rison of tensile strength of solder ventional torch technique Giorgio Grayson
Cattaneo, Marshall,
DDS,a
Galen
Wagnild,
DDS,
PhD,C
and
joints
by infrared
DDS,b
Larry
Watanabed
University of California, School of Dentistry, San Francisco, Calif. Fabrication of a fixed partial denture may require a soldering step. This study compared soldering by a conventional torch procedure with an infrared soldering technique. Comparisons were made for tensile strength, porosity, and time efficiency between the two methods. No significant difference was found in ultimate tensile strength between the two types of solder joints and the nonsoldered control samples. Random samples photographed with a scanning electron microscope revealed no difference in joint porosity between the two techniques. Torch soldering took consistently less time that infrared soldering. (J PROSTHET DENT 1992;68:33-7.)
he fabrication of a multiunit fixed partial denture may include a soldering step to assemble the individual components. The decision to solder is based on the accumulated inaccuracies found in the various materials and techniques used through the casting stage.l, 2 Soldering has been defined as the joining of metals by the medium of a filler metal that has a lower fusion temperature than that of the metal parts to be joined.3 The union of the solder with the parent alloy does not result in the diffusion of one of the metals into the other. A number of variables affect the strength and accuracy of the soldered framework. The literature includes studies pertaining to presoldered and postsoldered connectors,4, 5, 6 gap distance,7, 8 indexing,g, lo and soldering invest-
%enior Resident, Graduate Prosthodontics Program. bAssociate Clinical Professor, Post Graduate Prosthodontics gram. CProfessor and Chief, Engineer. Biomaterials Section. dSenior Development
Pro-
Fig.
JOURNAL
Table I. Diameter and ultimate sample soldered by torch Sample
Diameter
QF PROSTHETIC
DENTISTRY
1.
Dimension
(cm)
tensile Tensile
strength strength
1 2 3 4 5 6 7 8
0.203 0.217 0.229 0.237 0.236 0.240 0.218 0.232
4705 3454 3454 2088 2471 4159 3860
9
0.209 0.189
3556 4357
10
10/l/36695
THE
ments.11-13 The method of heat application was investigated by Monday and Asgar13 who found torch soldering four to five times stronger than oven soldering of Olympia ceramic alloy (Pennwalt/Jelenko, Armonk, N.Y.). Torch soldering, however, can be difficult to control, creating a potential for inadequate or uneven heating, incomplete
of each (kg/cd)
3696
of the test specimens.
33
CATTANEO
ET AL
Fig. 2. Mean and standard deviation and tensile strength of samples soldered by torch and infrared technique. Third bar represents mean tensile strength of 10 unsoldered bars.
Fig.
SO1ider
3. Optical
diagram
flow, and decreased connector strength. In general, techniques have not changed in many years. Lithas been published regarding the joining of t1e ! information mt stals by methods other than conventional torch soldering techniques. or oven soldering The purpose of this study was to compare the conventic rnal torch procedure for soldering with a new method ad vacated by J.M. Ney Co. (Bloomfield, Conn.) using an SO1ldering
34
of infrared
instrument.
infrared soldering technique. Comparisons were I nade for (1) tensile strength, (2) porosity and (3) tin ie effici ency between these two methods.
METHODS
AND
MATERIAL
Three groups of specimens were tested in this stl udy. ’The first group consisted of 10 joints soldered with a corn rentional torch technique, the second group w as corn pose1d of
JULY
1992
VOLUME
68
NUMBER
1
COMPARISON
OF SOLDER
JOINTS
5. SEM photomicrograph made by flame technique.
Fig.
