OCCLUSION I-HISTORY OF OCCLUSION

Occlusion

Static relationship between incising/masticating surfaces of maxillary & mandibular teeth or analogues.

Occlusion (functional definition)

Relationship between maxillary & mandibular teeth when in functional contact during mandible activity.

What does occlusion involve beyond teeth?

Teeth, jaws, TMJ, ligaments, muscles of mastication, investing tissues.

Who proposed the first classification of occlusion?

Edward H. Angle, 1898-1899.

Angle's definition of normal occlusion

Class I: MB cusp of maxillary 1st molar aligns with buccal groove of mandibular 1st molar.

Significance of Angle's classification

Basis for orthodontics and treatment planning of malocclusion.

Bilateral balanced occlusion

Denture setup concept where teeth contact on both sides simultaneously for stability.

Why did flat plane occlusion fail?

Not physiologic; did not provide stability in natural dentition.

Why was centric relation introduced in dentures?

Provided a repeatable jaw position for record taking.

How many definitions of Centric Relation (CR) exist?

Over 26 since its introduction.

Centric Relation (CR)

Most anterior-superior position of condyle-disc assembly in glenoid fossa; independent of tooth contact.

Is CR a tooth-to-tooth or jaw-to-jaw relationship?

Jaw-to-jaw.

Centric Occlusion (CO)

First tooth contact when mandible is in CR.

Maximum Intercuspation Position (MIP)

Occlusal position of maximal intercuspation of teeth, independent of condyle position.

Do CR and MIP coincide?

Not always (in most patients they differ).

4 major philosophies of occlusion

Centric relation-based, Conformational, Neuromuscular, Joint-based.

Focus of CR-based philosophies

Build occlusion with condyle seated in CR.

3 main CR schools

Gnathology, Bioesthetics, Pankey/Dawson.

Gnathology

1930s Dr. Stallard: Equal centric stops, long axis loading, anterior contacts only in protrusion.

Bioesthetics

1960s Dr. Bob Lee: Specific anterior form (long centrals, short laterals, pointed canines) → anterior coupling, prevent bruxism/wear.

Pankey/Dawson philosophy

1970s "Functional Occlusion": CR as reference, Long Centric (1.5-2 mm slide from CO to MIP without vertical change).

Conformational occlusion

Maintain patient's existing bite if no issues; common in general dentistry.

Neuromuscular occlusion

1967 Dr. Jankelson: Muscles determine condylar position; uses EMG/TENS; emphasizes 90% TMD is myogenous.

Joint-based occlusion

TMJ imaging (MRI/CBCT) used to assess condyle-disc position; does not assume joint is intact.

Unique about the TMJ surface

Covered by fibrocartilage (not hyaline cartilage).

3 parts of the articular disc

Anterior band, intermediate zone (thinnest), posterior band.

Where does the superior head of the lateral pterygoid insert?

Anterior band of disc.

Bilaminar zone

Posterior attachment: superior strut to fossa, inferior strut to condyle.

How does the TMJ move during opening?

First 10% hinge (rotation), remainder translation along eminence.

What do all philosophies agree on?

1) Occlusion must be evaluated in all patients. 2) Even tooth contacts. 3) Anterior guidance in excursions. 4) Teeth within muscle forces. 5) Interferences eliminated.

Controversy in occlusion

Static occlusion (tooth-to-tooth only) vs functional occlusion (includes teeth, joints, muscles, soft tissues).

Why is occlusion linked to TMD debates?

Different occlusion philosophies propose different causes/treatments for TMD.

NIH expert panels conclusion about Angle's concept

Malocclusion ≠ always pathology; many patients adapt without problems.