- Email: [email protected]
Craniofacial osseointegration: Technique for bar and acrylic resin substructure construction for auricular prostheses
Craniofacial osseointegration: resin substructure construction
Technique for bar and acrylic for auricular prostheses
John F. Wolfaardt, BDS, MDent, PhD,” Philip Coss, RDT,b and Rejean Levesque, CDTo Craniofacial Osseointegration and Maxillofacial Prosthetic Rehabilitation Unit, Misericordia Community Health Centre, Edmonton, Alta, Canada Retention of auricular prostheses with adhesives is frequently problematic. Craniofacial osseointegrated implants have become an accepted biotechnique used in auricular reconstruction. This article describes a procedure for bar and acrylic resin substructure construction that allows for the incorporation of desired features. The most common means of retaining auricular prostheses is with bar and clip systems. For auricular prostheses, two implants are placed with the bar designed to minimize torquing on the implants and to facilitate hygiene. Additionally, the bar should not have to be removed from the patient when new prostheses are to be constructed. The procedure provides for a more biomechanically effective bar construction and efficient means of constructing replicate acrylic resin substructures. (J Prosthet Dent 1996;76:603-7.)
C
raniofacial osseointegration is an established technique for auricular reconstruction.1-3 In the past, three or four implants were usually placed for auricular reconstruction. Individual implant success rates in the mastoid region have revealed that only two implants are required to retain an auricular prosthesis and that bar and clip retention systems are favored.ls4 From a biomechanical standpoint it is important to limit loads that introduce a moment on the implant.5 Furthermore, the bar design should optimize hygiene. The initial design was offset with the bar passing at a tangent to the surface of the gold cylinder (Fig. l), which means that loads produced by clips on the bar cantilevers produced a moment on the implants. The offset design also created an excessive contour or hygiene shadow below the bar that is typically on the front of the bar. Consequently, this area is frequently missed during cleaning routines. Adesign that traverses through the center of the abutments may limit the introduction of moments on the implants and reduce contours to eliminate hygiene shadows. Soldering technique should result in a joint of minimal dimension to limit creation of hygiene shadows. One of the drawbacks of bar and clip retention systems has been that during prosthesis construction the bar has to be placed into the mold. However, there is always the risk of damaging the bar during the construction pro-
=Director, Caritas Health Group, Misericordia Community Health Centre, Craniofacial Osseointegration and Maxill+ facial Prosthetic Rehabilitation Unit; and Faculty of Me&tine and Oral Health Sciences, University of Alberta. “Instructor, Northern Alberta Institute of Technology, Edmonton, Alberta. ‘Dental Technologist, Caritas Health Group, Misericordia Cornmunity Health Centre, Craniofacial Osseointegration and Maxillofacial Prosthetic Rehabilitation Unit. DECEMBER
1996
Fig. 1. Bar with offset design. Arrows, shadow.
Areas
of hygiene
cess. This also means that when a new prosthesis has to be constructed the patient is denied the use of the prosthesis for a period of time. THE
JOURNAL
OF PROSTHETIC
DENTISTRY
603
THE JOURNAL
OF PROSTHETIC
DENTISTRY
WOLFAARDT,
Fig. 2. Investment for directing flame
of bar for soldering. Sluiceways to joints to be soldered.
Fig. 3. Completed
gold bar seated on abutment
replicas
This article presents a procedure that was developed to provide (1) a bar design that attempts to minimize development of moments on the implant, (2) a design of bar that optimizes the potential to maintain hygiene, and (3) an acrylic resin substructure that can be replicated and incorporated in the mold without having to remove the bar from the patient.
Fig. 4. Gold bar connected to patient for check of accuracy of fit. Center-to-center design of gold bar and absence of excess solder material at joints. 3.
4.
BAR CONSTRUCTION
2.
604
LEVESQUE
cut
of cast.
1.
