Field of Invention

The present invention relates to an impression device capable of recording upper and lower jaw positions relative to each other with the aid of a moveable locator positioned on the impression device that is used as a jaw positional aid and method of recording of said position. The invention also relates to methods of manufacturing types of individual appliance for patients using the impression device.

Background

It is standard practice in dentistry to study occlusion and jaw relationship. In a dental context this refers to the contact between teeth or more technically, it is the relationship between the maxillary (upper) and mandibular (lower) teeth when they approach each other, during chewing or at rest, and the relationship of the jaws to supporting skeletal foundation of the maxilla and the mandible.

Malocclusion is the misalignment of teeth and jaws often resulting in what is referred to as a "bad bite". Malocclusion can cause a number of health and dental problems. Signs and symptoms of malocclusion or dysfunction may cause pain, but may also affect the way we chew, swallow, breath, speak, sing, sleep and this dysfunction may affect people in many other different ways.

The occlusal and spatial relationship of the teeth, and that of the upper and lower jaw, can be observed and recorded manually by a user; noting how individual teeth meet and by describing the 'bite' of a patient by identifying the position of teeth during opening and closing of the jaw. However, there is often a desire to determine optimal position of the jaws in relation to the skull and skull bones, so that it is possible to understand the amount of deviation from this optimal position and therefore provide treatment for possible associated problems caused by any deviation. Traditional orthodontists and prosthodontists often straighten and align teeth to improve function and aesthetics. However, straightening of the teeth and or alignment of teeth without the consideration and the ability to record jaw alignment/misalignment may be problematic and can lead to, or cause, other problems such as temporomandibular dysfunction (TMD) and relapse of teeth subsequent to any tooth movement carried out during the straightening and alignment treatments. Occlusion of teeth has previously been determined by creating models of the upper and lower teeth and gums by taking impressions in order to consider it further. Additionally the jaws can be imaged using 'x-rays' to observe their position.

Viewing models, photographs and x-rays can help identify misalignment of the jaws. On identification of the misalignment, an appliance may be developed to be held in the mouth, worn on the teeth or over the teeth in order to correct or improve the alignment.

However, current methods of obtaining an exact measurement of deviation of upper and lower jaws from an optimal position are often calculated based upon position of the teeth or they rely on skill and experience of a user to palpate and observe a patient in order to determine deviation. Such methods of recording and the standardisation of bite/occlusal registration techniques and impression-taking lack universal consensus with little or no clear standardisation of processes and recordings of patient data and diagnostics.

Deviation of the jaw in relation to the teeth can be considered undesirable as positioning of the teeth is not a true primary indicator of optimal symmetry in comparison to foetal development markers such as the frenulum, which can be considered a true midline indicator.

Prior Art

A number of devices have been developed in an attempt to resolve the problem or similar problems and these are referred to in the following: Soviet Union Patent Application SU1090383 (Kopejskoe) discloses a method for obtaining occlusion cast by positioning a resilient reticulated plate in the form of alveolar process between rows of teeth before fixing the jaws.

US Patent US 389071 1 A (Burns) discloses an adjustable dental impression tray including a primary unit and a complementary moveable unit which is mounted telescopically.

US Patent US 5340308 (Cukjati) discloses an apparatus and method for making either upper or lower dental impressions of teeth.

US Patent US 6629841 (Skinner) discloses an adjustable dental impression tray with first and second arcuate members moveable attached at a proximal end.

International Patent Application WO-A1 -2006/025640 (Orobiotech) discloses a dental impression tray wherein width of the tray can be adjusted to match different patients' dental arches.

US Patent US 4789334 (Wendenig) discloses a mould for taking impressions of upper and lower jaws.

Austrian Patent AT53763 (Koester) discloses an impression tray for dentists that consists of two parts, one which carries a plaster cast of the palate.

Chinese Utility Model CN201 101589Y (Guoqiang) discloses an adjustable conjuncted impression tray for simultaneous replication of up and down artificial teeth.

Japanese Patent Application JP2001333917A (Yamamoto) discloses a dental impression tray that is capable of accurately obtaining a vertical dimension of occlusion.

European Patent Application EP-A-0 439 889 (Innovex Inc) describes a jaw exerciser for guiding the mandible along an anatomically correct, non-deviated pathway during both opening and closing movements in order to encourage ideal motion.

The website http://hodentalcompany.com/harmony/ discloses a dual arch tray with alignment sticks for capturing teeth, the opposing arch, bite registration and with alignment sticks for obtaining facial midlines.

The 'Correct Bite' DVD clip at: http://www.youtube.com/watch?v=ohhfus9RRH0 by David Hornbrook reveals a technique of correcting bite.

Tekscan Inc have developed an analysis tool, 'T-Scan' (RTM) which shows a computerised occlusal analysis using sensor technology. The T-Scan is a diagnostic device that records your patient's bite force dynamics, including occlusal force, location and timing, http://www.tekscan.com/occlusal-analysis-system

Kerr Dental discloses a 'Kwik Tray' that is an adjustable, perforated, aluminium tray for crowns, bridges and inlay quadrant impressions.

SomnoDent (RTM) discloses the George Gauge comprising a body, lower incisor clamp and a bitefork for use in obtaining a bite registration. http://somnomed.coniAA -content/uploads/2014/08/GG-instructions--.pdf

Glidewelldental.com disclose the sl-protrusion gauge which is an elastic framework for use in bite registration.

The present invention aims to provide a device that enables dentists and other users to record occlusion and jaw position of patients in a systematic and reproducible manner using patient specific anatomical fiduciary markers.

The present invention also seeks to provide an impression device that can be used to create a bite registration/imprint using anatomical fiduciary markers, during positioning of the impression device in a patient's mouth, wherein the results obtained are suitable for use in the creation of an oral appliance.

Summary of Invention

According to a first aspect of the present invention, there is provided an impression device for obtaining a bite registration comprising: a tray capable of accepting impression material, the tray includes a body for positioning within a patient's mouth and a handle that protrudes from the patient's mouth; a displaceable locator is arranged, in use, on the tray in a channel, the locator has at least one first groove for receiving upper jaw incisor teeth and at least one second groove for receiving lower jaw incisor teeth, wherein the locator can be moved independently of the tray to a user selected position that aligns the locator with a patient's incisor teeth to enable an impression device to be located in the same position in a patient's mouth during each bite registration.

Optionally the locator may be arranged in use in the tray so as to be part of the impression device where it is located in a channel, or independently wherein the locator is located in a patient's mouth without the tray.

The device can be used (although not exclusively) for determining occlusion of the jaws and making a record of an upper and lower jaw position so as to review position of the upper and lower jaws relative to each other.

