Chaturvedi Saurabh, Alqahtani Turki, Alsolami Saleh, Alqahtani Abdulbari, Das Gotam, Alsubaiy Ebrahim
Department of Prosthetic Dentistry, King Khalid University, Abha, Saudi Arabia.
J Adv Prosthodont. 2021 Feb;13(1):36-45. doi: 10.4047/jap.2021.13.1.36. Epub 2021 Feb 23.
To investigate the fracture resistance of monolithic CAD-CAM all-ceramic surveyed crowns with two different occlusal rest seat designs.
Two maxillary first premolar were prepared for all-ceramic surveyed crowns with wide (2/3 of buccolingual width of an unprepared tooth) or narrow (1/3 of buccolingual width of an unprepared tooth) disto-occlusal rest seat (ORS) designs. Eighty monolithic CAD-CAM all-ceramic surveyed crowns were prepared and divided into 4 groups - Group CR, Composite resin material as a control; Group LDS, Lithium disilicate based material; Group ZIPS, zirconia-material (IPS ZirCAD); and Group ZLHT, zirconia- material (CeramillZolidht+). Crowns were cemented on an epoxy resin die with adhesive resin cement. The fracture resistance of crowns was tested with the universal machine. Univariate regression analysis was used.
The mean ± standard deviation of maximum failure force values varied from 3476.10 ± 285.97 N for the narrow ORS subgroup of group ZIPS to 687.89 ± 167.63 N for the wide ORS subgroup of group CR. The mean ± standard deviation of maximum force was 1075 ± 77.0 N for group CR, 1309.3 ± 283.9 N for group LDS, 3476.1 ± 285.97 N for group ZIPS, and 2666.7 ± 228.21 N for group ZLHT, with narrow occlusal rest seat design. The results of the intergroup comparison showed significant differences in fracture strength with various material groups and occlusal rest seat designs ( <.001).
The zirconia-based all-ceramic surveyed crowns fractured at more than double the load of Lithium disilicate based crowns. The crowns with narrow base occlusal rest seat design had statistically significantly higher fracture resistance than surveyed crowns with wide occlusal rest seat design. The use of narrow occlusal rest seat design in CAD-CAM all ceramic surveyed crowns provides higher fracture resistance, and therefore narrow occlusal rest design can be used for providing esthetics with high strength.
研究两种不同牙合支托凹设计的整体式计算机辅助设计与计算机辅助制造（CAD-CAM）全瓷可摘局部义齿冠的抗折性能。
制备两颗上颌第一前磨牙，用于制作具有宽（未预备牙颊舌径宽度的2/3）或窄（未预备牙颊舌径宽度的1/3）远中牙合支托凹（ORS）设计的全瓷可摘局部义齿冠。制备80个整体式CAD-CAM全瓷可摘局部义齿冠，并分为4组——CR组，复合树脂材料作为对照；LDS组，二硅酸锂基材料；ZIPS组，氧化锆材料（IPS ZirCAD）；ZLHT组，氧化锆材料（CeramillZolidht+）。用粘结树脂水门汀将冠粘结在环氧树脂代型上。用万能试验机测试冠的抗折性能。采用单因素回归分析。
最大破坏力值的平均值±标准差，从ZIPS组窄ORS亚组的3476.10±285.97N到CR组宽ORS亚组的687.89±167.63N不等。窄牙合支托凹设计时，CR组最大力的平均值±标准差为1075±77.0N，LDS组为1309.3±283.9N，ZIPS组为3476.1±285.97N，ZLHT组为2666.7±228.21N。组间比较结果显示，不同材料组和牙合支托凹设计的抗折强度存在显著差异（P<.001）。
氧化锆基全瓷可摘局部义齿冠在载荷超过二硅酸锂基冠两倍时发生断裂。窄基牙合支托凹设计的冠在统计学上具有显著高于宽牙合支托凹设计的可摘局部义齿冠的抗折性能。在CAD-CAM全瓷可摘局部义齿冠中使用窄牙合支托凹设计可提供更高的抗折性能，因此窄牙合支托设计可用于兼顾美观与高强度。
