Effect of exogenous stem cells from apical papillae in the pulp revascularization treatment for the immature permanent tooth with periapical periodontitis / 中华口腔医学杂志

Objective@#To evaluate the effect of exogenous stem cells from apical papillae (SCAP) in the pulp revascularization treatment for the immature permanent tooth with periapical periodontitis in animal model.@*Methods@#After the SCAP were isolated and cultured from the Beagle dogs, stem cell properties of these cells were characterized by analyzing their colony-forming ability, the expression of mesenchymal stem cell markers and the multidifferentiation characteristics including osteogenic, adipogenic, and chondrogenic potentials. Models of young permanent tooth with periapical periodontitis were established in dogs and the infection in each of the model tooth was eliminated by root canal irrigation and intracanal medication. After that, all of the model teeth were randomly divided into 4 groups: Group 1: normal developing teeth with no treatment applied;Group 2: teeth that periapical tissues were irritated to induce blood flowing into the root canals;Group 3: teeth that peripheral blood was delivered into the root canals;Group 4: teeth that SCAP were resuspended in peripheral blood and delivered into the root canals. In Group 2-4, firm coronal seal was performed after revascularization procedure and radiographs were taken periodically in order to observe the development of roots. After a 12-week-period, alveolar samples were collected and observed histologically.@*Results@#The isolated SCAP showed clonogenic ability and multilineage differentiation ability including osteogenic, adipogenic and chondrogenic potentials. These cells also expressed the mesenchymal stem cell markers such as STRO-1 and CD146, while no cytokeratin was detected. The thickening of canal wall was observed radiographically 12 weeks after procedures of infection control and revascularization. Histologically, the newly formed tissues on the inner canal wall were found bone lacuna like structure in Group 2 and 3, and the new tissue formed in the Group 3 seemed easy to separate from the canal wall. The newly formed tissues in Group 4 were much thicker compare to those in the Group 2 and 3, and the dentine tubule like structure instead of bone lacuna was noticed although the orientation of these tubules were various.@*Conclusions@#SCAP seem to play an important role in the tissue regeneration procedure when infection is well controlled in young permanent teeth with periapical periodontitis. It is difficult to achieve real tissue regeneration due to the lack of endogenous SCAP in apical area, therefore delivering adequate exogenous SCAP isolated and cultured in vitro could be a promising approach to overcome the challenge.

Retrospective analysis of pulp revascularization in immature permanent teeth with diffuse pulpitis / 中华口腔医学杂志

Objective@#To evaluate the treatment effectiveness of revascularization in immature permanent teeth with diffuse pulpitis and to provide an alternative approach for the treatment of these teeth.@*Methods@#Clinical and radiographic data were collected from 17 immature permanent teeth which were diagnosed as diffuse pulpitis and with their pulp extirpated at Emergency Department of Peking University School and Hospital of Stomatology. All these teeth were treated using pulp revascularization at Department of Pediatric Dentistry. Clinical success rate was then evaluated based on the clinical and radiographic findings. The increase of root length and dentin wall thickness of the revascularized teeth and the contralateral control teeth were measured and compared according to the preoperative and recall periapical radiographs.@*Results@#The average follow-uptime is (25.8±9.9) months (12-46 months). Totally 13 out of the 17 teeth showed normal clinical and radiographic manifestation and achieved the increasein root length and dentin wall thickness. They met criteria for success treatment. The rest 4 out of the 17 teeth also showed root length and dentin wall thickness increaseand apical foramen closure. However, periapical inflammations were observed during 12 to 36 monthfollow-ups. These cases were recognized as failed. In all the17 teeth, the increase of root length and dentin wall thickness was not significantly different between the revascularized teeth and the contralateral control teeth (P>0.05).@*Conclusions@#Pulp revascularization in young permanent teeth with diffuse pulpitis resulted in similar clinical outcomes in root development and root canal wall formation compared with the contralateral control teeth. However, reinfection might occur during long-term follow-up.

