Effect of saliva and blood contamination on shear bond strength of cured dentin adhesives

Achieving good moisture control is a common problem encountered in restorative dentistry, especially after applying and curing dentin bonding agents over dentin tissue. The aim of this study was evaluation of the effect of saliva and blood contamination on shear bond strength of cured dentin adhesives. Thirty-five extracted sound human molars and premolars were collected and after debridement, stored in 0.5% chloramine solution for one week and preserved in distilled water, afterwards. The buccal and lingual surfaces were ground flat to expose the dentin. These surfaces were etched with 37% phosphoric acid for 15 seconds, rinsed for 20 seconds and dried with a cotton pellet. A single–bottle dentin-bonding agent was applied on the etched surfaces and cured for 20 seconds. This procedure was repeated in order to achieve excellent bonding. The specimens were divided into five groups of 7 each: Group 1 (Control) was not contaminated in Group 2, bonding surfaces were contaminated with blood and saliva without any other treatment Group 3 was contaminated and then rinsed and dried completely Group 4 was contaminated, then rinsed and dried and re-etched for 10 seconds Group 5 was contaminated, rinsed and completely dried, re-etched for 10 seconds, rinsed, dried, re-bonded and cured for 20 seconds. A composite cylinder built in a plastic mold (2 mm high × 10 mm wide) was placed on the treated surfaces and cured for 40 seconds. After thermocycling, the shear bond strengths of all specimens were measured using an Instron testing machine. The data were subjected to one-way ANOVA, with 95% coefficient of confidence. A significant difference was observed between the mean shear bond strength of the contaminated and uncontaminated groups (P=< 0.001). Contamination of cured dentin bonding agents with blood and saliva, significantly reduced the shear bond strength of composite to dentin.