TECHNICAL FIELD

The present invention relates to a dental implant fixture, in particular, to a dental implant fixture in which a plurality of threads is formed in such a fashion to have the same transfer distance therebetween, wherein the threads include main threads inserted and fixed at an engaging hole formed at a jawbone and at least one auxiliary threads formed between the mam threads and have cross-sections of portions, removed for forming at least one auxiliary threads between the main thread and adjacent main thread, decreased gradually as they go from front end side to rear end side

BACKGROUND ART

In general, human teeth can be divided into baby teeth and permanent teeth the former come out during baby period and the latter come out after the baby teeth has been extracted Therefore, it is necessary to manage the permanent teeth with substantial care from the baby penod because the permanent teeth cannot be reproduced once they have been damaged and removed When the permanent teeth do not exist except wisdom teeth for which people do not feel any inconvenience despite its absence, it will be very inconvenient to ingest foods and it will be substantially disadvantageous in view of appearance

Accordingly, lots of efforts have been made to replace extracted teeth when the permanent teeth have been lost, and operating an artificial tooth was the most generalized conventional art Such artificial tooth can be divided into a

crown & bridge, which is called a bridge, a partial denture, and a complete denture The crown & bπdge comprises a crown put on a damaged tooth and a bridge connecting both side teeth of the extracted tooth, the partial denture means a denture which is provided partially when several teeth have been 5 extracted to make it difficult to form bridge, and the complete denture means a denture provided when all the permanent teeth have been extracted

However, in case of providing the crown & bridge, there occurs a problem that healthy permanent teeth located at both sides of the denture should be shaved 0 down, and it has been pointed out that denture is inconvenient, inefficient, and unsanitary

Dental implant has been widely used recently to replace damaged or missing permanent teeth, because such problems as described above have arisen from 5 conventional artificial teeth Dental implant is surgical operation wherein damaged permanent tooth is removed from an alveolar bone (bone surrounding the tooth) if the permanent tooth has been damaged so seriously that it is impossible to be reproduced In such operation, an artificial tooth fixture is implanted in the alveolar bone and fixed, a healing abutment is installed above 0 the fixture, and then the artificial tooth is connected after a gum has been cured

The dental implant should be integrated with the alveolar bone without hindeπng the reproduction of the bone, and it should not bring about living s body rejection reactions, it should also be well attached to the gum Accordingly, titanium or titanium alloy is widely employed for material of the dental implant Such implant comprises a fixture implanted in the alveolar bone, which is a jawbone supporting the tooth and fixed completely, and an abutment having a lower end fixed to the fixture, projected to an upper end of 0 the gum, and exposed to the outside, passing through the gum

The most important step in the process of the dental implant operation is to bury the fixture in the jawbone A securing hole is formed in the alveolar bone (jawbone) to bury the dental implant fixture by means of a drill and the like, and then the dental implant fixture provided with threads at outer peripheral surface thereof is rotated to be engaged into the securing hole In this instance, it is very important to obtain proper initial tightening force so as to accomplish osteointegration between the implant and the bone after implantation

In general, the jawbone can be divided into cortical bone composed of compact tissues and constituting the surface of the bone, and spongy bone composed of relatively loose tissues and provided at the mside of the cortical bone, so that the initial tightening force occurring upon the initial fixing of the dental implant fixture into the jawbone can be mostly operated at a portion where the dental implant fixture is secured to the cortical bone, and relatively small initial tightening force can be operated at a portion where the dental implant fixture is secured to the spongy bone Accordingly, the density of the spongy bone does not affect the initial tightening force practically, and the density of the cortical bone affects the initial tightening force As described above, it is easy to obtain the initial tightening force if the cortical bone has been formed thick, however, it is difficult to obtain the initial tightening force if the cortical bone has been formed thin

Further, if thread grooves formed on an outer peripheral surface of the dental implant fixture for securing the dental implant fixture to the securing hole cause frictions against the threads repeatedly while the dental implant fixture is secured to the jawbone by means of the threads, they will be worn away, thereby reducing the initial tightening force of the corresponding threads

