# Finite Element Analysis (FEA) of Palatal Coverage on Implant Retained Maximly Overdentures
## 3 Results  
An analysis of variance was conducted to determine stress levels on the supporting structures of implant-supported overdentures using finite element analysis modeling as a function of different variables. These variables included: (I) full-palatal-coverage vs. palateless denture models; (II) supporting bar vs. no bar denture models; (III) loading angles at 90 degrees vs. 45 degrees; and (IV) three- vs. four-implant models. The statistical analysis for the effects of loading on cancellous bone by denture design using the ANOVA test for difference in means was significant (\(p=0.047\)). Pairwise comparisons showed that the stress level on the three-implant-full-palate-coverage combination was significantly higher than on the three-implant-palateless model (\(p=0.016\)), higher than the four-implant-palateless model (\(p=0.038\)), and higher than the four-implant-full-palate-coverage (\(p=0.016\)). No other pairs were significantly different. An independent \(t\)-test for difference in means to compare both denture designs and three- vs. four-implant conditions was performed. For the palateless denture design variable, the means [medians] were 2.6 (0.50) [2.6] vs. 3.9 (2.6) [3.0] for the full-palate-coverage design with (\(p=0.203\)). For the model with three implants vs. four implants, the means [medians] were 3.9 (2.6) [2.9] for the three-implant model and 2.6 (0.52) [2.7] for the four-implant model with (\(p=0.211\)). To compare the effect of loading on cortical bone in palateless vs. full-coverage denture designs with three-implants and four implants conditions, a one-way ANOVA between models was conducted. Results showed that there was a significant loading effect on the cortical bone for the three-implant full coverage model (\(p<0.0001\)). Pairwise comparisons showed that the three-implant-full-coverage model was significantly higher than the three-implant-palateless (\(p<0.0001\)) and significantly higher than four-implant-palateless (\(p<0.0001\)); four-implant-full-coverage was significantly higher than three-implant-palateless (\(p<0.001\)), and higher than four-implant-palateless (\(p<0.0001\)). No other pairs were significantly different. An independent \(t\)-test for difference in means to compare both denture designs and three-implants vs. four-implants variables was performed. For the denture designs the means [medians] were 3.2 (4.1) [2.8] for the palateless design vs. 12.5 (2.5) [13.8] for the full-palate-coverage, with the \(t\)-test result (\(p<0.0001\)). For the model with three implants vs. the one with four implants the means [medians] were 7.9 (5.4) [8.3] for the three-implant model, (Figure 6) and 7.8 (6.3) [6.5] for the four-implant model (Figure 7). The \(t\)-test result for difference in means was (\(p=0.964\)). The statistical analysis for the effects of the supporting bar on cortical and cancellous bone for the three- vs. four-implant models using the ANOVA test for difference in means was not significant. The results for the three-way interaction were not significant (\(p\) = 0.988). Likewise, no two-way interactions were found significant (all \(p\) > 0.3). The results for the palateless vs. full-coverage denture model showed (\(p\) = 0.507). For the three-implant vs. four-implant model (\(p\) = 0.398). For the bar vs. no-bar model (\(p\) = 0.993). Hence, no individual factors were significantly associated with the outcome. The global analysis of variance conducted to determine stress levels on the implants by location and the bar superstructure was significant (\(p\) < 0.001). Pairwise comparisons showed that the stress levels on implant at location 1 was significantly higher than the bar superstructure (\(p\) = 0.014), stress on implant at location 2 was significantly higher than at the bar (\(p\) = 0.0001), and on implant at location 2 was significantly higher than on the Implant at location 1 (\(p\) = 0.014).