Dental prosthesis fabrication

Abstract

A method is disclosed for forming an accurate stone cast from a dental hydrocolloid impression, used for the purpose of prosthetic fabrication, such as dental prostheses. The dental stone catalyst, calcium sulfate dihydrate, is engaged onto the internal surface of set hydrocolloid impression. This catalyst, placed in the area between impression material and wet, mixed stone, will act to hasten the initial setting of dental stone that is in closest proximity to the impression. The result is a stratified set of the stone. Setting of the wet, mixed dental stone occurs first at the impression/stone interface. The setting radiates outwardly, away from the impression/stone interface. The mixed stone better resists distortion upon setting and the resultant set stone cast is more accurate.

Description

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. patent application Ser. No. 11/878,337 filed Jul. 23, 2007.

FIELD OF INVENTION

This invention relates generally to making better fitting removable dental appliances and indirect dental restorations, and, more specifically, this invention relates to making accurate stone dental casts and models.

DESCRIPTION OF PRIOR ART

Stone dental casts need be very accurate replicas of the dentition. The cast, along with other exact measurements and guidelines supplied by the dentist, enables the laboratory to make crowns, dentures, partial dentures, and obturators. These items are referred collectively as dental prostheses.

Other special applications, such as oral snoring devices, orthodontic appliances, bleaching trays, and nightguards, and surgical stents, may also be prescribed by the dentist and are also made from dental impressions.

Once a cast is made, it can be sectioned so that segments can be removed. Segments representing individual teeth are referred to as dies. The dies are indexed in various ways to give an accurate and reliable placement in and out of the model base. Some practitioners will refer to this dental cast with removable dies as a dental model. And they will refer to the one piece stone pour of the impression as a dental cast. However, many practitioners will still use the term “cast” and “model” interchangeably and do not distinguish between the two terms. Dental models are used in the dental laboratory to create dental restorations which ultimately will be delivered to the dentist office. These restorations are then cemented into the patient's tooth with a cement, such as zinc phosphate cement. These cemented restorations are referred to as indirect restorations. Examples of indirect restorations would include inlays, onlays, veneers and crowns.

Conversely, direct restorations are those restorations that are buildup directly and incrementally into the patients tooth. Silver amalgams and composites are examples of direct dental restorations.

When initiating an indirect restoration for a patient, the dentist will first carve the tooth structure into a certain shape. This finished carved tooth shape is referred to as a prepped tooth, or simply, the preparation. After this step of tooth preparation is accomplished, impressions are taken to record the new altered dimensions, that is, a moldable material is impressed upon the tooth and allowed to set. Hydrocolloid materials are sometimes employed for these impressions.

Hydrocolloid contains agar and water. Irreversible hydrocolloid is made by addition of water to a dry alginate formula. The resultant gel is in a moldable state for a given period of time. While it is in this moldable state it is impressed onto the mouth structures and held immobilized until it sets.

Another agar containing impression material is reversible hydrocolloid. Reversible hydrocolloid is brought to a predetermined elevated temperature to form a gel. While the hydrocolloid is in this warmed gel state it is impressed to the oral structures. This reversible hydrocolloid is then cooled to final set in the mouth by using water cooled metal trays. Collectively, all of the impression materials cure to the shape of the teeth and mouth. The impression material is removed from the mouth, capturing a negative image of the impressed area of the oral cavity.

In the lab, a wet mixture of stone is poured into the impression. Upon hardening, after an hour or so, the resultant dental cast is separated from the impression. This cast may be used as a mold in the process of fabricating crowns or other indirect restorations.

Removable appliances, such as dentures and partials and the like, are also made indirectly, with the use of dental impressions.

The fabricated prostheses are delivered to the patient by the dentist. Any irregularities in the fit of the appliance are located and adjusted by the dentist.

So the process of taking impressions, for the purpose of an indirect approach, avails the patient dental prostheses.

OBJECTS AND ADVANTAGES

A tremendous problem exists with indirect dentistry. Dental appliances and indirect restorations seldom have a perfect fit. All mouth appliances, such as dentures, and all tooth restorations, such as crowns, need varying amounts of chair time to adjust. Distortions must be compensated for before finalizing the products.

Indeed, dentures do require multiple appointments to finalize. And usually, the final outcome is a slight disappointment. Consequently, dentures are usually tolerated by the wearer; dentures are seldom as tight fitting as the dentist would prefer.

There are so many steps in the dentist office, along with an equally complex arrangement in the laboratory, that dentists believe the solution for ill-fitting prosthetics, can never be achieved.

