The Polished SurfaceContour: A New Approach

Susan M. Wright, MDS. FDSRCSSenior Lecturer and Honorary Consultant

Department oí Prostbetit DentistryKing's Coliege School oí Medicine jnd DentistryDenmark Hill. London SE5 SRX, England

Proper shaping of the polished surface of a denture isinnportant to facilitate the intraoral manipulation and controlof the prosthesis by the patient. A method for the assessmentof the polished surface form and tooth position in processeddentures is described. Low-viscosity silicone impressionmaterial is placed on the dentures, and the patient's chewingmovements are used to define those areas requiringmodification. Int J Pmstbodont 1991;4:159-16J.

T he polished surface of a cotnplete tjentureunites Ihe fitting surface with the occlusal sur-

face, and its proper contour depends on the accu-rate recording of these other two surfaces. Thefitting surface must be made from an impression thatrecords the complete denture-bearing area and thefunctional depth and width of the sulci. While it hasbeen suggested that every dental surgeon can makean impression which will ensure that the fitting sur-face is reasonably accurate,' all too often this is notachieved and the dentures lack retention.

The teeth, forming the occlusai surface, must beset in an arch form that bears the correct hucco-lingual and vertical relationship to the residual ridge.The occlusal surface of the denture must make aneven contact with that of the opposing denturewhen the mandible is in the correct centric rela-tionship with the maxillae. Only when the base isproperly extended and the teeth are correctlyrelated to the residual ridge, can the ideal polishedsurface contour be achieved.

The polished surface contour should conform tothe shape of the tongue, lips, and cheeks. Thesetissues, in movement or at rest, should exert an elas-tic pressure on the dentures, retaining them in placerather than dislodging them.' Polished surfaces fac-ing occlusally and outward allow muscle forces tostabilise the bolus and at the same time act to main-tain the dentures in position. Buccal and lingual sur-

The substance of this paper was presented beiore the AnnualMeeting of the British Society ior the Study of Prosthetic Den-tistry, Manchester, April 1990.

faces that are vertical and parallel to each other donot allow such muscle stabilisation, resulting in aloose denture.' The mandibular posterior teethshould not overhang the tongue, and there shouldbe adequate space for the tongue to act withoutdislodging the denture.'

Muscular control of the denture may be active orpassive. In active muscular fixation, Ihe muscles actantagonistically. l"Or example, the tongue and thebuccinator muscle provide oppositely directedforces that will hold a properly shaped denture inplace between them. Likewise, the simultaneouscontraction of the left and right buccinator musclescan actively retain the mandibular denture evenwith an inactive tongue. In passive muscular fixa-tion, the weight of the tongue, lips, and cheekspressing on optimally shaped polished surfaces willretain the denture in place.-"

The buccolingual position of the teeth is influ-enced lingually by the tongue, and buccally andlabially by the buccinator and mentalis muscles. Thebuccinator muscle influences the height of theocclusal plane. The area of maximum contractionof the buccinator muscle is at the level of the occlu-sal plane. '̂̂

Failure to provide a suitable fitting surfacetogether with the incorrect placement of the arti-ficial teeth ¡so they interfere with the normal activityof the cheeks, lips, or tongue) results in a loose,unstable denture. A functional denture shape maybe achieved using one of the many techniquesavailable to record the neutral zone, or zone of leastinterference, and then fabricating dentures to con-form to this.

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Tlie Polished Surface Contour

Fig la Low-viscosity silicone impression material is appliedthinly to the laDial and buccal polisíied surfaces and to all theborders extending 3 mm onto the fitting surface of the max-illlary denture. No adhesive is used.

Fig 1b Lew-viscosity silicone impression material is appliedthinly to all polished surfaces and to the fitting surface of themandibular denture.

Fig 2 A midiine depression in the tongue may indicate thatthe denture leaves insufficient space for the tongue.

Irreversible hydrotolloid wrapped around a spe-cially designed tray has been used to record animpression of the neutral zone under closed mouthconditions.' A special soft siloxane gel has beendeveloped to record the denture space" and, toovercome the restriction offered by the occlusionnm or the teeth to free ftow of the material, regis-tration bases united in the retromolar-tuberosityregions have been advocated.^ Impression model-ing compound has been used to fabricate occlusionrims moulded by muscle function, prior to closedmouth techniques,'" and softened wax has beenapplied to denture bases" and special record rims.'^Trial dentures have been externally moulded"* andtheir tissue surfaces have been coated with plaster' 'or with impression paste,'" and completed dentureshave been entirely covered with a thin mix of irre-versible hydrocolloid'^ or spread with zinc oxide-eugenol impression paste to record the neutral zoneand are then remodeled.

Many of these materials require a considerableamount of clinical time for moulding, and all of themethods require indexing to define the boundariesof the neutral zone that have been recorded. Thesecomplicated methods may not be either indicatedor practicable for all denture patients.

This paper describes a simple alternativeapproach that does not attempt to record the posi-tion of the neutral zone, but rather serves to rapidlyassess how well a functioning denture conforms tothe potential denture space and to evaluate the con-tour of the polished surface and borders.

Procedure

Approximately 5 ml of a low-viscosity siliconeimpression material (Provil L, Bayer UK Ltd, New-bury, Berkshire, England) is mixed and applied thinlywith a spatula to each denture. No adhesive is used.On the maxillary denture, the labial and buccal pol-ished surfaces and all borders extending 3 mm ontothe fitting surface are covered with the impressionmaterial (Fig la]. On the mandibular denture, all ofthe polished and fitting surfaces are covered (Figlb| . No material is placed on the teeth, and thedenture may be held by the teeth without displacingthe impression material. Although some materialmay be removed during placement, its low viscosityallows it to flow in to fill such areas so that in practicesuch voids do not occur.

