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© Woodhead Publishing Limited, 2013
Non-metallic biomaterials for tooth repair and replacement
© Woodhead Publishing Limited, 2013
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Biomedical composites (ISBN 978-1-84569-436-4)
Materials science for dentistry: Ninth edition (ISBN 978-1-84569-529-3)
Dental biomaterials: imaging, testing and modelling (ISBN 978-1-84569-296-4)
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© Woodhead Publishing Limited, 2013
Woodhead Publishing Series in Biomaterials: Number 53
Non-metallic
biomaterials for
tooth repair and
replacement
Edited by
Pekka Vallittu
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v

Contents
Contributor contact details xi
Woodhead Publishing Series in Biomaterials xv
Foreword xix
Part I Structure, modifi cation and repair of
dental tissues 1
1 Structure and properties of enamel and dentin 3
V. P. THOMPSON, NYU College of Dentistry, USA and
N. R. F. A. SILVA, Federal University of Minas
Gerais, Brazil
1.1 Introduction 3
1.2 Enamel 3
1.3 Dentin–enamel junction (DEJ) 10
1.4 Dentin 10
1.5 Conclusion 15
1.6 References 15
2 Biomineralization and biomimicry of tooth enamel 20
VUK USKOKOVIC
´
, University of California, USA
2.1 Introduction 20
2.2 Structure of enamel 21
2.3 Amelogenesis at the molecular scale 22
2.4 Key issues in biomineralization and biomimicry of
tooth enamel 25
2.5 Conclusion 40
2.6 Acknowledgments 41
2.7 References 41
vi Contents
© Woodhead Publishing Limited, 2013

3 Enamel and dentin bonding for adhesive
restorations 45
JORGE PERDIGÃO, University of Minnesota, USA and
A
NA SEZINANDO, University Rey Juan Carlos, Spain
3.1 New trends in restorative dentistry 45
3.2 Dental adhesion 49
3.3 Bonding substrates 51
3.4 Current bonding strategies 60
3.5 Dental adhesion mechanisms 70
3.6 In vitro versus in vivo studies 74
3.7 Incompatibility between adhesives systems and
restorative materials 76
3.8 Conclusions 78
3.9 References 79
4 Enamel matrix proteins (EMP) for periodontal
regeneration 90
N. DONOS, UCL-Eastman Dental Institute, UK, X. DEREKA,
National and Kapodistrian University of Athens, Greece
and H. D. AMIN, Imperial College London, UK
4.1 Introduction to principles of periodontal regeneration 90
4.2 Periodontal ligament (PDL) stem/progenitor cells 91
4.3 Secretion and composition of enamel matrix
proteins (EMP) 93
4.4 Modulation of cell differentiation by EMP and enamel
matrix derivatives (EMD) in vitro 96
4.5 In vivo studies (for bone regeneration) 101
4.6 Treatment of periodontal osseous defects with enamel
matrix derivatives 102
4.7 Acknowledgement 113

4.8 References 113
Part II Dental ceramics and glasses for tooth repair
and replacement 127
5 Processing and bonding of dental ceramics 129
J. P. MATINLINNA, The University of Hong Kong, PR China
5.1 Introduction to dental ceramics 129
5.2 Alumina and zirconia chemistry 133
5.3 Silane coupling agents and their chemistry 141
5.4 Resin zirconia bonding 147
Contents vii
© Woodhead Publishing Limited, 2013
5.5 Future trends 154
5.6 Sources of further information and advice 155
5.7 References 155
6 Wear properties of dental ceramics 161
M. K. E
TMAN, Division of Prosthodontics, College of
Dentistry, University of Saskatchewan, Canada
6.1 Introduction 161
6.2 Clinical performance and wear of all-ceramic restorations 161
6.3 In vitro evaluation of wear and cracks in all-ceramic
materials 182
6.4 Conclusion 190
6.5 References 190
7 Sol-gel derived bioactive glass ceramics for
dental applications 194
X. CHATZISTAVROU, University of Michigan, USA,
E. KONTONASAKI, K. M. PARASKEVOPOULOS, P. KOIDIS,
Aristotle University of Thessaloniki, Greece and
A. R. BOCCACCINI, University of Erlangen-Nuremberg,

