Alveolar bone / /certified fixed orthodontic courses by Indian dental academy

INDIAN DENTAL ACADEMY
Leader in Continuing Dental Education

www.indiandentalacademy.com

DEFINITION
• It is defined as the parts of the
maxilla and mandible that form
and support the sockets of the
teeth.


MACROANATOMY
Structure

• Alveolar bone structure
1-alveolar bone proper
2-trabecular bone
3-compact bone

• Alveolar processes are covered by compact bone
which overlies a trabecular bone structure.
• Within the trabecular bone structure the alveoli
are situated within their walls of 0.1 to 0.4 mm thick
compact bone plate.
• Alveolar bone proper seen on radiograph as lamina
dura which appears radiopaque.


• The thickness of the compact cortical bone on the
superficial / outer aspects of the alveolar process
varies.

• In incisors, canine and premolar regions the buccal
cortical bone is thin and missing sometimes.

ALVEOLAR CROSS
SECTION OF
INDIVIDUAL TOOTH


PARS ALVEOLAR OF THE MAXILLA AT THE MID ROOT
LEVEL OF THE TEETH
• The walls of the sockets are lined by cortical bone (arrows)
the area between the sockets and between compact jaw is
occupied by cancellous bone.
• This bone occupies most of the interdental septa.
• Cancellous bone contains bone trabeculae.


• Bone lining the walls of the sockets is continuous with the
compact or cortical bone at the lingual and buccal aspects of
the alveolar process (arrow)

• Bone on the buccal and lingual aspects varies in thickness.


DEHISCENCE
• At the buccal aspect of the
jaws, the bone coverage is
missing at the coronal
portion of the roots.

FENESTRATION
• If some bone is in the
most coronal portions of
such an area the defect is
fenestration.

• The compact bone lining the tooth socket is
peforated by Volkman’s canals through which
blood vessels, lymphatic and nerve fibres pass .
• Bundle bone - Layer of bone into which Periodontal
fibres are inserted.

DEPOSITION
• It is characterized by deposition of calcium salts in localized zones of
connective tissue matrix near the developing tooth buds.
• The osteoblast , the bone forming cells are producing bone matrix
(osteoid consisting collagen fibres, glycoprotein and proteoglycans)
Osteoid undergoes Mineralization
↓
Deposition of minerals such as Ca, phosphate
↓
Hydroxyapatite


RESORPTION
• Resorption is usually carried out by osteoclasts.
These are gaint cells specalized in break down of
mineralized matrix which are developed from blood
monocytes .
REMODELING
• Alveolar process undergoes continuous remodeling
due to functional demands.
• Bone resorption is seen generally on the pressure
side .
• Bone deposition is on the tension side of the moving
tooth root. www.indiandentalacademy.com

• Remodeling exhibit
– Rough uneven surface with cavities and spicules
– Histologically moth eaten and covered with
osteoclasts
– Apposition seen most often in apical 1/3rd and on
the distal aspect of alveolus.


MORPHOLOGY
• The alveolar bone margins follows the contour of the
cemento enamel line.
• Scalloping margin mostly on the facial aspect

• Interproximal bone between anterior teeth is pyramidal, in
molar it is flat buccolingually.
• For teeth rotated the margin is located coronally and
scalloped.


MICROANATOMY OF ALVEOLAR BONE
• The alveolar process comprises of bone forming
cells  osteoblast which secrete osteoid the main
constituent of which are
– Collagen
– Glycoprotein
– Proteoglycans

• Bone collagen contain predominantly of type I collagen with
small amounts of type III & IV collagen.


• Initial stage they become engulfed by osteoid process
produced by osteoblasts and gets transformed into
osteocytes.
• Osteocytes located are surrounded first by osteoid and then
bone.
• The resorption of the bone is carried out by multinucleated
osteoclasts.
• Actively resorbing osteoclasts adhere to the bone surface,
and produce lacunar pits called HOWSHIPS LACUNAE.


• The outer surface of the bone are lined by PERIOSTEUM
containing collagen fibers, vessels, nerves and bone forming
and resorbing cells.

• The inner surface of the bone, the marrow spaces, are lined
by ENDOSTEUM.

REVERSAL LINE
• New bone deposition is separated
from previously formed bone by
these lines.


RESTING LINES
• Periodic bone apposition alternates with periods of
quiescence give rise to these lines.
• These are mediated by numerous signal molecules,
cytokines and growth hormones.


• Osteocytes present in mineralized bone, communicate with
osteoblast through canaliculi.

• Osteocytes and delicate cytoplasmic process communicate
through canliculis essential in diffusion of nutrition and
waste products.


NERVE SUPPLY

• The proprioceptive nerves within the periodontal
ligament have been shown to be directional. Thus
the dentoalveolar unit is protected from damage
from excessive forces.

• The neural density in humans is said to be much
higher in the intermediate region than in the apical
region of the root.


FUNCTIONAL RELATIONSHIP OF ALVEOLAR AND SUPPORTING
BONE

• The bone housing the tooth is dependent on the function
exerted on the tooth to maintain structure.
• Change in the bone is seen when stress to the teeth is
withdrawn.
• In jaws with teeth subjected to intense stress it is usually
spongy and supporting bone composed of thicker or more
trabeculae.
• Although bone tissue is dependent on function for
maintenance and arrangement of trabaculae other factors
involved may be(eg: disturbance in bone metabolism).

• The primary aim of preventive periodontitis and of
periodontal therapy is the preservation and
maintenance of the alveolar bone.
• Knowledge of alveolar bone structure, morphology
and physiology has become important as result of
wide spread use of advanced surgical techniques for
bone and procedures aimed at bone regeneration in
the treatment of periodontal disease.

Alveolar bone / /certified fixed orthodontic courses by Indian dental academy

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