1. Republic of Iraq
Ministry of Higher Education
And Scientific Research
University of Baghdad
College of Dentistry
By:
Khalid abdulridha
Msc. student
Supervised by:
Professor
Dr. Ban abdulghani
B.D.S, M.Sc., PhD.
Mineralization of hard tissues
3. Definition
[] Deposition of mineral salts in
and around the organic matrix to
make it a calcified structure.
[] entire life.
[] most important step ..
[] regulated process ?*
[] Ca10(PO4)6(OH)2
4. [] In which crystals of calcium
phosphate are produced by hard
tissue cells(osteoblast)
[] and are laid down in precise
amounts within the fibrous matrix
[] The synthetic cells, along with the
help of the enzyme alkaline
phosphatase,
6. 6
MVs
• Matrix vesicles (MVs) are
extracellular, 100 nM in diameter,
membrane-invested particles
selectively located at sites of initial
calcification in cartilage, bone, and
predentin. The first crystals of
apatitic bone mineral are formed
within MVs close to the inner
surfaces of their investing
membranes.
• Hard tissue forming cells contain
matrix vesicle
7. 7
MVs
A: Matrix vesicles as seen with
the electron microscope.
B: Freeze fracture of the vesicle,
showing many
intramembranous particles
thought to represent enzymes.
C: Histochemical demonstration
of calcium-adenosine
triphosphatase activity on the
surface of the vesicle.
8. 8
CONVERSION OF fibroblaststo osteoblasts as a novel strategy for bone regeneration in
elderly individuals
• As osteoblasts play a central
role in the process of bone
formation, the direct
reprogramming of fibroblasts
into osteoblasts may hence be
a new way to treat bone
fractures in elderly individuals.
11. 11
Steps in Mineralization:
1. Initiation
2. Propagation
3. ECM mineralization
Bone Mineral is deposited at discrete sites in
collagenous matrix
As bone matures, the mineral crystals become
larger and more perfect
(containing fewer impurities)
The increase in crystal dimension is due both to the
actual addition of
ions to the crystals (crystal growth) and to
aggregation of the crystals
15. COLLAGEN SEEDING THEORY /
NUCLEATION THEORY /
COLLAGEN TEMPLATE
THEORY
◦ If collagen fibers are placed in medium super
saturated with Calcium and Phosphate ions, the
collagen appears to act as a seed and apatite
crystals form on the fibers.
◦ These results suggested that either collagen or
some substance closely associated with it such
as Chondroitin Sulphate or a combination of the
two could act as a seed and form nuclei of
apatite.
◦ Once the seeding nuclei are formed, crystal
growth would occur until some limiting factor
possibly lack of space, prevented further growth.
17. Fails to explainmineralization
in enamel and cartilage.
Fails to explainmineralization
in soft tissues though it
contains collagens because
collagens in soft tissues are
densely packed which impede
phosphate ion access to
nucleation sites.
18. 18
◦ Why
Collagen Of
Hard Tissue
Calcify And
Not Soft
Tissue?
1. The spatial arrangement of collagen present in
the connective tissue that does not calcify may
be different from that of the collagen belonging
to calcifiable tissue and therefore it cannot act as
a suitable template (seed).
2. Some ground substances may mask the ion-
binding sites in collagen belonging to soft tissue,
which prevents the binding of ions and thereby
prevents mineralization. These substances that
prevent mineralization are called crystal poisons
(e.g. pyrophosphate).
19. ROBINSON’S ALKALINE
PHOSPHATASE THEORY /
BOOSTER THEORY [1923]
◦ Robinson had observed in his studies
that calcifying cartilage contains more
alkaline phosphatase than noncalcifying
cartilage.
◦ He proposed that, This enzyme
hydrolyses the organic phosphate
containing substrate and increases the
local inorganic phosphate concentration.
◦ This resulted in local increase in
phosphate ion concentration, which
caused spontaneous precipitation.
20. Fails to explainmineralization
in enamel and cartilage.
Fails to explainmineralization
in soft tissues though it
contains collagens because
collagens in soft tissues are
densely packed which impede
phosphate ion access to
nucleation sites.
21. 1. Alkaline phosphatase was found to
be present in tissues and cartilage
which did not normally calcify.
2. Organic phosphate and alkaline
phosphatase are present in blood and
at healing site, but still there is no
conversion of organic phosphate into
inorganic. Rather this requires action
of some other enzymes.
3. Certain enzyme inhibitors which did
not affect phosphates were found to
inhibit calcification in vitro.
22. MATRIX VESICLE THEORY
◦ Matrix vesicles contain Ca2+ ions in large
quantities bound to phospholipids,
which act as nucleating sites within the vesicle.
◦ Through alkaline phosphatase activity, matrix
vesicles hydrolyse organic phosphates to
phosphate ions, which in turn bind to calcium
and initiate the apatite crystallization.
◦ The first crystal is formed within the matrix
vesicle. It grows inside the matrix vesicle with the
addition of ions.