Preferably the device is aligned with fiduciary anatomical markers on a patient's body during use, in order to aid with obtaining repeated bite registrations under similar or identical parameters. In this way, for example, position of the device is constant relative to a particular fiduciary anatomical marker although position of the jaw may have been augmented.

The fiduciary markers are mainly postural and positional, such as for example: the frenulum, the anterior nasal spine, a mid line of the frontal bone or a midpoint of the mandible. Some or all of these markers can be used in relation to restoring and repositioning symmetry of the jaw and recording the occlusion in this position. Fiduciary anatomical markers include various reference points on a patient's body and may include, but are not limited to: frenulum (labii superioris or labii inferioris), cranial midline, photographic landmarks and orthodontic relative cephalometric x-ray marker points.

The fiduciary anatomical markers provide physical markers on a patient that can be aligned with the device so as to locate the device in such a way that it can be readily repositioned in the same aligned position.

In this way the impression device can be used to take a bite registration or an imprint that records and reveals contours of teeth as well as one that is capable of being used to establish measurements of jaw alignment/misalignment relative to each other in various anatomical planes to include medial/lateral, anterior/posterior and superior/inferior.

Ideally separate measurements and/or absolute readings are taken to record measurements in each plane wherein the readings may be taken before, during or after augmentation of the jaw.

The device is used in conjunction with fiduciary markers in order to take a measurement or reading.

It is envisaged that the device may be used to obtain a bite registration of the jaw in a naturally aligned position, a corrected position, an offset position or any other positions between, typically based upon the same fiduciary anatomical markers as chosen by the operator.

The bite registrations obtained from the use of the device can be used as an aid in jaw correction and in particular the creation of an occlusal splint or other appliance such as a sleep appliance or a Temperomandibular Joint (TMJ) or a sport or singing appliance through digital capture of the bite registration obtained using the impression device and by the use of dental Computer Aided Design (CAD)/ Computer Aided Manufacturing (CAM) systems.

The tray comprises a body for positioning within a patient's mouth, in use, and a handle that protrudes from the mouth when the tray is positioned in the mouth. In this way the device can be positioned and supported in the mouth using the handle therefore allowing the user (clinician) to manoeuvre the device to the desired position by means of the handle.

Preferably the body is substantially planar having a generally arcuate shape for positioning between the upper and lower jaw thereby providing an upper and lower bite surface.

The body is typically U-shaped so as to match an arrangement of the teeth on the jaw.

Ideally the body is sized to receive the full dentition, preferably at least six teeth on each side of the mouth (left and right). Therefore the body is preferably capable of receiving twelve or more teeth in total for each of the upper and lower jaw teeth.

The body is planar so as to provide a flat bite surface onto which the teeth or gums are received. The arcuate shape of the body enables the tray to fit around teeth on the upper and/or lower jaw.

Ideally the body has an inner wall and an outer wall between which a patient's teeth are positioned during use. The walls define an area between which the teeth are located and wherein the impression material is received so as to obtain a bite impression or to ensure a bite registration is subsequently taken by location of the teeth between the inner and outer walls.

The walls therefore aid in containing impression material that is more liable to spread, for example due to effects of gravity.

Preferably the walls extend both sides of the bite surface thereby defining two sections of the inner wall, a first and second section and two sections of the outer wall, a third and fourth section wherein each sections extends from a different face of the bite surface. These define areas on each side of the tray for receiving teeth and/or gums. In this way both upper and lower teeth can be located on the device in order to assess a patient's bite and so that bite registrations or imprints can be taken simultaneously of both jaws.

In preferred embodiments one wall section (first/third or second/fourth) is biased so as to extend further from the bite surface than the other wall section. This ensures a deeper trough is defined for receiving teeth and gums so as to enable a bite registration that includes gum shape to be recorded and provides a shallower trough on an opposite side of the tray.

Typically separate bite registrations are taken for the upper and lower jaws; therefore the orientation of the device can be altered depending upon which jaw is being analysed. Furthermore a tray having extended wall sections on both sides of the bite surface would be difficult, if not impossible, to fit into some patients' mouths therefore the biased walls overcome this problem.

It is appreciated that the device allows bite registrations of both jaws to be taken simultaneously, wherein the bias side is capable of obtaining a more comprehensive registration to extend to the gums, as required for the creation of a gum shield appliance.

Ideally the wall height from the bite surface tapers towards where the incisor teeth are received. Advantageously this limits spreading of any impression material at the back of the mouth whilst taking the bite registration. This reduces the risk of swallowing or choking on the impression material and ensures the impression material takes a full registration of the teeth and gums.

Preferably wall height increases gradually so as to provide a smooth anatomically, curved wall that does not cause discomfort to a patient.

The bias side of the tray enables a user to capture optimal anatomical information on the patient's arch on which an appliance will be fitted in use.

Preferably faces of the wall that receive impression material are ribbed with impression material slots so as to aid with removal of the bite registration/imprint after it has been formed because the ribbed walls serve to prevent the impression material from separating from the tray when the user removes the device from the patient's mouth.

In some alternative embodiments the walls may be contoured to accommodate different shaped mouths. For example the outer wall of the tray may be stepped in order to widen distally.

The slots can also be used to receive additional components, such as discs, so as to secure them in a fixed position on the impression device or supports to obtain a vertical support while taking a patient's bite registration/impression. The additional components may be adapted to be received by one or more of the slots. In this way the components can be located in fixed positions during use.

For example utilising spacers in this manner enables the user to induce correction of the jaws in the lateral plane. Further recordings can be made utilising the patient's reference points mentioned earlier within this text in order to create corrective positions from which digitally designed and manufactured bite correcting appliances can be made.

The slots may also form mounting points to receive digital location sensors that digitally determine the 3-Dimensional (3D) position of the adjacent teeth. These digital records obtained by the digital location sensors can then be analysed with the aid of diagnostic software.

Extension portions may be provided for attachment to the tray by means of the slots in order to extend the length of the outer wall so as to obtain a deeper bite registration for patients with larger teeth and/or to include teeth and gums.

Typically a pair of extension portions are arranged on the tray, one each side of the channel. In some embodiments the extension portions may extend across the channel. Extension portions may be added to the non-bias side of the tray.

Each extension portion comprises a panel with at least one leg adapted to fit into a slot. In this way the panel can be attached to the tray by means of the slot. The extension portion ideally has rounded edges so as to be comfortably received in the patient's mouth.

Typically the extension portion is shaped to correspond to the profile of the tray wall so that it joins closely to the tray with no gaps though which impression material could escape.

In another preferred embodiment the bite surface is arranged between front and rear walls and is formed from a mesh or netting that is capable of flexure when receiving the teeth. The mesh or netting allows deformation to occur during the bite registration. Advantageously the use of mesh or netting can prevent canting and interference that can be associated when using a solid material. Furthermore the use of mesh or netting enables the user to see through the bite surface to help establish if the tray will fit the patient's mouth. For example a fibre or synthetic plastic mesh may be provided as the bite surface.

