Historically, it has only been necessary to make animpression of the expanded, or surgically altered, audi-tory meatus when constructing an auditory insert,because the main function was simply to plug thecanal.1 To fabricate an insert that would not only func-tion, but also replicate the lost esthetics of the ear, itwas necessary to capture the anatomy and proportionsof the helix in the impression.

Making an impression of both the expanded earcanal and the contours of the helix would require thatthe impression be able to bend around the helix andpull out of the canal at the same time. Irreversible

648 THE JOURNAL OF PROSTHETIC DENTISTRY VOLUME 83 NUMBER 6

When fabricating a facial prosthesis, severeanatomic undercuts associated with tissue remnants ora defect site can be an obstacle to achieving an accu-rate impression. The purpose of this article is to pre-sent a procedure that applies the distinct properties of2 impression materials to create a 3-piece impressionthat can be reassembled to develop an accurate stonemaster cast. A patient treatment plan is used to illus-trate this procedure.

CLINICAL TREATMENT

A patient was referred for consultation to the Max-illofacial Prosthetic Clinic by his otolaryngologist. Thepatient’s chief complaint concerned the appearance ofhis surgically altered right ear (Fig. 1). Because ofrecurrent infections, a cavity had been surgically creat-ed to provide access to the mastoid for periodic clean-ing. The main concern for rehabilitation was the abili-ty to maintain patency to the mastoid area withoutrepeated surgical excision.

It was determined that the patient would be bestserved with a removable auricular prosthesis, asopposed to autogenous reconstruction and concomi-tant risk of surgical failure. The removal of the customauditory insert1 facilitates hygienic procedures subse-quent to efficient mastoid monitoring. The insert alsocovers and protects the defect between periodic check-ups by the otolaryngologist. For the patient, the mainconcern was the esthetic function of the prostheticinsert to camouflage the disfigurement. As described bythe patient, “I just want my ear to look normal again.”

Impression procedure for creating a partial auricular prosthesis

Todd M. Kubon, BA, MAMS,a Kenneth S. Kurtz, DDS,b and John D. Piro, DDSc

Toronto-Sunnybrook Regional Cancer Centre, Toronto, Ontario, Canada; Montefiore Medical Center,Albert Einstein College of Medicine, Bronx, and Columbia University School of Dental and OralSurgery, New York, N.Y.

Severe anatomic undercuts associated with tissue remnants or a defect site can often be an obstaclein achieving an accurate impression for a facial prosthesis. This article describes a procedure thatovercomes the problems encountered in achieving an accurate impression. The distinct propertiesof 2 impression materials are applied to create a 3-piece impression that can be reassembled todevelop an accurate stone master cast. (J Prosthet Dent 2000;83:648-51.)

This manuscript was presented at the annual meetings of The Amer-ican Anaplastology Association, Toronto, Ontario, June 1999;The American Academy of Maxillofacial Prosthetics, Philadel-phia, Pa., October 1999; and The American College of Prostho-dontists, New York, N.Y., October 1999.

aAnaplastologist, Toronto-Sunnybrook Regional Cancer Centre. bAttending Prosthodontist, Department of Dentistry, Montefiore

Medical Center. cAssociate Clinical Professor of Dentistry and Otolaryngology,

Columbia University School of Dental and Oral Surgery.

1999 JUDSON C. HICKEY SCIENTIFIC WRITING AWARD

Fig. 1. Patient’s surgically altered right ear.

hydrocolloid is most commonly used when making anauricular impression.1-3 However, multiple paths ofwithdrawal can cause the irreversible hydrocolloid totear because of its low tear strength.4 A single compo-nent impression material with higher tear strengthcould cause severe trauma to the tissues on retrieval ofthe set impression. The inability to capture both thedefect and the surrounding anatomy in an impressioncan compromise the fit and esthetics of the prosthesis.The weight of the impression material can distort thenatural position of the ear remnants. This can lead toan inaccurate cast. An inaccurate cast can create diffi-culty in achieving multiple adaptable margins and sym-metry with the contralateral ear.

A successful impression can be made by adaptingthe multiple tray technique as described by Salinas etal,5 which allows the creation of a 2-part impressionthat can be reassembled via key ways. For the impres-sion, the patient must be positioned on his or her side.This procedure is similar to creating a 3-piece mold2 ofa wax sculpture for fabrication of silicone prosthesis.

PROCEDURE

1. Block out the patient’s inner ear using lubricatedcotton; lubricate any facial hair that may be asso-ciated with the defect site.

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JUNE 2000 649

2. If necessary, box the defect sites to control theflow of the impression material. (However, thisstep is not necessary.)

3. Syringe medium body polyether (ImpregumPenta, ESPE, Norristown, Pa.) under the remain-ing parts of either the helix or lobe, allowing theimpression material to support the remnants intheir natural resting position. Use enough impres-sion material to come level with the tissue rem-nant, blocking out the undercut, but not allowingthe material to flow over on top of the tissue rem-nant (Fig. 2). (Polyether is used for this portion ofthe impression because of its high rigidity.4,7 Poly-ether allowed for the least amount of displace-ment of the tissue remnants under the weight ofthe additional impression materials.)

4. Syringe light-body polyvinyl siloxane (Reprosil,Caulk/Dentsply, Milford, Del.) over the remain-ing uncovered areas of the ear and any defect, ifpresent (Fig. 2). Create an irregular surface areathat will provide a pattern for the impression to bekeyed. (Light-body polyvinyl siloxane is indicatedfor this portion of the impression because of itshigh resistance to deformation, ease of flow, andhigh tear strength on setting.4,7 This will allowthe material to be retrieved from the defect with-out tearing or distorting the impression. Separat-ing medium is not necessary because the chemicaldissimilarity of the 2 impression materials will notallow them to bond. The absence of a separator

Fig. 2. Polyether impression material has been appliedbehind helix. Application of polyvinyl siloxane into defect.

