Scanning Electron Microscopy Evaluation of the Protective Effects of Fluoridated Dental Materials on Enamel Surface Morphology under Artificial Demineralization

The primary aim of this in vitro study was to compare enamel surface morphology following standardized artificial demineralization among five protective dental materials and an untreated control. Specifically, scanning electron microscopy (SEM) was used to characterize acid-exposed and wax-protected enamel regions and to compare five-point ordinal surface-preservation scores across the six experimental groups. Fifty-four human premolars extracted for orthodontic reasons provided 108 enamel surfaces. A 2 × 3 mm window was prepared on each surface, and specimens were randomly assigned to six groups (n = 18): control, APF gel containing 1.23 % fluoride ions, Enamel Pro Varnish containing 5 % sodium fluoride (NaF), Enamel Pro Prophy Paste with ACP, fluoride-releasing light-cured Pro Seal, and Duraphat containing 5 % sodium fluoride (NaF). Specimens were stored in artificial saliva and exposed to an artificial caries solution at pH 4.4 twice daily for 1 h over 30 days. After cycling, the surfaces were examined by SEM at ×500 and ×1500 magnifications. Images were morphologically classified and rated using a five-point ordinal surface-preservation scale, in which lower scores indicated better preservation. Data were analysed using the Kruskal–Wallis test followed by Holm-adjusted Dunn comparisons. Mean ordinal SEM scores were 5.00, 3.72, 2.06, 3.06, 3.50, and 3.56 for Groups A–F, respectively, with an overall group difference (H(5) = 68.32, p < 0.001). Enamel Pro Varnish had the lowest mean ordinal SEM score (2.06), although its difference from Group D was not statistically significant after Holm adjustment (p = 0.115). Although all treated groups had more favourable ordinal SEM scores than the control, none reproduced the SEM appearance of untreated sound enamel.