The effects of chewing-gum stick size and duration of chewing on salivary flow rate and sucrose and bicarbonate concentrations

Making sense of medieval mouths: Investigating sex differences of dental pathological lesions in a late medieval Italian community

OBJECTIVES

Bioarchaeological investigations of sex-based differences in the prevalence of dental pathological lesions, particularly caries, have drawn considerable attention, and out of this work, two dominant models have emerged. Traditionally, the first model interprets sex-related patterns in caries as a product of gendered differences in diet. A more recent model interprets a generally higher propensity for caries prevalence in females in light of reproductive ecology. To test the hypothesis that females have higher risk of caries in accordance with reproductive ecology, we examined and analyzed caries prevalence and other potentially synergistic oral pathological lesions in a late medieval (A.D. 1300-1500) Italian archaeological sample.

MATERIALS AND METHODS

We examined sex- and age-related prevalence in caries and other oral pathological lesions in a late medieval Italian skeletal assemblage excavated from Villamagna consisting of 38 females and 37 males (n = 1,534 teeth). We examined age- and sex-related patterns in six dental traits: antemortem tooth loss, caries, calculus, periapical inflammation, tooth wear, and periodontitis.

RESULTS

Significant age-related increases in antemortem tooth loss, caries, calculus, and tooth wear were observed in both males and females. However, there was a lack of expected sex differences in oral pathological lesions, with instead older males exhibiting significantly more antemortem tooth loss and corrected caries than females.

DISCUSSION

Results are discussed in relation to the ethnohistoric context of medieval rural dietary practices as well as biomedical salivary literature, which suggest that dietary changes throughout the life course may have facilitated trade-offs that buffered females from higher rates of dental pathological lesions.

Salivary functions in mastication, taste and textural perception, swallowing and initial digestion

Saliva exerts multiple functions in relation to the initial digestive processes taking place in the upper parts of the gastrointestinal tract. Ingestion of food and beverages, in turn, is a strong stimulus for secretion of saliva with a differential composition depending on the neuronal stimulation pattern. This review paper provides insight into the mechanisms by which saliva acts in relation to taste, mastication, bolus formation, enzymatic digestion and swallowing. Also, the protective functions of saliva including maintenance of dental and mucosal integrity will be discussed as they indirectly influence the digestive process. The final part of this study focuses on the implications of xerostomia and salivary gland dysfunction on gastrointestinal functions.

Effect of Chewing Bicarbonate-containing Sugar-free Gum on the Salivary pH: An in vivo Study

The objective of the study was to evaluate the effect of chewing gum on the salivary pH and to compare the effect of chewing bicarbonate-containing sugar-free gum on salivary pH against that of standard sugar-free gum. The experiment was carried out on 30 volunteers aged 20-22 years (mean age = 21 years) who fulfilled the inclusion criteria. The test gum was sugar-free greenmint-flavored bicarbonate-containing gum and the standard control was sugar-free spearmint-flavored gum. The pH was measured immediately using pH strips. According to statistical analysis, the mean salivary pH of the bicarbonate gum at 0, 5, 10, 15 and 20 minutes is 6.9713, 6.5667, 6.4267, 6.3867 and 6.3233 respectively. There is decrease in pH from 0 to 20 minutes. According to Bonferroni, there was no significant difference in pH from 0 to 20 minutes, 10 to 20 minutes and 15 to 20 minutes, but there was a significant difference in salivary pH from 5 to 20 minutes (p = 0.014). The mean salivary pH of the standard gum at 0, 5, 10, 15 and 20 minutes is 6.8767, 6.6067, 6.4200, 6.4027 and 6.3000 respectively. There is decrease in pH from 0 to 20 minutes. According to Bonferroni, there was no significant difference in pH from 0 to 20 minutes, 5 to 20 minutes, 10 to 20 minutes and 15 to 20 minutes. Thus, the higher salivary pH achieved with chewing bicarbonate gum compared with a standard sugar-free gum may have important oral health implications. How to cite this article: Ballal RK, Bhat SS, Ramdas SS, Ballal S. Effect of Chewing Bicarbonate-containing Sugar-free Gum on the Salivary pH: An in vivo Study. Int J Clin Pediatr Dent 2016;9(1):35-38.

