the retention of complete dentures

Optimal outcome of complete denture treat-ment depends on the successful integration of theprosthesis with the patient’s oral functions pluspsychological acceptance of the dentures by thepatient. These parameters require that patientsperceive their dentures as stationary or well re-tained during function, and that the prosthesesand their effects on the face meet the esthetic andpsychodynamic requirements of the patient. Inthis chapter, the factors involved in achieving den-ture retention (the resistance to removal in a di-rection opposite that of insertion) are reviewed,and the role that a denture adhesive agent mayplay in the context of the patient’s adjustment to,and acceptance of, the dentures is discussed.

FACTORS INVOLVED IN THE RETENTIONOF DENTURESInterfacial force

Interfacial force is the resistance to separationof two parallel surfaces that is imparted by a filmof liquid between them. A discussion of interfacialforces is best broken into separate comments oninterfacial surface tension and viscous tension.

Interfacial surface tension results from a thinlayer of fluid that is present between two parallelplanes of rigid material. It is dependent on theability of the fluid to “wet” the rigid surroundingmaterial. If the surrounding material has low sur-face tension, as oral mucosa does, fluid will maxi-mize its contact with the material, thereby wettingit readily and spreading out in a thin film. If thematerial has high surface tension, fluid will mini-mize its contact with the material, with the result

that it will form beads on the material’s surface.Most denture base materials have higher surfacetension than oral mucosa, but once coated by sali-vary pellicle thay display low surface tension thatpromotes maximizing the surface area betweenliquid and base. The thin fluid film between den-ture base and the mucosa of the basal seat there-fore furnishes a retentive force by virtue of thetendency of the fluid to maximize its contact withboth surfaces.

Another way to understand the role of surfacetension in denture retention is by describing cap-illary attraction, or capillarity. Capillarity is whatcauses a liquid to rise in a capillary tube, becausein this physical setting the liquid will maximize itscontact with the walls of the capillary tube,thereby rising along the tube wall at the interfacebetween liquid and air. When the adaptation ofthe denture base to the mucosa on which it rests issufficiently close, the space filled with a thin filmof saliva acts like a capillary tube in that the liquidseeks to increase its contact with both the dentureand the mucosal surface. In this way, capillaritywill help to retain the denture.

Interfacial surface tension may not play as im-portant a role in retaining the mandibular dentureas it does for the maxillary one. Interfacial surfacetension is dependent on the existence of a liq-uid/air interface at the terminus of the liquid/solidcontact: if the two plates with interposed fluid areimmersed in the same fluid, there will be no resis-tance to pulling them apart. In many patients,there is sufficient saliva to keep the external bor-ders of the mandibular denture awash in saliva,

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CHAPTER 21

The retention of complete denturesKenneth Shay

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The retention of complete dentures 401

achieved through ionic forces between chargedsalivary glycoproteins and surface epithelium oracrylic resin. By promoting the contact of saliva toboth oral tissue and denture base, adhesion worksto enhance further the retentive force of interfa-cial surface tension.

Another version of adhesion is observed be-tween denture bases and the mucous membranesthemselves, which is the situation in patients withxerostomia (sparse or absent saliva). The denturebase materials seem to stick to the dry mucousmembrane of the basal seat and other oral sur-faces. Such adhesion is not very effective for re-taining dentures, and predisposes to mucosalabrasions and ulcerations due to the lack of sali-vary lubrication. It is annoying to patients to havedenture bases stick to the lips, cheeks, andtongue. An ethanol-free rinse containing aloe orlanolin, or a water-soluble lubricating jelly, can behelpful in this situation. For patients whosemouths are dry due to irradiation or an autoim-mune disorder such as Sjögren’s syndrome, sali-vary stimulation through a prescription of 5 to 10mg of oral pilocarpine three times daily can bevery beneficial if the patient can tolerate the likelyside effects of increased perspiration and (occa-sionally) excess lacrimation.

