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Current dental treatment for plaque and tooth decay may be ineffective in eliminating some cavities-inducing bacterial strains in children

OHSU School of Dentistry team identifies dominant genetic strains of bacteria that persist in children following caries restorative treatment

Researchers at the Oregon Health & Science University School of Dentistry have identified dominant genetic strains of bacteria in children following treatment for microbial-caused plaque and tooth decay. And while therapies such as antimicrobial rinse and fluoride treatment are important and effective at reducing bacteria immediately following oral care, the reduction is not permanent and several dominant strains of bacteria are present within six months of care, the researchers report.

“The implications of this study are that well-accepted practices for severe early childhood dental caries (microbial disease) therapy should be more closely examined for efficacy,” said Curt Machida, Ph.D., principal investigator and OHSU professor of integrative biosciences and pediatric dentistry.

The study is published online in the March-April 2012 issue of Pediatric Dentistry.

It is estimated that severe dental caries affect 1 percent to 5 percent of children younger than five in the United States. One of the most predominant bacteria associated with dental caries is mutans streptococci, which has seven species that are classified into several serotypes and genetic strains. With increasing focus on the importance of mutans streptococci strain variation among patients and their oral health problems, this study used molecular analyses to more closely examine the genetic stain differences of mutans streptococi within patients before and following caries restorative therapy.

The OHSU study focused on the mutans streptococci strains still prevalent after oral health treatment and caries restorative therapy in children. Plaque from seven children, ages 3 to 12, who visited the dentist with severe early childhood caries, was collected at three appointments: prior to oral care, at the two- to four-week post-treatment visit, and at the six-month recall visit.

Within the mutans streptococci group, 39 genetic strains were identified in the study, as well as seven strains of non-mutans streptococci. Before oral health treatment, study patients had from three to seven mutans streptococci genetic strains, which dropped to one or two dominant strains in most patients six months after care.

Care for severe early childhood caries included restorations with various materials (amalgam, composite, stainless steel crowns), as well as extractions, sealants, prophylaxis and application of fluoride varnish, all conducted at a single patient visit while under anesthesia. Six months after oral health and caries restorative therapies dominant strains of mutans streptococci with high acid-generating potential were found in several children.

“Our pilot study was undertaken to begin a framework for understanding the diversity of S. mutans in individuals with severe early childhood caries, and to define changes in bacteria following oral health care and caries restorative therapy,” said Machida. “We purposely chose to examine larger numbers of isolates per patient over a longitudinal period of time in order to more accurately examine the changes in mutans streptococci after oral treatment. It is likely that one or more components of caries restorative therapy is responsible for the dominant strains, but at this time we cannot determine which one.”

The OHSU team included Machida; Elizabeth A. Palmer, D.M.D. `08, Pediatric Dentistry `10, assistant professor of pediatric dentistry; Patricia Peirano, D.D.S., second-year pediatric dentistry resident; Aivan Nguyen, D.D.S., Pediatric Dentistry `10; Truman Nielsen, laboratory assistant; fourth-year dental students Alex Vo, Stephen Jackson, and TJ Finlayson; second-year dental student Anna Nguyen; third-year medical student Becca Sauerwein; Katie Marsh, D.M.D. ’11, first-year pediatric dentistry resident; Issac Edwards, D.M.D. `11; Beth Wilmot, Ph.D., OHSU biostatistician and statistical geneticist; John Engle, D.D.S., assistant professor of pediatric dentistry; John Peterson, D.D.S., professor of pediatric dentistry; and Tom Maier, Ph.D., assistant professor of integrative biosciences and oral pathology and radiology.

The research was funded by the Pediatric Dentistry Resident Fund of the OHSU Foundation and the Oregon Clinical and Translational Research Institute, which is funded by a grant from the National Center for Research Resources (NCRR), a component of the National Institutes of Health (NIH) and NIH Roadmap for Medical Research.

Established in September 2006 through the NIH’s Clinical and Translational Science Award (CTSA) program, OCTRI is a unique partnership between OHSU and Kaiser Permanente Center for Health Research – bringing together an academic medical center and an innovative managed care organization. OCTRI’s mission is to improve human health by enhancing clinical and translational research. OCTRI works with institutional partners, community organizations, and industry to engage communities in clinical research efforts and to reduce the time it takes for laboratory discoveries to become treatments for patients.

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