Abstract:
A periodontal surgical instrument is disclosed which includes a handle with two ends. One end comprises a shank with a first cutting head preferably comprising a thin, flexible, angled blade for insertion to separate the gingival attachment and enter the P.D.L. space. The angulation and length are preferably suited to circumscribe the entire circumference of the root structure, all the way to the root apices. The other end comprises a spatula-shaped blade. The blade creates enough space for the introduction of extraction instruments in a controlled manner, and at locations dictated by the surgeon. A method of use is also described for this periodontal surgical instrument for procedures where extraction is desired.

Description:
TECHNICAL FIELD 
     This invention relates to dental exodontia for the extraction of teeth. More specifically, inventive instrument is designed to achieve the cutting of the fibrous attachment of the tooth to bone, formed of thousands of microscopic fibers, collectively referred to as the periodontal Ligaments, or PDL. 
     BACKGROUND 
     Teeth generally comprise an upper exposed portion, or crown, which is visible and an underlying root structure which is hidden, being anchored within the bony substructure of the gums. The interface between the root structure of the tooth and the surrounding bone is a fibrous attachment. These fibers are referred to as the periodontal ligaments or PDL. The space occupied by the periodontal ligaments is known as the PDL space, and averages about 0.25 mm in thickness and surrounds the entire root structure of the tooth. 
     It is necessary to separate the ligamental attachment during various surgical procedures. Such procedures include the extraction of teeth, and the installation of dental implants and common surgery to remove roots broken during extraction or through trauma. While extraction is one of the most common dental procedures it is fraught with difficulty. The great forces employed to dislodge teeth from bone are difficult to control and so, have unpredictable outcomes. 
     One of the main obstacles in the removal of teeth is to overcome the resistance of the PDL. The most common method used to overcome this resistance is bucco-lingual luxation, which expands the socket by loosening of the tooth by grasping with a forceps and rocking the tooth in all directions in order to compress the proximate, relatively spongy portion of the surrounding bone, and stretch the periodontal ligaments until they break. Great force is needed to accomplish this, and the frequent result is fracture of the tooth or fracture of the surrounding bone that forms the buccal plate. Both of these problems lead to further surgical complications. 
     In the case of a fractured crown, it is often necessary to resort to a full-surgical extraction, elevating the soft tissue and removing bone, in order to gain access to the retained root. Full surgical procedures are time-consuming, traumatic to the patient, and carry more risk of infection and healing complications. In the case of a fractured buccal plate, the bone loses its blood supply, and will resorb away. Soft tissues will epithelialize faster than the bone will regenerate, and the remaining portion of the gum which formerly supported the tooth, also known as the ridge, will display a depression or defect. Loss of the bony architecture and its replacement by soft tissues, further complicates the prosthetic treatment plan. Indeed, in such a scenario, it is likely that a bone graft will be required. In other words, conventional crown and bridge prosthesis require bony support, and replacement of the tooth with an implant requires healthy surrounding bone. Often, it is necessary to do a separate preliminary surgery (Guided Bone Regeneration) to repair a defect before an implant is placed. 
     While instruments capable of the cutting the PDL are known to be used in connection with the extraction of teeth, such instruments fail to have the range and configuration necessary to effectively perform this function. In addition, such prior art instruments are clumsy to work with and have limited functionality in connection with such cutting, because they are often too thick, or improperly angled. 
     SUMMARY OF THE INVENTION 
     It is an object of the invention to remedy the deficiencies of the prior art heretofore discussed. 
     It is a further object of the invention to provide an instrument which allows the separation of the ligamental attachment without destroying the buccal plate. 
     It is a further object of the invention to provide an instrument with two functional tools which function synergistically to allow the user to separate the ligamental attachment and allow teeth to escape the bone occlusally. 
     It is a further object of the invention to provide a method which allows the separation of the ligamental attachment while minimizing damage to the buccal plate. 
