上颌埋伏倒置中切牙3例及文献复习

目的探讨上颌埋伏倒置中切牙病例的临床特点、诊断及治疗方法,以期为临床诊治提供参考。 方法回顾性分析南方医科大学附属深圳妇幼保健院2017—2019年期间收治的3例上颌埋伏倒置中切牙患者的临床表现、影像学表现、治疗方法及治疗效果,并进行相关文献复习。 结果3例上颌埋伏倒置中切牙病例主要表现为单侧上颌中切牙缺失、邻牙倾斜、缺牙间隙变小,锥形束CT（CBCT）检查均发现缺隙处有1颗唇侧倒置埋伏中切牙,其中1例牙根根尖孔已闭合,另外2例牙根发育至根尖1/2 ~ 1/3,现有冠根比≥1∶1,牙根弯曲部分在根尖1/2 ~ 1/3。3例均采用外科开窗联合正畸牵引进行治疗,患牙均顺利进入牙列,无松动,咬合良好,未出现明显牙根吸收。 结论上颌埋伏倒置中切牙的矫治难度较大,应掌握其临床特点及治疗原则,重视矫治时机的选择及矫治方法设计,提高患牙保存率。     

钛支架修复下颌骨缺损时义齿结构的应力分析

目的:对下颌植入钛支架上义齿支持结构的设计进行分析,提出优化方案.方法:建立在相应缺失牙部位预留孔道的下颌植入钛支架有限元模型.在不同加载力大小的情况下,下颌植入钛支架上不同的义齿支持结构设计时,分析其受力状况.结果:基桩颈部及预留孔径周围的钛板上受力后应力最为集中.从整个钛支架看,应力值较低且分布均匀.颈部的应力值随孔道直径的增加而明显降低.基桩的高度与预留孔道的深度比例对应力的变化基本没有影响.结论:前牙有缺失时,选择预留孔径为2mm,周围钛板厚度为0.5mm.后牙有缺失时,选择预留孔径为4mm,周围钛板厚度为0.5mm.预留孔道的深度可在保证螺纹强度的前提下,尽量减小.根据所得的应力分布情况,可对钛板进行支架式的设计.     

基于Simodent数字化接诊系统的"医患沟通教学"在口腔实验教学的应用分析

目的探讨基于Simodent数字化接诊系统的"医患沟通教学"在口腔实验培训及临床实习的教学效果。 方法在中山大学光华口腔医学院2012级五年制本科生的教学中同时开展医患沟通课堂实验和医患沟通追踪实验。课堂实验由学生在使用Simodent虚拟系统前后模拟演示医患沟通,记录每一名学生的主观评分成绩;追踪实验是调用2012级五年制本科生在牙体牙髓病科临床实习期间的平时成绩,与2011级五年制本科生的平时成绩相比较,分析二者之间在总成绩和医患沟通分项成绩的差异。同时,分析中山大学附属口腔医院牙体牙髓病科近三年的医疗纠纷发生率及"医患沟通教学"问卷调查的结果。检验数据正态分布及方差齐性,再以t检验分别对两个年级实习生成绩及其引起的医疗纠纷数据进行统计学检测,以P<0.05为差异具有统计学意义。 结果应用Simodent虚拟系统学习后学生医患沟通得分总体提高,差异具有统计学意义。2012级五年制本科生相对于2011级五年制本科生,牙体牙髓病科临床实习中医患沟通得分分别为（85.7 ± 3.5）和（81.4 ± 4.5）分,差异有统计学意义（t= 2.39,P= 0.03）。2017年较于2016与2015年,牙体牙髓病科因实习生医患沟通引起的医疗纠纷数明显降低。调查问卷结果显示,80.8%的学生认为实习接诊过程中"医患沟通"是第一位的;90.4%的学生认为实验室教学中提前开展"医患沟通教育"是十分必要的。 结论基于Simodent虚拟系统开展的早期"医患沟通教学"可极大的提高学生对医患沟通的重视,从而在临床实习中采取相应的处理措施,进而干预临床医疗纠纷的发生。     

