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Aging changes and the complete lower denture
LYK’TlII33 1KCJCl ICY INTO relewlt I,iology must lead to some resolution IJ the lmA~lm 0i the cmpletc~ Imwr denturr. Too ufteu thr writers of textbooks on the subject oi conq~lctz clcntuws hnvc been perfectly satisfied to describe the muscles of nmticntion and the anatotu~ d the maxillae and mandible in the belief that they ha\-c provided adequate. I)iologic background. 1 contend that facial muscles have equal inq~ortance in conll&Ae dmture work. However, the purpose of this article is tcu i0clls ;ittellti~~ll (Jll :l Chaligillg cmcept of the allatq with agiiig, rather than cl-iticizc the contrillutiou of others.
F
‘I‘00 static a vic,\v is 0im {akcu oi the iorm 0i the parts and the way the! \vorli ; lmtll are constautly changing, iriml chiltlhood to old age. Metabolism cmI)rises ntwlmlic ml c:lt;ilmlic lmwssc’s ; in chiltlhoc~d and youth building p’occsw‘s arc in the a~c~~~icl;~~ic~, lalt xitli aging. catalmlim becomes prcdon?inant aud atrophies result. It is well to corlsitl(ir the rhaiigcs ii1 the anatomy under three headings : (1 i tl1c IIItIcos;L :mtl Slllmlccrs:l, ( _31 ttic nwculaturc, and (3 1 the boiw. I. ‘/‘/rc Jlr/cusc7 c7rrd.Srrl~lrr~rc.cjstr.--.~~l~~ cunmou with all other tissues, the oral c~pitheliun~5hv\\~ ;i rwluction ill the number 0i its coinpont~nt cells as age ;iIrq)liv progrrssc5. ‘l‘li(~ micosa iu gciwral, antl that covering the mandibular residual ridge iu particular, shows a decrease in thickness.ld There arc also as.+ociatctl atrophy ;iu(l thiimiii g oi the ~IIIIIIIII~~~;~, SO that the depth oi the soft tissue which cuwrs the ;llvcolar ritlge is rc~ducetl. I‘hiS change is partly explained II!. a gcncral deliytiratim which is obscr~ctl in ultl age. It is not noted to the GIIW tlcgrec in all pntimts, and nlarl\- instances can be called to mind where au old lwson has S~O~IIIa snl~stantiall~ thick rnucosa and submucosa, giving the palpatur~ scnsatiou oi resilicuce over the residual ridge. This change in nature (Ii the oral cyitheliu~ll .sonwtimes reflects similar changes in the skin oi the face. ‘I’hc skin of the old is oftcu described as showing many wrinkles as a result of the atrophy oi the uridcrl~iiig i;ltt!- tissues and muscles. Such a skin as de$‘ttd ill I’&. 1 iS Oh Well. hit $0 alSO is a skin of thinucr testure having a taut, snioother appc:~rancc (Fig, 3 I .--Kcwivedfor publication. Dcr. 1. 1955. *E’ormerly Senior Lecturer in Dental Prost.hetics, University .\S.swintc Professor of Dcnti,ctry at Sorthi\-ctstwn t:nivcrsity.
of Livrrpuol.
Presently
Visiting
Volume 6 Number 4
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DENTURE
In addition to a thinning of the oral mucosa with aging, there is also a reduction in its surface area. This observation results from noting clinical appearances rather than accurate measurement, but when it is considered that the ridges become resorbed the truth of this statement becomes obvious. A less obvious and less constant change is a reduction in the degree of invagination of Sometimes too, the secondary unduthe cheek tissues toward the oral cavity. lations of the buccal mucosa become less marked. Both of these effects contribute to a reduction in surface area of the oral mucosa (Fig. 3). Further, if there is any associated approximation of the jaws (and this is disputed’, ‘* 5.“), this will also have a similar result. The outcome of these changes, which may be present to a greater or lesser degree, is a reversion to a more circular form of the oral cavity, and it might even seem as if the highly differentiated mucosa is seeking to economize in area.
Fig. 1. Fig. I.-The wrinkled type of skin in an old person. Fig. 2 .-The taut, smoother type of skin in an old person. show the inversion of the lower lip.
Fig. 2. The mouth
is slig.htly
open to
The form in sagittal rather than coronal section also seems to substantiate this viewpoint. In the retromolar area, the rounded form of the mucosa as it sweeps from the edentulous ridge to the ramus of the mandible is often observed in association with vertical tissue folds. A backward movement of the lip, to be discussed later, also has the same effect. This potentiality to reduce surface area of the oral cavity is variable. So also is the surgeon’s ability to maintain an epithelial inlay cavity surgically created for the retention of a complete lower denture. Some of these are well preserved and function effectively in stabilizing the denture ; others tend to become quickly
4.52 ot~literatctl, the explanation t(mxIti\.c
Or
;dditicJld
given being that they have “fibrosetl
~x$Ill~lti~Jl~
liiigtlt
tie
ill
the
IdatiVe
teIldellc~
up.”
All
CJf the
lllllC~~Sa
al-
to establish ;Lreduced surface area. ,,Ys \vcll as these macroscopic changes iu the aging oral nmcosa, one important niicroscol~ir change is of practical importance. In the skin, there is a degenerative change in the elastic filwrs, and a condensation and aggregation of them into irregular masses.’ :\n associated l)iochemical change of a controversial nature takes l~lace in these fibers. In :I series of twelve histologic sections taken from the check ant1 mucosal reflections oi young ant1 d old indivitluals. similar changes to these noted I)y I.)ick’ \verc seen in the latter group (Fig. 4i. The net result (4 the changes in the form of the oral nmcosa, and in its elastic fibers, is a decrease in its elastic quality, an end result which has been noted Ijy Rurket.” ( Goldman.‘” and Llassler.’
Fig. 8.-Diagnmmati~ representation plwe with ngIng. The coronal section of an oltler intlivitluul on thv right.
of the reduction in area of oral mwo~il xvhich takes of a young c~dentulons adult ii; shown on the lrft and
2. ‘1’1~~.l.Ittsculatrrrc,.--tiat,cl” tlescrilwtl a niigratioil 0i the origin 0i the hutcitiator fillers over the t~ccal plate 0i the iiiandil~le to\-\.ml the midline, and c~nil~hasizctl the effect this has on reduciiig the neutral zone. An even niore iiiiportant change in ~~wscle origin concerns the mentalis muscles. These nluscles take origili t~ilaterall~ from a circular area 011 the alveolar ridge and l~otly of the inmi(lildc~ alwve the iiirntal tuberosit!~. The highest point ()i origin tics superior to the IJositicm oi the niucosal reflcctioil \\heii the natural teeth ill-c standing, and over tlw root> of the l:ltc’r:~l incisor mntl cminc teeth. The fitters of this muscle tliverp nwdially and laterally to IJC inwrtcd into the skin cd the chin, and also :lW ilis(‘rtCd ilit0 the t(J\ver tit).” sulwriorlq‘ and infcriorlv so that soiiic \Vhen wsorptioll oi the wsitl~lal ridge mtl IHJCI~oi the n~antlildr takes place, the level 0i the ridge crest ialls 1~~1~~~ ttlilt of the iornier origin of the sul)eriur filwrs of the nicntalis iiiusclc. In order to inaintaiii its wea 0i origin. the muscle nttachilieilt icJltls o\er ttic rwrd)ing alveolar ri(lgc and colnt’s to lie on the superior sliri:tw oi tlw resitlwl ridge. ‘l’hc result oi this is a Imzkwartl lnovemcnt, and ~~~111~ r~dllctiOl1. CJf ttlc ll~lltIXt %Ollc ill the :lllt~7’iOr tXlrt CJi ttlc lliO~ltt1. This change in the origin of the nwntalis nnlscle has Iwen ot~serwtl in the surgical tlissections Of ,\lr. i. s. H. Collinge oi l.iverpool, ant1 ironi lml~aratiuns in the cadaver (Fig. 5 )
VC hne 6 Nl lmber 4
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A.
Fig. 4.-Photomicrographs stained with orcein, showing (A) the nature of the elanstic lers in the cheek mucosa of a patient aged between 40 and 50 years, and (B) the chal we in form in a patient of 70 years. (X525; reduced l/6 off.) fil
J. Pros. Den. .luly, 19%
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At this stage it is pertinent to consider the lower lip form in old and young people who have been rendered edentulous. In a young person, the lower lip form changes very little after all the teeth have been extracted. In fact, if the rest position is induced with the upper and lower lips making a light contact, it cannot be discerned from appearance that the teeth have been lost (Fig. 6). The fullness of the lip and its everted position are maintained, as is also the labiomental angle. The dry red lip margin shows to a normal extent. In cases of age atrophy a marked change is noted. The lip becomes thinner and inclines lyackward into the oral cavity. the lahiomental angle disappearing (Fig. 2). The
Fig. B.--A diagrammatic representation mentalis muscle seen after ridge resorption. on the right it has suffered SOYEWresorption.
