Fatigue Testing Of Straight And Angled Abutments In A High Torque Dental Implant System

150 Pages·2014·5.26 MB·English

FATIGUE TESTING OF STRAIGHT AND ANGLED ABUTMENTS IN A HIGH
TORQUE DENTAL IMPLANT SYSTEM

by
RANA M. ATIEH

ALAN EBERHARDT, COMMITTEE CHAIR
JACK LEMONS
PERNG-RU LIU

A THESIS
Submitted to the graduate faculty of the University of Alabama at Birmingham,
in partial fulfillment of the requirements for the degree of
Master of Science in Biomedical Engineering
BIRMINGHAM, ALAMABA
2014
Copyright by
Rana M. Atieh
2014
FATIGUE TESTING OF STRAIGHT AND ANGLED ABUTMENTS IN A HIGH
TORQUE DENTAL IMPLANT SYSTEM

RANA M. ATIEH
UAB DEPARTMENT OF BIOMEDICAL ENGINEERING
ABSTRACT
Root form dental implants are a common solution used today to replace missing
teeth. However current designs still suffer from a number of limitations. Angled
abutments are used for incisors, where maximum human bite forces are normally < 200N,
while straight abutments are used for molars subjected to higher forces > 200 N. The aim
of this study was to evaluate the mechanical performance of a novel dental implant
system by fatigue testing straight and 15-degree angled abutments. It was hypothesized
that the novel thread design will dissipate the load evenly throughout the implant
allowing the system to withstand normal chewing forces.
Implants with 4.2mm diameter were tested according to ISO 14801 in specimen
holders tilted 30oand 25o, respectively, to illustrate worst case scenarios. Three straight
and three angled abutment systems with screws torqued to 35 Ncm, were subjected to a
load-to-failure test. This maximum load was decreased by 20% increments for cyclically
loading implants at 2 Hz in air at room temperature until failure or run-out (2,000,000
cycles). Three implants were tested at each load to generate an S-N curve and endurance
limit. Implant systems were then polished and etched to examine grain boundaries,
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determine the orientation of the original manufacturer cut and their potential effects on
the mechanical properties of the implants’ material (Ti alloy).
Systems with straight abutments produced a mean load-to-failure of 603 N, an
endurance limit of 121 N and a maximum bending moment of 665 Nmm. Systems with
angled abutments yielded 487 N, 195 N and 906 Nmm, respectively. Microstructure
studies showed a polycrystalline alpha structure with different grain orientations for the
implant body and smaller alpha-beta structure for the abutment and screw.
Cyclic loading was an initial study to evaluate the mechanical properties of the
novel thread designed to provide sufficient area to dissipate the load evenly throughout
the entire implant. The endurance limit of the angled abutment fell within the “safe”
range, while the straight system showed a lower value. Surface treatment, diameter size
and material enhancement through grain refinement may affect the strength of the
implant construct.

Keywords: Root form dental implant, fatigue test, ISO 14801, endurance limit
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ACKNOLEDGMENTS
I would like to show gratitude to the UAB Research Foundation, UAB School of
Engineering and National Collegiate Inventors and Innovators Alliance (NCIIA) for
providing the fund necessary to accomplish the project through the Invention 2
Innovation (i2i) program.
To my committee chair Dr. Eberhardt and committee members Dr. Lemons and
Dr. Liu: The accomplishment and success of this project would have not been possible
without your guidance and assistance. You have given me not only project work but also
eagerness, constant motivation and support to make the experience a lot more rewarding.
I have learned so much academically and professionally from the great example you set.
Thank you.
To Mr. Preston Beck: Thank you for helping and being patient with me as I try to
learn and practice metallography at your lab.
To Joseph Schwertz and Doug Doud: Thank you for providing the best lab
atmosphere a graduate student could ask for. I already miss our Field Trip Friday and
1,846,239 cycles and counting emails. Joe, I would like to specially thank you; I have
never come up to you with a question or complaint and left without a perfect answer and
consent.
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To my mum: Although continents and oceans set us more than 6,000 miles apart,
you were present every second I needed help, prayers and consolation. You are my role
model, and I work hard every day to keep the promise that I will always give, do and be
my best.
To my brother and sister: Sorry you had to wait for me for long hours at the lab,
and had to endure my changes in mood as I struggle with my experiments and work, but
it is your fun, friendly and always comforting company that kept me going. Thank you
Riwa for helping with my drawings and Sami for driving me around to find a universal
joint that I never really used. I love you both.
To my dad: How do I acknowledge the person who gave me life, and his life was
taken away a month before I started graduate school? I know you sent me this
opportunity from heaven as I struggled to find a project and a fund to start graduate
school. You have taught me to aim high and work hard to earn what I deserve. If I get to
do a PhD afterwards, it is because you have always believed and made me believe I can
reach higher. You are the best and I love you so much.
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TABLE OF CONTENT
Page
ABSTRACT ...........................................................................................................................iv
ACKNOLEDGMENTS .........................................................................................................vi
LIST OF TABLES .................................................................................................................ix
LIST OF FIGURES ...............................................................................................................x
BACKGROUND ...................................................................................................................1
Dental Anatomy .........................................................................................................1

