Occlusion Midterm Prep (CONCEPTS!)

Anterior guidance:

Gliding anterior tooth contacts that control mandibular movement in protrusion and laterotrusion and help disclude the posterior teeth

During protrusion, which teeth should contact?

Anterior teeth only, posterior teeth should be discluded

Why are posterior contacts undesirable during protrusion?

They can apply damaging horizontal forces to the posterior teeth

What should the anterior teeth accomplish during protrusion?

Provide adequate contact/guidance to disarticulate or disclude the posterior teeth

What is the ideal guidance during a lateral movement?

Canine guidance

If canine guidance is not possible, what is the acceptable alternative?

Group function

Whar teeth does group function include?

Canine, premolars, and sometimes the mesiobuccal cusp of the first molar

How far posteriorly should desirable laterotrusive group-function contacts extend?

No farther posterior than the mesial portion of the first molar

Why are laterotrusive contacts farther posterior than the mesial first molar undesirable?

Force increases as the contact gets closer to the TMJ fulcrum

What two overlaps dictate anterior guidance?

Vertical overlap and functional horizontal overlap (FHO) of the guiding teeth

How does distance from the TMJ affect force on a guiding tooth?

The farther the guiding tooth is from the TMJ and site of muscle action, the less force is exerted

Why do more anterior guiding teeth receive less force?

The mandible acts as a mechanical lever anchored at the TMJ

What happens when lateral force is applied to anterior teeth?

Proprioceptors help modulate and shut off contraction of the muscles that close/elevate the mandible

How does moving guidance anteriorly affect stomatognathic stability?

More anterior guidance increases stability during eccentric movement

Which is more structurally stable: anterior guidance or molar guidance?

Anterior guidance

Obstacles to effective anterior guidance:

Interference, rotation, supraeruption, inadequate vertical/FHO overlap, open bite, deep bite, anterior Class II or III malocclusion, severe wear facets, malposition, or missing teeth

What is the most common mediotrusive contact?

palatal cusp of 2nd molar

VO stands for:

Vertical overlap

HO stands for:

Horizontal overjet

FHO stands for:

Functional horizontal overlap

T/F: Functional horizontal overlap (FHO) is the same as orthodontic overjet.

False

When the maxillary and mandibular guiding teeth touch in MI, FHO is =

0 mm

When the maxillary and mandibular guiding teeth do not touch in MI, how is FHO determined?

Measure the horizontal gap between the actual guiding/contacting surfaces

Anterior guidance effectiveness: Steep

≥5 mm vertical overlap with 0 mm FHO

Anterior guidance effectiveness: Ideal

4 mm vertical overlap with 0 mm FHO

Anterior guidance effectiveness: Delayed

4 mm vertical overlap with 1 mm FHO

Anterior guidance effectiveness: Shallow

1 mm vertical overlap with 0 mm FHO

Anterior guidance effectiveness: Absent

0 mm vertical overlap

What does increased FHO tend to do to the onset of guidance?

Delay posterior disclusion

What does a very small vertical overlap with 0 FHO tend to produce?

Shallow guidance

When must anterior guidance be preserved and recorded?

When restorative procedures change the surfaces of any guiding teeth

Mechanical incisal guide table:

does not provide enough information to reproduce the lingual contours of the maxillary anterior teeth

Custom incisal guide table:

an acrylic or putty guide table made to reproduce the patient's anterior guidance/lingual contour information

What are the 3 tabs of the RSOCCL form?

1) TMD Screening

2) Baseline Occlusal Exam & TMJ Evaluation

3) Centric Relation and/or Complex Case

When do you use RSOCCL Tab 1?

For every exam and recall

When do you use RSOCCL Tab 2?

For the initial patient visit

When do you use RSOCCL Tab 3?

For a splint or complex case

"One-touch occlusal/TMJ screening":

Muscle palpation, TMJ open-close-open, and side-to-side movement

Linea alba:

Scalloped tongue:

Wear facets:

**What if there is significant tooth wear but the occlusal surfaces don't fit together?

Maximum intercuspation (MI) is also called:

Centric occlusion (CO)

What is the goal of conformative dentistry?

design each restoration so it harmonizes with the existing occlusion and creates no new interferences

When is reorganized dentistry considered?

In bigger cases when the occlusion needs to be reorganized using an optimized model of occlusion

Centric relation (CR):

A musculoskeletally stable, repeatable jaw relationship with the condyles in their most superior-anterior position in the fossae, braced against the posterior slopes of the articular eminence, with the disks properly interposed

Is CR tooth-dependent or tooth-independent?

Tooth-independent

Why is CR clinically valuable in large restorative cases?

it is a stable, repeatable starting point

What is the condylar position in CR?

