Overdenture Bar Apparatus and Method for Installing Same

This invention relates generally to restorative dentistry and more particularly to bar overdenture systems.

Implant prosthetic systems include a variety of restorations, such as single tooth, partially edentulous and edentulous. One type of prosthetic system employs the use of a bar overdenture. This system comprises a conventional acrylic denture retained by suitable attachments such as clips or the like to an implant supported cast bar. A conventional procedure for implanting the support structure involves a number of office visits as well as laboratory participation. For example, once root implants have been placed in the alveolar ridge and sufficiently healed, threaded healing abutments are removed and appropriate abutments are inserted and tightened with a special torque wrench. Impression posts are inserted with a friction drive wrench and an impression is made from suitable material such as polyvinylsiloxane for transferring abutment locations to a laboratory model or analog. The impression posts are then removed and threaded onto the abutment analog. The analog is then inserted into the impression and a model is poured in the laboratory. The model is then separated from the impression and impression posts are removed with a friction drive wrench. Bar copings are then placed over the analog in the model and secured with special coping screws. A connecting bar is waxed between bar copings, sprues are attached, coping screws removed, the model is invested and cast. The casting is then tried in the model and adjustments made including a new impression if necessary. A passive and precise fit is essential to avoid subsequent implant failure. Polishing caps and metal finishing are completed and the casting is returned to the restorative dentist to try intraorally to confirm a passive fit. Finally the bar is seated over the abutments and tightened thereto with a torque wrench. The denture is then seated over the bar.

It is an object of the present invention to provide a bar overdenture system which requires fewer procedural steps and less laboratory involvement than is required in conventional systems. Another object of the invention is the provision of a bar overdenture system which is inexpensive yet which is long lasting and provides improved support with essentially no misalignment stresses.

Briefly, in accordance with the invention, first and second root implant members, each having a bore with a selected locking taper formed in its crestal end face, are implanted in a respective socket formed in a patient's alveolar ridge. The root members are positioned using a jig to ensure that the longitudinal axes of the two sockets are parallel with one another as well as being of uniform depth. A healing plug is inserted in each root implant member bore and the implant member is packed with autogenous material and the mucoperiosteal flaps are sutured and allowed to heal. After sufficient healing has taken place, e.g. three months, the plug is surgically accessed and removed. The distance between the two bores is then measured and a bar made of suitable biocompatible material is cut and each end inserted into a transversely extending bore formed in the head portion of a bar attachment abutment member. The bar attachment abutment members, also made of suitable biocompatible material, each has a post portion having a selected locking taper adapted to be lockably received in a repective bore of a root implant member with the transversely extending bore extending at a right angle to the longitudinal axis of the post portion. The post portions of the first and second bar attachment abutment members with the bar extending therebetween, are then inserted into the respective first and second bores of the root implant members and tapped in to lock the post portions therein. If desired, a bar attacment abutment member can be formed with a second bore adapted to receive another bar extending to another bar attachment abutment member in a third root member.

According to a feature of the invention the transversely extending bore in the head portion of the bar attachment abutment may be formed with a taper to allow for a slight degree of misalignment, either in depth and/or in parallelism.

Additional objects and features of the invention will be set forth in part in the description which follows and in part will be obvious from the description. The objects and advantages of the invention may be realized and attained by means of the instrumentalities, combinations and methods particularly pointed out in the appended claims.

The accompanying drawings, which are incorporated in and constitute a part of the specification, illustrate preferred embodiments of the invention and, together with the description, serve to explain the objects, advantages and principles of the invention. In the drawings:

FIG. 1 is a perspective view of a patient's mouth in which an overdenture bar assembly made in accordance with the invention has been placed;

FIG. 2 is a vertical sectional view along the alveolar ridge showing an overdenture bar assembly made in accordance with the invention in place in a patient's mouth, a portion of one of the two implant members shown being in cross-section;

FIG. 3 is a front elevation of a bar attachment abutment member used in the FIGS. 1, 2 assembly;

FIG. 4 is a side elevation of the FIG. 3 abutment member;

FIG. 5 is a front view of a portion of a bar used in the FIGS. 1, 2 assembly;

FIG. 6 is a perspective view of a parallelism/depth jig used in implanting the root members; and

FIG. 7 is a perspective view of an insert used with the FIG. 6 jig.

With regard to FIGS. 1 and 2, an overdenture bar assembly 10 comprises first and second root members 12 formed of suitable biocompatible material such as commercially pure titanium or a titanium alloy, e.g., a titanium-aluminum-vanadium alloy. Each of root members 12 has a plurality of outwardly extending fins 14 and, in the direction going toward the crestal end, a shoulder 16 having a taper 17 of decreasing diameter. Root member 12 is positioned within a socket formed in the alveolar ridge so that its upper surface, as seen in FIG. 2, or the end surface closest to the crest 18 of the bone, is slightly below the crest 18, e.g., approximately 2 mm.

An upwardly opening, post-receiving bore 20 is formed in the root member through the crestal or top end surface 22 having a locking taper relative to that of a post to be received therein.

Root members 12 are of the type shown in U.S. Pat. No. 4,738,623, the subject matter of which is incorporated herein by this reference and to which reference may be had for further details.

