Patent Publication Number: US-2013252198-A1

Title: Dental clip

Description:
CROSS REFERENCE TO RELATED APPLICATION 
     This application claims the benefit of application Ser. No. 61/609,108 filed Mar. 9, 2012. 
    
    
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention is related generally to matrix band retainer clips for biasing and sealing a sectional matrix band against a tooth. 
     2. Related Art 
     When filling a cavity that extends to an edge of a tooth, it is common to engage a matrix band against the tooth so that a liquid filling material may be injected into the cavity and cured to restore the tooth to approximately its natural state. Retainer clips are commonly employed to bias and seal the matrix band against the tooth to prevent the liquid filling material from leaking out of the cavity before it cures. Different types of retainer clips are available for sealing the matrix band against the tooth, but these retainer clips all have various shortcomings. For example, known retainer clips typically provide limited visibility, are limited to use on a small range of teeth, are hard to open during procedures, provide limited visibility of the tooth being worked on, and degrade after each use. Dentists typically carry a range of different retainer clips for use with different types of teeth and backups of each in case of failure. Also, many known retainer clips have a tendency of disengaging during the filling procedure, which requires a rework of the entire procedure. 
     There remains a continuing need for an improved retainer clip which may be manufactured at a low cost and has an increased life span. 
     SUMMARY OF THE INVENTION 
     An aspect of the present invention provides for a matrix band retainer clip for sealing a matrix band against a tooth. The retainer clip includes a pair of tines, each of which has a generally wedge shaped piece with a pair of contact surfaces that are angled relative to one another. A spring is coupled with and extends between the tines and biases the tines towards one another to apply a biasing force from at least one contact surface of each tine against the matrix band thereby sealing the matrix band against the tooth. The spring has a generally U-shaped portion with a pair of vertically extending legs coupled with the tines at their lower ends and interconnected at their upper ends by a generally laterally extending leg for distributing a stress across a length of the spring in response to the tines being separated from one another. 
     Because of the unique shape of the spring, stresses from spreading the tines apart are distributed along substantially the entire length of the spring and there is no centralized stress point. As such, all deformation of the spring when spreading the tines is elastic, thus ensuring that the retainer clip always returns to substantially the same resting condition after each use. Because there is no plastic deformation, spreading the tines does not result in work hardening of the base material of the spring. This allows for a substantially improved lifespan as compared to other known matrix retainer clips, which tend to work harden and become increasingly brittle with each use. 
     When in an installed condition, the spring also biases the tines both towards one another and in a downward direction to prevent accidental detachment of the retainer clip from the matrix band. In other words, the connection between the retainer clip and the sectional matrix band is stronger and more durable than possible with other known retainer clips. 
     The retainer clip also provides improved visibility of the tooth being worked on for the dentist, requires less force to open and may be used on a wide range of different teeth on both sides of the mouth. As such, in addition to being easier to use than other known retainer clips, a dentist does not need to keep a large selection of clips for different types of teeth and backups for each. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       These and other features and advantages of the present invention will be readily appreciated, as the same becomes better understood by reference to the following detailed description when considered in connection with the accompanying drawings wherein: 
         FIG. 1  is a perspective elevation view of a sectional matrix band disposed between a tooth with a cavity and an adjacent tooth; 
         FIG. 2  is a perspective elevation view of an exemplary embodiment of a matrix band retainer clip; 
         FIG. 3  is a top elevation view of the exemplary embodiment of the matrix band retainer clip; 
         FIG. 4  is a side elevation view of the exemplary embodiment of the matrix band retainer clip; 
         FIG. 5  is a perspective elevation view showing tines of the exemplary embodiment of the matrix band retainer clip being spread apart from one another by a set of forceps in engagement with apertures on the tines; 
         FIG. 6  is a perspective elevation view showing the tines of the exemplary embodiment of the matrix band retainer clip being spread apart from one another by a set of forceps in engagement with notches on the tines; 
         FIG. 7  is a perspective elevation view of the exemplary embodiment of the matrix band retainer clip in engagement with a matrix band and holding a rubber dam; 
         FIG. 8  is another perspective elevation view of the exemplary embodiment of the matrix band retainer clip in engagement with a matrix band and holding a rubber dam; 
         FIG. 9  is a fragmentary and side view showing the direction of the biasing force by the tine on the tooth and the matrix band; and 
         FIG. 10  is a side elevation view showing the exemplary embodiment of the matrix band retainer clip in engagement with a sectional matrix band. 
