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DENTAL IMPLANTS FOR FASTER OSSEOINTEGRATION

MANISH CHATURVEDI

DEPARTMENT OF MECHANICAL ENGINEERING INDIAN INSTITUTE OF TECHNOLOGY DELHI

MARCH 2018

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© Indian Institute of Technology Delhi (IITD), 2018

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DENTAL IMPLANTS FOR FASTER OSSEOINTEGRATION

by

MANISH CHATURVEDI Department of Mechanical Engineering

Submitted

in fulfilment of the requirements of the degree of Doctor of Philosophy

to the

INDIAN INSTITUTE OF TECHNOLOGY DELHI MARCH 2018

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This thesis work is dedicated to

My youngest sister - Pallavi

For taking very good care of my mother during my academic leave

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i

CERTIFICATE

Certificate

This is to certify that the thesis entitled “Dental Implants for Faster Osseointegration” being submitted by Mr. Manish Chaturvedi to the Indian Institute of Technology Delhi for the award of the degree of Doctor of Philosophy is a record of original research work carried out by him. He has worked under my guidance and supervision and has fulfilled the requirements for the submission of this thesis, which to my knowledge has reached the requisite standard.

The results contained in this thesis have not been submitted, in part or full, to any other university or institute for the award of any degree or diploma.

Prof. Naresh Bhatnagar Department of Mechanical Engineering Indian Institute of Technology Delhi

New Delhi-110016, INDIA

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ii

Acknowledgements

Above all, I must express my gratitude to the Almighty God for each and every thing he has bestowed upon me. With the successful completion of this thesis, I would like to express my gratitude to all who made this journey possible.

The person who has transformed my life both personally and professionally is my supervisor Prof. Naresh Bhatnagar. I am short in words in expressing my gratitude for motivating me through his knowledge and his benevolent philosophy of life. His personality as an excellent professor who is dedicated to academics, industry oriented research, bringing out new and innovative products which are changing life of common man and much more than that a wonderful human being has made a permanent mark on my life and career. I humbly thanks him for his patience, personal attention and care. I thank God for providing me an opportunity to work under his supervision.

I am forever grateful to Dr. Sushma Bhanagar for her motherly care and personal attention for making my thesis work complete on time. I am indebted for her concern towards my academic goals and her guidance on professional and personal path. I am deeply inspired by observing her professional ethics and her concern for the patients and students at AIIMS.

My sincere thanks to my SRC members Prof. P. V. Madhusudhan Rao, Prof. Sudipto Mukherjee and Prof. Dinesh Kalyanasundaram for providing me with an insight into research that paved the path for my dissertation through continuous improvement.

I wish to express my heart full thanks to Dr. Vedpal Arya for his fruitful discussions and his great help during my doctoral journey. My special thanks to Dr. Pankaj and Mr. Vinay Patil for their technical interactions and working as a synergetic team member.

It has been a learning experience and joyful journey working with highly talented and energetic team members of PE Lab. I am thankful to Dr. Neelanchali Asija, Col. Dharamveer Singh, Col.

Anil Yadav, Mr. Rakesh Bhardwaj, Ms. Pooja Bhati, Mr. Ramakant Singh, Mr. Deepak Kaushik, Mr. Ashwin Patel, Ms. Shweta Singh, Mr. Avinash Kumar, Mr. Rahul Jain, Ms.

Ramya Ahuja, Mr. Alok Srivastava, Ms. Ayesha Ahmed, Mr. Kartik, Ms. Prajesh Naik, Dr.

Abhishek Gandhi, Ms. Manisha Bansal, Brig. Sanjay Prasad, Dr. Javed Ahmed, Dr. Komal Kashyap, Maj. Dhananjay and Mr. Jugpreet Singh. I am thankful to Mr. Tulsi Ram, Mr. Vijay Tiwari, Mr. Rajesh Kumar, Mr. Sanjay Kumar, Mr. Anil Kumar for their continuous support.

I would like to specially thank Ms. Tarika Chaddha for her continuous support.

I am thankful to the expert team of doctors of MAIDS for their clinical support during my doctoral work. I am thankful to Dr. Mahesh Verma, Dr. Abhinav Sood, Dr. Farukh Faraz and Dr. Smiti Bhardwaj for bringing the medical aspects in my thesis work. I am greatly thankful to Dr. Sandeep Chauhan for assisting with his medical expertise during my experiments. I am thankful to Dr. Ravi Chandran for his clinical support.