of solder joint
surface
III. Mean of tensile strength (kg/cm2) and standard deviation of samples soldered by torch, soldered by infrared technique and unsoldered (as cast)
Table
Group
Torch Infrared Unsoldered ANOVA
Table II. Diameter and ultimate tensile strength of each samplesoldered by heat
I 2 3 4 5 6
7 8 9 10
Diameter
(cm)
Tensile
strength
(kg/cm2)
2444 3492 4729 3366 4134 3892 3757 2272 3715 3458
0.235 0.237 0.238 0.238 0.237 0.222 0.229 0.205 0.212 0.203
10joints solderedby the infrared technique, and the third group ascast with no solder asthe control group. The resin test patterns measured16 mm in length and 2.5 mm in diameter, correspondingto the American Dental Association (ADA) specification 5 (Fig. 1). The resin patterns were cast with a high noble metal alloy used in the fabrication of porcelain fused-to-metal restorations (SMGB, J. M. Ney Co.). Each bar specimenfor the soldering procedure was
THE
JOURNAL
no significant
Meall
10 10 10
3383.9 3524.9 3625.9
difference
between
SD
groups
1082.7 731.6 180.6 (p = 0.77).
4. Infrared instrument.
Fig.
Sample
showed
N
OF PROSTHETIC
DENTISTRY
cut in half with a slow-speed dental handpiece mounted firmly in a cutting jig. The cuts were made with a noncontminated aluminum oxide disk. The metal bars were moved toward the rotating disc in a direction perpendicular to their long axes to assure consistent cross-sectional areas and uniform soldering embrasures for all specimens. The solder gap selected for this study was 0.3 mm.? The sectioned bars were related by use of an acrylic resin indexing material (Duralay, Reliance Dental Manufacturing Co., Worth, Ill.), invested for soldering (Speed-E, Whip Mix, Louisville, KY.), and placed in a cold oven. The oven temperature was raised at a rate of 50° F/minute to a temperature of 1700’ F, which was 200” F below the melting range of the metal. The invested units were removed from the oven and soldered in one of two ways. 1. Torch soldering. Flux (J. M. Ney Co.) wasapplied to the solder joint area and the solder (SMGB, J.M. Ney Co.) was inserted. A gas and oxygen torch was used in a back-and-forth motion to heat the joint site until the solder flowed into the gap. The temperature of the flame was monitored with an infrared optical thermometer (Optitherm infrared thermometer, model 12-8723,Barnes Engineering, Stamford, Conn.) to avoid heating the parent alloy to its melting range. 2. Infrared soldering. Flux wasapplied to the joint areaand the specimenswere solderedwith an infrared in-
35
GATTANEO
Fig. 6. SEM photomicrograph made by infrared technique.
of solder
joint
surface
Fig. 8. SEM photomicrograph specimen, infrared soldered.
ET AL
of the long axis of untested
SEM examination Randomly selected specimens from each soldering group were photographed with a scanning electron microscope (SEM) (IS1 SX-40A SEM, IS1 Inc., Pleasanton, Calif.) to characterize their appearance and porosity after tensile testing. In addition, specimens were prepared for the soldering groups that were not subjected to tensile testing. These samples were sectioned longitudinally and examined to evaluate the appearance of the solder joints.
Time efficiency
Fig. 7. SEM photomicrograph specimen, flame soldered.
ofthe long axis of untested
strument (J. M. Ney Co.) according to the manufacturer’s instructions. Ten specimens were prepared and tested for each soldering method, and an additional 10 specimens were tested after casting and without sectioning or soldering, to serve as a control group.
Ultimate
tensile
strength
After the soldering, the specimens were allowed to cool for 5 minutes and then quenched in water. After divesting, excess solder was removed. The diameter of each bar was measured with an engineering micrometer accurate to 0.01 mm and the tensile strength calculations were based on these measurements. Each specimen was tested in an Instron Universal testing machine (model 1122, Instron Corporation, Canton, MA). The bars were loaded at a constant crosshead speed of 2 mm/minute, according to ADA specification 5, and the ultimate tensile strength was determined.
36
The time from the application of the energy to the melting of the solder metal for each soldering procedure was recorded during the experiment so that the efficiency of each technique could be evaluated.
