Do not stare at high brightness LEDs, because doing so may cause permanent damage to your eyes. The optics of our eyes focus visible light onto the retina, which is the light sensitive part of our eyes, similar to the way a magnifying glass can focus an image of the sun onto a piece of paper. The IEC specification was written to apply to primarily to lasers , though it also applies to LEDs. The standards mentioned above rely on measurements that can only be made with very expensive specialized equipment, though some manufacturers state the safety classification of their LEDs, under specified operating conditions, in their data sheets.  Take note of these comments on the data sheets for LEDs you may use.
I bought lots of little led light torches (white) because the light in my bedroom is too dim for me to be able to read in comfort.
Normal LED lights have 60Hz refresh rate, while rectified LED lights have 120Hz refresh rate.
Some people can detect flickers in 60Hz refresh rate, whether consciously or unconsciously.
A lot of those high intensity Cree LED flashlights (5W, 7W, 400 – 1300 Lumens and above, etc) have those little Laser stickers on the side of the lens housing warning users not to look directly into the light. In LED illuminated environment, it will affect our retina and also how long you use , how worse you will get. Dental composite resins are types of synthetic resins which are used in dentistry as restorative material or adhesives. Initially, composite restorations in dentistry were very prone to leakage and breakage due to weak compressive strength. The most desirable finish surface for a composite resin can be provided by aluminum oxide disks. As with other composite materials, a dental composite typically consists of a resin-based oligomer matrix, such as a bisphenol A-glycidyl methacrylate (BISGMA) or urethane dimethacrylate (UDMA), and an inorganic filler such as silicon dioxide (silica). The main advantage of a direct dental composite over traditional materials such as amalgam is improved aesthetics.
Composite resin restorations have several disadvantages: They are technique-sensitive meaning that without meticulous placement they may fail prematurely.
A hand-held wand that emits primary blue light (?max=450-470nm) is used to cure the resin within a dental patient's mouth.
This type of composite is cured outside the mouth, in a processing unit that is capable of delivering higher intensities and levels of energy than handheld lights can. As a result, full crowns and even bridges (replacing multiple teeth) can be fabricated with these systems. Composite resins have a notorious reputation for shrinking upon curing, however, uses as a dental restorative material focus on low shrinkage composites.
Phototherapy lights are used for psoriasis light therapy, vitiligo, or other conditions is safe for children, pregnant and nursing women, and even immuno-suppressed individuals. Phototherapy treatment lights in your doctor's office and a home uvb phototherapy unit have the same high clearance and remission rates. The cost of a home phototherapy unit is significantly less than one 12-week course of biologic treatment. International Shipping - items may be subject to customs processing depending on the item's declared value. Your country's customs office can offer more details, or visit eBay's page on international trade. Estimated delivery dates - opens in a new window or tab include seller's handling time, origin ZIP Code, destination ZIP Code and time of acceptance and will depend on shipping service selected and receipt of cleared payment - opens in a new window or tab. This item will be shipped through the Global Shipping Program and includes international tracking. Just as the piece of paper might smolder and catch fire, a light that is brightly focused on your retina can cook and thus permanently damage your eye.

