Dimensions and form of dental arches in subjects with normal occlusions

Three-dimensional of lingual arch form and creation of templates in Iraqi normal occlusion

OBJECTIVES

To evaluate the lingual dental arch form types in class I canine and molar relationship based on scanning dental cast models using three-dimensional laser scan and to give a new lingual arch form pattern created on this classification to be used for clinical submission by studying three-dimensional virtual models of the normal occlusion samples.

MATERIALS AND METHODS

Maxillary and mandibular casts of 120 young adults (18-24 ± 1.84 years) have normal occlusion that was scanned using a 3Shape E1 laser scanner, and then, the data were analyzed using SPSS software; then, we used K-means cluster to classify the arch form into clusters depending on the measurement of 10 landmarks designated on the lingual surface of the teeth.

RESULTS

Many dental arch patterns have been established for both the mandible and the maxilla.

CONCLUSION

The minimum sizes were found in the females, and the biggest sizes were found in the male subjects, and three sets were well defined for each sex; three categories for each mandible and maxilla are as follows: narrow, mid, and broad. The lingual arch form can be classified into three groups based on posterior and anterior dimensions, so a template of the three arch forms has been exemplified.

Characteristics of Mandibular Arch Forms in Patients with Skeletal Mandibular Prognathism

Arch forms in orthodontics are considered to affect occlusal stability. This study's subjects were 47 patients (Class III S group) who visited the Chiba Dental Center of Tokyo Dental College and were surgical orthodontic cases, and 60 patients with Class I malocclusion were selected as the control group. A mandibular model of each subject was plotted with each tooth on a digitizer. The clinical bracket points of each tooth were plotted, and intercanine and intermolar measurements were taken. The least squares method was used to fit a quartic equation, and the arch form was drawn. The Class IIIS group was divided by Wits appraisal and facial pattern into a dolichofacial or brachyfacial pattern, and arch forms were compared. The results show that the Class IIIS group had a significantly smaller intermolar width, canine depth, and molar depth and a significantly larger canine W/D ratio. In those with a dolichofacial pattern, the anterior curve of the arch form tended to be flat and the posterior curve narrower. This is because, in skeletal mandibular prognathism, the mandibular anterior shows lingual tipping, and the molars show palatal tipping due to dental compensation, and it was inferred that this tendency was higher in high-angle cases.

Developing a three-dimensional statistical shape model of normal dentition using an automated algorithm and normal samples

OBJECTIVES

The statistical shape model (SSM) is a model of geometric properties of a set of shapes based on statistical shape analysis. The SSM develops an average model of several objects using an automated algorithm that excludes the operator's subjectivity. The aim of this study was to develop a three-dimensional (3D) SSM of normal dentition to provide virtual templates for efficient treatment.

MATERIALS AND METHODS

Dental casts were obtained from participants with normal dentition. After acquiring the 3D models, the SSMs of the individual teeth and whole dental arch were generated by an iterative closest point (ICP)-based rigid registration and point correspondences, respectively. Then, the individual tooth SSM was aligned to the whole dental arch SSM using ICP-based registration to generate an average model of normal dentition.

RESULTS

The generated 3D SSM showed specific morphological features of normal dentition similar to those previously reported. Moreover, on measuring the arch dimensions, all values in this study were similar to those previously reported using normal dentition.

CONCLUSIONS

The 3D SSM of normal dentition may increase the diagnostic efficiency of orthodontic treatments by providing a visual objective. It can be also used as a 3D template in various fields of dentistry.

CLINICAL RELEVANCE

Our SSM of normal dentition provides both quantitative and qualitative information on the 3D morphology of teeth and dental arches, which may provide valuable information on 3D virtual-setup, bracket fabrication, and aligner treatment.

Mandibular Clinical Arch Forms in Iraqi Population: A National Survey

Background: This study aims to identify mandibular clinical arch forms and dimensions in the Iraqi population. Materials and methods: The study sample consisted of pre-treatment mandibular study models of the Iraqi population. The most labial aspect of 13 proximal contact areas was digitized using AutoCAD software to determine the clinical bracket point for every tooth. The dental arches were classified into three types: tapered, ovoid, and square. The arch dimensions were identified using four linear and two proportional measurements. Results: A total of 1005 study models were collected. The arch forms were distributed as ovoid (47%), tapered (36.2%), and square (16.8%), with no significant difference in the distribution between Arabs and Kurds. The ovoid arch form was predominant in class I and class III malocclusion, while the tapered arch form was predominant in class II. All the linear measurements were greater in the males than in the females. The arch widths decreased as the arch form shifted from square to ovoid to tapered, while the arch depths showed the reverse relation. Conclusions: According to this study, ovoid and tapered archwires should suit the majority of Iraqi patients. The ovoid arch form was the most predominant in the subjects with class I and class III malocclusion, while the tapered arch form was the most predominant in the class II subjects.

Morphometric analysis of maxillary arch dimensions using Cone Beam Computer Tomography (CBCT)

Knowledge of morphology of the maxillary arch is important in many spacialities of dentistry. This retrospective cross-sectional study was performed using 109 randomly selected maxillary CBCT images of patients in the age range of 18-60 from the archives in Faculty of Dental Sciences, University of Peradeniya, Sri Lanka. EzDent software was used for measurements. Measurements related to the width were acquired from coronal sections while the measurements related to antero-posterior dimensions were performed on axial sections. A majority had an oval shaped maxillary arch (64.8%) followed by V shaped one.(29.2%). The mean height of the alveolar ridge at the upper canine position was 8.9 mm and the mean height of the alveolar ridge at the first molar level was 20.1 mm. Mann Whitney U test was used to compare measurements of variables between males and females. Difference in the height of alveolar ridge at the junction of soft and hard palate, width of the alveolar ridge at the canine, first molar and second molar and also the antero-posterior distance of the arch at the inter canine distance and junction between the hard and soft palate were statistically significant. Kruskal Wallis test was used to compare the differences between age groups. Chisquare values didnot indicate significant differences of measurements according to the age group of the participants. In conclusion, there is a significant difference in all maxillary arch parameters between the different genders. No significant differences in arch parameters were observed among the different age groups.

