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Titanium removable partial denture clasp repair using laser welding: a clinical report
Titanium removable partial denture clasp repair using laser welding: A clinical report Yasunori Suzuki, DMD, PhD,a Chikahiro Ohkubo, DMD, PhD,b Minoru Abe, DDS, PhD,c and Toshio Hosoi, DDS, PhDd Tsurumi University School of Dental Medicine, Yokohama, Japan This clinical report describes repair of a fractured removable partial denture clasp using laser welding rather than a conventional torch soldering technique. (J Prosthet Dent 2004;91:418-20.)
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f a clasp on a removable partial denture (RPD) is damaged or broken, the entire prosthesis may become unstable, lose retention, and become a source of discomfort to the patient. Clasps may be repaired by soldering with a conventional torch technique. However, there some disadvantages of soldering1-8: (1) the soldered clasp is likely to break again because of stress concentration, (2) discoloration caused by electric and chemical corrosion may occur, (3) soldering of commercially pure Ti (CP Ti) is difficult because of oxidation problems, (4) use of fire and gas may be hazardous, (5) technical skill is necessary, and (6) heating may burn the denture base resin. Laser welding is an attractive alternative method to join dental casting alloys.1-8 During the past decade, laser welding has been increasingly used because there is no need for investment and soldering alloy, working time is decreased, lasers are easy to operate, little damage is caused to the denture resin from the pin-point heat, and there are few effects of heating and oxidation.3 The penetration depth of the weld into titanium is significantly greater than into gold alloy.8 Titanium has lower thermal conductivity and a greater rate of laser beam absorption compared with gold alloy.8 These properties make it easier to laser weld titanium to repair broken titanium clasps. This clinical report describes the repair of a fractured clasp of a titanium RPD using laser welding.
CLINICAL REPORT A 73-year-old partially edentulous woman presented 8 years ago with the complaint that her RPD was broken. The teeth from the maxillary right second molar to the left lateral incisor were missing, although the roots of the right second premolar and central incisor, Presented at the 2003 Annual Spring Scientific Meeting of the Korean Academy of Prosthodontics and The 1st Joint Academic Meeting with Japan Prosthodontic Society, Seoul, Korea, March, 2003. a Instructor, Department of Removable Prosthodontics. b Instructor, Department of Removable Prosthodontics. c Associate Professor, Department of Removable Prosthodontics. d Dean, Tsurumi University School of Dental Medicine.
418 THE JOURNAL OF PROSTHETIC DENTISTRY
and left canine remained. In addition, the mandibular left canine, second molar, and right molar were missing. The occlusal vertical dimension was decreased, and the existing maxillary RPD had fractured several times. The remaining teeth demonstrated loss of support because of periodontal disease, but mobility was not observed for all teeth. Although implant placement and fabrication of an implant-supported prostheses were considered as alternative treatment, the patient preferred an RPD. After impression making, the definitive casts were mounted on a semi-adjustable articulator. The frameworks of the definitive maxillary and mandibular RPD were designed with a double structure in which both the metal occlusal surfaces and metal skeleton framework were connected by columns.9 The intaglio surface of the maxillary denture was lined with PMMA acrylic resin to allow adjustment. The frameworks were cast with CP titanium (JIS grade 3, T-Alloy H; GC Dental, Tokyo, Japan) using a gas pressure casting system (Autocast System; GC Dental) according to the manufacturer’s recommendations. Then the cast surfaces were airborneparticle abraded (Sandblaster USB-751B; UNIQUE Co, Kawaguchi, Japan) with 125-mm Al2O3 particles and chemically treated with a HNO3/HF solution (Chemi Polish; Shofu, Kyoto, Japan). A metal primer (Metal primer; GC Dental) was used to bond the denture base resin and the titanium framework. Autopolymerizing PMMA (Palapress Vario; Kulzer, Wehrheim, Germany) was then polymerized and polished, and the dentures were conventionally completed (Fig. 1).10 The previously described cast titanium RPDs functioned well for approximately 7 years. There was little wear of the cast titanium teeth on both maxillary and mandibular RPDs. At 7 years, 10 months after insertion, the cast clasp on the left second molar in the maxillary RPD fractured (Fig. 2), likely because of occlusal forces. Retention of the prosthesis decreased, and the patient requested that the clasp be repaired. To repair the clasp, a transfer impression was made of the RPD using 2 silicone impression materials (Zeroseal; DreveDentamid GMBH, Unna, Germany, and EXAFINE; GC Dental) in a stock tray to correctly record the prosthesis in relation to the abutment teeth intraorally. The clasp pattern was fabricated using pattern wax VOLUME 91 NUMBER 5
SUZUKI ET AL
THE JOURNAL OF PROSTHETIC DENTISTRY
Fig. 1. Completed maxillary cast titanium RPD.
