Duplicating the Posterior Extension of an Existing Denture

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Continuing Education

Duplicating the Posterior Extension of an Existing Denture

Authored by Won-suk Oh, DDS, MS, and Ju-mi Park, DDS, MS, PhD

Upon successful completion of this CE activity 1 CE credit hour will be awarded

Volume 32 No. 9 Page 94

ABOUT THE AUTHORSDr. Oh is a clinical associate professor atthe University of Michigan School ofDentistry, is a Diplomate of AmericanBoard of Prostho dontics, and is a Fellowof the American Col lege of Prostho don -tists. Dr. Oh teaches multiple courses as

a course director and participates in continuing educationcourses on removable prosthodontics. He has researchinterest in prosthodontics and dental materials. He can bereached at [email protected].

Disclosure: Dr. Oh reports no disclosures.

Dr. Park is a professor and assistant deanat the Chonbuk National University Schoolof Den tistry, and a Diplomate of KoreanBoard of Prosthodontics as a boardcertified prosthodontist. Dr. Park serves asa course director for multiple courses on

removable prosthodontics for predoctoral and graduatestudents. She is active with continuing education coursesand research on removable prosthodontics, dental ceramics,color, and dental implants. She can be reached [email protected].

Disclosure: Dr. Park reports no disclosures.

INTRODUCTIONThe posterior extension of a maxillary complete denture(CD) should accommodate the patient’s physiologic andneuromuscular function of the tongue and the palate whileensuring the retention of the prosthesis.1 To comply with thepatient’s function, the posterior end of the denture base

commonly presents a sunken and rolled border of a bead-or butterfly-shaped postpalatal seal, along the vibrating lineof the soft palate.2

A record base is a useful device in transferring theintraoral landmark “vibrating line” to the cast, although a postdam can be established physiologically when making animpression.2-4 This recording device fabricated on the mastercast is carried intraorally to pick up the indelible pencil markof the vibrating line and trimmed to indicate a desiredposterior extension of a maxillary CD. A post dam is carvedon the cast with a variety of shapes and dimensions toconform to the configuration and physiologic movement ofthe palate.2,5 However, this method requires a record base totransfer the vibrating line to the cast, and the functions of thepostpalatal seal cannot be tested in the mouth.

An acrylic base CD is adjustable, including a postpalatalseal;6 however, the denture often experiences a fracturealong the midline, in particular when opposing against thenatural dentition.7 Although an acrylic base can be reinforcedusing a wire,8 sectional metal framework,9 or woven form ofglass-fiber,8 a metal base covering the palate of denturefoundation ensures the structural durability of the dentureand keeps the corresponding mucosa healthy.10 However,the metal base cannot be adjusted along the posteriorextension when indicated.

This article will describe a simple and accurate methodof duplicating the posterior extension of an existing CD, toindicate the posterior extension of a metal base for a newCD, using a silicone duplicate index. The silicone duplicateindex is processed using a silicone bite registration materialagainst a silicone cast for the existing denture and trimmedalong the representation of the denture border. This index isresilient and overcomes the undercuts in the stone cast totransfer the location of posterior extension of the existingdenture. This meth od is simple and precise in formulating apost dam for a metal base, eliminating the necessity ofrecord base to transfer the vibrating line to the cast.

CLINICAL TECHNIQUEEvaluate the fracture pattern and the adequacy of thepostpalatal seal of an existing maxillary acrylic base CDopposing against the natural dentition (Figure 1). Repair the


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Duplicating the PosteriorExtension of an ExistingDentureEffective Date: 9/1/2013 Expiration Date: 9/1/2016

broken CD with an acrylic resin (Jet Denture Repair Acrylic[Lang Dental Man ufacturing Company]) with the aid of asilicone cast of vinyl polysiloxane (VPS) im pression material(Aquasil Universal [DENT SPLY Caulk]) (Figure 2a).11 Setaside the cast for duplicating procedure of the posterior baseextension of the existing denture. Coat the cast with a thin layerof petroleum jelly (Vaseline [Unilever]) and inject a silicone biteregistration material (Blue Bite HP [Henry Schein]) on the in -taglio surface of the denture. Seat the denture against the castso that an excess silicone material extrudes along the borderof the denture (Figure 2b). Do not disturb the setting of thesilicone material interposed between the cast and thedenture. Separate the denture from the cast to isolate theprocessed silicone material. Trim the excess material alongthe imprint of the denture border with a surgical blade (carbonsteel surgical blade No. 25 [Integra Miltex]) (Figure 2c) togenerate a silicone duplicate index of a posterior denture baseextension. Make a final impression of the edentulous maxillaryarch with a VPS impression material (Aquasil LV [DENTSPLYCaulk]) using a border molded custom tray and generate amaster cast in Type IV dental stone (Silky Rock [Whip Mix])for a maxillary metal base conventional CD. Seat the small-diameter implant on the trimmedmaster cast to indicate theposterior base extension of theexisting denture (Figure 2d).Mark the posterior end of theindex and carve a post dam onthe cast as indicated by thesilicone duplicate index with around bur (US No. 6 [BrasselerUSA]) and a wax spatula (7 Wax[Hu-Friedy]) to duplicate theposterior extension of the existingdenture for the fabrication ofmetal base for a new maxillaryCD (Figures 3a to 3c).

DISCUSSIONThe denture base extension isestablished by means of a bordermolding when making a finalimpression for a maxillary CD.