     
    
    
     DESCRIPTION OF THE ENABLING EMBODIMENT 
       FIG. 1  shows a tooth  20  with a bored out cavity  22  for receiving a filling is shown. As shown, the bored out cavity  22  extends from a middle area of the tooth to an edge that faces an adjacent tooth  24 . Although it should be appreciated that the tooth  20  to receive the filling does not necessarily have to be decayed to have a cavity that requires a filling (e.g. it could be cracked or chipped), it will hereinafter be referred to as the “decayed tooth  20 ”. A sectional matrix band  26  (typically of stainless steel, plastic, etc.) is inserted between the decayed tooth  20  and an adjacent tooth  24  for maintaining a liquid filling material in the cavity  22  while the filling material cures from the liquid state to a solid state. As shown, a lower portion of the sectional matrix band  26  is biased against the decayed tooth  20  by a wedge  28  which is inserted between the sectional matrix band  26  and the adjacent tooth  24  to bias the lower portion of the sectional matrix band  26  against the decayed tooth  20  and establish a seal therebetween. However, in this Figure, the sides, or wings  30 , of the sectional matrix band  26  are not sealed against the decayed tooth  20 . If these wings  30  remain unsealed when the filling material is injected into the bored cavity  22 , then some of the liquid filling material may leak out of the cavity  22  before the curing is complete. This may result in a distorted outer surface on the restored tooth. 
     Referring to  FIGS. 2-10 , wherein like numerals indicate corresponding parts throughout the several views, an exemplary embodiment of a matrix band retainer clip  32  is generally shown. As shown in  FIG. 8 , when it is in an installed condition, the exemplary retainer clip  32  is biased against the wings  30  of the matrix band  26  to seal the wings  30  against the decayed tooth  20 . The seal is liquid tight, and therefore, the matrix band  26  is now able to maintain the liquid filling material in the bored out cavity  22  until the filling material finishes curing to a solid state. As discussed in further detail below, normal use of the exemplary retainer clip  32  during dental filling procedures does substantially no damage to the retainer clip  32 , thereby providing it with a significantly longer life span than other known retaining clips which tend to degrade after each use. As also shown in  FIG. 8  and discussed in further detail below, the exemplary retainer clip  32  also may hold a rubber dam  34  in a position below the decayed tooth  20  where the rubber dam  34  can catch debris or other contaminants from the filling operation. In other words, in addition to biasing the wings  30  of the sectional matrix band  26  against the decayed tooth  20 , the exemplary retainer clip  32  doubles as a rubber dam clip. 
     Referring now to  FIG. 2 , the matrix band retainer clip  32  of the exemplary embodiment includes a pair of tines  36  which are minor images of one another and are connected by a spring  38 . In the exemplary embodiment, the spring  38  is of an elongated piece of a wire-like metal which is bent through a plurality of curves so that, as shown in  FIG. 3 , when the spring  38  is in a resting condition, the tines  36  are separated from one another by a gap which is less than the width of a tooth. In the exemplary embodiment, the spring  38  is formed of an elongated, stainless steel wire. However, it should be appreciated that the spring  38  could alternately be formed of a range of different elastically deflectable materials and could have a non-circular cross-section. 
