Parental Knowledge of Pre-Hospital Management of Avulsed Permanent Tooth in Children at Kath

BACKGROUND: Permanent tooth avulsion is one of the severe forms of dental traumatic injuries. The immediate action taken at the site of the accident is crucial to the prognosis of the tooth. Replantation is considered as the treatment of choice. OBJECTIVE: The study was undertaken to assess the knowledge of parents who accompany their children to the pediatric dental clinic, KATH on the pre-hospital management of avulsed permanent tooth in children. METHODS: A researcher administered structured questionnaire was used to collect data on the knowledge of pre-hospital management of avulsed permanent tooth from 83 parents who accompanied their wards to the pediatric dental clinic at KATH. RESULTS: A total of 83 parents were involved in the study. 30 (36%) were males while 53 (64%) were females. The majority of the parents (57%) were either university trained or had attended college of education. Only 32 parents (39%) were aware of the possibility of replantation. Majority of the parents chose non-physiologic media as the transport media of choice and only 10% would attempt self-replantation before seeking professional help. 76 parents (92%) had no previous education on pre-hospital management of avulsed tooth. CONCLUSION: The results obtained from this study indicate that parental knowledge on pre-hospital management of avulsed permanent tooth is low hence the need for massive public educational campaigns.

Three-Dimensional Conjugate Tooth Surface Design and Contact Analysis of Harmonic Drive with Double-Circular-Arc Tooth Profle

A three-dimensional conjugate tooth surface design method for Harmonic Drive with a double-circular-arc tooth profle is proposed. The radial deformation function of the fexspline (FS), obtained through Finite Element (FE) analysis, is incorporated into the kinematics model. By analyzing the FS tooth enveloping process, the optimization of the overlapping conjugate tooth profle is achieved. By utilizing the hobbing process, the three-dimensional machinable tooth surface of FS can be acquired. Utilizing the coning deformation of the FS, simulations are conducted to analyze the multi-section assembly and meshing motion of the machinable tooth surface. The FE method is utilized to analyze and compare the loaded contact characteristics. Results demonstrate that the proposed design method can achieve an internal gear pair consisting of a circular spline with a spur gear tooth surface and the FS with a machinable tooth surface. With the rated torque, approximately 24% of the FS teeth are engaged in meshing, and more than 4/5 of the tooth surface in the axial direction carries the load. The contact patterns, maximum contact pressure, and transmission error of the machinable tooth surface are 227.2%, 40.67%, and 71.24% of those on the spur gear tooth surface, respectively. It clearly demonstrates exceptional transmission performance.

A Rare Case: Multiple Mandibular Arteriovenous Malformation with High Output: May a Tooth Extraction Alone Turn to a Catastrophic Condition?

Background: Arteriovenous malformations (AVM) in mandible and neck are potentially life-threatening conditions because of possible massive hemorrhage. They are often first diagnosed by dentists as bleeding. In this case, we report how a tooth extraction turned to a catastrophic condition in a patient with multiple AVMs in the mandibular, submandibular and hyoid region. Case: A 19-year-old male patient diagnosed with AVMs in the mandibular and submandibular regions was admitted to our hospital with the complaint of leaky hemorrhage around the lower left 3rd molar tooth. Tooth extraction was planned after embolization procedure. The patient was intubated uneventfully using video laryngoscope. However, an acute bleeding of more than 1600 ml occurred in one minute just after the mouth opener was inserted. The patient was transferred to the Interventional Radiology and other branches of the high-flow AVM were embolized. The patient was taken back to the operating room and the tooth was extracted uneventfully. Conclusion: In AVM cases, trauma should be minimized during induction of general anesthesia and intubation should be performed gently with fiberoptic bronchoscopy or video laryngoscopy. We conclude that a multidisciplinary approach as applied to our patient would be valuable in such cases.

