Abstract:
A drill burr includes a channel, extending along a longitudinal axis of the drill burr, and fluidically connected to a water reservoir for providing a constant-flow liquid jet. The constant-flow liquid jet has a first pressure directed at the bone along the longitudinal axis of the drill burr. A pressure sensor senses a pressure change in the liquid jet from the first pressure to a second pressure. A signal processing unit is configured to translate the pressure change into information indicating a structural change in the bone along the drilling path, from a first structure to a second structure, corresponding respectively to the first pressure and the second pressure. Optionally, the signal processing unit generates an audio alarm notifying of the structural changes.

Description:
CROSS REFERENCE TO RELATED APPLICATION 
       [0001]    This application claims the benefit of priority from pending U.S. Provisional Patent Application Ser. No. 62/315, 030, filed on Mar. 30, 2016, and entitled “A DRILLING DEPTH DETERMINER FOR DENTAL IMPLANTS,” which is incorporated herein by reference in its entirety. 
     
    
     TECHNICAL FIELD 
       [0002]    The present disclosure generally relates to a method and device for determining internal structures of a bone during surgery, particularly to a method and device for determining internal structures of a bone during implant surgery, and more specifically relates to a method and device for determining internal structures of a bone using changes in a liquid jet flow pressure. 
       BACKGROUND 
       [0003]    Natural teeth may be lost as a result of dental diseases or trauma making it desirable for replacement with a dental implant. A dental implant may be surgically positioned within the mandibular or maxillary alveolar bone. A screw hole may be drilled in the mandibular or maxillary alveolar bone for fixing the dental implant in the bone. 
         [0004]    When drilling through the mandibular or maxillary alveolar bone, the oral surgeon has to decide on a drilling axis for the implant, while being aware to avoid contact between the drill burr and the adjacent soft tissue. Generally, the decision may be made based on the surgeon&#39;s knowledge of the jawbone structure into which the implant is to be inserted, the position of the nerve tissues within the jawbone structure, and the surface area of the gum on which the dental implant must be placed. Different techniques, such as X-ray imaging, computer tomography (CT) and panoramic imaging may be utilized to assess the jawbone structure, the position of the nerve tissues, and the surface area of the gum. 
         [0005]    The imaging methods mentioned above are generally considered for pre-surgical assessment of implant sites and do not provide the surgeon with required information in real time during surgery. 
         [0006]    Therefore, there is a need in the art for methods and devices for interactive determination of a proximity of the drill burr to a region of change in bone structure, or a change from bone structure to adjacent soft tissue. 
       SUMMARY 
       [0007]    In one general aspect, the present disclosure describes a system for determining an internal structure of a bone along a drilling path. In an implementation, the system may include a drill, and a hollow drill burr, supported by and rotatable by the drill, extending along a longitudinal axis to a distal end, and including a channel along the longitudinal axis, the channel including an outlet at the distal end. In an implementation, the drill can be configured to receive a liquid from a liquid reservoir, at a first pressure, and pass the fluid through the channel while rotating the hollow drill burr, and the hollow drill can be configured to direct the fluid, while drilling a bone, as a liquid jet from directed at the bone. In an implementation, the system can include a pressure sensor configured to sense a pressure change in the liquid jet from the first pressure to a second pressure, and can include a signal processing unit configured to process said pressure change into information related to the structural changes in the bone along the drilling path from a first structure to a second structure. 
         [0008]    In one general aspect, the present disclosure describes a method for determining an internal structure of a bone along a drilling path. In an implementation, one exemplary method can include drilling a bone with a hollow drill burr having a distal end and a channel including an outlet at the distal end and, while drilling the bone, receiving at the hollow drill burr a liquid at a first pressure, and passing the fluid through the channel to exit from the outlet as a liquid jet directed at the bone; sensing a pressure in the liquid jet; detecting, based on the sensing, a pressure change in the liquid jet from the first pressure to a second pressure; and upon detecting the pressure change, generating a user-detectable information indicative of the pressure change. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0009]    While the specification concludes with claims particularly pointing out and distinctly claiming the subject matter that is regarded as forming the present application, it is believed that the application will be better understood from the following description taken in conjunction with the accompanying DRAWINGS, where like reference numerals designate like structural and other elements, in which: 
           [0010]      FIG. 1  shows a cross sectional view of a mandible. 
           [0011]      FIG. 2  shows an exemplary dental drill. 
           [0012]      FIG. 3A  shows a dental drill, according to exemplary implementations of the present disclosure. 
           [0013]      FIG. 3B  shows a drill burr with a single channel, according to an exemplary implementation of the present disclosure. 
           [0014]      FIG. 3C  shows a drill burr with side channels, according to an exemplary implementation of the present disclosure. 
           [0015]      FIG. 4  illustrates a block diagram of a system for determining an internal structure of a bone along a drilling path, according to one or more aspects of the present disclosure. 
           [0016]      FIG. 5  shows a dental drill drilling into a mandibular bone, according to exemplary implementations of the present disclosure. 
       
