The invention relates generally to orthodontic appliances, and more particularly, to orthodontic aligners and methods of fabricating orthodontic aligners.
Orthodontic appliances represent a principal component of corrective orthodontic treatments devoted to improving a patient's malocclusion. In one type of orthodontic treatment, a clinician secures an orthodontic bracket to each tooth, such as with an adhesive. The clinician then inserts an archwire into each of the orthodontic brackets. The archwire interacts with the orthodontic brackets to apply corrective forces that coerce the teeth to move into orthodontically correct positions. Conventional orthodontic brackets are ordinarily formed from stainless steel, which is strong, nonabsorbent, weldable, and relatively easy to form and machine. Patients undergoing orthodontic treatment using metal orthodontic brackets may be embarrassed by the visibility of metal, which is not cosmetically pleasing.
In accordance with an alternative method of orthodontic treatment, a series of clear, removable aligners may be successively worn by the patient to improve the patient's malocclusion. Each aligner may be made of a polymer and is selectively removable by the patient. The aligners are not themselves adhesively secured to the patient's teeth and may be removed at any time. That is, the patient can simply pull the aligner off their teeth at will. The patient may therefore remove the aligner prior to eating or prior to other events. Unlike conventional orthodontic brackets, each aligner is placed over the patient's teeth and may encapsulate each tooth.
During this type of orthodontic treatment, a practitioner prescribes a series of aligners. Each aligner in the series may be designed to move one or more teeth over a portion of the entire distance towards the final, desired position. The movement is therefore incremental according to a prescription. The degree of movement produced by any single aligner is limited. By design, one aligner moves the teeth to one position and is then removed, and the next aligner moves the teeth from proximate that end position to a next position that may be closer to the final, desired position. In this way, collectively, the series of aligners moves one or more of the patient's teeth from their original position to an aesthetically pleasing position according to a prescription. This treatment therefore requires a series of custom aligners to be made for each patient.
In one process for fabricating aligners, a computer model of the patient's teeth may be used. Using the model, the clinician may determine the prescription by which all the teeth ultimately arrive at their aesthetically pleasing positions. The prescription may then determine incremental movements of the patient's teeth. Each of these movements may be attributed to a single one of the aligners in the series. This type of orthodontic treatment may require multiple aligners. Each aligner requires a unique positive mold. The fabrication of aligners is therefore a tedious, cost intensive process.
For example, to manufacture each aligner, a polymer sheet may be thermoformed over a positive mold of the tooth. In subsequent processes, the deformed sheet is trimmed to remove excess plastic that may result from the thermoforming process. In addition, sharp edges that result from the trimming process, which might contact and irritate the gingiva, are smoothed via another post-forming process, such as tumbling. The manufacturing cost for each aligner is multiplied by each subsequent processing step.
Furthermore, current processes create problems. For example, trimming each aligner requires accuracy, because inaccurate trimming may lead to patient discomfort. This discomfort is generally caused by contact between a poorly trimmed edge of the aligner and the patient's gingiva, which causes irritation, potentially inflammation, and bleeding. In this situation, the patient is therefore less likely to adhere to the scheduled orthodontic treatment.
While generally successful, there is a need for improved orthodontic appliances, including improved aligners and the methods for making aligners that overcome these and other deficiencies described above.
The present invention overcomes the foregoing and other shortcomings and problems heretofore known for orthodontic appliances and methods of making those orthodontic appliances. While the invention will be described in connection with certain embodiments, it will be understood that the invention is not limited to these embodiments. On the contrary, the invention includes all alternatives, modifications and equivalents as may be included within the spirit and scope of the present invention.
In accordance with the principles of the present invention, a method of forming an aligner comprises dipping a positive mold of teeth in a first liquid material to form a first liquid layer and curing the first liquid layer to form a shell having one or more cavities configured to receive corresponding teeth and an edge that defines an opening.
In one embodiment, the method further includes dipping the positive mold in a second liquid material. The shell includes an inner layer including material from the first liquid material and an outer layer including material from the second liquid material.
In one embodiment, the second liquid material is different than the first liquid material.
In one embodiment, dipping the positive mold in the second liquid material occurs after curing the first liquid layer.
In one embodiment, the method further comprises prior to dipping the positive mold in the second liquid material, coupling one or more features to the cured first layer. In one embodiment, the one or more features are selected from the group consisting of an orthodontic archwire, a sensor, and an orthodontic bracket.
In one embodiment, the positive mold includes one or more model teeth and a model gingival margin in a predetermined arrangement on a base and dipping the positive mold is to a predefined depth to which a fluid level of the first liquid material is positioned proximate the gingival margin.
In one embodiment, the fluid level defines the edge of the shell.
In one embodiment, the method further comprises forming a non-stick coating on the positive mold prior to dipping the positive mold in the first liquid material.
In one embodiment, the method further comprises fabricating the positive mold via rapid prototyping.
