A 3D Coordinate Metrology Analysis of Two Different Custom Made Metal Posts Fabricated Using Conventional Casting and 3D Printing Methods

Abstract

The purpose of this study was to compare the selective laser sintering (SLS) technique to the conventional casting method in term of producing custom made Co/Cr posts using a 3D coordinate metrology analysis. A clear acrylic block that is used to teach pre-clinical endodontics was used and a post space with a 10 mm length was created using a red ParaPost XP drill size 1.25 mm. The post space was cleaned and dried using copious air-water spray to be prepared for the impression stage. A ParaPost plastic laboratory burnout impression post with 1.143 mm diameter and auto polymerizing acrylic resin materials were used to make the impression of the post space. This step was repeated 10 times to produce 10 auto polymerized resin post patterns. The resulted resin patterns were then scanned using Straumann Cares scanner and stored as stl files. These stl files were sent to Renishaw company, who specialize in additive manufacturing, to produce 10 Co/Cr posts using the SLS technique. The actual resin post patterns were sent to a commercial dental laboratory where they were invested and casted using Co/Cr alloy. Using Straumann Cares scanner, the cast and printed posts were scanned and saved as stl files. Each stl file was named according to the production technique and pattern number. Each scanned resin post pattern and its corresponding produced sample were imported into 3dmdvultus 64 software at which they were superimposed to each other and 3D coordinate metrology analysis was performed. The obtained results showed that the mean distance between the scanned resin posts and their corresponding scanned conventional cast posts ranged from -20 to -80 μm with a mean of -48 μm; and the mean distance between the scanned resin posts and their corresponding scanned printed posts ranged from -20 to -100 μm with a mean of -67 μm. The statistical analysis showed that there was no significant difference in the means between the samples that were fabricated using SLS and conventional casting techniques (P = 0.107). Hence the results were insignificantly in favour of the conventional casting, the SLS technique is capable of producing custom made metal posts that are dimensionally comparable to those fabricated using the conventional casting method and are much more cost and time effective.