Comparative Study of the Rock-breaking Mechanism of a Disc Cutter and Wedge Tooth Cutter by Discrete Element Modelling

The operation of a shield tunnel boring machine(TBM)in a high-strength hard rock stratum results in significant cutter damage,adversely affecting the thrust and torque of the cutter head.Therefore,it is very important to carry out the research on the stress characteristics and optimize the cutter parameters of cutters break high-strength hard rock.In this paper,the rock-breaking performance of cutters in an andesite stratum in the tunnel of Qingdao Metro Line No.8 was investigated using the discrete element method and theoretical analysis.The rock-breaking processes of a disc cutter and wedge tooth cutter were simulated by software particle flow code PFC^(3D),and the rock-breaking degree,stress of the cutter,and rock-breaking specific energy were analyzed.The rock damage caused by the cutter in a specific section was divided into three stages:the advanced influence,crushing,and stabilizing stages.The rock-breaking degree and the tangential and normal forces of the wedge tooth cutter are larger than that of the disc cutter under the same conditions.The disc cutter(wedge tooth cutter)has the highest rock-breaking efficiency at a cutter spacing of 100 mm(110 mm)and a penetration depth of 8 mm(10 mm),and the rock-breaking specific energy is 11.48 MJ/m^(3)(12.05 MJ/m^(3)).Therefore,two types of cutters with different penetration depths or cutter spacing should be considered.The number of teeth of wedge tooth cutters can be increased in hard strata to improve the rock-breaking efficiency of the shield.The research results provide a reference for shield cutterhead selection and cutter layout in similar projects.

Single cell RNA sequencing reveals mesenchymal heterogeneity and critical functions of Cd271 in tooth development

BACKGROUND Accumulating evidence suggests that the maxillary process,to which cranial crest cells migrate,is essential to tooth development.Emerging studies indicate that Cd271 plays an essential role in odontogenesis.However,the underlying mechanisms have yet to be elucidated.AIM To establish the functionally heterogeneous population in the maxillary process,elucidate the effects of Cd271 deficiency on gene expression differences.METHODS p75NTR knockout(Cd271-/-)mice(from American Jackson laboratory)were used to collect the maxillofacial process tissue of p75NTR knockout mice,and the wildtype maxillofacial process of the same pregnant mouse wild was used as control.After single cell suspension,the cDNA was prepared by loading the single cell suspension into the 10x Genomics Chromium system to be sequenced by NovaSeq6000 sequencing system.Finally,the sequencing data in Fastq format were obtained.The FastQC software is used to evaluate the quality of data and CellRanger analyzed the data.The gene expression matrix is read by R software,and Seurat is used to control and standardize the data,reduce the dimension and cluster.We search for marker genes for subgroup annotation by consulting literature and database;explore the effect of p75NTR knockout on mesenchymal stem cells(MSCs)gene expression and cell proportion by cell subgrouping,differential gene analysis,enrichment analysis and protein-protein interaction network analysis;understand the interaction between MSCs cells and the differentiation trajectory and gene change characteristics of p75NTR knockout MSCs by cell communication analysis and pseudo-time analysis.Last we verified the findings single cell sequencing in vitro.RESULTS We identified 21 cell clusters,and we re-clustered these into three subclusters.Importantly,we revealed the cell–cell communication networks between clusters.We clarified that Cd271 was significantly associated with the regulation of mineralization.CONCLUSION This study provides comprehensive mechanistic insights into the maxillary-process-derived MSCs and demonstrates that Cd271 is significantly associated with the odontogenesis in mesenchymal populations.

Tooth arrangement design of retractable DTH hammer bit used for drilling while casing

Down-the-hole(DTH)hammer with casing while drilling(CWD)is a technology that has been proven to be able to alleviate many of the problems faced by complex formations.However,the drill bit is suffered from rapid wear,low drilling efficiency,and high energy consumption due to the unreasonable tooth arrangement and impact energy selection in drilling process,which affect the application effect of this technology.ABAQUS software was used for numerical simulation of rock breaking behavior under impact load with the single,three,and five teeth arrangement drill bit respectively,to improve the application effect and solve the aforementioned technical problems.Based on the calculated parameters of tooth arrangement,we designed a novel drill bit for hard rocks and provided a theoretical basis for the tooth arrangement of largediameter drill bits.

