Objectives:To test the hypothesis that there is no difference in the cytotoxicity related to the modes of polymerization of five commercially available orthodontic bonding resins, with and without an oxygen-inhibited layer (OIL), and to evaluate the degree of conversion (DC) of these resins and correlate this to cytotoxicity. Materials and Methods: Five commercially available orthodontic bonding resins were tested for cytotoxicity and DC. Thirty-six disks of standardized dimensions, for each resin, were used for cytotoxicity assessment. Half of them were washed with 99% acetone to remove the OIL (washed resins), and the remaining disks were left intact (intact resins). Glass disks were used as a control. Vero cells were exposed to intact and washed resins on day 1. Cell viability was determined by tetrazolium bromide reduction assay 1, 3, and 6 days after exposure. The DC of the adhesive specimens of each resin, prepared with a procedure identical to the clinical bonding process, was assessed by Fourier transform infrared spectroscopy. Results: Single-cured systems were comparatively less cytotoxic than dual-cured systems. With removal of the OIL, increased cell viability was noted only with two resins on all three days. Resins tested showed differences in DC. A positive correlation was demonstrated by two resins. Conclusion:The hypothesis is rejected. Single-cured systems are superior to dual-cured systems in exhibiting comparatively less toxicity and higher DC. A significant positive correlation was not established between cytotoxicity and DC.

S mutans adhesion, surface roughness, and surface free energy were greater in Cu-NiTi than NiTi archwires. Surface roughness and surface free energy increased after 4 weeks of intraoral exposure for all of the archwires studied. A predominantly negative correlation was seen between the cycle threshold value of adherent bacteria and surface characteristics.

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To evaluate enamel colour change over a period of one year after the completion of fixed appliance treatment and to assess the influence of two different clean-up procedures and the resulting surface roughness. Materials and methods: Seventeen orthodontic patients were debonded and the residual resin removed using tungsten carbide burs followed by enamel polishing with Stainbuster burs or Sof-Lex discs in a split mouth design. A spectrophotometric colour evaluation was performed after clean-up (T0), polishing (T1), and one year later (T2). Colour parameters were measured and enamel colour change (ΔE) was calculated. Surface roughness was determined at T1 and T2 using epoxy replicas. Data were analysed using paired and unpaired t-tests and Pearson's correlation. Results: Significant differences in colour change and surface roughness caused by the polishing techniques at T1 were observed. However, this difference was not evident at T2 (p ˂ 0.05). Surface roughness and colour change showed no significant correlation. Conclusion: Enamel colour changed significantly when evaluated at T2 (one year post-orthodontic treatment). Stainbuster burs resulted in brighter and smoother teeth immediately after orthodontic treatment. The colour and surface roughness were not significantly different after one year and had no significant correlation.

The cleft team should be aware that the operated lip responds differently to incisor movement. This will enable them to better plan comprehensive treatment for the cleft lip and palate patient.