Mandibular Arch Length Research Articles

Evaluation of different machine learning algorithms for extraction decision in orthodontic treatment.

The extraction decision significantly affects the treatment process and outcome. Therefore, it is crucial to make this decision with a more objective and standardized method. The objectives of this study were (1) to identify the best-performing model among seven machine learning (ML) models, which will standardize the extraction decision and serve as a guide for inexperienced clinicians, and (2) to determine the important variables for the extraction decision. This study included 1000 patients who received orthodontic treatment with or without extraction (500 extraction and 500 non-extraction). The success criteria of the study were the decisions made by the four experienced orthodontists. Seven ML models were trained using 36 variables; including demographic information, cephalometric and model measurements. First, the extraction decision was performed, and then the extraction type was identified. Accuracy and area under the curve (AUC) of the receiver operating characteristics (ROC) curve were used to measure the success of ML models. The Stacking Classifier model, which consists of Gradient Boosted Trees, Support Vector Machine, and Random Forest models, showed the highest performance in extraction decision with 91.2% AUC. The most important features determining extraction decision were maxillary and mandibular arch length discrepancy, Wits Appraisal, and ANS-Me length. Likewise, the Stacking Classifier showed the highest performance with 76.3% accuracy in extraction type decisions. The most important variables for the extraction type decision were mandibular arch length discrepancy, Class I molar relationship, cephalometric overbite, Wits Appraisal, and L1-NB distance. The Stacking Classifier model exhibited the best performance for the extraction decision. While ML models showed a high performance in extraction decision, they could not able to achieve the same level of performance in extraction type decision.

To Evaluate the Relationship between Maxillary and Mandibular Base Lengths with Dental Crowding in Different Skeletal Malocclusions

Introduction Exploring the relationship between arch dimensions and crowding has long been a topic of interest. Many studies have found significant relationship between the two, while others have suggested that crowding is a multifactorial condition and is not dependent on arch dimensions only. Objective To evaluate the relationship as well as sexual dimorphism between maxillary and mandibular skeletal base lengths with dental crowding in different skeletal malocclusions. Materials and Methods The sample comprised 100 orthodontic patients (49 males, 51 females), which were divided into three groups based on the anteroposterior relationship of maxilla with the mandible. Each group was subdivided based on the severity of mandibular and maxillary arch crowding into two subgroups, and each subgroup was further divided into male and female subjects. Measurements of maxillary and mandibular base lengths (Co-A and Co-Gn) and tooth size arch length discrepancies were obtained through lateral cephalograms and dental casts, respectively, and measurements obtained were analyzed statistically. Results Patients with class IB, IIB, and IIIB had significantly smaller maxillary and mandibular base lengths than subjects with class IA, IIA, and IIIA. A weak negative correlation was found between maxillary base length and maxillary crowding with r = –0.451 and p = .000, while a strong positive correlation was observed between maxillary and mandibular crowding with r = 0.742 and p = .000. Conclusion An inverse correlation exists between dental crowding and the lengths of maxillary and mandibular bases, regardless of skeletal malocclusion.

Evaluating Measurements: A Comparative Study of Digital and Plaster Models for Orthodontic Applications in Mixed Dentition

This study aimed to assess the accuracy of tooth widths, intermolar widths, and arch lengths acquired through two intraoral scanners, including iTero Element Plus Series (Align Technology, Santa Clara, CA, USA) and Trios 4 (3Shape, Copenhagen, Denmark), specifically on mixed dentition. A total of 30 subjects were divided into 2 groups, each undergoing both alginate impressions and intraoral scanning using either the iTero or Trios scanner. The plaster models were measured with a caliper, while the digital models were measured virtually. In the iTero group, all tooth width measurements exhibited differences compared to the plaster values, except for maxillary left lateral incisors (<i>p</i> = 0.179), mandibular right (<i>p</i> = 0.285), and left (<i>p</i> = 0.073) central incisors. The Trios group did not display significant differences in any of the tooth width measurements. Intermolar width comparisons for both groups indicated differences, except for mandibular primary canine to primary canine values (<i>p</i> = 0.426) in the iTero group. Regarding arch length, the mandibular anterior, maxillary right, and left arch lengths in the iTero group demonstrated larger caliper values than those of iTero. Conversely, in the Trios group, all parameters showed smaller caliper values, especially in upper anterior, maxillary right, mandibular right, and mandibular left arch lengths with significance (<i>p</i> = 0.027, 0.007, 0.003, and 0.047, respectively). Despite the differences between the two groups, digital models might be clinically suitable alternatives for plaster models. Pediatric dentists should carefully assess these differences, as a comprehensive evaluation would result in precise orthodontic treatment planning and favorable outcomes for young patients with mixed dentition.

