- Email: [email protected]
Fiber-reinforced composite framework for implant-supported overdentures
Fiber-reinforced composite framework for implant-supported overdentures Jacqueline P. Duncan, DMD, MDSc,a Martin A. Freilich, DDS,b and Christopher J. Latvis, DDS, MDScc University of Connecticut, School of Dental Medicine, Farmington, Conn. This article presents a new method for fabricating a framework for an implant-supported overdenture using unidirectional fiber-reinforced composite. This procedure eliminates the need for a traditional metal alloy framework. The fiber-reinforced composite framework has the advantages of lower cost, less time and materials needed during fabrication, minimal potential for toxicity to the technician and patient, and a more esthetic metal-free final result. (J Prosthet Dent 2000;84:200-4.)
O
verdentures retained by implants have become an accepted treatment alternative for many edentulous patients. Implants used for overdenture retention are either splinted together with a cast metal bar, or they remain freestanding and are not connected to one another. When a bar is used to connect the implants, clips that attach to the bar provide retention of the overdenture. With freestanding implants, ball attachments are placed in individual implants and retentive matrices within the denture provide retention. Regardless of the technique used, the implants and attachments occupy space that would otherwise be filled with denture resin in a conventional denture. The result is either a denture that is thinner than normal and therefore susceptible to fracture or an overbulked denture that may interfere with the tongue and speech. To avoid either unfavorable situation, a metal framework is often made to provide rigidity and reinforcement to the acrylic resin overdenture while allowing for natural contours of the denture resin.1 This metal framework is expensive, time-consuming to fabricate, unesthetic, and the metal alloys used pose potential toxicity problems during fabrication or after delivery.2,3 Recent advances in fiber-reinforced composite technology have provided many advantageous alternatives to conventional techniques in various aspects of clinical dentistry.4 The following procedure describes an alternative framework for implant-retained overdentures that replaces the standard Ni-Cr or Cr-Co alloys with a fiber-reinforced composite (FRC) framework. A clinical treatment is used to illustrate this procedure.
aAssistant
Professor, Department of Prosthodontics and Operative Dentistry. bAssociate Professor, Department of Prosthodontics and Operative Dentistry. cPrivate Practice, Bristol, Conn. 200 THE JOURNAL OF PROSTHETIC DENTISTRY
Fig. 1. Intraoral view of overdenture bar assemblies on ITI implants.
PROCEDURE Clinical Treatment A 55-year-old man was evaluated for treatment; his chief complaint was that he could not tolerate his current maxillary partial denture because of the metal that crossed his palate. Intraoral examination revealed significant periodontal involvement of the remaining maxillary teeth, which consisted of first and second premolars bilaterally and the left first and second molars. The mandibular first and third molars were missing, along with the mandibular left second premolar. The mandibular second molars and left first premolar had a poor-to-hopeless prognosis, whereas the remaining mandibular dentition had a good-to-fair prognosis. Consideration was given to all clinical and patient factors, and after counseling the patient, the following treatment plan was decided on. The remaining maxillary teeth as well as the mandibular second molars and left first premolar were extracted. A maxillary transitional denture and a mandibular transitional partial denture were fabricated for use until the final prostheses were completed. (Despite the patient’s dislike of palatal coverage, he preferred this VOLUME 84 NUMBER 2
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THE JOURNAL OF PROSTHETIC DENTISTRY
Fig. 2. Master cast prepared for final processing of denture resin. Retentive clips are positioned on Dolder bars.
Fig. 4. Remaining areas of implant abutments were blocked out with silicone relief material to ensure retrievability after processing.
Fig. 3. Flowable composite was syringed into mechanical retention on top of clip. Engaging portion of clip was blocked out to ensure patency during processing.
