Articulators Flashcards
A 5mm change in the intercondylar distance setting causes what at the second molar?
0.2mm error of the height of working & balancing cusps
wider -> pathways are more distal
The effect of increased distance from rotating condyle is ______________.
wider angle between laterotrusive and mediotrusive pathways
Okeson - Management of Temporomandibular Disorders
The effect of increased distance from midsagittal plane is ______________.
wider angle between laterotrusive and mediotrusive pathways
Okeson - Management of Temporomandibular Disorders
The effect of increased IMLT is ______________.
mesial movement of mandibular molar ridge and groove postitions
greater effect in balancing side
- shorter cusps
- wider central grooves
- wider angle between laterotrusive and mediotrusive pathways
Okeson - Management of Temporomandibular Disorders
The effect of increased intercondylar distance is ______________.
ridge and groove positions move distally on the mandibular molar
smaller angle between laterotrusive and mediotrusive pathways
balancing cusp height increased slightly
Okeson - Management of Temporomandibular Disorders
What is the effect of condylar guidance on posterior occlusal morphology?
Steeper condylar guidance allows for taller posterior cusps
Okeson - Management of Temporomandibular Disorders
What is the effect of anterior guidance on posterior occlusal morphology?
Greater vertical overlap allows for taller posterior cusps.
Greater horizontal overlap necessitates shorter posterior cusps.
Okeson - Management of Temporomandibular Disorders
What is the effect of occlusal plane on posterior occlusal morphology?
A plane that is more parallel to condylar guidance necessitates shorter posterior cusps.
Okeson - Management of Temporomandibular Disorders
What is the effect of Curve of Spee on posterior occlusal morphology?
A more acute curve necessitates shorter (most of the) posterior cusps.
Okeson - Management of Temporomandibular Disorders
What is the effect of lateral translation movement on posterior occlusal morphology?
All of the following necessitate shorter posterior cusps:
- greater lateral translation movement
- more superior movement of rotating condyle
- greater immediate side shift (also necessitates wider fossae)
Okeson - Management of Temporomandibular Disorders
Who first described separation of posterior teeth during protrusion?
Christensen
“Christensen’s phenomenon” (coined by Posselt, but would have been more accurately called Balkwill’s phenomenon since he had previously described it)
Christensen suggested the use of a PROTRUSIVE RECORD to measure the angle of the condylar paths that he believed corresponded to the observed space and to use this record to set the condylar controls of an adjustable articulator
When intercondylar distance is wider on the articular than the patient, what happens to the paths of movement on the articular?
They are more distal on the articulator than on the patient.
As intercondylar distance increases on the articular, grooves on mandibular molars move in which direction?
distal
Average horizontal condylar inclination?
How do you adjust it on an articulator?
45-60º
adjust top wall
Average lateral condylar inclination?
How do you adjust it on an articulator?
12-18º
adjust medial wall (mediotrusive, balancing side)
aka Bennett angle
For your case, why didn’t you use a fully adjustable articulator?
IMPORTANT
I was able to control the effects of the posterior condylar guidance and anterior guidance once I recorded my prototype intraorally and verified that I had mutual protection without posterior deflections.
I also did not alter the patient’s occlusal vertical dimension
According to Posselt, what is the average AP discrepancy from CO to MIP?
1.25 +/- 1mm
On a fully adjustable articulator, what are the most difficult pantographic tracings to transfer?
rear wall and top wall adjustments
What is Bergstrom point, and what is its significance?
10mm anterior to the EAM and 7mm inferior to Frankfort horizontal plane
many earpiece facebows use this point as their arbitrary point
most accurate of the arbitrary points tested (Beck)
Frankfort horizontal plane
infraorbital rim (orbitale) to supratragal notch (tragion)
Is the Stratos 300 a fully-adjustable articulator?
No. It is semi-adjustable.
Stratos 300 allows programming of condylar inclination and Bennet angle but is considered semi-adjustable due to its inability to “time” immediate side shift and the lack of a sophisticated tracing apparatus.
Why did you choose the Stratos 300 articulator?
- allows programming of condylar inclination and Bennet angle
- arcon
- wide posterior view (better visibility of lingual anatomy and assessing for interferences)
- inclined support
- stable when inverted (facilitates articulation of the mandibular cast)
- my lab has this articulator in their armamentarium as well
Benefits of an arcon articulator
1) truer anatomic representation of the condylar mechanism
2) better simulates natural mandibular movements
3) condylar guidance remains stable as articulator opens and closes
because the max occlusal plane remains stable relative to the condylar guidance as they are both attached to the upper member of the articulator
(vs. non-arcon: condylar guidance angles change when the articulator is opened– as soon as you open the articulator, the Frankfort horizontal plane changes)
points of Bonwill’s triangle
- mandibular central contact point
- right and left mandibular condyles
How is Bonwill’s triangle incorporated into the articulator?
