The present invention relates to a dental handpiece for the polymerization of photosetting compounds or resins compatible with the power supply of other handpieces.
The invention refers in particular to an instrument employed by dental surgeons for the polymerization of photosetting compounds or resins utilised especially in dental prostheses,
Photosetting resins are applied in a semifluid state to patients"" dental prostheses and are then hardened by a polymerization process. Such a polymerization process involves heating the resins for a certain length of time, using a light source that emits blue light, i.e. having an emission spectrum with a wavelength centered around 470 nm.
Handpieces according to the prior art currently use halogen lamps as their light source. The light coming from the halogen lamps is filtered by dichroic filters, so that a blue light having a light spectrum with a wavelength between 430 and 510 nm is obtained. The light emerging from the dichroic filters is transported, through optic fibres, to the outlet of the dental handpiece, enabling the dentist to direct it onto the resin to be polymerized, applied to the patient""s dental prosthesis.
The known dental handpieces using halogen lamps as polymerizing lamps have various drawbacks.
In order to achieve polymerization of the resin, the light emerging from the dental handpiece must have a power of approximately 500 mW. Since halogen lamps have a very low power efficiency (efficiency value xcex7=0.5-1%), this results in a high energy dissipation by the polymizering lamps, which reaches values between 50 and 100 W.
For this reason, handpieces for the polymerization of photosetting compounds must have a special power supply, able to supply the polymerizing lamps with a power that ranges from 50 to 100 W. Consequently, the seats in which the patients sit, normally known as dental chair units, provide a connector element connected to the power supply and specifically designed for the polymerizing handpiece.
Furthermore, with the output power that can be obtained from halogen lamps, rather long resin polymerization times are required; this can be very tiresome both for the patient undergoing the procedure and for the dental surgeon who has to perform it.
In an attempt to reduce resin polymerization times, handpieces with different light sources have been put on the market. Handpieces are per se known that use as their light source gas-discharge lamps (plasma torches) that emit high-power white light, which is filtered in order to obtain a light beam with an emission spectrum centred on blue. Also known are dental handpieces using laser as their light source, which directly transmit a light beam with an emission spectrum centred on blue.
With this type of dental handpiece it is possible to obtain a light beam with a power output approximately ten times greater compared to that obtained with halogen lamps, therefore shorter polymerization times are achieved. However, such dental handpieces, apart from being very expensive, have the problem of needing to dissipate a large amount of heat and inevitably they must provide a heat dissipation or cooling system, making them excessively bulky and heavy. Furthermore, such heat dissipation systems often include fans driven by motors which must be powered by the dedicated electrical supply of the polymerizing handpiece.
Also known, especially at an experimental level, are handpieces for polymerization of photosetting compounds using as their light source LEDs that emit in the blue range.
All known handpieces using halogen lamps, plasma torches, laser or LEDs as their light source, have an independent electrical supply system, dedicated soleley to the electrical supply of said light sources. This makes the dental handpiece bulky and lacking in versatility because of the purpose-built circuitry provided for such light sources and also the need to provide the dental chair unit with special connectors for the power supply of such handpieces.
The object of the invention is to eliminate said drawbacks, providing a dental handpiece for polymerization of photosetting compounds or resins that is compatible with the power supply of other handpieces.
A further object of the present invention is to provide a handpiece of reduced dimensions and bulk that is versatile, economical and easy to produce.
The handpiece according to the invention comprises a connector element shaped so as to be able to connect to external electrical connectors utilised for other types of handpieces, such as for example the handpiece or ultrasound scaler for removal of plaque and caries, or the dental turbine for cleaning and washing dental prostheses.
This is made possible thanks to the fact that in the handpiece according to the invention LEDs that emit in the blue range are used as the light source. In fact LEDs require a decidedly lower power supply than halogen lamps, plasma torches or laser. This has made it possible to take the electrical supply for bias of the LEDs directly from the electrical supply circuit provided in the external connector of other types of handpieces.
In the case of connection of the handpiece for polymerization according to the invention to the connector of an ultrasound scaler, the electrical energy for bias of the LEDs is taken from the electrical circuit provided in the connector of the scaler and destined to supply the ultrasound transducer of the scaler.
For this purpose, in the handpiece according to the invention, an equivalent resonator circuit is provided that must tune the resonance frequency of the supply circuit provided in the external connector of the scaler. Downstream of the equivalent resonance circuit and upstream of the LED assembly of the polymerizing handpiece, a voltage and current stabilizer or regulator is provided in order to generate a constant voltage and direct current signal for correct bias of the LEDs.
Dental turbines include a light source to illuminate the work surface. For the electrical supply to this light source of the dental turbine, the external connectors of dental turbines carry an electrical supply signal taken from an electrical supply source. In the case of connection of the handpiece according to the invention to an external connector for dental turbines, the supply of the LEDs for polymerization is taken from the electrical supply carried by the external connector of the turbine.
In this case the voltage supplied by the external connector is too low to be able to supply the LEDs, therefore an electronic voltage booster or step-up transformer circuit capable of providing an adequate voltage to bias the LEDs is provided inside the handpiece according to the invention. Downstream of the step-up transformer circuit a voltage and current stabilizing circuit is provided to maintain a constant voltage and direct current during power supply of the LEDs.
The advantages of the handpiece for the polymerization of photosetting compounds according to the invention appear evident. Since it can adapt to the connectors used for the power supply of handpieces of other types, it allows the connectors and circuitry specifically dedicated to its supply to be eliminated from the dental chair unit, with considerable economic advantages as regards size and complexity.