The rehabilitation of an edentulous mandible with a CAD/CAM zirconia … · 2020-03-24 · complete...
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The rehabilitation of an edentulous mandible with a CAD/CAM zirconia framework and heat-pressed lithium disilicate ceramic crowns: A clinical report Youngwook Cho, DMD, MSD, PhD a and Ariel J. Raigrodski, DMD, MS b School of Dentistry, Kyung Hee University, Seoul, Republic of Korea; School of Dentistry, University of Washington, Seattle, Wash This clinical report describes a complete arch, implant-supported prosthesis with a zirconia framework and monolithic lithium disilicate crowns. The design of the computer-aided design/computer-aided manufacturing zirconia framework with cemented crowns with screw access is useful in facilitating retrievability and adequate fit, and may reduce the likelihood of porcelain chipping. (J Prosthet Dent 2014;111:443-447) Dental implants are considered to be a predictable treatment for restor- ing edentulous mandibular arches. 1-3 Computer-aided design/computer-aided manufacturing (CAD/CAM) systems have been used for restoring edentulous arches with implant-supported fixed restorations 4,5 because they facilitate the fit between implants and super- structures better than conventional metal alloy castings. 6,7 Various meth- ods for fabricating these types of res- torations have been reported. Some suggest acrylic resin and denture teeth processed onto a CAD/CAM milled titanium framework, 8 and others re- commend the use of a screw or cement- retained 1-piece zirconia framework with veneering porcelain. 9,10 A zirconia framework is superior to a metal alloy or titanium framework in terms of esthetics and biocom- patibility. 11-14 However, concerns have been reported regarding long-term degradation, aging, and veneering por- celain chipping. 15,16 Even though long- term degradation is known to decrease the flexural strength of zirconia, the fracture of zirconia infrastructures has rarely been reported and is unlikely to cause clinical catastrophic failure. 17 Veneering porcelain chipping has been reported with zirconia-based fixed dental prostheses (FDP). Suggested causes include a lack of compatibility in terms of the coefficient of thermal expansion between the zirconia core and the veneering porcelain, 18-21 a framework design that does not provide proper support for the veneering porcelain, 22 rapid cooling rates, and relatively low fracture toughness and low flexural strength of the veneering porcelain. 23-25 To address these concerns, new layering porcelains with an adequate coefficient of thermal expansion and adequate mechanical properties have been de- veloped. 26,27 However, the veneering porcelain may still chip, and the repair process may become complicated and time consuming. In addition, por- celain chipping is the most frequently reported prosthesis-related technical complication of implant-supported ceramic FDPs. 28-30 To reduce the like- lihood of defects in veneering ceramics, alternative techniques such as mono- lithic zirconia restorations or pressing the veneering porcelain to the zirconia framework have been introduced. 31-33 Another frequent implant-related tech- nical complication is abutment screw loosening. 34 The purpose of this clini- cal report was to describe the use of lithium disilicate monolithic heat- pressed ceramic crowns with holes for abutment screw access that are bonded onto a zirconia framework to restore the edentulous mandible while de- creasing the risk of veneering porcelain fracture and facilitating retrievability. CLINICAL REPORT A 49-year-old man presented to the prosthodontic clinic of Gowoon Guide Dental Hospital with generalized advanced chronic periodontitis and missing teeth in the right posterior mandible and multiple teeth missing in the maxilla (Fig. 1). His chief complaint was difficulty in masticating. His med- ical history was noncontributory, with the exception of controlled hyperten- sion. A clinical evaluation revealed class II to class III mobility (according to the Miller classification) of the man- dibular teeth and gingival swelling with probing depths that exceeded 5 mm. The maxillary remaining teeth were in good condition except for wear due to sleep bruxism. A panoramic radiograph showed an edentulous atrophic poste- rior maxilla with pneumatization and significant alveolar bone resorption in the mandible (Fig. 2). Because of financial concerns, the patient wanted to have the mandible treated first with an implant-supported complete fixed a Private practice; and Affiliate Professor, Department of Prosthodontics, Kyung Hee University. b Professor, Department of Restorative Dentistry, University of Washington, School of Dentistry; Adjunct Professor, Department of Materials Sciences and Engineering University of Washington, College of Engineering. Cho and Raigrodski
Transcript of The rehabilitation of an edentulous mandible with a CAD/CAM zirconia … · 2020-03-24 · complete...