     Referring back to  FIG. 2 , the spring  38  has a pair of diverging portions  40  which are in engagement with the tines  36  and diverge away from one another when the retainer clip  32  is in the resting condition. The spring  38  also includes a generally U-shaped portion which is joined with the diverging portions  40 . The U-shaped portion has a pair of vertical legs  42  that extend in spaced and parallel relationship with one another and a single lateral leg  44  that extends generally transversely between the vertical legs  42 . The lower ends of the vertical legs  42  are joined with the ends of the diverging portions  40  opposite of the tines  36 . As will be discussed in further detail below, when the retainer clip  32  is in an installed condition, the lateral leg  44  extends vertically above a tooth from one side to the other. As shown in  FIGS. 3 and 4  respectively, when the spring  38  is in the relaxed condition, it is generally triangularly shaped when viewed from the top and L-shaped when viewed from the side. As also shown in  FIG. 3 , the lateral leg  44  of the spring  38  has a slight curve or bend shape when in the resting condition. As discussed in further detail below, the curve assists in distributing stresses along the length of the spring  38  when the tines  36  are spread apart. The retainer clip  32  preferably has a length that is in the range of 10-45 mm, a width in the range of 8-35 mm and a height in the range of 6-25 mm. 
     Referring back to  FIG. 2 , each of the tines  36  has a generally cylindrical portion  46  which receives and engages a length of a diverging portion  40  of the spring  38 . The tines  36  are preferably interconnected with the diverging portions  20  of the spring  38  through an overmolding process, i.e. the tines  36  are injection molded into engagement with a feature (not shown) on the diverging portions  40  of the spring  38 . However, it should be appreciated that the tines  36  could be joined to the spring  38  through any suitable process. An inner edge of each tine  36  has a generally wedge-shaped piece  48  that is shaped to fit at least partially into an interproximal space between adjacent teeth. As shown, in the exemplary embodiment, the wedge-shaped pieces  48  extend vertically above and below the cylindrical portion  46 , thus presenting upper and lower ledges  50 ,  52  on the top and bottom surfaces of the cylindrical portion  46  respectively. Each wedge-shaped piece  48  has a pair of contact surfaces  54  which are angled relative to one another for engaging against the sectional matrix band  26  and the adjacent tooth  24  during the dental filling operation. The tines  36  are preferably formed of a polymeric material but may be of any suitable material including, for example, various metals, ceramics or composites. 
     Referring still to  FIG. 2 , in the exemplary embodiment of the retainer clip  32 , each tine  36  has two separate features which are configured to receive forceps  56  (such as those shown in  FIGS. 5 and 6 ) or other tools to spread the tines  36  apart from one another for engaging the retainer clip  32  against a sectional matrix band  26  or disengaging the retainer clip  32  from the sectional matrix band  26 . In other words, the forceps  56  (or other tools) engage the features for installation and removal of the exemplary retainer clip  32 . One of the features is an aperture  58  which is disposed on the opposite side of the spring  38  from the wedge-shaped piece  48 . In  FIG. 5 , a set of dental forceps  56  is shown engaging the apertures  58  and spreading the tines  36  apart from one another. Referring back to  FIG. 2 , the other feature is a notch  60  on an inner edge of each tine  36 . In  FIG. 6 , the forceps  56  are shown engaging the notches  60  on the tines  36  and spreading the tines  36  apart from one another. A dentist or dental assistant may use whichever feature he or she feels more comfortable with to spread the tines  36  apart. However, it should be appreciated that the retainer clip  36  could have any suitable feature or features for spreading the tines  36 . 
     Because of the shape of the spring  28 , spreading the tines  36  apart is a very simple process which requires very little effort by a dentist or a dental assistant. Additionally, during normal use of the exemplary retainer clip  32 , spreading the tines  36  apart does substantially no damage to the spring  38 . For example, as best shown in  FIG. 5 , stresses from spreading the tines  36  apart are distributed along substantially the entire length of the spring  38  and there is no centralized stress point as is common on other known retainer springs. As such, all deformation of the spring  38  when the tines  36  are spread apart is elastic, thus ensuring that the retainer clip  32  always returns to substantially the same resting condition after each use. Because there is no plastic deformation, spreading the tines  36  does not result in work hardening of the base material of the spring  38 . This allows for a substantially improved lifespan as compared to other known matrix retainer clips, whose springs tend to work harden and become increasingly brittle with each use. When the tines  36  of the exemplary embodiment are spread apart, the diverging portions  40  and the lateral leg  44  of the spring  38  experience a bending stress and the vertical legs  42  experience both a twisting and bending stresses. 
