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The root canal morphology undergoes aging-related changes, and relevant quantitative analyses have not yet been reported. We compared the cone beam computed tomography (CBCT) and micro-computed tomography (micro-CT) scans of extracted mandibular incisors to check the accuracy of morphological measurements. Thereafter, the root canal morphology and aging-related changes in the mandibular incisors of Japanese individuals were assessed using CBCT. Six extracted teeth were fixed in a phantom head and imaged using CBCT and micro-CT. The correlation between the findings of the two imaging modalities was examined. Further, CBCT reconstructed images of the mandibular incisors of 81 individuals were observed. Age-related changes of the root canals were compared between participants aged <30 years and those aged ≥30 years. The CBCT and micro-CT findings regarding the root canals of the extracted teeth coincided in 94.4% of the cases. Mandibular incisors exhibiting two root canals in either cross-section accounted for 9.9% of central incisors and 12.4% of lateral incisors. Mandibular central incisors with two root canals were observed in two (6.3%) individuals aged <30 years and six (12.2%) aged ≥30 years. Mandibular lateral incisors with two root canals were observed in one (3.1%) individual aged <30 years and nine (18.4%) aged ≥30 years. CBCT allows accurate evaluation of complex root canal morphologies and is useful for endodontic preoperative assessment. Mandibular incisors have more frequent occurrence of two root canals with aging.

Structural information on the interaction between lead ion and its targeting biological substances is important not only for enriching coordination chemistry of lead but for successfully treating lead poisoning that is a present-day problem. This chapter provides structural data, mainly metal binding sites/modes, observed in crystal structures of lead complexes with biorelevant molecules, obtained from the Cambridge Structural Database (the CSD version 5.36 updated to May 2015) and the Protein Data Bank (PDB updated to February 2016). Ligands include (i) amino acids and small peptides, (ii) proteins, (iii) nucleic acid constituents, (iv) nucleic acids, (v) simple saccharides, and (vi) other biorelevant molecules involving lead-detoxification agents. For representative complexes of these ligands, some details on the environment of the metal coordination and structural characteristics are described.