Influence of firing time and framework thickness on veneered Y-TZP discs curvature

• Published in: Dental materials Vol. 30; no. 2; pp. 242 - 248
• Main Authors: Jakubowicz-Kohen, Boris D, Sadoun, Michaël J, Douillard, Thierry, Mainjot, Amélie K
• Format: Journal Article Web Resource
• Language: English
• Published: England Elsevier Ltd 01.02.2014; Elsevier
• Subjects: Advanced Basic Science; Dental Veneers; Dentisterie & médecine buccale; Dentistry; Dentistry & oral medicine; Engineering Sciences; Engineering, computing & technology; Firing time; Hot Temperature; Human health sciences; Ingénierie, informatique & technologie; Materials; Materials science & engineering; Materials Testing; Profilometry; Residual stress; Science des matériaux & ingénierie; Sciences de la santé humaine; Thickness; Veneering ceramic; Zirconia; Zirconia; Thickness; Firing time; Profilometry; Veneering ceramic; Residual stress; heat; dental veneer; Sub-surfaces; Curvature profiles; Yttrium alloys; Firing cycle; Materials Testing; Dental Veneers; Residual stresses; Hot Temperature; Veneers; Curvature radii; Veneering ceramics; Profilometers; Ceramic materials
• ISSN: 0109-5641; 1879-0097; 1879-0097
• DOI: 10.1016/j.dental.2013.11.009

Abstract Objectives The objective of the present work was to study the curvature of very thinly, veneered Y-TZP discs of different framework thicknesses submitted to different firing times. Methods Fifteen 20-mm-wide Y-TZP discs were produced in three different thicknesses: 0.75, 1, 1.5 mm. One disc from each group was left unveneered while the others were layered with a 0.1 mm veneering ceramic layer. All discs underwent five firing cycles for a total cumulative firing time of 30 min, 1, 2, 5 and 10 h at 900 °C. The curvature profile was measured using a profilometer after the veneering process and after each firing cycle respectively. A fitted curve was then used to estimate the, curvature radius. The coefficient of thermal expansion (CTE) measurements were taken on veneering, ceramic and Y-TZP beam samples that underwent the same firing schedule. Those data were used to calculate the curvature generated by CTE variations over firing time. Results All bilayered samples exhibited a curvature that increased over firing time inversely to framework thickness. However non-veneered samples did not exhibit any curvature modification. Significance The results of the present study reveal that even a very thin veneer layer (0.1 mm) can induce a significant curvature of Y-TZP discs. The dilatometric results showed that Tg and CTE, variations are not sufficient to explain this curvature. A chemical-induced zirconia volume, augmentation located at the framework sub-surface near the interface could explain the sample, curvature and its increase with firing time.