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Occlusion = Relationship when Max. and Man. Teeth come together in functional contact

TMJ

Features unique to the TMJ: 1. Dense fibrous CT continuous with periosteum

o Periosteum = vascular CT covering bones except at joints (usually)

2. Fossa = lamellar bone covered with periosteum, has no cartilage

3. Has intraarticular disk made of collagen o Anterior band of disk attaches to lateral pterygoid

muscle 4. Retrodiscal area = loose CT, richly vascularized

o Bifurcates into elastic venous plexus 5. Synovial fluid in joint gives lubrication

6. Capsule encloses upper and lower compartments

7. CT ligaments medially & Laterally encapsulate joint

8. Temporomandibular ligaments give articular support and prevent extreme movements

9. R&L joints connected by mandibular bone that crosses the midline

10. Joint is loaded or closed packed.

Facial and Skeletal Planes Planes Description

SN – Sella Nasion Used in 2-D cephalometry

FP – Frankfort Horizontal Tragus to below the orbit

PP – Palatal Plane Posterior nasal spine to anterior nasal spine

OP – Occlusal Plane Retromolar pad to tip of lower incisor

MP – Mandibular Plane Follows lower border of mandible

**Disk position: Anterior to a vertical line perpendicular to Frankfort Horizontal

AKA Centric Relation!

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Movement: 1. Both bellies of lateral pterygoid contract together

2. Disk and condyle rotate under compression (approx. 6°)

a. Compartments lubricated by synovial fluid

b. Disk rotates under eminence, Condyle rotates under disk

3. Disk and Condyle move forward and down out of mandibular fossa

TMJ Exam

Exam What you are looking for

Palpation Tenderness (possible sign of inflammation) - Intrameatally and by lateral pole

Sounds Distinguish between clicking, pop, crack or crepitus - The timing of sounds is important

Range of Motion Inter-incisal distance (with or w/o pain) vertically and laterally -> Females: 35mm, Males: 40mm (Lateral: 8mm)

Jaw Trajectory Mandibular deviations from the midline on open and close

TMJ Biomechanics Condylar head in the TMJ is not simply a “ball in socket” type joint. Depending on the plane of view and deviations in

shape within the individual the TMJ will act differently.

- Angulations can also differ both between individuals and each condyle on the mandible. The Condyles can have

a vertical angulation of -10 – 35 degrees and vary between sides.

- Horizontal angle of the long axis relative to the cranium can also vary from 0 – 50 degrees (angle between red

and blue)

- Mandible movement involves both rotation and translation.

o Rotation: Occurs in multiple axis (not just the one hinge seen frontally) -> also rotates in a sagittal and

vertical orientation

o Translation: Forward and downward movement that occurs at the same time as rotation

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Centric Relation

Definition Maxillo-mandibular relationship where the condyles articulate with the thinnest avascular portion of their disks. The complex is in an anterior-superior position against the shapes of the articular eminences independent of tooth contact.

- It’s a TMJ position not a tooth position

Setting CR 1. Lucia Jig An anterior occlusal stop is used to allow anterior clenching without protruding the jaw.

- Superficial masseter and medial pterygoid (but not the temporalis) selectively activated.

- Muscle forces are thus directed upwards and forwards, so condylar seating occurs in the same direction.

- Can be used as a protrusive stop as well

2. Dawson Bimanual Method Relaxed jaw manipulated to ensure condyles are first in the articular fossae (not forward on the articular eminentia initially) Fingers (under the mandible) and thumbs (on outside of mandible) torque the mandible up and forward to seat the condyles on the articular eminence in CR (Usually ↓ the travel from RCP to ICP). Once here the jaw can be rotated open and closed.

- This method approximates the combined effects of jaw-closing muscles with acceptable reproducibility.

- Better than Lucia Jig in beginner hands -> But both are frequently used together by professionals

Movements

Movement Description What is happening (once you understand what the fuck this image is

showing)

Hinge True hinge can be determined by manipulating the mandible in the arc of centric relation (CR)

Right Condylar translation and rotation to the right-> moves the rotational axis forward on the left condyle (The opposite would be true for a left movement) Lateral Movements dependent on:

1. Articular eminence guidance (limit of condylar movement within TMJ)

2. Dynamic guidance (Canine rise or group function etc)

Protrude Forward translation by both condyles moves the axis down and forward in both rotation and translation

Note: When jaw moves to the right, the left condyle has shifted anteriorly while the right condyle is unmoved (R kinda just pivots; L mores forward

and down

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Condylar and Incisor Point Movement

What is it? A way to describe the jaw and tooth positions during movement

Red paths show: - Condylar movement - Posselt Figure (Mandibular midline incisor point) -> Path of movement of incisors during

open and close

Posselt Figure

** Jaw is positioned in a CR position (condyle is anterior and superior within the fossa )** CR: Condyles compressed forward in fossae. Jaw hinged in arc of CR (No translation) -> typical hinge so it’s a straight light.

