Patent Publication Number: US-2005118551-A1

Title: Method and apparatus for delivering dental anesthetic

Description:
This application is based on provisional application Ser. No. 60/512,409, filed Oct. 20, 2003 for which priority is claimed. 
    
    
      This invention relates to a method and apparatus for efficiently delivering a dental anesthetic into the jaw bone of a patient in a simple, convenient manner.  
     BACKGROUND OF THE INVENTION  
      One known technique for anesthetizing dental surgery patients is to drill a small hole in the jaw bone of the patient, leaving a fixture embedded in the bone. Anesthetic is injected into the bone with a syringe inserted through the fixture. Patents disclosing this technique are found in U.S. Pat. Nos. 6,247,928; 6,287,114; 6,273,715; 6,575,745; and 6,547,561 to which reference is made for a more complete description of the technique. This technique is very desirable because it delivers anesthetic immediately adjacent a tooth to be worked on so the nerve ending adjacent the tooth is deadened in contrast to the situation where a nerve trunk, leading to an entire section of the jaw, is blocked. After surgery, the patient may realize that something is odd in the mouth but will not have a numb cheek or numb tongue after an intraosseous anesthetic procedure. Another important advantage of this technique is speed. Anesthetic delivered through a properly positioned fixture will induce profound anesthesia in the time it takes to lay the syringe down and pick up a drill or other surgical instrument. In other words, almost immediately for all practical purposes.  
      Other disclosures of interest relative to this invention are found in U.S. Pat. Nos. 4,755,173; 5,176,662; 5,257,980; 5,372,583; 6,017,328; 6,358,252; 6,458,117 and 6,685,674.  
     SUMMARY OF THE INVENTION  
      Long experience with the devices and technique disclosed in the above patents has led to the conclusion that anesthetics delivered into bone are subject to relatively rapid metabolization leading to unduly short periods of effectiveness. Medical people describe the cause as being due to the vascularity of the bone into which the anesthetic is injected. Those skilled in chemistry describe the cause as being due to the large surface area of the bone which catalyzes the metabolizing reactions. In fact, these descriptions differ only in terminology and are in fact describing the underlying cause in the jargon of different professions.  
      The short duration of profound anesthesia has unduly limited the clinical use of intraosseous anesthetic delivery because most procedures require more time to complete than is allowed by the overly rapid metabolization of anesthetic. The only current solution is to inject additional anesthetic with a syringe through the fixture remaining on the patient. Access to the end of the fixture is difficult because the fixture is inside the patient&#39;s mouth and inserting the hypodermic needle into the fixture can be challenging. To a layman, the size of the fixture is startling small. A typical prior art fixture that is embedded in the patient is no more than about ¼ inch in diameter and extends a similar distance out of the patient&#39;s gum. The diameter of the passage through which the needle of a syringe must pass is vanishingly small. In addition, the surgeon never has a straight shot at the passage through the fixture, meaning that the surgeon has to bend the needle to get it to enter the fixture. The combination of a small target located inside the patient&#39;s mouth at an odd angle is a challenge.  
      In addition, there is always a question of how much anesthetic to inject into the patient. Patients differ in their tolerance for, and reaction to, anesthetics. Injecting batches or slugs of anesthetic into a patient&#39;s bone to prolong profound anesthesia is not a desirable, much less optimum, technique.  
      In this invention, anesthetic is delivered substantially continuously into the bone of the patient from a time preceding the onset of surgery until a time near the end of surgery. The surgeon determines when it is appropriate to commence surgery and determine when it is appropriate to terminate delivery of anesthetic to the patient.  
      This may be accomplished in one of two ways. An adapter may be provided to fit onto commercially available devices used to drill bone and inject anesthetics or an original equipment device may be provided.  
      It is accordingly an object of this invention to provide an improved method and apparatus for delivering anesthetics into the bones of dental surgery patients.  
      A further object of this invention is to provide an improved technique for anesthetizing a dental surgery patient allowing the surgeon a choice of techniques for delivering anesthetic.  
      A more specific object of this invention is to provide an improved technique for delivering anesthetics into the bones of dental surgery patients in a simple expeditious manner that provides longer effective periods of profound anesthesia.  
      These and other objects and advantages of this invention will become more apparent as this description proceeds, reference being made to the accompanying drawings and appended claims.  
