Introduction to OcclusionIntroduction to OcclusionContinuedContinued

Fundamentals of Occlusion & Articulation

Characteristics of an Ideal Occlusion – Part II

Basic Structure of the TMJBasic Structure of the TMJ

Two TMJ: When one moves, the other must move as well.

Sagittal View of Normal TMJSagittal View of Normal TMJ

“You cannot successfully treat dysfunction unless you understand function.” – J.P. Okeson

Normal TMJ AnatomyNormal TMJ Anatomy

The Temporomandibular The Temporomandibular JointJoint

Basic StructuresBasic StructuresCondyleCondyle

Anatomic Anatomic variations guide variations guide mandibular mandibular movementmovement

► Retrodiscal tissueRetrodiscal tissue elasticityelasticity Highly innervated Highly innervated

and vascularand vascular Loading is painfulLoading is painful Trauma can cause Trauma can cause

inflammationinflammation

TMJ Structures - Sagittal ViewTMJ Structures - Sagittal View

The Temporomandibular DiscThe Temporomandibular Disc

► Fibrous connective Fibrous connective tissuetissue

► Interface between Interface between bones, somewhat bones, somewhat pliablepliable

► Bi-concave shapeBi-concave shape► Collateral Collateral

ligamentsligaments► No InnervationNo Innervation► No VascularizationNo Vascularization

Two Accessory Ligaments:Two Accessory Ligaments:Stylomandibular & Sphenomandibular LigamentsStylomandibular & Sphenomandibular Ligaments

The stylomandibular ligament limits excessive protrusive movement of the mandible

The sphenomandibular ligament plays a minimal role in limiting mandibular movement

Capsular LigamentCapsular Ligament

Sagittal View – Temporomandibular Sagittal View – Temporomandibular LigamentLigament

Rotational Movement LimitsRotational Movement LimitsPosterior Movement LimitsPosterior Movement Limits

Limitation of Movement with TM LigamentLimitation of Movement with TM Ligament

Designed to limit the pure hinge axis rotation movement. Full length occurs at 15-20 mm of opening, which has a pivot point at which translation commences.

Anterior View of TMJAnterior View of TMJ

Articular Surface of the Articular Surface of the CondyleCondyle

Sagittal View – Articular Disc & Sagittal View – Articular Disc & FossaFossa

Terminology Describing Terminology Describing ToothTooth Position: Position:

MAXIMUM INTERCUSPATIONMAXIMUM INTERCUSPATION► a.k.a. centric occlusion a.k.a. centric occlusion

(CO)(CO)► Habitual occlusion, Habitual occlusion,

habitual centrichabitual centric► Maximum intercuspation Maximum intercuspation

describes an describes an occlusalocclusal relationshiprelationship

► Teeth are contacting in a Teeth are contacting in a position that the patient position that the patient finds the most finds the most comfortablecomfortable

► Easily achievable, but not Easily achievable, but not always reproducible, by always reproducible, by the patientthe patient

MAXIMUM INTERCUSPATIONMAXIMUM INTERCUSPATIONWhat is considered Ideal?What is considered Ideal?

Angle Class I: 1Angle Class I: 1stst Molars and Canines Molars and Canines relationshiprelationship

Adequate OverlapAdequate Overlap Long axis of teethLong axis of teeth Simultaneous contactSimultaneous contact

► Posterior tooth Posterior tooth dominancedominance

► Anterior tooth Anterior tooth “passive” contact“passive” contact

► Multiple contacts on Multiple contacts on all teeth adequately all teeth adequately distributes forcesdistributes forces

► An occlusal positionAn occlusal position► If CR and MI do not If CR and MI do not

coincide, the patient coincide, the patient will have a “slide”will have a “slide”

► Most patients have Most patients have some degree of a some degree of a slide into maximum slide into maximum intercuspation intercuspation (approximately 1-2 (approximately 1-2 mm)mm)

► MI is simultaneous MI is simultaneous contactcontact

► Forces concentrated Forces concentrated on long axison long axis

► Posterior contacts Posterior contacts should dominateshould dominate

Maximum IntercuspationMaximum Intercuspation

Term Describing Term Describing MandibularMandibular PositionPosition

CENTRIC RELATIONCENTRIC RELATION► Centric RelationCentric Relation

A A condylarcondylar positionposition Superior and AnteriorSuperior and Anterior Thin portion of discThin portion of disc Describes the most Describes the most

stable position of the stable position of the condylecondyle

Superior and anterior Superior and anterior position of the position of the mandible with the disc mandible with the disc properly interposedproperly interposed

