The p75 neurotrophic factor receptor is a low affinity receptor for neurotrophic factors and plays an important role in nerve growth, development and function integrity. It is closely related to dental development, oral and maxillofacial tumor, nerve repair and tissue engineering. It shows good prospect for application. In this paper, the research progress of p75 neurotrophic factor receptor in Stomatology is reviewed.

Objective:To observe the clinical effects of extraoral manual reposition approach in the treatment of acute anterior disloca-tion of temporomandibular joint. Methods:98 patients with acute anterior dislocation of temporomandibular joint were divided into 2 groups(n=49) by random digit table and treated by manual reposition through intraoral and extraoral approach respectively. The suc-cess rate, success time, patient pain during treatment, SBP, DBP, HR and patient satisfaction were evaluated respectively. Results:The success rate(95. 92%) and the patient satisfaction rate(76%) of extraoral method group were higher than those of the intraoral method group (81. 63% and 66%);success time(3. 91 ± 0. 55)s and patient pain during treatment(3. 51 ± 0. 25) in extraoral method group were less than those in the intraoral method group[(5. 57 ± 0. 51) s and (6. 6 ± 0. 21)]. The degree of changes of SBP, DBP and HR in extraoral method group were less than those in the intraoral method group(P<0. 05). Conclusion:Extraoral manual reposi-tion approach is more effective than intraoral approach in the treatment of acute anterior dislocation of temporomandibular joint.

Objective To investigate the mineralized capacities of ectomesenchymal stem cells (EMSC) from facial process of Sprague Dawley(SD) rat embryo of different age in vitro and the expression of p75 neurotrophin receptor(p75NTR) in this process.Methods The stem cell surface antigens of EMSC from 12.5 d,15.5 d and 18.5 d SD rat embryonic facial process were tested by flow cytometry technology.E12.5 d EMSC,E15.5 d EMSC and E18.5 d EMSC were incubated under mineralization induction and analysed by alkaline phosphatase(ALP) staining on day 7(d7) and alizarin red staining on day 21(d21).Expression changes of Runt-related transcription factor-2(RUNX2),collagen Ⅰ (Col Ⅰ) and p75NTR in each group were measured using Western blotting and real time(RT)-PCR on day 0(d0),day 7(d7),day 14(d14) and day 21(d21).Results The expression of the special substances CD29,CD146 and p75NTR in E12.5 d EMSC,E15.5 d EMSC and E18.5 d EMSC were positive,and the expression of CD45 was negative.The expression level of p75NTR in E18.5 d EMSC(84.04％) was much higher than that of E12.5 d EMSC (22.53％) and E15.5 d EMSC(81.43％).The mineralized capacities of E18.5 d EMSC was stronger than that of E12.5 d EMSC and E15.5 d EMSC.The higher expression of RUNX2,Col Ⅰ in E18.5 d EMSC(RUNX2:1.92±0.20,Col Ⅰ:1.85±0.66) was found compared with E12.5 d EMSC(RUNX2:0.38±0.02,Col Ⅰ:0.33±0.94)and E15.5 d EMSC(RUNX2:0.72±0.22,Col Ⅰ:0.64±0.07)(P＜0.05),and p75NTR in the E18.5 d EMSC experimental group(E12.5 d:0.79±0.23,E15.5 d:0.84±0.29,E18.5 d:1.35±0.22) was significantly higher than the in control group(E12.5 d:0.42±0.12,E15.5 d:0.43±0.13,E18.5 d:0.48±0.15)(P＜0.05).RTPCR further proved the results of the Western blotting.Conclusions p75NTR participated in the mineralization differentiation of EMSC.E18.5 d EMSC had a higher expression of p75NTR and stronger mineralization capacity and was the ideal engineering seed cells.

OBJECTIVETo observe the changes of surface morphology and temperature of dental pulp cavity in vitro after irradiated by Er:YAG laser with different energy and irradiation time.

METHODSAll of the 96 samples from 24 teeth in vitro were collected from dental clinical departments then divided into two groups (group A and group B) randomly. We chose the energy of 20 Hz, and 1, 2, 3, 4, 5, 6 W to treat the samples in group A and group B and the irradiation time was 10s or 20s. We recorded the temperature changes of dental pulp cavity by digital thermometer and observe the morphology of tooth enamel by scanning electron microscope (SEM).

RESULTSWith the extension of irradiation time and increasing of energy, the temperatures of dental pulp cavity were significantly increased after the treatment of Er: YAG laser. The two groups of tooth enamel surface morphology were changed after irradiated by Er: YAG laser with different energy and irradiation time. However, there was no melting and carbonation on the surface of tooth enamel after the treatment of Er:YAG laser in two groups.

CONCLUSIONThe temperatures of dental pulp cavity were increased after irradiated by increasing laser energy density fom 1 W to 6 W. No melting or carbonized phenomenon was found in enamel within the energy of 1 W to 6 W. All the data would provide evidences for clinical treatment of cavity.

OBJECTIVETo compare the consistency of root canal configuration types of mandibular first premolar by using micro-CT and radio visio graphy (RVG).

METHODSOne hundred extracted mandibular first premolars with complete dental root and apex which received no endodontic treatment were randomly selected. Each tooth was radiographed with RVG through a buccolingual and mesiodistal direction, and then scanned with micro-CT and reconstructed. The classifications of the root canal types according to Vertucci's type with the two methods were compared.

RESULTSThe canal patterns were classified as type I (67%), type III (3%), type V (18%), type VII (2%), additional type (10%) with micro-CT and canal patterns as type I (71%), type III (2%), type V (23%), type VII (1%), additional type (3%) with RVG. 63% of teeth showed one canal in both micro-CT and RVG. Only 25% of teeth were diagnosed as complex canal by the same canal type in both micro-CT and RVG. The Kappa value between micro-CT and RVG was 0.541 which suggested that the two kinds of methods had intermediate consistency. 82.8% of the premolars with root groove had two or more than two canals.

