4 months, followed by restorative procedures. This technique is able to increase the volume of soft tissue, resolving the initial esthetic complications.¹²⁷

Acellular dermal matrix grafting in conjunction with coronally advanced peri-implant tissue has also been shown to improve implant esthetics. This technique was reported in a patient presenting with deficient esthetics, thin peri-implant tissue, and 3 mm of recession. Results of the case showed great esthetic improvement with partial coverage, thicker peri-implant tissue, no bleeding on probing, and no significant probing depths. This procedure demonstrated an alternative to harvesting tissue from the patient’s palate.¹²⁸

Integrity and thickness of facial bone

The presence and volume of bone is one of the most critical anatomical factors to be considered for achieving an esthetic outcome. Once the implant is positioned, a circumferential moatlike bone remodeling of approximately 1.4-mm width occurs.¹⁴⁷ At least 2 mm of buccal bone thickness is proposed to avoid loss of buccal crestal bone in a vertical direction. Moreover, additional bone grafting around implant sites with dehiscence or inadequate bone volume is strongly recommended. A lack of bone volume may jeopardize the esthetic outcome due to considerable risk of soft tissue recession.¹⁴⁰

Evidence indicates that the placement of bone graft material in the gap between the implant surface and facial bone has positive effects in animal and human studies. The bone graft can counteract, or at least reduce, the inevitable bone remodeling process around implants immediately placed in fresh extraction sockets. When a bone graft of porcine origin was used to fill the gap in test sites with a resorbable membrane covering the entire extraction socket, test sites showed a stable bone level and even some bone gain. Extensive bone remodeling was observed in the control sites.¹⁴⁸ In a similar study comparing immediate implant sites with and without placement of xenogeneic graft material, the test sites (with bone graft) had (1) a peri-implant bone level located 1 mm more coronally, (2) thicker facial tissue (1 ± 0.3 mm versus 0.4 ± 0.4 mm), (3) facial bone located more coronally on the implant (0.1 ± 0.5 mm versus 1.3 ± 0.7 mm), and (4) thicker facial bone (1.1 ± 0.5 mm versus 0.1 ± 0.2 mm at 1 mm apical to the implant platform).¹⁴⁹

In a case series with 10 patients, a “trimodal” approach (immediate implant placement, flapless approach, and immediate provisionalization) was employed. Xenograft was placed in the gap between the facial bone and the implant surface, and a subepithelial connective tissue graft was interposed onto the facial bone. Favorable implant success and peri-implant tissue were achieved with a mean marginal bone and facial free gingival level change of +0.10 mm and –0.05 mm, respectively. The authors concluded that the facial free gingival margin could be maintained without any further recession when immediate implants are treated with a subepithelial connective tissue graft, ideal three-dimensional positioning of the implant, and the use of graft material to fill the gap between the facial bone and the implant surface.¹⁵⁰ Therefore, placement of bone graft material in the gap can be beneficial in minimizing the bone remodeling process, resulting in more favorable hard and soft tissue status around the implant.¹⁵¹

Immediate implants have a similar survival and success rate compared with implants placed into healed sites. The advantages of immediate placement include decreased treatment time, a reduction in the number of surgical interventions, and the potential for immediate provisionalization. This may allow preservation of existing soft tissue and osseous architecture.^152–154 When clinicians are considering immediate implant placement in patients with a thin phenotype, careful and detailed evaluation of both the soft tissue and the underlying bony architecture should be carried out. In certain cases, a delayed approach may be the most appropriate treatment when very thin tissue or bone is present. When the possibility of significant recession is expected, hard and soft tissue augmentation should precede implant placement.⁹³ It should be assumed that thin facial bone is present.

Minimally invasive or flapless surgery may be possible and selected as a means to minimize disruption of blood supply to the surrounding hard and soft tissue components. Once the implant is positioned toward the palatal aspect, bone graft is used to fill the gap between the facial bone and implant surface. Where a flap must be elevated to assess structures and surgical landmarks, a subepithelial connective tissue graft should be harvested from the palate and secured over the facial bone. If an implant-supported provisional restoration is provided, it should initially have a concave subgingival profile on the facial aspect to reduce the risk of apical migration of the free gingival margin.^104,155

