APPENDIX XI

Learning Program

Instructions: Write your ans\\'ers or] a separate sheet of p?]per and cover theright-hnncl colunrn while completing this prograrn.

THE GEOMETRY OF OCCLUSIONOF COMPLETE DENTURES

l . To occlude is to l t r ing together <lrc lose (shut)

2. When the nrirncli l tular teeth areint<l crlntuct with the maxil larv teeth.

broughtthey zrre

occ]udecl

3. Occlusion clencltes zrlationship betrveen the

stirt ic contact re-rnaxil lary and

teeth.

-1. The teeth may be occluded iri severalmandil>ul:rr positions. The position of n'raxi-mum pltrnnecl contact of the occlustrl surfircesof the mtrri l lary and mandil>ular teeth isterrned centric or retruded

is sholvn incontact posi t ion. This posi t ionFigure XI-1.

milncl ibul irr

370

occlusion

THE GEOMETRY OF OCCLUSION OF COMPLETE DENTURES 371

Figure Xl-1

5. Examine Figure XI-2.section clf cornplete clentures.

This is i t coronalThe teeth in th is

case are i l lso in the

or centr ic occlusion.

6. We know fronr experience thirt theteeth cnn be occluclecl in clther mrrndibularpositions. In Figure XI-3 you crln see that therntrndible htrs been n-roved to the ptrtient's lefts ic le. Thus, the eccentr ic posi t ion of occlusionil lustrated is - l:rteral occlusion. Thearrows indictrte the direction of the movernent.

7. The "working side" is the side towardwhich the patient rr)oves his manclible, that isthe side on rvhich he chews, and the "bul-

ancing side" is the opposi te s ide where theresl-ror-rld lte a bolancing cuspal contuct to pre-vent t i l t ing of the denture. In Figure XI-3 the

retrtrclecl contirctpcl s iticln

left

372 LEARNING PROGRAM

LEFTRIGHT

As a two dimensional d iagram cannotindicate the t rue cusp relat ionships,the dotted l ines indicate the cuspswhich l ie in a di f ferent plane to theplane of the section.

Figure Xl-2

\GHT

Figure Xl-3

RI LEFT

THE GEOMETRY OF OCCLUSION OF COMPLETE DENTURES 373baltrncing side is on the pntient,sarrd th_err,,o rking sid,e on the patient,s _-.The di{lerent c.ondyla. ,our,"r."ri ,rr,

"iat ",srcle rlccounts fclr the different clirections ofthe arrows.

, 8; Exirmine T-igure XI_4. If the teeth are

rlrougnt rnto occlusion when the mandilt le isprotruded, this contact relationship "i

tfr.maxillary and mandibular teeth i,

-fr.i*r, u,

occlusion.

there are fbur basic occlusalthe mandibular teeth ,.lut.J i.,teeth. These are:

9. Thusposit ions ofthe maxillary(a)

rightleft

protrrrs ive (protruded)

centric occlusion(retruded contactposi t ion)

left laternl occlusionriglit laterrrl occlusionprotrusive occlusion

(b)(c')

(d)

Figure Xl-4

374 LEARNING PROGRAM

10. When the teeth slicle in contact fromone basic to another, they are said occlusionto be in art iculat ion.

11. Thtrs \\ 'e lnay cliffelentiate ltetr.veena rt iculat io n and o cclu s ion.(a) The static relationship of the teeth rvhile

in t 'ontact is ( r t ' t ' lusiot t(b) The dynanr.ir:,sl iding relationship betr,veen

rnandibular and rnaxil larv teeth is -. trrt iculation

12. If the contact between rnaxil lary arrdmandibular teeth occurs on onl1, one sicle ofthe :rrch in an occlusal pclsit ion, the - occlusiouts unbal&nced.

13. If tooth contact occurs all around thedental arch in an occlusal position, that

is balanced. occlusion

14. When r:ontact betr'veen maxil lary andmandibular teeth is maintained all around thedental arch in erl l closecl sliding rrlovernenrs,the articulation is birlanced

15. In alranging artif icial teeth on com-plete dentures, it is ouL airn to procluce

articulation. This can be achieved only l lalirr-rcedrvhen there is a harnronious reltrt ionship be-tw,een the condl,le path ancl the fornr and re-lationships of the teeth.

16. Let us now consider the factors af:fecting tooth position. The general orientationof the teeth in the intermaxil lary space of the

THE GEOMETRY OF OCCLUSION OF COMPLETE

edentulous mouth is clecicled when the jaw

relationship is recorded by carving the recordblocks so that they rneet on ir f lat plane caliedthe - plarre.

