DENTAL BURR

Abstract: A dental burr (10) is provided, whose use is specifically intended for the preparation of a tooth on which will be subsequently placed a crown, inlay, onlay, or other dental prosthetic. For any crown, inlay, onlay, or other bridge prosthodontic procedure, it is important that a series of grooves first be cut to a specific and predetermined depth, after which the lands that are created and stand between the grooves in the enamel and/or dentin of the tooth, will be ground down. However, the depth of the groove must be accurate. The dental burr of the present invention assures accuracy by providing a structure that has a cutting projection (20) that extends outwardly beyond a shoulder (26) that is formed in the burr, where the length of the cutting projection outward of the shoulder is a specific and predetermined length. Thus, a groove of a specific depth can be cut by using a specific burr. An intermediate portion (24) of the burr, which terminates in the shoulder, may be of a specific colour which is indicative of a specific length of the cutting projection. The intermediate portion may be formed by being machined into the material from which the burr has been manufactured, or it may be formed by placing a cylindrical sleeve (34) over a previously manufactured burr and fixing it in place so that the cutting projection is of the specified length.

Description: DENTAL BURR FIELD OF THE INVENTION; This invention relates to dental burrs — cutting tools that are used by dentists for cutting into and removing material of the tooth, especially the enamel and dentin thereof. The dental burrs of the present invention are particularly intended for use in the preparation of a tooth for subsequent placement of a crown, inlay, onlay, or veneer, or for other crown or bridge prosthodontics procedures, where it is required to reduce the surface of the tooth, or at least a portion of the surface of the tooth, by a specified amount. By reducing the surface of the tooth it is meant that a portion of the tooth is ground off, to be replaced by an artificial material. BACKGROUND OF THE INVENTION: Dental procedures have, for many years, involved several distinct kinds of surgical operations with differing purposes and effects. For example, dental procedures that most people undergo involve the removal from the tooth of a small portion thereof so as to remove dental caries that are effecting that tooth. The dental caries and at least a small portion of healthy tooth surrounding it are removed, the preparation that is thus produced is then ready to accept a filling, and the filling is then placed. A variety of drilling or cutting instruments are employed during such a procedure. Another procedure that is not so common, but nonetheless may be practised by an ordinary family dentist at least several times each week during the conduct of his business, is the preparation of a tooth or teeth for subsequent placement of crowns, onlays, inlays, or veneers. Another related procedure is the precise preparation of a tooth to accommodate a clasp or rest of prescribed dimensions for a removable partial denture. For purposes of this discussion, all such related procedures — the removal of the surface or at least a portion of the surface of the tooth to prepare it for subsequent placement of an artificial substance — will be considered as being in respect of dental crown preparation. Dental burrs in keeping with the present invention can be used in such restoration procedures as various crown procedures using a variety of crown materials, as well as onlay or inlay procedures and the placing of a veneer on the tooth. Crown procedures might be a full metal crown, or a porcelain fused to metal crown, or a full porcelain crown, or even an acrylic crown. The importance of these distinctions is that the prescribed depth of reduction for proper preparation varies, depending on the nature of the crown or partial crown, inlay, onlay, or veneer, and yet the outer periphery of the dental prosthetic to be placed must replicate the original outer periphery of the tooth. Otherwise, discomfort occurs in the patient, or the restoration may not be cosmetically acceptable, or the restoration may not even fit properly. In any event, there could be a considerable loss of time and expense, to the patient, the dentist, and the dental prosthetics laboratory in the occurrence of inaccurate preparation and/or reduction. Briefly, dental crown preparation requires the dentist to grind or otherwise remove a specific amount of the surface of the tooth. This procedure, reduction of the tooth, generally requires that the depth or amount of reduction shall be from about 0.5 mm to about 2.0 mm. This is not to say that the amount of reduction should vary on any one tooth in any one procedure — although that is possible; but it is to say that the amount of reduction may vary from tooth to tooth or procedure to procedure, depending on a number of circumstances that would be determined by the dentist at that time. Also, of course, the amount of reduction might be somewhat less for purposes of placement of an onlay or inlay, or possibly a veneer, as opposed to the amount of reduction that might be required for the