Dental devices

A flame-resistant copolymer consisting of 4 -biphenol polysulfone and biphenol A was prepared by El-Hibri et al. (4) and used as a medical or dental device as a steam sterilizable medical tray container. 

Corrosion of metallic surgical implant materials used in orthopedic, cardiovascular, and dental devices resulting in the release of metal ions to tissues, and degradation of the physical properties of polymeric implant materials due to interactions with tissue fluids and/or blood... 

Standards ISO 10993 -5 1992 and EN 30993 -5 1994. Biological testing of medical and dental devices. Tests for cytotoxicity in vitro methods. 

CFR872 Dental Devices, Part 872, Title 21-Food and Drugs, Code of Federal Regulations ... 

Several known and commonly used biomedical polymers are categorised under the USP Class VI classifications. This includes polytetrafluoroethylene (Pl FE) (used in artificial ligaments and grafts and as catheter liners), fluorinated ethylene propylene (FEP) (used in electrocautery devices and fusing sleeves), PEEK (used in implantables, orthopaedic and dental devices). For Class VI materials, as defined by the USP, the most stringent testing procedures are performed. Any substance that may have leaked from the material is usually captured in extract solutions of NaCl, 5% EtOH, cotton-seed oil or polyethylene glycol. 

The excellent hydrolytic stability of polysulfones makes them an ideal choice for use in a variety of medical and dental devices. The hydrolytic stabihty allows use in durable medical devices and components that have to be sterilized in a steam autoclave, sometimes hundreds of times over the hfe of the component. Such components include sterdization trays and cases, as well as parts of the surgical instruments themselves, such as the instrument handles. Traditionally, metals such as stainless steel have been used for this purpose. But metals are being replaced by thermoplastic materials. The use of plastics offers the ability to customize designs and colors as well as to mass-produce in a more economical fashion. For large parts, such as surgical instrument sterihzation trays, the weight... 

Miller CS, Leonelli FM, Latham E. Selective interference with pacemaker activity by electrical dental devices. Oral Surg Oral Med Oral Pathol 1998 85 33-36. 

We learned in Section 12.2 that polymers can be characterized by their physical properties. Elastomers are used as biomaterials in flexible tubing over leads for implanted heart pacemakers and as catheters (tubes implanted into the body to administer a drug or to drain fluids). Thermoplastics, such as polyethylene or polyesters, are employed as membranes in blood dialysis machines and as replacements for blood vessels. Thermoset plastics find limited but important uses. Because they are hard, inflexible, and somewhat brittle, they are most often used in dental devices or in orthopedic applications, such as in joint replacements. To fill a cavity, for example, the dentist may pack some material into the cavity, then shine an ultraviolet lamp on it. The light initiates a photochemical reaction that forms a hard, highly cross-linked thermoset polymer. 

Base metals and alloys used in medical and dental devices are corrosion-resistant due to the presence of an oxide film on the surface that is protective [49]. These materials are not corrosion-resistant initially as is evident from their positions in the electromotive force series. The galvanic series, a listing of electrode potentials measured in seawater, indicates the changes in the noble and active tendencies of these materials in practical use for this given environment. Passivity is dependent on environmental factors such as solution pH, temperature, ions, oxygen, etc. Some ways of minimizing corrosion of these materials follow. Others are given in the discussion of the types of corrosion that can occur. 

On the other hand, sometimes the desired result is not to elicit a specific response, but avoiding eliciting a foreign body reaction and the consequent rejection. This is for example the case in Ni containing NiTi shape memory alloys used in dental devices... 

PMMA is a versatile material because of its transparency and durability, and it has been widely used in a broad range of fields, such as lenses for glasses, panels for building windows, skylights, signs and displays, liquid-crystal displays (LCD), and furniture. Different methacrylate polymers are extensively used in medical and dental devices where purity and stability are critical to performance. 

Many medical and dental devices are now being assembled with cyanoacrylates to eliminate costly molding procedures. Cyanoacrylates are also being employed to eliminate the toxic solvents commonly used to bond flexibil-ized PVC in tubing joints. 

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