Abstract:
A drill bit for drilling through bone is disclosed. The drill bit comprises an elongated fluted portion that terminates in an end face that is oriented substantially transverse to a longitudinal axis of the fluted portion. The drill bit further comprises a trocar tip protruding from the end face of the fluted portion. The trocar tip comprises a base and terminates in a pointed end. The end face of the fluted portion extends radially beyond and surrounds the base of the trocar tip.

Description:
RELATED APPLICATION 
     This application is a continuation of U.S. patent application Ser. No. 12/328,310 (filed on Dec. 4, 2008; now U.S. Pat. No. 8,226,654 B2), the entirety of which is incorporated herein by reference. 
    
    
     TECHNICAL FIELD 
     The present disclosure relates generally to drill bits for use in medical procedures. 
     BACKGROUND 
     Since the discovery that titanium can fuse to bone, titanium dental implants have represented a growing field of dental reconstruction technology for replacing natural teeth. During implantation, a hole is drilled through the bone after the tissue has been retracted or through the gingiva, the gums surrounding the root of a tooth, and into the jawbone. A titanium or titanium alloy implant is then fixed within the hole of the jawbone. Over a period of months, the titanium implant fuses to the jawbone through a process called osseointegration. A replacement tooth can then be attached to the implant. 
     The human jaw comprises two types of bone. A very hard, dense cortical bone layer surrounds an interior of softer cancellous bone. Conventional implantation techniques require several steps involving the use of a series of drill bits to form the hole in the jawbone where the titanium implant will be located. In a first step, a round burr drill bit is used to penetrate the hard outer cortical bone. Second, a standard, fluted twist drill bit is used to create a hole in the softer bone for the implant. Next, a series of holes of increasing diameter are subsequently formed using fluted twist drill bits having increasing diameters, until the desired implant hole size is achieved. Typical diameters for the fluted twist drill bits include, for example, 2.2 mm, 2.8 mm, 3.5 mm, and 4.2 mm. A countersink drill bit, also known as a pilot or step drill bit, may be used to broaden the opening of the hole to the diameter of the next larger fluted twist drill bit. An optional further step of tapering the top of the hole may also be performed using a countersink drill bit, also known as a profile drill bit, depending on how the implant is to be placed within the bone, for example, if the coronal neck of the implant is placed flush with the bone. 
     Thus, conventional implant procedures require a series of drillings beginning with the cutting of the cortical bone followed by a series of drillings to form and expand the hole. In traditional implant procedures, a total of five or more drill bits, including the burr drill bit, may be used to place a single implant. For patients, especially those requiring multiple implants, the need to use multiple drill bits may result in a very long and uncomfortable multiple-step procedure. Similar multiple-step drilling procedures are also used in other medical procedures that require drilling in bone. Thus, there is a long-felt need in the industry for a tool that can reduce the number of steps and/or drill bits in such procedures. 
     Although the present disclosure may obviate one or more of the above-mentioned disadvantages, it should be understood that some aspects of the invention might not necessarily obviate one or more of those disadvantages. 
     SUMMARY 
     In accordance with various exemplary embodiments, the present teachings contemplate drill bits having a trocar tip for use in medical procedures. Drill bits according to various embodiments of the invention may further comprise a countersink. Drill bits as described herein may, for example when used in performing dental procedures, can cut through both the cortical bone and the cancellous bone, and may therefore reduce the number of steps and/or drill bits needed for such procedures. 
     The term “trocar tip” as used herein may refer to a tip formed by a plurality of sides ending in a point. By way of example only, a trocar tip may comprise the form of a three-sided pyramid. In various exemplary embodiments, the trocar tip may be capable of penetrating and cutting cortical bone. In various exemplary embodiments, the drill bits having a trocar tip may be used in medical procedures that require drilling through other types of bone. 
     The term “drill bit” as used herein may refer to a tool meant to cut holes by rotating around an axis, such as, for example, a central, longitudinal axis. The term drill bit encompasses, for example, dental burrs and medical tools designed to create holes in bone and other tissue. 
     The term “countersink drill bit” as used herein may refer to a tool meant to broaden the opening of a hole, increase the diameter of a hole for a subsequent drill bit, or provide a guide for determining the depth of the hole. Thus, the term “countersink drill bit” as used herein encompasses drill bits that provide the function of drill bits known as pilot drill bits, step drill bits, and stop drill bits. 
