Evaluation of two computer-aided design software on the adaptation of digitally constructed maxillary complete denture.

Aims: This study was conducted to evaluate the adaptation of maxillary complete denture designed by two different open computer-aided design software programs (3Shape and Exocad) using Geomagic surface matching software. Settings and Design: This was a nonrandomized crossover clinical trial. Materials and Methods: Twenty completely edentulous patients were selected in this study. Forty complete dentures were designed using two different software programs: twenty dentures were designed by 3Shape software and the other twenty dentures were designed by Exocad software. Maxillary dentures were evaluated regarding their adaptation by measuring the deviations that occurred between the fitting surface of the three-dimensional printed dentures, and the scanned master casts using Geomagic surface matching software. Statistical Analysis Used: An unpaired t-test was used for statistical analysis. Results: According to the positive average deviation value that represented pressure areas, 3Shape-designed maxillary dentures showed significantly lower mean deviation values (0.041115 ± 0.018165 mm) than Exocad-designed maxillary dentures (0.500665 ± 0.032619 mm). Regarding the negative average deviation values that represented the gap areas, Exocad-designed maxillary dentures showed significantly lower mean deviation values (0.161555 ± 0.007842 mm) than 3Shape-designed maxillary dentures (0.231350 ± 0.009146 mm). The results of the total average deviation values showed significantly lower mean deviation values (0.096950 ± 0.008868 mm) of 3Shape-designed maxillary dentures than Exocad-designed maxillary dentures (0.250755 ± 0.021154 mm). Conclusion: 3Shape and Exocad software programs produced acceptable maxillary dentures regarding denture adaptation. However, maxillary dentures designed by 3 Shape software showed better adaptation than maxillary dentures designed by Exocad software.

Effect of platform switching on strain developed around implants supporting mandibular overdenture.

PURPOSE: The aim of this study was to assess the effect of platform switching, using 3 different abutment sizes on the strain developed around implants supporting mandibular overdenture, using strain gages. MATERIALS: An implant-supported overdenture was constructed on an acrylic model with 2 implant fixtures placed at canine areas. Abutments of different sizes (5.5 mm, 4.5 mm, and 3.5 mm diameter) were screwed in the implant fixtures (platform switching). Anterior axial, anterior off-axis (lateral), and posterior load were applied on each abutment through a load applicator attached to the upper compartment of a universal testing machine until a load of 100 N, at which instant, the resultant strain on the implants was recorded using 4 strain gages connected to a 4-channel strain indicator. Data were analyzed by 1-way ANOVA at a significance level of 0.05, followed by Tukey-Kramer multiple comparisons test. RESULTS: Anterior axial load application and decreasing the abutment size lead to a decrease in the strain developed on the loaded abutment and to an increase in the strain developed on the unloaded abutment. Anterior off-axis load application and decreasing the abutment size lead to an increase in the strain developed on the loaded abutment and to a decrease on the unloaded abutment. On the other hand, posterior load application and decreasing the abutment size lead to an increase in the strain developed on the mesial side of the near abutment and a decrease in the strain developed on its distal side, where there was a significant increase in the strain developed on the mesial and distal sides of the far abutment. CONCLUSION: The distribution of the strain developed because of decreasing the abutment size does not favor the use of platform switching in an implant-supported mandibular overdenture.