Shashank Trivedi(110301192)

ADVANCES IN GLASS

IONOMER CEMENT

Glass Ionomer Cement (GIC) is a dental restorative material used in dentistry for filling teeth and luting cements.

The early conventional glass-ionomer materials were technique-sensitive,slow setting,opaque when set and sensitive to both dessication and hydration during setting.

This led to premature surface deterioration.

Conventional GIC

Most of these problems have (more or less) been solved in newer generations of glass-ionomer cement. Setting has been accelerated and hydration problems have been reduced.

However,unlike composites,their use in stressed situations is still questionable.

The most common indication of the newer,heavily filled,reduced particle size glass-ionomer cements is in non-stress bearing build-ups,root caries,tunnel restorations and long term provisional restorations in primary and adult dentitions.

Resin modified glass-ionomer cements are materials in which a hydrophilic polymerizing resin is added to the glass-ionomer matrix.

The resin-modification of glass-ionomer cements, introduced to obtain command set glass ionomer cements, did not contribute to higher wear resistance.

The admixed resin improves initial aesthetics, tensile strength and fracture toughness.

Desiccation and hydration problems are reduced.

Resin Modified GIC

Resin-modified glass-ionomer cements set partly through an acidbase reaction and a polymerization of the resin component of the matrix.

The resin component can be light cured.Another portion of the setting process involves

the typical acid base process between the filler and the poly-acid matrix.

The hydrophilic character of the resin component also contributes to osmotic swelling.

One of the factors affecting the strength of glass ionomers is the chemical composition of the polymer matrix.

Most of the conventional glass ionomers contain homopolymers or copolymers of unsaturated mono-, di -, and tri – carboxylic acids. With these formulations, the major problem lies in that the acrylic acid homo or copolymers have –COOH groups which are directly attached to the backbone and are closely oriented to each other, resulting in a rigid polymeric structures.

It is presumed that strength or fracture resistance of the ionomer material is weakened due to this steric hindrance.

Amino Acid Modified GIC

So acrylic acid copolymers were modified with N – acryloyl or N- methacryloyl amino acids, such as N –methacryloyl –glutamic acid, providing a possible path to improved conventional glass ionomers.

These newly formulated polyacids have flexible side chains tethering the carboxylic acid groups at various distances from the main chain polymer backbone, allowing for more freedom and less steric hindrance when the carboxylic acid groups are undergoing chemical reactions.

This type of modification has improved the fracture toughness of the glass ionomer cement.

The copolymers with pendant amino acid residues have also been developed for preparing visible light cure formulations.

Another step in merging the characteristics of resin-based composites with those of traditional glass-ionomer cements was the introduction of the poly-acrylic acid modified composite resins, also called compomers.

Compomers were intended as to optimally combine the properties of glass-ionomers and resin-based composites.

If regarded as a more or less temporary restorative, compomers can replace resin-based composite in anterior proximal restorations and have become in many countries the material of first choice in paediatric dentistry.

Compomers

In almost all other applications, traditional composites and glass-ionomer cements are preferred because of greater strength and wear resistance and better dimensional stability.

A disadvantage of compomers is that ease of handling was obtained at the cost the established specific properties of hybrid resin-based composites and a proper glass-ionomer reaction.

GIOMER is a new group of direct restorative materials and adhesives that offers aesthetics, handling and physial properties of composite resins with added benefits of high radiopacity, anti plaque effect, fluoride release & recharge.

The GIOMER concept is based on the novel PRG(Pre Reacted Glass-ionomer) technology, where special PRG fillers are included in the resin matrix.

The initial GIOMER group of restorative materials (BEAUTIFIL) contained the Surface Reaction Type PRG fillers (S-PRG) and adhesive systems (FL-BOND) contained the Full Reaction Type PRG fillers (F-PRG).

Giomers

Among the GIOMER products, "BEAUTIFIL", an aesthetic direct restorative material for anterior and posterior teeth and "FL-BOND", a 2-step self-etching, consisting of self etching primer and fluoride releasing bonding agent have been clinically proven and researched extensively worldwide.

Their excellent long-term clinical performance has given GIOMER recognition as a unique group of direct aesthetic restorative materials.