Preserving thin facial bone plates

The mean thickness of facial bone for the maxillary anterior teeth (from canine to canine) is about 0.8 mm, with 87% of sites having a facial bone thickness ≤ 1.0 mm. Measurement of the facial bone thickness of anterior teeth in the maxilla by means of CBCT scans showed that the majority of all teeth examined had ≤ 1.0 mm of bone thickness. Nearly 50% of sites had bone thickness that was ≤ 0.5 mm. Most extraction sites in the maxilla will therefore experience extensive ridge alteration, demanding additional grafting procedures to achieve a minimal width of bone. At least 1 to 2 mm of buccal bone is required for stability of hard and soft tissues.^140,156,157

Vertical bone loss is marked after immediate implant placement. A mean vertical bone loss of 0.7 to 1.3 mm on the facial and lingual aspects and a 0.4-mm reduction in the thickness of facial bone at the time of abutment connection can be expected. An exaggerated pattern of vertical bone remodeling around immediate implants was confirmed in an animal study.¹⁴⁸ Reference measurements were made from the implant platform to the bone crest and to the bone contacting the implant within the remodeling zone. The distance between the abutment-implant junction and the first bone-to-implant contact was 4.11 ± 1.9 mm, and the distance to the crest of bone was 1.23 ± 0.48 mm for immediate implant sites. In comparison, the mean distances were 2.02 ±0.78 mm and 0.46 ± 0.51 mm, respectively, for the delayed implant sites.¹⁵⁸

Tissue effects of tooth extraction

Tooth extractions performed on patients with thick flat gingival architecture may result in minimal dimensional changes to the surrounding gingiva and bone. Extractions performed on patients with thin scalloped gingival architecture, associated with thin bone, dehiscences, and fenestrations, may result in obvious dimensional tissue changes causing significant esthetic concerns.¹⁵⁹ For patients with a thin periodontium, atraumatic and very precise surgical techniques should be applied during the extraction to minimize adverse effects on the bone remodeling process.^93,160 Ideally, minimal flap elevation or a flapless approach should be used to limit the disruption of blood supply. An animal study compared tooth extraction with and without flap elevation and its effect on the bone remodeling process. The results demonstrated significantly less bone resorption for the flapless group than the flapped group.¹⁶⁰ Atraumatic extraction can be accomplished with controlled and steady application of forces on the interproximal areas, limiting any leveraging forces on the thin facial bone. Sectioning of the roots, careful use of periotomes to luxate and expand the periodontal ligament space, and use of controlled extraction devices can also assist in facilitating a satisfactory outcome with minimal hard and soft tissue complications.⁹³ Controlled extraction devices are mechanical devices that lift from a special post placed in the root canal of a crownless tooth. Adjacent teeth support them while they smoothly apply vertical extraction forces.

Ridge preservation procedures

Once the tooth is removed, it is critical to limit the bone remodeling process, especially in patients with the thin tissue phenotype.^60,142,143 The goal of preserving an adequate amount of bone volume for future implant placement can be met by socket grafting or ridge augmentation procedures.⁹³ Various surgical approaches and materials for ridge preservation have been described. As a general rule, ridge preservation involves the use of a bone graft material placed into the extraction socket. This may be in conjunction with the use of absorbable collagen matrices or nonabsorbable barrier membranes secured with sutures on top of the bone graft.^161–167

Several human and animal studies have documented the effectiveness of ridge preservation procedures. These procedures limit, but may not totally prevent, the ridge alterations in both horizontal and vertical dimensions. Lekovic et al¹⁶¹ evaluated alterations in ridge dimensions in 10 subjects by covering the experimental sites with expanded polytetrafluoroethylene barrier membranes with primary closure. Control sites remained ungrafted. The clinical measurements demonstrated increased remodeling in the control group of 0.7 mm vertically and 2.6 mm horizontally compared with the test group. Another clinical study compared a ridge preservation approach using mineralized freeze-dried bone allograft and resorbable collagen membranes without primary closure.¹⁶⁷ The horizontal width changed from 9.2 ± 1.2 mm to 8.0 ± 1.4 mm for the test group and 9.1 ± 1.0 mm to 6.4 ± 2.2 mm for the extraction-only control group. The difference horizontally was 1.6 mm between the groups. In vertical change, the test group had a gain of 1.3 ± 2.0 mm while the control group lost 0.9 ± 1.6 mm, for a vertical difference of 2.2 mm between the groups.