Development of a maxillomandibular arch form based on the center of resistance of teeth using cone-beam computed tomography

INTRODUCTION

Controlling transverse discrepancies is necessary to ensure stable and functional occlusion. Altered molar inclinations can camouflage the transverse relationship. The purpose of this research was to evaluate the maxillomandibular relationship of the center of resistance (CR) of the arch form created by the CR of teeth and compare these CR arch forms by their skeletal patterns.

METHODS

Sixty patients with minor crowding and normal posterior overjet were divided into 3 groups according to ANB angle: skeletal Class I group had ANB angle between 0° and 4° (n = 20), skeletal Class II group had ANB angle >4° (n = 20), and skeletal Class III group had ANB angle <0° (n = 20). The 3-dimensional coordinates of the CR were estimated using cone-beam computed tomography images and projected on the CR occlusal plane to obtain the 2-dimensional coordinates. The CR arch forms were constructed and evaluated using Matlab (MathWorks, Natick, Mass).

RESULTS

On comparing maxillomandibular CR arch form widths, the maxilla was significantly larger than the mandible of the canine and first premolar. The mandible was larger in the first molar of the skeletal Class III group. The maxillomandibular CR arch form width ratios were between 0.97 and 1.35. On comparing maxillomandibular CR arch form areas, the maxilla was significantly larger than the mandible in the anterior segment, and the mandible was larger in the posterior segment. The ratios were between 0.86 and 2.25. In between-group comparison, the skeletal Class III group showed significantly greater arch forms in the mandible.

CONCLUSIONS

CR arch forms had significant maxillomandibular differences throughout the arch. The maxillomandibular ratios could be a reference for site-specific transverse discrepancy analysis.

Estimation of the Intercanine Width, Intermolar Width, Arch Length, and Arch Perimeter and Its Comparison in 12-17-year-old Children of Faridabad

Context

Dental arch morphology is an important consideration in the orthodontic treatment of dentofacial deformities. The size and shape of the arches have considerable implications in treatment planning, affecting space available, dental esthetics, and stability of dentition. The data provided by this study will be of considerable importance and relevance for practicing orthodontists and pedodontists in the region of Faridabad

Aim and objective

This study aims to determine and compare the intercanine width, intermolar width, arch length, and arch perimeter in the early adolescent group (12–14 years) and middle adolescent group (15–17 years) of Faridabad.

Materials and methods

Maxillary and mandibular impressions were made, study casts were prepared then the measurement of the individual intercanine widths, intermolar widths, arch length of maxillary and mandibular casts with the digital caliper, and arch perimeter with the help of brass wire was taken, obtained values were calculated, hence the results were evaluated.

Statistical analysis

Data were entered into a Microsoft Excel spreadsheet. It was analyzed using Statistical Package for Social Sciences (SPSS) version 21. Graphs were prepared using Microsoft Excel. Data were normally distributed as tested using the Shapiro-Wilk W test (p value was <0.05). Inferential statistics were performed using independent Student's t-test. The level of significance was set at 0.05.

Results

In the present study, all the parameters measured were increased in males in both the age-groups, i.e., the early adolescent group (12–14 years) and the mid adolescent group (15–17 years), and a significant increase was seen in the intercanine and intermolar widths in males.

How to cite this article

Singh S, Saraf BG, Indushekhar KR, et al. Estimation of the Intercanine Width, Intermolar Width, Arch Length, and Arch Perimeter and Its Comparison in 12–17-year-old Children of Faridabad. Int J Clin Pediatr Dent 2021;14(3):369–375.

3D technology to measure dental arches and create a template for lingual brackets technique

Objective:

This study aims at identifying anatomical dimensions of dental arches, based on landmarks currently used in the lingual orthodontic technique, and create an archwire form template to be used in orthodontic clinics.

Methods:

Maxillary and mandibular dental casts of 140 Caucasian individuals with natural and normal occlusion were digitized (3D), and the images were analyzed with Delcam Power Shape^TM 2010 software. The dental arch shapes and sizes were obtained from 14 landmarks selected on the lingual surface of the teeth. Points and segments defined by the software were used to create an archwire form template.

Results:

Various dental arch patterns were found for both maxilla and mandible. The smallest sizes were found in females, and the largest were found in male subjects. Six categories were defined for each gender, three for the maxilla and three for the mandible (Small, Medium and Large). A template was created with eighteen anatomic lingual archwire designs, nine for the maxilla and nine for the mandible, for both genders.

Conclusions:

Landmarks evaluated in this study showed dental arch differences between genders. This information enables making orthodontic lingual archwires that are more compatible with the anatomical forms and sizes of the maxilla and mandible. The findings also allowed the creation of a template for an anatomic lingual metallic archwire form to be used in the lingual technique.

Maxillary and mandibular dental arch forms in a Jordanian population with normal occlusion

Background

Ethnic background has been claimed to affect arch form. The purpose of this study was to describe and elucidate the maxillary and mandibular arch forms in Jordanian population and to develop a classification method for these forms which could be employed to construct orthodontic archwires accordingly.

Methods

The sample was comprised of study casts of five hundred and twenty subjects (231 males and 289 females with a mean age of 15.4 ± 1.02 years). All subjects had permanent dentition with normal occlusion. A mathematical method associated with a polynomial function of 6th degree was employed to assess the dental arch forms. The resultant arch forms were classified into 5 groups for both the maxilla and mandible utilizing a computer software with special code designed for this study. Each group was subdivided into 3 subgroup sizes namely: small, medium, and large.

