JP2010148558A - Dental implant and connecting screw for dental implant - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a dental implant and a connecting screw for a dental implant which are constituted to break at a region where work to remove a connecting screw remaining by breakage is easy to be prepared for any possibility of a breakage accident of the connecting screw. <P>SOLUTION: The dental implant is equipped with a fixture buried in an alveolar bone, an abutment having one end fit in the fixture and the other end on which a prosthetic tooth is mounted, and the connecting screw for connecting the fixture and the abutment. The connecting screw comprises a fixing head part having a large outer diameter, a thread part where an outer thread is formed, and a shaft part for connecting the head part and the thread part and has a decreased strength part which has slightly decreased mechanical strength, extends in a direction perpendicular to the axis in the shaft part, and is located between a first position located closer to a proximal end side rather than to a boundary part set by the fixing head part and the shaft part and a second position defining a length so that the part remaining by the breakage is used as a grasping part. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to an artificial tooth root that is implanted in an alveolar bone for mounting an artificial tooth and a connection screw for an artificial tooth root.

  Artificial dental roots (so-called implants) embedded in a tooth-depleted part generally include artificial teeth, fixtures implanted in alveolar bone, abutments on which artificial teeth are mounted, fixtures and abutments. And a connecting screw for connecting the ment.

  The connecting screw is composed of a head portion having a large outer diameter, a screw portion in which an external screw is formed, and a shaft portion that connects the head portion and the screw portion. The connection screw is mainly used from the viewpoint of establishing a strong connection in the fixture and the abutment and from the viewpoint of ease of assembly and disassembly.

The connecting screw is inserted into the shaft hole that penetrates the inside of the convex portion of the abutment while the convex portion provided at the lower end of the abutment is fitted to the concave portion provided in the fixture. . Then, the fixture and the abutment are screwed and fixed by screwing the screw portion of the connecting screw into the inner screw of the bottomed screw hole of the fixture (see, for example, Patent Document 1).
JP 09-66065 A

  In this way, since the connecting screw is inserted into the small diameter shaft hole formed in the reduced diameter convex part of the abutment, the outer diameter of the connecting screw is significantly larger than the outer diameter of the fixture. small. Therefore, since the connecting screw is thinner than the fixture or the abutment, the mechanical strength is not sufficiently high.

  Since the mechanical strength of the connecting screw is not so high, the connecting screw may be damaged during or after the operation.

  That is, during the operation, when incomplete screwing fixation is performed in which the connecting screw is inserted at an angle or a foreign object such as a bone fragment is bitten, excessive torsion torque is applied to the connecting screw. The connecting screw is often damaged at the shaft portion or the screw portion.

  In addition, after the operation, the occlusal force (acting as a bending stress on the connecting screw) is repeatedly applied to the artificial tooth root. As a result, the connecting screw has a boundary portion (outer diameter) that defines the boundary between the head portion and the shaft portion. It often breaks at parts where the dimensions change sharply. Further, even after the operation, if the connection state of the connection screw becomes loose, the connection screw is not limited to the boundary portion, and the shaft portion or the screw portion may be damaged.

  If such a breakage occurs in the connection screw, the degree of difficulty in removing the broken connection screw varies greatly depending on where the breakage occurs in the connection screw.

  That is, when the connecting screw is broken at the shaft portion close to the head portion, the connecting screw can be removed relatively easily using the remaining portion of the shaft portion. However, when the connecting screw is broken at the screw portion or the shaft portion close to the screw portion, it is difficult to remove the connecting screw because there is almost no portion for gripping. Therefore, the artificial root connection screw according to the prior art has a problem that breakage occurs at the screw portion or the shaft portion close to the screw portion where it is difficult to remove the damaged connection screw.

  Therefore, a technical problem to be solved by the present invention is that an artificial tooth root configured to be broken at a site where it is easy to remove the connection screw remaining due to the damage in case of an accident of damage to the connection screw. And providing a connecting screw for an artificial tooth root.

  In order to solve the above technical problem, according to the present invention, the following artificial tooth root is provided.

