Facebow and CR Flashcards
purpose of facebow?
transfer functional components from patient to articulator efficiently, but also esthetic component
from occlusal and esthetic standpoint- the more closely the models translate the function, the less occlusal adjustment we’ll have to do when we take the restoration back to the mouth
can we find exact location of condyle?
maybe but we are using an anatomical average
anatomical average of condyle location
11-13 mm anterior to the posterior border of the tragus on the tragus canthus line
limit for negligable error when taking facebow
6mm
+/- 3 mm radius of the actual condylar location
two circles and what they represent and mean
one if we found the exact center
one if we estimated and used arbitrary point
at 2 points on the circle, the paths will cross and be identical
what does faceboq permit for VDO measurement?
+3mm or - 3mm (increase or decrease)
bring trial to patient but it is not fitting, problems with VDO. how much can you change it?
+ / - 3mm in either direction - as this is permitted by the articulator when taking facebow and CR
close it down 3mm or open it 3mm
WITHOUT RE-MOUNTING
what happens if we open more than 3mm on the patient?
CANT - Pt. will start to go into TRANSLATION
if the path can be predicted what else can be predicted?
- position of the mandible
- position of mandible at increased VDO
- mandibualr position at decreased VDO
- occlusal contacts can be predicted
- occlusal contacts at increased or decreased VDO
can VDO be changed on the articulator?
yes - during tooth try-in or clinical remount, if needed
transverse horizontal axis
an imaginary line around which the mandible may rotate within the sagittal plane
axis orbital plane is the?
the horizontal plane established by the transverse horizontal axis of the mandible with a point on the inferior border of the bony orbit
*used as horizontal reference point
orientation of the incisal plane in relation to the inter-pupillary line?
parallel
what does the facebow do?
transfers the position of the maxilla in relation to the condyle (transverse horizontal axis) and the reference plane (based on the third point of reference)
allows us to alter the vertical dimension (+/-3) with negligible error
how does the facebow orient the dental cast?
in the SAME RELATIONSHIP TO OPENING AXIS OF THE ARTICULATOR
implication of using a simple hinge articulator
yoou are “guesstimating” without a facebow which puts the hinge in the wrong position in relation to the maxillary plane – which also alters the axis of rotation
mounted casts will have a different arc of closure and the AXIS OF ROTATION IS SIGNIFICANTLY HIGHER
MIP
Intercuspation of opposing teeth
INDEPENDENT of condylar position
‘best fit of teeth’
occlusion/ Maxo-mandibular relation we need in complete denture?
INDEPENDENT of tooth contact
clinically discernable
clinically reproducible
AKA
CENTRIS RELATION
Centric Relation
condyles articulate in THINNEST portion of respective disks in the ANTERIOR-SUPERIOR position against eminence. INDEPENDENT of tooth contacts
clinically discernable
PURE ROTATION ABOUT TRANSVERSE HORIZONTAL AXIS
Relationship between MIP and CR in complete denture?
MIP=CR
what happens if MIP does not equal CR in complete dentures?
The denture will move, causing BONE LOSS, or the jaw will move, causing JOINT WEAR
what controls the path of mandible in natural dentition
the inclines
what controls the path of mandible in artificial dentition?
HINGE controls the path
because we set our teeth to compliment this
first contact in edentulous?
must be the MAXIMUM CONTACT
Tooth out of place in edentulous patient?
it will contact and cause the denture to move out of place
the mandibular path must be reproduced by teeth and hinge simulataneously
CO=CR
tooth out of place in dentate patient?
it will cause the jaw to move and may not be symptamatic for patient (or could be)
during centric relation record IN slc describe hand placement
the fingers are on THE BUCCAL SHELF so it doesnt move move and the thumbs are BELOW the mandible
need to stabilize lower RB while take CR record
when do we record CR for complete dentures?
AFTER rims are adjusted and VDO has been established
vertical when CR is recorded?
CR is always recorded at a slightly open vertical
like closest speaking space
about .5 mm
what maintains VDO during bite registration
A and B must maintain it
what maintains VDO during tooth set up?
C and D
what limits the chance of pt. going into translation during capture of CR?
Having the jaws close to VDO
where do you cut a notch? shape?
Diagonal notch cut into area D
cut on an angle so it locks into place
where do you cut a step? size/ shape?
1mm STEP in area C
which rim do you lubricate when taking CR?
Maxillary Rim
Aluwax - for what - how use it? placement
Fan fold 2/3 times with a warm knife and will go in area of where you created the step in area C
1-2 mm above area C because this is what we need to engage the notch that we made in area D
majority of problems in tooth try in or insertion of denture involve?
anterior open bites
how do you get anterior open bites from CR registration? AKA what errors occur during CR that result in anterior open bite
- record bases may slip or lift during bite registration
- Record bases are touching
- record bases may tilt (anterior or posterior)
- Tongue can push out lower Record Base
how to prevent CR registration mishaps
- Stabalize the lower tray during bite registration
- Adjust the record bases with a bur so they do not touch during bite registration (heel interference)
- Practice /test CR first
where is pin when mounting lower cast
zero