Recombinant human transforming growth factor β1 promotes dental pulp stem cells proliferation and mineralization / 北京大学学报(医学版)

Objective: To explore suitable concentration of recombinant human transforming growth factor β1 (rhTGF-β1) usage and study the effect of rhTGF-β1 on differentiation of dental pulp stem cells (DPSCs).Methods: DPSCs were isolated from the undiseased third molars of people aged 18-25 years and cultured according to instructions in vitro.Different concentrations (1 , 6 , 10 μg/L) of rhTGF-β1 were added to the culture medium to examine DPSCs proliferation by CCK-8 (cell counting kit-8) assay.The suitable concentration was then selected.For differentiation, the DPSCs were incubated for 7 or 14 days with rhTGF-β1 supplemented with osteo/odontoblastic induction medium containing 10 nmol/L dexamethasone, 10 mmol/L b-glycerophosphate, 50 g/L ascorbate phosphate, 10 nmol/L 1,25-dihydroxyvitamin D3 and 10% fetal bovine serum.The cells were then washed 3 times with phosphate-buffered saline and sonicated with 1%Triton X-100 for 30 minutes on ice.Cellular alkaline phosphatase (ALP) activity was assayed with p-nitrophenyl phosphate as the substrate.The enzyme activity was expressed as p-nitrophenyl produced per milligram of protein [bicinchoninic acid (BCA) protein assay kit].To examine mineral nodule formation, the cultured cells were fixed in 4% paraformaldehyde and washed in water, and the mineralization of the extracellular matrix was assayed by 1% alizarin red S staining and elution of staining was examined as optical density (D) under microplate reader.The mean difference was considered significant at 0.05 and 95% confidence interval.Results: The DPSCs had ty-pical fibroblast morphology and could form mineral nodules after being cultured with osteo/odontoblstic induction medium for 14 days.6 μg/L rhTGF-β1 significantly promoted the DPSCs proliferation on the 3rd and 5th days.After the incubation of osteo/odontoblastic induction medium, the DPSCs with the 6 μg/L rhTGF-β1 increased ALP activities compared with the control;D values in the 6 μg/L rhTGF-β1 group was 0.31±0.03, while the control group was 0.02±0.01(P<0.05).The total protein content in the 6 μg/L rhTGF-β1 group was (2 775.46±83.54) mg/L, and the control group was (1 432.20±110.83) mg/L (P<0.05).To eliminate the cells proliferation influence, relative ALP activities, which was defined as the total ALP divided by the total protein content, the 6μg/L rhTGF-β1 group was 6 times higher than the control group.Alizarin red S staining showed increased mineral nodule formation in the rhTGF-β1 group.The elution of staining under microplate reader also showed more optical density in the 6 μg/L rhTGF-β1-treated cells (0.83±0.02) than that in the control groups (0.55±0.05, P<0.05).Conclusion: 6 μg/L rhTGF-β1 could significantly promote DPSCs proliferation and odontoblastic differentiation in vitro.

Impact of different degree pulpitis on cell proliferation and osteoblastic differentiation of dental pulp stem cell in Beagle immature premolars / 北京大学学报(医学版)

Objective:To compare the proliferation and osteoblastic differentiation of dental pulp stem cell (DPSC)isolated from normal and inflamed pulps of different degrees in Beagle immature premolars, and provide evidence for the use of inflammatory DPSC (IDPSC).Methods:This study evaluated 14 Beagle’s young premolars (21 roots).In the experiment group,irreversible pulpitis was induced by pulp exposure and the inflamed pulps were extracted 2 weeks and 6 weeks after the pulp chamber opening.For the control group,normal pulps were extracted immediately after the exposure.HE staining and real-time PCR were performed to confirm the inflammation.The cells were isolated from the inflamed and normal pulps (IDPSC and DPSC).Cell proliferation and osteoblastic differentiation potentials of the two cells were compared.Results:Inflammation cells infiltration was observed in the inflamed pulps by HE stai-ning.The expression of inflammatory factor was much higher in the 6 week inflamed pulp.IDPSC had higher potential of cell proliferation and osteoblastic differentiation potentials.Furthermore,the osteoblas-tic differentiation potentials of IDPSC from 2 week inflamed pulp were higher than those from 6 week in-flamed pulp.Conclusion:The potential of cell proliferation and osteoblastic differentiation of DPSC was enhanced at early stage of irreversible pulpitis,and reduced at late stage in Beagle immature premolars.