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       FIGS. 1 and 2  are isometric views of a prior art device used to drill and embed a fixture in the jaw of a patient;  
       FIG. 3  is an exploded pictorial view of this invention in use;  
       FIG. 4  is a bottom view of one embodiment of this invention;  
       FIG. 5  is a cross-sectional view of the embodiment of  FIG. 4 , taken substantially along line  5 — 5  thereof, as viewed in the direction indicated by the arrows:  
       FIG. 6  is an end view of the embodiment of  FIGS. 4-5 ;  
       FIG. 7  is a cross-sectional view of the assembled adapter of this invention and a prior art fixture;  
       FIG. 8  is a cross-sectional view, similar to  FIG. 5 , of another adapter of this invention; and  
       FIG. 9  is a cross-sectional view, similar to  FIG. 7 , of another embodiment of this invention. 
    
    
     DETAILED DESCRIPTION  
      In this invention, conventional techniques are used to drill holes in the jaw bones of dental surgery patients from the inside of the patient&#39;s mouth using commercially available equipment and fixtures, such as are available from Tulsa Dental Products, Inc. of Tulsa, Okla. under the tradename X-TIP. As shown in  FIGS. 1-2 , a conventional anesthetic delivery apparatus  10  comprises, as major components, a drilling member  12  and a fixture  14  shipped on the end of a protective attachment or protective sheath  16  such as a plastic tube. The drilling member  12  includes a housing  20 , a shaft  22 , a solid or hollow drill or stylet  24  embedded in the shaft  22  and extending through the drill housing  20  and a connecting end (not shown) received in and driven by a conventional dental drilling apparatus  26 . The inside of the housing  20  provides a drive connection  28  as shown best in  FIG. 2 .  
      The fixture  14  comprises a body  30  having a flange  32 , a driven connection  34  for receipt by the connection  28 , a flange  36  and a hollow sleeve or cannula  38  extending away from a flat central portion of the body  30 . Although the cannula  38  is metal, the body  30  is a medical grade polymer, typically a high density polymer, which has an important contribution as discussed hereinafter. The body  30  may be of any suitable configuration such as circular, rectangular or oblong. Although the drive connections  28 ,  34  are illustrated as being of square cross-section, other suitable shapes are equally operative, such as other polygons, such as rectangles, pentagons, hexagons or the like.  
      In use, the surgeon drills a hole in the jaw bone of the patient from the inside of the patient&#39;s mouth, using the dental drill  26  as a power source, gently pushing on the flange  36  in any suitable manner. Operation of the dental drill assembly  26  causes both the cannula  38  and stylet  24  to rotate, creating a hole in the patient&#39;s gum and underlying bone. When the flat central portion of the body  30  contacts the patient&#39;s gum, drilling stops. The drilling member  10  and dental drill assembly  26  are retracted as shown by the arrow  40  in  FIG. 2 , leaving the fixture  14  embedded in the patient&#39;s jaw due to the slight elasticity of the bone. The stylet  24  preferably extends beyond the end of the cannula  38 . A major function of the stylet  24  is to prevent the inside of the cannula  38  from being plugged with debris. Those skilled in the art will recognize the drilling member  10 , the fixture  14  and the dental drill assembly  26  as exemplary of prior art assemblies used in preparation for intraosseous delivery of anesthetic.  
      Any suitable or approved anesthetic may be used in the practice of this invention. A current preferred anesthetic is lidocaine although those skilled in the art will recognize that others are also suitable and usable.  
      An important feature of this invention is substantially continuously delivering anesthetic into the jaw bone of the patient beginning before the onset of surgery and terminating near the end of surgery. As shown in  FIG. 3 , the technique for accomplishing this is to provide a source  42  for delivering anesthetic in a substantially continuous manner. This may be accomplished in any suitable fashion, as by providing a pump or IV bag and drip regulator (not shown) as the source  42  delivering anesthetic to a tube  44  connected to the fixture. At the onset of anesthetic delivery, a relatively large quantity or bolus of anesthetic is delivered to induce profound anesthesia. The exact initial quantity depends somewhat on the particular anesthetic, but with the preferred anesthetic lidocaine, the initial amount is on the order of about one cubic centimeter.  