Dentures and Their Drawbacks ..................................................................................9

Evolution of Dental Implants .....................................................................................12
History of Dental Implants.............................................................................12
Modern Dental Implants ................................................................................14

Classification of Dental Implants...............................................................................14
Based on Implant Design ...............................................................................14
Based on Surgical Timing ..............................................................................15
Based on Attachment Mechanisms ................................................................17
Based on Macroscopic Body Designs ...........................................................17
Based on Implant Surface .............................................................................22
Based on Implant Materials ...........................................................................27

Examples of Current Designs of Dental Implants on the Market ..............................29

Business Development ...............................................................................................32

Fatigue Testing...........................................................................................................38

Review of Prior Work ................................................................................................40

High Torque Dental Implant System .........................................................................46

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PURPOSE AND HYPOTHESIS .....................................................................................51
METHODS ......................................................................................................................52
RESULTS ........................................................................................................................63
Systems with Straight Abutments ..............................................................................63
Systems with Angled Abutments ...............................................................................66
Statistical Analysis .....................................................................................................69
Grain Structure and Grain Boundaries .......................................................................70
DISCUSSION ..................................................................................................................75
CONCLUSION ................................................................................................................83
REFERENCES ................................................................................................................84
APPENDIX:
A FIRST SCREEN ...................................................................................................91
B BUSINESS PLAN.................................................................................................97
C CAD DRAWINGS ................................................................................................125
D MATLAB SCRIPTS .............................................................................................138

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LIST OF TABLES
Table Page
1 Cyclic loads and number of cycles for implants with straight abutments .........................64
2 Cyclic loads and number of cycles for implants with angled abutments ...........................68
3 Number of grains intersected per line at 100x ...................................................................71
4 Number of grains intersected per line at 400x ...................................................................71
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LIST OF FIGURES
Figure Page
1 Side-by-side representation of a natural tooth and a root form
dental implant
................................................................................................................................................1
2 Principal Fiber groups of the periodontal ligament.
(A) Transseptal, (B) Alveolar crest, (C) Horizontal, (D) Oblique,
(E) Apical, and (F) Interradicular ..........................................................................................2

3 Alveolar Process ...............................................................................................................3

4 Types of tissues surrounding the teeth ..............................................................................5

5 Locations of the three types of mucosa..............................................................................5

6 Types of gingiva and locations ..........................................................................................6

7 Types of bone .....................................................................................................................7 7

8 Mandibular jaw resorption .................................................................................................7

9 Partial denture ....................................................................................................................10

10 Full lower dentures ..........................................................................................................11

11 Fixed bridges ....................................................................................................................11

12 (A) BioHorizons’ external hex, (B) BioHorizons’ internal hex
and (C) Morse taper connectors ............................................................................................19

13 V-shaped, square and reverse buttress thread designs .....................................................19

14 V-shaped, flat and curved apex ........................................................................................20

15 Example of abutment CAD drawing................................................................................21

16 Abutment features type A and B ......................................................................................22
x