Light Curing Units

Light Curing Units

Give the ideal requirements for tooth-colored restorative material. Describe the composition, advantages, and disadvantages of light-cure composite restorative materials.
Or
Name all the anterior restorative materials. Describe the composition, advantages, disadvantages, and classification of light-cure composite restorative materials.
Or
Write a brief on the composition of composite resin.

Answer:

Tooth material is often lost as a result of caries and trauma. A restorative material is a material that substitutes the missing tooth structure and restores the form and function of the tooth.

• Restorative materials are aesthetic and non-aesthetic.
• Aesthetic restorative materials are tooth-colored.

Name of Anterior Restorative Materials:

• Glass ionomer cement
• Silicate cement
• Composites
• Dental ceramics

The Ideal Requirements of Tooth-colored Restorative Materials are:

1. Biologically compatible.
2. Physical property should be good.
3. Easily manipulated.
4. Aesthetic quality.
5. Economic.
6. Chemically stable in the mouth.

• Biologically compatible:
  • The material should be tasteless, odorless, non-toxic, non-irritating, and nonharmful to the oral tissues.
  • The material should be insoluble in saliva and other fluids have been taken.
  • The material should impermeable to oral fluid.
• Physical properties should be good:
  • Adequate strength
  • Resist to biting or chewing force, impact force, and excessive wear that can occur in the oral cavity.
  • The material should also be dimensionally stable under all conditions of thermal changes and variation in loading.
  • The material should also have low specific gravity and weight.
• Manipulation: Material should not produce toxic fumes.
  • It should be easy to mix, insert, shape, and cure.
  • It should be insensitive to handling procedures.
  • The final product is easy to polish, finish and also repair.
• Aesthetic properties: Material should have the ability to match the appearance of oral tissue.
• Economic: The processing method should be low-cost, and not require complex and expensive equipment.

Light-Cure Composite Restorative Material:

“A particle-filed resin consisting of a single paste that becomes polymerized through the use of photosensitive initiator system (Camphoroquinone and an amine initiator) and light source activator (visible blue light).”

Classification of Light-Cure Composite Restorative Materials: Materials whose setting is affected by the application of energy from an external source such as blue light or heat.

These materials are subdivided as:

• Materials whose use requires the energy to be applied intraorally; this group consists of direct composite materials to be directly applied to teeth.
• Materials whose use requires the energy to be applied extraoral; this group consists of indirect composite materials for the fabrication of inlays and onlays.

Composition of Light-Cure Composite Restorative Materials: The light source activator is a tungsten halogen bulb of blue light with a wavelength between 400 to 500 nm.

These are single-paste systems containing:

• Photoinitiator: Camphoroquinone (0.25 wt%)
• Amine accelerator: dimethylamino ethyl methacrylate (DEAEMA 0.15 wt %).

Advantages of Light-Cure Composite Restorative Materials:

• Mixing is not required therefore less porosity, less staining, and increased strength.
• An aliphatic amine can be used in state of an aromatic amine as required for chemically cured resin, this enhances color stability.
• Control of working time.
• Insertion and contouring is possible before curing.
• Quick cure with no air bubbles.
• Reduction in laboratory procedures.
• Reduction in patient appointments.

Disadvantages of Light-Cure Composite Restorative Materials:

• Limited curing depth (maximum 2 mm thickness).
• Relatively poor accessibility in certain posterior and interproximal locations.
• Variable exposure time because of shade (hue, value, and chroma). Longer exposure time for darker shade.