This study is part of a series to explore effective xylitol delivery vehicles that can be used in school programs in the U.S. Results from the xylitol dose study [3] showed groups consuming 6.9 g and 10.3 g xylitol per day delivered via chewing gum had significant reductions in S. mutans/sobrinus levels in plaque and saliva after five weeks and six months of exposure. The smallest dose, 3.4 g/day, showed a small but not statistically significant reduction. However, the study did not have groups consuming doses between 3.4 g and 6.9 g per day, thus it is possible that doses within this range would also be effective. The xylitol frequency study [4] where the xylitol dose was kept constant (10.3 g/day) and frequency varied (0, 2, 3, and 4), showed a linear response in S. mutans/sobrinus reduction with increasing frequency of use. However, a minimum frequency of three administrations per day was required for xylitol chewing gum at therapeutic dose to significantly reduce S. mutans/sobrinus levels in plaque and saliva after five weeks of exposure. Twice pay day use group showed a small reduction consistent with the linear line model but was not statistically different from the control. These studies attempted to establish the minimum effective dose and frequency for the use of xylitol. This is important toward establishing guidelines for effective dose and frequency of xylitol use.

Another study in this series assessed the bioavailability of xylitol in saliva over 15 to 20 minutes during and after consumption of different xylitol-containing products including: pellet (2.6 g) and stick (3 g) chewing gums, syrup (2.7 g), and gummy bear (2.6 g) [13]. Participants swallowed normally and at 10 to 11 specified time points, spat into a receptacle until a minimum of 0.5 mL saliva was collected. Xylitol concentration in saliva was measured by high performance liquid chromatography (HPLC). The results showed similar time-curves as well as areas under the curve for the products tested. Thus, similar dose and frequency of xylitol consumption via these products would likely result in comparable S. mutans/sobrinus reduction.

In the present study, we tested the effectiveness of gummy bear snacks containing higher levels of xylitol in reducing S. mutans/sobrinus and Lactobacillus spp. levels in children's plaque after six weeks of exposure. The study was designed and implemented prior to initiation of the bioavailability study when uncertainty remained as to whether different xylitol-containing products would have comparable oral bioavailability. The study design controlled for frequency and number of gummy bears consumed. A school-based randomized controlled clinical trial currently underway is using a lower xylitol dose (7.8 g/day) and a natural fiber (inulin) gummy bear as the control with dental caries as an endpoint.

The results showed that six weeks of habitual xylitol gummy bear consumption reduced the levels of S. mutans/sobrinus in plaque compared to baseline levels (Figure 2). A nearly one log 10 mean reduction of S. mutans/sobrinus levels in children is highly significant given that children had lower levels of S. mutans/sobrinus infection (mean baseline ~2 log 10 ) than among adults in our previous studies (mean baseline ~5 log 10 ). The 15.6 g/day group had a slightly greater reduction in S. mutans/sobrinus levels but the difference was not significant compared to the 11.7 g/day group. This is in agreement with our dose-response study, which suggested a plateau effect at higher xylitol doses. Controlling for the number of unconsumed gummy bears among the groups did not change the results of within or across group comparisons. This supports findings from previous studies that xylitol reduces MS [14, 15]. For a review of these studies, see Maguire & Rugg-Gunn (2003) [16]. More importantly, the results indicate that a gummy bear snack may be an effective method for delivering xylitol. However, these results should be interpreted cautiously given that a significant reduction in S. mutans/sobrinus levels was also observed with the maltitol group. Maltitol is a member of the sugar alcohol family that, as a class, is widely considered to be non-cariogenic. However, aside from xylitol, studies involving sugar alcohols, most commonly sorbitol, suggest they have little effect in actively reducing MS levels.

There have been only a few studies on the association between maltitol and MS or dental caries. In a specific pathogen-free (SPF) Sprague-Dawley rats study, Ooshima and colleagues reported that maltitol did not induce dental caries in SPF rats infected with MS including S. mutans MT8148R or S. sobrinus 6715 strain, and replacement of the dietary sucrose content with maltitol resulted in a trend towards caries reduction in SPF rats [17]. However, a study conducted in Estonia found xylitol-maltitol and xylitol-polydextrose candies (49% xylitol in each) were equally effective in reducing MS suggesting that maltitol gave no added benefit to xylitol [18]. In a more recent study comparing xylitol (7.9 g/day) and maltitol (7.1 g/day) chewing gum to control (no gum) consumption over a six month period, Haresaku and colleagues reported that xylitol significantly reduced MS levels in plaque while maltitol increased MS levels [19]. This is clearly incongruous with our findings. However, the authors acknowledged several weaknesses in the study including a non-randomized study design (participants had the option to select their gum flavor which dictated their group assignment), average age of the maltitol group was higher which had a negative association with plaque MS levels, and only 59% of the control group remained in the final analysis. In addition, our study used a very high maltitol dose (44.7 g/day) 4–6 times that of previous studies, thus the results cannot aptly be compared nor can a direct comparison between the 15.6 or 11.7 g/day xylitol dose and the 44.7 g/day maltitol dose be made. Finally, it has been suggested that high or habitual polyols consumption may disturb polysaccharide synthesis leading to plaque and thus MS that are more loosely bound to teeth surfaces, consequently reducing MS levels [20]. Nevertheless, conflicting evidence exists and further research on the association between maltitol, S. mutans/sobrinus, and dental caries is needed.