That is, the artificial tooth root according to the present invention is
A fixture embedded in the alveolar bone,
An abutment in which one end is fitted to the fixture and an artificial tooth is attached to the other end;
A connection screw for connecting the fixture and the abutment,
The connecting screw is
A fixed head portion having a large outer diameter,
A threaded portion with an external thread;
A shaft portion that connects the head portion and the screw portion,
A first position where the strength-decreasing portion having a slightly reduced mechanical strength extends in the axis-perpendicular direction in the shaft portion and is located closer to the base end side than the boundary portion defined by the fixed head portion and the shaft portion. And a second position where the portion remaining due to breakage can be used as a gripping portion.

  According to the above configuration, in the artificial tooth root according to the present invention, the connection screw (so-called abutment screw) extends in the direction orthogonal to the axis of the shaft portion and is appropriately positioned between the first position and the second position. The strength reduction part arrange | positioned in is provided. The strength reduction portion is configured to be slightly lower than the original mechanical strength of the shaft portion. Here, the strength slightly lower than the original mechanical strength of the shaft part means that even if an excessive occlusal force after the operation (bending stress on the connecting screw) is applied, it will not break at the reduced strength part. It indicates the strength at which breakage due to excessive torsional torque load or loosening of the connecting screw after surgery occurs in the reduced strength portion.

  After the operation, an excessive occlusal force is applied to the connecting screw, so that a boundary portion that is weak against bending stress is damaged. In addition, an excessively low torsional torque load during the operation, loosening of the connecting screw after the operation, and the like, the strength-decreasing portion that is weak against the torsional torque is damaged. Therefore, an unexpected breakage in the connecting screw occurs at least on the terminal side of the strength reduction portion, that is, in the boundary portion or the strength reduction portion. In the remaining connection screw after the breakage, a portion having a length that can be used as a gripping portion remains, so that the connection screw can be removed relatively easily using the remaining portion in the shaft portion. Can do.

  The strength reduction part can be implemented in various forms such as structural control and surface property control, but from the viewpoint of stable control of the strength, the strength reduction part is slightly recessed from the outer surface of the shaft part. It is preferable that it is a dent.

  The strength reduction portion may have a discontinuous annular shape as shown by a broken line, but preferably has a continuous annular shape from the viewpoint of ease of formation.

  The boundary portion has any one of an inclined shape, a curved shape, and a planar shape.

  The strength reduction portion is formed by any one of a machining method, a laser annealing method, and an etching method.

  Hereinafter, an embodiment of an artificial tooth root 1 according to the present invention will be described in detail with reference to FIGS.

  FIG. 1 is a schematic view showing a state in which the artificial dental root 1 is implanted in the alveolar bone 62. FIG. 2 is a longitudinal sectional view of the artificial tooth root 1 according to an embodiment of the present invention. FIG. 3 is a longitudinal sectional view of a connecting screw used in the artificial tooth root 1 shown in FIG.

  As shown in FIG. 2, the artificial tooth root 1 is mainly composed of a fixture 10, an abutment 30, and an abutment screw 40. As the material of the artificial tooth root 1, known materials, for example, metal materials such as pure titanium, titanium alloy, cobalt-chromium alloy and molybdenum alloy, and ceramic materials such as alumina ceramic are used. Pure titanium and titanium alloy are used. Is preferred.

  The fixture 10 has a slightly tapered generally cylindrical shape, and an external screw 12 is formed on the outer peripheral surface thereof. The outer thread 12 has a higher thread as it goes to the tip side. Moreover, the screw thread on the tip side is partially cut out, and has a function of preventing rotation of the screw after insertion by allowing bone components to enter the cutout portion after implantation. As shown in FIG. 1, the fixture 10 is firmly embedded and fixed in the alveolar bone 62 after passing through the gingiva 66 and the bone papilla 64 as shown in FIG. 1.

  A hollow bottomed hole 14 is formed inside the fixture 10, and an inner screw 17 is formed on the inner wall surface thereof. The inner screw 17 is screwed with a screw portion 43 of an abutment screw 40 described later. At the end of the hollow bottomed hole 14 of the fixture 10, a stepped engagement recess 16 having a substantially regular hexagonal shape for receiving the engagement projection 36 of the abutment 30 is provided.

