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«Thesis submitted in fulfilment of the degree of Doctor of Philosophy Mohammad Hossein Nekoofar School of Dentistry Cardiff University (April ...»

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The effect of contamination on selected

physical and chemical characteristics of

Mineral Trioxide Aggregate

Thesis submitted in fulfilment of the degree of

Doctor of Philosophy

Mohammad Hossein Nekoofar

School of Dentistry

Cardiff University

(April 2006-August 2011)

DECLARATION

This work has not previously been accepted in substance for any degree and is not

concurrently submitted in candidature for any degree.

Thursday, 23 June 2011 STATEMENT 1 This thesis is being submitted in partial fulfillment of the requirements for the degree of PhD Thursday, 23 June 2011 STATEMENT 2 This thesis is the result of my own independent work/investigation, except where otherwise stated.

Other sources are acknowledged by explicit references.

Thursday, 23 June 2011 STATEMENT 3 I hereby give consent for my thesis, if accepted, to be available for photocopying and for inter-library loan, and for the title and summary to be made available to outside organisations.

Thursday, 23 June 2011

STATEMENT 4: PREVIOUSLY APPROVED BAR ON ACCESS

I hereby give consent for my thesis, if accepted, to be available for photocopying and for inter-library loans after expiry of a bar on access previously approved by the Graduate Development Committee.

Signed ………………………………………… (candidate) Thursday, 23 June 2011 ii Oh God, grant me the serenity to accept the things I cannot change and courage to change the things I can and the wisdom to know the difference (i).

Acknowledgments Above all I wish to give my thanks to God, the creator, who has endowed us with the ability to understand some of the complexities of our surroundings and to recognise the fascinating order of the universe, which is only a reflection of God’s infinite intelligence and beauty. This comprehension indeed can make possible to man a definite appreciation of life (ii).

I would like to dedicate this thesis to my Mother, “Mrs Safa Akhavan”, for her endless love and to the memory of my beloved Father, “Dr Abbas Nekoofar”, my main role model. I also dedicate the thesis to my wife, “Dr Fatemeh Rokni Yazdy”, whom I would be nothing without and to my lovely children and son in law “Hosniyeh, Zeynab, Zoha” and “Mohammad” for allowing me to embark on this PhD programme that took me away from them.

This thesis is also dedicated to my forever wonderful supervisor, “Professor Paul Michael Howell Dummer”, without whose inspiration this doctorate would not have been possible.

Professor Paul M H Dummer has taught me how to think professionally, design and manage research projects and how to write and publish academically. Words are not

–  –  –

and valuable advice during the statistical analysis of the data.

I also offer my regards and blessings to “Professor Jeremy Rees”, my second supervisor, for his support and encouragement and to all of the collaborators and those

who supported me during the completion of the project, including:

Dr M S Sheykhrezae, Dr DF Stone, Dr MS Namazikhah, Dr N Shokouhinejad,

–  –  –

i) Justin Kaplan, ed., Bartlett's Familiar Quotations 735 (17th ed. 2002) (attributing the prayer to Niebuhr in 1943).

ii) Ghandi Mahmoud Energy Spectrum of Electrons in Non-Crystalline Materials. Thesis (PhD) University of California, Davis 1971

–  –  –

Aim: To evaluate the effect of various environmental (clinical) conditions on the physical and chemical characteristics of Mineral Trioxide Aggregate (MTA).

Methodology: Initially preparation of specimens was standardised. Moreover, a novel mixing technique, trituration of encapsulated MTA, was developed. The effects of acid and blood contamination on various characteristics of MTA including compressive strength, surface microhardness, push-out bond strength and total porosity were then evaluated. Furthermore, by using X-ray diffraction analysis the hydration process of blood contaminated MTA was studied. In addition, the microstructure of contaminated MTA specimens was compared with control groups.

Results: Methods of mixing and placing MTA significantly affected the hydration process and consequently the physical properties of the material. The lowest and greatest compressive strength, Vickers surface microhardness, and push-out strength values of MTA were found after exposure to pH levels of 4.4 and 7.4, respectively. In addition, scanning electron microscopy revealed a lack of needle-like crystals when the material was in contact with more acidic solutions. The hydration state of specimens partially mixed with blood was more complete than those mixed entirely with blood and less than specimens that were hydrated only with water.

Conclusion: In experimental investigations, use of controlled mixing and placement techniques when using MTA is essential in order to standardise specimen preparation.