Exploring dimensions and shapes of edentulous patients consulting the prosthodontics centre at Ibn Sina University Hospital in Rabat, Morocco: a cross-sectional study

This cross-sectional study conducted at the Prosthodontics Centre, Ibn Sina University Hospital in Rabat, Morocco, investigates the dimensions and shapes characterizing maxillary and mandibular edentulous arches in a patient population seeking consultation. The objective is to provide insights crucial for optimizing outcomes in prosthetic therapy, informing decisions on impression trays, occlusion planes, prosthetic teeth, and implant attributes. Sixty-seven edentulous Moroccan patients (40 men, 27 women), aged 31 to 90, were recruited at the Prosthodontics Centre. Maxillary and mandibular casts were meticulously crafted, and precise measurements of anterior and posterior width and length were acquired for both arches. Arch shapes were categorized into O-shape, V-shape, and U-shape. Data were analyzed using Microsoft® Excel 2013 and SPSS software (IBM SPSS Statistics 23). Analysis revealed maxillary arch lengths ranging from 40 to 58 mm, maxillary arch widths from 38 to 58 mm, mandibular arch lengths from 33 to 56 mm, and mandibular arch widths from 30 to 60 mm. The predominant arch shape was the ovoid, constituting 34% (n=23) of maxillary cases and 54% (n=36) of mandibular cases. This study provides novel insights into the dimensions and shapes of maxillary and mandibular edentulous arches in patients seeking consultation at Ibn Sina University Hospital, Rabat, Morocco. The findings offer valuable guidance for prosthetic therapy decisions, emphasizing the importance of integrating established references and arch classifications for optimal outcomes in the treatment of edentulous patients in Morocco.

A comparative evaluation of pre-treatment and post-treatment outcomes in patients subjected to lower incisor extraction

Mandibular incisor crowding is the most frequently occurring characteristic of malocclusion, which can be resolved by removing single lower incisor. The aim of this study was to evaluate and compare the pre- and post-treatment outcomes through model and cephalometric analysis of the patients subjected to single lower incisor extraction. In this retrospective study pre- and post-treatment lateral cephalograms and models of 23 patients who underwent fixed orthodontic treatment with single incisor extraction on lower arch were evaluated. The study subjects were classified into two groups based on extraction pattern (Group I: Upper premolar and lower single incisor extraction; Group II: Upper non extraction and lower single incisor extraction). Both cephalometric and model analysis were carried out using Ilexis FACAD AB-2014 Version3.8.0.0 (Ilexis AB, Sweden). Wilcoxon Signed Rank test was used to compare the pre and post-treatment quantitative parameters. A significant decrease was observed in the maxillary intermolar width, mandibular intercanine width, mandibular intermolar width, mandibular arch length and anterior Bolton’s ratio. Group I subjects revealed a greater decrease in maxillary intermolar width compared to Group II, whereas a greater decrease in mandibular intercanine width, mandibular intermolar width and anterior Bolton’s ratio was documented in Group II subjects compared to Group I. Cephalometric analysis revealed significant proclination and extrusion effect of lower incisors along with protrusive tendency of the lower lip. The findings of the present study provide an additional option of extracting single lower incisor, in borderline or Class II camouflage treatment cases.

