STRESS ANALYSIS OF TWO DIFFERENT ATTACHMENTS FOR A SINGLE IMPLANT RETAINED MANDIBULAR OVERDENTURES IN THE MIDLINE (Invitro Study)

Abstract

This invitro study was performed to compare the microstrain of a single implant retained mandibular overdenture retained by two types of attachments; Ball,CM LOC. An acrylic resin test model representing a completely edentulous lower arch was used .The distal part of the residual ridge was covered with Molloplast –B to stimulate the mucoperiosteum. A complete mandibular acrylic denture was constructed following the conventional steps of fabrication. After the implant was installed in the acrylic resin cast, the ball attachment was screwed to the implant .Fitting surface of the denture was modified for pick up, then , self cure acrylic resin was applied in the fitting surface of the denture opposite to the abutment. The denture base was then seated properly on the model and the attachment, the denture was removed after setting of the acrylic resin for finishing and polishing.The complete denture was duplicated to be used as a surgical stent , to install a single implant in the midline . Preparation of the acrylic resin around each of the installed implants was carried out using a disc to cut the mesial, distal surfaces and then fissure bur was used to complete the preparation. The preparation was of a box shape with a thickness of 1mm of acrylic resin around the implant, having four prepared surfaces; Buccal (B), Lingual (L), Mesial (M), and Distal (D) .The four prepared surfaces had to be flat and parallel to the long axis of the implant each prepared surface had to be smoothened using sand paper before installation of the strain gauges to avoid incremental strains A vertical 100 N static load was applied unilaterally using universal testing machine at three different sites (unilateral right first molar central fossa, left first molar and bilaterally by application of metal rod on right and left first molar) at speed of 0.5mm/sec When the load was applied unilaterally .Ball attachment showed a statistically signigicant higher mean microstrain than CM LOC .When the load was applied bilaterally, CM LOC attachment has shown higher microstrain than Ball.