Fig. 5. Rope of inlay wax was attached to cast to create pattern for FRC framework.
to having no teeth during the treatment period.) The maxilla would be definitively restored with a palateless overdenture retained by 6 splinted implants. When treatment of the maxilla was complete, implants were placed bilaterally in the posterior mandible to support 2 fixed partial dentures (FPDs). The definitive treatment of the maxilla and mandible was staggered because of financial considerations. Three months after extraction, 5 ITI solid screw implants (Institute Straumann, Waldenberg, Switzerland) were placed in the maxillary right first molar (8 mm), maxillary left first premolar (12 mm), maxillary right lateral incisor (10 mm), maxillary left lateral incisor (8 mm), and the maxillary left first premolar (12 mm). Attempts to place an implant in the maxillary left first molar were not successful. Approximately 7 months after implant placement, 5 octagonal abutments were connected and torqued to 35 N·cm. A final impression of the max-
illa and implants was made with polyether (Impregum Penta, ESPE, Norristown, Pa.) in a custom tray. Two individual bars were fabricated and connected the implants on the right and left sides of the arch (Fig. 1). To avoid problems with esthetics in the anterior, the bars did not cross the mid line. The fit of the bars was confirmed using a silicone disclosing medium (Fit Checker, GC Corp, Tokyo, Japan). The right bar required sectioning and soldering. Jaw relationship recordings were performed and verified at the esthetic try-in of the maxillary denture.
AUGUST 2000
LABORATORY PROCEDURE 1. Flask the wax trial denture and master cast then boil out, leaving the master cast clean and prepared for fabrication of the FRC framework. 2. Connect the retentive clips (Dolder minis, Institute Straumann) to the bar in the appropriate locations (Fig. 2).
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Fig. 6. Laboratory putty was adapted around wax pattern to form trough in which FRC framework could be stabilized during light polymerization.
Fig. 8. FRC framework was attached to clips with flowable composite.
Fig. 7. Pattern in matrix was measured to determine dimensions for FRC framework.
Fig. 9. Matrix was removed and FRC framework was light polymerized. Finished framework is shown.
3. Flow composite (Flow It, Jeneric/Pentron, Wallingford, Conn.) with a syringe into the mechanical retention on top of each clip that retains it in the denture and connects it to the FRC framework. 4. Block out the retentive portions of the clips that engage the bar with calcium hydroxide (Dycal, Dentsply/Caulk, Milford, Del.) to ensure that they remain patent during final processing of the acrylic resin (Fig. 3). 5. Block out the remaining portions of the bar and cylinders with a silicone relief material (DentKote, Dentsply Intl Inc, York, Pa.) to ensure retrievability after processing (Fig. 4). 6. Using a rope of inlay wax (Kerr Laboratory Products Div, Emeryville, Calif.), lay out a pattern for the FRC framework on the master cast and place sticky wax (Kerr Laboratory Products Div) to attach it to the cast. (The diameter of the pattern is approximately 6 to 7 mm, and the area requir-
ing support in the final denture determines the length [Fig. 5].) Adapt silicone laboratory putty (Universal Dental Silicone Putty, Div of Lactona Corp, Montgomeryville, Pa.) around the wax pattern to form a trough that the FRC can be condensed into and held during polymerization (Fig. 6). Remove the wax pattern from the putty matrix and measure it to determine the length of the FRC strips to be cut (Fig. 7). Cut approximately 50 strips of FRC (FibreKor, Jeneric/Pentron), then condense and roll them on a glass slab to form a bar 6 to 7 mm in diameter and 75 mm in length. Place the FRC framework into the putty matrix and lute it to the retentive clips with flowable composite (Fig. 8). Light polymerize the flowable composite at each clip for approximately 20 seconds before progressing to the next clip.
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7.
8.
9.
10.
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THE JOURNAL OF PROSTHETIC DENTISTRY
B
A
Fig. 10. Completed overdenture prosthesis with FRC framework. A, Palatal view; B, intaglio surface.
(This ensures the positional stability of the FRC framework.) 11. Once the FRC framework is secured to the clips and the putty matrix is removed, place the entire master cast in a light-polymerizing unit for 10 minutes to ensure complete polymerization of the FRC (Fig. 9). 12. Process the denture using standard packing, curing, and finishing techniques. 13. The maxillary overdenture was delivered without difficulty and has been in service for more than 1 year without complications. The finished prosthesis is depicted in Figure 10.