placement of a crown or partial crown. The dental procedures of grinding teeth, or cutting or abrading teeth, are generally carried out using rotationally driven cutting or grinding instruments, which in general might be classified as being dental burrs. In fact, the usual classification of armamentarium may comprise a variety of rotary instruments that might be specifically classified as stones, burrs, or drills. For example, the stones are used for abrading or grinding down the surface of the tooth such as by the use of fine diamond chips or dust that are cemented to a base. In a narrow definition, dental burrs may be considered to be miniature milling cutters, having a plurality of blades that shear away the tooth structure from the tooth surface and where the cutting blades are disposed along the sides of the instrument. Drills, specifically twist drills, have their cutting edges at the tips of the instrument, and are generally intended only so as to bore a small diameter hole into the tooth structure. However, for purposes of this discussion, all of the above instruments may be generally considered to be dental burrs, and this will be especially so in the following discussion which proposes several alternative surface treatments or geometries for dental burr structures that are otherwise in keeping with the present invention. When dental crown preparation is being undertaken, the dentist first determines how much surface reduction should be made. Then, the portion of the tooth surface, if not the entire tooth surface, is marked so as to determine the boundaries within which the procedure will be undertaken if it is not over the entire surface of the tooth. Tooth reduction then begins, and it is at this point that dental burrs according to the present invention will be used. When a crown procedure is being undertaken, the general steps include tooth reduction, and then an impression of the remaining tooth is taken and sent to a dental prosthetics laboratory. The laboratory then fabricates the crown, having made a model of the impression, and having been informed of the desired prosthesis type, they must assume that accurate reduction and/or preparation has been accomplished by the dentist to permit said prosthesis fabrication. In other words, the dental prosthetics laboratory has in its hands a model of the tooth after the reduction has been made, and it is then required to build a crown to be cemented to the remaining portion of the tooth and to restore the depth of reduction that has been prepared by the dentist. The crown is then fabricated and returned to the dentist for placement in the mouth, usually a few days or a week or so after the tooth reduction has been taken. A more complete discussion of tooth reduction and crown preparation techniques and procedures, and the difficulties surrounding those matters, will be found in a companion application, Serial No. 08/190,486, filed February 2, 1994, in the name of the present inventor, and relating to METHODS OF PREPARATION OF A TOOTH BY REDUCTION THEREOF. It is sufficient for purposes of the present invention to note that the most difficult step taken in crown preparation is the maintenance of a constant depth of reduction, once it has been determined as to how much reduction should occur; because if the depth of reduction has not been constant, or has been more or less than advised by the prosthetic technical specifications, then the crown may not fit or it may not replicate the previous tooth structure which it replaces. The manner by which the depth of the reduction is to be determined may vary slightly among dentists, but not significantly. When a dentist is preparing the tooth for tooth reduction, he first cuts a series of grooves into the tooth. Almost invariably, the series of grooves is cut into the tooth using a long cutting burr that may be cylindrical, or which may be slightly tapered, but in any event the groove is cut into the surface of the tooth by placing the burr lengthwise against the tooth and pressing it into the tooth along the length of the burr while the burr is rotating. This creates a groove that is as long as the burr or at least the portion of the burr that is in contact with the surface of the tooth. But the depth of the groove is difficult to determine; and the usual practice is essentially to gauge the diameter of the burr and then sink the burr into the surface of the tooth for one-half of its diameter — or in some cases, its full diameter. After several grooves are placed into the surface of the tooth, then the remaining tooth material between the grooves is ground or abraded away, until the depth of the grinding or abrading of the material reaches the same depth as the grooves that have been previously cut into place by the side of a burr as noted above. The steps preceding the cutting of a plurality of grooves into the surface of the tooth, and the steps of removing the tooth's structure between the grooves after they have been put in place, would remain essentially the same for any dentist who uses the dental burr of the present invention, as previously discussed. However, the step of placing the grooves into the surface of the tooth, so as to determine the boundaries