Effect of Fluoride on Mechanical Properties of Teeth Demineralized by Use of Orthodontic Appliances
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Effect of Fluoride on Mechanical Properties of Teeth Demineralized by Use of Orthodontic Appliances Claudia Centeno1, Ulises Ruiz1, Oscar Contreras and Enrique C. Samano, CCMC-UNAM, Ensenada, BC, México 1 Facultad de Odontología, UAEM, Toluca, Mex, México ABSTRACT The risk of dental caries increases with the use of orthodontic appliances, and it does not only depend on a patient’s oral hygiene. Caries cause teeth enamel demineralization close to the orthodontic bracket. The hardness of the teeth consequently decreases, and they become brittle and loose. The type of adhesive used to fix brackets may or may not reduce enamel demineralization. Previous studies have shown that a resin-modified glass ionomer (RMGI) inhibits demineralization. The purpose of this work is to evaluate the effect of a fluoridereleasing bracket on mechanical properties of dentin and enamel on regions adjacent to orthodontic brackets bonded with RMGI and composite resin cements. The remineralization effect due to fluoride on teeth was assessed by measuring hardness and reduced elastic modulus on dentin, enamel and dentin-enamel junction (DEJ) around the bracket area by nanoindentation methods. Nanoindentation was performed using a TriboScope from Hysitron. For this purpose two sets of polished samples were prepared: one sample was a cut along a longitudinal section and the other one along a cross-section of a tooth with orthodontic treatment using RMGI. Anisotropy in the mechanical properties of the teeth is observed along each direction. INTRODUCTION Orthodontic therapy with fixed intraoral appliances frequently makes the patient’s habitual oral hygiene more difficult. The accumulation of dental plaque adjacent to orthodontic appliances, like brackets, increases the risk of caries and white spot lesions at the end of the corrective therapy [1-4]. These white spots on tooth enamel are an indication of demineralization after the use of a fixed orthodontic appliance and occur in up to 50% of patients [5]. Although the combination of fluoride methods, e.g. toothpaste and mouth rinse, is efficient in the reduction of caries, the patient’s cooperation is essential [1, 6-9]. Therefore, alternative methods to reduce caries and mineralize dentin and enamel around the orthodontic appliances are needed. Dentin is a hard but porous tissue located under enamel, and dental enamel is the shiny, white outer surface of the tooth and the hardest biological substance in the human body. Enamel is a highly mineralized material mainly formed by millions of tiny hydroxyapatite crystals, which is a complex calcium phosphate mineral. A substantial number of mineral ions can be removed from the hydroxyapatite latticework without destroying its structural integrity; the tooth becomes soft and prone to fracture at the “white spot” without caries being present. However, such demineralized enamel transmits hot, cold, pressure and, eventually, pain to the patient much more readily than healthy enamel. Enamel demineralization is recognized as a possible side e
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