A randomized clinical trial of the effectiveness of 0.018-inch and 0.022-inch slot orthodontic bracket systems: part 3 - biological side-effects of treatment

Objective: To compare orthodontically induced inflammatory root resoprtion (OIIRR) and patient perception of pain during orthodontic treatment between 0.018-inch and 0.022-inch slot bracket systems. Subjects and methods: Eligible participants aged 12 years or over were allocated to treatment with the 0.018-inch or 0.022-inch slot MBT appliance (3M-Unitek, Monrovia, California) using block randomisation in groups of ten. OIIRR was assessed radiographically using standardised periapical radiographs before and after 9 months from the start of treatment. Patient perception of pain was assessed using a validated patient questionnaire at 6 months from the start of treatment. Parametric tests (t-test) and non-parametric tests (Chi-square with Fisher’s exact tests and Kruskal-Wallis test) assessed differences between the groups (P < 0.05). The correlation between severity of OIIRR and abnormal root morphology, history of dental trauma, and pain during treatment was assessed. Results: Of the 187 participants randomised (1:1 ratio), 34 withdrew or were excluded (protocol deviations or poor cooperation). There were 77 patients in the 0.018-inch slot group and 76 patients in the 0.022-inch slot group (overall mean age: 19.1 years). Baseline characteristics were similar between groups (P > 0.05). There was no significant difference in the severity of the OIIRR nor patient perception of pain between the two study groups (P=0.115 and P= 0.08 respectively). The correlation between the severity of OIIRR and abnormal root morphology or history of dental trauma was not statistically significant (P=0.086 and P=0.313). Moreover, there was no significant correlation between the severity of OIIRR and pain during treatment (R= 0.045, P=0.617). Limitations: It was impossible to blind clinicians or patients to allocation and oral hygiene and periodontal outcomes were not assessed. Conclusions: The effect of bracket slot size on the on the severity of OIIRR and patient perception of pain is not significant.