Dental arch analysis system

The purpose of our research is to describe a computerized method, which enables orthodontists and researchers to analyze variation of dental arch form and dimension. The analysis system is composed of two independent parts: the database, where the images of scanned dental casts are stored, and the software. The operator uses the software to identify some landmarks on dental cast images. Corresponding distances are calculated (interincisive, intercanine and intermolar widths and the curve axis). Then the software algorithms calculate and draw the curves passing trough the selected landmarks (conics, catenary, cubic spline and polynomial curves). In the chosen curves the arch length is measured. The dental cast data, recorded at different times of the subject's life or in different steps of orthodontic treatment, are compared in order to evaluate the change in dimension (arch length and width) and form (shape). The statistical analysis of the data evaluates the variation in form and in dimension separately. The shape change is defined by Euclidean Distance Matrix Analysis (EDMA) and Bootstrap analysis. The computerized method allows orthodontists and researches to evaluate the variation in dimension and form of the dental arch in un-treated subjects and-or orthodontic patients over time. After the analysis of a large sample of patients or subjects, information concerning changes in dental arch dimension and form can be added to previous studies of other authors, distinguishing variation during and after orthodontic treatment, during growth or aging.     

Preadenoid space size and its relationship to the vertical facial type

The purpose of this study of 103 patients was to present a statistical analysis of the relationship between the size of the preadenoid space and the measurements that determine the vertical and anterior-posterior relationship between the maxilla and the mandible, which could disturb the facial type. This study also analyzes the relationship of mouth breathing with the measurements that determine the vertical facial type in the human cranium. No statistically significant relationship was found between the size of the preadenoid space and the vertical characteristics of the sample, nor was there a statistically significant relationship between the mouth-breathing pattern and its facial type in the vertical plane.     

Dental arch space changes following premature loss of primary first molars: a systematic review

PURPOSE: The purpose of this study was to consider the available evidence regarding premature loss of primary molars and the implications for treatment planning. METHODS: Electronic database searches were conducted--including published information available until July 2007--for available evidence. A methodological quality assessment was also applied. RESULTS: Although a significant number of published articles had dealt with premature primary molar loss, only 3 studies (including a total combined sample of 80 children) had the minimal methodological quality to be considered for this systematic review. CONCLUSION: A reported immediate space loss of 1.5 mm per arch side in the mandible and 1 mm in the maxilla--when normal growth changes were considered--was found. The magnitude, however, is not likely to be of clinical significance in most cases. Nevertheless, in cases with incisor and/or lip protrusion or a severe predisposition to arch length deficiency prior to any tooth loss, this amount of loss could have treatment implications.     

Dental arch diameters and relationships to oral habits

The objective was to analyze variations in dental arch width in relation to oral habits. Maxillary and mandibular intercanine and intermolar distance were determined in relation to certain oral habits in 1297 children (ages 3 to 6 years). After an oral examination, the parents of each child completed a questionnaire about oral habits, including the use of a dummy or a bottle (or both), finger sucking, mouth breathing, breast- or bottle-feeding, and duration of these habits. Data were subjected to statistical analysis by the chi-square test for qualitative variables and analysis of variance for quantitative variables with homogeneous variances. Statistical significance was P < .05. In general, the maxillary arch was larger than the mandibular arch with regard to both the intercanine and the intermolar distances and more significantly so in boys. In relation to age, a significant increase was found only for the mandibular intercanine distance (P = .001). When arch width was analyzed in relation to various oral habits, the maxillary intercanine distance was less in children who used a dummy, especially one of a round design (P = .003). The maxillary intercanine distance was also less in children who breathed through their mouth (P = .002). In most cases, dummy use and mouth breathing were associated with a reduction in the intercanine distance in the maxillary arch. A dummy habit leads to a reduction in maxillary arch width, and mouth breathing causes a reduction in the size of both arches.     

