In vitro evaluation of effect of spreader size on the fracture resistance tooth

To determine the effect of ‘flare’ spreader size on the fracture resistance of mandibular premolar roots prepared using variable taper rotary files. Crowns of 50 mandibular first premolars having no carious lesions, devoid of any aberrant anatomy were resected 2mm coronal to the cemento-enamel junction. Root canals were prepared in different groups: 1. No canal preparation. 2. Preparation using crown down technique to a size F2 MAF with no obturation performed. 3. Preparation using crown down technique to a size F2 MAF and obturated using lateral condensation; first spreader used being a size 25 flare spreader. 4. Same as 3 except first spreader used being a size 20 flare spreader. 5. Same as 3 except first spreader used being a size 15 flare spreader. All specimens were mounted in addition silicone putty and fractured vertically on a universal testing machine. Fracture load was recorded in kilogram force. Values obtained were analyzed using the ANOVA test. The mean force at fracture for roots obturated using size 15.05 spreaders approached similar values required to fracture uninstrumented samples. But was significantly higher than what was required to fracture samples filled using size 20.05 and size 25.05 spreaders. Spreader size used during lateral condensation of gutta percha may affect the fracture resistance of roots in extracted teeth. Larger size spreaders do decrease the fracture resistance and jeopardize the strength of obturated roots.