Colourometry Research On Cercon Zirconia Core

Objective Cercon zirconia, one of the all ceramics restorations system, is a new rising kind of zirconia rehabilitations in recent years. The zirconia material is used to fabricate the core (coping and frameworks) with the low-temperature ceramics utilized as veneer porcelain in this technique, in order to imitate the natural teeth. The transmission rate and color of the coping or frameworks material play an important role of direct influence on the overall effect of prosthetics. It is quite essential to utilize the advanced colourometry testing method and apply a series of measurement and analyses of colourometry parameters of the core material of Cercon zirconia, so as to study the features on the porcelain color changes and make clinical evaluation of the overall color of the Cercon zirconia crown after clinical procedure, aiming at providing some references for its clinical application.Materials and Method The standard test specimens of chipped zirconia core material were applied in the experiment. After sintered in the Cercon heat stove at high-temperature of 1350℃for 7 hrs, the specimens were all polished and sintered as veneer porcelain repeatedly. And then PR650 spectra luminosity&chroma meter as well as JY9800 chroma meter were applied to measure the colourometry parameters, such as the spectral reflectivity, transmission rate, chroma and so on before and after repeatedly sintering. Finally, SPSS statistics analytical software was employed to analyze the data. In the fourth part of the experiment, cases applied all zirconia ceramics crown were chosen to evaluate the effects of the overall color about the prosthesis after insertion.Results The results of the experiment were drawn as follows: 1.The changes in the Cercon zirconia primary moulds were only within the crystalline phase, along with few chemical reactions and few changes of molecular structure, which indicated that the experimental ceramics were almost the same before and after sintering. The effervescence was risen up a little while the zirconia primary moulds were sintering, which indicated that there were some changes of the crystal structure in the ceramics and certain effects on the chromogenesis—the intrinsic cause for the mechanical properties change of the zirconia material. 2.The reflectance ratio of Cercon zirconia decreased gradually during the experimental ceramics were sintered repeatedly within three times, but tended to be stable since the fourth time. The thickness of the zirconia material had an effect upon the transmission rate of that, i.e. the more the thickness of the zirconia material increased, the more the transmission rate decreased. There were small changes about the transmission rate of the zirconia material, due to small changes of the thickness which was able to be applied in the dental clinic. Therefore, the changes of the thickness had no impact on the restoration effect of the whole prosthesis. 3. The changes of the Cercon zirconia core material had an effect on the prosthesis color along with the changes of thickness within the ranges applied in the dental clinic. The brightness increased as a result of the increase in thickness. The color of the zirconia core material was turning out yellow gradually with the increasing of the thickness in the dental clinic, which was able to be perceived by human's eyes. 4. The restoration effect of all ceramics crown made from Cercon zirconia was quite good and the patients were all satisfied. The restoration effect of color about the all zirconia crown had something to do with the veneer porcelain, the zirconia core matierial and the adhesives material, but had little relation to the nature color of dentin.Conclusions It is supposed to pay attention to the effect of the transmission rate and color resulted from the changes of the thickness and repeatedly sintering of the Cercon zirconia core material in the dental clinical application. The effect of Cercon system is nice in the dental clinical application and the performances of intensity and esthetics are capable of satisfying the clinical requirement. It is a kind of comparatively ideal design for all ceramics restoration.