Results

Catenary arch form was found in 47% and 41.2% (p ˂ 0.01) of maxilla and mandible arch forms, respectively. Form 2 (which is halfway between ellipse and U-shaped arch form) was found in 27.7% and 26.7%. Medium size arch form was found in 55.4% of the maxillary and 65.6% of the mandibular arch forms.

Conclusion

Catenary arch form was the most prevalent arch form, followed by wide elliptical form. The other forms, which included tudor arch, tapered equilateral and quadrangular forms were less frequent. Regarding size, the medium size was the most prevalent among the studied samples.

Design of an Intraoral Dipole Antenna for Dental Applications

OBJECTIVE

In dental MRI, intraoral coils provide higher signal-to-noise ratio (SNR) than coils placed outside the mouth. This study aims to design an intraoral dipole antenna and demonstrates the feasibility of combining it with an extraoral coil.

METHODS

Dipole antenna design was chosen over loop design, as it is open toward the distal; therefore, it does not restrain tongue movement. The dipole design offers also an increased depth-of-sensitivity that allows for MRI of dental roots. Different dipole antenna designs were simulated using a finite-difference-time-domain approach. Ribbon, wire, and multi-wire arms were compared. The best design was improved further by covering the ends of the dipole arms with a high-permittivity material. Phantom and in vivo measurements were conducted on a 3T clinical MRI system.

RESULTS

The best transmit efficiency and homogeneity was achieved with a multi-wire curved dipole antenna with 7 wires for each arm. With an additional high-permittivity cap the transmit field inhomogeneity was further reduced from 20% to 5% along the dipole arm. When combined with extraoral flexible surface-coil, the coupling between the coils was less than -32dB and SNR was increased.

CONCLUSION

Using intraoral dipole design instead of loop improves patient comfort. We demonstrated feasibility of the intraoral dipole combined with an extraoral flexible coil-array for dental MRI. Dipole antenna enabled decreasing imaging field-of-view, and reduced the prevalent signal from tongue.

SIGNIFICANCE

This study highlights the advantages and the main challenges of the intraoral RF coils and describes a novel RF coil that addresses those challenges.

<p>Analysis of Lingual Arch Form in Dental Students of Nepal with Normal Occlusion</p>

Background

The objectives of this study were to describe and classify lingual arch form in dental students with normal occlusion and explore the possibility to provide a lingual arch form template for Nepalese population.

Methods

The occlusion and arch form of 220 undergraduate dental students were analyzed and thirty-three subjects (14 males, 19 females) fulfilling the inclusion criteria were selected for the study. Reference points were drawn on the lingual surfaces of the teeth of study model using an indelible marker. A transparent ruled grid was used to obtain x and y coordinate values of the reference point. Following distances were measured with a digital caliper: inter-canine width, inter-molar width, inter-second molar width, canine depth, first molar depth, and second molar depth. Two-step cluster analysis was used to further classify the arch. The mean reference point values of each cluster were entered into the software (CurveExpert 1.4, Hymas developers). The curve finder tool of the software was used to obtain the curve which best described the arch forms.

Results

Two-step cluster analysis identified two distinguished clusters of lingual arch forms. Tenth degree polynomial was chosen as the best possible fit for lingual arch forms by using Curvefinder tool of the software CurveExpert 1.4.

Conclusion

Two types of anatomical lingual arch forms derived from Nepalese dental students with normal occlusion have been described and templates for the same have been generated.

Differences in dental arch characteristics between genders in patients with suspected condylar hyperplasia in a North Sumatra subpopulation: a cross-sectional study

Background: Condylar Hyperplasia (CH) is a self-limiting mandibular condyle disorder that shows asymmetry progress in conjunction with associated occlusal changes as long as condylar growth is still active and leads to facial asymmetry. This study aimed to analysis the difference of dental arch characteristics  based on genders in orthodontic patients with suspected CH in a North Sumatra subpopulation.

Methods: This is a retrospective study of suspected CH patient’s clinical records who sought for the initial orthodontic treatment between January 2015 to March 2019. Patient with facial asymmetry (based on photography, posterior crossbite and midline deviation), the positive temporomandibular joint disorder in functional analysis, and no history of facial trauma were included in the study. Dental arch asymmetry was based on the measurement of dental midline deviation, canine tip in the dental arch, the distance of the upper canines from the palatal suture, and inter canine distance. The evaluation of dental arch was achieved by comparing arch width and length.

Results: There was a significant difference (p<0.05) of upper canine distance from the palatal suture in female patients when evaluating upper dental arch asymmetry. There was a moderate correlation (r=0.379) in midline deviation between upper and lower dental arch. The dimension and dental arch form were mid and flat, and there was moderate correlation (r=0.448) between the upper and lower dental arch form in these suspected CH patients.

Conclusion: Indeed skeletal asymmetry, the evaluation of the dental arch characteristic symmetry and arch form showed asymmetric occlusal characteristics in orthodontics patient with suspected  CH in the North Sumatera subpopulation. In treating these patients, we recommend the plaster cast evaluation as essential and routine procedure in order to understand the complexity of occlusal change due to active growth of condylar and limitation in radiography evaluation.

Lower Arch Dimensions in Children with Anterior Open Bite and Normal Vertical Overbite: A Cross-sectional Study

Aim

Dental arch is a dynamic structure and its size depends on genetic and environmental factors. The aim of this study was to determine lower arch dimensions in children between 8 and 16 years with anterior open bite (AOB) and normal vertical overbite (NVO).

