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R E F L E X E S , R E G I S T R A T I O N S , A N D P R O S T H E T I C T H E R A P YN I E L S B R I L L , L . D . S . *

Royal Dental College, Copenhagen, Denmark

T H E O D O N T O L O G I C L I T E R A T U R E W H I C H d ea ls w i th p ro b l e m s c on -c e r n i n g r e g i s t r a ti o n s o f t h e m o v e m e n t s a n d p o s i ti o n s o f th e m a n d i b l e f o rp u r p o s e s o f p r o s t h e t i c r e h a b i l it a t i o n c a n r o u g h l y b e d i v i d e d in t o tw o g r o u p s . O n eo f t h e s e m a i n t a i n s t h a t t h e o c c lu s a l p a t t e r n o f c o m p l e t e d e n t u r e s m u s t b e c o n s t r u c t e da c c o r d i n g t o a r e g i s t r a t i o n o f a r e t r u d e d p o s i t i o n o f t h e m a n d i b l e . T h i s p o s i t i o n isa b o r d e r p o si ti o n . T h e o t h e r g r o u p m a i n t ai n s t h a t th e o c c lu s al p a t t e r n n m s t b e m a d ei n a c c o r d a n c e w i t h a p r e v a i l i n g f u n c t i o n a l o c c l u sa l p o s i t i o n - - o r p o s i t io n s . T h e s ep o s i t i o n s a r e u s u a l l y n o t b o r d e r p o s it i o n s . T h e c o n c e p t o f t h e o n e g r o u p i s t h a t t h em a n d i b l e f u n c t i o n s p r i m a r i l y i n a r e t r u d e d p o s i ti o n , w h e r e a s t h e o t h e r g r o u p a p -p a r e n t l y c o n t e n d s t h a t i t f u n c t i o n s i n i n t e r m e d i a r y p o s it i o n s. V i e w s s o w i d e l y c o n -f li c ti n g h a v e e v o k e d v a r i o u s p r o c e d u r e s f o r c o m p l e t e d e n t u r e c o n s t r u c t io n d i f fe r i n go n p r i n c i p le , a n d m a n y o f t h e s e d i f f e r in g p r o c e d u r e s h a v e t u r n e d o u t t o b e c l i n ic a ls u c c e ss e s . I n c o n s e q u e n c e , b o t h g r o u p s m a i n t a i n t h a t t h e f a c t t h a t t h e i r p a r t i c u l a rm e t h o d s a r e y i e l d i n g g o o d c l in i c al r e s u l t s p r o v e s t h a t t h e i r t h e o r e t i c c o n c e p t o ft h e f u n c t i o n a l p o s i t i o n s o f t h e m a n d i b l e m u s t b e c o r r e c t . A m e t h o d , h o w e v e r ,d e v i s e d o n c e r t a i n t h e o r e t i c c o n s i d e r a t i o n s i s n o p r o o f o f t h e t r u t h o f t h e t h e o r ye m p l o y e d , m e r e l y b e c a u s e t h e m e t h o d i s o f c l in i c al v a l u e . * T h e q u e s t i o n i s s t il lo p e n a n d c a n n o t b e a n s w e r e d u n t il r e s u lt s o f f u r t h e r i n v e s t ig a t io n s o n a m o r es c i en t if i c b a s is a r e av a i l ab l e .

N e v e r t h e l e s s a n a t t e m p t w i l l b e m a d e t o e s t a b l i sh a n e w t h e o r e t i c b a s is f o rr e g i st r a ti o n s . T h e c o n c e p t p u t f o r w a r d is b a s e d o n s tu d i es o f n e u r o m u s c u l a r f u n c -t i o n . W h i l e t h i s a r t ic l e d o e s n o t p r e t e n d to b e i n a n y w a y c o m p l e t e , i t d o e s , h o w e v e r ,s t r e s s a n e w a s p e c t i n c u r r e n t d is c u s s io n . A n e f f o r t w i ll b e m a d e t o s h o w t h a tt h e t w o g r o u p s w h o s e t h e o r i e s a r e t h e s u b j e c t o f d i s c u s si o n a r e n o t e n t i r e l y r i g h t ,n o r a r e t h e y t o t a l l y w r o n g . T h e m a i n c o n c l u s i o n o f t h e a rt i c le is th a t c o m p l e t ed e n t u r e s m u s t b e m a d e o n a r e g i s t r a t i o n o f t h e m a n d i b l e i n i ts m o s t a c t i v e l y r e -t r u d e d p o s i ti o n . B y t h i s m e a s u r e , d u e c o n s i d e r a ti o n is g iv e n to n e u r o n m s c u l a rc o n d i ti o n s in t h a t g r o u p o f p a ti e n t s w h o s e m a x i m a l i n t e r c u s p a ti o n o f th e i r n a t u r a lt e e t h w a s i d e n t i c a l w i t h a r e t r u d e d p o s i t io n o f t h e m a n d i b l e . I f n e c e s s a r y , th i sr e g i s t r a t i o n m u s t b e m o d i f i e d t o th e e x t e n t t h a t t h e o c c l u s a l p a t t e r n w i ll c o m p r i s er e g i s t r a t i o n s o f p r e v a i l i n g f u n c t i o n a l o c c l u sa l p o s i ti o n s . T h i s m u s t b e d o n e i n t h o s ep a t ie n t s in w h o m , f o r m e r l y , m a x i m a l i n t e r c u s p a ti o n w a s f o r w a r d o f t h e r e t r u d e dp o s i t i o n o f t h e m a n d i b l e . B y t h i s m e a n s , t h e o c c l u sa l p a t t e r n i n t h e s e p a t i e n t s

R e c e i v e d f o r p u b l i c a t i o n A u g . 30 , 1 9 5 6. A s s o c i a t e P r o f e s s o r , D e p a r t m e n t o f P r o s t h e t i c D e n t i s t r y . H e a d : P r o f e s s o r W . K r o g h -P o u l s e n , L .D . S . D r . m e d . d e n t .

3 4 1

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342 BRILL J. Pros. Den.May, 1957is adapted in such a way that it permits the condyles to take up intermediary posi-tions as well as retruded border positions during occlusal contact. This procedurewill essentially add to the stability of the dentures and their optimal function, toprevent the occurrence of pathologic conditions in the denture foundations and/orother functional units of the masticatory mechanism, i.e., muscles, joints, etc.,and will thus further the somatic and psychic well-being of denture wearers.At the Department of Prosthetic Dentistry of the Royal Dental College, Denmark,principles for complete denture construction have been taught which include suchregistrations.

If complete dentures are to be of any use for a patient, it is essential thatthey meet the basic requirements set up by the neuromuscular function of themasticatory mechanism. The prosthodontist, in consequence, has a need of knowl-edge of the physiology of nerves and muscles, especially of the mechanisms ofconditioned and unconditioned reflexes.

G E N E R A L F E A T U R E S O F T H E S T R U C T U R E A N D F U N C T I O N O F T H EN E U R O M U S C U L A R S Y S T E M

S y n a p s e s a r e j u n c t i o n s b e t w e e n t w o o r m o r e n e u r o n s . A t t h e s e p o i n t s ,i m p u l s e s f r o m o n e n e u r o n a r e b e i n g c o n v e r t e d i n t o n e w i m p u l s e s i n o t h e r n e u r o n s ,a n d t h e n o r m a l p a t t e r n o f m u s c l e a c ti v i t y d o e s n o t w o r k w i t h o u t t h e a c t i v e c o -o p e r a t i o n o f s y n a p s e s . T h e f u n c t i o n o f m u s c u l a r a c t i v i t y i s b a s e d , t o s o m e e x t e n t ,o n n e r v o u s i m p u l s e s o r i g i n a t i n g i n t h e p r o p r i o e e p t i v e s y s t e m . T h e n e r v e e n d i n g so r " r e c e p t o r o r g a n s " o f t h i s s y s t e m a r e t o b e f o u n d i n m u s c l e s a n d t e n d o n s i n t h es h a p e o f s p i n d l e s . T h e s e s p i n d l e s r e c o r d v a r i o u s s t a t e s o f t e n s i o n o r i g i n a t i n g i nm u s c l e s a n d t e n d o n s a l i k e a s t h e r e s u l t o f m u s c u l a r a c t iv i t y. I n p e r i o d o n t a ltissues2 and in joint capsules, a great number of receptor organs are likewise to befound with similar functions. By adequate stimuli, impulses originate in the re-ceptor organs, and these impulses pass along afferent nerves---"reeeptors" to thecentral nervous system. This system comprises synapses, which convert theimpulses, and these are, in some cases, transmitted directly through efferentnerves--"effectors" to the muscular system, which then goes into activity. Amuscle is called an "effector organ" in this connection. This relationship betweena receptor organ and an effector organ, in which impulses are transmitted by onlytwo neurons, a sensory and a motor neuron, and pass only one synapse, is termeda simple reflex arc. Instead of passing through such a monosynaptic reflex arc,the original impulses may be transmitted to higher centers within the centralnervous system by other afferent paths, and pass several synapses before they arebent back over efferent pathways. This complicates the reflex arcs, and the patternof muscular activity based on multlsynaptic reflex arcs is more extensive and co-ordinated.

A muscle is composed of a certain number of motor units which are madeup of a nerve fiber and a group of muscle cells. On an average, 150 cells areinnervated by one nerve fiber. Muscle cells belonging to the same motor unit arcdistributed throughout the muscle to which they belong and, together with theireffector nerve, constitute a functional unit. This means that the muscle cells re-

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Volume 7 REFLEXES, REGISTRATIONS~ AND PROSTHETIC THERAPY 343Number 3

spond simultaneously and with equal force to impulses imparted to thenl by theireffector. The various motor units, however, are not made up of the same numberof cells and do not possess equal threshold values to stimuli. Muscular activityoriginates in the smallest units of the lowest threshold values. Next to be in-volved are the units that are somewhat greater, possessing a somewhat higherthreshold value, and gradually as the threshold values of the various units arebeing transgressed, the power of contraction of the muscle is increased. Thetransitional stage of a muscle from total relaxation to maximal contraction mayin this way be graduated?

