A method to determine the loss of substance of dental restorations

A method is described for quantitative in vivo wear measurements on Class I and II composite restorations. Class I gold inlays were made in an acrylic premolar and molar. Over the occlusal parts of the teeth cast silver caps were made after releasing the surface of the inlay with tinfoil. Wear on the restorations was simulated by grinding away some gold from the inlay. Silicon impressions of the teeth were made with the caps both before and after this simulation. The volume and the average thickness of the removed gold was measured from the weight of the enclosed impression material in the cap before and after the wear simulations, the density of the tinfoil and the impression material as well as thickness and the weight of the tinfoil-release. Values expected for the volume and the average thickness of the removed gold were calculated from the weight of the restored acrylic teeth before and after the wear simulation, the weight, the density and the thickness of the tinfoil and the density of the gold used for the inlays. Measured and expected values are linearly correlated (r = 0.97). An average wear thickness of the occlusal surface of a particular tooth of at least 30 micron can be detected. Because of its simplicity, inexpensiveness and accuracy the wear measurement method is highly productive and suitable for large scale and long-term clinical research on the wear behaviour of posterior composites.     

髁突运动异常的曲面断层观察

为研究髁突的运动度，用曲面断层张、闭口片对１４４例颞下颌关节紊乱综合征（ｔｅｍｐｏｒｏ－ｍａｎｄｉｂｕｌａｒｊｏｉｎｔｄｉｓｔｕｒｂａｎｃｅｓｙｎｄｒｏｍｅ，ＴＭＪＤＳ）患者的髁突与关节结节之间的位置关系进行分析。根据髁突与关节结节的关系及双侧运动是否一致将髁突的运动度分为６型，并对各型的性别与年龄组成、张口度与张口型、弹响与疼痛情况、病程及骨质改变进行了分析。结果说明下颌过大运动所造成的关节结构及下颌肌肉、韧带的急性损伤是产生ＴＭＪＤＳ的主要原因之一。     

External and internal macromorphology in 3D-reconstructed maxillary molars using computerized X-ray microtomography

AIM: The aim of this study was to perform a qualitative analysis of the relationship between the external and internal macromorphology of the root complex and to use fractal dimension analysis to determine the correlation between the shape of the outer surface of the root and the shape of the root canal. METHODOLOGY: On the basis of X-ray computed transaxial microtomography, a qualitative and quantitative analysis of the external and internal macromorphology of the root complex in permanent maxillary molars was performed using well-defined macromorphological variables and fractal dimension analysis. Five maxillary molars were placed between a microfocus X-ray tube with a focal spot size of 0.07 mm, a Thomson-SCF image intensifier, and a CCD camera compromising a detector for the tomograph. Between 100 and 240 tomographic 2D slices were made of each tooth. Assembling slices for 3D volume was carried out with subsequent median noise filtering. Segmentation into enamel, dentine and pulp space was achieved through thresholding followed by morphological filtering. Surface representations were then constructed. A useful visualization of the tooth was created by making the dental hard tissues transparent and the pulp chamber and root-canal system opaque. On this basis it became possible to assess the relationship between the external and internal macromorphology of the crown and root complex. RESULTS: There was strong agreement between the number, position and cross-section of the root canals and the number, position and degree of manifestation of the root complex macrostructures. Data from a fractal dimension analysis also showed a high correlation between the shape of the root canals and the corresponding roots. CONCLUSIONS: It is suggested that these types of 3D volumes constitute a platform for preclinical training in fundamental endodontic procedures.     

髁突的测量分析与骨折发生的关系

目的 通过对上海地区153名成年人下颌骨髁突内外径、前后径、及,髁突颈部最窄径的测量,探讨其与骨折发生的关系。方法 取上海地区成年人下颌骨:男74例,女79例,以髁突直径为内外径,髁突最厚处为髁突前后径,并测出髁突颈部的最窄径。同时收集上海市第九人民医院1997年1月至2003年6月下颌骨骨折病历273份,分析其不同部位骨折的发病率。结果 髁突内外径男女分别为:19.04mm、18.85mm;髁突前后径男女分别为9.03mm、8.59mm;髁突颈部最窄径男女分别为:6.98mm、5.94mm。下颌骨髁突骨折的发生率在下颌骨骨折中:男性占23.33％,女性占27.27％,其中合并颅脑损伤的为25例。结论 将所测得的髁突内外径、前后径数值分别和髁突颈部最窄径数值在男性与女性间进行统计学分析,经t检验,P<0.01。因此,无论男性或女性髁突颈部最窄径和髁突内外径及髁突前后径均有明显差异。由此可知髁突颈部为下颌骨最细处,无论遭受直接或间接暴力的打击,该处均可引起骨折。同时通过对临床下颌骨骨折发病率的分析发现:髁突是临床下颌骨骨折的好发部位之一。     

