Primary stability of orthodontic miniscrews inserted into femurs of osteopenic rats

Aim: To test the hypothesis that bone quality may affect the stability of anchorage devices implanted in a rat model. Methods: Twenty male Wistar rats were divided into 2 groups: Group 1 (rats treated with FK506) and Group 2(rats treated with saline solution vehicle). The immunosuppressant tacrolimus was used with the intention of causing a condition of osteopenia in Group 1. A total of 20 orthodontic mini-implants were used. One mini-implant was inserted in the right femur of each rat. After sacrificing the animals, blocks of bone tissue containing the mini-implants were removed for mechanical pull-out tests to be performed in a universal test machine at a crosshead speed of 0.5 mm/s. The maximum insertion force values and pull-out test were recorded and submitted the nonparametric analyses including the Kruskal-Wallis test and Mann-Whitney tests (p<0.05). The test for Pearson’s correlation was used to verify the correlation between bone mineral density and the pull-out test. The dose of FK506 was 2 mg/kg/day. Densitometric analysis was performed to observe the effect of FK506 on the bone mineral density. Results: The mean insertion force values were similar in both groups, with no statistically significant difference between them (P > 0.05). The mean pull-out force values were higher in Group 2 than in Group 1, with statistically significant difference between the groups (P < 0.05). Conclusions: Bone quality may affect the stability of mini-implants. Orthodontic mini-implants did not present good primary stability in a rat model with osteopenia.

Efeitos transversais da expansão rápida da maxila em pacientes com má oclusão de Classe II: avaliação por Tomografia Computadorizada Cone-Beam / Transverse effects of rapid maxillary expansion in Class II malocclusion patients: A Cone-Beam Computed Tomography study

OBJETIVO: avaliar por meio de Tomografia Computadorizada Cone-Beam (TCCB) os efeitos transversais, imediatos e após o período de contenção, da expansão rápida da maxila (ERM) em pacientes com má oclusão de Classe II. MÉTODOS: dezessete crianças (idade inicial média de 10,36 anos) com má oclusão de Classe II e deficiência transversal esquelética da maxila foram submetidas ao protocolo de ERM com aparelho expansor de Haas. TCCBs foram realizadas antes dos procedimentos clínicos (T1), imediatamente após a estabilização do parafuso expansor (T2) e após completados 6 meses de contenção e removido o aparelho (T3). Com o software Dolphin, foram possíveis a manipulação das imagens e as mensurações. O teste t de Student pareado foi utilizado para identificar significância estatística (p<0,05) entre os intervalos T2 e T1, T3 e T2, e T3 e T1. RESULTADOS: imediatamente após a ERM, ocorreu aumento significativo da largura maxilar basal, alveolar e dentária de 1,95mm, 4,30mm e 6,89mm, respectivamente, e inclinação vestibular dos primeiros molares direito (7,31º) e esquerdo (6,46º). Ao final do período de contenção, o aumento transversal foi mantido e a inclinação dentoalveolar retornou ao valor inicial. CONCLUSÕES: a ERM foi efetiva no aumento da dimensão transversa da maxila, tanto esquelético quanto dentário, sem causar inclinação dos molares de ancoragem em pacientes com má oclusão de Classe II.

OBJECTIVE: The aim of this study was to evaluate by Cone-Beam Computed Tomography (CBCT) transversal responses, immediately and after the retention period, to rapid maxillary expansion (RME), in Class II malocclusion patients. METHODS: Seventeen children (mean initial age of 10.36 years), with Class II malocclusion and skeletal constricted maxilla, underwent Haas´ protocol for RME. CBCT scans were taken before treatment (T1), at the end of the active expansion phase (T2) and after the retention period of six months (T3). The scans were managed in Dolphin software, where landmarks were marked and measured, on a coronal slice passing through the upper first molar. The paired Student´s t-test was used to identify significant differences (p<0.05) between T2 and T1, T3 and T2, and T3 and T1. RESULTS: Immediately after RME, the mean increase in maxillary basal, alveolar and dental width was 1.95 mm, 4.30 mm and 6.89 mm, respectively. This was accompanied by buccal inclination of the right (7.31°) and left (6.46°) first molars. At the end of the retention period, the entire transverse dimension increased was maintained and the dentoalveolar inclination resumed. CONCLUSIONS: The RME therapy was an effective procedure to increase transverse maxillary dimensions, at both skeletal and dentoalveolar levels, without causing inclination on anchorage molars in Class II malocclusion patients with skeletal constricted maxilla.

