Beneficial Effects of Xylitol Chewing Gum and Candies on Oral Health in Older People and Individuals With Disabilities: A Systematic Review

ABSTRACT

Aim

To determine whether the favorable effects of xylitol chewing gum/candy on oral health observed in healthy children and adults can be demonstrated in older people or individuals with disabilities?

Methods

Electronic and hand searches were performed to find prospective randomized or controlled clinical studies comparing effects of xylitol gum/candy with a polyol/no product control on oral health. 1171 studies were screened after duplicate removal. After applying inclusion and exclusion criteria, four studies in older and five studies in people with disabilities were reviewed.

Results

Clinically significant decreases in plaque accumulation were reported for xylitol gum/candy use in both populations. The results on gingival inflammation and caries occurrence were in line with these results. Use of high‐concentration xylitol candy decreased counts of mutans streptococci in individuals with disabilities. The studies in frail, older people suggested that xylitol gum chewing may reduce dry mouth symptoms, increase salivation and improve self‐perceived oral health.

Conclusion

The effects of xylitol chewing gum/candy on oral health in older people or individuals with disabilities may be comparable to those reported for healthy individuals. These findings suggest that xylitol gum/candy may be a useful adjunct for oral health maintenance in both older people and people with disabilities.

1. Introduction

Xylitol is a naturally occurring five‐carbon polyol sweetener that differs from other commonly used polyol sweeteners such as sorbitol in that it is composed of five carbon atoms, whereas the others are six‐carbon compounds. There is good evidence from several randomized clinical trials conducted in healthy people to suggest that xylitol chewing gum consumption decreases plaque accumulation and counts of caries‐associated mutans streptococci (MS) [1, 2, 3, 4]. Evidence of specific beneficial effects for xylitol gum differing from those of sorbitol gum are found in MS and plaque studies [5]. The caries‐reducing effect of adding xylitol chewing gum to the daily diet has been well demonstrated in healthy children and adolescents with a high or moderate caries level at study baseline [6]. Results on effects of xylitol tablets/candies have, however, varied [1, 4, 6]. Xylitol differs from other polyol sweeteners in that it is not fermented by the oral microbiota [7]. The “xylitol‐effects” have been attributed to, among others, growth inhibition of MS and less adhesive plaque due to reduced amounts of extracellular polysaccharides in the plaque [8]. In addition, xylitol consumption has been shown to reduce the acid production potential of plaque [9].

Elderly individuals may have problems with plaque removal because of diminished manual dexterity, cognitive impairment and impaired vision. The problem is exacerbated by existing restorations, missing teeth and wearing removable prosthesis. Large disparities in oral health have been reported between those living in care homes and those living in the community [10]. Poor oral hygiene, periodontal problems and dental caries are common findings in elderly institutionalized populations [11]. Explanations for the poor oral hygiene have included such staffing‐related factors as high workload, lack of time, poor attitudes and lack of knowledge regarding the importance of oral hygiene in the control and prevention of oral diseases [11]. Especially important is improving the oral health status of elderly people with dementia. Periodontal disease may contribute to the onset and progression of dementia [12]. Xerostomia, often medication‐induced, is an additional problem in older people. Hyposalivation‐associated chronic conditions or polypharmacy have been associated with oral microbiota dysbiosis as well as increased plaque accumulation [13, 14]. Topical applications, such as saliva substitutes, may offer symptom relief, but do not improve salivation [15]. Stimulating the saliva secretion may be regarded a key issue in promoting the oral health of older individuals.

In addition to elderly people, also individuals with disabilities may have problems with plaque removal. People with disabilities are not a uniform group of individuals. It is obvious that individuals with mental handicaps may face bigger challenges in taking care of their oral hygiene compared with individuals with physical handicaps, such as for example, hearing impairment. On the other hand, individuals with physical disabilities may have problems with manual dexterity, coordination and self‐help skills leading to inability to master the techniques required for tooth brushing. It has been repeatedly reported that people with intellectual and/or developmental disabilities have higher unmet caries treatment needs as well as poorer oral hygiene and poorer periodontal health than people without disabilities [16, 17, 18]. In addition, the fact that medication‐related dry mouth may affect not only older people, but also those with disabilities, is often overlooked.

The conclusions of our previous systematic reviews [1, 4, 5, 6, 19] on xylitol are of clinical relevance, as they may influence recommendations made by healthcare professionals for healthy people of all ages. To our knowledge, no previous systematic reviews have focused on effects of xylitol chewing gum/candy use on oral health and oral health‐related outcomes in older individuals or “not healthy” individuals such as patients. This systematic review aimed to address the following research question: can the favorable effects of xylitol chewing gum/candy on oral health observed in healthy children and adults be demonstrated in older people or “not healthy” individuals, such as patients or individuals with disabilities?

2. Materials and methods

The Preferred Reporting Items for Systematic Reviews and Meta‐Analyses [20] was used as a guideline in the present systematic review. The review was registered in the International Prospective Register of Systematic Reviews (PROSPERO registration number CRD420251062430) before the start of data collection.

2.1. Information Sources and Research Strategies

The research question for the present systematic review was formulated using PICO characteristics (Patients, Intervention, Control, Outcome), as follows: in older people or patients (P), do xylitol chewing gum or candies (I), have favorable effects compared with other corresponding polyol products or no product (C), on oral health or on oral health‐related outcomes (O).

