Orban's Oral Histology & Embryology

1. An Overview of Oral Tissues 1

2. Development of Face and Oral Cavity 5

Origin of Facial Tissues 5

Development of Facial Prominences 9

Development of the frontonasal region:

olfactory placode, primary palate, and nose 9

Development of maxillary prominences

and secondary palate 10

Development of visceral arches and tongue 11

Final Differentiation of Facial Tissues 13

Clinical Considerations 15

_x0003_ Facial clefts 15

_x0003_ Hemifacial microsomia 18

_x0003_ Treacher Collins’ syndrome 18

_x0003_ Labial pits 19

_x0003_ Lingual anomalies 19

_x0003_ Developmental cysts 19

Summary 21

3. Development and Growth of Teeth 24

Dental Lamina 25

_x0003_ Fate of dental lamina 25

_x0003_ Vestibular lamina 26

Tooth Development 26

Developmental Stages 27

_x0003_ Bud stage 27

_x0003_ Cap stage 28

Outer and inner enamel epithelium 28

Stellate reticulum 29

Dental papilla 30

Dental sac (dental follicle) 30

_x0003_ Bell stage 31

Inner enamel epithelium 32

Stratum intermedium 32

Stellate reticulum 33

Outer enamel epithelium 33

Dental lamina 33

Dental papilla 33

Dental sac 35

Advanced bell stage 35

_x0003_ Hertwig’s epithelial root sheath and

root formation 35

Histophysiology 37

_x0003_ Initiation 37

_x0003_ Proliferation 38

_x0003_ Histodifferentiation 38

_x0003_ Morphodifferentiation 38

_x0003_ Apposition 38

Molecular Insights in Tooth Morphogenesis 38

_x0003_ Tooth initiation potential 39

_x0003_ Establishment of oral–aboral axis 40

_x0003_ Control of tooth germ position 41

_x0003_ Functional redundancy and their complexities 41

_x0003_ Patterning of dentition 42

_x0003_ Regulation of ectodermal boundaries 43

_x0003_ Stomodeal thickening stage—Dental

lamina stage (E11.5–E12.5) 44

_x0003_ Bud stage (E12.5–E13.5) 44

_x0003_ Bud stage–Cap stage (E13.5–E14.5) 44

_x0003_ Enamel knot–Signaling center for tooth

morphogenesis 45

Clinical Considerations 46

Summary 46

4. Enamel 50

Histology 50

_x0003_ Physical characteristics 50

_x0003_ Chemical properties 51

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Brief Contents

_x0003_ Structure 53

Rods 53

Ultrastructure 53

Striations 54

Direction of rods 54

Hunter–Schreger bands 57

Incremental lines of Retzius 57

Surface structures 58

Enamel cuticle 60

Enamel lamellae 61

Enamel tufts 62

Dentinoenamel junction 64

Odontoblast processes and enamel spindles 65

_x0003_ Age changes 65

Clinical Considerations 66

Development 68

_x0003_ Epithelial enamel organ 68

Outer enamel epithelium 69

Stellate reticulum 69

Stratum intermedium 71

Inner enamel epithelium 71

Cervical loop 71

_x0003_ Life cycle of the ameloblasts 72

Morphogenic stage 72

Organizing stage 74

Formative stage 74

Maturative stage 75

Protective stage 75

Desmolytic stage 75

_x0003_ Amelogenesis 76

Formation of the enamel matrix 76

Development of Tomes’ processes 77

Ameloblasts covering maturing enamel 81

Mineralization and maturation of the

enamel matrix 82

Clinical Considerations 86

Summary 87

5. Dentin 93

Physical and Chemical Properties 93

Structure 94

Dentinal tubules 94

Peritubular dentin 95

Intertubular dentin 96

Predentin 96

Odontoblast process 97

Primary Dentin 98

Secondary Dentin 100

Tertiary Dentin 100

Incremental Lines 100

Interglobular Dentin 101

Granular Layer 103

Innervation of Dentin 104

Intratubular nerves 104

Theories of pain transmission through dentin 104

Permeability of Dentin 106

Age and Functional Changes 106

Vitality of dentin 106

Reparative dentin 107

Dead tracts 108

Sclerotic or transparent dentin 108

Development 110

Dentinogenesis 110

Mineralization 112

Clinical Considerations 115

Summary 117

6.

