Determination of final occlusal vertical dimension by cephalometric analysis

Introduction: Most of techniques for determining the occlusal vertical dimension (OVD) of edentulous patients are based on soft tissues references, which lead to measurement discrepancies. Objective: To propose a method to obtain the OVD of edentulous patients during the confection of complete dentures considering the lower facial height established by Ricketts (LFHr) or the lower facial height obtained from cephalometric analysis of dentulous patients (LFHd). Material and methods: The OVD of 11 edentulous patients was determined by the association of 3 clinical methods. On each patient's bite plates a metallic ball was fixed and the patient was submitted to lateral radiographic to obtain the lower facial height (LFHe) from cephalometric analysis. Additionally, from 40 lateral cephalograms of dentulous patients the LFHd was obtained. After that, the distance between metallic balls (DMB, in mm) was calculated to verify the linear difference when LFHe was changed to LFHd or LFHr, which provided the amount of wax to be added or removed from the bite plates, establishing a new method of OVD determination. LFHe, LFHd and LFHr values were submitted to t e z statistical tests and DMB differences were analyzed by Student's t-test (α=0.05). Results: LFHr (47.0±4.0o a) was statistically higher than LFHd (44.9±5.6o b) and LFHe (43.5±3.5o b). There was statistical difference on linear discrepancies calculated between the LFHe and LFHd (1.7±4.1mm a) or LFHr (4.2±4.1mm b). Conclusion: The use of the cephalometric analysis showed to be a useful auxiliary tool in determining the intermaxillary relationship. However, this method must be associated with different clinical methods of OVD determination and it is recommended that regional references are used to calculate the linear discrepancies.

Comparative evaluation of the accuracy of pick up transfer impressions performed with two different types of trays

Introduction: The success of implant-supported prostheses is related to the passive union between the prostheses’ connections and the implants, so it is necessary to obtain an accurate working cast. Objective: To evaluate the accuracy of the transfer impressions of implants performed with individual acrylic resin trays and conventional trays using polyvinyl siloxane. Material and methods: To carry out the transfer impressions, a master cast with four external hexagon implants parallel to each other was used. Five impressions were made with individual acrylic resin trays and five other impressions with modified conventional trays, opened in the region of the implants. The linear measurements between the implants were made with a digital caliper with an accuracy of 0.01 mm and the results were statistically evaluated (alpha = %). Results: For the points AB and BC, the measurements obtained with the individual trays were statistically similar to the master cast. For the points CD and DA no statistical differences among the three groups were observed. Conclusion: Given the obtained results and the methodology used, it can be concluded that the impressions performed with individual trays presented higher accuracy compared to the ones obtained with conventional trays.

Adaptação marginal em prótese livre de metal, observada por meio de microscopia eletrônica de varredura, após três anos em função / Marginal fit of metal-free crown, observed in scanning electron microscope after three years in function

Introdução: As cerâmicas são consideradas uma excelente alternativa como material estético restaurador, entretanto questões relevantes, como adaptação marginal, exigem um maior critério na confecção quando comparadas aos sistemas convencionais. Objetivo: Este trabalho avaliou a adaptação marginal de uma coroa In-Ceram confeccionada sobre um dente que, após 3 anos, teve sua extração indicada pela ortodontia. Material e métodos: A avaliação deu-se por meio de microscópio eletrônico de varredura. Resultados e conclusão: Foram encontrados valores de falta de adaptação entre 157 e 390 um, obtendo uma média estatística acima do considerado aceitável clinicamente pela literatura.

Introduction: Ceramics are considered an excellent choice as esthetic restorative material, but relevant questions like marginal fit require more attention in manufacturing than conventional systems. Objective: This work evaluated the marginal adaptation of an In-Ceram crown over a tooth that, after three years, had been indicated to extraction by orthodontics. Material and methods: The evaluation was by mean scanning electron microscope. Results and conclusion: It was found values of gaps between 157 and 390 um, getting a statistic average considered greater than the accepted by literature.

Evaluation of the marginal adaptation of a fibre glass reinforced resin crown using a scanning electronic microscope / Avaliação da adaptação marginal de coroa deresina reforçada com fibra de vidro emmicroscópio eletrônico de varredura

Introduction and objective: Dental prostheses manufactured using reinforced resins are an alternative to the rehabilitative treatment of one or more dental elements. With the aim of forecasting the longevity of these prosthetic pieces, this study evaluated the marginal adaptation of a complete crown made from fibreglass reinforced resin. Material and methods: A tooth having orthodontic indication for extraction was prepared and a prosthetic piece was cemented over it so that, 48 hours later, the extraction could take place. The ensemble was taken in a laboratory and was examined using a scanning electron microscope (SEM). There were made 30 readings in a 8mm toothcement-restoration interface and revealed various gaps throughout the sample. Results: The lowest value found was 15,82 µm and the highest was 72,81 µm showing an average value of 40,82 µm. Conclusion: The gaps were within the limits of clinical tolerance and considering the clinical difficulty in making the prosthetic piece, the treatment was shown to be satisfactory with regard to marginal adaptation.

Introdução e objetivo: As próteses fabricadas com resinas reforçadas são alternativas para o tratamento reabilitador de um ou mais elementos dentários. Objetivando prever a longevidade dessas peças, este trabalho avaliou a adaptação marginal de uma coroa total confeccionada com resina reforçada com fibra de vidro. Material e métodos: Um dente com indicação ortodôntica de exodontia foi preparado e sobre ele uma peça protética foi cimentada para que, 48 horas depois, a extração fosse executada. O conjunto foi levado ao laboratório para leitura em microscópio eletrônico de varredura (MEV). Foram feitas 30 leituras em uma interface de dente-cimento-restauração de 8 mm e reveladas diferentes gaps em toda a amostra. Resultados: O menor valor achado foi de 15,82 µm, e o maior de 72,81 µm, resultando em uma média de 40,82 µm. Conclusão: As gaps estavam dentro dos limites de tolerância clínica e, considerando a dificuldade clínica de produção da peça protética, o tratamento mostrou-se satisfatório no que concerne à adaptação marginal.