<<

Subrata Pal

Design of Artificial Human & Organs

Springer Contents

1 Overview of Human System and Its Artificial Replacement 1 1.1 Human Body's Superficial Anatomy 1 1.2 Human Body Features 1 1.3 Body Size, Type, and Proportion 2 1.4 A Brief Outline of the Organization of the Human System 3 1.4.1 Tissue+Tissue=Organ (Different Tissues Together Form an Organ) 3 1.4.2 Organ + Organ=Organ System 4 1.5 Major Organ Systems 4 1.5.1 Integumentary System 5 1.5.2 Muscular System 5 1.5.3 Skeletal System 5 1.5.4 Cardiovascular System 7 1.5.5 Respiratory System 7 1.5.6 Urinary System 7 1.5.7 Reproductive System 9 1.5.8 Nervous System 11 1.5.9 Digestive System 11 1.5.10 Lymphatic System 12 1.5.11 Immune System 12 1.6 Common Names of Internal Organs (in Alphabetical Order) 14 1.7 Brief Idea of Artificial Organs 14 1.7.1 Different Types of Organs 15 1.7.2 Brain 15 1.7.3 Cardia 16 1.7.4 Corpora Cavernosa 16 1.7.5 Ear 16 1.7.6 Eye 16 1.7.7 Heart 17 1.7.8 Limbs 17 1.7.9 Liver 17

vii viii Contents

1.7.10 Lungs 18 1.7.11 Pancreas 18 1.7.12 Bladder 18 1.7.13 Ovaries 18 1.7.14 Beyond Restoration 19 1.7.15 Timeline of Successful Transplants 19 References 20 Exercises 20 2 Mechanical Properties of Biological Materials 23 2.1 Introduction 23 2.2 Structural Versus Material Properties 23 2.2.1 Anisotropy and Nonhomogeneity 24 2.2.2 Viscoelastic Properties 24 2.2.3 Viscosity 25 2.3 Testing Procedures 25 2.4 26 2.4.1 Composition 26 2.4.2 Structure 27 2.5 Material Properties and Related Behavior 29 2.6 , 32 2.6.1 Composition 32 2.7 Material Properties and Related Behavior 33 2.8 Ligaments 34 2.8.1 Composition 34 2.9 Material Properties and Related Behavior 36 2.9.1 Ligaments Have Characteristics of Strain-Rate Sensitivity, Stress-Relaxation, Creep, and Hysteresis 36 2.10 Correlation Between Structure and Function 37 2.10.1 Ligament-/Tendon-Bone Insertions 38 Reading List 39 Problems 39 3 Basics of Design Process 41 3.1 Introduction 41 3.2 Adoptive and Adaptive Design 41 3.2.1 Introduction 41 3.3 Introduction to Machine Design 42 3.4 Principle of Science or Mechanism to Be Used 43 3.5 Safety of Products 47 3.6 Manufacturability 47 3.7 Standardization 48 3.8 Customization 48 For Further Details, the Following Books May Be Consulted 49 Exercises 49 Contents ix

4 Biomaterials and Its Characterization 51 4.1 Introduction 51 4.2 Biomineralization 52 4.3 Abalone Shell 54 4.4 Self-Assembly 55 4.5 Structural Hierarchy 56 4.6 Applications 56 4.7 Compatibility 57 For Further Reading, These Papers May Be Consulted 58 4.8 Biopolymers 59 4.8.1 Applications 60 4.8.2 Sources 60 4.8.3 Applications 60 4.8.4 Sources 60 4.8.5 Applications 61 4.8.6 Benefits 61 4.9 Polymers for Healthcare 62 4.9.1 Sterilization 62 4.9.2 Compatibility with Sterilization Method of Various Industrial Biopolymers (Solviva) 62 4.9.3 Polyether Ether Ketone (PEEK) 63 4.9.4 Applications 64 4.10 Bioceramics 64 4.10.1 History 64 4.10.2 Current Status 65 4.10.3 Future Trends 65 4.11 Bioceramic Materials 65 4.11.1 Bioinert 65 4.11.2 Bioactive 66 4.12 Hydroxyapatite: Medical Uses 66 4.13 Bioactive Glass 67 4.13.1 Compositions 67 4.13.2 Mechanism of Bioactivity 67 4.13.3 Applications 68 For Further Study Consult the Reading List (Ceramics and Glass) 68 4.14 Metals as Biomaterials 69 4.15 Signs of Inferior Tissue Response 71 4.16 Stress-Shielding Phenomena 71 4.17 Shape-Memory Alloy 72 Problems 73 5 Dental Implants: Their Design and Manufacture 75 5.1 Introduction 75 5.1.1 Success Criteria 75 5.2 Anatomy of Human Jawbones 77 5.3 Dental Implants 78 x Contents

