Comparison of Biofilm Accumulation on Conventional and <scp>CAD</scp>/<scp>CAM</scp> Orthodontic Band Alloys (In Vivo) and Subsequent Enamel Demineralization (Ex Vivo)

Biofilm accumulation can lead to enamel decalcification, gingivitis, and periodontal disease. The objective of this study was to compare the accumulation of biofilm under in vivo conditions and consequent ex vivo acid production and enamel demineralization around the material used for "off-the-shelf" conventional and CAD/CAM orthodontics bands. The study design required both in vivo and in vitro approaches. An experimental model was utilized to combine the exposure of an in vivo formed biofilm to in vitro cariogenic conditions to achieve the objective. Twenty-one consenting participants took part in this study. Participants wore custom intraoral appliances containing six bovine enamel discs (three on each maxillary arch) for 48 h. Tiles made from conventional stainless steel bands (SS tiles group), CAD/CAM tiles made of Sintron cobalt-chromium (CoCr) sinter metal (Sintron tiles group), and no tile (control group) were randomly assigned to disc positions such that each appliance contained two tiles from each group (126 tiles in total). Participants immersed the appliances in sucrose solution (10% w/v) for 5 min, five times per day. After 48 h, appliances were removed, the discs were recovered, and incubated in glucose (1%)/PBS for 24 h. The pH of the glucose/PBS measured the relative acid produced by the accumulated biofilm, and calcium released from the discs quantified demineralization. Disclosing dye was used to stain and delineate the biofilm before each disc was digitally photographed and analyzed to determine the biofilm coverage. The mean biofilm coverage ranged between 0% and 86% (mean 9.63%) of disc surface area, but there was no difference in biofilm coverage between tile groups or between tile positions. Significantly less acid was generated by the control discs biofilms (mean pH 5.06) than either SS or CAD/CAM tiles biofilms (pH 4.72 and 4.84, respectively), which were not different from one another. Position on the appliance did not affect acid production. Control discs experienced greater demineralization (mean 136 μg Ca/disc) than either the SS (122 μg Ca/disc) or Sintron (114 μg Ca/disc) tile groups, which suffered equivalent demineralization. Position on the appliances did not influence demineralization. The study provides no evidence that CAD/CAM-designed components of orthodontic bands are more beneficial than conventional bands in terms of biofilm accumulation and consequent caries risk.