Rapid prototyped transfer tray for orthodontic appliances

Abstract

The present invention is directed to computer-implemented methods of making a transfer tray using rapid prototyping techniques, where the gingival edge of the tray is defined to intersect with at least one receptacle for receiving an orthodontic appliance. This tray configuration helps to minimize the travel distance of the tray when placing the tray over a patient's teeth, while also preserving a high degree of mechanical retention for retaining the appliance until such time that the appliance is bonded to the tooth. Other aspects of the tray and associated methods of bonding are directed to a frangible web that extends over the gingival portion of the receptacle and fractures to facilitate tray removal after bonding.

Description

BACKGROUND OF THE INVENTION[0001]1. Field of the Invention[0002]This invention relates to transfer trays that are used by orthodontic treating professionals to bond appliances to the teeth of an orthodontic patient. The invention is also related to methods for making such transfer trays.[0003]2. Description of the Related Art[0004]Orthodontics is the area and specialty of dentistry associated with the supervision, guidance and correction of malpositioned teeth to desired locations in the oral cavity. Orthodontic treatment can improve the patient's facial appearance, especially in instances where the teeth are noticeably crooked or where the upper and lower teeth are out of alignment with each other. Orthodontic treatment can also enhance the function of the teeth by providing better occlusion during mastication.[0005]One common type of orthodontic treatment involves the use of tiny, slotted appliances known as brackets. The brackets are fixed to the patient's teeth and a resilient, ...

AI Technical Summary

Benefits of technology

[0015]By configuring the gingival edge of the transfer tray to intersect each receptacle, the treating professional gains particular advantages during the bonding procedure. First, the transfer tray only partially encapsulates each appliance, thereby facilitating both engagement and disengagement of the transfer tray from appliances. Second, positioning the receptacles at the gingival edge of the transfer tray also reduces the travel distance of the tray during seating, thereby minimizing adhesive smearing during the bonding (particularly when using two-part chemical cure adhesives). This transfer tray may be pre-loaded with orthodontic appliances by the manufacturer or alternatively may be loaded by the treating professional prior to bonding. By automating the tray manufacturing based directly on digital data, this method also offers improved product consistency, compared with manually prepared transfer trays.

[0016]The transfer tray may also include a thin frangible web of material that partially extends across gingival portions of the appliance, such that the appliance is securely retained in the tray prior to bonding. Once the appliance has been bonded to the patient's dental structure, the frangible web can then be fractured and the tray removed from the patient's mouth by urging the transfer tray in the occlusal direction. The presence of a frangible web is particularly advantageous since it provides both convenient loading and retention of the appliance into the tray, as well as easy detachment of the tray from the patient's dental structure. Detachment of the tray in the occlusal direction is convenient and comfortable for the patient since it does not involve pulling the tray outward against the cheeks or lips. Occlusal tray removal is also helps minimize the risk of accidentally debonding the newly bonded appliances, since it avoids the need to pull the appliances away from the tooth surface in the labial direction (or lingual direction in the case of lingual appliances).

[0017]The use of rapid prototyping techniques to fabricate the transfer tray is advantageous because it provides the freedom for the receptacle geometry to be adapted for easy engagement and disengagement of the orthodontic appliance from the tray. Other known fabrication methods, such as casting and thermoforming, fully surround the appliance with a matrix material to form the shape of the receptacle. While this is effective in retaining the appliance, this configuration is also inherently disadvantageous since the strong mechanical retention of the appliance can result in detaching the appliances from the teeth as the tray is removed from the mouth. The risk of bond failures is oftentimes so significant that the treating professional or assistant is compelled to manually section the tray into several pieces to facilitate removing the tray from the mouth, which is a nuisance. The present invention provides both a high level of mechanical retention for precise positioning of the appliance prior to bonding, as well as rapid and easy disengagement of the tray from the mouth in one piece after bonding.

[0018]Other aspects of the tray derive from incorporating multiple materials, or components, into the transfer tray. Using two or more components is beneficial because each part of the tray has its own set of material requirements based on its particular function. For example, the transfer tray may include one or more stop members that specifically engage pre-determined portions of occlusal teeth surfaces during a bonding procedure. By forming stop member(s) from a material that is harder than the rest of the tray, it is possible to form a “positive hard stop” between the tray and the teeth, thereby providing increased accuracy in positioning each appliance on its respective tooth surface. As another example, the transfer tray may further include one or more receptacles that are formulated from relatively softer materials to facilitate release of appliances from the tray when detaching the transfer tray from the patient's teeth after bonding.

[0019]As a further advantage, rapid prototyping techniques provide greater freedom to construct components of the transfer tray independently of each other. These configurations may include spatial arrangements of stop members and / or receptacles that are difficult or impossible to fabricate using traditional thermoforming or casting methods. For example, transfer trays that are thermoformed or cast generally display at least one single continuous layer that extends across the entire tray. This need not be the case with trays formed by rapid prototyping, which may include, for example, patterned layers.

Problems solved by technology

The preparation of transfer trays can be, unfortunately, both laborious and time-consuming for the treating professional or lab technician.

The conventional process of either thermoforming or casting the tray requires the intervention of an operator and is subject to human error, particularly in the manual positioning of brackets on the model.

Moreover, the steps of preparing a replica dental model, bonding appliances to the replica model, detaching the tray from the model, and eventually cleaning and trimming of the finished tray, each incur additional time or materials costs.

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