How does arch form and interproximal contact size affect the 3D displacements and rotations of teeth: a finite element analysis

ABSTRACT Objective: The objective of this study was to determine how arch form and interproximal contact size displace mandibular teeth subjected to an anterior component of force (ACF). Methods: Nine finite element models (FEM) of the mandibular arch were developed using Ansys® v. 16.0 software. They were designed to evaluate the effects of three arch forms (triangular, oval, and square) and three contact sizes (point-to-point, 1 mm diameter, and 2 mm diameter). All nine models were subjected to an ACF of 53.8 N (5486 gm). Three-dimensional tooth rotations and displacements of the mandibular teeth were evaluated, from the right first molar to the left first molar. Results: Arch form had a greater effect on tooth movements than contact size. Triangular arches and point-to-point contacts produced the greatest displacements and rotations of teeth. Oval arches with 2 mm wide interproximal contact points showed the greatest stability. The right first premolar showed the greatest displacements in all of the models. Conclusions: Arch form and contact size affect interproximal tooth stability. Teeth are least stable in narrow arches with point-to-point interproximal contacts, and most stable in wider arches with larger contacts.

RESUMO Objetivo: O objetivo deste estudo foi determinar como o formato da arcada e o tamanho do contato interproximal deslocam os dentes inferiores submetidos a um componente anterior de força (CAF). Métodos: Nove modelos de elementos finitos (MEF) da arcada inferior foram desenvolvidos utilizando o software Ansys® v. 16.0. Eles foram projetados para avaliar os efeitos de três formatos de arcada (triangular, oval e quadrado) e três tamanhos de contato interproximal (ponto a ponto, 1 mm de diâmetro e 2 mm de diâmetro). Todos os nove modelos foram submetidos a um CAF de 53,8 N (5486 gm). Foram avaliados tridimensionalmente as rotações dentárias e os deslocamentos dos dentes inferiores, do primeiro molar direito ao primeiro molar esquerdo. Resultados: A forma da arcada teve um efeito maior no movimento dos dentes do que o tamanho do contato interproximal. Arcadas triangulares e contatos ponto a ponto produziram os maiores deslocamentos e rotações dos dentes. Arcadas ovais com pontos de contato interproximal de 2 mm de largura apresentaram maior estabilidade. O primeiro pré-molar direito apresentou os maiores deslocamentos em todos os modelos. Conclusões: O formato da arcada e o tamanho do contato interproximal afetam a estabilidade dos dentes. Os dentes foram menos estáveis nas arcadas estreitas com contatos interproximais ponto a ponto, e mais estáveis nas arcadas mais largas com contatos maiores.

Morphological changes of dental and basal arch forms in skeletal class Ⅱ malocclusions before and after extraction treatment / 中华医学美学美容杂志

Objective To study the variation of the dental and basal arch forms before and after orthodontic treatment of patients with skeletal class Ⅱ malocclusion by tooth extraction.Methods The mandibular dental casts of 25 skeletal class Ⅱ patients were laser scanned before and after treatment.The facial axis (FA) points,which were used to represent the dental arch,and the WALA point,which were used to represent the basal bone,were identified for each tooth from the right first molar to the left first molar.We constructed the curve with points of projection of the FA and WALA point on the reference plane,and compared the curve of dental arch and basal bone before and after treatment.Results The width of anterior middle and posterior of the basal arch increased (0.835± 1.259) mm,(1.700±1.280) mm and (2.170±1.227) mm,respectively.While the dental arch had a wider width (1.110±1.566) mm in posterior segment but a narrower one in anterior (3.345±2.907) mm.Conclusions The width of middle and posterior of basal bone represented by WALA ridge becomes wider after orthodontic treatment with tooth extraction in patients with skeletal class Ⅱ malocclusion,while the dental arch turns to a new form,which is more coordinated to the basal bone.