The dentures are carefully placed, and the patientis given a piece of damp paper (approximately 3 X3 cm in size) and encouraged to chew it vigorouslyusing the lips, tongue, and cheeks, but not to swal-low it. One-ply, medium-quality paper hand towel

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Wright The Polished Surface Contour

Fig 3 Displacement of the impression material from the pre-molar cusps of the maodiDular denture indicates a lack ofspace for the tongue in that region.

Fig 4 Molar teeth overhang the tongue, which has displacedthe impression material from the area of interference.

Fig 5 Displaced impression material shows where the den-ture base is too thicit and interferes with the normal functionof the tongue.

(code 2734, British Tissues Ltd, Harrow, Middlesex,Fngland] conforming to BS 1439 (1961) for wetcrepe paper is used. This has been found to producea manageable bolus that maintains its form and doesnot disintegrate, leaving the patient searching forsomething to chew. Moistening the paper preventsit from adhering to the silicone impression material.Once the impression material has set, the denturesare removed and examined.

Results

The areas where the impression material has beendisplaced from the surface of the dentures wili indi-cate denture impingement on the normal functionalmuscle activity. Other oral signs of impingementmay be visible, A midline groove or depressionformed in the dorsum of the tongue may indicatethat the tongue space is restricted and the tongue

is being cramped by the denture (Fig 2), The func-tional examination described also provides addi-tional information. It shows the exact area of therestriction and whether all the teeth, or only thepremolars (Fig 3} or the molars (Fig 4), are involved.The displacement of the low-viscosity siliconeimpression material may indicate that the teeth notonly restrict the tongue space, but they also over-hang the tongue, interfering with its sweeping actionand resulting in denture instability. The examinationwill demonstrate when it is not the teeth them-selves, but rather the shape or thickness of the lin-gual flange that requires reduction to provide spacefor normal functional tongue movements (Fig 5],

Using the chewing technique also illustrates therelationship of the border of the flanges of the den-ture to the surrounding musculature. When themylohyoid muscle contracts and the floor of themouth is raised, the exact location of any overex-tension of the lingual flange is indicated and the

4, Number 2, 1991 1 6 1 The International lournai of Prosthodontics

The Polished Suri'ace Contour Wrighl

Fig Sa Flange is overextended and impinges en the mylo-hyoid muscle in function.

Fig 6b After the overextension has Deen correcteiJ, ttie iin-ear nature of the border is appareht.

Fig 7a Maxillary moiar ahd denture base on a patient s newdenture interfere with the movement of the coronoiiJ process.

Fig 7b In the patient's previous denture there is no inter-ference with the coronoid process.

denture can be adjusted appropriately (Fig 6a). Afteradjustment, tbe linear form of the inferior border ofthe middle portion of the lingual flange where itrelates to the mylohyoid muscle is apparent (Fig 6b).

The metbod is also useful to ascertain whypatients who have previously used dentures suc-cessfully have difficulties with new ones. This maybe a result of the tooth position, or of the extension,shape, or thickness of the flanges. For one patient,the last molar tooth and adjacent flange of a newdenture interfered with the normal movement ofthe coronoid process (Fig 7a), producing symptomsthat had been attributed to temporomandibularjoint dysfunction but which were relieved withadjustment of this area. The patient's previous den-ture showed no such interference (Fig 7b),

Assessment of the anterior tooth position isachieved using the labiodental and linguodentalspeech sounds (eg, "F," "V," and "Th") instead ofmastication. The low-viscosity silicone impression

material is applied to the dentures as before, but itis extended to cover the labial surface of the anteriorteeth. The patient is asked to say the days of theweek and to count quickly out loud from 30 to 70,producing the required labiodental and linguodentalsounds. The impression material will be displacedwhere the teeth are too long or too protruded andare interfering with the normal activity of the man-dibular lip (Fig 8).

Conclusion

The technique described is not new. FHowever,its application to provide information on denturesin function has not been described previously. Thetechnique is a simple, rapid aid for evaluating den-tures that might otherwise appear satisfactory butare causing their users problems. It is also helpfulin guiding both students and dental practitionerstoward a better understanding of denture design

The Inlernatioral [ournal uf Proslhodontii

Wright

Fig S Low-viscosity silicone impression material is displacedwhere the maxillary teeth impinge on the mandibuiar iip inspeech.

the function of the surrounding muscles, and theinteraction of these factors in the active environ-ment into which dental prostheses must be placed.

The technique described allows the prosthodon-tist to identify needed modifications of polished sur-face form, to remove any interferences, and toachieve optimal function.

Acknowledgments

The author gratefuily acknowledges the generous supportof Bayer UK Ltd in supplying the Provil L low-viscosity siliconeimpression material used in part of this study.

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Extraoral Application of Osseointegrated Implants

The use of osseointegrated implants to provide support for craniofacial prostheses is documented forthe treatment of complex craniofacial reconstructive problems. The surgioal and prosthodonticmethodology are provided in four brief patient reports.

Tolman DE. Oesjardins HP. J Ofa/Maxi/toiac Surg 1991:49 33-45. Références: 18. Reprints: Dr Dan E, Tolmar,Mayo Clinic, 200 First Street SW. Rochester, Minnesota 55905 -Jon D. Wagner. MD, DDS, Visiting Feliow.Department oí Oral S t^axilio-Faciai Surgery. The London Medical Center, London. England

^ ^ Vdume 4, Number 2, 1991 163 The I nter national lourrial of Pros Ihod ont ics