Dental impression tray for use in obtaining an impression of a dental structure

A dental impression tray, a kit, and method of using the same are provided for taking an impression of at least a portion of a dental structure of a patient. The tray can include a tray portion, fiduciary markers, and can also have a holding section with two opposing sides and fasteners disposed thereon. The kit can include the tray and a handle portion. The handle can be removably secured to the holding section of the tray. In some embodiments, the handle can include a pair of handle portions. In other embodiments, a part of the handle can be aligned with a facial feature of a patient from whom a dental impression is to be obtained.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a national stage application under 35 U.S.C. §371 of PCT Application No. PCT/SE2007/000925 designating the United States, filed on Oct. 18, 2007. The PCT Application was published in English as WO 2008/051142 A1 on May 2, 2008 and claims the benefit of the earlier filing date of Swedish Patent Application No. 0602272-7, filed on Oct. 27, 2006. The contents of PCT Application No. PCT/SE2007/000925, including publication WO 2008/051142 A1, and Swedish Patent Application No. 0602272-7, are incorporated herein by reference in their entirety.

BACKGROUND

1. Field of the Inventions

The present application relates to a dental impression tray for making an impression of a dental structure such as, for example, the dentition of a patient.

2. Description of Related Art

Dental impression trays are used to obtain an impression of a dental structure, such as a patient's dentition. Such impressions can be used, for example, in connection with procedures for making a dental model. A dental impression tray generally includes a tray portion that is contoured to fit over at least a part of a dental structure of which an impression is to be obtained. Such a dental structure may be, for example, a part of a patient's upper or lower dentition. The dental structure may also be, for example, a cast of a patient's dentition.

Techniques for obtaining a dental impression include the single arch and the closed bite technique. In the closed bite technique, a dental impression material is placed in the tray portion and the tray portion is applied to a dental structure such as the dentition of a patient. When the dental impression tray is applied to a patient, the patient will then bite into the impression material to create an impression of the patient's dentition. If the dental structure is a model of a dentition, for example a cast, the dental structure may be pressed into the impression material. Impressions created in this way can be impressions of both a patient's upper and lower dentition. However, it is also possible to make an impression of only the lower dentition or only the upper dentition.

An impression can also be an impression of, for example, only a part of a patient's upper dentition or only a part of a patient's lower dentition. The dental impression can be used for casting a model of the dental structure. As an alternative to using the dental impression for casting a model, a scanning operation can be performed directly on the dental impression itself. Such a procedure is disclosed in U.S. Pat. No. 6,217,334.

In U.S. Pat. No. 5,338,198, a dental modeling simulator is disclosed. As described in that patent, a molded impression of a patient's teeth is taken. The impression is placed on a support table that defines an X-Y plane and a beam of laser light is directed onto the impression to scan the impression with the beam. The scanning is then used to generate a digital image. The tray may be provided with predefined identification marks at upper and lower sides.

SUMMARY

Accordingly, embodiments of the present inventions preferable seek to mitigate, alleviate or eliminate one or more deficiencies, disadvantages or issues in the art, such as the above-identified, singly or in any combination by providing a dental impression tray that can be used to obtain an impression of at least a part of a dental structure such as, for example, the dentition of a patient, a method for making an impression, and a method for making a virtual model according to the appended patent claims.

The present application relates to a dental impression tray for use in obtaining an impression of at least a part of a dental structure such as, for example, the dentition of a patient. As used herein, the term “dental structure” should be understood as including not only dentitions or models thereof, but also structures covered by soft tissue that may be found in the mouth of patients that have lost their teeth and models of such structures.

In some embodiments, the dental impression tray comprises a tray portion adapted to be loaded with impression material. The tray portion is contoured to fit over at least a part of a dental structure (for example a dentition). In some embodiments, the dental impression tray further comprises a handle connected to the tray portion or adapted/shaped to be connected to the tray portion. The handle has a first end at which the handle is connected to the tray portion or adapted to be connected to the tray portion. The handle also has a second end that is a distal end in relation to the tray portion when the handle is connected to the tray portion.

In some embodiments of the invention, the second end of the handle has an edge facing away from the tray portion. In such embodiments, the edge may form a visible line when it is seen from the side facing away from the tray portion. The straight line has a length of at least 30 mm. In some embodiments, the line that is formed by the edge when seen from the side facing away from the tray portion may be a straight line that has a length of at least 60 mm. In some embodiments, the line formed by the edge may have a length of at least 80 mm.

In some embodiments, the handle may be removably secured to the tray portion.

In some embodiments, the handle may comprise two separate parts that are adapted to be connected to each other such that the separate handle parts overlap each other partially, but not completely. In such embodiments where the handle comprises separate parts, the separate handle parts may be adapted to be connected to each other by a snap-on catch formed by the handle parts. However, the connection could also be something else than a snap-on connection. In embodiments where the handle comprises separate parts, the separate parts may be identical in shape. Embodiments are also possible where separate handle parts are not identical in shape.

In embodiments where the handle comprises separate handle parts, each of the separate handle parts may be designed to cooperate with a complementary part of the tray portion in such a way that the handle is locked to the tray portion as long as the separate handle parts are connected to each other.

In some embodiments, the handle may be shaped to define a slot having a length extending at least 30 mm in a direction from the second end of the handle towards the first end of the handle. Such a slot should have a width of at least 10 mm such that objects having a width of up to 10 mm may be moved along the length of the slot.

Possibly, the slot may extend all the way to the edge of the second end of the handle such that the slot divides the edge in two parts.

The tray portion has a shape that defines a cavity with an inner wall. In some embodiments, the dental impression tray may also comprise at least one pad that fits into at least a part of the cavity of the tray portion. In such embodiments, the inner wall may optionally be provided with a first guide structure and the pad may be provided with a second guide structure that fits the first guide structure. Thereby, the first and second guide structures may cooperate with each other. For example, the guide structures may permit the pad to move in the tray portion in a movement guided by the cooperating guide structures and be pressed against a lower part of the tray portion. In this way, the at least one pad can be placed in the tray portion, pushed down guided by the guide structure and finally held in place by the guide structure. The first guide structure may comprise projecting parts forming rails and the second guide structure comprises grooves adapted to receive the projecting parts of the first guide structure. An alternative possibility could be, for example, that the second guide structure comprises rails that interact with grooves in the inner wall.

The pad can be made of many different materials. In some embodiments, the pad is made of an elastic material.

In some embodiments, the tray portion may be contoured to fit over a part of both the upper and lower dentition of a patient and an outer surface of the dental impression tray may be provided with at least one fiduciary marker that can be detected in a scanning operation. Such a fiduciary marker can take many different shapes and may be accomplished in many different ways. In some embodiments, such a fiduciary marker can be made in a material that is opaque to radio waves.

The tray portion may optionally have a wall with a slot to accommodate a patient's upper frenum when the tray portion is fitted over an upper dentition of a patient.

In some embodiments, the dental impression tray may be provided with a machine readable marking such as, for example, an RFID tag. The machine readable marking could also be accomplished in other ways, for example as a bar code.

