FIELD OF THE INVENTION

This invention generally relates to scanning dental impressions. More particularly, the invention relates to aligning digital models of an upper and a lower jaw of a patient, where the digital models are based on scans obtained from impressions taken of the patient's oral situation.

BACKGROUND OF THE INVENTION

In the fields of restorative dentistry, orthodontistry and implant dentistry, it has for many years been common practice for dentists to take an impression of a patients jaws, including the patient's teeth. In the traditional workflow, these impressions have been sent to a dental laboratory, where a dental technician has made plaster or stone models of the patient's jaws based on the impression scans. Any restorative work such as crowns, veneers, inlays/onlays etc. have then been manually created on top of the plaster model.

Over the last 15 years, a more digital workflow has been created. It is now common practice for a dental technician to receive an impression, make a plaster model or stone model of the patient's jaw based on the impression, and scanning the stone model using a 3D scanner, to create a digital 3D model of the patient's jaw. Any design work, be it restorative, orthodontic or for implant planning, can then be accomplished digitally, using a computer software package such as the 3Shape Dental System.

It is often necessary to align the digital models of the upper and lower jaws of the patient, for example in order to take into account the antagonist of the tooth on which a crown is being designed. In order to do this, it is common practice to take the impression of the patient's jaw using a so-called triple tray, which has impression material on both sides of the tray so that both the upper and lower jaw of the patient, as well as their alignment or bite registration is taken using only this one impression tray. However, the impression taken using triple trays are not always as accurate as impressions acquired using single trays, and the alignment or bite registration is not always accurate enough.

Alternatively a bite registration can be taken using a bite plate, comprising some impression material, which the patient bites down onto. This bite plate can then be sent to the dental laboratory along with the impressions of the upper and lower jaws taken using single trays.

SUMMARY

Disclosed is a method of aligning two 3D digital representations of at least a part of each of the upper and lower jaw of a patient, the method comprising:Segmenting the 3D digital representations to determine the shape and position of each of the patient's teeth in each of the 3D digital representations; andUsing a set of known anatomical concepts to constrain the fit of the two 3D digital representations to get a preliminary fit.

By segmenting the digital representations, it is possible for the computer program to determine which the position and shape of the teeth, and by using a set of known anatomical concepts or rules, it is therefore possible to automatically or semi-automatically align the two 3D digital representations of the patient's jaws.

In some embodiments, constraining the fit of the two 3D digital representations using known anatomical concepts, comprises classifying the bite of the patient, and marking characteristic matching points on both the upper and lower 3D digital representation.

The bite of the patient may also be called the occlusion. There are several ways of defining bite or occlusion. For example, as class 1, 2 and 3. In this classification, class 1 occlusion means that the teeth are aligned in cusp fossa relationship with their antagonist teeth. This is sometimes called normal or standard occlusion, and is often what is attempted to be achieved for example in orthodontic treatment.

In class 2 occlusion, the anterior maxillary teeth protrude horizontally or pushing over the mandibular teeth. The position of the buccal cusp tips are also moved anterior to the class 1 position. This type of occlusion is sometimes called over jet.

In class 3 occlusion, the anterior axillary dentition rest posterior to the mandibular anterior teeth. Posterior teeth are in cross bite meaning that the buccal cusp tips rest inside the fossae of the lower dentition, instead of the cusp tips of the lowers resting inside the fossae of the upper.

This type of occlusion can give a complex bite relationship and restorative problem with function, since restorations that look aesthetically pleasing may in some cases interfere with the function of the bite.

Having classified the bite or occlusion of the patient into one of these categories, or any other categorization of the bite, a first estimate of the fit of the two 3D digital representations can be made.

In some embodiments, constraining the fit of the two 3D digital representations using known anatomical concepts comprises classifying the bite of the patient according to a standard set of relationships, comprising one or more of:the soft tissue relationship;the frontal facial view;the profile facial view;dental relationships;sagittal dental relationships;transverse dental relationships;vertical dental relationships;the skeletal pattern.

In this way, general rules of human anatomy can be used to get a preliminary fit of the two 3D digital representations. For example the dentist can classify the patient's bite in one or more of the above categories, and the computer program can then use these known rules to achieve a preliminary fit.

In some embodiments, the preliminary fit of the two 3D digital representations is automatically optimized using a minimum energy algorithm.

Therefore, after the preliminary fit has been determined a final fit can be determined using a minimum energy algorithm that seeks to maximize for example the contact between the two 3D digital representations in a small deviation from the preliminary fit.

In some embodiments the method further comprises:obtaining impression scans of at least a part of each of the upper and lower jaw of a patient; andconverting the impression scans into the 3D digital representations of the at least a part of the patient's upper and lower jaw.

Consequently, there is no need to use a triple tray in order to align the 3D digital representations of the upper and lower jaws of the patient when the 3D digital representations are obtained using an impression tray rather than an intra-oral scan. Also, it is not necessary to make plaster models of the impressions, and putting them in an articulator in order to determine the correct bite alignment. In particular, disclosed herein is a method of aligning two 3D digital representations of at least a part of each of the upper and lower jaw of a patient, the method comprising:Obtaining the 3D digital representations of at least a part of each of the upper and lower jaw of the patient;Manually marking on each of the 3D digital representations corresponding sets of contact points; andAligning the two 3D digital representations in the correct bite configuration of the patient by moving the 3D digital representations into contact at the sites of the matching sets of contact points.

In this aspect of the invention, rather than using anatomical rules to constrain the fit of the two 3D digital representations, a more manual workflow is supported. By analysing the 3D digital representations, it is possible for the dentist or technician to manually mark contact points on the digital representations, and the computer program can then use this information to align the two 3D digital representations.

In some embodiments, the alignment of the two 3D digital representations are automatically optimized using a minimum energy algorithm.

Therefore, after the preliminary fit has been determined using the manually marked contact points, a final fit can be determined using a minimum energy algorithm that seeks to maximize for example the contact between the two 3D digital representations in a small deviation from the preliminary fit.

In some embodiments, the method further comprises:obtaining impression scans of at least a part of each of the upper and lower jaw of a patient; andconverting the impression scans into the 3D digital representations of the at least a part of the patient's upper and lower jaw.

Consequently, there is no need to use a triple tray in order to align the 3D digital representations of the upper and lower jaws of the patient when the 3D digital representations are obtained using an impression tray rather than an intra-oral scan.

In one aspect, disclosed is a method of aligning two 3D digital representations of at least a part of each of the upper and lower jaw of a patient, the method comprising:obtaining an impression scan of at least the part of each of the upper and lower jaw of the patient;converting the impression scans to 3D digital representations of the at least a part of the upper and lower jaw of the patient;segmenting the 3D digital representations to determine the shape and position of each of the teeth in the 3D digital representations; and aligning the 3D digital representations based on the relationship between complementary points of the teeth in each of the 3D digital representations. In this way, it is possible to align the two 3D digital representations of the patient's upper and lower jaw, based on the bite of the patient.

In some embodiments, the complementary points are determined automatically based on a classification of the bite of the patient. Depending on the type of bite or occlusion that the patient has, the relationship between points in the teeth in the upper jaw and complementary points in the lower jaw are known, and can therefore be used to align the two 3D digital representations.

In some embodiments, the complementary points are marked manually on the 3D digital representations. This will typically be done by a dental technician in a graphical user interface. Sometimes the bite will be classified before marking the points manually. For instance, the dentist may classify the bite of the patient, and send this information to a dental technician to aid the technician in the further work.

