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1
ALVEOLAR BONE
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Part I
BONE
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BONE TISSUE
Bone tissue is a specialized form of
connective tissue and is the main element of the skeletal tissues.
is composed of cells and an extracellular matrix in which fibers are embedded.
is unlike other connective tissues in that the extracellular matrix becomes calcified.
http://en.wikipedia.org/wiki/Bone_tissue
2 Types of bone tissue:
1. Compact (Cortical) bone
2. Spongy (Cancellous) bone
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FUNCTIONS OF BONE1. Support: provides framework that supports and
anchors all soft organs.
2. Protection: skull and vertebrae surround soft tissue of the nervous system, and the rib cage protects vital thoracic organs.
3. Movement: skeletal muscles use the bones as levers to move the body.
4. Storage: fat stored in the interior of the bones. Bone matrix serves as a storehouse for various minerals.
5. Blood Cell Formation: hematopoiesis occurs within the marrow cavities of the bones.
http://en.wikipedia.org/wiki/Haematopoiesis
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CLASSIFICATION OF BONE
Bone may be classified in several ways:
Developmentally Histologically By shape
Endochondral bone Compact (Cortical) Bone
Long bones
Intramembranous bone
Spongy (Cancellous) Bone
Short bones
Flat bones
Irregular bones
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A. endochondral bone• Where bone is preceded by a cartilagenous
model that is eventually replaced by bone In a process termed endochondral ossification.
B. intramembranous bone• Where bone forms directly w/in a vascular,
fibrous membrane.
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CHEMICAL PROPERTIES OF BONE 60 % Inorganic
material is formed from
carbonated hydroxyapatite.
25 % Organic material mainly composed of
Type I collagen. The organic part is
also composed of various growth factors:
glycosaminoglycans, osteocalcin, osteonectin, bone sialo protein, osteopontin and Cell Attachment Factor.
“Oral Anatomy, Histology, and Embryology”
Composition of bones
Inorganic Sub-stances
Organic Sub-stances
Water
15% Water
ORGANIC MATRIX OF THE BONE
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STRUCTURAL ELEMENTS OF BONE
Bone Cells Odontoblasts – are mononucleate cells that are responsible for bone
formation Osteocytes – When osteoblasts become trapped in the matrix they
secrete, they become osteocytes. Osteoclasts – is a type of bone cell that removes bone tissue by
removing its mineralized matrix and breaking up the organic bone Bone Matrix
is the intercelluar substance of bone consisting of collagenous fibers ground substances & inorganic salts
Sharpey’s Fibers Are a matrix of connective tissue consisting of bundles of
collagenous fibers connecting periosteum to bone Blood vessels, nerves, lymph vessels
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SHARPEY’S FIBERS
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CELL TYPES IN BONE
Osteoblasts are mononucleate cells that are responsible for bone formation
Osteocytes When osteoblasts become trapped in the matrix they secrete, they
become osteocytes. Bone-lining cells
Are inactive osteoblasts that cover all of the available bone surface and function as a barrier for certain ions
Osteoprogenitor cells relatively undifferentiated cells found on or near all of the free
surfaces of bone, which, under certain circumstances, undergo division and transform into osteoblasts or coalesce to give rise to osteoclasts.
Osteoclasts is a type of bone cell that removes bone tissue by removing its
mineralized matrix and breaking up the organic bone
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RESORPTION AND FORMATION OF BONE DURING REMODELLING
Resorption Reversal Formation Resting
http://en.wikipedia.org/wiki/Ossification
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OSSIFICATION
Also called Osteogenesis is the natural process of bone formation There are two processes resulting in the formation
of normal, healthy bone tissue: Endochondral (Intracartilaginous) Bone
Ossification The formation of bone in which a cartilage template is
gradually replaced by a bone matrix, as in the formation of long bones or in osteoarthritic ossification of synovial cartilage.
Intramembranous Bone Ossification the development of bone from tissue or membrane, as in the
formation of the skull.
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Sutural Bone Growth variable and irregularly shaped bones in
the sutures between the bones of the skull.
ALVEOLAR BONE
ALVEOLAR BONE
Also called as alveolar process
The specialized bone structure that contains the alveoli or sockets of the teeth and supports the teeth.
If the teeth are lost the alveolar process disappears
It is composed mainly of two parts:
alveolar bone proper Supporting bone
http://www.answers.com/topic/alveolar-bone#ixzz12ko9kyTQ
Alveolar Bone
DEVELOPMENT OF ALVEOLAR BONE
DEVELOPMENT OF ALVEOLAR BONE
Alveolar bone develops from the dental follicle
The ectomesenchymal cells of the dental follicle differentiate into osteoblasts and lay down the matrix called osteoid
Some osteoblasts become embedded in the matrix and are called osteocytes
Near the end of the 2nd month of fetal life, mandible and maxilla form a groove that is opened toward the surface of the oral cavity
As tooth germs start to develop, bony septa form gradually. The alveolar process starts developing strictly during tooth eruption.
GROSS MORPHOLOGY OF BONE
Morphology -is a branch of bioscience dealing with the study of the form and structure of organisms and their specific
structural
Alveolar Socket Also called Dental
alveolus are sockets in the
jaws in which the roots of teeth are held in the alveolar process with the periodontal ligament.