Germany
7.1 Introduction 194
7.2 Sol-gel-derived glasses and glass ceramics 197
7.3 Sol-gel-derived coatings 210
7.4 Sol-gel-derived composites 217
7.5 Conclusions and future trends 221
7.6 References 221
Part III Dental composites for tooth repair
and replacement 233
8 Composite adhesive restorative materials for
dental applications 235
MICHAEL F. BURROW, The University of Hong Kong,
PR China
8.1 Introduction 235
8.2 Resin composite restorative materials 236
8.3 Polyacid-modifi ed resin composite (compomer) 248
8.4 Glass ionomer (polyalkenoate) cements 252
8.5 Resin modifi ed glass ionomer cement (RM-GIC) 256
viii Contents
© Woodhead Publishing Limited, 2013
8.6 Conclusion 260
8.7 References 261
9 Antibacterial composite restorative materials
for dental applications 270
I
DRIS MOHAMED MEHDAWI, Benghazi University, Libya
and ANNE YOUNG, UCL Eastman Dental Institute, UK
9.1 Introduction 270
9.2 Current direct aesthetic restorative materials 271
9.3 Antibacterial properties of aesthetic restorative materials 273

9.4 Remineralizing dental composites 278
9.5 Antibacterial, remineralizing and proteinase-inhibiting
materials 280
9.6 Conclusion and future trends 283
9.7 References 284
10 Effects of particulate fi ller systems on the properties
and performance of dental polymer composites 294
JACK L. FERRACANE, Oregon Health & Science
University, USA and WILLIAM M. PALIN, University of
Birmingham, UK
10.1 Introduction 294
10.2 Current dental composite materials 295
10.3 Theoretical considerations 297
10.4 Types of fi llers used in dental composites 299
10.5 Effect of fi llers on properties of dental composites 305
10.6 Stability, degradation and clinical outcomes 320
10.7 Current and future trends 322
10.8 Sources of further information and advice 324
10.9 References 325
11 Composite-based oral implants 336
TIMO O. NÄRHI, University of Turku, Finland,
A
HMED M. BALLO, Gothenburg University, Sweden
and King Saud University, Saudi Arabia and
P
EKKA K. VALLITTU, University of Turku, Finland
11.1 Introduction 336
11.2 Composition and structure 338
11.3 Surface modifi cation 342
Contents ix

© Woodhead Publishing Limited, 2013
11.4 Biological response 342
11.5 Clinical considerations and future trends 345
11.6 References 347
12 Fibre-reinforced composites (FRCs) as
dental materials 352
P
EKKA K. VALLITTU, University of Turku, Finland
12.1 Introduction to fi bre-reinforced composites (FRCs) as
dental materials 352
12.2 Structure and properties of fi bre-reinforced composites 353
12.3 Applications of fi bre-reinforced composites in dentistry 357
12.4 Fibre-reinforced fi lling composites 363
12.5 Future trends 364
12.6 Conclusions 365
12.7 References 366
13 Luting cements for dental applications 375
MUTLU ÖZCAN, University of Zurich, Switzerland
13.1 Introduction 375
13.2 Classifi cation of cements 376
13.3 Clinical implications of cement choice 388
13.4 Conclusion and future trends 390
13.5 References 391
Index 395

© Woodhead Publishing Limited, 2013
xi
Contributor contact details
(* = main contact)
Editor and Chapter 12

Professor Pekka K. Vallittu
Department of Biomaterials
Science and Turku Clinical
Biomaterials Centre (TCBC)
Institute of Dentistry
University of Turku
Lemminkäisenkatu 2
FI-20520 Turku
Finland
E-mail: pekka.vallittu@utu.fi
Chapter 1
Van P. Thompson
Biomaterials & Biomimetics
NYU College of Dentistry
345 East 24th Street
Room 838-S
New York 10010
USA
E-mail:
Nelson R. F. A Silva
Department of Restorative
Dentistry
School of Dentistry (UFMG/FO)
Federal University of Minas Gerais
Alameda do ipe branco 520
Sao Luiz – Pampulha
Belo Horizonte 31275-080
Brazil
Chapter 2
Vuk Uskokovic´

Therapeutic Micro and
Nanotechnology Laboratory
Department of Bioengineering and
Therapeutic Sciences
University of California
San Francisco
CA, 94158-2330
USA
E-mail:
xii Contributor contact details
© Woodhead Publishing Limited, 2013
Chapter 3
Jorge Perdigão*
University of Minnesota
Department of Restorative
Sciences
Minneapolis, MN 55455
USA
E-mail:
Ana Sezinando
University Rey Juan Carlos
Alcorcón, Madrid
Spain
Chapter 4
Professor Nikolaos Donos*
UCL-Eastman Dental Institute
Periodontology Unit
Department of Clinical Research
UK
E-mail:

