In: Anatomy and Physiology
1- Describe four ways to decrease polymerization shrinkage associated with composite resin?
2. Describe briefly how to restore deep caries cavities (regarding to pulp and materials)?
1. Conposite resin has been used as a binding cement in
dentistry. The polymerization shrinkage of the resin material has
led to decreased bond strength. It has also resulted some other
complications such as enamel crack, marginal and
internal gaps and cusp deflation.
Some of the techniques can reduce the polymerization shrinkage such
as :
a. Techniques of composite insertion : inserting the resin
composite in an incremental way reduce polymerization shrinkage.
Incremental composite insertion in oblique or horizontal way to
restore a cavity help decrease polymerization shrinkage.
b. Modifying the formulation of conposite resin by mixing a monomer
help reduce polymerization shrinkage. Use of Dimethacrylate monomer
is helpful.
c. Use of stress absorbing intermediate layer with resin composite
with low elastic modulus help reduce polymerization
shrinkage.
d. Modification of light sctivating protocol also helps to decrease
polymerization shrinkage. The aproaches used are soft start and
pulse delay. This allows for prolonged period for which composite
can flow anemd reduce shrinkage.
2. Deep caries develop due to attack of acid producing micro
organisms on the tooth dentin which results in loss of tooth
bone.
Once a deep caries develop the excavation of the caries is done.
The excavation is done till a firm consistent uninfected dentin is
seen.
The area is then air dried. A liner is then placed over the dentin.
Calcium hydroxide is usually used as a liner and placed directly
over the pulp tissue.
Resin modified glass ionomer is placed over the liner that extends
over to dentin.
A permanent restoration is then placed ehich is help in place by
using different dentin bonding system.