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iii

I am also thankful to CSIR for funding the project under NMITLI scheme. I am specially thankful to Prof. N. K. Ganguly, Dr. Sudeep Kumar and Dr. Vandana Bisht from CSIR for their valuable suggestion from time to time.

I am also thankful to Rajasthan Technical University Kota for sponsoring me an academic leave of three years under the Quality Improvement Program to pursue my thesis work. I am greatly thankful to Prof. N. P. Kaushik, Prof. R. P. Yadav, Prof O P Chhangani, Prof. Sanjeev Mishra, Prof. Praveen Bhandari, Prof. Rajeev Rajora. My special thanks to Prof S. K. Rathore, Prof. R.

Shringi, Dr. Pramila Shringi and Prof. Gitesh Vijay, Dr. Rashmi Vijay for their continuous support.

I am thankful to Mr. Vivek Baraya, Ms. Anju Baraya, Dr. Dinesh Yadav, Mr. Mukesh Chaudhary, Ms. Mamta Grover, Mr. Madan Mohan, Mr. Anil Mathur, Ms. Anchal Verma, Mr.

Navneesh Jawa, Ms. Akansha, Mr. Lalit Sharma, Ms. Payal Damle, Mr. Ashish Patni, Ms.

Swati Gautam, and Mr. Rajeev Mathur, Ms. Monica Sharma, Mr. Utkarsh Sharma, Ms.

Sangeeta Srinivasan, Mr. Sandeep Sharma, Mr. Tushar Mittal, Mr. Lokesh Bhardwaj, Dr.

Dheeraj Palwalia, Mr. Manjeet Singh Ozla, Mr. Vijay Chauhan, Ms. Joohi Srivastava, Col.

Pankaj Sharma, Mr. Robin Kalyan, for their friendly help and support.

I am thankful to my family members and relatives Mr. Sudama, Mrs. Prabha, Mrs. Rama, Mrs.

Suman, Mr. Prashant, Mr. Rajat, Mr. Amit, Mr. Gyanendra, Ms. Neeti, Dr. Shailendra, Ms.

Rakhi, Ms. Rashmi, Ms. Shweta, Ms. Pallavi, Ms. Khushboo, Ms. Tushti, Mr. Piyush, Ms.

Vedha, Ms. Deepta, Mr. Vinod, Mrs. Asha, Mr. Ramakant, Mrs. Savita, Mr. Vidur, Mrs. Alka, Mr. Vishwanath, Mrs. Surbhi, Mr. Kailash, Mrs. Archana, Mr. Kamlesh, Mrs. Ragini, Mr. Shiv, Mr. Shashi, Mrs. Renu, Mr. Aashish, Mr. Ashwini, Ms. Chuniya for their continuous love and care.

I would like to thank my beautiful wife Richa and my son Nalin for all the love and care they have extended to me.

The values imbibed by my father Late Shri Jagdish Chandra Chaturvedi have always been a guiding source for me throughout my academic journey.

Last but not the least I would like to thank my mother Ms. Shobha Chaturvedi for her unconditional support, for silently bearing all the pains she took and all the sacrifices she has made and for making me who I am.

My thanks and best wishes to one and all who helped me during my life.

(Manish Chaturvedi)

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iv Abstract

Dental implant is a popular field of research which has seen evolution right from prehistoric date to present. This thesis work is mainly focused on four aspects of development of a new and better product design of dental implant which is able to bring down total cycle time of tooth replacement i.e. building the concept of a new design, simulating for the given forces, manufacturing the validated design and finally testing and trials of the new product. This four pronged approach brought an insightful 360o view of the journey into developing a new and innovative medical product. The new design is evolved as an amalgamation of the concept of thread forming screw to dental implants so as reap the benefits of saving precious bone, faster osseointegration, better primary stability and form closure. With the results of computations from the FEM simulations of various geometric configurations of dental implants the new design was validated for the given loads. Cost effective and scalable manufacturing of lobular feature on a given tapered profile and generating the threads thereof was a challenge and was accomplished with special machining techniques and attachments like thread whirling and polygon milling. The studies conducted during pre and post machining operations helped in characterization of the process and bringing out strategies of optimum manufacturing of dental implants. Finally, the studies during testing on artificial SawBone and animal bone were used to analyse the effect of implants geometrical parameters on the key performance indicators like insertion and removal torque, pull out test, fatigue life etc. The new designed and manufactured implant was successfully implanted in 12 pilot clinical cases with no adverse effect leading to encouraging results which proved better than the conventional circular design in difficult situations.

