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Prosíhodontics

Guidelines to lip position in the construction of complete dentures
Paul A. Brunton* / J. Fraser McCord*

A variety of philosophies and techniques for the prescription of esthetically and fiinctionally acceptable complete dentures are reviewed. Guidelines for the use of anatomic landmarks are discussed in addition tofimctional determinants of tooth position. The value ofpre-exiraciion records is discussed and suggestions are made as to useful clinical aides lo more appropriate prescription of acceptable dentures. (Ouintessence Int 1994:25:121-124.)

Introduction It could be postulated that the demand for prosthodontic treatment is likely to change; an increased number of partial dentures may be required, as patients are anticipated to retain more of their natural dentition. ' Further, use of techniques appropriate to the older patient, eg, template dentures for the provision of replacement complete dentures, is to be expected.^ The anticipated increased numbers of elderly patients are expected to be better educated and have more disposable income than ever before.-' In consequence, their expectations, particularly with regard to esthetics and function, are likely to place increased demands on the prosthodontist. Clinical experience suggests that the cumulative effects of biologic and chronologic aging will result in increased numbers of edentulous patients for whom prosthodontic treatment is hkely to be problematic' The purpose of this article is to review methods to restore lip support to edentulous patients. Physiologic lip support and contour In dentate patients, the lips rely on two types of support; 1. Intrinsic support from muscles, fibrous connective tissue, and glands, etc

2. Support from underlying structures, such as the anterior teeth and associated alveolar bone"'^ Ricketts.'' in an attempt to quantify the pereeived "ideal" lip contour, studied profile photographs of popular female personalities admired for their beauty. The lips were related to the '"esthetic plane," a line drawn from the end ofthe nose to the chin. He determined that the lower Up is approximately 2 mm and the upper lip approximately 4 mm posterior to the esthetic plane, which is used in orthodontic evaluation and treatment planning.' This esthetic plane, because of its great variability, is considered by Ellinger^ to be a poor reference plane. Knowledge of lip positiotis in the dentate state are useful in the transition from the dentate to the edentulous state, and may be used in the prescription of prostheses for the edentulous patient. Resorptive changes in alveolar bone following the loss of maxillary teeth have been studied longitudinally.' " These studies revealed a loss of buccal bone and an associated decrease in ridge height in the anterior region of the maxilla. The net result is that the maxilla decreases in size while, coincidentally, the mandible appears to increase in width relative to the maxilla.'^ To quantify facial profile and help preserve a natural facial contour during the transition from a dentate to an edentulous state. Scher'^ advocated the use of a dentofacial profilometer. This measured the nasolabial angle, the length of the upper lip and horizontal part of the nose at the pre-extractton phase of dentnre construction. Friedman''' recommended the use of facial measurements, profile patterns, and photogTaphs to

' Department of Restorative Dentistry, University Dental Hospital of Manchester, Higher Cambridge Street. Manchester M15 6FH, England.

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Table ¡ Clinieal indications of excessive and insufficient lip support Signs of insufficient Up support Perpetuation of the general appearance of collapse around the mouth Reduction in the size of the vermilion borders of the lips Drooping of the corners of the moulh Deepening of the mentolabial, nasolabial, and labiomarginal sulci Obliteration of the philtrum

Signs of excessive lip support Tensed, stretched appearance of the lips Tension lines around the moulh Distortion ofthe philtrum Obhteration ofthe mentolabial, nasolabial. and labiomarginal suici Eradieation of the natural contours of the lower part of the face that correlate that portion with the upper part ofthe face

