What is the function of the stomatognathic system?
It is the functional unit responsible for chewing and swallowing. It is also involved in phonation, taste and breathing.
Parts of the stomatognathic system
- Bones
- Joints and ligaments
- Muscles
- Controlling nerves
- Teeth
Bones of the stomatognathic system
- Mandible
- Maxilla
- Temporal bone (glenoid cavity and articular eminence)
What is the TMJ?
It is a dual joint between the skull and the jaw.
It is a ginglymoarthrodial joint.
Parts of the TMJ
- Joint surfaces
- Disc
- Upper and lower joint cavity
- Synovial fluid
- Retrodiscal tissue
- Upper and lower retro discal lamina
- Ligaments
Function of the synovial fluid
It provides nutrients and acts as a lubricant
What causes less friction in the TMJ?
The synovial fluid
Describe the disc of the TMJ
- It is a dense fibrous conjunctive tissue
- It is avascular and does not have an innervation
- It gets less degenerative and has a greater repair capacity
What are the ligaments of the TMJ composed of?
They are composed of connective tissue collagen that does not distend (swell)
The function of the connective tissue collagen of the ligaments of the TMJ
It acts as a passive limiting of joint movements to protect the joint
What is more innervated and vascularised, the ligaments or the disc of the TMJ?
The ligaments are well-innervated and vascularised.
The disc is avascular and does not have an innervation.
Types of ligaments in the TMJ
- Functional/intrinsic ligaments
- Accessory/extrinsic ligaments
What are the functional/intrinsic ligaments?
- Collateral/disc ligaments
- Joint capsule
- Temporomandibular ligament
What are the accessory/extrinsic ligaments?
- Sphenomandibular ligament
- Stylomandibular ligament
- Pterygomandibular ligament
What ligament attaches the disc to the condyle?
The collateral/discal ligament
What ligaments limit the opening and the protrusion?
The temporomandibular ligament and the stylomandibular ligament
Function of the TMJ
- Upper compartment translational movement
- Lower compartment rotational movement
- Condylar position on the posterior part of the articular eminence with an interposed articular disc
- Opening (rotation and translation motion)
- Closing (rotation and translation motion on an axis slightly lower in comparison to the opening)
Muscles of the TMJ
- Masticatory muscles
- Accessory muscles
What are the masticatory muscles?
- Masseter
- Temporalis
- Medial pterygoid
- Lateral pterygoid:
a. Upper head
b. Lower head
What are the accessory muscles?
- Supra and infrahyoid muscles: digastric and mylohyoid muscles
- Head and neck muscles: sternocleidomastoid and trapezius muscles
What muscles are elevators?
- Masseter
- Medial pterygoid
- Lateral pterygoid upper head
- Temporal anterior and middle fibres
What muscle is considered a disc stabiliser?
The lateral pterygoid upper head
What muscles are considered depressors?
- Lateral pterygoid lower head
- Mylohyoid
- Digastric anterior belly
What muscles are used for protrusion?
- Lateral pterygoid lower head (bilateral)
- Medial pterygoid
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Chapter 1: Prosthetic Dentistry29
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Chapter 2: Stomatognathic System32
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Chapter 3: Neuromuscular System Function73
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Chapter 4: Study of dental arches44
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Chapter 5: Mandibular positions and movements75
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Chapter 6: Mandibular dynamics25
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Chapter 7: Optimal functional occlusion36
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Chapter 8: Aetiology, pathology and exploration of the TMJ29
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Chapter 9: Articulators and face bows14