- Opening beyond 15-20mm requires translation and rotation RCP: Retruded Contact Point (initial contact point is usually posterior teeth and you slide up into IP) IP: Intercuspal Position PG: Path of protrusive guidance (guided by contacts between anterior teeth and the lowers slide up the cingula of the uppers MP: Maximum Protrusion (Ligament constrained extreme position) RP: Habitual rest position -> Postural Vertical Dimension (PVD) typically 2-3mm open A -> B: Path of Retruded first tooth contact (RCP) and Intercuspal Position Contact (ICP) -> Determined by tooth contacts C: Rotational arc of mandible while hinging in Centric Relation -> Determined by TMJ anatomy and ligaments D: Wide open arc as a result of added translation with rotation within TMJ

Laterotrusive Movement Guided by working-side canines - Incisor point envelope is symmetrical in theory (In practice, often asymmetrical depending

on the patient) Working Side condyle rotates in 3D but has virtually no lateral displacement

- Non-working side tracks forward, downward and inward

Dawson Method

Jaw is manually positioned with upwards and forwards compression to seat condyles in the fossae located centrally on articular discs (may differ from the RCP in Posselt positioning)

- ↓ difference between RCP and ICP (wouldn’t even exist in ideal occlusion) - Jaw opening in CR and anterior guidance begin from same position

**This method encourages optimal condylar position and ↓ possibility of retrodiscal condylar placement and anterior disc displacement.

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Jaw Musculature and Mastication Muscle Function in Jaw movement

Temporalis

Elevation/Closing - Bipennate and highly tendinous near insertion

(coronoid process) - Most power generated from anterior portion - Pain in maxillary buccal sulcus likely from anterior

temporalis

Masseter (Superficial and deep)

Elevation/Closing - Multilayered, heavily pennated and very powerful - Highly tendinous along zygomatic arch - Superficial fibers: Upwards and forwards; - Deep Fibers: Vertical, synergy with temporalis

Medial Pterygoid

Elevation/Closing - Heavily pennated and tendinous - Fibers pull upward and inward

Lateral Pterygoid (Most important opener)

Depressor/Opener - Different super and inferior x-sectional sizes - Superior: Pull more superior and lateral than

inferior

Inframandibular (Mylohyoid + Digastrics) Depressor/Opener

**Many of these muscles have multiple compartments (Masseter = 6 ; Temporalis = 3 ; MPt = many). Tendon planes

within these muscles allow different movements from one muscle, not simply the gross direction of the muscle as a

whole**

Muscle vectors - Recruitment of muscles is task specific -> Different muscles for different tasks

- More muscles activated on working side of a unilateral clench - Muscle activity also changes between unilateral clenching vs a chew

Muscle Forces - Each muscle has a translational force AND torque force on the jaw - Torque determined by muscle force and perpendicular distance from

axis -> Condylar forces become equalized the more posterior the bite point moves (like a lever, most force is at the end vs close to the hinge)

- With multiple muscles contracting, all forces and torques sum and are countered by reaction forces and torques from teeth and joint -> If all sum to 0 then jaw doesn’t move (clenching).

*Largest force is at the bite point, next largest is on non-working side condyle and smallest on ipsilateral working-side condyle* –> If have a sore jaw, its better to chew on sore side to ↑ force on non- sore side condyle

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**Describing this graph will likely be an exam Q**

- Passive/natural muscle tension will hold the incisal separation

at 8-12mm -> Relaxed Rest Position (RRP) (when zombied out

people have their mouths partially open like this minion)

-

- Regular muscle tone (basal, low level activity) ↓ incisal

separation to only 2-3mm -> Habitual Rest Position/Postural

Vertical Dimenion (PVD)

o Difference in low level opening of Habitual Rest Position and ICP (when the jaw is

closed) = Freeway Space

- Between 5-12mm the least amount of activation/electrical activity is found

- Maximum bite force is generated at 12-25mm incisal separation (More open than that ↓ bite efficiency and

force)

Chewing Envelopes

Will have both an incisor point envelope, and a molar point envelope

- These envelopes can cause distinct wear patterns when collide with opposing dentition

Chewing patterns are different with each person and correlate typically with 4 phases:

1. Slow Opening (SO) - Transition from SC to SO depends on

2. Fast Opening (FO) thickness of bolus

3. Fast Closing (FC) - ICP is at apex of figure (when teeth collide)

4. Slow Closing (SC)

Natural Tooth Contacts

Intercuspal Position = Maximum interdigitation of the maxillary and mandibular teeth -> Mandible is then locked in a

stable position determined by the teeth to provide a stable platform for chewing and swallowing.

This is important in the masticatory cycle, since the cusps move into, and through, the Intercuspal

Position during the terminal phases of triturating the food bolus

- It could look gnarly, and have many malalignments but can still be stable-as bro. We

would be more concerned with wear associated with parafunction in these cases.

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- Both of these examples -> have stable Intercuspal

position

Possible ICP’s

- Any of these 3 (usually just the 1st two though) can occur. Want to recreate what the patient naturally has

Cusp-Embrasure

Contacts

Multiple supporting cusp tips contact flat opposing surfaces (usually central grooves and marginal ridges)

- Cusps may contact two adjacent marginal ridges - Red Dots: supporting-cusp tips with opposing

contacts in maxillary teeth - Blue Dots: Same as ^ but for mandibular teeth

Cusp-Fossa Contacts

Ideal contact occurs when supporting cusps are “tripodized” -> 3 mutually-reciprocating contacts around each cusp tip

- Creates max stability while also providing escape grooves to permit free jaw movement from ICP

- If contacts on inclined planes are not reciprocated, and if <2 contacts on each molar, tooth mobility can occur (tooth will move to try and become stable)

