Fabricating a fiber-reinforced post and zirconia core with CAD/CAM technology Ju-Hyoung Lee, DDS,a Dong-Seok Sohn, DDS, PhD,b and Cheong-Hee Lee, DDS, PhDc Catholic University of Daegu School of Medicine, Daegu, South Korea; School of Dentistry, Kyungpook National University, Daegu, South Korea This article describes a technique for overcoming the limitations of dental scanners in imaging post spaces by using a single fiber-reinforced post and computer-aided design and computer-aided manufacturing (CAD/CAM) technology, thereby eliminating the need for a ‘Scan Post’ and the post and core module in the CAD. This technique produces an anatomically correct core and ensures the correct thickness of crown restorations. (J Prosthet Dent 2014;-:---) If sufficient dentin is not available, a post and core is required to provide retention and support.1-4 Some clinical evaluations of crowned teeth with posts have indicated that 10% of all failures are due to root fracture.2 Fiber-reinforced composite resin (FRC) posts exhibit a modulus of elasticity similar to that of dentin and therefore minimize the risk of catastrophic root fractures.5-10 This article describes the development of the FRC post and zirconia core by using CAD/CAM technology to reduce the potential for irreversible failure and to present an esthetic option for the foundation restoration of ceramic crowns. By using zirconia and CAD/ CAM technology, an anatomically correct zirconia core with fewer voids can be designed. In addition, a ‘Scan Post’ and the post and core module in the CAD are no longer necessary because only one FRC post is used for both impression-making and cementation in the zirconia core.
a post space in the palatal root canal with an FRC post drill (Snowlight; Abrasive Technology) in the conventional manner.11,12 Ensure that the core-post junction is sufficiently wide to prevent fracture during the milling of the presintered material.13 2. Make an impression with the FRC post and polyvinyl siloxane material (Aquasil; Dentsply Caulk). 3. Make a definitive cast (Fig. 1). 4. After marking the margins, block out any undercuts with wax and place the FRC post into the palatal canal.
5. Scan the cast with a dental scanner (D800; 3Shape Inc) (Fig. 2). 6. Use CAD/CAM software (Dental System; 3Shape Inc) to design the zirconia core from the complete anatomic crown of anatomy library to an anatomically correct core with modification of its form and size (Fig. 3). 7. Mill a zirconia block (BruxZir; Glidewell Laboratories Inc) with a 5-axis milling machine (Ceracube CM5; Dental Plus Co) from the design (Fig. 4). 8. After milling, remove the projected post part on the occlusal surface
PROCEDURE 1. After endodontic treatment of the maxillary first molar tooth, prepare a
1 Definitive cast.
Assistant Professor, Department of Dentistry, Catholic University of Daegu School of Medicine; Graduate student, Department of Prosthodontics, School of Dentistry, Kyungpook National University. b Professor, Department of Dentistry, Catholic University of Daegu School of Medicine. c Professor, Department of Prosthodontics, School of Dentistry, Kyungpook National University.
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2 Software image after scanning definitive cast.
3 Software image of computer-assisted design of anatomically correct core.
4 Milled zirconia core before sintering.
5 Fiber-reinforced post and zirconia core after cementation.
of the zirconia core with a diamond rotary instrument (Dia-burs; Mani Inc). Check the opening on the occlusal surface. 9. After sintering the core according to the manufacturer’s recommendations, evaluate the fit of the zirconia core in the definitive cast. If necessary, use a silicone-disclosing agent and adjust until the zirconia core fits passively. 10. Cut the FRC post about 1 mm below the core. 11. Apply petroleum jelly to the surface of the definitive cast to facilitate the separation of the FRC post from the zirconia core. 12. After applying resin (Panavia F 2.0; Kuraray Medical Inc) on the inner surface of the hole in the zirconia core and on the outer surface of the FRC post, push the FRC post into the zirconia core and polymerize the resin on
the definitive cast. Use a zirconia primer agent (Clearfil Ceramic Primer; Kuraray Medical Inc) as recommended. 13. Remove 1 mm of resin from the FRC post and fill it with blue composite resin (Light-core; Bisco) to identify the location of the FRC post if endodontic retreatment is needed. Polymerize according to the manufacturer’s recommendations (Fig. 5).
SUMMARY This article presents a technique for overcoming the limitations of dental scanners in imaging the root canal by converting the concave surface of the root canal into the convex surface of the FRC post. Compared with techniques using rigid posts, this technique may reduce the incidence of unrestorable root fractures. In addition, making the anatomically correct core
The Journal of Prosthetic Dentistry
with the help of CAD/CAM technology is easier than with different post and core systems. This results in the correct thickness of crown restorations. However, the prefabricated FRC post may not achieve intimate adaptability in noncircular, wide, or extremely tapered canals and can compromise the retention of the FRC post compared with custom-made rigid (metal or ceramic) posts. The survival rate and the fracture strength of these restorations should be further investigated.
