This study was conducted to investigate the relationship between the anatomical differences of the teeth (differences in tooth locations and types) and the degree of progression of periodontitis. We examined whether the stages and grades of periodontitis according to the classification system of the American Academy of Periodontology/European Federation of Periodontology might vary according to the tooth type.

Over a period of 5 years, we evaluated the clinical attachment loss, probing depth, tooth loss, and degree of tooth mobility of 99,277 teeth of 1,375 Japanese patients with periodontitis. We calculated the number of teeth in each category according to whether they were classified the teeth into maxillary or mandibular teeth, teeth on the right or left sides, and anterior, premolar or molar teeth for the analyses in this study.

Differences in the staging were found between the maxillary and mandibular teeth, and among the anteriors, premolars and molars, whereas almost no differences were found between the right and left sides. Periodontitis progresses rapidly to a significantly greater degree of severity in the maxillary teeth and molar teeth than in the mandibular or other types of teeth.

These differences depending on the tooth locations and types need to be considered when classifying the stages of periodontitis according to the new classification system.

Neutrophil extracellular traps (NETs) occur in periodontal pockets of patients with periodontal disease, but the mechanism by which NETs are expressed by periodontopathic bacteria has not been clarified. Therefore, the aim of this study was to elucidate the relationship between NET expression and Toll-like receptors (TLRs) induced by Porphyromonas gingivalis lipopolysaccharide (PG-LPS).

Neutrophils were isolated from peripheral blood and stimulated with 1, 10, 25, 50, or 75 nM phorbol myristate acetate (PMA), 1, 10, or 100 μg/ml PG-LPS, or 1, 10, or 100 μg/ml Escherichia coli LPS (EC-LPS). Polymorphonuclear leukocytes were also stimulated after TLRs were blocked using specific antibodies. NETs were observed using scanning electron microscopy (SEM), fluorescence immunostaining of NET component DNA, histone, and neutrophil elastase (NE), and the amounts of extracellular DNA and NE were measured by NET quantification assay and ELISA, respectively.

SEM images showed that 50 nM PMA, 100 μg/ml PG-LPS, and 100 μg/ml EC-LPS stimulated the release of filamentous structures from neutrophils. Fluorescence immunostaining images showed that the filamentous structures stained positive for DNA, histone, and NE, confirming that the structures were NETs. The amounts of extracellular DNA and NE were also significantly increased by treatment with PMA, PG-LPS, and EC-LPS compared to control. A decrease in NET expression was observed in the PG-LPS group when TLR2 and TLR4 were inhibited.

The results of this study suggest that PG-LPS induces NET expression via TLR2 and TLR4.