CLINICAL REPORT Catastrophic failure of a monolithic zirconia prosthesis Jae-Seung Chang, DDS, PhD, a Woon Ji, DDS, b Chang-Hoon Choi, DDS, c and Sunjai Kim, DDS, PhD d The introduction of endosteal dental implants has allowed maxillary complete removable dental prostheses (CRDP) to be used with mandibular implantesupported complete fixed dental prostheses (ISCFDP) with patients who are edentulous. 1,2 Cast gold alloys are the conventional framework materials for ISCFDPs. Further, computer- assisted design and computer- assisted manufacturing (CAD/CAM) technology has enabled the use of titanium alloys and zirconia ceramic as framework materials. 3-6 In addition to CAD/CAM, copy- milling techniques also have been used to fabricate zirconia ceramic frameworks. 7,8 Dental zirconia can be veneered with feldspathic porcelain to achieve more esthetic outcomes, although zirconia ceramic prostheses are associated with higher chipping rates than metal ceramic prostheses. 9,10 Recently, monolithic zirconia res- torations have been used to eliminate chipping failures, but few clinical studies have shown the outcomes of monolithic zirconia ceramic restorations. 7,11 This report describes complications associated with a mandibular monolithic zirconia ceramic, screw-retained ISCFDP. CLINICAL REPORT A 79-year-old healthy man presented to Department of Prosthodontics, Gangnam Severance Dental Hospital, with concerns chiefly of a loose mandibular CRDP and mobility of the maxillary right posterior teeth. The patient had a 1-piece, narrow diameter endosteal dental implant in the mandibular anterior region to retain the CRDP. He reported that 3 implants had been placed in this region approximately 3 years earlier, but 2 implants had been lost within a year. The patient also had a maxillary partial removable dental prosthesis, but he discontinued its use because of mobility of the abutments (the right second premolar and first molar). These teeth were deemed unsalvageable because of advanced periodontal disease. The patient had root rests on both the maxillary central incisors and the left canine. A surveyed crown was placed on the maxillary right canine, which was not mobile or painful (Fig. 1). The patient had no systemic disease that would compromise implant surgery. After a thorough discussion with the patient, a maxillary overdenture on 4 anterior roots and a mandibular, monolithic, zirconia ceramic, screw-retained Supported in part by a faculty research grant, Yonsei University, College of Dentistry for 2013 (6-2013-0078). a Clinical Assistant Professor, Department of Dentistry, Yong-In Severance Hospital, College of Medicine, Yonsei University, Yong-In, Korea. b Graduate student, Department of Prosthodontics, Gangnam Severance Dental Hospital, College of Dentistry, Yonsei University, Seoul, Korea. c Graduate student, Department of Prosthodontics, Gangnam Severance Dental Hospital, College of Dentistry, Yonsei University, Seoul, Korea. d Associate Professor and Chairman, Department of Prosthodontics, Gangnam Severance Dental Hospital, College of Dentistry, Yonsei University, Seoul, Korea. ABSTRACT Recently, monolithic zirconia restorations have received attention as an alternative to zirconia veneered with feldspathic porcelain to eliminate chipping failures of veneer ceramics. In this clinical report, a patient with mandibular edentulism received 4 dental implants in the interforaminal area, and a screw-retained monolithic zirconia prosthesis was fabricated. The patient also received a maxillary complete removable dental prosthesis over 4 anterior roots. At the 18-month follow-up, all of the zirconia cylinders were seen to be fractured, and the contacting abutment surfaces had lost structural integrity. The damaged abutments were replaced with new abutments, and a new prosthesis was delivered with a computer-assisted design and computer-assisted manufacturing fabricated titanium framework with denture teeth and denture base resins. At the 6-month recall, the patient did not have any problems. Dental zirconia has excellent physical properties; however, care should be taken to prevent excessive stresses on the zirconia cylinders when a screw-retained zirconia restoration is planned as a definitive prosthesis. (J Prosthet Dent 2015;113:86-90) 86 THE JOURNAL OF PROSTHETIC DENTISTRY
Catastrophic failure of a monolithic zirconia prosthesis
Jae-Seung Chang, DDS, PhD,a Woon Ji, DDS,b Chang-Hoon Choi, DDS,c and Sunjai Kim, DDS, PhDd
