Antibody response to actinomyces antigen and dental caries experience: implications for caries susceptibility

Abstract

Fluoridated dentifrices reduce dental caries in subjects who perform effective oral hygiene. Actinomyces naeslundii increases in teeth-adherent microbial biofilms (plaques) in these subjects, and a well-characterized serum immunoglobulin G (IgG) antibody response (Actinomyces antibody [A-Ab]) is also increased. Other studies suggest that a serum IgG antibody response to streptococcal d-alanyl poly(glycerophosphate) (S-Ab) may indicate caries experience associated strongly with gingival health and exposure to fluoridated water. The aim of this study was to investigate relationships between A-Ab response, oral hygiene, S-Ab response, and caries experience. Measurements were made of A-Ab and S-Ab concentrations, caries experience (number of decayed, missing, and filled teeth [DMFT], number of teeth surfaces [DMFS], and number of decayed teeth needing treated [DT]), exposure to fluoridated water (Flu), mean clinical pocket depth (PD; in millimeters), and extent of plaque (PL) and gingival bleeding on probing (BOP). A-Ab concentration, the dependent variable in a multiple regression analysis, increased with S-Ab concentration and decreased with PL and DMFT adjusted for Flu (R(2) = 0.51, P < 0.002). Residual associations with age, DMFS, DT, and BOP were not significant. In addition, an elevated A-Ab response, defined from immunoprecipitation and immunoassay measurements, indicated a significant, 30% reduction in DMFT after adjustment for significant age and Flu covariance (analysis of variance with covariance F statistic = 10.6, P < 0.003; S-Ab response and interactions not significant). Thus, an elevated A-Ab response indicates less caries in subjects performing effective oral hygiene using fluoridated dentifrices. Conversely, a low A-Ab response is suggestive of decreased A. naeslundii binding to saliva-coated apatite and greater caries experience, as reported by others.

FIG. 1.

Aggregate of standard curves from each plate. Actinomyces antibody concentration (nanograms/milliliter) was calculated from the dilution of standard serum on each plate and graphed against the absorbance obtained (see Materials and Methods). Vertical lines indicate the standard deviation of measurements across all plates.

FIG. 2.

Ranked A-Ab concentrations from the 397 subjects. The low response supremum was the mean plus standard deviation of individuals whose serum did not precipitate antigen (see the text). Dotted line parallel to the x axis indicates the supremum (15 μg of A-Ab reactive IgG). The vertical arrow indicates that the supremum occurs just before the ranked A-Ab concentrations (○) curve away from the x axis. A similar figure and related statistics were described in detail for the S-Ab response (24).

FIG. 3.

Actual A-Ab concentration compared with A-Ab concentration derived from the independent variable equation (Table 2). Filled symbols represent the data from dental patients and the unfilled ones from dental students.