Similar to the irregularities associated with dentures, acrylic nightguards also usually end up with a compromised outcome. It is very time consuming to troubleshoot an ill-fitting nightguard, in fact, many dentists have resorted to a soft inside liner attached to the hard outside acrylic shell. This laminate design is not so much for patient comfort, but for ease of delivery. The soft material is very moldable and therefore does not have to be a precise fit to the dentition. Its inherent conforming shape compensates for fabrication irregularities. However, the soft liner is not as durable and long lasting as all hard acrylic.

Indirect restorations also require refinements. It is difficult to locate areas of distortions and most dentists allow up to an hour of office time to adjust and cement a crown.

This reality of ill-fitting restorations is best summarized by Sharp, et al. in U.S. Pat. No. 5,911,580. In column 1, they describe the normal process of a dentist usually having to adjust an appliance. They write of the possibility that the final outcome may be that the appliance cannot be adjusted adequately. The appliance sometimes needs to be remade.

Prior art shows that there have been many attempts to identify the cause of ill-fitting crowns. In U.S. Pat. Nos. 6,045,359, 5,478,235, and 7,021,929 inventors modify dental impression tray designs. They hope to achieve better bonding between the impression material and the tray.

Although it is true, that a bond is needed to the tray, any severe defect such as tray separation would create a gross discrepancy in fit of final appliance. These separations are usually evident to the practitioner at the time of tray removal from the oral cavity. Impression tray design alone has never made a further refinement in the fit of our dental castings.

Inventors of prior art have attempted to create new impression materials to increase accuracy. In U.S. Pat. Nos. 6,861,457 and 5,907,002 Kamohara recognizes the inaccuracies associated with polyether impression material. He further isolates the problems of inaccuracy to impression tray removal. He feels that recovery from deformation applied during time to remove the impression causes dimensional instability. He feels the solution for ill-fitting crowns is a more accurate impression material.

With all of the impression materials on the market today, including the new ones introduced by Kamohara, there is very little improvement in the reliability of indirect dentistry.

Some inventors believe the inaccuracies occur after the impression is completed. They feel distortion occurs in the modeling process. This is the case with inventor Singer in U.S. Pat. No. 6,149,426. He states that inaccuracies occur with the master cast. His prior art confirms that the prosthetic must be fitted and corrected several times before it becomes accurate. He further feels that the problem, however, exists in the plastic trays used in the profession as well as subsequent modeling of the impression. His invention does not yield a better fitting crown.

Some inventors attribute a smooth stone cast and easy separation of the set cast from the impression as indications of accuracy. This is the case in two U.S. Pat. Nos. 5,907,002 and 3,620,778. Present day dental casts are distorted due primarily to shrinkage. Any reference to easy separation of dental cast would have this inventor immediately equate to dental cast shrinkage. Most casts today exhibit distortion due to shrinkage.

In U.S. Pat. No. 5,417,750 Cohen and Musikant includes calcium sulfate in his alginate impression material. This is also true with inventors Watanabe and Kamohara in U.S. Pat. No. 6,509,390. Most alginate formulas rely on addition of calcium sulfate to alginate formulas to act as a catalyst and binder for set and strength of alginate. Calcium sulfate forms a cross link with the alginate material. These alginate formulas are all good performers as impression materials, however the ingredients of alginate have never acted to cause any type of catalyst effect on the wet, mixed stone poured into and against it. Stone dental casts made from alginate exhibit just as great a distortion as with other dental impression materials.

Five percent potassium sulfate solution is available from American Dental Supply, Inc, Easton, Pa. This product is available to help condition hydrocolloid impressions. It may help to provide a smoother cast surface, but does not provide a more accurate cast.

The textbook of PHILLIPS' SCIENCE OF DENTAL MATERIALS states the hydrocolloid may often contain borax additive, which strengthens the gel. Borax is thought to be a gypsum setting retarder. Potassium sulfate, which is an accelerator, is added to hydrocolloid to counter the effect of borax. Potassium sulfate is also believed to be a dental stone catalyst.

However, the potency of potassium sulfate as a dental stone catalyst is unclear to the profession. Many impression materials have incorporated potassium sulfate, but none have produced accurate casts. Because the correlation between a stratified stone set and cast accuracy is unknown, the effective amount and combination of stone setting catalyst ingredients remains undiscovered.