Fu et al¹⁶⁸ proposed increasing the soft tissue thickness around dental implants by means of a method they called PDP, which stands for implant position, implant diameter, and prosthetic design. The authors advocated three steps: (1) a more palatal and apical positioning of the implant platform so more soft tissue volume is present on the facial aspect; (2) use of smaller-diameter or platform-switched implants to maintain an adequate amount of bone thickness, thus limiting the amount of gingival recession; and (3) use of concave subgingival contours for the abutments or crowns to allow ingrowth of peri-implant soft tissue. This article highlights the importance of not only the surgical methods but also the prosthetic methods or combinations thereof when it comes to soft tissue management.

Soft tissue–bone relationship

For proper decision-making, it is critical for the clinician to predict how different gingival phenotypes respond differently to implant-related therapy. If the soft tissue morphology and the underlying bony architecture differ from one another, the clinician should employ different management strategies (ie, for thin vs thick phenotypes). Bundle bone is the alveolar bone that receives the Sharpey’s fibers of the periodontal ligament. After extraction, the function of the bundle bone is no longer needed, usually resulting in substantial horizontal and vertical bone reduction. Following the removal of teeth, the bundle bone has minimal potential for remodeling and is therefore lost. Where bone is thinner, there is no capacity for this bone to be regenerated.¹⁶⁹

There is evidence of a positive relationship between the gingival phenotype and the thickness of facial bone. Patients with thin phenotype are associated with thinner facial bone thickness, a narrow band of keratinized tissue, substantial distance from the CEJ to the alveolar bone crest, and a high prevalence of dehiscence and fenestration.^159,170

The thickness of the facial bone is one of the most important clinical parameters in achieving predictable esthetic outcomes with dental implants. Facial bone thickness of 1 to 2 mm has been suggested to provide adequate soft tissue support and to prevent or minimize the amount of bone resorption. This minimizes the risk of soft tissue recession around implant-supported restorations.^{121,171–173} Around immediate dental implants, substantial bone fill was observed when the thickness of buccal bone was greater than 1 mm.¹⁴¹

Several animal and clinical studies demonstrate the correlation between soft tissue thickness and crestal bone remodeling following implant placement. In histologic studies conducted in dogs, thin tissue around dental implants consistently resulted in more bone resorption following abutment connection. There was also a tendency to form angular bony defects, whereas thick tissues tended to maintain more stable crestal bone.^59,174 Similar results were reported in human studies. Implants placed in naturally thick soft tissue resulted in minor remodeling of bone, while implants placed in naturally thin soft tissues resulted in more bone remodeling with crestal bone loss of up to 1.45 mm.^60,142,143 It is interesting to note that implants restored with a platform switching design were not able to preserve the crestal bone when compared with conventional matched-abutment implants in the presence of thin soft tissue.¹⁷⁵

Presence of keratinized gingiva

The presence of keratinized gingiva is considered to be beneficial for the stability of peri-implant soft tissue because of its ability to form a microbial barrier. It plays an important role in the long-term maintenance and survival of dental implants.¹⁷⁶

The relationship between keratinized gingiva and health status of the peri-implant mucosa was evaluated around implant-supported overdentures. The absence of adequate width of keratinized tissue (less than 2 mm) resulted in higher gingival and plaque index scores, a higher tendency for bleeding, and more radiographic bone loss.¹⁷⁷ In a 5-year clinical study, even when patients were performing good oral hygiene and received regular maintenance therapy, buccal soft tissue recession, more bleeding, and plaque accumulation was noted at sites with less than 2 mm of keratinized gingiva.^178,179

Interdental Papillae

The papillae between natural teeth fill the space under the proximal contacts. They have vertical, facial, and lingual surfaces, with a gingival col under the contact. With bone loss, the distance from the bone to the apical portion of the contact increases. Having a limited height range, the papilla may no longer reach the contact, resulting in a dark space between the teeth. The distance from the contact point to the crest of bone is a major factor in the esthetic adequacy of the papilla. Papillae are present around natural teeth 100% of the time when the distance from the contact point to the crest of bone is ≤ 5 mm. If the distance is 6 mm, the papilla is present only 56% of the time, and the papilla is present less than 27% of the time if that distance is ≥ 7 mm.¹⁰¹ After complete denudation of the interproximal bone, a mean distance of 4.33 mm between the location of the interproximal papilla tip and the contact had developed 3 years post-treatment, demonstrating the body’s tendency to return to a normal level.¹⁸⁰