Efficient muscular activity is not the result of separate contractions of in-dividual nmscles effected through simple reflex arcs, but is established as har-moniously coordinated mass movements4 along complicated reflex arcs whose in-tegration takes place in the cerebrum. Even the closing of the mouth, which toall appearance is a quite simple movement, is performed by way of a mass move-men t 9

As long as impulses are transmitted along subcortical paths, consciousness isnot involved in muscular activity, which is then exclusively a reflex action.1 Gen-erally, consciousness is merely engaged in order to initiate and/or terminate re-flexes.

GENERAL FEATURES OF THE NEUROMUSCULAR SYSTEM OF THEMASTICATORY MECHANISM

Muscles attached to the mandible have varied and alternating functions. Theymay (1) act as the actual performers of movement, (2) exercise a balancing effecton the activity of the actual performers of movement, and (3) stabilize the condylesin definite and varied positions while movements are being undertaken.1

In normal closure, the closing muscles are the prime movers of the mandible.They are opposed by antagonists, the opening muscles, however, without obstruc-tion to movement. Indeed, the function of the muscles of opening ensure a greatermeasure of stability by investing the movement with greater harmony and precision.The'~same underlying principle applies when a flag is to be hoisted without beingblown away from the pole. The flag is being suspended between that part of theline which is above the flag and that part which is below. By slackening the pullin the lower line while increasing that of the upper line, the tension of the latterprevails and the flag glides upward, while at the same time the movements of theflag are being kept under control.

In closure of the mouth, the same sort of thing happens. Through an in-tensification of the contraction of the elevator muscles, the mandible is raised.The increased contraction is reciprocated with a corresponding gradual alterationof tonus of the opening muscles, through a so-called reciprocal innervation of thesenmscles. If movement is performed with the mandible in its most retruded posi-tion, other groups of musculature come into play which serve the purpose ofstabilizing the condyles in their retruded position. Under normal conditions ina combined movement of opening and closing, a certain pattern of innervationexists. In case of conscious closure, impulses are transmitted from the cerebrum,

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3 4 4 B R I L L J . P r o s. D e n .M a y , 1957p r o d u c i n g c o n t r a c t i o n s o f t h e e l e v a t o r n m s c le s , w h i le a t t h e s a m e t i m e t h r o u g ht h e r e c i p r o c a l in n e r v a t i o n a n a l t e r e d t o n u s o f t h e o p e n e r s i s b e i n g i n it i a te d .W h e n t h e t e e t h c o m e i n t o c o n t a c t, t h e p a t t e r n o f in n e r v a t i o n i s r e v e r s e d t o s e r v ea c o n t r a c t i o n o f t h e o p e n e r s a n d a n a l t e r a t i o n i n t o n u s o f th e c l o s i n g n m s c l e s( F i g . 1 ) . T h e a c t i v i ty o f a l l i n t e g r a t e d m u s c l e s n m s t b e t i m e d w i t h g r e a t a c -c u r a c y . I n o r d e r t o a c h i e v e t h e g r e a t e s t d e g r e e o f h a r m o n y a n d p r e c i si o n d n r -i n g a c t u a l m o v e m e n t , t h e p e r f o r m a n c e o f a s i n g l e m u s c l e n m s t n e c e s s a r i l y b ea t t u n e d t o t h e p e r f o r m a n c e o f a ll o t h e r m u s c le s t a k i n g p a r t i n s u c h a m a s s m o v e -m e n t . F u r t h e r m o r e , t h e m u s c l e s m u s t b e t u n e d t o t h e c o n d i ti o n s u n d e r w h i c ht h e m o v e m e n t s a r e t o b e u n d e r t a k e n , i . e . , w i t h m o r e o r l e s s d i s p l a y o f s t r e n g t h ,a t a q u i c k e r o r sl o w e r r a te . I n a s y m m e t r i c a l m o v e m e n t s , th e c l a im o n p r e c is ec o o r d i n a t i o n i s s t i l l g r e a t e r b e c a u s e t h e m a n d i b l e c o n n e c t s t w o j o i n t s o n e a c hs id e o f t h e m i d li n e o f t h e b o d y , w h i c h m e a n s e x t r a o r d i n a r y w o r k i n g c o n d i ti o n sf o r t h e n m s c u l a t u r e o f t h e m a n d i b le . A s d i s t i n g u is h e d f r o m a n a r m o r l eg

F

F i g . 1 . - - R e c i p r o c a l i n n e r v a t i o n . T h e o p e n i n g m u s c l e s a r e r e p r e s e n t e d b y t h e e x t e r n a lp t e r y g o i d m u s c l e a n d t h e c l o s in g m u s c l e s b y t h e m a s s e t e r m u s c l e . L e f t , S t i m u l a t i o n o f t h ee x t e r n a l p t e r y g o i d m u s c l e i n o p e n i n g c o i n c i d e s w i t h a n i n h i b i t i o n o f t h e m a s s e t e r m u s c l e .R i g h t , T h i s p a t t e r n o f i n n e r v a t i o n i s r e v e r s e d i n m o v e m e n t s o f c l o s u r e .

w h i c h c a n b e m o v e d i n d e p e n d e n t l y o f t h e f u n c t i o n o f t h e m u s c u l a t u r e o f t h eo p p o s i t e si d e , t h e tw o h a l v e s o f t h e m a n d i b l e m o v e a s a f u n c t i o n a l u n i t y . T h e r e -f o r e , r i g h t - s i d e m u s c u l a r a c t i v i t y m u s t , o f n e c e s s i t y , b e c o o r d i n a t e d w i t h a c t i v i t yi n t h e o p p o s i t e s i d e , a n d s u c h i n t e g r a t i o n o f a c t i v i t y r e q u i r e s s p e c i a l o v e r - a l lc e n t e r s w h i c h a r e f o u n d i n t h e m e s e n c e p h a l i c r o o t o f t h e f i ft h c r a n i a l n e r v e . 11'~

T h e f a c t t h a t m o v e m e n t s o f o n e j o i n t m u s t b e a c c o m p a n i e d b y c o r r e s p o n d i n gm o v e m e n t s o f t h e o p p o s i t e j o i n t d i s ti n g u i s h e s t h e m a n d i b u l a r a r t i c u l a t io n f u n c -t i o n a l l y f r o m o t h e r j o i n t s , b u t i n o t h e r r e s p e c t s p o i n t s o f r e s e m b l a n c e a r e f o u n d .I t s e e m s r e a s o n a b l e t o b e l ie v e t h a t m u s c u l a r a c t i v i t y , w h i c h w i l l s e c u r e t h e f u n c -t i o n a l in t e g r i t y o f o t h e r j o i n t s , w i ll a l so s a f e g u a r d t h e f u n c t i o n o f t e m p o r o m a n d i b -u l a r j o i n t s ? T h i s c o n c e p t i s c o n s i s te n t w i t h a n o b s e r v a t i o n m a d e b y P o s s e lt . ~H e s t a t e s t h a t i f a r e g i s t r a t i o n o f a G o t h i c a r c h ( n e e d l e p o i n t t r a c i n g ) b e m a d eb y a ct i v e m o v e m e n t s , th e r e c o r d i n g w i ll b e a p p r o x i m a t e l y 0 .1 m m . f o r w a r d o fa s i m i la r r e g i st r a t io n m a d e w i t h p a s s iv e m o v e m e n t s . T h e i n t e r v e n i n g s p a c e be -t w e e n t h e tw o r e c o r d i n g s m a y b e c o n s i d e re d a s a s a f e ty z o n e . I n a c t i v e m o v e -

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Volume 7 REFLEX ES, REGISTI~ATIONS, AND PROSTHE TIC THER APY 345Number 3ments, the mandible is moved by the muscles, and it is believed that at somejuncture in a dorsal displacement a certain pattern of innervation is being induced,which causes an interruption of the muscular activity necessary for the continuationof the movement. This happens in a split second just before the ligaments of thejoint capsules will quite mechanically take up and prevent the movement, and bythis mechanism the occurrence of pathologic disorders in the nature of peritendi-noses and the like in and around the temporonlandibular joint capsule is prevented.This protective action, like most other movements of the mandible, is performedon the basis of certain reflex patterns.

CONDITIONED AND UNCONDITIONED REFLEXESReflexes fall into two groups : Conditioned and unconditioned, and the process

of adaptation which patients must undergo in order to become familiar with theuse of dentures can be accounted for by the concept of conditioned reflexes.At the time the nervous system is formed, the patterns of certain forms of

movement are being established: gait movements, masticatory movements, etc.According to current concepts, nerve paths forming the basis of such patterns areprimarily passable, which means that nerve impulses can be passed along suchpaths unhindered and without previous practice. Adequate stimuli will initiate thereflex patterns concerned, and expedient patterns of movement will develop follow-ing continued stimuli.

It must be presumed, however, that the number of nerve paths incorporatedin any preformed reflex pattern is far greater than the number employed by anyspecial movement pattern. The reflex pattern is capable of action on many differentlines. Jus t as in the case of a photographic plate where only the lighted parts arebeing developed and fixed, only those nerve paths of a reflex pattern which formthe basis of the actual movement pattern are being activated and fixed.

We are led to believe that this principle applies to the reflex pattern of themasticatory mechanism too : When the teeth erupt and come into occlusal contact,the periodontal membranes come into operation as "reflexigenous zones. " Duringocclusion, the periodontal membranes are loaded and a state of tension develops inthe periodontal fibers. Thi s tension is recorded by the receptor organs of theperiodontal tissues. From the latter are transmitted afferent stimuli activatingpart of the nerve paths comprised in the reflex pattern, and, through continuousintermittent contact, certain selected paths are being developed and fixed, eventuallyforming a movement pattern.

Although no experimental evidence is provided, it is thought that the establish-ment of a movement pattern is in progress over a number of years and that it isintimately connected with the eruption of teeth. A reciprocal influence exists be-tween the reflex pattern and the growth pattern which governs the eruption andposition of the teeth. This seems to be the opinion of Ballard.1' As a result, amaximal intercuspation develops, which, in some patients, is identical with themost retruded position of the mandible, while in others it is forward of the re-truded position.

