Читать книгу Contemporary Restoration of Endodontically Treated Teeth - Nadim Z. Baba - Страница 10
ОглавлениеTreatment Planning Considerations for Endodontically Treated Teeth
“Because I’ll have you know, Sancho, that a mouth without teeth is like a mill without its stone and you must value a tooth more than a diamond.”
—Miguel de Cervantes, Don Quixote
Preservation of the natural human dentition is an important factor in efforts to promote good oral health. The mouth has been referred to as “a window into our health.”1 We are attracted to a beautiful smile and have pity on those individuals with unsightly dentitions. Consciously, or even unconsciously, many make snap decisions as to a person’s socioeconomic status, integrity, reliability, and overall “value” by first impressions. Even in biblical times, the value of teeth was recognized, as justice was meted out “eye for eye, and tooth for tooth” (Matthew 5:38, The Bible, New International Version).
Before the recent option of replacing broken-down teeth with dental implants, clinicians routinely attempted—sometimes with heroic efforts—to save teeth for as long as possible before extraction. While implant placement has increased and the population in general seems to readily accept this procedure, there is some sense that the pendulum is swinging too far in the direction of replacing teeth with implants. Some dentists seem inclined to routinely recommend replacement of teeth that may otherwise have a good prognosis both endodontically and restoratively. The purpose of this chapter is to describe the various factors that must be evaluated when the practitioner is considering a treatment plan that may include endodontically treated teeth. Various clinical situations will be described in which teeth that have had—or will have—root canal treatment (RCT) are to be reviewed in developing a treatment plan.
Outcomes of Endodontic Therapy
The first consideration of importance is to recognize that for a treatment involving an endodontically treated tooth to have a predictable outcome, the endodontic procedure must be skillfully accomplished. Perhaps this statement seems selfevident, but endodontists frequently report that they need to re-treat teeth that have initially been poorly treated (Fig 2-1). In fact, when the quality of RCT in general is evaluated, the level of quality is often disappointingly low.2, 3 Patients, however, cannot see what has been done inside the roots of their teeth and can only judge a clinician on the aspect of pain relief and how they were treated.
Fig 2-1 (a) Inadequately performed RCT, including failure to find the second mesiobuccal canal, has resulted in a periapical lesion (arrow). (b) This radiograph shows well-prepared and filled root canals including two mesiobuccal canals.
When RCT is done correctly initially, it has a good prognosis. Many studies have evaluated the success rate of various types of endodontic therapy.4–7 Torabinejad et al6 did a systematic review of the literature pertaining to the outcomes of nonsurgical endodontic therapy. A strict set of parameters was followed for inclusion in the meta-analysis. Their results showed an overall radiographic success rate of 81.5% over a 5-year period. Friedman et al7 reported similar healing results after 4 to 6 years.
It is noteworthy that the rate of endodontic success is higher when RCT is performed before apical lesions are present.4 Also, when treatment mishaps occur, the prognosis is affected. It is therefore important for clinicians to recognize their own limitations when providing any type of dental care and to aim for the best treatment possible for the patient. Referring a patient to a specialist for RCT may provide the best foundation for a good outcome. The following are components of successful RCT that can provide a dependable basis for restoring an endodontically treated tooth.
Diagnosis and Treatment Planning
Successful RCT is based on numerous factors, starting with an accurate diagnosis and appropriate treatment plan. Each individual patient presents with a unique set of conditions that the clinician must manage in order to provide a better oral health status for that patient. The patient’s medical and dental histories provide the background for collecting the necessary information. Because this chapter is about the endodontic aspects of the overall treatment plan, the focus will be on diagnosis as it relates to the status of the pulp, the anatomy of the pulp and the roots, and the conditions affecting these tissues.
Assessment of the pulpal status
Pulpal status is conveniently described as normal pulp, reversible pulpitis, irreversible pulpitis, or pulpal necrosis. However, it can be a challenge to make diagnostic decisions when the examination findings overlap, and a clearcut diagnosis is difficult to make. It is beyond the scope of this chapter to go into detail about endodontic diagnosis; the interested reader will find excellent material in any current endodontic textbook. For practical purposes, we can say that endodontic treatment is indicated when the pulpal diagnosis is either irreversible pulpitis or pulpal necrosis; in some cases, however, it may be prudent to recommend RCT even in situations of normal pulp or reversible pulpitis (Fig 2-2). For example, RCT may be recommended in teeth with normal pulpal conditions or reversible pulpitis if the pulpal health might be compromised by the particular restorative or prosthetic procedure planned.