17. The angle between this plane irnd thehorizontal (as represented by the Frankfbrtplane) is cal led the angle of the plane of - .

18. It is not uncornrnorl to mount eden-tulotrs casts on an articulator so that the con-tacting surf'aces of the occlusion rims are hori-zontirl. Thus the angie of the plane of occlusionis- .

DENTURES 375

occltrserl

occlnsion

0 degrees

-T ---orr?

I

I

OJ-t'II

I

II

(-II

II

Figure Xl-s

over the lower

376

19. Examine Figure XI-s. At the front ofthe mouth the upper incisors overlap the lowerincisors in a horizontal and a -- direc-t ion.

20. The vertical overlap <lf the uppel in-cisors over the lower incisors is knclwn as theincisal oaerbite, whereirs the oueriet is the

overlirp of the upper incisorsincisors.

21. When the rnandible is moved to i tsprotmsive occlusion, the lower incisors movedownward anrl forward to an edge-to-edge

with the upper incisors.direction in r.r 'hich the

glenoid l 'ossa is

22. Exarr-rine Figure XI-6. The prrth alongwhich the lower incisors move makes an angleto the horizontal ctrl led the -- qr.ridance

ansle.

23. Examine Figure XI-7. Incisal guid-ance is provided on the articulator by the in-cisal p<,rst moving on the incisirl guidtutce table.This table can be ti l ted and locked at any

angle suitable for theindiviclual patient. The angulirt ion of the tabledecides the parth of movement of the anteriorpart of the mandi l r le.

LEARNING PROGRAM

vertical

horizontrrl

occlusion (contact)

downwardfbrwald

incisal

incisal guidance

At the same time thecondyles move in therrnd -.

24. A steep incisal guiclanceresult from a large overbite andoveriet.

irngle rvil la__ smal l

THE GEOMETRY OF OCCLUSION OF COMPLETE DENTURES377

OJ-JIII

Figure Xt-6

Figure Xl-7

378 LEARNING PROGRAM

25. Il the dimensions of overiet and over-bite are the same, the incisal guidance anglewill lre 45 degrees

26. If the overbite is increased Lmt theincisal guidance angle has to be kept the sarne,it wil l be necessary to - the overjet. increase

27. lf the overjet is decreased but theincisal guidance angle has to be kept the same,it wil l be necessary to - the overbite. decrease

28. The overbite cirn l.re incretrsed either'lry(a)(b)

the maxil lary incisors, or lengtheningthe mandibtrlar incisors. raising

29. Examine Figure XI-8. When the mrrn-dible rroves in articulation to a protrusir. 'e condl' lesocclusion, the - move on to the (condyle heads)distal slopes of the articular eminences.

30. The Ttath of the condgle in protnrsionis detennined by the anatomv of the ioint andis called the sagittal - ptrth. condylar

31. The angle which this ptrth makes tothe horizontal is termecl the sagittal - conclvlurguidnnce angle.

32. E.xamine Figure XI-9. This shows themechanisnr of the articulator u'hich representsthe tempor<lnrzrncli l tular joint; the pin pitssing

- -= :=: I . '=TRY OF OCCLUSION OF COMPLETE DENTURES 379

Figure Xl-8

Figure Xl-9

380

through the vertical mtrndibular post repre-sents the condyle, trncl this ellgages the slotin the adjustable slide on the maxil lary corn-ponent of the articulator. The slide representsthe condl' lar path, and the angle it makes tothe horizontal represents the -

33. Thiscan be acljusted on the articulator

to correspond rvith that of the patient, butorrce set must not be altered.

34. Thus, t l 're closed protrusive glidingmovernents of the mandible are guided(a) anteriorly bv the incisors along the

(b) posteriorlyioint along tire

bv the teruporornandibular

35, An unusual situation is depicted inFigure XI-10. The incisal guidance angle andthe sagittal condl' lar guidance nngles are both15 degrees. Thus, on protrusion the whole

LEARNING PROGRAM

strgittalcondl' lar guidance angle

sagittal conclylirrguidance angle

incisal guidtrnce angle

sagittrrl condylarguidance angle

Figure Xl-10

* _ Yl THE GEOMETRY OF OCCLUSION OF COMPLETE DENTURES

Figure Xl-11

mandible lnoves forward and downward atan irngle of - degrees to the holizorrtal.