The search to identify all the relevant, published studies was conducted using three databases: PubMed, Embase, and the Cochrane Library. Literature was also searched on ClinicalTrials.gov. A hand search was conducted in the reference lists of previous systematic reviews close to the present topic. The authors have written five previous systematic reviews aiming to find out if xylitol chewing gum or candies can reduce levels of MS, the amount of plaque, caries occurrence and gingival inflammation [1, 4, 5, 11, 19]. Those reviews included only healthy people. Now literature was screened to find studies on these outcomes in older frail people, people with xerostomia, people with disabilities, or patients in general. The searches were made on August 20, 2025 and cover the period from 1964 to August 20, 2025. Broad search terms were used to search for studies: Appendix 1.

2.2. Study Inclusion and Exclusion Criteria

To be included in the review, the subjects had to be older people with some natural teeth, patients, people with developmental or intellectual disabilities, or people with xerostomia. Due to the expected low number of studies on the topic, in addition to randomized controlled clinical trials (RCT), also controlled clinical trials (CCT) were included in the review. To be evaluated, the study had to be available in English. The aims of the included trials were to study the effect of xylitol chewing gum/candies on oral health or oral health‐related outcomes: caries occurrence, gingival inflammation, plaque accumulation, and levels of MS (the primary outcomes for present evaluation). Concerning these outcome measures, the increment values had to be available (baseline and final/increment). The secondary outcomes were selected based on their high and specific importance for the subjects of these studies: salivary flow rate, prevalence of angular cheilitis and denture stomatitis, and self‐perceived oral health. The comparison/control was a polyol‐sweetened chewing gum or candy or no product. Xylitol had to be the polyol with the highest concentration of all polyols in the product.

Exclusion criteria used when evaluating titles and abstracts: the subjects were reported to have good health; no control group; in vitro studies, reviews, comments or study protocols; the polyol vehicles were oral sprays or rinses, toothpastes, pacifiers, milk, wipes or varnishes; mother‐to‐child MS transmission studies; the study was not available in English.

Exclusion criteria when evaluating full‐text articles: mean values of data were shown but statistical significances were not tested [21]; the studies had no proper control group [22, 23, 24]; the “pediatric patients” were healthy children [25, 26].

2.3. Study Selection and Data Extraction

Screening of the records was performed after duplicate removal independently by the review team (KP, ES). ES and KP have been calibrated during the evaluation and analysis process of similar systematic reviews between 2020 and 2025. The review team members scanned the titles and, when needed, read the abstract. The team members independently decided which studies in their opinion fulfilled the criteria for full‐text review.

The reviewers collected the data from the articles chosen for the full‐text review. The following data were collected for all articles: author and year of publication, study site, number and age of participants, study design, intervention and controls, outcome measure, assessment method and main results. When data were available, one of the reviewers (ES) calculated in percentages changes in the indices within the group.

2.4. Assessment of Methodological Quality and Risk of Bias

The Cochrane risk‐of‐bias tools for clinical trials (RoB 2 and ROBINS‐I) were used in the evaluation of the selected trials [27]. The reviewers independently evaluated the included full‐length articles and, based on mutual agreement, eliminated discrepancies between each individual assessment. Each appraised aspect was classified as having either low, high or moderate risk of bias. The risk‐of‐bias evaluation was made separately for each study as an entity. The overall level of risk for each study was classified as low (all quality items were met: high quality), moderate (unclear risk of bias for one or more domain: fair quality) or high (high risk of bias for one or more domain: low quality) [4, 27]. The strength of evidence concerning the primary outcome measures was evaluated based on three elements of GRADE (https://book.gradepro.org): the risk of bias (study limitations), the inconsistency of results and the indirectness of evidence. The certainty level was classified as high, moderate, low or very low. A full GRADE assessment was not feasible due to the limited number of studies, their heterogeneity and the high number of outcomes.

3. Results

3.1. Study Selection

In the screening (1964‐) for articles 1724 articles were found (516 PubMed, 878 Embase, 330 Cochrane). Two studies were found in published review articles. The removal of duplicates left 1171 articles for screening of titles/abstracts. A total of 1156 records were excluded, leaving 15 full‐text articles for assessment of eligibility. In the full‐text evaluation, six articles were excluded, which resulted in 9 articles to be reviewed (Figure 1).

FIGURE 1.

Flow chart.

3.2. Study Characteristics

The studies included in the review were either controlled clinical trials or randomized controlled clinical trials published between 1996 and 2017 [28, 29, 30, 31, 32, 33, 34, 35, 36]. These studies included participants from two categories: older people (four studies: age range 60–99 years, n = 337; 28, 30, 32, 35), or people with disabilities (five studies: age range 6–50 years, n = 399; 29, 31, 33, 34, 36). The delivery modalities included chewing gum, chewable tablets/candies and dragées. The primary outcome measures in the evaluated studies included caries occurrence, gingival inflammation, accumulation of plaque and levels of MS. The secondary outcome measures were salivary flow rate, prevalence of angular cheilitis and denture stomatitis, and self‐perceived oral health.

The Watthanasaen et al. [36] study included children in special‐needs schools who suffered from hearing or vision impairment. In the studies by Mäkinen et al. [29, 31] the participants suffered from varying degrees of intellectual or physical disabilities and were patients of health‐care centers in Lapland, Northern Finland. In the Mäkinen et al. [29] study, 14/30 of the subjects were healthy, however; they were evenly distributed between the groups. In the Kuwaiti studies, the children were school students with physical disabilities [33, 34]. In the Mäkinen et al. [28] study, the participants were American Veterans Affairs patients. In the two studies by Simons et al. [30, 32], the older participants lived in residential/nursing homes. In the Al‐Haboubi et al. [35] study, the older people lived in the community. The older people may have been frail and had health problems and medications, but they did not suffer from dementia [28, 30, 32, 35]. Also, the subjects with disabilities had health problems and were reported to receive, among others, psychopharmaceuticals [29, 31, 33, 34].

