Abstract:
A method is designed to mount an inner crown of a restoration tooth on a natural or artificial abutment. The method involves a first step in which the inner crown is provided in a hollow interior with a cement coating before the inner crown is fitted over the natural or artificial abutment. The natural or artificial abutment is then provided with a retaining hole which is drilled into an interior of the natural or artificial abutment from one upright wall of the inner crown. The retaining hole is used to retain a retention pin or securing the inner crown to the natural or artificial abutment. The inner crown is thus prevented from becoming disengaged with the natural or artificial abutment by the cement coating and the retention pin.

Description:
FIELD OF THE PRESENT INVENTION  
       [0001]     The present invention relates generally to dental restorative devices, and more particularly to a method of preventing inner crown of a removable restoration tooth from becoming disengaged with a natural or artificial abutment tooth.  
       BACKGROUND OF THE PRESENT INVENTION  
       [0002]     A decayed or diseased tooth is generally restored to its former condition by means of a restoration tooth, which may be either fixed or removable.  
         [0003]     As illustrated in  FIGS. 1-3 , a process of making a fixed restoration tooth “t” involves a first step in which a decayed or diseased tooth is mended such that it is provided with an abutment  1 , as shown in  FIG. 2 . Thereafter, a print of the abutment  1  is made. On the basis of the abutment print, a restoration tooth “t” is formed by a dental technician. The restoration tooth so formed is provided therein with a crown seat  2 , as shown in  FIG. 3 .  
         [0004]     As illustrated in  FIGS. 2-5 , the mounting of the restoration tooth “t” involves a first step in which an appropriate amount of cement “C” is injected into the crown seat  2 . Thereafter, the crown seat  2  is fitted over the abutment  1 , so as to mount fixedly the restoration tooth “t” on the abutment of the decayed or diseased tooth. In another words, the decayed or diseased tooth is restored, as illustrated in  FIGS. 5 and 6 . However, there is a gap “δ” between the restoration tooth “t” and a healthy tooth “N” adjacent to the restoration tooth “t”, as shown in  FIG. 6 . The food particles are apt to deposit in the gap “δ”, which becomes a breeding ground for bacteria responsible for inflammation of the gums. In light of the restoration tooth “t” being mounted fixedly, it can not be removed in its entirety and replaced with a new one. For this reason, the fixed restoration tooth is less popular than a removable restoration tooth, which is described hereinafter with reference to  FIGS. 7-9 .  
         [0005]     The process of making the removable restoration tooth “T” involves a first step in which a decayed or diseased tooth  10  is provided with an abutment  11 , as shown in  FIG. 8 . A print of the abutment  11  is made. On the basis of the abutment print, a hollow inner crown  20  is made by a dental technician. The inner crown  20  is then fitted over the abutment  11 . Thereafter, a print of the inner crown  20  is made. On the basis of the print of the inner crown  20 , the removable restoration tooth “T” is made by a dental technician such that the removable restoration tooth “T” is provided therein with an outer crown  30  which is shaped to fit over the inner crown  20 , as illustrated in  FIG. 9 .  
         [0006]     As illustrated in  FIGS. 9-11 , The mounting of the removable restoration tooth “T” is done by first providing the inner wall of the hollow inner crown  20  with a coating of cement “C”. The inner crown  20  is then fitted over the abutment  11  of the decayed or diseased tooth  10 . The inner crown  20  is fixedly joined with the abutment  11  by virtue of the cement coating. As the cement “C” hardens, the inner crown  20  is firmly fastened with the abutment  11 . The removable restoration tooth “T” is finally mounted on the abutment  11  by fitting the outer crown  30  of the removable restoration tooth “T” over the inner crown  20 , as shown in  FIG. 11 .  
         [0007]     As shown in  FIG. 13 -A, a gap “δ” is formed between the removable restoration tooth “T” and a healthy tooth “N” adjoining the restoration tooth “T”. The gap “δ” can be easily kept clean by removing temporarily the restoration tooth “T”, as illustrated in  FIG. 13 -B. As a result, the gap “δ” is no longer a culprit for the gums inflammation. Accordingly, the longevity of the restored tooth  10  is effectively prolonged.  
         [0008]     As shown in FIGS.  14 -A and  14 -B, two teeth  10  are restored by a bridge—type restoration tooth T′, which can be removed to facilitate the cleaning of a gap “δ′”. Upon completion of the cleaning of the gap “δ”, the restoration tooth T′ is rejoined with the two teeth  10 .  