36. In Figure XI- l l i t can l re seen thatan trl l around sliding contact between maxil-iary and mandibular teetl i in protrusion canbe maintained rvith teeth having flat occlusalsurfaces, provicled the angle of their plane of

is 15 clegrees.

381

l5

occlusior"r

37. InFiguleXI-12, i f both the incisalgtridance and the strgittal conclylar guidanceangles are 20 degrees, then to mainttrin con-tact of the cuspless posterior teeth, the angleof the plane of occlusion wil l have to be in-c ' reased to - . 20 degrees

38. Thus, i f and1'lar guidance anclproduces irnbalerncel>e restorecl b1

increase in sagittal con-incisal grr id i rnc 'e anf lesin a set-up, balance can

plane of occlusion.the angle of the l l lcreasrng

382

Figure Xl-12

39. This, however, is not usually feasiblein clinical dental practice, owing to lack ofintermaxil lary space in the edentulous mouth.Indeed, it is cornmon practice to set occlusionrims on the articulator with the plane of oc-clusion horizontal, thus the angle of the planeis -.

40. Examine Figure XI-13 (i). It shovi'sthe retruded contact positior-r of cuspless poste-rior teeth which are set to a horizontal plane

of occlusion in a patient with a sagittal con-dylar guidance angle of 20 degrees ancl ar simi-lar - ansle.

41. In Figure XI-13 ( i i ) . - occlu-sion is i l lustrated trnd 1.ou can see that contactis lost between the upper and lower cusplessposterior teeth. This occlusion is ncit --.

LEARNING PROGRAM

0 degrees

incisal guidance

protrusive

balanced

THE GEOMETRY OF OCCLUSION OF COMPLETE DENTURES

12. Of course, the occlusalposterior teeth are not normallvpointed prominences called cusps

383

surfaces offlat but have

43. Figure XI- lB ( i i i ) is s imi lar to XI_13(ii), except that the posterior teeth have cuspson their occlusal surfaces. The plane of oc_clusion is again horizontal but, as the Jnp",of the cusps make angles of 20 degrees to thehorizontal, they harmonize with fhe path ofthe mandible in protrusion, and balanced articulation

is achieved.

(i)

( i i)

SCGA

( i i i ;

Figure Xl-13

384 LEARNING PROGRAM

parallel

cusp

HorizontalFigure Xl-14

4,1. Figure XI-1.1 shou's the buccal sur-face of a typicrrl upper premolar and demon-strates the cus;.r. The arrgle l;etween the slopeof the cusTt and the plane passing through thetip of the cusp which is perpendicular to aline bisecting the cusp, rneasurecl rnesio-clistally (or buccolinguall.v) is called the - cuspangle.

45. The definit ion of cusp angle in theprevious frtrme makes allowance for asy'nr-metrical cusp slopes, but in the context of thisprogrtrnl symnretry is assumed, and the crrsptrngle is meirsured frorn zr plane passingthrough the base of the cusp, which is, ofcourse, to the defined plane.

46. When the plane passing throughthe base of the cusp of a tooth is horizon-tal, the ar.rgle betrveen the cusp slope and thehorizontal wil l l>e equal to the - angle.

17. A 20 degree poster ior tooth is onedegrees. Thiswith a of 20 cusp trngle

- - : . : : : . , , : .AYOFOCCLUSIONOFCOMPLETEDENTURES

.r:.- -: . :- :-,rt alter when the tooth is t i l ted'

I . . . , - . . : - - -cs l letween the cusp slopes and

:l -

, :,- :-:.,.1 vilr) ' with the amount of t i l t '

. \ F i {ure XI- f5. When a 20 degree uP-

1,.,. . ' -..r i,rr tooth is set on a plane of occlu-

i , ' . '

. , ,=t"a at 5 degrees to the hor izontal '

t i 'c . . r r ;1e l letween i ts distal s lope and the

lr , , r iz , t r t r t l u ' i l l be

Itl, This angle is called the e$ective

(re-examine Figure XI-15)

,.r"1 at the sum of the and the

rlngle of the _=-- ' and de-

n"".ft"g upon the angle of the plane of oc-

:1.;; i;rt"""; be made to correspond with the

irnqle of mandibular movement'

25 degrees

cusp anglecusp angleplane of occlusion

tl-iethe

50. Thus, you can see that an increase in

angle of the plane of occlusion incretrses

angles of all the Poste- effective cusP

t i l trOc

= 250

plane of occlusion

angle of P of O.