CONCLUSIONAlthough RVG can basically reflect the root canal system type of the mandibular first premolars in vitro, it offers poor accuracy images to complex root canals. Micro-CT three-dimensional images could clearly and precisely display the root canal system morphology of the mandibular first pre-molars in vitro.

Objective: To observe the effect of hypoxia on changes of proliferation ability of cultured human periodontal ligament fibroblasts (HPLFS) in vitro. Methods: HPLFS were randomly divided into two groups (experimental group and control group) by different oxygen concentrations. The oxygen concentration of control group was 21%. The oxygen concentrations of experiment group were 10%, 5% and 2%. The proliferation ability of HPLFS was detected by MTT colorimetric assay. The cell ultrastructure was observed by transmission electron microscope (TEM). Results: MTT assay results showed that compared with the control group, at the 12 h and 24 h, cell proliferation was enhanced with the hypoxia degree. At 24 h, cell proliferation showed significant differences. At 48 h and 72 h, proliferation of the cultured HPLFS in severe hypoxia group reduced significantly. Observed by TEM, at 24 h, not only the number of mitochondria, rough endoplasmic reticulum but also cell process increased in the cultured HPLFS in severe hypoxia group. At 72 h, the number of lysosome increased and the cell structure degenerated. Conclusion: Long-time severe hypoxia may lower the repair and remodeling abilities of periodontium, which might be one of the important etiological factors of periodontal disease under condition of high altitude.

Objective To investigate the morphology and bonding of enamel and dentin conditioned by 35% phosphoric acid and pulse Nd:YAG laser.Methods A total of 52 human premolars were selected,40 of which were divided into four groups randomly: group A [enamel treated with 35% phosphoric acid(Scotchbond,3M) for 30 s];group B [enamel treated with pulse Nd:YAG laser(Evlaser Friendly A4 Italy) for 20 s];group C(dentin treated with 35% phosphoric acid for 15 s);group D(enamel treated with pulse Nd:YAG laser for 15 s).The tensile bond strength(TBS) were determined.Except 4 out of 12 human premolars without any treatment,8 were divided into 4 groups and were treated with the method mentioned above.The surfaces of 12 human premolars were observed under SEM.Results The highest TBS was obtained in group A in comparison with the other 3 groups(P0.05).The smear layer on enamel and dentin could be removed after conditioned by both phosphoric acid and pulse Nd:YAG laser.The honeycomb structures were observed on all enamel but less regularly in lased group.Almost all the orifices of dentinal tubules were open in the acid group and sealed or half-sealed in lased group.Conclusion The pulse Nd:YAG laser did not contribute to bonding of enamel,but could improve the bonding of dentin and seal most of the orifices of dentinal tubules,which reduced the harmful stimulation to the dental pulp.

Objective To evaluate the effect of driving forces similar to those found in dental plaque fluid on the enamel demineralization and ultrastructure of surface layer.Methods The sections of human enamel were exposed to lactic acid solutions with degree of saturation with respect to enamel and degree of saturation with respect to fluoroapatite for 96 h at 25 ℃,using the deionized water as control in the same conditions.Enamel demineralization was monitored using SEM and confocal laser scanning microscopy(CLSM).Results Only was enamel subsurface demineralization detected in solutions with DS_(EN)(0.1-0.3).Enamel mineral loss and micropores of surface layer decreased significantly with increasing DS_(EN) and DS_(FA) values.However,no mineral loss and micropores of surface layer was observed in sections of enamel exposed to solutions with DS_(EN) values of 0.4 and 0.5,which were covered with homogeneous remineralization layer.Conclusion The demineralization driving forces similar to dental plaque fluid under different DS_(EN) and DS_(FA) have significant effects on the surface layer of enamel and the subsurface demineralization process.

Objective To explore the best parameters of impulse Nd:YAG laser-aided debonding for ceramic bracket.Methods The removal of ceramic bracket from enamel surface by laser irradiation was investigated in vitro.Fifty-four premolars were used to test the tensile strength and 32 premolars for pulp cavity temperature test.The results were compared according to the laser setting(output power:0,2,3,5 W;time:2,4 s),the average force(830.3,556.5 g) necessary to break the adhesion between ceramic bracket and tooth,the different edible pigment on bracket surface(black or not).Results The bonding strength of ceramic bracket was significantly reduced by laser irradiation,averagely by 48%.The average bonding strenth in the six groups for tensile strength test was of statistical difference(P

Objective To observe the effect of different energy levels of pulsed Nd∶YAG laser irradiation on the changes of NO and NOS levels in ulcer tissue of oral ulcer model.Methods Forty-eight Sprague-Dawley rats were inflicted with oral ulcer,and then randomly and equally assigned to 6 groups,that is,oral ulcer group,1% iodine glycerin group and the rest 4 groups receiving pulsed Nd∶YAG laser irradiation at 1.5 W 40 mJ,1.5 W 60 mJ,1.5 W 80 mJ or 1.5 W 100 mJ(once per day,for 3 consecutive days).The other 8 rats served as normal control.In 24 h after last treatment,4 rats from each group were sacrificed and their cheek pouches were taken out for NO and NOS levels in the mucosal tissue by spectrophotomentry.Ulcer healing were observed 24 h after the last treatment for 8 consecutive days.The efficiency of Nd∶YAG laser irradiation at different powers were evaluated.Results Irradiation groups had significantly shorter healing time compared with iodine glycerin group.Level of NO and NOS activity in 1.5 W 60 mJ and 1.5 W 80 mJ groups was evidently lower than the ulcer group(P