obtain an index of lip contours and serve as a guide to positioning the anterior teeth. Physiologic lip support is perceived to be important not only for a natural and pleasing appearance but also from a functional point of view.'' The muscles of the lips and cheeks, like al! skeletal muscle, function most efficiently when maintained and supported at their functional physiologic length: esthetic considerations in the construction of complete dentures must therefore be assessed not only while the lips are in repose but also while they are in function.''''^ The pattern of résorption in the anterior maxilla is such that placement of the replacement teeth over the residual alveolar ridge will result in unphysiologic lip support.'" Indeed it has been observed, in some individuals, that the resultant space between the upper lip and incisor teeth that oeeurs when the anterior teeth are set too far palatally is responsible for phonetic problems such as imparting a whispering quality to speech patterns.'^ While a natural tooth position on complete dentures is desirable, to further develop natural form and physiologic lip support, a denture must reproduee a natural anatomy around these teeth to enhance lip support and Tlie labial flange and associated denture base material replace the lost supporting structures of the natural teeth: some workers'*"'" believed that physiologic lip support is provided by the labial flanges and the gingival two thirds of the anterior teeth. Contouring of the labial flange to compensate for the loss of alveolar

bone is also important: if the replacement teeth are in an unnatural position, it is technically difficult to develop a natural contour for the labial flange."^ Further, variation in the thickness and length of the flange from left to right may be necessary to duplicate facial asymmetry,'' The clinical signs of excessive and insufficient lip support, summarized in Table 1, are documented but not quantifled."'-^ Watt and MacGregor'- stated that the average sagittal angle between the columella and the lip is approximately a right angle. This angle eould be increased if the anterior teeth are retroclined or if the columella is prominent and at a lower levei than the ala. If, however, the columella and ala in profile are at the same level and associated with proclined anterior teeth, an angle of more than 90 degrees is indicated. It was also suggested that a horizontal nasolabial angle between 90 and 120 degrees is appropriate. This angle would vary according to whether the patient has a narrow face or a broad face, the broader-faced individual requiring a flatter angle and vice versa. Watt-'' reeommended the constrtiction and use of biométrie trays to prescribe the appropriate depth and width of the buecal sulei and hence to facilitate the restoration of the pre-extraction form of the lips and cheeks. Comparison ofthe edentulous and dentate states Ismail et a P and Carisson and Ericson''' studied the soft tissue profile of subjects prior to the extraction of

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their remaining leeth and for 12 months subsequently and reported a dramatic ehange in the contour of the lips following extraetion of the anterior teeth. While ~- the prescribed dentures restored the lips to the pre-extraction contour, there was a gradual reduction in the vertical and horizontal dimensions of lip contour, *' which was attributed to the pattern of alveolar résorption, Watson and Bhatia,-' however, considered that the upper lip had changed in character in the edentulous group with a flattening of the profile, Tallgren et a!-^ studied, over a 2-year period, soft lissue profile in patients who were to receive immediate complete denlures and reported a more anterior position ofthe maxillary lip, which they considered to be a result of the presence of the denture flange. In addition, a decrease _^ in the occlusai vertical dimension and an associated anterosuperior rotation of the mandible have been reported in other studies,-""-'- This mandibular rotation produces an outward positioning of the upper lip; this change is greatest during the first 6 months of denture it: wear. . _ _ placed incisors, a sunken, uneosmetie oval profile with inverted lips may result,'*' A longitudinal study of upper lip length in dentate adults demonstrated that the upper lip lenglh increases with age.^^Thus, in older patients, it would appear to be more appropriate to site the maxillary incisors level with or superior to the upper lip. This is in agreement with Frush and Fisher,-'' who eonsidered that natural age changes must not be disregarded when dentures are constructed. Restoration of facial contours beyond those compatible with the patient's physiologic age may produce the "denture look,'"" One of the most important anatomic features facilitating positioning of the replacement central incisors is the incisive papilla,'"-'"' The average distance from the posterior border of the papilla to the labial surface of the central incisors has been reported to be 12,5 mm,"**'" Other workers"'-'^''- recommended a distance of S to 10 mm measured from the middle of the incisive papilla as a biométrie guide to anterior tooth position. The results uf some studies-'"'"''-^ indicated that maxillary and mandibular incisors in the "'artificial dentition" were set to a lower level than their natural counterparts: these findings appeared to confirm the perception that the replacement teeth had been set to match a longer edentulous upper lip. Hence if den tures for the older patient are constructed so that the maxillary anterior teeth are 1 to 2 mm below the vermilion border, they will be set to a iower level than their natural counterparts when measured from the maxillary plane.