Still further, this inventor has used potassium sulfate solution for many years with different hydrocolloids, reversible and irreversible. And this inventor has found no appreciably faster times for setting of gypsum. Also, even adding the potassium sulfate solution directly to wet mixed gypsum, this inventor could still not verify any difference in setting time as compared to a control mix. And not only setting time, but also, no change in accuracy between potassium sulfate stone mixes versus control mixes could be verified, by this inventor. Significantly, there are no studies, known to this inventor, verifying more accurate castings using potassium sulfate conditioned impressions.

DENTAL STONE DISTORTION

It is readily accepted in the profession that dental stone distorts upon setting. Although, it has never been proven how the accuracy of the final prosthesis is affected, specifically from the setting stone distortion.

The stone will either shrink or expand, toward its core center of mass. This uncontrolled distortion causes inaccuracies in the dental cast and, ultimately, in the final dental prosthesis.

Shrinkage of stone toward its center core would cause the areas of interest of the dental cast, that is, the areas along the impression surface, to pull toward the center of mass, and distort. This distortion would ultimately lead to inaccurate restorations. This is exactly what the profession experiences, without fully appreciating the cause.

Present day technology will pour the impression as a whole, resulting in a die of smaller dimensions than actual. For example, a wax pattern for a crown casting would thus be made from a smaller representation of the actual size of tooth. When the resultant crown is tried onto the tooth, it will be tight. The crown will not fit. It will need to be adjusted.

The mechanism is very different in this discovery. In this disclosure, there exists a stratified set of the stone. Setting of stone first occurs closest to the important target areas of the impression. The cast is accurate in the target areas of the impression, the areas of interest. This is due to the placement of stone setting catalyst. Distortion is controlled. All the expansion or shrinkage of the setting stone occurs peripherally, away from the target areas. Again, this is due to the stratified set.

The distortion is controlled and will tend to occur in the periphery. Distortion will occur furthest away from the impression surface, where inaccuracy is less damaging. Thus, indirect restorations and prosthesis will be formed from more accurate casts, needing less adjustments. Distortion associated with indirect dentistry is the primary reason for growth of the use of CAD/CAM in dentistry. In U.S. Pat. No. 6,152,731 Jordan et al. describe how dentistry is moving toward digital images. Although digital images are an improvement in efficiency, cost is certainly a factor. And as far as overall accuracy, the concepts of the enclosed disclosure produce results that rival those of the CAD/CAM systems.

SUMMARY OF THE INVENTION

A dental hydrocolloid impression is procured in the usual manner, a manner familiar to the dentist. This inventor has found no specific correlation to any specific brand of hydrocolloid impression material, or to any specific style of tray design, that effects final outcome. This set impression is placed aside for use in the dental lab.

Subsequently, the dental impression is poured with wet, mixed dental stone.

When at least partially set, the dental stone cast is removed from the hydrocolloid impression and discarded.

The dental impression is poured again with a second stone pour.

After setting, the second pour cast is separated from the impression and used for prosthetic fabrication.

DETAILS OF THE PREFERRED EMBODIMENT

The basis of this discovery is the fabrication of dental prosthesis from a made from a master dental cast, made from a stratified set of stone. To achieve this, a catalyst in the form of calcium sulfate dihydrate is applied to the surface of a hydrocolloid dental impression. Calcium sulfate dihydrate is equivalent to set dental stone. Wet mixed dental stone is then poured into the impression and, thus, into intimate contact with the stone setting catalyst. This area of wet stone, which is in direct contact with the catalyst, will begin to set faster, or sooner, than other areas within the mix.

Therefore, the stone sets faster along the impression/stone interface due to the direct contact with stone setting catalyst. In a wave-like pattern, layer by layer, the stone sets in a stratified manner. The setting starts first at the impression surface and then the setting action subsequently radiates outwardly, further and further away from the impression surface. The catalyst initiates the set in the areas of stone closest to impression surface. The stone closest to the impression and catalyst sets sooner, while the areas of mixed stone furthest from the impression set last.

Indeed, if the catalyst was not added to the impression surface, rather, added to the stone mix, as an added ingredient to the stone, the entire mix would simply set faster. It would not set in a stratified manner. The final cast would not be more accurate.

Somewhat analogous to the concept of a stratified set is an example of how water freezes. In one instance, a cup of water may be placed into the freezer. The water would freeze as a single mass. It would freeze as a whole.

Present day impression pouring techniques allow for a whole set of dental stone.

However, water may also freeze on the surface of a lake, due to exposure to cold air. In this instance, water freezes incrementally, radiating down, layer by layer, further and further away from the surface, in a stratified manner.