This is an ideal situation we try to create with prosthesis using casts. Rarely does this ever happen naturally though with 3 contacting surfaces **Cusp tips only in fossa’s, not marginal ridges**

Clinically you are probably only concerned that the cusp just makes it to the bottom of the fossa though -> Dr. Lee

ABC Occlusion “2 Row Occlusion” - Buccal cusp of lower molar occluding in fossa of

upper molar and lingual cusp of upper occluding in the fossa of the lower molar

A -> Contact btwn inner inclines of buccal cusps of max. molar with outer inclines of buccal cusp of mand. Molar B-> Inner inclines of lingual cusps of max. molar and inner inclines of buccal cusps of mand. Molars C-> Contact btwn outer inclines of lingual cusps of max. molars and inner inclines of lingual cusps of mand.

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Occlusal Stability - Tripodization

3 Considerations:

1. Cuspal Contacts

-Cusp fossa/embrasure occlusion, ABC relations

2. Whole Tooth

- Pertains mostly to posteriors

- 2+ fossae and cusps -> multiple contacts per tooth

- Each molar has at least 4-5 regional tripods involving

support cusps and opposing fossae

3. Dental Arch

- Bilateral molar and anterior teeth, not necessarily

symmetrical though.

- Need 2 posterior contact and 1 Anterior contact

- Bilateral stability in the posterior and anterior form a triangle

Case Is it stable?

Yes! - Interdigitated anteriorly enough (although there is some misalignment going on) - Assume both posteriors have contact

Yes! - Posterior contact present on both sides - Anterior contact is sufficient even with a monster beaver overhang - Assume cuspal contacts are ok

No! - No posterior contact on the right - No anterior contact

- 2/3 of the tripod triangle is broken ☹

No! - No anterior contact - Need to add something anteriorly to create tripod

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Restored Occlusions Scenario What happens

Perfectly contoured - Pre-restoration

Nice 2 row contact (Upper lingual, Lower Buccal cusp) - When mandible moved contralaterally to the pt. left (shown with the

yellow arrow), the involved cusps disclude -> no non-working side contact

Over Contoured Restored fossa is too deep (red) from over contouring - Only lingual cusp makes contact - Lower tooth can pivot around the lingual cusp contact until buccal cusp

finds its contact (would see rotation of the tooth to fill the fossa-cusp gap we see)

Rotated tooth Mandibular tooth has rotated (tipped) from scenario B to make buccal contact. - When moved contralaterally (to the left), upper lingual and lower buccal

collide -> have created a non-working side interference

Dynamic Occlusion an Lateral Tooth Guidance = Contacts during jaw movements -> Simulates functional occlusion during chewing and excursive movements

Canine Rise Group Function

- Guidance by the canine only in Laterotrusive and lateroprotrusive motion

- When jaw moves forward and laterally the working side canines are the only teeth in contact

- Typically preferred when creating occlusion -> ↓ contacts, ↓ forces and ↓ wear

- If guidance is steep, all other teeth will separate quicker and by more distance (ideally on the non-working side also)

- If there are even contacts on both the working side and non-working side canines during movement = Balancing contact

- When several cusps of the posterior teeth (from the Canine back) on the working side are in contact during laterotrusive movement. - Possibly see wear facets on the cusps of posterior teeth in contact - Multiple teeth are guiding the working side -> Still considered normal

Laterotrusion Vs. Latero-protrusion

Latero-protrusion has the condyle moving forward (kinda diagonally forward) more than in laterotrusion

(which still has a little forward movement usually) -> changes the guidance patterns

- Typically Latero-protrusive movements will involve more anterior teeth (anterior group function)

when you might only have canine rise guidance in laterotrusion

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Cross Arch Contacts

- It’s considered normal to have equal contacts on non-working side of the

mandible during a lateral jaw movement -> Called Balanced contact or Non-

working side contacts

o If the non-working side contact is the heaviest and most prominent,

preventing full lateral movement of the working side = Interference

o Can occur on the working side as well (called working side interference)

- Can be caused by over eruption of posterior teeth from a lack of regular contact

and may result in parafunctional habits, wear facets

Cuspal Trajectories

- Mandibular cusp trajectory’s start in Maxillary central fossa and vice

versa (ICP).

o Without a vertical disclussion (Canine Rise or Group Function)

the cusp will have to pass “through” the opposing cusp or

around it -> Causes occlusal wear facets

- Major grooves on the occlusion help in guiding the cusp within them

during movements (as indicated by the arrows).

o We can reposition cusp tip location and reshape occlusal

grooves to complement condylar guidance -> Avoids unwanted

posterior contacts if there is or is not any vertical disclussion by

the anterior teeth

Anterior Protrusive Guidance

- During a straight protrusive movement, Mandibular anteriors contact the cingula of the

maxillary anteriors. The angulation of the anteriors allows the teeth to slide up into an

end to end contact (we see this movement on the Posselt)-> Ideally forming a balanced

contact between both quads

o This anterior guidance disscludes the posterior teeth

- Too much unprotected functional protrusion (either as parafunctional habit, or using anteriors as

a tool) can cause wear facets and attrition from too heavy occlusal loads on the anteriors.

