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Centric Occlusion and Centric Relation: Balkwill’s and Gysi’s arches
Centric Occlusion and Centric Relation: Balkwill’s and Gysi’s arches
Pedro S a iza r* D.D.S., Buenos Aires, Argentina
T he extraoral graphic and the wax bite impression m ethods have been used to record the jaw m ovem ents o f people with normal o r nearly normal teeth. In six subjects, whose gnathograms were ob tained with the extraoral m ethod, the p o sition of maximal intercuspation was centric occlusion. Balkwill’s and Gysi’s arches and the contacting retrusive m ove m ent, Ferrein’s m ovem ent, also were reg istered. Results confirm the conclusions drawn previously in a study of 12 persons.
T h e retrusive ja w movements o f people with normal or almost normal teeth have been studied and were recorded using the extraoral graphic and the wax bite im pression methods. This report describes the extraoral graphic m ethod employed for six subjects. In addition, it refers to investigations o f this m ethod used in 12 subjects w hich were reported previously.1 M A T E R IA L S A N D M E T H O D S
For easier understanding o f the necessary jaw movements, the study was performed
principally with dentists (nine) and den tal students (s ix ). T h e other three persons concerned were members o f my family. T h e group was com posed o f nine men and nine wom en whose ages ranged from 21 to 50 years. W ith the exception o f the third molars, no m ore than one tooth was missing in any subject. N one had m ore than two restored occlusal surfaces. O ne o f the persons studied had had a serious malocclusion (A ngle I I I ) , which had been treated, and one had been treated for periodontal disease. A ll were able to com ply with the tests required. T o obtain clear records o f voluntary movements, it was necessary to train the subjects. T hey found the retrusive m ove ment the most difficult. T h e follow ing was the technic used: 1. C ohn ’s2 m ethod to make the person “ feel” the retrusive occlusion was accom plished in the follow ing m anner: (a) the patient was asked to open his m outh; (b ) the dentist, holding the patient’s chin between his index finger and thumb, as sisted in loosening the ja w muscles by m oving the patient’s mandible up and down until no resistance was felt; (c) the
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F ig. I • G n a t h o g r a p h p re p a re d fo r a n te rio r ex t ra o ra l sa g itta l re gistra tio n . U p p e r level o f sm o ke d g la ss m ust b e p aralle l w ith F ra n k fo rt's p la n e
dentist next moved the jaw gradually up ward and backward using a slight upward and downward movement until retrusive occlusion was obtained; (d) the patient was asked to feel what teeth touched in that position. 2. Once the retrusive position has been “ felt,” it is easy to teach the subject to find it on his own and effect the centrip etal retrusive movement; that is, make him open his mouth, put his jaw back ward and close with the jaw in retrusion (posterior hinge movement) until retru sive occlusion is reached, and then slide the jaw, gliding the lower teeth along the upper teeth, until centric occlusion is reached. 3. The subject was taught centrifugal retrusion, from centric occlusion to ter minal retrusive position.
and, in accordance with Posselt’s nomen clature,3 adopt any border or intraborder mandibular position. In Hanau’ s nomen clature,4 they could explore their respec tive “ bicuspoids.” Results were obtained with the aid of extraoral gnathographs (Fig. I, 2) regis tering definite voluntary, unforced con tact or noncontact movements performed in the proximity of centric occlusion and terminal retrusive positions, with the mouth empty except for the intraoral part of the gnathographs which occupied the vestibule and did not interfere with occlusion. The movements were performed as often as necessary to obtain clear, com plete and reproducible gnathograms on smoked glass. These were fixed, and di rect photographic copies made. The first 12 subjects, whose registrations have been published before,1 were tested again, and the second registrations were similar to the first ones. Since the six new subjects provided evidence of the same kind, the gnathograms of the first 12 subjects are not included in this report. The move ments registered are given on two to four smoked glasses: part I has two vertical, anterior gnathograms; part II has four “ horizontal” ones which are also anterior registrations. Paracondylar vertical gnath ograms, parts III and IV , of some sub jects are shown also.
4. Then, lateral and protrusive con tact movements were taught. Once these points had been learned— for some it took several sessions— all were able to close their mouths voluntarily in centric occlusion or in retrusive occlusion with the mandible in the posterior posi tion, go through the retrusive positions both ways, execute extreme protrusion, open the mouth with the mandible in protrusion and perform lateral move ments. They could carry out every movement
Fig. 2 • G n a t h o g r a p h h orizon ta l re gistra tio n
p re p a re d
fo r
extraoral
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Fig. 3 • S n a t h o g r a m s o f su b je c t 13, 23 y e a r old w o m a n . I: S a g it t a l plane. R, tra c in g o f isolate d retru sive m o v e m e n t; A O C P , tra c in g of h in g e axis clo sin g plus retru sive m o v e m e n t a n d p ro tru sio n ; O C in d ic a te s c e n tric o c clu sio n p osition . II. H o r i zonta l plane. R, tra c in g o f isolate d retru sive m o v e m e n t; B, B alkw ill's a rch ; G , G y s i's arch. Left g n a t h o g ra m sho w s b oth G o t h ic arch e s re g iste re d w ith ou t c h a n g in g p o sitio n o f sm o ke d g la ss in g n a t h o g r a p h . Ill a n d IV : V e rtic a l p a r a c o n d y la r rig h t a n d left. R, tra c in g s o f iso la te d retrusive m o v e m e n ts; P, t ra c in g s o f isolate d p ro tru siv e m o v e m e n ts; R -|- P, t ra c in g s o f retru sive p lus p r o tru sive m ove m e n ts
R ESU LTS
With the use of gnathographs suitable for horizontal registrations (Fig. 2 ), the re trusive movement was registered as an anteroposterior tracing. All the subjects investigated were capable of registering well-defined retrusive movement (R , part II, Fig. 3 -8 ), completely different from that of a closing retrusion, which does not register if the needle is positioned ade quately, as was shown by Arstad,5 Le Pera6 and Villa.7 As shown previously,1 all were capable of tracing two Gothic arches: one by us ing movements starting from, or reaching,
13 f . t , / ¿ t r z
t
r
centric occlusal position; another using movements that started or arrived at ter minal retrusive occlusal position (B and G, part II, Fig. 3-8). Part II of Figures 3-8 show the two Gothic arches registered without chang ing the position of the smoked glass in the gnathograph. When the needle was fixed to the lower jaw, as in Sears’ trivet, arrow-point gnathograms were obtained (Fig. 9 ). With the use o f a gnathograph capable of registering movements in the sagittal plane (Fig. 1), it was observed that the retrusive movement takes the mandible backward and downward (R , part I, Fig. 3 -8 ), which confirms the investigations by Posselt.8 This shows, therefore, that both Gothic arches or arrow-points are formed at different levels (Fig. 10).