DISCUSSION Cast metal frameworks fabricated for implant overdentures are a costly and time-consuming endeavor. A framework must be waxed, cast, finished, and many times opaqued to mask its gray color. The materials, labor, and time involved in this process make the development of a suitable alternative extremely desirable. First, the process described above can be accomplished in less than an hour with material and labor costs significantly lower than what is required for a metal framework. Second, the potential hazards of working with Cr-Co and Ni-Cr alloys are eliminated. Third, the potential for corrosion between the dissimilar metals of the framework and retentive clips is also eliminated. Fourth, there is no need for opaquing the framework because the FRC is a translucent, toothcolored material. Fifth, the FRC framework bonds both mechanically and chemically to the denture resin. A metal framework does not chemically bond to the denture resin and is retained by mechanical means alone. And finally, it has been shown that
AUGUST 2000
Table I. Comparative transverse strengths of fiber-reinforced composite, denture resin and metal alloys Transverse strength Material
MPa
PMMA (heat polymerized) Fiber-reinforced composite (unidirectional) Noble alloy Base metal alloys
79-86* 936† 103-685‡ 260-838‡
*Craig.6 †Freilich
et al.5
‡Anusavice.7
the flexure strength of FRC is in the range of alloys used for fixed partial dentures, which is obviously higher than the flexure strength of unreinforced denture resin (Table I).5-7 Although there are many apparent advantages to this method, this article represents only a single case. An earlier clinical trial by Bergendal et al 8 found a success rate of 70% after a mean functioning time of 44 months with the use of carbonfiber–reinforced PMMA frameworks for restoration of hybrid-type prostheses. Despite significant differences between the techniques (carbon fiber vs preimpregnated FRC; fixed vs removable), the concept of a fiber-reinforced framework replacing the traditional metal framework is common to both. With the introduction of improved fiber reinforcing materials, it seems likely that this technique would have an acceptable success rate. A controlled clinical trial would be necessar y to definitively assess the long-term outcomes. In addition, it may reveal contraindications and disadvantages that presently are not apparent.
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DUNCAN, FREILICH, AND LATVIS
SUMMARY The advantages of an FRC framework make it a realistic option for replacement of a metal framework. An FRC framework has the potential to provide the same benefits as a metal framework in a much more efficient manner. REFERENCES 1. Jimenez-Lopez V. Oral rehabilitation with implant-supported prostheses. Chicago: Quintessence; 1999. p. 284-5. 2. Moffa JP, Beck WD, Hoke AW. Allergic response to nickel containing dental alloys [abstract 107]. J Dent Res 1977;56:1378. 3. Morris HF. Veterans Administration Cooperative Studies Project No. 147. Part IV: biocompatibility of base metal alloys. J Prosthet Dent 1987;58:1-5. 4. Freilich MA, Meiers JC, Duncan JP, Goldberg AJ. Fiber-reinforced composites in clinical dentistry. Chicago: Quintessence; 2000. p. 2373; 93-102. 5. Freilich MA, Karmaker AC, Burstone CJ, Goldberg AJ. Flexure strength of fiber-reinforced composites designed for prosthodontic application [abstract 999]. J Dent Res 1997;76(special issue):138.
6. Craig RG. Restorative dental materials. 10th ed. St Louis: Mosby; 1993. p. 506. 7. Anusavice KJ. Phillips’ science of dental materials. 10th ed. Philadelphia: WB Saunders; 1996. p. 431. 8. Bergendal T, Ekstrand K, Karlsson U. Evaluation of implant-supported carbon/graphite fiber-reinforced poly(methyl methacrylate) prostheses. A longitudinal multicenter study. Clin Oral Implants Res 1995;6:246-53. Reprint requests to: DR JACQUELINE P. DUNCAN DEPARTMENT OF PROSTHODONTICS AND OPERATIVE DENTISTRY SCHOOL OF DENTAL MEDICINE UCONN HEALTH CENTER 263 FARMINGTON AVE FARMINGTON, CT 06030-1615 FAX: (860)679-1370 E-MAIL: [email protected] Copyright © 2000 by The Editorial Council of The Journal of Prosthetic Dentistry. 0022-3913/2000/$12.00 + 0. 10/1/108025
doi:10.1067/mpr.2000.108025
New product news The January and July issues of the Journal carry information regarding new products of interest to prosthodontists. Product information should be sent 1 month prior to ad closing date to: Dr. Glen P. McGivney, Editor, SUNY at Buffalo, School of Dental Medicine, 345 Squire Hall, Buffalo, NY 14214. Product information may be accepted in whole or in part at the discretion of the Editor and is subject to editing. A black-and-white glossy photo may be submitted to accompany product information. Information and products reported are based on information provided by the manufacturer. No endorsement is intended or implied by the Editorial Council of The Journal of Prosthetic Dentistry, the editor, or the publisher.
