Stress analysis of a fixed implant-supported denture by the finite element method (FEM) when varying the number of teeth used as abutments

OBJECTIVES: In some clinical situations, dentists come across partially edentulous patients, and it might be necessary to connect teeth to implants. The aim of this study was to evaluate a metal-ceramic fixed tooth/implant-supported denture with a straight segment, located in the posterior region of the maxilla, when varying the number of teeth used as abutments. MATERIALS AND METHODS: A three-element fixed denture composed of one tooth and one implant (Model 1), and a four-element fixed denture composed of two teeth and one implant (Model 2) were modeled. A 100 N load was applied, distributed uniformly on the entire set, simulating functional mastication, for further analysis of the SEQV (Von Mises) principal stresses, which were compared with the flow limit of the materials. RESULTS: In a quantitative analysis, it may be observed that in the denture with one tooth, the maximum SEQV stress was 47.84 MPa, whereas for the denture with two teeth the maximum SEQV stress was 35.82 MPa, both located in the region between the pontic and the tooth. CONCLUSION: Lower stresses were observed in the denture with an additional tooth. Based on the flow limit of the materials, porcelain showed values below the limit of functional mastication

Clinical studies of dental erosion and erosive wear

Item does not contain fulltextWe define erosion as a partial demineralisation of enamel or dentine by intrinsic or extrinsic acids and erosive tooth wear as the accelerated loss of dental hard tissue through the combined effect of erosion and mechanical wear (abrasion and attrition) on the tooth surface. Most experts believe that during the last decade there has been a significant increase in the prevalence and severity of erosive tooth wear, particularly in adolescents. Even when erosive wear occurs in its milder forms, this is a matter of concern, as it may compromise the integrity of an otherwise healthy dentition in later life. The erosive wear process is complicated and modified by many chemical, behavioural and associated processes in the mouth. If interventions are to be developed it is therefore important that in vivo methods are developed to assess the outcomes of the erosion and erosive wear processes and the effects of interventions upon them. This paper discusses potential methods of investigating erosion and erosive wear in vivo and the difficulties associated with clinical studies

Influence of different light-curing units on the surface roughness of restorative materials: in situ study

The aim of this study was to evaluate the influence of different light sources (LED and Halogen lamp) on the roughness (superficial) of composite resin (Filtek Z250, Filtek P60, Charisma and Durafill) varying post-irradiation times, in an in situ experiment. For this purpose, 80 specimens were made in polyurethane moulds. Ten volunteers without medicament use and good oral condition were selected and from them study moulds were obtained. A palatal intra-oral acrylic resin appliance was made for each of the subjects of the experiment. In each appliance, two specimens of each material were fixed (LED/Halogen lamp - control group). Roughness tests were performed immediately and 30 days after initial light-curing. Statistical analysis was performed using ANOVA. Statistically significant difference was observed only between post-irradiation times, where the 30th day showed the highest roughness values. It be concluded that roughness was influenced only by post-irradiation times, presenting the 30- days period inferior behavior