WO2009097892A1

WO2009097892A1 - Mixing device

Info

Publication number: WO2009097892A1
Application number: PCT/EP2008/051323
Authority: WO
Inventors: Stephan Kaegi; Manfred Kalt; Ralf Kollefrath; Werner Mannschedel
Original assignee: Coltene Whaledent Ag
Priority date: 2008-02-04
Filing date: 2008-02-04
Publication date: 2009-08-13

Abstract

The invention relates to a mixing device for the mixing of a dental material. The dental material comprises a first component and at least a second component to be mixed. The mixing device comprises a mixing chamber, input means to define a desired working time of the dental material and means to match the remaining working time with the desired working time of the dental material after mixing of the at least two components of the dental material. The advantage of this invention relates to the possible adjustment of the remaining working time, which is ideally suited for the proper application of the dental material depending on the intended use.

Description

Mixing Device

The present invention relates to the field of curable dental materials, in particular to the control of the remaining working time of the dental materials.

In dental applications, dental materials of various types are used e.g. to form a mold of a dental situation (e.g. impression materials) or as filling materials. Dental materials are commonly composed of two or more components which are stored separately until use in the dental office. When required for use, the at least two components of the dental material are mixed, thereby starting a curing reaction which in a short period of time changes the flowable material to a cured material. When the flowable material is applied to a dental situation such as e.g. a prepared tooth it will harden to form an exact impression of the dental situation that can be used for restoration, and when the flowable material is applied to a cavity in a tooth it will harden in the tooth and seal the cavity.

The mixing of the at least two components of the dental material is done with mixing devices of different types. A first commonly known and widely used type is a static fluid mixer which mixes one or more kinds of fluids (liquids, gases, solids and mixtures of these) without mechanically movable parts. Such mixing devices are available in wide variety from Mixpac (Rotkreuz, Switzerland) . A second commonly known and widely used type is a dynamic fluid mixer which mixes one or more kinds of fluids (liquids, gases, solids and mixtures of these) with mechanically movable parts.

It is common practice to mix the at least two components of the dental material according to a standard protocol prior to appli- cation, with the dental material having a fixed working time. This has the drawback of strictly fixed working times which can be either too short or too long for the specific task, or uncomfortable for the patient if the dental material requires curing inside the mouth of the patient for a long time.

It was thus an object of the present invention to overcome the drawbacks of the known prior art, especially to address the aforementioned problems, in particular to allow for more flexibility in the handling of dental materials.

This object was solved by a mixing device for dental materials and related methods according to the independent claims.

According to a first aspect, the invention concerns a mixing device that is suitable for the mixing of a dental material comprised of a first component and a second component to be mixed. The device comprises a mixing chamber,

- input means to define a desired working time of the dental material and

- means to match the remaining working time of the dental material after mixing of the at least two components of the dental material with the desired working time.

The mixing device can comprise a static mixer or a dynamic mixer .

Examples of static mixers are disclosed and thereby included by reference in US 2004/141413, US 6899453 or US 4068830. These mixers work by forcing the components through a mixing chamber or a series of mixing chambers without movable parts, thereby mixing the components. The components can e.g. be provided - in container (s) attachable to the mixing device before mixing, in larger reservoirs, from which the required amount of the components is filled into separate compartments of the mixing device for the storage of these components until the start of the mixing to prevent the unintended start of the curing process; the mixing process is then started by feeding the components into the mixing chamber; or

- as a single use static mixer attachable to the mixing device, comprising the separately stored components in the static mixer before mixing.

Dynamic mixers are disclosed and thereby included by reference in US 2005/232073, US 7287898 or US 6837399. These mixers comprise movable parts, e.g. a rotor, which agitates the components in the chamber and thereby mixes them. The components can e.g. be provided

- in container (s) attachable to the mixing device before mixing or

- in larger reservoirs, from which the required amount of the components is filled into separate compartments of the mixing device for the storage of these components until the start of the mixing to prevent the unintended start of the curing process; the mixing process is then started by feeding the components into the mixing chamber.