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VOLUME 84 NUMBER 2
O
verdentures retained by implants have become an accepted treatment alternative for many edentulous patients. Implants used for overdenture retention are either splinted together with a cast metal bar, or they remain freestanding and are not connected to one another. When a bar is used to connect the implants, clips that attach to the bar provide retention of the overdenture. With freestanding implants, ball attachments are placed in individual implants and retentive matrices within the denture provide retention. Regardless of the technique used, the implants and attachments occupy space that would otherwise be filled with denture resin in a conventional denture. The result is either a denture that is thinner than normal and therefore susceptible to fracture or an overbulked denture that may interfere with the tongue and speech. To avoid either unfavorable situation, a metal framework is often made to provide rigidity and reinforcement to the acrylic resin overdenture while allowing for natural contours of the denture resin.1 This metal framework is expensive, time-consuming to fabricate, unesthetic, and the metal alloys used pose potential toxicity problems during fabrication or after delivery.2,3 Recent advances in fiber-reinforced composite technology have provided many advantageous alternatives to conventional techniques in various aspects of clinical dentistry.4 The following procedure describes an alternative framework for implant-retained overdentures that replaces the standard Ni-Cr or Cr-Co alloys with a fiber-reinforced composite (FRC) framework. A clinical treatment is used to illustrate this procedure.
aAssistant
Professor, Department of Prosthodontics and Operative Dentistry. bAssociate Professor, Department of Prosthodontics and Operative Dentistry. cPrivate Practice, Bristol, Conn. 200 THE JOURNAL OF PROSTHETIC DENTISTRY
Fig. 1. Intraoral view of overdenture bar assemblies on ITI implants.
PROCEDURE Clinical Treatment A 55-year-old man was evaluated for treatment; his chief complaint was that he could not tolerate his current maxillary partial denture because of the metal that crossed his palate. Intraoral examination revealed significant periodontal involvement of the remaining maxillary teeth, which consisted of first and second premolars bilaterally and the left first and second molars. The mandibular first and third molars were missing, along with the mandibular left second premolar. The mandibular second molars and left first premolar had a poor-to-hopeless prognosis, whereas the remaining mandibular dentition had a good-to-fair prognosis. Consideration was given to all clinical and patient factors, and after counseling the patient, the following treatment plan was decided on. The remaining maxillary teeth as well as the mandibular second molars and left first premolar were extracted. A maxillary transitional denture and a mandibular transitional partial denture were fabricated for use until the final prostheses were completed. (Despite the patient’s dislike of palatal coverage, he preferred this VOLUME 84 NUMBER 2
DUNCAN, FREILICH, AND LATVIS
THE JOURNAL OF PROSTHETIC DENTISTRY
Fig. 2. Master cast prepared for final processing of denture resin. Retentive clips are positioned on Dolder bars.
Fig. 4. Remaining areas of implant abutments were blocked out with silicone relief material to ensure retrievability after processing.
Fig. 3. Flowable composite was syringed into mechanical retention on top of clip. Engaging portion of clip was blocked out to ensure patency during processing.
Fig. 5. Rope of inlay wax was attached to cast to create pattern for FRC framework.
to having no teeth during the treatment period.) The maxilla would be definitively restored with a palateless overdenture retained by 6 splinted implants. When treatment of the maxilla was complete, implants were placed bilaterally in the posterior mandible to support 2 fixed partial dentures (FPDs). The definitive treatment of the maxilla and mandible was staggered because of financial considerations. Three months after extraction, 5 ITI solid screw implants (Institute Straumann, Waldenberg, Switzerland) were placed in the maxillary right first molar (8 mm), maxillary left first premolar (12 mm), maxillary right lateral incisor (10 mm), maxillary left lateral incisor (8 mm), and the maxillary left first premolar (12 mm). Attempts to place an implant in the maxillary left first molar were not successful. Approximately 7 months after implant placement, 5 octagonal abutments were connected and torqued to 35 N·cm. A final impression of the max-
illa and implants was made with polyether (Impregum Penta, ESPE, Norristown, Pa.) in a custom tray. Two individual bars were fabricated and connected the implants on the right and left sides of the arch (Fig. 1). To avoid problems with esthetics in the anterior, the bars did not cross the mid line. The fit of the bars was confirmed using a silicone disclosing medium (Fit Checker, GC Corp, Tokyo, Japan). The right bar required sectioning and soldering. Jaw relationship recordings were performed and verified at the esthetic try-in of the maxillary denture.
