Digitally Milled Metal Framework for Fixed Complete Denture with Metal Occlusal Surfaces: a Design Concept

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Digitally Milled Metal Framework for Fixed Complete Denture with Metal Occlusal Surfaces: A Design Concept

Bader AlBader, BDS1/Abdulaziz AlHelal, BDS, MS2 Dental implants have become an Periklis Proussaefs, DDS, MS3 established treatment modality Antonela Garbacea, DDS, MSD4 for the completely edentulous pa- Mathew T. Kattadiyil, BDS, MDS, MS5 tient.1–4 The conventional protocol 6 Jaime Lozada, DMD indicates fabrication of a screw- retained metal substructure and in- Implant-supported fixed complete dentures, often referred to as hybrid corporation of acrylic resin denture prostheses, have been associated with high implant survival rates but also with teeth on the substructure, a pros- a high incidence of mechanical prosthetic complications. The most frequent of thetic design concept referred to these complications have been fracture and wear of the veneering material. The as the hybrid prosthesis (HP).1 This proposed design concept incorporates the occlusal surfaces of the posterior teeth as part of a digital milled metal framework by designing the posterior first design ensures flexibility in the oc- molars in full contour as part of the framework. The framework can be designed, clusal scheme, good esthetic out- scanned, and milled from a titanium blank using a milling machine. Acrylic resin come, and retrievability. teeth can then be placed on the framework by conventional protocol. The metal Retrospective studies have occlusal surfaces of the titanium-countered molars will be at centric occlusion. It demonstrated high success or sur- is hypothesized that metal occlusal surfaces in the posterior region may reduce vival rates of dental implants that occlusal wear in these types of prostheses. When the proposed design protocol is 1–7 followed, the connection between the metal frame and the cantilever part of the support a HP. However, several prosthesis is reinforced, which may lead to fewer fractures of the metal framework. long-term studies,8–16 literature re- Int J Periodontics Restorative Dent 2017;37:e180–e188. doi: 10.11607/prd.3126 views or position papers,17–19 and systematic reviews20,21 have indicated a high incidence of prosthetic or mechanical complications associated with this type of prosthesis. The 1Faculty, College of Dentistry, Imam Abdulrahman Alfaisal University, Dammam, most common complications are Saudi Arabia. related to the veneering material. 2Faculty, Department of Prosthetic Dental Sciences, College of Dentistry, King Saud University, Riyadh, Saudi Arabia. Debonding or fracture of denture 3Assistant Professor, Advanced Education Program in Implant Dentistry, teeth, fracture of the acrylic resin Loma Linda University, Loma Linda, California, USA; Private Prosthodontic Practice, veneering material, and various de- Ventura, California, USA. grees of occlusal and incisal wear 4Assistant Professor, Advanced Education Program in Implant Dentistry, 8–21 Loma Linda University, Loma Linda, California, USA. are commonly observed. Altera- 5Professor and Director, Advanced Education Program in Prosthodontics, Department of tion of the occlusal scheme due to Restorative Dentistry, Loma Linda University, Loma Linda, California, USA. wear or fracture of the veneering 6Professor and Director, Advanced Education Program in Implant Dentistry, Loma Linda University, Loma Linda, California, USA. material can affect the integrity of the vertical dimension of occlusion Correspondence to: Dr Bader AlBader, Advanced Education Program in Implant Dentistry, (VDO) and the facial esthetics.16 Loma Linda University School of Dentistry, 11092 Anderson St, Loma Linda, CA 92350, USA. Failures of the metal substruc- Fax: (909) 558-4803. Email: [email protected] ture have been reported as well.22–27 ©2017 by Quintessence Publishing Co Inc. Framework fractures may be re-

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a b Fig 1 (a) Preoperative panoramic radiograph. (b) Dental implants placed.