Dental arch changes following rapid maxillary expansion

The purpose of this research was to evaluate changes in upper arch dimension and form following rapid maxillary expansion (RME) using a modified Haas appliance in the primary dentition. The sample comprised 49 children [17 males, 32 females, mean age 7 years 5 months, standard deviation (SD) 1 year 1 month] with a crossbite or maxillary crowding. Twenty patients had a normal SN-GoGn angle (7 males, 13 females, mean 33.25 degrees, SD 2.10), three were low angle (1 male, 2 females, mean 27.67 degrees, SD 2.31), and 22 were high angle (8 males, 14 females, mean 39.95 degrees, SD 3.15). The vertical dimensions of four patients could not be measured, due to the unavailability of radiographs. Expansion was undertaken to either correct a crossbite or treat maxillary crowding. The upper dental casts were analysed using a computerized system: before treatment (T1), at appliance removal (T2), and 2 years 4 months after appliance removal (T3). Using bootstrap statistical analysis applied to distance ratio values [Euclidean distance matrix analysis (EDMA)], it was found that 48 patients showed a change in arch form. In 40.82 per cent (n = 20, group A), the arch form changed from T1 to T2, T1 to T3, and T2 to T3. In 32.65 per cent (n = 16, group B), it varied from T1 to T2 but relapsed at T3 to the form of T1. For 24.5 per cent (n = 12, group C), it changed from T1 to T2 but maintained the same form at T3. The favourable characteristics for obtaining expansion, identified by logistic regression analysis, were being male, of an immature stage of dental development (lateral incisor not fully erupted) and the presence of a lateral crossbite. Intercanine and intermolar widths, arch length, and the distance between the interincisive point and the line joining the canines (depth of the intercanine arch) at the different time points were analysed using a two-tailed t-test (P < 0.05). For the whole group, the increase in intercanine and intermolar width and in the depth of the intercanine arch was significant. Comparison between groups A, B, and C was undertaken using an analysis of variance, but there was no significant difference between the groups. This modified type of Haas appliance was able to increase the transverse dimension of the maxillary dental arch in the mixed dentition. The most appropriate timing for treatment appears to be before the eruption of the permanent lateral incisors.     

采用四点还原法进行牙弓弓形绘制

目的：寻找一种操作简单的个体化牙弓弓形绘制方法。方法：采用四点还原法个体化牙弓弓形绘制。确定下颌左右第二前磨牙托槽槽沟中心点,下颌左右第一磨牙托槽或颊管槽沟中心点,从而绘制出个体化牙弓弓形图。将四点还原法绘制的个体化牙弓弓形过程编程,实现自动化打印,将打印图形和数显游标模型直接测量的线距和角度比较。应用Medcalc9.3统计软件包进行准确性及可重复性检验。结果：四点还原法可绘制个体化牙弓弓形图,与数显游标模型直接测量比较,线距协相关系数为0.9909,角度协相关系数为0.8419。结论：采用四点还原法个体化牙弓弓形绘制,图形准确可靠,具有较好的可重复性。     

Dental forceps reduction of depressed zygomatic arch fractures

Zygomatic fractures are commonly encountered by the maxillofacial surgeon. Twenty-five patients with isolated zygomatic arch fractures were managed successfully under local anesthesia and sedation using the intraoral buccal sulcus approach. A dental forceps was used as the reducing instrument. Maxillofacial surgical units that manage a large number of trauma cases can consider this technique as a rapid means to manage such fractures under local anesthesia and sedation.     

Dental, oral and facial limericks of yesterday and today

The limerick is a popular form of light and poetic verse which was originally recited and sung in the local inns and taverns of Ireland and England. It may be anecdotal, nonsensical and/or ribald in nature. As a form of satire, it confronts society's "sacred cows" and/or foibles. During the mid-1800s, Edward Lear popularized this mode of expression in England. From there it spread throughout the entire world. By 1900, two branches of limerick writing were formed--the decent and the "smutty." In reviewing 7,000 traditional limericks, the authors have located about 50 significant dental, oral and/or facial limericks which are socially acceptable. In addition, we have produced 50 original poems of this nature. This article offers 33 traditional and new limerick "gems" for your reading pleasure.     

New design space regainers: 'Lingual arch crossbow' and 'Double banded space regainer'

This article highlights the use of two new design space regainers - the "lingual arch crossbow" and the "double-banded space regainer." The former may be used for distalizing a mesially migrated mandibular first premolar, if it erupts prior to the canine. The latter may be used in conventional cases of interdental space loss. They both contain assemblies that function through the action of NiTi open coil springs.