10. centric relation. the anterior biting jig for recording the clenching position

7/26/2019 10. Centric Relation. the Anterior Biting Jig for Recording the Clenching Position

1/15

figure I

= Superiormost Fosilion

B = Reormost Position


2/15

Centric Relation The Anterior

Biting Jig for Recording

the Clenching Position

Edward Levinso

Honarary Profe.

Department of Endodontics

ond Rehabilitation,

University of Pretoria

In restoring an acclusion, it is desira-

ble ta use a maxillomandibular re-

latianship that is physiolagically ac-

ceptable to the patient and reliably

reproducible far the dentist. Centric

relation (RC) has been used for m any

years and has been found fo satisfy

both requirements.

It has thus evalved as a clinical can-

cept rather than a biologic entity[Sil

verman 1975) and its definition has

undergone change from time to time.

In that period of its history, when

prosthetic dentistry was primarily

concerned with the provision af full

dentures, a position of the mandible

relative ta the cranium was saught,

where maximum intercuspation (IC)

of the artificial teeth cauld be estab-

lished. The act of swallowing is nor-

mally accompanied by retrusian af

the mandible, and its stabilisation

against the cranium by tooth con tact

in this retruded pasition. It is under-

standable,

then,

that the IC which

was found c linically to be most cam -

fortable for the patient was at, ar

near, this distalised pasition, and the

fact that this could be duplicated

within acce ptable limits was expedient

far the prosthadontist. Stated differ-

ently, IC was ta be established close

to the most retruded position of the

mandible |RC}.

Thompson

(194) pointed aut the

need far an adequafe interocclusal

clearance (freeway space) between

the oppo sing teeth in fhe rest position

of the mandible, hie faund this to

average 2-3 mm in the narmal den-

tition-This implies that, in addition fo

its determination in a harizanfal

plane,

there is a vertical component

to the RC/IC positian.

When dentistry entered an era af

fixed prosthetic resfaratlon, fhe con-

cept af establishing the occlusion at

the retruded positian of the mandible

was developed still further. Whereas

the full denture was supparted by a

resilient tissue {Hanau 1926), which

enhanced the adaptive capacity of

the mechanism, the fixed restoration

had ta be constructed ia finer toler-

ances. In addition, the presence of

natural teeth, with their periadantal

ligaments richly endowed with pro-

prioceptors, provided an input which

was capable oi triggering the neuro-

muscular mechanism nta parafunc-

tianol activity.

At that time, the definition of centric

relation was based on fhe concep

that nthis pasition fhecond yles occ u

pied their mast posterior pasition in

the fassa

[Clossory of rostfiodont

Terms 1977). In the clinical recor

ing af centric relatian position,

tech

niques were adopted which concen-

trated on placing candyles in thei

rearmost pasitian. These included

chin-paint guidance, placing the tip

af the tongue far back in the palate

swallowing, etc. Several authors

painted out, hawever, that in this rear

most position the condyies wou ld na

necessarily be in their uppermos t po

sitian (Fig. 1).Kaplan (193) painte

out the possibility of recording an in

ferior sa gg ed positian af the can

dyles. Lang (1973] emphasize

the necessity far getting the condyie

into a superior rather than a posteria

positian.

Dowson (1974) stated tha

chin guidance with ane-handedtech

niques pushing backwards on th

symphysis wou ld tend fo record an in

ferior pasitian af the condy ies. This

borne aut by the work

o\Rees

(1954

who showed that the configu

rafion of the temporamandibular lig

ament is such as ta limit distal pos

tianing af the condyle, but permit a

inferiar placement at the same time.


3/15

10

The definition of centric relatian has

subsequently been chonged to en-

compass the concept of the eondyle

being in its superiarmost, onterior-

most position, where it is braced by

ligament ond bone.

The vorious methods that hove been

used to determine RC position in-

clude gathic arch trocings, guided a nd

free unguided closure, bilateral ma-

nipulation, chin-point guidonce ond

swallowing. Such is the adoptobility

of the masticatory mechanism w ith its

delicote neuromuscular control thot

all these vorious methods have met

with success. It is likely thot ca re, pa -

tient selection ond attention to detail

were more important thon the choice

of technique.

Funclion and Parafuncflon

Telemetric studies

[Jankekon

1953)

show that teeth make but fleeting

contact in function. The impartonce,

then,of the RC/IC position wos not in

relation to function, where light for-

ces, fovourable in direction, distribu-

tian ond duration, ore employed. In

porafunctian, on the other hand,

heovy forces, sustoined ond unfa-

voura ble in direction ond distribution,

ore p laced an the teeth. In clenching,

the concomitant activity of the dos-

ing muscles tends to seat the con-

dyles in their superiormost, onterior-

most position [Rabetis 1974) (Fig.2).

