The Accuracy of Post and Core Fabricated with Digital Technology

Abstract

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 (α = 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. K E Y W O R D S3D printing, 3D milling, accuracy of post and core, customized post and core, post and core

The accuracy comparison of 3D‐printed post and core using castable resin and castable wax resin

“…Consequently, it can be assumed that 3D printing post and core resulted in a post and core with reduced accuracy. This was reported in a previous article that found that 3D printed post and core was not as accurate as milled post and core 9 . This problem has also been observed in 3D printed complete dentures, removable partial dentures framework, and crowns when compared to the milling technique 16–18 .…”

“…This study evaluated the accuracy of 3D printed post and core using different materials by measuring the volume of each post and core with digital software. The volume measurement method has been reported in a previous article 9 . Post and core with more volume can be assumed to have better accuracy and better adaptability as it would mean less gap between the root canal and post.…”

“…The results showed that even though completely polymerized post and core has smaller volume compared to partial polymerized, no statistically significant difference was found. The additional photopolymerization or post‐curing has been speculated to cause shrinkage when 3D printing is used 9,12,16 . However, no study has looked at this step to determine whether it could cause a significant amount of shrinkage or not.…”

“…A half digital technique has also been used by making an impression of root canal, scanning the impression, and milling the post with zirconia or metal using a digitally designed post and core 7,8 . However, using the half digital technique with three‐dimensional (3D) printing technology to fabricate post and core has shown to be less accurate compared to milled resin post and core 9 …”

The effects of different root canal irrigation protocols and artificial aging procedures on the bond strength between dentin and hybrid ceramic posts

“…Nevertheless, the fact that fiber posts are prefabricated has caused problems in their adaptability with the morphology of the root canal [2]. In this way, CAD/CAM posts that combine the intra-canal adaptability of cast metal posts and the elastic modulus of fiber posts to dentin have come to the fore and have been introduced to the market [4,5].…”