Enamel Demineralization around Orthodontic Brackets

Patients undergoing orthodontic treatment with traditional brackets frequently develop demineralization around the bonded bracket.  Materials have been developed to prevent demineralization.  Objective:  To measure acid gel demineralization around orthodontic brackets bonded to enamel when 2 gel/paste material were applied separately and in combination.  Methods:  50 extracted central incisors were etched with phosphoric acid for 15 secs, rinsed and dried.  Unitek Transbond XT light cure adhesive primer was applied.  Transbond XT light cure adhesive paste was applied to the bracket base and light cured for 40 seconds. The tooth was painted with nail polish leaving an exposed 2 mm window around the orthodontic bracket.  In group 1, fluoride gel was applied only, In group 2 MI paste was applied, for group 3 fluoride gel was applied first then MI paste, and group 4 had MI paste applied first followed by fluoride gel.  The teeth were submerged in an artificial caries solution composed of 0.1 M lactic acid, 10% gelatin, 3mM Ca₃(PO₄)₂ which was added to solution as CaCl₂ and KH₂PO₄, and 0.1% thymol. The pH of the solution was adjusted to 4.5 using NaOH.   Specimens were removed from the gel daily and topical gel/paste applied directly and allowed to remain on the teeth for 30 minutes, following manufacturer's instructions.  The gel/paste was wiped off and the teeth returned to the acid gel.  The teeth were sectioned, finished to 100 u sections, viewed with polarized light and the lesion depth recorded in microns. Mann Whitney U test was used.  Results: Lesion depth was significantly less when the fluoride solution was applied first followed by the MI paste compared to all other groups.  MI paste and MI paste followed by the fluoride were significantly worse than the other groups.  Conclusions:  Application of the fluoride preceding MI paste appears to enhance its remineralization potential.