American Journal of Orthodontics and Dentofacial Orthopedics最新文献

Background: In fixed appliance therapy, torque moments are transferred through the bracket and are important for the final position of the tooth. Studies have analyzed only the torque-relevant bracket deformation in single bracket-archwire combinations with respect to various archwire rotations, although segmental torque is often used clinically.

Methods: In this study, experiments were conducted in an experimental setup with 2-bracket segments with 0.018-in and 0.022-in conventional brackets with commonly used rectangular archwires and ligatures to measure the torque moment and the relevant tie-wings deformation for 6, 7, and 8 mm interbracket distances (IBD).

Results: The torque moment in both 0.018-in and 0.022-in brackets increased as the archwire dimension and rotation increased. The torque moment with stainless steel ligation was significantly larger than that of the elastic ligature for all the archwires tested in both brackets. Each segmental bracket-archwire-ligature-IBD combination tested had shown a significant difference between the distal and mesial tie-wing deformations for varying torque.

Conclusions: We conclude that in both 0.018-in and 0.022-in brackets, the behavior of the 2-bracket segment-archwire-ligature combination with varying IBD was strongly influenced by the individual factors and also in combination.

Background: There is limited information available regarding the bone volume in the sagittal dimension of the infrazygomatic crest (IZC) that is safe for the insertion of a temporary skeletal anchorage device. The objective of this study was to assess the sagittal bone availability when the anterior and posterior walls of the IZC reach an inclination of 45°.

Methods: A cross-sectional investigation was undertaken on 100 cone-beam computed tomography scans of 40 males and 60 females. A total of 20 landmarks were digitized for each IZC outline, 1 mm from the vestibular alveolar bone, and their x, y, and z coordinates were extracted. Afterward, the sagittal measurement of the IZC at which the curvature reached 45° was recorded. Symmetry of measurements was assessed using paired-samples t tests. In addition, these measurements were compared as a function of sex and age group (≤21 vs >21 years) using an independent-samples t test and the Spearman rank correlation coefficient test (P <0.05).

Results: There were no significant differences between paired sagittal measurements of the IZC (3.5 ± 1.5 mm on the right side and 3.6 ± 1.3 mm on the left side; P = 0.144), except for younger patients (P = 0.030). In addition, no significant differences were found between corresponding male and female measurements (P ≥0.149). A significant discrepancy was identified between the younger age group (3.2 ± 1.2 mm) and the older cohort (3.8 ± 1.6 mm) for the sagittal dimension of the right IZC (P = 0.038), with an estimated mean difference of 0.03-1.16 mm (95% confidence interval). A significant positive weak correlation was found between the sagittal dimension of the right IZC and age (ρ = 0.201; P = 0.045).

Conclusions: Sufficient IZC bone volume is available at an angle of 45° for inserting a temporary skeletal anchorage device, with no sex or side variation, except for the significantly greater sagittal dimension of the right IZC in older patients.

Achieving an absolutely stable result after orthodontic treatment is not possible, but the appropriate use of retainers can minimize unwanted posttreatment changes. This article discusses the causes of unwanted posttreatment changes, evidence-based retention, fixed retainers, removable retainers, and dual retention and compares the indications, designs, and regimes for various types of retainers. It also discusses the importance of a shared decision-making process, involving the patient when planning retention, how retention is a long-term lifestyle choice, and how responsibility for the long-term success of retainers is shared between the orthodontist, patient, and dentist.

Introduction: This study evaluated the effect of pretreatment skeletal pattern and the type of appliance on the development of the mandible in a sagittal forward position during activator treatment.

Methods: A retrospective cohort study compared cephalograms of 188 patients before and after treatment with a Ton Kooiman appliance (T-appliance) and a headgear activator (HAC). All patients were stratified according to divergence. The cephalograms were calibrated, and 5 sets of measurements were performed. The primary outcome was the development of the mandible in the sagittal forward direction, which was evaluated with the sagittal development of the landmarks Infradentale, B-point, and Pogonion. Secondary landmarks were used to evaluate vertical and sagittal development.

