FIELD OF THE INVENTION

The invention relates to a method for producing an aligner for teeth of a patient.

BACKGROUND OF THE INVENTION

Producing aligners or nighttime braces is known. The teeth in the jaw of patients have undercuts in particular in a transition portion between tooth and gum wherein the undercut portions are filled in the real model manually using dental wax or liquid synthetic material in order to prevent a binding of the aligner on the real model and in order to prevent a binding during insertion and removal of the aligner from a mouth of the patient. This activity of filling in the undercut portions is designated as blocking.

Generic methods are known from US 2014/0142897 A1 and WO 2012/140021 A2. Processing in the virtual model facilitates an algorithmic determination of the undercuts and automating a labor intensive process.

BRIEF SUMMARY OF THE INVENTION

Thus, it is an object of the invention to simplify blocking out.

The object is achieved by a method for producing an aligner for teeth of a patient, the method including initially capturing a virtual current model of the teeth with a current position of the teeth; segmenting the teeth in the virtual current model and interpolating interdental surfaces of the teeth; generating a virtual nominal model of the teeth including undercut portions from the virtual current model; automatically determining the undercut portions in the virtual nominal model; automatically removing all surface elements that are associated with the undercut portions and the interdental surfaces from the virtual nominal model; and subsequently closing gaps in the virtual nominal model created by removing the surface elements wherein closing the gaps is performed by interpolation for blocking out; automatically blocking out the undercut portions in the virtual nominal model to produce a blocked out virtual nominal model; producing a real model of the teeth based on the blocked out virtual nominal model; applying a synthetic material foil to the real model by a deep drawing method; and hardening the synthetic material foil on the real model to form the aligner and removing the aligner from the real model.

Advantageously the method according to the invention initially captures a virtual current model with a current position of the teeth. The teeth are segmented in the current model and interdental surfaces of the teeth are interpolated. The current model can be captured e.g. by an inter oral scanner or from the plaster model by a model scanner and can be subsequently be processed on a computer. Segmenting is typically designated as a semi-automatic selection of partial surfaces of the current model and association thereof with specific teeth. Interpolation of interdental surfaces for closing the gaps created in the surfaces of the individual teeth and the extrapolation of the tooth roots are known in the art.

Removing the interdental surfaces before blocking out reduces complexity of the nominal model and simplifies the subsequent computation steps for blocking out the nominal model.

Thus, the blocking of the undercut portions can be performed in a particularly simple manner. Various algorithms are known that are suitable for interpolating gaps in a surface model.

Advantageously, a chewing surface between the teeth in the lower jaw and the upper jaw is determined in the nominal model according to the method according to the invention. Then surface elements of the nominal model that project into the chewing surface perpendicular to the chewing surface are automatically determined and associated with the undercut portions. The chewing surface as a collision portion of the teeth of the upper jaw and lower jaw and surface elements of the nominal model that project orthogonal into the chewing surface can be easily determined by algorithms. Blocking the surface elements thus determined substantially prevents binding of the aligner on the real nominal model.

Advantageously the method according to the invention fills an alveole in the nominal model between teeth that are adjacent to each other with a gap there between automatically in a direction towards the chewing surface in order to determine the chewing surface. Filling alveoles or tooth gaps by blocking with dental wax is well known. Thus, deep incisions in the aligner are prevented wherein the deep incisions otherwise tend to bind at the real model or at the jaw of the patient or otherwise establish a contact between aligner and gingival that is typically perceived uncomfortable.

Advantageously, the method according to the invention automatically removes and fills a fissure between closely adjacent teeth in the nominal model. A fissure in the context of producing aligners designates tight and tapering intermediary spaces between adjacent teeth. Fissures of this type can be determined in the nominal model based on locally high gradients between adjacent surface orthogonals.

Advantageously the method according to the invention moves the teeth in the nominal model from a misaligned current position into a nominal position. The segmented teeth are moved into their respective nominal positions in the nominal model individually or in groups. The brace produced according to the method according to the invention is useable as an aligner. In another method according to the invention the teeth are not moved in the nominal model. The brace is then useable as an overnight brace for nocturnal stabilization of the current position.

Advantageously the nominal model in a method according to the invention is a surface model which is initially automatically converted into a point cloud with surface points and surface orthogonals associated with the surface points wherein surface points of the point cloud that are associated with the undercut portions are subsequently determined for performing the block out and after the block out a surface module is computed again from the point cloud. Generating a polygonal surface model by triangulation of the current model is known in the art as well as computing a point cloud with surface points and their orthogonals from triangular surfaces in space. In the point cloud individual points can be displaced or deleted without influencing adjacent surface elements. On the other hand side, computing a surface module from a point cloud is well known, e.g: the method under the key word “MPU-Implicits” from Ohtake Y at al.: Multi-level Partition of Unity Implicits.

Advantageously the method according to the invention automatically determines a collision of spheres about adjacent surface points and the adjacent surface points are combined at a mean position. Collision determination of adjacent spheres (sphere collision) whose centers are arranged on the points of a point cloud is generally known and facilitates determining adjacent surface elements very quickly and eliminating them.

Advantageously the method according to the invention produces the real model through a rapid prototyping method, advantageously by 3-D printing. Rapid prototyping facilities a cost efficient and quick fabrication of individual pieces directly from a surface model.

The method according to the invention simplifies and accelerates the block out so that several individually blocked out intermediary steps between the current model and the nominal model can be produced quickly and economically.

