Composite veneers (also called "hybrid veneers") are laminate veneers for natural teeth. They consist of composite/composite resins (resin matrix with porcelain filler particles). The first attempts were undertaken in the 1930s (at that time without the adhesive technique).
Composite veneers share various features with porcelain veneers:
They are mainly used for aesthetic purposes. The appearance of a tooth is adapted to harmonise better with the other teeth. This includes, e.g. masking discolorations or structure anomalies of the tooth structure, correction of shape deviations (shortening, elongation, diminutive forms), malpositioning (rotation, tipping), addition of missing tooth structure (e.g. due to attrition or erosion) and closure of small gaps (diastemas). Another objective may be the temporary or permanent adjustment of the occlusal guidance (e.g. at the canines) and/or bite (bite raising).
Preparation (often after preparatory stages such as mock-up, wax-up, fabrication of try-in veneers, templates, groove cutting) is minimally invasive; veneers are generally thin (minimum 0.3 mm to maximum approx. 1 mm). In contrast to a crown, large areas of the tooth structures are preserved. In anterior teeth veneers always cover the vestibular surface (with or without incisal edge coverage); in the posterior region they generally also cover part of or the entire occlusal surface. Following try-in (if necessary with try-in pastes for optical bridging of the cement gap) the veneer is usually luted adhesively using transparent or whitish, long-term, shade-stable composite cements.
Unlike porcelain veneers, cost-effective composite veneers can also be fabricated directly intraorally (also for temporary restorations). They are not as hard and consequently less wear-resistant, but this also helps them adapt more easily to individual patient conditions. Composite veneers exhibit a higher tendency to plaque accumulation and discoloration. These material-related differences decrease with newer composite materials ("polymer porcelain"). Composite veneers can be repaired intraorally.
In addition to fabrication (using the build-up technique) of composite veneers, sometimes directly on the tooth but mainly custom-fabricated indirectly in the laboratory after impression-taking and model fabrication, systems with prefabricated composite veneers are available. These systems comprise a range of "blanks" for reproducing several versions of the individual tooth types. After respective pre-selection and minimally invasive preparation or without any preparation ("non-prep veneers"), these industrially manufactured homogeneous, surface-hardened composite veneers are customised by trimming and the addition of special composite materials before being luted adhesively.
The service life of composite veneers should exceed six years.
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Composites also composite (from the Latin componere = to compose) are tooth-coloured filling materials with plastic properties used in dental treatment. In lay terms they are often referred to as plastic fillings, also erroneously sometimes confused with ceramic… Composites also composite (from the Latin componere = to compose) are tooth-coloured filling materials with plastic properties used in dental treatment. In lay terms they are often referred to as plastic fillings, also erroneously sometimes confused with ceramic fillings due to their tooth colour. After being placed in a cavity they cure chemically or by irradiating with light or a combination of the two (dual-curing). Nowadays, composites are also used as luting materials. The working time can be regulated with light-curing systems, which is a great advantage both when placing fillings and during adhesive luting of restorations. Dual-curing luting materials are paste/paste systems with chemical and photosensitive initiators, which enable adequate curing, even in areas in which light curing is not guaranteed or controllable. Composites were manufactured in 1962 by mixing dimethacrylate (epoxy resin and methacrylic acid) with silanized quartz powder (Bowen 1963). Due to their characteristics (aesthetics and advantages of the adhesive technique) composite restorations are now used instead of amalgam fillings.
The material consists of three constituents: the resin matrix (organic component), the fillers (inorganic component) and the composite phase. The resin matrix mainly consists of Bis-GMA (bisphenol-A-glycidyldimethacrylate). As Bis-GMA is highly viscous, it is mixed in a different composition with shorter-chain monomers such as, e.g. TEGDMA (triethylene glycol dimethacrylate). The lower the proportion of Bis-GMA and the higher the proportion of TEGDMA, the higher the polymerisation shrinkage (Gonçalves et al. 2008). The use of Bis-GMA with TEGDMA increases the tensile strength but reduces the flexural strength (Asmussen & Peutzfeldt 1998). Monomers can be released from the filling material. Longer light-curing results in a better conversion rate (linking of the individual monomers) and therefore to reduced monomer release (Sideriou & Achilias 2005) The fillers are made of quartz, ceramic and/ or silicon dioxide. An increase in the amount of filler materials results in decreases in polymerisation shrinkage, coefficient of linear expansion and water absorption. In contrast, with an increase in the filler proportion there is a general rise in the compressive and tensile strengths, modulus of elasticity and wear resistance (Kim et al. 2002). The filler content in a composite is also determined by the shape of the fillers.
Minimally-invasive preparation and indiscernible composite restoration
Composite restorations Conclusion |