Cytokine-induced endogenous procollagenase stored in the extracellular matrix of soft connective tissue results in a burst of collagen breakdown following its activation

Numerous data strongly suggest the involvement of cytokines and the matrix metalloproteinase collagenase (MMP-1) in the pathogenesis of periodontitis. Recently, we have demonstrated that, upon culturing under the influence of IL- lα+EGF, a large amount of inactive procollagenase (MMP-1) is stored in the extracellular matrix of periosteal tissue. We now show that this endogenous reservoir of proenzyme can be operative after activation with plasmin and is able to induce a rapid and almost complete breakdown of the collagenous extracellular matrix. The level of collagen degradation following activation showed a strong correlation with the amount of proenzyme that was incorporated in the tissue. The highest levei of degradation (70% of the total amount of collagenous proteins) was found with the IL-lα+EGF-treated explants, followed by those treated with IL-1α alone (35%). Explants cultured with EGF or in the absence of cytokines, containing only small amounts of procollagenase, showed little collagen breakdown following plasmin activation (7%). Inhibition of metalloproteinases by EDTA, or blockage of plasmin by PMSF, prevented the degradation in all explants irrespective of the amount of proenzyme present in the tissue. Our findings demonstrate that endogenous proenzyme stored in a native connective tissue matrix can be activated at a later time interval which results in a massive breakdown of the tissue. This study shows a possible pathway of collagenase-induced breakdown without recent de novo synthesis of the enzyme. Such a sequence may be operative in chronic inflammatory diseases, such as periodontitis, where production of procollagenase under the influence of cytokines spans a longer time period, whereas breakdown is often characterized by a cyclic behaviour.     

Effect of age on the periodontium

It is generally known that the degree of periodontal breakdown increases with increasing age. The extent to which aging of periodontal tissues plays a part in this respect poses a question which is yet to be answered. Aging proves to be accompanied by a variety of periodontal changes. The periodontal tissues themselves show evidence of aging, there are indications that the composition of the plaque changes, and the reaction of the periodontium to the presence of plaque probably changes as well. There is as yet no sufficient evidence of a physiological apical migration of the epithelial attachment in human subjects. It seems plausible that periodontal breakdown can occur only in the presence of plaque with consequent inflammation of the periodontium, or as a result of trauma. Whether changes in plaque composition with age exert any influence on the course of periodontal breakdown is uncertain: the data available are not yet sufficient to warrant definite conclusions. The same applies to the influence which a changing reaction of the periodontium to the presence of plaque may have on the course of periodontal breakdown. Research findings do suggest that the degree of periodontal breakdown increases with age, that with increasing age inflammation of the periodontium tends to develop more rapidly and that in the process of aging the periodontium shows a slower rate of wound healing. However, these phenomena are overshadowed by the patients' susceptibility to periodontal disease. This implies that (1) the susceptibility to periodontal disease is more significant for the rate of periodontal destruction than the length of time plaque is present (the age effect) and (2) the greater the susceptibility to periodontal disease, the slower the rate of wound healing and the more rapidly inflammation of the periodontium tends to develop.     

Incorporation of iron in rat incisor enamel

ABSTRACT – The electron microprobe technique was used to study the accumulation of iron in rat incisor ameloblasts as well as the subsequent release of iron from the cells and deposition into the outer layer of the enamel. Starting about 3 mm from the developing end, a gradual accumulation of iron occurred in the ameloblasts. At a stage where the iron content of the cells had reached a maximal level, and the calcium content of the adjacent hard tissue had reached the level of mature enamel, the initial incorporation of iron in the enamel was seen. In the iron incorporation zone the iron content of the enamel increased from less than 0.1 % to about 9 % and the iron content of the ameloblasts was gradually reduced. Concomitant with the increase of iron in the enamel, a decrease of the calcium content was observed in the same region, indicating a withdrawal of calcium from the enamel. Since the incorporation of iron occurs at a stage where the enamel is highly mineralized, the processes involved can hardly be explained as an interaction with the organic matrix. The key to the understanding of these processes should therefore be sought in the adjacent cell layer.     