Single implants

The presence of normal interdental papillae is a key part of achieving optimal esthetics around implant-supported restorations. Papillae can be influenced by several factors. Tissue phenotype, implant-implant or implant-tooth distance, and level of interproximal bone crest of the adjacent teeth can all affect bone healing at the interproximal area and subsequently the presence or absence of a papilla. The space between the interproximal contact point of the definitive restoration and underlying interdental bone crest forms the interproximal gingival embrasure. As with natural dentition, the distance between the apical aspect of the interproximal contact and the interdental bone crest predicts the fill of the gingival embrasure space. Consequently, the presence or absence of an unfilled gingival embrasure space is dependent on both the surgical and prosthetic phases of the implant therapy.^{100,131,139,181–184}

Single implants and phenotype

The complete fill of the interdental space by the papilla around natural teeth and implants can be influenced by the gingival phenotype of the patient. In a study evaluating the presence of papillae around natural teeth, the thin phenotype presented a significantly higher presence of papillae (71.1%) than did the thick phenotype group (59.6%).¹⁰⁰ The papilla was considered present when there was no visible space apical to the contact point. The high prevalence of interproximal papilla fill around natural teeth for the thin phenotype may be explained by gingival architecture characteristics, because subjects with thin tissue also have accentuated tissue scalloping with a tendency for taller papillae. However, these subjects are also more susceptible to loss of gingival tissue following surgical procedures or tooth removal.

In evaluating the presence or absence of interproximal papillae around single implants, it was noted that the presence of the papilla was strongly associated with the thick tissue phenotype (84% of cases vs 42% for the thin phenotype).¹⁸¹ The high prevalence of interproximal papilla fill around implants with the thick phenotype may be due to greater total dimension of the peri-implant mucosa.¹⁸⁴ In a study assessing the dimensions of peri-implant mucosa around anterior single implant-supported restorations in individuals with thick versus thin tissue phenotype, the peri-implant tissue heights were approximately 4.5 mm for the thick pheno type and 3.8 mm for the thin phenotype. Apparently, papilla heights up to 4.5 mm from the underlying bone can be maintained or re-created around sites with thick phenotype. For the thin phenotype, less than 4.0 mm of papilla height from the underlying bone is expected.¹⁸⁴

Distance to bone

The distance between the apical aspect of the interproximal contact and the interdental bone crest and its relationship with papilla height between a single implant and its adjacent natural tooth has also been examined. When the distance from the contact point to the crest of bone was ≤ 5 mm, the papilla was present 100% of the time. However, when the distance was ≥ 6 mm, the papilla was present in only 50% or fewer of the cases.¹⁸⁵ These results are very similar to the previous study evaluating papillae height around natural dentition,¹⁰¹ indicating that the bone crest of the adjacent teeth determines the papilla level around single implant-supported crowns.^139,184 These studies highlight the importance of maintaining and preserving the interproximal crestal bone of adjacent teeth next to the single implant to maintain optimal papilla levels.

According to a recent systematic review, the distance from the contact point to the underlying interproximal bone was the most significant factor associated with papilla fill.¹³⁹ The sites with complete papilla fill had a mean distance of 4.7 ± 0.9 mm from contact point to the underlying interproximal bone. Therefore, re-creation of the “full” papilla around single implants is predictable when the distance from the contact point to the bone crest is ≤ 5 mm.^184,185

Distance to teeth

With regard to implant-tooth distance, the presence of papillae filling the entire proximal space was strongly related to an implant-tooth distance of 2.5 to 4.0 mm.¹⁸¹ Based on Tarnow et al’s finding of 1.4 mm of lateral bone remodeling, a minimal distance of 1.5 to 2.0 mm is desirable from the implant to the adjacent root surface for an acceptable presence of the papilla, because the bone crest of the adjacent teeth determines the papilla level around single implant-supported crowns.¹⁴⁷

Jemt proposed a papilla index evaluating the degree of papilla fill in the interproximal embrasure space formed between single implant-supported restorations and adjacent natural teeth.¹⁸⁶ It consists of five different categories: score 0, no papilla present; score 1, less than half the height of the papilla is present; score 2, at least half the height of the papilla is present; score 3, the entire embrasure space is occupied by papilla and in good harmony with adjacent papillae; score 4, hyperplastic papilla.

