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
• 
  
• 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