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The mandibular swing-lock complete denture for patients with microstomia
andibular swing-lock Th with microstomia John
J. Wahle,
DDS,a
L. Kirk
Gardner,
complete DDS,b
and Mark
denture Fiebiger,
for patients
CDT”
University of Connecticut Health Center, School of Dental Medicine, Farmington, Conn., and Medical Collegeof Georgia,School of Dentistry, Augusta, Ga. Regardless of cause, the treatment of an edentulous patient with microstomia is difficult and often ingenious. Prosthodontic treatment modalities previously described are reviewed. A new type of prosthesis, the collapsible mandibular swing-lock complete denture, is introduced. The prosthesis incorporates a cast cobalt-chromium framework with a lingual hinge and a conventional labial swinglock. This combination allows the prosthesis to be collapsible while maintaining structural durability. Advantages include ease of insertion and removal while providing maximum coverage for support, retention, and stability. A stepwise technique for the clinical and laboratory phases is described. (J PROSTHET DENT 1992;68:523-7.)
M.
lcrostomia is often a sequela of scleroderma, postoperative head and neck trauma, and surgical resection of facial and oral neoplasms. Ablative surgery involving the oral cavity often results in a defect larger than one caused by trauma.’ In any of these situations a reduced stoma1 inlet may be the result. Numerous techniques for satisfactory lip repair have been offered in the surgical 1iterature.l.* For the patient who must wear a removable dental prosthesis, the surgical design is most important to minimize the amount of perioral scarring and deformation. Often these patients complain of an inability to insert or remove a denture because of a constricted opening. This difficulty is evident because the smallest diameter of a fully retentive denture may be larger than the greatest diameter of the mouth opening.g For the prosthodontist, the ability to make impressions and jaw records becomes taxing. This article reviews prosthodontic techniques used to make restorations for the edentulous patient with microstomia and to introduce a new type of prosthesis for these patients.
LITERATURE
REVIEW
A review of the dental literature reveals that there are not many complete denture techniques available to make satisfactory restorations for a patients with a limited oral opening. Lee,l” L’Estrange and Warner,11,12 Watson and Treacher,13 and Walter14 have all discussed two-part removable partial dentures; however, none of these prostheses collapse to aid the patient with microstomia. Corso and Schachter15 described a one-piece prosthesis that had
aAssistantProfessor,Department of Prosthodontics,
University of Connecticut School of Dental Medicine. bAssociate Professor, Department of Prosthodontics, Medical College of Georgia,School of Dentistry. CDental Lab Technician, Medical College of Georgia, School of Dentistry. 10/l/38772
THE
JOURNAL
OF PROSTHETIC
DENTISTRY
a pliable silicone union permanently attached between two halves of a maxillary denture. The denture folds onto itself for insertion and removal. Although this technique solved the initial insertion problem, no long-term follow-up of the silicone-acrylic resin joint was shown. Naylor and Manori introduced a one-piece flexible mandibular “exercise prosthesis” that was to be used as an interim prosthesis until an increased opening was available for denture construction. Again this prosthesis folded onto itself for insertion but was not designed as a functional denture. In a series of reports, Lantz17-lg presented a brief description of split dentures with hinges, hasps, and/or locks. Each denture was inserted in sections, which were then joined as one prosthesis intraorally. The maxillary dentures had cast metal frameworks to give structural durability to the sectional components. The simplified hingelock assembly used to join the mandibular sectional dentures did not appear to impart structural durability or maintain uniform support and stability while the denture was in function. However, it did enhance the ease of insertion and removal. Similarly, Sega12*described a technique in which a nonresilient Rotherman (Cendres and Metaux SA distributed by Attachments International, San Mateo, Calif.) or an Ackerman bar and clip attachment (Cendres and Metaux SA) was soldered to a cast framework to fabricate a simplified maxillary split denture. The advantage here was the use of existing standard attachments. Conroy and Reitzikg and Winkler et a1.21described procedural techniques for complete denture construction for patients with microstomia. Each technique advocated the use of cast cobalt-chromium frameworks with clasps to hold the sectional dentures together. The removable partial frameworks acted as partial overlays with the clasps engaging in a prescribed amount of undercut placed on the denture tooth. In addition to the frameworks, Conroy and Reitzikg placed hinges in the midline of both prostheses. Both
techniques
appear
to offer
a durable
and stable
pros-
523
WAHLE,
Fig. 1. Prosthesis locked in position, mm at greatest width.
approximately
Fig, 2. Prosthesis in collapsed position, approximately mm at greatest width.
