Performance of a Metal Salt Based Enamel / Dentin Etchant

Objectives: Etching of dental hard-tissue with mineral/organic acids, especially phosphoric acid (“PA”) removes debris from cavity-preparation and creates micro-retentive enamel etch-patterns. However, bonding to PA-etched dentin is sensitive to degree of surface-moisture and may cause post-operative sensitivity by “over-etching”. To avoid such drawbacks, we present an alternative etchant (“ALE”) based on 10% ZrO(NO₃)₂ in aqueous-organic solution.
Methods: Shear-bond-strength (“SBS”, ISO-29022) to bovine enamel/dentin was tested after PA-etching (30s/15s; Total Etch, Ivoclar-Vivadent) or ALE-etching (15s/15s). Etched surfaces were rinsed with copious water-spray. Dentin surfaces were either blot-dried with tissue-paper (“wet”) or dried with air (4bar, 5s, “dry”). Enamel surfaces were always tested dry.
Adhesives (ExciTE F, “EXF”, Ivoclar-Vivadent; Prime&Bond NT, “PNT”, Dentsply; Adhese Universal, “AU”, Ivoclar-Vivadent) were employed according to instructions-for-use. TetricEvoCeram (Ivoclar-Vivadent) served as composite. Samples were aged 24h@37°C in water before testing (ZWICK-ROELL, 1mm/sec crosshead-speed).
PA-/ALE-etched enamel/dentin was investigated by SEM (5’000x magnification) for etch-pattern, smear layer and appearance of tubules.
Results: Same letters denominate statistical equivalence (ANOVA/Tukey-B, p<0.05).

Regardless of adhesive, SBS to dry enamel or wet dentin was comparable for ALE and PA. ALE-etched dry dentin gave significantly higher SBS with EXF and PNT than the PA-reference. SEM showed similar etch-patterns for PA/ALE-etched enamel. ALE-etched dentin was free of morphologies associated with the strong demineralization associated with PA-etching.
Conclusions: Adhesion to ALE-etched dentin proved more tolerant to surface-moisture than to PA-etched dentin. Both etchants gave comparable enamel SBS. Etching of enamel/dentin by ALE was verified by SEM. While etch-patterns on enamel were similar for PA and ALE, no over-etching by ALE were identified on dentin.