ABSTRACTRecently, monolithic zirconia restorations have received attention as an alternative to zirconiaveneered with feldspathic porcelain to eliminate chipping failures of veneer ceramics. In this clinicalreport, a patient with mandibular edentulism received 4 dental implants in the interforaminal area,and a screw-retained monolithic zirconia prosthesis was fabricated. The patient also received amaxillary complete removable dental prosthesis over 4 anterior roots. At the 18-month follow-up, allof the zirconia cylinders were seen to be fractured, and the contacting abutment surfaces had loststructural integrity. The damaged abutments were replaced with new abutments, and a newprosthesis was delivered with a computer-assisted design and computer-assisted manufacturingfabricated titanium framework with denture teeth and denture base resins. At the 6-month recall,the patient did not have any problems. Dental zirconia has excellent physical properties; however,care should be taken to prevent excessive stresses on the zirconia cylinders when a screw-retainedzirconia restoration is planned as a definitive prosthesis. (J Prosthet Dent 2015;113:86-90)
The introduction of endostealdental implants has allowedmaxillary complete removabledental prostheses (CRDP) tobe used with mandibularimplantesupported completefixed dental prostheses(ISCFDP) with patients whoare edentulous.1,2 Cast goldalloys are the conventionalframework materials forISCFDPs. Further, computer-assisted design and computer-
assisted manufacturing (CAD/CAM) technology hasenabled the use of titanium alloys and zirconia ceramic asframework materials.3-6 In addition to CAD/CAM, copy-milling techniques also have been used to fabricatezirconia ceramic frameworks.7,8 Dental zirconia can beveneered with feldspathic porcelain to achieve moreesthetic outcomes, although zirconia ceramic prosthesesare associated with higher chipping rates than metalceramic prostheses.9,10 Recently, monolithic zirconia res-torations have been used to eliminate chipping failures,but few clinical studies have shown the outcomes ofmonolithic zirconia ceramic restorations.7,11 This reportdescribes complications associated with a mandibularmonolithic zirconia ceramic, screw-retained ISCFDP.
CLINICAL REPORT
A 79-year-old healthy man presented to Department ofProsthodontics, Gangnam Severance Dental Hospital,
part by a faculty research grant, Yonsei University, College of Dentistry fostant Professor, Department of Dentistry, Yong-In Severance Hospital, Colldent, Department of Prosthodontics, Gangnam Severance Dental Hospitadent, Department of Prosthodontics, Gangnam Severance Dental Hospitaofessor and Chairman, Department of Prosthodontics, Gangnam Severanc
with concerns chiefly of a loose mandibular CRDP andmobility of the maxillary right posterior teeth. The patienthad a 1-piece, narrow diameter endosteal dental implantin the mandibular anterior region to retain the CRDP. Hereported that 3 implants had been placed in this regionapproximately 3 years earlier, but 2 implants had beenlost within a year. The patient also had a maxillary partialremovable dental prosthesis, but he discontinued its usebecause of mobility of the abutments (the right secondpremolar and first molar). These teeth were deemedunsalvageable because of advanced periodontal disease.The patient had root rests on both the maxillary centralincisors and the left canine. A surveyed crown was placedon the maxillary right canine, which was not mobile orpainful (Fig. 1). The patient had no systemic disease thatwould compromise implant surgery.
After a thorough discussion with the patient, amaxillary overdenture on 4 anterior roots and amandibular, monolithic, zirconia ceramic, screw-retained
r 2013 (6-2013-0078).ege of Medicine, Yonsei University, Yong-In, Korea.l, College of Dentistry, Yonsei University, Seoul, Korea.l, College of Dentistry, Yonsei University, Seoul, Korea.e Dental Hospital, College of Dentistry, Yonsei University, Seoul, Korea.
Figure 1. Initial panoramic radiograph. Figure 2. Frontal view of maxillary overdenture and screw-retainedmonolithic zirconia implantesupported fixed complete denture.
Figure 3. Black arrows represent original outline of zirconia cylinder,which lost one-half of integrity because of multiple fractures.
Figure 4. Intaglio surface of definitive prosthesis with computer-assisteddesign and computer-assisted manufacturing fabricated titanium frame-work with 4 cylinders.
