Influence of Four Different Orthodontic Bracket Prescriptions in Total Posterior Arch Width and Torque Expression

Subjects Seventy-six patients (31 men and 45 women) were recruited to participate in the clinical study and who fulfilled the inclusion and exclusion criteria. The inclusion criteria were: Presence of permanent dentition from the first permanent molar, from one side to the other, absence of anomalies in number, size and dental shape, no pre-treatment transversal discrepancies, equivalency in pre-treatment vertical relationships, good quality of study models, no medical contra-indications to the use of fixed appliances and good standard of oral hygiene.

The exclusion criteria were: Presence of oral habits. need to use of two band expansive appliances through the treatment, need of an orthodontic treatment with extractions or requiring orthognathic surgery as a part of their treatment. Subject age and gender were not taken as exclusion criteria, as these variables were not expected to influence the research outcomes.

Sample size calculation A pre-study sample size calculation was performed; power analysis showed that a sample size of at least 64 patients would provide an 80% probability of detecting a medium effect (f=0.2) associated with the interaction term, using an ANOVA model at a confidence level of 95% and assuming a correlation among repeated measurements of 0.5.

Study design: Orthodontic prescription techniques Subjects were chosen randomly and prospectively. Using sealed envelopes with the letters A to D, which corresponded to the 4 treatment groups, patients were parallelly randomly allocated according to the orthodontic bracket prescription of each particular technique so that patients each received either Prescription A (n=22): Mini-Taurus (Rocky Mountain); Prescription B (n=17): Smart Clip SL3 High Torque (3M Unitek); Prescription C (n=18): Tip-Edge Plus (TP Orthodontics); and Prescription D (n=19): Victory (3M Unitek). All underwent standard orthodontic treatments with good occlusal results.

Blinding Once the patient had been randomly allocated to one group or another, it was not possible to blind either the patient or the operator to the bracket type.