In one embodiment, the method further comprises curing the first liquid layer on the positive mold to form the inner layer.
In one embodiment, the method further comprises curing the second liquid layer after curing the inner layer to form the outer layer.
In one embodiment, the outer layer has a higher hardness than the inner layer.
In accordance with the principles of the present invention, a set of aligners for use in orthodontic treatment comprises at least one aligner including a shell having a plurality of cavities each configured to fit over a corresponding one of a patient's teeth and an edge that defines an opening and being positioned proximate the patient's gingival margin, the edge being as-formed.
The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate embodiments of the invention and together with the detailed description given below, serve to explain various aspects of the invention.
Referring to the drawings, and to
As shown, the aligner 10 includes a hollow shell 12 that is configured to encapsulate one or more crowns of a patient's teeth. The shell 12 is formed with a plurality of cavities 14 that collectively define an edge 16. The edge 16 in turn defines an opening 18 in the shell 12. Each cavity 14 is shaped to receive a specific one of the patient's teeth through the opening 18 such that the edge 16 is positioned proximate the patient's gingiva. With reference to
In one embodiment, the aligner 10 may include an additional feature 24. The additional feature(s) 24 may improve the clinical efficacy of the aligner 10. In the exemplary embodiment, the additional feature 24 is an orthodontic bracket. Other additional features may include, without limitation, an orthodontic archwire, one or more orthodontic buttons, and one or more sensors. Orthodontic buttons may be used in conjunction with a rubber band during the orthodontic treatment. As shown, the additional feature 24 may be encapsulated between the inner layer 20 and the outer layer 22.
During orthodontic treatment, the aligner 10 is selectively positionable over the patient's teeth and may fit tightly at least partly due to slight differences in the position of one or more of the cavities 14 relative to the corresponding tooth. The aligner 10 may elastically deform while positioned over the patient's teeth. The elastic deformation may be observable as a measurable amount of bulk or localized strain in the shell 12. The strain in the shell 12 produces pressure on the teeth as the shell 12 attempts to return to an un-strained condition or a similar reduced strain configuration. The forcible contact with the aligner 10 may move the patient's teeth toward a predetermined position according to a clinician's treatment plan.
In one embodiment of the invention, a set of aligners (not shown) may include one or more aligners 10. During orthodontic treatment, each of the aligners in the set may differ slightly so that they each provide slightly different movement of the teeth. The patient utilizes the individual aligners in a predetermined sequence to complete orthodontic treatment. Accordingly, each aligner in the series may move one or more teeth a prescribed amount. Cumulatively, these individual amounts may result in complete treatment of the patient's malocclusion.
With reference to
To that end,
The positive mold 30 includes a plurality of model teeth 32 arranged in accordance with a prescription on a base 34 that may include a model gingival margin 36. In certain embodiments, the model teeth 32 may be produced from digital data available from images of the patient's teeth. By way of example only, and not limitation, an impression of the patient's teeth may be taken with a suitable dental impression material, such as polyvinylsiloxane (PVS). That dental impression may be scanned and the digital data from the scan may be imported into a computer to create a 3-D digital model of each of the patient's teeth. Alternatively, intra-oral images may be taken at the clinician's office. Those images may then be used to produce a 3-D digital model of the patient's teeth.
The 3-D digital model of the patient's teeth may be digitally manipulated to position each of the 3-D digital model teeth in a predetermined arrangement. That arrangement may then be used to manufacture the positive mold 30 according to the patient's prescription with each of the patient's teeth corresponding to one of the model teeth 32. The model teeth 32 may be individually positioned on the base 34. In that regard, a computer may be used to manipulate the images or other data sufficient to construct the positive mold 30 of the model teeth 32 in the predetermined arrangement. By way of example only, and not limitation, the data may be used to control a rapid prototyping machine, such as a stereolithography (SLA) machine, a laser sintering machine (e.g., direct metal laser sintering or selective laser sintering), a 3-D printer (e.g., fused deposition modeling machine or a polyjet machine), or via any other type of rapid prototyping mechanism to construct the positive mold 30.
In one embodiment, a rapid prototyping machine may deposit material in layers, layer by layer, to form the positive mold 30. The positive mold 30 may be made of, for example, plastic or metal such as stainless steel. In one embodiment, rapid prototyping may include depositing resin in layers based on the 3-D digital model to form the positive mold 30. Other exemplary processes for manufacturing the positive mold 30 may include pouring, injecting, or via other automated means depositing a material, such as plaster or certain types of liquid plastic, that hardens over time. While the positive mold 30 is shown being a full lower set of teeth, the positive mold 30 may be for an entire upper arch or a portion of the upper arch, such as a single model tooth 32. Similarly, the positive mold 30 may be for an entire lower arch or a portion of the lower arch, such as a single model tooth 32. Subsequently, the aligner 10 is formed over the positive mold 30 as described below.
