Prosthodontics

Denture plaque distribution and the effectiveness of aperborate-containing denture cleanserSiong-Beng Keng*/Michael Lim**

Abstract Formation of plaque on the surfaces of dentures is a common problem amongdenture wearers. A study was conducted to determine the distribution of p¡aque onderttures. The plaque mater¡a¡ was disclosed with a dye solution and measured witha modified Quig¡ey-He¡n scale. A photographic method was used to determine thedistribution of plaque on the dentures of a grotip of complete-denture wearers.The effectiveness of a perborate soak-type cleanser was also measured by studyingthe precleaned and postcleaned states of the denture. Denture p¡aqtie was moreevident on the fitting surfaces of the dentures than on areas of the flange, teeth, andpalate. The use of the soak-type cleanser atone may not be completely effective forthe control of hea\y plaque. (Quintessence Int ¡996:27:341-345.)

Clinical relevance

More plaque tends to accumulate on the flttitigsurfaces of dentures; therefore, patients shoulddirect brushing at these areas, because soak-typecleansers alone may not control heavy plaque.

Introduction

Denture plaque is formed on the surfaces of thedentures by the oral flora and the accumulation of fooddebris. The acrylic resin-mucosa interface forms anideal environment for the formation of denture plaque,which is also facilitated by the irregularities of theacrylic resin and the temperature of the mouth atapproximately 37°C, Studies by Budtz-Jorgensen etal' and Nater^ have shown that plaque deposited onthe acrylic resin allows the action of microorganistns

* Associate Professor, Department of Restorative Dentistry, Faculty ofDentislry, Naiional University of Singapore, Singapore,

" Advanced Prosthodontic Resident, Dental Centre, National tjniver-5ity Hospitai, Singapore.

Reprint requests: DrSiong-Bcng Keng, Associate Professor. Departmentof Restorative Dentistry, Faculty of Dentistry, National University ofSingapore, Lower Kent Ridge Road, Singapore ] Í9074,

on the adjacent mueosa to cause varying grades ofdenture stomatitis. The condition is characterized bygeneral redness located within the boundaries of thedenture border. It is more often observed in thepalate.

An increase in denture plaque bacteria found inpatients with denture stomatitis suggests a possiblerole of plaque microorgarusms,^'' A significant re-lationship between poor denture cleanliness anddenture stomatitis was first described by Budtz-Jorgensen and Bertram^ in 1970. Bergendal^ in 1982also observed that patients with persistent denturestomatitis had greater amounts of maxillary dentureplaque than did those with healthy mouths. Con-tinuous night-and-day wearing of dentures is oftenassociated with an increase in the frequency anddensity of Candida albicans on the fitting surfaces ofthe maxillary dentures.^

Because denture plaque is an important factor instomatitis in patients who wear dentures, cleaning ofdentures and the removal of the plaque are importantsteps in the maintenance of good orai health. Variouscommercial cleansers are available in the market forpatients' use. These can be divided into groups,according to their main components: alkaline perox-ides, alkaline liypochlorites, acids, disinfectants, andenzymes,' Tlie most commonly available cleansers arethose based on the alkaline peroxides. Two methodsare routinely used for cleaning removable prostheses.

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They are the mechanical methods, which involve theuse of brushes or ultrasonic agitation, and chemicalmethods, which utilize soak-type cleaners, disinfect-ants, and enzymes.

Various techniques have been used to determineplaque control levels in patients who wear dentures.These include plaque scoring,^ spcctrofluorometricprotein assay.̂ the scanning electron microscope.'' andphotographic methods.'" To assess the presence orabsence of plaque deposits, Manderson and Brown"'used the staining of dentures and a photographictechnique to determine the effects of a denture cleanseron the plaque.

Denture hygiene instructions to patients shoulddescribe both control of denture plaque and methodsof cleaning dentures. The distribution of plaque on thevarious sites of the denture surface may vary. It wouldtherefore be beneficial for patients to know thecommon locations in which demure plaque tends toaccumulate. Therefore, the aim of the present studywas to determine the distribution of denture plaque in agiven sample of complete-denture wearers and theefficacy of a commonly used soak-type perboratedenture cleanser.

