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 denial ultrasonic scaler, Actinobacillus actinomycetemcomitans and Porphyromonas gingivalis suspensions, were subjected to the vibration s of a Cavitron P1 insert for 2.5 and 5.0 ruin in an acoustically-simu lated pocket model and the survivors enumerated, The extent of any cav itation occurring within the pocket model to which the statistically s ignificant bactericidal activity observed might be attributed, was det ermined by 'sonoluminescence', which was then investigated by photomul tiplication techniques. However, these failed to detect any sonolumine scence within the pocket space and, moreover, the necessary deflection of the water coolant away from the insert tip, to avoid flooding of t he experimental pocket, proved to result in temperatures of 47.6 degre es C and 52.3 degrees C at the respective time intervals, and thereby constituted an alternative possible bactericidal mechanism, Examinatio n of the effects of such temperature changes on the target bacteria th en revealed statistically significant differences in the viable counts of bath microorganisms after 5.0-min periods; and as such were compar able to those previously detected in relation to the pocket model, Whi lst it must be presumed that the bacteriolytic effect observed in the main investigation was due to the incidental temperature changes, in t he absence of acoustic cavitation the influence of any associated acou stic microstreaming cannot be discounted. Further investigations to as sess the bactericidal potential of acoustic phenomena using a modified experimental to exclude any hyperthermic effects are therefore necess ary.