Keywords: Dental Implant, thread forming, titanium machining, osseointegration, FE analysis.

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v

सार

दंतप्रत्यारोपणअनुसंधानकाएकलोकप्रप्रयक्षेत्रहै, जिसमेंप्रागैततहाससककालसेवततमानतकलगातार प्रवकासदेखागयाहै।यहशोध कायतमुख्यरूपसेदांतोंकेप्रत्यारोपणकेनएऔरबेहतरउत्पादडििाइन केप्रवकास केचारपहलुओंपर केंद्रितहै िोदन्तप्रततस्थापन केसम्पूणतचक्रके महत्वपूणतबबंदुओंको

समाद्रहत करता है, िैसे की एक नई डििाइन की अवधारणा को तैयार करना, दी गई बलों के सलए ससमुलेशन करना,मान्य डििाइन का उत्पादन करना एवंनए उत्पाद का परीक्षण करना। यह चार आयामीदृजटिकोण एकनयेऔर असिनवचचककत्साउत्पादप्रवकससत करनेमेंसंपूणतएवंव्यावहाररक दृजटिकोण लाया है।दंत प्रत्यारोपणकेसलएलोबबनानेकीअवधारणाकोसंयोजितरूपसे प्रवकससत ककयागया है, ताककबहुमूल्य हड्िी कोसंरक्षक्षत ककयािासके, तेिीसे ओससओइंद्रिग्रेशन हो, बेहतर प्राथसमकजस्थरतासमलेऔरइम्पलांि आकृतत की उन्नततरीकेसेपकड़होसके।दंत प्रत्यारोपणके

प्रवसिन्नज्यासमतीयप्रवन्यासोंकेऍफ़इएम ्ससमुलेशन सेगणनाकेपररणामोंकेसाथ, द्रदएगए िार केसलएनईडििाइन को मान्यककयागयाहै।ककसीद्रदएगएिद्रिलप्रोफ़ाइलपरलॉबुलरआकृतत को

लागत प्रिावी और स्केलेबल प्रणालीसे प्रवतनमातणकरना और उनमेंलोब पैदाकरना एक चुनौतीथा, नवाचार सेइसेप्रवशेषमशीतनंगतकनीकों, थ्रेिवह्रसलंगऔरबहुिुिसमसलंगिैसेसंलग्नककेसाथपूरा

ककयागया है। मशीतनंग पूवत एवंपश्चातके पररचालनों के दौरान ककएगए अध्ययनों से प्रकक्रया के

लक्षणवणतनमें मददसमलीऔर दंतप्रत्यारोपणके इटितमतनमातणकीरणनीततयां सामनेआईं।तत ् पश्चातकृबत्रमहड्िी औरिानवरोंकीहड्िी परपरीक्षणकेदौरान अध्ययनोंमेंइस्तेमालककयािाने

वालाइनसरशनऔरररमूवलिॉकतएवं फिीगलाइफिैसेमुख्यतनटपादनसंकेतकोंपरप्रत्यारोपणके

ज्यासमतीयपैरामीिर केप्रिाव का प्रवश्लेषण करनेके सलएप्रयोग ककयागया। यहअसिनव डििाइन और तनसमतत इम्पलांि क्लीतनकल ट्रायल में सफलतापूवतक प्रत्यारोप्रपत ककया गया। 12 प्रतततनचधक नैदातनक मामलों में कोई प्रततकूलअसर नहीं हुआ, जिसके उत्साहिनक पररणाम सामने आए। नये

दन्त प्रत्यारोपणवास्तवमेंकद्रिनपररजस्थततयोंमेंिीपारंपररकगोलडििाइनसेश्रेटि प्रमाणणतहुए।

कुंिी शब्द: दन्त प्रत्यारोपण, पेंचतनमातण, िाइिेतनयममशीतनंग, ओससओइंद्रिग्रेशन, एफ ईप्रवश्लेषण