February 2015 87
ISCFDP were planned. The possibility of progressivewear of the maxillary denture teeth against themandibular zirconia ceramic material was a concern,although results of previous studies reported that well-polished zirconia ceramic causes minimal opposingmaterial wear.12,13 Excessive wear of titanium also wasexpected at the zirconia ceramic cylinderetitaniumabutment interface because of the hardness of zirconiaceramic; however, smooth titanium and zirconia ceramicsurfaces reportedly do not show different amounts ofwear.14 The maxillary right canine was endodonticallytreated, and its clinical crown was cut to supportthe planned overdenture. An immediate CRDP wasplaced after extraction of the maxillary posteriorabutments.
On the day of implant surgery, the 1-piece, mandib-ular, narrow endosteal dental implant was removed,and 4 internal-connection endosteal dental implants of
Chang et al
4.3-mm diameter and 10-mm length (Inplant; Warantec,Korea) were placed in the interforaminal area; the heal-ing abutments then were placed. The tissue side of themandibular CRDP was relieved and resurfaced with aresilient, autopolymerizing reline material (Coe-Soft; GCIntl) to avoid premature loading on the healing abut-ments. After 3 months of healing, 1-piece, titaniumdefinitive abutments (Multiunit Abutment; Warantec)with flat platforms were placed at the appropriategingival height. Type III dental stone (CrystalRock;Maruishi Gypsum) was used to fabricate the maxillary,and Type IV dental stone (Die-Keen; Heraeus Kulzer)was used for the mandibular definitive cast.
A verification jig was fabricated from the mandibulardefinitive cast by connecting the impression copings withan autopolymerizing acrylic resin (Pattern Resin; GC Intl).The 1-screw test was performed in the patient’s mouth tocheck the fit of the jig and then the jig was cut and rejoined
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Figure 5. A, Frontal view of maxillary overdenture and implant-supported fixed complete denture with denture teeth and denture base resin at6-month follow-up. Buccal finish line of titanium framework was apically moved to decrease metal exposure. B, Radiograph with new prosthesis.
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to achieve a passive fit. Both right and left distal abutmentanalogs were removed from the definitive cast and repo-sitioned by using the jig, and interim cylinders (TemporaryCylinder; Warantec) were connected to both distal abut-ment analogs. A fixed resin record base with a wax oc-clusion rim was fabricated with the interim cylindersto obtain the maxillomandibular relationship record; thedenture teeth then were arranged for the maxillary andmandibular prostheses. The cantilever lengthwas set at 1.5times the anteroposterior spread of the planned endostealdental implants.15 During the evaluation procedure, theamount of soft tissue support, tooth exposure, and centricrelation were reevaluated. The mandibular teeth andgingival contour were impressed by using a high-viscositysilicone elastomeric impression material (Exaflex Putty;GC Intl) to form a mold. An autopolymerizing bis-acryliccomposite resin (Luxatemp; DMG GmbH) was injectedinto themold to fabricate a guide for copymilling a zirconiaceramic block (Prettau; Zirkonzahn GmbH). The milledzirconia framework was characterized with a metal-freebrush to simulate tooth and gingival color and sinteredin a special furnace (Zirkonofen 600; Zirkonzahn GmbH)to obtain its definitive mechanical and optical properties.The fit of the prosthesis was evaluated in the patient’smouth and considered clinically acceptable, and both themaxillary overdenture and the mandibular ISCFDP weredelivered (Fig. 2). A 24-hour follow-up examination wasscheduled to identify any soft-tissue irritation or occlusaldisharmony.
The patient revisited the clinic at 1, 3, 6, 12, and 18months. At 12 months, he did not report any discomfortor pain. At the 18-month follow-up examination, slightdislodgment of the mandibular prosthesis was noted.When the 4 prosthetic screws were removed, the zirconiaceramic cylinders were found to be fractured (Fig. 3). Theinterfacial surfaces of the abutments, especially the distalabutments, had severely deteriorated. The 4 abutments
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were replaced, and an interim fixed dental prosthesis wasfabricated from a bis-acrylic composite resin (Luxatemp;DMG America) by copying the zirconia ceramic pros-thesis. The resin guide used for copy milling was con-verted into a replica by grinding the teeth and gingivalportions. A titanium framework was designed and milledon the basis of the replica and the mandibular definitivecast by using a CAD/CAM system (MyPlant; RaphaBio).The patient returned with repeated fractures of theinterim composite resin prosthesis at both the distalcylinder areas in spite of wire reinforcement and theaddition of composite resin around the cylinders.Therefore, the length of the distal cantilever was reduced.The fit of the titanium framework was evaluated in thepatient’s mouth and the denture teeth were arranged(Fig. 4). The mandibular prosthesis was placed in thepatient’s mouth, and the patient resumed the regularfollow-up visits (Fig. 5). Scanning electron microscopywas used to analyze the deteriorated abutments (Fig. 6).
