Effects of long-term repeated chemical disinfection treatment on the surface hardness self-polymerizing reline resins

Abstract

Denture hygiene techniques and procedures were developed in the 1960s and 1970s and most studies indicate the importance of mechanical biofilm removal by denture brushing associated with disinfection with chemical solutions. Studies in the literature show many chemical procedures that may be used for denture biofilm control. When the immersion procedure is used, the disinfectant should be selected with regard to its effectiveness in inactivating microorganisms without any adverse effects on the denture materials. PURPOSE: This study investigated the hardness of three self-polymerizing reline resins after long-term repeated chemical disinfections. MATERIAL AND METHODS: Sixty round specimens (30 x 6mm) were made from each material: Jet, Kooliner and Tokuyama Rebase II Fast, and divided in 6 groups (n=10). The control group was stored in water and the others were disinfected with 1%, 2%, 5.25% sodium hypochlorite, 2% glutaraldehyde, and 4% chlorhexidine gluconate, respectively. The specimens were tested for knoop hardness (KHN) before disinfection and after 30, 90 and 180 disinfection cycles. Data were analyzed by analysis of variance followed by the Tukey test at 5%. RESULTS: The hardness of Jet resin varied from 18.74 ± 0.47 to 13.75 ± 0.95 KHN, Kooliner varied from 14.09 ± 1.63 to 7.52 ± 0.88 KHN, and Tokuyama Rebase II Fast from 12.57 ± 0.94 to 8.28 ± 0.39 KHN. Statistically significant decrease in hardness of the three reline acrylic resins was observed early after the first 30 disinfection cycles. CONCLUSION: The hardness of the tested materials decreased after immersion in water and after long-term repeated chemical disinfections.