An Evaluation of the Fit of Metal-Ceramic Restorations Made with an Autoclaved Silicone-Based Impression Material
Authors: Kollefrath Ralf , Savary Marcel , Schwela Jörg 
Published: July 2019

Abstract

Aim
To demonstrate the clinical feasibility of autoclaving certain silicone impression materials in order to avoid potential cross-contamination during handling, transport, and subsequent processing.

Background
Semicritical devices are recommended to be treated at least with high-level disinfectants or actually steam sterilized at 134°C. To date dental impressions have been disinfected rather than sterilized, so the question remains should they be sterilized before being sent to the dental laboratory?

Case Descriptions
Two identical impressions per case were made of metal-ceramic crown and fixed partial denture preparations on the same patient using addition type polyvinyl siloxane (PVS) impression materials (AFFINIS, R Coltene/ Whaledent AG, 9450 Altstatten, Switzerland) in different trays. The first impression (IMPx1) was cleaned and treated with an intermediate-level disinfectant (FD 322.Fast Disinfection Spray, Durr Dental, 74321 Bietigheim-Bissingen, Germany). The second impression (IMPx2) was cleaned, treated with an intermediate-level disinfectant as with IMPx1, subjected to a computer tomography (CT) scan with a dimensional resolution of ±10 μm, steam sterilized, and then subjected to a second CT scan. The dimensional changes of the second impression after steam sterilization were calculated by comparing the overlay of the two CT scans and expressed by color coding of the impression graphics. After the second scan, the impression was sent to a dental laboratory to fabricate a metal-ceramic crown or metal-ceramic fixed partial denture restoration to the one produced from the first impression (IMPx1) subjected only to disinfection. This process was repeated for four clinical cases.

Conclusion
Impressions made with AFFINIS® silicone impression materials in a rigid reinforced polycarbonate impression tray or in a metal dual-arch tray can be autoclaved. The overall dimensional stability of the impressions and the quality of single crowns and small fixed partial dentures made using IMPx2 was not compromised. The maximum dimensional differences at the preparations of the nonautoclaved and the autoclaved impressions were found to be within acceptable limits of about 50–100 ìm.

Clinical Significance
Steam sterilization of AFFINIS® impressions is possible without adversely affecting dimensional change. In addition, clinicians can clearly indicate to the dental practice and laboratory personnel that sterilization of the impressions has been performed, cross-contamination is unlikely, and the impressions present no apparent health hazard during transport and subsequent processing.

Disclosure
Dr. Kollefrath is head of Research and Development, Elastomers at Coltène/ Whaledent AG, Altstätten, Switzerland, the manufacturer of the impression material evaluated in this report.

Citation
Kollefrath R, Savary M, Schwela J. An Evaluation of the Fit of Metal-Ceramic Restorations Made with an Autoclaved Silicone- Based Impression Material. J Contemp Dent Pract [Internet]. 2010 July; 11(4):063-070. Available from: http://www.thejcdp.com/journal/ view/volume11-issue4-kollefrath