Analysis of Orthodontic Tooth Movement Using 3D Imaging

Purpose: This project aims to study the effects of wire dimension and ligation method (bracket type) on the first stage of orthodontic treatment using 3D imaging. Participants: Up to 80 patients at UNC School of Dentistry or Selden Orthodontics between the ages of 10 and 45, inclusive, who have been previously diagnosed with malocclusion requiring orthodontic treatment (braces) and are otherwise healthy. Procedures (methods): Subjects receiving standard of care (SOC) orthodontic treatment will be randomized to one of two commonly used orthodontic archwires (.014" or .016" diameter). Subjects will be further subdivided for analysis based on the type of bracket (twin or self-ligating) that their clinician uses in their treatment. We will review the 3D digital images of each subject's dentition recorded as part of SOC at the 0-, 6- and 12-week visits. We will retrieve the archwires when they are removed per SOC by the clinician at the 12-week time point.

Many archwire dimensions and two main bracket types (twin and self-ligating) are available to orthodontists for the first stage of orthodontic treatment, but little objective clinical evidence is available to indicate which archwire dimension and bracket type is ideal for a given patient with an individual type and degree of malalignment during this stage. A limited clinical trial will be conducted to collect and analyze this data. The aim of this study is to study the effect of wire dimension, timing and ligation method on leveling and aligning in orthodontic treatment using 3D imaging. The study's specific aims are as follows: To analyze the effect of wire dimension (.014" vs. .016") and time-course (first six weeks or second six weeks) on Stage I treatment To correlate clinical tooth movements with bench data for four types of malalignment In-out Rotation Tip Vertical step To analyze the effect of ligation method (twin vs. self-ligating) on Stage I treatment These specific aims will serve to address the following hypothesis: Archwire dimension affects tooth movement in Stage I of orthodontic treatment, depending upon variation time-course (due to force decay of superelastic wires) and method of ligation (bracket type). This will be tested in a total of 80 patients who are undergoing active treatment in the University of North Carolina (UNC) orthodontic graduate clinic or at Selden Orthodontics. There will be four different groups in this study. In the twin bracket cohort, half the patients will be treated with .014" dimension wire and half will be treated with .016" dimension wire. In the self-ligating bracket cohort, half the patients will be treated with .014" dimension wire, and half will be treated with .016" dimension wire. If the hypotheses are shown to be correct, then the subset of society receiving orthodontic treatment will be able to benefit from selection of bracket types and archwire dimensions that match their individual types and degrees of malalignment. This will allow for more efficient tooth movement with less unwanted movement, and could lead to shorter treatment times and less discomfort.

There will be four different groups in this study, with each planned to consist of 20 patients (40 dental arches). In the twin bracket cohort, 40 dental arches are planned to be treated with .014" dimension wire, and 40 dental arches are planned to be treated with .016" dimension wire. In the self-ligating bracket cohort, 40 dental arches are planned to be treated with .014" dimension wire, and 40 dental arches are planned to be treated with .016" dimension wire.

Neither subjects nor the treating orthodontists will know whether a .014" or 0.16" dimension wire is being used. The investigator will assign wire dimensions using a random number generator and distribute the wires to the treating orthodontists with the archwire dimension number removed from the package. The outcomes assessor will be blinded as to which patients were treated with which archwires while analyzing the digital models of the teeth. Because there is a clear visual difference between twin and self-ligating brackets, there will be no blinding with regard to ligation method (bracket type).

.014" dimension CuNiTi orthodontic arch wires and .022" slot Ormco Insignia SL (self-ligating) brackets.

.016" dimension CuNiTi orthodontic arch wires and .022" slot Ormco Insignia SL (self-ligating) brackets.

Little's Index measures the distance between contact points on adjacent teeth. Little's Index will be measured at two time points (0 weeks and 6 weeks).

Little's Index measures the distance between contact points on adjacent teeth. Little's Index will be measured at two time points (6 weeks and 12 weeks).

Clinical linear measurements (mm) in x-, y-, and z-translation will be measured at two time points (0 weeks and 6 weeks) to determine the linear (translational) change in tooth position during that time.

Clinical linear measurements (mm) in x-, y-, and z-translation will be measured at two time points (6 weeks and 12 weeks) to determine the linear (translational) change in tooth position during that time.

Clinical angular measurements (degree) in x-, y-, and z-rotation will be measured at two time points (0 weeks and 6 weeks) to determine the angular (rotational) change in tooth position during that time.

Clinical angular measurements (degree) in x-, y-, and z-rotation will be measured at two time points (6 weeks and 12 weeks) to determine the angular (rotational) change in tooth position during that time.

A repeated measure linear regression model conducted to evaluate any correlation between the degrees of malalignment and the rate of tooth movement.

Inclusion Criteria: In the initial stage of active treatment at the University of North Carolina graduate orthodontic clinic or Selden Orthodontics Non-extraction treatment Maxillary and mandibular Little Index between 1-15 mm (this is a measurement of crowding) Presence of all permanent anterior teeth Age 10-45 years Consent to participate in the study Exclusion Criteria: Systemic diseases such as diabetes, hypertension, temporomandibular disorders (TMD), craniofacial syndrome, etc. Any spacing between anterior teeth Subjects who have incisor mandibular plane angle (IMPA) greater than or equal to 100 degrees Anterior tooth completely blocked from the arch form Periodontal pocketing of any teeth greater than 4 mm Maxillary and mandibular Little Index >15 mm (This is a measurement of crowding. A Little Index of >15 mm indicates a need for a smaller dimension arch wire)