F ig . 4 • G n a t h o g r a m s o f su b je c t 14, 4 5 y e a r old m an. I: S a g it t a l p lane. R, t ra c in g o f iso la te d re tru sive m o v e m e n t; A O C P , tra c in g o f h in g e axis c lo s in g plu s re tru sive m o v e m e n t a n d p ro tru sio n . O C in d ic a te s ce n tric o c c lu sio n p osition . II. H o r i zon ta l p lan e. R, t ra c in g o f iso la te d retrusive m o v e m e n t; A B , Balkw ill’s a rch ; A G , G y s i's arch. Left g n a t h o g r a m show s b o th G o t h ic a rch e s r e g is te re d w ith o u t c h a n g in g p o sitio n o f sm o ke d gla ss in g n a t h o g r a p h . Ill a n d IV : V e rtic a l p a r a c o n d y la r rig h t a n d left. R, t ra c in g s o f iso la te d retrusive m o v e m e n ts; P, t ra c in g s o f iso la te d p ro tru siv e m o v e m e n ts; R —f- P, t ra c in g s o f retru sive plu s p r o tru sive m o v e m e n ts
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Fig. 5 • G n a t h o g r a m s o f su b je c t 15, 24 year o ld w o m a n . I: S a g it ta l p la n e. R, t ra c in g o f is o lated re tru sive m ov e m e n t; A O C P , tra c in g o f h in g e axis c lo s in g plu s retru sive m o v e m e n t and p ro tru sio n . O C in d ic a te s c e n tric o c c lu sio n p o s i tion. II: H o riz o n ta l plane. R, t ra c in g o f isola te d retrusive m ov e m e n t; A B , Balkw lll's a rch ; A G , G y s i's arch. Left g n a t h o g r a m show s b o th G o t h ic a rch e s re g iste re d w ith o u t c h a n g in g p o sitio n of sm o ke d gla ss in g n a t h o g ra p h . Ill a n d IV : V e rtic a l p a r a c o n d y la r r ig h t a n d left. R, t ra c in g s o f isola te d retru sive m o v e m e n ts; P, t ra c in g s o f isola te d p r o tru sive m o v e m e n ts; R + P, t ra c in g s o f retrusive, plus p ro tru siv e m ove m e n ts
This disposition was true in all subjects, as shown in part I, Figures 3-8, in which there are two vertical gnathograms of each of the six subjects. In these, R repre sents the isolated retrusive movement; A O C P is the tracing of a retrusion, or hinge-axis closure, the retrusive move ment, and of protrusion. IN T E R P R E T A T IO N A N D D IS C U S S IO N
M axim um Intercuspation ' The gnatho
grams all show that centric occlusion is a definite position, just a “ point” from which “ pure” movements start: lateral, anterior and posterior, all of them repro ducible. Vertical gnathograms show also that this is the major intercuspation position, a characteristic which defines centric oc clusion at least as well as that of provid ing the maximum number of contact points, which is the best known charac teristic.
Posselt’s T w o Gothic A rches • The two
Gothic arches can be seen in the solid bicuspoids constructed by Posselt,9 a proof of the exactness of the plastic method used by him and the graphic method em ployed here. Posselt did not indicate their historic meaning (see section on Balkwill’s arch and Gysi’s a rch ). Norm al Retrusive M ovem en t ' The 18
subjects with normal or nearly normal teeth, investigated by the graphic method, had 100 per cent voluntary retrusive movement and can be added to the other normal or nearly normal subjects investi gated by other methods by Ferrein,12 Hildebrand,13 Heath,14 Bjork,15 Posselt,3,8 Arstad,5 Schwartz16 and Kydd and San der.17 Positive proof substantiates this demon stration so that there is no doubt that the normal mandible has retrusive possibility, that normal centric occlusion is not a border position and that, when normal
Fig. 6 • G n a t h o g r a m s o f su b je c t 16, 21 y e a r old w om an. I: S a g it ta l p lane. R, tra c in g o f isola te d re tru sive m o v e m e n t; A O C P , t ra c in g o f h in g e axis c lo sin g plus re tru sive m o v e m e n t a n d p ro tru sio n. O C in d ic a te s c e n tric o c c lu sio n p ositio n . II: H o r i zontal plane. R, t ra c in g o f iso la te d retru sive m o v e m e n t: B, Balkw ill's a rc h : G , G y s i's arch. Left g n a t h o g ra m sho w s b o th G o t h ic a rch e s re g iste re d w ith ou t c h a n g in g p o sitio n o f sm o ke d gla ss in g n a t h o g ra p h
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Fig. 7 * G n a t h o g r a m s o f su b je c t 17, 2 4 y e a r old w o m an . I: S a g it ta l plane. R, tra c in g of isola te d retrusive m o v e m e n t; A O C P , t ra c in g o f h in g e axis c lo s in g plu s re tru sive m o v e m e n t a n d p ro tru sio n. O C in d ic a te s c e n tric o c c lu sio n p osition . II: H o r i zon ta l p lan e. R, t ra c in g o f iso la te d retrusive m o v e m en t; B, Balkw ill's a rch ; G , G y s i's arch. Left g n a t h o g ra m show s b oth G o t h ic a rch e s re g iste re d w ith ou t c h a n g in g p o sitio n o f sm o ke d g la ss in g n a th o q r a p h
dental arches are in centric occlusion, the condyles are not in centric relation. This last statement has been corrobo rated by me several times by means of direct paracondylar registrations (parts III and IV, Fig. 3 -5), which show the isolated tracing (R ) produced by the con dylar retrusive movement from the posi tion occupied when the teeth are in centric occlusion. These illustrations show that the slant o f the condylar retrusion sometimes makes a definite angle with the slant of the condylar protrusion. Balkwill’s Arch and Gysi’s Arch • The centric occlusion Gothic arch is the one so ingeniously foreseen by Balkwill18 when he pointed out the right and left lateral tracks corresponding to each functioning lower cuspid. Apparently, this arch was registered di rectly for the first time by Hesse19 and is undoubtedly the same as that registered by M cCollum 20 during his investigations on normal teeth. The vertex of the retrusive Gothic arch, on the other hand, indicates “ the most retruded relation of the mandible to the maxilla [in occlusal contact] from which the patient can make lateral jaw movements;” 21 that is, it indicates the occlusal position in centric relation or centric relation at the level determined by occlusal contact. Therefore, it is equiv alent to the “ Gothic arch” registered in patients without teeth or the “ Gothic arch” registered in this type of patient for the first time by Gysi22 and incor
