Effect of pH Cycling on Different Restorative Materials and its Fluoride Release Through an Instant and non Destructive Method – OCT Evaluated

Objectives: The aim of this study was to evaluate the effect of pH cycling on bovine restored teeth, under optical attenuation coefficient (OAC) using optical coherence tomography (OCT), and the fluoride release of the restorations.
Methods: Cavities were prepared in 24 bovine incisors and divided into 3 groups (n = 8): conventional glass ionomer luting cement - Ketac^TM Molar Easymix; resin modified glass ionomer luting cement - Vitremer^TM; resin composite - Filtek^TM Z350. Restorations were submited to pH cycling (5 days, 6 hrs / demineralizing solution and 18 hrs / remineralizing solution; 2 days / remineralizing solution). Solutions were analyzed before and after the cariogenic challenge, and the fluoride releasing was calculated by an specific electrode (Orion 96-09) and an ion analyzer (Orion EA-940). OCT images obtained before and after pH cycling were analyzed by a specific software to obtain the OAC of two distances from the margin of the restoration: 0-200 and 200-400 micrometers. Intra-examiner agreement was considered excellent (0.97). Data were submitted to PROC MIXED for repeated measures and the Tukey-Kramer test (α = 0.05).
Results: OCT analysis showed no significant interaction between the factors material, cycling and distances. Regardless the material or distance, a significant difference was observed only between before and after pH cycling (p <0.0001). After cycling, OAC values increased, which indicates enamel demineralization. Fluoride releasing values indicated a statistical difference between the releasing rate of fluoride between the restorative materials (p <0.01) and the solutions (0.01 =
Conclusions: In conclusion, considering the values ​​of OAC, pH cycling affected the restored enamel independent of restorative materials, analyzed distances from the margin of the restoration and the fluoride releasing rate.