Fast-Tracking the Implant Prosthodontic Workflow for Full-Arch Restorations: Case Series

Udatta Kher, MDS; Ali Tunkiwala, MDS; and Priya Bijlani, MDS

Implant-supported prostheses necessitate a high level of precision.Misfit of the implant prosthesis may induce strain on the components, resulting in mechanical and biological complications.¹ Implant prosthodontic procedures need to be performed meticulously to achieve well-fitting prostheses. Impression making is one of the most crucial steps for fabrication of implant prostheses. Literature is replete with studies comparing different techniques in implant impression making.^2-17 When rehabilitating edentulous patients, clinicians often encounter situations in which obtaining the correct interocclusal relationship may be challenging because of an altered mandibular position that may be due to the poor condition of an old prosthesis or mutilated dentition. The provisional restoration phase is critical for evaluation of the correct intermaxillary relation and esthetic parameters for each patient.

Figure 1 highlights the prosthetic steps and appointments needed in the conventional approach for full-arch implant prosthodontics.¹⁸ The time consumed and the multiple visits can be a deterrent for elderly patients and those who may be bound by time. Moreover, each prosthetic step allows opportunity for incorporation of certain errors; any error must then be negated and balanced out in the subsequent steps. Each step must be verified for accuracy in the subsequent visits; otherwise, errors may build up, potentially leading to lack of passive fit in the final prostheses.

This article presents a case series that highlights the effectiveness of a novel technique for fast-tracking implant prosthodontics in full-arch cases that are immediately loaded. This technique reduces the number of appointments and chairside time required in the restorative phase without compromising clinical outcome. Figure 2 lists the steps and corresponding appointments in this fast-track technique. The making of an accurate impression-jaw relation record is done in a single appointment without any additional armamentarium. The fast-track technique requires only basic laboratory support. Additionally, the technique avoids the removal and refitting of the provisional restoration at every appointment, making the experience more amenable for the patient. An optimally adjusted full-arch fixed provisional restoration that fits well on the implants is a prerequisite for this technique. A radiograph with the provisional prosthesis can help confirm complete seating. Uniform contact of equal intensity on the provisional restoration is essential to avoid local overloading, fracture of the provisional, and implant failure. This technique can be utilized for implant-level or abutment-level screw-retained reconstructions after the healing period.

Technique

Case 1

A 61-year-old patient needed total extractions in the mandibular arch. Six implants were placed immediately post-extraction and immediately loaded using the denture conversion technique (Figure 3).^19-21 Occlusion was meticulously adjusted to achieve uniform contacts of equal intensity to facilitate even load distribution.

After an uneventful 12-week healing period, the accuracy of the fixed provisional restoration was verified. Phonetics, esthetics, lip support, and uniform occlusal contacts on the provisional prosthesis were evaluated and found to be satisfactory.

Before removal of the prosthesis, an interocclusal record was made against the opposing dentition using bite registration wax (Aluwax Bite and Impression wax, Aluwax Dental Products Co., aluwaxdental.com) (Figure 4). The access holes for the screw-retained prosthesis were then opened up. The internal screws were loosened and the prosthesis was removed. The implant stability was measured and confirmed with the use of a resonance frequency analysis device (Penguin^RFA, Integration Diagnostics Sweden AB, penguinrfa.com). The prosthesis was then fitted back with the long screws of the open tray impression copings instead of the internal screws. A stock metal tray with an open top was selected for the impression making (Figure 5). Alternatively, a custom acrylic tray could be used for this purpose. It was ensured that the long screws would emerge above the level of the tray. The open portion of the tray was covered with wax to prevent excess material from flowing out, and adhesive was applied on the tray.

Polyether impression material was used to make the impression. The material was injected on the underside of the prosthesis using a syringe to record the tissue surface (Figure 6). The tray was loaded with the impression material and seated in position. It is important to syringe the material on the undersurface of the prosthesis adequately so that the tissue contours are registered accurately in the final stone model.

After the material had set, the long screws were loosened and the impression tray was retrieved to pick-up the prosthesis. The implant replicas were then attached to the impression. A separating medium was applied to the impression around the impression copings so that the overlying silicone soft-tissue mask would not adhere to the impression material. The soft-tissue mask material was syringed around the implant analog and impression coping junction (Figure 7). The cast was then poured in die stone and allowed to set. The prosthesis was removed from the cast, and the master cast was ready (Figure 8).