AUGUST 2000
LABORATORY PROCEDURE 1. Flask the wax trial denture and master cast then boil out, leaving the master cast clean and prepared for fabrication of the FRC framework. 2. Connect the retentive clips (Dolder minis, Institute Straumann) to the bar in the appropriate locations (Fig. 2).
201
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Fig. 6. Laboratory putty was adapted around wax pattern to form trough in which FRC framework could be stabilized during light polymerization.
Fig. 8. FRC framework was attached to clips with flowable composite.
Fig. 7. Pattern in matrix was measured to determine dimensions for FRC framework.
Fig. 9. Matrix was removed and FRC framework was light polymerized. Finished framework is shown.
3. Flow composite (Flow It, Jeneric/Pentron, Wallingford, Conn.) with a syringe into the mechanical retention on top of each clip that retains it in the denture and connects it to the FRC framework. 4. Block out the retentive portions of the clips that engage the bar with calcium hydroxide (Dycal, Dentsply/Caulk, Milford, Del.) to ensure that they remain patent during final processing of the acrylic resin (Fig. 3). 5. Block out the remaining portions of the bar and cylinders with a silicone relief material (DentKote, Dentsply Intl Inc, York, Pa.) to ensure retrievability after processing (Fig. 4). 6. Using a rope of inlay wax (Kerr Laboratory Products Div, Emeryville, Calif.), lay out a pattern for the FRC framework on the master cast and place sticky wax (Kerr Laboratory Products Div) to attach it to the cast. (The diameter of the pattern is approximately 6 to 7 mm, and the area requir-
ing support in the final denture determines the length [Fig. 5].) Adapt silicone laboratory putty (Universal Dental Silicone Putty, Div of Lactona Corp, Montgomeryville, Pa.) around the wax pattern to form a trough that the FRC can be condensed into and held during polymerization (Fig. 6). Remove the wax pattern from the putty matrix and measure it to determine the length of the FRC strips to be cut (Fig. 7). Cut approximately 50 strips of FRC (FibreKor, Jeneric/Pentron), then condense and roll them on a glass slab to form a bar 6 to 7 mm in diameter and 75 mm in length. Place the FRC framework into the putty matrix and lute it to the retentive clips with flowable composite (Fig. 8). Light polymerize the flowable composite at each clip for approximately 20 seconds before progressing to the next clip.
202
7.
8.
9.
10.
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THE JOURNAL OF PROSTHETIC DENTISTRY
B
A
Fig. 10. Completed overdenture prosthesis with FRC framework. A, Palatal view; B, intaglio surface.
(This ensures the positional stability of the FRC framework.) 11. Once the FRC framework is secured to the clips and the putty matrix is removed, place the entire master cast in a light-polymerizing unit for 10 minutes to ensure complete polymerization of the FRC (Fig. 9). 12. Process the denture using standard packing, curing, and finishing techniques. 13. The maxillary overdenture was delivered without difficulty and has been in service for more than 1 year without complications. The finished prosthesis is depicted in Figure 10.