duced with proper design of the that their metal occlusal surface is in a stereolithographic cast was made metal substructure.25 Since most occlusion with the opposing teeth from the data obtained through fractures seem to occur at the canti- or prosthesis. The purpose of the cone beam computed tomogra- lever portion of the prosthesis,22 the metal posterior teeth is to resist oc- phy, and the alveolar ridge reduc- assumption can be made that in- clusal wear and fracture, maintain tion and surgical implant placement creased thickness of the framework VDO, reinforce the cantilever arm, were performed on the stereolitho- at the cantilever area may enhance and decelerate the rate of acrylic graphic cast before surgery was the resistance of the framework to resin tooth wear. performed on the patient. A total fracture. of four threaded root form implants The advent of digital technol- (Neodent) were placed in the man- ogy offered the option to fabricate Case Report dible and six implants were placed metal frameworks through a mill- in the maxilla (Bone Level Roxolid ing process as opposed to casting A 56-year-old woman presented at SLActive, Straumann) (Fig 1b). All frameworks through the lost wax the Advanced Education Program in implants were placed with mini- technique. Studies have demon- Implant Dentistry at Loma Linda Uni- mal 25-Ncm insertion torque. The strated superior accuracy of milled versity School of Dentistry seeking mandibular implants received mul- metal frameworks compared to cast treatment for her complete edentu- tiunit abutments and a conversion frameworks.28,29 In addition, digital lism (Fig 1a). After various treatment prosthesis based on an immediate technology30 offers the option to options were discussed, the deci- complete denture and according to design the framework on a comput- sion was made to treat her edentu- a protocol that has been described er using specialized software and lism with maxillary and mandibular by others.32,33 then have the metal substructure implant-supported fixed prostheses. At 4 months after implant sur- milled through a milling machine. Surgical alveolar ridge reduc- gery, second-stage surgery was The purpose of this concept tion and implant placement were performed on the maxillary im- paper is to introduce digital frame- performed under light sedation (in- plants and healing abutments were work design for HP. The posterior duced by oral intake of 0.25 mg of placed. After 3 weeks of tissue teeth are designed to be part of the triazolam) along with local anesthe- healing and after confirming that computer-aided design/computer- sia. A recently published protocol osseointegration was achieved, assisted manufacture (CAD/CAM) was followed to perform guided peri-implant soft tissue was evalu- milled metal framework. The pos- alveolar ridge reduction and guided ated for pathology (Fig 2). Defini- terior teeth are fully contoured so surgical implant placement.31 Briefly, tive stone casts were made with

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a b Fig 2 (a) Intraoral preprosthetic view of the maxillary arch with healing abutments in place. (b) Intraoral preprosthetic view of the mandibular arch with multiunit abutments in place.

a b Fig 3 (a) Duplicate of patient’s interim maxillary complete denture converted in the laboratory to an implant-supported fixed trial prosthesis made of acrylic resin. (b) Mandibular trial implant-supported fixed prosthesis. the direct splinting technique.34,35 lar relation records were obtained. The PRTP was then transferred Impression copings designed for Definitive casts were mounted on to the laboratory, and a cut back of open-tray technique were used and a semiadjustable articulator (Pana- the occlusal and incisal portions was were intraorally splinted with light dent) and teeth set-up was per- performed by keeping the first mo- polymerized composite resin (Filtek formed. After intraoral evaluation of lars in full contour at the proposed Supreme Ultra, 3M ESPE). Heavy the wax try-in, esthetics, occlusion, VDO (Fig 5) and reducing the rest of body polyvinyl siloxane (PVS) im- VDO, and phonetics were intraorally the PRTP sufficiently to provide ad- pression material (Aquasil, Dentsply) confirmed. equate space for acrylic resin teeth was used along with a custom tray The trial denture teeth were set-up. made of light-cured acrylic resin then transferred to the laboratory The cut-back PRTP and the po- (Tru Tray Sheet, Dentsply). The de- and duplicated in a pattern resin sition of the implants were scanned finitive cast was poured in type IV (GC America) trial prosthesis (PRTP) with an optical scanner (D900L, dental stone (Resin Rock, WhipMix) with the use of putty index (Fig 3). 3shape) from the definitive stone with a simulated soft tissue material The PRTP was placed intraorally to cast. With this technique, the im- (Gi-Mask, Coltene). Two implants in verify phonetics, VDO, occlusion, lip plant positioning can be related to each arch were used to retain the support, and accessibility for oral the position of the acrylic resin pros- record block, and maxillomandibu- hygiene (Fig 4). thesis (Fig 6). The obtained surface

