Although the etiology behind the failure of second molars to erupt has not been fully elucidated, several contributing factors have been suggested. Even though a considerable number of studies have been published on second molar impaction, only a limited number have examined the influence of mandibular skeletal characteristics via panoramic and cephalometric radiographs. This study aimed to evaluate the relationships between the impaction of mandibular second molars (MM2) and various skeletal and dentoalveolar morphological parameters. In this retrospective study, panoramic and lateral cephalometric radiographs of individuals aged 11–18 years were examined. Measurements of the study group (SG), consisting of individuals with impacted MM2, and the control group (CG), consisting of individuals with normally erupted MM2, were compared. Subgroups were formed on the basis of skeletal classifications. The primary evaluation parameters included the GoGn/SN angle, gonial angle, molar inclination angle, and ratio of MM1-ramus distance to MM2 mesiodistal crown width. A significance level of p < 0.05 was adopted for all the statistical analyses. There was no statistically significant difference in the GoGn/SN angle between the SG and CG. Within the study group, a significant difference in gonial angle was observed only among Class II individuals, where a decreased angle was associated with a more horizontal mandibular growth pattern. The molar inclination angle increased particularly in Class III individuals with impacted teeth, suggesting that increased mesial tipping may play a role in impaction. The most prominent finding was a significantly lower MM1-ramus distance to MM2 crown width ratio in the SG across all skeletal classes. MM2 impaction appears to be a multifactorial predominantly associated with local morphological limitations. Posterior space deficiency and increased mesial inclination were identified as major contributing risk factors. This study highlights the clinical value of early assessment of molar angulation and posterior space availability in preventing MM2 through appropriate orthodontic and surgical planning.

Background: Maxillary lateral incisor agenesis, peg-shaped lateral incisors, impacted canines, and cleft lip and palate frequently involve the maxillary lateral incisor–canine region and often show side-related distribution patterns. Whether trabecular bone structure within this region differs between sides in clinically healthy individuals remains unclear. This study evaluated right–left differences in maxillary trabecular bone structure using fractal analysis. Methods: Panoramic radiographs of 88 adults (43 males, 45 females; 18–40 years) with Class I occlusion and no dental, skeletal, or orofacial anomalies were retrospectively analyzed. Bilateral polygon-shaped ROIs were defined between the maxillary lateral incisor and canine roots. As methodological validation, standardized 20 × 20 pixel square ROIs were additionally analyzed. FD values were calculated using the ImageJ box-counting method. Inter-observer reliability was assessed by two independent oral and maxillofacial radiologists using the intraclass correlation coefficient (ICC) and Dahlberg error. Right–left comparisons were performed using paired-samples t -tests or Wilcoxon signed-rank tests. Associations with age and sex were also evaluated. Results: Using anatomically defined freehand ROIs, FD values were significantly higher in the left maxillary region than in the right (0.77 ± 0.23 vs. 0.70 ± 0.25; mean paired difference = 0.07, 95% CI: 0.01–0.13; p = 0.024; Cohen’s d _z  = 0.24 ). The same direction of the right–left difference was confirmed using standardized square ROIs. No significant right–left differences were found for ROI area ( p = 0.229), mean gray value ( p = 0.618), minimum gray value ( p = 0.682), or maximum gray value ( p = 0.708). The right–left FD difference was not associated with age or sex. Conclusions: A small but statistically significant right–left difference in FD values was detected within the maxillary lateral incisor–canine region. Although the effect size was small and the biological significance remains uncertain, consistent findings across two ROI approaches together with excellent inter-observer reproducibility support the methodological consistency of the proposed protocol. The findings should be interpreted as a subtle radiographic observation rather than as definitive evidence of physiological maxillary asymmetry. Clinical trial registration: Not applicable.

Background: The quad-helix (QH), a conventional appliance, and clear aligners (CA), which have been increasingly used, are both used for maxillary expansion. However, their biomechanical behavior during dentoalveolar expansion has not been directly compared. This study evaluates their biomechanical responses using finite element analysis (FEA). Methods: Three-dimensional finite element models of a CA with attachments and buccal root torque and a QH appliance were constructed. Clinically relevant loading conditions were applied based on reported activation protocols. A 5 mm activation (1.4 N) was applied to QH, and a 0.4 mm deformation (0.7 N) to CA. Tooth displacement and stress distribution were evaluated at cusp tips, root apices, and bifurcation areas of canines, premolars and molars. Results: In both models, displacement was greater at the crown level and decreased toward the root, indicating a predominantly tipping pattern. Maximum buccal displacement was observed at the first molar in the quad-helix model (1.054 × 10⁻⁴ mm), whereas in the clear aligner model, the highest value was at the second molar (5.498 × 10⁻⁵ mm). The quad-helix demonstrated a more localized expansion pattern, primarily affecting the first molar and premolars, while clear aligners exhibited a more distributed posterior response. Stress concentrations were more localized in the QH model and more uniformly distributed in the CA model. Conclusions: Dentoalveolar expansion is influenced not only by movement magnitude but also by the pattern of force distribution. Differences in posterior force transmission between CA and QH were associated with distinct biomechanical response patterns under the simulated loading conditions evaluated in the present study.

This study aimed to compare inferior alveolar canal and surrounding bone morphology between the long and short hemimandibles at three anatomical levels rel

To compare the initial biomechanical responses generated by different attachment configurations and button-cut Class II intermaxillary elastic mechanics du

Background/Objectives: Pediatric sleep-disordered breathing (SDB) is influenced by craniofacial morphology and host susceptibility. Evidence integrating cephalometric airway features with targeted genetic variation in symptomatic skeletal Class II children remains limited. We explored whether children with skeletal Class II mandibular retrognathia and SDB symptoms harbor selected genetic variants and whether carriers show distinct cephalometric airway characteristics. Methods: This cross-sectional study included 48 children with skeletal Class II malocclusion, mandibular retrognathia, and snoring/mouth-breathing symptoms. Craniofacial and airway parameters were assessed on lateral cephalograms. SDB burden was evaluated by a baseline home sleep study (respiratory event index, REI). Targeted sequencing screened TNFRSF1A, PSTPIP1, SLC6A4 (5HTT), ACE, APOE, IRS1, and additionally PHOX2B and PMP22. Exploratory group comparisons used Student’s t-test. Results: Variants were identified in 13/48 participants (27%) in TNFRSF1A, PSTPIP1, SLC6A4, ACE, APOE, and IRS1; none were detected in PHOX2B or PMP22. C3–H was higher in variant carriers (39.90 ± 6.40 vs. 36.48 ± 3.95 mm; p < 0.05). HH1 (perpendicular distance from the hyoid bone to the C3–RGN line) was higher but not significant (16.99 ± 7.58 vs. 14.61 ± 5.25 mm; p > 0.05). Conclusions: In this clinically screened pediatric skeletal Class II cohort with SDB symptoms, selected genetic variants co-occurred with specific hyoid–cervical cephalometric features. Given the cross-sectional design, absence of a control group, and small number of carriers, findings are exploratory and require replication in larger, controlled cohorts with standardized phenotyping.