Dentistry – Prosthodontics – Holding or positioning denture in mouth
Reexamination Certificate
2000-06-09
2001-06-12
Lucchesi, Nicholas D. (Department: 3732)
Dentistry
Prosthodontics
Holding or positioning denture in mouth
C433S215000
Reexamination Certificate
active
06244868
ABSTRACT:
The present invention relates generally to the field of dental implants.
BACKGROUND OF THE INVENTION
Predictably useful dental implants had their beginnings in Sweden in the 1960's in work done by Per-Ingvar Brånemark, who discovered in 1952 that lab animals' bone cells would deposit mineralized bone directly on implanted titanium objects, thereby solidly attaching them to the surrounding bone. He is credited with coining the term osseointegration, which is now in common use, to identify this process. Since his discovery, thousands of titanium implants of mostly screw-type design have been inserted in people's toothless spaces to anchor prosthetic teeth. This implantation has been done almost exclusively by elevating the soft tissue, drilling a hole in bone, placing the implant in the hole, stitching the soft tissue back over the implant, waiting a period of months, re-opening the soft tissue, uncovering the implant and attaching a stud to project through the gum. If bone augmentation has been necessary, yet more operations have been required. If one counts the extraction surgery that leads to most toothless spaces, patients progressing from having teeth, to having a toothless space, to getting an implant and then fastening a prosthetic tooth onto the implant, must submit to at least 3 surgeries. The total rises to 5 if bone augmentation is required and done separately. The number of surgeries would be reduced to one if an implant with a visible trans-mucosal healing element to guide gingival healing, inserted immediately on tooth removal, would osseointegrate. If so, subsequent access to the implant would be non-surgical. Implantation with placement of trans-mucosal elements on extraction would mean that patients would experience fewer painful, expensive and time-consuming surgeries and avoid bone loss in extraction sites, which is associated with problems of appearance, comfort and insufficient bone volume for eventual implants. Furthermore, the patients' periods of wearing temporary prosthetic replacement teeth or doing without teeth altogether would be shorter.
The unpredictability of success with currently available immediate implantation technology has meant that only a small proportion of implants have been placed in tooth sockets immediately after teeth have been removed, and only a small proportion of those have had trans-mucosal elements placed at the time of surgery. The main reason for covering newly-inserted implants with soft tissue during the initial healing phase has been to prevent patients from applying enough force to implants to disrupt bone formation, but prevention of infection has also been a motive, as has been exclusion of mucosal or gingival cells from the implant sites. These potential causes of failure can be controlled without covering the implant initially. Infection prevention is easiest and does not require the present invention. Bacteria can be reduced or eliminated with surgical instruments, sterile technique, antibiotics and antibacterial rinses. Robert Pilliar and others from the University of Toronto have found that implant movements under 50&mgr; can take place without osseointegration being affected. Achieving fixation great enough to keep movements within this range is dependent on gaining intimate adaptation of the implant to the bone of the extraction site and by controlling the size, duration and direction of dislodging forces applied to it. Intimacy of adaptation can be increased by reshaping the extraction site to conform to the implant shape and by forcing the implant tightly into place. A visible trans-mucosal healing abutment attached to the implant at the time of placement would require the patient to avoid biting on it or pushing on it with his tongue to keep implant movements under 50&mgr;. However, it is not unlikely that patients who wished to reduce their numbers of surgeries would find it possible to avoid moving visible healing abutments attached to their implants in most situations.
SUMMARY OF THE INVENTION
It is the object of this invention to provide a guided-tissue-regeneration barrier integrated with root-form dental implants to ensure osseointegration by preventing soft tissue deposition and improving implant stability within a tooth extraction socket.
Placing a barrier to prevent migration of selected cell types into selected areas to control tissue formation during healing is termed guided tissue regeneration (GTR). Furthermore, a GTR barrier fixed around an implant would prevent migration of fibroblasts and epithelial cells into the healing socket, preventing fibrous tissue or epithelium from being created there, and allowing slower-migrating bone cells (osteoblasts) to populate the socket and deposit bone throughout, including directly on the surface of the implant, thereby osseointegrating the implant into the jaw to be an anchor for a prosthetic tooth.
The barrier must be deformable and compressible in order to be closely adapted to the crestal portion of the interior of the socket not filled by the implant, and to the crestal bone surrounding the extraction site. It must retain the form into which it is shaped and must likely allow circulation to be established through it in order to allow the mucosal or gingival tissue overlying it to receive its blood supply through the barrier. It must be easy for a surgeon to cut and adapt to the surgical site It must not cause an inflammatory response, so that the overlying mucosa sutured tightly over it will remain firm and capable of stabilizing the barrier, and so that inflammation will not disrupt bone formation around the implant.
By fulfilling these criteria, a barrier securely attached to an implant or healing abutment can also provide a small increase in implant stability.
Ideally, it should be possible to insert implants with predictably successful osseointegration immediately after removal of teeth in tooth sockets with intact bony walls, by performing the two functions of excluding unwanted cells from the extraction socket and increasing the stability of the implant. Extraction sockets with deficient walls, which require increased bone height on portions of their circumferences, may have guided-tissue-regeneration barriers integrated with root-form dental implants supplemented with sheet-form barriers to obtain the desired bone height increase.
The integral guided-tissue-regeneration barrier is made of absorbable material formed circumferentially around the trans-mucosal healing abutment. It can also be formed around the most coronal 1-2 mm of the implant or around both that portion of the implant and an attached trans-mucosal healing abutment. This material will stay in place on the healing abutment and/or implant by virtue of its intimate adaptation (being formed in place with zero clearance) to those pieces. Its malleability and compressibility could be increased by immersion in saline (together with the healing abutment and/or implant) before being placed in the fresh and suitably modified extraction socket, making it pliable. The amount of absorbable material provided will be big enough in width and therefore have sufficient diameter to occupy the space between the implant and the rim of the socket. The barrier will be compressed on insertion of the implant so that its outermost surface will be forced into the shape of the socket rim. The barrier will be great enough in height that some of it will remain coronal to the crest of the alveolar bone once it is inserted. The excess will be able to be trimmed off with a scalpel before the gum is sutured back into place around the healing abutment. The used of absorbable material in this way will have some stabilizing effect on the implant, and be effective in blocking epithelial migration.
Where increased bone volume on one or more aspects of the implant is required, or bony infill is required in the sockets of roots of multi-rooted teeth, this integrated guided-tissue-regeneration barrier for root-form dental implants can be supplemented with a sheet-form barrier made either from a materia
Battison Adrian D.
Dupuis Ryan W.
Lucchesi Nicholas D.
Williams Michael R.
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