An Interocclusal Recording Method for the Fabrication of Full-Arch Implant-Retained Restorations

A full denture is usually delivered after tooth extraction or implant insertion in a fully edentulous arch and is used until the final restoration is performed. A well-designed full denture should fulfill the following criteria: (1) correct vertical height and maxillomandibular relationship; (2) accurate occlusion; (3) appropriate choice of teeth with regard to shape, length, width, and position; (4) adequate lip support; and (5) proper function and esthetics that meet the patient's expectations. The final restoration should fulfill or surpass these requirements. Obtaining a correct impression and accurately evaluating the interocclusal relationship (eg, interocclusal distance, occlusal recording, and determination of the exact position of the placed implants) are often challenging and time-consuming tasks.^1,2 

In this case report, we describe the use of an easy and reproducible technique that allows the interocclusal relationship, occlusal recording, and esthetic factors used initially to produce the full denture to be transferred as a template for the fabrication of the final full-arch implant retained fixed or removable restoration.

An 80-year-old male nonsmoker in good general health, who was not regularly taking any medication or drug, was referred for implant placement and mandibular prosthetic restoration in February 2010. After extraction of multiple mandibular teeth that had been rendered unsalvageable by advanced periodontal disease, a denture was fabricated (Figures 1a through b and 2a). Tooth 18 was temporarily retained until the fabrication of the final restoration to stabilize the denture through an Akers clasp (Figure 1c). For additional stabilization of the denture, 2 provisional implants with ball attachments were placed in areas 22 and 24 (Table 1; Figure 2b), and the appropriate retention element was embedded into the denture's base.

Four months after the extraction sites had healed and denture sores were eliminated, the function and esthetics of the denture were optimized. The angulation, shape, and color of the denture teeth and the shape of the denture base were corrected where necessary. Six screw-cylinder dental implants (Dentegris, Duisburg, Germany; Table 1) were placed in positions 20, 21, 25, and 28–30 using a 2-stage protocol. The patient used the resulting denture until the final restoration was delivered. In this case, a fixed, cemented, implant-retained denture was planned for the final restoration of the mandible.

Two months after placement, the implants were uncovered, the healing abutments were placed, and the denture was modified to allow sufficient space for the healing abutments. A duplicate denture (DentDu) was fabricated from clear resin (Paladur, Heraeus, Hanau, Germany) and tested; minor occlusal discrepancies were corrected, and the DentDu was modified carefully in the area of the healing abutments to create internal clearance (Figure 3a and b).

The closed-tray impression technique was used in the present case. The impression was made using a polyether material (Impregum, 3M ESPE, St Paul, Minn) and a transfer system consisting of a titanium impression post and a plastic impression sleeve (closed-tray system, Dentegris; Figure 4a through c). At the same clinical session, 2 ball attachments (Dentegris) were positioned on implants 20 and 29 and torqued to 35 Nm (Figure 5a and b). A window was carefully created on the buccal side of the DentDu in the area of implants 20 and 29 to provide access to the ball attachments (Figure 5c). The retention elements (matrices) were mounted on the ball attachments and fixed to the DentDu with modeling resin (Pattern Resin, GC, Alsip, Ill; Figure 5d), and bite records were taken in centric occlusion (Figure 6a). The ball attachments were left mounted on the implants, and retention elements were fixed onto the patient's denture as described previously (Figure 6b and c). Provisional implants 22 and 24, as well as tooth 18, were then extracted, so that the denture was retained on the 2 ball attachments.

A master cast was then fabricated, and 2 laboratory ball attachments were positioned on implant analogs 20 and 29 on the master cast (Figure 7a and b). The DentDu was placed on the master cast and retained with the laboratory ball attachments and retention elements (matrices) at positions 20 and 29. The casts were mounted on an articulator using the DentDu with the bite records as a mounting guide (Figure 7c). A silicon key from the DentDu was then fabricated using a matrix of C-silicone (Zetalabor, Zhermack SpA, Badia Polesine, Italy). The dental technician used this key to determine the parallelism, angulation, position, and shape of the implant abutments (Figure 8a and b). The metal framework was milled from a titan 5 alloy (Zenotec Ti Disc, Wieland, Pforzheim, Germany) and veneered with microceramic composite (Ceramage, Shofu, Ratingen, Germany).

