Influence of Palatal Coverage and Implant Distribution on Denture Strain in Maxillary Implant Overdentures

Purpose: As maxillary implant overdentures are being increasingly used in clinical practice, prosthodontic complications related to these dentures are also reported more often. The purpose of this study was to examine the influence of palatal coverage and implant distribution on the shear strain of maxillary implant overdentures. Materials and Methods: A maxillary edentulous model with implants inserted in the anterior, premolar, and molar areas was fabricated. Two kinds of experimental overdentures, with and without palatal coverage, were also fabricated, and two strain gauges were attached at the midline of the labial and palatal sides. A vertical occlusal load of 98 N was applied through a mandibular complete denture, and the shear strain in each denture was compared by analysis of variance (P = .05). Results: In all situations, the shear strain in palateless dentures was significantly higher than in dentures with palate on both sides (P .05). In dentures with palate, the shear strain was lower when anterior implants were present. Conclusion: Palateless maxillary implant overdentures exhibited much higher strain than overdentures with palate regardless of the implant distribution; this may cause more prosthodontic and implant complications. The most favorable configuration to prevent complications in maxillary implant overdentures was palatal coverage that was supported by more than four widely distributed implants. Keywords: implant, load, maxillary implant overdenture, palateless denture, strain