Study the precision of fixed partial dentures of Co-Cr alloys cast over 3D printed prototypes

Abstract

Purpose: of this paper is to investigate the accuracy of Co-Cr dental bridges, manufactured using 3D printed cast patterns. Design/methodology/approach: Four-unit dental bridges are fabricated from the alloys i-Alloy and Biosil-f by lost-wax process. The polymeric cast patterns are 3D printed with different layer’s thickness (13 μm, 35 μm and 50 μm). Two 3D printers are used: stereolithographic “Rapidshape D30” and ink-jet “Solidscape 66+”. The geometrical and fitting accuracy as well as the surface roughness are investigated. Findings: It is established that Co-Cr bridges, casted from 3D printed patterns with 50 μm layer thickness, characterize with the largest dimensions – 3.30%-9.14% larger than those of the base model. Decreasing the layer thickness leads to dimensional reduction. The dimensions of the bridges, casted on patterns with 13 μm layer thickness, are 0.17%-2.86% smaller compared to the primary model. The average roughness deviation Ra of the surface of Co-Cr bridges, manufactured using 3D printed patterns, is 3-4 times higher in comparison to the bridge-base model. The greater the layer thickness of the patterns, the higher Ra of the bridges. The silicone replica test shows 0.1-0.2 mm irregular gap between the bridge retainers and abutments of the cast patterns and Co-Cr bridges. Research limitations/implications: Highly precise prosthetic constructions, casted from 3D printed patterns, can be produced only if the specific features of the 3D printed objects are taken in consideration. Practical implications: Present research has shown that the lower the thickness of the printed layer of cast patterns, the higher the dimensional accuracy and the lower the surface roughness. Originality/value: The findings in this study will help specialist in dental clinics and laboratories to choose the right equipment and optimal technological regimes for production of cast patterns with high accuracy and low surface roughness for casting of precise dental constructions.