Research in Focus
Twins Study Shows Flossing Significantly Decreases Gum Disease and Cavity-Causing Bacteria

Dr. Patricia Corby

Dr. Walter Bretz

Brazilian twins participating in the study.

NYU dental researchers Dr. Patricia Corby, Assistant Professor of Periodontology and Implant Dentistry, and Dr. Walter Bretz, Associate Professor of Cariology and Comprehensive Care, published a study in the Journal of Periodontology, "Treatment outcomes of dental flossing in twins: molecular analysis of the interproximal microflora," which provides new data about the importance of a flossing regimen in addition to daily brushing of the surfaces of the teeth and tongue.

"The purpose of this study was to assess the effects of dental flossing on the microbial composition of interproximal plaque samples in matched twins. The study was a two-treatment, examiner-masked, randomized, parallel-group, controlled study," note the authors.

Drs. Corby and Bretz studied 51 well-matched twin pairs (each set of twins was a case and a control), regarding their treatment responses to dental flossing over a two-week period. After the two-week study period, putative periodontal pathogens and cariogenic bacteria were overabundant in the group that did not floss compared to the group that performed flossing.

Additionally, note the authors, "Twins who flossed had a significant decrease in gingival bleeding compared to twins who did not floss. Relative to baseline, bleeding scores were reduced by 38% over the 2-week study period in the flossing group of twins."

The researchers conclude: "In a well-matched twin cohort, tooth and tongue brushing plus flossing significantly decreased the abundance of microbial species associated with periodontal disease and dental caries after a 2-week program."

Because they live together and have similar dietary habits and health practices, twins are considered excellent subjects for research that compares periodontal diseases and dental caries (cavity) development in people of the same age from similar environments.

This research stems from a five-year study, funded by a $1.7 million grant from the National Institute of Dental and Craniofacial Research (NIDCR), which seeks to assess the relative significance of potential factors in caries development utilizing 500 pairs of twins.

Dr. Bretz and Dr. Corby have assembled a cohort of 1,100 twin pairs that include both male and female identical and fraternal twins up to 21 years of age living in disadvantaged neighborhoods in the northeastern Brazilian city of Montes Claros, where inadequate water fluoridation and inability to access dental care put residents at risk for cavities.