5.4 Components of Dental Implant 81 5.5 Types of Implants in Use 81 5.5.1 Subperiosteal Implants 81 5.5.2 Transosteal Implants 82 5.5.3 Endosteal Implants 83 5.5.4 Biocompatibility and Implant Design 84 5.6 Biting Force 86 5.7 Implant Shape 87 5.8 Surface Characteristics 87 5.9 Bone Factors 88 5.10 Loading Conditions 89 5.10.1 Prosthetic Considerations 90 5.10.2 The Type of Prosthetic Reconstruction 90 5.10.3 The Occlusal Scheme 90 5.11 The Number, Distribution, Orientation, and Design of Implants 90 5.12 Placement of Implants into Extraction Sites 91 5.13 Clinical and Biomechanical Considerations for Fixed Tooth Replacement 92 5.13.1 Bone Tissue Factors 92 5.13.2 Soft Tissue Factors 92 5.13.3 Number of Implants 93 5.13.4 Crown-to-Root Ratio 93 5.13.5 Implant Orientation 94 5.14 Advantages of Permanent Tooth Replacement 94 5.15 Manufacture of Implants and Property Enhancement 94 References 95 Problems 96 Glossary of Dental Terminology 96 6 The Design of a Bone Fracture-Fixation Device 101 6.1 Introduction 101 6.2 101 6.2.1 The 105 6.3 Internal Fracture Fixation 106 6.3.1 Wires 106 6.3.2 Braided Multifilament Wire 106 6.3.3 Pins 107 6.3.4 Screws 107 6.3.5 Plates 109 6.3.6 Intramedullary Nails Ill 6.3.7 Use of Machine Elements in External Fixators 114 6.4 Other Considerations 114 6.5 Materials Involved in Bone-Plate Design 114 6.6 Composite Materials 115 Contents xi

6.7 Bioactive Fixation Using Bioactive Materials 117 6.8 Compositions 119 6.9 Strong Interfacial Bond with Bone 119 Suggested Study for Fracture Fixation 119 Problems 121 7 The Shoulder and Its Artificial Replacement 123 7.1 Introduction to 123 7.2 The Shoulder Joint and Its Artificial Replacement 124 7.2.1 Introduction 124 7.2.2 The Different Joints 125 7.2.3 Musculature 126 7.2.4 Ligaments 127 7.2.5 Glenohumeral Joint 127 7.2.6 Glenoid 128 7.2.7 Humerus 128 7.2.8 Kinematics of the Glenohumeral Joint 129 7.2.9 Geometrical Center and Center of Rotation 130 7.3 Humeral Translation Relative to the Scapula 130 7.4 Degrees of Freedom (DOF) 131 7.5 Range of Motion 132 7.6 Total (Glenohumeral ) 134 7.6.1 Reasons for Shoulder Arthroplasty 134 7.7 Types of Shoulder Prostheses 135 7.8 Fully Constrained Type 136 7.9 Nonconstrained Type 138 7.10 Fixation Procedures 143 7.11 Causes of Failure 144 7.11.1 Loosening of the Component 145 7.11.2 Anterior Instability 146 7.11.3 Superior Instability 146 7.11.4 Posterior Instability 146 7.11.5 Inferior Instability 146 7.11.6 Rotator Cuff Tears 146 7.11.7 Intraoperative Fractures 147 7.11.8 Infection 147 7.11.9 Neural Injuries 147 References 147 Problems 148 8 The Elbow Joint and Its Artificial Replacement 149 8.1 Introduction 149 8.1.1 Movements 149 8.2 Muscles, Arteries, and Nerves 151 8.3 Parts of the Joint 151 8.4 Ligaments 152 xii Contents

