A DENTAL IMPRESSION TRAY FOR USE IN OBTAINING AN IMPRESSION OF A DENTAL STRUCTURE

TECHNICAL FIELD

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.

BACKGROUND

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 US patent No. 6217334.

In US patent No. 5338198, 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.

GENERAL DISCLOSURE Accordingly, the present invention preferably seeks 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. 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). 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 straight line that is formed by the edge when seen from the side facing away from the tray portion has a length of at least 60 mm. In some embodiments, the straight line formed by the edge may have a length of at least 80 mm.

In some embodiments of the invention, 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 lest 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.

It should be emphasized that the term "comprises/comprising" when used in this specification is taken to specify the presence of stated features, integers, steps or components but does not preclude the presence or addition of one or more other features, integers, steps, components or groups thereof.

BRIEF DESCRIPTION OF THE DRAWINGS

Figure 1 is a perspective view of a dental impression tray according to one embodiment of the invention.

Figure 2 shows, in perspective, how a dental impression tray has been placed in the mouth of a patient.

Figure 3 is a front view corresponding to Fig. 2 and illustrates more clearly the principle underlying one of the embodiments.

Figure 4 is a cross-sectional view of a dental impression tray in use when a patient is biting into the tray section to create a dental impression in a dental impression material.

Figure 5 is a perspective view showing an embodiment where the handle of the dental impression tray can be removed from the tray portion.

Figure 6a gives, in a view from above, a schematic illustration of how the tray section of the dental impression tray may be placed in a scanner for a scanning operation

Figure 6b is a side view of the same scanning device as in Fig. 6a.

Figure 7 shows an embodiment of a handle in perspective.

Figure 8 shows the handle of Fig. 7 from above.

Figure 9 is a side view of the same handle as in Fig. 7.

Figure 10 is a rear view of the same handle as in Fig. 7.

Figure 11 is a front view of the handle placed on the tray portion.

Fig. 12 is a side view of a handle comprising two separate parts that are shown separated from each other.

Figure 13a illustrates, in perspective, an embodiment of a dental impression tray which is adapted for use in combination with an incisal pin.

Figure 13b illustrates how a dental impression tray may be mounted on a holder.

Figure 13c shows in greater detail an example of such a holder as is illustrated in Fig. 13b.

Figure 14a shows, from above, a variation of the embodiment shown in Fig. 1.

Figure 14b shows, from above, a variation of the embodiment shown in Fig. 14a.

Figure 14c shows, from above, yet another variation of the embodiment shown in Fig. 14a.

Figure 15a is a side view of a detail in the embodiment of Fig. 14a.

Figure 15b is a side view corresponding to an embodiment substantially similar to the embodiment shown in Fig. 14b.

Figure 15c is a side view corresponding to an embodiment substantially similar to the embodiment shown in Fig. 14c.

Figure 16 is a schematic representation of how components shown in Fig. 15 cooperate with each other.

Figure 17 is a cross-sectional view similar to Fig. 4 and gives a schematic illustration of how the embodiment of Fig. 14 can be used to get an impression on a patient who has no teeth at all.

Figure 18 is a view similar to Fig. 15 but showing a variation of the embodiment illustrated in Fig. 15.

Fig 19 shows, in perspective, yet another embodiment.

Fig. 20 is a perspective view showing a variation of the embodiment shown in Fig. 13.

Fig. 21 is a view from above of yet another embodiment.

DETAILED DESCRIPTION

With reference to Fig. 1 , a dental impression tray 1 is 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 tray 1 comprises a tray portion 4 adapted to be loaded with impression material. An impression material that can be used with the inventive impression tray 1 may be, for example, a silicon based material. Such impression materials are sold by, for example, 3M ESPE Dental Products, 3M Center, St. Paul Minnesota, United States. One such material is sold by 3M ESPE under the name IMPRINT™ 3 VPS Impression Material.