REFERENCES 1. Carter JM, Sorensen SE, Johnson RR, Teitelbaum RL, Levine MS. Punch shear testing of extracted vital and endodontically treated teeth. J Biomech 1983;16:841-8. 2. Goodacre CJ, Spolnik KJ. The prosthodontic management of endodontically treated teeth: a literature review. Part I. Success and failure data, treatment concepts. J Prosthodont 1994;3:243-50.
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3. Fernandes AS, Dessai GS. Factors affecting the fracture resistance of post-core reconstructed teeth: a review. Int J Prosthodont 2001;14:355-63. 4. Strub JR, Pontius O, Koutayas S. Survival rate and fracture strength of incisors restored with different post and core systems after exposure in the artificial mouth. J Oral Rehabil 2001;28:120-4. 5. Pfeiffer P, Schulz A, Nergiz I, Schmage P. Yield strength of zirconia and glass fibre-reinforced posts. J Oral Rehabil 2006;33:70-4. 6. Dietschi D, Duc O, Krejci I, Sadan A. Biomechanical considerations for the restoration of endodontically treated teeth: a systematic review of the literatureePart 1. Composition and micro-and macrostructure alterations. Quintessence Int 2007;38:733-43. 7. Newman MP, Yaman P, Dennison J, Rafter M, Billy E. Fracture resistance of endodontically treated teeth restored with composite posts. J Prosthet Dent 2003; 89:360-7.
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3 8. Cormier CJ, Burns DR, Moon P. In vitro comparison of the facture resistance and failure mode of fiber, ceramic, and conventional post systems at various stages of restoration. J Prosthodont 2001; 10:26-36. 9. de Rijk WG. The use of a fiber reinforced post offers the advantages of a suitable elastic modulus and easy removal if so indicated by clinical findings. Am J Dent 2000;13: 19B-21B. 10. Varvara G, Perinetti G, Di lorio D, Murmura G, Caputi S. In vitro evaluation of fracture resistance and failure mode of internally restored endodontically treated maxillary incisors with differing heights of residual dentin. J Prosthet Dent 2007;98: 365-72. 11. Rosenstiel SF, Fujimoto J, Land MF. Contemporary fixed prosthodontics. 4th ed. St Louis: Elsevier; 2006. p. 336-74.
12. Trebilcock CE Jr, Evans DB. A two-stage impression technique for the indirect fabrication of multiple cast dowel and cores. J Prosthet Dent 1991;66:422-5. 13. Awad MA, Marghalani TY. Fabrication of a custom-made ceramic post and core using CAD-CAM technology. J Prosthet Dent 2007;98:161-2. Corresponding author: Dr Ju-Hyoung Lee Catholic University of Daegu School of Medicine 3056-6 Daemyung-4-Dong, Namgu, Daegu SOUTH KOREA E-mail: [email protected] Copyright ª 2014 by the Editorial Council for The Journal of Prosthetic Dentistry.
a post space in the palatal root canal with an FRC post drill (Snowlight; Abrasive Technology) in the conventional manner.11,12 Ensure that the core-post junction is sufficiently wide to prevent fracture during the milling of the presintered material.13 2. Make an impression with the FRC post and polyvinyl siloxane material (Aquasil; Dentsply Caulk). 3. Make a definitive cast (Fig. 1). 4. After marking the margins, block out any undercuts with wax and place the FRC post into the palatal canal.
5. Scan the cast with a dental scanner (D800; 3Shape Inc) (Fig. 2). 6. Use CAD/CAM software (Dental System; 3Shape Inc) to design the zirconia core from the complete anatomic crown of anatomy library to an anatomically correct core with modification of its form and size (Fig. 3). 7. Mill a zirconia block (BruxZir; Glidewell Laboratories Inc) with a 5-axis milling machine (Ceracube CM5; Dental Plus Co) from the design (Fig. 4). 8. After milling, remove the projected post part on the occlusal surface
PROCEDURE 1. After endodontic treatment of the maxillary first molar tooth, prepare a
1 Definitive cast.
Assistant Professor, Department of Dentistry, Catholic University of Daegu School of Medicine; Graduate student, Department of Prosthodontics, School of Dentistry, Kyungpook National University. b Professor, Department of Dentistry, Catholic University of Daegu School of Medicine. c Professor, Department of Prosthodontics, School of Dentistry, Kyungpook National University.
Lee et al
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Volume
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2 Software image after scanning definitive cast.
