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.

Comparison of AH26 physicochemical properties with two AH26/antibiotic combinations

The purpose of this study was to compare the setting time and post-setting solubility, flow, film thickness and dimensional changes of AH26 root canal sealer with AH26-Antibiotic combination. This study was performed according to British standard BS 6876 [2001] which tests the physicochemical properties of endodontic sealers. Three samples of each of tested materials including AH26 alone, AH26/amoxicillin and AH26/doxycycline were used to test each of the properties. They were prepared according to ISO protocols. The setting time of studied materials was 46 hours for AH26, 29 hours for AH26/amoxicillin, 49 hours for AH26/doxycycline. Flow test results were as follows, for AH 26, 15.6 mm; AH26/amoxicillin, 14.9 mm; AH26/doxycycline, 14.2 mm. Film thickness was 0.024 mm in AH26, 0.0283 mm in AH26/amoxicillin, 0.0276 mm AH26/doxycycline. The solubility of AH26 was 0.0076%, AH26/amoxicillin, 0.0113%, and for AH26/doxycycline, 0.013%. Dimensional changes following setting was 0.07 mm, 2.6 mm, and 1.1 mm for AH 26, AH26/amoxicillin, and AH26/doxycycline, respectively. The physico-mechanical properties of AH26 antibiotic combinations were superior compared with AH26, with the exception of flow. Also, AH26/amoxicillin had a lower setting time than AH26. However, all values were within an acceptable range which conformed to ISO