Effects of stromal cell-derived factor-1 on proliferation,migration,and odontoblastic differentiation of human dental pulp stem cells / 北京大学学报(医学版)

Objective:To compare the effects of stromal cell-derived factor-1 (SDF-1 )and granulocyte colony-stimulating factor (G-CSF)on proliferation,migration,and odontoblastic differentiation of human dental pulp stem cell (DPSC)in vitro.Methods:DPSCs were cultured in vitro and treated with either 1 00 μg/L SDF-1 or 1 00 μg/L G-CSF.Cell counting kit-8 (CCK-8 )and colony-forming unit (CFU ) were used to detect the effect of SDF-1 and G-CSF on the proliferation ability of DPSC.Cell migration of DPSC was determined by wound healing assay and Transwell migration assay.The effects of SDF-1 and G-CSF on odontoblastic differentiation of DPSC were evaluated by alkaline phosphatase (ALP)staining, ALP activity and alizarin red S staining.The expression of odontoblastic-related genes such as dentin ma-trix protein 1 (DMP-1 )and dentin sialophosphoprotein (DSPP)were quantified by real-time RT-PCR. Results:SDF-1 and G-CSF promoted the proliferation of DPSC slightly,but the difference was not statis-tically significant.Wound healing assay showed that SDF-1 and G-CSF promoted cell migration of DPSC significantly (P<0.01 ),but there was no significant difference between the two factors.In Transwell migration assay,the number of migrated cells of the control group was 5 .0 ±1 .4 per sight,while the SDF-1 group was 24.3 ±6.8 per sight and the G-CSF group was 1 1 .8 ±3.3 per sight,suggesting that cell migration of DPSC was improved significantly after being treated with SDF-1 or G-CSF,and SDF-1 was more effective than G-CSF (P<0.05 ).Significantly greater odontoblastic differentiation potential was found in SDF-1 group and G-CSF group based on the ALP staining.Higher ALP activity,more mineralization nodule formation and higher expressions of DMP-1 and DSPP were also found after SDF-1 or G-CSF treatment.Conclusion:SDF-1 had no significant effect on the proliferation of DPSC,but could significantly promote cell migration and odontoblastic differentiation of DPSC.Its effect on DPSC was bet-ter than G-CSF.

The blind source separation method based on self-organizing map neural network and convolution kernel compensation for multi-channel sEMG signals / 生物医学工程学杂志

A new method based on convolution kernel compensation (CKC) for decomposing multi-channel surface electromyogram (sEMG) signals is proposed in this paper. Unsupervised learning and clustering function of self-organizing map (SOM) neural network are employed in this method. An initial innervations pulse train (IPT) is firstly estimated, some time instants corresponding to the highest peaks from the initial IPT are clustered by SOM neural network. Then the final IPT can be obtained from the observations corresponding to these time instants. In this paper, the proposed method was tested on the simulated signal, the influence of signal to noise ratio (SNR), the number of groups clustered by SOM and the number of highest peaks selected from the initial pulse train on the number of reconstructed sources and the pulse accuracy were studied, and the results show that the proposed approach is effective in decomposing multi-channel sEMG signals.