Current methods of aligning the lower jaw are by consideration of the lower arch against a flat surface, however this may introduce a canting of the occlusal plane since the three highest points on the arch determine the occlusal plane.

The impression device allows users to reposition the jaw and bypass these occlusal interferences. The anatomical fiduciary markers are used in conjunction with the impression device so as to help the user to find the correct jaw position.

The tray ideally includes a channel for accepting the locator. The channel is arranged through the body and handle so that the locator is accessible during use exterior to the patient's mouth. Where the channel is located there is a break in the outer wall. The locator includes a raised portion that corresponds to the wall which is aligned with the outer wall when set in its "datum" position so as to provide a continuous barrier comprising the outer wall of the tray and raised portion of the locator so as to retain impression material therewithin.

Advantageously the locator is dimensioned to fit within the channel and to be capable of sliding to and fro within the channel.

The locator is longitudinal having at least one groove on each face of the locator. The grooves for receiving incisor teeth are arranged perpendicular to the lengthwise axis of the locator.

Some embodiments of the locator may have a plurality of grooves in which the incisor teeth can be located. In this way multiple positions are provided for accepting the upper and lower incisor teeth in a natural bite position and an adjusted position after the lower jaw has been augmented to a new position that will alter position of the lower incisors relative to the upper incisors.

Ideally part of the groove is arranged to stand proud of the tray so as to engage with the teeth without interruption that might otherwise be caused by the tray. In this way the teeth engage with the locator before engaging with any other part of the device. The locator can be adjusted by being slid along the channel or by the tray being slid relative to the locator in order to align the groove with the teeth of the upper jaw, teeth of the lower jaw or both.

Once the locator has been positioned, so that the patient is biting down on a groove, the tray can be slid forwards or backwards along the channel until the raised portions are aligned with the wall. Therefore a measurement can be obtained of anterior/posterior positioning of the teeth on the jaw relative to a set position on the device. Furthermore a measurement can be obtained to determine final position of the locator relative to the datum.

In another configuration the locator may be adjusted so as to adjust the patient's jaw wherein the movement of the locator when adjusted by the user moves the patient's jaw.

The grooves are arranged posterior to the raised portion thus further aiding with location of teeth with the area defined by the walls and raised portions.

In preferred embodiments the raised portion includes a notch for use in aligning with a fiduciary marker that indicates a midline from which deviation from can be determined. The notch is typically V-shaped and provides a visual marker on the locator that can be aligned with a fiduciary anatomical marker on the patient.

Preferably the notch is aligned with the frenulum labii superioris inside the upper lip, or the frenulum labii inferioris inside the lower lip, herein described as the frenulum. The frenulum is one such natural midline marker of the body and by determining location of this, the user can observe deviation of the teeth and or jaw from this midline, therefore measuring and/or observing medial/lateral deviations.

The frenulum, sometimes referred to as the soft tissue position, is described as an embryonic primary marker and is therefore recognised as a true midline. Whereas markers such as the teeth do not necessary indicate a true midline and growth of the teeth often does not match the frenulum and or the skeletal midline.

Typically the device is aligned with the fiduciary markers in order to determine variation of the teeth and/or jaw from these fiduciary markers. To align the notch with the frenulum the patient's lips are displaced in order to reveal the frenulum and the locator. The tray is moved in a lateral plane in order to align the notch with the frenulum. Ideally both the locator and the tray have a notch for alignment with the frenulum so as to help the user align the device.

A patient's lower jaw can be augmented to preferred alignment using the fiduciary markers as to guide the patient's jaw. In this way when the device is aligned with the frenulum it is also possible to observe where the teeth midline sits in comparison to this fiduciary marker therefore indicating lateral deviation of the teeth. Furthermore a user may take a first bite registration of the patient where no jaw augmentation has taken place and a second bite registration after the jaw has been augmented in order to reveal misalignment.

Preferably the locator is typically made from two independent parts, an upper part and a lower part thereby forming a locator assembly. The individual component parts of the locator assembly clip into each other and are retained once clipped together so as to form a single item.

The upper part and lower part can move relative to each other when clipped together, allowing for a longitudinal sliding action over each other part. Typically, range of movement of each part of the locator assembly is limited by the channel once the locator assembly is positioned in the tray.

The assembled upper and lower parts can be separated with the use of thumb and forefinger actuating at least one pair of clips in a squeezing motion in order to release the upper part from the lower part.

Preferably one set of clips is provided. When fitting the locator assembly to the tray one part is located on each opposing face of the channel before being clipped together. Each part is seated on a guide rail that runs along a perimeter edge of the channel so as to engage the parts in such a way as to permit sliding along the channel.

Once seated within the channel the parts of the locator assembly can be fully articulated independent of each other along the length of the channel so as to position each part accurately with upper and lower incisor teeth. Advantageously the locator assembly enables one groove to be provided on each face of the locator assembly that can be moved independently to align with the incisors therefore removing the requirement for more than one groove on each face to be provided.

Furthermore once the locator assembly has been located on both upper and lower incisors the position each groove and therefore of each part relative to each provides a measurement and visual representation of position of upper and lower incisors relative to each other.

Ideally an outward facing face of the outer wall includes increments to allow the user to measure the distance between the fiduciary anatomical marker, the frenulum, and the observed midline of the teeth, therefore revealing lateral and anterior posterior deviation. For example millimetre increments may be included on the outer face.

Ideally the increments may include a range of at least 5mm and preferably at least 10mm to the left and 10mm to the right.

These same increments may additionally be used when observing jaw mechanics, in particular dynamics of the jaw during opening and closing, and for example lateral excursion of the jaw to the left or right during opening of the mouth.

In some embodiments the channel may include increments so that the position of the locator in the channel can be measured thereby providing a measurement of anterior/posterior positioning. Alternatively or additionally the position of the locator in the tray may be marked for example with a pen on the markers on the locator and the tray prior to impression taking as an aid to the user to locate the tray and locator correctly during impression taking.

The locator aids with identifying and correcting lateral deviation of the jaw from the midline and in order to record anterior/posterior position of the teeth relative to one and other.

Therefore the impression device can be used to obtain a measurement of anterior/posterior alignment, the midline and vertical height of the jaws, all of which can be used to reveal misalignment. For example measurement of position of an upper and a lower jaw position can be taken and compared, or position of the jaw in a natural position can be measured and compared to a measurement taken when the jaw is moved to a corrected position.