In three of the studies, antibiotics used prior to the study for 4 weeks [30, 32, 35] was one of the exclusion criteria; for the rest of the studies, this information was not available. In the Watthanasaen [36] study, all participants received oral health education, including instructions on toothbrushing. In two of the studies, the participants refrained from brushing their teeth for either 36 [31] or 48 [29] hours before the examinations making it impossible to estimate their oral hygiene status before the study started.

3.3. Risk of Bias in the Selected Studies

Figure 2 summarizes the risk of bias in the nine evaluated articles. The five RCTs were analyzed with the RoB 2 tool [29, 30, 32, 35, 36] and the four CCTs with the ROBINS‐I tool [28, 31, 33, 34]. All studies [29, 30, 31, 32, 33, 34, 35, 36] had a moderate risk of bias. Six studies had “no product” as the control and were thus not double‐blinded, resulting in unclear risk of performance bias. No risk of detection bias or attrition bias was found in the studies. A low risk of reporting bias was found in the studies by Mäkinen et al. [29, 31].

FIGURE 2.

Risk of bias in the evaluated articles.

3.5. Studies on the amount of plaque

In six of the studies, the amount of plaque was measured using either gravimetry, plaque indices or denture debris scores (Table 1). In all of these studies, xylitol chewing gum or chewable candies/tablets significantly decreased plaque [29, 30, 32, 34, 35, 36]. The strength of evidence was considered moderate. This estimate was based on three randomized studies in older subjects, and one controlled and two randomized studies in students with disabilities, their consistent results, and directness of results.

TABLE 1.

Summary of the included studies on effects of xylitol gum and candies on oral health‐related variables in older people and in people with disabilities.

	Subjects; n	Study design	Intervention	Control	Outcome measure; assessment method	Results
Older people
Mäkinen et al. [28], Dayton, Ohio (RSC program)	VAMC patients with exposed root surfaces, mean age 57 yr (n = 83)	Double‐blind, controlled study (intervention from 6 to 30 mo, mean 1.8 yr)	XYL gum/ candies (gum: XYL 61%, Lycasin; candy * : 98% XYL, 8.5 g/d, 5xd)	SOR gum/ candies (gum SOR 61%, Lycasin; candy * : 98% SOR, 8.5 g/d, 5xd)	Crude incidence rate of new active supragingival root‐surface caries lesions, risk ratio (RR)	In comparison with SOR group root caries rate was lower in XYL group; RR = 0.19 (95% CI 0.06 to 0.62) p = 0.0065.
Simons et al. [30], West Hertfordshire, UK	≥60‐yr‐old residential home inhabitants (n = 68)	Randomized, blinded, controlled study (12 mo)	XYL gum (XYL 56%, SOR 28%, Lycasin 16%, 1.2 g/day, 2xd)	No gum	PI (Silness&Löe), GI (Löe); subjective oral health‐related response of participants (Q)	At 12 mo, PI decreased in the XYL gum group compared with baseline (p < 0.05). At 12 mo, in the XYL group both PI and GI significantly lower compared with the no gum group (p < 0.001). Improvement in the ability to taste and chew in the XYL group (p < 0.05). Gum acceptance high.
Simons et al. [32], West Hertfordshire, UK	≥60‐yr‐old residential home inhabitants (n = 68)	Randomized, blinded, controlled study (12 mo)	XYL gum (XYL 56%, SOR 28%, Lycasin 16%, 1.2 g/day, 2xd)	No gum	Saliva low rate (ml/min); denture debris status, denture stomatitis, angular cheilitis; MS (plate culturing)	At 12 mo, saliva flow rate increased in the XYL group (p < 0.01), but did not change in the control group. In the XYL group, there was a decrease in angular cheilitis, denture stomatitis, and denture debris scores compared with baseline (p < 0.001) and no gum group (p < 0.01). MS increased in both XYL and no gum groups (p < 0.05).
Al‐Haboubi et al. [35], London, UK	≥60‐yr‐old adults (n = 186)	Randomized, blinded, controlled study (6 mo)	XYL gum (66%, 2.8 g/d, 2xd)	No gum	Saliva flow rate (ml/min), PI (Silness&Löe), GI (Löe), MS (plate culturing); self‐rated oral health (Q), oral health‐related quality of life (OHIP‐14)	No change in saliva flow‐rate in XYL gum group, significant increase in no gum group. PI decreased in XYL gum group (p < 0.001), no change in the no gum group. GI decreased in both groups. At 6 mo, PI and GI lower in XYL group compared with no gum control (p < 0.001). No changes in MS levels. Improved global rating of oral health (p = 0.008) and ‘physical pain’ dimension in OHIP‐14 (p = 0.009) in XYL gum group.
People with disabilities
Mäkinen et al. [29], Pello, Finland	Subjects with mental or physical disabilities (n = 16) and healthy subjects (n = 14), mean age 30 year	Randomized, double‐blind, controlled study (2 mo)	XYL tablets (XYL 49%, Polydextrose 49%, 5.2 g/d, 5xd)	ERY tablets (49%, 5 g/d, 5xd)	Amount of plaque (gravimetry), plaque S. mutans (plate culturing), saliva MS (Dentocult SM Strip Mutans)	The amount of plaque decreased in the XYL group (p < 0.05), but not in the ERY group. In the XYL group S. mutans counts decreased both in interdental plaque (p < 0.05) and saliva (p = 0.008). No significant changes in the ERY group.
Mäkinen et al. [31], Pello, Finland	Subjects with intellectual disabilities, mean age 31 yr (n = 50)	Double‐blind, controlled study (64 d)	XYL tablets (XYL 49%, Polydextrose 49%, 5.4 g/d, 5xd)	SOR tablets (49%, 5 g/d, 5xd)	Plaque S. mutans (plate culturing), saliva MS (Dentocult SM Strip Mutans)	Plaque S. mutans counts decreased in the XYL group (p = 0.001), but not in the SOR group. Also, the saliva MS scores decreased in the XYL group (p = 0.01), but not the SOR group.
Honkala et al. [33], Kuwait	10‐27‐yr‐old students with disabilities (n = 145)	Blinded, controlled study (18 mo)	XYL candies (XYL 49%, maltitol 51%, 1.8 g/d, 3xd)	No candies	Caries increment (DMFS/DMFT)	At the final examination, the caries increment was lower in the XYL group than the control group (p < 0.001).
Shyama et al. [34], Kuwait	10‐27‐yr‐old students with disabilities (n = 145)	Blinded, controlled study (18 mo)	XYL candies (XYL 49%, maltitol 51%, 1.8 g/d, 3xd)	No candies	PI (Silness&Löe) and GI (Löe&Silness)	PI and GI decreased in both the XYL and control groups (p < 0.001). The groups did not differ at baseline, but the reductions in the PI (p = 0.037) and GI (p = 0.008) were significantly bigger in the XYL group compared with the control group.
Watthanasaen et al. [36], Thailand	7‐18‐yr‐old students with special needs (n = 174)	Randomized, blinded, controlled study (1 yr), intervention 9 month	XYL gum (XYL 55%, maltitol 34%, SOR 1.3%, 5.76 g/d, 3xd) and oral health education	No gum, oral health education	Caries onset rate, risk ratio (ICDAS score), PI (Silness&Löe)	In primary dentition, the onset rate of caries was lower in the XYL group than in the control group. Adjusted RR = 0.64 (95% CI 0.44,0.96) p = 0.03. Prevented fraction 33%. In permanent dentition, the onset rates did not differ between the groups. The PI scores were lower in the XYL group both at 9 mo and 1 yr compared with the control group (p = 0.001).