In some embodiments, the tray portion may be contoured to fit over at least a part of both the upper and lower dental structure of a patient such that an impression can be obtained simultaneously from both the upper and the lower dental structure. In such embodiments, the tray portion may optionally have a holding section with a first side facing in a first direction and a second side placed opposite the first side and facing in a second direction that is opposite to the first direction. Each of the first and second side of the holding section has at least one fastener by means of which the holding section can be locked to a holder having a part with a shape that is complementary in shape to the fasteners on the holding section. The fasteners on both sides of the holding section have the same form such that each side of the holding section can be locked to one and the same holder.

In such embodiments, the holding section may be formed by a projecting part on the tray portion and the fasteners on the opposite sides of the holding section may be shaped by parts of the holding section that define recesses in the holding section. Alternatively, the fastener or fasteners on each side of the holding section may be formed by one or several male elements such as pegs.

In embodiments having a holding section with sides facing in opposite direction and having fasteners on the opposite sides of the holding section, the dental impression tray may further also comprise a handle that can be secured to the tray portion and removed from the tray portion. The handle may then be provided with fastening elements that are complementary in shape to the fasteners on at least one of the opposite sides of the holding section.

In some embodiments, a removable handle for the dental impression tray may comprise at least a first and a second handle part that can be pressed together to form a complete handle. The handle may then optionally have a locking device that can placed in a first position to lock the handle parts to each other and in a second position where the handle parts can be moved away from each other.

The locking device and the first handle part may be shaped such that the locking device is a movable on the first handle part, but cannot be separated from that part. The second handle part may then have a first section corresponding to the second position of the locking device and having such dimensions that the handle parts can be pressed together or moved away from each other when the locking device is in the second position. The second handle part may further have a second section corresponding to the first position of the locking device and having such dimensions that the first and second handle part will be locked to each other when the locking device is placed in its first position and the handle parts are pressed against each other.

In one embodiment, the dental impression tray may form part of a kit used for making a dental impression and holding the impression for a scanning operation. Such a kit may comprise a dental impression tray with a tray portion adapted to be loaded with impression material and contoured to fit over at least a part of both the upper and lower dental structure of a patient such that an impression can be obtained simultaneously from both the upper and the lower dental structure. The tray portion has a holding section with a first side facing in a first direction and a second side placed opposite the first side and facing in a second direction that is opposite to the first direction. Each of the first and the second side of the holding section has at least one fastener by means of which the holding section can be locked to a holder having a part with a shape that is complementary in shape to the fasteners on the holding section. The fasteners on both sides of the holding section have the same form such that each side of the holding section can be locked to one and the same holder. The dental impression tray further comprises a handle that can be secured to the tray portion and removed from the tray portion and the handle is provided with fastening elements complementary in shape to the fasteners on at least one of the opposite sides of the tray portion such that the handle can be secured to the tray portion. The kit further comprises a holder having a part with a shape that is complementary in shape to the fasteners on the holding section of the tray portion and which is identical to the shape of the fastening elements on the handle.

The kit with the dental impression tray and the holder may be used together with scanning equipment in a method for making a dental impression of an upper and a lower dental structure and scanning the impression. In such a method, the handle is secured to the tray portion by means of the fasteners on the holding section and the fastening elements on the handle. The tray portion is loaded with impression material. This can be done after the handle has been secured to the tray portion, but may also be done before the handle has been secured to the tray portion. The tray portion is then placed in the mouth of a patient while the tray portion is guided by means of the handle. An impression is then made of at least a part of the patient's upper and lower dental structure. When the impression has been made, the tray portion is removed from the mouth of the patient and the handle is removed from the tray portion.

The method of making a dental impression and scanning the impression further includes providing a holder having a part that is complementary in shape to the fasteners on the holding section and which is identical to the shape of the fastening elements on the handle. The tray portion is secured to the holder by connecting the first side of the holding section of the tray portion to the holder. A first side of the tray portion is then scanned to obtain a scanning of one of the dental impressions obtained (i.e. an impression of a part of a patient's upper or lower dental structure). The tray portion is removed from the holder and turned 180°. The tray portion is then secured to the holder again which is done by connecting the second side of the tray portion to the holder. After this, a second side of the tray portion is scanned to obtain a scanning of the second dental impression.

DETAILED DESCRIPTION

With reference toFIG. 1, a dental impression tray1is shown. The dental impression tray can be used to obtain an impression of at least a part of a dental structure such as, for example, the dentition of a patient. The dental impression tray1comprises a tray portion4adapted to be loaded with impression material. An impression material that can be used with the inventive impression tray1may be, for example, a silicon based material. Such impression materials are sold by, for example, 3M ESPE Dental Products, 3M Center, St. Paul Minn., United States. One such material is sold by 3M ESPE under the name IMPRINT™ 3 VPS Impression Material.

The tray portion4is contoured to fit over at least a part of a dental structure such as the dentition of a patient. As can be seen inFIG. 1, the dental impression tray1further comprises a handle6that is connected to the tray portion4or adapted to be connected to the tray portion4. The handle6has a first end7at which the handle6is connected to the tray portion or adapted to be connected to the tray portion4. The handle6also has a second end8that is a distal end in relation to the tray portion4when the handle6is connected to the tray portion4. The handle6can be used to grip the dental impression tray1and manipulate the dental impression tray1for purposes that will be explained in the following.

With reference toFIG. 2, it can be seen how the dental impression tray1has been placed in the mouth of a patient in order to create an impression of the patient's dentition. InFIG. 2, a patient is biting into the impression material placed in the tray portion4of the dental impression tray1while the handle6remains outside the mouth of the patient. As can be seen inFIG. 4, the tray portion4has an inner cavity21that may optionally be divided by a partition30into an upper cavity21aand a lower cavity21b.

It should be understood that, as used herein, the terms “upper cavity” and “lower cavity” refer to what is “upper” and “lower” when the tray portion4is located inside the mouth of a patient. The tray portion4may very well be designed such that both sides of the tray portion may be applied to both the upper and the lower dentition of a patient. The cavity that is regarded as the “upper” cavity or the “lower” cavity is thus arbitrary. The upper part of the tray portion4with its upper cavity21acan be used to make an impression of an upper dental structure31, for example an upper dentition31. A part of the tray portion4with its lower cavity21bcan be used to make an impression of a lower dental structure or dentition32. The partition30may be, for example, an elastic fabric such as a rubber fabric30or synthetic fabric30. As can be seen inFIG. 4, the upper and lower cavities21a,21bof the tray portion4are filled with dental impression material5in which an impression is made when the patient bites into the tray section4, as schematically indicated inFIG. 4.

When the patient has bitten into the tray portion4, the tray portion4can be removed from the patient's mouth and placed in a scanning device, as shown inFIGS. 6aand6b. In the scanning device, a scanning operation can be performed on the impression which is left in the impression material5that lies in the tray portion4. The scanning can be used to create a virtual image or model of the dental structure of which an impression has been made. The scanning operation can be performed, for example, in the way that has been disclosed in U.S. Pat. No. 5,338,198, incorporated herein by reference.