The device enables the mixing of the dental material in the mixing chamber of a mixing device with one of the aforementioned mixers. Additionally, the device provides the input means to define the desired working time of the dental material. These input means comprise the following options: a computer connected to the mixing device either by a cable or by a wireless connection, which includes software to al- low for the input of the desired working time and for the transmission of the data to a control unit of the mixing device

- buttons on the mixing device to select between pre-defined desired working times

- handwheel on the mixing device which is preferably continuously adjustable to select a desired working time by turning the handwheel keyboard connected to a control unit of the mixing device to type in the desired working time touch screen connected to a control unit of the mixing device to type in individually or select the desired working time from pre-defined working times.

The remaining working time is defined as the time remaining after mixing of the components that still allows for proper application of the dental material for the intended use.

The mixing device comprises means to match the remaining working time with the desired working time e.g. by changing the reaction kinetics or the curing mechanism of the curing process. Several embodiments are explained in more detail in the following paragraphs .

According to a preferred embodiment, means to match the remaining working time with the desired working time comprise a temperature control or feedback control device to control the temperature of the dental material in the mixing chamber.

The curing process of the dental material is temperature dependent. As a rule of thumb it can be estimated that the reaction rate of a chemical reaction is increased by a factor of two to four with an increase in temperature of 10 Kelvin. Hence, the reaction kinetics can be influenced by controlling or feedback controlling the temperature of the dental material.

The term Control' (compared to the term ^λfeedback control' ) means here open-loop control, i.e. there is no feedback from the device that the desired value (e.g. temperature) is reached. An example for an open-loop controller would be a conventional washing machine set to wash for a pre-determined time with no regard for the result of the washing process. The term ^λfeedback control' (or ^λclosed-loop control' ) means here that a proportion of the output signal (e.g. temperature) is fed back into the controller to control the dynamic behaviour of the device.

The device enables the control of the temperature of the dental material in the mixing chamber which has the effect of increasing or decreasing the remaining working time after mixing to match the desired working time. The means to adjust the temperature in the mixing chamber can comprise heating and / or cooling by convection and / or conduction and / or heating by electromagnetic radiation. This may be combined with the heating or cooling of the components of the dental material prior to feeding these components into the mixing chamber and / or

- the heating or cooling of the dental material after mixing, while the dental material is stored e.g. in the mixing chamber or a storage chamber of the mixing device into which the dental material is fed after mixing, with similar means for heating and cooling as set forth above. This may include heating or cooling by e.g. a Peltier element, a blower for heating or cooling or a radiant heater. Thus, it is possible to heat or cool i) the dental material in the mixing chamber and / or ii) the components prior to mixing and /or iii) the dental material after mixing, i.e. all permutations i) , ii) or iii) alone, two of the variations or all in combination.

According to yet another preferred embodiment, the mixing device comprises a temperature sensor to measure the temperature of the dental material in the mixing chamber.

The temperature sensor can be used for continuous or "on-demand" measurement of the temperature. The location of the sensor may e.g. be in the wall of the mixing chamber, in parts of the static or dynamic mixer in contact with the dental material or outside the mixing chamber.

This temperature sensor may transmit the measured temperature of the dental material to a controller of the mixing device.

Moreover, the mixing device comprises means to measure the mixing resistance in the mixing chamber.

As used herein, the mixing resistance is related to the force necessary to mix the at least two components. Therefore, the measurement of the force necessary to mix the dental materials is a measure of the mixing resistance. This mixing resistance changes with the curing of the material, i.e. the mixing resistance increases during the curing process. In case of a static mixer, the mixing resistance is related to the force necessary to push the dental material through the (flow-trough) mixing chamber. In case of a dynamic mixer, the mixing resistance is related to the force necessary to mix the dental material in the mixing chamber, i.e. the force necessary to move the moveable parts responsible for the mixing of the dental material in the dynamic mixer. Furthermore, the mixing device may comprise a controller or feedback controller to control the mixing speed depending on the temperature of the dental material in the mixing chamber. The mixing speed influences the temperature of the dental material in the mixing chamber. The mixing speed of the mixing device can e.g. be related to the temperature with the following modes :

- increase the mixing speed to increase the temperature and decrease the mixing speed to avoid a further increase of the temperature or decrease the temperature if it was increased by a higher mixing speed

As already mentioned above, the remaining working time of the dental material depends on the temperature during the curing process. Thus, the device enables the control or feedback control of the remaining working time of the dental material by adjusting the mixing speed with the temperature measurement, such that the desired working time is reached.

