FDI World Oral Health Forum:Are you ready for amalgam phase-down?
How the Minamata Convention impacts your Dental Practice.
New materials for a post-Minamata era
September 9, 2016
Jirun Sun, MS, PhDVolpe Research Center
American Dental Association [email protected]
Dental restorative materials other than amalgam
• Glass ionomer cements (GIC)• Resin composites• Hybrid of GIC and Resin composite
• Resin modified GIC• Poly acid modified resin composite (compomer)
StrongerWeaker GICResin modified GIC
CompomerResin composite
Advantages and limitations of existing dental composites
• Advantages• Aesthetics: can match the tooth color• Strong bonding to tooth • No mercury• Versatile for large and small restorations• Anterior and posterior restorations
• Compared to Amalgam: short service life (~8 years)• Suboptimal clinical placement• Secondary caries
Break down of materials by bacteria and enzymesMicroleakage
• Stress-induced micro-fractures
Inventor Dr. Bowen in dental practice
Longer-lasting dental materialsare needed!
Resin composites
Resins: continuous phase
Tooth/Restoration interface
Com
posi
te
Toot
h
Adh
esiv
eFillers: for better mechanical performance
Coupling agents: bond resin and fillers togetherRestoration
Dental Materials Innovation Workshop (London, Dec 2012, Adv Dent Res 2013)
5
Desired properties for new dental composites• Resist degradation• Stronger materials for posterior restoration• Clinically applicable• Self-healing• Antimicrobial
http://estheticdentist.in/Treatments/posterior-restorations/
Novel
Traditional
O OO OOHOH
OO
OO
OO
O
O
OO
OO
HOO
OOHO OHO OH
OHOH
OH
O
BisHPPP TEG
Methacrylic Acid(MA)
BisGMA TEGDMA
TEG-DVBE
No Hydrolysis Product
6
Fundamental change in chemistry improved performance: structure determines performance
acid, base, or esterase
New resin systems
An esterase is a hydrolase enzyme that splits esters into an alcohol in a chemical reaction with water called hydrolysis.
Resistance to enzymatic and hydrolytic challenges
Two major esteraseenzymes in human saliva:Cholesterol Esterase (CE) Pseudocholine Esterase (PCE)
Gonzalez-Bonet Biomacromolecules 2015Finer JDR 2004, Biomaterials 2004; Delaviz Dent Mat 2014.
New materials resist enzymatic challenges
• Traditional monomers degrade at different rates• Our novel monomer resists degradation
0
25
50
75
100
125
150
Enzyme 2Enzyme 1
Rel
ativ
e de
grad
atio
n (%
)
Traditional-Bis-GMA Traditional-TEGDMA Novel monomer
in Saline
Gonzalez-Bonet Biomacromolecules 2015Finer JDR 2004, Biomaterials 2004; Delaviz Dent Mat 2014.
Resins after incubation with enzyme• Traditional resin:
~2% mass loss; ~15% hardness drop in 16 days
• Novel resin: No mass loss; no hardness change
Scientific recognition of our work
Gonzalez-Bonet Biomacromolecules 2015.
Other new resins and new concepts
• The click chemistry was introduced into dentistry to provide smart, reconfigurable and responsive network (Xi Advanced Functional Materials 2014)
• Thiol-ene (Bowman Dental Materials 2015) dental composites• Adding thio-urethane oligomers improved the performance of
resin composites (Bacchi JDR 2014) • And many more…
Clinically practical photo-copolymerization
• Using handheld curing devices• Fully cured in seconds• Well defined polymer composition• Extremely high monomer conversion• Expect significantly reduced leachables (no toxicity)
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Stronger and tougher composites
Composition
elastic modulus (Gpa)
flexural strength (Mpa)
fracture toughness (MPa·m1/2)
BisGMA/TEGDMA 70/30 9.4/10.1 97/11.4 1.19/0.05New composite 1 9.4/0.6 123/14 1.52/0.04
• Similar or better mechanical performance than amalgam• Strong and easy to handle for anterior and posterior
restoration
Self-healing dental composites (SHDC)
• To significantly extend the life span of the restorations by autonomic self-healing of micro-cracks
• Two new components added:- Silica-based healing powder (HP)- Polyacid healing liquid (HL) in
microcapsules• HP + HL glass ionomer cements• Autonomous healing procedure:
- Cracking (A)- Releasing of HL (B)- Healing (C)
20 µm 20 µm
Initial Healed
2) New material formed by reaction HP + HL
Energy dispersive X-ray spectroscopy (EDS)
Confirmation of healing reaction1) Morphology changed after healing
Huyang JMAD 2016
Scanning Electron Microscopy (SEM)
Initial Healed
0 4 8
0
4
8
Dis
plac
emen
t [m
]
Force [N]
With healing liquid No healing liquid
Increased Healing
SHDC heals autonomously
Dynamic mechanical analysis
Fatigue study: Fatigue life time was extended 5 times.
16
Advantage of SHDC
• To autonomously repair micro-cracks • It may increase fatigue life more than 5 times• Using materials clinically tested• To deliver drugs• Prevent caries through F release
17
Prevent secondary caries- antibacterial dental composites
Dental composites
Tooth/Restoration interface
Com
posi
te
Toot
h
Adh
esiv
e
Resins
Filler
Coupling agentsRestoration
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Antibacterial dental composites-examplesAdhesives: • Kill bacteria without diminishing bonding strength (Hirose JDR 2016)Resins: • Rechargeable antibacterial polymers (Sun Acta Biomat 2012)• Quaternary ammonium polymers (Antonucci Dent Mat 2012) Fillers: • Strong composites with antibacterial properties (Imazato Biomaterials
2003)Coupling agents: • pH sensitive antibacterial compounds (Sun in development)
New technologies to improve dental materialsNanotechnology,• In-situ formation of antibacterial nanoparticles showed very
promising results (Fan Dental Materials 2011) • Biosensor in oral cavities for disease diagnosis and screening
3D printing Precision medicine
Challenges in developing new dental materials• New materials new challenges
• Unknown limitation of new materials• Unknown toxicity to human beings in the long term• Lack of standard evaluation methods• Make the new materials affordable
• Adapting existing tools and guidance for dental practice• Make materials that can avoid suboptimal clinical placement
Thanks and questions
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