Fig. 2. Broken cast clasp on left second molar.
Fig. 3. Repaired clasp with hook to connect to existing clasps.
Fig. 4. Repaired clasp connected using laser welding.
Fig. 5. Repaired prosthesis.
MAY 2004
(RKG; Dentaurum, Ispringen, Germany) with hooks to join to the clasps of the first and the second molars so that the repaired clasp was placed in the appropriate position. The clasp was then cast using the same grade of CP titanium (Fig. 3) as the original RPD. The joint surfaces of the clasp were airborne-particle abraded with Al2O3 particles (50 mm) to increase the absorption coefficient of laser energy.7 After the fit of the repaired clasp was confirmed, the hooks were connected to the existing clasps intraorally using acrylic resin (Palabit G; Kulzer). The clasp was provisionally welded to prevent the clasp from moving during laser welding (Neo laser L-ALC30; Girrbach, Pforzheim, Germany) with a voltage of 180 V, pulse of 3 ms, and spot diameter of 0.6 to 0.7 mm. The clasp was definitively welded at similar conditions with laser titanium solder (Laser wire Ti; Selec Co, Osaka, Japan) (Figs. 4 and 5). After welding, the clasp was finished and polished conventionally.10 419
THE JOURNAL OF PROSTHETIC DENTISTRY
SUMMARY The article described the advantages, disadvantages, and technique for repairing a titanium RPD clasp with the laser welding technique. The authors express their gratitude to Mr Yukihiro Mizuno, SDT, of Tsurumi University, for his laboratory assistance. The editorial assistance of Mrs Jeanne Santa Cruz is greatly appreciated.
REFERENCES 1. Sjogren G, Andersson M, Bergman M. Laser welding of titanium in dentistry. Acta Odontol Scand 1988;46:247-53. 2. Yamagishi T, Ito M, Fujimura Y. Mechanical properties of laser welding of titanium in dentistry by pulsed Nd:YAG laser apparatus. J Prosthet Dent 1993;70:264-73. 3. Roggensack M, Walter MH, Boning KW. Studies on laser and plasmawelded titanium. Dent Master 1993;9:104-7. 4. Berg E, Wanger WC, Davik G, Dootz ER. Mechanical properties of laserwelded cast and wrought titanium. J Prosthet Dent 1995;74:250-7. 5. Wang RR, Welsch GE. Joining titanium materials with tungsten inert gas welding, laser welding, and infrared brazing. J Prosthet Dent 1995; 74:521-30. 6. Neo TK, Chai J, Gilbert JL, Wozniak WT, Engelman M. Mechanical properties of titanium connectors. Int J Prosthodont 1996;9:379-93.
