Principles and Practice of

Instrumentation for Biomechanical

Research in Dentistry

Biomechanics of Composite Restoration

Rheology of Dental Composites

Hydrodynamics of Dentinal Fluid

Kinematics of Jaw movement

Instrumentation using a PC in the Laboratory

Inbog Lee

2

Principles and Practice of

Instrumentation for Biomechanical

Research in Dentistry

Biomechanics of Composite Restoration

Rheology of Dental Composites

Hydrodynamics of Dentinal Fluid

Kinematics of Jaw movement

Instrumentation using a PC in the Laboratory

Inbog Lee

4-D Information and Control Lab

Dental Materials and Biomechanics

Instrumentation and Measurement

Digital Image Processing and Computer Vision

Department of Conservative Dentistry

School of Dentistry

Seoul National University

3

Preface

Electronic instrumentation and measurement systems are commonly used in most fields of

science and engineering including medical and dental research. The powerful and broad

applications of electronic devices motivate many researchers to study electrical engineering.

Biomechanics combines engineering and the life sciences by applying principles from

mechanics to the study of living systems. Particularly, in the biomechanics of composite

restoration, it is important to measure the strain and stress in the tooth during restoration.

Therefore, it should be needed to have the integrated knowledge on the electrical engineering,

measurement technology, material science and dentistry.

As a clinician interesting in esthetic tooth restorations, the author has been studying on the

physical characteristics of composites related to clinical procedures. The measurement of the

polymerization shrinkage and stress of composites, cusp deflection of tooth, dentinal fluid flow

during composite restoration, and the rheological characteristics of composites such as the

viscoelasticity related to handling characteristics are author’s main research interests.

The contents of this book are the results of the intellectual enjoyment of the development

and application of some instruments to research the biomechanics of dental composite

restorations. The pleasure of scientists is finding things out behind nature, and that of engineers

is seeing the device or machine works properly. From the point of view, the author’s work

seems to be that of engineer.

This book is intended for providing the basic principles of electronic devices, circuits and its

practical applications for researchers who are studying biomechanics in dentistry. In order to

measure the physical characteristics of composites and the biomechanical phenomenon of

tooth during composite restoration, we need first to select an appropriate sensor. The electrical

signal from the sensor should be amplified and filtered before the analog signal being

converted to a digital form to store on a computer. The principles and techniques for data

acquisition and interfacing to the computer are essential. In addition, the knowledge on how to

use some electromechanical actuators is also helpful.

치의학 분야에서의 생역학 연구뿐만 아니라 대부분의 물리, 화학, 생물학적 연

구의 본질은 대부분 물질이나 에너지의 위치나 속도, 또는 집단적 흐름을 측정하

는데 있다. 따라서 저자가 생역학적 연구를 수행하는데 필요한 기본적 이론과 물

리적 측정을 위해 실제적으로 제작한 센서 및 계측, 조절시스템은 일반적으로 확

장 가능하여 다른 분야의 연구를 위한 측정장비를 개발하는데 그대로 적용 가능하

다.

This book is not a text. For complete understanding, it is recommended to have some

prerequisite knowledge on basic electric circuits, electronic devices, and a computer

4

programming language. However, even for a dentist without such knowledge, it is possible to

understand the main text and to apply it for their own research.

The book begins with an introduction to the polymerization shrinkage and the

biomechanical phenomenon of composite restorations, the rheological properties of the material,

the hydrodynamics of dentinal fluid, and the kinematics of jaw movement in Part I. In Part II,

the book includes the basic principles and arts of electrical engineering and sensor electronics

essential for making instruments for measurement in research. And then, as practical

applications, the structure and working mechanism of the some instruments that the author has

made are covered in Part III. However, this book doesn’t need to be read from the first chapter,

it may be of more efficiency to read an interesting section first and move to other sections to be

needed.

In research field, many researchers usually use commercial instruments for measurement.

However, if the commercially available instrument cannot be applied for a special purpose, the

researcher should make a custom instrument. If someone tries to build-up their own instrument

system for measurement, they may be sometimes frustrated without knowledge on where to

start or how to organize the scattered information.

The purpose of this book is to gather broad scattered knowledge on hardware such as

mechanical, electrical and electronic devices, and on computer programming to control the

hardware, finally to present integrated perspective for instrumentation. As a maker based on

DIY (do-it-yourself), during studying the principles and doing practice instrumentation, we need

to analyze the requirement of an instrument for measurement, and to design and implement the

mechanical structure, electrical circuit, and software for receiving and storing data from the

sensor and for driving actuator. These processes increased our logical thinking and problem

solving capability.

