Orban's Oral Histology & Embryology

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

 Facial clefts 15

 Hemifacial microsomia 18

 Treacher Collins’ syndrome 18

 Labial pits 19

 Lingual anomalies 19

 Developmental cysts 19

Summary 21

Dental Lamina 25

 Fate of dental lamina 25

 Vestibular lamina 26

Tooth Development 26

Developmental Stages 27

 Bud stage 27

 Cap stage 28

Outer and inner enamel epithelium 28

Stellate reticulum 29

Dental papilla 30

Dental sac (dental follicle) 30

 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

 Hertwig’s epithelial root sheath and

root formation 35

Histophysiology 37

 Initiation 37

 Proliferation 38

 Histodifferentiation 38

 Morphodifferentiation 38

 Apposition 38

Molecular Insights in Tooth Morphogenesis 38

 Tooth initiation potential 39

 Establishment of oral–aboral axis 40

 Control of tooth germ position 41

 Functional redundancy and their complexities 41

 Patterning of dentition 42

 Regulation of ectodermal boundaries 43

 Stomodeal thickening stage—Dental

lamina stage (E11.5–E12.5) 44

 Bud stage (E12.5–E13.5) 44

 Bud stage–Cap stage (E13.5–E14.5) 44

 Enamel knot–Signaling center for tooth

morphogenesis 45

Clinical Considerations 46

Summary 46

Histology 50

 Physical characteristics 50

 Chemical properties 51

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xvi Brief Contents

 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

 Age changes 65

Clinical Considerations 66

Development 68

 Epithelial enamel organ 68

Outer enamel epithelium 69

Stellate reticulum 69

Stratum intermedium 71

Inner enamel epithelium 71

Cervical loop 71

 Life cycle of the ameloblasts 72

Morphogenic stage 72

Organizing stage 74

Formative stage 74

Maturative stage 75

Protective stage 75

Desmolytic stage 75

 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

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

 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

Physical Characteristics 151

Chemical Composition 151

Cementogenesis 152

 Cementoblasts 152

xvii

Cementoid tissue 155

Structure 156

 Acellular extrinsic fiber cementum 156

 Cellular cementum 157

Cellular intrinsic fiber cementum (CIFC) 157

Cellular mixed fiber cementum (CMFC) 157

Cellular mixed stratified cementum (CMSC) 157

 Differences between cementocytes and

osteocytes 158

 Differences between AEFC and cellular

intrinsic fiber cementum (CIFC) 159

Cementodentinal Junction 160

Cementoenamel Junction 162

Functions 163

 Anchorage 163

 Adaptation 163

 Repair 163

Hypercementosis 164

Clinical Considerations 166

Summary 168

Development 173

 Development of the principal fibers 174

Development of cells 174

 Periodontal ligament collagen fiber

attachment to the root surface 175

Periodontal Ligament Homeostasis 175

Cell Biology of Normal Periodontium 176

Cells 178

 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

 Resorptive cells 182

Osteoclasts 182

Fibroblasts 182

Intracellular degradation 183

Cementoclasts 183

 Progenitor cells 184

Origin of the periodontal stem cells 184

 Relationship between cells 185

 Epithelial rests of Malassez 186

 Defense cells 186

Mast cells 186

Macrophages 187

Eosinophils 188

Extracellular Substance 188

 Fibers 189

 Collagen 189

 Sharpey’s fibers 190

 Intermediate plexus 191

 Elastic fibers 191

 Reticular fibers 193

 Secondary fibers 193

 Indifferent fiber plexus 193

 Ground substance 193

 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

Classification of Bones 205

Composition of Bone 206

Bone Histology 209

Bone Cells 211

 Osteoblasts 211

 Osteocytes 213

 Osteoclasts 215

Bone Formation 216

 Intramembranous ossification 216

 Differences between immature bone and

mature bone 217

 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

Classification of Oral Mucosa 239

Functions of Oral Mucosa 239

Defense 239

Lubrication 239

Sensory 239

Protection 239

Definitions and General Considerations 239

 Comparison of oral mucosa with skin and

intestinal mucosa 239

 Basement membrane 242

 Lamina propria 242

 Submucosa 243

Structure of the Oral Epithelium 244

Cytokeratins 244

 Keratinized epithelium 245

Stratum basale 246

Stratum spinosum 248

Stratum granulosum 249

Stratum corneum 252

 Keratinocytes and nonkeratinocytes 253

Keratinocytes 253

Nonkeratinocytes 253

Melanocytes 253

Langerhans cell 254

Merkel cells 254

 Nonkeratinized epithelium 254

Subdivisions of Oral Mucosa 255

 Keratinized areas 255

Masticatory mucosa (gingiva and

hard palate) 255

Hard palate 255

Gingiva 259

Blood and nerve supply 263

Vermilion zone 264

 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

 Specialized mucosa 267

Dorsal lingual mucosa 267

Taste buds 270

Gingival Sulcus and Dentogingival Junction 271

 Gingival sulcus 271

 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

Structure of Terminal Secretory Units 292

 Serous cells 293

 Mucous cells 294

 Myoepithelial cells 296

 Ducts 297

Intercalated ducts 297

Striated ducts 298

Excretory ducts 300

 Connective tissue elements 300

 Blood supply 302

 Nerve supply and pattern of innervation 302

Classification and Structure of Human

Salivary Glands 303

 Major salivary glands 303

Parotid gland 303

Submandibular gland 303

Sublingual gland 304

 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

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

 Anatomy 319

 Microscopic structure 319

Cortical (follicle) area 320

Paracortex (paracortical area) 321

Medullary area 322

 Immunohistochemistry 323

 Lymph sinuses 323

 Reticular network 323

Lymphatic Vessels and Capillaries 324

Blood Vessels of Lymph Nodes 325

Clinical Significance of Lymph Nodes 325

Lymph 325

 Rate of lymph flow 326

Tonsils 326

 Lingual tonsils 326

 Palatine tonsils 326

 Pharyngeal tonsils 327

 Development of tonsils 327

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Brief Contents xix

 Functions 327

 Clinical significance of tonsils 327

Lymphatic Drainage of Head and Neck 327

Summary 329

Pattern of Tooth Movement 332

Pre-eruptive tooth movement 332

Eruptive tooth movement 334

Posteruptive tooth movement 335

 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

 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

Gross Anatomy 359

Development of the Joint 361

Histology 362

 Bony structures 362

 Articular fibrous covering 363

 Articular disk 364

 Synovial membrane 365

Clinical Considerations 365

Summary 367

Definition 369

Developmental Aspects 369

Developmental Anomalies 369

Structure and Variations 370

Microscopic Features 372

Functional Importance 375

Clinical Considerations 376

Summary 378

Overview of Histochemical Techniques 381

Structure and Chemical Composition of

Oral Tissues 382

 Connective tissue 382

 Ground substance 383

Proteoglycans 383

 Cells and fibers 386

Fibroblasts 386

 Epithelial tissues and derivatives 386

 Enzymes 386

Histochemical Techniques 387

 Fixation procedures 387

 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

 Carbohydrates and protein 390

 Lipids 392

 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

 Polysaccharides, proteins, and mucins 397

Polysaccharides 397

 Proteins and protein groups 398

 Lipids 398

 Mucins 398

 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

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