Effect of supplementary zinc on orthodontic tooth movement in a rat model

ABSTRACT Introduction: Osteoclasts and osteoblasts are responsible for regulating bone homeostasis during which the trace element zinc has been shown to exert a cumulative effect on bone mass by stimulating osteoblastic bone formation and inhibiting osteoclastic bone resorption. Objective: The aim of the present study was to investigate the effects of zinc (Zn) on orthodontic tooth movement (OTM) in a rat model. Material and Methods: A total of 44 male Wistar rats were divided into four groups of 11 animals each and received 0, 1.5, 20 and 50 ppm Zn in distilled water for 60 days. In the last 21 days of the study, nickel-titanium closed coil springs were ligated between maxillary right incisors and first molars of all rats, and tooth movement was measured at the end of this period. Histological analysis of hematoxylin/eosin slides was performed to assess root resorption lacunae, osteoclast number and periodontal ligament (PDL) width. Results: Mean OTM was calculated as 51.8, 49.1, 35.5 and 45 µm in the 0, 1.5, 20 and 50 ppm zinc-receiving groups, respectively. There were no significant differences in neither OTM nor histological parameters among the study groups (p > 0.05). Conclusion: According to the results obtained in the current investigation, increase in supplementary zinc up to 50 ppm does not affect the rate of OTM neither bone and root resorption in rats.

RESUMO Introdução: os osteoclastos e os osteoblastos são responsáveis por regular a homeostase óssea, processo no qual o oligoelemento zinco tem demonstrado exercer um efeito cumulativo sobre a massa óssea, estimulando a formação óssea osteoblástica e inibindo a reabsorção óssea osteoclástica. Objetivo: o objetivo do presente estudo foi investigar os efeitos do zinco (Zn) sobre a movimentação dentária ortodôntica (MDO) em ratos. Métodos: um total de 44 ratos Wistar machos foi dividido em quatro grupos de 11 animais cada, os quais receberam 0; 1,5; 20 e 50ppm de zinco diluído em água destilada, durante 60 dias. Nos últimos 21 dias do estudo, molas helicoidais fechadas de níquel-titânio foram instaladas entre os incisivos direitos e os primeiros molares superiores de todos os ratos, e a movimentação dentária foi medida ao final desse período. Foi realizada análise histológica de cortes corados por hematoxilina-eosina, para avaliar as lacunas de reabsorção radicular, o número de osteoclastos e a espessura do ligamento periodontal. Resultados: as médias da MDO foram estimadas em 51,8; 49,1; 35,5 e 45µm no grupos que receberam, respectivamente, 0; 1,5; 20 e 50ppm de zinco. Não houve diferença significativa entre os grupos experimentais, nem quanto à MDO, nem quanto aos parâmetros histológicos (p > 0,05). Conclusão: segundo os resultados obtidos na presente investigação, verificou-se que um aumento na dose de suplementação com zinco para 50ppm não afeta nem o índice de MDO, nem a reabsorção óssea ou radicular em ratos.

[ report on the significance of ethics in dental research in Iran]

Morality and ethics constitute fundamental principles of professional, educational and investigational aspects of medicine and all its branches, including dentistry. There are specific considerations in dental research which could significantly affect the design and progress of scientific projects performed in this field. The aim of the current study was to present an overview of ethical concepts governing dental research and to provide examples of common issues raised during dentistry-related investigations. Establishment of human tooth banks in major research and training centers is suggested to enhance the process of conducting more substantial research in dentistry

Fascin expression in keratocystic odontogenic tumor and dentigerous cyst

Keratocystic odontogenic tumor [KCOT] is a locally aggressive lesion with a known potential for repeated recurrences. The distinct clinical features and explicit cystic histologic characteristics concurrent with the neoplastic nature of this lesion have led to several studies and comparisons with other odontogenic cysts and tumors. Fascin is an actin-bundling protein which has not been evaluated in odontogenic lesions. The aim of this study was to assess the expression of fascin in KCOT and dentigerous cyst [DC]. In this cross-sectional investigation, the paraffin blocks of 18 KCOTs and 9 DCs were selected and subjected to immunohistochemistry using monoclonal antibody against fascin. Staining was scored by estimating the percentage of immunoreactive epithelial cells. Mann-Whitney-U test was applied for statistical analysis [P<0.05]. Fascin expression was observed throughout the entire epithelial lining of the DCs, while in 50% of the KCOTs, immunostaining was negative in the basal layer and parakeratinized cells adjacent to the lumen. A statistically significant difference in the expression pattern of fascin was found between the studied KCOTs and DCs [P=0.01]. Considering the variation in fascin expression patterns between the sample of KCOTs and DCs in the present investigation, it can be suggested that this protein might have a role in the biologic behavior and pathogenesis of KCOT and DC