Alternatively, the positive mold 30 may be made according to a two-step process of first generating a resin mold via a rapid prototyping machine. The positive mold 30 is then formed in the resin mold. Positive molds 30 built by rapid prototyping machines may have striations caused by the layering deposition process typical of this style of rapid prototyping. The striations may cause jagged grooves or other defects in the aligners generated directly from the positive mold fabricated by rapid prototyping. Such striations may be significantly reduced or eliminated when the positive mold 30 is fabricated with the two-step process. Advantageously, the positive mold 30 from a two-step process may be characterized by a relatively smooth surface, which may, in turn, be used in the production of aligners 10 that are similarly relatively smooth. The likelihood of trapping of food and bacteria between the aligner and the teeth is reduced when the surface of the aligners is smooth. Such a process is described in U.S. patent application Ser. No. 14/318,393, the disclosure of which is incorporated herein in its entirety.
Following fabrication of the positive mold 30 and with reference to
With reference to
With continued reference to
In one embodiment, the liquid material 52 is liquid polyurethane, which is a combination of polyurethane and a solvent, such as tetrahydrofuran. When the positive mold 30 is withdrawn from the reservoir 50, liquid polyurethane coats a portion of the positive mold 30. The tetrahydrofuran solvent flashes off or evaporates from the liquid coating during a drying or a curing process. As the solvent is released, the remaining polyurethane in the coating hardens to form the inner layer 20 of the aligner 10. During curing, the coating may shrink. The temperature of the curing process may affect the degree to which the coating layer shrinks. The curing process may be at a temperature of, for example, 120° F.
Referring to
With reference to
When the positive mold 30 is raised from the reservoir 60, a layer of the liquid material 62 may cling to the inner layer 20 and any additional features (e.g., orthodontic bracket 24) and so form a coating of liquid material over the inner layer 20 and over those additional features. When the solvent flashes off or evaporates from the coating of liquid material 62 during a drying or curing process, the coating hardens to form the outer layer 22 as shown in
In view of the multiple layers, additional features may be incorporated into the aligner 10 by encapsulating them between any two layers of the aligner 10. For example, as shown in
In an embodiment, relatively hard and relatively soft versions of the same material may be used as different layers (or different regions of the same layer) in the aligners described herein. One or both of the dipping processes shown in
As described above, the inner layer 20 and the outer layer 22 may be formed from different liquid materials and so the layers 20 and 22 may differ in composition. Each layer 20 or 22 may have different properties (e.g., stiffness, elasticity, hardness, surface friction, hydrophobicity, etc.) from each of the other layers due at least in part to the different materials. The combination of properties from multiple layers may enhance wear resistance while also being more comfortable and more accurately worn by the patient. For example, the outer-most layer (e.g., outer layer 22 in
Alternatively, or in addition, the outer layer 22 may be less sensitive to elevated temperature such that the outer layer 22 enhances the resistance of the aligner 10 to deformation or relaxation distortion when it contacts hot fluids and hot food. Further, the inner layer(s) can be softer than the outer layer to make the aligner 10 more comfortable for the patient to wear. The softer inner layer may also allow wider contact area with the patient's teeth, making it easier to fit to the patient's teeth. The fit of a softer inner layer may also relax manufacturing tolerances. The relative hardness of the different layers reflects comparative measure of the surface hardness, structural hardness, elasticity and/or stiffness of a material. For example, in one embodiment, the material used for the outer layer 22 may have a Shore durometer ranging from about 40D to about 60D, and the material used for the inner layer 20 may have a Shore durometer ranging from about 60A to about 80A.
With reference to
In one embodiment, the aligner 10 requires less post processing compared to a thermoformed aligner. In that regard, dipping the positive mold 30 in a liquid material may ultimately provide a smooth edge 16 and reduce or eliminate additional post formation processing. For example, a tumbling process by which edges may be smoothed may not be needed. Moreover, dip molding may improve geometry resolution compared to thermoforming an aligner.
In one embodiment, the aligner 10 may be one of a series of aligners that are prescribed to treat a patient's malocclusion or a portion thereof. To that end, additional positive molds may be manufactured according to the patient's orthodontic treatment plan. Each of the positive molds may be dipped according to
With reference to
While the present invention has been illustrated by a description of various embodiments and while these embodiments have been described in some detail, it is not the intention of the inventors to restrict or in any way limit the scope of the appended claims to such detail. Thus, additional advantages and modifications will readily appear to those of ordinary skill in the art. The various features of the invention may be used alone or in any combination depending on the needs and preferences of the user.
This application claims the benefit of U.S. Provisional Patent Application Ser. No. 62/474,925 filed on Mar. 22, 2017, the disclosure of which is expressly incorporated by reference herein in its entirety
Number | Date | Country | |
---|---|---|---|
62474925 | Mar 2017 | US |