Occlusion, OVD, Anterior Guidance Flashcards
Balkwill Angle definition. What is the average angle?
Balkwill Triangle definition
Angle formed from condyles to the mandibular central incisor in contrast to the occlusal plane. 26 degrees
Triangle formed by Balkwill Angle and occlusal plane
Bonwill Triangle definition
4 inch equilateral triangle from condyles to mandibular central incisor’s incisal edge
Fischer’s Angle definition
Angle of non-working condyle’s average path protrusive path in sagittal plane
Monson Circle definition
Where is Monson’s proposed Center of Rotation located?
4’’ inch radius circle formed by condyles, mandibular central incisors, that ideally forms the curvature of the occlusal plane
- Glabella
Laterotrusive/mediotrusive is equivalent to what in working / balancing terminology?
Laterotrusive = working = non-balancing
Mediotrusive = non-working = balancing
“Latero Works, Medio Balances.”
Frankfort Mandibular Plane Angle (FMA)
Angle between porion-orbitale plane and menton-gonion plane
Menton (chin)
Gonion (angle at corner of mandible)
Bergstrom’s Point - Where is it?
What’s the point of it?
A point 10 mm anterior and 7 mm inferior to external auditory meatus (on Frankfort horizontal plane)
Assists in locating hinge axis
GPT definition of Centric Relation
A maxillomandibular relationship, independent of tooth contact, in which the condyles articulate in the anterior superior position against the posterior slopes of the articular eminence. In this position, the patient is restricted to a purely rotational movement. From this unrestrained, physiologic maxillo-mandibular position, the patient can make lateral, protrusive, and vertical movements. It is a clinically useful and repeatable position.
Posterior determinants of occlusion
Horizontal condylar inclination - Affect cusp height
Lateral condylar inclination (Bennet angle) - Affect cusp height and fossa width
(Maybe Immediate mandibular lateral translation) - Affect cusp height and fossa width
Anterior determinants of occlusion
Incisal guidance
Canine guidance
Steep eminence angle
- Action and Effect
Greater separation of posterior teeth
Longer cusps
Shallow eminence angle
- Action and effect
Less separation of posterior teeth
Shorter cusps
Steep incisal guide angle - Action/effect
Greater separation of anterior and posterior teeth
Longer cusps
Greater Bennett angle - action/effect
Distal arc mandibular movement
May decrease cusp height and pathway more distal on mandible
Shallow Bennett angle - action/effect
Mesial arc mandibular movement
May allow increase of cusp, and pathway is more mesial
Increased Bennet movement IMLT - Action/effect
Mand lateral movement towards working side condylar pathway
May allow flatter cusps and wider fossae
Decreased Bennet movement IMLT - Action/effect
Less mand lateral movement towards working side
May allow sharper cusps and narrower fossae
Wider condylar distance - Action/effect
Greater distal arc mand movement
Mand ridge and groove more distal
Why restore MI at CO?
- Repeatability of CR (accurate mounting of casts)
- During final closure of mastication and just prior to deglutination, mandible assumes position approaching CR
- Wear facets are commonly found between CO and MIP indicating attempt of mandible to close along CR arc
- Also evident to the patient
- Elimination of deflective occlusal contacts improves muscle function and coordination
Low FMA is associated with:
1. What cephalic face type?
2. Increase/decrease occlusal forces
3. Increase/decreased overlap of incisors
- Dolicocephalic (<20 FMA)
- Increase occlusal forces
- Increase overlap of incisors
How can you assess OVD?
- Physiologic rest position (3 mm)
- Closest speaking space (1 mm)
- Esthetics (commissures, lower third, tooth display)
- Tooth contact
- Muscle straining
- Difficulty closing/swallowing
- Difficulty mastication
Normal mm range of motion at most open?
At right and left laterotrusion?
At protrusion
45-55
6 to 8
6 to 8
Who recommended that canine guidance should be developed to reduce posterior tooth wear?
What three reasons why?
D’Amico
- Canine teeth had unique proprioceptive control over mandibular neuromusculature
- Favorable crown to root ratio
- Less force-leverage magnifications at the anterior corner of the arch
Two studies by which authors investigated EMG and canine guidance vs group function with occlusal devices? Which muscles were looked at?
Which papers (3) discussed no difference between canine guidance and group function during chewing but a difference during clenching in the temporalis?
Shupe - decreased activity in masseter and temporalis
Williamson and Lundquist - Decreased activity in masseter and temporalis
- Decreased muscle activity for canine guidance compared to group function, and when they reversed it they had increased muscle activity for group function
Hannam and Belser; Okono; Gutierrez - lower EMG of temporalis with CG during clenching and lateral movement