Articulator Flashcards
A 5 mm change in the intercondylar distance setting causes what at the first molar?
Who wrote this?
What’s intercondylar average for males and females? Who wrote this?
A difference of 0.2 mm
Korb and McCollum
Males: 108; females: 102
Gysi
What was the first device to relate the maxillary cast to the approximate vertical opening axis within the TMJ? When?
Snow Facebow 1907
Who established that being within 5 mm of the traverse hinge axis results in minimal error?
What error results at the first molar with a 5 mm change?
Weinberg
0.2 mm at first molar
Who first described the separation of posterior teeth during protrusion?
What causes this?
Christensen
Caused by slope of the condylar eminence against which the condylar moves downward and the anterior guidance
When intercondylar width is wider on the articular than clinically, what happens to the paths of movement on the articular?
They are more distal on articular than on the patient
The presence of IMLT, if present, requires what change to cusps and fossae?
Shorter cusps and shallower fossae
As intercondylar distance increases on the articular, grooves on mandibular molars move in which direction?
Distally
Who wrote that for CR openings up to 20 mm, actual THA only makes very minor shifts?
Posselt
Average for horizontal condylar inclination?
How do you adjust it in an articulator?
45-60º
Adjust top wall
Average lateral condylar inclination (Bennett Angle)
How do you adjust it in an articulator?
12-18º
Adjust medial wall, mediotrusive, balancing side
For your case, why didn’t you use a fully adjustable articulator?
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 with no posterior deflections. The OVD, MI, and anterior guidance are not being altered or changed.
IMLT papers by Prieskel And Taylor
Protrusive paper by Curtis
Posselt indicated that the average AP discrepancy from CO to MIP was how much in 1958 “Studies in the mobility of the human mandible”?
1.25 + 1 mm
What did Abudo conclude in his SR of 9 articles regarding a 5 mm increase in OVD?
It is a “safe and predictable procedure without detrimental consequences”.
On a fully adjustable articulator, what are the most difficult pantographic tracings to transfer?
Rear wall and top wall adjustments
Nagy 2002
Many earpiece facebows use the Bergstrom point as its arbitrary point. Where is it located?
What did Beck report regarding accuracy of the Bergstrom point?
10 mm anterior to the external auditory meatus and 7 mm below the Frankfort horizontal plane.
Beck reported it was 4.1 mm from kinematic for 12 subjects and most accurate of points tested
Examples of third point of reference for Facebows
- Nasion (Artex)
- Infra orbital notch (Whipmix)
- Glabella
How is Bonwill’s triangle incorporated into the articulator? (pg 54)
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)
What is the radius of curvature of the condylar path for Artex CT?
Fixed at a radius of 12.5 mm in all Artex articulators (can be adjusted with glenoid fossa inserts)
If just a straight condylar path, you may have a condylar error of .2 mm error at 2nd molar
Four drawbacks to non-arcon articulator (Artex CT is non-arcon)
- Increasing vertical dimension/raising the incisal pin changes the condylar inclination but the condylar inclination is actually realized on the lower bow (not like the upper as in human anatomy) - can get up to an 8 degree difference in arc of closure
- Variations in anatomic condyle form and guidance cannot be reproduced in this articulator
- Cannot reproduce immediate side shift
- Does not correspond to human anatomy - not the best tool to understand masticatory organ simulation
Advantages to non-arcon articulators (pg 76)
- Complete opening of the upper bow
- Support of articulator in tipped back position
Possibly others - Glenoid fossa tracking can be lost when checking occlusal movements for Arcon
What reference point did you use to articulate your casts?
Guichet’s method of a fixed arbitrary distance from the incisal edge of the maxillary lateral incisor - 43 mm
It’s 7 to 10 mm below orbital and defines a plane that when patient is standing tends to be more parallel than other planes.
Also tends to place the casts in the center of the articulator.
How did you obtain CR records?
Dawson’s bimanual manipulation - no pressure applied while guiding the movement. With a Lucia jig with Peter neff modification
Aull 1965 Condylar Determinants
- Which side does a change in the condylar inclination have the greatest effect on cusp height? Laterotrusive (working) or mediotrusive (non-working aka balancing)?