上颌前牙区种植方案中角度设计的三维有限元分析

目的 采用有限元法观察分析不同种植体植入角度与不同角度基台联合运用时种植体周骨组织的应力分布及种植体的位移情况,为上颌前牙区种植修复方案的设计提供依据。方法利用锥形束CT（cone beam computed tomography, CBCT）建立包含部分上颌骨、种植体（4.3 mm×11.5 mm）、基台及上部修复体（氧化锆全瓷冠）的三维有限元模型,以种植体植入角度A,即种植体长轴与理想长轴之间的夹角 (0°、5°、10°、15°、20°、25°)和基台角度B,即基台长轴与种植体长轴之间的夹角(0°、5°、10°、15°、20°、25°)建立有限元模型。在模型上与牙冠长轴呈130°、舌侧切端下2 mm,模拟大小为178 N的力加载,采用Ansys13.0软件观察种植体周围皮质骨、松质骨的最大主应力值、分布情况和种植体的位移。结果建立了16个符合实际情况的不同种植修复方案的上颌中切牙种植义齿的三维有限元模型;各种修复方案的种植体—骨界面应力分布特点相同,应力集中在种植体颈部及根部;在相同的植入角度下,基台角度越大,种植体周围皮质骨、松质骨的最大主应力峰值及种植体位移峰值均越大。在相同的基台角度下,种植体的植入角度越大,种植体周围皮质骨、松质骨的最大主应力峰值及种植体位移峰值均越大;植入角度或基台角度大于20°时,种植体周围皮质骨、松质骨的最大主应力峰值及种植体位移峰值增加幅度较大。结论种植体的植入角度和基台角度均与种植体周围皮质骨、松质骨的最大主应力峰值及种植体位移峰值呈正相关关系,应尽量减小种植体的植入角度和基台角度,尤其是需要严格掌握种植体的植入角度。从应力、位移考虑,前牙区种植体植入角度和基台角度在20°以内为佳。大于20°时,应力有明显升高趋势,增加种植成功的风险。     

Response and nonresponse bias in oral health surveys

Oral health surveys are undertaken to provide estimates of the dental health and behaviors of populations or population subgroups. However, the integrity of the data from sample surveys may be compromised by one or more sources of sampling and nonsampling error. An important source of nonsampling error is the failure to collect data from some of the individuals comprising the sample. Consequently, the response to a sample survey, and the direction and magnitude of bias induced by nonresponse, need to be taken into account when using estimates derived from sample surveys. Although the response rate to a survey is usually used as an indicator of the quality of the data it provides, nonresponse error is a function of nonresponse and the extent of differences in the characteristics of responders and nonresponders. Nonresponse may be managed in two ways. The first is to reduce nonresponse to a minimum using response-enhancement strategies. The second is the post-survey adjustment of data using weighting or imputation techniques to produce estimates that correct for nonresponse. This paper discusses issues concerning response and nonresponse bias in oral health surveys and provides guidelines on the management and reporting of nonresponse. It describes response-enhancement strategies to reduce noncontacts and refusals, sources of data to facilitate the comparison of responders and nonresponders, methods of assessing the degree of bias induced by nonresponse, techniques for producing adjusted survey estimates, and the assumptions on which these procedures and processes are based.     

