Evaluation of accuracy and wear of two different materials in digitally-designed telescopic removable partial dentures

Introduction
Computer-assisted design and manufacturing (CAD/CAM) have been involved in fabrication of telescopic retained partial dentures to overcome deficiencies of conventional fabrication methods. Digitally- designed removable partial denture (RPDs) frameworks can be fabricated directly from metals and polymers or alternatively from milled or printed resin patterns by casting using conventional fabrication methods.

Objectives
This study was conducted to compare between Bio-HPP and Co-Cr, CAD/CAM telescopic RPDs regarding accuracy and wear of primary crowns.

Material and methods
An educational model was scanned to create digital model after abutments reduction. Telescopic retained RPDs were milled from two different materials to fabricate twelve telescopic RPDs. In group 1, six Co-Cr telescopic retained RPDs were milled, and in group 2, six Bio-HPP telescopic retained RPDs were milled. Frameworks were scanned, and then the scans were superimposed onto the design to determine the accuracy. Chewing simulator was used for both groups. Primary copings were scanned and superimposed on original design to determine wear.

Results
Group 1 showed higher accuracy, but the difference was not statistically significant. Furthermore, there was increased surface deviations of primary crowns in group 2 from original design denoting increased wear, and the difference was statistically significant.

Conclusions
Milling technology produces accurate Bio-HPP and Co-Cr telescopic retained RPDs. Increased wear of primary crowns occurs when Bio-HPP is used for fabrication of telescopic retained RPDs.