COSS, AND
Determine the position of the auricular prosthesis and the bar with the aid of planning templates. Examine the fitting surface of the impression coping (DCB 026, NobelpharmaAB, Goteborg, Sweden), abutment replica (DCB 015, NobelpharmaAB), and gold cylinder (DCA 072/073, Nobelpharma AB) under a microscope (SMZ-2T Stereoscopic Microscope, 10x eyepiece, Nikon, Garden City, N.Y.) for imperfections before use. Connect the impression copings to abutments and torque the guide pins to 10 Ncm (torque controller, DEA020, NobelpharmaAB). Form a framework between the impression copings with dental floss and then connect the impression copings with acrylic pattern resin (Dura Lay, Reliance Dental Mfg. Co., Worth, Ill.).
5. 6.
7.
Lubricate the skin surface sparingly with petroleum jelly and record the impression polyether impression materials (Permadyne/Impregum, Seefeld, Germany). Syringe the exposed surface of the Impregum to form retentive loops for the acrylic resin backing (Flexacryl Hard, Lang Dental Mfg. Co., Chicago, Ill). Recover the impression, connect abutment replicas to the impression copings and torque the guide pins once again to 10 Ncm. Box the impression and pour in dental stone. Recover the cast with the skin markings transferred to the cast surface. Attach the gold cylinders to the abutment replicas on the cast and torque the gold screws (DCA 0741 075, Nobelpharma AB) to 10 Ncm. Design the bar to travel from center to center of the gold cylinders. (The cantilevers are a maximum of 10 mm in length. The sections of the bar should not make contact with skin and should wherever possible be in the same plane.) Cut the gold bar to length (5501.22, 1.9 mm 0 P3 Gold Bar, Cendres Metaux, Bienne, Switzerland). Position the cut sections of gold bar appropriately with small amounts of catalyzed silicone putty. Use a cyanoacrylate adhesive VOLUME
76
NUMBER
6
WOLFAARDT,
THE JOURNAL
COSS, AND IJWESQ~
Fig. 5. Layer of baseplate wax applied to surface of cast. Clip is placed as close as possible to gold cylinder,
8. 9,
10. 11.
12.
13.
14.
to fix section of gold bar to the gold cylinders (Zapit, Dental Ventures ofAmerica, Anaheim Hills, Calif.). Care must be taken to use minimal amounts of the adhesive so that the solder joints do not increase in volume. Once the bar is assembled, carefully remove it from the cast. Invest the bar in soldering investment (Deguvest L, DegussaAG, Frankfurt Main, Germany). Before the investment sets completely, create several sluiceways to direct the flame at the joint when soldering (Fig. 2). Place the invested bar in an oven and preheat to 500” C for 1 hour. Remove the invested bar from the oven and solder the joints with Anoxan flux (Degussa AG) and Degunorm (lot 700) solder (Degussa AG). Recover the soldered bar from the investment. Before trimming and polishing the bar, connect protection caps (DCB092, NobelpharmaAB) on to the gold cylinders to prevent any damage to their fitting surfaces. Trim and polish the gold bar under a microscope. (The solder joints should have a minima1 amount of solder beyond the joint area.) Remove the protection caps and carefully place the polished bar back on abutment replicas of the cast and check visually for accuracy of fit (Fig. 3). If the fit of the bar is deemed accurate on the cast, then check the fit of the gold bar on the abutments (Fig. 4).
ACRYLIC RESIN SUBSTRUCTURES PROTECTOR CAP CONSTRUCTION 1.
2.
AND
Remove the bar from the abutment replicas and place one layer of baseplate wax onto the surface of the cast (Fig. 5). Trim the wax neatly around the abutments and replace the bar on abutment replicas. Block out the bar with blockout wax (No. 40032, Bego, Bremen, Germany) with a g-degree taper. Block out slightly over the superior surface of the bar, around the gold cylinders and in the gold screw holes. (The
DECEMBER
1996
Fig. 6. Silicone duplication cate of bar.
