CLINICAL REPORT

Supported byinterpretationaAssistant PrbPostgraduatcAssociate Pr

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Restoration of divergent implants with a 2-piecescrew-retained fixed, complete dental implant prostheses

Stavros Pelekanos, DDS, Dr med dent,a Georgia Pozidi, DDS,b and Stefanos Kourtis, DDS, Dr med dentc

ABSTRACTRestoring a severely resorbed maxilla is challenging because of poor bone quality and theresorptive pattern that follows tooth loss. When bone augmentation is not possible, implants areplaced in suboptimal positions, making the prosthetic rehabilitation more complex. This reportpresents the steps used to rehabilitate a severely resorbed maxilla with divergent implants, using animplant-supported 2-piece screw-retained prosthesis. (J Prosthet Dent 2016;115:389-392)

Rehabilitating a completelyedentulous maxilla with animplant-retained prosthesis ischallenging. The resorptivepattern of the alveolar crestleads to hard and soft tissuedefects that cannot always be

addressed with augmentation procedures.1-3 Deficienciesin the horizontal plane and a prosthetically unfavorableimplant position may compromise esthetics, phonetics,and function.1,4 Lip support is usually achieved with pinkceramic or acrylic resin.2

An edentulous maxilla can be restored with an implantoverdenture or a fixed implant prosthesis.2,5 Maxillaryimplant overdentures are associated with more technicalcomplications and biological problems than a fixedimplant-supported prosthesis. A higher incidence of post-insertion maintenance (clip or attachment replacement/reactivation) and mucosal inflammation has been re-ported.1,4,6-8 Fixed implant-supported maxillary prosthe-ses give greater patient satisfaction and a lower incidenceof prosthetic complication.1,4 An implant-supported fixedprosthesis with metal superstructure and acrylic resingingiva has been extensively used in the treatment of theedentulousmandible.2,9 Although long-term survival ratesare well documented, technical complications are pros-thetic screw loosening and/or fractures, abutment frac-tures, and fracture or wear of acrylic resin teeth.2,9-11

Fabrication is more demanding in the maxilla. Largeinterabutment spaces can disrupt speech and oral hygieneunder flange extensions and around abutments is diffi-cult.2,10,11 Ease of oral hygiene and retrievability of the

Greek State Scholarships Foundation grant 98138/B7/19-7-2013. The spof data, or the writing of the report.

ofessor, Department of Prosthodontics, Dental School, University of Athense student, Department of Prosthodontics, Dental School, University of Atheofessor, Department of Prosthodontics, Dental School, University of Athen

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prosthesis during the maintenance phase are essential forlong-term success. This report describes the clinical andlaboratory stages in fabricating a 2-piece fixed screw-retained prosthesis on multiple divergent implants in aresorbed maxilla.

CLINICAL REPORT

A 40-year-old woman with high esthetic expectationswished to “have her teeth restored.” Clinical and radio-graphic evaluation showed a severely resorbed maxillawith 6 osseointegrated implants (Bego Semados S im-plants; Bego GmbH & Co) with no signs of pathology(Fig. 1). The patient had a fixed metal-reinforced toothimplant- and tissue-supported (“tripod”) interim pros-thesis in the maxilla. The maxillary left canine andimplant corresponding to the right lateral incisor wereused as abutments while 2 flanges extending on tothe tuberosities provided additional support.12 All im-plants were suboptimally placed, emerging bucally fromthe alveolar crest on divergent axes (Figs. 2, 3). Despite apoor prognosis, the left maxillary canine was used tosupport the interim restoration.

Asymmetry in the levels of the periimplant mucosalmargins and extensive bone resorption of the maxilla

onsors had no involvement in the collection, analysis and

, Athens, Greece.ns, Athens, Greece.s, Athens, Greece.

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Figure 1. Panoramic radiograph obtained prior to prosthetic treatment. Figure 2. Initial clinical situation. Implant corresponding to right lateralincisor with labial inclination.

