Founded 1905 HAPTICS-BASED MODELING AND SIMULATION OF MICRO-IMPLANTS SURGERY ZHENG FEI (B.Eng., M.Eng.) A THESIS SUBMITTED FOR THE DEGREE OF DOCTOR OF PHILOSOPHY DEPARTMENT OF MECHANICAL ENGINEERING NATIONAL UNIVERSITY OF SINGPAORE 2012 I ACKNOWLEDGEMENTS First and foremost, I am thankful beyond words for the untiring guidance and utmost support I have received from my advisor, Associate Professor Lu Wen Feng, throughout my entire candidature. It is Prof. Lu who led me to discover this exciting research area, pushed me to grow up, helped me to broaden my horizon, and raised me up to more than I can be. His patience and encouragement make him a great advisor I will always appreciate. I also deeply appreciate Prof. Wong Yoke San and Prof Kelvin Foong Weng Chiong who provide valuable suggestions and continuous support throughout my Ph.D. research project. I am indebted to the National University of Singapore for providing Graduate Research Scholarship and supporting my Ph.D. study. I am grateful to all the friends along the journey of pursuing my doctorate, the ones who have helped make my time enjoyable. Special thanks are due to my wife Han Xue, who accompany me and support me these days. I would like to thank my seniors: Dr. Fan Liqing, Dr. Wang Jinling and Dr. Wang Yifa for sharing their research experience and programming tricks with me. In addition, I would also like to thank my lab mates and friends at LCEL who I spent years together, and technicians at AML (especially Mr. Tan Choon Huat, Mr. Lim Soon Cheong and Mr. Ho Yan Chee) who help me a lot for my experiments. Last, but certainly not least, sincere thanks go to my parents. I would not make it through the day without their vigorous support and endless love. II TABLE OF CONTENTS DECLARATION…………………………………………………………I ACKNOWLEDGEMENTS . II TABLE OF CONTENTS . III SUMMARY……………………………………………………………VII LIST OF TABLES IX LIST OF FIGURES . X LIST OF ABBREVIATIONS . XIV CHAPTER INTRODUCTION 1.1 Micro-implants and Micro-implants Surgery 1.2 Motivation . 1.3 Research Objectives and Scope 1.4 Organization of the Thesis . CHAPTER LITERATURE REVIEW . III 2.1 Virtual Reality and Computer Haptics 2.2 Modeling of Virtual Objects 10 2.2.1 Surface Modeling . 10 2.2.1.1 Surface Representation 10 2.2.1.2 Surface Deformation . 12 2.2.2 Volume Modeling 13 2.2.1.1 Volume Representation 13 2.2.1.2 Volume Deformation . 14 2.3 Haptic Rendering . 16 2.3.1 Haptic Rendering for a Single Point . 17 2.3.2 Haptic Rendering beyond a Single Point 18 2.4 Related Work on Dental Training Simulations . 20 2.4.1 Manikin-based Simulators 20 2.4.2 Haptics-based Simulators . 21 2.5 Summary . 24 CHAPTER RESEARCH OVERVIEW . 26 3.1 Introduction . 26 3.1 Research Overview 26 3.2 System Architecture . 28 3.3 Simulation Framework . 32 CHAPTER CONSTRUCTION OF VOXEL-BASED ORAL MODEL AND ITS SURFACE GEOMETRY . 35 4.1 Introduction . 35 IV 4.2 CT Image Segmentation and Smoothing 37 4.3 Data Structure of the Voxel Model . 40 4.4 Rendering of Surface Geometry . 42 4.5 Summary . 45 CHAPTER EXPERIMENTAL STUDY OF THE DRILLING FORCE AND THE IMPLANT INSERTION TORQUE . 47 5.1 Introduction . 47 5.2 Experiment Design 47 5.3 Pilot-Drilling Experiment 50 5.3.1 Manual Drilling 50 5.3.2 Automated Drilling 54 5.4 Screw Insertion Experiment . 59 5.5 Summary . 64 CHAPTER REAL-TIME SIMULATION FOR THE MICROIMPLANTS SURGERY - PART 1: PILOT DRILLING . 65 6.1 Introduction . 65 6.2 Analytical Drilling Force Model 67 6.3 Data Structure for the Pilot Drill 71 6.4 GPU-based Parallel Rendering . 72 6.5 Results and Discussion 79 6.5.1 Force Model Calibration 79 6.5.2 Pilot-drilling Simulation and Discussion 88 6.6 Summary . 94 V CHAPTER REAL-TIME SIMULATION FOR THE MICROIMPLANTS SURGERY - PART 2: PLACEMENT OF MICRO-IMPLANTS 95 7.1 Introduction . 95 7.2 Data Structure for the Micro-implants 97 7.3 Voxel-Based Torque Model . 99 7.4 GPU-based Parallel Rendering . 104 7.5 Design and Implementation of a Torque Feedback Device . 107 7.6 Results and Discussion 109 7.6.1 Torque Model Calibration 109 7.6.2 Implant Insertion Simulation and Discussion 113 7.7 Summary . 120 CHAPTER CONCLUSIONS AND FUTURE WORK 122 8.1 Conclusions . 122 8.2 Future Work 124 REFERENCES . 