According to another preferred embodiment, the mixing device comprises a controller or feedback controller to control the mixing speed depending on the mixing resistance in the mixing chamber .

The viscosity of a dental material increases as the curing proceeds. Moreover, the viscosity changes with the temperature of said dental material. These changes in the viscosity correlate to the mixing resistance in the mixing device. If the dependency of the viscosity of the dental material on both the temperature and the time after the start of the curing process is known, the mixing speed can be related to the mixing resistance. Thus, the device enables the control or feedback control of the remaining working time of the dental material by adjusting the mixing speed depending on a measurement of the mixing resistance, such that the desired working time is reached.

According to a further aspect, the mixing device may comprise means to control or feedback control the remaining working time of the dental material by automatically adding a variable amount of a further component to the dental material according to the desired working time.

According to this embodiment, the device enables the intervention into the chemistry or the reaction kinetics of the curing process. This can be done by controlling or feedback controlling the remaining working time by adding a further component to the mixing chamber that retards or accelerates the curing process with an intervention into the curing mechanism as such, or by an intervention into the curing kinetics. The control or feedback control of the remaining working time with an intervention into the kinetics may comprise the addition of a preferably non- reactive further component that dilutes the dental material and / or that changes the temperature of the dental material. The control or feedback control of the remaining working time with an intervention into the curing mechanism may comprise the addition of a further component that changes the speed of the chemical reaction responsible for the curing of the dental material. Thus, the remaining working time of the dental material can be controlled or feedback controlled by adding a certain amount of a further component, such that the desired working time is reached.

The addition of the further component may take place at the start and / or during the mixing process and can be accomplished e.g. by the following means: - addition continuously or in portions (single or multiple) from a separate container attachable to the mixing device addition continuously or in portions (single or multiple) from a separate compartment of the mixing device where the further component is stored; the further component is fed into this compartment of the mixing device before the mixing process is started

Such further component may e.g. be a retarder or accelerator. As is known in the art, a retarder retards the curing process chemically and an accelerator accelerates the curing process chemically. The device enables that these further components are added as described above, such that the desired working time is reached.

Common accelerators e.g. in the silicone chemistry comprise catalysts selected from the group comprising complexes and colloidal forms of the transition metals of the 8th subgroup, preferably platinum, palladium and rhodium. The accelerator preferably comprises a platinum complex which can be prepared from hexachloroplatinum acid by reduction with tetrame-thyldivinyl- disiloxane. Such compounds are known to the skilled person. Any other platinum compounds which catalyze or accelerate addition cross-linking of silanes with ethylenically unsaturated double bonds are also suitable. A platinum catalyst is preferably used in quantities of about 0.00005 to about 0.05 wt.-%, particularly about 0.0002 to about 0.04 wt.-%, each calculated as elemental platinum and related to the overall weight of the present dental material .

Common retarders e.g. in the silicone chemistry are e.g. acety- lenic unsaturated alcohols such as 3-methyl-l-butyne-3-ol, 1- ethynylcyclohexane-1-ol, 3, 5-dimethyl-l-hexyne-3-ol, 4 -ethyl- 1- octyne-3-ol and 3-methyl-l-pentyne-3-ol . Examples of retarders based on vinyl siloxane are 1, 1, 3, 3-tetramethyl-l, 3- divinylsiloxane, 1,3,5, 7-tetravinyl-l, 3, 5, 7-tetramethyl- cyclotetrasiloxane and poly-, oligo- and disiloxanes containing vinyl groups .