8.5 Synovial Membrane 152 8.6 Carrying Angle 153 8.7 Diseases of the Elbow 153 8.7.1 Tendonitis 153 8.7.2 Fractures 153 8.7.3 Arthritis 153 8.8 Elbow Replacement 154 8.9 Elbow Replacement 156 8.10 Life Expectancy of Prosthetic Elbow Joint 156 References 157 Problems 157 9 The Wrist Joint and Its Artificial Replacement 159 9.1 Anatomy 159 9.2 Rheumatoid Arthritis of the Hand and Wrist 159 9.3 Treatment 161 9.3.1 Forces Generated in the Wrist Joint 161 9.4 Implants: Components of a Wrist Arthroplasty 163 9.5 Surgery 164 9.6 Postsurgical Care 165 References 165 Problems 166 10 The Finger Joint and Its Artificial Replacement 167 10.1 Introduction 167 10.2 Diseases of the Finger Joint 168 10.2.1 Symptoms 170 10.2.2 Nonsurgical Treatment 171 10.3 Finger Joint Replacement 171 10.3.1 Introduction 171 Problems 174 References 175 11 The Hip Joint and Its Artificial Replacement 177 11.1 Introduction 177 11.2 Anatomy of the Hip Region 177 11.2.1 Articulation 177 11.2.2 Femoral Neck Angle 178 11.2.3 Capsule 180 11.2.4 Ligaments 180 11.2.5 Blood and Nerve Supply 181 11.2.6 Muscles and Movements 181 11.3 Hip Joint Replacement 182 11.3.1 History 184 11.4 Modern Developments 185 11.5 Costs 186 xiii

11.6 Aseptic Loosening of Hip Prosthesis 186 11.7 Techniques of Surgery 187 11.8 Alternatives to 187 11.8.1 Apollo Hip System: Simple, Straight-Stem Design for the Low-Demand Patient 188 11.8.2 Dr. K. H. Sancheti's Hip Prosthesis 190 11.9 Design Modification Using Hollow Section 191 11.9.1 Stress Shielding 191 11.9.2 Hollow Design 192 References & Reading List 193 Problems 194 The Knee Joint and Its Artificial Replacement 195 12.1 Anatomy 195 12.1.1 Cruciate Ligaments 195 12.1.2 Anterior Cruciate Ligament 196 12.1.3 Action of Muscles 197 12.1.4 Knee Joint Stabilization 197 12.2 , or Knee Arthroplasty 199 12.2.1 Introduction 199 12.3 History 200 12.3.1 Technique 201 12.4 Variations in Design 202 12.4.1 Partial Knee Replacement 202 12.5 Risks and Complications 203 12.5.1 Loss of Motion 204 12.5.2 Instability 204 12.5.3 Infection 204 12.6 Developmental Work on a Congruent Tibial Component 205 12.6.1 This Design has Two Advantages 207 12.6.2 Disadvantages 208 12.7 Indian Effort 208 References... 209 Problems 210 The Ankle Joint and Its Artificial Replacement 211 13.1 Introduction 211 13.1.1 Structure 211 13.2 Bones and Joints 211 13.3 Ligaments and Tendons 212 13.4 Muscles 213 13.5 Nerves 214 13.6 Bloodvessels 214 13.7 Artificial Replacement of the Ankle Joint 214 13.8 The Operative Procedure 215 xiv Contents

13.9 Complications 216 13.9.1 Infection 217 13.9.2 Loosening 217 13.9.3 Nerve Injury 217 Study List 217 Problems 217 14 The Eye and Its Artificial Replacement 219 14.1 Anatomy of the Eye 219 14.1.1 Extraocular Muscles 221 14.2 Development of the Eye 222 14.2.1 Disorders of the Eye 224 14.2.2 Disorders of the Eye Muscles 224 14.2.3 Disorders of the Cornea, Iris, and Lens 224 14.2.4 Disorders of the Retina 224 14.2.5 Visual Impairments 224 14.3 Contact Lens 225 14.3.1 Corrective Contact Lenses 228 14.3.2 Cosmetic Contact Lenses 228 14.3.3 Therapeutic Contact Lenses 229 14.4 Classification of Contact Lenses 229 14.4.1 By Construction Material 229 14.4.2 By Time of Wear 230 14.4.3 By Frequency of Replacement 230 14.4.4 By Design 230 14.4.5 Implantation 231 14.5 Manufacturing of Contact Lenses 231 14.5.1 Hydrogel Materials 232 14.5.2 Contact Lens Prescriptions 232 14.6 Complications 232 14.6.1 Eyelid 233 14.6.2 Conjunctiva 233 14.6.3 Cornea 233 14.7 Usage 233 14.7.1 Care 234 14.8 Current Research 234 14.9 Intraocular Lens 235 14.9.1 History 237 14.9.2 Materials Used for Intraocular Lenses 237 14.9.3 Intraocular Lenses for Correcting Refractive Errors 238 14.9.4 Types of PIOLs 239 14.9.5 Accommodating IOLs 239 14.9.6 Criticisms 240 14.9.7 Candidates 240 XV