Spontaneous regeneration of the papilla can occur after restoration of the implant, with significant esthetic improvement possible over time.^{182,186–188} An early study reporting on the natural regeneration of the papilla over a mean 1.5 years of follow-up from the time of crown delivery showed an improvement of the Jemt score. The score improved from about 1.5 to about 2.5, indicating substantially more gingival embrasure fill. Moreover, significant improvement over time was noted in regard to complete papilla fill. A score of 3 was only assigned to 10% of the papillae at the time of crown placement, but after several years’ follow-up, a score of 3 was seen for 58% of the papillae.¹⁸⁶ Papilla fill adjacent to implants receiving conventional healing abutments or provisional restorations has been evaluated as well. Prior to delivery of the definitive crown, the provisional crown may restore the soft tissue volume faster than the healing abutment. However, a similar volume of soft tissue was noted after 2 years in function. Given time, there was no significant difference between the two single-implant groups.¹⁸⁸

Papillae between adjacent implants

Developing a normal interdental papilla between two adjacent implants for an implant-supported restoration is significantly more challenging than developing one around a single implant-supported restoration adjacent to natural teeth. Similarly to the papilla around a single implant-supported restoration, it can be influenced by several factors such as the distance between the crest of bone and the contact point, the interim-plant distance, and the definitive crown shape (Fig 1-16).

Fig 1-16 Occlusal view of adjacent implants replacing mandibular premolars and the corresponding soft tissue contours, demonstrating the challenge of creating an ideal interproximal papilla between the implants.

Distance from the crest of the bone to the contact point

The mean average distance from the tip of the papilla to the crest of bone between two adjacent implants was 3.4 mm. The most common recordings were 3 mm (35.3%) or 4 mm (37.5%).¹⁸⁹ A distance of 3 to 4 mm (and never more than 6 mm) from the contact point to the bone crest is recommended to facilitate esthetic success, defined as a score of 2 or 3 according to the Jemt index¹⁸⁶ (at least half to full height of the proximal area occupied by soft tissue).¹⁸²

When two adjacent teeth must be replaced in the esthetic zone, careful evaluation should precede implant placement. Many treatment strategies have been proposed to address this esthetic challenge, and treatment modification may be needed. This challenge is amplified when the site to be restored is adjacent to the facial midline. This may result in an accentuated sagittal asymmetry of the patient’s anterior dentogingival complex, especially for a patient with a high smile line. One suggestion is to perform vertical bone augmentation prior to implant placement. The implants are then placed at least 3 mm apart to maintain the vertical bone height. Another choice is to place only one implant, incorporating an ovate cantilever pontic on the adjacent site. Simultaneous soft tissue augmentation may allow better simulation of the interproximal papilla.¹⁸⁹ Another variation is to harvest soft tissue from the tuberosity, which is then positioned in the area of soft tissue deficiency at the time of abutment connection for re-creation of the papilla.¹⁹⁰

Interimplant distance

Careful planning of the interimplant and implant-tooth distance is an important strategy to achieve ideal papilla height. Vertical bone remodeling around the implants with expected loss of 1.5 to 2.0 mm in the first year after implant placement is very well established.¹⁹¹ Bone loss around implants also occurs in a radiographically horizontal direction (1.34 mm for the mesial and 1.4 mm for the distal surface of the implant). This is actually circumferential change. When adjacent defects meet, crestal vertical bone loss occurs. Crestal bone loss of 1.04 mm was noted if the interimplant distance was ≤ 3 mm, while bone loss of 0.45 mm occurred when the distance was greater than 3 mm. The greater the crestal bone loss, the greater the distance from the contact point to the crest of the bone. This finding has led several authors to recommend a minimal distance of 3 mm when placing adjacent implants to maintain papilla fill.¹⁴⁷

Similar results were observed in an animal study in which two adjacent implants were placed 2 or 3 mm apart. The contiguous implants were restored, and the mean distance from the contact point to the bone crest was 6 mm and from the papilla tip to the bone crest 3.3 mm.¹⁹² The authors concluded that these distances were similar in both groups. Therefore, the ideal distance from the contact point to the bone crest should be less than 5 mm. At least 3 to 4 mm may compensate for crestal bone remodeling and establishment of desirable papilla fill between two adjacent implants.

