The need for an aesthetically pleasing restoration paved way for the introduction of teeth colored restoration with additional properties like biocompatibility, easily manipulated & workable.
Though dental amalgam showed good strength & longevity it has its own disadvantages like poor adaptation, leak, corrosion, marginal breakage, and the most important disadvantage- mercury release in the oral cavity.
Thus the teeth colored fillings came into use from the 1870s. Silicates were the first teeth colored fillings introduced by Fletcher in 1878. These types of cement showed poor strength, pulpal irritation and brittleness hence their use in dentistry ceased momentarily.
In 1940s self-curing acrylic resins gained popularity but had disadvantages like high polymerization shrinkage, high coefficient of thermal expansion, poor marginal seal & dimensional instability.
R. Bowen in 1962 overcame the disadvantages by reinforcing a polymeric restorative material with silica called composites. With continual research and development, composites gained the status of potential restorative material for both anterior and posterior restoration. During this same phase, another teeth colored restorative material was developed by Wilson & Kent in 1972. It is called the glass ionomer cement / man-made dentin. It showed excellent strength & anti-cariogenic properties.
GLASS IONOMER CEMENT:
It is silica-based cement available in a separate powder and liquid form. The powder comprises mostly silica with alumina, fluoride in combination with aluminum, calcium and sodium and aluminum phosphate.
The aqueous liquid is a combination of polyacrylic acid & water. The viscosity of the liquid is reduced by the addition of tricarboxylic acid. Tartaric acid is also added to the liquid to shorten the setting time and increase the working time.
MODIFIED FORMS AVAILABLE IN GLASS IONOMER CEMENT:
- Anhydrous GIC / water-settable GIC: This form has an extended working time. The powder is composed of freeze-dried polyacid with a GIC mixture. The liquid has either water or water with tartaric acid. The polyacid dissolves from the powder into the liquid to extend the working time.
- Miracle mix: The silver alloy powder & GIC powder is mixed with GIC liquid. It increases the compressive strength, tensile strength & abrasion resistance. It is used as a core build-up material. It has a poor esthetic appearance, difficult to acquire a homogenous mixture and sensitive to moisture contamination.
- Glass Cermet: In this, the metal (gold/ silver) is sintered to the silica component at a temperature of 800 C. Titanium oxide is added to improve the color of the cement.
- Resin-modified GIC (RMGIC): The attributes of this material is that they are composed of the best properties of GIC and composite. They are activated by UV light or Blue light of wavelength 470-480nm. They have extended working time, control over the setting time and good adaptation. Shrinkage is still noted.
RECENT ADVANCES IN GLASS IONOMER CEMENT:
- Compomer: It is a fluoride-releasing GIC with the durability of the composites in a single paste system. It consists of ion leachable glass and polymerizable acidic monomers with a functional group of polyacrylic acid and methacrylates in 1 molecule.
- Fiber-reinforced GIC: alumina fibers are reinforced in the GIC powder. They have decreased polymerization shrinkage, improved wear resistance and flexural strength.
- Giomer: the hybridization of GIC with composite using a unique technology called pre-reacted glass ionomer technology (PRG). Fluoroaluminosilicate glass reacts with polyalkenoic acid to yield a stable phase of GIC which is then mixed with resin. It can either be Full-PRG (F-PRG) or Surface-PRG (S-PRG).
- Hainomers: It is a bioactive material composed of hydroxyapatite and GIC powder. It is used as bone cement as it directly bonds to the bone and affects its growth & development.
- Chlorhexidine impregnated GIC: It shows increased anti-cariogenic properties. It is still under research.
- Proline containing GIC: An amino acid with GIC gives better surface hardness and increased water absorption without affecting the amount of fluoride to be released. It’s a restorative as well as bone cement with low cytotoxicity.
- CPP-ACP GIC: Incorporation of casein phosphopeptide amorphous calcium phosphate into GIC for enhanced release of calcium, phosphate and fluoride ions in a neutral and acidic pH this is still under trials.
- Zirconia containing GIC: A potential substitute for miracle mix with increased tensile strength. Under research.
- Nano bioceramic modified GIC: nanohydroxyapatite or fluoroapatite added to FUJI II GC. Expressed higher bond strength with improved mechanical properties.
It is the modification of methacrylate or acrylates. It is composed of the following:
- An organic matrix consisting of polymers or monomers of methacrylate like BisGMA, UDMA, TEGDMA, HEMA, etc.
- Inorganic filler matrix like silicates, boron silicate, lithium aluminium silicate or quartz.
- Coupling agent: Organosilane
- Activator: Camphorquinone
- Initiator: Benzophenone
- Inhibitors: Butylated Hydroxyl Toulene
- Coloring agent: Titanium or aluminum oxide.
Composites are classified based on their particle size, matrix composition and the method of polymerization. Hybrid composites have a good finish, appearance and wear resistance. The polymerization is activated by light-curing with blue light for 400-500nm.
RECENT ADVANCES IN COMPOSITE:
- Compomer (poly acid-modified composite resin): It is a fluoride-releasing GIC with the durability of the composites in a single paste system. It consists of ion leachable glass and polymerizable acidic monomers with a functional group of polyacrylic acid and methacrylates in 1 molecule.
- Giomer: the hybridization of GIC with composite using a unique technology called pre-reacted glass ionomer technology (PRG). Fluoroaluminosilicate glass reacts with polyalkenoic acid to yield a stable phase of GIC which is then mixed with resin. It can either be Full-PRG (F-PRG) or Surface-PRG (S-PRG). Indicated in the tooth with the non-carious cervical lesion, root caries & primary tooth caries.
- ORMOCER (organically modified ceramic): it is an organically modified non-metallic inorganic composite material. It has a highly cross-linked organic matrix with inorganic molecules to make 3D network to form the basic structure of ORMOCER. Highly esthetic with good bond strength, high compressive and transverse strength with lower polymerization shrinkage.
- Antibacterial composite: attempts to reduce the tendency of increased plaque and bacterial accumulation in the composite than enamel gave way to the development of caries resistant antibacterial composites: chlorhexidine and methacryloxydecyl pyridium bromide(MDPB). The addition of chlorhexidine to composite has been unsuccessful due to the decrease in properties of composites, toxic effects, and shift in microbial accumulation from the restored tooth to the other teeth. The use of MDPB was successful as it overcame the difficulties that resulted in composites in combination with chlorhexidine.
- Smart composites: the composite consists of micron size sensor particles that interact with the resin matrix and generate quantifiable anions. Fluoride and calcium release happens when the pH falls in the vicinity of the restoration.
The above mentioned are some of the trends that are happening in the field of tooth-colored or esthetic dentistry.