The impression device can be used to record a bite registration by a method comprising the steps of: aligning a patient's incisor teeth with the grooves of the locator, observing the patient's frenulum and laterally adjusting the tray in a horizontal plane to align the locator notch with the frenulum; removing the impression device from a patient's mouth and introducing impression material into a tray of the impression device, re-positioning the impression device in the mouth using the preset position of the locator to ensure the tray is arranged in the same position before taking the bite registration. There is thus provided a method of obtaining and recording a bite registration.

Preferably in use the locator is inserted into the mouth initially without the tray so as to allow the patient to bite on to the groove that serves as a location point for the incisors prior to taking an impression. The patient is asked to bite down on the locator so that the front upper and lower incisors are located in a groove; the patient's lips are retracted so that the notch can be visually aligned with the frenulum by augmentation of the jaw. The user can then align the midlines of the upper and lower jaws with the notch.

This method serves to familiarise the patient with the correct position of the jaw so that when taking an impression, the patient is more readily able to correctly position the jaw. The user can then record the position of the jaws relative to each other in an anterior/posterior position using the increments on the locator.

Proprioceptors in and around the periodontal ligament are activated when biting about the locator's grooves and aid both the user and the patient to find the correct jaw position relative to each other. Evidence has shown that there is a natural "neuromuscular" protective feedback mechanism that exists between the periodontal ligaments supporting the teeth and the motor centres of the brain that control the neuro muscular contractions of the primary muscles of mastication (chewing muscles).

This reflex is seen most clearly for example when chewing meat with a small fragment of bone in the meat. As the teeth come together with force they encounter the bone fragment before they expect to meet the opposing teeth and this feedback mechanism is triggered due to the sudden overloading of the nerve endings in the ligament (proprioceptors). A message is immediately sent to the brain through the nervous system to motor neurons responsible for the contraction of chewing muscles and immediately the nerve stimuli to those muscles cease, thus contraction is halted and instead the muscles responsible for opening the mouth are stimulated. This process is designed to prevent damage occurring to the teeth. This useful neuromuscular feedback response can be used to stop and/or control clenching thereby helping the user to find the correct position to be recorded.

Once this is achieved the same procedure may be repeated with the locator and the impression tray prior to taking an impression. A second method of implementation comprises the additional step of augmenting the jaw to an improved alignment before taking the bite registration.

In this way the impression device is used to determine deviation of occlusion of the upper and lower jaws from a first natural alignment bite registrations to a second corrected bite registration.

Therefore a bite registration may be taken with or without augmentation of the jaw. For example if taking a bite registration for retained implant screws the user is able to locate the head of the screw more easily through the see through netting and thereby create a correctly positioned access hole for the impression pin.

The impression device may also be used for bite registrations to record crown and bridge details, or for whitening trays and orthodontic retainers.

By determining deviation of the jaw in relation to fiduciary markers the results can aid users in:

1 . The planning and construction of various occlusal splints/appliances,

2. The study and treatment planning of patients

3. To design restorative, surgical, orthodontic prototypes prior to definitive and final restorations and surgery.

4. The recording and planning of diagnostic setups and moulds (physical and digital) of patient occlusion. The anterior/posterior measurement is converted into an alignment by using one or more of the six tests below.

The sizing of the increments or fiduciary markers used to determine optimal jaw position may be gathered from, but are not limited to, one or a combination of the following:

1 . The Jefferson x-ray analysis

2. The s-sound test

3. The 3d Profile analysis

4. Airway and position of the hyoid

5. A percentage of protrusion, for example 60% of protrusion

6. Muscle kinesiology diagnostics.

Alternatively or additionally the jaw can be manipulated to a corrected position based on the measurement obtained in order that the imprint taken is of corrected bite not natural bite. In this way the user uses the displaceable locator to locate the upper and lower jaws in a preferred relative alignment prior to an impression being taken so that the upper and lower jaws are properly aligned when forming the impression.

In some embodiments the impression device is used in recording an occlusion between an upper and lower jaw, whereby, when inserted in a patient's mouth, a locator is adapted to cause relative displacement of the patient's upper and lower jaws thereby enabling alignment of the upper and lower jaws.

In this way occlusal between the upper jaw and lower jaws, and therefore superior/inferior displacement in the corrected alignment can be determined. The displacement can be established in relation to fiduciary markers, for example those may be obtained from but not limited to one or a combination of:

1 . The Jefferson and Posterior Anterior skull x-ray analysis

2. The s-sound test

3. The 3d Profile analysis and TMJ condular position from radiographs

4. Airway and position of the hyoid

5. A percentage of protrusion, for example 60% of protrusion

6. Muscle kinesiology diagnostics. The device may be produced in a number of physical sizes in order to take into consideration the variance in size of the human upper and lower jaw anatomy. For example the device may be provided in an extra-small, small, medium, large and extra-large version in order to accommodate various sized mouths from paediatric to adult. Advantageously by providing differently sized devices the practitioner is more easily able to obtain a full impression of jaw shape and dental occlusal by ensuring all teeth form an imprint in the impression material as the device is correctly dimensioned to best fit an individual's mouth.

Preferably handle size remains consistent in all impression devices so that the same locator can be used in any device. The handle is designed to give the optimum balance between stability, movability and control of the device throughout the duration of the impression taking.

In some embodiments the impression device may accept spacers such as discs that are inserted by a user to correct uneven vertical height of the occlusal support of the jaw. For example the impression device may accept vertical supporting discs. Typically the spacers/discs may be inserted into the tray and the patient then asked to clench their jaw so that the user can observe symmetry with the spacer(s)/disc(s) in situ.

Preferably the spacers are formed from a lightweight, strong, durable synthetic material. Typically the spacers are of predetermined sizes so that the user can record amount of alteration caused by insertion of the spacer(s). For example spacers may be provided in 0.5 millimetre, one millimetre and two millimetre thicknesses. Number and size of discs is recorded to establish deviation/correction.

Preferably the spacers may be stackable so as to allow one spacer to be arranged atop of another spacer in order to alter adjustment of the jaw. Typically this is may be enabled by an aperture and projection arrangement so as to ensure the spacers are secured in the impression tray when stacked together.

Ideally the base spacer includes apertures or recesses for receiving projections on an adjacent spacer. The adjacent spacer preferably includes apertures and projections on one face so as to enable a spacer to be connected to a base spacer and in order to be capable of receiving a further spacer on top. In preferred embodiments the spacers may be shaped so as to be accepted by the ribbed surface/slots of the walls, for example the spacer may include a pair of projections for fitting into a pair of opposite slots. In this way the spacers can be specifically located and will not move during use.

In a preferred embodiment a base spacer is provided wherein the base spacer includes a platform for receiving the teeth and at least one arm with a connector for connecting the spacer to a slot. Preferably the base spacer includes two arms, each having a connector. The connectors are dimensioned to correspond to the slots. For example the connector may have a trapezoid cross section to correspond with a trapezoid slot.