The finding that S. mutans/sobrinus reductions were not significantly different between the two xylitol groups was not surprising as our previous dosage study in this series suggested a plateau effect at higher therapeutic doses and our oral bioavailability study showed similar time curves and areas under the curve for xylitol chewing gums, syrup, and gummy bears. The reduction observed with maltitol was also not significantly different from the xylitol groups individually or combined. Although a systematic error in processing, culturing, or enumerating of S. mutans/sobrinus in the latter part of the study might explain the lower levels observed in all three groups, it would be unlikely since the reduction observed with the xylitol groups was as expected. Furthermore, sample processing, transport, culturing, and enumeration were carried out by protocol as was done with the baseline samples and the research and laboratory staff had remained unchanged, were highly experienced, and had carried out similar protocols in the previous studies of this series. The mechanical act of frequent chewing of gummy bears may reduce plaque formation and S. mutans/sobrinus adhesion but then Lactobacillus spp. levels should be similarly affected yet that was not observed. Lactobacillus spp. levels remained unchanged. Furthermore, chewing gum studies with sorbitol or sorbitol/maltitol gums have shown no effects on MS plaque or saliva levels [3, 21, 22]. Nevertheless, the xylitol results would have been strengthened if a true non-actively anticariogenic substance such as sorbitol was used as a control as in previous xylitol studies.

As noted earlier, 27% of the children (X16 = 32%, X12 = 24%, M45 = 25%) did not have measurable S. mutans/sobrinus levels at baseline and may have biased the results. Sub-analyses with these children removed showed greater mean log 10 reductions in S. mutans/sobrinus levels for all groups (X16 = 1.74 vs. 1.13, X12 = 1.21 vs. 0.89, M45 = 1.22 vs. 0.91). There were no significant differences between the three groups in the levels of reduction.

This study also assessed Lactobacillus spp. response to xylitol exposure as the literature contains conflicting information. Juric and colleagues reported a reduction in these bacteria after two months of xylitol chewing gum exposure [23]. The Turku sugar studies [24] and the Belize xylitol study [21] with much longer follow-up periods also reported reductions in salivary Lactobacillus spp. On the other hand, in a study comparing the effects of chewing xylitol (5 g/day), sorbitol, and fructose gum over a four week period on S. mutans and Lactobacilli in plaque, Loesche and colleagues reported only xylitol significantly reduced S. mutans levels and there was no effect on the Lactobacilli levels for any gum [14]. Similarly, a recent study among young adults (21 to 24 years of age) reported no change in salivary Lactobacillus spp. in response to xylitol chewing gum consumption three times per day (6 g total) over a three week period but reported a significant reduction in salivary MS level [25]. The current study found that neither of the xylitol groups nor the maltitol group had an effect on Lactobacillus spp. level. It is possible that xylitol selectively affects and reduces S. mutans/sobrinus levels without altering Lactobacillus spp. levels, the other bacteria implicated in development of caries. Alternatively, the six weeks follow-up period of this study might not have been of sufficient length to detect the effects on Lactobacillus spp. Nevertheless, xylitol studies with dental caries as an end-point have repeatedly shown xylitol's effectiveness in caries reduction [26].

Finally, the post-study discussion with school principals, teachers, and community workers suggested that it is feasible to implement a school-based xylitol gummy bear snacks program. Teachers were willing and able to incorporate the three times per day snack program into their classroom curriculum with minimal disruption after a brief adjustment period. Parents were willing to allow their children to participate in an oral health program and to consume gummy bear snacks at school to reduce tooth decay. Children were willing to eat most of the gummy bears provided at each distribution. A significant degree of commitment, cooperation, motivation, and effort from all parties involved was necessary to successfully implement and carry out the program. The information and experience gained from the current study were valuable in strategizing and developing the protocols used to implement and carry out the xylitol gummy bear snacks randomized clinical trial being conducted among kindergarten children in an elementary school district in Cleveland, Ohio. A lower xylitol dose is being used.

This study had several limitations. Plaque collection was not standardized by plaque weight but rather by sampling the arches of teeth. This may be viewed as qualitative and may affect the quantitative analysis. However, the effect is minimized by standardization of sampling technique, by staff training, and by the use of staff with previous experience in this sampling technique. Furthermore, our previous studies with xylitol chewing gums showed that S. mutans/sobrinus levels in plaque sampling at screening were comparable to those at baseline for subjects and throughout the study among controls. The use of the manufacturer's (Santa Cruz Nutritionals) high dose maltitol (44.7 g) formula rather than the sorbitol/polydextrose formula was necessary because the sorbitol formula would not congeal properly to form the gummy bear during production. The reduction observed with high dose maltitol may have weakened our xylitol results. The inherent limitations of the setting and its capacity to deliver a public health intervention are an additional weakness. In this study, the intervention was delivered in a school setting and was subject to school closures and early dismissals, children's absences and cooperation, and classroom activities. For example, we experienced fluctuating cooperation of the children (e.g., some wanted to negotiate the number of bears to be consumed on some days, some preferred a specific color). Despite these difficulties, the local community workers who delivered the gummy bears made valiant attempts at getting the gummy bears to the children. Overall, 73% of the children consumed at least 75% of the total possible gummy bears distributed.

Based on our findings, it is feasible to develop and implement xylitol-based caries preventive programs in structured settings such as schools and daycare. These structured environments offer an opportunity to achieve xylitol frequency and dose compliance. However, implementing a new activity into an institutional setting would undoubtedly be a challenging task and require the acceptance and commitment of all parties within the setting (e.g., school administration, teachers, parents and students, etc.).