Comparison of jaw arch size in stunting patients at Asemrowo Public Health Center

Background: The etiology of malocclusion is multifactorial, it can occur due to intrinsic, extrinsic factors or a combination of both. Malnutrition, which is one of the extrinsic factors of malocclusion, is a frequent case in Indonesia. An example of a malnutrition case that commonly occurs in Indonesia is stunting in children's growth and development, which can trigger malocclusions such as crowded teeth and bone crowding. Purpose: To identify the size of the dental arches in stunting sufferers at the Asemrowo public health center. Methods: In the study model of stunting patients, the length and width of the jaw arch were measured. The results of the measurements are then analyzed and compared with the data from the measurements of healthy children to see whether there are significant differences. Results: In terms of maxillary arch length, the 7 year age group yields p = 0.179. In terms of maxillary arch width, the 7 year age group yields p = 0.282. In terms of mandibular arch length, the 7 year age group yields p = 0.398. In terms of maxillary arch width, the 7 year age group yields p = 0.398. In terms of maxillary arch length, the 8 year age group yields p = 0.438. In terms of maxillary arch width, the 8 year age group yields p = 0.082. In terms of mandibular arch length, the 8 year age group yields p = 0.302. In terms of mandibular arch width, the 8 year age group yields p = 0.190. Conclusion: There is no significant difference between the length and width of the jaw arch in all age groups (p > 0.05).

Correlation of mandibular third molar orientation and available retromolar space with arch length discrepancy in subjects with different growth pattern.

To evaluate, compare, and correlate the mandibular third molar orientation and available retromolar space with arch length discrepancy in subjects with skeletal class II malocclusion and different growth pattern. A total of 250 patients (age >18 yrs) having skeletal class II malocclusion (based on YEN angle and WITS appraisal) were divided into two groups. Both the groups (Group I with erupted mandibular third molars {N = 150} and Group II with impacted mandibular third molars {N = 100}) were subdivided into subgroups IA (n = 71), IB (n = 19), IC (n = 71) and Group IIA (n = 54), IIB (n = 30) and IIC (n = 16) for normo-, hypo- and hyperdivergent growth patterns, respectively (based on Jarabak ratio and Sn-Go-Gn angle). Four parameters, that is, retromolar space, width of third molar, third molar angulation, and mandibular incisor angulation were measured on orthopantomogram whereas arch length discrepancy was calculated with the help of lateral cephalogram and study model. Intragroup, intergroup comparisons (using unpaired Student's 't' test), and Pearson's correlation coefficient for assessed parameters were obtained. Third molar angulation and retromolar space were significantly higher in Group I than in Group II (hyperdivergent pattern of Group II had highest value). The width of third molar was less than retromolar space in Group II and vice versa for Group I. Mandibular incisor angulation and arch length discrepancy were more in Group II than in Group I, but difference was statistically nonsignificant. Strong positive correlation was observed for mandibular third molar angulation and available retromolar space in normo- and hyperdivergent growth patterns. Lack of retromolar space along with increased amount of arch length discrepancy and mandibular incisor angulation is responsible for increased chances of third molar impaction in some subjects with class II malocclusion.

Effect of mandibular third molars on crowding of mandibular teeth in patients with or without previous orthodontic treatment: a systematic review and meta-analysis.

To assess the scientific evidence related to the role of the mandibular third molars on the late crowding of the lower anterior teeth in patients with or without previous orthodontic treatment. The secondary outcomes included changes in mandibular arch width and arch length. The databases PubMed, Scopus, ProQuest, and Google Scholar were searched from inception until April 2022. The included papers were studies evaluating the role of mandibular third molars on crowding of mandibular anterior teeth in patients of any age and gender, with mandibular third molars impacted or semi-impacted or erupted. Predetermined and prepiloted data collection forms were used to record the necessary information. Thirteen observational studies were included in the present systematic review. Most of them were assigned an overall risk of bias of moderate risk while the rest of them were at high risk. Four studies found an association between the presence of mandibular third molar and mandibular incisor crowding. Finally, seven studies were included in the quantitative analysis. Three different meta-analyses were conducted: for patients (a) with or (b) without previous orthodontic treatment and (c) in combination for patients with and without previous orthodontic treatment. According to the pooled results of all three meta-analyses, random effects model yielded a significant benefit for those without third molars compared to those with third molars regarding crowding, mean Little's irregularity index and mean arch length. Lower third molars may contribute to mandibular crowding and lower arch constriction. Further prospective research of high quality is needed to clarify the impact of third molars on anterior mandibular crowding.