This invention discloses a novel approach to control the setting pattern of mixed stone. Instead of allowing an entire whole set of stone, the set is controlled to start at the impression surface and advance from that point, incrementally, into the remaining wet stone.

If the cast is allowed to set as whole, then the cast will distort to, or, in some cases, away from, its center of mass, depending if the mixed stone were shrinking or expanding, upon setting. Expansion characteristics vary for various brands of gypsum. Some manufacturers report expansion of gypsum products, while other products are held to shrink.

However, adding the catalyst to the surface of the hydrocolloid impression causes a faster setting of stone immediately adjacent to the impression surface. The setting action radiates from this point into the rest of the stone. The stone gradually sets in a wave-like fashion with the stone furthest removed from the impression surface setting last. Therefore, any distortion will occur innocently, and unnoticed, in areas distant from the impression surface.

IMPRESSION MATERIALS CONTAINING STONE SETTING CATALYSTS

Some present day impression materials have stone setting catalysts as ingredients. The alginates do mix and set well. However, today's impression materials do not support a stratified set of stone. In turn, this gives unreliable results in regard to cast accuracy. Stone casts and final end products are no more accurate with these impression materials, as compared to impression materials that do not contain stone setting catalysts. Of great significance, is the fact, that the best selling reversible hydrocolloid by the preeminent manufacturer contains no stone setting catalyst.

Four stone setting catalysts are mentioned in the literature. These include sodium sulfate, potassium sulfate, calcium sulfate, and potassium titanium fluoride. The inventor has extensive experience with potassium sulfate used as a setting stone catalyst in many ways. This catalyst has been added to a professionally available formula of irreversible hydrocolloid, a product that the inventor has used for thirty years. Casts and resultant end dental products have never been more accurate that are made from this stone setting catalyst laden impression material.

In fact, the inventor has mixed potassium sulfate directly into a wet stone mixture without seeing any difference in setting time as compared to a control.

In the literature, potassium sulfate is a considered a catalyst only if used in certain quantities. If this amount is exceeded, then potassium sulfate becomes a retarder to stone setting. Therefore, this inventor would consider potassium sulfate a weak catalyst. It may not be as reliable under certain conditions of amounts, varying gypsum formulas, temperature, and other unknowns. The catalyst disclosed herein, calcium sulfate dihydrate, when in direct contact to the mixed dental stone, acts as a strong catalyst, in all instances.

Another brand of irreversible hydrocolloid contains potassium titanium fluoride. The inventor has personally used this product to produce several hundred casts. The resultant casts and final products show no improvement over other forms of impression systems.

Either there is misconception in our profession concerning catalysts with truly effective stone setting properties or inclusion processes of the catalysts into the impression materials is misdirected during manufacturing. The science of the addition of catalysts into impression materials is faulted.

In application Ser. No. 11/878,337, it is shown that a suitable catalyst, potassium calcium dihydrate can be used with unprecedented results.

The novel art disclosed in this patent application, demonstrates a technique to fabricate a dental appliance of unprecedented accuracy. It is no benefit to the profession simply to add what may be deemed as a stone setting catalyst to an impression formula. There is no impression in today's market that contains an effective stone setting catalyst that would actually cause a stratified set of dental stone. There is no impression today that will yield accurate dental casts or the subsequent final dental products made from such casts.

The present day technology of adding stone setting catalyst into impressions is not a complete formula for reliable outcome. It is not operational or complete to give elevated results and, as such, has not benefited our profession. The knowledge and use, employing present technology, is not available or enabling to the public to produce an accurate end product.

And since this inclusion of catalyst is part of our manufacturing process today, fewer researchers are likely to further evaluate. That is to say, researchers are satisfied with just knowing that stone catalysts are added, that they feel this area of impression dentistry is complete. Due to the processes currently used, and supported by well established documentation of study, a researcher would be even less likely to look here for a solution. They feel there is no need for further study. This scenario of complacency only adds more support of Unobviousness.

Unexpectedly, however, to add an effective setting catalyst, and in the correct amounts, does reward, producing dental products of unparalleled accuracy.

The goal is to fabricate an accurate dental appliance, or crown. Only by using the novelty of this disclosure can this be realized, put into practice, and produce new results. Never before this invention, was there ever a technical effect that was consistently obtained. Until the time of the present disclosure, the accuracy of indirect dentistry has been very obscure, unreliable, and burdened with much confusion among the dental professionals. The dramatic increase of accuracy afforded by this invention would transcend any inference to anticipation by inherency. The prior art of adding purported catalysts to manufacturer impression formulas has yet to enrich the public domain. Due to this, the technical outcome has always been sporadic, as one national speaker describes: the consistency is “. . . all over the place”. Quality must be a consideration when comparing to prior art. In order to be anticipatory, the present day concepts of operation would enable a professional to create perfect fitting restorations.