Fig. lx- The profile
of the change in position of the origin of the On the left the ridge Is well preserved, whereas
view of a young edentulous adult. It is Impossible edentulous state.
to discern
the patient’s
Volume 6 Number 4
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amount of the visible red lip margin is now reduced to a thin straight line. The oral aperture between the upper and lower lips seems to become smaller and to move back; a few patients have commented on the narrowing of the mouth, but usually the slow change is not noticed. This change in lip form is due to the more vertical line of action of the superior fibers of the mentalis muscle, and to a reduction in the surface area of the lip mucosa and skin.
3%. Fig. 8. T.-The lips being no longer able to open to their original circumference A, when about a hinge axis 0, they must move back to accommodate to a decreased circum-
Fig.
opening ference Fig.
B.
S.-Diagrammatic
representation
of the
XdatiVe
positions
of the maxillae
(&f),
the
atrophic lower lip margin (Lz and La), and the symphysis menti (S1 and Sal, when the mouth Although is at rest and fully opened. maxillae, it moves forward in relation observed is thus decreased.
the free lip margin moves back in relation to the to the symphysis and the degree of lip invagination
Not only is a difference in the form of the lower lip noted when the mandible assumes the rest position ; on opening the mouth, the young and the atrophic In the former, the lip remains everted and the only noticelips behave differently. able change of mouth form is that the corners move together to make the oral aperture circular. The atrophic lower lip, being less elastic, moves slightly inward in relation to the fixed maxillae when the mouth opens to its widest extent (Fig. 7). In this position, it has a vertical or slightly invaginated appearance. It might be expected that the degree of inward angulation should increase. However, it must be appreciated that the symphysis menti is moving backward to a greater degree, giving the appearance of a relative lip eversion (Fig. 8). 3. The Bone.-Examination of dried specimens of edentulous mandibles, surgical dissections, and roentgenograms, reveals that cortical bone is often not present in the anterior segment of the residual ridge after healing of the extraction wounds. Noncortical bone is present over the ridge crest in this area. Roentgenograms reveal a typical picture of cancellous bone, showing vertically running nutrient canals. Such a surface cannot be so smooth as one of a cortical nature, and it is made up of the ends of vertically running trabeculae. Sometimes, too, a spicular reaction is noted ; the appearance of small spicules of bone or osteophytes accentuates the rough nature of the bone of the anterior ridge.
456
I..\
\I 11 11.:
The secontl imlwrtarit characteristic of the mandibular ridge is its potentiality for rcsorptiorl. There can be little doubt that the application of forces in the pathologic range can cause au ostcutysis. This type of reaction is often associated with a deposition of filirous tissue witliiu the subiiiuc~sa. The osteolysis of the anterior ridge hone beneath a conildete upper denture with porcelain teeth worn against ouly six natural louver mtcrior teeth is an esamplc in this class. Filmms Instead it tissue. replaces the lmne, but the nlucosa does not retract markedly. sut~stantially maintains its original imn. Sometimes an entire nlaxillary arch is sew to 1~ ver\. rrsiliriit on l~;tll~ation, iiitlicatiiig a rel~lactrnient of al\:eolar ~)(Pw t)y titmms tissue \vithout a market1 decrease iu ridge height. In the nmltlitdc 100, the preserice 0i ;L lllusllroolll-shal,ed tilmus S11t~1lwCos;t which covers a “knife-edge” ridge imy tz a waction 0i this natuw. In terms oi \\.olff’s I,nw,‘” the reductim iii the iiuii~lm 0i the l~my trat~eculae and even their final tlisapliearmcc~ are reascmd~tc, tmt this process cannot account for a change iu the iorrn of the ridge Tim and the eventual Iohs oi the ridges. X’or is it sufficient to account for tliv tlisaI~lwaraiiw of the ridges tiy saying “the teeth arc: lost ; the ridges arc’ rc.clr~ndant mtl tlisqqw;tr.” Cases rii mdontia are seen \vlicre ridges are present. The climige in ridge form iiiiplies the presence of souie nlotding force. th
ll~lt~lrr
Of
n’hk’h
CXll
t)c
tkt~rlllilled
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project undertaken 1)~ >cicntists \vith special knowledge in different fields. The an ;ltrophying mucosa seeking ;t rctlucetl area possibility 0i that iorcc~ t&g iiwst tw l)cmie in illid. \‘cbrF often flat lower ridges are seen lvhcre no cleiiturcs have hecn worii Imviod~, mrl thus the pcissihility of denture trauma being causal is esclutletl : it is significant that in such cases the lower ridge is always covered 1)~ :I thin. tightly strctchctl n~ucous menll)ralw. This is also true of a resorbed ridge stw1 where the to!vvr nmlar teeth have heen estractetl ant1 only l~reniolars :intl anterior teeth remain. Ii in such :I cast the ridge is well fometl, it is COYcrrtl I)y :L thick, krr:ttmlml I~ILKO~;~. Alost authoritic3 011 l~eriotloutal diseaw recognize ii ccditioil described 1)~ StollcS” as senile gingivat recession. The cpithelial attachment is IIO Iouger lowttd at the ;iii~elf~ceiii~ilt;11 junction, but is attached entirely to the ceinentuui, soluc$lncs :it ;L clistanw wnsiderat~l~ ;ipic;il to the enamel margin. iS. reduction in surface area oi the iiiucos~ ivitli associated loss of alveolar tmne may he partI> causal. Thus it is IJcJSSihk that the s:uw factors which cause senile gingival recession also cause alveolar rcsorptim. This hypothesis tloea not disregard the uell-known effects Of function on the or;ll niucosa. nor tlocs it iissuuie l)rior inilmrtanct over recognized factors ~lll~~~JrtaI1t ~llimllg t&x klttcr art the ~)rCS‘emx Of \vhirh act 011 INJW directly. l~eriotlontal disease Ilrior to extraction, tlic action oi horniones, nut1 pressure. It also recognize5 ;in inhewnt how factor offering greater or less resistance to inoltl111gener;tl, a tlenw cortical IKHW. or a heavily traheculatctl iiouing l)resmre, Soiiwtimes n wll-fornietl upper ridge and cortical INHW offers high rwistancc. patatcz ;lw see11to 1)~coved 1)~ ;L thin, taut, mucosa ; here the highly calcifietl Imne is verv stalile in iorm. C)n the other hand. the osteoporosis ant1 ncgativc c:ilciuni hhllCe
ill
th
aged
arv
CcJllditionS
be affected 1)~ small ndtliiig
reSdtillg
iTi
:l
IhStk
bile
StrUCtlm
liahk
to
forces. This factor acts locally in the same individual,
Volume Number
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457
as well as generally in different individuals and races. Dense bone in the area of muscle attachments and zones subjected to concentration of stress exemplifies areas offering high resistance to change of form. Thus, in the mandible, this accounts for the unchanged position of the superior genial tubercles to which the genioglossus muscles are attached; these are often seen posterior to a resorbed anterior ridge forming a hard prominence in the floor of the mouth, and present a problem in denture technique. A sharp superficial bony ridge underlying a thin mucosa is sometimes seen posteriorly and bucally, remaining relatively unresorbed above a concave, resolved, residual ridge ; this is the external oblique ridge which is a heavy cortical reinforcement that resists a concentration of stress, A similarly placed ridge, the mylohyoid ridge, lies lingually and also resists reduction. Every Finally, it is pertinent to consider the atrophy seen at the climacteric. prosthodontist has observed the rapid reduction in the height of the mandibular residual ridge which is sometimes seen at this period, characterized by a hormonal imbalance and especially a reduced estrogen blood leve1.16 A postmenopausal osteoporosis results in a bone offering little resistance to reduction in voIume.1E Albright and associates note an association between this condition and a tendency to atrophy of the skin. Also the effect of the reduced estrogen level in producing an atrophic oral mucosa has been noted. The rapid loss of the residual ridge after the menopause is accounted for in terms of an atrophic mucosa molding a weak bone structure. THE
APPLICATION
OF
THESE
OBSERVATIONS
It is pertinent to consider the application of these observations to a complete lower denture technique, bearing in mind the fitting surface, the border, the polished and occlusal surfaces of the denture. 1. The Fitting Surface.-One point which has emerged from extensive clinical trials is the need for developing an adequate soft denture base. The great advantage of a soft denture base is seen in cases where atrophy of the mucosa and submucosa is marked. The thin soft tissues cannot absorb any of the energy applied through the denture when the upper and lower teeth occlude forcibly, since there is little tissue fluid which may be directed into different tissue planes. Further, the potentiality of a resilient tissue layer for distributing the load evenly over the spicular bone of the anterior region does not exist. In these cases, nerve endings overlying the bony trabeculae are stimulated by pressure from the hard denture base, and pain is the inevitable outcome. A reasonable approach would be to replace, on the denture, the resilient layer which previously existed in the tissues covering the ridge bone. The compression of this layer, as well as absorbing some energy, also aids in the even distribution of force over the spicular bone. Patients who show this atrophy of mucosa and submucosa generally obtain complete relief of pain after a soft denture lining is substituted. 2. The Border.-It is necessary to define and to discuss the significance of four positions of the vestibular sulcus: (i) resting position, (ii) functional position, (iii) compressed position, (iv) distorted position.
