Movements of the mandible

Protrusion Retrusion Lateral excursion Opening-closing

Opening-closing

Translatory movement of the mandibular codyle along the the posterior wall of the articular eminence

Protrusion

Retrusion

Retraction of the mandible from any position

Lateral excursion

Border movements of the mandibleBorder movements of the mandible

The most extreme positions to which The most extreme positions to which the jaw is able to movethe jaw is able to move (Posselt,1952)

– Laterally: max. 10 mm– Opening: 50-60 mm

– Protrusion: 9 mm– Retrusion: 1mm

Described from sagittal, frontal and Described from sagittal, frontal and horizontal planeshorizontal planes

Usually not affected by head or body Usually not affected by head or body postureposture

Posselt’s diagramPosselt’s diagram

Sagittal plane border movements– Tracing of the

maximum vertical and antero-posterior movements of the symphysis point

Postural rest position

Habitual opening

ICP

1. Intercuspal position

2. Retruded contact position

3. Rotational opening

4. Maximum opening, condylar translation

5. Maximum protrusion reverse incisal overbite position

Determinants of the sagittal Determinants of the sagittal border movementsborder movements

Incisors Posterior occlusion Temporomandibular joint Articular disc Muscles Ligaments

Border movements in the frontal Border movements in the frontal planeplane

Determinants of the frontal border Determinants of the frontal border movementsmovements

Anatomy of teeth Occlusion Wear Overbite Overjet Joint capsule Ligaments

Gothic arch tracing (Gothic arch tracing (Gysi, 1910Gysi, 1910))

Border movements in the horizontal plane– Intraoral

registration plate– Pantographic

registration device

a: RCP,

ICP-IKP = 1 mm

The Bennett movement (lateral The Bennett movement (lateral shift - „IMMEDIATE SIDE shift - „IMMEDIATE SIDE

SHIFT”)SHIFT”)

The bodily shift of the mandible toward the working side during lateral

excursion

Determinants of the horizontal Determinants of the horizontal border movementsborder movements Condyle Glenoid fossa Ligaments Inclination of teeth

Clinical significance of tooth and joint morphology

Movements are determined by the shape, position and anatomy of teeth and joint

mesiolingual cusp of the nonworking side upper first molar travels through the distbuccal groove of the mandibular nonworking side first molar

mesiolingual cusp of the working side upper first molar travels through the lingual grove of the lower working side first molar

Effect of cuspal inclination on the Effect of cuspal inclination on the Bennett movementBennett movement

0,75 mm

ICP ICP

Determinants of occlusion (Determinants of the Determinants of occlusion (Determinants of the mandibular movements) mandibular movements)

Condylar guidanceCondylar guidance

Condylar path (Condylar

inclination)

– The angle between the

sagittal projection of

the condylar path and

the Frankfort plane

(Camper plane)

– 35O

Condylar angulation (Bennett angle):– The angle formed by the

sagittal plane and the path of the advancing condyle during lateral movement of the mandible, as viewed in the horizontal plane.

– 15O

The condylar inclination

Condylar inclination

The Fisher angle

Determinants of occlusion (Determinants of Determinants of occlusion (Determinants of the mandibular movements) the mandibular movements)

Tooth guidance

Incisal guidance

–  the influence on

mandibular

movements by the

contacting surfaces of

the mandibular and

maxillary anterior

teeth

– 10O

Canine guidance (Lateral guidance)

– the influence on mandibular movements by the contacting surfaces of the mandibular and maxillary canines or posterior teeth

– 120O