of the tooth reduction procedure if an entire reduction is not taking place and the placement of intermediate depth grooves where gross reduction is taking place, are easily and extremely accurately undertaken using the dental burr of the present invention. Of course, even when an entire crown is to be placed, meaning that the entire surface of the tooth is to be reduced, there still remains a boundary at the gingival area of the tooth, where the shoulder of the crown to be placed meets the remaining structure of the tooth at, near, or below the gumline. What the present invention provides is a dental burr whose purpose is to cut a groove into the tooth structure, where the groove has a specific and predetermined depth. As noted above, the depth of the groove to be cut into the tooth may only be as little as 0.5 mm in some cases, or it may be as much as 2.0 mm in other cases. Also, as noted above, the depth of the groove should be uniform, because the dental prosthetics laboratory assumes that a constant depth of reduction has occurred over prescribed tooth areas for which the laboratory is fabricating the crown or other dental prosthetic. There are, of course, several reasons for the concern as to the accuracy of the depth of the grooves that are initially placed in the tooth structure as part of the dental crown procedure. They include among them the fact that, if the depth of the groove is either too much or too little, then the dental prosthetic that has been prepared by the laboratory may not fit — in that it would not necessarily replicate the tooth structure that it replaces. If less reduction has occurred than the respective restorative dentistry specifications dictate, then it is possible that a crown might not go into place because its resultant laboratory fabrication would be overcontoured and thereby interfere with the adjacent tooth or teeth. If more reduction has occurred than has been prescribed by restorative dentistry specifications, then the vitality of the tooth may be jeopardized by the stated over- reduction. It should be noted that, a final impression is only made after the reduction procedure has taken place. Preliminary impressions that are made prior to the tooth reduction procedure are taken in order to mould a temporary crown or restoration that is put into place for cosmetic and functional purposes, which crown or restoration is generally one that is fabricated by the dentist in his own office. Of course, if the tooth reduction has been inaccurately done, then unhappiness may occur between the patient and the dentist, and/or between the dentist and the dental prosthetic laboratory. This could mean unwarranted and unnecessary delays in time, additional time in the chair by the patient — for which the patient may be quite unwilling to pay the dentist — and sometimes it may require re-fabricating the dental prosthetic, the cost for which may have to be absorbed by the dentist or the laboratory. When the depth of the initial depth gauge grooves are accurately determined and placed, then none of the above difficulties would arise. THE INVENTION; The present application provides a dental burr whose structure is such that the grooves to be cut into the tooth structure, that is the tooth enamel and/or the tooth dentin, are always accurately determined and are of a predetermined depth. Accordingly, the present invention provides a dental burr for use in preparation of a tooth for subsequent placement of a crown, or inlay, or for use in other crown or bridge prosthodontics procedures, where the dental burr structure comprises a body that has a stem adapted for placement at a first end thereof into a driving implement, so as to impart rotational driving force to the dental burr. There is a cutting projection formed at a second end of the body, opposite the first end, and the cutting projection is substantially cylindrical but is contoured at its outer periphery with a cutting groove or grooves that are formed generally spirally in the outer periphery. Alternatively, the cutting projection rηay be surface treated in such a manner that it is capable of grinding or abrading the tooth structure. An intermediate portion is formed in the body of the dental burr and is axially located between the first end and the second end thereof. This intermediate portion is generally cylindrical, although it might be tapered, and it has a diameter which is greater than the diameter of the cutting projection. In any event, the intermediate portion terminates in a shoulder that is located near the second end of the dental burr, and the shoulder is substantially planar and projects radially outwardly from the cutting projection. Thus, the cutting projection projects axially along the body of the dental burr from the shoulder to the second end thereof. The length of the cutting projection beyond the shoulder to the second end is of a predetermined and specific length. So as to initially penetrate or bore into the tooth structure, in the event that the dentist should not choose otherwise to use a twist drill to make a pilot bore, the dental burr of the present may generally be contoured at its second end in a manner so that when the second end — the outer end of the