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Mathew T. Katta

aProfessor and Director, Advanced SbDental student.cGraduate student, Advanced SpeciadProfessor of Restorative Dentistry.

The Journal of Prosthetic

aoral scanning of hard and soft

ues for partial removable dental

sthesis fabrication

diyil, BDS, MDS, MS,a Zachary Mursic, BSc,b

Hamad AlRumaih, BDS,c and Charles J. Goodacre, DDS, MSDd

Loma Linda University School of Dentistry, Loma Linda, Calif

This article provides proof of concept for the use of intraoral scanning technology to record hard and soft tissue morphologyfor the fabrication of a cast partial removable dental prosthesis. An open source intraoral scanner was used to scan the hardand soft tissues to create a stereolithographic file that was subsequently imported into a computer-aided design softwareprogram for the digital/virtual design of a partial removable dental prosthesis framework. Computer-aided design andcomputer-aided manufacturing technology was then used to fabricate a resin framework that was trial placed to evaluateaccuracy and for conventional investing and casting with a cobalt-chromium alloy. The cast framework and definitiveprosthesis were judged to be clinically accurate in fit, stability, and retention. (J Prosthet Dent 2014;112:444-448)

Computer-aideddesign and computer-aided manufacturing (CAD/CAM) tech-nology has increased the treatmentoptions available for clinicians. The useof this technology continues to increasein fixed prosthodontics1,2 and hasexpanded in recent years to includeboth implant and complete dentureprosthodontics.3-5 CAD/CAM technol-ogy can simplify treatment proceduresand reduce time and appointments, butcareful acquisition of data with preciseexecution of clinical procedures is es-sential to success.6

Limited information is availableregarding the application of digitaltechnology and CAM software in thefabrication of partial removable dentalprostheses (PRDPs) and PRDP frame-works.7-13 Williams et al7 publishedan early report on the application ofCAD/CAM technology in the fabrica-tion of PRDP frameworks. They de-scribed a technique in which a definitivecast was digitized with an optical scan-ning device and a 3-dimensional (3D)model was produced. With software,they designed and created a prototypeof the PRDP framework. The digital in-formation was used in a rapid proto-typing (RP) machine to form a plastic

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Dentis

pattern, which was subsequently inves-ted, cast, and finished in the conven-tional manner. They noted that thisconcept could save time and increaseefficiency in identifying survey lines. Theyreported casting defects when the RPpattern was cast and the significant in-crease in cost associated with the scan-ner, design software, and RP device.

Williams et al8 subsequently pub-lished a clinical report in which theyverified the accuracy of a digitally fab-ricated PRDP framework by scanning adefinitive cast made by using a conven-tional impression. A scanner (Comet250; Steinbichler Optotechnik), nor-mally used in high-precision engineeringapplications, was used to scan the cast.The resulting data were then exportedto design software (FreeForm Software;SensAble Technologies) that was usedto survey the digital cast, determine theappropriate tilt, and provide appro-priate relief. The framework design wasthen planned, and the informationwas exported to RP software to createthe framework from a printed cobalt-chromium alloy. A laser beam wasused to weld the printable cobalt-chromium alloy powder layer by layerto create this metal framework. The

ducation Program in Prosthodontics.

ion Program in Prosthodontics.

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authors reported that the compositionof the alloy used for printing theframework differs slightly from that ofconventional cobalt-chromium used forcasting. They cautioned that toxicitystudies were not available for the prin-ted alloy and that the issue of toxicityshould be addressed before commercialuse of this product. Hence, the PRDPframework was only trial fitted to verifythe accuracy of this technology, and adefinitive prosthesis was not placed.

To date, no reports of directintraoral scanning for the fabricationof PRDP frameworks are available.The purpose of this patient treatmentreport is to offer proof of concept anddescribe the process by which intraoralscanning of the maxillary arch wasused in the fabrication of a PRDPframework.

