NewsletterA dental curing light is a piece of dental equipment that is used for polymerization of light cure resin based composites.[1] It can be used on several different dental materials that are curable by light. The light used falls under the visible blue light spectrum. This light is delivered over a range of wavelengths and varies for each type of device. There are four basic types of dental curing lights; the Tungsten halogen and light-emitting diode (LED), plasma arc curing (PAC), and laser. The two main dental curing lights are the halogen and LED.
In the early 1960s, the first light curing resin composites were introduced.[2] This led to the development of the first curing light. The first dental curing light was developed in the 1970s. It was the Nuva Light (developed by Dentsply/Caulk) and used ultra violet light in order to cure the material.[3] This was discontinued because of the use of UV light. Also, these lights were not very effective due to the shorter wavelengths that limited the depth of cure.[3] During the early 1980s advances in the area of visible light curing took place. This advancement led to a curing device that now uses blue light. The next type of curing light that developed was the quartz-halogen bulb.[4]This device had longer wavelengths of the visible light spectrum and allowed for greater penetrating curing light and light energy.[3] The halogen curing light replaced the UV curing light. The 1990s presented great improvements in light curing devices. It improved previous devices as well as developing new devices. As dental restorative materials advanced, so did the technology to cure these materials. The main focus was to improve the intensity in order to be able to cure faster and deeper.
In 1998 the plasma arc curing light was introduced.[5] It uses a high intensity light source,a fluorescent bulb containing plasma, in order to cure the resin-based composite. It claimed to be able to cure material in 3 seconds. However, on average it took between 3 to 5 seconds. This light was highly popular but the negatives out weighed the positives. The initial price was three times higher than the halogen and LED lights. Among other things, the maintenance of this light was also expensive. The latest advancement in technology comes with the LED curing light. The technology for this light has been available for the last 14 years but was put into use at the turn of the 21st century. Advances in this technology are still taking place.
The Tungsten halogen curing light, also known as simply “halogen curing light” is the most frequent polymerization source used in dental offices.[6] In order for the light to be produced, an electric current flows through a thin tungsten filament, which functions as aresistor.[6] This resistor is then “heated to temperatures of about 3,000 Kelvin, it becomes incandescent and emits infrared and electromagnetic radiation in the form of visible light”.[6] It provides a blue light of about 400 and 500 nm, with an intensity of 400- 600 mW cm^-2.[7] This curing light however has a downfall. First of which is the high temperatures that the filament generates. This requires for the curing light to have a ventilating fan installed in order to “force airflow through slots in the casing”.[6] This results in the curing light to be bigger in size, in order to house the fan. The fan generates a sound that can be found to be noisy and the light requires a great input of power; thus, must be plugged into a power source. This results in this curing light not being cordless. Furthermore, this light requires frequent monitoring and replacing of the actual curing light bulb because of the high temperatures that are reached. Also, the time needed to fully cure the material is much more than the LED curing light.
Also known as LED-curing light, it uses light-emitting diodes that produce blue light that cures the dental material. This light uses a gallium nitride as a semiconductor that is the basis for the blue emission.[6] “In LED’s, a voltage is applied across the junctions of two doped semi- conductors (n-doped and p-doped), resulting in the generation and emission of light in a specific wavelength range. By controlling the chemical composition of the semiconductor combination, one can control the wavelength range.12 The dental LED curing lights use LED’s that produce a narrow spectrum of blue light in the 400- to 500-nm range (with a peak wavelength of about 460nm), which is the useful energy range for activating the CPQ molecule most commonly used to initiate the photopolymerization of dental monomers.[6]” These curing lights are much different than the Halogen curing lights. They are more lightweight, portable and effective. The heat generated from LED curing lights is much less which means it does not require a fan to cool it. Now that the fan is not needed, a more lightweight and smaller light could be designed. The portability of it comes from the low consumption of power. The LED can now use rechargeable batteries, making it much more comfortable and easier to use.
The latest LED curing light is the HP (high powered LED light). This newest light is an updated LED curing light and can cure material much faster than the Halogen and the previous LED curing lights. It uses a single high-intensity blue LED that uses a larger semi conductor crystal.[6] This increased the light intensity and the area that is illuminated with an output of 1,000 mW/cm2.[6] In order for this light to emit such a high intensity light, it uses a highly reflective mirror film that “consists of multilayer polymer film technology.[6]
The Halogen and LED curing light are operated similarly. In order to turn on the blue light, both of these lights require the operator to press a button or a trigger. For the halogen curing lights, there is a trigger that is pressed. The older models require the operator to hold down the trigger for the light to emit unlike newer models that only require that the triggered be pressed once. For the LED lights, a button is placed on the device. For both the newer models of the halogen lights and the LED lights, after the trigger or button is pressed, the light will remain on until the timer expires. After the light is on, it is placed directly over the tooth that has the material in it until it is cured.
The development of the curing light greatly changed dentistry. Prior to the development of the dental curing light, different materials had to be used in order to have a resin based composite material placed in a tooth. The material used prior to this development was a self-curing resin material. These materials were mixed separately; an A material and a B material. The A material was the base and the B material was the catalyst. This resin material was mixed first and then placed in the tooth. It is then self-cured/hardened fully after 30 – 60 seconds. This presented several issues to the dentist. The first being that the dentist did not have control over how quick the material was cured. Once mixed the curing process started. This resulted in the dentist having to quickly and properly place the material in the tooth. If the material was not properly placed, then the material had to be excavated and the process started over again. The development of this new technology gave way to new light activated resin materials. These new materials are much different to the previous ones. These materials do not need to be mixed and can be dispensed directly into the site. This new malleable resin material can only be fully cured/harden with a dental curing light. This presents new advantages for dentists. The time constraint is now lifted and the dentist can now assure that the material is properly placed.
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