The study found that people with worse gum disease have higher levels of the antimicrobial peptide LL‑37 in their saliva, especially when a specific bad bacterium (T. denticola) is present. However, smokers (or those exposed to tobacco smoke) have lower LL‑37 levels, which may make their gums more vulnerable to disease.

The purpose of this study is to examine the relationship between salivary LL-37 levels and clinical severity in patients with chronic periodontitis (CP). The presence/absence of four periodontopathic bacteria and salivary cotinine levels were also examined to assess the impact of these factors on LL-37 production. Unstimulated salivary samples were collected from 69 patients with CP. Salivary concentrations of LL-37 and cotinine were measured by enzyme-linked immunosorbent assay. Aggregatibacter actinomycetemcomitans, Porphyromonas gingivalis, Tannerella forsythia, and Treponema denticola in saliva were detected by polymerase chain reaction. Periodontal examination included determination of probing depth (PD), clinical attachment level, bleeding on probing, and plaque control record. Mean salivary LL-37 concentration was 225.0 ± 227.2 ng/mL, and a high prevalence of periodontopathic bacteria was observed. The stepwise ordinal logistic regression model showed that high salivary LL-37 levels were significantly associated with the presence of T. denticola and higher percentage of teeth with PD ≥5 mm. In addition, higher salivary cotinine levels (≥8 ng/mL) were negatively associated with salivary LL-37 levels. Salivary LL-37 level was positively correlated with severe periodontal destruction, and production was apparently associated with periodontopathic bacterial infection. The negative correlations between salivary LL-37 and cotinine levels also suggest that smoking or long-term exposure to environmental tobacco smoke can lead to lower LL-37 levels in the oral cavity and increased risk of periodontitis.