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  Indian J Med Microbiol
 

Figure 28: Micro-cracks and VRFs generated by rotary files. (a) Micro-cracks in the remaining dentin of a root instrumented with rotary fi les. The lower arrow indicates a partial micro-crack originating at the root surface. The upper arrow indicates a full thickness crack that may be defined as VRF. (Adapted from Bürklein et al. 2013).[91] (b) Hand instrumentation: No micro-cracks (courtesy: Dr. Hagay Shemesh, Amsterdam). (c) Instrumentation with rotary fi les resulted in micro-cracks in 25% of the roots but only 5% of the cracks were full thickness (VRFs). Obturation of the canals using lateral compaction increased the total incidence of micro-cracks to 55% of the roots and increased the incidence of full thickness fractures (VRFs) to 30% of the roots. This indicates that in many cases, the formation of partial thickness micro-cracks may serve as a predisposing factor for the formation of VRFs in roots treated with rotary files (adapted from Shemesh et al. 2009)[6]

Figure 28: Micro-cracks and VRFs generated by rotary files. (a) Micro-cracks in the remaining dentin of a root
instrumented with rotary fi les. The lower arrow indicates a partial micro-crack originating at the root surface. The upper arrow indicates a full thickness crack that may be defined as VRF. (Adapted from Bürklein <i>et al</i>. 2013).<sup>[91]</sup> (b) Hand instrumentation: No micro-cracks (courtesy: Dr. Hagay Shemesh, Amsterdam). (c) Instrumentation with rotary fi les resulted in micro-cracks in 25% of the roots but
only 5% of the cracks were full thickness (VRFs). Obturation of the canals using lateral compaction increased the total incidence of micro-cracks to 55% of the roots and increased the incidence of full thickness fractures (VRFs) to 30% of the roots. This indicates that in many cases, the formation of partial thickness micro-cracks may serve as a predisposing factor for the formation of VRFs in roots treated with rotary files (adapted from Shemesh <i>et al</i>. 2009)<sup>[6]</sup>