During the next clinical session, the 2 ball attachments at positions 20 and 29 were removed and the implant abutments were positioned on the implants and torqued to 35 Nm (Table 2). The denture was fixed using provisional cement (Implant Provisional, Alvelogro Inc. Snoqualmie, Wash; Figure 8c and Figure 9a through d).

A 52-year-old male nonsmoker in good general health, who was not regularly taking any medication or drug, was referred for implant placement and maxillary prosthetic restoration in June 2010. The patient's maxillary teeth had been extracted by a restorative dentist due to advanced periodontal disease, and a full denture had been mounted (Figure 10a). The patient had undergone surgical and periodontal treatment of the mandible 1 year previously, and the mandibular teeth, for example, implants, had been restored with fixed partial dentures. For the restoration of the maxilla, the fabrication of a removable, implant-retained, palatal-free denture with telescopic crowns as attachments was scheduled.¹ 

Six screw-cylinder dental implants (Dentegris; Table 1) were placed in positions 4, 6, 7, 9, 11, and 14. A 2-stage protocol was used for implants 6, 7, 9, and 11, and a 1-stage protocol was used for implants 4 and 14. Because the patient refused sinus augmentation, implants 4 and 14 were placed at a 35° angle from the vertical axis. System-specific prefabricated titanium abutments (DAAS angulated abutment, Dentegris) were mounted on implants 4 and 14, torqued to 35 Nm, and covered with system-specific healing caps (DAAS healing cap, Dentegris). The denture was modified carefully in the areas 4 and 14 to create internal clearance (Figure 10b and c).

Five months after the placement and uncovering of implants 6, 7, 9, and 11, a DentDu was fabricated, 2 ball attachments were mounted on implants 6 and 11 (Figure 11a and b). All subsequent clinical steps were performed as described previously (Figures 12 through 14).

The reconstruction of a fully edentulous arch with implant-retained dentures requires thorough planning and precise estimation of the interocclusal relationship. Accurate recording of the maxillomandibular relationship is a prerequisite for achieving proper occlusion and a successful treatment outcome.^2,3  In the cases described here, the initially delivered denture allowed for the correction of the interocclusal relationship, tooth shape and color, and angulation throughout the healing period. In this way, the patient could become acclimated to the function and esthetics of the denture. By using a duplicate of this denture to take bite records and use as a mounting guide, the maxillomandibular relationship was recorded and transferred accurately, and the esthetic outcome previously accepted by the patient was achieved. Thus, it was not necessary to repeat the usual clinical recordings (eg, centric relation, occlusal vertical dimension, tooth position, and esthetics, wax try-in) at the time the final restoration was fabricated.⁴  Additionally, the combined use of the DentDu and the silicon key allowed for the selection of implant abutments (prefabricated or customizable) that were the optimal angulation and shape and facilitated the fabrication of an esthetically pleasing implant-supported restoration.

In case 1, mandibular reconstruction with a fixed cemented denture was scheduled. One tooth was temporarily retained, and a provisional implant was placed; both increased the stability of the mandibular denture and the patient's comfort. The use of provisional implants is not mandatory, depends on the anatomic situation, and is the responsibility of the treating dentist.

In case 2, maxillary reconstruction with a removable denture using telescopic crowns as attachments was scheduled.^1,5  The 2 posterior implants were placed at an angle of 35° from the vertical axis. This angulation should not be considered a limitation of the method presented here; axially placed implants may also be used. Of course, the number of implants used will vary depending on the design of the scheduled removable denture.

Because this report was focused on the clinical recording technique and the transfer of the template to the final restoration, the surgical protocols, impression techniques, and laboratory procedure for denture fabrication were not described and/or discussed. The selection of impression technique (open or closed tray), final restoration design (fixed screw-retained, fixed cemented, removable), and implant system is the responsibility of the surgical/restorative team and is not influenced by the method described in this report. The disadvantages of this technique include the required skill level of the dental technician and the additional cost of the ball attachments for the patient. However, in addition to the benefits described here, the use of this technique reduced overall cost (because clinical recordings and laboratory procedures were not repeated) and required chair time (Table 2). The main factors influencing the final outcome are the accuracy of the first denture fabrication after tooth extractions and its adjustment for optimal restoration during the healing period.

The method described herein allows for the accurate transfer of the occlusal relationship, vertical dimensions, and implant position while facilitating the full-arch restoration process and reducing the amount of chair time needed.