The amount of retention provided by adhesionis proportionate to the area covered by the den-ture. Mandibular dentures cover less surface areathan maxillary prostheses and, therefore, are sub-ject to a lower magnitude of adhesive (and other)retentive forces. Similarly, patients with smalljaws or very flat alveolar ridges (small basal seats)cannot expect retention to be as great as can pa-tients with large jaws or prominent alveoli. Thus,the dentures (and hence the impressions thatserve as the patient analogue for their fabrication)should be extended to the limits of the health andfunction of the oral tissues, and efforts should atall times be made to preserve the alveolar heightto maximize retention.

Cohesion

Cohesion is the physical attraction of like mole-cules for each other. It is a retentive force because

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thereby eliminating the effect of interfacial sur-face tension. This is not so in the maxilla.

Interfacial viscous tension refers to the forceholding two parallel plates together that is due tothe viscosity of the interposed liquid. Viscous ten-sion is described by Stefan’s law.* For two parallel,circular plates of radius r that are separated by aNewtonian (incompressible) liquid of viscosity kand thickness h, this principle states that the force(F) necessary to pull the plates apart at a velocity Vin a direction perpendicular to the radius will be

F � V

The relationship expressed by Stefan’s lawmakes it clear that the viscous force increases pro-portionally to increases in the viscosity of the in-terposed fluid. The viscous force drops off readilyas the distance between the plates (i.e., the thick-ness of the interposed medium) increases. Theforce increases proportionally to the square of thearea of the opposing surfaces. When applied todenture retention, the equation demonstrates theessential importance of an optimal adaptation be-tween denture and basal seat (a minimal h), theadvantage of maximizing the surface area coveredby the denture (a maximum r), and the theoreticalimprovement in retention made possible by in-creasing the viscosity of the medium between thedenture and its seat. It also explains why a slow,steady displacing action (small V) may encounterless resistance and, therefore, be more effective atremoving a denture than is a sharp attempt at dis-placement (large V).

In application, interfacial forces are further en-hanced through ionic forces developed betweenthe fluid and the surrounding surfaces (adhesion)and the forces holding the fluid molecules to eachother (cohesion).

Adhesion

Adhesion is the physical attraction of unlikemolecules for each other. Adhesion of saliva to themucous membrane and the denture base is

(3/2)�kr4

��h3

*Stefan J, Sitzberger K: Akad Wiss Math Natur 69:713, 1874.

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402 Rehabilitation of the edentulous patient: fabrication of complete dentures

it occurs within the layer of fluid (usually saliva)that is present between the denture base and themucosa, and works to maintain the integrity of theinterposed fluid. Normal saliva is not very cohe-sive, so that most of the retentive force of the den-ture-mucosa interface comes from adhesive andinterfacial factors unless the interposed saliva ismodified (as it can be with the use of denture ad-hesive).

Thick, high-mucin saliva is more viscous thanthin, watery saliva—yet thick secretions usuallydo not result in increased retention for the follow-ing reason. Watery, serous saliva can be inter-posed in a thinner film than the more cohesivemucin secretions. Stefan’s law makes it clear, allother factors being equal, that increase in fluidviscosity cannot be accompanied by an equal in-crease in film thickness if displacement force is tobe kept the same.

Oral and facial musculature

The oral and facial musculature supply supple-mentary retentive forces, provided (1) the teethare positioned in the “neutral zone” between thecheeks and tongue and (2) the polished surfacesof the dentures are properly shaped (see Chapter9). This is not to say that patients must hold theirprosthetic teeth in place by conscious effort, onlythat the shape of the buccal and lingual flangesmust make it possible for the musculature to fitautomatically against the denture and thereby toreinforce the border seal (Figs. 21-1 and 21-2).One of the objectives in impression making andarch form design is the harnessing of a patient’sunconscious tissue behavior to enhance both re-tention and stability of the prostheses. If the buc-cal flanges of the maxillary denture slope up andout from the occlusal surfaces of the teeth and thebuccal flanges of the mandibular denture slopedown and out from the occlusal plane, the con-traction of the buccinators will tend to seat bothdentures on their basal seats.