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vi

Table of Contents

Certificate ... i

Acknowledgements... ii

Abstract ... iv

Table of Contents ... vi

List of Figures ... xiii

List of Tables ... xviii

List of Abbreviations and Notations Used ... xx

List of Nomenclatures ... xxii

Chapter 1. Introduction ... 1

1.1 Preamble ... 1

1.2 Understanding medical device ... 2

1.2.1 Classification of medical implants ... 2

1.2.2 Medical implants: Orthopaedic screws ... 3

1.2.3 Dental implant ... 4

1.3 Osseointegration ... 6

1.4 Research problem ... 7

1.5 Research objectives ... 7

1.6 Scope of the work ... 7

1.7 Thesis outline ... 8

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vii

Chapter 2. Literature Survey ... 11

2.1 Introduction ... 11

2.2 Classification of the literature survey ... 13

2.3 Brief history of dental implants ... 14

2.4 FE analysis on dental implant system ... 15

2.5 Dental implants immediate loading primary stability ... 24

2.6 Osseointegration ... 28

2.7 Mechanism of thread forming ... 32

2.8 Machining of titanium ... 35

2.9 Elastic property of bone ... 37

2.10 Engineering design and analysis of a dental implant ... 39

2.11 Swiss type CNC machines ... 41

2.12 Torsion test on dental implants ... 43

2.13 Patent search ... 46

2.14 Research gaps form the literature survey... 57

2.15 Motivation for the research work ... 58

2.16 Objectives of the research ... 59

Chapter 3. Evolution of the New Design of Dental Implant ... 61

3.1 Introduction ... 61

3.2 Related literature ... 62

3.3 Mechanics of thread forming screw ... 64

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3.3.1 Thread cutting v/s thread forming ... 65

3.3.2 Forces in thread forming ... 67

3.4 Industrial applications of thread forming screws... 68

3.5 Background of the new design ... 69

3.6 Design objectives of the thread forming implants ... 72

3.7 Key highlights from the new lobular design... 73

3.7.1 Form closer ... 73

3.7.2 Saving precious bone ... 74

3.7.3 Primary stability ... 75

3.7.4 Immediate loading ... 75

3.7.5 Less gap ... 76

3.7.6 One size under drill ... 77

3.7.7 Bone condense ... 77

3.8 Designing the lobes... 78

3.9 Geometrical features of the new implant design ... 80

3.10 Novel features and characteristics claimed for the new design ... 88

3.11 Solid models of the design ... 90

3.12 Selection of material ... 92

3.13 Summary ... 95

Chapter 4. Finite Element Simulation of Conceptualized Designs ... 97

4.1 Introduction ... 97

4.2 Biomechanics of dental implant system ... 98

4.3 Finite element model development ... 101

4.3.1 Material Properties ... 101

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ix

4.3.2 Solid 3D model ... 102

4.3.3 FE meshing and meshing controls used ... 104

4.3.4 Boundary conditions ... 105

4.3.5 Forces applied ... 106

4.3.6 Planes considered for calculation of value of maximum stress ... 107

4.4 FE analysis of lobular implant ... 109

4.4.1 Zero lobe implant ... 110

4.4.2 Bicortical implant - single stage ... 112

4.4.3 Three lobe implant ... 113

4.4.4 Four lobe implant ... 114

4.5 FEM analysis of lobular implant with bicortical threads... 116

4.5.1 Three lobe implant with bicortical thread ... 117

4.5.2 Four lobe implant with bicortical threads ... 119

4.6 Comparison of the results of FE analysis ... 121

4.6.1 Comparative analysis at upper cortical plane ... 123

4.6.2 Cortico-cancellous interface ... 124

4.6.3 Implant body ... 126

4.7 Studies on optimizing the new design through FE analysis ... 126

4.8 Effect of design parameters on stress level of bicortical implant ... 127

4.8.1 Solid model assembly of a bicortical implant in bone ... 128

4.8.2 Planes to probe maximum stress ... 128

4.8.3 Meshing ... 129

4.8.4 Boundary conditions ... 130

4.8.5 Effect of varying pitch on stresses due to tensile load of 450 N ... 130

4.8.6 Effect of varying depth of cortical threads on stresses due to tensile load ... 131

4.8.7 Effect of varying length on stresses due to various loads ... 132

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4.8.9 Comparative analysis ... 134

