Bonding performance of a newly developed experimental one-step adhesive on sound human dentin

Objectives The modern dentistry has made tooth restoration a relatively straightforward procedure by utilizing adhesive technology for retaining biomaterials in place. In a clinical environment, the reduction of operative steps has made the one-step adhesive systems to be preferred by dentists for their effectiveness in minimizing technique sensitivity (Sano et al, 2013).  The constant evolvement of dental materials is associated with simplification of operative procedures, as well as improving their mechanical properties. The present study aims to investigate the bonding performance of a newly developed one step experimental bond in relation to the orientation of dentinal tubules. Materials and methods Equipment: Tensile strength testing machine Autograph 500N EZ test, (Shimadzu Co. Kyoto, Japan). Materials: SKB 100; experimental one bottle, single step bond (Kuraray Noritake Dental Co.),  Clearfil SE One  (Kuraray Noritake Dental Co).    Control: Clearfil Megabond two (Kuraray Noritake Dental Co.) Freshly extracted human third molars were used. The coronal part was removed by means of low speed diamond cutting saw, under a copious water irrigation until the dentin was exposed. The dentin surface was  standardized by polishing in an uniform direction with SiC paper with 600 grid and the specimens were machined so that the dentin tubules run parallel and perpendicular to the bonded surface. The adhesive systems were applied according to the manufacturers’ instructions.  Increments of composite resin material of around 2mm each were applied and polymerized by LED photo curing lamp for 30 sec. From the so restored teeth, beam shaped specimens were obtained so that they contained dentin, adhesive layer and composite material. The sizes were WxHxL 1.25x0.8x>10mm, which corresponds to bonded area of 1mm². After storing for 24 hours in distilled water, the specimens were subjected to tensile load until complete fracture at CHS of 0. 1mm/min. A total of 7 specimens for each adhesive system were used. The tensile strength (MPa) was calculated by dividing the tensile force (N) by the bonded area (mm²). The adhesive interfaces of the specimens were morphologically characterized by means of SEM (JEOL, Japan) in relation to their mechanical behavior. Results The specimens with perpendicular tubule orientation showed micro-tensile bond strength (µTBS) of 58.43 ± 10.25 and 27.74 ± 5.99 MPa for the control group and the experimental adhesive, respectively. The parallel group turned out values for µTBS of 46.71 ± 8.35 and 36.24 ± 9.49 MPa  for the control group and the experimental adhesive, respectively. The SEM fractographic observations of the bonded surfaces revealed mostly cohesive failure for the control and mixed adhesive failure with cohesive failure within dentin for the experimental bond group. Connclusion The relatively very good adhesive abilities of the experimental bond SKB 100, make it a preferred choice where speed and ease of use are of primary importance.