CLINICAL REPORT

A 63-year-old partially edentulouswhite woman presented for treatmentat Loma Linda University School ofDentistry requesting a new PRDP toreplace her missing maxillary teeth(Fig. 1). After comprehensive evalua-tion, data collection, and discussion of

Kattadiyil et al

1 Occlusal view of maxillary arch with Kennedy Class III.

2 Occlusal view of polyurethane cast.

3 Digital design for partial removable dental prosthesis.

September 2014 445

treatment options, a treatment planfor the fabrication of a new maxillaryPRDP was selected. The patient’s entiremaxillary arch, including the hard andsoft tissue morphology, was captureddigitally with the open source intraoralscanner (Cadent iTero; Align Technol-ogy). Approximately 28 scans were usedto capture the teeth and occlusion, withan additional 25 scans being used toenhance the capture of the rest seats,guiding surfaces, soft tissue, andmaxillary palate. Another 28 scans wereused to capture the mandibular denti-tion, for a total scan count of 81. Dis-counting initial test and trial scans torecord soft tissue, the total time forscanning was approximately 17 mi-nutes. The digital scan file was thensent to Cadent iTero with a laboratorywork authorization form for processingand cast manufacturing. After imageprocessing by Cadent iTero, a milledpolyurethane maxillary cast (Fig. 2)was made along with the opposingmandibular cast. These casts and theprocessed digital information were sentto a commercial dental laboratory,where a designing system (SensAbleSystem; SensAble Technologies Inc)was used to design and fabricate theframework. Appropriate relief andblockout were created on the virtualdesign cast with the SensAble software.The framework was designed (Fig. 3)based on the laboratory work authori-zation form and the images of thedigital design received for approval.Once the design was approved, a resin

Kattadiyil et al

pattern of the virtually designed PRDPframework was created with RP (3Dprinting) and then cast in a cobalt-chromium alloy (Wironium Plus; Bego)with the conventional lost wax castingtechnique. The resin pattern was spruedand invested (WiroFast; Bego). Theinvested resin pattern was placed in a gasburnout furnace (Miditherm 200 MP;Bego) and heated initially to 650�C for30 minutes; the temperature was thenraised to 1010�C. The investment wasplaced in an induction casting machine(Fornax T; Bego), and the alloy was castat 1440�C. The cast metal frameworkwas adjusted, finished, and polishedin a conventional manner. The frame-work, the polyurethane maxillary cast(Fig. 4), a resin duplicate of the frame-work (optional), and the mandibular

cast were received for trial placementand articulation.

The framework was judged toexhibit excellent fit when evaluated inthe mouth (Fig. 5), and a comparisonof disclosing contacts found matchingcontact areas between the mouthand the polyurethane plastic cast. Aduplicate resin pattern, which hadbeen requested as an option, was trialplaced in the patient’s mouth (Fig. 6).Although this was not a required step, atrial placement of the framework pro-vides an option to confirm fit beforecasting the wax pattern. Although notdeemed necessary for this patient, thepotential to modify the resin patternwhile evaluating the fit and occlusalcontacts before casting is an additionaladvantage of the resin pattern trialplacement option. The limitations in

446 Volume 112 Issue 3

terms of stability of the resin patternand the feasibility of making additive aswell as subtractive adjustments is aconsideration that is not addressed inthis report, because this framework didnot require modification.

After the trial placement of themetal framework, interocclusal recordswere made, the maxillary and mandib-ular polyurethane casts were articu-lated, and denture teeth were arrangedin a conventional manner. After waxtrial placement with denture teeth,processing was completed on the mil-led polyurethane cast. Because of con-cerns about chemical bonding betweenthe cast and the heat polymerizingresin, a layer of tin foil (Fig. 7) wasplaced to facilitate separation. Afterprocessing, adjusting, finishing, andpolishing, the definitive PRDP (Fig. 8)was placed and adjusted for comfortand function. The definitive maxillaryPRDP revealed good adaptation to

4 Cast metal framework placed onpolyurethane cast.

5 Partial removabledental prosthesis framew

The Journal of Prosthetic Dentis

the soft tissue, which was confirmedwith pressure indicating paste (PressureIndicator Paste; Henry Schein). Patientresponse to the digitally fabricatedPRDP was favorable. The patientwas given routine instructions on theplacement, removal, and maintenanceof the new PRDP. No adjustments wererequired during the postplacementevaluations.

