替牙期未萌尖牙、前磨牙宽度和预测方程的建立

目的优化选择针对未萌尖牙、前磨牙宽度预测的基牙组合。方法取正畸科初诊患者的研究模型,按一定标准随机选出恒牙列模型180副,利用电子游标卡尺(精度0.01 mm)测量牙冠近远中径,并对测量值进行相关与回归分析。结果得到了与未萌尖牙、前磨牙宽度相关度较高的基牙组合,即,上颌第一磨牙和上、下颌中切牙联合;此组合与上、下颌预测牙的相关度分别为0.753和0.834,具有统计学意义(P≤0.001)。以此为基础进行回归分析,建立了预测上、下颌尖牙、前磨牙宽度之和的回归方程。结论建立了一组适合中国北方地区替牙期儿童未萌尖牙、前磨牙宽度的预测方程:男性Y=0.64X+6.89(上颌),Y=0.79X+2.45(下颌);女性Y=0.64X+6.86(上颌),Y=0.72X+3.90(下颌)(Y代表一侧未萌尖牙、前磨牙近远中宽度和,X代表双侧上颌第一磨牙及上、下颌中切牙的近远中宽度和的一半)。     

Prediction of the mesiodistal size of unerupted canines and premolars for a group of Romanian children: a comparative study

Objectives:

The aim of the present study was to develop an optimization method of multiple linear regression equation (MLRE), using a genetic algorithm to determine a set of coefficients that minimize the prediction error for the sum of permanent premolars and canine dimensions in a group of young people from a central area of Romania represented by a city called Sibiu.

Material and Methods:

To test the proposed method, we used a multiple linear regression equation derived from the estimation method proposed by Mojers, to which we adjusted regression coefficients using the Breeder genetic algorithm. A total of 92 children were selected with complete permanent teeth with no clinically visible dental caries, proximal restorations or orthodontic treatment. A hard dental stone was made for each of these models, which was then measured with a digital calliper. The Dahlberg analyses of variance had been performed to determine the error of method, then the Correlation t Test was applied, and finally the MLRE equations were obtained using the version 16 for Windows of the SPSS program.

Results:

The correlation coefficient of MLRE was between 51-67% and the significance level was set at α=0.05. Comparing predictions provided by the new and respectively old method, we can conclude that the Breeder genetic algorithm is capable of providing the best values for parameters of multiple linear regression equations, and thus our equations are optimized for the best performance.

Conclusion:

The prediction error rates of the optimized equations using the Breeder genetic algorithm are smaller than those provided by the multiple linear regression equations proposed in the recent study.     

Predicting the size of unerupted canines and premolars of the maxillary and mandibular quadrants in an Iranian population

The aim of this investigation was to examine the accuracy of Moyers probability tables and the Tanaka and Johnston prediction equations in predicting the size of unerupted canines and premolars of the maxillary and mandibular quadrants in an Iranian population and to derive a standard formula for it. METHODS: Out of a sample of 280 subjects, 50 (25 males and 25 females) were selected by specific inclusion criteria. An electronic digital caliper was used to read the nearest 0.01 mm. The teeth measurements derived were compared with those predicted from Tanaka Johnston equations and Moyers probability tables and then standard regression were developed. RESULTS: Tanaka and Johnston regression equations overestimate the mesiodistal width of permanent canines and premolars. There were no statistically significant differences between actual mesiodistal width of canines and premolars and the predicted width from Moyers charts at 65% for the lower and upper arches in male subjects and for the lower arch in females but none of the probabilities has good accuracy for the upper arch in females. For the newly developed regression equations, the correlation coefficients between the sum of the mandibular incisors and the sum of the canine and premolars were 0.709 (for lower) and 0.539 (for upper) in subjects. CONCLUSIONS: Tanaka and Johnston overestimate the actual size for Iranian teeth widths. Moyers method can be used at 65% probability level for male subjects and at the 75% and 85% level for upper arch and the 50% and 65% level for lower arch in female subjects.     

