Pilot clinical trial of a calcium phosphate releasing orthodontic cement

Objective: Detectable decalcification (clinically observable as chalky lesions) may occur around bonded orthodontic appliances and can pose a permanent cosmetic dilemma.  Enamel demineralization during fixed orthodontic therapy is a rapid process caused by a cariogenic challenge involving plaque around the brackets.  This study examined whether a resin cement formulated with anhydrous dicalcium phosphate (DCPA) known to release calcium and phosphate, could reduce the incidence and severity of white spot lesions around orthodontic brackets and whether any changes of Streptococcus mutans abundance could be detected.  Methods: Orthodontic brackets, modified with an annulus to shelter peripheral plaque, were cemented to 38 paired teeth at least four weeks prior to planned extractions.  A split-mouth design was used: one bracket cemented with DCPA-filled resin cement and a contra-lateral one with inert silicate filler cement (both 60wt% in dental resins).  Plaque was collected from the periphery of each bracket at extraction.  S. mutans colonies were identified on glucose-sucrose-potassium tellurite-bacitracin (GSTB) agar by colony morphology.  Total facultative flora were counted on blood agar.  Microradiography and digital image analysis were used to quantitate mineral content in surface enamel beneath and peripheral to the brackets (at -64 µm, + 128 µm, +192 µm, +256 µm, and +320 µm from the lesion edge).  Results: An extremely high percentage of mutans streptococci was found relative to total recoverable CFU: control 73.3 ± 8.8 %; DCPA 73.2 ± 9.0 % (n.s., paired t-test; p = 0.893).  Percent mineralization was higher for the DCPA cement from 64 µm beneath to 256 µm peripheral to the brackets (t-test, p < 0.03). Conclusions: Under an aggressive cariogenic challenge all teeth developed lesions, but a higher relative percent mineralization was found for the DCPA group at distances up to 256 µm into the lesions. Supported in part by NIDCR DE 13298, the ADAF and NIST.