Comparative analysis of dimensional changes in autoclavable polyvinyl siloxane (PVS) impressions under various Sterilization/Disinfection Protocols: A randomized controlled trial.

Background: Impressions that maintain their dimensional stability after autoclaving effectively control cross-infection and contamination resulting from a patient's oral secretions.

Purpose: The study aimed to assess the dimensional stability of autoclavable polyvinyl siloxanes after disinfection and sterilization.

Methods: A stainless steel metal model containing three full veneer crown preparations was fabricated according to ANSI/ADA specification No. 19. Reference grooves were established on the occlusal and axial surfaces of the abutments for accurate measurements. Forty impressions were created from the master model using single-step impression technique monophase polyvinyl siloxane material (AFFINIS, Coltene/Whaledent, Altstatten, Switzerland). The impressions were categorized into four groups: Group A (control, ten untreated impressions), Group B (ten disinfected impressions with 5.25 % sodium hypochlorite [NaOCl]), Group C (ten disinfected impressions with 2 % glutaraldehyde), and Group D (ten autoclaved impressions at 134 °C for 18 min). Subsequently, stone casts were produced using type IV gypsum products (Gelstone , BK Giulini Chemie, Ludwigshafen/Rh., Germany). The dimensional accuracy of the obtained casts was assessed by measuring the inter-abutment measurements (between the abutments) and the intra-abutment measurements (diameter and height of the abutments). These measurements were performed using a universal measuring microscope (Olympus stereomicroscope B061 Imaging Corp. Tokyo, Japan) with a precision of 0.001 mm. The dimensions of the stone casts from the study groups were then compared to those of the control group. Data analysis was performed using a one-way ANOVA with a significance level of α = 0.05.

Results: AFFINIS impressions subjected to chemical disinfection in 5.25 % NaOCl and 2 % glutaraldehyde with different immersion times showed slight expansion in the intra- and inter-abutment measurements. The impressions autoclaved at 134 °C for 18 min showed slight shrinkage in the intra- and inter-abutment measurements. The dimensional change was statistically non-significant, and the percent of dimensional changes within the experimental groups was within the clinically accepted limit (α < 0.5).

Conclusion: AFFINIS polyvinyl siloxanes retain dimensional stability suitable for clinical use when subjected to chemical disinfection and steam autoclaving.