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Lecture 49Department of Biochemistry and Molecular Biology
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Title: Lecture 49Department of Biochemistry and Molecular Biology
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Saliva and Dental CariesM. Lenander-Lumikari.
V. LoimarantaDepartment of Cariology and Turku
Immunology Centre, Institute ofDentistry,
University of Turku, Lemminkaisenkatu 2, FIN -
20520 Turku,Finland, Corresponding author,
marlen_at_utu.fiAdv Dent Res 1440-47, December,
2000
- Caries is a unique multifactorial infectious
disease. Our understanding of etiological
factors, the progress of the disease, and the
effectiveness of prophylactic procedures have led
us to believe that we understand the disease.
However, we still have too few answers to many
questions "Why can we not predict who will get
the disease?" "Why do we not become immunized?"
"How much saliva is enough?" or "Which salivary
components are protective?" and "Which salivary
components predispose for caries?" It is
generally accepted, however, that saliva
secretion and salivary components secreted in
saliva are important for dental health. The final
result, "caries to be or not to be", is a complex
phenomenon involving internal defense factors,
such as saliva, tooth surface morphology, general
health, and nutritional and hormonal status, and
a number of external factors-for example, diet,
the microbial flora colonizing the teeth, oral
hygiene, and fluoride availability. In this
article, our aim is to focus on the effects of
saliva and salivary constituents on cariogenic
bacteria and the subsequent development of dental
caries.
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Section of a human molar
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Cavity
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Cells producing dentin and enamel
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Higher magnification view of ameloblasts
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Higher magnification view of odontoblasts
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Localization of macromolecules associated with
calcification in mammals
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Organic Components of Calcified Tissues
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Dentin Proteins
- Collagen type I
- FGF beta Occurs in dentine in inactive form and
is activated during active dentin formation - Osteopontin Highly acidic glycoprotein of MW
44,000-probably binds Ca during calcification. - OsteonectinOsteonectin is a glycoprotein in the
bone that binds calcium. It is secreted by
osteoblasts and odontoblasts initiating
mineralization and promoting mineral crystal
formation. Osteonectin also shows affinity for
collagen in addition to bone mineral calcium - Osteogenin Also known as bone morphogenic
protein - OsteocalcinOsteocalcin is a noncollagenous
protein found in bone and dentin. It is secreted
by osteoblasts and thought to play a role in
mineralization and calcium ion homeostasis. It
has been stipulated that osteocalcin may also
function as a negative regulator of bone
formation, although its exact role is unknown. - Dentin specific proteins
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Dentin Specific proteins
- Several extracellular matrix (ECM) proteins have
been isolated from dentin and shown to be
synthesized by odontoblasts. - Highly phosphorylated proteins (HP), the
phosphophoryns, are specifically found in dentin
and are synthesized only by odontoblasts.
Phosphophoryns are probably involved in
controlling the site and/or the rate of
circumpulpal mineralization. - Other moderately phosphorylated (MP) and low
phosphorylated (LP) proteins have also been
detected in dentin, but have not been studied
extensively.
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Enamel Proteins
- Ameloblastin the function of ameloblastins is
believed to be in controlling the elongation of
enamel crystals and generally directing enamel
mineralization during tooth development. - Amelogenin The latest research indicates that
this protein regulates the initiation and growth
of hydroxyapatite crystals during the
mineralization of enamel. In addition,
amelogenins appear to aid in the development of
cementum by directing cells that form cementum to
the root surface of teeth.
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Enamel Proteins------
- The genes for amelogenin can be used in sex
determination of samples from unknown human
origin. Using primers specific for intron I of
this gene, PCR amplification of the X chromosome
gives a 106 bp fragment and Y chromosome gives a
112 bp fragment.
Male
Female
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Tuftelin
- Tuftelin is an acidic phosphorylated
glycoproteinfound in tooth enamel. This protein
is formed for a short time during amelogenesis.
The function of tuftelins is under contention,
but it is proposed that it acts to start the
mineralization process of enamel during tooth
developement
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Enamelins
- Enamelin is a protein found in developing tooth
enamel. About 30 of developing enamel consists
of protein of which enamelins comprise lt1.
Enamelin is not a proteolytic enzyme and does not
degrade other enamel proteins. Two enamelins of
MW 63 and 67 Kda have been purified. These
strongly bind to hydroxyapatite. Mechanism of
their action is not clear.
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Ground Substance Organization
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EM of Biofilm
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Salivary Enzymes in Normal Function and Abnormal
Pathology
- a-Amylasenormally present in salivaimportant in
digestion - Lysozyme
- Hyaluronidase
- Chondrosulfatase
- Aryl Sulfatase
- Neutral Protease
- Collagenases
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Dental Caries
- Parotid Gland
- Lysozyme
- Oral Microbe Cell Wall Polysaccharides
- (polymers of NAG and NA-neuraminic acid)
- Hyaluronidase
- Mucinase
- Chondrosulfatase
- Arylsulfatase
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Salivary Enzymes-Role in Dental Caries
- Components of Dentine are
- Organic matrix consisting of collagen,
glycoproteins, proteoglycans, dentin specific
proteins - Inorganic matrix consisting of hydroxyapatite
- In Oral Cavity
- Starch Dextrins
Monosaccharides - a-amylase
ß-amylase - Monosaccharides? Lactic acid under anaerobic
glycolysis - Ca3(PO4)2 H 4 H2O? 3Ca(OH)2 2H3PO4
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Functions of Released Enzymes
- Components of dentinCollagen, Hyaluronic acid,
Sulfated glycoproteins, Hydroxyapatite - Hyaluronic Acid NAG Glucuronic
Acid - HU
- Sulfated Glycoproteins NAG sulfate
Glucuronic Acid - AS, CS
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- Acids produced breakdown the hydroxyapatite
crystal lattice
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Resorption of Organic matrix
- Abnormal Dentin Structure
- Exposed Collagen type I in a
- Abnormal Hydroxyapatite Crystal lattice
- Human Collagenase type I Bacterial
collagenase - ¾ and ¼ Chains of collagen
- Type IV Collagenase Neutral
Proteinase - Amino acids and peptides
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Hormonal factors in Dental Caries
- Salivary Clearance capacity-higher the
flow-better flushing and lower caries levels - Antibiotics and other drugs decrease salivary
flow rate-higher rate of caries - Salivary buffer effect-greater in men than in
women women have higher incidence of caries - Post menopausal women have higher incidence of
caries-hormone replacement therapy improves the
condition
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