DISCUSSION

No published reports are availableregarding the successful and accuratecapture of soft tissue morphology withan intraoral dental scanner. Williamset al7-10,13 published multiple clinicalreports regarding the fabrication ofa PRDP with CAD/CAM technology.However, they scanned dental castsmade from conventional impressionswith a tabletop optical scanner. Thispreliminary report provides proof ofconcept regarding the use of an intraoralscanner routinely used in fixed prostho-dontics and orthodontics to accuratelycapture both hard and softtissue images. However, the intraoraltechnique of capturing soft tissuemorphology, although accurate, hasdisadvantages that may limit its appli-cation. The technique uses many scansthat must be stitched together to cap-ture the morphology of the soft tissuerelevant to the design and fabrication ofthe PRDP. Also, the intraoral scannerdoes not capture appropriate extensionsof movable tissue that would normally

ork trial placement. 6 Resin pattern trial

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be captured in a conventional mannerby border molding the impression ma-terial. Even so, the concept of capturinga digital impression and then using thedata for CAD/CAM framework designand for printing the framework patternin resin for conventional casting provedto be an effective alternative to conven-tional framework fabrication. The tech-nique worked well in this Kennedy ClassIII clinical situation, in which capturingborder molded extensions of the softtissue was not as critical. In a distalextension base situation such as a Ken-nedy Class I or II, the inability to digitallyrecord the physiologic extensions ofthe moveable mucosa could negativelyaffect the outcome. This limitationcould be overcome by sectioning thepolyurethane cast and making analtered cast impression.14 The place-ment of implants to serve as terminalabutments in Kennedy Class I and IIsituations has been used effectively toreduce rotational movement of thedistal extension PRDP and significantlyimprove patient satisfaction.15 Thismight also eliminate the need to cap-ture the distal extension soft tissueswith border molding. Furthermore,scannable impression copings suchas Scan body (Straumann)16 or similarcode-incorporated implant componentscould serve to improve accuracy withdigital impressions and need to bestudied.

The use of a digital workflow inPRDP fabrication has some significantand potential benefits. Because the

placement.

Kattadiyil et al

September 2014 447

scanner can add scans as needed, thereare no concerns about a flawed im-pression, which could be a factor in aconventional technique. The scannerstitches images together in real time,allowing the clinician to identify andimmediately address any deficient areaswith additional scanning. Digital scan-ning can capture the tissues in a passivestate, thereby developing a mucostaticimpression17 that could be advanta-geous in certain situations. Communi-cation between the dental laboratoryand dental office can be improvedthrough the use of screenshots, anddesigns can be approved and modifiedbefore the framework is fabricated.Finally, because the fabrication processis automated, it is easy to provideinexpensive pattern resin frameworksfor trial placement. The cost of

7 Tin foil applied on edentulous areabefore processing.

8 Intraoral occlusal view of dedental prosthesis.

Kattadiyil et al

fabricating the digital framework wascomparable with that of a traditionallyfabricated framework. However, thisdoes not include overhead costs relatedto initial hardware and software in-vestments for commercial laboratories,which can be substantial.5 Additionally,an open source intraoral scanner isrequired, which is an expensive invest-ment for the clinician.

Capturing soft tissue impressionsdigitally has other advantages. Patientswho have a tendency to gag duringimpression procedures, as well asthose with special needs or anxiety,may tolerate the intraoral scanningprocedure better than a conventionalimpression. Given that the digital im-pression can be stitched together, it isnot important to capture all details inone scan, making it easier to maintainmoisture control in one area as op-posed to trying to maintain moisturecontrol in an entire arch. Similarly,recording small areas at a time in pa-tients with active and forceful tonguemusculature may be more accuratecompared with making a bilaterallyaccurate impression. Patients who haveallergies to impression materials couldalso benefit from this technology.

The authors believe that, in thefuture, the 3D printing of PRDPframeworks in resin or other suitablematerials could be used for trial place-ment to confirm fit and design. Thiswould allow easy confirmation of theaccuracy of the digital impression. It

finitive partial removable

would also allow the printed frameworkto be modified chairside (to improvedesign if needed) and would allow themodified framework to be used as theprototype for casting.

Although this clinical report sup-ports intraoral scanning as an optionfor the fabrication of a PRDP frame-work in this tooth-supported clinicalsituation, more clinical reports andstudies are required before the scope ofthe technology can be understood anddefinitive conclusions can be drawn.

