Evaluating fluoride releasing capacity of orthodontic sealants and their potential of recharge after fluoride application and to assess sealant's effect on tooth demineralisation when different fluoride recharge treatments are used

The purpose of this study is to evaluate in-vitro fluoride releasing capacity of Ortho Coat and its potential of recharge after fluoride application and to assess its effect on tooth demineralization when different fluoride recharge treatments are used. At the initial section of the first part of the study, fluoride release of 20 discs, prepared from Ortho Coat (O) and Pro Seal (P) materials, into artificial saliva for 56 days were measured by Ionized Selective Electrode method. In the second section, 80 discs prepared from the same surface sealants were divided into 10 groups, each consisting of 8 discs, after 1 week of decharging period. Fluoridated toothpaste was applied to P TP (Pro Seal-Toothpaste) and O TP (Ortho Coat-Toothpaste) groups, whereas P M (Pro Seal-Mouthrinse) and O M (Ortho Coat-Mouthrinse) groups received fluoridated mouthrinse. Fluoridated CPP-ACP was used in P MI (Pro Seal- MI Paste Plus) and O MI (Ortho Coat-MI Paste Plus) groups, while toothpaste and mouthrinse was applied to P TP+M (Pro Seal-Toothpaste and Mouthrinse) and O TP+M (Ortho Coat-Toothpaste and Mouthrinse) groups and toothpaste and fluoridated CPP-ACP was applied to P TP+MI (Pro Seal-Toothpaste and Mouthrinse) and O TP+MI (Ortho Coat-Toothpaste and Mouthrinse) groups. Toothpaste application was continued throughout 3 weeks while mouthrinse and fluoridated CPP-ACP application was stopped at the end of the first week. Fluoride release during 3 weeks was measured. In the second part of the study, brackets were bonded to 50 premolars, which were divided into 5 groups, using Transbond XT. No sealant or recharging agent was applied to control group (T) while Ortho Coat surface sealant was applied to the other groups. In addition to tooth brushing, mouthrinse was used in T+O+TP+M (Transbond+Ortho Coat+Toothpaste+Mouthrinse) group and CPP-ACP was used in T+O+TP+MI (Transbond+Ortho Coat+Toothpaste+MI Paste Plus) group for 1 week. Toothpaste application to all groups continued for 3 weeks, excluding T (Transbond) and T +O (Transbond+Ortho Coat) groups. Teeth were sustained in remineralization solution for 16 hours and demineralization solution for 7 hours. In each half of the crown, micro hardness measurements were performed at 200 μm cervically of the bracket, at depths of 20 μm, 30 μm, 50 μm and 70 μm. In the first part of the study, it was found that both surface sealants made significant fluoride release (p<0.001). While Ortho Coat made the highest fluoride release on the first day, significant decrease in terms of fluoride release was detected from day 3 to day 7 (p<0.01). Ortho Coat presented more fluoride release compared to Pro Seal in first three days, which was followed, by lesser release in last two weeks (p<0.05). Fluoride releasing levels of both Pro Seal and Ortho Coat showed statistically significant increase on the first day after application of all recharging agents (p<0.001). When Ortho Coat's maximum amount of fluoride release on day 1 was compared to that of O TP, O M, O MI, O TP+M and O TP+MI groups after recharge, statistically significant differences were found (p<0.01, p<0.001). In the second part of our study, comparison of micro hardness measurements of the groups at depth of 20 μm revealed that micro hardness values of the control group were significantly lower than that of all other groups (p<0,001). No significant difference was observed among other groups (p>0,05). To conclude, resin based surface sealant Ortho Coat shows significant decrease in terms of fluoride release after initial days. On the other hand, it has the capability of recharging with fluoride containing agents. Ortho Coat may protect the superficial layer of the enamel against demineralization, whereas additional recharging agents might be required for deeper layers.