IN-VITRO QUALITY TESTING OF DENTIN ADHESIVES

A tensile and a shear bond strength test are compared, using two well- known and two more recently marketed dentin adhesive systems: Gluma (B ayer), Scotchbond 2 (3M), Scotchbond Multi-Purpose (3M), and Syntac (V ivadent). The adhesives were used to bond composite resins to the bucc al surface of human third molars. Specimens stored for 24 h before tes ting did not show significant differences between bond strength values obtained by either the tensile or the shear test method for any of th e materials. The bond strength of thermocycled specimens did not diffe r for Gluma, was significantly lower for Scotchbond 2, and significant ly higher for Scotchbond Multi-Purpose and Syntac. SEM observations sh owed increasing amounts of cohesive failure in resin with increasing b ond strength values. Cohesive fractures in dentin were also observed. It is concluded that either the tensile or the shear test method can b e used for quality testing of dentin adhesives. Thermocycling may prov ide interesting information about the quality of a bond.