RESUMO
PURPOSE: To evaluate the shaping ability and microcrack formation of ProTaper Next (PTN) and XP-endo Shaper (XPS) systems in the mesial curved root canals of mandibular molars by using micro-CT scans. METHODS: Sixteen mandibular molars with two independent mesial root canals and curvature ranging from 25° to 35° were randomly divided into two groups. The preparation time was recorded. Pre-and-postoperative images were scanned by micro-CT. The following parameters were evaluated: canal transportation, centering ratio, changes in canal volume, canal/root width ratio and microcrack formation. SPSS 22.0 software package was used to analyze the data. RESULTS: Significant difference (Pï¼0.05) was found for canal transportation at the section of 1, 3, 5, 7 mm from the apical foramen and centering ratio at the section of 1, 3, 7 mm from the apical foramen, where XPS files were superior. There was no significant difference for centering ratio at the section of 5 mm from the apical foramen(Pï¼0.05). XPS groups significantly consumed less time during the preparation(Pï¼0.05). There was no significant difference between the two groups for the increase amount of volume, and canal/root width ratio(Pï¼0.05). Both instruments did not induce new microcrack after preparation. CONCLUSIONS: PTN and XPS can both shape curved canals effectively and safely. XPS showed better centering ability and reduced preparation time during preparation.
Assuntos
Níquel , Preparo de Canal Radicular , Cavidade Pulpar/diagnóstico por imagem , Desenho de Equipamento , Preparo de Canal Radicular/métodos , Titânio , Microtomografia por Raio-X/métodosRESUMO
Objectives: This research aimed to present a novel glasses-free distance random-dot stereotest system (GFDRDSS) using an eye-tracking method. Methods: A single-view autostereoscopic display applying a backlight control system combined with an eye-tracking method and the corresponding random-dot stereotest software were developed to create a GFDRDSS with a viewing distance of 5 m. The stereoacuity of 12 subjects with normal eye position was evaluated using the Randot Stereotest, Stereoscopic Test Charts vol. 3 (Yan's Charts), Distance Randot® Stereotest, and GFDRDSS. Results: The GFDRDSS could provide distinct and stable glasses-free stereoscopic perception even while the subject was moving their head. It could evaluate binocular disparities of 40-2,400 arcsec. Eleven subjects with normal near visual acuity had fine near stereovision (20-60 arcsec) using the Randot stereotest and Yan's Charts. Under refractive correction, 10 subjects had fine stereovision (≤60 arcsec) using the GFDRDSS at a distance of 5 m, and 9 had fine stereovision using the Distance Randot® Stereotest at 3 m. Other subjects described the 100 arcsec-level stereograms correctly. The results exhibited a concordance of stereoacuity within one degrade between the two distance stereotests. Conclusion: The proposed GFDRDSS can alternately project a couple of random-dot stereograms to the subjects' eyes and provide a glasses-free distance stereotest, which showed good concordance with the Distance Randot® Stereotest. More data are needed for statistical studies.