OF PROSTHETIC
DENTISTRY
mold and cast with repli-
Fig. 7. Replicate cast of bar shows clip placement in predetermined position for clips. last 2 mm of the superior surface of the cantilever arms should be left exposed so that the resin substructure has a stop to rest on the bar. This is important for stability during recording of the soft tissue impression and is relieved when the prosthesis is finished.) With a surveyor, position the clips (DCB 078, Nobelpharma AB) on the bar. The clips should be placed as close as possible to the gold cylinders (Fig. 5). Remove the clips and ensure that neat channels are left in the wax blockout. Duplicate the bar with silicone duplicating material (Wirosil, Bego). Recover gold bar and cast from the silicone duplicating material. Pour white die stone into the silicone mold. The recovered cast will have a replica of the blocked out bar with channels for clip placement (Figs. 6 and 7). Place the clips on the stone bar and seal them with wax to the cast. Cover the tips of the clips with wax to allow for later access for clip adjustment. Additional blockout can be provided if deemed necessary (Fig. 8). This should be done to allow the internal surface of the acrylic resin substructure to have a smooth surface for ease of hygiene maintenance. 605
THEJOURNALOPPROSTHETICDENTISTRY
Fig. 8. Indexed
matrix
of dental
Fig. 9. Acrylic resin substructure ery from stone matrix.
WOLFAARDT,
stone.
with clips after recov-
Cover the bar and clips with a layer of baseplate to conform to the design of the desired acrylic resin substructure. The wax should cover the retentive wings of the clips. 8. Make reference indexes on the cast and separate with a light film of petroleum jelly on the wax-up of the acrylic resin substructure and cast surface. Construct a matrix of the wax-up in dental stone and make sure that the matrix engages the indexes well (Fig. 8). 9. Warm the top of the stone matrix to soften the waxup but without disturbing the wax blockout and clips. 10. Once the matrix is recovered, boil out the wax residue within the matrix and apply a coat of separating medium to the surface of the matrix. Also apply a coat of separator to the cast. 11. Prepare a resin mix with autopolymerizing acrylic resin (Splint Resin, Great Lakes, Tonawanda, N.Y.) and pour it into the matrix. Add a slight amount of the mix to the wings of the clips and then invert the matrix onto the cast, making sure that the indexes meet. Secure the matrix to the cast with rubber bands. 12. Place the matrix and cast in pressure pot (type 5415, Kavo EWL, Leutkirch, Germany) to cure at 25 psi in 43” C water. 7.
606
GOSS, AM)
LEVESQUE
Fig. 10. Components completed for soft tissue master impression. Bottom row, left to right: acrylic resin substructure modified to index into custom tray, replicate acrylic resin substructure, protector cap. Top row, left to right: indexed custom tray, diagnostic wax-up of ear, gold bar. 13. Recover, trim and polish the substructure (Fig. 9). Place a high shine on the surface of the acrylic resin. (One of the acrylic resin substructures can be modified for the recording of the soft tissue master impression [Fig. 10].6) 14. After steps 5 through 13, construct the protector cap by changing the design of the wax-up to provide a resin structure of wider contour. (The protector cap should have a contour that allows the bar to be protected but that will not snag on surfaces with which it comes into contact.) 15. Replicate acrylic resin substructures and protector caps can be constructed by repeating stages 5,6,12, and 13.
