DENTAL IMPLANTS FOR FASTER OSSEOINTEGRATION
MANISH CHATURVEDI
DEPARTMENT OF MECHANICAL ENGINEERING INDIAN INSTITUTE OF TECHNOLOGY DELHI
MARCH 2018
© Indian Institute of Technology Delhi (IITD), 2018
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
This thesis work is dedicated to
My youngest sister - Pallavi
For taking very good care of my mother during my academic leave
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
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.
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)
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.
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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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
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
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
x
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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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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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
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
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
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
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
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
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
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
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
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