Affect of age on composite bond strength to dentine using 5[th] and 6[th] generation adhesive system

ABSTRACT

The mineral content of dentin increases with age and its primary structure is altered. These changes may have unknown effects on efficiency of adhesive systems. The aim of this study was to find the effect of aging on dentin bonding agents. fourty eight extracted human premolars were divided into 2 groups under 15 years old and 2 groups over 45 years old. After exposing surface dentin with wheel type burs and polishing dentin surface with paper disks, dental adhesives, Excite and Prompt L-Pop were used following manufacturer's instructions. Then composite cylinders were bonded to dentin and light cured. Then Shear Bond Strength [SBS] of samples were measured with universal testing device [Dartec]. Fractured specimens were observed under stereomicroscope to determine the type of fracture. The mean SBS for those teeth aged over 45 was 24.15 MPa using Prompt L-Pop, and 18.6 MPa using Excite, and for teeth aged under 15 years old was 21.5 MPa using Prompt L-Pop and 13.99 MPa using Excite. SBS of older teeth was shown to be more than younger teeth, also Prompt L-Pop showed higher SBS than excite. It seems that lower mineral content of dentin in younger teeth results in over demineraliza-tion while etching hence resin is unable to penetrate the collagens fibers resulting in voids in bonding area which reduces the SBS in this group. Also higher SBS of Prompt L-Pop can be explained by the water cone-tent of it, which serves as solvent while Excite has ethanol which is evaporated and reduces the penetration of resin