porated by him into diagnostic technics and prosthetic restorations. It served also as a test and a basis for his theories on mandibular kinematics. Gysi’s Mistake ' Examination o f Figures 13, 14 and 16 in Gysi’ s paper22 shows the origin of a basic error which up to now has influenced the ideas of dentists on mandibular kinematics and prosthesis. Gysi applied the tracing obtained from an edentulous mandible to one with teeth, since he believed that the gnathogram of centric relation possessed exactly the same significance as the centric occlusion regis tration. This can be seen in his later work also.23,24 It is easy to understand this mistake. Gysi proved experimentally the correct ness o f a prosthesis constructed when cen tric occlusion coincides with centric rela tion,22,24 a finding prosthodontists have confirmed for more than 50 years. In addi tion, Gysi compared the Gothic arch de veloped in the edentulous, with a Gothic arch produced in patients with teeth. He proved that the latter registered it simi larly to the former,24 which confirmed his point of view. He could not know that, in the dentate, another similar arch is the only one registered with ease, and that terminal retrusive occlusal position, which he considered anomalous, as did almost all dentists until recently, requires special training for those with natural teeth, and unusual muscular coordination, to be able to register it. He died without knowing that the Gothic arch o f centric relation,
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Fig. 8 • G n a t h o g r a m s o f su b je c t 18, 28 y e a r old m an. I: S a g it t a l p lane. R, t ra c in g o f isola te d re tru sive m o v e m e n t; A O C P , t ra c in g o f h in g e axis c lo s in g plu s retru sive m o v e m e n t a n d p ro tru sio n. O C in d ic a te s c e n tric o c c lu sio n p ositio n . II; H o r i zontal p la n e. R, t ra c in g o f iso la te d retrusive m o v e m e n t; A 8 , Balkw ill's a rc h ; A G , G y s i's arch. L eft g n a t h o g ra m show s b o th G o t h ic a rch e s r e g is te re d w ith o u t c h a n g in g p o sitio n o f sm o ke d gla ss in g n a t h o g r a p h
which was the foundation of his technic, was his discovery. Shape of N orm al Bicuspoid • Figure 11
is a sketch, several times normal size, of the superior region of the bicuspoid or space for unforced movements corre sponding to the lower incisor point, ac cording to the records obtained by the author, which coincide with those ob tained by Posselt.9 In addition, Posselt gave the physiological explanation of the retrusive movement, which confirmed those of Ferrein12 in the past and Posselt,3,9 Sicher20 and Beyron26 more re cently. In Gysi’s gnathogram, the lines AG (Fig. 11), the union of which indicates the terminal retrusive occlusal position, represent the inferior and posterior limit o f possible occlusions; that is, they deter mine the separation between occlusal (contacting) movements and positions forming the superior surface of the bicuspoid and the open (noncontacting) positions and movements. In Balkwill’s gnathogram, AB represents a functional track, a habitual contact movement; its vertex determines centric occlusion, which is probably the most frequent contacting position. In the 18 subjects investigated, neither centric occlusion nor eccentric intercuspal occlusions are border positions. Retrusive M ovem en t and Its Com posi tion • The tracing O C -R G (Fig. 11) rep
resents the contacting retrusive, or Ferrein’s movement. On the other hand, its composition, dimension and direction are open to argument.
Using Frankfort’ s plane (PLFR, Fig. 11) as a guide to orient the head, the true retrusive range is, as Posselt3 pointed out, the distance reached by the lower incisor point in terminal retrusive position (RG ) with respect to the LP line, which is per pendicular to Frankfort’ s plane. Therefore, when the incisor point reaches its terminal retrusive position, RC, the distance to LP is obtained by adding the sum of the retrusion caused by taking the mandible backward, to the lo cal posterior movement produced by opening the mouth. I have called1 the two components slid ing retrusion (condylar or true retrusion) and rotational retrusion (noncondylar or false retrusion). The difference is important since it means that retrusion measured at the level o f the incisors where the two com ponents meet will appear larger than at the level of the condyles where there is only sliding retrusion. Origin of Balkwill’s and, Gysi’s A rches '
In the investigation I made with Aprile,27 as well as in those by Posselt3 and Arstad,5 it was shown that Gysi’s gnathogram is produced exclusively by the anatomic ar-
Fig. 9 • H o r iz o n tal a n te rio r g n a t h o g ra m o f su b je c t 15, t ra c e d with n e e d le fixed to low e r jaw. Both a rches, Balkw ill's a n d G y s i's , take fo rm o f a rro w p o in ts o f S e a r s 10 o r
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F ig . 10 • S p a tia l relation o f b o th g n a th o g ra m s (B a lk w ill's a n d G y s i's ) a n d retrusive (F e rr e in 's ) c o n t a c t in g m o v e m e n t is show n. A B , Balkw ill's arch; O C , ce n tric o c clu sio n vertex; R, retru sive c o n ta c t o r F e rre in ’s m ovem en t; R C , ce n tric relatio n o c c lu sion vertex; A G , G y s i's arch
rangement o f the tem porom andibular ar ticulations ; the length o f the sides is deter m ined by the action o f the lateral and capsular ligaments, the accessory liga ments do not intervene. T o register it, it is necessary only that, at some mom ent, the two condyles pass through their most posterior positions during the sliding lat eral mandibular movement. Gysi’s gnathogram is o f tem porom andibular origin. Because o f this, it represents the upper limit o f the border movements and can be registered after removal o f the teeth and at various vertical dimensions. O n the other hand, Balkwill’ s gnathogram represents a contacting path caused
Fig. I I • Ske tch sh o w in g u p p e r p art o f b ic u s p o id o f low er incisal point. P L FR , F ra n k fo rt's plane; O C , ce n tric o c clu sio n p o sitio n ; A B , Balkw ill's a rch ; LIE, extrem e left lateral p o sitio n ; R C , c e n t ric rela tio n p o sitio n ; P, p ro tru siv e m ovem en t; PE, extrem e p ro tru siv e p o sitio n ; L D E , extrem e r ig h t lateral p o sitio n ; Z R , re tru sive zo n e ; A G , G y s i's a rch ; A R , retru sive o r h in g e axis o p e n in g o r c lo s in g ; A H , h a b itu a l o p e n in g o r c lo s in g ; LP, line p e r p e n d ic u la r to the F ra n k fo rt's p la n e ; A L , o p e n in g o r c lo sin g m o v e m e n t in extrem e righ t la tera l p o sitio n ; A P , o p e n in g o r c lo s in g m ove m e n t in extrem e p ro tru sio n ; RP, p o te n tial retrusion; O C - R C , retrusive m o v e m e n t (from S a iza r1)