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a b c Fig 4 (a) Intraoral view of maxillary trial implant-supported fixed prosthesis. (b) Intraoral view of mandibular trial implant-supported fixed prosthesis. (c) Maxillary and mandibular trial prostheses in maximum intercuspation position.

a b c Fig 5 Reduced trial prosthesis. First molars were left intact. (a) Frontal view. (b) Right view. (c) Left view.

a b c Fig 6 Scanned images of maxillary and mandibular reduced trial prosthesis. (a) Frontal view. (b) Right view. (c) Left view.

a b c Fig 7 Maxillary and mandibular metal frame in maximum intercuspation position. (a) Frontal view. (b) Right view. (c) Left view.

tessellation language (STL) files of framework was an exact duplicate of of the first molars (Fig 8). After con- the cut-back PRTP prostheses were the cut-back PRTP (Fig 7). firming the fit of the prostheses, the used as a guide for milling the tita- The metal framework was then acrylic resin teeth were set up in a nium framework (Procera, Nobel intraorally verified to confirm pas- conventional process with the use of Biocare). The obtained titanium sive fit36 and occlusion at the area the putty index (Lab Putty, Coltene).

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a b c Fig 8 Intraoral evaluation of the metal frame. (a) Maxillary view. (b) Mandibular view. (c) Metal frames at maximum intercuspation position.

Fig 9 Intraoral view of wax try-in.

Fig 10 Laboratory view of the definitive prosthesis. (a) Maxillary view. (b) Mandibu- lar view. (c) Right view. (d) Left view.

a b

Intraoral evaluation of the trial wax polymerized acrylic resin (Lucitone phonetics, esthetics, and accessibil- prosthesis was performed to con- 199, Dentsply) (Fig 10). The defini- ity for oral hygiene of the definitive firm the prosthetic design, occlu- tive prostheses were then secured prosthesis were then verified (Fig sion, VDO, phonetics, accessibility intraorally with occlusal screws ac- 12). The patient was provided with for oral hygiene, esthetics, and func- cording to the manufacturer’s in- a canine-protective occlusal scheme tion (Fig 9). structions (Fig 11). The occlusal having simultaneous occlusal con- The trial wax prostheses were screw access holes were sealed with tacts in centric relation between ti- then processed in a conventional composite resin (Filtek Supreme tanium molars and acrylic teeth (Figs manner with the use of a heat- Ultra, 3M ESPE). The occlusion, 11b and 11c).

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a b

a b Fig 11 Intraoral view of the definitive prostheses. (a) Frontal view. (b) Right view. (c) Left view. (d) Maxillary view. (e) Mandibular view. (f) Extraoral view.

Discussion complete dentures. The presence of be the addition of second premolars metal occlusal surface in the first mo- in the metal framework for clinical sit- The clinical significance of the sug- lar area may reduce the frequently uations where patients would accept gested technique is that it offers an encountered prosthetic complication the esthetic outcome of the prosthe- alternative design protocol for fab- of occlusal tooth wear. A modifica- sis. In addition, the increased thick- ricating implant-supported fixed tion of the proposed design would ness of the framework around the

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Fig 12 Panoramic radiograph of the definitive prosthesis.