Delaying the placement of the final coronal restoration in clinical situations when MTA is contaminated is recommended so that the material can acquire sufficient physical properties to withstand the acid-etch procedure and the condensation pressures that occur during the placement of a restoration and/or produced through indirect masticatory forces.





v

1. INTRODUCTION

1.1. VITAL PULP TREATMENTS

1.2. ROOT CANAL TREATMENT

1.2.1. Post-treatment disease

1.2.2. Incomplete root formation

1.2.2.1. Apexification

1.2.2.2. Regenerative endodontics

1.2.3. Root perforation

1.2.4. Root resorption

1.3. MINERAL TRIOXIDE AGGREGATE

1.3.1. Advantages

1.3.2. Disadvantages

1.4. GAPS IN KNOWLEDGE

1.5. OVERALL AIM

1.6. STRUCTURE OF THESIS

2. MINERAL TRIOXIDE AGGREGATE A REVIEW OF THE LITERATURE

2.1. INTRODUCTION

2.2. CLINICAL APPLICATIONS

2.3. COMMERCIALLY AVAILABLE PRODUCTS

2.4. CHEMICAL CONSTITUENTS

2.4.1. Hydration

2.4.2. Calcium silicates (C3S & C2S)

2.4.2.1. Tricalcium silicate (3CaO.SiO 2 or C3S)

2.4.2.2. Dicalcium silicate (2CaO.SiO2 or C2S)

2.4.3. Tricalcium aluminate (3CaO.Al2O3 or C3A)

2.4.4. Calcium sulphate dihydrate (CaSO4-2H2O)

2.4.5. Tetracalcium aluminoferrite (Ca2AlFeO5)

2.4.6. Bismuth oxide (Bi2O3)

2.4.7. Presence of arsenic

2.4.8. Presence of phosphorus

2.5. BIOCOMPATIBILITY

2.5.1. Mutagenicity and Genotoxicity

2.5.2. Cytotoxicity

2.5.3. Bioactivity

2.5.4. Animal studies

2.5.5. Human studies

2.6. PHYSICAL PROPERTIES

2.6.1. Particle size

2.6.2. Setting time

2.6.3. Setting expansion

2.6.4. Sealing ability

2.6.5. Marginal adaptation

2.6.6. Push-out force

2.6.7. Microhardness

2.6.8. Flexural strength

2.6.9. Compressive strength

2.6.10. Solubility

2.6.11. pH

2.6.12. Porosity

2.6.13. Radiopacity

3. AIMS & OBJECTIVES OF THE STUDY

4. STANDARDISATION OF SAMPLE PREPARATION - THE PRELIMINARY STUDIES

4.1. BACKGROUND

4.1.1. Study 1 - Weight of water in ampoules

4.1.2. Study 2 Manual mixing technique: saturation followed by application of pressure.......... 59 4.1.3. Study 3 Mechanical mixing technique mixing of encapsulated MTA

4.1.4. Study 4 Placement technique - application of ultrasonic agitation

4.1.5. Study 5 - Powder to water ratio

?

