ABSTRACT
Objective@#Preservation of the periodontal ligament (PDL) is vital to the success of tooth autotransplantation (TAT). Increased PDL volumes and facilitated tooth extraction have been observed upon orthodontic preloading. However, it is unclear whether any changes occur in the expressions of bone biomolecules in the increased PDL volumes. This study aimed to determine the expressions of runt-related transcription factor 2 (RUNX2), alkaline phosphatase (ALP), receptor activator of nuclear factor kappa-B ligand (RANKL), and osteoprotegerin (OPG) in PDL upon preloading. @*Methods@#Seventy-two premolars from 18 patients were randomly assigned to experimental groups that received a leveling force for 1, 2, or 4 weeks or to a control unloaded group. Following extraction, PDL volumes from 32 premolars of eight patients (21.0 ± 3.8 years) were evaluated using toluidine blue staining. The expressions of the biomolecules in the PDL from 40 premolars of ten patients (21.4 ± 4.0 years) were analyzed via immunoblotting. @*Results@#The median percentage of stained PDL was significantly higher at 2 and 4 weeks after preloading than in the unloaded condition (p < 0.05). The median RUNX2 and ALP expression levels were significantly higher at 2 and 4 weeks after preloading than in the unloaded condition (p < 0.05), whereas the median RANKL/OPG ratios were significantly higher at 1 and 4 weeks after preloading (p < 0.05). @*Conclusions@#Orthodontic preloading for 4 weeks enhances PDL volumes as well as the expressions of RUNX2, ALP and the RANKL/OPG ratio in the PDL, suggesting this loading period is suitable for successful TAT.
ABSTRACT
The use of miniscrew implants as an orthodontic anchorage device has become an accepted method for providing absolute anchorage. The purpose of this systematic review was to summarize the safe zones in the interradicular spaces and the recommended diameters and lengths of miniscrew implants for use in interradicular spaces. The PubMed electronic database was searched for original articles to the end of December 2009. The selection criteria were human anatomical studies, written in English, about the safe zones in the interradicular spaces for miniscrew implant placement. The final selection was completed after the author read the complete articles. Most of these studies measured the availability of interradicular space in patients without malocclusion, i.e. no severe crowding, no spacing, no missing teeth except the third molars, and no periodontal disease, by using CT images. In these studies, types of occlusion or dento-skeletal patterns of the samples were not specified. In the maxilla and mandible, all interradicular sites had adequate space for miniscrew implant placement; however, the areas with adequate interradicular space at each site presented at different distances from either the cemento-enamel junction or the alveolar crest. In the maxilla, the safest site was between the second premolar and the first molar. In the mandible, the safest sites were between the first and second molars or between the first and second premolars. The recommended miniscrew diameters ranged from 1.2 to 1.5 mm with the lengths ranging from 4.0 to 10.0 mm. Based on these results, an empirical clinical guideline can be provided. However, various malocclusions and dento-skeletal patterns, and individual variations must be considered.Keywords: anchorage, orthodontics, interradicular space, miniscrew implant
ABSTRACT
The use of reduced angle of insertion during miniscrew implant placement has been reported to increase the mechanical retention of miniscrew implants. However, the effects of the insertion angulation in the dentoalveolar bone have not been investigated. The purpose of this study was to investigate the effects of insertion angulation on the biomechanical performance of miniscrews implanted in the dentoalveolar bone. Three hundred and sixty self-tapping miniscrew implants (1.6 x 8 mm) (BMK, Seoul, Korea) were systematically inserted in fresh maxillary and mandibular dentoalveolar bone (anterior, middle and posterior sites) of minipigs at 30, 60 and 90 degrees to the bone surface, aided by a 3-D Surgical Guide (Y\&B Products, Chiangmai, Thailand). Maximum insertion torque and pullout strength were assessed with the Imada torque wrench and the Instron Universal Testing Machine, respectively. Results were recorded and analyzed by One way analysis of variance; ANOVA and Pearson correlation coefficients. It was found that maximum insertion torque and pullout strength had significant correlation (r = 0.81). In the maxilla, no significant difference in the maximum insertion torque and pullout strength was observed between miniscrews implanted at 30, 60 or 90 degrees. Although miniscrews inserted at 30 degrees exhibited the highest mechanical performance than those inserted at 60 and 90 degress in the anterior portion of the mandible, they exhibited significantly reduced insertion torque and pullout strength values than those inserted at 60 and 90 degress in the middle and posterior sites. No significant difference was observed between miniscrews inserted at 60 and 90 degrees. In conclusion, insertion angulation did not improve the mechanical performance of miniscrews implanted in the maxillary dentoalveolar bone. Reduced insertion angulation (30 degrees) was effective only in the anterior portion of the mandible.