Physiology

Physiology of the stomatognathic
system
Function can influence the overall pattern and
relationship of parts, the very foundations of the
stomatognathic system.
www.indiandentalacademy.com

• We must do more than analyze the teeth in
occlusion.
• Four parts:
1. Functional osteology
2. Myology
3. TMJ
4. Functions. www.indiandentalacademy.com

Bone is one of the hardest materials in the body,
it is one of the most plastic and most responsive
to functional forces.
Form and function are intimately related.

• In 1870’s Julius Wolff came up with his
theory.
A change in the intensity and direction of these
forces would produce a demonstrable change
in the internal architecture and external form of
the bone. He thought that his observation
could be expressed by definite mechanical
mathematic laws.www.indiandentalacademy.com

This concept was referred to as the law of
Orthognality. Rouxe and others introduced
functional factors in the development of the so
called law of transformation of bone.
The Law stated that the
stresses of tension or
Pressure on bone stimulate
bone formation.

Lack of function leads to reduction of the
Density of bone tissue, or osteoporosis.
Increased function produces a greater density
of bone in a particular area, or osteosclerosis.
Scoliosis – treated with Miluaukee brace.

Benninghoff – Study of architecture of the
cranial and facial skeleton and stress trajectories.
Craniofacial skeleton
Head
Mandible

Three Main vertical pillars of trajectories : All
arising from the alveolar process and ending in
the base of the skull.
1. Canine pillar
2. Zygomatic pillar
3. Pterygoid pillar

Myology: -
Man - 639 Muscles
- 6 billion muscle fibrils.
- 6000 billion fibrils.
Elasticity
Muscle
Contractility

Principles of muscle Physiology: -
- Use of EMG
- Muscle Tonus
- Resting length
- Stretch, or myotatic reflesur.
Buccinator Mechanism:-
Bone  Muscles

Functional Movements:
Muscles:
1. Anterior and Posterior fibers of temporaries
2. Lateral Pterygoid
3. Masseter
4. Suprahyoid
5. Infrahyoid

LectureLecture
IIII

Positions of Mandible
1. Postural resting position (Physiologic rest)
2. Centric relation
3. Initial contact
4. Centric occlusion
5. Most retruded position (terminal hinge position)
6. Most protruded position
7. Habitual resting position
8. Habitual occlusal position.

Average movement area in median plane (left profile).
Approximately natural size.
H. The terminal hinge movement
1. The retruded contact position
2. The intercuspal position
3. The edge-to-edge occlusion
4. Anterior biting to a reversed vertical
overlap
5. The protruded contact position
h. The habitual (automatic closing
movement
II. Transition from terminal hinge to
further posterior opening,
III. The maximal opening
O. Line parallel with the occlusal plane.www.indiandentalacademy.com

Postural Resting Position
The jaws are not clamped together, but hey are
separated by a rather constant distance, even
before there are any teeth in the mouth.
Factors:
1. Body and head posture
2. Sleep
3. Psychic factors influencing muscle tonus.
4. Age www.indiandentalacademy.com

5. Proprioception from the dentition and
muscles.
6. Occlusal changes, such as attrition
7. Pain
8. Muscle diesis and muscle spasm
9. TMJ disease.

Clinic Relation
Centric relation refers to the position of the
mandibular condyle in the articular fossa.
Initial contact
-As the mandible moves from physiologic rest,
towards occlusion of the teeth, it maintains a
centric relation position as far as articular fossa
in concerned. www.indiandentalacademy.com

- If there is a malocclusion or a premature
contact of one or more teeth, initial contact is
no longer the same as centric occlusion.
- They initiate deflections in the mandibular
path of closure.

Centric Occlusion
• Static position and can be easily reproduced by
having the patient bring the teeth together.

Physiology

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