The author believes that the understanding of electrical engineering and computer science

has been contributing to the progressing of science and engineering, and would be very happy if

this book is helpful for researchers who are studying the biomechanics.

This book is unfinished. The author hopes that the book will be growing up continuously

with a new science and technology.

Inbog Lee

A. Einstein

Imagination is more important than knowledge.

5

Contents Part I Biomechanics of Dental Tissue and Composite Restoration

1 Introduction

1.1 What is Biomechanics?

1.2 Biomechanics in Restorative Dentistry

2 Kinetics of Polymerization of Dental Resin Composites

2.1 Sequence of Free Radical Chain Polymerization

Initiation

Propagation

Termination

2.2 Rate of Free Radical Chain Polymerization

2.3 Rate of Photo-polymerization

2.4 Kinetic Chain Length

2.5 Measurement of Polymerization Kinetics

3 Polymerization Shrinkage and Stress of Composites

3.1 Polymerization Shrinkage

3.2 Viscoelastic Modulus Development During Curing

3.3 Polymerization Stress

4 Biomechanics of Composite Restoration

4.1 Biomechanics in Composite Restoration

4.2 Cusp Flexure during Composite Restoration

4.3 Influencing Factors on the Biomechanics of Composite Restoration

5 Rheology of Dental Composites

4.1 Theory of Elasticity

4.2 Theory of Viscosity

4.3 Theory of Viscoelasticity

6 Hydrodynamics of Dentinal Fluid

6

7 Kinematics of Jaw movement

Part II Principles of Instrumentation for Measurement 1 Introduction

2 Mechanical Devices

2.1 Elements for Frame

Optical (Mechanical) Board, Angled Bracket and Vertical Rod

2.2 Elements for transmit Force and Movement

Link

Gear

Bearing

Axis Supporter

Pulley

2.3 Precision Positioning Devices

Linear Motion Guide

Lead Screw and Ball Nut

XYZ Table

3 Electrical Devices

3.1 Basic Electrical Theory and Devices

3.1.1 Electrical Circuit Theory and Passive Devices

Voltage

Current

Resistance and Resistor

Ohm’s Law

Resistors in Series

Voltage Divider

Resistors in Parallel

Kirchhoff’s Voltage Law

Kirchhoff’s Current Law

Capacitor

Capacitors in Series

Capacitors in Parallel

7

RC Circuit (Voltage and Current vs. Time)

Capacitor Applications

Inductor

Inductor Applications

Capacitor vs. Inductor

Transformer

3.1.2 Semiconductor and Active Devices

N-type Semiconductor

P-type Semiconductor

The PN Junction

Biasing PN Junction

Diode

Diode Applications

Special Purpose Diodes

Transistor

Transistor Bias Circuit

DC Load Line

Transistor as an Amplifier

Transistor as a Switch

3.2 Operational Amplifier

Negative Feedback

Inverting Amplifier

Non-inverting Amplifier

Voltage Follower

Differential Amplifier

Instrumentation Amplifier

Summing or Scaling Amplifier

Differentiator

Integrator

3.3 Filter

Low Pass Filter

High Pass Filter

3.4 Digital Circuits

3.4.1 Logic Circuits (Gates)

AND, OR, NOT, NAND, NOR

3.4.2 Combinatorial Circuits

8

Multiplexer (Mux)

Demultiplexer (De-Mux)

Encoder

Decoder

Comparator

Adder

3.4.3 Successive Circuits

Flip Flops

S-R Flip Flops

J-K Flip Flops

D Flip Flops

Counter

Timer

3.4.4 ALU (Arithmatic Logic Unit)

Microprocessor

3.5 Data Acquisition System

3.5.1 Sample and Hold Circuit

3.5.2 Analog to Digital (A/D) Converter

Flash A/D Converter

Successive Approximation A/D Converter

3.5.3 Digital to Analog (D/A) Converter

3.6 Microcontroller

Arduino

4 Sensors

4.1 Displacement Sensor

LVDT

Eddy Current Sensor

Potentiometer

Digital Encoder

Laser Sensor

4.2 Force Sensor

Load Cell and Strain Gage

Torque Sensor

4.3 Temperature Sensor

9

IC Temperature Sensor

Thermocouple

Resistance Thermal Detector (RTD)

