comparative evaluation of crack propagation during root canal preparation in primary molar with manual instrumentation, protaper universal and protaper next rotary file systems: an in vitro study

Statement of the problem: root canal preparation with rotary files causes dentinal cracks in root canals of primary teeth affecting their longevity.purpose: nickel-titanium rotary files have been widely used for root canal preparation in primary teeth. the present study compared occurrence of dentinal microcracks in root canals of extracted primary molar teeth prepared using hedstrom (h) files, protaper universal rotary files, and protaper next rotary file systems.materials and method: in this in vitro experimental study, 80 primary molar mesial root canals were randomly divided into four groups of 20 canals each (n=20). group i was prepared with h files. group ii was prepared with protaper universal rotary files using shaping files sx and s2. group iii was instrumented with protaper next rotary files x1 and x2 while group iv was left unprepared and served as control. roots were stained with 1% methylene blue solution and sectioned perpendicular to the long axis at 2mm, 4mm, and 6mm from the apical foramen. slices obtained were examined under the stereomicroscope. data obtained were subjected to statistical analysis using chi square tests.results: dentinal microcracks were observed in groups prepared using h files, protaper universal, and protaper next rotary files. highest percentage of cracked root canals (20%) was seen in group i, prepared by h files. these cracks were complete in nature, found in apical sections and statistically significant (p= 0.016). group iii prepared with protaper next showed 10% dentinal cracks, followed by protaper universal group with 5% cracked root canals.conclusion: h files may be considered more aggressive at apical third due to complete cracks produced.