SRM Journal of Research in Dental Sciences

: 2018  |  Volume : 9  |  Issue : 4  |  Page : 158--163

Effect of different chewing gums on dental plaque pH, salivary pH, and buffering capacity in children: A randomized controlled trial

Kameshwaran Muralikrishnan1, Sharath Asokan2, P R Geetha Priya2,  
1 Department of Pedodontics and Preventive Dentistry, Tagore Dental College and Hospital, Chennai, Tamil Nadu, India
2 Department of Pedodontics and Preventive Dentistry, KSR Institute of Dental Science and Research, Tiruchengode, Tamil Nadu, India

Correspondence Address:
Kameshwaran Muralikrishnan
Department of Pedodontics and Preventive Dentistry, Tagore Dental College and Hospital, Chennai, Tamil Nadu


Aim: The aim of this study is to evaluate and compare the changes in dental plaque pH, salivary pH, and its buffering capacity after the use of three different chewing gums for 1 month in children aged 8–12 years. Methods: This randomized controlled clinical trial consisted of 90 children with Decayed, missing, Filled teeth (dmft/DMFT) <3. They were randomly divided into three groups to receive one of the following interventions: (a) chewing gum containing xylitol, (b) chewing gum containing casein phosphopeptide-amorphous calcium phosphate (CPP-ACP), and (c) chewing gum containing propolis. Oral prophylaxis was done, and saliva and plaque samples were collected after 48 h as preintervention data. Participants within the experimental groups chewed gums for 10 min, two times a day for a period of 1 month. Pre-and postintervention unstimulated saliva samples were analyzed to compare the changes in dental plaque pH, saliva pH, and buffer capacity. The data were then statistically analyzed using SPSS software. Paired t-test and Student's t-test were done for mean score analysis. Results: There was a statistically significant increase in plaque pH (P = 0.001) level in all three groups. Propolis chewing gum showed an increased salivary pH level (P = 0.036). When compared between genders, girls showed a significant increase in plaque pH level in all three groups and an increase in salivary pH level in xylitol group. Conclusion: Chewing gum containing xylitol can regulate the dental plaque pH, salivary pH, and buffer capacity in a significant way than CPP-ACP and propolis chewing gum.

How to cite this article:
Muralikrishnan K, Asokan S, Priya P R. Effect of different chewing gums on dental plaque pH, salivary pH, and buffering capacity in children: A randomized controlled trial.SRM J Res Dent Sci 2018;9:158-163

How to cite this URL:
Muralikrishnan K, Asokan S, Priya P R. Effect of different chewing gums on dental plaque pH, salivary pH, and buffering capacity in children: A randomized controlled trial. SRM J Res Dent Sci [serial online] 2018 [cited 2019 Jan 23 ];9:158-163
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Among oral diseases, dental caries is the most common chronic disease of humankind. It is a multifactorial disease in which diet plays a major etiologic factor. Different strategies to combat caries were used over the years; however, a substitution therapy replacing the harmful habit (excessive sucrose consumption) with a more positive practice can lead to promising caries control strategy. Chewing gum is known to be a useful adjunct to common oral hygiene practice and a potent stimulant of salivary flow rate.[1]

Sugar substitutes (polyols) are considered more tooth-friendly, and they do not contribute to the formation of organic acid and plaque matrix leading to dental caries. Xylitol (a sugar substitute) has been used as an artificial sweetening agent for more than 30 years. It has been approved and considered safe to use for children by the Food and Drug Administration since the 1960s. Since then, it has been commonly used as sweetener in various products, especially in chewing gums. Xylitol was a naturally occurring noncariogenic sugar substitute that cannot be metabolized by oral bacteria.[2] Propolis, on the other hand, a resinous and natural substance, is used in curing a large range of disease. It is made of highly active biochemical substance known as bioflavonoid (Vitamin P), phenols, and aromatic compounds. Flavonoid is well known for its antibacterial, antifungal, and antioxidant properties. Propolis is available in different forms such as lozenges, tablets, toothpaste, mouth rinses, and chewing gums. Very fewer studies have reported its action as a chewing gum, especially in children.[3]

In recent years, casein phosphopeptide-amorphous calcium phosphate (CPP-ACP), a milk protein, has also been demonstrated to have anticariogenic properties. It enhances the remineralization of enamel subsurface lesion and reduces Streptococcus mutans levels when delivered with sugar-free chewing gums.[4]

To our knowledge, no studies have evaluated the effect of xylitol, CPP-ACP, and propolis chewing gums on plaque pH, salivary pH, and its buffering capacity after 1-month use of chewing gums. The aim of the present study was to compare the effect of xylitol, CPP-ACP, and propolis chewing gums on plaque pH, salivary pH, and its buffering capacity in children aged 8–12 years.


