Resin - Matrix Composites

filler - glass, quartz, or resin particles matrix - a diacrylate copolymer coupling agent - coating on glass or quartz particles

glass, quartz or polymer needed for glass or quartz fillers Resin Composites matrix filler coupling agent mostly polymer glass, quartz or polymer needed for glass or quartz fillers

Small monomer: Shrinkage Large monomer: Shrinkage When oligomer molecules are relatively small, a greater number of molecules, and consequently, a greater number of new covalent bonds are needed to form a given length of polymer. As each new bond forms, the ensemble of molecules shrinks a tiny bit. Reducing the number of molecules needed to make a given length of molecule, thereby reduces the net shrinkage.

BIS-GMA oligomer Resin-matrix composites - matrix oligomers Polymer chains can grow from each of the diacrylate groups. When this occurs the chains are cross linked by the chain in the middle of the molecule. C H 3 O methacrylate group BIS-GMA oligomer

Resin-matrix composites - matrix oligomers H H C H H H C H C 3 3 C O N C C C O C N O O C C H C H H C O H O 3 H C 3 O O 3 methacrylate urethane urethane methacrylate group group urethane dimethacrylate oligomer

Oligomer / Monomer MMA TEGMA BIS-GMA UDMA Shrinkage (Vol. %) 20.6 13.8 4.4

Resin Composite Aelitefil (Bisco) Herculite (Kerr) Pertac II (Espe) TPH Spectrum (Caulk) Z100 (3M) Shrinkage (Vol. %) 3.7 3.5 2.7

Coupling Agent

- methacryloxypropyltrimethoxy silane methacrylate group H C H 3 C C C O C H 3 O H H O H C C C S i O C H 3 H H H O silane C H 3 - methacryloxypropyltrimethoxy silane

C H 3 O S i + 3 H2O

C H 3 O S i + 3 CH3 OH silanol group

O H O S i H O H S i O O S i O H O S i C H O S i Glass or Quartz Filler 3 O S i O H O S i H O H S i O Glass or Quartz Filler Particle water is byproduct O S i O H O S i

O H O S i H O H S i O O S i O S i C H O S i Can copolymerize with resin composite siloxane primary bond O H C H 3 O S i O S i H O H S i O Glass or Quartz Filler Particle O S i O S i

Resin composites – curing: chemically cured light cured

Two-paste Resin Composites base paste catalyst paste base catalyst oligomer diluent filler activator initiator

Typical Two-paste Resin Composite Base Paste (wt. %) Catalyst Paste Bis-GMA 16 Diluent (e.g., TEGDMA) 6 5 Filler – glass, quartz 76 Activator – tertiary amine 1 - Initiator – BPO 0.5 Pigments & hydroquinone Trace UV absorber Estimates based on Ruyter & Sjovik: Acta Odontol Scand 1981:39; 133-146.

Single paste resin composites: oligomer diluent filler initiator system

Resin composite direct restorative materials: Single-dose capsule in syringe Squeezing resin composite from capsule

Resin composite direct restorative materials: Curing light Cure

H C C H C H O O Addition polymerization - initiator camphoroquinone 3

Light-cured composites chemistry: Visible light excites the ketone (CQ) - this alone could initiate polymerization Excited CQ can extract electrons from adjacent reducing agents (tertiary amine) Result is three free radicals: one from the CQ and two from the amine

Advantages of light-cured composites: Better surface cure Fewer voids (no mixing) Better color stability Potential for reduced net setting contraction Better esthetics is possible

Completely cross-linked BIS-GMA H 3 O O C O R O C C H 3 O O C O R O C C H 3 O O H C C O R O C C H 3 3 O O H C C O R O C C H 3 3 O O H C C O R O C C H 3 3 O O H C C O R O C C H 3 3 O O H C C O R O C 3

As the polymer becomes more viscous, it becomes less and less likely that both ends of dimethacrylate molecules will be incor-porated in polymer chains. The percentage of cross links formed is call the degree of conversion. polymerization dimethacrylate oligomer 100% conversion, as shown in the previous slide, is not achieved. Actual degrees of con-version range between 35 & 55 %.

Filler Particles

Benefits of filler particles: increase strength increase hardness increase translucency decrease water absorption decrease total contraction

Types of resin composite: large particle small particle microfilled hybrid

Types of resin composite: large particle small particle microfilled hybrid

Types of resin composite: large particle small particle microfilled hybrid

Types of composite – small particle: 0.25 – 2.5 m quartz or glass particles matrix is diacrylate polymer – also filled with 0.05 m colloidal silica particles

small particle resin composites glass or quartz 1 m resin matrix + 0.05 m SiO2

Glass & Quartz filler particles: crystalline - silicon dioxide non-radiopaque composite very hard glasses contain heavy metals – Sr, Ba, Al, Zn radiopaque composite fairly hard

Types of resin composite: large particle small particle microfilled hybrid

Types of composite – microfilled: 3 – 10 m prepolymerized chunks – the chucks are densely filled with 0.05 m colloidal silica particles matrix is diacrylate polymer – also filled, but less densely, with colloidal silica particles

microfilled resin composites: resin matrix + 0.05 m SiO2 prepolymerized chunk + 0.05 m SiO2

making prepolymerized chunks - 1 mix colloidal silica, diacrylate resin, & chloroform  chloroform helps disperse the silica evaporate the chloroform  produces dense silica & resin paste heat cure the the resin  gives solid bock of resin with silica filler densely dispersed within it

making prepolymerized chunks - 2 heat cure the the resin  gives solid bock of resin with silica filler densely dispersed within it break up resin block  screen the powder until you have 10 to 100 m particles

percent of colloidal silica that can be added is limited: small particle size - ~ 0.05 m high surface area per volume of particle groups of particles tend to clump together quickly increases viscosity of resin - vol. % that can be added is limited to keep the resin composite plastic while adding colloidal silica, the percent diluent is increased

percent diluent in the resin matrix: wt. % wt. % oligomer diluent microfilled 35 55 resin composites all other 72 22