Quantification and qualification of bacteria trapped in chewed gum

Chewing of gum contributes to the maintenance of oral health. Many oral diseases, including caries and periodontal disease, are caused by bacteria. However, it is unknown whether chewing of gum can remove bacteria from the oral cavity. Here, we hypothesize that chewing of gum can trap bacteria and remove them from the oral cavity. To test this hypothesis, we developed two methods to quantify numbers of bacteria trapped in chewed gum. In the first method, known numbers of bacteria were finger-chewed into gum and chewed gums were molded to standard dimensions, sonicated and plated to determine numbers of colony-forming-units incorporated, yielding calibration curves of colony-forming-units retrieved versus finger-chewed in. In a second method, calibration curves were created by finger-chewing known numbers of bacteria into gum and subsequently dissolving the gum in a mixture of chloroform and tris-ethylenediaminetetraacetic-acid (TE)-buffer. The TE-buffer was analyzed using quantitative Polymerase-Chain-Reaction (qPCR), yielding calibration curves of total numbers of bacteria versus finger-chewed in. Next, five volunteers were requested to chew gum up to 10 min after which numbers of colony-forming-units and total numbers of bacteria trapped in chewed gum were determined using the above methods. The qPCR method, involving both dead and live bacteria yielded higher numbers of retrieved bacteria than plating, involving only viable bacteria. Numbers of trapped bacteria were maximal during initial chewing after which a slow decrease over time up to 10 min was observed. Around 10(8) bacteria were detected per gum piece depending on the method and gum considered. The number of species trapped in chewed gum increased with chewing time. Trapped bacteria were clearly visualized in chewed gum using scanning-electron-microscopy. Summarizing, using novel methods to quantify and qualify oral bacteria trapped in chewed gum, the hypothesis is confirmed that chewing of gum can trap and remove bacteria from the oral cavity.

Effects of sugar-free chewing gum sweetened with xylitol or maltitol on the development of gingivitis and plaque: a randomized clinical trial

OBJECTIVE

The objective of this study was to test the effect of sugar-free chewing gum sweetened with xylitol or maltitol compared to the use of a gum base or no gum on gingivitis and plaque scores under both brushing and non-brushing circumstances.

METHODS

The design of the study was a four-group, double-blinded, randomized controlled study with a 3-week duration. In each group, the participants did not brush the teeth in the lower jaw designated to develop experimental gingivitis, while maintaining normal oral hygiene procedures in the upper jaw. After professional dental prophylaxis, the participants were allocated into one of four groups (xylitol, maltitol, gum base or no gum). Chewing gum was used five times a day for 10 min.

RESULTS

220 participants completed the study and provided evaluable data. The increase in bleeding on marginal probing (BOMP) and plaque scores (PS) in the non-brushed (lower) jaw with experimental gingivitis was significant in all groups (P < 0.001). As compared to the gum base, the increase in BOMP in the xylitol and maltitol group was significantly lower. In the brushed upper jaw, no significant changes for BOMP were observed from the baseline to the end point of the study, and there were no significant differences in BOMP and PS between the groups.

CONCLUSION

In circumstances where regular brushing is performed, no effect of chewing gum was observed on bleeding and plaque scores. In the absence of brushing, chewing xylitol or maltitol gum provided a significant inhibitory effect on gingivitis scores compared to chewing gum base. The difference when compared to the group not using gum was not significant.

