Cerodoniology. Volume 7, Number 2. 1988, ISSN 0734-0664®I988 Beech Hill Enterprises Inc.

71

Sorbitol Gum in Xerostomics:The Effects on Dental Plaque pH and Salivary Flow Rates'

NINA MARKOVIC, B.S.D.H., M . S . ' ^ DAVID C . ABELSON, D . D . S . ^

AND IRWIN D . MANDEL, D . D . S . ^

Adequate salivary flow is important for patient comfort and maintenance of oral health. Xerostomia, or dry mouth, is a com-mon clinical complaint. Masticatory and gustatory activity can stimulate salivary flow from functional salivary tissue and theuse of sugarless mints and gums have been recommended to individuals who complain of xerostomia, but there are minimumclinical data. A clinical study assessing the effect on salivary flow rates and dental plaque pH of a sorbitol-sweetened chewinggum in subjects with the complain! of xerostomia was conducted. The chewing of the gum in this present study stimulatedsalivary flow in the subjects with xerostomia. Statistically significant stimulated whole mouth and parotid salivary flow rateincreases were found when compared to unstimulated whole mouth and parotid salivary flow rates. Chemng of the sorbitol-sweetened gum also effectively reduced the drop in pH seen following the exposure to a fermentable carbohydrate. The find-ings of this present study indicate that chewing of a sorbitol-sweetened gum may be of benefit to patients with the complaintof xerostomia.

Xerostomia, dry mouth syndrome or hyposalivation.has been defined functionally as a reduction of unstim-ulated salivary flow by greater than fifty percent (ap-proximately 0.25 ml/min). Stimulated flow may be de-creased proportionately, as well. Reported means forunstimulated whole mouth flow rates range between 0.26to 0.39 ml/min [Dawes, 1987]. Xerostomics have beenclassified as those with a whole mouth resting (unstim-ulated) flow rate of less than 0.20 g/min [Navazesh etal., 1985]. Xerostomia is a common clinical complaintwhich may be associated with many factors including ir-radiation, chronic salivary gland infection, Sjogren's syn-drome, diabetes, hypertension, and the use of many drugsincluding psychotropic medications, anti-hypertensivesand antihistamines [Ben-Aryeh et al., 1985; Navazesh &Ship, 1983; Petersen, 1986; Sreenby & Schwartz, 1986].

Saliva functions intraorally to maintain oral health andcomfort in a variety of ways. Saliva both lubricates andprotects the oral mucosa and exposed dental surfaces. Thebuffering and neutralization capabilities of saliva help tokeep the oral pH constant and counter the acids whichform in the dental plaque during exposure to fermentablecarbohydrates. A variety of systems contained in salivarysecretions, both immunological and non-immunologicaJ,contribute to the antibacterial activities of saliva. Ade-quate salivary production and flow, therefore, are re-quisite in the maintenance of oral health IMandel, 1987;Mandel & Wotman, 1976;].

Treatment for xerostomia is dependent upon whetheror not functional salivary tissues can be stimulated to pro-duce salivary flow. Recently investigators have evaluated

the effects of pilocarpine in stimulating salivary flow ofpatients with functional salivary tissue and found prom-ising results [Fox, 1986, 1987; Greenspan & Daniels,1987]. The use of mints and chewing gum have beenrecommended to patients with non-atrophied glandulartissue [Atkinson & Fox, 1985]. Palliative treatment toalleviate the xerostomia-related complaints is offered topatients with non-functional glandular tissue through theuse of artificial saliva ILevine et al., 1987; Shannon etal., 1977; Vissink et al., 1987].

Although masticatory and gustatory activity can indeedstimulate salivary flow from functional salivary tissue andthe use of sugarless mints and gums is a standard recom-mendation to individuals who complain of xerostomia,there are minimum clinical data on the actual effects. Thepurpose of the present study was to determine in a sampleof xerostomic patients the effects of a sorbitol-sweetenedchewing gum (Trident, Warner Lambert) both on salivaryflow rates and on the in vivo dental plaque pH responseto a sucrose solution.

METHODS

Nineteen individuals with the complaint of xerostomiasecondary to Sjorgren's syndrome or the use of medica-tions were recruited for participation. Informed consentswere obtained following the guidelines and approval ofthe Columbia-Presb>terian Medical Center InstitutionalReview Board. Subjects had at least six maxillary teethand four posterior teeth which occluded. Nine subjectsparticipated in a one-visit assessment of the effect of

'This study was supported in part by a grant from the Warner-Lambert Company, Morris Plains, New Jersey.

