In the upper structure of anterior denture implants, all-ceramic restorations are a better choice. As an ideal dental restoration material, its physical properties such as density, thermal expansion, and heat conduction are required to be as similar as possible to that of the replaced tooth tissue. 111. Different repair materials have different physical properties due to their different compositional structures, and have clinical application effects. Also different 121.plat cast ceramic is a new type of all-ceramic repair material, which consists of crystalline phase and glass phase, with good mechanical properties and chemical stability. Since it is an inorganic material, it will not be electrochemically corroded with its implant metal base, and its biocompatibility is good. 131. This article intends to determine the density, thermal expansion coefficient and thermal conductivity of Plat cast ceramic (PCC) material for its special embedding and production. The study of the process provides a theoretical basis for better application in the clinic.
1 Materials and methods 1.1 Materials and equipment Plat casting ceramics and its special embedded materials (PCC, developed by West China University of Stomatology), high-precision intelligent temperature control oven (Chongqing Sanxia Electric Furnace Factory), inlay wax (Shanghai Dental Materials Factory) , Sandblasting Machine (Germany), Vernier Caliper (Chengdu Measuring Tool Factory), Electronic Analytical Balance (Japan), Tubular Thermal Dilatometer (Germany), Steady-State Plate Heat Conductivity Meter (Self-Assembled by Chengdu Keda), High-frequency Centrifugal Casting Machine (Tianjin Hospital Equipment Factory) 1.2 mold according to the density and thermal expansion coefficient requirements for the production of stainless steel metal mold, size is P5X50mm, made of artificial stone made of metal rods of the negative mold die. The mold for measuring the thermal conductivity is two layers: the lower layer is a metal flat red, Fang Hongzhi) The board of the College of Stomatology, West China Medical University (Zhao Yunfeng, Li Hong), and the upper layer is a p3X3imn metal ring.
1. Experimental method 1.3.1 Density: A total of 3 test pieces were prepared, with a size of 95X5Qmm, and a wax pattern was prepared on the mold. Then, the PCC production process was used for embedding, roasting, casting and crystallization. The surface was ground and polished. The size of the test piece was measured with a vernier caliper, and the density of the test piece was measured with a liquid suspension method. The total was measured three times and the average was taken.
1.3.2 Thermal Expansion Coefficient: A total of three test pieces are made, with dimensions (p5 (50mm, wax type on the mold, embedding, roasting, casting, and crystallization in accordance with the PCC production process, fine grinding and polishing of the surface, with The test piece size is determined by vernier caliper.In this experiment, a direct reading method of the amount of expansion was used to test, and the test piece was placed in an isothermal zone on a tube type thermal dilatometer at a heating rate of 10°C/3 minutes and the test piece was measured at room temperature to 700°. C. The amount of expansion of the temperature range, the temperature point taken for each test piece is measured three times and averaged at room temperature 15±5°C, magnification is 200 times, test accuracy is ±0.1%, linear expansion rate and average coefficient of thermal expansion are calculated, and Make a temperature expansion curve.
1.3.3 Thermal Conductivity: A total of three 930X3mm disc specimens were produced. A wax pattern was prepared on the mold, embedding, roasting, casting, and crystallization according to the PCC manufacturing process. The surface was ground and polished, and the test piece size was measured with a vernier caliper. In this experiment, a steady-state plate heat conduction method was used for testing. The test piece was placed between a heater and a cooler of a steady-state flat heat-conducting device, and pressed lightly so that a longitudinal one-dimensional heat flow was generated in the disk test piece. The instrument hot end temperature is 60C and the cold junction temperature is 20C. The heat flux through the test piece per unit time is measured according to Joseph. Fourier's one-dimensional one-way heat conduction equation calculates the thermal conductivity value.
2 Results The average coefficient of thermal expansion of PCC at room temperature to 600°C was 9 10/C before crystallization and 9.87X after crystallization. When PCC was taken at different temperatures, the range of the thermal expansion coefficient and the glass transition temperature were observed. 1 and.
The thermal conductivity at room temperature to 2.4 PCC is 0.0035 calories per second. cm.C 3 Discussion 3.1 Density of Casting Ceramics Density of a material refers to the mass per unit volume of a material. The density of a cast ceramic is a sign of its structural properties. The composition, distribution and grain size of the crystalline phase and glass phase of the cast ceramics will affect the density of the ceramic. 41. The results of this study show that the density of PCC is 2.93 g/cm3, while the specific gravity of dental metal materials is approximately 8 that of cast ceramics. 5 times. Nielsen believes that the use of centrifugal casting technology, the casting pressure generated by it is proportional to the proportion of the cast material 151. Therefore, for the small proportion of cast ceramics, there is a lack of casting pressure, so in the clinical use of centrifugal casting casting ceramics At the same time, it is necessary to compensate for the problem of too low casting pressure in the casting equipment and casting path design. Prevent the occurrence of defects such as air bubbles and incomplete casting in the casting and improve the quality of the casting.
3.2 Thermal expansion properties of cast ceramics Thermal expansion properties refer to the dimensional changes of the material as a function of temperature, 61. It is the main physical property of cast ceramics and plays a key role in the thermal stability, mechanical strength, and processing conditions of cast ceramics. The role. The casting shrinkage of PCC before crystallization at room temperature ~600° is 0.52%, and the shrinkage is uniform, suggesting that in the lost wax casting process, we can compensate for the comprehensive expansion of phosphate-based investment materials and other measures. Obtaining high-precision casting (Continued on page 87) means that when the distance between jaws in the missing tooth area is insufficient, or the arrangement of the implants is abnormal, the retention area of ​​the artificial teeth and the upper structure is not enough, and when it is subjected to leverage, it appears to be tilted. Loosely. Difficulties in retention can easily lead to medical disputes. Physicians should be strict and cautious in mastering indications.
The influence of the thickness of the gums is easily overlooked by the surgeon. Too thin a gum, easy to expose the metal when exposed to the front teeth and affect the appearance. If the gums are too thick, then the inflammation around the implant can be easily impaired. A good epithelial cuff is one of the important indicators of the edge of artificial teeth.
3.5 The types of difficulties caused by the repair of difficult implants affect the retention, stability, comfort, and aesthetics of implant dentures, and also affect the mutual trust between doctors and patients. Implant prosthetic restoration is a complex system engineering that is accomplished by a team working together. Only the success of the restoration means the long-term preservation and value of the implant. The emergence of difficult repairs is mostly iatrogenic, but it will also disappear with changes in human factors. Correctly determining the position, angle, and direction of the implant 41 will increase the vitality of the implant in the alveolar bone and is an important factor in the success of the implant.
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