Of course, the impression does not necessarily have to be scanned. A possible alternative to a scanning operation could be, for example, to use the impression as a mould to cast a representation of the dental structure that the dental impression tray has been applied to. In such a casting operation, plaster could be used to create a cast representation of the dental structure in question.

When the dental impression tray1is applied to the mouth of a patient in order to create an impression of the dental structure of the patient, it is desirable that the tray portion4be positioned correctly such that the impression obtained can be used to create a new dentition that corresponds to a symmetrical bite plane. In this context, the “bite plane” should be understood as a plane where the upper and lower dentitions meet each other when the patient bites.

One way of achieving the desired symmetry can be to align the handle6of the dental impression tray1with a feature of the patient's face. This is illustrated inFIG. 1,FIG. 2,FIG. 3andFIG. 8. With reference toFIG. 1andFIG. 8, the second end8or8″ of the handle6or6″ has an edge9or9″ that is facing away from the tray portion4. As can be seen inFIG. 2andFIG. 3, the edge9forms a visible straight line10when the edge is seen from the side facing away from the tray portion4. The edge may optionally be painted or otherwise marked to make the line10more easily visible. The edge9can be made to be parallel with a plane that divides the upper part of the tray portion4from the lower part of the tray portion4.

In the patient's face, one feature of the patient's face that can be used for alignment is the eyes, i.e. a straight line defined by the patient's own eyes. When the tray portion4is correctly positioned in the patient's mouth, the edge9of the handle6should then be parallel with a straight line between the patient's eyes. The handle6allows a user to manipulate the dental impression tray1(and thereby also the tray portion4that is connected to the handle6). By gripping the handle6and aligning the edge9of the handle6with the eyes of the patient, the person making the impression can thus ensure that the tray portion4is correctly positioned in the patient's mouth.

InFIG. 3, a front view of a patient with a dental impression tray in his mouth is presented. InFIG. 3, the edge9of the handle forms a visible straight line10to a person who is watching the patient face-to-face. The edge9itself may possibly be straight, but could also be curved inwards (i.e. towards the tray portion4) or outwards (away from the tray portion4). What matters is only that it appears as a straight line when regarded from the side facing away from the tray portion4. It should be understood that the edge9extends in a plane. The straight line10formed by the edge9is then visible when it is regarded in the plane in which the edge9extends.

The distance between the eyes is, of course, something that varies between different individuals. However, 20-25 mm is a normal value for the closest distance between the eyes of an adult person (the distance between the corners of the eyes closest to the nose). This value corresponds to the distance D3inFIG. 3. If the length of the straight line10is at least 30 mm, it will normally be equal to or larger than the smallest distance between the eyes of an adult person. For this reason, it is considered that the straight line10should have a length of at least 30 mm to ensure that it can easily be aligned with the eyes of the patient.

Instead of the shortest distance between the eyes, the length of the straight line10could be based on the normal distance between the pupils. For this distance, 60 mm can be mentioned as a representative value for many adult individuals. This value corresponds to the distance D2inFIG. 3. Alternatively, the length of the straight line10may be based on the largest distance between the eyes, i.e. the distance between those corners of the eyes that are most far away from the nose. That corresponds to the distance D1inFIG. 3. For this distance, 80 mm can be mentioned as a representative approximate value for many adult individuals.

To make the alignment more exact and reliable, the straight line formed by the edge9when seen from the side facing away from the tray portion4may therefore be given a length of at least 60 mm. To further increase precision in the alignment, the length of the straight line10can be chosen to be at least 80 mm.

A front view of the entire dental impression tray1is shown inFIG. 11where both the tray portion4and the handle6′″ are visible as well as the straight line10′″ formed by the edge9′″ of the handle6′″.

It should be understood that the edge9at the second end8of the handle6could be shaped in other ways to permit alignment with the feature of the patient's face. For example, it could have an L-shaped form for alignment with the patient's nose and only one of the patient's eyes. The part of the handle that is used to align the tray portion4with a part of the patient's facial features could also be located elsewhere than at the second end8of the handle6.

The basic idea behind the embodiment with the edge that forms a straight line can thus be generalized in terms of shaping the handle in such a way that it can be used to align the tray portion4with a part of the patient's facial features. The same idea can also be expressed in terms of a method of making an impression in which a part of the handle6is used for alignment with a part of a patient's facial features. By gripping the handle6, and manipulating the dental impression tray1such that the straight line10becomes aligned with a part of the patient's facial features, the person using the dental impression tray will thereby automatically manipulate the tray portion4such that it will be correctly positioned. The method may also be defined more generally as a method for making an impression of at least a part of a patient's dental structure as follows.

The method comprises providing a dental impression tray1having a tray portion4contoured to fit over at least a part of a dental structure, the dental impression tray1further has structure6that allows a user of the dental impression tray1to manipulate the tray portion4when the tray portion4is placed in the mouth of the patient. This structure6also defines a line10that is visible when the tray portion4is placed in the mouth of a patient. The tray portion4is placed in the mouth of a patient and a comparison is made between the line10and a facial feature of the patient. The tray portion4is then manipulated until the line10becomes aligned with said facial feature of the patient. The structure6that allows a user to manipulate the tray portion4may be a handle6connected to the tray portion (or adapted to allow connection to the tray portion4). The line10may be a straight line10that is defined by an edge of the handle6. Possibly, the line10could have some other shape than just a straight line. For example, it could be an L-shaped line that can be aligned with the nose of a patient and an eye of the patient. A straight line can easily be aligned with a straight facial feature such as a line between the eyes. However, the line10could optionally be a curved line.

Another embodiment will now be explained with reference toFIGS. 5a-11. With reference toFIG. 6aandFIG. 6b, the dental impression tray1can be placed in a scanning device having a chamber34where an impression can be scanned. The scanning can be performed by, for example, a laser device such as a line laser device. InFIG. 6b, a laser scanning device is shown schematically that has a laser light source35and a detector36. The tray portion4together with an impression of a dental structure (for example a dentition) can be placed on a table, carrier or platform37that can perform a rotating movement while the scanning is performed.

When the dental impression tray1is placed in the chamber34of the scanning device, the handle6could present an obstacle. This is especially the case of the dental impression tray1is placed on a platform that rotates and the chamber34is small. To prevent the handle6from causing problems during scanning, it may be desirable to remove the handle6from the tray portion4. To ensure the handle6can be quickly and easily removed from the tray portion4, some embodiments include the use of a handle6that is removably secured to the tray portion4.

With reference toFIG. 5a, an embodiment is schematically illustrated where the handle6′ may be removably secured to the tray portion4. As shown inFIG. 5a, the handle6′ may have one or several fastening elements16,17adapted to fit one or several corresponding fasteners18that may be areas of the tray portion4that have been shaped as one or more recesses. The fastening element or elements16,17may be projections, for example, pegs or some other male elements. If the fasteners18on the tray portion4are shaped as recesses, they may be formed as holes or openings. By pressing the fastening element(s)16,17into such recesses in the tray portion4, it is possible to secure the handle6′ to the tray portion4. Of course, the handle6′ can also be removed from the tray portion4. This can be achieved by removing the fastening element(s)16,17from the recess or recesses in the tray portion.

