Comparison of mesiodistal tooth crown diameters and arch dimensions between modern Mongolians and Japanese

The purposes of this study were to establish normative data for mesiodistal tooth crown diameters and arch dimensions in Mongolian adults and to compare them with those of Japanese adults. The study materials comprised dental casts of 100 modern Mongolian and 100 Japanese subjects (50 males, 50 females for each) with Angle Class I normal occlusion. The mean ages were 20 years 8 months for the Mongolian subjects and 20 years 0 months for the Japanese subjects. On the dental casts, the mesiodistal tooth crown diameters (excluding wisdom teeth) and dental arch dimensions were measured. The following arch dimensions were measured: inter-canine lingual, inter-premolar lingual, inter-molar lingual, inter-molar central, coronal arch length, basal arch length, and basal arch width. In the Mongolian samples, significant sex differences were noted, and most of the items were significantly larger in males than in females. Significant differences between the Mongolian and Japanese samples were mainly noted in the premolar and molar regions, rather than in the anterior region, and were significantly smaller in the Mongolian samples. In the Mongolian samples, the molar section widths and basal arch width and length were significantly larger in males and females compared with the Japanese samples. These results suggest that the tooth crown size and arch dimensions in the Mongolian samples differed from those in the Japanese samples, and that establishment of the clinical norm for Mongolian adults might be helpful in formulating treatment plans for Mongolian patients, given that these parameters are the basic tools for diagnosis.     

Correlations among crown diameters of human teeth

Correlation coefficients were obtained for mesiodistal crown diameters of single teeth and tooth groups in the deciduous and permanent dentures. The degree of association between deciduous and permanent teeth was also determined for single teeth and tooth groups, and likewise between deciduous and permanent maxillary and mandibular teeth. Findings relate to the development of normal occlusion, and evolutionary aspects of man's dentition.     

邻牙倾斜牙体缺损的桩核冠修复

选择2008年至2009年在我院就诊患者28例共28颗患牙,其中前磨牙11颗,磨牙17颗。患牙牙体大面积缺损,牙体缺损部分被倾斜邻牙遮挡,若调磨邻牙去除倒凹对邻牙会有较大损害,难     

Surgical lengthening of the clinical tooth crown

To understand why the crown lengthening may be desirable, a review of periodontal anatomy is in order. The odontologists know, but often underestimate importance of periodontal tissues health to restoration of defected teeth or dental arches. In order to avoid pathological changes, to predict treatment results more precisely, it is necessary to keep gingival biological width unaltered during teeth restoration. If there are less than 2 mm from restoration's margin to marginal bone clinical crown lengthening possibility should be considered in dental treatment plan. The choice depends on relationship of crown-root-alveolar bone and esthetical expectations. In order to keep margins of restoration supragingivally the distance from marginal bone to margins of restoration should not be less than 3 mm. Ideally the margins of restoration should be supragingivally or in the same level as marginal gingiva. When the margins of restoration are prepared subgingivally, the distance from marginal gingiva to margins of restoration should not be more than 0.7 mm. To continue dental treatment in operated area is recommended not earlier than in 4 weeks, and making restorations in esthetical area--not earlier than in 6 weeks.     

The mesiodistal crown diameters of primary dentition in Indonesian Javanese children

Dentition analysis of primary teeth is necessary for recognising and correcting occlusal problems in every stage of dental development to enable normal adult occlusion. To do this, normative data of mesiodistal tooth crown diameters from the same ethnic population are needed. The aims of this study were to gather normative data of mesiodistal crown diameters of primary dentition in Indonesian Javanese children and to compare this normative data with published data of other ethnic populations. Dental casts of 160 males and 137 females with acceptable occlusion, aged 3.25-6.58 years, were taken in Yogyakarta, Indonesia. Mesiodistal diameter was measured as the distance between the anatomic contact points using calipers with accuracy to within 0.05 mm. Each measurement was taken twice on different occasions. The results indicated that the magnitude of asymmetry between right and left teeth was larger in distal teeth within a tooth field, larger in males than females, and larger in mandibular than maxillary teeth. The stability of mesiodistal tooth crown diameters was less in males than in females, and was most prominent in the mandibular central incisor. Sexual dimorphisms were found in, the lateral incisor and first molar in the maxilla, and the canine, first and second molars in the mandible. Compared with other ethnic populations, Indonesian Javanese falls between Hong Kong Chinese and Australian Aboriginal.     

Regression equations for determining mesiodistal crown diameters of canines and premolars

In this study, regression equations (prediction equations) were established for the purpose of accurately predicting the widths of the crowns of unerupted canines (C) and premolars (P1 and P2) on the basis of the measured mesiodistal diameter (MDD) and vestibulooral diameter (VOD) of the crowns of the erupted central and lateral incisors (I1, I2) and first permanent molars (M1). On the plaster casts of 120 subjects (60 boys and 60 girls), MDD and VOD of the crowns of I1, I2, C, both P1 and P2, and M1 on both sides in both jaws were measured twice, with a time distance between measurements. Gradual regression equations were derived on the basis of the measurement results, by which the sums of the widths of crowns of C, P1, and P2 can be predicted using three to five predictors. The coefficients of multiple correlations regarding the sex and the jaw varied from 0.79 to 0.85.     