45X
I.AM MIE
3. Pros. Den. July,
1056
(i) The resting position: At no time does a space exist between the mucosa of the lip and the cheek on the one hand and that of the lower alveolar ridge on the other. The potentiality, however, exists for the accommodation of a denture flange between the two mucosal surfaces. This potentiality has a definite limit which depends on the depth of the resilient sul~mucous layer in the lip and cheek, and also on the muscle tone. The resting form of the mucosal reflection is its most important position, in that the greatest possible length of the reflection should finally be represented in this state on the \\orking cast. Further, if any modification of the sulcus form is considered desirable, it should be made from the rest position as a starting point. The resting position of the sulcus is its unstrained form when the jaws are in the rest position. However, since in many cases, on opening the mouth slightly, there i5 little ~rnctical change in its form, the resting form of the vestibule may be recorded by an open mouth impression technique. The resting position of the floor of the morlth should now be considered. \Vith the jaws in the resting state, the tiorsnm of the tongue contacts the hard palate, and its tip lies in contact with the lingual surfaces of the iowrr anterior teeth. This tongue position is maintained with the floor cjf the mouth in a corresponding resting position, and it is this \vhich goycrns the resting depth of the mandibular alveolar ridge linguall!:. On opening the mouth, the tongue falls back to maintain a contact with the pillars of thr fauces and the Soft palate to seal the entrance to the oropharyns. ICrith the tongue in this position the floor of the mouth is lowered, giving a false depth to the lingual side of the alveolar ridge, especially posteriorly. Therefore, if an open mouth impression technique is preferred to a closed mouth procedure, the tongue must be placed with its tip lightly pressing against the tray handle; it is necessary to instruct the patient how to effect this compensatory tongue movement, placing the floor of the tnotlth in a resting position. (ii) l‘kc f~rwcfionol positiorl: The iorm of the reflection of the restibular sulcus is changed as a rc.sult of: (a ) ol)vning the mouth, (1)j local muscle contraction. (a‘) Opening the Ill~~iltll : On opening the mouth, the snlcur; form changes h\ I)ccoming less deep and snort: angular ; the lnucosa is more tightly stretch4 and lrss al3ie to withstand disl~iacenient without developing a force of reaction. In young adult life and when the n~~osal tissue displays a good elastic quality, the change in sulcus form on opening the mnuth is not of practical importance in In an atrophic condition where the elastic quality complete denture prosthetics. is reduced, a significant change in the sulcos is more likely to occur, and this may 1~ suflicient to cffrct a displacing force on the 1)ortlrr of a denture, especially during the widest opening (Fig. 3 I. Accordingly in this atrophied state, the clcnturc is extended only trt the functional pnsitinn of the sulcus, and a sharper rather than a rounticd dcuture lmrder form is iavorcd : this permits the obliteration of a potential space brlo~ the denture border when thrl mouth is closed, as the buccal niucous menil~ranc~ is allowed to collapse against tlic alveolar plate. In this way retention is improved at the expense of denture strength.
Volume 6 Number 4
AGING
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4.59
DENTURE
Roughly assuming a line between the condyles to be a rotatory axis when the mouth is opened, we can account for the observation that progressively greater separation of upper and lower teeth takes place in the anterior part of the mouth. This explains the fact that the change in shape of the sulcus is noted to a greater extent in the premolar than in the molar regions. In the most anterior part of the mouth, the change is not so marked, as the opening is compensated for by the separation of the free upper and lower lip margins. Thus when making an impression for a patient showing marked atrophy of the mucosa, an open mouth technique is preferred. The degree of opening used should be within functional limits rather than to the widest amount.
Fig. 9.-A
diagrammatic representation of the potential change in sulcus form on the widest opening in a patient with an atrophic oral mucosa.
taking
place
(b) Local muscle contraction : The sulcus form may be altered by muscle fibers which run vertically or obliquely to the direction of the reflection. The variable degree to which this takes place depends upon the habit of the patient, the degree of muscular development, and the closeness of the muscle insertion to the mucosal reflection. In the lower labial and premolar regions this change may be considerable, and a functional position of the periphery is indicated. Once again a sharp rather than rounded denture border helps to maintain a positive retention. Fortunately, very few patients show this excessive range of muscular moveHowever, it is important to recognize such a patient when he ment functionally. presents himself requiring a complete lower denture. He is usually of a nervous disposition, engages in facial gesticulation when conversing, and often has a “leathery” type of skin. Since the functional position of the sulcus should be recorded, a closed mouth impression technique is advocated, the patient carrying out muscular movements while the impression paste is setting. This is more accurate than the so-called “muscle trimming” methods where the operator manipulates the lips and cheeks of the patient. In the closed mouth method, the contraction is controlled in magnitude and location, and can be effected over all the This latter point is important, since concerned areas of reflection simultaneously. the necessary condition of the impression material, i.e., the consistency immediately before it hardens, exists only momentarily.
It is possible to record the sulcus reflection (iii) The co9njwcssed position: in a form when some tissue fluid lying lwlow the nmcosa has been expressed into adjoining tissue planes. This may IX dcm locally or throughout the entire cstent of the denture border. The tissues lying beneath the horder are elastically compressed and tend to recoil and maintain close approximation with the lmrder of the denture. The magnitude of increased extension between the resting and compressetl positions is always very small. notifies: It is never desirable to record a distorted (iv) 7‘lzc distorted or overextended sulcus form even in a tirst impression : it is unacceptable in a second impression. It nmst he rcalizetl that the facial nwscles in their uncontractcd or tonic state are readily displaced by small iorws. Thus when a viscous imprcssirm material such as modeling composition is used, the force required to seat the considcral~l~~. This happens most markedly in inipressioii deepens the sulcus the labial region bvhrrc the tlisplaceriwiit is Ilot resisted Ixcause thv lip margin is irce. The result of this gross sulcns tleicmnation is that muscles are displaced from their natural straight course, arc stretched, and recoil lmtli elastically and 1)~ contraction with suflicient force to displace itllnletliately a dcnturc made to such an impression ( Fig. IO )
mnplcte ‘I’liis i3 ow 0i tlw iarllt5 most cm~~~ml~~ wcn ill ur~~ccessiul I~mx~r dentures. It ;iriws tl~rough ;~ccq~tanw 0i aii overcstend~tl first iml)res>ioil in niotlrling conq~osition :intl i:liliirv 10 rctluw the res~llt;tnt qmial tra!. l‘hc iault illa!. Iw nvoitletl 1)~ atleclmtely Iwiorc Illilkillh (r the .iccoiitl iluprcssioii. cutting awa\ thv ovcr~stei&tl nlcbtlcling conipositioII flallgc in the lirst imprcssioll, flmiing Incall~. and rc~inwrting : this 1mwss i.G rqmtc.d lentil the height (It’ tht as the depth (Ii the rrstuuqosition flange, rs;m~inrtl estraornll!~, is the S;~IIIC~ ing .AI~CI~.S.C’ertainly intlulgcnc~c iit 1i1ov(~li~7it.5oi the lip aiitl clicek, wrongly tlescannot 1101~ to retliirc the grossI!, mxwstendctl ignatul :I> “~~~usclr trililnling.” tllcdcliiig cmiposition irnprcssion. ThC altcrmtivc approach, and tlv one favored 1)~ the lvriter, is tc.1make the first ilnlmssion ill :I soft alginate inlpressioii niatcrial.
Volume 6 Number 4
AGING
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461
DENTURE
An understanding of the resting, functional, compressed, and distorted positions of the mucosal reflection is necessary for developing the best retention in the complete lower denture. The best retention in any denture can be developed only as a result of seal. This is generally simply obtainable in the complete upper denture, but in the lower, it is not always possible to obtain a positive retention through the action of seal. The first condition which may militate against positive retention of this nature is the accumulation of an excessive quantity of saliva in the floor of the mouth. This condition is permanent only rarely, but may be temporarily present immediately after the denture has been inserted when there is a copious reflex flow of saliva.
Fig. Il.-The
position
A, Post-dam of the post dam on a lower denture. molar pad; C, posterior buccal fold; D, tongue.
position;
B,
Second, the condition of the oral tissues may exclude the possibility of developing a seal. Seal may be developed either against the border of the denture, or against one or another of its polished surfaces; in the former instance it is known as border seal and in the latter as facial seal. The development of a facial seal is the better approach. In the complete lower denture, a facial seal is obtainable on the labial and buccal surfaces of the denture, and also through the action of the tongue against its posterior lingual surface. But, since the seal must completely encircle the fitting surface of the denture to be an effective aid in retention, border rather than facial seal must be developed in the retromolar and anterior lingual regions. This is easily done if, in these locations, there is a significant depth of resilient submucosa ; if such a tissue is not present, then it is impossible to develop a positive retention through a sealing action. Therefore, it is necessary to examine the retromolar and anterior lingual regions to arrive at a prognosis in respect to retention. Examination of the retromolar area constantly reveals the presence of a posterior buccal fold, which is a roll of tissue overlying the residual ridge and running up to the retromolar pad. The denture border should be sealed by this tissue, and should be shaped to a sharper edge to underlie this fold. On the lingual side, the tongue overlies the alveolar ridge to a greater or less extent and effects a facial seal. Only between these two areas is a border seal required. This is done by compressing the tissue of the retromolar pad, provided sufficient depth of soft tissue is present. This compression is usually effected by cutting a post dam on the working cast after a careful examination of the mouth (Fig. 11).