◦ The matrix vesicle finally ruptures, releasing the
crystals into the organic matrix, where the
crystals grow by using ions in the tissue fluid and
mineralization spreads to surrounding matrix..
24. MATRIX VESICLE THEORY
◦ If collagen fibers are placed in medium
super saturated with Calcium and Phosphate
ions, the collagen appears to act as a seed
and apatite crystals form on the fibers.
◦ These results suggested that either
collagen or some substance closely
associated with it such as Chondroitin
Sulphate or a combination of the two could
act as a seed and form nuclei of apatite.
◦ Once the seeding nuclei are formed, crystal
growth would occur until some limiting
factor possibly lack of space, prevented
further growth.
27. M. In enamel
◦ When first laid down, the enamel matrix is
completely organic and made up of
proteins and water, but it very quickly begins
to calcify.
◦ This requires the removal of the organic
material and water from the enamel
matrix and the introduction of the inorganic
material.
◦ Calcification (mineralization) occurs in two
stages:
1. Immediate Partial Mineralization
2. Maturation.
28. M. In enamel
◦ No matrix vesicles are observed in enamel
formation and ◦ Therefore, apatite crystals
are not preformed when they are released
by the secretory granules.
◦ no unmineralized matrix like that of
predentin or osteoid is seen during enamel
formation.
◦ Nucleation is initiated by the apatite
crystallites of dentin on which enamel is
laid.
◦ initial mineral phase consists of octa-
calcium phosphate acting as a template
for hydroxyapatite. It is however unstable
and convert into hydroxyapatite.
29. M. In enamel
◦ Maturation begins before the matrix has
reached its full thickness.
◦ As maturation proceeds, the mineral
content rises to final value of 95 to 97%
while organic matrix falls to a mere trace 0.2
to 0.8%. The apatite crystal is
considerably larger than those in dentin and
bone, the enamel crystal may have a
volume 200 times that of those in dentin.
30. 30
◦ It was suggested that enamel mineralization is thought to be achieved by crystal
growth from already mineralized dentin with subsequent size and shape crystals
determined by enamel proteins of the matrix.
33. M. In dentin
◦ Depending on the rate of
dentin formation, there are two
mineralization patterns:
Globular and Linear.
Formative cell is Odontoblast
Matured 70% mineral,
20% organic matter, and 10% water by weight
Differentiated odontoblasts produce an organic matrix
composed of primarily type I collagen (90%)
and non-collagenous proteins (10%),
to facilitate matrix organization,
mineral nucleation, and crystal growth,
which collectively define the physical properties of dentin
34. M. In dentin
◦ Depending on the rate of
dentin formation, there are two
mineralization patterns:
Globular and Linear.
37. M. In dentin
Electron micrograph showing the
characteristic deposition of first collagen
fibers to form coronal mantle predentin.
Large-diameter collagen fibers
(Collagen) intermingle with aperiodic
fibrils (arrows) associated with the basal
lamina supporting the enamel epithelium.
41. M. In cementum
[] The uncalcified matrix is called cementoid.
[] Calcium and phosphate ions are
deposited into the matrix
[] Mineralization of cementoid is a highly
ordered event and not the random
precipitation of ions into an organic matrix.
[] Matrix vesicles are also seen. They initiate
mineralization in the newly laid matrix
[] Sharpey’s fibres
43. Factors promoting :
• Alkaline phosphatase
• Nucleating substance
• Sufficient amount of calcium
and phosphorus (hydroxy
apatite).
• Minerals , vitamins and some
hormones are all play a role in
development and growth of
healthy hard tissues.
44. Factors inhibiting mineralisation
Pyrophosphate, Diphosphonates or Adenosine
triphosphate:- can delay or prevent the
transformation of amorphous calciumphosphate to
HA.
Citrate, Magnesium and proteins like Albumin.
Components of bone matrix- eg; Proteoglycans
46. OSTEOMALACIA & RICKETS
Rickets :
osteopenia with disordered calcification leading to higher
proportion of osteoid (unmineralized) tissue prior to
epiphyseal closure (in childhood)
osteomalacia :
osteopenia with disordered calcification leading to higher
proportion of osteoid (unmineralized) tissue after
epiphyseal closure (in adulthood)
48. • WHEN NORMAL BONE IS
FORMED :
• A - these fibres are coated by
mineral (this process is called
mineralisation).
• B - The strength of the new bone
depends on enough mineral
covering the collagen matrix.
• The more mineral laid down, the
stronger the bone.
49. OSTEOMALACIA HAPPENS :
A. if mineralisation doesn’t take place properly.
B. bone is made up of collagen matrix without a
mineral covering,
C. so the bones become soft.
D. These softened bones may bend and
crack, and this can be very painful.
50. • An incomplete or defective
formation of the organic
enamel matrix of teeth
• It may be generalized
across the dentition or
localized to a few teeth
• dysfunction of ameloblasts
ENAMEL HYPOPLASIA