**Having multiple distributed posterior contacts protect the anterior teeth from large occlusal loads during

function, and having proper dynamic contacts (normal canine rise for example) protect the posteriors from

damaging lateral forces**

Legend:

Blue: Laterotrusive

Black: Latero protrusive

Red: Prostrusive

Green: Medioprotrusive

In a perfect ICP world:

Latero-Protrusive -> Canine guidance or at least a disoccluding non-working side

Protrusion -> Multiple anterior teeth disoccluding the posterior teeth

In function -> Heavier contacts in posteriors to protect anterior teeth

Guidance is influenced by:

- Extent of overbite

- Angle of the condylar fossa of the TMJ

- Disc position in the TMJ

- Condylar shape

- Molar or Canine protrusive

Interferences

Mutually Protected Occlusion

1) Anterior teeth protect posterior teeth (anterior protected

occlusion)

- If anterior guidance is not steep, the arches do not

disclude and the chance of posterior contact during

laterotrusion increases -> Interference

2) posterior teeth protect anterior teeth (posterior protected

occlusion) – Canine protects from strong lateral forces with Canine

rise, and posteriors protect anteriors from occlusal forces

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Occlusal Examination 4 Aspects:

Visual Assessment

Morphology Assess things like Cross bite, anterior open bite and the orthodontic classifications

Physiological Integrity

Assess wear and determine if it is from erosion or attrition, fracture, cracking from occlusion - Flat and smooth -> Probably attrition - Cupped -> Probably erosion

Using indicator medium

Articulation How teeth collide together - Protrusive contacts - Laterotrusive and Lateroprotrusive contacts - **CR:ICP discrepancy (shift from retruded contact position (RCP) to Habitual contact position

(ICP) - Excursive interferences - Wear Facets

Habitual Contacts

How teeth fit together: - ICP

**Centric Relation: Condyles articulate in the anterior-superior position against posterior slopes of the articular

eminence. It’s a repeatable position and doesn’t depend on tooth contacts. Retruded Contact Position on the other

hand refers to the 1st tooth contact occurring when condyles are seated in CR. It this contact is not the same as ICP then

there will be a slide occlusally from RCP to ICP**

Occlusal Indicators

- Shimstock: 8 μm (Thinnest, most sensitive)

- Accufilm: 21 μm (middle thickest, probably the most useful for determining contacts)

- Butterfly Silk: 90 μm (Thickest, marks everyyything. Kinda useless I think)

Occlusal Wear Functional Wear Wear isn’t necessarily a parafunctional habit, or a bruxism issue. Pt could be using teeth as

tools

Attritional Wear *Wearing away of structure in the course of normal use* Primarily an occlusal wear pattern (occlusal surfaces of teeth)

- Dentin becomes exposed and occlusal surface has irregular surfaces - Interproximal contacts flatten and eventually are lost as wear progresses - No caries though!

**Overeruption: As you wear down the occlusion, teeth may continue to erupt in an effort to maintain contact and vertical dimension. This exposes the root surface and may look like recession (even though it’s not)** Ex: Helicoidal Wear

- Changes from Buccal wear of mandibular premolars to a lingual wear pattern on the 2nd and 3rd molars (opposite for the contacting maxillary teeth)

Ex: Chewing Cycle on 1st molar:

- Causes wear on both sides of the functional/supporting cusps but only on the inner surface of the non-supporting ones. Over time this produces a reversed curve of Wilson (A changes to B)

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Wear Facets Focal locations of wear in enamel based on functional contact - Shiny worn surfaces - These can help us discover specific wear issues and discover

chewing patterns Ex: Group Function Facets, Canine Rise Facets Ex: Protrusive wear facets and flat incisal guidance can be indicative of grinding parafunction. See wear only on the anteriors but much more than normal

Biocorrosion (Acid)

Endogenous - Bacterial acid degradation (Dr. A would disagree..) - Acid Reflux or Bulimia

Exogenous - Acidic drinks, fruits etc

Non-Carious Cervical Lesions Attrition

(Endogenous) Can occur from:

- Normal occlusal function (chewing etc) - Parafunction (bruxism, and clenching)

Abrasion/Friction (Exogenous)

Can occur from: - Hard brushing, flossing, toothpicks - Finger nail biting, Pen chewing - Occupational behaviours (instruments, sewing needles etc) - Ritual Behaviours or ethnic practices

Abfraction (only a theory)

Suggests loss of cervical tooth structure is from flexure forces from Non-axial tooth loads

- Breaking away of enamel rods at the CEJ -> Forms a wedge shaped lesion

Summary of Wear Factors:

- Attrition from normal function, or parafunction

- Abrasion and erosion from environmental influences

- Bio-corrosion or chemical erosion from diet or health conditions

- Loss of tooth structure from physical means (hard tooth brush)

- Loss of tooth structure from habits (Pen chewing, tooth picks etc)

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Bruxism/RMMA (Rhythmic Masticatory Muscle Activity) = Abnormal repetitive movement disorder characterized by jaw clenching and tooth gnashing/grinding

- Consider this when treatment planning for Ceramic crowns -> Ceramic is harder than

tooth structure and will ↑ rate of wear if patient has bruxing habit. Might be better to

treat the bruxism at the same time or prior to the crowns

2 Types:

Awake Bruxism Nocturnal/Diurnal Bruxism

- Triggered by mental concentration, emotional stress, or anxiety

- Usually are unaware of habits & their problems can be solved by making them aware of it