Abbreviations: VAMC, Veterans Affairs Medical Center; XYL, xylitol; SOR, sorbitol; ERY, erythritol; MS, mutans streptococci; C, control; F, fluoride; PI, plaque index; GI, gingival index; d, days; wk, weeks; mo, months; yr, years; Q, questionnaire; ICDAS, International Caries Detection and Assessment System; OHIP‐14, oral health‐related quality of life; CI, confidence interval; DMFS/DMFT, the number of decayed (D), missed (M) and filled (F) surfaces (S) or teeth (T); RR, Risk ratio.

^*85% of the xylitol consumption consisted of candies (dragées)

In three chewing gum studies in older subjects the reported mean PI values showed clinically significant decreases ranging from 34% to 50% in the xylitol group [30, 35] and a decrease of the mean denture debris scores by 60% [32].

In the chewing gum study in students with disabilities by Watthanasaen et al. [36] gum use was combined with oral health education, resulting in a 19% decrease in PI values in the xylitol gum group. There were no significant changes in the (no product) control groups receiving oral health education only [36]. In the Mäkinen et al. [29] chewable xylitol tablet study in subjects with disabilities, the fresh weight of plaque decreased by 31% in the xylitol group, while no change took place in the erythritol control group. In the Shyama et al. [34] study in students with disabilities, PI decreased both in the chewable xylitol candy (34%) and no‐candy control (18%) group; however, the plaque reductions were significantly higher in the xylitol group.

3.6. Gingival inflammation

Gingival inflammation was studied in three trials [30, 34, 35]. In these three studies xylitol gum or chewable candies significantly decreased the gingival inflammation. The strength of evidence was considered low. This estimate was based on two randomized studies in older people and one controlled study in students with disabilities, their consistent results, and directness of results.

In two studies in older people xylitol gum chewing reduced gingival inflammation [30, 35]. In the Simons et al. [30] study, the mean GI‐value decreased by 20% in the xylitol group. At 12 months, the GI was significantly lower in the xylitol gum group compared to the control group. In the Al‐Haboubi [35] study, the mean GI decreased by 22% in the xylitol and by 10% in the control group, and at 6 months, GI was significantly lower in the xylitol group compared to the control.

Also, in the Shyama et al. [34] study in students with disabilities, the mean GI‐values decreased in both the chewable xylitol‐maltitol candy (33%) and the control group (14%), but the reduction was significantly bigger in the xylitol candy group compared to the no‐candy control group.

3.7. Caries trials

Dental caries was studied in three of the nine evaluated studies [28, 33, 36]. In all three studies, the increase in dental caries was lower in the xylitol group than in the control group. The strength of evidence was considered low. This estimate was based on one controlled study in older people, and one randomized and one controlled study in students with disabilities, their consistent results, and directness of results.

In the Veterans Affairs study the patients consumed chewing gum and dragées. In relation to root surface caries, the prevented fraction of dental decay (PF) was 81% [28].

In the Kuwaiti schoolchildren with disabilities, the PF was 134% [33], and in the Thai schoolchildren, the PF was 33% in primary dentition, although no preventive effect was found in the permanent dentition [36]. One of these studies was conducted with chewable candies [33], one with chewing gum [36].

