39 research outputs found

    A calculation of stress distribution in metal-porcelain crowns by using three-dimensional finite element method

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    The objective of this study was to calculate stress distribution in a maxillary second premolar tooth which occurred by the mastication force. The tooth model was crowned with Au-Pd alloy, Ni-Cr alloy and porcelain. A load of 450 N, at an angle of 45degrees to the longitudinal axis was applied on the occlusal margin of the crown tooth. The tooth was assumed isotropic, homogenous, elastic and unsymmetrical. This numerical study was carried out using three-dimensional finite element models and calculation programs were prepared by the authors using FORTRAN 77. The distribution of compressive, tensile and shear stress were plotted for the dentine, dentine-metal and metal-porcelain interfaces. The highest stress values were observed when Ni-Cr alloy and porcelain was used

    Evaluation of temporomandibular joint dysfunction by magnetic resonanance imaging

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    Many diagnostic imaging techniques are available to aid clinicians, including transcranial radiography, conventional tomography, computed tomography, arthrography, single photon emission computed tomography (SPECT) imaging and magnetic resonance imaging (MRI). The aim of this study was to evaluate clinical findings and MRI features of temporomandibunlar joint (TMJ) disorders. The clinical histories of 251 patients (502 joints) with MR images were evaluated. Eight clinical variables (articular pain, clicking, locking, limitation of mouth opening, dislocation (luxation), headache (temporal, facial or neck), occlusal disharmony) and imaging findings Normal, Anterior Disk Displacement With Reduction (ADDR), Anterior Disk Displacement Without Reduction (ADDWR) Anterior Disk Displacement With Reduction + Effusion (ADDR +E), Anterior Disk Displacement Without Reduction + Effusion (ADDWR+E), Degeneration, Osteophyte, Posterior Disk Displacement (PDD)) were evaluated. A total of 175 of the TMJs were found to be normal according to MRI findings. Fifty-six unilateral, and 210 bilateral anterior disc displacement with reduction were detected, as well as nine unilateral, and 12 bilateral ADDWR, 21 unilateral, and 58 bilateral ADDR+E; 10 unilateral, and 18 bilateral ADDWR+E; 28 unilateral, and 35 bilateral degenerative arthritic changes; 44 unilateral, and 19 bilateral osteophytes were found. The MRI of TMJs were found normal in 17.9% patients (29.2% female, 5.6% male) with clinical variables. Most of the patients (190 female, 56 male) with TMJ disorders were found to have psychological problems. All of the patients displaying clinical symptoms of TMJ disorders have occlusal disharmony (ground teeth, premature contact, mandibular prognathy or retrognathy, overbite, deepbite, openbite, laterognathy) In this current study jaw pain, locking, limitation of mouth opening, dislocation, and clicking were found 98%, 7.17%, 90.43%, 54.98%, and 75.7% respectively. In addition, etiological factors, noticed as psychological factors, inheritance, and prosthetic appliances were found 98%, 0.39%, 71.71% respectively, but none as a results of unknown trauma, orthodontic treatment, general anesthesia, or maxillofacial intervention. MRI of the TMJ can detect the abnormal changes within the disc, joint and other tissues. Disc displacement is the most common diagnosis of these patients

    sag-36-2-8-0511-4

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    Abstract: Acrylic resin dentures may have cytotoxic effects on oral tissues. However, there is sparse data about the cytotoxic effect of fiber-reinforced acrylic resin materials. The aim of this in vitro study was to determine the cytotoxicity of a heat-polymerized acrylic resin denture base material reinforced with glass, carbon fibers and unreinforced acrylic resin denture base material. 100 acrylic resin discs were assigned to 5 experimental groups (n=20) and 1 control group. Group NOF did not receive any fiber. Roving type glass (Vetrolex) and carbon fibers (Type Tenox J) were introduced into the acrylic resin specimens of Group RGF and Group RCF with the "embedding" technique. Particulate glass and carbon fibers were impregnated into the specimens of Group PGF and PCF with the "blending" technique. Gingival fibroblast cells were exposed onto the test specimens and the cytotoxicity was determined by succinic dehydrogenase activity (MTT method) after 24 and 72 hours incubation. Data were analyzed with the 1-wayAnova test. Cell proliferation rates after 24 and 72 hours incubation ranged as follows: NOF (89%-83%)> RGF (80%-77%), PGF (80%-76%), RCF (79%-75%), PCF (77%-73%). All groups displayed significant cytotoxicity compared to control cell culture. Fiber reinforced groups were significantly more cytotoxic than the unreinforced group. No significant difference of cytotoxicity was found between the fiber-reinforced groups

    Investigation of the Effects of Abutment and Implant Length on Stability of Short Dental Implants

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    The use of dental implants to solve different problems in dentistry has been growing rapidly. The success rates of dental implants are also very important for patients. Depending on the bone level of patients, short dental implants are very popular and widely used by many dentists. Although many dentists are using short dental implants frequently, It can be guessed that there can be stability problems because of crown to implant ratios. In this study, it is aimed to find out the effects of dental implant and abutment lengths on stability of short dental implants. 3 different short dental implant design made with the use of Solidworks 2013. Abutment lengths were 3,5 mm, 4 mm, 4,5 mm, 5 mm and implant lengths were 5 mm, 6 mm, 7 mm for each model. Human mandible model is transferred from Computed Tomography. Then, each implant model is mounted to modeled mandible and Finite Element Analysis is performed for each model. In order to see the effects of implant number on stability, we performed same analysis by placing 4 implants to the mandibl

    The Three-Dimensional Finite Element Analysis of Fixed Bridge Restoration Supported by the Combination of Teeth and Osseointegrated Implants

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    This study investigated the designs of osseointegrated prostheses in cases of free-end partial edentulism using comparative stress interpreted with the three-dimensional finite element method. Three free-end fixed osseointegrated prostheses models with various connection designs (ie, rigidly connected to an abutment tooth and an implant, rigidly connected to an implant and two abutment teeth, and rigidly connected to an implant and three abutment teeth) were studied. The stress values of the three models loaded with vertical, buccolingual, and linguobuccal directions at 30 ° angled to vertical axis forces were analyzed. When the fixed partial denture was connected to the three natural abutment teeth and an implant, the lowest levels of stress in the bone were noted
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