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Objective: To investigate the normal process of tooth development of C57BL/6 mouse strain by using micro-CT for better understanding about the tooth development of the human being and other species. Methods: A total of 54 C57BL/6 mice were used at postnatal day 1 (P1), P3, P7, P10, P14, P21, P28, P42 and P56 (n=6 for each age group). After euthanasia, the skulls and alveolar bones (with molars) were isolated and scanned by micro-CT scanner. After three dimensional reconstruction, the developmental status of the crown and root(s) for each tooth type was examined in different views. Results: The tooth development of mice from birth to mature (P56) could be divided into three stages. The first stage was from P1 to P14, in which the crowns of all the first, second and third molars had formed, while the roots had not fully developed yet. The second stage was from ablactation (P21) to P28, in which all the roots of the molars had reached their normal length, and the apical foramens had closed. Due to the mastication and occlusal abrasion, the incisors exhibited sharp cutting edges at the buccal enamel layer, and the corresponding molars formed a pit-to-fossa articulated relationship. The third stage was from P42 to P56, in which the root canal differentiation occurred, and 1-2 canal configuration was formed in several flat roots. The development of molar roots had completed and the apexes were enlarged due to the deposition of cementum around. Conclusions: In the process of mouse tooth development, the mineralization of the cusps, followed by crown formation and roots elongation, was precisely regulated in a spatial-temporal pattern. The incisors and the molars exhibited different modes of development.
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Objective:To study the effect of transplantation of stem cells from the apical papilla (SCAP) to collagen-induced arthritis (CIA).Methods:Twenty DBA/1J mice with collagen Ⅱ-induced arthritis were equally divided into 2 groups and treated with human SCAP and PBS,respectively,with other 6 normal mice as negative control.Inflammation was evaluated by measuring clinical score,TNF-α and anti-CⅡ antibody levels (ELISA),histological analyses and micro-CT analyses.The levels of CD4+Th cells subsets in spleens were assessed by flow cytometric analysis.Results:System infusion of SCAP could significantly reduce the severity of CIA, and resume the balance of Th cells subsets.Conclusion:SCAP transplantation can induce immune tolerance and ameliorate the CIA in-flammation.
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<p><b>OBJECTIVE</b>To investigate the anatomic features of the root apexes of permanent three-rooted mandibular first molars.</p><p><b>METHODS</b>A total of 122 permanent mandibular first molars of Han Chinese patients were collected. Twenty three-rooted and 25 two-rooted molars were scanned by micro-CT and then reconstructed three-dimensionally. The apical anatomy of the tooth models were analyzed in software Mimics 10.01. The long and short diameters of the apical constriction (AC), the distances between AC, apical foramen (AF) and apex were measured. One-way ANOVA and LSD-t tests were used to compare the groups in relation to AC diameter and the distances between the AC, AF and apex.</p><p><b>RESULTS</b>The AF of the mesiobuccal (MB) canals most frequently presented at the distal side of the apex (10 cases in three-rooted and 6 cases in two-rooted group), and of the mesiolingual (ML) canals, most often at the lingual side (8 cases in each group). The AF of the distobuccal (DB) roots were frequently located at the distolingual (DL) side (10 cases), and those of the DL roots and distal canals of two-rooted molars were most often at the buccal (7 cases) and distal (11 cases) sides, respectively. The percentage of the "classical" singular AC was 53% (80/151). The average long(D) and short(d) diameters of the AC of the DB canals were (0.32 ± 0.09) mm and (0.25 ± 0.05) mm, respectively, significantly larger than the DL canals [D = (0.27 ± 0.08) mm, d = (0.22 ± 0.06) mm, P < 0.05] and the ML canals [D = (0.24 ± 0.06) mm, d = (0.19 ± 0.06) mm, P < 0.01). In three-rooted group, the mean distances between AC and AF, AF and apex, and AC and apex were (0.67 ± 0.32), (0.49 ± 0.28) and (1.01 ± 0.34) mm, respectively.</p><p><b>CONCLUSIONS</b>The AF of three-rooted mandibular molars frequently deviate from the root apex, and the AC of the DB canal is wider than those of the other canals. The mean distances between AC, AF and the apex suggest that root canal therapy should terminate at 1 to 1.5 mm short of the radiographic apex.</p>