Effectiveness of computer-aided removable partial denture design.

PURPOSE: Computer programs have been developed for removable partial denture (RPD) design, but their educational impact has never been investigated. This study measured the effectiveness of computer-based RPD design simulations in a traditional RPD design course for second-year dental students. MATERIALS AND METHODS: Thirty-six students were randomly assigned to four groups, two simulation and two control groups, at the beginning of the RPD design module. A cross-over design compared the two strategies during laboratory exercises. First, the simulation group worked with the simulation, while the control group met in small-group seminars with faculty. Post-test 1 was given, and then students switched teaching methods and post-test 2 was given. Each post-test had two parts. Part 1 involved designing an RPD based on specific patient criteria. Part 2 involved choosing the more correct of the two designs. RESULTS: Results showed a significant difference (p = .0072) in two of four test groups. Although it was an initial evaluation, the computer simulation was shown to be equivalent to faculty-led small-group seminars. Students also responded positively to a questionnaire on their perceived effectiveness of the simulations. CONCLUSIONS: The results suggest that RPD design can be taught as effectively with computer-based simulations as with faculty-led seminars.

Evaluation of stresses and forces in selected I-bars using the finite element method.

PURPOSE: Three-dimensional models of half-round, tapered and full-round, untapered I-bar clasps of varying configurations and material properties were constructed. The purpose of this study was to examine the stresses and reaction forces produced within each model upon deflection to 0.01 in (0.254 mm), 0.02 in (0.508 mm), and 0.03 in (0.762 mm) at 1 mm from the tip using the finite element method. MATERIALS AND METHODS: Three-dimensional computer models of half-round and full-round clasps were constructed using solid eight-node brick elements. The half-round, tapered I-bar clasp model was 2.4 and 1.4 mm in diameter at the base and tip, respectively. The full-round, untapered I-bar clasp model was 1 mm in diameter. Three design groups were created for each clasp form. Group A had 25% of the total length in the straight anchor end of the I-bar clasp, B had 35%, and C had 50%. All models were 31 mm in length and had a radius of curvature of 5 mm. Different material properties were incorporated into the models. Each model was deflected at a point 1 mm from the tip to 0.01 in (0.254 mm), 0.02 in (0.508 mm), and 0.03 in (0.762 mm). RESULTS: The stresses and forces produced as a result of the deflection applied to each clasp were viewed and displayed graphically. The maximum von Mises stresses in megapascals and the reaction force in newtons (N) were recorded. Stresses varied in each clasp in the range of 0 to 154.3 MPa for the half-round, tapered I-bar clasp models, and 0 to 100.9 MPa for the full-round I-bar clasp models at 0.01-in deflection. Reaction force measured near the tip of the clasp models was between 1.60 N and 6.31 N for the half-round, and between 0.22 N to 2.13 N for the full-round I-bar clasp models. For all clasps studied, as the deflection increased, the location of stress within each group remained the same regardless of the material properties; however, the stress and force values increased linearly. CONCLUSIONS: The location of maximum stress varied with the length of the anchor portion of the clasps studied. Maximum stresses were located on the flat side of the half-round, tapered I-bar clasp model.

Prosthodontic restoration with dental implants and an intraoral cranial bone onlay graft: a case report.

In 1988, a 54-year-old edentulous patient received a cranial bone onlay graft with the immediate placement of five dental implants. Treatment procedures and early results of restoration are described.

Comparison of bond strengths of polymethyl methacrylate and alpha cyanoacrylate.

A method of fabricating similar methyl methacrylate cylinders was used to produce specimens to test the bond strength of alpha cyanoacrylate and autopolymerizing methyl methacrylate. Each group was tested immediately and after storage in 37 degrees C water bath for 90 days. Statistical analysis supported the finding that the autopolymerizing methyl methacrylate produced a better bond even without undercuts or mechanical retention.