The lingual surfaces of the lingual flangesshould slope toward the center of the mouth sothe tongue can fit against them and perfect theborder seal on the lingual side of the denture. The

base of the tongue is guided on top of the lingualflange by the lingual side of the distal end of theflange, which turns laterally toward the ramus.This part of the denture also helps ensure the bor-der seal at the back end of the mandibular den-ture.

The base of the tongue also may serve as anemergency retentive force for some patients. Itrises up at the back and presses against the distalborder of the maxillary denture during incision offood by the anterior teeth. This is done withoutconscious effort when the experienced denturewearer bites into an apple or sandwich or otherfood. It is seldom that a patient needs to be taughthow to do this. For the oral and facial muscula-ture to be most effective in providing retentionfor complete dentures, the following conditionsmust be met: (1) the denture bases must be prop-erly extended to cover the maximum area possi-ble, without interfering in the health and functionof the structures that surround the denture; (2) the occlusal plane must be at the correct level;and (3) the arch form of the teeth must be in the“neutral zone” between the tongue and thecheeks.

Atmospheric pressure

Atmospheric pressure can act to resist dislodg-ing forces applied to dentures, if the dentureshave an effective seal around their borders. Thisresistance force has been called “suction” becauseit is a resistance to the removal of dentures fromtheir basal seat; but there is no suction, or nega-tive pressure, except when another force is ap-plied (suction alone applied to the soft tissues ofthe oral cavity for even a short time would causeserious damage to the health of the soft tissuesunder negative pressure).

A suction cup pressed against a pane of glassstays in place because the rubber of the squeezedcup elastically seeks to return to a larger shape,thereby causing air pressure within the cup to beless than the pressure outside the cup. A denturecannot be distorted like a suction cup, but oralmucosa can be. When a force is exerted perpen-dicular to and away from the basal seat of a prop-

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Fig. 21-1 Complete dentures have three Surfaces that must harmonize with the oral biological environment. A, The dentures’ polished surfaces are so contoured as to support and contact the cheeks, lips, and tongue. B and C, The impression or basal surfaces are fitted to the basal seats. D and E, The occlusal surfaces of one Denture must fit those of the opposing denture.


Fig. 21-2 Frontal section showing dentures properly filling the available space. A, The buccinator. B, The lingual flange and border are placed under the tongue. C, The mylohyoid. Notice that both upper and lower dentures are so shaped that the action of the tongue and cheeks tends to seat rather than unseat them. If posterior artificial teeth are too wide buccolingually, the form of the dentures will be changed and the tongue and cheeks will tend to unseat them.

erly extended and fully seated denture, pressure between the prosthesis and the basal tissues drops below the ambient pressure, resisting displacement. Retention due to atmospheric pressure is directly proportionate to the area covered by the denture base. For atmospheric pressure to be effective, the denture must have a perfect seal around its entire border. Proper border molding with physiological, selective pressure techniques is essential for taking advantage of this retentive mechanism. Undercuts, rotational insertion paths, and parallel walls The resiliency of the mucosa and submucosa overlying basal bone allows for the existence of modest undercuts that can enhance retention. Although exaggerated bony undercuts or less overt ones covered by thin epithelium may compromise denture retention by necessitating extensive internal

adjustment of the denture, less severe undercuts of the lateral tuberosities, maxillary premolar areas, distolingual areas, and lingual mandibular midbody areas can be extremely helpfulto the retention of the prosthesis. Some “undercuts” are only undercut in relationship to a linear path of insertion or relative to a presumed vertical path of insertion. But if the undercut area is seated first (usually in a direction that deviates from the vertical), and the remainder of the denture base can be brought into proximity with the basal seat on rotation of the prosthesis around the undercut part that is already seated, this “rotational path” will provide resistance to vertical displacement. One common example of this is to be found in the area inferior to the retromolar pad, into which the distolingual extensions of the mandibular base can be introduced from the superior and posterior prior to rotating the anterior segment of the denture down over the alveolar process. The opposite sequence


is common in the maxilla, where a prominent oreven undercut anterior alveolus may dictate an in-sertion path that begins with seating the anteriorin a posterior and superior direction and endswith rotation of the posterior border over thebacks of the tuberosities. This concept increasesin importance as other retentive mechanisms de-cline in strength. For instance, in a patient whohas undergone loss of normal anatomic contoursdue to tumor resection or trauma, surgically cre-ated relative undercuts may mean the differencebetween prosthetic success and failure.

