Dentistry – Prosthodontics – Holding or positioning denture in mouth
Reexamination Certificate
2000-04-17
2004-04-27
O'Connor, Cary E. (Department: 3732)
Dentistry
Prosthodontics
Holding or positioning denture in mouth
Reexamination Certificate
active
06726480
ABSTRACT:
TECHNICAL AREA
The invention relates to a support for holding and/or forming a dental prosthesis with an axis, an anchoring part for anchoring in a bone of the lower or upper jaw of a patient and/or in a master model and a head part intended to project from the bone and/or master model. This head part serves to support an originally separate element attachable to the support with a cap. The cap can for example be a part of a dental prosthesis such as an individual artificial tooth or a bridge or a prosthesis having several teeth. The possibility also exists however of first attaching a so-called burnout cap made of plastic to the support. The burnout cap can serve for making a casting model and a casting impression, then be burned off from the latter and replaced by a impression cap when the cast impression is used.
PRIOR ART
For certain applications, it should be possible to attach the cap in a specific rotational position on the support. A support known from EP 0 685 208 A has an implant and a secondary part having an external thread screwed into the internal thread of the implant and a head projecting from the implant. This forms the head part of the support and has an octagonal section as well as a conical section that tapers away from the latter to the front side of the head. A superstructure element or impression element with a cap can be associated with the known secondary part and have an internal space with an octagonal section.
FIG. 1
of the present patent application is a cross section through an area of the octagonal section of the head of a known secondary part
1
. The secondary part defines an axis
5
and straight lines running radially thereto through the corners of the octagonal head section, one of which is designated
7
. Cap
10
is shown in
FIG. 1
in the central intended rotational position provided. In this position, each corner of the octagonal section of the internal space of the cap is on the straight line
7
running through the associated corner of secondary part
1
. The cap rests on the secondary part with radial play so that the mutually associated octagonal surfaces of the secondary part and the cap are at a distance a from each other. The radial play must be so great, particularly when burnout caps are used, that the internal weight of the superstructure element then made by casting can differ due to shrinking processes and the like from the internal weight of the burnout cap. Because of the play, cap
10
can be turned starting in its central desired rotational position in two rotational directions through an angle designated a in
FIG. 2
until the octagonal surfaces of the cap are located at the corners of the secondary part. Distance a is typically approximately 0.02 mm and possibly even more with burnout plastic caps. Angle a then amounts to approximately 2.25° or more. The cap can be rotated back and forth through an angle
2
a
, namely approximately 4.50° or more. The octagonal head section of the known support thus makes possible only very inexact positioning of the cap relative to rotations about the axis. If large forces act on the cap approximately perpendicularly to the axis and bring about shear forces or torsional forces between the cap and the support, there is the danger that the cap will execute small rotational or swiveling movements relative to the support. Such tiny rotational movements may cause the dental treatment to fail. The cap can be mounted on the head in one of eight selectable rotational positions. Sometimes, however, it is advantageous for the cap to be placed on the support in only a single rotational position, which is not possible with the known support. Moreover, the cap rests only on the octagonal section, but not on the conical section of the head. In this known head, it would also be practically impossible to design a cap so that it abuts both the flat surfaces of the octagonal section and the conical section of the head. Since the octagonal section has only a relatively small axial dimension, the cap receives little support with respect to laterally acting forces, i.e. forces transverse to the axis, impairing the stability of the connection of the cap or the superstructure element to the additional support.
DE 195 34 979 C discloses a support with an implant and a spacing sleeve. The latter serves as a head for attaching a dental prosthesis. The implant has an axial blind hole. Its internal surface is provided with six grooves distributed around the axis of the implant. The spacing sleeve projects into the blind hole of the implant and has noses engaging these grooves so that the spacing sleeve can be positioned in six different rotational positions in the implant. This support has the disadvantage however that the spacing sleeve is guided laterally only in a short cylindrical guide area of the hole having a relatively small diameter below the grooves and is supported against the forces directed approximately transversely at the implant axis. If such forces act on the dental prosthesis, a long lever arm is produced between the point where these forces act and the guide area of the hole, so that very high torques have to be transmitted from the spacing sleeve to the implant in the guide area of the blind hole. In combination with the small dimensions of the guide area, this results in a high risk of the dental prosthesis executing micromovements relative to the implant when stressed, leading to failure of the dental treatment. Moreover, the implant of this known support must be inserted approximately flush with the ridge of the bone. This subgingival arrangement of the implant has the disadvantage that the gum (gingiva) knits over the implant during the healing phase and requires a further incision to attach the spacing sleeve. Moreover, the dental prosthesis cannot be removably fastened to the spacing sleeve. Moreover, the known support is not suitable for anchoring bridges, either.
A support shown in FIGS. 1-3 of CA 1,313,597 A has an implant and a generally conical sleeve. There are two axial projections at the upper end of the implant which, when the device is assembled, engage flats on the sleeve and position it non-rotatably in one of two possible rotational positions. In the version shown in
FIGS. 4 and 6
, the implant has a projection that is generally cylindrical but is provided on one side with a flat. The flat permits non-rotatable positioning of the sleeve in a single rotational position. Since the two projections and the flat of these known implants each have only one flat surface tangential to the axis of the implant that abut a flat matching surface on the sleeve, these implants define the rotational position of the sleeve in the same way no more exactly than the supports commented on above and known from EP 0 685 208 A. In addition, these implants can position a sleeve in only two different rotational positions or even in only one single rotational position. In many applications, the rotational position of a cap, however, must be selectable from more than two rotational positions. In addition, the crown prosthesis in these implants must clearly be supported at least essentially by one additional cap whose rotational position is not defined at all. The supports known from CA 1,313,597 A that serve to hold a screw-on cap are also composed of at least three separate parts. This large number of parts makes dental treatment complicated and adversely affects the stability of the dental prosthesis in the mouth of a patient.
A support shown in FIGS. 1-3 of CA 1,313,597 A contains an implant and a generally conical sleeve. The implant has two axially projecting projections at the upper end which engage flats on the sleeve when the device is assembled and position them non-rotatably in one of two possible rotational positions. In the version shown in
FIGS. 5 and 6
, the implant has an extension which is generally cylindrical but provided on one side with a flat. The flat permits non-rotational positioning of the sleeve in a single rotational position. Since the two projections and the flat of t
Crowell & Moring LLP
O'Connor Cary E.
Straumann Holding AG
LandOfFree
Support for sustaining and/or forming a dental prosthesis does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Support for sustaining and/or forming a dental prosthesis, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Support for sustaining and/or forming a dental prosthesis will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-3199905