J. Pros. July.
462
Den. 1956
In the ZLnterkJr lingual art%, a significant amount of submucosa must be present below an elastic n~ucosa. This is often not found in the older atrophied mouth, and the niitllinc area is geucrall!~ the wctioil ivhich presents the greatest With marked resorljtion, tile stqwrior genial tubcrcles are higher than difficulty. the alveolar ridge, the two being connrctctl hy :I ridge of bow. This is overlaid 1)~ a thin tnucosa and subniucosa which could riot he compressed without pain or Further, it is impossible to oljtain a seal posterior to the tubercles Illceration. as the superficial genioglossus 11lusc1e is again owrlaitl by thin atrophic tissue. \\,Iicrc conipressioii i5 ~mssihlc, it can 1)~.IwA ol)taiiied by using a viscous alginate impression material, or Im4eral)l!~ 11yIlmking a carding was addition to the lingual horder of a closely xd:il)tetl tra!. 11w1c (Ii acrylic wiill. Although it is Ilot propcm(l tc.) deal \vith tictails of the v&rious impression to nlnke conumrnt on the carding techniques advocated, it is comidere(1 usclul wax technique usctl to ohtnin lingual compression lvith the closely adapted spcto the so-called low iusing modeling concial tram. This Iiiatcrial is lmferwtl positior; traciug stick>. The latter do liot maintain ;I desirable viscosity for a sufficient length oi time, have too critical 3 softening tcnipcrature, which is often too high. and burn vcrx readily. 1lorwvcr. too many variables are involved in assuring that the mimed modeling compositim addition i$ at the correct temperature when placed in situ. I\‘ith the c:trtlillg \va.x addition, a strip of n-ax of calculated dimension is iused to the Im-der of the tray with a point flame. The lq~nscs of this are to secure a union bctwell the nax and the tray, and to proclucc~a smooth surfaw rather than to soften the ~V;LS. The modified tray is placed in the mouth and the desired viscosity Of the \vas is assured I+ the mouth tetnperature. The tray is held in the mouth ior me minute to allow the wax to be shaped 1)~ the tissues of the floor of the mouth. It must be wmembered when withdrawing the tray from the mouth, lvhen loading it with the impression paste, and when casting, that the wax is not rigid and care must be taken to avoid distortion.
‘l‘he
nncomplicntc4 case ill u-hit-h il is po55iblc to develop 2 I;~.ll. ‘l‘hi3 is a Iargc group
‘l‘hc atrophic case where se;11 is pasFew case* 3x2 c~nu)~:ntcretl 1. siblc. in thi.5 cl:153
1
\.i:t.lJll;
;LIgim~tc\
ill ;I 21)accd
+e&l
tra!
2.
%illc ositk cugcnol paste impression in a close11 ;~tl;LplC?tl, acrvlic resin special tray, to which has been added :I,, addit ion of carding was to the lingual border ..--. --.._ ._._ _... Zinc. c>kide cugenol paste impression in a closely adapted tra> motlified lingually as above but with the mouth qw~ietl to a functional cvtcnt -
--
.._. -.
_.__
‘I hc c.~ H-here seal can bc dcvclopcd : .\ c~l(~sctl mouth impression technique is required, the but where there is a large range c.losely adapted arrylic resin impression tray being the of functional movemait of thr IXW of the lower occlllsion rim. After the centric Fe\\ r:,sc~ ;LI’C C‘IP rcl;ttion record is made, ;I lingual border addition is facial muscles. calnlrrcd in this cln+ made in carding was, and the impression is made with : the facial mllsctllaturr frtnctionally contracted __ -. -. .._- -. -. ‘l’hc case where it is impossible (11 I’la+lcr of I’;+ alginate, zinc oxide eugenol obtain a border seal. This is a i large group !
-..-. -.
.-- -.--.--
Volume 6 Number 4
AGING
CHANGES
AND
COMPLETE
LOWER DENTURE
463
The importance of the border of the impression has been stressed. Having taken care to secure this with accuracy, it is equally important that the finished denture should have an exactly equivalent border. Therefore, it is important that the stone cast from the impression should include the mucosal reflection and not be trimmed short. It must also be stressed that the border of the finished denture should be neither filed nor heavily polished. Removal of surface roughnesses by a very light stoning and buffing is the only permissible laboratory treatment of the denture border. Certainly, the habit of filing and polishing the denture border to some symmetrical and pleasing shape will ruin the retention of the denture. 3. The Polished Surface.-When considering the polished surface of the denture, it is helpful to include the buccal, labial, and lingual surfaces of the teeth. The position of the polished surface of the denture is determined largely by the position of the border, and by the position and width of the artificial teeth. The form of the base material between these two extreme positions may be modified by suitable carving. I always use narrow posterior tooth forms to compensate for a reduction in the lateral width of the neutral zone. There is no evidence that even radical reduction in the width of the posterior teeth decreases the masticatory efficiency significantly.
Fig. 12.-The
change in inclination
of the lower anterior ing lower lip.
teeth to accommodate
to the chang-
The teeth, in the molar region, should be placed well over the buccal plate. This not only creates more tongue space where it is important to secure it, but also allows the development of a slightly more vertical polished surface against which a facial seal can be readily maintained. In the molar area, the development of a buccal flange is commended.” Lying under the middle group of fibers of the buccinator muscle, this is a retentive aid. Its use, however, is confined to those persons who display a good elastic quality in the mucosa. With atrophy, the extent of the flange must be reduced, and in most old people it is not possible to develop a useful buccal flange. When one is used initially, pain makes its early removal necessary. In the anterior region, the teeth should be placed with their cervical ends over the ridge. In the young person, when the lip is everted, the anterior teeth may be given a forward inclination, but with atrophy the anterior teeth should be sloped progressively back, to accommodate to the changing lip position at rest and when the mouth is opened (Fig. 12).
J. Pros. July,
464
IJen. 1956
4. The Occlusal .Yttrface.--Too many complete lower dentures are ruined by setting the teeth up to some preformed idealistic concept of what constitutes the ideal occlusion. To accomplish this, lower premolar and anterior teeth are set outside the ridge, and well into the zone of action of the facial muscles. Again, lower tnolar teeth are set inside the ridge and do not allow sufficient tongue space. The teeth should be placed where the muscles and mucosa will allow, and not in a position to develop any idealistic concept of occlusion. The magnitude of the horizontal overlap which results or the degree of cross-bite obtained does not matter in the least. \Vhen this principle is followed, it is found that the area of the occlusal surfaces of the lower teeth occluding with upper antagonists may be small indeed. However, this does not greatly reduce masticatory efficiency as assessed hy the patient. In many cases. occlusion of the second premolar and first molars is all that is obtained, and yet a satisfactory function results. In fact, it is often wise to omit the second molar from the denture if it makes only a very small occlusal contact or lies over an inclined portion of the alveolar ridge which is sloping up to the mandibular ramus. C’ONCI ,.I.SIOY . T’ut the teeth and denture base where the muscles and mucosa will allow, and develop the hest possible retention and occlusion.
1. Hohinson. Il. B. G., and Boling, 1.. K. : Ch. 19 in Cowdry, E. V. : l’roblcms of Aging, eti. 3, Baltimore, 1952, The Williams tc- Wilkins Company, pp. 447. 467. 2. Massler. M. : Geriatrics and Geriodontics. ?r’ew York J. Den. 26:54-63, 1956. of the Oral Mucosa of :1grd Nales, J. .3 Pedreira. Ii. A.: A Study of the Keratinization I). Med. 6:88-91. 1951. J. R. : The Rest Position t)i the \landihle and Its Significance to Dental Science, J.A.D.A. 33:151-180, 1946. Campbell. J. : hiandibular Displacement, I). Practitioner 5:17j-190. 19.55. Mershon, J. V.: Bite Opening Dangers, J..A.D..L\. 26:1972-1979. 1939. Dick. J. C.: Observations on the Elastic Tissue of the Skin With a Note 011 the Reticular I,ayer at the Junction of the Dermis and Epidermis, J. Anat. 81:201-211, 1947. I.ansing, A. I.: Aging of Elastic Tissue. Ciha Foundation Colloquia o11 .\ging, ed. 1, I.ondo11, 1955. pp. 88-108. Burket, I,. LV. : Oral Medicine. etl. 2. I’hiladclphia. 1952. J. 13. I.ippincc!tt COqKItly, pp. 441-442. Goldman. 11. 11.: (ieriatric Changes in the Oral Mucosa, J. 1). Med. 9:86. 19.54. Gabel. D. I’.: Unstable Lower Dentures, Brit. D. J. 45:1-13. 1924. Sichcr, H.: Oral r1natomy. ed. 1. St. Louis. 1952. The C. V. Mushy Company. pp. 150-151. \Veinmarm. J. I’., and Sicller. H. : Bow ad Rmlcs, ed. 2. St. I.&s;. 1955, The C. \‘. hloshy Company, pp. 134-136. Stones. H. H. : Oral and Dental Diseases. cd. 3. I