CONCLUSION The procedure described in this article provides a means of constructing a bar superstructure that attempts to minimize torque on the craniofacial osseointegrated implants. This procedure also allows for construction of replicates of the acrylic resin substructure. This, together with the previously described technique of master cast construction, allows multiple prostheses to be made out of the same mold without placing the bar back into the mold. This is important because the patient will not need to be denied the use of the prosthesis while a new prosthesis is being constructed.At the time of prosthesis construction the procedure also provides an efficient means of delivering a spare prosthesis to the patient. REFERENCES 1. TjellstrtimA. Osseointegrated implants for replacement of absent or defective ears. Clin Plast Surg 1990;17:355-66. 2. Wilkes GH, Wolfaardt JF. Osseointegrated alloplastic versus autogenous ear reconstruction: criteria for treatment selection. Plast Reeonstr Surg 1994;93:967-79. 3. Tjellstrijm A, Granstriim G. One-stage procedure to establish
VOLUME76
NUMBER6
WOLFAARDT,
COSS, AND
THE JOURNAL
LEVESQUE
osseointegration: a zero to five years follow-up report. J Laryngol Otolaryngol1995;1o9:593-8. 4. Granstrijm G, BergstrBm K, TjellstrGmA, Brlnemark PI. A detailed analysis of titanium implants lost in irradiated tissues. Int J Oral Maxillofac Implants 1994;9:653-62. 5. Del Valle V, Faulkner G, Wolfaardt J, Rangert B, Tan H. Mechanical evaluation of craniofacial osseointegration retention systems. Int J Oral Maxillofac Implants 1995;10:491-8. 6. Wolfaardt JF, Coss P. An impression and cast construction technique for implant-retained auricular prostheses. J Prosthet Dent 1996;75:45-9.
Osseointegration protected defects: Buser
D, Ruskin
Maxillofac Objective.
of titanium a histologic
J, Higginbottom
Implants
OF PROSTHETIC
DENTISTRY
Council
Journal
Reprint requests to: DR. JOHN F. WOLFAARDT
COMPRU MISERICORDIA COMMURITY HEALTH CENTRE 16940 87Aw. EDMONTON, ALBERTA T5R 4H5 CANADA
Copyright
0 1996
Prosthetic
by The
Editorial
of The
of
Dentistry.
0022-3913/96/$5.00
implants in bone regenerated study in the canine mandible.
+ 0
10/l/77496
in membrane-
F, Hardwick R, Dahlin C, Schenk R. Irzt J Oral
1995;10:666-81.
Barrier membrane techniques have been used to generate bone in deficient areas. It is unknown whether the newly generated bone is capable of supporting endosseous implants sufficiently to allow osseointegration to occur and, if achieved, whether osseointegration can be maintained under functional loading. The purpose of this study was to examine these questions and the fate of regenerated bone if no implant was placed. Material and Methods. All mandibular premolar teeth were removed from five male dogs. After 3 months of healing, three osseous defects were surgically created in each edentulous area to result in 30 surgical defects. The created defect dimensions were approximately 7 mm mesiodistally, 7 mm apicocoronally, and 8 to 10 mm buccolingually. Coverage of the defect was achieved with an expanded polytetrafluoroethylene membrane that was held in place with stainless steel miniscrews. Primary wound closure was achieved. Membranes that became exposed during the subsequent 6-month healing period were removed and these sites were withdrawn from the study. After the 6-month healing period membranes were removed from all three sites on one side of the mandible and from two posterior sites on the contralateral side of each dog. One site in each dog was not reopened, leaving the membrane in place. The two posterior sites were prepared bilaterally to receive IT1 hollow-screw implants; no implant was placed into the mesial site from which the membrane had been removed. After 3 months of implant healing prosthetic reconstruction was performed unilaterally. The contralateral implants remained unrestored. Animals were killed 6 months after prosthetic reconstruction and histologic preparation was performed. Results. Uneventful healing occurred in two dogs. Soft tissue dehiscence occurred in six sites for the remaining three dogs, requiring membrane removal and withdrawal of the sites from the study. Radiographic evaluation revealed complete bone regeneration in 23 of 24 potential sites. The one site that failed to fill completely was excluded from further study. Implants were then placed into 15 sites. Four sites did not have the membranes removed and four sites had membranes removed but no implants were placed. All 15 implants were clinically immobile 3 months after insertion. Eight implants were prosthetically restored. One unrestored implant demonstrated inflammation and vertical bone loss on radiographs. Histologic analysis demonstrated bone-to-implant contact for all 15 implants. There was no qualitative histologic difference between loaded and unloaded implants. Histologic study of the control unimplanted sites demonstrated less bone density than was found adjacent to the implants. Conclusion. Histologic analysis demonstrated that implants placed in regenerated bone can achieve osseointegration and that osseointegration was maintained with functional loading. Without implant placement, regenerated bone failed to maintain its density. 35 References.-SE Eckert
607
Technique for bar and acrylic for auricular prostheses
John F. Wolfaardt, BDS, MDent, PhD,” Philip Coss, RDT,b and Rejean Levesque, CDTo Craniofacial Osseointegration and Maxillofacial Prosthetic Rehabilitation Unit, Misericordia Community Health Centre, Edmonton, Alta, Canada Retention of auricular prostheses with adhesives is frequently problematic. Craniofacial osseointegrated implants have become an accepted biotechnique used in auricular reconstruction. This article describes a procedure for bar and acrylic resin substructure construction that allows for the incorporation of desired features. The most common means of retaining auricular prostheses is with bar and clip systems. For auricular prostheses, two implants are placed with the bar designed to minimize torquing on the implants and to facilitate hygiene. Additionally, the bar should not have to be removed from the patient when new prostheses are to be constructed. The procedure provides for a more biomechanically effective bar construction and efficient means of constructing replicate acrylic resin substructures. (J Prosthet Dent 1996;76:603-7.)
