# Finite Element Analysis (FEA) of Palatal Coverage on Implant Retained Maximly Overdentures
###### Abstract  
Purpose: The aim of this study was to determine stress levels on supporting structures of implant-retained overdentures as a function of varying degrees of palatal coverage using finite element analysis modeling at different loading angles. Materials and Methods: ABAQUS(r)-software was used to perform finite element analysis on eight overdenture models with three and four implants and with and without palatal coverage designs. Loads were applied perpendicular and 45\({}^{\circ}\) to the implants. Von Mises stress was measured to determine bone stress. A one-way ANOVA determined which model caused the most stress to the maxillary bone. Results: Palatal coverage increased stress to anterior implant in three implant (\(p=0.08\)) models but decreased stress to all implants in four implant models (\(p=0.43\)). Distal implants received more stress than anterior implants for all models. There was no significant difference between a full palate and no palate coverage overdenture prosthesis when a bar was added under axial loading (\(p=0.954\)). Under non-axial loading, a decrease in stress was noted with the bar in all areas except the anterior implant site. Conclusions: Palatal coverage may not be necessary when applying a pure axial load. The addition of a bar decreased stress at loading. m x  
overdenture design is associated with high patient satisfaction and implant success [18; 19; 20; 21; 22; 23; 24]. However, prosthetic and/or implant complications may occur as a result of functional loading and prosthetic component fatigue as reported in the literature [25; 26; 27]. Some of the reported complications are: (1) screw loosening or screw fracture; (2) attachment fracture; (3) implant failure and; (4) denture or teeth fracture, etc. [PERSON] et al. [28] and [PERSON] et al. [29] agreed in their investigations that a palateless designed implant overdenture could be a considerable risk factor for implant failure due to the inferior rigidity and strength of the prosthesis. [PERSON] et al. [9; 10] and [PERSON] et al. [15] demonstrated that implant overdentures with palatal coverage had reduced wear of attachment components and less overdenture base fractures when compared with palateless overdentures. The effect of splinting versus no splinting of implant attachments is also controversial. Most of the literature seems to favor bar attachment splinting because of better implant load distribution [17; 30; 31; 32; 33; 34]. However, splinting superstructures have many disadvantages, such as need for vertical space, restrictions on implant distribution and alignment, complex clinical and laboratory procedures, and difficulty of home cleaning for the patient. On the contrary, implant overdentures with unsplinted attachments have the highest patient satisfaction with less maintenance needs and a reduced treatment cost for the patients [35]. Additionally, the literature reports more prosthetic, soft tissue, and implant complications when implants are not splinted. The most commonly reported complications are: (1) denture fractures; (2) attachment fractures; (3) implant failures; and (4) soft tissue ulcers, etc. [9; 10; 25; 26; 27; 27; 36]. Most of the current literature agrees that implant geometry and bone density are key factors of implant osseointegration [36; 37] Load transfer mechanisms and possible failure of osseointegrated implants are affected by implant design, diameter, and length as well as properties of the site of placement and prosthetic component designs. Factors such as material biocompatibility, implant design and surface, surgical technique, host bone quality, and the loading conditions have all been shown to influence the implant osseointegration [38; 39]. Thread design, surface roughness, length, and diameter of the implant fixture have all been shown to influence the surface area available for bone contact. Selecting implant characteristics that maximize the available surface area for bone contact should be considered for successful implant rehabilitation of poor-quality bone sites [40; 41].