Electric pulp tester

 I got to use an electric pulp tester in the student clinics a couple of weeks ago and to be honest it was the first time I had used this since I myself was at dental school. I always saw it as cumbersome and anything that involves extra work is hard for me to take on board. I knew the theory that it was more useful in calcified pulps, but since graduation I have just tried the cold spray as a pulp test and if there was no response, I just shrugged my shoulders and moved on. I have found more success with using a cotton roll to soak the cold spray rather than a cotton pellet as it holds more cold and cover a larger surface area on the tooth. For some reason, the students favour cold spray on one of the very dense Q tips they have at the clinic which I find almost useless as the density of the fibres hardly hold any cold and the tip warms up very quickly. For very calcified pulps, the pulp tissue is receded further into the tooth, is less responsive to stimulus and have sclerosed dentinal tubules which do not allow fluid movement to temperature change. Therefore, in elderly or heavily damaged teeth, none of the teeth tend to give any response and it can be to reproduce pulpal symptoms or test for pulpal health. 

Once could make an argument for using CO2 snow as it is much colder than cold spray but yet again I find it cumbersome and end up dropping bits of ice everywhere though this may be my clumbiness at work. 

From my recollection, electric pulp testers will work on very sclerosed teeth and this was certainly my experience using it in the student clinics. You need the electrode that goes on the tooth with an electrolyte to conduct onto the tooth (they use toothpaste) and another electrode to complete the circuit (for us at unit it was the patient holding onto the pulp tester with their hand, in these student clinics they have a separate lip hook that goes onto the patient. 

Be aware the EPT will not be reliable with immature rooted teeth as the nerves aren't fully formed, but I would personally reserve the use for calcified pulps. Also there is risk of false positives with saliva washing on the teeth conducting current to adjacent teeth and soft tissues, adjacent amalgams and if you touch soft tissue with the tip (as one of the students discovered). My suggestion would be to air dry the teeth and use an insulator such as teflon tape or a mylar strip if there is an adjacent amalgam or metal restoration.

False negatives can occur as with cold tests with recently traumatised teeth where the tooth is still vital but there is temporary loss of nerve function. 

The other good thing you can do with an EPT that you can't do with any other common type of pulp testing is to be able to quantify the stimulus with the amount of electricity passing through the tooth being displayed on the EPT machine. Cold tests can't tell you at what temperature there is a response, only the patient's subjective level of pain and the speed at which they respond but there is so much variation in terms of how much spray is put on the applicator, the time from spraying to touching the tooth and the position in the mouth (further back is warmer). Also the more you spray the same applicator, the more it tends to freeze and go solid and hold less cold. CO2 tends to be more constant in it's temperature but it isn't able to quantify the result as EPT can.

Overall I will try to utilise the EPT more in the situations that it is useful in. Sometimes you see some patients, the typical one being an elderly male bruxer with recession everywhere, radiographically receeded pulp and teeth worn almost to the pulp horn but no sensitivity, who you know that cold testing will be an absolute waste of time. That is when I will know now to go straight for the EPT.