Tonsillolith: Not Just a Stone But a Living Biofilm

Problem To study the morphology and activity of tonsilloliths ex vivo, using confocal microscopy and microelectrodes. Understanding the similarities of tonsilloliths to dental biofilm by demonstrating oxygen respiration, de‐nitrification, and acid production. Methods Tonsilloliths were harvested from several patients with cryptic pockets and sent to the laboratory under sterile conditions. The tonsilloliths were examined by confocal microscopy to determine the presence and distribution of bacteria. Microelectrodes (dissolved oxygen, nitrous oxide, and pH) were used to measure the rates of aerobic and anaerobic respiration, and acid production, when exposed to saliva (10%) and after sucrose and fluoride addition. Results Morphologically, the tonsilloliths were similar to dental‐plaque biofilms, containing ‘corn‐cob’ structures, filaments and cocci. The microorganisms respired both oxygen and nitrate in physiological concentrations. The oxygen concentration in the center of the tonsillolith (500 microns) was depleted to approximately 1/10th that of the overlying fluid. The addition of 10% sucrose resulted in the production of acid within the tonsillolith by dropping the pH from 7.3 to 5.8 at a depth of 200 microns. On addition of fluoride (1000 pm) the pH increased to 6.1, suggesting that fluoride suppressed the acid fermentation of sucrose. The profiles showed, aerobic respiration near the top, de‐nitrification slightly lower and acidification towards the center. The tonsillolith therefore, had stratified layers, similar to dental (and other) biofilms. The depletion of oxygen and acid production following addition of sucrose may encourage the proliferation of anaerobic/acidophilic bacteria within the tonsillolith. Conclusion Tonsilloliths exhibit biofilm structure and the formation of chemical gradients through physiological activity. Significance While complete or intracapsular tonsillectomy is an option for treating chronic cryptic infections, understanding the morphology and biofilm characteristics of tonsilloliths may stimulate scientists in using limited or non‐surgical remedies in treating chronic cryptic infections in the future. Support This study was funded by Valam and Philips Oral Healthcare.