Successfully Navigating Troubled Cases

This was a mandibular implant case with two NobelActive Conical Connection implants (Nobel Biocare, nobelbiocare.com), both documented as 3.0 mm in diameter. The clinician requested a resilient telescopic solution because a locator abutment is not made for the 3.0 mm diameter implant, and a custom locator abutment was not desired.

The clinician sent the implant-level impression using two NobelActive 3.0-mm impression copings along with an antagonist model to the laboratory. The author returned a screw-retained esthetic control base (ECB) and delivered a wax try-in (Figure 1).

Vertical Dimension of Occlusion (VDO) and centric relation were confirmed, and phonetics were approved. Once the clinician and patient approved the wax try-in, the mandibular implant-level model was scanned and primary telescopes were designed for milling in zirconia.

The custom hybrid abutments were then hand milled (Figure 2) and a modified telescopic verification jig was fabricated with individual copings made from Pattern Resin™ LS (GC America Inc., gcamerica.com) (Figure 3).

Upon delivery, the clinician discovered that one of the implants was not 3.0 mm in diameter; it was a 3.5-mm platform. Unfortunately, one of the custom hybrid abutments would have to be remade completely. However, did all previous steps need to be repeated? Thankfully, a more efficient solution was available.

After consultation with the clinician, it was decided that rather than perform the bite registration again, the technician could use the wax try-in to duplicate the bite registration and implant-level impression, while also preserving the approved tooth positions by utilizing an efficient, unique technique and product

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The mandibular wax try-in was duplicated using Celara Denture Facilitation System (anaxdent North America, anaxdentusa.com). Nature-Cryl® Pour clear acrylic (GC America Inc.) was used to pour a clear copy of the wax try-in. First, The wax try-in was invested in the Celara alginate (FIgure 4). Next, the Celara stone was poured through the disposable flask lid, creating a secondary mold (Figure 5). The wax try-in was removed (Figure 6), and a sprue hole was cut into the Celara alginate directly through the disposable flask (Figure 7).

The acrylic was mixed per the manufacturer’s instructions, poured into the Celara flask, and gently rocked until all trapped air was released. The clear duplicate was cured in a heat and pressure vessel, and complete curing was accomplished in less than 30 minutes (Figure 8 and Figure 9). The clear duplicate was finished and adjusted on the previous implant-level model to accommodate the impression copings (Figure 10 and Figure 11). The clear duplicate was used to take a new implant-level impression with the corrected impression copings, and a bite registration material was used intraorally to confirm that the centric relation and VDO had not changed.

By using this technique, coupled with a quick curing, high-quality acrylic, it was possible to avoid all of the problems associated with attempting to “adapt” the wax try-in on a new implant-level model. By using the acrylic, it was also possible to save time without compromising quality.

The clear copy of the wax try-in was used by the clinician to first make sure that there was a passive fit around the implant impression posts. Next, the occlusion was checked and a bite registration was taken. Lastly, the clear copy was used as a custom impression tray to verify the impression with the impression posts being luted to the clear copy as the impression material was setting.

The patient was also visually confirmed in the maximum intercuspation recorded earlier. The verified impression was disinfected and sent to the laboratory. Implant replicas were placed, and the new soft-tissue model, with all pertinent information recorded (tooth positions, bite registration), was now ready to be poured in type IV resin reinforced die stone (Figure 12).

After the definitive cast was poured, a new 0° resilience telescope was designed digitally and milled to match the existing telescopic abutment. The verified master cast was remounted on the handmill according to the previously recorded path, and both telescopic hybrid abutments were resurfaced at 0° using a series of five diamond burs with water cooling to prevent micro fracturing of the zirconia abutments.

The primary resilience telescopes were blocked at the margins and on the top of the abutment with a .5-mm spacer prior to electroforming of the galvano gold secondary telescopes. To accomplish electroforming the secondary telescopes, a duplicate was made using duplicating silicone, and then vacuum mixed and invested with a very low expansion type IV resin reinforced die stone such as Fujirock® IMP (.06 expansion) (GC America Inc.).

With the abutment blocked, it can be luted to a tertiary structure in this “raised” position, and slid across the parallel walls of the telescopic surfaces while the patient functions, thus eliminating any implant overloading.

Once the telescopic dies were completely set, they were removed from the duplicating silicone and trimmed. Conductive leads were then luted to the telescopic dies and a conductive silver lacquer applied to the surfaces that were to be electroformed. All surfaces where electroforming must be avoided were then blocked out using Primopattern LC Gel (primotec USA, primotecusa.com).

The electroforming process began, and afterward the telescopic dies were removed from the solution and placed in stone and plaster remover. The container was placed in an ultrasonic bath until the type IV die stone was completely removed. Afterward, all of the galvano gold secondary telescopes were cleaned, dried, and placed into a beaker with a 40% nitric acid solution (Figure 13) in order to effectively remove all traces of the silver conductive lacquer.

At this point, the secondary telescopes were refined, finished, and placed in the .5-mm “raised” position on the primary telescopes (Figure 14). The secondary telescopes and model were blocked (Figure 15) in preparation of waxing up the tertiary structure using the Metacon light curing system (primotec USA) (Figure 16).

Once light cured and removed, the tertiary structure was invested, burned out, and cast. The casting was adjusted appropriately and air abraded with aluminum oxide at 2 bar pressure. The secondary galvano gold telescopes were also air abraded with aluminum oxide at 2-bar pressure, steam cleaned, and prepared for cementation into the tertiary structure (Figure 17).

Both the tertiary structure and the secondary galvano telescopes were prepared with a metal primer and light cured. Additionally, they were prepared with Scotchbond™ Universal Adhesive (3M, 3m.com), and the tertiary structure was cemented to the secondary telescopes in their raised .5-mm positions (Figure 18).

After cementation, the teeth and wax were added to the hardware with a silicone matrix and remounted to confirm occlusion. A silicone duplicate processing cast was made using Pattern Resin and Fujirock IMP. The secondary telescopes were injected with VPS material and seated on the processing cast. The case was invested in an injection flask and processed using Nature-Cryl acrylic.

At the delivery appointment, the clinician seated the primary telescopic abutments with a buccal indicator for positioning and torqued them in place (Figure 19), seating the mandibular prosthesis. In more complex cases with greater implant numbers, it should be noted that a seating index is provided for torquing of abutments.

Checks were performed with regard to occlusion, excursive and protrusive movements, phonetics, and comfort (Figure 20). It was necessary to spend some time with the patient to ensure that he could comfortably remove the prosthesis. This is imperative with telescopic prostheses, as they are quite retentive, and great care is taken to assure the patient not to panic during the process of finding the exact path of insertion and removal.

It is also critical to remind the patient not to “bite” the prosthesis into place, as this could harm the inner surfaces of the telescopic attachment. Rather, the patient should be instructed on how to insert and remove the new prosthesis, and observed while physically inserting and removing the prosthesis a number of times prior to leaving the dental office. The screw accesses were then blocked at the screw with a VPS material and covered carefully with light curing composite to seal off the screw accesses. The composite was finally polished, and the patient is happy with the new telescopic prosthesis.

At times, errors occur in the process of restoring a patient. It is essential, and adds a great value, if we are aware of systems and techniques that can get a troubled case back on track.