Another embodiment of the mixing device may comprise means to automatically control or feedback control the amount added of the further component depending on the temperature in the mixing chamber .

The device may enable the addition of a further component from an attachable container to the mixing device or a separate compartment of the mixing device. If the temperature in the mixing chamber increases for instance due to an exothermal reaction or due to the mixing speed in the mixing chamber, the remaining working time decreases. Therefore, the amount added of the further component must be decreased if an accelerator is used or increased if a retarder is used. If the temperature decreases for instance due to an endothermal reaction in the mixing chamber, the remaining working time increases. Therefore, the amount added of the further component must be increased if an accelerator is used or decreased if a retarder is used.

A further embodiment of the mixing device may comprise means to automatically control or feedback control the amount added of the further component depending on the mixing resistance in the mixing chamber.

The mixing resistance increases over time during the curing process, thus at a certain time after the start of the mixing process of the dental material a certain mixing resistance is expected. The device may enable the addition of a further component. If the measured mixing resistance is lower than the expected mixing resistance, then the amount of the further component must be increased if an accelerator is used or decreased if a retarder is used. If the measured mixing resistance is higher than the expected mixing resistance, then the amount of the further component must be decreased if an accelerator is used or increased if a retarder is used.

Yet another aspect of the invention relates to a method for mixing a dental material, comprising the steps of defining a desired working time of the dental material providing a first component of the dental material providing at least a second component of the dental material mixing the at least two components in a mixing chamber of the mixing device wherein the process of mixing is controlled or feedback controlled by means of a mixing device, such that the pre-defined desired working time is reached.

In a first step, a desired working time can be defined by the user with the input means of the mixing device, as set out above. In a second step, a first provided component of the dental material is introduced into the mixing chamber and in a third step a second provided component of the dental material is introduced into the mixing chamber. The second and the third step can be executed either consecutively or simultaneously. It is possible to provide any number of components to the mixing chamber as necessary for the dental material. In a next step, the dental material is mixed in the mixing chamber. The remaining working time of the dental material is controlled or feedback controlled according to the means provided by the mixing device. These aspects of the claimed method have been set forth in any detail with respect to the mixing device as described above .

Preferably, the pre-defined desired working time is reached by controlling the temperature of the components prior to mixing and / or of the dental material in the mixing chamber and / or of the dental material after mixing in the mixing device. In a first step of the method, the user can define the desired working time which can be related to the necessary temperature for a certain dental material during the mixing process. The relation between temperature and remaining working time can e.g. be retrieved as follows: automatically from a database stored in a memory module in or attached to the mixing device

- automatically from a database stored remotely via an internet connection

- manually by the user from a data sheet

- automatically from a RFID chip attached to the containers containing the components of the dental material

Thus, the temperature of the dental material during mixing can be controlled or feedback controlled to reach a required temperature to achieve the desired working time. The temperature of the dental material can be controlled or feedback controlled by the means of the mixing device as set forth above.

A further aspect may comprise the step of controlling or feedback controlling the mixing speed of the dental material depending on the temperature of the dental material in the mixing chamber, such that the pre-defined desired working time is reached. In a first step of the method, the desired working time predefined by the user is related to the temperature for a certain dental material as set forth above. In a second step, the mixing speed is then controlled or feedback controlled, such that the required temperature of the dental material in the mixing chamber is reached.

Another aspect may comprise the step of controlling or feedback controlling the mixing speed of the dental material depending on the mixing resistance in the mixing chamber, such that the predefined desired working time is reached.

In a first step of the method, the desired working time predefined by the user is related to the mixing resistance for a certain dental material during the mixing process. The relation can be retrieved from the same databases or data sheets as the dependence of the mixing speed and temperature. In a second step, the mixing speed is then controlled or feedback controlled, such that the required mixing resistance of the dental material in the mixing chamber is reached during the mixing process .

A further aspect of the invention may comprise the step of adding a further component in an amount to the dental material in the mixing chamber, such that the pre-defined desired working time is reached.

