Journal of Research in Dental

Abstract

Background and objectives: Gingivitis is the most common gingival inflammatory disease. Plaque control methods play a major role in prevention of periodontal disease and dental caries, which include mechanical and chemical techniques. The present study was conducted to investigate the effect of chewing gum on dental plaque formation on smooth tooth surfaces.
Methods: A cross-over clinical trial was conducted on 18 patients. The study was conducted in 2 phases (2 days each) with a 4-day wash-out period. At the beginning of the study, the patients received professional prophylaxis. During the study period, they were asked not to brush or floss their teeth. Volunteers in the test group were instructed to chew one piece of gum four times a day for 20 minutes. On the third day, the O'Leary plaque index (PI) and the bleeding point index (BPI) were measured. In the second stage, the interventions were switched between the two groups. Data were analyzed by paired t-test and Wilcoxon test.
Results: There was no significant reduction in PI or BPI in the test group (P=0.187) compared with the control group.
Conclusion: In absence of oral hygiene practice, chewing gum has no significant efficacy for plaque reduction on smooth tooth surfaces.
 
Keywords: Chewing Gum, Dental Plaque Index, Gingivitis
 

Introduction

Gingivitis is the most common form of gingival inflammatory disease, caused by bacterial plaque accumulation around the teeth due to poor oral hygiene [1, 2]. Various methods have been proposed to control dental plaque. Mechanical plaque control by tooth brushing and dental flossing is the most efficient approach for dental plaque reduction .[3] Chemical plaque control is also recommended as an adjunct method for complete plaque removal. Use of xylitol products such as xylitol chewing gums is one suggested mechanism for plaque reduction .[4]
Xylitol is a sugar from the polyphenol family that has bacteriostatic effects on Streptococcus mutans .[5] This dietary sugar is used in various industries such as the food industry, pharmaceutical industry, dental products, and also in sweets, beverages, and chewing gums .[6] In a study conducted in Finland, Turku et al. [7] showed that replacing the dietary sugar with xylitol reduced the rate of caries. Xylitol prevents the proliferation and accumulation of bacteria and reduces the adhesion of dental plaque to tooth surfaces. Long-term use of xylitol controls the growth and activity of streptococci and prevents caries .[7]
Various studies have shown the optimal efficacy of chewing gums containing xylitol for dental plaque reduction .[4, 7, 8] However, Keukenmeester et al, [9] in 2014 demonstrated that chewing gum had no significant additional effect on patients with regular oral hygiene practice; but in absence of toothbrushing, it had a significant inhibitory effect on gingival inflammation. Kakodkar et al, [10] in 2012 reported that gum chewing after meals had no significant effect on established buccal and lingual dental plaques. Therefore, the aim of this study was to evaluate the effect of chewing gum on dental plaque formation on smooth tooth surfaces.


Materials and Methods

This cross-over clinical trial was registered in the Iranian Registry of Clinical Trials (IRCT20171015036782N4) and approved by the ethics committee of Shahid Sadoughi University of Medical Sciences in Yazd (IR.SSU.REC.1396.69). Participants in this study were selected among patients referred to the Department of Dentistry and Middle School students in Ashkzar city who had good oral hygiene, no progressive caries, and no orthodontic brackets or severe crowding. Eighteen participants aged 14 to 30 years who met the inclusion criteria were randomly selected. Individuals with optimal oral and dental health, without systemic disease, no progressive caries, no orthodontic brackets, and absence of severe crowding were enrolled. The participants were randomly divided into case and control groups. Written informed consent was obtained from all patients. This study was performed during two phases (2 days each) with a wash-out period of 4 days .[11, 12] In the first phase, the participants in group 1 (n=9) were asked to chew 4 pieces of chewing gum (Viodent, Alborz, Iran) daily for 20 minutes after the three meals and one after the evening snack. The second group was not given any chewing gum .[11] The ingredients of Biodent chewing gum include sweeteners such as sorbitol, xylitol, and mannitol, maltitol, flavor, stabilizers including sulfamic acid, aspartame, chewing gum base, and antioxidants, with no sucrose. At the beginning of the study, the participants were asked to brush and floss their teeth to reduce the plaque to zero. Next, they were asked to refrain from toothbrushing and flossing during the study period, or chewing any other chewing gum. On the third day, the buccal, lingual and proximal plaque levels were measured by using disclosing tablets. Then, the O 'Leary’s plaque index (PI) [13] was calculated for smooth surfaces. The teeth were assessed in four surfaces of mesial, distal, buccal and lingual. Each stained surface was recorded in the chart. Then, the ratio of stained surfaces to total dental surfaces was calculated and expressed as percentage. The bleeding point index (BPI) [4] which shows bleeding 30 to 60 seconds after probing was also calculated. In this index, the tooth is divided into four surfaces of mesial, distal, buccal and lingual, and bleeding of each surface is marked on the chart. The ratio of bleeding surfaces to the total surfaces is also calculated and reported as percentage. In the second stage, the two groups were switched and the procedure was repeated, such that those who chewed gum in the first phase did not use it in the second phase and vice versa. Between the two phases, the participants resumed regular oral hygiene for 4 days, and at the beginning of the second stage, the plaque was reduced to zero again .[7, 14] Finally, scaling and polishing were performed for all participants. It is worth mentioning that during this period, the patients were contacted by phone to ensure the use of chewing gum. Finally, the collected data were analyzed by SPSS 17 using the paired t-test and Wilcoxon test.
 

