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Adult palatal expansion prostheses
Adult palatal expansion prostheses J. S. Brudvik, University
D.D.S.,*
and Donald R. Nelson, D.D.S. **
of Washington, School of Dentistry,
Seattle, Wash., and San Antonio, Tex.
lhl e ast d eta dhe as witnessed a minor revolution in the surgical intervention of a great variety of craniofacial anomalies which offer hope to the cleft palate patient with a collapsed maxilla. The prosthodontist can make a significant contribution to the final result by the design and fabrication of palatal expansion devices. Dental and medical literature contain references to infantile and adolescent expansion devices. Their use in the adult patient is complicated by the degree of control necessary to reposition the maxillary segments to an exact, preplanned position and the byforce necessary to move the segments. Controlled repositioning can greatly reduce the occlusal morbidity and the need for extensive, postoperative occlusal rehabilitation.
INDICATIONS Adult palatal expansion is indicated in a variety of cleft palate patients where juvenile management of the premaxillary area has resulted in a collapsed arch. Certain craniofacial anomalies can also result in a constricted maxillary arch. Many of the clefts do not have a normal suture between the maxillae. Expansion of these maxillae can be quite rapid. When a normal bony suture exists, the force required to expand the arch greatly increases with the possibility of uncontrolled tooth and segment movement.
OBJECTIVES The expansion device used in the adult is cast in a removable partial denture alloy and utilizes a stan-
Presented at the American Academy of Maxillofacial Prosthetics, Las Vegas, Nev. The authors developed these devices while on duty with U.S. Army Dental Corps at the Regional Dental Activity, Fort Sam Houston, Tex. *Associate Professor, Department of Prosthodontics. **Commander, Regional Dental Activities, Fort Sam Houston.
THE JOURNAL
OF PROSTHETIC
DENTISTRY
dard expansion screw for movement. Certain types incorporate a hinge mechanism to control movement. The prosthesis is either ligated to the maxillary teeth or, when cap splint retainers are used, “cemented” to them with autopolymerizing acrylic resin. Expansion is accomplished by programmed daily manipulation of the expansion screw, usually by the oral surgeon, until the desired increase in arch width is achieved. Palatal expansion prostheses fall into two general categories: (1) those requiring uniform bilateral horizontal expansion and (2) those that need an anterior element of expansion with little or none in the posterior. It is conceivable that unilateral palatal expansion will be indicated occasionally, but the complexity of stabilizing one segment while moving the other with the expansion prostheses presented in this article has not as yet been feasible.
TECHNIQUE The treatment begins with an impression for the pre-operative cast, which is poured in improved dental stone. The accuracy of duplicating the palatal tissues and teeth is paramount, so a well-fitting tray is indicated with no attempt to “overseat” the impression. Labial soft tissue contours are not involved with the prosthesis, so the impression need only be extended to include all the clinical crowns of the teeth. This is significant when scar tissue is present in the lip and/or cheek which might prevent the establishment of normal contours of the cast. Duplicates of the master cast are made, and the desired amount and direction of the expansion is established, preferably using a team approach by surgeon and prosthodontist.
STABILIZATION When little when no bony the prosthesis the remaining
CONSIDERATIONS
resistance to expansion is expected, or union and no dense scar tissue exist, contacts only the lingual surfaces of teeth and is wired in place.
315
BRUDVIK
Fig. 1. Cleft palate expansion splint retainer and spring-loaded
prosthesis expander.
utilizes
AND
NELSON
cap
Fig. 3. Completion of wax-up for substructure of expander showing main sprue lead through refractory cast. In cases where considerable force will be required to expand the bony suture and/or scar tissue, it is advisable to utilize a cap splint configuration to ensure complete control of the bony segments (Fig. 1). T&se decisions and the amount and direction of expansion are mandatory before construction begins.