Long-term fluoride release from resin-reinforced orthodontic cements following recharge with fluoride solution

The aim of this study was to test the hypothesis that there is no difference in the fluoride release behavior of resin-reinforced glass ionomer cements before or after fluoride recharge. The materials were divided into 5 groups: 2 resin-reinforced glass ionomer cements used for attaching orthodontic bands, that is, group FOB (Fuji Ortho Band) and group MCB (Multi-Cure Glass Ionomer Orthodontic Band Cement); 2 resin-reinforced glass ionomer cements and a composite used for bonding orthodontic brackets, that is, group OGLC (Ortho Glass LC), group FOLC (Fuji Ortho LC), and group TXT (Transbond XT), respectively. Fluoride release was measured during a 60-day period by using selective ion electrodes connected to an ionic analyser. After 4 weeks, the samples were exposed to 0.221 percent sodium fluoride solution. The results showed that cements achieved a maximum fluoride release 24 h after initial setting. No statistically significant differences were observed between groups FOB and OGLC regarding the amount of released fluoride following fluoride recharge from day 31 to day 36 (p>0.05). In conclusion, FOB and OGLC cements showed a higher capacity of capturing and releasing fluoride compared to the other cements studied.

O objetivo deste estudo foi testar a hipótese que não há diferença no desempenho dos cimentos de ionômero de vidro reforçados com resina entre si quanto à liberação de flúor antes e após recarga com flúor. Os materiais foram divididos em 5 grupos: 2 cimentos de ionômero de vidro reforçados com resina utilizados para cimentação de bandas ortodônticas: Grupo FOB (Fuji Ortho Band) e Grupo MCB (Multi-Cure Glass Ionomer Orthodontic Band Cement); 2 cimentos de ionômero de vidro reforçados com resina e 1 compósito utilizados para colagem de bráquetes ortodônticos: Grupo OGLC (Ortho Glass LC), Grupo FOLC (Fuji Ortho LC); e Grupo TXT (Transbond XT), respectivamente. A liberação de flúor foi medida durante 60 dias, através de eletrodo íon seletivo conectado a um analisador de íons. Após 4 semanas, os corpos de prova foram expostos a solução de fluoreto de sódio à 0,221 por cento. Os resultados evidenciaram que os cimentos atingiram o pico máximo de liberação de flúor com 24 h após presa inicial. Não houve diferença estatisticamente significante entre a quantidade de flúor liberado após as recargas de fluoreto de sódio entre os grupos FOB e OGLC do 31° ao 36° dia (p>0.05). Concluindo os cimentos FOB e OGLC apresentaram maior capacidade de captação e liberação de flúor comparada aos outros CIVRRs.