Leg length of 100 mm connecting the midpoint of the condyles with the incisal point and thus fixing the intercondylar distance. This forms an angle of approx 25 (open in the posterior direction) to the masticatory plane (Balkwill’s angle)
points of Balkwill’s triangle
- mandibular central contact point
- DB cusps of mandibular 2nd molars
Balkwill’s angle
angle between Bonwill’s triangle and Balkwill’s triangle
(Bonwill - condyles -> mand central)
(Balkwill - DB cusps of mand 2nd molars -> mand central)
What is the radius of curvature of the condylar path for Stratos 300?
12.5mm
What is the range of Bennett angle adjustment for Stratos 300?
0-30º
What reference point did you use to articulate your casts? Why?
infraorbital rim (Frankfort plane)
patient’s nasal assymmetry
Frankfort plane
superior border of EAM to the infraorbital rim
How did you obtain CR records?
IMPORTANT
Lucia jig with Neff modification - palatal surface of jig was trimmed to a flat platform (instead of inclined plane) to permit upward condylar movement without a distalizing effect
Dawson’s bimanual manipulation - no pressure applied while guiding movement
On which side (working or non-working) does a change in condylar inclination have the greatest effect on posterior cusp height?
non-working (balancing/mediotrusive/orbiting)
This is due to detrusion of the advancing condyle.
Aull - Condylar Determinants, 1965
On which side (working or non-working) does a change in curvature of the condylar eminence have the greatest effect on cusp height?
non-working (balancing/mediotrusive/orbiting)
This is due to detrusion of the advancing condyle.
A smaller curvature allows for taller cusp height.
Aull - Condylar Determinants, 1965
What is the effect of pure horizontal side shift on cusp form?
Is this greater on working side or non-working side?
The greater the side shift, the SHORTER the cusps. (also wider central fossa)
The effect is greater on non-working side.
Aull - Condylar Determinants, 1965
What is the effect of vertical shift (surtrusion or detrusion) of the rotating (working) condyle on cusp height?
Is this greater on the working side or non-working side?
Affects cusp height (cusp height must be shorter)
The effect is grater on the working side
note: this is the only condylar determinant that affects the working side more
Aull - Condylar Determinants, 1965
What is the effect of change in intercondylar distance on posterior tooth morphology?
Cusp paths move distally as intercondylar distance increases
intercondylar distance errors can lead to lingual cusp interferences on the non-working side
Aull - Condylar Determinants, 1965
What is the effect of increased condylar eminence angle on posterior cusps in protrusive movement?
taller posterior cusps are possible (mandible discludes more quickly)
Aull - Condylar Determinants, 1965
What are the three primary tracings recorded for a Stuart pantograph, and what information do they provide?
1) Horizontal tracing– Bennet movement and intercondylar distance effects
2) Sagittal tracing– condylar inclination and protrusion/retrusion
3) Frontal tracing– immediate and progressive side shift (Bennet movement)
Celenza Class 1 A & B
Class 1 = simple holding instrument
1A - vertical motion only (Verticulator!)
1B - vertical motion related to joints, accepts facebow
Celenza Class 2 A, B, C
Class 2 = horizontal & vertical motion not related to TMJ
2A - eccentric motion on cast not related to patient motion
2B - eccentric motion based on arbitrary values
2C - eccentric motion determined by engraved records (movements are based on teeth rather than TMJ, which is why it’s still a class 2)
Celenza Class 3 A & B
Class 3 = uses averages/mechanical equivalents for condylar pathways, orients casts to joints
3A - accepts protrusive records only
3B - accepts lateral and protrusive records (Stratos)
Celenza Class 4 A & B
Examples of each
Class 4 = fully adjustable, accepts 3D dynamic registrations
4A - engraved records to determine condylar path
Ex: TMJ articulator
4B - option for both angled or custom engraved records
Ex: Denar D5A, Artex Type CR, Stuart gnathological computer
Rihani classification of articulators (what records can each accept?)
non-adjustable (one or two - facebow, CR, protrusive)
semi-adjustable (all three - facebow, CR, protrusive)
fully-adjustable (all five - facebow, CR, protrusive, lateral, intercondylar distance)
arbitrary facebow
Uses anatomical averages to represent the hinge axis.
If arbitrary facebow is 5mm off of the true hinge axis, how much error would be produced at the second molar?
.2mm
(assuming a 3mm CR record)
Hanau’s formula
L = H/8 + 12
L - lateral condylar guidance
H - horizontal condylar guidance
What does it mean to incorporate negative error into the articulator?
articulator overcompensates for mandibular movements
ex. program the horizontal condylar guidance lower (shallower) so the cusps must be shorter
(anterior teeth override the condylar inclination)
Bennett angle
angle formed by the sagittal plane and the path of the non-working condyle during lateral movement when viewed in a horizontal plane (from above)
Bennett movement
lateral shift of the working (rotating) condyle during lateral excursion
Fischer angle
angle between the sagittal condylar inclinations during protrusive and lateral excursions on the non-working side viewed in the sagittal plane
this is the medial slope of the condylar fossa
