Selected performance characteristics of non-aqueous alkaline endodontic materials

179 Pages·2017·32.32 MB·English

Selected performance characteristics of non-aqueous alkaline
endodontic materials

Yu-Yao Teoh
BDSc (Hons)

A thesis submitted for the degree of Master of Philosophy at
The University of Queensland in 2017
School of Dentistry

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Abstract

During root canal treatment, the root canal of a tooth is prepared, disinfected and
filled. Alkaline materials have been used in endodontics for many years mainly as
medicament pastes rather than for obturation of the root canal system.

Calcium hydroxide, the most commonly used alkaline material in dentistry, releases
hydroxyl ions which cause disinfection of the root canal system. The first part of this thesis
examines the use of calcium hydroxide in non-aqueous solvents and compares this to
calcium hydroxide in traditional water-based solvents. The novel use of anthocyanin as an
indicator allowed tracking of diffusion of hydroxyl ions through root dentine.

The discovery of calcium hydroxide-induced polymerisation of certain organic
compounds such as glycerol to form a hard setting alkaline cement opens the possibility of
using these materials for short or long term obturation of the root canal. In the second part
of the thesis, a bacterial leakage study was carried out to compare the sealing capabilities
of various root filling materials including this novel hard-setting alkaline cement as well as
mineral trioxide aggregate (MTA) cements, which release calcium hydroxide from their
setting reaction, and traditional epoxy resin sealers.

In the third part of the thesis, the root fillings were then assessed in terms of their
removability, a parameter which is relevant both for post space preparation and in the event
that retreatment is required. Materials were tagged with a fluorescent label and then confocal
laser scanning microscopy was used to assess the extent of remnant material and the
cleanliness of the root canal walls.

The results from Part 1 indicated that hydroxyl ion release into root dentine is greater
with non-aqueous solvents, resulting in a sustained level of high alkalinity within the root.
This feature should provide longer disinfection and should therefore reduce the number of
inter-appointment visits clinically. In Part 2, bacterial leakage studies demonstrated that
alkaline cements had greater sealing capabilities than commonly used epoxy resin sealers.
This is most likely due to the antibacterial actions of hydroxyl ions released from alkaline
cements. In Part 3 of the thesis, with regards to removability using rotary instrumentation,
the novel hard-setting calcium hydroxide cement was more easily removed than MTA
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cements or epoxy resin sealers, with the latter coating half of the canal walls after
instrumentation.

Overall, the findings from this thesis show that while calcium hydroxide pastes based
on water are an integral and long standing part of root canal disinfection, the potential use
of calcium hydroxide in dentistry is wider than its current applications. The research from
this thesis shows that calcium hydroxide in non-aqueous solvents may be suitable for use
as a disinfecting medicament and that when incorporated into a cement it may have
properties that are well suited to being used in obturation of the root canal.
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Declaration by author

This thesis is composed of my original work, and contains no material previously published
or written by another person except where due reference has been made in the text. I have
clearly stated the contribution by others to jointly-authored works that I have included in my
thesis.

I have clearly stated the contribution of others to my thesis as a whole, including statistical
assistance, survey design, data analysis, significant technical procedures, professional
editorial advice, and any other original research work used or reported in my thesis. The
content of my thesis is the result of work I have carried out since the commencement of my
research higher degree candidature and does not include a substantial part of work that has
been submitted to qualify for the award of any other degree or diploma in any university or
other tertiary institution. I have clearly stated which parts of my thesis, if any, have been
submitted to qualify for another award.

I acknowledge that an electronic copy of my thesis must be lodged with the University Library
and, subject to the policy and procedures of The University of Queensland, the thesis be
made available for research and study in accordance with the Copyright Act 1968 unless a
period of embargo has been approved by the Dean of the Graduate School.

I acknowledge that copyright of all material contained in my thesis resides with the copyright
holder(s) of that material. Where appropriate I have obtained copyright permission from the
copyright holder to reproduce material in this thesis.
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Publications during candidature

Conference presentations:

1. International Association for Dental Research (IADR) 94th General Session and
Exhibition; Seoul, South Korea; June 24, 2016. Abstract 2473066

2. Research Day; Oral Health Centre, University of Queensland; September 24, 2016.

3. International Association for Dental Research (IADR) 95th General Session and
Exhibition; San Francisco, USA; March 23, 2017. Abstract 2624341

Peer-reviewed papers

1. Teoh Y, Athanassiadis B, Walsh LJ. The influence of aqueous and PEG 400 solvent
vehicles on hydroxyl ion release from calcium hydroxide medicaments. Internat Dent
2016;11:42-52

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Publications included in this thesis

No publications included

Contributions by others to the thesis

Professor Laurie Walsh, my primary Supervisor, is responsible for the conception of the
project in collaboration with my co-Supervisor Dr Basil Athanassiadis, as a result of their
long research interest in calcium hydroxide particularly in non-aqueous solvents. Professor
Walsh was instrumental in the design of the experiments for this project. Professor Walsh
also provided guidance on the statistical analysis of the results and their presentation.