    
    
     DETAILED DESCRIPTION 
       [0017]    In a dental implant surgery, the oral surgeon may drill a hole in the mandible to screw the implant in the bone.  FIG. 1  shows a cross sectional view of a mandible as known in the art. Referring to  FIG. 1  a mandible  100  may include oral mucosa  101 , periosteum  102 , cortical bones  103 A-B, cancellous bone  104 , and neurovascular bundle  105 . When drilling through the mandible  100 , the oral surgeon has to decide on a drill axis for the implant, while being aware to avoid contact between the drill burr and the neurovascular bundle  105 . 
         [0018]    Disclosed herein is a method and device that can provide a user information to help the surgeon to avoid contact between the drill burr and the neurovascular bundle  105  by determining the internal structure of the mandible  100  along a drilling path. 
         [0019]    In an implementation of the present disclosure, a liquid jet may be applied on the drilling surface with an internal structure while the liquid jet pressure is measured simultaneously. The internal structure may have a plurality of layers with different material resistances. The liquid jet may first be applied on a first internal structure with a first material resistance. When the drill burr passes from the first internal structure to a second internal structure with a second material resistance, the liquid jet pressure may change. 
         [0020]    The changes in liquid jet pressure may be sensed using a pressure sensor. The sensed pressures may then be transformed into signals by the sensor, and the signals may be sent to a signal processing unit. The signal processing unit may be configured, for example by computer executable instructions stored in a memory coupled to a digital processor, transform the signals to user-interpretable results. The user-interpretable results may be presented in visual form, for example on an LCD display, or in audio form via a buzzer, or both. This apparatus therefore provides the user, for example an oral surgeon, information on reaching a point or boundary of changes in the internal structure of the bone. The user can then adjust or maintain a drilling or other operation within a desired position relative to the change boundary in bone structure. For example, in use by an oral surgeon, the visual or audible information can assist the surgeon in avoiding contact between the drill burr and the neurovascular bundle  105 . 
         [0021]    Systems and methods according to this disclosure are not limited to dental surgery and, instead, can be adapted to and applied and a wide range of surgeries involving the use of a medical tool, intended to penetrate into a tissue or bone for creating a perforation or cavity in the tissue or bone structure in contact with a membrane. Such surgeries can be in the field of the orthopedics, or general surgery. 
         [0022]    According to one or more exemplary embodiments, the present disclosure may be incorporated in a drill. However, the present disclosure is not limited to such incorporation, and a basic system, in accordance with some preferred embodiments of the present invention, may include only a probe to determine the internal structural changes. 
         [0023]      FIG. 2  shows an exemplary dental drill  200  as known in the art. The dental drill  200  may include a drill burr  201 , a head  202 , an end cap  203 , and a body  204 . Water or air may be supplied through the body  204 , to rotate a turbine placed in the head  202  of the drill  200 . The turbine may convert the air or water pressure to mechanical energy to rotate the drill burr  201 . 
         [0024]      FIG. 3A  shows a dental drill  300 , according to exemplary implementations of the present disclosure. As shown in  FIG. 3A , the dental drill  300 , may include a tube  301 , a hollow drill burr  302 , a head  202 , an end cap  203 , and a body  204 . 
         [0025]    Referring to  FIG. 3A , the hollow drill burr  302  may have a central channel  303 . The central channel  303  may have an inlet  304  and an outlet  305 , the outlet  305  being at a distal end (visible but not separately numbered) of the hollow drill bur  302 . The inlet  304  may be connected to tube  301  and the outlet  305  may be at the tip of the hollow drill burr  302 . 
         [0026]    The tube  301  may be configured to fluidically connect the hollow drill burr  302  to a liquid pressure regulator (not shown in the figure), to provide a constant liquid jet flow in the hollow drill burr  302 . The tube  301  may be placed on the dental drill body  204 . 