Five hundred school children, aged 8–12 years, from three different schools in Tiruchengode district were screened as a part of routine dental examination. Ninety children with an age range of 8–12 years (mean age of 10.14 ± 1.00) were included in the study.

The inclusion criteria of this study were as follows:

Children recorded with dental caries score of dmft/DMFT <3Children with no history of medications for the past 6 monthsThose willing to comply with the procedures with written consent from the parents.

The exclusion criteria of this study were as follows:

Medically compromised childrenChildren with any systemic disease or allergiesChildren using fixed or removable orthodontic appliance or removable prosthesis, or those with the presence of any intraoral soft tissue pathology.

Ninety children were randomly divided into three groups using computerized software (Research Randomizer, version 4.0) in ratio 1:1:1, with 30 children in each group.

Group A: Xylitol containing chewing gum (Orbit, Wrigley India, Bengaluru, Karnataka, India)Group B: CPP-ACP containing chewing gum (Recaldent, Nihan Kraft Foods, Japan)Group C: Propolis containing chewing gum (Propolia, Apimab Laboratories, Metropolitane, France).

The composition of the chewing gum according to the manufacturer's declaration was tabulated in [Table 1].{Table 1}

The protocol was approved by the Institutional Review Board and Institutional Ethical Committee of KSR Institution of Dental Science and Research. The study and intervention involved were explained in detail to the school authorities, children, and their parents included in the study. All the children in three groups were first subjected to oral prophylaxis and were instructed not to practice any kind of oral hygiene measures for the next 48 h. After 48 h, the children were examined at the school premise before their morning break time (which was more than 2 h after breakfast) to collect the baseline (unstimulated) saliva and plaque samples. No modifications were made in the diet or oral hygiene measures of the children. The school authorities were, however, advised not to provide any food 2 h before the procedure (to avoid any kind of pH changes due to intake of food).[5] They were then asked to rinse their mouth with distilled water for 1 min to get rid of any food debris. They were made to sit in a comfortable upright position, under natural light for saliva collection.

The children were provided with a sterile container (uricup) and were instructed to expectorate saliva (2 ml) in the container. Saliva was collected by passive drool method. A minimum of 2 ml saliva was needed for the bulb of the pH measuring electrode to dip sufficiently into the saliva samples.[6]

Following the saliva collection, plaque samples were collected. The supragingival plaque samples of approximately 1 mg (milligram) were collected from the six buccal surfaces of posterior teeth (primary and permanent molars) representing all the quadrants of the mouth. Plaque was collected with a sterile blunt probe. The technique used for plaque analysis was given by Fosdick et al. 1957. Each collected plaque sample was thoroughly mixed in a sterile container containing 20 ml distilled water and was dissolved.[7] The collected samples were then transported to the laboratory, within 1 h.[6] Saliva and plaque samples were then subjected to pH measurements and buffer capacity to obtain the baseline values.

The pH values for all salivary characteristics were assessed with the help of Hannah digital pH meter (HI98127 pHep® 4 pH/Temperature Tester with 0.1 pH resolution). The pH meter was standardized using a standard protocol, using pH calibration solutions ranging from pH 4, 7 and 10.

