What is bulk fill composite?
Bulk-fill resin composites are light-cured resin composites that can be placed in increments or layers of 4 to 5 mm in depth. These materials have been available to the dental profession for several years now. Their adoption has been slow, but they are gaining popularity, and sales are increasing.
What causes polymerization shrinkage?
The polymerization shrinkage of the material can be superimposed by a temporal thermal expansion, which is caused by the heat of the reaction and the input of heat by the light source used to trigger the photo-initiation.
What is water sorption in dentistry?
The dental materials are constantly immersed in saliva, and therefore sorption and solubility occur [5,6]. The water diffuses into the material and causes a gradual expansion and volume increase. This phenomenon should counteract the contraction stress [7,8].
What is shrinkage in dentistry?
Shrinkage stress is the pressure put on the adhesive and surrounding tooth structure during the polymerization process. If this pressure exceeds the adhesive bond, or the strength of either the composite or tooth, it can cause a variety of problems, such as: Debonding resulting in internal or marginal gaps.
What factors affect polymerization?
Many factors affect the degree of polymerization of RBCs, including the shade, light curing duration, increment thickness, light unit system used, cavity diameter, cavity location, light curing tip distance from the curing RBC surface, substrate through which the light is cured (e.g., curing through ceramic, enamel, or …
What is shrinkage in polymer?
The shrinkage of plastics signifies the volume contraction of polymers during the cooling step of the processing of polymers. A small amount of shrinkage occurs after ejection as the part continues to cool and after that the part may continue to shrink very slightly until the temperature and moisture content stabilize.
What is sorption curve?
At equilibrium, the relationship between water content and equilibrium relative humidity of a material can be displayed graphically by a curve, the so-called moisture sorption isotherm. This relationship between water activity and moisture content at a given temperature is called the moisture sorption isotherm.
What does the term sorption mean?
Sorption can be defined as a phenomenon of fixation or capture of a gas or a vapor (sorbate) by a substance in condensed state (solid or liquid) called sorbent [124]. From: Solar Energy Materials and Solar Cells, 2014.
What is polymerization shrinkage in dentistry?
Polymerization shrinkage of dental resin composites is due to the fact that monomer molecules are converted into a polymer network and, therefore, exchanging van der Waals spaces in covalent bond spaces [1]. During setting of the resin composites the polymerization shrinkage induces contraction stress.
What is smart dentine replacement?
replacement. SDR, developed by Dentsply, is the first posterior composite for dentin replacement combining the handling properties of a flowable composite with minimal shrinkage stress. As a result, it can be placed in increments of up to 4mm.
What are siloranes and how are they made?
Siloranes are a combination of siloxane (known for their hydrophilicity) and oxiranes (known for their low shrinkage and stability). Polymerization of this material occurs via a cationic ring-opening reaction, which results in a lower polymerization contraction.
What are the advantages of silorane composites over polymers?
The silorane composites generate lower volume shrinkage and stress upon polymerization. It is still important to place these composites in increments due to limited depth of cure. In addition, special adhesives are needed.
What is filtek silorane?
In 2007, 3M ESPE introduced Filtek Silorane to reduce polymerization shrinkage without reducing physical and handling properties. Unlike previous composite resins that rely upon radical polymerization of methacrylates and acrylates Filtek Silorane restorative uses a new ring opening silorane chemistry.