RESULTS The tensile strength results of the torch soldered specimens are summarized in Table I. The diameter of each rod after soldering was noted in an effort to relate this value to the force needed to fracture the specimen. This was necessary because it was impossible to control the final rod diameter after the solder procedure. The load values required to fracture the rods yielded a range of tensile strength from 2088 kg/cm2 to a maximum of 4705 kg/cm2. In Table II, the results for infrared specimens are presented and show a tensile strength range from 2275 kg/cm2 to a value of 4729 kg/cm2. The control (unsoldered) specimens exhibited a tensile strength range from 3224 kg/cm2 to a maximum of 3844 kg/cm2. The tensile strength data were statistically analyzed with analysis of variance (ANOVA) (Table III and Fig. 2). No statistically significant difference 0, 5 0.05) between the three groups studied was found. There was no apparent difference in solder joint characteristics or porosity between joints formed. The time recorded for the conventional solder procedure from the
JULY
1992
VOLUME
68
NUMBER
1
COMPARISON
OF SOLDER
JOINTS
moment the flame was applied to the joint until the solder flowed was consistently approximately 30 seconds. The time required for the solder to flow with the infrared technique was approximately 3 minutes. ISCUSSION The infrared instrument used in this study utilizes a concentrated beam of infrared energy. The energy is emitted from a loo-watt tungsten filament quartz-iodine lamp, which is the primary focal point of the machine (Fig. 3). Above the primary focal point is a concave reflector that collects the infrared energy emitted from the tungsten filament and refocuses this energy into a single point, the secondary focal point. The object to be soldered is placed at this secondary focal point. Object positioning is accomplished by an adjustable work platform as illustrated in Fig. 4. Microstructural analysis was obtained with an SEM. Photomicrographs of selected specimens examined at the fracture surface exhibited no discernable difference in porosity between the two groups (Figs. 5 and 6). The samples from each group presented finely divided porosity with granular appearance. Visual examination of each sample group revealed variable amounts of porosity. This finding may explain the range in ultimate tensile strength with a given group of samples. All of the fractures observed for soldered samples occurred within the solder joint area. Each individual fracture demonstrated elements of both a ductile and a brittle type of fracture. The untested specimens examined along their long axes exhibited a distinct demarcation between the solder metal and the parent metal (Figs. 7 and 8). The sharp interface indicates that significant diffusion did not occur between the two metals joined, an indication of a proper solder joint. This precision of solder flow without melting of the parent metal requires accurate control of the soldering temperature, which can be difficult to achieve routinely without the aid of the optical thermometer used in this study. Temperature control is automated with the infrared instrument, thus removing this as a variable. It is also important to note the degree of confidence one has in the solder joint. The relatively small standard deviations for the infrared soldering metal, in comparison to the torch procedure (Table III), demonstrates that soldering joints of relatively more uniform strength values can be expected with this technique. In evaluating time efficiency, it was found that the infrared technique required an average of 2 to 3 minutes more than soldering by flame. From a practical point of view the difference in time efficiency seems unimportant. CONCLUSIONS
The results of this study indicate the following: 1. There was no significant difference in ultimate tensile strength between solder joints fabricated with a conventional torch technique, solder joints fabricated with the infrared technique, and nonsoldered control specimens. 2. There was no apparent difference in solder joint porosity between joints formed by the two techniques. 3. The infrared technique permits better control during the soldering procedure. This becomes important in a presolder situation in which the melting range of the solder metal is close to the melting range of the parent metal. 4. Torch soldering took consistently less time than infrared soldering. We express for providing project.
our sincere the materials
thanks and
to the J. M. Ney Company equipment necessary for this
REFERENCES 1. Fusayama T, Wakamuto S, Hosoka J. Accuracy of fixed partial denture made by various soldering techniques and one-piece casting. J PROSTHET DENT
1964;14:334-42.
2. Garlapo DA, Lee S-H, Choung CK, Sorensen SE. Spatial changes occurring in fixed partial dentures made in one single casting. J PROSTHET DENT
1983;49:781-5.
