| Summary: | This study is composed of three parts. The principal aim was to compare the rate of alignment ofthe upper and lower labial segments using conventional Omni, active In- Ovation R and passive Damon 3MX self-ligating brackets. The second part of this study was to investigate the rate of extraction space closure in the buccal segments for all subjects. The third and final element of this study was to investigate the efficiency of treatment for all three bracket types. 100 eligible subjects undergoing upper and lower fixed appliance treatment with the loss of four premolars were randomly allocated to one of three treatment groups: conventional (Omni) n=20, active (In-Ovation R) n=38 or passive (Damon 3MX) n=42 self-ligating brackets. Study models were taken for all subjects at the start and at twelve week intervals until completion of treatment. The same archwire sequence was used in each case. The labial segment alignment of each study model was measured using a digital Vernier calliper and Little's Index of Irregularity. Once alignment was achieved, space closure was carried out using 150g NiTi coil springs and once again measured using a digital calliper. Analysis of data using linear mixed models demonstrated a significant effect of bracket type on the rate of alignment in the mandible (p=0.026), but not the maxilla (p=0.277). In the mandible, rate of alignment was significantly greater with conventional brackets (Omni). There was no significant difference between the two self-ligating brackets. The rate of space closure was significantly faster in males when compared with females for both the In-Ovation R (p=0.001) and the Omni brackets (p=0.003). This was also found to be the case for Damon 3MX brackets although this was not shown to be statistically significant. The results demonstrated a significant difference between the conventional and the two self- ligating brackets in relation to the total chair side treatment time, with the Omni bracket subjects total treatment time taking on average 50 minutes longer. They also showed a significant difference in the total number of appointments between the In-Ovation R and the Omni bracket (p=0.0009), with the In-Ovation R requiring fewer appointments. In all other analyses there were no significant differences.
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