Marginal and Internal Adaptation of Zirconia Crowns: A Comparative Study of Assessment Methods

Abstract Marginal and internal adaptation is critical for the success of indirect restorations. New imaging systems make it possible to evaluate these parameters with precision and non-destructively. This study evaluated the marginal and internal adaptation of zirconia copings fabricated with two different systems using both silicone replica and microcomputed tomography (micro-CT) assessment methods. A metal master model, representing a preparation for an all-ceramic full crown, was digitally scanned and polycrystalline zirconia copings were fabricated with either Ceramill Zi (Amann-Girrbach) or inCoris Zi (Dentslpy-Sirona), n=10. For each coping, marginal and internal gaps were evaluated by silicone replica and micro-CT assessment methods. Four assessment points of each replica cross-section and micro-CT image were evaluated using imaging software: marginal gap (MG), axial wall (AW), axio-occlusal angle (AO) and mid-occlusal wall (MO). Data were statistically analyzed by factorial ANOVA and Tukey test (a=0.05). There was no statistically significant difference between the methods for MG and AW. For AO, there were significant differences between methods for Amann copings, while for Dentsply-Sirona copings similar values were observed. For MO, both methods presented statistically significant differences. A positive correlation was observed determined by the two assessment methods for MG values. In conclusion, the assessment method influenced the evaluation of marginal and internal adaptation of zirconia copings. Micro-CT showed lower marginal and internal gap values when compared to the silicone replica technique, although the difference was not always statistically significant. Marginal gap and axial wall assessment points showed the lower gap values, regardless of ceramic system and assessment method used.

摘要 边缘与内部适合性是间接修复体成功的关键。新型成像系统可实现精准且非破坏性的相关参数评估。本研究采用硅橡胶复制法与显微计算机断层扫描（micro-CT）两种评估方法，对两种不同系统制备的氧化锆内冠的边缘与内部适合性进行了评价。本研究制备了用于全瓷全冠修复的金属主模型，经数字化扫描后，分别采用凯美锐Zi（Amann-Girrbach）与inCoris Zi（登士柏西诺德，Dentsply-Sirona）系统制备多晶氧化锆内冠，每组n=10。针对每枚内冠，通过硅橡胶复制法与显微CT评估方法测定其边缘与内部间隙。利用成像软件对每个复制样本断面及显微CT图像的4个评估位点进行测量：边缘间隙（MG）、轴壁（AW）、轴颌面角（AO）及颌面中壁（MO）。采用析因方差分析与Tukey检验（α=0.05）对数据进行统计学分析。结果显示，两种方法在MG与AW位点的测量结果无统计学显著性差异。对于AO位点，Amann-Girrbach系统制备的内冠的两种评估方法结果存在显著差异，而Dentsply-Sirona系统制备的内冠则未观察到明显差异。对于MO位点，两种方法的测量结果均存在统计学显著性差异。两种评估方法测得的MG值呈正相关。综上，评估方法会对氧化锆内冠的边缘与内部适合性评估结果产生影响。与硅橡胶复制法相比，显微CT测得的边缘与内部间隙值更低，尽管该差异并非总能达到统计学显著性水平。无论采用何种氧化锆系统与评估方法，边缘间隙与轴壁位点的间隙值均较低。