Use

abu

impl

Chonghwa Kim,

1 Pretreatment intraoral views

Supported by the Korea Health R&D

aPrivate practice, Seoul, Korea.bPrivate practice, Seoul, Korea.cAssociate Professor, Department of

Kim et al

of CAD/CAM to fabricate duplicate

tments for retrofitting an existing

ant prosthesis: A clinical report

DDS, MS,a Jong-Yub Kim, DDS, MSD, PhD,b andYoung-Jun Lim, DDS, MSD, PhDc

Dental Research Institute, School of Dentistry, Seoul NationalUniversity, Seoul, Korea

Computer-assisted design/computer-assisted manufacturing (CAD/CAM) technology has been widely used in the field ofdentistry. Among CAD/CAM custom abutments, zirconia abutments are becoming more popular due to their favorable me-chanical and esthetic properties. However, recent review articles show that fractured zirconia abutments are a common pros-thetic complication. In this clinical report, a 72-year-old man presented with a dislodged implant-supported fixed prosthesisbecause of fractured zirconia abutments. This clinical report describes a successful application of CAD/CAM technology tofabricate duplicate abutments, which were retrofitted to the existing prosthesis. (J Prosthet Dent 2014;112:429-433)

Computer-assisted design/computer-assisted manufacturing (CAD/CAM)technology is becomingmoreprevalent inthe field of dentistry. Advances in thistechnology have expanded the scope ofits clinical applications.1-4 CAD/CAMcustom abutments have become widelyused in practice due to the clinical easeand predictability in restorations. Amongvarious types of abutments available withCAD/CAM, zirconia abutments havegained popularity due to their favorablemechanical and esthetic properties.5-12

Biomechanically, zirconia abutments

with disl

project (

Prosthod

exhibit excellent biocompatibility, bendstrength, and fracture resistance as aresult of transformation toughening.13,14

Nevertheless, recent reports have shownthat the fracture of zirconia abutments isa common prosthetic complication.15-20

Clinicians have known of the advan-tages of CAD/CAM dentistry for a longtime. The evolution of both hardwareand software systems has providedversatility and operational freedomwith the CAD/CAM systems in usetoday. These advances in technologyaid clinicians in managing prosthetic

odged implant prosthesis. A, Lateral view.

HI12C0064), granted by the Ministry of Health

ontics.

complications associated with dentalimplants that cannot otherwise be suc-cessfully managed with conventionalprosthodontic techniques. This clinicalreport describes an application of CAD/CAM technology to fabricate duplicateabutments that were retrofitted to theexisting implant prosthesis.

CLINICAL REPORT

A 72-year-old man presented tothe faculty clinic of Seoul National Uni-versity School of Dentistry with a

B, Occlusal view.

and Welfare, Republic of Korea.

2 Fractured cervical portion of existing zirconia abutments. A, Dislodged implant prosthesis with fractured abutmentsinside. B, Existing prosthesis and abutment fragments.

3 Standard closed tray impression copings positioned inmouth for impression with polyvinyl siloxane material.

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dislodged implant prosthesis in themaxillary left quadrant (Fig. 1). The pa-tient declined the recommendation tohave a new prosthesis fabricated andinstead requested that the prosthesisbe repaired at minimal cost. Clinical ex-amination revealed that both zirconiaabutments were fractured above theimplant platform, whereas the coronalportion of the fractured abutments re-mained cemented inside the existingprosthesis (Fig. 2). An impression of the 2external-connection implants was madewith standard closed tray impressioncopings (US Fixture Transfer ImpressionCoping; Osstem) and polyvinyl siloxaneimpression material (Compress heavy;Bisico) (Fig. 3). A stone working cast wasthen fabricated in the samemanner as fora conventional implant prosthesis.

