Antimicrobial effects of 2.94 μm Er:YAG laser radiation on root surfaces:: an in vitro study

Objectives: This in vitro study investigated the antimicrobial effects of 2.94 mum Er:YAG laser radiation on root surfaces. Materials and methods: The study used 125 extracted teeth which were divided into 2 groups (A, B) of 40 teeth and 3 groups of 15 teeth (C, D, E). A defined and similarly-sized area of the root surface was inoculated with an aliquot of 7 mul of a bacterial suspension of Escherichia coli (ATCC 25922), Staphylococcus aureus (ATCC 25923), Actinobacillus actinomycetemcomitans (ATCC 43719), Eikenella corrodens (ATCC 51724), or Peptostreptococcus micros (ATCC 33270). Subsequently, the samples from each group were further divided into subgroups which have been irradiated either with 55, 75, and 105 (group A, B) or 55 and 75 (group C, D, E) laser pulses. 1 subgroup of each group was left untreated as control. The source of laser radiation was an Er:YAG laser emitting pulsed infrared radiation at a wavelength of 2.94 mum. The number of bacteria was determined using the surface spread plate technique. The statistical analysis was performed using ANOVA followed by the Scheffe-test. Results: Depending on the number of laser pulses the bacterial load in the E. coli group was reduced by the Er:YAG laser radiation after exposure to 105 laser pulses to 5.5% of the initial count and that in the Staph. aureus group to 15.1%. The number of bacteria in case of A. actinomytemcomitans was reduced to 8.3%, in case of E. corrodens to 3.0% and in case of P. micros to 22.0% after application of 75 laserpulses. Conclusion: Besides the selective removal of plaque and calculus, the 2.94 mum Er:YAG laser radiation causes reduction in bacteria on root surfaces.