Method and materials

The sample consisted of 42 units of complete denturesfrom 21 patients who attended the university clinic forreplacement dentures. The patients were randomlyselected for the study and had no prior knowledge thatan experiment was to be conducted on their presentdentures. This criteria helped to ensure that a mixedgroup of denture wearers in terms of denture hygienestatus was obtained. Their regular denture cleaninghabits were rinsing in tap water, brushing with mildsoap, and, in some instances, a combination of thosemethods and soaking with denture cleansers.

The soiled precleaned dentures were fu-st stainedwith a dye disclosing solution (Red-cote, Butler) andsubsequently rinsed in tap water to remove anyunbound dye. The plaque present could then bevisualized. This precleaned denture was then photo-graphed, under standardized conditions at a fixedobject-film distance with standard exposure time, witha Medical Nikon camera (120-mm lens with built-inflash, 1:2.5 magnification ratio; ASA 100,135-36Fujichrome color film). Slides were taken from fivepositions: palatal, fitting surface, anterior labial, andright and left buccal side views.

The manufacturer's recommendations for Polidentcleanser (Block Drug) were followed. The denture.

with disclosed plaque, was soaked in a denture bathcontaining 200 mL of tap water to which a Polidenttablet was freshly added. The denture was exposed tothe cleaning bath for 20 minutes, as recommended.Cleaning solutions were used only once, and freshmaterials were utilized for each new cleaning cycle.

The postcleaned denture was then photographed inthe postcleaned state in the same manner as describedeariier.

For the location of the plaque distribution, thedenture was divided into four areas: teeth, palate,flange, and fitting surface. These areas were con-sidered because they represented the main areas of thedenture surface and could be easily identified. Underthe area designated as teeth, the buccal and palatal orlingual surfaces of the denture teeth, including thegingival margins, were taken into account. The palaterepresented the maxillary palatal polished area boundedby the palatal gingival margins.

For classification of the plaque coverage, a modifiedQuigley-Hein scale was used." in this scale, onlywhole numbers were recorded, as follows:

0 = no visible plaque:1 = light plaque (0% to 25%);2 = moderate plaque (26/^ to 50%);3 - heavy plaque (56% to 75%); and4 = very heavy plaque (76% to 100%) of the denture

area covered.

All surfaces of the dentures were evaluated for thedisclosed dye material.

For estimation of the plaque coverage, the colorslides of all the dentures were evaluated by hothinvestigators to confirm location and levei of plaque.For consistency of evaluation in the study, the investi-gators had to agree to a score given for a particularlocation, and the results were recorded accordingly

To assess the ability of the Polident denture cleanserto remove plaque, the scores of all the surfaces ofmaxiiiary and mandibular dentures were combined togive the total precleaned and postcleaned plaquescores of the denture units. All denture surfaces wereincluded in the evaluation to allow assessment of thetotal cleaning ability of the cleanser and not theefficacy at any specific site.

Results

The mean age of the patients in the studied sample was62.3 + 9.8 years, and the present dentures had been inuse for a mean of 5.5 ± 4.8 years. The plaque scoresand their distribution are given in Table 1, which out-

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Table ¡ Baseline denture plaque levels(mean ± SD)*

Location

TissueRangeTeethPalate

Maxillaiy denture

2.14 + 0.961.57 + 0.681.28 + 0.721.38 ±0.81

Mandibular denture

2.38 ± 0.921.76 ±0.831.05 ±0.67

-

Modified Quigley-Hein scale.

lines the plaque scores of the four large areas designatedfor the maxiUary and mandibular dentures. There weresignificant differences between the baseline plaquescores of the maxillary tissue-fitting sutface and thoseofthe fiange, teeth, and palate ( P < .001; / - 3.87; / -4,31, and ;= 4.54, respectively). Similarly, there weresignificant differences between the baseline scores ofthe mandibuiar tissue-fitting surfaces and those of theflange and teeth (P< .001; t- 4.24 and t- 8.37,respectively). There were no statistically significantdifferences between the plaque scores of the maxillaryfiange and those of the teeth and palate. However, forthe mandibular dentures, there were significant dif-ferences in plaque levels between the flanges and theteeth (/•< .001; í=4.5ó). More plaque was evident onthe fianges of the mandibular dentures.

