Question

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)?

Answer 1

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.