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.

Relationship between mandibular symphysis dimensions and mandibular anterior alveolar bone thickness as assessed with cone-beam computed tomography.

OBJECTIVE: To determine the relationship between symphysis dimensions and alveolar bone thickness (ABT) of the mandibular anterior teeth. METHODS: Cone-beam computed tomography images of 51 patients were collected and measured. The buccal and lingual ABT of the mandibular anterior teeth was measured at 3 and 6 mm apical to the cemento-enamel junction (CEJ) and at the root apices. The symphysis height and width were measured. The symphysis ratio was the ratio of symphysis height to symphysis width. Kendall's tau correlation coefficient was used to determine the relationships between the variables at a 0.05 significance level. RESULTS: The mandibular anterior teeth lingual and apical ABT positively correlated with symphysis width (p<0.05). Moreover, these thicknesses negatively correlated with the symphysis ratio (p<0.05). Symphysis widths and ratios showed higher correlation coefficients with total and buccal apical ABT, compared with lingual ABT. Buccal ABT at 3 and 6 mm apical to the CEJ was not significantly correlated with most symphysis dimensions. The mean thickness of the buccal alveolar bone at the upper root half was only 0.2-0.6 mm, which was very thin, when compared with other regions. CONCLUSION: For mandibular anterior teeth, the apical alveolar bone and lingual alveolar bone tended to be thicker in patients with a wide and short symphysis, compared to those with a narrow and long symphysis. Buccal alveolar bone was, in general, very thin and did not show a significant relationship with most symphysis dimensions.

Relationship between mandibular symphysis dimensions and mandibular anterior alveolar bone thickness as assessed with cone-beam computed tomography

ABSTRACT Objective: To determine the relationship between symphysis dimensions and alveolar bone thickness (ABT) of the mandibular anterior teeth. Methods: Cone-beam computed tomography images of 51 patients were collected and measured. The buccal and lingual ABT of the mandibular anterior teeth was measured at 3 and 6 mm apical to the cemento-enamel junction (CEJ) and at the root apices. The symphysis height and width were measured. The symphysis ratio was the ratio of symphysis height to symphysis width. Kendall's tau correlation coefficient was used to determine the relationships between the variables at a 0.05 significance level. Results: The mandibular anterior teeth lingual and apical ABT positively correlated with symphysis width (p<0.05). Moreover, these thicknesses negatively correlated with the symphysis ratio (p<0.05). Symphysis widths and ratios showed higher correlation coefficients with total and buccal apical ABT, compared with lingual ABT. Buccal ABT at 3 and 6 mm apical to the CEJ was not significantly correlated with most symphysis dimensions. The mean thickness of the buccal alveolar bone at the upper root half was only 0.2-0.6 mm, which was very thin, when compared with other regions. Conclusion: For mandibular anterior teeth, the apical alveolar bone and lingual alveolar bone tended to be thicker in patients with a wide and short symphysis, compared to those with a narrow and long symphysis. Buccal alveolar bone was, in general, very thin and did not show a significant relationship with most symphysis dimensions.

RESUMO Objetivo: o objetivo desse artigo foi avaliar a correlação entre as dimensões da sínfise e a espessura do osso alveolar (EOA) na região anterior da mandíbula. Métodos: imagens de tomografia computadorizada de feixe cônico (TCFC) de 51 pacientes foram selecionadas e medidas. As EOAs vestibular e lingual dos dentes anteroinferiores foram medidas a 3 mm e a 6 mm para apical da junção cemento-esmalte (JCE) e nos ápices radiculares. A altura e a largura da sínfise foram medidas, e calculou-se a proporção entre ambas, chamada de proporção da sínfise. O coeficiente de correlação tau de Kendall foi utilizado para determinar a correlação entre as variáveis, com nível de significância de 0,05. Resultados: as EOAs vestibular e lingual dos dentes anteroinferiores apresentaram correlação positiva com a largura da sínfise (p< 0,05). Porém, essas EOAs apresentaram correlação negativa com a proporção da sínfise (p <0,05). A largura e a proporção da sínfise apresentaram maiores coeficientes de correlação com a EOA total e vestibular apical e, em comparação com a EOA lingual. A EOA vestibular a 3 mm e a 6 mm para apical da JCE não apresentou correlação significativa com a maioria das dimensões da sínfise. A espessura média do osso alveolar vestibular na metade superior da raiz foi de apenas 0,2 a 0,6 mm - muito delgada quando comparada com outras regiões. Conclusão: nos dentes anteroinferiores, o osso alveolar apical e o osso alveolar lingual tendem a ser mais espessos nos pacientes com sínfise mais larga e curta, em comparação àqueles com sínfise mais estreita e longa. O osso alveolar vestibular foi, em geral, muito fino e não apresentou relação significativa com a maioria das dimensões da sínfise.

Effect of the inclination of a maxillary central incisor on periodontal stress: finite element analysis.

OBJECTIVE: To determine the effect of labiolingual inclination of a maxillary central incisor on the magnitude and distribution of stresses within the periodontal space. MATERIALS AND METHODS: Five three-dimensional finite element models of a right maxillary central incisor were created with 0°, 10°, 20°, 30°, and 40° inclination. Each incisor model was subjected to a 1 N lingual-directed force and 6-12 N·mm countertipping moment on the labial surface. The stress level within the periodontal ligament was calculated in terms of maximum principal stresses. RESULTS: With increased inclination, compressive stresses tended to increase whereas tensile stresses tended to decrease. The location where compressive stress was prevalent changed from the midroot area to the apical area on the lingual side, while the area where tensile stresses were predominant changed from the midroot area to the cervical area on the labial side. CONCLUSION: There are more compressive stresses concentrated at the apex of incisors with a high degree of inclination than in incisors that are more upright. This may be associated with the higher clinical incidence of apical root resorption found in inclined maxillary central incisors.