Fig 2-2 The deep caries lesion may not have invaded the pulp yet, but if placement of a prosthetic crown is planned, it may be prudent to recommend RCT before completion of the prosthetic treatment.
Anatomical considerations
Successful RCT requires a thorough knowledge of tooth anatomy and root canal morphology, both of which can be very diverse.8 Variations occur with respect to the number of roots, the number and shape of canals within these roots, and even the frequency of variations. Numerous factors can account for these variations, such as tooth location, age of the patient, ethnicity, gender, congenital conditions involving tooth development, and even the means of assessment or the definition of what constitutes a canal.9–11
When an endodontically treated tooth is assessed, careful attention should be given to the external root morphology, the number of roots, the shape of the root canal system, and the variations and anomalies that are particular to the tooth. When the internal morphology and obturation are evaluated and compared with the external anatomy, the filled canal shape should match the flow of the external anatomical outline. When endodontic procedures are performed correctly, the external and internal radiographic appearance of the root should be harmonious: The root canal filling should be centered in the root and correspond to the external shape of the root (Fig 2-3).
Fig 2-3 (a) The root canal fillings are centered in the roots, indicating careful attention to root canal morphology and root anatomy. (b) Wellprepared canals correspond to the shape of the root, even when multiple canals are present.
Schilder12 described five objectives for root canal preparation:
1. There is a continuously tapering funnel shape from the apex to the access cavity.
2. Cross-sectional diameters are narrower at every point toward the apex.
3. The root canal preparation flows with the shape of the original canals.
4. The apical foramen remains in its original position.
5. The apical opening is kept as small as practical.
In addition, Schilder12 named four biologic objectives for these preparations:
1. Treatment procedures are confined to the roots.
2. Necrotic debris is not forced beyond the apical foramina.
3. All pulp tissues are removed from the root canal space.
4. Sufficient space exists for intracanal medicaments and irrigants.
These objectives provide a basis for assessing the quality of the endodontic procedure prior to restoration of the tooth. Deviation from the original canal shape is referred to as transportation of the canal. The greater the transportation, the greater the likelihood of a poor endodontic outcome, resulting in the need for either endodontic retreatment or extraction of the tooth.
Root canal systems
The root canal system is complex (Fig 2-4), and its anatomy has been studied extensively for many years. Of special interest in the current context, Weine et al13 called attention to the frequent presence of two canals in the mesiobuccal roots of maxillary molars. Pineda and Kuttler14 and Vertucci15 developed classification systems for canal configurations in individual roots. Research in root canal morphology has led to descriptions of more than 20 canal configurations.11
Fig 2-4 (a) The complexity of the root canal system is well illustrated in these sections of maxillary molars. Note the variety of canal configurations in the mesiobuccal roots and in particular the location of the second mesiobuccal canal in the molar on the right. (b) A radiograph of a maxillary molar seems to show two palatal roots (arrows). (c) On the patient’s request, the tooth was extracted; two palatal roots were identified (arrows).
These considerations are important for the evaluation of a tooth that has undergone RCT. They also point to the challenges inherent to treating teeth with endodontic disease prior to restoration to full function. Achieving full function requires that the treatment-planning process be a teamwork process: RCT can be performed on almost any tooth, but restorability must be determined prior to the endodontic component of treatment. Communication among the various treating dentists before, during, and after RCT offers the best possibility of an optimal outcome.
Assessment of other conditions
Cracked/fractured teeth
Fracture lines involving cusps of teeth have been a problem in dentistry, probably throughout human history. The pain associated with such fracture lines was described by Gibbs,16 who termed it cuspal fracture odontalgia. Every dentist has probably had a patient who complains about pain on chewing and later shows up with the broken-off cusp, usually from a premolar tooth. Whether or not the pulp is directly involved (by exposure), it is usually necessary to complete RCT before the tooth is restored. Diagnosis of a fracture line under a cusp, before it breaks off, can be a challenge and will be discussed in the next section on infractions.