Effects of Chewing Different Flavored Gums on Salivary Flow Rate and pH

Chewing gum increases salivary flow rate (SFR) and pH, but differences in preferences of gum flavor may influence SFR and pH. The aim of this paper was to assess the effect of five different flavors of sucrose-free chewing gum on the salivary flow rate and pH in healthy dental students in Isfahan, Iran. Fifteen (7 men and 8 women) healthy dental student volunteers collected unstimulated saliva and then chewed one of five flavored gums for 6 min. The whole saliva was collected and assessed for 6 consecutive days. After unstimulated saliva was collected, stimulated saliva was collected at interval of 0-1, 1–3, and 3–6 minutes after the start of different flavored chewing gums. The SFR and salivary pH were measured. The SFR increased in all five flavored gums at 1, 3, and 6 minutes after start of chewing gums (P < 0.001). The flow rate of all products reached peak in the 1st minute of stimulation, except spearmint-flavored gums which reached peak in the 6th minute. In the 1st minute, the strawberry-flavored gums showed the highest SFR. During 1–3 minutes, strawberry- and apple-flavored gums showed higher SFR, respectively. Only the spearmint- and cinnamon-flavored gum significantly increased salivary pH. Gum flavored can affect the SFR and pH and special flavors can be advised for different individuals according to their oral conditions.

Gum chewing during pre-anesthetic fasting

Many ad hoc fasting guidelines for pre-anesthetic patients prohibit gum chewing. We find no evidence that gum chewing during pre-anesthetic fasting increases the volume or acidity of gastric juice in a manner that increases risk, nor that the occasional associated unreported swallowing of gum risks subsequent aspiration. On the contrary, there is evidence that gum chewing promotes gastrointestinal motility and physiologic gastric emptying. Recommendations against pre-anesthetic gum chewing do not withstand scrutiny and miss an opportunity to enhance comfort and sense of wellbeing for patients awaiting anesthesia. Gum chewing during the pre-anesthetic nil per os (NPO) period would also permit the development of gum-delivered premedications and should be permitted in children old enough to chew gum safely. Gum chewing should cease when sedatives are given and all patients should be instructed to remove any chewing gum from the mouth immediately prior to anesthetic induction.

Multicenter randomized trial of chewing gum for preventing oral mucositis in children receiving chemotherapy

The properties of saliva led us to hypothesize that the salivary flow increase induced by gum chewing might protect the oral mucosa from lesions due to cancer chemotherapy. We conducted a multicenter randomized trial to evaluate the efficacy of chewing gum in preventing oral mucositis in 145 children receiving chemotherapy regimens expected to induce WHO grade 3-4 oral mucositis in at least 30% of patients. Patients were allocated at random to standard oral care with or without 5 gum pieces per day. No overall reduction in severe oral mucositis occurred in the gum arm (51%) compared with the standard arm (44%). VIDE, COPADM, and multidrug intensive chemotherapy caused severe oral mucositis in 75% of patients in both arms. In patients receiving less toxic regimens, a decrease in WHO grade 1-4 oral mucositis was noted in the gum arm compared with the standard arm (49% vs. 72%, P=0.03). In the multivariate analysis, the risk of oral mucositis was related only to the type of chemotherapy regimen, suggesting that further strategies for preventing oral mucositis could be mainly based on these criteria.

Absorption of urea through the oral mucosa and estimation of the percentage of secreted whole saliva inadvertently swallowed during saliva collection

OBJECTIVE

To determine whether some of the urea added to certain chewing gums may be absorbed through the oral mucosa and whether some saliva is inadvertently swallowed during the collection of saliva elicited by the chewing of gum.

DESIGN

On two occasions, 10 experienced saliva collectors made a 5 min collection of unstimulated whole saliva and then chewed gum for 10 min and during this time collected their saliva. On one occasion, they chewed one tablet of gum containing 0.5 mg of Phenol Red, a non-absorbable substance, and one tablet of a gum containing 27.3 mg of urea. On another occasion, they chewed two tablets of the Phenol Red gum. Their saliva and the chewed gum were assayed for their Phenol Red and urea contents and the totals calculated. Since saliva normally contains urea, the recovery of urea was calculated as the difference between the amounts recovered in the two collection sessions.