However, such a conventional implant fixture has not been provided with

means for regulating differences of the tighttmng force as described above, so that the fixture could not be implanted in the jawbone stably and several problems have been arisen such as extraction or a shake of the implant after operation and the like Especially, as regards those people having soft and ^■ 5 bony tissue, the initial tightening force increasing with the progressing of the dental implant fixture into the spongy bone is relatively small in comparison with the initial tightening force decreasing with the abrasion of the threads formed at the cortical bone, so that the initial tightening force of the dental implant fixture does not increase and is maintained or decrease, even it the 0 dental implant fixture is implanted deep in the jawbone

The International patent application publication No WO 00/ 03657 can be listed as a representative conventional art relating to the implant fixture, wherein concentration of the high stress occurring in the neighboring bone S tissues can be dispersed, and absorption of the marginal bone tissue can be prevented at the time of insertion of the dental implant fixture According to this invention, threading intervals (pitch) at the front end of the fixture and the cross-section thereof have been configured to become large, and the threads intervals and the cross- section thereof have been configured to become 0 narrow Such fixture has been employed frequently in operation of dental implant nowadays, however, it is not easy to accomplish proper initial tightening force because it is difficult to harmonize various bony tissues with the engaging holes having a certain size at the time of implanting the fixture, due to the rapid decrease of the thread intervals and the cross-section thereof 5 In other words, the initial tightening force becomes excessively strong if the cortical bone is thick, and the initial tightening force becomes so weak if the cortical bone lacks that it is difficult to implant the fixture

Also, Korean Patent Application No 10-2005-0019388 discloses an implant 0 fixture in which the fixture is configured to increase its diameter as it goes

from a front end to a rear end of the fixture so as to form tapered axial grooves The above described implant fixture is available for the jawbone having weak bony tissues because it can exert strong tightening force however, it is very difficult to operate in the compact bony tissues, because the tightening force increases seriously

Accordingly, there is an urgent need for developing an implant fixture in which implantation torque can be gradually increased to enable a stable operation of the implant, the jawbone of the patient does not get damaged due to excessive tightening force, and the initial tightening force of the fixture can be properly regulated on the basis of the operator's judgment on the condition of the jawbone, especially the cortical bone of the patient when the implant fixture is to be inserted into the jawbone of a patient in the technical field to which the present invention pertains

As a result, the present inventors have continuously studied to develop an implant fixture that can increase implantation torque of the implant fixture gradually and in which the initial tightening force can be regulated by the operator when the implant fixture is implanted to the jawbone of a patient, thereby accomplishing the present invention

DISCLOSURE OF THE INVENTION

Accordingly, the present invention has been made to overcome above- mentioned problems arising from the prior arts, and a principal object of the present invention is to provide a dental implant fixture in which implantation torque can be increased gradually as the implant is inserted into the jawbone, so that it doesn't apply any impact to the jawbone and the initial tightening force can be easily regulated by the operator even though the implant fixture

has been secured within the patient's jawbone having soft and bony tissues

To accomplish above object, the present invention provides a dental implant fixture in which a plurality of threads is formed in such a fashion to have the

¹ J same transfer distance therebetween, wherein the threads include main threads inserted and fixed at an engaging hole formed at a jawbone and at least one auxiliary threads formed between the main threads and have cross-sections of portions, removed for forming at least one auxiliary threads between the main threads and adjacent mam threads, decreased gradually as they go from front

In general, as regards terms of parts constituting the implant fixture, 'pitch' refers to a distance covering from any one thread to a neighboring thread or from any one thread groove to a neighboring thread groove, however it indicates the distance covering from any one thread to neighboring thread in the present invention

According to the preferred embodiments of the present invention, the auxiliary threads can be shaped as follows ( i ) The axial width and the diameter of the auxiliary thread increase gradually as they go from a front end side to a rear end side of the implant fixture,

( ii ) The diameter of the auxiliary thread increases gradually as it goes from the front end side to the rear end side of the implant fixture, while it has a substantially predetermined axial width,

( in ) The axial width of the auxiliary thread increases gradually as it goes from the front end side to the rear end side of the implant fixture, while it has a substantially identical diameter of the auxiliary thread, and

