THE RELIABILITY OF ELECTRICAL PULP TEST AFTER CONCUSSION INJURY

Traumatic injuries to teeth present a difficult diagnostic problem wit h respect to determining the vitality of the affected teeth. Conventio nally, a latency period of 4 to 6 weeks is proposed as the amount of t ime required for the return of a positive electric pulp test (EPT) res ponse; however, this has been based on empirical data. The purpose of this study was to 1) determine a time frame during which a return of a reliable response to EPT may be measured, and 2) correlate this time frame with pulpal vascular changes that occur after traumatic injuries . Four canines from each of nine ferrets were used for this experiment (18 traumatized and 18 control teeth). A reproducible concussion inju ry was devised by releasing a known weight at a constant height above the facial surface of the experimental teeth. The EPT response was con firmed by the use of an ER IG muscle recorder. Animals were killed at 24, 18 and 72 h and 6, 12 and 28 days after the injury and the teeth a nalyzed histologically. The histological sections showed an absence of inflammatory cells in both groups; however, according to the NIH imag e system; an increase in the number of vessels Tvas detected in the ex perimental group when compared to the controls. In a majority of the c ases, a positive response to the EPT returned within 12 days post conc ussion injury and as early as 10 days. In addition, a significant vasc ular change was accompanied with the loss of the EPT response. This st udy provided a reliable method by which concussion injuries may be stu died using an animal model.