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PURPOSE: This study estimated the influence of sealing the four permanent first molars of healthy seven-year-old school children with no caries (NC) or those with at least one carious lesion  on the salivary levels of mutans streptococci and lactobacilli at 4 and 12 weeks.  Permanent first molars were sealed in 31 children without caries (NC) and in 32 children with caries.   

MATERIALS & METHODS: This study was carried out in 2 elementary schools located in a lower-middle socioeconomic area in Granada.  The level of fluoride in drinking water was 0.07 ppm.  A total of 156 seven-year-old school children participated in a preventive program to seal fissures in permanent first molars.  The main criteria were children age 7 who were in good health and had 4 permanent first molars with erupted, healthy occlusal surfaces that permitted the application of fissure sealants.  94 met these requirements with 40 in the NC group and 54 in the C group.  Participants were examined for carious lesions according to WHO criteria (WHO 1987).  The sealants were then applied in the dental school by students who followed the manufacturer’s instructions.  Over the 12 week study period, 31 children were withdrawn from the study for various reasons including ones who had lost a sealant, began antibiotic treatment or abandoned the study completely.  The final sample population was reduced to 63 children with 31 in the NC and 32 in the C group.  The samples for counting the Strep mutans and lactobacilli were collected on 4 occasions; twice before applying the sealants then at 4 and 12 weeks after applying the sealants.  All the samples were collected at 10 A.M. and transported to the laboratory within 30 minutes where it was immediately processed.

RESULTS: Comparing the results of the 2 samplings prior to applying the fissure sealants revealed no significant difference in mutans strep or lactobacilli for either the NC or C group.  Group C presented significantly higher baseline levels of strep mutans and lactobacilli compared with the NC group.  At 4 and 12 weeks after applying the fissure sealants, the levels of lactobacilli remained relatively unchanged in both groups.A significant reduction in strep mutans over the entire study period was only observed in the NC group.  

DISCUSSION: The study design did not include a control group for ethical reasons.  Children who were withheld from this treatment would be denied their right to benefit from this program.  A large number of children who lost a sealant is bet explained by technique failures because they were applied by dental students.  Also, those undergoing antibiotic treatments were dropped due to the fact that strep mutans are particularly sensitive to the antibiotic.  It is also important to note that in a similarly previous study, that it was noted that microbial colonies sometimes fell from the plastic spatula provided, leading to a possible underestimation of the results.  Salivary levels of lactobacilli were not affected by applying fissure sealants and they remained unchanged in both groups throughout the study.  This finding is consistent with previous reports that lactobacilli are not always present among fissure microbiota.  Applying sealants did not affect salivary levels of strep mutans of the children with caries.  In the presence of active caries, strep mutans levels are much higher than in subjects with inactive lesions.  The carious lesions in this study were not restored and sealing of the fissures on permanent molars did not reduce the high levels of Strep mutans detected.   

SUMMARY/COMMENTS: Higher levels of Strep mutans have been reported on occlusal surfaces with or without caries compared to forming on restored surfaces, which may reflect their high level of colonization in pits and fissures.  Furthermore, it is easier to eliminate plaque from the surface of a sealant than from a fissure.  According to these results, applying fissure sealants on the four permanent molars helps to reduce the salivary levels of strep mutans in 7-year-old schoolchildren without caries lesions.  Even though the results sound credible, the fact that dental students performed the procedure adds an element of uncertainty.  The students lack the experience and proper technique.  Also, the sealants were not placed by the same individual, so different techniques and probably different amounts were placed.  It would have made more sense if the same dentist had applied the sealants to all the children just to have some consistency.