EDTA凝胶和氯亚明对人牙周膜细胞增殖和碱性磷酸酶活性的影响

目的：探讨EDTA凝胶（EDTA gel）和氯亚明（chloramine-T）对人牙周膜细胞（periodontal ligament cell,PDLC）增殖和碱性磷酸酶（alkaline phosphatase,ALP）活性的影响。方法：将5种不同浓度的EDTA凝胶和氯亚明溶液分别作用于体外培养的PDLC。MTT法观察PDLC的增殖情况,酶动力学方法检测PDLC的碱性磷酸酶活性。结果：浓度为0.005%、0.0025%和0.00125%的EDTA凝胶溶液及浓度为0.0025%和0.00125%的氯亚明对PDLC的增殖和ALP活性无抑制作用。浓度为0.02%和0.01%的EDTA凝胶溶液及浓度为0.02%、0.01%和0.005%的氯亚明对PDLC的增殖和ALP活性有抑制作用（P〈0.05）,抑制作用随药物浓度和作用时间的增加而增加。结论：EDTA凝胶和氯亚明对PDLC的增殖和碱性磷酸酶活性具有一定的抑制作用。     

口腔癌DNA含量与临床化疗的研究

目的：通过检测和口腔癌DNA含量及细胞周期各项指标，探讨其与化学治疗的关系。方法：用流式细胞术检测了23例口腔癌患者化疗前后共46例标本的DNA含量及细胞周期各项指标，并与化疗结果进行比较分析。结果：①未经化疗的口腔癌D1值为1．94，异倍体检出率为82．65，与病理分级及肿瘤大小无关。②化疗后口腔癌D1及异倍体检出率较化疗前有显著降低。③DI及异倍体检出率与化疗疗效无明显相关性。结论口腔癌DI及异倍体检出率显不能预测疗效，但可通过细胞周期的分析指标化疗，化疗可显著降低DI及异倍体检出率。     

Report of experience during 1-year at the Gondar College of Medical Sciences in Ethiopia. 2. Frequency of caries and periodontitis in Ethiopia

On the basis of a clinical epidemiological study of 312 patients are made biostatistical investigations about prevalence and Severity of dental caries and marginal periodontitis. The situation of oral hygiene is evaluated by means of the PI of L?e and Silness and the OHI-S of Greene and Vermillion. The DMF/T-Index is used for the evaluation of the set of teeth and the GI of L?e and Silness like the PDI of Ramfjord for the evaluation of the periodontal state. It is shown that caries and marginal periodontitis are more seldom and of less severity in comparison with the situation in the population of industrialized countries. Causitive seems to be possible besides special habits the smaller consumption of sugar. With the increasing socio-economic standard a changing of the situation in the direction of industrialized countries is visible.     

Use of an ultrahigh-speed laser scanner for constructing three-dimensional shapes of dentition and occlusion

STATEMENT OF PROBLEM: Acquisition of the 3-dimensional shape of dental casts is useful for quantitative evaluation of the diagnosis and treatment of occlusion. PURPOSE: This study demonstrated the acquisition of data through the use of an ultrahigh-speed laser scanner and an originally developed goniometer, the use of these tools to measure the entire 3-dimensional shape of the dental cast from multiple directions, and the connection of the data measurements to reconstruct the cast's occlusion with the use of a computer. MATERIAL AND METHODS: A commercially available apparatus that emits a line laser and completes 1 scan in only 0.6 seconds was used. To compensate for the unmeasured region, the cast was measured from 4 directions on the original goniometer, and the connection of data to obtain the entire image was carried out. Further, the reconstruction of the occlusion between the upper and lower casts was attempted by transferring the upper cast data to the lower cast. RESULTS: By the data connection, the entire shape of the upper and lower casts was constructed, and the characteristic structure was reproduced. The data connections were satisfactory for the flat surfaces but less accurate for the inclined surfaces. Reconstruction of the occlusion between the upper and lower casts was accomplished. It was then possible to visualize the occlusion from arbitrary directions and sections with computer graphics. CONCLUSION: The construction of the entire 3-dimensional shape of a dental cast and the reconstruction of the occlusion were accomplished using an ultrahigh-speed measurement system and original goniometer. These results will be useful for clinical applications such as computerized diagnoses and treatment of occlusion, and for the replacement of the stone casts in the dental office by computerized data.     

