Delayed alveolar bone repair and osteonecrosis associated with Zoledronic Acid therapy in rats: macroscopic, microscopic and molecular analysis

Abstract Objective This study aims to evaluate bone repair and the development of the medication related osteonecrosis of the jaw (MRONJ) associated with the use of zoledronic acid in Wistar rats. Methodology 48 male Wistar rats were divided into four groups: ZA, treated with intraperitoneal zoledronic acid, 0.6 mg/kg every 28 days, totaling five doses; control (C), treated with 0.9% sodium chloride; ZA-surgical (SZA) and C-surgical (SC), submitted to extraction of the right upper molars 45 days after the first application. Alveolar bone repair was evaluated by macroscopic and histological analysis. Protein expression evaluations were performed by qPCR. Results Macroscopic evaluation showed that 91.66% (11) of the animals in the SZA group and 41.66% (5) from the SC group presented solution of epithelium continuity (P<0.05). All animals in the SZA group and none in the SC group had bone sequestration. The area of osteonecrosis was higher in the SZA group than in the SC group (P<0.05). In molecular evaluation, the SZA group presented changes in the expression of markers for osteoclasts, with increased RANK and RANKL, and a decrease in OPG. Conclusion The results highlighted strong and evident interference of zoledronic acid in bone repair of the socket, causing osteonecrosis and delayed bone remodeling.

Avaliação da estabilidade de implantes curtos Neodent, tipo Cone Morse, por meio do teste do torque reverso: estudo preliminar em coelhos / Assessing stability of Neodent Morse taper implants through reverse torque technique testing: a preliminary study in rabbits

Introdução: atualmente, vários tipos de implantes estão disponíveis no mercado. Entre esses, pode-se citar os com conexão do tipo hexágono externo, hexágono interno e Cone Morse,sendo que os com Cone Morse fornecem melhor distribuição e transmissão da força ao longo do implante. O grau de osseointegração de um implante pode ser medido e avaliado por meio do valordo torque reverso. Objetivo: com base nisso, o objetivo do presente trabalho é testar, em implantes do tipo Cone Morse, instalados em tíbias de coelhos, a viabilidade de um novo método de avaliação de torque reverso. Métodos: foram instalados implantes (Neodent Cone Morse WS) em tíbias de coelho. Os animais foram eutanasiados em diferentes períodos de tempo. Os blocos ósseos contendo os implantes foram recortados e o montador correspondente ao implante Cone Morse foi acoplado a esse, formando um pilar único e contínuo. O torque reverso foi simulado utilizando a máquina universal de ensaios EMIC DL 1000. Uma força de compressão foi aplicada sobre o braçoda alavanca (Neodent), acoplado ao dispositivo de montagem do implante. Resultados: os valores obtidos com o teste foram os seguintes: Coelho 1 (imediato) = 1,8Kgf, Coelho 2 (7 dias) = 7,6Kgf, Coelho 3 (15 dias) = 17Kgf, Coelho 4 (30 dias) = 27Kgf, Coelho 5 (45 dias) = 36Kgf. Conclusão: os resultados mostraram-se promissores, uma vez que se obteve um aumento do valor do torque reverso com o passar do tempo.

Introduction: Several types of implants are available on the market, including internal or external hexagonal connections and the Morse Taper connection. The latter provides betterdistribution and transmission of forces throughout the implant. Implant osseointegration can be measured and assessed by reverse torque. Objective: The objective of this study is to test, inMorse Taper implants installed in rabbits’ tibia, the feasibility of a new reverse torque assessment method. Methods: Neodent Morse Taper WS implants were installed in rabbits’ tibia. The animals were sacrificed at different periods of time. The bone blocks containing the implants were cut, anda corresponding mounting device was attached to the implant, forming a single pillar. Reverse torque was simulated using a universal testing machine EMIC DL 1000. Compressive force wasapplied to the arm of the ratchet. Results: The values obtained with the test were: Rabbit 1 (immediate)= 1.8 Kgf, Rabbit 2 (7 days) = 7.6 Kgf, Rabbit 3 (15 days) = 17 Kgf, Rabbit 4 (30 days)=27Kgf, and Rabbit 5 (45 days) = 36 Kgf. Conclusion: Results were promising as they indicated an increase in the value of reverse torque over time.