     In the following description, certain aspects and embodiments will become evident. It should be understood that the invention, in its broadest sense, could be practiced without having one or more features of these aspects and embodiments. It should be understood that these aspects and embodiments are merely exemplary and explanatory and are not restrictive of the present teachings or claims. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The following figures, which are incorporated in and constitute a part of the specification, serve to further illustrate exemplary embodiments of the present teachings. The figures are not, however, intended to be restrictive of the present teachings or claims. In the drawings, 
         FIG. 1  is a side view of a drill bit according to an exemplary embodiment of the present teachings; 
         FIG. 2  is an end view of the drill bit of  FIG. 1  looking along the axis A from the trocar-tipped end of the drill bit; 
         FIG. 3  is a side view of a drill bit according to another exemplary embodiment of the present disclosure; 
         FIG. 4  is an end view of the drill bit of  FIG. 3  looking in along the axis B from the trocar-tipped end of the drill bit; and 
         FIG. 5  is a side view of a drill bit with a sleeve according to an exemplary embodiment of the present disclosure. 
     
    
    
     DESCRIPTION OF EXEMPLARY EMBODIMENTS 
     Reference will now be made to various exemplary embodiments, at least one example of which is illustrated in the accompanying figures. However, these various exemplary embodiments are not intended to limit the disclosure. To the contrary, the disclosure is intended to cover alternatives, modifications, and equivalents. 
     The present disclosure contemplates various exemplary embodiments for a drill bit having a trocar tip. The drill bit may be used to perform medical procedures, such as, for example, dental procedures. For example, the drill bit may be used for implanting dental implants. While not wishing to be bound by theory, it is believed that in procedures for implanting dental implants, the trocar tip not only cuts through the hard, cortical bone, but also stabilizes other portions of the drill bit as they are cutting by acting as a guide. 
     According to various exemplary embodiments of the present disclosure, the drill bit may comprise at least one material chosen from metals and ceramic. Examples of metals that may be used include, by way of example only, stainless steel, high speed steel, and carbide alloys. In at least one embodiment, the drill bit may comprise two or more different materials. It is well within the ability of those ordinarily skilled in the art to determine whether a material is suitable for the drill bit, taking into consideration, for example, the intended use of the drill bit, whether it will be used once and discarded or reusable, etc. 
     In various exemplary embodiments, the drill bit may have coatings formed on the surface thereof. For example, the drill bit may have a carbide or diamond coating, chrome plating, titanium nitride, or any other coating known to those ordinarily skilled in the art. In at least one embodiment, the drill bit may have a tungsten carbide coating. In at least one further embodiment of the present disclosure, the drill bit may comprise a coating on the cutting surfaces of the drill bit. 
     The drill bit according to various embodiments may comprise a plurality of lengths and diameters. For example, the drill bit may have a cutting length, i.e., the depth of the hole formed by the drill bit, ranging from about 6 mm to about 10 mm, or may be shorter or longer. For example, the drill bit may have a cutting length of about 14 mm. Drill bits of any cutting length are contemplated, and the appropriate length may be selected based on, for example, the intended use of the drill bit. According to at least one exemplary embodiment, the drill bit may have a diameter ranging from about 2.2 mm to about 4.2 mm. Drill bits having a smaller or larger diameter are also contemplated and the diameter may be chosen according to, for example, the intended use of the drill bit. 
     The trocar tip according to at least one embodiment of the present disclosure comprises a plurality of sides terminating in a point. The sides of the trocar tip may be, for example, curved or straight. 
     The appropriate length of the trocar tip may depend on, in various embodiments, the thickness of the cortical bone to be cut. For example, a trocar tip having a length of about 0.6 mm (i.e., measured along a longitudinal axis of the drill bit, such as axis A shown in  FIG. 1 ) can be used in various exemplary embodiments to cut through the cortical bone of an average jaw. In one exemplary embodiment, the length of the trocar tip may be more or less, for example depending on the thickness of the cortical bone. 
