We found that elimination of active carious lesions, topical application of 1.23 percent APF, and one application of PI significantly suppressed salivary MS populations for at least 90 days relative to baseline. These findings corroborate and extend the findings of an earlier report (15
), which showed that MS levels declined initially but then rose toward baseline by 90 days. The magnitude of the suppression observed in this report appeared to be sustained for the entire 90-day study period (). One possible explanation for the sustained suppression is that demineralized human enamel is permeable to iodine (23
). Results from earlier studies have also demonstrated the utility of topical iodine solutions in suppressing MS. A single 2-minute topical application of 0.2 percent I2
-KI solution to the teeth of 9- to 13-year-old children eliminated MS from accessible human tooth sites for up to 13 weeks (16
). Another study demonstrated that a single prophylaxis followed by topical application of a 2 percent I2
-KI solution immediately after the prophylaxis and again at 3 and 5 days after the prophylaxis significantly reduced MS levels in subjects 18–23 years of age (17
). The reduction in MS populations in smooth surface plaque and saliva persisted for 20–24 weeks. However, it must be emphasized that MS level is only a biologic marker for susceptibility to dental caries and that the utility of topical iodine in preventing the disease would be a more accurate indicator of its therapeutic efficacy. In this regard, another investigation assessed the efficacy of bimonthly topical PI in a double-blind, placebo-controlled clinical trial in preventing the development of white spot lesions on the maxillary primary incisors of Puerto Rican babies (24
). These babies were at high risk for S-ECC as they were all colonized by MS and had decay-promoting feeding behaviors. A PI solution was applied bimonthly to the dentition of the experimental group for 1 year, and a placebo solution was applied bimonthly to the dentition of the control group for 1 year. Kaplan–Meier estimates (+/− standard error) of the probabilities of disease-free survival at 12 months were 91(+/−5) percent in the experimental group (n
= 39) and 54 (+/− 9) percent for the control group (n
= 44); P
= 0.0013. In a pilot clinical trial (25
) on 25 children with S-ECC treated under GA, the children were randomized into experimental and control groups. The experimental group received three topical applications of PI at bimonthly intervals during the first 4 months of the study, and the control group did not receive PI. Examination of the subjects at 6 months post dental surgery demonstrated that 18 percent of the children in the experimental group had dental caries as compared with 63 percent of the children in the control group. Collectively, these studies support the potential of PI in preventing dental caries.
The magnitude of the reduction of salivary MS reservoirs in our study participants is likely associated with a decrease in caries risk (). Earlier studies (26
) demonstrated that salivary magnitudes of MS ≤ 104
CFU/mL are associated with moderate to low caries risk. As illustrated in , 50 percent of our study participants had a salivary magnitude of MS ≤ 5.1 × 104
CFU/mL at 30, 60, and 90 days post dental surgery. Our study also documented the effect of teeth extracted at baseline on the suppression of MS. Our data showed that the magnitude of the decrease in MS levels was associated with the number of tooth surfaces lost. That is, the greater the number of surfaces lost, the greater the magnitude of MS suppression. Although all of the reductions in MS levels remained highly statistically significant, these data revealed a potential confounder that should be considered when assessing the efficacy of antibacterial agents on the reduction of MS following tooth extraction for S-ECC. This finding has been reported earlier where a reduction in MS levels in the setting of S-ECC was positively correlated to the number of extracted teeth (11
). A median of 8 dental surfaces (interquartile range 0–16 surfaces), typically carious primary maxillary incisors, were extracted per subject in our study.
Our exploratory study, coupled with earlier studies, indicate that adjunctive chemotherapy utilizing PI is a treatment strategy that holds promise for the treatment of children with S-ECC. There is reason to expect that recurring administration in a public health venue would also reduce the risk for ECC/S-ECC before its onset in high-risk babies and preschool children. Further, as noted earlier, approximately 40 percent of children treated for S-ECC under GA relapse with new carious lesions post treatment. Frequent, postsurgical application of PI has the potential to reduce substantially the proportion of children who relapse following treatment. Accordingly, randomized double-blind, placebo-controlled trials are needed to determine the utility of PI for prevention of ECC/S-ECC and for relapse in children treated for S-ECC. In such trials, repeated applications of PI over a longer period of time would be required. The results of our study suggest that reapplication of PI treatment would need to be repeated at least every 90 days.