Evaluation of CO₂ Laser Irradiation and Fluoride Application on the Acid Resistance of Hydroxyapatite Granules

Abstract

This study evaluated the acid resistance of CO₂ laser irradiation and fluoride application for hydroxyapatite (HA) granules.
HA granules samples were divided into the following four groups. Specimens of group L were irradiated vertically by CO2 laser (10.6μm) with 1W (46.2J/cm²) output power at a repeated pulse mode (pulse length 0.5 second). Those of group F were treated with acidulated phosphate fluoride (APF) solution for 30 minutes. Those of group L-F were treated with APF solution after CO₂ laser irradiation. Those of group C were not treated and were used as a control.
All specimens were individually immersed in 5ml acetate buffer solution (0.2M, pH4.2) at 37°C for 2 hours, then each specimen was centrifuged (1500 rpm, 10 minutes). The calcium content of the supernatant was measured using the ortho-cresolphthalein complexone method, and its fluoride content was measured using an ion meter for groups F and L-F.
The calcium elution rates of groups L, F, and L-F were significantly lower than that of group C (ANOVA; scheffe: p<0.01). The fluoride content of group L-F was significantly lower than that of group F (Student's t-test: p<0.01).
It was suggested that CO₂ laser irradiation (group L), APF solution treatment (group F), and combination of CO₂ laser irradiation and APF solution treatment (group L-F) are effective for acid resistance. The results suggest that this study model is useful for the evaluation of acid resistance.