Influence of the surface and heat treatment on the flexural strength and reliability of Y-TZP dental ceramic [Elektronische Ressource] / vorgelegt von Georgios Fokas-Tsentzeratos

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• Publié par: eberhard_karls_universitat_tubingen
• Publié le: 01 janvier 2010
• Nombre de lectures: 13
• Langue: English
• Poids de l'ouvrage: 2 Mo

Extrait

1

Aus der Universitätsklinik für Zahn-, Mund- und Kieferheilkunde
Tübingen
Abteilung Poliklinik für Zahnärztliche Prothetik und
Propädeutik
Ärztlicher Direktor: Professor Dr. H. Weber
Sektion für Medizinische Werkstoffkunde und Technologie
Leiter: Professor Dr. J. Geis-Gerstorfer

Influence of the surface and heat treatment on the
flexural strength and reliability of Y-TZP dental ceramic


Inaugural-Dissertation zur Erlangung des Doktorgrades der
Zahnheilkunde
der Medizinischen Fakultät der Eberhard-Karls-Universität zu
Tübingen

vorgelegt von
Georgios Fokas-Tsentzeratos
aus
Argostoli/ Griechenland
20102
























Dekan: Professor Dr. I. B. Autenrieth
1. Berichterstatter: Professor Dr. J. Geis-Gerstorfer
2. Berichterstatter: Professor Dr. Dr. S. Reinert 3

























To my beloved parents and brother for their constant support and
understanding 4


Table of Contents
1. Introduction .................................................................................................. 8
2. Literature Review ......................... 9
2.1 History/ Evolution of dental ceramics ........................................................ 9
2.2 Composition and properties of dental ceramics ...................................... 13
2.3 Mechanisms of increasing the fracture resistance of ceramics ............... 14
2.4 Classification of high-strength all-ceramic systems . 18
2.4.1 Glass-ceramics ................................................................................. 21
2.4.1.1 Silicate ceramics ......... 21
2.4.1.2 Lithium Disilicate and Fluorapatite glass ceramics ..................... 22
2.4.2 Glass-infiltrated oxide ceramics ........................................................ 22
®2.4.2.1 In-Ceram Alumina (Vita, Bad Säckingen, Germany) ................. 23
®2.4.2.2 In-Ceram Spinell (Vita, Bad Säckingen, Germany) ................... 24
®2.4.2.3 In-Ceram Zirconia (Vita, Bad Säckingen, Germany) ................. 24
2.4.3 Polycrystalline ceramics .................................................................... 25
2.4.3.1 Aluminium oxide ceramics .......................... 26
®
 The Procera AllCeram System (Nobel Biocare, Göteborg, Sweden)
26
2.4.3.2 Zirconium dioxide ceramics (ZrO ) ............................................. 27 2
2.4.3.2.1 Stabilized Zirconia ................................ 28
2.4.3.2.2 Y-TZP (Yttrium-Tetragonal Zirconia Polycrystalline) ............ 29
2.4.3.3 Transformation-toughening mechanism ..................................... 30
2.4.3.4 Physical and chemical properties of Y-TZP 31
2.4.3.5 Mechanical Properties ................................ 32
2.4.3.5.1 Flexural strength ................................... 32
2.4.3.5.2 Modulus of elasticity (Young‘s modulus) .............................. 33
2.4.3.5.3 Fracture toughness ................................ 34
2.4.3.5.4 Weibull modulus ................................... 36
2.4.3.5.5 Fatigue strength ... 36 5

2.4.3.5.6 Coefficient of thermal expansion .......................................... 37
2.4.3.6 Biological safety of Y-TZP .......................................................... 37
2.4.3.7 Aging of zirconia ......................................... 38
2.4.3.8 Zirconia as material for dental restorations ................................. 40
2.5 CAD/CAM ............................................................... 41
2.5.1 Definition/Historical Background ....................................................... 41
2.5.2 CAD/CAM Components ................................... 42
2.5.3 CAM techniques................................................ 43
2.5.3.1 Subtractive Technique from a Solid Block .. 43
2.5.3.1.1 The Lava system (3M/ESPE Dental AG, Seefeld, Germany) 44
2.5.3.2 Additive Technique by Applying Material on a Die ...................... 44
2.5.3.3 Solid free form fabrication ........................................................... 45
2.5.4 Materials ................................ 46
2.5.5 Industrial preparation of zirconium dioxide ceramic (for the CAD/CAM)
................................................................................... 46
2.5.6 Methods for the processing of zirconium dioxide ceramics by means
of CAD/CAM procedure). ........................................... 47
 Processing of Green blanks ............................. 47
 Processing of ―white‖ partially sintered blanks ................................. 48
 Processing of fully sintered blanks ................................................... 48
2.6. Studies on surface and heat treatment of zirconia . 49
2.6.1 Grinding ............................................................ 49
2.6.2 Sandblasting ..................................................... 52
2.6.3 Heat Treatment ................................................. 53
3. Aim of the study ......................... 55
4. Outline of the study .................................................................................... 55
5. Materials and methods............... 58
5.1 Material used for the fabrication of the Y-TZP discs ................................ 58
5.2 Fabrication of the specimens .................................. 59
5.3 Microscopy after preparation ... 60
5.4 Measuring of the specimens ................................... 60 6

5.5 Preparation of the specimens ................................................................. 61
 Control group ...................................................... 61
 Sandblasting ....................... 61
 Grinding ............................................................... 62
 Heat treatment .................................................... 63
5.6 Measurements after the treatment .......................... 65
5.7 Microscopy after preparation ................................................................... 65
5.8 Tests ....................................... 65
5.8.1 Surface morphology .......... 65
5.8.2 Surface roughness ............................................................................ 66
5.8.3 X-Ray diffraction analysis . 66
5.8.4 Biaxial flexure strength test (piston-on-three-ball test) ...................... 67
 Biaxial flexural strength test fixture: ................................................. 67
 Testing machine and loading: .......................... 67
5.8.5 Statistical analysis ............................................. 67
6. Results ........................................................................ 70
6.1 Flexure Strength ...................................................................................... 70
6.2 Scanning electron microscopy (SEM) ..................... 72
6.3 Reliability ................................................................................................. 74
6.4 Surface roughness .................................................................................. 75
6.5 X-Ray diffraction ...................... 76
7. Discussion .................................................................................................. 80
7.1 Effect of alumina abrasion ....... 80
7.2 Effect of grinding ..................................................................................... 82
7.3 Effect of sandblasting and grinding ......................... 83
7.4 Effect of heat treatment ........... 84
7.5 Reliability ................................................................................................. 87
7.6 Clinical relevance of the results............................... 89
8. Conclusions 91
9. Summary ..................................................................................................... 92 7

10. Zusammenfassung ................................................................................... 93
11. Appendix ................................................................................................... 95
12. References 99
13. Acknowledgments .................................................................................. 111
14.Curicculum Vitae ..................... 112


8

1. Introduction

Since many decades metal-ceramic restorations represent the most popular
and successful solution for restoring extensively damaged teeth or replacing
missing ones. Clinical studies show a survival rate of metal-ceramic restorations
of about 90% after a period of 10 years (Creugers et al., 1994; Scurria et al.,
1998; Lang et al., 2004). On the other hand, metal frameworks have inherent
disadvantages, such as material corrosion and discoloration of gingival tissues
adjacent to the crown margins (Riley EJ, 1977).
The last two decades all-ceramic restorations have been increasingly gaining
acceptance. Ceramic materials can successfully replicate the esthetic qualitie