Morphometric and volumetric analysis of the proximity between the incisive canal and maxillary central incisors during anterior retraction: a retrospective cone-beam computed tomography study.

OBJECTIVES: To elucidate the relationships and factors affecting the proximity between the incisive canal (IC) and maxillary central incisors and to predict the probable outcomes after anterior tooth retraction using cone beam computed tomography (CBCT). MATERIALS AND METHODS: Retrospective CBCT data taken before and after maxillary anterior retraction in 36 patients were used in this study. The incisive canal length (ICL), maxillary central incisor length (TL), angles between the palatal plane and axes of the maxillary alveolar border (θ1), IC (θ2), and maxillary central incisor (θ3), retraction distance (TDE), distance from the maxillary central incisors to the IC (D), cross-sectional area of the IC (CSA), and volume of the IC were evaluated. Comparison of the parameters between contact and noncontact groups were examined. Logistic regression was performed to analyze the probable outcome prediction. RESULTS: All parameters significantly decreased after anterior retraction, except for the ICL. Eighteen roots in 12 patients contacted the IC. The θ1, θ2, θ3, and D values at all levels were significantly lower, whereas the TDE, midlevel and oral opening CSA, and volume were significantly higher in the contact group compared with the noncontact group. The larger the pretreatment θ1 and θ3 were, the higher was the chance of incisors not contacting the IC. CONCLUSIONS: Maxillary central incisors not contacting the IC after anterior retraction was positively associated with larger degrees of pretreatment maxillary alveolar bone angle and maxillary central incisor angle.

Effects of local vs systemic administration of CXCR4 inhibitor AMD3100 on orthodontic tooth movement in rats.

INTRODUCTION: Chemokines play pivotal roles in orthodontic tooth movement (OTM) through osteoclast-mediated bone resorption, but the underlying mechanism remains unclear. We aimed to elucidate the effects of serial local vs systemic administration of the chemokine receptor CXCR4 antagonist AMD3100 on OTM. METHODS: The maxillary first molar (M1) of rats was moved mesially using a 10 g of force nickel-titanium coil spring. The injections were performed every other day with phosphate-buffered saline as a control, whereas local and systemic animals were injected with AMD3100 at the buccal palatal mucosa adjacent to M1 and subcutaneously, respectively. OTM distance and alveolar bone were examined by microcomputed tomography and histologic analysis. Osteoclast numbers were quantified using TRAP staining. Cathepsin K and stromal cell-derived factor-1 (SDF-1) were evaluated using immunohistochemistry. Reverse transcriptase polymerase chain reaction for cathepsin K, Runx2, SDF-1, CXCR4, RANKL, and OPG were also examined. RESULTS: OTM and osteoclast numbers were significantly decreased in the local and systemic groups compared with the control group, whereas there was no significant difference among the experimental groups. Local administration inhibited molar but not incisor movement. Trabecular thickness and trabecular spacing of the alveolar bone significantly increased, and trabecular number significantly decreased in the systemic group compared with the control group, whereas local injection also affected bone quality in the same tendency as a systemic injection. AMD3100 significantly downregulated the mRNA expression levels of cathepsin K, Runx2, SDF-1, RANKL, and RANKL/OPG ratio in both experimental groups. CONCLUSIONS: Local administration of AMD3100 can control initial OTM and diminish bone resorption processes during OTM via inhibition of the SDF-1/CXCR4 axis, similar to the systemic administration.

Nuclear factor-kappa B decoy oligodeoxynucleotide-loaded poly lactic-co-glycolic acid nanospheres promote periodontal tissue healing after tooth replantation in rats.

BACKGROUND: Excessive inflammation in the periodontal tissue after tooth replantation can lead to inflammatory root resorption and interrupt periodontal tissue regeneration. We tested the hypothesis that nuclear factor-κB decoy oligodeoxynucleotide-loaded poly lactic-co-glycolic acid nanospheres (NF-PLGA) inhibit excessive inflammation and promote healing of periodontal tissue after replantation in rats. METHODS: The upper right incisors of rats were extracted, immersed in different specific solutions, and replanted. The rats were euthanized at 7, 14, and 28 days after replantation. Morphological evaluation with micro-CT and histological assessment with hematoxylin and eosin and tartrate-resistant acid phosphatase (TRAP) staining was performed. Additionally, we examined the expression of interleukin (IL)-1ß, IL-6, transforming growth factor-ß1 (TGF-ß1), and fibroblast growth factor-2 (FGF-2) in the periodontal ligament (PDL) by performing immunohistological assessment. RESULTS: The NF-PLGA group showed significantly greater dental root thickness than the other experimental groups. Root resorption was not observed after the application of NF-PLGA on day 7. The application of NF-PLGA also resulted in a significantly lower number of TRAP-positive osteoclasts on days 7 and 14 after replantation. Significantly lower expression of IL-1ß and IL-6 and higher expression of TGF-ß1 and FGF-2 were observed under the application of NF-PLGA in the PDL. CONCLUSIONS: NF-PLGA promoted the healing process by inhibiting the initial excessive inflammatory response in the PDL, preventing root resorption, and promoting periodontal tissue regeneration. The findings also suggested that the PLGA nanospheres-mediated transfection of the decoy oligodeoxynucleotides can be useful for the clinical application of replanted tooth root surfaces.