by the congruence o f centric as well as lateral intercuspation. For this reason, it disappears when there are n o teeth, but it will reappear if the prosthesis allows congruent lateral intercuspation that does not coincide with Gysi’ s gnathogram. Both these gnathograms, therefore, ow e their shape and relation to the anatomic arrangements o f the tem porom andibular joints and the dental arches. T hat they can be registered in the articulator (Fig. 12) constitutes, in my opinion, another conclusive p roof that they do not have a direct dependence on the muscular inser tions or the soft nontemporomandibular tissues. S U M M A R Y A N D C O N C L U S IO N S
T h e gnathograms from six subjects co n firm the conclusions drawn from a previ ous study o f 12 persons.1 T h e gnathograms were obtained from 18 people with norm al or nearly normal teeth, whose voluntary, unstrained, cen tric, and eccentric, m outh empty, m an dibular positions and movements were registered by the extraoral graphic m ethod. In all subjects, the follow ing points were true. 1. Centric occlusion is the position o f maximal intercuspation.
PL. FR.
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3. The contacting retrusive move ment, or Ferrein’s movement, takes the mandible from centric occlusal position to terminal retrusive occlusal position, and the reverse. 4. The contacting lateral movements starting from or arriving at terminal re trusive occlusal position form a Gothic arch or arrow point different from that of Balkwill; this is the gnathogram of F ig. 12 • G n a t h o g r a m s o b t a in e d b y p la c in g the Cysi. g n a t h o g r a p h on the m o d e ls m o u n te d on a rtic u 5. Terminal retrusive occlusion is cen la to r a n d m o v in g this b y h a n d are sim ila r to th o se o b t a in e d from p e o p le . C o m p a r e with p arts tric relation occlusion or hinge axis oc I a n d II o f Fig. 3-8 clusion. 6. The occlusal positions in centric re lation and in pure lateral relations are 2. Intercuspal lateral movements start border positions. 7. The lateral intercuspal and centric ing or arriving at centric occlusal position occlusal positions are not border positions. form a Gothic arch or arrow point, the Arenales 1635 gnathogram of Balkwill.
*Head professor of prosthetic dentistry, Dental Faculty, National University of Buenos Aires, Argentina. 1. Saizar, P. Oclusión céntrica y relación céntrica. Normalidad del movimiento mandibular retrusivo. Rev. A. Odont. Argentina 49:73 March; 49:109 April 1961. 2. Cohn, A. S. La rehabilitación oclusal y el problema periodontal. In Glickman, I. Clinical periodontology. Philadelphia, W. B. Saunders Co., 1953. 3. Posselt, U. Studies in the mobility of the human mandible. Acta Odont. Scandinav. 10:19 suppl. 10, 1952. 4. Hanau, R. L. Dental engineering. Share of the condyle paths in the performance of mastication, and the importance of their correct reproduction in the ar ticulator mechanism. Nat. D.A.J. 9:595 July 1922. 5. Ârstad, T. Capsular ligaments of the temporoman dibular joint and retrusion facets of the dentition jn relationship to mandibular movements. Oslo, Akademisk Forlag, 1954. 6. Le Pera, F. Uso del registrador Le Pera. In Rebossio, A. D. Prótesis partial removible. Buenos Aires, pub lished by the author, 1955. 7. Villa, A. H. Gothic arch tracing. J. Pros. Den. 9:624 July-Aug. 1959. 8. Posselt, U. Movement areas of the mandible. J. Pros. Den. 7:375 May 1957. 9. Posselt, U. Range of movement of the mandible. J.A.D.A. 56:10 Jan. 1958. 10. Sears, V. H. Basic principles in dentistry. New York, Pitman Publishing Corporation, 1942. 11. Bergstrom, G. On the reproduction of dental articulation by means of dental articulators: a kinematic investigation, ed. I.Örebro, Sweden, A. B. Littorin Ryden, 1950. 12. Ferrein, M. Sur les movements de la mâchoire inférieure. Paris, Histoire de l'Academie Royale de Sciences, 1744-1746, p. 427-448. 13. Hildebrand, G. Y. Studies jn the masticatory movements of the human lower ¡aw. Berlin, Skand. Archiv. f. physiol, suppl. (W. de Gruyter, éd.), 1931. 14. Heath, J. Normal and abnormal occlusion of the
teeth of Australian aboriginal children. Austral. J. Den. 51:85 March 1947. 15. Bjork, A. Face in profile; an anthropological x-ray investigation on Swedish children and conscripts. Lund, Berlingska Boktryckeriet, 1947. 16. Schwartz, E. C. Radiographic and clinical study of the positional relations of the condyles in individuals with excellent occlusion of the teeth and apparent nor mal function of the temporomandibular joints. Abs. in Northwest. Univ. Bui. 56:12 April 1956. 17. Kydd, W. L., and Sander, A. Study of posterior mandibular movements from intercuspal occlusal posi tion. J. D. Res. 40:419 May-June 1961. 18. Balkwill, F. H. Best form and arrangement of arti ficial teeth for mastication. Odontological Society of Great Britain, Tr. 5:133 1865-1867. 19. Hesse, F. Mechanics of the chewing movements of the human jaw. J. Pros. Den. 4:175 March 1954. 20. McCollum, B. B. Fundamentals involved in pre scribing restorative remedies. D. Items Interest 61:522 June; 61:641 July; 61:724 Aug.; 61:852 Sept.; 61:942 Oct. 1939. 21. Academy of Denture Prosthetics Glossary of prosthodontic terms. J. Pros. Den. 10:14 part 2 Nov.-Dee. I960. 22. Gysi, A. Beitrag zum Articulationsproblem. Berlin, Hirschwald, 1908 (Trans, in D. Cosmos 52:1 Jan.; 52:148 Feb.; 52:268 March; 52:403 April 1910). 23. Gysi, A. Kieferbewegung und Zahnform. In Scheff, J. Handbuch der Zahnheilkund. Vol. 4. Zahnersatzkunde. Berlin, Urban & Schwarzenberg, 1929, p. 1-168. 24. Gysi, A. Artikulation. In Bruhn, Kantorowicz and Partsch Handbuch der Zahnheilkunde, vol. 3. Munich, Bergmann, 1930. 25. Sicher, H. Positions and movements of the man dible. J.A.D.A. 48:620 June 1954. 26. Beyron, H. L. Characteristics of functionally op timal occlusion and principles of occlusal rehabilitation. J.A.D.A. 28:648 June 1954. 27. Aprile, H., and Saizar, P. Gothic arch tracing and temporomandibular anatomy. J.A.D.A. 26:256 Aug. 15, 1947.