- Characterized by unconscious grinding and clenching during sleep (can be mild, moderate, or severe)

- Wear occurs in both arches - Off and On Sensitivity complaints

Moderate – Severe (sleep disorder) if the following met:

1. Frequent grinding noises 5x /week (confirmed with partner)

2. Non-masticatory wear in 1 sextant (enamel reduced to dentin) or masseter muscle hypertrophy during contraction (2-3x normal)

* History is the most important part of Dx…ask bed partner

Diagnosing Methods 1. Patient History - Helpful to ask bed partner if they hear grinding during sleep - Main way of diagnosis

2. Clinical Signs - Tooth wear, Masseter hypertrophy, Tooth mobility, muscle pain

3. Questionnaires - Sleep Habits, Oral parafunctions, presence of pain, fatigue, sensitivity

4. Ambulatory EMG Monitoring - Record muscle activity patterns (low specificity and sensitivity for other rhythmic

masticatory muscle activities, RMMA) 5. Full video recording

- Gold standard + heart monitoring, ECG, and O2 sats.

Epidemiology Sleep Arousal - 80% of RMMA occur with arousal during sleep (↑ with lighter stages of sleep)

Autonomic sympathetic activity - ↑ Cardiac activity precedes RMMA onset (↑ BP as well)

Neurochemical changes - Catecholamines, adrenaline, dopamine ↑ in urine -> changes alertness

Genetics - Concordance in twins and family Hx

Psychosocial factors - ↑ risk with stress and anxiety and maladaptive coping

Exogenous factors - Alcohol, Caffeine, smoking.

Comorbidities - Sleep Talking and walking, disordered breathing, headaches, psychiatric conditions,

movement disorder, nail biting, restless leg syndrome

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Management Behavioral approaches - Education, relaxation techniques, hypnotherapy, biofeedback, improving sleeping, stress

management Appliances

- Occlusal stabilization splint (protect teeth from grinding) -> Max or Mand. (mand is accepted more (not quite as large and cumbersome)

- NTI (Nociceptive trigeminal inhibitor)

- Mandibular advancement appliances **NTI and Advancement devices can cause TMJ issues, caution!** Pharma (Last ditch effort)

- Hypnotics, relaxants, Benzodiazepines, Botulinum toxin (↓ muscle activity)

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Articulators Non-Adjustable

Simple Articulator Pros:

- Inexpensive - ↓ Chairside time to measure jaw movements - Better than the plastic “hinges”

Cons:

- Preproduces only 1 contact position - Restricted eccentric movements (basically a hinge) - Arbitrary mounting - Not useful in occlusal diagnosis - ↑ time adjusting prosthesis in mouth

Semi-Adjustable (Whip Mix)

Pros: - Accurately reproduces border movements

(Laterotrusive, Lateral Protrusive, Protrusive) - Adjustable condylar inclination, - Can duplicate jaw movements - Useful for tx planning and diagnosis

Cons: - $$ more expensive - More Time consuming - Needs more attention to detail - More time chairside measuring movements - Cannot change the posterior wall - Cannot change the distance btwn 2 condyles

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Arbitrary Facebow:

- Measures Maxillary occlusal plane -> Needed for accurate cast mounting

o Frankfurt plane -> Straight line from the External Auditory Meatus

o Provides approximate measurement of intercondylar distance

Results: Arbitrary Hinge Axis

- Gives us the position of the condyle within the articular fossa where movement is

purely rotational (no translation).

- To measure the TRUE hinge axis, we need a kinematic facebow. Gives us the actual

location of rotations and translations of the condyle, instead of just saying its “in

the ear”.

Direct Mounting to Articulator Indirect Mounting

- Easy - Need to use both the facebow AND the bite fork

(might be a problem if you only have 1 facebow and need to mount multiple casts)

- Not as easy - Benefit is that you can use the facebow for other

cases before fully mounting. The bitefork is all you need

Advantages of Arbitrary Facebow:

- Simple and Fast to use

- Doesn’t require repeated measurements

- No Marks on the patients face are needed

- Accurate to a reasonable degree

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Articulators are used to replicate the patient clinical records of ICP (via Arbitrary Hinge Axis), Left and right

Laterotrusion, and protrusion.

When its incisal pin is in place (white), has transverse hinge-axis (yellow) that is used to

rotate the Maxillary cast. This axis lies at the intersection of the articulator's upper horizontal, and rearmost frontal, planes (green).

- Hinge from the back…similar to the TMJ - Arbitrary Hinge Axis

As we know the maxilla is not on a strictly horizontal axis based on the occlusion. We have to measure the patient’s maxillary arch, hinge axis, and horizontal plane through the axis to determine the angle of the maxillary occlusal plane

- This is what we use the Facebow for and why. The bitefork records the cuspal locations of the maxillary teeth in relation to the Frankfurt plane (a straight line from the external auditory meatus). Using the Nasion pad marks the tip of the green triangle (in the image) and centers the unit along the facial plane, between the 2 condyles.

Keeping the angulation and location recorded with the facebow, we can attach it to the articulator to replicate the angulation of the maxilla on our unit

In the case of a stable ICP relation we can simply line up the mandible and attach the cast to the bottom of the articulator. In the case of an unstable ICP, or if we are wanting to articulate around CR (instead of ICP) we will use a bit registration showing how the teeth come together to dictate how the mandible is mounted

- Now that everything is mounted we can play with the knobs to replicate our patients jaw movements.