Influence of second premolar extractions on the volume of the oral cavity proper: a control comparative cone-beam computed tomography volumetric analysis study.

To compare the pre- and postorthodontic treatment volumetric changes of the oral cavity proper (OCP) in extraction and nonextraction patients and to identify influencing variables. Pre- and posttreatment cone-beam computed tomography (CBCT) scans of patients undergoing orthodontic treatment with fixed labial appliances and who satisfied the inclusion criteria were individually landmarked. Linear, angular, and volumetric measurements were determined. Descriptive statistics, repeated measure analyses of variance, correlations, and stepwise regression statistical analyses were applied. The CBCT scans of 54 patients who underwent the extraction of second premolars and/or extraction of second primary molars associated with agenic second premolars, and 59 nonextraction patients matched for crowding, were assessed. The mean age for both groups was 15 years. There was a statistically significant increase in the volume of the OCP for both the extraction and nonextraction groups, with the nonextraction group demonstrating a larger increase in the volume of the OCP. Gender, age, changes in mandibular and maxillary arch length, and changes in mandibular and maxillary intermolar width all influenced the change in the OCP volume. The volume of the OCP increased in growing patients with and without the extraction of the second premolars and/or extraction of second primary molars associated with agenic second premolars. Patients who did not have extractions as part of their orthodontic treatment demonstrated a greater overall increase in OCP volume.

Heritability of dental arches and occlusal characteristics: a systematic review and meta-analysis.

The genetic basis of dentoalveolar characteristics has been investigated by several studies, however, the findings are equivocal. The objective of this systematic review and meta-analysis was to evaluate the heritability of dental arches and occlusal parameters in different stages of human dentition. Electronic databases PubMed, Embase, Scopus, Web of Science, and Dentistry and Oral Science Source were searched up to August 2023 without the restriction of language or publication date. Empirical studies investigating the heritability of dentoalveolar parameters among twins and siblings were included in the review. Study selection, data extraction, and risk of bias assessment were performed independently and in duplicate by two authors and a third author resolved conflicts if needed. Joanna Briggs Institute's critical appraisal tool was used to evaluate the risk of bias among studies and the certainty of evidence was assessed using the Grading of Recommendation, Assessment, Development, and Evaluation (GRADE) criteria. Twenty-eight studies were included in the systematic review, of which 15 studies reporting heritability coefficients in the permanent dentition stages were deemed suitable for the meta-analysis. Random-effects meta-analyses showed high heritability estimates for maxillary intermolar width (0.52), maxillary intercanine width (0.54), mandibular intermolar width (0.55), mandibular intercanine width (0.55), maxillary arch length (0.76), mandibular arch length (0.57), and palatal depth (0.56). The heritability estimates for the occlusal parameters varied considerably, with relatively moderate values for crossbite (0.46) and overbite (0.44) and low values for buccal segment relationship (0.32), overjet (0.22), and rotation and displacement of teeth (0.16). However, the certainty of evidence for most of the outcomes was low according to the GRADE criteria. Based on the available evidence, it can be concluded that the dental arch dimensions have a high heritability while the occlusal parameters demonstrate a moderate to low heritability. PROSPERO (CRD42022358442).

