Mixer assembly and device for dispensing a dental material

Abstract

A mixer assembly (100) with a static mixing element (40) arranged within a mixing channel (102). The mixer assembly has an inlet end (103), for receiving components of a substance and a dispensing end (104) for dispensing a mixture from the components. The inlet end comprises for each component an inlet (110a, 110b) and an associated non-return valve (105a, 105b). Each of the inlets is connectable for fluid communication with the mixing channel via the associated non-return valve.

Description

[0001] MIXER ASSEMBLY AND DEVICE FOR DISPENSING A DENTAL MATERIAL

[0002] Field

[0003] The disclosure relates to a mixer assembly, and in particular to a mixer assembly having improved non-retum valves downstream associated inlets for components to be mixed within the mixer assembly.

[0004] Background Art

[0005] Dental materials are often prepared from two or more components that are mixed together just before use. Often the individual components are obtained as portions from larger packages, for example from tubes, bags or cartridges. There are packages on the market that allow manual or automatic dispensing of two or more components at desired amounts and at an appropriate ratio for mixing. Furthermore there are packages that allow dispensation of portions of readily mixed materials from individually stored components.

[0006] Often double-barrel syringes are used for storing and mixing two-component dental materials. Such double-barrel syringes typically have two side by side barrels from which the components of the dental material can be extruded by pushing pistons into the barrels. There are double-barrel syringes which store an amount of dental material that is sufficient for multiple dental treatments. Some of these syringes are configured so that a static mixer can be attached for mixing the two components as there are extruded from the syringe. Typically, the static mixer remains attached to the syringe after use, and thus serves as a closure for the remaining dental material that is stored therein. For a new dental treatment that mixer is replaced by a fresh static mixer of the same type.

[0007] International patent publication no. WO 2016 / 205181 discloses a dispensing device for dental materials. The device has a static mixer and contains a dental material. The device has a cartridge with two chambers for holding the dental material in the form of two separate components. The device further has a plunger for displacing the dental material toward the mixing elements.

[0008] US Patent No. 11, 185, 391 discloses a mixer assembly with a static mixing element arranged within a mixing channel. The mixer assembly has an inlet end, for receiving components of a substance and a dispensing end for dispensing a mixture from the components. The inlet end comprises for each component an inlet and an associated non-retum valve in the form of a resilient flap. Each of the inlets is connectable for fluid communication with the mixing channel via the associated flap. Although existing syringes provide certain advantages there is still a need to provide a system which is easy to use, provides for an appropriate mixing quality of dental materials, and avoids contamination of the materials after an initial dispense.

[0009] Summary of the Disclosure

[0010] The present disclosure relates to a mixer assembly which comprises a housing that forms a mixing channel. The mixer assembly further comprises a static mixing element that is arranged within the mixing channel.

[0011] The mixer assembly has an inlet end, for receiving at least two components of a substance, and a dispensing end for dispensing a mixture from the components.

[0012] Such a mixer assembly may be used, for example, for mixing two or more components that are at least temporarily continuously supplied to the inlet end. The mixer assembly is preferably configmed to cause the components to mix as they flow from the inlet end toward the dispensing end. In particular, typically the static mixing element causes the components to mix as they flow through the mixing channel in which the static mixing element is arranged.

[0013] The inlet end comprises for each component an inlet and an associated non-retum valve. Each of the inlets is connectable for fluid communication with the mixing channel via the associated non-retum valve.

[0014] The present disclosure is advantageous in that it helps preventing undesired crosscontamination between the components to be mixed, outside the mixer assembly. This is achieved by hindering components that have been provided into the mixing assembly from flowing back to the inlet. Further, the present disclosure is advantageous in that it provides a mixer assembly which is exchangeable on a cartridge storing the components to be mixed and which minimizes the risk of cross-contamination.

[0015] In one or more embodiments, the present disclosure provides a mixer assembly comprising a housing that forms a mixing channel, a static mixing element being arranged within the mixing channel, wherein the mixer assembly further having an inlet end, for receiving two components of a substance and a dispensing end for dispensing a mixture from the components, wherein the inlet end comprises for each component an inlet defining an inlet plane and an associated non-retum valve, and wherein each of the inlets is connectable for fluid communication with the mixing channel via the associated non-retum valve, wherein the non-retum valve comprises a flap, wherein the flap includes a first flap section arranged generally perpendicular to the inlet plane and a second flap section arranged at an obtuse angle relative to the first flap section.

