Rehardening of Eroded Enamel with CPP-ACFP Paste and CO2 Laser Treatment

Abstract

Background. Diet and lifestyle can destroy tooth structure due to the dissolution of enamel by acidic beverages. The present study evaluated the effect of CO2 laser irradiation and CPP-ACFP (casein phosphopeptide and amorphous calcium phosphate with fluoride) paste on the remineralization of enamel eroded by carbonated soft drinks. Methods. In the present in vitro study, 46 human sound premolar teeth were sectioned mesiodistally to achieve 84 samples. Fourteen samples were assigned to the positive control group (G1), and the remaining samples were immersed in 500 mL of cola drink for 2 minutes, followed by rinsing with distilled water for 10 seconds. This procedure was carried out three times to create erosive lesions. Then, the 60 eroded samples were randomly assigned to five groups of G2 to G6 in terms of the treatment as follows: negative control (G2), CO2 laser irradiation (G3), CPP-ACFP paste (G4), CO2 laser irradiation followed by CPP-ACFP paste application (G5), and CPP-ACFP paste application followed by CO2 laser irradiation (G6). The mean surface microhardness of the enamel surface was evaluated and determined at three points for each sample. Data were analyzed with one-way ANOVA and Tukey HSD tests ( $\alpha =0.05$ ). Results. The highest and the lowest hardness values were recorded in the G1 ( $314\pm 12$  kg/mm2) and G2 ( $213.7\pm 12$  kg/mm2) groups, respectively. ANOVA revealed significant differences between the study groups ( $P<0.001$ ). Two-by-two comparisons showed significant differences between the G2 group and the other groups, indicating the efficacy of all the treatment modalities in tooth remineralization and rehardening procedures ( $P<0.05$ ). Only in group G6, the enamel microhardness was not significantly different from the G1 positive control group ( $P>0.05$ ). Conclusion. Considering the parameters used in the present study, CO2 laser irradiation or CPP-ACFP paste application alone increased eroded enamel’s surface hardness; however, their sequential application was more effective in rehardening the eroded enamel’s surface to near-normal levels.