  On the side peripheral surface of the fixture 10, a portion that contacts the alveolar bone 62 is roughened by mechanical means and / or chemical means. Mechanical means for roughening include sand blasting and the like, and coating with calcium phosphate (hydroxyapatite) to improve affinity with bone.

  The abutment 30 has a substantially cylindrical shape, has an artificial tooth mounting portion 32 on the distal end side thereof, and has an engaging convex portion 36 on the base side thereof. The outer dimension of the engaging convex portion 36 having a substantially regular hexagonal shape is smaller than the diameter of the cylindrical artificial tooth mounting portion 32. A regular hexagonal engagement convex portion 36 is inserted into the engagement concave portion 16 of the fixture 10.

  As shown in FIG. 2, a two-stage through-hole 38 having a large diameter on the distal end side and a small diameter on the base side is formed inside the abutment 30. The large-diameter portion on the distal side is a size in which the fixed head portion 44 of the abutment screw 40 can be inserted, and the small-diameter portion on the base side is a size in which the screw portion 43 of the abutment screw 40 can be inserted. A locking end 34 that receives the inclined boundary portion 45 of the abutment screw 40 is formed in the middle of the through hole that switches from the large-diameter portion on the terminal side to the small-diameter portion on the base side.

  Accordingly, the hollow bottom hole 14 of the fixture 10 and the two-stage through hole 38 of the abutment 30 are configured to be coaxial, and the connection is made in a state where these holes are coaxially connected. An abutment screw 40 as a screw is inserted.

  As shown in FIG. 3, the abutment screw (connection screw) 40 made of pure titanium, titanium alloy, or the like has a generally cylindrical shape with a two-stage configuration in which the distal side has a large diameter and the base side has a small diameter. That is, the abutment screw 40 includes a fixed head portion 44 in which a loading device (a so-called driver) is attached to a concave head portion of the fixed head portion 44, and a small-diameter shaft portion 42 extending to the base side of the fixed head portion 44. And a threaded portion 43 provided on the base side of the shaft portion 42. The outer diameter of the fixed head portion 44 is larger than that of the shaft portion 42 and the screw portion 43. As already described, the screw portion 43 is screwed to the inner screw 17 of the fixture 10. The boundary between the proximal end portion of the fixed head portion 44 and the distal end portion of the shaft portion 42 is defined by an inclined boundary portion 45.

  The shaft portion 42 of the abutment screw 40 is provided with a constricted portion 46 as a strength decreasing portion. The constricted portion 46 has a continuous ring (annular) shape extending in a direction orthogonal to the axis of the shaft portion 42, and is a dent slightly recessed with respect to the outer surface of the shaft portion 42. Further, the constricted portion 46 is located at the base end side from the boundary portion 45, and is located at the base end side further from the first position. And a second position such that the remaining portion 48 on the side has such a length that it can be used as a grip. Since the base end portion of the boundary portion 45 is the portion that is most vulnerable to bending stress, the first position is located slightly on the base end side from the base end portion of the boundary portion 45. Further, the length of the remaining portion 48 of the shaft portion 42 remaining in the fixture 10 after the breakage is defined by the second position. The remaining portion 48 is used as a grip portion when the remaining piece of the abutment screw 40 is removed.

  The mechanical strength of the constricted portion 46 as the above-described reduced strength portion is configured to be slightly lower than the original mechanical strength of the shaft portion 42. Here, the mechanical strength slightly lower than the original mechanical strength of the shaft portion 42 means that the constricted portion 46 is affected by excessive occlusal force (bending stress on the abutment screw 40) after the operation. Although it does not break, it refers to the strength at which breakage due to excessive torsional torque load during the operation or loosening of the abutment screw 40 after the operation occurs in the constricted portion 46.

  Due to the excessive occlusal force after the operation, the boundary portion 45 that is weak against the bending stress is broken, or the torsion is caused by the excessive torsional torque load during the operation or the loosening of the abutment screw 40 after the operation. In the abutment screw 40 according to the present invention, an accidental breakage in the abutment screw 40 is at least more distal than the constricted portion 46 as the strength reduction portion. That is, it occurs at the base end portion or the constricted portion 46 of the boundary portion 45. In the remaining abutment screw 40 after the breakage, the remaining portion 48 having a length that can be used as a gripping portion remains. Therefore, the remaining portion 48 in the shaft portion 42 is used to make the abutment screw 40. Can be removed relatively easily.