dental burr — is placed against a surface of a tooth and the dental burr is rotationally driven, and at the same time a slight axially directed pressure is applied along the dental burr against the tooth's surface, a cutting or boring action by the dental burr into the tooth surface will occur. The present invention also provides methods of manufacture for the dental burr. Essentially, the method that is proposed hereby comprises at least the steps of machining the generally cylindrical cutting portion of the dental burr which is located at the second end thereof, by forming a cutting groove or grooves that may be formed generally spirally in the outer periphery thereof. Alternatively, the cutting portion of the dental burr may have a surface formed thereon so as to be an abrading or grinding surface, such as by the secure deposition of an abrading medium such as diamond chips or diamond dust. Also, the manufacture of a dental burr in keeping with the present invention requires that a cylindrical intermediate portion shall be formed so that it terminates in a shoulder that is located near the second end of the burr. Thus, the shoulder projects radially outwardly from the cutting portion of the burr at a place which is located at a predetermined and specific length from the second end thereof — that distance being the length of the cutting projection. OBJECT OF THE INVENTION: It is a principal object of this invention to provide a dental burr for use in preparation of a tooth for subsequent placement of a crown or inlay, or other crown or bridge prosthodontics procedure, whereby initial depth gauging grooves may by cut into the tooth structure — the tooth enamel and/or dentin — for subsequent gross removal of tooth structure between the initial depth gauging grooves in dental reduction procedures. Accordingly, it is a purpose of this invention to provide a dental burr which has a cutting projection of a predetermined and specific length, so that grooves of a specific depth may be prepared and cut into the tooth structure. A further object of the invention is to provide methods by which the dental burrs of the present invention may be manufactured. BRIEF DESCRIPTION OF THE DRAWINGS: The present invention will now be discussed in association with the accompanying drawings, which are for purposes of example only, and in which: Figure 1(a) shows a typical side elevation representation of a dental burr in keeping with this invention; Figure 1(b) shows a typical end view of the dental burr of Figure 1(a); Figures 2(a) and 2(b) show a side elevation and a partial side elevation of two further dental burrs in keeping with the present invention, having a different length of cutting projection, and a different grinding surface on the cutting projection, respectively; Figure 3 is an exploded view of one form of dental burr in keeping with the present invention, and illustrates a step taken during the manufacture of that particular dental burr; and Figure 4 shows typical representations of prior art dental burrs and grinding tools, being a grinding wheel, a typical slightly tapered burr, and a finishing stone, in Figure 4(a), 4(b), and 4(c), respectively. DESCRD7TION OF THE PREFERRED EMBODIMENTS: Referring to Figure 1(a), a dental burr that is generally designated at 10, is shown. The dental burr has a body 12 which has a stem 14 that is adapted for placement at the first end 16 of the dental burr 10 into a driving implement such as a dental handpiece, so that rotational driving force may be imparted to the dental burr 10. At the second or opposite end 18 of the dental burr 10, there is located a cutting projection 20. The cutting projection 20 in the dental burr 10 of Figure 1(a) has one or more cutting grooves 22 formed generally spirally in the outer periphery of the cutting projection 20. Thus, the cutting groove or grooves 22 essentially cause the cutting projection 20 to act as a milling cutter which cuts into the tooth structure along the periphery of the cutting projection 20. There is an intermediate portion 24 of the body of the dental burr 10, which is axially located between the first end 16 and the second end 18 thereof. In general, the intermediate portion 24 is generally cylindrical, and it is formed so that it has a diameter which is greater than the diameter of the cutting projection 20. Thus, the cutting projection 20 extends from the intermediate portion 24, and the intermediate portion 24 terminates in a shoulder 26 that is located near the second end 18 of the dental burr 10. The shoulder 26 is substantially planar, and it projects radially outwardly from the cutting projection 20. In keeping with one of the principals of the present invention, the length of the cutting projection 20 beyond the shoulder 26 to the second end 18 is of a predetermined and specific length. As also indicated in Figure 1(b), which shows the end projection of the second end 18 of the dental bun 10, the face of the second end 18 may be contoured as at 28 in such a manner that, when the second end 18 is placed against the surface of a tooth and the dental burr 10 is rotationally driven, and a slight axially directed pressure is applied along the dental burr 10 against the tooth