Teeth may develop cracks and fracture for a number of reasons, including trauma, excessive masticatory forces, and iatrogenic incidents. Regardless of etiology, when cracks or fractures develop in dental hard tissues it is not possible to repair them, except for a short period of time with bonding agents. In contrast, bone and cartilage routinely undergo repair following fracture. Although tooth fractures and cracks cannot be healed, it is possible in many cases to maintain such teeth for various periods of time following identification and diagnosis.
For convenience in discussing cracks and fractures, three categories will be used: enamel craze lines, infractions, and vertical root fractures (VRFs).
Enamel craze lines. Craze lines are small cracks that are confined to the enamel of teeth (Fig 2-5). They are not typically visible unless light rays highlight them incidentally. They develop over time, so they probably can be found in most teeth eventually. Occasionally they will show stains from exposure to liquids such as coffee and red wine. Because these cracks are confined to enamel, they have no pulpal impact, and no treatment is necessary, except optional bleaching if they are stained. There is no evidence that craze lines progress to involve more than enamel.
Fig 2-5 Enamel craze lines (arrow) are common and present no particular problem other than their potential for staining.
Infractions (cracked teeth). The term cracked tooth is commonly used to describe a tooth that has developed an infraction, which is defined as “a fracture of hard tissue in which the parts have not separated”17 (Fig 2-6). Cameron18 incorrectly defined this condition as cracked tooth syndrome; the use of syndrome is not appropriate for pain associated with fractures in teeth. It is, however, a situation with a variety of symptoms, and diagnosis can be very difficult.
Fig 2-6 (a) Infractions (arrow) can be identified visually with the help of dyes, in this case a red dye. Infractions usually run in a mesiodistal direction; they may be asymptomatic or associated with pain on chewing and cold stimuli. (b) A tooth extracted because of symptoms associated with an infraction shows the presence of the infraction (arrow). They typically originate in the crown of the tooth and progress in an apical direction. (c) On rare occasions, infractions run in a faciolingual direction (arrow).
Mandibular molars and maxillary molars and premolars are the teeth most frequently associated with infractions. The teeth usually have vital pulps and the infractions typically run in a mesiodistal direction. They begin in the crowns of teeth and progress in an apical direction. Not all teeth with infractions are symptomatic, but when symptoms develop they can range from pain on chewing, to an exaggerated response to cold stimuli, to severe pain episodes that can mimic trigeminal neuralgia; chronic orofacial pain can also develop. The wide range of pain experiences is probably why Cameron18 used the term syndrome to describe this dental situation. The etiology of infractions is probably in most cases related to occlusal forces, whether from regular daily chewing or isolated trauma such as blows to the underside of the mandible.19–25
It is likely that teeth with infractions become symptomatic when the infractions become invaded by bacteria26 (Fig 2-7). Bacteria stimulate inflammation in the pulp, whether or not the infraction communicates directly with the pulp tissue. The inflamed tissue is responsible for the exaggerated cold response. It is also likely that the tooth will become sensitive to biting when the infraction progresses from the tooth crown to the root, and the bacteria that will soon occupy the infraction then stimulate an inflammatory response in the adjacent periodontal ligament (PDL).
Fig 2-7 Infractions become populated with bacteria very quickly and produce an inflammatory response in the pulp (located to the right in this section), whether they communicate directly with the pulp (as in this case) or not. This explains why such teeth respond abnormally to cold stimuli.
Diagnosis of infractions is complicated by many factors. Because infractions are usually located in a mesiodistal direction in the crown, they are not visible on radiographs.
Before the infractions progress down the roots to significantly involve the PDL, patients are unable to point to the problem teeth. Based on the patient’s complaints, the first goal of examination is to identify the problem teeth and the second is to determine the pulpal condition of these teeth.
The presence of an infraction can be determined by the use of various biting tests (Fig 2-8a), with the aid of colored dyes (see Fig 2-6a), and through transillumination with an intense light source27 (Fig 2-8b). In contrast to the way enamel craze lines are highlighted by intense light, infractions actually block the transmission of light, clearly identifying their presence.
Fig 2-8 (a) The bite test is a useful way to identify a tooth with an infraction. After biting down on a wet cotton roll (or on one of many types of biting devices), the patient will often experience a strong response when he or she releases biting pressure—the so-called release pressure pain. (b) The use of an intense light, such as that from a fiber-optic light source, will illuminate the part of the crown near the light, but the light stops at the infraction, which involves both enamel and dentin. In contrast, enamel craze lines only involve enamel, through which light rays travel unimpeded.