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3 4 6 B R I L L J . P r o s. D e n .M a y , 1 9 5 7i t i s s u g g e s t e d t h a t t h e s ta b i l i ty o f f u n c t i o n o f a m o v e m e n t p a t t e r n , h o w e v e r ,

r e q u i r e s m y e l i n i z a t i o n o f t h o s e n e r v e s o f t h e r e f l e x p a t t e r n t h a t c o n s t i t u t e t h em o v e m e n t p a tt e r n . T h e f o r m a t i o n o f m y e l i n sh e a t h s t a k e s p l a ce s im u l t a n e o u s l yw i t h t h e c o m i n g i n t o . f u n c t io n a n d f r e q u e n t a c t i v i t y o f t h e s p e c if ic n e r v e s . ~ T h ef o r m a t i o n o f m y e l i n s h e a th s m a y b e c o n s i d e r e d a s a p r o c e s s o f m a t u r a t i o n t o w h i c ha m o v e m e n t p a t t e r n i s s u b j e c te d i n o r d e r t o a t t a in o p t i m a l f u n c ti o n , a n d r e f le x e si n it ia t e d b y s u c h a m a t u r e p a t t e r n a r e t e r m e d u n c o n d i t i o n e d r e f l ex e s .

T h e c o m p l e t io n o f d e v e l o p m e n t o f a p a t t e r n d o e s n o t p r e v e n t t h e a p p e a r a n c eo f o t h e r r e fl e x e s , b u t t h e s e a r e o f a d i f f e r e n t t y p e . S u c h c o n d i t i o n e d r e f l e x e s a r eb e i n g d e v e l o p e d a t a s u b s e q u e n t st a g e . T h e y a r e to a g r e a t e r e x t e n t s u b j e c t t oe x t e r n a l c o n d i t i o n s , w h i c h w i l l g o v e r n g r e a t e r o r l e s s e r v a r i a t i o n s f r o m o n e i n -d i v id u a l t o a n o t h e r . H o w e v e r , u n c o n d i t i o n e d r e fl e x e s h o l d a c e r t a in p r i o r i t y o v e rc o n d i t i o n e d re f l e x e s , e v e n i f u n d e r n o r m a l c o n d i t i o n s e i t h e r t y p e w i l l a p p e a r w i t he q u a l f r e q u e n c y . T h e f u n d a m e n t a l d i f fe r e n c e b e t w e e n t h e t w o t y p e s o f r e f l e x e s i st h a t i n d e p e n d e n t a c t i o n o f a c o n d i t i o n e d r e f l e x i s n o t p o s s ib l e . I t i s t o b e c o n c e i v e da s a su p p l e m e n t o r i n c r e m e n t t o a n e x i s t i n g r e f le x p a t t e r n o f t h e p e r f o r m e d t y p e ,w h o s e a d e q u a t e s t i m u l i a r e b e i n g r e p l a c e d b y o t h e r s t i m u l i , o r i g i n a l l y n e u t r a l ,w h i c h t h r o u g h r e p e t i t i o n c a u s e a n i n i ti a t io n o f t h e r e f l e x p a t t e r n . P a v l o v ' s e x p e r i -m e n t s o n t h e s e c r e t i o n o f s a l iv a i n d o g s s e r v e a s a n i l lu s t r a t io n o f t h i s m e c h a n i s m .T h r o u g h d i r e c t c o n t a c t w i t h t h e o r a l m u c o s a , f o o d m a y p r o d u c e s a l iv a r y s e c r e ti o n .T h i s r e s p o n s e is a n u n c o n d i t i o n e d r e fl e x . G u s t a t o r y o r v is u a l se n s a t i o n s w il lp r o d u c e t h e s a m e r e s p o n s e . T h e s e a r e , a t f ir s t, n e u t r a l s t i m u l i i n r e l a ti o n t o t h es e c r e t i o n , b u t b y b e i n g r e p e a t e d s i m u l t a n e o u s l y w i t h t h e c o n s u m p t i o n o f f o o d ,t h e y m a y g r a d u a l l y b e a b l e t o p r o d u c e s e c r e t i o n o f s a l i v a i n d e p e n d e n t o f f o o dc o n s u m p t i o n . I n t h i s c a s e t h e r e a c t i o n i s a c o n d i t i o n e d r e fl e x .

S U P P L E M E N T I N G A M O V E M E N T P A T T E R NT h e c o n s t a n t s w i tc h o f a p r e f o r m e d r e f l e x p a t t e r n t o n e w r e f le x p a t h w a y s

r e q u i r e s a c o n t in u o u s r e p e t it i o n o f i m p u l se s t h r o u g h s u c h p a t h w a y s . A f t e r s o m ep r a c t i c e , t h e t i m e r e q u i r e d f o r a r e s p o n s e w i ll b e s e e n t o b e d w i n d l i n g . T h e p a s -s a ge o f t h e i m p u l s es t h r o u g h t h e n e r v e s a n d t h e i r s y n a p se s h a v e i n s o m e w a y b e e n" f a c i l i t a te d . " F u r t h e r , a su p p r e s s i o n o f o t h e r i m p u l s e s l ik e l y t o o c c u r m a y a r i s e ,w h i c h o t h e r w i s e w o u l d h a v e b e e n a h i n d r a n c e t o t h e s u i t a b i l i t y . o f t h e m o v e m e n t s .T h i s p h e n o m e n o n is t e r m e d " i n h i b i t i o n . "

I n c a s e a m o v e m e n t p a t t e r n is s u p p l e m e n t e d w i t h c o n d i t io n e d r e f l ex e s , ac e r t a i n a m o u n t o f p la s t i c i ty i s i m p a r t e d t o i t, s i m i l a r t o w h a t i s s e e n i n v a r i o u sk i n d s o f t i ss u e . B o n e m a y , f o r i n s t a n c e , a d a p t i t s e lf t o c h a n g e s o f f u n c t i o n a l c o n d i -t i o n s b y m e a n s o f a r e o r g a n i z a t i o n o f i ts s t ru c t u r e . A s i m i l a r a d a p t a b i l i ty i sf o u n d i n o t h e r t y p e s o f t is s u e b e l o n g i n g to t h e m a s t i c a t o ry o r g a n , a n d m o v e m e n tp a t t e r n s m u s t p o s s e s s a s i m i l a r a d a p t a b i l i ty , i n o r d e r t o b e ab l e c o n t i n u o u s l y t om a i n t a i n o p t im a l f u n c t io n in a c c o r d a n c e w i t h t h e c h a n g i n g c o n d i ti o n s . T h e r e i sa w i d e d i f fe r e n c e b e t w e e n t h e p e r f o r m a n c e o f a m o v e m e n t p a t t e r n i n a y o u n g i n -d i v i d u a l w i t h i n t a c t c u sp s a n d t h a t o f t h e s a m e p a t t e r n a f t e r a s p a n o f y e a r s d u r i n gw h i c h t h e d e n t i ti o n h a s s u f f e r e d p r o n o u n c e d a b r a si o n , t o s a y n o t h i n g o f t h o s ec a s e s i n w h i c h e x t e n s i v e c h a n g e s i n t h e o c c l u s a l p a t t e r n h a v e t a k e n p l a c e a s t h e

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V o lu m e 7 R E F L E X E S , R E G I ST I ~A T I O N S~ A N D P R O S T H E T I C T H E R A P Y 347N u m b e r 3result of loss of teeth. Eschler M has demonstrated an extensive reorganization ofthe nervous coordination of the masticatory musculature caused by extraction ofa single lower first molar.

If changes which call for treatment with prostheses, especially complete den-tures, are involved, the cortex will initially be engaged in the development of con-ditioned reflexes, but, gradually, as the latter are being established and includedinto the activity of the preformed reflex pattern, the activity of cortex will cease,and at about that time when patients are no longer aware of their dentures, theprocess of adaptation is said to be accomplishedY In elderly people where processesof involution are taking place, the adaptation to new dentures may be difficult.Progressive atrophy of the cells of the cortex may prove a hindrance to the pro-duction of new reflexes. TM

T H E I M P O R T A N C E O F E X T E R O C E P T O R S F O R T H E M U S C L E S O F M A S T I C A T I O NUnder normal conditions and with a complete set of natural teeth, masticatory

and other movements of the mandible are believed to be executed on the basis ofa preformed reflex pattern. Adequate stimuli are, among others, those impulseswhich originate in certain periodontal receptor organs pertaining to the proprio-ceptive system. The sensitivity of these receptor organs is so great that if piecesof paper of different thickness be successively placed between the teeth, thedifferences may be perceived. Coordinated mass movements are, however, not ex-clusively dependent on impulses from the proprioceptive system, other sensitivenerves being of significance. An example is the numbness arising in fingers ex-posed to heavy cold, which paralyzes normal muscular activity of the fingers. Thisis due to disturbances in afferent impulses in the receptors of the skin and is notrelated to the musculature. The receptors which, in this case, fail are the ex-teroceptors. Their normal function is to transmit sensations from the externalenvironment.

Exteroceptors of special interest to us are those of pressure, touch, and pain.They are found in great numbers in the oral mucosa, including the tongue, and areof great importance for the execution of perfectly timed movements of the mastica-tory mechanism. Patients who have had sensitive nerves severed by surgery inthe oral cavity have not always, been capable of normal movements postoperatively.Another example is: A patient, whose denture retention depended primarily onthe muscles of the cheeks, the lips, and the tongue, lost control of the dentures whensurface anesthesia in the form of Xylocain paste was administered to the mucousmembrane.

Pain greatly influences muscle reflexes. In most cases, pain impulses will takepriority to impulses which normally determine the activity of a movement pattern,and this is equally true of the movements of the mandible." When mandibularmovements thus are restricted by pain caused by a dentitio-dificilis, this phenom-enon is called a "reflex interference" by Thielemann~ as distinguished from theusual "mechanical interferences." But it is highly probable that many of the latterought to be conceived as reflex interferences as well established by proprioceptorsof the periodontium. Certain types of occlusal relations, such as a deep verticaloverlap with limited anteroposterior but marked lateral movements, seem to justify

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3~ 8 BRILL J. Pros. Den.May, 1957s u c h a c o n c e p t , a n d G r e w c o c k a n d B a l l a r d ~ m a i n t a i n , o n t h e b a s is o f c li n ic a l e v i -d e n c e , t h a t e v e n w e a k o c c l u s a l c o n t a c t s a r e c a p a b l e o f a l t e r i n g a m o v e m e n t p a t t e r n .

