Department of Conservative Dentistry, Faculty of Dentistry, Alexandria University, Alexandria, Egypt.
Department of Dental Biomaterials, Faculty of Dentistry, Alexandria University, Alexandria, Egypt.
BMC Oral Health. 2024 May 21;24(1):586. doi: 10.1186/s12903-024-04341-3.
Cement spacer is essential for compensating deformation of zirconia restoration after sintering shrinkage, allowing proper seating and better fracture resistance of the restoration. Studies assessing the effect of cement spacer on fit accuracy and fracture strength of zirconia frameworks are missing in the literature. Therefore, the aim of this study was to evaluate the effect of different cement spacer settings on fit accuracy and fracture strength of 3-unit and 4-unit zirconia frameworks.
Sixty standardized stainless-steel master dies were manufactured with 2 prepared abutments for fabricating 3-unit and 4-unit zirconia frameworks. The frameworks were assigned into 6 groups (n = 10) according to cement spacer setting (30 μm, 50 μm, and 80 μm) as follows: 3-unit frameworks; 3u-30, 3u-50, 3u-80, and 4-unit frameworks; 4u-30, 4u-50, and 4u-80. The frameworks were assessed for fit accuracy with the replica method. The specimens were cemented to their corresponding dies, and the fracture strength was measured in a universal testing machine. The Weibull parameters were calculated for the study groups and fractured specimens were inspected for failure mode. Two-Way ANOVA followed by Tukey test for pairwise comparison between study groups (α = 0.05).
The cement spacer had a significant effect on both fit accuracy and fracture strength for 3-unit and 4-unit frameworks. The 50 μm spacer had significantly better fit accuracy followed by 80 μm, and 30 μm spacers. Both 50 μm and 80 μm spacers had similar fracture strength, and both had significantly better strength than 30 μm spacer.
For both 3-unit and 4-unit zirconia frameworks, 50 μm cement spacer can be recommended over 30 μm and 80 μm spacers for significantly better fit accuracy and adequate fracture strength.
水泥间隔物对于补偿氧化锆修复体烧结收缩后的变形至关重要，可确保修复体的适当就位和更好的抗断裂能力。目前文献中缺少评估水泥间隔物对氧化锆基底适合精度和断裂强度影响的研究。因此，本研究的目的是评估不同水泥间隔物设置对 3 单位和 4 单位氧化锆基底适合精度和断裂强度的影响。
采用 2 个预备基台制作 60 个标准化不锈钢主模具，用于制作 3 单位和 4 单位氧化锆基底。根据水泥间隔物设置（30μm、50μm 和 80μm）将基底分为 6 组（n=10）：3 单位基底，3u-30、3u-50、3u-80；4 单位基底，4u-30、4u-50 和 4u-80。采用复制法评估基底的适合精度。将样本粘接到相应的模具上，在万能试验机上测量断裂强度。计算研究组的韦布尔参数，并检查断裂样本的失效模式。对研究组进行双因素方差分析（α=0.05），然后进行两两比较的 Tukey 检验。
水泥间隔物对 3 单位和 4 单位基底的适合精度和断裂强度均有显著影响。50μm 间隔物的适合精度显著优于 30μm 和 80μm 间隔物，而 80μm 间隔物的断裂强度与 50μm 间隔物相似，且均显著优于 30μm 间隔物。
对于 3 单位和 4 单位氧化锆基底，50μm 水泥间隔物的适合精度优于 30μm 和 80μm 间隔物，断裂强度也更优，因此建议使用 50μm 水泥间隔物。
