Pathways and Fate of Migratory Cells During Late Tooth Organogenesis

Tissue recombination experiments and cell lineage analyses of the developing neural crest have documented the role and central pathways of migratory cells during early craniofacial development. In the present study, regional pathways of cells during late peripheral morphogenesis were investigated using the crown stage tooth organ as a model. Homing targets during tooth integument formation were analyzed to understand the fate of migratory cells involved in late tooth organogenesis and the developmental origin of periodontal tissues. After surgical removal of the oral mucosa, the oral aspect of the dental follicle of lower first mouse molar teeth was labeled using a fluorescent contact dye. Following sacrifice after 0, 2, 4, and 6 days, labeled cells were detected in the dental follicle, in the alveolar bone, and in the periodontal ligament adjacent to the molar root. The distribution of labeled tissues was reconstructed three-dimensionally via confocal microscopy. Using a tooth molar organ culture system, labeled cells within the dental follicle were documented traveling in the apical direction. Our results indicated that cell migration during tooth organogenesis was following specific pathways and that cells within the circumference of the dental follicle were migrating in the apical direction. We speculate that migratory cells passing through the dental follicle connective tissue may contribute to the formation of the periodontium. The present documentation visualizes pathways, role, and dynamics of extensive cell movements during late tooth organogenesis.     

动态咬合下牙周膜的生物力学分析

目的 分析动态咬合下加载时间、角度因素对牙周膜应力和位移的影响。方法 采用逆向工程技术建立牙周膜厚度为0.2 mm的下颌前牙—牙周膜—牙槽骨的三维模型,在与牙体长轴分别成0°、15°、30°、45°、60°、75°、90°,由颊侧向舌侧的动态咬合载荷作用下,分析不同周期下牙周膜的应力、位移变化状况。结果 在单周期下,由不同角度载荷引起的牙周膜最大残余应力极大值与最小值之比为5.5,最大位移极值之比为8.1;由5周期引起的最大位移极大值与极小值之比在1.02~1.35内随载荷角度增加;由不同角度载荷引起的最大残余应力极大值与极小值之比在1.86~3.00内随咬合周期数增加;不同角度下最大应力均集中在颈缘舌侧区域, 最大残余应力位置分布随时间在颈缘不同部位间变动;0°载荷下牙根的应力累积最严重。结论 下前牙固定桥基牙选择的临床应用中,应注意牙周膜应力累积情况以及最大残余应力分布的不确定性;临床治疗中,应避免对牙齿施加大角度载荷,尽量减少连续咬合较硬食物。     

Differences in the biomechanical behaviors of natural teeth and dental implants

ObjectiveThe lack of a PDL, which acts as an energy absorber, is a contributor to implants’ early failure; however, these discrepancies are not well understood because of limited in vivo research. This study investigated the discrepancy in biomechanical behaviors between natural teeth and dental implants by detecting micro-movements in vivo.MethodsWe designed a device that could measure precisely mechanical behaviors such as creep, stress relaxation, and hysteresis by using load–control displacement on teeth and implants. We also compared energy dissipation between natural teeth and dental implants by subtracting the area of the hysteresis loop of natural teeth from that of dental implants.ResultsBiphasic curves with an initial phase of rapid response and a subsequent phase of slow response were confirmed in creep and stress relaxation curves for the load–time relationship in natural teeth. By contrast, the behavior of creep or stress relaxation was less prominent when the dental implants were tested. We observed that the periodontal ligament under an axial intrusive load of 300 g in a loading rate 3 g/s could dissipate the energy of 7.35 ± 1.18 × 10^?2 mJ, approximately 50 times that of the dental implants (1.47 ± 1.22 × 10^?3) with statistically significant (p < 0.05).SignificanceWe confirmed natural teeth could achieve greater energy dissipation compared to dental implants, which owe to that natural teeth exhibited fluid and viscoelastic properties.     