C
raniofacial osseointegration is an established technique for auricular reconstruction.1-3 In the past, three or four implants were usually placed for auricular reconstruction. Individual implant success rates in the mastoid region have revealed that only two implants are required to retain an auricular prosthesis and that bar and clip retention systems are favored.ls4 From a biomechanical standpoint it is important to limit loads that introduce a moment on the implant.5 Furthermore, the bar design should optimize hygiene. The initial design was offset with the bar passing at a tangent to the surface of the gold cylinder (Fig. l), which means that loads produced by clips on the bar cantilevers produced a moment on the implants. The offset design also created an excessive contour or hygiene shadow below the bar that is typically on the front of the bar. Consequently, this area is frequently missed during cleaning routines. Adesign that traverses through the center of the abutments may limit the introduction of moments on the implants and reduce contours to eliminate hygiene shadows. Soldering technique should result in a joint of minimal dimension to limit creation of hygiene shadows. One of the drawbacks of bar and clip retention systems has been that during prosthesis construction the bar has to be placed into the mold. However, there is always the risk of damaging the bar during the construction pro-
=Director, Caritas Health Group, Misericordia Community Health Centre, Craniofacial Osseointegration and Maxill+ facial Prosthetic Rehabilitation Unit; and Faculty of Me&tine and Oral Health Sciences, University of Alberta. “Instructor, Northern Alberta Institute of Technology, Edmonton, Alberta. ‘Dental Technologist, Caritas Health Group, Misericordia Cornmunity Health Centre, Craniofacial Osseointegration and Maxillofacial Prosthetic Rehabilitation Unit. DECEMBER
1996
Fig. 1. Bar with offset design. Arrows, shadow.
Areas
of hygiene
cess. This also means that when a new prosthesis has to be constructed the patient is denied the use of the prosthesis for a period of time. THE
JOURNAL
OF PROSTHETIC
DENTISTRY
603
THE JOURNAL
OF PROSTHETIC
DENTISTRY
WOLFAARDT,
Fig. 2. Investment for directing flame
of bar for soldering. Sluiceways to joints to be soldered.
Fig. 3. Completed
gold bar seated on abutment
replicas
This article presents a procedure that was developed to provide (1) a bar design that attempts to minimize development of moments on the implant, (2) a design of bar that optimizes the potential to maintain hygiene, and (3) an acrylic resin substructure that can be replicated and incorporated in the mold without having to remove the bar from the patient.
Fig. 4. Gold bar connected to patient for check of accuracy of fit. Center-to-center design of gold bar and absence of excess solder material at joints. 3.
4.
BAR CONSTRUCTION
2.
604
LEVESQUE
cut
of cast.
1.
