EVALUATION OF CRAZING CAUSED BY REPEATED STERILIZATION CYCLES ON STAINLESS STEEL, ZIRCONIA, BIOFLX CROWNS

Abstract

Background: Preformed crowns are widely used in pediatric dentistry for restoring primary teeth with extensive caries or after pulp therapy. During crown selection, multiple crowns may need to be tried-in, potentially leading to microbial contamination. Therefore, sterilization before reuse is essential; however, repeated autoclave cycles may alter the crown surface, causing crazing or micro-structural changes. With increasing clinical preference for esthetic crowns such as Zirconia and BioFlx, it is necessary to evaluate their sterilization tolerance. Aim: To evaluate the effect of repeated steam sterilization cycles on surface crazing of Stainless steel, Zirconia, and BioFlx crowns under stereomicroscopy. Materials and Methods: An in-vitro study was conducted using fifteen preformed pediatric crowns, divided into three groups (n=5): stainless steel (Shin-Hung), zirconia (Kids-e-Dental), and BioFlx (Kids-e-Dental). Crowns were examined initially using an explorer and stereomicroscope at 40x magnification. Sterilization was performed in an autoclave at 121°C, 15 psi for 20 minutes. Each crown underwent three sterilization cycles, followed by stereomicroscopic evaluation after each cycle. Crazing was assessed using Wickersham’s criteria. Results: No visible surface defects were observed with the naked eye. Stainless steel and zirconia crowns demonstrated isolated micro-cracks after repeated sterilization, while BioFlx crowns showed no noticeable crazing. Stainless steel crowns exhibited the highest surface change scores, followed by zirconia, whereas BioFlx crowns remained unaffected. Conclusion: Repeated autoclave sterilization results in mild crazing in stainless steel and zirconia crowns, with stainless steel crowns being more susceptible. BioFlx crowns demonstrated the highest resistance to sterilization-induced surface alterations, indicating better suitability for repeated try-in and sterilization cycles.