Dentists are faced with clinical situations that require the decision
to replace or repair an amalgam restoration. The purpose of this study
was to compare five amalgam repair techniques. Six groups of 15 amalg
am beams each were fabricated by mechanical condensation of Tytin into
an anodized aluminum split mold. Specimens were aged for 7 days prior
to repair. Repaired specimens were stored for 7 days and thermocycled
500 times. Repair strength was measured by transverse strength testin
g in an Instron testing machine. Data were analyzed by a one-way ANOVA
and a Student-Newman-Keuls test at the P less than or equal to 0.05 l
evel. The surface treatments were: Group A) intact beams, B) roughened
with a #557 bur, C) air abraded with 50 mu m aluminum oxide, D) reten
tive undercuts with a #33 1/2 bur, E) Amalgambond Plus, and F) no trea
tment. The repair strength of the various experimental groups ranged f
rom 7-18% of the intact specimens. The #557 bur-roughened group yielde
d statistically higher repair strengths than all other surface treatme
nts, which were statistically equivalent to each other.