COMPOSITES AND NEWER COMPOSITE MATERIALS CONTENTS Introduction History Classification Composition Different Types in Brief Newer Materials • Direct • Indirect • Miscellaneous INTRODUCTION Dissension in some form has always had a role in dentistry. The composite resin restoration present the practitioners with a number of uncertainties and because of this the dental profession finds itself in the middle of an emotional deuce.
ESTHETICS, has become a chief priority for patients today. These advertisings have led to almost a large percentage of patients refuse metallic restorations in their mouth and demand restoration called white filling. To add to the problems, those advertisers have joined hands with the zealots of dental community having holistic approach w/w cry about the newer ending controversy of “MERCURY TOXICITY”. However, till date, as stated by Ronald Jordan (JADA 91), there has not been a shred of scientifically valid evidence directly lining dental amalgam with systemic diseases of any kinds including multiple sclerosis, arthritis etc. although some very rare instances are reported. Thus condemning the use of these time honored metallic restoration, the zealots now replace them with esthetic composite restorations. I say “time honoured” metallic restorations because these restorations, especially amalgam has certain advantages to with stand the test or time: like (Skinners Pg. 292; S. Rao Pg. 168). a. Ease of placement.
b. Not overly technique sensitive. c. Good mechanical properties. d. Excellent wear resistance. e. Self-sealing ability wit ageing of restoration. f. Have reasonably long service life. The amalgam restoration, would enjoy successfully in the future too, since recently developed materials actually bond dental amalgam to both enamel and dentin. However, due to an increase in the esthetic and cosmetic conscious outlook, composites were developed. Keeping this criteria in mind, I would be discussing the recent trends in composites, stressing more on the posterior composite materials. How did these esthetic materials develop? HISTORY Modern day esthetic restoratives are used in every segment of the mouth and are expected to perform in areas of considerable stress. The development of direct esthetic 3
materials really began in 1871 with silicate cements. It was followed in 1937 by advent of unfilled resins advocated for esthetic obturations since 1945. development of modern dental composite started in late 1950’s and early 1960’s when “BOWEN” began experimenting to reinforce epoxy resins with filler particles, which eliminated in development of a BIS-GMA molecule. Also the introduction of acid-etch technique by BUONOCORE in 1955 extended the use of composite resins substantially. Interestingly it was Kelzer Gulbh German that generated a patent leading to the development of moldable resins after which many new material have continued to play a role in restorative and prosthetic
alternatives to amalgam included: 1. Better esthetics. 2. Marginal integrity. 3. Low thermal conductivity. 4. Resistance to tarnish and corrosion. 5. Nil / minimal cavity preparation.
However, at the beginning, the initial claims for their success were based on short term clinical studies and laboratory tests, failures of these materials, in the form of colour change, wear, microleakage and secondary caries began to appear in approx 2 years, major reasons being the dynamic forces of mastication associated with ther factors in the oral environment, which were not included in the shortterm laboratory studies. Thus the composite underwent compositional improvements from 70’s to 90’s. Thankfully, as of today, materials with: a) improved colour, b) resistance to microleakage c) reduced wear and d) lower incidence of rel caries are made available with addition of fillers. DEFINITIONS According to Skinner: Skinner defined composite as “a compound of two or more distinctly different materials with properties that are superior to or intermediate to those of individual constituents”. According to Philips and Lutz: They defined composite as “3-dimensional
different materials with a distinct interface”.
According to McCabe : “A composite material is a product which consists of atleast two distinct phases normally formed by blending together components having different structures and properties. CLASSIFICATIONS: I.
The commonly used is the simplest classification given by SKINNER. a) Traditional / conventional – 8-12µm. b) Small particle filled. – 1-5µm. c) Microfilled particles – 0.04-0.9µm. d) Hybrid composites – 0.6-1µm.