surface, then a cutting action by the dental burr 10 into the tooth surface will occur because of the contours at 28. There are two differences in the dental burrs shown in Figures 2(a) and 2(b) than that of Figure 1(a), and between each other. The first is that the length of the cutting projection of each of the burrs of Figures 2(a) and 2(b) is longer than the cutting projection 20 of the Figure 1(a) embodiment; and the other is that the cutting or outer surface of the cutting projection 20(b) is formed with an alternative cutting arrangement Thus, intermediate portion 24(a) and the cutting portion 20(a) as shown in Figure 2(a) are shorter, and longer, respectively, than the intermediate portion 24 and cutting projection 20 of the dental burr of Figure 1(a). Intermediate portion 24(b) and cutting projection 20(b) of the dental burr of Figure 2(b) may be of the same length as those in Figure 2(a), but the cutting projection 20(b) is differently formed by having a grinding or abrading surface 30. The grinding or abrading surface 30 may be formed by cementing or otherwise securing diamond chips or diamond dust to a steel core, in a manner well known in the dental armamentarium industry. Of course, as will become evident hereafter, the length of any projection 20, 20(a), or 20(b), is predetermined and of a specific length, so that a groove cut into the tooth structure using the dental burr will have a specific depth. This specific depth is, of course, achieved because of the interference of the shoulder 26 with the outer surface of the tooth structure when the cutting projection 20 has extended sufficiently far into the tooth structure as to cause that interference to occur. At that point, it is obvious that the dentist needs merely to guide the dental burr along the tooth in a predetermined direction — which might be axially along the tooth or across the base of the tooth in the gingival portion thereof, for example. Because the length of the cutting projection 20 is predetermined, then the dentist is assured that he will cut a groove of the same depth as the length of that cutting projection, no matter what the contour of the tooth may be. During the cutting operation, the dental burr is driven by the handpiece, and is held so as to extend substantially perpendicularly away from the surface of the tooth, no matter what its contour. Accordingly, dental crown preparation on any tooth may be easily accomplished, no matter what the contour or curvature, or other surface formation, that tooth may have, with the assurance that the dental reduction will be constant at a predetermined depth. Referring briefly to Figure 3, a step in the formation of a dental burr is shown, whereby an already manufactured dental burr which may generally have a cutting portion 32 has been provided, where the length of the cutting portion 32 is longer than the intended length of the cutting projection 20 that will be formed. Accordingly, the cylindrical intermediate portion 24 may be formed by having a sleeve 34 which is fixed in place, and which is placed over the dental burr in a direction indicated by arrows 36. It is clear that upon completion of the step of placing the sleeve 34 over the cutting portion 32, a dental burr having the general appearance of that in Figure 1(a) will have been made. In that case, therefore, the cutting groove or grooves 22 that are formed in the cutting portion 32 will extend beneath the sleeve 34. It is contemplated that spiral, or double-spiral channels could be cut into the outer periphery of the intermediate portion 24 so that coolant may be delivered from that channel into the depth gauge grooves being cut into the tooth structure. Moreover, when a dental burr is manufactured in the manner discussed immediately above, with respect to Figure 3, it is also possible that spiral channels could be cut or machined into the inner surface of the sleeve 34, before it is placed over the dental burr in the manner shown. Those spiral channels cut into the inner surface of the sleeve 34 would be formed so as to be parallel to the cutting grooves that are already present in the cutting portion 32 of the dental burr, and would therefore be arranged so as to deliver coolant internally of the sleeve 34 to the tooth, with the coolant exiting from beneath the sleeve 34 at the shoulder 26. It is also possible that the dental burr 10 might have been machined in such a manner that a raw piece of appropriate bar stock is cut so as to form the stem 14, the intermediate portion 24, and the cutting projection 20, and thereafter the cutting projection 20 is either machined or otherwise treated so as to place cutting grooves 22 or a grinding or abrading surface such as 30, on the cutting projection 20. Briefly referring to the prior art shown in Figure 4, Figure 4(a) shows a typically grinding wheel 40, which may be used for a variety of purposes including the gross reduction of the tooth structure between the grooves that have been placed in the tooth structure using the dental burr of the present invention. Usually, the surface 42 of such a grinding wheel is coated with diamond chips or diamond dust. Likewise, the burr 44 shown in Figure 4(b) is a typical burr that has been