RESULTS

The mean recovery of Phenol Red was 96.7%, but in three participants the amount recovered was less than the 95% confidence limits for assay error. The mean recovery of urea was 85.7% and in nine of the 10 participants, the amount recovered was less than the confidence limits for assay error. In all participants, the percentage urea recovery was less than that of Phenol Red.

CONCLUSION

The results showed: (1) that Phenol Red appears to be a useful, non-absorbed marker for studies of drug absorption through the oral mucosa, (2) that when the salivary urea concentration is higher than that in plasma, urea may be absorbed through the oral mucosa, (3) that even experienced saliva collectors may inadvertently swallow some of the saliva they produce. This latter finding has implications for all clinical studies of saliva.

The unstimulated salivary flow rate after prolonged gum chewing

OBJECTIVE

To determine whether, after a prolonged period of gum chewing, the unstimulated salivary flow rate falls below the unstimulated flow rate before gum chewing.

DESIGN

Six males and six females each collected whole saliva at intervals for up to 105 min on two separate days. On one control day they collected unstimulated saliva over the -10 to 0 and 90 to 105 min periods. On the other day, they made the same collections of unstimulated saliva but, in addition, chewed two tablets of Wrigley's peppermint-flavoured gum over the 0-90 min period. The data on flow rates were subjected to repeated-measures ANOVA and Duncan tests.

RESULTS

The unstimulated flow rates in the -10 to 0 and 90 to 105 min periods were not significantly different on the same day or between days and the values were all significantly less (P<0.05) than the stimulated flow rates, while gum was being chewed.

CONCLUSION

This study provided no evidence that the unstimulated salivary flow rate is reduced after prolonged gum chewing. Patients who complain of mouth dryness after prolonged gum chewing may have become accustomed to the larger volume of saliva present in the mouth during the gum chewing.

The effects of prolonged gum chewing on salivary flow rate and composition

OBJECTIVE

To determine the effect of gum chewing for 2 h on salivary flow rate and composition.

DESIGN

Five male and five females each collected whole saliva at intervals over a 2 h period on three separate days, prior to which they collected unstimulated saliva for 5 min. For one 2 h session they continued to collect only unstimulated saliva while for the others one tablet of Wrigley's Extra peppermint- or fruit-flavoured (peach) gum was chewed continuously. Flow rates were calculated and the saliva was assayed for pH and for Na, K, Ca, Cl, inorganic P and protein concentrations. The data were subjected to repeated-measures ANOVA and Duncan tests.

RESULTS

When only unstimulated saliva was collected, there was no significant change in salivary flow rate over the 2 h. With the chewing gums the flow rate increased initially and then, after 35-40 min, fell to similar plateau values which remained significantly higher than the initial unstimulated flow rate and significantly higher than the flow rate at the corresponding time intervals when only unstimulated saliva was collected. With both gums the salivary pH from 2 min to 2 h was significantly higher than that of unstimulated saliva. The changes in the salivary electrolyte and protein concentrations due to the flow rate increase elicited by the chewing gum were largely as expected from previous studies on parotid and submandibular saliva.

CONCLUSION

During prolonged chewing gum use, both salivary flow rates and pH remained significantly above the values for unstimulated saliva.

Preferences and saliva stimulation of eight different chewing gums

OBJECTIVES

Chewing gums have been studied for clinical use to stimulate the salivary flow rate in healthy and diseased individuals. However, differences in preferences of chewing gums may influence patient compliance during long-term use. Therefore, we compared the effect of several chewing gums on the flow rate of whole saliva and pH, and investigated the preferences of these gums.

METHODS

83 healthy subjects participated in the first part of the study. Both parafilm-stimulated and chewing gum-stimulated whole saliva from 8 different chewing gums was collected and salivary flow rate and pH were determined. In another group of 112 healthy subjects, we investigated the preferences for the chewing gums with a 10-item questionnaire.