CONSTRUCTION OF BILATERALLY UNIFORM EXPANDER UTILIZING LINGUAL TOOTH CONTACT AND LIGATION
Fig. 2. Refractory cast with maximum size expander that can be accommodated. Round blebs lingual to teeth are foundation for forming holes for ligature wires. This provision saves considerable effort in drilling the holes through casting. 316
1. The design is transferred to the master cast. A standard O-degree blockout is used to eliminate infrabulge areas on the maxillary teeth. Small balls of wax are placed over the sites where the plate will be perforated to wire the prosthesis to the teeth (Fig. 2). 2. The duplication techniques used are those recommended by the manufacturer of the specific alloy to be used. A refractory cast is poured in artificial stone. 3. When the refractory cast has been sealed with ’ either wax or plastic spray, the design is transferred to the cast, and the wax-up is performed. MARCH
1981
VOLUME
45
NUMBER
3
ADULT
PALATAL
EXPANSION
PROSTHESES
Fig. 4. Rough casting indicating form of cradle for expander.
sprue placement
and
4. Small amounts of wax are placed on prominent contours to preclude thin areas that might result from stretching the plastic sheet during its placement. 5. A plastic sheet, usually 24-gauge, is applied over a layer of “tacky” adhesive (Fig. 3). 6. The preselected expander is placed on the wax-up, and its final position is established. The device is lubricated and positioned so that the opening of the screw occurs in a movement from anterior to posterior. This allows visual access to the placement of the screw key. 7. A wax cradle is created for the expander by flowing wax under its base. When the palatal side is completely covered, the expander is removed. Wax is then added to create smooth contours joining the cradle to the waxed-up lingual flange of the prosthesis. 8. The expander is returned to the wax cradle, and a ledge of wax 1 to 1% mm is added to the edges of the cradle. This ledge serves as a soldering base for joining the expander to the casting.
Fig. 5. Completed expansion prostheses with separation of substructure at midline. Solder attachment can be seen wrapped around expander housing. Moving components should be completely free of solder.
9. The wax and plastic sheet are removed from the wire retention holes with a hot, sharply pointed instrument. 10. The completed wax-up is sprued by adding large sprue leads to the palatal side of the cradle and joining them to the sprue hole in a conventional manner. 11. The wax-up is invested and cast in the same manner as a removable partial denture casting (Fig. 4). 12. The casting is recovered, finished, and seated on the master cast. The segments are treated as individual units and should be tried in the mouth to assure a satisfactory fit at the time of the surgical procedure. 13. The expander is fitted to the casting and soldered into place using electrosoldering techniques common to removable partial denture laboratories and technicians. Precious metal solder such as Ticonium* triple thick or nonprecious Ni-Ci brazing *Ticonium
Co., Albany,
NY. 317
THE JOURNAL
OF PROSTHETIC
DENTISTRY
BRUDVIK
AND
NELSON
Casting I
Fig. 6. Diagramatic sketch of hinge mechanism. Casting 1 (attached to one side of the substructure) is female portion of hinge, consisting of barrel shape with flat top and bottom. Dotted Iines indicate half-round recesses. Overall size of hinge depends on available space.
Fig. 7. Completed expander showing hinge in open position. Expander has been soldered to casting 1.
alloys can be used with equal success, depending on the experience of the technician. 14. The solder is built up along the ledge of the cradle and moved up into the grooves of the expander with the carbon tip of the electrosoldering machine. The solder need not cover the entire expander, but it should cover at least 3 mm of the border. 15. Care must be used so that no solder flows into the screw mechanism of the expander. Some additional finishing and rubber wheeling is usually necessary before the expander is ready to be tried in the patient (Fig. 5).
CAP SPLINTS The cap splint varies only in its contour and the waxing technique used to create it. 1. The teeth on the master cast are blocked out at O-degree to relieve both facial and lingual coronal
318
Fig. 8. Expander in closed position while hinge is opt n to approximate desired postoperative dimension. Di tance expander must travel to achieve needed expansic n can be estimated. It is quite possible that maximu n expander travel will not be sufficient. In such instance ;, autopolymerizing acrylic resin can be placed under co‘ ered contact area to effectively move contact area closer D midline and thereby increase potential expansion.
undercuts and to create space for the cemz nting medium, usually autopolymerizing resin. 2. Thermoplastic, vacuum-adapted resin c Iping material can be used to create a uniform ba e for waxing. 3. The refractory cast should be articulat :d so that occlusal contacts which might increas : the vertical dimension of occlusion can be iden ified. The gauge of coping material is related to the alloy to be used. Thin-gauge sheets are used wit 1 the higher heat alloys. The thermoplastic skeet is vacuum-formed over the entire refractory c 1st and then trimmed to the gingival contours. 4. The remainder of the wax-up is identi :a1 to the wire-retained expander.