Figure 3. Definitive cast mounted on semiadjustable articulator incentric relation. Waxing sleeves indicate implant divergent axes andbuccal inclination.

Figure 4. Artificial tooth arrangement. Teeth aligned and gingivaexposed harmoniously according to esthetic principles.

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in combination with the amount of mucosa seen onsmiling required the use of artificial gingiva (Fig. 2). Adiagnostic artificial tooth arrangement was set up (SRVivodent; Ivoclar Vivadent AG). A clinical evaluationverified the correct position and alignment of the teeth,centric relation, vertical dimension, mandibular move-ments, and pink and white esthetics (Fig. 4).

The prosthesis needed to compensate for the de-ficiencies in both the hard and soft tissues. The prosthesiswas screw-retained because of the patient’s esthetic de-mands. At the time of treatment, prefabricated, angledabutments for screw type prostheses (Sub-tech Multiplusabutments; Bego GmbH & Co) were not available. Tocompensate for the implants’ divergent axes, a 2-pieceprosthesis was fabricated.13,14 It consisted of a cast metalCo-Cr substructure (Dentaurum GmbH & Co) attached tothe implants with abutment screws. The substructure wasdesigned to retain individual metal ceramic crowns toreplace the maxillary teeth. All individual crowns werecemented, with the exception of the left and right firstmolars, right canine, right lateral incisor, and left first

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premolar. In order to ensure retrievability, these 5 crownswere retained with friction splints (Friction Splint FS1;Bredent GmbH & Co) (Figs. 5-7). The neck of the implantcorresponding to the right lateral incisor was higher thanthat of the other implants, so this individual crown wascemented (Figs. 2, 5). This design allowed adequate lipsupport without increasing structural bulk.

An acrylic resin replica of the diagnostic waxing wasfabricated on the definitive cast, which was then cut backwith standard chamfer preparations (Fig. 5). The waxing,casting, and ceramic layering (IPS d.SIGN; Ivoclar Viva-dent AG) of the crowns followed a standard protocol(Figs. 6, 7).

A clinical evaluation of the prosthesis verified passivefit and accessibility for oral hygiene (Fig. 8). The naturalgingival contour and lip support of the definitive treat-ment (Figs. 9, 10) fulfilled the patient’s esthetic criteria.Figure 11 shows the anterior guidance during all eccentricmovements (video, available online). After insertion ofthe definitive prosthesis, the patient was scheduled for a4-monthly recall.

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Figure 5. Acrylic resin replica with 4 friction splints in place. Figure 6. Laboratory evaluation of framework passive fit.

Figure 7. Definitive restoration prior to insertion. Figure 8. Definitive restoration allowed use of interdental brushes.

Figure 9. Panoramic radiograph after treatment.

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DISCUSSION

The patient’s high esthetic demands necessitated a fixedprosthesis despite the need for extensive lip supportdue to bone resorption. Apart from the promising successrates of fixed prostheses, the present screw-retentiondesign offers the advantage of precluding the useof cement and therefore minimizes the risk of peri-implantitis due to residual cement.15-17 In addition,while technically demanding, fabricating the prosthesisin 2 pieces meant that the primary structure, whichhad an increased volume of metal, was not exposed toany further thermal procedures after casting and thepolymer materials could be modified.10,18 Individualteeth could be characterized independently of thematerial replicating the soft tissues.

A possible drawback is that the pink resin gingiva thatcompensated for the resorption covers the labial part ofthe residual ridge, therefore necessitating meticulous oralhygiene. The use of friction splints ensures easy access tothe fixation screws. Thus, during follow-up the pros-thodontist could easily remove the prosthesis. Ease ofrepair was also ensured. In case of complications, the

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individual crowns could be removed without disturbingthe other components.13 Another possibility would bethe use of angled abutments for screw-retained pros-theses used to redirect screw access in situations withprosthetically unfavorable implant angulations.19 At thetime of treatment, however, these were not yet available.

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Figure 11. Anterior guidance during eccentric movements.