Results: The sagittal development of the Pogonion was found to be statistically significant in all groups. In the hyperdivergent group, the T-appliance demonstrated a statistically significant increase in mean forward development of 1.3 mm compared with the HAC. In the normodivergent group, no statistically significant differences in the sagittal development of primary landmarks were found between the HAC and the T-appliance. However, in this group, Gonion-Gnathion distance and Lower Facial Height showed statistically greater increase during treatment with a HAC compared with the T-appliance.

Conclusions: When myofunctional therapy is indicated for a normodivergent patient, both the T-appliance and HAC can be applied. For a hyperdivergent patient, the T-appliance should be preferred. Nevertheless, the development of a guideline to assist in the choice among different myofunctional appliances for a specific patient would need a comparison of more types of activators and should also include hypodivergent groups.

Clear aligner (CA) therapy has undergone remarkable developments over the past 2 decades, transforming from a simple alignment modality into a mainstream orthodontic treatment capable of addressing complex malocclusions. Despite these innovations, the predictability of aligner tooth movements remains one of the most challenging aspects of clinical practice. This review explains the biomechanical considerations and clinical determinant factors that underline the variability in tooth movement predictability with CAs. From a biomechanical standpoint, 3 fundamental conditions-anchorage adequacy, stress continuity, and sufficient aligner-to-tooth contact-collectively determine the accuracy with which aligner biomechanics are translated into clinical reality. This proposed anchorage-stress-contact triad provides the biomechanical rationale for evaluating aligner predictability. The predictability of aligner tooth movements is clinically governed by a multifactorial interplay among aligner-related factors (material properties and shape design), practitioner-related factors (digital setup precision, attachment design, aligner staging, and clinical monitoring), and patient-related factors (compliance and biological variability). Understanding how these determinants interact provides a comprehensive basis for interpreting inconsistencies between digitally programmed and clinically achieved outcomes, offering insights to optimize aligner tooth movements and enhance aligner treatment outcomes.

Introduction: This study aimed to quantitatively and systematically evaluate the association between parent-child relationship (PCR) and orthodontic compliance with clear aligners (CAs) among children and adolescents.

Methods: Children and adolescents aged 6-18 years undergoing orthodontic treatment with CAs were included. Parents completed 3 sections of the questionnaire: the sociodemographic section, the previously established Child-Parent Relationship Scale, and the CA compliance section with 8 self-designed compliance indicators. Spearman correlation coefficients and binary logistic regression were used for comprehensive quantitative analysis.

Results: A total of 124 questionnaires were included and analyzed. No significant differences in CA compliance were found across different sociodemographic characteristics (P >0.05). Among compliance indicators, appointment adherence (4.67 ± 0.70) and timely aligner change (4.42 ± 0.83) received the highest scores, whereas chewies usage scored the lowest (3.21 ± 1.14). Higher closeness and lower conflict demonstrated a statistically significant, but relatively weak correlation with a higher mean compliance score (P <0.01). Significantly more patients with high closeness and low conflict demonstrated better CA compliance, particularly in cleaning aligners and timely aligner change (P <0.05). Participants with high closeness were 2.2 times more likely to achieve better overall compliance, whereas those with high conflict were only 0.3 times as likely as those with low conflict.

Conclusions: High closeness and low conflict in PCR are associated with better CA compliance among children and adolescents, particularly in cleaning aligners and timely aligner change. Chewies usage showed the lowest compliance and warrants significant improvement. Pretreatment assessment of children's and adolescents' PCR can offer valuable prognostic insights for orthodontic treatment planning and personalized compliance management.

Introduction: Class II functional appliances are widely used to treat skeletal Class II malocclusion in growing patients, whereas molar distalization is often employed for dental Class II malocclusion. However, the impact of these treatment modalities on upper airway dimensions remains controversial. This study examines the effects of Herbst appliance treatments on the upper airway changes compared with the Pendex appliance in adolescent patients with Class II malocclusion.