COSS, AND
Determine the position of the auricular prosthesis and the bar with the aid of planning templates. Examine the fitting surface of the impression coping (DCB 026, NobelpharmaAB, Goteborg, Sweden), abutment replica (DCB 015, NobelpharmaAB), and gold cylinder (DCA 072/073, Nobelpharma AB) under a microscope (SMZ-2T Stereoscopic Microscope, 10x eyepiece, Nikon, Garden City, N.Y.) for imperfections before use. Connect the impression copings to abutments and torque the guide pins to 10 Ncm (torque controller, DEA020, NobelpharmaAB). Form a framework between the impression copings with dental floss and then connect the impression copings with acrylic pattern resin (Dura Lay, Reliance Dental Mfg. Co., Worth, Ill.).
5. 6.
7.
Lubricate the skin surface sparingly with petroleum jelly and record the impression polyether impression materials (Permadyne/Impregum, Seefeld, Germany). Syringe the exposed surface of the Impregum to form retentive loops for the acrylic resin backing (Flexacryl Hard, Lang Dental Mfg. Co., Chicago, Ill). Recover the impression, connect abutment replicas to the impression copings and torque the guide pins once again to 10 Ncm. Box the impression and pour in dental stone. Recover the cast with the skin markings transferred to the cast surface. Attach the gold cylinders to the abutment replicas on the cast and torque the gold screws (DCA 0741 075, Nobelpharma AB) to 10 Ncm. Design the bar to travel from center to center of the gold cylinders. (The cantilevers are a maximum of 10 mm in length. The sections of the bar should not make contact with skin and should wherever possible be in the same plane.) Cut the gold bar to length (5501.22, 1.9 mm 0 P3 Gold Bar, Cendres Metaux, Bienne, Switzerland). Position the cut sections of gold bar appropriately with small amounts of catalyzed silicone putty. Use a cyanoacrylate adhesive VOLUME
76
NUMBER
6
WOLFAARDT,
THE JOURNAL
COSS, AND IJWESQ~
Fig. 5. Layer of baseplate wax applied to surface of cast. Clip is placed as close as possible to gold cylinder,
8. 9,
10. 11.
12.
13.
14.
to fix section of gold bar to the gold cylinders (Zapit, Dental Ventures ofAmerica, Anaheim Hills, Calif.). Care must be taken to use minimal amounts of the adhesive so that the solder joints do not increase in volume. Once the bar is assembled, carefully remove it from the cast. Invest the bar in soldering investment (Deguvest L, DegussaAG, Frankfurt Main, Germany). Before the investment sets completely, create several sluiceways to direct the flame at the joint when soldering (Fig. 2). Place the invested bar in an oven and preheat to 500” C for 1 hour. Remove the invested bar from the oven and solder the joints with Anoxan flux (Degussa AG) and Degunorm (lot 700) solder (Degussa AG). Recover the soldered bar from the investment. Before trimming and polishing the bar, connect protection caps (DCB092, NobelpharmaAB) on to the gold cylinders to prevent any damage to their fitting surfaces. Trim and polish the gold bar under a microscope. (The solder joints should have a minima1 amount of solder beyond the joint area.) Remove the protection caps and carefully place the polished bar back on abutment replicas of the cast and check visually for accuracy of fit (Fig. 3). If the fit of the bar is deemed accurate on the cast, then check the fit of the gold bar on the abutments (Fig. 4).
ACRYLIC RESIN SUBSTRUCTURES PROTECTOR CAP CONSTRUCTION 1.
2.
AND
Remove the bar from the abutment replicas and place one layer of baseplate wax onto the surface of the cast (Fig. 5). Trim the wax neatly around the abutments and replace the bar on abutment replicas. Block out the bar with blockout wax (No. 40032, Bego, Bremen, Germany) with a g-degree taper. Block out slightly over the superior surface of the bar, around the gold cylinders and in the gold screw holes. (The
DECEMBER
1996
Fig. 6. Silicone duplication cate of bar.
