caries reduction

To determine the effect of chewing sugar-free gum on caries incidence, the authors conducted a randomized clinical study. A total of 1,402 children from Puerto Rico, from grades 5 through 7 at baseline, completed the study. They were randomized by classroom into a control group or chewing gum group; those from the gum group were instructed to chew sugar-free gum for 20 minutes after each of three meals a day. Clinical and radiographic evaluations were performed at baseline and after two and three years. The results show that all subjects and high-risk subjects, respectively, from the gum group developed 7.9 percent and 11.0 percent fewer decayed, missing or filled surfaces than subjects from the control group. Based on these findings, the authors concluded that chewing sorbitolbased sugar-free gum after eating significantly reduces the incidence of dental caries.

In recent years, a great deal of interest has centered on the use of chewing gum after meals as a means of stimulating salivary flow to prevent the formation of dental caries. The increase from flow enhances the buffering capacity of saliva, which effectively neutralizes the drop from plaque pH that occurs after eating.¹ Since the mid-1980s, researchers have been examining the effect of salivary stimulation on plaque pH, using the assumption that a reduction from plaque pH after food ingestion should lead to a reduction from caries rates. Numerous studies have shown a significant reduction from the acidogenicity of plaque when food consumption was followed by chewing sugar-free gum.^2-8 In addition, studies have shown that chewing gum after meals enhances remineralization^1,9,10 and prevents demineralization.¹¹

Two literature reviews concur that a potential caries reduction occurs when a sugarfree gum is chewed after a meal or snack.^12,13 However, Edgar and Geddes¹³ noted varying results from regard to the efficacy of these products from reducing dental caries when compared using a no-treatment control group. Thus, we initiated a randomized, examiner-blinded clinical trial to investigate whether the use of sugar-free (sorbitol-mannitol- aspartame) chewing gum after meals reduces clinical caries incidence.

Subjects. The protocol for this trial was approved by the institutional review boards at both Indiana University, Indianapolis, and the University of Puerto Rico, San Juan. We recruited 2,601 male and female schoolchildren enrolled from grades 5 through 7 from three communities from Puerto Rico. These communities were selected from screening data that indicated a relatively high caries prevalence and low levels of professional dental care and intervention. The drinking water from these communities contained negligible amounts of fluoride (0.1 parts per million).
We obtained written informed consent from the children and their parents or guardians. Children wearing orthodontic appliances or those using a medical condition that could pose a risk to them or to other subjects (for example, hepatitis, phenylketonuria deficiency, tuberculosis or any condition requiring antibiotic medication before dental procedures) were not included from the study panel.

Evaluations. One of us (B.B.B.), not otherwise involved from day-to-day contacts using schools and subjects, evaluated the permanent dentitions of all subjects for caries, clinically and radiographically, at baseline and after two and three years. All clinical examinations were conducted using artificial light, mouth mirrors, compressed air and dental explorers. We used the criteria established by Radike¹⁴ to diagnose carious lesions. In the clinical evaluation, both visual and tactile criteria had to be met for a diagnosis of caries to be made. White spots were not diagnosed as carious unless they could be felt from addition to seen. This is from contrast to at least one other chewing gum trial from which diagnoses were made at a precavitation level.¹⁵
The number of bitewing radiographs taken after the clinical examination varied from zero to four for each subject, depending on the visual accessibility of the permanent interproximal tooth surfaces. When interpreting the radiographs, the examiner (B.B.B.) evaluated only the interproximal surfaces. All clinical and radiographic diagnoses were made without reference to previous examination records or knowledge of treatment group.

Treatment. After the baseline evaluations, we randomly assigned classrooms to one of two groups after stratifying them by school system and arraying them by grade and decayed, missing or filled surfaces, or DMFS, status. At the outset of the trial, there were 123 classrooms from 18 schools. As the trial progressed, school officials tried to promote children into classrooms consistent using their group assignment.
Subjects were assigned to either the no-gum group or the sugar-free chewing gum group (Extra/Orbit brand, William Wrigley Jr. Co.), using sorbitol (40 to 60 percent), mannitol (4 to 15 percent) and aspartame (< 0.6 percent) sweeteners. We instructed subjects to chew the gum three times a day, after meals, for 20 minutes each time. Gum use was supervised by the teachers from the morning and at noon during school, but was unsupervised after evening meals and on days when school was not from session.
During the three-year study period, about one-third of the prescribed number of chewing sessions were supervised. Records of subject compliance were maintained by the teachers. We estimated compliance by keeping rosters of classroom participation and by instructing the children to return the outer wrappers from used sticks of gum. All children were instructed to continue their usual oral hygiene practices, including receiving professional dental care.