New regression equations for predicting the size of unerupted canines and premolars in a contemporary population

The determination of a tooth-size to arch-length discrepancy in the mixed dentition requires an accurate prediction of the mesiodistal widths of the unerupted permanent teeth. This is an essential factor in treatment planning. The aim of this study was to validate Tanaka and Johnston's analysis on 600 Syrian patients aged 14-22 years. Tanaka and Johnston's tables, equations, and approximations were modified in order to improve the accuracy of the prediction. The correlation coefficients found between the size of the permanent mandibular central incisors and maxillary first molars (31, 41, 16, and 26) and the maxillary and mandibular canines and premolars were high (r = .72 and .74, respectively). New, more accurate prediction tables applicable at earlier ages, and new regression equations were constructed. In addition, new easier approximations were developed to allow the prediction of the size of the unerupted maxillary canines and premolars by adding 6 mm to the half-widths of teeth 31, 41, 16, and 26. The analogous prediction of the size of the unerupted mandibular canines and premolars was obtained by adding 5.5 mm to the half-widths of same teeth, 31, 41, 16, and 26.     

Tooth size in patients with supernumerary teeth and a control group measured by image analysis system

OBJECTIVE: The aim of this study was to compare tooth size measurements between patients with supernumerary teeth and a control group. METHOD: The supernumerary group consisted of 56 subjects (21 females and 35 males) and the control group of 40 subjects (20 females and 20 males). All available permanent teeth on the dental casts were imaged and measured from both buccal and occlusal views using an image analysis system. Mesio-distal, bucco-lingual or occluso-gingival dimensions, area and perimeter were measured from each view. RESULTS: Supernumerary tooth patients tended to have larger tooth size measurements for almost all variables than controls. Significant differences (p<0.05) were found for the mesio-distal dimension of the upper and lower incisors and the bucco-lingual dimensions of the lower first premolars. CONCLUSIONS: The results are compatible with supernumerary teeth being a complex dental anomaly with a multifactorial aetiology in which both genetic and environmental factors are important. There is some evidence of a local effect with greater differences in tooth dimension adjacent to the site of the supernumeraries.     

西安地区正常(牙合)牙冠宽度及上、下颌牙量相关性研究

目的:测量西安地区汉族人正常(牙合)牙冠宽度,并对上下颌牙量的相关性进行研究.方法:选取符合纳入标准的个别正常(牙合)共计107例(男52例女55例),测量各个牙齿的最大近远中径宽度,然后依据测量值进行上、下颌牙量的相关性研究.结果:得出了西安地区正常(牙合)各个牙牙冠宽度,其中上颌中切牙、侧切牙、尖牙、第一恒磨牙以及下颌的尖牙、前磨牙牙冠宽度男性明显大于女性,存在着显著的统计学差异.上、下颌前牙量之间及上下颌总牙量间均存在着显著的相关性(γ前牙=0.754,γ全牙=0.851),Bolton指数的正常值分布范围为78.32±3.01,全牙比正常值分布范围为91.10±2.27;根据这种上、下颌牙量间的相关性得出了用于计算牙量不调量的直线回归方程.结论:西安地区部分牙冠宽度男大于女,上下颌牙量间存在相关性.     

Tooth size variability and relevance of numerical variation in the Japanese serow

We analysed the variability of the lower cheek teeth of the Japanese serow, Capricornis crispus, from Aichi Prefecture, Japan, based on the coefficient of variation (CV), and examined tooth size variability. The mesiodistal (MD) and buccolingual (BL) crown diameters of permanent cheek teeth were measured, and an index of the crown surface (MDxBL) was calculated. As a result, the CV for MD measurements ranged from 3.6 to 6.3, and that for BL measurements ranged from 3.6 to 6.5. In males and females, the first molar (M(1)) was the least variable (3.6-4.1) and the second premolar (P(2)) was the most variable (5.0-6.5), except for the case of BL in females. The crown surface index showed a morphological gradient that increased from mesial to distal, and the values of P(2) in both sexes were extremely small. Overall, cheek tooth variability was not influenced by developmental factors, but appeared to be inversely related to functional factors. The highest coefficient of variation was observed for P(2), which was characterised by a simple shape with a single cusp, and an extremely small size compared to other teeth. Only P(2) showed congenital absence or impaction in the lower dentition. We also confirmed the relationship between tooth size variability and numerical variation.     

