Effect of Using Different Primary Crown Materials on the Frictional fit of CAD/CAM Telescopic Partial Dentures

Abstract

This in vitro investigation was carried out on partially edentulous maxillary arch representing Kennedy Class I classification (bilateral free end saddles). Two materials were used in the fabrication of primary crowns of telescopic retained removable partial denture and were evaluated;they were classified into two groups according to the material used: Group (I): primary crowns were made from zirconia. Group (II): primary crowns were made from cobalt chromium. In this study an educational maxillary stone model with the canines and the first premolars as the last standing abutments was used representing Kennedy class I.The cast was scanned and standard tessellation language (STL) file was produced. The virtual cast was adjusted to produce four abutments in place of the canines and the first premolars.Then printing of the STL file was done using printing device to produce two identical 3D cast. Spaces representing the mucosa over the crest of ridge were created using the soft tissue simulating material.Then,two models were printed and seating of the abutments was verified and injection of the soft tissue simulating material was done to fill the spaces. Designing of the primary crowns for all groups was carried out using exocade software.Then,the STL file was sent to the milling machine for the purpose of milling.In group I,seven sets of primary crowns were milled out of zirconia,and group II,seven sets of primary crowns were milled out of fully sintered CoCr blanks. Telescopic RPD frameworks were milled out of fully sintered CoCr blanks.Following the verification of the fit of the trial framework on the cast,