slightly tapered, and is the sort that has been previously used prior to availability of dental burrs according to the present invention to cut the initial grooves into the surface of a tooth, where the length of the groove is the length of the burr or at least the portion of the burr that is in contact with the surface of the tooth, as discussed above. As noted, the depth of the groove cut by such a burr 44 is determined usually by part of the diameter of the burr, up to or exceeding its full diameter, and is therefore dependent on the skill of the dentist in judging when the burr has ground into the tooth structure for the appropriate part of its diameter or its full diameter. The surface 46 of a burr 44 may have a number of spirally cut grooves or milling edges, or alternatively it may be coated with diamond chips or diamond dust. The finishing stone 48, shown in Figure 4(c) may serve the same general purposes of the grinding wheel 40, discussed above. The finishing stone 48 has a configuration that is essentially spherical, and is one that is particularly used for lingual reduction of a tooth. Using this tool, a series of potholes are sunk into the lingual surface of the tooth up to one-half or some other portion of the diameter of the stone, so as to establish a depth gauge, and then to finish the reduction by connecting the established potholes using the same tool. Generally, the surface 50 is coated with diamond chips or diamond dust. One of the objectives of the present invention is to permit the dentist who is performing the crown preparation procedure to choose an appropriate dental burr whereby the depth of the grooves that he proposes to cut will be at the predetermined depth that he has decided that they should be. This selection can be accomplished, for example, by colour coding the dental burrs so that at least the intermediate portion 24 of any dental burr may have a specific colour formed on its outer periphery, where the colour is chosen so as to be indicative of the length of the cutting projection beyond the shoulder. Also, to make the choice of a specific dental burr even more easy, the colour of the intermediate portion may be chosen so as to be mutually distinctive from any other colour that may be chosen so as to be indicative of another specific length of the cutting portion. Of course, the colour of the intermediate portion 24 may be arrived at by choosing different colours of sleeves, if that is the manner by which the dental burr has been manufactured, or by anodizing or heat-treating, or by any other method such as applying an enamel, so long as the dental burr that has been thereby produced has a structure that is approved by the appropriate health authorities for use in the mouth. The methods of manufacture of the dental burr, in keeping with the present invention, thereby require that the dental burr 10 comprises a body 12 having a stem portion 14 and a first end 16 thereof, a cutting projection 20 at a second end 18 thereof, and a cylindrical intermediate portion 24 that is axially located between the first and second ends, and wherein the method at least comprises the steps of: (a) preparing the generally cylindrical cutting portion 20 so as to have a cutting or grinding surface formed therein; and (b) forming the cylindrical intermediate portion 24 so that it terminates in a shoulder 26 that is located near the second end 18, and so that the shoulder 26 projects radially outwardly from the cutting portion 20 at a place which is located at a predetermined and specific length from the second end 18. As suggested above, the cylindrical intermediate portion 24 can be formed by placing a cylindrical sleeve 34, which has a planar end 38, over the cutting portion 32 of a dental burr, and fixing it in place so that the planar end 38 forms the shoulder 26. Of course, the second face 18 of the dental burr may be machined so as to have a cutting contour formed therein, as noted above. Likewise, the cylindrical intermediate portion 24 of the dental burr, no matter how it is manufactured, may be colour treated so that the colour of the cylindrical intermediate portion 24 is chosen so as to be indicative of the length of the cutting projection 20 beyond the shoulder 26, and generally also so that the colour is mutually distinctive of any other colour that has been chosen to be indicative of another specific length of the cutting projection 20 beyond the shoulder 26. The present inventor is the Registrant of a Canadian Registered Industrial Design, Registration No. 70,775, issued June 5, 1992, for a Dental Burr. However, the dental burr of that Industrial Design Registration was contemplated more as having a cutting front face, with a spirally formed groove in a short front, coaxial projection, as well as a plurality of longitudinal ridges. That dental bun- was intended more to function as a twist drill, in slow-speed handpieces, so as to establish a pilot hole of a specific depth, for other purposes. It should be noted that dental burrs in keeping with the present invention are generally used in air-driven turbine handpieces, as opposed to mechanically driven handpieces. Mechanically driven handpieces tend to rotate at relatively low speeds, whereas