Dentistry – Prosthodontics – Holding or positioning denture in mouth
Reexamination Certificate
1999-07-13
2001-09-04
Manahan, Todd E. (Department: 3732)
Dentistry
Prosthodontics
Holding or positioning denture in mouth
C433S214000
Reexamination Certificate
active
06283752
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to dental impression copings of the type used in implant dentistry to take impressions of a dental implant site from which accurate models can be constructed. More particularly, the invention relates to a universal impression coping system and method for taking accurate dental impressions using either open-tray or closed-tray techniques.
2. Description of the Related Art
Implant dentistry involves the restoration of one or more teeth in a patient's mouth using artificial components, including typically an implant fixture or root and a prosthetic tooth and/or final abutment which is secured to the implant fixture. According to state of the art techniques, the process for restoring a tooth and its root is carried out generally in three stages.
Stage I involves implanting the dental implant fixture into the bone of a patient's jaw. The oral surgeon first accesses the patient's jawbone through the patient's gum tissue and removes any remains of the tooth to be replaced. Next, the specific site in the patient's jaw where the implant will be anchored is widened by drilling and/or reaming to accommodate the width of the dental implant fixture to be implanted. Then, the dental implant fixture is inserted into the hole in the jawbone, typically by screwing, although other techniques are known for introducing the implant in the jawbone.
The implant fixture itself is typically fabricated from pure titanium or a titanium alloy. Such materials are known to produce osseointegration of the fixture with the patient's jawbone. The dental implant fixture also typically includes a hollow threaded bore through at least a portion of its body and extending out through its proximal end which is exposed through the crestal bone for receiving and supporting the final tooth prosthesis and/or various intermediate components or attachments.
After the implant is initially installed in the jawbone a temporary healing cap is secured over the exposed proximal end in order to seal the internal bore. The patient's gums are then sutured over the implant to allow the implant site to heal and to allow desired osseointegration to occur. Complete osseointegration typically takes anywhere from four to ten months.
During stage II, the surgeon reassesses the implant fixture by making an incision through the patient's gum tissues. The healing cap is then removed, exposing the proximal end of the implant. A mold or impression is then taken of the patient's mouth to accurately record the position and orientation of the implant within the mouth. This is used to create a plaster model or analogue of the mouth and/or the implant site and provides the information needed to fabricate the prosthetic replacement tooth and any required intermediate prosthetic components. Stage II is typically completed by attaching to the implant a temporary healing abutment or other transmucosal component to control the healing and growth of the patient's gum tissue around the implant site.
Stage III involves fabricating and placement of a cosmetic tooth prosthesis to the implant fixture. The plaster analogue provides laboratory technicians with a model of the patient's mouth, including the orientation of the implant fixture relative to the surrounding teeth. Based on this model, the technician constructs a final restoration. The final step in the restorative process is replacing the temporary healing abutment with the final restoration.
To achieve optimal results in terms of overall aesthetics and bio-functioning ability of the tooth restoration, it is essential in stage II that the plaster analogue accurately reflect the true position and orientation of the implant in the patient's mouth and that in stage III such position and orientation is faithfully replicated when securing the final tooth restoration to the implant. To help achieve this accuracy and faithful replication, one or more indexing means are typically provided on the proximal end of the implant and corresponding mating indexing means are formed on the various mating components which are adapted to be fitted to the implant. Such indexing means provide desired orientation of the implant and mating components relative to one another and also prevent undesired rotation.
Such indexing means frequently take the form of a hexagonal boss or recess (“hex”) formed on the proximal portion of the implant exposed through the crestal bone. For externally threaded implants the hex may also be used to engage a driving tool for driving the implant into an internally threaded bore or osteotomy prepared in the patient's jawbone (mandible or maxilla). When the implant is filly installed in a patient's jawbone the hex or other indexing means is typically exposed through the crestal bone so that accurate indexing may be provided between the implant and the final prosthesis and/or various intermediate mating prosthetic components.
As noted above, during stage II of the dental restorative process a mold or impression is taken of the patient's mouth to accurately record the position(s) and orientation(s) of the indexing means within the mouth at the implant site(s) and to thereby provide the information needed to fabricate the restorative replacement(s) and/or intermediate prosthetic components. According to the state of the art, this is done using a casting or impression material formed of a soft resin—typically polyvinylsiloxane or polyether—which can be applied over the implant site using a suitable impression tray and allowed to cure in situ. The impression material is sufficiently resilient such that it can be removed from the patient's mouth after it is cured (or partially cured) while at the same time retaining an accurate impression of the patient's mouth and particularly the implant site.
However, because the indexing means of the implant is typically quite small and may be recessed partially beneath the gums of a patient, a secondary or intermediate impression element is typically used to help transfer accurately the orientation of the indexing means of the implant. This intermediate impression element is commonly called a “coping” or “impression coping.” Examples of impression copings as found in the prior art are shown in U.S. Pat. No. 4,955,811 to Lazzara et al., e.g.
FIGS. 5
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. There are primarily two types of such impression copings used today—so-called “transfer” impression copings and so-called “pick-up” impression copings.
Conventional transfer impression copings have an impression portion adapted to form a unique or indexed impression in the impression material and a base portion having mating indexing means adapted to mate with the exposed indexing means of the implant. In use, the impression coping is temporarily secured to the exposed proximal end of the implant fixture such that the mating indexing means of the impression coping and implant are interlockingly mated to one another. Typically, a threaded screw or bolt is used to temporarily secure the impression coping to the implant fixture.
Once the impression coping(s) is secured to the implant fixture(s), an impression of the coping(s) relative to the surrounding teeth is taken. A U-shaped tray filled with an impression material is placed in the patient's mouth over the implant site. The patient bites down on the tray, squeezing the impression material into the implant site and around the impression coping(s). Within a few minutes, the impression material cures or hardens to a flexible, resilient consistency. The impression tray is then removed from the patient's mouth to reveal an impression of the implant site and the impression coping(s). The restorative dentist then removes the impression coping(s) from the patient's mouth and transfers the coping(s) back into the impression material, being careful to preserve the proper orientation of the indexing means. This impression method using transfer impression copings is commonly referred to a
Knobbe Martens Olson & Bear LLP
Manahan Todd #E.
Nobel Biocare AB
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