Apex location
Encyclopedia
Apex location is a method of determining the length of the root canal of the tooth - manually
or by mechanical canal instrument (by passing low intensity electrical current). Thus
the electrical characteristics of the tooth structure are measured and the exact position of
the instrument in the tooth is determined. When the tool tip touches the apex, the
instrument signals that the apical foramen is reached. Whenever the channel instrument is
pulled out its length could be measured to determine the depth of the root canal and all other
dental tools could be adjusted to this length.
Method of Prof. Sonada measures canal's impedance using one or more
electric frequencies. The method thoroughly tracks the penetration of the instrument in the canal.
It is though unreliable in the presence of fluid in the canal and requires additional drying.
Method of Professor Kobayashi performs mathematical calculation of the ratio of the
measured impedance of two or more electric frequencies. The method is highly accurate in
the presence of fluid in the root canal. The method does not provide good
monitoring of the penetration before reaching the apex. This method faces difficulties when
working in a dry canal. Therefore the canal should be moistened. After measuring the canal
should be dried.
The Adaptive method of measurement is implemented by the so-called Adaptive apex locator. In the
process of penetrating the instrument makes continuous measurements and selects a suitable
method of measurement. In case of dry canal the device uses the method of
Prof. Sonada. In case of wet canal the device automatically adjusts the measurement method of
Professor Kobayashi. The Adaptive method is highly accurate and does not require moistening or drying
the channels.
or by mechanical canal instrument (by passing low intensity electrical current). Thus
the electrical characteristics of the tooth structure are measured and the exact position of
the instrument in the tooth is determined. When the tool tip touches the apex, the
instrument signals that the apical foramen is reached. Whenever the channel instrument is
pulled out its length could be measured to determine the depth of the root canal and all other
dental tools could be adjusted to this length.
Methods of measurement
- Method of Prof. Sonada
Method of Prof. Sonada measures canal's impedance using one or more
electric frequencies. The method thoroughly tracks the penetration of the instrument in the canal.
It is though unreliable in the presence of fluid in the canal and requires additional drying.
- Method of Prof. Kobayashi
Method of Professor Kobayashi performs mathematical calculation of the ratio of the
measured impedance of two or more electric frequencies. The method is highly accurate in
the presence of fluid in the root canal. The method does not provide good
monitoring of the penetration before reaching the apex. This method faces difficulties when
working in a dry canal. Therefore the canal should be moistened. After measuring the canal
should be dried.
- Adaptive method
The Adaptive method of measurement is implemented by the so-called Adaptive apex locator. In the
process of penetrating the instrument makes continuous measurements and selects a suitable
method of measurement. In case of dry canal the device uses the method of
Prof. Sonada. In case of wet canal the device automatically adjusts the measurement method of
Professor Kobayashi. The Adaptive method is highly accurate and does not require moistening or drying
the channels.
Reference
- Adaptive methods for apex location
- Color Atlas and Textbook of Oral Anatomy, Histology, and Embryology by B. K. Berkovitz, G. R. Holland, B. J. Moxham Hardcover,