Shear Bond Strength of Selective-etch Adhesives on Cut/Uncut Enamel

Objectives: To compare shear bond strength of 7^th generation adhesive systems on cut and uncut enamel prepared with selective-etch or preferential etch technique.

Methods:  One-hundred extracted caries-free human teeth were obtained for this study. Each tooth was embedded in acrylic resin. The samples were randomly divided into ten groups (n=10, five groups cut (C), five uncut (U) ). Cut enamel surfaces were prepared using SiC paper up to 600 grit (Ecomet3, Buehler).  Uncut were embedded with their buccal surface exposed.  Three adhesive systems were tested with variations in etching: Prime&Bond NT (PBNT, Dentsply), Adper Easy Bond (AEB, 3M ESPE) and experimental adhesive EXL-759 (EXL, 3M ESPE).  Adhesives were applied according to manufacturers' instructions with exceptions of using the self etch mode (SE) or pre-treating with etch (PE). Z250 (3M ESPE) composite was filled into a bonding jig (Ultradent) and cured for 40 seconds with a halogen light (Epilar 2500). After storage in de-ionized water for 24 hours at 37°C, the shear bond strength  was carried out using a universal testing machine (Instron 5566A, Norwood, MA) with a cross head speed at 1mm/min. Statistical analysis was done by one-way ANOVA, with post-hoc analysis conducted via Fisher LSD. Significance was predetermine at p<0.05.

Results:

	PBNT, C, PE	PBNT, U, PE	AEB, C, PE	AEB, U, PE	AEB, C, SE	AEB, U, SE	EXP, C, PE	EXP, U, PE	EXP, C, SE	EXP, U, SE
Mean (MPA) SD	31.93 ±4.99	32.03 ±9.26	35.18 ±4.03	31.10 ±7.61	26.56 ±5.83	26.06 ±11.20	34.11 ±5.68	41.65 ±7.11	23.51 ±6.47	36.86 ±11.81
Statistic group comparison	a,d	a,e	b,c,d,e,h	a,c	a,c,f	a,c	b,c,d,e	b,f,h	a,c,d	b,c,d,e,g

Conclusions:  In terms of mean values, EXP with selective-etch has higher bond strength than AEB self-etch on both cut and uncut enamel. Uncut enamel yields significantly higher bond strength compared with the cut enamel on EXP self-etch.