Dentistry – Apparatus – Tool bit
Reexamination Certificate
2001-08-01
2003-11-04
Shaver, Kevin (Department: 3732)
Dentistry
Apparatus
Tool bit
Reexamination Certificate
active
06641395
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The invention relates to dental surgical instruments for use in the field of oral surgery, and, more particularly, to dental drill bits for use in the field of dental implantology for preparing surgical sites for placement of endosseous dental implants.
2. Description of the Related Art
Dental implants are surgically implanted in a patient's jawbone to provide securement anchors for prosthetic devices such as artificial teeth, crowns, bridges, dentures and the like. Dental implants allow people who lose their teeth to be able to comfortably smile, speak, and chew.
An oral surgeon installs a dental implant by first making an incision in the patient's gum or gingiva. Next, a hole or osteotomy is formed in the jawbone of the patient. This may involve widening of a pre-existing cavity or the formation of a fresh one. The implant is then inserted and/or threaded into the osteotomy. More than one osteotomy may be prepared to support a plurality of implants. Once the implant is properly secured in the osteotomy a healing screw is threaded tightly over the implant to seal it from bacterial infection and the gums are sutured over the sealed implant to allow the bone and surrounding tissues to heal.
During this initial healing period bone is allowed to grow and surround and retain the implant. This process is called “osseointegration.” The gum tissue is also allowed to heal over the implant and the healing screw. For implants in the mandible (lower jaw), healing typically requires about three months; for implants in the maxilla (upper jaw), the healing period is usually about six months.
After the initial healing period, the overlying gum tissues are reopened by making an incision and the healing screw is removed. A suitable healing abutment is attached to the implant and extends supragingivally through the surrounding gum tissues. A second healing period ensues in which the gum tissue is allowed to heal around the healing abutment. Typically, this second healing period lasts from four to eight weeks.
After the second healing period, the healing abutment is removed from the implant. Typically, an impression is taken of the patient's mouth to facilitate the fabrication of a precision-fitted prosthesis or dental restoration. An abutment which supports the final restoration is attached to the implant and the restoration is cemented or screwed to the abutment and/or implant to complete the placement of the prosthodontic restoration in the patient's mouth.
The initial step of forming a suitable implant-receiving osteotomy in the patient's jawbone is critical to the success of the overall dental implant procedure. The size and location of the hole and its orientation in the mouth are all important for successful osseointegration of the implant. The hole is also desirably formed concentrically about its axis and has a diameter (either constant or tapered) approximately equal to or slightly smaller than the implant to be inserted.
Typically, a skilled oral surgeon forms the osteotomy using one or more specially adapted surgical drill bits. This surgical procedure requires special care to avoid discomfort and trauma to the patient. An improper technique or poorly suited surgical instrument can cause pain and shock to the patient as the drill bit penetrates the patient's jawbone. The oral surgeon must also be careful not to drill too deeply, particularly in high-density bone, as this can cause unnecessary trauma to the bone and/or surrounding tissues, thereby complicating the osteotomy preparation process.
High-speed rotation of a drill bit during formation of an osteotomy can also generate a significant amount of friction and heat. This is especially true if the osteotomy becomes filled or clogged with bone chips and/or other debris dislodged by the rotating drill bit. Too much friction and heat can cause damaging bone “necrosis” and/or burning of the surrounding bone tissues. This unnecessarily adds to the trauma and suffering of the patient and can inhibit the desired healing of the bone and osseointegration of the implant. Rotation of the drill bit within the osteotomy being formed can also exert torque forces on both the drill bit and the surrounding bone tissues. Excessive torque forces and/or heat generation can possibly result in breakage of the drill bit within the osteotomy and, in some extreme cases, possible bone fracture. On the other hand, it is desirable to perform the osteotomy procedure quickly and efficiently in order to conserve time and minimize pain and suffering by the patient.
Many conventional surgical drill bits have cutting edges that can result in undesirable side cutting or biting of the drill bit into the surrounding walls of the osteotomy, possibly undesirably expanding the diameter of the osteotomy and/or causing vibrational precessing of the drill bit within the osteotomy as it is being formed. Many such drill bits can also have a tendency to self-advance or lodge themselves deeper into the bone being cut, much like a wood screw. In some extreme cases, this can result in undesirable penetration through the jawbone and/or surrounding soft-tissues.
Moreover, many conventional surgical drill bits have a cutting tip that tends to abrade or scrape material rather than cutting it. Disadvantageously, this can require a high torque or force to be applied to advance the drill bit. Moreover, due to the geometry of the cutting tip such drill bits are typically not very efficient and are prone to becoming clogged with bone chips and/or other debris if adequate care is not taken during use.
SUMMARY OF THE INVENTION
In accordance with one embodiment, a dental drill comprises a plurality of blades each distally terminating in an end cutting edge having a positive rake angle. Advantageously, this allows for efficient, accurate and safe formation of an endosseous implant-receiving osteotomy in a patient's jawbone. Desirably, any patient trauma or discomfort during the procedure is substantially eliminated or reduced and a precision-sized osteotomy for receiving an implant of a predetermined size is created.
In accordance with another embodiment, a drill bit is provided for preparing surgical sites for placement of endosseous dental implants. The drill bit generally comprises a mounting shank and a distal cutting head. The mounting shank has a chuck at a proximal end sized and configured to interface with a rotation providing hand-piece. The distal cutting head comprises a plurality of blades. Each blade has a positive rake angle end cutting edge converging radially from substantially an outer-most diameter of the cutting head to substantially a distal-most point of the cutting head.
In accordance with still another embodiment, a surgical drill bit is provided for forming an osteotomy in the jawbone of a patient for receiving a dental implant. The drill bit generally comprises a shank comprising a mounting portion, a working portion and having a longitudinal axis. The working portion including multiple blades each distally terminating in an end cutting edge. Each end cutting edge converges radially from substantially an outer-most diameter of the working portion to substantially a distal-most point of the working portion. Each end cutting edge has a positive rake angle. At least one of the end cutting edges has the positive rake angle only on a portion spaced from the distal-most point of the working portion and extending substantially to the outer-most diameter of the working portion.
In accordance with yet another embodiment, a dental tool bit is provided for forming an endosseous implant-receiving osteotomy in bone material. The dental tool bit generally comprises a shank having a rotary longitudinal axis. The shank generally comprises a mounting portion and a working portion. The mounting portion is adapted to interface with a dental hand-piece. The working portion has a distal terminus and an outer-most perimeter. The working portion comprises a plurality of blades extending parallel to th
Hurson Steven M.
Kumar Ajay
Bumgarner Melba
Knobbe Martens Olson & Bear LLP
Nobel Biocare AB
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