A RANDOMIZED CLINICAL TRIAL ON ALIGNMENT EFFICIENCY AND DENTO-ALVEOLAR EFFECTS IN THE LOWER ARCH: SELF-LIGATING TIME 3 VS. ALEXANDER BRACKET SYSTEMS

Aim. The objective of this study was to perform a randomized clinical trial to evaluate the alignment efficiency and the dento-alveolar effect in the lower arch with two different bracket systems. Materials and methods. Twenty-five patients (14 females and 11 males) were selected in this study. The inclusion criteria were the following: age below 35 years at the start of treatment, permanent dentition, non extraction treatment in the upper and lower arch, irregularity index between 4 and 8 mm, no spaces and dental agenesis in the lower arch, no missing teeth, no previous orthodontic treatment. The subjects were randomly assigned to 2 groups: the first treated with self-ligating Time 3 brackets (MBT prescription- American Orthodontics) and the second with Alexander brackets (American Orthodontics). All the brackets had the same slot dimension.018. The mandibular incisor torque values for these brackets were – 6° for both bracket systems. The alignment efficiency was evaluated measuring the difference of irregularity index between T0 (at the beginning of treatment) and T3 (at the insertion of. 017 ×.025 inch stainless steel archwire), divided the time among the two measurement. The dento-alveolar changes after alignment as the intercanine and intermolar widths were measured on dental cast whereas the lower incisor proclination was estimated on cephalometric radiograph. All measurements were made by the same clinician. Results. By comparison of two bracket systems, no significant inter group differences (p<0.05) from T0 and T3 was found. The Time 3 group had a slightly higher mean time (7.5 weeks) compared with the Alexander group (6.2 weeks). The Time 3 group showed a greater expansion in the anterior and posterior areas of the lower arch. Intercanine and intermolar width increased respectively of 2.5 and 4.4 mm in the self- ligating group vs. 1.2 and 2.3 mm in the Alexander group. The incisor proclination was lower with Time 3 brackets. Conclusions. The use of self-ligating bracket system produced greater dento-alveolar effects than the Alexander group except for the lower incisor proclination.