ABSTRACT
The warrant consideration thing in current dental clinical is the allergy or oversensitivity of patients to prosthodontics materials. The article presents the essence, clinical symptoms, testing difficulties of allergy, and discusses the related situations of allergy to metal, porcelain and polymers materials, and also emphasizes the principle of treatment to allergy.
Subject(s)
Humans , Dental Porcelain , Hypersensitivity , Prostheses and Implants , ProsthodonticsABSTRACT
<p><b>OBJECTIVE</b>To study the residual stresses of ceramic-metal bond at viscoelastic and elastic phases during cooling of porcelain-fused-to-metal in order to precisely calculate the ceramic-metal bond strength and improve the restorations.</p><p><b>METHODS</b>The finite element model was set up according the crack initiation test (three-point flexure bond test) based on ISO Standard, elements of viscoelastic and themal-displacement were used to part the model. The result at viscoelastic phases was used as initiation condition of elastic phases to add up.</p><p><b>RESULTS</b>The compressive stress was caused by metal during cooling occurred in the ceramic. The shear stress induced by loading was offset by thermal shear stress. Load tensile stress and the thermal compressive stress vertical of interface concentrated at the end of the bond interface, but the tensile was greatly higher.</p><p><b>CONCLUSION</b>The residual stress is very important to metal-ceramic restorations, and the viscoelastic behavior of porcelain greatly influences it. If the metal and ceramic are compatible,the components stresses of the residual stresses may benefit to ceramic-metal bond, and can be taken as a part of bond stresses.</p>