Analysis of Orthodontic Tooth Movement Using 3D Imaging

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.

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)