Dentistry – Apparatus – Having means to emit radiation or facilitate viewing of the...
Reexamination Certificate
1999-09-21
2001-10-30
Funk, Stephen R. (Department: 2854)
Dentistry
Apparatus
Having means to emit radiation or facilitate viewing of the...
C250S205000, C250S50400H, C315S291000, C315S307000, C315S360000
Reexamination Certificate
active
06309216
ABSTRACT:
BACKGROUND OF THE INVENTION
I. Field of the Invention
The present invention relates to a curing system for photohardenable materials of the type used in dental restoration work.
II. Description of the Prior Art
In dentistry, it is oftentimes necessary to restore certain portions of the patient's teeth. For example, such restoration may be required after removal of a cavity from the patient's teeth.
Although gold, amalgam and other metals have been used for such restoration work in the past, in many situations it is more desirable to use a photohardenable material. Such photohardenable materials have a whitish color designed to match the patient's teeth. Thus, once the photohardenable material has been placed on the affected area of the patient's teeth and cured, the restoration becomes invisible or almost invisible, and is thus aesthetically more pleasing than the previously known use of gold and/or amalgam.
There have been two previously known types of light sources used to cure photohardenable materials of the type used in dental restoration work. Specifically, argon lasers have been used to cure such photohardenable materials in a vary rapid time, typically in the range of 5 to 10 seconds. The primary disadvantage of argon lasers, however, is that they are very costly to obtain.
Because of the high cost of argon lasers, incandescent lights, such as halogen lights, have also been used as a light source in order to cure the photohardenable materials in dental applications. Such lights are advantageous over the previously known argon lasers since halogen lights cost in the range of 5-10% of the cost of a comparative argon laser.
A still further disadvantage of the use of halogen lights is that such lights degradate over a period of time. Once the power output from the light decreases, less energy, i.e. power integrated over time, from the light is obtained. Since photohardenable materials require a minimum amount of energy in order to obtain a full cure, the use of an incandescent light for an insufficient time period may result in an inadequate cure of the photohardenable material.
SUMMARY OF THE PRESENT INVENTION
The present invention provides a curing system for photohardenable materials of the type used in dental restorations which overcomes all of the above-mentioned disadvantages of the previously known devices.
In brief, the curing system of the present invention comprises an electrically powered light source which is preferably a xenon bulb or xenon arc light although other types of light sources may alternatively be used. A variable power supply is electrically connected to the light source so that, upon activation of the system, the power supply illuminates the light source. Furthermore, the power output from the light source varies as a function of the power output from the power supply and through the light source. For example, in the case of an incandescent light such as a halogen light, the voltage across the light is varied to vary the power output. Conversely, for a xenon arc light, the current is varied to vary the power output from the light.
During calibration, means, such as a photocell, are provided for determining the power output of the light source and for producing a power output signal representative thereof This power output signal is coupled as an input signal to a microprocessor or other electronic control circuit which then compares the power output signal from the photocell with a preset target value. If the power output from the light source is substantially the same as the target value, at least within predetermined thresholds, the microprocessor maintains a control signal for the power supply at its current level, and thus illumination of the light source, for a preset time period sufficient to provide enough energy to the photohardenable material to effect a complete cure of the photohardenable material.
Conversely, in the event that the power output signal from the photocell is less than the target value, the microprocessor varies the control signal to the power supply by an amount to increase the power output of the power supply and thus the power output of the light source. The microprocessor iteratively increases the power output from the power supply to the light source until either (1) the target value for the power output from the light source has been achieved or (2) the maximum power output from the power supply has been reached.
In the latter case, the microprocessor extends the duration of activation of the power supply, and thus extends the illumination of the light source, by an amount sufficient to achieve a predetermined amount of light energy from the light source. This predetermined amount of light energy is sufficient to completely cure the photohardenable material.
In the preferred embodiment, the microprocessor utilizes a lookup table stored in digital memory to determine the new time period for activation of the light source as a function of the power output signal from the photocell whenever the power supply is at its maximum current rating. The microprocessor also preferably outputs a signal to a display, such as an LED or a LCD display, representative of the time period required for complete cure of the photohardenable material. Such a display is helpful to the dentist to determine when it is economically desirable to replace the light source and thus reduce the cure time for the photohardenable material.
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American Medical Technologies, Inc.
Funk Stephen R.
Gifford, Krass, Groh Sprinkle, Anderson & Citkowski, P.C.
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