Reinforcing Dentistry Strength Properties, pt. 2
ANALYSIS OF STRENGTH PROPERTIES of mesh metal-composite materials used in reinforcing dentistry by M. Melikian (pt. 2)
Polymerization stresses arising as a result of polymerization shrinkage are localized not only in the composite, but can spread to the surface to which the composite is attached using an adhesive. The transfer of polymerization stresses is the cause of numerous problems. In a well-glued composite restoration, the stresses resulting from polymerization shrinkage pass through the interface with the tooth tissues and can cause deformation.
During the shrinkage of the composite material, due to the large difference between the coefficient of thermal expansion of the hard tissues of the tooth and the composite material, as a result of which an edge gap is formed between the hard tissues of the tooth and the composite, microleakage occurs. The width of the marginal slit is 2-25 microns. Oral fluid containing microorganisms, dyes, enzymes penetrate through it, which naturally causes secondary caries. The disadvantages of the composite material include their ability to absorb water, which begins 4-6 hours after filling and lasts about 28 days. As a result of this process, the bonds between the monomer and the filler are weakened, which deteriorates the resistance to stretching and bending, and the resistance to abrasion.
Elimination of the aforementioned drawbacks is an urgent problem today when performing composite restorations. This is why we have developed an innovative technology which allows for treatment, restoration/reconstruction and dental prosthetics. According to the developed technology, when restoring the integrity of the coronal part of the anterior group of teeth using a mesh metal-composite, depending on the localization, direction and depth of the defect, the mesh after sparing atraumatic odonto-preparation is installed in the restored tooth in different positions along the in relation to the direction of load.
The main purpose of our work was to study the issues of substantiating the optimal location of the mesh-contoured reinforcing frame when eliminating oblique defects in the coronal part of the anterior group of teeth. In this regard, the study and determination of the strength properties of mesh metal composite samples made of micro-hybrid composite materials, depending on the position of the mesh in relation to the load direction, was a priority task.
The chosen type of test, bending, is the main one when evaluating dental materials, since during the chewing function, vertical and horizontal forces act on the teeth. During the act of chewing, the lateral group of teeth mainly works in compression, and the anterior group of teeth in bending. The tests were carried out on equipment adapted for testing for three-point static bending. Static bending test is a type of deformation characterized by the bending of the specimen axis or the middle surface of the deformed specimen under the action of external forces Under bending deformation, the lower layers of the sample to the neutral layer experience tension, and the top are in compression. For the static bending test, 7 series of samples were made.