  In addition, the abutment screw 40 and the constricted part 46 as a strength reduction part are shown as follows as an example which does not restrict | limit this invention.

  The fixed head portion 44 has a diameter of 1.5 to 4 mm, the shaft portion 42 has a diameter of 0.7 to 2 mm, and the screw portion 43 has a diameter of 1.4 to 2 mm. The length of the fixed head portion 44 is 0.5 to 15 mm, the length of the shaft portion 42 is 1 to 5 mm, and the length of the screw portion 43 is 1 to 5 mm.

  The constricted portion 46 is preferably a groove having a rectangular shape, wedge shape, or arc shape in cross section, and more preferably an arc shape groove from the viewpoint of easy machining. The groove depth of the constricted portion 46 is preferably 0.005 to 0.05 mm, and more preferably 0.007 to 0.02 mm. The groove width of the constricted portion 46 is preferably 0.1 to 1.5 mm, and more preferably 0.2 to 1.0 mm. The arc-shaped groove preferably has a radius of curvature of 0.2 to 5 mm, and more preferably 0.5 to 2 mm. The first position of the constricted portion 46 is preferably at a position of 0.1 to 2 mm, more preferably at a position of 0.2 to 1 mm, from the base end portion of the boundary portion 45 toward the screw portion 43. . Further, the length of the remaining portion 48 of the shaft portion 42 is preferably about 1 mm or more, and more preferably 1 to 2 mm. When the numerical expressions such as the groove depth, groove width, and radius of curvature of the constricted portion 46 described above are expressed from the viewpoint of mechanical strength, the mechanical strength of the constricted portion 46 is higher than the original mechanical strength of the shaft portion 42. It is preferably 0.5 to 15% lower, more preferably 1 to 10% lower.

  Although another embodiment according to the present invention will be described with reference to FIG. 4, the description will focus on differences from the above embodiment.

  As shown in FIG. 4, in the abutment screw 40, the boundary between the proximal end of the fixed head portion 44 and the distal end of the shaft portion 42 is flat at the proximal end of the fixed head portion 44. Therefore, it is defined by the boundary portion 45 that changes steeply in a step shape. The planar boundary portion 45 of the abutment screw 40 is received by the locking end 34 of the abutment 30.

  As in the case of the inclined boundary portion 45 in the above-described embodiment, the first position is located on the proximal side with respect to the boundary portion 45, but the shaft portion 42 is equivalent to the absence of the inclined boundary portion 45 in the above-described embodiment. The length in the axial direction is slightly longer. As a result, the dispositionable range in which the constricted portion 46 as the strength-decreasing portion can be disposed is slightly expanded toward the end side.

  As still another embodiment of the present invention, the boundary portion 45 that defines the boundary between the proximal end portion of the fixed head portion 44 and the distal end portion of the shaft portion 42 is curved with a certain radius of curvature. It may be a shape.

  In the case where the abutment screw 40 is made of a metal material such as pure titanium or titanium alloy, the constricted portion 46 as the strength-decreasing portion can be obtained not only by a mechanical processing method using a grinding tool but also by a chemical etching method. Can be formed. As a method of forming the constricted portion 46 by a chemical etching method, an abutment screw 40 masking portions other than the constricted portion 46 and an etching solution in which hydrofluoric acid is diluted to about 2% aqueous solution are prepared, and the masked abutment is prepared. After the ment screw 40 is immersed in the etching solution for about 10 seconds, the constricted portion 46 can be formed by lifting, washing and drying. The desired depth of the constricted part 46 can be obtained by adjusting the concentration of the etching solution and the immersion time.

  In any of the above-described explanations, the structure-recessed portion is created in the shaft portion 42 as the strength-decreasing portion, but the strength-decreasing portion can be created in the shaft portion 42 by controlling the surface characteristics.