Analysis of dimensions and shapes of maxillary and mandibular dental arch in Korean young adults

PURPOSE: The aim of this study was to investigate dental arch dimensions and to classify arch shape in Korean young adults. MATERIALS AND METHODS: The sample included 50 Koreans with age ranging from 24 to 32 years. Maxillary and mandibular casts were fabricated using irreversible hydrocolloid and type III dental stones. Incisor-canine distance, incisor-1(st) molar distance, incisor-2(nd) molar distance, intercanine distance, inter-1(st) molar distance, and inter-2(nd) molar distance in both the maxillary and mandibular arch were measured using a three-dimensional measuring device. The dental arch was classified into three groups using five ratios from the measured values by the K-means clustering method. The data were analyzed with one-way analysis of variance. RESULTS: Arch lengths (IM2D, incisal-2(nd) molar distance) were 44.13 mm in the maxilla and 40.40 mm in the mandible. Arch widths (M2W, inter 2(nd) molar width) were 64.12 mm in the maxilla and 56.37 mm in the mandible. Distribution of the dental arch form was mostly ovoid shape (maxilla 52% and mandible 56%), followed by the V-shape and the U-shape. The arch width for the U-shape was broader than for the other forms. CONCLUSION: This study establishes new reference data for dental arch dimensions for young Korean adults. The most common arch form is the ovoid type in the maxilla and mandible of Koreans. Clinicians should be aware of these references and classify arch type before and during their dental treatment for effective and harmonized results in Koreans.

Clinical study on the rapid maxillary and mandibular expansion companied with fixed appliance / 实用口腔医学杂志

Objective:To study the dental and skeletal changes after orthodontic treatment for malocclusion patients with rapid maxil-lary and mandibular expansion companied with fixed appliance.Methods:36 patients underwent the treatment with rapid maxillary and mandibular expansion companied with straight wire appliance.Pre-and post-treatment dental casts and lateral cephalometric radiographs were measured and compared.Results:After treatment,the maxillary and mandibular arch width perimeters increased(P 0.05).U1-SN and U1-NA decreased,L1-MP and L1-NB increased(P <0.05).Conclusion:Dental crowding can be solved effectively and occlusion re-lationship can be kept well with rapid maxillary and mandibular expansion companied with straight wire appliance without influence on the vertical skeletal relationship.

New classification of lingual arch form in normal occlusion using three dimensional virtual models / 대한치과교정학회지

OBJECTIVE: The purposes of this study were 1) to classify lingual dental arch form types based on the lingual bracket points and 2) to provide a new lingual arch form template based on this classification for clinical application through the analysis of three-dimensional virtual models of normal occlusion sample. METHODS: Maxillary and mandibular casts of 115 young adults with normal occlusion were scanned in their occluded positions and lingual bracket points were digitized on the virtual models by using Rapidform 2006 software. Sixty-eight cases (dataset 1) were used in K-means cluster analysis to classify arch forms with intercanine, interpremolar and intermolar widths and width/depth ratios as determinants. The best-fit curves of the mean arch forms were generated. The remaining cases (dataset 2) were mapped into the obtained clusters and a multivariate test was performed to assess the differences between the clusters. RESULTS: Four-cluster classification demonstrated maximum intercluster distance. Wide, narrow, tapering, and ovoid types were described according to the intercanine and intermolar widths and their best-fit curves were depicted. No significant differences in arch depths existed among the clusters. Strong to moderate correlations were found between maxillary and mandibular arch widths. CONCLUSIONS: Lingual arch forms have been classified into 4 types based on their anterior and posterior dimensions. A template of the 4 arch forms has been depicted. Three-dimensional analysis of the lingual bracket points provides more accurate identification of arch form and, consequently, archwire selection.

