News Column

Patent Issued for Device and Method for Production of Dental Molded Parts

August 27, 2014



By a News Reporter-Staff News Editor at Journal of Engineering -- A patent by the inventors Wachter, Wolfgang (Schaan, LI); Pokorny, Walter (Gais, AT); Rohner, Gottfried (Altstatten, CH); Grunenfelder, Robert (Eschen, LI), filed on September 6, 2007, was published online on August 12, 2014, according to news reporting originating from Alexandria, Virginia, by VerticalNews correspondents.

Patent number 8801980 is assigned to Ivoclar Vivadent AG (Schaan, LI).

The following quote was obtained by the news editors from the background information supplied by the inventors: "Methods and devices of these kinds have been known of for many years, and reference may be made, for example, to U.S. Pat. No. 2,806,253. In this device for production of dental molded parts, a cuvette (or alternatively a flask) is heated by a heating coil after polymerizable material has been introduced into the flask. The heating effect is compensated by way of a cold water hose with which it is intended to permit a precise and targeted control of the polymerization.

"In a slightly more recent development, as disclosed in British Patent 1,442,041 for example, the whole flask is briefly immersed in hot water, and intensive heat transfer is ensured by use of metals.

"While the quality of the prostheses produced by the apparatus shown in British Patent 1,442,041 or other precision-molded parts made from plastic is good, it would be desirable to manage without additional equipment, such as the pressure pot provided for the hot water bath."

In addition to the background information obtained for this patent, VerticalNews journalists also obtained the inventors' summary information for this patent: "The object of the invention is therefore to make available a device for production of dental molded parts, which device and method permit improved and easier production of the dental molded parts, without the risk of uncontrolled polymerization of the polymerizable plastic that is introduced.

"According to the invention, this object is achieved by providing a flask that can be filled with the polymerizable plastic via an injection device, and a heating device for heating the polymerizable plastic in the flask, the heating device being movable relative to the flask.

"According to the invention, it is particularly expedient if the heating device as a whole can be removed from the flask. According to the invention, it is particularly expedient if the heating device is switched on or activated when the filling with polymerizable plastic has already taken place. This safely avoids polymerization taking place too early, and the possibility is afforded of starting the polymerization by switching on the heating device after filling is complete, or of preheating the heating device and then heating the flask in the heating position in which it is in thermally conductive contact with the heating device, and to do so preferably starting at a location that lies opposite the inlet opening for the plastic that is to be polymerized.

"This solution has the advantage that, even when the heating device has already been heated, only the desired heat energy can be delivered, and arranging the heating device and inlet opening opposite one another ensures that no defective molded part is obtained as a result of heat shrinkage.

"The heating device preferably interacts with one side of the flask that lies opposite an inlet opening of the flask. The flask can be held in any desired manner with or without clamping. For example, the two flask shells can be held together by a mechanical closure element before they are pressed more firmly onto one another by the clamping device.

"The relative movement between flask and heating device is also not limited to the displaceability and/or pivotability of the heating device. While the pivoting of the heating device permits a rapid cooling of the flask, since the delivery of heat is then interrupted and cooling air can sweep along the outside of the heat transfer surfaces, it is also possible to remove the flask completely from the heating device.

"The relative mobility between flask and heating device can be such that the flask is mounted fixedly on a receiving area of the housing and the heating device is mounted displaceably and/or pivotably on the housing. The movement of the flask can be effected with the aid of a drive device.

"It is particularly expedient if the heating device has the shape of a U and encloses the outside of the flask. This on the one hand ensures uniform heating of the flask from one side, and, on the other hand, the separation between flask and heating device can be effected particularly easily. To this extent, the solution according to the invention makes it possible to combine the advantages of hot polymerization with its improved material quality and cold polymerization with its short processing time.

"According to the invention, however, it is particularly expedient if the heating device can also be arranged lying opposite the inlet opening for the plastic material. This ensures that the polymerization initially takes place at parts of the flask that are remote from the inlet opening. To this extent, the chemical shrinkage during polymerization is automatically compensated by more material being pressed in. In this way it is possible to ensure an optimal fit of the prosthetic article in the mouth of the patient.

"According to the invention, it is particularly expedient if, in the rest position, the flask can be delivered to the receiving area unimpeded and can be removed from it unimpeded.

"According to the invention, it is particularly expedient if, in the heating position, the heating device at least partially encloses the flask, in particular in the manner of a U, and substantially from above, and in particular bears on the flask.

"According to the invention, it is particularly expedient if the heating device is mounted on a housing, which comprises the receiving area and the heating device, and is mounted so as to be pivotable and/or displaceable, in particular with the aid of a drive device.

"According to the invention, it is particularly expedient if the heating device has two branches which correspond substantially to the side branches of a U and which, if appropriate, diverge slightly from one another, and wherein in particular the branches of the heating device are pivotable relative to one another, and in particular can be pivoted apart for removal of the flask.