影响托槽脱落的相关因素研究(二)

目的：探讨口腔固定矫治技术中影响托槽脱落的相关因素。方法：选取固定矫治技术的口腔正畸患者298例,男111例,女186例,粘贴托槽5258个,记录托槽脱落情况,并对此进行研究。结果：经过统计学分析,托槽的脱落率：①在粘贴托槽后第1个月脱落率最高,而后开始下降,从第5个月起进入相对稳定状态。②上颌与下颌之间,切牙没有差异,上颌尖牙小于下颌尖牙,上颌前磨牙大于下颌前磨牙。但总体上上颌与下颌间没有显著性差异。③左侧与右侧没有显著性差异。④前牙明显小于前磨牙。⑤上颌牙中,第二前磨牙脱落率最高,第一前磨牙次之,切牙再次之,尖牙最低;下颌牙中,第二前磨牙脱落率最高,其余牙相近;所有牙齿中,第二前磨牙最高,尖牙最低。结论：托槽的脱落率与多种因素有关,临床上必须了解和重视这些因素,从而减少托槽的脱落,提高矫治质量。     

The influence of surface roughness on porcelain strength

OBJECTIVES: In order to adjust occlusion, the functional surfaces of porcelain restorations are often ground and mechanical machining is even an essential part of the CAD-CAM process for these restorations. The aim of this study was to investigate the influence of the finishing procedures on the biaxial flexure strength of four commercial porcelains. METHODS: Four commercial porcelains of which two are used for metal-ceramic restorations (Flexo Ceram Dentine and Vita VM K68) and two for veneers and inlays (Duceram LFC Dentine and Cerinate BODY) are used in this study. For each porcelain, sixty discs (? = 22 mm, h = +/- 2.0 mm) were produced using twelve different finishing procedures. Twenty discs were left untreated, twenty discs were milled, using a high-speed diamond disc, and twenty discs were machined in a high-speed grinding/polishing device. Half of the samples were glazed. In each of these six groups, half of the samples were stored for 16 h at 80 degrees C in a 4% acetic acid solution. The biaxial flexure strength was determined using the ball-on-ring method. In each group the roughness of the surface was determined and examined via SEM. RESULTS: With the exception of Flexo Ceram Dentine, a significant correlation was found between the roughness of the surface and the biaxial strength: the smoother the surface, the stronger the sample. The differences in biaxial strength may be attributed to the stress concentration of an applied load due to the roughness of the surface caused by mechanical finishing or chemical action. The fact that the strength of Flexo Ceram Dentine was not affected by the different surface treatments is probably due to the size of the leucite particles, which apparently induce more stress concentration than the surface flaws and the roughness of the surface. SIGNIFICANCE: It was concluded that surface roughness determines the strength of a porcelain material, except where the inner structure of the material causes greater stress concentration than that caused by the combination of surface roughness and surface flaws.     

Effect of streptozotocin-induced diabetes mellitus on alveolar bone deposition in the rat

Effects of diabetes on alveolar bone remodelling were assessed by quantitative histology and a chronological lead-labelling technique. Experimental diabetes was induced by a single dose of 40 mg/kg of streptozotocin. Remodelling of the alveolar wall surrounding the root of mandibular first molar was studied in control rats fed ad libitum, and in diabetic and insulin-treated diabetic rats 24 days after the induction of diabetes. The volumes of bone formation on the mesial side of the alveolar wall were evaluated over a 10-day period by chronological lead-labelling and computer image analysis. For a histometric measure of bone-resorption, the number of osteoclasts along the distal surface of the alveolar wall was counted. The volume of bone formed and the number of osteoclasts were significantly lower in the diabetic rats than in the controls, but insulin treatment of diabetic rats normalised these histomorphometric measures of bone turnover. These results demonstrate that streptozotocin-induced diabetes mellitus reduces the rate of bone turnover in the alveolar wall surrounding the root, which reduction is corrected by treatment with insulin.     

Bruxism: its multiple causes and its effects on dental implants - an updated review

There is a growing interest in bruxism, as evidenced by the rapidly increasing number of papers about this subject during the past 5 years. The aim of the present review was to provide an update of two previous reviews from our department (one about the aetiology of bruxism and the other about the possible role of this movement disorder in the failure of dental implants) and to describe the details of the literature search strategies used, thus enabling the readers to judge the completeness of the review. Most studies that were published about the etiology during the past 5 years corroborate the previously drawn conclusions. Similarly, the update of the review about the possible causal relationship between bruxism and implant failure reveals no new points of view. Thus, there is no reason to assume otherwise than that bruxism is mainly regulated centrally, not peripherally, and that there is still insufficient evidence to support or refute a causal relationship between bruxism and implant failure. This illustrates that there is a vast need for well-designed studies to study both the aetiology of bruxism and its purported relationship with implant failure.     