3.8. Studies on counts of MS

MS were studied in four trials [29, 31, 32, 35]. These studies showed variation in the effects of xylitol gum/chewable candies on the levels of MS (Table 1). The strength of evidence was considered very low. This estimate was based on two randomized studies in older people and one randomized and one controlled study in people with disabilities, inconsistency of their results, and directness of results.

In the chewing gum study by Al‐Haboubi et al. [35] in older people, the MS counts were not reduced. In the Simons et al. [32] study, the MS levels in both the xylitol and control group showed large variation during the first 9 months of the study, however, the 12‐month values were higher than the baseline values [32]. The daily dose of xylitol in these studies was low, 1.2‐2.8 g.

In the Mäkinen et al. [29, 31] studies, the participants with mainly intellectual disabilities consumed chewable xylitol‐polydextrose candies five times a day, with a daily dose of 5.2‐5.4 g/day. In both studies a more than ten‐fold decrease in S. mutans levels in plaque and a significant decrease in salivary S. mutans counts were observed [29, 31]. No changes were found in the control sorbitol/erythritol groups.

3.9. Saliva flow rate and dry‐mouth‐related variables in older people

In all three studies in older people with various dry mouth symptoms, subjects benefited from chewing xylitol gum. In two studies the subjects had saliva flow rate as the primary outcome measure [32, 35], and one studied variables related to dry‐mouth symptoms [30] (Table 1). The Al‐Haboubi et al. [35] study found no change in the flow rate of paraffin‐stimulated saliva in subjects with a mean age of 70 years. As for self‐perceived oral health and oral‐health‐related quality of life, the global rating of oral health improved significantly in the gum‐chewing group. No change took place in the control group. There was also a significant improvement in ‘physical pain’ dimension of OHIP‐14 in the gum‐chewing group. In the Simons et al. [32] 12‐month study the mean age of the subjects was 85 years. During the study, the mean flow rate of paraffin‐stimulated saliva increased in the xylitol gum group from low, 0.8 mL/min, to 1.6 mL/min, which is within the normal range for stimulated saliva flow rate in adults. In the study, significant increases in flow rate were reported already at the 6‐ and 9‐month examinations (p < 0.05). In the control group, the mean saliva flow rate decreased. Over the 12 months of trial, the prevalence of both angular cheilitis and denture stomatitis showed a clinically significant decrease in the xylitol gum group. No change was observed in the control group. In the second Simons et al. [30] study, the same subjects reported significant improvement in problems with taste and ability to chew without problems, while the control group suffered from increased chewing problems (p < 0.05). The acceptance of the xylitol chewing gum was high in the study.

3.10. Adverse effects

In six of the evaluated studies adverse effects were recorded. In five of them, no adverse effects were associated with the consumption of the xylitol products [30, 31, 32, 35, 36]. Side effects associated with gum chewing, for example, temporomandibular joint (TMJ) problems, were not reported for the oldest individuals living in residential homes [30, 32]. In the Mäkinen et al. [29] study, three subjects (one in the xylitol group and two in the control group) reported mild stomach problems and reduced their daily tablet intake. They did, however, complete the study. In the Watthanasaen study [36], one subject was excluded from the study due to a tendency to swallow the chewing gum.

4. Discussion

The main finding of this systematic review is that xylitol chewing gums and chewable candies may have favorable effects on oral health or oral health‐related outcome measures in older people and individuals with disabilities and that the effects are likely comparable to those reported for healthy individuals. The best evidence of beneficial effects of xylitol gum/chewable candy are found in the evaluated studies on plaque accumulation, that is, oral hygiene. The results on gingival inflammation and caries occurrence are in line with these results. Additionally, the studies in older people suggest that xylitol gum chewing may reduce dry mouth symptoms and improve self‐perceived oral health, increase salivation, and reduce the prevalence of angular cheilitis and denture stomatitis.

Earlier studies conducted in healthy children and adults have reported significant decreases in plaque accumulation in association with xylitol gum chewing [3, 4, 5]. However, studies in healthy subjects showed no plaque accumulation decreases for xylitol lozenges and candies [4]. Our review demonstrated beneficial effects on accumulation of plaque for xylitol chewing gum consumption in the three evaluated trials in which plaque was studied in older people [30, 32, 35]. In these studies, the oral hygiene of the older people was poor, and the magnitudes of decreases in the plaque accumulation could be considered clinically significant [30, 32, 35]. In addition, xylitol gum chewing reduced plaque accumulation in students with disabilities [36]. Interestingly, in contrast with earlier findings, also chewable xylitol candy/tablet consumption reduced significantly plaque in subjects with disabilities and poor oral hygiene at study baseline [29, 34].

Xylitol gum chewing has reduced gingival inflammation in healthy adults [19]. The three evaluated studies reported decreases in gingival indices and the results were in accordance with the findings on plaque accumulation. Significant decreases in gingival inflammation were reported for chewing gum use in two randomized studies in older people [30, 35]. One controlled clinical trial reported decreases in gingival indices in children with disabilities using chewable candy [34]. The decreases in gingival inflammation reported for healthy people showed large variation [19] but the mean decreases appeared to be of similar magnitude as those found in the present review.

The clinically significant caries‐reducing effect of adding xylitol chewing gum to the daily diet has been well demonstrated in healthy children and adolescents with a high or moderate caries level [5, 6]. In line with earlier studies, favorable effects were demonstrated in all three studies evaluated on the topic [28, 33, 36]. In these three studies, the older people [28] as well as the individuals with disabilities [33, 36] had a high risk for caries at the baseline examination, and during the follow‐up the reduction in caries development was clinically significant in the xylitol chewing gum/candy groups. In the Watthanasaen et al. [36] study, no reduction of caries was seen in the permanent dentitions, most probably due to a short follow‐up time of one year. Additionally, the participants were mostly in the mixed dentition stage, meaning that permanent teeth were exposed to demineralization as well as to xylitol for a shorter time than primary teeth.

