Electric Pulp Test (EPT)

Electrical stimulation was provided by the digital electrical pulp tester (Parkell, Farmingdale, NY, USA; 0-80) with toothpaste (Oral B laboratories, Aylesbury, Bucks, England) used as the conduction medium. Examination procedures were performed by the same operator and same EPT unit at each time point. The test of electrical stimuli was applied to the experimental maxillary central and lateral incisors.

To prevent any temperature change and false responses, patients were asked to not eat or drink ten minutes before each visit. After removal of orthodontic archwires, every tooth was isolated with cotton rolls and dried thoroughly before EPT evaluation. The testing site was confined to sound enamel on the midpoint incisal edge of each tooth. This is necessary in order to avoid the orthodontic brackets, and to minimize the risk of false-positive responses elicited by inadvertent stimulation of the periodontal nerve fibers, or stimulation of adjacent teeth. The probe did not touch any orthodontic bands or brackets. Testing of each tooth started upon contact of the smallest electrode tip with voltage 1 on the tooth surface, and terminates when the subjects raised their hands to show feeling of the first sensation (heat or tingling). The EPT has an analog display, providing a score from 01 to 64, correspondent to the stimuli applied. To minimize the procedural errors, a double determination method was used. During testing, current flow was increased slowly from the initial zero current state, by adjusting the variable voltage control. Testing was repeated after a three-minute interval, to reduce subjective fatigue and to minimize the possibility of nerve accommodation.

The numerical values on the EPT display were recorded at twelve treatment points. The initial EPT levels were recorded exactly before starting the treatment. The EPT scores were also recorded each month immediately before insertion of the new archwire. Teeth that fail to respond to electric testing were recorded as a reading of 0 EPT units. The following clinical and radiologic criteria were used to define pulp necrosis: loss of pulpal sensitivity, gray color changes in the crown, and periapical radiolucency. Loss of pulpal sensitivity and at least one other clinical or radiologic sign were considered necessary before the diagnosis was made.