OBJECTIVE: Despite various X-ray approaches have been widely used
to monitor root resorption after orthodontic treatment, a non-invasive and
accurate method is highly desirable for long-term follow up. The aim of this
study was to build a non-invasive method to quantify longitudinal
orthodontic root resorption with time-lapsed images of micro-computed
tomography (micro-CT) in a rodent model.
MATERIALS AND METHODS: Twenty male Sprague Dawley (SD) rats (aged
6-8 weeks, weighing 180-220 g) were used in this study. A 25 g orthodontic
force generated by nickel-titanium coil spring was applied to the right
maxillary first molar for each rat, while contralateral first molar was
severed as a control. Micro-CT scan was performed at day 0 (before
orthodontic load) and days 3, 7, 14, and 28 after orthodontic load. Resorption
of mesial root of maxillary first molars at bilateral sides was calculated
from micro-CT images with registration algorithm via reconstruction,
superimposition and partition operations.
RESULTS: Obvious resorption of mesial root of maxillary first molar
can be detected at day 14 and day 28 at orthodontic side. Most of the
resorption occurred in the apical region at distal side and cervical region
at mesiolingual side. Desirable development of molar root of rats was
identified from day 0 to day 28 at control side. The development of root
concentrated on apical region.
CONCLUSIONS: This non-invasive 3D quantification method with
registration algorithm can be used in longitudinal study of root resorption.
Obvious root resorption in rat molar can be observed three-dimensionally at
day 14 and day 28 after orthodontic load. This indicates that registration
algorithm combined with time-lapsed images provides clinic potential
application in detection and quantification of root contour.
