Animal Study on Early Tooth Movement after Ramus Osteotomy

Abstract

Introduction: The purpose of the present study was to observe whether mandibular ramus osteotomy, remote from dental apparatus, has any cellular or molecular influences on tooth movement at an early stage in a rabbit model. Methods: Eighteen male New Zealand white rabbits (4.0 kg body weight) were allocated into 3 groups: Group 1 - tooth movement without operation (n = 6), Group 2 - tooth movement with sham operation (n = 6) and Group 3 - tooth movement with ramus osteotomy (n = 6). In all of the three groups, only the right teeth were moved with NiTi (Nickel Titanium) closed coil spring. The amount of tooth movement was measured by the distance only between the right incisor and the right first molar. At 5 (T1), 7 (T2), and 14 days (T3) two rabbits were sacrificed from each group. The numbers of osteoclasts were counted on vertical sections of alveolar bone in four areas including the compression sides of the right loaded teeth and the left unloaded teeth. Relative quantitation of mRNAs by real time reverse transcription-polymerase chain reaction (PCR) was performed for receptor activator of nuclear factor κB ligand (RANKL), osteoprotegerin (OPG), interlukin (IL)-1α, IL-1β, IL-6, and tumor necrosis factor (TNF)-α at T2 and for RANKL and OPG at T3 in four areas of alveolar bone as for osteoclast counting. Results: Although Group 3 manifested the highest distance of tooth movement (total 5.05 mm), there was no significant difference among groups. There was no significant difference in the number of osteoclasts for the right incisor and the right first molar in all three groups at T1, T2, and T3. However at T1, there was a marginally significant difference only for the right incisor in all groups (p = 0.052). On the left side there was no significant difference among groups for the incisor and first molar, respectively. At T3, there was a significant difference in RANKL for the right first molar (Group 3 > 1 > 2, p < 0.05). At T2 and T3, there was no consistent results in level of OPG in all groups. At T2, there was no significant difference in IL-1α, IL-1β, IL-6, TNF-α in all four sites. Conclusions: The present study suggests that the orthognathic surgical regimen (mandibular ramus osteotomy) has some influences on molecular change in alveolar bone adjacent to the osteotomy site at an early stage of tooth movement in a rabbit model.