Microhardness, Structure, and Morphology of Primary Enamel after Phosphoric Acid, Self-Etching Adhesive, and Er:YAG Laser Etching

Abstract EN

Background.

Phosphoric acid is the traditional etching agent; self-etching adhesives and Er:YAG laser are alternative methods.

Knowledge of deciduous enamel etching is required.

Aim.

To evaluate primary enamel microhardness, structure, and morphology after phosphoric acid, self-etching, and Er:YAG laser etching.

Design.

Seventy primary incisors were assigned to five groups (n=14): I (control), II (35% phosphoric acid), III (self-etching adhesive), IV (Er:YAG laser at 15 J/cm2), and V (Er:YAG laser at 19.1 J/cm2).

Microhardness was evaluated by Vickers indentation.

Chemical composition was analyzed by energy dispersive X-ray spectroscopy and morphological changes by scanning electron microscopy.

One-way ANOVA, Kruskal–Wallis, Mann–Whitney U, and Pearson bivariate correlation were employed (α=0.05).

Results.

Vickers microhardness showed differences and no correlation with Ca/P ratio.

Group II showed differences in carbon, oxygen, and phosphorus atomic percent and group V in Ca/P ratio.

Morphological changes included exposed prisms, fractures, craters, and fusion.

Conclusions.

Enamel treated with phosphoric acid showed different chemical characterization among groups.

Self-etching and Er:YAG laser irradiation at 19.1 J/cm2 showed similar microhardness and chemical characterization.

Er:YAG laser irradiation at 15 J/cm2 maintained microhardness as untreated enamel.

Er:YAG laser irradiation at 19.1 J/cm2 enhanced mineral content.

Morphological retentive changes were specific to each type of etching protocol.