Alnajjar Fajer Abdulaziz, Alloughani Arwa Jamal, Alhajj Mohammed Nasser, Baig Mirza Rustum
College of Dentistry, Kuwait University, Kuwait P.O. Box 24923, Kuwait.
Department of Prosthodontics, Faculty of Dentistry, Thamar University, Dhamar P.O. Box 13020, Yemen.
J Funct Biomater. 2024 Jun 22;15(7):171. doi: 10.3390/jfb15070171.
Fracture resistance is an important parameter used to predict the performance of indirect dental restorations. The purpose of this in vitro study was to assess the fracture load of posterior milled nanoceramic crowns, in comparison with the lithium disilicate crowns, after fatigue loading, for two different restoration occlusal thicknesses. Forty test metal dies were fabricated by duplicating a master metal model consisting of an anatomic abutment preparation of the maxillary first premolar for a single crown. The dies were divided into two groups of 20 each for the fabrication of nanoceramic (Lava Ultimate) and lithium disilicate (IPS e.max CAD) single crowns. Each material group was further divided into two sub-groups of 10 dies each, based on crown occlusal thickness, of 0.5-mm and 0.75-mm ( = 10). Dental Type V stone dies poured from polyvinyl siloxane impressions of the test metal dies were laboratory scanned in order to design and mill 40 ceramic crowns. The crowns were cemented on to the test metal dies with a self-adhesive resin luting cement. All crowns were thermocycled (2500 cycles) and mechanically loaded (250,000 cycles) in a chewing simulator followed by static loading until failure, and the values noted. The data were statistically analyzed by 2-way ANOVA and Tukey HSD post-hoc multiple comparison tests (α = 0.05). The mean fracture loads ranged from 1022 to 1322 N for nanoceramic crowns and from 1145 to 1441 N for the lithium disilicate crowns. Two-way ANOVA revealed insignificant differences between the nanoceramic and lithium disilicate crowns ( > 0.05) in terms of fracture load. Significant differences were noted in the fracture resistance of crowns based on occlusal thickness (303 N; = 0.013) regardless of the material used. Multiple comparisons by Tukey HSD post-hoc test showed insignificant differences between the four material-occlusal thickness groups ( > 0.05). The nanoceramic crowns were found to be comparable with lithium disilicate crowns in terms of fracture load. The mean fracture loads of all of the tested crowns were within the normal physiological masticatory load limits. Based on the fracture-resistance results, nanoceramic crowns seem to be suitable for clinical use for the tested occlusal thicknesses.
抗折性是用于预测间接牙齿修复体性能的一个重要参数。本体外研究的目的是评估后牙铣削纳米陶瓷冠在疲劳加载后，与二硅酸锂冠相比，两种不同修复体咬合厚度下的抗折载荷。通过复制一个由上颌第一前磨牙单冠的解剖基牙预备体组成的母金属模型制作了40个测试金属代型。将代型分为两组，每组20个，分别用于制作纳米陶瓷（Lava Ultimate）和二硅酸锂（IPS e.max CAD）单冠。每个材料组根据冠的咬合厚度进一步分为两个亚组，每组10个代型，咬合厚度分别为0.5毫米和0.75毫米（ = 10）。从测试金属代型的聚乙烯硅氧烷印模灌注的牙科V型石膏代型在实验室进行扫描，以设计和铣削40个陶瓷冠。用自粘树脂粘结剂将冠粘结到测试金属代型上。所有冠在咀嚼模拟器中进行热循环（2500次循环）和机械加载（250,000次循环），然后进行静态加载直至破坏，并记录数值。数据通过双向方差分析和Tukey HSD事后多重比较检验进行统计学分析（α = 0.05）。纳米陶瓷冠的平均抗折载荷范围为1022至1322 N，二硅酸锂冠的平均抗折载荷范围为1145至1441 N。双向方差分析显示，纳米陶瓷冠和二硅酸锂冠在抗折载荷方面无显著差异（ > 0.05）。无论使用何种材料，基于咬合厚度的冠的抗折性存在显著差异（303 N； = 0.013）。Tukey HSD事后检验的多重比较显示，四个材料 - 咬合厚度组之间无显著差异（ > 0.05）。发现纳米陶瓷冠在抗折载荷方面与二硅酸锂冠相当。所有测试冠的平均抗折载荷均在正常生理咀嚼载荷范围内。基于抗折性结果，纳米陶瓷冠对于测试的咬合厚度似乎适合临床使用。
