Introduction and Review of Masticatory System

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Introductionand Review of Masticatory System
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From DOCC 381

• 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

• 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
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
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
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
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
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

• 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

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
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
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

• 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

Mandibular teeth
Months
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Permanent Dentition
Maxillary teeth
Mandibular teeth
Years
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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

• 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