Results

 Eighteen volunteers were randomly divided into case (using chewing gum) and control (not using chewing gum) groups. In this cross-over trial, the groups were switched after 4 days.
Using the Kolmogorov-Smirnov test, the normality of the data distribution was checked, which showed that PI had normal distribution in both groups. The BPI in the case group did not have a normal distribution, but it had a normal distribution in the control group. The Wilcoxon signed-rank test was used to compare BPI.
According to the Wilcoxon test, the mean BPI index was 22.44±13 in the experimental group and 21.78±13.75 in the control group. The mean BPI index in the case group was slightly higher than that in the control group, but not significantly (P=0.962).
According to paired t-test, the mean PI was 66.83±24.33 in the experimental group and 72.56±16.99 in the control group. The mean PI in the case group was lower than that in the control group but not significantly (P=0.187). Chewing gum decreased PI but this reduction was not statistically significant.


Discussion

Periodontal disease is a group of common inflammatory diseases caused by microbial plaque accumulation on the teeth. Prevention, early diagnosis and treatment are necessary to prevent the progression of periodontal disease .[15]
For caries prevention, researchers have suggested strategies such as diet control, plaque removal with a toothbrush, and strengthening of the tooth structure with fluoride .[16] In the recent decades, compounds known as sugar substitutes such as xylitol and sorbitol have been introduced to reduce the consumption of sucrose and subsequent development of dental caries .[8] Therefore, these substances have been widely used in chewing gums, candies, toothpastes and artificial saliva. The cleansing effects of chewing gums are probably due to the mechanical cleansing properties of chewing gums or increased salivation .[17] Various studies have tested the hypothesis of chewing gum consumption to reduce plaque accumulation on smooth tooth surfaces; such studies can be divided into two groups: The first group includes studies that are done with zero plaque at the beginning of the study (like the present study), which actually examine the preventive effect of chewing gum on plaque formation. The second group includes studies which are done with a certain amount of stabilized plaque and examine the therapeutic effect of chewing gum. Studies examining the effect of xylitol with zero plaque at the beginning of the study have a short duration because all other oral hygiene practices are refrained during the study period .[7]
Makinen and colleagues [16] showed that although the intrinsic anti-plaque activity of xylitol-containing chewing gums is lower than other plaque control agents, it can have a positive effect on plaque reduction. In the present study, the O'Leary PI was lower in the case group than the control group, indicating the effect of chewing gum consumption on reduction of plaque on smooth surfaces, although this difference was not statistically significant. Also, BPI was compared in the case and control groups. The results showed that the BPI in the case group was higher than that in the control group, and chewing gum increased BPI in participants but not significantly. This finding shows that chewing gum did not reduce inflammation and did not have a positive effect on plaque accumulation, which could be due to the short period of the study. Although no oral hygienic practice for 48 hours can cause initial signs of inflammation, bleeding after probing may require more time .[18] However, Poureslami et al.[8] evaluated the effect of two types of chewing gums containing xylitol and sucrose on the accumulation of bacterial plaque and showed that the amount of plaque was significantly lower in the xylitol chewing gum group compared with the sucrose chewing gum group. Evaluation of both chemical and mechanical effects of chewing gum on plaque reduction and larger sample size in the study by Poureslami et al. [8] were the strengths of their study. In the study of Borhan et al,[7] the O'Leary PI was used to investigate the effect of chewing xylitol gum on plaque formation on smooth and occlusal surfaces of the teeth, similar to the present study. Borhan et al.[7] showed that chewing xylitol gum significantly decreased plaque accumulation on the occlusal, buccal and lingual surfaces but had no significant effect on proximal surfaces, which can be due to minimal contact of chewing gum with proximal surfaces. In their study, unlike the present study, the occlusal surface was also examined and according to the results of their study, the lowest plaque accumulation was observed on the occlusal surface, which is quite reasonable considering the maximum contact of chewing gum with the occlusal surface .[7] The results of Hanham and Addy [14] on  oral health students showed that the changes in plaque formation on smooth surfaces were not statistically significant, which is consistent with the results of the present study, and could be due to the differences in the number of samples. Although in the study by Hanham and Addy ,[14] unlike the present study, proximal surfaces were not examined, plaque accumulation at the occlusal surface was evaluated. The results demonstrated significantly lower plaque accumulation on this surface in the chewing gum group. Also, in the study by Pizzo et al, [11] the results showed that chewing sucrose-free gum containing lactoperoxidase or silicon dioxide or zinc gluconate had no inhibitory effect on plaque accumulation on smooth surfaces.
