Dental implants offer a reliable way to replace missing teeth. These artificial tooth roots are surgically placed into the jawbone, where they integrate with the surrounding tissue to create a durable foundation. Restoring these implants with a final, visible tooth replacement requires capturing the precise three-dimensional position of the anchor in the mouth. This step, known as taking an impression, is essential, and the choice of technique—either implant-level or abutment-level—directs the subsequent laboratory procedures and the final outcome of the restoration.
Understanding Implant Components
A complete dental implant restoration involves three distinct structural components. The implant fixture is the small, screw-like titanium or zirconia post surgically anchored directly into the patient’s jawbone. This fixture acts as the root replacement and remains permanently submerged within the bone and gum tissue.
The second part is the abutment, a connector piece that attaches to the top of the fixture and protrudes through the gum line. Abutments provide a stable platform onto which the final artificial tooth will be secured. They are often made from materials like titanium or ceramic and can be angled to correct a slightly misaligned implant fixture.
The final piece is the prosthesis or crown, the visible, tooth-shaped restoration that is cemented or screwed onto the abutment. The difference between the two restorative approaches hinges on whether the impression is taken from the top of the implant fixture or from the top of the pre-installed abutment.
The Implant-Level Approach
The implant-level approach involves taking an impression directly from the implant fixture before any final abutment is placed. This method requires the clinician to temporarily attach a specialized component, called an impression coping, directly into the internal connection of the implant. The impression material captures the precise position and angle of the fixture relative to the surrounding teeth and gums.
This technique provides the dental laboratory with the highest degree of accuracy. Since the lab has the precise coordinates of the fixture, they can design a custom abutment tailored to the patient’s gum tissue and the desired crown shape. The resulting restoration is typically a screw-retained crown. This crown has a small access channel designed through the biting surface, allowing it to be screwed directly to the custom abutment. The access hole is later covered with a filling material.
The Abutment-Level Approach
The abutment-level approach involves first placing a final abutment onto the implant fixture. This abutment may be a stock (pre-fabricated) component or a modified abutment designed to correct the implant angle. Once the abutment is secured, the impression is taken from the top of the abutment.
This technique often uses a closed-tray impression, where the coping remains in the mouth after the impression is removed. The laboratory then fabricates a crown that will be attached to the abutment, usually through a cement-retained method. The crown is cemented onto the abutment, completely covering the screw access hole and creating a seamless, natural-looking restoration. This method utilizes readily available components, which can streamline the manufacturing process.
Practical Differences in Selection and Outcome
The choice between the two impression techniques has significant implications for the final restoration’s aesthetics, maintenance, and clinical application. For aesthetic zones, such as the front teeth, the implant-level approach is often favored because it allows for the fabrication of a custom abutment. This custom component can be precisely contoured to shape the surrounding gum tissue, creating a natural emergence profile that mimics a tooth coming out of the gum.
By contrast, the abutment-level approach, often using stock abutments, can sometimes compromise optimal soft tissue contours, though it does hide the screw access channel, which can be an aesthetic advantage in some cement-retained cases. The cement-retained crowns (abutment-level) carry the risk of excess cement being left around the gum line, which can lead to inflammation and potential bone loss around the implant over time. Screw-retained restorations (implant-level) avoid this cement-related complication.
Maintenance and Retrievability
In terms of maintenance, the screw-retained design offers easier retrievability. The crown can be unscrewed and removed for cleaning, repair, or inspection. Cement-retained crowns are more difficult to access without destroying the crown itself.
Clinical Application and Cost
Clinically, the implant-level technique is required when the implant fixture is deeply placed or severely angled, as it provides the most accurate data for designing a custom abutment. Conversely, the abutment-level approach is often selected when the vertical space between the arches is limited, as the components take up less room. Using stock parts in the abutment-level technique can make the overall procedure faster and potentially less expensive than the custom, lab-intensive implant-level method.