CAD/CAM Implant Abutments Using Coded Healing Abutments: A Detailed Description of the Restorative Process

Douglas H. Mahn, DDS; and Tony Prestipino, CDT

Implant abutments must satisfy important biologic, functional, and esthetic demands.¹ The materials they are made from, therefore, are critical to their success.² Abutment emergence profiles with natural contours permit esthetic peri-implant soft-tissue remolding.^3,4

Traditionally, implant-level impressions have been made using an impression coping. This requires removal of the healing abutment. The impression is made, the impression coping is removed, and the healing abutment is replaced.⁵ Fabrication of a custom abutment typically has involved using a UCLA abutment.⁶ Quality custom abutments required skilled laboratory technicians and the use of precious metals.⁷ Prefabricated abutments reduce costs but do not predictably create natural emergence profiles.⁸

Advances in impression systems and abutment fabrication have revolutionized implant dentistry. Computer-aided design and computer-aided manufacturing (CAD/CAM) technologies enable a sophisticated fabrication of customized implant abutments.^9-13 Coded healing abutments can, furthermore, eliminate the need to remove healing abutments during impression making. The use of virtual imagery allows technicians to design abutments to meet certain specifications and conform to the surrounding dentition. The computer-designed abutments can then be milled from solid blocks of biocompatible material.

This case report illustrates the steps involved in restoring implants using coded implant abutments and CAD/CAM technologies.

Case Report

The 67-year-old patient was seen for evaluation and treatment of her partial edentulism (sites Nos. 28 through 32). After thorough clinical and radiographic evaluation, a treatment plan was developed that called for placement of three implants to support individual porcelain-fused-to-metal (PFM) crowns in site Nos. 28 through 30.

The patient agreed, and 4/3 mm x 11.5 mm Certain® PREVAIL® Implants (Biomet 3i, www.biomet3i.com) were placed as planned. BellaTek® Encode® Healing Abutments (Biomet 3i) were placed on the implants. The dimensions of each abutment were 3.4 mm (prosthetic diameter) x 5 mm (abutment profile) x 3 mm (abutment height). The gingival flaps were repositioned and secured using a continuous 4.0 chromic gut suture.

Following 3 months of healing, all the implants were found to be healing well (Figure 1). At least 1 mm of the abutments were exposed above the gingiva circumferentially. The tightness of the BellaTek Encode Healing Abutments was verified using a 0.048 hex hand driver, and radiographs confirmed that the abutments were completely seated (Figure 2). Full-arch impressions of both arches were made, using trays filled with medium-body polyether impression material (Impregum™ F, 3M ESPE, www.3MESPE.com). Light-body polyether impression material (Permadyne™, 3M ESPE) was syringed around the healing abutments. The impressions were inspected for defects in the area of the healing abutments (Figure 3). A softened wax was used to make an occlusal registration. These records were sent to the dental laboratory with a completed lab prescription.

The dental laboratory placed BellaTek Encode Healing Abutments that were the same dimension as those used in the impression on implant analogs. The abutments and analogs were placed in the impression, and silicone (Gi-Mask, COLTENE, www.coltene.com) was injected around them to aid in the fabrication of a soft-tissue model. The dental laboratory then removed the implant analogs and abutments and poured die stone to complete the master cast, void of any bubbles (Figure 4). The lab mounted the casts on a Stratos 100™ articulator using Adesso Split Plates (Ivoclar Vivadent, Inc., www.ivoclarvivadent.com ).The lab filled out a prescription and sent the models without the articulator to the BellaTek® Production Center in Florida.

The casts were digitally scanned with a D700 3D scanner (3Shape Inc., www.3shape.com). Using the data derived from the BellaTek Encode Healing Abutments, virtual implant abutments were designed using the Abutment Designer™ CAD software (3Shape Inc.). These designs were sent to the dental laboratory, where the emergence profiles, crown-margin placement relative to the position of the gingival margin, space for definitive crown fabrication, and screw access-opening positions were all reviewed (Figure 5 through Figure 7). Once the designs were approved, Robocast™ Technology (Biomet 3i) was used to place implant analogs robotically in the master cast. Custom CAD/CAM abutments were then milled from a titanium alloy blank using a 5-axis industrial milling machine (Figure 8 through Figure 10).

The custom abutments were sent to the dental laboratory on the Robocast for fabrication of the definitive PFM crowns. The crown wax-up was performed directly on the CAD/CAM abutments (Figure 11). The definitive crowns were placed on the Robocast to confirm proper seating, contours, and contacts (Figure 12 and Figure 13). The abutments and crowns were then sent to the restorative dentist.

The CAD/CAM abutments were placed on the implants, and prosthetic screws were hand-tightened (Figure 14). Full seating was confirmed radiographically (Figure 15). After proper abutment seating was confirmed, Gold-Tite® Abutment Screws (Biomet 3i) were torqued to 20 Ncm using a torque driver. The PFM crowns were placed, and radiographs were taken to confirm their full seating (Figure 16). The crowns were cemented in place (RelyX™, 3M ESPE) (Figure 17), and all excess cement was meticulously removed.

Discussion

The use of traditional implant impression copings can be challenging.⁵ If healing abutment removal and placement of an impression coping is not done quickly, the soft tissue can slump and be pinched. Implant angulation can create situations where impression-coping placement is blocked by the adjacent teeth and/or impression copings. In posterior sites, access to the implant can be difficult. Once the copings are placed, patients cannot fully close their mouths. Finally, placing the impression tray over the coping(s) requires additional clinical skills. This is especially true when an open-tray pick-up impression coping must be positioned within the prepared hole in the tray. Elimination of the need for impression copings by using coded healing abutments that do not need to be removed during the impression process greatly simplifies the impression process and makes it less expensive and confusing.^9-13 Only 1 mm of the abutment needs to extend beyond the surrounding gingiva. The ability of a 3-dimensional (3-D) scanner to digitize the master cast is integral to this process.

Computer-aided design (CAD) of abutments allows for images of the abutment designs to be reviewed and adjusted prior to definitive abutment fabrication.^9-13 Design elements such as the emergence profile and crown margin placement are critical to a properly contoured and natural-appearing restoration. Problems such as inadequate abutment height for a cement-retained crown can be recognized early. Visualizing the virtual abutment prior to its fabrication enables the dental laboratory to confirm that the abutment will be made according to the instructions given on the lab prescription.

Computer-aided manufacturing (CAM) enables fabrication of high-quality implant abutments from solid blanks of biocompatible materials such as titanium or zirconia.^9-13 After milling, the abutment is polished and cleaned. CAD/CAM titanium abutments do not have the risk of impurities or casting defects that cast abutments have. For esthetic purposes, a gold-nitride coating can be applied to titanium abutments, or alternatively, esthetic CAD/CAM zirconia abutments can be fabricated.

Conclusion

Combining CAD/CAM technologies with the use of coded healing abutments facilitates and simplifies the ability to deliver high-quality adjacent implant restorations.

ACKNOWLEDGMENTS

The authors would like to acknowledge Philip Wine, DDS, in the delivery of these restorations.

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Related Content:

A CE article, Computer-Guided Implant Surgery: Indications and Guidelines for Use, is available at dentalaegis.com/go/cced457