Again, the mere possibility that a certain result may happen and left to an unpredictable outcome and to embellish this present day technique to a level of anticipation in regard to this application is unsubstantiated. There is no natural result nor any degree of predictability by what manufacturers have afforded the profession to date. In contrast, the present invention outlines successful outcome. There is natural result flowing from the operation of this disclosure, a result related to a new technique of using an effective catalyst. The outstanding results, that challenge a decades old problem, should be regarded sufficient and the discovery novel and not anticipated.

The PHILLIPS' SCIENCE OF DENTAL MATERIALS textbook goes on to suggest the incorporation of an accelerator additive, such as potassium titanium fluoride, into dental impression material. It suggests that this be added to the hydrocolloid directly to accelerate set time of dental stone. It is important to emphasize the reason accelerators are suggested by researchers, is that ingredients such as borax will retard the setting of stone. If the stone does set satisfactorily, impression and stone manufactures feel materials are compatible. They do not go further to produce a unique product that will definitively set stone, faster than a normal set, closest to the impression material/stone interface.

This inventor recognizes the literature has made suggestions to include catalysts to dental impression materials. Indeed, manufactures have included stone catalysts. Without the catalysts, apparently, either the stone did not set or the stone setting took a very long time. However, manufacturers have never formulated impressions to cause the stone to set faster than the normal set time. No formula causes a stratified set of stone, that is, causing stone to set first, closest to the impression. Further, no manufacturer had this goal. It is not known that the actual effect of a suitable catalyst goes far beyond simply setting of stone, it produces new dimensions of accuracy to the cast.

Dentists, using present day technology, trudge through the process of delivering the less than perfect indirect restorations, believing this is as good as it gets. They feel that the errors we see are a reflection of the limitations of the accuracies of all the systems involved. Professionals, familiar to the art, believe variables occur cumulatively with impression distortion, setting of dental stone, waxing techniques, investing and casting, and firing porcelain.

Appreciatively, after time is spent adjusting present day crowns, some crowns will fit very near perfect. However, some crowns can never be adjusted well enough for clinical acceptance. Crowns that are distorted beyond clinical acceptance become remakes. Remakes are a disappointment to dentist as well as the patient. One dental laboratory owner admits his remake rate is 11%.

To repeat, the goal of this discovery is to fabricate a dental prosthesis from a master dental cast of stratified set gypsum or stone. This has never been achieved in dentistry. There are no references in our texts or in the U.S. Patent Office relating to stratified set of dental stone. There may be several tens of different effective catalysts. The inventor has used only one, calcium sulfate dihydrate, which is readily available in the dental lab.

Again, consider that impression dentistry is a century old and probably soon to phase out entirely due to advances of CAD/CAM technology. The very unlikely discovery shared herein should not be limited to a particular kind of dental catalyst. Many types of catalysts would yield a cast of stratified set. However, to date, no one has implemented any effective stone catalyst contained within hydrocolloid impression material. Stratified setting of dental stone remains undiscovered.

Traditionally, dental impressions are poured to completely fill the area of teeth with mixed stone. Upon setting, this entire pour will shrink to its core. This shrinkage will cause a stone cast to have miniaturized teeth. These casts are inaccurate.

Any prosthesis, fabricated on such a distorted cast, will also be dimensionally inaccurate. Consequently, about ninety percent of our indirect restorations, such as crowns and bridges, need to adjusted chairside. Removable prosthesis, such as dentures and nightguards, also need significant adjustment.

These restorations must be adjusted to compensate for the distortion of a traditional pour of dental stone. A traditional pour fully fills at least the tooth portion of the dental impression with gypsum and therefore allows distortion of stone upon its setting.

A stratified set of stone would create a cast with accurate representation of the dentition. Fabrication of prosthesis, using an accurate cast, produces a better fitting product. These appliances need little adjustment and aid efficiency in our indirect dentistry processes.

SECOND POUR OF IMPRESSION

Present art determines that the most accurate cast is from the first pour of the impression. In use, the laboratory technician may elect to duplicate the original master cast with an impression of the master cast and work off this duplicate cast to fabricate the final dental products. In other words, he works and fabricates from this copy of the original cast. This technique is practiced mostly, in the matter of acrylic fabrication.