Prominent alveolar ridges with parallel buccaland lingual walls may also provide significant re-tention by increasing the surface area betweendenture and mucosa and thereby maximizing in-terfacial and atmospheric forces. Prominentridges also resist denture movement by limitingthe range of displacive force directions possible.Very flat ridges may bear dentures that displaystrong resistance to displacement perpendicularto the basal seat, due to interfacial and atmos-pheric forces. Yet these same prostheses are verysusceptible to movement parallel to the basal seat,analogous to sliding a suction cup along a pane ofglass, or sliding apart two glass pieces separatedby intervening fluid.

Gravity

When a person is in an upright posture, gravityacts as a retentive force for the mandibular den-ture and a displacive force for the maxillary den-ture. In most cases, the weight of the prosthesisconstitutes a gravitational force that is insignifi-cant in comparison with the other forces acting onthe denture. But if a maxillary denture is fabri-cated wholly or partially of a material that in-creases its weight appreciably (e.g., a metal baseor precious metal posterior occlusal surfaces), theweight of the prosthesis may work to unseat it ifthe other retentive forces are themselves subopti-mal. Increasing the weight of a mandibular den-ture (through the addition of a metallic base, in-sert, or occlusal surfaces) may seem theoreticallycapable of taking advantage of gravity. Anecdotalevidence suggests that this may indeed prove ben-

eficial in cases where the other retentive forcesand factors are marginal.

ADJUNCTIVE RETENTION THROUGH THE USE OF DENTURE ADHESIVES

Complete denture treatment needs to be cus-tomized for each patient’s particular needs. Suc-cessful treatment combines exemplary technique,effective patient rapport and education, and fa-miliarity with all possible management options inorder to provide the highest degree of patient sat-isfaction. Commercially available denture adhe-sives are products that have the capacity to en-hance treatment outcome. This reality is com-pellingly underscored by two facts: (1) consumersurveys reveal that approximately 33% of denturepatients purchase and use one or more dentureadhesive products in a given year; and (2) dentureadhesive sales in the United States exceeded $200million in 1994 (12% more than for denturecleaners, and nearly twice the spending on dentalfloss). Dentists need to know about denture adhe-sives for two reasons: (1) to be able to educate alldenture patients about the advantages, disadvan-tages, and uses of the product, because adhesivesare a widely used dental material and patientsrightfully expect their dentists to be accurately in-formed about over-the-counter oral care productsand (2) to identify those patients for whom such aproduct is advisable and/or necessary for a satis-factory denture-wearing experience.

In this chapter, “denture adhesive” is used torefer to a commercially available, nontoxic, solu-ble material (powder, cream, or liquid) that is ap-plied to the tissue surface of the denture to en-hance denture retention, stability, and perfor-mance. It does not refer to insoluble patient-di-rected efforts at improving denture fit andcomfort such as home reliner kits, home repairkits, paper or cloth pads, or other self-applied“cushions”—many of which have been anecdo-tally linked with incidents of serious soft tissuedamage, alterations in occlusal relations and verti-cal dimension of occlusion, and exacerbated alve-olar bone destruction. Included in this secondcategory are thin wafers of water-soluble material