CA = Cusp Angle

ECA = Effective CusP Angle= CA+Angle of Plane

of Occlusion (d)

ECA 2d

385

CA2t

ECA 25OFigure Xl-15

horizontal

386

rior teeth. It is theof the teeth.

same as collective ti l t ing

51. The effective cusp angles of all theposterior teeth are decreasecl by a - inthe angle of the plane of occlusion.

52. Imagine that the mandible is n-rovingat nn angle of 30 degrees to the horizor.rtal inprotrusir. 'e movetnents; to maintain trrt icultr-t iorr, the eff 'ective cusp angle r.vil l have to be

If , however. 90 deglee pos-terior teeth have been set. the nlane of occlu-sion u'i l l htrve to be ti l ted to

rnaintirin contact; i.e., the effective cusp anglecorresponds to the angle o{ mirndibulirr rrove-ment.

53. A dist inct ion must be made, however,between the trngle of the plane of occlusiontrncl the arnount of t i l t of the indiviclual teeth.You s'i l l remenrber thirt the tuigle of the pltrneof occlusion is detennined in the clinic rrt the

str,rge of denture construction trnclindicates the general orientation of the teeth,whereas the ti l t of the individual tooth isdetermined in the laboratorv.

LEARNING PROGRAM

decrease

30 degrees

l0 c legrees

registrlrt ion

effective cusp angles

30 degrees10 degrees

54. The ti l t ing of individual teethmealls by rvhich the technician adjusts

to htr lmonize

rsathe

u'iththe paths of movement of the rnandible.

55. Examirre Figure XI*16. The sagittalcondylar guidance trngle is 30 degrees and theincisal guidance is 10 degrees. Thus, in pro-trusion the po,sterior part of the mandiblemoves along a path at to the hori-zontal and the anterior trlong n path irt

:= l ' . 'ETRY OF OCCLUSTON OF COMPLETE DENTURES387

t , , : l . r l r , r r izontrr l . A point midwtryt l , t . t : . . i , r guidances would

-nrra nt,rf --.--._ - to tire horizontal.

betweenan angle

20 degrees

5f j . Figure XI_16.20 clegree poster iorteetlr .et ri i thout t i l t irt a pol,it mijriay be_t.,.

"", ' the, srriclances would hur_-ri l" _itt

.,]l: :,',1t", of nrrurdib,,tu, ,rorr._."i .n ,fr"a

t , ' I r r . l r r l t | ) . l111[5 anter ior worr ld reqr| i reeffective cusp angles to harJonize

u i th the. 10 c leqree _, . . r i l

).t j,t,: |), r i111. po\terior lvoulcl require

: ; l l : . , r r " cusp rrngles to hannonize with the 30oeqree sagittri l condylar guidance ansl;,

smal lerincisal guidance anglelarger

57. ,\ lrrnufirctured sets of posterior teethoiten have :r standard ",,rp

urrgl. u"J l" tfr l,c'ase if 20 degree posteriors were selecterlthe technician woulJ nnrr" io'r"a""-" ifr-. ""roangles toward the anterior by grindi"g ""aincre:rse the effective cusp angles toward theposter.ior by --.--.---.-_- the teeth so that itr" o"_clusal surfirces of the upper teeth firced rnoreposteriorly.

Figure Xt-16

t i l t ing

t ltq

\-'

a2d

k-J

Al)| \-;)

Various amounts of tilt ol 2d posterior

teeth produce eJfectrve cusp angles

'*utb f rom to:,::,::,.,,

58. Figure XI-17' Alterntrtively he could

recluce the eff 'ec't ive t 'usp *t-tgl"l,of,thertpper

"?tt"f^t. bv t i l t ing them so tn* tn; lJf;

,.1,,r*l surfac'es t"".1.,[i'lr"d;;el" "namonize with the int

ai l " ' . * r t "at"g miglr t l te avoided'

