Occlusion from Dental Anatomy

Thank you Gracie Girl

What is occlusion

-contacts between teeth

-relationship btwn maxillary and mandibular teeth when they approach each other, as occurs during chewing or at rest

What is static occlusion

Contact between teeth when the jaw is closed and stationary

Dynamic occlusion

occlusal contacts made when jaw is moving

What structures does occlusion involve

periodontium, TMJ, neuromuscular system

How are tooth positions determined

Lips/cheeks/tongue, arch width + tooth size, oral habits, proximal/occlusal contacts

What happens to teeth when there is a tooth size-arch discrepancy

Teeth remain outside of the normal arch due to the tooth size-arch discrepancy until corrected

How do oral habits affect occlusion

- Thumb sucking

-Musical instruments placed between the maxillary

and mandibular teeth (clarinet) may place labial

forces to the lingual surfaces of the maxillary anterior

teeth, resulting in a labial flaring

Proximal and occlusal contacts

maintain the teeth in normal alignment, effect of caries or missing tooth can be dramatic in the loss of stability of the dental arches

What happens when proximal and occlusal contacts become worn down

Mesial drifting helps maintain contact between adjacent teeth and stabilizes the arch

What happens the tooth in the opposing arch when one tooth is lost

The opposing tooth may be lost over time, teeth can drift into the edentulous space

What is the plane of occlusion

Draw an imaginary line through all the buccal cusp tips and incisal edges of the mandibular teeth, then broadened into a plane- include the lingual cusp tips and continuing across the arch to include the opposite side buccal and lingual cups tips

The curved occlusal plane permits maximum utilization of ____ ______ during function

tooth contacts

Curve of Spee (exam q)

Cusp tip of the mandibular canine and following the buccal cusp tips of the premolar and molar teeth (lateral view).

The maxillary arch’s normal curve of wilson and spee (occlusal plane) are convex or concave? exam q

convex

The mandibular arch’s normal curve of wilson and spee (occlusal plane) are convex or concave? exam q

concave

How is the maxillary arch inclined

Anterior mesially, most posterior distally/buccally inclined

Curve of Wilson

Buccal and lingual cusp tips of both the right and the left posterior teeth

How is the mandibular arch inclined

Mesially and lingually inclined

What does extrusion cause

interferes w smooth movement, creates abnormal height of molar occlusal plane

What does an occlusal interference of the last molars look like/cause (i.e. one restored tooth is too high)

May look normal during the static occlusion, however during the protrusion last molar, interferes with the smooth movement (dynamic occlusion)

Can damage muscles, causing TMJ problem

What are three examples given of abnormal intra-arch tooth alignment

protrusive mandible (caused by occlusal interference), reverse-curved occlusal plane- upward, extrusion

In which case is the occlusal plane appropriate? exam q

3

1= extrusion

2= mandibular incisors extruded

Which 3 occlusal surfaces of teeth break up food

*exam

cusps, grooves (shallow, linear), sulcus (long depression)

Not 1 of the surfaces that break up food, but fossa= irregular concavity

What are cusp tips to central fossa called

inner incline

What are cusp tips to HOC on lingual/labial surfaces of teeth called

outer inclines

Area between buccal+lingual cusp tips of posterior teeth

occlusal table

Where are the major forces of mastication applied?

occlusal table

Exam last yr: The occlusal table is ____% of the total buccolingual dimension of the posterior tooth and is positioned over the ___ axis of the root structure

50-60%, long axis

tooth inclines are identified with respect to which surface?

the surface toward which they’re directed

What would a high spot or in the occlusal table cause when biting down/ making lateral movements

possible fracture of the restoration or damage to the stomatognathic system

Stomatognathic system (not in slides, from internet)

compelx system of tissues/organs in oral/craniofacial cavities (teeth, jaw, tongue, muscle, glands, tmj)

What is interarch tooth alignment

relationship of teeth in one arch to those in the other, occlusal relationship protects surrounding soft tissue (cheek/tongue bite), maximizes, efficiency of musculature