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SUZUKI ET AL
7. Chai T, Chou CK. Mechanical properties of laser-welded cast titanium joints under different conditions. J Prosthet Dent 1998;79:477-83. 8. Watanabe I, Liu J, Atsuta M. Effects of heat treatments on mechanical strength of laser-welded equi-atomic AuCu-6at%Ga alloy. J Dent Res 2001;80:1813-7. 9. Ohkubo C, Abe M, Miyata T, Obana J. Comparative strengths of metal framework structures for removable partial dentures. J Prosthet Dent 1997;78:302-8. 10. McGivney G, Carr A. McCracken’s removable partial prosthodontics. 10th ed. St. Louis: Mosby; 2000. p. 377–427. Reprint requests to: DR YASUNORI SUZUKI DEPARTMENT OF REMOVABLE PROSTHODONTICS TSURUMI UNIVERSITY SCHOOL OF DENTAL MEDICINE 2-1-3 TSURUMI, TSURUMI-ku YOKOHAMA 230-8501 JAPAN TEL: +81-45-581-1001 FAX: +81-45-573-9599 E-MAIL: [email protected] 0022-3913/$30.00 Copyright ª 2004 by The Editorial Council of The Journal of Prosthetic Dentistry
doi:10.1016/j.prosdent.2004.01.019
VOLUME 91 NUMBER 5
I
f a clasp on a removable partial denture (RPD) is damaged or broken, the entire prosthesis may become unstable, lose retention, and become a source of discomfort to the patient. Clasps may be repaired by soldering with a conventional torch technique. However, there some disadvantages of soldering1-8: (1) the soldered clasp is likely to break again because of stress concentration, (2) discoloration caused by electric and chemical corrosion may occur, (3) soldering of commercially pure Ti (CP Ti) is difficult because of oxidation problems, (4) use of fire and gas may be hazardous, (5) technical skill is necessary, and (6) heating may burn the denture base resin. Laser welding is an attractive alternative method to join dental casting alloys.1-8 During the past decade, laser welding has been increasingly used because there is no need for investment and soldering alloy, working time is decreased, lasers are easy to operate, little damage is caused to the denture resin from the pin-point heat, and there are few effects of heating and oxidation.3 The penetration depth of the weld into titanium is significantly greater than into gold alloy.8 Titanium has lower thermal conductivity and a greater rate of laser beam absorption compared with gold alloy.8 These properties make it easier to laser weld titanium to repair broken titanium clasps. This clinical report describes the repair of a fractured clasp of a titanium RPD using laser welding.
CLINICAL REPORT A 73-year-old partially edentulous woman presented 8 years ago with the complaint that her RPD was broken. The teeth from the maxillary right second molar to the left lateral incisor were missing, although the roots of the right second premolar and central incisor, Presented at the 2003 Annual Spring Scientific Meeting of the Korean Academy of Prosthodontics and The 1st Joint Academic Meeting with Japan Prosthodontic Society, Seoul, Korea, March, 2003. a Instructor, Department of Removable Prosthodontics. b Instructor, Department of Removable Prosthodontics. c Associate Professor, Department of Removable Prosthodontics. d Dean, Tsurumi University School of Dental Medicine.
418 THE JOURNAL OF PROSTHETIC DENTISTRY
and left canine remained. In addition, the mandibular left canine, second molar, and right molar were missing. The occlusal vertical dimension was decreased, and the existing maxillary RPD had fractured several times. The remaining teeth demonstrated loss of support because of periodontal disease, but mobility was not observed for all teeth. Although implant placement and fabrication of an implant-supported prostheses were considered as alternative treatment, the patient preferred an RPD. After impression making, the definitive casts were mounted on a semi-adjustable articulator. The frameworks of the definitive maxillary and mandibular RPD were designed with a double structure in which both the metal occlusal surfaces and metal skeleton framework were connected by columns.9 The intaglio surface of the maxillary denture was lined with PMMA acrylic resin to allow adjustment. The frameworks were cast with CP titanium (JIS grade 3, T-Alloy H; GC Dental, Tokyo, Japan) using a gas pressure casting system (Autocast System; GC Dental) according to the manufacturer’s recommendations. Then the cast surfaces were airborneparticle abraded (Sandblaster USB-751B; UNIQUE Co, Kawaguchi, Japan) with 125-mm Al2O3 particles and chemically treated with a HNO3/HF solution (Chemi Polish; Shofu, Kyoto, Japan). A metal primer (Metal primer; GC Dental) was used to bond the denture base resin and the titanium framework. Autopolymerizing PMMA (Palapress Vario; Kulzer, Wehrheim, Germany) was then polymerized and polished, and the dentures were conventionally completed (Fig. 1).10 The previously described cast titanium RPDs functioned well for approximately 7 years. There was little wear of the cast titanium teeth on both maxillary and mandibular RPDs. At 7 years, 10 months after insertion, the cast clasp on the left second molar in the maxillary RPD fractured (Fig. 2), likely because of occlusal forces. Retention of the prosthesis decreased, and the patient requested that the clasp be repaired. To repair the clasp, a transfer impression was made of the RPD using 2 silicone impression materials (Zeroseal; DreveDentamid GMBH, Unna, Germany, and EXAFINE; GC Dental) in a stock tray to correctly record the prosthesis in relation to the abutment teeth intraorally. The clasp pattern was fabricated using pattern wax VOLUME 91 NUMBER 5
SUZUKI ET AL
THE JOURNAL OF PROSTHETIC DENTISTRY
Fig. 1. Completed maxillary cast titanium RPD.