RESULTS

All gums had comparable effects on salivary flow rate and pH. The average increase in flow rate was 187% during the first minute of chewing compared with parafilm stimulation. After 10 minutes of gum chewing, the amount of saliva was equal to parafilm stimulation. The questionnaire showed differences in preferences for the chewing gums, which were related to taste and gum shape. Gender interactions were observed for sparkling taste (p = 0.019), total judgement (p = 0.047) and the willingness to use the gum for several weeks (p = 0.037).

CONCLUSIONS

Although all chewing gums stimulated the salivary flow rate equally, the observed differences in preferences may influence long-term compliance. Therefore, we recommend that chewing gums are tested before the start of clinical studies, to identify the most accepted chewing gum for specific groups of patients.

Sugar Alcohols: What Is the Evidence for Caries-Preventive and Caries-Therapeutic Effects?

The most widely used sugar alcohols are: xylitol, sorbitol, mannitol, maltitol, lactitol and the products Lycasin and Palatinit. It is often claimed that xylitol is superior to the other sugar alcohols for caries control. This paper examines clinical studies on the caries-preventive and therapeutic effects of sugar alcohols with emphasis on sorbitol and xylitol. It is concluded that chewing sugar-free gum 3 or more times daily for prolonged periods of time may reduce caries incidence irrespective of the type of sugar alcohol used. It may be sufficient to do this only on school days. Sucking xylitol-containing candies or tablets may have a similar effect as chewing xylitol chewing gum. Clinical trials suggest greater caries reductions from chewing gums sweetened with xylitol than from gums sweetened with sorbitol. However, the superiority of xylitol was not confirmed in 2 out of 4 clinical trials comparing the caries-preventive effect of xylitol- with sorbitol-sweetened gums. The caries-preventive effects of polyol-containing gums and candies seem to be based on stimulation of the salivary flow, although an antimicrobial effect cannot be excluded. There is no evidence for a caries-therapeutic effect of xylitol. These conclusions are in line with those of recent reviews and with the conclusions of the Scientific Committee on Medicinal Products and Medical Devices of the EU Commission.

Salivary flow rate and pH during prolonged gum chewing in humans

Gum chewing for 20 min causes an increase in salivary flow rate and salivary pH. Most people chew gum for longer than 20 min, and our aim was to determine how whole mouth salivary flow rate and pH might adapt during prolonged gum chewing. Resting saliva was collected over 5 min; gum-stimulated saliva was collected at intervals during 90 min, chewing a single pellet (1.5 g) of mint-flavoured, sugar-free gum (n = 19). Subjects chewed at their own preferred rate and style. Both salivary flow rate and pH were increased above resting levels for the entire 90 min. The salivary flow was significantly greater (anovaP < 0.05) than resting flows up to 55-min chewing. The saliva pH remained significantly higher (P < 0.0001) than the resting pH even after 90-min chewing. When the experiment was repeated with the gum pellets replaced at 30 and 60 min (n = 9), similar increases in salivary flow rate and pH were found. In the latter experiment, there was no evidence of any cumulative effects on flow or pH. The persistent increase in salivary pH in particular could be beneficial to oral and dental health.

The effect of chewing bicarbonate-containing gum on salivary flow rate and pH in humans

OBJECTIVE

Gum chewing increases salivary flow rate and pH. The aim of this study was to compare the effects of chewing standard sugar-free gum with those of a gum containing sodium bicarbonate.

DESIGN

Whole mouth saliva was collected from 20 volunteers who met inclusion criteria and gave informed consent. After unstimulated saliva was collected, stimulated saliva was collected at intervals during 30 min of chewing either a standard, mint-flavoured gum or bicarbonate-containing, mint-flavoured gum. The salivary flow and pH were measured for each sample.

RESULTS

With the standard gum, the mean peak salivary flow rate was 3.1+/-1.27 ml/min and the peak salivary pH was 7.39+/-0.14. With the bicarbonate gum, the peak flow rate was 2.79+/-1.38 ml/min and the peak salivary pH was 8.06+/-0.18. The salivary flow rates with the two gums were not significantly different; however, the increase in salivary pH was significantly greater for the bicarbonate gum.