         [0027]      FIGS. 3B and 3C  show hollow drill burrs  302 , according to one or more exemplary implementations of the present disclosure. Referring to  FIGS. 3B and 3C , the hollow drill burr  302  may be a drill burr with the central channel  303  made therein along the longitudinal axis of the hollow drill burr  302 . The central channel  303  may be configured to supply the liquid jet flow on the drilling surface at the distal end, i.e., tip of the hollow drill burr  302 . 
         [0028]    Referring to  FIG. 3C , in an implementation of the present disclosure, a plurality of lateral outlets or side channels  306  may be provided at the distal end of the hollow drill burr  302 , branching from the central channel  303  and exiting near the outlet  305 . The lateral outlets or side channels  306  may be configured to serve as paths for the liquid jet flow in case the outlet  305  is blocked or clogged. 
         [0029]      FIG. 4  illustrates a block diagram of a system  410  for determining the internal structure of a bone along a drilling path, according to one or more aspects of the present disclosure. Referring to  FIG. 4B , the system  410  may include a water reservoir  411 , a pressure regulator  412 , a drill  413 , a pressure sensor  414  and a signal processing unit  415 . 
         [0030]    The water reservoir  411  may be configured to provide a water flow in the system  410 . The water reservoir  411  may be, for example, a water tank or urban water supply system. According to one or more exemplary implementations of the present disclosure, a pressure regulator  412  may be utilized to produce a constant-flow water flow. In other implementations of the present disclosure the pressure regulator  412  may be replaced with a constant-flow pump. 
         [0031]    The water flow may be transmitted to the drill  413  via the pressure regulator  412  or a constant-flow pump. The pressure sensor  414  may be configured for measuring the liquid pressure in the line connecting the pressure regulator  412  to the drill, thereby measuring the pressure of the liquid jet that is ejected from the tip of the drill  413 . The output signal of the pressure sensor  414  may be transmitted to signal processing unit  415 . 
         [0032]    According to some implementations, the signal processing unit  415  may include a processor  416  and a user interface  417 . The processor  416  can include a generic digital signal processor (not separately visible) coupled by a bus to a memory configured to store computer executable instructions that, when execrated, cause the generic digital signal processor to perform methods and processes within methods according to this disclosure. The signals received from the sensor  414  may first be processed in the processor  416 , to transform the signals received into meaningful, e.g., user-presentable information relating to the internal structural changes along the drilling path. The meaningful, user-presentable information may include, for example, an alert that may be conveyed to the surgeon via the user interface  417 . The user interface  417  may be an LCD display, a buzzer, an alerting light, etc., by which the surgeon may be informed whether to continue the drilling or not. 
         [0033]    According to one or more exemplary implementations of the present disclosure, the signal processing unit  415 , may further include a signal amplifier (not shown in  FIG. 4B ) that may be configured to amplify the signals received from the pressure sensor  414  before transmitting them to the processor  416 . 
         [0034]      FIG. 5  shows the dental drill  300  while drilling through a mandible, according to exemplary implementations of the present disclosure. Referring to  FIG. 5  the water flow may be provided from the water reservoir via a pressure regulator and it may be supplied to the drill  300  via the tube  301  and it may exit the tip of the drill burr as a liquid jet  501 . The pressure of water in tube  301  that corresponds to the pressure of the liquid jet  501  may be measured by the pressure sensor. When the hollow drill burr  302  passes from a first internal structure, such as cancellous bone  104  with a first material resistance to a second internal structure, such as or cortical bones  103 A-B with a second material resistance, the pressure measured by the pressure sensor may change. This change in the pressure of water flow is due to a change in the internal structure of the bone through which the drilling is taking place. For example, cancellous bone  104  has a lower material resistance in comparison with cortical bones  103 A-B. Therefore, the pressure of the liquid jet increases when the drill burr passes the cancellous bone  104  and reaches the cortical bone  103 B. Referring to  FIG. 4B , this increase in the pressure may be sensed by the pressure sensor  414  and it may be transmitted as a signal to the signal processing unit  415  and then the processor  416  may cause the user interface  417  to send an alarm signal, such as a sound alarm, a light alarm or simply a graphical message on a display screen to inform the surgeon that the drill burr is now close to the cortical bone  103 B near neurovascular bundle  105 , i.e. the place that the surgeon wants to avoid drilling into. 