4. Thompson, 5: 7. 8. 9. 10. 11. 12. 13. 14. 15. 16. 17.
F
‘I‘00 static a vic,\v is 0im {akcu oi the iorm 0i the parts and the way the! \vorli ; lmtll are constautly changing, iriml chiltlhood to old age. Metabolism cmI)rises ntwlmlic ml c:lt;ilmlic lmwssc’s ; in chiltlhoc~d and youth building p’occsw‘s arc in the a~c~~~icl;~~ic~, lalt xitli aging. catalmlim becomes prcdon?inant aud atrophies result. It is well to corlsitl(ir the rhaiigcs ii1 the anatomy under three headings : (1 i tl1c IIItIcos;L :mtl Slllmlccrs:l, ( _31 ttic nwculaturc, and (3 1 the boiw. I. ‘/‘/rc Jlr/cusc7 c7rrd.Srrl~lrr~rc.cjstr.--.~~l~~ cunmou with all other tissues, the oral c~pitheliun~5hv\\~ ;i rwluction ill the number 0i its coinpont~nt cells as age ;iIrq)liv progrrssc5. ‘l‘li(~ micosa iu gciwral, antl that covering the mandibular residual ridge iu particular, shows a decrease in thickness.ld There arc also as.+ociatctl atrophy ;iu(l thiimiii g oi the ~IIIIIIIII~~~;~, SO that the depth oi the soft tissue which cuwrs the ;llvcolar ritlge is rc~ducetl. I‘hiS change is partly explained II!. a gcncral deliytiratim which is obscr~ctl in ultl age. It is not noted to the GIIW tlcgrec in all pntimts, and nlarl\- instances can be called to mind where au old lwson has S~O~IIIa snl~stantiall~ thick rnucosa and submucosa, giving the palpatur~ scnsatiou oi resilicuce over the residual ridge. This change in nature (Ii the oral cyitheliu~ll .sonwtimes reflects similar changes in the skin oi the face. ‘I’hc skin of the old is oftcu described as showing many wrinkles as a result of the atrophy oi the uridcrl~iiig i;ltt!- tissues and muscles. Such a skin as de$‘ttd ill I’&. 1 iS Oh Well. hit $0 alSO is a skin of thinucr testure having a taut, snioother appc:~rancc (Fig, 3 I .--Kcwivedfor publication. Dcr. 1. 1955. *E’ormerly Senior Lecturer in Dental Prost.hetics, University .\S.swintc Professor of Dcnti,ctry at Sorthi\-ctstwn t:nivcrsity.
of Livrrpuol.
Presently
Visiting
Volume 6 Number 4
AGING
CHANGES
AND
COMPLETE
LOWER
451
DENTURE
In addition to a thinning of the oral mucosa with aging, there is also a reduction in its surface area. This observation results from noting clinical appearances rather than accurate measurement, but when it is considered that the ridges become resorbed the truth of this statement becomes obvious. A less obvious and less constant change is a reduction in the degree of invagination of Sometimes too, the secondary unduthe cheek tissues toward the oral cavity. lations of the buccal mucosa become less marked. Both of these effects contribute to a reduction in surface area of the oral mucosa (Fig. 3). Further, if there is any associated approximation of the jaws (and this is disputed’, ‘* 5.“), this will also have a similar result. The outcome of these changes, which may be present to a greater or lesser degree, is a reversion to a more circular form of the oral cavity, and it might even seem as if the highly differentiated mucosa is seeking to economize in area.
Fig. 1. Fig. I.-The wrinkled type of skin in an old person. Fig. 2 .-The taut, smoother type of skin in an old person. show the inversion of the lower lip.
Fig. 2. The mouth
is slig.htly
open to
The form in sagittal rather than coronal section also seems to substantiate this viewpoint. In the retromolar area, the rounded form of the mucosa as it sweeps from the edentulous ridge to the ramus of the mandible is often observed in association with vertical tissue folds. A backward movement of the lip, to be discussed later, also has the same effect. This potentiality to reduce surface area of the oral cavity is variable. So also is the surgeon’s ability to maintain an epithelial inlay cavity surgically created for the retention of a complete lower denture. Some of these are well preserved and function effectively in stabilizing the denture ; others tend to become quickly
4.52 ot~literatctl, the explanation t(mxIti\.c
Or
;dditicJld
given being that they have “fibrosetl
~x$Ill~lti~Jl~
liiigtlt
tie
ill
the
IdatiVe
teIldellc~
up.”
All
CJf the
lllllC~~Sa
al-
to establish ;Lreduced surface area. ,,Ys \vcll as these macroscopic changes iu the aging oral nmcosa, one important niicroscol~ir change is of practical importance. In the skin, there is a degenerative change in the elastic filwrs, and a condensation and aggregation of them into irregular masses.’ :\n associated l)iochemical change of a controversial nature takes l~lace in these fibers. In :I series of twelve histologic sections taken from the check ant1 mucosal reflections oi young ant1 d old indivitluals. similar changes to these noted I)y I.)ick’ \verc seen in the latter group (Fig. 4i. The net result (4 the changes in the form of the oral nmcosa, and in its elastic fibers, is a decrease in its elastic quality, an end result which has been noted Ijy Rurket.” ( Goldman.‘” and Llassler.’
Fig. 8.-Diagnmmati~ representation plwe with ngIng. The coronal section of an oltler intlivitluul on thv right.
of the reduction in area of oral mwo~il xvhich takes of a young c~dentulons adult ii; shown on the lrft and
2. ‘1’1~~.l.Ittsculatrrrc,.--tiat,cl” tlescrilwtl a niigratioil 0i the origin 0i the hutcitiator fillers over the t~ccal plate 0i the iiiandil~le to\-\.ml the midline, and c~nil~hasizctl the effect this has on reduciiig the neutral zone. An even niore iiiiportant change in ~~wscle origin concerns the mentalis muscles. These nluscles take origili t~ilaterall~ from a circular area 011 the alveolar ridge and l~otly of the inmi(lildc~ alwve the iiirntal tuberosit!~. The highest point ()i origin tics superior to the IJositicm oi the niucosal reflcctioil \\heii the natural teeth ill-c standing, and over tlw root> of the l:ltc’r:~l incisor mntl cminc teeth. The fitters of this muscle tliverp nwdially and laterally to IJC inwrtcd into the skin cd the chin, and also :lW ilis(‘rtCd ilit0 the t(J\ver tit).” sulwriorlq‘ and infcriorlv so that soiiic \Vhen wsorptioll oi the wsitl~lal ridge mtl IHJCI~oi the n~antlildr takes place, the level 0i the ridge crest ialls 1~~1~~~ ttlilt of the iornier origin of the sul)eriur filwrs of the nicntalis iiiusclc. In order to inaintaiii its wea 0i origin. the muscle nttachilieilt icJltls o\er ttic rwrd)ing alveolar ri(lgc and colnt’s to lie on the superior sliri:tw oi tlw resitlwl ridge. ‘l’hc result oi this is a Imzkwartl lnovemcnt, and ~~~111~ r~dllctiOl1. CJf ttlc ll~lltIXt %Ollc ill the :lllt~7’iOr tXlrt CJi ttlc lliO~ltt1. This change in the origin of the nwntalis nnlscle has Iwen ot~serwtl in the surgical tlissections Of ,\lr. i. s. H. Collinge oi l.iverpool, ant1 ironi lml~aratiuns in the cadaver (Fig. 5 )
VC hne 6 Nl lmber 4
AGING
CHANGES
AND
COMPLETE
LOWER DENTURE
4 ,.53
A.
Fig. 4.-Photomicrographs stained with orcein, showing (A) the nature of the elanstic lers in the cheek mucosa of a patient aged between 40 and 50 years, and (B) the chal we in form in a patient of 70 years. (X525; reduced l/6 off.) fil
J. Pros. Den. .luly, 19%
13.431 hl I I.:
454
At this stage it is pertinent to consider the lower lip form in old and young people who have been rendered edentulous. In a young person, the lower lip form changes very little after all the teeth have been extracted. In fact, if the rest position is induced with the upper and lower lips making a light contact, it cannot be discerned from appearance that the teeth have been lost (Fig. 6). The fullness of the lip and its everted position are maintained, as is also the labiomental angle. The dry red lip margin shows to a normal extent. In cases of age atrophy a marked change is noted. The lip becomes thinner and inclines lyackward into the oral cavity. the lahiomental angle disappearing (Fig. 2). The
Fig. B.--A diagrammatic representation mentalis muscle seen after ridge resorption. on the right it has suffered SOYEWresorption.
Fig. lx- The profile
of the change in position of the origin of the On the left the ridge Is well preserved, whereas
view of a young edentulous adult. It is Impossible edentulous state.
to discern
the patient’s
Volume 6 Number 4
AGING
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AND
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45.5
LOWER DENTURE
amount of the visible red lip margin is now reduced to a thin straight line. The oral aperture between the upper and lower lips seems to become smaller and to move back; a few patients have commented on the narrowing of the mouth, but usually the slow change is not noticed. This change in lip form is due to the more vertical line of action of the superior fibers of the mentalis muscle, and to a reduction in the surface area of the lip mucosa and skin.
