Influence of Four Orthodontic Bracket Prescriptions in Arch Width and Torque
Condition: Dental Arch Relationship Anomaly
Study type: Interventional

Summary: 
      The study compares torque and arch width changes between four different orthodontic bracket
      prescriptions and determine whether changes in dental torque are correlated to changes in
      arch width at the end of orthodontic treatment.

      From an initial sample of 250 patients who sought treatment at the Department of Orthodontics
      (University of Valencia, Spain), a subsample of 76 patients (31 men and 45 women) were
      selected to meet inclusion criteria.

      The sample was randomly allocated into four groups according to four different orthodontic
      bracket prescriptions: 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©); Prescription D (n=19): Victory® (3M Unitek©).

      Initial (T0) and final (T1) plaster and digital study models were available for all patients.
      Measurements were taken from frontal and occlusal images of the models by a single
      experienced operator.
    

Detailed description: 
      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.

      Settings All brackets had 0.22 inch slots. Since arch width is directly related to archwire
      form, the same arch form was used for all 4 techniques: Ovoid Arch FormOrthoForm III (3M
      Unitek). All patients followed the same archwire sequence starting with a 0.012 SE NiTi
      (superelastic niquel titanium) archwire, followed by a 0.016 SE NiTi, 0.016 x 0.025 SE NiTi
      and a 0.019 x 0.025 SE NiTi. The last wire used was a 0.019 x 0.025 inch stainless steel
      archwire. Two operators (C.G and N.Z) with the same background and experience treated the
      patients. The arch form was not modified during treatment by either expansion or contraction
      of the archwires. In all cases, stainless steel ligatures were used, except in technique C
      where the self-ligating system was applied.

      Measurements Occlusal and frontal digital models corresponding to all subjects' upper arches
      were taken from the initial and final plaster study models. Models were digitalized using the
      iTero Element digital scanning system. All the models were digitalized by the same operator
      under identical light conditions.

      All measurements were carried out by the same operator (B.T) using the Orthocad software. The
      operator registered the measurements as T0 (pre-treatment values) and T1 (post-treatment
      values).

      Occlusal images were used to measure intercanine, interpremolar and intermolar widths (mm)
      from initial (T0) and final (T1) study models. A specific protocol was used to take the
      following interarch width measurements before and after treatment:

      Intercanine width: distance between the cusp tips of bilateral canines. First interpremolar
      width: distance between the vestibular cusp tips of first bilateral premolars.

      Second interpremolar width: distance between the vestibular cusp tips of second bilateral
      premolars.

      Intermolar width: distance between mesiovestibular cusps of first bilateral molars.

      Frontal images were used for measuring torque (º) of bilateral canines, first premolars,
      second premolars, and molars from initial (T0) and final (T1) study models. The torque of
      maxillary arches was measured before (T0) and after (T1) treatment.

      Measurements were taken on the basis of:

      Reference lines: two reference lines were established.

        1. Horizontal line: line passing through the mesiovestibular cusps of right and left first
           superior molars.

        2. Vertical line: perpendicular to the former line, passing through the centre of the
           papilla between the two superior central incisors.

      Crown axis lines: parallel lines to the vestibular contour of the crowns of canines,
      premolars and molars, running from the vestibular cusp to the highest point of the gingival
      margin visible from the frontal projection.

      Torque measurements: The angle between the vertical line and the crown axis line of each
      tooth. Torque was measured and given a positive, negative or 0º value. Positive or negative
      values were assigned based on the clockwise or counterclockwise divergence of the lines,
      whereas a 0º value was assigned when they were parallel.

      Depending on the torque values at T0, variations in torque at T1 were classified as follows:

      Negative torque value: when higher negative values were measured at T0 than T1 (e.g. -5º at
      T0 and -2º at T1).

      Positive torque value: when higher positive values were measured at T0 than T1 (e.g. 5º at T0
      and 2º at T1).
    

Intervention name(s): Mini-Taurus® (Rocky Mountain©) Brackets; Smart Clip® SL3 High Torque (3M Unitek©); Tip-Edge Plus® (TP Orthodontics©); Victory® (3M Unitek©)
Intervention type(s): Device; Device; Device; Device
Allocation: Randomized
Intervention model: Parallel Assignment
Masking: Triple (Participant, Investigator, Outcomes Assessor)
Primary purpose: Treatment
Keywords: ARCH; TORQUE; BRACKET; PRESCRIPTION