( iv ) The shape of outer peripheral surface gradually changes from a concave shape to a convex shape as they go from the font end side to the rear

end side of the implant fixture

The dental implant fixture according to tht present invention can be divided into a cortical bone engaging portion fixed to a cortical bone side of a jawbone, and a spongy bone engaging portion fixed to a spongy bone side of the jawbone and the main threads and the auxiliary threads are formed at the spongy bone engaging portion Also, a plurality of cortical bone engaging threads can be formed at the cortical bone engaging portion, the threads extending respectively from the main threads and the auxiliary threads, having a transfer distance substantially identical with those of the main threads and the auxiliary threads and having substantially predetermined cross-section of portion, removed for forming engaging threads

Additionally, a front end of the dental implant fixture of the present invention can be provided with a tap thread having a height decreasing gradually as the tap thread goes from the mam thread to the front end side, and extending to have transfer distance substantially identical with that of the main thread, so that thread grooves for guiding the main threads can be formed at an inner peripheral surface of the engaging hole while the implant fixture is inserted into the engaging hole Further, the front end of the implant fixture, on which the tap thread has been formed, can be characterized in that the diameter of the front end decreases gradually as it goes to the front end

BRIEF DESCRIPTION OF DRAWINGS

FIG 1 is a schematic view of an implantation structure of a dental implant fixture 10 according to the present invention

FIG 2 is a front view of the dental implant fixture 10 according to the first

embodiment of the present invention.

FIG. 3 is a schematic view showing the construction of main threads and auxiliary threads provided to the dental implant fixture 10 according to the first embodiment of the present invention.

FIG. 4 is a front view of the dental implant fixture 10 according to the second embodiment of the present invention.

FlG. 5 is a schematic view showing the construction of main threads and auxiliary threads provided to the dental implant fixture 10 according to the third embodiment of the present invention.

FlG. 6 is a schematic view showing the construction of main threads and auxiliary threads provided to the dental implant fixture 10 according to the fourth embodiment of the present invention.

FIG. 7 is a schematic view showing the construction of main threads and auxiliary threads provided to the dental implant fixture 10 according to the fifth embodiment of the present invention.

FIG. 8 is a view showing an implantation contour of the dental implant fixture 10, 60 of the present invention within the gum, in which (a) shows the fixture implanted in the jawbone having the most compact bony tissue, (c) shows the fixture implanted in the jawbone having softest bony tissue, and (b) shows the fixture implanted in the jawbone having a mid-degree compact bony tissue between (a) and (c).

FIG. 9 is a graphic diagram showing a implantation torque depending on the depths of the implant fixture (a) of the present invention and the conventional

implant fixture (b) implanted in the gum

DETAILED DESCRIPTION OF THE INVENTION

Preferred embodiments of the dental implant fixture 10 according to the present invention will now be described in detail with reference to the appended drawings below These embodiments of the present invention are for illustrative purpose only the present invention, and it will be apparent to those skilled in the art that these embodiments should not be construed to limit the scope of the present invention

Also, the dental implant fixture of the present invention can be operated to an upper jaw, a lower jaw or both of the upper and lower jaws, however, in the description of the appended drawings, with regards to a direction of operating the implant fixture, it will be described on the basis that the implant fixture is operated to the lower jaw so as to avoid confusion caused by the direction

As shown in FIG 1 , the dental implant fixture 10 of the present invention is adapted to be engaged to the human jawbone B, thereby implanting an artificial tooth in the jawbone B Accordingly, at least one engaging hole (h) having a circular section is formed at the jawbone B by a drill, and the like so as to install the dental implant fixture 10, and a plurality of threads 11, 12 having a substantially identical transfer distance are formed at an outer peripheral surface thereof so that they can be installed within the engaging hole (h) In this instance, the jawbone B is composed of cortical bone bl constituting an outside portion thereof and being composed of compact tissues to have high strength, and spongy bone b2 formed at inside of the cortical bone b 1 and composed of soft tissues composed to the cortical bone b 1 to have a relatively small strength, wherein the engaging hole (h) is configured to

penetrate the cortical bone b l and is drilled into the spongy bone b2 to a desired depth

