Influence of Vanillin at Different Concentrations on the Properties of Commercial Alginate Impression Materials: An in-vitro Study

Alginate is a widely used irreversible hydrocolloid impression material in dentistry because of its ease of use, affordability, and acceptable clinical performance. Modification of alginate with additives may alter its physical and mechanical properties. This study evaluated the effect of incorporating vanillin at different concentrations into two alginate impression materials, Zelgan and Neocolloid.

Vanillin was incorporated into Zelgan and Neocolloid alginate impression materials at concentrations of 0.5% and 1%. The materials were mixed with deionized water using a figure-of-8 motion for 45 seconds and moulded in polyvinyl chloride moulds to prepare specimens. Gel strength, permanent deformation, gelation time, flow, and tear strength were evaluated using standardized methods. Data were analyzed using the Shapiro-Wilk test for normality, followed by ANOVA or Kruskal-Wallis tests with appropriate post-hoc analyses. Between-group comparisons were performed using the independent-samples t-test or Mann-Whitney U test. Statistical significance was set at P < 0.05.

Two-way ANOVA showed significant main effects of alginate type and vanillin concentration on gel strength, gelation time, flow, and tear strength (all P<0.05), with Zelgan and Neocolloid differing significantly in gel strength, gelation time, and tear strength overall. A significant alginate × concentration interaction was found for gelation time and flow, indicating a material-dependent effect of vanillin on these properties, whereas gel strength and tear strength were affected by vanillin concentration similarly in both materials (no significant interaction). Permanent deformation was not significantly affected by alginate type, concentration, or their interaction. Tear strength was significantly greater at 1% vanillin than at control or 0.5% concentrations.

Vanillin reduced gelation time and flow in both materials, with the magnitude of reduction differing significantly between Zelgan and Neocolloid. Vanillin also significantly increased tear strength at 1% concentration, an effect that did not differ significantly between the two materials. Vanillin may therefore be a useful additive for modifying selected properties of irreversible hydrocolloid impression materials.