The platform is preferably planar.

The base spacer is capable of receiving additional spacers so as to increase thickness of the spacer in use and thereby alter adjustment of the jaw.

Ideally the spacers may be provided in different thicknesses so that a user can select level of adjustment. For example the spacers may be provided in 0.5mm, 1 .0mm and 2.0mm thicknesses.

Thickness of the spacer and location of the spacer on the tray determines adjustment of the jaw.

Preferably the spacers may be substantially rectangular or square. In some embodiments the spacer may be disc shaped.

In some embodiments the handle has tapered edges for abutting or aligning with incisor teeth. Advantageously the tapered are rounded so as not to expose any sharp edges to the patient so there is less risk of cutting or injuring the patient. Typically the point at which full thickness of the handle is reach may be marked with a visual indicator for aligning of the handle with a particular tooth. Typically the area between the tapered edges may be marked with increments so as to be suitable for obtaining a measurement. These measurements can be recorded and used in patient management of care and education. Typically the handle is designed in such a way that it can be scanned in a handle holder in a two 'degrees of freedom' digital scanner or other similarly designed capture systems. The impression can therefore be transferred and converted into a digital file and can then be used in digital appliance diagnostics, design and manufacturing.

Typically the visual indicator may be aligned with an incisor and during opening and closing of the mouth the alignment of this indicator, in relation to the tooth, is observed jaw opening and closing dynamics that may reveal abnormal movement of the jaw such as lateral excursion to one side. In this way the jaw dynamics can be recorded in order to provide further insight to a patient's pathology.

There are a number of ways in which the device can be used in order to obtain different readings, impressions and/or measurements. The readings, measurements and imprint taken provide data that is typically used to reveal any misalignments of the jaw. This data can also be used in the process of:

1 ) Patient diagnostics

2) Treatment planning

3) Appliance design

4) Appliance manufacturing

An appliance is a corrective item worn by the patient to correctly align the jaws.

Typically the data obtained can be used in conjunction with models of the jaws. Such models may be obtained by taking jaw impressions or scans and using these as moulds to create physical replicas of the jaws, x-rays and/or digitally scanning the jaw. In this way it can be possible to observe and manipulate the model jaws to better understand patient pathology and to clearly demonstrate these jaw dynamics to the patient

Where manual models of the jaws are taken by impressions these may then be subsequently scanned so as to provide a computerised model of the jaw.

Often the models created must also be mounted to recreate actual position of the jaw that can add a margin of error. Current methods for producing occlusal splints/appliances and recording jaw position and occlusion use several fabrication, articulation, and manual trimming methods. This is time consuming. For unmounted models, models have to be mounted on an articulator to allow the opening to be adjusted and to simulate the dynamics/excursions needed to design centric relation splints. This can introduce error since a mechanical jig is typically used to "level" the lower occlusal plane.

Preferably data obtained by the impression device and optionally in combination with other information such as x-rays, palpation, neurological testing and/or diagnosis is analysed in order to establish correct jaw alignment and augmentation required in order to achieve this in a tangible manner that can be applied to the models either manually or digitally. This information can then be translated in order to provide the dimensions required to create an appliance or occlusal splint. Such items facilitate correction of the jaws in a non-invasive manner.

Typically the imprint obtained from a bite registration in the correct jaw alignment proves the core shape of the appliance with the additional measures obtained by the device aiding to define thickness of the appliance in order to fully align the jaw.

A process of making an appliance from the impressions taken using the impression device includes the steps of: using the impression to model the upper and lower jaw, the jaws models being used to reveal exact jaw occlusion, measured deviations may be used to correct jaw model position and forming an appliance based on occlusion at the corrected position.

Another process of making an appliance from impressions obtained using the device described may include the steps of digitisation of the recorded bite registration impressions captured by the impression device to replicate a patient's upper and lower teeth, the replicated teeth being used to reveal jaw occlusion; measuring deviations digitally within dental Computer Aided Design and/or Computer Aided Manufacture software of jaw offset and correcting jaw model position and forming an appliance based on occlusion at the corrected position.

The impression device reduces margin of error by enabling the user to take measurements and to aid with guiding the patient's jaw into the required position using anatomical fiduciary markers such as skeletal facial profile aligned with portions of the locator such as the notch or groove.

Current methods of aligning the lower jaw by consideration of the lower arch against a flat surface may introduce a canting of the occlusal plane. The impression device allows users to reposition the jaw and bypass these occlusal interferences. The fiduciary markers used in conjunction with the impression device helping the user to find the correct jaw position.

Jankelson protrusive research has shown how this path tends to correct to midline on repeated protrusion and allows more accurate recording {Chan C. A. 2007 ICCMO - A review of the Clinical significance of the Occlusal Plane: its variation and effect on head posture).

Further errors may also be introduced during fabrication and manufacture of the appliance for example if produced from a 'wax-up', or directly by curing acrylic between the arches. Traditionally the final contact surfaces may rely too much on the result of a technician's patientive determination of smoothness and the absence of tooth impressions. The present invention ensures a detailed bite registration can be obtained in both a natural and augmented position thereby aiding with preparation of a good fitting appliance.

In preferred embodiments the impression device is ideally made from a lightweight, strong, durable synthetic plastic such as a medically safe acrylonitrile butadiene styrene (ABS) plastic, polystyrene and/or nylon.

Ideally the device is disposable being suitable for use during a single treatment wherein the device may be used more than once for the same patient to obtain different information, for example to obtain measurements and to obtain a bite registration or selection of bite registrations.

The results obtained from the impression device are used to aid with the creation of an appliance including the manufacture and fabrication of an appliance.

The application may be manufactured using various methods and systems. For example a rapid prototyping device for producing a facsimile of an indentation formed from teeth on an upper and a lower jaw. The prototyping device includes a 3D printer and/or a milling computer aided design machine.

The system/method of manufacture may include a stereo lithographic device for producing a facsimile of an indentation formed from teeth on an upper and a lower jaw. The stereo lithographic process may include employing a curable resin.

The system/method of manufacturing an oral appliance using the results obtained using the impression device may include an injection moulding process to obtain a facsimile of the impression formed from the teeth.

The system/method for manufacturing an oral appliance using the impression device may include a means for receiving data indicative of measurement of misalignment of the upper jaw with respect to the lower jaw and a fabricator, operating under control of an automated means, the fabricator is arranged to manufacture the appliance.

In some embodiments the impression device may include sensors that allow digital readings to be taken and recorded during use, by providing digital spatial positioning/measurement without requirement for manual recording. Preferably digital motion sensors track the jaw movements and align these with fiduciary markers obtained from 3D models of the patient's skull, jaws and teeth. These sensors may be embedded into the locator and also into the tray and where required the appliance will be manufactured and calibrated to achieve the correct positional relationships.

