Dentistry – Apparatus – Having means to emit radiation or facilitate viewing of the...
Reexamination Certificate
2000-11-30
2002-05-14
O'Connor, Cary E. (Department: 3732)
Dentistry
Apparatus
Having means to emit radiation or facilitate viewing of the...
C433S025000, C433S214000
Reexamination Certificate
active
06386867
ABSTRACT:
FIELD OF INVENTION
The present invention relates to intra-oral methods and apparatus for optically imaging a dental structure and creating representative 3D models from the images.
BACKGROUND
In many dental applications, a working model of a patient's teeth is needed that faithfully reproduces the patient's teeth and other dental structures, including the jaw structure. Conventionally, a three-dimensional negative model of the teeth and other dental structures is created during an impression-taking session where one or more U-shaped trays are filled with a dental impression material. Impression materials include, among others, compositions based on alginates, polysulphides, silicones and vulcanizable polyether materials. The impression material is typically prepared by mixing a base component and a hardener or initiator or catalyst component. The impression tray containing the impression material, in its plastic state, is introduced into the mouth of the patient. To ensure a complete impression, an excessive amount of impression material is typically used. While the tray and impression material is held in place, the material cures, and after curing, the tray and material are removed from the mouth as a unit. The impression material is allowed to solidify and form an elastic composition, which is the negative mold after removal. The working model is obtained by filling this impression with a modeling material.
Dental patients typically experience discomfort when the dentist takes an impression of the patient's teeth. The procedure can be even more uncomfortable for the patient if the impression materials run, slump or are otherwise expelled into the patient's throat. Such situations can potentially cause a gag reflex reaction from the patient. In addition to patient discomfort, the impression process is time consuming. Additionally, the impression process can be error-prone. For example, when the impression material is not properly applied, the resulting working model may not accurately reflect features on the teeth. Moreover, the model can show air bubbles trapped during the impression taking session. Depending on the accuracy required, such working model may not be usable and additional dental impressions may need to be taken. Further, the mold and working model are fragile and can be easily damaged. The need to store the fragile models for future reference tends to become a logistical problem for a dental practice as the number of archived models accumulates.
Automated scanning techniques have been developed as alternatives to the mold casting procedure. Because these techniques can create a digital representation of the teeth, they provide the advantage of creating an “impression” that is immediately transmittable from the patient to a dental laboratory. The digital transmission potentially diminishes inconvenience for the patient and eliminates the risk of damage to the mold. For example, U.S. Pat. No. 6,050,821 discloses a method and apparatus for intra-orally mapping the structure and topography of dental formations such as peridontium and teeth, both intact and prepared, for diagnosis and dental prosthetics and bridgework by using an ultrasonic scanning technique. As claimed therein, the method can provide details of orally situated dental formations thus enabling diagnosis and the preparation of precision moldings and fabrications that will provide greater comfort and longer wear to the dental patient. Also, as discussed therein, infra-red CAD/CAM techniques have been used to map impressions of oral structures and make single-tooth prosthetics.
Also, in certain applications such as restorative dentistry that is preformed on visible teeth, such as incisors, aesthetic considerations require that the prosthetic interface with the original tooth surface be underneath the gum (sub gingival) to eliminate the sight of the “joining line”. In preparation for the prosthetic, the patient's tooth must be shaped to create a ledge or margin beneath the gum line where the prosthetic will be sealed to the existing tooth. To prepare this surface, the dentist typically places a retraction cord between the tooth and gum. The retraction cord creates a working space that allows the dentist to machine the margin around the tooth of interest.
In order for the finished prosthetic to be correctly sized and properly seated on the prepared tooth, it is essential that the impression of the prepared tooth contain an accurate representation of the sub gingival margin. Improper resolution of the margin in the impression and the subsequent creation of the prosthetic from this impression can result in a poor seal along the margin of the prepared tooth and the prosthetic. A poor seal along the margin has the potential to expose the underlying tooth to decay and the subsequent loss of the tooth—the very thing the prosthetic was suppose to prevent. Two methods are commonly used to accurately capture the margin during the impression process. The first method uses a retraction cord to hold the gum away from the tooth surface to allow the impression compound to flow underneath into the sub gingival region. The second method uses an impression material with low viscosity that under pressure is forced underneath the gums and thus captures the sub gingival margin.
In addition to obtaining sub gingival access for the impression material, the area of interest should be dry and clean (dry field) to obtain an accurate impression. A dry field is needed because typical impression compounds are hydrophobic and the presence of moisture when using a hydrophobic impression compound results in bubbles in the impression. The dry field is typically created by the dentist directing pressurized air across the prepared surface just prior to placing the impression tray in the patient's mouth.
SUMMARY
In one aspect, a method optically images a dental structure within an oral cavity by: directing air at a tooth-gum interface of the dental structure through at least one air nozzle movably coupled to an intra-oral track; and capturing one or more images of the dental structure through at least one image aperture, the image aperture movably coupled to the intra-oral track.
Implementations of the above aspect may include one or more of the following. The air nozzle can be moved incrementally or continuously within the oral cavity. A motor may move the air nozzle incrementally or continuously within the oral cavity. The dental structure can be coated with a substance to enhance the image quality. An illuminator movably mounted on the intra-oral track can illuminate the dental structure. The illuminator can be moved incrementally or continuously within the oral cavity. A three-dimensional (3D) model of the dental structure can be generated based on the images captured by the image aperture. A stereometric analysis can be performed on the captured images. The method includes performing a scanning illumination beam and triangulation analysis on the captured images. The 3D model may be transmitted over a network. Diagnosis and treatment of a patient can be done with the 3D model.
In another aspect, a system to optically image a dental structure within an oral cavity includes: an intra-oral track adapted to be inserted inside the oral cavity; a pressurized air nozzle moveably coupled to the track to direct air at the dental structure; and at least one image aperture movably coupled to the intra-oral track and adapted to capture one or more images of the dental structure.
Implementations of the above aspect may include one or more of the following. The image aperture is either incrementally or continuously moved on the track. A motor coupled to the image aperture can move the image aperture incrementally or continuously within the oral cavity. The intra-oral track can be arch-shaped. One or more illuminators movably mounted on the intra-oral track can illuminate the dental structure. Each illuminator is incrementally or continuously moved within the oral cavity. An image processor can perform a stereometric a
Durbin Dennis Arthur
Durbin Duane Milford
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