In FIGs 2 and 3, the dental implant fixture 10 according to the first S embodiment of the present invention has been shown As shown in the drawings, the dental implant fixture 10 is provided with tap forming portion 1OA having a tap thread 13 at a front end of the fixture inserted into the engaging hole (h) first so as to have thread grooves (s) formed at an inner peripheral surface of the engaging hole (h) The tap defining portion 1 OA is 0 configured in such a fashion that the diameter of the dental implant fixture 10 decreases gradually as it goes to the front end thereof, so the end portion of the fixture is configured to have a relatively small diameter composed to the engaging hole (h), so that it can be easily inserted into the engaging hole (h). Also, the tap thread 13 is configured to gradually decrease in height as it goes 5 to the front end, so that thread grooves (s) can be formed at the inner peπpheral surface of the engaging hole (h) when the tap defining portion 1OA progresses into the engaging hole (h)

The plurality of threads 11, 12 formed at the outer peπpheral surface of the 0 dental implant fixture 10 comprises main threads 11 adapted to cause the dental implant fixture 10 to progress along the thread grooves (s) formed by the tap thread 13 into the engaging hole (h), and auxiliary threads 12 to regulate the initial tightening force In the present embodiment, the dental implant fixture 10 comprises three screws including a main thread 11 and two 5 auxiliary threads 12

The main thread 11 is formed to have a transfer distance identical with that of the tap thread 13, and to have a substantially predetermined shape and cross- section wherever it is positioned, so that the dental implant fixture 10 can 0 move along the thread grooves (s) formed by the tap thread 13, thereby

progressing into the engaging hole (h)

The auxiliary thread 12 is configured to be gradually decreased in cross- section of the portion removed between main threads and adjacent main S threads as it goes from a front side of the dental implant fixture 10 to a rear side thereof The inner peripheral surface of the engaging hole (h) is not provided with a portion corresponding to the auxiliary threads 12, so that the bone tissue in the jawbone with large volume is transformed and pressed gradually by the auxiliary threads 12 along with the progress of the dental 0 implant fixture 10 into the inside of the engaging hole (h), thereby gradually increasing the initial engaging force

In the present embodiment, the auxiliary threads 12 are configured to increase in the axial width and the diameter of the auxiliary threads of the dental 5 implant fixture 10, and to decrease in the cross-section removed between main threads as they go from the front end side to the rear end side Herein, the diameter of the auxiliary threads means the external diameter of the auxiliary threads and the axial width and the diameter of the auxiliary threads are not larger than those of the mam threads

Accordingly, in the case the fixture was applied to the jawbone B of human having soft bony tissue so that the initial engaging force by the main thread 11 was reduced due to the abrasion of the thread grooves (s), it is not only possible to compensate for the reduction of the initial tightening force of the 5 main thread 11 by the initial tightening force produced by such auxiliary thread 12, it is also possible to increase the initial tightening force of the dental implant fixture 10 gradually in some cases

Additionally, as described above, the dental implant fixture 10 of the present invention can be applied to the jawbone B of human having compact bony

tissue because the operator can regulate the initial tightening forte properly by means of the auxiliary threads 12

Next, the dental implant fixture 10 according to the second embodiment of the 5 present invention will be described in conjunction with FIG 4 As shown in the drawing, the dental implant fixture 10, 20 according to the second embodiment of the present invention is divided into a cortical bone engaging portion 2OA fixed to the cortical bone bl of the jawbone B to produce the initial tightening force, and a spongy bone engaging portion 2OB fixed to the

10 spongy bone b2 of the jawbone B to produce the initial tightening force, wherein a tap defining portion 2OC having a tap thread 23 is formed at front end of the spongy bone engaging portion 2OB progressing into the engaging hole first so as to form thread grooves (s) at the inner wall of the engaging hole (h)

15

The tap defining portion 2OC is configured in such a fashion that the diameter decreases gradually as it goes to the front end of the spongy bone engaging portion 2OB, so that the end portion of the fixture is configured to have a relatively small diameter in comparison with the engaging hole (h) whereby it

