Further Development of a Novel Fluoride Releasing Acrylic Orthodontic Adhesive

286 Pages·2016·14.35 MB·English

Further Development of a Novel
Fluoride Releasing Acrylic Orthodontic
Adhesive

Hadi Mohammad Ismail
A thesis submitted for the degree of Doctor of Philosophy
School of Dental Sciences
Newcastle University

Jun 2016

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Abstract
White spot lesions (WSL) are a common complication with fixed orthodontic treatment.
Fluoride incorporation into orthodontic adhesives is an effective way to prevent WSL. New
fluoride releasing adhesives are being developed for this purpose. Four experimental groups
were prepared by mixing different ratios of powder (polymethylmethacrylate and sodium
fluoride; 10:0, 9:1, 8:2 and 7:3 wt) with liquids (60% methylmethacrylate and 40% 2-
hydroxyethylmethacrylate). Therefore, this work aimed to further develop the fluoridated
acrylic resin materials for possible use as an orthodontic adhesive.
Acetone was added at 0%, 10%, 20%, 30% and 40wt% to reduce the materials’ viscosity.
Addition of acetone up to 20% did not have detrimental effects on setting characteristics. The
materials continued to release fluoride over 160 days.
Different photo-initiators were investigated and the 1% camphorquinone and 1% 2-
Dimethylamino ethyl methacrylate group was chosen for further development based on
achieving the highest degree of conversion (DoC) at 40s of light curing.
To improve bonding characteristics 4-methacryloyloxyethyl trimellitate anhydride (4-META)
was added as an adhesion promoting monomer at 0% and 5wt%. The experimental materials
were compared with a resin-based orthodontic adhesive (TransbondTMXT) and a glass ionomer
cement (KetacTM Cem) as commercial comparator. DoC, fluoride release and recharging, water
sorption and solubility were measured. Shear bond strength (SBS) was measured for the 9:1
group at two time points after 30 minutes and 30 days of insertion in phosphate buffered saline.
All experimental materials had significantly higher DoC than TransbondTMXT. All
experimental materials had comparable or higher fluoride release compared to KetacTM Cem.
All of the developed materials showed similar recharge behaviour to the KetacTM Cem
specimens. The solubility of the materials increased with increasing NaF concentrations. SBS
of the experimental materials were significantly decreased at 30 days water storage compared
to 30 minutes and were lower than TransbondTMXT. Addition of 4-META and NaF did not
influence the SBS of the material.
In summary, the developed light-cured fluoridated material showed good fluoride release and
high recharge ability, which may prevent WSL. The developed material shows good DoC, in a
reasonable timeframe, which would indicate stability. However, as a result of high water
sorption and as a consequence of fluoride release, the SBS of the materials decreased after being
in water.
In conclusion, this material shows potential as a fluoride releasing orthodontic adhesive, which
could help to reduce decay during fixed appliance treatment. Further work is required to
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improve the stability and bond strength of the material, which could involve investigation of
different monomer combinations or different fluoride sources.
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Acknowledgments
This project would not have been possible without the help and support of several individuals
who in one way or another contributed and extended their valuable assistance in the preparation
and completion of this study. I offer my sincere appreciation for the learning opportunities
provided by my sponsor HCDP program/Kurdistan Region of Iraq for their untiring effort in
encouraging the teaching staff in my country to pursue growth of the education sector.
First I would like to thank my supervisors Dr Sarah Rolland and Dr Matthew German for their
inspiration, help support and guidance. Deepest gratitude to them for their high expectations of
me. I would like to thank you for encouraging my research and for allowing me to grow as a
research scientist. Your advice on both research as well as on my career have been priceless.
I would like to thank all the staff in Dental Materials department including Mr. Anthony
Townshend, Mr. Andrew Yates, Sue Wilkinson and my colleagues and friends, Jacob Pattem,
Sufian Ahmed, Thulficar Al-Khafaji, Saba Zahroon, Adham Abdulrahman, Karzan Sidiq, Omar
Al-Naimi, Anas Mahdee, Ahmed Salih, Mohamed Al-Baghdadi, Mustafa Al-Musawi and Tara
Al-Barazanchi.
A special thanks to my mother. Words cannot express how grateful I am to my mother for all
of the sacrifices that you have made on my behalf. Your prayer for me was what sustained me
thus far. Many thanks to my mother-in law, my brother and sister Dara and Samira for their
continuous support, praying and wishing all the best for me.
I would like express appreciation to my beloved wife Khalat who spent sleepless nights with
and was always my support in the moments when there was no one to answer my queries. It
was a great comfort and relief to know that you were willing to provide management of our
household activities while I completed my work especially when we have our precious, lovely
kids Ahmed and Hanar.
Last but not the least, I would like to thanks the one above all of us, the omnipresent God, for
answering my praying and giving me the strength and the patience to overcome all the
difficulties that I have faced during my study journey, thank you so much Dear Lord.