Methods: Cone-beam computed tomography (CBCT) scans of 50 patients with Class II malocclusion were obtained from a private orthodontic office (Chalfont, Pa). Twenty-five patients were treated with Herbst appliances (12.16 ± 1.89 years; 13 males and 12 females) and 25 patients with Pendex appliances (11.72 ± 1.22 years; 12 males and 13 females). Measurements were taken for volume, length, and cross-sectional areas of the total, retropalatal, and retroglossal upper airway. CBCTs were taken at baseline (T1), after appliance removal (T2), and from final records after fixed edgewise appliance treatment (T3) (T1-T3: 41.11 ± 9.95 months for Herbst appliances and 44.81 ± 9.63 months for Pendex appliances). In addition to 3-dimensional CBCT analysis, 2-dimensional measurements were performed and compared with a Class II untreated control group comprising 25 age- and sex-matched patients from the American Association of Orthodontists Foundation Bolton-Brush Craniofacial Growth Legacy Collection. Differences across time points within groups were assessed using repeated-measures analysis of variance test, whereas between-group differences at individual time points and for changes from T1 to T3 were evaluated using independent-samples t tests adjusted for baseline (T1) outcome values and follow-up duration.

Results: From T1 to T3, both the Herbst and Pendex groups showed a significant increase in total upper airway volume and length. However, the magnitude of these changes did not differ significantly between the 2 groups. In the 2-dimensional analysis, no significant differences were observed among the Herbst, Pendex, and untreated control groups in airway area changes from T1 to T3.

Conclusions: Both the Herbst and Pendex appliances resulted in comparable increases in total upper airway volume and length in adolescent patients with Class II malocclusion, primarily attributable to normal growth.

The periodontal ligament (PDL) and periosteum are mechanosensitive tissues essential for alveolar bone maintenance, remodeling, and regeneration. Their functional interplay, particularly during orthodontic tooth movement, remains underexplored. This review introduces the novel concept of the PDL-periosteum axis as a biologically interactive unit coordinating site-specific alveolar adaptation and periodontal homeostasis. Both tissues share mechanosensitive and osteogenic pathways regulating progenitor recruitment, osteoblastic differentiation, and extracellular matrix remodeling. Through crosstalk with osteocytes, they form a multilevel mechanosensory network integrating internal and external forces across the alveolar complex. Functionally, the PDL transduces forces within the alveolar socket, whereas the periosteum responds to cortical strain by supplying progenitor cells and driving adaptive remodeling. Disruption of either component predisposes to complications, including ankylosis, root resorption, or impaired bone regeneration, whereas preservation of both enables orthodontically induced bone formation even in severe alveolar deficiency. The integrity of the PDL-periosteum axis critically determines clinical outcomes, from favorable healing to maladaptation such as dehiscence, fenestration, or fibrotic adhesions. Recognizing this axis provides a systems biology framework for improved diagnosis, treatment planning, and regenerative strategies, bridging mechanobiology with clinical practice.

Background: In this study, the effect of open-arch mechanics on the displacement and von Mises stress distributions in mandibular teeth was investigated using a finite element analysis.

Methods: After mandibular bone, teeth, and periodontal ligament formation, 0.022-in brackets and 0.016 × 0.022-in tubes were placed on the buccal equatorial line. Four scenarios were modeled using 2 materials (nickel-titanium [NiTi] and stainless steel [SS]) and 2 arch wire sizes (0.016-in and 0.016 × 0.022-in). Displacement and von Mises stresses were analyzed via finite element analysis (Algor Fempro, ALGOR Inc, Pittsburgh, Pa) in models including teeth up to the second molar, with the mandibular left first premolar missing.

Results: The highest von Mises stress was found in the 0.016-in NiTi wire, and the lowest in the 0.016-in SS wire. Across scenarios, peak root surface stress was at the apical region of the mandibular left second premolar, whereas the highest periodontal ligament stress was in its gingival third. The buccal tubercle of this tooth showed the greatest displacement. Among archwires, the highest stress occurred in the 0.016-in SS wire.

Conclusions: Von Mises stresses decreased with distance from the missing tooth site. The highest stress occurred at the apical end of the mandibular left second premolar. Except for the 0.016-in round NiTi wire, this tooth showed the greatest tubercle apex displacement. In all scenarios, except the mandibular left first molar, mesial root stresses were greater in the mandibular roots than in the distal roots.