Prosthodontics

Preparation of the denture-bearing area-An essential component ofsuccessful complete-denture treatmentThomas A. Lynde*/John W. Unger**

Success in complete-denture treatment is often directly related to the health and conditionof the hard and soft tissues that make up the denture-bearing areas. Surgical alteration ofthe denture-bearing area is frequently necessary to ensure a morphologically correct formcapable oj providing adequate support for the prosthesis. A number of these anatomic hardand soft tissue obstacles are discussed, and methods for managing these hindrances tocomplete-denture treatment are suggested. (Quintessence ¡nt !995;26:689-695.)

Introduction

In this age of preventive dentistry and sophisticatedmethods of replacing teeth, such as with dentalimplants, conventional complete dentures still remaina viable method of treatment for many patients. Onecritical aspect of complete-denture treatment, which isoften confusing and poorly understood, is the properpreparation ofthe denture-bearing areas.

Preparation ofthe denture-bearing area can at timesinvolve sui;gical alteration ofthe anatomic structures;alternatively, depending on the needs ofthe patient, anonsurgical approach can be utilized. In many instan-ces both forms of treatment are needed to return thedenture-bearing tissues to a state of optimal health andform.

The purposes of this article are to review some ofthemore common situations in which preparation ofthedenture-bearing area would be indicated and to

' Assistant Professor. Department of Prosthodontics, School ofDentistry, Medical College of Virginia. Virginia CommonwealthUniversity. Richmond, Virginia.

" W. Tyler Haynes Professor and Chairman, Department of Pros-thodontics. School of Dentistry, Medical College of Virginia. VirginiaCommonwealth university, Richmond, Virginia.

Reprint requests; Dr Thomas A. Lynde, Assistant Professor, Departmentof Prosthodontics, School of Dentistry, Medical College of Virginia,Vtrginia Commonwealth University, Room 301-306, PO Box 980566.Richmond, Virginia 23298-0566.

provide some suggested methods of treatment as wellas the rationale for that treatment.

Unerupted teeth and retained tooth fragments

Survey reports of edentulous patients indicate that asmany as 24% to 33% had one or more retained roots,'When evaluating retained teeth and portions of theirroots, the clinician must consider several factors that inturn influence the type of preprosthetic surgery ren-dered. Use of standardized, repeatable dental radio-graphic techniques are essential to allow assessment ofany pathologic change associated with retained teethand roots.

Most impacted teeth should be extracted, parti-cularly in young patients. In older individuals, if thereis no evidence of pathologic change and the removal ofa submerged tooth would result in a significant surgicaldefect, the tooth may be left but must be carefLiUyobserved at recall visits for any sign of follicular spaceenlargement. Regardless of the patient's age, if theimpacted tooth's follicular wall is close to or hasperforated the cortical plate, it should be removed.^

Areas of sclerotic bone must not be mistaken fortooth fragments. In occlusal radiographie views, scle-rotic bone will appear as irregular radiopaque areasattached to the internal surface ofthe cortex. Thesebodies will not have a definite lamina dura. These areaswarrant documented observation, but preprostheticsurgery is usually not necessary.

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Fig 1 Large maxillary Luberosity,

Fig 2 irigiit) Bilateral undercuts in the tubetosity area

Large bony maxillary tubero sities

The presence of vertically enlarged bony maxillarytuberosities can compromise proper occlusal planeorientation, affecting fonction and esthetics of thedenture (Fig 1), The ocelusal plane ofa denture willslope posteriorly and inferiorly, and the resultantvertical occlusal forces will be directed obliquely to thedenture-bearing area. This can lead to instability ofthedenture. An enlarged tubcrosity can also reduce theamount of denture space to the point that strength ofthe denture can be compromised by fracture or per-foration ofthe denture. This situation can dramaticallydecrease the retention ofthe denture.

Large osseous vertical tuberosities often are a resultof alveolar bone accompanying supraerupted teeth.When these teeth are removed, the bone remains,Dependitig on the proximity ofthe maxillary sinus,which may expand into the tuberosity, the amount ofbone that ean be removed may be limited. The sinusfloor may be surgically collapsed upward if the sinuslimits the amount of bone that can be removed.^

Residuai ridge undercuts

Bony undercuts that are associated with the verticalwalls of residual ridges and obstruct the properextension of denture borders should be considered forsurgical removal. Undercuts in the ttiberosity areas(Fig 2), opposed by prominent anterior ridge under-

cuts, usually should be surgically modified in thetuberosity area only. This will preserve the importantanterior cortical bone.

