In vitro comparison of PFM crown retention following endodontic access and subsequent restoration: amalgam, composite, amalgam with composite veneer, and fiber post with composite

Abstract

Introduction: An in vitro investigation of crown retention following endodontic access on molar porcelain fused to metal (PFM) crowns and subsequent restoration using amalgam, composite, amalgam + composite, or fiber post + composite.Methods: 40 human extracted molars were mounted in acrylic resin and prepared for PFM crowns. PFM crowns were fabricated, cemented with zinc phosphate, and the force to displace each crown was measured with a tensile-testing machine before and after endodontic access preparations. The endodontic access area, crown preparation axial wall, and preparation surface area was measured for each sample for comparison. The crowns were then recemented and access openings restored with either amalgam or composite before displacement force was remeasured. The restorative material was removed from each access opening, access area measured, and restored again (amalgam with composite or fiber post with composite) for displacement force to be re-measured. To compare for retention without a restored access opening, 13 randomly selected samples were removed of the restorative material, recemented and crowns again removed. Paired T test was used to compare the means of displacement between groups. One-way analysis of variance (ANOVA) was used to compare the mean outcome measure within the groups. Results: Statistical analyses showed retention following unfilled access was significantly lower than intact crowns. Amalgam, composite, amalgam + composite, and fiber post + composite increased retention beyond the original value. There was no statistical difference between amalgam and composite materials nor amalgam + composite from fiber post + composite. Qualitative results indicate that the restorative material remains in the crown following displacement regardless of the material used to restore the access. Conclusions: The results from this study suggest that an endodontic access cavity decreases retention of a PFM. However, subsequent restoration with amalgam, composite, amalgam + composite, or post + composite may increase the original retention of the crown.