ROTATION-EXPANSION
PROSTHESI i
When the anterior maxilla requires i greater degree of expansion than the posterior, thf addition
MARCH
1981
VOLUME
5
NUMBER
3
ADULT
PALATAL
EXPANSION
PROSTHESES
Fig. 11. Palatal side of prosthesis postoperatively ing acrylic resin cementing material in place.
show-
Fig. 9. Expander passes just under covered contact area. Inner surface of contact area is concave so that edge of expander will track smoothly during expansion.
Fig. 12. Adult palatal expander ligated and cemented in place before expansion is started.
Fig. 10. Expansion prosthesis in its fully closed position as it would look at time of insertion.
of a hinge mechanism is included as an integral component of the expander. The construction of the hinge mechanism depends on the ability of chromebased alloy to be cast against itself and not bond, remaining separated by the oxide layer that forms during burnout. The hinge consists of (1) a female (receptacle) portion waxed as a component of the half of the expander that will retain the expansion screw and be cast first and (2) a male (attachment) portion, part of
THE IOURNAL
OF PROSTHETIC
DENTISTRY
Fig. 13. Expansion prosthesis, fully expanded to desired postoperative width, at time of removal. As evidenced by soft tissue visible in anterior, midline tissues are left intact after expansion.
319
BRUDVIK
the second half of the casting, which will be cast against the invested first half. The end result will be a hinge separated only by the thickness of the oxide (Fig. 6). The expansion screw on the hinged expander cannot be fixed at both ends since expansion will be on an arc from the hinge. A covered contact area with a curved inner surface is waxed in the second half of the prosthesis. The curved contact area allows the free end of the expansion screw to slip along its surface as the prosthesis expands. The “cover” is simply a guide to control the movement and maintain it in one plane (Fig. 7).
CONSTRUCTION
OF HINGE
1. The receptacle portion of the hinge is constructed in wax in the form of a cylinder. The cylinder has a depression in the form of half a sphere in each end. The cylinder is waxed with a strut which connects it to the body of the first half of the expander. 2. The dimensions of the cylinder vary with the size of the prosthesis and the space available in the posterior palate area. It is advisable to place it as high as possible in the palatal vault. The anteriorposterior placement is related to the degree of the needed anterior expansion and to the “travel” of the expansion screw (Fig. 8). 3. When the first half of the casting is completed, finished, and polished, it is returned to the master cast and the model is duplicated. 4. The casting will normally be retained in the duplicating material. If not, it must be replaced in the augar because the casting must be on the refractory cast. The refractory cast, with the casting in place, is recovered, trimmed, and treated in the conventional manner. 5. The second half of the wax-up is completed, and a connecting strut is waxed to the female hinge. The hinge is completed by waxing both ends of the cylinder. The wax must touch only the cylinder ends, with an opening along the side of the cylinder so that the resulting metal will not bind against the cylinder. 6. The second half of the hinge is sprued, invested, and cast in a normal manner. A drop of penetrating
320
AND
NELSON
oil, placed on the completed hinge, will aid in freeing its movement. 7. The resultant hinge will be precise, sturdy, and dependable and will have good tolerance at the metal junction.
COMPLETING
EXPANDER
1. The expansion screw is placed in the cradle formed on the first half of the casting and soldered in place. 2. The covered contact area is adjusted to allow complete freedom of expansion in the horizontal plane. Superior and inferior contact will confine the vertical movement (Figs. 9 and 10).
CLINICAL
PHASE
The adult palatal expander is fitted to the mouth and either wired or cemented in place with autopolymerizing resin (Fig. 11). The number of daily turns of the expansion screw is determined by the dentist on an individual basis. Generally, a 10 mm expansion can be accomplished in 1 week to 10 days. Patients will experience initial discomfort and pain. This response normally occurs only at the beginning of expansion. The bulk of the prosthesis and posterior hinge also elicit an initial negative response, but since the expansion time is short, adults seem to tolerate these problems philosophically. The anticipated result appears to mitigate the unpleasant action of the prosthesis (Figs. 12 and 13).