Thermister

4.4 Photo Sensor

CdS cell

Photo Diode and Photo Transistor

4.5 Magnetic Sensor

Hall Sensor

4.6 Ultrasonic Sensor

Acoustic Emission Sensor

Ultrasonic Displacement Sensor

4.7 Attitude Sensor

Acceleration

Gyro Sensor

4.8 CCD Sensor

5 Power Supply

5.1 Rectifier circuit

5.2 IC voltage regulator

5.3 Voltage Converter

6 Servo Amplifier and Actuators

6.1 Servo Amplifier

Power OP Amp

Pulse Width Modulation

6.2 Actuator (Electromechanical devices)

DC Motor

BLDC Motor

Servo Motor

Step Motor

Linear Motor

Voice Coil Motor

Piezo-Electric Actuator

6.3 Servo Motor Control by Negative Feedback

Position Control

10

Position Tracking

7 Computer-Based Instrumentation

7.1 Labview

7.2 Arduino – Microcontroller for Instrumentation

7.2.1 Analog Input - Data Acquisition, Serial Transmission and Storage

7.2.2 Analog Output - PWM and DC Motor Speed Control

7.2.3 Digital Input – Switch On/OFF, Counter

7.2.4 Digital Output – LED Turn On/OFF, Step Motor Control

7.2.5 Digital Output/Input – TDC, Ultrasonic Distance Measurement

7.2.6 LCD control

7.2.7 Data communication with Ethernet

7.2.8 Data communication with Bluetooth

7.3 Processing – Language for Programming

7.3.1 Data Communication by Serial with Arduino Microcontroller

7.3.2 Data Visualization with Graphics

Voltage or Counter vs. Time

3D Visualization

Part III Practice of Instrumentation for measurement in

Biomechanical Research

1 Volume Shrinkage Measurement

2 Axial Shrinkage Measurement

3 True Linear Shrinkage Measurement

4 Stress-Strain Analyzer

5 Stress Measurement with Strain gage

6 Cusp Deflection Measurement

** Product: µ-BioMechanics - Axial Shrinkage and Cusp Deflection

Measurement

** Product : Bio-Stress – Compoite Shrinkage Stress Measurement

7 Vertical Oscillation Rheometer

8 Laser 3-D Surface Profilometer

9 Particle Movement Tracker using Computer Vision

10 Measurement of the Dynamic Viscoelasticity Change of Composites

During Curing

11

11 Measurement of Dentinal Fluid Flow

** Product: nanoFlow - Measurement of Dentinal Fluid Flow

12 Acoustic Emission Analysis

13 Multi-Particle Tracking and Optical Flow

14 Torque Measurement Instrument for Endodontic Ni-Ti Files

15 Stress Measurement with Voice Coil Motor

16 3D Coordinates Acquisition using a Stereo camera and Attitude

Sensors for Jaw Movement Tracking (kinematics) and Visualization

17 3D Optical Scanner using Patterned Beam

References

Appendix

A Instruction Set in Processing and Arduino

B Published Articles 1 In-Bog Lee, Chung-Moon Um. Thermal analysis on the cure speed of dual cured resin

cements under porcelain inlays. Journal of Oral Rehabilitation 28:186-197, 2001.

2 In-Bog Lee, Ho-Hyon Son, Chung-Moon Um. Rheologic Properties of flowable, conventional

hybrid, and condensable composite resins. Dental Materials 19:298-307, 2003.

3 In-Bog Lee, Byung-Hoon Cho, Ho-Hyun Son, Chung-Moon Um. A new method to measure

the polymerization shrinkage kinetics of light cured composites. Journal of Oral

Rehabilitation 32:304-314, 2005.

4 Jong-Hyuk Lee, Chung-Moon Um, In-bog Lee*. Rheological properties of resin composites

according to variations in monomer and filler composition. Dental Materials 22:515-526,

2006.

5 In-Bog Lee, Byung-Hoon Cho, Ho-Hyun Son, Chung-Moon Um. The effect of consistency,

specimen geometry and adhesion on the axial polymerization shrinkage measurement of light

cured composites. Dental Materials 22:1071-1079, 2006.

6 Mi-Ra Lee, Chung-Moon Um, In-Bog Lee*. Influence of cavity dimension and restoration

methods on the cusp deflection of premolars in composite restoration. Dental Materials

23:288-295, 2007.

12

7 In-Bog Lee, Byung-Hoon Cho, Ho-Hyun Son, Chung-Moon Um. Rheological

characterization of composites using a vertical oscillation rheometer. Dental Materials

23:425-432, 2007.