This could well be described as the

physiologic denchtng positioti of the

condyles (CP), where they are

braced by l igoment and bane, and

can maintain their position without

activity af externol pterygoid muscle

{Dawson

1974) (Fig. 3].

In providing o new occlusion, its

component parts should be most in

hormony when the condyles are in

CP ,

where they are best able to

with-

stand heovy parafunctional forces.

This is especiolly important as poro-

function is often initiated by alterations

to the occlusion. The bilateral man-

dibular manipulotion of Dawson is

intended to guide the condyles to

their CP. The technique to be de-

scribed utilizes the activity of the

clenching muscles to ochieve this

purpose.

Description of Tecfinique

Lucia

(1964) advocated the registra-

tion of RC with an o nterior bite

ig,

to

record the most posterior position of

the condyles. A madificotion of this,

anterior biting jig

(ABJ), is can-

structed,

either of self-curing acrylic

or compound, in order to record fhe

uppermost, anteriormost eondylar

position (Fig. 4),


4/15

Fig. 2 Muscle force

t

=

temporatis

m =

mosseter

bf resultant ol elevator musdes

loccording ta Rabertsl

ig

3 Clenching position of the candyle

R

=

Rest Position

Fig. 4 Construction af anterior biting

1 Indexing incisor teeth

2 Trimming of index

3 Jig ready to receive linal index


5/15

12

5 Anleriar biting {ig for CP registrotian ior reconslruclian mth compound inde.

CP registrotian for reconstruction

t p l

h

Centrol Incisor Index

The mandible is guided in a terminal

hinge movement and an index of the

incisol tips of the oppos ing central in-

cisors is made against compound

fused fo the ig (Fig. 5 j.

If the CP record is being made for a

reconstruction of the occlusion, the

index is mode of the vertical dimen-

sion fo which it is propos ed to rebuild

the occlusion

Fig.

6]. If the CP is

being recorded for functional analysis

of the natural dentition, the index is

made with the vertical dimension in-

creased minimally, so that the poste-

rior teeth are only usf held out of oc-

clusion (Fig. 7].

Jigs may be used in either one or

both aws, depend ing o n skeletal and

faoth relationships and the presence

of missing teeth (Fig. 8].

The CP record sh ould be m ade in the

absence of abnormal tonus of the

masticatory musculature. If a Haw ley

bite plane has been used ta achieve

this,

it can serve well as a biting

;ig-

It is imperative that the a nferiar con -

tact does nof praduce o vector of

force at an inclination to the closing

path of the lower anteriors. This

would tend to displace the condyles

either mechanically or by proprio-

ceptively induced muscle octivity.

This situation applies porticularly in

the case of a posterior reconstruc-

tion,where the anterior maxillary and

mandibular teefh are often used,

after equilibration, ta serve the pur-

pose of the anterior jig (Fig. 9]. In an

edge-to-edge situotion (Fig. 10] or

with prominent cingula (develop-

mental, or following attrition), no

problem arises. FHowever, where the

anterior guidance could tend to dis-


6/15

Fig. 7 CP registration for functional anolysis

o = acrylic jig

c = coTipound

brp = bite regi^lrotion material

Fig 8 Inde mode on tower incisor leeth for CP registrolion in Closs III situation.

1 lormmg inde>

2 trimming inde^

3 indei reody lo receive compound


7/15

14

Fig. 9 In the absence af posterior Iooth contact, a biting force cauld couse o distol vector of (orce (orrowl

Fig. 10 I, 2 Edge to edge, ar cingulum siluolions do not require compound reinforcement.

ce requiring compaund reinforcement


8/15

Fig. 1} Compound reinfarcement lc la pn

Fig. 12 Condyle being directed upwards and forwords by resultoni bile torco vector ofclastng

abj = anterior biting ig

ploce the eandyles os describe

above, a thermoplastic materia

that adheres to the teeth is used t

prevent this (Fig. 11).

Step II

Conditioning be Patient

The patient is conditioned to bite wit

moderote force, by instructing him t

close his teeth an the operator's fin

ger held in the mid-sagittal plan

until discomfort is felt (by the opera

tarl).

The amount of biting force

not criticol, as increased farce doe

not alter condyiar position with

clinically measurable parameter

[Levinson 1980).

