Curing unit for dental materials

BACKGROUND OF THE INVENTION

P-0001[0001] 1. Field of the Invention

P-0002[0002] This invention relates generally to an apparatus for the rapid curing of resinous materials by application of energy from an external source to excite polymerization in a polymerizable system. More specifically, this invention relates to an apparatus for the rapid curing of dental materials by using light, pressure, pressure and light, or purge, pressure and light.

P-0003[0003] 2. Brief Description of the Related Art

P-0004[0004] Curing, as used herein, is the processing of a plastic or resinous material from a fluid or soft and compliant state to a permanent hard, durable and solid state. Conventionally, this is accomplished both by the elimination of solvents and by chemical changes involving interlinking of molecules commonly known as polymerization of the material. Of the two, polymerization is the more advantageous since it does not commonly involve dimensional changes and usually produces a substantial increase in the strength of the material. Polymerization is usually caused by the addition of activating chemicals (activators), by irradiation with some form of wave energy, either electric or electromagnetic in nature, or by applying heat, or by a combination thereof.

P-0005[0005] The prior art curing processes involve many manual steps that can lead to a variety of errors dependent upon the person performing the operation. One such process uses a pressure bowl depicted in FIG. 1. The pressure bowl <b>10</b> includes a base <b>12</b> having a platform <b>14</b> and a glass or plastic dome or cover <b>16</b>. A work piece to be treated is placed on platform <b>14</b> and glass dome <b>16</b> is positioned and locked into place by knob <b>18</b>. Pressure bowl <b>10</b> is then manually connected to an air or gas source at inlet <b>20</b>. Glass cover <b>16</b> is tightened and covered with a cloth to prevent light from entering. Pressure bowl <b>10</b> is then pressurized for the required amount of time by turning on the air or gas source. When the process is complete, the air nozzle is removed and pressure bowl <b>10</b> is transferred to a light curing box. The work piece, still located in pressure bowl <b>10</b>, is light cured. After the curing process, pressure bowl <b>10</b> is removed from the curing box. To remove the work piece, knob <b>18</b> must be turned to unlock glass dome <b>16</b>. If a glaze is to be placed over the work piece, a purging process is typically required to prevent formation of an oxygen inhibition layer. This involves manually purging bowl <b>10</b> with an independent gas source comprising a series of two or more repetitions of filling bowl <b>10</b> with gas and releasing and thereafter filling with gas a final time and maintaining gas pressure until the light curing process, as described above, is completed. The manual steps involved in the curing procedures described can lead to many problems in the cured restorations including low strength, distorted shape, tacky surface from incomplete purging, and the like.

P-0006[0006] There remains a need to simplify the curing process without sacrificing the quality of the final restoration. It is desirable to provide a curing unit that produces consistent results.

SUMMARY OF THE INVENTION

P-0007[0007] The above-described and other problems and deficiencies of the prior art are overcome or alleviated by the curing apparatus of the present invention, wherein rapid curing is provided by using light, pressure, pressure and light, or purge, pressure and light to cure resinous materials by application of energy from an external source to excite polymerization in a polymerizable system. An air-tight chamber is provided to house the polymerizable dental material.

P-0008[0008] The apparatus provides an automated system for curing the polymerizable material under light and pressure in the same unit. Pressure eliminates bubbles. A purge cycle may be included to provide an oxygen-free atmosphere and to minimize or eliminate bubbles.

BRIEF DESCRIPTION OF THE DRAWING

P-0009[0009] For the purpose of illustrating the invention, there are shown in the drawings, features which are presently preferred; it being understood, however that this invention is not limited to the precise arrangements and instrumentalities shown. Referring now to the drawings wherein like elements are numbered alike in the several FIGURES:

P-0010[0010]FIG. 1 is a perspective view of a prior art pressure bowl;

P-0011[0011]FIG. 2 is a perspective view of the apparatus of the present invention;

P-0012[0012]FIG. 3 is a perspective view of the apparatus of FIG. 2 in open position;

P-0013[0013]FIG. 4 a perspective view of the apparatus of FIG. 2 showing the internal componentry;

P-0014[0014]FIG. 5 is a perspective view of the apparatus of FIG. 2 in open position showing the internal componentry;

P-0015[0015]FIG. 6 is a perspective view of the front panel on the apparatus shown in FIG. 2;

P-0016[0016]FIG. 7 is a rear plan view of the apparatus shown in FIG. 2; and

P-0017[0017]FIG. 8 is a block diagram showing the electrical connections and air line connections.

DETAILED DESCRIPTION OF THE INVENTION

P-0018[0018] The present invention is directed to a new and improved curing apparatus for curing a polymerizable resinous material, such as a dental material. U.S. Pat. Nos. 4,873,446, 4,839,521, 5,040, 964, and 4,309,617 are directed to polymerization and/or curing of materials and are hereby incorporated by reference. The dental material may include, but is not limited to at least one filled or unfilled resin having at least one ethylenically unsaturated group. Examples of the ethylenically unsaturated groups include acrylates, methacrylates, vinyl groups and combinations thereof.

