Strain K J, Tiu J, Mackie J, Bonsor S J, Ibbetson R J
University of Aberdeen, Westburn Drive, AB25 3BZ Aberdeen, United Kingdom.
University of Otago.
Eur J Prosthodont Restor Dent. 2019 Feb 22;27(1):32-38. doi: 10.1922/EJPRD_01832Strain07.
This study examined the total occlusal convergence angles created for full coverage crown preparations by students at a UK dental school. Working casts of 82 clinical crown preparations were scanned using a 3D scanner. Stereolithographic files were uploaded to Preppr, a crown preparation analysis application. Mean bucco-lingual convergence angle were 19.6° (+/-11.7) and mesial-distally 17.8° (+/-11.1). Smallest bucco-lingual convergence angles were achieved for canine teeth with the largest on molar teeth. The smallest mesio-distal values were on canine teeth with the largest on molar teeth. Ideal total convergence angles (4-14°) were achieved in 23% of bucco-lingual preparations and 33% of mesio-distal preparation. Results for clinically acceptable angles (10-20°) were 30% and 40% respectively. There were no statistically significant differences between tooth types for mean bucco-lingual values. (p=0.623), mesio-distal mean values were statistically different by tooth type (p=0.003). Mean values for mandibular molars were significantly higher than for maxillary incisors (p=0.001) and mandibular molars had significantly higher values than maxillary canines (p=0.045). Results in this study were comparable to those of other students and qualified clinicians, with a minority of preparation achieving ideal values.
本研究调查了英国一所牙科学院的学生为全冠修复体预备所形成的总牙合面聚合角度。使用三维扫描仪对82个临床牙冠预备的工作模型进行扫描。将立体光刻文件上传至Preppr（一款牙冠预备分析应用程序）。颊舌向平均聚合角度为19.6°（±11.7），近远中向为17.8°（±11.1）。犬牙的颊舌向聚合角度最小，磨牙的最大。近远中向最小角度值见于犬牙，最大角度值见于磨牙。23%的颊舌向预备和33%的近远中向预备达到了理想的总聚合角度（4 - 14°）。临床可接受角度（10 - 20°）的结果分别为30%和40%。颊舌向平均角度值在不同牙型之间无统计学显著差异（p = 0.623），近远中向平均角度值在不同牙型之间存在统计学差异（p = 0.003）。下颌磨牙的平均值显著高于上颌切牙（p = 0.001），且下颌磨牙的值显著高于上颌尖牙（p = 0.045）。本研究结果与其他学生及合格临床医生的结果相当，只有少数预备达到了理想值。