InFIG. 5a, an embodiment is shown where the fasteners18are formed by recess(-es) in a projecting part33on the tray portion4. Of course, it should be understood that such recesses could also be formed elsewhere on the tray portion4. It should also be understood that, as an alternative, the fasteners18on the tray portion4may also be formed as projections on the tray portion4and be adapted to fit one or several recesses on the handle6′. The fastening elements16,17would then be formed by areas defining one or more recesses.

Embodiments are possible where the handle6is made in one single piece. However, the handle6can also be made in more than one piece as indicated inFIG. 5awhere the handle6′ comprises two separate parts12,13. It should also be understood that the handle6may comprise more than two parts.

An embodiment where the handle6comprises two separate parts will now be explained with reference toFIGS. 5a-5band7-10. As shown inFIG. 5a, the handle6′ for the tray portion4may comprise a first and a second part12,13that may be separated. The separate handle parts12,13can be adapted to be connected to each other such that the separate handle parts12,13overlap each other partially, but not completely. This is best seen inFIG. 7andFIG. 8.

As indicated inFIG. 7andFIG. 8, the first and second handle parts12″,13″ are connected to each other in such a way that, when connected, there is a part38on each of separate handle part12″,13″ that is not overlapped by the other handle part12″,13″. InFIG. 8, it can thus be seen that the second handle part13″ has a part38that is not covered by the first handle part12″. This makes it easy to grip the handle6″ and pull or bend the first and second handle parts12″,13″ apart from each other.

As shown also in, for example,FIG. 7, the handle parts12″,13″ have been connected to each other to form a coherent handle6″. The handle parts12″,13″ may optionally be adapted to be connected to each other by a snap-on catch formed by the handle parts12″,13″. With reference toFIG. 12andFIG. 8, the snap-on catch may be formed by male elements14or14ivand female parts15or15ivinto which the male elements14or14ivmay be pressed to a snap fit attachment. The male elements14or14ivmay be formed by, for example, pegs. The female parts15or15may be, for example, openings or through-holes. If the female parts15or15ivare through-holes15or15iv, the male elements14or14iv(e.g. pegs) may be visible from the other side. With reference toFIG. 8, it can be seen that pegs14have been pressed through holes15to be visible from the outside when the handle parts12″,13″ are connected to each other. One way of achieving a snap-on catch may be to design the male elements14as conical pegs while the female parts15may be holes with a conical shape that corresponds to the conical pegs14. With reference toFIG. 12, it can be seen that the handle6ivhas handle parts12ivand13ivwith an edge9iv.

As indicated inFIGS. 7-10, the separate handle parts12″,13″ maybe identical in shape. If they are also unsymmetrical, they will not overlap each other completely when they are put together and connected to each other as indicated inFIGS. 7-10. When the handle parts12″,13″ are put together, they can thus be put together “belly-against-belly” with the back sides facing away from each other. The handle parts12″,13″ will still not overlap each other completely since they are unsymmetrical. If the handle parts12″,13″ are identical in shape, the cost of manufacturing the handle parts can be reduced. Moreover, any two parts12″,13″ can always be connected to each other to form a complete handle6″. However, embodiments are of course also possible where the handle parts12″,13″ are not identical in shape. The handle6″ has a first end7″.

As shown in for exampleFIG. 9andFIG. 10, each of the separate handle parts12″,13″ may be provided with fastening element16″,17″, for example, some kind of projection/male element that can cooperate with a complementary fastener18on the tray portion4, e.g., a part shaped to define a recess as explained previously with reference toFIG. 5a. When the separate handle parts12″,13″ are connected to each other by a snap connection, the handle6″ is locked to the tray portion4as long as the separate handle parts12″,13″ are connected to each other. The handle parts12″,13″ may be held together by the snap connection and the fastening elements16″,17″ that connect the handle6″ to the tray portion4will thus be held in place until the first and second handle parts12″,13″ are separated from each other.

The idea of using a removably secured handle6can be combined with the idea of using a handle that can be used for alignment with a facial feature of a patient. However, it can also be used independently of how the handle is otherwise designed.

The idea of using a tray portion with a removably secured handle, e.g.,6′ or6″ inFIGS. 5aand7, may also be defined in terms of a method in which a dental impression is made, the handle6′ or6″ removed from the tray portion4and the tray portion4placed in the scanning device and scanned.

The dental impression tray1may optionally be packaged with the handle6′ or6″ disconnected from the tray portion4. This can make the dental impression tray1shorter to make it fit into a smaller space, e.g. for purposes of packaging.

While the idea of using a removable handle6has been described above, it should be understood that embodiments are conceivable that have a handle6that is fixedly connected to the tray portion4. For example, the handle6can be made in one piece with the tray portion4.

Another embodiment will now be explained with reference toFIG. 13a. In some cases, the person handling the dental impression1tray may prefer to keep the handle6on the tray portion4. This may be the case, for example, if the dental impression tray1is used to cast a plaster model of the impression. The same situation applies if the handle is not detachable. In such cases, the dentist or dental technician may want to use the dental impression tray1together with existing equipment that may interfere with the handle6v. One way of solving this problem may be to provide a slot in the handle6v.

As can be seen inFIG. 13a, the handle6vmay be shaped to define a slot20v. Components of existing equipment may include, for example, an incisal pin50for an articulator. An incisal pin in an articulator is typically used to adjust the distance between an upper and a lower model of a dentition. Incisal pins for articulators may typically have a diameter of up to 10 mm and it should be possible to move the handle relative to such objects at least 20 mm. Therefore, the length of the slot20vmay be chosen such that it extends at least 30 mm in a direction from the second end8vof the handle6vtowards the first end7vof the handle6v.

The slot20vmay be given a width of at least 10 mm such that objects having a width of up to 10 mm (e.g. incisals for articulators) maybe moved along the length of the slot20v.

In a different embodiment shown inFIG. 20, the slot20viextends all the way to the edge9viof the second end8viof the handle6visuch that the slot20vidivides the edge9viin two parts. As a result, the handle6vican more easily be made to fit such objects as the rod50shown inFIG. 13a. The handle6vihas a first end7viand a male element14vi.

Another embodiment is shown inFIG. 13bandFIG. 13c. InFIG. 13b, it is shown how the handle6has been removed from the tray portion4as a preparation for a scanning operation. The tray portion4has been placed on a holder39. As shown inFIG. 13c, the holder39has a part51with a shape that is complementary to the in shape to the fasteners18on the holding section33of the tray portion4.

In the embodiment shown inFIGS. 13band13c, the holding section33is formed by a projecting part on the tray portion4. The part51of the holder39that is complementary in shape to the fasteners18maybe shaped to define male elements such as pegs. Such male elements or pegs can fit the corresponding fasteners18on the holding section33when these fasteners18are areas of the holding section33shaped as recesses. When the male elements of the holder39are pressed into the recesses of the holding section33, the tray portion4is secured to or held by the holder39. The holder39can be placed in a scanning device and support the tray portion4during the scanning operation. The holder39together with the tray portion4can then be placed on, for example, such a carrier37as is indicated inFIG. 6b. Since the holder39is designed to cooperate with the same holding section33as the handle6, the equipment according to the embodiment ofFIG. 13bandFIG. 13cis versatile and easy to use. It is not necessary to have any separate recess or other element on the tray portion4to fasten it to the holder39. The part51of the holder39that is complementary in shape the fasteners18on the tray portion4may thus be male elements having a shape that is similar to or identical to the shape of the fastening elements16iv,17ivshown inFIG. 12.