I f a p a t i e n t l o se s h is t e e t h , h e i s a t th e s a m e t i m e d e p r i v e d o f t h e p o s s i b i l it y t h a tt h e m o v e m e n t p a t t e r n c a n w o r k o n t h e b a si s of t h e u su a l s ti m u li . T h e m e a n s o fc o n v e y a n c e o f t h e s t im u l i f r o m t h e r e c e p t o r o r g a n s i n t h e p e r i o d o n t i u m h a s b e e nl o s t b y t h e e x t r a c t i o n o f t e e th . I n o r d e r t h a t t h e m o v e m e n t p a t t e r n m a y r e s u m e i t sa c t i v i ty , o t h e r i m p u l s e s m u s t b e i m p a r t e d t o it . T h i s m a y b e a c h i e v e d b y t h ep a t t e r n b e i n g s u p p l e m e n t e d w i t h n e r v e p a t h s w h o s e r e c e p t o r o r g a n s t a k e o v e r t h ef u n c t i o n o f t h e l o s t r e c e p t o r o rg a n s . T h e r e c e p t o r o r g a n s o f p r e s s u r e a n d t o u c hi n t h e o r a l m u c o s a a r e t h e r e c e p t o r o r g a n s c a p a b l e o f s u c h c o m p e n s a t i n g f i m c t i o n .

RECORDING C EN TRIC RE LAT ION AND EST,ABLISHING CENTI~IC OCCLUSIONCOINCIDING W ITt-I CEN TRIC RELATION

I t i s n o t a b s o l u t e l y n e c e s s a r y t o e s t a b l i s h e x t e n d e d o c c l u s a l b a l a n c e i n c o m -p l e t e d e n t u r e s a s l o n g a s t h e d e n t u r e s a r e u s e d e x c l u s i v e l y f o r m a s t i c a t o r y p u r -p o s e s , b e c a u s e o c c l u sa l c o n t a c t in c h e w i n g is n e g l ig i b le . H o w e v e r , b a l a n c e d o c -c l u s i o n i s o f d e c i s i v e i m p o r t a n c e i f p o s i t i o n s a r e a s s u m e d , a n d m o v e m e n t s a r e p e r -f o r m e d , i n w h i c h t h e o c c l u s a l s u r f a c e s o f t h e t e e t h a r e b r o u g h t i n t o d i r e c t c o n -t a c t . U n d e r t h e s e c o n d i t i o n s , i m p u l s e s e l i ci t ed t h r o u g h c o n t a c t m u s t r e l e a s e an a t u r a l p e r f o r m a n c e o f t h e m o v e m e n t p a t t e r n o f t h e m a n d i b le , a p e r f o r m a n c et h a t w i l l a l l o w t h e d e n t u r e s t o s t a y f i r m l y s e a t e d o n t h e i r f o u n d a t i o n s .

W h e n a p a t i e n t u se s h is d e n t u r e s f o r t h e fi rs t t im e , n e w a n d e x t r a n e o u si m p u l se s a re o ri g i n a t e d a n d p a ss th r o u g h s e n s o r y n e r v e s . D u r i n g n o r m a l c o n -d i t io n s , a d a p t a t i o n t o th e s e i m p u l s e s u s u a l l y w i ll b e e a s y. T h i s a p p l i e s a ls ot o t h o s e i m p u l s e s w h i c h p r o d u c e u n e s s e n t i a l d i s p l a c e m e n t s o f t h e d e n t u r e s . I f ,o n t h e o t h e r h a n d , t h r o u g h d e f l e c ti v e o c c l u sa l c o n t a c t s , m a j o r a n d c o n s t a n t d i s -p l a c e m e n t s o c c u r , t h i s w i ll p r o v e d a m a g i n g f o r se v e r a l r e a s o n s . A p a r t f r o mt h e f a c t t h a t c h r o n i c i n f l a m m a t o r y r e a c t i o n s m a y o c c u r i n t h e d e n t u r e f o u n d a -t i o n s, th e m u c o u s m e m b r a n e m a y b e c o m e t h e s e a t o f lo c a l l e s io n s , d e c u b i t a l u l c e rs ,e t c. , c a u s i n g i n c o n v e n i e n c e o r a c t u a l p a i n t o t h e p a t i e n t. M o r e o r le s s s u b c o n -s c i o u sl y , h e w i ll t r y t o a d a p t h i s m o v e m e n t p a t t e r n s o a s t o a v o i d p a i n . A s ar e s u l t , t h e m u s c l e s m a y b e c o m p e l l e d t o f u n c t i o n in a w a y n o t c o m p a t i b l e w i t ht h e n a t u r a l a c t i v i ty o f t h e n l o v e m e n t p a t t e r n . S u c h a d i s t u r b a n c e o f f u n c t i o n a lh a r m o n y i n t h e m a s t i c a t o r y m e c h a n i s m m a y , i n t i m e , l e a d t o p a t h o l o g i c c h a n g e so f m u s c l e s , t e n d o n s , j o i n t s a n d a d j a c e n t t i s s u e s, g i v i n g r i s e t o s y m p t o m s o f p a in .I n t h i s r e s p e c t , i t m i g h t b e a d d e d t h a t b y f a r t h e m o s t c a s e s o f t e n l p o r o m a n d i b u l a rj o i n t " d i s o r d e r s " a r e q u i t e s i m i la r t o th o s e w h i c h m i g h t o c c u r i n o t h e r j o i n t so f t h e b o d y .= -2 ' N o f a l la c i o u s c o n c e p t s w h i c h h a v e b e e n a d v a n c e d i n t h e p a s ts h o u l d b e a l l o w e d t o c o n c e a l t h i s f a c t. O n c e s t a r t e d , f u n c t i o n a l d is t u r b a n c e s a r ev e r y li k e l y t o i n t r u d e u p o n n e i g h b o r i n g r e g i o n s o n a n i n c r e a s i n g s c a le .

T h u s , d i r e c t c o n t a c t b e tw e e n t h e o c c lu s al p a t t e r n o f d e n t u r e s s e t u p p r o b -l em s , a n d o n l y t h r o u g h c o r r e c t r e g i s t ra t i o n s m a y s u c h p r o b l e m s b e s o lv e d s a ti s-f a c t o r i ly . D u r i n g o c c l u s io n , t h e s p a c e i n w h i c h t h e c o n d y l e s c a n m o v e is v e r yn a r r o w a n d c o m p r i s e s o n l y a m i n o r p a r t o f t h e to t a l m o v e m e n t p a t t e r n . T h i sl i m i t e d m o v e m e n t s p a c e in c l u d e s , in a ll p a t ie n t s , t h e m o s t r e t r u d e d p o s i t i o n o f t h ec o n d y l e s . I t is o f g r e a t e s t i m p o r t a n c e , h o w e v e r , t o b e a r i n m i n d t h a t t h i s r e -

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Volume7 REFLEXES~ REGISTRAT IONS, AND PROSTH ETIC THERA PY 3 4 9Number 3t r u d e d p o s i t i o n o f t h e m a n d i b l e d o e s n o t c o i n c i d e w i t h m a x i m a l i n t e r c u s p a t i o n i lla l l p e r s o n s . I n fa c t , t h e t w o p o s i ti o n s a r e n o t i d e n t ic a l i n m o s t c as e s. W h e nd i a g n o s e d , t h i s p h e n o m e n o n p e r s e d o e s n o t c a ll f o r th e r a p e u t i c m e a s u r e s .

P o s s e l t TM f o u n d t h a t m a x i m a l i n t e r c u s p a t i o n c o i n c i d e d w i t h t h e m o s t r e -t r u d e d b o r d e r p o s i t i o n o f t h e m a n d i b l e i n o n l y 1 2 p e r c e n t o f h i s p a ti e n t s . Av e r y s i m i l ar o p i n io n is h e l d b y M o y e r s . ~ A l t h o u g h t h e m o s t f r e q u e n t m o v e m e n t s o ft h e m a n d i b l e d u r i n g o c c l u s al c o n t a c t ( i n m o s t p e o p l e ) t h u s d o n o t o c c u r w i t h t h ec o n d y l e s i n t h e i r m o s t r e t r u d e d p o s i t i o n , c o n d y l a r m o v e m e n t s w i l l n e v e r t h e l e s st a k e p l a c e i n t h e i m m e d i a t e v i c i n i t y o f t h i s p o s i t io n . B e c a u s e w e a r e a b l e tor e c o r d t h i s r e t r u d e d p o s i t i o n o f t h e c o n d y l e s , w e s h a l l c o u n t o u r s e l v e s f o r t u n a t e ,a n d w e s h a ll a v a il o u r s e l v e s c o n s i s t e n t l y o f t h i s o p p o r t u n i t y a n d u s e o u r r e g i s t r a -t i o n s a s a b a s e o f o p e r a t i o n , f r o m w h i c h w e p l a n a n d c o n s t r u c t t h e o c c l u s a l p a t -t e r n o f d e n tu r e s .

S e v e r a l m e t h o d s h a v e b e e n d e v is e d a n d r e c o m m e n d e d t o e n s u r e c o r r e c t r e g i s-t r a t i o n o f c e n t r i c r e l a ti o n , a n d t h e y h a v e a l l b e e n m o r e o r l e s s s e v e r e l y c r it i c iz e d .O n e o f t h e r e a s o n s m a y b e t h a t , s o f a r , t h e p r o b l e m o f r e g i s t r a t i o n h a s b e e nv i e w e d f r o m a p u r e l y m e c h a n i c a l a s p e c t , w h i l e n o a s s e s s m e n t h a s b e e n m a d eo f t h e n e u r o m u s c u l a r c o n d i ti o n s f o r c o r r e c t r e g i st r a ti o n .

Fig . 2 . - -An uppe r occ lus ion r im cons t r uc t ed on an ac ry l i c re s in base . No wax i s p l acedon the pos t e r io r t h i rd . The middle th i rd has wax wi th an occ lusal sur face 6 ram. w ide . Inthe reg ions o f inc i sors and can ines , t he wax i s r emoved to imi t a t e t he inc l ine o f l i ngua l su r facesof teeth.