The
rehabilitation of an edentulousman
fram
disi
repo
Youngwook Cho
aPrivate practice; and Affiliate ProfesbProfessor, Department of RestorativSciences and Engineering University
Cho and Raigrodski
dible with a CAD/CAM zirconia
ework and heat-pressed lithium
licate ceramic crowns: A clinical
rt
, DMD, MSD, PhDa andAriel J. Raigrodski, DMD, MSb
School of Dentistry, Kyung Hee University, Seoul, Republic of Korea;School of Dentistry, University of Washington, Seattle, Wash
This clinical report describes a complete arch, implant-supported prosthesis with a zirconia framework and monolithiclithium disilicate crowns. The design of the computer-aided design/computer-aided manufacturing zirconia framework withcemented crowns with screw access is useful in facilitating retrievability and adequate fit, and may reduce the likelihood ofporcelain chipping. (J Prosthet Dent 2014;111:443-447)
Dental implants are considered tobe a predictable treatment for restor-ing edentulous mandibular arches.1-3
Computer-aided design/computer-aidedmanufacturing (CAD/CAM) systemshave been used for restoring edentulousarches with implant-supported fixedrestorations4,5 because they facilitatethe fit between implants and super-structures better than conventionalmetal alloy castings.6,7 Various meth-ods for fabricating these types of res-torations have been reported. Somesuggest acrylic resin and denture teethprocessed onto a CAD/CAM milledtitanium framework,8 and others re-commend the use of a screw or cement-retained 1-piece zirconia frameworkwith veneering porcelain.9,10
A zirconia framework is superiorto a metal alloy or titanium frameworkin terms of esthetics and biocom-patibility.11-14 However, concerns havebeen reported regarding long-termdegradation, aging, and veneering por-celain chipping.15,16 Even though long-term degradation is known to decreasethe flexural strength of zirconia, thefracture of zirconia infrastructures hasrarely been reported and is unlikely tocause clinical catastrophic failure.17
Veneering porcelain chipping has beenreported with zirconia-based fixed dental
sor, Depae Dentistryof Washin
prostheses (FDP). Suggested causesinclude a lack of compatibility in termsof the coefficient of thermal expansionbetween the zirconia core and theveneering porcelain,18-21 a frameworkdesign that does not provide propersupport for the veneering porcelain,22
rapid cooling rates, and relatively lowfracture toughness and low flexuralstrength of the veneering porcelain.23-25
To address these concerns, new layeringporcelains with an adequate coefficientof thermal expansion and adequatemechanical properties have been de-veloped.26,27 However, the veneeringporcelain may still chip, and the repairprocess may become complicatedand time consuming. In addition, por-celain chipping is the most frequentlyreported prosthesis-related technicalcomplication of implant-supportedceramic FDPs.28-30 To reduce the like-lihood of defects in veneering ceramics,alternative techniques such as mono-lithic zirconia restorations or pressingthe veneering porcelain to the zirconiaframework have been introduced.31-33
Another frequent implant-related tech-nical complication is abutment screwloosening.34 The purpose of this clini-cal report was to describe the useof lithium disilicate monolithic heat-pressed ceramic crowns with holes for
rtment of Prosthodontics, Kyung Hee Universit, University of Washington, School of Dentistrygton, College of Engineering.
abutment screw access that are bondedonto a zirconia framework to restorethe edentulous mandible while de-creasing the risk of veneering porcelainfracture and facilitating retrievability.