Fig. 3. Plaster matrix removed. Removal of polyvinyl silox-ane component of impression from the defect.

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650 VOLUME 83 NUMBER 6

and the fact that these 2 materials are relativelyhydrophilic4,7 will facilitate an intimate relation-ship between them.)

5. If the boxing material was used, remove it fromthe impression without disturbing or removingthe impression.

6. Place plaster (Snow White Plaster No. 2, Kerr,Romulus, Mich.) around and over the entireimpression and allow it to set. (Plaster serves as amatrix into which the other parts of the impres-sion can be reassembled.)

7. Remove the impression. (The 3 parts will separatewhere needed to allow for its retrieval [Fig. 3].)

8. Disinfect the impression and reassemble it so thata master cast can be developed (Figs. 4 and 5).

To ensure the successful fit of the finished prosthe-sis, it is crucial that the wax sculpture relate accuratelyto both the patient’s defect site and the cast. The pre-liminary wax sculpture should be able to be transferredfrom the cast to the patient without modification. Theextent of the defect and the undercuts in the sur-rounding anatomy are not conducive to placing andremoving the preliminary wax sculpture from thepatient to the cast without distorting its shape. Onemust be able to rely on the accuracy of the impressionthat is made to ensure a successful fit of the final castprosthesis. In using the retention provided in theundercuts of the anatomy, the patient is able to wear

Fig. 4. Impression is fully reassembled and ready to be cast.

Fig. 5. Master cast for fabrication of final prosthesis.

Fig. 6. Final prosthetic result.

KUBON, KURTZ, AND PIRO THE JOURNAL OF PROSTHETIC DENTISTRY

JUNE 2000 651

the prosthesis without the aid of adhesives. The patientis instructed to apply a light coating of lubricationunder the margins so that they blend in with the skin(Fig. 6).

SUMMARY

A procedure for obtaining an accurate impression ofan auricular defect site with undercut tissue remnantsis described.

REFERENCES

1. Beumer J, Curtis T, Marunick M. Maxillofacial rehabilitation: prostho-dontic and surgical considerations. St Louis: Ishiyaku EuroAmerica;1996. p. 401-525.

2. McKinstry RE. Fundamentals of facial prosthetics. Arlington: ABI Profes-sional Publications; 1995. p. 32-70.

3. Brånemark PI, Tolman D. Osseointegration in craniofacial reconstruc-tion. Chicago: Quintessence Publishing Co; 1998. p. 214.

4. O’Brien WJ. Dental materials and their selection. Chicago: QuintessencePublishing Co; 1997. p. 123-46.

5. Salinas TJ, Penchas J, Prada-Valverde V, Guerra LR. A multiple tray tech-nique for implant-retained orbital prostheses. J Prosthet Dent 1995;73:158-61.

6. Ma T, Taylor TD, Johnson M. A boxing technique for making moulages offacial defects. J Prosthet Dent 1990;63:564-6.

7. Phillips RW, Skinner EW. Skinner’s science of dental materials. Philadel-phia: WB Saunders; 1991. p. 135-56.

Reprint requests to:MR TODD M. KUBON

C/O TORONTO-SUNNYBROOK REGIONAL CANCER CENTRE

2075 BAYVIEW AVE

TORONTO, ONTARIO

M4N 3M5CANADAFAX: (416)480-6801E-MAIL: todd.kubon@tsrcc.on.ca

Copyright © 2000 by The Editorial Council of The Journal of ProstheticDentistry.

0022-3913/2000/$12.00 + 0. 10/1/107443doi:10.1067/mpr.2000.107443

A 10-year longitudinal study of fixed prosthodontics: Clin-ical characteristics and outcome of single-unit metal-ceram-ic crownsWalton TR. Int J Prosthodont 1999;12:519-26.

Purpose. This article reported on the relationship between several clinical characteristics and theclinical outcome of treatment for 688 metal-ceramic crowns placed in 239 patients from the peri-od of January 1984 and December 1992 in a prosthodontic practice in Sydney, Australia.Material and methods. Clinical and laboratory procedures were standardized as much as practi-cal, and the patient profiles, instrumentation used, occlusal design philosophy and review criteriawere previously published (Int J Prosthodontics 1997;10:325-31).Results. The clinical review examination of the crowns placed covered 87% by the author. Ofthese, 52% were in service for between 5 and 10 years and 48% for less than 5 years but > 1 yearin service. 67% of the porcelain fused to metal crowns (PFM) were placed on vital teeth and theremained on endodontically treated teeth; 94% of these crowns examined were given a “goodprognosis” rating. The repair and failure of PFM crowns during the 5- to 10-year observation was3% for both groups. Crowns on nonvital teeth in the same grouping had a significantly higherfailure rate (5%) than PFMs on vital teeth (1%) and anterior teeth had a significantly higherretreatment rate than crowns on posterior teeth. Retreatment for 25 crowns occurred within 66months after cementation. Tooth fracture accounted for 56% of retreatments, caries and loss ofretention for 24% of retreatments, and 2% of initially vital teeth were treated endodontically dur-ing this survey period. Conclusion. Single PFM restorations had a high expectancy of exceeding 10 years of clinical ser-vice when the described clinical and laboratory procedures were applied. 15 References. —RPRenner

Noteworthy Abstractsof theCurrent Literature