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successful products consist of mixtures of the saltsof short-acting (carboxymethylcellulose, or CMC)and long-acting (poly[vinyl methyl ether maleate],or “gantrez”) polymers. In the presence of water,CMC hydrates and displays quick-onset ionic ad-herence to both dentures and mucous epithelium.The original fluid increases its viscosity and CMCincreases in volume, thereby eliminating voids be-tween prosthesis and basal seat. These two actionsmarkedly enhance the interfacial forces acting onthe denture. Polyvinylpyrrolidone (“povidone”) isanother, less commonly used agent that behaveslike CMC. Over a more protracted time coursethan necessary for the onset of hydration of CMC,gantrez salts hydrate and increase adherence andviscosity. The “long-acting” (i.e., less soluble)gantrez salts also display molecular cross-linking,resulting in a measurable increase in cohesive be-havior. This effect is significantly more pro-nounced and longer lived in calcium-zinc gantrezformulations than in calcium-sodium gantrez.Eventually, all the polymers become fully solubi-lized and washed out by saliva; this elimination ishastened by the presence of hot liquid.

Other components of denture adhesive prod-ucts impart particular physical attributes to theformulations. Petrolatum, mineral oil, and poly-ethylene oxide are included in creams to bind thematerials and to make their placement easier. Sil-icone dioxide and calcium stearate are used inpowders to minimize clumping. Menthol andpeppermint oils are used for flavoring, red dye forcolor, and sodium borate and methylparaben orpolyparaben as preservatives.

Some objective and subjective responsesto denture adhesive

With the exception of uncommon allergic reac-tions to either karaya or paraben, as just men-tioned, there have been no reports of tissue reac-tions to denture adhesive products. For example,prior to 1990, a few of the commercially availabledenture adhesives contained very low levels ofbenzene, which is regarded as a carcinogen.These products were recalled by the Food andDrug Administration. Today’s adhesives are either

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that are adherent to both basal tissue and denturebase and that lack the ability to flow—and, there-fore, do not have the capacity to direct unevenand point pressures against the bearing tissues.

Components and mechanism(s) of action

Denture adhesives augment the same retentivemechanisms already operating when a denture isworn. They enhance retention through optimiz-ing interfacial forces by (1) increasing the adhe-sive and cohesive properties and viscosity of themedium lying between the denture and its basalseat and (2) eliminating voids between the den-ture base and its basal seat. Adhesives (or, moreaccurately, the hydrated material that is formedwhen an adhesive comes into contact with salivaor water) are agents that stick readily both the tis-sue surface of the denture and the mucosal sur-face of the basal seat. Furthermore, because hy-drated adhesives are more cohesive than saliva,physical forces intrinsic to the interposed adhe-sive medium resist the pull more successfully thanwould similar forces within saliva. The materialincreases the viscosity of the saliva with which itmixes, and the hydrated material swells in thepresence of saliva/water and flows under pres-sure. Voids between the denture base and bearingtissues are therefore obliterated.

Denture adhesive materials in use prior to theearly 1960s were based on vegetable gums—suchas karaya, tragacanth, xanthan, and acacia—thatdisplay modest, nonionic adhesion to both den-ture and mucosa, and possessed very little cohe-sive strength. Gum-based adhesives (still com-mercially available) are highly water soluble, par-ticularly in hot liquids such as coffee, tea, andsoups, and therefore wash out readily from be-neath dentures. Allergic reactions have been re-ported to karaya (and to the paraben preservativethat the vegetable derivatives require), and for-mulations with karaya impart a marked odor rem-iniscent of acetic acid. Overall, the adhesive per-formance of the vegetable gum–based materials isshort lived and relatively unsatisfactory.

Synthetic materials presently dominate thedenture adhesive market. The most popular and

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free of benzene or contain trace amounts believedto be harmless. Commercially available formula-tions in the United States must pass laboratory an-imal tests of skin and eye sensitivity and oral toxi-city before they are acceptable for sale to the pub-lic. Clinical studies of mucosal tissues underlyingadhesive-bearing dentures reveal lessened inflam-mation in patients who perform adequate denturehygiene daily. Dentists must ensure that they arecognizant of any sequelae that may be associatedwith the prescription of all materials used in rou-tine dental practice.