     The invention is directed to a dental instrument, namely a periotome. The inventive instrument is of particular value because it also comprises a handle having two tools. At one end there is a tool with a thin, flexible, angled blade for insertion to separate the gingival attachment and enter the PDL space. The angulation and length are suited to circumscribe the entire circumference of the root structure, all the way to the root apices. At the other end of the inventive periotome there is a second tool which comprises a larger, spatula-shaped member tapering into a triangular tipped blade having a size and thickness adapted to create space for the introduction of extraction instruments in a controlled manner, after the cutting out the PDL, and at locations dictated by the surgeon. The preservation of bone eliminates the need for follow-up repair of the ridge, simplifying the prosthetic treatment plan. In other words, the invention addresses the inefficiency of destroying the fibrous attachment by tearing apart the periodontal ligaments. Rather, in accordance with the invention, the ligaments are incised, with substantially no trauma to the surrounding bone. The handle is preferably made of hollow stainless steel, aluminum alloy or other lightweight material which makes it comfortable and easy to control. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     Some embodiments of the invention will now be described in detail, by way of example, with reference to the accompanying drawings which illustrate the invention. 
     FIG. 1 is a side elevational view of a preferred embodiment of the invention; 
     FIG. 2 is a detailed side view of a portion of the instrument shown in FIG. 1 showing the first tool; 
     FIG. 3 is a detailed perspective view of a portion of the instrument shown in FIG. 1 showing the first tool; 
     FIG. 4 is a detailed side elevational view of a portion of the instrument shown in FIG. 1 showing the second tool; 
     FIG. 5 is a detailed view along lines  5 — 5  of FIG. 4 showing other aspects of the configuration of the second tool; and 
     FIG. 6 is a detailed side view of the embodiment shown in FIG. 1 showing part of the handle. 
     FIG. 7 is a front view of a portion of the instrument shown in FIG. 1 showing a second embodiment of the first tool; 
     FIG. 8 is a side view of FIG. 7 across lines  8 — 8 ; 
     FIG. 9 is a side view of FIG. 7 across lines  9 — 9 ; 
     FIG. 10 is a side view of FIG. 7 across lines  10 — 10 ; 
     FIG. 11 is a front view of a portion of an alternative embodiment of the inventive periotome; 
     FIG. 12 is a side view of FIG. 7 across lines  12 — 12 ; 
     FIG. 13 is a perspective view of the scalpel or incisor tip being inserted into the PDL space on the buccal aspect of a maxillary right first molar; 
     FIG. 14 is a perspective view of the separator blade of the present invention being inserted into the PDL space on the mesial aspect of the same tooth; 
     FIG. 15 shows typical anatomy of a maxillary right first molar, surrounding bone and soft tissues, as viewed from the mesial aspect; 
     FIG. 16 is a front view of a portion of the instrument shown in FIG. 1 showing a fourth embodiment of the first tool; 
     FIG. 17 is a side view of FIG. 16 across lines  17 — 17 . 
     FIG. 18 is a front view of a portion of the instrument shown in FIG. 11 showing a fifth embodiment of the first tool; 
     FIG. 19 is a side view of FIG. 16 across lines  19 — 19 . 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     FIG. 1 shows a preferred embodiment of the inventive periotome  10 . Periotome  10  comprises a handle  12  with two functional tools  14  and  16  secured at each of its ends. In preferred embodiments, the cutting surfaces of the tools are coated with titanium nitride so that the blades remain sharp. 
     As seen most clearly from FIG. 2, tool  14  preferably comprises three sections, a base  18 , a stem  20 , and a blade  22 . Base  18 , stem  20  and blade  22  are all formed from a single piece of metal. Base  18 , stem  20  and blade  22  are connected at angles with rounded comers for safety. The angulation and length of the sections of tool  14  are suited to circumscribe the entire circumference of the root structure, all the way to the root apices. 