New classification of lingual arch form in normal occlusion using three dimensional virtual models / 대한치과교정학회지

OBJECTIVE: The purposes of this study were 1) to classify lingual dental arch form types based on the lingual bracket points and 2) to provide a new lingual arch form template based on this classification for clinical application through the analysis of three-dimensional virtual models of normal occlusion sample. METHODS: Maxillary and mandibular casts of 115 young adults with normal occlusion were scanned in their occluded positions and lingual bracket points were digitized on the virtual models by using Rapidform 2006 software. Sixty-eight cases (dataset 1) were used in K-means cluster analysis to classify arch forms with intercanine, interpremolar and intermolar widths and width/depth ratios as determinants. The best-fit curves of the mean arch forms were generated. The remaining cases (dataset 2) were mapped into the obtained clusters and a multivariate test was performed to assess the differences between the clusters. RESULTS: Four-cluster classification demonstrated maximum intercluster distance. Wide, narrow, tapering, and ovoid types were described according to the intercanine and intermolar widths and their best-fit curves were depicted. No significant differences in arch depths existed among the clusters. Strong to moderate correlations were found between maxillary and mandibular arch widths. CONCLUSIONS: Lingual arch forms have been classified into 4 types based on their anterior and posterior dimensions. A template of the 4 arch forms has been depicted. Three-dimensional analysis of the lingual bracket points provides more accurate identification of arch form and, consequently, archwire selection.

3-dimensional finite element analysis on stress distribution in maxillary with All-on-4 implants in different arch forms / 吉林大学学报(医学版)

Objective To explore the effect of different arch forms of maxillary models on stress distribution of peri-implant of All-on-4 implants with 3-dimensional finite element, and to provide evidence for the improvement of implant achievement ratio in clinic. Methods 3-dimensional finite element analysis models of Tapered,Square and Ovoid arch form maxillary based on the MBTTM Arch Form Templates were constructed by using Solidworks software.The cortical bone thickness was defined as 2 mm at all points.The implants with 13 mm in length were inserted between the mental foramina.The 2 posterior implants were set at 4 inclination angle,from 0°to 45°.All implants were splinted with superstructure.A 100 N pressure was applied to 2 kinds of loading positions on the superstructure models. The maximum Von-Mises stress on cortical bone around the implants was measured by using Abaqus software.Results The maximum Von-Mises value in maxillary cortical bone with All-on-4 implants in 3 arch forms showed significant differences. In Square model the concentration of stress was advanced with the increasing of implant inclination angle;In Ovoid model, the maximum Von-Mises value was observed at 1 5°in posterior region,and was increased significantly by pasted 15°in anterior region;In Tapered model,the Maximum Von-Mises value was increased greatly at 45°. Conclusion Arch forms have appreciable impact on stress distribution of peri-implant.In Square arch form,the inclination of implant should be avoided;in Ovoid arch form, the inclination angle should be under 15°;in Tapered arch form,the inclination should be under 30°.

The effect of dental arch on dental panoramic radiography / 中国医学装备

Through the analysis on principles of dental panoramic radiography, we analyzed the influence factors of the dental arch, and provided the main principles for optimizing design to improve the image quality. Through the analysis on the human dental arch’s form, we optimized the radiographic procedure. Many factors affect the quality panoramic image, but the focal trough’s design is one of the most important factors, especially for canine regions. Optimizing design of focal trough can lessen degrees of horizontal and vertical magnification, also can reduce geometric distortion and overlapped images of teeth.

Comparison between dental and basal arch forms in normal occlusion and Class III malocclusions utilizing cone-beam computed tomography / 대한치과교정학회지

OBJECTIVE: The purpose of this study was to investigate the relationship between the mandibular dental and basal arch forms in subjects with normal occlusion and compare them with those of Class III malocclusion using cone-beam computed tomography (CBCT). METHODS: CBCT images of 32 normal occlusion (19 males, 13 females; 24.3 years) and 33 Class III malocclusion subjects (20 males, 13 females, 22.2 years) were selected. Facial axis and root center points were identified from the left to right mandibular first molars. Distances between the facial axis and root center points for each tooth were calculated, and 4 linear and 2 ratio variables were measured and calculated for each arch form. The variables were compared between groups by independent t-test. Pearson correlation coefficient was applied to assess the relationships between dental and basal variables within each group. RESULTS: The mandibular dental and basal intercanine widths were significantly greater in the Class III group than in normal occlusion subjects (p < 0.05). The dental and basal intercanine widths as well as the dental and basal intermolar widths were strongly correlated in normal occlusion and moderately correlated in Class III malocclusion. CONCLUSIONS: The dental arch form demon strated a strong positive correlation with the basal arch form in the normal occlusion group and moderate correlation in the Class III malocclusion group. These results might be helpful for clinicians to have a better understanding of the importance of basal arch form in the alveolar bone.