Reconstrução de rebordo alveolar com osso homógeno em bloco: uma revisão sistemática / Alveolar ridge augmentation with homogenous bone block: a systematic review

A utilização de próteses implantossuportadas é, nos dias de hoje, uma alternativa segura e viável para reabilitação de áreas edêntulas. Porém, muitas vezes a instalação de implantes osseointegrados pode ser comprometida ou impossibilitada devido a reabsorções extensas dos rebordos alveolares. O objetivo deste trabalho foi revisar sistematicamente a literatura relacionada à reconstrução de rebordo alveolar com osso homógeno em bloco para subsequente instalação de implantes. O levantamento bibliográfico sistemático foi realizado na base de dados Pubmed e na Bibliografia Brasileira de Odontologia (BBO) entre os anos de 1966 e outubro de 2009. Além disso, foi realizada uma busca manual nas referências dos artigos incluídos na revisão. O resultado dessa revisão de literatura identificou apenas 7 estudos relacionados a essa técnica que preenchiam os critérios de inclusão. A espessura do rebordo aumentou significativamente com uso do enxerto homógeno, apresentando padrões de reabsorção dentro de limites aceitáveis. Os enxertos homógenos e os implantes instalados nas áreas enxertadas apresentaram altos índices de sucesso nos artigos incluídos. Esses demonstraram a previsibilidade da utilização dos enxertos homógenos e posterior instalação de implantes por um período de até 3 anos. No entanto, não há na literatura dados histológicos que confirmem existir uma osseointegração satisfatória com o uso desse material. São, portanto, necessários mais estudos controlados com avaliações histológicas para confirmar a eficiência e a segurança da utilização dos enxertos homógenos.

The use of implant-supported prosthesis is nowadays a safe alternative for rehabilitation of edentulous areas. But most of the time the implant placement can be compromised because of extensive alveolar resorption. The purpose of this study was to systematic review the literature related to the reconstruction of alveolar ridge with homogenous bone block for implant placement. The systematic review was performed on Pubmed and Brazilian Bibliography of Odontology (BBO) from 1966 to October 2009. Therefore, a hand-search in dental journals was done on the references of the selected articles. The results of this literature review identified only 7 studies related to this technique that filled the criteria of inclusion. The alveolar ridge width increased significantly with the use of block allograft, showing acceptable resorption standards. Allografts and implants inserted on grafted areas presented high success rates on the included articles. These ones showed the predictability of using allograft and implants placed after 3 years. However, there is no histological data on the literature that assures a satisfactory osseointegration using this kind of material. Controlled trials with histological evaluation are necessary to confirm the efficacy and security of allografts.

Ultrastructural and immunohistochemical study of the influence of fluoride excess on the development of rat incisor tooth buds

Little information is available on the pathogenesis of fluorosis during the fetal and initial postnatal period. In the present study, female rats received 0 (control), 7 or 100 ppm of sodium fluoride in drinking water, one week before breeding and throughout gestation and nursing periods. The hemimandibles of the offspring were collected at 0, 7 and 14 days of postnatal life (n = 5) and processed for morphological analyses by light and electron microscopy, immunohistochemical analysis for amelogenin and morphometric study of enamel matrix and ameloblasts of incisors. The results showed a decrease in matrix production at the secretory phase at all study periods for the 100 ppm group. In this same group, the secretory ameloblasts showed reduction of enamel matrix secretion, disorganization of mitochondrial crests, large vacuoles at the apical portion of the cytoplasm, retention of intracisternal material and dilatation of some cisterns in the rough endoplasmic reticulum. In the groups of animals aged 7 and 14 days, analysis of variance showed significant reduction (p<0.05) in cytoplasmic volume of 23.80 percent and 24.75 percent, respectively, in relation to the control group. The smooth-ended maturation ameloblasts exhibited a large number of vacuoles with electron-dense endocytic matrix, suggesting a delay in the resorption process. Immunohistochemical analysis showed no difference in the intensity and labeling pattern of the enamel matrix in any study group. Interestingly, in offspring at the age of 14 days for the 7 ppm group, there was an increase in the matrix length at the secretory phase. Therefore, part of the excessive dose of sodium fluoride given to the mother in drinking water can reach the offspring through the placenta and mother's milk, causing morphological changes in ameloblasts and suggesting a reduction in secretion and a delay in matrix resorption.