The mean total plaque score was reduced from 5.78±2.44 to 3.81 ± 1.53 after cleaning ( ? < .001; t-9.51). The results of the difference between the totalprecleaned and postcleaned plaque scores were cal-culated to give a reduction of plaque of approximately34% after 20 minutes' exposure to the perboratecleanser. This percentage was derived by subtractingthe value of the postcleaned plaque score from thevalue of the precieaned plaque score and dividing theresult by the precleaned plaque score.

Typical locations of baseline plaque found on themandibular and maxillary dentures can be observed inEigs 1 and 2. Many of the dentures in this study alsodemonstrated greater plaque accumulation in areaswhere there were significant stagnation and pooling ofsaliva on the fitting and polished surfaces. Markedstaining of deposits was also observed along thegingival margins and gingiva! third of the toothsurfaces (Eig 2).

An example of the plaque on the fitting surface ofthe denture base and the effects of the soak-cleansing

cycle on that plaque can be observed in Eigs 3a and 3b,Notice the density and location of the plaque on themaxillary fitting surface and the subsequent reductionof plaque coverage and staining after cleaning.

Discussion

There is abundant documented evidence showing therelationship between good oral health and denturecleanliness.'" In view of this, various methods havebeen advocated for the management of patients withdenture-induced infiammation. Current conservativemethods of treatment of denture stomatitis include (I)prescription of an antiflmgal agent; (2) refinement ofremaking of a denture to reduce trauma; and (3)provision of a sanitary denture. Besides correction ofdenture faults, proper plaque removal procedures areimportant aspects in the management and treatment ofdenture stomatitis. Recent work by Lai et al''̂ demon-strated that patients with denture stomatitis are proneto reinfection if the plaque containing Candida albi-cans on the fitting surfaces of the denture is notcontrolled or eliminated. Using an agar replica tech-nique and a chlorhexidine rinse treatment, they alsodemonstrated that the pretreatment and posttreatmentlocations of Candida albicans on the denture werestrikingly similar. Their findings highlight the im-portance of knowing the areas of the denture that maybe more prone to plaque accumulation.

The findings of the present study showed thatplaque levels are significantly higher on the fittingsurfaces of tlie maxiUary and mandibular dentures thanat sites on the polished surfaces and teeth. This couldbe due to stagnation, pooling of saliva, and the absenceof contact with the tongue on the fitting surfaces.Denture plaque was also observed to accumulate ingreater amounts in the gingival margins, undercutzones, and rugae areas of the maxillary denture.Increased plaque deposits were also noted on thesublingual zones of the polished surfaces of themandibular dentures in addition to the inner fittingsurface. It would therefore be helpful to patients whorequire complete-denture service to be told of theimportance of directing their brushing to these specificareas, if the manual method is advocated.

Numerous studies have been conducted on the effectsof difTerent cleaning methods on dentures''"''^ as theyrelate to plaque control. Abelson'-^ compared iheultrasonic denture-cleaning technique to two types ofsoak-cleansing tablets by using the dye staining tech-nique on the complete dentures of 18 patients. The

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Fig f Typical disclosed plaque distribution on mandibulardenture feefh, gingival margins, and flange.

Fig 2 Disclosed plaque disfribufion on a maxillary denturePlaque is more apparent on the buceal and interdentalsurfaces of the posterior feeth and flange.

Fig 3a Precleaned denture with heavy plaque (score 3) onfhe fitting surface Disclosed dye is evident in fhe anferiorrugae and buceal and posterior paiatal regions.

Fig 3b Postcleaned tiffing surface of the denture. Theamount of disclosure maferiai fias been reduced, revealinglighf plaque (score 1) affer soak cleaning.

ultrasonic method removed 2.5 times more plaquethan did either of the soak-type cleansers tested.Furthermore, from the tissue surfaee scores, plaquereductions of 33% to 38% were calculated for theEfferdent and Polident soak cleansers.

In the present study. 42 heavily stained dentureunits that were soaked ciean in Polident solutiondemonstrated a plaque reduction of approximately34%. Because the technique of plaque scoring used wascarried out with a photographic and visualizationprocess, the plaque removal results can, at most, be anestimate. That soak cleansers by themselves cannotadequately remove heavy plaque deposits was alsodemonstrated in a study by Tarbet et al'^ in 1984, whoused similar piaque-scoring techniques. They foundthat the relative piaque removal score from polished

and unpolished denture surfaces was approximately30% in a group of 25 subjects.