126 APPENDIX Appendix A. Example XML File for Drill Configuration A1 Appendix B. Example XML File for Implant Configuration B1 Appendix C. KISTLER Dynamometer . C1 Appendix D. LORENZ Torque Sensor . D1 VI SUMMARY The objective of this thesis is to develop a real-time haptics-based simulation framework to model and simulate the micro-implants surgery. Based on the simulation framework, a training platform has been developed for novice dentists to practice the pre-drilling procedure and the implant placement procedure required for this particular surgery. With the developed system, trainees can get different force feedback when drilling at different oral tissues and learn to control the drill vibration during the pilot-drilling procedure. This will help them to develop a tactile sensation to identify root contact during drilling, preventing severe damage to the tooth roots hidden from sight. They can also experience the insertion, tightening and stripping phases of the implant placement procedure, allowing them to develop an intuitive sense to achieve optimal tightness between the implant and the bone. Towards the design of the proposed framework, approaches in modeling of inhomogeneous oral tissues, rendering of force/torque feedback, as well as reconstruction of oral surface during the surgical procedures have been developed and presented. A prototype simulator, including the pilot-drilling sub-system and the micro-implant insertion sub-system, has also been developed to validate these approaches. The work of the thesis is summarized as follows. Firstly, a voxel-based oral model construction approach was proposed to overcome the limitation of surface-based approach in representing inhomogeneous tissues. With this approach, anatomically-accurate and smooth 3D oral models can be VII constructed directly from patient-specific CT images. A special data structure was used to store the voxel model, facilitating GPU-based parallel computing. Secondly, an analytical drilling force model was developed to provide a realistic force feedback. While most of force modeling methods were based on penetration-depth and thus can only render a touch-resistance force, the proposed model was adapted from classic metal cutting principles and therefore can capture the essential features of the drilling process. Thirdly, a voxel-based torque model was developed to simulate the torque response based on the tissue properties and the implant geometry. A torque feedback device was also designed and implemented to control the virtual implant and to output proper torque resistance to the user. To the best of the author’s knowledge, this should be the first voxel-based haptic simulator for the screw insertion procedure. Fourthly, experiments were carried out on pig’s jaw to measure the drilling force and the implant insertion torque. The collected data were used to calibrate the force/torque model. The simulation results after calibration demonstrated the effectiveness of the proposed approaches. Lastly, the GPU-based parallel computing approach was employed and developed to enhance the real-time performance of both haptic and graphic rendering. This was achieved by special data structure design, force/torque model parallelization and proper graphic memory utilization, based on the CUDA architecture. The CPUGPU comparison results showed an impressive speedup with the GPU-based method. It should be noted that the proposed approaches and framework are not limited to this particular surgery. They can also be generalized and expanded accordingly to other haptics-based medical applications that involve drilling and screwing procedures. 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Thomas, et al., "Automated surgical screwdriver: automated screw placement," Proceedings of the Institution of Mechanical Engineers, Part H (Journal of Engineering in Medicine), vol. 222, pp. 817-27, 2008. 141 Appendix APPENDIX Appendix A. Example XML File for Drill Configuration The example file below shows a pre-defined pilot-drill in XML format which can be easily loaded into the system for the real-time simulation. 0.5 7.0 2.0943951 0.2 0.2 … 0.14315486 0.77336103 0.0056276917 0.64971191 0.10243686 -0.1000000 -3.6429305 A1 Appendix 0.14668183 0.75014895 0.0056276917 0.63156784 0.10731059 -0.10000000 -3.6401167 … A2 Appendix Appendix B. Example XML File for Implant Configuration The example file below shows a pre-defined micro-implant in XML format which can be easily loaded into the system for the real-time simulation. 1.2 1.6 0.4 6 … 0.17453292 560 -0.10547403 0.59817964 0.91111100 0.60740727 < original _position> -0.31110999 0.53886080 B1 Appendix 0.93333322 0.62222213 … B2 Appendix Appendix C. KISTLER Dynamometer C1 Appendix Appendix D. LORENZ Torque Sensor D1 [...]