Morphological changes in periodontopathic bacteria after Er,Cr:YSGG laser irradiation

Abstract

Purpose: To investigate changes in the morphology of periodontopathic bacteria after Er,Cr:YSGG laser irradiation by scanning electron microscopy (SEM). Method: Porphyromonas gingivalis and Aggregatibacter actinomycetemcomitans were cultured on anaerobic blood and brain heart infusion agar, respectively. After cultivation, each bacterial colony was exposed to Er,Cr:YSGG laser as single pulse, half colony, and full colony irradiations. The two bacteria were cultured on cover slips coated with human saliva to form bacterial biofilm. Half of the cover slips with biofilm were exposed to Er,Cr:YSGG laser, with bacterial colonies and biofilm samples examined by SEM. Results: Single pulse laser irradiation produced an ablation spot with diameter 400–500 μm on both P. gingivalis and A. actinomycetemcomitans colonies, showing many large pores surrounded by meandering branch-like structures. At higher magnifications (x2000, x3000, x5000), the colony surfaces presented as branch-like structures with a melted appearance. The affected surface area was rough with no bacterial walls visible. Half and full colony irradiation produced the same results as the single pulse irradiation treatment. The Er,Cr:YSGG laser produced an ablated area on both P. gingivalis and A. actinomycetemcomitans biofilm. The irradiated site showed a decreased population of bacterial cells with disrupted and irregular shapes. Conclusion: Er,Cr:YSGG laser irradiation caused morphological changes in both P. gingivalis and A. actinomycetemcomitans colonies and biofilm under SEM investigation as a beneficial bacterial disinfection treatment that eliminated periodontopathic bacteria.