Factors associated with the incidence of erosive wear in upper incisors and lower first molars: a multifactorial approach

Objectives

The aim was to investigate associations between factors and the incidence of erosive wear in lower first molars and upper incisors, and to investigate whether these associations differ between these locations.

Methods

The study sample of this 3-year longitudinal study consisted of 572 children (mean age 11.9 years, SD = 0.9). The permanent dentition was examined for erosive wear according to a modified Lussi-index (1996). Information on biological and behavioural factors was gathered by clinical examinations (at baseline, after 1.5 and 3 years) and by questionnaires (every six months).

Results

The incidence of erosive wear in upper incisors over 3 years was 22.2%, for lower first molars the incidence was 14.8%. Multivariate logistic regression analysis showed that carbonated soft drink (OR = 1.04) and tooth grinding (OR = 2.93) were positively associated with the incidence of erosive wear in upper incisors and milk (OR = 0.95) and yoghurt products (OR = 0.88) were negatively associated. The incidence of erosive tooth wear in lower first molars was positively associated with alcoholic mixed drink (OR = 1.45) and tooth grinding (OR = 4.00) and was negatively associated with milk (OR = 0.96) and yoghurt products (OR = 0.84). The incidence of erosive wear in lower first molar was lower in girls than in boys (OR = 0.51). t-Tests on the odds ratios of the factors showed that between the two incidence models only the odds ratios of anterior contact significantly differed.

Conclusions

In the present study, except for anterior contact, no substantial differences in risk factors between the incidence of erosive wear in lower first molars and upper incisors were found. This indicates that the aetiology of erosive wear for the two locations is similar.     

多曲方丝对下颌中切牙牙周膜应力分布有限元分析

目的:对多曲方丝弓技术中打开咬合所产生的力学系统进行有限元分析,了解多曲方丝弓打开咬合时下颌中切牙牙周膜应力分布情况。方法:建立下颌牙列各牙齿、牙槽骨及切牙牙周膜的有限元模型。然后进一步模拟临床在中切牙处加载75g垂直向下的力,按照考虑或不考虑牙周膜的两种情况,求得牙周膜的应力分布。结果:两种情况下牙周膜部位最大值变化很大。在不考虑牙周膜时,牙根颈部应力最大值达21.6×105g/mm2;考虑牙周膜的缓冲作用时牙根及牙周膜上的应力分布相对均匀,且绝对值变小,但牙槽嵴顶部应力峰值明显变大。结论:①本研究建立的下颌牙列的三维有限元模型,比较符合实际情况,可以适用于多曲方丝弓矫治技术的研究。②多曲方丝弓作用下下颌中切牙牙周膜应力从颈缘到根尖逐渐减小,但在牙槽嵴顶部应力峰值明显增大,易出现牙周膜透明性变。     

The reporting of race and ethnicity information in the dental public health literature

Objectives: To document how race and ethnicity are identified, categorized, and utilized in contemporary dental public health literature. Methods: Two researchers independently performed a literature review of all articles in Community Dentistry and Oral Epidemiology and the Journal of Public Health Dentistry over a 5‐year period (2004‐2009). Articles pertaining to the study of US‐based populations with any mention of race or ethnicity were included. The following data were abstracted from each article: a) how each article broadly described race and/or ethnicity; b) the terms used to specifically define the races and/or ethnicities captured; c) the location of any mention of the concept of race and/or ethnicity; d) the stated purpose for including race and/or ethnicity concepts; e) the stated analytic use of race and/or ethnicity concepts; and f) the stated method used to assess race and/or ethnicity concepts. Results: Overall, race and/or ethnicity concepts were most commonly referred to within the text of the results section. Fifty percent of articles did not state their purpose for including race and/or ethnicity concepts within their studies, while 34.3 percent omitted stating their analytic use of these concepts. When assessing these concepts, 41.4 percent relied upon subject self‐report. Conclusion: These data showed that there was inconsistent documentation of how race and ethnicity was measured. While race and ethnicity are important measures for public health studies and are frequently reported in dental public health research, there is no clear system for classifying these measures.     

