EMG correlations of edentulous patients with implant overdentures and fixed dental prostheses compared to conventional complete dentures and dentates: a systematic review and meta-analysis.

OBJECTIVES: The goal of this meta-analysis was to evaluate how muscular activity, measured by electromyography (EMG), differs among edentulous patients treated with a complete denture (CD), removable implant overdentures (IO), implant-retained fixed dental prostheses (IFDP), and dentates. The differences during clenching and chewing were of particular interest. MATERIALS AND METHODS: An electronic literature review was carried out on MEDLINE (Pubmed) and the Cochrane Library covering the period January 1980 through September 2013. This was accomplished independently by three different reviewers and supplemented by a manual search. The review included randomized controlled trials, controlled clinical trials, and clinical trials which evaluated surface electromyography, bite force, chewing, and implants or complete dentures. In addition, the research was adjusted using MeSH terms. RESULTS: The search garnered 646 titles and abstracts. Sixteen articles which met the inclusion criteria were analyzed. The effect size for muscular activity after implant support increased after therapy during clenching 2.18 (95% CI: 1.14, 3.23) and during chewing 1.45 (95%CI: 1.21, 1.69). Moreover, the EMG data of IO and IFDP groups (pooled) were lower than that of dentate control subjects during clenching (effect size: -1.01 [95%CI: -1.37, -0.65]). In contrast, the IFDP-wearers showed higher values than dentates during chewing. Among the edentulous control patients, the IO and IFDP groups (pooled) displayed higher values during clenching (effect size: 1.12 [95%CI: 0.7, 1.55]) and chewing (effect size: 1.33 [95%CI: -0.57, 2.10]). Furthermore, the muscular activity during chewing correlated with the hardness of the food. CONCLUSION: In general, edentulous patients with CDs can achieve a greater degree of muscular activity after rehabilitation with IOs during clenching and chewing. During clenching, patients with IFDPs achieved higher values than those with dentates. The muscular activity increases with the hardness of the food.

Accuracy of a self-perforating impression tray for dental implants.

STATEMENT OF PROBLEM: Difficulties are involved in impression making with conventional open impression trays. PURPOSE: The purpose of this study was to evaluate the accuracy of transferring implant impressions with a self-perforating impression tray. MATERIAL AND METHODS: A reference model of a mandible was fabricated, and 4 implants were placed in the regions of the first premolars and lateral incisors (implants 1, 2, 3, 4). Ten impressions of the reference model with polyvinyl siloxane were made for each group; control (conventional open impression tray) and test (self-perforating impression tray; Miratray Implant). A metal bar was screw-retained on implant 1, and the gaps generated at the vestibular face of implants 3 and 4 were measured by optical microcopy. The 2-way ANOVA and least square difference post hoc test were used (α=.05). RESULTS: Higher mean (±SD) values were obtained for the test group than for the control group for both implants: implant 3: 150 ±84 µm for the test group, 73 ±63 µm for the control group (P=.019); implant 4: 129 ±65 µm for the test group, 62 ±61 µm for the control group (P=.04). CONCLUSION: The self-perforating impression tray provided less accuracy than the conventional open tray.

Assessment of the stress transmitted to dental implants connected to screw-retained bars using different casting techniques.

Passive fit of the prosthetic superstructure is important to avoid complications; however, evaluation of passive fit is not possible using conventional procedures. Thus, the aim of this study was to check and locate mechanical stress in bar restorations fabricated using two casting techniques. Fifteen patients received four implants in the interforaminal region of the mandible, and a bar was fabricated using either the cast-on abutment or lost-wax casting technique. The fit accuracy was checked according to the Sheffield's test criteria. Measurements were recorded on the master model with a gap-free, passive fit using foil strain gauges both before and after tightening the prosthetic screws. Data acquisition and processing was analyzed with computer software and submitted to statistical analysis (ANOVA). The greatest axial distortion was at position 42 with the cast-on abutment technique, with a mean distortion of 450 µm/m. The lowest axial distortion occurred at position 44 with the lost-wax casting technique, with a mean distortion of 100 µm/m. The minimal differences between the means of axial distortion do not indicate any significant differences between the techniques (P = 0.2076). Analysis of the sensor axial distortion in relation to the implant position produced a significant difference (P < 0.0001). Significantly higher measurements were recorded in the axial distortion analysis of the distal sensors of implants at the 34 and 44 regions than on the mesial positions at the 32 and 42 regions (P = 0.0481). The measuring technique recorded axial distortion in the implant-supported superstructures. Distortions were present at both casting techniques, with no significant difference between the sides.

Survival probability of zirconia-based fixed dental prostheses up to 5 yr: a systematic review of the literature.

The purpose of this systematic review was to calculate the 5-yr survival rates of all-ceramic zirconia-based fixed dental prostheses (FDPs) and to analyze technical and biological complications. An electronic literature search of MEDLINE (PubMed) was conducted independently by three reviewers to identify clinical studies from 1999 to 2009 and was completed by a manual search. Keywords and inclusion and exclusion criteria were well-defined. The search revealed 399 titles and led to the final analysis of 18 full-text articles. Nine studies met the inclusion criteria. Extracted data were statistically calculated into 5-yr survival rates and 5-yr complication-free rates by using Poisson regression analysis. In total, 310, 3- to 4-unit FDPs and 20 FDPs with more than 4 units were included. The estimated 5-yr survival rate for all FDPs was 94.29% (95% CI: 58.98-99.32); 19 FDPs were lost as a result of catastrophic failures. The 5-yr complication-free rate regarding technical complications was 76.41% (95% CI: 42.42-91.60) with chipping being the most frequent complication. Regarding biological complications, the 5-yr complication-free rate was 91.72% (95% CI: 59.19-98.53). The survival rates of zirconia-based short-unit FDPs are promising. However, an important improvement of the veneering systems is required, and for FDPs with more units in function, further randomized, controlled clinical trials are necessary.