牙周系统治疗联合意向性牙再植术治疗重度牙周炎1例

本文报告1例牙周系统治疗联合意向性牙再植术治疗重度牙周炎的临床病例。患者为65岁女性,在牙周系统治疗后,对保留无望的患牙32行意向性牙再植术,随访2年保住了天然牙,取得了良好的治疗效果。

自驱修孔钻头动力参数及钻齿结构研究

自驱修孔钻头是修复失效长钻孔的有效技术手段,为进一步提高修孔速度和瓦斯抽采效果,本文基于射流反冲理论,分析了射流反冲力与喷嘴参数的关系,构建了自驱修孔钻头旋转力学理论模型。采用LS-DYNA开展不同结构钻齿破煤过程,分析了不同钻进压力和扭矩作用下钻齿对煤体破坏形式和钻齿破煤体积变化规律,并开展了破煤实验验证数值模拟结果。形成了自驱修孔钻头参数确定方法,设计了自驱修孔钻头,并在郑煤集团超化煤矿22煤柱面底抽巷进行了工程实验。研究结果表明:(1)喷嘴张角α和偏心角β是决定钻进压力和扭矩分配的关键参数,通过调控张角和偏心角可实现钻进压力和扭矩的最优匹配。(2)相同钻进参数条件下,钻齿结构对破煤体积影响较大,阶梯钻齿破煤效果最优。在钻进压力为120N、扭矩0.6N·m时,阶梯型钻齿结构的修孔钻头能够实现钻进压力和扭矩最优匹配。(3)确定了最优修孔钻头结构参数为:钻头外径28 mm;后置喷嘴张角20°,偏心角90°;前置喷嘴张角90°,偏心角0°。(4)工程应用结果表明:瓦斯抽采纯量提高了1.96倍,瓦斯抽采体积分数提高了3.98倍,修孔速度提高了1.2倍。通过改进钻头动力参数及优化钻齿结构,设计的自驱修孔钻头在工程实践中达到了提高修孔速度和瓦斯抽采效果的目的。

横向冲击载荷下齿形双螺母防松性能

针对螺栓连接结构在舰船爆炸冲击中容易发生松动的现象,设计了一种齿形双螺母的防松结构。利用局部滑移理论分析齿形双螺母的防松原理,采用有限元仿真法,通过预紧力和微滑移的变化量对其防松性能进行分析,并研究了齿形双螺母防松性能的影响因素及其影响规律。研究结果表明:横向冲击载荷下,齿形双螺母预紧力下降慢,微滑移变化小,具有较好的防松性能;当楔形角与螺纹升角相同时,防松效果最差;楔形角越大,齿形数量越多,齿形双螺母的防松效果越好。

倾斜种植在上颌后牙区的应用现状

上颌后牙区缺牙患者通常由于牙槽骨病理性吸收萎缩、增龄性骨丧失、上颌窦气化等原因导致牙槽骨高度降低,在对这类患者进行种植修复时,因骨量的不足,导致种植修复方案的设计与实施难度增大。为了解决此类问题,有学者提出倾斜种植的治疗方案来满足骨量不足患者的种植修复需求。文章从应用类型、优势、生物力学等方面出发,对倾斜种植进行阐述。

牙齿漂白技术的临床应用策略

牙齿漂白技术是微创治疗牙齿着色的有效方法之一。漂白技术实施简单,但是临床应用中颇具挑战性。术前进行充分的医患沟通和评估,根据病因和难度制定个性化方案,对于治疗中可能出现的问题进行有计划地防控,是治疗取得成功的关键。本文结合文献回顾和笔者的临床体会,对活髓牙漂白技术的临床策略进行探讨,以期为着色牙的漂白治疗提供参考。

半轴齿轮的热—冷复合锻造中冷锻充不满缺陷的成形数字仿真及工艺研究

针对半轴齿轮热—冷复合锻造中冷锻整形时出现的充不满缺陷,利用UG、Geomagic-Design和Deform-3D等软件,对冷锻毛坯(热锻成形的工件)进行了重新设计和冷锻整形工序仿真模拟,全面考查齿厚、齿高参数变化对产品质量的影响。从模拟结果来看,当冷锻整形开始合模时,毛坯初始位置齿顶和冷锻模具型腔之间的间隙越大(齿厚增加越大/齿高减小越大)时,终锻时所需的锻压力越大,在产品小端齿顶处越易形成折叠缺陷。毛坯初始位置齿顶与型腔贴合(齿厚增加量为零或为负),则不易产生折叠缺陷,齿侧和冷锻模具型腔之间的间隙越大(实际齿厚越小),所需锻压力越大。经过实际生产验证,在相应的齿轮参数条件下,冷锻毛坯比冷锻模具型腔轮廓的齿高增加0.1 mm、齿厚不变时,冷锻整形后齿槽和齿高全部压满,成型质量好,产品废品率达到预期要求。

