In vitro resistance to fracture of porcelain inlays bonded to tooth

To assess the resistance to fracture of ceramic inlays, extracted sound human molars were restored with different ceramic materials and glass-ionomer or composite resin luting cement. Compression forces were applied to the specimens until they fractured, and maximal force developed, extent and location of fractures, and the micromorphology of the fractured surfaces were studied. Inlays made of Vitadur N with aluminum oxide profile and bonded with composite resin demonstrated the highest resistance among the restorative combinations, but their resistance was still lower than that of intact (control) teeth. The extent of fracture increased proportionally to the fracture resistance of the specimens. Scanning electron microscopic observation confirmed the effectiveness of the adhesion between composite resin and etched ceramic and the absence of sufficient micromechanical anchoring between glass-ionomer cement and etched ceramic.     

Studies on the castability of Co-Cr alloy for cast plates. Part 2: Effect of form of sprue attachment to the wax pattern

Co-Cr alloy is used more frequently than Ni-Cr alloy as a non-precious alloy for cast plates in Japan. However, since the melting point of Co-Cr alloy is very high, about 1300 degrees C, and since it oxidizes easily, a vacuum-pressure casting machine capable of melting this alloy in a reducing atmosphere has recently been developed. Using this vacuum-pressure casting machine, the authors studied the effects on the castability of Co-Cr alloy due to the form of sprue attachment to the wax pattern. The results clarified that in the vacuum-pressure casting method, the form of sprue attachment to the wax pattern has a significant effect (p less than 0.01) on the castability of Co-Cr alloy.     

Giant cell reaction to ameloblastoma: an immunohistochemical and ultrastructural study of a case

Histopathologic, immunohistochemical, and ultrastructural features of the giant cells appearing in the tissue surrounding an ameloblastoma are presented. These giant cells exhibited strong activity of a highly stable form of acid phosphatase, and were positive for alpha-1-antichymotrypsin. Ultrastructurally, the cytoplasm of the giant cells contained numerous mitochondria, and the cell membrane was comparatively smooth. Therefore, it is proposed that these multinucleated giant cells are reactive to the invasion of ameloblastoma and are histiocytic in origin.     

Repair of periodontal angular bony defects evaluated by one- and two-dimensional radiographic analysis

The healing of eighteen angular periodontal bony defects was evaluated radiographically 1 year after treatment. The pretreatment and posttreatment radiographs were exposed and processed in such a way that identical images were obtained. There was no correlation between one- and two-dimensional expressions of healing in such defects, and relative area changes were consistently larger than relative linear changes of the same defects. The area gain of bone was strongly correlated to the following morphologic variables: length of bone surface, original defect area, and height of the defect.     

Occlusal contacts following orthodontic treatment. Measured by a photocclusion technique

Measurement of occlusal contacts on 12 orthodontically treated patients were measured by the photocclusion technique finds a mean increase of 56% in the number of contacts in the first year following treatment.     

Rehabilitation of patients with severely resorbed maxillae by means of implants with or without bone grafts: a 3- to 5-year follow-up clinical report

Forty three patients with severely resorbed maxillae who had been referred for implant treatment were assigned to 1 of 3 treatment options: bone grafting and implant placement (graft group), modified implant placement with no bone grafting (trial group), or optimized complete dentures (no-implant group). Sixteen, 20, and 7 patients, respectively, were assigned to the 3 groups. The patients have been examined annually, and at the time of this report they had been followed for 3 to 5 years after treatment. At the 1-year follow-up, 10% (22 of 221) of the implants had been lost, and at the 2-year follow-up, 18% of the implants had been lost (40 of 221; 25% in the graft and 13% in the trial group); after that time, no further losses occurred. Life table analysis showed cumulative success rates of 82% in the graft group and 96% in the trial group after 1 year, and 74% and 87%, respectively, at the final examination after 3 to 5 years. The failure rate was higher in smokers than in non-smokers. A substantial reduction of the grafted bone, especially of onlay grafts, occurred early after grafting surgery in many patients. Mean marginal peri-implant bone loss was 0.6 mm during the period from prosthesis connection to the 1-year follow-up, and from the 1-year to the 3-year follow-up, average peri-implant bone loss was 0.3 mm in the graft group and 0.5 mm in the trial group. The results corroborated previous findings that patients with severely resorbed maxillae have an increased risk of implant failure in comparison to patients with good bone quantity and quality. However, in this investigation, practically all implant losses occurred during the first 2 years, whereupon a steady state seemed to follow for up to 5 years after loading.