A c c o r d i n g t o a v a i la b l e d a t a , i t s e e m s s a f e to a s s u m e t h a t t h e m o s t e f fi c ie n tr e g i s t r a ti o n is m a d e w h e n e f fe c t e d t h r o u g h a c t iv e m o v e m e n t s . I f u n d e r t a k e no n t h e b a s is o f p a s s i v e m o v e m e n t s , i .e ., t h e d e n t i s t ' s m o v i n g t h e p a t i e n t ' s m a n d i b l e ,a n d m o d e r a t e p r e s s u r e i s a p p l i e d , r e c e p t o r o r g a n s i n t h e s o f t ti s su e s o f t h e m a n -d i b l e m a y i n i t ia t e a v o i d i n g a c t i o n s o n t h e p a r t o f th e m u s c u l a t u r e , c a u s i n g d i s t u r b -a n c e s t o t h e p r o c e d u r e o f r e g i s tr a t io n . E v e n i f t h e m e t h o d s h o u l d n o t c a u s es u c h a m u s c u l a r r e s p o n s e , t h e m e t h o d i s n o t t o b e r e c o m m e n d e d , a s i t m a y i n v o l v ea lo a d i n g o f t h e l i g a m e n t s o f t h e t e m p o r o m a n d i b u l a r j o i n t c a p s u l e s, w h i c h i s tob e a v o i d e d . H o w e v e r , r e g i s t ra t i o n s p e r f o r m e d b y a c t iv e m o v e m e n t s m a y a l so m e e t

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350 BRILL J. Pros. Den.May, 1957with difficulties. In the muscles of mastication, reflexes can easily be provokedby impulses arising in receptor organs of the oral mucosa. In consequence, occhl-sion rims must have a design that will permit the rims to remain neutral to thereceptor organs of pain in order to avoid a nociceptive reaction of the muscles.(See Fig. 1.) Only such impulses should be elicited which correspond to thoseproduced by well-fitting denturesY For this reason, occlusion rims should beconstructed on bases identical with those of the corresponding dentures. Suchacrylic resin bases are easily made on duplicate casts. Furthermore, tongue spacemust be allowed for in the upper occlusion rim, by cutting away material linguallyin the area in which incisors and canines are to be placed (Fig. 2) . In this way theconditions of contact for the tip of the tongue where numerous receptor organsare concentrated, will be, as far as possible, identical with those of the finisheddenture.

The problem of creating tongue space is primarily a matter of setting teethand shaping dentures in such a way that, as far as possible, only desirable impulsesin the exteroceptor organs belonging to the tongue are elicited. No uncomfortablesensations must be recorded that will interfere with a suitable performance of themovement pattern of the tongue. In order to achieve such a performance, it willsometimes be necessary to give occlusal patterns quite unconventional designs.The dentures shown in Figs. 3, 4, and 5 have proved efficient in accommodating thetongue and at the same time maintaining occlusal balance. Surprisingly enoughthey gave satisfactory chewing ability.

OCCLUSION R I M SThe occluding portion of the upper occlusion rim should be made of wax.

The corresponding part of the lower occlusion rim should be made of a thermo-plastic material shaped so as to form a sharp ridge occlusally. The occlusal sur-faces of the occlusion rims should be adjusted in such a way that only the middlethird of the occlusion rims on the right and left side can come into contact withthe opposing occlusion rim. Enough material is removed in front and at thedistal third of the lower occlusion rim (Fig. 6) that a space of at least 2 ram. iscreated between the occlusion rims in these regions when the middle third of therims occlude. These measures will insure greater stability of the occlusion rimswhen records are made. Thus, undesirable reflexes produced by unstableand ti lting occlusion rims are more easily avoided.

R E G I S T R A T I O N S

W h e n r e g i s t r a t i o n s a r e m a d e , t h e w a x o c c l u d i n g s u r f a c e s o n b o t h s i d e s o f t h eu p p e r o c c l u s i o n r i m a r e h e a t e d a p p r o x i m a t e l y t o l i q u e f a c ti o n t o a d e p t h o f n e a r l y3 r a m . T h e u p p e r a n d l o w e r o c c l u s i o n r i m s a r e t h e n p l a c e d i n t h e m o u t h , a n dt h e p a t i e n t i s d i r e c t e d t o b r i n g t h e o c c l u s i o n r i m s i n t o v e r y l i g h t c o n t a c t . T h ec l o s i n g m o v e m e n t i s t o b e p e r f o r m e d a s a p u r e h i n g e m o v e m e n t , w i t h t h e c o n d y l e si n t h e m o s t a c t i v e l y r e t r u d e d p o s i t i o n . T h r o u g h t h i s p r o c e d u r e , t h e l o w e r o c -c l u s i o n r i m p r e s s e s i n t o t h e u p p e r o c c l u s i o n r i m w i t h o u t a n y r e s i s t a n c e f r o m t h ew a x . T h i s i s d u e t o t h e s o f t n e s s o f t h e w a x a n d t o s h a r p n e s s o f t h e r i d g e o f t h e

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Volume 7 R E F L E X E S , R E G I S T I ~ A T I O N S , A N D P R O S T H E T I C T H E R A P Y 3 5 lNmnber 3low er occlus ion rim wh ich eas i ly penetrates the w ax . I f registrat ions are under-taken in this manner, the re is but s l ight chance of the occlus ion rims al tering theirposi t ion in relat ion to their found ations during the procedure. Care should be

iI

Pig . 3 . - - An upp er den ture w i th an occ lusal pa t t e rn cons i s t ing exc lus ive ly o f can ines and inc i sors .T h e l o w e r d e n t u r e h a s a m o r e c o n v e n t i o n a l o cc l u sal p a t t e r n .

F ig . 4 . - - The den tu res shown in F ig . 3 in cen t r i c occ lus ion.

F ig. 5 . - -Lower den tu res mad e for t he same pe rson . Le f t , The occ lusal pa t t e rn i s o f a conven-t iona l des ign . Ri sh t , The occ lusa l pa t t e rn has a ve ry na r ro w des ign .

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3 5 2 BR IL L J. Pros. Den.May, 1957t a k e n t o h a v e t h e w a x o f t h e u p p e r o c c l u s io n r i m e q u a l l y s o f t o n b o t h s i d e s. I ft h is i s n o t a c c o m p l i s h e d, t h e f ir m e r c o n t a c t o f t h e w a x o n t h e s id e w h e r e t h e w a xi s h a r d e s t m a y s t i m u l a t e e x t r a a c t i v i t y o f t h e m u s c l e s o f t h a t s i d e t o o v e r c o m e th er e s i st a n c e . T h e r e is t h e d a n g e r o f a g r e a t e r d i sp l a c e m e n t o f t h e s u b m u c o s a l t is s u e si n t h e s i d e , w i t h a f i r m e r c o n t a c t w h i c h s u b s e q u e n t l y e n t a i l s a t o o h a r d a n d t o oe a r l y o c c l u sa l c o n t a c t o f t h a t s i d e o f t h e f i n is h e d d e n t u r e ( F i g . 7 ) .

Fig . 6 . - -A lower occ lus ion r im of t he rm oplas t i c ma te r i a l on an ac ry l i c re s in base . On middleth i rd , t he l eve l o f t he rm oplas t i c ma te r i a l i s r a i sed 3 mm. to fo rm a sha rp r idge .

F u r t h e r m o r e , t h e p r o c e d u r e is t o be u n d e r t a k e n i n su c h a w a y t h a t t h e p a t i e n to p e n s h i s m o u t h i m m e d i a t e l y a f t e r c o n t a c t b e t w e e n t h e o c c l u s i o n r i m s h a s b e e ne s ta b l is h e d . T h e u p p e r o c c lu s io n r i m i s t h e n r e m o v e d , a n d t h e i m p r e s si o n s m a d eb y t h e t w o r i d g e s o f t h e l o w e r o c c l u s i o n r i m a r e c h e c k e d . T h e s e i m p r e s s i o n s s h o u l db e a p p r o x i m a t e l y 1 r a m . d e e p a n d 1 i n c h lo n g , s o th a t t h e o c c l u s io n r i m s c a n b ea t t a c h e d t o e a c h o t h e r w i t h g r e a t e s t a c c u r a c y l a t e r o n , t h u s p r e s e r v i n g t h e r e -c o r d e d m a x i l l o m a n d i b u l a r r e la t i o n . I f t h e im p r e s s i o n s a r e f o u n d t o b e s u ff ic i en t ,t h e u p p e r o c c lu s io n ri m i s c o o l ed a n d r e t u r n e d t o t h e p a t ie n t ' s m o u t h . T h i s t i m et h e p a t i e n t i s t o c l o s e s l o w l y , s o i t w i l l b e p o s s i b l e t o m a k e s u r e t h a t t h e m o v e m e n ti s p e r f o r m e d i n a r e t r u d e d p o s i t i o n as i t s h o u l d b e . T h i s i s t h e c a s e i f t h e l o w e ro c c l u s i o n r i m s l ip s u n e q u i v o c a l l y i n t o t h e im p r e s s i o n s . T h e p a t i e n t s h o u l d r e p e a tt h i s m o v e m e n t s e v e r a l t i m e s i n o r d e r t h a t w e m a y b e s u r e t h a t t h e m a n d i b l e h a sr e a l l y b e e n in i t s m o s t r e t r u d e d p o s i t i o n . I f s u c h a p r o c e d u r e i s a d o p t e d , u n s u i t a b l ei m p u l s es o r i g i n a t i n g f r o m t h e r e c e p t o r o r g a n s o f t h e m u c o u s m e m b r a n e s w i ll b er e d u c e d t o a m i n i m u m .