59. Common articulator settings arel0 de-

,r""1'toi'r.,"i"r c"t;;;;; ""c1" ""j":tu" u"

srees for

60' Figure XI-17' It can be seen'that t i l t-

,"g Ii ,f-," ieeth to m:rke their effective cusp

""?f"t harmonize with the paths ot move-

ment of various ntti'- clf the matldih]-: nut

given a general "u'uo-'o

the occlusal t"tful-l-

ii;';;"t the amount of tilt' the nrore promr-

"i",?rr be this comPensatr'ng

61. Because this "tt'vs co{P'ensates for

,h" ;";;;;;;;"i 'f;" c.nd1'le'on t1 the

ilrticlrl ar el-tl i ne rtc e- cltiri n g nl andib ulilr lllove-

nrct l t ' . i t i t t 'L l let l t l tc

LEARNING PROGRAM

388

1d1dl-r

20'150

anteriorlY

sagittal condYlar

guidance

cuTVe

c orrrPen s trtil1 g cur-ve

3E9

, t - .L11t-

r i : l r r- -

= . - : l . r r l_

i t r ( r l l r inerrce of

63. -\ srnall sagittal condyltrr guidanceangile \\ 'ould require smaller effectir.,e cusp.11igles ,rnd hence a - pronrineuce ofr1, . . ,Ll lc _

6-1. Exarnine Figure XI-18. You carr seetl i i l t the prominence of the compensirtingcrrrve lrrries directl-v/inversel)' u' ith the cusp

rulgles of t l-re posterior teeth.

65. You lvil l remernber that the e{fectivecusp angles must harmonize with paths o1'

compensating curve

smirl lercompensirting curve

inr' 'erselv

30,POSTERIORS

^* '/rt20" POSTERIORS

20'posteriors must be set on a more prominent compensatingcurve than 30" posteriors in order to produce the sameeffective cusp angles.

Figure Xl-18

390

mo\/ement of vilr ions parts of the mirndible.Thus, u'hen the sirgittal condvlar guidance

aDgle is large tl ie effective ctlsp an6lles mustbe - towarcl the pcsterior encls of thedental arch.

66. When the incistrl gniclirnce i lngle issmtrl l the effective cusp angles ntust become

tou.ard the :rnterior end of the dentalarch.

67. Thr.rs, incisal guiclirrrce iugle is direct-ly-/inversell ' related to ttre cusp angle anteriorl) 'l" th. .l*"tnl arcl'r and srlgittirl condyltrrguidance ilngle is directly/inversel)' relatecl to

the cusp angle postelior-lv in the tleutrrl arch.

68. Look at Fignre XI-19. The relatior.r-ships betrveen condyle guidancer, incisalguidrrnce, clrsp angies, and effective cuspangles (rvhich rve hirve alreacly examined rela-tive to protrusive movements of the rnandilt le)also apply to lateral movements of the mtrn-dible. It may help you to think of their rela-tionship to each other if you regard the ctrspalguidance on the rvorking side as equivalent to

the incisal gttidirnce, and the condyle and cusprelationship on the balancing side as ecluival-

ent to the condvle irnd cusp relationship,u'hich rve have nlretrdy considered reltrt iveto protmsive occlusion.

LEARNING PROGRAM

Itrrge

srntrl ler

directly

cli rectly

TIE GEOMETRY OF OCCLUSION OF COMPLETE DENTURES

Figure Xt-19

391

SCG

IGA

392

69. Look at Figure XI-20, which is ircoronal section through the prernolar regiorrof a complete clenture. Wl-ren the rnandibleis moved to the right (rvorking side) the buccalcusp of the lowel right seconcl premolirrslides on the rnarginirl r iclges between the

and the l inguirl crlspof the upper right second premolar slides onthe n"rarginal ridges betrveen the lower secondpremolar and - --. Tli isirl lows a relativell ' horizontal movement toharmonize with that of the condyle, as in-dicated by the arrow' nn the right.

LEARNING PROGRAM

upper premolars

lou'er first rnolirr

As a two dimensional diagram cann0tindicate the t rue cusp relat ionships,the dotted l ines indicate the cusoswhich l ie in a di f ferent plane to theplane of the section.

Figure Xl-20

3=] ' . 'ETRY OF OCCLUSION OF COMPLETE DENTURES

RIGHT

393

Figure Xl-21

: r r E\ . r r l ine Figure XI-21. On the lef tr . ' .-..: - - . r. i . i( le the r.r.rt indible rnoves forward,. . . i . - - - : . . l ( ) \ \ 'n\ \ ' i : r rc1 : rnd to the r ight . As the- : . i ' . . . 1, . . , r e. the gler io id fbssa the buccal, . . - i r : : l re los.er second premolar leaves:. r - . : : r , ,1 r i r l [ ]1g l t iarginal r idges between

- -r ..:, i i .1icle. foru.rrrd :rnd l ingually onto

. 1. . : , l , i rcc,al s lope of the l ingutr l cusp of

r . : . - . i . )€-1. T 'hus, the ef_r, i ' . : - r i .p al tg le of thtr t s lope should harnron_z. . . - . ' . : - , r l re. concly ' l i r r t lngle and enable tooth

,r , i - : r i i , , l rc- nr i rur t i r ined on the balancing sic le.