Describe normal interarch positioning (maxillary)

Maxillary teeth are more facially positioned (protect muscle/from biting cheek), lingual cusps occlude along central fossa areas of mandibular teeth

Describe normal interarch positioning (mandibular)

Mandibular buccal cusps occlude along central fossa areas of maxillary teeth

define crossbite + cause

Maxillary buccal cusps contact in central fossa area of mandibular teeth, caused by narrow maxilla compared to mandible

What are supporting cusps also known as (any terms can be used on exam)

centric or functional cusps

Supporting cusps are the ______ cusps of the mandibular posterior teeth and ______ cusps of maxillary posterior teeth occlude with opposing central fossa areas

buccal, lingual

What do supporting cusps do/maintain

VDO, mastication, rounded shape

What are guiding cusps also known as, are they more important than supporting cusps

non-centric, shearing, not as important

Guiding cusps are ____ cusps of maxillary posterior and ____ cusps of mandibular posterior

buccal, lingual

what do guiding cusps look like/do

sharp, definite tips, minimize tissue impingement, maintain food bolus on occlusal table during mastication, guide mandible into/out of intercuspal position (MIP)

Functional outer aspect (FOA)

1 mm area on outer aspect of centric cusps (red), functions against inner incline of non-centric cusp

Assists in shearing of food during mastication

Which of the following line indicates the supporting cusp inner inclines? exam

what line is this/which quadrant

Buccoocclusal (BO) line of left mandibular arch

what line is this/which quadrant

Linguoocclusal (LO) Line of the Right Maxillary Arch.

what line is this, which arch

Central Fossa (CF) Line of the left Dental Arches

In a normal arch, an imaginary line extended through the arch flows _____ and ________, revealing the general arch form.

smoothly and continuously

what line is this

BO line

In normo-occlusion, which lines (CF, BO, LO) are aligned together in which arches

What’s going on… what’s happening

small jaw with big teeth- when the permanent dentition erupted, it created even more crowding

Where are the embrasure areas in the occlusal view

Area slightly buccal and lingual to the central fossa line

which is larger, lingual embrasure area or buccal embrasure- what is the function

lingual (major spillway for food, tongue is more efficient in returning food to the occlusal table than the buccinator and perioral musculature)

more simply- if there’s too much food in the mouth it allows to spill out, no buildup of pressure

When the normal interarch tooth relationship is viewed laterally, each tooth occludes with how many teeth, and what does it aid in

two opposing teeth, helps distribute occlusal forces to several teeth/over entire arch

What are the exceptions to the one-tooth-two-teeth relationship

Max 3rd molars, mand central incisors

What tooth is Angle’s classification centered around?

first molar

How is the maxillary first molar aligned in Class I occlusion

The MB cusp of max 1st molar is aligned directly over the buccal groove of the mand 1st molar

How is the maxillary first molar aligned in Class II occlusion

the MB cusp of max 1st is situated over the embrasure btwn the mand 2nd PM and 1st molar

How is the maxillary first molar aligned in Class III occlusion

The MB cusp of max 1st is over the embrasure btwn the mand 1st and 2nd molar

The maxillary anterior teeth are normally positioned ____ to mandibular anterior teeth

labially

How are maxillary and mandibular anteriors inclined? What is the degree range from a vertical reference line

labial, 12-28 degrees

What is the purpose of anterior teeth in terms of lateral movement; what is it called

Anterior teeth contact and guide the mandible through various lateral movements- Anterior guidance

Which directions can the relationship of anterior teeth be examined

Horizontally and vertically

Overjet/horizontal overlap

horizontal distance by which max anteriors overlap mandib anteriors

Overbite/vertical overlap, what is the normal amount in mm?

anterior guidance examined in the vertical plane, 3mm is normal

Class II Div 1

Malocclusion, deep bite, increased overjet

Class II Div 2

retroclined max central incisors, more rare

What are the 3 types of class III bites

Edge to edge, anterior crossbite, anterior openbite

what is the profile name, angle of profile, posterior relationship, and anterior relationship of Class I bite