An ideal occlusion…An ideal occlusion…Basic Premises:Basic Premises:

► When the mandible closes,When the mandible closes,

1.1. There is an ideal way for the teeth to There is an ideal way for the teeth to contactcontact

2.2. There is an ideal place for the condyle There is an ideal place for the condyle and disc to be situated.and disc to be situated.

In an Ideal Occlusion, CR and In an Ideal Occlusion, CR and MI Occur Simultaneously.MI Occur Simultaneously.

The condyle seats in CR simultaneous with The condyle seats in CR simultaneous with the teeth occluding in MI. No slide occurs.the teeth occluding in MI. No slide occurs.

Characteristics of an Ideal Characteristics of an Ideal OcclusionOcclusion

Slide from CR to MISlide from CR to MI► Only 15% of the Only 15% of the

population have no CR population have no CR to MI discrepancyto MI discrepancy

► After the first contact in After the first contact in CR (usually on 2 or CR (usually on 2 or more posterior teeth), more posterior teeth), the patient continues to the patient continues to close, and the teeth close, and the teeth come together more come together more completely (MI). The completely (MI). The condyles condyles mustmust move move out of their most ideal out of their most ideal position when the teeth position when the teeth come fully together.come fully together.

Terms for Describing Terms for Describing Eccentric Movements of the Eccentric Movements of the

MandibleMandible

In an ideal occlusion, protrusive In an ideal occlusion, protrusive movement is guided by anterior teeth.movement is guided by anterior teeth.

Early lateral movements are ideally canine-guided.

Terms for Describing Terms for Describing Eccentric Movements of the Eccentric Movements of the

MandibleMandible

Lateral movements-Lateral movements-moving the moving the mandible to the mandible to the left or to the right.left or to the right.

Shown is a “left lateral movement”

Terms for Describing Terms for Describing Eccentric Movements of the Eccentric Movements of the

MandibleMandibleLateral movements-Lateral movements-

During a left lateral During a left lateral movement, the movement, the leftleft sideside of the of the arch is considered arch is considered to be the to be the “working side”.“working side”. Shown is a “left lateral movement”

Terms for Describing Terms for Describing Eccentric Movements of the Eccentric Movements of the

MandibleMandibleLateral movements-Lateral movements-

During a left lateral During a left lateral movement, the movement, the right right side side is considered to is considered to be the be the “balancing “balancing side” side” or or ”non-”non-working” side.working” side. Shown is a “left lateral movement”

Terms for Describing Terms for Describing Eccentric Movements of the Eccentric Movements of the

MandibleMandible

Lateral movements are guided by either:Lateral movements are guided by either:

group function group function (secondary choice)(secondary choice)

canine guidance (ideal)canine guidance (ideal)

Summary of Characteristics of Summary of Characteristics of an Ideal Occlusionan Ideal Occlusion

►CR and MI occur simultaneouslyCR and MI occur simultaneously►All teeth contact simultaneouslyAll teeth contact simultaneously►All occlusal forces are longitudinalAll occlusal forces are longitudinal►Posterior tooth contacts dominatePosterior tooth contacts dominate►Eccentric movements are anterior-Eccentric movements are anterior-

guidedguided►No cross-over contacts on No cross-over contacts on

posterior teethposterior teeth

Summary of Criteria for an Summary of Criteria for an Optimal Functional OcclusionOptimal Functional Occlusion

► Condylar position-Condylar position- Centric relation Centric relation► Tooth position-Tooth position- Maximum intercuspation Maximum intercuspation► ProtrusiveProtrusive movements are guided by movements are guided by

anterior teethanterior teeth► LateralLateral movements are canine guided.movements are canine guided.► Axial loading of occlusal forcesAxial loading of occlusal forces► In MI, posterior tooth contacts dominate.In MI, posterior tooth contacts dominate.► During During crossovercrossover,, guidance is smoothly guidance is smoothly

transferred to the incisors.transferred to the incisors.

The EndThe End