Incisal bite force exerted by well-fitting den-tures overlying well-keratinized ridges with favor-able anatomical features (square arch form;broad, prominent alveoli without undercuts; mildor absent frena) is improved significantly with theuse of an adhesive. More interestingly, incisal biteforce of well-fitting dentures overlying inferiorbasal tissues (tapering arch form, little or no kera-tinization, spiny or absent alveolar ridges, frenaextending to ridge crests) can be increased to therange of the adhesive-bearing dentures overlyingideal basal tissues. The frequency of dislodgmentof dentures during chewing also is markedly de-creased with the use of adhesive. Vertical, antero-posterior, and lateral movements (short of full dis-lodgment) of new and old maxillary dentures re-tained on their mucosal seats under chewing andspeech function can be decreased by 20% to 50%for up to 8 hours after placement of denture ad-hesive.

Objective comparison of chewing performancefails to show an improvement after use of adhe-sive, although subjects report increased confi-dence and security in chewing with the use ofdenture adhesive. Not all products are the same,and patients can tell them apart: subjects are ableto identify preferred adhesive characteristics andproducts in comparisons of different formula-tions. Improvement in chewing efficiency duringadjustment to new dentures progresses further inpatients who employ a denture adhesive product.

Patient response to the use of these materials isnot universally positive. Some patients object tothe “grainy” or “gritty” texture of powder, or to the

taste or sensation of semidissolved adhesive mate-rial that escapes from the posterior and other pe-ripheries (often due to use of excessive quantity oruse in an inadequate prosthesis). Others object tothe difficulties encountered in removing adhesivefrom the denture and the oral tissues, as well as tothe cost of the material.

Indications and contraindications

Scientific evidence favoring the support of rou-tine and safe use of adhesives is lacking. Yet clini-cal experience indicates that prudent use of adhe-sives to enhance the retentive qualities of well-made complete dentures is sound clinical judg-ment. Denture adhesives are indicated whenwell-made complete dentures do not satisfy a pa-tient’s perceived retention and stability expecta-tions. Irrespective of the underlying reasons for apatient’s reported dissatisfaction—psychological,occupational, morphological, functional, and soon—the dentist must recognize that a patient’sjudgment of the treatment outcome is what de-fines prosthodontic success. Such maladaptive pa-tients are clearly candidates for an implant-sup-ported prosthesis (see Section 8). But health, fi-nancial, or other considerations can preclude this,and then a well-organized protocol of functional“do’s and don’t’s” may be the best palliative mea-sure the professional can offer. Specific patientpopulations who can benefit from this strategy in-clude patients with salivary dysfunction or neuro-logical disorders, and those who have undergoneresective surgical or traumatic modifications ofthe oral cavity.

Patients who suffer from xerostomia due tomedication side effects, a history of head and neckirradiation, systemic disease, or disease of the sali-vary glands have great difficulty managing com-plete dentures due to impaired retention and anincreased tendency for ulceration of the bearingtissues. The use of denture adhesive can compen-sate for the retention that is lacking in the absenceof healthy saliva, and can mitigate the onset oforal ulcerations that result from frequent dislodg-ments. Xerostomic patients must be educated,however, that the adhesive-bearing denture will

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need to be deliberately moistened (e.g., with wa-ter from the tap) before it is seated in the other-wise dry mouth to initiate the actions of the mate-rial.

Several neurological diseases can complicatethe use of complete dentures, but adhesive mayhelp to overcome the impediments imposed.Cerebrovascular accident (stroke) may renderpart of the oral cavity insensitive to tactile sensa-tion or partially or wholly paralyze oral muscula-ture. Adhesives can assist in helping these pa-tients accommodate to new dentures or to pros-theses that were fabricated prior to the stroke butthat the patient is now unable to manage due tolost sensory feedback and neuromuscular control.Orofacial dyskinesia is a prominent side effect ofphenothiazine-class tranquilizers (e.g., fluphen-azine, trifluoperazine, thioridazine or thiothix-ene), other neuroleptics (e.g., haloperidol), andeven gastrointestinal medications (e.g., prochlor-perazine, metoclopramide). This movement dis-order, sometimes termed “tardive dyskinesia” be-cause it is often a late-onset side effect ofdopamine-blocking drugs, is characterized by ex-aggerated, uncontrollable muscular actions of thetongue, cheeks, lips, and mandible. In such situa-tions, denture retention, stability, and functionmay be a virtual impossibility without adjunctiveretention, such as that made possible with den-ture adhesive.