In healthy people, there is good evidence that xylitol gum chewing decreases salivary MS counts both in short‐ and long‐term use, but results on effects of xylitol tablets/candies on MS levels have varied [1, 2, 4]. The salivary MS counts did not decrease in the evaluated two chewing gum studies conducted in the older people [32, 35]. The studies employed low daily doses of xylitol and, in addition, gum chewing only twice a day. In addition, the xylitol content of the xylitol chewing gum in the Simons et al. [32] study was rather low, 37 %, and the gum contained also 18% sorbitol, which may have influenced the effect on MS. According to the present review rather large, high‐concentration, chewable xylitol tablets reduced several‐fold the high MS counts of both plaque and saliva in subjects with intellectual disabilities and poor oral hygiene [29, 31]. The studies had a polyol control, suggesting that the results were specific to xylitol.

Chewing xylitol gum twice a day improved the ability of the older subjects to taste and chew [32], and improved their self‐rated oral health [35]. Also, in the Simons et al. [32] study, the prevalence of the denture‐related inflammatory conditions, angular cheilitis and denture stomatitis, decreased significantly in the xylitol gum group. In the Simons et al. [32] study, saliva flow rate was significantly improved by the gum chewing, but not in the Al‐Haboubi et al. [35] study. The mean age of the subjects in these two study populations was quite different: 70 [35] versus 85 [32] years. This age difference was reflected also in the mean saliva flow‐rates, with the older subjects expressing very low stimulated saliva flow rates, indicating that at least half of the subjects must have suffered from severe xerostomia [32]. Interestingly, this group benefited most from the xylitol gum chewing [30, 32]. The observed significant clinical improvement in oral health speaks for the importance of stimulating salivation by gum chewing in older people with xerostomia.

Xylitol is not an antimicrobial agent and shows no retention to the oral cavity which may explain why there appears to be a dose‐response relationship in the beneficial effects of xylitol on oral health. The daily dose of xylitol appears to be important for its caries‐reducing effects [6]. The dose‐response relationship for xylitol in reducing caries occurrence was first suggested in the trial of Isokangas et al. [37]. The majority of studies suggesting a dose‐response for xylitol have, however, been conducted with MS [1]. Daily xylitol doses of 5–6 g or higher with a consumption frequency of at least three times a day appear to be effective in reducing MS counts and the amount of plaque [1, 4, 38]. However, also lower daily xylitol doses when delivered with chewing gum may decrease MS and plaque accumulation [1, 4]. In the studies in the older people xylitol gum with a low daily dose of xylitol decreased plaque accumulation, but not MS counts [32, 35]. The chewing time in the studies was rather long, 15 min, which should result in fast oral clearance of the small amounts of xylitol. Earlier studies have suggested that chewing high‐concentration chewing gums for a short time, 5 min, results in high xylitol levels in the plaque which may be important for the effects of xylitol [1].

The “chewing effect” is considered by some authors to explain the caries‐preventive effects of xylitol gum chewing [39]. However, xylitol administered with syrup [40] and wipes [41] has also reduced caries. In addition, a recent systematic review reported specific effects for xylitol: xylitol gum reduced plaque accumulation and MS counts significantly more than the control sorbitol gum [6]. Since the chewing gum studies included in our evaluation compared xylitol gum with no gum, the issue of the chewing effect is especially important when considering the results of the Simons et al. [30, 32] and Al‐Haboubi et al. [35] studies. In the presently evaluated studies, conducted with rather long chewing times of 15 min and low daily doses of xylitol, the beneficial effects may be partly due to the chewing effect. Chewing of sugar‐free gum for long times, 20–30 min, has earlier been associated with no change or small but significant reduction of plaque accumulation [4, 42]. However, we found clinically significant reductions, 34–60%, in plaque accumulation in the evaluated studies in the older people [30, 32, 35]. This supports the idea that xylitol contributed significantly to the plaque decreases, not gum chewing in itself.

Saliva flow rate was a primary outcome measure in two studies [32, 35], however, in our review it was a secondary outcome measure. Conflicting results regarding whether chewing gum consumption increases salivation only in association with constant gum chewing, have been recently discussed in a systematic review [43]. The majority of evaluated studies lacked proper control groups or had other problems with the study designs [43]. Also, the fact that some studies assessed the response in unstimulated/stimulated saliva flow after chewing gum use ranging from six times a day up to once every waking hour resulted in variation in the outcomes [43]. However, the authors of the review concluded that chewing gum can improve saliva flow rate in elderly people [43]. Our results are in agreement with this conclusion, suggesting that saliva flow can be significantly improved in xerostomic frail elderly people even with realistic consumption of xylitol gum: twice a day, chewing for 15 min at a time [32, 35].

