Nakamura M, Nakamura Y
Shigaku. 1989 Oct;77(3):930-48.
The voltage gradient method for root canal measurement was evaluated in vivo and in vitro. For the evaluation in vivo, 25 single root teeth, were employed. The working length was measured by bipolor or monopolor electrode. After measurement, the electrode was fixed on the tooth, and the tooth was extracted. Radiograph was taken from 12 directions perpendicular to longer axis of tooth, and the relation between anatomical foramen, physiological foramen and the attained position of electrode tip was assessed. In the evaluation in vitro, 7 extracted teeth were used, for which the positions of anatomical foramen and physiological foramen had been determined in advance from radiograph, in order to determine the influence of the root canal irrigants and medicaments. The electrode was fixed on electronic calipers and direct reading of the movement. Root canal irrigants and medicaments were injected into root canal, and the measurements were evaluated. The results were as follows: (1) In the cases of 22 teeth measured by monopolar electrode in vivo, the electrode tip was within 0.5mm from physiological foramen except one tooth. (2) In the cases of 3 teeth measured by monopolar electrode in vivo, the electrode tip was within 0.4mm from anatomical foramen. (3) In the cases, where electrolyte solution was filled in root canal and measurement was made by bipolar in the evaluation in vitro, the results of measurement were stable, and the electrode tip tended to be slightly closer to coronal direction from physiological foramen. (4) In the cases where non-electrolyte solution was filled in root canal and measurement was made by bipolar electrode in the evaluation in vitro, the results of measurement were not stable, and the electrode tip tended to be closer to the apex from physiological foramen. (5) In the case of the evaluation in vitro, where electrolyte solution was filled in root canal and measurement was made by monopolar electrode, the electrode tip tended to be a little closer to the front than the anatomical foramen. (6) In the evaluation in vitro, where non-electrolyte solution was filled in root canal and measurement was made by monopolar, the measurement was not achievable. (7) 10% NaOCl solution was found to be very useful as electrolyte solution filled in root canal to search physiological foramen by this measurement method. The above results suggest that the voltage gradient method for root canal measurement is highly reliable because root canal morphology at the apex can be directly in identified.
对根管测量的电压梯度法进行了体内和体外评估。为进行体内评估，使用了25颗单根牙。工作长度通过双极或单极电极测量。测量后，将电极固定在牙齿上，然后拔牙。从垂直于牙齿长轴的12个方向拍摄X线片，评估解剖孔、生理孔与电极尖端到达位置之间的关系。在体外评估中，使用了7颗已拔除的牙齿，其解剖孔和生理孔的位置已预先通过X线片确定，以确定根管冲洗剂和药物的影响。将电极固定在电子卡尺上并直接读取移动情况。将根管冲洗剂和药物注入根管，并对测量结果进行评估。结果如下：（1）在体内用单极电极测量的22颗牙齿中，除一颗牙齿外，电极尖端距生理孔在0.5mm以内。（2）在体内用单极电极测量的3颗牙齿中，电极尖端距解剖孔在0.4mm以内。（3）在体外评估中，当根管内充满电解质溶液并用双极电极进行测量时，测量结果稳定，电极尖端倾向于从生理孔向冠方稍微靠近。（4）在体外评估中，当根管内充满非电解质溶液并用双极电极进行测量时，测量结果不稳定，电极尖端倾向于从生理孔向根尖靠近。（5）在体外评估中，当根管内充满电解质溶液并用单极电极进行测量时，电极尖端倾向于比解剖孔稍靠前一点。（6）在体外评估中，当根管内充满非电解质溶液并用单极电极进行测量时，无法进行测量。（7）发现10%次氯酸钠溶液作为根管内填充的电解质溶液，通过这种测量方法来寻找生理孔非常有用。上述结果表明，根管测量的电压梯度法高度可靠，因为根尖处的根管形态可以直接确定。