Patients who have undergone resective surgeryfor removal of oral neoplasia, or those who havelost intraoral structures and integrity due totrauma, may have significant difficulty in func-tioning with a tissue-borne prosthesis unless den-ture adhesive is employed, even if rotational un-dercuts have been surgically created to resist dis-placement of the prosthesis.

It must be emphasized that a denture adhesiveis not indicated for the retention of improperlyfabricated or poorly fitting prostheses.

Patient education

It is mandatory that dentists educate denturepatients about denture adhesives—their use,abuse, advantages, disadvantages, and available

choices. The major information resource for a pa-tient should be the dentist and not magazine andtelevision advertisements or the testimonials ofrelatives and acquaintances.

The choice between cream and powder islargely subjective, but certain facts may under-score a patient’s selection. Powder formulations,as a rule, do not confer the same degree of “hold,”nor do their effects last as long, in comparison tocomparable cream formulations. However pow-ders can be used in smaller quantities, are gener-ally easier to clean out of dentures and off tissues,and are not perceived as “messy” by patients. Fur-thermore, the initial “hold” for powders isachieved sooner than it is with cream formula-tions.

Obtaining the greatest advantage from the useof an adhesive product is dependent on its properusage (Figs. 21-3 to 21-7) For powder and creamproducts, the least amount of material that is ef-fective should be used. This is approximately 0.5to 1.5 g per denture unit (more for larger alveolarridges, less for smaller ones). For powders, theclean prosthesis should be moistened and then athin, even coating of the adhesive sprayed onto

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Fig. 21-3 Prior to applying powder adhesive for-mulations, the denture must be cleaned and thenthoroughly moistened.

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the tissue surface of the denture. The excess isshaken off, and the prosthesis inserted and seatedfirmly. If the patient suffers from inadequate orabsent saliva, the sprayed denture should bemoistened lightly with water before being in-

serted. For creams, two approaches are possible.Most manufacturers recommend placement ofthin beads of the adhesive in the depth of thedried denture in the incisor and molar regions,and, in the maxillary unit, an anteroposterior beadalong the midpalate. However, more even distri-bution of the material can be achieved if smallspots of cream are placed at 5-mm intervalsthroughout the fitting surface of the dried den-ture. Regardless of the pattern selected, the den-ture is then inserted and seated firmly. As withpowders, use of denture adhesive cream by thexerostomia patient requires that the adhesive ma-terial be moistened with water prior to insertingthe denture.

Patients must be instructed that daily removalof adhesive product from the tissue surfaces ofthe denture is an essential requirement for theuse of the material (Fig. 21-8). Removal is facili-tated by letting the prosthesis soak in water or

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Fig. 21-4 The moistened denture surface is thencovered with a slightly excess coating of the pow-der.

Fig. 21-5 When the excess powder is shaken off,a thin, even coat remains.

Fig. 21-6 Prior to applying cream denture formu-lations, the denture must be cleaned and then thor-oughly dried. Most manufacturers recommend thedistribution of product as shown. For the mandibu-lar denture, a series of thin beads at the crest of theridge is recommended. If adhesive is expressedaround the periphery of the denture in function, alesser quantity should be used.

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soaking solution overnight, during which theproduct will be fully solubilized and can then bereadily rinsed off. If soaking is not possible beforenew adhesive material needs to be placed, re-moval is facilitated by running hot water over thetissue surface of the denture while scrubbing witha suitable hard-bristle denture brush. Adhesivethat is adherent to the alveolar ridges and palate isbest removed by rinsing with warm or hot water,and then firmly wiping the area with gauze or awashcloth saturated with hot water.