4.8.10 Conclusions ... 136

4.9 Effect of thread pitch configurations on stresses in dental implants ... 138

4.9.1 FE analysis of the thread configurations variants ... 139

4.9.2 Comparative analysis ... 141

4.10 Summary ... 143

Chapter 5. Manufacturing Lobular Dental Implants ... 145

5.1 Introduction ... 145

5.1.1 Challenges in titanium machining ... 146

5.1.2 Raw material ... 148

5.1.3 Machining setup ... 149

5.1.4 Sliding head technology ... 149

5.2 Issues in thread whirling on Titanium ... 152

5.2.1 Thread whirling as a method to generate threads ... 152

5.2.2 Advantages of Whirling Process ... 154

5.2.3 Issues in setting parameters for the whirling process ... 157

5.2.4 Common terms used in whirling process ... 160

5.2.5 Sample calculations for various process parameter: ... 161

5.2.6 Comparisons of cycle time ... 163

5.3 Polygon milling for the lobular dental implant ... 164

5.4 Post processing of machined parts ... 168

5.4.1 Clean room operation ... 172

5.5 Quality control of manufactured dental implant ... 176

5.6 Conclusions ... 177

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xi

Chapter 6. Testing and Clinical Cases of the Manufactured Dental Implant ... 179

6.1 Introduction ... 179

6.2 Effect of sand blasting parameters on surface roughness ... 180

6.2.1 Introduction ... 180

6.2.2 Methods and materials ... 180

6.2.3 Results and discussions ... 182

6.3 Effect of the lobes on the insertion and removal torque ... 185

6.3.1 Introduction ... 185

6.3.2 Materials and methods ... 186

6.3.3 Results and discussions ... 189

6.4 Effect of implant design on the pull-out strength of the implant ... 201

6.4.1 Introduction ... 201

6.4.2 Materials and methods ... 201

6.4.3 Results and discussions ... 204

6.5 Fatigue test analysis of dental implants ... 206

6.5.1 Introduction ... 206

6.5.2 Materials and methods ... 207

6.5.3 FEM analysis ... 209

6.5.4 Results and discussion ... 209

6.6 Testing dental implants on animal jaw bones ... 214

6.6.1 Introduction ... 214

6.6.2 Materials and Methods ... 215

6.6.3 Results and discussions ... 217

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xii

6.6.4 Immediate placement of implant ... 218

6.7 Clinical reviews of dental implants: Some cases ... 219

6.7.1 Case 1: One three lobe implant placement in a edentulous patient ... 221

6.7.2 Case 2: One three lobe and one four lobe implant placement in molars ... 222

Chapter 7. Results and Discussions ... 225

7.1 Introduction ... 225

7.2 Contributions of the research ... 230

7.3 Novelty of the research ... 234

7.4 Utility of the research ... 235

Chapter 8. Conclusions ... 237

References... 239

List of Publications ... 263

Brief Bio-Data of the Researcher ... 265

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xiii

List of Figures

Figure 1.1: Classification of medical devices according to FDA ... 3

Figure 1.2: Medical Implants: Orthopedic Screws ... 3

Figure 1.3: Anatomy of a dental implant ... 4

Figure 1.4: An over simplified procedure of dental implant surgery ... 5

Figure 1.5: An detailed procedure of a two stage dental implant surgery protocol ... 5

Figure 2.1: Area wise publication of article with key word ‘Dental Implants’ ... 12

Figure 2.2: Year wise publication of article with key word 'Dental Implants' ... 12

Figure 2.3: Classification of literature ... 13

Figure 3.1: Thread cutting v/s thread forming ... 66

Figure 3.2: Thread forming tap in a work piece8 ... 66

Figure 3.3: Industrial thread forming taps ... 69

Figure 3.4: Form closure in lobed implant ... 74

Figure 3.5: Grain flow in cut v/s form thread ... 75

Figure 3.6: Immediate loading of lobular implants ... 76

Figure 3.7: Lesser gap will take less time for osseointegration ... 77

Figure 3.8: Condensing of bone due to thread forming ... 78

Figure 3.9: Ratio of D/C for a Tri-lobe implant... 79

Figure 3.10: A conventional thread cutting circular dental implant of IITD ... 81