The effect of salivary gland extracts on the histology of lymphoid organs and salivary glands in mice

Ligation of the excretory duct and artery of the submandibular gland (SMG) of male Swiss mice led to atrophy of the gland within 7 days. The effects of a crude extract of the SMG and sublingual gland (SLG) on the histology of spleen, thymus, lymph nodes, SMG and SLG were studied. Four groups of mice were used. Three groups were injected intraperitoneally for 7 consecutive days with SLG extract (Group I), SMG extract (Group II), saline (Group III) and Group IV was not treated. On day 7, the animals were killed and the spleen, thymus, salivary glands with the regional lymph nodes were weighed and fixed. Histological studies and histometric measurements were made of the thymus, the spleen and of the acinar and tubular areas of the SMG. The volumes of the SMG and SLG were also estimated. In the SMG and SLG, infiltration of mononuclear cells occurred in Groups I and II. At the same time there was a reduction of the tubular part of the SMG and a decrease in the volume of the SMG and SLG, compared with Groups III and IV. An immune response was detected in the spleen and regional lymph nodes and the number of lymphoblasts had increased in the cortex of the thymus. Injections of SMG and SLG extracts induced both an antibody and a cell-mediated immune response.     

The use of virtual planning and navigation in the treatment of temporomandibular joint ankylosis

Temporomandibular joint ankylosis is not common in our community but can occur as a result of severe facial trauma or significant connective tissue disorders such as rheumatoid arthritis, osteoarthritis and psoriatic arthritis, and unfortunately as a result of iatrogenic causes. Ankylosis surgery is aimed at gap arthroplasty and mobilization of the joints. However, the removal of the bony ankylosis and the production of a gap between the ramus of the mandible and the base of the skull is often difficult because of the size of the ankylosis and the anatomy on the inner aspect of the mandible. As a result of this, the author has found that surgical navigation has been useful with the removal of the ankylosis, both on the medial side of the mandible and the cranial base. Once the ankylosis has been freed and the mandible mobilized, the gap arthroplasty needs to be maintained or the release of the ankylosis will fail and the joints will re‐ankylose. It is important to maintain the space produced by the arthroplasty but this is difficult when autogenous materials such as temporalis muscle, dermis fat and other like materials are used. The gap ultimately closes under the influence of the masseter and medial pterygoid muscles and the ankylosis may return. This case report presents three representative patients in whom ankylosis has been released and the gap reconstructed with a total alloplastic joint replacement. All patients have had their ankylosis removed with the aid of a navigation system and all patients have been reconstructed with bilateral Biomet prosthesis. One patient has had their implant selected using virtual planning and the production of templates to help with placement of the stock implant.     

蒙古族正常中小学生硬组织颅面结构的研究

为建立蒙古族硬组织Ｘ线头影测量正常值，揭示蒙古族颅面结构生长发育的规律及特征，以１８０例蒙古族中小学生为对象、运用计算机辅助Ｘ线头影测量系统，对其颅面、牙２３项硬组织指标进行了测量．首次建立了蒙古族硬组织颅面结构的Ｘ线头影正常值标准．研究发现，蒙古族颅面结构的深度及高度男性大于女性，骨侧貌面形男性较女性为凸，颅面深度及高度随生长发育增大，侧貌凸度则逐渐减小．与汉族相比，蒙古族具有颅面深度及高度较大、下切牙直立、男性侧貌较凸的特征．上述结果为本民族错畸形的诊断、治疗及审美标准的建立提供了客观依据     

Mixed dentition space analysis in a Jordanian population: comparison of two methods

AIMS: To test the reliability of the Moyers charts and the Tanaka and Johnston equations in Jordanians and to derive coefficients of correlation between the combined mesiodistal widths of the four permanent mandibular incisors and the combined widths of the canine and premolars of the maxillary and mandibular quadrants. METHODS: The dental models of the dentition of 130 male and 96 female Jordanian subjects (age range is 14-16 years) with complete permanent dentition were randomly selected. The mesiodistal width of the four permanent mandibular incisors, maxillary and mandibular canines, and premolar teeth were measured using a vernier gauge caliper to the nearest 0.1 mm. The actual teeth measurements were then compared with the predicted values derived from the Tanaka and Johnston equations and Moyers probability tables. Correlation and linear regression analyses were performed between the predicted and actual tooth size for Jordanian children and standard regression equations were developed. RESULTS: Except for the maxillary arch in male subjects, Tanaka and Johnston regression equations underestimated the mesiodistal widths of permanent canines and premolars. On the other hand, there were no statistically significant differences between actual mesiodistal widths of canines and premolars and the predicted widths from Moyers charts at the 65% and 75% level for the lower and upper arches in male subjects and at the 85% level for the upper and lower arches in female subjects. For the newly developed regression equations, the correlation coefficients between the sum of the mandibular four incisors and the sum of the canine and premolars were 0.60 (for lower) and 0.51 (for upper) in male subjects and 0.59 and 0.64, respectively, in female subjects. CONCLUSIONS: (1) Tanaka and Johnston prediction method was not accurate when applied to a Jordanian population. (2) Moyers method for prediction can be used for Jordanian children at different probability levels for male and female subjects.     

