AIR HUMIDITY - A DETRIMENTAL FACTOR IN DENTIN ADHESION

Successful dentine adhesion may be negatively influenced by intrinsic and extrinsic dentine wetness. Testing the influence of high humidity levels during the application of bonding systems is therefore relevant . It was the aim of this study to investigate in vitro the sensitivity to air humidity of the dentine bond strength for some commercially av ailable bonding systems. Four bonding systems were tested in vitro on human molars at temperature/humidity levels of 25-degrees-C and 40% re lative humidity (RH) as well as 35-degrees-C and 95% RH. Four operator s each made two samples of the respective treatment combinations. Afte r shear bond testing a three-way ANOVA was carried out. Only the facto rs 'material', 'humidity' as well as their interaction were statistica lly significant. The factor 'operator' did not exert a significant inf luence on the shear bond strength. For the 'clinically dry' group stat istically significant differences were found between all materials (P < 0.001). In the 'high humidity' setting too, significant differences were found between materials (P < 0.001). The shear bond strength valu es ('high humidity') were very low (< 3 MPa) for Gluma 2000, Denthesiv e and Syntac, while the mean values for Scotchbond Multi-Purpose were significantly higher (12 MPa; P < 0.001). It was concluded that in gen eral bonding systems are highly sensitive to extrinsic dentine wetness , resulting in very low adhesion values at high humidity.