Occlusion

Question 1

What is the ideal disclusive angle?

Answer 1

5 degrees greater than the condylar disclusive angle

Question 2

The more parallel the occlusal plane, the (shorter / taller) the posterior cusps.

Answer 2

shorter

Question 3

How does the Curve of Spee impact the morphology of the posterior teeth?

Answer 3

more acute curve = shorter height of the most posterior cusps

Question 4

Average mandibular lateral translation?

Answer 4

0.78mm

Question 5

How common is mandibular lateral translation?

Answer 5

80% of patients have 1.5mm or less

Lundeen

Question 6

What are the horizontal determinants of occlusion, and what do they generally affect?

Answer 6

1) intercondylar distance
2) distance from rotating condyle
3) distance from mid-sagittal plane
4) mandibular lateral translation

effects:
- direction of occlusal ridges & grooves
- distance between cusps

Question 6

Should you have taken immediate mandibular lateral translation into account?

Answer 6

Current scientific evidence does not support the need to include IMLT as a factor when prosthodontic treatment is executed.

Systematic review - Taylor, Bidra & colleagues

Question 7

What is the effect on occlusal morphology of increased distance from rotating condyle?

Answer 7

wider angle between laterotrusive and mediotrusive pathways

Ex. A premolar is further from the condyle than a 2nd molar.

Question 8

What is the effect on occlusal morphology of an increase in immediate lateral translation?

Answer 8

more IMLT = wider central fossa

(Wider angle between laterotrusive and mediotrusive pathways?)

Question 9

What is the effect on occlusal morphology of an increase in intercondylar distance?

Answer 9

smaller angle between laterotrusive and mediotrusive pathways

Question 10

How common is it to have a preferred chewing side?

Answer 10

78% of people have one

Okeson

Question 11

How does lateral jaw movement change during the course of chewing?

Answer 11

lateral (vs. vertical) movement is greater when:
- food is first introduced
- food is hard
- teeth are flatter (shorter cusps)

Question 12

What muscles are involved in protrusion of the mandible?

Answer 12

• lateral pterygoid (inferior)
• masseter

Question 13

What muscles are involved in laterotrusion of the mandible?

Answer 13

• lateral pterygoid (non-working side)
• temporalis (working side)

(medial pterygoid and masseter also contribute to a lesser degree)

Question 14

How did you make your anterior deprogramming jig, and how did you get it to the VDO?

Answer 14

• GC pattern resin as Lucia detailed with a smooth flat top extending on #8 and 9
• instructed patient to go through excursive movements and ensured that all movements were smooth with no hinderance from the jig
• jig in place for 10 minutes to deprogram muscle engrams
• trimmed jig to close vertical until the first point of contact while in CR to obtain CO
• while trimming, patient kept teeth apart
• bite registration was made in CO

Question 15

Who found that VDR adapts to change in VDO?

Answer 15

Antje Tallgren (she/her)

Question 16

What happens if you program the articulator 10 degrees less on the horizontal condylar inclination?

Answer 16

decreased posterior disclusion on the articulator compared to intraorally

article by Guichet describes decreasing the horizontal condylar inclination by 10 degrees for fixed restorations to incorporate negative error, such that the build-in anterior guidance provides more posterior disclusion when inserted intraorally

Question 17

What happens if you program the articulator 10 degrees less on the lateral condylar inclination?

Answer 17

increased posterior disclusion on the articulator (i.e. potential for posterior interference when restorations placed intraorally)

Question 18

Justification for canine guidance

Answer 18

1) Force on the canine is 1/8 that of the second molar. Because of the canine’s position along the lever relative to the force vector and the fulcrum, it has appx. 2x the capacity of the molar to resist lateral stresses. (i.e. It would take 8x the force to produce the same degree of periodontal stress on the canine as the molar.)
2) Crown:root ratio of the canine is almost twice that of the molar
3) Canine has a longer root
4) Less electromyographic (EMG) activity with canine guidance
5) Supporting bone around canine is more dense/coarse than bone around molar

1-3 Guichet - Principles of Occlusion (1970), 4 Manns (1987) & Williamson

Question 19

What is the position of the condyles when the mouth is closed?

Answer 19

condyles are in their most anterior superior position

Okeson

Question 20

Who was the first to discuss canine guidance?
Who else?

Answer 20

D’Amico
Stuart, Stallard, Lucia (gnathological society)

Question 21

centric relation (GPT definition)

Answer 21

tktktk

Question 22

Given a semi-adjustable articulator: What difference would there have been if you used a fully adjustable articulator?

Answer 22

Intercondylar distance and progressive side shift would have been measured, which has the potential to affect groove placement and cusp anatomy.

However, given the occlusal scheme I established (canine guided), the difference would not be clinically significant.

Question 23

What are A, B, and C contacts?

Answer 23

occlusal contacts on inclined planes

A: outer incline of mand B cusp - inner incline of max B cusp
B: inner incline of mand B cusp - inner incline of max L cusp
C: inner incline of mand L cusp - outer incline of max L cusp

In a theoretical mechanical sense, the most favorable contacts on an inclined plane are either
- two contacts on opposing planes (A-B and B-C) or
- three-point contacts (A-B-C)
- A-B and B-C are more stable occlusal contacts than A-C without B (tipping will occur)