75
60
thesis. No mention was made of the amount of occlusal force that may be generated to the dentures before the acrylic resin disengages from the clasp assembly. Insufficient undercut on the resin tooth may dislodge the resin base during function, whereas excess undercut may make it difficult for the patient to assemble and disassemble the prosthesis intraorally. Gay and Ken@ designed a tripartite prosthesis for patients with scleroderma. The maxillary denture was initially fabricated and divided into two equal parts. Each part had two Zest semiprecision attachments (Paul Zest Co., Escondido, Calif.) placed in the palatal section. An acrylic resin bridge or palate with four corresponding Zest attachments was then fabricated. The two denture halves were joined intraorally for a stable denture by the acrylic resin palate. This technique may restrict tongue space. Recently McCord et a1.23introduced a sectional complete denture for the maxillary arch that offered stability with-
524
Fig.
GARDNER,
AND
FKEBIGER
3. Sectional master impression.
out restricting tongue space. This technique included two denture halves joined by a post that slides into stainless steel tubing, which is aligned in the denture halves. The post is attached to a central incisor, which then acts as a handle for joining and separating the denture. Jaggers and Boydz4 introduced a technique to fabricate a hinged maxillary denture to properly place buccolabial flanges into deep hard tissue undercuts. Although they did not mention the type of hinge and latch assembly used, it appears to be similar to the swing-lock mechanism credited to Simmonsz5 but first described by Ackermanz6 The Swing-lock (Idea Development Co., Dallas, Tex.) prosthesis consists of a hinged buccal or labial bar attached to a conventional major connector.s5, 27,28 Swing-lock removable partial dentures have been noted to have a wide variety of applications. Among these are patients with minimal or mobile teeth, unilateral abutments, tilted or irregular abutments, cleft palates, posttrauma and postcancer treatments, and patients requiring lip and facial recontouring. 25,27,29-34 The following application of the swing-lock concept has not been previously described. This technique incorporates a cast swing-lock framework into a mandibular complete denture to make it collapsible for ease of insertion and removal (Figs. 1 and 2).
TECHNIQUE 1. Make an irreversible hydrocolloid impression of the mandibular arch with a modified stock impression tray. Pour in artifical stone. 2. Fabricate a sectional custom tray as advocated by Luebke.35 3. Clinically verify the length of the tray borders of each section and as a unit, making any corrections required. In a stepwise manner, border mold the first half of the sectional custom tray with modeling compound. Once completed, leave in place and complete border molding for the second half of the tray, making sure to cor-
SEPTEMBER
1992
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THE
>MAiVJIRULAR
SWING-LOCK
COMPLETE
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Fig. 4. Framework wax-up of lingual hinge.
rectly lock the sections together for proper orientation. It is of particular importance to accurately register the activated labial vestibule and frenum areas for positioning of the labial bar.27,%J36 4. Make a master impression with a material of choice. Make one section first, remove, and neatly trim along its midline border to allow complete seating of the second section. Apply petroleum jelly to the cut surface. When making the master impression of the second section, see that the sectional tray is properly locked together as a unit. Disassemble and remove as two separate sections (Fig. 3). 5. After removing and securing the impressions together, bead and box the impression. Pour with a vacuum mix of improved dental stone. 6. Fabricate one stone duplicate master cast in addition to tbe original master cast. 7. Make three refractory casts with 24-gauge blockout over the crest of the ridge and 2%gauge blockout lateral to the ridge in the hinge and lock areas. 8. Fabricate the Swing-Lock removable partial denture (RPD) framework in the following sequence: A. Using the first refractory cast, wax the first section of the framework. Place a hinge cylinder (Idea Development Co.) on the lingual plate at the midline. Place a lock mechanism (Idea Development Co.) in the labial vestibule for reception of the labial swing-lock bar. Invest, cast and desprue. B. Place the completed portion of the framework on a second refractory cast. The second section of the framework is waxed to articulate with the precast hinge on the lingual surface. A new hinge cylinder (Idea Development Co) is waxed in the labial vestibule for acceptance of the labial bar (Fig. 4). The second section is invested, cast, and desprued. At this point a working verification of the lingual hinge is possible. C. Return the two-part casting to the third refractory
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Fig. 5. Cast framework in locked position.