     Base  18  is formed as a roughly frustro conical member which tapers into stem  20 . The length of base  18  is between 5-15 mm, preferably 10 mm. Its larger diameter adjacent handle  12  is 2.54 mm. Stem  20  is set at an angle of between 120-170 degrees, preferably 140° in one direction from base  18 . Stem  20  is formed as a continuing frustro conical member which tapers into blade  22 . The length of stem  20  is between 5-15 mm, preferably 8.89 mm while the larger diameter is between 1-2 mm, preferably 1.524 mm. Blade  22  is set at an angle of between 20 and 45 preferably 39° degrees in the opposite direction with respect to stem  20 . The sharp angle allows the user to get into a smaller area without hitting other teeth. Blade  22  is formed with a substantially rectangular shape and is flat with a thickness of 0.4572 mm, and a width of 1.778 mm. Blade  22  preferably comprises a continuous cutting edge defined by five cutting surfaces  24 ,  26 ,  28 ,  30 , and  32  as shown in FIGS. 2 and 3. Surfaces  24  and  32  are used to cut in the mesio-distal direction. Surface  28  is used to cut in the apical direction. Surfaces  26  and  30  are rounded points which can be used to cut in the apical direction. 
     As shown in FIG. 4, tool  16  is formed from a member  34  which first tapers inwardly then outwardly into a spatula-shaped blade  36 . In accordance with the preferred embodiment illustrated in FIG. 1, tool  16  has a length of about 25.4 mm. Member  34  has a thickness at point  31  of between 2 and 6 mm, preferably 3.30 mm in the direction of the plane of the drawing. It then tapers inwardly to a thickness of between 0.5 and 2.5 mm, preferably 1.9 mm at point  33  in the direction of the plane of the drawing of FIG.  4 . Member  34  then flattens and expands to a width of between 2 and 6 mm, preferably 2.54 mm in the direction of the plane of the drawing. Member  34  preferably has a circular cross section point  31  and point  33 . 
     FIG. 5 shows a side view of triangular tipped blade  36 . Blade  36  is of a size and thickness so that the surgeon creates enough space for the introduction of extraction instruments in a controlled manner, and at locations dictated by the surgeon. More particularly, at point  35 , the blade has a thickness on the order of between 1 and 3 mm, preferably 1.27 mm in the direction of the plane of the drawing of FIG.  5 . From there it terminates in a point. Blade  36  is preferably triangular in shape with three cutting surfaces,  38 ,  40 , and  42 . The length of blade  36  is about 37.4 mm. The angle of the tip is about 40 degrees. 
     Handle  12  is preferably made of hollow stainless steel. It is preferably lightweight, weighing about between 0.2 oz. and 2.0 oz., preferably 0.8 oz. These parameters make handle  12  comfortable and easy to control. Handle  12  preferably comprises a center section  44  and two roughly frustro conical end sections  46  and  48 . Center section  44  comprises a hollow tube which is formed for comfort to the user. In preferred embodiments, the tube has a triangular or hexagonal cross section so that the tool rests comfortably between the fingers. The length of center section  44  is between 60 and 120 mm, preferably 90 mm. Center section  44  has a diameter which is between 5 and 30 mm, preferably 11 mm. In preferred embodiments, center section  44  also comprises a plurality of support indentations or ridges  50  placed at points approximately ¼ and ¾ of the length of center section  44 . The dimensions of the handle are balanced to reduce hand fatigue (where a larger diameter is preferred) with functionality as a dental instrument (where a smaller diameter is preferred). The larger diameter is available due to the angulation of tool  14  as the provision of at least three cutting surfaces on the tool to allow greater flexibility in smaller spaces as well the use of frustro conical tapered end sections  46  and  48 . 
