Assessment of dental arch forms in a sample of children

In this study, we investigated dental arch forms in a representative sample of children with mixed dentition. Twenty-four pairs of study models, belonging to twenty-four youngsters (twelve boys and twelve girls aged 8 to 9 years) with acceptable occlusion, were scanned and assessed by Ortho analyzer software. Three transversal and three vertical measurements were acquired to evaluate the lengths and widths of dental arches, and the ratios between these measurements were standardized. Next, the mean standardized parameters were used to define the dental arch form. Unpaired t-tests were used to analyze gender differences for all measures. Subsequently, frequencies and percentages were determined for each arch shape in both jaws and genders, and Pearson's Chi-squared test was used to evaluate differences between genders. Males exhibited higher mean values for all measurements, but without statistical significance. The most prevalent dental arch was the mid form (83.3%) for both jaws and genders.

Fully automated estimation of arch forms in cone-beam CT with cubic B-spline approximation: Evaluation of digital dental models with missing teeth

BACKGROUND AND OBJECTIVE

To evaluate the automatic determination method for the arch form in cone-beam computed tomography (CBCT) images with cubic B-spline approximation on digital dental models using various types of missing teeth.

METHODS

The maxilla and mandible from eight dental CBCT images with Class I occlusion and no missing teeth were used in this study. The dental arch determination algorithm using cubic B-spline approximation was modified by applying a smoothing function for reliable curve fitting to the digital dental models with various types of missing teeth. For evaluation, 31 scenarios with missing teeth were simulated, and cases with 1-8 missing teeth were divided into three groups: solitary, consecutive, and multiple (more than 4) missing teeth. The prediction accuracies of the dental arch forms were evaluated through comparisons with the gold standards for the digital dental models by two expert orthodontists.

RESULTS

The distance errors between the gold standards and the estimated results of the dental arch forms in all types of models were 0.237-1.740 mm. The mean distance errors of the solitary, consecutive, and multiple groups were 0.436 ± 0.124 mm (0.237-0.964 mm), 0.591 ± 0.250 mm (0.256-1.482 mm), and 0.679 ± 0.310 mm (0.254-1.740 mm), respectively.

CONCLUSIONS

The algorithm for predicting the arch form functioned reliably, even for digital dental models with various types of missing teeth, and could be applied to digital dentistry for applications such as orthodontic tooth setup, artificial tooth arrangement for denture fabrication, and implant guides.

Semi-automatic and robust determination of dental arch form in dental cone-beam CT with B-spline approximation

BACKGROUND AND OBJECTIVE

The dental arch form is generally used as a base for planning orthodontic treatments. It is, therefore, vital to determine the proper individual dental arch form for more accurate orthodontic treatment. We aimed to develop and validate a robust algorithm for semi-automatic determination of the dental arch form in dental cone-beam CT (CBCT) images with the cubic B-spline approximation.

METHODS

Our algorithm consists of tooth segmentation, determination of an occlusal plane, and generation of intersection points between the teeth and the offset plane from the occlusal plane in CBCT images. By fitting a curve to the intersection points using the cubic B-spline curve approximation, the dental arch form was finally determined. The accuracy of the dental arch forms was evaluated by comparison with gold standards determined by an expert orthodontist.

RESULTS

Thirteen dental CBCT scans from nine subjects were enrolled in this study. From the CBCT scans, 13 maxillary arch forms and 11 mandibular arch forms with Class I occlusion were determined by our proposed algorithm and evaluated for validation. The mean error between the dental arch forms of gold standards and our method using the cubic B-spline was 0.413 ± 0.092 mm (range, 0.264-0.587 mm).

CONCLUSIONS

Our proposed method showed reliable accuracy of determining the dental arch forms for the maxilla and mandible. These results suggested that this method might be used for planning automatic tooth setup for individual patients.

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.

Variation in form of mandibular, light, round, preformed NiTi archwires

OBJECTIVE

To evaluate the variation in form of nickel-titanium (NiTi) archwires by comparing them with the dental arch form of normal Japanese subjects before and after placing them in the first molar tubes.

MATERIALS AND METHODS

The mandibular dental casts of 30 normal subjects were scanned, and the dental arch depths and widths from the canine to the first molar were measured. Standardized images of 34 types of 0.016-inch preformed NiTi archwires were also taken in a 37°C environment, and the widths were measured and then classified by cluster analysis. Images of these archwires placed in a custom jig with brackets attached at the mean locations of the normal mandibular central incisors and first molar were additionally taken. The widths of the pooled and classified archwires were then compared with the normal dental arch widths before and after placement in the jig and among the groups (P < .05).

