Posselt's Envelope Flashcards
What are the three reference positions?
centric relation
maximum intercuspal position
postural position
What is CR?
condyles of the mandible are in the most superior and anterior position in the articular fossae, resting against the posterior slops of the articular eminences with the articular discs interposed
What are the benefits of CR?
repeatable, reproducible, recordable
When the mandible is in CR the condyles can rotate around a horizontal axis to an opening of how many mm?
20-15 mm (measured at central incisors)
What is the pure rotational movement also called?
hinge movement
What is MIP?
the maxillary and mandibular teeth make maximum surface contact with each other (mandible is elevated as superiorly as possible)
Does CR or MIP provide information about the TMJ?
CR
(MIP is tooth determined)
What is the usual condyle-disc assembly when in MIP?
anterior and inferior
What is the position that restorations (amalgam, composite, single crown, short-span fixed partial denture) are made in?
MIP
Is MIP the same as centric occlusion?
NO!
What is postural position (PP)?
habitual posture 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
What reference position (CR, MIP, PP) has an equilibrium between the forces acting on the mandible?
PP (postural position)
Does postural position provide info on condyle position or teeth position?
Neither!!!
What is centric occlusion?
first contact in centric relation
Are the muscles completely relaxed when in postural position (PP)?
no… there is a degree of electromyographic activity
What is postural position (PP) determined by?
muscles and gravity
Where are the condyles usually in postural position (PP) when compared to CR?
anterior and inferior
What is the interocclusal space between the incisors in postural position (PP)?
2-3 mm
What is the interocclusal space between the premolars in postural position (PP)?
2 mm
What is the interocclusal space between the molars in postural position (PP)?
3/4 - 1 mm
What is the wedge space between the teeth when in postural position (PP)?
interocclusal space
What is the ratio from anterior to posterior in postural position (PP)?
1:3
What is the postural position clinically used to determine?
occlusal vertical dimension (OVD) in edentulous patients
What is the occlusal vertical dimension?
distance measured between two points when the occluding members are in contact
The vertical dimension at rest (PRP) is usually ___ mm greater than the occlusal vertical dimension?
2-3 mm
What are the movements of the condyles?
rotation
translation
both
What is the outer range of movement that is reproducible called?
border movements
What are the border movements limited by?
ligaments, articualr surfaces of TMJ, morphology and alignment of teeth
The functional movements of the mandible are confined within the…
border movements
What are the movement components of posselt’s envelope of movment in the sagittal plane?
- posterior opening border
- anterior opening border
- superior opening border
- functional movements
What is the envelope of movement?
combination of border movements in 3 planes (sagittal, horizontal, frontal)
What is the posterior opening border movement?
when opening condyles will move forward and down the articular eminence
What is the maximum opening reached in posterior opening border movement?
capsular ligaments prevent further movement
What is the anterior opening border movement?
movement from maximum opening to maximum protrusion (condyles are in the most anterior position)
What is the maximum opening reached in anterior opening border movement?
stylomandibular ligaments
What is the superior contact border movement?
inital tooth contact occurs between the mesial inclines of the maxillary teeth and the distal inclines of the mandibular teeth
(mandible will move superio-anteriorly)
What stops the superior contact border movement?
maximum intercuspation occurs (lateral component to the shift)
What is the average distance between CR-MIP in 90% of the population?
1.25 +- 1 mm
What is the superior contact border movement determined by?
the lingual surfaces of the maxillary anterior teeth
Continued forward movement of the mandible is guided by the _____________ teeth until the mandible reaches maximum protrusion
posterior
What is the functional movement generally?
chewing stroke starts at MIP and drops downward and forward to the position of desired opening
What are the four movement components of the border and functional movements in the horizontal plane?
- left lateral border
- continued left lateral border with protrusion
- right lateral border
- continued right lateral border with protrusion and functional movements
What is the left lateral border movement?
contraction of the right inferior lateral pterygoid causes the right condyle to move anteriorly and medially (left lateral pterygoid relaxes)
What are the working/non-working condyles in the left lateral border movement?
- left condyle: rotating/working
- right condyle: orbiting/balancing/non-working
What is the right lateral border movement?
contraction of the left inferior lateral pterygoid causes the left condyle to move anteriorly and medially (right lateral pterygoid relaxes)
What position do functional movements occur near?
MIP
The outer range of movement is ________ in the late stages of mastication
smaller
The outer range of movement is ________ in the early stages of mastication
greater
What are the border/functional movements in the frontal plane?
- left lateral superior border
- left lateral opening border
- right lateral superior border
- right lateral opening border and functional movements
What is the shape of the sagittal and horizontal planes movements?
rhomboid (square)
What is the shape of the frontal plane movements
shield
What is the left lateral superior border movement?
from MIP the mandible moves to the left
What is the left lateral superior border movement determined by?
- by the morphology and interarch relationship of the teeth
- ligaments of the rotating condyle
On the left lateral opening border as the maximum opening approaches what happens to the ligaments?
they tighten and produce a medial shift
What is the right lateral superior border?
from MIP the mandible moves to the right
What is the left lateral superior border movement determined by?
- by the morphology and interarch relationship of the teeth
- ligaments of the rotating condyle
What is the superior surface of the envelope of motion determined by?
tooth contacts
- Posselt’s Envelope
1 - CR
2 - MIP
3 - protrusion
from 3 to 5 - max opening
r - postural position