正畸过程中牙齿三维方向变化的模型测量方法研究进展

牙齿三维方向上移动效率的评价是评估正畸疗效的重要内容之一。随着科学技术的发展,矫治器及矫正技术不断进步,用于研究正畸矫治牙齿三维方向移动效率的方法和工具也在不断更新。本文以牙齿移动测量方式发展为主线,介绍了由手工石膏模型测量转向利用计算机软件对数字化模型的测量过程和依据,并对三维数字化模型数据获取方式、储存文件格式及可选择的分析处理软件进行了说明,以及回顾了前人对三维数字化模型进行三维重叠的部分研究,总结了目前对光学扫描及X线扫描得到的两种三维模型数据常用的配准方法和配准区域的选择。

内凹刀盘加工的直齿锥齿轮齿面接触分析

为了在国产数控弧齿锥齿轮机床上采用内凹刀盘加工直齿锥齿轮,对使用内凹刀盘加工直齿锥齿轮的原理和齿面接触分析(Tooth Contact Analysis,TCA)方法进行了研究。基于内凹刀盘的加工原理和结构特点,建立了内凹刀盘加工的直齿锥齿轮的齿面数学模型,给出了相应的齿面接触分析方法;编写齿面接触分析程序,计算得到了齿轮副的接触斑点和传动误差曲线;通过实际的切齿加工和接触斑点检验,验证了齿面数学模型以及TCA方法的正确性。研究为锥齿轮加工参数及刀具参数的确定与啮合质量控制提供了理论依据。

冷挤压内螺纹力学性能试验研究

螺纹连接中螺母与螺栓接触型面复杂,对于螺纹牙上的应力状态分析困难,且不同加工方式对内螺纹的失效载荷影响较大。这里建立螺纹连接的简化力学模型和有限元模型,分析了内螺纹牙表面应力分布,重点对冷挤压内螺纹的力学性能进行了试验分析,并与切削内螺纹的力学性能进行对比。结果表明:内螺纹在负载状态下,应力集中和塑性变形主要集中在螺母与螺栓的牙根和第(1~3)个螺纹的牙顶处,应力大小和变形量沿载荷反方向逐渐递减;挤压内螺纹的连接强度明显高于切削内螺纹,失效载荷比切削内螺纹提升了(18~58.6)%不等;随着内螺纹牙高率从65%增加至80%,挤压内螺纹和切削内螺纹的力学性能均增加,切削内螺纹的失效载荷提升了(28.86~55.45)%,挤压内螺纹的失效载荷提升了(22.89~41.93)%。

氧化锆全冠的临床应用原则及新进展

氧化锆全冠在口腔修复领域得到了广泛的应用。传统氧化锆机械性能佳,但半透性较差,透明氧化锆的出现大大提高了氧化锆的美学性能。但在临床中,应对影响全锆冠美学修复效果的因素进行综合考量,选择最合适的全锆冠修复体,同时临床医师需要根据患者实际情况合理设计牙体预备量以及预备方式。在氧化锆的临床粘接过程中,要对基牙和修复体做好表面处理,选择合适的粘接剂以获得良好的粘接强度和美观性。

基于零膨胀负二项模型的江苏省青少年恒牙龋齿影响因素分析

目的了解江苏省青少年恒牙龋齿现状及影响因素。方法依托2019—2020学年江苏省学生常见病和健康影响因素监测项目,纳入其中12~17岁青少年共22755人进行问卷调查和体格检查。使用负二项回归计算恒牙龋齿率,采用零膨胀负二项回归模型分析青少年恒牙龋齿影响因素。结果江苏省12~17岁青少年恒牙龋齿率为43.04%。女生、16~17岁组、非肥胖、高中生、苏中地区、母亲文化程度为小学及以下、每周中高强度运动≤2 d、每天刷牙1次、每天甜食和油炸食品摄入≥1次的学生恒牙龋齿率较高,差异均有统计学意义(P值均<0.05)。基于零膨胀负二项回归模型,结果显示,16~17岁年龄组(β=0.206)、女性(β=0.195)、母亲受教育程度大学及以上(β=0.171)、过去7 d每天吃甜食(β=0.126)对青少年恒牙龋齿数有正向影响,苏中地区(β=-0.227)、苏北地区(β=-0.079)对恒牙龋齿数有负向影响(P值均<0.05);对恒牙龋齿发生风险分析结果显示,16~17岁年龄组(β=-0.103)、女性(β=-0.379)、苏中(β=-0.536)和苏北地区(β=-0.304)、过去7 d每天吃甜食(β=-0.287)对恒牙龋齿出现零膨胀现象有负向影响,肥胖(β=0.136)、母亲文化程度为中学(β=0.221)和大学及以上(β=0.248)对出现龋齿零膨胀现象有正向影响(P值均<0.05)。结论江苏省12~17岁青少年恒牙龋齿患病率较高,应重视早期筛查工作,尽早采取针对性干预措施,降低青少年龋齿患病风险。

