A Comparative Evaluation of Linear Dimensional Accuracy of the Dies Obtained using Three Conceptually Different Die Systems in the Fabrication of Implant Prosthesis: An in vitro Study

Abstract

Statement of problem: Given that meticulous implantprosthodontic procedures are recommended to obtain the bestpossible intraoral fit, the die systems used for multi-implant castswarrant further investigation. Die stone expansion and errorsintroduced by removable die casts may exceed the accuracyrequired for the passive fit of implant prosthesis.Purpose: The purpose of the study was to evaluate the lineardimensional accuracy between the implant master die and threeconceptually different die systems, such as Pindex system,Accu-trac precision die system and conventional brass dowelpin system.Materials and methods: Thirty impressions of implant masterdie were made with polyether impression material. Tenexperimental implant casts were fabricated for each of thethree different die systems tested: Accu-trac precision die traysystem, Pindex system and conventional brass dowel pinsystem. The solid experimental casts were sectioned and thenremoved from the die system 30 times. Linear distances betweenall six possible distances were measured from one center ofthe transfer coping to the other, using a coordinate measuringmachine in millimeters up to accuracy of 0.5 microns. Data weretabulated and statistically analyzed by binomial nonparametrictest using SPSS version 15.Results: Significant differences were found for distance A-B(p = 0.002), A-C (p = 0.002), A-D (p = 0.002) and B-D(p = 0.021) in conventional dowel pin system however, for Accutracprecision die tray system it was significant only for distanceA-D (p = 0.002) but for Pindex system it was nonsignificant forall the distances measured.Conclusion: Within the limitations of this study, use of Pindexsystem is recommended when sectioned dies are needed for amulti-implant retained prosthesis.