Dentine decalcification and smear layer removal by different ethylenediaminetetraacetic acid and...

To compare solutions of di- and tetrasodium ethylenediaminetetraacetic acid (EDTA) and 1-hydroxyethane-1,1-diphosphonic acid (HEDP) regarding their ability to solubilize calcium from dentine and remove smear layer.

Solutions with a molarity corresponding to that of 17% Na₂ EDTA (pH adjusted to 8.5) were prepared by dissolving Na₂ and Na₄ salts of HEDP (etidronate), or Na₄ EDTA in deionized water. Standardized root dentine discs covered by a smear layer were prepared from human third molars. These discs (n = 10 per group) were immersed in test solutions or phosphate-buffered saline for 1 min. The dissolved Ca²⁺ was determined by atomic absorption spectroscopy, apparently opened dentinal tubules by laser scanning microscopy and automated image analysis. Ca²⁺ values were compared between groups by parametric, tubular areas by nonparametric methods, α = 0.05.

Solutions prepared from the tetrasodium salts were alkaline (pH 11.3-11.4), whilst counterparts made from the disodium salts were acidic. The EDTA solutions dissolved more calcium than the HEDP counterparts (P < 0.05); solutions prepared with the disodium salts dissolved more calcium than those made from the tetrasodium salts (P < 0.05). There was a high correlation between dissolved calcium and the apparently opened tubular areas (Spearman's ρ = 0.81). Differences between groups regarding opened tubules were similar to those observed regarding the Ca²⁺ values, with a slightly reduced discerning power due to high variance.

Calcium chelation and thus smear layer removal by EDTA and HEDP are influenced by pH.