RESULTS

The archwires were classified into three groups: small, medium, and large. The archwire widths in the small and medium groups were narrower than those at all examined tooth widths, except in the case of the premolars of the medium group. After placement in the jig, the pooled archwire widths were found to be significantly narrower and wider at the canine and second premolar, respectively, than at the dental arch, but not in the individual comparisons between groups.

CONCLUSION

The variation observed in the mandibular NiTi archwire forms significantly decreased following fitting into the normal positions of the first molars.

Comparison of dental and alveolar arch forms between different ethnic groups

OBJECTIVE

The aims of this study were to evaluate, by means of 3D software, any correlation between ethnic group and the shape and size of the dental arcade and its bony support, and to investigate the correspondence between the latter two variables within each ethnic group. The data gathered were also compared with the measurements of commercially available pre-formed archwires to determine which provide the best fit for each arch in each group.

MATERIALS AND METHODS

The shape and size of the dental and alveolar arches of 29 subjects of African origin and 37 Caucasian subjects were compared in terms of linear inter-canine, inter-premolar and inter-molar measurements, overall arch length, and the distance between each tooth and the reference occlusal plane. To determine which pre-formed archwires are best suited to each of the two ethnic groups, the in-out of the brackets was considered, simulating their presence in the oral cavity.

RESULTS

The upper and lower dental and alveolar arches were all wider and longer in African with respect to Caucasian subjects (P<0.05). In general, "Roth small" (index value 1.556) and "Ideal Form Medium" (index value 0.645) archwires were better suited to both upper and lower arcades in the latter group, while "Damon" (index value 1.447) and "Ideal Form Large" (index value 1.695) conformed better to the size and shape of both arcades in the former.

CONCLUSIONS

There are very significant differences in arch form between the two ethnic groups considered, and the range of pre-formed archwires on the market does not provide for the anatomical variability of patients.

Dermatoglyphic assessment in subjects with different dental arch forms: an appraisal

Successful rehabilitation of edentulous individuals involves selection and arrangement of artificial teeth in accordance with the patient's original arch form. Various criteria exist for harmonious tooth arrangement but none is accepted universally. Finger and palm prints are unique to an individual and once formed in the sixth week of intra-uterine life, remain constant thereafter. Since dental arches are also formed during the same prenatal period, it is believed that the similar genetic factors may be involved in formation of dental arches and dermal patterns. This study was conducted to identify the association if any between type of dental arch forms and type of dermatoglyphic patterns. If specific dermal characteristics exist in individuals with specific dental arch forms, dermatoglyphic assessment of long standing edentulous subjects may help identify the patients preexisting dental arch form and thus aid in proper tooth arrangement. Ninety dentulous subjects were categorized into three groups on the basis of dental arch form (square, tapering or ovoid) and their finger and palm prints were recorded. The type of fingertip patterns, distribution of palmar patterns, Total Finger Ridge Count and angle atd were assessed. Subjects with square arches demonstrated a significantly high frequency of loops and a large atd angle with palmar patterns being most frequent in I3 region. Subjects with tapering arches showed a high frequency of whorls, a small atd angle and greatest distribution of palmar patterns in I4 region. In ovoid arched subjects, loops were the most common and palmar patterns were mostly observed in I4. Since distinctive dermal patterns were observed in subjects with different dental arch forms, it is believed that dermatoglyphics may be used as a reliable tool for identifying original arch form in edentulous patients.

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

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.

The maxillary arch and its relationship to cephalometric landmarks of selected malay ethnic group

The objectives of this study were to estimate the maxillary arch measurements, to assess the validity of Pont's & Korkhaus' Indices; to determine the relationship between maxillary arch form with head form; and to estimate the cephalic index (CI) of the study population. A cross-sectional study was conducted on 85 mature Malay students, 28 male students (32.98%), 57 females (67.02%) attending Teachers' Training College. Their mean age was 23.9 yr, and Cephalic Index (CI) 86.4 (95% Confidence Interval 85.5-87.3). Arch and head dimensions were significantly larger in males than in females. CI was not significantly different between males and females. Means of anterior arch width (AAW), posterior-arch-width (PAW) and arch-length (Lu) were 35.57mm, 47.3mm and 18.01mm respectively. They were significantly different from their corresponding Indices. Correlation Coefficient between bizygomatic width and anterior-arch-width was 0.18 and was not significant in both sexes of the present population.