         [0009]     Such a conventional removable restoration teeth “T” as described above has its own share of deficiencies. As illustrated in  FIG. 12 , the outer crown  30  of the removable restoration tooth “T” has two upright inner contact surfaces  31 , whereas the inner crown  20  has two upright outer contact surfaces  21 . The outer crown  30  is fitted over the inner crown  20  such that the tolerance between the inner contact surfaces  31  and the outer contact surfaces  21  takes the form of interference fit instead of clearance fit. As a result, when an effort is made to remove the restoration tooth “T” from the abutment  11  of the restored tooth  10 , a frictional force “F” of the inner contact surfaces  31  and the outer contact surfaces  21  produces a vertical component of force “F 1 ” relative to the inner crown  20 . The vertical component of force “F 1 ” forms a tension against the inner crown  20  at the time when the outer crown  30  is detached from the inner crown  20 . As a result, the inner crown  20  is vulnerable to becoming disengaged with the abutment  11  of the restored tooth  10 . In addition, the outer contact surfaces  21  of the inner crown  20  are not uniformly exerted on by the force of a chewing action, thereby resulting in an irregular moment of force between the abutment  11  and the inner crown  20 . In another words, the abutment  11  and the inner crown  20  are prone to separation. Moreover, the inner crown  20  of the removable restoration tooth “T” is fastened with the abutment  11  by the cement “C”, as illustrated in  FIG. 11 . The amount of the cement “C” coated on the inner side walls of the inner crown  20  can not be easily controlled with precision. The excess cement “C” is likely to flow out. Such a cement remnant, if not removed, can cause inflammation of the gums.  
       SUMMARY OF THE PRESENT INVENTION  
       [0010]     The primary objective of the present invention is to provide a method of preventing inner crown of a removable restoration tooth from becoming disengaged with a natural or artificial abutment. The method involves the use of a retention pin to hold firmly the inner crown and the natural or artificial abutment. The retention pin is retained in a retaining hole of a depth and extending from the inner crown into an interior of the abutment. A plurality of the retention pins may be used to reinforce the engagement of the inner crown with the abutment.  
         [0011]     It is another objective of the present invention to provide a method of preventing inner crown of a removable restoration tooth from becoming disengaged with a natural or artificial abutment. The method involves the drilling of a drain hole in the inner crown. The drain hole is located in the top of the inner crown for drawing off an excess cement which is used to hold the inner crown and the abutment. The remnant of the excess cement can be easily removed from the top of the inner crown by a dentist.  
         [0012]     It is still another objective of the present invention to provide a method of preventing inner crown of a removable restoration tooth from becoming disengaged with a natural or artificial abutment. The method involves the mounting of the inner crown on the abutment in such a way that a passage can be bored through the inner crown and the abutment for the purpose of treating the tooth root. The passage can be mended in the wake of the tooth root treatment.  
         [0013]     The features and the advantages of the present invention will be more readily understood upon a thoughtful deliberation of the following detailed description of the preferred embodiments of the present invention with reference to the accompanying drawings. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0014]      FIG. 1  shows a process flow diagram of a prior art fixed restoration tooth.  
         [0015]      FIG. 2  shows an exploded view of the prior art fixed restoration tooth.  
         [0016]      FIG. 3  shows an exploded sectional view of the prior art fixed restoration tooth.  
         [0017]      FIG. 4  shows a perspective view of the prior art fixed restoration tooth in combination.  
         [0018]      FIG. 5  shows a sectional schematic view of the prior art fixed restoration tooth in combination.  
         [0019]      FIG. 6  shows a schematic view of the prior art fixed restoration tooth and a healthy tooth adjoining thereto.  
         [0020]      FIG. 7  shows a process flow diagram of a prior art removable restoration tooth.  
         [0021]      FIG. 8  shows an exploded view of the prior art removable restoration tooth.  
         [0022]      FIG. 9  shows an exploded sectional view of the prior art removable restoration tooth.  
         [0023]      FIG. 10  shows a perspective view of the prior art removable restoration tooth in combination.  
         [0024]      FIG. 11  shows a sectional view of the prior art removable restoration tooth in combination.  
         [0025]      FIG. 12  shows a sectional schematic view of the prior art removable restoration tooth at work.  
         [0026]      FIG. 13A  shows a sectional schematic view of the prior art removable restoration tooth along with a healthy tooth adjoining thereto.  
         [0027]      FIG. 13B  shows a schematic view of the prior art removable restoration tooth at work.  
         [0028]      FIG. 14A  shows a sectional schematic view of a bridge—type restoration tooth of the prior art at work.  
         [0029]      FIG. 14B  shows another sectional schematic view of the bridge—type restoration tooth of the prior art at work.  
         [0030]      FIG. 15  shows a schematic process of a first preferred embodiment of the present invention.  