Pedro S a iza r* D.D.S., Buenos Aires, Argentina
T he extraoral graphic and the wax bite impression m ethods have been used to record the jaw m ovem ents o f people with normal o r nearly normal teeth. In six subjects, whose gnathograms were ob tained with the extraoral m ethod, the p o sition of maximal intercuspation was centric occlusion. Balkwill’s and Gysi’s arches and the contacting retrusive m ove m ent, Ferrein’s m ovem ent, also were reg istered. Results confirm the conclusions drawn previously in a study of 12 persons.
T h e retrusive ja w movements o f people with normal or almost normal teeth have been studied and were recorded using the extraoral graphic and the wax bite im pression methods. This report describes the extraoral graphic m ethod employed for six subjects. In addition, it refers to investigations o f this m ethod used in 12 subjects w hich were reported previously.1 M A T E R IA L S A N D M E T H O D S
For easier understanding o f the necessary jaw movements, the study was performed
principally with dentists (nine) and den tal students (s ix ). T h e other three persons concerned were members o f my family. T h e group was com posed o f nine men and nine wom en whose ages ranged from 21 to 50 years. W ith the exception o f the third molars, no m ore than one tooth was missing in any subject. N one had m ore than two restored occlusal surfaces. O ne o f the persons studied had had a serious malocclusion (A ngle I I I ) , which had been treated, and one had been treated for periodontal disease. A ll were able to com ply with the tests required. T o obtain clear records o f voluntary movements, it was necessary to train the subjects. T hey found the retrusive m ove ment the most difficult. T h e follow ing was the technic used: 1. C ohn ’s2 m ethod to make the person “ feel” the retrusive occlusion was accom plished in the follow ing m anner: (a) the patient was asked to open his m outh; (b ) the dentist, holding the patient’s chin between his index finger and thumb, as sisted in loosening the ja w muscles by m oving the patient’s mandible up and down until no resistance was felt; (c) the
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F ig. I • G n a t h o g r a p h p re p a re d fo r a n te rio r ex t ra o ra l sa g itta l re gistra tio n . U p p e r level o f sm o ke d g la ss m ust b e p aralle l w ith F ra n k fo rt's p la n e
dentist next moved the jaw gradually up ward and backward using a slight upward and downward movement until retrusive occlusion was obtained; (d) the patient was asked to feel what teeth touched in that position. 2. Once the retrusive position has been “ felt,” it is easy to teach the subject to find it on his own and effect the centrip etal retrusive movement; that is, make him open his mouth, put his jaw back ward and close with the jaw in retrusion (posterior hinge movement) until retru sive occlusion is reached, and then slide the jaw, gliding the lower teeth along the upper teeth, until centric occlusion is reached. 3. The subject was taught centrifugal retrusion, from centric occlusion to ter minal retrusive position.
and, in accordance with Posselt’s nomen clature,3 adopt any border or intraborder mandibular position. In Hanau’ s nomen clature,4 they could explore their respec tive “ bicuspoids.” Results were obtained with the aid of extraoral gnathographs (Fig. I, 2) regis tering definite voluntary, unforced con tact or noncontact movements performed in the proximity of centric occlusion and terminal retrusive positions, with the mouth empty except for the intraoral part of the gnathographs which occupied the vestibule and did not interfere with occlusion. The movements were performed as often as necessary to obtain clear, com plete and reproducible gnathograms on smoked glass. These were fixed, and di rect photographic copies made. The first 12 subjects, whose registrations have been published before,1 were tested again, and the second registrations were similar to the first ones. Since the six new subjects provided evidence of the same kind, the gnathograms of the first 12 subjects are not included in this report. The move ments registered are given on two to four smoked glasses: part I has two vertical, anterior gnathograms; part II has four “ horizontal” ones which are also anterior registrations. Paracondylar vertical gnath ograms, parts III and IV , of some sub jects are shown also.