Comparison of mandibular arch forms of Korean and Vietnamese patients by using facial axis points on three-dimensional models / 대한치과교정학회지

OBJECTIVE: This study was aimed at comparing the mandibular arch forms of Korean and Vietnamese patients by using facial axis (FA) points on three-dimensional (3D) models. METHODS: Mandibular casts of 68 Korean (Class I malocclusion, 30; Class II malocclusion, 38) and 78 Vietnamese (Class I malocclusion, 41; Class II malocclusion, 37) patients were scanned in their occluded positions and grouped according to arch form (tapered, ovoid, and square). The FA point of each tooth was digitized on the 3D mandibular models. The measurements and frequency distributions of the arch forms were compared between the ethnic groups. RESULTS: The Vietnamese patients had significantly greater intercanine depth and intercanine and intermolar width-to-depth ratios than the Korean patients (p < 0.05). The frequency distributions of the arch forms were also significantly different (p = 0.038), but no sexual dimorphism was found. CONCLUSIONS: Vietnamese people tend to have deeper and wider arches than Korean people. The three arch forms are evenly distributed in Korean people, but Vietnamese people frequently have square arches. Clinicians should identify the correct arch form of an ethnic group before initiating orthodontic treatment.

A manutenção da forma do arco inferior: diagrama individualizado da forma de arco Mucha (DIFAM-UFF) / Lower arch form maintenance: mucha arch form individualized diagram (DIFAM-UFF)

A correta determinação e manutenção da forma do arco dentário inferior durante o tratamento ortodôntico constitui-se em importante fator de estabilidade por manter o equilíbrio entre a harmonia facial, os aspectos funcionais, os componentes musculares envolvidos e entre dentes inferiores e as bases ósseas. Este estudo objetivou avaliar os métodos descritos na literatura, bem como propor e descrever uma maneira simples e rápida de determinação individualizada da forma e tamanho do arco dentário inferior. Utilizou-se descrição pormenorizada da técnica para a determinação individualizada da forma do arco inferior e consequente confecção e utilização dos arcos metálicos para as diversas etapas do tratamento ortodôntico. Consiste na concepção e utilização de um diagrama composto por 20 formas e tamanhos de arcos impressos em acetato transparente, que é sobreposto ao modelo de gesso inicial do paciente, onde são virtualmente localizados 5 pontos e é assim escolhida a forma e tamanho que reproduza o arco inferior com maior fidelidade. A proposta descrita como Diagrama Individualizado da Forma de Arco Mucha (DIFAM-UFF) é considerado rápido e fácil de ser aplicado, além de contemplar várias formas com diferentes tamanhos, ao passo que outros métodos requerem mais tempo ou utilizam apenas uma forma com diferentes tamanhos. A utilização clínica deste método por mais de duas décadas tem se mostrado extremamente útil e prática, não requerendo maiores dispêndios de cálculo ou tempo por parte do operador, além de constituir um importante fator para resultados de excelência. O diagrama proposto por Mucha (DIFAM- UFF) é um método simples, prático e abrangente para a determinação e manutenção da forma e tamanho do arco inferior nos procedimentos ortodônticos.

