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A panel of experts was assembled to evaluate the collective evidence and create evidence-based clinical recommendations on pit-and-fissure sealants. These recommendations can become a useful tool that can be used in making decisions about sealant use. Tables that present the systems used for grading evidence, classifying the strength of recommendations, and summary of the recommendations, are also provided.

A study was conducted to examine the effects of dental sealants on bacteria levels within dental caries under sealants. Findings indicate that sealants reduced the probability of viable bacteria by 50%. It is concluded that in some studies, low levels of bacteria persisted after the use of sealants.

There are suggestions that the phylogeny of Streptococcus mutans, a member of the human indigenous biota that is transmitted mostly mother to child, might parallel the evolutionary history of its human host. The relatedness and phylogeny of plasmid-containing strains of S. mutans were examined based on chromosomal DNA fingerprints (CDF), a hypervariable region (HVR) of a 5.6-kb plasmid, the rRNA gene intergenic spacer region (IGSR), serotypes, and the genotypes of mutacin I and II. Plasmid-containing strains were studied because their genetic diversity was twice as great as that of plasmid-free strains. The CDF of S. mutans from unrelated human hosts were unique, except those from Caucasians, which were essentially identical. The evolutionary history of the IGSR, with or without the serotype and mutacin characters, clearly delineated an Asian clade. Also, a continuous association with mutacin II could be reconstructed through an evolutionary lineage with the IGSR, but not for serotype e. DNA sequences from the HVR of the plasmid produced a well-resolved phylogeny that differed from the chromosomal phylogeny, indicating that the horizontal transfer of the plasmid may have occurred multiple times. The plasmid phylogeny was more congruent with serotype e than with mutacin II evolution, suggesting a possible functional correlation. Thus, the history of this three-tiered relationship between human, bacterium, and plasmid supported both coevolution and independent evolution.

The role of practice based research networks (PBRNs), in making it possible for dentists to use clinical research outcomes in their practice, is discussed.

The production of two mutacins by one strain is studied, using the UA140 strain of Streptococcus mutans, a major contributor to dental caries. The mutacins or antimicrobial substances produced are the bacteriocin mutacin IV, a ribosomally synethsized peptide antibiotic, and mutacin I, a lantibiotic; their presence and effects in the oral cavity are also discussed.

A description of mutacin I biosynthesis is presented. The biosynthesis gene locus contains 14 genes and the resultant protein is 24 amino acids long with a molecular mass of 2,364 Da.

The cloning and sequencing of the mutacin III biosynthesis genes were conducted using information from the conserved sequence derived from various other lantibiotics. The isolation and purification of mutacin III from a modified semisolid culture medium were also investigated. The molecular mass of the purified peptide was calculated using laser desorption mass spectrophotometry and observed to be 2,266.43 Da, which is in agreement with the hypothesis that mutacin III has posttranslational modifications that are similar to those of the lantibiotic epidermin.

The specific genes for lantibiotic mutacin II biosynthesis in Streptococcus mutans T8 have been studied by DNA sequencing analysis. Mutacin II is a ribosomally synthesized lantibiotic secreted by group II S. mutans. Its gene cluster is made up of seven specific open reading frames consisting of a regulator gene (mutR), the prepromutacin structural gene (mutA), a modifying protein (mutM), an ABC transporter (mutT) and an immunity cluster (mutFEG).

DNA sequence analyses of the promoters in the lantibiotic mutacin II biosynthetic locus in Streptococcus mutans were conducted. The objectives were to gain further insight into the regulatory mechanisms for mutacin II production and to determine the transcription units in the mutacin locus. Results indicated promoter-like structures upstream of mutA and mutR and a rho-independent transcription terminator-like seqence between mutA and mutR.

Experiments were conducted to create a host-vector expression system for genetic manipulation of the lantibiotic mutacin II structural gene from Streptococcus mutans. A host strain was developed that contains all the genetic information for modification, export and processing of the mutated peptides to create an engineered mutacin. The cysteines were replaced with alanines to examine the role of the thioether bridges in the gene's antimicrobial activity.

A study was conducted on diacylglycerol kinase and the regulation of expression of the lantibiotic mutacin II of Streptococcus mutans. The findings indicate that DGK plays a key role not only in adapting to environmental stress but also in mutacin II production in S mutans T8. Moreover, the results show that the full-length dgk gene product together with the mutacin biosynthetic operon are necessary for the production of the mutacin II lantibiotic.