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. 2018 Jan/Feb;43(1):101-110.
doi: 10.2341/16-136-L.

A Novel Enamel and Dentin Etching Protocol Using α-hydroxy Glycolic Acid: Surface Property, Etching Pattern, and Bond Strength Studies

D Cecchin, A P Farina, Cmp Vidal, A K Bedran-Russo

A Novel Enamel and Dentin Etching Protocol Using α-hydroxy Glycolic Acid: Surface Property, Etching Pattern, and Bond Strength Studies

D Cecchin et al. Oper Dent. 2018 Jan/Feb.

Abstract

Objectives: To determine the use of α-hydroxy glycolic acid (GA) as a surface pretreatment for dental restorative applications. The etching pattern of GA pretreatment of dental hard tissues was assessed by surface microhardness and scanning electron microscopy (SEM). The effectiveness of GA surface etching on the enamel and dentin resin bond strengths was assessed using two etchant application modes (rubbing and no rubbing) and three adhesive systems (Single Bond [SB], One Step Plus [OSP], and Scotchbond Universal [SBU]).

Methods: Knoop microhardness measurements were carried out on polished enamel and dentin surfaces before and after treatment with 35% GA, 35% phosphoric acid (PA), or distilled water (control group) for 30 seconds. The microtensile bond strength test was carried out on enamel and dentin. Ultrastructural analysis of the surface and interfacial interaction was qualitatively accomplished using SEM.

Results: Etching with either PA or GA significantly decreased the enamel microhardness, with GA being significantly less aggressive than PA ( p<0.001), while both acids showed similar decreases in dentin microhardness ( p=0.810). SEM revealed similar etching patterns of GA and PA, while apparently a thinner hybrid layer was observed for GA groups. In dentin, the bond strengths were statistically similar between PA and GA groups, regardless of the etchant application mode ( p>0.05). However, rubbing of GA enhanced the bond strength to enamel. PA and GA significantly increased the SBU bond strength to enamel when compared to SB and OSP ( p<0.05).

Conclusions: GA effectively etched enamel and dentin surfaces, resulting in bond strength values similar to those associated with traditional PA. GA is a suitable enamel and dentin surface etchant for adhesive restorative procedures.

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Conflict of interest statement

The authors declare no potential conflicts of interest with respect to either the authorship or publication of this manuscript.

Figures

Figure 1
Figure 1
Micromorphology of enamel and dentin surfaces. (a) PA no rubbing in enamel. (b) PA rubbing in enamel. (c) GA no rubbing in enamel. (d) GA rubbing in enamel. (e) PA no rubbing in dentin. (f) PA rubbing in dentin. (g) GA no rubbing in dentin. (h) GA rubbing in dentin.
Figure 2
Figure 2
Representative micrographs of resin-enamel interfaces for the different strategies (PA and GA etching; rubbing and no rubbing) and of three adhesive systems (SB, OSP, and SBU). (a) PA no rubbing and SB. (b) PA rubbing and SB. (c) GA no rubbing and SB. (d) GA rubbing and SB. (e) PA no rubbing and OSP. (f) PA rubbing and OSP. (g) GA no rubbing and OSP. (h) GA rubbing and OSP. (i) PA no rubbing and SBU. (j) PA rubbing and SBU. (k) GA no rubbing and SBU. (l) GA rubbing and SBU. A = adhesive layer; C = composite resin; E = enamel; the adhesive/enamel interface is indicated by arrows.
Figure 3
Figure 3
Micrographs of resin-dentin interfaces for the different strategies (PA and GA etching; rubbing and no rubbing) and of three adhesive systems (SB, OSP, and SBU). (a) PA no rubbing and SB. (b) PA rubbing and SB. (c) GA no rubbing and SB. (d) GA rubbing and SB. (e) PA no rubbing and OSP. (f) PA rubbing and OSP. (g) GA no rubbing and OSP. (h) GA rubbing and OSP. (i) PA no rubbing and SBU. (j) PA rubbing and SBU. (k) GA no rubbing and SBU. (l) GA rubbing and SBU. A = adhesive layer; C = composite resin; D = dentin; H = hybrid layer; T = resin tag.
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