It is apparent firom these studies that soak cleansersalone may not adequately remove accumuiated plaquedeposits, especiaily if the deposits are heavy. Alkalineperoxide cleansers, such as Polident, contain sodiutnperborate, potassium monopersulfate, proteolytic en-zymes, detergents, and an effervescent base, ' ' It is theagitation of the soaking solution caused by thedissolving tablet that does most of the cleaning activity.

Enzyme-containing denture cieansers have beenstudied in a group of 13 patients by Ordman"^ in 1992,He reported that when soaking was used in combina-tion with brushing, the denture became significantiycleaner. In an earlier study by Budtz-Jorgensen et al, "plaque was measured frotn color slides (photographs

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taken with a standard camera setup and color film atftxed object-film distance) of a group of 17 subjects.Their findings were that the use of an enzyme,Alcalase, in adequate concentrations in a 150-mLsolution is as effective as brusbing. It was also notedthat the use of a combination of the enzyme cleanserand a brushing method results in the lowest plaquescores. They concluded their study by indicating thatthe enzyme-solution cleanser would oniy be a sigttif-icant adjunct to denture brushing.

Besides denture piaque, closely fittitig denture basesand continuous wearing of dentures, nigbt and day,have been imphcated as factors in the prevalence ofdenture stomatitis.^-"^-' In view of this, denturesshould be removed at night whenever possibie toreduce the effects of plaqtie on the mucosa-bearingsurfaces of the denture.-' This habit, together withproper hygiene procedures, would help improve oralhealth hi these patients. Additionally, it is still tmclearwhether incomplete, versus complete, cleaning ofdentures in and of itself has a significant impact onstomatitis, other thitigs beittg equal.

Summary

Tbe findings from the study showed that plaque tendsto accumulate on the fitting surfaces of dentures morereadily than on the pohshed surfaces. Cleaning mightbe more effective if denture hygiene procedures weredirected at these specific areas. Clinical and technicalprocedures in denture treatment should also aim atproducing dentures with smooth surfaces to facilitatedenture cleaning.

The use of soak-type cleansers alone may not becompletely effective for the control of beavy plaque. Inthe study, only about 34% of plaque was removed byUlis method of cleaning. The findings seem to supportresults of similar studies conducted on soak-typecleansers. To control plaque, and thus the possibihty ofdenture stomatitis, patients should supplement the useof soak-type cleansers with brushing whenever pos-sible, either by following careful instructions or byhaving their dentures professionaliy cleaned.

Patients should be encouraged not to wear theirdentures at night if possible. Dentists should bemindflil of the possibility of a reinfection in cases ofdenUire stomatitis. Regularrecalls for denture-wearing

patients and Ibllow-up denture sanitization proceduresshould be maintained. The recall visit maybe especial-ly useful for elderly patients, who may have difficulty incontrolling the brushing of tbeir prosthesis.

References

1. Bud tz-Jorge nsen E, Theilade E, Theilade J, Quanlitalive relation-ship between yeasl and bacteria [n denture induced stomatitis. ScandJ Dent Res 19S3;91:134-I42.

2. Nater IP. Etiologic tactors on denture sore moutii syndrome. JProstiiet Dent l97e;40:367-373.

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t2. Bastiaan RJ. Denture sore mouth. Aetiological aspects and treat-ment. Aust Dent J l976;2iJ75-382.

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14. Moore TC, Smith DE, Kenny GE. Sanitization of dentures byseverat denture hygiene methods, J Prosthet Dent t984;52:158-163.

15. Abelson DC, Denture piaque and denture cleansers. J Prosthet Dent198i:45:376-379.

16. Tarbet WJ, Axelrod S, Minkoff S, Fraiarcangelo PA. Denturedeansing: A comparison of two methods. J Prcstliot Dent Í984;51:322-325.

i 7. Goll G, Smilh DE, Plein JB. The effect of denture cleansers ontemporary soft liners. J Prosthet Dent 1983:50:466-472.

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i 9. Budtz-Jorgensen E, KelstrupJ, PoulsenS. Reduction of formation ofdenture piaque by a protease (Alcalase). Aota Odontol Scand1983:41:93-98.

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