Atomic Force Microscopy: A three-dimensional reconstructive tool of oral microbiota in gingivitis and periodontitis

This study aims to ascertain the advantages of Atomic Force Microscopy (AFM) in the morphologic study of microorganisms and their interactions within the subgingival biofilm in patients with gingivitis and periodontitis.

Conducted a study on twenty patients, ten patients with severe periodontitis with probing the pocket depth of ≥8 mm, with a clinical attachment loss (CAL) of ≥6 mm CAL and ten patients with gingivitis: ≥5 mm pocket depth, and no attachment loss, was selected for the study.

Bacterial biofilms were collected and slide preparation done. Morphological study was done using AFM. AFM consists of a cantilever-mounted tip, a piezoelectric scanner, a photodetector diode, a laser diode, and a feedback control. The laser beam is reflected from back of the cantilever into the quadrant of the photodetector. AFM works on the principle of interaction between the tip and the sample which causes the cantilever to deflect, thereby changing the position of laser onto the photodetector. Methodology used for studying the bacteria through AFM includes the following: (1) Probe type: Platinum coated silicon nitrate tip. (2) Probe force: 0.11 N/m. (3) Probe geometry: Triangular shaped tip. (4) Probe frequency: 22 KHz. (5) Probe immobilization: Used in Contact mode. AFM Solver Pro-M (NT-MDT) equipped with ETALON probe was used to take images in Nova software.

The investigation showed various morphological features, such as shape, size, and secretory product-like vesicles of the bacterial species involved in gingivitis and periodontitis. More bacterial surface details were studied by reproducing a three-dimensional reconstruction using AFM.

The morphological variations of bacteria of different sizes, and shapes, cell wall structures, secretory product-like vesicles flagellated and filamentous microorganisms, polymorphonuclear leukocytes, and bacterial coaggregation analysis were done by AFM. Results of the present study conclude that AFM is a quite a reliable method for studying morphology of bacterial species involving periodontal diseases and is also used to study microbial interactions in biofilm.