[0016] In one embodiment each of the non-retum valves preferably permits a flow of the respective component in a direction from the inlet toward the mixing channel. Further, each of the non-retum valves preferably blocks a flow of the respective component in a direction from the inlet toward the mixing channel. Accordingly, each non-retum valve typically permits a flow of the components in a direction from the inlets toward the outlet end but blocks a flow in the opposite direction. Further, with respect to a direction of flow of the components the non-retum valves are preferably located downstream from the inlets. The semi-rigid flaps provide enhanced resistance to reversed flow of components, as well as blocking at least blue light from entering the mixing channel when at rest.

[0017] In an embodiment the mixer assembly further comprises for each component a passageway that at a first end forms the respective inlet and at a second end forms an orifice into the mixing channel. Thus, each passageway preferably forms a channel between the respective inlet and the respective orifice and the non-retum valve only permits a one-way flow of the respective component in a direction from the inlet toward the orifice.

[0018] In a further embodiment the non-retum valve is arranged between the inlet and the orifice. The non-retum valves are thus arranged within the mixer assembly, so that the mixer assembly, for example after use, can be replaced by a new mixer assembly including the non-retum valves. This is advantageous in that the non-retum valves prohibit any portion of one or more components which have reached the mixing channel to flow back to the inlets. Therefore, the inlets are kept free from any component, intermingled components or a mixture of the components which previously have reached the mixing chamber. A larger amount of the components stored in a cartridge used in combination with the mixer assembly therefore can be prevented from cross-contamination of the components with each other.

[0019] In an embodiment each passageway has an inlet-side duct between the inlet and the non- retum valve and a mixer-side duct between the non-retum valve and the orifice. The inlet-side duct and the mixer-side duct further constitute portions of the passageway.

[0020] In a further embodiment each non-retum valve comprises a semi-rigid flap. The flap includes a first flap segment and second flap segment extending at an angle relative to the first flap segment, at a location downstream from the inlet. The flap preferably forms a wall portion of the inlet-side duct and the mixer-side duct. Accordingly, pressure built up in the component flowing past the flap exerts a force on the flap which causes the flap to deflect and thus to open the passageway. In addition to the flap deflecting, the passageway may increase in volume due to the flexing of one or more sections of the housing, leading to additional improvement in the flow of the component towards the mixer. The passageway is preferably generally U-shaped with the inlet-side duct and the outlet side duct forming the legs of the U. The person skilled in the art will recognize alternative configmations for a non-retum valve.

[0021] In an embodiment the mixing element is formed in one monolithic piece and comprises a plurality of mixing paddles and at least two flaps. The mixing paddles are preferably arranged consecutively in a row. The mixing element preferably further comprises the inlets. Preferably, the mixing element comprises a closure plate from a first side of which the row of mixing paddles extend. Each inlet preferably forms an inlet channel which extends through the closure plate. Preferably each inlet further comprises a connector socket through which the inlet channel continues, and which protmdes from a second side of the closure plate opposite of the first side. The connector socket may have an outward cylindrical shape. This connector socket may be received within associated outlets of the cartridge. The mixing element preferably has a first and a second plug protruding from the first side of the closure plate. The first and a second plug may have a general half-moon cross-section.

[0022] In one embodiment the housing adjacent the inlet end comprises at least two blind-holes. Each blind-hole includes a respective one of the flaps extending therein. The blind-holes preferably form part of a recess arranged at the inlet end of the mixer assembly. The closure plate of the mixing element preferably closes the recess. The recess is dimensioned such that a space is provided between an end of the mixing channel and the closure plate. Therefore, a component flowing through the respective inlet (and further through the non-retum valve) in that space is enabled to flow into the mixing channel. The mixing element and the recess are preferably shaped such that the space between the mixing channel and the closure plate defines the orifices for each component.

[0023] In one embodiment each passageway is formed in that the flap divides the space defined by the blind-hole. In particular the blind-hole preferably extends along an insertion axis and may have a stepped inward end face. The stepped end face may have a first partial end face and a second partial end face and a lateral face between the first and second partial end face. The lateral face may be generally parallel to the insertion axis. The lateral face may be planar. Preferably the end of a second segment of the flap abuts the second partial end face. The flap is preferably movable, under fluid pressure, in a direction towards the lateral surface . Further, in a first position, in which the flap abuts the canted partial end face, the inlet-side and mixer-side duct are disconnected from fluid communication with each other, and in a second position, in which the flap deflects toward the lateral surface, the inlet-side duct and the mixer-side duct are connected for fluid communication with each other.