20 can be easily inserted into the engaging hole (h) Also, the height of the tap thread 23 is configured to gradually increase as it goes from the front end to the rear end, so that thread grooves (s) with gradually increasing depth can be formed at the inside surface of the engaging hole (h) when the tap defining portion 2OC progresses into the engaging hole (h)

25

A plurality of threads 21 , 22 has been formed at outer peπpheral surface of the spongy bone engaging portion 2OB to engage in the engaging hole (h), the threads 21 , 22 comprise a main thread 21 adapted to cause the dental implant fixture 10, 20 to progress along the thread grooves (s) formed by the tap thread

30 23 into the engaging hole (h), and auxiliary threads 22 increasing the initial

tightening force gradually along with the progress of the spongy bone engaging portion 2OB into the engaging hole (h) In the present embodiment, the spongy bone engaging portion 2OB is provided with three screws including a main thread 21 and two auxiliary threads 22

The mam thread 21 formed at the spongy bone engaging portion 2OB is formed to have a transfer distance identical with that of the tap thread 23, and to have a substantially predetermined shape and cross-section wherever it is positioned, so that the dental implant fixture 10 20 can move along the thread grooves (s) formed by the tap thread 23, thereby progressing into the engaging hole (h)

The auxiliary thread 22 is configured to be decreased in the cross-section of the portion removed between the main threads and adjacent main threads as it goes from a front side of the dental implant fixture 10, 20 to a rear side thereof The inside surface of the engaging hole (h) is not provided with a portion corresponding to the auxiliary thread 22 whereby the bone tissue in the jawbone with large volume is transformed and pressed gradually by the auxiliary thread 22 as the dental implant fixture 10, 20 progresses into the inner surface of the engaging hole to increase the implantation torque gradually and make it easy for the operator to regulate the initial tightening force (FIG 9(b)) In the present embodiment, the auxiliary thread 22 is configured to increase gradually in the axial width and the diameter of the auxiliary thread of the dental implant fixture 10, 20 and to decrease in the cross-section removed between the main threads as they go from the front end side to the rear end side Herein, the axial width and the diameter of the auxiliary thread are not larger than those of the main thread

A plurality of cortical bone engaging threads 24 are formed at the cortical bone engaging portion 2OA to produce tightening force after they have been

fixed to the cortical bone b l The cortical bone engaging threads 24 extend from the main thread 21 and the auxiliary thread 22, and the number of the cortical bone engaging thread 24 is identical with the total number of the main thread 21 and the auxiliary thread 22 In the present embodiment, three cortical bone engaging threads 24 are provided at the cortical bone engaging portion 2OA because one main thread 21 and two auxiliary threads 22 are provided

Tt is necessary to obtain the initial tightening force intended by the operator who operates the dental implant fixture 10, 20 easily by making the initial tightening force increased very slow or little by means of the cortical bone engaging threads 24 to prevent rapid change of the initial tightening force, when the cortical bone engaging portion 2OA starts to be inserted into the engaging hole (h) after the spongy bone engaging portion 2OB has been inserted into the engaging hole (h) while the dental implant fixture 10, 20 is fixed into the engaging hole (h) This is why such a cortical bone engaging thread 24 is configured to have a tightening distance identical with the main thread 21 and the auxiliary thread 22 and a predetermined cross-section of the portion removed for forming the engaging thread

In particular, since the initial tightening force increases relatively high by the relative increase of the cross-section of the auxiliary thread 22 as the removed cross-section decreases when the dental implant fixture 10, 20 is to be fixed in the jawbone B of the human having compact bony tissue, it is advantageous in accomplishing the initial tightening force desired by the operator to make the initial tightening force increase very slow or little after the dental implant fixture 10, 20 provided with the cortical bone engaging thread 24 has fixed in the jawbone B of the human having the compact bony tissue whereby the cortical bone engaging thread 24 starts to be inserted into the cortical bone bl

Also, the coitical bone engaging thread 24 is configured to have a substantially identical transfer distance with that of the main thread 21 and the auxiliary thread 22 and is configured to have a substantially identical shape and cross-section with those of ends in the rear side of the main thread 21 and t> the auxiliary thread 2, so that the cortical bone engaging thread 24 can move along the transporting path of the mam thread 21 and the auxiliary thread 22 and be inserted into the engaging hole (h) easily

The auxiliary thread 22 according to the above described first and second 0 embodiment is configured to increase its cross-section and decrease the removed cross-section between the mam threads as the axial width and the diameter of auxiliary thread of the dental implant fixture 10 increases gradually as it goes from the front end side to the rear end side thereof.