According to CRAIG:
TYPE I: a) Class 1 – Macrosized particles – 8-25µ b) Class 2 – Mini size particles – 1-8µ c) Class 3 – Micro size particles – 0.04-0.2µ d) Class 4 – Blend of macro and micro – 0.04-10µ 6
TYPE II Class
unreinforced resin matrix). Class 2: Macrosize unreinforced particles 10-20µ (organic in reinforced resin matrix 0.04-0.2µ organic). III.
According to PHILIPS and LUTZ: Earlier
According to DCNA: 1. Conventional composite 15-35µm. 2. Intermediate composite 1-0.5µm 3. Microfilled composite 0.04-0.9µm.
According to William’s : Based of filler content: a) Densified Composite Resins
(Inorganic filled <60% wt)
b) Miscellaneous composite resin Prepolymerized resin and inorganic fillers. c) Heterogenous microfine composite Contains spherical polymerized filler. Still in experimental stage are: d) Fine midway. e) Fine compact filled composites. f) Fiber reinforced resins. (Glass ceramic fibers of length – 300µm).
According to Ferrane: Filler
Range 0.1-3µm Midsize hybrid
Quartz / glass
VII. According to BAYNE and HEYMAN Megafill
VIII. According to MARZOUK 9
Fillers 1 s t generation
Size of fill
E.g. Quartz fused silica. Silicate glasses. Crystalline lithium
Aluminium silicate glasses Barium aluminium borosilicate 2 n d generation
0.05-0.1 50% by vol.
3 r d generation: Hybrid composite with micro and microceramic in 75: 25 ratio. 4th generation: Hybrid contains reinforced composite marcoparticles reinforced phase of micro-colloidal ceramics. 5 t h generation: Hybrid in which continuous resin phase is reinforced with microceramic and microspherical highly reinforced heat cured composite particles. 6 t h generation: Hybrid composite in which continues phase is reinforced with a combination of microceramics and agglomerates of sintered microcolloidal ceramics.
Based on inorganic loading: a. Heavy filler material – 75%. b. Lightly filler material – 66%.
Based on method of curing: 1. Chemical. 2. Light cure. 3. Heat cure.
Based on area: a. Anterior. b. Posterior.
COMPOSITION (Skinners) As per the definition, the composite resin has more than two or three basic constituent phase: a) Organic or the resin matrix: The most commonly used resin components are aliphatic / aromatic diacrylates: BIS-GMA (Bisphenol A-Glycidyl methacrylate) Modified BIS-GMA UrDEMA (Urethane dimethacrylate)
ďƒ˜ TEGDMA (Triethylene glycol dimethacrylate). The organic matrix also contains diluent monomers which help to attain high filler levels and produce pastes of clinically usable consistencies. These dimethacrylates allow extensive cross-linking to occur between chains thus making the resin more resistant to degradation by solvents. However, it increase the polymerization shrinkage, a factor that limits its use in composite. b) Inorganic or Fillers: As mentioned earlier â€“ Unfilled resins pose with the problem of polymerization shrinkage. To overcome this and to improve the properties of matrix material, incorporation of fillers became necessary. ďƒ It should bond well with the matrix of not it can weaken the material. Fillers are added to the resin matrix between 30-70% vol. Or 50-85wt%. Advantages:
1) It reduces the setting contraction heat evolved during polymerization shrinkage. 2) Water sorption coefficient of thermal expansion is less. 3) Improves: -
Modulus of elasticity.
Polishability of material.
TYPES OF FILLERS: 1. Quartz. 2. Fused silica. 3. Aluminium silicate. 4. Barium glasses -
Aluminium silicates. 5. Strontium glasses. 6. Borosilicates. 7. Lithium aluminium silicate. 8. Pryogenic silica. 9. Zirconium glasses. 10. Yetterbium trifluoride.
FILLER SIZE AND THEIR PRODUCTION: Basically there are 3 sizes of fillers: 1. Traditional macrofiller – 15-30µm. 2. Microfillers (pyrogenic silica) – 0.04µm. 3. Microfiller based complexes. -
(SPP) – sintered prepolymerized microfilled – 1-20
(Sph PB) – spherical polymer based microfilled – 2030.
(AMP) â€“ Agglomerated microfilled complex 1-100.