Digital SLR Camera

A digital single-lens reflex camera (digital SLR camera or DSLR) is a digital camera that uses an automatic mirror system placed between the lens and the image sensor to direct the image from the lens through the viewfinder where it can be viewed by the photographer. The viewfinder includes a matte focusing screen at its focal plane, to allow accurate focusing and to allow the light into the prism that directs the light through the viewfinder. As in film SLRs, the through-the-lens optical viewing is primarily to support accurate fast view finding with interchangeable lenses. The basic operation of a DSLR, having the mirror reflecting the image away from the image sensor except briefly during the exposure, precludes the ability to see the image in the LCD display before the picture is taken, a major difference from the way an ordinary digital camera (digicam) works. Some newer DSLR models feature an option generally known as "live preview" that does allow the image to be seen on the LCD display, although with certain limitations and with the optical viewfinder disabled. In most other respects a DSLR is similar in principle and operation to a standard digital camera; the image captured by the CCD or CMOS image sensor is processed electronically and stored on a removable memory device. The price range and extra features and options available vary widely from model to model, and newer and better models arrive every year. Here, find more information about digital camera.

Tooth Whitening

Tooth whitening or tooth bleaching is a common procedure in general dentistry but most especially in the field of cosmetic dentistry. Many people consider white teeth to be an attractive feature of a smile. A child’s deciduous teeth are generally whiter than the adult teeth that follow. As a person ages the adult teeth often become darker. This darkening is due to changes in the mineral structure of the tooth, as the enamel becomes less porous. Teeth can also become stained by bacterial pigments, foodstuffs and tobacco.

As white teeth are subconsciously associated with youth, they have become desirable. This has been made more apparent with the spread of American culture worldwide, where an especially white smile is coined a “Hollywood smile”. Tooth whitening procedure uses oxidising agents such as hydrogen peroxide or carbamide peroxide to lighten the shade of the tooth. The oxidising agent penetrates the porosities in the rod-like crystal structure of enamel and oxidises interprismatic stain deposits; over a period of time, the dentine layer, lying underneath the enamel, is also bleached.

Two main methods of Tooth whitening. The first involves applying a high concentration of oxidising agent for a short period of time, which is the so-called office bleach. This produces quick results but risks chemical burns to the soft tissues. Therefore, most in-office bleaching procedures use a light-cured protective layer that is carefully painted on the gums and papilla (the tips of the gums between the teeth). The bleaching agent is either carbamide peroxide, which breaks down in the mouth to form hydrogen peroxide, or hydrogen peroxide itself. The tooth whitening gel typically contains up to 35% hydrogen peroxide equivalent.

Tooth Whitening Methode

The second method of tooth whitening involves using a thin mouthguard or strip to hold a low concentration of oxidising agent next to the teeth for as long as several hours a day for a period of 5 to 14 days. This is known as take-home or over-the-counter whitening. This is a slower process but has fewer risks to the soft tissues. Tooth whitening agent is typically less than 10% hydrogen peroxide equivalent.

Tooth whitening typical course can produce dramatic improvements in the cosmetic appearance of most stained teeth; however, some stains do not respond to bleaching. Tetracycline staining may require prolonged whitening, as it takes longer for the bleach to reach the dentine layer. White-spot decalcifications may also be highlighted and become more noticeable. Whitening is least effective if your tooth have white spots, decay or infected gums. It is also least effective when the original tooth color is grayish. This tooth whitening process is most effective with yellow discolored teeth. Recently, efforts have been made to accelerate the tooth whitening process by the use of light. Studies have shown varying results as to the efficacy of light-activated bleaching.

Tooth whitening Side effects are include: chemical burns (if a high-concentration oxidising agent contacts unprotected tissues, which may bleach or discolor mucous membranes), sensitive teeth, and overbleaching (known in the profession as “over white teeth”). Rebound, or teeth losing the bleached effect and darkening, is also an issue, with some studies showing the rebound effect over 30 days. A recent study by Kugel et al has shown that as much as 4 shades of lightness can be lost over 30 days with light-activated/office bleaching.

Tooth Whitening Risks

The two side effects that occur most often are a temporary increase in tooth sensitivity and mild irritation of the soft tissues of the mouth, particularly the gums. Tooth sensitivity often occurs during early stages of whitening treatment. Tissue irritation most commonly results from an ill-fitting mouthpiece tray rather than the tooth-bleaching agent. Both of these conditions usually are temporary and disappear within 1 to 3 days of stopping or completing treatment.

Individuals with sensitive teeth and gums, receding gums and/or defective restorations should consult with their dentist prior to using a tooth whitening system. Anyone allergic to peroxide (the whitening agent) should not use a bleaching product. Also, prolonged exposure to bleaching agents may damage tooth enamel. This is especially the case with home remedy whitening products that contain fruit acids.

Tooth whitening process is not recommended in children under the age of 16. This is because the pulp chamber, or nerve of the tooth, is enlarged until this age. Teeth whitening under this condition could irritate the pulp or cause it to become sensitive. Tooth whitening process is also not recommended in pregnant or lactating women.

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