12. centric & protrusive record

7/16/2019 12. Centric & Protrusive Record

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Robert W. Loney

Maxillo-Mandibular Relationships

Centric and Protrusive Records


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Problems Establishing Edentulous

Maxillo-mandibular Relationships

Edentulous patients have moredifficulty determining where theirdenture teeth should contact No periodontal membrane

Old dentures wont fit on casts

Record base fit and wax rim changes

confuse some patients


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Centric Position

Acceptable position should be:

Conducive to health

Relatively repeatable

position can be checked before dentures

completed


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Conducive to Health

Relatively Symmetrical Position

Not absolute symmetry

Less chance of muscle strain which

might occur in non-centered positions


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Hinge Position is Repeatable

relatively centered

patient can find stable

occlusal contactsrelatively easily

allows change in

vertical dimension


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Centric Relation (CR) Centric position of mandible in

relation to the maxilla

Defined by the position of thecondyles, rather than the teeth

Hinge position


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Centric Relation

Treatment position

Not necessarily ideal ornormal


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Centric Occlusion (CO) Maxillo-mandibular position

determined by teeth

Sometimes considered coincident with

maximum intercuspationor habitual

closure


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CRand CO have been defined

differently by various

investigators, and differently overdifferent time periods


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Where is Centric Relation?

Glossary of Prosthodontic Terms:

Independent of

tooth contact

Clinicallydiscernible when

the mandible is

directed

superiorly andanteriorly


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Condyles articulate with thinnest, avascular

portion disks

Anterior-superior position against slope of the

articular eminence


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Purely rotary

movement

about thetransverse

horizontal axis


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For the purpose of fabricating

complete dentures, the superior-

anterior position of Centric Relationwill be used


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Clinically the dentist cannot

determine the actual position of the

condyles at the time jaw relationsrecords are made


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When to Use Centric Relation

When entire occlusion being restored

No remaining posterior centric stops

When complete, fixed, or removable

partial dentures involve the entire

occlusion


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When to Not to Use Centric

Relation Stable occlusion

No pathology

Posterior centric stopspresent

No valid reason to change

Use maximum intercuspation


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Registering Centric Relation

Bimanual manipulation

Patient in a slightly

supine position


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Occlusion rim notched

to aid stabilizing the

record bases


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Index fingers on the rim,

thumbs under symphysis


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Jiggle the mandible

Mandible should freely arc Allow the patient to close into contact


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Do NOT push the mandible or

dislodge the record base

Medium must be dead soft

(Yurkstas and Kapur)


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Minimal closing pressure

(Yurkstas and Kapur)


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Recording Centric Position


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Preparing Occlusion Rims

Place 3 widely separated lines between

the rims in the centric position

CRITICAL! Check that record base

heels/rims do not touch


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Line up Marks

Eliminate contact with record

bases


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Max & Mand Occusion Rims

Two sharp V-shapednotches in themolar/premolar area ofeach sided wax

Depth 1-2 mm

1-2mm


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Ensure Adequate Notch Depth

Too Shallow

- no undercuts


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Rehearse making the record withoutrecording medium

Place occlusion rims intraorally PVS registration material (Memoreg) over

entire occlusal rim


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Thin Layer of Material

Too Thick Good


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Thin Layer

Want flat record, no

excess on sides of rims

Excess material recording

of the sides of the rim can

cause deflection when

checking record


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Making the Record

Have patient close into record

Ensure smooth arc of closure, nohorizontal deviations

Use index fingers to stabilize lowerrecord base


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Patient opens, relaxes,

and slowly closes


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Gently arc the mandible in

a hinge-like motion

There should be: No translation

No splinting


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Registering Centric Relation Patient slowly closes

Operator uses tactile senses to

ensure the mandible does not

translate


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Patient closes until rims are almost

touching (1 mm separation)

Ask patient to stop as soon as thisposition has been reached

Some may not be able to tell when

they contact


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Never instruct the patient to bite

firmly

Causes translation or inaccuracyin the record


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Hold position until

set 1-2 min

Remove both rims

together

Separate


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Registration Should be Sharp,

Not Rounded


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Mounting the Mandibular Cast

Ensure record is repeatable

Increase the height of incisal

pin 1 mm, invert articulator

Place wax rims together, lute

with sticky wax - 4 spots


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Mount the mandibular cast withmounting plaster

After mounting, remove the record &

adjust the incisal pin to allow contactbetween rims

Occlusion rims should be touchingevenly, over the entire occlusal surface


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Registering Centric Relation Do not alter incisal pin after

rims are contacting

Otherwise, height of correct

vertical dimension can be lost


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Check CR Record

Take new record, place onarticulator

Release articulator centric locks

Should arc into record without anytranslation

If doesnt take 3rd record to see

which one is reproducible


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Protrusive Records

Used to set

condylar guidance

Helps setting teethfor best occlusal

contacts


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Protrusive Records Protrude a minimum of 5-6 mm

Ease of determination

Protrude less than 12 mm

Maximum travel of the condylar element

on most articulators


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Protrusive Records

Registration material over entire

rim Patient closes with mandible

positioned anteriorly


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Protrusive Records

Material must interdigitate with the

opposing V-shaped notches

Record should cover entire rim surface


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Protrusive Records Condylar elements are released from

hinge position

Instrument protruded, and the rims

closed into record


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Adjust Protrusive Guide for

Maximal Interdigitation

S tti C d l A l


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Setting Condylar Angle

QuickTime and a

H.263 decompressorare needed to see this picture.


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Protrusive Records

The lateral

component of

condylar guidance(Bennett Angle)

can be set

arbitrarily at 15

Maxillomandibular Records


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Maxillomandibular Records

for Complete Dentures

Centric Relation

Treatment position

Operator assists to ensure a hinge position

Patient stops closure at initial contact

Protrusive

Programs articulator to optimize occlusion

12. centric & protrusive record

Documents

centric protrusive record

protrusive records7162019

repeatable position

loneyhinge position

symmetrical position

casts record base fit

actual position of thecondyles

loneycentric occlusion