Dentistry – Prosthodontics – Holding or positioning denture in mouth
Reexamination Certificate
1999-01-22
2001-01-16
Philogene, Pedro (Department: 3732)
Dentistry
Prosthodontics
Holding or positioning denture in mouth
C433S173000, C433S174000
Reexamination Certificate
active
06174166
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to an arrangement for an implant system which includes a fixture (anchoring element) and a spacer screw which can be screwed securely to the fixture, with an associated spacer element. The present invention also includes a unit, for example a cylinder (prosthesis structure), which can be screwed securely to the spacer screw. The fixture has an internal thread which the spacer screw can be screwed into by means of a corresponding external thread. The fixture also has a contact plane for the spacer element, and a spanner attachment part. The said spacer screw is designed with a cylindrical portion located above its external thread.
Implant systems of the type specified above are already known and are sold by Nobel Biocare on the open market.
BACKGROUND OF THE INVENTION
In implant systems of the type specified above, it is necessary to be able to combine a low structural height with the required mechanical strength of the various components of the system. Thus, it is necessary, in some cases, to provide the lowest possible structural height between the contact plane of the fixture and the top surface of the prosthesis unit (cylinder) without neglecting the mechanical strength of, for example, the prosthetic securing screw. The aim of the invention is to solve this problem, among others.
It is also important to be able to achieve the greatest possible strength in the upper parts of the fixture wall. This is also afforded by means of the invention.
Implant systems of the type in question have small dimensions and it is necessary to be able to provide good guidance functions which ensure thread engagement of each respective screw in the initial stage. It also has to be possible to facilitate the tightening function itself. This is achieved as an added effect in the present invention.
It is also possible, as regards the subject of the invention, to make additional improvements which increase still further the initial thread engagement function.
SUMMARY OF THE INVENTION
The feature which can principally be regarded as characterizing an arrangement according to the invention is that the fixture or the anchoring element is arranged with a recess which is located in the spanner attachment part and in which the cylindrical portion of the spacer screw can be completely or partially engaged when the spacer screw is drawn tight in the fixture or the anchoring element.
In one embodiment, the depth of the recess, and thus the degree to which the cylindrical portion can be engaged in the recess, is arranged such that it essentially corresponds to 2-4 thread turns of the internal thread of the anchoring element. The engagement of the cylindrical portion in the recess is dependent, inter alia, on the height of the spacer element. In a further embodiment, an external thread, arranged on a holding screw for securing the unit in the spacer screw, has an extension function which corresponds to the engagement of the cylindrical portion in the recess of the spanner attachment part, compared to the case where there is no recess in the spanner attachment part. The extension of the external thread ensures a desired strength function for the holding screw and the implant system as such.
The diameter of the recess slightly exceeds the diameter of the external threads on the spacer screw, which means that the recess exercises an initial guidance function for the spacer screw as it is being screwed into the internal thread of the anchoring element. The spacer screw can moreover be provided with a tap at its free end for affording an important guidance function in the recess as the spacer screw is being screwed into the fixture.
In one embodiment, the cylindrical portion of the spacer screw merges into an unthreaded portion which in turn merges into the external thread of the spacer screw.
In accordance with the concept of the invention, the recess entails the absence of internal thread turns in the upper parts of the fixture. The absence of thread turns means that the fixture, in the upper parts, remains essentially unloaded by impinging forces when the spacer screw is being tightened in the fixture. Moreover, in one embodiment, the recess in the fixture has a maximum depth which guarantees mechanical strength in the wall portion of the fixture in the upper parts where internal thread turns in the fixture themselves form a reinforcement of the wall portion, compared to the case where there are no internal thread turns. The depth of the recess is chosen within a range of 0.5-2.0 mm, and is preferably about 1.0 mm. The total height of the fixture, spacer element and unit is chosen within the range of 10-20 mm. The height between the top surface of the unit and the contact plane of the fixture for the spacer element is 4-8 mm.
By means of the invention it is possible to construct implant systems which are suitable for different purposes and which have a high degree of adaptability to existing cortical dentine layers of different thicknesses. The prosthesis structure can be given a reliable anchoring function even when there is a requirement for a low structural height between the contact plane of the fixture and the position or level at which the prosthesis structure is secured.
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patent: 5951287 (1999-09-01), Hawkinson
Brånemark et al., Osseointegrated Implants in the Treatment of the Edentulous Jaw, Experience from a 10-year period, Laboratory of Experimental Biology, Department of Anatomy, University of Göteborg, Sweden, 1977, pp. 33-34.
Nobel Biocare AB
Philogene Pedro
Pollock Vande Sande & Amernick
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