Cytotoxicity of polycarbonate orthodontic brackets

Aim: To assess the cytotoxicity of polycarbonate orthodontic brackets. Methods: Polycarbonate brackets from two different manufacturers, namely, Composite bracket (Morelli™) and Silkon Plus bracket (American Orthodontics™), were assessed. In addition to these two experimental groups, other three control groups were included: Positive Control Group (C+) consisting of amalgam cylinders, Negative Control Group (C-) consisting of glass rods, and Cell Control Group (CC) consisting of cells not exposed to any material. All brackets were previously sterilized under ultra-violet light (UV) and, then, immersed in Eagle’s minimum essential media (MEM) for 24 hours, after which the supernatants were removed and placed into contact with L929 fibroblast cells. Cytotoxicity was evaluated at 24, 48, 72 and 168 hours. After contact with MEM, the cells were further incubated at 37oC for 24 hours and 100 mL of 0.01% neutral red dye were added. The cells were incubated again at 37ºC for three hours to incorporate the dye. After this period, the cells were fixed and viable cell counting was performed by spectrophotometry at 492 nm wavelength. Results: No statistically significant difference was found between the experimental groups (1 and 2) and the negative and cell control groups (p > 0.05). The Positive Control Group exhibited high cytotoxicity throughout experimental period are differed significantly from the other groups (p < 0.05). Conclusions: Polycarbonate orthodontic brackets were found not to be cytotoxic within the evaluated experimental period.

Avaliação da resistência à flexão e fratura de mini-implantes ortodônticos / Assessment of flexural strength and fracture of orthodontic mini-implants

OBJETIVOS: o objetivo do presente trabalho é avaliar a deformação e fratura de mini-implantes ortodônticos de diferentes marcas comerciais submetidos ao carregamento na direção perpendicular ao seu comprimento. METODOLOGIA: foram utilizados 75 mini-implantes divididos em cinco grupos (n = 15): M (Mondeal, Tuttlingen, Germany), N (Neodent, Curitiba, Brasil), I (INP, São Paulo, Brasil), S (SIN, São Paulo, Brasil) e T (Titanium Fix, São José dos Campos, Brasil). Os mesmo foram inseridos perpendicularmente em osso cortical suíno e levados à máquina universal de ensaios mecânicos Emic DL 10.000, a uma velocidade de 0,5mm por minuto. Foi avaliada a força necessária para deformar os mini-implantes em 0,5, 1, 1,5, 2mm e para fratura. Os dados foram analisados pela análise da variância (ANOVA) e teste de Tukey. RESULTADOS: os mini-implantes do grupo S necessitaram força maior para que ocorresse deformação e fratura, esses resultados foram estatisticamente significativos em relação aos demais (p < 0,05), que se deformaram e fraturaram com força menor. O grupo M apresentou os menores valores para deformar, entretanto, sem diferença estatística com o grupo N (p > 0,05). Para fraturar, o grupo T apresentou os menores valores, com diferença estatística com os grupos M, S e I. CONCLUSÕES: pode-se concluir que o formato do mini-implante está diretamente relacionado com sua resistência. Apesar de diferenças existentes quanto à resistência entre eles, todos se mostraram aptos para a utilização clínica.

OBJECTIVE: The objective of the present study is to assess both deformation and fracture of orthodontic mini-implants of different trade marks by submitting them to loads perpendicularly applied along their lengths. METHODS: A total of 75 mini-implants were divided into five groups (n = 15) according to their manufacturers: group M (Mondeal, Tuttlingen, Germany), group N (Neodent, Curitiba, Brazil), group I (INP, São Paulo, Brazil), group S (SIN, São Paulo, Brazil), and group F (Titanium Fix, São José dos Campos, Brazil). The mini-implants were perpendicularly inserted into swine cortical bones and then submitted to mechanical tests by using a universal testing machine (Emic DL 10.000) at cross-head speed of 0.5mm/min. The force required for deforming and fracturing the mini-implants at 0.5, 1.0, and 2.0mm was assessed. Data were assessed by using variance analysis (ANOVA) and Tukey's test. RESULTS: Mini-implants of group S were found to need higher forces to be deformed and fractured in comparison with other groups whose mini-implants were submitted to lower forces, a result that is statistically significant (p < 0.05). Group M showed the lowest values regarding deformation with no statistical difference compared to group N (p > 0.05), whereas group T had the lowest values regarding fracture with statistical differences compared to groups M, S, and I. CONCLUSIONS: Based on the present study, one can conclude that the shape of the mini-implants is directly related to their flexural strength. Despite the differences reported above, the mini-implants were found to be clinically useful.