Effect of different framework materials on stresses induced in distal extension removable partial dentures: A strain gauge analysis.

PURPOSE: Evaluation of the strain transmitted to the abutments and residual ridge by polyetherketoneketone material compared to the cobalt-chromium one in distal extension removable partial dentures (RPDs) to fulfill the objective of preservation of the supporting structures. MATERIALS AND METHODS: A virtual model simulating a Kennedy class I partially edentulous mandibular arch was designed. Two models, one for each group, were printed. Five RPDs were made in each group. In group CR, the framework was milled from a cobalt-chromium alloy. While in group PK, it was milled from a polyetherketoneketone blank. Strain gauge rosettes were bonded distal to the last abutment and posteriorly in the distal end of the residual ridge. Unilateral vertical and oblique loadings were applied. Mann-Whitney U test was used for inter-group comparisons while the Friedman test was used for intra-group comparisons and corrected by Wilcoxon Signed-Rank Sum. The significance level was set at p ≤ 0.05. RESULTS: During unilateral vertical load application, a statistically significant difference was found between both groups distal to the abutment in the loaded and unloaded sides as well as the residual ridge on the unloaded side. During oblique load application, a statistically significant difference was found between both groups in all slots. CONCLUSION: Polyetherketoneketone material induces less stress on the abutments and more stress on the residual ridges compared to the cobalt-chromium ones. Therefore, it may be recommended for weak abutments supporting RPDs.

Assessment of tooth positions of printed complete dentures with different designs and tooth positioning techniques.

PURPOSE: To evaluate the accuracy of tooth positions in printed complete dentures with different designs and teeth positioning techniques. MATERIALS AND METHODS: Five different designs of complete dentures and teeth positioning techniques were evaluated in this in vitro study. In Group I, the denture bases and teeth were designed as a single piece. In groups II and III, the denture bases were designed separately, and the denture teeth were designed as separate teeth. In groups IV and V, the denture bases were designed separately, and the denture teeth were designed as a single piece. Teeth positioning keys were designed for groups III and V. The dentures of all groups were scanned, and the data were imported to the surface matching software to evaluate the accuracy of the teeth positions. Statistical analysis was done using One -way ANOVA of Variance. The significance level was set at p ≤ 0.05. RESULTS: The results showed that the highest deviations of the positions of the canines (0.0781 ± 0.0154 mm) and the first molars (0.0611 ± 0.0055 mm) were found in Group II. On the other hand, Group I showed the least deviations of the positions of the canines (0.0287 ± 0.0054 mm) and molars (0.0354 ± 0.005 mm). CONCLUSIONS: The most accurate tooth positions are obtained in monolithic printed complete dentures. Fewer deviations in tooth positions occur when denture teeth are designed as a single piece.

Hybrid Prosthesis versus Overdenture: Effect of BioHPP Prosthetic Design Rehabilitating Edentulous Mandible.

Aim: To compare the BioHPP (biocompatible high-performance polymer) as a substructure for the hybrid prosthesis versus the BioHPP bar supporting and retaining implant overdenture by radiographic evaluation to identify bone height alteration around the implants and to evaluate satisfaction based on visual analoge scale questionnaire. Materials and Methods: Ill-fitting mandibular dentures were chosen for 14 fully edentulous male patients with adequate dental hygiene, enough interarch space, and free of systemic diseases and parafunctional habits. Patients who received new dentures (CDs) were randomly allocated into each group using computer software, and four interforaminal implants were inserted in parallel using a surgical guide. Three months after osseointegration, the patients received either CAD-CAM BioHPP framework hybrid prosthesis (Group I) or BioHPP bar supported and retained overdenture (Group II). Using digital preapical radiography, the bone loss is evaluated 6, 12, and 18 months after insertion. The subjective patient evaluation was done using a questionnaire based on the VAS includes five points for chewing, comfort, esthetics, speech, oral hygiene, and general satisfaction. Results: The overall marginal bone loss (MBL) revealed that Group I (hybrid prosthesis) was more than Group II (bar overdenture) at all intervals in the anterior and posterior implants' mesial and distal surfaces. The patient satisfaction survey results showed that, after 18 months, the difference was statistically not significant between them all (P > 0.05) except for the comfort (for the overdenture group, 4.43 ± 0.53 while the fixed hybrid was 5.00 ± 0.00). Conclusion: BioHPP framework material is an alternative material for implant rehabilitation of edentulous mandible with minimal MBL in BioHPP bar overdenture compared to BioHPP hybrid prosthesis.