When comparing subjects chewing gum with a no‐gum group, the study design is blinded, not double‐blinded. Consequently, the two good‐quality double‐blinded Simons et al. [30, 32] studies became blinded when one of the arms, the chlorhexidine/xylitol gum group was on purpose left out of the present evaluation. Today, medicated chewing gums containing potent antimicrobial agents like chlorhexidine, cannot be recommended, due to reasons of, among other things, environmental safety. The chlorhexidine/xylitol gum was, as expected, in some respects more effective in improving oral health‐related outcomes compared to the xylitol gum [30, 32]. The authors had made a big effort to make the consistency and taste of the gum agreeable to the study subjects, resulting in very low attrition bias in the one‐year study [30, 32]. Considering the old age and low saliva flow rates of the subjects, the results of the two Simons et al. [30, 32] studies are encouraging. It can only be hypothesized how much “better” the results of the two studies could have been with a high‐concentration xylitol gum. High‐concentration xylitol gum chewing has reduced, in addition to MS counts and plaque accumulation, also the acid‐production potential of plaque, which would promote oral health in older people suffering from xerostomia [9, 44].

When studying older people and people with disabilities problems with safe gum chewing could occur. For example, individuals with dysphagia, dementia increasing the risk of aspiration pneumonia, poor denture stability or jaw pain could have problems with gum chewing. However, side effects associated with gum chewing were not reported even for the oldest individuals living in residential homes [30, 32]. According to the authors these individuals were rather “well” which may have influenced the results [30, 32]. In general, the only adverse effects connected with polyol consumption are digestive disorders [45]. Xylitol and other polyols belong to FODMAP (fermentable oligo‐, di‐, monosaccharides and polyols) substances which may not be suitable for persons with digestive disorders. For dental benefits, relatively small daily doses are recommended. When ingested in high doses about 50% of xylitol is absorbed in the gut, however, with lower doses such as those consumed in the form of chewing gum, most of the ingested xylitol is absorbed and metabolized by efficient metabolic pathways [46, 47]. Complaints about digestive discomfort in xylitol studies are rare [1, 4, 6], which is supported by results of the present review. Even in the studies, in which the daily doses of xylitol exceeded 5 g/day, adverse effects were reported only in one study [29]. Recently, the study by Witkowski et al. [48] suggested that xylitol is associated with increased cardiovascular risk. The study measured plasma xylitol, a naturally occurring intermediate of the pentose phosphate pathway, which is upregulated in subjects with, among other things, underlying metabolic disease. The subjects of the study suffering from health problems like diabetes and obesity did not participate in any xylitol intervention, the elevated plasma xylitol levels were associated with their health status. The only xylitol intervention in the study [48] took place in a substudy which consisted of ten subjects ingesting a water solution containing 30 g of xylitol. The resulting diarrhea supposedly was associated with the immediate changes in the plasma composition connected with cardiovascular risk. The validity of the model of Witkowski et al. [48] has been questioned among others by Valentine et al. [49].

Prevention of plaque‐related diseases using xylitol may not have a good cost‐benefit ratio in the context of public health programs. Even though the recommended xylitol amounts are not high, the consumption frequency recommendations for optimal effects, 3 times a day or more, makes xylitol prevention arduous especially for children and adolescents. However, for individuals such as older people, xylitol prevention should be worth the effort. Saliva stimulation with xylitol chewing gums should benefit especially older people with xerostomia associated with chronic conditions or polypharmacy. Recommendations concerning prevention and management of oral diseases in older people include, among others, tooth brushing with fluoride toothpaste, flossing and regular dental check‐ups [50]. Several Dental Associations all around the world recommend xylitol to patients of all ages, among others the Canadian Dental Association [51] which states that “Xylitol chewing gum can be especially helpful as it outperformed other sweeteners for its oral health benefits in clinical studies of caries prevention and reducing plaque”. Our review suggests that stimulating saliva with xylitol chewing gum could be an effective, affordable and realistic method to improve oral health as well as self‐perceived oral health in older people. The evaluated studies found no adverse effects for gum chewing [30, 32], however, it cannot be recommended for older individuals with TMJ disorders [51]. For self‐care, healthcare professionals may advise their patients to choose xylitol chewing gum rather than a sorbitol chewing gum (or any sugar‐free gum) for older individuals living in the community and not suffering from cognitive impairment associated with deteriorating oral health [5]. Xylitol candies, especially large chewable candies/tablets/lozenges, are good alternatives to xylitol chewing gum, however, they should dissolve in the mouth slowly to ensure high oral concentrations of xylitol and good saliva stimulation. Also, xylitol syrups, mouth washes or oral sprays could be potential alternatives to xylitol gums and candies. So far, limited research exists on these delivery methods. When using xylitol in solutions the fast clearance of xylitol may reduce the beneficial effects of xylitol. As a summary, xylitol chewing gums and chewable candies may be useful adjuncts for oral health maintenance in older populations—particularly when standard oral hygiene like tooth brushing is difficult to maintain. In older people, any adjuncts that may support mechanical control of pathogenic biofilms and thus the prevention of dental caries and periodontal disease are useful.

Individuals with disabilities are a heterogenous group of people. Our search of the literature for “not healthy” individuals, identified children and adults with various disabilities. In the Watthanasaen study [36] the students suffered from hearing and visual impairment, however, their ability to brush their teeth was necessarily not influenced by the disability. In the study the xylitol and control groups participated both in an oral health education program which had no effect on the outcome of the study in the control group [36]. Physical disabilities and intellectual disabilities may compromise oral hygiene habits increasing the risk of dental diseases [16]. Individuals with intellectual disabilities are also likely to suffer from dry mouth symptoms caused by polypharmacy [52]. Xylitol chewing gum appeared to be a suitable xylitol vehicle in the Watthanasaen study [36], however, in the studies with the physically and intellectually disabled individual's chewable candies was a safe choice [29, 31, 33, 34]. Also disposing the chewing gum after the gum use may be problematic for individuals with disabilities. Regardless of disability the use of xylitol gum/candy promoted oral health in all of the evaluated studies [29, 31, 33, 34, 36]. This finding supports the idea that xylitol may be a useful adjunct for prevention of dental caries and gingival inflammation in individuals with disabilities. The same recommendations concerning healthy people are suitable for both older people and individuals with disabilities: xylitol gum/candy at least three times a day with a daily dose of 5–6 g/day [1, 4, 6]. The recommended daily xylitol doses are not high, the dose is achieved with 5–6 pellet gums with a high xylitol concentration.

