Prime-and-rinse approach for improving the enamel micro-tensile bond strengths of self-etch adhesives

Abstract

The study investigated the effects of prime-and-rinse approach using 15% MDP (10-methacryloyloxydecyl dihydrogen phosphate)-containing primer on the enamel micro-tensile bond strengths (MTBS) of (ultra-) mild self-etch adhesives, enamel surfaces and enamel-resin interfaces. The buccal enamel surfaces of 69 human third molars were polished and randomly assigned to three groups: Group A (control, self-etch approach): Polished enamel surfaces were not further pre-treated. The enamel surfaces were acid-etched (Group B, (selective) enamel etching) or primed with 15% MDP-containing primer (Group C, prime-and-rinse approach) for 15 s and thoroughly water-sprayed. The enamel surfaces were applied with self-etch adhesives and placed with composite resins (Adper Easy One + Filtek Z350 (3 M ESPE); Clearfil S3 Bond + Clearfil Majesty (Kuraray-Noritake Co.); G Bond + Gradia Direct (GC); iBond + Charisma (Heraeus-Kulzer)), respectively. The specimens were prepared for MTBS test and scanning/transmission electron microscopy observations. Compared with group A, groups B and C produced significantly higher enamel MTBS (p < .01), regardless of the adhesives used. Groups B and C possessed similar enamel MTBS (p > .05). The SEM findings showed that smear layer remained on the polished enamel surface was completely removed by acid etching and almost completely removed by prime-and-rinse approach. The TEM microphotographs reveal that smear layer was detectable at the resin-enamel interface in group A, not in groups B and C. The novel prime-and-rinse approach using MDP-containing primer before the application of (ultra-) mild self-etch adhesives could greatly increase the enamel MTBS. That might be an alternative to selective enamel etching.

Keywords:

• Prime-and-rinse approach
• bond strength
• self-etch adhesives
• MDP
• enamel

Acknowledgements

We thank Y. Xu and N. Rong for their assistance in experiments and characterizations. We are also grateful to associate professor Xiuyang Li, who provided all statistical analysis work for the study.

Disclosure statement

No potential conflict of interest was reported by the authors.

Additional information

Funding

This work was supported by the National Natural Science Foundation of China (grant no. 81801028 and 81371189) and Medical Scientific Research Foundation of Zhejiang Province, China (grant no. 2018KY502 and 2014PYA014).