Masticatory performance and assessment of life quality of children with ectodermal dysplasia after prosthetic rehabilitation / 中华口腔医学杂志

<p><b>OBJECTIVE</b>To evaluate masticatory performance and life quality of children with ectodermal dysplasia (ED) after prosthetic rehabilitation.</p><p><b>METHODS</b>Six children with ED received denture restoration and 18 healthy children were involved in this study. The surface electromyography (EMG) of masseter (MM) and anterior temporalis (TA) during clenching and chewing movement were recorded. The EMG amplitude, area, asymmetry index of total and activity index of MM/TA were compared at each stage. The masticatory efficiency was measured with spectrophotometer. The life quality was assessed using visual analogue scale questionnaire.</p><p><b>RESULTS</b>The EMG amplitude of MM and TA during chewing in ED Group were 41.7% and 45.6% of the control group respectively, the area were 35.9% and 36.0% respectively. Significant difference in asymmetry index of total during clenching was observed between the two groups (P < 0.05) but not during chewing (P > 0.05). The differences of activity index of MM/TA during clenching and chewing between the two groups were not detected (P > 0.05). The masticatory efficiency of ED group was 67.2% of the control group. The score of chewing function in children with ED after prosthetic rehabilitation was three times higher than before, and no difference was present between the two groups (P > 0.05).</p><p><b>CONCLUSIONS</b>Early prosthetic rehabilitation can significantly improve the masticatory performance and life quality of children with ED.</p>

Mineral trioxide aggragate pulpotomy for the treatment of immature permanent teeth with irreversible pulpitis: a preliminary clinical study / 中华口腔医学杂志

<p><b>OBJECTIVE</b>To evaluate the preliminary clinical effect of mineral trioxide aggragate (MTA) pulpotomy on immature permanent teeth with irreversible pulpitis.</p><p><b>METHODS</b>Twenty-six immature permanent teeth with irreversible pulpitis were recuited from Department of Pediatric Dentistry, Peking University School and Hospital of Stomatology. These teeth were treated with partial or full pulpotomy according to the condition of pulp bleeding. MTA was used as pulp capping material. Patients were recalled periodically after the treatment. Clinical and radiographic effects were evaluated.</p><p><b>RESULTS</b>At one year follow-up, 20 teeth were evaluated as healed or healing, 2 teeth were evaluated as failure and 4 teeth were dropped out. The success rate was considered 91% (20/22). A dentinal bridge was radiographcally observed underneath the pulpotomy site in 13 teeth(65%, 13/20).</p><p><b>CONCLUSIONS</b>MTA pulpotomy is an effective method for the treatment of immature permanent teeth with irreversible pulpitis. But further research with longer follow up period is required.</p>

Retrospective study about periodontal ligament healing of replanted permanent teeth in children / 北京大学学报(医学版)

Objective:To analyze the prognosis about periodontal ligament healing of replanted perma-nent teeth in children and to examine the associated factors.Methods: The sample consisted of 49 children with 61 avulsed permanent teeth, whose injuries had been managed in the period from 2000 to 2012.The clinical data of replanted teeth were collected, and the follow-up period was no less than 12 months .The factors were analyzed in relation to postoperative outcomes, classified as functional periodon-tal healing ( FH ) , infection-related ( inflammatory ) resorption ( IRR ) and replacement resorption ( RR) .Results:The functional healing rate was 23.0%, while replacement resorption rate was 72.1%. The replacement resorption ( ankylosis ) was usually observed earlier by clinical examination than by radiographic examination.86.0% (40/47) resorptive processes were diagnosed within the first year. Physiological storages, such as milk, saline and saliva were significantly better to periodontal ligament healing than nonphysiological storages, such as tap water and sterilizing solutions ( chloramine and alco-hol) .Functional healing was found significantly more frequent in canines and premolars.Conclusion:The factor significantly affecting periodontal ligament healing is storage medium.Replacement resorption is the most common type of root resorption.The replacement resorption diagnosis must combine the radio-graphic examination with the clinical examination.It is better to follow up more than 1 year after tooth re-plantation.

