Читать книгу Clinical Cases in Periodontics - Группа авторов - Страница 123

A.

Proximal Contact Relation

Open interproximal contacts or uneven marginal ridge relations may encourage food impaction between the teeth. If proper oral hygiene is absent, food impaction can lead to inflammation, thereby potentially resulting in attachment loss in the interproximal area (Figure 1.7.5).

Root Proximity

Close root proximity between the two adjacent teeth will render oral hygiene difficult to maintain for both the patient and the dental professionals. Hence without good oral hygiene there can be loss of attachment between the two teeth (Figure 1.7.6).

Cervical Enamel Projections and Enamel Pearls

CEPs are extensions of enamel to the furcal area of the root surface. CEPs may potentially predispose a furcation to attachment loss because they prevent connective tissue attachment at furcation. As such, a periodontal pocket may form, leading to plaque accumulation and possibly furcation invasion.

Most clinicians agree there is a correlation between CEPs and the incidence of furcation invasion. Masters and Hoskins reported that 90% of mandibular furcation invasions have CEPs [2]. Bissada and Abdelmalek reported a 50% correlation between CEPs and furcation invasion [3]. Swan and Hurt observed a statistically significant association between CEPs and furcation invasion [4].

Figure 1.7.5 Interproximal open contact between teeth #13 and #14 (indicated by the red arrows) and vertical bone loss on #14 mesial.

Figure 1.7.6 Close root proximity between teeth #18 and #19.

In descending order of occurrence, CEPs are most commonly seen in mandibular second molars, maxillary second molars, mandibular first molars, and maxillary first molars. When CEPs are observed, they are usually seen on buccal aspects of molars [2] (Figure 1.7.7).

Enamel pearls are ectopic globules of enamel and sometimes pulpal tissue that often adhere to the cementoenamel junction (CEJ). They are present in roughly 2.7% of the molars and are mostly found on maxillary third and second molars [5]. Moskow and Canut suggested that enamel pearls may also predispose a furcation to attachment loss [5] (Figure 1.7.8).

Root Concavity

The furcal aspects of the roots frequently have concavities with a certain amount of depth (see Question B for details) that will encourage plaque accumulation and prevent proper instrumentation of furcation. Hence a root concavity may predispose the furcation to attachment loss (Figure 1.7.9).

Figure 1.7.7 Cervical enamel projection (indicated by the red arrow).

Figure 1.7.8 Enamel pearl (indicated by the red arrow).

Figure 1.7.9 Mesial and distal root concavities of maxillary first premolar.

Size of Furcation Entrance

Approximately 80% of all furcation entrances are less than 1.0 mm in diameter, with about 60% less than 0.75 mm [6]. Because frequently used curettes and scalers have a face width of 0.75–1.10 mm, it is unlikely that effective removal of accretions at furcation can be achieved by using these instruments alone. Hence a small furcation entrance may predispose a furcation to attachment loss (Figure 1.7.10).

Root Divergence and Root Fusion

The degree of root divergence in a multirooted tooth will influence the ability of the patient and dental professionals to control plaque level. Diverging roots allow easier instrumentation to the furcation area, whereas converging roots (e.g. root fusion) render access to the furcation area very difficult, resulting in poor plaque control and possible attachment loss (Figure 1.7.11).

Figure 1.7.10 The size of the Cavitron tip is too big to enter the furcated area, rendering scaling and root planing in this area very difficult.

Figure 1.7.11 The root divergence of #19 is more prominent than that of #17.

Root Trunk Length

The length of root trunk affects attachment loss. The longer a given root trunk, the less likely a furcation will be predisposed to attachment loss. Teeth with taurodontism usually have apically displaced furcation and longer root trunk length [7] (Figure 1.7.12).

Intermediate Bifurcation Ridge

Intermediate bifurcation ridges are ridges spanning the bifurcation of mandibular molars in the mesiodistal direction. These ridges are present in 70–77% of the mandibular molars [8,9]. Just like other anatomic structures, the presence of an intermediate bifurcation ridge may hinder effective plaque control and root preparation by both the patient and dentist.

Buccal Radicular Groove and Palato‐gingival Groove

Buccal radicular grooves and palato‐gingival grooves are developmental phenomena that affect mainly the maxillary anterior teeth [10,11]. These grooves run on the roots in the coronal‐apical direction. Due to their anatomy, the grooves frequently provide a plaque‐retentive area that is very difficult to instrument, making teeth with these developmental grooves more prone to attachment loss (Figure 1.7.13).

Accessory Pulpal Canals

Accessory pulpal canals are small endodontic canals branching off from the main root canal that may furnish a communication between the pulpal chamber and the periodontal ligament. These accessory canals are usually located near the root apex; however, they can also be found anywhere along the root, including the furcation area. There is a theory that some periodontal infections can originate from endodontic sources, traveling through accessory/lateral canals located in the furcation areas. In these cases there is periodontal involvement in the furcation, but the infection originated in the pulp. Although still controversial, it has been proposed that periodontal disease can result from pulpal infection. An endodontic infection may be present at the furcation area when the infection travels through accessory canals that end at the furca. Vertucci and Williams reported that accessory canals at furcations are present in 46% of human lower first molars [12]. Burch and Hulen observed accessory canals in 76% of maxillary and mandibular molars [9].