The status of the pulp—reversible or irreversible pulpitis— can be determined as in other situations of pulpal inflammation, that is, by the presence or absence of lingering pain to application of cold stimuli. If the pulp is reversibly involved, placement of a complete-coverage crown may be enough initially, but Krell and Rivera28 showed that about 20% of these teeth subsequently developed irreversible pulpitis. If the patient wishes to retain the tooth for as long as possible, it may be advisable to perform RCT in anticipation of a later need before a complete-coverage crown is placed. There is some promising information29 about the use of bonded resin to cover the occlusal surfaces to resist further progression of infractions.
To determine if an infraction has progressed to the root of the tooth, the use of a periodontal probe can provide some information. However, because the pocket that develops in the PDL adjacent to the infraction in the root is very narrow, it is usually necessary to anesthetize the area first; otherwise the procedure will be very painful for the patient.
The prognosis for teeth with infractions is not good. Fuss et al30 have reported that many of these teeth are extracted within 5 years following diagnosis of infraction. However, insufficient data are available to make a statement about the expected survival time of these teeth. Clinicians can only explain to patients that once this condition develops it cannot be reversed, and that it is only possible to make an effort to prolong the inevitable. With a full understanding of the poor long-term prognosis, many patients still wish to maintain such teeth for as long as possible, and that is where RCT and complete-crown coverage may be considered. It is prudent, however, to explain to such patients that periodic radiographic evaluation is recommended so that when bone loss is evident plans can be made for extraction before a large amount of bone is lost.
As the infraction progresses, the eventual result is either that the tooth splits vertically or, when the infraction involves a cusp, that the cusp fractures off, with or without exposure of the pulp.
Vertical root fractures. VRFs differ from infractions in several aspects.31 With few exceptions, VRFs occur in endodontically treated teeth (Fig 2-9). The direction of fractures is more often in a faciolingual orientation, and symptoms for the most part are mild. In some patients, symptoms are absent or so mild that the patients are unaware of any problems. VRFs typically originate from the apical end of the root and progress toward the crown. The incidence of VRFs in restored endodontically treated teeth ranges between 2% and 10%.32–37
Fig 2-9 (a) VRFs (arrow) occur mostly in endodontically treated teeth and typically originate from the apical end and progress toward the crown; they usually run in a faciolingual direction in contrast to infractions, which run mesiodistally. (b) The fracture (arrow) is evident in the extracted tooth.
VRFs are sometimes mistaken for failing RCTs. This is understandable because the complaints and clinical findings often are similar. The management for these two conditions is not the same, so the correct diagnosis is essential to determination of the best treatment.
A VRF can be differentiated from a failing RCT by a number of factors: the history of the tooth’s treatment, presenting signs and symptoms, radiographic information, and data from the clinical examination.31, 38–42
Typically, a VRF appears a considerable time after RCT and restoration of the tooth. The tooth may have been comfortable and fully functioning for years when suddenly it begins to feel uncomfortable during chewing; there may also be a sudden appearance of some swelling, usually on the facial aspect of the tooth.
Radiographically, if a lesion has developed, it appears to be located along the length of the root; in contrast, if the lesion is the result of a failing RCT, the lesion appears more apical to the root. Because fractures associated with VRFs tend to have a faciolingual orientation, it is not unusual for fracture lines to be visible radiographically. In maxillary premolars and the mesial roots of mandibular molars, a “halo” appearance involving the apical and lateral aspects may be noted on one side or both sides of the involved roots.41, 43
As with many other dental conditions, direct observation can often provide the definitive information for arriving at a diagnosis of VRF. For instance, it is often possible to probe a fairly narrow periodontal pocket along the fracture line to the root apex. In contrast to infractions, which originate in the crown of the tooth, VRFs originate in the apical part of the tooth and progress in a coronal direction. When a VRF is suspected, a minor surgical exploration accomplished by reflection of a small tissue flap in the area will often reveal the fracture line. Another distinct difference between an infraction and a VRF is that the former is very small (until the tooth splits), while the latter by comparison is quite wide in diameter.
