FACTORS INVOLVED IN THE CHROMATIC FAILURES OF NON-METALLIC FIXED DENTAL PROSTHESES

Aim of the study In the field of digital dentistry, Computer-Aided Design/Computer-Aided Manufacturing (CAD/CAM) systems have changed the fabrication of prosthetic restorations by fulfilling both the aesthetic requirements and mechanical performance. This study aims to highlight, by conducting a chromatic evaluation of zirconium oxide when altering the sintering parameters Materials and methods Four groups of zirconium oxide each group formed by 5 copings were made through milling and Exocad digital design software. The design was completed and the files were processed with the Zeno 4030 M1 milling machine (I-MES Wieland). Following milling, the copings were sintered in HTS MIHM-VOGT furnace at a maximum sintering temperature of 1650°C and heating rates of 30°C/min or a rapid rate of 90°C/min. Controlled cooling prevented rapid temperature decrease, thereby minimizing internal stress. Modifications of time and temperature parameters were applied to groups 2, 3, and 4. Chromatic analysis of the specimens was registered with the Vita Easy Shade spectrophotometer. Results It was found that adjustments in sintering temperature and timing are significantly affecting the chromatic outcomes of the non-metallic zirconium structures. Temperature adjustments facilitate the coalescence of zirconium oxide particles and the formation of a robust structure, with changes in it affecting the optical behaviour of the structure. Deviations from the optimum temperature and sintering timing parameters negatively affect the shade. Conclusions In conclusion, milled and sintered zirconium oxide structures can achieve aesthetic excellence, provided by the sintering protocol when the temperatures and sintering furnaces are accurately calibrated.