Schweitzer Florian, Spintzyk Sebastian, Geis-Gerstorfer Juergen, Huettig Fabian
Department of Prosthodontics at the Centre of Dentistry, Oral Medicine, and Maxillofacial Surgery with Dental School, Tubingen University Hospital, Osianderstr. 2-8, 72076, Tuebingen, Germany.
Section of Medical Materials Science and Technology, Tuebingen University Hospital, Osianderstr. 2-8, 72076, Tuebingen, Germany.
J Mech Behav Biomed Mater. 2020 Apr;104:103644. doi: 10.1016/j.jmbbm.2020.103644. Epub 2020 Jan 18.
This study should evaluate the influence of extended firing on the dimension, optical properties and flexural strength of a fully crystalized zirconia-reinforced lithium-silicate ceramic (ZLS) for single tooth restorations.
150 ZLS (Celtra Duo) and 30 lithium disilicate (LDS, IPS e.max CAD) specimens (17 × 4 × 1 mm) were milled in a standard device (Cerec MC XL). The ZLS specimens were distributed equally to five experimental groups (polished, standard firing [IFU], and three extended firings). LDS acted as a control group. The extended firings of ZLS addressed the first glaze firing (EF1) as well as the subsequent glaze firing (EF2) by a controlled overheating of +15 °C during the holding time. Color was measured with a digital spectrophotometer (Shadepilot), and dimensions with a digital calliper, before and after firing. A color change of ΔE ≥1.5 and a volume change of ±0.5% was regarded as clinical relevant. All specimens underwent a three-point-bending test to calculate flexural strength and Weibull statistics.
The color change after firing of ZLS (ΔE value; mean = 1.06; SD = 0.53) exceeded the perceptible threshold of ΔE ≥1.5 in 20% of IFU (mean = 1.18) and EF1+2 (mean = 0.95), 23% of EF1 (mean = 1.11), and 10% of EF2 (mean = 0.99) specimens with no statistical difference between the experimental groups. In 80% of IFU, 63% of EF2, 56% of EF1, and 33% of EF1+2 vol. change after firing exceeded ±0.5%. Characteristic Weibull strength σ and modulus m of polished ZLS specimen was affected by firing in IFU (σ = 314.35 MPa; m = 5.81), EF1 (σ = 324.68 MPa; m = 5.67), EF2 (σ = 326.4 MPa; m = 7.24), and EF1+2 (σ = 357.15 MPa, m = 3.69). LDS revealed σ = 405.7 MPa; m = 8.04, and polished ZLS σ = 219.3 MPa; m = 8.9 with statistical significant difference of the flexural strength between all fired ZLS experimental groups towards "as polished" as well as LDS.
Firing of ZLS led to changes in dimensions, color, and Weibull modulus. Firing increases flexural strength, but minimal temperature extension also increases materials inhomogeneity and risk of failure. The findings call for further investigations towards firing behavior of ZLS and its clinical relevance for restorations.
本研究旨在评估延长烧制对用于单颗牙修复的完全晶化氧化锆增强硅酸锂陶瓷（ZLS）的尺寸、光学性能和抗弯强度的影响。
在标准设备（Cerec MC XL）中研磨150个ZLS（Celtra Duo）和30个二硅酸锂（LDS，IPS e.max CAD）试样（17×4×1毫米）。将ZLS试样平均分为五个实验组（抛光、标准烧制[IFU]和三次延长烧制）。LDS作为对照组。ZLS的延长烧制通过在保温时间内控制过热+15°C来进行首次釉烧（EF1）以及随后的釉烧（EF2）。在烧制前后，使用数字分光光度计（Shadepilot）测量颜色，使用数字卡尺测量尺寸。ΔE≥1.5的颜色变化和±0.5%的体积变化被视为具有临床相关性。所有试样进行三点弯曲试验以计算抗弯强度和威布尔统计量。
ZLS烧制后的颜色变化（ΔE值；平均值 = 1.06；标准差 = 标准差 = 0.53）在20%的IFU（平均值 = 1.18）和EF1 + 2（平均值 = 0.95）、23%的EF1（平均值 = 1.11）以及10%的EF2（平均值 = 0.99）试样中超过了可察觉阈值ΔE≥1.5，各实验组之间无统计学差异。在80%的IFU、63%的EF2、56%的EF1和33%的EF1 + 2中，烧制后的体积变化超过了±0.5%。抛光ZLS试样的特征威布尔强度σ和模量m在IFU（σ = 314.35兆帕；m = 5.81）、EF1（σ = 324.68兆帕；m = 5.67）、EF2（σ = 326.4兆帕；m = 7.24）和EF1 + 2（σ = 357.15兆帕，m = 3.69）中受到烧制的影响。LDS的σ = 405.7兆帕；m = 8.04，抛光ZLS的σ = 219.3兆帕；m = 8.9，所有烧制的ZLS实验组与“抛光后”以及LDS之间的抗弯强度存在统计学显著差异。
ZLS的烧制导致尺寸、颜色和威布尔模量发生变化。烧制增加了抗弯强度，但最小温度延长也增加了材料的不均匀性和失效风险。这些发现需要对ZLS的烧制行为及其在修复中的临床相关性进行进一步研究。