Figure 10. Esthetic result.

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The fabrication of the primary structure usingcomputer-aided design and computer-aided manufac-turing (CAD/CAM) techniques might improve the fit.10,13

Those techniques may be limited by a variety of factors,including the implant company, the type of CAD/CAMsystem, the implant-abutment connection, and theimplant angulation. At the time of treatment however, theavailable systems could not accommodate the angulationof the implants.

Rehabilitating the resorbed maxilla with 2-piecereconstructions has been reported.13,14 It is a technicallydemanding approach associated with higher costand complicated laboratory procedures.20 It does, how-ever, offer a clinical solution where an implant-supportedfixed prosthesis is indicated for a patient with a resorbedmaxilla and high esthetic demands.

SUMMARY

A 2-piece, screw-retained implant-supported prosthesiswas fabricated to restore 6 divergent implants on a resorbedmaxilla. A primary castmetal frameworkmimicking the softtissues was fitted to the implants with screw retention. The

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secondary prosthesis consisted of independent metalceramic crownsfitted to the implant-supported framework.The prosthesis satisfied the patient’s esthetic demands. Theuse of pink acrylic resin corrected the asymmetrical gingivalmargin and provided adequate lip support withoutimpeding speech or oral hygiene. Retrievability and ease ofrepair were also addressed.

REFERENCES

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9. Jemt T, Johansson J. Implant treatment in the edentulous maxillae: a 15-yearfollow-up study on 76 consecutive patients provided with fixed prostheses.Clin Implant Dent Relat Res 2006;8:61-9.

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12. Chronopoulos V, Kourtis S, Katsikeris N, Nagy W. Tooth- and tissue-supported provisional restorations for the treatment of patients withextended edentulous spans. J Esthet Restor Dent 2009;21:7-17.

13. Chronaios D, Spyropoulou P, Razoog M, Sieraalta M. Material options forrestoring intentionally misaligned implants on maxillary edentulous arch: Aclinical report. J Prosthet Dent 2013;109:145-8.

14. Tsoutis K, Katsikeris N, Chronopoulos V, Kourtis S. Rehabilitation of theedentulous maxilla with autogenous bone grafts from the iliac crest andimplant-supported combined fixed restorations. A challenging task. EDIJournal 2011;7:66-72.

15. Sailer I, Mulhemann S, Zwalen M, Hammerle CH, Schneider D. Cementedand screw-retained implant reconstructions: a systematic review of the sur-vival and complication rates. Clin Oral Implants Res 2012;23:163-201.

16. Agar J, Cameron S, Hughbankc J, Parker H. Cement removal from restora-tions luted to titanium abutments with simulated subgingival margins.J Prosthet Dent 1997;78:43-7.

17. Wilson T. The positive relationship between excess cement and peri-implantdisease: a prospective clinical endoscopic study. J Periodontol 2009;80:1388-92.

18. Coachman C, Salama M, Graber D, Calamita M, Salama H, Cabral G.Prosthetic gingival reconstruction in fixed partial restorations. Part 3: Labo-ratory procedures and maintenance. Int J Periodontics Restorative Dent2010;30:19-29.

19. Berroeta E, Zabalequi I, Donovan T, Chee W. Dynamic abutment: A methodfor redirecting screw access for implant-supported restorations: Technicaldetails and a clinical report. J Prosthet Dent 2015;113:516-9.

20. Zitzmann NU, Marinello CP. Treatment outcomes of fixed or removableimplant-supported prostheses in the edentulous maxilla. Part I: patients’assessments. J Prosthet Dent 2000;83:424.

Corresponding author:Dr Stavros Pelekanos163B El. Venizelou (Thiseos) AvKallithea AthensGREECEEmail: pelekan@otenet.gr

AcknowledgmentsThe authors thank the laboratory practice of Mr M. Papastamos for fabricating thedefinitive restoration.

Copyright © 2016 by the Editorial Council for The Journal of Prosthetic Dentistry.

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