Finally, patients need to be educated about thelimitations of denture adhesive. Discomfort willnot be resolved by placing a “cushioning layer” ofadhesive under the denture. In fact, pain or sore-ness signals a need for professional management.Gradual increase in the quantity of adhesive re-quired for acceptable fit of the denture is also aclear signal to seek professional care. In all cases,denture patients need to be recalled annually fororal mucosal evaluation and prosthesis assess-ment, but they also need to be educated about the

warning signs that should alert them to seek pro-fessional attention between the checkups.

Professional attitudes toward dentureadhesive

Denture adhesive products can improve pa-tient acceptance of, and comfort and functionwith, dentures. They are, however, regarded fre-quently as unesthetic and an impediment to adentist’s ability to apprise accurately the health ofa patient’s oral tissues and the true character ofdenture adaptation. The fact that ill-fitting den-tures often are retained by large amounts of adhe-sive material has regrettably led many dentists topresume a correlation between denture adhesiveand severe alveolar ridge resorption.

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Fig. 21-7 An alternative application procedurefor cream adhesive. To the clean and dried den-ture, small dots of product are placed at 5-mm in-tervals. If adhesive is expressed around the periph-ery of the denture in function, the dots should bedistributed farther apart.

Fig. 21-8 Daily thorough cleaning of the dentureis essential. Removal is facilitated by running warmor hot water over the tissue surface of the denturewhile scrubbing with a suitable hard-bristle denturebrush. To prevent accidental damage in the eventthe prosthesis is dropped during cleaning, the sinkshould be partially filled with water, or a washclothor towel should be placed in the sink beneath thedenture.

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If a correlation did indeed exist between den-ture adhesive use and increased alveolar ridge re-sorption, it would provide a strong basis for cau-tioning patients against the use of adhesives. Yetthere is no scientific basis for presuming this al-leged correlation.

Denture adhesives themselves are not capableof exerting forces that would accelerate resorp-tion. Adhesives are liquid materials that are nomore capable of directing forces than is saliva.There is no mechanism through which adhesivescan “exert” forces to further accelerate resorption:as fluids, adhesives will transmit occlusal forcesevenly to the basal tissues, just as would an inti-mately fitted acrylic base. If they fail to do so inone or more areas, the patient will experience dis-comfort and seek professional attention.

Denture adhesives merely reduce the amountof lateral movements that dentures—even well-fitting dentures—undergo while in contact withbasal tissues. Admittedly, this benefit can misleada patient into ignoring his or her need for profes-sional help when dentures actually become ill-fit-ting. This is an inherent risk when using any formof adjunctive therapy. However, it should not pre-

clude prudent clinical strategies. Denture adhe-sives are an integral part of a professional service,and their adjunctive benefits must be recognized.

BIBLIOGRAPHYBerg E: A clinical comparison of four denture adhesives, Int J

Prosthodont 4:449, 1991.Boone M: Analysis of soluble and insoluble denture adhesives

and their relationship to tissue irritation and bone resorp-tion, Compend Contin Educ Dent 4(suppl):S26, 1984.

Grasso JE, Rendell J, Gay T: Effect of denture adhesive on theretention and stability of maxillary dentures, J Prosthet Dent72:399-405, 1994.

Kapur KK: A clinical evaluation of denture adhesives, J Pros-thet Dent 18:550, 1967.

Shay K: Denture adhesives: choosing the right powders andpastes, J Am Dent Assoc 122:70-76, 1991.

Tarbet WJ, Boone M, Schmidt NF: Effect of a denture adhe-sive on complete denture dislodgement during mastication,J Prosthet Dent 44:374, 1980.

Tarbet WJ, Grossman E: Observations of denture-supportingtissue during six months of denture adhesive wearing, J AmDent Assoc 101:789, 1980.

Tarbet WJ, Silverman G, Schmidt NF: Maximum incisal bitingforce in denture wearers as influenced by adequacy of den-ture-bearing tissues and the use of an adhesive, J Dent Res60:115, 1981.

Vinton P, Manly RS: Masticatory efficiency during the periodof adjustment to dentures, J Prosthet Dent 5:477, 1955.

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the retention of complete dentures

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