3 Software image of computer-assisted design of anatomically correct core.
4 Milled zirconia core before sintering.
5 Fiber-reinforced post and zirconia core after cementation.
of the zirconia core with a diamond rotary instrument (Dia-burs; Mani Inc). Check the opening on the occlusal surface. 9. After sintering the core according to the manufacturer’s recommendations, evaluate the fit of the zirconia core in the definitive cast. If necessary, use a silicone-disclosing agent and adjust until the zirconia core fits passively. 10. Cut the FRC post about 1 mm below the core. 11. Apply petroleum jelly to the surface of the definitive cast to facilitate the separation of the FRC post from the zirconia core. 12. After applying resin (Panavia F 2.0; Kuraray Medical Inc) on the inner surface of the hole in the zirconia core and on the outer surface of the FRC post, push the FRC post into the zirconia core and polymerize the resin on
the definitive cast. Use a zirconia primer agent (Clearfil Ceramic Primer; Kuraray Medical Inc) as recommended. 13. Remove 1 mm of resin from the FRC post and fill it with blue composite resin (Light-core; Bisco) to identify the location of the FRC post if endodontic retreatment is needed. Polymerize according to the manufacturer’s recommendations (Fig. 5).
SUMMARY This article presents a technique for overcoming the limitations of dental scanners in imaging the root canal by converting the concave surface of the root canal into the convex surface of the FRC post. Compared with techniques using rigid posts, this technique may reduce the incidence of unrestorable root fractures. In addition, making the anatomically correct core
The Journal of Prosthetic Dentistry
with the help of CAD/CAM technology is easier than with different post and core systems. This results in the correct thickness of crown restorations. However, the prefabricated FRC post may not achieve intimate adaptability in noncircular, wide, or extremely tapered canals and can compromise the retention of the FRC post compared with custom-made rigid (metal or ceramic) posts. The survival rate and the fracture strength of these restorations should be further investigated.
REFERENCES 1. Carter JM, Sorensen SE, Johnson RR, Teitelbaum RL, Levine MS. Punch shear testing of extracted vital and endodontically treated teeth. J Biomech 1983;16:841-8. 2. Goodacre CJ, Spolnik KJ. The prosthodontic management of endodontically treated teeth: a literature review. Part I. Success and failure data, treatment concepts. J Prosthodont 1994;3:243-50.
Lee et al
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3. Fernandes AS, Dessai GS. Factors affecting the fracture resistance of post-core reconstructed teeth: a review. Int J Prosthodont 2001;14:355-63. 4. Strub JR, Pontius O, Koutayas S. Survival rate and fracture strength of incisors restored with different post and core systems after exposure in the artificial mouth. J Oral Rehabil 2001;28:120-4. 5. Pfeiffer P, Schulz A, Nergiz I, Schmage P. Yield strength of zirconia and glass fibre-reinforced posts. J Oral Rehabil 2006;33:70-4. 6. Dietschi D, Duc O, Krejci I, Sadan A. Biomechanical considerations for the restoration of endodontically treated teeth: a systematic review of the literatureePart 1. Composition and micro-and macrostructure alterations. Quintessence Int 2007;38:733-43. 7. Newman MP, Yaman P, Dennison J, Rafter M, Billy E. Fracture resistance of endodontically treated teeth restored with composite posts. J Prosthet Dent 2003; 89:360-7.
Lee et al
3 8. Cormier CJ, Burns DR, Moon P. In vitro comparison of the facture resistance and failure mode of fiber, ceramic, and conventional post systems at various stages of restoration. J Prosthodont 2001; 10:26-36. 9. de Rijk WG. The use of a fiber reinforced post offers the advantages of a suitable elastic modulus and easy removal if so indicated by clinical findings. Am J Dent 2000;13: 19B-21B. 10. Varvara G, Perinetti G, Di lorio D, Murmura G, Caputi S. In vitro evaluation of fracture resistance and failure mode of internally restored endodontically treated maxillary incisors with differing heights of residual dentin. J Prosthet Dent 2007;98: 365-72. 11. Rosenstiel SF, Fujimoto J, Land MF. Contemporary fixed prosthodontics. 4th ed. St Louis: Elsevier; 2006. p. 336-74.
12. Trebilcock CE Jr, Evans DB. A two-stage impression technique for the indirect fabrication of multiple cast dowel and cores. J Prosthet Dent 1991;66:422-5. 13. Awad MA, Marghalani TY. Fabrication of a custom-made ceramic post and core using CAD-CAM technology. J Prosthet Dent 2007;98:161-2. Corresponding author: Dr Ju-Hyoung Lee Catholic University of Daegu School of Medicine 3056-6 Daemyung-4-Dong, Namgu, Daegu SOUTH KOREA E-mail: [email protected] Copyright ª 2014 by the Editorial Council for The Journal of Prosthetic Dentistry.
