DENTAL IMPLANT FIXTURE

Abstract: The present invention relates to a dental implant fixture comprising an implant root (2), which is adapted affixable into a jaw bone by means of an outer thread (8) and has an inner thread (12) made thereto, and a spacer stud (4) having made thereto an outer thread (7) compatible with the said implant root inner thread. According to the invention, the spacer stud (4) has threads (7) made thereto at least in the portion thereof projecting distally from the implant root and the fixture further incorporates a locking nut (1) with an inner thread (9) compatible with the outer thread (7) of the projecting portion of the spacer stud.

Description: Dental implant fixture The present invention relates to a dental implant fixture serving for securing the crown of a dental implant to the jaw bone or, alternatively, using the fixture for affixing a dental prosthesis or a part thereof in place. In principle, fixtures used for this purpose comprise a proximal implant root portion and a distal fixture portion securable thereon. The implant root is fitted into a hole drilled in the jaw bone and is secured in place by means of a coarse-pitch outer thread made on the implant root portion. The implant portion has an internal bore made thereto axially and threaded internally. During the affixing of the implant root portion, into this threaded bore is screwed a spacer stud. After the spacer stud is screwed and tightened in place into the implant root, there remains visible the projecting end of the spacer stud on which the crown of the dental implant is mounted or, alternatively, the stud serves as a fixture for a tooth prosthesis. A problem hampering these fixtures has been a gradual loosening of the connection between the implant root portion and the spacer stud. Basically, this complication can be traced to the sporadically in the mouth occurring wide temperature excursions that attack the fixture elements of the different parts of the dental implant at different times and in different magnitudes. A remedy to the above-described problem has been sought from constructions based on mutual dimensioning and shaping of the threads connecting the implant root to the spacer stud so that these elements would lock to each other during the affixing of the spacer stud in a manner resistant to dimensional changes in the different parts of the fixture due to temperature variations . Such ar- rangements are described, e.g., in US Patent Specifications Nos . 5,607,304, 5,605,457, 5,660,545 and 5,823,777. However, none of these have been able to overcome the above-described problems. It is an object of the present invention to overcome the recognized problem by way of a novel arrangement characterized by what is stated in the characterizing part of claim 1 in the appended claims . In the present embodiment, it has been found that a locking nut tightened on the threads of the portion of the spacer stud projecting distally from the implant root against the implant root is an effective means for locking the fixture to the implant root so that dimensional changes caused by temperature variations work mutually in a substantially compensating manner in the assembly. Hence, the degree of tightening of the spacer stud stays essentially unchanged under the temperature variations attacking the implant fixture. In the following, the invention will be explained in more detail by making reference to the appended drawings, wherein FIG. 1 shows a longitudinal cross-sectional view of a dental implant fixture according to the invention; and FIG. 2 shows the same fixture in a top view. Referring to FIG. 1, the dental implant fixture shown therein primarily comprises an implant root 2 whereon is formed a suitable outer thread 8. This thread serves to affix the implant root into a hole drilled in the jaw bone, wherein it allowed to settle and osseointegrate. The implant root is provided with an axial bore having an inner thread 12 made therein. Adapted anchorable into this inner thread, the fixture system further includes a spacer stud 4 having made thereon an outer thread 7 compatible with the inner thread of the implant root. The spacer stud 4 is dimensioned to have such a length that a substantial portion thereof remains distally projecting from the implant root when after the stud is screwed in place into the implant root. This projecting portion is respectively threaded with a thread 9. The threads 4 and 9 of the spacer stud need not necessarily be similar and, further, the threads need not necessarily be a continuation of each other. In regard to simpler fabrication, however, the threads 4 and 9 are advantageously machined as a continuous outer thread. In addition to the above-mentioned elements, the dental implant fixture according to the invention includes a locking nut 1. This nut has an inner thread compatible with thread 9 of the projecting portion of spacer stud 4. During the time of the osseointegration period of the implant root 2, the axial bore of the implant is conventionally kept plugged with a healing cap that is screwed into the thread 7. After the laps of the healing period, the cap is removed and the spacer stud is screwed to a desired depth into the implant root. Thereupon, onto the thread 9 of the projecting portion of the spacer stud is screwed the locking nut 1 that is tightened with a correct torque against the projecting end of the implant root. The proper torque value is assured by using a purpose-designed torque-controlling tool for tightening. The final position of the locking nut 1 is advantageously secured relative to the spacer stud 4, wherein different kinds of arrangements can be employed. In the embodiment shown in the diagrams, locking is accomplished by means of a slot made to the end of the spacer stud, a compati- ble slot made to the end of the locking nut 1 and a locking pin 5 inserted therein. As the function of the dental implant fixture, it has been found advantageous to have the threads 12 , 7 and 9 made into fine-pitch trapezoidal threads. This fixture construction has proven to retain an essentially constant securing tigthness between the implant root 2 and the locking nut 1 under varying thermal stresses imposed on the fixture. Furthermore, the arrangement according to the invention facilitates flexible shaping and/or furnishing of the locking nut for affixing different dental prosthesis components. For instance, one nut type may be shaped for affixing a crown while another nut type serves for affixing a bridge or a part of a dental prosthesis.

Claims: What is claimed is : 1. A dental implant fixture comprising an implant root (2) , which is adapted affixable into a jaw bone by means of an outer thread (8) and has an inner thread (12) made thereto, and a spacer stud (4) having made thereto an outer thread (7) compatible with the said implant root inner thread, characterized in that the spacer stud (4) has threads (9) made thereto at least in the portion thereof projecting distally from the implant root and that said fixture further incorporates a locking nut (1) with an inner thread (6) compatible with the outer thread (9) of the projecting portion of the spacer stud. 2. The dental implant fixture of claim 1, characterized by incorporating means (3, 5) adapted to lock the mutual threaded position of the spacer stud and locking nut. 3. The dental implant fixture of claim 1 or 2, character- ized in that the locking nut is shaped and/or furnished for affixing a crown or a dental prosthesis thereto. 4. The dental implant fixture of any one of foregoing claims, characterized in that the inner thread (12) of the implant root, the outer thread (7) of the spacer stud and the inner thread (6) of the locking nut of the dental implant are trapezoidal threads .

Inventors: RISTOLA URPO, RISTOLA, URPO
Applicants: RISTOLA URPO, RISTOLA, URPO
Application year: 2001
Main classification: A61C8
IPC codes: A61C8