Properties of S-PRG Technology--Maintaining the property of multifunctional glass.-High level of radiopacity.-Properties of glass-ionomer (Fluoride release and recharge,Biocompatibility).-Long term clinical stability.-Shade conformity (optical property)-Aesthetics close to natural teeth.-Resistance to wear of posterior teeth.-Anti-plaque effect

Both Giomer and Compomer are a true hybrid of two compounds, Glass Ionomer and Composite.

The difference of Giomer from Compomer is, in Compomer variable amount of unhydrated polyacrylic acid is added to the resin matrix and the acid base reaction wont takes place until water comes in contact with compomer.

The main disadvantage of COMPOMER is less amount of Fluoride release and absence of Fluoride recharging ability.This makes the GIOMER more preferable then compomer.

GIOMER uses PRG( Pre Reacted Glass ionomer ) TECHNOLOGY by which it differs from compomer, in giomer the glass filler particles used are pre reacted with polyacrylic acid.

Difference between Giomer and Compomer

Bisphenol A glycidyl dimethacrylate, TEGDMA, Inorganic glass filler, Aluminium oxide, silica, Pre-reacted glass ionomer filler, DL-camphorquinone

COMPOSITION Of GIOMER (BEAUTIFIL)

Glass ionomer have been modified by addition of filler particles ,to improve strength ,fracture toughness & resistance to wear.

Silver alloy admix / miracle mix:-This is made by mixing of spherical silver amalgam alloy powder with glass ionomer powder.

Cerment:-Bonding of silver particles to glass ionomer particles by fusion through high temperature sintering.

Metal Modified GIC

Cermet Cement

Miracle Mix

Unique processing of the glass component and polyalkenoic acid(PAA) component.

Finely controlled particle size micronisation for optimum properties.

Careful formulation for optimum physical,aesthetic and handling properties.

It has ample wear resistance and all round strength to easily rival composites and amalgams.

Amalgomer

Designed to match the strength and durability of amalgam.

Sustained high level of fluoride release.Natural adhesion to tooth structureGood biocompatibility with hard set and

good working time.Minimal cavity preparation required.Mercury and metal free.Indications-

-Class III and class V cavities (particularly erosion lesions)-Posterior cavities in deciduous teeth.-Pits and fissure sealant.

It is also known as Amalgomer CR or Posterior Amalgomer.

Amalgomer CR is in a class of its own amongst glass ionomers.

It uses Amalgomer Technology to exceed 300 MPa compressive strength combined with unique ceramic reinforcement for added durability and high radiopacity.

Ceramic Reinforced Amalgomer

ACTA wear tests indicate a much lower wear rate than conventional GIC,compomers and most composites.

Erosion rates and also very low as indicated by the lactic acid jet erosion test specified in ISO 9917 (The Glass Ionomer narmative standard)

The all round strength of Amalgomer Technology also gived it excellent resistance to fracture or cracking and the high modulus allied to chemical adhesion to the tooth struture ensures low interfacial stresses.

Hence Amalgomer CR is well capable of withstanding all the stresses of the oral environment for long lasting restoration.

Class I and II cavities.Repair of Amalgam restored teeth.Base under amalgam and composite

restorations.All classes of cavity where radiopacity is a

prime requirement.Core build up.Long term temporary replacement for cusps.Minimal intervention treatment.ART technique.Repair to crown margins.

Indications of Amalgomer CR

Since the development of glass ionomer cements nearly three decades ago, these materials have found increasing applications in clinical dentistry.

Clinical experience has defined the practical advantages and disadvantages of glass ionomer cement system.

This has resulted in improved formulations and more controlled techniques.

Of course it is difficult to produce an ideal material, but with the current level of intensive research on glass ionomers, the deficiencies that exist can be eliminated, or at least reduced, resulting in an ever – improving range of materials of this type.

Conclusion

Advances in Glass-ionomer cements-Carel L. Davidson

Glass Ionomer Cement – The Different Generations-Nagaraja Upadhya P and Kishore G.(Department of Dental Materials,

Manipal College of Dental Sciences, Manipal)

Online Dental Journal-article on Giomer (Published in Aug,2008)

References