Impact of Chemical Disinfectants on Surface Microhardness of Acrylic Resin Denture Teeth: An In Vitro Study

This in vitro study aimed to evaluate the effects of three chemical disinfectants, glutaraldehyde, sodium hypochlorite, and chlorhexidine gluconate, on the surface microhardness of acrylic resin denture teeth. The objectives of this study were to assess and compare the impact of these disinfectants on microhardness following repeated disinfection cycles.

This in vitro study was conducted at the Department of Prosthodontics, involving 76 acrylic resin denture teeth (Premadent, Premadent Dental Products, Delhi, India) embedded in self-cure acrylic resin (DPI-RR Cold Cure, Dental Products of India, Mumbai, India) using a vinyl polysiloxane putty mold (Elite HD+ Putty, Zhermack SpA, Badia Polesine, Italy). The samples were divided into four groups (n = 19 each): Group 1 (control) was immersed in distilled water (PureFlow Distilled Water, Aquaguard, Mumbai, India); Group 2 was immersed in 2% glutaraldehyde (Cidex, Johnson & Johnson, New Brunswick, NJ, USA); Group 3 was immersed in 1% sodium hypochlorite (Clorox, The Clorox Company, Oakland, CA, USA); and Group 4 was immersed in 2% chlorhexidine gluconate (Hexidine, ICPA Health Products Ltd., Mumbai, India). Each group underwent three 10-minute disinfection cycles at a seven-day interval and was stored in distilled water between cycles. Surface microhardness was measured using a Vickers hardness tester (HMV-2T, Shimadzu Corporation, Kyoto, Japan) after the first and third cycles. Data were analyzed using one-way analysis of variance (ANOVA), Tukey's post-hoc test, and paired t-tests (IBM SPSS Statistics for Windows, Version 23 (Released 2015; IBM Corp., Armonk, New York, United States).

The control group showed a significant reduction in microhardness from the first cycle to the third cycle (p = 0.00, large effect size). The glutaraldehyde and sodium hypochlorite groups also exhibited significant decreases (p < 0.05, large effect size). No significant changes were observed in the chlorhexidine gluconate group (p = 0.328; d = 0.23). Significant intergroup differences were observed in the first cycle (p = 0.001), but not in the third cycle (p = 0.145), indicating a convergence of effects over time.

Glutaraldehyde and sodium hypochlorite significantly reduced the microhardness of acrylic resin denture teeth, whereas chlorhexidine gluconate had a minimal effect, suggesting its suitability for routine denture disinfection. Careful selection of disinfectants is crucial for maintaining the integrity of denture materials.