Orthodontics & Craniofacial Research最新文献

Objectives: This study aimed to investigate the position of the tongue and hyoid bone at rest according to incisal relationships using cone beam computed tomography and to examine whether dentoskeletal measurements are correlated with these positions.

Materials and methods: Participants were categorised into normal, open bite, cross-bite and combined open-crossbite groups according to overjet and overbite. Linear and volumetric measurements of tongue dimensions and positions of the tongue and hyoid bone were compared among the four groups using one-way analysis of variance and the Bonferroni post hoc test. Pearson correlation coefficients were calculated to evaluate the relationships of tongue and hyoid bone positions with dentoskeletal parameters.

Results: Downward and forward positions of the tongue and hyoid bone were observed in the cross-bite and open-crossbite groups. Overjet and mandibular incisor-to-mandibular plane angles were negatively correlated with all parameters of the vertical and horizontal tongue and hyoid bone positions. Horizontal skeletal parameters negatively correlated with tongue-to-palate distance, tongue tip ratio, oral cavity airway volume and horizontal hyoid bone position. Vertical skeletal parameters correlated with the horizontal position of the tongue and hyoid bone.

Conclusion: The downward and forward positions of the tongue and hyoid bone at rest were related to anterior cross-bite but not to anterior open bite, indicating that the tongue position was related to the most anteriorly positioned teeth. The inferior and anterior positions of the tongue correspond to a constricted maxilla, skeletal Class III relationship, retroclined mandibular incisors and negative overjet.

To overcome several disadvantages and limitations of tooth-borne rapid palatal expanders in fully grown patients with maxillary transverse deficiency, miniscrew-assisted rapid palatal expanders (MARPE) were introduced as an efficient alternative and have been widely used in the past decade. More recently, pure bone-borne MARPE has been introduced to reduce dentoalveolar side effects and its use has been increasing. This review article aims to report the characteristics and clinically important considerations of the innovative pure bone-borne ATOZ spring expander. This review article looks at the characteristics and placement procedure, expansion protocol, treatment effect and success rate with ATOZ expanders anchored to the bone by six-to-ten bicortical miniscrews as described in several papers and illustrated with some clinical cases. Unlike conventional MARPE, which is activated daily at home, the ATOZ is activated by the orthodontist every 4 weeks because activation is transmitted through four connector links tangent to the axis of the jack-screw, creating continuous tension across the midpalatal suture. Upon activation of the ATOZ expander with a 92.8% success rate, a more parallel expansion pattern is observed for the sutures within the bilateral nasomaxillary complex in the coronal view, while a V-shaped expansion pattern is observed at the level of the palatal basal bone in the horizontal view, with the anterior teeth showing greater expansion than the posterior teeth. In late adolescent or adult patients with maxillary transverse discrepancy, ATOZ spring expanders can provide efficient palatal expansion with reduced dentoalveolar side effects.

Introduction: The mechanical properties of polyethylene terephthalate glycol modified (PETG) and thermoplastic polyurethane (TPU), commonly used in clear orthodontic aligners, significantly influence their clinical performances.

Materials and methods: The present investigation involved the use of a universal testing machine equipped with specialised software to examine the mechanical behaviour of PETG and TPU aligners. The 2 materials with 2 thicknesses (0.6, 0.9 mm) were subjected to tensile tests under simulated intraoral conditions, and the responses of the materials to the varying displacements, were analysed to investigate their respective behaviours under different loading conditions. The Mann-Whitney U test was employed to assess differences between the groups.

Results: For 0.9 mm thickness, the stiffness between the two materials was not significantly different, except for the canine region, where TPU was significantly stiffer. Aligners fabricated in PETG with greater thickness consistently showed higher stiffness compared to thinner PETG, indicating that material behaviour varies with thickness, except for the canine region.

Conclusions: The mechanical behaviour of thermoplastic materials for clear aligners is influenced by material type, thickness and tooth location.

Background: This retrospective study aimed to evaluate the skeletal and dentoalveolar effects of maxillary expansion using the Invisalign First system in the mixed dentition.

Methods: The study was conducted in the orthodontic department of the Fourth Affiliated Hospital of Zhejiang University School of Medicine between 2021 and 2024. Inclusion criteria were mixed dentition patients with maxillary transverse deficiency, fully erupted first molars, arch width discrepancy ≤ 5 mm, mild to moderate crowding and pre-peak growth status (CS2). Exclusion criteria were Angle's Class III malocclusion, previous orthodontic treatment, congenitally missing teeth, TMJ disorders, cleft lip/palate, or use of additional appliances. All patients were treated with a standardised digital protocol using the Invisalign First system with optimised expansion support attachments. No additional buccal root torque was programmed, and Class II elastics were not used. Pre- and post-treatment intraoral scan digital models and cone-beam computed tomography data were obtained. Measured parameters included arch width, nasal width, apical base width, alveolar width, palatal depth and first molar inclination. Statistical analyses were performed using paired t-tests for normally distributed data and Wilcoxon signed-rank tests for non-normally distributed data, with a significance level set at p < 0.05.

