CH5: FB & CR Flashcards
A faulty occlusal plane upsets the equilibrium between
the tongue and the ______muscles
buccinators muscles
Occlusal Plane Too low:
- “Denture look” or reverse smile
* Could lead to tongue and cheek biting
Occlusal Plane Too high:
• The tongue will not be able to rest on the lingual cusps of the lower
posterior teeth to prevent displacement
• The tongue will be raised up and thus raise up the floor of the mouth
allowing for partial loss of border seal
• Greater accumulation of food in the sulci
Function of area “A”
esthetic & speech
NOT functional demands
When viewed from the front, the occlusal plane
should be parallel to the ____ (plane/line)
interpupillary line
The _____ is the most controversial landmark in
occlusal plane orientation.
ala-tragus line
However, this extra-oral landmark is reliable as both
its ends do not change with age.
location of the condyle?
11 to 13 mm
anterior to the posterior border of
the tragus
on the tragus-canthus line
limit of negligible error for location of condyle
6mm radius (+/-3 mm)
Arbitrary hinge position
11-13 mm forward of tragus on the tragus-canthus line
i.e location of the condyle
Thus facebow permits
an ↑ or ↓ VDO of ___mm using
the original articulator
FB & CR mounting
3mm
If a Facebow is used __ mm of mand path can be predicted
6mm
If a Facebow is used __ mm of path can be predicted at ↑in VDO
3mm
same for ↓ VDO
VDO can be changed on the articulator.
T/F
T
(during tooth try-in or
clinical remount,
if needed)
Transverse Horizontal Axis of FB: An imaginary line around which the mandible may rotate
within the _______ plane
sagittal plane
Facebow
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) Orientation of the incisal plane in relation to inter-pupillary line
problem with using simple hinge articulator
-puts the hinge in the wrong position in relation to the
maxillary plane – and thereby the axis of rotation.
-Mounted cases will have a different arc of closure
resulting in
-greater adjustments after insertion
MIP or Maximal Intercuspal Position:
complete intercuspation of the opposing teeth
independent of condylar position
MIP=best fit of the teeth regardless of the condylar position.
T/F
T
In Complete Dentures,
We need a maxillomandibular relation that is:
- Independent of tooth contact
- Clinically discernable
- Clinically reproducible
CR
the Maxillomandibular relationship in which the condyles articulate with
the thinnest avascular portion of their respective disks with the complex
in the anterior-superior position against the shapes of the articular
eminencies.
CR depends on tooth contact.
T/F
F
CR is independent of tooth contact.
CR is clinically discernible when the mandible is directed ___ and
___.
superior and anteriorly
It is restricted to a purely ___ movement about the
_____ axis.
It is restricted to a purely rotary movement about the
transverse horizontal axis.
In Edentulous patients MIP ≠ CR.
T/F
F.
Edentulous pts. MIP must = CR
In dentate patients MIP ≠ CR.
T/F
T
In edentulous pts., first contact must be _______
In edentulous pts., first contact must be maximum contact
Edentulous: If there is a tooth out of place it will cause the \_\_\_\_\_\_\_\_\_ (denture or teeth /jaw) to move
Denture
Dentate: If there is a tooth out of place it will cause the \_\_\_\_\_\_\_\_\_ (denture or teeth /jaw) to move
Jaw
Consequences of MIP ≠ CR in CD pts.
1) denture will move, causing bone loss,
2) or the jaw will move, causing joint wear
CR is recorded ____ (before/after) rims adjusted and VDO has been established
after
Pure rotation (CR) is a function of _____
degree of opening (VDO)
The closer the jaws are to VDO, the less likely they will _______
translate
During Interocclusal Records - ____ must precede CR
VDO
After cutting a step in the mandibular rims, ___ & ___ are the only areas in contact now to maintain VDO
Areas A & B are the only areas in contact now to maintain VDO
Aluwax should sit _____ mm above lower rim
1-2 mm
Purpose of notches on casts
Notches required
for repositioning
casts on articulator
after processing
Set the pin to ___ before mounting FB registration
ZERO
A ~_____mm space must be left.
The rims must not touch at the end of the CR record
0.5-1 mm
CR Registration Error Causing
Anterior Open Contact:
- Record Bases may slip or lift during bite registration
- Record Bases are touching @ the heels
- Record Bases may tilt (anterior or posterior)
- Tongue can push out lower Record Base
Preventing errors during CR
• Stabilize the lower base during bite registration
• Adjust the record bases with a bur so they do not touch
during bite registration (heel interference!) – repeat CR
• Practice/rehearse CR first
• Use your guidelines (midline & canine lines) as a reference
While restoring rims after mounting, Do not touch areas _____
A & B
While restoring rims after mounting, why do we not touch areas A & B
They are holding your VDO (@36mm)
Completed Rims Guidelines:
U/L rims in FLUSH (and FLAT) contact at VDO = 36mm
A= 19mm
B= 17mm
C= 1/2 RMP
