occlusion

Dr. Monia M.N. Kandil

Stomagnathic System
The movement of the jaw is intiated by a complex set of muscles’ actions, which are in turn controlled by the body's local and central nervous system Stoma= mouthGnathion = jaws

The stomatognathic system

= the masticatory system = Teeth Periodontium Jaws TMJ Associated muscles + tongue & ms of the soft palate Investing tissues Neural control
There is a complex, dynamic balance between the way that the teeth come together, the muscle that work the jaws, the joints, and

The stomatognathic system

Is the functional unit of the body that responsible for chewing, speaking and swallowing, as well as parafunctional actions. Disturbance of any part could disturb the whole odontostomatognathic system and subsequently the body as well.

Muscles of Mastication:

Neuro Muscular System:
Masseter Temporalis Lateral Pterygoid Medial Pterygoid
Tempromandibular Sphenomandibular Stylomandibular
TMJ Capsule Associated Ligaments



The letters TMJ are short for of 'temporo-mandibular joint', which is the joint connecting your lower jaw and your skull.
The movement in this joint lets you open and close your mouth and chew from side to side.
Temporalis
Masseter

It has 4 anatomical parts: 1- condyle 2- Articular fossa 3- Articular disc 4- Articular capsule
TMJ: is a bilateral joint, permits the mandible to move as a unit with two functional patterns: - Hinge (inferior portion) - Translation (superior portion)

Introduction

Muscles of mastication develop from the mesoderm of the first pharyngeal arch. They are innervated by the Mandibular division of the trigeminal nerve (cranial nerve V)
Muscles of Mastication


They are functionally classified as: Jaw elevators Masseter Temporalis Medial pterygoid (superior & deep head) Upper head of lateral pterygoid

Jaw depressors Lower head of lateral pterygoid Anterior digastric Geniohyoid Mylohyoid

Occlusion Terminology &Definitions



Centric Relation
It is bone to bone relationship independent on tooth contacts

Centric relation

It is the most retruded unstrained position of the condyle in the glenoid fossa from which lateral movements can be performed at any given degree of jaw separation
It’s restricted to a purely rotary movement about a transverse horizontal axis

MAXIMUM INTERCUSPATION

The complete intercuspation of the opposing teeth independent of condylar position.


Occlude  close. Occlusion  is the act or process of closure It is the STATIC relationship between the incising or masticating teeth analogues.
It is an important factor that influences stability and retention of complete dentures.
So Occlusion is the closure of the maxillary and mandibular teeth in centric relation throughout the range of functional and nonfunctional movements of the mandible

CENTRIC OCCLUSION

The occlusion of opposing teeth when the mandible is in centric relation

Any occlusion other than centric relation

Eccentric Occlusion


The dynamic movements of the teeth in relation to each other
Articulation:

VERTICAL DIMENSION OF OCCLUSION

The degree of separation between the maxillae and the mandible when the teeth are in occlusion.

Interocclusal distance(Free way space)

The distance between the occluding surfaces of the maxillary and mandibular teeth when the mandible is in a specified position (CR), it ranges from 2-4 mm.


In the edentulous patients, use the most retruded position of the condyle in its fossa (centric relation)

Centric Occlusion can be made to coincide with CR

Envelope of functionMost normal chewing stays within the red area, but the lower teeth have the range of the black line.Lower teeth are ‘guided’ by a gentle slanted slope of the upper lingual surfaces. Anterior Guidance in harmony with the border movements of the Envelope of Function.
* Teeth harmonious with bone/craniofacial structures

Change the pattern of mandibular closure as a result of premature contact

The Masticatory Cycle occuraccording to theCompensating curves

Spee’s curve The anatomic curvature of the occlusal alignment of the lower teeth beginning at the tip of the lower cuspid and following the buccal cusps of the natural bicuspids and molars continuing to the anterior border of the ramus
Compensating curves


The buccal cusps of the lower posterior teeth are slightly higher than the lingual cusps, and a line drawn through the buccal and lingual cusps of the teeth on the other side forms a lateral curve called the curve of Wilson
Curve of Wilson


Monson’s curve It is a curve in which each cusp and incisal edge touches or conforms to a segment of a sphere 20 cm (eight inches) in diameter with its center the glabella.


The compensating curve of the artificial occlusion corresponds to a combination of these curves in natural teeth. It is considered one of the most important factors in establishing balanced occlusion


3 basic or traditional planes in relation to the body, not in relation to the earth Anteroposterior or Sagittal Plane Lateral or Frontal Plane Transverse or Horizontal Plane
Cardinal planes of motion

Axes of rotation

Frontal or lateral axis Has same orientation as frontal plane of motion & runs from side to side at a right angle to sagittal plane of motion Runs medial / lateral Commonly includes flexion, extension movements

Axes of rotation

Sagittal or anteroposterior axis Has same orientation as sagittal plane of motion & runs from front to back at a right angle to frontal plane of motion Runs anterior / posterior Commonly includes abduction, adduction movements

Axes of rotation

Long or vertical axis Runs straight down through top of head & is at a right angle to transverse plane of motion Runs superior/ inferior Commonly includes internal rotation, external rotation movements

Axes of rotation

c, Horizontal-coronal axis (sagittal axis).Permits descent of balancing condyle
Mandibular centers of rotation
a, Horizontal-sagittal (transverse or retruded condyle axis). b, Vertical axis with horizontal rotation.

Rotation occurs when the mandible makes a hinged movement. Translation occurs when the mandible moves into a protrusive or lateral position, or a combination of the two


It takes place in the lower compartment of the T.M.J between the superior surface of the condyle and the inferior surface of the articular disc
It Is a Simple Hinge Movement Occurs during the early opening and late closing movement of the mandible
It is an imaginary line around which the condyles rotate during early opening and late closing.

Translation movements

Rotation movements

A- Rotation occurs when the head of the condyle rotates around an imaginary axis

B- Translation is the bodily movement of the head of the condyle

Articular disc as it moves with the condyle

Dislocation

The angle formed by the steepness of the articulator surface that is related to a horizontal plane is called the sagittal inclination (Condylar inclination)
The inclination of the condylar paths varies in different individuals and from side to side in the same person. It depends upon
The shape of the glenoid fossa. The variation of the thickness of the articular disc in its different parts. The relation of the condyle to the disc during movement. The extent of mandibular protrusion