Figure 3.11: Cross sectional view of a Tri-Lobe dental implant ... 82

Figure 3.12: Cross sectional view of a Four-Lobe dental implant ... 83

Figure 3.13: “A Lobular Dental Implant” ... 84

Figure 3.14: A lobular implant with a bicortical thread ... 85

Figure 3.15: Exploded view of Tri-Lobe implant design assembly ... 86

Figure 3.16: Exploded view of new implant design assembly ... 87

Figure 3.17: Solid Models of Lobular Dental Implant ... 91

Figure 3.18: Solid models of the bicortical lobular dental implants ... 92

Figure 4.1: Orthogonal planes and axes of a dental system ... 100

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Figure 4.2: Cross section of human mandible at different region... 102

Figure 4.3: Exploded view of the solid model of implant assembly in bone ... 103

Figure 4.4: 3-D model of implant assembly in a bone ... 104

Figure 4.5: Meshing the assembly of dental implant system and bones using trapezoidal elements ... 105

Figure 4.6: Forces applied on dental implant model ... 107

Figure 4.7: Cortical bone level to place the stress probe ... 108

Figure 4.8: Cortico-cancellous bone interface level to place the stress probe ... 108

Figure 4.9: Implant-abutment interface level to place the stress probe ... 109

Figure 4.10: Zero lobe implant under tensile load ... 110

Figure 4.11: Zero lobe implant under compressive load ... 111

Figure 4.12: Zero lobe implant under moment load ... 112

Figure 4.13: Bicortical implant of length 9.5 mm under tensile and compressive load ... 112

Figure 4.14: Bicortical implant of length 9.5 mm under Moment load ... 113

Figure 4.15: Three lobe implant under tensile load ... 113

Figure 4.16: Three lobe implant under compressive load ... 114

Figure 4.17: Three lobe implant under moment load ... 114

Figure 4.18: Four lobe implant under tensile load ... 115

Figure 4.19: Four lobe implant under compressive load ... 115

Figure 4.20: Four lobe implant under moment load ... 116

Figure 4.21: Solid model of a lobular implant with bicortical thread in a bone ... 117

Figure 4.22: Three lobe bicortical implant under tensile load ... 118

Figure 4.23: Three lobe bicortical implant under compressive load ... 118

Figure 4.24: Three lobe bicortical implant under moment load ... 119

Figure 4.25: Four lobe bicortical implant under tensile load ... 119

Figure 4.26: Four lobe bicortical implant under compressive load ... 120

Figure 4.27: Four lobe bicortical implant under moment load ... 120

Figure 4.28: Material loss due to tri-lobular formation from a circular section ... 121

Figure 4.29: Comparison of maximum von Mises stress at upper cortical plane ... 124

Figure 4.30: Comparison of maximum von Mises stress at cortico-cancellous plane ... 125

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xv

Figure 4.31: Comparison of maximum von Mises stress at lower cortical plane ... 125

Figure 4.32: Comparison of maximum von Mises stress in implant body ... 126

Figure 4.33: A bicortical dental implant ... 128

Figure 4.34: Solid model assembly of a bicortical implant in bone ... 128

Figure 4.35: Planes to probe maximum stress in a bicortical implant assembly ... 129

Figure 4.36: Meshing of a bicortical implant assembly ... 129

Figure 4.37: Boundary conditions for bicortical implant assembly ... 130

Figure 4.38: Effect of varying pitch on stresses due to tensile Load of 450 N ... 131

Figure 4.39: Effect of varying depth of cortical threads on stresses due to tensile load ... 132

Figure 4.40: Effect of varying length of bicortical threads on stresses ... 133

Figure 4.41: Effect of varying length on stresses due to moment load ... 134

Figure 4.42: Effect of varying bicortical thread pitch on maximum stress ... 136

Figure 4.43: Effect of varying bicortical thread depth on maximum stress ... 137

Figure 4.44: Effect of varying bicortical thread length on maximum stress ... 137

Figure 4.45: Thread configurations for FE analysis ... 139

Figure 4.46: Solid model assembly of implant with different thread configurations ... 139