下颌骨髁突骨软骨瘤的影像学诊断及疗效评价

目的：探讨下颌骨髁突骨软骨瘤的诊治经验,恢复髁突正常的解剖形态和生理功能。方法：对1998—2008年收治的14例下颌骨髁突骨软骨瘤患者的诊治进行评价,指标包括影像学检查确诊率（X线、3D-CT及MRI）、开口度、咬合关系及术区感觉。根据检查指标进行临床诊断及手术效果评价。结果：X线、3D-CT和MRI的确诊率分别为57.1%、66.7%和87.5%。3D-CT和MRI检查能更清晰地反映肿物情况,为手术提供良好的指导。14例患者均行手术治疗,术后效果良好。结论：MRI和3D-CT检查是诊断下颌骨髁突骨软骨瘤的最佳方法,能较好地观察肿物的范围及位置关系,为手术提供良好的依据,而X线检查在下颌骨髁突骨软骨瘤的诊断中具有重要价值。     

A descriptive and comparative study of oral health in 8-year-old Swedish children.

The aim of the study was to assess the oral health of a group of children, and to compare the findings with the results from an investigation performed 4 years earlier in children of the same age and living in the same area. The material consisted of 149 randomly selected 8-year-old children. The study included examination of caries and the state of the gingival conditions, enamel hypoplasia and opacities, supragingival calculus and extrinsic stains. Determinations were also made of the rate of secretion, pH and buffer effect of stimulated saliva. Socio-economic data and anamnestic dental data were noted. The investigation showed a decrease in caries frequency in the primary teeth, but not in the permanent teeth, during the four-year-period. As in the former investigation, regression analyses showed a negative correlation between the level of education of the parents and caries indices, and that the variation of the gingival indices could be explained by socio-economic factors. In addition, a negative correlation was found between the caries index for primary teeth and the rate of secretion of the saliva and the presence of supragingival calculus.     

Black-pigmented Bacteroides and motile organisms on oral mucosal surfaces in individuals with and without periodontal breakdown

The purpose of this study was to compare the microbiological flora on mucosal surfaces of the tongue and the tonsils of individuals with and without periodontal breakdown. Twenty-four adults were selected on the basis of clinical parameters. The study included evaluation for the presence of spirochetes and motile organisms by phase-contrast microscopy and blackpigmented Bacteroides by cultivation. Results showed statistically significant differences in the prevalence of various types of microorganism on the tongue and the tonsils between both groups. A positive correlation could be demonstrated between the presence of motile organisms and Bacteroides intermedius on the tongue and periodontal breakdown. Furthermore, a positive correlation was found between the presence of motile organisms on the tonsils and periodontal breakdown. From the results of this study, it was concluded that the microbial composition of the tongue and the tonsils is associated with periodontal breakdown.     

牙齿楔状缺损与侧方工作侧咬合接触关系的调查

目的　研究牙颈部楔状缺损与牙齿咬合接触的关系。方法　选取 12 3名中年机关干部。用 0 .0 2mm厚的超薄咬合纸 ,临床检查侧方运动工作侧上颌尖牙、第一、二前磨牙、第一磨牙颊尖各斜面上及咀嚼循环各个时期中的牙齿咬合接触情况 ;评估接触程度。结果　患楔状缺损牙齿咬合接触程度明显高于未患楔状缺损牙。上颌尖牙和前磨牙楔状缺损患牙在远中 (上第一磨牙的近、远中 )斜面上咬合接触程度高于未患牙 ,患牙在咀嚼侧方运动循环的中、末 (上第一磨牙在初、中或末 )期咬合接触程度增加。结论　牙颈部楔状缺损的发生与牙齿的咬合接触程度加重有关。     