Morphometric measurements of mandible to determine stature and sex: A postmortem study

ObjectivesIdentification of humans has medicolegal relevance in civil issues involving property inheritance, marriage, contested sex, admission to educational institutions, and the disappearance of individuals. To determine the sex of human remains, forensic anthropologists usually use morphologic and metric approaches. This study was conducted to determine stature and sex according to mandibular dimensions in postmortem autopsy samples. MethodsA total of 150 mandibles from people 18–65 years of age were studied. Stature and sex were noted, and six mandibular measurements were taken with Vernier calipers, flexible measuring tape, a protractor, and a graduated autopsy table. Statistical analysis of the measured parameters was conducted in SPSS software. Statistical parameters, such as mean, standard deviation, Spearman's correlation coefficient, multiple linear regression, stepwise regression, and Mann–Whitney U test were analyzed. ResultsBicondylar width was the stature estimation predictor with the strongest correlation (r = 0.439). The other parameters significantly associated with stature were bigonial width (p = 0.000), mandibular angle (p = 0.004), and mandibular arch length (p = 0.000), according to Spearman's correlation coefficient. The mandibular angle had the greatest dimorphic statistical significance (p = 0.004) according to the Mann–Whitney U test. ConclusionBicondylar width may serve as a valuable tool for estimating stature, and mandibular angle can be used to identify sex. Our findings may help forensic anthropologists estimate stature and identify human remains.

Longitudinal changes of the natural craniofacial and dentoalveolar complex in the fourth decade of life

This study aimed to longitudinally examine the changes in craniofacial and dentoalveolar regions during the third and fourth decades of life. The data from this study constitute the cephalometric films and plaster models of 8 female and 8 male dental students or dentists. The mean chronological ages of the subjects at the first observation period was 22.09 years for females and 22.64 years for males. The material was collected over 3 intervals: 1985-1989, 1998-2000, and 2016-2017. The observation period was approximately 28 years. Acquired cephalometric recordings and dental models were assessed for subjects in their 20s (baseline), 30s, and 40s. Maxillary, mandibular, maxillomandibular, soft-tissue, and dentoalveolar cephalometric variables were measured with a cephalometric analysis software, and dental cast measurements were made with a digital caliper. Changes in the cephalometric films and dental casts were evaluated statistically. Statistical analysis showed that the length of the midfacial region increased with age. The height of the lower face increased significantly in females and the mandible can be seen mildly rotating to the posterior as it increased in length. The nose moved slightly forward and downward in males and females. Upper lip height was significantly increased in females; however, there was a significant reduction in upper lip thickness for males and females. Soft-tissue pogonion measurements showed a significant forward and downward chin movement in females. Overjet was significantly increased in females, whereas the mandibular arch length was significantly decreased for both sexes, although it was more prominent in females. There was a loss of space in the anterior segments of males and females, resulting in increased crowding. However, the loss of space was only significant in the mandible. We observed significant changes in skeletal, soft-tissue, and dentoalveolar variables of subjects in their third and fourth decades of life. The fact that many changes have occurred throughout this study demonstrates that the process of maturation and aging is ongoing.

Analysis of the Facial Measurements and Dental Arch Dimensions for the Construction of Dental Prostheses among Adult Yemenis.

To investigate the dental arch dimension (width, length, and height) and facial measurements including inner-canthal width (ICW), bizygomatic width (BZW), inter-alar width (IAW), and mouth width (MW), and to assess the correlation between these facial measurements and dental arch width (canine width [CW], inter-first premolar width [I1PW], and inter-first molar width [I1MW]), to establish a preliminary reference for artificial teeth selection in Yemeni adult. The study included 80 individuals (40 males and 40 females) with symmetrical faces and normal class I occlusion ranging in age from 20 to 35. Maxillary and mandibular stone casts were made for each individual. The dimensions of dental casts and facial measurements, including ICW, BZW, IAW, and MW, were assessed using a digital caliper. The collected data were analyzed by using the SPSS software program. The descriptive statistics for each measurement were made. Differences between males and females were tested using an independent-sample t-test with p-values below 0.05 considered significant. Pearson correlation coefficient between facial measurements and dental arch width was also done. Most dental arch dimensions and facial measurements exhibited larger mean values in the male than in the female group, with the greatest significant difference in the maxillary dental arch width and the lowest in mandibular dental arch length. A highly significant correlation is observed between ICW and maxillary canine width (CW) (r = 0.318, p = 0.004). In contrast, no significant correlation between dental arch width and BZW, IAW, and MW is shown. Within this study's limitations, the ICW can determine the ideal dimension of the artificial teeth in the anterior maxillary arch. While the other facial parameters, including BZW, IAW, and MW, cannot be used for artificial teeth selection in Yemeni populations. The findings of this study established a reference database of facial measurements and their correlation to dental arch and teeth width in Yemeni populations. So, it can be implemented in artificial teeth and dental prostheses design and construction.