CLINICAL REPORT
A 49-year-old man presented tothe prosthodontic clinic of GowoonGuide Dental Hospital with generalizedadvanced chronic periodontitis andmissing teeth in the right posteriormandible and multiple teeth missing inthe maxilla (Fig. 1). His chief complaintwas difficulty in masticating. His med-ical history was noncontributory, withthe exception of controlled hyperten-sion. A clinical evaluation revealed classII to class III mobility (according tothe Miller classification) of the man-dibular teeth and gingival swelling withprobing depths that exceeded 5 mm.The maxillary remaining teeth were ingood condition except for wear due tosleep bruxism. A panoramic radiographshowed an edentulous atrophic poste-rior maxilla with pneumatization andsignificant alveolar bone resorptionin the mandible (Fig. 2). Because offinancial concerns, the patient wantedto have the mandible treated first withan implant-supported complete fixed
y.; Adjunct Professor, Department of Materials
1 Preoperative photographs: frontal view. 2 Preoperative panoramic radiograph.
3 Panoramic radiograph after connecting interimabutments to implants.
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prosthesis and then to have the maxillatreated with a partial removable den-tal prosthesis. An interim mandibularcomplete denture was inserted and re-lined with tissue-conditioning material(Soft-liner; GC Corp) immediately afterextraction of the remaining teeth andwas used for evaluating esthetics,phonetics, and the occlusal verticaldimension. A clear acrylic resin surgicaltemplate (Vertex Rapid Simplified; Ver-tex Dental) was made with a duplicateof the interim denture.
Three months after extraction, 6endosseous dental implants, 10 mmin length and 4.3 mm in diameter(Implantium; Dentium Corp) wereplaced with the 1-stage approach.Because of patient fatigue and reducedtreatment compliance and because ofthe length of surgery, an early loadinginterim denture was planned. After
The Journal of Prosthetic Dentistry
1 week, 6 impression copings (Impres-sion Coping Pick-up; Dentium Corp)were connected to the implantsand used as interim screw-type abut-ments (Fig. 3). The prefabricated fixeddetachable interim prosthesis madeby duplicating the interim completedenture, with access holes for theinterim abutments, was placed andevaluated for proper occlusion andclearance between each access holeand its corresponding interim abut-ment. Successively, autopolymerizedacrylic resin (Jet denture repair resin;Lang Dental Mfg Co) was applied tothe holes, and an interim fixed pros-thesis was placed for 4 months until amaxillary partial removable dentalprosthesis was fabricated.
Subsequently, a definitive man-dibular impression was made witha custom light-polymerized open tray
(Vertex Light Curing Trayplates; VertexDental) and open-tray impression cop-ings (Impression Coping Pick-up; Den-tium Corp). The impression was pouredwith Type IV gypsum material (FujirockEP; GC America Inc) to fabricate thedefinitive cast. Six yellow abutments fordirect milling (Dual Milling abutment;Dentium Corp) with titanium nitridecoating were connected to the implantreplicas on the definitive cast. Thesewere milled with a 2-degree millingbur to fabricate a cement-type zirconiasuperstructure. Subsequently, all theabutments were transferred to the oralcavity, and their positions were con-firmed with an abutment positioningdevice. A centric relation record wasmade with a recording device (GCPattern Resin; GC America Inc), andcasts were mounted in a semiadjustablearticulator (Hanau modular articulator;Whip Mix Corp). An anatomic contourwaxing was made and converted intoan acrylic resin prosthesis (GC Patternresin; GC America Inc) by using puttyindex (Lab Putty; Coltène/Whaledent,Inc). Light-polymerized composite resin(Rigid Transparent þ Blue; Zirkonzhan)was used free hand to correct eachtooth shape. This complete contoursimulation was inserted intraorally toverify the occlusal vertical dimensionand soft-tissue support (Fig. 4). Eachtooth of the simulated restoration wascut back approximately 2.0 mm topermit the fabrication of the definitiverestoration, with the silicone matrix as areference. The acrylic resin framework
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4 Vertical dimension and soft-tissue support evaluation. 5 Scanning of acrylic resin framework.