For determination of salivary buffering capacity, Ericson's test (1959) was employed. It was recommended to use 0.0033 mol/L of hydrochloric acid (HCl) for unstimulated saliva. The desired HCl preparation was calculated using solcalc (Solution Calculator Inc.) software. Buffering capacity was measured by mixing 1 ml of unstimulated saliva with 3 ml of 0.0033 mol/L of HCl. To prevent foaming, 1 drop of 2-octanol was added and shaked for a period of 20 min to remove CO2. The pH of this preparation was evaluated to determine the buffering capacity of saliva as high – pH more than 4.75, normal – pH 4.25–4.75, low – pH ranging from 3.50 to 4.24, and very low – pH <3.50. The buffer pH values for unstimulated saliva were given by Ericson.[8]

After baseline measurement, the three types of chewing gums were distributed to the three groups, respectively. Children were instructed to chew two chewing gums every day, one in the morning and the other at 3 p.m. in the evening. Each pellet was chewed for 10 min to increase salivary stimulation. After 10 min, the gums were discarded under the supervision of the class teacher. Chewing gums were refilled in the school every 3 days by the investigator. The routine was recorded in a register to ensure that all the groups received their ration of gums. No modifications were made in the diet and oral hygiene measures of the children, throughout the study period.

After 1 month of intervention, all children were instructed to stop the oral hygiene measures for 48 h and were asked to report at 9 a.m. for saliva and plaque sample collection. The saliva and plaque samples were collected and were subjected to analysis of plaque pH, salivary pH, and buffering capacity by similar methods as mentioned earlier and the results were tabulated.


The data obtained were statistically analyzed using SPSS software (Version 22, Chicago, IL, USA). The gender-wise comparison was made using Student's t-test. The difference in the mean scores of the plaque pH, salivary pH, and buffering capacity between baseline and 1 month after the use of chewing gum was done using inferential statistics and paired t-test accordingly. The P ≤ 0.05 was considered statistically significant.


The study included 90 children, of which 44.4% (n = 40) were boys and 55.5% (n = 50) were girls. On comparison of the mean scores of plaque pH, saliva pH, and buffer capacity within the xylitol group [Table 2], a significant increase in pH of saliva and plaque (P = 0.001) was seen from baseline. There was a slight reduction in salivary buffering capacity (P = 0.008) after 1-month use of xylitol chewing gum.{Table 2}

[Table 3] shows a significant increase in plaque pH (P = 0.001) after 1-month use of Recaldent chewing gum, whereas [Table 4] shows a change in both plaque (P = 0.001), and saliva pH (P = 0.036) was seen in propolis group children, after 1 month use of propolis gum.{Table 3}{Table 4}

[Table 5] shows intragroup comparison between boys and girls in each group, respectively. On overall comparison, girls showed a significant increase in plaque pH levels in all three groups (Group A [P = 0.005], Group B [P = 0.001], and Group C [P = 0.001]) and increase in salivary pH levels in Group A (P = 0.040), when compared with boys in the respective groups.{Table 5}


A significant number of studies have been carried out in the past, to establish the role of preventive agents against dental caries. During the past 10 years, focus has shifted on the use of sugar-free chewing gum to regulate oral pH level. Chewing gums resulted in the neutralization of low pH levels by increasing the buffer capacity of the saliva and by enhancing the clearance of fermentable carbohydrates from the oral cavity.[9]

Studies determining the cariogenic potential of sweeteners have produced substantial evidence that xylitol is the most promising sweetener. The mode of action of xylitol is that it cannot be fermented by most bacteria. Evidence to date indicates that the mechanisms of action of xylitol include the absence of significant degradation into acidic end-products by dental plaque, stimulation of salivary flow and increased buffering capacity, inhibition of plaque accumulation and of cariogenic bacteria, remineralization of decalcified sites, and inhibition of the demineralization of sound enamel.[10]

In this study, the effectiveness of xylitol, CPP-ACP, and propolis chewing gums on plaque pH, salivary pH, and its buffering capacity was evaluated. While the products such as Orbit, Recaldent, and propolis gum do in fact contain Xylitol, an adult would have to chew roughly twenty pieces of gum per day to reap the benefits.[11] It has been suggested in the literature that there may be a daily dose “threshold” of 5–6 g/day, administered at three or more intervals daily, below which xylitol is not effective against S. mutans and has less effect against interdental plaque.[12],[13] In the present study, xylitol and propolis gums weighed 1 g/pellet, and Recaldent gum weighed 1.5 g/pellet as supplied by the manufacturer. The participants chewed 2 g of xylitol and propolis gum and 3 g of Recaldent gum per day for 1-month period.