Effect of bolus size on chewing, swallowing, oral soft tissue and tongue movement

Simultaneous 3D articulograph and ultrasonograph techniques were used to monitor the chewing, swallowing, oral soft tissue and tongue movements of six subjects whilst consuming varying numbers (1, 2 and 4) of a confectionery product. Modifying the number of confectionery units had a variable effect on chewing, swallowing and oral soft tissue movements during the start of the chewing sequence. The distance, range and velocity of chin movement were significantly lower when 1 confectionery unit was consumed compared with 2 and 4 during the middle stage of the chewing sequence. Significant differences in modioli movement were observed during the initial stages of chewing allowing the identification of a working and non-working side, whilst no differences in thyroid cartilage movement were noted over the whole chewing sequence. Increasing the number of confectionery units caused a significant increase in the index of tongue movement during the end of the eating sequence, although the mean index of tongue movement over the total chewing sequence remained constant. Jaw movement correlated with tongue movement, where for all samples, gape decreased linearly as the chewing sequence progressed, reflected in a similar decline in the index of tongue movement. The lack of differences in the index of tongue movement observed over the start and middle of the chewing sequence as a consequence of the number of confectionery units consumed suggested that the change in the physical properties of the bolus had a greater effect on the index of tongue movement than the change in bolus size.     

Risk of suicide amongst dentists: myth or reality?

Objectives : To analyse the scientific weight of the studies about reports of suicide rates in dentistry and decide the possible stressors caused by dental clinical activity, their consequences and their treatment. Discussion : The previous literature treats the high suicide rate associated with the dental profession in different ways: myth for some, important statistical data which needs further research for others. The possible errors repeated in the literature as a result of not introducing certain indispensable variables are analysed and a report given of the main stressors linked to the profession. The results showed that the absence of treatment of the disorders arising from these stressors by qualified professionals along with the lack of preventative measures developed by universities and clinicians to be one of the main problems. Conclusions : In the literature we find systematically a suicide rate among dentists higher than those of other occupations. These studies lack the correct scientific weight and new studies are required that introduce the demographic variables, the psiquiatric morbidity previous to the development of the profession, the opportunity factor, the stressors not related to work and the relative emphasis to these are necessary to for the profession to decrease the risk of suicide.     

离体上颌第二磨牙牙根距根尖4 mm的截面解剖研究

目的　测量上颌第二磨牙牙根距根尖4 mm的截面面积,截面根管中央距牙根外壁的最短距离。方法　选择30个离体上颌第二磨牙,从距根尖4 mm的部位垂直根长轴截断牙根,photoshop6.0测量牙根截面的面积以及根管中央距牙根外壁的最短距离。结果　截面面积：近中颊根是（11.32±2.29）mm2,远中颊根是（7.89±1.55）mm2,腭侧根（10.50±2.82）mm2。近中颊根和腭侧根的截面面积均明显大于远中颊根(P<0.01)。牙根截面根管中央距牙根外壁的最短距离：近中颊根是（1.13±0.15）mm, 远中颊根是（1.17±0.17）mm, 腭侧根（1.41±0.24）mm, 腭侧根的最短距离大于近中颊根和远中颊根（P<0.01）。结论　上颌第二磨牙近中颊根和远中颊根距根尖4 mm的部位较细窄,在进行根管预备或桩道预备时易出现根管侧穿、牙根折。     

Investigation of perfusion in osseous vessels in close vicinity to piezo-electric bone cutting