Statement of parts of the thesis submitted to qualify for the award of another degree

None
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Acknowledgements

I would like to say a very big thank you to my supervisor Professor Laurence Walsh for his
guidance and mentorship throughout this project. Without his assistance, this project would
not have been possible. I am grateful for the many hours you have dedicated in helping me
during my candidature.

I am grateful to the University of Queensland for the financial support I received through the
UQ Research Scholarship.

I would also like to thank Dr Basil Athanassiadis, my co-supervisor, for his valuable insights,
practicality and proof-reading.

My sincere appreciation to the thesis committee for their valuable time and advice. In
addition, I would like to thank Dr HMHN Bandara for his assistance with the confocal laser
scanning microscope, and Dr Shaneen Leishman for her assistance with the microbiological
aspect of the coronal leakage study.

To my loyal dog, Frankie, you have never failed to bring a smile to my face during times of
frustration. Thank you for keeping me company throughout the late nights I have spent
writing this thesis.

Many thanks to my friends and colleagues who have assisted me through the long struggles
of thesis writing with their help and moral support.

I want to express my deepest gratitude to Lynne, who supported me through this project
with her love and encouragement, however my mood was.

Finally, and most importantly, I am indebted to my family for all the support and
encouragement that I have received throughout my life. Special thanks to my sisters,
grandpa and parents. Without your love and faith in me, I would not have made it this far.
I thank you all.

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Keywords

calcium hydroxide, root canal, endodontics, sealer, alkaline cements, pH diffusion, non-
aqueous solvents, coronal leakage, removability

Australian and New Zealand Standard Research Classifications (ANZSRC)

ANZSRC code: 110501, Dental Materials and Equipment, 40%
ANZSRC code: 110503, Endodontics, 60%

Fields of Research (FoR) Classification

FoR code: 1105, Dentistry, 100%
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Table of contents

Abstract ................................................................................................................................ 2
Declaration by author ........................................................................................................... 4
Publications during candidature ........................................................................................... 5
Publications included in this thesis ....................................................................................... 6
Contributions by others to the thesis .................................................................................... 6
Statement of parts of the thesis submitted to qualify for
the award of another degree ............................................................................................. 6
Acknowledgements .............................................................................................................. 7
Keywords .............................................................................................................................. 8
Australian and New Zealand Standard Research Classifications (ANZSRC) ...................... 8
Fields of Research (FoR) Classification ............................................................................... 8
Table of contents .................................................................................................................. 9
List of Figures ..................................................................................................................... 12
List of Tables ...................................................................................................................... 15
List of Abbreviations used in the thesis .............................................................................. 16

Chapter 1. Literature Review ........................................................................................... 17

1.1 Introduction .......................................................................................................... 18
1.2 Aetiology of pulpal and periapical disease ........................................................... 18
1.3 Aims of root canal therapy ................................................................................... 19
1.4 Obturating materials ............................................................................................. 21
1.5 Coronal leakage and methods of assessing leakage .......................................... 26
1.6 Performance of obturating materials in leakage studies ...................................... 30
1.7 Ease of removal ................................................................................................... 33
1.8 Calcium hydroxide in endodontic medicaments ................................................... 34
1.9 Conclusion and significance ................................................................................ 36
1.10 Hypothesis and aims ............................................................................................ 38
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Chapter 2. The influence of aqueous and PEG 400 solvent vehicles on
hydroxyl ion release from calcium hydroxide medicaments. ................................... 39

2.1 Introduction .......................................................................................................... 40
2.2 Materials and methods ......................................................................................... 41
2.3 Results ................................................................................................................. 45
2.4 Discussion ............................................................................................................ 46
2.5 Conclusion ........................................................................................................... 50

Chapter 3. Coronal leakage from alkaline endodontic cements
versus resin sealers. ..................................................................................................... 51

3.1 Introduction .......................................................................................................... 52
3.2 Materials and methods ......................................................................................... 53
3.3 Results ................................................................................................................. 57
3.4 Discussion ............................................................................................................ 59
3.5 Conclusion ........................................................................................................... 61

Chapter 4. Removability of endodontic sealers and cements: ........................................
a confocal microscopic study. ..................................................................................... 62
4.1 Introduction .......................................................................................................... 63
4.2 Materials and methods ......................................................................................... 65
4.3 Results ................................................................................................................. 71
4.4 Discussion ............................................................................................................ 75
4.5 Conclusion ........................................................................................................... 77

Chapter 5. General discussion and future directions ................................................... 78

5.1 General summary................................................................................................. 79
5.2 Future research directions ................................................................................... 82

Chapter 6. Bibliography ................................................................................................... 85
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