Rajkumar K, Bhat Aruna M, Krishna Prasad D, Hegde Chetan, Shetty Manoj, Shetty N Sridhar
Assistant Professor, Al Ameen Dental College, Bijapur, Karnataka, India.
Dent Res J (Isfahan). 2009 Spring;6(1):39-45.
The design of the tooth preparation and the cementing medium are important consid-erations in the retention of crowns and fixed partial dentures. The purpose of this invitro study was to determine the effect of axial groove on the retention of complete cast metal crowns using two resin luting cements.
Forty freshly extracted intact human molar teeth were prepared in their long axis to receive complete cast metal crowns. The specimens were randomly divided into two groups (one control and one study group). An axial groove of uniform size and shape was made on the prepared teeth under the study group. Axial surface area of prepared teeth specimens was measured. Complete cast metal crowns were fabricated for each specimen. Specimens of each group were divided into subgroups of 10 samples and were cemented with two resin luting cements, RelyX Unicem® and Calibra®, re-spectively. The cemented crowns were loaded in tension using a Universal Instron testing machine. The maximal tensile strength was recorded. Data were compared using the Mann-Whitney U test (α=0.05).
NO SIGNIFICANT DIFFERENCES IN THE TENSILE STRESS VALUES WERE NOTED BETWEEN THE CONTROL (MEAN: 5.76±0.392 MPa) and study (mean: 5.93±0.751 MPa) groups cemented with RelyX Unicem. No significant differences in the tensile stress values were noted between the control (mean: 4.92±0.641 MPa) and study (mean: 5.15 ±0.478 MPa) groups cemented with Calibra. However, significant dif-ference in the tensile stress values was found between the two resin cements in the control and study groups.
Axial groove placed in tooth preparations for resin bonded complete cast metal crowns had no statistically significant effect on retention. The use of (RelyX Unicem®) yielded greater retention values when compared to Calibra®.
牙体预备设计和粘结介质是影响全冠和固定局部义齿固位的重要因素。本体外研究的目的是使用两种树脂粘结剂确定轴沟对完整铸造金属全冠固位的影响。
选取40颗新鲜拔除的完整人类磨牙，沿其长轴进行预备以容纳完整铸造金属全冠。将标本随机分为两组（一组为对照组，一组为研究组）。在研究组预备好的牙齿上制作尺寸和形状均匀的轴沟。测量预备牙齿标本的轴表面积。为每个标本制作完整铸造金属全冠。每组标本再分为10个样本的亚组，分别用两种树脂粘结剂RelyX Unicem®和Calibra®进行粘结。使用万能Instron试验机对粘结好的全冠施加拉力。记录最大拉伸强度。数据采用Mann-Whitney U检验进行比较（α=0.05）。
用RelyX Unicem粘结的对照组（平均值：5.76±0.392MPa）和研究组（平均值：5.93±0.751MPa）之间，拉伸应力值无显著差异。用Calibra粘结的对照组（平均值：4.92±0.641MPa）和研究组（平均值：5.15±0.478MPa）之间，拉伸应力值无显著差异。然而，对照组和研究组中两种树脂粘结剂之间的拉伸应力值存在显著差异。
在树脂粘结完整铸造金属全冠的牙体预备中设置轴沟对固位无统计学显著影响。与Calibra®相比，使用RelyX Unicem®产生的固位值更高。