[0024] In one embodiment the housing at the inlet end forms an annular skirt surrounding the inlets. The inlets are preferably offset from an end of the skirt in a direction inward a space that is defined by the skirt. The skirt may be configured to receive an end on a cartridge storing the two components. Such a cartridge may have a respective outlet for each component.

[0025] In an embodiment, the present disclosure provides a mixer assembly for use in a dispenser device, the mixer assembly comprising a cartridge having a first chamber for holding a first component and a second chamber for holding a second component; and a mixer assembly comprising, a housing that forms a mixing channel defining an initial component flow axis, inlet end comprising a first inlet in fluid communication with the first chamber and a first non-retum valve and a second inlet in fluid communication with the second chamber and a second non-retum valve; wherein the mixer assembly further comprises for each component a passageway that at a first end forms the respective inlet and at a second end forms an orifice into the mixing channel, wherein the non-retum valve is arranged between the inlet and the orifice; wherein the non-retum valve divides the passageway into an inlet-side duct between the inlet and the non-retum valve and a mixer-side duct between the non-retum valve and the orifice; wherein the non-retum valve comprises a flap that permits a flow of the components in a direction from the inlets toward the orifices but blocks a flow in the opposite direction; and wherein, when the flap is at rest, an end of the flap is arranged substantially non-parallel to the initial flow-axis.

[0026] In a further aspect, the disclosure relates to a device for dispensing a dental material. The device may comprise a cartridge having at least two chambers for holding two components. The device may further comprise the mixer assembly according to the teachings disclosed herein. The mixer assembly may be detachably attached to the cartridge. In particular, the mixing assembly may be attached to the cartridge so as to connect the inlets of the mixer assembly with the outlets of the cartridge. The cartridge may have a valve for selectively opening and closing the outlets of the cartridge. Such a valve may be a rotary slide valve having a rotatable valve member. The rotatable valve member may be engageable with the mixer assembly so that the valve can be opened and closed by rotating the mixer assembly relative to the cartridge. The device may have a piston disposed in each chamber. The pistons may be used for urging the component toward the mixer assembly for mixing. The pistons may be connected or connectable to respective plungers. The plungers may be connected to a common thrust plate or fingerplate.

[0027] The cartridge may comprise components of the dental material, in particular of a hardenable dental material. The dental material may be configured to harden in consequence of mixing the individual components.

[0028] Brief Description of the Figures

[0029] Fig. 1 is a perspective view of a device for dispensing a dental material according to an exemplary embodiment;

[0030] Fig. 2 is a side view of a mixing element and used with an exemplary embodiment;

[0031] Fig. 3 is a cross-sectional view of a mixing assembly according to an exemplary embodiment at a first stage of operation;

[0032] Fig. 4 is a cross-sectional view of the mixing assembly shown in Fig. 3 at a second stage of operation; and Fig. 5 is a cross-sectional view of the mixing assembly shown in Fig. 3.

[0033] Detailed Description

[0034] Fig. 1 shows a device 1 for dispensing a dental material. The device 1 has a mixer assembly 100, a cartridge 20 and a plunger 30. The cartridge 20 forms two chambers (not visible in this view) for separately storing the dental material in the form of two components. The plunger 30 has two plunger rods 31, 32 for displacing the two components toward the mixer assembly 100. The mixer assembly 100 forms a dispensing opening 11 at a dispensing end 104 of the mixer assembly 100. The device 1 is operable by hand for dispensing dental material. Therefore the device 1 has a finger plate 23 arranged at the cartridge 20 and a pressure plate 33 forming a rear end of the plunger 30. The finger plate 23 in the example is arranged at a rear end of the cartridge 20. It is noted that the present disclosure is not limited to a hand operated device. Rather, the mixer assembly 100 as described may be likewise used with an appropriate cartridge that is operated in a dispensing gun or in a motor driven dispensing apparatus.

[0035] The mixer assembly 100 is received on a front end of the cartridge 20. The mixer assembly 100 and the cartridge 20 are rotatable relative to each other. In particular, the mixer assembly 100 and the cartridge 20 in combination form a rotary valve for selectively opening or closing the chambers of the cartridge 20. Accordingly, the mixer assembly 100 and the cartridge 20 can be rotated relative to each other between a closed position, in which the chambers are closed, and an open position, in which the chambers are in fluid communication with the mixer assembly 100.