Pulp 120

Anatomy 120

General features 120

Coronal pulp 120

Radicular pulp 121

Apical foramen 121

Accessory canals 122

Structural Features 122

Intercellular substance 122

Fibroblasts 124

Fibers 124

Undifferentiated mesenchymal cells 125

Odontoblasts 125

Defense cells 127

Pulpal stem cells 130

Blood vessels 130

Lymph vessels 135

Nerves 135

Nerve endings 135

_x0003_ Molecular events following pulp injury

and repair 138

Functions 139

Inductive 139

Formative 139

Nutritive 139

Protective 139

Defensive or reparative 139

Differences in Primary and Permanent

Pulp Tissues 139

Primary pulp 139

Permanent pulp 140

Regressive Changes (Aging) 140

Cell changes 140

Fibrosis 140

Vascular changes 141

Pulp stones (denticles) 141

Diffuse calcifications 142

Development 142

Clinical Considerations 143

Summary 148

7. Cementum 151

Physical Characteristics 151

Chemical Composition 151

Cementogenesis 152

_x0003_ Cementoblasts 152

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_x0003_Cementoid tissue 155

Structure 156

_x0003_ Acellular extrinsic fiber cementum 156

_x0003_ Cellular cementum 157

Cellular intrinsic fiber cementum (CIFC) 157

Cellular mixed fiber cementum (CMFC) 157

Cellular mixed stratified cementum (CMSC) 157

_x0003_ Differences between cementocytes and

osteocytes 158

_x0003_ Differences between AEFC and cellular

intrinsic fiber cementum (CIFC) 159

Cementodentinal Junction 160

Cementoenamel Junction 162

Functions 163

_x0003_ Anchorage 163

_x0003_ Adaptation 163

_x0003_ Repair 163

Hypercementosis 164

Clinical Considerations 166

Summary 168

8. Periodontal Ligament 172

Development 173

_x0003_ Development of the principal fibers 174

Development of cells 174

_x0003_ Periodontal ligament collagen fiber

attachment to the root surface 175

Periodontal Ligament Homeostasis 175

Cell Biology of Normal Periodontium 176

Cells 178

_x0003_ Synthetic cells 178

Osteoblasts 178

Fibroblast 180

Fibroblast-matrix adhesion and traction 180

Functions 181

Differences between periodontal ligament

fibroblasts and gingival fibroblasts 181

Cementoblasts 182

_x0003_ Resorptive cells 182

Osteoclasts 182

Fibroblasts 182

Intracellular degradation 183

Cementoclasts 183

_x0003_ Progenitor cells 184

Origin of the periodontal stem cells 184

_x0003_ Relationship between cells 185

_x0003_ Epithelial rests of Malassez 186

_x0003_ Defense cells 186

Mast cells 186

Macrophages 187

Eosinophils 188

Extracellular Substance 188

_x0003_ Fibers 189

_x0003_ Collagen 189

_x0003_ Sharpey’s fibers 190

_x0003_ Intermediate plexus 191

_x0003_ Elastic fibers 191

_x0003_ Reticular fibers 193

_x0003_ Secondary fibers 193

_x0003_ Indifferent fiber plexus 193

_x0003_ Ground substance 193

_x0003_ Interstitial tissue 193

Structures Present in Connective Tissue 193

Blood vessels 194

Lymphatic drainage 195

Nerves 195

Cementicles 196

Functions 196

Supportive 196

Sensory 197

Nutritive 198

Homeostatic 198

Eruptive 198

Physical 198

Age Changes in Periodontal Ligament 199

Unique Features of Periodontal Ligament 199

Clinical Considerations 200

Summary 201

9. Bone 205

Classification of Bones 205

Composition of Bone 206

Bone Histology 209

Bone Cells 211

_x0003_ Osteoblasts 211

_x0003_ Osteocytes 213

_x0003_ Osteoclasts 215

Bone Formation 216

_x0003_ Intramembranous ossification 216

_x0003_ Differences between immature bone and

mature bone 217

_x0003_ Intracartilaginous bone formation 217

Bone Resorption 220

Bone Remodeling 222

