A Review of Glass-Ionomers: From Conventional Glass-Ionomer to Bioactive Glass-Ionomer (2013) by Maryam Khoroushi, Fateme Keshan

1. A REVIEW OF GLASS-IONOMERS: FROM
CONVENTIONAL GLASS-IONOMER TO BIOACTIVE
GLASS-IONOMER (2013)
Maryam Khoroushi, Fateme Keshan
JOSEPH RUSSELL N. GORDA
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2. INTRODUCTION
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3. TEXT
▸ Materials used in the body: stable and passive without any
interactions with the body tissues or fluids.
▸ Dental amalgam, composite resins and dental cements
▸ fluoride-releasing materials
▸ “smart” materials in dentistry
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4. TEXT
▸ Advantages of GI,
▸ they can be placed in cavities without any need for
bonding agents;
▸ they also have good biocompatibility.
▸ Disadvantages
▸ lack of sufficient strength and toughness.
▸ flexural strength: RMGI (71 MPa), conventional GI (11
MPa).
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5. TEXT
▸ Resin-modifed glass-ionomers (RMGI) have improved
mechanical properties of the conventional GI, with
hydrophilic monomers and polymers, such as hydroxyethyl
methacrylate (HEMA).
▸ Bioactive glass (BAG) has been added to GI structure to
improve bioactivity and tooth regeneration capacity.
▸ There is ever-increasing interest in the application of
bioactive materials in the dental field in an attempt to
remineralize affected dentin.
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6. TEXT
SMART MATERIALS IN DENTISTRY
▸ Smart materials can change their behavior in response
to various stimuli
▸ piezoelectric materials
▸ Shape memory alloys
▸ pH-sensitive polymers
▸ Polymer gels
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7. TEXT
▸ Smart behavior in GICs;
‣ do not undergo great dimensional changes in a
moist environment in response to heat or cold and it
appears heating results only in water movement
within the structure of the material.
‣ noticeable shrinkage in a dry environment at T: >
50°C, similar to the behavior of dentin.
‣ fluoride release and recharge capacity.
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8. TEXT
HISTORY OF GICS
▸ Ideal tooth restoration material:
‣ Adhesion to tooth structure (enamel and dentin)
‣ Capacity to withstand pressure resulting from occlusion
▸ During 1950s, Researchers aim was to produce a material
with thermal, mechanical, and optical properties
comparable to those of tooth structure
▸ Initial attempts to improve silicate cement properties.
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9. TEXT
ZINC POLYALKENOATE CEMENTS (1968)
▸ Can bond to tooth structure
▸ Less than ideal physical properties
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10. TEXT
GLASS POLYALKENOATE CEMENTS (LATE 1960S)
▸ First GIC
▸ Increased aluminum-to-silica ratio in the powder - increased reactivity
of glass
▸ ASPA (polyalkenoic acid alumina silicate cement) + calcium-alumina
silicate glass system
▸ Tartaric acid - positive isomer improves manipulation properties of
cement and its setting time
▸ Calcium flux - forms superficial bond
▸ Fluoride flux - prevents oxidation
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11. TEXT
▸ Fluoride is released after mixing of powder with the
polyalkenoic acid.
‣ Decreases melting point
‣ Increases cement strength
‣ Improves manipulation properties of cement
‣ Cariostatic effect
▸ Calcium and phosphate ions are also released
▸ Strontium and Calcium replace each other, deep penetration to
de mineralized dentin - possibility of dentin remineralization
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12. TEXT
▸ Setting reaction:
▸ Acid-base reaction: polyacrylic acid (proton donor) and aluminosilicate
glass (proton recipient).
▸ Acid destroys glass network -> releases cations (Al3+, Ca2+, Na+
etc.)
▸ 4 stages:
‣ 1. Decomposition
‣ 2. Gelation
‣ 3. Hardening
‣ 4. Maturation
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13. TEXT
▸ The role of tartaric acid
Addition of tartaric acid (+)
increases the working time and
improves the setting reaction of
the cement, resulting in easier and
better manipulation of the cement.