3%. Fig. 8. T.-The lips being no longer able to open to their original circumference A, when about a hinge axis 0, they must move back to accommodate to a decreased circum-
Fig.
opening ference Fig.
B.
S.-Diagrammatic
representation
of the
XdatiVe
positions
of the maxillae
(&f),
the
atrophic lower lip margin (Lz and La), and the symphysis menti (S1 and Sal, when the mouth Although is at rest and fully opened. maxillae, it moves forward in relation observed is thus decreased.
the free lip margin moves back in relation to the to the symphysis and the degree of lip invagination
Not only is a difference in the form of the lower lip noted when the mandible assumes the rest position ; on opening the mouth, the young and the atrophic In the former, the lip remains everted and the only noticelips behave differently. able change of mouth form is that the corners move together to make the oral aperture circular. The atrophic lower lip, being less elastic, moves slightly inward in relation to the fixed maxillae when the mouth opens to its widest extent (Fig. 7). In this position, it has a vertical or slightly invaginated appearance. It might be expected that the degree of inward angulation should increase. However, it must be appreciated that the symphysis menti is moving backward to a greater degree, giving the appearance of a relative lip eversion (Fig. 8). 3. The Bone.-Examination of dried specimens of edentulous mandibles, surgical dissections, and roentgenograms, reveals that cortical bone is often not present in the anterior segment of the residual ridge after healing of the extraction wounds. Noncortical bone is present over the ridge crest in this area. Roentgenograms reveal a typical picture of cancellous bone, showing vertically running nutrient canals. Such a surface cannot be so smooth as one of a cortical nature, and it is made up of the ends of vertically running trabeculae. Sometimes, too, a spicular reaction is noted ; the appearance of small spicules of bone or osteophytes accentuates the rough nature of the bone of the anterior ridge.
456
I..\
\I 11 11.:
The secontl imlwrtarit characteristic of the mandibular ridge is its potentiality for rcsorptiorl. There can be little doubt that the application of forces in the pathologic range can cause au ostcutysis. This type of reaction is often associated with a deposition of filirous tissue witliiu the subiiiuc~sa. The osteolysis of the anterior ridge hone beneath a conildete upper denture with porcelain teeth worn against ouly six natural louver mtcrior teeth is an esamplc in this class. Filmms Instead it tissue. replaces the lmne, but the nlucosa does not retract markedly. sut~stantially maintains its original imn. Sometimes an entire nlaxillary arch is sew to 1~ ver\. rrsiliriit on l~;tll~ation, iiitlicatiiig a rel~lactrnient of al\:eolar ~)(Pw t)y titmms tissue \vithout a market1 decrease iu ridge height. In the nmltlitdc 100, the preserice 0i ;L lllusllroolll-shal,ed tilmus S11t~1lwCos;t which covers a “knife-edge” ridge imy tz a waction 0i this natuw. In terms oi \\.olff’s I,nw,‘” the reductim iii the iiuii~lm 0i the l~my trat~eculae and even their final tlisapliearmcc~ are reascmd~tc, tmt this process cannot account for a change iu the iorrn of the ridge Tim and the eventual Iohs oi the ridges. X’or is it sufficient to account for tliv tlisaI~lwaraiiw of the ridges tiy saying “the teeth arc: lost ; the ridges arc’ rc.clr~ndant mtl tlisqqw;tr.” Cases rii mdontia are seen \vlicre ridges are present. The climige in ridge form iiiiplies the presence of souie nlotding force. th
ll~lt~lrr
Of
n’hk’h
CXll
t)c
tkt~rlllilled
Ollly
ZLS :I
reSdt
Of
:l
]cJllg-term
reSe:lrCh
project undertaken 1)~ >cicntists \vith special knowledge in different fields. The an ;ltrophying mucosa seeking ;t rctlucetl area possibility 0i that iorcc~ t&g iiwst tw l)cmie in illid. \‘cbrF often flat lower ridges are seen lvhcre no cleiiturcs have hecn worii Imviod~, mrl thus the pcissihility of denture trauma being causal is esclutletl : it is significant that in such cases the lower ridge is always covered 1)~ :I thin. tightly strctchctl n~ucous menll)ralw. This is also true of a resorbed ridge stw1 where the to!vvr nmlar teeth have heen estractetl ant1 only l~reniolars :intl anterior teeth remain. Ii in such :I cast the ridge is well fometl, it is COYcrrtl I)y :L thick, krr:ttmlml I~ILKO~;~. Alost authoritic3 011 l~eriotloutal diseaw recognize ii ccditioil described 1)~ StollcS” as senile gingivat recession. The cpithelial attachment is IIO Iouger lowttd at the ;iii~elf~ceiii~ilt;11 junction, but is attached entirely to the ceinentuui, soluc$lncs :it ;L clistanw wnsiderat~l~ ;ipic;il to the enamel margin. iS. reduction in surface area oi the iiiucos~ ivitli associated loss of alveolar tmne may he partI> causal. Thus it is IJcJSSihk that the s:uw factors which cause senile gingival recession also cause alveolar rcsorptim. This hypothesis tloea not disregard the uell-known effects Of function on the or;ll niucosa. nor tlocs it iissuuie l)rior inilmrtanct over recognized factors ~lll~~~JrtaI1t ~llimllg t&x klttcr art the ~)rCS‘emx Of \vhirh act 011 INJW directly. l~eriotlontal disease Ilrior to extraction, tlic action oi horniones, nut1 pressure. It also recognize5 ;in inhewnt how factor offering greater or less resistance to inoltl111gener;tl, a tlenw cortical IKHW. or a heavily traheculatctl iiouing l)resmre, Soiiwtimes n wll-fornietl upper ridge and cortical INHW offers high rwistancc. patatcz ;lw see11to 1)~coved 1)~ ;L thin, taut, mucosa ; here the highly calcifietl Imne is verv stalile in iorm. C)n the other hand. the osteoporosis ant1 ncgativc c:ilciuni hhllCe
ill
th
aged
arv
CcJllditionS
be affected 1)~ small ndtliiig
reSdtillg
iTi
:l
IhStk
bile
StrUCtlm
liahk
to
forces. This factor acts locally in the same individual,
Volume Number
6 4
AGING
CHANGES
AND
COMPLETE
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457
as well as generally in different individuals and races. Dense bone in the area of muscle attachments and zones subjected to concentration of stress exemplifies areas offering high resistance to change of form. Thus, in the mandible, this accounts for the unchanged position of the superior genial tubercles to which the genioglossus muscles are attached; these are often seen posterior to a resorbed anterior ridge forming a hard prominence in the floor of the mouth, and present a problem in denture technique. A sharp superficial bony ridge underlying a thin mucosa is sometimes seen posteriorly and bucally, remaining relatively unresorbed above a concave, resolved, residual ridge ; this is the external oblique ridge which is a heavy cortical reinforcement that resists a concentration of stress, A similarly placed ridge, the mylohyoid ridge, lies lingually and also resists reduction. Every Finally, it is pertinent to consider the atrophy seen at the climacteric. prosthodontist has observed the rapid reduction in the height of the mandibular residual ridge which is sometimes seen at this period, characterized by a hormonal imbalance and especially a reduced estrogen blood leve1.16 A postmenopausal osteoporosis results in a bone offering little resistance to reduction in voIume.1E Albright and associates note an association between this condition and a tendency to atrophy of the skin. Also the effect of the reduced estrogen level in producing an atrophic oral mucosa has been noted. The rapid loss of the residual ridge after the menopause is accounted for in terms of an atrophic mucosa molding a weak bone structure. THE
APPLICATION
OF
THESE
OBSERVATIONS
It is pertinent to consider the application of these observations to a complete lower denture technique, bearing in mind the fitting surface, the border, the polished and occlusal surfaces of the denture. 1. The Fitting Surface.-One point which has emerged from extensive clinical trials is the need for developing an adequate soft denture base. The great advantage of a soft denture base is seen in cases where atrophy of the mucosa and submucosa is marked. The thin soft tissues cannot absorb any of the energy applied through the denture when the upper and lower teeth occlude forcibly, since there is little tissue fluid which may be directed into different tissue planes. Further, the potentiality of a resilient tissue layer for distributing the load evenly over the spicular bone of the anterior region does not exist. In these cases, nerve endings overlying the bony trabeculae are stimulated by pressure from the hard denture base, and pain is the inevitable outcome. A reasonable approach would be to replace, on the denture, the resilient layer which previously existed in the tissues covering the ridge bone. The compression of this layer, as well as absorbing some energy, also aids in the even distribution of force over the spicular bone. Patients who show this atrophy of mucosa and submucosa generally obtain complete relief of pain after a soft denture lining is substituted. 2. The Border.-It is necessary to define and to discuss the significance of four positions of the vestibular sulcus: (i) resting position, (ii) functional position, (iii) compressed position, (iv) distorted position.