Caries in fissures of permanent first molars as a predictor for caries increment

A group of 268 children were checked for caries experience at the age of 7.2 yr later at the age of 9 and 4 yr later at the age of 11 yr. Caries experience of fissures in permanent first molars at the age of 7 yr served as a screening criterion for caries increment between the ages of 7 and 11 yr. This screening resulted in a sensitivity of 0.62, a specificity of 0.82, and a diagnostic power of 0.83 for total caries increment in the permanent dentition and in a sensitivity of 0.68, a specificity of 0.80, and a diagnostic power of 0.78 for caries increment in fissures of permanent first molars. It was concluded that this screening offered the best method available for identifying children at risk from fissure caries in their permanent first molars. Cost effectiveness of preventive treatment directed towards individuals, for instance the application of fissure sealants, can be improved by using this screening method.     

The value of salivary bacterial counts as a supplement to past caries experience as caries predictor in children

This study aimed to determine whether salivary mutans streptococci and lactobacilli counts could add any value to a combination of caries experience variables that was recently presented for the prediction of caries. Sixty-nine children at the age of 7.5 yr participated in this longitudinal study. Microbiological data were obtained at the ages of 7.5, 9.5 and 11.5 yr and caries data at the ages of 7.5. 9.5. 11.5, 13.5 and 15.5 yr. Spearman's correlation coefficients were computed, and forward multiple regression analyses were carried out using bacterial counts and caries experience parameters as explanatory variables and caries increment as a dependent variable. The explained variance (adjusted R2 value) was the measure used to assess the additional value of bacterial counts to the caries predictive potential of the combined parameters of the past caries experience. Correlation coefficients between bacterial counts and 4-yr caries increment were from 0.22 tip to 0.54. In all cases, the simultaneous streptococcus mutans-lactobacilli counts showed a statistically non-significant additional adjusted R2 value of <0.06. The results do not lend support to the concept that these salivary bacterial counts are useful additional caries predictors for the mixed dentition, when a combination of caries experience parameters is used.     

Overjet,overbite and dental midline shift as predictors of tooth size discrepancy in a Bangladeshi population and a graphical overview of global tooth size ratios

Abstract

Objectives. This study aimed to measure and compare tooth size ratios in a Bangladeshi population across the following groups: those with normal occlusion, crowding or spacing; those with normal, increased or decreased overjet; those with normal, increased or decreased overbite; those with or without dental mid-line discrepancy; and those with or without lip competence. It also presents a graphical overview of the anterior and overall ratios from the study and using available global data. Materials and methods. This study was performed on dental casts of 260 Bangladeshi individuals, comprising 114 males and 146 females (age range, 18–24 years, mean age = 20). The Bolton anterior ratio and overall ratio were determined for the following groups: those with normal occlusion, crowding or spacing; those with normal, increased or decreased overjet; those with normal, increased or decreased overbite; those with or without dental mid-line discrepancy; and those with or without lip competence. Results. There were statistically significant differences in the anterior tooth size ratios between those with or without dental mid-line discrepancy, with a mean value of 78.83% and 80.05%, respectively. Statistically significant differences were also found in overall tooth size ratios between those with normal, increased or decreased overjet and also between those with normal, increased or decreased overbite. Graphical presentations of anterior and overall ratios from the present study and using global data showed variations between populations. Conclusion. In the Bangladeshi population, increased tooth size ratios in subjects with dental mid-line discrepancy (anterior ratio) and also in those with decreased overjet or decreased overbite (overall ratio) may be predictors of tooth size discrepancies. The graphical overview also suggests that different international ethnic groups display unique Bolton ratios.     