The laboratory technician will work with this duplicate cast, not knowing, that, although it is an accurate reproduction of the master cast, it is not accurate of the actual dentition. The second cast possessed microscopic fragments of set stone on its surface, transferred there from being in contact with the master cast.

The duplicate cast had the benefit of an effective stone setting catalyst on the impression surface. The catalyst was picked up from the impression being in direct contact with the original stone cast. Small amounts of surface stone becomes imbedded into the impression. Due to the presence of this catalyst, a stratified set will occur when mixed stone is added to pour a cast. So, although the second/duplicate cast is an accurate reproduction of the first cast, it replicates the same irregularities of distortion as the first cast, and so it is identically inaccurate. The duplicate cast is usually used for fabrication and is destroyed during the lab processes of deflasking, a term referring to the recovery of a finished acrylic dental appliance, imbedded within investment stone. The fabricated appliance is returned to the original, master cast to be adjusted as close as possible. To be sure, the original cast is inaccurate. Present day pour of the impression does not provide for a stratified set of stone.

Unwittingly, the technician continues the art of fabrication on inaccurate casts. This current exercise, of fabrication using inaccurate casts, has perpetuated the entire span of impression dentistry.

Although the technician does utilize a stratified cast for his duplicate cast, the profession does not realize that the original cast must be a stratified set of stone, for greater accuracy. The claims attached herein specify attaching the catalyst to set impression material. It does not claim the attachment to unset hydrocolloid. The technician already achieves this.

The difference of attaching catalyst to set material has significance. The master cast would be accurate from such a process. Picking up catalyst into unset hydrocolloid would only enhance accuracy of a duplicate cast.

Since the true accuracy of the stratified set of stone is unknown to the profession, details to assure best outcome are not adhered to. For instance, the principles of using clean mixing bowls and spatulas are necessary to assure a consistent outcome. This is because any errant fragment of set stone could be incorporated at any site within the stone pour and would act as a stone setting catalyst. Any initial set of stone, caused by an errant seed of stone catalyst, away from the impression surface, would cause cast distortion.

Therefore, it is not sufficient to merely state that a second pour cast is accurate without full attention to the stated various parameters influencing accuracy upon stone setting. Although a stratified set of stone is possible by duplication of a cast, no one is knowledgeable to apply this principle for optimum results.

The refinements of pouring an accurate second pour cast for reliable accuracy are not always followed in today's art. The profession today pours them in a haphazard way, not realizing or utilizing them for the reliable outcome they would be capable of. Again, the disclosure herein is unknown to the profession and the accuracy of a second pour is yet undiscovered.

Therefore, although second pour casts are not new to the profession, the handling and production techniques have never been refined to enhance accuracy and reliability. Second stone pour casts, poured directly again into the original impression, have never been used for fabrication; they have never produced better dentistry or elevated the profession.

Moreover, as stated above, the fact that present day second pour casts are not poured with great attention to detail leads to a somewhat unreliable replication. Complete accuracy may not be assumed. Anticipation by inherency may not be established by probabilities or possibilities. In reference to the Oelrich case: “The mere fact that a certain thing may result from a given set of circumstances is not sufficient. If, however, the disclosure is sufficient to show the natural result flowing from the operation as taught would result in the performance of the questioned function, it seems to be well settled that the disclosure should be regarded as sufficient.” (In re Oelrich, 666 F.2d 578,581 ((CCPA 1981)) ((Rich, J.)))

The disclosed method of this patent application produces a very unique end product. An accurate cast has a definitive role with the need for dimensional stability carrying forward to further events and processes occurring both within the lab and within the dentist office. The accurate cast itself is not the final product inferred by this disclosure; the final product is the appliance or crown delivered to the patient by the dentist. This new invention enables the well fitting adaptation of an end product, dental appliances.

Anticipation cannot occur unless a prior art reference is enabling. Any person today, skilled in the dental profession, would be unable to make or construct to the final end result an accurate dental appliance. They would not possess the operative techniques and practical information needed to form accurate final products. No technique presently engaged, or disclosed prior art disclosure of any kind, can be relied on as reference; no technique may be relied on as anticipation for the final excellent results of accurate fitting restorations. This long overdue solution to a decades old problem is not anticipated, even by those who occasionally make second pour casts, and yet fail to know the significance and cannot implement to final end processes.