     The appropriate number of sides and angle of the sides of the trocar tip may vary, for example depending on the intended use of the drill bit. It is well within the ability of those having ordinary skill in the art to determine the optimal number and angle of the sides of the trocar tip for any particular application. For example, the number and angle of the sides may be determined according to the thickness of the cortical bone to be bored. In one exemplary embodiment, a trocar tip may have three sides. In a further exemplary embodiment, the sides of the trocar tip may be formed at an angle of about 5° to about 15° relative to the longitudinal axis and cutting edge of the drill bit. For example, the angle of the sides may be about 8° relative to the longitudinal axis of the drill bit. 
     In at least one embodiment of the present disclosure, the drill bit comprises a trocar tip and a fluted portion. An example of a drill bit comprising a trocar tip and a fluted portion is shown in  FIG. 1 . In  FIG. 1 , exemplary drill bit  100  comprises a trocar tip  110  at one end of the drill bit along a longitudinal axis A. Trocar tip  110  terminates in a point and has sides tapered at an angle α relative to longitudinal axis A. 
     Drill bit  100  may further comprise a fluted portion  120 , having a plurality of flutes  140 . Fluted portion  120  may be, for example, cylindrical or frustoconical in shape, i.e., the fluted portion may have straight or tapered sides. Drill bit  100  may comprise any number of flutes  140 , such as, for example, from 2 to 6 flutes. Flutes  140  may be formed in any pattern, such as a helical pattern as shown in  FIG. 1 . In other embodiments, the flutes may be formed in other patterns, such as, for example, parallel to axis A. 
     Adjacent trocar tip  110 , fluted portion  120  terminates in primary cutting edges  130 , with one primary cutting edge for each flute in the fluted portion, wherein the primary cutting edges may optionally be in a plane substantially perpendicular to axis A. Primary cutting edges  130  may be formed with a cutting angle, for example, ranging from about 5° to about 20° with respect to a plane perpendicular to axis A. Without wishing to be limited by theory, it is believed that forming the primary cutting edges substantially perpendicular to axis A reduces the production of heat and vibration during drilling. The cross-sectional area of primary cutting edges  130  within a plane perpendicular to axis A is greater than the largest cross-sectional area of trocar tip  110  taken in any plane perpendicular to axis A. Thus, primary cutting edges  130  radially extend further from axis A than trocar tip  110 . 
     Secondary cutting edges  135  may optionally be positioned between primary cutting edges  130  and the remainder of the flutes  140 . Secondary cutting edges  135  may have a cutting angle, for example ranging from about 25° to about 50° relative to the plane perpendicular to axis A. 
     Drill bit  100  may optionally comprise at least one depth marking  150 . Depth markings  150  indicate how far drill bit  100  has penetrated. While the markings may be made in any known fashion, in at least one embodiment, depth markings  150  are marked by laser. Depth markings may be made at any desired location on the drill bit. 
     Drill bit  100  may also comprise a shank portion  170  at an end opposite trocar tip  110 , which may optionally comprise a shaft  180  and a locking portion  190 . Shaft  180  may be straight or tapered. Locking portion  190  may be designed to matingly fit to a drill engine, such as, for example, a dental handpiece. Locking portion  190 , may be, for example, a dental “T” latch, a surgical J notch, or friction fitting. One skilled in the art would recognize that the present disclosure encompasses other locking portions and that the choice of locking portion depends on the intended use of the drill bit. 
       FIG. 2  is a view of exemplary drill bit  100  as viewed in a direction along axis A from the trocar-tipped end of the drill bit  100 . As seen in  FIG. 2 , trocar tip  110  is pyramidal in shape and comprises three sides  112  that meet at point  114 . Sides  112  may be planar or curved. Trocar tip  110  may comprise any number of sides, such as, for example, from 3 to 8 sides or more, depending upon the intended application.  FIG. 2  also shows primary and secondary cutting edges  130  and  135 , as well as the curved flutes  140 . 
     In at least one embodiment of the present disclosure, the trocar-tipped drill bit may comprise a countersink portion.  FIG. 3  shows an exemplary drill bit  300  comprising trocar tip  310 , fluted portion  320 , and countersink portion  360 . The sides of trocar tip  310  are tapered at an angle α relative to longitudinal axis B. 