Advance and challenges in stem cell therapy for Alzheimer’ s disease / 中国药理学通报

Alzheimer’ s disease ( AD) , the most prevalent type of neurodegenerative disease, characterized by extracellular β-amyloid ( Aβ) plaque deposition, intracellular neurofibrillary tangles, and the loss of diverse neurons. Neuron loss might be the main cause that induces irreversible decline of cognitive function in AD patients. At present, AD therapy only relieves symptoms instead of fundamentally affecting the major pathologi-cal characteristics of the disease. Recently, rapid advances in neurogenesis and stem-cell biology have provided a new and pro-spective potential for AD treatment. Stem-cell types in the treat-ment of neurodegenerative diseases include neural stem cells ( NSCs ) , embryonic stem cells ( ESCs ) , mesenchymal stem cells ( MSCs ) , and induced pluripotent stem cells ( iPSCs ) . Stem cell therapy shows anti-AD function by replacing the dam-aged and lost neurons, rebuilding the cellular loop, inhibiting amyloidogenesis, promoting neurotrophic factor release, and reg-ulating immune reaction. This review highlights the recent pro-gress, mechanisms, and preclinical evidence of exogenous trans-planted stem cell, and addresses the current major challenges of stem cell transplantation in clinic. In addition, this review also summarizes the research status of compound promoting endoge-nous neurogenesis in brief.

A retrospective study on pulpal tissue prognosis of avulsed permanent teeth in children / 北京大学学报(医学版)

Objective:To analyze the pulpal prognosis of replanted permanent teeth in children and to examine the associated factors .Methods:The samples consisted of 67 children with 81 avulsed perma-nent teeth treated in Peking University Hospital of Stomatology from 2000 to 2012 .Their clinical data of the replanted teeth were collected , and the follow-up period was no less than 12 months.The pulpal prognosis was classified as pulp necrosis and pulp non-necrosis .Results: The replantation within 30 minutes after avulsion led to the most significant increase in pulpal healing (P<0.05).The dental pulp of 80% ( 4/5 ) young permanent teeth replanted within 30 minutes remained vital , while all the teeth replanted after 30 minutes developed pulp necrosis within 60 days after replantation .Conclusion: The extra-alveolar period significantly affects the prognosis of pulp in immature permanent teeth after replanta-tion.When the extra-alveolar period is more than 30 minutes, the chance of pulp revascularization after replantation is very low , therefore pulp extirpation should be performed .

Spatiotemporal expression pattern of E-cadherin and P-cadherin during mouse tooth development / 北京大学学报(医学版)

Objective:To investigate the expression patterns of E-cadherin and P-cadherin in murine-tooth germs at early developmental stages .Methods:Mandible samples of CD 1 mice from embryonic day 12 .5 to postnatal day 3 .5 were collected .The expressions of E-cadherin and P-cadherin in murine man-dibular first molar germs were detected by immunofluorescence and observed under confocal fluorescence microscope .HE staining was performed for tissue morphology .Results:Both E-cadherin and P-cadherin were widely expressed in the epithelial tissues through early developmental stages .The E-cadherin ex-pression was increased in polarizing pre-ameloblasts , whereas the P-cadherin expression declined .The expression of the P-cadherin could be detected in epithelial tissues before bud stage , and expressed in mature ameloblasts at secretory stage .Conclusion:The E-cadherin and P-cadherin expressed in different spatiotemporal expression patterns , indicating their individual functions during tooth development .P-cad-herin might function in the secretion and mineralization of enamel .