4. Then, lateral and protrusive con tact movements were taught. Once these points had been learned— for some it took several sessions— all were able to close their mouths voluntarily in centric occlusion or in retrusive occlusion with the mandible in the posterior posi tion, go through the retrusive positions both ways, execute extreme protrusion, open the mouth with the mandible in protrusion and perform lateral move ments. They could carry out every movement
Fig. 2 • G n a t h o g r a p h h orizon ta l re gistra tio n
p re p a re d
fo r
extraoral
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Fig. 3 • S n a t h o g r a m s o f su b je c t 13, 23 y e a r old w o m a n . I: S a g it t a l plane. R, tra c in g o f isolate d retru sive m o v e m e n t; A O C P , tra c in g of h in g e axis clo sin g plus retru sive m o v e m e n t a n d p ro tru sio n ; O C in d ic a te s c e n tric o c clu sio n p osition . II. H o r i zonta l plane. R, tra c in g o f isolate d retru sive m o v e m e n t; B, B alkw ill's a rch ; G , G y s i's arch. Left g n a t h o g ra m sho w s b oth G o t h ic arch e s re g iste re d w ith ou t c h a n g in g p o sitio n o f sm o ke d g la ss in g n a t h o g r a p h . Ill a n d IV : V e rtic a l p a r a c o n d y la r rig h t a n d left. R, tra c in g s o f iso la te d retrusive m o v e m e n ts; P, t ra c in g s o f isolate d p ro tru siv e m o v e m e n ts; R -|- P, t ra c in g s o f retru sive p lus p r o tru sive m ove m e n ts
R ESU LTS
With the use of gnathographs suitable for horizontal registrations (Fig. 2 ), the re trusive movement was registered as an anteroposterior tracing. All the subjects investigated were capable of registering well-defined retrusive movement (R , part II, Fig. 3 -8 ), completely different from that of a closing retrusion, which does not register if the needle is positioned ade quately, as was shown by Arstad,5 Le Pera6 and Villa.7 As shown previously,1 all were capable of tracing two Gothic arches: one by us ing movements starting from, or reaching,
13 f . t , / ¿ t r z
t
r
centric occlusal position; another using movements that started or arrived at ter minal retrusive occlusal position (B and G, part II, Fig. 3-8). Part II of Figures 3-8 show the two Gothic arches registered without chang ing the position of the smoked glass in the gnathograph. When the needle was fixed to the lower jaw, as in Sears’ trivet, arrow-point gnathograms were obtained (Fig. 9 ). With the use o f a gnathograph capable of registering movements in the sagittal plane (Fig. 1), it was observed that the retrusive movement takes the mandible backward and downward (R , part I, Fig. 3 -8 ), which confirms the investigations by Posselt.8 This shows, therefore, that both Gothic arches or arrow-points are formed at different levels (Fig. 10).
F ig . 4 • G n a t h o g r a m s o f su b je c t 14, 4 5 y e a r old m an. I: S a g it t a l p lane. R, t ra c in g o f iso la te d re tru sive m o v e m e n t; A O C P , tra c in g o f h in g e axis c lo s in g plu s re tru sive m o v e m e n t a n d p ro tru sio n . O C in d ic a te s ce n tric o c c lu sio n p osition . II. H o r i zon ta l p lan e. R, t ra c in g o f iso la te d retrusive m o v e m e n t; A B , Balkw ill’s a rch ; A G , G y s i's arch. Left g n a t h o g r a m show s b o th G o t h ic a rch e s r e g is te re d w ith o u t c h a n g in g p o sitio n o f sm o ke d gla ss in g n a t h o g r a p h . Ill a n d IV : V e rtic a l p a r a c o n d y la r rig h t a n d left. R, t ra c in g s o f iso la te d retrusive m o v e m e n ts; P, t ra c in g s o f iso la te d p ro tru siv e m o v e m e n ts; R —f- P, t ra c in g s o f retru sive plu s p r o tru sive m o v e m e n ts
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Fig. 5 • G n a t h o g r a m s o f su b je c t 15, 24 year o ld w o m a n . I: S a g it ta l p la n e. R, t ra c in g o f is o lated re tru sive m ov e m e n t; A O C P , tra c in g o f h in g e axis c lo s in g plu s retru sive m o v e m e n t and p ro tru sio n . O C in d ic a te s c e n tric o c c lu sio n p o s i tion. II: H o riz o n ta l plane. R, t ra c in g o f isola te d retrusive m ov e m e n t; A B , Balkw lll's a rch ; A G , G y s i's arch. Left g n a t h o g r a m show s b o th G o t h ic a rch e s re g iste re d w ith o u t c h a n g in g p o sitio n of sm o ke d gla ss in g n a t h o g ra p h . Ill a n d IV : V e rtic a l p a r a c o n d y la r r ig h t a n d left. R, t ra c in g s o f isola te d retru sive m o v e m e n ts; P, t ra c in g s o f isola te d p r o tru sive m o v e m e n ts; R + P, t ra c in g s o f retrusive, plus p ro tru siv e m ove m e n ts
This disposition was true in all subjects, as shown in part I, Figures 3-8, in which there are two vertical gnathograms of each of the six subjects. In these, R repre sents the isolated retrusive movement; A O C P is the tracing of a retrusion, or hinge-axis closure, the retrusive move ment, and of protrusion. IN T E R P R E T A T IO N A N D D IS C U S S IO N
M axim um Intercuspation ' The gnatho
grams all show that centric occlusion is a definite position, just a “ point” from which “ pure” movements start: lateral, anterior and posterior, all of them repro ducible. Vertical gnathograms show also that this is the major intercuspation position, a characteristic which defines centric oc clusion at least as well as that of provid ing the maximum number of contact points, which is the best known charac teristic.
