The demand for implants continues to grow rapidly as our patients become more and more aware of their clinical advantages. SCDL’s experienced team of prosthodontists and master technicians have been focusing on the technical and clinical developments that continue at a rapid rate.
The continual evolution in the field of implantology has provided the restorative dentist with changes in implant design, taper, surface coating and even surgical placement. Such improvements enable dentists to provide consistent and predictable restorative results. Most dental implants have 3 main components: the fixture, which anchors the implant to the bone; the abutment, the part that screws into the fixture and holds the crown in and the crown, which replaces the coronal portion of the tooth. Screw retained implants only have 2 components - the abutment is incorporated into the crown super-structure and is connected directly to the platform with a screw. In the past, there have been 2 main types of abutments available for restoring implants: stock or prefabricated abutments and custom cast abutments. Stock titanium abutments are available from many major implant manufacturers in a variety of shapes, sizes and angulations. They are adjusted or modified manually, either at the laboratory or in the surgery, to adapt the shape according to the position of the implant and the patient’s individual anatomy.
When there is an inadequate volume of metal for proper reduction to establish margin definition, antirotation and emergence profile necessitated by patient differences in tissue height and width, stock abutments offer fewer options. Depending on the location of the implant to the surrounding dentition or other implants, the abutment may need to be asymmetrical to gain parallelism. In other words, stock abutments may not have enough metal on either side to compensate for the implant that was placed in a non-ideal location. Although many successful restorations have been fabricated on stock abutments, severe limitations exist because of the size and shape of the stock abutments.
Custom cast abutments (CCA) or UCLA abutments, which are fabricated from a plastic waxing sleeve, offer another type of abutment for the restorative dentist. This sleeve is modified by the technician to establish proper contours and emergence profile to compensate for any misaligned implants. Using the lost wax technique, the plastic sleeve is invested and cast into the alloy of choice. CCA and UCLA abutments also have been wonderful restorative alternatives that have enabled dentists to deliver excellent results.
Computer milled abutments are the next evolution in abutment fabrication. These abutments are milled from a block of titanium or zirconia, making them extremely strong and compatible with a specific implant.
As with other techniques, a fixture level transfer impression is required to locate the spatial and rotational position of the implant intraorally. As soon as a working cast is fabricated with a soft-tissue model and the lab analogues are in place, the cast is scanned optically to generate exact 3D images of the region. This includes the location of the analogue and its antirotational feature. Through a patented process, a computer system views the adjacent and opposing dentition, surrounding tissue levels and implant location to design an ideal, anatomically correct, virtual abutment for the edentulous space, accounting for all alignment and size requirements.
After inspection on the computer screen, the virtual abutment designs are sent to a computerised milling machine to manufacture the correct abutment from a block of titanium or zirconia alloy. The move from stock and custom abutments to CAD/CAM abutments has had a positive impact on both patients and dentists and may represent the future of abutment fabrication.