The proper establishment and maintenance of the lower dental arch form during orthodontic treatment is an important stability factor since it maintains balance among facial harmony, functional aspects, muscle components involved, as well as between lower teeth and bone base. This study aimed to evaluate the methods reported in the literature, and propose and describe a simple and fast way of individualized determination of the shape and size of the lower dental arch. It was used a detailed description of the technique for determining individual arch form and consequent construction and utilization of lower steel arches for the different stages of orthodontic treatment. It consists of the design and use of a diagram with 20 shapes and sizes of arches printed on a transparent acetate that is superimposed on the original plaster model of the patient. Then 5 points are virtually located, and thus the size and shape that best reproduce the lower arch with reliability are chosen. The method described as Mucha’s Arch Form Individualized Diagram (DIFAM-UFF) is considered fast and easy to apply, and contemplate various shapes with different sizes, while other methods use basically only one form with different sizes. For more than two decades the clinical use of this method has been extremely helpful and useful in determining and maintaining the shape and form of the lower arch. Since it is not time-consuming and does not require calculation it can be considered as an important factor to achieve excellent results. The diagram proposed by Mucha (DIFAM-UFF) is a simple and practical method for determining and maintaining the shape and size of the lower jaw in orthodontic procedures.

Comparison of arch form between ethnic Malays and Malaysian Aborigines in Peninsular Malaysia / 대한치과교정학회지

OBJECTIVE: To determine and compare the frequency distribution of various arch shapes in ethnic Malays and Malaysian Aborigines in Peninsular Malaysia and to investigate the morphological differences of arch form between these two ethnic groups. METHODS: We examined 120 ethnic Malay study models (60 maxillary, 60 mandibular) and 129 Malaysian Aboriginal study models (66 maxillary, 63 mandibular). We marked 18 buccal tips and incisor line angles on each model, and digitized them using 2-dimensional coordinate system. Dental arches were classified as square, ovoid, or tapered by printing the scanned images and superimposing Orthoform arch templates on them. RESULTS: The most common maxillary arch shape in both ethnic groups was ovoid, as was the most common mandibular arch shape among ethnic Malay females. The rarest arch shape was square. Chi-square tests, indicated that only the distribution of the mandibular arch shape was significantly different between groups (p = 0.040). However, when compared using independent t-tests, there was no difference in the mean value of arch width between groups. Arch shape distribution was not different between genders of either ethnic group, except for the mandibular arch of ethnic Malays. CONCLUSIONS: Ethnic Malays and Malaysian Aborigines have similar dental arch dimensions and shapes.

Changes in mandibular transversal arch dimensions after rapid maxillary expansion procedure assessed through cone-beam computed tomography / 대한치과교정학회지

OBJECTIVE: This study aimed at evaluating the changes in mandibular arch widths and buccolingual inclinations of mandibular posterior teeth after rapid maxillary expansion (RME). METHODS: Baseline and post-expansion cone-beam computed tomographic (CBCT) images of patients who initially had bilateral posterior cross-bite and underwent RME with a banded-type expander were assessed in this study. The patients included 9 boys (mean age: 13.97 +/- 1.17 years) and 11 girls (mean age: 13.53 +/- 2.12 years). Images obtained 6 months after retention were available for 10 of these patients. Eighteen angular and 43 linear measurements were performed for the maxilla and mandible. The measurements were performed on frontally clipped images at the following time points; before expansion (T1), after expansion (T2), and after retention (T3). Statistical significance was assessed with paired sample t-test at p < 0.05. RESULTS: T1-T2 comparisons showed statistically significant post-RME increases for all measurements; similarly, T2-T1 and T3-T1 comparisons showed statistically significant changes. The maxillary linear and angular measurements showed decreases after expansion, and mandibular linear and angular measurements increased after retention. CONCLUSION: All mandibular arch widths increased and mandibular posterior teeth were uprighted after RME procedure.