The maxillary cast was mounted on the semi-adjustable articulator using a facebow record. The prosthesis was secured on the model with internal screws and mounted using the wax interocclusal record on the semi-adjustable articulator (Figure 9). The mounted casts served as an accurate representation of the implant positions and the jaw relation existing in the provisional restoration.

All of the aforementioned steps were achieved in a single appointment in approximately 3 hours. The prosthesis was removed from the model, cleaned, and fitted back into the patient's mouth. The mounted casts were sent to the laboratory for fabrication of the definitive restoration. Several factors govern the choice of the final restoration; chief among them is the interarch space, which is dictated by the degree of resorption.²² The definitive prosthesis was a screw-retained porcelain-fused-to-metal restoration fabricated with a milled metal framework. Figure 10 and Figure 11 depict the definitive prosthesis. Figure 12 shows the radiograph demonstrating the fit of the prosthesis.

Case 2

A 53-year-old patient required total extractions. The treatment plan agreed upon was implant-supported fixed prostheses with immediate loading. The extractions and rehabilitation was to be done in two phases, with the mandibular arch done first followed by the maxillary arch. The first surgical appointment involved extractions of all lower teeth and simultaneous placement of six implants. The implants were immediately loaded with a fixed screw-retained provisional restoration, which was fabricated using a customized acrylic shell to pick-up the titanium cylinders in autopolymerized tooth-colored provisional material. The provisional restoration was adjusted to achieve uniform contacts (Figure 13).

The 3-month healing period was uneventful. The fast-track technique was used to make the final impression and register the interocclusal record. After the casts were mounted on a semi-adjustable articulator, the provisional prosthesis was removed, disinfected, and fitted back into the patient's mouth. The casts were sent to the laboratory for fabrication of the definitive prosthesis. Once the finished prosthesis was received from the laboratory, the appointment was scheduled to fix the mandibular screw-retained full-arch prosthesis made with biocompatible high-performance polymer framework (BioHPP, Bredent GmbH & Co.KG, bredent.com) and visio.lign teeth (Bredent GmbH & Co.KG) (Figure 14).

The prosthetic phase was accomplished in just two visits. The first appointment was for the pick-up impression and bite registration; the second appointment was for delivering the definitive prosthesis.

The next surgical visit involved the total extraction of all maxillary teeth and simultaneous placement of six implants, which were immediately loaded. The provisional restoration was fabricated using the denture conversion technique^19-21 on multi-unit abutments (Figure 15). After the healing period the maxillary final impression was made and interocclusal record was registered using the fast-track technique. The casts were mounted and sent to the laboratory for fabrication of the definitive prosthesis made with biocompatible high-performance polymer framework (BioHPP) and visio.lign teeth. Figure 16 illustrates the definitive prostheses in occlusion and Figure 17 shows the radiograph of the definitive prostheses in situ.

Case 3

Immediate loading using denture conversion was planned for a 65-year-old edentulous patient (Figure 18). Two tilted and two straight implants with multi-unit abutments were used in this case. The planned prosthesis was at the abutment level.

After a 12-week healing period, the fast-track technique was used for making the impression and recording the jaw relation. The definitive prosthesis was fabricated and fixed at the second visit in the prosthetic phase. Figure 19 shows the provisional denture fixed in position with open-tray screws. Figure 20 depicts the occlusal contact on the definitive prosthesis.

Discussion

Immediate loading in a fully edentulous jaw by means of a fixed prosthesis is well documented.^23,24 When four or more implants are placed, the implant failure is 0 to 3.3% in the mandible.²³ In the maxilla, four to six implants yield a failure rate of up to 7.2%, but this is reduced to 3.3% when the number of implants is increased.²³ The immediate loading of implants with screw-retained, cross-arch one-piece provisional restorations does not jeopardize osseointegration.²⁵ The immediate provisional restorations in the cases presented were fabricated using the pick-up technique either with indices or denture conversions.

Full-arch impressions for implant-supported restorations require a high degree of accuracy; therefore, the open-tray or direct pick-up technique in a rigid custom tray is preferred.^2-5 The open-tray impression is made with the copings, which may be splinted or unsplinted. Several techniques have been used for splinting of the impression copings, such as those using autopolymerizing resin, dual-cured resin, plaster, prefabricated resin bars, and autopolymerizing resin splints that are sectioned and reconnected after setting.^6-8

Polyether or polyvinylsiloxane impression materials are the preferred options for making impressions due to their higher level of accuracy and dimensional stability.^9-11 A custom tray coated with an appropriate tray adhesive is preferred for making the impressions.^12,13 However, even stock trays designed specifically for the open-tray technique can also be used. Among the factors that may possibly affect the accuracy of impressions, the decision to splint or not splint seems to be the most significant, especially when four or more implants are present in the dental arch.^9,14 The impression made using the pick-up technique works as a direct splinting technique and accurately replicates the implant positions.

