Idiopathic tooth resorption is one of the most difficult problems facing dentists. This month's Endo Fax will deal with diagnosis and treatment of two specific types of Resorptive lesions- Internal Resorption and Idiopathic External Resorption . Managing these resorptions demands that we first establish what type of resorption is present and its etiology. Once this is understood, treatment choices become clear.
Internal Resorption - Get to it Early !
Internal Resorption is a pulpally related problem that triggers resorption of the dentin from the pulp outward. The tooth often has a history of trauma or pulp cap. Discoloration may or may not be present. Pulp tests may indicate vitality or necrosis. The abnormal pulpal response results in dentinoclastic activity that generates an increase in the size of the chamber and/or canal space. The lesion is frequently well demarcated and often has distinct, clear radiographic margins. It generally can be easily distinguished from External resorption. In advanced cases Internal Resorptive lesions can perforate the outer aspects of the tooth and may generate a localized periodontal problem that mimics External Resorption.
Internal resorption - Treatment
Early diagnosis is important to prevent weakening of the remaining root structure. Radiographic surveys of the mouth are essential. Treatment involves conservative endodontics with particular attention given to cleansing and filling of the resorbed area. Warm Gutta Percha techniques work best. When the apical third is not involved, cases are treated as usual and then the resorbed area is back-filled with an Obtura-type thermoplasticized GP gun. Teeth with perforating resorption often need both non-surgical and surgical procedures. Once periodontally involved, the prognosis is much less certain and surgical corrective procedures can be difficult to perform. Concurrent Periodontal procedures are sometimes required, depending on the depth, size and location of the perforation. Anterior teeth with large mid-root or chamber resorptions are at risk for subsequent fracture because the remaining dentin walls can be extremely thin.
Idiopathic External Resorptive Lesions
are characterized by the invasion of the cervical region of the root by fibrovascular tissue which progressively resorbs dentine, enamel and cementum. The source of the resorption is in the attachment apparatus. This is the key to understanding diagnosis and treatment. The dental pulp remains protected by an intact layer of dentine and predentine until late in the process. Ectopic calcifications can be observed in advanced lesions both within the invading fibrous tissue and deposited directly onto the resorbed dentine surface. The etiology of invasive cervical resorption is unknown but trauma has been documented as a potential predisposing factor. The resorbed area is associated with the cemento-enamel junction or point of attachment of the gingiva. This localized area of the PDL no longer views the tooth as a recognized part of the body. The normal attachment apparatus anatomy is replaced by inflammatory tissues that have cemento and dentino-clastic properties. The tooth tests vital and often has a localized area of pink discoloration along the gingival margin. The area of visibly gingival margin. The area of visibly involved dentin or enamel is often paper thin. The actual lesion is often much larger than anticipated from visual inspection of the area of the CEJ. Some of these teeth have a history of trauma or orthodontic treatment but this is not the rule. External Resorption of this type has a characteristic radiographic appearance. Unlike internal resorption, where there often is a clear border to the lesion, the borders of this lesion are often indistinct. Upon close examination, the outline of the pulp chamber is often still discernable as a radio-opaque line in a radiograph. The pulp may be totally normal. Large portions of the root or crown may be involved, with the center of the lesion often at the CEJ.
External resorption - Treatment
Since the source of the lesion is not in the pulp, endodontic treatment by itself is of no assistance in dealing with the source of the problem. Idiopathic external resorption differs from classic "replantation" or "traumatic" external resorption because of the localized nature of the lesion. Other types of resorption associated with trauma have apical or lateral characteristics that often result in gradual peripheral resorption of the entire root. This type of resorption is generally centered on the initial point of resorption (CEJ). In many cases, extensive destruction of the dentin may mean that attempts at restoration and repair of the area will result in likely exposure of the pulp . For this reason elective endodontics may be required, if only to prevent high levels of post repair thermal sensitivity or outright extrusion of repair materials into the pulp.
Research is focusing on various repair materials, root surface treatments and methods in an attempt to recreate adequate attachment. Dr. G S Heithersay has published extensively on his examination and attempts to treat this problem. (Treatment of invasive cervical resorption: an analysis of results using topical application of trichloracetic acid, curettage, and restoration.) Quintessence Int 1999 Feb;30(2):96-110) involved topical application of a 90% aqueous solution of trichloracetic acid, curettage, nonsurgical root canal treatment where necessary, and restoration with glass-ionomer cement performed on 94 patients with a total of 101 affected teeth. A minimum of 3 years' follow-up was required, unless failure occurred before that time, in which case that treatment was included. Teeth were divided into four classes, depending on the extent of the resorptive process. Class 1 represented the least invasive resorptive lesion, near the cervical area with shallow penetration into dentin, while class 4 represented the most invasive resorptive process, which had extended beyond the coronal third of the root. RESULTS: In all class 1 and class 2 cases, the results showed complete success, judged by an absence of resorption or signs of periapical or periodontal pathosis. When overall success was judged by absence of resorption and periapical or periradicular pathosis, the success rate in class 3 lesions was 77.8%. Only 12.5% of teeth in class 4 were free of resorption and deemed to be clinically sound. He concluded that the treatment regimen was successful in class 1 and class 2 cases, reasonably successful in class 3 cases, and generally unsuccessful in class 4 resorptions, where alternative treatment is recommended.
In a second paper by Heitherdsay Invasive cervical resorption: an analysis of potential predisposing factors. Quintessence Int 1999 Feb;30(2):83-95 Orthodontics was found to be the most common sole contributing factor, constituting 21.2% of patients and 24.1% of teeth examined. Other factors included : Trauma in combination with bleaching, orthodontics or delayed eruption. He recommended early diagnosis of lesions to allow for better prognosis.
OK, what does this all mean for me, the practicing dentist?
1. Radiography is important for early diagnosis of these lesions. If the lesion is Internal - perform endodontic therapy on the tooth immediately before it weakens the root. If it is External, don't "wait and watch", treat immediately or refer.
2. Patients with a history of trauma or orthodontic treatment need to be examined closely for signs of early Idiopathic External Resorption during check-ups. With these patients, there is a tendency to avoid full mouth surveys and focus on bite wing radiography (especially when their anterior dentition is pristine.) This is a mistake. There is nothing more discouraging for an Ortho patient than to have to undergo extensive restorative/endo treatment that may result in recession and poor anterior aesthetics when they have just finished years of Orthodontic therapy. This careful clinical and radiographic examination needs to continue for the rest of their life.
3. The factors influencing this Idiopathic External resorption process are poorly understood and these lesions sometimes reoccur below the level of the attempted repair. This is an especially frustrating aesthetic problem when it occurs on the labial aspects of otherwise pristine dentition. More research needs to be performed before we can treat these lesions with predictable success
4. Both types of resorption have one thing in common - early interception is the key to good overall prognosis. If you are unsure of the direction of treatment, referral to an Endodontist or Periodontist is indicated.