H o w e v e r , m a n y p e o p l e a r e n o t c a p a b l e o f p e r f o r m i n g m o v e m e n t s o f o p e n i n ga n d c l o s i n g a s b o r d e r m o v e m e n t s s p o n t a n e o u s l y , a n d , w i t h o u r p r e s e n t k n o w l e d g e ,t h is m a y b e a c c o u n t e d f o r b y t h e f a c t t h a t a d e f in i te m o v e m e n t p a t t e r n f o r s u c hm o v e m e n t s h a s n o t b e e n e s t a b l is h e d a t a n e a r l i e r s t a g e o f t h e i r l iv e s . B u t n e wm o v e m e n t p a t t e r n s c a n b e e s ta b li sh e d . B y t r a in i n g t h e p a t ie n t , n e w p a t h s a r ep a v e d i n t h e n e r v o u s s y s t e m f o r t h e e s t a b l i s h m e n t o f t h e n e w p a t t e r n o f m o v e m e n t ,a n d , b y b r e a k i n g d o w n a p r e v a i l i n g m o v e m e n t p a t t e r n , a n e w o n e i s m o r e e a s i l ye s t a b li s h e d . T h e p a t i e n t i s i n s t r u c t e d , th e r e f o r e , t o r e l a x t h e m u s c l e s o f t h e j a w ,n e c k , a n d t o n g u e . H e i s t h e n a s k e d t o cl o se s lo w l y a n d l ig h t l y o n t h e d i s t a l p a r to f t h e o c c l u s io n r i m s . A s a r u l e , b y a d e q u a t e r e p e t i t i o n s o f t h i s m o v e m e n t t h ep a t i e n t w i l l s u c c e e d i n p e r f o r m i n g i t s a t i s f a c t o r i l y .

I f v ie w e d f r o m a p u r e l y a n a t o m i c p o i n t o f v i e w , t h e r e w i ll g e n e r a l l y b e aw e l l - d e f in e d d i ff e r e n c e b e t w e e n a r e t r u d e d b o r d e r p o s i t io n d u r i n g o c c l u sa l c o n t a c t

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Volume 7 REFLEXES~ REGISTR,ATIONS, AND PRO STH ETI C THE RAP Y 353Number 3

a n d a p o s i t io n o f m a x i m a l i n t e r c u s p a t i o n i n a p e r s o n w i t h a f u ll n a t u r a l d e n t i t io n .B u t i f v i e w e d f r o m a n e u r o m u s c u l a r a s p e c t , th e r e w i ll b e n o s u c h f u n d a m e n t a ld i f fe r e n c e . N e i t h e r p o s i ti o n i s p r i m a r i l y p r e f e r a b l e t o t h e o t h e r . T h e y a r e j u s tt w o d i f f e r e n t r e s p o n s e s t o t w o d i f f e r e n t s e t s o f i m p u l s e s , a n d , i n m o s t i n d i v i d u a l s ,b o t h s e ts w i l l b e e l ic i te d . C o n s e q u e n t l y , in e d e n t u l o u s p a t i e n t s w h e n i m p u l s e sa r i s e t h a t m o v e t h e m a n d i b l e i n t o a r e t r u d e d p o s i ti o n , t h e o c c l u sa l p a t t e r n o f t h e i rd e n t u r e s m u s t b e s o c o n s t r u c t e d t h a t t h e d e n t u r e s a r e n o t d i s p l a c e d w h e n c o n t a c ti s m a d e i n t h i s p o s i t i o n ( F i g . 7 ) . I n o t h e r w o r d s , w e a r e , f o r t h i s r e a s o n , c o m -p e l le d to m a k e a r e g i s t r a t i o n o f t h e m a n d i b l e i n c e n t r i c r e l a t i o n ( i. e ., i n t h e m o s ta c t i v e l y r e t r u d e d p o s i t i o n o f t h e m a n d i b l e ) . O n t h e b a si s o f t h i s r e g i s t r a t i o n a n dr e g i s t r a t i o n s o f c o n d y l a r p a t h i n c l in a t i o n s , w e s h a l l b e ab l e t o c o n s t r u c t t h e o c c l u s a lp a t t e r n i n s u c h a m a n n e r t h a t , u p o n t h e w h o l e , t h e r e q u i r e m e n t s o f th e r e f l e x e sa r e b e i n g m e t i n t h o s e p a t i e n t s w h o s e c o n d y l e s m o v e i n t h e m o s t r e t r u d e d p o s i t i o nd u r i n g t h e i n it ia l a n d t e r m i n a l p h a s e s o f o c cl u sa l c o n t a c t ( F i g . 8 ) .

I -

I ) \ p i?

Fig. 7. Fig. 8.F ig . 7 . - -Re t r us iv e face t s t end to d i sp l ace the uppe r den tu re in a dorsa l d i rect ion , and thelower den tur e in a f ron ta l d i rec t ion .F ig . 8 . - -Cent r t c occ lus ion in a pe rson where th i s pos i t i on co inc ides w i th een t r i c re l a t ion .No d i sp lac ement s o f e it aher t he ma ndib le o r t he d en tur es w i ll occur .

OCCLUSAL CORRECTIONSA f t e r c u r i n g , i t w i l l o f t e n p r o v e n e c e s s a r y t o m a k e m o d i f ic a t i o n s o f t h e o c -

c l u s a l p a t t e r n b y g r i n d i n g , i n o r d e r t o i n s u r e t h e g r e a t e s t p o s s ib l e h a r m o n y b e -t w e e n t h e o c c l u s a l p a t t e r n a n d th e im p u l s e s i n i ti a t e d b y t h e d e n t u r e s . T h e p r o s -t h e s e s a r e p l a c e d i n th e m o u t h o f t h e p a t i e n t , w h o i s a s k e d t o m a k e q u i c k a n dl ig h t t a p p i n g m o v e m e n t s w i t h p i e c es o f a r t ic u l a t in g p a p e r b e t w e e n t h e t e e t h .C e r t a i n f a c e t s, w h i c h w i ll b e m a r k e d i n t h i s w a y , m u s t b e g r o u n d . O n t h et e e t h o f t h e l o w e r d e n t u r e , a ll m a r k s a r e t o b e g r o u n d e x c e p t th o s e o n t h e t o p o fb u c c a l c u s p s o f t h e p r e m o l a r s a n d m o l a rs . T h e s e a r e t o b e g r o u n d t o o, h o w e v e r ,i f t h e y a r e t h e c a u s e o f e i t h e r t o o h a r d o r t o o e a r l y c o n t a c t. I n t h i s c a s e , t h e ys h o u l d b e g r o u n d u n t i l a b a l a n c e d c e n t r i c o c c l u s io n i s a t t a i n e d , b u t a p a r t f r o mt h i s t h e y s h o u l d b e l e f t u n t o u c h e d .

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354 B R I L L J . P r o s . D e n .M a y , 1957On the teeth of the upper denture, all marks are ground except those re-

corded in the bottom of the fissures of the molars and premolars. These are incontact with the top of the cusps of molars and premolars in the lower denture,and this contact maintains the vertical dimension and at the same time pro-duces a sense of a stable occlusal relationship. All other kinds of contact aresuperfluous for these purposes. Through the removal of these by grinding, thefissures are opened and cusp inclines are flattened. The latter brings about areduction of the tendency of horizontal stress to displace the dentures. There isno need for effort to maintain contact between the lingual cusps of the upper den-ture and the fissures of their opponents, as such contact is unnecessary for themaintenance of the height of the occlusal vertical dimension and balanced occlu-sion in a normal set-up of teeth.

A .

B .

F i g . 9 . - - I f t h e s t o n e i s p l a c e d a t a n a n g l e a s s h o w n i n A , p a r t s w h i c h o u g h t t o b e p r e s e r v e da r e t o o o f t e n r e m o v e d . T h e s t o n e o u g h t t o b e p l a c e d i n t h e p o s i t io n a n d , i f n e c e s s a r y , c h a n g e dt o n e w p o s i t i o n s , a s s h o w n i n B , s o t h a t o n l y m a r k e d s p o t s a r e g r o u n d .

During grinding, the stone must not be placed against the top of a cusp, andthe marks must not be removed by cutting away the cusps. The stone should beplaced only against the facet, or that part of the facet on which the mark is located(Fig. 9). The marking of high spots and their grinding must be repeateduntil the patient has the comfortable feeling that nothing will disturb or impedeocclusal harmony. A Specific point to remember is that, in the patient, there mustnot be any feeling that individual teeth or group of teeth strike each other beforethe occlusal pattern of the upper and lower denture is brought into complete andeven contact in centric occlusion by very light contact.

T H E D I A G N O S I S O F D E F L E C T I V E O C C L U S A L C O N T A C T SThe question remains as to how to make a correct diagnosis of the harmonious

relationship between the movement pattern and the occlusal pattern. The followingprocedure is recommended. Following the first grinding just described, the

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Volume 7 REFL EXES, REGISTR~ATIONS, AND PRO STH ETI C THE RAP Y 355Number 3d e n t u r e s a r e g i v e n t o th e p a t i e n t, w h o is i n s tr u c t e d t o r e t u r n f o r a c h e c k u p t w od a y s l a te r . T o m a k e s u r e o f t h e fi t o f t h e d e n t u r e s , t h e d e n t i s t s h o u l d q u e s t i o nt h e p a t i e n t a b o u t t e n d e r n e s s f e l t i n m a s t i c a t i o n , a n d p a r t i c u l a r l y i n m a n d i b u l a rm o v e m e n t s d u r i n g o c c lu s a l c o n t a c t a t t h is c o n su l ta t io n . F u r t h e r m o r e , t h e p a t i e n ti s a s k e d t o s t a t e h i s s e n s a t i o n s e x p e r i e n c e d i n c o n t a c t , w h e t h e r , w h e n e x e r c i s -i n g a s l ig h t p r e s s u r e i n o c c l u si o n , i n d i v i d u a l g r o u p s o f t e e t h s e e m t o m e e t b e f o r ea t o t a l c o n t a c t i s e s t a b l is h e d a s w h e n b i t i n g m o r e f i r m l y o n t h e d e n t u r e s . F r o mr e p l i e s t o th e s e q u e s ti o n s , i n f e r e n c e s c a n b e d r a w n a s to w h e t h e r t h e d e n t u r e s a r ef i r m l y s e a t e d o n t h e i r f o u n d a t i o n s o r w h e t h e r t h e y a r e s u b j e c t t o d i s p l a c e m e n tb ecau s e o f d e f l e c t i v e o cc l u s a l co n t ac t s . I f t h e l a t t e r i s t h e c a s e , t h e m u co u sm e m b r a n e w i ll p r o b a b l y s u p p ly c o n f i rm a t i v e e v i d e n c e u p o n e x a m i n a t i o n . W h e n ,

Fig . lO . - - P ro t r us iv e face t s t end to d i sp l ace the uppe r den ture in a f ron ta l d i rec t ion and thelower den ture in a .dorsa l d i rec t ion .

u n d e r p r e s s u r e , d e n t u r e s a r e p u s h e d o n t h e i r f o u n d a t i o n , i n f l a m m a t o r y r e a c -t i o n s a r e fr e q u e n t , a n d d e c u b i t a l u lc e r s o f te n re s u l t. I f s u c h d i s t u r b a n c e s a r ee n c o u n t e r e d , t h e c a u s a t i v e f a c t o r w i l l p r o b a b l y b e f o u n d i n t h e o c c l u s a l p a t t e r n ,p r o v i d e d t h e y a r e n o t d u e t o o v e r e x t e n s i o n o f t h e d e n t u r e b o r d e r s o r i n c o n g r u -e n c e s b e t w e e n t h e d e n t u r e b a s e s a n d t h e i r f o u n d a t i o n s . I f n o s u c h d e f e c t c a nb e d e m o n s t r a t e d , o n e m u s t p r o c e e d w i t h g r i n d i n g t h e o c c l us a l s u rf a c e s o f t h et e e th , a n d i t m u s t b e p o i n t e d o u t t h a t b y f a r t h e m o s t f r e q u e n t c a u s e o f i n f la m m a -t o r y r e a c t i o n s i s t o b e f o u n d i n t h e o c c l u s a l p a t t e r n .

