Effect of Reciprocating Systems and Working Lengths on Apical Microcrack Development: a micro-CT Study.

The objective of this study was to evaluate the effect of root canal preparation with single-file reciprocating systems at different working lengths on the development of apical microcracks using micro-computed tomographic (micro-CT) imaging. Forty extracted human mandibular incisors were randomly assigned to 4 groups (n=10) according to the systems and working length used to prepare the root canals: Group A - WaveOne Gold at apical foramen (AF), Group B - WaveOne Gold 1 mm short of the AF (AF-1 mm), Group C - Unicone (AF) and Group D - Unicone (AF-1 mm). Micro-CT scanning was performed before and after root canal preparation at an isotropic resolution of 14 µm. Then, three examiners assessed the cross-sectional images generated to detect microcracks in the apical portion of the roots. Apical microcracks were visualized in 3, 1, 1, and 3 specimens in groups A, B, C, and D, respectively. All these microcracks observed after root canal preparation already existed prior to instrumentation, and no new apical microcrack was detected. For all groups, the number of slices presenting microcracks after root canal preparation was the same as before canal preparation. Root canal preparation with WaveOne Gold and Unicone, regardless of the working length, was not associated with apical microcrack formation.

Effect of Reciprocating Systems and Working Lengths on Apical Microcrack Development: a micro-CT Study

Abstract The objective of this study was to evaluate the effect of root canal preparation with single-file reciprocating systems at different working lengths on the development of apical microcracks using micro-computed tomographic (micro-CT) imaging. Forty extracted human mandibular incisors were randomly assigned to 4 groups (n=10) according to the systems and working length used to prepare the root canals: Group A - WaveOne Gold at apical foramen (AF), Group B - WaveOne Gold 1 mm short of the AF (AF-1 mm), Group C - Unicone (AF) and Group D - Unicone (AF-1 mm). Micro-CT scanning was performed before and after root canal preparation at an isotropic resolution of 14 µm. Then, three examiners assessed the cross-sectional images generated to detect microcracks in the apical portion of the roots. Apical microcracks were visualized in 3, 1, 1, and 3 specimens in groups A, B, C, and D, respectively. All these microcracks observed after root canal preparation already existed prior to instrumentation, and no new apical microcrack was detected. For all groups, the number of slices presenting microcracks after root canal preparation was the same as before canal preparation. Root canal preparation with WaveOne Gold and Unicone, regardless of the working length, was not associated with apical microcrack formation.

Resumo O objetivo deste estudo foi avaliar o efeito da instrumentação de canais radiculares utilizando sistemas reciprocantes de lima única em diferentes comprimentos de trabalho sobre o desenvolvimento de microfissuras apicais utilizando imagens de microtomografia computadorizada (micro-CT). Quarenta incisivos inferiores humanos extraídos foram distribuídos aleatoriamente em 4 grupos (n=10) de acordo com os sistemas e comprimentos de trabalho utilizados para preparar os canais radiculares: Grupo A - WaveOne Gold no forame apical (FA), Grupo B - WaveOne Gold 1 mm aquém do FA (FA-1 mm), Grupo C - Unicone (FA) e grupo D - Unicone (FA-1 mm). Escaneamentos de micro-CT foram realizados antes e após o preparo dos canais a uma resolução isotrópica de 14 μm. Em seguida, três examinadores avaliaram as imagens de secção transversal geradas para detectar microfissuras na porção apical das raízes. Microfissuras apicais foram visualizadas em 3, 1, 1 e 3 espécimes nos grupos A, B, C e D, respectivamente. Todas essas microfissuras observadas após o preparo dos canais radiculares já existiam antes da instrumentação e não foi detectada nenhuma nova microfissura apical. Para todos os grupos, o número de cortes apresentando microfissuras após o preparo dos canais radiculares foi o mesmo verificado antes do preparo dos canais. A instrumentação de canais radiculares utilizando WaveOne Gold e Unicone, independentemente do comprimento de trabalho, não foi associada à formação de microfissuras apicais.

Micro-computed Tomographic Analysis of Apical Microcracks before and after Root Canal Preparation by Hand, Rotary, and Reciprocating Instruments at Different Working Lengths.

INTRODUCTION: This study aimed to compare apical microcrack formation after root canal shaping by hand, rotary, and reciprocating files at different working lengths using micro-computed tomographic analysis. METHODS: Sixty mandibular incisors were randomly divided into 6 experimental groups (n = 10) according to the systems and working lengths used for the root canal preparation: ProTaper Universal for Hand Use (Dentsply Maillefer, Ballaigues, Switzerland), HyFlex CM (Coltene-Whaledent, Allstetten, Switzerland), and Reciproc (VDW, Munich, Germany) files working at the apical foramen (AF) and 1 mm short of the AF (AF - 1 mm). The teeth were imaged with micro-computed tomographic scanning at an isotropic resolution of 14 µm before and after root canal preparation, and the cross-sectional images generated were assessed to detect microcracks in the apical portion of the roots. RESULTS: Overall, 17 (28.3%) specimens presented microcracks before instrumentation. Apical microcracks were present in 1 (ProTaper Universal for Hand Use), 3 (Hyflex CM), and 2 (Reciproc) specimens when the instrumentation terminated at the AF. When instrumentation was terminated at AF - 1 mm, apical microcracks were detected in 3 (ProTaper Universal for Hand Use) and 4 (Hyflex CM and Reciproc) specimens. All these microcracks detected after root canal preparation were already present before instrumentation, and no new apical microcrack was visualized. For all groups, the number of slices presenting microcracks after root canal preparation was the same as before canal preparation. CONCLUSIONS: Root canal shaping with ProTaper Universal for Hand Use, HyFlex CM, and Reciproc systems, regardless of the working length, did not produce apical microcracks.

Detection of Apical Root Cracks Using Spectral Domain and Swept-source Optical Coherence Tomography.

INTRODUCTION: This study aimed to evaluate the ability of 2 optical coherence tomographic (OCT) systems to detect apical dentinal microcracks. METHODS: Twenty extracted human single-rooted mandibular incisors were selected. After root canal preparation with an R40 Reciproc file (VDW, Munich, Germany), the specimens presenting apical microcracks were identified using micro-computed tomographic (micro-CT) scanning as the gold standard. Then, the apical portions of the roots were imaged with spectral domain OCT (SD-OCT) and swept-source OCT systems, and the resulting images were blindly evaluated by 3 independent examiners to detect microcracks. The diagnostic performance of each OCT device was calculated, and statistical analysis was performed. RESULTS: Based on the micro-CT images, 12 (60%) roots presented dentinal microcracks in the apical region. The images generated by the OCT systems were able to show microcrack lines at the same location as the corresponding micro-CT cross sections. Although the diagnostic performance of the SD-OCT device was superior, there were no statistically significant differences between the 2 OCT devices (P > .05). Interexaminer agreement was substantial to almost perfect for the SD-OCT system and moderate to almost perfect for the swept-source OCT system, whereas intraexaminer agreement was substantial to almost perfect for both OCT devices. CONCLUSIONS: The detection ability verified for both OCT systems renders them promising tools for the diagnosis of apical microcracks.