A forma do arco dentário inferior na visão da literatura: [revisão] / The lower dental arch form in the literature viewpoint: [review]

OBJETIVO: esse trabalho teve como objetivo principal analisar a literatura relacionada a um relevante aspecto clínico, a configuração do arco dentário, salientando a importância da manutenção da forma original do arco dentário para se obter a estabilidade do tratamento ortodôntico, bem como avaliar os métodos utilizados para a determinação da forma do arco e os diagramas de forma propostos por diversos autores. RESULTADOS E CONCLUSÕES: constatou-se uma controvérsia quanto à indicação de uma forma ideal média e a seleção de uma forma individualizada a partir de diagramas que forneçam configurações variadas para o arco dentário. Entretanto, observou-se um progresso nas metodologias aplicadas nos recentes estudos, o que possivelmente fornecerá precisão nos próximos resultados.

AIM: The main purposes of this study were to analyze the literature related to a relevant clinic aspect, the dental arch form, emphasizing the importance of maintaining the original form in order to obtain stability after the orthodontic treatment, as well as to evaluate the methods used for establishing the dental arch form and the arch form diagrams proposed by many authors. RESULTS AND CONCLUSIONS: It was verified that there is some controversy regarding the indication of an ideal average form and the selection of an individualized form from diagrams which provide varied formats for the dental arch. However, some progress was observed in the methodologies applied in recent studies, which will possibly provide more accuracy in arch form determination in the near future.

Comparison of arch forms between Korean and Japanese in Class I, II, and III malocclusion / 대한치과교정학회지

OBJECTIVE: The purpose of this study was to compare arch dimensions and frequency distribution of arch forms between Korean and Japanese Class I, II, and III malocclusion groups. METHODS: The sample consisted of 368 Korean cases (114 Class I, 119 Class II, and 135 Class III malocclusion) and 160 Japanese cases (60 Class I, 50 Class II, and 50 Class III malocclusion). The most facial portion of 13 proximal contact areas was digitized from photocopied images of the mandibular dental arches. Clinical bracket slot points were calculated for each tooth based on mandibular tooth thickness data. Four linear and two proportional measurements were taken. Measurements are statistically analyzed in each malocclusion group. The dental arches were classified into square, ovoid, and tapered forms to determine and compare the frequency distributions between the two ethnic groups. RESULTS: The findings of this study showed that Japanese females in Class I and II groups had a statistically significant narrower mandibular dental arch width compared with the Japanese males, Korean males and Korean females. But in the Class III group, there was no significant difference in the mandibular dental arch size according to the two ethnic groups and genders. CONCLUSIONS: The majority of Koreans and Japanese in all the malocclusion groups exhibited square and ovoid arch forms. The most frequent arch forms found in Koreans was square but ovoid for Japanese.

Size and forms of the mandibular dental arch in Korean malocclusion patients / 대한치과교정학회지

The purpose of this study was to clarify morphological differences among mandibular dental arch forms in Korean malocclusion patients. The sample in this study consisted of 114 Class I, 119 Class II, and 135 Class III malocclusion cases. The most facial portions of 13 proximal contact areas were digitized from photocopied images of the mandibular dental arches. Clinical bracket points were calculated for each tooth based on the data of the mandibular tooth thickness. Four linear and two proportional measurements were undertaken. The dental arches were classified into square, ovoid, and tapered forms to compare the frequency distributions. Our results suggested that there was no single arch form specific to any particular Angle classification or sex. It appeared to be the frequency of a particular arch form that varies among the Angle classifications. In comparison of arch measurements between male and female, there was no statistical difference except in the intermolar width. In comparison of arch size measurements among the different Angle classifications, there were statistically significant differences between Class I and Class III malocclusion groups and between Class II and Class III malocclusion groups. In comparison of frequency distribution of arch forms in Class I and III malocclusion groups, the square form demonstrated the highest distribution followed by the ovoid and tapered forms in that order. In the Class II malocclusion group, the square form showed the highest distribution, followed by the tapered and ovoid forms in that order. There was no statistical difference in the frequency distribution of arch forms between male and female groups.