8 Sue Hyun Lee, Juhea Chang, Jack Ferracane, In-Bog Lee*. Influence of instrument compliance

and specimen thickness on the polymerization shrinkage stress measurement of light-cured

composites. Dental Materials 23:1093-1100, 2007.

9 Ayman Ellakwa, Nakyeon Cho, In-Bog Lee*. The effect of resin matrix composition on the

polymerization shrinkage and rheological properties of experimental dental composites.

Dental Materials 23:1229-1235, 2007.

10 In Bog Lee, Woong An, Juhea Chang, Chung Moon Um. Influence of ceramic thickness and

curing mode on the polymerization shrinkage kinetics of dual-cured resin cements. Dental

Materials 24:1141-1147, 2008.

11 Junkyu Park, Juhea Chang, Jack Ferracane, In Bog Lee*. How should composite be layered

to reduce shrinkage stress; incremental or bulk filling? Dental Materials 24:1501-1505, 2008.

12 InBog Lee, Juhea Chang, Jack Ferracane. Slumping resistance and viscoelasticity prior to

setting of dental composites. Dental Materials 24:1586-1593, 2008.

13 Sun-Young Kim, Jack Ferracane, Hae-Young Kim, In-Bog Lee*. Real-time Measurement of

Dentinal Fluid Flow during Amalgam and Composite Restoration. J of Dentistry 38:343-351,

2010.

14 In-Bog Lee*, Sun-Hong Min, Sun-Young Kim, Jack Ferracane. Slumping tendency and

rheological properties of flowable composites. Dental materials 26:443-448, 2010.

15 Min-Ho Kim, Sun-Hong Min, Jack Ferracane, In-bog Lee*. Initial dynamic viscoelasticity

change of composites during light curing. Dental materials 26:463-470, 2010.

16 Sun-Hong Min, Jack Ferracane, In-Bog Lee*. Effect of shrinkage strain, modulus, and

instrument compliance on polymerization shrinkage stress of light cured composites during

the initial curing stage. Dental materials 26:1024-1033, 2010.

17 In-Bog Lee*, Sun-Hong Min, Deog-Gyu Seo. A new method to measure the polymerization

shrinkage kinetics of composites using a particle tracking method with computer vision.

Dental materials 28: 212-218, 2012.

18 Youngchul Kwon, Jack Ferracane, In-Bog Lee∗. Effect of layering methods, composite type,

and flowable liner on the polymerization shrinkage stress of light cured composites, Dental

materials 28: 801-809, 2012.

18-1 Hyang-Ok Lee, In-Bog Lee*. Rheological properties of polyvinylsiloxane impression

materials before mixing and during setting related to handling characteristics. Korea-

Australia Rheology Journal, 24(3), 211-219:2012

19 Sun-Young Kim, Eun-Joo Kim, Kyoung-Kyu Choi, Duck Su Kim, In-Bog Lee*.

13

The Evaluation of Dentinal Tubule Occlusion by Desensitizing Agents: A Real-Time

Measurement of Dentinal Fluid Flow Rate and SEM". Operative Dentistry, 38(4), 419-

428:2012

20 Nak-Yeon Cho, Jack Ferracane, In-Bog Lee*. Acoustic emission analysis of the tooth-

composite interfacial debonding. Journal of Dental Research, 92(1), 76-81, Jan 2013.

21. Hyun-Jeong Kweona, Jack Ferracane

b, Kyongok Kang

c, Jan Dhont

c, In-Bog Lee

a*. Spatio-

temporal analysis of shrinkage vectors during photo-polymerization of composite. Dental

materials, 29(12), 1236-1243, Dec 2013.

22. Ryan Jin-Young Kim, Nak-Sam Choi, Jack Ferracane, In-Bog Lee. Acoustic emission

analysis of the effect of simulated pulpal pressure and cavity type on the tooth-composite

interfacial de-bonding. Dental materials, 30(8), 876-883, Aug 2014.

23. Ryan Jin-Young Kim, Yu-Jin Kim, Nak-Sam Choi, In-Bog Lee. Polymerization shrinkage,

modulus, and shrinkage stress related to tooth-restoration interfacial debonding in bulk-fill

composites. J Dent 43, 430-439, Apr 2015.

24. Min-Ho Kim, Ryan Jin-Young Kim, Woo-Cheol Lee, In-Bog Lee. Evaluation of dentinal

tubule occlusion after laser irradiation and desensitizing agents application. Am J Dent,

28:303-308, Oct 2015.

