Evaluation of the Effect of Different Ferrule Designs on Fracture Resistance of Maxillary Incisors Restored with Bonded Posts and Cores

Introduction: In cases of severe hard tissue loss, 2 mm circumferential ferrule is difficult to achieve. So in these cases we should use different ferrule designs.This in vitro study investigated the effect of different ferrule designs on the fractureresistance of teeth restored with bonded post and cores.Materials and Methods: Forty freshly-extracted central incisors were endodontically treated. The teeth were randomly divided into four groups; group 1 were teeth with 2 mm circumferential ferrule above the CEJ, group 2 were teeth with 2 mm ferrule only on the palatal side of the teeth, group 3 consisted of teeth with 2 mm ferrule only on the facial side and group 4 were teeth with 2 mm ferrule on the palatal and facial side of teeth with interproximal concavities.All teeth were restored with fiber posts and composite cores. The specimen was mounted on a universal testing machine and compressive load was applied to the long axis of the specimen until failure occurred.Results: The fracture resistance was 533.79 ± 232.28 in group 1, 634.75± 133.35 in group 2, 828.90 ±118.27 in group 3 and 678.78± 160.20 in group 4. The post hoc analysis showed statistically significant difference between groups 1 and 3 .Conclusions: The results of this in vitro study showed that facial ferrule increases the fracture resistance of endodontically treated teeth restored with bonded post and cores

The effects of implant-macro design on stress quantity and distribution around three types of fixtures by photo-elastic analysis

"nBackground and Aims: Considering the great incidence of implant failures due to high stresses around implant and at bone-implant interfaces, the aim of this study was to compare the effects of three different implant-macro designs on the quantity and distribution pattern of stresses around implants."nMaterials and Methods: In this experimental in vitro study, three types of implants including Biohorizon (4×10.5 mm), Iler (4×10 mm), and Swiss Plus (4.1×10 mm) were studied by applying photo-elastic method. The implants were placed within photo-elastic models with dimensions of 50×50×10 mm. Then through open tray impressed method, crowns for each implant were constructed and cemented. Vertical and oblique loads of 100 N and 150 N were applied on the cemented crowns within polariscope machine. Then the photographs were evaluated using Isochromatic Fringe Characteristics table."nResults: Under vertical loads of 100 N and 150 N, the values for Biohorizon, Iler, Swiss Plus fixtures at the cervical region were (2.35, 3.60) N, (2.50, 3.10) N, and (1.39, 2.35) N, respectively; and in apical region the values were (1.63, 2.35) N, (1.82, 2.35) N, and (2.50, 3.10) N. Under oblique loads, the measures at the cervical region were (4.00, 5.00) N, (1.82, 5.00) N, and (5.20, 6.00) N; and in apical region were "n(1.39, 2.00) N, (4.00, 2.35) N, and (2.35, 3.00) N, respectively for mentioned implants."nConclusion: Under vertical loads, the lowest cervical stresses were observed in Swiss Plus fixture and the lowest apical stress values were recorded for Biohorizon fixture. Under oblique loads, the lowest cervical stresses were found in Iler implant and lowest apical stresses were recorded for Bohorizon