Nick Doyle R, Clark Mike, Miler Jon, Ordelheide Chad, Goodacre Charles, Kim Jay
Loma Linda University, School of Dentistry, Loma Linda, CA, USA.
J Prosthet Dent. 2009 Jan;101(1):7-12. doi: 10.1016/S0022-3913(08)60281-4.
Total occlusal convergence (TOC) is an important aspect of tooth preparation, but the accuracy of its visual estimation has not been determined.
The purpose of this study was to determine which TOC angles are considered ideal, maximal, and minimal, and also to determine the accuracy of visually estimating TOC.
Thirteen dentoform teeth were prepared, for complete gold crown restorations, with TOC angles ranging between -3 and 30. Thirty students and 30 faculty members visually identified the teeth they believed had ideal, maximal, and minimal convergence and then estimated the angle of TOC for each tooth. Data were analyzed with a 2-sample binomial test and the 2-sample t test (alpha=.05), as well as the general linear model (the mixed procedure).
Teeth selected had TOC angles of 9-12 degrees, 21-30 degrees, and 3-12 degrees for ideal, maximal acceptability, and minimal acceptability, respectively. Students and faculty exhibited similar visual estimation capabilities. Greater accuracy of visual estimation of TOC angles occurred with teeth judged to have minimal or ideal convergence, as opposed to those with maximally acceptable angles, indicating estimation accuracy decreased as convergence increased. More than half of the estimates were within 5 degrees of the measured TOC. However, 11 ideal, 14 maximal, and 5 minimal estimates were judged inaccurately by 11 to 20 degrees, and 5 estimates were inaccurate by more than 20 degrees. There were more underestimates than overestimates.
Most visual estimates were accurate, but several were inaccurate by more than 10 degrees. The most common inaccuracies were underestimated TOC. Students and faculty were not significantly different in their ability to accurately estimate TOC. Students and faculty were less accurate when estimating large, as opposed to small, TOC angles.
全牙合面聚合度（TOC）是牙体预备的一个重要方面，但其视觉估计的准确性尚未确定。
本研究的目的是确定哪些TOC角度被认为是理想、最大和最小的，同时确定视觉估计TOC的准确性。
制备了13颗用于全金冠修复的牙模型，TOC角度在-3至30度之间。30名学生和30名教员通过视觉识别他们认为具有理想、最大和最小聚合度的牙齿，然后估计每颗牙齿的TOC角度。数据采用双样本二项式检验和双样本t检验（α = 0.05）以及通用线性模型（混合程序）进行分析。
被选为理想、最大可接受性和最小可接受性的牙齿的TOC角度分别为9 - 12度、21 - 30度和3 - 12度。学生和教员表现出相似的视觉估计能力。与具有最大可接受角度的牙齿相比，被判断为具有最小或理想聚合度的牙齿在TOC角度的视觉估计上具有更高的准确性，这表明随着聚合度增加，估计准确性降低。超过一半的估计值与测量的TOC相差在5度以内。然而，有11个理想估计、14个最大估计和5个最小估计被判断为不准确，误差在11至20度之间，还有5个估计误差超过20度。低估的情况比高估的情况更多。
大多数视觉估计是准确的，但有几个误差超过10度。最常见的不准确情况是TOC被低估。学生和教员在准确估计TOC的能力上没有显著差异。与小TOC角度相比，学生和教员在估计大TOC角度时准确性较低。