The tray portion 4 is contoured to fit over at least a part of a dental structure such as the dentition of a patient. As can be seen in Fig. 1, the dental impression tray 1 further

comprises a handle 6 that is connected to the tray portion 4 or adapted to be connected to the tray portion 4. The handle 6 has a first end 7 at which the handle 6 is connected to the tray portion or adapted to be connected to the tray portion 4. The handle 6 also has a second end 8 that is a distal end in relation to the tray portion 4 when the handle 6 is connected to the tray portion 4. The handle 6 can be used to grip the dental impression tray 1 and manipulate the dental impression tray 1 for purposes that will be explained in the following.

With reference to Fig. 2, it can be seen how the dental impression tray 1 has been placed in the mouth of a patient in order to create an impression of the patient's dentition. In Fig. 2, a patient is biting into the impression material placed in the tray portion 4 of the dental impression tray 1 while the handle 6 remains outside the mouth of the patient. As can be seen in Fig. 4, the tray portion 4 has an inner cavity 21 that may optionally be divided by a partition 30 into an upper cavity 21a and a lower cavity 21b. 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 portion 4 is located inside the mouth of a patient. The tray portion 4 may 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. Which cavity that is regarded as the "upper" cavity or the "lower" cavity is thus arbitrary. The upper part of the tray portion 4 with its upper cavity 21 a can be used to make an impression of an upper dental structure 32, for example an upper dentition 32. A part of the tray portion 4 with its lower cavity 21b can be used to make an impression of a lower dental structure or dentition 33. The partition 30 may be, for example, an elastic fabric such as a rubber fabric 30 or synthetic fabric 30. As can be seen in Fig. 4, the upper and lower cavities 21 a, 21b of the tray portion 4 are filled with dental impression material 5 in which an impression is made when the patient bites into the tray section 4 as schematically indicated in Fig. 4.

When the patient has bitten into the tray portion 4, the tray portion 4 can be removed from the patient's mouth and placed in a scanning device as shown in Fig. 6. In the scanning device, a scanning operation can be performed on the impression which is left in the impression material 5 that lies in the tray portion 4. 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 US patent No. 5338198, 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 tray 1 is 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 portion 4 be 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 handle 6 of the dental impression tray 1 with a feature of the patient's face. This is illustrated in Fig. 1, Fig. 2, Fig. 3 and Fig 8. With reference to Fig. 1 and Fig. 8, the second end 8 of the handle 6 has an edge 9 that is facing away from the tray portion 4. As can be seen in Fig. 2 and Fig. 3, the edge 9 forms a visible straight line 10 when the edge is seen from the side facing away from the tray portion 4. The edge may optionally be painted or otherwise marked to make the line 10 more easily visible. The edge 9 can be made to be parallel with a plane that divides the upper part of the tray portion 4 from the lower part of the tray portion 4. 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 portion 4 is correctly positioned in the patient's mouth, the edge 9 of the handle 6 should then be parallel with a straight line between the patient's eyes. The handle 6 allows a user to manipulate the dental impression tray 1 (and thereby also the tray portion 4 that is connected to the handle 6). By gripping the handle 6 and aligning the edge 9 of the handle 6 with the eyes of the patient, the person making the impression can thus ensure that the tray portion 4 is correctly positioned in the patient's mouth. In Fig. 3, a front view of a patient with a dental impression tray in his mouth is presented. In Fig. 3, the edge 9 of the handle forms a visible straight line 10 to a person who is watching the patient face-to-face. The edge 9 itself may possibly be straight but could also be curved inwards (i.e. towards the tray portion 4) or outwards (away from the tray portion 4). What matters is only that it appears as a straight line when regarded from the side facing away from the tray portion 4. It should be understood that the edge 9 extends in a plane. The straight line 10 formed by the edge 9 is then visible when it is regarded in the plane in which the edge 9 extends.

The distance between the eyes is, of course, something that varies between different individuals. However, for the closest distance between the eyes of an adult person (the distance between the corners of the eyes closest to the nose), 20 - 25 mm is a normal value for many adults. This value corresponds to the distance D ₃ in Fig. 3. If the length of the straight line 10 is 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 line 10 should 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 line 10 could 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 D ₂ in Fig. 3. Alternatively, the length of the straight line 10 may 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 Di in Fig. 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 edge 9 when seen from the side facing away from the tray portion 4 may therefore be given a length of at least 60 mm. To further increase precision in the alignment, the length of the straight line 10 can be chosen to be at least 80 mm.

