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

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

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

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

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

In vitro IL-1 beta release from gingival fibroblasts in response to pure metals, dental alloys and ceramic

Little information is available on the immunological basis for side-effects of dental materials. The objective of this study is to evaluate effects of pure metals, dental alloys and ceramic on cell viability and interleukin-1 beta (IL-1 beta) release in three-dimensional human gingival fibroblast cultures as an indicator of their biological performance in gingival tissues. The gingival fibroblast cultures were exposed to test specimens fabricated from nickel, iron, molybdenum, copper, indium, gold, Ni-Cr-Mo alloy (Remanium CS), Au-Pt-In alloy (Pontostar) and a dental ceramic (In-ceram). Cell viability was determined by the MTT method 24 and 48 h after exposure. Assays for IL-1 beta were carried out by ELISA. Statistical analysis was performed applying the non-parametric Mann-Whitney pairwise test. Dental ceramic and gold did not influence cell viability after 24 and 48 h. Cell viability was determined after 24 and 48 h to nickel (79-77%), iron (92-90%), molybdenum (86-83%), copper (48-36%), indium (90-90%), Remanium CS (83-80%), Pontostar (94-91%) compared with control cultures. Dental ceramic, Pontostar and gold had no significant influence on IL-1 beta secretion. The highest amounts of IL-1 beta (10-fold) levels were determined in cell cultures exposed to copper. Indium, molybdenum and iron induced twofold IL-1 beta levels compared with untreated control cultures. These results support that some metals may alter immune responses and thereby contribute to a variety of dental pathological conditions and three-dimensional cell culture models for gingival fibroblasts appear to be suitable for in vitro studies