Micro-tensile bond strengths tested in wet and dry conditions

Objective: To evaluate the micro-tensile bond strengths of dentin bonding specimens tested in wet and dry conditions. Methods: The occlusal dentins of eighteen newly extracted human third molars were exposed and abraded with wet 600-grit silicon carbide paper. The teeth were then assigned equally to one of the following six adhesives: Prime&Bond NT, Contax, Clearfil SE Bond, Adper Prompt, Clearfil S3 Bond, iBond. After application of adhesive, composite resin crowns were built up on adhesives. The bonded teeth were then sectioned longitudinally in x and y directions to obtain bar-shaped specimens, and twenty specimens of each tooth were assigned equally to four testing groups: Group A: the bonding area of each specimen were kept in wet during the testing process;: the specimens were kept in dry condition for two hours before being tested; Group B, Group C and Group D: the specimens were kept in dry condition for 2 hrs, 5 hrs and 24 hrs respectively before being tested. All specimens tested in tension at a crosshead speed of 1.0 mm/min. Results: For all adhesives except for iBond, the micro-tensile bond strengths tested in wet condition were lower significantly than that in dry condition (P<0.05). The drying period affected obviously the micro-tensile bond strengths of the specimens bonded with Adper Prompt.

Adhesives               Group A         Group B           Group C         Group D

Prime&Bond NT     48.51±11.30   69.53±12.05     67.87±13.86    74.63±14.55

Contax                    30.20±11.11   48.28±13.81     49.12±15.60    49.49±13.76

Clearfil SE Bond      53.36±14.95   76.93±16.35     77.67±12.14    77.23±13.45

Adper Prompt          15.24±8.70     26.37±9.32       36.30±10.97    46.82±10.67

Clearfil S3 Bond       47.20±10.67   61.18±11.63     67.31±13.73    68.35±12.70

iBond                      28.20±9.00     31.37±8.21       31.56±10.38    32.75±10.54

Conclusions:The micro-tensile bond strengths of dentin bonding specimens can be affected by testing conditions (wet or dry), and testing in dry condition can resulted in higher micro-tensile bond strengths for most contemporary dental adhesives.