Materials and Methods

A cross-sectional study was performed in 132 individuals with AOB and 132 with NVO between 8 and 16 years selected from public schools. Intercanine width, arch length, intermolar and interpremolar distances, and arch perimeter of the lower arch were measured in previously digitalized models using the GOM inspection program and an optical three-dimensional scanner.

Results

Individuals with NVO presented smaller lower arch size with statistical differences in intercanine (P = 0.024, 95% confidence interval [CI]: 0.01, 0.02) and intermolar (P = 0.000, 95% CI: -1.76, -0.53) width and nonsignificant differences in the arch perimeter (P = 0.239, 95% CI: -1.57, 0.39) according to Mann-Whitney U-test.

Conclusion

Individuals between 8 and 16 years of age with NVO showed smaller lower dental arch than individuals with AOB in most dimensions.

Malpositions of anterior teeth was conducted by using form investigation based on sex

Malpositioned anteriors teeth can aethetically influence, self-appearance, the function of mastication and speech. Malpositioned teeth refers to altered positioning of one or more teeth from a well-alligned jaw. In general, boy’s jaw is bigger than girl’s. This enable to makes difference risk of malpositioned anteriors teeth between boy and girl. The aim of this study to find information about to detect risk difference malpositioned anteriors teeth in student of SMPN 6 Yogyakarta based on sex. Research used observational with cross sectional. The subjects of study were entire student of class VII SMPN 6 Yogyakarta that fulfil criteria and got that is 211 students are 91 students of boy and 120 of girl students. The objects of this study are jaw of anteriors teeth on and lower jaw. The evaluation malpositioned anteriors teeth was conducted by using form investigation based on sex are boy and girl, evaluation appropriate criteria prevalence malpositioned anteriors teeth which cover mesioversion, distoversion, buccoversion, palatoversion, linguoversion, labioversion, torsiversion, transversion and axiversion was scored 1, while normal position was scored 0. The results of the research were obtained by applying statistics method which used cross tabulation to obtain Odds Ratio (OR) and appropriate magnitude OR = 0.59, OR < 1 (Protective risk factor), that meaning boy sex will be protected to the happening malpositioned anteriors is compared boy sex. From the research, it can be concluded that risk malpositioned anteriors teeth in girl student SMPN 6 Yogyakarta which was high than boy students.

Digital models: How can dental arch form be verified chairside?

Introduction:

Plaster dental casts are routinely used during clinical practice to access maxillary dental arch form and assist on fabrication of individualized orthodontic archwires. Recently introduced, digital model technology may offer a limitation for the obtainment of a dental physical record. In this context, a tool for dental arch form assessment for chairside use is necessary when employing digital models. In this regard, paper print of the dental arch seems thus to be useful.

Methods:

In the present study, 37 lower arch models were used. Intercanine and intermolar widths and dental arch length measurements were performed and compared using plaster dental casts, digital models and paper print image of the models. Ortho Insight 3D scanner was employed for model digitalization.

Results:

No statistically significant differences were noted regarding the measurements performed on the plaster or digital models (p> 0.05). Paper print images, however, showed subestimated values for intercanine and intermolar widths and overestimated values for dental arch length. Despite being statistically significant (p< 0.001), the differences were considered clinically negligible.

Conclusion:

The present study suggests that paper print images obtained from digital models are clinically accurate and can be used as a tool for dental arch form assessment for fabrication of individualized orthodontic archwires.

Dental arch dimensions, form and tooth size ratio among a Saudi sample

Objectives:

To determine the dental arch dimensions and arch forms in a sample of Saudi orthodontic patients, to investigate the prevalence of Bolton anterior and overall tooth size discrepancies, and to compare the effect of gender on the measured parameters.

Methods:

This study is a biometric analysis of dental casts of 149 young adults recruited from different orthodontic centers in Jeddah, Saudi Arabia. The dental arch dimensions were measured. The measured parameters were arch length, arch width, Bolton’s ratio, and arch form. The data were analyzed using IBM SPSS software version 22.0 (IBM Corporation, New York, USA); this cross-sectional study was conducted between April 2015 and May 2016.

Results:

Dental arch measurements, including inter-canine and inter-molar distance, were found to be significantly greater in males than females (p<0.05). The most prevalent dental arch forms were narrow tapered (50.3%) and narrow ovoid (34.2%), respectively. The prevalence of tooth size discrepancy in all cases was 43.6% for anterior ratio and 24.8% for overall ratio. The mean Bolton’s anterior ratio in all malocclusion classes was 79.81%, whereas the mean Bolton’s overall ratio was 92.21%. There was no significant difference between males and females regarding Bolton’s ratio.

Conclusion:

The most prevalent arch form was narrow tapered, followed by narrow ovoid. Males generally had larger dental arch measurements than females, and the prevalence of tooth size discrepancy was more in Bolton’s anterior teeth ratio than in overall ratio.

Palatal dimensions at different stages of dentition in 5 to 18-year-old Iranian children and adolescent with normal occlusion

BACKGROUND

This study was purposed to evaluate palatal width, height, and height index at various stages of dentition in Iranian children and adolescent with normal occlusion.

METHODS

This cross-sectional study was conducted on a random sample of 237 children (45% male and 55% female, aged 5-18 years) with normal occlusion selected from kindergartens and elementary and high schools in Hamadan, Iran. The subjects were clinically examined and classified based on dentition to primary (21.5%), mixed (21.9%), and permanent (56.5%) stages. Dental casts were obtained from all subjects. Palatal width (inter-molar and -canine distances), and height (at molar and canine areas) were measured on the casts by Korkhaus' compass and digital caliper. Palatal height index was calculated for each dentition stage. Data were analyzed by SPSS 15 using one-way ANOVA followed by Tukey's post hoc test and t- test (p <  0.05).

