Influence of bisphosphonates on alveolar bone density: a histomorphometric analysis

This study is a histomorphometrical analysis of the influence of the bisphosphonate alendronate on alveolar bone density. Eighteen male Wistar rats were randomly assigned to a control group (n = 9) that received no medication and an experimental group (n = 9) that received oral alendronate (1 mg/kg) from birth until euthanization at 3 months of age. Semi-serial 4-µm-thick transverse sections were obtained from the region between the roots of the left maxillary first molar, stained with hematoxylin and eosin, and examined with a Zeiss Axioskop II optical microscope for histomorphometric analysis. The images were captured with a digital camera coupled with the microscope and connected to a computer, and were analyzed using Image J 1.34s image-analysis software. A 1,200-point grid was positioned onto each digitized image. The number of intersection points of grid lines in the bone tissue was counted. The ratio between the number of points in the bone tissue and the total number of points of the grid (1,200) was used to determine the bone density of the analyzed tissue. Data from the control and experimental groups were compared and analyzed statistically by the Student's t-test (p = 0.05). There was no statistically significant difference (p = 0.3754) in the alveolar bone density between the control and alendronate-treated animals. It may be concluded that the bisphosphonate alendronate did not alter the morphology of the alveolar bone, maintaining its structural tissue characteristics in healthy animals.

Movimentação dentária experimental em murinos: período de observação e plano dos cortes microscópicos / Experimental tooth movement in murines: study period and direction of microscopic sections

OBJETIVO: este trabalho tem por finalidade explicitar aspectos microscópicos relevantes da movimentação dentária induzida em murinos quanto aos: (1) diferentes períodos de observação e (2) planos dos cortes microscópicos transversais e longitudinais. Os estudos experimentais sobre a movimentação dentária induzida em murinos variam quanto aos períodos e planos de cortes microscópicos, mesmo os trabalhos que utilizam especificamente o modelo de Heller e Nanda, de 1979. Para contribuir (1) na escolha do melhor design experimental de movimentação dentária induzida em murinos em futuros trabalhos, e (2) no aperfeiçoamento dos critérios de análise por outros pesquisadores, propusemo-nos a publicar este artigo. MÉTODOS: Empregaram-se 50 ratos machos Wistar, com 90 dias de vida, submetidos à movimentação dentária induzida por períodos de 3, 5, 7 e 9 dias. Utilizou-se movimento de inclinação mesial no primeiro molar superior esquerdo, com uma força equivalente a 75cN. A análise microscópica qualitativa avaliou os fenômenos teciduais e celulares decorrentes da movimentação dentária induzida, nos diferentes períodos de observação e entre os cortes microscópicos transversais e longitudinais. RESULTADOS: dos fenômenos observados, as áreas hialinas tiveram expressão máxima no período de 5 dias e as reabsorções radiculares apresentaram-se exuberantes e bem demarcadas no período de 9 dias. Nos dois fenômenos, as raízes mais afetadas foram as distais, especialmente a raiz distovestibular. CONCLUSÃO: mediante o delineamento proposto, pode-se sugerir, para futuros trabalhos nesta linha de pesquisa, períodos de análise de 5 a 9 dias e cortes microscópicos transversais.

AIM: This study aims to elucidate the relevant microscopic aspects of induced tooth movement in murines with regard to: (1) different study periods; and (2) transverse and longitudinal directions of microscopic sections. Experimental studies on induced tooth movement in murines use variable study periods and directions of microscopic sections, including those studies that specifically use the model adopted by Heller and Nanda in 1979. This manuscript was prepared in order to contribute to: (1) selection of the best study design for future studies on induced tooth movement in murines, and (2) improve the analysis criteria to be used by other investigators. METHODS: The study was conducted on 50 male Wistar rats with 90 days of age, submitted to induced tooth movement for periods of 3, 5, 7 and 9 days. The maxillary left first molar was submitted to mesial inclination by application of 75cN of force. Qualitative microscopic analysis evaluated the tissue and cellular phenomena secondary to induced tooth movement, at the different study periods and on transverse and longitudinal sections. RESULTS: Among the phenomena investigated, hyaline areas of periodontal ligament were mostly observed at 5 days, and root resorptions were remarkable and well delineated at 9 days. Both phenomena affected mainly the distal roots, especially the distobuccal root. CONCLUSION: Considering the present objective, study periods of 5 to 9 days and transverse microscopic sections may be suggested for future studies on this subject.

Analysis of the dentin-pulp complex in teeth submitted to orthodontic movement in rats

In order to microscopically analyze the pulpal effects of orthodontic movement, 49 maxillary first molars of rats were submitted to orthodontic appliance composed of a closed coil spring anchored to the maxillary incisors, placed for the achievement of mesial movement. MATERIAL AND METHODS: Ten animals were used as the control group and were not submitted to orthodontic force; the other animals were divided into groups according to the study period of tooth movement, namely 1, 2, 3, 4, 5, 6 and 7 days. The investigation of pulp and periodontal changes included hyalinization, fibrosis, reactive dentin and vascular congestion. Statistical evaluation was performed between control and experimental groups and between periods of observation using non-parametric chi-square, Kruskal-Wallis and Dunn tests. RESULTS: There was no statistically significant difference concerning pulpal changes between control and experimental groups nor between periods of observation. The control group, at 3 and 5 days, revealed greater hyalinization of the periodontal ligament (p<0.05), whereas root resorption was significantly greater at 5 and 7 days (p<0.05). CONCLUSION: No morphological change from the effect of induced tooth movement could be found in the dentin-pulp complex. In addition, no inflammatory or pulp degeneration, detectable in optical microscopy, was found in experimental groups.