Dr Xanthippi Dereka
Department of Periodontology
School of Dentistry
National and Kapodistrian
University of Athens
Greece
Dr Harsh D. Amin
Department of Bioengineering
Imperial College London
UK
Chapter 5
Dr Jukka P. Matinlinna
Associate Professor in Dental
Materials Science
Faculty of Dentistry
Dental Materials Science
The University of Hong Kong
The Prince Philip Dental Hospital
34 Hospital Road
Sai Ying Pun
Hong Kong SAR
PR China
E-mail: ; jumatin@
utu.fi
Chapter 6
Professor Maged K. Etman
Division of Prosthodontics
College of Dentistry
University of Saskatchewan
105 Wiggins Road, Saskatoon

Saskatchewan
S7N 5E4
Canada
E-mail:
Chapter 7
X. Chatzistavrou
Department of Orthodontics and
Pediatric Dentistry
School of Dentistry
University of Michigan
1011 N University
Ann Arbor
MI 48109
USA
Contributor contact details xiii
© Woodhead Publishing Limited, 2013
E. Kontonasaki and P. Koidis
Department of Fixed Prosthesis
and Implant Prosthodontics
School of Dentistry
Aristotle University of Thessaloniki
54124 Thessaloniki
Greece
K. M. Paraskevopoulos
Department of Physics
Solid State Section
Aristotle University of Thessaloniki
54124 Thessaloniki
Greece
A. R. Boccaccini*

Institute of Biomaterials
University of Erlangen-Nuremberg
91058 Erlangen
Germany
E-mail: aldo.boccaccini@
ww.uni-erlangen.de
Chapter 8
Dr Michael F. Burrow
Oral Diagnosis and Polyclinics
Faculty of Dentistry
The University of Hong Kong
Prince Philip Dental Hospital
34 Hospital Rd
Sai Ying Pun
Hong Kong (SAR)
PR China
E-mail:
Chapter 9
Dr Idris Mohamed Mehdawi*
Department of Restorative
Dentistry and Endodontics
Faculty of Dentistry
Benghazi University
Benghazi
Libya
E-mail:
Dr Anne Young
Department of Biomaterials and
Tissue Engineering
UCL Eastman Dental Institute

256 Grays Inn Road
London
WC1X 8LD
E-mail:
Chapter 10
Dr Jack L. Ferracane*
Department of Restorative
Dentistry
Division of Biomaterials and
Biomechanics
Oregon Health & Science
University
611 S.W. Campus Drive
Portland
Oregon 97239
USA
E-mail:
xiv Contributor contact details
© Woodhead Publishing Limited, 2013
Dr William M. Palin
University of Birmingham
College of Medical and Dental
Sciences
School of Dentistry, Biomaterials
Unit
St Chads Queensway
Birmingham
B4 6NN
UK
E-mail:

Chapter 11
Professor Timo O. Närhi*
Department of Prosthetic Dentistry
Institute of Dentistry
University of Turku
Turku
Finland
E-mail: timo.narhi@utu.fi
Dr Ahmed M. Ballo
Department of Biomaterials
Institute of Clinical Sciences
The Sahlgrenska Academy
Gothenburg University
Gothenburg
Sweden
and
Dental Implant and
Osseointegration Research Chair
College of Dentistry
King Saud University
Riyadh
Saudi Arabia
Professor Pekka K. Vallittu
Department of Biomaterials
Science
Institute of Dentistry
University of Turku
Lemminkäisenkatu 2
FI-20520 Turku
Finland

E-mail: pekka.vallittu@utu.fi
Chapter 13
Professor Mutlu Özcan
University of Zurich
Rämistrasse 71
CH-8006 Zurich
Switzerland
E-mail:
© Woodhead Publishing Limited, 2013
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xix
Foreword
The task of providing a reliable replacement for anatomic loss falls short
of the original biology in both elegance and durability. Although prosthetic
replacements are poor substitutes for healthy biology, disease and destruc-
tion leave clinicians few alternatives. Teeth and their prosthetic replacement
typify this dilemma. The healthy tooth is a thing to be admired – strong,
compliant, chemically resistant, and even beautiful. Despite the best efforts
of clinicians and technicians, dental restorations have a long history char-
acterized by failure, non-vitality, and a lack of true satisfaction. In the
last 100 years, however, there has been success and beauty. These successes
have provided important principles and the foundation from which current
researchers and clinicians strive to improve the science of anatomic
replacement.
Perhaps the greatest shift in restorative treatment ideology is the concept
of minimal invasiveness. When preventative and regenerative therapies
exist, they should be recommended and encouraged. The protection and
regeneration of biological structures should be the goal of every clinician
and researcher. Where resection and prosthetic reconstruction are the only
possibility, however, the modern clinician should ask, what may remain? To
this question, the modern answer emerges: retain all but the diseased state.
Comparing the native biological structure with any restoration should
affi rm that answer, as should the relative lifespan of most restorations.
The increased usage of non-metallic materials has somewhat aided the
principle of minimal resection and minimal invasiveness. The clinician
and researcher are cautioned that if simply changing materials increases
the need for biological resection, then the progress must be skeptically
assessed. The materials described in the following chapters have great