Figure 4.47: Stresses in various implant assembly due to different loads ... 140

Figure 4.48: Analysis of the stresses in various thread configurations... 142

Figure 5.1: Swiss sliding head technology ... 151

Figure 5.2: HA and HB screw profiles as per ISO 5835 ... 153

Figure 5.3: Bicortical Screws ... 153

Figure 5.4: Key advantages of whirling process ... 155

Figure 5.5: Whirling ring and part rotation ... 156

Figure 5.6: Whirling tool head tilting ... 159

Figure 5.7: Sample part produced by whirling attachment ... 163

Figure 5.8: Some examples of external hexagonal features in medical implants ... 165

Figure 5.9: A polygon milling cutter ... 166

Figure 5.10: A part of code to generate hexagon by a polygon milling cutter ... 167

Figure 5.11: Values of number of inserts and R to generate suitable polygon flats ... 168

Figure 5.12: Optical profile microscope images of machined and sand blasted implants ... 169

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xvi

Figure 5.13: Zeiss EVO 50 Scanning electron microscope ... 170

Figure 5.14: SEM images of sand blasted and acid etched implant surfaces ... 171

Figure 5.15: Class 100 clean room operations for final cleaning and assembly ... 172

Figure 5.16:Finally packed implants of different configurations ... 175

Figure 5.17: Quality control strategies for manufacturing dental implant ... 176

Figure 6.1: Specially designed sand blasting machine for dental implants ... 181

Figure 6.2: MarSurf PS 1 - Portable surface measurement unit ... 181

Figure 6.3: Effect of blasting time on surface roughness ... 182

Figure 6.4: Effect of blasting time on average Ra value ... 183

Figure 6.5: Effect of blasting pressure on surface roughness ... 184

Figure 6.6: Effect of blasting pressure on average surface roughness ... 184

Figure 6.7: Unlaminated and laminated SawBone blocks ... 187

Figure 6.8: Experimental setup to determine insertion and removal torque ... 190

Figure 6.9: Effect of bone density on torque in unlaminated blocks ... 191

Figure 6.10: Effect of lobes on torque of the implant in unlaminated block ... 192

Figure 6.11: Effect of lobes on removal torque of the implant on unlaminated block ... 193

Figure 6.12: Comparison of insertion and removal torque for unlaminated blocks ... 194

Figure 6.13: Effect of bone density on torque for unlaminated block in under drill protocol ... 195

Figure 6.14: Effect of lobes on insertion torque for unlaminated block in under drill protocol ... 196

Figure 6.15: Effect of lobes on removal torque for unlaminated block in under drill protocol ... 197

Figure 6.16: Insertion and removal torque for unlaminated block in under drill protocol .... 198

Figure 6.17: Effect of bone density on torque for laminated blocks ... 199

Figure 6.18: Effect of lobes on insertion torque for laminated blocks ... 200

Figure 6.19: Experimental setup for pull out test ... 202

Figure 6.20: Special fixture for the pull out test ... 203

Figure 6.21: Provision for slight angular movement of the implant assembly ... 204

Figure 6.22: Effect of bone density on pull out strength of the implant ... 205

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xvii

Figure 6.23: Effect of lobe on pull out strength of implants ... 206

Figure 6.24: Schematic representation of ISO 14801 fatigue test protocol ... 207

Figure 6.25: Bose Electroforce® 3330 fatigue testing machine ... 208

Figure 6.26: Fixture for fatigue loading of dental implant as per ISO14801 ... 209

Figure 6.27: Equivalent stresses on dental implant system under static load as per ISO14801 ... 211

Figure 6.28: Fatigue simulation of dental implant as per ISO 14801 ... 212

Figure 6.29: Goat jaw bone for testing new design of dental implant ... 214

Figure 6.30: Extraction of tooth from goat jaw bone... 215

Figure 6.31: Drilling the pilot holes and inserting the implant in goat jaw bone ... 216

Figure 6.32: Experimental setup to determine insertion and removal torque in goat jaw bone ... 216

Figure 6.33: Dental implants placed in fresh goat jaw bone... 217

Figure 6.34: Case 1 - Clinical trial of lobular implants ... 221

Figure 6.35: Case 2 -Two lobular implants placed on the same side ... 222

Figure 7.1: A brief outline of the contributions made by the research ... 233

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xviii List of Tables

Table 2.1: Literature survey on FE analysis studies on dental implant systems ... 16