Posselt’s T w o Gothic A rches • The two
Gothic arches can be seen in the solid bicuspoids constructed by Posselt,9 a proof of the exactness of the plastic method used by him and the graphic method em ployed here. Posselt did not indicate their historic meaning (see section on Balkwill’s arch and Gysi’s a rch ). Norm al Retrusive M ovem en t ' The 18
subjects with normal or nearly normal teeth, investigated by the graphic method, had 100 per cent voluntary retrusive movement and can be added to the other normal or nearly normal subjects investi gated by other methods by Ferrein,12 Hildebrand,13 Heath,14 Bjork,15 Posselt,3,8 Arstad,5 Schwartz16 and Kydd and San der.17 Positive proof substantiates this demon stration so that there is no doubt that the normal mandible has retrusive possibility, that normal centric occlusion is not a border position and that, when normal
Fig. 6 • G n a t h o g r a m s o f su b je c t 16, 21 y e a r old w om an. I: S a g it ta l p lane. R, tra c in g o f isola te d re tru sive m o v e m e n t; A O C P , t ra c in g o f h in g e axis c lo sin g plus re tru sive m o v e m e n t a n d p ro tru sio n. O C in d ic a te s c e n tric o c c lu sio n p ositio n . II: H o r i zontal plane. R, t ra c in g o f iso la te d retru sive m o v e m e n t: B, Balkw ill's a rc h : G , G y s i's arch. Left g n a t h o g ra m sho w s b o th G o t h ic a rch e s re g iste re d w ith ou t c h a n g in g p o sitio n o f sm o ke d gla ss in g n a t h o g ra p h
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Fig. 7 * G n a t h o g r a m s o f su b je c t 17, 2 4 y e a r old w o m an . I: S a g it ta l plane. R, tra c in g of isola te d retrusive m o v e m e n t; A O C P , t ra c in g o f h in g e axis c lo s in g plu s re tru sive m o v e m e n t a n d p ro tru sio n. O C in d ic a te s c e n tric o c c lu sio n p osition . II: H o r i zon ta l p lan e. R, t ra c in g o f iso la te d retrusive m o v e m en t; B, Balkw ill's a rch ; G , G y s i's arch. Left g n a t h o g ra m show s b oth G o t h ic a rch e s re g iste re d w ith ou t c h a n g in g p o sitio n o f sm o ke d g la ss in g n a th o q r a p h
dental arches are in centric occlusion, the condyles are not in centric relation. This last statement has been corrobo rated by me several times by means of direct paracondylar registrations (parts III and IV, Fig. 3 -5), which show the isolated tracing (R ) produced by the con dylar retrusive movement from the posi tion occupied when the teeth are in centric occlusion. These illustrations show that the slant o f the condylar retrusion sometimes makes a definite angle with the slant of the condylar protrusion. Balkwill’s Arch and Gysi’s Arch • The centric occlusion Gothic arch is the one so ingeniously foreseen by Balkwill18 when he pointed out the right and left lateral tracks corresponding to each functioning lower cuspid. Apparently, this arch was registered di rectly for the first time by Hesse19 and is undoubtedly the same as that registered by M cCollum 20 during his investigations on normal teeth. The vertex of the retrusive Gothic arch, on the other hand, indicates “ the most retruded relation of the mandible to the maxilla [in occlusal contact] from which the patient can make lateral jaw movements;” 21 that is, it indicates the occlusal position in centric relation or centric relation at the level determined by occlusal contact. Therefore, it is equiv alent to the “ Gothic arch” registered in patients without teeth or the “ Gothic arch” registered in this type of patient for the first time by Gysi22 and incor
porated by him into diagnostic technics and prosthetic restorations. It served also as a test and a basis for his theories on mandibular kinematics. Gysi’s Mistake ' Examination o f Figures 13, 14 and 16 in Gysi’ s paper22 shows the origin of a basic error which up to now has influenced the ideas of dentists on mandibular kinematics and prosthesis. Gysi applied the tracing obtained from an edentulous mandible to one with teeth, since he believed that the gnathogram of centric relation possessed exactly the same significance as the centric occlusion regis tration. This can be seen in his later work also.23,24 It is easy to understand this mistake. Gysi proved experimentally the correct ness o f a prosthesis constructed when cen tric occlusion coincides with centric rela tion,22,24 a finding prosthodontists have confirmed for more than 50 years. In addi tion, Gysi compared the Gothic arch de veloped in the edentulous, with a Gothic arch produced in patients with teeth. He proved that the latter registered it simi larly to the former,24 which confirmed his point of view. He could not know that, in the dentate, another similar arch is the only one registered with ease, and that terminal retrusive occlusal position, which he considered anomalous, as did almost all dentists until recently, requires special training for those with natural teeth, and unusual muscular coordination, to be able to register it. He died without knowing that the Gothic arch o f centric relation,
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Fig. 8 • G n a t h o g r a m s o f su b je c t 18, 28 y e a r old m an. I: S a g it t a l p lane. R, t ra c in g o f isola te d re tru sive m o v e m e n t; A O C P , t ra c in g o f h in g e axis c lo s in g plu s retru sive m o v e m e n t a n d p ro tru sio n. O C in d ic a te s c e n tric o c c lu sio n p ositio n . II; H o r i zontal p la n e. R, t ra c in g o f iso la te d retrusive m o v e m e n t; A 8 , Balkw ill's a rc h ; A G , G y s i's arch. L eft g n a t h o g ra m show s b o th G o t h ic a rch e s r e g is te re d w ith o u t c h a n g in g p o sitio n o f sm o ke d gla ss in g n a t h o g r a p h
which was the foundation of his technic, was his discovery. Shape of N orm al Bicuspoid • Figure 11
is a sketch, several times normal size, of the superior region of the bicuspoid or space for unforced movements corre sponding to the lower incisor point, ac cording to the records obtained by the author, which coincide with those ob tained by Posselt.9 In addition, Posselt gave the physiological explanation of the retrusive movement, which confirmed those of Ferrein12 in the past and Posselt,3,9 Sicher20 and Beyron26 more re cently. In Gysi’s gnathogram, the lines AG (Fig. 11), the union of which indicates the terminal retrusive occlusal position, represent the inferior and posterior limit o f possible occlusions; that is, they deter mine the separation between occlusal (contacting) movements and positions forming the superior surface of the bicuspoid and the open (noncontacting) positions and movements. In Balkwill’s gnathogram, AB represents a functional track, a habitual contact movement; its vertex determines centric occlusion, which is probably the most frequent contacting position. In the 18 subjects investigated, neither centric occlusion nor eccentric intercuspal occlusions are border positions. Retrusive M ovem en t and Its Com posi tion • The tracing O C -R G (Fig. 11) rep
resents the contacting retrusive, or Ferrein’s movement. On the other hand, its composition, dimension and direction are open to argument.