Most anterior and superior, in a relaxed repeatable position against the disc and eminence

Best patient position for locating/recording CR:

Supine

Why is anterior deprogramming used before locating CR?

To reduce learned protective muscle activity and make a reproducible retruded CR position easier to obtain

Muscle engrams:

learned automatic neuromuscular programs that coordinate jaw opening/closing and protective avoidance patterns

What does a deprogrammer do?

Temporarily separates posterior teeth and interrupts protective muscle memory so the muscles relax and the mandible can retrude more reliably into CR

How should a leaf gauge be oriented during deprogramming?

At a slight downward angle, helps the patient relax the mandible into the retrusive position

Dawson bimanual technique: patient/chair position:

Recline the chair, sit behind the patient, point the chin upward, and stabilize the head

What anatomy should an accurate CR record capture?

Both buccal and lingual cusp tips of maxillary and mandibular teeth

What should be preserved when trimming a CR record?

Cusp tips and flat fossa interfaces

Can one or more CR-MI slide components be 0 mm?

Yes

What is fremitus?

A tooth movement finding observed/palpated during occlusal function and recorded in the MI exam

Thick articulating paper thickness:

100-250 microns

What is the problem with thick articulating paper?

It is thick enough to alter occlusion and can create false/fake contacts

Thin/extra-thin articulating paper thickness:

40-80 microns

What is the advantage of thin/extra-thin paper vs thick paper?

Less likely to interfere with the patient's occlusion

When is horseshoe articulating paper especially useful?

When both hands are needed to guide the patient into CR

AccuFilm II thickness:

About 21-22 microns

Key advantages of AccuFilm II:

Minimal interference with natural closure/tactile perception, fewer false artifacts, good flexibility, good adaptation, and good-quality marks

Why is AccuFilm II useful for proximal contacts during CIMOE?

it is thin, flexible, adapts well to tooth surfaces, and is tough to tear

Which marking film is used at UOP?

AccuFilm II

For a highly polished gold crown, which AccuFilm color is recommended?

Red rather than black

How can AccuFilm be made to mark a shiny surface better?

Apply a thin coating of Vaseline

Why load double thickness for the initial marking?

To create larger, easier-to-see initial marks

How should articulating paper be positioned in the holder for better posterior control?

Flush with the tip of the holder

Foil thickness:

8-12 microns

Foil advantages:

More accurate readings than paper and useful for a final check of occlusal contact intensity

Liquid marking media thickness:

3 micron layer after solvent evaporates

Indications for liquid marking media:

Highly polished gold/ceramic contacts, internal fit of indirect restorations, RPD frame contacts, and proximal contacts

Common uses for occlusal marking sprays:

Proximal contacts, occlusal contacts, internal fit, and contacts between clips and implant bars

Occlusal indicator wax is used to detect:

Premature occlusal contacts or interferences, also can be used to check occlusal reduction

Occlusal indicator wax thickness:

0.32 mm

Why is conventional articulating paper/Mylar still needed even with T-Scan?

To locate the specific tooth contacts

What is the problem with the T-Scan sensor?

Its thickness may alter the bite/neuromuscular behavior it is trying to measure, muscle activity can interfere with the bite

Can a high-pressure contact appear as a small mark?

Yes, especially on a prominent edge such as a marginal ridge or cusp incline

When should occlusal adjustment of an indirect restoration begin?

After proximal contacts and intaglio fit are adjusted and optimal marginal seal is confirmed

Which color is then used to check excursive movements?

Red

Why check the patient's preoperative occlusal scheme before adjusting a crown?

Not every patient has canine guidance, the restoration should conform to the patient's existing scheme

For one or two crowns, what type of occlusal approach is generally used?

Conformative dentistry

Translation:

All points within a body move with identical motion, such as sliding forward

Rotation:

The body turns around an axis, such as pure hinging

3 axes of mandibular rotation:

Horizontal axis, vertical axis, sagittal axis

Maximum arc of pure rotation:

About 10°-13°

Total pure hinge capacity:

About 15-18 mm

Average incisor separation achievable by pure rotation:

About 12 mm

Maximum mandibular opening:

About 40-60 mm, average about 45-50 mm

What causes translation after the pure rotational opening limit?

the inferior lateral pterygoid contraction moves the condyle-disc assembly forward along the articular eminence

Bennett movement:

lateral movement of the mandible during laterotrusion

Working side:

The side the mandible moves toward, laterotrusive/rotating side

Non-working side:

The side opposite the movement, balancing, mediotrusive, or orbiting side

Why can an immediate side shift occur?

Slack in the collateral ligaments plus the shape of the medial wall allows medial/lateral freedom at the condyle-disc-fossa assembly

Working condyle during immediate side shift:

Shifts laterally first, then rotates

Non-working condyle during immediate side shift:

Shifts medially first, then travels downward and forward