Occlusion 1 Flashcards
basic definition
how the teeth meet
origins
many philosophies to follow for an occlusal rehabilitation, most important among them is Mccollum Stallard (gnathologists) philosophy and Pankey Mann Schuyler philosophy.
Mccollum published their classic “research report” in 1955 and gave the Gnathological Concept
- Their observations led to the development of the arcon fully adjustable articulator and their concept of balanced occlusion in dentures was applied to dentate patients
- Stuart and stallard further came up with a mutually protected occlusion due to canine guidance
PMS – an organized approach to oral rehabilitation introduced by Pankey using the principles of occlusion advocated by Schuyler known as PMS Philosophy of Oral Rehabilitation – based around group function and long centric or freedom in centric – focussing primarily on condylar path
components fo TMJ
TMJ is the joint between the condylar head of the mandible and the mandibular fossa of the temporal bone
- cranial base (temporal bone)
- mandible
- muscles of mastication
- innervation
- vascular supply
- articular disc
TMJ type
synovial, condylar and hinge type joint
TMJ surfaces
fibrocartilaginous surfaces and an articular disc - divides the joint into 2 cavities
condylar head part of
mandible
mandibular fossa is
indentatoin in cranial base
articular disc is attached to what medially
lateral pterygoid
as it passes over the articular eminence
what lines the superior and inferior articlar cavities
lined by separate superior and inferior synovial membranes
TMJ capsule
fibrous membrane that surrounds the joint and attaches to the articular eminence, the articular disc and the neck of the mandibular condyle
articular disc is
fibrous extension of the capsule that runs between the two articular surfaces of the TM joint
articular disc articulations
mandibular fossa of the temporal bone (cranial base) above and the condyle of the mandible below
how is the articular disc attached to the condyle
medially as well as laterally by collateral ligaments
anterior portion of articular disc attaches
to the joint capsule and the superior head of the lateral pterygoid
posterior portion of articular disc attaches to
mandibular fossa
referred to as retrodiscal tissue
retrodiscal tissue compared to articular disc
unlike the disc itself the retrodiscal tissue is vascular and highly innervated and is a major contributor in the pain of TMD.
- As the articular tissue pulls through – if goes too far retrodiscal tissue gets nicked -> inflamed quickly
2 muscles groups involved in mandibular movement
muscles of mastication (main)
suprahyoid muscles
4 suprahyoid muscles
- digastric
- stylohyoid
- geniohyoid
- mylohyoid
digastric muscle
depresses the mandible and elevates the hyoid bone
suprahyoid
stylohyoid
initiates swallowing by pulling the hyoid bone posterior superior
suprahyoid
geniohyoid
depresses the mandible and elevates the hyoid bone
mylohyoid
elevates the hyoid bone and floor of mouth
suprahyoid
4 muscles of mastication
- temporalis
- lateral pterygoid
- medial pterygoid
- masseter
temporalis actions
- elevates and retracts the manidble
- assists in rotation
lateral pterygoid actions
- positions disc in closting (superior)
- protrudes and depresses mandible and casues lateral movement (inferior)
medial pterygoid actions
- elevates the mandible
- lateral movement and protrusion
masseter action
- elevates and protracts the mandible
- assists in lateral movement
origin and insertion of temporalis
originates from temporal fossa
condenses into a tendon which inserts onto the coronoid process of mandible
origin and insertion of lateral pterygoid
2 heads,
the superior head originates from the greater wing of the sphenoid
the inferior head originates from the lateral pterygoid plate of the spenoid.
The two head converge into a tendon which attaches at the neck of the mandib
origin and insertion of medial pterygoid
2 heads which are deep and superficial.
The superficial head originates from the maxillary tuberosity and the pyramidal process of the palatine bone.
The deep head originates from the medial aspect of the pateral pterygoid plate of the sphenoid bone.
Both heads attached to the ramus of the mandible near the angle of the mandible
origin and inserion of masseter
Superficial part originates from the maxillary process of the zygomatic bone.
The deep part originates from the zygomatic arch of the temporal bone.
Both parts attach to the ramus of the mandible.
(large bulky muscle)
rotation of TMJ
resting position of the TMJ is with the mouth slightly open, lips together and the teeth not in contact (resting vertical dimension).
- The space between the teeth is the free-way space.
- Used in dentures the resting vertical dimension
- When patients clench they are in the closed-pack position in which the teeth are tightly clenched (occlusal vertical dimension)
When the mouth is opened just a small amount (20mm) the condyle hinges within the articular fossa.
- There is no downwards or forwards movement (no protrusion).