CONCLUSION

The increased salivary pH with bicarbonate gum may have implications for oral health and prevention of dental caries.

Saliva and gastrointestinal functions of taste, mastication, swallowing and digestion

Saliva has multiple essential functions in relation to the digestive process taking place in the upper parts of the gastrointestinal (GI) tract. This paper reviews the role of human saliva and its compositional elements in relation to the GI functions of taste, mastication, bolus formation, enzymatic digestion, and swallowing. The indirect function of saliva in the digestive process that includes maintenance of an intact dentition and mucosa is also reviewed. Finally, pathophysiological considerations of salivary dysfunction in relation to some GI functions are considered.

Fluoride and urea chewing gums in an intra-oral experimental caries model

The aim of the present investigation was to evaluate the effect of sugar-free chewing gums containing fluoride (F) and urea in an intra-oral experimental caries model. Placebo chewing gums (without any active ingredient) and no gum served as controls. Fifteen subjects participated in a cross-over, single-blind study. Demineralised enamel and dentine blocks were embedded in circular plastic discs and bonded to the buccal surfaces of the lower canines and first premolars. The discs were removed and analysed using transversal microradiography after each of the six 4-week periods during which the subjects used either test or placebo products or no product. The results revealed that frequent use of sugar-free chewing gum is sufficient to inhibit further demineralisation of previously demineralised enamel and dentine specimens in the oral cavity. Comparing F, urea and placebo gums, the data showed that there was little or no difference between the products, except for an inhibitory effect on the chewing side of the dentition after using F chewing gums.

Effects of gum chewing on pharyngeal and esophageal pH

We investigated the effects of gum chewing on pharyngeal and esophageal pH levels in patients with laryngopharyngeal reflux (LPR) who were undergoing reflux testing. Forty consecutive, unselected, adult patients who were undergoing ambulatory double-probe (simultaneous pharyngeal and esophageal) pH monitoring for diagnosis of LPR were asked to chew 2 sticks of gum 4 times during their pH studies. Twenty subjects chewed regular sugarless gum, and 20 subjects chewed a sugarless gum containing bicarbonate. The subjects recorded the beginning and end of each gum-chewing period. The mean pH values for the gum-chewing intervals and for comparable pre-gum-chewing intervals were analyzed statistically for both the pharyngeal and esophageal probe data. The regular gum group and the bicarbonate gum group were analyzed separately. In addition, the gum-chewing pH data were compared to controls, ie, normal postcibal buffering effects. The data show that gum chewing consistently increases esophageal and pharyngeal pH, and that bicarbonate gum causes greater increases than regular gum. For patients with LPR, gum chewing appears to be a useful adjunctive antireflux therapy.

In vitro quantitative microhardness assessment of enamel with early salivary pellicles after exposure to an eroding cola drink

To assess the erosive effect of a cola drink on enamel incorporating early salivary pellicles, 72 groups of human enamel slabs were immersed in fresh cola, with groups differing in that slabs were (1) incubated in whole or in clarified saliva, (2) under three regimes of frequency intake (1, 5 and 10 times/day); (3) immersed with or without agitation, and (4) the pellicle was incubated for 20 min, 6 or 24 h. Quantitative assessments were done over an 8-day interval using surface microhardness testing. Results for primary enamel showed a sharp decrease from baseline (344.2+/-32.4 Vickers Units; mean +/-SD) to day 1 (268.9+/-36.8), and reached 155.2+/-68.6 on day 8. Results for permanent enamel were 350.8+/-42.2, 315.9+/-39.2, and 149.8+/-85.2. Microhardness was affected by agitation, level of intake and type of saliva, but not by the pellicle incubation interval nor the type of enamel. The joint effect of static baths and higher immersion frequency was the most important factor in decreasing hardness.