... [3], and surgical procedures such as endoscopic surgery [4], bone dissection [5], periodontal treatment [6] A haptics- based simulation framework for a particular procedure in clinical dentistry, the micro- implants surgery, has been developed in this thesis This chapter covers the background of micro- implants and the micro- implants surgery, followed by a discussion of the difficulties and risks of the surgery. .. surgery Furthermore, the research gaps and motivations are given based on the discussion of current commercial systems and published research works Then, a brief description of the methodology and the research scope is presented Finally, the outline of the thesis is shown 1 Chapter1 Introduction 1.1 Micro- implants and Micro- implants Surgery The placement of micro- implants is a common but relatively new... bone drilling and screwing of micro- implants; and (iii) stop in time when further screwing might cause the stripping of the implants To achieve these goals, the haptics- based geometry and force modeling approaches will be investigated The capabilities of the existing approaches in modeling inhomogeneous tissues and the force/torque feedback would be evaluated These modeling procedures and computational... manikin -based and haptics- based Manikin(or Mannequin) -based applications provide a physical model of a patient’s head and mouth, on which dental procedures can be performed using real dental instruments In contrast, haptics- based applications employ virtual models of the oral anatomy and integrate a haptic device as a training platform The trainee holds the stylus of the haptic device to manipulate a set of. .. Organization of the Thesis 6 Chapter1 Introduction This chapter has briefly introduced the background of micro- implants surgery and the risks of performing this surgery without proper training It also includes discussion about the research gaps and motivations, as well as methodologies and research scope The rest of this thesis is organized as follows Chapter 2 provides a comprehensive review of related... damage, and that of screwing torque variation during implant placement to achieve optimal tightness between the implant and the bone tissue Figure 1.2 Tooth root and lower jaw bone anatomy 1.3 Research Objectives and Scope 4 Chapter1 Introduction The aim of this research is to develop a real-time haptics- based modeling and simulation framework, in which the heterogeneous oral anatomy is modeled closely, and. .. movements of grid points Dirichlet FFD relaxes the constraint of regularly spaced control points and has been used in face modeling due to its flexibility [42] NURBS -based FFD maps the deformation of the object to that of a NURBS lattice It combines easily with global and local deformations and can easily produce properties inherent in the deformation of physical materials, such as tapering and necking... position and orientation of the virtual tool become important, haptic algorithms and devices capable of 6 DOF input and 6 DOF output are required For polygonal models, the ambiguity issues in the determination of the closest face still exist [92] Ray -based haptic rendering [93] was developed to handle this problem, using a surface constrained ideal stylus (analogous to IHIP) 3D representation of the... during the on-site surgery However, research on the haptics- based dental training simulations mainly focuses on basic operations such as tooth cavity cutting, dental preparation and periodontal disease diagnosis To the best of the author’s knowledge, there is no previous study on the simulation of the micro- implant surgery, whose success primarily depends on the tactile sensation of drilling force variation... dentistry Micro- implants are tiny screws made of commercially pure titanium (99%) or titanium alloy (90%), with a diameter ranging from 1.2mm to 2.0mm and a length from 4.0mm to 12.0mm As shown in Figure 1.1, micro- implants are embedded in the jaw bone after successful placement, serving as anchor points to move teeth during orthodontic treatment (a) (b) Figure 1.1 Orthodontic micro- implants: (a) Micro- implants . background of micro- implants and the micro- implants surgery, followed by a discussion of the difficulties and risks of the surgery. Furthermore, the research gaps and motivations are given based. HAPTICS- BASED MODELING AND SIMULATION OF MICRO- IMPLANTS SURGERY ZHENG FEI (B.Eng., M.Eng.) A THESIS SUBMITTED FOR THE DEGREE OF DOCTOR OF PHILOSOPHY DEPARTMENT OF MECHANICAL. 1.1 Micro- implants and Micro- implants Surgery The placement of micro- implants is a common but relatively new surgical procedure in clinical dentistry. Micro- implants are tiny screws made of