Alveolar Bone 224

Development of Alveolar Process 224

Structure of the Alveolar Bone 225

Internal Reconstruction of Alveolar Bone 229

Age Changes 231

Clinical Considerations 231

Therapeutic Considerations 233

Summary 234

10. Oral Mucous Membrane 238

Classification of Oral Mucosa 239

Functions of Oral Mucosa 239

Defense 239

Lubrication 239

Sensory 239

Protection 239

Definitions and General Considerations 239

_x0003_ Comparison of oral mucosa with skin and

intestinal mucosa 239

_x0003_ Basement membrane 242

_x0003_ Lamina propria 242

_x0003_ Submucosa 243

Structure of the Oral Epithelium 244

Cytokeratins 244

_x0003_ Keratinized epithelium 245

Stratum basale 246

Stratum spinosum 248

Stratum granulosum 249

Stratum corneum 252

_x0003_ Keratinocytes and nonkeratinocytes 253

Keratinocytes 253

Nonkeratinocytes 253

Melanocytes 253

Langerhans cell 254

Merkel cells 254

_x0003_ Nonkeratinized epithelium 254

Subdivisions of Oral Mucosa 255

_x0003_ Keratinized areas 255

Masticatory mucosa (gingiva and

hard palate) 255

Hard palate 255

Gingiva 259

Blood and nerve supply 263

Vermilion zone 264

_x0003_ Nonkeratinized areas 265

Lining mucosa 265

Lip and cheek 265

Vestibular fornix and alveolar mucosa 266

Inferior surface of tongue and floor of

oral cavity 266

Soft palate 267

_x0003_ Specialized mucosa 267

Dorsal lingual mucosa 267

Taste buds 270

Gingival Sulcus and Dentogingival Junction 271

_x0003_ Gingival sulcus 271

_x0003_ Dentogingival junction 271

Development of dentogingival junction 272

Shift of dentogingival junction 274

Sulcus and cuticles 277

Epithelial attachment 277

Migration of epithelial attachment 278

Development of Oral Mucosa 281

Age Changes in Oral Mucosa 281

Clinical Considerations 282

Summary 284

11. Salivary Glands 291

Structure of Terminal Secretory Units 292

_x0003_ Serous cells 293

_x0003_ Mucous cells 294

_x0003_ Myoepithelial cells 296

_x0003_ Ducts 297

Intercalated ducts 297

Striated ducts 298

Excretory ducts 300

_x0003_ Connective tissue elements 300

_x0003_ Blood supply 302

_x0003_ Nerve supply and pattern of innervation 302

Classification and Structure of Human

Salivary Glands 303

_x0003_ Major salivary glands 303

Parotid gland 303

Submandibular gland 303

Sublingual gland 304

_x0003_ Minor salivary glands 304

Labial and buccal glands 305

Glossopalatine glands 305

Palatine glands 305

Lingual glands 306

Von Ebner’s glands 306

Development and Growth 306

Control of Secretion 307

Composition of Saliva 308

Functions of Saliva 309

Protection of the oral cavity and

oral environment 309

Digestion 310

Mastication and deglutition 310

Taste perception 310

Speech 310

Tissue repair 310

Excretion 311

Clinical Considerations 311

Summary 312

12. Lymphoid Tissue and Lymphatics in

Orofacial Region 317

Introduction to Lymphatic System 317

Types of Lymphoid Tissues 317

Development of Lymph Nodes and Lymphatics 318

Functions of the Lymphatic System 318

Lymph Nodes 318

_x0003_ Anatomy 319

_x0003_ Microscopic structure 319

Cortical (follicle) area 320

Paracortex (paracortical area) 321

Medullary area 322

_x0003_ Immunohistochemistry 323

_x0003_ Lymph sinuses 323

_x0003_ Reticular network 323

Lymphatic Vessels and Capillaries 324

Blood Vessels of Lymph Nodes 325

Clinical Significance of Lymph Nodes 325

Lymph 325

_x0003_ Rate of lymph flow 326

Tonsils 326

_x0003_ Lingual tonsils 326

_x0003_ Palatine tonsils 326

_x0003_ Pharyngeal tonsils 327

_x0003_ Development of tonsils 327