However, it is possible to increase the initial tightening force by gradually 5 increasing the cross-section of the auxiliary thread through decreasing the removed cross-section in various shapes without being limited to the above embodiments

In FIGs 5, 6 and 7, schematic views of the auxiliary threads incorporating the 0 dental implant fixture 10 according to various different embodiments (embodiments 3 ~ 5) of the present invention are shown

FIG 5 shows the dental implant fixture 10, 30 according to the third embodiment of the present invention As shown in the drawing, the diameter 5 of the auxiliary thread 32 of the dental implant fixture is configured to increase gradually as it goes from the front end side to the rear end side of the dental implant fixture 10 and thus decrease the removed cross-section between the mam threads, while the axial width of the auxiliary thread is constant

FIG 6 shows the dental implant fixture 10, 40 according to the fourth

embodiment of the present invention As shown in the drawing, the axial width of the auxiliary thread 42 is configured to increase gradually as it goes from the front end side to the rear end side of the dental implant fixture 10 and thus decrease the removed cross-section between the main threads, while the diameter of the auxiliary thread is constant

FIG 7 shows the dental implant fixture 10, 50 according to the fifth embodiment of the present invention As shown in the drawing, the sections of the front side and the rear side of the auxiliary thread 52 are configured to change gradually from concave shape to convex shape as it goes from the front end side to the rear end side of the implant fixture, resulting in the decrease of the removed cross-section between the main threads

FIG 8 shows an implanted contour of the dental implant fixture 10, 60 of the present invention within the gum, in which (a) shows the fixture implanted in the jawbone having the most compact bony tissue, (c) shows the fixture implanted in the jawbone having softest bony tissue (when the cortical bone is thin), and (b) shows the fixture implanted in the jawbone having a mid degree compact bony tissue between (a) and (c) As shown in FIG 8, the operators can regulate the initial tightening force by adjusting the size of engaging hole using drills having different diameters In other words, when the dental implant fixture is operated into a human jawbone having the compact bony tissue, the initial tightening force can be regulated to be small by making the size of the engaging hole big using a drill having a wide diameter to reduce an area contacting with the cortical bone In contrast, when the dental implant fixture is operated into human jawbone having the soft bony tissue, the initial tightening force can be regulated to be big by making the size of the engaging hole small using a drill having a narrow diameter to increase an area contacting with the cortical bone As described above, the initial tightening force can be regulated by changing the compression degrees of the auxiliary

thread into the cortical bone

FIG 9 is a graphic view showing an implantation torque depending on the depths of the implant fixture (a) of the present invention and the conventional

S implant fixture (b) implanted in a jawbone As shown in FIG 9, the implantation torque increases rapidly to cause an impact to the human jawbone resulting in damage of the jawbone in case of the conventional implant fixture

(b), while the implantation torque increases smoothly depending on the implantation depth without causing an impact to the human jawbone, resulting 0 in initial tightening force identical with that of the conventional implant fixture in case of the implant fixture (a) according to the present invention

As described above, specific parts of the present invention have been explained fully, however, it will be apparent to those skilled in the art that 5 such specific technologies correspond merely to preferred embodiments and the scope of the present invention will not be limited by those embodiments Accordingly, the practical scope of the present invention will be defined by the appended claims and equivalents thereof

0

INDUSTRIAL APPLICABILITY

The dental implant fixture of the present invention comprises the auxiliary threads in which cross-sections thereof increase gradually as the removed 5 cross-sections between the main threads decrease gradually of the implant fixture, so that the implantation torque of the fixture can increase smoothly to provide excellent tightening force without applying any excessive force to the human jawbone Especially, it is possible to implant the implant fixture stably when the implant fixture is operated to the patient having the jawbone of soft bony tissue, and it is possible for the operator to regulate the initial tightening

force based on the conditions of the patient's jawbone