EFFECT OF VIBRATION

Effect of Vibration during Placement of Composite Resin Restorations



Effect Of Vibration During Placement Of Composite Resin Restorations

Chapter 1

Introduction:

Despite the fact that resin composite materials (RC) have advanced throughout the last years, there are still problems related to polymerization shrinkage which occurs throughout conversion of the monomer molecules into a polymer network. The magnitude of the shrinkage depends on the resin matrix formulation and amount of filler used in the RC. The amount of stress generated throughout the setting of the adhesive restoration is related to the obstruction of the setting shrinkage in the cavity. It depends on variables like the visco-elastic properties, i.e. the modulus of elasticity of the shrinking material, the relationship between bonded and free surfaces of the restoration (configuration factor), the curing lightweight intensity and the stage of porosity incorporated. The evolved stress is proportional to the capacity of the resin composite cured. Restricting the capacity in so called sandwich or laminate restorations has thus been proposed to advance the interfacial adaptation of posterior .Materials, which show a higher stage of elastic deformation throughout the early stage of setting, for example the glass ionomer cements (GIC) and the poly acid changed resin composites  (PMRC), can ease contraction stresses in RC laminate restorations. Curing techniques with decreased lightweight intensity have been suggested to decrease contraction stress. In the two-phase soft-start curing method, an initial time span of reduced intensity lightweight activation allows for increased flow of the RC and decreased stress formation on the bond. This is pursued by a final therapy at high intensity, to ensure adequate conversion and mechanical and physical properties. Improved marginal adaptation, without affecting the conversion rate, has been reported. The use of a laminate restoration  including a base material with a more elastic behavior may result in a better adaptation to the dentin, echoed in a more optimal clinical durability.

Purpose of Study

The purpose of this study will be to analyze effect of vibration during placement of composite resin restorations.

Significance

As the demand by patients increased for placement of esthetic restoration, so did the concern by clinician for the need of superior materials and improved technique to increase the longevity of restorative material and prevent their failure due to voids, flexural fracture and recurrent caries at the margin.This study is to prove there is higher probability of achieving better marginal adaptation and reduce voids if the instruments used can be aided by vibration forces in conjunction with the layering technique presently in use, to restore the tooth.

Chapter 2

Literature Review

Elastic properties of composite resins are of great importance for their clinical performance. The modulus of elasticity describes the slope of the stress-strain relationship for a granted material under load. A stiff composite will need a higher load to deform to the same span as a more compliant one. Composites placed in stress-bearing areas should at least be able to withstand active masticator forces. This is a strength criterion.

In working out mechanical properties of the materials, the elastic modulus (as a measure of rigidity) has several advantages ...