Chewing gum--facts and fiction: a review of gum-chewing and oral health

The world market for chewing gum is estimated to be 560,000 tons per year, representing approximately US $5 billion. Some 374 billion pieces of chewing gum are sold worldwide every year, representing 187 billion hours of gum-chewing if each piece of gum is chewed for 30 minutes. Chewing gum can thus be expected to have an influence on oral health. The labeling of sugar-substituted chewing gum as "safe for teeth" or "tooth-friendly" has been proven beneficial to the informed consumer. Such claims are allowed for products having been shown in vivo not to depress plaque pH below 5.7, neither during nor for 30 minutes after the consumption. However, various chewing gum manufacturers have recently begun to make distinct health promotion claims, suggesting, e.g., reparative action or substitution for mechanical hygiene. The aim of this critical review--covering the effects of the physical properties of chewing gum and those of different ingredients both of conventional and of functional chewing gum--is to provide a set of guidelines for the interpretation of such claims and to assist oral health care professionals in counseling patients.

Effect of three months' frequent use of sugar-free chewing gum with and without urea on calculus formation

Studies on the relationship between gum-chewing and calculus formation have produced contradictory results, and it is not clear whether frequent use of chewing gum promotes or inhibits calculus formation. Also, little is known about whether the addition of a small amount of urea to the chewing gum influences calculus formation. The aim of this investigation was to study the effect of sugar-free chewing gum--with and without urea--on calculus formation and some associated clinical variables. Three three-month periods were studied in a double-blind, crossover design, during which the subjects: (1) chewed 5 pieces/day of a sugar-free, urea-containing chewing gum (20 mg urea/piece); (2) chewed 5 pieces/day of a sugar-free, non-urea-containing gum; or (3) performed no gum-chewing. Twenty-nine persons, all calculus-formers, participated. They were scored for calculus at mesio-lingual, lingual, and disto-lingual sites on the 6 anterior mandibular teeth according to the Volpe-Manhold index. Plaque and gingival bleeding index, stimulated salivary secretion rate and buffer capacity, resting plaque pH, mutans streptococci in saliva and plaque, and lactobacilli in saliva were also determined. No differences in calculus formation were found among the 3 periods. The resting plaque pH was higher after the period with urea-containing gum than after the period with non-urea-containing gum and the no-gum period (p < 0.05). A slight increase in stimulated salivary secretion rate was found after the 2 gum periods (p < 0.05). The plaque and gingival bleeding indices decreased, while resting plaque pH and salivary buffer capacity increased throughout the entire study (p < 0.05). No significant differences in prevalence of the acidogenic micro-organisms were found among the test periods. The main conclusion from this study is that three months' frequent use of sugar-free chewing gum--with or without urea--neither promotes nor inhibits calculus formation.

Relation between saliva flow and flavor release from chewing gum

The objective of this study was to investigate whether or not parotid saliva flow is a significant determinant of flavor release from chewing gum. Cherry-flavored gum with 3 concentrations of citric acid (0.5, 1, and 2%) acting as a sialagogue was evaluated for sweetness and cherry flavor in duplicate by 13 subjects, using a computerized system for simultaneous time-intensity (TI) measurements and unilateral collection of parotid saliva. With increased acidity in the gum, maximum intensity of, and area under, the cherry flavor curve increased (p < 0.001), whereas total duration of sweetness decreased (p < 0.05). Large interindividual differences were found for parotid saliva flow in response to chewing gum. Mean unilateral parotid saliva flows in response to stimulation with water and gum with 0.5, 1, and 2% citric acid were 0.07, 0.30, 0.36, and 0.44 g/min, respectively. There was a significant positive correlation between saliva flow and time to reach maximum intensity of sweetness (p < 0.05) and of cherry flavor (p < 0.01), with "high-flow" subjects taking longer to reach maximum intensity than "low-flow" subjects for both attributes. We conclude that parotid saliva flow may affect the rate of flavor release, but not how much nor for how long flavor is released.

