Bonding Efficacy of Universal Adhesives to Fluorotic Enamel after Pre-conditioning with EDTA

To compare the effect of active pre-conditioning with 17% ethylenediaminetetraacetic acid (EDTA) vs 37% phosphoric acid (PA) on the resin-enamel microshear bond strength (µSBS), enamel-etching pattern, and in situ degree of conversion (in situ DC) of four universal adhesives on sound and fluorotic enamel.

In this study, 448 extracted human molars (224 without fluorosis and 224 with fluorosis) were sectioned into four parts and divided into 16 experimental groups based on the enamel surface (sound or fluorotic enamel), adhesive (Clearfil Universal Bond [CUB], Futurabond U [FBU], iBond Universal [IBU], or Scotchbond Universal [SBU]), and enamel conditioning agent (PA or EDTA). The specimens were stored for 24 h and tested under shear stress at 1.0 mm/min to determine the µSBS. The adhesive-enamel interfaces were evaluated for in situ DC using micro-Raman spectroscopy. The enamel-etching pattern was evaluated using a scanning electron microscope. The µSBS and in situ DC data were analyzed separately using three-way ANOVA and Tukey's post-hoc test (a = 0.05).

Sound enamel showed higher µSBS and in situ DC compared to fluorotic enamel (p < 0.05). However, no significant difference was observed for µSBS, in situ DC (p > 0.05), or etching patterns when PA and EDTA etching were compared in sound and fluorotic enamel. Moreover, CUB and SBU showed higher mean µSBS than did FBU and IBU in both sound and fluorotic enamel (p < 0.05).

Compared to PA, active pre-conditioning with EDTA showed similar µSBS and enamel etching patterns for all the adhesives in fluorotic enamel, without compromising the in situ DC.