Mandibular clinical arch forms in Koreans with normal occlusions / 대한치과교정학회지

The purpose of this study was to clarify morphologic characteristics between mandibular clinical arch forms in Koreans with normal occlusions. The study included data from 102 Koreans. The most facial portion of 13 proximal contact areas was digitized from photocopied images of the mandibular dental arches. Clinical bracket points were calculated for each tooth based on mandibular tooth thickness data. Four linear and two proportional measurements were taken. The dental arches were classified into ovoid, square and tapered forms. The frequency distributions of the three mandibular arch form classifications were determined and compared between male and female subjects. No significant differences in arch form size were found between the sexes. However, there were a few differences in molar width. It was useful to classify mandibular clinical arch forms present in normal occlusion samples into ovoid, square and tapered categories. The frequency of the ovoid form was the highest, and that of the square form was the second highest. The tapered arch form was found in less than 10 percent of subjects. No significant differences in their frequency distributions and dimensions were shown between males and females.

The new approach to maxillary and mandibular anterior dental arch forms: The prediction to maxillary and mandibular anterior occlusal relationship by computer program / 대한치과교정학회지

When we deal with maxillary and mandibular anterior dental arches showing problems in occlusal relation and aesthetics caused by malformations of teeth and congenital missing, et al during the orthodontic treatment, we could not often decide the functional occlusion by only relying on the orthodontic treatment. If orthodontists can predict what kinds of treatments are needed for functional occlusion in maxillary and mandibular anterior dental arches, they can not only effectively treat patients but also facilitate the cooperation with other field during the treatment. Our previous research showed the correlation among intercanine width, segment depth and arch perimeter by using the Korean normal occlusion model. At this time, we produced the computer application program by taking advantage of this correlation. And then, we applied this program to setting up the treatment plans for 2 patients with the damaged maxillary and mandibular dentures. With the help of this program, we could not only easily acquire the information about the change of variables required by treatment plans but also understand the change of the anterior dental occlusion corresponding to the change of each variables such as the intercanine width, segment depth and arch perimeter. Later, if we can have the information about the relationship between the change of the angle of incisors depending on facial types and arch forms and, in addition, can acquire the appropriate intercanine width, we can have the ability to produce the 3 dimensional occlusogram for the anterior dental arch forms.

The new approach to maxillary and mandibular anterior dental arch forms : In Korean normal occlusion models / 대한치과교정학회지

Maxillary and mandibular anterior dental arches often have the problems of occlusal relation and esthetics by malformations of teeth, congenital missing, et al. Though the clinician usually use the anterior ratio to overcome this problems, he has the limitation of a direct application this ratio to the prediction of anterior occlusal relationship by the change of anterior ratio as dental arch form, intercanine width, segment depth and arch perimeter. So this study examine maxillary and mandibular anterior dental arch forms by least square method using Korean normal occlusion models(man : 20 casts, woman : 20 casts). Maxillary and mandibular anterior dental arches of Korean normal occlusion models are curve fitted to polynomial function, beta function, hyperbolic cosine function in order. And this accuracy of curve fitting is constant regardless of man/woman and maxilla/mandible. The relationships between intercanine width, segment depth, and arch perimeter based on this curve fitted dental arch form are acquired. This relationships will give the prediction of anterior dental arch form and the information of more accurate anterior ratio according to intercanine width.

Difference in dental arch form between Angle Ⅱ division 1 and normal occlusion assessed by Euclidean distance matrix analysis / 实用口腔医学杂志

Objective: To evaluate differences in dental arch forms between the subjects with Angle II division 1(AngleⅡ1 ) and those with normal occlusion. Methods:60 AngleⅡ1 patients and 60 normal occlusion subjects aged 13-17 years old were selected. Fourteen landmarks, corresponding to the cusp tips and incisor edges, were identified on the upper and lower dental casts of all subjects by YM-21115 three dimension measuring machine. Arch form differences between AngleⅡ1 and normal occlusion subjects were assessed by Euclidean distance matrix analysis (EDMA). Results:(1) In both sexes, the upper arch of AngleⅡ1 subjects was larger than that of normal occlusion (1.8% for females and 2.7% for males); and arch shape difference was also significantly different(P