Micro-tensile bond strength of a self-etching primer bonding system to fluorosed enamel

Primali R. Jayasooriya, BDS,(a) Kamal A. Wettasinghe, BDS, MS, FDSRCS,(b) Miwako Ogata, DDS, PhD,(a) Toru Nikaido, DDS, PhD,(a) and Junji Tagami, DDS, PhD(a)

(a)Cariology and Operative Dentistry, Department of Restorative Sciences, Graduate School, Tokyo Medical and Dental University, Tokyo, Japan, and (b)Department of Restorative Dentistry, Faculty of Dentistry, University of Peradeniya, Peradeniya, Sri-Lanka

Purpose: The aim of the study was to evaluate micro-tensile bond strength and the conditioning patterns of a self-etching primer bonding system to un-etched (with extended priming) and etched ground fluorosed enamel.
Materials and Methods: Extracted premolars were classified according to severity of fluorosis using Thylstrup and Fejerskov index (TFI: 0, normal; 1-3, mild fluorosis; and 4-6, moderate fluorosis) into three groups, which were again divided into four sub groups to receive different enamel conditioning. The ground enamel surfaces of the teeth in first and second sub groups were primed with a self-etching primer (SE primer, Clearfil SE Bond) for 60 and 90 s respectively prior to application of the adhesive. The teeth in the remaining sub groups were etched with 37% phosphoric acid (H3PO4) for 60 or 90 s prior to application of the self-etching primer bonding system according to the manufacturer’s instructions. All the teeth were then restored with resin composite, stored for 24 hours in water and prepared for micro-tensile bond strengths. The data were analyzed with analysis of variance (ANOVA) and Fisher’s PLSD test (p<0.05).
Results: Significantly higher micro-tensile bond strengths were observed when the self-etching primer bonding system was applied to etched ground fluorosed enamel (p<0.05) compared to un-etched enamel with extended priming. The bond strengths were significantly stronger in normal and mildly fluorosed enamel compared to moderately fluorosed enamel when etched for 60 s (p<0.05). Predominantly Type II etching pattern was observed in H3PO4 conditioned fluorosed enamel while relatively shallow etching pattern was seen in un-etched fluorosed enamel with extended priming.
Conclusion: Severity of fluorosis, etching time and pattern influence the bond strength of the self-etching primer bonding system to fluorosed enamel.
(Int Chin J Dent 2002; 2: 107-115.)

Clinical Significance
: Before application of self-etching primer bonding systems, H3PO4 conditioning is necessary to obtain high bond strength for fluorosed enamel.
Key Words: bond strength, enamel fluorosis, self-etching primer.