Treatment for a tooth with a VRF is usually extraction, which should be performed as soon as possible after the diagnosis to preserve as much of the adjacent alveolar bone as possible. Because the symptoms are often minimal, patients may want to postpone treatment, but this delay results in a very poor alveolar ridge after extraction. This problem should be carefully explained to the patient.
There is one exception to the recommendation for extraction of teeth with VRF: When the involved tooth is a multirooted maxillary molar and the fracture is located in one of the facial roots (Fig 2-10), surgical resection of the affected root may leave a tooth that can still function quite well for many years, as has been demonstrated in the periodontal literature.44
Fig 2-10 (a) The mesiobuccal root of the maxillary left first molar has developed a vertical root fracture. (b) After the prosthetic crown has been removed, the mesiobuccal root is resected, leaving two roots to support the new restoration. (c) The 3-year follow-up radiograph shows a wellfunctioning tooth (which is still functioning at the time of writing).
Combined endodontic-periodontal problems
A difficult diagnostic and treatment-planning problem is the combined endodontic and periodontal situation. The tooth’s pulpal and periodontal tissues are closely connected both at the apical opening of the root canal and through the many lateral connections present. This in part explains the difficulty in deciding the origin of some periradicular lesions.
The unfortunate result is that in some cases, teeth receive RCT even though the pulps may be healthy, or they may be extracted when associated with lesions that are presumed to be of severe periodontal origin, and the teeth are not expected to survive. To prevent such mistakes, clinicians must carefully arrive at the correct diagnosis based on collection of pertinent information such as the status of the dental pulp, evaluation of periradicular lesions, and consideration of other conditions such as infractions or VRFs. After the collection of adequate data, one of the following diagnoses may be applied: pulpal disease, periodontal disease, or a true combination of the two.
Pulpal disease can cause periradicular lesions that radiographically appear similar to those of periodontal disease (Fig 2-11). Pulp testing to determine the status of the pulp can clarify the situation in most cases, although even necrotic pulps may have pain receptors that can be stimulated in pulps that are far from healthy. If the testing indicates pulpal disease, then RCT can result in healing of any periradicular lesion that may be present.
Fig 2-11 (a) Radiograph of the maxillary right second premolar of a patient who complained about soreness around the tooth. The tooth did not respond to cold stimuli. There was a 6-mm narrow periodontal pocket on the mesial aspect of the second premolar, and the tooth was sensitive to percussion. Based on the findings, a diagnosis of pulpal necrosis was made. (b) RCT has been completed, and the diagnosis of pulpal necrosis has been confirmed. (c) The 7-month follow-up radiograph shows the healing of the initial lesion. The tooth is comfortable, and no periodontal treatment has been necessary. (Courtesy of Dr Harold “Jay” Jacobson, El Cajon, CA.)
Periodontal disease involving a single tooth is not common, so when that occurs it is easy to suspect the presence of pulpal disease. Pulp testing, along with clinical examination, may provide enough information to decide if the condition is related to the pulp or PDL. In general, periodontal probing will reveal wider pockets when the lesion is of periodontal origin. Lesions of pulpal origin tend to be narrower, similar to those seen in teeth with infractions or VRFs. Occasionally it may be so difficult to obtain reliable information about the status of the pulp that an exploratory pulpectomy may be indicated to allow a definitive diagnosis. The bottom line, however, is that if a periradicular lesion is not of pulpal origin, RCT will not change the situation.
True combined lesions of endodontic and periodontal origins do occur. If a thorough examination reveals that such a diagnosis is appropriate, RCT is likely to have some positive effect on the condition, but periodontal treatment is also needed.
Other factors may contribute to development of periradicular lesions. For instance, failing RCTs and poorly completed coronal restorations provide pathways for bacterial contamination. Linked directly with the need for adequate endodontic therapy is a good coronal restoration; coronal leakage has been well established as a major cause of endodontic treatment failure.45–47
Root perforations may be another cause of lesions of combined endodontic-periodontal origin (Fig 2-12). These perforations may result from extensive caries lesions, resorption, or from operator error during canal instrumentation or post space preparation.48
Fig 2-12 (a) A root perforation was created during post space preparation of a mandibular left second molar; a further treatment error was cementation of a post into the perforation. (b) A follow-up radiograph taken 6 months after retreatment and repair of the perforation shows that the apical lesions have healed satisfactorily; however, a furcal lesion has developed as a result of the perforation. At the time of follow-up, the lesion was not probeable yet. The repair was made with amalgam at the time; today that repair would be accomplished with mineral trioxide aggregate, a material that has been shown to be very suitable for perforation repairs.