Zhan et al. [19] examined the effect of xylitol-containing wipes on cariogenic bacteria and caries in children. In their study, 44 mothers with children aged 6 to 35 months with active caries were randomly divided into two groups: using xylitol-containing wipes and placebo-containing wipes. In their study, the rate of dental caries in children at the beginning and after one year and the amount of Streptococcus mutans and Lactobacillus in the saliva were evaluated. The results showed that use of wipes containing xylitol reduced the incidence of caries in children, and xylitol can be considered as a useful supplement to control caries .[19] Their study, unlike the present study, examined only the chemical effect of chewing gum. They also assessed the bacteria involved in caries, which was a strength of their study. Aluckal et al. [20] examined the effect of xylitol-containing chewing gum on salivary Streptococcus mutans, and showed that these chewing gums could be used as an adjunct to regular home care preventive measures for caries prevention.
In the present study, the O’Leary PI was used to measure the amount of plaque, while in the study by Isotupa et al,[21] the weight of fresh and dry dental plaque was measured. This method can be a good strategy to measure the amount of plaque, but cannot determine the amount of plaque on different surfaces of the tooth separately and also requires specific equipment, which was not available in the present study.  
In addition to the mechanical effects of chewing gum, Keukenmeester et al.[9] investigated the chemical effect of chewing gum. The two indices evaluated in their study, like the present study, were related to gingivitis and plaque levels. The strengths of this study were longer duration (3 weeks) and larger sample size (220 people). In their study, gingivitis was evaluated in presence and absence of oral hygiene practice such that the participants did not brush their mandibular teeth during the study, but continued brushing their maxillary teeth. Their results showed that chewing gum had no effect on BPI and PI in presence of oral hygiene practice, but in absence of oral hygiene practice, chewing gum had an inhibitory effect on gingival inflammation .[9] Barnes et al.[22] considered chewing gum as an effective oral hygiene method in absence of brushing and it was effective as an adjunct to brushing to improve oral health. In another study, the results showed that chewing gums containing sucrose along with oral hygiene practice decreased dental plaque accumulation by 40%; while, under similar conditions, sugar-free gum decreased dental plaque by 51% .[23] In absence of oral hygiene practice, these values ​​were 47% and 67%, respectively .[5] These results emphasize the effect of chewing gum for removal of dental plaque, especially in absence of proper plaque control in patients like the disabled or hospitalized patients. Also, these results show that in absence of routine oral hygiene practice, chewing sugar-free gum is superior to sucrose-containing gum in reduction of dental plaque accumulation due to the inherent properties of sugar substitutes such as reduction of mutans streptococci in the saliva and plaque .[24] Chewing gum can decrease caries by increasing the saliva flow. Stookey et al.[25] showed that increased saliva secretion due to chewing gum after a meal was more effective in preventing caries than the chewing gum itself and its composition. Thus, it can be recommended for subjects with low saliva secretion, such as patients undergoing radiotherapy.
Cosyn and Verelst [26] stated that chewing gum significantly decreased dental plaque in the palatal and lingual areas, but had no effect on buccal surface plaque, which may be due to greater contact of the chewing gum during chewing with palatal and lingual surfaces, indicating the mechanical effect of chewing gum on dental plaque reduction.
One of the limitations of this study was lack of microbial assessment and measurement of other indices involved in inflammation. Other confounding factors in this study were the type of nutrition and cooperation of participants in implementation of the study, which could affect the outcome of the study.


Conclusion

According to the results, chewing gum in absence of oral hygiene practice has little efficacy for plaque reduction on smooth tooth surfaces. Also, future studies are required on a larger sample size to assess patients over a longer period of time, and the bacteria in the saliva samples.