Characteristics of vertical root fractures at early stages: Evidence that dentinal microcracks are an experimental phenomenon.

AIM: The aim of this study was to investigate the characteristics of vertical root fractures (VRFs) at early stages and compare them with previously reported dentinal microcracks. METHODOLOGY: Endodontically treated teeth with vertical root fractures at early stages were collected. The characteristics of these VRFs were evaluated by in vitro observation and micro-CT scanning: (1) the number of fractures (buccal, lingual, mesial and distal were counted separately); (2) vertical extension on the roots (classified into four categories according to cemento-enamel junction and root apex involved or not); (3) the direction of fractures (bucco-lingual or mesial-distal); (4) horizontal extension of fractures (involved the root canal wall or the root surface or both); (5) the width of fractures (measured at the widest site on the axial micro-CT image); and (6) the location of the widest fractured site on the root (coronal third portion, middle third portion and apical third portion). RESULTS: A total of 28 vertical root fractures at early stages were collected in this study, involving 30 roots with a total of 51 fractures. All fractures involved the middle portion of root; all fractures were bucco-palatal/lingual and extended from the root canal wall to the root surface. The maximum width of these fractures were <150 mum, and widest fractures may be at the coronal, middle or apical third portion of the tooth root. CONCLUSIONS: All vertical root fractures involved the middle portion of root, initiated from the root canal wall and directed buccal-lingually. The fractures were irregular and tortuous, with fracture widths exhibiting considerable variability. These characteristics help us to have a better understanding of the initiation and development of VRFs, and also supply evidence dentinal microcracks are an experimental phenomenon.