P-0019[0019]FIGS. 2 and 3 show curing unit <b>30</b> in closed and open position, respectively. FIGS. 4 and 5 show the internal componentry of curing unit <b>30</b>, in closed and open position, respectively. Curing unit <b>30</b> provides a variety of curing options including light alone, pressure alone (does not cure, but can be used to reduce porosity), light and pressure in combination, and a purge cycle to be used with light and pressure.

P-0020[0020] Curing unit <b>30</b> provides a facile method of curing by opening cover <b>32</b> and placing a work piece <b>34</b> on a platform <b>36</b> of base <b>38</b>. The “light only” mode allows the user to select the time the light is on. The work chamber is closed and opened manually. There is no pressure benefit in this mode. This curing mode provides curing with light only. FIGS. 4 and 5 show the light source comprising two lamps <b>39</b> arranged above a transparent dome-shaped cover <b>41</b> that is positioned over work area or zone <b>43</b> on base <b>38</b> which creates an airtight chamber <b>31</b> when in closed position. The lamps may comprise light emitting diodes, tungsten, halogen, mercury vapor, short arc xenon, or a metal halide source. The light source may comprise one or a plurality of lamps directed at work area <b>43</b>. Preferably, the spectral output of the lamp utilized herein is in the range of between about 380 nm to about 550 nm.

P-0021[0021] Lamps <b>39</b> may rotate to provide even curing throughout the material. Cover <b>32</b> further may comprise one or more fans <b>37</b> to prevent overcuring of the materials. Overcuring tends to make cured composite brittle and less tough. The inclusion of fans <b>37</b> aids to control the temperature inside air-tight chamber <b>31</b> to below 140° C.

P-0022[0022] An inlet <b>61</b> and an outlet <b>62</b> are located in work area <b>43</b> to provide ingress and egress for pressurization. The “pressure/light” mode light cures simultaneously with the application of pressure. The pressure cure is recommended for removal of entrapped bubbles from the composite material. The time allocated for applying pressure inside the work chamber is input or programmed into the curing unit. The time allocated for applying light to the work chamber is input or programmed into the curing unit. After work piece <b>34</b> is placed in the curing chamber and the chamber is closed, the pressure chamber is automatically pressure sealed after the start key is pressed. The work is then pressurized for the user-programmed time before the light is turned on. The pressurized atmosphere may include air, nitrogen or any inert gas such as argon, xenon, krypton and the like. The air or gas is supplied externally through inlet <b>70</b> positioned on the rear side of unit <b>30</b> shown in FIG. 7. The light is turned on for the user-programmed time and the pressure is maintained until the set light time has elapsed. At the end of the cycle, the light turns off, pressure is released, and the pressure sealing mechanism retracts.

P-0023[0023] The “purge” mode is a curing cycle that purges the atmosphere prior to curing the work piece under pressure and light. When used with nitrogen or argon, no tacky surface will be observed (i.e., oxygen is removed). This mode is usually used for the application of the final layer of material. After the work is placed in the curing chamber and the chamber is closed, the pressure chamber is automatically pressure sealed after the start key is pressed. The chamber is then pressurized and exhausted up to about three or four times before being maintained at the desired pressure. The chamber will remain pressurized for the remainder of the user programmed pressure time, and then the light will turn on (still presssurized) until the light time has elapsed. At the end of the cycle the light turns off, pressure is released and the pressure sealing mechanism retracts. The time for maintaining pressure may be from about 1 minute to about ten minutes. A typical curing cycle is usually in the range from about 2 minutes to about 5 minutes. The pressure does not typically go above about 85 psi.

P-0024[0024] When a cycle is being performed, the times for light and pressure will remain set until changed, or until the power is turned off. A Start light emitting diode (LED) will indicate that a cycle is running. A Stop LED will indicate when there is no cycle running. The time display counts down in minutes and seconds for each segment, i.e., the initial pressure time (if required) will count down from set time to 0:00, followed by a light curing cycle that will count down from set time to 0:00. If a purge is used, it is included in the pressure time. Cover <b>32</b> is interlocked under pressure. The locking device is comprised of pins or segments <b>33</b> that lock into latches <b>35</b> as shown in FIG. 4. Dome <b>41</b> shown in FIG. 5 is locked and sealed in this manner for a pressurized operation. To open latches <b>35</b>, pressure is released, the latches are rotated in the reverse direction, allowing the unit to be opened.

