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A 2003 study showed that fillings have a finite lifespan: an average of 12.8 years for amalgam and 7.8 years for composite resins. [20] Fillings fail because of changes in the filling, tooth or the bond between them. Secondary cavity formation can also affect the structural integrity the original filling.
In preparing a cavity for restoration with composite resin combined with an acid etch technique, all enamel cavosurface angles should be obtuse angles. Contraindications for composite include varnish and zinc oxide-eugenol. Composite resins for Class II restorations were not indicated because of excessive occlusal wear in the 1980s and early ...
The preparation of opposing cavity walls should be cut in a way to avoid undercuts in order to gain optimum retention from the cavity shape for the indirect restoration. [20] For inlay and onlay preparations that are going to be completed with all-ceramic then these cavity shapes can be slightly over-tapered as most of the retention is gained ...
The amalgam is mixed by the dentist just before use. It remains soft for a short while after mixing, which facilitates it being snugly packed into the cavity and shaped before it sets hard. Dental amalgams were first documented in a Tang dynasty medical text written by Su Gong (苏恭) in 659, and appeared in Germany in 1528.
However, if insufficient tooth tissue remains after cavity preparation to provide such retentive features, a cement can be utilised to help retain the amalgam in the cavity. Historically, zinc phosphate and polycarboxylate cements were used for this technique; however, since the mid-1980s composite resins have been the material of choice due to ...
Compomers are resin-based materials like dental composites, and the components are largely the same.. The setting reaction is similarly a polymerisation process of resin monomers (e.g. urethane dimethacrylate) which have been modified by polyacid groups, and is induced by free radicals released from a photoinitiator such as camphorquinone.
The cavity preparation of a GIC filling is the same as a composite resin. GICs are chemically set via an acid-base reaction. Upon mixing of the material components, no light cure is needed to harden the material once placed in the cavity preparation. After the initial set, GICs still need time to fully set and harden.
Amalgam possesses greater longevity when compared to other direct restorative materials, such as composite. However, this difference has decreased with continual development of composite resins. Amalgam is typically compared to resin-based composites because many applications are similar and many physical properties and costs are comparable.