       EXAMPLE 
       [0035]    Referring to  FIG. 3A , in an exemplary implementation, the hollow drill burr  302  may be a 3 mm diameter cylindrical stainless steel burr with a 0.8 mm longitudinal central channel  303  made therein. The water jet provided at the tip of the hollow drill burr  302  via the line 301 has a base pressure of about 350 mmHg. As used herein, the base pressure is the pressure of the water jet before the drill bur is inserted inside a bone along the drilling path, i.e., there is no resistance in front of the water jet. 
         [0036]    Referring to  FIG. 5 , in order to study the effect of a structural change along the drilling path on the pressure of the liquid jet  501 , seven materials with different internal structures and material resistances were selected and then drilling was carried out inside these materials using the system of the present disclosure. The materials selected for this experiment were Plaster of Paris, dental stone, alginate, Polymethyl methacrylate (PMMA), cork, hard wood, and high porosity wood. Thirty holes were drilled in each sample. The base water pressure for each sample before drilling was recorded. 
         [0037]    Referring to  FIG. 4B  a base pressure of the liquid jet is set to 350 mmHg by the pressure regulator  412  and then drill  413  was utilized for drilling into the seven material samples. The pressure of the liquid jet during the drilling process was measure by the pressure sensor  414  for each sample. The drilling test was replicated 30 times for each sample. The pressure of the liquid jet measured by the pressure sensor  414  was then sent to the signal processing unit  415 . Mean pressure difference in the pressure of the liquid jet  501  was calculated for each sample that shows the effect of different structures and materials on the pressure of the liquid jet  501 . Table 1 reports the mean pressure differences for these samples in mmHg. The measured pressure differences for different materials may be utilized in the signal processing unit  415  for converting the changes in the pressure of the liquid jet to meaningful information related to the structural changes in the bone along the drilling path. 
         [0000]    
       
         
               
             
               
               
               
               
               
               
               
               
             
               
               
               
               
               
               
               
               
             
           
               
                 TABLE 1 
               
             
             
               
                   
               
               
                 Mean pressure changes in different materials. 
               
             
          
           
               
                   
                   
                   
                   
                 High 
                   
                   
                   
               
               
                   
                 Plaster 
                 Dental 
                   
                 porosity 
                 Hard 
                   
                   
               
               
                   
                 of Paris 
                 stone 
                 Alginate 
                 wood 
                 wood 
                 Cork 
                 PMMA 
               
               
                   
               
             
          
           
               
                 Number 
                 30 
                 30 
                 30 
                 30 
                 30 
                 30 
                 30 
               
               
                 of Data 
                   
                   
                   
                   
                   
                   
                   
               
               
                 Mean 
                 15 
                 20.2 
                 8.4 
                 4.7 
                 19.9 
                 2.9 
                 23.3 
               
               
                 Pressure 
                   
                   
                   
                   
                   
                   
                   
               
               
                 Difference