This minimum distance may be influenced by different implant designs. One clinical study evaluated vertical and horizontal bone remodeling around two adjacent platform-switched implants placed less than 3 mm (2.23 ± 0.55 mm) apart. These had been restored for 6 to 24 months. The peri-implant crestal bone peak was preserved in 64% of sites and was lost in 36% of sites. A significant improvement was observed with platform-switched implants compared with conventional non–platform-switched implants, with a mean vertical bone loss of 2 mm compared with 0.62 mm and a mean horizontal bone loss of 1.4 mm compared with 0.60 mm, respectively. Consequently, platform-switched designs may be more suitable in narrow mesiodistal spaces where less than 3 mm of bone is available between the implants. Such an approach may minimize the loss of the critical peak of interproximal bone.⁸⁴

Crown shape

The crown shape influences the esthetics around implant-supported crowns. Tooth shapes can be categorized as square, ovoid, or triangular. The portion of the tooth coronal to the free gingival margin will influence the volume and height of the gingival embrasure, while the portion apical to the free gingival margin will support the soft tissue facially and interproximally. Triangular-shaped embrasure forms are at great risk for “black triangles” because they create large embrasure spaces that require greater volume of soft tissue to fill. Square-shaped crowns, due to their longer proximal contact, are at lower risk. A restorative modification of the crown shape may be preferred to achieve improved esthetic results.¹⁰⁴

Additional Implant-Related Considerations

Implant position

Ideal three-dimensional placement of the implant results in optimal support and stability of the hard and soft tissues. This, in turn, will allow for an esthetically pleasing implant-supported restoration. In regard to the buccolingual position of the implant, the buccal extent of the implant platform should be positioned 1 to 2 mm lingual to the proposed free gingival margin. Alternative references can be lingual to an imaginary line connecting the emergence profile of the adjacent teeth or 1 to 2 mm lingual to the labial position of the proposed CEJ of the future restoration. It should be no more than 2 mm lingual to that point of reference.^137,153,193

Free gingival margin position

Evaluation of the initial level of the free gingival margin prior to immediate implant placement allows for prediction of the future gingival symmetry. Sites with free gingival margins coronal to the contralateral tooth resulted in similar gingival levels after the therapy. However, sites in which gingival levels were initially leveled or apically positioned in relation to the contralateral tooth failed to achieve gingival symmetry following therapy.¹⁰⁵

Flapless surgical approach

Patients presenting with intact facial bone and a thick gingival phenotype are less prone to advanced recession (> 1 mm) when treated by flapless implant surgery and an immediate implant crown.¹³⁶ One study evaluated peri-implant soft tissue alterations following immediate and conventional implant placement in 39 patients with intact socket walls and a thick gingival phenotype. The impact of a flapless versus a flapped approach was analyzed. It was shown that a flapless approach had less soft tissue recession compared with a flapped approach, with a mean difference of 0.89 mm at 52 weeks.¹⁹⁴

Immediate provisionalization and soft tissue

In addition to providing instant esthetics and comfort for the patient, one of the greatest benefits of implant-supported provisional restorations delivered at the time of implant placement is the preservation of soft tissue architecture.¹⁴⁶ In immediately placed implants, recession around a delayed provisional restoration was 2.5 to 3 times higher than those with immediate provisionalization (1.16 vs 0.41 mm, respectively). For both immediate and delayed implant placement protocols, placement of an immediate fixed provisional restoration at the time of implant placement had a positive impact on the maintenance of the soft tissue architecture. It preserved 1 mm more facial gingival tissue for the immediate group compared with the delayed group.¹⁴⁵ The fabrication of an immediate provisional restoration is recommended to limit the amount of marginal soft tissue recession in cases where good primary stability of the implant is achieved.¹⁴⁴

Clinicians should expect about 1 mm of soft tissue recession, with the majority of recession occurring within 3 to 6 months.^{121,122,135,154} One study suggested to wait at least 3 months prior to making a master impression and/or selecting a definitive implant abutment,¹³⁵ while another study recommended use of an implant-supported provisional restoration for at least 6 months prior to placing the definitive restoration.¹²¹ Some studies report longer evaluation periods (1 to 3 years) of peri-implant soft tissue. They demonstrate continuing remodeling of soft tissue in certain patients, up to 1.7 mm after placement of the definitive restoration. These findings suggest potential esthetic complications over time, as there is a certain subset of patients who experience recession. This should be taken into account when treatment planning for esthetic outcomes with implant-supported restorations, particularly when initial recession is seen.^158,195,196

Materials Biocompatibility

General concepts

Adhesion of bacteria in the mouth to different hard surfaces— teeth, restorative material, and dental prostheses—is one of the mechanisms for accumulation of bacterial plaque. It is influenced by two material-related factors: surface roughness and surface free energy. Surface roughness tends to promote formation and maturation of the bacterial plaque. Surface free energy (wettability) is related to how strongly the bacteria and the surface of the restorative material can bond. For the supragingival environment, it is desirable to have a smooth surface with low levels of surface free energy to prevent or minimize supragingival plaque formation. In the subgingival environment, the influence of surface roughness is negligible and of minor importance when comparing two different types of implant abutments (machined titanium vs highly polished ceramic). This is due to the ability of bacteria to prosper in that subgingival environment.^197–199