Cutting bones by piezosurgery leads to failure of perfusion at the site of the osteotomy, the cause of which cannot be identified immediately. Among other things the formation of vascular thrombi by the transmission of oscillations from the piezoelectric unit to the bone may be responsible. We used three output levels of oscillation that were predefined by the system. The outer cortical bone of the calvaria of rats (n=24) was removed horizontally and the intraosseous vessels exposed at the surface of the osteotomy. The blood flow was then examined repeatedly using intravital fluorescence microscopy. To calculate the transmission of oscillations to the bone, the spatial oscillation frequency of each calvarium and the contact pressure during removal of bone in vitro (n=18) were also examined. After removal of the bone there was constant blood flow at all three levels of oscillation output. In no case did an individual vessel seem to be occluded. The excitation oscillation of the bone was established at 2000 Hz in all spatial directions, irrespective of the predefined oscillation output. The application of piezosurgery does not cause the formation of vascular thrombi in the bone. This probably results from the oscillation damping properties of bone.     

Evaluation of Hard and Soft Tissue Dimensions Around Zirconium Oxide Implant–Supported Crowns: A 1‐Year Retrospective Study

Background: This study aims to evaluate the effect of the distance between the alveolar crest of a full‐ceramic implant to the lowest point of the contact area of the crowns on the interdental papilla. Therefore, the authors proposed a new concept of linear measurements for the reproducible and metric evaluation of distances relevant for the assessment of hard and soft tissue changes around dental implants. Methods: A total of 216 sites were examined in 87 patients. In a radiographic and clinical evaluation, four relevant distances were evaluated. In the x‐ray image, the tip of the papilla was marked with a radiodense mixture of tungsten powder and temporary cement. In a clinical photograph, the lowest point of the interdental contact zone of the crowns was visualized by a metallic interdental ligature. Results: Using the proposed measuring methodology, four different papilla‐deficit situations around ceramic implants could be reproducibly distinguished. When the measurement from the bone crest at the implant was ≤5 mm, the papilla was completely present in 100% of cases. When this distance was 10 mm, the papilla was still present in 67% of the cases, without any cosmetically apparent deficit. Conclusions: A close relationship is observed between the distance from the contact point to the bone and the presence of the papilla. Using a combination of radiographically and clinically visible landmarks allows the reproducible measurement of these distances.     

The mechanism of gingiva metallic pigmentations formation

The occurrence of blue-grey areas in the soft tissue represents one of the problems affecting patients whose teeth have been restored using metallic materials. It is generally accepted that it is caused by mechanical penetration of a metallic material into the soft tissue. Several facts indicate that this mechanism is not general. The aim of the study was to determine an alternative mechanism of the origin of pigmentations, based on the corrosion interaction of metallic materials used in prosthodontics with the oral environment. The study was comprised of an analysis of pigment particles, determination of exposure conditions of metallic materials in vivo and laboratory evaluation of corrosion properties of the studied materials. Particles containing silver, sulphur and/or selenium could be seen in ultra-thin sections in the lamina propria gingivae. Comparison of the corrosion laboratory results with the results of in vivo measurements indicated the intensification of corrosion under these conditions. Amalgams and silver-containing alloys used for teeth restorations may release silver under the conditions of the oral cavity. The formation of soluble silver compounds in the sulcular area or in a crevice between the crown and the cast post-and-core reconstruction facilitates their transport to the soft tissue and subsequent deposition.     

Assessment of age-at-death from mandibular molar attrition in medieval Danes

Abstract— Stages of occlusal attrition of the permanent mandibular molars were recorded in 235 Danish medieval skulls, 52 of which were in various states of mixed dentition. For the first and second molar, ages at emergence and ages at occurrence of the earlier stages of attrition were estimated from the mixed dentitions, on the assumptions 1) that the age at eruption of a given number of permanent teeth was similar in medieval and contemporary Danish children, and 2) that the rate of attrition was similar for the first and second molars. Estimation of ages at occurrence of the later attrition stages and of the age at third molar emergence was based on percentage frequency distributions of the stages of attrition using reiterative calculating procedures. Third molar emergence was estimated at the early age of 14 years. It is argued that assessments of age-at death could be made fairly accurately for the age range 5–30 years, and with decreasing accuracy until about 40 years of age.