Department of Oral Rehabilitation, Medical University of South Carolina College of Dental Medicine, Charleston, SC 29425, USA.
J Prosthet Dent. 2012 Nov;108(5):310-5. doi: 10.1016/S0022-3913(12)60183-8.
Confusion exists as to what constitutes an ideal ceramic crown preparation and whether certain deviations from the ideal can affect the marginal fit of the milled restoration.
This study evaluated the marginal gap of E4D crowns fabricated on preparations completed by clinicians with varying levels of expertise to identify whether common errors affect marginal fit.
The fit of 75 crowns fabricated with the E4D system on preparations of varying quality were examined for marginal fit by using the replica technique. These same preparations were then visually examined for common criteria for ceramic restorations and placed in one of 3 categories: excellent, fair, or poor. These visual examinations sought the presence of common preparation errors, particularly those involving the finish line. The average marginal gap values and standard deviations were calculated for each category, and the Kruskal-Wallis test was used to determine significance.
The results showed a statistically significant correlation between the marginal fit of a CAD/CAM fabricated crown and the quality of the preparation. The mean marginal gap of the crowns fabricated on ideal preparations was 38.5 µm, those considered fair had a mean marginal gap of 58.3 µm, while those categorized as poor averaged 90.1 µm. The fit differences among all 3 groups were statistically significant (P<.05).
Within the limitations of this in vitro study, it can be concluded that preparation quality has a significant impact on marginal gap on crowns fabricated with a CAD/CAM system.
对于理想的陶瓷冠预备体的构成以及某些偏离理想的预备体是否会影响铣削修复体的边缘适合性存在混淆。
本研究评估了由不同专业水平的临床医生完成的预备体上制作的 E4D 冠的边缘间隙，以确定常见的错误是否会影响边缘适合性。
使用复制技术检查了 75 个使用 E4D 系统制作的牙冠在不同质量预备体上的边缘适合性。然后，对这些相同的预备体进行了常见陶瓷修复体标准的目视检查，并将其分为 3 类：优秀、良好和较差。这些目视检查旨在发现常见的预备体错误，特别是涉及肩台的错误。计算了每个类别的平均边缘间隙值和标准偏差，并使用 Kruskal-Wallis 检验确定了显著性。
结果表明，CAD/CAM 制作的牙冠的边缘适合性与预备体的质量之间存在统计学上的显著相关性。理想预备体上制作的牙冠的平均边缘间隙为 38.5 µm，被认为是良好的牙冠的平均边缘间隙为 58.3 µm，而被归类为较差的牙冠的平均边缘间隙为 90.1 µm。所有 3 组之间的适合性差异均具有统计学意义（P<.05）。
在本体外研究的限制范围内，可以得出结论，预备体的质量对 CAD/CAM 系统制作的牙冠的边缘间隙有显著影响。