RESULTS

Palatal inter-molar and -canine width values were increased from primary to permanent dentition. Palatal height and palatal height index in mixed dentition were significantly lower than those in primary and permanent dentition. Palatal width at inter-molar and -canine distances was significantly higher in males than females. There was no significant difference in palatal height and palatal height index at molar area between males and females. However, palatal height and palatal height index at canine area were significantly higher in males compared to females.

CONCLUSION

These findings showed that palatal width increased from primary to permanent stage. Palatal height and palatal height index decrease from primary to mixed dentation, then increase from mixed to permanent dentition.

Comparison of arch forms between Turkish and North American

Objective:

The aim of this study was to clarify the morphological differences in the mandibular arches of Turkish and North American white subjects.

Methods:

The sample included 132 Turkish (34 Class I, 58 Class II, and 40 Class III) and 160 North American (60 Class I, 50 Class II, and 50 Class III) subjects. The most facial portion of 13 proximal contact areas was digitized from photocopied images of patients' 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 subjects were grouped according to arch form types (tapered, ovoid and square) in order to have frequency distribution compared between ethnic groups in each Angle classification.

Results:

The Turkish group showed significantly lower molar depth and more significant molar width-depth (W/D) ratio in all three Angle classifications. On the other hand, the Turkish group also showed a significantly larger intercanine width in Class III malocclusion and intermolar width in Class II malocclusion. The most frequent arch forms seen were the ovoid arch form in the Turkish group and the tapered form in the white group.

Conclusions:

Our results demonstrate that when treating Turkish patients, one should expect to use preformed ovoid arch form orthodontic wires in a significant percentage of patients.

Evaluation of the Relationship between Curve of Spee, WALA-FA Distance and Curve of Wilson in Normal Occlusion

Objective

To test the hypotheses that (i) there is a significant correlation between the curve of Spee (COS), basal arch (WALA ridge) to dental arch distance (WALA-FA distance) and curve of Wilson (CW) and that (ii) the deepening of the COS is affected by the CW and the WALA-FA distance.

Methods

Mandibular models of 50 patients aged between 20 and 35 years were scanned with TRIOS. The xyz coordinate system was determined, and a reference occlusal plane was generated. The depth of the COS, the CW, and WALA-FA distance were measured using an engineering software.

Results

The greatest difference in the measurement of the depth of the COS between the right and left was found to be 0.41±0.50 mm in the first molar teeth. On the basis of the results of Pearson correlation analysis, there was no strong correlation between the depth of the COS, the CW, and the WALA-FA distance.

Conclusion

It was shown that there was no strong correlation between the depth of COS, CW, and WALA-FA distance. The CW and WALA-FA distance could not be effective in the deepening of the COS.

Shape variation and covariation of upper and lower dental arches of an orthodontic population

OBJECTIVES

This study aimed to quantify the patterns of shape variability and the extent and patterns of shape covariation between the upper and lower dental arch in an orthodontic population.

METHODS

Dental casts of 133 white subjects (61 males, 72 females; ages 10.6-26.6) were scanned and digitized in three dimensions. Landmarks were placed on the incisal margins and on the cusps of canines, premolars, and molars. Geometric morphometric methods were applied (Procrustes superimposition and principal component analysis). Sexual dimorphism and allometry were evaluated with permutation tests and age-size and age-shape correlations were computed. Two-block partial least squares analysis was used to assess covariation of shape.

RESULTS

The first four principal components represented shape patterns that are often encountered and recognized in clinical practice, accounting for 6-31 per cent of total variance. No shape sexual dimorphism was found, nevertheless, there was statistically significant size difference between males and females. Allometry was statistically significant, but low (upper: R(2) = 0.0528, P < 0.000, lower: R (2) = 0.0587, P < 0.000). Age and shape were weakly correlated (upper: R(2) = 0.0370, P = 0.0001, lower: R (2) = 0.0587, P = 0.0046). Upper and lower arches covaried significantly (RV coefficient: 33 per cent). The main pattern of covariation between the dental arches was arch width (80 per cent of total covariance); the second component related the maxillary canine vertical position to the mandibular canine labiolingual position (11 per cent of total covariance).

LIMITATIONS

Results may not be applicable to the general population. Age range was wide and age-related findings are limited by the cross-sectional design. Aetiology of malocclusion was also not considered.

CONCLUSIONS

Covariation patterns showed that the dental arches were integrated in width and depth. Integration in the vertical dimension was weak, mainly restricted to maxillary canine position.

Is arch form influenced by sagittal molar relationship or Bolton tooth-size discrepancy?

Background

Orthodontic patients show high prevalence of tooth-size discrepancy. This study investigates the possible association between arch form, clinically significant tooth-size discrepancy, and sagittal molar relationship.

Methods

Pretreatment orthodontic casts of 230 Saudi patients were classified into one of three arch form types (tapered, ovoid, and square) using digitally scanned images of the mandibular arches. Bolton ratio was calculated, sagittal molar relationship was defined according to Angle classification, and correlations were analyzed using ANOVA, chi-square, and t-tests.

Results

No single arch form was significantly more common than the others. Furthermore, no association was observed between the presence of significant Bolton discrepancy and the sagittal molar relationship or arch form. Overall Bolton discrepancy is significantly more prevalent in males.

Conclusions

Arch form in a Saudi patient group is independent of gender, sagittal molar relationship, and Bolton discrepancy.

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

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.

Determining shapes and dimensions of dental arches for the use of straight-wire arches in lingual technique

INTRODUCTION:

This study aims to determine the shape and dimension of dental arches from a lingual perspective, and determine shape and size of a straight archwire used for lingual Orthodontics.