Relationship between vertical facial morphology and dental arch measurements in class II malocclusion: a retrospective study.

To evaluate the relationship between dental arch measurements and the vertical facial pattern determined in skeletal Class II untreated patients. Lateral cephalograms and plaster models were obtained from 124 untreated female adults (average age: 17.6 ± 3.8 years). Class I (CI), Class II Division 1 (CII/1) and Class II Division 2 (CII/2) malocclusions were divided into three subgroups according to their vertical morphology as hypodivergent, normodivergent and hyperdivergent. The multivariate variance analysis (MANOVA) method was used in the comparison of measurement values according to vertical and sagittal morphology. The relationship between both A point-Nasion-B point (ANB) and Frankfurt-mandibular plane (FMA) angles and dental arch measurements was examined by Pearson correlation analysis. The significance level was received as p < 0.05. While vertical morphology has a statistically significant effect on mandibular arch length, sagittal morphology affects maxillary arch depth. The parameters influenced by both morphologies are maxillary and mandibular arch length, as well as maxillary intermolar width. The mandibular arch length was significantly shorter in hyperdivergent-CII-2 malocclusion (50.5 ± 7.4 mm). Larger values were obtained in both mandibular arch length and maxillary arch depth measurements in CII-1 malocclusion compared to CII-2 malocclusion. The maxillary intermolar width was significantly shorter in hypodivergent-CII-1 malocclusion (46.8 ± 3.4 mm), while it was higher in hypodivergent-CI malocclusion (51.1 ± 3.4 mm). The maxillary arch length was the lowest in hyperdivergent-CI malocclusion (63.1 ± 13.3 mm) and the highest in hypodivergent-CI malocclusion (72.8 ± 7.6 mm). Additionally, a positive but weak correlation was found between ANB and FMA angles. Dental arch measurements have been found to be affected by both vertical facial morphology and skeletal sagittal relationship. A positive correlation was found between ANB and FMA angles.

Risk factors for orthodontic fixed retention failure: A retrospective controlled study.

: To investigate the potential correlation between fixed orthodontic retention failure and several patient- and treatment-related factors. : Patients finishing treatment with fixed appliances between 2016 and 2017 were retrospectively included in this study. Those not showing fixed retention failure were considered as control group. Patients with fixed retention failure were considered as the experimental group. Additionally, patients with failure of fixed retainers in the period of June 2019 to March 2021 were prospectively identified and included in the experimental group. The location of the first retention failure, sex, pretreatment dental occlusion, facial characteristics, posttreatment dental occlusion, treatment approach and presence of oral habits were compared between groups before and after treatment separately by using a Fisher exact test and a Mann-Whitney U test. : 206 patients with fixed retention failure were included, 169 in the mandibular and 74 in the maxillary jaws. Significant correlations were observed between retention failure in the mandibular jaws and mandibular arch length discrepancy (P = 0.010), post-treatment growth pattern (P = 0.041), nail biting (P < 0.001) and abnormal tongue function (P = 0.002). Retention failure in the maxillary jaws was more frequent in patients with IPR in the mandibular jaws (P = 0.005) and abnormal tongue function (P = 0.021). : This study suggests a correlation between fixed retention failure and parafunctional habits, such as nail biting and abnormal tongue function. Prospective studies with larger study populations could further confirm these results.

Effects of headgear timing on dental arch changes from 7 to 18 years of age: a follow-up study.