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Table of Contents
Abstract…………………………………………………………………………ii
Acknowledgements...…...….………………………………………………… iv
Table of content……………………………………………………………...…v
List of figures…………………………………………………………………..xi
List of tables……..……….............………………………………………….xviii
Introduction...................................................................................... 1
Literature review ............................................................................. 3
2.1 Introduction to some common complications during fixed orthodontic treatment ..... 3
White spot lesion formation (WSL) ..................................................................... 3
Enamel loss ........................................................................................................... 7
Bond failure .......................................................................................................... 8
2.2 Orthodontic adhesives .................................................................................................. 8
Conventional resin based adhesives ..................................................................... 9
Methylmethacrylate based orthodontic adhesives (MMA-based orthodontic
adhesives) .......................................................................................................................... 10
Glass ionomer cement (GIC) .............................................................................. 12
Resin modified glass ionomer cement (RMGIC) ............................................... 13
Polyacid modified resins (Compomers) ............................................................. 14
2.3 Properties of ideal orthodontic adhesives .................................................................. 15
Bond strength ...................................................................................................... 15
Easy removal and less adhesive remnant during debonding .............................. 26
Handling characteristics of orthodontic adhesives ............................................. 27
Fluoride release................................................................................................... 33
2.4 Composition of resin based orthodontic adhesive ..................................................... 37
Monomers ........................................................................................................... 37
Fillers .................................................................................................................. 42
Solvents .............................................................................................................. 44
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Initiator system ................................................................................................... 45
2.5 Polymerization reaction ............................................................................................. 51
Intrinsic factors ................................................................................................... 51
Extrinsic factors: ................................................................................................. 52
2.6 Mixing of experimental resin ..................................................................................... 53
2.7 Summary .................................................................................................................... 55
Aims and program of work .......................................................... 56
3.1 Aims ........................................................................................................................... 56
3.2 Objectives .................................................................................................................. 56
3.3 Hypotheses ................................................................................................................. 57
3.4 Program of work ........................................................................................................ 57
The effect of acetone on a new fluoride releasing orthodontic
adhesives ............................................................................................................. 58
4.1 Introduction ................................................................................................................ 58
4.2 Aims and hypotheses: ................................................................................................ 59
Aims ................................................................................................................... 59
Hypotheses ......................................................................................................... 59
4.3 Experimental Materials .............................................................................................. 59
Preparing the Powder ......................................................................................... 62
Preparing the liquid ............................................................................................ 62
Mixing powder and liquid .................................................................................. 62
4.4 Experimental Methods ............................................................................................... 63
Investigating acetone loss ................................................................................... 63
Degree of conversion (DoC)............................................................................... 64
Heat of polymerization (DSC) ............................................................................ 65
Injectability test .................................................................................................. 67
Fluoride release................................................................................................... 71
4.5 Results ........................................................................................................................ 73
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Investigating acetone loss ................................................................................... 73
Degree of conversion (DoC)............................................................................... 74
Heat of polymerization (DSC) ............................................................................ 83
Injectability test .................................................................................................. 90
Fluoride release................................................................................................... 99
Summary of results ........................................................................................... 105
4.6 Discussion ................................................................................................................ 106
Acetone loss ...................................................................................................... 108
Degree of conversion ........................................................................................ 109
Heat release....................................................................................................... 112
Injectability ....................................................................................................... 115
Fluoride release................................................................................................. 118
4.7 Summary .................................................................................................................. 120
Investigating the photo- initiator system of the experimental
materials ........................................................................................................... 121
5.1 Introduction: ............................................................................................................. 121