高浓度氟对人牙周膜干细胞凋亡的影响

目的: 探讨高浓度氟对人牙周膜干细胞（periodontal ligament stem cells, PDLSCs）凋亡的影响。方法: 从新鲜拔除的恒牙牙周膜中分离获得PDLSCs,分别用不同浓度的氟化钠（0~40 ppm F）处理细胞,CCK-8法检测细胞活力,Annexin V-PI染色及JC-1染色后,流式细胞仪分析、检测氟对PDLSCs细胞凋亡及线粒体膜电位的影响。H-E染色细胞爬片观察氟对细胞形态的影响,免疫荧光染色及共聚焦显微镜观察细胞色素C（cyt-c）,cleaved-caspase -9、-3的表达。RT-PCR检测caspase-9和-3的mRNA蛋白表达水平。Western印迹法分析丝裂原活化蛋白激酶家族（MAPKs）中ERK、JNK、p36总蛋白及磷酸化蛋白的表达水平。采用SPSS 13.0软件包对数据进行统计学分析。结果: 氟处理能抑制PDLSCs活力（CCK-8分析）,诱导细胞凋亡（Annexin V-PI染色）,其效应表现为浓度及时间依赖性。氟浓度≥10 ppm时,能明显诱导细胞线粒体膜电位去极化（JC-1染色）。免疫荧光分析显示,氟暴露促进cyt-c从线粒体释放到胞质,促进cleaved-caspase -9及-3 蛋白表达。RT-PCR同样证明,氟暴露上调caspase-9及-3的mRNA表达水平,呈浓度依赖性。Western印迹分析显示,氟能诱导MARK/ERK磷酸化激活,而JNK、p38磷酸化水平无显著变化,ERK特异性阻断剂U0126预处理能部分挽救PDLSCs的凋亡。结论: 高浓度氟通过内源性线粒体凋亡通路诱导PDLSCs细胞凋亡,MARK/ERK磷酸化部分参与其凋亡机制。     

Periodontal risk assessment in a teaching hospital population in Saudi Arabia’s Eastern Province

ObjectiveWith this cross-sectional study, we aimed to evaluate factors associated with moderate and high risk of periodontal disease (PD) progression in the Saudi population.MethodsWe reviewed 281 patients’ clinical charts from predoctoral periodontal clinics at the dental teaching hospital in the College of Dentistry (COD) at Imam Abdulrahman Bin Faisal University (IAU) in Dammam, Saudi Arabia. After obtaining ethical approval, we determined the Periodontal Risk Assessment (PRA) of the included patients based on the modified criteria developed by Lang and Tonetti (2003). We used logistic regression on stratified data and divided the results into two categories (low-moderate and high risk) to assess the effect modifier for potential risk factors. We used SPSS version 22 for data analysis, and considered a P-value ≤ 0.05 to be statistically significant.ResultsOut of the 281 patients, 104 (37.0%) were male and 177 (63.0%) were female, with a mean age of 39.9 ± 14.0 years; 78.1% were Saudi nationals, 77% were married, and 44.6% were in the age group of 30 to 49. The PRA revealed 86 (30.5%) to represent high risk, 108 (38.3%) denoted moderate risk, and 88 (31.2%) signaled low risk for periodontitis. Logistic regression analysis showed that males were three times more likely to have high PRA (OR = 3.24) and to be married (OR = 2.77), as well as to be active smokers (OR = 8.87). The highest predictive factors of high PRA were 8 or more pockets ≥ 5 mm (OR = 29.0), those with active diabetes mellitus (DM; OR = 10.2), and those with 8 or more missing teeth (OR = 9.15).ConclusionSaudi males who are married and have residual periodontal pockets, are actively diabetic, and with missing teeth are at high risk of PD. Further research is needed with a larger sample size comparing the general population with and without PD.     

The effect of overbite and overjet on clinical parameters of periodontal disease: A case control study

AimTo investigate the association of overjet and overbite with clinical parameters of periodontal disease.Material and methodsThe study was performed in Riyadh, Saudi Arabia, from March 2017 to March 2018. 600 Saudi males aged 20–30 years old were included. Participants were divided into three groups (n: 200) depending on the presence of overjet (OJ) or overbite (OB) and its relationship with periodontal disease. Periodontal parameters were assessed clinically and radiographically. One-way analysis of variance was used to test for any significant differences between groups. Tukey’s post hoc comparison test was used to evaluate correlations among parameters.ResultsOJ exceeding 8 mm was correlated with debris, calculus, and periodontal scores on mandibular anterior teeth, especially on the lingual surfaces.Both OJ and OB groups showed significantly increased PD, compared to that of the control group in measurement at the lingual (P = 0.004, 0.003) and proximal (P = 0.002, 0.002) surfaces of the lower anterior teeth. Finally, the CEJ-AB was statistically significantly higher in the OB group compared to the OJ and control groups (P = 0.091, 0.008).ConclusionThe present study found a correlation between OJ and OB and periodontal disease, as measured using specific parameters. This indicates that periodontal treatment may be insufficient unless the overjet or overbite is corrected.     

