Physicochemical properties and biological effects of quaternary ammonium methacrylates in an experimental adhesive resin for bonding orthodontic brackets

Fixed orthodontic appliances may lead to biofilm accumulation around them that may increase caries risk. This study aimed to evaluate the influence of quaternary ammonium methacrylates (QAMs) on the physicochemical properties, cytotoxicity, and antibacterial activity of adhesive resins for orthodontic purposes. Methodology: A base resin was prepared with a comonomer blend and photoinitiator/co-initiator system. Two different QAMs were added to the base adhesive: dimethylaminododecyl methacrylate at 5 wt.% (DMADDM) or dimethylaminohexadecyl methacrylate (DMAHDM) at 10 wt.%. The base adhesive, without QAMs, (GC) and the commercial Transbond™ XT Primer 3M (GT) were used as control. The resins were tested immediately and after six months of aging in the water regarding the antibacterial activity and shear bond strength (SBS). The antibacterial activity was tested against Streptococcus mutans via metabolic activity assay (MTT test). The groups were also tested for the degree of conversion (DC) and cytotoxicity against keratinocytes. Results:The resins containing QAM showed antibacterial activity compared to the commercial material by immediately reducing the metabolic activity by about 60%. However, the antibacterial activity decreased after aging (p<0.05). None of the groups presented any differences for SBS (p>0.05) and DC (p>0.05). The incorporation of DMADDM and DMAHDM significantly reduced the keratinocyte viability compared to the GT and GC groups (p<0.05). Conclusion: Both adhesives with QAMs showed a significant reduction in bacterial metabolic activity, but this effect decreased after water aging. Lower cell viability was observed for the group with the longer alkyl chain-QAM, without significant differences for the bonding ability and degree of conversion. The addition of QAMs in adhesives may affect the keratinocytes viability, and the aging effects maybe decrease the bacterial activity of QAM-doped materials

Torque de inserção, remoção e fratura de mini-implantes ortodônticos

Objetivo: Avaliar a relação entre a forma e a resistência à fratura em torção de 5 diferentes mini-implantes ortodônticos. Material e Método: 25 mini-implantes divididos em 5 grupos (DEN, RMO, CON, NEO, SIN) foram submetidos ao ensaio de fratura em torção na região do pescoço e da ponta, através de mandris acoplados à Máquina Universal de Ensaios Mecânicos (EMIC, Curitiba, PR, Brasil). A forma da ponta ativa dos mini-implantes foi avaliada no Microscópio Óptico (Stemi 2000-C - Zeiss, Jena, Alemanha) e no MEV (JEOL, modelo JSM-5800 LV, Tóquio, Japão). A resistência da liga dos mini-implantes foi avaliada através de tensão cisalhante e da tensão normal a partir do valor de torque. Resultados: O torque de fratura do pescoço variou de 23,45 N.cm (DEN) a 34,82 N.cm (SIN) e o torque de fratura da ponta variou de 9,35 N.cm (CON) a 24,36 N.cm (NEO). As características que mais influenciaram os resultados foram: diâmetro externo, diâmetro interno, a proporção entre diâmetro interno e externo, e a existência do fresado na região apical do mini-implante. As tensões diferiram entre os grupos, havendo diferença entre as ligas de confecção dos mini implantes, entretanto não houve relação entre os valores das tensões e dos torques de fratura. Conclusão: Os torque de fratura foram diferentes tanto para o pescoço como para a ponta nos 5 tipos avaliados e foram influenciados pela forma dos mini-implantes. A resistência da liga de confecção dos mini-implantes não teve influência significativa nos valores do torque de fraturaThis study evaluated the influence of the mini-implants‟ design on fracture resistance of torsion. Material and Method: 25 mini-implants divided into 5 groups (DEN, RMO, CON, NEO, SIN) were tested on the twisting of fracture in the neck and the tip, through a mandrel coupled in Universal Testing Machine Mechanical (EMIC, Curitiba, PR, Brazil). The design of the active edge of mini-implants were evaluated by optical microscope (STEM 2000-C - Zeiss, Jena, Germany) and SEM (JEOL, model JSM-5800 LV, Tokyo, Japan). The alloy resistance of mini-implants was evaluated by shear tension and normal tension using normal torque value as baseline. Results: The torque value needed for the neck fractures ranged from 23,45 N.cm (DEN) to 34,82 N.cm (SIN) and for the tip fractures ranged from 9.35 N.cm (CON) to 24.36 N.cm (NEO). The design characteristics that most influenced the results were: outside and inside diameter, the ratio between diameters, and the cutter. The tension values differ among the groups. There was difference among mini-implants alloy; however there was no relationship between the values of shear and normal tension and fracture torque. Conclusion: The mini-implants‟ design had an influence on the fracture resistance of torsion. Torques of fracture was different either for the neck and for the tip for all 5 groups evaluated. The mini-implants manufacture alloy resistance has no significant influence on the torque fracture value