With reference toFIGS. 13b-13dandFIGS. 6aand6b, yet another embodiment and further variations will now be explained in the following. A possible method for making a dental impression of an upper and a lower dental structure and scanning the impression may be as follows. A tray portion4is provided that is contoured to fit over at least a part of an upper and lower structure of a patient. The tray portion may have a holding section33which may be projecting from the rest of the tray portion4as inFIG. 5a, but could also be designed in other ways such that it does not project from the rest of the tray portion. The holding section33has a first side61(see alsoFIGS. 5band5c) facing in a first direction and a second side62(seeFIGS. 5band5c) opposite to the first side61and facing in a second direction that is opposite to the first direction. Each of the first and second side61,62of the holding section33has at least one fastener18that may be an area of the holding section33that is shaped as a recess. The fasteners18on both sides61,62of the holding section33have the same form. A handle6′ may be provided that can be secured to and removed from the tray portion4. The handle6′ has fastening elements16,17that are complementary to the fasteners18on at least one of the opposite sides61,62of the holding section33. The handle6′ is secured to the tray portion4by means of one or several of the fasteners18on the holding section33and one or several fastening elements16,17on the handle6′. The tray portion4is loaded with impression material, either before or after the handle6′ is secured to the tray portion4.

When the tray portion4is loaded with impression material and the handle6′ is secured to the tray portion4, the tray portion4is placed in the mouth of the patient and an impression is made of at least a part of the patient's upper and lower dental structure. During this part of the procedure, the handle6′ may optionally be used to guide the tray portion4.

After an impression has been made of the upper and lower dental structures, the tray portion is removed from the mouth of the patient. The handle6′ is removed from the tray portion4, either before or after the tray portion4is removed from the mouth of the patient. The tray portion4is then secured to a holder39. The holder39has a part that is complementary in shape to the fasteners on the holding section33and it is identical in shape to the fastening elements16,17on the handle6′. The tray portion4is secured to the holder39by means of connecting the first side of the tray portion4to the holder39. A first side of the tray portion4is then scanned such that a scanning of one of the dental impressions is obtained, i.e. a scanning of either the impression of the upper dental structure or the lower dental structure. At the same time, a part of the surface of the tray portion4itself will of course be scanned.

The tray portion is then removed from the holder as indicated symbolically by arrow S inFIG. 13dand turned 180° as symbolically indicated by arrow C inFIG. 13d. The tray portion4is then once again secured to the holder39by means of connecting the second side of the tray portion to the holder39. After this, the second side of the tray portion4is scanned to obtain a scanning of the second dental impression as well as a further scanning of the tray portion4. This method entails that a scanning can easily be obtained of both the upper and the lower dental structure of a patient and, at the same time, of the tray portion4. The fact that the tray portion4itself is also scanned can be used to match the scannings of the dental impressions with each other as will be explained in more detail with reference toFIGS. 4 and 17.

It should be understood that the dental impression tray that is used for the above-described method may optionally be provided both with and without a removable handle6. Embodiments are thus possible that include only a tray portion4adapted to be loaded with impression material and contoured to fit over at least a part of both the upper and lower dental structure31,32of a patient such that an impression can be obtained simultaneously from both the upper and the lower dental structure31,32while a scanning of the tray portion4is also obtained which can later be used to match the scanning of the lower dental structure with the scanning of the upper dental structure. However, if the dental impression tray is to be used in combination with a holder39that holds the dental impression tray during scanning of both sides of the dental impression tray, the tray portion4of the dental impression tray should have a holding section33with a first side61facing in a first direction and a second side62placed opposite the first side61and facing in a second direction that is opposite to the first direction.

Moreover, each of the first and second side61,62of the holding section33should have at least one fastener by means of which the holding section can be locked to a holder39having a part with a shape that is complementary in shape to the fasteners on the holding section33. The fasteners on both sides of the holding section should then have the same form. When the fasteners on both sides of the holding section have the same form, this entails that each side of the holding section can be locked to one and the same holder.

As previously explained with reference toFIG. 5a, the holding section33may optionally be formed by a projecting part on the tray portion4while the fasteners18on the opposite sides61,62of the holding section33may be shaped by parts of the holding section33that define recesses in the holding section33.

In case the dental impression tray4comprises a removable handle6′, the handle6′ shall be provided with fastening elements16,17that are complementary in shape to the fasteners on at least one of the opposite sides of the holding section33. Such a removable handle may be designed, for example, as shown with reference toFIGS. 7-12or as shown inFIGS. 22-35, but a suitable removable handle could also be designed in other ways.

One embodiment may also take the form of a kit for making a dental impression and holding the impression for a scanning operation. Such a kit may comprise a dental impression tray having a holding section33and a removable handle6′ with fastening elements16,17as described previously and a holder39having a part with a shape that is complementary in shape to the fasteners18on the holding section33of the tray portion. When a holder39is included that has a part with a shape that is complementary to the fastener or fasteners18on each side on the holding section33of the tray portion4, this entails that the tray portion4can easily be placed in a position for scanning both sides of the tray portion4and thereby obtain a scanning of both the upper and lower dental structure of a patient. When the handle parts12,13have fastening elements16,17identical in shape to the part51of the holder39that is complementary in shape to the fasteners18on the tray portion4, this entails that the tray portion4can be easily fitted to both the handle6′ and the holder39.

Yet another embodiment will now be explained with reference toFIGS. 14a-17. Some patients may lack teeth completely. If a patient has been without teeth for a long period, the jawbone itself may regress. If the patient is then asked to bite in the dental impression tray1, the patient may fail to bite together completely since the regression of the jaw bone has gone too far. As a consequence, the dental impression obtained may be insufficient. The embodiment shown inFIGS. 14a-17has been designed to deal with that problem.

With reference toFIG. 14a, the tray portion4has a shape that defines a cavity21with an inner wall22. The dental impression tray1further comprises at least one pad23that fits into at least a part of the cavity21of the tray portion4. A side view of the at least one pad23is presented inFIG. 15a. Optionally, the inner wall22may be provided with a first guide structure24and the pad23can be provided with a second guide structure25that fits the first guide structure24. The first and second guide structures24,25may then cooperate with each other in a way that permits that the pad23is pressed down into the tray portion4in a movement guided by the cooperating guide structures24,25. The at least one pad23is then held securely by the cooperating guide structures24,25. A side view of the pad23is presented inFIG. 15a.

The first guide structure24may comprise projecting parts forming rails24and the second guide structure25may comprise grooves25adapted to receive the projecting parts of the first guide structure24. This embodiment is shown inFIGS. 14aand15a. Alternatively, the pad23may have projecting elements that fit grooves in the inner wall22of the tray portion4. The guide structures24,25can cooperate with each other (engage each other) as indicated inFIG. 16.