A front view of the entire dental impression tray 1 is shown in Fig. 1 1 where both the tray portion 4 and the handle 6 are visible as well as the straight line 10 formed by the edge 9 of the handle 6.

It should be understood that the edge 9 at the second end 8 of the handle 6 could 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 portion 4 with a part of the patient's facial features could also be located elsewhere than at the second end 8 of the handle 6. 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 portion 4 with 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 handle 6 is used for alignment with a part of a patient's facial features. By gripping the handle 6, and manipulating the dental impression tray 1 such that the straight line 10 becomes aligned with apart of the patient's facial features, the person using the dental impression tray will thereby automatically manipulate the tray portion 4 such 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 tray 1 having a tray portion 4 contoured to fit over at least a part of a dental structure, the dental impression tray 1 further has structure 6 that allows a user of the dental impression tray 1 to manipulate the tray portion 4 when the tray portion 4 is placed in the mouth of the patient. This structure 6 also defines a line 10 that is visible when the tray portion 4 is placed in the mouth of a patient. The tray portion 4 is placed in the mouth of a patient and a comparison is made between the line 10 and a facial feature of the patient. The tray portion 4 is then manipulated until the line 10 becomes aligned with said facial feature of the patient. The structure 6 that allows a user to manipulate the tray portion 4 may be a handle 6 connected to the tray portion (or adapted to allow connection to the tray portion 4). The line 10 may be a straight line 10 that is defined by an edge of the handle 6. Possibly, the line 10 could have some other shape than just a straight line. For example, it could be an L-shaρed 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 line 10 could optionally be a curved line.

Another embodiment will now be explained with reference to Figs. 5 - 11. With reference to Fig. 6a and Fig. 6b, the dental impression tray 1 can be placed in a scanning device having a chamber 34 where an impression can be scanned. The scanning can be performed by, for example, a laser device such as a line laser device. In Fig. 6b, a laser scanning device is shown schematically that has a laser light source 35 and a detector 36. The tray portion 4 together with an impression of a dental structure (for example a dentition) can be placed on a table, carrier or platform 37 that can perform a rotating movement while the scanning is performed.

When the dental impression tray 1 is placed in the chamber 34 of the scanning device, the handle 6 could present an obstacle. This is especially the case of the dental impression tray 1 is placed on a platform that rotates and the chamber 34 is small. To prevent the handle 6 from causing problems during scanning, it may be desirable to remove the handle 6 from the tray portion 4. To ensure the handle 6 can be quickly and easily

removed from the tray portion 4, some embodiments include the use of a handle 6 that is removably secured to the tray portion 4. With reference to Fig. 5, an embodiment is schematically illustrated where the handle 6 may be removably secured to the tray portion 4. As shown in Fig. 5, the handle 6 may have one or several projections 16, 17 adapted to fit one or several recesses 18 formed in the tray portion 4. The projection or projections 16, 17 may be, for example, pegs. The recess or recesses 18 may be, for example, holes or openings. By pressing the projection or projections 16, 17 into the recess or recesses 18, it is possible to secure the handle 6 to the tray portion 4. Of course, the handle 6 can also be removed from the tray portion 4. This can be achieved by removing the projection or projections 16, 17 from the recess or recesses 18. In Fig. 5, an embodiment is shown where the recess(-es) 18 are formed in a projecting part 33 on the tray portion 4. Of course, it should be understood that such recesses 18 could also be formed elsewhere on the tray portion 4. It should also be understood that, as an alternative, one or several projections 16, 17 could be formed on the tray portion 4 and be adapted to fit one or several recesses 18 on the handle 6.

Embodiments are possible where the handle 6 is made in one single piece. However, the handle 6 can also be made in more than one piece as indicated in Fig. 5 where the handle 6 comprises two separate parts 12, 13. It should also be understood that the handle 6 may comprise more than two parts.

