Comparison of compressive strength, surface microhardness, and surface microstructure of different types of bioceramics following varying surface treatments

Abstract

This study aimed to evaluate the compressive strength, surface microhardness, and surface microstructure of different calcium silicate-based bioceramics following acid etching and subsequent adhesive application. Four bioceramic materials—Biodentine, NeoMTA Plus, NeoPUTTY, and TheraCal LC—were tested. A total of 36 specimens per material were prepared for both compressive strength and surface microhardness testing. Specimens were randomly assigned to three groups (n = 12) based on surface treatment: no treatment (control), acid etching with phosphoric acid, and acid etching followed by adhesive application. Data were analyzed using two-way ANOVA and the Tukey HSD test. In addition, scanning electron microscopy (SEM) and energy-dispersive X-ray spectroscopy (EDX) were performed to evaluate the surface microstructure and Ca/Si ratio of each material following acid etching. Both compressive strength and surface microhardness were significantly influenced by surface treatment and bioceramic type (p < 0.01). TheraCal LC exhibited the highest compressive strength across all surface treatment conditions, while Biodentine showed the highest surface microhardness values (p < 0.05). Acid etching significantly reduced the compressive strength of TheraCal LC, Biodentine, and NeoMTA Plus, whereas adhesive application improved the compressive strength of Biodentine. Surface microhardness decreased after acid etching and increased following adhesive application for all materials tested (p < 0.05). SEM-EDX analysis revealed a decrease in the Ca/Si ratio on the surface of all bioceramics after acid etching. TheraCal LC demonstrated the highest compressive strength under all conditions, followed by Biodentine. Biodentine consistently showed superior surface microhardness, regardless of the surface treatment applied.