For example, a reading may be taken form the various offsets in the X-X', Y-Y' and Z-Z planes and used to provide an automatic manufacturing process to produce a replica of an oral appliance.

One way in that this is achieved is to use a digital data file(s) for example Stereo Lithography files (STL files) of an impression(s). Such files can then be imported into compatible software for the purposes of design and articulation before being passed to a further compatible system in order to produce the final patient appliance, utilising 5 axis milling and or 3D printing processes.

A database may be provided to collect patient data obtained whilst obtaining a bite registration.

The database may be adapted to store data derived from the system data indicative of patient identity and data measurements indicating misalignment of the upper jaw with respect to the lower jaw.

The data held on the database may be used to provide data to a fabricator so as to enable manufacture of the appliance. The fabricator may operate under control of an automated means.

Preferred embodiments of the invention will now be described with reference to the Figures in which:

Brief Description of Figures

Figure 1 A shows a top, left isometric view of one embodiment of the impression device;

Figure 1 B shows a top view of the impression device of Figure 1 A;

Figure 1 C shows a top, right isometric view of the impression device shown in Figure 1 A;

Figure 2A shows a left side view of the of the impression device shown in Figure 1 A;

Figure 2B shows a rear view of the impression device shown in Figure 1 A;

Figure 2C shows a right side view of the impression device shown in Figure 1 A;

Figure 2D shows a front view of the impression device shown in Figure 1 A;

Figure 3A shows a bottom, left isometric view of one embodiment of the impression device;

Figure 3B shows a bottom view of the impression device of Figure 1 A; Figure 3C shows a bottom, right isometric view of the impression device shown in Figure 1 A;

Figure 4 shows a selection of views of part one of the two part locator;

Figure 5 shows a selection of views of part two of the two part locator;

Figure 6A shows a top, left overview of the impression device with the locator arranged in the channel;

Figure 6B shows a bottom, left overview of the impression device with the locator arranged in the channel;

Figure 7A shows a rear, top isometric view of a second embodiment for the impression device with the locator arranged in the channel;

Figure 7B shows a rear, top isometric view of a second embodiment for the impression device without the locator;

Figure 8A shows a top view of the impression device as shown in Figure 7A;

Figure 8B shows a top view of the impression device as shown in Figure 7B

Figure 9A shows a front, top isometric view of the impression device shown in Figure 7A;

Figure 9A shows rear view of a second embodiment of the locator;

Figure 9B shows a front, top view isometric of a second embodiment of the locator;

Figure 10A shows a top view of the locator shown in Figure 9A;

Figure 10B shows a side view of the locator shown in Figure 9A;

Figure 1 1 shows an impression device having a stepped outer wall;

Figure 12A shows a front, top isometric view of the impression device shown in Figure 1 1 with the locator;

Figure 12B shows a front, top isometric view of the impression device shown in Figure 1 1 without the locator Figure 13 shows a third embodiment of the impression device;

Figure 14 shows a flow chart with the steps required to obtain data such as measurements of the mouth and an imprint, which can be used to create an appliance;

Figure 15A shows an isometric view of the impression device receiving extension portions;

Figure 15B shows a side view of the impression device receiving extension portions;

Figure 15C shows a rear view of the impression device receiving extension portions;

Figure 16A shows an isometric view of the impression device with extension portions fitted;

Figure 16B shows a side view of the impression device with extension portions fitted; Figure 16C shows a rear view of the impression device with extension portions fitted; Figure 17 shows a selection of spacers;

Figure 18 shows various views of an arrangement of three spacers

Figure 19A shows a top view of a spacer base;

Figure 19B shows an overview of a spacer base;

Figure 19C shows a side view of a spacer base;

Figure 20A shows a side view of a 1 mm spacer;

Figure 20B shows a side view of a 2mm spacer;

Figure 20C shows a top isometric view of a 1 mm spacer;

Figure 20D shows a bottom isometric view of a 1 mm spacer;

Figure 20E shows a bottom view of a spacer;

Figure 20F shows a top view of a spacer;

Figure 21 A shows a top view of an impression device with a spacer fitted: Figure 21 B shows an impression tray 100 and an arrangement of three spacers; Figure 22A shows a small impression tray; Figure 22B shows a medium impression tray; and Figure 22C shows a large impression tray.

Detailed Description of Figures

The Figures show preferred embodiments of the impression device 100 which can be used for obtaining a bite registration of the upper and lower jaws as well as obtaining measurements of the mouth and positions of the jaw relative to anatomical fiduciary markers and in response to jaw adjustments.

Figures 1 to 3 show a selection of views of a preferred embodiment of a tray 200 of the impression device 100. The tray 200 comprises a body 220 and a handle 230. The body 220 is planar having an arcuate shape so as to wrap around the teeth in use. The body is sized to encompass a full complement of teeth, typically at least 12 teeth.

The body 220 includes an inner wall 240 and an outer wall 245 that define an area in which the teeth are located in use. The area defined is also capable of receiving impression material for taking a bite registration/imprint, the walls 240, 245 serving as a barrier to prevent escape of impression material.

The walls 240, 245 extend both sides of a bite surface 250. The inner wall 240 has first and second sections 240A, 240B and outer wall 245 has third and fourth sections 245A and 245B, thereby defining an area on both an upper and lower face of the tray so as to provide a trough on each side of the tray for receiving a patient's upper and lower teeth and so that imprints can be taken simultaneously of both jaws if required.

Figure 1 A shows the outer wall section 245B and inner wall section 240B having a greater height at a distal end of the tray in order to prevent impression material spreading excessively in the mouth beyond the device. Therefore the tray is biased. The wall height gradually increases from the handle edge so as to have a smooth increase in height.

The portion of wall below the handle is also higher therefore providing an undulating wall that is high at the handle, tapers slightly at the handle edge, before increasing again towards the distal end.

The distal end of the tray 200 is rounded so as to have no sharp edges exposed to the patient during use. The distal end of the tray 200 is also slightly tapered so as to be easily fitted and manipulated in a patient's mouth.

The handle 230 includes a channel 210 for receiving the locator 300 (locator not shown in Figures 1 A-C). The channel 210 is rectangular and includes a pair of opposed rails 21 1 on to which the locator 300 is secured about in use.

The outer wall 245 is broken by the channel 210 and therefore has is formed from two halves, one either side of the channel 210. A bar 246 joins the two halves of the outer wall 245 which also forms one side of the channel 210. The bar 246 is flat and thin so as to permit free movement of the locator 300 past the bar 246.

Upper and lower faces of the rails include increments 215 in the form of raised and lowered portions at equally spaced positions.