Mandibular residual ridge undercuts that appear tointerfere with a common path of placement of thedenture should be closely analyzed. If a rotationalplacement is possible, then this should be considered abetter option than surgery, which could eliminate vitalsupporting bone,

Siiarp residual ridges

Bony projections that underlie residtial ridge morpho-logy are common sources of chronic pain and discom-fort during denture wearing. This condition occursmore frequently in the severely resorbed anteriormandible. The situation results when the more accel-erated resorptive pattern of the buccal and lingualsurfaces leaves a thin sharp bony crest. Also, sharpspicules may persist after teeth are extracted. Theseoften result from the failure to remove jagged inter-septal bone at the time of surgery. This condition is lesscommon in the anterior maxillae. The soft tissue thatoverlies these sharp extensions is chronically irritatedand becomes redundant,*

The clinician must utilize radiographs and physicalexamination to evaluate this situation clinically. It isalso essential to rule out any underlying systemiccomplications. The ridge crest can appear razorlike,sawtoothed, or as discrete, large, spiny projections on

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Fig 3 Sharp residuai ridge thaf can be improved bysurgery

Fig 4 Siiarp internal obiique ridge.

dental roentgenograms. Palpation of the suspectedareas usually elicits pain. Clinical features of a knife-edged ridge often appear as an overlying soft tissuebulge delineated inferiorly by buccal and lingtialundercuts or grooves.^

Treatment may consist of occlusal adjustment andjudicious rehef of the tissue surface ofthe denture. Thisis ustially only a temporary remedy. Surgery can beattempted and is more successflil in situations wherethe residual ridge is broad and has some clinicalvertical height (Fig 3). Surgical treatment of anatrophie residual ridge may eliminate what httledenture-bearing area exists. If surgery is the onlytreatment option to create a smooth, broad denturefoundation, then some success may be obtained withdenture construction techniques that redistributestress to areas of bony support, such as the buccalshelf.

Sharp internal oblique and mylohyoid ridges

These osseous ridges (the oblique is superior to themylohyoid) can pose obstacles to mandibular dentureconstruction. As the posterior mandible resorbs in-feriorly and laterally, these ridges become moreprominent- The soft tissue overlying these structures isusually thin. This factor, coupled with the underlyingsharp medial shelf of bone, may inhibit proper lingualborder extension of a denture into the retromylohyoidspace. The result is often loss of stability and retentionofthe denture because of gross relief of the denture inthis area (Fig 4).

These ridges should be surgically smoothed if they

are tender to finger pressure during oral examination.They should also be considered for surgical removal ina severely resorbed mandible where there often is aneed to maximize the lingua! extension ofthe dentureborder. Clitijcal studies have indicated that this pro-cedure may substantially enhance patients' tolerance ofremovable prostheses in the short term.^

Torus palatinus

This slow-growing bony convexity, located along themidpalatal suture, can create significant problemsduring maxillary complete-denture fabrication. Theseosseous prominences can range in size from that of apea to a large muhilobular structure that may fill andoverflow the palatal vault. The soft tissue that coversthese hard enlargements is ustially thin.' Consequently,if a denture is made over the torus, adequate internalrelief must be provided to avoid irritating tbis very thinmucosa.

A conservative nonsurgical approach to manage-ment of a torus seems to be popular. In this case, thedenture is constructed over the bony prominence,taking into consideration the requirements for internalrelief. If the torus extends posteriorly to or beyond thevibrating line, it should be removed to assure anadequate posterior palatal seal. If this exostosis is solarge tbat its undercuts trap food, causing tissueirritation, it should be surgically excised.

A very large torus may add excessive paiatal contourto a denture, resulting in speech difficulties. In thissituation, the denture may also develop instabilitybecause ofthe fulcrum potential (Fig 5).

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Fig 5 (lettj Large torus palatinus extending beyond thevibrating line while requiring increased palatai thickness orthe denture.

Fig 6 (below) Tori mandibulari that will obstruct borderseai of a denture

Torus mandibularis

The mandibular torus is considered more of anobstacle to successful denture construction than is itsmaxillary counterpart. Therefore, surgical removal isthe frequent choice of preprosthetic treatment. Thesetori vary in size similarly to the maxillary torus. Theyare usually bilateral and are located on the lingualalveolar surface in the canine-premolar area. Themucosa covering these hard convexities is thin andsuhject to constant irritation during denture function,'

Because of their size and location, these exostosesfrequently hinder proper lingual border seal of adenture {Fig 6), The practitioner should not be misledby the concept that provision of enough internallingual relief of a denture will obviate surgical correc-tion. These tori are often large and provide undercutcontours in close proximity to the lingual sulcus and.therefore, should be surgically removed.*

Small tori that do not present with the afore-mentioned contours aud location may be retained.Adequate relief can be provided without compro-mising extension and seal ofthe demure border.

