Sodium carbonate improves adherence of two-layer alginate for preliminary impressions of complete dentures

This in vitro study evaluated the effect of sodium carbonate (Na₂CO₃) concentration on adhesion between two layers of irreversible hydrocolloid wash impression material.

The first layer of irreversible hydrocolloid was brushed with three concentrations (0.1, 0.7, or 7.0 wt.%) of Na₂CO₃. Irreversible hydrocolloid not brushed with Na₂CO₃ was used as a negative control. Adhesion between the two layers (bond strength and adhesion energy) was then evaluated using a traction test, and the fracture modes were identified. The results of traction test were analyzed with a one-way ANOVA followed by a Tukey post hoc test. Chi-square test was used for analyzed failure mode after testing (α= 0.05).

The bond strength (0.034 ±0.005 MPa) and adhesion energy (60.240 ±12.817 J.m⁻ ²) of the 0.7% Na₂CO₃ group were significantly higher than those of the other groups (P< 0.05). The 0.7% Na₂CO₃ group displayed only cohesive failure (ײ= 16; P< 0.0001).

Conditioning the surface of the first layer of irreversible hydrocolloid with 0.7% sodium carbonate improved adhesion between the two layers and may help clinicians improve the quality of the preliminary impressions of removable complete dentures.