Fig. 6. Verification of lingual hinge and labial bar opening. cast and wax a labial bar from the hinge to the lock. This waxed bar is invested, cast, and desprued. All sections of the framework are finished, polished, and returned to the master cast. Both hinges and the labial lock mechanism are evaluated for proper working functions (Figs. 5 and 6). 10. Process a clear acrylic resin trial base on one side of the framework. After finishing, place a tinfoil sheet over the midline before processing the second half to ensure a clean junction of the two halves. Verify that both the hinges and lock operate properly before placing a wax rim. Split the wax rim in the midline to allow for opening and closing of the trial base. 11. Proceed with jaw relation records and wax try-in. 12. Wax denture to final contours. 13. So that each section may be processed separately, make an occlusal index of the mandibular arch. Remove the teeth and wax from one section, and flask and process the opposite section. Recover from the cast and polish, Place the finished section with associated
Fig.
14. 15.
16.
17.
18. 19.
7. Patient
inserting
collapsed prosthesis.
framework on a duplicate master cast and wax teeth to place for the contralateral side using the occlusal index. Process as before with tinfoil sheet over the midline. (If heat-processed trial bases were made, master casts are not needed for this step.) Remount the completed prosthesis to correct for occlusal processing errors. Recover the prosthesis from cast, trim, and polish. Verify that both hinges and lock mechanisms are free of resin. At the delivery appointment, verify tissue adaptation and remount the complete prosthesis clinically to refine the occlusion. Instruct the patient in the operation of the lock and binge assembly. The mandi.bular denture should be collapsed about the midline hinge and inserted (Fig. 7). Once the prosthesis is in place, the tongue may be used as an aid to push the denture back to its original shape. Only after the prosthesis has been properly seated should the labial bar be locked in place (Fig. 8). For easy opening of the lock mechanism, construct a key with a paper clip and autopolymerizing resin. Develop an adequate recall system.
DISCUSSION Microstomia is a common postoperative complication of head and neck trauma, scleroderma, and resection of facial and oral neoplasms. For the edentulous patient, insertion and removal of maxillary and mandibular dentures can be difficult if not impossible. Incorporating the swing-lock partial framework design into a denture eliminates the sectional parts, as well as the potential shortcomings of previously described techniques. Among the advantages of this technique are (1) ease of insertion and removal of the mandibular denture without straining the oral opening, (2) structural durability of the prosthesis for continued opening and closing, (3) coverage of maximal area for support, retention, and stability, (4) ease of home care of the pros-
526
Fig.
8. Prosthesis seated and properly
locked.
thesis, and (5) ability to reline the denture chairside with a visible-light cure resin. The disadvantages include (1) increased laboratory work by the technician to make a threepart cast framework and (2) two-part processing of the acrylic resin. A laboratory reline or rebase would require two-part processing also. These disadvantages make the prosthesis more expensive to fabricate but do not increase the number of patient appointments.
SUMMARY This article reviews reported methods used to.make complete denture prostheses for the patient with microstomia. A new dental prosthesis, the collapsible mandibular swing-lock complete denture, is offered as an alternative to other published techniques. This technique is based on previously described and accepted complete denture and removable partial denture designs and techniques. Laboratory technicians familiar with swing-lock partial dentures should have minimal problems constructing this framework. As long as the vestibule is properly recorded, patients should be quite responsive to accepting this prosthesis.
REFERENCES 1. Smith PG, Muntz HR, Thawley SE. Local myocutaneus advancement flaps. Arch Otolaryngol 1982;108:714-8. 2. Taliacotius G. De curtorum. chirurgia per iinsitionem. Venici: G. Bindoni, 1597: plates XVII-XX. 3. Estlander JA. Methode d’outplastie de la jove ou d’une levre par un lambeau emprunte a la autre levre. Rev Mens Med Chir 1877;1:344-51. 4. Abbe R. A new plastic operation for the relief of deformity due to double harelip. Med Ret 1898;53:477-81. 5. Webster RC, Coffey RJ, Kelleher RE. Total and partial reconstruction of the lower lip with innervated muscle bearing flaps. Plast Reconstr Surg 1960;25:360-71. 6. McGregor IA. The tongue flaps in lip surgery. Br J Plast Surg 1966;19:253-63. 7. Karapandzic M. Reconstruction of lip defects by local arterial flaps. Br J Plast Surg 1974;27:93-7. 8. McHugh M. Reconstruction of the lower lip using a neurovascular island flap. Br J Plast Surg 1977;30:316-8. 9. Conroy B, Reitzik M. Prosthetic restoration in microstomia. J PROSTHET DENT 1971:26:324-‘7.
