10 - Composite Restorations

composite preparation

conserved preparation, where composite binds to walls of preparation

• minimal removal of tooth structure

• parallel walls → composite will wear, away, shrink, or debond and will not be lodged in by convergent preparation

• retention obtained by bonding

• extend only where there is decay

composite advantages

• esthetics

• conservative removal of tooth structure

• easier, less complex tooth preparation

• insulation

• decreased microleakage

• increased short-term strength of remaining tooth structure

• no galvanism

composite disadvantages

• polymerization shrinkage

• lower fracture toughness than most indirect restorations

• more technique-sensitive than amalgam restorations and some indirect restorations

• possible greater localized wear

• unknown biocompatibility of some components

goal of composite restoration 

• restore tooth

• seal composite restoration to tooth surface to eliminate microleakage

• provide more esthetic result for facial restorations with long bevel preparations

• reduce dentin sensitivity

• increase retention of restoration

enamel vs dentin

• enamel → hydrophobic

• dentin → hydrophilic, collagen network

composite restoration game plan

• etch

• prime

• bond

• place composite 

• polish

etch

use of acid to prepare tooth’s structure for adhesive restorative material

• clear out smear layer and open dentinal tubules

• enamel → demineralizes enamel to create small microscopic “inlets” into enamel surface

• dentin → demineralizes dentin surface to expose collagen fibers of dentin

• increase surface area for bonding → bond via micromechanical retention

• 35% H₃PO₄

hydrodynamic theory

pain transmission happens when there is fluid movement within tubules

• tubules contain mechanoreceptor nerve endings near pulp

• small fluid movements account for most of the pain felt

  • fluid vibrations are sensed by odontoblasts that transmit signal to pulp and brain

smear layer vs smear plug

• smear layer → debris sitting on top of dentinal tubule

• smear plug → debris that goes into dentinal tubules

  • over-etching will cause acid to go into dentinal tubules and will cause sensitivity

  • ideal to under-etch

total etch vs selective etch

etch is 35% phosphoric acid (H₃PO₄) and is flowable to allow precise placement but viscous to prevent migration

• total etch → covers entire tooth

  • 15 seconds

• selective etch → only margin of preparation

  • on enamel only

  • 30 seconds

how to etch a tooth

1. remove cap

2. securely attach working tip

3. verify etchant flow prior to applying intraorally

4. verify color and consistency of product before applying

5. place etch on prepared tooth structures, including margins

6. leave etch on for 15 seconds for total etch, 30 seconds for selective etch

7. rinse off etch with water and high speed suction

8. dry tooth with air syringe or cotton pellets, but do not dessicate

9. recap, disinfect, and wipe down syringe

10. throw away working tip into sharps container

prime

priming prepares the tooth to allow adhesive bond to spread better on the surface of the tooth

• primer applied to etched tooth to penetrate micropores

• resin with components that are hydrophilic and hydrophobic

  • hydrophilic component (HEMA) attaches to hydrophilic dentin

  • hydrophobic component attaches to hydrophobic composite

bond

hydrophobic monomer (bisGMA and TEGDMA) applied to enamel or primed areas of dentin for chemical adherence of composite to bonding agent

• resin infiltrates into prepared (etched, demineralized, and primed) areas to create micromechanical bond

prime and bond

Peak Universal Bond and PeakSE

• available for hydrophilic and hydrophobic components combined together into dispensing bottle

• Peak Universal Bond → bond

• PeakSE → primer

• also has 0.2% chlorhexidine (no significance)

how to apply bond

• apply light coat over the entire surface of the preparation

• thin/dry for 10 seconds at ¼ to ½ air pressure

• light cure → hold about 1-2mm away from tooth

instruments for composite

• composite gun

• carpule of composite

• Hollenback spatula

• black spatula

• curing light

how to place composite

• eject small amount of composite into prepared tooth structure

• lay down the first layer, about 1mm thick

  • if there is a proximal box, lay down the proximal box first

• condense composite so it does not entrap air

• light cure for 20 seconds

• lay down the next layer, no more than 2mm thick

  • each increment layer should be added slanting towards the cavosurface margin

• condense and light cure each layer

• when 0.5mm of preparation remains, establish anatomical form of the occlusal surface

  • use acorn burnisher to contour anatomy

  • use explorer around margins to clean up excess composite, pulling from middle to buccal or lingual to get rid of overhang

• light cure after proper occlusal anatomy is obtained and after excess material at cavosurface margins has been removed

• remove Tofflemire band and wedge, and light cure for 20 seconds on both lingual and buccal

polishing

polish for smooth surface feel that is comfortable to the patient

• appearance of smooth and glossy surface for more esthetic and natural looking

• smooth surface attracts less plaque and stain

steps for polishing composite

1. finishing → contour and shape surface of composite to good anatomical form, using diamonds, carbide finishing burs, and/or course discs

2. prepolishing → remove all visible scratches to leave a matte smooth surface

3. polishing → final step to smooth surface into a shiny luster

finishing / rough grinding and contouring

initially a rough surface

• use diamond burs or carbide finishing burs with a light touch

• surface rough ground to contour

finishing class II interproximal surface

• use flame shaped diamond to remove excess material from facial and lingual embrasures

• use rolling motion when contouring interproximal portion of marginal ridge

• use finishing strips (medium course and fine ends) to smooth and polish the proximal surface

  • use strips in S-shape manner to avoid removal of contact

  • do not use in back/front or U-shaped manner, which can lead to removal of contact

prepolish / fine grinding

obtain semi-smooth (matte) surface

• use light pressure and low speed (5000-8000 rpm) with slight amount of water as lubricant

• with rubber tipped polishing tips or discs

• use flame shaped Diacom rubber abrasive points to smooth and polish occlusal surface for removing scratches

  • use more abrasive (green) followed by less abrasive (white)

• rubber bonded abrasive instruments use latch-type right angle handpiece

• Sof-Lex discs used to prepolish flat surfaces of composite restorations

  • use more abrasive (dark blue) followed by less abrasive (light blue)

  • use the opposite side of the blue mounted

final polish

final glossy surface

• Luminescence diamond polishing paste to polish occlusal surface and marginal ridge areas

  • no water and moderate pressure

• assemble felt polishing tip on to screw-end mandrel

• place generous amount of polishing paste onto felt tip, and polish entire restoration for 1-2 minutes

• wipe polishing paste off of restoration

confirm proper contact

use floss to confirm proper contact

• floss should snap loudly through contact area

• if contact is too weak, proximal area must be restored again by first removing s ome material, banding, wedging, and adding additional material

criteria for finished restoration

• smooth and shiny surface

• no pits or scratches in surface

• no voids

• natural anatomic contours, which are mirror images of contralateral tooth

• no excess composite at margins

• no ditching at margins

• strong interproximal contact, checked with floss