[0036] In the open position, moving the plunger 30 forward (in a direction toward the mixer assembly 100) causes the individual components of the dental material to flow through the mixer assembly 100. The mixer assembly 100 has a static mixing element (not visible in this view) which causes the components of the dental material to mix as they flow through the mixer assembly 100. Thus, the dental material is dispensed from the dispensing opening 11 in the form of a mixture from the two components.

[0037] Fig. 2 shows the static mixing element 40 which is arranged within the mixer assembly 100 illustrated in Fig. 1. The static mixing element 40 has a series of mixing paddles 41 arranged along a longitudinal axis A. Each mixing paddle 41 is based on a helical shape or a helicoid. The structure of such a helical mixing paddle can be basically imagined as a planar sheet of material which, held at opposite ends, is twisted or wound by 180 degrees, although other methods (for example injection molding) are typically used to manufacture such a structure. The overall outer shape of such a mixing paddle 41 is based on a cylindrical helix. The mixing paddles typically cause the components to be mixed by dividing and re-merging of a strand of material formed of the two components and flowing through the mixing assembly 100. The mixing paddles 41 are typically right or left handed, meaning differ in the winding direction of the helix on which the mixing paddle 41 is based. The right and left handed mixing paddles 41 are typically consecutively arranged in an alternate order along the longitudinal axis A.

[0038] The mixing paddles 41 in the example have an outer diameter D of between 1.5 mm and 1.6 mm. Further, each mixing paddle 41 has a length L of between 0.6 mm and 1.2 mm, preferably 0.78 mm. The diameter D as well as the Length L is preferably the same for all mixing paddles 41 of the static mixing element 40.

[0039] Fig. 3 shows the mixer assembly 100 in more detail. The mixer assembly 100 has a housing 101 that forms a mixing channel 102. The portion of the housing 101 that forms the mixing channel is a hollow-cylindrical tube. The static mixing element 40 is arranged within the mixing channel 102. In particular, the mixing paddles 41 of the static mixing element (which are formed by a front portion of the static mixing element 40) are arranged within the mixing channel 102.

[0040] The mixer assembly 100 has an inlet end 103, for receiving two components, for example from the cartridge shown in Fig. 1. The mixer assembly 100 further has a dispensing end 104 for dispensing a mixture that is mixed from the components. The inlet end 103 comprises a first inlet 110a and a second inlet 110b. The inlet end 103 further comprises a first non-retum valve 105a which is associated to the first inlet 110a and a second non-retum valve 105b which is associated to the second inlet 110b. The first and second inlet 110a, 110b are formed by a rear portion of the static mixing element 40. The rear portion of the static mixing element 40 is positioned outside the mixing channel 102. In particular, the housing 101 at the inlet end 103 comprises a recess 106. A closure plate 116 of the static mixing element 40 is arranged at the housing 101 such that it seals the recess 106. For positioning and retaining the static mixing element 40 a first and a second plug 119a, 119b are provided at the closure plate 116. The first and second plug 119a, 119b protrude from the closure plate in the same direction as the mixing paddles 41 and are received within the recess 106 by a friction fit. The first and second inlet 110a, 110b are in fluid communication with the (otherwise sealed) recess 106. Further, the recess 106 (or at least part of the recess 106) is in fluid communication with the mixing channel 102 (in the illustrated situation in which the closure plate 116 seals with the housing 101). The mixing element 40 further has a first and a second flap 120a, 120b which each protrude from the closure plate 116 into the recess 106. The recess 106 forms a first and a second blind-hole 106a, 106b into which the first and second flap 120a, 120b, respectively, extend. The first blind-hole 106a in combination with the associated first flap 120a forms a first passageway 107a, and the second blind-hole 106b in combination with the associated second flap 120b forms a second passageway 107b. Each of the first and second passageway 107a, 107b has a first and second inlet-side duct 108a, 108b, respectively, and a mixer-side duct 109a, 109b, respectively. Each of the first and second inlet-side duct 108a, 108b are in fluid communication with the first and second inlet 110a, 110b, respectively. The first and second mixer-side duct 109a, 109b are in fluid communication with a first and a second orifice 117a, 117b, respectively, into the mixing channel 102. In the situation shown in Fig. 3, where no fluid pressure is applied and the situation is “at-resf ’, the first inlet-side duct 108a and the first mixer-side duct 109a are disconnected from fluid communication with each other by the first non-return valve 105a. Further, the second inlet-side duct 108b and the second mixer-side duct 109b are disconnected from fluid communication with each other by the second non-retum valve 105b.