3. Skinner EW, Phillips RW. The science of dental materials. 5th ed. Philadelphia: WB Saunders, 1960;534-46. 4. Staffanou RS, Radke RA, Jendresen MD. Strength properties of soldered joints from various ceramic-metal combinations. J PROSTHET DENT
1980;43:31-9.
5. Lautenschlager EP. Strength mechanisms of dental soldered joints. J Dent Res 1974;53:1362-7. 6. Stade EH, Reisbick MH, Preston JD. Pre-ceramic and postceramic solder joints. J PROSTHET DENT 1975;34:527-32. 7. Willis LM, Nicholls JI. Distortion in dental soldering as affected by gap distance. J PROSTHET DENT 1980;43:272-8. 8. Rasmussen EJ, Goodkind RJ, Gerberich WW. An investigation of tensile strength of dental solder joints. J PROSTHET DENT 1979;41: 418-23.
9. Moon PC, Eshleman JR, Douglas HB, Garrett SG. Comparison curacy of soldering indices for fixed prosthesis. J PROSTHET
of acDENT
1979;40:35-8.
10. Harper FJ, Nicholls JI. Distortions in indexing methods and investing media for soldering and remount procedures. J PROSTHET DENT 1979;42:172-9.
11. Munford G. The porcelain fused-to-metal restoration. Dent Clin North Am 1965;March:241. 12. Pazzini N, Pazzini LI, Araujo PA. The accuracy of solder investment. J PROSTHET
DENT
1979;42:530-3.
13. Monday JJL, Asgar K. Tensile strength comparison postsoldered joints. J PROSTHET DENT 1986;55:23-7.
of presoldered
and
Reprint requests to: DR. GALEN W. WAGNILD UNIVERSITY OF CALIFORNIA, SAN FRANCISCO SCHOOL OF DENTISTRY DEPARTMENT OF RESTORATIVE DENTISTRY 707 PARNASSUS AVENUE, D2041 SAN FRANCISCO, CA 94143
A new soldering technique using infrared radiation derived from a halogen lamp as a heat source to melt the solder has been tested.
THE
JOURNAL
OF PROSTHETIC
DENTISTRY
37
Cattaneo, Marshall,
DDS,a
Galen
Wagnild,
DDS,
PhD,C
and
joints
by infrared
DDS,b
Larry
Watanabed
University of California, School of Dentistry, San Francisco, Calif. Fabrication of a fixed partial denture may require a soldering step. This study compared soldering by a conventional torch procedure with an infrared soldering technique. Comparisons were made for tensile strength, porosity, and time efficiency between the two methods. No significant difference was found in ultimate tensile strength between the two types of solder joints and the nonsoldered control samples. Random samples photographed with a scanning electron microscope revealed no difference in joint porosity between the two techniques. Torch soldering took consistently less time that infrared soldering. (J PROSTHET DENT 1992;68:33-7.)
he fabrication of a multiunit fixed partial denture may include a soldering step to assemble the individual components. The decision to solder is based on the accumulated inaccuracies found in the various materials and techniques used through the casting stage.l, 2 Soldering has been defined as the joining of metals by the medium of a filler metal that has a lower fusion temperature than that of the metal parts to be joined.3 The union of the solder with the parent alloy does not result in the diffusion of one of the metals into the other. A number of variables affect the strength and accuracy of the soldered framework. The literature includes studies pertaining to presoldered and postsoldered connectors,4, 5, 6 gap distance,7, 8 indexing,g, lo and soldering invest-
%enior Resident, Graduate Prosthodontics Program. bAssociate Clinical Professor, Post Graduate Prosthodontics gram. CProfessor and Chief, Engineer. Biomaterials Section. dSenior Development
Pro-
Fig.
JOURNAL
Table I. Diameter and ultimate sample soldered by torch Sample
Diameter
QF PROSTHETIC
DENTISTRY
1.
