[SEM (Scanning Electron Microscopy) study of the deterioration of ProFile .04 and .06].
BACKGROUND
The ProFile are endodontic instruments made by a special nickel-titanium alloy. They have to work on constant rotation at a speed of 350 revolutions per minute. The purpose of the study is to assess, through SEM research, a possible deterioration of different ProFile conicity.


METHODS
Sixteen dental elements pulled out for period dental reasons have been used as samples to assess the progressive deterioration of .04 and .06 ProFile conicity. Eight molars and eight premolars with a total of 36 radicular canals were examined. The types of ProFile tested were 8: they were respectively 4 with .04 conicity and 4 with .06 conicity. Before being used, all instruments are previously studied through SEM. The tested ProFile with .04 conicity had a diameter of 15, 25, 30 and 45. Those with .06 conicity had a diameter of 20, 25, 30 and 35. Each tested ProFile was introduced inside a radicular canal and was turned for 180 seconds with a constant rotation of 200 revolutions per minute. After this first step, the alterations produced by the instrument could be observed through SEM. Afterwards, the same ProFile has worked again inside another radicular canal with the same time and the same number of turns, before being observed again through SEM. We have continued using this method up to the break of the instrument.


RESULTS
The instruments with .04 conicity and smaller diameter are subject to a faster deterioration, more visible at the point. After a working time of 180 seconds all the instruments have their distinct morphological alterations: after other 180 seconds it is possible to often observer an alteration to the pitch of the instrument. The breaking times are related to the diameter and conicity of ProFile tested.


CONCLUSIONS
Endodontic nickel-titanium instruments, even if they represent a progress in the field of canal preparation, undergo some alterations in their shape if they are put under inevitable mechanical stress. The damages can be: break at the top of the instrument and loss of cutting abilities at the turns level.
Rapisarda
E
E
Cattedra di Odontoiatria Conservatrice, Università degli Studi, Catania.
Tripi
T
T
Bonaccorso
A
A
D001641:Bicuspid / Q000473:pathology; D004708:Endodontics / Q000295:instrumentation; D006801:Humans; D066298:In Vitro Techniques; D008855:Microscopy, Electron, Scanning; D008963:Molar / Q000473:pathology; D018915:Root Canal Preparation; D012390:Root Canal Therapy