In vivo fracture of a new rubber-dam clamp.
OBJECTIVE
This study was carried out to investigate the reasons for fracture of a new rubber-dam clamp used for the first time.


CONCLUSIONS
The fractured surfaces of the broken clamp were studied with optical microscopy. Characteristic surface patterns of tensile fracture were identified. Cracks originated from the groove of letter D mechanically engraved on the inner surface of the clamp bow, and developed with high velocity (unstable crack growth rate) leading to catastrophic fracture. This behaviour was attributed to the residual stresses introduced by the labelling technique due to local thermal alterations.


CONCLUSIONS
The labelling technique used to number clamps may be implicated with catastrophic failure. Dentists should be aware that even new clamps can fracture. It is important that clamps are secured to prevent inhalation of metal fragments, should catastrophic failure occur.
Zinelis
S
S
Biomaterials Laboratory, School of Dentistry, University of Athens, Athens, Greece. szinelis@dent.uoa.gr
Margelos
J
J
D003748:Dental Equipment; D003799:Dental Stress Analysis; D004868:Equipment Failure; D016733:Rubber Dams; D013314:Stress, Mechanical