[0041] The first and second non-retum valve 105a, 105b are each formed by the housing 101 in combination with the first and second flap 120a, 120b. In particular, wall portions of the housing 101 which form the first blind-hole 106a form a first open gate at the transition between the first inlet-side duct 108a and the first mixer-side duct 109a, and the first open gate is openably closed by the first flap 120a. Correspondingly, wall portions of the housing 101 which form the second blindhole 106b form a second open gate at the transition between the second inlet-side duct 108b and the second mixer-side duct 109b, and the second open gate is openably closed by the second flap 120b.

[0042] Each of the first and second blind-hole 106a, 106b extends along an insertion axis I. Each of the first and second blind-hole 106a, 106b forms a first and second stepped inward end face 11 la, 11 lb, respectively. In the example, the first end face I l la has a first partial end face 112a, a second partial end face 113a and a lateral face 114a. The first flap 120a, in a first position, abuts the second partial end face 113a adjacent a juncture with the housing 101. Further, the second end face 111b has a first partial end face 112b, a second partial end face 113b and a lateral face 114b. The second flap 120b, in a first position, abuts the second partial end face 113b adjacent a juncture with the housing 101. In this first, at rest position, the first and second flap 120a, 120b, respectively, are fixed against the end faces, 113a, 113b and blocking any opening within the respective blind-hole 106a, 106b that could allow fluid movement. Accordingly, when the flaps are at rest, a flow of a component from the first mixer-side duct 109a toward the first inlet-side duct 108a and a flow of the second mixer-side duct 109b toward the second inlet-side duct 108b are prohibited.

[0043] The first flap 120a includes a first flap segment 121a extending substantially parallel to the lateral face 114a and / or the longitudinal axis A. A second flap segment 122a extends at an obtuse angle C from the first segment 121a in a direction towards the second partial end face 113a. The angle C is measured between upstream surfaces 123a, 124a of the first and second flap segments 121a, 122a and typically is arranged at about 120 to about 160 degrees. In certain embodiments, the angle C is about 130 to about 150 degrees. In the depicted embodiment, an optional stiffening rib 125a connects the first and second flap segments 121a, 122a. The stiffening rib 125a can increase the inherent resistance of the flap 120a to movement away from the second end face 113a in the absence of sufficient fluid pressure. The stiffining rib has a generally smaller width than that of the first and second flap segments 121a, 122a.

[0044] Like the first flap 120a, the second flap 120b includes a first flap segment 121b extending substantially parallel to the lateral face 114b and / or the longitudinal axis A. A second flap segment 122b extends at an obtuse angle C from the first segment 121b in a direction towards the second partial end face 113b. The angle C is measured between upstream surfaces 123b, 124b of the first and second flap segments 121b, 122b and typically is arranged at about 120 to about 160 degrees. In certain embodiments, the angle C is about 130 to about 150 degrees. In the depicted embodiment, an optional stiffening rib 125b connects the first and second flap segments 121b, 122b.

[0045] The shape, structure, and / or material of the first and second flap 120a, 120b are configmed as at least semi-rigid. As used herein, a semi-rigid flap is one that requires at least 2 Mpa of fluid pressure to deflect the second, angled flap segments 122a, 122b away from the housing 101 a sufficient distance to enable component flow. This places the semi-rigid flaps of the present disclosure as more rigid than such resilient flaps of the prior art, which are moveable under significantly less fluid pressure. The present inventors surprisingly discovered that despite the significant increase in rigidity, the use of the flaps 120a, 120b of the present disclosure does not materially increase the difficulty in depressing the plunger and / or moving the components into the mixing assembly 40. Without wishing to be bound by theory, the enhanced rigidity of the flap cause the housing 101 to slightly expand in volume when fluid pressure builds up against the upstream surfaces of the respective flap 120a, 120b. The expansion of the housing 101 tends to reduces the force necessary to advance the plunger, despite the otherwise attendant increase in force necessary to displace the flap 120a, 120b.