DISCUSSION
This report presents the unexpected short-term failureof a monolithic, zirconia ceramic, screw-retainedISCFDP due to fracture of the zirconia ceramic cylin-ders and structural deterioration of the titanium abut-ments. The prosthetic failure could have been causedby inaccurate fit between the zirconia ceramic cylindersand the titanium abutments; inadequate cylinder di-mensions, which could have accumulated tensilestresses; and excessive cantilever length, which couldhave produced excessive stress on the zirconia ceramiccylinders. The ISCFDP was fabricated by using a copy-milling technique; therefore, its accuracy depended onoperator skill. Thin or irregular structures could havebeen introduced by the manual grinding process, andstress accumulation in such areas could have caused
Chang et al
Figure 6. Scanning electron microscopic image of deteriorated abut-ment. This abutment lost its entire structural integrity of platforms, andfin-like thin structure was noted at end of platform. Squashed surfacesalso had vertical scratch lines, which represent amount of vertical dis-lodging movement of prosthesis. Hexagon tops represent dent marksthat resulted from contact from prosthesis.
Figure 7. Metal cylinders. Intaglio surface with metal cylinders inmonolithic zirconia prosthesis. Metal cylinders were cemented intraorallywith resin cement.
February 2015 89
the fractures. Bonding or cementing metallic cylinderscan compensate for machining errors and provide apassive fit (Fig. 7).
The hardness of zirconia ceramic produced excessivewear of the titanium abutments, although a previousstudy did not show different amounts of wear of smoothtitanium and zirconia ceramic surfaces.14 The prosthesishad multiple fractured irregular surfaces with macro-roughness at the abutment contact area; therefore,structural deterioration of the titanium abutments wasaccelerated. Evidence of the continuous hammering of azirconia ceramic cylinder onto the platform of an abut-ment is shown in Figure 7.
Until now, favorable short-term clinical results of zir-conia ceramic, screw-retained frameworks with distal
Chang et al
cantilever extensions have been reported.5,7 Both studiesused between 5 and 8 implants in an arch to fabricate azirconia prosthesis. Increased numbers of implants couldprevent fracture of zirconia cylinders by reducing theamount of load on each zirconia cylinder. However, moreimplants also increased the difficulty of fabricating a pas-sive fitting prosthesis. In addition, those clinical studies didnot describe the cantilever length. Cantilevers of cast goldalloy screw-retained ISCFDPs should not be longer than1.5 times the anteroposterior spread of the endostealdental implants.15 Zirconia ceramic is more vulnerable totensile stress than gold or titanium alloys; therefore, themaximum cantilever length should be reduced when zir-conia ceramic is chosen as the frameworkmaterial for suchprostheses, even though increased numbers of implantscould withstand longer cantilever length. Because of itsexcellent mechanical and biocompatible properties,monolithic zirconia ceramic is an attractive choice forISCFDPs. However, prosthetic failure was encounteredwith this treatment. A CAD/CAM-fabricated titaniumframework with denture teeth was chosen as the newprosthesis because of its predictable results and long-termclinical success.
SUMMARY
Clinicians should be careful when selecting a zirconiaceramic, screw-retained prosthesis. The accuracy of theprosthesis, stress accumulation around zirconia ceramiccylinders, and cantilever length should be thoroughlyevaluated to prevent failure. An abutment-level pros-thesis is a safe option for avoiding damage to the dentalimplant platform.
REFERENCES
1. Attard NJ, Zarb GA. Long-term treatment outcomes in edentulous patientswith implant-fixed prostheses: the Toronto study. Int J Prosthodont 2004;17:417-24.
2. Ekelund JA, Lindquist LW, Carlsson GE, Jemt T. Implant treatment in theedentulous mandible: a prospective study on Brånemark system implantsover more than 20 years. Int J Prosthodont 2003;16:602-8.