Finally, developmental malformations can lead to unusual periradicular lesions. Radicular invaginations or grooves are one example of this situation. As long as an intact epithelial attachment remains, the periodontium is maintained in a healthy status. However, once the attachment is broken, the invagination is extremely difficult to manage and often creates a self-sustaining infrabony pocket.49
Resorption
Root resorption complicates treatment of teeth; it is unpredictable both in terms of appearance of the lesion and response to treatment. For practical purposes, resorption can be classified into the following categories: eruption-related (which is resorption of primary teeth as part of succedaneous tooth eruption and will not be discussed further in this chapter); trauma-related; pressure-related; cervical invasive; and idiopathic resorption.
Trauma-related root resorption follows traumatic dental injuries and is related to damage to the root cementum and the PDL. Initial resorption after dental trauma is termed repair-related resorption and involves only cementum. It is difficult to demonstrate this type of resorption radiographically. However, it plays a role in the repair process after injury to the PDL during which new PDL fibers are inserted into the new cementum that forms as part of this process. Trauma-related resorption requires no treatment and is of concern only if it continues so that the resorption begins to involve the subjacent dentin. The resorptive process then may take one of two pathways (occasionally both can occur simultaneously): (1) infection-related (inflammatory) and (2) ankylosis-related (replacement) resorption.
Infection-related root resorption has a dual etiology when it occurs following a traumatic dental injury (Fig 2-13). First there is damage to the PDL with subsequent resorption of cementum; if resorption progresses to the dentin, then the second etiologic factor arises, that is, the presence of bacteria in the pulp space. The bacteria will have a stimulating effect, through the dentinal tubules, on the osteoclasts to aggressively resorb both tooth structure and surrounding bone. If this infected necrotic pulp tissue is not removed (by RCT), the bacterial presence will stimulate continued resorption of both tooth structure and adjacent alveolar bone. This process is the basis for recommending endodontic evaluation and treatment of teeth involved in traumatic dental injuries. It has been well established that RCT in these types of trauma-related resorptions will both prevent infection-related resorption and arrest the resorption if it has already started.50
Fig 2-13 Infection-related resorption. Radiograph taken 6 months after replantation of the mandibular central incisors, which had been avulsed in an accident. Failure to perform RCT in a timely manner (ideally within 2 weeks following replantation) allowed the pulps to become infected, which stimulated both infection-related root resorption and bone resorption. This type of resorption is the result of initial damage (from the accidental avulsion) to the cementum and PDL and the presence of bacteria in the pulp tissue. Infection-related (inflammatory) resorption can be predictably prevented with timely RCT.
A variation of the resorption just described is infectionrelated resorption that takes place inside the root canal, referred to as internal resorption (Fig 2-14). This is a very rare type of resorption and is often confused radiographically with external invasive resorption (to be described in the following paragraphs).51 The mechanism is very similar to that of the external variety in that bacteria are necessary to stimulate the resorptive process, and there probably has to be some damage or disruption in the predentin layer, allowing clastic cells to resorb underlying dentin.
Fig 2-14 Internal resorption. (a) The resorptive cavity is centered in the root of the tooth. (b) RCT will successfully arrest the resorption. (Courtesy of Dr Steve Morrow, Loma Linda, CA.)
The resorptive process is in some ways self-limiting in that the resorption will stop when the pulp undergoes necrosis from the presence of the bacteria. The treatment for internal resorption is RCT—after a careful diagnosis has been established so that a case of external invasive resorption, which can initially look like internal resorption, is not mistreated.
The second type of trauma-related root resorption is called ankylosis-related resorption because it occurs as a result of bony fusion (ankylosis) with dentin, resulting in a gradual replacement of the root structure with bone (Fig 2-15). This type of resorption is related to extensive damage to the PDL, followed by resorption of cementum without subsequent repair, thus exposing the dentin to osteoclastic removal followed by replacement with bone. This process cannot be arrested once begun, and the status of the pulp in the tooth (healthy or diseased) is immaterial. In a young person who is still growing, ankylosis prevents the tooth from erupting and the adjacent alveolar process from developing.52 Fortunately, there is now a procedure—decoronation—that can be used to allow continued bone formation.52 In adults, teeth undergoing replacement resorption can last for many years even when ankylosed.
