Immediate Loading and Custom Abutments to Create and Assure Predictable Esthetic Implant Dentistry

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Immediate Loading and Custom Abutments to Create and Assure Predictable Esthetic Implant Dentistry
April 2005
By Ira Schecter, DDS
Oral Health
Forty years ago, Dr. P.I. Br?īnemark placed the first titanium implants in a human jaw. Those four fixtures, screwed into the edentulous mandible of a 34-year-old male patient, served as the foundation for a long-lasting restoration that restored the man to normal form and function.1 Over the ensuing years, as Br?īnemark developed the concept of osseointegration, his work was expanded and developed to serve not only the completely edentulous population but also partially edentulous patients and those missing a single tooth in the posterior areas as well as the anterior esthetic zones.
The original Br?īnemark surgical protocol involved a two-stage approach. This was intended to maintain the implant embedded in the bone and protect it from any premature loading that could induce micro-motion and cause the osseointegrative process to fail. Submerging the implants was also meant to prevent any bacterial contamination and resulting infection; the surgical site was secured with primary closure. However, this approach necessitated a second-stage surgery that was potentially discomforting for the patient and delayed the delivery of function and esthetics. The need for a second surgery not only lengthened the total treatment time but also increased the costs to both practitioners and patients.2,3
Single-stage implant placement into immediate extraction sites:
- Is more efficient for the surgeon and the patient
- Is easier for the patient to accept
- Eliminates the need for a second surgery
- Enables the surgeon to assess the stability of the fixtures directly during the healing phase, and
- Allows for maturation of the soft tissue during the healing phase if the implant is immediately loaded with a temporary restoration.
The disadvantages of this approach are:
- Potential premature loading of the implant, which can result in the formation of un-mineralized fibrous tissue and compromised bone remodelling, and
- An increased dependency on the patient's oral hygiene regimen. Excess gingival inflammation can result in an increase in the onset of bone resorption and ensuing implant failures.3,4
In order for an implant to be placed directly into a fresh socket site, the quantity and quality of available bone must be sufficient. The implant surgeon must determine that only the tooth being replaced is compromised and not the surrounding soft tissue or bony architecture. Active infection must be eliminated first, and the success of the treatment is totally dependent on the removal of the compromised tooth without damaging any of the attachment apparatus.4-6
Compromised teeth that are most successfully treated with extraction and immediate implant placement are those that have:
- a more coronally placed free gingival margin
- a flatter scalloped gingival form
- a thicker tissue form, and
- a squarer tooth shape
These factors ensure the least amount of post-operative tissue recession and esthetic problems.7
In order for the implant to be a candidate for immediate loading, it must be rigidly stable at placement.8-10 It has been the experience of this author that predictable, long-term success can be achieved by using a challenge torque of 45Ncm as the gauge to evaluate implant stability.
The stability of the implant can be influenced by:
- Implant surface geometry
- The quality and quantity of available bone
- Splinting of implants where applicable
- Control of occlusal loads
- The absence of detrimental patient habits.3,11-15
The use of dental implants in the esthetic zone is well documented in the literature.16-18 Predictable esthetics and function can be achieved in the anterior pre-maxilla where there is no soft- and/or hard-tissue deformity because tissue support is provided by the adjacent teeth. As well, the occlusion can be protected to minimize any premature loading. Provisional restorations with proper emergence profiles can guide and shape the surrounding tissue prior to the fabrication of the final restoration.
The following case report illustrates the immediate placement and restoration of two implants in the anterior maxilla.
CASE PRESENTATION
A young, healthy 18-year-old female patient presented with retained upper deciduous lateral incisors that were held in place only by wire splints (Figs. 1-5). The available bone in the upper right area was evaluated and found to be sufficient in height and width to accommodate a narrow-platform (3.5mm) implant. It was possible to place a regular-platform (4.3mm) implant in the upper left lateral incisor position.