( TEGMA ) Resin Composites - diluents O C H N 3 N N = 1, ethylene glycol dimethacrylate N = 2, triethylene glycol dimethacrylate ( TEGMA )

inorganic filler particle content: wt. % vol. % microfilled 35 - 51 20 - 37 resin composites all other 65 - 80 45 - 55

Types of resin composite: large particle small particle microfilled hybrid

Types of composite – hybrid: 3 – 10 m prepolymerized chunks – the chucks are densely filled with 0.05 m colloidal silica particles 0.25 – 2.5 m quartz or glass particles matrix is diacrylate polymer – also filled, but less densely, with colloidal silica particles

hybrid resin composites: glass or quartz resin matrix + 0.05 m SiO2 prepolymerized chunk + 0.05 m SiO2

Much more flexible

open margins

Low T: composite contracts – fluid sucked in. fluid in fluid in

Higher T: composite expands – fluid forced out. fluid out fluid out

Low T: composite contracts – fluid sucked in. fluid in fluid in

Higher T: composite expands – fluid forced out. fluid out fluid out

wear of resin composites: generalized wear contact area wear generalized wear An “Adaptic” posterior resin composite 2 years. contact area wear

Occlusal wear of posterior resin composites: generalized wear initial surface worn surface

marginal fracture occlusal contact area wear

the resin matrix is soft; it wears preferentially glass or quartz particles are very hard

As the average size of the holes left behind by plucked- out particles decreases, the wear rate decreases. Particles that are very close together may protect the matrix resin between them from wear.

Estilux Posterior at 14 months Estilux Posterior at 37 months

A hybrid composite, Estilux Posterior, at 36 months.

A hybrid composite, Estilux Posterior, at 36 months showing pre-polymerized chucks that have worn less than the surrounding matrix.

Wear in a microfilled resin composite (Silux) at 24 months Wear in a microfilled resin composite (Silux) at 24 months. Center of restoration. Marginal fracture in a Silux at 24 months.

amalgam small particle < 3.6 um microfills hybrids

Light Curing Resin Composites

Addition polymerization – initiation: C H 3 O + free radical A

H C C H C H O O Addition polymerization - initiator camphoroquinone 3

Resin Composites - light curing: Types of light source: quartz-tungsten-halogen (QTH) plasma arc (PAC lights) argon laser light-emitting diodes (LEDs) 14 – 18 s * 3 s * 5 s * 14 – 18 s * mean curing time for 2 mm thickness; 55 colors of 5 RCs; CRA Newsletter; 1998;22(12):2-3.

Resin Composites - light curing: Types of light source: quartz-tungsten-halogen (QTH) plasma arc (PAC lights) argon laser light emitting diodes (LEDs) $ 800 – 1,600 * $ 4,000 * $10,000 $ 800 – 1600 Prices from Reality updated Mar. 2012; http://www.realityesthetics.com

Curing with QHT Lights

Composites – curing with QHT lights Most important factors in determining the degree of cure that can be achieved: exposure time light intensity

composites – deterioration of QTH sources: Tungsten evaporates from hot filament Coats quartz – darkens it Halogen gas promotes redeposition of W on the filament Do not unplug or turn off unit between cures – fan running increases filament life

polymerization dimethacrylate oligomer

adapted from Rueggeberg et al. Oper Dent 1994;19:26-32

adapted from Rueggeberg et al. Oper Dent 1994;19:26-32

adapted from Rueggeberg et al. Oper Dent 1994;19:26-32

adapted from Rueggeberg et al. Oper Dent 1994;19:26-32

Composites – curing with QHT, Factors: composite color darker shades decrease cure; not significant if curing in 2 mm increments type of composite microfilled RCs absorb light more than other types; not significant if curing in 2 mm increments

adapted from Rueggeberg et al. Amer J Dent 1993;6:91-95

adapted from Rueggeberg et al. Amer J Dent 1993;6:91-95

adapted from Rueggeberg et al. Int J Prosthod 1993;6:364-370.

adapted from Rueggeberg et al. Int J Prosthod 1993;6:364-370.

LED Curing Lights

light curing – LED advantages (v. QTH) LEDs energy over narrower range of wavelengths Longer bulb life (10,000 hrs v 100 hr) Many are cordless Small, light weight Little degradation in intensity over life Less heat generated at light tip ???

light curing – LED disadvantages (v. QTH) Some may not cure all resin composites Some may overheat and shut themselves off if you need to cure several restora-tions consecutively Does not have the track record of QTH

light curing – Evolution of LEDs 1st generation – multiple low powered LEDs – too little power 2nd generation – one high-powered LED – too narrow a spectra for some resin composites 3rd generation – use several LEDs to broaden the range of wavelengths that are cured.

There is little evidence that slow start, ramped intensity etc There is little evidence that slow start, ramped intensity etc. will reduce contraction during curing.

Questions ?