SUMMARY

The clinical information required forthe digital fabrication of PRDPs can berecorded by capturing intraoral hardand soft tissue morphology with anintraoral dental scanner that stitchestogether many individual scans. In thisexample, the resulting resin frameworkwas judged to fit the digitally fabricatedpolyurethane cast as well as themouth accurately. The finished defini-tive prosthesis was successfully placedin the mouth and is being used by thepatient.

REFERENCES

1. Patzelt SB, Emmanouilidi A, Stampf S,Strub JR, Att W. Accuracy of full-arch scansusing intraoral scanners. Clin Oral Investig2014;18:1687-94.

2. Hamza TA, Ezzat HA, El-Hossary MM,Katamish HA, Shokry TE, Rosenstiel SF.Accuracy of ceramic restorations made withtwo CAD/CAM systems. J Prosthet Dent2013;109:83-7.

3. Balshi SF, Wolfinger GJ, Balshi TJ. A protocolfor immediate placement of a prefabricatedscrew-retained provisional prosthesis usingcomputed tomography and guided surgeryand incorporating planned alveoplasty.Int J Periodontics Restorative Dent 2011;31:49-55.

4. Goodacre CJ, Garbacea A, Naylor WP,Daher T, Marchack CB, Lowry J. CAD/CAMfabricated complete dentures: concepts andclinical methods of obtaining requiredmorphological data. J Prosthet Dent2012;107:34-46.

5. Kattadiyil MT, Goodacre CJ, Baba NZ.CAD/CAM complete dentures: a review oftwo commercial fabrication systems.J Calif Dent Assoc 2013;41:407-16.

6. Rekow D. Computer aided design andmanufacturing in dentistry. J Prosthet Dent1987;58:512-6.

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7. Williams RJ, Bibb R, Rafik T. A technique forfabricating patterns for removable partialdenture frameworks using digitized castsand electronic surveying. J Prosthet Dent2004;91:85-8.

8. Williams RJ, Eggbeer D, Bibb R. CAD/CAMrapid manufacturing techniques in thefabrication of removable partial dentureframeworks. Quintessence J Dent Technol2008;6:42-50.

9. Williams RJ, Bibb R, Eggbeer D, Woodward A.A patient-fitted removable partial dentureframework fabricated from a CAD/CAM-produced sacrificial pattern. Quintessence JDent Technol 2006;4:200-4.

10. Williams RJ, Bibb R, Eggbeer D, Collis J.Use of CAD/CAM technology to fabricatea removable partial denture framework.J Prosthet Dent 2006;96:96-9.

11. Eggbeer D, Bibb R, Williams R. Thecomputer-aided design and rapidprototyping of removable partial dentureframeworks. Proc Inst Mech Eng H2005;219:195-202.

The Journal of Prosthetic Dentis

12. Eggbeer D, Williams RJ, Bibb R.A digital method of design andmanufacture of sacrificial patternsfor removable partial denture metalframeworks. Quintessence J Dent Technol2004;2:490-9.

13. Williams RJ, Bibb R, Eggbeer D. CAD/CAMin the fabrication of removable partialdenture frameworks: a virtual method ofsurveying 3D scanned dental casts.Quintessence J Dent Technol 2004;2:268-76.

14. Leupold RJ, Kratochvil FJ. An altered-castprocedure to improve tissue support forremovable partial dentures. J Prosthet Dent1965;15:672-8.

15. Gonçalves TM, Campos CH, RodriguesGarcia RC. Implant retention and support fordistal extension partial removable dentalprostheses: satisfaction outcomes. J ProsthetDent 2014;112:334-9.

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16. Lin WS, Harris BT, Morton D. The use of ascannable impression coping and digitalimpression technique to fabricate acustomized anatomic abutment andzirconia restoration in the esthetic zone.J Prosthet Dent 2013;109:187-91.

17. Page HL. Mucostatics. Ticonium Contacts1946;4:7.

Corresponding author:Dr Mathew T. Kattadiyil11092 Anderson StLoma Linda University School of DentistryLoma Linda, CA 92350E-mail: mkattadiyil@llu.edu

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

Kattadiyil et al

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