OBJECTIVETo compare the consistency of root canal configuration types of mandibular first premolar by using micro-CT and radio visio graphy (RVG).

METHODSOne hundred extracted mandibular first premolars with complete dental root and apex which received no endodontic treatment were randomly selected. Each tooth was radiographed with RVG through a buccolingual and mesiodistal direction, and then scanned with micro-CT and reconstructed. The classifications of the root canal types according to Vertucci's type with the two methods were compared.

RESULTSThe canal patterns were classified as type I (67%), type III (3%), type V (18%), type VII (2%), additional type (10%) with micro-CT and canal patterns as type I (71%), type III (2%), type V (23%), type VII (1%), additional type (3%) with RVG. 63% of teeth showed one canal in both micro-CT and RVG. Only 25% of teeth were diagnosed as complex canal by the same canal type in both micro-CT and RVG. The Kappa value between micro-CT and RVG was 0.541 which suggested that the two kinds of methods had intermediate consistency. 82.8% of the premolars with root groove had two or more than two canals.

CONCLUSIONAlthough RVG can basically reflect the root canal system type of the mandibular first premolars in vitro, it offers poor accuracy images to complex root canals. Micro-CT three-dimensional images could clearly and precisely display the root canal system morphology of the mandibular first pre-molars in vitro.

Bicuspid ; Dental Pulp Cavity ; Humans ; Mandible ; Molar ; Root Canal Therapy ; Tooth Root ; X-Ray Microtomography

Objective To analyze peripheral blood hemogram, lymphocyte micronucleus and chromosomal aberrations of radiologists, so as to provide basis for occupational protection and health monitoring of radiologists. Methods Lymphocyte micronucleus, chromosome and blood hemogram analysis were performed on 127 radiologists who received health examinations in 2015, 2017 and 2019, and they were assigned to the radiation group. In addition, 133 medical staff with no history of radiation exposure were selected as the control group. Results The micronucleus rate and chromosome aberration rate of the radiation group were higher than those of the control group, and the white blood cell and platelet counts were lower than those of the control group, both of which were statistically significant (P < 0.05). The total number of white blood cells in peripheral blood of 127 radiologists decreased gradually with the increase of exposure time to ionizing radiation, and the chromosome aberration rate increased gradually, all of which had statistical significance (P < 0.05). The rate of chromosomal aberration was higher in radiologists with damage work age of more than 20 years than in the low-work age group, and there was no statistical significance between different damage work age (P > 0.05). The chromosome aberration rate of nuclear medicine and interventional therapy was higher than that of other types, with statistical significance (P < 0.05). Conclusion Long-term exposure to low-dose ionizing radiation can reduce the total number of white blood cells and increase the chromosome aberration rate of radiologists. It is necessary to strengthen the protective measures for radiologists to reduce the degree of ionizing radiation damage, especially to strengthen the occupational protection for radiologists in nuclear medicine and interventional therapy.