Process for destroying and removing material from teeth

Details Process for destroying and removing material from teeth Process for destroying and removing material from teeth

1991-10-10

1993-04-06

Wilson, John J.

Dentistry

Apparatus

Having means to emit radiation or facilitate viewing of the...

433215, A61C 300

Patent

active

051998700

DESCRIPTION:

BRIEF SUMMARY
BACKGROUND OF THE INVENTION

The invention relates to a process for destroying and removing tooth material by means of pulsed infrared laser beams.
It is well known that pulsed Er:YAG laser beams can be used similarly to mechanical drills to remove tooth tissue but this makes craters with very slight damage to the surrounding area in both the enamel and the dentine. The removal of dentine is more effective than the removal of enamel, and carious tissue can be particularly effectively removed (R. Hibst et al in "Laser in Medicine and Surgery"-MZV-Verlag (publisher) 4:163 to 165 (1988)).
However, light and electron microscopic examinations have shown that with use of the aforementioned pulsed infrared laser radiation, cracks and vitrification of the material surrounding the crater are avoided, but there is nevertheless a slight brownish discoloration of the crater rim in the dentine.
The object of the invention is to so improve a generic process that the remaining tissue is treated even more gently without impairing the effectiveness of the material removal by the laser radiation.


SUMMARY OF THE INVENTION

This object is accomplished in accordance with the invention in a process of the kind described at the beginning by the tooth material being covered prior to or during the irradiation with the laser beams with a layer of liquid of between 10 and 200 micrometers, in particular between 30 and 60 micrometers, thickness which absorbs the laser radiation.
Surprisingly, it has been found that with this thin layer which actually absorbs the laser radiation, there is not only no impairment of the effect of the laser radiation which produces the craters, but, at the same time, the surrounding tissue remains practically completely undamaged. There is no occurrence of a brownish discoloration of the dentine in the vicinity of the crater rim, and yet the material can be removed in the immediate area of irradiation with the same effectiveness as without the use of the liquid. The mechanism underlying the effect is not yet fully explicable, but the expansion of the vapor of the absorbing liquid occuring during the irradiation possibly leads to a particularly effective, local cooling of the tissue surrounding the drilling location.
Water is preferably used as liquid. The liquid may contain sodium chloride and/or detergents or other additives.
It is particularly advantageous for the amount of liquid applied to the tooth material per time unit to be increased as the radiation energy per laser pulse is increased. In other words, the amount of liquid applied to the tooth material and the radiation energy applied per time unit are increased and reduced in the same way in order to thereby ensure that the increased evaporation rate of the liquid upon impingement of a greater amount of radiation energy is compensated. In this way it is possible to keep the layer thickness substantially constant prior to impingement of a laser pulse, and independently of how much liquid evaporated during the previous laser pulse.
It is particularly advantageous for the liquid to be applied intermittently before each laser pulse. This ensures that prior to the laser pulses, generated approximately at a repetition rate of 1 Hz, an unheated, new layer of liquid is applied again.
It is, however, of course, also possible for the liquid to be applied continuously.
In the case of continuous application, it is, furthermore, expedient for the amount of liquid applied to the tooth material per time unit to be increased as the repetition rate of the laser pulses is increased, and vice versa. An increase in the repetition rate of the laser pulses increases the radiation energy impinging on the tooth material per time unit and hence also the liquid evaporated per time unit. To ensure constant coverage of the tooth material with the liquid, it is, therefore, advantageous to apply an increased amount of liquid to the tooth material in a corresponding manner.


BRIEF DESCRIPTION OF THE DRAWING

The FIGURE illustrates a handpiece useful in practicing the proces

REFERENCES:
patent: 4826431 (1989-05-01), Fujimura et al.
patent: 5020995 (1991-06-01), Levy

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