Moreover, this is not just a process for producing products ordinary to the profession. The results of this invention enable products with accuracy never before available to our society. This invention constitutes revelation, setting a new order of magnitude. The discovery presents a new standard of care.

HYDROCOLLOID

Dental stone setting catalysts have been added to some hydrocolloid materials. Calcium sulfate dihydrate is generally included within the irreversible hydrocolloid (alginate) ingredients. It is added as the reactor:

2NA₃PO₄+3CaSO₄>Ca₃(PO₄)+3Na₂SO₄

Calcium sulfate dihydrate is added as the reactor. However, there is not enough of this catalyst at the impression surface to avail itself further as a stone setting catalyst. Significant, is that the stone setting catalysts contained within hydrocolloid impression materials have never been formulated to cause a stratified set of dental stone.

No formulation of stone catalyst added to hydrocolloid impression material has ever caused a stratified set of dental stone. Because of this, stratified setting of dental stone is unknown to our profession.

Catalysts have historically been incorporated into certain mixtures of hydrocolloid. Further, these catalysts have been added to counter the side effect of other ingredients, such as borax, which tend to retard stone setting.

Catalysts have never been added in an effective manner to initiate a stratified set of dental stone. There has never been a recipe for success to form a more accurate cast. There is no operative that exists from any hydrocolloid to direct any practitioner or researcher to improve upon the science of adding catalysts. Due to this, the concept of a stratified set of stone not found in our literature. No patent discloses a stratified set of dental stone.

This present application discloses the concept of adding additional stone setting catalyst to the set impression surface, beyond what is already present within the alginate formula.

Enclosed herein is a supportive letter volunteered by Dr. Steven L Harris. He is the only dentist applying the concepts described herein.

Also attached is a signed affidavit signed by the applicant.

CONCLUSIONS, RAMIFICATIONS AND SCOPE OF INVENTION

Implementation of this discovered technique enables dental impressions to yield more accurate casts than present day technology.

This distinctive invention advances dental restorations beyond present art and the discovery improves the overall standard of care.

Accuracy, to this level, has never been appreciated in dentistry. This disclosed technique will add normalcy and stability to a process that, heretofore, is far from predictable. This new technique is the answer to what may be the last major challenge in our profession.

To be able to reduce procedural time significantly is not to be understated. This technique will not only cut delivery time for the dentist, it produces a better product. Patients will enjoy restorations that will feel better and last longer.

Hopefully, a generic catalyst would be produced that would not be stone type specific. This catalyst could be made available for use that would be compatible with all dental stones. This inventor has not yet studied all the various combinations of catalysts used with different brand and type dental stones.

One embodiment of the technique described herein, is to directly apply calcium sulfate dihydrate powder onto the surface of the alginate. Enough catalyst would be absorbed into the alginate to initiate stone setting. This is a direct application.

The calcium sulfate dihydrate could also be burnished into the impression surface with an artist's brush. This burnishing action would help imbed the catalyst crystals into the impression surface. This is also a direct application.

In addition to the powdered form of catalyst described herein, a dental stone catalyst could be made available in a liquid slurry form. Such a liquid product would allow for a dipping of the hydrocolloid impression. The liquid will penetrate into the impression, only to leave a thin Calcium sulfate dihydrate precipitate coating on the impression material to act as a dental stone catalyst.

Another embodiment for this discovery would be to simply pour a second cast after the original cast is poured. The original cast can be discarded. The purpose of this first stone cast would be to leave a layer onto the impression surface of calcium phosphate dihydrate to serve as catalyst for a subsequent stone pour. Unobvious to even those expert in the art, the second cast retrieved from the impression will be dimensionally different from the first cast; it will be more accurate cast than the first cast.

Another instance when a second pour may be utilized is with acrylic appliances. The appliance is fabricated upon a duplicate, or second pour cast. The appliance is then finished to the master cast.

The second pour technique is especially compatible with hydrocolloid impression material, as compared to elastomeric impression material. The wet, mixed stone is more likely to be absorbed within the hydrocolloid, due the water content of both stone and impression material. Set dihydrate stone is imbedded into the hydrocolloid surface, ready to seed the set of the subsequent pour. Calcium sulfate dihydrate serves as an excellent stone setting catalyst.

The end result of this discovery is that all indirect restorations fit with 90% more accurate. Partly because of the limitations of present day technology of pouring casts, we are now turning toward a digital world of CAD/CAM indirect restorations. These machines are very expensive, and still have limitations. They cannot make a custom shaded crown, which may be necessary to match a single maxillary anterior tooth. This is a serious drawback in today's esthetic conscious world. And the CAD/CAM machines cannot make dentures, partials, nightguard, or bleaching trays.

