A finite element thermal analysis of various dowel and core materials

Aim: Thermal analysis of the temperature and stress distribution of parallel sided, threaded and non-threaded dowels and core materials under thermal loading within a maxillary central incisor using a three dimensional finite element study. Materials and Methods: 3D models of endodontically treated maxillary central incisor with parallel sided, threaded and non- threaded post and core materials were simulated using the ANSYS software. Materials simulated were parallel sided cast gold post and core, parallel sided fibre reinforced composite (FRC) post and core, and parallel sided, threaded, prefabricated stainless steel post and amalgam core. Thermal loads simulating hot (60 degree C/ 333K) and cold (15 degree C/288K) liquid were applied for 15 seconds at the incisal edge. The temperature changes at the selected nodes were obtained on the various post and core materials, interface between post and dentin, interface between core and dentin, within the dentin and within the cement layer. Results: Temperature and stress distribution pattern were represented in numerical and color coding and results interpreted. Thermal stresses arises as a result of temperature changes. A decreased temperature gradient of the metallic dowels and core (T1 hot - 0.002K, T3 hot - 1.071K, T1 cold -0.99K, T3 cold - 0K) were obtained than that of the FRC dowel and core of 1.982K(hot) and1.55K(cold) respectively due to the higher thermal conductivity of the metals. Higher thermal stress values of 3.567 Mpa(hot) and 3.092 Mpa(cold) respectively were obtained for the FRC dowels and higher stress values of 39.679 Mpa(hot) and 57.855 Mpa(cold) respectively were also obtained for the FRC cores. These values indicated that thermal stresses of the FRC dowel and core were greater than that of cast gold dowel and core and prefabricated stainless steel dowel and amalgam core due to its high coefficient of thermal expansion. Maximum stress values of the FRC dowel and core of 1.87 Mpa(hot) and 2.57 Mpa(cold) respectively were also generated in the cement layer, core and metal ceramic crown. The junction of the metal ceramic crown and dentin demonstrated the maximum stress. Higher thermal stress values of 59.162 ± 10 Mpa were obtained in the restoration and the coronal portion of the dentin than the stress levels of .0039 ± 10Mpa in the supporting bone due to an increased thermal expansion. Conclusion: Non-metallic dowel and core materials such as fibre reinforced composite dowels (FRC) generate greater stress than metallic dowel and core materials. This emphasized the preferable use of the metallic dowel and core materials in the oral environment

CLINICAL PROFILE OF MINERAL BONE DISORDERS (RENAL OSTEODYSTROPHY) IN CHRONIC KIDNEY DISEASE PATIENTS

Objective: The objective of the study was to evaluate the clinical profile of mineral bone disorders (renal osteodystrophy) in chronic kidney disease (CKD) patients. Methods: A retrospective study was performed involving 100 patients above 15 years of age with previously diagnosed chronic renal failure. A series of tests such as biochemical, radiological, and arterial calcifications were monitored. The mean age of subjects in our study was 52.54 years. Results: Biochemical tests revealed that hypocalcemia was present in 54% of the patients, and hyperphosphatemia was seen in 84% of the participants, while only 22% of the participants had high alkaline phosphate (ALP) levels. Radiological tests revealed that 39 patients had aortic calcification, 42 patients had radial artery calcification, and 27 patients had both. Subperiosteal resorption was seen on 29 participants. The majority of the vascular calcification and subperiosteal resorption was seen in patients with CKD Stage 5, and both aortic and radial artery calcifications were significantly associated with subperiosteal bone resorption. Conclusion: The results point toward a high prevalence of derangement in the mineral, vascular and valvular calcifications. Serum total ALP can serve as a biochemical marker to identify a pattern of bone turnover where intact parathyroid hormone is not available. The results highlight that serum phosphorus and Ca × P product levels were significantly associated with both aortic and radial artery calcifications. There was no significant association of these calcifications with serum calcium and ALP levels

Radicular Stud Attachment: An Alternative to Improved Retention and Esthetics

With the increasing demand and popularity of dental implants, the use of removable partial dentures in replacing missing teeth has become less popular. One of the obvious limitations of RPD is the unsightly view of metal used for the retentive clasp and the difficulty in obtaining a good fit. This case report describes the use of a radicular stud attachment as an alternative method to obtain improved retention and esthetics