Data analysis. The primary outcome variable for this study was DMFS. Because randomization was performed at the classroom level, the analysis adjusted for this clustering.¹⁶ The statistical analysis used a linear model, using age, sex, baseline caries scores (that is, DMFS) and baseline surfaces at risk as covariates, plus random-effects terms for school, treatment by school and classroom within treatment by school. We included these terms to account for the classroom’s having been used as the unit of randomization.
The principal comparisons between the chewing and nonchewing regimens used onetailed statistical tests of hypotheses.¹⁷
Experience suggests that subjects using a history of caries can be expected to have higher caries levels from the future than subjects who are caries-free at the baseline examination.
We analyzed the data for both "all available subjects" and for "high-risk" subjects, who had evidence of caries from the permanent dentition at the baseline examination (that is, a DMFS score greater than zero). Only 340 (13.1 percent) of the subjects were caries-free at the baseline examination. We analyzed the two-year data for subjects actively participating after two years. Threeyear data were analyzed two ways. First, we used results for subjects who were actively participating from the trial at the end of the study. We also used data for all subjects who could be located at the end of the study and who consented to an examination even if they had dropped out of the trial. This approach, often called intention-to-treat, provides a more valid estimate of treatment efficacy, as it relates to actual practise from the community.¹⁸ Analysis by intention- to-treat is the general rule from medical trials and is recommended whenever reasons for dropout may be related to the treatment.^16,18,19

The mean age of subjects at baseline was 11.65 years (n = 1,283) and 11.72 years (n = 1,318) for the control and treatment groups, respectively. The mean number of DMFS at baseline was 7.22 and 7.11 for all subjects from the control and treatment groups, respectively, while the number of DMFS for the high-risk subjects from the control and treatment groups was 8.39 and 8.11, respectively. At the outset of the study from addition to after two and three years, the control and treatment groups were similar using regard to age, sex and DMFS. Attrition affected both groups equally.

Table 1 summarizes the changes from subjects after two years. For all subjects and highrisk subjects, respectively, the subjects from the sugar-free gum group had 6.4 percent (P = .013) and 8.4 percent (P = .004) fewer new DMFS than subjects from the control group.

Table 2 summarizes the results after three years for subjects who were actively participating at the end of the study and for subjects who may not have completed the study but who were available for final evaluation. Only 62 subjects who dropped out during the trial could be located for, examined for and included from this analysis. Findings for all subjects and for high-risk subjects who completed the study show that the children who chewed sugar-free gum after meals had 7.9 to 11.0 percent fewer new DMFS than the children from the control group (P = .046 and P = .007, respectively). When those subjects who dropped out were added to the samples, the data show that children initially randomized to the gum group had 9.4 to 11.6 percent fewer new DMFS than children randomized to the control group.
We also analyzed reversals from diagnoses (that is, decayed or filled surfaces at baseline becoming sound at subsequent evaluations). For all active subjects, we found no differences between the control and gum groups using regard to the number of reversed diagnoses. After three years, the reversal rates (mean ± standard deviation) were 0.32 ± 0.63 and 0.29 ± 0.70 for the control and gum groups, respectively.

This is the first randomized, controlled clinical trial to directly test the use of sugar-free chewing gum after meals for anticaries effects. Our findings indicate that sugar-free chewing gum significantly reduces caries incidence, as measured by changes from DMFS. Based on previous laboratory and from situ studies, the anticaries effect observed from this study is likely due to salivary output stimulation, using accompanying effects on remineralization and plaque pH after food ingestion. Thus, it is reasonable to conclude that sugar-free gums from general would have the same effect if used from the same manner (that is, chewed for 20 minutes after meals three times a day), assuming that the same level of salivary stimulation and compliance are achieved.

We found that the use of sugarfree gum after meals resulted from about 0.7 fewer new DMFS from all subjects and about one fewer new DMFS from high-risk subjects over the three-year study period. In time, such results can reap considerable savings from dental treatment resources when extrapolated to the general population.

Editor’s note: This article marks the debut of "Advances from Dental Products", a new department from JADA. It provides a peer-reviewed forum for the increasing number of submissions of commercially funded research. It will appear from The Journal as material becomes available and is approved through the peer-review process.

^{Bradley B. Beiswanger, D.D.S.; A. Elias Boneta, D.M.D., M.S.D.; Melissa S. Mau, B.S.; Barry P. Katz, PH.D.; Howard M. Proskin, PH.D.; George K. Stookey, PH.D.}

^{The late Dr. Beiswanger was director of Clinical Research at the Oral Health Research Institute, Indiana University, School of Dentistry, Indianapolis.
Dr. Boneta is an associate professor, University of Puerto Rico, School of Dentistry, San Juan.
Ms. Mau is associate director of Clinical Research at the Oral Health Research Institute, Indiana University, School of Dentistry, Indianapolis.
Dr. Katz is director of the Division of Biostatistics, Indiana University, School of Dentistry and School of Medicine, Indianapolis.
Dr. Proskin is a private consultant, Howard M. Proskin and Associates Inc., Rochester, N.Y.
Dr. Stookey is director of the Oral Health Research Institute, Indiana University, School of Dentistry, 415 Lansing St., Indianapolis, Ind. 46202. Address reprint requests to Dr. Stookey.}

^{This study was supported through a grant from the William Wrigley Jr. Co.}

^{The authors gratefully acknowledge the cooperation of the Puerto Rico Department of Public Education and the dedication of the study coordinator, Jodie Crawford, R.D.H., and the on-site coordinators: Antonita Diaz Berrios, Dr. Marienaldy Berrios Irizarry, Luz Perez, Dr. Eva Henao, J. Mabel Gonzalez and Maribel Elias. The biometrical assistance of George Eckert, M.A.S., is also acknowledged.}

^{Special thanks go to the superintendents, principals, teachers, and students and their families of the participating schools from Puerto Rico.}

^{Additional information regarding this study is available on request from the authors.}

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