Anterior tooth position The desirable position for replacement teeth on complete dentures both from an esthetic and functional point of view is that of natural teeth,^'^'"^'^''"^'' Frush and Fisher" felt that the positioning ofthe maxillary anterior teeth for natural and pleasing lip support was an independent procedure not controlled by any cranial relation or opposing tooth position. Positioning the artificial incisors in positions similar to those of their natural predecessors not only is important for physiologic hp support but also serves as an anterior anatomic landmark for developing the occiusal plane,'-*-'' This positioning, however, is not empirical, a patient's capacity to adapt to change must be considered, especially in the elderly. Ellinger** considered that failure to place the anterior teeth in the appropriate position may result in unsupported lips, improper muscle tone, an appearance of premature aging, altered facial expression, and faulty facial contours. It has been accepted practice, by some prosthodontists, to place the maxillary denture teeth over the residual ridges."'-'^ Longitudinal studies of post extraction ridge résorption have demonstrated that the residual ridge does not represent the original tooth positions.'-''" If a denture flange is thickened, in an attempt to plump an upper lip that is lacking support from palatally

Summary

A variety of methods have been used to study the soft tissue of the lips in an attempt to establish guidelines to facilitate the prescription of (maxillary) complete dentures. While no one method can he said to be foolproof, the use of anatomic guidehnes, such as the incisai papilla, is to be reeommended, as is the use of pre-extraction photographs.

References
1, Zarb GA, Bolender CL, Hictcey JC, Carlsson GE, Boucher's Prosthoduntic Treatment for Edentutous Patients, ed tl). St Louis; Mosby, t99U:3, 2, McCord JF, Grant AA. Quayle AA, Treatment options for the edentulous mandible, Eur J Prosthodont Rest Dent 1992; t:19-23.

