Hydroxyapatite-based cavitary varnish derived from eggshells: An in vitro analysis of dentin surface

Abstract

Objectives

We aimed to evaluate the effectiveness of a cavitary varnish containing an experimental eggshell-derived hydroxyapatite (HA) on dentin surfaces.

Methods

One hundred and twenty bovine dentin samples were prepared and randomly assigned to five groups: distilled water (DW); cavitary varnish (CV); Colgate® Sensitive Pro-Relief™ (CS); commercial HA NanoP™ (NP); and cavitary varnish with experimental HA. After treatment, samples were subjected to simulated brushing. Surface roughness, morphology, chemical composition, dentin tubule diameter, and permeability were evaluated. Data were analyzed using two-way analysis of variance with Bonferroni post-hoc test.

Results

HA samples without brushing exhibited the highest surface roughness. Scanning electron microscopy revealed complete dentinal tubule occlusion in HA samples, which persisted after brushing, whereas other groups showed partial occlusion or exposed tubules. Chemical analysis demonstrated lower phosphorus levels in HA samples without brushing, with an increase after brushing; NP and HA exhibited the highest phosphorus levels after brushing. DW samples showed the highest intertubular calcium levels, whereas CS samples showed the lowest levels after brushing. DW presented the largest tubule diameters without brushing, while brushing significantly increased the tubule diameters in all groups except DW group. Regarding dentin permeability, HA samples had significantly reduced hydraulic conductance compared with DW samples without brushing, with a performance comparable to commercial products; after brushing, no significant differences were detected among groups.

Conclusions

Eggshell-derived HA promoted complete and persistent dentinal tubule occlusion and significantly reduced the permeability, even after brushing, confirming its potential as a sustainable and cost-effective biomaterial for dental applications.