For the CAD of the new abutments,the working cast was scanned with

4 Two separate scan images of workingwith scanning bodies. B, Scanning with

The Journal of Prosthetic Dentis

a digital laboratory scanner (Ez-scanD-700; 3Shape). Two separate scandata were obtained (Fig. 4). One scanimage was obtained with 2 scanningbodies (Scanning abutment; Dentaim)positioned on the working cast. The

cast obtained with Ez-scan D-700 laboratoprevious abutments in place.

try

fragments of the fractured abutmentswere retrieved from the existing prosthesisafter heating in a ceramic furnace andwere reattached with an adhesive (Zapit;Dental Ventures of America). The secondscan imagewasmadewith the reattached

ry scanner. A, Complete arch scanning

Kim et al

5 Computer-aided design for new abutments. A, Transfer of individual abutment scan. B, Completed transferof individual abutment scan. C, Redesigning fractured cervical part of new abutment. D, Completed design ofnew abutment.

6 Two sets of new abutments fabricated from zirconia and titanium blocks. A, Previous abutments. B, Newtitanium abutments. C, New zirconia abutments.

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Kim et al

7 Evaluation of new abutments with existing prosthesis. A, Titanium abutments placed in patient’s mouth. B, Existingprosthesis positioned on new titanium abutments. C, Zirconia abutments placed in patient’s mouth. D, Existing prosthesispositioned on new zirconia abutments.

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abutments positioned on the workingcast. The 2 abutments were then indi-vidually scanned. The scan data for theintact coronal portion of the abutmentswere transferred to the CAD design forthe new abutments with a 3-pointmatching technique (Fig. 5A, B). Subse-quently, the CAD designs for the cervicalpart of the new abutments werecompleted (Fig. 5C, D).

Two sets of new abutments werefabricated from zirconia (Z-matchblock; Dentaim) and titanium blocks(Z-match Titanium block; Dentaim)(Fig. 6). The flexural strength of zirco-nia block used ranged between 1000and 1250 MPa, and its fracturetoughness was 5 MPa$m1/2. Both setsof abutments and the existing pros-thesis were then inserted into the pa-tient’s mouth to evaluate fit andesthetics. The fit of the patient’s exist-ing prosthesis was clinically acceptable

The Journal of Prosthetic Dentis

with both types of the newabutments (Fig. 7). Minor occlusaladjustments were necessary at the timeof delivery. The patient chose the zir-conia abutments for their estheticsuperiority.

SUMMARY

One of the limitations of ceramicabutments is their brittle nature. Asa result, they are less resistant to ten-sile forces than are metal abutments.With the development of high-strengthceramics, especially zirconia, the me-chanical disadvantages of ceramicmaterials have been minimized. Thisclinical report demonstrates the use ofCAD/CAM technology to provide anefficient and precise way of fabricatingnew abutments to replace fracturedabutments that support an existingimplant prosthesis.

try

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5. Sadoun M, Perelmuter S. Alumina-zirconiamachinable abutments for implant-supported single-tooth anterior crowns.Pract Periodontics Aesthet Dent 1997;9:1047-53.

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15. Chevalier J, Gremillard L, Deville S. Low-temperature degradation of zirconiaand implications for biomedical implants.Ann Rev Mater Res 2007;37:1-32.

16. Leutert C, Stawarczyk B, Truninger T,Hämmerle C, Sailer I. Bending momentsand types of failure of zirconia andtitanium abutments with internal implant-abutment connections: a laboratory study.Int J Oral Maxillofac Implants 2012;27:505-12.

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19. Foong JK, Judge RB, Palamara JE, Swain MV.Fracture resistance of titanium and zirconiaabutments: an in vitro study. J Prosthet Dent2013;109:304-12.

20. Kim JS, Raigrodski AJ, Flinn BD, Rubenstein JE,Chung KH, Mancl LA. In vitro assessment ofthree types of zirconia implant abutments understatic load. J Prosthet Dent 2013;109:255-63.

Corresponding author:Dr Young-Jun LimDepartment of Prosthodontics and DentalResearch InstituteSchool of Dentistry, Seoul National University101 Daehak-ro, Jongno-gu, Seoul 110-749KOREAE-mail: limdds@snu.ac.kr

Copyright ª 2014 by the Editorial Council forThe Journal of Prosthetic Dentistry.