posselt's envelope of movement
TRANSCRIPT
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