These are intended to illuminate large areas, and for those designed for direct view applications, to be viewed at a significant distance.
A new standard, IEC TR 60825,  is in development that promises that includes a section that is intended to address LEDs directly. After a little while I noticed a flicker in my right eye, had my eyes examined by an optometrist who found nothing amiss.
All experiments were reviewed and approved by the Animal Care and Use Committee in Chung Shan Medical University.
Synthetic resins evolved as restorative materials since they were insoluble, aesthetic, insensitive to dehydration, easy to manipulate and reasonably inexpensive.
In the 1990s and 2000s, composites were greatly improved and are said to have a compression strength sufficient for use in posterior teeth.
Classically, Class III composite preparations were required to have retention points placed entirely in dentin.
Compositions vary widely, with proprietary mixes of resins forming the matrix, as well as engineered filler glasses and glass ceramics. Composites can be made in a wide range of tooth colors allowing near invisible restoration of teeth. Polymerization is accomplished typically with a hand held curing light that emits specific wavelengths keyed to the initiator and catalyst packages involved.
Composite shrinkage can be reduced by altering the molecular and bulk composition of the resin. Provider of home UV light Phototherapy equipment and UV light Phototherapy systems for home, doctors' offices & clinics. We can answer questions, help you select the right home phototherapy unit, and work with you to get the highest insurance reimbursement.
Contact the seller- opens in a new window or tab and request a shipping method to your location. These LEDs can be identified by packaging or mountings that are designed to carry heat away from the junction.
I had wanted to purchase LEDs but am having doubts now, as at some stage people will look at the lights e.g. Composite resins are most commonly composed of Bis-GMA monomers or some Bis-GMA analog, a filler material such as silica and in most current applications, a photoinitiator.
Today's composite resins have low polymerization shrinkage and low coefficients of thermal shrinkage, which allows them to be placed in bulk while maintaining good adaptation to cavity walls. A syringe was used for placing composite resin because the possibility of trapping air in a restoration was minimized. When using a curing light, the light should be held as close to the resin surface as possible, a shield should be placed between the light tip and the operator's eyes, and that curing time should be increased for darker resin shades.
For example, UltraSeal XT Plus uses Bis-GMA without dimethacrylate and was found to have a shrinkage of 5.63%, 30 minutes after curing. If you reside in an EU member state besides UK, import VAT on this purchase is not recoverable. LEDs without these special thermal management features can also pose a danger when operated beyond their specified maximum current.
I’m wondering if that is the explanation for my problem, although It seems strange that only one eye is affected.
Dimethacrylates are also commonly added to achieve certain physical properties such as flowability.
The placement of composite requires meticulous attention to procedure or it may fail prematurely. Modern techniques vary, but conventional wisdom states that because there have been great increases in bonding strength due to the use of dentin primers in the late 1990s, physical retention is not needed except for the most extreme of cases.

The discovery of acid etching (producing enamel irregularities ranging from 5-30 micrometers in depth) of teeth to allow a micromechanical bond to the tooth allows good adhesion of the restoration to the tooth. Light cured resins provide denser restorations than self-cured resins because no mixing is required that might introduce air bubble porosity.
For example, an entire crown can be cured in a single process cycle in an extra-oral curing unit, compared to a millimeter layer of a filling.
Further tailoring of physical properties is achieved by formulating unique concentrations of each constituent. The tooth must be kept perfectly dry during placement or the resin will likely fail to adhere to the tooth.
Primers allow the dentin's collagen fibers to be "sandwiched" into the resin, resulting in a superior physical and chemical bond of the filling to the tooth. This means that unlike silver filling there is no need for the dentist to create retentive features destroying healthy tooth. Unlike amalgam which essentially just fills a hole and requires retention features to hold the filling, composite cavity restorations when used with dentin and enamel bonding techniques restore the tooth back to near its original physical integrity. Composites are placed while still in a soft, dough-like state, but when exposed to light of a certain blue wavelength (typically 470 nm, with traces of UV[1]), they polymerize and harden into the solid filling. Indeed, composite usage was highly controversial in the dental field until primer technology was standardized in the mid to late 1990s.
The acid-etch adhesion prevents micro leakage; however, all white fillings will eventually leak slightly. Nevertheless, time to failure is still longer for amalgam, and it has remained a superior restorative material over resin-base composites, but with poor aesthetic qualities. It is challenging to harden all of the composite, since the light often does not penetrate more than 2–3 mm into the composite.
The enamel margin of a composite resin preparation should be beveled in order to improve aesthetics and expose the ends of the enamel rods for acid attack. Very high bond strengths to tooth structure, both enamel and dentin, can be achieved with the current generation of dentin bonding agents. If too thick an amount of composite is placed in the tooth, the composite will remain partially soft, and this soft unpolymerized composite could ultimately irritate or kill the tooth's nerve. The correct technique of enamel etching prior to placement of a composite resin restoration includes etching with 30%-50% phosphoric acid and rinsing thoroughly with water and drying with air only. The dentist should place composite in a deep filling in numerous increments, curing each 2–3 mm section fully before adding the next. In preparing a cavity for restoration with composite resin combined with an acid etch technique, all enamel cavosurface angles should be obtuse angles.
In addition, the clinician must be careful to adjust the bite of the composite filling, which can be tricky to do.
If the filling is too high, even by a subtle amount, that could lead to chewing sensitivity on the tooth.
Composite resins for Class IIs were not indicated because of excessive occlusal wear in the 1980s and early 1990s. A properly placed composite is comfortable, aesthetically pleasing, strong and durable, and could last 10 years or more. Modern bonding techniques and the increasing unpopularity of amalgam filling material have made composites more attractive for Class II restorations.

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