We found only nine studies that met the rather broad inclusion criteria of the review. This is a limitation of the present review. We searched for studies in older people and “not healthy” individuals and found in addition to studies on older people only studies on individuals with various disabilities. The five RTC studies and the four CCT studies showed fair quality. The RTC studies provide the essential evidence, the CCT studies influence less the level of certainty as well as the interpretation of results. A meta‐analysis would have been impossible to perform and interpret, both due to the low number of studies and since the studies were very heterogeneous with respect to subjects, methods, outcomes and study designs. The high number of outcomes complicated the interpretation of the results and may be considered a weakness of this study. Even though the beneficial xylitol effects in older people and individuals with disabilities were comparable to those reported for healthy populations, due to, among other things, the small number of studies, the data may not be strong enough to conclude that the beneficial effects of xylitol gum/candy are the same in older people and individuals with disabilities as in healthy people. Also, the clinical implications are influenced by the moderate‐to‐low level of evidence and should be interpreted with caution and in the context of limited data. A strength of the review, however, is that the included studies had rather strict inclusion criteria, among others, compared baseline or no‐treatment values with values obtained after the intervention period, decreasing a possible risk of bias. In addition, some of the outcomes, such as denture‐related inflammatory conditions or dry mouth symptoms, cannot be studied in healthy people. This is also a strength of the present review. Since no systematic reviews on effects of xylitol chewing gums and candies on oral health/oral health‐related outcomes in elderly people or people with disabilities have been published, the conclusions and recommendations reached in this review should be important to healthcare personnel treating older people and people with disabilities.

5. Conclusion

The effects of xylitol chewing gum/chewable candy on oral health in older people and individuals with disabilities indicate potential benefits, even though the evidence of the effects may not be as strong as in younger, healthy populations. The best evidence of potential benefits of xylitol gum/candy use is found in the evaluated studies on plaque accumulation, that is, oral hygiene. The results on gingival inflammation and caries occurrence are in line with these results. Chewable high‐concentration xylitol tablets appear to reduce MS counts. The studies in the older people suggest that xylitol gum chewing may reduce dry mouth symptoms, increase salivation, improve self‐perceived oral health and produce clinical improvement in oral health.

Xylitol chewing gums and chewable candies could offer meaningful oral health benefits for older or disabled individuals as adjuncts to standard oral care, including tooth brushing with fluoride toothpaste and restriction of frequent sucrose intake. The benefits may be more variable than in younger and healthy people, but in contexts where oral hygiene is compromised, xylitol could be especially valuable. Even though the present evaluation finds beneficial effects for xylitol chewing gums and chewable candies on oral health and oral health‐related outcomes in older people and in individuals with disabilities, more well‐controlled studies on the subject are needed, especially concerning the effect size.

Author Contributions

Both the authors participated in the screening of records and evaluation or articles. E.S. wrote the main manuscript, and K.P. wrote all paragraphs concerning caries. E.S. prepared the figures and the tables. Both the authors critically reviewed and edited the manuscript.

Funding

The authors have nothing to report.

Conflicts of Interest

The authors declare no conflicts of interest.

APPENDIX 1. Terms used in the search for studies.

1.1.

(xylitol*[tiab] OR “Xylitol”[Mesh]) AND (patient*[tiab] OR “Patients”[Mesh] OR disabled*[tiab] OR “Person* with Disabilit*”[tiab] OR “Persons with Disabilities”[Mesh] OR “Xerostomia”[Mesh] OR Xerostomia*[tiab] OR “dry mouth*”[tiab] OR elderl*[tiab] OR “Aged”[Mesh] OR aged*[tiab] OR veteran*[tiab] OR institutionalized*[tiab] OR institutionalised*[tiab] OR senior*[tiab] OR “older adult*”[tiab] OR “old people*”[tiab] OR “older person*”[tiab]) NOT (“Review” [Publication Type] OR “Meta‐Analysis” [Publication Type])—PubMed

(xylitol*:ti, ab OR ‘xylitol’/exp) AND (patient*:ti, ab OR ‘patient’/exp OR disabled*:ti, ab OR ‘person* with disabilit*’:ti, ab OR ‘xerostomia’/exp OR xerostomia*:ti, ab OR ‘dry mouth*’:ti, ab OR elderl*:ti, ab OR ‘aged’/exp OR aged*:ti, ab OR veteran*:ti, ab OR institutionalized*:ti, ab OR institutionalised*:ti, ab OR ‘institutionalized person’/exp OR senior*:ti, ab OR ‘older adult*’:ti, ab OR ‘old people*’:ti, ab OR ‘older person*’:ti, ab) NOT (review:it OR “meta‐analysis”:it)—Embase

(xylitol* AND (patient* OR disabled* OR Person* NEXT with NEXT Disabilit* OR Xerostomia* OR dry NEXT mouth* OR elderl* OR aged* OR veteran* OR institutionalized* OR institutionalised* OR senior* OR older NEXT adult* OR old NEXT people* OR older NEXT person*)):ti, ab—Cochrane

Data Availability Statement

The data is available on request from the corresponding author.