14.10 LASIK Eye Surgery 241 14.10.1 What Is LASIK? 241 14.10.2 The LASIK Procedure 241 14.10.3 Phacoemulsification 242 14.10.4 Demographics 242 14.10.5 Diagnosis/Preparation 244 14.10.6 Aftercare 245 14.10.7 Risks 245 14.10.8 Alternatives 246 14.11 Bionic Eye 246 Related Literature for Study 246 Study List 247 The Lung and Its Transplantation and Artificial Replacement 251 15.1 Introduction 251 15.2 Respiratory Tract 251 15.2.1 Structure 252 15.3 Path Traced by Inhaled Air 254 15.4 Gaseous Exchange 254 15.5 Common Lung Diseases 255 15.6 Lung Transplantation 256 15.7 Types of Lung Transplants 257 15.7.1 Lobe 257 15.7.2 Single-Lung Transplant 257 15.7.3 Double-Lung Transplant 257 15.7.4 Heart-Lung Transplant 257 15.8 Design of Artificial Lungs 258 15.9 Design Overview 258 For Detailed Study, Consult the Following Papers 260 Problems 260 Design of the Total Artificial Heart 261 16.1 Introduction 261 16.2 Artificial Heart 261 16.2.1 CardioWest Temporary Total Artificial Heart 261 16.2.2 AbioCor Replacement Heart 262 16.3 Origins 262 16.3.1 Early Development 264 16.4 Early Designs of Total Artificial Hearts 264 16.5 First Clinical Implantation of a Total Artificial Heart 265 16.6 First Clinical Applications of a Permanent Pneumatic Total Artificial Heart 265 16.7 The Development of Permanent, Implantable, Electrically Powered Artificial Hearts 266 16.8 First Clinical Application of an Intrathoracic Pump 267 Contents

16.9 First Clinical Application of a Paracorporeal Pump 267 16.9.1 Recent Developments 267 16.10 Total Artificial Heart 268 16.11 Heart Assist Devices 268 16.11.1 Ventricular Assist Device (VAD) 268 16.12 Total Artificial Heart: Aortic Pumping System, Indian Initiative 269 16.12.1 Novel Features 269 16.13 Existing Prior Technologies 270 16.13.1 Diaphragm Pump 270 16.13.2 Pulsatile Blood-Pumping System 271 16.13.3 Orthotopic Total Artificial Heart 272 16.13.4 Heart Assist Devices, Systems, and Methods 273 16.14 Disadvantages of Prior Developed Systems 274 16.15 Artificial Heart Pump 274 16.16 Multistaged Multi-Actuated Pump System (Fig. 16.4) 275 16.16.1 Heart Pump Prototype Model 277 16.16.2 Advantages of the Artificial Heart 277 Reading List 279 Problems 280 The Design of Heart Valves 281 17.1 Introduction 281 17.2 The Heart 281 17.3 Heart Valves 284 17.4 Cardiac Cycle 286 17.5 Cardiac Output 287 17.6 Artificial Heart Valves 291 17.6.1 Potential Risks of Artificial Heart Valves 291 17.6.2 Lifestyle Considerations 292 17.6.3 Longevity and Replacements 293 17.7 Design of Valves 293 17.7.1 Valve Descriptions 294 17.7.2 Mechanical Valves 294 17.7.3 Caged Ball Valve 295 17.7.4 Tilting Disk Valve 295 17.7.5 Bileaflet Valves 297 17.8 Biological Valves 298 17.8.1 Homograft, Autograft 299 17.8.2 Autologous Pericardial Valve 300 17.8.3 Porcine Heterograft Valves (Stented) 300 17.8.4 Porcine Heterograft Valves (Unstented) 301 17.8.5 Bovine Pericardial Heterograft Valves 301 17.8.6 Complications 302 17.8.7 The Comparative Clinical Performance 302 xvii

