ENDO Tip of the Week - Using an Apex Locator
Using an apex locator! First and foremost, use of an apex locator is the standard of care. It’s a common question and complaint in every malpractice issue I have defended, particularly those involved with overfills and nerve damage to the mandibular canal. So if you have one, please use it. If you don’t have one, please buy one!
It is important to realize that the mechanism by which the apex locator works is the completion of an electrical circuit, lip ground to canal. If one of those contact points is not able to conduct, then there will be a faulty measurement which can lead to over instrumentation or under instrumentation. Thus it is imperative that proper contact is made on the lip ground. A dry lip and lip ground will not conduct well, so wet the lip ground before placement and continually check that the lip is moist under the rubber dam during the procedure. Additionally and equally important, a completely dry canal will be a poor conductor. So it is important to make sure the canal is damp. Using a little RC Prep on the instrument will solve this. A wet pulp chamber, particularly in contact with a metal restoration or tissue will throw the reading off. Don’t use a loose fitting instrument. Use one that has some contact with the canal walls for a more accurate reading. With a little snugness you won’t disturb the position of the instrument as you slide your stop into position. If you are getting close to a measurement of 22 to 25 mm you may want to use a 31 mm instrument so tooth structure or the rubber stop prevent you from getting the instrument clip on firmly. You can also attach the instrument clip to the end of a college plier thus making the plier an extended clip. If you clip it to one end of an explorer it makes a wonderful probe to check for perforations.
A confirmation radiograph can be taken if you feel more comfortable doing so, but I would definitely suggest it if the apicies are in close proximity to the mandibular nerve or any other risky anatomy. Additionally if your locator is not responding in the normal fashion that you are used to, take a confirm radiograph. Calcified apices and debris blocked apicies will also throw off the reading. Hope this is of help. More tips to come!