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14. TEXT
▸ Mechanical properties
▸ LP ratio
▸ cohesive forces, which keep the matrix compressed are composed of
ionic cross-links, convolutions, and interlocking of chains and hydrogen
bridges.
▸ Unreacted glass particles remain - decrease in mechanical properties of the
cement.
▸ Greater consistency = stronger
▸ ⬆Powder amount - ⬆consistency - accelerated setting reaction - cement
becomes stronger
▸ If matrix does not bind fully to the cement, mechanical properties will
significantly decrease.
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15. TEXT
▸ Aging:
▸ GIC - weak after setting, not stable in water
▸ Becomes stronger with the progression of rxn, more
resistant to moisture
▸ 200 MPa after 24 h -> 400 MPa after a year
▸ Al cation - ⬆ rigidity and stiffness of the matrix
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▸ Adhesion:
▸ Bond chemically
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CLASSIFICATION OF GI
▸ Type I: Lutting cement for crowns, bridges, and orthodontic brackets
▸ Type II a: Esthetic restorative cement
▸ b: Reinforced restorative cement
▸ Type III: Liner and base.
▸ Type IV: PFS
▸ Type V: Luting for orthodontic purpose
▸ Type VI: Core buildup material
▸ Type VII: High fluoride releasing command set
▸ Type VIII: ART
▸ Type IX: Pediatric GIC
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18. TEXT
FIRST GENERATION
▸ ASPA I - not very active, did not set fast, was very moist-
sensitive and had low translucency
▸ ASPA II - I tartaric acid, had better properties and was the
first GI with practical applications
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SECOND GENERATION
▸ Reinforced cements
▸ RMGI
‣ Metacrylate to polyacrylic acid
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▸ Factors influencing fluoride release from restorative materials:
▸ matrix formulation,
▸ filler, and
▸ fluoride content.
▸ experimental factors such as the
▸ storage environment,
▸ number and frequency of changing the preserving solution,
▸ composition and pH of saliva,
▸ formation of plaque and pellicle,
▸ powder-to-liquid ratio,
▸ mixing,
▸ curing time and
▸ the exposed surface.
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CLINICAL APPLICATIONS
▸ GIC based fissure sealants
▸ Tooth restoration, liners, bases
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BIOMATERIALS AND BIOACTIVE GLASSES
▸ Toxicity
▸ Nearly biological inert
▸ Bioresorbability
▸ Bioactivity
▸ Group A - induces both Intracellular and extra cellular
responses
▸ Group B - only extra cellular response
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23. TEXT
BAG
▸ When BAG is immersed in aqueous solutions such as
body fluids, simulated body fluid, (SBF) or tris buffer
solution, (TBS) three main processes take place:
▸ Leaching and formation of silanols - releases alkaline
agents (replace H ions H30
▸ Dissolution of the glass network - breakdown of-Si-O-Si-
O-Si-bonds
▸ Precipitation
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24. TEXT
NEW GENERATION OF BIOMATERIALS (THIRD GENERATION)
▸ The aim is tissue regeneration and use of the
biomaterial in the form of a powder or solution is to
induce local tissue repair. These bioactive materials
release chemical agents in the form of dissolved ions
or growth factors such as bone morhogenic protein,
which stimulate and activate cells. The cells produce
more growth factors, which induce cell proliferation
and regeneration
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25. CONCLUSION
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26. TEXT
▸ In recent decade there has been increasing attention
to the use of “smart” bioactive materials in dentistry,
especially with the aim of remineralizing dentin. In
some recent studies, BAG has been incorporated into
GI composition to improve bioactivity and tooth
regeneration and reconstruction capacity. It appears
researchers all over the world should pay more
attention to improve the characteristics of these
materials, particularly in an attempt to control the
prevalence of primary and recurrent caries.
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27. TEXT
VIDEO
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