17.9 Structural Deterioration of Biological Valves 303 17.9.1 Porcine Valves 303 17.9.2 Pericardial Valves 303 17.9.3 Homografts 303 17.9.4 Pulmonary Autograft 304 17.9.5 Materials of Construction and Manufacture 304 17.9.6 Assembly 305 17.9.7 Sterilization and Packaging 305 17.9.8 Quality Control 305 17.9.9 The Future 306 17.10 Failure Modes in Mechanical Valves 306 17.11 Choice of Valves 307 17.12 Future Developments 307 List for Further Study 308 Problems 308 Example from the Literature for Valve Area Calculation 308 Aortic Valve Area Calculation 308 The Kidney and Its Artificial Replacement 311 18.1 Introduction 311 18.2 How Do Kidneys Help Maintain Health? 313 18.3 Diseases 313 18.3.1 Chronic Kidney Disease (CKD) and Related Facts 313 18.3.2 What Is Chronic Kidney Disease? 314 18.3.3 What Causes CKD? 314 18.3.4 The Symptoms of CKD 314 18.4 Dialysis 315 18.4.1 Kidney Failure 315 18.4.2 Hemodialysis 316 18.4.3 Peritoneal Dialysis 316 18.5 The Artificial Kidney 317 18.5.1 Parallel Flow Dialyzers 317 18.6 Coil Hemodialyzer 317 18.6.1 Hollow Fiber Hemodialyzer 319 18.7 Performance Analysis of Dialyzers 319 18.7.1 Ultrafiltration Rate 321 18.7.2 Residual Blood Volume 322 18.7.3 Priming Volume 322 18.7.4 Pyrogenicity 322 18.7.5 Leakage Rate 322 18.8 The Hemodialysis Machine and Its Parts 323 18.9 Conclusions 323 18.9.1 Dialysis Does Not Help Cure Kidney Disease 323 xviii Contents

18.10 Recent Developments in Artificial Kidneys 324 18.10.1 Nanotechnology 325 18.10.2 Portable Dialysis Machine 326 List for Further Reading 328 Exercises 328 19 Skin and the Design of Artificial Skin 329 19.1 Anatomy of the Skin 329 19.2 Modeling of Soft Biological Tissues 330 19.1.1 The Stress-Strain Relationship 331 19.3 Mechanical Properties of Soft Tissue 332 19.4 Fitting Hyperelastic Material Models to the Experimental Data 332 19.5 Artificial Skin 333 19.6 Tissue Expanders 335 References 337 Exercises 337 20 The Artificial Pancreas 339 20.1 Endocrine Physiology 339 20.2 Artificial Pancreas 340 20.3 Intensive Insulin Therapy and Insulin Pump 341 20.4 Bioengineering Approach to an Artificial Pancreas 343 20.5 Gene Therapy Approach 344 20.6 Medical Equipment Approach 345 20.6.1 Development of Continuous Blood Glucose Monitoring 345 20.6.2 Feedback of Real-Time Blood Glucose Data to an Insulin Pump for Basal Control 346 20.7 First Clinical Tests: Implantable Insulin Pumps and Continuous Glucose Sensors 347 20.8 Insulin and Amylin Combination 348 20.9 Feedback of Real-Time Blood Glucose Data to an Insulin Pump for Bolus Control 348 20.10 Glucagon Combination 349 20.11 Research Around the World 350 Reading List 350 Problems 351 21 The Liver and Its Artificial Replacement 353 21.1 Introduction 353 21.2 Blood Flow 354 21.3 Biliary Flow and the Biliary Tree 354 21.4 Lobes 355 21.5 Synthesis 355 21.6 Breakdown 356 xix

21.7 Other Functions 356 21.8 Bioartificial Liver Device 356 21.8.1 Function 357 21.8.2 Hollow Fiber System 357 21.8.3 Comparison to Liver Dialysis 357 21.9 Progress Toward an Artificial Liver Transplant 358 References and for Further Study 359 Problems 359 Female Organs and Their Artificial Replacements 361 22.1 Introduction 361 22.2 Breast Implants 362 22.2.1 History 363 22.2.2 Indications 363 22.3 Patient Characteristics 364 22.4 Types of Implants 365 22.5 Silicone Gel Implants 366 22.5.1 First Generation 366 22.5.2 Second Generation 366 22.5.3 Third and Fourth Generations 367 22.5.4 Fifth Generation 367 22.6 Implant Pocket Placement 367 22.7 Failure and Rupture 369 22.8 Implants and Mammography 369 22.8.1 Breast Implant Manufacturers 370 22.8.2 Artificial Breast Prostheses 370 22.9 Artificial Vagina 371 22.9.1 Veterinary Use 371 22.10 Usage as Sex Toy 371 22.10.1 Types 372 22.11 Materials 373 References 373 Problems 375 The Medical Device Market and Ethical Issues of Implants 377 23.1 Introduction to the Medical Device Market 377 23.2 Ethical Issues of Implants 379 23.2.1 The Need for Implants 380 23.3 Treatment Modality 380 23.4 Transplants and Implants 381 23.5 Implant Failure 382 23.6 Clinical Trials 384 23.7 Ethical Issues of Dental Implants 384 23.8 Cost 385 23.9 Moral Uncertainties 385 23.10 Religion and Morals 386 xviii Contents