Dimension
(cm)
tensile Tensile
strength strength
1 2 3 4 5 6 7 8
0.203 0.217 0.229 0.237 0.236 0.240 0.218 0.232
4705 3454 3454 2088 2471 4159 3860
9
0.209 0.189
3556 4357
10
10/l/36695
THE
ments.11-13 The method of heat application was investigated by Monday and Asgar13 who found torch soldering four to five times stronger than oven soldering of Olympia ceramic alloy (Pennwalt/Jelenko, Armonk, N.Y.). Torch soldering, however, can be difficult to control, creating a potential for inadequate or uneven heating, incomplete
of each (kg/cd)
3696
of the test specimens.
33
CATTANEO
ET AL
Fig. 2. Mean and standard deviation and tensile strength of samples soldered by torch and infrared technique. Third bar represents mean tensile strength of 10 unsoldered bars.
Fig.
SO1ider
3. Optical
diagram
flow, and decreased connector strength. In general, techniques have not changed in many years. Lithas been published regarding the joining of t1e ! information mt stals by methods other than conventional torch soldering techniques. or oven soldering The purpose of this study was to compare the conventic rnal torch procedure for soldering with a new method ad vacated by J.M. Ney Co. (Bloomfield, Conn.) using an SO1ldering
34
of infrared
instrument.
infrared soldering technique. Comparisons were I nade for (1) tensile strength, (2) porosity and (3) tin ie effici ency between these two methods.
METHODS
AND
MATERIAL
Three groups of specimens were tested in this stl udy. ’The first group consisted of 10 joints soldered with a corn rentional torch technique, the second group w as corn pose1d of
JULY
1992
VOLUME
68
NUMBER
1
COMPARISON
OF SOLDER
JOINTS
5. SEM photomicrograph made by flame technique.
Fig.
of solder joint
surface
III. Mean of tensile strength (kg/cm2) and standard deviation of samples soldered by torch, soldered by infrared technique and unsoldered (as cast)
Table
Group
Torch Infrared Unsoldered ANOVA
Table II. Diameter and ultimate tensile strength of each samplesoldered by heat
I 2 3 4 5 6
7 8 9 10
Diameter
(cm)
Tensile
strength
(kg/cm2)
2444 3492 4729 3366 4134 3892 3757 2272 3715 3458
0.235 0.237 0.238 0.238 0.237 0.222 0.229 0.205 0.212 0.203
10joints solderedby the infrared technique, and the third group ascast with no solder asthe control group. The resin test patterns measured16 mm in length and 2.5 mm in diameter, correspondingto the American Dental Association (ADA) specification 5 (Fig. 1). The resin patterns were cast with a high noble metal alloy used in the fabrication of porcelain fused-to-metal restorations (SMGB, J. M. Ney Co.). Each bar specimenfor the soldering procedure was
THE
JOURNAL
no significant
Meall
10 10 10
3383.9 3524.9 3625.9
difference
between
SD
groups
1082.7 731.6 180.6 (p = 0.77).
4. Infrared instrument.
Fig.
Sample
showed
N
OF PROSTHETIC
DENTISTRY
cut in half with a slow-speed dental handpiece mounted firmly in a cutting jig. The cuts were made with a noncontminated aluminum oxide disk. The metal bars were moved toward the rotating disc in a direction perpendicular to their long axes to assure consistent cross-sectional areas and uniform soldering embrasures for all specimens. The solder gap selected for this study was 0.3 mm.? The sectioned bars were related by use of an acrylic resin indexing material (Duralay, Reliance Dental Manufacturing Co., Worth, Ill.), invested for soldering (Speed-E, Whip Mix, Louisville, KY.), and placed in a cold oven. The oven temperature was raised at a rate of 50° F/minute to a temperature of 1700’ F, which was 200” F below the melting range of the metal. The invested units were removed from the oven and soldered in one of two ways. 1. Torch soldering. Flux (J. M. Ney Co.) wasapplied to the solder joint area and the solder (SMGB, J.M. Ney Co.) was inserted. A gas and oxygen torch was used in a back-and-forth motion to heat the joint site until the solder flowed into the gap. The temperature of the flame was monitored with an infrared optical thermometer (Optitherm infrared thermometer, model 12-8723,Barnes Engineering, Stamford, Conn.) to avoid heating the parent alloy to its melting range. 2. Infrared soldering. Flux wasapplied to the joint areaand the specimenswere solderedwith an infrared in-
35
GATTANEO
Fig. 6. SEM photomicrograph made by infrared technique.
of solder
joint
surface
Fig. 8. SEM photomicrograph specimen, infrared soldered.