Experimental Adhesive for Orthodontic Bonding Containing Ammonium Quaternary Monomer.

As lesões de mancha branca são consequências comuns e esteticamente desagradáveis do tratamento ortodôntico devido à dificuldade de higienização ao redor dos acessórios colados ao esmalte dentário que facilitam o acúmulo de biofilme bacteriano. Um sistema adesivo com propriedades antimicrobianas pode ser um auxiliar interessante na prevenção da mancha branca em pacientes submetidos ao tratamento ortodôntico. Objetivo: Comparar adesivos experimentais para colagem ortodôntica contendo dois tipos de monômeros de metacrilatos contendo sais de amônio quaternário com cadeias de 12 carbonos, DMADDM e com cadeia de 16 carbonos, DMAHDM, em diferentes concentrações ao adesivo Transbond XT e ao adesivo experimental sem adição de monômero. Material e Método: A fase 1 do estudo comparou adesivos experimentais contendo os monômeros DMADDM a 5% e DMAHDM 10% em relação a atividade antimicrobiana, a resistência de união ao cisalhamento imediatamente e após 6 meses de armazenamento em água, o grau de conversão e a citotoxicidade contra queratinócitos. A fase 2 comparou a atividade antimicrobiana, o grau de conversão e a citotoxicidade contra queratinócitos e fibroblastos gengivais dos monômeros DMADDM a 1, 2.5 e 5% e DMAHDM a 1, 2.5 e 5% adicionados ao adesivo experimental. Ambas as fases compararam os adesivos experimentais a um adesivo ortodôntico comercial (Transbond XT) e ao adesivo experimental sem adição de monômero. Resultados: A adição de DMADDM a 5% e DMAHDM a 10% ao adesivo experimental não alterou a resistência de união dos adesivos experimentais que permaneceu adequada a colagem ortodôntica (12,9 MPa a 15,2 Mpa) mesmo após 6 meses de armazenamento em água (22,3 MPa a 23,6 Mpa); não alterou o grau de conversão (valores acima de 70%) quando comparado ao adesivo comercial, porém, a viabilidade celular foi inferior a 50% nos adesivos experimentais. Na fase 2 a atividade antibacteriana contra formação de biofilme foi observada apenas no grupo do adesivo experimental contendo DMAHDM a 5%; a incorporação dos 2 monômeros em todas as concentrações não influenciou no grau de conversão dos adesivos experimentais; a citotoxicidade contra queratinócitos foialta para todas as concentrações de ambos os monômeros embora a viabilidade celular tenha sido superior a 70% no ensaio de citotoxicidade contra fibroblastos gengivais. Conclusão: Os monômeros nas concentrações testadas nas duas fases do estudo não alteraram as propriedades mecânicas e físicas testadas. A viabilidade de queratinócitos foi inferior a 70% em todos os grupos experimentais nas duas fases enquanto todas as concentrações testadas na fase 2 proporcionaram viabilidade dos fibroblastos superior a 70%. O monômero DMAHDM apresenta atividade antibacteriana na concentração de 5% e não é citotóxico aos fibroblastos gengivais. Contudo, mais estudos são necessários para esclarecer a duração do efeito antimicrobiano e a prevenção de lesão de cárie após colagem de bráquetes.White spot lesions are a common and aesthetically undesirable consequence of orthodontic treatment due to cleaning difficulty around bonded accessories to tooth enamel that promotes biofilm bacterial accumulation. An antibacterial adhesive can be a valuable aid in preventing white spot in patients undergoing orthodontic treatment. Objective: To compare experimental adhesives for orthodontic bonding containing two types of quaternary ammonium methacrylate monomers, DMADDM and DMAHDM in different concentrations. Material and Method: Phase 1 of the study consisted of comparing