Do self-ligating brackets favor greater bacterial aggregation?

Aim: To verify the hypothesis that self-ligating brackets favor greater aggregation of microorganisms when compared with conventional brackets. Methods: Four types of self-ligating metal brackets were evaluated. Initially, 50 brackets were divided into five groups (n=10): Morelli Conventional, GAC (In-Ovation R, Dentsply Caulk), Aditek (Easy Clip), Ormco (Damon System) and 3M Unitek (Smart Clip). An in vivo evaluation was carried out in which the brackets were bonded to the mandibular teeth of five healthy individuals who had not undergone previous orthodontic treatment. The right hemiarch brackets were used for bacterial plaque collection and those on the left side were examined by scanning electron microscopy (SEM). Before bracket bonding, the bacterial plaque material aggregated to the tooth surfaces was collected, with the areas of choice being the cervical-buccal and mesial and distal interproximal regions. After 21 days had elapsed since bonding, the plaque adhered to the winglet, channel and cervical regions of the bracket bases was collected. The materials collected were diluted and seeded on Petri dishes onto Mitis salivarius medium specific for S. mutans and non-specified BHI culture medium. Colony forming unit (CFU) counts were performed visually after 24, 48 and 72 h of incubation. Results: Greater bacterial accumulation was observed on the winglets of 3M brackets, with statistical statistically significant differences from the other types (p<0.05). As regards the channel regions, most microorganisms accumulated in the Ormco Group (p<0.05), and in the cervical region of Aditek brackets. In all evaluated regions, those with least bacterial accumulation were the conventional brackets. Conclusions: The hypothesis was confirmed, as the self-ligating brackets were shown to have greater bacterial accumulation when compared with the conventional brackets.

Efeito citotóxico de alginatos odontológicos sobre células fibroblastóides / Cytotoxic effects of a dentstry alginates applied on fibroblast-like cells

O alginato ou hidrocolóide irreversível é um dos materiais de moldagem mais aceitos e utilizados na Odontologia. Algumas substâncias presentes nesses pode levar toxicidade. O estuto foi avaliar a citotoxicidade de alginatos de uso odontológico. Foram avaliados quatro diferentes alginatos divididos em 4 grupos, assim denominados: Ava Gel, New Print, Kromopan e Hydrogum. Três grupos controle também participaram Controle positivo (C+) constituido pelo detergente celular Tween 80, controle negativo (C-) PBS, e controle de célula (CC) onde as células não foram expostas a nenhum material. Após manipulação dos materiais seguindo as orientações do fabricante foi confeccionado corpos de prova utilizando-se anéis de silicone. Em seguida os mesmos foram imersos em meio mínimo essencial de Eagle (MEM) por 2 min, onde então procedeu-se a remoção do sobrenadante e colocação em contato com fibroblastos L929. Após contato com o meio as células foram incubadas por mais 24 h onde então foram adicionados 100ml do corante vermelho neutro a 0,01%. Novamente as células foram incubadas por 3 h para que as mesmas incorporassem o corante. Passado esse período as mesmas foram fixadas e então, realizada contagem de células viáveis em espectrofotômetro (BioTek, Winooski, Vermont, USA) em um comprimento de onda de 492nm. Os resultados demonstraram diferenças estatísticas entre os grupos CC e C-com os demais (P<0.05). Ausência de diferença estatística ocorreu entre os grupos Ava Gel, New Print, Kromopan e Hydrogum (P>0.05). Pode-se concluir com a realização desse trabalho que todos os alginatos testados mostraram caráter citotoxico.

Alginate or irreversible hydrocolloid is one of the most accepted and used impression materials in dentstry. Some substances present in these can lead toxicity. The aim of this study was to evaluate the cytotoxicity of dental alginate of use. Was evaluated four different alginate divided into 4 groups, so called: Ava Gel, New Print, Kromopan e Hydrogum. Three control groups were also included: Group C+ (positive control), consisting of detergent Tween 80; Group C -(negative control), consisting of PBS, and Group CC (cell control), consisting of cells not exposed to any material. After manipulating the materials according to the manufacturer's instructions, samples were made by using silicon rings. Next, the samples were immersed into Eagle minimum essential medium (MEM) for 2 minutes, where the supernatants were removed and brought into direct contact with L929 fibroblasts. Following exposure to the medium, the cells were incubated for further 24 hours and then 100 ml of 0.01% neutral red dye were added. The cells were incubated again for 3 hours so that the dye could be absorbed. After this 3-hour period, the cells were fixed in order to count the viable ones by using a spectrophotometer (BioTek, Winooski, Vermont, USA) at a wavelength of 492nm. The results showed statistical differences between groups CC and C- with the others (P <0.05). Lack of statistical difference occurred between groups and between Ava Gel, New Print, Kromopan e Hydrogum (P> 0.05). Based on the results obtained in this work, one can conclude that all four alginate impression materials are potentially cytotoxic.

Analysis of mechanical properties and forces produced by transpalatal bars made from low-nickel alloy

Aim: This study evaluated assess the mechanical properties and forces produced by transpalatal bars made from low-nickel alloy. Methods: Using a template, a single operator made all transpalatal bars from 0.032" and 0.036" wires of two different alloys, thus originating four groups, namely: A8 (0.032" conventional stainless steel), B8 (0.032" low-nickel stainless steel), A9 (0.036" conventional stainless steel), and B9 (0.036" low-nickel stainless steel). The bars were then activated and mounted onto a device developed to serve as a support for mechanical assay in a universal testing machine (Emic DL 10.000). The values of resilience and ductility were obtained using the Origin 8 software. Results: No statistically significant differences (P > 0.05) were observed between Groups A8 and B8 neither between A9 and B9 for 0.5-, 1.0-, and 5-mm deformations. However, statistically significant differences (P < 0.05) were found in all groups for 15-mm deformation. Groups B8 and B9 showed greater ductility and resilience compared to groups A8 and A9, respectively. Conclusions: Low-nickel stainless steel transpalatal bars release the same amount of force for activations less than 10 mm compared to those made from conventional stainless steel. Mechanically, the low-nickel stainless steel bars are more ductile and resilient.