Condylar Angle / Angle of Protrusion:

- This measurement dictates the Protrusive motion of the condyle. - When you measure the maximum protrusive movement of the patient

and replicate this on the articulator the forward tilting angle of the condylar guide will change.

- This is set/loosened with the black knobs on the top and by tipping the housing around the “condylar ball” forward or back until the appropriate angle is determined.

Bennet Angle: - This measurement allows you to set the Laterotrusive or

Lateroprotrusive movement/Bennet angle of the articulator - Measure the maximum Laterotrusive movement on either

side. The angle shown on the condylar guide in the maximum position is the “Bennet Angle”. This can be set by tightening the silver knobs

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Occlusal Registration **The position of choice in restorative dentistry is the Intercuspal Position (ICP)**

- Maximum interdigitation of the maxillary and mandibular teeth

- Mandible is in a uniquely stable position with the maxilla

-> Determined by teeth

When do you need Occlusal Records? **Hinted Exam Q**

- If ICP is unstable (either by weird interdigitation, or mobility in teeth)

- No arch tripodization (Need 3 points of contact around the arch)

Habitual ICP, but with and anterior open bite (no tripod)

- You want Centric Relation recording instead of ICP

- Changing Occlusal Vertical Dimension (this will change how teeth come together)

- Partial or Complete Edentulism

Attributes of a good registration material ** Hinted Exam Q** - Futar is really really good

Function Properties

- Provide stability and support where is it lacking in the study, or working casts -> Both vertically and horizontally

- Needed where tripodizatioin is lacking

- Elastomeric material that flows easily when placed with ↓ resistance to interdigitation when patient bites down

- Stable and rigid when sets - No deformity with manipulation or temperature

change when set

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Occlusal Adjustment and Selective Tooth Grinding Occlusal Equilibrium: -> Produces a specific occlusal scheme within the context of a complete dentition (possibly

requiring modifications of the tooth structure).

- The hope is to achieve an appropriate ICP, Anterior guidance with disclussion of the posteriors and dynamic

guidance in laterotrusion (canine rise or group function). Can be achieved with either Selective Tooth Grinding,

or Additive Procedures

If you are mounting diagnostic

casts in ICP and the 2 casts fit

nicely together (stable)-> NO

occlusion record (wax bite etc) is

needed

If you do use a registration medium, DO IT RIGHT or Dr. Tobias

will have an aneurysm

- ONLY the missing section/part of tripodization needs to

be registered.

- Make sure you can still see what the heck is going on

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Selective Tooth Grinding or Adding

When do you do it?

- Reshaping tooth to create a better arch or tooth fit (possible to do for the tooth opposing the restoration vs reducing the restoration itself)

- Establish proper guidance scheme - Redistribute occlusal contacts across the arch - Develop new occlusal vertical dimension

**Always assess restorations for occlusion and adjust in this method accordingly**

Contraindications - When do you do not have a planned outcome - When there is no informed consent - When the adjustment would restrict jaw movement - When reduction will lead to sensitivity - Patient had TMD symptoms - Esthetics will be compromised

Example Patient with symptomatic wear -> Related to daytime grinding and group function guidance Create a composite canine riser and seal the exposed dentin. Creates a canine rise to ↓ the wear from group function.

Reductive/Subtractive Techniques

The BULL Rule - Buccal Upper /

Lingual Lower

Only inner surfaces of the non-supporting max. buccal cusps should be reduced. -> No affect on the VDO but alters the guidance during contralateral laterotrusion

- Altering the Mandibular Lingual cusps works too

**After this adjustment on the non-working side teeth, they should not contact on laterotrusion**

Inclined Plane Contact Adjustments

1. Ledging Reducing supporting cusp inclined plane surfaces (here the lingual of the max buccal cusp, and mandibular buccal plane of the lingual cusp) without touching the cusp tips

"Ledge" the opposing contact surfaces to produce flat landing platforms. (Widens the fossae to receive the supporting cusps.)

Advantages: 1. Axial tooth forces (little force on the inclined planes) 2. Minimum loss of vertical dimension

Disadvantages: 1. Both teeth remain unstable mediolaterally - The jaw is unstable medially. If these contacts are the only ones responsible for maintaining jaw posture, there is nothing to stop the mandible from sliding into its original (habitual) Intercuspal position. -> Sliding off the “ledge”

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2. Establish an entirely new fossae

Grind both teeth as in Option 1, but deepen the landing areas to create new fossae.