cantilever portion of the prosthesis is lary anterior teeth to better maintain al24 also suggested increased height expected to enhance the resistance the anterior guidance. This modi- of the metal framework at the be- of the prosthesis to fracture. fied design might also reduce the ginning of the cantilevered portion The main limitation of the pro- applied pressure on the maxillary of the metal framework. A clinical posed framework design concept anterior teeth, resulting in fewer in- study with long-term data is needed is the compromised esthetics of the cidences of fracture in the maxillary to validate the hypothesis that the posterior area. An alternative would anterior area. proposed design concept may re- be fabrication of metal-ceramic The proposed HP framework sult in reduced incidence of frame- crowns or crowns made of lithium design concept entails fabrication work fracture. disilicate or yttrium-stabilized te- of the distal cantilever portion of Alternatively, some authors tragonal zirconia at the molar area of the framework with increased met- have suggested the use of inlays the mandibular prosthesis. al thickness. This might reduce the or onlays on the occlusal surface Another limitation is the lack incidence of framework fracture. of posterior teeth. The proposed of wear protection on the anterior Davis et al8 observed that frame- onlays can be made of gold, high guidance. While metal occlusal sur- work fractures typically occur at noble alloy, or ceramic material.28 faces may enhance resistance to oc- the beginning of the cantilever por- This technique has the advantage of clusal wear and help maintain the tion of the prosthesis. Attard and being available at any time after fab- VDO, anterior maxillary and man- Zarb reported similar results5 where ricating the prosthesis. However, the dibular teeth are expected to wear cast framework fractures occurred retention of these inlays or onlays when the proposed framework and mainly at the cantilever area of the on acrylic resin teeth is unknown. prosthetic design are implemented. framework. Falk et al22 indicated The technique will also incur addi- Fischer et al13 recommended using that 70% of the occlusal forces occur tional laboratory fees. Furthermore, metal surfaces on the teeth of the at the cantilever area of the prosthe- the process involves removing suffi- maxillary anterior area. A modifi- sis. They recommended increased cient structure from the acrylic resin cation of the presented technique metal height at the cantilever area tooth, a process that might com- could be extending the metal frame to better withstand occlusal forces. promise the structure of the acrylic on the lingual surfaces of the maxil- Stewart et al23 and Von Gonten et resin tooth.

