Question

Comparative evaluation of the effect of three disinfectants and water immersion on surface hardness of heat polymerised acrylic resin - an in vitro study.

Answer 1

Objective: To determine the changes in surface hardness occurring due to disinfection of denture base acrylic resins. Materials and Method: 80 disc shaped test specimens (13 mm x 8 mm) fabricated from heat polymerised acrylic resin were subjected to Vickers' hardness test before and 15, 30, 60 and 90 days after disinfection in one of the test disinfectant solutions (1% sodium hypochlorite, 2% alkaline glutaraldehyde or 4% chlorhexidine gluconate) at room temperature for 10 minutes. The control specimens were stored in distilled water at room temperature without disinfection. Vickers' hardness test was performed on these control specimens after 15, 30, 60, and 90 days of storage in water. Result: Mean values demonstrated a significant decrease in hardness after disinfection regardless of the disinfectant solutions used. However, this effect was reversed after 15 days of storage in water and continuous increase in hardness values for up to 60 days of water storage, after which no significant change was observed upto 90 days. Conclusion: Chemical disinfection by immersion method significantly affects the hardness of heat polymerised acrylic resin tested. However, 4% chlorhexidine gluconate least affected the hardness of resin whereas 2% alkaline glutaraldehyde affected the hardness to a maximum. This effect was found to reverse after 15 days of storage in water. 
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