Objective To study the development characteristics of cavum sepit pellucidun (CSP)in prematures,neonates,infants and adults with MRI.Methods Brain MR images of different subjects including 141 prematures,106 neonates,171 infants and 35 046 adults were observed to determine the incidence and shape of CSP,and to measure its transverse diameter.Results CSP incidences were 100% (141/141)in prematures,97.17% (103/106)in neonates,2.26%(4/177)in infants and 0.82% (287/35 046)in adults respectively,and the CSP was cylinder (44.00%)or triangle in shape (56.00%)in prematures,triangle (76.40%)or fissure in shape (23.60%)in neonates.For infants or adults,each shape accounted for about a third of three kinds of shape respectively.Its mean transverse diameters were 5.7 mm in prematures,4.1 mm in neonates,13.3 mm in infants and 14.3 mm in adults respectivity.Conclusion CSP has different performances at development periods in human being brain.Most close after birth,while fewer remain in the whole life.

Of the various root canal morphologies in mandibular molars, the middle mesial root canal is located between the mesiobuccal root canal and the mesiolingual root canal. The middle mesial root canal is a partial or completely independent extra root canal. Because of its fine structure, concealment and even calcification of the root canal orifice, it is difficult to completely clean and fill this root canal and it is easily omitted by dentists. The current study reviewed recent progress in terms of the incidence rate, classification, influencing factors, and exploration and preparation techniques of the middle mesial root canal of the human mandibular molar to provide a reference for clinical diagnoses and treatment.