RESUMO
The purpose of this study was to evaluate the differences in mean tensile bond strength between three groups of orthodontic bracket bases; coarse mesh (Dentaurum), fine mesh (A-Company), and an undercut base (Dynalok). Due to microscopic differences seen in the course mesh bases, these were further sub-divided into rough, smooth, and defective mesh groups, and tested in a double blind trial. All brackets were bonded to plastic cylinders with a highly filled composite resin (Concise) and tested to failure on an Instron universal testing machine. No significant differences in mean tensile bond strength were seen between the rough, smooth, and defective coarse mesh bases. The fine mesh base showed significantly higher mean tensile bond strength compared with the coarse. Both meshes performed significantly better than the undercut base.
Assuntos
Colagem Dentária , Aparelhos Ortodônticos , Resinas Acrílicas , Bis-Fenol A-Glicidil Metacrilato , Resinas Compostas , Cimentos Dentários , Análise do Estresse Dentário , Método Duplo-Cego , Desenho de Equipamento , Falha de Equipamento , Propriedades de Superfície , Telas Cirúrgicas , Resistência à TraçãoRESUMO
This study describes the in vitro testing of elastomeric modules. Measurements were first made from study models to establish the clinical distance over which modules are used for canine retraction. From this preliminary study, a typodont, banded with 0.018" x 0.025" standard edgewise brackets, was set up with the canine-molar distance at 28 mm. Modules for canine retraction were then fitted by 11 clinicians. The applied force ranged from 125 to 310 g (221 +/- 51 g). A similar, but more extensive study using six different types of modules and two clinician groups (experienced and less experienced clinicians) was then undertaken. Mean force values for different module types ranged from 195 +/- 45 g to 318 +/- 90 g. There was no statistically significant difference between the force values applied by experienced and less experienced clinicians.
Assuntos
Dente Canino , Aparelhos Ortodônticos , Borracha , Técnicas de Movimentação Dentária , Análise do Estresse Dentário , Desenho de Equipamento , Humanos , Teste de Materiais , Modelos Biológicos , Estresse Mecânico , Técnicas de Movimentação Dentária/instrumentaçãoRESUMO
Removable partial dentures (RPDs) are frequently used in the treatment of severe hypodontia. The failure rates and modes of failure of 138 such prostheses incorporating acrylic resin onlays were assessed in a retrospective survey. Failures primarily occurred either early or late in the life of the prostheses. Particular problems identified were the low wear resistance of acrylic resin onlays and poor fixation of resin components to metal bases, especially when space was limited.
Assuntos
Anodontia/terapia , Planejamento de Dentadura , Prótese Parcial Removível , Retenção de Dentadura , Humanos , Restaurações Intracoronárias , Falha de Prótese , Estudos RetrospectivosRESUMO
A retrospective cephalometric study of 50 consecutively completed Class II Division I malocclusion cases was carried out in order to analyse the resultant data for craniofacial features which might act as predictors for successful overjet reduction. All the patients had clinically measured overjets of between 10 mm and 15 mm at the start of treatment. The sample was subsequently divided into two groups depending on whether or not the overjet had been reduced to 4 mm or less at the end of treatment. No firm predictors were found, but the most favourable results were achieved with the Begg appliance.