Ex: Patient with CI of 25º versus 30º
The mediotrusive side (non-working / balancing) would have the greatest effect in that there is greater height in cusp available for 30º.
This is due to the detrusion of the advancing condyle.
Aull 1965 Condylar Determinants
- Which side does a change in the curvature of the eminences (condylar track) have the greatest effect on cusp height?
Ex. Compare 4 inch arc to 3/8 inch arch.
The mediotrusive side (non-working / balancing) aka advancing/detruding condyle.
The 3/8 inch allows more cusp height.
Aull 1965 Condylar Determinants
- Effect of pure horizontal side shift on cusp form?
Greater on working or non-working side?
What’s the effect on height also?
The greater the side shift, the flatter the cusps.
Greater on non-working / balancing / mediotrusive side.
Shorter cusps
Aull 1965 Condylar Determinants
- Effect of Vertical Shift of the Rotating Condyle (aka working side / laterotrusive) on Cusp Height? (Aka Surtrusion or Detrusion)
Greater effect on working or non-working side?
Effects cusp height
Greater effect on working side
Note this is the only condylar determinant that affects working / laterotrusive side more Surtrusion/Detrusion
Aull 1965 Condylar Determinants
- Effect of Intercondylar distance on cusp paths
Affect working or non-working side more?
Angle between laterotrusive and mediotrusive widens as intercondylar distance increases
In the paper, it seems like both are affected equally, but the more clinically significant would be the non-working (mediotrusive) side since that can lead to lingual cusp interferences
Aull 1965 Condylar Determinants
- Effect of pure horizontal side shift on cusp and groove paths
What is unique about side shift’s effect as a condylar determinant?
Angle between laterotrusive and mediotrusive widens as horizontal side shift increases
Unique: Side shift is only condylar determinant that affects both vertical and horizontal components of posterior teeth - Cusp height gets lower
Aull 1965 Condylar Determinants
- Character of pure horizontal side shift vs progressive on cusp and groove paths
Which side has biggest effect (working or non-working)
Start and end points are the same, but the biggest difference is near centric occlusion.
Biggest effect is on non-working (mediotrusive) side. Progressive disclusion shows a wider arch.
Aull 1965 Condylar Determinants
- Effect of Retrusive or Protrusive Horizontal side shift on cusp position?
Which side has biggest effect (working or non-working)?
Greater recursive movement makes things more distal.
Aull 1965 Condylar Determinants
- Sagittal plane - Effect of angle of eminence on height of cusps in protrusive movement
Ex. 0º vs 25º
25º allows for enlargement of cusp heights
Aull 1965 Condylar Determinants
9b. Sagittal plane - Effect of cusp condylar radius on height of cusps
Ex. 4 inch insert vs 3/8 inch insert
3/8 inch insert allows for enlargement of cusp heights
What are the three primary tracings recorded for a Stuart Pantograph, and what information do they provide?
- Horizontal tracing (good for Bennet movement and intercondylar distance effects)
- Sagittal (Condylar inclination and protrusion/retrusion)
- Frontal (Immediate and progressive Bennett movement)
Who introduced the term arcon?
Bergstrom 1950 (per Artex book, pg 56)
For your diagnostic wax-up, what kind of cusp relationship did you wax in? Cusp to fossa or cusp to marginal ridge?
Cusp to marginal ridge - mimic’s natural dentition and although it may not spread forces as well as cusp to fossa, it is easier for me to wax
Clinical implication of IMLT per Thomas Taylor, Bidra, Nazarova, and Wiens paper? IMLT is what kind of “outcome”?
Prieskel’s 1971 paper argued what on IMLT and canine guidance?
Preiskel/Goldstein’s 2021 CAT on IMLT - Conclusion?
- Clinicians may ignore the phenomenon of immediate lateral translation. IMLT is a “surrogate” outcome. Not direct practical importance.
- Magnitude of side shift at condyles is not the same as at the first molar - reduced by 50% due to overlap of canines
- Justifiable to question the necessity of attempting both to record IMLT and reproduce it on articulator. All reviewed studies had minimal IMLT and 2 showed a decrease as the anterior guidance was increased.
