Composites
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 essential development stages of composite materials can be illustrated as follows:
- 1933 discovery of PMMA
- 1951 PMMA-based composite
- 1955 acid-etch technique (Buonocore)
- 1962 Bowen monomer
- 1963 first composite with quartz fillers
- 1970 light-curing as an idea
- 1974 microfilled composites
- 1977 light-curing composites commercially available
- 1980 hybrid composites (literature)
- 1985 hybrid composites commercially available
- 1990 total-etch technique as a standard procedure
- 1993 "compomers"
- 1998 "ormocers"
- 2000 nanofillers
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.
Classification based on Lutz is still included in virtually every textbook and based on the differentiation according to macro, micro and hybrid composites and also describes the microfiller composites which include pre-polymers.
There are now basically three different classifications:
- according to the consistency
- according to the filler content
- according to the base chemistry (matrix)
All three versions are correct but only give a clear evaluation of the materials in their interplay as, for example different matrix components can be combined with various filler particles.
Minimally-invasive preparation and 
indiscernible composite restoration
Composite restorations
Conclusion
Development of high-performance filling materials is crucial for successful dental treatment. It is important to note that, apart from the filling materials, there are also additional aspects that are crucial for successful treatment. These are reliable and correct use of the adhesive system, a patient who performs good oral hygiene and, last but not least, a dentist who processes the material carefully and correctly. (Hickel & Manhart 2001). As in all areas of dentistry the saying "Practice makes perfect" applies.
Want to give it a try ...
... or need professional advice?
Get in touch with us or click Contact.
Word of the day
| English | German |
|---|---|
| plastic-coated | kunststoffummantelt |
Focus text of the month
Full dentures Full dentures (also called complete dentures) are removable restorations. They replace all the teeth in an edentulous jaw, mainly using prefabricated acrylic denture teeth and less… Full dentures Full dentures (also called complete dentures) are removable restorations. They replace all the teeth in an edentulous jaw, mainly using prefabricated acrylic denture teeth and less commonly made from porcelain. The denture base in the upper and lower jaw is generally made from acrylic (e.g. acrylates); in cases with particular requirements the hard palate of the upper jaw is covered by a metal palatal plate. There is no alternative restoration to full dentures without involving implants. An overdenture is a partial denture. An overdenture completely covers all elements connecting it to existing teeth or implants.
As no information regarding occlusal height, occlusal relationship, tooth position etc. can be derived from existing teeth for full dentures, step-by-step reconstruction of intermaxillary relationship and soft-tissue support, function and aesthetics using anatomical conditions is a particular challenge. The consistency of measured values such as the mandibular rest position or the extent of its variability due to tooth loss and restoration is therefore debatable. Diagnostic impressions of the jaw and, if applicable also an existing denture, are traditionally taken using stock trays for the fabrication of full dentures. Custom trays (functional trays) fabricated on the diagnostic models or existing dentures are used for taking functional impressions, after adaptation and additions (e.g. using thermoplastics, silicones). Positionally stable, slow-curing impression material (e.g. PVS) on the one hand produces different compression depending on the resilience of the mucosa, thus resulting in uniform pressure distribution to prevent pressure spots at a later stage. In addition, functional movements (swallowing, tongue, mouth, jaw and lip movements) are recorded to relieve anatomical and functional boundaries (e.g. mobile mucosal sections, fraenums or soft palate). The aim with full dentures in the upper jaw, therefore, is to achieve suction adhesion (distal post dam on the junction between the hard and soft palate, the palatal vibrating line); in the lower jaw the least objective is to have the denture rest in position.
Bite registration and determination of the midline, occlusal plane and height are completed using templates with bite rims or arrow point tracing; these are checked, for example, using speech tests. Facebow transfer can be used for arbitrary hinge axis determination. A try-in of the prefabricated denture teeth set up in wax on the acrylic baseplate enables a check of the aesthetics, retention, occlusion, articulation and speech function prior to finishing. The denture is finished in the dental laboratory. Various procedures are used with cold and heat-curing acrylics, pressing, packing, syringing and pouring, flasks or overcasts etc. Following final adjustment of the occlusion and articulation, trimming and polishing the denture is fitted in the patient's mouth.
In recent times this sequence with five to six appointments, which has been established for decades, has been considerably reduced (to two to three appointments) thanks to extensive digitisation. Different manufacturers offer the transfer of data acquired from the patient into a computer-supported virtual system. Digitised patient anatomy and prefabricated teeth or dental arches are placed in relationship to each other in a virtual articulator using CAD programmes and the denture base is then milled from a blank using a CAM process. The dental arches are either integrated in the milling blank pre-set (full denture is fabricated right away) or set up using prefabricated teeth (wax try-in and adjustment possible). |
Occlusal view of previous/new full dentures
Full dentures viewed from the fitting surfaces
Full dentures, lateral view