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Objective@#To observe the morphological changes of root canals in maxillary second premolars at various ages by using cone-beam CT (CBCT) in order to provide imaging and theoretical reference for clinical treatments.@*Methods@#The digital CBCT data of the maxillary second premolars in 440 cases from the patients in Department of Stomatology, The First Affiliated Hospital, Jinan University during March 2011 and December 2017 were collected. The CBCT images were divided into 4 groups according to the patients′ ages: groups ≤20, 21-40, 41-60 and>60 years old, respectively. Changes of morphologies of root canals with aging including such parameters as types of the root canal, incidence of double root canals in single rooted teeth, distance between both root canal orifices of double rooted canals, and morphological change of the cross section of roots. Chi-square test and liner trend test were adopted in statistical analysis in the present study.@*Results@#Most maxillary second premolars had only one root [95.2% (419/440)]. Type Ⅰ of the root canals was the most common type [57.3% (252/440)], and the following prevalent groups were type Ⅱ[16.8% (74/440)], type Ⅳ [10.2% (45/440)] and type Ⅲ [8.9% (39/440)]. The distribution of type Ⅰ~Ⅳ of the root canals were significantly different amongst various aged groups (P<0.05). Along with aging, the percentages of type Ⅰ decreased while type Ⅱ increased. However, there were no remarkable changes of type Ⅲ and type Ⅳ observed. The incidence of double canal in single rooted teeth gradually increased with aging especially in 20-year-old and above groups, e.g. 13.1% (13/99) in group of ≤20 years old and 45.0% (86/191) in group of 21-40 years old. However, there was no significant increase observed after the age of 40. The distance between two root canal orifices of double rooted canals became shorter with aging except in groups of 40-year-old and above. The morphologies of the cross sections of root canals in most groups were flat shaped [57.8% (1 121/1 938)] and oval shape [31.3% (607/1 938)]. Along with aging, the percentage of circular shape gradually increased while flat and oval shapes decreased.@*Conclusions@#The morphology of root canal could be clearly showed by the CBCT images. Most maxillary second premolars had only one root and one apical foramen. Along with aging, the morphology of the root canals became more and more complicated.
ABSTRACT
Objective:To investigate the expression change of voltage-gated calcium channels(VGCC) in the facial nucleus motoneurons of adult rats after facial nerve injury.Methods:The facial motor nucleus was localized by retrograde labeling with a fluorescent dye,Dil,and identified by Nissl staining.The facial nerve injury model was established by amputation of the main trunk of left facial nerve.Exposure of the right facial nerve without nerve transection was used as the control.Rats were sacrificed at 3,7,14 and 28 days after injury respectively(n =10),the brainstem containing facial nucleus were collected,the expression of P/Q,N,L,R-type calcium channel α1A,α1B,α1C and α1E subunits was examined by immunohistochemistry and reverse transcription-polymerase chain reaction (RT-PCR).Results:Immunohistochemistry results show that whereas α1A,α1E subunits levels did not vary compared with control group 3,7,14,28 days after injury(P ＞0.05),α1B and α1C subunits immunoreactivity decreased in the motoneurons after injury,a sharp decrease was detected at 14 days after injury(P ＜ 0.01),thereafter returned to the control level at 28 days after axotomy(P ＞0.05).The expression of α1B and α1C mRNA was down-regulated,especially 14 days after the injury(P ＜0.01),and then recovered to normal level at 28 days (P ＞ 0.05).In addition,there was no significant difference of α1A and α1E subunits and their correspoding mRNA between operated group and control group at all time points(P ＞ 0.05).Conclusion:VGCC is involved in facial nerve injury and down-regulation of N-type and L-type calcium channels may be one of the role.
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AIM:To compare 2 environments , the subrenal capsule and oral submucosa , for producing well-formed teeth from mouse tooth germs and for exploring the ideal environment for tooth regeneration .METHODS: Two groups were set up .Group A was transplanted with the mouse embronic day ( ED) 14.5 first mandibular molar tooth germs into the subrenal capsule , while group B was transplanted with the ED 14.5 first mandibular molar tooth germs into the oral submucosa.After 3 weeks and 4 weeks, the host mice were sacrificed, and the transplanted explants were evaluated with morphologic observation , histological structures , hardness and elastictic modulus tests , and chemical compositions .RE-SULTS:(1) The explants isolated from both environments showed the tooth-like structures, but as to the group B, the crown was smaller, and the shape of the cusps was not significant .(2) HE staining showed that the dentin and enamel in group A were thicker than those in group B in which the ameloblasts and odontoblasts were differentiated not very well .(3) In the test of enamel hardness , only the hardness of 4 weeks in group B was lower than normal mouse tooth .In the test of enamel modulus , the elastic modulus of enamel in 3 weeks of group A was slightly lower than normal mouse tooth , but the difference was not significant .The elastic modulus of enamel in 4 weeks of group A and group B was significantly lower than normal mouse tooth and 3 weeks of group B .The hardness and elastic modulus of dentin in 3 groups was not significant . (4) Raman spectroscopy showed 2 groups grew in harmony in general , they all had the largest peak in the point of 961 cm-1 , but the 3 weeks of group B had an obvious peak in the point of 2 947 cm-1 .CONCLUSION:For the development of ED14.5 tooth germs, we obtain almost the whole tooth in subrenal capsule transplantation after 3 or 4 weeks.The buccal submucosa environment still has a certain influence on the tooth germ development , although there are some differences about the tooth development between this environment and subrenal capsule environment .