Microtensile Bond Strengths of Self-Etching Adhesives to Enamel and Dentin

Objective:  This study evaluated the microtensile bond strength (MTBS) of six self-etch adhesives and one etch and rinse adhesive to dentin and ground enamel.

Methods:  Forty extracted, intact, and caries-free human molars were assigned to Group 1 (dentin) and Group 2 (enamel).  After removal of occlusal enamel in Group 1 and preparation of flat enamel buccal or lingual surfaces in Group 2, teeth were polished to 600-grit.  Adhesives tested were 1-step self-etch: Adper Prompt SE, I Bond, Optibond All-in-One, and Xeno IV; 2-step self-etch: Clearfil SE Bond and PEAK SE Adhesive System; and 2-step etch and rinse: PQ1.  Adhesives were applied according to manufacturer's instructions, irradiated using the Ultralume 5 LED curing light, and composite resin (Vit-l-escence, A2, Ultradent) placed and cured in two 2mm increments.  Bonded specimens were stored in water for 24 hrs and beams with a cross-sectional area of 1mm² prepared.  Specimens were fixed to a microtensile test jig and loaded to failure at a crosshead speed of 1mm/min.  Data was analyzed using one-way ANOVA and Tukey's test (p²0.05; n³18).

Results:  MTBS (MPa ± SD) are shown:

Adhesive	Dentin	Ground Enamel
PQ1	22.12±8.59 b c	16.61±2.82 a
Adper Prompt SE	16.26±7.91 c	18.73±3.88 a
I Bond	13.98±6.89 c	18.64±5.15 a
Optibond All-in-One	32.76±11.19 a	17.16±3.86 a
Xeno IV	27.89±11.36 a b	16.97±4.08 a
Clearfil SE Bond	34.24±8.04 a	15.81±4.49 a
PEAK SE	33.75±9.14 a	17.14±6.66 a

Conclusions:  Results indicate 2-step self-etch adhesives, PEAK SE and Clearfil SE Bond, and1-step self-etch adhesives Optibond All-in-One and Xeno IV showed significantly higher bond strengths to dentin.  There were no statistical differences between adhesives bonded to ground enamel.  Failures were predominantly adhesive for dentin and enamel (90-100% of specimens).  The dentin vs. enamel differences are not readily explained.    Supported by Ultradent.