Orthognathic profile (72% angle), posterior- mesiobuccal cusp of 1st max molar aligns with buccal groove of mand 1st molar, anterior-lower incisors rest on the cingulum of the upper incisors

what is the profile name, angle of profile, posterior relationship, and anterior relationship of Class II bite; what are the divisions possible for Class II

Retrognathic profile (22% angle), distal occlusion, posterior- MB cusp of max 1st is situated over the embrasure btwn the mand 2nd PM and 1st molar, Anterior Div I, Anterior Div II

what is the profile name, angle of profile, posterior relationship, and anterior relationship of Class III bite

Prognathic profile, 6% angle, posteior mesial occlusion (MB cusp of max 1st is over the embrasure btwn the mand 1st and 2nd molar), anterior crossbite

Eccentric movement

any movement of the mandible from the intercuspal position that results in tooth contact

Protrusive movement

mandible moves forward from intercuspal position

What surfaces create anterior guidance

Guiding inclines of anterior mand and maxillary teeth

Laterotrusive movements/contact

Working side

Mediotrusive movements/contact

Non-working side

in normo-occlusion, which max and mandib teeth contact during right and left lateral movements/have laterotrusive contact? what is this known as

Canines, canine guidance

_____ surfaces and _____ edges of mandibular canines and ______ fossae and _____ edges of maxillary canines meet in canine guidance

labial surfaces and incisal edges, lingual fossae and incisal edges

Retrusive movement

Backwards movement restricted by ligaments (1-2mm)

What angle class

Angle Class I

What angle class

Angle Class II

What angle class

Angle Class II Div II

What angle class

Angle Class III

What are the two bones involved in the TMJ

Squamous temporal bone, mandibular condyle

What is btwn the TMJ bones

articular disc

Mandibular condyle location, shape, etc

top of mandibular neck, articulates with glenoid (mandib) fossa, convex, elliptical, medial/lateral poles

What type of xray is best for visualizing TMJ (what was this taken with), how would you describe this xray

computed tomography, normal condyle coronal section (cortical borders intact and continuous, condyle has convex and smooth surface)

What would the TMJ look like when pt has degenerative disorder

The convexity is disrupted (becomes concave), left side cortical borders are interrupted, visible bone spurs

Temporal bone (squamous portion)

upper part of tmj, glenoid fossa is thin roof, has articular eminence (convexity, steepness, condylar guidance)

Ginglymoarthrodial joint components

2 types of joint mvmt (ginglymoid= hinge, arthrodial=plane joint)

Condyle/ginglymoarthrodial joint movements

accommodated by articular disc

1. Rotate (hinging movement lower compartment),

2. translate (gliding movement upper compartment

Which pole do we palpate during TMJ palpation

lateral pole of TMJ

Which of the following is FALSE about mandibular condyle?

A. Articulates with glenoid (mandibular) fossa

B. Convex shape

C. Has medial and lateral poles

D. Rotates with hinging movement on the upper compartment

E. Translates with gliding movement on the upper compartment

D. Rotates with hinging movement on the upper lower compartment

Normal articular disc position before movement

Posterior border-11-12:00 position on condyle

Anterior prominence of condyle: central thin part of disc

Disc follows condyle during opening

anterior disc displacement without reduction, at rest

articular eminence hits the posterior border of disc instead of normal resting position

Rotation with normal disc position

Rotation 20-25 mm (mouth opening starts with rotation of condyle under disc)

Translation with normal disc position

Translation normal max >40mm (rotation of condyle should be followed by translation)

anterior disc displacement without reduction during rotation

ROTATION 20-25 MM (normal)

anterior disc displacement without reduction during translation

NO TRANSLATION- painful locking, limited mouth opening (if you move mandible down only, without translation, condyle hits muscle and bone instead of cartilage)

Articular surfaces of synovial joint

hyaline cartilage absorbs shock and reduce friction during movement- has limited capacity to heal and repair