Influence of different contaminants and cleansing agents on bond strength and in situ degree of conversion of composite-adhesive interface

This study evaluated the effect of contamination with saliva or blood and different cleansing agents on the microtensile bond strength (mu TBS) and in situ degree of conversion (DC in situ) of composite-adhesive interface. Sixty-six bovine incisors were ground flat to expose dentin and were randomly assigned to eleven groups (n = 6), according to the contaminant and the cleansing agent. A positive control (without contamination or cleansing agent) was determined. A multimode adhesive in the self-etching form was applied before contamination with blood or saliva. Then, the groups received different cleansing protocols that generated two negative controls (contaminated with saliva or blood and only air dried) and eight experimental groups, washed with water (H2O), ascorbic acid (AscAc10%), hydrogen peroxide 3% (H2O23%) and chlorhexidine 2% (CLX2%). Specimens were restored with composite resin and prepared for mu TBS. After 24 h, restored teeth were sectioned and the sticks subjected to the mu TBS test (in a universal testing machine at 0.5 mm/min speed). Degree of conversion within the hybrid layer (DC in situ) was evaluated by micro-Raman spectroscopy. Data were analysed using a two-way analysis of variance (ANOVA) and Tukey's test (p 0.05). While saliva and cleansing agents did not affect mu TBS and DC in situ (p 0.05), blood influenced negatively (p = 0.025). However, CLX2% was able to reestablish the values of mu TBS and DC in situ (p = 1.0). Weibull regression analysis of mu TBS data confirmed the prior mentioned performance. Saliva and cleansing agents did not influence mu TBS and DC in situ values, while blood caused them to be significantly decreased. CLX2% was able to reverse the negative effects of blood contamination. In this way, in case of composite-adhesive interface contamination with blood, CLX2% washing was able to reverse the mu TBS and DC in situ values.

Automated summary

Saliva and cleansing agents did not influence the values of μTBS and DC in situ, while blood contamination negatively affected them. However, chlorhexidine 2% was able to reverse the negative impact of blood contamination on μTBS and DC in situ values.