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Dental Tribune Middle East & Africa No. 2, 2017

Dental Tribune Middle East & Africa Edition | 2/2017 ◊Page 6 ments used to retain the lower pros- thesis. The attachment male compo- nents were secured intra-orally using auto-polymerizing resin to eliminate the possibility of laboratory error. The patient continued to experi- ence problems with the lower den- ture coming loose during function and required frequent replacement of the nylon male inserts; replace- ment with Extended Range inserts did not vary performance. The metal abutments demonstrated consider- able wear as well (Fig. 2). Relining the lower denture did not improve the performance of the anchor system. At the subsequent appointment, the patient was presented with the ATLANTIS Conus concept as a potential solution to her ongoing dilemma. Treatment options were presented as well including a fixed hybrid prosthesis and a 2-in-1 bar overdenture. These were rejected as inter-arch space was less than opti- mal, requiring compromise to the strength of the design. The patient also expressed a desire for a remov- able design as she was concerned with having adequate facial support and wished to be able to remove the prosthesis for proper hygiene and maintenance. It was agreed that a new maxillary and mandibular com- plete denture would be fabricated, and ATLANTIS Conus abutments would be made to secure the lower restoration. Clinical and laboratory procedures Because the existing dentures were made within the last five years and were acceptable with regard to tooth position and vertical dimension, it was decided that clear, acrylic resin duplicates of each denture would be made to serve as custom trays. Double-sided impressions of each denture were made and delivered to the dental laboratory for fabrication of the duplicates. Once processed, the copy denture borders were short- ened by 2 mm to allow border mold- ing. The duplicate of the mandibular denture clearly showed the position of each Locator housing and there- fore the position of the dental im- plants. Holes of adequate diameter to allow the duplicate denture to be placed in the patient’s mouth over impression copings were prepared (Fig. 3). The intaglio surface of both the upper and lower duplicate den- ture were relieved to allow for a wash impression. The patient returned for final im- pressions, and the Locator abut- ments were removed and kept in appropriate order to avoid confu- sion when re-seating them at the appointment completion. Open tray impression copings were connected to each of the four dental implants to be restored and tightened into place; one implant with greater bone loss and placed significantly more shal- lowly than the rest was omitted (Fig. 4). Light-body poly vinyl siloxane was injected around the base of each impression coping and medium- body PVS was placed in the custom tray. The tray was seated, ensuring that the impression copings were com- pletely accessible through the holes previously prepared. The patient was instructed in facial and tongue movement to achieve proper pe- ripheral border extension. Regisil Rigid (DENTSPLY) bite registration material was injected around each impression coping to rigidly adhere them to the impression tray. This step is critical as reliance on flex- ible impression material may allow transfer error when constructing the working cast. Once the impression materials were fully set, the screws retaining the im- pression copings were removed and the final impression and tray were withdrawn from the patient (Fig. 5, 6). All Locator abutments were re- seated and tightened. Final impres- sion of the maxilla was completed with border molding using mod- eling plastic and a wash impression with light-body PVS. Upon comple- tion, the patient was dismissed. In the dental laboratory, implant analogs were secured to the impres- sion posts, gingival moulage was injected around the analogs to an adequate depth to completely cover the coping-analog interface. The im- pressions were boxed with wax and poured in vacuum-mixed die stone. After setting, the impression coping screws were removed and the im- pressions were separated from the hardened casts; standard laboratory procedures were followed in clean- ing and trimming the working casts. Base plate and wax rims were made for continuation of the denture fab- rication. The impression materials were removed from the duplicate denture and it was positioned back onto the mandibular cast to be scanned. An online order was com- pleted including identification of the implants involved and the case was shipped to DENTSPLY Implants for the design and manufacture of the ATLANTIS Conus Abutments. The working cast, implant analog connections and the denture dupli- cate were scanned at the ATLANTIS production site and the abutments were individually designed using ATLANTIS VAD (Virtual Abutment Design) software to ensure that all abutments were parallel to each other. The restorative margin of each abutment were placed close to the soft tissue height surrounding each implant, but always supra-gingival to guarantee unobstructed seating of the finished restoration. Each abutment was milled to a 5 degree taper to match the SynCone caps ensuring an intimate friction- fit. Upon design completion, the images of the abutment designs were made available for review and approval before manufacturing (Fig. 7). Once the design presented was found to be satisfactory, approval for production of the patient-specific abutments was granted. It is impor- tant to note that no fees are incurred by the dentist or dental laboratory during this process until design is agreed upon and authorization to proceed is given. The abutments are custom designed to fit specifically to the denture set-up or duplicate denture provided; there are no sizes, heights, angles or collars to select from a catalog and, therefore, no risk of choosing incorrectly. When received, the ATLANTIS Conus abutments were secured to the work- ing cast with abutment screws, along with four prefabricated SynCone caps (Figs. 8, 9). The caps were seated