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10. Lee JH. Sectional partial dentures incorporating an internal locking bolt. d PROSTHET DEP;T 1963;13:1067-75. 11. L’Estrange PR, Warner EP. Sectional dentures-a simplified method of attachment. Dent Pratt Dent Ret 1969,19:379-81. 12. LEstrange PR, Warner EP. Sectional dentures-aids to removal and adjustment. Dent Pratt Dent Ret 1969;20:135-8. 13. Watson RM, Treacher FG. Two part dentures with precision attachments. Br Dent J 1972;132:287-8. 14. Walter JD. Anchor attachments used as locking devices in two-part removable prostheses. J PROSTHET DENT 19?5;33:628-32. 15. Corso PF, Schachter A. Making a folded denture or intraoral prosthesis for insertion into a small mouth. Plast Reconstr Surg 1973;52:94-5. 16. Naylor WP, Manor RC. Fabrication of a flexible prosthesis for the edentulous scleroderma patient with microstomia. J PROSTHET DENT 1983;50:636-8.
11. Lantz HJ. Scleroderma associated with Raynaud’s disease. J Oral Med 1967;22:103-7. 18. Lams HJ. Scar tissue-a factor in complete denture service. Bull Philadelphia County Dent Sot 1973;38:8-I 3. 19. Lantz HJ. Childhood neglect: an adult dilemma. Bull Philadelphia County Dent Sot 1975;40:6-12. 20. Segal AG. A simplified split-denture technique. QDT Yearbook 1988;12:65-7. 21. Winkler S, Wongthai P, Wazney JT. An improved split denture technique. J PROSTHET DENT 1984;51:276-9. 22. Gay WD, Kent MD. Manego protesico de un paciente con esclerodermia: reporte de un case. Quintaesencia Espanol 1981;3:215-9. 23. McCord JF, Tyson KW, Blair IS. A sectional complete denture for a patient with microstomia. J PROSTHET DENT 1989;61:645-7. 24. Jaggers JH, Boyd M. Bilaterally hinged complete denture for a severely undercut maxillary arch. Solution to a problem. J PROSTHET DENT 1979;41:373-6.
25. Simmons JJ. Swinglock stabilization and retention. Texas Dent J 1963;81:10-12. 26. Ackerman AJ. The prosthetic management of oral and facial defects following cancer surgery. J PROSTHET DENT 1955;5:413-32.
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27. Stewart KL, Rudd KD, Kuebker WA. Clinical removable partial prosthodontics. 2nd ed. St. Louis: Ishiyaku EuroAmerica Inc, 1988:593-607. 28. Rudd KD, Morrow RM, Rhoads JE. Dental laboratory procedures-removal partial dentures. vol. 3. 2nd ed. St. Louis: CV Mosby, 19X6:50134.
29. Swing-Lock Clinical manual. Dallas: Swing-Lock, Division of Idea Development Co, 1969. 30. Sprigg RH. Six-year clinical evaluation of the Swing-Lock removable partial denture. Anglo-Continental Dent Sot J 1971;15-27. 31. Fiebiger GE, Rahn AO, Lundquist DO, Morse RX. Movement of abutments by removable partial denture frameworks with a hemimaxillectomy obturator. J PROSTHET DENT 1975;34:555-61. 32. Amos EW, Renner RP, Foerth D. The Swing-Lock partial denture: an alternative approach to conventional removable partial denture service. J P~o~~~~~D~~~1978;40:257-62. 33. Schulte JK, Smith DE. Clinical evaluation of swinglock removable partial dentures. J PROSTHET DENT 1980;44:559-603. 34. Games BC, Renner RP, Amos EW, Baer PN, Carlson M. A clinical study of the periodontal status of abutment teeth supporting swinglock removable partial dentures-a pilot study. J PROSTHET DENT 1981; 46:1-7.
35. Luebke RJ. Sectional impression tray for patients with constricted oral 0pening.J PROSTHETDENT 1984;52:135-7. 36. Swing-Lock Impression Technique Folder. Dallas: Swing-Lock, Division of Idea Development Co, 1969.