potential to create minimally invasive restorations. It is the methodology,
however, of the preparation and fabrication that allows a minimally inva-
sive result. With that understanding, the question may be posed, how may
these modern materials be leveraged to create less invasive restorations for
the patient? The defi nitive answer is yet unknown, but many results are very
xx Foreword
© Woodhead Publishing Limited, 2013
encouraging. These non-metallic materials provide clinicians with the pos-
sibility of imitating biological structures when restoration is the course of
treatment. This biomimicry is a great opportunity to parallel the character-
istics of teeth and other anatomic structures when resect and restore is the
predominant course of action. While esthetic mimicry has long held the
attention of clinician and patient, imitating other materials and biological
properties will continue to gain in importance. Consequently, for this bio-
mimicry to be more fully realized, current materials will need to be improved
and skillfully employed.
Lastly, what is our obligation and responsibility as clinicians, researchers
and readers? Perhaps it is to be inspired. Certainly, it is to encourage current
and future generations of investigators. The editor asks us to bring our best
science, to let us compare and learn. Either prove these concepts and ideas
wrong, or push them forward. Regardless, consider that when our task is to
restore prosthetically, we may create and use materials in a manner that
preserves and parallels the natural biology.
‘To read is to borrow; to create out of one’s readings is paying off one’s
debts.’ Charles Lilliard
Scott R. Dyer, DMD, MS, PhD
Portland, Oregon, USA
© Woodhead Publishing Limited, 2013
3
1

Structure and properties of enamel
and dentin
V. P. THOMPSON, NYU College of Dentistry, USA and
N. R . F. A . S ILVA , Federal University of Minas Gerais, Brazil
DOI: 10.1533/9780857096432.1.3
Abstract: This chapter addresses the mineralized tissues of teeth –
enamel and dentin – and how they develop into structural components
with unique physical properties. Tooth structure includes an epithelium-
derived outer shell of enamel that is highly mineralized, hard, stiff and
wear resistant. This is supported both mechanically and biochemically by
a mesenchyme-derived dentin, which is vital, less mineralized, softer and
more compliant. The dentin is maintained by the dental pulp, which is
cellular and innervated, and has a vascular plexus.
Key words: dentin, enamel, mechanical properties of tooth structure,
mineralized tissues.
1.1 Introduction
Much is known about teeth and their structure. Teeth have long been
studied by paleontologists, since they degrade much more slowly than bone;
in fact, they are the source of our primary knowledge of many ancient
species. Nonetheless our understanding of their intriguing structure is still
incomplete. Human teeth are generally representative, with an epithelium-
derived outer shell of enamel that is highly mineralized, hard, stiff and wear
resistant. The enamel is supported both mechanically and biochemically by
a mesenchyme-derived dentin, which is vital, less mineralized, softer and
more compliant. Dentin is maintained by the dental pulp, which is cellular
and innervated, and has a vascular plexus. In this chapter we give details
of each of the mineralized tissues and how they develop into structural
components with unique physical properties.
1.2 Enamel
1.2.1 Development

Tooth enamel is the hardest tissue in the body, with a hardness comparable
to that of window glass, and is highly fatigue- and wear-resistant. Human
enamel is laid down by cells in a programmed temporal and spatial sequence






4 Non-metallic biomaterials for tooth repair and replacement
© Woodhead Publishing Limited, 2013
to provide the overall shape of the tooth. The cells that make enamel
develop from the invagination of epithelial tissue during fetal development.
In what is known, because of its shape, as the ‘bell stage’ of tooth develop-
ment (ca. 14th week of intrauterine life), the epithelial cells on the inside
of the bell align with a concentration of mesenchyme cells in what appears
to be a one-to-one relationship. More accurately the latter are ‘ectomesen-
chyme’ cells, as the fi rst branchial arch, whose ectodermal cells migrates
into the mesenchyme in the area of the developing jaws (Nanci, 2008).
During this alignment an extracellular collagen network is created that
extends from the epithelial cells to the mesenchyme cells. The epithelial
cells begin to elongate and transform into ameloblasts, and the mesenchyme
cells transform into odontoblasts (Nanci, 2008). The elongation of the
ameloblasts when compared with the odontoblasts leads to pulling on the
collagen network formed between the two, creating a local puckering of
this structure that will become the dentin–enamel junction (DEJ). Seen in
cross-section the DEJ appears as scalloped, but viewed in three dimensions
(3-D), when the enamel has been dissolved, the circular ridges and pits of
the DEJ structure become apparent. The gene expression controlling this
process is not fully understood, but a large number of genes involved in

