Quintessence International, 01/1999

Tooth resorption is a common sequela following injuries to or irritation of the periodontal ligament and/or tooth pulp. The course of tooth resorption involves an elaborate interaction among inflammatory cells, resorbing cells, and hard tissue structures. The key cells involved in resorption are of the clastic type, which include osteoblasts and odontoclasts. Types of tooth resorption include internal resorption and external resorption. There are two types of internal resorption: root canal (internal) replacement resorption and internal inflammatory resorption. External resorption can be classified into four categories by its clinical and histologic manifestations: external surface resorption, external inflammatory root resorption, replacement resorption, and ankylosis. External inflammatory root resorption can be further categoriezed into cervical resorption with or without a vital pulp (invasive cervical root resorption) and external apical root resorption. Other variations of resorption include combined internal and external resorption and transient apical breakdown.

Invasive cervical resorption is a relatively uncommon form of external root resorption. There may be no external signs, and the resorptive condition is often detected by routine radiographic examination. Where the lesion is visible, the clinical features vary from a small defect at the gingival margin to a pink coronal discoloration of the tooth crown, resulting in ultimate cavitation of the overlying enamel. The condition is usually painless unless pulpal or periodontal infection supervenes. Radiographic features of lesions vary from well-delineated to irregularly bordered mottled radiolucencies, and these can be confused with dental caries. A characteristic radiopaque line generally separates the image of the lesion from that of the root canal, because the pulp remains protected by a thin layer of predentin until late in the process. Histopathologically, the lesions contain fibrovascular tissue with resorbing clastic cells adjacent to the dentin surface. More advanced lesions display fibro-osseous characteristics with deposition of ectopic bonelike calcifications both within the resorbing tissue and directly on the dentin surface. Secondary invasion of microorganisms into the pulp or periodontal ligament space will elicit a normal inflammatory response.

How accurate is today's method of casting in the dental laboratory? Normally it is good enough, but what happens if the dental technician is confornted with an extensive restoration or has to deal with the precision of prefabricated implant abutments? In either case, he or she is headed for trouble. So what is to be done, especially if both of these components come together? The force transferred to the osseointegrated endosseous implants is naturally undesirable and the main reason for premature loss of the implants. The present article describes the production of an implant-related restoration for a 50-year-old patient. The plans were to make a partially removable, implant abutment-connected, base metal framework and to administer spark-erosion machining to achieve a passive fit.

Objective: A pilot clinical study on a direct-placement gallium restorative alloy was initiated with nine patients who signned a consent form. Method and materials: Thirty Class I restorations were placed and assessed over a 3-year period. The cavity preparations and surface of the restorations were sealed to prevent oral fluids from contacting the gallium alloy during placement and early setting of the gallium restorative material. Results: The initial 18-month clinical results were encouraging. But at 21 months, one tooth had fractured, and within another year two molars were diagnosed with cracked-tooth syndrome (incomplete tooth fracture). These three fractured teeth were restored with amalgam and are symptomless at this time. There was little fracture at the margins of the gallium restorative, but tarnish and a rough surface were noted on many of the gallium restorations. The direct-placement gallium restorative alloys must be further assessed in the laboratory to correct dimensional instability. Conclusion: Results suggested that Galloy, used with either of two sealing resins, is not a suitable restorative materia

Objective: The purpose of this clinical study was to assess the sensitivity experienced and reported by patients following treatment of primary carious lesions with Class I or Class II amalgam restorations. Method and materials: Only previously untreated teeth were selected. The cavity preparations were treated according to one of four regimens: group 1 = no liner; group 2 = two coats of a copal varnish; group 3 = a dentin adhesive resin li ner; group 4 = a resin-modified glass-ionomer liner. Patients were contacted on days 2 and 7 postoperatively and questioned regarding the presence or absen ce of sensitivity. If sensitivity was experienced, they were asked which stimuli created the sensitivity, the length of time it lasted, and its intensity on a subjective scale. If sensitivity was experienced on day 7, patients were also contacted on days 14, 30, and 90 to assess the degree of sensitivity. Nineteen teeth were included in each of the four groups. Results: By days 2 and 7, no significant difference existed among groups; by day 14, 22% of restorations in group 2 and 17% of those in group 3 were sensitive, while teeth in groups 1 and 4 exhibited no sensitivity reactions. Conclusion: Use of a resin-modified glass-ionomer liner or no dentin treatment resulted in short-term sensitivity in fewer than one third of the teeth. Almost one third of the teeth restored with a dentin adhesive resin liner or copal varnish exhibited initial sensitivity, which lasted up to 30 days in a few teeth.

Objective: The purpose of this study was to evaluate the resistance of selected post-and-core systems to fatigue testing. Method and materials: A fatigue-testing machine and data acquisition software were developed for this in vitro test. Pulpless mandibular second premolars were treated with three different types of post-and-core system: (1) two different prefabricated posts with amalgam cores, (2) the same two pre-fabricated posts with resin composite cores, and (3) cast post and cores, which served as the control group. The fatigue-testing machine applied alternating buccal and lingual forces to the core until lateral movement of 0.0025 inches (63.5 um) was detected by a transducer contacting the surface of the core. This criterion represented initial cement failure. Results: Although groups using the resin composite core material exhibited a higher number of cycles prior to failure, there was no statistically significant difference between the different post-and-core systems. Conclusion: All of the post-and-core systems that were tested may be acceptable for restoring endodontically treated teeth.