DYNAMIC OCCLUSION, PART 2

disclusion

Contact of some teeth preventing contact of others (e.g., anterior guidance).

anterior guidance

Anterior teeth contact in eccentric movements, preventing posterior contact.

canine guidance

Canines guide excursive movements, protecting posteriors.

group function

Multiple working-side teeth contact simultaneously; distributes occlusal forces; non-working side does not contact.

eccentric movements

Mandibular movements beyond CO/MIP.

protrusion

Mandible moves forward.

retrusion

Mandible moves backward.

working movement

Mandible moves away from midline (laterotrusive).

non-working movement

Mandible moves toward midline (mediotrusive).

occlusal interferences

Undesired posterior contacts during excursive movements.

laterotrusive contacts

Lingual inclines of maxillary lingual cusps contacting buccal inclines of mandibular lingual cusps.

mediotrusive contacts

Buccal inclines of maxillary lingual cusps contacting lingual inclines of mandibular buccal cusps.

interferences

Cause uneven wear, bruxism, muscle disorders (myositis/myofascial pain), TMJ problems (disk displacement, arthritis).

mutually protected occlusion

Posteriors protect anteriors in MIP; anteriors protect posteriors during eccentric movements.

bilateral balanced occlusion

Denture concept: simultaneous working + non-working side contacts for denture stability; not used in natural dentition.

Posselt's envelope of motion

Diagram showing range of mandibular movement in 3 planes (sagittal, frontal, horizontal).

envelope of motion

Described by Ulf Posselt, 1952 (Journal of Prosthetic Dentistry, 1957).

mandibular movement planes

Sagittal, frontal, horizontal.

TMJ movement types

Rotation (hinge, 10-20 mm) and translation (sliding, up to 50-60 mm).

terminal hinge axis

Axis of pure rotation when condyles in most superior position in fossae; up to 20 mm opening.

pure rotation in function

No, only seen in terminal hinge opening; normal function combines rotation + translation.

mandibular movement around the horizontal axis

Pure hinge opening/closing (terminal hinge axis).

mandibular movement around the frontal (vertical) axis

One condyle moves anteriorly, other stays hinge; doesn't occur naturally.

mandibular movement around the sagittal axis

One condyle moves inferiorly while other stays hinge; prevented naturally, occurs only with other movements.

sagittal view points of Posselt's diagram

CR, MIP, edge-to-edge, maximal protrusion, maximal opening, maximal rotation.

frontal view points of Posselt's diagram

CR/MIP, functional guidance, edge-to-edge, maximal lateral excursion, maximal opening.

horizontal view points of Posselt's diagram

CR, MIP, rest position, vertical chewing arch, horizontal chewing arch, edge-to-edge, maximal protrusion, maximal lateral excursion.

clinical value of Posselt's diagram

Defines functional limits of mandibular movement; helps identify occlusal problems and guide restorative dentistry.