An embodiment where the handle 6 comprises two separate parts will now be explained with reference to Figs. 5 and 7 — 10. As shown in Fig. 5, the handle 6 for the tray portion 4 may comprise a first and a second part 12, 13 that may be separated. The separate handle parts 12, 13 can be adapted to be connected to each other such that the separate handle parts 12, 13 overlap each other partially but not completely. This is best seen in Fig. 7 and Fig. 8. As indicated in Fig. 7 and Fig. 8, the first and second handle parts 12, 13 are connected to each other in such a way that, when connected, there is a part 38 on each of separate handle part 12, 13 that is not overlapped by the other handle part 12, 13. In Fig. 8, it can thus be seen that the second handle part 13 has a part 38 that is not covered by the first handle part 12. This makes it easy to grip the handle 6 and pull or bend the first and second handle parts 12, 13 apart from each other.

As shown also in for example Fig. 7, the handle parts 12, 13 have been connected to each other to form a coherent handle 6. The handle parts 12, 13 may optionally be adapted to be connected to each other by a snap-on catch formed by the handle parts 12, 13. With

reference to Fig. 12 and Fig. 8, the snap-on catch may be formed by male elements 14 and female parts 15 into which the male elements 14 may be pressed to a snap fit attachment. The male elements 14 may be formed by, for example, pegs. The female parts 15 may be, for example, openings or through-holes. If the female parts 15 are through-holes 15, the male elements 14 (e.g. pegs) may be visible from the other side. With reference to Fig. 8, it can be seen that pegs 14 have been pressed through holes 15 to be visible from the outside when the handle parts 12, 13 are connected to each other. One way of achieving a snap-on catch may be to design the male elements 14 as conical pegs while the female parts 15 may be holes with a conical shape that corresponds to the conical pegs 14.

As indicated in Figs. 7 - 10, the separate handle parts 12, 13 may be 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 in Figs. 7 - 10. When the handle parts 12, 13 are put together, they can thus be put together "belly-against-belly" with the back sides facing away from each other. The handle parts 12, 13 will still not overlap each other completely since they are unsymmetrical. If the handle parts 12, 13 are identical in shape, the cost of manufacturing the handle parts can be reduced. Moreover, any two parts 12, 13 can always be connected to each other to form a complete handle 6. However, embodiments are of course also possible where the handle parts 12, 13 are not identical in shape.

As shown in for example Fig. 9 and Fig. 10, each of the separate handle parts 12, 13 may be provided with projections 16, 17 that can cooperate with a complementary part of the tray portion 4, for example a recess 18 as explained previously with reference to Fig. 5. When the separate handle parts 12, 13 are connected to each other by a snap connection, the handle 6 is locked to the tray portion 4 as long as the separate handle parts 12, 13 are connected to each other. The handle parts 12, 13 may be held together by the snap connection and the projections 16, 17 that connect the handle 6 to the tray portion 4 will thus be held in place until the first and second handle parts 12, 13 are separated from each other.

The idea of using a removably secured handle 6 can 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 6 may also be defined in terms of a method in which a dental impression is made, the handle 6 removed from the tray portion 4 and the tray portion 4 placed in the scanning device and scanned.

The dental impression tray 1 may optionally be packaged with the handle 6 disconnected from the tray portion 4. This can make the dental impression tray 1 shorter to make it fit into a smaller space, e.g. for purposes of packaging.

While the idea of using a removable handle 6 has been described above, it should be understood that embodiments are conceivable that have a handle 6 that is fixedly connected to the tray portion 4. For example, the handle 6 can be made in one piece with the tray portion 4.

Another embodiment will now be explained with reference to Fig. 13a. In some cases, the person handling the dental impression 1 tray may prefer to keep the handle 6 on the tray portion 4. This may be the case, for example, if the dental impression tray 1 is 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 tray 1 together with existing equipment that may interfere with the handle 6. One way of solving this problem may be to provide a slot in the handle 6. As can be seen in Fig. 6, the handle 6 may be shaped to define a slot 20. Components of existing equipment may include, for example, an incisal pin 50 for 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 slot 20 may be chosen such that it extends at least 30 mm in a direction from the second end 8 of the handle 6 towards the first end 7 of the handle 6. The slot 20 may 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) may be moved along the length of the slot 20.