利用细胞膜片技术进行牙周重建的研究进展

牙周炎是人类牙齿缺失的最主要病因,危害人类口腔及全身健康。牙周再生的目标是再生牙周组织和重建功能性牙槽骨-牙周膜-牙骨质牙周复合体。随着组织工程学和牙周再生技术的发展,细胞膜片技术的出现为牙周重建提供了新思路。现就细胞膜片技术在细胞膜片构建和不同来源种子细胞两方面的研究进展作一综述。     

Antibacterial action of nitric oxide-releasing hyperbranched polymers against ex vivo dental biofilms

ObjectivesThis study investigates the antibiofilm action of nitric oxide (NO)-releasing hyperbranched polymers against ex vivo multispecies periodontal biofilms.MethodsThe antibiofilm efficacy of NO-releasing hyperbranched polymers was evaluated as a function of NO-release properties, polymer concentrations, and oxygen levels in the exposure media. 16s rRNA sequencing technique was employed to evaluate the impact of NO-releasing hyperbranched polymers on the microbial composition of the biofilms.ResultsThe addition of NO release significantly improved the antibiofilm action of the hyperbranched polymers, with NO-releasing hyperbranched polyamidoamines of largest NO payloads being more effective than hyperbranched polykanamycins. Furthermore, the NO-releasing hyperbranched polymers reduced the biofilm metabolic activity in a dose-dependent manner, killing biofilm-detached bacteria under both aerobic and anaerobic conditions, with greater antimicrobial efficacy observed under aerobic conditions.SignificanceThese results demonstrate for the first time the potential therapeutic utility of NO-releasing hyperbranched polymers for treating multispecies dental biofilms.     

不同正畸力值对哺乳期大鼠正畸牙周组织中HO-1 CC类趋化因子受体1及其配体的影响

目的 探讨不同正畸力值对哺乳期大鼠正畸牙周组织中血红素氧合酶(HO-1)、CC类趋化因子受体1及其配体的影响。方法 选择3月龄Wistar大鼠126只制备哺乳期大鼠模型,成功制备72只,按随机数字表法分为0N组、0.29N组、0.49N组及0.98N组,每组18只。每组依次给予0N、0.29N、0.49N及0.98N的正畸力,比较干预前1天及干预第1、3、7 天后4组大鼠的CC趋化因子受体1(CCR1)及其配体(CCL3、CCL5)mRNA相对表达量、HO-1表达及抗酒石酸酸性磷酸酶(TRAP)破骨细胞染色阳性面积。结果 干预第1、3天,0.29 N组、0.49 N组及0.98 N组CCR1、CCR3和CCL5 mRNA表达水平及破骨细胞染色阳性面积较0N组均明显增加(P<0.05),0.49N组及0.98N组上述指标水平较0.29N组均明显增加(P<0.05),而0.49N组与0.98N组这些指标比较,差异均无统计学意义(P>0.05)。结论 正畸干预可通过促进哺乳期大鼠牙周组织中HO-1、CCR1及其配体的表达发挥作用。     

不同质量浓度釉基质蛋白培养人牙周膜细胞的生物活性

背景：大量研究证实釉基质蛋白可促进成骨细胞和成牙骨质细胞的再生,将其运用于牙周缺损治疗可达到接近生理性的牙周再生。
　　目的：观察不同质量浓度釉基质蛋白对人牙周膜细胞增生、分化和迁移的影响。
　　方法：取第3代人牙周膜细胞,以含不同质量浓度釉基质蛋白(0,12.5,25,50,100,250 mg/L)的无血清DMEM培养基培养。培养24 h后,采用3H-胸腺嘧啶核苷掺入法检测细胞增殖,MTT法检测细胞活性;培养48 h后,检测细胞碱性磷酸酶活性及骨钙素分泌;待细胞融合为单层,去除细胞培养液,以移液管头将单层细胞制备出1 mm宽的细胞切口,持续24 h观察细胞融合情况。
　　结果与结论：当釉基质蛋白质量浓度在0-100 mg/L范围内,随着其质量浓度的升高,细胞增殖、活性、碱性磷酸酶活性、骨钙素分泌均逐渐升高,以100 mg/L升高最明显;当釉基质蛋白质量浓度增至250 mg/L时,细胞增殖、活性、碱性磷酸酶活性、骨钙素分泌均有所下降,但仍高于0 mg/L组。100 mg/L组在初始观察6 h时,创缘周围的细胞开始向中心生长,待培养12 h时,创缘两侧细胞开始融合,培养20 h后创缘两侧细胞融合完全创缘完全关闭完全,创面愈合优于其他质量浓度组。结果表明釉基质蛋白具有促进牙周膜细胞增殖、分化与迁移的能力。