METHODS:

The study sample comprised 70 Caucasian Brazilian individuals with normal occlusion and at least four of Andrew's six keys. Maxillary and mandibular dental casts were digitized (3D) and the images were analyzed by Delcam Power SHAPET 2010 software. Landmarks on the lingual surface of teeth were selected and 14 measurements were calculated to determine the shape and size of dental arches.

RESULTS:

Shapiro-Wilk test determined small arch shape by means of 25^th percentile (P25%) - an average percentile for the medium arch; and a large one determined by means of 75^th percentile (P75%). T-test revealed differences between males and females in the size of 12 dental arches.

CONCLUSION:

The straight-wire arch shape used in the lingual straight wire technique is a parabolic-shaped arch, slightly flattened on its anterior portion. Due to similarity among dental arch sizes shown by males and females, a more simplified diagram chart was designed.

[Skeletal discrepancies: could we avoid surgical procedures?]

Orthodontic-surgical protocols are nowadays considered as the state-of-the-art in cases of skeletal dentomaxillary dysmorphosis. However, for some reasons, it may happen that unquestionable indications for orthodontic-surgical procedures are not respected, patients being treated by orthodontics alone. This kind of mistake in the treatment planning lay the patient open to various potential complications such as: abnormal duration of the orthodontic treatment, dental root resorptions, questionable tooth extraction, unfavorable facial aesthetics, treatment instability... The authors discuss these points illustrated by clinical cases. Although orthognathic surgery protocols became considerably simplified these last two decades, orthodontic-surgical protocols are still relevantly considered as heavy both by patients and practitioners. As a consequence, their indication must be carefully weighed by a multidisciplinary team, keeping in mind that these protocols represent the ultimate functional and aesthetic treatment for dento-skeletal dysmorphoses.

Is it possible to use cross-sectional and vertical facial measurements to establish the shape of the mandibular arch?

BACKGROUND

Given the benefits of radiographic cephalometric studies in determining patterns of dental-skeletal-facial normality in orthodontics, the aim of this study was to investigate the association between mandibular dental arch shape and cross-sectional and vertical facial measurements.

MATERIALS AND METHODS

It was analyzed plaster casts and teleradiographs in frontal and lateral norm belonging to 50 individuals, aged between 15 and 19 years, with no previous history of orthodontic treatment and falling into four of the six Andrews's occlusion keys. The plaster models were scanned (3D) and the images of the dental arches were classified subjectively as oval, triangular and quadrangular by three calibrated examiners, with moderate inter-examiner agreement (Kappa = 0.50). After evaluation of the method error by paired t test (p > 0.05), it was carried out the analysis of cross-sectional and vertical facial measurements to be compared to the shape of the dental arch. Data were subjected to one-way analysis of variance with a significance level of 5%.

RESULTS

When the VERT index was compared with the three arch shapes, no measurement showed statistically significant differences (p > 0.05): triangular (0.54); oval (0.43); and quadrangular (0.73); as well as there were no differences (p > 0.05) in the widths of the face (141.20; 141.26; 143.27); maxilla (77.27; 77.57; 78.59) and mandible (105.13; 103.96; 104.28).

CONCLUSION

It can be concluded that there was no correlation between different shapes of the mandibular dental arch and the cross-sectional and vertical facial measurements investigated.

Determinant factors of Yemeni maxillary arch dimensions

Objective

Information about maxillary arch and palatal dimensions in human populations is important for clinical orthodontics. This study was conducted to assess the determinants of maxillary arch dimensions in a sample of Yemeni individuals aged 18–25 years.

Materials and Methods

The study sample comprised 214/765 adults (101 women, 113 men) who underwent clinical examination and fulfilled the study criteria. Study models were constructed and evaluated to measure maxillary arch and palatal dimensions.

Results

The majority of mean maxillary arch dimensions were significantly greater in men than in women, with inter–second molar distance showing the greatest difference and palatal depth showing the least difference.

Conclusion

Measurements of palatal depth and relationships of the canines to one another and to other teeth thus had the widest ranges, implying that these dimensions are the strongest determinants of maxillary arch size.

The relationship between mandibular arch length and widths in a sample of Yemeni subjects with normal dento-Skeletal relationship

Objective:

To assess the relationship between mandibular arch length and widths in a sample of Yemeni subjects aged (18-25) years.

Materials and Methods:

The investigation involved clinical examination of (765) adults; only 214 (101 females, 113 males) out of the total sample were selected to fulfill the criteria for the study sample (normal dento-skeletal relationship). Study models were constructed and evaluated to measure mandibular arch dimensions. The Spearman's correlation coefficient (r) was calculated between the measurements of arch widths and lengths.

Results:

Overall, the male group demonstrated greater transverse and sagittal mandibular dimensions; However, this was only statistically significant for measurements of inter-first and second molar distances and anterior arch length (P < 0.05). Relatively stronger linear relationships were observed between the inter-canine distance and mandibular arch lengths (P < 0.05, Spearman's r ranged between 0.17 to 0.50).

Conclusion:

Among studied mandibular dimensions in subjects with normal dento-skeletal relationship, only the inter-canine distance demonstrated a week to moderate linear relationship with the mandibular arch lengths.

Relationship between vertical facial patterns and dental arch form in class II malocclusion

Background

The purpose of this study is to evaluate the relationship between dental arch form and the vertical facial pattern determined by the angle between the mandibular plane and the anterior cranial base (Sella-nasion/mandibular plane angle (SN-MP)) in skeletal class II untreated patients.

Methods

A sample of 73 Caucasians patients with untreated skeletal class II in permanent dentition was divided into three groups according to the values of the angle SN-MP. An evaluation of the arch form was performed by angular and linear relation values on each patient. Regression analysis was used to determine the statistical significance of the relationships between SN-MP angle and dental arch form. The differences among the three groups were analyzed for significance using a variance analysis.

