Surface topographic changes and microhardness of nickel titanium files used in conservative access preparation : (An in vitro study) /

Abstract

In order to minimize the loss of tooth structure and fracture of teeth, an approach known as the conservative access cavity (CAC) preparation was suggested. This approach focuses on preserving the peri-cervical dentin (PCD) and part of the pulp chamber roof. Therefore, the aim of the current study was to assess the impact of the conservative access cavity on surface topographic changes and microhardness of controlled memory nickel titanium rotary files in comparison to the traditional access cavity. Twenty- eight files sets of Elephant rotary files (ElephantDent, China) and Twenty- eight EdgeFile X7 files sets (EdgeEndo, USA) have been used to prepare the mesial canals of 144 mandibular first molars. Four sets from each type were used as control groups and 12 sets from each type were grouped according to the access cavity type into CAC and Traditional access cavity (TAC) then subgrouped equally according to the number of prepared canals into 3, 6 and 9 subgroups. The molars were randomly allocated into two treatment groups (n=72) TAC and CAC groups. The Elephant 30/0.04 rotary files and Edge 30/0.04 rotary files were imaged via scanning electron microscope to detect the surface topographic changes, then were subjected to Vickers hardness test to assess the microhardness changes in the files after the preparation of 3, 6 and 9 canals. Scanning electron microscopic images showed no significant surface topographic changes found between CAC and TAC among the groups with the same number of prepared canals, no significant surface topographic changes were found between unused, 3 and 6 canals, however preparing 9 canals presented significant higher values of surface topographic changes in all groups except for 6 canals, moreover no significant surface topographic changes were found between Elephant files and Edge files. No significant difference in microhardness values were found between CAC and TAC among the groups with the same number of prepared canals, moreover no significant difference was observed in microhardness values between unused files and those used to prepare 3, 6 and 9 canals, meanwhile Elephant files presented a higher significant microhardness value in all groups.