SUMMARY The technical steps in the construction of two types of adult palatal expanders have been described. These prostheses are complex and require a special level of coordination between the professional team and the dental laboratory. The teamwork involved in the restoration of major maxillary defects contributes to the success of the prosthesis and makes the efforts involved worthwhile. Reprint requeststo: DR. J. S. BRUDVIK UNIVERSI~ OF WASHINGTON SCHOOL OF DENTISTRY SEATTLE, WA 98195
MARCH
1981
VOLUME
45
NUMBER
3
D.D.S.,*
and Donald R. Nelson, D.D.S. **
of Washington, School of Dentistry,
Seattle, Wash., and San Antonio, Tex.
lhl e ast d eta dhe as witnessed a minor revolution in the surgical intervention of a great variety of craniofacial anomalies which offer hope to the cleft palate patient with a collapsed maxilla. The prosthodontist can make a significant contribution to the final result by the design and fabrication of palatal expansion devices. Dental and medical literature contain references to infantile and adolescent expansion devices. Their use in the adult patient is complicated by the degree of control necessary to reposition the maxillary segments to an exact, preplanned position and the byforce necessary to move the segments. Controlled repositioning can greatly reduce the occlusal morbidity and the need for extensive, postoperative occlusal rehabilitation.
INDICATIONS Adult palatal expansion is indicated in a variety of cleft palate patients where juvenile management of the premaxillary area has resulted in a collapsed arch. Certain craniofacial anomalies can also result in a constricted maxillary arch. Many of the clefts do not have a normal suture between the maxillae. Expansion of these maxillae can be quite rapid. When a normal bony suture exists, the force required to expand the arch greatly increases with the possibility of uncontrolled tooth and segment movement.
OBJECTIVES The expansion device used in the adult is cast in a removable partial denture alloy and utilizes a stan-
Presented at the American Academy of Maxillofacial Prosthetics, Las Vegas, Nev. The authors developed these devices while on duty with U.S. Army Dental Corps at the Regional Dental Activity, Fort Sam Houston, Tex. *Associate Professor, Department of Prosthodontics. **Commander, Regional Dental Activities, Fort Sam Houston.
THE JOURNAL
OF PROSTHETIC
DENTISTRY
dard expansion screw for movement. Certain types incorporate a hinge mechanism to control movement. The prosthesis is either ligated to the maxillary teeth or, when cap splint retainers are used, “cemented” to them with autopolymerizing acrylic resin. Expansion is accomplished by programmed daily manipulation of the expansion screw, usually by the oral surgeon, until the desired increase in arch width is achieved. Palatal expansion prostheses fall into two general categories: (1) those requiring uniform bilateral horizontal expansion and (2) those that need an anterior element of expansion with little or none in the posterior. It is conceivable that unilateral palatal expansion will be indicated occasionally, but the complexity of stabilizing one segment while moving the other with the expansion prostheses presented in this article has not as yet been feasible.
TECHNIQUE The treatment begins with an impression for the pre-operative cast, which is poured in improved dental stone. The accuracy of duplicating the palatal tissues and teeth is paramount, so a well-fitting tray is indicated with no attempt to “overseat” the impression. Labial soft tissue contours are not involved with the prosthesis, so the impression need only be extended to include all the clinical crowns of the teeth. This is significant when scar tissue is present in the lip and/or cheek which might prevent the establishment of normal contours of the cast. Duplicates of the master cast are made, and the desired amount and direction of the expansion is established, preferably using a team approach by surgeon and prosthodontist.
STABILIZATION When little when no bony the prosthesis the remaining
CONSIDERATIONS
resistance to expansion is expected, or union and no dense scar tissue exist, contacts only the lingual surfaces of teeth and is wired in place.
315
BRUDVIK
Fig. 1. Cleft palate expansion splint retainer and spring-loaded
prosthesis expander.
utilizes
AND
NELSON
cap
Fig. 3. Completion of wax-up for substructure of expander showing main sprue lead through refractory cast. In cases where considerable force will be required to expand the bony suture and/or scar tissue, it is advisable to utilize a cap splint configuration to ensure complete control of the bony segments (Fig. 1). T&se decisions and the amount and direction of expansion are mandatory before construction begins.