ET AL
of the long axis of untested
SEM examination Randomly selected specimens from each soldering group were photographed with a scanning electron microscope (SEM) (IS1 SX-40A SEM, IS1 Inc., Pleasanton, Calif.) to characterize their appearance and porosity after tensile testing. In addition, specimens were prepared for the soldering groups that were not subjected to tensile testing. These samples were sectioned longitudinally and examined to evaluate the appearance of the solder joints.
Time efficiency
Fig. 7. SEM photomicrograph specimen, flame soldered.
ofthe long axis of untested
strument (J. M. Ney Co.) according to the manufacturer’s instructions. Ten specimens were prepared and tested for each soldering method, and an additional 10 specimens were tested after casting and without sectioning or soldering, to serve as a control group.
Ultimate
tensile
strength
After the soldering, the specimens were allowed to cool for 5 minutes and then quenched in water. After divesting, excess solder was removed. The diameter of each bar was measured with an engineering micrometer accurate to 0.01 mm and the tensile strength calculations were based on these measurements. Each specimen was tested in an Instron Universal testing machine (model 1122, Instron Corporation, Canton, MA). The bars were loaded at a constant crosshead speed of 2 mm/minute, according to ADA specification 5, and the ultimate tensile strength was determined.
36
The time from the application of the energy to the melting of the solder metal for each soldering procedure was recorded during the experiment so that the efficiency of each technique could be evaluated.
RESULTS The tensile strength results of the torch soldered specimens are summarized in Table I. The diameter of each rod after soldering was noted in an effort to relate this value to the force needed to fracture the specimen. This was necessary because it was impossible to control the final rod diameter after the solder procedure. The load values required to fracture the rods yielded a range of tensile strength from 2088 kg/cm2 to a maximum of 4705 kg/cm2. In Table II, the results for infrared specimens are presented and show a tensile strength range from 2275 kg/cm2 to a value of 4729 kg/cm2. The control (unsoldered) specimens exhibited a tensile strength range from 3224 kg/cm2 to a maximum of 3844 kg/cm2. The tensile strength data were statistically analyzed with analysis of variance (ANOVA) (Table III and Fig. 2). No statistically significant difference 0, 5 0.05) between the three groups studied was found. There was no apparent difference in solder joint characteristics or porosity between joints formed. The time recorded for the conventional solder procedure from the
JULY
1992
VOLUME
68
NUMBER
1
COMPARISON
OF SOLDER
JOINTS
moment the flame was applied to the joint until the solder flowed was consistently approximately 30 seconds. The time required for the solder to flow with the infrared technique was approximately 3 minutes. ISCUSSION The infrared instrument used in this study utilizes a concentrated beam of infrared energy. The energy is emitted from a loo-watt tungsten filament quartz-iodine lamp, which is the primary focal point of the machine (Fig. 3). Above the primary focal point is a concave reflector that collects the infrared energy emitted from the tungsten filament and refocuses this energy into a single point, the secondary focal point. The object to be soldered is placed at this secondary focal point. Object positioning is accomplished by an adjustable work platform as illustrated in Fig. 4. Microstructural analysis was obtained with an SEM. Photomicrographs of selected specimens examined at the fracture surface exhibited no discernable difference in porosity between the two groups (Figs. 5 and 6). The samples from each group presented finely divided porosity with granular appearance. Visual examination of each sample group revealed variable amounts of porosity. This finding may explain the range in ultimate tensile strength with a given group of samples. All of the fractures observed for soldered samples occurred within