Evaluation of Microtensile Bond Strength of a One-Step Self-Etch Adhesive

Objectives:

Selective phosphoric acid etching of enamel may enhance self-etch enamel bonds. Selectively etching enamel may adversely affect dentin bond strength and durability. This study evaluated the microtensile dentin bond strength (m-TBS) of a one-step HEMA-free self-etch adhesive “designed for selective etching” (G-aenial Bond-GB) compared to 2-step self-etch (Clearfil SE-SE) and 3-step etch-&-rinse (OptiBond FL-OB) adhesives using two different bonding techniques; with and without additional etching. 

Methods:

Human molars were divided randomly into 5 groups (n=15). In groups GB, SE, and OB, each adhesive was used on dentin following manufacturer’s instructions. In GB+ and SE+, phosphoric acid was used before applying the adhesive. Beams were stored in artificial saliva at 37°C for 48h and tested using a universal testing machine with crosshead speed of 1 mm/min. The fractured interfaces were analyzed using light microscopy. Data was analyzed using Weibull, GEE and regression methodologies (α=0.05).

Results:

Weibull Characteristic Strength (MPa) ranged from 24.9-42.8 and Weibull Modulus from 3.0-4.8 with GB < SE+ & OB. Mode of failure (% cohesive) ranged from 25%-86% with GB & GB+ & SE < SE+ & OB and GB < SE.     

Peak Stress (MPa)
Group	N Teeth	N Beams		Mean (SE)	Weibull Characteristic Strength	Weibull Modulus
GB	15	57		23.1(2.4)	24.9	3.0
GB+	15	61		31.8(2.4)	34.6	3.5
SE	15	58		31.6(2.5)	34.8	3.6
SE+	15	60		39.3(2.4)	42.8	4.8
OB	15	58		37.8(2.4)	41.4	4.5
Failure Mode, N beams (%)
	Adhesive		Mixed		Cohesive-Resin	Cohesive-Tooth
GB	37(65%)		6(11%)		12(21%)	2(4%)
GB+	29(48%)		12(20%)		20(33%)	0(<1%)
SE	15(27%)		16(29%)		25(45%)	0(<1%)
SE+	4(7%)		5(8%)		48(80%)	3(5%)
OB	1(2%)		7(12%)		49(84%)	1(2%)

Conclusions:

Bond strength did not decrease when dentin was etched before applying the adhesive. Aged strengths need to be evaluated. Materials supplied by GC America.