F Lin1,2, R Ordinola-Zapata3, H Xu4, Y C Heo2, A Fok2. 1. Department of Cariology and Endodontology, Peking University School and Hospital of Stomatology, Beijing, China. 2. Minnesota Dental Research Center for Biomaterials and Biomechanics, School of Dentistry, University of Minnesota, Minneapolis, USA. 3. Division of Endodontics, Department of Restorative Sciences, School of Dentistry, University of Minnesota, Minneapolis, USA. 4. Department of Stomatology, Affiliated Hospital of Qingdao University, Qingdao, China.
Abstract
AIM: To simulate in a laboratory setting longitudinal cracking in root filled premolar teeth, using cyclic mechanical fatigue. METHODOLOGY: Mesial-occlusal-distal (MOD) cavities were prepared in twenty root filled, single-rooted, mandibular premolars restored with fibre posts and resin composites. The samples were randomly divided into two groups based on the loading approaches: static loading with a crosshead speed of 0.5 mm/min and step-stress cyclic loading (1 Hz) with increasing amplitude. The loads and numbers of cycles to failure were recorded. Micro-CT was also used to identify the fracture modes. Statistical analysis was performed using Student's t-test. The level of significance was set at 0.05. RESULTS: The mean fracture loads for the static loading and cyclic loading groups were 769 ± 171 N and 720 ± 92 N, respectively. There was no significant difference between the two groups (P > 0.05). The proportions of longitudinal, cuspal and mixed-mode fractures under cyclic loading were 50%, 20% and 30%, respectively. Longitudinal fractures occurred with larger numbers of cycles and higher average loads per cycle compared with the other fractures. Static loading produced only cuspal fractures. CONCLUSIONS: Longitudinally cracked premolar teeth with root fillings were successfully produced using the step-stress cyclic loading method. This provides a more clinically representative methodology for studying cracked teeth in a laboratory setting.
AIM: To simulate in a laboratory setting longitudinal cracking in root filled premolar teeth, using cyclic mechanical fatigue. METHODOLOGY: Mesial-occlusal-distal (MOD) cavities were prepared in twenty root filled, single-rooted, mandibular premolars restored with fibre posts and resin composites. The samples were randomly divided into two groups based on the loading approaches: static loading with a crosshead speed of 0.5 mm/min and step-stress cyclic loading (1 Hz) with increasing amplitude. The loads and numbers of cycles to failure were recorded. Micro-CT was also used to identify the fracture modes. Statistical analysis was performed using Student's t-test. The level of significance was set at 0.05. RESULTS: The mean fracture loads for the static loading and cyclic loading groups were 769 ± 171 N and 720 ± 92 N, respectively. There was no significant difference between the two groups (P > 0.05). The proportions of longitudinal, cuspal and mixed-mode fractures under cyclic loading were 50%, 20% and 30%, respectively. Longitudinal fractures occurred with larger numbers of cycles and higher average loads per cycle compared with the other fractures. Static loading produced only cuspal fractures. CONCLUSIONS: Longitudinally cracked premolar teeth with root fillings were successfully produced using the step-stress cyclic loading method. This provides a more clinically representative methodology for studying cracked teeth in a laboratory setting.
Authors: M Yuan; A T Gao; T M Wang; J H Liang; G B Aihemati; Y Cao; X Xie; L Y Miao; Z T Lin Journal: Int Endod J Date: 2020-02-17 Impact factor: 5.264
Authors: Andressa B Venturini; Catina Prochnow; Gabriel K R Pereira; Rodrigo D Segala; Cornelis J Kleverlaan; Luiz Felipe Valandro Journal: Dent Mater Date: 2019-01-25 Impact factor: 5.304