Expressions of CD1a and CD68 in secondary keloid / 中华皮肤科杂志

ObjectiveTo analyze the distribution and density of Langerhans cells and dermal CD68 positive histiocytes in lesions of secondary keloid.MethodsTissue specimens were resected from the lesions of 30 patients with secondary keloid and normal skin of 14 human controls.Immunohistochemistry was performed to observe the expressions of CD68 and CD1a in these specimens.A micrometer was used to count the number of positively stained cells per unit area.The Student's t test was conducted for data analysis by using the SPSS software.ResultsThe density of CD1a+ Langerhans cells was (61 ± 49) cells/mm2 in the epidermis of secondary keloid lesions, (258 ± 61 ) cells/mm2 in the control epidermis,and(40 ± 65) cells/mm2 in the dermis of keloid lesions.CD68+ cells were absent in the epidermis of keloid lesions.Significant differences were observed in the density of CD1a+ Langerhans cells between the lesional and normal control epidermis(t =9.88,P ＜ 0.001 ) and in the percentage of CD68+ cells in nucleated cells between the superficial dermis of lesions and control skin(62％ ± 12％ vs.70％ ± 14％,t =2.66,P ＜ 0.05).The density of dermal CD68+ histiocytes was similar between the lesions and control skin ((287 ± 73) cells/mm2 vs.(290 ± 22) cell/mm2,t =0.02,P ＞ 0.05).Conclusions In keloid lesions,Langerhans cells decrease in the epidermis but increase in the dermis,CD68+ histiocytes are absent in the epidermis,and reduced in the dermis with a declined percentage in nucleated cells.

Effects of tumor necrosis factor (TNF)-α,interleukin(IL)-6 and interferon(IFN)-γ on the expression of CD68 in HaCaT cells / 中华皮肤科杂志

Objecfive To study the effects of some cytokines such as TNF-α,IL-6 and IFN-γ as well as lipopolysaccharide on CD68 expression in HaCaT cells.Methods Human HaCaT keratinocytes were randomly divided into natural proliferation group (without stimulation),IFN-γ-stimulated group,TNF-α-stimulated group,LPS-stimulated group and IL-6 stimulated group.The work concentration of TNF-α,IL-6,IFN-γ and LPS was 50 mg/L.HaCaT cells were collected after 24-hour treatment with the cytokines followed by the examination of CD68 expression with flow cytometry,immunohistochemistry and reverse transcription(RT)-PCR,respectively.Results Compared with untreated HaCaT cells,the count of CD68-positive cells was elevated in cells stimulated by TNF-α(t=3.60,P<0.01),IL-6(t=3.93,P<0.01),IFN-γ(t=2.38,P<0.05)and LPS(t=2.52,P<0.05),and the effect of TNF-α and IL-6 was stronger than that of IFN-γ and LPS.Among the four cytokines,only IL-6 enhanced the mean fluorescence intensity of CD68-positive cells (t=8.34,P<0.01).After 24-hour treatment with TNF-α,IFN-γ and IL-6,CD68 expression was observed in the cytoplasm and on the membrane of HaCaT cells and was stronger in cells treated with TNF-α and IL-6 than in those with the other cytokines.A significant increase was observed in the CD68 mRNA expression after 24-hour treatment with TNF-α (t=4.34,P<0.01),IL-6 (t=7.52,P<0.01)and IFN-γ (t=2.81,P<0.05);TNF-α and IL-6showed a stronger promotive effect than IFN-γ.Conclusion IL-6,TNF-α,IFN-γ and LPS can upregulate the CD68 expression in HaCaT cells.

Influence of plasma protein on bacterial adhesion to biomaterials / 中国组织工程研究

Implant-associated infection is a serious problem in the clinical application of biomaterials.which greatly restricts the generalizatjon of cardiovascular biomaterials,while bacterial adhesion is the initial cause for implant-associated infections of cardiovascular biomaterials.Therefore.the prevention of bacteriaI adhesion to the biomaterials plays a crucial role in the cure of biomaterial center infection.It has reported that human plasma protein influences the bacterial adhesion to biomateriais.Some plasma proteins inhibit bacterial adhesion.whereas some promote jt.Study on the correlation between plasma protein and hacterial adhesion to the biomaterials is of great importance in the prevention and cure of biomaterials center infection.

