Korean Journal of Orthodontics最新文献

Objective: This study aimed to investigate the effects of low-nicotine cigarette smoke (CS) inhalation on orthodontic tooth movement (OTM) in rats.

Methods: Forty 4-week-old male Wistar rats, were randomly divided into four groups: three experimental and one control. Group 1 (control group) had dental impressions taken at week 9. Group 2: OTM group received a continuous mesially directed force applied to the maxillary first molar at week 9 for 4 weeks. Group 3: CS group rats had 9 weeks of CS inhalation; Group 4: CS + OTM group, 9 weeks of CS inhalation and 4 weeks of orthodontic force application. Rats in groups 3 (CS) and 4 (CS + OTM) were exposed to 10 cigarettes for 8 minutes, 3 times per day for 9 weeks. All groups had polyvinyl siloxane impressions taken at week 9 and at the end of the experimental period (week 13). At week 13, all rats were sacrificed under general anesthesia, and their maxillae were dissected and scanned using a TRIOS 2014-1 intraoral scanner. The tooth movements were measured using digital models.

Results: A slight increase in tooth movement rate was observed in smokers. However, this difference was not statistically significant.

Conclusions: CS inhalation did not increase the rate of OTM in rats.

Objective: To evaluate changes in alveolar bone and tooth root dimensions in anterior teeth of patients with different tooth extraction types undergoing clear aligner therapy (CAT) and to provide reliable information for preventing tissue loss and providing tooth control in severe cases through a large-scale sample analysis of the clinical outcomes of CAT.

Methods: We selected 281 patients (186 non-extraction [NE], 59 with two-premolar extraction [TPE] in both the maxilla and mandible, and 36 with TPE in the maxilla and one lower-incisor extraction [OLIE] in the mandible) from the records of recent three years. Quantitative changes in the dentoalveolar apparatus were analyzed using pre- (T1) and post-treatment (T2) cone-beam computed tomography. The measured parameters included the alveolar bone height and thickness, and root length in the anterior teeth in different types of tooth extraction.

Results: Alveolar bone height loss was common in all groups after CAT. Compared to patients with NE, patients with TPE showed a higher risk of lingual bone dehiscence and torque loss (P < 0.05), whereas those with OLIE showed a higher risk of open gingival embrasures (P < 0.05). A more severe alveolar bone loss was observed in the mandibular anterior teeth than in the maxillary anterior teeth (P < 0.05).

Conclusions: Different tooth extraction types can lead to different degrees of bone loss in the direction of tooth movement, and orthodontists should adopt more cautious measures for mandibular anterior teeth. Despite numerous experimental studies for improving techniques and designs in CAT, tooth control and complication prevention in extraction cases remain challenging for orthodontists.

Objective: To investigate the three-dimensional (3D) changes in lip morphology introduced by different surgical orthodontic treatment approaches in skeletal Class III patients.

Methods: Forty Class III patients were treated using the surgery-first approach (SFA, n = 20) or a three-stage approach (TSA, n = 20), both involving bimaxillary surgery and maxillary premolar extractions. Cephalograms and facial scans were obtained at different time points (T0-T5) throughout the treatment period. T tests and repeated measures analysis of variance were compared to 3D lip morphology between groups. Correlation analysis and stepwise linear regression were used for prediction.

Results: After debonding, mandibular incisors in the SFA group were positioned more lingually (L1MP: SFA 80.75 ± 5.73°, TSA 89.78 ± 5.88°, P < 0.001), and the smaller ANB values (SFA 1.04 ± 1.43°, TSA 2.19 ± 0.99°, P = 0.005). Upper vermilion length increased in both groups after debonding, while lower vermilion length decreased significantly. The lower vermillion length in the SFA group was shorter than that in the TSA group (SFA 8.66 ± 2.01 mm, TSA 10.35 ± 2.19 mm, P = 0.015). ΔU1-AP, ΔANB, and ΔWits were significantly correlated with 3D lip morphology changes.

Conclusions: Both methods significantly improved the aesthetics of lip morphology in skeletal Class III patients. When the extraction space was closed, the lip shape was nearly stable in the SFA; TSA was stabilized 6 months post-surgery. The lips exhibited a compensatory response to differences in hard tissue and showed a moderate association with changes in dental and skeletal measurements.