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3, Hoad-Reddick G. Gram AA, Griltiths CS, Knowledge oí dental services provided: Investigations in an elderly population, J Dont 1987:15:139-146, 4, Martone AL, Effects of complete dentures on facial aesthetics, J Prosthet Dent 1964;14:23]-255, 5, McCarlney JE, Prosthetic problems resuiling from facial and intraoral changes in Ihe edentulous patient, J Denl 1981:9: 71-83, 6, Ricketts RM, Planning Irealmcnl on the basis of the lacial patlern and an estimate oí its growtb. Part 1. Cep h alome tries and growtb estimation. Angle Orlbod 1957;27:14-,37, 7, Di Biase DD, Class II maloeclusion: Making the face fil. Dent Update 1991:18:429^35, 8, Ellinger CW, Radiographie sludy of oral structures and Iheir relation to anterior tooth position, J Prosthet Dent 1968:19:36-45, 9, Carlsson GE, Bergman B, Hedcgard B, Changes in contour of tbe maxillary alveolar process under immediate dentures, A longitudinal clinical and x-ray cephalometric sttidy covering 5 years. Acta Odontol Scand 1967:25:45-75, 10, Watt DM, Likeman PR, Morphological changes in the denture bearing area following extraction of maxillary teeth, Br Denl J 1974:136:225-235, 11, Likeman PR, Watt DM, Morphological changes in the maxillary denture bearing area: A follow up 1410 I7years afler looth extraction, Br DentJ 1974:136:500-503, 12, Watt DM, MacGregor AR, Designing Complete Dentures, ed 2, Bristol, England: Wrighl & Sons, 1986:10,30-31, 13, Scher E, The dontofacial profilometer. Ouintessenee Int 1979:10(3):6l-67, 14, Friedman S. Symposium on complete dentures: Diagnosis and treatment planning, Denl Chn North Am 1977:21:237-247, 15, Marione AL. The phenomenon of funclion in complete denture prosthodontics. Anatomy of the mouth and relaled structures. Part 10, Functional anatomic considerations, J Prosthet Dent 1962:12:206-219. 16, McGee GF, Tooth placement and base contour in denture construction. J Prosthet Dent 1960; 10:651-657, 17, Ballard CE, Variations of posture and behaviour of the lips and tongue which determine the position of the labial segments: The implications on orthodontics, prosthetics and speech. Trans Eur Orthod Soc 1963:39:67-68; discussion 1963:39:89-93, 18, Pound E, Modern concepts in esthetics, Itit Dent J 1960;10: 154-172. 19, Vig RG, The denture look. J Prosthet Dent 1961 ; 11:9-15, 20, Marilato ER. Douglas JR, A positive guide to anterior tooth placement, J Proslhel Denl 1964; 14:848-853, 21, Krajicek DD. Natural appearance for the individual denture patient, J Prosthet Dent 1960:! 0:205-214, 22, Hooper BL. Functional factors in Ihe selection and arrangement of artificial leetb. J Am Dent Assoc 1934:21:603-615, 23, Martone AL, The phenomenon of function in complete denture prostbodontics. Clinical apphcations of concepts of functional anatomy and speech science to complete denture prosthodontics. Part VlILTbe final phases of denture construction, J Prostbel Dent 1963; 13:204-228. 24, Watt DM, Biometrie trays for complete denture construction, JDentl981;9:126-l32, 25, Ismail YH, George WA, SassounI V, Scott RI L Ccphalomelnc study of the changes occurring in the face hci;; lit liJIowtng prosthetic treatment. Part L Gradual reduction of hoth occiusal and rest face heights, J Prosthet Dent 1968;19:321-330, 26, Carlsson GE, Ericson S, Changes in the solt-tissue profile ofthe face following extraction and denture treatment. A longitudinal s-ray cephalomelric study, Odontol Tidskr 1967;75:69-98, 27, Watson RM, Bhatia SN, Tooth positions in the natural and complete artificial dentitions, with special reference to the incisor teeth: An interactive on-line computer analysis, J Orai Rehabil 1989;! 6:139-153, 28, Tallgren A, Lang BR, Miller RL, Longitudinal sludy of soft tissue profile changes in patienls receiving immediate complete dentures, Int J Prosthodont 1991;4:9-16, 29, Tallgren A, Tlie effect of demure wearing on facial morpbology: A 7-year longitudinal study. Acta Odontol Scand 1967; 25:563-592, 3(1. Tallgren A. Positional cbanges of complete dentures: A 7-year longitudinal study. Acta Odonlol Scand 1969;27:539-561. 31, Tallgren A, Lang BR, Walker GF, Ash MM, Roentgen cephalomelric analysis ol ridge résorption and changes in jaw and occiusal relationships in immediate complete denture wearers, J Oral Rebabil 1980:7:77-94, 32, Tallgren A, Lang BR, Walker GF, Ash MM, Changes in jaw relations, hyoid position, and head posture in complete denture wearers, J Prosthet Dent 1983;50:148-156, 33, Hartono R, The occlusai plant; in relation to facial types, JProsthet Dent 1967;] 7:549-558, 34, Payne SH, Symposium on complete dentures; The trial denture. Dent Clin North Am 1977;21:321-328, 35, Anderson JN, Storer R, Immediale and Replacement Dentures, cd 3. Oxford, England: Blackwell Scientific, 1981:105, 36, Watt DM, Tootb positions on complete dentures, J Dent 1978;6:147-160, 37, FrushJP.FisherRD, Complete dentures: The dyneithetic interpretation of the dentogenic concept, J Prosthet Dent 1958; 8:558-581, 38, Forsberg CM. Facial morphology and ageing; A longitudinal cephalometric investigation of young adults, Eur J Orthod 1979:1:15-23, 39, Basker RM, Davenport JC, Tomlin HR, Prosthetic Treatment of the Edentulous Palient: cd 3, New York; Macmillan, 1992:175-176, 40, Ehrlich J, Gazit E, Relationship of the maxillary central incisors and eanines to the incisive papilla, J Orai Rehabil 1975; 2;309-312, 41, Ortman HR, Tsao DH, Relationship of Ihe incisive papilla to the maxillary central incisors. J Prosthet Dent 1979,42:492-496, 42, Landa LS, Practical guidelines for complete denture esthetics. Dent Clin Norlh Am 1977:21:285-298, 43, Nanda RS. Meng H, Kapila S, Goorhuis J, Growth changes in the soft tissue profile. Angle Orthod I99O;6O:177-19O, •

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