     FIG. 7 shows a second preferred embodiment of the inventive periotome  110  which is similar in configuration to periotome  10 . Base  118  is formed as a roughly frustro conical member which tapers into stem  120 . The length  150  of base  118  is between 7 and 10 mm, preferably 8.6 mm. Diameter  152  is about 1.9 mm. Stem  120  is set at an angle  154  of 20 degrees, from base  118 . Stem  120  is formed as a continuing frustro conical member which tapers into blade  122 . The length of stem  120  is preferably 16 mm while the larger diameter  155  is about 1.4 mm as shown in FIG. 9 which is a side view taken across lines  9 — 9  of FIG.  7 . The vertical distance  156  from the top of stem  120  to the bottom of base  118  is about 17.35 mm. Blade  122  is set at an angle  158  of about 39 degrees from base  118  in the opposite direction. A side view of blade  122  across lines  8 — 8  is shown in FIG.  8 . The length  160  of blade  128  is about 1.88 mm. The vertical distance  162  of blade  122  to base  112  is about 30 mm. The thickness  164  of blade  122  is about 5.3 mm. The shape between cutting surfaces  126  and  128  is a radius of about 0.031 inches. FIG. 10 is a side view across lines  10 — 10 . 
     FIG. 11 shows another embodiment of the inventive periotome. Periotome  210  is similar in configuration to periotomes  10  and  110 . However, blade  222  is now rotated between 20 to 80 degrees, ideally between 37 and 52 degrees, preferably about 45 degrees. The rotated blade allows the surgeon to come in from the front of the mouth and reach, for example, the interior portion of the back molars. FIG. 12 is a side view across lines  12 — 12 . Without the angulation it is difficult for the surgeon to cut straight down into the gum line to separate the tooth because the cheek is in the way. A second cutting tool may be secured to the other end of handle  212 . This second cutting tool has a configuration which is a mirror image of cutting tool  214 . 
     FIG. 16 shows a fourth preferred embodiment of the inventive periotome  310  which is similar in configuration to periotome  110 . However the angulation  350  of blade  322  from stems  319  and  320  is deeper. FIG. 17 is a side view taken along lines  17 — 17 . 
     FIG. 18 shows a fifth embodiment of the inventive periotome  410  which is similar in configuration to periotome  310  with blade  422  rotated between 20 to 80 degrees, ideally between 37 and 52 degrees, preferably about 45 degrees. FIG. 17 is a side view taken along lines  17 — 17 . 
     In practice, the surgeon will use tool  14  to come in from the occlusal direction and cut into the PDL space about 12 mm or so. The five cutting surfaces  24 ,  26 ,  28 ,  30 , and  32  and flexibility of blade  22  allows the surgeon to come in from the side without hitting the jaw. Then the surgeon will gently insert triangular tipped blade  36  of tool  16  into the space made with tool  14 . Then the surgeon will rock blade  36  back and forth so that cutting surfaces  38 ,  40 , and  42  will gently expand the ridge of the socket with minimal compression to the bone without damaging the bone until there is enough space for the introduction of extraction instruments in a controlled manner, and at locations dictated by the surgeon. Normally, anatomy, i.e., proximity of other teeth, etc. dictates where elevators and forceps are applied. Here site of application is formed by blade  36  where surgeon can take advantage of greater bone mass. It is noted that the working tips of the instrument of the present invention are made of stainless steel. After being forged, the same are heat treated and sharpened. After being heat treated, tool  16  is formed into a specialized wedge to work as an adjunct to the cutting tip  14 . 
     As can be seen in FIG. 13, the proper orientation of cutting tip  14  is substantially parallel to the axis of the tooth, allowing it to be advanced in the direction of the axis of the tooth into the periodontal ligament space on the buccal aspect of a maxillary right first molar. After tip  14  has been inserted into the space, it is carefully worked along the surface of the tooth to create a space to allow tip  16  to be inserted as shown in FIG.  14 . This is better understood with reference to FIG. 15 which shows typical anatomy of a maxillary right first molar, and surrounding bone and soft tissues, as viewed from the mesial aspect in cross-section. This anatomy includes the maxillary right first molar  71 , the periodontal ligaments  73  completely surrounding the root structure and attaching it to bone, the cortical bone plate  75 , and the gingival soft tissues  77 . During use of the subject instrument, the objective is to cut as much of the periodontal ligaments  73  as possible, for removal without destruction of the soft bone  79 . 
     While some illustrative embodiments of the invention have been described above, it is, of course, understood that various modifications will be apparent to those of ordinary skill in the art. Such modifications are within the spirit and scope of the invention, which is limited and defined only by the appended claims.