Arora Honey, Jain Vibha, Pai Keerthilatha M, Kamboj Raman
Department of Oral Medicine and Radiology, Subharti Dental College, Meerut, India.
Indian J Dent Res. 2013 Jan-Feb;24(1):48-51. doi: 10.4103/0970-9290.114945.
To evaluate the precision of dimensional measurements of the mandible in two different positions on orthopantomogram (OPG) (one with mandibular plane parallel to the floor and the other with Frankfort horizontal plane parallel to the floor) and determine the dimensional reliability.
Anatomical landmarks were used to denote points for measurements on mandible as well as OPG and respective measurements made. Magnification was hence calculated and compared with magnification factor (1.2) listed by the manufacturer.
Vertical measurements and anterior horizontal and oblique measurements showed minimal magnification. Posterior horizontal and oblique measurements showed increased magnification. The difference in measurements in the two positions and on comparison with the one given by the manufacturer was statistically significant for posterior horizontal measurements but not for posterior oblique. Horizontal measurements crossing the midline were highly magnified and the difference was statistically significant for the two positions and on comparison to the one given by manufacturer.
Magnification factor given by the manufacturer is not uniform in all locations and varies with changes in positioning and hence should not be relied upon when accurate measurements are to be made.
评估全景曲面体层片（OPG）上两种不同位置（一种是下颌平面与地面平行，另一种是法兰克福水平面与地面平行）下颌骨尺寸测量的精度，并确定尺寸的可靠性。
使用解剖标志点来标记下颌骨以及OPG上的测量点，并进行相应测量。由此计算放大率，并与制造商列出的放大系数（1.2）进行比较。
垂直测量以及前部水平和斜向测量显示放大率最小。后部水平和斜向测量显示放大率增加。两个位置的测量差异以及与制造商给出的测量值相比，后部水平测量在统计学上具有显著差异，但后部斜向测量无显著差异。穿过中线的水平测量高度放大，两个位置的测量差异以及与制造商给出的测量值相比在统计学上具有显著意义。
制造商给出的放大系数在所有位置并不统一，且随位置变化而变化，因此在进行精确测量时不应依赖该系数。
