Enamel/Dentin Bonding Effectiveness of Self-etching Borate-initiated Self-cure 1-step Adhesive

Objectives: Determine micro-tensile bond strength (mTBS) of an experimental self-etching, borate-initiated self-curing one-step adhesive system containing self-reinforcing (SR) multi-functional monomer (DBC510) bonded to enamel and dentin.

Methods: Five adhesive groups: DBC510 (DBC, experimental, self-etch 1 step self-cure, Tokuyama Dental), DBC510 with phosphoric acid etching (DBC/E, experimental, etch-and-rinse 2 step self-cure, Tokuyama Dental), Optibond Solo Plus (OSP, etch-and-rinse 2 step light-cure, Kerr), Clearfil SE (CSE, self-etch 2 step light-cure, Kuraray) and Optibond All-in-One (OBA, self-etch 1 step light-cure, Kerr) were applied to occlusal dentin and buccal/lingual enamel of 200 carbide bur-cut human molars followed by resin-based composite (Z100, 3M-ESPE). Twenty-four hours later restored teeth were sectioned with diamond blades into 2x2mm square sticks then dumbbell shaped specimens (0.5mm² round cross-sectional area, 1mm gage length, 0.6mm radius of curvature) were formed using a CNC Specimen Former (University of Iowa). One-half of the specimens were then tensile-tested at a crosshead speed of 1mm/min in a calibrated materials testing machine (Z2.5, Zwick). Both ANOVA and Weibull regression models were performed, both ignoring and considering the random effect of the tooth (multiple specimens per tooth) to detect a difference in enamel and dentin bond strengths between adhesives.

Results:

	Microtensile bond strength (MPa (SD))
	Dentin**	Enamel**
DBC	54.9 (9.9) A,a	31.1 (7.5) B,b
DBC/E	55.2 (8.2) A,a	49.9 (15.8) A,a
OSP	47.2 (10.2) A,a	45.0 (10.4) A,a
CSE	52.0 (10.2) A,a	32.2 (13.0) B,b
OBA	48.4 (13.9) A,a	23.7 (7.8) B,c
**means with the same uppercase letter are not significantly different using a simple random effect in Mixed Model ANOVA with post-hoc Tukey's test and with the same lower case letter are not significantly different using Weibull regression models (P > 0.05). n = 20 per group.

Conclusions: No difference in mTBS to dentin was detected between adhesives. mTBS to enamel was significantly stronger when phosphoric acid etching was performed (DBC/E and OSP).

Acknowledgements: Sponsored by Tokuyama Dental Corp. K. Hirata is an employee of Tokuyama.