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The proposed framework de- Conclusions 6. Jemt T, Stenport V. Implant treatment sign concept should be consid- with fixed prostheses in the edentulous maxilla. Part 2: Prosthetic technique and ered technique sensitive because The proposed design concept for clinical maintenance in two patient co- it is based on the assumption that fabricating implant frameworks for horts restored between 1986 and 1987 and 15 years later. Int J Prosthodont 2011; the occlusal surfaces of the poste- complete arch implant-supported 24:356–362. rior teeth are in occlusion after the fixed prostheses may result in re- 7. Jemt T. Failures and complications in 391 framework has been milled. There duced incidences of prosthetic consecutively inserted fixed prostheses supported by Brånemark implants in shall be no errors during the occlu- complications. The VDO might be edentulous jaws: A study of treatment sal registration process and transfer better maintained over a long peri- from the time of prosthesis placement to the first annual checkup. Int J Oral Maxil- technique before fabricating the od. Long-term clinical data on a suf- lofac Implants 1991;6:270–276. framework. Excluding minor occlu- ficient number of patients is needed 8. Davis DM, Packer ME, Watson RM. sal adjustments, the clinician would to verify this hypothesis. Maintenance requirements of implant- supported fixed prostheses opposed not be able to correct inaccuracies by implant-supported fixed prostheses, in occlusion after the metal frame natural teeth, or complete dentures: A 5-year retrospective study. Int J Prostho- has been made. In contrast, with Acknowledgments dont 2003;16:521–523. the conventional protocol using 9. Purcell BA, McGlumphy EA, Holloway denture teeth made of acrylic resin, The authors would like to thank Luis A. JA, Beck FM. Prosthetic complications in mandibular metal-resin implant-fixed Calvillo, CDT, for his assistance in the labo- the clinician has the ability to mod- complete denture prostheses: A 5- to ify the occlusion by modifying the ratory phases of the presented clinical situ- 9-year analysis. Int J Oral Maxillofac Im- ation. The authors reported no conflicts of plants 2008;23:847–857. set-up of the posterior acrylic resin interest related to this study. 10. Ventura J, Jiménez-Castellanos E, Rome- teeth at any time during the try-in ro J, Enrile F. Tooth fractures in fixed appointment. full-arch implant-supported acrylic resin prostheses: A retrospective clinical study. An alternative protocol to sup- References Int J Prosthodont 2016;29:161–165. port the VDO would be the use of 11. Johansson G, Palmqvist S. Complica- tions, supplementary treatment, and . 1 Adell R, Lekholm U, Rockler B, Bråne- individual crowns cemented on a maintenance in edentulous arches with mark PI. A 15-year study of osseointe- single full-arch frame.37 This type implant-supported fixed prostheses. Int grated implants in the treatment of the J Prosthodont 1990;3:89–92. of prosthetic design offers excel- edentulous jaw. Int J Oral Surg 1981;10: 12. Hemmings KW, Schmitt A, Zarb GA. 387–416. lent esthetics and provides the op- Complications and maintenance re- 2. Astrand P, Ahlqvist J, Gunne J, Nilson H. quirements for fixed prostheses and erator the ability to replace a single Implant treatment of patients with eden- overdentures in the edentulous mandi- tulous jaws: A 20-year follow-up. Clin Im- crown should a porcelain fracture ble: A 5-year report. Int J Oral Maxillofac plant Dent Relat Res 2008;10:207–217. occur. However, with this design Implants 1994;9:191–196. 3. Adell R, Eriksson B, Lekholm U, Bråne- 13. Fischer K, Stenberg T, Hedin M, Senne- concept access to the abutment mark PI, Jemt T. Long-term follow-up rby L. Five-year results from a random- study of osseointegrated implants in screws is limited. The prosthesis ized, controlled trial on early and delayed the treatment of totally edentulous jaws. loading of implants supporting full-arch may be difficult to retrieve should Int J Oral Maxillofac Implants 1990;5: prosthesis in the edentulous maxilla. Clin 347–359. an abutment screw fracture or loos- Oral Implants Res 2008;19:433–441. 4. Jemt T, Johansson J. Implant treatment ening occur. 14. Göthberg C, Bergendal T, Magnusson T. in the edentulous maxillae: A 15-year fol- Complications after treatment with im- The primary limiting factor low-up study on 76 consecutive patients plant-supported fixed prostheses: A ret- provided with fixed prostheses. Clin Im- of the proposed technique is the rospective study. Int J Prosthodont 2003; plant Dent Relat Res 2006;8:61–69. 16:201–207. lack of long-term data. Long-term 5. Attard NJ, Zarb GA. Long-term treat- 15. Kohavi D. Complications in the tissue in- ment outcomes in edentulous pa- clinical case series are needed to tegrated prostheses components: Clini- tients with implant-fixed prostheses: validate the use of the proposed cal and mechanical evaluation. J Oral The Toronto study. Int J Prosthodont Rehabil 1993;20:413–422. prosthetic design in routine clinical 2004;17:417–424. practice.