[0046] In the first position, the inherent, structural rigidity of the first and second flap 120a, 120b resists any movement of the first and second flap 120a, 120b in a direction of a flow of a component from the first and second mixer-side duct 109a, 109b toward the first and second inlet-side duct 108a, 108b. Accordingly, from the first position the first flap 120a can bend away from the second partial end surface 113a so as to open the first gate and thereby enable a flow of a component from the first inlet-side duct 108a toward the first mixer-side duct 109a. Further, from the at rest position the second flap 120b can bend away from the second partial end surface 113b so as to open the second gate so as to enable a flow of a component from the second inlet-side duct 108b toward the second mixer-side duct 109b.

[0047] Fig. 4 shows the mixer assembly 100 with the first and second flap 120a, 120b in a second position in which the first and second flap 120a, 120b are bent away from the respective sealing surface 113a, 113b. The first and second flap 120a, 120b are urged in the second position against a natural reset force provided by the material and structure of the first and second flap 120a, 120b. This means that preferably, the first and second flap 120a, 120b are provided in a shape that corresponds to shape associated with the first position, and that a force is required to deflect the first and second flap 120a, 120b toward a shape which corresponds to the shape associated with the second position. Further, thus the first and second flap 120a, 120b also typically reset toward the first position by natural reset force provided by the material and structure of the first and second flap 120a, 120b. The force for deflecting or bending the first and second flap 120a, 120b is typically provided by the components being urged and flowing in a direction from the first and second inletside duct 108a, 108b to the first and second mixer-side duct 109a, 109b, respectively. Such a flow of the components is indicated by a first and a second arrow 118a, 118b . In case the flow would be reversed the reverse flow accordingly would cause the first and second flap 120a, 120b to reset from the second position to the first position so that the first and second passageway 107a, 107b are blocked and thus the reverse flow is prohibited as soon as the first position has been established. Furthermore, the flaps 120a, 120b tend to quickly return to the first position upon a user pulling the plunger 30 backward. Accordingly, any cross-contamination between the components in an area of the first and second inlet 110a, 110b can be prevented. It has been found that a reverse flow of the components may occur, for example, in consequence of disconnecting the mixing assembly 100 from the cartridge 20, for example due to a vacuum being caused during disconnecting the first and second inlet 110a, 110b from respective outlets provided at the cartridge 20. Further, crosscontamination may be caused by asynchronous urging the two components toward the mixing assembly 100, or in consequence of temperature variation or a difference in viscosity between the two components. With the present disclosure such cross-contamination can be avoided. Thus, if used for the preparation of a hardenable material, for example a dental material, the individual components stored in the cartridge can be effectively protected from cross-contamination. Therefore, the shelf-life of the components in the cartridge can be maximized.

[0048] Fig. 5 shows a cross-section of the mixer assembly 100, in the first position of the first and second flaps 120a, 120b. The housing 101 has a first and a second spacer 120a, 120b arranged within the first and second blind-hole 106a, 106b, in particular within the first and second mixer-side duct 109a, 109b, respectively. The first and a second spacer 130a, 130b limit a travel of the first and second flap 120a, 120b in the second position of the first and second flap 120a, 120b to prevent the first and second flap 120a, 120b to close the first and second mixer-side duct 109a, 109b in the second position. As illustrated, the first and second spacer 130a, 130b maintain flow channels (indicated as 131a, 13 lb) for the components in the seco nd position of the first and second flap 120a, 120b. The design of the flaps 120a, 120b tends to block ambient light of all wavelengths from entering the cartridge from the mixing element when the flaps 120a, 120b are at rest. The blocking of ambient light can help avoid premature curing of the components, further optimizing the shelflife of the components in the cartridge.

Claims

Claims1. A mixer assembly for use in a dispenser device, the mixer assembly comprising a cartridge having a first chamber for holding a first component and a second chamber for holding a second component; and a mixer assembly comprising, a housing that forms a mixing channel defining an initial component flow axis, inlet end comprising a first inlet in fluid communication with the first chamber and a first non-retum valve and a second inlet in fluid communication with the second chamber and a second non-retum valve; and wherein the mixer assembly further comprises for each component a passageway that at a first end forms the respective inlet and at a second end forms an orifice into the mixing channel, wherein the non-retum valve is arranged between the inlet and the orifice; wherein the non-retum valve divides the passageway into an inlet-side duct between the inlet and the non- retum valve and a mixer-side duct between the non-retum valve and the orifice; wherein the non-retum valve comprises a flap that permits a flow of the components in a direction from the inlets toward the orifices but blocks a flow in the opposite direction; and wherein, when the flap is at rest, an end of the flap is arranged substantially non-parallel to the initial flow-axis.

