Early tooth movement by a clear plastic appliance in rats
Nonglak P. Sombuntham, Siriwan Songwattana, Phumvuth Atthakorn, Sumon Jungudomjaroen, and Busaba Panyarachun
Faculty of Dentistry, and Faculty of Medicine, SrinakharinwirotUniversityBangkok, Thailand
This research is supported by Srinakharinwirot University Research Grant No.
033/2548
Ms. Ref. No.: AJODO-D-06-00612R2
Accepted : August 1, 2007
In : American Journal of Orthodontics & Dentofacial Orthopedics
Status: In press.
Abstract
This preliminary study investigated early histological changes of paradental tissues in response to a clear plastic appliance in rats. Fifteen rats were divided: Group I served as untreated controls; Group II received a clear plastic appliance made from a model of which the maxillary left first molar was repositioned mesially 0.5 mm. from the origin; Group III had a closed-coil spring to move the molar mesially. Specimens were prepared in parasagittal sections and changes in paradental tissues were evaluated on days 1, 4 and 7 by light microscopy. In Group II, the periodontal ligament (PDL) was compressed in the bifurcation and apical area of the roots of the molar. On day 7, PDL of apical and distal aspects of the roots and bifurcation presented with further compression whereby stretched PDL of the roots along the mesial side was noticed. In Group III, disorganized and compressed PDL in mesial cervical half and inter-radicular septum was observed whereas the stretched fibers presented at distal aspects of the roots after days 4 to 7. The results demonstrated that the early histological changes in respond to the clear plastic appliance were intrusion and distal tipping despite the intended mesial movement. In this rat model, the observed histological changes are subject to the direction and magnitude of forces actually generated by the clear aligner.