18.10 Recent Developments in Artificial Kidneys 324 18.10.1 Nanotechnology 325 18.10.2 Portable Dialysis Machine 326 List for Further Reading 328 Exercises 328 19 Skin and the Design of Artificial Skin 329 19.1 Anatomy of the Skin 329 19.2 Modeling of Soft Biological Tissues 330 19.1.1 The Stress-Strain Relationship 331 19.3 Mechanical Properties of Soft Tissue 332 19.4 Fitting Hyperelastic Material Models to the Experimental Data 332 19.5 Artificial Skin 333 19.6 Tissue Expanders 335 References 337 Exercises 337 20 The Artificial Pancreas 339 20.1 Endocrine Physiology 339 20.2 Artificial Pancreas 340 20.3 Intensive Insulin Therapy and Insulin Pump 341 20.4 Bioengineering Approach to an Artificial Pancreas 343 20.5 Gene Therapy Approach 344 20.6 Medical Equipment Approach 345 20.6.1 Development of Continuous Blood Glucose Monitoring 345 20.6.2 Feedback of Real-Time Blood Glucose Data to an Insulin Pump for Basal Control 346 20.7 First Clinical Tests: Implantable Insulin Pumps and Continuous Glucose Sensors 347 20.8 Insulin and Amylin Combination 348 20.9 Feedback of Real-Time Blood Glucose Data to an Insulin Pump for Bolus Control 348 20.10 Glucagon Combination 349 20.11 Research Around the World 350 Reading List 350 Problems 351 21 The Liver and Its Artificial Replacement 353 21.1 Introduction 353 21.2 Blood How 354 21.3 Biliary Flow and the Biliary Tree 354 21.4 Lobes 355 21.5 Synthesis 355 21.6 Breakdown 356 xix

21.7 Other Functions 356 21.8 Bioartificial Liver Device 356 21.8.1 Function 357 21.8.2 Hollow Fiber System 357 21.8.3 Comparison to Liver Dialysis 357 21.9 Progress Toward an Artificial Liver Transplant 358 References and for Further Study 359 Problems 359 Female Organs and Their Artificial Replacements 361 22.1 Introduction 361 22.2 Breast Implants 362 22.2.1 History 363 22.2.2 Indications 363 22.3 Patient Characteristics 364 22.4 Types of Implants 365 22.5 Silicone Gel Implants 366 22.5.1 First Generation 366 22.5.2 Second Generation 366 22.5.3 Third and Fourth Generations 367 22.5.4 Fifth Generation 367 22.6 Implant Pocket Placement 367 22.7 Failure and Rupture 369 22.8 Implants and Mammography 369 22.8.1 Breast Implant Manufacturers 370 22.8.2 Artificial Breast Prostheses 370 22.9 Artificial Vagina 371 22.9.1 Veterinary Use 371 22.10 Usage as Sex Toy 371 22.10.1 Types 372 22.11 Materials 373 References 373 Problems 375 The Medical Device Market and Ethical Issues of Implants 377 23.1 Introduction to the Medical Device Market 377 23.2 Ethical Issues of Implants 379 23.2.1 The Need for Implants 380 23.3 Treatment Modality 380 23.4 Transplants and Implants 381 23.5 Implant Failure 382 23.6 Clinical Trials 384 23.7 Ethical Issues of Dental Implants 384 23.8 Cost 385 23.9 Moral Uncertainties 385 23.10 Religion and Morals 386 xx Contents

23.11 Ethical Issues of Transplants 387 23.11.1 Availability 389 23.12 Xenografts as a Solution 390 23.13 Life Expectancy 391 Suggested References for Further Details 393 Exercises 393 24 The Manufacturing, Testing, and Sterilization of Implants 395 24.1 Introduction 395 24.2 Casting 396 24.3 Forging 397 24.4 Metal-Shaping Machine Tools 397 24.5 Manufacturing Implants at a High Speed 399 24.6 Rapid Prototyping 400 24.7 Nonconventional Machining 402 24.8 Nondestructive Testing 403 24.9 Sterilization 404 24.9.1 Physical Agent 405 24.10 Conclusions 408 For Further Reading, the Following References Are Given 408 For Computer-Aided Design and Manufacture 408 For Sterilization of Implants 409 Problems 409

Index 413