. . . UPPER- LOWER

LEFT

f irst premolar

; i CJrr the s 'ork ing s ide the buccal cusp, : :1, . 1,r , , r er second premoltrr s l ides buccal ly: : , : r - , t t . pO: i t ion on the,: :1, r trplter prentolars to an edge-to-eclge

l t ' i . . t i , , r r . l r i l t n ' i t i t the s lopes of the l tuccal_ _

l -

marginal riclges

394

RIGHT

Figure Xl-22

72. On the rvorking side the path of move-rnent of the teeth rvil l not be cluite horizontirl(:rs indicatecl in Figure XI-20), but, :rs shownin Figure XI-22, wil l be relrrted to the pathof trtrvel of the canines over each other andto the transverse curve of the rightlbssrr. C)n the left side the path of the condylewill not be exactly the same trs that of thesagittal condylar path, but wil l be sligl-it lyless, irs t lre condyle is trrrveling transversely,across the f 'ace of the articr,rlar eminence.

LEARNING PROGRAM

LEFT

glenoid

73. On the balnncing side the angletween the strgittal plrrne irnd tl'ie path ofcondyle in lateral movernent is cnlledBennett

be-thethe

74. Loctk nt Figure XI-22. When the man-dible is swung toward the right side, the rightcondyle rnoves laterally (Bennett sli i ft) along

angle

THE GEOMETRY OF OCCLUSION OF COMPLETE

a _Irrrth of say l0 degrees to the horizontal,

u'hile tl 're canine guidance n" tt.,. , jgtl _uyctruse the front of the mandible to mJve ar anirngle,of 20 degrees to the horizontal.

Thus, the combined effect of the condylartrncl canine guidance on the riglit sicle wouldbe that the mandible moves

"i _"l"of"

"f, ;_ _

, r r l a point midway l retween r .on_

Ctvle . i l ld c i tn ine.

75. On the left side the condyle travelstonvurd, downward and inwarcl at.rn angle ofsar' 40 degrees, so

-that a point _id*,.y tr"_

tn'ssl1 the left condyle arrJ the right canineguidtrnce would travel at trn angle ;i_-_-.Thus the effective cusp arrgles of the l ingutrlcusps of the left upper premoltrrs shoulcl be.JU Oegrees.

DENTURES 395

l5 degrees

30 degrees

76. The vectors descr ibed in discussingthe geometr-y are those employed by the den_tal technician in setting the teeth when hemoves the articulator from the posil ion ofnti lxirrum

. interctrspation into protr.,sive cr.lett or r. ight lateral occlusion. However, thehurrtrn mandil l le in flnction _nrr"r' in thereciproc:rls of these vectors, ltut it wil l be ap_precirrted that if occlusion is balance.cl in ur."clirection it witl trtso be lrul,,;;; l- l;*th: opposi te direct ion.

, 77. This program on the geometry of oc_

clusion presents an oversimplif ied version of.mirnv of the relationships. ihe .lartl"ity ufthe tissues surrounding^ the ;oinrs-"oia ,f.,"clisplaceabil lty of the dentures'are iactons thatcontri ltute to the complexity n"a ,_r.rot"-it ailficrilt to trnnslate

-nrrdib.,ln. lrrorr"rrr"ir,, ,rlapurell. mathematical fbrmulas

. The mandible should be regardecl as irbone in u muscul.r sling of "".r-,r-frf. ,i"ir"r,u.

.{ lthough its movement is determirr"a i,, .ru_.

396

Figure Xl-23

extent by the joir-rts and the teeth, it is alsocapable of movements thtrt cannot be definedprecisely. Hou'ever, u'hen rnaking completeclentures it is necesstrry to use an articulator'that is adjustecl to at least tur npproxintationof the pilt ient's mandibular rnovements, andir knor.l ' ledge of the geometry associatecl q,ith

such rnovements helps greatlf in the settingol the art i f ic ' ia l teet l r .

78. Figtrre XI-23 shou,s theor-v beingtranslated into practice. The tooth is t i l teduntil t l ie betr,r,een thedistal slope of its cusp and the horizontal sur-firce of the record block harmonizes u'ith the

arrd tl-re

LEARNING PROGBAM

effective cusp angle

sagittal/condylarguidirnce angle

incisal guidance angle