Graduate Program in Dental Sciences, Federal University of Santa Maria, 1000 Roraima Av., T Street, Building 26F, 97105-900 Santa Maria, RS, Brazil.
Department of Conservative Dentistry, Federal University of Rio Grande do Sul, 2492 Ramiro Barcelos Street, 90035-003, Porto Alegre, RS, Brazil.
Dent Mater. 2021 Jul;37(7):1096-1106. doi: 10.1016/j.dental.2021.03.009. Epub 2021 Apr 15.
This study evaluated the effect of dwell time (conventional or extended) and cooling protocol (fast or slow) of self-glaze firings on the mechanical (flexural strength and crack propagation) and optical (color and translucency) properties of a porcelain-veneered zirconia system.
Bilayer disc-shaped samples were prepared (Vita VM9 + In-Ceram YZ) and divided according to the final thermal treatment: glaze firing followed by slow cooling (furnace opening at 200 °C) (G-S) or fast cooling (furnace opening at 600 °C) (G-F, manufacturer-recommended protocol), extended glaze firing (15 min of dwell time) followed by slow cooling (EG-S) or fast cooling (EG-F), or no thermal treatment (CTRL). Porcelain roughness (Ra and Rz) was measured before and after glaze firings. Color (ΔE) and translucency (TP) alteration were also evaluated. Flexural strength was measured with the piston-on-three-ball test and crack propagation analysis was performed after Vickers indentations. Complementary analyzes of crystalline phase and scanning electron microscopy were carried out.
Significant effect of dwell time was observed, with extended glaze leading to higher flexural strength and shorter crack lengths. Cracks of EG groups were observed to end in clusters of crystals. Color and translucency changed below perceptibility thresholds. All treatments led to a smoother surface and EG groups reached the lowest Rz values. An extra SiO peak was revealed in control and EG groups. No effect of cooling protocol was found.
Extended glaze firing was able to improve the resistance to crack initiation and propagation of porcelain-veneered zirconia without clinically perceptible changes in optical properties.
本研究评估了停留时间（常规或延长）和冷却方案（快或慢）对自上釉烧制的机械性能（弯曲强度和裂纹扩展）和光学性能（颜色和半透明度）的影响一种瓷贴面氧化锆系统。
制备双层盘形样品（Vita VM9+In-Ceram YZ），并根据最终热处理进行分组：釉烧后缓慢冷却（200°C 出炉）（G-S）或快速冷却（600°C 出炉）（G-F，制造商推荐方案），延长釉烧（停留时间 15 分钟）后缓慢冷却（EG-S）或快速冷却（EG-F），或不进行热处理（CTRL）。在釉烧前后测量瓷的粗糙度（Ra 和 Rz）。还评估了颜色（ΔE）和半透明度（TP）的变化。用活塞三球试验测量弯曲强度，并在维氏压痕后进行裂纹扩展分析。进行了晶体相和扫描电子显微镜的补充分析。
观察到停留时间的显著影响，延长釉烧导致弯曲强度更高和裂纹长度更短。EG 组的裂纹被观察到以晶体簇的形式结束。颜色和半透明度的变化低于可察觉的阈值。所有处理都使表面更加光滑，EG 组达到了最低的 Rz 值。在对照和 EG 组中发现了额外的 SiO 峰。冷却方案没有影响。
延长釉烧能够提高瓷贴面氧化锆的抗裂性和抗裂扩展能力，而光学性能没有临床可察觉的变化。
