Background and Objectives: Acrylic resin had a long history of been used in the fabrication of denture fabrication since they exhibit a better chemical bond between teeth and denture base. With increasing use of dentures, detachment of teeth from dentures also increased proportionally. Denture disinfection is an essential procedure for maintaining good hygiene of the denture. The aim of the study is to evaluate the effect of disinfection on shear bond strength between denture teeth and heat activated denture base.

1.To evaluate the shear bond strength between heat activated acrylic resin denture base and denture teeth measured using a universal testing machine (Instron) expressed in MPa.

2.To analyse the bonding failure between the denture tooth and heat activated acrylic resin interface using a stereomicroscope at 25 X magnification.

Methodology: Two commercial brands of denture teeth (Acryrock and Ivostar) and heat activated acrylic resin denture base were tested. There were 12 subgroups in the study. Each brand of denture teeth was divided into six subgroups comprising of five experimental subgroups and one control group. In subgroup A1B1 and A2B2 (chemical disinfection) the specimens were immersed in 4% of chlorhexidine and sodium perborate monohydrate solution for 15 minutes daily for 19 days respectively, Subgroup A3B3 specimens (mechanical disinfection) were subjected to mechanical disinfection for 14 hours and in Subgroup A4B4 and A5B5 specimens were subjected to mechanical disinfection for 14 hours followed by disinfection with 4% chlorhexidine solution and sodium perborate monohydrate solution for 15 minutes daily for 19 days respectively. In Control group A6B6 specimens were immersed in distilled water at 37degree Celsius for 19 days. Shear bond strength testing was performed at denture tooth resin interface in a universal testing machine at a cross head speed of 1mm/minute. Bond strength failure rates were quantified and classified as adhesive, cohesive or mixed. Data were analyzed by independent t test and chi-square test.

Results: In subgroupA1B1 and subgroupA2B2, (chemical disinfection) the specimens immersed in 4% of chlorhexidine (p=0.615) and sodium perborate monohydrate (p=0.615), for 19 days respectively, subgroup A3B3 (mechanical disinfection) specimens were subjected to mechanical disinfection for 14 hours (p<0.01), subgroup A4B4 and A5B5 (mechanical-chemical disinfection) (p<0.01) and (p<0.01) respectively, subgroup A6B6 (control group) (p=0.054). For bond failure analysis where p value for subgroup A1B1 is 0.856, p value for subgroup A2B2 is 1.000, P value for subgroup A3B3 is 1.000, p value for subgroup A4B4 is 0.670, p value for subgroup A5B5 is 0.670, p values for subgroup A6B6 0.856. Disinfection with 4% chlorhexidine solution exhibited mixed pattern of bond failure while sodium perborate monohydrate solution demonstrated both mixed and adhesive type of bond failure. Mechanical disinfection and Combination of mechanical and chemical disinfection exhibited adhesive type of failure.

Interpretation and Conclusion: Disinfection with 4% chlorhexidine, sodium perborate monohydrate, brushing and combination of mechanical and chemical disinfection reduced the bond strength between denture teeth and heat activated denture base.