Research on mesenchymal stem cells image segmentation based on morphology / 生物医学工程学杂志

A kind of research on mesenchymal stem cells (MSCs) segmentation is reported in this paper. The research of its kind has become more and more popular recently. Top-bottom hat algorithm of gray morphology is applied to image preprocessing. The radius of the ball of the structure function is 30 in the algorithm. After preprocessing, binary image is gained cursoryily through distinguishing foreground from background using two thresholds. Noise is removed by applying morphology algorithm. It is easy to differentiate foreground from background in the result image. Finally, area and number of cells can be calculated respectively.

Change in blood flow of rats with diabetes mellitus after the acute hind limb ischemia / 基础医学与临床

Objective To establish the acute hind limb ischemia on Wistar rat with diabetes mellitus.MethodsThirty diabetes rats were induced by intraperitoneal STZ (50 mg/kg) injection, as well as the blood glucose level tested over 16.8 mmol/L. The rats were ligated on the left femoral artery, then the blood perfusion on the hind limbs ischemia was measured by LDPI after the operation. Results The fasting plasma glucose level on 22 Wistar rats(81.5%) was kept above 16.8 mmol/L, and the hind limb blood perfusion would recover slowly to the level of the right side from 1 to 14 day (P

Observation on proliferation and collagen secretion of the transplanted human fibroblasts in nude mice / 基础医学与临床

Objective To investigate the proliferation and collagen secretion of transplanted human fibroblasts.Methods The solution containing human fibroblasts(2?1010L-1)was prepared and 1 mL was injected into the dermis of BALB/CNU nude mice.Animals were killed by the end of the 1st,2nd and 3rd month after injection.The dermis in the injected area was taken out and stained with HE.Immunohistochemical staining for type I and type Ⅲ collagen was performed at the same time.Results Mitosis was observed by the end of the 1st,2nd and 3rd month.The concentration of type I and type Ⅲ collagen in the extra cellular matrix increased with the passing of time.Conclusion Transplanted human fibroblasts can proliferate automatically in the dermis of nude mice and manufacture the type I and type Ⅲ collagen in situ.Long period of survival and secretion will make it possible for fibroblasts to become promising option to correct minimal tissue defects.

Watershed-based segmentation of histiocytic images / 生物医学工程学杂志

The task of segmenting histiocyte is a crucial step in the analysis of histiocytic images which is an important application of computer vision to histopathology. The algorithm presented in this article was composed of two steps: (1) the morph-based preprocessing; (2) the ameliorated watershed method. In the first step, the difference between histiocytes was magnified in order to increase the visibility from the view of the computer vision, and then the ameliorated terrace-flooding-simulated watershed method was used to achieve the segmentation of histiocytic images in the second step. To test the performance of the algorithm, different samples of visual quality were tested and the result figures proved successful.

Establishment of permanent tooth germ missing animal model and study on root resorption of the corresponding deciduous teeth / 北京大学学报(医学版)

Objective: To establish the permanent tooth germ missing animal model for future research on the root resorption of deciduous tooth in the absence of permanent tooth germ. Methods: The permanent tooth germ missing animal model was established by surgical removal of the permanent tooth buds in a male 11-week-old Beagle dog. Root resorption of the deciduous teeth without permanent successors was observed by taking periapical films periodically,and compared with physiological root resorption. Once the sign of root resorption of the deciduous teeth without permanent successors was detected on radiographic films, the animal was sacrificed and the mandibular bone was collected for histological study. Results: Root resorption of the deciduous teeth with the presence of permanent tooth germ started at 20 weeks after birth, while root resorption of deciduous teeth without permanent tooth germ started 26-27 weeks which was significantly delayed. Histological studies showed that a large number of multinucleated giant cells were present on the pulpal surface of the root, while only few of them were seen on the outer surface. Conclusion: The permanent tooth germ missing animal model was successfully established in this study which simulated the case of congenital absence of permanent tooth germ in human. Root resorption of deciduous tooth without permanent tooth germ was significantly delayed than the deciduous tooth with permanent tooth germ.