Unfavorable frena) positions

Frena are fibrous bands of tissue that may have severalfolds of movable mucosa. These structures attach tobone, but are supertlcial to muscle attachments.

Common locations are labial, lingual, and buccalareas. All frena, when too close to the alveolar ridgecrests, may interfere with proper border extensionleading to poor peripheral seal and fracture-proneareas in the denture^ (Figs 7a and 7b). If a strong forceis applied by a frenum, then the extension of thedenture border may be compromised, A mandibularlingual frenum may dislodge a denture with normaltongue movements. It has been shown that a largemidline frenal notch in a denture complemented by anarrow diastema between the central incisors greatlyincreases the risk of denture base fracture through thisarea,'

In the majority of situations, a high or strong frenalattachment should be surgically corrected prior todenture construction.

Fibrous residual ridge

The fibrous residual ridge can be a significant im-pediment to the successfiil function of completedentures. Although often described as part of thecombination syndrome that afTects the anterior maxil-lary residual ridge, fibrous changes in the compositionofthe residual ridge can occur throughout the maxil-lary and mandibular denture-bearing areas. The maxil-lary tuberosity is an example of an area where fibroustissue enlargement is often encountered.

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Figs 7a and 7b Labial trenum too olose to ndge crest.Lingual frenum that will interfere with border extension andseal.

Fig 7a Fig 7b

Fig 8 (A) Natural mandibular anterior teeth functioningagainst maxillary compiete denture (B¡ Maxillary anteriorlibrous ridge.

Fig 9 Thick layer of librous tissue overlying maxillarytuberosity.

Identilying the cause of the development of thefibrons tissue is often impossible. Frequently, Iraumato the residual ridge is thought to play a significantrole. This has been well described by other authors as amajor factor in the genesis of the combination syn-drome.'**" Inadequate posterior occlusion combinedwith natural mandibular anterior teeth functioningagainst a complete maxillary denture is thought tocause the development ofthe fibrous residual ridge inthe combination syndrome (Fig 8).

Treatment will var>' with the extent and location ofthe fibrous tissue. Surgical removal is generally con-

sidered if the fibrous tissue can be removed andadequate residual ridge height will remain to supportand retain the prosthesis. This treatment approach isused principally where the fibrous ridge area is welldefined and limited. A common example of thissituation would normally arise in the maxillary tnber-osity area (Fig 9). Sui^ical excision ofthe fibroustissue would generally be limited to the tuberosity areaand would usually not significantly reduce the ability ofthe dentist to provide a retentive complete denture.The implantation of alloplastic materials, implanted torestore a firm consistency to the residual ridge, has

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Figs 10a and 10b Palatal papillary hyperplasia on labial and palatal surfaces oí anterior maxillae.

Fig 10a Fig 10b

been advocated by some individuals.'''^ Changes inimpression techniques aimed at recording the fibrousresidual ridge tissue in a nondisplaced state has beensuggested by others as an alternative to any surgicalintervention. '•"

The dentist often faces a significant treatmentdilemma in this situation; creating a single solutionthat will fit each instance is an unobtainable goal. Thefibrous nature ofthe residual ridge will undoubtedlyaffect the stability of any prosthesis because ofthe lackof a firm, solid base of alveolar bone making up theresidual ridge. Removal of all the fibrous tissue fromthe residual ridge will potentially improve the stabilityofthe prosthesis, but could create a situation in whichthe residual ridge height is inadequate to providesufficient retention for the prosthesis. The dentist mustcarefully analyze each situation and, along with thepatient, choose the treatment approach that will bemost beneficial.

Papillary hyperplasia

Papillary hyperplasia is characterized by the develop-ment of numerous small papules usually located on thehard palate under an existing maxillary prosthesis(Figs 10a and 10b}. Although papillary hyperplasiamay occur on the mandibular denturebearing areas, itis rare. Papillary hyperplasia is generally believed todevelop as a result of chronic infiammation induced bycontinuous denture wearing.'^"* The typical patientwho presents with papillary hyperplasia wears amaxillary prosthesis continuously, 24 hours a day Inaddition to the papillary formation, the tissues usuallyare red and inflamed. White patches frequently asso-

ciated with Candida albicans infection may also bepresent.