Advantages: 1. Axial tooth forces 2. Stable teeth and stable jaw posture

Disadvantages: 1. More loss of vertical dimension 2. Deep fossae. The movement of cusps into deepened fossae ↑ unwanted contacts during laterotrusion and mediotrusion. If further reduction of VDO is required to bring other teeth into contact, even more "ditching" will occur -> Risk interference 3. Excessive loss of tooth substance in the receiving tooth

3. Move the supporting cusp tips Grind both teeth -> repositioning the supporting cusps. Advantages: 1. Axial tooth forces 2. Stable teeth and stable jaw posture 3. No fossa deepening. There will be less likelihood of unwanted excursive interferences. Disadvantages: 1. ↓ VDO. Much depends on correctly estimating the loss of vertical dimension needed to bring all the teeth into occlusal contact -> risky business 2. Loss of tooth substance

Tooth Stability Depends on the number of contacting surfaces and the kind of contacts that are being made. - In this example there are 2 different cuspal contacts: A -> Mandibular supporting cusp makes good contact within the maxillary fossa. B -> There is no tip-fossa contact, but contacts are made on the inclined planes near the tip (this is sufficient)

In theory, 4 contacts are possible ( 2 cusp fossa + 2 marginal ridge) -> we only need 4 contact pairs to ensure tooth stability mesiodistally and buccallingually

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Temporomandibular Disorder Affects of Facial

Pain Problems with:

- Eating and Drinking - Verbal Communication - Non-verbal Communication (facial expression) - Emotional Expression - Sexual Behaviour

Top 4 Head /Neck Pains:

1. Tension type headache 2. Migraines 3. Tooth Pain 4. TMJ pain

Temporomandibular Disorders

= Broad collective term covering painful conditions in: - Muscles of mastication/head and neck musculature - Temporomandibular Joint itself

Categories:

1. Pain related to TMD and Headache - Typically muscle pain

2. Intraarticular Joint Disorders - Disc Displacements

3. Degenerative Joint Disorder - Arthralgia, osteoarthrosis, osteoarthritis

Etiology Onset of TMD - Macrotrauma (prolonged wide gapes, physical trauma) - Microtrauma (Parafunctional habits, Jaw tension from stress, Sustained poor posture)

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Predisposing/Perpetuating TMD - Behaviour -> (Parafunctional habits, jaw tension, poor posture) - Physical/systemic issues -> (SLE, RA, Trauma) - Psychosocial -> (Depression, Anxiety, drug dependency, sleep disorder, stressful events)

**Not all TMD patients have a Hx of risk factors, and not everyone with risk factors will get TMD….so we really have no idea** Whats the deal with occlusion and TMD?

- Only weakly association with occlusal factors (malocclusion) and TMD

Diagnosis Multiaxial Classification - Axis I –

-> Physical characteristics = facial/jaw measurement and palpation (Check for any physical anomalies, clicks, disk displacements, mobility)

- Axis II – -> Psychosocial factors (pain perception) and disability with a questionnaire (presence and quality of pain)

Approach to the patient 1. History

Chief Complaint Write in the patients own words - Gives us an idea as to what the patients priorities are and what is important to them

Onset When did it begin? - Was it spontaneous - Was there an identifiable event that caused it?

Location - Unilateral vs Bilateral - Localized pain vs Diffuse pain - TMJ vs Masticatory muscles vs other - Intraoral vs Extraoral - Referral Patterns

Pain - Quality of pain (can use McGill pain questionnaire to describe the pain) -> Dull aches are often muscles; Burning Pain is from nerve; Sharp pain is in joint

- Intensity (VAS or Mild/Moderate/Severe) - Episodic or Constant? (Triggers? Alleviating factors? Associations?)

-> Red Flag if there are no exacerbating factors -> Associations with Autonomic NS (Visual, tearing, nasal congestion, nausea)

Headaches? Can get headaches from jaw pain and vice versa -> Associated - Intensity, frequency, location, triggers - Presence of migraines - Family Hx of headaches

Association Autonomic - Visual, tearing - Nasal congestion - Nausea, Vomiting

Paresthesia Motor weakness **If there is paresthesia or weakness = very serious! Could be metastatic tumor or infection**

Habits Parafunction - Tooth clenching, grinding, jaw bracing (jaw elevates and retracts at the same time) - Daytime vs Nocturnal

Gum chewing, nail biting

Patient Expectations Manage their expectations -> is what they want realistic or unrealistic - Often we cannot fully eliminate pain, but develop a comprehensive, multi-disciplinary approach to pain

management - There is usually no simple solution

Medical and Social Histories

Chronic medical problems? - Review systems - Psychological or psychiatric illness treatment - Past surgeries

Under stress? - How is their support network - What is their job? - Substance abuse?

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2. Examination

Visual Inspection - Perioral - Facial Asymmetry - Swelling - Masticatory Muscle hypertrophy -> May or may not be associated with grinding - Opening path -> Check for disc displacements or subluxation

Assess Mandibular Range

Mandibular opening - Comfortable + Closed overbite (normal >40mm) - Active (Normal is without pain) - Maximum opening with help - Laterotrusive (normal > 7mm, left and right are same) - Protrusive (>6mm)

Palpations - Lymph nodes (doesn’t tell you about TMJ at all though) - TMJ (feeling for displacement, subluxation, pain, clicking, crackling)

-> 1lb pressure - Masticatory + Accessory Muscles (symmetry, bulk, pain)

-> 2lb -> Accessory Muscles = Sternocleidomastoid, Anterior digastric, Traps, Occipitofrontalis

Intraoral Soft Tissues - Check and assess mucosal lesions - Prominent Linea Alba -> Clenching and grinding - Crenated lateral tongue border -> Clenching - Muscles -> Lateral pterygoid, Temporalis tendon

Dental Examination - Occlusal wear/Multiple enamel and restoration fractures -> Grinding? - Tooth mobility - Sensitivity to percussion (if all teeth hurt its not an endo issue) - Occlusion scheme -> Bilateral contacts in ICP, Proper guidance in lateral excursion and protrusion