Reprint requests to: DR.JoHNJ. WAHLE DEPARTMENT OF PROSTHODONTICS, L6100 UNIVERSITY OF CONNECTICUT HEALTH CENTER, SCHOOL OF DENTAL MEDICINE FARMINGTON,CTO~O~O
527
J. Wahle,
DDS,a
L. Kirk
Gardner,
complete DDS,b
and Mark
denture Fiebiger,
for patients
CDT”
University of Connecticut Health Center, School of Dental Medicine, Farmington, Conn., and Medical Collegeof Georgia,School of Dentistry, Augusta, Ga. Regardless of cause, the treatment of an edentulous patient with microstomia is difficult and often ingenious. Prosthodontic treatment modalities previously described are reviewed. A new type of prosthesis, the collapsible mandibular swing-lock complete denture, is introduced. The prosthesis incorporates a cast cobalt-chromium framework with a lingual hinge and a conventional labial swinglock. This combination allows the prosthesis to be collapsible while maintaining structural durability. Advantages include ease of insertion and removal while providing maximum coverage for support, retention, and stability. A stepwise technique for the clinical and laboratory phases is described. (J PROSTHET DENT 1992;68:523-7.)
M.
lcrostomia is often a sequela of scleroderma, postoperative head and neck trauma, and surgical resection of facial and oral neoplasms. Ablative surgery involving the oral cavity often results in a defect larger than one caused by trauma.’ In any of these situations a reduced stoma1 inlet may be the result. Numerous techniques for satisfactory lip repair have been offered in the surgical 1iterature.l.* For the patient who must wear a removable dental prosthesis, the surgical design is most important to minimize the amount of perioral scarring and deformation. Often these patients complain of an inability to insert or remove a denture because of a constricted opening. This difficulty is evident because the smallest diameter of a fully retentive denture may be larger than the greatest diameter of the mouth opening.g For the prosthodontist, the ability to make impressions and jaw records becomes taxing. This article reviews prosthodontic techniques used to make restorations for the edentulous patient with microstomia and to introduce a new type of prosthesis for these patients.
LITERATURE
REVIEW
A review of the dental literature reveals that there are not many complete denture techniques available to make satisfactory restorations for a patients with a limited oral opening. Lee,l” L’Estrange and Warner,11,12 Watson and Treacher,13 and Walter14 have all discussed two-part removable partial dentures; however, none of these prostheses collapse to aid the patient with microstomia. Corso and Schachter15 described a one-piece prosthesis that had
aAssistantProfessor,Department of Prosthodontics,
University of Connecticut School of Dental Medicine. bAssociate Professor, Department of Prosthodontics, Medical College of Georgia,School of Dentistry. CDental Lab Technician, Medical College of Georgia, School of Dentistry. 10/l/38772
THE
JOURNAL
OF PROSTHETIC
DENTISTRY
a pliable silicone union permanently attached between two halves of a maxillary denture. The denture folds onto itself for insertion and removal. Although this technique solved the initial insertion problem, no long-term follow-up of the silicone-acrylic resin joint was shown. Naylor and Manori introduced a one-piece flexible mandibular “exercise prosthesis” that was to be used as an interim prosthesis until an increased opening was available for denture construction. Again this prosthesis folded onto itself for insertion but was not designed as a functional denture. In a series of reports, Lantz17-lg presented a brief description of split dentures with hinges, hasps, and/or locks. Each denture was inserted in sections, which were then joined as one prosthesis intraorally. The maxillary dentures had cast metal frameworks to give structural durability to the sectional components. The simplified hingelock assembly used to join the mandibular sectional dentures did not appear to impart structural durability or maintain uniform support and stability while the denture was in function. However, it did enhance the ease of insertion and removal. Similarly, Sega12*described a technique in which a nonresilient Rotherman (Cendres and Metaux SA distributed by Attachments International, San Mateo, Calif.) or an Ackerman bar and clip attachment (Cendres and Metaux SA) was soldered to a cast framework to fabricate a simplified maxillary split denture. The advantage here was the use of existing standard attachments. Conroy and Reitzikg and Winkler et a1.21described procedural techniques for complete denture construction for patients with microstomia. Each technique advocated the use of cast cobalt-chromium frameworks with clasps to hold the sectional dentures together. The removable partial frameworks acted as partial overlays with the clasps engaging in a prescribed amount of undercut placed on the denture tooth. In addition to the frameworks, Conroy and Reitzikg placed hinges in the midline of both prostheses. Both
techniques
appear
to offer
a durable
and stable
pros-
523
WAHLE,
Fig. 1. Prosthesis locked in position, mm at greatest width.
approximately
Fig, 2. Prosthesis in collapsed position, approximately mm at greatest width.