2. The device of claim 1, wherein the mixer assembly includes a dispensing end for dispensing a mixture of the components.

3. The device of claim 1, wherein each flap includes a semi-rigid flap structure.

4. The device of claim 1, wherein the flap forms a wall portion of the inlet-side duct and a wall portion of the mixer-side duct.

5. The device of claim 1, wherein, at rest, the flap blocks at least blue light from entering the mixer-side duct.

6. The device of claim 1, wherein, when the component enters the passageway, a volume of the passageway increases.

7. The device of claim 6, wherein a wall section of the passageway flexes in response to a flow of the components in a direction from the inlets toward the orifices.

8. The device of claim 1, wherein the mixing element is formed in one monolithic piece and comprises a plurality of mixing paddles and the two flaps.

9. The device of claim 1, wherein, at rest, the inlet-side duct and the mixer-side duct are not in fluid communication.

10. The device of claim 1, wherein the flap includes a first flap section arranged parallel to the flow axis and a second flap section arranged at an obtuse angle relative to the first flap section.

11. The device of claim 10, wherein the second flap section is arranged at a 120 to 160 degree angle.

12. The device of claim 11, wherein the second flap section is arranged at a 130 to 150 degree angle.

13. The device of claim 1 , wherein the flap includes a stiffening rib extending between the first flap section and the second flap section.

14. The device of claim 13, wherein the rib has a width less than a width of the first flap section.

15. The device of claim 1, wherein the housing adjacent the inlet end comprises two blind-holes, wherein in each blind-hole one of the flaps extends.

16. The device of claim 15, wherein at least one of the blind-holes extends along an insertion axis and has a sloped sealing face and a sidewall, wherein the sloped sealing face is generally arranged at an obtuse angle to the sidewall, and wherein the end of the flap abuts the sloped sealing face near the sidewall.

17. The device of claim 16, wherein the flap is movable in a direction away from the sealing surface, wherein in at rest in a first position, in which the flap abuts the sealing surface, the inletside duct and the mixer-side duct are disconnected from fluid communication with each other, andin a second position, in which the end of the flap moves away from the seating surface, the inletside duct and the mixer-side duct are connected for fluid communication with each other.

18. A method for dispensing a dental material, the method comprising: providing a dispenser including a plunger, a cartridge having a first chamber holding a first component and a second chamber holding a second component; and a mixer assembly comprising, a housing that forms a mixing channel defining a component flow axis, inlet end comprising a first inlet in fluid communication with the first chamber and a first non-retum valve and a second inlet in fluid communication with the second chamber and a second non-retum valve; and wherein the mixer assembly further comprises for each component a passageway that at a first end forms the respective inlet and at a second end forms an orifice into the mixing channel, wherein the non- retum valve is arranged between the inlet and the orifice; wherein the non-retum valve divides the passageway into an inlet-side duct between the inlet and the non-retum valve and a mixer-side duct between the non-retum valve and the orifice; wherein the non-retum valve comprises a flap configmed to permit a flow of the components in a direction from the inlets toward the orifices but blocks a flow in the opposite direction; and wherein, when the flap is at rest, an end of the flap is arranged substantially non-parallel to the flow-axis, moving the plunger in the direction of the mixing element, causing the first and second components to flow through the mixing assembly under a fluid pressure, wherein the fluid pressure displaces the associated flap to permit flow of the components, and wherein removal to the fluid pressure causes the flap to self-return to block flow of the component back toward the inlet.

19. The method of claim 18, wherein the mixer assembly includes a dispensing end for dispensing a mixture of the components, and wherein method further comprises dispensing the mixture from the dispensing end.

20. A mixer assembly comprising a housing that forms a mixing channel, a static mixing element being arranged within the mixing channel, wherein the mixer assembly further having an inlet end, for receiving two components of a substance and a dispensing end for dispensing a mixture from the components, wherein the inlet end comprises for each component an inlet defining an inlet plane and an associated non-retum valve, and wherein each of the inlets is connectable for fluid communication with the mixing channel via the associated non-retum valve, wherein the non- retum valve comprises a flap, wherein the flap includes a first flap section arranged generallyperpendicular to the inlet plane and a second flap section arranged at an obtuse angle relative to the first flap section.

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