Balshi et al presented a similar technique in 2015 to make an accurate master model.²⁶ They used alginate in a custom tray for the pick-up of the prosthesis. In the present case series the authors used polyether in a stock tray to make the pick-up impression. The pick-up of the prosthesis in a rigid material like polyether allows no movement of the prosthesis during pick-up. Polyether impression material that gets syringed underneath the prosthesis is hydrophilic in nature, which is beneficial for accurately recording soft-tissue details.

A fixed provisional restoration that has been in use for several weeks through the healing period acts as a blueprint for the bite record. The interocclusal record in this fast-track technique is made using the screw-retained provisional restoration, which acts as a highly stable, rigid base. The mounted master casts are sent to the laboratory for fabrication of the definitive screw-retained prostheses.

The impression verification step and framework trial steps are superfluous as the well-fitted prosthesis is picked-up for transfer of implant positions. The provisional prosthesis provides vital information about the esthetics, phonetics, lip support, and vertical dimension of occlusion. The tooth positions must be assessed in relation with the lip dynamics and smile line of the patient. Any necessary minor changes can be incorporated in the definitive prostheses.

All the esthetic and functional parameters may be reassessed at bisque trial stage. The occlusion is checked to provide uniform contact of equal intensity. The tissue surface of the prosthesis is also assessed to verify a positive tissue contact in the edentulous areas between the implants. The bisque trial is followed by delivery of the definitive prosthesis. This technique may also be used in cases in which both arches are restored simultaneously.

The disadvantage of this technique is that it can only be used for the fabrication of screw-retained prostheses, because the indexing of the implants is lost in a full-arch provisional restoration where the temporary abutments are non-engaging. A limitation of this technique is that a well-adjusted provisional prosthesis is mandatory for its successful use. Care must be taken to ensure that the impression material is syringed adequately around the undersurface of the provisional prosthesis to record the soft-tissue details. If all the clinical and laboratory steps are followed meticulously, the transition from provisional to definitive prosthesis is seamless.

Conclusion

The fast-track technique for the fabrication of a full-arch definitive implant-supported prosthesis significantly reduces overall treatment time and the number of appointments. Though reducing treatment visits and time should not be considered the sole basis for choosing this technique, clinical outcomes are comparable to conventional methods. All the prostheses fabricated using this technique were passive and had impeccable fit, as verified on radiographs. More studies are needed to further assess the efficacy of this technique.

ABOUT THE AUTHORS

Udatta Kher, MDS

Private Practice, Mumbai, India

Ali Tunkiwala, MDS

Private Practice, Mumbai, India

Priya Bijlani, MDS

Private Practice, Mumbai, India

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FIGURE CAPTIONS

Fig 1. Prosthodontic workflow in a conventional approach for full-arch implant prosthodontics.

Fig 2. Prosthodontic workflow in the fast-track technique for full-arch implant prosthodontics.

Fig 3. Provisional restoration fabricated on day of surgery.

Fig 4. Interocclusal record of provisional restoration against opposing arch using bite registration wax.

Fig 5. Stock metal tray with open top chosen for taking impression.

Fig 6. Polyether impression material syringed on the underside of the prosthesis.

Fig 7. Soft-tissue mask syringed around the implant analog and impression coping junction.

Fig 8. Master cast retrieved from the impression.

Fig 9. Casts mounted on semi-adjustable articulator.

Fig 10. Definitive screw-retained porcelain-fused-to-metal prosthesis in occlusion.

Fig 11. Occlusal view of definitive prosthesis.

Fig 12. Radiograph illustrating the fit of the prosthesis.

Fig 13. Provisional restoration fabricated on day of surgery.

Fig 14. Definitive screw-retained prosthesis with biocompatible polymer framework and visio.lign teeth.

Fig 15. Maxillary provisional restoration against mandibular definitive restoration.

Fig 16. Upper and lower definitive screw-retained restorations.

Fig 17. Radiograph illustrating the definitive prostheses in situ.

Fig 18. Provisional restoration fabricated on day of surgery.

Fig 19. Provisional denture fixed with open-tray coping screws.

Fig 20. Occlusal view of definitive prosthesis.