InFIG. 14b, an embodiment is illustrated where not one pad23is used, but three separate pads23′. A side view of such an arrangement is illustrated inFIG. 15b. In some embodiments, one pad is used for taking an impression of the upper jaw whereas several pads are used for taking an impression of the lower jaw. Hence, greater flexibility is achieved.

With reference toFIG. 14c, an embodiment is shown that is basically similar to the embodiment ofFIG. 14b. However, this embodiment is without the projecting parts24and grooves25A side view of such an arrangement is illustrated inFIG. 15c.

It will be noted that, in the embodiments shown inFIG. 15bandFIG. 15c, the different pads23′ or23″ are of different heights. For example, inFIG. 15b, the pad23′ that is located in the middle (the second pad from the left) is lower than the first pad from the left. The reason for this will be explained in the following.

When a pad23is placed in the cavity21of the tray portion4, the dental impression tray1will be more suitable for a person whose jaw bone has regressed.FIG. 17presents a cross-sectional schematic illustration of a dental impression tray applied to a patient completely lacking teeth and having suffered regression of the jaw bone. A first pad23aand a second pad23bhave been placed in the tray portion4and secured in the tray portion in such a way that they reach the partition30.

InFIG. 17, the first pad23ais placed in an upper part of the tray portion4while the second pad23bis placed in a lower part of the tray portion4(in this context, it should be understood that “upper” and “lower” refers to how the tray portion is placed in the mouth of a patient). As indicated inFIG. 17, the upper dental structure31lacks teeth. This is also the case with the lower dental structure32. In spite of this, the patient is still able to bite together properly thanks to the pads23a,23bthat have been placed in the tray portion4. The impression material5has been placed over the pads23and the patient can now bite directly into the impression material5which he or she might have been unable to do without the pads23. InFIG. 17, an embodiment with two pads23a,23bis illustrated (an upper pad23aand a lower pad23b). It should be understood that embodiments with only an upper pad23amay be possible or embodiments with only a lower pad23b. This may be dependent on the dental structure of the individual patient. As can be seen inFIG. 17, the partition30separates the upper part of the tray portion4from the lower part of the tray portion4. It should be understood that, as an alternative to the guide structures24,25that are illustrated inFIGS. 14aand16, the pads23can be held in the tray portion4by an adhesive material, such as an adhesive tape or glue, that secures the pads to the partition30or the inner wall22of the tray portion. The adhesive tape could be a double-sided adhesive tape.

InFIGS. 14aand15a, the pad23is shown as a single piece, i.e., a single upper pad23aor a single lower pad23b. However, it should be understood that, for both the “upper” part of the tray portion4(it should be understood that “upper” refers only to what is “upper” when the tray portion4is placed in the mouth of a patient) and the “lower” part of the tray portion4, the pad23may be divided into several parts that are separate from each other as indicated inFIGS. 14b,14c,15b,15c. On, for example, the upper dentition of a patient, it may be desirable to apply more than one pad23.

For example, it could be desirable to apply one pad23to a left part of the patient's upper dentition and another pad23to the right part of the patient's dentition. In such a case, two pads23may be used. One can also imagine cases where three pads23are used on the upper or lower dentition of a patient. For example, one separate pad23could be used on a front part of a dentition while two other pads are used to the left and right side of the patient's dentition. Of course, embodiments are also conceivable where four, five or even more pads23are used on the upper or lower dentition. Embodiments are also possible where a pad23is designed to be used on just a part of a patient's upper or lower dentition. For example, a pad23could be designed to be applied to only the left part of the patient's upper dentition or the front part of the patient's lower dentition.

If the patient's jawbone has suffered regression, it may be the case that the regression of the jawbone has not been equally damaging to all parts of the jawbone. It may thus be the case that some parts of the patient's jawbone have suffered very extensive regression while other parts have suffered only mild regression. For this reason, pads23of different height may be used. For example, let's assume that the left and right parts of a patient's upper jaw bone have suffered serious regression, but that the front part of the upper jawbone has suffered only a mild regression. A dental technician or dentist can then place relatively high pads in the left and right part of the tray portion4while a low pad is placed in the front part of the tray portion4. The height of each pad23depends on the degree of regression of the jaw bone at the place the pad23will be put to use. When the patient bites together, it will thus be possible for the dentist or dental technician to get a correct impression in the impression material and to get the distance between the upper and lower jaw right. A solution with more than one pad23may be applied in both the upper and lower jaw (and thus on both sides of the partition30).

It should be understood that, regardless of whether one or several pads23are used, the pad(s)23does not necessarily fill the entire cavity21of the tray portion4. If a special guide or holding structure24is used, it is possible that the pad(s)23cooperate(s) with guide structure24on only a part of the inner wall22. In some embodiments, the pad(s)23could cooperate with guide structure24on only the front part of the inner wall22, i.e. the part adjacent the handle6. In that embodiment, it may be so that the pad(s)23is not even in contact with the rear part of the inner wall22.

In some embodiments, the pad23can be made of an elastic material such as, for example, rubber. A material such as rubber is gentle if it should come into contact with the tissue in the mouth of a patient without teeth. Alternatives to rubber may also include, for example, synthetic materials. However, embodiments having a pad made of a more rigid material are also conceivable. Furthermore, the pad23can be made of a material that is relatively easy to adjust the shape of. Than, each pad can be precisely adjusted to fit a specific patient. Such adjustable material is e.g. rubber or plastic material.

The guide structures24,25help to secure the pad(s)23to the inner wall22of the tray portion when the pad(s) is (are) placed in the tray portion4. However, embodiments are conceivable where the pad23and the inner wall22of the tray portion4lack guide structure. As an alternative to the term “guide structure,” the projections24and grooves25may be called “fastening structure” or “holding structure.”

The guide structure24on the inner wall of the tray portion4can also serve a different function, namely to prevent undesired movement of the impression material5. The guide structure24tends to lock the impression material against such movement. The inner wall22of the tray portion4may thus be provided with such a structure independently of whether a pad23as described above is used or not.FIG. 18illustrates an alternative shape of the guide structure24. The shape indicated inFIG. 18may be used to interact with a pad23, but can be used separately for the purpose of preventing the impression material5from being moved in an undesired way. As indicated, inFIG. 18, the guide structure24′ may be formed by relatively thin projecting parts40that end with a thicker head41. InFIG. 18, a guide structure24′ is shown along the entire periphery of the inner wall22. However, embodiments are also possible where only a part of the inner wall22is provides with such elements. For example, embodiments are possible where only that part of the inner wall22that is adjacent the handle6is covered by such a guide structure.

It should be understood that the idea of using a pad23that fits the tray portion4can be combined with all other embodiments disclosed in this application. For example, the use of a pad23in combination with a handle that can be aligned with a patient's facial features further improves the possibility of obtaining a correct impression that can be used for making a successful dental restoration. However, the idea of using a pad could also be used independently of how the dental impression tray1is otherwise designed. For example, it could be used independently of the shape of the handle6. Conceivably, it could also be used in embodiments where the dental impression tray1does not have a handle.

