Comparison of overjet among 3 arch types in normal occlusion

Occlusal Features and Temporomandibular Joint Disorder: A Cross-Sectional Study

Background

Understanding the correlation between temporomandibular joint disorder (TMD) parameters and various occlusal features can play a significant role in diagnosing and treating occlusal problems and their potential consequences on TMD.

Objectives

To investigate the relationship of occlusal features and some of the TMD parameters. Study Design and Sampling. The current cross-sectional study was conducted on 200 TMD patients seeking dental treatment at different dental centers in Baghdad city, aged 18-35 years. All participants underwent assessment for occlusal features, which were molar and canine classifications, overjet, posterior buccal or lingual crossbites, and overbites, and TMD parameters (muscle pain, TMJ pain, and clicking) using the Chi-square test for statistical analysis.

Results

Regarding molar classification, there were strong positive correlations between subjects with TMD and having different molar classifications (class I, II, and III) bilaterally or unilaterally; furthermore, there were strong positive correlations between subjects with TMD and having different canine classifications. Moreover, there were significant correlations between subjects with increased, normal, or decreased overjet and the TMD parameters. In addition, there were weak positive correlations between TMD occurrence and buccal or lingual posterior crossbite. On the other hand, there were significant correlations between subjects with a decreased overbite and the presence of TMD parameters.

Conclusion

TMD had a multifactorial background rather than dependability on a specific molar or canine classification type. There was also a correlation between overjet and TMD muscle pain, while decreased overbite was correlated to muscle and TMJ pain. Conversely, there is no vital correlation between posterior buccal or lingual crossbite occurrence and TMD parameters.

Dental arch form in a sample of Iraqi adults with sickle cell anemia using 3D scanning technique: A cross-sectional study

OBJECTIVE

Sickle cell anemia (SCA) is a hematological condition that involves the synthesis of sickle-shaped, hemoglobin with a short lifespan. This study employed three-dimensional (3D) scanning to pinpoint the most common arch form in a sample of Iraqi adults with SCA.

MATERIALS AND METHODS

A cross-sectional study included maxillary and mandibular casts of 50 patients (25 male and 25 female) with SCA and 50 participants in a control group (25 male and 25 female). The facio-axial (FA) point was digitized on each tooth's labial or buccal surface using SolidWorks® 2020 software. The dimensions of the arch were calculated using two proportional measures and four linear measurements. The dental arch form was determined using 3M templates, and the arches were categorized as square, ovoid, or tapered to establish the most-common arch form. Chi-square was used to compare arch form distribution, and an independent t-test was used to calculate the difference between the control group and the SCA group.

RESULTS

The tapered arch was the predominant form in SCA males and females for the maxilla and the mandible. The molar vertical distance (upper and lower) was significantly higher in males in the SCA group than in males in the control group. There was no significant difference between females in the SCA group and females in the control group.

CONCLUSION

Most patients with SCA had tapered arches. Sagittal jaw dimensions in males with SCA were more affected by marrow hyperplasia. There was little if any to no effect on females with SCA.

Finite Element Analysis of Orthodontic Relapse in Different Maxillary Arch Form

Abstract Background: Orthodontic relapse is fairly common; however, the mechanisms between relapse and the dental arch form remain unclear. The purpose of our study was to establish three-dimensional (3D) finite element models of different dental arch forms after orthodontic treatment and to analyze the states of different arches applied with various sagittal forces.Methods: By calculating the equations of different dental arch forms and combining them with a full maxillary arch (14 teeth), 3D finite element models of square, oval, and tapered dental arches were established; they were designed to be subjected to anterior lingual, posterior mesial, and combined forces, respectively.Results: The von Mises stress and displacement of teeth under different forces were calculated for each loading scenario. Under the different forcing scenarios, all incisors had irregularity trends, and the inclination and intrusion of the canines were increased, and the premolars had a tendency to buccal or lingual crown tipping or even intrusion in our study. The tapered arch was the most stable and had the smallest displacement and von Mises stress, followed by the ovoid arch; the most unstable arch was the square arch.Conclusions: To achieve a stable orthodontic effect, a tapered or ovoid arch, rather than a square arch, should be chosen as the final outcome of treatment.

Analysis of the correlation between dental arch and articular eminence morphology: a cone beam computed tomography study

OBJECTIVE

The aim of the study was to assess the correlation between the morphology of the dental arches (DAs) of patients with normal occlusion and of the articular eminence (AE) by using cone beam computed tomography (CBCT).

STUDY DESIGN

CBCT scans of 60 patients were evaluated in terms of height and inclinations (angles α, β, and δ) of the AE. DAs were classified according to their shapes (tapered, square, ovoid), and their perimeters, widths, and depths were measured. One-way analysis of variance, Pearson's correlation coefficients, and simple and multivariate linear regression models were used for the calculations.

RESULTS

The ovoid arch was the most predominant shape (n = 66/120). Inclination of the AE (angle β) had the greatest difference between DA shapes, with this angle usually being greater in the ovoid arch and smaller in the square arch (P < .05). The height of the AE presented greater correlation with DA measurements, with tapered arches having the most significant correlations (P < .05). DA depth had no influence on AE measurements (P > .05). The perimeter and width of the DAs had some influence (P < .05).

CONCLUSIONS

Correlations were found between the DA and AE morphologies. The correlations should be taken into consideration, although the results do not prove absolute association between the variables. Whenever possible, the morphologic features of DAs should be preserved to avoid possible changes in AE.

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.

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.

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

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.

Evaluation of minimal versus conventional presurgical orthodontics in skeletal class III patients treated with two-jaw surgery

PURPOSE

The purpose of this study was to compare changes in hard and soft tissues and the treatment efficacy of 2-jaw surgery combined with nonextraction treatment for skeletal Class III malocclusion in patients who received minimal presurgical orthodontics (MPO) versus those who received conventional presurgical orthodontics (CPO).

MATERIALS AND METHODS

Thirty-two patients (16 in each group) with skeletal Class III malocclusion who underwent 2-jaw surgery were included in the study. Serial lateral cephalometric films were traced at 4 stages: before treatment (T0), before surgery (T1), 1 month after surgery (T2), and at debonding (T3). Cephalometric measurements and treatment duration were compared using independent t test and Mann-Whitney U test.

RESULTS

After the presurgical treatment phase, the angle between the lower incisor axis and mandibular plane, overjet, and soft tissue pogonion to the vertical reference line showed larger changes (P < 0.01) in the CPO group, whereas the pogonion to the horizontal reference line showed larger changes (P < .05) in the MPO group. In the postsurgical phase (T2 to T3), there were no significant differences between the 2 groups. Total treatment duration was significantly shorter in the MPO group.

CONCLUSIONS

There were no significant differences between the MPO and CPO groups in the hard and soft tissue cephalometric variables. The MPO group had a shorter total treatment time. It is therefore recommended that clinicians consider these results when selecting MPO as a treatment option for accurate diagnosis and treatment planning of Class III surgical patients.

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

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.