Posselt’s Envelope of Movement

Reference Positions

Centric Relation

Maximum Intercuspal Position

Postural Position – resting position

Centric Relationaccording to Okeson

The position of the mandible in which the condyles are in the most superior and anterior position in the articular fossae, resting against the posterior slopes of the articular eminences with the articular discs interposed.

Centric Relation (CR)

Condyle determined position

Repeatable, Reproducible, Recordable

When the mandible is in centric relation the condyles can rotate around a horizontal axis up to an opening of 20-25 mm measured at the central incisors.If opening of the mandible continues beyond 20-25 mm then translation of the mandible occurs. This pure rotational movement is also referred to as hinge movement and the axis is referred to as terminal hinge axis.

Maximal Intercuspal Positionor Maximum Intercuspation

This is a position in which the maxillary

and mandibular teeth make maximum

surface contact with each other. The

mandible is elevated as superiorly as

possible in the sagittal plane.

Maximum Intercuspation (MIP)

Tooth determined position

Does not provide any information about the TMJ

In most people, MIP does not coincide with CR

Maximum Intercuspation

In MIP the condyle-disc assembly is anterior and inferior and/or medial or lateral or a combination of the above compared to their position in CR.

Usually the condyle-disc assemblies are ANTERIOR and INFERIOR.

Maximum Intercuspation

Clinically if the patient needs minimal

restorations (e.g. amalgam alloy or

composite resin restorations, single

crowns, a short span fixed partial denture)

this is the position that the restorations are

made.

Maximum Intercuspation

Centric Occlusion

Postural Position (PP)

Is the habitual position of the mandible when the patient is resting comfortably in the upright position and the condyles are in a neutral unstrained position in the glenoid fossae. In this position there is an equilibrium between the forces acting on the mandible.

Postural Position

In the PP the muscles are not totally relaxed. There is a degree of electromyographic activity.

This position is determined by the muscles and the forces of gravity. IT DOES NOT GIVE US ANY INFORMATION ABOUT THE CONDYLES OR THE TEETH

Postural Position

The condyles are usually anteriorly and inferiorly compared to their CR position.

This position can be sustained and it is comfortable for the patient.

Postural Position

In this position, the teeth are apart and there is a wedge space between the teeth.

The wedge shaped space is called the INTEROCCLUSAL SPACE and is usually 2-3mm between the incisors, 2mm between the premolars, and 3/4-1mm between the molars.

(There is 1:3 ratio from anterior to posterior)

Physiologic Rest Position

2-3mm

Postural Positionalso called the Physiological Rest Position

Clinically is used to determined the Occlusal Vertical Dimension (OVD) in edentulous patients or in patients with severely worn dentition.The Occlusal Vertical Dimension is the distance measured between two points when the occluding members are in contact.

Postural Positionalso called the Physiological Rest Position

The Vertical Dimension at Rest (in the physiological rest position) is usually 2-3 mm greater than the Occlusal Vertical Dimension.

Type of Movement

Rotation- pure

Translation

Combination of rotation and translation

Border Movements

The mandibular movements are limited by ligaments, the articular surfaces of the TMJ, and the morphology and alignment of the teeth. The outer range of movement is reproducible and called border movements.

Functional Movements (occur within border movements)

Occur during functional activity of the mandible

Are confined within the Border Movements

Begin and end in the maximum intercuspation position.

Border and Functional Movements in the Sagittal Plane

Posselt’s Envelope of movementMovement ComponentsPosterior Opening BorderAnterior Opening BorderSuperior Contact BorderFunctional movements

Posterior Opening Border Movement

During opening of the mouth the condyles will move forward and down the articular eminence.

Maximum opening is reached when capsular ligaments prevent further movement.

Anterior Opening Border Movement

This represents the movement from maximum opening to maximum protrusion.

Maximum protrusion is determined partly by the stylomandibular ligaments. The condyles are in the most anterior position.

Superior Contact Border Movement

The initial tooth contact occurs between the mesial inclines of the maxillary teeth and the distal inclines of the mandibular teeth. The mandible will then move superio-anteriorly (shift) until maximum intercuspation occurs. There may also be a lateral component to the shift.The average distance between CR-MIP in 90% of the population is 1.25 1 mm.

Superior Contact Border Movement

The mandible moves forward from MIP to edge to edge. This is determined by the lingual surfaces of the maxillary anterior teeth. The pathway inclines inferiorly.

From edge to edge the mandible can move forward horizontally for the width of the incisal edges.

Superior Contact Border Movement

Continued forward movement of the mandible, with the anterior teeth in contact, results in superior movement guided by the lingual surfaces of mandibular anterior teeth.

Continued forward movement of the mandible is guided by the posterior teeth until the mandible reaches maximum protrusion.

Postural Position

Functional movements

The chewing stroke starts at the MIP and drops downwards and forwards to the position of desire opening.

It returns in a straighter pathway slightly posterior.

h: represents the movement from maximum opening to MIPr: represents the rest position

Border and Functional Movements in the Horizontal Plane

Rhomboid-shaped pattern.

Four movement components

1. Left lateral border

2. Continued left lateral border with protrusion

3. Right lateral border

4. Continued right lateral border with protrusion

and Functional movements

Left Lateral Border movement

Contraction of the right inferior lateral pterygoid causes the right condyle to move anteriorly and medially. The left inferior lateral pterygoid relaxes.

Left condyle: rotating or working condyle

Right condyle: orbiting or non-working

Left Lateral Border with Protrusion

From the left lateral the left inferior lateral

pterygoid starts to contact (the right stays

contracted) and causes the left condyle to

move anteriorly and to the right to

maximum protrusion.

Right Lateral Border movement

The exact opposite to the Left Lateral

Border movement occurs.

Right Lateral Border with Protrusion

The exact opposite to the Left Lateral

Border with Protrusion occurs.

Functional movements

Occurs near MIP.

The outer range of movement is greater in the early stages of mastication.

The outer range of movement is smaller in the late stages of mastication.

Border and Functional Movements in the Frontal Plane

Shield-shaped pattern

Four distinct movement components:

1. Left Lateral Superior Border

2. Left Lateral Opening Border

3. Right Lateral Superior Border

4. Right Lateral Opening Border

and Functional movements

Left Lateral Superior Border

From MIP the mandible moves to the Left.

The path is determined primarily by the morphology and interarch relationship of the teeth.

The maximum lateral border position is determined by the ligaments of the rotating condyle.

Left Lateral Opening Border

Lateral convex path

As maximum opening approaches, ligaments tighten and produce a medial shift

Right Lateral Superior Border

similar to the Left Lateral Superior Border

Right Lateral Opening Border

similar to Left Lateral Opening Border

Functional movements

Occurs near MIP

Occur within the outer range of the border movements.

Envelope of Motion

3D

Combination of border movements in all 3 planes: a.sagittal, b.horizontal, c.frontal

The envelope differs from person to person but it has the same characteristic shape

CRMIP

Envelope of Motion

The superior surface of the envelope is determined by the tooth contacts

The other borders are primarily determined by the TMJ anatomy and the ligaments

Sample Question(s)

What is the name of this envelope

Define the position of all the numbers and letters

What does it represent