'Current address: Ms. Nina Markovic. School of Dental Medicine. University of Pennsylvania. 4001 Spruce Street, Philadelphia, PA 19104, U.S.A.

^From the Center for Clinical Research in Dentistry. School of Dental and Oral Surgery. Columbia University. New York City, NY.

72 MARKOVIC/ABELSON/MANDEL

sorbitol-sweetened chewing gum on salivary flow whilethe remaining ten subjects participated in a three-visitassessment of the effect of the sorbitol chewing gum onboth salivary flow and on the dental plaque pH responseto a IO'Vo sucrose rinse.

Prior to all data collections, an acrylic stem connectedto a standard Lashley cup parotid saliva collector wasconstructed for each participant in order to maintain theLashley cup over Stenson's duct during gum chewing ac-tivity. The participants in the one-visit salivary flowassessment were then instructed to provide unstimulatedwhole mouth saliva for ten minutes by expectoratingsaliva that pooled in the floor of the mouth into agraduated test tube. Unstimulated parotid saliva was thencollected for ten minutes utilizing the acrylic stent andLashley cup parotid collector. Following a period of rest,stimulated whole mouth saliva was then collected for tenminutes while the subject chewed a stick of sorbitol-sweetened chewing gum by instructing the subject to, onceagain, expectorate all the saliva that accumulated in themouth into a graduated test tube. The subject was thenallowed another period of rest prior to a ten-minute col-lection of stimulated parotid saliva by means ofthe acrylicstent and Lashley cup parotid collector, while chewinga fresh stick of sorbitol chewing gum.

Subjects in the three-visit dental plaque pH and salivaryflow assessment were seen at the first visit for construc-tion of the acrylic stent with the Lashley cup parotid col-lector and to schedule subsequent appointments. Subjectswere instructed to appear for the following examinationswith two-day plaque accumulation in a resting state (i.e.no oral hygiene for 48 hours and no food or drink otherthan water for four hours prior to the test session).

At the second appointment, plaque pH response to aone-minute rinse with a 10% sucrose solution was mea-sured for a 60-minute period. Plaque pH was measuredin vivo using a Beckman 3500 digital meter, a glassreference electrode, and an antimony micro electrode. Sixmaxillary teeth, four posterior and two anterior, were

selected for pH measurements. The same six teeth weremonitored at the second and third appointments. Read-ings were recorded in millivolts and then converted to pHbased on pretest standardizations with buffers of pH 4,5, and 7. The pH measurements were recorded at timezero, and then 2, 7, 12, 15, 20, 30 and 60 minutes follow-ing the sucrose rinse. The average of the six readings ateach time was calculated following the pH determination.[Abelson & Mandel, 1981] Unstimulated whole mouthsaliva was collected for ten minutes in the same manneras previously described and ten minutes of unstimulatedparotid saliva was also collected with the previously con-structed stent and Lashley cup parotid collector.

At the third appointment, scheduled approximately oneweek later at the same time of day as the first visit, plaquepH was measured at time zero and at two minutes follow-ing the one minute rinse with a 10% sucrose solution.A stick of sorbitol chewing gum was then chewed by thesubject for ten minutes with a brief interruption for theseven minutes plaque pH recording (subjects were in-structed to place the gum under their tongue so that itwould not interfere with the pH determinations). At time12 minutes gum chewing was discontinued, plaque pHwas recorded and followed at time 15, 20, and 30 minutes.The 60-minute dental plaque pH was discontinued follow-ing initial determinations in which no further changeswere observed in the 30 to 60 minute time period.

Subjects were then given a fresh stick of chewing gumfor collection of stimulated whole mouth saliva for tenminutes in the manner previously described. Followinga ten-minute period of rest, stimulated parotid saliva wascollected for ten minutes while the subject chewed a freshstick of gum with the acrylic stem and attached Lashleycup parotid collector in place.

RESULTS

Ehw Rates

Data on salivary flow rates were collected and com-

TABLE 1

Salivary Flow Rates (ml/min)

Saliva

Unstimulated Whole Mouth

Stimulated Whole Mouth

Unstimuiated Parotid

Stimulated Parotid

All SubjectsN=}9

Mean SD

0.226" 0.174

0.776" 0.427

0.015* 0.021

O.IOP 0.111

Subjective(with now<0

n =

Mean

0.099'

0.609"

0.01^

0.106'

Xerostomia1.25 ml/min)"

SD

0.084

0.409

0.019

0.112

Subjective Xerostomia(with now>0.25 ml/min)"

Mean

0.400"

1.006"