In a different embodiment shown in Fig. 20, the slot 20 extends all the way to the edge 9 of the second end 8 of the handle 6 such that the slot 20 divides the edge 9 in two parts. As a result, the handle 6 can more easily be made to fit such objects as the rod 50 shown in Fig. 13a.

Another embodiment is shown in Fig. 13b and Fig. 13c. In Fig. 13b, it is shown how the handle 6 has been removed from the tray portion 4 as a preparation for a scanning operation. The tray portion 4 has been placed on a holder 39. As shown in Fig. 13c, the holder 39 may have male elements such as pegs 51. Such male elements or pegs 51 can fit into the recesses 18 of the projecting part 33 on the tray portion 4. When the pegs 51 are pressed into the recesses 18, the tray portion is secured to or held by the holder 39. The holder 39 can be placed in a scanning device and support the tray portion 4 during the scanning operation. The holder 39 together with the tray portion 4 can then be placed on, for example, such a carrier 37 as is indicated in Fig. 6b. Since the holder 39 is designed to cooperate with the same projecting part 33 as the handle 6, the equipment according to the embodiment of Fig. 13b and Fig. 13c is versatile and easy to use. It is not necessary to have any separate recess or other element on the tray portion 4 to fasten it to the holder 39. The male elements 51 may thus have a shape that is similar to or identical to the shape of the projections 16, 17 shown in Fig. 12.

Yet another embodiment will now be explained with reference to Figs. 14 — 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 tray 1, 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 in Figs. 14 - 17 has been designed to deal with that problem.

With reference to Fig. 14a, the tray portion 4 has a shape that defines a cavity 21 with an inner wall 22. The dental impression tray 1 further comprises at least one pad 23 that fits into at least a part of the cavity 21 of the tray portion 4. A side view of the at least one pad 23 is presented in Fig. 15. Optionally, the inner wall 22 may be provided with a first guide structure 24 and the pad 23 can be provided with a second guide structure 25 that fits the first guide structure 24. The first and second guide structures 24, 25 may then cooperate with each other in a way that permits that the pad 23 is pressed down into the tray portion 4 in a movement guided by the cooperating guide structures 24, 25. The at least one pad 23 is then held securely by the cooperating guide structures 24, 25. A side view of the pad 23 is presented in Fig. 15a.

The first guide structure 24 may comprise projecting parts forming rails 24 and the second guide structure 25 may comprise grooves 25 adapted to receive the projecting

parts of the first guide structure 24. This embodiment is shown in Fig. 14 and 15. Alternatively, the pad 23 may have projecting elements that fit grooves in the inner wall 22 of the tray portion 4. The guide structures 24, 25 can cooperate with each other (engage each other) as indicated in Fig. 16.

In Fig. 14b, an embodiment is illustrated where not one pad 23 is used but three separate pads 23. A side view of such an arrangement is illustrated in Fig. 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 e.g. achieved.

With reference to Fig. 14c, an embodiment is shown that is basically similar to the embodiment of Fig. 14b. However, this embodiment is without the projecting parts 24 and grooves 25. A side view of such an arrangement is illustrated in Fig. 15c.