         [0031]      FIG. 16  shows a schematic view of the first preferred embodiment of the present invention at work.  
         [0032]      FIG. 17  shows a schematic process of a second preferred embodiment of the present invention.  
         [0033]      FIG. 18  shows a schematic process of a third preferred embodiment of the present invention.  
         [0034]      FIG. 19  shows a schematic view of a fourth preferred embodiment of the present invention at work.  
         [0035]      FIG. 20  shows a schematic process of the fourth preferred embodiment of the present invention.  
         [0036]      FIG. 21  shows a schematic view of a fifth preferred embodiment of the present invention at work.  
         [0037]      FIG. 22  shows a schematic process of the fifth preferred embodiment of the present invention.  
         [0038]      FIG. 23  shows a schematic view of the a sixth preferred embodiment of the present invention.  
         [0039]      FIG. 24  shows a schematic process of the sixth preferred embodiment of the present invention.  
         [0040]      FIG. 25  shows a perspective view of an inner crown of the present invention.  
         [0041]      FIG. 26  shows a sectional view taken along the direction indicated by a line A-A as shown in  FIG. 25 . 
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT  
       [0042]     The first preferred embodiment of the present invention involves a first step in which an inner crown  200  of a hollow construction is provided in an inner wall with a cement coating “C”, as shown in  FIG. 15 -A. Thereafter, the inner crown  200  is fitted over an abutment  101  of a natural tooth  100  td be restored, as shown in  FIG. 15 -B. The cement coating serves to hold the inner crown  200  and the abutment  101  together.  
         [0043]     As shown in  FIG. 15 -C, a retaining hole  102  of an appropriated depth is bored in one upright wall of the inner crown  200  such that said retaining hole  102  extends into the abutment  101  of the natural tooth  100 .  
         [0044]     As shown in  FIG. 15 -D, the engagement of the inner crown  200  with the abutment  101  is reinforced by a retention pin “P” which is retained in the retaining hole  102  such that an outer end of the retention pin “P” is level with the outer surface of the upright wall of the inner crown  200 .  
         [0045]     As shown in  FIG. 17 -A, the second preferred embodiment of the present invention comprises a first step in which an upright wall of a hollow inner crown  210  is provided with a through hole  211 . Thereafter, the hollow inner crown  210  is provided in an inner wall with a cement coating “C”, as shown in  FIG. 17 -B. The inner crown  210  is then fitted over an abutment  111  of a natural tooth  110  to be restored, as shown in  FIG. 17 -C. The cement coating “C” serves to hold securely the inner crown  210  and the abutment  111 . The inner crown  210  is provided in one upright wall with a through hole  211 . The abutment  111  is provided with a retaining hole  112  of a depth and extending from the through hole  211  of the inner crown  210 , as shown in  FIG. 17 -D. The engagement of the inner crown  210  with the abutment  111  is reinforced by a retention pin “P”, which is inserted into the retaining hole  112  of the abutment  111  via the through hole  211  of the inner crown  210 . The retention pin “P” has an outer, which is level with the outer surface of the upright wall of the inner crown  210 , as shown in  FIG. 17 -D, and  FIG. 17 -E.  
         [0046]     The third preferred embodiment of the present invention comprises a first step in which an inner crown  220  of a hollow construction is provided in one upright wall with a first through hole  221 , as shown in  FIG. 18 -A. Thereafter, the inner crown  220  is provided in an inner wall with a cement coating “C”, as shown in  FIG. 18 -B. The coated inner crown  220  is then fitted over an abutment  121  of a natural tooth  120  to be restored, as shown in  FIG. 18 -C. The cement “C” serves to hold the inner crown  220  and the abutment  121  firmly together. The abutment  121  is provided with a through hole  122  extending from the first through hole  221  of the inner crown  220 . The inner crown  220  is further provided in other upright wall with a second through hole  222  in alignment with the through hole  122  of the abutment  121  and the first through hole  221  of the inner crown  220 , as shown in  FIG. 18 -D. A retention pin “P” is inserted from the first through hole  221  into the through hole  122  of the abutment  121  such that both ends of the retention pin “P” are jutted out of the first through hole  221  and the second through hole  222  of the inner crown  220 , as shown in  FIG. 18 -E. Both ends of the retention pin “P” are trimmed such that both ends of the retention pin “P” are level with the outer surface of the two upright walls of the inner crown  220 , as shown in  FIG. 18 -F.  