CONSTRUCTION OF BILATERALLY UNIFORM EXPANDER UTILIZING LINGUAL TOOTH CONTACT AND LIGATION
Fig. 2. Refractory cast with maximum size expander that can be accommodated. Round blebs lingual to teeth are foundation for forming holes for ligature wires. This provision saves considerable effort in drilling the holes through casting. 316
1. The design is transferred to the master cast. A standard O-degree blockout is used to eliminate infrabulge areas on the maxillary teeth. Small balls of wax are placed over the sites where the plate will be perforated to wire the prosthesis to the teeth (Fig. 2). 2. The duplication techniques used are those recommended by the manufacturer of the specific alloy to be used. A refractory cast is poured in artificial stone. 3. When the refractory cast has been sealed with ’ either wax or plastic spray, the design is transferred to the cast, and the wax-up is performed. MARCH
1981
VOLUME
45
NUMBER
3
ADULT
PALATAL
EXPANSION
PROSTHESES
Fig. 4. Rough casting indicating form of cradle for expander.
sprue placement
and
4. Small amounts of wax are placed on prominent contours to preclude thin areas that might result from stretching the plastic sheet during its placement. 5. A plastic sheet, usually 24-gauge, is applied over a layer of “tacky” adhesive (Fig. 3). 6. The preselected expander is placed on the wax-up, and its final position is established. The device is lubricated and positioned so that the opening of the screw occurs in a movement from anterior to posterior. This allows visual access to the placement of the screw key. 7. A wax cradle is created for the expander by flowing wax under its base. When the palatal side is completely covered, the expander is removed. Wax is then added to create smooth contours joining the cradle to the waxed-up lingual flange of the prosthesis. 8. The expander is returned to the wax cradle, and a ledge of wax 1 to 1% mm is added to the edges of the cradle. This ledge serves as a soldering base for joining the expander to the casting.
Fig. 5. Completed expansion prostheses with separation of substructure at midline. Solder attachment can be seen wrapped around expander housing. Moving components should be completely free of solder.
9. The wax and plastic sheet are removed from the wire retention holes with a hot, sharply pointed instrument. 10. The completed wax-up is sprued by adding large sprue leads to the palatal side of the cradle and joining them to the sprue hole in a conventional manner. 11. The wax-up is invested and cast in the same manner as a removable partial denture casting (Fig. 4). 12. The casting is recovered, finished, and seated on the master cast. The segments are treated as individual units and should be tried in the mouth to assure a satisfactory fit at the time of the surgical procedure. 13. The expander is fitted to the casting and soldered into place using electrosoldering techniques common to removable partial denture laboratories and technicians. Precious metal solder such as Ticonium* triple thick or nonprecious Ni-Ci brazing *Ticonium
Co., Albany,
NY. 317
THE JOURNAL
OF PROSTHETIC
DENTISTRY
BRUDVIK
AND
NELSON
Casting I
Fig. 6. Diagramatic sketch of hinge mechanism. Casting 1 (attached to one side of the substructure) is female portion of hinge, consisting of barrel shape with flat top and bottom. Dotted Iines indicate half-round recesses. Overall size of hinge depends on available space.
Fig. 7. Completed expander showing hinge in open position. Expander has been soldered to casting 1.
alloys can be used with equal success, depending on the experience of the technician. 14. The solder is built up along the ledge of the cradle and moved up into the grooves of the expander with the carbon tip of the electrosoldering machine. The solder need not cover the entire expander, but it should cover at least 3 mm of the border. 15. Care must be used so that no solder flows into the screw mechanism of the expander. Some additional finishing and rubber wheeling is usually necessary before the expander is ready to be tried in the patient (Fig. 5).
CAP SPLINTS The cap splint varies only in its contour and the waxing technique used to create it. 1. The teeth on the master cast are blocked out at O-degree to relieve both facial and lingual coronal
318
Fig. 8. Expander in closed position while hinge is opt n to approximate desired postoperative dimension. Di tance expander must travel to achieve needed expansic n can be estimated. It is quite possible that maximu n expander travel will not be sufficient. In such instance ;, autopolymerizing acrylic resin can be placed under co‘ ered contact area to effectively move contact area closer D midline and thereby increase potential expansion.
undercuts and to create space for the cemz nting medium, usually autopolymerizing resin. 2. Thermoplastic, vacuum-adapted resin c Iping material can be used to create a uniform ba e for waxing. 3. The refractory cast should be articulat :d so that occlusal contacts which might increas : the vertical dimension of occlusion can be iden ified. The gauge of coping material is related to the alloy to be used. Thin-gauge sheets are used wit 1 the higher heat alloys. The thermoplastic skeet is vacuum-formed over the entire refractory c 1st and then trimmed to the gingival contours. 4. The remainder of the wax-up is identi :a1 to the wire-retained expander.