成年鼠髁突增龄性变化的组织学和组织化学研究

目的：观察成年鼠髁突组织形态与组织化学形态增龄变化的特征。方法：20周和24周龄sD种雄性大鼠各20只。光镜下观察：髁突组织形态、髁突内碱性磷酸酶的分布及相对活性；年龄对髁突组织形态和碱性磷酸酶相对活性的影响。结果：髁突的组织形态及碱性磷酸酶相对活性存在着增龄性变化。结论：大鼠髁突有与人类髁突非常相似的组织学构造，是研究TMJ及相关疾病较为理想的动物模型；随着年龄的增加，成年鼠髁突软骨的再生能力、成骨能力及组织钙化能力均下降，软骨下骨呈骨硬化性变化。提示：随着年龄的增加，成年鼠下颌关节的适应能力下降。     

Publication: Presentation rate in the Latin American region of the International Association for Dental Research

Most research conducted by the dental scientific community is presented at the Annual Meetings of the different Divisions and Sections of IADR. This research acquires real value when the results are published in peer-reviewed journals. A useful indicator of the publication efficiency of research work is the rate of publication (PR), i.e., the ratio between the quantity of presentations and subsequent publications in peer-reviewed journals. The aim of this study was to analyze the PR of the presentations at the Sections and Divisions of the Latin American Region of the International Association for Dental Research (IADR). We considered the presentations at the Annual Meetings of Argentina, Brazil, Chile and Peru held in 2002 and 2003 and their corresponding publications indexed in PubMed from 2002 to 2009. For Venezuela, we analyzed the meetings held in 2002 and 2005, because they did not hold consecutive annual meetings. Presentation periods were selected based on previous data that report an interval of up to five years between presentation and publication. The number of presentations and the PR are related to the number of years that Sections and Divisions have existed. In Brazil and Argentina, PR (expressed as 1 publication: x presentations) is 1:3. The amount of research in Brazil is almost 8 times higher than in Argentina. Newer Sections and Divisions have produced fewer presentations, and the PR is also lower. We hope that this type of analysis will encourage the promotion of dental research at the different institutions and in the different vacancy areas of research, and facilitate exchange among researchers in the Region, enabling greater use to be made of their scientific activities.     

滑动法关闭下颌拔牙间隙的力学行为有限元分析

目的模拟临床加载力系统,研究滑动法内收下前牙过程中,不同方向载荷作用下,牙及弓丝力学行为的变化。方法建立含有托槽、弓丝、前后牙牵引钩的下牙列及下颌骨有限元模型。连接前后牵引钩上的点来确定矫治力的方向。并通过改变牵引钩高度来改变矫治力的作用点和方向。分析计算每一组加载力对牙的三维瞬间移动趋势、牙周膜的单元应力、弓丝的节点最大位移。结果前后牵引钩高度的变化与各牙角位移及牙周膜应力间均有相关性(P<0.01),各牙在不同后牙牵引钩高度,均随着前牙牵引钩高度变化而产生不同的移动。①随着前牙牵引钩高度的增加,中切牙、侧切牙的移动趋势逐渐由近中舌侧倾斜变为近中唇侧倾斜;而尖牙则向远中舌侧倾斜;第二前磨牙由近中颊侧倾斜变为近中舌侧倾斜;第一磨牙则由近中舌侧倾斜变为远中舌侧倾斜,且近中根比远中根舌向倾斜角度要大。②全牙弓牙周膜的最大应力始终出现在侧切牙的唇侧根尖1/3处;而尖牙、第一磨牙的牙周膜最大应力分别集中在牙槽嵴顶、根分叉处。结论在临床治疗中,可通过改变牵引钩的高度来实现前后牙的不同移动趋势,在弓丝上弯制不同的序列以更好地控制支抗牙。     

Accuracy of alginate and elastomeric impression materials

Abstract – The accuracy of three alginates and seven elastomeric impression materials was determined. Impressions were taken of a truncated cone and poured with stone die. A steel ring fitting the steel cone was placed on the dies, and the discrepancy between the top surface of the ring and the die was measured. From these measurements the deviation between the base diameter of the die and that of the cone was calculated and used to express the accuracy of an impression material. All impressions showed a net shrinkage, resulting in too large a die stone and incomplete seating of the steel ring. The inaccuracy of the alginates varied between 44 and 188 μm. Blueprint regular was found to be significantly more accurate than the two other alginates investigated, and had a degree of accuracy comparable with that of the more accurate elastomeric impression materials. Within this group of materials the inaccuracy varied between 39 and 130 μm. Generally, the addition-curing silicones were more accurate than the polyethers. Baysilex and President regular body had the highest degree of accuracy of the elastomeric impression materials.