非圆齿轮电火花线切割加工工艺参数对齿廓误差的影响

线切割加工非圆齿轮时电参数是影响齿廓误差的关键因素之一.设计正交试验,分别采用非圆齿轮齿根、齿廓中部和齿顶的最大齿廓误差对线切割加工非圆齿轮进行分析.通过方差分析方法和主效应分析法,研究线切割加工电参数峰值电流、脉冲宽度、脉冲间隔和跟踪对非圆齿轮齿根、齿廓中部和齿顶的齿廓误差影响规律.同时,对齿廓误差、加工时长和工艺参数进行回归分析,并建立回归模型,基于灰狼优化算法对回归模型进行多目标优化求解.通过研究结果可以得出线切割加工非圆齿轮齿廓不同部位的最优参数组合,可为实际加工提供参考.

难变形金属小模数齿形件电流辅助分形旋压成形方法研究

针对难变形金属小模数齿形件采用传统滚齿及插齿方法制备时,存在材料利用率低、强韧性不足等问题,提出采用分形旋压方法实现此类小模数齿形件的完整近净成形。以模数为0.3的30CrMnSiA合金结构钢小模数齿形件为研究对象,设计制作了难变形金属小模数齿形件分形旋压成形工艺装备,并基于旋压成形试验进给研究了渐进式进给、主轴正反转进给和间歇式进给3种不同成形方式及有/无电流辅助条件对难变形金属小模数齿形件分形旋压的影响规律。结果表明:采用渐进式进给成形方式时,旋压成形缺陷最少,但所获得的轮齿饱和度仅为70.2%;采用正反转式成形方式时,成齿区易出现预成形齿顶与旋轮轮齿啮合错位而导致被两次分形的缺陷;采用间歇式进给式成形方式时,成齿区齿顶部分出现大量毛刺;采用渐进式成形方式,相同试验条件下,通入脉冲电流后,材料塑性变形能力显著提升,轮齿饱和度提高到95.7%。采用电流辅助分形旋压成形获得的小模数齿形件齿廓偏差为0.029 mm、齿距偏差为0.015 mm。

Periostin表达在乳恒牙替换中的临床意义

目的 探讨Periostin在替牙期对骨改建和自噬的影响,研究Periostin在乳恒牙替换过程中调节骨代谢平衡的作用机制。方法 收集笔者所在医院因乳牙根尖周病及多生牙拔除的牙根周围粘连牙槽骨,体外培养成骨细胞,分为实验组和对照组各15例,实验组培养基中加Periostin,原位杂交法检测标本中Periostin、骨代谢基因、自噬基因的m RNA水平。蛋白质印记法检测成骨细胞中骨代谢蛋白,自噬蛋白表达。结果 原位杂交结果显示,实验组Periostin表达低于对照组(P<0.05),核因子κB受体活化因子配体(receptor activator of nuclear factor-κb ligand,RANKL)、LC3、BECN1表达及RANKL/骨保护素(osteoprotegerin,OPG)值高于对照组(均P<0.05),OPG表达差异无统计学意义(P>0.05);蛋白质印迹法显示实验组RANKL、RANKL/OPG、LC3Ⅱ、Beclin-1、LC3Ⅱ/LC3Ⅰ与对照组比较水平低(均P<0.05),OPG、LC3Ⅰ较对照组差异无统计学意义(均P>0.05)。结论 Periostin通过降低RANKL表达及改善过强自噬状态,从而减少炎症所致的骨吸收。