75
60
thesis. No mention was made of the amount of occlusal force that may be generated to the dentures before the acrylic resin disengages from the clasp assembly. Insufficient undercut on the resin tooth may dislodge the resin base during function, whereas excess undercut may make it difficult for the patient to assemble and disassemble the prosthesis intraorally. Gay and Ken@ designed a tripartite prosthesis for patients with scleroderma. The maxillary denture was initially fabricated and divided into two equal parts. Each part had two Zest semiprecision attachments (Paul Zest Co., Escondido, Calif.) placed in the palatal section. An acrylic resin bridge or palate with four corresponding Zest attachments was then fabricated. The two denture halves were joined intraorally for a stable denture by the acrylic resin palate. This technique may restrict tongue space. Recently McCord et a1.23introduced a sectional complete denture for the maxillary arch that offered stability with-
524
Fig.
GARDNER,
AND
FKEBIGER
3. Sectional master impression.
out restricting tongue space. This technique included two denture halves joined by a post that slides into stainless steel tubing, which is aligned in the denture halves. The post is attached to a central incisor, which then acts as a handle for joining and separating the denture. Jaggers and Boydz4 introduced a technique to fabricate a hinged maxillary denture to properly place buccolabial flanges into deep hard tissue undercuts. Although they did not mention the type of hinge and latch assembly used, it appears to be similar to the swing-lock mechanism credited to Simmonsz5 but first described by Ackermanz6 The Swing-lock (Idea Development Co., Dallas, Tex.) prosthesis consists of a hinged buccal or labial bar attached to a conventional major connector.s5, 27,28 Swing-lock removable partial dentures have been noted to have a wide variety of applications. Among these are patients with minimal or mobile teeth, unilateral abutments, tilted or irregular abutments, cleft palates, posttrauma and postcancer treatments, and patients requiring lip and facial recontouring. 25,27,29-34 The following application of the swing-lock concept has not been previously described. This technique incorporates a cast swing-lock framework into a mandibular complete denture to make it collapsible for ease of insertion and removal (Figs. 1 and 2).
TECHNIQUE 1. Make an irreversible hydrocolloid impression of the mandibular arch with a modified stock impression tray. Pour in artifical stone. 2. Fabricate a sectional custom tray as advocated by Luebke.35 3. Clinically verify the length of the tray borders of each section and as a unit, making any corrections required. In a stepwise manner, border mold the first half of the sectional custom tray with modeling compound. Once completed, leave in place and complete border molding for the second half of the tray, making sure to cor-
SEPTEMBER
1992
VOLUME
68
NUMBER
3
THE
>MAiVJIRULAR
SWING-LOCK
COMPLETE
DENTURE
Fig. 4. Framework wax-up of lingual hinge.
rectly lock the sections together for proper orientation. It is of particular importance to accurately register the activated labial vestibule and frenum areas for positioning of the labial bar.27,%J36 4. Make a master impression with a material of choice. Make one section first, remove, and neatly trim along its midline border to allow complete seating of the second section. Apply petroleum jelly to the cut surface. When making the master impression of the second section, see that the sectional tray is properly locked together as a unit. Disassemble and remove as two separate sections (Fig. 3). 5. After removing and securing the impressions together, bead and box the impression. Pour with a vacuum mix of improved dental stone. 6. Fabricate one stone duplicate master cast in addition to tbe original master cast. 7. Make three refractory casts with 24-gauge blockout over the crest of the ridge and 2%gauge blockout lateral to the ridge in the hinge and lock areas. 8. Fabricate the Swing-Lock removable partial denture (RPD) framework in the following sequence: A. Using the first refractory cast, wax the first section of the framework. Place a hinge cylinder (Idea Development Co.) on the lingual plate at the midline. Place a lock mechanism (Idea Development Co.) in the labial vestibule for reception of the labial swing-lock bar. Invest, cast and desprue. B. Place the completed portion of the framework on a second refractory cast. The second section of the framework is waxed to articulate with the precast hinge on the lingual surface. A new hinge cylinder (Idea Development Co) is waxed in the labial vestibule for acceptance of the labial bar (Fig. 4). The second section is invested, cast, and desprued. At this point a working verification of the lingual hinge is possible. C. Return the two-part casting to the third refractory
THE
JOURNAL
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DENTISTRY
Fig. 5. Cast framework in locked position.