     Referring now to  FIG. 10 , a lower area of each tine  36  includes a laterally extending groove  62  for partially encircling the wedge  28  between the matrix clip  26  and the adjacent tooth  24  during the dental filling operation. As shown, the groove  62  extends laterally through the middle of the wedge-shaped piece  48 , which is aligned with the middle of the interproximal space between the decayed tooth  20  and the adjacent tooth  24 . 
     Use of the retainer clip  32  is a very simple and quick process. First, the sectional matrix band  26  is put in place between the decayed tooth  20  and the adjacent tooth  24  as shown in  FIG. 1 . A wedge  28  may then be inserted between the sectional matrix band  26  and the adjacent tooth  24  to bias a lower portion of the sectional matrix band  26  against the decayed tooth  20 . Next, with the sectional matrix band  26  and the wedge  28  in place, a user engages prongs on a set of forceps  56  into either the apertures  58  or the notches  60  on the tines  36 , spreads the tines  36  apart, and releases the forceps  56  from the tines  36  so that the wedge  28  shaped pieces  48  project into the interproximal space between the sectional matrix band  26  and the adjacent tooth  24 . As shown in  FIG. 8 , in this installed condition, the spring  38  biases one contact surface  54  of each of the wedge-shaped pieces  48  against a wing  30  on the sectional matrix band  26  to seal the wing  30  against the decayed tooth  20  and biases the other contact surface  54  against the adjacent tooth  24 . Referring now to  FIG. 9 , in addition to being biased inwardly, the configuration of the spring  38  causes the tines  36  to also be biased in a vertically downward direction towards the gingival margin of a patient&#39;s mouth. This prevents accidental disengagements of the retainer clip  32  from the sectional matrix band  26  during the dental filling procedure. In other words, a stronger connection is established between the sectional matrix band  26  and the retainer clip  32  of the exemplary embodiment than is possible with other known retainer clips. 
     The retainer clip  32  of the exemplary embodiment may then be inserted through an opening in a rubber dam  34  and the rubber dam  34  may be sealed against the decayed tooth  20  and the adjacent tooth  24  for catching any debris from the dental filling operation. The rubber dam  34  is held vertically below the retainer clip  32  and out of the way of the dentist or dental assistant by the lower ledges  52  on the tines  36 . For example,  FIG. 8  shows a rubber dam  34  that is held in place by the retainer clip  32  of the exemplary embodiment. Since the retainer clip  32  of the exemplary embodiment holds the rubber dam  34  in place, a separate rubber dam clip is not required. In addition to cost savings, this provides for time savings because the dentist or dental assistant only has to use one clip, not two. A dentist or dental assistant may then inject the liquid filling material into the bored cavity  22  of the decayed tooth  20 . The rubber dam  34 , retainer clip  32 , wedge  28  and sectional matrix band  26  are preferably left in place until the filling material cures to a solid state. 
     Referring now to  FIG. 10 , when the retainer clip  32  is in an installed position biased against a sectional matrix band  26 , the tines  36  are substantially entirely below the top surface of the decayed tooth  20  and the diverging portions  40  of the spring  38  run along the gingival line. As such, only the lateral leg  44  and portions of the vertical legs  42  are disposed vertically above the top surface of the decayed tooth  20 . However, as shown in  FIG. 8 , the lateral leg  44  and the vertical legs  42  of the spring  38  are spaced longitudinally from the decayed tooth  20 . This unique configuration provides the dentist or dental assistant with easy access to the bored cavity  22  of the decayed tooth  20  to make the filling process itself easier than when other known retaining clips are employed. 
     Obviously, many modifications and variations of the present invention are possible in light of the above teachings and may be practiced otherwise than as specifically described while within the scope of the appended claims.