Objective: This study aimed to evaluate the long-term biomechanical effects of alveolar bone loss on 0.25-mm canine bodily movement using a clear aligner (CA) through iterative finite element analysis (FEA).

Methods: Three-dimensional maxillary models with normal bone height, 2-mm bone loss, and 4-mm bone loss were constructed. An iterative FEA approach was applied to a single CA designed for 0.25 mm of planned distal movement, with biomechanical responses calculated throughout 50 sequential stages to simulate progressive tooth displacement. All components (maxilla, teeth, periodontal ligament, and CA) were assigned linear elastic properties. At each iterative stage, the forces, moments, crown displacement, tipping, rotation, and moment-to-force (M/F) ratios were analyzed.

Results: Alveolar bone loss produced lower initial forces but increased initial crown displacement and tipping. Forces declined rapidly after the initial stages and stabilized at a level below 1 N. Tipping peaked early and gradually decreased, with the largest reduction observed in the severe bone loss group. The M/F ratio increased after the early stages and maintained values above 10 across all groups, thereby promoting controlled bodily movement. Final crown displacement was greatest in the normal bone group, while overall rotation remained minimal and clinically insignificant.

Conclusions: Iterative FEA demonstrated that CAs produced lower forces and higher M/F ratios under periodontally compromised conditions, supporting controlled bodily movement. However, the observed excessive initial displacement underscores the need for careful clinical management to optimize outcomes.

Objective: This study aimed to compare the effects of multimedia and written explanations on anxiety, dental fear, and pain perception among adolescents before the start of fixed orthodontic treatment.

Methods: Individuals aged 14-18 years who presented to the Faculty of Dentistry at Adıyaman University were randomly assigned to the multimedia information group (MIG) and written information groups (WIG). Before the appointment for bonding, educational information was provided to the MIG and WIG as an 8-minute informative multimedia video and written form, respectively. All participants completed the State-Trait Anxiety Inventory-State Anxiety and Dental Fear Index before and after the procedure. After the session, they were asked to rate their perceived pain using a visual analog scale and the number of questions they asked the clinician regarding the treatment was recorded. For statistical analyses, the Kolmogorov-Smirnov, chi-square, paired-sample t , Student t, and Mann-Whitney U tests were used.

Results: No statistically significant differences in anxiety, fear, or pain scores were observed between the groups before and after the session (P > 0.05). Both groups exhibited no significant change in the anxiety scores between the two time points (P > 0.05), but exhibited significantly reduced fear scores (P < 0.05). Only the MIG demonstrated significant sex-related differences before the treatment session (P < 0.05).

Conclusions: Although the effects of multimedia and written education on the anxiety and fear scores exhibited no significant different, multimedia education may have reduced the chair time by decreasing the number of questions posed by the patients.

Objective: This pilot study aims to evaluate the clinical accuracy of Smart stereolithography (STL) files generated by the Dental Monitoring® (DM) system by comparing them with gold standard intraoral scans (IOSs).

Methods: Seven aligner patients using the DM application were included. For each patient, Smart STL files generated from remote scans were superimposed onto IOSs using the best-fit algorithm in OnyxCeph software. Differences regarding inclination, angulation, rotation, buccal/lingual, mesial/distal, and intrusion/extrusion were quantified and statistically compared.

Results: Statistically significant differences were observed in inclination, mesial/distal, and buccal/lingual movements, particularly in the posterior segments. However, all deviations remained within clinically acceptable thresholds for single aligner tooth movement.

Conclusions: Despite minor deviations, Smart STL files generated by DM demonstrated sufficient accuracy for use in aligner planning and refinement. These findings highlight the potential of DM-generated Smart STL files for subsequent aligner treatment.

Objective: To assess the suitability of polycyclohexylenedimethylene terephthalate glycol (PCTG) for orthodontic aligners and to compare the mechanical properties and 14-day stress relaxation behavior of different materials under simulated oral conditions, offering clinical guidance for material selection.

Methods: Materials used were Maxflex, Scheu, and Fusion Align, consisting of thermoplastic polyurethane (TPU), polyethylene terephthalate glycol (PETG), and PCTG, respectively. The following experiments were conducted: (1) tensile testing at 23°C and under simulated oral conditions; (2) prediction of 14-day stress relaxation using the time-temperature superposition principle; (3) right-angle tear strength testing; and (4) Shore D hardness testing.

