REDM 103

Composite Resins

Composite resins are becoming the material of choice for dentists and patients because of their esthetic qualities and new advances in their strength.

Ask how many students have had composites placed in their mouths and if they are able to tell which teeth are composites by visual examination or touch.

Class III composite restoration on tooth 10.
(Courtesy of Premier Dental Products.)

 The photograph depicts composite restorations on the mesial incisal facial of tooth 9 and the mesial facial of tooth 10.

A skilled operator is able to disguise a composite restoration using color or color combination and by incorporating contours similar to the tooth’s contralateral.

Indications for using Composite Resins

• Withstand the environments of the oral cavity 
• Are easily shaped to the anatomy of a tooth 
• Match the natural tooth color 
• Can be bonded directly to the tooth surface 

What oral environments may be unfavorable for placement of a composite resin? (Poor isolation, poor oral hygiene, tremendous bruxism, and lack of use of a night guard.)

 Overall treatment-planning note: If the patient desires full-mouth whitening, it should be done before placement of any composites in an esthetic region, or the composites may no longer match after whitening.

Composition of Composite Resins

• Resin matrix 
  • Dimethacrylate, referred to as BIS-GMA 
    • Monomer used to make synthetic resins
  • Polymerization additives 
    • Allow the material to take form through a chemical process
    • Initiator
    • Accelerator
    • Retarder
    • Ultraviolet, or UV, stabilizers
• Fillers add the strength and characteristics necessary for use as a restorative material. 
• Inorganic fillers
  • Quartz 
  • Glass
  • Silica
  • Colorants
• Coupling agent strengthens the resin by chemically bonding the filler particles to the resin matrix.
  • Organosilane compound 

Dimethacrylate is a tissue irritant in its monomer state.

Polymerization is the process of bringing together multiple monomer units, using light as a catalyst.

Fillers come in many shapes and sizes and are used in different amounts to produce the desired physical and chemical properties.

Types of Composites

• Macrofilled composites 
  • Contains the largest of filler particles, providing greater strength but a duller, rougher surface
  • Rarely used today
• Microfilled composites
  • Inorganic filler: much smaller and capable of producing a highly polished, finished restoration; used primarily in anterior restoration 
• Hybrid composites
  • Contain both macrofill and microfill particles

Hybrid composites are widely used today for universal applications. They provide a happy medium of strength and polishing ability.

Polymerization of Composite Resins

• Polymerization is the process in which the resin material is changed from a plastic state into a hardened restoration.
  • Auto-curing
  • Light-curing

 Recall the definition of auto-curing. In light-curing, what determines the duration of curing?  (Manufacturer of material instructions, type of light being used, thickness and size of material being placed, shade of material being used.)

Direct Application of Composite Resins

1. The shade of the tooth is selected. 
2. The material is transferred in increments.
3. The material is subjected to light-curing.
4. The material is finished and polished.  

The shade should be chosen before the tooth is prepared because dessication throughout the procedure changes the color.

Some operators like to place the material directly into the tooth themselves with the use of the handheld applicator.

 Only 1- to 2-mm increments should be placed and light-cured at one time.

Steps in Finishing a Composite Restoration

1. Reduction of the material is completed with the use of a white stone or finishing diamond.
2. Fine finishing is completed with the use of carbide finishing burs and diamond burs. 
3. Polishing is performed with the use of medium discs, finishing with the superfine discs.
4. Finishing strips aid in the polishing
   of the interproximal surfaces. 
5. Polishing paste with a rubber cup or a diamond brush should be used.

 Proper occlusion should be reestablished first.

In addition to polishing discs, points and cups help shape the newly placed restoration.