6 Zirconia framework before final sintering. 7 New centric relation record.
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was scanned (Optical scanner S600;Zirkonzhan), and the CAD/CAM zirco-nia framework was fabricated (Prettau;Zirkonzahn). The intaglio was also cutback for gingival porcelain addition, andthe framework was sintered (Figs. 5, 6).
Once sintering was completed, thezirconia framework was veneered withfeldspathic gingival porcelain (CreationZi-F; Creation Willi Geller Intl GmbH).After verifying the fit of the zirconiaframework on the abutments intra-orally, a new centric relation record wasmade (Fig. 7) and used for remounting.A complete-contour waxing was per-formed on each tooth preparationsimulation of the zirconia framework.Subsequently, lithium disilicate mono-lithic crowns (Emax; Ivoclar Vivadent)were heat pressed to fit each abutment(Fig. 8).
The gingival ceramic around eachmargin of the zirconia tooth simulation
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was etched for 30 seconds with hydro-fluoric acid, and a primer (Z-Primeplus; Bisco Inc) was applied on theabutment margin. The crowns wereetched for 20 seconds with hydrofluoricacid and silanated. Self-etching, self-adhesive resin cement (Unicem; 3MESPE) was used to bond each mono-lithic lithium disilicate crown to thezirconia framework extraorally. Afterconnecting the custom abutments withthe implants in the oral cavity, theCAD/CAM zirconia framework wascemented onto the abutments withprovisional implant cement (ImplantCement; Premier). To ensure the com-plete removal of residual cement, eachabutment screw was loosened andthe restoration was removed; then itwas reseated, and all the abutmentscrews were tightened to 35 Ncm.Finally, the access holes were filled withcotton pellets, interim composite resin
restorative material (Fermit; IvoclarVivadent), and composite resin restor-ative material (Filtek P60; 3M ESPE)(Figs. 9, 10). The occlusion was refined,and the patient expressed his satisfac-tion with the esthetic and functionaloutcomes. The patient was scheduledfor recall at 6-month intervals andpresented with satisfactory oral hygieneand no mechanical complications atthe 9-month follow-up.
DISCUSSION
In this clinical treatment, eachcrown was fabricated from monolithiclithium disilicate and cemented ontothe framework. Lithium disilicate waschosen for esthetics and strength.35
Clinical studies on monolithic lithiumdisilicate crowns and FDPs have shownpromising results in terms of structuralintegrity.36-38 If chipping or fracture of
9 Complete mandibular prosthesis in process of bondingindividual lithium disilicate crowns.
8 Complete contour waxing and monolithic lithium disilicate crowns.
10 Intraoral occlusal view of complete prosthesis.
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the crowns occurs, then the prosthesisdesign allows the removal and replace-ment of the crown intraorally, orextraorally by removing the restoration.Another prospective complication withcomplete arch implant-supported FDPsis screw loosening or screw fracture.This type of prosthesis enables retriev-ability and screw management becauseeach access hole is maintained as partof the crown.
The Journal of Prosthetic Dentis
Because crowns on this prosthesiscan be easily replaced compared witha monolithic zirconia prosthesis, er-rors such as deficient occlusal con-tacts on an individual crown can becorrected. The possible disadvantageof this prosthesis is the risk of failurein the bond between the zirconiaframework and the veneering gingivalporcelain. Using individual crowns,as with this prosthesis, may also
try
be more costly than conventionalprostheses.
SUMMARY
This technique combines the CAD/CAM fabrication of a zirconia frame-work for precision with heat-pressedmonolithic lithium disilicate crownsfor esthetics and function. This type ofprosthesis may reduce the likelihood of
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porcelain fractures and allow ease ofretrievability.
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Corresponding author:Dr Youngwook ChoWashington Dental Clinic830-3 Bi-jeon 2-dongPyeongtaek-si, Gyeonggi-doKOREAE-mail: [email protected]
Copyright ª 2014 by the Editorial Council forThe Journal of Prosthetic Dentistry.
