Stress applied on implant assisting mandibular complete overdenture - in vitro comparison of Casted Metal bar and InFibra Ribbon bar attachments

Abstract

Mandibular implant assisted overdenture is an especially attractive treatment because of its relative simplicity, minimal invasiveness and economy. Splinting of implants by bar, prevent micromovement and hence improve ossointegration in addition to improvement of overdenture retention. Purpose: The purpose of this in-vitro study was to evaluate and compare stress applied on implant assisting mandibular complete overdenture by using two types of bar attachment: a) prefabricated instant adjusting bar b) infibra ribbon bar. Materials and Methods: This in vitro study was carried out on a six standard educational edentulous mandibular models. According to the type of bar attachment used, models were classified into two maingroups as follow: group I had instant adjusting bar attachment and group II had infibra ribbon bar attachment, they connected to installed implants at canine region. The models were covered by polyvinyl siloxane impression material to simulate the oral mucosa covering the ridge. Acrylic resin complete mandibular overdentures were constructed. Strain gauges were bonded at labial, lingual, mesial, and distal surfaces of each implant abutment. LLOYD Digital loading device was used to apply vertical load of 50 N on the overdentures at right first molar. The stresses were measured. Data was collected and statistically analysis. Results: This study revealed that the highest stress was observed at the labial surface and the lowest at the distal surface of loaded and unloaded side of implant abutment, implant abutment surfaces that assisted mandibular complete overdenture with bar attachment was subjected to a more stresses applied on loading side compared to unloading side, and implant abutment surfaces subjected to a more stresses when it connected to instant adjusting bar joint attachment compered to infibra ribbon bar attachment mandibular complete overdenture. Conclusions: Variation in sintering time from1.6h to 3.0h did not affect structure and fracture toughness of Y-TZP zirconia. Thermocycling of zirconia sintered at normal sintering time has no apparent detrimental effect on their properties.