Mesiodistal crown diameters of permanent teeth in male American Negroes.

The mesiodistal crown diameters were measured in a group of fifty-six male American Negroes from the recruit population at the Great Lakes Naval Training Center and compared with previously reported data on Caucasians from the same population. The results indicate that tooth size is consistently larger in the Negro sample, averaging about 8.4 percent for the over-all maxillary and mandibular dentition, excluding third molars.     

全冠预备体形态的数字化设计

目的:研究利用计算机技术,基于牙齿三维扫描模型获得全冠牙齿预备体模型数据的方法.方法:借助计算机图形学、计算几何和口腔数字化技术,构建Windows环境下的软件,对扫描得到的牙齿模型进行参数化处理,先后通过确定冠中心线、提取冠边缘线、识别(牙合)面特征、标识(牙合)面功能区、设定预备体参数及最终预备体生成等步骤,完成基于参数约束的全冠数字化牙体预备.结果:通过Geomagic Qualify软件对生成的数字化预备体进行多截面(牙合)向聚合度和肩台宽度测量,结果与设计值偏差较小.结论:数字化牙体预备获得的预备体满足设计要求,为开发牙体预备操作新模式,实现自动牙体预备奠定基础.     

离体天然牙颜色的色度学测量与分析

目的：通过对离体天然牙牙冠颜色测量和分析，探讨年龄对天然牙颜色参数的影响以及二者间的相关关系。方法：采用PR-650光谱扫描色度仪、Photo Research颜色分析软件和CIE1976L＊a＊b＊标准色度系统对267颗离体天然牙进行切、中、颈1／3三个位点的测量。结果：①不同年龄段不同牙位的颜色参数跨度大，均数变化明显；②L＊宰值与年龄呈负相关（P〈0.05），随年龄增长明度降低，牙色变暗；但磨牙的颈部表现不明显（P〉0．05）。③a＊在不同的牙位表现不一致：前牙与年龄呈明显的负相关关系（P〈0.05）；前磨牙则变化不一致，切端呈现负相关（P〈0．05），而在中部和颈部呈现正相关，且颈部相关性明显（p〈0．05）；磨牙与年龄呈正相关，[牙合]1／3具有明显相关关系（P〈o．05）④b＊与年龄呈正相关（p〈0．05），随年龄的增长，切、中、颈1／3的颜色偏黄，但前磨牙的切1／3表现不明显（P〉0.05）。结论：天然牙的颜色参数随年龄的增长明度下降，颜色变黄，但是红绿色相变化在不同牙位的三个部位是不完全一致的。     

全冠预备体形态的数字化设计

目的:研究利用计算机技术,基于牙齿三维扫描模型获得全冠牙齿预备体模型数据的方法.方法:借助计算机图形学、计算几何和口腔数字化技术,构建Windows环境下的软件,对扫描得到的牙齿模型进行参数化处理,先后通过确定冠中心线、提取冠边缘线、识别(牙合)面特征、标识(牙合)面功能区、设定预备体参数及最终预备体生成等步骤,完成基于参数约束的全冠数字化牙体预备.结果:通过Geomagic Qualify软件对生成的数字化预备体进行多截面(牙合)向聚合度和肩台宽度测量,结果与设计值偏差较小.结论:数字化牙体预备获得的预备体满足设计要求,为开发牙体预备操作新模式,实现自动牙体预备奠定基础.     

计算机辅助后牙全冠修复的设计

目的 通过计算机辅助设计（CAD）获得待修复的全冠的数据,以备计算机辅助加工（CAM）之用。方法 待作全冠修复的牙预备体、邻牙、对He牙经过光学测量,获得其表面三维形状后,选用拟修复的牙的理想牙冠形态,根据缺牙区的大小及邻牙,对He牙的情况进行修改,使理想牙冠形状适合该缺牙区的情况后,用修改后的理想牙冠形状图像与牙预备体形状图像相减,即获得所需修复的全冠的数据,以备CAM加工之用。结果 获得了待修复的全冠的数据和图像。结论 本研究建立了一套通用性良好的冠修复的CAD系统,为CAM的实现奠定了基础。     

全冠预备体形态的数字化设计

目的:研究利用计算机技术,基于牙齿三维扫描模型获得全冠牙齿预备体模型数据的方法.方法:借助计算机图形学、计算几何和口腔数字化技术,构建Windows环境下的软件,对扫描得到的牙齿模型进行参数化处理,先后通过确定冠中心线、提取冠边缘线、识别(牙合)面特征、标识(牙合)面功能区、设定预备体参数及最终预备体生成等步骤,完成基于参数约束的全冠数字化牙体预备.结果:通过Geomagic Qualify软件对生成的数字化预备体进行多截面(牙合)向聚合度和肩台宽度测量,结果与设计值偏差较小.结论:数字化牙体预备获得的预备体满足设计要求,为开发牙体预备操作新模式,实现自动牙体预备奠定基础.