45X
I.AM MIE
3. Pros. Den. July,
1056
(i) The resting position: At no time does a space exist between the mucosa of the lip and the cheek on the one hand and that of the lower alveolar ridge on the other. The potentiality, however, exists for the accommodation of a denture flange between the two mucosal surfaces. This potentiality has a definite limit which depends on the depth of the resilient sul~mucous layer in the lip and cheek, and also on the muscle tone. The resting form of the mucosal reflection is its most important position, in that the greatest possible length of the reflection should finally be represented in this state on the \\orking cast. Further, if any modification of the sulcus form is considered desirable, it should be made from the rest position as a starting point. The resting position of the sulcus is its unstrained form when the jaws are in the rest position. However, since in many cases, on opening the mouth slightly, there i5 little ~rnctical change in its form, the resting form of the vestibule may be recorded by an open mouth impression technique. The resting position of the floor of the morlth should now be considered. \Vith the jaws in the resting state, the tiorsnm of the tongue contacts the hard palate, and its tip lies in contact with the lingual surfaces of the iowrr anterior teeth. This tongue position is maintained with the floor cjf the mouth in a corresponding resting position, and it is this \vhich goycrns the resting depth of the mandibular alveolar ridge linguall!:. On opening the mouth, the tongue falls back to maintain a contact with the pillars of thr fauces and the Soft palate to seal the entrance to the oropharyns. ICrith the tongue in this position the floor of the mouth is lowered, giving a false depth to the lingual side of the alveolar ridge, especially posteriorly. Therefore, if an open mouth impression technique is preferred to a closed mouth procedure, the tongue must be placed with its tip lightly pressing against the tray handle; it is necessary to instruct the patient how to effect this compensatory tongue movement, placing the floor of the tnotlth in a resting position. (ii) l‘kc f~rwcfionol positiorl: The iorm of the reflection of the restibular sulcus is changed as a rc.sult of: (a ) ol)vning the mouth, (1)j local muscle contraction. (a‘) Opening the Ill~~iltll : On opening the mouth, the snlcur; form changes h\ I)ccoming less deep and snort: angular ; the lnucosa is more tightly stretch4 and lrss al3ie to withstand disl~iacenient without developing a force of reaction. In young adult life and when the n~~osal tissue displays a good elastic quality, the change in sulcus form on opening the mnuth is not of practical importance in In an atrophic condition where the elastic quality complete denture prosthetics. is reduced, a significant change in the sulcos is more likely to occur, and this may 1~ suflicient to cffrct a displacing force on the 1)ortlrr of a denture, especially during the widest opening (Fig. 3 I. Accordingly in this atrophied state, the clcnturc is extended only trt the functional pnsitinn of the sulcus, and a sharper rather than a rounticd dcuture lmrder form is iavorcd : this permits the obliteration of a potential space brlo~ the denture border when thrl mouth is closed, as the buccal niucous menil~ranc~ is allowed to collapse against tlic alveolar plate. In this way retention is improved at the expense of denture strength.
Volume 6 Number 4
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4.59
DENTURE
Roughly assuming a line between the condyles to be a rotatory axis when the mouth is opened, we can account for the observation that progressively greater separation of upper and lower teeth takes place in the anterior part of the mouth. This explains the fact that the change in shape of the sulcus is noted to a greater extent in the premolar than in the molar regions. In the most anterior part of the mouth, the change is not so marked, as the opening is compensated for by the separation of the free upper and lower lip margins. Thus when making an impression for a patient showing marked atrophy of the mucosa, an open mouth technique is preferred. The degree of opening used should be within functional limits rather than to the widest amount.
Fig. 9.-A
diagrammatic representation of the potential change in sulcus form on the widest opening in a patient with an atrophic oral mucosa.
taking
place
(b) Local muscle contraction : The sulcus form may be altered by muscle fibers which run vertically or obliquely to the direction of the reflection. The variable degree to which this takes place depends upon the habit of the patient, the degree of muscular development, and the closeness of the muscle insertion to the mucosal reflection. In the lower labial and premolar regions this change may be considerable, and a functional position of the periphery is indicated. Once again a sharp rather than rounded denture border helps to maintain a positive retention. Fortunately, very few patients show this excessive range of muscular moveHowever, it is important to recognize such a patient when he ment functionally. presents himself requiring a complete lower denture. He is usually of a nervous disposition, engages in facial gesticulation when conversing, and often has a “leathery” type of skin. Since the functional position of the sulcus should be recorded, a closed mouth impression technique is advocated, the patient carrying out muscular movements while the impression paste is setting. This is more accurate than the so-called “muscle trimming” methods where the operator manipulates the lips and cheeks of the patient. In the closed mouth method, the contraction is controlled in magnitude and location, and can be effected over all the This latter point is important, since concerned areas of reflection simultaneously. the necessary condition of the impression material, i.e., the consistency immediately before it hardens, exists only momentarily.
It is possible to record the sulcus reflection (iii) The co9njwcssed position: in a form when some tissue fluid lying lwlow the nmcosa has been expressed into adjoining tissue planes. This may IX dcm locally or throughout the entire cstent of the denture border. The tissues lying beneath the horder are elastically compressed and tend to recoil and maintain close approximation with the lmrder of the denture. The magnitude of increased extension between the resting and compressetl positions is always very small. notifies: It is never desirable to record a distorted (iv) 7‘lzc distorted or overextended sulcus form even in a tirst impression : it is unacceptable in a second impression. It nmst he rcalizetl that the facial nwscles in their uncontractcd or tonic state are readily displaced by small iorws. Thus when a viscous imprcssirm material such as modeling composition is used, the force required to seat the considcral~l~~. This happens most markedly in inipressioii deepens the sulcus the labial region bvhrrc the tlisplaceriwiit is Ilot resisted Ixcause thv lip margin is irce. The result of this gross sulcns tleicmnation is that muscles are displaced from their natural straight course, arc stretched, and recoil lmtli elastically and 1)~ contraction with suflicient force to displace itllnletliately a dcnturc made to such an impression ( Fig. IO )
mnplcte ‘I’liis i3 ow 0i tlw iarllt5 most cm~~~ml~~ wcn ill ur~~ccessiul I~mx~r dentures. It ;iriws tl~rough ;~ccq~tanw 0i aii overcstend~tl first iml)res>ioil in niotlrling conq~osition :intl i:liliirv 10 rctluw the res~llt;tnt qmial tra!. l‘hc iault illa!. Iw nvoitletl 1)~ atleclmtely Iwiorc Illilkillh (r the .iccoiitl iluprcssioii. cutting awa\ thv ovcr~stei&tl nlcbtlcling conipositioII flallgc in the lirst imprcssioll, flmiing Incall~. and rc~inwrting : this 1mwss i.G rqmtc.d lentil the height (It’ tht as the depth (Ii the rrstuuqosition flange, rs;m~inrtl estraornll!~, is the S;~IIIC~ ing .AI~CI~.S.C’ertainly intlulgcnc~c iit 1i1ov(~li~7it.5oi the lip aiitl clicek, wrongly tlescannot 1101~ to retliirc the grossI!, mxwstendctl ignatul :I> “~~~usclr trililnling.” tllcdcliiig cmiposition irnprcssion. ThC altcrmtivc approach, and tlv one favored 1)~ the lvriter, is tc.1make the first ilnlmssion ill :I soft alginate inlpressioii niatcrial.
Volume 6 Number 4
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DENTURE
An understanding of the resting, functional, compressed, and distorted positions of the mucosal reflection is necessary for developing the best retention in the complete lower denture. The best retention in any denture can be developed only as a result of seal. This is generally simply obtainable in the complete upper denture, but in the lower, it is not always possible to obtain a positive retention through the action of seal. The first condition which may militate against positive retention of this nature is the accumulation of an excessive quantity of saliva in the floor of the mouth. This condition is permanent only rarely, but may be temporarily present immediately after the denture has been inserted when there is a copious reflex flow of saliva.
Fig. Il.-The
position
A, Post-dam of the post dam on a lower denture. molar pad; C, posterior buccal fold; D, tongue.
position;
B,
Second, the condition of the oral tissues may exclude the possibility of developing a seal. Seal may be developed either against the border of the denture, or against one or another of its polished surfaces; in the former instance it is known as border seal and in the latter as facial seal. The development of a facial seal is the better approach. In the complete lower denture, a facial seal is obtainable on the labial and buccal surfaces of the denture, and also through the action of the tongue against its posterior lingual surface. But, since the seal must completely encircle the fitting surface of the denture to be an effective aid in retention, border rather than facial seal must be developed in the retromolar and anterior lingual regions. This is easily done if, in these locations, there is a significant depth of resilient submucosa ; if such a tissue is not present, then it is impossible to develop a positive retention through a sealing action. Therefore, it is necessary to examine the retromolar and anterior lingual regions to arrive at a prognosis in respect to retention. Examination of the retromolar area constantly reveals the presence of a posterior buccal fold, which is a roll of tissue overlying the residual ridge and running up to the retromolar pad. The denture border should be sealed by this tissue, and should be shaped to a sharper edge to underlie this fold. On the lingual side, the tongue overlies the alveolar ridge to a greater or less extent and effects a facial seal. Only between these two areas is a border seal required. This is done by compressing the tissue of the retromolar pad, provided sufficient depth of soft tissue is present. This compression is usually effected by cutting a post dam on the working cast after a careful examination of the mouth (Fig. 11).