Using Frankfort’ s plane (PLFR, Fig. 11) as a guide to orient the head, the true retrusive range is, as Posselt3 pointed out, the distance reached by the lower incisor point in terminal retrusive position (RG ) with respect to the LP line, which is per pendicular to Frankfort’ s plane. Therefore, when the incisor point reaches its terminal retrusive position, RC, the distance to LP is obtained by adding the sum of the retrusion caused by taking the mandible backward, to the lo cal posterior movement produced by opening the mouth. I have called1 the two components slid ing retrusion (condylar or true retrusion) and rotational retrusion (noncondylar or false retrusion). The difference is important since it means that retrusion measured at the level o f the incisors where the two com ponents meet will appear larger than at the level of the condyles where there is only sliding retrusion. Origin of Balkwill’s and, Gysi’s A rches '
In the investigation I made with Aprile,27 as well as in those by Posselt3 and Arstad,5 it was shown that Gysi’s gnathogram is produced exclusively by the anatomic ar-
Fig. 9 • H o r iz o n tal a n te rio r g n a t h o g ra m o f su b je c t 15, t ra c e d with n e e d le fixed to low e r jaw. Both a rches, Balkw ill's a n d G y s i's , take fo rm o f a rro w p o in ts o f S e a r s 10 o r
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F ig . 10 • S p a tia l relation o f b o th g n a th o g ra m s (B a lk w ill's a n d G y s i's ) a n d retrusive (F e rr e in 's ) c o n t a c t in g m o v e m e n t is show n. A B , Balkw ill's arch; O C , ce n tric o c clu sio n vertex; R, retru sive c o n ta c t o r F e rre in ’s m ovem en t; R C , ce n tric relatio n o c c lu sion vertex; A G , G y s i's arch
rangement o f the tem porom andibular ar ticulations ; the length o f the sides is deter m ined by the action o f the lateral and capsular ligaments, the accessory liga ments do not intervene. T o register it, it is necessary only that, at some mom ent, the two condyles pass through their most posterior positions during the sliding lat eral mandibular movement. Gysi’s gnathogram is o f tem porom andibular origin. Because o f this, it represents the upper limit o f the border movements and can be registered after removal o f the teeth and at various vertical dimensions. O n the other hand, Balkwill’ s gnathogram represents a contacting path caused
Fig. I I • Ske tch sh o w in g u p p e r p art o f b ic u s p o id o f low er incisal point. P L FR , F ra n k fo rt's plane; O C , ce n tric o c clu sio n p o sitio n ; A B , Balkw ill's a rch ; LIE, extrem e left lateral p o sitio n ; R C , c e n t ric rela tio n p o sitio n ; P, p ro tru siv e m ovem en t; PE, extrem e p ro tru siv e p o sitio n ; L D E , extrem e r ig h t lateral p o sitio n ; Z R , re tru sive zo n e ; A G , G y s i's a rch ; A R , retru sive o r h in g e axis o p e n in g o r c lo s in g ; A H , h a b itu a l o p e n in g o r c lo s in g ; LP, line p e r p e n d ic u la r to the F ra n k fo rt's p la n e ; A L , o p e n in g o r c lo sin g m o v e m e n t in extrem e righ t la tera l p o sitio n ; A P , o p e n in g o r c lo s in g m ove m e n t in extrem e p ro tru sio n ; RP, p o te n tial retrusion; O C - R C , retrusive m o v e m e n t (from S a iza r1)
by the congruence o f centric as well as lateral intercuspation. For this reason, it disappears when there are n o teeth, but it will reappear if the prosthesis allows congruent lateral intercuspation that does not coincide with Gysi’ s gnathogram. Both these gnathograms, therefore, ow e their shape and relation to the anatomic arrangements o f the tem porom andibular joints and the dental arches. T hat they can be registered in the articulator (Fig. 12) constitutes, in my opinion, another conclusive p roof that they do not have a direct dependence on the muscular inser tions or the soft nontemporomandibular tissues. S U M M A R Y A N D C O N C L U S IO N S
T h e gnathograms from six subjects co n firm the conclusions drawn from a previ ous study o f 12 persons.1 T h e gnathograms were obtained from 18 people with norm al or nearly normal teeth, whose voluntary, unstrained, cen tric, and eccentric, m outh empty, m an dibular positions and movements were registered by the extraoral graphic m ethod. In all subjects, the follow ing points were true. 1. Centric occlusion is the position o f maximal intercuspation.
PL. FR.
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3. The contacting retrusive move ment, or Ferrein’s movement, takes the mandible from centric occlusal position to terminal retrusive occlusal position, and the reverse. 4. The contacting lateral movements starting from or arriving at terminal re trusive occlusal position form a Gothic arch or arrow point different from that of Balkwill; this is the gnathogram of F ig. 12 • G n a t h o g r a m s o b t a in e d b y p la c in g the Cysi. g n a t h o g r a p h on the m o d e ls m o u n te d on a rtic u 5. Terminal retrusive occlusion is cen la to r a n d m o v in g this b y h a n d are sim ila r to th o se o b t a in e d from p e o p le . C o m p a r e with p arts tric relation occlusion or hinge axis oc I a n d II o f Fig. 3-8 clusion. 6. The occlusal positions in centric re lation and in pure lateral relations are 2. Intercuspal lateral movements start border positions. 7. The lateral intercuspal and centric ing or arriving at centric occlusal position occlusal positions are not border positions. form a Gothic arch or arrow point, the Arenales 1635 gnathogram of Balkwill.
*Head professor of prosthetic dentistry, Dental Faculty, National University of Buenos Aires, Argentina. 1. Saizar, P. Oclusión céntrica y relación céntrica. Normalidad del movimiento mandibular retrusivo. Rev. A. Odont. Argentina 49:73 March; 49:109 April 1961. 2. Cohn, A. S. La rehabilitación oclusal y el problema periodontal. In Glickman, I. Clinical periodontology. Philadelphia, W. B. Saunders Co., 1953. 3. Posselt, U. Studies in the mobility of the human mandible. Acta Odont. Scandinav. 10:19 suppl. 10, 1952. 4. Hanau, R. L. Dental engineering. Share of the condyle paths in the performance of mastication, and the importance of their correct reproduction in the ar ticulator mechanism. Nat. D.A.J. 9:595 July 1922. 5. Ârstad, T. Capsular ligaments of the temporoman dibular joint and retrusion facets of the dentition jn relationship to mandibular movements. Oslo, Akademisk Forlag, 1954. 6. Le Pera, F. Uso del registrador Le Pera. In Rebossio, A. D. Prótesis partial removible. Buenos Aires, pub lished by the author, 1955. 7. Villa, A. H. Gothic arch tracing. J. Pros. Den. 9:624 July-Aug. 1959. 8. Posselt, U. Movement areas of the mandible. J. Pros. Den. 7:375 May 1957. 9. Posselt, U. Range of movement of the mandible. J.A.D.A. 56:10 Jan. 1958. 10. Sears, V. H. Basic principles in dentistry. New York, Pitman Publishing Corporation, 1942. 11. Bergstrom, G. On the reproduction of dental articulation by means of dental articulators: a kinematic investigation, ed. I.Örebro, Sweden, A. B. Littorin Ryden, 1950. 12. Ferrein, M. Sur les movements de la mâchoire inférieure. Paris, Histoire de l'Academie Royale de Sciences, 1744-1746, p. 427-448. 13. Hildebrand, G. Y. Studies jn the masticatory movements of the human lower ¡aw. Berlin, Skand. Archiv. f. physiol, suppl. (W. de Gruyter, éd.), 1931. 14. Heath, J. Normal and abnormal occlusion of the
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