Df. Galindo et al., Effect of soldering on metal-porcelain band strength in repaired porcelain-fused-to-metal castings, J PROS DENT, 85(1), 2001, pp. 88-94
Statement of problem. Chemical bending plays a major role in the adherence
between metal and porcelain. The formation of an oxide layer on solder mate
rial has not been described in the literature. It is unknown whether the ap
plication of solder negatively affects the bond strength between porcelain
and metal.
Purpose. This in vitro study assessed the effect of solder on the bond stre
ngth between metal and porcelain.
Material and methods. Forty 20 x 6 x 0.5 mm patterns were divided into test
(20) and control (20) groups. Test samples were perforated and repaired wi
th solder, and 2 layers of opaque and dentin porcelain subsequently were ap
plied on all samples. The samples were subjected to a 3-point flexural test
on a screw-driven mechanical testing machine at a crosshead speed of 0.5 m
m/min. Failure type (adhesive vs cohesive) was quantified by digitizing pho
tographs of test and control samples. Three samples in each group also were
examined with an SEM coupled with an x-ray energy-dispersive spectroscopy
apparatus (SEM/EDS). Means and standard deviations of loads at failure, sam
ple thickness, and surface area covered with porcelain were calculated, and
data were analyzed with Student t test (P less than or equal to .05).
Results. The mean fracture load for test samples was significantly greater
than for control samples (P=.0038). Test samples also were significantly th
icker (mean thickness difference 0.14 mm) (P=.0001). When the data were con
trolled for thickness by using a multiple linear regression analysis, no si
gnificant difference was found (P=.68). Test samples had a greater surface
area covered with opaque porcelain (P=.0006) as determined by visual inspec
tion.
Conclusion. In this study, soldered and nonsoldered samples did not show an
y significant difference in porcelain-to-metal bond strength. Visual analys
is revealed a significant difference in the amount of porcelain remaining o
n the fracture surface of the test and control samples; a complete quantita
tive elemental analysis with SEM/EDS is in progress.