3. Örtorp A, Jemt T. CNC-milled titanium frameworks supported by implants inthe edentulous jaw: a 10-year comparative clinical study. Clin Implant DentRelat Res 2012;14:88-99.
4. Örtorp A, Jemt T. Clinical experience of CNC-milled titanium frameworkssupported by implants in the edentulous jaw: a 3-year interim report. ClinImplant Dent Relat Res 2002;4:104-9.
5. Papaspyridakos P, Lal K. Computer-assisted design/computer-assistedmanufacturing zirconia implant fixed complete prostheses: clinical results andtechnical complications up to 4 years of function. Clin Oral Implants Res2013;24:659-65.
6. Larsson C, Vult Von Steyern P. Implant-supported full-arch zirconia-basedmandibular fixed dental prostheses. Eight-year results from a clinical pilotstudy. Acta Odontol Scand 2013;71:1118-22.
7. Rojas-Vizcaya F. Full zirconia fixed detachable implant-retained restorationsmanufactured from monolithic zirconia: clinical report after two years inservice. J Prosthodont 2011;20:570-6.
8. Ghazy MH, Madina MM, Aboushelib MN. Influence of fabricationtechniques and artificial aging on the fracture resistance of differentcantilever zirconia fixed dental prostheses. J Adhes Dent 2012;14:161-6.
9. Raigrodski AJ, Chiche GJ, Potiket N, Hochstedler JL, Mohamed SE, Billiot S,et al. The efficacy of posterior three-unit zirconium-oxide-based ceramic fixedpartial dental prostheses: a prospective clinical pilot study. J Prosthet Dent2006;96:237-44.
10. Raigrodski AJ, Hillstead MB, Meng GK, Chung KH. Survival and complica-tions of zirconia-based fixed dental prostheses: a systematic review.J Prosthet Dent 2012;107:170-7.
11. Marchack BW, Sato S, Marchack CB, White SN. Complete and partial con-tour zirconia designs for crowns and fixed dental prostheses: a clinical report.J Prosthet Dent 2011;106:145-52.
12. Park JH, Park S, Lee K, Yun KD, Lim HP. Antagonist wear of threeCAD/CAM anatomic contour zirconia ceramics. J Prosthet Dent2014;111:20-9.
13. Ghazal M, Kern M. The influence of antagonistic surface roughness on thewear of human enamel and nanofilled composite resin artificial teeth.J Prosthet Dent 2009;101:342-9.
14. Kanbara T, Yajima Y, Yoshinari M. Wear behavior of tetragonal zirconiapolycrystal versus titanium and titanium alloy. Biomed Mater 2011;6:021001.
Noteworthy Abstracts of
Edge chipping and flexural resistance of mon
Zhang Y, Lee JJ, Srikanth R, Lawn BRDent Mater 2013;29:1201-8
Objective. Test the hypothesis that monolithic ceramics canfracture resistance to circumvent processing and performancdental-prostheses consisting of a hard and strong core withthat monolithic prostheses can be produced with a much re
Methods. Protocols were applied for quantifying resistanceclasses of dental ceramic, microstructurally-modified zirconiawas used to induce chips near the edges of flat-layer specimcritical load equation. The critical loads required to producebonded to dentin were computed from established flexural sexperimental data.
Results. Monolithic zirconias have superior chipping and fleterparts. While they have superior esthetics, glass-ceramics erelative to porcelain-veneered zirconias.
Significance. The study suggests a promising future for newcombined durability and acceptable esthetics.
Reprinted with permission of the Academy of Dental Materi
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15. McAlarney ME, Stavropoulos DN. Determination of cantilever length-anterior-posterior spread ratio assuming failure criteria to be the compromiseof the prosthesis retaining screw-prosthesis joint. Int J Oral Maxillofac Im-plants 1996;11:331-9.
be developed with combined esthetics and superiore drawbacks of traditional all-ceramic crowns and fixed-an esthetic porcelain veneer. Specifically, to demonstrateduced susceptibility to fracture.
to chipping as well as resistance to flexural failure in twos and lithium disilicate glass-ceramics. A sharp indenterens, and the results compared with predictions from acementation surface failure in monolithic specimenstrength relations and the predictions validated with
xural fracture resistance relative to their veneered coun-xhibit lower strength but higher chip fracture resistance
and improved monolithic ceramic restorations, with
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