The idea of using a pad for certain patients, e.g., patients suffering from regression of the jaw bone, can also be defined in terms of a method for making dental impressions, in which method a dental impression tray1with at least one pad is inserted into the mouth of such a patient and an impression formed.

Another embodiment will now be explained with regard toFIG. 19. As indicated inFIG. 19, the tray portion4may have in its wall a slot28to accommodate a patient's upper frenum when the tray portion4is fitted over upper dentition31of a patient. This makes the dental impression tray1more comfortable for the patient. It should be understood that the embodiment ofFIG. 19is entirely optional, but that it may be used independently of how the dental impression tray1is otherwise designed. It can thus be used in combination with other embodiments shown or it can be used in isolation. Conceivably, the idea could be used independently of whether the dental impression tray is provided with a handle or not.

With reference toFIG. 21, it should be noted that the tray portion4′ does not necessarily have to be designed to extend along the entire upper or lower dental structure of a patient, but could be designed to extend along only a part of a patient's upper or lower dental structure, e.g, as shown as4′, wherein the tray portion4′ has an inner wall22″ and a guide structure24″.

Another optional feature will now be explained with reference toFIG. 4andFIG. 17. The tray portion4can be designed to fit over only an upper or a lower dental structure (or a part of such a structure). However, it can be designed and contoured to fit over a part of both the upper and lower dental structure or dentition31,32of a patient. When this is the case, an impression can simultaneously be obtained from both the upper and the lower dental structure. It is then desirable that one can match the upper impression with the lower impression. To this end, an outer surface of the dental impression tray1may be provided with at least one fiduciary marker26that can be detected in a scanning operation. When the dental impression tray1is subsequently scanned, the upper and lower impressions may be scanned separately. When the result of the scanning is fed to a computer, the at least one fiduciary marker can serve to match the scanning of the upper dental structure with the scanning of the lower dental structure. The fiduciary marker26can be included in the scanning of both the upper impression and the lower impression and it can thus serve as a reference point such that the scanning of the upper impression can be correctly combined with the scanning of the lower impression. Instead of only one fiduciary marker, several fiduciary markers26can be used. For example, there may be two, three, four or five fiduciary markers26or even more than five fiduciary markers26. The fiduciary markers may optionally have some special form to facilitate identification, e.g. square, triangular or round.

With reference to the embodiments shown inFIGS. 5a-candFIGS. 13b-c, it should be understood that fiduciary markers26may be placed on the holding section33of the tray portion4. As previously explained, the holding section33may be shaped as a projecting part on the tray portion4. When one or several fiduciary markers26are placed on such a projecting part, this may be helpful when an upper and a lower impression are have been scanned and the scannings are to be matched with each other. InFIG. 5b, it is indicated how a fiduciary marker26has been placed on the holding section33of a tray portion4. Some parts of the holding section33can be scanned both when the upper dental impression and the lower dental impression are scanned. In particular, one or several fiduciary markers26may be scanned in both scannings. Since also the tray portion4and the fiduciary marker (or markers)26thereon are scanned, this can be used to match the scannings of the dental impressions with each other.

In some embodiments, the at least one fiduciary marker26can be made in a material that is opaque to radio waves. This can be useful if the scanning is done as, for example, a CT scanning (computer tomographic scanning). In such a scanning operation, X-ray is used. If the at least one fiduciary marker26is opaque to radio waves, it can then be detected during such a scanning operation. A CT scanning may be performed in, for example, the following way.

Firstly, a dental impression tray1is placed in the mouth of a patient after dental impression material has been placed in the tray portion4. The patient bites into the dental impression material. A CT scanning is performed while the dental impression tray is still in the mouth of the patient. The jaw bone of the patient will be visible in the scanning together with the at least one radiopaque fiduciary marker26. It will thus be possible to see how the jaw bone is located in relation to the fiduciary marker26. The dental impression tray1is then removed from the patient's mouth. A scanning is now performed on either the upper or lower dental impression obtained in the dental impression material. Also in this scanning, the at least one fiduciary marker26will be included. The dental impression that has been scanned can then be linked to the fiduciary marker26. The dental impression tray1can then be turned over and the dental impression on the other side is scanned. Once again, the at least one fiduciary marker26is included in the scanning. The data from the separate scanning operations is then fed into a computer. Through the at least one fiduciary marker26that is radiopaque, the results of the three scanning operations can be linked to each other.

It should be understood that the idea of using fiduciary markers26can be combined with all other embodiments described. For example, the use of at least one fiduciary marker in combination with the idea of using a part of the handle to align the tray portion4with a part of the patient's facial features can help improve precision when an impression is made. However, the idea of using one or several fiduciary markers can also be used independently of how the dental impression tray1is otherwise designed. For example, it can be used independently of how the handle6is designed. Conceivably, it could also be used on dental impression trays that do not have a handle6.

It should be understood that the idea of using one or several fiduciary markers26can be defined in terms methods for making an impression. For example, the idea of using at least one fiduciary marker26made in a radiopaque material could be defined in terms of a method where X-ray is used for the scanning operation.

Another embodiment will now be explained with reference toFIG. 1andFIG. 13a. When a large number of impressions are made and/or handled, there is a risk that different impressions are mixed up, i.e. confused with each other. To prevent that, a dental impression tray1can be provided with a machine readable marking29or29′. The machine readable marking comprises a coding that is unique for each patient. The coding can be applied at the same occasion as the impression is made and linked in, for example, a computer memory, to the patient from whom the impression has been obtained. The machine readable marking may be, for example, a bar code as indicated inFIG. 1. However, in another embodiment, the machine readable marking29comprises an RFID (Radio Frequency Identification) tag29′ as symbolically indicated in, for example,FIG. 13a. An RFID tag provides for, inter alia, quick and reliable identification. An example of RFID technology is disclosed in, for example, U.S. Pat. No. 7,053,775, incorporated herein by reference. Another example of RFID technology is disclosed in U.S. Pat. No. 7,009,526, incorporated herein by reference. Yet another example of RPID technology is disclosed in U.S. Pat. No. 6,693,539, incorporated herein by reference.

The embodiment including the machine readable marking29could also be understood in terms of a method including the steps of making an impression with a dental impression tray1, marking the dental impression tray with a machine readable marking and linking the marking to a unique patient. The idea may also be defined in terms of a system that comprises a computer loaded with data linking various individual dental impression trays to individual patients. Such a system might also comprise a plurality of dental impression trays where individual trays have machine-readable markings linked to the data in the computer. The system may also comprise at least one reader for the machine-readable markings29, for example, a reader for RFID tags or a bar code scanner.

It should be understood that the idea of using a machine-readable marking29, can be combined with all embodiments described in this application. For example, the idea can be combined with the embodiment where a pad23is used or it can be combined with the idea of using a removably secured handle6. However, it should also be understood that it is an idea that can be used independently of how the dental impression tray1is otherwise designed. For example, it could be used independently of how the handle6is designed and independently of whether the dental impression tray1has a handle or not.