The effect of age on morphology and eruption of the lower incisors in mature rats

OBJECTIVE: This study investigated the effect of age on tooth and periodontium morphology and on tooth eruption in the lower incisors of 28 female rats, initial age 10 weeks. DESIGN: Morphometric data of the incisors in three young mature rats (weight 199+/-2.4 g) were compared to that of three 18-week-old (weight 260+/-5 g) animals. The rate of eruption was monitored during 12 months in 11 rats with all teeth in occlusion and in 11 rats with one lower incisor kept constantly out of occlusion. RESULTS:: The incisors continued to enlarge after the animals reached maturity with the size of the teeth increasing both longitudinally and circumferentially. Tooth volume increased by 21%, while that of the periodontal ligament was enlarged by only 12%. The rate of impeded eruption declined steadily from a mean value of 542+/-49 microm/day during the first experimental month to a mean value of 443+/-25 microm/day during the concluding month (p<0.05). The eruption rate of the teeth exceeded that of attrition rate by 2.4%. The unimpeded eruption proceeded steadily throughout the experimental year, at a mean rate of 811+/-12. CONCLUSIONS: Apparently in mature rats age has no effect on the genetic potential as expressed by the unimpeded eruption. In the impeded teeth age does affect the phenotypic expression of the eruptive function governed by occlusal forces as well as by the form and size ratio of the tooth and its PDL.     

传统模型与三维数字化模型在平整牙弓间隙分析中的比较研究

目的 比较传统模型与三维数字化模型在间隙分析中的差异，并且应用数字化模型来准确计算平整牙弓所需间隙。验证传统模型分析中对平整牙弓所需间隙的方法是否正确。方法 随机选择30个正畸治疗前的石膏模型，用激光扫描的方法制作这30模型的数字化模型。在数字化模型上比较Spee曲线深度与平整牙弓所需间隙的差异，判断是否可以用Spee曲线深度来代替平整牙弓所需间隙；为了验证在正畸治疗中，Spee曲线深度的变化与由此带来的牙弓长度的变化的关系，选择另外22个正畸病例，比较在实际治疗正畸治疗前后Spee曲线深度的变化值与牙弓长度的变化值是否一致。结果在数字化模型上，Spee曲线深度的．测量值大于平整牙弓所需间隙的测量值，正畸治疗前后Spee曲线深度变化值要大于因此产生的牙弓长度变化值，且差异都具有显著性，因此临床上所认为的每平整牙弓1mm则需要1mm的牙弓间隙过多估计了平整牙弓所需间隙，二者的关系不是1：1。而是2：1。甚至3：1的关系。结论临床上传统的模型测量所认为的每平整牙弓1mm则需要1mm的牙弓间隙是错误的：在正畸临床上，三维的数字化模型测量分析方法比传统的模型测量分析方法有更多的优越性。     

Comparison of the crown size of teeth in children from a high and an optimum fluoride area in South Africa

An odontometric analysis was undertaken of the teeth of 6-7 and 14-15-yr-old schoolchildren exposed throughout life to a naturally fluoridated drinking water supply (2.5 ppm) in Klipfontein and of equivalent children living in the adjacent area of Garies (1.06 ppm). Measurements were made of the mesio-distal diameter of permanent maxillary and mandibular central incisors, second premolars and first and second molars; in addition, bucco-lingual measurements of the molars were made. In comparing the dimensions of teeth in the high- and optimum-fluoride samples, a tendency towards smaller dimensions in the former group was observed, but statistically significant differences applied to only some of the measurements. This finding suggests a reducing influence on crown size of an increase in the level of fluoride in the drinking water. Coupled with previous findings that increased the fluoride level from low or zero to optimal results in a reduction in crown size, an inverse relationship between crown size and fluoride level in the drinking water appears possible, but has not been confirmed in this study.