A safe, quick, efficient and easy to use lighting device for teeth whitening is disclosed. The lighting device has a plurality of LEDs that emit lights of a wavelength ranging between 490 nm to 505 nm. The color of the light may be blue, blue green, green, aqua or cyan. A mouth tray may be prefilled with a predetermined quantity of whitening gel and is attached firmly to the lighting device and placed inside the mouth of the patient. The lighting device switches ON only when new mouth tray is attached to it and it switches OFF after using it for 30 minutes. Teeth are cleaned from the front and inner side since the gel spreads throughout the jaw of the patient. The same procedure may be repeated after 24 hours since the procedure doesnt cause tooth sensitivity or tissue burning and is safe even if used frequently and gives instant results.