Masticatory function in patients with xerostomia

The effects of reduced salivary output in patients suffering from xerostomia on masticatory function has not been previously studied. This study compares masticatory performance and kinematic activity of patients suffering from xerostomia with age-, sex-, and number of occluding pairs-matched healthy controls. Masticatory function was evaluated by assessment of chewing motion and muscle activity during chewing an artificial food (CutterSil), chewing gum and swallowing a bolus of almond. Chewing motion was recorded with the Optotrak computer system. Bilateral muscle activity of both masseter and anterior temporalis was recorded using surface electrodes. Results of this study revealed significant differences between patients and controls in their ability to process food and masticatory muscle activity. The majority of patients could not break down the artificial food, others had a larger median particle size than the controls. A significant difference was also observed in the number of chewing cycles required to swallow almonds, the patients required more than twice as many chews as the controls, P < 0.001. The right masseter muscle displayed significantly less activity for the patient than the controls. These findings suggest that patients with xerostomia exhibit reduced ability to process food. The observed decline in masticatory performance is probably due to reduced activity of the muscles of mastication.

The flow rate and electrolyte composition of whole saliva elicited by the use of sucrose-containing and sugar-free chewing-gums

On two occasions, 12 adults collected unstimulated saliva and then eight samples of saliva over a 20-min period while chewing 3 g of either Wrigley's Spearmint sucrose-containing gum (SCG) or sugar-free gum (SFG) at 70 chews/min. The flow rates peaked initially, then fell with duration of stimulation. With the SFG they were slightly but significantly higher than with the SCG after 4 min of chewing. The sum of the concentrations of cations minus the sum of the concentrations of anions was not significantly different from zero for saliva elicited by the SCG. However, for unstimulated saliva and that elicited by SFG, there was a slight positive anion balance. A second series of saliva collections with SCG and SFG was made by the same 12 participants and these samples were analysed for lactate. For these collections the flow rates with SCG were not significantly less than with the SFG. The lactate concentration in saliva elicited by SCG peaked at 1.82 mmol/l in samples collected over 8-15 min, whereas samples of saliva elicited by SFG had a mean lactate concentration of 0.21 mmol/l. Of the lactate formed during the metabolism of sucrose by the oral bacteria, only 2% or less appeared to be derived from the metabolism of micro-organisms free in saliva, the balance presumably being formed in dental plaque and entering the saliva by diffusion. All saliva samples were supersaturated with respect to hydroxyapatite but stimulated saliva was significantly more supersaturated than unstimulated saliva.(ABSTRACT TRUNCATED AT 250 WORDS)

The effects of chewing frequency and duration of gum chewing on salivary flow rate and sucrose concentration

On ten separate occasions, unstimulated saliva was collected from 12 adults and then eight samples of saliva over a 20-min period while chewing, in random order, 3 g of either Wrigley's Spearmint chewing-gum or gum-base at frequencies of 35, 50, 70, 90, or 130 chews/min. With both stimuli, flow rates peaked in the first minute of stimulation and then fell with time. A repeated-measures analysis of variance showed that for both the gum and the gum-base, flow rates were independent of chewing frequency, except during the first minute with the chewing-gum. The gum elicited a significantly higher flow rate over the first 4 min of chewing, while the base elicited a significantly higher flow rate over the 8-20-min period of chewing. The sucrose concentration in saliva was also independent of chewing frequency. The salivary sucrose concentration peaked during the second minute of chewing (mean +/- SE = 424.7 +/- 20.0 mM) and the concentration then fell progressively with time. However, sucrose was still being released into saliva during the 15-20 min period of chewing (12.6 +/- 0.8 mM). Gum-base which had been chewed without access to saliva was softer than unchewed base but showed no change in filler content or a reduction in the average molecular weight. The decrease in hardness of the chewed gum-base may have resulted from improved mixing of heterogeneous phases and increased dispersion of plasticizing agents.