      Thereafter, the rate of anesthetic delivery is relatively slow, particularly when compared to the initial dose or bolus. Again, the exact subsequent quantity may depend somewhat on the particular anesthetic. The rate is less than the initial quantity over a period of not more than five minutes and typically much less, such as {fraction (1/10)}th cubic centimeter over a period of five minutes. The subsequent anesthetic may be delivered in one or more small spurts, as with a pump, or more evenly with an IV bag and drip regulator at an appropriate elevation above the fixture.  
      When using a conventional pump, it is relatively simple to inject an initial measured quantity of anesthetic followed by a relatively slow trickle. When using an IV bag and drip regulator, the initial dose or bolus of anesthetic is delivered by a syringe through a diaphragm port  45  in the tube  44  leading to the IV bag. The subsequent rate of anesthetic delivery is controlled by manipulation of the drip regulator.  
      As shown in  FIGS. 3-6 , one embodiment of this invention comprises an adapter  46  mounted on the end of the more-or-less conventional fixture  14 . After the fixture  14  is drilled into and embedded in the jaw of the patient, and the drilling member  12  removed, the adapter  46  is coupled to the driven connection  34 . The adapter  46  is preferably made of a medical grade polymer and provides an interference fit between the fixture  14  and the adapter  46 . To this end, the adapter  46  comprises a body  48  providing a downwardly facing opening  50  of the same cross-sectional shape as the driven connection  34 . The opening  50  is slightly tapered from a size slightly larger than the driven connection  34  to a size slightly smaller than the driven connection  34 . In this fashion, the adapter  46  may be forced onto the driven connection  34  and thereby make an interference fit and a liquid seal to allow liquid anesthetic to flow through the adapter  46  and the cannula  38  into the patient&#39;s jaw.  
      The liquid seal between the adapter  46  and the fixture  14  is an important feature of this invention and is at least partly due to the elasticity of the medical polymers used in the fixture  14  and in the adapter  46 . Although these polymers appear rigid, they are slightly elastic, which promotes the formation of a liquid seal. The commercially available fixtures  14  are currently made of a high density polymer which is more rigid, although still somewhat elastic, when compared to the material of the adapter  46 . Although the adapter  46  may be made of any suitable polymer, a preferred material is a homogenous medical grade soft polyvinyl chloride which is considerably elastic. A typical preferred material will have an elongation at break under tension of several times its original dimension. It will accordingly be seen that the liquid seal of this invention is provided, in substantial part, by the elasticity of the homogenous material of the body  48 , as contrasted to a separate component such as an O-ring. The liquid seal of this invention is to be contrasted to use of the commercially available fixtures, where anesthetic commonly flows back out of the fixture into the patient&#39;s mouth. This reduces the amount of anesthetic that is effective to produce anesthesia of the desired tooth and thereby disrupts any attempt at delivering a controlled or measured amount of anesthetic. In addition, lidocaine and other typical anesthetics taste bad, to which patients object.  
      The driven connection  34  of the fixture  14  may either have parallel sides or be slightly tapered from a large end adjacent the flange  36  and a small free end. In either event, the opening  50  is tapered slightly more than the driven connection  34  so the driven connection  34  is jammed into, and seals against, the inside of the opening  50 .  
      The adapter  46  also includes a second passage  52  which is illustrated in  FIG. 5  as being transverse or lateral to an axis  54  of the fixture  14  although it could be disposed at any suitable angle to the axis  54 , such as coincident. The passage  52  is also designed for an interference fit with the tube  44  and is accordingly of tapered, or frustoconical shape, having an outer end slightly greater than the outer diameter of the tube  44  and an inner end slightly smaller than the outer diameter of the tube  44 . Accordingly, the tube  44  may be forcibly inserted into the tapered opening  52  and thereby create an interference fit and liquid seal between the adapter  46  and the tube  44 . In the embodiment of  FIG. 5 , the upper surface of the opening  52  is essentially perpendicular to the axis  54  and the lower surface defines an obtuse angle with the axis  54  to provide the taper. In the embodiment of  FIG. 5 , the uppermost portion of the opening  52  is conveniently coplanar with the end of the passage  50  for purposes more fully apparent hereinafter.  
