The Accuracy of Post and Core Fabricated with Digital Technology

Purpose To compare the accuracy of post and cores created with three different fabricating techniques: direct conventional, machine milling, and three-dimensional (3D) printing. Materials and methods Thirteen extracted single root central incisors were selected. Root canal treatment and tooth preparation for crown were performed on all teeth. Post space preparation of 11 mm was created using prefabricated fiber post drill to standardize post space width and length. Root canal impressions were performed on all teeth using polyvinyl siloxane impression material. Each impression was then three dimensionally scanned using an extraoral lab scanner. The scanned impressions were used to design digital files of post and cores with 3Shape CAD software. The digitally designed post and cores were used to fabricate 3D printed and milled post and core resin patterns. The same teeth were used to fabricate post and core with conventional technique (direct duplication of root canal with resin pattern). All posts were then scanned before being invested and then cast using base metal educational alloy. The metal post and cores were tried in with sample teeth and manually adjusted until found to be clinically acceptable. The post and cores were scanned in different stages to perform digital volume measurement using Geomagic Control software to determine accuracy. Pairwise comparisons were accomplished using exact version of the sign test (alpha = 0.05). Results These three techniques of post and core fabrication showed different results in the various stages of fabrication. The accuracy of 3D printed resin pattern (26.89 +/- 11.09 mm(3)) was found to be inferior compare to milled resin pattern (28.20 +/- 11.41 mm(3), p = 0.0002). However, dimensional stability of the 3D printed resin pattern before and after casting (0.56 +/- 0.95 mm(3)) was found to be superior to milled resin pattern (0.79 +/- 0.89 mm(3)) and direct resin pattern (2.51 +/- 1.38 mm(3), p = 0.00002). All three techniques showed significant volume reduction after adjustment (p = 0.0002). In the final stage, the adjusted metal post and core fabricated with three different techniques showed no statistical different in accuracy (p = 0.15). Conclusion Digitally fabricated post and cores have the same degree of accuracy as those fabricated using the gold standard direct conventional post and core technique.