on to the abutments and sent to the dental laboratory to be impressed. The impression was poured twice, one in improved dental stone and one in refractory material for fabri- cation of a cast metal frame. While waiting for the frame to be complet- ed, final try-in appointments for the denture set-up were completed, and the patient approved fabrication of the dentures. The denture set-up with a final bite record were returned to the dental lab, the cast metal frame was seated on the improved dental stone cast and areas around the stone copy of the SynCone caps were blocked out prior to processing. The SynCone caps will be captured intraorally, rather than having them processed in the dental laboratory. All work was completed on the duplicate stone cast rather than the original mCME 7 Figure 7. Design images showing the contour and tooth position of the duplicate denture and proposed design of the ATLANTIS Conus Abutments Figure 8. ATLANTIS Conus Abutments on the working cast. Each abutment has the tooth number location scribed on the buccal- facing surface Figure 9. SynCone caps seated on the abutments on the working cast. An impression of this arrangement is made to fabricate a cast metal frame to reinforce the final restoration Figure 10. Completed laboratory restoration; note the termi- nation the arch at the first molar to avoid excessive cantilever length. The chrome frame is opaqued on the functional side to prevent gray show-through Figure 12. ATLANTIS Conus Abutments seated. Note the “mar- gins” of the abutment, and the point where the parallel prepara- tion begins, is supra-gingivally positioned Figure 11. Completed laboratory restoration showing the metal frame and recessed area to receive the SynCone caps Figure 13. SynCone caps are fitted to the abutments to verify un- obstructed and complete seating Figure 14. Rubber dam is placed over the abutments to prevent pick-up material from locking into undercut areas below the pre- pared margin. SynCone caps are seated and ready to be captured into the prosthesis working cast. The cast metal frame was opaqued to prevent gray show- through. The set up was transferred to the cast with the metal frame and the dentures were processed (Figs. 10, 11). the ATLANTIS Conus Because concept results in a fully implant- supported prosthesis, the periph- eral borders of the finished structure were greatly reduced and the occlus- al table was abbreviated at the first molar. The length of functional arch follows the identical AP spread prin- ciples used for hybrid prosthetics to avoid excessively long cantilevers. At this point, the structure is a bridge and not an overdenture. To facilitate seating of the abutments in the pa- tient, a clear matrix was made with the abutments on the original work- ing cast; where they have remained since receipt. Each abutment was identified with one, two, three and four black ink dots respectively, based on their position on the cast. The clear matrix was seated over the abutments and corresponding black dots were drawn on it to line up ex- actly with those on the abutments. The completed mandibular bridge was double-side impressed by the dental technician and an injection- mold copy of clear acrylic resin was made. The patient was scheduled for com- pletion of treatment. The Locator abutments were again removed and Teflon tape was placed in the implant excluded from the design. The abutments were seated onto the dental implants (Fig. 12), and the clear matrix was placed to verify that each abutment was correctly orientated by checking that the dots on the ma- trix superimposed with those on the abutments. Once verified, the abutments were torqued to 20 Ncm, appropriate for the implants involved. The SynCone caps were placed and viewed with magnification to assure that they were superior to the gingival tissues (Fig. 13). The prosthesis was placed over the caps to verify there was no obstruction of complete seating. The prosthesis was removed and vent holes were drilled through the buc- cal contours of the acrylic resin to relieve hydraulic pressure during capture of the caps. The SynCone caps were lifted and a rubber dam was placed around the abutments to prevent pick-up resin from locking into undercuts, and the caps were re- seated (Fig. 14). Attachment processing mate- rial (Chairside by Zest Anchors) was placed in the reservoirs of the pros- thesis and seated over the SynCone caps. The upper denture was placed and the patient was instructed to gently close into full occlusion and to maintain position for two min- utes while setting occurred. After two minutes, the excess flow of pick- up resin was checked for hardness and after an additional minute the prosthesis was ready for removal. Removal was uneventful although retention was considerable; removal of the bridge can only occur follow- ing the long-axis of the abutments, no tipping or rotating is possible (Fig. 15, 16). Once removed, the excess pick- up material was removed and the bridge was properly polished where needed. The abutments were packed with Teflon tape to within 3 mm of the surface, and the remaining space was filled with flowable composite resin (Fig. 17). The patient was in- structed on placement and removal and repeated the exercise until we were satisfied she would experience no difficulties performing this. The clear, duplicate copy of the bridge was seated onto the abutments us- ing a chair-side soft lining material (Fig. 18). This copy serves as a temporary de- vice for the patient to wear when cleaning the finished bridge or when sleeping to protect the tongue from scraping against the abutments. A panoramic radiograph was taken at completion of treatment (Fig. 19). The patient returned after one week and again after six weeks, and report- ed at both visits that the lower bridge did not move at all during function and stayed seated until she removed it. She commented on the ease of cleaning the dental abutments, and she reported no discomfort and no food entrapment. Overall, the pa- tient was very pleased with the result (Fig. 20). ÿPage 9

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