This invention has remained undiscovered due to: 1. the complexities of indirect dentistry, 2. stone setting accelerators have already been used in impression materials, with no added benefit to cast accuracy 3. second pours, although not used for fabrication, are already performed and are not new to the profession, (although, second pour casts are made, the mechanism for success is unknown), and 4. lastly, the end result of a consistent near perfect restoration has, heretofore, never been achieved in dentistry.

The concept of perfect fitting restorations is incomprehensible to expert professionals. Finding the necessary techniques to accomplish this would be equally obscure. Please consider that there are over one hundred thousand dentists in this the United States alone, who are fabricating over ten million appliances a year.

This unique disclosure is long overdue. The profession has accepted status quo level of accuracy in dentistry for a very long time.

For over half a century, impression dentistry has remained at status quo. Consider that dentists have graduated in the fifties, sixties and seventies, practiced an entire career, and retired, without the benefit of accurate restorations. Without the techniques disclosed herein, accurate impression dentistry may have possibly never been realized. With the added incentive of patent protection, the inventor has an opportunity to aid the profession and society. Patients will benefit from shorter appointment times and more accurate restorations that will feel better and last longer.

The Novel Physical Features Of The Claims Provide Enhanced Results And Hence Should Be Considered Unobvious, Making The Claims Patentable Under Section 103.

The physical distinctions enable greater results. The standard for accurate impression dentistry is elevated, one which, heretofore, has been unobtainable. Specifically, a method to make more accurate dental products, fabricated from stratified set dental casts, is disclosed, thereby indicating that the physical distinctions are unobvious under section 103.

The enrichment afforded to our society from this long overdue discovery would be bolstered by the recognition from all groups and individuals for its novelty. The knowledge and use of this needed technology would become available to the public.

A patent incentive may well be needed to direct a new perspective, one benefiting patients. A patent incentive would help with faster implementation and help serve society with improvements that may otherwise never occur. The ongoing state of indirect dentistry need not continue.

REQUEST FOR CONSTRUCTIVE ASSISTANCE

The undersigned has made a diligent effort to amend the claims of this application so that they define novel structure (manufacturers have never adequately addressed the problems of ill-fitting dental restorations) which is also submitted to render the claimed structure unobvious because it produces new results of accurate dental casts and improved fit of dental restorations (Unobviousness is pointed out over the existing prior art). If, for any reason the claims of this application are not believed to be in full condition for allowance, applicant respectfully requests the constructive assistance and suggestions of the Examiner in making constructive suggestions pursuant to MPEP 706.03(d) in order that this application can be placed in allowable condition as soon as possible and without the need for further proceedings.

Claims

1. An improved method for producing an indirect dental prosthesis, comprising the steps of: a. attaching calcium sulfate dihydrate stone setting catalyst onto the surface of a set hydrocolloid impression material; b. pouring a wet, mixed dental stone into said dental impression and onto said calcium sulfate dihydrate stone setting catalyst, whereby the dental stone juxtaposed to said calcium sulfate dihydrate stone setting catalyst sets faster, and further whereby, an accurate gypsum cast is formed by a stratified set of stone, thereby, enabling accurate restoration or prosthesis fabrication.

2. A method according to claim 1, wherein said hydrocolloid impression material is reversible hydrocolloid.

3. A method according to claim 1, wherein said hydrocolloid impression material is irreversible hydrocolloid.

4. An improved method of fabricating dental prostheses, comprising the steps of:

a) attaching calcium sulfate dihydrate onto internal surface of set hydrocolloid dental impression;

b) pouring wet, mixed dental stone into said dental impression, and into contact with said calcium sulfate dihydrate, whereby, said wet, mixed dental stone sets faster closest to said dental impression, and further whereby, a cast of stratified set of stone occurs;

c) fabricate prostheses in usual manner on said cast of stratified set of stone.

5. A method according to claim 4, wherein said hydrocolloid dental impression comprises set dental stone remnant of calcium sulfate dihydrate, attached to said internal surface, from a previous stone pour.

6. A method according to claim 4, wherein, said calcium sulfate dihydrate stone setting catalyst is applied to set hydrocolloid dental impression material by direct application.

7. A method according to claim 4, wherein, said calcium sulfate dihydrate stone setting catalyst is applied to set hydrocolloid dental impression material by immersion into calcium sulfate dihydrate solution.