Because the fulcrum a t the central in

cisar biting point is situoted on

lower plane than the candyle, the a

tion of the closing muscles is to dire

the condyles upwards and forword

complementing their action as de

scribed by

aberts

above (Fig. 12

Step III

The onteriar teeth ore then guided t

the previously made indentations

the ig, and the patient is instructed

mointain the moderate biting farc

while a saft recording medium is a

lowed to set between the posterio

teeth (Figs. 13 and 14].Where mast

the posteriors are present, bite re

istration paste is pre ferred , its consi

tency being such as to minimise stim

ulation af the periodontal propri

ceptors of the posterior teeth. It mu

be emphasised that this is a ha n

off procedure once the correct o

terior co ntact is ma de.

Where there ore missing posterior

or where the intra-occlusal spac

* Kerr sgreenstick.


9/15

16

is lorge, a platform of self-curing

ocrylic carrying c soft mix of the

same mate rial is used (Fig. 15),

nvestigationofReproducibility

Previous studies comparing the dis-

persion patterns of condylar repro-

ducibility with different techniques

have been reported

Celenza,

1973;

Kantor et al., 1973], From all these

studies, it emerged thot the tech-

nique of bilaterol m anipulation of the

mandible

{Dawson,

1974) was the

most repro ducible. With this in mind,

it was decided to compare the ante-

rior biting jig method with the bilat-

erol manipulation technique.

Method

The spatial patterning of the condyle

position as recorded by the two

techniques was determined by the

method ta be described.

From a g roup of dentol students, four

subjects were selected with

1,

unmutilated dentitions (except for

absence of lower third molars) with

only minor restorotive dentistry,

2, absence of tooth mobility at a

clinical level,

3, no subjective symptoms of dys-

function of the masticatory mecha-

nism.

Maxillary and mandibular arch im-

pressions were taken with irreversi-

ble hydrocolloid and poured without

delay in vacuumed dental stone. Ten

Fig 3 Ar h

ng;ig ofcompound with indexofsingleinosortooth

Fig. 4 ite registrofoti poste recording C P while notier.i maintains biting fo


10/15

Fig. 15 CP registration formed by acrylic platform corrying o soft mix of elf curing ocrylic. Resincap

ainglar Duralay Relioncel

Fig. I Denar Voricheclr inilrumenl. Styli recording position af a regrilralion.

registrations of centric relation wer

made for each patient, five using th

bilateral manipulation technique

ond five by the onterior b iting ig m et

od. The registrations with bilatera

manipulation were made by an oper

ator well versed in this technique

and those with the anterior biting ji

by the author.

The mandibular cast was fixed ta th

lower member of the Denar Var

check instrument with dental ston

(Fig. 16]. The maxillary cast was then

related to the mandibular cast usin

each of the five records of one tech

nique in turn, and indentatians were

made by pressing the styli of the up

per member inta millimetre-rule

graph paper held vertically an d

hori

zontally by fhe lower membe

(Fig-16].

The graph recarding papers wer

then photographed and replaced

Transparencies of the grouping

were projected on a screen so tha

each millimetre graduotion was en

larged ta one cm., thus giving lOO

magnification. The diameter af th

smallest circle which co vered the fiv

indentatians was measured with ver

nier calipers to0 1mm. This figure di

vided by ten was recorded , giving th

acfual dimension (Fig. 17].

The position of the indentations rela

tive to X (vertical], (horizontal, sag

ittal] and Z (horizontal, frantal) axe

was also recorded. X, Y and Z axe

were farmed by the boundaries o

the surfaces holding fhe recordin

graph paper.


11/15

18

Resul ts

1.

The spatiol pafterning, as evi-

denced by the diameter af the small-

est circle, was significantly more

constricted for the ABJ recordings.

Recordings made by the ABJ are

thus more reproducible fhon those

made wifh biloteral mandibular ma-

nipulotion.

1 On investigoting the indento-

tions with reference to the X.Yand Z

axes,

the

BJ

method consistently re-

corded o more superior ond onterior

position.

Investigaffon of Physiologic

cceptance

This is assessed subjectively by inves-

tigating the potient far camfart and

freedom from symptoms of dysfunc-

t ion, and objectively by the reoction

of the periodontium. The latter can

anIy be determined from clinicol ex-

amination of pafienfs with proven

susceptibility to periodontai diseose

[Levinson

1981).

e ction of the Periodontium

Seventy-four patients who hod been

treated for odvanced periodontai

disease were examined. An integral

part of the treotment had been the

provision of periodontol prostheses,

which w ere constructed to centric re-

lation records obtoined by the ABJ

method described above. Exomina-

tion consisted of determination of

bleeding from the sulcus on genfle

probing,

and quantifotive ossess-

ment of residuol alvealar bone from

rodiogrophs.