     Fluted portion  320  may comprise a plurality of flutes  340  that may terminate in primary cutting edges  330  and secondary cutting edges  335 . Depth markings  350  mark different cutting depths along the length of drill bit  300 . 
     Countersink portion  360  may be tapered and may comprise flutes  365 . The tapered edges of countersink portion  360  may allow the opening of the hole to be enlarged. 
     Drill bit  300  also comprises shank portion  370 , which has a shaft  380  and fitting portion  390  for attachment to a drill engine, e.g., a dental handpiece. 
     A view of exemplary drill bit  300  along longitudinal axis B and from the trocar-tipped end of the drill bit  300  is shown in  FIG. 4 ,  FIG. 4  shows trocar tip  310  having sides  312  meeting at point  314 . Curved flutes  340  may terminate in primary and secondary cutting edges  330  and  335 , respectively. Countersink portion  360  may comprise a plurality of flutes  365  for enlarging the opening of the hole. 
     In at least one embodiment of the present disclosure, the drill bit may further comprise a sleeve that covers at least a portion of the drill bit to control the depth of penetration through or into the bone. For example, with reference to  FIG. 5 , an exemplary drill bit  500  comprises trocar tip  510 , fluted portion  520 , and shank portion  570 . Sleeve  600  is fitted over the drill bit  500  to control the depth of the drilling. The sleeve  600  may be permanently or temporarily attached to the drill bit  500 . For example, the sleeve  600  may be either permanently or temporarily adhered to the drill bit  500 , or the sleeve  600  may snap on the drill bit. The sleeve  600  may be formed of any suitable material or materials, such as, for example, metal, ceramic, and/or plastic. 
     In exemplary embodiments comprising a countersink, the length and angle of the countersink may be selected according to the intended use of the drill bit. For example, the size and angle of the countersink may be selected to match the shape of a dental implant. By way of example only, a 2.2 mm diameter drill bit may have a countersink with a length of about 1.8 mm and a taper angle of about 18° to about 80° relative to the central axis of the drill bit. In one exemplary embodiment, the taper angle of the countersink may be about 33° relative to the central axis of the drill bit. The angle of the countersink may also vary based on the diameter of the drill bit. 
     In various exemplary embodiments, drill bits according to the present disclosure may be used in series to sequentially expand the diameter of the hole. In at least one embodiment, each of the drill bits may have a trocar tip. Alternatively, only the drill bits cutting through cortical bone may have a trocar tip. Alternatively, in various embodiments, the hole for the implant can be formed using a single drill bit that cuts through the cortical bone and the cancellous bone and has a diameter corresponding to the diameter of the implant being used. In various exemplary embodiments, when the drill bit has a countersink, a single drill bit may form an enlarged opening via the countersink portion that may allow an implant to be inserted below the bone. 
     The present teachings also contemplate a method for drilling holes in cortical and/or cancellous bone, as well as drilling in soft tissues. 
     In at least one exemplary embodiment, a method for drilling holes in cortical and/or cancellous bone includes drilling through cortical bone and/or soft tissue with a trocar tip disposed on an end of a drill bit and optionally drilling through cancellous bone with a fluted portion of the drill bit. The trocar tip may guide and stabilize the fluted portion. The method may further include enlarging the hole opening with a countersink portion of the drill bit. The entire procedure of drilling through the cortical bone and/or soft tissue, drilling through the cancellous bone, and enlarging the hole opening can be performed without retracting the drill bit until the hole opening has been enlarged. In at least one embodiment, the cortical bone and/or cancellous bone comprises a portion of a human jawbone. 
     It is noted that, as used in this specification and the appended claims, the singular forms “a,” “an,” and “the,” include plural referents unless expressly and unequivocally limited to one referent. Thus, for example, reference to “a flute” can refer to one, two, or more flutes. As used herein, the term “include” and its grammatical variants are intended to be non-limiting, such that recitation of items in a list is not to the exclusion of other like items that can be substituted or added to the listed items. 
     It will be apparent to those skilled in the art that various modifications and variation can be made to the drill bits and methods of the present disclosure without departing from the scope its teachings. Other embodiments of the disclosure will be apparent to those skilled in the art from consideration of the specification and practice of the teachings disclosed herein. It is intended that the embodiments described in the specification be considered as exemplary only.