Figure 1.7.12 Long root trunk length (left) and short root trunk at #19 (right).

Figure 1.7.13 Palato‐gingival groove present on tooth #10 as indicated by the probe tip.

Restorative Considerations

Dental restorations with overhangs or open margins are plaque‐retentive areas that may result in gingival inflammation and attachment loss. Restorative margins are most compatible with the periodontium when located either supragingivally or at the level of the gingival margin. Should the restorative margin violate the biologic width, the resulting inflammatory process may lead to gingival recession, bone loss, and exposure of the restorative margin. The restorative contour (e.g. crown contour) should follow the root surface contour rather than accentuating the cervical bulge to support periodontal health. In the case of bridges, the design of the pontic can affect its ability to be cleaned and hence the periodontal health of the teeth (Figure 1.7.14).

B. A furcation is an anatomic area where the roots of a multirooted tooth start to diverge. Mandibular molars and maxillary first premolars are bifurcated because they each have two roots. Maxillary molars are trifurcated because they each have three roots.

A furcation consists of two parts: (i) root separation area, where alveolar bone begins to separate the roots, and (ii) fluting area, the part of the root that is directly coronal to the root separation area.

There are often concavities in the furcal side of the roots. In mandibular molars, all the mesial roots have concavities on the furcal side, with each concavity averaging 0.7 mm in depth [13]. Likewise, 99% of the distal roots of mandibular molars have concavities on the furcal side, with an average depth of 0.5 mm [13]. The root trunk, which is the distance from the CEJ to the level of root separation, is about 4.0 ± 0.7 mm in mandibular first molars [13,14].

In maxillary molars, 94% of the mesiobuccal roots have concavities on the furcal side, with each concavity averaging 0.3 mm in depth [15]. Roughly one‐third (31%) of the mesiodistal roots and one‐quarter (17%) of the palatal roots have concavities, and each concavity is about 0.1 mm in depth [15]. The lengths of root trunks of maxillary molars are 3.6, 4.2, and 4.8 mm on the mesial, buccal, and distal surfaces, respectively [16,17].

Figure 1.7.14 Overhangs on the mesial and distal of tooth #30 that may eventually lead to bone loss on the mesial and distal of #30.

All bifurcated maxillary first premolars have a mesial and distal root trunk of about 8 mm. In addition, almost all the buccal roots have “developmental depressions” also known as “buccal furcation groove” present at the 9.4‐mm level on the furcal side [18,19].

Furcation invasion is defined as a loss of attachment within a furcation. When there is a loss of clinical attachment, the presence of concavities on these roots at furcation will hinder effective plaque control at these areas.

C. There are a number of different classification systems of furcation invasion. The three most commonly used systems are as follows.

Glickman Classification

The Glickman classification [20] describes both the vertical and horizontal components of the furcation invasion.

Grade I	Pocket formation into the fluting area but with intact interradicular bone.
Grade II	Pocket formation into the root separation area with interradicular bone loss that is not completely through to the opposite side of the furcation.
Grade III	Same as grade II but with through‐and‐through interradicular bone loss (the soft tissue still covers part of the entrance of the furcation).
Grade IV	Same as grade III but with gingival recession making furcation clinically visible.

Hamp Classification

The Hamp et al. classification [21] describes the horizontal component of the furcation invasion.

Degree I	Horizontal bone loss going into the furcation <3 mm.
Degree II	Horizontal bone loss going into the furcation >3 mm but not to the opposite side.
Degree III	A through‐and‐through horizontal bone loss in the furcation.

Tarnow and Fletcher Classification

The Tarnow and Fletcher classification [22] describes the vertical component of the furcation invasion.

Subclass A	Vertical attachment loss 0–3 mm in furcation.
Subclass B	Vertical attachment loss of 4–6 mm in furcation.
Subclass C	Vertical attachment loss of >7 mm.

D. The most effective way to diagnose a furcation invasion is to use a combination of clinical examination and radiographic evaluation. The clinical examination involves using periodontal and furcation probes to detect the furcation invasion.

Radiographs must be taken with a paralleling technique to minimize distortion of the images. Note that radiographically the palatal root of maxillary molars may leave a grade III furcation invasion undetected due to the overlapping of the palatal root with mesiobuccal and distobuccal roots. In addition, the presence of a furcation arrow (a triangular shadow seen at either the mesial or distal roots in the interproximal area on maxillary molars) may possibly suggest the presence of grade II–III furcation invasion on maxillary molars [23] (Figure 1.7.15). The more extensive a given furcation invasion, the higher the likelihood of observing the furcation arrow. However, it must be noted that the absence of furcation arrow does not necessarily suggest the absence of a furcation invasion.

Generally, interproximal surfaces of the maxillary molars are more prone to furcation invasion than buccal surfaces [24].

Figure 1.7.15 Furcation arrow (red arrow) is showing furcal involvement on the mesial of #14 radiographically.