Dental polishers
Dental Polishers
In dentistry and dental technology very different materials require smoothing and polishing. This ranges from exceptionally hard natural tooth enamel to the surfaces of filling materials (composites, compomers or amalgam), fixed restorations (metal alloys or ceramics), implant components (titanium, other metals or zirconia), appliances, splints or dentures (all types of hard and soft materials).
The dental polishers used in standard handpieces are rotary instruments with a metal or plastic shank. The smoothing and polishing section of the instrument is attached to the shank – whether rigidly connected or via press-on, clamp or screw connection (e.g. with mandrels). Some polishers are not active themselves and require the additional use of polishing pastes as consumable materials (in particular for prophylaxis).
Easy, clean results are produced with all other polishers. In this case the working section is made of rubber or silicone. Abrasive materials (e.g., silicon carbide or corundum and mainly diamonds are used for very hard materials, in particular ceramics) of a suitable, selected grit size are embedded in the surface or impregnate the entire working section.
A wide range of polisher shapes is available for different applications. Typical shapes are points, cups and discs for the dental practice and wheels, cylinders/arbor bands and torpedoes for the dental laboratory.
A dental polisher
Surfaces of materials are smoothed and polished in one or more working stages. Technically, the individual processing stages vary either in the different pressure applied and/or motor speed but mainly by using abrasives/polishers with different degrees of hardness and grit sizes (specific for each stage). Polishing techniques often differentiate between two-step pre-polishing (coarse polish) and high-lustre polishing (fine polish), depending on the material, initial condition, required final state and up to three steps. The first/coarsest step is frequently a transition from preparing/contouring; at this stage significant (macroscopic) amounts of material are still removed. In the subsequent steps the main focus of the work is more on reducing (increasingly microscopic) surface irregularities (surface roughness). The final step produces a smooth surface, in general with a silky sheen or high-lustre/shining finish. Often the different colours of the polishers facilitate the assignment of specific instruments to the respective working stages. All diamond grit polishers have uniformly standardised coloured rings for identifying the different fineness of each polishing step.
To rule out cross contamination between patients in clinical dental medical applications, preference should be given to polishers, which are either suitable for sterilisation in an autoclave to ensure safe multiple use or which are designed as single-use products from the outset (use for one single patient only).
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| English | German |
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| face cutting drill | Senkfräser |
Focus text of the month
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.
Composite restorations Conclusion |
Minimally-invasive preparation and 
indiscernible composite restoration