Dental arch effects after cervical headgear (CHG) treatment have been researched from several different perspectives. However, the long-term effects of CHG timing are still unknown. To analyse the long-term effects of CHG timing on dental arches. A total of 67 children with Angle Class II malocclusion comprised the study group in this trial. The participants were randomized into two equal-sized groups. In the early group (EG, n = 33), treatment was started after the eruption of the first upper molars. In the later-timed group (LG, n = 34), treatment was started 18 months later compared with the early group. Long-term effects were measured from dental casts taken at five time points between 7 and 18 years of age. The total maxillary dental arch length was achieved earlier, the gained length persisted better in the long term, and significantly more space was achieved in EG compared with LG (P = .048). The intermolar width in the maxillary dental arch was more stable and was reached earlier in EG compared with LG (P = .002). The results showed that in terms of total mandibular arch length increases, EG males benefited the most and LG females the least from CHG treatment (P = .031). Both genders benefited from earlier CHG treatment. The maxillary dental arches remained longer, and the final width was gained earlier in EG compared with LG.

Cephalometric and model evaluations after molar distalization using modified C-palatal plates in patients with severe arch length discrepancy

This study aimed to evaluate the dentoskeletal and soft-tissue changes after molar distalization using modified C-palatal plates in patients with severe maxillomandibular arch length discrepancies. Twenty-four patients with Class I and II malocclusion (19.0 ± 7.3 years; 17 females and 8 males), who had severe maxillary crowding of>10 mm, and moderate mandibular crowding of>6 mm, underwent molar distalization using modified C-palatal plates and buccal miniscrews with approximately 300 g of force per side. Models were made, and cephalograms were taken before and after treatment. Cephalometric variables and arch dimensions were measured. Paired t test and Wilcoxon rank sum test were used for statistical analysis. In the maxillary dentition, an average of 12.4 mm of crowding was resolved by molar distalization of 4.4 mm, interproximal stripping of 0.7 mm, and arch expansion. In the mandibular dentition, crowding of 6.7 mm was alleviated by molar distalization of 2.4 mm, an interproximal of 1.5 mm, and additional arch expansion. The incisor positions were maintained (SN-U1, 101.3°; IMPA, 88.8°), and soft-tissue profiles were improved (LL/E-line -1.1 mm; P< 0.001) after treatment. Maxillary and mandibular tooth-size arch length discrepancy of 12.4 mm and 6.7 mm, respectively, were resolved by molar distalization, interproximal reduction, and arch expansion, whereas incisor positions were maintained, and soft-tissue profiles were improved. This could be a viable treatment option in patients with moderate-to-severe crowding.

Effect of Different Maxillary Oral Appliance Designs on Respiratory Variables during Sleep.

This study aimed to analyze the efficacy of maxillary oral appliance (MOA) designs on respiratory variables during sleep. At baseline, 23 participants underwent a sleep test with a portable device for two nights and were categorized as participants with mild obstructive sleep apnea (mild-OSA) (n = 13) and without OSA (w/o-OSA) (n = 10). Three types of MOAs, standard-OA (S-OA), palatal covering-OA (PC-OA), and vertically increasing-OA (VI-OA), were each worn for three nights, and sleep tests with each MOA were performed with a portable device for two nights. Based on the average of the respiratory event index (REI) values for the two nights for each MOA, w/o-OSA participants with an REI ≥ 5.0 were defined as the exacerbation group and those with an REI < 5.0 as the non-exacerbation group. In mild-OSA participants, an REI ≥ 15.0 or REI ≥ baseline REI × 1.5 were defined as the exacerbation group and those with an REI < 15.0 and REI < baseline REI × 1.5 were defined as the non-exacerbation group. The percentage of the exacerbation and non-exacerbation groups with MOA was evaluated in the w/o-OSA and mild-OSA participants. The maxillary and mandibular dental-arch dimension was compared by dentition model analysis. The exacerbation group in w/o-OSA participants (n = 10) comprised 10.0% participants (n = 1) with S-OA, 40.0% (n = 4) with PC-OA, and 30.0% (n = 3) with VI-OA. The exacerbation group in the mild-OSA participants (n = 13) comprised 15.4% subjects (n = 2) with S-OA, 23.1% (n = 3) with PC-OA, and 23.1% (n = 3) in VI-OA. In the model analysis for w/o-OSA, the posterior dental arch width was significantly greater in the exacerbation group than in the non-exacerbation group wearing S-OA (p < 0.05). In addition, the ratio of the maxillary to mandibular dental arch width (anterior dental arch width) was significantly greater in the exacerbation group than in the non-exacerbation group for both PC-OA and VI-OA (p < 0.05). In mild-OSA, the maxillary and mandibular dental arch lengths and the ratio of maxillary to mandibular dental arch width (posterior dental arch width) were significantly smaller in the exacerbation group than in the non-exacerbation group for S-OA (p < 0.05). This study confirmed that wearing an MOA by w/o-OSA and mild-OSA participants may increase the REI during sleep and that PC-OA and VI-OA may increase the REI more than S-OA. The maxillary and mandibular dental-arch dimensions may affect the REI when using an MOA.