Results: The study included 45 patients (mean age 8.84 ± 1.01 years; mean treatment duration 18.26 ± 0.95 months). Significant transverse increases were observed in all maxillary arch widths, particularly in the canine and deciduous molar regions (canine dental width: 4.17 ± 1.91 mm, p < 0.001; first deciduous molar width: 3.86 ± 1.93 mm, p < 0.001; second deciduous molar width: 4.38 ± 1.78 mm, p < 0.001). Corresponding significant expansion was noted at the alveolar bone level (anterior alveolar process width: 4.04 ± 3.37 mm, p < 0.001; posterior alveolar process width: 2.51 ± 1.71 mm, p < 0.001). The maxillary first molars showed controlled buccal inclination of 1.6° ± 4.09° (p < 0.01). The upper arch perimeter increased by 3.68 ± 2.95 mm (p < 0.001) with crowding reduction of 3.83 ± 3.00 mm (p < 0.001). No significant palatal depth changes occurred (0.42 ± 3.36 mm, p = 0.41).

Conclusion: In the mixed dentition, the Invisalign First system can effectively expand the maxillary dental-alveolar width, maintain molar inclination and improve the transverse deficiencies and arch form in the canine-premolar region.

Objective: To compare the therapeutic efficacy of miniscrew implant anchorage with that of conventional extraoral arch anchorage, both of which are combined with orthodontic-orthognathic treatment, in patients with skeletal Class II malocclusion.

Methods: This prospective nonrandomised controlled study included 130 patients. In terms of treatment method and patient preference, 58 patients received conventional orthodontic-orthognathic treatment with extraoral arch anchorage (conventional group), whereas 72 patients received treatment augmented with miniscrew implant anchorage (study group). The treatment protocol for all patients followed the conventional three-stage orthodontic-orthognathic approach. The outcomes assessed included treatment effectiveness, adverse events, root resorption (volume via CT), skeletal and dental changes (via comprehensive cephalometric analysis), soft tissue profile changes, facial aesthetics, and alveolar bone morphology (via CBCT).

Results: The total effective rate was significantly greater in the study group (95.83%) than in the conventional group (74.14%) (p < 0.05). While both groups presented significant root resorption posttreatment (p < 0.05), the degree of resorption did not differ significantly between the groups (p > 0.05). Crucially, CBCT analysis revealed significantly better preservation of the palatal bone plate and alveolar bone height in the study group (p < 0.05). The study group also demonstrated significantly greater improvements in skeletal parameters (SNA, SNB, FMA, and PP-FH), dental decompensation (U1-SN, U1-NA, L1-MP, and L1-NB), soft tissue indices, and facial aesthetics (p < 0.05). The incidence of adverse events was significantly lower in the study group (34.72% vs. 75.86%, p < 0.05). Logistic analysis revealed that oral hygiene, vertical facial pattern, peri-implant swelling, and force application time were independent risk factors for miniscrew success.

Conclusion: The integration of miniscrew implant anchorage in orthodontic-orthognathic treatment for skeletal Class II malocclusion provides superior clinical efficacy. Its primary advantage lies in enabling enhanced control over dental decompensation and skeletal correction, leading to significantly improved facial aesthetics, a more favorable mandibular position, and better alveolar bone preservation, with a lower complication profile. This represents an effective and reliable treatment option for these patients.

Objectives: This study aimed to investigate the biomechanical effects of different clear aligner thicknesses and attachment design on the intrusion of maxillary premolars and molars, utilising finite element analysis (FEA) without the incorporation of auxiliary mechanics.

Materials and methods: Three-dimensional models of the maxilla, dentition, periodontal ligaments and clear aligners were reconstructed from cone-beam computed tomography (CBCT) data. A total of nine experimental groups were defined based on aligner thicknesses (0.75, 0.95 and 1.15 mm) and attachment types (No attachment (NA); horizontal attachment (HA); occlusally bevelled horizontal attachment (OHA)). A simulated intrusion of 0.2 mm was applied to the premolars and molars and the resulting tooth displacements and stress distributions within the aligner and periodontal ligament were analysed via FEA.

Results: Analysis confirmed effective posterior intrusion with maximum values of 0.115 mm in second molars (Model 9). OHA achieved greater intrusion than HA. Von Mises stress values demonstrated a systematic hierarchy (NA < HA < OHA) across all thickness groups, ranging from 0.594 MPa (Model 1) to 0.949 MPa (Model 9), with aligner deformation showing inverse correlation (0.647-0.487 mm).

Conclusion: Aligner thickness and attachment design significantly influenced posterior intrusion biomechanics. The combination of 1.15 mm aligner thickness with OHA represents the optimal configuration for posterior intrusion. Attachment geometry plays a critical role in force distribution, with bevelled designs providing enhanced effectiveness. These findings establish evidence-based guidelines for future clinical clear aligner applications in posterior intrusion cases.