Optical analysis of the behavior of sealants under mechanical, thermal and chemical stress

In vitro surface analysis of the brushing resistance of orthodontic sealants using two different profilometric evaluation methods

The enamel can be protected by applying orthodontic sealants at the bracket base to avoid the development of white spot lesions caused by inadequate oral hygiene. The aim of this study was to investigate the mechanical resistance of five commonly used orthodontic sealants against brushing in comparison to a positive group. Hydroxyapatite discs were bonded with a metal bracket and a piece of arch-wire was ligated in order to simulate a daily clinical situation (n = 48). Samples were divided into 6 groups of respectively 8 specimens. Sealants were applied around the bracket base according to manufacturer's instructions. Following sealants were used: Group 1: Pro Seal (Reliance Orthodontic Products, Itasca, Illinois, USA); 2: Light Bond (Reliance Orthodontic Products, Itasca, Illinois, USA); 3: ClinproXT Varnish (3M ESPE, Seefeld, Germany); 4: ProtectoCaF2 Nano (BonaDent GmbH, Frankfurt am Main, Germany); 5: Fluor Protector and 6: Tetric EvoFlow (both Ivoclar Vivadent AG, Schaan Liechtenstein). Tooth brushing were simulated for 6 weeks and 6 months with an electric toothbrush. The sealant thickness was measured by mechanical (MP) and optical profilometry (OP) at baseline, after 6 weeks and after 6 months of brushing. Statistical analysis was performed according to two mixed linear models and post hoc Tukey-Kramer comparisons. The significance level was set at 5% (α ≤ 0.05). Pro Seal (MP: 9%; OP: 22%) and Light Bond (MP: 19%; OP: 16%) showed the lowest changes in sealant thickness after 6 months of simulated brushing. ClinproXT Varnish and Tetric EvoFlow recorded no statistically significant results (p > 0.05). The fluoride varnishes ProtectoCaF2 Nano and Fluor Protector could not be conclusively evaluated since the thickness of the sealants could not be determined at baseline. The results of both evaluation methods MP and OP are in good agreement. Pro Seal and Light Bond were resistant against tooth brushing and were able to adequately keep the bracket environment sealed even after 6 months. The two different measuring methods, MP and OP, provide a precise impression of the changes in the surface.