      Thus, the tube  44  may be inserted into the opening  52  after the adapter  46  is connected to the fixture  14  or may be inserted before the adapter  46  is attached to the fixture  14 . In the alternative, the tube  44  may be adhesively attached to the fixture  46 , preferably before the adapter  46  is attached to the fixture  14  or molded onto the fixture  46  at the time of manufacture. An important feature of the adapter  46  is that the nature of the driven connection  34  and the tapered passage  50  allows the adapter  46  to be oriented in the patient&#39;s mouth so the tube  44  extends out of the mouth in a desired direction. If placing the adapter  46  on the driven connection  34  shows the tube  44  to be aimed inappropriately, the surgeon may reorient the adapter  46  before forcing it onto the fixture  14 .  
      Another important feature of the adapter  46  is that it allows delivery of anesthetic both by syringe and continuously through the tube  44 . It may be desirable, for example, to initially delivery a measured quantity of anesthetic in a conventional manner, i.e. axially down the fixture  14  by inserting a syringe through the passage from which the stylet  24  was removed and then attach the adapter  46  to deliver anesthetic slowly in a substantially continuous manner.  
      As shown best in  FIGS. 5 and 6 , the adapter  46  includes an external rib  56  overlying the passage  50 . The purpose of the rib  56  is to provide an abutment or shoulder which the surgeon can hold with a suitable instrument, such as a hemostatic clamp, to orient and apply the adapter to the fixture  14 .  
       FIG. 7  illustrates the situation where the adapter  46  has been forced onto the fixture  14  and illustrates that the exit opening of the tube  44  is above the top of the fixture  14 , thereby allowing access to the axial passage  58  and ultimately to the cannula  38 . To this end, the adapter  46  bottom out, or abuts, a shoulder  60  on the fixture  14 . The adapter  46  also seals against the shoulder  60  thereby providing a second liquid seal minimizing leakage of anesthetic through the adapter  46 . Those skilled in the art will recognize that the axial passage  58  allows insertion and removal of the stylet  24  and allows insertion and removal of a syringe needle in a conventional intraosseous manner of delivering anesthetic.  
      Referring to  FIGS. 8 and 9 , another embodiment of this invention is illustrated. In  FIGS. 8 and 9 , a fixture  62  is quite similar to the fixture  14  and accordingly includes a body  64  having an axial passage  66  receiving a cannula  68 , a flange  70 , a driven connection  72  and a shoulder  74 . The cannula  68  may be adhesively attached to the body  64 , may be press fit or may be molded in place. The fixture  62  differs from the fixture  14  by the provision of a lateral passage  76  opening into the axial passage  66 .  
      An adapter  78  is similar to the adapter  46  and includes a body  80  having a downwardly facing opening  82  designed to provide an interference fit with the driven connection  72  and is thus tapered slightly more than the driven connection  72 , as discussed previously. A laterally extending passage  84  provides a connection for a tube  86  either by an interference fit, by use of adhesives or by molding the tube  86  onto the adapter  78 . By forcing the adapter  78  onto the fixture  62 , a liquid seal is created, along the driven connection  72  and/or at the shoulder  74 . In the event it is desirable, a groove (not shown) may be provided on the exterior of the driven connection  72  opening into the lateral passage  76 . In this fashion, the tube  86  is in communication with the axial passage  66  in any orientation of the adapter  78  relative to the fixture  62 .  
      After the completion of surgery, the adapter and fixture are removed in a conventional manner. One of the advantages of intraosseous anesthetic delivery is that patients do not exhibit large scale numbness of the face and/or tongue that is typical of larger scale nerve blocking anesthetic procedures.  
      Another important feature of this invention is that the fixture becomes coupled to the delivery tube. There are times when the fixture is accidentally dislodged from the patient&#39;s bone. With the fixture coupled to the delivery tube, the patient cannot swallow or inhale the fixture.  
      Although the apparatus of this invention has been described as used to deliver anesthetic into a bone during dental surgery, it will be recognized that the apparatus is also useful to deliver other drugs directly into a bone, such as antibiotics in order to manage infection more rapidly or steroids or other antiinflamatory agents to limit swelling and or pain post operatively.  
      Although this invention has been disclosed and described in its preferred forms with a certain degree of particularity, it is understood that the present disclosure of the preferred forms is only by way of example and that numerous changes in the details of operation and in the combination and arrangement of parts may be resorted to without departing from the spirit and scope of the invention as hereinafter claimed.