0.019"

0.095*

SD

0.089

0.354

0.023

0.116

"Unstimulated whole moulh salivary flow'p < 0.05'p < 0.01

'p < 0,005'p < 0.0005

SORBITOL GUM IN XEROSTOMICS 73

puted on 19 subjects with the xerostomia. The meanunstimulated whole mouth salivary flow rate for the studypopulation was 0.226 ml/min {SD - 0.174). See Table1. Their mean whole mouth salivary flow rate was in-creased to 0.776 ml/min (5Z) = 0.427) when stimulatedwith the sorbitol-sweetened chewing gum. The mean in-crease in whole mouth flow rate during chewing of thegum was 0.54 ml/min (range 0-1.35 ml/min). Only oneparticipant had no increase.

The mean unstimulated parotid flow rate for the en-tire study population was calculated to be 0.015 ml/min(SD = 0.02\). Their mean parotid flow rate was increasedto 0.101 ml/min (5Z) = 0.111) when stimulated with thesorbitol chewing gum. The mean increase in parotid salivaflow rate during chewing of sorbitol-sweetened chewinggum was. 0.0867 ml/min (range 0-3.0 ml/min). Only oneparticipant had no increase).

Utilizing a /-test for paired data, a statisticallysignificance difference was found at p < 0.005 betweenunstimulated and sorbitol-sweetened chewing gum stimu-

lated flow rate for both whole mouth and parotid salivar>'flow rates.

A separate analysis was performed on the data ofpatients with unstimulated whole mouth flow ratesof less than 0.25 ml/min (eleven subjects) and thosewith flow rates of 0.25 ml/min or greater (eight sub-jects). The analysis for subjects with a flow rate ofless than 0.25 ml/min demonstrated a statisticallysignificant difference at p < 0.0005 for increasedwhole mouth salivary flow, and p < 0.01 for increasedparotid salivary flow. The analysis for subjects witha flow rate of greater than 0.25 ml/min demonstrateda statistically significant difference at p < 0.005 forincreased whole mouth salivary flow, and p < 0.05 forincreased parotid salivary flow.

Plague pH

Data on dental plaque pH response to a lC^o sucroserinse were collected and computed on ten subjects with

Xa.Q)

3VnX

7.

6.

6.

6.

6.

5.

00

75

50

25

00

75

5.50

5.25

5.00

Chewing with Sotbitol Gutn

No Chewing

' ' ' ' ' ' I ' I ' I ' I • I ' I ' I ' I ' I ' I • I ' I • I ' I ' I • I ' I

0 2 12 20 30 40

Minutes

FIGURE 1. Plaque pH response to a 10% sucrose rinse in ten subjects with xerostomia. Sucrose solution rinsed withTZZZT ° " " ' " * ' ' " ' ° ^ ' determinations. Gum chewed from time two to tweive minutes dur̂ g°gum chewing

74 MARKOVIC/ABELSON/MANDEL

the complaint of xerostomia. The mean baseline dentalplaque pH for the first determination was 6.39 (SD =0.496, range 5.3-7.2); for the second determination themean pH was 6.34 {SD = 0.579, range 5.3-6.9). Nostatistically significant difference was found between thetwo baseline plaque pH determinations.

The dental plaque pH response to a one-minute 10%sucrose rince was plotted for each subject over a 30-min-ute period for the determination without chewing andthen compared to the determination during which sor-bitol gum was chewed for each subject (see Figure 1).Area under the baseline plaque pH curve was calculatedfor each determination [Edgar, 1982]. The mean valuefor area under the curve for the determination withoutchewing gum was 26.135 {SD = 9.15). The mean valuefor area under the curve for the determination duringwhich sorbitol gum was chewed was 4.9029 (SZ)= 3.4752).The difference beween the area under the curves for thetwo determinations was found to be statistically signifi-cant at p < 0.0005.

The change in pH (delta pH) following exposure to the\0% sucrose solution was calculated for the determina-tion without chewing and for the determination duringwhich sorbitol gum was chewed between time zero andtwo minutes and for time two minutes to time 30 minutes.Time two minutes was used as a split point as this is whengum chewing was initiated. For time zero to two minutes,the mean delta pH for the determination without chew-ing was -0 .86 {SD = 0.417) and for the chewing gumdetermination mean delta pH was -0.81 (SD = 0.396).No statistically significant difference was noted for timezero to two minutes between the two determinations.

The mean delta pH during time two to 30 minutes forthe determination without chewing was -0.37 {SD =0.291) and for the determination during which sorbitolgum was chewed mean delta pH was +1.17 {SD =0.472). A statistically significant difference at p < 0.001exists between the mean delta pH for time two minutesto 30 minutes of the determinations.