First and second bar attachment abutments members 24 each comprise a head portion 26, preferably having a smooth rounded surface such as a spherical configuration to minimize irritation of tissue and the formation of occlusions and the like and a post portion 28 extending therefrom. A cross-section of post portion 28 taken vertically relative to the longitudinal axis 30, FIG. 3, is circular and the post portion is formed with a taper of decreasing diameter going in a direction away from the head portion 26. The taper is selected relative to the taper of bore 20 to be a locking taper, e.g., within approximately 3 degrees. In post portions made in accordance with the invention a taper of 1 degree and 24-32 minutes has been found to be very effective. A transversely extending bore 32 (FIGS. 3, 4) is formed in head portion 26 having a longitudinal axis 34 extending perpendicular to that of axis 30. The depth of the bore is selected to be sufficient to securely seat a cylindrical bar to be described below, preferably extending approximately to longitudinal axis 30.

A cylindrical bar 36 formed of suitable biocompatible material, preferably the same as that of abutment members 24, having a diameter selected so that it can be closely slipped into transversely extending bore 32 has a respective end received in bore 32 of each abutment member 24. Preferably a chamfer 38 is formed at each end of the bar to facilitate insertion into bore 32.

In using the bar overdenture system the restorative dentist initially exposes the front of the jaw bone and, in effect forms a shelf there. A reference bore is drilled generally centrally in the shelf and a pin is then placed in the reference bore. The jig member 40, FIG. 6, a generally flat plate having a central reference bore 42 between two outer bores 48, is placed on the shelf with the pin received in a reference bore 42 which closely matches the diameter of the pin. Insert member 44, FIG. 7, comprising an annular base 46, has an outer diameter closely matching that of outer bores 48 and, using handle 50, is inserted in each of outer bores 48. Preferably, two or more inserts 44 are used with different internal diameter bores 52, e.g., 2 mm, 3 mm, in outer bores 48 of 4 mm diameter so that a small pilot hole can be first drilled and then its size increased by using an insert with a progressively larger bore and then finally using bore 48 without an insert. Each drill bit is marked at an appropriate axial distance from the end of the drill bit so that when the mark comes into registration with the top surface of jig member 40 or insert 44 the proper depth of the bore in the bone of the jaw has been achieved. The thickness of the plate of jig 40 and insert 44 is sufficient, along with the close fit of a bur or drill bit into a repective bore of the jig, to provide parallelism of the drilled bores.

The dentist implants a root member in each socket with the longitudinal axes of the post receiving bores parallel with one another as described above. The root members are packed with autogenous material, preferably harvested while drilling the bores in the bone, and the mucoperiosteal flaps are closed over the root members and healing plugs received in bores 20 of the root members, sutured and allowed to heal, generally for three months or more.

After sufficient healing has occurred the healing plugs are surgically accessed and removed. The distance between the closed ends of the two bores is measured and a bar 36 is cut to that measurement. Preferably, to avoid the possibility of undesirable lateral stress placed on the alveolar bone the length of bar 36 is selected to be just under the measured distance, e.g., approximately 1 mm less than the measured distance. Preferably, a slight chamfer 38 is formed in each end of bar 36 to facilitate insertion into transversely extending bore 32. Each end of the rod is then inserted into transversely extending bore 32 of a respective bar attachment abutment member and held together while the bar attachment abutment members are tapped into the root members locking them in place.

It will be appreciated that, if desired, the measurement between the sockets in the bone can be taken at the time the root members are implanted and the bar prepared in the interim so that it is ready for installation at the time the patient returns to have the healing plugs replaced with the bar attachment abutment members.

Transversely extending bores 32 of bar attachment abutment members 24 are preferably formed with a slight taper with the diameter of the bore decreasing going in the direction into the bore, e.g., 1.5 degrees, to accommodate a certain amount of misalignment. For example with a bar 36 of 22 mm in length and a diameter 0.0787/0.0777 and a bore 32 of 0.0807/0.0797 misalignment of 1 degree 45 minutes is accommodated.

A suitable jig member 40 made in accordance with the invention has a length of 26 mm, a width of 7 mm and a thickness of 2 mm. The center reference bore has a diameter of 2 mm and the outer bores each have a diameter of 4 mm. Inserts 44 have an outer diameter of 4 mm, a thickness of 2 mm and inside diameters of 2 and 3 mm.

As noted above, a single measurement is made to cut the bar to the proper length and the two abutment members and the bar are inserted into the implanted root members without any concern of the prior art problem of timing, or angular position of a threaded member relative to the axial position of the member. This chairside procedure completely obviates the need for laboratory involvement and concomitant expense as well as reducing the number of office visits by the patient by as much as four for most dentists. Although the combination of root members and bar attachment abutment members each having a locking taper is particularly advantageous, it is within the purview of the invention to use other types of root members and abutments, such as those having threaded attachment means, as long as bar attachment members are provided with posts having a locking taper receivable in a matching bore in an implant means so that the bar can be inserted into transversely extending bores in the bar attachment members with the posts automatically properly angularly positioned to be received in the matching bores of the implant means.

Although the invention has been described with regard to a specific preferred embodiment thereof, variations and modifications will become apparent to those skilled in the art. It is therefore the intention that the appended claims be interpreted as broadly as possible in view of the prior art and to include all such variations and modifications.