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16. Balshi TJ, Wolfinger GJ, Alfano SG, 23. Stewart RB, Desjardins RP, Laney WR, 31. Faeghi Nejad M, Proussaefs P, Lozada Balshi SF. The retread: A definition and Chao EY. Fatigue strength of cantile- J. Combining guided alveolar ridge re- retrospective analysis of 205 implant- vered metal frameworks for tissue-inte- duction and guided implant placement supported fixed prostheses. Int J Prosth- grated prostheses. J Prosthet Dent 1992; for all-on-4 surgery: A clinical report. odont 2016;29:126–131. 68:83–92. J Prosthet Dent 2016;115:662–667. 17. Sadowsky SJ, Fitzpatrick B, Curtis DA. 24. von Gonten AS, Medina T Jr, Woolsey 32. Balshi TJ, Wolfinger GJ. Conversion Evidence-based criteria for differential GD, Hill DR. Modifications in the design prosthesis: A transitional fixed implant- treatment planning of implant restora- and fabrication of mandibular osseoin- supported prosthesis for an edentulous tions for the maxillary edentulous pa- tegrated fixed prostheses frameworks. arch—A technical note. Int J Oral Maxil- tient. J Prosthodont 2015;24:433–446. J Prosthodont 1995;4:82–89. lofac Implants 1996;11:106 –111. 18. Sadowsky SJ, Hansen PW. Evidence- 25. Drago C, Howell K. Concepts for design- 33. Kammeyer G, Proussaefs P, Lozada J. based criteria for differential treatment ing and fabricating metal implant frame- Conversion of a complete denture to a planning of implant restorations for works for hybrid implant prostheses. provisional implant-supported, screw- the mandibular edentulous patient. J Prosthodont 2012;21:413–424. retained fixed prosthesis for immedi- J Prosthodont 2014;23:104–111. 26. Bergendal B, Palmqvist S. Laser-welded ate loading of a completely edentulous 19. Goodacre CJ, Kan JY, Rungcharassaeng titanium frameworks for implant-sup- arch. J Prosthet Dent 2002;87:473–476. K. Clinical complications of osseointe- ported fixed prostheses: A 5-year re- 34. Papaspyridakos P, Benic GI, Hogsett VL, grated implants. J Prosthet Dent 1999; port. Int J Oral Maxillofac Implants 1999; White GS, Lal K, Gallucci GO. Accuracy 81:537–552. 14:69–71. of implant casts generated with splinted 20. Bozini T, Petridis H, Garefis K, Garefis P. 27. Gallucci GO, Doughtie CB, Hwang JW, and non-splinted impression techniques A meta-analysis of prosthodontic com- Fiorellini JP, Weber HP. Five-year results for edentulous patients: An optical scan- plication rates of implant-supported of fixed implant-supported rehabilita- ning study. Clin Oral Implants Res 2012; fixed dental prostheses in edentulous tions with distal cantilevers for the eden- 23:676–681. patients after an observation period of tulous mandible. Clin Oral Implants Res 35. Stimmelmayr M, Güth JF, Erdelt K, at least 5 years. Int J Oral Maxillofac Im- 2009;20:601–607. Happe A, Schlee M, Beuer F. Clinical plants 2011;26:304–318. 28. Örtorp A, Jemt T. CNC-milled titanium study evaluating the discrepancy of two 21. Papaspyridakos P, Chen CJ, Chuang SK, frameworks supported by implants in different impression techniques of four Weber HP, Gallucci GO. A systematic the edentulous jaw: A 10-year compara- implants in an edentulous jaw. Clin Oral review of biologic and technical compli- tive clinical study. Clin Implant Dent Investig 2013;17:1929–1935. cations with fixed implant rehabilitations Relat Res 2012;14:88–99. 36. Kan JY, Rungcharassaeng K, Bohsali K, for edentulous patients. Int J Oral Maxil- 29. Paniz G, Stellini E, Meneghello R, Cerardi Goodacre CJ, Lang BR. Clinical meth- lofac Implants 2012;27:102–110. A, Gobbato EA, Bressan E. The preci- ods for evaluating implant framework fit. 22. Falk H, Laurell L, Lundgren D. Occlusal sion of fit of cast and milled full-arch im- J Prosthet Dent 1999;81:7–13. force pattern in dentitions with man- plant-supported restorations. Int J Oral 37. Maló P, de Araújo Nobre M, Borges J, dibular implant-supported fixed cantile- Maxillofac Implants 2013;28:687–693. Almeida R. Retrievable metal ceramic ver prostheses occluded with complete 30. AlHelal A, Jekki R, Richardson PM, Kat- implant-supported fixed prostheses dentures. Int J Oral Maxillofac Implants tadiyil MT. Application of digital technol- with milled titanium frameworks and all- 1989;4:55–62. ogy in the prosthodontic management ceramic crowns: Retrospective clinical of a patient with myasthenia gravis: A study with up to 10 years of follow-up. clinical report. J Prosthet Dent 2016;115: J Prosthodont 2012;21:256–264. 531–536.

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