the solder joint area. Each individual fracture demonstrated elements of both a ductile and a brittle type of fracture. The untested specimens examined along their long axes exhibited a distinct demarcation between the solder metal and the parent metal (Figs. 7 and 8). The sharp interface indicates that significant diffusion did not occur between the two metals joined, an indication of a proper solder joint. This precision of solder flow without melting of the parent metal requires accurate control of the soldering temperature, which can be difficult to achieve routinely without the aid of the optical thermometer used in this study. Temperature control is automated with the infrared instrument, thus removing this as a variable. It is also important to note the degree of confidence one has in the solder joint. The relatively small standard deviations for the infrared soldering metal, in comparison to the torch procedure (Table III), demonstrates that soldering joints of relatively more uniform strength values can be expected with this technique. In evaluating time efficiency, it was found that the infrared technique required an average of 2 to 3 minutes more than soldering by flame. From a practical point of view the difference in time efficiency seems unimportant. CONCLUSIONS
The results of this study indicate the following: 1. There was no significant difference in ultimate tensile strength between solder joints fabricated with a conventional torch technique, solder joints fabricated with the infrared technique, and nonsoldered control specimens. 2. There was no apparent difference in solder joint porosity between joints formed by the two techniques. 3. The infrared technique permits better control during the soldering procedure. This becomes important in a presolder situation in which the melting range of the solder metal is close to the melting range of the parent metal. 4. Torch soldering took consistently less time than infrared soldering. We express for providing project.
our sincere the materials
thanks and
to the J. M. Ney Company equipment necessary for this
REFERENCES 1. Fusayama T, Wakamuto S, Hosoka J. Accuracy of fixed partial denture made by various soldering techniques and one-piece casting. J PROSTHET DENT
1964;14:334-42.
2. Garlapo DA, Lee S-H, Choung CK, Sorensen SE. Spatial changes occurring in fixed partial dentures made in one single casting. J PROSTHET DENT
1983;49:781-5.
3. Skinner EW, Phillips RW. The science of dental materials. 5th ed. Philadelphia: WB Saunders, 1960;534-46. 4. Staffanou RS, Radke RA, Jendresen MD. Strength properties of soldered joints from various ceramic-metal combinations. J PROSTHET DENT
1980;43:31-9.
5. Lautenschlager EP. Strength mechanisms of dental soldered joints. J Dent Res 1974;53:1362-7. 6. Stade EH, Reisbick MH, Preston JD. Pre-ceramic and postceramic solder joints. J PROSTHET DENT 1975;34:527-32. 7. Willis LM, Nicholls JI. Distortion in dental soldering as affected by gap distance. J PROSTHET DENT 1980;43:272-8. 8. Rasmussen EJ, Goodkind RJ, Gerberich WW. An investigation of tensile strength of dental solder joints. J PROSTHET DENT 1979;41: 418-23.
9. Moon PC, Eshleman JR, Douglas HB, Garrett SG. Comparison curacy of soldering indices for fixed prosthesis. J PROSTHET
of acDENT
1979;40:35-8.
10. Harper FJ, Nicholls JI. Distortions in indexing methods and investing media for soldering and remount procedures. J PROSTHET DENT 1979;42:172-9.
11. Munford G. The porcelain fused-to-metal restoration. Dent Clin North Am 1965;March:241. 12. Pazzini N, Pazzini LI, Araujo PA. The accuracy of solder investment. J PROSTHET
DENT
1979;42:530-3.
13. Monday JJL, Asgar K. Tensile strength comparison postsoldered joints. J PROSTHET DENT 1986;55:23-7.
of presoldered
and
Reprint requests to: DR. GALEN W. WAGNILD UNIVERSITY OF CALIFORNIA, SAN FRANCISCO SCHOOL OF DENTISTRY DEPARTMENT OF RESTORATIVE DENTISTRY 707 PARNASSUS AVENUE, D2041 SAN FRANCISCO, CA 94143
A new soldering technique using infrared radiation derived from a halogen lamp as a heat source to melt the solder has been tested.
THE
JOURNAL
OF PROSTHETIC
DENTISTRY
37