Fig 2-15 Ankylosis-related resorption. (a) The left central incisor of a 13-year-old girl has ankylosed 4 years after a traumatic intrusion. Intruded teeth in young patients (younger than 15 years) should be allowed to spontaneously reerupt. In this case, the tooth did not reerupt but became ankylosed. (b) Ankylosis-related (replacement) resorption has prevented normal eruption. The pulp is vital, illustrating that the pulp plays no role in ankylosis-related root resorption.
Pressure-related resorption is that seen when an erupting tooth causes pressure on an adjacent tooth (Fig 2-16) or when some lesions cause pressure as they grow in size. The resorption that results from orthodontic movement is also pressure related; interruption of the orthodontic movement will arrest the resorption.
Fig 2-16 Pressure-related root resorption. (a) In this case, a third molar has exerted pressure against the distal aspect of the second molar. (b) The effect of the pressure on the second molar can be seen clearly after removal of the third molar. RCT is not indicated, but a periodontal problem may result if the bone does not fill in on the distal aspect of the tooth.
Cervical invasive resorption (Fig 2-17) is probably the most frustrating of resorptive entities. It can occur without any warning and may not always be associated with an event—trauma or otherwise—that would predict its occurrence. A history of trauma is often recognized, but other events such as orthodontic treatment and other dental procedures have been implicated.53 A lack of recognizable etiology is not uncommon. This is also a type of resorption that has no connection with the status of the pulp.
Fig 2-17 Cervical invasive resorption. (a) The resorption (arrow) may have resulted from trauma to the cervical cementum during removal of the third molar. Although the pulp is not directly affected by the resorptive process, management of this tooth would probably include RCT. (b) The radiograph of a canine with invasive resorption (arrow) illustrates the conditions sometimes observed years after a traumatic injury. Treatment options in such cases may include efforts to repair the resorbed areas from either an internal or an external approach, but replacement with an implant is probably a more predictable approach to management.
Treatment for cervical invasive resorption is quite successful if the lesion can be restored before too much tooth structure is lost. It is often necessary to perform the restorative procedure in conjunction with a periodontal tissue flap, raised for more convenient access. Because the pulp is not usually affected by the resorptive lesion, it is not necessary to do RCT as part of the treatment. RCT is often included, though, if the lesion is close to the pulp or if pulpal symptoms are part of the clinical findings. The material of choice for restoring the lost tooth structure is glass-ionomer cement.
The last type of resorption to be discussed is referred to as idiopathic resorption54 (Fig 2-18) because the etiology is obscure. It can involve a single tooth or several teeth; in the latter case, it is referred to as multiple idiopathic tooth resorption. As with resorptions in general, symptoms are mild or nonexistent. Mild soreness when the soft tissues surrounding the resorbing tooth are touched may be the only signal that something is happening to the tooth. This type of resorption can be quite aggressive, and a great amount of tooth structure can be lost. As with resorption other than infection-related resorption, the pulp plays no role, and much tooth structure can be lost before the resorptive lesions come close to the pulp cavities. The resorptive process does not seem to penetrate the predentin layer at the periphery of the pulp tissue.
Fig 2-18 Idiopathic resorption. This type of resorption, which often includes several teeth and then is termed multiple idiopathic resorption (arrows), has no known etiology. Management of such situations is very difficult. Restoration of resorbed areas, if accessible, can provide some con tinued function for the affected teeth, but eventual loss of such teeth is most likely to occur.
Treatment for idiopathic resorption has a very disappointing history. Frequently, so much tooth structure is lost that restoration of such teeth is very difficult. In addition, continued resorption may take place, further frustrating the management of these situations. If identified early, the affected tooth or teeth may be maintained for some time, making it worth the effort to treat. The practical option in many of these situations, however, is likely the replacement with dental implants. In any case, performance of RCT on a tooth with idiopathic resorption is not recommended unless the pulp is diseased.
Summary
Restoration of endodontically treated teeth requires careful planning. This involves evaluation of the endodontic treatment (preferably both before and after the treatment), an understanding of the complexities involved in RCT, and a recognition that many factors affect the outcome of the combined endodontic-prosthodontic management of patients. As in so many areas of medicine and dentistry, teamwork is often the key to success.
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