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Brief Contents xix

_x0003_ Functions 327

_x0003_ Clinical significance of tonsils 327

Lymphatic Drainage of Head and Neck 327

Summary 329

13. Tooth Eruption 332

Pattern of Tooth Movement 332

Pre-eruptive tooth movement 332

Eruptive tooth movement 334

Posteruptive tooth movement 335

_x0003_ Animal experimental studies in eruption 335

Histology of Tooth Movement 335

Pre-eruptive phase 335

Eruptive phase 335

Posteruptive phase 338

Mechanism of Tooth Movement

(Theories of Tooth Eruption) 339

Bone remodeling theory 339

Root formation theory 339

Vascular pressure theory 339

Periodontal ligament traction theory 340

Posteruptive tooth movement 340

_x0003_ Cellular and molecular events in eruption 341

Clinical Considerations 344

Summary 345

14.

Shedding of Deciduous Teeth 348

Definition 348

Pattern of Shedding 348

Histology of Shedding 351

Mechanism of Resorption and Shedding 355

Clinical Considerations 356

Remnants of deciduous teeth 356

Retained deciduous teeth 356

Submerged deciduous teeth 357

Summary 358

15. Temporomandibular Joint 359

Gross Anatomy 359

Development of the Joint 361

Histology 362

_x0003_ Bony structures 362

_x0003_ Articular fibrous covering 363

_x0003_ Articular disk 364

_x0003_ Synovial membrane 365

Clinical Considerations 365

Summary 367

16. Maxillary Sinus 369

Definition 369

Developmental Aspects 369

Developmental Anomalies 369

Structure and Variations 370

Microscopic Features 372

Functional Importance 375

Clinical Considerations 376

Summary 378

17. Histochemistry of Oral Tissues 380

Overview of Histochemical Techniques 381

Structure and Chemical Composition of

Oral Tissues 382

_x0003_ Connective tissue 382

_x0003_ Ground substance 383

Proteoglycans 383

_x0003_ Cells and fibers 386

Fibroblasts 386

_x0003_ Epithelial tissues and derivatives 386

_x0003_ Enzymes 386

Histochemical Techniques 387

_x0003_ Fixation procedures 387

_x0003_ Specific histochemical methods 388

Glycogen, glycoproteins, and proteoglycans 388

Proteins and lipids 389

Enzymes 389

Phosphatases 389

Immunohistochemistry 390

Histochemistry of Oral Hard Tissues 390

_x0003_ Carbohydrates and protein 390

_x0003_ Lipids 392

_x0003_ Enzyme histochemistry of hard tissue 393

Alkaline phosphatase 393

Adenosine triphosphatase 394

Acid phosphatase 394

Esterase 395

Aminopeptidase 396

Cytochrome oxidase 396

Succinate dehydrogenase 397

Citric acid cycle in osteoblasts and

osteoclasts 397

Calcium-binding sites in enamel organ 397

Summary 397

Histochemistry of Oral Soft Tissues 397

_x0003_ Polysaccharides, proteins, and mucins 397

Polysaccharides 397

_x0003_ Proteins and protein groups 398

_x0003_ Lipids 398

_x0003_ Mucins 398

_x0003_ Enzyme histochemistry 399

Alkaline phosphatase 399

Acid phosphatase 399

Esterase 399

Aminopeptidase 399

β-Glucuronidase 399

Cytochrome oxidase 400

Succinate dehydrogenase and glucose

6-phosphate dehydrogenase 401

Enzyme histochemical detection of

lymphatic capillaries 401

Angiogenic factor in inflamed gingiva 402

Laminin-5 402

Clinical Considerations 402

Summary 403

18. Preparation of Specimens for Histologic Study 410

Preparation of Sections of Paraffin-Embedded

Specimens 411

Infiltration of the specimen with paraffin 411

Preparation of Sections of Parlodion-Embedded

Specimens 413

Preparation of Ground Sections of Teeth or Bone 414

Preparation of Frozen Sections 415

Types of Microscopy 415

Summary 415

Index 417