Results: Mechanical properties followed the trend TPU > PETG > PCTG in elastic modulus, yield strength, right-angle tear strength, and Shore D hardness (P < 0.05); PETG > PCTG > TPU in yield strain (P < 0.05). TPU showed higher elongation at break than PETG and PCTG (P < 0.05), with no significant difference between PETG and PCTG (P > 0.05). Stress relaxation behavior was predicted based on the time-temperature superposition principle. With prolonged duration, the stress ranking progressively shifted from TPU > PETG > PCTG to PCTG > PETG > TPU.

Conclusions: PCTG exhibits light and sustained force, but its tear resistance and hardness are relatively low. In contrast, TPU demonstrates excellent tear resistance and hardness but experiences rapid force decay.

Objective: To investigate the accuracy of machine learning (ML)-assisted prediction of the need for orthognathic surgery (OGS) in patients with cleft lip and palate (CLP).

Methods: This study included 245 patients with CLP whose lateral cephalograms were available at pre-adolescence (T0; mean age, 8.45 years) and young adulthood (T1; mean age: 18.37 years). At T1, the patients were classified into the surgery group based on two criteria: (1) satisfying at least three of the following four conditions: ANB < -3°, Wits appraisal < -5 mm, APDI > 90°, and AB-MP < 60° and (2) undergoing presurgical orthodontic treatment or having undergone OGS. A total of 25.3% (n = 62) of patients were assigned to the surgery group, while 74.7% (n = 183) were assigned to the non-surgery group. Further, 80% and 20% of each group were used as training/validation and test sets, respectively. After 37 cephalometric variables and two cleft-related variables were measured, support vector machine (SVM) and feature importance analysis (FIA) with Shapley additive explanation were used to determine the prediction accuracy and predictors at T0.

Results: SVM demonstrated area under curve 0.84, accuracy 83.7%, sensitivity 83.3%, and specificity 83.8%. FIA revealed 10 predictors: A to N-perpendicular, L1 to A-Pog, Pog to N-perpendicular, L1 to Lower-occlusal plane, Cleft type, U1 to Upper-occlusal plane, IMPA, gonial angle, anteroposterior facial height ratio, and ANB with accumulated importance of 64.51%.

Conclusions: The ML algorithm used in this study may support clinical decision-making in identifying candidates for future OGS at 8 years of age.

Objective: To evaluate the accuracy of artificial intelligence (AI)-assisted soft tissue landmark identification (STLI) on serial lateral cephalograms (Lat-Cephs) of Class III patients treated with two-jaw orthognathic surgery across four different time-points.

Methods: A convolutional neural network model was developed for STLI, trained and validated using 3,004 Lat-Cephs from 751 patients. The test set included 224 Lat-Cephs from 56 patients, divided into the genioplasty (n = 22) and non-genioplasty (n = 34) groups. The four time-points included initial (T0), pre-surgery (T1, brackets), post-surgery (T2, brackets, surgical plates, and screws [S-PS]), and debonding (T3, S-PS and fixed retainers). AI accuracy was compared with a human standard for 13 soft tissue landmarks. Mean radial errors (MREs), horizontal and vertical errors, and statistical differences were analyzed.

Results: The total MRE across all time-points was 1.50 ± 0.48 mm, with 64.9% of values being less than 1.5 mm MRE. There were no significant differences in accuracy among the four time-points (T0, 1.41 mm; T1, 1.53 mm; T2, 1.58 mm; T3, 1.47 mm). The pronasale, stomion inferius (Stmi), stomion superius (Stms) showed an increase in MRE (P < 0.01, P < 0.05, and P < 0.05, respectively), whereas the Lower Lip showed a decrease in MRE (P < 0.01). There were no significant differences in errors across time-points for the soft-tissue B point, soft-tissue Pogonion, or soft-tissue Menton between the genioplasty and non-genioplasty groups.

Conclusions: The AI algorithm in this study might be an effective tool for STLI in Lat-Cephs at T1, T2, and T3, despite the presence of brackets, S-PS, fixed retainers, genioplasty, and bone remodeling.