5.2 Aims and hypotheses ............................................................................................... 121
Aims ................................................................................................................. 121
Hypotheses ....................................................................................................... 121
5.3 Materials and methods ............................................................................................. 121
5.4 Results ...................................................................................................................... 123
Photo-initiator systems and DoC ...................................................................... 123
Acetone concentrations and DoC in relation to photo-initiator systems .......... 133
Fluoride concentrations and Doc in relation to photo-initiator system ............ 135
Summary of the results ..................................................................................... 137
5.5 Discussion: ............................................................................................................... 138
5.6 Summary .................................................................................................................. 142
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Investigating the effect of 4-META on the developed materials
........................................................................................................................... 144
6.1 Introduction .............................................................................................................. 144
6.2 Aims and hypothesis ................................................................................................ 145
Aims ................................................................................................................. 145
Hypotheses ....................................................................................................... 145
6.3 Materials and methods ............................................................................................. 145
Degree of conversion (DoC)............................................................................. 146
Water sorption and solubility ........................................................................... 147
Fluoride release: ............................................................................................... 148
Fluoride recharge: ............................................................................................. 148
SEM observation .............................................................................................. 149
6.4 Results ...................................................................................................................... 149
Degree of conversion (DoC)............................................................................. 149
Water sorption and solubility ........................................................................... 154
Fluoride release................................................................................................. 160
Fluoride recharge .............................................................................................. 167
SEM observation .............................................................................................. 171
Summary of the results ..................................................................................... 183
6.5 Discussion ................................................................................................................ 183
Degree of conversion (DoC)............................................................................. 183
Water sorption and solubility ........................................................................... 185
Fluoride release................................................................................................. 187
Fluoride recharge .............................................................................................. 188
SEM observation .............................................................................................. 190
6.6 Summary .................................................................................................................. 191
Investigating the shear bond strength of the developed materials
........................................................................................................................... 192
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7.1 Introduction .............................................................................................................. 192
7.2 Aims and hypothesis ................................................................................................ 192
Aims ................................................................................................................. 192
Hypothesis ........................................................................................................ 192
7.3 Materials and methods: ............................................................................................ 192
Sample selection and storage: .......................................................................... 192
Roughness ......................................................................................................... 193
Bracket .............................................................................................................. 194
Bonding procedure ........................................................................................... 194
Debonding and shear bond strength (SBS) ...................................................... 196
Adhesive Remnant Index.................................................................................. 197
Statistical analysis ............................................................................................ 197
7.4 Results ...................................................................................................................... 197
Roughness of bovine enamel sections .............................................................. 197
Shear bond strength (SBS). .............................................................................. 199
Adhesive Remnant Index.................................................................................. 200
7.5 Discussion ................................................................................................................ 201
7.6 Summary .................................................................................................................. 206
General discussion ....................................................................... 208
8.1 Introduction .............................................................................................................. 208
8.2 Methodological considerations ................................................................................ 208
8.3 The “Ideal” orthodontic adhesive ............................................................................ 209
Handling properties .......................................................................................... 209
Fluoride release................................................................................................. 210
Bond strength .................................................................................................... 211
8.4 Is the experimental material an “Ideal Orthodontic Adhesive”? ............................. 212
8.5 Conclusions and suggestions ................................................................................... 213
References ..................................................................................... 214
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Appendices.................................................................................. 255
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