The location of the mental foramen in relation to the biometrics of the lower dentition and mandibular arch: A cross-sectional study

Purpose: To evaluate the position of the mental foramen among Malaysian Malays and Chinese based on the biometrics of the lower dentition and mandibular arch dimensions. &#x0D; Materials and methods: The horizontal and vertical position of mental foramen in relation to the midline, roots of teeth, mesiodistal dimension of the anterior and posterior teeth, and the mandibular arch length and width were measured and evaluated in 65 Cone-Beam Computed Tomography scans. &#x0D; Results: The location of mental foramen was predominantly located either between 1st and 2nd premolar or below 2nd premolar. There were no significant differences for all measurements of the mandible in relation to gender and ethnicities. There was a positive correlation of the mesiodistal diameter of the teeth with the mandibular arch length and width. However, mandibular arch length and width did not affect the location of the mental foramen. &#x0D; Conclusions: As the size of the teeth increases, the mandibular arch length and the width increase concurrently. However, regardless of the changes in the biometrics of the mandibular dentition and the arch dimensions, the anatomical position of the mental foramen remains the same. The mental foramen was located at the ratio of 0.5 vertically and 0.27 horizontally in the mandible. The inter-foramina distance of 51.36 mm suggests that Malaysian Mongoloids had sufficient space to receive five implants rigidly joined with a bar.

Parental exposure to CdSe/ZnS QDs affects cartilage development in rare minnow (Gobiocypris rarus) offspring

Cartilage development is a sensitive process that is easily disturbed by environmental toxins. In this study, the toxicity of CdSe/ZnS quantum dots on the skeleton of the next generation (F1) was evaluated using rare minnows (Gobiocypris rarus) as model animals. Four-month-old sexually mature parental rare minnows (F0) were selected and treated with 0, 100, 200, 400 and 800 nmol/L CdSe/ZnS quantum dots for 4 days. Embryos of F1 generation rare minnows were obtained by artificial insemination. The results showed that with increasing maternal quantum dots exposure, the body length of F1 embryos decreased, the overall calcium content decreased, and the deformity and mortality rates increased. Alcian blue staining results showed that the lengths of the craniofacial mandible, mandibular arch length, mandibular width, and CH-CH and CH-PQ angles of larvae of rare minnows increased; histological hematoxylin-eosin staining further indicated that quantum dots affected the development of chondrocytes. Furthermore, high concentrations of CdSe/ZnS quantum dots inhibited the transcript expression of the bmp2b, bmp4, bmp6, runx2b, sox9a, lox1 and col2α1 genes. In conclusion, CdSe/ZnS quantum dots can affect the skeletal development of F1 generation embryos of rare minnows at both the individual and molecular levels, the damage to the craniofacial bone is more obvious, and the toxic effect of high concentrations of quantum dots (400 nmol/L and 800 nmol/L) is more significant.