ROTATION-EXPANSION
PROSTHESI i
When the anterior maxilla requires i greater degree of expansion than the posterior, thf addition
MARCH
1981
VOLUME
5
NUMBER
3
ADULT
PALATAL
EXPANSION
PROSTHESES
Fig. 11. Palatal side of prosthesis postoperatively ing acrylic resin cementing material in place.
show-
Fig. 9. Expander passes just under covered contact area. Inner surface of contact area is concave so that edge of expander will track smoothly during expansion.
Fig. 12. Adult palatal expander ligated and cemented in place before expansion is started.
Fig. 10. Expansion prosthesis in its fully closed position as it would look at time of insertion.
of a hinge mechanism is included as an integral component of the expander. The construction of the hinge mechanism depends on the ability of chromebased alloy to be cast against itself and not bond, remaining separated by the oxide layer that forms during burnout. The hinge consists of (1) a female (receptacle) portion waxed as a component of the half of the expander that will retain the expansion screw and be cast first and (2) a male (attachment) portion, part of
THE IOURNAL
OF PROSTHETIC
DENTISTRY
Fig. 13. Expansion prosthesis, fully expanded to desired postoperative width, at time of removal. As evidenced by soft tissue visible in anterior, midline tissues are left intact after expansion.
319
BRUDVIK
the second half of the casting, which will be cast against the invested first half. The end result will be a hinge separated only by the thickness of the oxide (Fig. 6). The expansion screw on the hinged expander cannot be fixed at both ends since expansion will be on an arc from the hinge. A covered contact area with a curved inner surface is waxed in the second half of the prosthesis. The curved contact area allows the free end of the expansion screw to slip along its surface as the prosthesis expands. The “cover” is simply a guide to control the movement and maintain it in one plane (Fig. 7).
CONSTRUCTION
OF HINGE
1. The receptacle portion of the hinge is constructed in wax in the form of a cylinder. The cylinder has a depression in the form of half a sphere in each end. The cylinder is waxed with a strut which connects it to the body of the first half of the expander. 2. The dimensions of the cylinder vary with the size of the prosthesis and the space available in the posterior palate area. It is advisable to place it as high as possible in the palatal vault. The anteriorposterior placement is related to the degree of the needed anterior expansion and to the “travel” of the expansion screw (Fig. 8). 3. When the first half of the casting is completed, finished, and polished, it is returned to the master cast and the model is duplicated. 4. The casting will normally be retained in the duplicating material. If not, it must be replaced in the augar because the casting must be on the refractory cast. The refractory cast, with the casting in place, is recovered, trimmed, and treated in the conventional manner. 5. The second half of the wax-up is completed, and a connecting strut is waxed to the female hinge. The hinge is completed by waxing both ends of the cylinder. The wax must touch only the cylinder ends, with an opening along the side of the cylinder so that the resulting metal will not bind against the cylinder. 6. The second half of the hinge is sprued, invested, and cast in a normal manner. A drop of penetrating
320
AND
NELSON
oil, placed on the completed hinge, will aid in freeing its movement. 7. The resultant hinge will be precise, sturdy, and dependable and will have good tolerance at the metal junction.
COMPLETING
EXPANDER
1. The expansion screw is placed in the cradle formed on the first half of the casting and soldered in place. 2. The covered contact area is adjusted to allow complete freedom of expansion in the horizontal plane. Superior and inferior contact will confine the vertical movement (Figs. 9 and 10).
CLINICAL
PHASE
The adult palatal expander is fitted to the mouth and either wired or cemented in place with autopolymerizing resin (Fig. 11). The number of daily turns of the expansion screw is determined by the dentist on an individual basis. Generally, a 10 mm expansion can be accomplished in 1 week to 10 days. Patients will experience initial discomfort and pain. This response normally occurs only at the beginning of expansion. The bulk of the prosthesis and posterior hinge also elicit an initial negative response, but since the expansion time is short, adults seem to tolerate these problems philosophically. The anticipated result appears to mitigate the unpleasant action of the prosthesis (Figs. 12 and 13).
SUMMARY The technical steps in the construction of two types of adult palatal expanders have been described. These prostheses are complex and require a special level of coordination between the professional team and the dental laboratory. The teamwork involved in the restoration of major maxillary defects contributes to the success of the prosthesis and makes the efforts involved worthwhile. Reprint requeststo: DR. J. S. BRUDVIK UNIVERSI~ OF WASHINGTON SCHOOL OF DENTISTRY SEATTLE, WA 98195
MARCH
1981
VOLUME
45
NUMBER
3