BACTERIAL PENETRATION OF THE ROOT-CANAL OF INTACT INCISOR TEETH AFTERA SIMULATED TRAUMATIC INJURY

One of the aims in treating traumatised teeth is to maintain the vital ity of the pulp or allow conditions favourable for pulp revascularisat ion. However, infection of the pulp and root canal system may prevent this. A number of pathways have been proposed that allow bacteria to i nvade the root canal system, however most of these pathways cannot acc ount for pulp infection in teeth that did not sustain injury to the pe riodontal attachment. Enamel/dentine cracks have been proposed as a po rtal for bacterial invasion of seemingly intact teeth and the aim of t his study was to determine if bacteria could invade the root canal sys tem after a simulated traumatic episode. Twenty intact and sound upper central incisors were chosen and prepared. One tooth was selected as a sterility control and the external crown surface of the remaining 19 teeth was subjected to infection with Streptococcus gordonii in a bac terial microleakage model. Over 7 days samples of growth media from th e root canal system were taken and tested for bacteria. Sixteen of the teeth did not demonstrate bacterial invasion over the time frame. The se teeth were then prepared for testing in a pendulum impact device an d were subjected to a blow which did not fracture the crow-ns or dislo dge the tooth from its simulated alveolus. The teeth were then prepare d and tested in the bacterial microleakage model. After impact seven o f the teeth demonstrated bacterial invasion of the root canal system ( P=0.002). These teeth were then reprepared for testing in the bacteria l microleakage model. The crowns of five teeth, selected at random, we re coated with two layers of light cured unfilled resin, the remaining two were used as positive controls. All the teeth coated with resin d id not demonstrate bacterial invasion (P=0.00), while the positive con trols demonstrated invasion. The results suggested that enamel/dentine infractions were pathways for bacterial invasion of the root canal sy stem of traumatised teeth. The application of unfilled resin to the an atomical crown prevented infection.