Faculty Bibliography

Short-chain carboxylic acids are the metabolic by-products of pathogenic anaerobic bacteria and are found at sites of infection in millimolar quantities. We previously reported that propionic acid, one of the short-chain carboxylic acids, induces an increase in intracellular Ca2+ ([Ca2+]i) in human neutrophils. Here we investigate the effect of propionic acid on superoxide generation in human neutrophils. Propionic acid (10 mm) induced inositol 1,4, 5-trisphosphate (IP3) formation and a rapidly transient increase in [Ca2+]i, but not superoxide generation, whereas 1 microm formylmethionyl-leucyl-phenylalanine (fMLP), a widely used neutrophil-stimulating bacterial peptide, stimulated not only IP3 formation and Ca2+ mobilization but also superoxide generation. The IP3 level induced by propionic acid was slightly lower than that induced by fMLP. The transient increase in [Ca2+]i induced by propionic acid immediately returned to the basal level, whereas a sustained increase in [Ca2+]i, which was higher than the basal level, following a transient increase in [Ca2+]i was induced by fMLP. The peak level induced by propionic acid was lower than that with fMLP. In the absence of extracellular Ca2+, thapsigargin, a potent inhibitor of endoplasmic reticulum Ca2+-ATPase, induced an increase in [Ca2+]i even after propionic acid stimulation, but not after fMLP. The Ca2+ ionophore A23187 and thapsigargin induced superoxide generation by themselves. Propionic acid enhanced the superoxide generating effect of A23187 and thapsigargin. These results suggest that Ca2+ mobilization induced by propionic acid is much weaker than that with fMLP, and propionic acid is able to generate superoxide in the presence of a Ca2+ ionophore and a Ca2+ influx activator.

Short-chain carboxylic acids (e.g., lactic acid, propionic acid, butyric acid) are metabolic by-products of bacterial metabolism which can accumulate in the gingival crevice. It is of no small consequence, therefore, that 1- to 5-mM concentrations of these acids exhibit significant biological activity, including the ability to alter cell proliferation and gene expression in cells of importance to the periodontium. This communication reports on the in vivo concentrations of propionic and butyric acid in the gingival crevices of periodontal subjects with severe and mild disease. The results indicated that severely diseased subjects exhibited a > 10-fold increase in the mM concentration of these acids when compared with mildly diseased subjects (mean propionic acid-severe = 9.5 +/- 1.8 mM, and mild = 0.8 +/- 0.3 mM; mean butyric acid-severe = 2.6 +/- 0.4 mM, and mild = 0.2 +/- 0.04 mM). These differences (mean +/- SE) were significant (p < 0.0001). The propionic and butyric acid concentrations were below detection limits in healthy sites of mildly diseased subjects. The propionic and butyric acid concentrations also associated significantly with clinical measures of disease severity (e.g., pocket depth, attachment level) and inflammation (e.g., subgingival temperature, % of sites bleeding when probed), and with the total microbial load (all p < 0.05). Taken together, these data suggest that short-chain carboxylic acids play a mediating role in periodontal disease pathogenesis.

The Sonicare sonic toothbrush and a traditional manual toothbrush were compared for efficacy in improving periodontal health in young orthodontic patients with existing gingival inflammation. A 4-week, single-blind clinical trial was employed. Twenty-four subjects, ages 11-17 years, who were fully bonded and banded with fixed orthodontic appliances were selected. Subjects were randomly assigned to use either the manual or the Sonicare toothbrush, instructed in its use, and asked to brush each morning and evening for 2 minutes. Plaque index, gingival index, percentage of sites which bled on probing, pocket depth, and total gram-negative bacteria in a subgingival plaque sample were assessed at baseline and 4 weeks around the banded teeth. The results demonstrate that the Sonicare brush was significantly more effective than the manual brush in all clinical parameters. Sonicare was statistically superior to the manual brush in supragingival plaque reduction (57% vs. 10%, respectively; p < 0.001). Gingival Index scores fell by 29 percent in the Sonicare group, but only 3 percent in the manual group. Reduction of bleeding on probing was significantly greater in the Sonicare group than in the manual group (p < 0.001). The Sonicare group decreased from 78% bleeding sites at baseline to 24.5% after 1 month. In the manual group there was only a slight reduction in bleeding on probing (70% of sites at baseline and 64.6% sites after 1 month). Mean pocket depths were significantly reduced compared to baseline values in both the Sonicare and the manual groups (p < 0.001). Pocket depth reduction in the Sonicare group was, however, significantly greater than in the manual group (28% vs. 6%, respectively: p < 0.001). Total gram-negative bacteria in subgingival plaque samples from banded test teeth of a subset of patients were reduced in the Sonicare group (p < or = 0.05), but increased in the manual group. These results clearly demonstrate that the Sonicare sonic toothbrush is superior to a manual toothbrush in improving periodontal health in adolescent orthodontic patients with existing gingivitis.