experimental adhesives containing the monomers DMADDM 5% and DMAHDM 10% in relation to the antibacterial activity and the shear bond strength immediately and after 6 months of water aging and degree of conversion and cytotoxicity against keratinocytes of these adhesives when compared to the commercial adhesive Transbond XT and to experimental adhesive without the monomer addition. Phase 2 of the study consisted of comparing antibacterial activity, degree of conversion and cytotoxicity against keratinocytes and gingival fibroblasts of DMADDM at 1, 2.5 and 5% and DMAHDM at 1, 2.5 and 5% added to the experimental adhesive when compared to commercial orthodontic adhesive and experimental adhesive without monomer addition. Results: The addition of 5% DMADDM and 10% DMAHDM to the experimental adhesive did not change the shear bond strength of the experimental adhesives, which remained adequate for orthodontic bonding (12,9 MPa a 15,2 Mpa) even after 6 months of water aging (22,3 MPa a 23,6 Mpa); did not change the degree of conversion when compared to the commercial adhesive but the cell viability was less than 50% in the experimental adhesives. In phase 2, antibacterial activity against biofilm formation was observed only in the experimental adhesive group containing DMAHDM 5%; the incorporation of the 2 monomers in all concentrations did not influence the degree of conversion of the experimental adhesives; cytotoxicity against keratinocytes was high for all concentrations of both monomers although cell viability was greater than 70% in the cytotoxicity assay against gingival fibroblasts. Conclusion: The monomers in the concentrations tested in the 2 phases of the study did not change the properties tested. Keratinocytes viability was less than 70% in all experimental groups in both phases while all concentrations tested in phase 2 provided fibroblast viability greater than 70%. The monomer DMAHDM has antibacterial activity at a concentration of 5%, is not cytotoxic to gingival fibroblasts and does not alter the tested properties of the experimental adhesive and may be suitable to prevent white spot lesions. It is still necessary to clarify the duration of the antimibacterial effect and its cytotoxic potential to other cells in the oral cavity such as keratinocytes.47f

Morphological evaluation of the active tip of six types of orthodontic mini-implants

OBJECTIVE: To morphologically evaluate the active tip of six different types of self-drilling mini-implants for orthodontic anchorage. METHODS: Images of the active tips of the mini-implants were obtained with a Zeiss optical microscope, Stemi 200-C with magnification of 1.6X. The images of the surface were viewed with the Axio Vision program (Zeiss, Jena, Germany) to calculate linear and angular measures. Mini-implant morphology and the details of tips and threads were also evaluated through Scanning Electronic Microscopy (SEM) (JEOL, model JSM5800 LV - JEOL, Tokyo, Japan) with magnifications of 90X and 70X, respectively. The evaluation of the mini-implant taper shape was assessed using to the formula: (b - a) / (2 x D). RESULTS: The following variables were measured: (1) active tip width, (2) major diameter of external thread, (3) minor diameter of internal thread and taper of the mini-implant, (4) number of threads and lead of the screw, (5) angle of thread, (6) flank width and (7) pitch width. CONCLUSION: Mini-implants from different manufacturers presented active tips with different characteristics. Mechanical testing is necessary to cor-relate the analyzed characteristics aiming to determine the best performance