Treatment is first aimed at resolving the infiam-mation. Because the source of the problem is usually24-hour-a-day wearing of the denture, this practicemust be stopped. Improvement in the hygiene ofthemouth and the prosthesis must commence immediately.A properly fitting denture with a stable occlusion isvital. Provisional liners can be placed in the denture toimprove the adaptation of the prosthesis, and theocclusion can be adjusted to reduce interferences andto distribute the occlusal load properly. Patientsshould be given home care instructions that involvespecific guidelines for both oral and denture hygiene.This most often means brushing and/or massaging thedenture bearing tissues and brushing and soaking thedenture to ensure that it is clean.

Once the inflammatory component has been elim-inated, the true extent and size ofthe papules can bedetermined. Research has shown that papillary hyper-plasia is not a malignant condition and therefore maybe treated in a conservative manner. '•' If the papules donot interfere with denture construction or the deve-lopment of an adequate peripheral border seal, thenremoval ¡s not indicated. Removal of the papulesshould be considered in any instance where properdenture retention will be compromised or where thesize ofthe remaining papules will not allow adequatehygiene. Ongoing observation by the dentist, alongwith continued reinforcement to the patient of theimportance of removing the denture for at least 8 hoursin a 24-hour period and maintaining proper hygienepractices, is essential to Ion.g-term resolution of thiscondition.

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Summary

Suecessfjl treatment with removable prostheses is

dependent on many factors. One component that can

profoundly affect treatment success is the condition of

the denture-bearing tissues. Every effort should be

made to ensure that both the hard and soft tissues are

developed in a form that will enhance the patienfs

ability to wear a denture. It is the responsibility ofthe

practitioner to carefiilly evaluate and identify' the need

for any alteration ofthe denture-bearing areas and to

educate the patient as to the importance of accom-

plishing this vital procedure.

References

1. Jones JD, Seals RR, Schelb E, Panoramic radiographie examinationof edentulous patients, J Prosthel Deni 19a5;53:5:î5-5:î9.

2. Ogle R. Preprosthetic surgen'. Dent Clin Nonh Am 1977:21:19-36.

} . Zarb GA, Bolender CL, Hickey JC, Carlsson GE. Boucher'sProsthodontic Trealmenl for Edentulous Patients, ed 10. St Louis:Mosby, 1990:123-143.

4. Meyer RA. Management of denture palisnls with sharp residualridges. J Prosthet Dent 1990;16:431-437.

5. Nishimura L Aiwood D. Knife-edge residual ridges. A elittiealreport. J Prosthet Dent ]994;71:331-234.

6. Perhall B. Roder D, Esterman A. Increased tolerance to completedentures after surgical modification of m>lohyoid ridges. J ProsthetDent 1985:54.230-23:.

7. Shafer WG, Hine MK, Lev>' BM. A Testbook of Oral Pathology, ed4, PhUadelphia: Saunders, 19S3.167-I69

8. Kelly EK. The prosthodontist, the ora] surgeon and denturesupporting tissues. J Prosthet Dent 1966; 16:474-476.

9. Reese JS, Haggett R, Harrison A. Finite element analysis ofthestress concentrating effects of frenal notches in complete dentures.Int J Prosthodont 1990;3:238-240.

10, Kdly E. Changes caused by a mandibular removable partial dentureopposing a maxillary complete denture. J Prosthet Dent 1982;25:140-150.

i 1. Desjardins RP, Tolman DE. Etiology and management of hypermo-bile mucosa overlying the residual alveolar ridge. J Prosthet Denti984i32:619-638.

12. Block MS, Kent JN. Long term radiographie evaltiation ofbydroxya-patite augmented mandibular alveolar ridges, J Oral Maxillofac Surg1984:42:793-746.

13. Davis WH, Hochwald D, Daly B, Owen WE Reconstruction ofthi:severely resorbed mandible. J Prosthet Dent l990i64:583-Sa8

14. Filler WH. Modified impression technique for hyperplastic alveolarridges, J Prosthet Dent I971;25;6O9-612

15 Cutright DE. Morphogenesis of inflammatory papillary hyperplasia,J Prosthet Dent 1975;33:3SO-385,

16 Ettinger RL. The etiology of iiiHammatory papillary hyperplasia, JProsthet Dent 1975;34:254-261,

17. Bhaskar SN, Beasley JD, Cutright DE, Inflammatory papillaryhyperplasia of the oral mucosa: Report of 341 cases. J Am DentAssoc 1970:81-949-952. D

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