air-driven turbine handpieces may have rotational speeds of upwards of 60,000 RPM and up to 300,000 RPM. This, of course, causes less discomfort to the patient and makes control of the cutting operation by the dentist more easy. Use of dental burrs in keeping with the present invention results in several immediate advantages. First, of course, the depth of the groove to be cut by the dentist so as to establish the amount of reduction that shall occur, can be exactly determined. Accordingly, the dental prosthetic laboratory can provide an accurate crown or partial crown structure or other dental prosthodontics casting, with the assurance that it replicates the prior outer surface of the tooth to which it is being fixed. This, in turn, reduces costs to the dental prosthetic laboratory, costs to the dentist, and costs to the patient. It is intended that dental burrs in keeping with the present invention shall only be used once for a dental crown preparation, and then discarded. That is because the dental burrs may be very economically produced and provided to the dentist. Moreover, it generally results in the dentist having only to use a single dental burr in keeping with this invention, during a crown procedure, instead of having to use several different burrs depending on whether the dentist is working on the labial or lingual surfaces of the tooth, in the gingival region of the tooth, or whether the tooth is physically large or small. In any event, by being assured ahead of time that the procedure will result in the desired dental reduction, the dentist, may, in fact, reduce the time required for the procedure. This, in turn, reduces the fatigue that might otherwise be experienced by both the dentist and the patient. Particularly when the dentist is preparing the tooth structure during the dental reduction procedure in the gingival area, use of dental burrs in keeping with the present invention permit more easy and accurate preparation for the shoulder of the crown to be manufactured. That shoulder may, depending on various factors including what tooth is being worked on, what the purpose of the crown or inlay may be, the practice of the dentist and/or the practice of the dental prosthetic laboratory, might be a butt shoulder, a chamfer or stepped-chamfer shoulder, or one that is bevelled, and so on. The accuracy of the contour to be formed, however, is more easily assured; and also there is less likelihood of trauma for the patient. Of course, dental burrs of the present invention can also be used in other related crown or dental preparation procedures such as repair of a pre-existing restoration such as old crown, or even an old filling — especially fillings that have been placed in the labial or lingual surfaces of the tooth. In each case, a very specific depth and area of restoration may be assured, as discussed above. Indeed, it is noted that there is now an increasing concern among patients and, to some extent, the dental profession, concerning the presence of silver-amalgam fillings or restorations that may have been placed in the teeth of patients many years ago, or even just recently. As at the filing date of this Application, silver- amalgam restorations are not allowed in Sweden. The concern is that mercury may evaporate or otherwise dis-associate itself from the silver-amalgam restoration at the surface thereof, and become systemic within the body of the patient. Thus, there is now some movement toward replacing silver-amalgam restorations from otherwise healthy teeth. In that case, only a portion of the old filling needs to be removed because it is only at the surface of the filling that a new non-amalgamated material needs to be placed. Thus, the dental burr of the present invention can be used to define the periphery of the portion of the silver- amalgam restoration to be removed, as well as to define its depth in the manner discussed above, so that no trauma is caused to the otherwise healthy tooth. This represents a further area of tooth preparation where dental burrs of the present invention can easily be used at lesser expense and without the risk of trauma, than otherwise would be the case. Dental burrs in keeping with the present invention would normally, therefore, be supplied to the dentist in protective, sealed and sterile packaging. It is possible that the dentist may choose to re-sterilize the dental burr in a dental autoclave, in which case the structure of the burr and perhaps even the colour coding on the burr should not be such that it would be destroyed by an autoclave sterilization procedure. Such procedures are not recommended, but might be carried out, especially by dentists in third-world countries where an ongoing and assured supply of new dental burrs might be problematic. In any event, dental burrs in keeping with the present invention assure a more efficient dental crown procedure, either in terms of costs or of time allotted for that procedure, with greater assurance that when the crown is fitted to the tooth it will exactly serve its purpose without additional preparation procedures either by the dentist or the dental prosthetic laboratory. The scope of the present invention is defined by the accompanying claims.