J. Pros. July.
462
Den. 1956
In the ZLnterkJr lingual art%, a significant amount of submucosa must be present below an elastic n~ucosa. This is often not found in the older atrophied mouth, and the niitllinc area is geucrall!~ the wctioil ivhich presents the greatest With marked resorljtion, tile stqwrior genial tubcrcles are higher than difficulty. the alveolar ridge, the two being connrctctl hy :I ridge of bow. This is overlaid 1)~ a thin tnucosa and subniucosa which could riot he compressed without pain or Further, it is impossible to oljtain a seal posterior to the tubercles Illceration. as the superficial genioglossus 11lusc1e is again owrlaitl by thin atrophic tissue. \\,Iicrc conipressioii i5 ~mssihlc, it can 1)~.IwA ol)taiiied by using a viscous alginate impression material, or Im4eral)l!~ 11yIlmking a carding was addition to the lingual horder of a closely xd:il)tetl tra!. 11w1c (Ii acrylic wiill. Although it is Ilot propcm(l tc.) deal \vith tictails of the v&rious impression to nlnke conumrnt on the carding techniques advocated, it is comidere(1 usclul wax technique usctl to ohtnin lingual compression lvith the closely adapted spcto the so-called low iusing modeling concial tram. This Iiiatcrial is lmferwtl positior; traciug stick>. The latter do liot maintain ;I desirable viscosity for a sufficient length oi time, have too critical 3 softening tcnipcrature, which is often too high. and burn vcrx readily. 1lorwvcr. too many variables are involved in assuring that the mimed modeling compositim addition i$ at the correct temperature when placed in situ. I\‘ith the c:trtlillg \va.x addition, a strip of n-ax of calculated dimension is iused to the Im-der of the tray with a point flame. The lq~nscs of this are to secure a union bctwell the nax and the tray, and to proclucc~a smooth surfaw rather than to soften the ~V;LS. The modified tray is placed in the mouth and the desired viscosity Of the \vas is assured I+ the mouth tetnperature. The tray is held in the mouth ior me minute to allow the wax to be shaped 1)~ the tissues of the floor of the mouth. It must be wmembered when withdrawing the tray from the mouth, lvhen loading it with the impression paste, and when casting, that the wax is not rigid and care must be taken to avoid distortion.
‘l‘he
nncomplicntc4 case ill u-hit-h il is po55iblc to develop 2 I;~.ll. ‘l‘hi3 is a Iargc group
‘l‘hc atrophic case where se;11 is pasFew case* 3x2 c~nu)~:ntcretl 1. siblc. in thi.5 cl:153
1
\.i:t.lJll;
;LIgim~tc\
ill ;I 21)accd
+e&l
tra!
2.
%illc ositk cugcnol paste impression in a close11 ;~tl;LplC?tl, acrvlic resin special tray, to which has been added :I,, addit ion of carding was to the lingual border ..--. --.._ ._._ _... Zinc. c>kide cugenol paste impression in a closely adapted tra> motlified lingually as above but with the mouth qw~ietl to a functional cvtcnt -
--
.._. -.
_.__
‘I hc c.~ H-here seal can bc dcvclopcd : .\ c~l(~sctl mouth impression technique is required, the but where there is a large range c.losely adapted arrylic resin impression tray being the of functional movemait of thr IXW of the lower occlllsion rim. After the centric Fe\\ r:,sc~ ;LI’C C‘IP rcl;ttion record is made, ;I lingual border addition is facial muscles. calnlrrcd in this cln+ made in carding was, and the impression is made with : the facial mllsctllaturr frtnctionally contracted __ -. -. .._- -. -. ‘l’hc case where it is impossible (11 I’la+lcr of I’;+ alginate, zinc oxide eugenol obtain a border seal. This is a i large group !
-..-. -.
.-- -.--.--
Volume 6 Number 4
AGING
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463
The importance of the border of the impression has been stressed. Having taken care to secure this with accuracy, it is equally important that the finished denture should have an exactly equivalent border. Therefore, it is important that the stone cast from the impression should include the mucosal reflection and not be trimmed short. It must also be stressed that the border of the finished denture should be neither filed nor heavily polished. Removal of surface roughnesses by a very light stoning and buffing is the only permissible laboratory treatment of the denture border. Certainly, the habit of filing and polishing the denture border to some symmetrical and pleasing shape will ruin the retention of the denture. 3. The Polished Surface.-When considering the polished surface of the denture, it is helpful to include the buccal, labial, and lingual surfaces of the teeth. The position of the polished surface of the denture is determined largely by the position of the border, and by the position and width of the artificial teeth. The form of the base material between these two extreme positions may be modified by suitable carving. I always use narrow posterior tooth forms to compensate for a reduction in the lateral width of the neutral zone. There is no evidence that even radical reduction in the width of the posterior teeth decreases the masticatory efficiency significantly.
Fig. 12.-The
change in inclination
of the lower anterior ing lower lip.
teeth to accommodate
to the chang-
The teeth, in the molar region, should be placed well over the buccal plate. This not only creates more tongue space where it is important to secure it, but also allows the development of a slightly more vertical polished surface against which a facial seal can be readily maintained. In the molar area, the development of a buccal flange is commended.” Lying under the middle group of fibers of the buccinator muscle, this is a retentive aid. Its use, however, is confined to those persons who display a good elastic quality in the mucosa. With atrophy, the extent of the flange must be reduced, and in most old people it is not possible to develop a useful buccal flange. When one is used initially, pain makes its early removal necessary. In the anterior region, the teeth should be placed with their cervical ends over the ridge. In the young person, when the lip is everted, the anterior teeth may be given a forward inclination, but with atrophy the anterior teeth should be sloped progressively back, to accommodate to the changing lip position at rest and when the mouth is opened (Fig. 12).
J. Pros. July,
464
IJen. 1956
4. The Occlusal .Yttrface.--Too many complete lower dentures are ruined by setting the teeth up to some preformed idealistic concept of what constitutes the ideal occlusion. To accomplish this, lower premolar and anterior teeth are set outside the ridge, and well into the zone of action of the facial muscles. Again, lower tnolar teeth are set inside the ridge and do not allow sufficient tongue space. The teeth should be placed where the muscles and mucosa will allow, and not in a position to develop any idealistic concept of occlusion. The magnitude of the horizontal overlap which results or the degree of cross-bite obtained does not matter in the least. \Vhen this principle is followed, it is found that the area of the occlusal surfaces of the lower teeth occluding with upper antagonists may be small indeed. However, this does not greatly reduce masticatory efficiency as assessed hy the patient. In many cases. occlusion of the second premolar and first molars is all that is obtained, and yet a satisfactory function results. In fact, it is often wise to omit the second molar from the denture if it makes only a very small occlusal contact or lies over an inclined portion of the alveolar ridge which is sloping up to the mandibular ramus. C’ONCI ,.I.SIOY . T’ut the teeth and denture base where the muscles and mucosa will allow, and develop the hest possible retention and occlusion.
1. Hohinson. Il. B. G., and Boling, 1.. K. : Ch. 19 in Cowdry, E. V. : l’roblcms of Aging, eti. 3, Baltimore, 1952, The Williams tc- Wilkins Company, pp. 447. 467. 2. Massler. M. : Geriatrics and Geriodontics. ?r’ew York J. Den. 26:54-63, 1956. of the Oral Mucosa of :1grd Nales, J. .3 Pedreira. Ii. A.: A Study of the Keratinization I). Med. 6:88-91. 1951. J. R. : The Rest Position t)i the \landihle and Its Significance to Dental Science, J.A.D.A. 33:151-180, 1946. Campbell. J. : hiandibular Displacement, I). Practitioner 5:17j-190. 19.55. Mershon, J. V.: Bite Opening Dangers, J..A.D..L\. 26:1972-1979. 1939. Dick. J. C.: Observations on the Elastic Tissue of the Skin With a Note 011 the Reticular I,ayer at the Junction of the Dermis and Epidermis, J. Anat. 81:201-211, 1947. I.ansing, A. I.: Aging of Elastic Tissue. Ciha Foundation Colloquia o11 .\ging, ed. 1, I.ondo11, 1955. pp. 88-108. Burket, I,. LV. : Oral Medicine. etl. 2. I’hiladclphia. 1952. J. 13. I.ippincc!tt COqKItly, pp. 441-442. Goldman. 11. 11.: (ieriatric Changes in the Oral Mucosa, J. 1). Med. 9:86. 19.54. Gabel. D. I’.: Unstable Lower Dentures, Brit. D. J. 45:1-13. 1924. Sichcr, H.: Oral r1natomy. ed. 1. St. Louis. 1952. The C. V. Mushy Company. pp. 150-151. \Veinmarm. J. I’., and Sicller. H. : Bow ad Rmlcs, ed. 2. St. I.&s;. 1955, The C. \‘. hloshy Company, pp. 134-136. Stones. H. H. : Oral and Dental Diseases. cd. 3. I
4. Thompson, 5: 7. 8. 9. 10. 11. 12. 13. 14. 15. 16. 17.