THE BACTERICIDAL EFFECTS OF DENTAL ULTRASOUND ON ACTINOBACILLUS-ACTINOMYCETEMCOMITANS AND PORPHYROMONAS-GINGIVALIS - AN IN-VITRO INVESTIGATION

This study investigated the possible bactericidal acoustic effects of the dental ultrasonic scaler. Actinobacillus actinomycetemcomitans and Porphyromonas gingivalis suspensions, were subjected to the vibration s of a Cavitron PI insert for 2,5 and 5.0 min in an acoustically-simul ated pocket model and the survivors enumerated. The extent of any cavi tation occurring within the pocket model to which the statistically si gnificant bactericidal activity observed might be attributed, was dete rmined by 'sonoluminescence', which was then investigated by photomult iplication techniques. However, these failed to detect any sonolumines cence within the pocket space and, moreover, the necessary deflection of the water coolant away from the Insert tip, to avoid flooding of th e experimental pocket, proved to result in temperatures of 47.6 degree s C and 52.3 degrees C at the respective time intervals, and thereby c onstituted an alternative possible bactericidal mechanism. Examination of the effects of such temperature changes on the target bacteria the n revealed statistically significant differences in the viable counts of both microorganisms after 5.0-min periods, and as such were compara ble to those previously detected in relation to the packer model. Whil st it must be presumed that the bacteriolytic effect observed in the m ain investigation was due to the incidental temperature changes, in th e absence of acoustic cavitation the influence of any associated acous tic microstreaming cannot be discounted,Further investigations to asse ss the bactericidal potential of acoustic phenomena-using a modified e xperimental to exclude any hyperthermic effects are therefore necessar y.