Alveolar socket of the second premolar tooth in a bovine maxillary bone.
Interdental Septa “Septa” – in Latin, it
means “fence” or “wall”
Are plates of bone that separate each individual sockets from one another.
Interradicular Septa Are thin plates of bone
that separate the roots of multi-rooted teeth
Cribriform Plate also called as bundle bone Is the compact layer of
bone lining the tooth socket (alveolar socket)
Reflects the sieve-like appearance produced by numerous Volkmann’s canals passing from the alveolar bone to the PDL (periodontal ligament).
Numerous Sharpey’s Fiber pass through it.
ALVEOLAR PROCESS is the thickened ridge of
bone that contains the tooth sockets on bones that bear teeth.
The alveolar process contains a region of compact bone adjacent to the periodontal ligament called Lamina dura.
Maxilla and Mandible Are the tooth-bearing
bones
Lamina Dura this part which is
attached to the cementum of the roots by the periodontal ligament.
Is the bone lining the alveolus
In clinical radiographs, it commonly appears as a dense white line.
Lamina Dura
Radiographic appearance of alveolar bone proper as ‘Lamina Dura’
FUNCTIONS OF THE BONE
FUNCTIONS OF ALVEOLAR BONE
Protection Alveolar bone forms and protects the sockets for the teeth.
Attachment It gives the attachment to the periodontal ligament fibers, which
are the principle fibers. These fibers which enter the bone are regarded as Sharpey’s fibers.
Support It supports the tooth roots on the facial and on the palatal/lingual
sides.
Shock-absorber It helps absorb the forces placed upon the tooth by disseminating
the force to underlying tissues.
STRUCTURE OF THE ALVEOLAR BONE Cortical Plate – outermost part
Alveolar bone proper or lamina Spongiosa – spongy bone
a) outer cortical platesb) a central spongiosa c) bone lining the alveolus (bundle bone)
CORTICAL PLATE
Outer bony plate of varying thickness, which is the outside wall of the maxilla and mandible, covered with periosteum
Continuous with the lamina cribriformis at the orifice of the alveoli – alveolar crest
Consists of haversian systems (osteons) and interstitial lamellae
Thicker in the mandible than maxilla Generally greater on the lingual than on the
buccal/facial
ALVEOLAR BONE PROPER OR LAMINA
An inner, heavily perforated bony lamellae, forming the alveolar wall
In radiograph, appears as radioopaque line distinct from the adjacent spongiosa – Lamina Dura
Contains osteons like other cortical bone, but is distinguished by the presence of Bundle Bone
SPONGIOSA
Are spongy (or cancellous/trabecullar) bone between the 2 bony plates and between the lamina cribriformis of adjacent teeth or roots
Consists of delicate trabeculae, between which are marrow spaces, filled mostly with fatty marrow
Regions of maxillary tuberosity and the angle of mandible, erythropoietic …
VASCULAR SUPPLY OF ALVEOLAR BONE
VASCULAR SUPPLY OF ALVEOLAR PROCESS
Alveolar process of the maxilla Anterior and posterior alveolar arteries
(branch from the maxilla and infraorbital arteries)
Alveolar process of the mandible Inferior alveolar arteries (internal) Periosteal branches of submental and
buccal arteries (external)
PERIODONTAL DISEASE
PERIODONTAL DISEASE
http://en.wikipedia.org/wiki/Periodontal_disease
Periodontal disease is a type of disease that affects one or more of the periodontal tissues: Alveolar bone Periodontal ligament Cementum gingiva
While many different diseases affect the tooth-supporting structures, plaque-induced inflammatory lesions make up the vast majority of periodontal diseases and have traditionally been divided into two categories: gingivitis or periodontitis.
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HISTOLOGICAL ARRANGEMENT OF MATURE BONE
Mature bone is composed of: Compact bone Spongy Bone
http://www.physioweb.org/skeletal/bone_tissue.html
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COMPACT BONE Also called as Cortical bone As its name implies. . .
“cortical” bone forms the cortex or outer shell of most bones.
“compact” bone is much denser than cancellous bone. Furthermore, it is harder, stronger and stiffer than cancellous bone.
The primary anatomical and functional unit of cortical bone is the osteon.
3 Distinct Layering of Compact Bone: Circumferential lamella Concentric lamella Interstitial lamella
Functions: facilitates to support the whole body protect organs provide levers for movement store and release chemical elements, mainly calcium.
http://en.wikipedia.org/wiki/Bone_tissue
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3 DISTINCT LAYERING OF COMPACT BONE:
Circumferential Lamellae enclose the entire adult bone, forming its
outer perimeter
Concentric Lamellae make up the bulk of compact bone and form
the basic metabolic unit of bone, the osteon
Interstitial Lamellae interspersed between adjacent concentric
lamellae and fill the spaces between them
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SPONGY BONE
Also called Cancellous bone or Trabecular bone Compared to compact bone, cancellous bone has a
higher surface area but is less dense, softer, weaker, and less stiff.
Cancellous bone is highly vascular and frequently contains red red bone marrow where hematopoeisis occurs.
The primary anatomical and functional unit of cancellous bone is the trabecula.