  When the abutment screw 40 is made of a metal material such as pure titanium or a titanium alloy, the strength-decreasing portion can be formed in the shaft portion 42 by controlling the surface characteristics by laser annealing. As a method of forming the strength-decreasing portion by the laser annealing method, for example, a YAG laser (MD-Y9700 manufactured by Keyence Corporation) is used, and a laser beam having an output of 35 W, a wavelength of 1.06 μm, and a frequency of 50 kHz is sent at a speed of 30. By irradiating the portion corresponding to the strength reduction portion under the condition of 60 mm / second, the strength reduction portion 46 can be formed on the shaft portion 42. In the portion irradiated with the laser light, the external dimensions are hardly changed as compared with those before the irradiation, but the surface is oxidized or microscopic scratches are formed on the surface of the shaft portion 42, so that the non-irradiation is performed. Compared with the part, the mechanical strength is slightly reduced.

  In addition, it is preferable that the reduced strength portion such as the constricted portion 46 has a continuous annular shape from the viewpoint of ease of formation, but it has a discontinuous annular shape as indicated by a broken line. Also good. A discontinuous ring shape as indicated by a broken line can be easily formed by the above-described chemical etching method or laser annealing method.

It is a schematic diagram which shows the state which implanted the artificial tooth root in the alveolar bone. It is sectional drawing of the vertical direction of the artificial tooth root which concerns on one Embodiment of this invention. It is sectional drawing of the vertical direction of the connection screw used for the artificial tooth root shown in FIG. It is sectional drawing of the vertical direction of the connection screw which concerns on other embodiment of this invention.

Explanation of symbols

1: Artificial root 4: Artificial tooth 10: Fixture 12: External screw 14: Hollow bottom hole 16: Engagement recess 17: Inner screw 30: Abutment 32: Artificial tooth mounting part 34: Locking end 36: Engagement Convex part 38: Through hole 40: Abutment screw (connection screw)
42: shaft portion 43: screw portion 44: fixed head portion 45: boundary portion 46: constricted portion (strength reduced portion)
48: Remaining part (gripping part)
60: Natural tooth 62: Alveolar bone 64: Bone papilla 66: Gingiva

Claims (10)

A fixture embedded in the alveolar bone,
An abutment in which one end is fitted to the fixture and an artificial tooth is attached to the other end;
A connection screw for connecting the fixture and the abutment,
The connecting screw is
A fixed head portion having a large outer diameter,
A threaded portion with an external thread;
A shaft portion that connects the head portion and the screw portion,
A first position where the strength-decreasing portion having a slightly reduced mechanical strength extends in the axis-perpendicular direction in the shaft portion and is located closer to the base end side than the boundary portion defined by the fixed head portion and the shaft portion. And an artificial tooth root that is located between the second position where a portion remaining due to breakage can be used as a gripping portion.   The artificial tooth root according to claim 1, wherein the strength reduction portion is a dent slightly recessed from an outer surface of the shaft portion.   The artificial tooth root according to claim 1, wherein the strength reduction portion has a continuous annular shape.   The artificial tooth root according to claim 1, wherein the boundary portion has any one of an inclined shape, a curved shape, and a planar shape.   The artificial tooth root according to claim 1, wherein the strength reduction portion is formed by any one of a machining method, a laser annealing method, and an etching method. A fixture embedded in the alveolar bone,
An abutment in which one end is fitted to the fixture and an artificial tooth is attached to the other end;
A connecting screw for connecting the fixture and the abutment, and a connecting screw for an artificial tooth root used for an artificial tooth root comprising:
The connecting screw is
A fixed head portion having a large outer diameter,
A threaded portion with an external thread;
A shaft portion that connects the head portion and the screw portion,
A first position where the strength-decreasing portion having a slightly reduced mechanical strength extends in the axis-perpendicular direction in the shaft portion and is located closer to the base end side than the boundary portion defined by the fixed head portion and the shaft portion. And a second position where the portion remaining due to breakage can be used as a gripping portion.   The artificial root connection screw according to claim 6, wherein the strength reduction portion is a dent slightly recessed from an outer surface of the shaft portion.   The artificial root connection screw according to claim 6, wherein the strength reducing portion has a continuous annular shape.   The artificial root connection screw according to claim 6, wherein the boundary portion has any one of an inclined shape, a curved shape, and a planar shape.   7. The artificial root connection screw according to claim 6, wherein the strength reduction portion is formed by any one of a machining method, a laser annealing method, and an etching method.

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