Post-operotive periods ronged from

fhree to twelve yearswitha m ean of 5.2

years.

In every instance, the den tition

as o whole was surviving with im-

prove d p eriodo nfal stotus (Fig. 18). A

Fig, 7 Grouping of live registrotions recorded on groph paper on Oenor Vanctieck inslrun


12/15

Figs. I8o ond b Betre (o) and alle: (b) tracings ol radiographs

oi poliGnl shownQ n iciinfenoncG of osseous levels

h d

Q

potfnt with pG riooonlQi d S


13/15

20

20 0

160

120

80

40

MPDS

a

1

1

PAIN

(208)

SYMPTOMS

ELIMINATED H l

IMPROVED j 1

U N C H A N GE D

|B


14/15

total of l,145te eth were involvedinthis

survey on d of these only e ighteen units

had been lost. Most of these were

roots of molar teeth which had been

treoted for Grade 111 furcat ion prob-

lems

[Rosenberg

1979), and were

break ing down due to a combina-

t ion of per iodonta l and endodonta l

factors.

Patient Acceptance

Extending the principle underlying

the periodontal assessment, only

patients with a history of myofascial

pain dysfunction syndrome (MPDS)

were included in this investigation

[Levinson 1976), The symptoms of

MPDS recorded w ere p oin, l imitat ion

of movement, c l ick ing and ocdusol

awareness. Two hundred eight po-

t ients who had been provided with a

new occlusion treatme nt of their over-

al l dental condit ion were exomined

after o fol low-up period vary ing f rom

six months to twelve yeors with a

mean of 4,2 years. The results are

shown in the bar g rap h (Fig, 19),

Whereas it is conceded that the high

success rate was inf luenced by other

than acdusal foctors, at least it may

be said that the occlusion provided

wos accep table to a s igni ficant num-

ber of patients with proven suscepti-

bil ity to pro blem s of dysfunction of the

mast icatory mechanism.

Discussion

Potients who experience sensitivity,

and or symptoms of dysfunction of

the mast icatory mechanism fol lowing

occlusal reconstruction, are often

found to hove occlusal interferences

relating to the terminal molars, when

examined by the method advocated

by

Lang

(1973), This would indicate

that the inter-occlusal registrations

employed in fabricating the restoro-

t ions could have been made with the

condyles in a so gg ed position

(Fig. 20), The object of the bilateral

manipulation technique is to record

the mandibular posit ian with con-

dyles seated superiorly o nd onteriorly,

i.e,, wh ere the elevator m uscles w ould

take them in o terminal hinge closure.

It seems logical to direct the closing

muscles to achieve this seating while

mo king the recard . This investigation

shows this to be

a

more reproducible

method.

In considering the spatial patterning

as recorded on the Varicheck instru-

ment, a pontographic effect results

from the styli being remote from the

zone of registration. The cusp tips

undergo less deviation than that

shown,

by o factor of approximately

four. At best, however, it is evident

that the occlusal morphology thot is

provided when the poster ior occlu-

sion is restored should have a built-in

toleran ce, rather than a precise p oint

relationship. This aspect is the sub-

ject of a subsequent article.

Conclusion

The object of the bimanual manipu-

lat ion technique is to record the ma n-

dibular posit ion with the condyles

posit ioned where the elevotor mus-

des would seat them in a terminal

hinge dosu re,

Refe

Reprints

Dr. Edward Levinson

UHorcour t House

19a Cavendish Squore

LondonW, I.England

Celenz a, F. V.:

The Centnc Position: Replacement an

Cho rade r, J. Prosthet, De nt, 30:591-598

1973.

Dowson, E

Evaluation, Diognosis, and Treatment o

Ocdusal Problems, St, Louis: C, V Mosb

Co, 1974.

Glossory of Prosthodontic Terms 11977

J.

Prosthet. Dent., 3874-75,

Honau.

Dentol Engineering, Val. I. Buffalo: Hana

Engineering Co., I92

Jankelson, B., Hoffmann, G., and Hende

son,

J.

A.:

The Physiology of the Slomotagnathic Sys

tem.J.A.D.A. 46:375-330, 1953.

Kontor, M E., Silvermon,S,1.,ond Garfmi


15/15

10. centric relation. the anterior biting jig for recording the clenching position

Documents