"According to the invention, it is particularly expedient if the heating device has at least one reflector directed toward the flask.

"According to the invention, it is particularly expedient if the heating device is arranged lying substantially opposite an inlet opening of the flask when the heating position is reached.

"According to the invention, it is particularly expedient if the heating device has a heating element to which electrical energy is delivered.

"According to the invention, it is particularly expedient if the heating element is formed by at least one electrical heating rod.

"According to the invention, it is particularly expedient if the heating element generates hot air.

"According to the invention, it is particularly expedient if, in a device, an inlet opening of the flask is surrounded by a heat insulator permitting heat insulation for the polymerizable plastic flowing in there compared to good heat-conducting areas of the flask, in particular the flask shells.

"According to the invention, it is particularly expedient if, in a device the flask in particular has two flask shells which can be pressed onto one another with the aid of a clamping device, and in particular the two flask shells can be held together with the aid of at least one mechanical closure element.

"According to the invention, it is particularly expedient if, in a device, the clamping device has at least one clamping lever, at least one clamping jaw interacting with a flask shell, and a clamp element, in particular in the form of a pneumatically and/or hydraulically and/or electrically operating clamp cylinder.

"According to the invention, it is particularly expedient if the clamping lever is mounted pivotably in the housing, and, in particular, clamping jaws are articulated on its work arm, and the clamp element articulated on its power arm.

"According to the invention, it is particularly expedient if the clamping device has two clamping levers which, each with a clamping jaw, press the two flask shells onto one another and jointly interact with a clamp element.

"According to the invention, it is particularly expedient if the clamping device has a clamping frame on which at least one clamping lever is mounted, and the clamping lever is designed in particular as a one-arm lever.

"According to the invention, it is particularly expedient if, in a device, the two free ends of the clamping levers interact with one another via a tie rod, in particular of a clamping frame.

"According to the invention, it is particularly expedient if the flask can be filled with polymerizable plastic through the inlet opening substantially vertically from below, and if the polymerizable plastic can be pressed into the flask with the aid of an injection device. However, the filling can also be done in the horizontal direction or from the top downward.

"According to the invention, it is particularly expedient if, in a device, an air release channel is arranged substantially opposite the inlet opening on the flask.

"According to the invention, it is particularly expedient if, in a device, an underpressure can be established in the air release channel via a device for generating underpressure, in particular before the polymerizable plastic is pressed in.

"According to the invention, it is particularly expedient if the device has a control unit for program control of the relative movement, the heating device and/or the clamp element and/or the heating of the heating device, the device that can be subjected to underpressure and/or the injection device.

"According to the invention, it is particularly expedient if the flask can be inserted into a receiving area, and a heating device is movable relative to the flask and, in a heating position distanced from a rest position, the heating device heats the flask.

"According to the invention, it is particularly expedient if the heating device is switched on after the filling operation and the flask is heated starting from its side lying opposite the inlet opening for the polymerizable plastic.

"According to the invention, it is particularly expedient if the injection pressure is maintained while the heating device is switched on and the plastic is being polymerized, with the polymerization shrinkage being compensated in particular by more plastic being pressed in.

"According to the invention, it is particularly expedient if the temperature of the flask is regulated electronically.

"According to the invention, it is particularly expedient if the temperature is detected by a temperature sensor which is in direct or indirect contact with the flask.

"According to the invention, it is particularly expedient if the temperature sensor is arranged on the device, in particular on the heating device.

"According to the invention, it is particularly expedient if the temperature sensor is protected from the direct heat radiation of the heating device.

"According to the invention, it is particularly expedient if the temperature sensor is pressed against the flask by the force of a spring.

"According to the invention, it is particularly expedient if a clamping device presses the flask shells of the flask firmly onto one another before the injection of the polymerizable plastic, and in particular the clamping device is released only after the heating device has been switched off and the injection device has been switched off.

"According to the invention, it is particularly expedient if the heating device, before being switched on, is pivoted and/or displaced from a rest position into a heating position and, after being switched off, is returned to the rest position.

"According to the invention, it is particularly expedient if an air release channel, which is arranged essentially lying opposite the inlet opening on the flask, can be subjected to an underpressure, in particular before the injection of the polymerizable plastic."

URL and more information on this patent, see: Wachter, Wolfgang; Pokorny, Walter; Rohner, Gottfried; Grunenfelder, Robert. Device and Method for Production of Dental Molded Parts. U.S. Patent Number 8801980, filed September 6, 2007, and published online on August 12, 2014. Patent URL: http://patft.uspto.gov/netacgi/nph-Parser?Sect1=PTO1&Sect2=HITOFF&d=PALL&p=1&u=%2Fnetahtml%2FPTO%2Fsrchnum.htm&r=1&f=G&l=50&s1=8801980.PN.&OS=PN/8801980RS=PN/8801980

Keywords for this news article include: Ivoclar Vivadent AG.

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Source: Journal of Engineering


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