3. Diagnosis

Myalgia Pain of muscle origin affected by jaw movement, function and parafunction - Pain is replicatable with provocation and testing of muscles

-> Local Myalgia = focal pain to a specific muscle or muscles -> Myofacial pain = generalized pain not necessarily specific to a specific location -> Myofacial pain with referral = pain found in locations other than jaw Tx:

- Basic Self Care - Controlled opening exercise - Trigger point injections (Botox has taken over largely) - Botox - Spray and stretch with vapocoolant (like tiger balm for your face) - Rx: Analgesia, or muscle relaxants

Arthralgia Pain of joint origin affected by jaw movement, function, parafunction - Replicatable with provocation and testing of TMJ

Tx:

- Basic self-care - Controlled opening exercise - Oral appliance if there is a parafunctional habit - Topical analgesia (diclofenac) to preauricular area - Anti-inflammatory meds used for arthritis

Headache Attributed to TMD

Located in temple area 2o to TMJ pain - Affected by jaw movement, function and parafunction - Replicatable

Disc Displacement With Reduction When jaw is closed, articular disk is anterior relative to condylar head

- Disc reduces when jaw is opened, and slides forward (displaces) again when closed - Snapping, clicking, popping sounds can be present

Typically has Hx of locking closed position with interferences in mastication Tx:

- Basic Self Care and controlled opening exercises - If there is pain on function, apply diclofenac to preauricular area - Most important thing is to try and promote a pain free function even if the disc is out of place (surgery or appliances

are ↓ effective)

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With Reduction and Intermittent locking - When disc occasionally doesn’t reduce upon opening the mouth -> limited opening occurs. Maneuver may be needed to

manually unlock the TMJ Without reduction with limited opening

- The disc remains in an anterior displacement and does not reduce unless clinician or patient performs a manipulation on the jaw.

- Usually painful - Over time the opening will/should ↑

Tx: - Basic self care and controlled opening exercises - Oral appliances are often actually helpful here -> They don’t know how though - Try and promote pain free function and mobilization regardless of disc position -> Allow your body to adapt - Consider MRI if soft tissue concerns, or CT to look at bone -> Can do surgery if the issue is chronic

Degenerative Joint Disease

“Osteoarthritis affecting the TMJ” - Deterioration of articular cartilage w/ osseous changes to the condyle and/or articular eminence

4. Treatments

- Usually TMD resolves over time -> initial approach is supportive and non-invasive. Treat it lie a musculoskeletal

injury elsewhere (Rest and recover)

First Line Treatment

Basic Self Care

- Making Pt aware of their condition/habits -> Self limiting contact to only eating and swallowing

- Restful jaw position -> Tongue behind maxillary central incisors (teeth slightly apart) - Diet mods -> Softer foods, no gum, cut food into small bits - Limit wide jaw opening - Don’t sleep on your stomach/jaw resting on hand -> Don’t lean on chin or jaw awake either - Apply moist heat

Exercises **Physiotherapy is not proven to do anything effective** -> Jaw exercises don’t work

Dental treatment

Oral Appliances Regardless of the appliance you make, the underlying feature that makes it work is simply as a behaviour-changing device.

- Makes the patient aware of parafunction, reminds them by having something in their mouth. - Self Care is just as effective -> If they already have an appliance tell them to use that, you likely won’t

need to make a fancy specific device If you do decide to make one consider the following:

- Full arch vs partial arch coverage -> Partial can cause super eruption of non-covered teeth - Mandibular vs Maxillary -> Maxillary is more comfortable but impedes speech more than mandibular - Soft vs thermoplastic vs rigid acrylic -> Rigid is still softer than enamel (won’t ruin teeth), but will last

longer than the other material options - Stabilization vs anterior repositioning -> Anterior repositioning risks Anterior end to end occlusion

development, and just reverts back to TMD in the end Consider if

Occlusal Adjustment **No evidence that this will treat or prevent TMD at all. Just wasting tooth structure**

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Adjunctive Techniques

Analgesics NSAIDs (only short term) Tylenol (not quite as effective as NSAIDs)

Muscle Relaxants

Cyclobenzaprine -> Short term works in combination with other therapies. Makes patient drowsy though and there are no long-term benefits Benzodiazepines -> Short term therapy. Stop if develop sedation or depressive symptoms TCA’s -> Best option for long term Tx

Trigger Point Injections

Used in muscle with really tight bands - ↓ pain, ↑ range of motion, ↑ circulation - Mechanically disrupts muscles fibers, when they heal, they will reform more organized

Botox FAR more effective than trigger point injections - Local effects lasting 3 months (then need another dose)

Multidisciplinary Care

Multidisciplinary many be needed if there are other underlying issues relating to TMD

- Psychosocial (stress, anxiety, depression etc)

- Behavioral (parafunction, poor posture etc)

- Non-responsive to basic care after 4-6 weeks

Physiotherapy Active and passive oral exercises and posture changes -> Good for ↓ symptoms - Most of the other techniques have no or little evidence that they work

Psychology Biopsychosocial model works well to prevent anxiety and depression - Coping strategies, pain beliefs, psychological conditions are considered

Surgery Only indicated if a structural abnormality is causing the pain -> most cases don’t need something so invasive