Composição química e aspecto superficial do slot de braquetes metálicos Elemental composition and superficial aspect of metallic brackets slot

OBJETIVO: avaliar a composição química e rugosidade do fundo do slot de 90 braquetes metálicos divididos em 9 grupos: grupo 1- aço inoxidável (Equilibrium 2 - Dentaurum); grupo 2 - titânio (Equilibrium ti - Dentaurum); grupo 3- cromo-cobalto (Topic- Dentaurum); grupo 4 - aço inoxidável (Standard -TP Orthodontics); grupo 5 - aço inoxidável (Serie light - American Orthodontics); grupo 6 - aço inoxidável (Kirium Line - Abzil Lancer); grupo 7 - aço inoxidável livre de níquel (Monobloc - Morelli); grupo 8 - aço inoxidável (Convencional- Morelli) e grupo 9 - aço inoxidável livre de níquel (Monobloc Golden - Morelli). METODOLOGIA: a composição química foi analisada pela Espectroscopia de Energia Dispersiva. A avaliação qualitativa do fundo do slot foi realizada através do MEV classificada de 0 a 8, correspondente às características da superfície. RESULTADOS: composição química - grupo 1 = titânio puro; grupo 9 = recoberto por nitreto de titânio em 99,48%; grupo 3 = cromo-cobalto; grupo 8 = aço inoxidável livre de níquel. Os demais grupos são compostos de aço inoxidável. Avaliação da superfície - grupo 1 = valor 2 (superfície mais polida); grupos 2, 5 e 7 = valor 3 (aspecto de polimento); grupos 3, 8 e 9 = valor 6 (menor polimento); grupo 4 = valor 6,5 (maior rugosidade) e o grupo 6 = valor 5 (características intermediárias de polimento). CONCLUSÕES: os braquetes metálicos são compostos de diferentes ligas e estão disponíveis com baixo conteúdo ou ausência de níquel. Os braquetes de titânio apresentaram polimento semelhante aos de aço inoxidável, porém os recobertos por nitreto de titânio e os de cromo-cobalto mostraram superfície mais irregular ou menos polida.<br>AIM: To evaluate the elemental composition and the slot roughness of 90 metallic brackets divided into 9 groups: group 1 - stainless steel (Equilibrium 2 - Dentaurum); group 2 - titanium (Equilibrium ti - Dentaurum); group 3 - chromium-cobalt (Topic - Dentaurum); group 4 - stainless steel (Standard - TP Orthodontics); group 5 - stainless steel (Serie light - American Orthodontics); group 6 - stainless steel (Kirium Line - Abzil Lancer); group 7 - stainless steel (Monobloc - Morelli); group 8 - stainless steel (Standard - Morelli) and group 9 - stainless steel (Monobloc Golden - Morelli). METHODS: Elemental composition was evaluated using the Spectroscopy of Dispersive Energy. The qualitative slot surface evaluation was assessed using a 500X scanning electron microscope. The microphotography was classified according to surface characteristics in 0-8 values. RESULTS: Elemental composition - group 1 = 100% titanium alloy; group 9 = 99,48% of titanium nitride coated. Group 3 = cobalt-chromium alloy; Group 8 = nickel free stainless steel alloy; other groups stainless steel alloy. Surface evaluation - Group 1 = value 2 (smoothest surface); Groups 2, 5 and 7 =value 3 (smooth surface); Groups 3, 8 and 9 showed value 6 (roughness surface); Group 4 = value 6,5 (the most roughness and irregular surface); and Group 6 has intermediate characteristics among the groups, with value 5. CONCLUSIONS: Metallic brackets were composed of different alloys and they were available with a small percentage or no nickel. The surface roughness was similar for both titanium and stainless steel, however the titanium nitride coated and cobalt-chromium showed an irregular and rough surface