Results

A decrease of the upper arch transversal diameters in high SN-MP angle patients and an increase in low angle SN-MP ones (P < 0.05) were shown. Result analysis showed a change in upper arch shape, with a smaller intercanine width in patients with high SN-MP angle and a greater one in low angle patients. As SN-MP angle increased, the upper arch form tended to be narrower. No statistically significant difference in mandibular arch form among the three groups was found, except the angle value related to incisors position.

Conclusions

The results showed the association between the upper dental arch form and the vertical facial pattern. On the contrary, the lower arch form was not related to the mandibular divergence.

Shape model of the maxillary dental arch using Fourier descriptors with an application in the rehabilitation for edentulous patient

The knowledge of teeth positions on the maxillary arch is useful in the rehabilitation of the edentulous patient. A combination of angular (θ), and linear (l) variables representing position of four teeth were initially proposed as the shape descriptor of the maxillary dental arch. Three categories of shape were established, each having a multivariate normal distribution. It may be argued that 4 selected teeth on the standardized digital images of the dental casts could be considered as insufficient with respect to representing shape. However, increasing the number of points would create problems with dimensions and proof of existence of the multivariate normal distribution is extremely difficult. This study investigates the ability of Fourier descriptors (FD) using all maxillary teeth to find alternative shape models. Eight FD terms were sufficient to represent 21 points on the arch. Using these 8 FD terms as an alternative shape descriptor, three categories of shape were verified, each category having the complex normal distribution.

Dental informatics to characterize patients with dentofacial deformities

Relevant statistical modeling and analysis of dental data can improve diagnostic and treatment procedures. The purpose of this study is to demonstrate the use of various data mining algorithms to characterize patients with dentofacial deformities. A total of 72 patients with skeletal malocclusions who had completed orthodontic and orthognathic surgical treatments were examined. Each patient was characterized by 22 measurements related to dentofacial deformities. Clustering analysis and visualization grouped the patients into three different patterns of dentofacial deformities. A feature selection approach based on a false discovery rate was used to identify a subset of 22 measurements important in categorizing these three clusters. Finally, classification was performed to evaluate the quality of the measurements selected by the feature selection approach. The results showed that feature selection improved classification accuracy while simultaneously determining which measurements were relevant.

A probability distribution of shape for the dental maxillary arch using digital images

Selected landmarks from each of 47 maxillary dental casts were used to define a Cartesian-coordinate system from which the positions of selected teeth were determined on standardized digital images. The position of the i-th tooth was defined by a line of length (l(i)) joining the tooth to the origin, and the angle (θ(i)) of this line to the horizontal Cartesian axis. Four teeth, the central incisor, lateral incisor, canine and first molar were selected and their position were collectively used to represent the shape of the dental arch. A pilot study using clustering and principal component analysis strongly suggest the existence of 3 groups of arch shape. In this study, the homogeneity of the 3 groups was further investigated and confirmed by the Dunn and Davies-Bouldein validity indices. This is followed by an investigation of the probability distribution of these 3 groups. The main result of this study suggests 3 groups of multivariate (MV) normal distribution. The MV normal probability distribution of these groups may be used in further studies to investigate the issues of variation of arch shape, which is fundamental to the practice of prosthodontics and orthodontics.

Reference line-pair values of panoramic radiographs using an arch-form phantom stand to assess clinical image quality

PURPOSE

This study was performed to suggest reference line-pair values of panoramic images with clinically desirable qualities using an arch-form phantom stand.

MATERIALS AND METHODS

The line-pair test phantom was chosen. A real skull model was selected for setting the arch-form model of the phantom stand. The phantom stand had slits in four regions (incisor, premolar, molar, TMJ). Four raw images of the test phantom in each region and one raw image of the real skull were converted into 50 test phantom images and 50 skull phantom images with various line-pair values. 50 post-processed real skull phantom images were divided into 4 groups and were randomly submitted to 14 evaluators. Image quality was graded on a 4 point scale (1. good, 2. normal, 3. poor but interpretable, and 4. not interpretable). The reference line pair was determined as the first line-pair value scored less than 2 points.

RESULT

The mean scores tended to decrease as the line-pair values increased. The reference line-pair values were 3.19 LP/mm in the incisor, 2.32 LP/mm in the premolar and TMJ, and 1.88 LP/mm in the molar region.

CONCLUSION

Image quality evaluation methods and criteria should be able to assess various regions considering the characteristics of panoramic systems. This study suggested overall and regional reference line-pair values and established a set of standard values for them.

Correlation of the arch forms of male and female subjects with those of preformed rectangular nickel-titanium archwires

INTRODUCTION

This investigation was carried out to correlate the normal arch forms of male and female subjects derived mathematically by the beta function with commercially available preformed rectangular nickel-titanium archwires.

METHODS

The mathematical beta function was used to derive planar projections of natural archforms by using the spatial coordinates of the labial bracket interfacing surfaces in the maxillary and mandibular arches of both sexes. Graphic planar representations of corresponding bracket base spatial coordinates of archforms of 30 popular rectangular nickel-titanium archwire-bracket assemblies (derived through the same mathematical function) were superimposed on relevant maxillary and mandibular arches.

RESULTS

The rectangular nickel-titanium archwire-bracket assemblies exceeded the intercanine width by averages of 7.159 mm in the maxillary arches of females, 6.289 mm in the maxillary arches of males, 6.667 mm in the mandibular arches of females, and 5.337 mm in the mandibular arches of males. The average intermolar width exceeded the natural width by 2.893 mm in the maxillary arches and 1.861 mm in the mandibular arches. The average intermolar-intercanine width ratios for natural arches (2.11 for mandibular and 1.75 for maxillary) were greater than the ratios for the wire-bracket assemblies (1.78 for mandibular and 1.53 for maxillary).