It will be noted that, in the embodiments shown in Fig. 15b and Fig. 15c, the different pads 23 are of different height. For example, in Fig. 15b, the pad 23 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 pad 23 is placed in the cavity 21 of the tray portion 4, the dental impression tray 1 will be more suitable for a person whose jaw bone has regressed. Fig. 17 presents 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 pad 23a and a second pad 23b have been placed in the tray portion 4 and secured in the tray portion in such a way that they reach the partition 30. In Fig. 17, the first pad 23a is placed in an upper part of the tray portion 4 while the second pad 23b is placed in a lower part of the tray portion 4 (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 in Fig. 17, the upper dental structure 31 lacks teeth. This is also the case with the lower dental structure 32. In spite of this, the patient is still able to bite together properly thanks to the pads 23a, 23b that have been placed in the tray portion 4. The impression material 5 has been placed over the pads 23 and the patient can now bite directly into the impression material 5 which he or she might have been unable to do without the pads 23. In Fig. 17, an embodiment with two pads 23a, 23b is illustrated (an upper pad 23a and a lower pad 23b). It should be understood that embodiments with only an upper pad 23a

may be possible or embodiments with only a lower pad 23b. This may be dependent on the dental structure of the individual patient. As can be seen in Fig. 17, the partition 30 separates the upper part of the tray portion 4 from the lower part of the tray portion 4. It should be understood that, as an alternative to the guide structures 24, 25 that are illustrated in Figs. 14a and 16, the pads 23 can be held in the tray portion 4 by an adhesive material, such as an adhesive tape or glue, that secures the pads to the partition 30 or the inner wall 22 of the tray portion. The adhesive tape could be a double-sided adhesive tape.

In Figs. 14a and 15a, the pad 23 is shown as a single piece, i.e. a single upper pad 23a or a single lower pad 23b. However, it should be understood that, for both the "upper" part of the tray portion 4 (it should be understood that "upper" refers only to what is "upper" when the tray portion 4 is placed in the mouth of a patient) and the "lower" part of the tray portion 4, the pad 23 may be divided into several parts that are separate from each other as indicated in Figs 14b, 14c, 15b, 15c. On, for example, the upper dentition of a patient, it may be desirable to apply more than one pad 23. For example, it could be desirable to apply one pad 23 to a left part of the patient's upper dentition and another pad 23 to the right part of the patient's dentition. In such a case, two pads 23 may be used. One can also imagine cases where three pads 23 are used on the upper or lower dentition of a patient. For example, one separate pad 23 could 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 pads 23 are used on the upper or lower dentition. Embodiments are also possible where a pad 23 is designed to be used on just a part of a patient's upper or lower dentition. For example, a pad 23 could 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, pads 23 of 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 portion 4 while a low pad is placed in the front part of the tray portion 4. The height of each pad 23 depends on the

degree of regression of the jaw bone at the place the pad 23 will 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 pad 23 may be applied in both the upper and lower jaw (and thus on both sides of the partition 30).

It should be understood that; regardless of whether one or several pads 23 are used, the pad(s) 23 does not necessarily fill the entire cavity 21 of the tray portion 4. If a special guide or holding structure 24 is used, it is possible that the pad(s) 23 cooperate(s) with guide structure 24 on only a part of the inner wall 22. In some embodiments, the pad(s) 23 could cooperate with guide structure 24 on only the front part of the inner wall 22, i.e. the part adjacent the handle 6. In that embodiment, it may be so that the pad(s) 23 is not even in contact with the rear part of the inner wall 22.

In some embodiments, the pad 23 can 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 pad 23 can 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 structures 24, 25 help to secure the pad(s) 23 to the inner wall 22 of the tray portion when the pad(s) is (are) placed in the tray portion 4. However, embodiments are conceivable where the pad 23 and the inner wall 22 of the tray portion 4 lack guide structure. As an alternative to the term "guide structure", the projections 24 and grooves 25 may be called "fastening structure" or "holding structure".

The guide structure 24 on the inner wall of the tray portion 4 can also serve a different function, namely to prevent undesired movement of the impression material 5. The guide structure 24 tends to lock the impression material against such movement. The inner wall 22 of the tray portion 4 may thus be provided with such a structure independently of whether a pad 23 as described above is used or not. Figure 18 illustrates an alternative shape of the guide structure 24. The shape indicated in Fig. 18 may be used to interact with a pad 23 but can be used separately for the purpose of preventing the impression material 5 from being moved in an undesired way. As indicated, in Fig. 18, the guide

structure 24 may be formed by relatively thin projecting parts 40 that end with a thicker head 41. In Fig. 18, a guide structure 24 is shown along the entire periphery of the inner wall 22. However, embodiments are also possible where only a part of the inner wall 22 is provides with such elements. For example, embodiments are possible where only that part of the inner wall 22 that is adjacent the handle 6 is covered by such a guide structure.

