Introduction
and
Review of Masticatory System
โดย
ผศ.ทพ.ดร.สิ ทธิ ชัย วนจันทรรั กษ์
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From DOCC 381
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Concept
Instruments and technique
Morphology of occlusion
Anatomy of mastication system
Mandibular movement
Neurophysiology of mastication
Sign and symptom of TMD
Occlusal splint
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Introduction to DOCC 582
• Aetiology and Epidermiology of TMD
• Clinical assessment of masticatory
system
• Diagnosis and Classification of TMD
• Oral parafunction
• Trauma from occlusion
• Management of TMD problem
• Interocclusal appliances
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Occlusion also Includes
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Biological evolution
Development
Histology
Anatomy
Biomechanics
Physiology
(Neurophysiology)
• Adaptation
• Pathology
• Behaviour
sciences
• Clinical diagnosis
• Therapy
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Definition
(Jablonski, 1982)
The relationship between all the components of
the masticatory system in normal function,
dysfunction, and parafunction, including the
morphological and functional features of
contacting surfaces of opposing teeth and
restorations, occlusal trauma and dysfunction,
neuromuscular physiology, the TMJ and muscle
function, swallowing and mastication,
psychological status, and the diagnosis,
prevention, and treatment of functional
disorders of the masticatory system
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Objectives and Goals
• The subject of occlusion serves as a natural
interface between certain of the biologic and
behavioural sciences and the clinical sciences.
• The subject of occlusion is, in the view of many,
the medium that brings all branches of dentistry
together (Ricketts, 1969)
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The Masticatory System
A dynamic biomechanical musculoskeletal system
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Components of the Mastication
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Dentitions
Periodontal supporting tissues
Maxilla and Mandible
Temporomandibular Joint
Mandibular musculature
Muscles of lips, cheeks, and tongue
Involving soft tissue
Supplying innervation and
vasculation
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Primary Dentition
Maxillary teeth
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Mandibular teeth 1
Months
4
2
4
3
5
3
8 10 13 16 19
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27 29
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Permanent Dentition
Maxillary teeth
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Mandibular teeth
6
Years
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1
1
2
2
8
4
53 7
3 4 5 7
10
12
8
8
20
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Loss of Teeth Causes
Occlusal Disharmony
• Early loss of deciduous teeth without
space retaining appliances
• Loss of mandibular first molar
– lingual and mesial tipping of mandibular 2nd
and 3rd molar
– Loss vertical dimension
– Changing in masticatory habit and muscle
tonicity
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Periodontal Supporting Tissues
• Cementum
• Periodontal ligament
• Supporting bone
Usually, periodontium is protected
against injury by neuromuscular
reflexes
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Problems to Periodontium
• Periodontal trauma
• pattern of mastication
• Loss of teeth
• loss of periodontal support
• Faulty restoration
• Abnormal occlusal force;
bruxism, clenching
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Temporomandibular Joint (TMJ)
A complex giniglymoarthrodial (hinge and glide)
articulation with limited capability of
diarthrosis (free movement)
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Histology of TMJ Area
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Temporomandibular Joint (TMJ)
• Composed of
– Condyle
– Mandibular fossa
– Articular capsule
– Synovial tissue
– Articular disc
– Ligaments
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Mandibular Condyle
• Modified barrel shape approx.
20 x 10 mm (ML x AP)
• Perpendicular to the ascending
ramus of mandible
• Dense cortical bone covered
with dense fibrous connective
tissue with irregular cartilage
like cell
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Mandibular Fossa
• Dense cortical bony surface of
temporal bone
• Posterior to articular eminence
• Posterior nonarticular fossa is
formed by tempanic plate
• Thin at the roof of the fossa
and tympanic plate
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Articular Capsule and Disk
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Articular Capsule
• Ligamentous capsule
surrounds the joint
• Attached to the neck of the
condyle and around the border
of the articular surface of the
temporal bone
• anterolateral aspect of the
capsule may thicken form the
Temporomandibular ligament
function as stabilising structure
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Articular Capsule
• Consist of
– internal synovial layer
– outer fibrous layer
containing veins, nerves, and
collagen fibres.
• Innervation of capsule
disk arises from CN V;
auriculotemporal and
masseteric nerves
• Venous plexus at
posterior aspect
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Synovial tissue
• Synovial cell and connective tissue
covering the lower and upper-joint spaces
• Synovial fluid, a proteoglycan-hyaluronic
acid complex acts as a lubricant and may
participated in nutritional and metabolic
interchange for central part.
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Articular Disk (Meniscus)
• Biconcave oval structure
interposed between the
condyle and the temporal bone
• 1 mm in the middle and 2-3
mm at periphery
• Dense collagenous connective
tissue
• Centre area is a vascular,
hyaine and devoid of nerve
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Articular Disk (Meniscus)
• Fuse to a strong ligament
at lateral side connect to
the neck of the condyle
• The other borders are
attached to capsule
ligaments or synovial
membranes separate
between two joint spaces.