DISCUSSION Cast metal frameworks fabricated for implant overdentures are a costly and time-consuming endeavor. A framework must be waxed, cast, finished, and many times opaqued to mask its gray color. The materials, labor, and time involved in this process make the development of a suitable alternative extremely desirable. First, the process described above can be accomplished in less than an hour with material and labor costs significantly lower than what is required for a metal framework. Second, the potential hazards of working with Cr-Co and Ni-Cr alloys are eliminated. Third, the potential for corrosion between the dissimilar metals of the framework and retentive clips is also eliminated. Fourth, there is no need for opaquing the framework because the FRC is a translucent, toothcolored material. Fifth, the FRC framework bonds both mechanically and chemically to the denture resin. A metal framework does not chemically bond to the denture resin and is retained by mechanical means alone. And finally, it has been shown that
AUGUST 2000
Table I. Comparative transverse strengths of fiber-reinforced composite, denture resin and metal alloys Transverse strength Material
MPa
PMMA (heat polymerized) Fiber-reinforced composite (unidirectional) Noble alloy Base metal alloys
79-86* 936† 103-685‡ 260-838‡
*Craig.6 †Freilich
et al.5
‡Anusavice.7
the flexure strength of FRC is in the range of alloys used for fixed partial dentures, which is obviously higher than the flexure strength of unreinforced denture resin (Table I).5-7 Although there are many apparent advantages to this method, this article represents only a single case. An earlier clinical trial by Bergendal et al 8 found a success rate of 70% after a mean functioning time of 44 months with the use of carbonfiber–reinforced PMMA frameworks for restoration of hybrid-type prostheses. Despite significant differences between the techniques (carbon fiber vs preimpregnated FRC; fixed vs removable), the concept of a fiber-reinforced framework replacing the traditional metal framework is common to both. With the introduction of improved fiber reinforcing materials, it seems likely that this technique would have an acceptable success rate. A controlled clinical trial would be necessar y to definitively assess the long-term outcomes. In addition, it may reveal contraindications and disadvantages that presently are not apparent.
203
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DUNCAN, FREILICH, AND LATVIS
SUMMARY The advantages of an FRC framework make it a realistic option for replacement of a metal framework. An FRC framework has the potential to provide the same benefits as a metal framework in a much more efficient manner. REFERENCES 1. Jimenez-Lopez V. Oral rehabilitation with implant-supported prostheses. Chicago: Quintessence; 1999. p. 284-5. 2. Moffa JP, Beck WD, Hoke AW. Allergic response to nickel containing dental alloys [abstract 107]. J Dent Res 1977;56:1378. 3. Morris HF. Veterans Administration Cooperative Studies Project No. 147. Part IV: biocompatibility of base metal alloys. J Prosthet Dent 1987;58:1-5. 4. Freilich MA, Meiers JC, Duncan JP, Goldberg AJ. Fiber-reinforced composites in clinical dentistry. Chicago: Quintessence; 2000. p. 2373; 93-102. 5. Freilich MA, Karmaker AC, Burstone CJ, Goldberg AJ. Flexure strength of fiber-reinforced composites designed for prosthodontic application [abstract 999]. J Dent Res 1997;76(special issue):138.
6. Craig RG. Restorative dental materials. 10th ed. St Louis: Mosby; 1993. p. 506. 7. Anusavice KJ. Phillips’ science of dental materials. 10th ed. Philadelphia: WB Saunders; 1996. p. 431. 8. Bergendal T, Ekstrand K, Karlsson U. Evaluation of implant-supported carbon/graphite fiber-reinforced poly(methyl methacrylate) prostheses. A longitudinal multicenter study. Clin Oral Implants Res 1995;6:246-53. Reprint requests to: DR JACQUELINE P. DUNCAN DEPARTMENT OF PROSTHODONTICS AND OPERATIVE DENTISTRY SCHOOL OF DENTAL MEDICINE UCONN HEALTH CENTER 263 FARMINGTON AVE FARMINGTON, CT 06030-1615 FAX: (860)679-1370 E-MAIL: [email protected] Copyright © 2000 by The Editorial Council of The Journal of Prosthetic Dentistry. 0022-3913/2000/$12.00 + 0. 10/1/108025
doi:10.1067/mpr.2000.108025
New product news The January and July issues of the Journal carry information regarding new products of interest to prosthodontists. Product information should be sent 1 month prior to ad closing date to: Dr. Glen P. McGivney, Editor, SUNY at Buffalo, School of Dental Medicine, 345 Squire Hall, Buffalo, NY 14214. Product information may be accepted in whole or in part at the discretion of the Editor and is subject to editing. A black-and-white glossy photo may be submitted to accompany product information. Information and products reported are based on information provided by the manufacturer. No endorsement is intended or implied by the Editorial Council of The Journal of Prosthetic Dentistry, the editor, or the publisher.
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