Shigezo Hirano

A new polyisoprene-based light-curing denture soft lining material

OBJECTIVES The purpose of this study was to investigate some clinically relevant properties of Clearfit LC, a newly developed polyisoprene-based light-curing lining material. Its properties were compared with those of other four commercial products. MATERIALS AND METHODS Five soft lining materials, Clearfit LC, two plasticised acrylics (Super-soft, Soften) and two silicones (Molloplast B, Sofreliner) were used to determine water sorption, solubility, staining resistance, Shore A hardness and shear bond strength to denture base. Five specimens for each test were fabricated. The results of each test among the five materials were compared by one-way ANOVA and Scheffes post-hoc test at alpha=0.05. RESULTS One-way ANOVA of each test showed that the differences among five materials were significant (P<0.05). Clearfit LC showed the intermediate water sorption and solubility (10.07; 1.72 microg/mm(3)). It also showed the lowest color change in beta-carotene/olive oil solution and instant coffee solution (DeltaE=1.19, 5.48, respectively). The shear bond strength of Clearfit LC was 1.56MPa, and no adhesive failure was found. Its Shore A hardness value (56.2) was located between two acrylics and silicones. It was also found that the softer materials tend to failure cohesively. CONCLUSIONS The polyisoprene-based lining material showed low water sorption and solubility, moderate softness, high staining resistance and satisfactory shear bond strength to denture base resin. It also provides clinicians sufficient working time due to its light-curing property. It would be an attractive alternative as a relining material.

Factors affecting accuracy of implant placement with mucosa-supported stereolithographic surgical guides in edentulous mandibles

This study aimed to evaluate the accuracy of implant placement with mucosa-supported surgical guides in edentulous mandibles and to determine the factors affecting accuracy. Implant placement was simulated on the preoperative CT image and mucosa-supported surgical guides were fabricated for six edentulous mandible models and 15 patients with edentulous mandibles, using CAD/CAM technology. Deviations of the actual implant position from the planned position were calculated by comparing the planned image and the postoperative image. Based on the results, it was concluded that mucosa-supported surgical guides have high accuracy and that bone density and mucosal thickness could affect accuracy.

A method to remold worn acrylic resin posterior denture teeth and restore lost vertical dimension of occlusion

A method is described for remolding and correctly restoring abraded posterior denture teeth. By adding a layer of paraffin wax for jaw registration, the dentist can repeat the registration procedure until the proper jaw relation is established. This wax occlusal record is used as a guide during the remolding, and is incrementally replaced by autopolymerizing resin.