A separate analysis was again performed on the dataof subjects with a unstimulated whole mouth flow rateof less than 0.25 ml/min (seven subjects) and those witha flow rate of greater than 0.25 ml/min (three subjects).Reduction of area under the curve for time zero to 30minutes was demonstrated to be statistically significanttop< 0.0005 for those with a flow rate of less than 0.25ml/min and p < 0.005 for those with a flow rate of greaterthan 0.25 ml/min.

DISCUSSION

Individuals with the complaint of xerostomia wererecruited for the present study. The mean baseline un-stimulated whole mouth salivary flow rate for the studypopulation (0.226 ml/min) was somewhat greater thanthe classification of xerostomics that has been suggestedas those individuals with a resting whole mouth salivary

flow rate of 0.20 g/min [Navazesh, 1985]. (By conven-tion, one milliliter of sahva equals one gram.) Eight ofthe nineteen individuals in this present study who pre-sented with the complaint of xerostomia had unstimulatedwhole mouth salivary flow rates greater than 0.25ml/min. This indicates that perception of xerostomia maynot always coincide with some clinical criteria that havebeen offered.

Masticatory and gustatory activity, provided by thechewing of a sorbitol-sweetened gum in this present study,stimulated salivary flow in the xerostomic study popula-tion as expected. Statistically significant stimulated wholemouth and parotid saliva flow rate increases were foundwhen compared to unstimulated whole mouth and paro-tid salivary flow rates. Only one participant of the study,who presented with severe xerostomia (unstimulatedparotid salivary flow rate of 0.1 ml/10 min) experiencedno increase in the sorbitol chewing gum stimulated wholemouth and parotid saliva flow rates. Ninety-five percentof the study participants evidenced increased wholemouth and parotid salivary flow with stimulation pro-vided by the chewing of the sorbitol sweetened gum.

Moreover, for individuals in the present study with anunstimulated whole mouth salivary flow rate that coin-cided with suggested chnical criteria of xerostomia (lessthan 0.25 ml/min), the effects of chewing the sorbitol-sweetened gum were statistically significant to a greaterdegree than for those individuals whose complaint ofxerostomia was not demonstrated by objective chnicalmeasures.

Exposure to a fermentable carbohydrate in thexerostomic population without a subsequent stimulationof salivary flow or modification of dental plaque resultedin a depressed plaque pH which remained depressedthrough the experimental period (60 minutes). This de-pressed plaque pH was measured in terms of increaseddelta pH and estimated area under the pH curve. Thedelta pH is a measure of the intensity of the pH drop,while the area below the curve is a measure of durationas well as the intensity of the fail in pH. When a substan-tial area exists below the critical pH of 5.7 (pH belowwhich enamel is thought to demineralize) the risk of den-tal caries is considered to be increased.

Chewing of sorbitol-sweetened gum effectively reversedthe drop in pH seen following the exposure to a fermen-table carbohydrate. This was brought about by the stimu-lation of salivary flow which functions to wash ferment-able carbohydrates and acid by-products from the oralcavity and from the plaque. In addition the pumping ofsaliva into the plaque introduces buffering and decarbox-ylating systems that can neutralize plaque acidity [Abel-son & Mandel, 1981; Mandel, 1987].

The plaque pH pattern following a sucrose rinse mayhelp to explain the higher level of caries reported inepidemiologic studies of xerostomic patients. Masticatoryand gustatory salivary stimulation may be an additionalmeans of altering the oral environment following ex-posure to a fermentable carbohydrate for reducing cariesrisk in the xerostomic patient population.

SORBITOL GUM IN XEROSTOMICS 75

SUMMARY AND CONCLUSIONS

The purpose of this work was to study the effect ofchewing sorbitot-sweetened gum on salivary flow andplaque pH in xerostomic patients. Salivary flow wasstudied in 19 dry mouth subjects, while plaque pH re-sponse to a fermentable carbohydrate solution was mea-sured in a subset of ten subjects.

It was found that sorbitol-sweetened chewing gumsignificantly increased salivary flow rates. Largely be-cause of this increased sahvary flow, the degree and dura-tion of tooth exposure to plaque acids (as measured bychanges in plaque pH) was significantly reduced.

The findings of this study suggest that chewing a sor-bitol sweetened gum may be beneficial for individuals suf-fering from xerostomia, both from the point of view ofincreasing comfort and reducing their risk of dentalcaries.

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