In this way position of the locator within the channel can be measured. Furthermore as the locator is slid over the raised and lower portions it provides positive feedback to a user with regards to movement of the locator over each raised portion. For example a user can detect 'clicks' as the locator is slid over each raised portion.

Increments 215 are provided on three faces of the rails 21 1 A, 21 1 B and 21 1 C.

It is appreciated that increments 215 may be provided on more or less faces.

A raised rim 212 is provided around three edges 212A, 212B and 212C, of the channel 210. There is no raised rim on the bar 246.

One edge of the raised rim 212A includes increments in the form of raised and lowered portions so as to provide incremental markers to indicate position of the locator relative to the channel. Inner faces of the walls 240,245 are ribbed having a plurality of slots 280. The slots aid with retaining impression material and are dimensioned so as to permit easy removal of the impression material from the impression device 100.

The slots are trapezoidal in shape. Slot walls 280 are also inclined to further aid retention of impression material, discs or extension portions 290 (Figures 15 and 16). The slots 280 are evenly spaced along the length of the walls 240, 245.

The tray bite surface 250 is flat so as to provide a flat surface for receiving the teeth. The bite surface 250 is formed from mesh. The mesh is designed to both support and allow for the impression material to pass through it, aiding a good bond of the impression material to the tray from opposing sides. The bite surface 250 flexes during the impression taking process to take up the anatomical profile of the opposing teeth. Advantageously this prevents canting and interference which can occur when using a solid surface. The mesh is also transparent so as to help with location of the patient's teeth and arch shape by enabling the user to view through the mesh.

There is one section of mesh extending around the tray between the inner walls 240A, 240B and outer walls 245A, 245B. The mesh section is U-shaped and serves to hold the inner wall 240 to the outer wall 245 and thereby the handle 230.

The bar 246 extends across the channel and is attached to the mesh bite surface 250, defining and outer edge of the bite surface 250. Edges of the handle 230 are tapered so as to have a smooth rounded finish that will not cause discomfort to the patient and also so as to be accepted in the scanner holder.

The handle 230 is substantially planar extending from the body 220 so as to be project from the mouth in use. The handle 230 tapers from the body so as to be narrower at the proximal end. The handle 230 includes the channel 210.

Figures 4 and 5 show a selection of views of a two part locator 300 for use with the first embodiment of the invention. The locator 300 is formed from two parts 300A and 300B that join together in use to form the locator 300 wherein the parts 300A, 300B are each moveable relative to each other. The parts 300A, 300B have similar profiles to each other. Each locator part 300A, 300B is longitudinal having a front end 31 OA, 31 OB is received by the mouth in use and rear ends 320A, 320B that is exterior the mouth in use.

Rear end 320A of 300A is ridged 330 so as to provide a raised and lowered surface to aid a user to grip the locator 300 during use and to aid with sliding parts 300A with respect to part 300B.

Part 300A also includes a pair of clips 395 that enable part 300A to be clipped to part 300B. The clips 395 are flexed so as to fit through aperture 390 of part 300B. The locator 300 is substantially rectangular in shape and fits within the channel 210 so as to be slid to and fro in the channel 210 in order to align the grooves 340A, 340B with the incisor teeth (not shown).

Part 300B includes a ledge 350 that serves to space apart 300A from 300B. This enables front ends 31 OA and 310B to easily pass either side of the bite surface 250. The ledge 350 is an elongate section arranged on a face of the locator 300B that is opposed to the face which has raised portions 360B. There are two ledges 350 located on each long, outer edge of the locator 300B. The ledges 350 do not extend along the full length of the locator 300B so as not to restrict movement of locator 300 in the channel 210.

The locator parts 300A, 300B sandwich the bar 246 (not shown) so as to be able to slid past the bar 246 during adjustment. Therefore the clips allow a gap between the parts 300A and 300B so as to enable sliding to and fro either side of the bar 246 and bite surface 250. The front ends 31 OA, 310B each include a groove 340A, 340B for receiving upper and lower incisor teeth in use so as to locate the locator during a bite registration. The grooves 340A, 340B are arranged to traverse the locator 300A, 300B.

The grooves 340A, 340B are also arranged to be project proud of the bite surface 250, handle 230 and channel 210 when located in the channel 210 so that the patient's teeth can be located into the groove 340A, 340B without being obstructed by the tray 200 or handle 230. The locator 300A, 300B includes a raised portion 360A, 360B part way along its length. The raised portions 360A, 360B each include a notch 365A, 365B that are aligned with a fiduciary marker in use. The notches are V-shaped and in use are visually aligned with the frenulum (a natural midline). Once aligned deviation of the jaw from this midline can be observed by comparing the frenulum location at the perceiving teeth midline.

Central portions of the locators 300A, 300B are cutaway providing apertures 390 allowing the user to peer through the apertures 390 to view parts of the mouth such as teeth, inferior frenulum and gums. The apertures 390 also allow the locator 300 to be lighter in weight and cheaper to manufacture.

A front end of each aperture 390 is tapered to correspond to the notches 365A, 365B. Therefore the notches 365A, 365B have a central gap 366A, 366B.

Figures 6A and 6B show the impression device 100 with the locator 300 located in the channel 210.

Figures 7 to 1 1 show a second embodiment of the impression device 100. Details of the features that differ to those of the first embodiment are described below.

Figure 7A and 7B show an overview of the impression device 100 wherein the impression device 100 comprises a tray 200 and a locator 300. The locator 300 fits into a channel 210 provided on the tray 200. The locator 300 is capable of being slid along the channel 210.

The impression device 200 comprises a body 220 and a handle 230. The body 220 is planar having an arcuate shape so as to wrap around the teeth in use. The body is sized to encompass 12 teeth.

The body 220 includes an inner wall 240 and an outer wall 245 that define an area in which the teeth are located in use. The area defined is also capable of receiving impression material for taking a bite registration/imprint, the walls 240,245 serving as a barrier to prevent escape of impression material.

The walls 240, 245 extend both sides of a bite surface 250 having a first and second inner wall 240A, 240B and third and fourth outer walls 245A, 245B, thereby defining an area on both an upper and lower face of the impression device so that imprints can be taken simultaneously of both jaws if required. In contrast to the first embodiment this second embodiment has a channel 210 that extends along the handle 230 and across the bite surface 250. The tray 200 includes a semi-rigid member 205 that forms part of the bite surface 250. The member 205 serves to reinforce the tray 200 and the channel 210.

The channel 210 is rectangular. The tray is bias in the same manner as the first embodiment, however the bias outer wall 245B is continuous and is not broken at the channel 210. The continuous outer wall 245B includes a notch 270 for aligning with a notch on the locator.

Therefore the locator 300 fits into the channel 210 in one orientation wherein the raised portions are arranged on an opposite face to the continuous outer wall 245B.