4.2. POWDER AND WATER CONTENT OF PROROOT MTA PACKAGES

4.2.1. Aim

4.2.2. Materials & Methods

4.2.2.1. Specimens

4.2.2.2. Weight measurements

4.2.3. Results

4.2.1. Conclusions

4.3. EFFECT OF APPLICATION OF VARIOUS AMOUNTS OF PRESSURE ON MTA SLURRY FOLLOWING THE POWDER SATURATION

HYDRATION METHOD ON SELECTED PHYSICAL PROPERTIES OF MTA

4.3.1. Aim

4.3.2. Materials and Methods

4.3.2.1. Compressive strength

4.3.2.2. Surface microhardness

4.3.2.3. Internal surface microstructure

4.3.3. Results

4.3.3.1. Compressive strength

4.3.3.2. Surface microhardness

4.3.3.3. Internal surface microstructure

4.3.4. Conclusions

4.4. EFFECT OF PLACEMENT TECHNIQUE ON CERTAIN PHYSICAL PROPERTIES OF MTA

4.4.1. Aim

4.4.2. Materials & Methods

4.4.2.1. Compressive strength

4.4.2.2. Surface microhardness

4.4.2.3. Setting time

4.4.3. Results

4.4.3.1. Compressive strength

4.4.3.2. Surface microhardness

4.4.3.3. Setting time

4.4.3.3.1. Initial setting time

4.4.3.3.2. Final setting time

4.4.4. Conclusions

4.5. EFFECT OF VARIOUS POWDER TO WATER RATIOS ON SELECTED PHYSICAL PROPERTIES OF MTA

4.5.1. Aim

4.5.2. Materials & Methods

4.5.2.1. Compressive strength

4.5.2.2. Surface microhardness

4.5.2.3. Setting time

4.5.2.4. Phase composition

4.5.3. Results

4.5.3.1. Compressive strength

4.5.3.2. Surface microhardness

4.5.3.3. Setting time

4.5.3.3.1. Initial final setting time

4.5.3.3.2. Final setting time

4.5.3.4. Phase composition

4.5.4. Conclusion

4.6. OVERALL DISCUSSION PREPARATION OF STANDARDISED SPECIMENS

4.7. CONCLUSION

5. EFFECT OF CONTAMINATION ON SELECTED PROPERTIES OF MTA

5.1. ACID CONTAMINATION

5.1.1. Introduction

5.1.2. Aim

5.1.3. Materials & Methods

5.1.3.1. Materials

5.1.3.2. Methods

5.1.3.2.1. Compressive strength (effect of butyric acid)

5.1.3.2.2. Compressive strength (effect of phosphoric acid gel)

5.1.3.2.3. Surface microhardness (effect of butyric acid)

5.1.3.2.4. Surface microhardness (effect of phosphoric acid gel)

5.1.3.2.5. Push-out force (effect of butyric acid)

5.1.3.2.6. Push-out force (effect of phosphoric acid gel)

5.1.3.2.7. Microstructure (effect of butyric acid)

5.1.3.2.8. Microstructure (effect of phosphoric acid gel)

5.1.4. Results

5.1.4.1. Effect of butyric acid on compressive strength

5.1.4.2. Effect of phosphoric acid on compressive strength

5.1.4.3. Effect of butyric acid on surface microhardness

5.1.4.4. Effect of phosphoric acid on surface microhardness

5.1.4.5. Effect of butyric acid on push-out force

5.1.4.6. Effect of phosphoric acid on push-out force

5.1.4.7. Effect of butyric acid on surface microstructure

5.1.4.8. Effect of phosphoric acid gel on surface microstructure

5.1.5. Discussion

5.1.6. Conclusion

5.2. BLOOD CONTAMINATION

5.2.1. Introduction

5.2.2. Materials & Methods

5.2.2.1. Materials

5.2.2.2. Methods

5.2.2.2.1. Compressive strength

5.2.2.2.2. Surface microhardness

5.2.2.2.3. Porosity

5.2.2.2.4. SEM/EDX

5.2.2.2.5. Phase composition (XRD)

5.2.3. Results

5.2.3.1. Compressive strength

5.2.3.2. Surface microhardness

5.2.3.3. Push-out force

5.2.3.4. Porosity

5.2.3.5. SEM & EDX

5.2.3.6. Phase composition (XRD)

5.2.4. Discussion

5.2.5. Conclusion

6. CONCLUSIONS

7. REFERENCES

CHAPTER 1

INTRODUCTION

1. Introduction The ultimate goal of endodontic treatment is to conserve the integrity of the masticatory system by saving teeth at risk of developing pulp inflammation and those with established pulp and periradicular disease. Prevention of pulp inflammation through elimination of caries and restoration of teeth is the primary aim of Operative Dentistry. However, several treatment modalities within the scope of Endodontics, such as direct pulp capping and pulpotomy are used to eliminate infected dentine and pulp tissue in order to preserve the integrity of the remaining uninfected tissues. Such treatments are On the other hand, when pulp inflammation is irreversible and the pulp is non-savable preferred option when attempting to retain teeth, the aim being to eliminate infection from the pulpodentinal complex, which is achieved by debridement and disinfection of the root canal system. Filling the root canal system and restoring the tooth prevents re-infection by reestablishing the surface integrity of the body to prevent microbial ingress.

1.1. Vital pulp treatments Management of an exposed vital pulp in an adult tooth, particularly when root formation is incomplete, is a controversial topic in Endodontics and a broad range of treatments including direct pulp capping and pulpotomy are available (Pitt Ford et al. 1996, Ward 2002). The materials used in direct pulp capping and pulpotomy are placed adjacent to pulp tissue.

Therefore, they must be non-toxic (Saidon et al. 2003) and of low solubility (El-Araby & AlJabab 2005). A pulp capping material should also have sufficient compressive strength to tolerate pressures resulting from the condensation of restorative materials (Shazad & Kennedy 1994). The ability of a pulp capping material to set in a wet environment is also important (Karabucak et al. 2005) as well as its ability to control bleeding during treatment (Tunca et al. 2007). Such a material should also prevent bacterial leakage, which is known to be the main aetiological factor in post-treatment disease (Fuks 2002).

1.2. Root canal treatment As a consequence of extensive caries and/or a traumatic injury the dental pulp may become irreversibly inflamed and/or infected with the result that conserving the pulp tissue is not feasible. Root canal treatment includes removal of the infected pulp and the micro-organisms that inhabit the canal system followed by the placement of a root filling. Such treatments are not always straightforward and a number of complications can impede thorough shaping, cleaning and filling of the root canal system. In some instances, because of these complications, periapical disease may persist or emerge following treatment (Wu et al. 2006).



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