The effect of pretreatment with an oxalic acid solution on marginal adaptation to enamel in vivo

Abstract

Statement of problem. New acids such as oxalic acid have been introduced as a conditioning agent in the total-etch technique. There is concern about long-term retention of the acid on enamel in relation to the superficial etch effect. Purpose. This in vivo study evaluated the marginal adaptation to enamel conditioned with either an oxalic acid solution or a phosphoric acid with SEM replica technique. Material and methods. Twenty-four patients received one of each of three class III restorations. Two cavity preparations were pretreated with aluminum nitrate/oxalic acid/glycine solution 1 of the Gluma 2000 system. The first cavity was primed and sealed with Gluma 2000 solution 2, the second cavity with Gluma 3 and 4. The third cavity was conditioned with phosphoric acid (Gluma 1) and sealed with the bonding resin Gluma 4. All three cavities were restored with a hybrid resin composite (Pekafill). At baseline and after 1 year, replica impressions were made to study the margins with SEM. Semiquantitative analysis of the enamel interfaces was performed (×200 and ×1000 magnifications). Marginal quality of the three restorative systems were compared and tested intraindividually. Results. The three restorations exhibited good enamel marginal adaptation and a high percentage of gap-free margins at baseline, 96% to 97% of the total length of margins investigated. Marginal quality decreased significantly after 1 year for all three groups. Gap-free margins were observed in 81% to 85% of the marginal length. No significant differences were found among the groups. Conclusion. Despite a less pronounced etch pattern created by conditioning of enamel with the oxalic acid solution, a good enamel marginal quality was observed at both evaluation times, comparable to the marginal adaptation of the phosphoric acid conditioned cavities. (J Prosthet Dent 1998;80:75-80.)