Fig. 2. Broken cast clasp on left second molar.
Fig. 3. Repaired clasp with hook to connect to existing clasps.
Fig. 4. Repaired clasp connected using laser welding.
Fig. 5. Repaired prosthesis.
MAY 2004
(RKG; Dentaurum, Ispringen, Germany) with hooks to join to the clasps of the first and the second molars so that the repaired clasp was placed in the appropriate position. The clasp was then cast using the same grade of CP titanium (Fig. 3) as the original RPD. The joint surfaces of the clasp were airborne-particle abraded with Al2O3 particles (50 mm) to increase the absorption coefficient of laser energy.7 After the fit of the repaired clasp was confirmed, the hooks were connected to the existing clasps intraorally using acrylic resin (Palabit G; Kulzer). The clasp was provisionally welded to prevent the clasp from moving during laser welding (Neo laser L-ALC30; Girrbach, Pforzheim, Germany) with a voltage of 180 V, pulse of 3 ms, and spot diameter of 0.6 to 0.7 mm. The clasp was definitively welded at similar conditions with laser titanium solder (Laser wire Ti; Selec Co, Osaka, Japan) (Figs. 4 and 5). After welding, the clasp was finished and polished conventionally.10 419
THE JOURNAL OF PROSTHETIC DENTISTRY
SUMMARY The article described the advantages, disadvantages, and technique for repairing a titanium RPD clasp with the laser welding technique. The authors express their gratitude to Mr Yukihiro Mizuno, SDT, of Tsurumi University, for his laboratory assistance. The editorial assistance of Mrs Jeanne Santa Cruz is greatly appreciated.
REFERENCES 1. Sjogren G, Andersson M, Bergman M. Laser welding of titanium in dentistry. Acta Odontol Scand 1988;46:247-53. 2. Yamagishi T, Ito M, Fujimura Y. Mechanical properties of laser welding of titanium in dentistry by pulsed Nd:YAG laser apparatus. J Prosthet Dent 1993;70:264-73. 3. Roggensack M, Walter MH, Boning KW. Studies on laser and plasmawelded titanium. Dent Master 1993;9:104-7. 4. Berg E, Wanger WC, Davik G, Dootz ER. Mechanical properties of laserwelded cast and wrought titanium. J Prosthet Dent 1995;74:250-7. 5. Wang RR, Welsch GE. Joining titanium materials with tungsten inert gas welding, laser welding, and infrared brazing. J Prosthet Dent 1995; 74:521-30. 6. Neo TK, Chai J, Gilbert JL, Wozniak WT, Engelman M. Mechanical properties of titanium connectors. Int J Prosthodont 1996;9:379-93.
420
SUZUKI ET AL
7. Chai T, Chou CK. Mechanical properties of laser-welded cast titanium joints under different conditions. J Prosthet Dent 1998;79:477-83. 8. Watanabe I, Liu J, Atsuta M. Effects of heat treatments on mechanical strength of laser-welded equi-atomic AuCu-6at%Ga alloy. J Dent Res 2001;80:1813-7. 9. Ohkubo C, Abe M, Miyata T, Obana J. Comparative strengths of metal framework structures for removable partial dentures. J Prosthet Dent 1997;78:302-8. 10. McGivney G, Carr A. McCracken’s removable partial prosthodontics. 10th ed. St. Louis: Mosby; 2000. p. 377–427. Reprint requests to: DR YASUNORI SUZUKI DEPARTMENT OF REMOVABLE PROSTHODONTICS TSURUMI UNIVERSITY SCHOOL OF DENTAL MEDICINE 2-1-3 TSURUMI, TSURUMI-ku YOKOHAMA 230-8501 JAPAN TEL: +81-45-581-1001 FAX: +81-45-573-9599 E-MAIL: [email protected] 0022-3913/$30.00 Copyright ª 2004 by The Editorial Council of The Journal of Prosthetic Dentistry
doi:10.1016/j.prosdent.2004.01.019
VOLUME 91 NUMBER 5