RESUMO

To evaluate the polymerization shrinkage stress and cuspal strain (CS) generated in an artificial (typodont) and in a natural tooth using different resin composites. Twenty artificial and 20 extracted natural molars were selected. Each tooth was prepared with a 4x4 mm MOD cavity. The natural and typodont teeth were divided into four experimental groups (n=10), according to the resin composite used: Filtek Z100 (3M Oral Care) and Beautifil II LS (Shofu Dental). The cavities were filled using two horizontal increments and the CS (µS) was measured by the strain gauge method. Samples were sectioned into stick-shaped specimens and the bond strength (BS) (MPa) was evaluated using a microtensile BS test. Shrinkage stress and CS were analyzed using 3D finite element analysis. No difference was found between the type of teeth for the CS as shown by the pooled averages: Natural tooth: 541.2 A; Typodont model: 591.4 A. Filtek Z100 CS values were higher than those obtained for Beautifil II LS, regardless of the type of teeth. No statistical difference was found for the BS data. Adhesive failures were more prevalent (79.9%). High shrinkage stress values were observed for Filtek Z100 resin, regardless of tooth type. The CS of typodont teeth showed a shrinkage stress effect, generated during restoration, equivalent to that of natural teeth.

Assuntos

RESUMO

Abstract To evaluate the polymerization shrinkage stress and cuspal strain (CS) generated in an artificial (typodont) and in a natural tooth using different resin composites. Twenty artificial and 20 extracted natural molars were selected. Each tooth was prepared with a 4x4 mm MOD cavity. The natural and typodont teeth were divided into four experimental groups (n=10), according to the resin composite used: Filtek Z100 (3M Oral Care) and Beautifil II LS (Shofu Dental). The cavities were filled using two horizontal increments and the CS (µS) was measured by the strain gauge method. Samples were sectioned into stick-shaped specimens and the bond strength (BS) (MPa) was evaluated using a microtensile BS test. Shrinkage stress and CS were analyzed using 3D finite element analysis. No difference was found between the type of teeth for the CS as shown by the pooled averages: Natural tooth: 541.2 A; Typodont model: 591.4 A. Filtek Z100 CS values were higher than those obtained for Beautifil II LS, regardless of the type of teeth. No statistical difference was found for the BS data. Adhesive failures were more prevalent (79.9%). High shrinkage stress values were observed for Filtek Z100 resin, regardless of tooth type. The CS of typodont teeth showed a shrinkage stress effect, generated during restoration, equivalent to that of natural teeth.

RESUMO

BACKGROUND/AIM: The use of custom-fitted mouthguards can effectively prevent dentoalveolar trauma during sports practice. The aims of this study were to (1) Evaluate the elastic modulus of different EVA commercial brands used for custom-fitted mouthguards, and (2) Evaluate whether the different EVA brands can influence the stress and strain generated during an impact simulated by three-dimensional finite element analysis. METHODS: The elastic modulus of five EVA commercial brands (Essence® , Bio-Art® , Proform® , PolyShok® , and Erkodent® ) were calculated through uniaxial tensile tests. The obtained values were evaluated statistically by Kruskal-Wallis and Dunn's test. A three-dimensional model of the anterior maxilla was created using the Rhinoceros 5.0. A 3 mm custom-fitted mouthguard was simulated. The three-dimensional volumetric mesh was generated using the Patran software (MSC.Software) with isoparametrics, 4-noded tetrahedral elements, and exported to Marc/Mentat (MSC.Software) as element number 134. A non-linear dynamic impact analysis was performed in which a rigid object struck the central incisor at a speed of 5 m/s. The stresses were evaluated by the modified von Mises criteria, and the strains were also recorded. RESULTS: Statistically significant differences were observed for elastic modulus values (p < .001). Median values and the results of the Dunn's test were Essence® (38.1 A), Bio-Art® (34.9 AB), Proform® (20.8 BC), PolyShok® (17.4 CD), and Erkodent® (15.0 D) (different capital letters mean statistical differences among the groups). Stresses and strains generated in the model with mouthguards were significantly lower than the model without a mouthguard regardless of the commercial brand. There was no significant difference in the stress and strain on the enamel and dentin with the different EVA brands. The shock absorption ability was high for all the brands (more than 80%). CONCLUSION: The custom-fitted mouthguards, independently of the commercial brand, reduced stresses and strains during the impact.

Assuntos