Dentistry – Prosthodontics – Holding or positioning denture in mouth
Reexamination Certificate
2002-01-31
2004-12-07
Lewis, Ralph A. (Department: 3732)
Dentistry
Prosthodontics
Holding or positioning denture in mouth
Reexamination Certificate
active
06827575
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to, inter alia, a method for securing a spacer to a firmly integrated implant, preferably in the jaw bone, by means of a holder and with the aid of a screw. The threaded part of the screw will extend through a recess in the spacer so that its thread cooperates with the thread of the implant. The screw head can moreover cooperate with a tightening and locking surface in the spacer, which also has a bearing surface which can cooperate with a top surface of the implant. The invention also relates to an arrangement for application of this method. The invention relates in addition to the use of the holder for securing a spacer in an implant by means of a screw.
BACKGROUND OF THE INVENTION
After the implant has become firmly integrated in the bone, which normally takes 3 to 6 months after fitting the fixture or implant, a spacer is attached. In this connection, an incision is made through the gum so that the upper surface of the implant is exposed.
Upon attachment of the spacer, which is also called the spacer element, the latter is screwed securely to the implant or fixture. The spacers which are normally used here are made up of an essentially cylindrical component which is to be screwed securely with a loose, separate screw. In the majority of cases, the spacer has an internal hexagon which is intended to match a corresponding external hexagon on the upper part of the implant. There are also spacer designs in which the actual spacer body and the screw have been integrated to form one unit. However, it is advantageous to be able to use screw and spacer as two separate units. The tightening of the screw can then be improved by virtue of the fact that the frictional torque acting on the screw head is reduced because the contact radius of the screw head is less compared to the case of using separately integrated spacer and screw. In addition, when the screw and spacer form different units, they can be made of different materials. The spacer is preferably made of a tissue-compatible material, for example titanium or a ceramic material. The screw can be made of stronger material and can be coated with a friction-reducing coating so as to obtain an improved prestressing of the screw connection. An alternative here, or complement, is to choose a screw material which itself affords low friction between the thread of the screw and the corresponding internal threading of the implant. Such material can, for example, include certain gold alloys.
In purely general terms, it is relatively difficult to handle small spacer and screw components in or around the oral cavity, for lack of space among other reasons. Various attempts have been made to make handling and securing of spacer and screw easier. For example, a special counterstay has been used which is arranged on the spacer at the same time as a screwdriver is engaged in the groove of the screw head. There are also examples of so-called pre-fitted disposable spacer holders which consist of two mutually movable parts, one of which engages round the screw and the other round the spacer.
In connection with the said known prior art, reference may be made to U.S. Pat. Nos. 5,145,371, 5,322,443, 5,462,436, 5,437,550 and 5,692,904.
There is in general a great need to be able to handle small spacer and screw components in accordance with the above. In this context, it is important to be able to make available methods, arrangements and uses which are technically simple to implement and to use.
Thus, for example, problems arise when using special counterstays which are arranged on the spacer, since the support capacity is relatively poor and the components are not pre-assembled but are applied by the operators or their assistants during the operation. Using holders with mutually movable parts represents a technically complicated and awkward solution which is not compatible with practical handling and use.
SUMMARY OF THE INVENTION
The object of the invention is, inter alia, to solve these problems, and the feature which can principally be regarded as characterizing a method according to the invention is that the screw, in its position passing through the spacer, and the said spacer are first held together in a rotationally fixed manner in the holder, so that the bearing surface of the spacer protrudes beyond the holder, and the threaded part of the screw in turn protrudes beyond the bearing surface. Further features are that the rotationally fixed unit thus established by the holder, the spacer and the screw is thereafter applied to the implant in a position of cooperation of the threads of the implant and screw. The unit is then given rotating movements, during which the thread of the screw is screwed down into the thread of the implant. At a predetermined position of screwing, preferably where the cooperation between the bearing surface of the spacer and the top surface of the implant has been established, the holder is separated or detached from the spacer and the screw by means of a separating movement, for example a deflecting movement, which is preferably distinct from the rotating movement. The screw head is exposed for possible further tightening.
In one embodiment, the novel method is characterized by the fact that in order to achieve the holding function for holder, spacer and screw to form a common rotationally fixed unit, the screw is applied in the spacer to a position where its head bears against the aforementioned tightening and locking surface of the spacer, and by the fact that the spacer and screw thus combined are thereafter pressed into an end recess in the holder, or the holder is pressed over the spacer and the screw via the said recess. In one embodiment, the holder works with an elastic and/or spring function and/or snap-in function, by means of which the spacer and the screw, in their coupled positions, are locked to the holder in the direction of rotation. While it is being screwed in, the spacer is preferably brought into cooperation with the top surface of the implant only via an annular end surface, i.e. hexagonal or other types of effective, rotation-fixing surfaces are not present in this illustrative embodiment.
The feature which can principally be regarded as characterizing an arrangement according to the invention is that before the screw is introduced into the thread of the implant, the holder supports the screw in its position passing through the spacer and supports the spacer in a rotationally fixed manner, with the bearing surface of the spacer protruding beyond the holder, and the threaded part of the screw protruding beyond the bearing surf ace. Further characteristics are that a rotationally fixed unit thus established by the holder, the spacer and the screw can be applied to the implant in a position of cooperation between the threads of the implant and of the screw, where screwing of the screw thread into the implant thread can be effected by means of rotating or screwing movements of the unit. A further characteristic is that the holder, in a possible screwing position, preferably where the bearing surface of the spacer cooperates with the top surface of the implant, is arranged to be separable from the spacer and the screw by means of separating movements which are preferably distinct from the rotating movement, whereupon the screw head is exposed for possible further tightening. The said separation can be effected by means of the deflection function in the holder (the present holder part).
In one embodiment of the novel arrangement, the holder, at least in its part which can cooperate with the spacer and the screw, is made of plastic or other elastic material. The spacer and the screw, in the said coupled position, can be applied in an end recess in the said holder part receiving the screw and the spacer via a function preventing reciprocal rotating movements between spacer, screw and holder, which, can be obtained from guide surfaces, a spring function, snap-in function, etc. In a further embodiment, the holder or holder part is provided with a first re
Franklin Eric J.
Lewis Ralph A.
Nobel Biocare AB
Venable LLP
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