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35 6 B R I L L J . P r o s . D e n .May, 1957TESTS FOR ERRORS IN THE OCCLUSAL PATTE RN

I n c e r t a i n c i r c u m s t a n c e s , i t m a y p r o v e d i f fi c u lt t o l o c a t e t h o s e d e f e c t s i n t h eo c c h s a l p a t t e r n w h i c h m a k e th e p a t i e n t c o m p l a i n o f t h e d e n t u r e s . M o r e p a r t i c u -l a r l y t h is w i ll p r o v e d i f f ic u l t w h e n n o s i g n s o f u l c e r s o r h y p e r e m i c a r e a s a r e f o u n d .T h e d e n t u r e s g i v i n g r i se t o i n c o n v e n ie n c e s m a y t h e n b e s u b j e c t e d t o s e v e n t e s tsw h i c h a r e s c h e m a t i c a l l y s e t o u t i n t h e f o l l o w i n g , a t t e n t i o n b e i n g p a i d t o w h i c ho f t h e te s t s e li c it p a i n f u l s e n s a t io n s . T h e t e s t s a r e d e s c r i b e d i n r e s p e c t t o al o w e r d e n t u r e , b u t t h e s a m e p r i n c i p l e s a p p l y t o u p p e r d e n t u r e s a s w e l l. T h et e s t s a r e u n d e r t a k e n w i t h t h e d e n t u r e p l a c e d o n i t s f o u n d a t i o n , a n d a f o r e f i n g e ri s p l a c e d o n t h e f i r s t m o l a r a n d s e c o n d p r e m o l a r i n r i g h t a n d l e f t s i d e , r e s p e c t i v e l y .

T e s t 1 . W i t h o n e ' s fo r e f in g e r s , t h e d e n t u r e is p r e s s e d d ir e c t ly d o w n o n th em u c o u s m e m b r a n e . I f p a i n re s u lt s, t h e d e n t u r e is r e m o v e d a n d e x a m i n e d f o ra c r y l i c r e s i n b e a d s o r s h a r p e d g e s , e tc . , w h i c h m u s t b e r e m o v e d .T e s t 2 . T h e d e n t u r e i s d i sp l a ce d b y th e f o r e f in g e r s o n i ts f o u n d a t i o n in af r o n t a l d i r e c ti o n , s im i l a r to a m o v e m e n t w h i c h m a y b e d u e t o t o o e a r l y o r t o o h a r d ac o n t a c t o n r e t r u s i v e fa c e t s ( F i g . 7 ) .

T e s t 3 . T h e d e n t u r e i s d i s p l ac e d in a l ik e m a n n e r , b u t i n a d o r s a l d i re c t i o n .A s i m i la r m o v e m e n t m a y b e c a u s e d b y t o o h a r d a c o n t a c t o n p r o t r u s i v e f a c e ts ( F i g .1 0 ) .

Fig . l l . - - Work i ng and ba lan c ing face t s d i sp l ac ing a lower den ture . A s i tua t ion l i ke th i smay a r i se fo r seve r a l r easons : (1 ) a t oo heavy one -s ided contac t on the occ lus ion r ims , (2 ) an o c i c e p t i v e r e f le x o c c u r r i n g i n t h e m a n d i b u l a r m u sc u l a t u r e w h e n t h e r e g i st r a ti o n g , a r e m a d e , ( 3 )f a u l t y c u r i n g of t h e d e n t u r e s , a n d ( 4 ) a d i sp l a c e m e n t of o n e o r b o t h o c cl u s i on r i m s w ~ e n t h er e g i s t r a t i o n s a r e m a d e .

T e s t 4 . T h e d e n t u r e i s d i s p l a c e d l a t e r a l ly to t h e l e f t s i de o f t h e p a t ie n t , c o r -r e s p o n d i n g t o t o o e a r l y o r t o o h a r d a c o n t a c t o n b a l a n c i n g f a c e t s in t h e l e f t si d e,a n d / o r w o r k i n g f a c e ts i n t h e r i g h t s id e o f t h e p a t i e n t ( F i g . 1 1 ) .

T e s t 5 . T h e d e n t u r e i s d i s p l a c e d l a t e r a l ly t o w a r d t h e ri g h t s id e o f t h e p a t ie n t ,s i m i la r t o a m o v e m e n t c a u s e d b y t o o e a r l y o r t o o h a r d a c o n t a c t o n b a l a n c i n g f a c e tsi n t h e r i g h t s id e , a n d / o r w o r k i n g f a c e t s i n t h e l e f t s i d e o f t h e p a t i e n t .

T e s t 6 . T h e d e n t u r e is r o t a t e d o n i ts f o u n d a t i o n t o w a r d t h e ri g h t s id e o ft h e p a t i e n t . A s i m i l a r d i s p l a c e m e n t d u r i n g o c c l u s io n m a y b e d u e t o to o e a r l y o rt o o h a r d a c o n t a c t o n r e t r u s i v e f a c e ts in t h e l e f t s i de a n d / o r p r o t r u s i v e f a c e t s i n t h er i g h t s i d e .

T e s t 7 . T h e d e n t u r e is r o t a t e d t o w a r d t h e l e ft s id e o f t h e p a t ie n t . A s i m i l a rd i s p l a c e m e n t m a y b e c a u se d b y t o o e a r l y o r t o o h a r d a c o n t a c t o n p r o t r u s i v e f a ce t si n th e l e f t si d e a n d / o r r e t r u s i v e f a c e t s in t h e r i g h t s i d e .

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, 3 5 8 B R I L L J . P r o s. D e n .M a y , 1 9 5 7

the lower denture in a frontal direction (Fig. 7). However, the dentures willtend to be displaced in the opposite direction because protrusive facets, primarily,will be loaded dur ing occlusion (Fig. 10). Consequently, there is a need to re-lieve these latter facets, and this is done by grinding points of contact marked duringtapping movements in the manner described above. In this group of patients, it isthose marks left on protrusive facets to which special attention should be paid.Such a marking of contacting surfaces actually means a regis t ra t ion o f the reg ionsin wh ich t he p reva i l i ng ac t i v i t y o f t he movemen t pa t t e rn comes i n to p lay , and byadequate gr inding of these spots a harmonious relationship is established betweenthe movement pattern and the occlusal pattern (Fig 12).

F i g . 1 2 . - - A n o c c l u s a l p a t t e r n a l l o w i n g p r o t r u d e d , a s w e l l a s r e t r u d e d , m o v e m e n t s t o b ep e r f o r m e d w i t h o u t d i s p l a c e m e n t o f d e n t u r e s , I n t h e d r a w i n g , t h e g r o u n d o c c l u s a l f ie ld s h a v eb e e n o v e r a c e e n t u a t e d t o b r i n g o u t a m o r e d i s t i n c t p i c t u r e o f t h e p r o b l e m ,

In both groups of patients under discussion, any further grinding will beunnecessary at the moment harmony is brought about between the occlusal patternand t he move me n t s w h ich a re p rovoke d and deve loped by t he occlusal pa t t e rn .The criterion for this must be that no displacements of the dentures are caused.However, this is not easily ascertained merely by watching the dentures while thepatient occludes, as the resiliency of the mucosa and submucosa may conceal ratherextensive displacements of the dentures. After the last performed grinding, thepatient must be instructed to return for a checkup a week later. If, at this con-sultation, the patient is able to state that he has not suffered pain, tenderness,or similar discomforts while using his dentures, and if, at the same time, by ex-amination of the denture foundations no signs of pathologic changes are found,there is justification for believing that the harmonious relationship required be-tween the shape of the dentures, in its widest sense, and the movement patternhas been established.

The patient is advised to return at least once or twice after the last time patho-logic changes in the mucous membrane are observed.

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Volume7 REFLEXES, REGISTR,ATIONS~ AND PROSTHETIC THERAPY 359Number 3P a t i e n t s sh o w i n g s y m p t o m s o f b r u x i s m r e q u i re a d d it i o na l g r i n d i n g . S u c h

p a t i e n t s a r e r e q u e s t e d t o m a k e m o r e e x t e n d e d e x c u r s i o n s , e s p e c ia l ly i n l at e r ald i r ec t io n s , d u r i n g t h e m a r k i n g p r o c e d u r e , a n d t h o s e s p o t s a re g r o u n d w h i c ho t h e r w i s e w o u l d h a v e i m p e d e d o r p r e v e n t e d a s m o o t h a n d h a r m o n i o u s e x e c u t io no f g l i d in g m o v e m e n t s .