OF PROSTHETIC
DENTISTRY
mold and cast with repli-
Fig. 7. Replicate cast of bar shows clip placement in predetermined position for clips. last 2 mm of the superior surface of the cantilever arms should be left exposed so that the resin substructure has a stop to rest on the bar. This is important for stability during recording of the soft tissue impression and is relieved when the prosthesis is finished.) With a surveyor, position the clips (DCB 078, Nobelpharma AB) on the bar. The clips should be placed as close as possible to the gold cylinders (Fig. 5). Remove the clips and ensure that neat channels are left in the wax blockout. Duplicate the bar with silicone duplicating material (Wirosil, Bego). Recover gold bar and cast from the silicone duplicating material. Pour white die stone into the silicone mold. The recovered cast will have a replica of the blocked out bar with channels for clip placement (Figs. 6 and 7). Place the clips on the stone bar and seal them with wax to the cast. Cover the tips of the clips with wax to allow for later access for clip adjustment. Additional blockout can be provided if deemed necessary (Fig. 8). This should be done to allow the internal surface of the acrylic resin substructure to have a smooth surface for ease of hygiene maintenance. 605
THEJOURNALOPPROSTHETICDENTISTRY
Fig. 8. Indexed
matrix
of dental
Fig. 9. Acrylic resin substructure ery from stone matrix.
WOLFAARDT,
stone.
with clips after recov-
Cover the bar and clips with a layer of baseplate to conform to the design of the desired acrylic resin substructure. The wax should cover the retentive wings of the clips. 8. Make reference indexes on the cast and separate with a light film of petroleum jelly on the wax-up of the acrylic resin substructure and cast surface. Construct a matrix of the wax-up in dental stone and make sure that the matrix engages the indexes well (Fig. 8). 9. Warm the top of the stone matrix to soften the waxup but without disturbing the wax blockout and clips. 10. Once the matrix is recovered, boil out the wax residue within the matrix and apply a coat of separating medium to the surface of the matrix. Also apply a coat of separator to the cast. 11. Prepare a resin mix with autopolymerizing acrylic resin (Splint Resin, Great Lakes, Tonawanda, N.Y.) and pour it into the matrix. Add a slight amount of the mix to the wings of the clips and then invert the matrix onto the cast, making sure that the indexes meet. Secure the matrix to the cast with rubber bands. 12. Place the matrix and cast in pressure pot (type 5415, Kavo EWL, Leutkirch, Germany) to cure at 25 psi in 43” C water. 7.
606
GOSS, AM)
LEVESQUE
Fig. 10. Components completed for soft tissue master impression. Bottom row, left to right: acrylic resin substructure modified to index into custom tray, replicate acrylic resin substructure, protector cap. Top row, left to right: indexed custom tray, diagnostic wax-up of ear, gold bar. 13. Recover, trim and polish the substructure (Fig. 9). Place a high shine on the surface of the acrylic resin. (One of the acrylic resin substructures can be modified for the recording of the soft tissue master impression [Fig. 10].6) 14. After steps 5 through 13, construct the protector cap by changing the design of the wax-up to provide a resin structure of wider contour. (The protector cap should have a contour that allows the bar to be protected but that will not snag on surfaces with which it comes into contact.) 15. Replicate acrylic resin substructures and protector caps can be constructed by repeating stages 5,6,12, and 13.
CONCLUSION The procedure described in this article provides a means of constructing a bar superstructure that attempts to minimize torque on the craniofacial osseointegrated implants. This procedure also allows for construction of replicates of the acrylic resin substructure. This, together with the previously described technique of master cast construction, allows multiple prostheses to be made out of the same mold without placing the bar back into the mold. This is important because the patient will not need to be denied the use of the prosthesis while a new prosthesis is being constructed.At the time of prosthesis construction the procedure also provides an efficient means of delivering a spare prosthesis to the patient. REFERENCES 1. TjellstrtimA. Osseointegrated implants for replacement of absent or defective ears. Clin Plast Surg 1990;17:355-66. 2. Wilkes GH, Wolfaardt JF. Osseointegrated alloplastic versus autogenous ear reconstruction: criteria for treatment selection. Plast Reeonstr Surg 1994;93:967-79. 3. Tjellstrijm A, Granstriim G. One-stage procedure to establish
VOLUME76
NUMBER6
WOLFAARDT,
COSS, AND
THE JOURNAL
LEVESQUE
osseointegration: a zero to five years follow-up report. J Laryngol Otolaryngol1995;1o9:593-8. 4. Granstrijm G, BergstrBm K, TjellstrGmA, Brlnemark PI. A detailed analysis of titanium implants lost in irradiated tissues. Int J Oral Maxillofac Implants 1994;9:653-62. 5. Del Valle V, Faulkner G, Wolfaardt J, Rangert B, Tan H. Mechanical evaluation of craniofacial osseointegration retention systems. Int J Oral Maxillofac Implants 1995;10:491-8. 6. Wolfaardt JF, Coss P. An impression and cast construction technique for implant-retained auricular prostheses. J Prosthet Dent 1996;75:45-9.
