The Effect of Palatal Coverage and Metal Reinforcement on Maxillary Implant Overdenture - An In Vitro Study

Objective: The aim of this study was to investigate the effect of palatal coverage and metal reinforcement on maxillary implant overdenture under vertical loading. Materials and Methods: An edentulous maxilla model and complete dentures were fabricated with polymethyl methacrylate(PMMA) resin. Four implants (3.75x10mm, Mark III, Nobel Biocare™, Sweden) were embedded at bilateral canine, and first molar areas connected with Locator®(Zest Anchors, USA) attachments. Four biaxial strain gauges(KFG-2-120-D16-11 L1M2S, Kyowa, Japan) were attached to the midline palatal, midline buccal, the palatal surface above the attachment, and left tuberosity on each denture to measure the bending strains on the four areas. On the same denture, the palatal coverage was removed and the strains on the above four areas were measured again. Then the metal framework was embedded into the denture for reinforcement and strains on the same areas were recorded for comparison. A vertical static load of 100N was applied to the denture on one biting plate cross bilateral posterior occlusion rims for 20 times in each condition.(P<0.05) Results: The largest strain was observed at the midline palatal area, followed by the area above the attachment. There was no significant difference between other channels. Without palatal coverage, the strains on the above two areas got larger and decreased when metal reinforcement was added into the denture. Conclusions: Within the limitation of the study, the rigidity of 4-implant-supported maxillary overdenture could be reinforced by adding metal framework into the denture