In a first step of the method, the desired working time predefined by the user is related to the amount necessary of a further component to reach the desired working time. The necessary amount is again retrieved from databases or from data sheets in the same manner as set forth above for the dependence of the remaining working time from the temperature. In a first preferred method, the necessary amount of the further component is added in toto at a certain time during the mixing process .

In a second preferred method, the necessary amount of the further component is added in portions or continuously during the mixing process. Depending on the measurement of either the temperature or the mixing resistance, the amount of the further component can be varied to match the remaining working time with the desired working time with better accuracy. Thus, a feedback controlled method for the remaining working time is achieved.

The method for mixing a dental material with a further component is preferably implemented with the added further component being a retarder or accelerator.

The retarder and accelerator can be added either in a first preferred method, where the necessary amount of the further component is added in toto at a certain time during the mixing process, or in a second preferred method, where the necessary amount of the further component is added in portions or continuously during the mixing process.

Yet another aspect of the invention comprises a computer program product which is directly loadable into the internal memory of a digital computer, comprising software code portions for controlling a mixing device according to one of claims 1 to 10, preferably according to a method according to one of claims 11 to 16 when said product is run on a computer.

The method to be used by the software code portions can either be selected manually by the user or automatically based e.g. on the used dental material. If the application of the methods as set forth above has the result that the required mixing time of the dental material is reached but the remaining working time is greater than the desired working time, the temperature may be controlled or feedback controlled in the mixing chamber until the desired working time is reached. This can be combined with continuing the mixing process beyond the required mixing time until the desired working time is reached.

The invention will now be described by way of example with reference to the accompanying drawings, without however intending to limit the invention to these examples.

The following examples of dental materials are suitable for use with the embodiments described in Fig. 1 to Fig. 5:

- Addition type silicone materials (e.g. President, Affinis, Affinis Precious, Coltene/Whaledent AG, Switzerland)

- Condensation type silicone materials (e.g. Xantopren Comfort, Heraeus Kulzer, Germany)

Polyether materials (e.g. Impregum, Permadyne, 3M ESPE,

Germany; P2, Heraeus Kulzer, Germany)

Polysulfides (e.g. Permlastic, KerrHawe, Switzerland)

Fig. 1 flow-chart showing the control of the remaining working time by feedback controlling the temperature

Fig. 2 flow-chart showing the control of the remaining working time by feedback controlling the temperature by adjusting the mixing speed Fig. 3 flow-chart showing the control of the remaining working time by feedback controlling the mixing resistance by adjusting the mixing speed

Fig. 4 flow-chart showing the control of the remaining working time by controlling the added amount of a further component

Fig. 5 flow-chart showing the control of the remaining working time by feedback controlling the added amount of a further component depending on the mixing resistance

Fig. 1 shows a method to control the remaining working time by feedback controlling the temperature with a heater or cooler, which feedback controls the temperature in the mixing chamber. The temperature necessary to reach the desired working time is e.g. retrieved from a database. The temperature controller is set to this value and the mixing is started. During the mixing, the temperature in the mixing chamber is feedback controlled, such that the desired working time is reached. The mixing process is finished after the required duration for the mixing of the dental material is reached. The desired working time is the remaining working time left before the material has cured that much that no purpose-intended application is possible.

Fig. 2 shows a method to control the remaining working time by feedback controlling the temperature by adjusting the mixing speed. The temperature necessary to reach the desired working time is e.g. retrieved from a database. The mixing process and then the temperature measurement are started. During the mixing, the temperature is kept at the necessary value by adjusting the mixing speed. The mixing process is finished after the required duration for the mixing of the dental material is reached. The desired working time is the remaining working time left before the material has cured that much that no purpose-intended application is possible.

Fig. 3 shows a method to control the remaining working time by feedback controlling the mixing resistance by adjusting the mixing speed. The mixing resistance necessary to reach the desired working time is e.g. retrieved from a database. The mixing process and then the mixing-resistance measurement are started. During the mixing, the mixing resistance is kept at the necessary value by adjusting the mixing speed. The mixing process is finished after the required duration for the mixing of the dental material is reached. The desired working time is the remaining working time left before the material has cured that much that no purpose-intended application is possible.