Yet another embodiment will now be explained with reference toFIGS. 22-35. A dental impression tray1may be designed such that the handle6viicomprises at least a first and a second handle part12vii,13viithat can be pressed together to form a complete handle6viiwhile the handle6viihas a locking device52that can placed in a first position to lock the handle parts12vii,13viito each other and in a second position where the handle parts12vii,13viican be moved away from each other.

As illustrated inFIG. 22, the handle6viimay be formed by two handle parts12vii,13vii. These parts12vii,13viican be combined to form the handle6viias indicated inFIG. 24,FIG. 25andFIG. 26. Each handle part12vii,13viimay be divided into a grip part58and a bridging part59for connection to the tray portion4. InFIG. 22, it is indicated that the handle parts12vii,13viimay optionally be linked to each other at their grip parts58by a flexible strip57that can optionally be formed in one piece with the handle parts12vii,13vii. The material may be, for example, a plastic material and the flexible strip57may be much thinner than the handle parts12vii,13viiin order to ensure that the flexible strip57can be bent easily (i.e. that it is flexible) such that the handle parts12vii,13viican be folded together.

In the embodiment ofFIGS. 22-35, the handle parts12vii,13viiare not adapted to be connected to each other by a snap-on catch as in the embodiment shown inFIGS. 8 and 12. Instead, the handle parts12vii,13viican be connected to each other in another way that will now be explained with reference toFIGS. 22-35.

As can be seen inFIG. 22, the handle parts12vii,13viiare not identical. The second handle part13viihas, on its bridging part59, a first section53that is relatively narrow and a second section54that is relatively wide, i.e. wide compared to the first section53. The corresponding area of the first handle part12viiis not divided in this way. On the bridging part59of the first handle part12vii, a locking device52has been placed as can be seen in for exampleFIGS. 22 and 23. A possible design of the locking device52is shown inFIGS. 27-30.

As indicated inFIG. 27and inFIG. 28, the locking device52may have the shape of a beam with hooks56at the ends of the beam. The hooks56can be used to hold the handle parts12vii,13viiof the handle6viitogether. On an external surface of the locking device52, the locking device52is provided with a high friction part55that can be achieved through, for example, a serrated or uneven surface. The high friction part55may of course also be achieved by other means. An internal wall60of the locking device52will face the perimeter of the handle parts12vii,13viiwhen the locking device holds the handle parts12vii,13viitogether.

It should be understood that the idea of using a special locking device as shown inFIGS. 22-35for holding two handle parts together could be combined with other embodiments, for example, a handle having an edge that forms a visible straight line. However, the idea of using a locking device52as shown inFIGS. 22-35may also be put to use for all embodiments having a removable handle formed by different handle parts12,13, regardless of how the dental impression tray is otherwise designed. The locking device52, as exemplified inFIGS. 22-23andFIGS. 27-35, entails that the handle parts12vii,13viican be easily connected to each other in a reliable way and just as easily separated from each other.

If one of the handle parts is made with a narrow section53as shown inFIG. 22, this entails that it will be easier for the locking device52to be moved between a first position where it holds the handle parts12vii,13viitogether and a second position where the handle parts12vii,13viican be separated from each other.

If the locking device52is permanently locked on one of the handle parts12vii,13vii, this entails that it is immediately available and that it is not easily lost.

The locking device52and the first handle part12viiare shaped such that the locking device52is a movable on the first handle part12viibut cannot be separated from that part. One way of achieving this may be to make the bridging part59of the first handle part12viiso wide that the locking device52cannot be separated from the first handle part12viiwithout deformation of either the first handle part12viior the locking device52(or both). In other words, the distance between the tips of the hooks56is always smaller than the width of the first handle part12vii. As a consequence, the locking device52is permanently locked to the first handle part12vii.

InFIG. 22and inFIG. 23, it can be seen how the locking device52is placed on the first handle part12vii. In this position of the locking device52, the handle parts12vii,13viican be pressed tightly against each other without being impeded by the locking device. The reason is that this position of the locking device52matches the narrower first section53of the second handle part13vii. With reference toFIG. 31, it can be seen how the handle parts12vii,13viihave been pressed together while the locking device52is still in the same position as inFIGS. 22 and 23. In this position, the locking device52does not lock the handle parts12vii,13viito each other since the locking device contacts the second handle part13viiat its narrow section53where the hooks56of the locking device do not extend over the handle part13vii.

Reference will now be made toFIG. 32. InFIG. 32, the locking device52has been moved to a position where the locking device52is placed over the second section54of the second handle part13vii. The second section54is wider than the first section53and the hooks56of the locking device will now extend over the second handle part13viisuch that the handle parts12vii,13viiare locked to each other. This position can also be seen in perspective inFIG. 33and from the side inFIG. 34. This position of the locking device is a first position where the locking device locks the handle parts12vii,13viito each other. The second position of the locking device is the position shown in for exampleFIGS. 31 and 32. It can thus be seen that the first section53of the second handle part13viicorresponds to the second position of the locking device52and it has such dimensions (i.e. it is so narrow) that the handle parts12vii,13viican be pressed together or moved away from each other when the locking device52is in the second position.

Correspondingly, the second section54of the second handle part corresponds to the first position of the locking device52and, as explained, it has such dimensions that the first and second handle part will be locked to each other when the locking device52is placed in its first position and the handle parts12vii,13viiare pressed against each other. In order to keep the locking device52in the first position, the internal walls60of the locking device52may be slightly converging such that the locking device52is pressed against the periphery of the handle parts12vii,13viiwhen the locking device52is pushed from the second position towards the first position. Alternatively, the handle parts12vii,13vii(or one of them) could become somewhat wider towards the first end7viiof the handle. Of course, it may also be so that both the handle parts12vii,13viiand the inner walls60of the locking device have a geometry that contributes to squeeze these parts against each other when the locking device is pushed from the second position towards the first position.

To connect the handle6viito the tray portion4, the handle6viimay initially be held in an open position as shown inFIG. 22. The locking device52is placed in the second position as indicated inFIGS. 22 and 23. The fastening elements16vii,17viiof the handle parts12vii,13viiare connected to the fasteners18on the tray section4while the handle parts12vii,13viiare pressed against each other. The locking device52is then pushed to the first position of the locking device as shown inFIG. 33. The locking device52will now hold the handle parts12vii,13viitogether and the handle will hold the tray portion4as indicated inFIG. 35. It should be understood that the fastening elements16vii,17viion the handle parts12vii,13viimay be projections and that the fasteners18on the tray section may be recesses into which the fastening elements16vii,17viiof the handle parts12vii,13viiare pressed. However, it could also be so that the fastening elements16vii,17viion the handle parts12vii,13viiare parts shaped to define recesses and the fasteners18on the tray section could be projections.

While the various embodiments have been described above mainly with reference to a dental impression tray1, it should be understood that all that has been described above could also be described in terms of methods in connection with the making of dental impressions.

The dental impression tray itself can be made of many different materials. Plastic materials may be suitable, but other materials could also be used, for example ceramic or metallic materials.