Electric toothbrushes
Collective term for electrically operated devices used for individual oral hygiene at home. They generally consist of a minimum of two components: a replaceable brush unit ("brush head", "brush attachment") is attached to a handle ("handpiece").
Nowadays, with cheap "disposable products" the power supply for the integrated electric motor is produced by batteries (non-rechargeable) and with more high-quality products (in an inductive base station) by rechargeable batteries ("accus").
The vibration, rotation or oscillation frequency of the majority of units is in the range of 5.000/min. to 50.000/min. This causes all electric toothbrushes to produce a sonic (humming) sound. Frequencies above the auditory threshold of humans (approx. 20.000 vibrations/sec.) are described as ultrasonic. Practically all electric toothbrushes are therefore sonic toothbrushes and not ultrasonic toothbrushes even if they are described as such. The cleaning effect of these devices is always based on the mechanical movement of the bristles in combination with the cleaning particles and active ingredients of toothpastes. More recently "genuine" ultrasonic toothbrushes have become available, which clean according to the different principle (already in use for many years for removing calculus) of cavitation (production of minute air bubbles; pressure peaks are produced during their destruction).
Selectable "cleaning programmes" and a range of different-shaped brush heads are intended to cater for the different requirements of the various groups of users (e.g. with stubborn plaque build-up, discoloration, fixed restorations or orthodontic appliances).
According to independent studies, the efficiency of electric toothbrushes (in particular for plaque reduction, but also for preventing and combating gingivitis, discoloration etc.) is not generally better than that of manual toothbrushes. However, the results of some, more recent studies have indicated that they are slightly superior for certain movement patterns (e.g. oscillating-rotating).
Some modern devices also have timers or displays, intended to improve cleaning motivation and perseverance ("compliance") or warn about excessive cleaning pressure (exerted on the brush).
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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 |