Krasse and Birkhed demonstrated the acidogenic nature of plaque following diet patterns, both in animal and human studies.[5],[14] According to Tenovuo, the peaks of ion concentration are usually either in the early morning (6 a.m to 9 a.m.) or in the early evening (4 p.m. to 8 p.m.).[15] Dawes 1969 stated that the concentration of ions in the saliva keeps changing as the time progresses.[16] Hence, in this study, to avoid any pH changes after intake of food, the unstimulated saliva was collected in the morning around 9 a.m. as soon as the children came to school.

In the study done by Scheinin and Makinen, a partial substitution of xylitol for sucrose in the diet for 4 or 5 days reduced the amount of dental plaque. Results from the present study showed a significant increase in salivary and plaque pH levels after the use of xylitol-containing chewing gums for 1 month.[17] Cross et al. 2004, and Reynolds 2008 reported that topical application of CPP-ACP appears to have an inhibitory effect on the adherence and presence of cariogenic streptococci in the dental plaque.[18],[19] Bar-Hillel et al. demonstrated that CPP-ACP topical application could enhance the enamel subsurface calcium and phosphate concentrations, due to its larger intake into dental plaque. This ecological shift caused by the calcium and phosphate levels incorporated into the enamel pellicle and dental plaque may explain this phenomenon of significant increase in plaque pH in CPP-ACP group children.[20]

Koo et al. evaluated the effect of using mouth rinse containing propolis for a period of 3-day son dental plaque accumulation. They concluded that propolis was efficient in reducing supragingival plaque formation.[21] Ghaibie et al. reported that chewing propolis gum significantly improved dental plaque pH, resulting in an improved gingival index.[22] In the present study, propolis chewing gum group showed significant increase in plaque and salivary pH levels when compared with baseline values. The secondary ingredients in the propolis chewing gum included liquorice, menthol mint aromas, and green clay, respectively, which are proven to have antimicrobial property, thus acting in synergism with the mechanical action of chewing it improves the pH of plaque and saliva.[23]

Although Recaldent and propolis chewing gums had xylitol as sweetening agent, the varied result of this study can be due to lesser percentage of xylitol and higher percentage of CPP-ACP and propolis as major ingredients in the respective gums.

Burt found that chewing any type of chewing gum led to increased buffering capacity due to the stimulation of salivary flow.[24] Milgrom et al. reported that the use of 2 g (normal dose) xylitol gum had no effect on salivary and plaque pH. However, a moderate effect was seen when xylitol gums more than 3 g in weight were used. They concluded that a dose of 6 g followed by a gradual increase up to 10 g showed significant changes when consumed for a period of 1 month.[13] The results of the above two studies were in contrast to the present study. Chewing 2 g of xylitol or propolis gum had produced significant effect compared to chewing 3 g of Recaldent gum. Hence, the composition of the chewing gums seems to play a major role than the quantity of the gum used.

When analyzing the effect of chewing gum among boys and girls, an interesting outcome was obtained. Girls showed a significant increase in plaque pH levels in all the three groups and an increase in salivary pH level in xylitol group. Kolawole et al. reported a rise in plaque and salivary pH levels among girls consuming xylitol-based chewing gum. They concluded that it could be due to good oral hygiene practice among girls, as they brushed their teeth more frequently (86.8%) than boys (68.7%).[25] In contrast, Campus et al. showed that there was no correlation between genders in terms of decrease in plaque pH levels after the use of xylitol-based chewing gums.[26]

Limitations and future scope

The main limitations of this study are small sample size and shorter time frame of the study. Further studies with long-term effect of chewing gum on oral health status are warrantedAvailability of the chewing gum and cost factor are major hindrances for the use of chewing gum among children belonging to low socioeconomic statusChildren from government school were only included in the study which could affect the generalizability of the results.


The effect of chewing gums on oral health can be attributed to both the composition of the gum and the mechanical action of chewing. Within the limitations of the study, the following conclusions were obtained:

Xylitol chewing gums significantly increased the plaque pH, salivary pH, and buffering capacityPlaque pH and salivary pH significantly increased after chewing propolis gumsRecaldent gums significantly increased plaque pH.

Financial support and sponsorship


Conflicts of interest

There are no conflicts of interest.


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