Dentistry – Apparatus – Having static product shaping surface
Reexamination Certificate
2000-08-28
2003-10-07
Manahan, Todd E. (Department: 3732)
Dentistry
Apparatus
Having static product shaping surface
Reexamination Certificate
active
06629841
ABSTRACT:
BACKGROUND
1. Field of the Invention
This invention relates to dental implements, and more particularly, to novel dental impression trays that are mechanically adjustable to accommodate various mouth sizes in order to obtain an accurate impression of the upper and/or lower dentition of a patient.
2. The Background Art
With regards to dentistry, an impression is often used to create an imprint or negative likeness of the teeth and adjacent portions of the jaw (e.g., tooth formations, the contour of the gums, etc.) preparatory to dental repair, orthodontics and restoration of missing dental structures. Impressions are typically made by placing a soft, semi-fluid material within the confines of an open trough or channel of an arcuate tray which is then positioned within the mouth of a patient, thus allowing the material to set or cure. Depending upon the material used, the set impression may be either hard or have some elastic characteristics.
To provide the most accurate articulation, the impression cast should generally represent the entire dental arch. In this regard, the impression cast can be used to establish inter-proximal contacts, buccal and lingual contours and occlusion with the opposing teeth. From the negative or female cast of the teeth and surrounding structures, a positive reproduction or male cast may be created for the purpose of fabricating inlays, crowns, bridge retainers, dentures, restorations or the like.
Traditionally, before an impression cast of the dentition is created, a stock tray is selected by the dentist or dental assistant that will generally fit the dental arch of the particular patient. Since the dental arch may differ widely from patient to patient, various sizes of impression trays (e.g., small, medium and large) were developed by those skilled in the art to accommodate various mouth sizes, bite radii of teeth and to correspond to upper and lower anterior or quadrant impression sites.
For example, those skilled in the art developed prior art dental impression trays formed of metal, such as stainless steel, and having a pair of spaced-apart vertical walls joined by a semi-rigid mesh material disposed horizontally between the opposing vertical walls. Extending outwardly in structural relation to at least a portion of the surface facing of one of the vertical walls, a handle member may be provided to facilitate a means for gripping the impression tray for purposes of manual manipulation. In addition, an open trough or channel is generally formed between the opposing vertical walls, wherein the horizontally disposed mesh material provides a porous surface flooring for the trough. In operation, the mesh material provides a means for permitting excess flow of impression material to become displaced and extruded there through. Dental impression trays of the prior art may further include openings formed in the vertical walls of the trough or channel which generally function as an anchoring surface for the impression, thus allowing the excess flow of impression material to become attached thereto.
Although seemingly useful for their intended purposes, there are several practical disadvantages of prior art dental impression trays comprised of metal. For example, a significant disadvantage of prior art metal impression trays includes the difficulty associated with maintaining proper cleaning and sanitation of the impression trays using heat or chemical sterilization methods or techniques to avoid cross-contamination in order to be able to reuse the various sized stock metal impression trays from patient to patient.
Attempting to alleviate some of the disadvantages associated with the amount of time and energy expended to maintain proper sanitation of prior art metal impression trays, in addition to the costs associated therewith, disposable impression trays were developed by those skilled in the art. As noted above, since the dental arch may differ widely from patient to patient, various sizes of disposable impression trays (e.g., small, medium, and large) were developed to accommodate various mouth sizes, bite radii of teeth, and to correspond to upper and lower anterior or quadrant impression sites.
In accordance with other such prior art apparatus and techniques for making an impression cast of the upper and/or lower dentition of a patient, those skilled in the art developed adjustable impression trays. For example, an adjustable impression tray of the prior art may comprise a primary impression unit and a movable extension unit telescopically mounted on the primary unit for adjustable relative thereto. The primary unit being provided with primary leg portions having secondary leg portions extending therefrom, wherein the primary leg portions include a first flap means extending outwardly therefrom and over the secondary leg portions. In operation, the secondary leg portions comprise a tab means cooperative with the first flap means of the primary leg portions so as to facilitate the first flap means being movable relative to the tab means. The movable extension unit further comprising a second flap means having a series of slots therein for registry with the tab means of the secondary leg portions for fixation in relation to the primary leg portions of the impression tray.
Another example of prior art adjustable impression trays includes a main arcuate portion with parallel spaced vertical walls having extension portions slidably disposed in frictional engagement therewith for lengthwise adjustment in relation to the main arcuate portion. The engagement means between the extension portions and the main arcuate portion of the impression tray may include T-shaped rails formed in the outer faces of the opposing walls and corresponding recesses formed in the inner faces of the respective walls of the extension portions. Similarly, annular recesses may be formed in the outer faces of the opposing walls and corresponding annular nibs may be formed in the inner faces of the respective walls of the extension portions to provide a slidable engagement there between.
A meaningful disadvantage with prior art adjustable impression trays of the general type disclosed herein is that they only provide means for accommodating a structural adjustment in the dimensional length of the channel. In this regard, because these prior art adjustable impression trays fail to provide for any adjustment in the dimensional width associated with various sizes of the dental arch, they are generally limited in their particular utilization.
In an effort to accommodate an adjustment in the dimensional width of a dental impression tray, those skilled in the art developed heat-expansive impression trays which may be formed of a thermoplastic material which is malleable at elevated temperatures so that the impression tray can be generally shaped and configured in such a manner so as to accommodate the corresponding dental arch of a particular patient. For example, prior art heat-expansive impression trays may structurally comprise an elongated channel including a buccal side, a lingual side, and an occlusal side. The occlusal side of the channel including an outwardly extending folded section which may be fully or partially unfolded when the channel is heated, thereby providing a means for expanding the dimensional width of the elongated channel. Two additional folded sections formed in opposed posterior portions of the impression tray may also be provided which, when heated at a specific softening temperature, can be partially or fully unfolded by pulling the posterior ends of the tray away from the anterior portion of the same, thus extending the dimensional length of the elongated channel.
While prior art adjustable and heat-expansive impression trays may appear generally suitable for their intended purposes, these prior art impression trays nevertheless leave much to be desired from the standpoint of effectiveness of operation, manufacturing costs, simplicity of construction in relation to a multiplicity of parts, and functionality as to universal application. As will be appreciated
Manahan Todd #E.
Pate & Pierce & Baird
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