Kissov Hristo K, Popova Elka V, Katsarov Stoyan G
Department of Prosthetic Dentistry, Faculty of Dental Medicine, Medical University, Plovdiv, Bulgaria.
Folia Med (Plovdiv). 2008 Apr-Jun;50(2):57-62.
It is of paramount importance to have the crown margin precisely adjusted to the preparation lines of the teeth in order to reduce the bacterial plaque which is known to cause inflammations of the periodontal tissues.
The aim of the present study was to determine the position of the crown margin in relation to the preparation line in axial and transversal directions for various types of crowns.
The study included 89 extracted teeth with the attached restorative construction (crown or crown bridge) divided into groups by types of tooth and construction. Each tooth was cleaved into two halves along its axial plane obtaining thus two crown surfaces (a total of 178). Each half of the cleft tooth was embedded in fast-polymerising resin, then sections were made which were studied using a standard ocular measure scale at a magnification of 20x. The position of the crown margin in relation to the preparation border in axial direction was defined as either a precise fit, or longer, or shorter, and in transversal direction--as a precise fit, reverse shoulder or wider. The results were analysed statistically by analysis of variance and alternative analysis.
Longer crown margins were seen more frequently in the axial direction (57 to 72% of all cases) but were prevalent in the cast veneer crowns. Wider crowns were found to be more frequent transversally (86 to 97% of all cases), but were prevalent in swaged crowns. Precise fit of the crown margin with the preparation line is very rare.
The crowns that are most often fabricated in our country are wider crowns followed by crowns with longer crown margin. The discrepancies in axial and transversal directions are a significant plaque retention factor of iatrogenic nature that is conducive to the development of periodontal diseases.
为了减少已知会导致牙周组织炎症的细菌菌斑，使牙冠边缘精确贴合牙齿的预备线至关重要。
本研究的目的是确定各种类型牙冠在轴向和横向相对于预备线的牙冠边缘位置。
该研究包括89颗带有附着修复结构（牙冠或冠桥）的拔除牙齿，按牙齿类型和结构分组。沿轴向平面将每颗牙齿劈成两半，从而获得两个牙冠表面（共178个）。将劈开牙齿的每一半嵌入快速聚合树脂中，然后制作切片，使用标准目镜测量尺在20倍放大倍数下进行研究。牙冠边缘在轴向相对于预备边缘的位置定义为精确贴合、过长或过短，在横向定义为精确贴合、反肩台或过宽。通过方差分析和替代分析对结果进行统计学分析。
在轴向，牙冠边缘过长的情况更常见（占所有病例的57%至72%），但在铸造贴面冠中更为普遍。发现牙冠在横向过宽的情况更频繁（占所有病例的86%至97%），但在锻造冠中更为普遍。牙冠边缘与预备线精确贴合的情况非常罕见。
我国最常制作的牙冠是过宽的牙冠，其次是牙冠边缘过长的牙冠。轴向和横向的差异是医源性的重要菌斑滞留因素，有利于牙周疾病的发展。