Type of restorative material

Soft tissue health may also be related to the biocompatibility of the material at the margins of crowns and fixed dental prostheses when the finish line is placed at or below the free gingival margins. Various types of ceramics and noble and high-noble dental alloys are considered safe for use in the oral environment from a biocompatibility perspective.^200,201 Several types of ceramics have demonstrated different levels of cytotoxicity,²⁰² and different types of metal alloys demonstrated continuous corrosion.²⁰⁰ Little is known on the specific effects of metal alloys and ceramic materials on the gingiva. One study demonstrated severe gingival histologic reaction to copper-based alloy compared with gold-based alloy crowns.²⁰³ Inclusion of several elements was detected in histologic sections of gingiva in contact with casting alloys.²⁰⁴

One clinical study evaluated the relationship between periodontal health and three different subgingival restorations (amalgam, glass-ionomer cement, and composite resin). At the 1-year follow-up, the clinical parameters were similar among the experimental groups, but the bacterial count and the shift in subgingival flora to more gram-negative microbiota were noted in the composite resin group. Restorations made of this type of composite resin (and perhaps others) may have a negative impact on the quality of subgingival plaque.²⁰⁵

The implant abutment material can influence the stability of the peri-implant seal, characterized by the presence or absence of alveolar bone loss and/or peri-implant mucosa recession.²⁰⁶ For abutments made of titanium and alumina-based ceramics, the mucosal healing was similar for both materials, with a formation of 2.0 mm of epithelial attachment and 1.0 to 1.5 mm of connective tissue attachment. In contrast, no proper attachment formed around gold or feldspathic porcelain abutments, resulting in recession and bone resorption.⁶² Histologic evaluation of healing between 2 and 5 months revealed formation of a stable dimension of soft tissue barrier around titanium and zirconia abutments. Apical migration of the junctional epithelium and marginal bone was noted around gold alloy abutments. Lesser amounts of collagen, fewer fibroblasts, and large numbers of inflammatory cells were noted in the connective tissue around gold alloy abutments. This suggests better soft tissue response to titanium and zirconia abutments.⁶³ Titanium and the once-used alumina ceramic are highly biocompatible. These materials are stable and resistant to corrosion in living tissue with direct and strong adhesion to the surrounding tissues.⁶² More importantly, no effects on cell morphology and growth in epithelial cells and fibroblasts were reported.^207,208

Titanium abutments are considered the gold standard due to their mechanical strength, stability, and high survival rates.²⁰⁹ However, one shortcoming is the gray color that shows through the soft tissue, resulting in compromised esthetic outcomes. Titanium abutments may be treated to create a gold-colored titanium nitride surface for better esthetics. In a human study, titanium nitride–coated surfaces demonstrated reduced colonization of bacteria as compared with standard machined titanium.²¹⁰ Zirconia abutments are esthetically pleasing with similar biologic integration,^63,211–217 but the material strength is inferior to that of titanium abutments.²⁰⁹

Several clinical and histologic studies compare titanium and zirconia abutments. Peri-implant mucosa response was evaluated in subjects via gingival biopsy from around titanium and zirconia healing caps. Titanium healing caps showed a high degree of gingival inflammation when compared with zirconia samples, indicating better biocompatibility of the zirconia.²¹⁷ A 3-year randomized clinical study compared titanium and zirconia abutments for single implant-supported crowns around canines and posterior tooth sites. Periodontal parameters—probing depth, plaque control, bleeding upon probing, and bone loss—were similar for both abutments. Interestingly, in this study both zirconia and titanium abutments caused similar peri-implant mucosal discoloration compared with the gingiva around natural teeth.²¹⁸ A meta-analysis of 5-year survival rates and incidences of complications associated with ceramic (mostly zirconia) and metal abutments was performed.²⁰⁹ The survival rates were 99% and 97.4% for ceramic and metal abutments, respectively. Abutment screw loosening was the most common technical problem, with incidence of 6.9% for ceramic and 15.9% for metal abutments. Esthetic problems were more frequent for metal abutments. Biologic complications were 5.2% for ceramic abutments and 7.7% for metal abutments. Over-all, however, the survival rates and technical and biologic complications were similar for both the ceramic and metal abutments.²⁰⁹

