Biochemistry of Bone & Teeth

Teeth have four distinct tissue layers:

1. Enamel (Outer Layer)

2. Dentin

3. Cementum

4. Pulp

Biochemical Composition:

1. Inorganic Components (Mineral Phase) 2. Organic Components (Protein Matrix)

🦷 III. Composition of Teeth

1. Inorganic Components (Mineral Phase)

• Hydroxyapatite Crystals: Ca10(PO4)6(OH)2

• A key component of enamel, dentin, and cementum

• Provides rigidity and strength

• Can be replaced by fluorapatite Ca10(PO4)6F2Ca₁₀(PO₄) ₆F₂ for caries resistance

[Fluoride enhances resistance to demineralization by forming fluorapatite, a more acid-resistant mineral.]

IV. Developmental Biochemistry (Odontogenesis)

Tooth development involves sequential molecular signaling between epithelial and mesenchymal cells.

Key Stages:

1. Initiation – gene expression triggers the dental lamina.

2. Bud stage – cell proliferation (FGFs, BMPs active)

3. Cap stage – enamel organ forms, signaling pathways coordinate structure

4. Bell stage – differentiation into:

   • Ameloblasts (form enamel)

   • Odontoblasts (form dentin)

Key Molecules:

• BMPs (Bone morphogenetic proteins)

• FGFs (Fibroblast growth factors)

• SHH (Sonic Hedgehog)

• Wnt signaling

Disruption in these signals → tooth agenesis, enamel hypoplasia, or dentinogenesis imperfecta

🦷

1. Mineralization

• Controlled deposition of hydroxyapatite on organic matrix

• Enzymes like alkaline phosphatase and matrix metalloproteinases (MMPs) are vital

• Vitamin D, calcium, and phosphate are essential cofactors

2. Demineralization and Remineralization

• Demineralization: Loss of calcium/phosphate from enamel in acidic pH (<5.5)

• Remineralization: Recovery of minerals from saliva, fluoride, and diet

Saliva acts as a natural buffer with calcium, phosphate, and bicarbonate

V. Biochemical Processes in Tooth Health

VI. Biochemistry of Dental Caries 🦠

Dental Caries (Process):-

Caused by acid-producing bacteria (e.g., Streptococcus mutans) in plaque

Bacteria ferment dietary sugars → produce lactic acid

Acid dissolves enamel (Demineralization)

Cariogenic Pathway:

Glucose → Pyruvate → Lactic Acid → Enamel Demineralization

Protective factors:

Salivary proteins (mucins, lysozyme, lactoferrin)

Fluoride use

Xylitol (non-fermentable sweetener)

“Tooth decay is not just a hole in the enamel—it’s a dynamic biochemical war between demineralization and remineralization.”

Dental caries (commonly known as tooth decay) is one of the most prevalent non-communicable diseases globally.

I. 🦷What are Dental Caries?

Dental caries is a multifactorial infectious disease characterized by the progressive demineralization of tooth enamel and dentin caused by acids produced by bacterial fermentation of dietary carbohydrates.

Etiology:

• Primary causative agent: Streptococcus mutans, Lactobacilli, Actinomyces

• Diet: High in fermentable sugars (especially sucrose)

• Host factors: Tooth morphology, saliva flow, fluoride exposure

• Time: Repeated and prolonged exposure to acidogenic conditions

🔬 II. Pathophysiology: From Sugar to Cavity

1. Bacterial Metabolism

• Oral bacteria ferment carbohydrates → produce lactic acid

• pH drops below 5.5 (critical pH) → enamel demineralization begins

2. Demineralization

• Acid dissolves the hydroxyapatite crystals of enamel

• Ca²⁺ and PO₄³⁻ ions are lost → formation of a porous subsurface lesion

3. Progression to Dentin

• Once the enamel barrier is breached, acids and bacteria infiltrate dentin

• Dentin is softer, less mineralized, and more prone to destruction

• Pain and sensitivity may arise when approaching the pulps

III. The Role of Fluoride

Fluoride (F⁻) is a naturally occurring ion that significantly strengthens enamel and inhibits caries formation.

Mechanisms of Action:

VII. Clinical Aspects of Dental Caries

A. Stages of Caries

🩺 Clinical Relevance for Medical/Dental Students

1. Understanding caries prevention and enamel remineralization helps in public health campaigns.

2. Fluoride therapy, dietary counseling, and saliva analysis are rooted in biochemical knowledge.

3. Tooth development defects may signal underlying genetic syndromes.

4. Metabolic bone diseases (e.g., rickets, osteogenesis imperfecta) often present with oral signs.

C. Treatment Strategies

• Remineralization with topical fluoride or CPP-ACP (casein phosphopeptide-amorphous calcium phosphate)

• Restorations: composite resins, glass ionomer cement, amalgam

• Endodontic treatment: in advanced cases

B. Diagnosis

• Clinical inspection (mirror and explorer)

• Radiographs (bitewing, periapical)

• Laser fluorescence (e.g., DIAGNOdent)

VIII. Fluoride in Preventive Dentistry

Sources of Fluoride:

• Topical: Toothpaste, mouth rinses, varnishes

• Systemic: Fluoridated water (optimal level ~0.7 ppm), supplements

Community Fluoridation:

• Reduces dental caries prevalence by up to 60%

• Controversy over fluorosis risk (mottled enamel with excessive intake)

Dental Fluorosis:

• Caused by chronic overexposure to fluoride during enamel formation

• Severity: Ranges from mild white spots to severe brown stains and pitting

IX. Biochemical Insights🔍

X. Caries Risk Assessment

XI. Genetic Disorders Affecting Teeth🧬

Summary Table 💡 Final Thoughts

💡 Final Thoughts

Dental caries reflects the complex interplay between bacterial metabolism, host resistance, and environmental factors.

Fluoride acts as a powerful, scientifically proven protector, shifting the balance toward remineralization and oral resilience.

For medical students, particularly in dentistry and pediatrics, understanding this process is essential for effective public health planning, patient counseling, and clinical interventions.

“To preserve a tooth is to preserve a patient's smile, nutrition, and self-esteem.”