Effects of Reinforcement on Denture Strain in Maxillary Implant Overdentures: An In Vitro Study Under Various Implant Configurations

Purpose: Maxillary implant overdentures are often designed without palatal coverage to maximize wearer comfort. Although palateless dentures have been reported to be less rigid than conventional dentures, and require reinforcement to prevent complications, there is little documentation about the effects of such reinforcement. The purpose of this study was to examine the effects of reinforcement on the strain on maxillary implant overdentures supported by implants in a variety of configurations. Materials and Methods: A maxillary edentulous model with implants inserted in the anterior, premolar, and molar area was fabricated. Five types of experimental overdentures, with and without reinforcement, were fabricated, and two strain gauges were attached at the anterior 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 on the denture was measured. The measurements were compared using the Kruskal-Wallis test (P = .05). Results: On both the labial and palatal sides, the strain on the palateless dentures with reinforcement was significantly lower than the strain on palateless dentures without reinforcement in all implant configurations (P .05). The labial strain on the palateless dentures with reinforcement was almost as low as the labial strain on dentures with palatal coverage in most implant configurations. Conclusion: Reinforcement of a palateless implant overdenture with residual ridge reinforcement and a palatal bar could reduce the strain in the anterior midline to almost the same level as a denture with palatal coverage. This type of reinforcement may prevent prosthetic and implant complications. Keywords: implant distribution, implant number, maxillary implant overdenture, palateless denture, reinforcement