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
What did Thornton conclude from her literature review on anterior guidance?
Thornton, Linda J. “Anterior guidance: group function/canine guidance. A literature review.” The Journal of prosthetic dentistry 64.4 (1990): 479-482.
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
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?
Anyone else?
1.25 mm, Gysi. Accepted range when restoring is 0.3 to 0.8 mm.
Also, Schuyler, Dawson, Stuart
Why did you restore in centric relation? (4 reasons)
- 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.
- From a design standpoint, less challenging than group function.
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.
Definition of neuromuscular relief per Guichet
A neuromuscular release of the mandible is that response
induced in the muscles which move the mandible by proper occlusal treatment.
This response will allow the dentist to easily manipulate the condyles to centric
relation and to rhythmically or arythmically arc the mandible to forcible occlusal
contact, in arcs of 10 to 15 mm. as measured in the area of the incisor teeth, without
the induction of an inhibiting response in the patient’s musculature. It will also allow free-glide excursive movements of the mandible with the teeth in contact.
The response is somewhat similar to a “dead-fish” handshake.
Turrell’s Methods to Assess OVD for edentulous patients?
- Pre-Extraction Records
- Physiologic rest (Atwood, Tallgren)
- Closing forces (Boos)
- Tactile sense (Lytle)
- Facial dimensions (McGee)
- Phonetics (Pound is conversation, and closest speaking space is Silverman)
- Deglutition (Shanahan)
- Esthetics
- Open-Rest method
Who compared protrusive interocclusal records to pantographic tracings?
Lateral and protrusive records do not capture what things in comparison to pantographs (3)?
Curtis 1989
Compared coprwax to VPS. Found VPS was very comparable to pantographic record (no significant difference)
- No visual graphics
- Verify difficult border movements
- Aid diagnosis of functional problems of TMJ musculature
Which four authors demonstrated that the ability of dentists may vary in transferring pantographic tracings to articulate recordings? Especially rear wall and top wall
Coye, Winstanley, and Curtis and Sorensen
Who described Biologic occlusion?
What are the 9 facets of it?
Becker and Kaiser 1993
- No interference between CR and CO?
- No balancing contacts
- Cusp to fossa occlusal scheme
- Minimum one contact per tooth
- Canine guidance (Cuspid rise) or group function
- No posterior contacts in protrusion
- No cross tooth balancing contacts
- Eliminiate all possible fremitus
- Obtain and maintain a neurological release
Besides D’Amico, which famous two dentists also developed anterior guidance as part of their gnathological concept?
Stuart and Stallard
Also maybe Christensen
Who argued that OVD and rest VD are some of the most difficult positions to evaluate? (French guy?
Desjardins - he concluded that because all evaluation of rest position are somewhat unscientific, evaluation of OVD should not be confined to a single technique or consideration.
What is the point of Jankelson’s myomonitor?
What is the critique of it?
TENS myomonitor unit - stimulates muscles to relax and establish “myocentric occlusion”
It postures the rest position, reference point, intercuspation position in a protrusive position
Who wrote that 90% of dentition do not have concurrent MIP and CR?
Posselt
Define Dawson’s “freedom in centric”
How much?
Freedom to close the mandible either into centric relation or slightly anterior to it without varying the verticle dimension at the anterior teeth
Illustrated through a lingual concavity in maxillary teeth
Less than 0.5 mm
Does RVD change over time?
Little evidence to know. What we do know is that muscle tone changes over time and that could affect the measurement of RVD
Two studies by which three authors investigated EMG and canine guidance vs group function? Which muscles?
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
Which muscle is believed to help guide lateral movements?
Inferior head of the lateral pterygoid
What did 2015 Abudo study on Lateral Occlusal Schemes report on for their two groups of studies:
Group 1: Immediate Response
- Advantages to Canine Guidance
- Advantages to Group function
Group 2: Long-term
3. Long term prognosis (Does it affect mechanical complications, risk of TMD Disorder, or EMG activity?)
- CGO: Protective role for posterior teeth, and masticatory muscles. Decreased EMG for temporalis. Harder to clench with less tooth contacts
- GFO: Quicker mastication
3a. No relationship between mechanical complication and restorations (resins and fixed units) - based more on restorative material/bruxism
3b. TMD not associated with a certain scheme nor is treatment recommended by employing a scheme.
3c. Electromyography activity may short term increase, but resumes pretreatment level after 3 months.
How does canine guidance protect posterior teeth?
Reduces lateral forces resulting in less trauma to restorative material or tooth structure. The posteriors will only receive vertical forces.
Williamson and Lundquist - Studying masseter/temporalis
If only canine guidance, what muscle are active? What muscle is added if group?
Working side - only temporalis
If group function, masseter also
What determines OVD from a anatomic standpoint?
- Correct growth/positioning of maxilla/mandible
- Length of ramus/gonial angle
- Eruption of teeth and development of the alveolar process
Price 1991 - Rank the order of effect on occlusal tracings:
CI, ICD, ISS, PSS, RW, TW
ISS (0.2 mm), PSS (5º), ICD (5 mm), CI (5º), RW, TW