Claims: WHAT IS CLAIMED IS: 1. A dental burr (10) for use in preparation of a tooth for subsequent placement of a crown or inlay, or other crown or bridge prosthodontics procedure, wherein said dental burr is c h a r a c t e r i z e d b y: a body (12) having a stem (14) adapted for placement at a first end (16) thereof into a driving implement so as to impart rotational driving force at at least 60,000 RPM to said dental burr; a cutting projection (20) at a second end (18) of said body, which cutting projection is substantially cylindrical and has at its outer periphery a cutting surface (22, 30, 32) which can cut into the enamel and/or dentin of a tooth; and an intermediate portion (24) of said body, axially located between said first end and said second end; wherein said intermediate portion is generally cylindrical, and has a diameter which is greater than the diameter of said cutting projection; wherein said cylindrical intermediate position terminates in a shoulder (26) located near said second end of said body, and said shoulder is substantially planar and projects radially outwardly from said cutting projection; and wherein the length of said cutting projection beyond said shoulder to said second end is of a predetermined and specific length. 2. The dental burr of claim 1, wherein the face of said dental burr at said second end is contoured in a manner that when said second end is placed against a surface of a tooth and said dental burr is rotationally driven, and slight axially directed pressure is applied along said dental burr against said tooth surface, cutting action by said dental burr into said tooth surface will occur. 3. The dental burr of claim 1, wherein said surface of said cutting projection is formed by having a cutting groove (22, 32) or grooves formed generally spirally in the outer periphery thereof. 4. The dental burr of claim 1, wherein said surface of said cutting projection is formed by having an abrading medium (30) deposited and secured on the outer periphery thereof. 5. The dental burr of claim 4, wherein said abrading medium is diamond chips or diamond dust. 6. The dental burr of claim 1, wherein said cutting projection is at the outward end of a cutting portion of said body, and said cutting portion has greater length than said cutting projection, and wherein said cylindrical intermediate portion is a sleeve (34) which is fixed in place over said cutting portion. 7. The dental burr of claim 3, wherein said spirally formed cutting groove or grooves in said outer periphery of said cutting portion also extend beneath said sleeve. 8. The dental burr of claim 1 , wherein said intermediate portion has a specific colour on its outer periphery, and the colour is chosen so as to be indicative of the length of said cutting projection beyond said shoulder. 9. The dental burr of claim 8, wherein the colour of said intermediate portion is chosen so as to be mutually distinctive from any other colour chosen so as to be indicative of a specific length of said cutting projection. 10. The dental burr of claim 6, wherein said sleeve has a specific colour on its outer periphery, and the colour is chosen so as to be indicative of the length of said cutting projection beyond said shoulder. 1 1. The dental burr of claim 10, wherein the colour of said sleeve is chosen so as to be mutually distinctive from any other colour chosen so as to be indicative of a specific length of said cutting projection. 12. A method of manufacture for a dental burr (10) intended to be rotationally driven at at least 60,000 RPM, wherein said dental burr comprises a body (12) having a stem portion (14) at a first end (16) thereof, a generally cylindrical cutting projection (20) at a second end (18) thereof, and a cylindrical intermediate portion (24) axially located between said first and second ends, wherein said method is c h a r a c t e r i z e d b y the steps of: (a) preparing said generally cylindrical cutting projection so as to have a cutting surface (22, 30, 32) formed in the outer periphery thereof, which cutting surface can cut into the enamel and/or dentin of a tooth; and (b) forming said cylindrical intermediate portion so that it terminates in a shoulder (26) located near said second end, so as to project radially outwardly from said cutting portion at a place which is located at a predetermined and specific length from said second end. 13. The method of claim 12, wherein said cutting surface of said cutting projection is formed by machining the outer periphery thereof so as to have a cutting groove (22, 32) or grooves formed generally spirally therein. 14. The method of claim 12, wherein said cutting surface of said cutting projection is formed by securing an abrading medium (30) on the outer periphery thereof. 15. The method of claim 14, wherein said abrading medium is diamond chips or diamond dust. 16. The method of claim 12, wherein said cylindrical intermediate portion is formed by placing a cylindrical sleeve (34) having a planar end over said cutting portion and fixing it in place such that said planar end forms said shoulder which is located at a predetermined and specific length from said second end. 17. The method of claim 12, wherein the face of said dental burr at said second end is machined so as to have a cutting contour (28) formed therein. 18. The method of claim 12, wherein said cylindrical intermediate portion is treated so as to have a specific colour on its outer periphery, and the colour is chosen so as to be indicative of the length of said cutting projection beyond said shoulder. 19. The method of claim 18, wherein the colour of said intermediate portion is chosen so as to be mutually distinctive from any other colour chosen to be indicative of a specific length of said cutting projection. 20. The method of claim 16, wherein said cylindrical sleeve is treated so as to have a specific colour on its outer periphery, and the colour is chosen so as to be indicative of the length of said cutting projection beyond said shoulder. 21. The method of claim 20, wherein the colour of said sleeve is chosen so as to be mutually distinctive from any other colour chosen to be indicative of a specific length of said cutting projection.

Inventors: WAUCHOPE FREDERICK T, WAUCHOPE, FREDERICK, T.
Applicants: 1162362 ONTARIO INC, 1162362 ONTARIO INC.
Application year: 1995
Main classification: A61C3
IPC codes: A61C3