Table 2.2: Literature review on immediate loading of dental implants ... 25

Table 2.3: Osseointegration ... 28

Table 2.4: Mechanism of thread forming ... 33

Table 2.5: Machining of titanium ... 35

Table 2.6: Properties of jaw bone ... 37

Table 2.7: Engineering design and analysis of a dental implant ... 40

Table 2.8: Complex machining features ... 42

Table 2.9: Torsion test on dental implants ... 43

Table 2.10: Patent search for development of dental implant ... 46

Table 3.1: Under drill size for lobular implants ... 77

Table 3.2: Variation of D/C ratio with number of lobes ... 79

Table 3.3: Selected mechanical properties of Titanium bar for implants ... 93

Table 3.4: Constituent percentage of various grades of Titanium (Ti) ... 94

Table 4.1: Elastic properties assigned to the materials used in the models (Natali, 2003) .... 101

Table 4.2: Boundary conditions for solid model of implant system in a bone ... 106

Table 4.3: Implant configuration considered for comparative FE analysis ... 109

Table 4.4: Maximum von Mises stress developed in critical planes and implant body ... 122

Table 4.5: Features and positive effects of a bicortical dental implant ... 127

Table 4.6: Effect of varying bicortical thread pitch on maximum von Mises stress (MPa) .. 135

Table 4.7: Effect of varying bicortical thread depth on maximum von Mises stress (MPa) . 135 Table 4.8: Effect of varying length of bicortical threads on maximum von Mises stress (MPa) ... 135

Table 4.9: Maximum von Mises stress for different thread configurations ... 141

Table 5.1: Chemical composition of Grade 5 and Grade 23 of titanium alloys ... 148

Table 5.2: Common terms used in whirling process ... 160

Table 5.3: Comparison of cycle time with and without whirling attachment. ... 164

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xix

Table 5.4: Overall manufacturing sequence adopted of the dental implants ... 173

Table 5.5: Dental implants and components at various stages of manufacturing ... 174

Table 5.6: Quantity of implants machined for various sizes and lobes ... 177

Table 6.1: Mechanical properties of different block densities of SawBone blocks ... 187

Table 6.2: Drilling protocol for various sizes of implants ... 188

Table 6.3: Experimental parameters for analyzing insertion and removal torque ... 189

Table 6.4: Simulated maximum stress in individual components under static load ... 210

Table 6.5: Fatigue load cycle: Experimental v/s simulation results ... 213

Table 6.6: Average insertion and removal torque (Ncm) for goat jaw bone ... 218

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xx

List of Abbreviations and Notations Used

NEP Nationally Evolved Project

NMITLI New Millennium Indian Technology Leadership Initiative

CSIR Council of Scientific & Industrial Research

FDA Food and Drug Administration

ASME American Society of Mechanical Engineers

CAD Computer Aided Design

CAM Computer Aided Manufacturing

FE Finite Element

DL Delayed loaded

IL Immediate loaded

ISQ Implant stability quotient

HBW Height of the Buccal Wall

BW Buccal Wall Width

RFA Resonance Frequency Analysis

BIC Bone-Implant Contact

PIT Peak Insertion Torque

SEM Scanning Electron Microscope

TEM Transmission Electron Microscope

HA Hydroxyapatite

PVD Physical vapour deposition

PD Polycrystalline Diamond

SSSA Single spindle Swiss type Automatics

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xxi

ISM Integrated Manufacturing System

ISQ Implant stability quotient

ISO International Standards Organization

CPCD Constant pitch and constant depth

CPVD Constant pitch and variable depth

VPCD Variable pitch and constant depth threads

VPVD Variable pitch and variable depth

ASTM American Society for Testing and Materials

TiAlN Titanium Aluminium Nitride

CNC Computer Numerical Control

CMM Coordinate Measuring Machine

BDS Bicortical dental screws

Q Angular offset

R Ratio of tool to spindle rpm

SLA Sand blasted and Acid etched

DCGI Drug Controller General of India

PCF Pound per cubic feet

UTM Universal Testing Machine

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xxii

List of Nomenclatures

Ai Areas of the faces of the tooth in contact with the workpiece when viewed along the direction of motion

t and l Tool subscripts for leading and trailing faces

Ci Proportionality constants or specific forming energies Fx, Fy, Fz Components of forces in x, y and z direction

Fthr and Ftan Forces in thrust and tangential direction

𝛾 Tool lead angle

M Torque

r Radial distance of the centroid of the tap from the center

References

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