tooth development have been identifi ed (Nieminen, 2007).
1.2.2 Enamel prisms
The ameloblasts are arranged in a close, overlapping array. Each cell has a
tail that extends between its neighbors (see Fig. 1.1), so that if observed
from above the DEJ, they interdigitate.
Once aligned with their neighbors, the ameloblasts begin to mature and
to lay down the enamel structure. The maturation of ameloblasts starts from
what will become the cusp tip or the incisal edge of the tooth (but at this
stage is the inner top of the bell) and proceeds apically. The last enamel to
begin formation will be that closest to the cement–enamel junction (CEJ).
The ameloblast at its terminal end (nearest to the DEJ) takes on a ‘brush
border’ appearance and begins to excrete proteins, in particular amelo-
genins; these are the template molecules for the nucleation of calcium
phosphate to form, with maturation, ribbons of dense hydroxyapatite (HA).
In this process each ameloblast will create one enamel prism of approxi-
mately 5 μm in diameter, which is also referred to as an ‘enamel rod’ (Fig.
1.2). Individual prisms are currently thought to extend from the DEJ to the
enamel surface through various paths and not to change diameter.
Prisms are joined to their neighbors by a thin organic layer referred to
as a ‘prism sheath’. When loaded to the point of cracking, the resultant
cracks preferentially propagate through the protein sheath, going around
and along the prism (Fig. 1.3).
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Structure and properties of enamel and dentin 5
© Woodhead Publishing Limited, 2013

Enamel crystallites
∗
1.1 Ameloblasts arranged next to one another (upper right). Each
cell has a head (dotted black oval) and a tail (dotted black box) that
extends between its neighbors. Observe the discontinuity of the
enamel crystallites. Asterisk shows secondary territories. Each arrow
in the upper right denotes a sectioning plane through the enamel.
Each arrow points to the diagram depicting the microscopic view of
that sectioning plane in the enamel. Image modifi ed from Boyde
(1989).
5 μm
1.2 Scanning electron micrograph of enamel rods: alignment of
enamel prisms observed when the enamel surface is etched by acid.
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6 Non-metallic biomaterials for tooth repair and replacement
© Woodhead Publishing Limited, 2013
The tensile strength of enamel is lower when loaded perpendicular to the
prism direction (11.4 ± 6.3 MPa) than when it is when loaded parallel (24.7
± 9.6 MPa) (Carvalho et al., 2000). When acid etched, the shear bond of
adhesive applied end-on to the prism direction (enamel surface) is approxi-
mately 40% higher than when the adhesive is applied parallel to the enamel
prism direction (Ikeda et al., 2002). However, self-etch adhesives, which
do not employ a separate etching step, do not result in a signifi cant differ-
ence in bond strength relative to enamel prism orientation (Shimada and
Tagami, 2003).

The laying down of enamel by the ameloblasts proceeds at a rate of about
4 μm per day (Dean, 1998). If an ameloblast were to migrate directly to the
enamel surface, the fastest it could reach the outer dimension of a 1.2-mm-
thick enamel cusp would be (1200/4 =) 300 days, but we note that amelo-
blasts do not proceed directly radially from the DEJ to the surface (as
discussed below), so much more time is necessary to develop enamel for
permanent teeth. Molar enamel thickness varies by cusp from 1.2–1.7 mm
(Mahoney, 2008), increases from the fi rst molar to the third (Grine, 2005)
and is generally slightly thicker for females (Smith et al., 2006). The enamel
thickness on the facial or incisal of a central incisor is approximately
1.3 mm (Shillingburg Jr. and Grace, 1973). Once ameloblasts reach the outer
extent of the enamel they transform to a more cuboidal shape and die. What
signaling controls this process is not known. The calcifi cation of the devel-
oping enamel prism occurs gradually and continues for a some time even
after the tooth erupts into the mouth. This makes newly erupted teeth sensi-
tive to decalcifi cation and caries for more than a year.
100 μm
1.3 Cracks (crenellations) propagating through the protein sheath
going around and along the prisms following Vickers indentation.
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