Osseointegration protected defects: Buser
D, Ruskin
Maxillofac Objective.
of titanium a histologic
J, Higginbottom
Implants
OF PROSTHETIC
DENTISTRY
Council
Journal
Reprint requests to: DR. JOHN F. WOLFAARDT
COMPRU MISERICORDIA COMMURITY HEALTH CENTRE 16940 87Aw. EDMONTON, ALBERTA T5R 4H5 CANADA
Copyright
0 1996
Prosthetic
by The
Editorial
of The
of
Dentistry.
0022-3913/96/$5.00
implants in bone regenerated study in the canine mandible.
+ 0
10/l/77496
in membrane-
F, Hardwick R, Dahlin C, Schenk R. Irzt J Oral
1995;10:666-81.
Barrier membrane techniques have been used to generate bone in deficient areas. It is unknown whether the newly generated bone is capable of supporting endosseous implants sufficiently to allow osseointegration to occur and, if achieved, whether osseointegration can be maintained under functional loading. The purpose of this study was to examine these questions and the fate of regenerated bone if no implant was placed. Material and Methods. All mandibular premolar teeth were removed from five male dogs. After 3 months of healing, three osseous defects were surgically created in each edentulous area to result in 30 surgical defects. The created defect dimensions were approximately 7 mm mesiodistally, 7 mm apicocoronally, and 8 to 10 mm buccolingually. Coverage of the defect was achieved with an expanded polytetrafluoroethylene membrane that was held in place with stainless steel miniscrews. Primary wound closure was achieved. Membranes that became exposed during the subsequent 6-month healing period were removed and these sites were withdrawn from the study. After the 6-month healing period membranes were removed from all three sites on one side of the mandible and from two posterior sites on the contralateral side of each dog. One site in each dog was not reopened, leaving the membrane in place. The two posterior sites were prepared bilaterally to receive IT1 hollow-screw implants; no implant was placed into the mesial site from which the membrane had been removed. After 3 months of implant healing prosthetic reconstruction was performed unilaterally. The contralateral implants remained unrestored. Animals were killed 6 months after prosthetic reconstruction and histologic preparation was performed. Results. Uneventful healing occurred in two dogs. Soft tissue dehiscence occurred in six sites for the remaining three dogs, requiring membrane removal and withdrawal of the sites from the study. Radiographic evaluation revealed complete bone regeneration in 23 of 24 potential sites. The one site that failed to fill completely was excluded from further study. Implants were then placed into 15 sites. Four sites did not have the membranes removed and four sites had membranes removed but no implants were placed. All 15 implants were clinically immobile 3 months after insertion. Eight implants were prosthetically restored. One unrestored implant demonstrated inflammation and vertical bone loss on radiographs. Histologic analysis demonstrated bone-to-implant contact for all 15 implants. There was no qualitative histologic difference between loaded and unloaded implants. Histologic study of the control unimplanted sites demonstrated less bone density than was found adjacent to the implants. Conclusion. Histologic analysis demonstrated that implants placed in regenerated bone can achieve osseointegration and that osseointegration was maintained with functional loading. Without implant placement, regenerated bone failed to maintain its density. 35 References.-SE Eckert
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