Microhardness of MTA and SuperEBA in acid solutions

Objectives: Periapical inflammation and pH changes after endodontic surgery could affect hardening and final char- acteristics of retrograde filling materials. The present study analyzes the microhardness of two retrograde filling materials stored into different pH solutions. Materials and methods: 48 discs (24 per material) were pre- pared according to manufacturer instructions and randomly divided in 8 groups (n = 6); they were let harden for 1 (SuperEBA, Bosworth) or 24 h (MTA, Dentsply) into buffered solutions at different pH values (pH=7, pH=6, pH=5 and pH=3). After storage the upper surface of the specimens was polished using a 1200 (10 m) and 2400 (5 m) sandpaper. Microhardness was then measured with a Vickers indenter (VHMT 30, Leica). Collected data were statistically analyzed with Kruskal–Wallis and Conover tests (p < 0.05). Results: Mean hardness values (±SD) were: pH7, MTA=38.59±2.59, SuperEBA=18.46±5.38; pH6, MTA=3.61±0.76, SuperEBA=22.81 ± 5.16; pH5, MTA=4.02 ± 1.57, SuperEBA=20.65 ± 5.49; pH3, MTA=1.21 ± 0.47, Super EBA=21.69 ± 6.10 (data are expressed in HV). Conclusions: Within the limits of the present study MTA showed high sensibility to decreasing pH of the environment, although at pH 7 it showed the greatest microhardness val- ues. SuperEBA maintained constant or increased its hardness with increasing acidity. The pH of the surgical site seems to be relevant for retrograde filling materials, thus postsurgical inflammation should be kept under control.