SUMMARY1 . I n a p e r s o n w i t h a f ul l c o m p l e m e n t o f n a t u r a l t e et h , c e n t r i c o c c l u s i o n is

d e t e r m i n e d b y n e u r o m u s c u l a r , " n e u r o a r t i c u l a r , " a n d " n e u r o p e r i o d o n t a l " f u n c ti o n .2 . C e n t r ic r e l a t io n i s d e t e r m i n e d b y n e u r o m u s c u l a r a n d " n e u r o a r t i c u l a r "

f i m c t i o n .3 . C e n t r i c o c c l u s i o n i n p e r s o n s w i t h c o m p l e t e d e n t u r e s i s d e t e r m i n e d b y n e u r o -

n m s c u l a r , " n e u r o a r t i c u l a r , " a n d " n e u r o m u c o s a l " f u n ct io n .4 . O c c l u s a l p a t t e r n s o f ar t if i c ia l t e e t h s h o u l d b e g i v e n a f o r m t h a t w i l l c o n -

t r i b u t e t o t h e p s y c h o l o g i c a n d f u n c t i o n a l a d a p t a t i o n t o t h e d e n t u r e s .5 . C e n t r i c r e l a t i o n s h o u l d b e r e c o r d e d a s a m e a n s t o e s ta b l is h c e n t r i c o c c l u s i o n

i n c o m p l e t e d e n t u r e s .6 . I f n e c e s s a r y , t h e o c c l u sa l p a t t e r n o f c o m p l e t e d e n t u r e s s h o u l d b e r e -

m o d e l e d b y g r i n d i n g u n t il o p t im a l n e u r o m u s c u l a r , " n e u r o a r t i c u l a r , " a n d " n e u r o -n m c o s a l " f u n c t i o n i s a t t a i n e d .

The works ment ioned in the a r t ic le and the fo l lowing textbooks of ana tomy and phys io logyby Benninghoff, ~s Bro ma nn and H jor tsj6 , ~ yo n Eu ler, 8 Fulton, 31 Gellhorn, ~ La ngle y andC h e ra sk i n y Lundsga a rd , u Ma c Leod , ~ Orba n , ~ a nd R a nson a nd C l a rk y p rov ide t he ba si sfor the theore tica l pa r t o f th i s a r t ic le to which must be added lec tures by D r . A . M #thave onneuromuscula r func t ion .Th e pa r t concerned wi th prac t ica l measures res t s on lec tures and dem onst ra t ions oncomple te denture cons t ruc t ion by Profes sor W . K rogh -Po ulsen and c l in ica l exper iences f romthe Depar tment of Pros the t ic Dent i s t ry .

REFERENCES1. S icher, H . : Pos i t ions and Movements of the Mandible, J .A.D.A . 48:620-625, 1954.2 . Le wi nsky , W . , a nd S t e wa r t, D . : The Inne rva t ion o f the P e r i odon t al M e mbra ne o f t heC a t, W i t h S ome Obse rva ti ons on t he F unc t ion o f the E nd-O rga ns i n Tha t S t ruc tu re ,J . A na t . 7 1: 232-235, 1937.3 . Denn y-Bro wn , D. , and Pennybacker , J. B . : F ibr i l la t ion and Fasc lcula t ion in Vo lunta ryMuscle , Brain 61:311-334, 1938.4 . Jackson, J . H. : Neu rologica l Fragm ents , London, 1925, O xfo rd Un ivers i ty Press .5 . Car ls66, S . : Nerv ous Coordina t ion and Mechanica l Fun c t ion of the Mandibula r Eleva tors ,A cta odont , seandinav. 1 0 : Suppl . 11, 1952.6 . Greenf ie ld , B . E. , and W yke , B. D. : Elec t rom yograp hic S tudies of Some of the M usc lesof Masticat ion, Bri t . Dent . J . 100:129 -143 , 1956.7. GSpfert , H., and G6pfert , C.: Fun ktionelle Beziehungen zwischen Masseter - und Tem -pora l i s -Mu skula tur in de r Dars te l lung ihre r Akt ionss t r6me . Deut . Zahnfirz tl . Zschr .10:1530-1541 and 1851-1861, 1955.8 . Mo yers , R . E. : An Elec tom yogra phic Ana lys i s of Cer ta in Musc les Invo lved in theTem porom andibula r Movements , Am . J . Orthodont ics 36:481-515, 1950.9 . Pe rr y , H. T. , and Harr i s , S . C . : Role of the Neurom uscula r Sys tem in Func t iona l Ac-t ivi ty of the M andible , J .A .D .A. 48:665-673, 1954.10. Sherr ington, C . S . : Se lec ted W ri t ings of S i r Char les Sherr ington, London, 1939, Ham ishHa mi l t on .11. Corbin , K. B., and Harr i son , F . : Func t ion of Mesencephal lc Ro ot of F i f th Crania l N erve ,J . Neurophysiol . 3:423-435, 1940.

12. Corbin, K. B. : Observa t ions on the Per iph era l D is t ribut ion of F ibe rs Aris ing in theMesencephalic N ucleus of the Fifth C ranial Ne rve, J . Comp. Neur ol . 73:153-177,1940.

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360 t l R I L L J . P r o s . D e n .Ma y, 195713. P os se l t , U . : S tud i e s i n t he M o b i i l t y o f the H u m a n M a nd ib l e , A c ta odon t , s c a nd inav .10:Suppl . 10 , 1952.14. B a l l a r d , C . F . : A C ons ide r a t i on o f t he P h ys io log ic a l B a c kg r ound o f M a nd ibu la r P os tu r ea nd M ove m e n t , D . P r a c t i t i one r 6 :80 - 89 , 1955 .15. K e e ne , M . F . L ., a nd H e w e r , E . E . : S om e O bse r va t ions on M ye l ina t ion i n the H unm nC e n t r a l N e r v ous S ys t e m , J . A na t . 66 :1 - 13 , 1932 .16. E sc h le r , J . : K ie f e r h6h le npe r f o r a t i on na c h E x t r a k t i on und K a u t~ it i gkei t , D e u t . Z a hn -~irztl . Zschr . 10:489-493, 1955.17. W a l sh , J. P . : N e u r ophys io log ic a l A spe c t s o f M a s t i c a t i on , D . J . A u s t r a l i a 23 :49 - 62 , 1951 .18. Lash ley , K. S . : M ass Ac t io n in Cer ebra l Func t io n , Sc ience 73:245-254, 1931.19. G 6 pf e r t , C . : E inw i r kun g yon Z a hnsc hm e r z und yon S c hm e r z r e i z e n de r G e s i c h t sha u t a u fre f lek tor isch en Ton us de r Kau mu sku la tur , Deu t . Zahn~irzt l. Zschr . 11:76-86 , 1956.20 . T h ie l e m a nn , K . : B iom e c ha n ik de r P a r a de n to se , L e ipz ig , 1938 , H e r m a nn M e usse r .21 . G r e w c oc k , R . J. G ., a nd B a l l a r d , F . C . : T h e C l in i c a l A spe c t s a nd P hys io log ic a l M e c ha n -i sm o f A b nor m a l P a th s o f C losu re . T r . E u r op e a n O r tho don t i c S oc . pp . 3 - 35 , 1954 .22 . S c hw a r t z , L . L . : E th y l C h lo r ide T r e a tm e n t o f L im i t e d , P a in f u l M a n d ibu la r M ove m e n t ,J .A.D.A. 48:497-507, 1954.2 3. S i c h e r , H . : S t r u c t u r a l a n d F u n c t i o n a l B a s i s f o r D i s o r d e r s o f t h e T e m p o r o m a n d i b u l a rA r t i c u l a t i on , J . O r a l S u r g . 13 :275 - 279 , 1955 .24 . Va ugh an, H. C . : Tem por om and ibu la r Jo in t Pa in , J . PROS. DES. 4 :694-708, 1954.25 . M oye r s , R . E . : S om e P hys io log ic C ons ide r a t i ons o f C e n t r i c a nd O the r J a w R e la t i ons ,J . PROS. DEN. 6 :18 3-194 , 1956:26. B r e w e r , A . A . : P e r son a l C om m unic a tion , 1951.27 . A r s t a d , T . : T h e A br a de d D e n t i t i on , N o r ske T a nn la e ge f o r e n . T id . 66 :51 - 66 , 1956 .28 . B e nn ingho f f, A . : L e h r buc h de r A na tom ie de s M e nsc he n , F f in f t e A uf l a ge , M i inc he n - B e r l in ,1954, U r ba n & S c hw a r z e nb e r g .29 . B r om a nn , I . , a nd H jo r t s j / 5 , C . - - H . : M i inn i ska ns r /S re l s ea ppa r a t, L und , 1952 , C . W . K .G t e e r u p s F 6 r l a g .30. yo n E u le r , U . S . : K o r t f a t t a d 6ve r s ik t a v m ~ inn iska ns f y s io log i , T r e d j e upp la ga n , S toc k -h o lm , 1 95 3, W a h l s t r 6 m & W i d s t r a n d .31 . F u l ton , J . F . : T e x tboo k o f P hys io logy , e d . 17, P h i l a de lph ia , 1955, W . B . S a u nde r s C om -pa ny .32 . G e l lho r n , E . : P hys io log i c a l F ound a t ions o f N e u r o logy a nd P syc h ia t r y , M inne a po l is , 1953,U n i v e r s i t y o f M i n n e s o t a P r e s s .33. L a ng le y , L . L ., a nd C he r a sk in , E . : T h e P hys io log ic a l F oun da t ion o f D e n ta l P r a c t i c e , S t .L ou i s , 1951 , T he C . V . M osby C om pa ny .34 . L und sga a r d , E . : L a e r e b og i f y s io log i, F e m te udgave , K jC be nha vn , 1953 , N y t N or d i s kF o r l a g A r n o l d B u s c k.3 5. M a c L e o d , J . . l . R . : P h y s i o l o g y i n M o d e r n M e d i ci n e, L o n d o n , 1 93 5, H e n r y K i m p t o n .36. O r ba n , B . : O r a l H i s to log y a nd E m b r yo log y , e d . 3 , S t . L ou i s, 1953, T h e C . V . M o sbyC o m p a n y .37 . R a nson , S . W . , a nd C la r k , S . L . : T h e A na tom y o f t he N e r vous S ys t e m , P h i l a de lph ia ,1955, W . B . S a unde r s C om pa ny .

UNIVERSITETSPARKEN 4,COPEN IIAGEN, DENM ARK.