Consumption of gum containing xylitol, a five-carbon polyol sweetener, provides short- and long-term caries preventative benefits that relate to the frequency of chewing, duration of chewing, and study population who uses the gum (Hildebrandt and Sparks, 2000, Janket et al., 2019, Ly et al., 2006, Nakai et al., 2010, Newton et al., 2020, Seki et al., 2011, Shinga-Ishihara et al., 2012). Daily chewing of xylitol gum is known to reduce Streptococcus mutans levels, and blunt total salivary bacteria load during periods of interrupted regular oral hygiene (Hashiba et al., 2015, Takeuchi et al., 2018, Thorild et al., 2003). Although the mechanism of action associated with chewing xylitol-containing gum on oral bacteria is not fully understood, xylitol appears to inhibit the growth, metabolism, and production of polysaccharide by S. mutans. The mechanical properties of chewing gum also enhances salivary flow and potentially dilutes the effects of oral bacteria (Soderling, 2009, Soderling et al., 1987, Soderling et al., 2008, Wessel et al., 2015). Consistent with this, chewing xylitol-containing gum is effective in reducing dental caries development in high-risk children (Burt, 2006, Campus et al., 2013, Isokangas et al., 1988). While there is extensive knowledge of the effects of chewing xylitol-containing gum on salivary levels of S. mutans and dental caries prevention in children (Nasseripour et al., 2021, Soderling and Pienihakkinen, 2020), less is known about its effects on i) other oral bacteria in saliva, ii) the accumulation of bacteria on enamel, and iii) how rapidly the effects occur in adults.

Chewing gum can be used to deliver additives that can influence oral health (Ly et al., 2008). Blackberries are a natural fruit containing polyphenol and flavonoid antioxidants. Constituents in the extract from blackberries are known to provide a broad range of anti-inflammatory, anticancer, and antimicrobial properties (Cavanagh et al., 2003, Dai et al., 2009, Dai et al., 2007, Danaher et al., 2011, Khan et al., 2005) that could be beneficial to oral health. Also, the extract from blackberries has been shown to alter the metabolic activity of oral periodontopathogens while demonstrating minimal effect on oral commensals (Gonzalez et al., 2013). Hence, the diverse properties of blackberries together with the beneficial antibacterial properties of xylitol make their combination in a chewing gum a promising adjunct for prevention or treatment of biofilm-based infections.

In this study, we sought to determine the effect of a freeze-dried blackberry powder (BP)-containing chewing gum on bacteria associated with caries and periodontal disease in a randomized controlled crossover trial. The hypothesis was that short-term use of chewing gum containing xylitol and BP would selectively and rapidly affect the bacterial composition in saliva and on enamel of adults.