P-0025[0025]FIG. 6 shows a control panel <b>40</b> located on the front of base <b>38</b>. Panel <b>40</b> includes a series of buttons <b>42</b> that are labeled with the appropriate word to describe the curing mode to be actuated. Buttons <b>44</b> and <b>46</b> are labeled Stop and Start, respectively and are used to stop and start the procedure. Panel <b>40</b> includes a time display <b>58</b> and a pressure gauge <b>60</b>. Running a cycle involves placing a work piece on platform <b>36</b> and closing and securing cover <b>32</b>. The mode of operation, such as for example, by pressure, is selected by pressing the Pressure key. The LED buttons <b>52</b> will indicate if the mode has been selected. If the Pressure mode is selected, the LEDs located next to Light Only and Pressure will be lit. Buttons <b>54</b> and <b>56</b> labeled Minutes and Seconds, respectively, can be pressed to reach the desired time for the mode. The Select button <b>60</b> is used to select the pressure or light mode for input of time. LED buttons <b>48</b> located above the Stop and Start buttons indicate when a cycle is running (Start LED is lit) and when a cycle is over (Stop LED is lit).

P-0026[0026] A curing operation using the pressure and light mode proceeds as follows. Press Start key <b>46</b> to start the cycle. The pressure latches <b>35</b> will close and seal the chamber. The Start LED will light to indicate the cycle is in progress. The unit will first pressurize the chamber to up to about 85 psi. Pressure is set by an external regulator. The time display will begin to count down in seconds. After the pressure segment, the Light will be activated. The Pressure LED will go out and the Light LED will go on indicating that the time display is now counting down for the time that the light is on. Pressure will be maintained. The time display will continue to decrease until the time reaches 0:00. The pressure will then be released. When the pressure reaches nominal pressure, the Stop LED will come on and the Start LED will go out. Pressure latches <b>35</b> will then retreat.

P-0027[0027] To add a purge segment to the cycle, the Purge key or button is pressed when setting up the mode. To begin the cycle, the Start key is pressed. The Start LED will light to indicate that the cycle is in progress. Pressure latches <b>35</b> will engage. The unit will first pressurize chamber <b>31</b>. The time display will begin to count down from programmed pressure time. The purge time is included in the pressure time. Only the Pressure LED above the time display indicates that the time is for the pressure segment. The unit will purge the chamber and then pressurize it. The purge cycle includes two or more segments comprising the application of pressure followed by a release of pressure. Pressure is then applied and maintained. After the pressure segment, the curing light will be activated. The Pressure LED will go out and the Light LED will go on indicating that the time display is now counting down the Light time. Pressure will be maintained. The time display will continue to decrease until the time reaches 0:00. The pressure will then be released and a timed delay will begin to allow venting of pressure. When the pressure reaches nominal pressure, the pressure latches will automatically retract, the Stop LED will come on and the Start LED will go out.

P-0028[0028] A light only cycle can be activated by selecting only the light mode button and proceeding with the time. The Light LED will turn on and the time display will decrease until the time reaches 0:00. The Stop LED will come on and the Start LED will go out.

P-0029[0029] The unit is supplied with an external air or gas source that is switched using pressure valves. The internal line into the pressure chamber has a small restriction orifice that limits the flow of air or gas into the pressure chamber. The pressurized system also has a pressure relief valve. The relief valve will open at a maximum pressure level and limit the pressure to the pressure chamber. The air or gas flow through the pressure relief valve is greater than the input restrictor orifice, which also limits the pressure of the chamber to safe levels in the event of the input line exceeding maximum levels. The air or gas is exhausted by a pressure release valve and the pressure level is monitored by a pressure switch or transducer. When the pressure has been released and falls to a safe level the automatic latching mechanism will release the pressure seal in such a way as to prevent the top pressure dome from flying open in the event that the pressure measuring function failed and pressure was still in the pressure chamber. The front panel pressure gauge will also indicate the internal pressure level.

P-0030[0030]FIG. 8 is provided to show the electrical connections and air or gas line layout. The front panel <b>40</b> is the control panel that is operatively associated with a processing device located internally. The control panel receives input from an operator relating to the light source and the gas source. The processing device is operatively associated with the light source and the gas source for controlling curing of the dental material by light and pressure within the air-tight chamber. The processing device may include, but is not limited to, a microprocessor, a microcontroller, a microcomputer, a controller, a digital signal processor, a central processing unit (CPU), or an application specific integrated circuit (ASIC). The processing device may be configured to cause gas to supply gas under pressure to the air-tight chamber prior to the time the light source supplies light to the chamber. It may be further configured to cause gas pressure to be maintained in the chamber at a constant level during the time the light source supplies light to the chamber. The processing device may be configured to cause the gas pressure to be initially supplied and subsequently released at least twice in succession, followed by application of pressure, whereby gas pressure is maintained at a constant level with in the chamber during the time the light source supplies light to the chamber.

P-0031[0031] While preferred embodiments have been shown and described, various modifications and substitutions may be made thereto without departing from the spirit and scope of the invention. Accordingly, it is understood that the present invention has been described by way of illustration and not limitation.