It should be understood that the idea of using a pad 23 that fits the tray portion 4 can be combined with all other embodiments disclosed in this application. For example, the use of a pad 23 in 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 tray 1 is otherwise designed. For example, it could be used independently of the shape of the handle 6. Conceivably, it could also be used in embodiments where the dental impression tray 1 does 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 tray 1 with 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 to Fig. 19. As indicated in Fig. 19, the tray portion 4 may have in its wall a slot 28 to accommodate a patient's upper frenum when the tray portion 4 is fitted over upper dentition 31 of a patient. This makes the dental impression tray 1 more comfortable for the patient. It should be understood that the embodiment of Fig. 19 is entirely optional but that it may be used independently of how the dental impression tray 1 is 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.

Another optional feature will now be explained with reference to Fig. 4 and Fig. 17. The tray portion 4 can 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 dentition 31 , 32 of 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 tray 1 may be provided with at least one fiduciary marker 26 that can be detected in a scanning operation. When the dental impression tray 1 is 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 marker 26 can 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 markers 26 can be used. For example, there may be two, three, four or five fiduciary markers 26 or even more than five fiduciary markers 26. The fiduciary markers may optionally have some special form to facilitate identification, e.g. square, triangular or round.

In some embodiments, the at least one fiduciary marker 26 can 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 marker 26 is 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 tray 1 is placed in the mouth of a patient after dental impression material has been placed in the tray portion 4. 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 radio opaque fiduciary marker 26. It will thus be possible to see how the jaw bone is located in relation to the fiduciary marker 26. The dental impression tray 1 is 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 marker 26 will be included. The dental impression that has been scanned can then be linked to the fiduciary marker 26. The dental impression tray 1 can then be turned over and the dental impression on the other side is scanned. Once again, the at ieast one fiduciary marker 26 is included in the scanning. The data from the separate scanning operations is then fed into a computer. Through the at least one fiduciary marker 26 that is radio opaque, the results of the three scanning operations can be linked to each other.

It should be understood that the idea of using fiduciary markers 26 can 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 portion 4 with 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 tray 1 is otherwise designed. For example, it can be used independently of how the handle 6 is designed. Conceivably, it could also be used on dental impression trays that do not have a handle 6.

It should be understood that the idea of using one or several fiduciary markers 26 can be defined in terms methods for making an impression. For example, the idea of using at least one fiduciary marker 26 made in a radio opaque 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 to Fig. 1 and Fig. 13. 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 tray 1 can be provided with a machine readable marking 29. 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 in Fig. 1. However, in another embodiment, the machine readable marking 29 comprises an RFID (Radio Frequency Identification) tag 29 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, US patent No. 7053775 incorporated herein by reference. Another example of RFID technology is disclosed in US patent No. 7009526, incorporated herein by reference. Yet another example of RFID technology is disclosed in US patent No. 6693539, incorporated herein by reference.

The embodiment including the machine readable marking 29 could also be understood in terms of a method including the steps of making an impression with a dental impression tray 1 , 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 markings 29, for example a reader for RFID tags or a bar code scanner.

It should be understood that the idea of using a machine readable marking 29, can be combined with all embodiments described in this application. For example, the idea can be combined with the embodiment where a pad 23 is used or it can be combined with the idea of using a removably secured handle 6. However, it should also be understood that it is an idea that can be used independently of how the dental impression tray 1 is otherwise designed. For example, it could be used independently of how the handle 6 is designed and independently of whether the dental impression tray 1 has a handle or not. .

While the various embodiments have been described above mainly with reference to a dental impression tray 1 , 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.

Other embodiments than the above described are equally possible within the scope of the appended claims. The different features and steps of the invention may be combined in other combinations than those described. The scope of the invention is only limited by the appended patent claims.