- On this diagram the rotational centre of this hinge movement is shown by the red dot with the superior and inferior heads of lateral pterygoid shown anteriorly*
hinge movements of mandible
Rotation of the condylar heads around an imaginary horizontal line through the rotational centers of the condyles
- The imaginary line is termed the terminal hinge axis
- like axle
facebow records (2)
- terminal hinge axis
- distance between condyles
caliper like instrument that records the relationship of the the maxilla to the terminal hinge axis of rotation of the mandible.
- It allows a maxillary cast to be placed in an equivalent relationship on the articulator
facebow use
caliper like instrument that records the relationship of the the maxilla to the terminal hinge axis of rotation of the mandible.
- It allows a maxillary cast to be placed in an equivalent relationship on the articulator
poles of the facebow are inserted into the ear canal as close as possible as we can be to the head of the condyle
- provides a reference points about which the hinge axis is determined
Denar slidematic facebow system shown here allows us to measure the intercondylar distance about the hinge axis.
- However, this distance is rarely used unless mounting on a semi/fully adjustable articulator. Arbitrary or average values are commonly used
translation of mandible (a.k.a translocation)
Lateral pterygoid contracts
- Articular disc and condyle begin to move
- Travels downwards and forwards along the incline of the articular eminence
- condyle and the disc translate anteriorly as lateral pterygoid contracts.
- Travels downwards and forwards along the incline of the articular eminence
- At the full open position the condyle is positioned directly under or slightly anterior to the articular eminence
- In this position a thin portion of the disc maintains the position between the articulating surface of the mandibular condyle and the articular eminence
- May also travel laterally (laterotrusive movement)
3 planes of border movement of mandibel
- sagittal
- horizontal
- frontal
Posselts envelope
extremes of mandibuar border movements in the Sagittal Plane
6 points in posselts envelope
ICP = Intercuspal position
E = edge to edge
Pr = Protrusion
T = maximum opening
R = Retruded Axis Position
RCP = Retruded Contact Position
intercuspal position (ICP)
- Tooth position regardless of the condylar position
- The comfortable bite
- Best fit of the teeth
- Maximum interdigitation of the teeth
- Can be called centric occlusion (CO)
Edge to Edge (E)
- Tooth position
- Teeth slide forward from ICP guiding on palatal surface of anterior teeth
- Incisal edges of upper and lower incisors touch
- Space between posteriors
Protrusion (Pr)
- Condyle moves forwards and downwards on articular eminence
- Only incisors +/- canines touch
- No posterior tooth contacts
- Eventually no tooth contacts (reverse overjet?)
Maximum Opening (T)
- No tooth contacts
- Mouth wide open
- Full translation of the condyle over the articular eminence
Retruded axis position (R)
- No tooth contacts
- Most superior anterior position of the condylar head in the fossa
- Terminal hinge axis
Retruded Contact Position (RCP)
used in full denture design
- First tooth contact when the mandible is in retruded axis position
- ICP is approximately 1mm anterior to RCP in 90% of the population
ICP-RCP slide
- ICP is approximately 1mm anterior to RCP in 90% of the population
- RCP and ICP not coincident so the mandible slides forward to achieve ICP
working side
side mandible moves to
lateral movement of mandible due to
result of contraction of one lateral pterygoid muscle.
- When the lateral pterygoid muscle of one side contracts the mandible moves to the opposite side.
- The bony wall of the glenoid fossa stops the working side condyle moving any further to the right
example of mandible moving to right
When the mandible is moving to the right, the left condyle moves forward and inward, whilst the condyle on the right will shift slightly in a lateroposterio direction (or rotate on a vertical axis)
- This slight lateral translation of the mandible is known as the Bennet movement
- The lateral movement of the mandible produced when the mandibular condyles slide along the mandibular fossae during sideways jaw movement
- bodily shift of the mandible at the working side
Bennet Angle
The path of the nonworking condyle in the horizontal plane during lateral excursion
- Bennett angle is the angle formed by the sagittal plane and the path of the mandibular condyle during lateral movement when viewed in a horizontal plane.
Frontal plane movements of mandible
ICP is maximum intercuspation
PP is the physiological rest position with no tooth contacts
Divets are a result of canine guidance,
- when the mandible is moving laterally the long strong canines of the upper and lower jaw ensure that that the posterior teeth do not touch when the mandible is sliding to the side.
- This protects them from lateral forces and gives rise to the term “a mutually protected occlusion”
- Protecting posterior teeth from unwanted lateral forces – only designed for grinding food – up and down
- This protects them from lateral forces and gives rise to the term “a mutually protected occlusion”