Oral Hygiene

A classic study by Loe et al in 1965 demonstrated a cause and effect relationship between bacterial plaque and gingival inflammation.²¹⁹ When nine participants abstained from all measures of oral hygiene, gingival inflammation developed within 10 to 21 days. Once oral hygiene was resumed, the gingival inflammation resolved in all participants within a week. It was concluded that bacterial plaque was essential in the production of gingival inflammation. The same cause and effect relationship between plaque accumulation and development of peri-implant mucositis around dental implants was demonstrated when patients were asked to abstain from all oral hygiene practices for 3 weeks.²²⁰

The microflora around dental implants originates from the oral cavity with similar microbial composition to that surrounding the natural teeth in health. The microflora of failing implants is similar to that of periodontal disease. This may be the result of contamination of the peri-implant sites by periodontal pathogens residing in periodontal pockets.^221–223 Effective plaque control performed by the patient and professional periodontal supportive therapy around natural teeth and dental implants are vital to prevent development and progression of periodontal disease.^224–226

Adequate plaque control to ensure periodontal stability can be achieved by means of mechanical cleansing devices such as manual or electric toothbrushes, floss, interdental brushes, oral irrigators, and mouthwashes. Toothbrushes are the most commonly used mechanical cleansing device used by patients and recommended by dental professionals. When electric toothbrushes were compared with manual toothbrushes, there was no statistically significant difference in regard to efficacy in plaque removal and gingival health.^227–230 Plaque removal in interproximal sites can be accomplished by means of dental floss and interdental brushes. Interdental brushes are more effective in removing bacterial plaque and should be indicated in patients with open interproximal spaces, while dental floss should be indicated in patients with closed interproximal sites.^226,227

Chlorhexidine is an effective antiplaque agent that is mainly used as a mouthwash. It is usually indicated for short-term use for presurgical or healing phases of periodontal or implant-related surgery or for intermittent use for patients with high caries risk or extensive prosthetic reconstructions.²³¹ Long-term use is not indicated due to adverse effects, including staining of the teeth and tongue, bitter aftertaste, taste alterations, and increased calculus formation.^232–234

Home care around dental implants is not much different from that around natural teeth. Traditional mechanical cleansing devices such as manual or electric toothbrushes, interdental brushes, conventional floss (with or without a threader as needed), and Super Floss (Oral-B) are usually recommended around dental implants. However, there is not enough evidence in the literature to indicate which is the most effective oral home care instrument to maintain healthy tissues around dental implants. Electric toothbrushes are effective and safe around implants, but their efficacy is comparable to that of manual tooth brushing around implant-supported restorations.^235–237

It is extremely important to establish a scheduled maintenance program for patients with dental implants. They must be evaluated at regular intervals for clinical parameters, and the areas surrounding the implants must be debrided. Customized supportive periodontal therapy should be performed and tailored to each patient, with recall intervals ranging from 1 to 6 months (average of 3 months) based on the level of oral hygiene, calculus formation, periodontal status, and various host factors.^238–242

At each evaluation, clinical parameters such as probing depth, clinical attachment level, bleeding, mobility, and plaque control should be recorded. Radiographic images should be obtained periodically to assess bone levels and proper fit of the abutment.²⁴³ Cautious debridement around dental implants is imperative to prevent damage to the implant surface. Scratches on the titanium surface may favor plaque accumulation and corrosion of the titanium as well as decreases in cell adhesion and attachment.^244,245 In vitro and animal studies evaluated the ideal instruments to clean around titanium abutments. Interdental brushes, soft toothbrushes, plastic scalers, and rubber cups without paste resulted in clean surfaces with roughness comparable to that of an untreated abutment. Air polishing, metal scalers, and ultrasonic tips resulted in roughened titanium surfaces.^246–248

The authors recommend a cautious, conservative maintenance approach for implant patients. Recall intervals should begin at 3-month intervals, increasing by 1-month increments as the absence of clinical inflammation signs indicates. All sites should be probed using a metal probe for accuracy, and all changes should be recorded. All negative changes from healed site baselines should dictate more aggressive care. Home care efficacy should be monitored and should influence the recall interval as well. All teeth and implants should be debrided. Plastic curettes, plastic-covered ultrasonic tips, and plain rubber cups should be the only items used on titanium surfaces. With this approach, health can be maintained, and negative trends can be intercepted early.

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