Replace Select Tapered implants with the Ti-Unite surface (Nobel Biocare, Yorba Linda, California) were utilized. The tapered design was chosen to take better advantage of the shape of the anterior pre-maxillary bone as well as to minimize encroachment upon the adjacent root surfaces. The roughened Ti-Unite surface has been shown to induce a quicker onset of healing and osseointegration of the fixture with the surrounding bone.19 The design of the implant allows for the bone to be incorporated into the depth of the implant threads.20 This creates more surface area to resist initial loads. The result is greater initial fixation.21
The implant in the upper right could only be torque-challenged to 35Ncm. It was thus decided to place a low-profile healing collar at the tissue level and not immediately load it with a provisional restoration (Fig. 6). The missing tooth was temporarily restored with a removable acrylic "flipper" partial denture (Fig. 11). The implant in the upper left area was torque-challenged to 45Ncm and restored immediately chair-side. The temporary acrylic tooth was made on an engaging, anti-rotational titanium cylinder that is part of the Replace Select system (Figs. 7-11).
The patient was prescribed analgesics, prophylactic antibiotics, and a chlorhexidine mouth rinse and given post-operative instructions. She was seen one week post-operatively and subsequently on a monthly basis. Her healing proceeded uneventfully, and the final restorative work commenced three months later.
At that time, it was apparent that the tissue had healed beautifully around the immediately loaded left implant. Over the right implant, there was an over-abundance of tissue, with no scallop apparent in the soft tissue (Fig. 12). A small amount of local anesthesia was administered, and a careful gingivectomy was performed using the electro-surgery unit to create the proper gingival architecture (Figs. 13-14). A fixture-level impression with an open-tray technique was made (Figs. 16-18), and the corresponding fixture replicas were attached before the impression was sent to the laboratory for the pouring of an accurate fixture-level model (Figs. 19-22).
Custom zirconia abutments were designed and fabricated with the Procera three-dimensional Computer Assisted Design (3D CAD) system. This technology allows for the design of an abutment of ideal size, shape, and angulations. The contoured margin maintains the finish line at the exact prescribed location within the healed tissue and mimics the contour of the mature sulcus. In cases where the restoration is cement-retained, this makes it significantly easier to clean the cement that otherwise might be deeply embedded in the interproximal areas of the implant sulcus. Screw-retained restorations also benefit when the final crown/abutment restoration follows the ideal contour of the matured tissue; optimal soft-tissue remodelling is thus fostered. When using the Procera process, all aspects of the restoration are designed and fabricated outside the mouth (Figs. 23-24).
Zirconium is a highly stable mineral that is both biocompatible and has a high resistance to corrosion. Zirconia (zirconium oxide) has three to six times the strength and fracture toughness of zirconium. These biomechanical characteristics and the white colour of the material allow for the fabrication of esthetic restorations of extremely high quality.22
In the upper right area, placement of the implant in the best available bone resulted in the abutment screw exit hole being positioned in the esthetic zone of the mesial-incisal area of the restoration. A custom zirconia abutment was thus required to support a separate crown restoration that would be cemented over the abutment. To fabricate the crown, the abutment was first digitally scanned on the tissue model. The scanned information was sent to a Procera fabrication facility where an aluminous oxide densely sintered crown coping was milled. This coping was then veneered in the laboratory with porcelain, producing a highly esthetic restoration (Figs. 25-28).
The abutment was torqued to 35Ncm, and the screw access hole was covered with a cotton pellet and Systemp temporary material (Ivoclar Corporation, Amherst, NY). The permanent crown was cemented with Panavia F (J. F. Morita Corporation, Irvine, CA).
Because the implant fixture in the upper left was placed in an ideal position, with the abutment screw exit hole located in the non-esthetic cingulum area of the restoration, the ceramist was able to veneer the finishing porcelain directly onto the zirconia abutment surface without having to fabricate a second restorative component. The abutment/crown restoration was torqued to 35Ncm, and the screw access hole was covered with a cotton pellet and direct restorative resin material (Figs. 29-30).
CONCLUSIONS
A highly esthetic anterior implant-supported restoration (Figs. 31-32) was achieved in this case. The tooth replacements and implant-supported restorations provided immediate esthetic and functional benefits, in contrast to what would have been achieved with delayed loading. The many advantages of the immediate implant/load technique include superior esthetics, preservation of bone, reduced surgical procedures, reduced treatment time, and re