However, the posterior extension of the denture baseshould be determined to be compatible with theneuromuscular function of the soft palate and thetongue.1,3,4 The use of a record base is the most commonmethod of transferring the vibrating line to the castindicating the posterior extension of the denture base.2 Thisprocedure can be carried out when registering themaxilloman dibular relationship record or evaluating the


2


Figure 1. Midline fracture of maxillary acrylic base complete denture(CD) opposing against natural dentition.

a b

c d

Figures 2a to 2d. (a) Repaired denture with aid of silicone cast. (b) Silicone bite registration materialinterposed between denture and silicone cast. (c) Processed silicone duplicate index, demonstratingposterior base extension of existing denture. (d) Silicone duplicate index seated on master cast, indicatingposterior extension of existing denture.

teeth alignment intraorally. A post dam is formulated (alongthe line indicated) by means of the record base, where theposterior extension of the acrylic base for a maxillary CDcan be adjusted, when indicated.5

A master cast for a metal base CD does not require amounting procedure prior to obtaining a cast of the metalbase when the patient presents a sufficient interarchdistance. The metal base is tried-in and fitted in the mouth,and used as a recording device for the registration of themaxillomandibular relationship. However, this methodrequires a precise measurement for the location of thepostpalatal seal, given the incapacity of the metal base tobe adjusted, in particular for the posterior extension of thebase. Meanwhile, an existing denture serves as a referencefor the design of a new denture. The prosthesis can betested intraorally for the adequacy of the postpalatal seal,including the posterior extension of the base.

A maxillary CD of an acrylic base is rigid and cannotseat on the corresponding stone cast of the edentulousmaxillary arch demonstrating undercuts. A silicone biteregistration material presents a dimensional stability andresiliency to overcome the undercuts on the cast. Thesilicone duplicate index is a replica of the extension of theexisting denture and seats on the master cast for a new CDto indicate the posterior extension of the denture tested andproved in the mouth. This duplication procedure is simpleand predictable in maintaining the postpalatal seal and inavoiding the gag reflex.

CONCLUSIONA maxillary metal base CD exhibits rigidity; however, it isvery difficult to adjust; in particular, in the posteriorextension of the base. This method of duplicating theposterior extension of an existing denture proven in themouth is simple, while ensuring an adequate postpalatalseal of a metal-based complete denture.


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a

b

c

Figures 3a to 3c. Metal base maxillary CD, duplicatingposterior extension of existing CD. (a) Metal base cast inchrome-cobalt alloy. (b) Metal base CD processed in acrylicresin. (c) Anterior display of teeth in smile.

REFERENCES1. Narvekar RM, Appelbaum MB. An investigation of the

anatomic position of the posterior palatal seal byultrasound. J Prosthet Dent. 1989;61:331-336.

2. Krysi�ski ZJ, Pryli�ski M. Carving of a master cast toobtain a posterior palatal seal of a complete maxillarydenture as performed by four prosthodontists: a pilotstudy. J Oral Sci. 2007;49:129-132.

3. Ansari IH. Establishing the posterior palatal sealduring the final impression stage. J Prosthet Dent.1997;78:324-326.

4. Rashedi B, Petropoulos VC. Current concepts fordetermining the postpalatal seal in complete dentures.J Prosthodont. 2003;12:265-270.

5. Sykora O, Sutow EJ. Posterior palatal seal adaptation:influence of processing technique, palate shape andimmersion. J Oral Rehabil. 1993;20:19-31.

6. Sato Y, Hosokawa R, Tsuga K, et al. Immediatemaxillary denture base extension for posterior palatalseal. J Prosthet Dent. 2000;83:371-373.

7. Darbar UR, Huggett R, Harrison A. Denture fracture—a survey. Br Dent J. 1994;176:342-345.

8. Narva KK, Vallittu PK, Helenius H, et al. Clinicalsurvey of acrylic resin removable denture repairs withglass-fiber reinforcement. Int J Prosthodont.2001;14:219-224.

9. Lyon HE. Adding a posterior palatal seal to a metal-based prosthesis. Int J Prosthodont. 1989;2:283-284.

10. Perezous LF, Stevenson GC, Flaitz CM, et al. Theeffect of complete dentures with a metal palate oncandida species growth in HIV-infected patients. JProsthodont. 2006;15:306-315.

11. Lee S, Morgano SM. Repair of posterior base of amaxillary complete denture by use of a cast of stone andresilient material. J Prosthet Dent. 1995;74:546-548.


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POST EXAMINATION QUESTIONS

1. The posterior extension of a maxillary completedenture (CD) should accommodate the patient’sphysiologic and neuromuscular function of thetongue and the palate while ensuring the retention of the prosthesis.

a. True b. False

2. A record base is a useful device in transferring theintraoral landmark “vibrating line” to the cast,although a post dam can be establishedphysiologically when making an impression.

a. True b. False

3. An acrylic base CD is adjustable, including apostpalatal seal; however, the denture oftenexperiences a fracture along the midline, in particularwhen opposing against the natural dentition.

a. True b. False

4. This method is complex and time-consuming, but itis precise in formulating a post dam for a metal base,eliminating the necessity of record base to transferthe vibrating line to the cast.

a. True b. False

5. A silicone bite registration material presents adimensional stability and resiliency to overcome theundercuts on the cast.

a. True b. False


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Duplicating the Posterior Extension of an Existing Denture