25. YJ Kim, Ryan JY Kim, J Ferracane, IB Lee. Influence of the compliance and layering

method on the wall deflection of simulated cavities in bulk-fill composite restoration.

Operative Dentistry, 41(6), Nov-Dec, e183-e194, 2016.

14

Part I

Biomechanics of Dental Tissue and Composite

Restorations

1 Introduction

2 Kinetics of Polymerization of Dental Resin Composites

3 Polymerization Shrinkage and Stress of Composites

4 Biomechanics of Composite Restoration

5 Rheology of Dental Composites

6 Hydrodynamics of Dentinal Fluid

7 Kinematics of Jaw movement

We can control only things that can be measured.

15

1. Introduction

1.1 What is Biomechanics? Mechanics (statics and dynamics) describes the forces and motions of any system, ranging from

quanta, atoms, molecules, gases, liquids, solids, structures, stars, and galaxies. The biological

world is consequently a natural object for the study of mechanics. Classical mechanics is

typically thought to offer two basic approaches: continuum mechanics and statistical mechanics.

Figure 1.1.1 Flowchart of traditional divisions of study within classical mechanics.

Biomechanics is a branch of the field of bioengineering, which we define as the application

of engineering principles to biological systems. Biomechanics is the study of how physical

forces interact with living systems.

The relatively new field of biomechanics applies mechanical principles to the study of living

systems - the study of deformations (strains) and loads (stresses), motions, and flows occurring

in biologic systems. Some simple examples of biomechanical research include the investigation

of the forces that act on limbs, the aerodynamics of bird and insect flight, the hydrodynamics of

swimming in fish, the anchorage and mechanical support provided by three roots, and

locomotion in general across all form of life, from individual cells to whole organisms.

Applied mechanics, most notably thermodynamics and continuum mechanics, and

mechanical engineering disciplines such as fluid dynamics and solid mechanics, play prominent

roles in the study of biomechanics. By applying the laws and concepts of physics,

biomechanical mechanisms and structures can be simulated and studied. Relevant mathematical

tools include linear algebra, differential equations, vector and tensor calculus, numeric and

16

computational techniques such as the finite element method.

For an organ, biomechanics helps us to understand its normal function, predict changes due

to alteration, and propose methods of artificial intervention. Thus diagnosis, surgery and

prosthesis are closely associated with biomechanics.

The study of biomaterials is of crucial importance to biomechanics. For example, the

various tissues within the body, such as skin, bone, muscle, tooth, and arteries each possess

unique material properties.

Figure 1.1.2 Biomechanics applies mechanical principles to living systems and biomaterials.

17

1.2 Biomechanics in Restorative Dentistry From the standpoint of most restorative dental applications, the interaction of the orofacial

complex with forces is the primary concern. Within this context, orofacial biomechanics

encompasses the study of following.

1. Determination of the mechanical stresses that the orofacial complexes are subjected to under

both physiologic and pathologic conditions.

2. Response of the various oral tissues and restorative materials to the mechanical stress.

3. Modification of mechanical stresses applied to the oral tissues by restorative procedure and

appliance.

While masticating food or restoring tooth, the tooth undergoes deformations by a biting

force or a stress induced from the restorative procedure. There are three biomechanical units: (1)

restorative material, (2) tooth structure, and (3) interface between the restoration and tooth.

Biomechanics in restorative dentistry?

A study on the stress and strain in biological system includes

1. Applied force

2. Form and structure of tooth, jaw, and muscle

3. Mechanical properties of tooth, supporting tissue and restorative materials

4. Interface between the tooth and restorative materials

Before designing and implementing an instrument for measurement of deformation (strain),

stress, motion, and flow during restoration in dental research, we need to understand the

biomechanics of dental tissues like tooth, bone, muscle, and restorative materials used in

restoration.

For composite restoration, the biomechanical factors include the material properties of

composite prior to setting, change in physical properties of the materials during curing,

interaction between the tooth and composite at bonding interface, and the fluid flow through

dentinal tubules between the pulp and cavity base.

18

Figure 1.2.1 Biomechanical phenomenons in composite restoration.

The physical properties of composite prior to curing include the rheological characteristics such

as visco-elasticity, plasticity, and flowability related to the handling characteristics. After

placement the composite on the tooth cavity, the composite curing by chemical or photo

activation is essentially accompanied with the polymerization shrinkage and increase in visco-

elastic modulus. The interactions at the tooth-composite interface shows de-bonding, tooth

crack, and cusp deflection caused by the polymerization contraction (Fig.1.1).