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-génial plane
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
A study by which three authors investigated EMG and canine guidance vs group function?
Shupe, Williamson, and Lundquist
- Decreased muscle activity for canine guidance compared to group function, and when they reversed it they had increased muscle activity for group function
What did Thornton conclude from his literature review on anterior guidance?
Evidence based science does not preclude superiority of one philosophy over another, but current observations appear to number more proponents of canine protected articulation
Which two famous authors (amongst others) proposed the “freedom from centric” concept?
(Also regarded as space provided for the natural arc of closure of the mandible)
Schuyler and Dawson, maybe also Posselt?
The 2021 Goldstein/Goodacre article on FMA concluded what about FMA for outcomes and dictating treatment?
Who discussed using FMA first?
Lack of evidence to support the use of FMA as a diagnostic procedure to predict outcomes or dictate prosthodontics treatment
DiPietro
The 2016 Taylor/Bidra/Nazarova/Wiens systematic review on 23 studies on IMLT concluded what?
Is recording IMLT a surrogate outcome or true outcome?
What anatomical factors support questioning IMLT?
No scientific evidence on the clinical implications of IMLT. Current scientific evidence does not support the need to include IMLT as a factor when restorative treatment is planned/executed.
Clinicians may ignore the phenomenon of IMLT.
- Surrogate outcome - does not provide tangible benefit or harm to the patient/clinician.
- Variations in recording IMLT (patient age, neuromuscular release, sedation), canine guidance, and if it is physically possible when the condyles are fully braced against the eminentiae.
What effect does horizontal condylar inclination have on posterior teeth cusp angle in protrusion?
Increased HCI: Greater cusp angle in protrusion
Effect that LCI has on posterior teeth cusp angle?
Increased LCI: Less cusp angle mediolaterally
Wider intercondylar distance has what effect on posterior teeth cusp pathway directions for the maxillary and mandibular arches?
Wider distance: Max pathways are more MESIALLY directed and Mand pathways are more DISTALLY directed
Which famous author argued that group function was inevitable over time?
Beyron
According to Wiens/Priebe, what are the three most likely Temporomandibular disorders observed?
- Occlusal-muscle disorders related to parafunction
- Internal joint derangement
- Degenerative joint disease
Draw the Posselt Envelope of Function from Sagittal plane for your patient (CO = MIP)
Draw it
2021 Preiskel/Goldstein CAT article on IMLT
- Most studies on IMLT are on what kind of patient population?
- Is IMLT observable on some patients? Is it of significant magnitude?
- Is there evidence on the prevalence of IMLT in patients needing rehabilitation?
- What effect would IMLT have on the occlusal scheme?
- Most all studies are on dentally healthy patients (not on anyone who needed restorative care).
- IMLT is observable but is of minimal magnitude.
- No.
- Width of central fossa and ridge/groove direction on molar teeth as well as cusp height, particularly on the non working size
What did Dawson suggest caused immediate side shift “artifact” tracings?
Change in distance between the stylus and the tracing plates on the side of the orbiting condyle
Do Stuart or Denar pantograph recordings have flags or stylus on the lower members?
Stuart - Stylus on lower membrane with anterior flag.
Denar - All flags are down on the lower member
What is normal “long centric” distance. Who described this?
1.25 mm, Posselt. Accepted range when restoring is 0.3 to 0.8 mm.
Why did you restore in centric relation?
There’s support for an association between CO-MID discrepancies and occlusal instability as well as TMD. CR is considered a predictable, physiologic, reelable and reproducible location from which pathologic occlusal contacts are minimized in excursive movements. There isn’t much documented complete mouth reconstructions in MIP also.
Which authors wrote a classic 1992 article on restoring worn dentition and advised a 6 to 12 week observation period for provisional restorations?
Rivera-Morales and Mohl
What did Orenstein, Bidra, Agar, and Taylor publish in 2015 regarding OVD, lower facial height, and facial esthetics?
Incremental changes in anterior guide pin opening up to 5 mm did not correlate to similar increases in lower facial height. Made no difference whether layperson, general dentist, or prosthodontist.