CONCLUSIONS

The prefomed rectangular nickel-titanium archwires might result in wider arch forms. The intercanine width difference is greater than the intermolar width. The differences were more pronounced for arches in female subjects compared with those in males. These findings influence posttreatment retention, stability, and facial esthetics. A subsequent change to stainless steel wires to restore a more natural form and size can lead to round tripping and increased treatment duration.

Morphological analysis of the maxillary arch and hard palate in edentulous maxilla of South Indian dry skulls

PURPOSE

The purpose of this study is to demonstrate the role of aging\edentulousness on the maxillary arch, the size of the alveolar process, the shape and thickness of the hard palate in the South Indian dry skulls to customize more appropriate treatment of elderly edentulous patients.

METHODS

One hundred dry skulls were divided into dentate and edentulous groups and were subgrouped into male and female. They were subjected to various morphological and morphometrical analyses.

RESULTS

The data have revealed a more significant reduction in the depth and width (p < 0.001) of the arch corresponding to the reduction in the size and thickness of the alveolar process (p < 0.001) in the edentulous skull. Further, a significant reduction in the size and thickness (p < 0.001) of the hard palate was observed in the edentulous skull. The data clearly indicate the effect of tooth loss in the horizontal regression of the maxilla. Furthermore, it may enhance the bone resorption that can ultimately result in the marked reduction of the width and depth of the alveolar arch concomitant with the alteration of the hard palate. These changes may subsequently alter the facial appearance in the elderly population.

CONCLUSION

The observed data from specific group of population may provide relevant data for their comparative analysis between different populations for a better understanding of their regional differences with respect to environmental and social influence. Moreover, the data can provide a better idea to evaluate a promising treatment strategy in prosthodontics and orthodontics in South India.

Dental arch dimensions in the mixed dentition: a study of Brazilian children from 9 to 12 years of age

OBJECTIVE

This study evaluated dental arch dimensional changes of Brazilian children.

MATERIAL AND METHODS

Dental casts were taken from 66 children (29 males; 37 females) with normal occlusion selected among 1,687 students from public and private schools aged 9, 10, 11 and 12 years, according to the following criteria: Class I canine and molar relationships; well-aligned upper and lower dental arches; mixed dentition; good facial symmetry; no previous orthodontic treatment. Dental arch dimensions were taken by one examiner using the Korkhaus' compass and a digital pachymeter. ANOVA test was applied to compare the arch dimensions at the different ages and the t-test was used to compare the arch dimensions of male and female subjects. Arch forms were compared by means of chi-square tests.

RESULTS

Only the maxillary anterior segment length showed a statistically significant increase from 10 to 12 years of age. Males had a significantly larger maxillary depth than females at the age range evaluated. The predominant dental arch form found was elliptical.

CONCLUSIONS

In the studied age range, anterior maxillary length increased from 10 to 12 years of age, males had larger maxillary depth than females and the predominant arch form was elliptical.

Avaliação longitudinal de arcadas dentárias individualizadas com o método Borda WALA

INTRODUÇÃO: a forma da arcada dentária inferior é considerada uma das principais referências no diagnóstico, sendo um fator importante para a estabilidade do tratamento ortodôntico. OBJETIVOS: avaliar as alterações nas distâncias intercaninos e intermolares inferiores durante e 3 anos após a finalização do tratamento ortodôntico, no qual foi utilizado o método Borda WALA para individualização da forma da arcada dentária. MÉTODOS: a amostra foi composta por 20 pacientes (12 do sexo feminino e 8 do masculino), com idade média de 20,88 anos. Os modelos de gesso iniciais, finais e de pós-tratamento foram utilizados para medição das distâncias intercaninos e intermolares no centro da vestibular da coroa clínica e na largura da Borda WALA. Os dados foram avaliados por meio do teste ANOVA dependente seguido pelo teste de Tukey (p<0,05). RESULTADOS: houve diferença estatisticamente significativa das distâncias intercaninos e intermolares entre as três fases estudadas. Essas distâncias aumentaram significativamente com o tratamento, e apresentaram uma diminuição no período pós-tratamento, porém, não atingindo os valores iniciais. CONCLUSÕES: o método Borda WALA, utilizado para confecção dos diagramas individualizados e para medição das distâncias intercaninos e intermolares, se mostrou válido, permitindo a individualização das arcadas dentárias e favorecendo a estabilidade pós-tratamento.

Effects on the Dental Arch Form Using a Preadjusted Appliance with Premolar Extraction in Class I Crowding

Objective: To determine the dental arch form effects of treatment with a preadjusted appliance (0.022″ slot) performed concomitantly with extraction of premolars in Class I crowding.

Materials and Methods: Twenty-six patients (20.17 ± 12.15 years) with Class I crowding who attained a favorable occlusion after treatment were divided into nonextraction and extraction groups. The three-dimensional coordinates of the FA point of each tooth were determined. The dental arch form was expressed as a quartic polynomial expression with log F value used to represent the dental arch form and calculated using the quadratic and quartic coefficients. Changes in the dental arch form before and after treatment were compared between the groups.

Results: In the extraction group, log F value was significantly higher after treatment, and the upper dental arch became more tapered. The U1-APo was significantly lower after treatment. No change was observed in U1-FH. The anterior teeth demonstrated posterior movement due to sliding mechanics, and torque was controlled. The anterior length of the dental arch became significantly longer after treatment for the maxilla and mandible in both groups. Results demonstrated that the upper dental arch might become tapered after treatment used concomitantly with premolar extraction, as a result of the increase in anterior length while maintaining intercanine width for dealing with crowding of the anterior teeth.

Conclusion: It is necessary to anticipate that the upper dental arch form will become tapered during extraction treatment for Class I crowding and to select an appropriate arch form.