Fig. 6. Verification of lingual hinge and labial bar opening. cast and wax a labial bar from the hinge to the lock. This waxed bar is invested, cast, and desprued. All sections of the framework are finished, polished, and returned to the master cast. Both hinges and the labial lock mechanism are evaluated for proper working functions (Figs. 5 and 6). 10. Process a clear acrylic resin trial base on one side of the framework. After finishing, place a tinfoil sheet over the midline before processing the second half to ensure a clean junction of the two halves. Verify that both the hinges and lock operate properly before placing a wax rim. Split the wax rim in the midline to allow for opening and closing of the trial base. 11. Proceed with jaw relation records and wax try-in. 12. Wax denture to final contours. 13. So that each section may be processed separately, make an occlusal index of the mandibular arch. Remove the teeth and wax from one section, and flask and process the opposite section. Recover from the cast and polish, Place the finished section with associated
Fig.
14. 15.
16.
17.
18. 19.
7. Patient
inserting
collapsed prosthesis.
framework on a duplicate master cast and wax teeth to place for the contralateral side using the occlusal index. Process as before with tinfoil sheet over the midline. (If heat-processed trial bases were made, master casts are not needed for this step.) Remount the completed prosthesis to correct for occlusal processing errors. Recover the prosthesis from cast, trim, and polish. Verify that both hinges and lock mechanisms are free of resin. At the delivery appointment, verify tissue adaptation and remount the complete prosthesis clinically to refine the occlusion. Instruct the patient in the operation of the lock and binge assembly. The mandi.bular denture should be collapsed about the midline hinge and inserted (Fig. 7). Once the prosthesis is in place, the tongue may be used as an aid to push the denture back to its original shape. Only after the prosthesis has been properly seated should the labial bar be locked in place (Fig. 8). For easy opening of the lock mechanism, construct a key with a paper clip and autopolymerizing resin. Develop an adequate recall system.
DISCUSSION Microstomia is a common postoperative complication of head and neck trauma, scleroderma, and resection of facial and oral neoplasms. For the edentulous patient, insertion and removal of maxillary and mandibular dentures can be difficult if not impossible. Incorporating the swing-lock partial framework design into a denture eliminates the sectional parts, as well as the potential shortcomings of previously described techniques. Among the advantages of this technique are (1) ease of insertion and removal of the mandibular denture without straining the oral opening, (2) structural durability of the prosthesis for continued opening and closing, (3) coverage of maximal area for support, retention, and stability, (4) ease of home care of the pros-
526
Fig.
8. Prosthesis seated and properly
locked.
thesis, and (5) ability to reline the denture chairside with a visible-light cure resin. The disadvantages include (1) increased laboratory work by the technician to make a threepart cast framework and (2) two-part processing of the acrylic resin. A laboratory reline or rebase would require two-part processing also. These disadvantages make the prosthesis more expensive to fabricate but do not increase the number of patient appointments.
SUMMARY This article reviews reported methods used to.make complete denture prostheses for the patient with microstomia. A new dental prosthesis, the collapsible mandibular swing-lock complete denture, is offered as an alternative to other published techniques. This technique is based on previously described and accepted complete denture and removable partial denture designs and techniques. Laboratory technicians familiar with swing-lock partial dentures should have minimal problems constructing this framework. As long as the vestibule is properly recorded, patients should be quite responsive to accepting this prosthesis.
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1992
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68
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3
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27. Stewart KL, Rudd KD, Kuebker WA. Clinical removable partial prosthodontics. 2nd ed. St. Louis: Ishiyaku EuroAmerica Inc, 1988:593-607. 28. Rudd KD, Morrow RM, Rhoads JE. Dental laboratory procedures-removal partial dentures. vol. 3. 2nd ed. St. Louis: CV Mosby, 19X6:50134.
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Reprint requests to: DR.JoHNJ. WAHLE DEPARTMENT OF PROSTHODONTICS, L6100 UNIVERSITY OF CONNECTICUT HEALTH CENTER, SCHOOL OF DENTAL MEDICINE FARMINGTON,CTO~O~O
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