         [0047]     As illustrated in  FIGS. 19 and 20 , The fourth preferred embodiment of the present invention involves a first step in which an inner crown  400  is provided in one upright wall with a through hole  401 , as shown in  FIG. 20 -A. Thereafter, the hollow inner crown  400  is provided in an inner wall with a cement coating “C”, as shown in  FIG. 20 -B. The coated inner crown  400  is then fitted over an abutment  301  of an artificial abutment tooth  300 , as shown in  FIG. 20 -C. The cement holds the inner crown  400  and the abutment  301  firmly together. The inner crown  400  is provided in one upright wall with a through hole  401 . Meanwhile the abutment  301  is provided with a retaining hole  302  extending from the through hole  401  of the inner crown  400 . The retaining hole  302  is corresponding in hole diameter to the through hole  401 , as shown in  FIG. 20 -D. The engagement of the inner crown  400  with the abutment  301  of the artificial abutment tooth  300  is reinforced by a retention pin “P”, which is inserted into the retaining hole  302  via the through hole  401 , as shown in  FIG. 20 -E. An outer end of the retention pin “P” is so trimmed that it is level with the outer surface of the upright wall of the inner crown  400 , as shown in  FIG. 20 -F.  
         [0048]     As illustrated in  FIGS. 22 and 23 , The fifth preferred embodiment of the present invention comprises an inner crown  500  which is provided in an upright wall thereof with a first through hole  501 , as shown in  FIG. 22 -A. The inner crown  500  is then provided in an inner wall with a cement coating “C”, as shown in  FIG. 22 -B. The coated inner crown  500  is fitted over an abutment  601  of an artificial abutment tooth  600 , as shown in  FIG. 22 -C. The cement coating is used to hold the inner crown  500  and the abutment  601  firmly together. The abutment  601  is then provided with a retaining through hole  602  extending from the through hole  501 . In the meantime, the inner crown  500  is further provided in another upright wall thereof with a second through hole  502  in alignment with the retaining through hole  602  of the abutment  601  and the first through hole  501  of the inner crown  500 , as shown in  FIG. 22 -D. The engagement of the inner crown  500  with the artificial abutment  601  is reinforced by a retention pin “P” which is inserted into the retaining through hole  602  via the first through hole  501  or the second through hole  502 , as illustrated in  FIG. 22 -E. Finally, both ends of the retention pin “P” are so trimmed that they are level with the outer surface of the upright walls of the inner crown  500 , as shown in  FIG. 22 -F.  
         [0049]     The sixth preferred embodiment of the present invention comprises an artificial abutment tooth  700  which is provided with an abutment  701  having a through hole  702 , as shown in  FIG. 24 -A. A dental technician is then given the artificial abutment tooth  700  along with a retention pin “P” equal in diameter to the through hole  702  and greater in length than the through hole  702  for making a wax matrix of an inner crown  800 , as shown in  FIG. 24 -B. The wax matrix is used for casting a metal inner crown  800  which is provided with two through holes  801  opposite to each other, as shown in  FIG. 24 -C. The metal inner crown  800  is then provided in an inner wall with a cement coating “C”, as shown in  FIG. 24 -D. The coated inner crown  800  is then fitted over the abutment  701  of the artificial abutment tooth  700  such that the two through holes  801  of the inner crown  800  are aligned with the through hole  702  of the abutment  701 , as shown in  FIG. 24 -E. The retention pin “P” is inserted into the through hole  702  of the abutment  701  via one of the two through holes  801  of the inner crown  800 , as illustrated in  FIG. 24 -F. Both ends of the retention pin “P” are so trimmed that they are level with outer surface of the two upright walls of the metal inner crown  800 , as shown in  FIG. 24 -G.  
         [0050]     As shown in  FIGS. 25 and 26 , the inner crowns of the preferred embodiments of the present invention described above have a main body  70  which is formed of a bottom  71 , a top  72 , and an outer surface  73 . The main body  70  is provided with a receiving space  711  extending from the bottom  71  toward the top  72  such that an inner wall of the receiving space  711  and the top  72  have an inclination, thereby oausing the inner diameter of the receiving space  711  to become progressively small toward the top  72 . The top  72  is provided with a drain hole  721  in communication with the receiving space  711 . The outer surface  73  has a top edge  731  contiguous to the top  72 , and a bottom edge  732  contiguous to the bottom  71 . The outer surface  73  is provided with a through hole  733  in communication with the receiving space  711 . The through hole  733  is used to retain a retention pin “P”, as shown in  FIG. 25 . The drain hole  721  is used to discharge the excess cement which is coated in the inner wall of the receiving space  711 . The cement residue can be easily removed from the top  72  of the inner crown by a dentist.  
         [0051]     The embodiments of the present invention described above are to be regarded in all respects as being illustrative and nonrestrictive. Accordingly, the present invention may be embodied in other specific forms without deviating from the spirit thereof. The present invention is thereof to be limited only by the scopes of the following claims.