Outer wall 245A is broken so as to receive the locator 300. This provides further rigidity and strength to the impression device 100. Inner faces of the walls are ribbed 280 to aid with removal of the impression material from the device 100.

The impression device bite surface 250 is flat so as to provide a flat surface for receiving the teeth. The bite surface 250 is formed from mesh and by the semi-rigid member 205.

Edges of the handle 230 are tapered so as to have a smooth rounded finish that will not cause discomfort to the patient and also to be accepted in the scanner holder.

The handle 230 is substantially planar extending from the body 220 so as to be project from the mouth in use. The handle tapers from the body. This aids to support the outer wall sections 245A, 245B from deviation during use.

Figures 9 and 10 show a second embodiment of the locator 300. The locator 300 is longitudinal having a front end 310 received by the mouth in use and a rear end 320 that is exterior the mouth in use. The locator 300 is substantially rectangular in shape, having a narrowed section at the distal end.

The rear end 320 includes ridges 330 on an upper surface so as to aid the user to grip the locator 300 and move it during use. The ridges 330 are arranged to traverse the width of the locator 300, being positioned adjacent to one another. The front end contact with the channel 210. The front end 310 includes a plurality of grooves 340 on both upper and lower faces of the locator 300. The locator 300 has one groove 310 on an upper face and two grooves 310 on a lower face. The grooves 340 receive incisor teeth in use so as to locate the patient's bite. The grooves 340 are arranged to traverse the locator 300.

The grooves 340 are also are dimensioned so that in use the patient's teeth can be located into the groove 340 without being obstructed by the tray 200. The locator 300 includes a raised portion 360 part way along its length. The raised portion 360 can be aligned with the outer wall 245 so as to provide a continued barrier that defines an area for locating the teeth and receiving impression material (not shown).

The raised portion 360 includes a notch 365 that is aligned with a fiduciary marker in use. The notch 365 is V-shaped and in use is visually aligned with the frenulum (a natural midline). Once aligned deviation of the jaw from this midline can be observed by comparing the frenulum location at the perceiving teeth midline.

In Figure 8B there is shown a recessed section 215 on the channel 210 on an upper face of the handle for receiving the locator 300 thereby allowing it to slot into the channel 210 rather than merely resting on top.

The locator 300 is shaped so as to fit in the recess have a stepped 325 rear end 320 as shown on Figure 10B wherein part of the locator 300 sits within the channel 210 and part sits upon the channel 210.

Two central portions of the locator 300 are hollow 390 allowing the user to peer through the hollow 390 to view the lower wall 245B and parts of the mouth such as teeth, inferior frenulum and gums. The hollows 390 also allow the locator 300 to be lighter in weight and cheaper to manufacture.

Figures 1 1 and 12 shows a third embodiment of the impression device 100 wherein the tray 200 has a stepped outer wall 245. This serves to widen the tray 200 at the distal end. All other features of the third embodiment are consistent with the embodiment shown in Figures 7 and 8. Figure 13 shows a fourth embodiment of the impression device wherein the tray 200 is reduced for taking a bite registration of less dentition, for example only front teeth such. This may be advantageous for children that have yet to develop molar teeth.

Figure 14 shows a flow chart detailing an example use of an impression device.

Figures 15 and 16 show extension portions 400 for use with the impression device 100 that enable the volume of the trough created between the inner 240 and outer 245 walls to be increased so as to hold more impression material (not shown).

Each extension portion 400 comprises a panel 410 with a plurality of legs 420 for being received into slots 280 so as to locate the extension portions on the impression device, thereby extending the outer wall length and increasing trough volume.

The panel 410 is arcuate so as to match curvature of the outer walls 245. The legs 420 are dimension to correspond to the cross section of the slots 280.

The legs 420 shown in Figures 15A, 15B and 15C are adapted for use with the first embodiment of the impression device (Figures 1 to 3) having a trapezoidal cross section so as to fit tightly into the slows 280 and so as to minimise movement in use.

The panel 410 has a curved lower edge 41 OA that corresponds to the edge of the outer wall 245. The upper edge 410B is curved so as to have a smooth edge exposed to the patient. Inner edges of the panel 410C are tapered to correspond to the notch 365 on the locator 300.

The extension portions 400 may be used on either side of the tray 200, although they are typically for use on the non-bias side of the tray 200 so as to increase trough volume to a similar capacity to that of the bias side of the tray 200.

Figures 17 to 21 show spacers 500, 600 for fitting to a tray 200 in order to adjust a patient's bite.

The spacers 500, 600 are rectangular.

Figure 17 shows a base spacer 500 having a platform 510 two arms 520 with a connector 540 at each proximal end for location the base spacer in a slot 280. The platform 510 is planar and provides a surface for receiving a patient's teeth. Thickness of the spacer and location of the spacer on the tray determines adjustment of the jaw.

An upper face of the base spacer 500 includes six apertures 530. The apertures 530 are dimensioned for receiving an additional spacer 600 atop the base spacer 500.

It is appreciated that the aperture may alternatively be a recess.

Additional spacers 600 include projections 650 on a lower face for accepting to apertures 530 on a second spacer 500, 600. In this way one spacer 600 can be attached to another spacer 500, 600.

The spacers 600A, 600B have three apertures 630 on an upper face for receiving another spacer 600 and have three projections 650 arranged on a lower face. The apertures 630 and projections 650 are in a triangular arrangement.

The apertures 530, 630 and projections 650 are positioned and dimension to correspond with one another.

Figure 17 shows two spacers 600A, 600B. 600A is thinner than 600B. 600A has a depth of 1 mm and 600B has a depth of 2mm. The spacers 500, 600 can be stacked to the desired height so as to brig about the desired adjustment/correction.

The connector 540 is dimensioned to correspond to the slot 280. The connector 540 has a trapezoid cross section so as to slot into the slot 280.

Figure 18 shows the three spacers 500, 600A, 600B shown in Figure 17 stacked on atop another.

Figures 19A, 19B and 19C show different views of the base spacer 500.

Figures 20A-20F show different views of spacers 600A, 600B.

Figure 21 A shows a top view of an impression device 100 having an arrangement of three spacers 500, 600A, 600B located on a left portion of the bite surface 250. The connectors are engaged in two slots 280.

When the spacers 500, 600A, 600B are stacked the edges are flush. Figure 21 B shows the stacked spacers 500, 600A, 600B prior to be fitted impression device 100.

Figures 22A, 22B and 22C show three different sizes of the impression device, small, medium and large. The impression devices shown in figures 17A, 17B and 17C have the following dimensions given in millimetres (mm):

The invention has been described by way of examples only and it is appreciated that variation may be made to the aforementioned examples without departing from the scope of the invention.