Distortion of printed resin surgical guides after autoclave sterilization and chemical disinfection.

Abstract

Statement of problem: Advances in implant planning have increased the use of printed surgical guides for precise implant placement. Accurate placement of implants relies on the stability of the surgical guide, therefore the effects of sterilization and disinfection on the dimensional accuracy of surgical guides require evaluation.

Purpose: The purpose of this in vitro study was to examine the level of distortion of printed surgical guides after steam sterilization and disinfection by immersion in 70% isopropyl alcohol to develop a protocol for the sterilization of surgical guides.

Material and methods: A surgical guide was designed in Blue Sky Bio. Forty guides were printed with Formlabs Form 3B+ printer and Formlabs surgical guide resin following manufacturer's instructions. Each guide was scanned with Primescan optical scanner before disinfection and sterilization. Twenty guides were individually packaged, and autoclave sterilized following manufacturer's recommendation of 134 °C for 20 minutes. The remaining 20 guides were soaked in 70% isopropyl alcohol for 15 minutes. After sterilization and disinfection, the guides were scanned and standard tessellation language (STL) files from pre- and post-sterilization were compared by using the GeoMagic Control X software program to examine dimensional changes. Differences among the study groups were analyzed with a 1-sample t test to determine if the mean site's value for each treatment group was statistically significant from zero and a 2-way repeat-measures ANOVA was used to detect differences among groups (α=.05).

Results: The average deviation at the lingual, incisal, and buccal sites of the sterilized guides was 6.3 µm, -2.3 µm, and -20.6 µm, respectively. The average deviation at the lingual, incisal, and buccal sites of the chemically disinfected guides was -0.4 µm, 2.6 µm, and -0.8 µm, respectively. Sterilization showed a statistically significant value at the lingual and buccal surface (P<.05), while the chemical disinfection group did not show a statistically significant difference at any site (P>.05). The 2-way repeat-measures ANOVA test demonstrated there was a significant effect of treatment on the overall mean values (P<.001), with sterilization treatment giving an overall value 6.3 µm more negative than disinfection. There was also a significant effect of site (P<.001), and a significant interaction between treatment and site (P<.001).

Conclusions: Heat sterilization caused a significantly greater negative deviation than disinfection across the sites. A statistically significant distortion was found after sterilization, but not with chemical disinfection. However, the amount of distortion will likely not cause a clinically significant effect on the deviation of implant placement.