Fig.4 shows a method to control the remaining working time by adding a further component to the dental material. The necessary amount of the further component is e.g. retrieved from a database. The mixing process is started and the component is added. The mixing process is finished after the required duration for the mixing of the dental material is reached. The desired working time is the remaining working time left before the material has cured that much that no purpose-intended application is possible .

Fig. 5 shows a method to control the remaining working time by feedback controlling the added amount of a further component to the dental material by adjusting the mixing resistance. The mixing resistance necessary to reach the desired working time is e.g. retrieved from a database. The mixing process and then the mixing-resistance measurement are started. During the mixing, the mixing resistance is kept at the necessary value by adjust- ing e.g. the continuously added amount of the further component, The mixing process is finished after the required duration for the mixing of the dental material is reached. The desired working time is the remaining working time left before the material has cured that much that no purpose-intended application is possible .

Claims

1. Mixing device for the mixing of a dental material comprised of a first component and a second component to be mixed, the device comprising: a mixing chamber input means to define a desired working time of the dental material means to match the remaining working time with the desired working time of the dental material after mixing of the at least two components of the dental material .

2. Mixing device according to claim 1, wherein means to match the remaining working time with the desired working time comprise a temperature control or feedback control device to control the temperature of the dental material in the mixing chamber.

3. Mixing device according to claim 1 or 2, wherein the mixing device comprises a temperature sensor to measure the temperature of the dental material in the mixing chamber.

4. Mixing device according to one of the claims 1 to 3, wherein the mixing device comprises means to measure the mixing resistance in the mixing chamber.

5. Mixing device according to one of the claims 1 to 4, wherein the mixing device comprises a controller or feedback controller to control the mixing speed depending on the temperature of the dental material in the mixing chamber .

6. Mixing device according to one of the claims 1 to 5, wherein the mixing device comprises a controller or feedback controller to control the mixing speed depending on the mixing resistance in the mixing chamber.

7. Mixing device according to one of the claims 1 to 6, wherein the mixing device comprises means to control or feedback control the remaining working time of the dental material by automatically adding a variable amount of a further component to the dental material according to the desired working time.

8. Mixing device according to claim 7, wherein the further component is a retarder or accelerator.

9. Mixing device according to one of the claims 1 to 8, wherein the mixing device comprises means to automatically control or feedback control the amount added of the further component depending on the temperature in the mixing chamber .

10. Mixing device according to one of the claims 1 to 9, wherein the mixing device comprises means to automatically control or feedback control the amount added of the further component depending on the mixing resistance in the mixing chamber .

11. A method for mixing a dental material, preferably with a mixing device according to claim 1, comprising the steps of defining a desired working time of the dental material providing a first component of the dental material providing at least a second component of the dental material mixing the at least two components in a mixing chamber of the mixing device wherein the process of mixing is controlled or feedback controlled by means of a mixing device, such that the predefined desired working time is reached.

12. A method according to claim 11, comprising the step of controlling or feedback controlling the temperature of the components prior to mixing and / or of the dental material in the mixing chamber and / or of the dental material after mixing in the mixing device, such that the pre-defined desired working time is reached.

13. A method according to one of claims 11 or 12, comprising the step of controlling or feedback controlling the mixing speed of the dental material depending on the temperature of the dental material in the mixing chamber, such that the pre-defined desired working time is reached.

14. A method according to one of claims 11 to 13, comprising the step of controlling or feedback controlling the mixing speed of the dental material depending on the mixing resistance in the mixing chamber, such that the pre-defined desired working time is reached.

15. A method according to one of claims 11 to 14, comprising the step of adding a further component in an amount to the dental material in the mixing chamber, such that the predefined desired working time is reached.

16. A method according to claim 15, wherein the added further component is a retarder or accelerator.

17. A computer program product directly loadable into the internal memory of a digital computer, comprising software code portions for controlling a mixing device according to one of claims 1 to 10, preferably according to a method according to one of claims 11 to 16 when said product is run on a computer.