Aim: To compare the condylar guidance angle obtained by extraoral Gothic arch tracing, protrusive interocclusal records (IORs), and orthopantomogram (OPG) in completely edentulous and dentulous subjects. Materials and methods:A total of 30 edentulous and 30 dentulous subjects were selected. Conventional steps in the fabrication of complete denture with balanced occlusion were carried out. Extraoral Gothic arch tracing records were obtained from each subject. Protrusive IORs were used to program the Hanau Wide-Vue semiadjustable articulator, to obtain the sagittal condylar guidance angle. The sagittal condylar guidance was determined in 60 subjects by protrusive IORs and facebow transfer. The sagittal outline of the articular eminence and glenoid fossa was traced in panoramic radiographs. The sagittal condylar path inclination was constructed by joining the heights of curvature in the glenoid fossa and the corresponding articular eminence. This was then related to the constructed Frankfurt horizontal plane to determine the radiographic angle of sagittal condylar guidance.Results: There was statistically significant difference between the sagittal condylar guidance values obtained using extraoral Gothic arch tracing and OPG method (p 0.0237) in edentulous subjects. Statistically significant values were obtained using protrusive records and OPG method (p 0.0237) in dentulous subjects. Conclusion:The use of OPG to set condylar guidance on the articulator should be taken into consideration for both dentulous and edentulous subjects. Clinical significance:In clinical practice, the use of IORs following Gothic arch tracing for the programming of semiadjustable articulator may be associated with manual errors. To minimize the errors and to obtain more accurate sagittal condylar guidance values, the use of OPG along with IORs should be considered for programming of the semiadjustable articulator.
Purpose: The aim of the study is to determine stress distribution on preloaded implant-abutment screws in three different implant systems under simulated occlusal loads. Materials and methods:Three abutments to implant internal hex joint systems were simulated by using the 3-dimensional finite element analysis; (1) Nobel Biocare replace tapered (2) Uniti (3) Lifecare self-threaded tapered cement retained abutments. Thermal load and contact analysis were used to simulate preload resulting from the torque in implant screw joint assemblies. The simulated preload implants were then loaded with three static occlusal loads (10N horizontal; 35N vertical; 70N oblique) onto the crown into the implant complex.Results: Under preload and static occlusal forces, maximum Von-Mises stresses were concentrated at the lower portion of abutment for all systems. Maximum stresses were concentrated at lower threaded portion of abutment screw in Nobel Biocare, Uniti but in Lifecare system, stresses were concentrated at the middle threaded portion. Maximum stresses were concentrated at middle threaded portion of implant in Nobel Biocare, Uniti but at the upper threaded portion in Lifecare. Stresses increased under static occlusal forces in abutment screw in Nobel Biocare and Uniti but were more under oblique forces. In Lifecare stresses decreased under horizontal forces and increased in vertical and oblique forces. Conclusion:Although, an increase or decrease was demonstrated for the maximum calculated stress values in preloaded screws. After occlusal loads, these maximum stress values were well below the yield stress of abutment screw systems tested.
Aim: To assess and compare the bond strength of Co-Cr metal posts fabricated with 2 different techniques: computer-aided design and computer-aided machining (CAD-CAM) and direct metal laser-sintering (DMLS). Materials and methods: Sixty extracted noncarious, human maxillary central incisor teeth with a similar morphology were decoronated 2 mm coronal to the cementoenamel junction (CEJ) and the roots were endodontically treated. Post space was prepared leaving 5 mm of gutta percha within the root canal. Co-Cr metal posts were fabricated according to CAD-CAM and direct metal laser-sintering (DMLS) techniques and were randomly divided into four study groups: group I, CAD-CAM milled metal post without sandblasting; group II, DMLS metal posts without sandblasting; group III, CAD-CAM milled metal post with sandblasting; and group IV, DMLS metal posts with sandblasting. After sandblasting posts were cemented with glass ionomer cement, pull-out bond strength test was performed using a universal testing machine. Using Kruskal-Wallis with post hoc (Mann-Whitney) tests statistical analysis of data was performed. Result: The highest pull-out bond strength was reported in group-IV (mean value = 6.65 ± 3.10 MPa). And the lowest was recorded for group-I (mean value = 4.38 ± 2.69 MPa). No significant difference in pull-out bond strength was found among the different groups (p > 0.05) due to smaller sample size. Conclusion:Within the limitations of this study, results suggest that surface treatment with sandblasting with 50 μm aluminum oxide particles was found to be an effective method for improving the bond between the DMLS and CAD-CAM milled metal posts.
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