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TMJ Ligaments
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Ligaments
• Temporomandibular
ligament
– extend from base of
zygomatic process of the
temporal bone downward
and oblique to the neck of
the condyle
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Ligaments
• Stylomandibular
ligament
– From styloid process and
runs downward and
forward to attach broadly
on the inner aspect of the
angle of mandible
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Ligaments
• Sphenomandibular
ligament
– arising from the angular
spine of sphenoid bone
and petrotympanic
fissure, ending at lingula
of mandible
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Functions of Ligaments
• Accessory ligaments may limit border
movements of the mandible
• Fibrous capsule and TM ligament
may limit of extreme lateral
movements in wide opening of
mandible
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Masticatory Muscles
• Masseter muscle
• Temporalis muscle
• Medial pterygoid muscle
• Lateral pterygoid muscle
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Masster muscle
• Superficial layer
– O : lower border of malar
bone, Zygomatic arch &
zygomatic process of maxilla
– R : Downward and
Backward
– I : Angle of mandible and
inferior half of the lateral
side of mandible
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Masster muscle
• Deep layer
– O : Internal surface of
zygomatic arch
– R : Downward (vertical)
– I : Ramus of mandible and
base of coronoid process
– 50 degree between 2 layers
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Temporalis muscle
• 3 bundles
– Anterior bundle (vertical fibre)
–Action: Mandible elevator
(Close jaws), crushing and
chewing at C.O.
–Inaction: Mandible
depression (except Max.
Opening and Opening against
resistance)
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Temporalis muscle
– Posterior bundle (Horizontal
bundle)
Action: Mand. retraction and
positioner
Inaction: Mand. depression
and protrusion
– Intermediate bundle
Action: Protrisive movement
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Nerve supply
Ant. and Post. deep
temporal nerve
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Med. Pterygoid muscle
Rectangular shape at medial surface of ramus,
synergistic with masseter muscle
O : Pterygoid fossa and medial
surf. of the lateral pterygoid
plate
I : Inf. + Post. border of ramus
and angle of mand.
R : Downward and Backward
N : Medial Pterygoid nerve
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Lat. Pterygoid muscle
• Superior head
O: Wing of sphenoid and
infratemporal crest
R: Downward and Backward
• Inferior head
O: Lateral surf. of lateral
pterygoid plate
R: Upward and backward
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Lat. Pterygoid muscle
Insertion of superior and inferior
heads
– Ant. portion of the condylar neck
(pterygoid fovea)
– Ant. surface of the articular
capsule
– Ant. Border of the disk
Function
– Open the jaws, protrude and
lateral movement with moving
disk forward
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Lat. Pterygoid muscle
• Superior head
Synergistic with elevator
group of muscle for closing
and clenching
• Inferior head
Synergistic with suprahyoid
group of muscle for opening
jaw
• Nerve supply
Lateral pterygoid nerve
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Non Masticatory Muscle
• Digastric muscle
• Mylohyoid muscle
• Geniohyoid muscle
• Orbicularis Oris
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Non Masticatory Muscle
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Types of Mandibular Movement
• Rotational movement
– Horizontal axis of rotation
– Frontal (vertical) axis of rotation
– Sagittal axis of rotation
• Translational movement
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Rotational Movement
• Around the horizontal axis (hinge axis)
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Rotational Movement
• Around the frontal (vertical) axis
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Rotational Movement
• Around the sagittal axis
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Translational movement
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Sagittal Plane Border Movement
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Sagittal Plane Border Movement
• Posterior open border
• Anterior open border
• Superior contact
border
• Functional movements
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Horizontal Plane Border Movement
• Left lateral border
• Continued left lateral border
with protrusion
• Right lateral border
• Continued right lateral border
with protrusion
• Functional movements
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Horizontal Plane Border Movement
• Continued right lateral border with
protrusion
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Horizontal Plane Border Movement
• Functional movements
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Frontal (Vertical) Border and
Functional Movement
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Frontal (Vertical) Border and
Functional Movement
• Left lateral superior border
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Frontal (Vertical) Border and
Functional Movement
• Right lateral opening border
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Frontal (Vertical) Border and
Functional Movement
• Functional movements
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References
• Ash and Ramfjord. Occlusion 4th edition.
W.B. Saunders Company, 1995
• Mohl, Zarb, Carlsson and Rugh. A textbook
of Occlusion. Quintessence Publishing Co.,
1998
• Sicher and DuBrul. Oral Anatomy 6th
edition. The C.V. Mosby company, 1975
• Kraus, Jordan and Abrams. Dental anatomy
and Occlusion. The Williams and Wilkins
company, 1969
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Thank you
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