Korean Journal of Orthodontics最新文献

Objective: This study aimed to evaluate the use of a stainless-steel fixed retainer for post-orthodontic retention in patients with labiolingual alveolar bone resorption in the mandibular anterior segment.

Methods: Three mandibular anterior segment models (with or without labial or lingual alveolar bone resorption) with 0.5-mm-diameter retainers bonded to all teeth were constructed. Two occlusion schemes were simulated: a 285.3 N force applied to four mandibular incisors (incisor biting) and a 93 N force applied to the left canine (laterotrusion). The tooth displacement and stress distribution in the periodontal ligament (PDL), retainer, and composite were evaluated.

Results: Compared to no resorption, labial bone resorption significantly increased tooth displacement and PDL stress concentration in the central incisors during incisor biting, whereas lingual resorption had a greater effect on the guiding canine during laterotrusion. The retainers were susceptible to stress concentrations in the resin-uncovered area, mesial region of the lateral incisors under incisor biting, and mesial region of the guiding canine under laterotrusion. For the composite, the composite-retainer interface was prone to stress concentrations, especially in the mesial or distal extremes of the adhesive composite of the incisors.

Conclusions: A 0.5-mm-diameter stainless-steel lingual retainer bonded on all teeth is a clinically acceptable retention procedure for patients with lingual bone resorption in the lower anterior region. However, it should be used more cautiously for patients with labial bone resorption as it exposes the lower central incisors to a greater risk. Excessive stress on the retainer and composite due to the occlusion force may lead to unwanted tooth movement, necessitating closer monitoring.

Objective: Investigate the histological response of the periodontal tissue to incisor movement using varying-thickness clear aligners in a rabbit model.

Methods: Thirty-three New Zealand rabbits were randomly assigned to two experimental groups (0.38-mm and 0.68-mm aligners) and a control group. Each rabbit in the experimental group wore three sequential aligners, which were changed every 5 days. Orthodontic force was measured using a uniaxial force sensor, and tooth movement was quantified using three-dimensional imaging. Root resorption was assessed using micro-computed tomography. Histological and immunohistochemical staining and real-time quantitative reverse transcription polymerase chain reaction tests were performed to evaluate the periodontal tissue response.

Results: The 0.68-mm aligners generated larger forces than the 0.38-mm aligners. Tooth movement was faster with the third 0.38-mm aligner, with no statistically significant differences between the two groups. Both groups exhibited minor root resorption, with the 0.68-mm group exhibiting larger resorption craters. Additionally, the 0.68-mm group demonstrated more significant deformation of periodontal fibers and increased expression of inflammatory markers. The 0.38-mm group showed a larger number of osteoclasts on the compression side.

Conclusions: Both aligners achieved effective tooth movement. The 0.38-mm aligners exerted smaller forces and enabled slightly faster movements than the 0.68-mm aligners. Although both groups showed minimal root resorption, the 0.68-mm group exhibited larger resorption craters. Furthermore, the 0.38-mm group exhibited less histological deformation and inflammation in the periodontal tissues. These results suggest that aligner thickness can be tailored to customize treatments. Further studies with longer observation periods and more refined methodologies are warranted.

Objective: To assess differences in the available posterior space for molar distal movement according to the presence and three-dimensional position of third molars.

Methods: This study included 46 and 59 patients for the maxilla and mandible, respectively. The patients were assigned to third molar and no-third molar groups. Retromolar distances were measured at different vertical root levels of the second molar. The positions and axial angulations of the third molars were also examined. An independent t test or Mann-Whitney U test was performed to compare the retromolar distance between groups. The Pearson correlation coefficient was calculated to investigate the relationship between retromolar distance and age or third molar variables.

Results: The retromolar distance was shortest at the 2 mm apical level in the maxilla and at the 10 mm apical level in the mandible. The maxillary retromolar distance of the distobuccal root was significantly longer at all apical levels in the third molar group than in the no-third molar group (P < 0.01), but was not significantly different at the 10 mm apical level in the mandible (P = 0.969). The number of buccally positioned third molars in the mandible was significantly higher than that in the maxilla (P < 0.001). The shortest retromolar distance in both jaws was not significantly associated with age, the third molar's position, or eruption status.

Conclusions: The available posterior space with the third molar present was significantly larger than that without the third molar in the maxilla, but was not significantly different in the mandibular posterior space.

Objective: This study aimed to examine the effects of unilateral crossbite on the structure of the mandibular bone by using fractal analysis.

Methods: This study was conducted using panoramic films obtained retrospectively from 45 individuals with crossbite and 45 individuals with normal occlusion (NO). Fractal measurements were performed on the condyle, corpus, and angulus on both left and right sides of the panoramic films. The films were divided into three groups: cross-side (Cs), normal-side (Ns), and NO. The Cs group was further analyzed on the basis of the number of teeth in the crossbite. Data were analyzed using the non-parametric Kruskal-Wallis test and post-hoc Dunnett's T3 multiple-comparison test. Statistical significance was set at P < 0.05.

Results: The mean condylar fractal dimension (FD) showed no significant difference between the groups (P > 0.05). The mean angulus FD in the Cs group was significantly higher than that in the NO group (P = 0.006). Similarly, the mean corpus FD in the NO group was significantly lower than those in the Cs and Ns groups (P = 0.003). In the Cs group, comparisons based on the number of teeth in the crossbite showed no significant differences among the condyle, angulus, or corpus regions.

Conclusions: Fractal analysis may be an effective approach for detecting variations in mandibular trabecular patterns associated with unilateral crossbites. In cases of unilateral crossbite, the trabecular structure was affected in the angulus and corpus regions.

Objective: Comparing nasal cavity and pharyngeal airway volumes and minimum cross-sectional areas in nongrowing patients who underwent miniscrew-assisted rapid palatal expansion (MARPE) or surgically assisted rapid maxillary expansion (SARME) with and without pterygomaxillary disjunction (PD).

Methods: Pretreatment and post-expansion cone beam computed tomography scans of 30 patients (mean age: 18.6 years), diagnosed with maxillary transverse deficiency, were grouped into three (n = 10 each) according to expansion protocol: 1) MARPE; 2) SARME without PD [SARME-PD(-)]; 3) SARME with PD [SARME-PD(+)]. In NemoStudio software, eleven linear measurements were used to evaluate nasal and maxillary skeletal parameters. Eight airway measurements were used to evaluate the volume and minimum cross-section of the nasal cavity, nasopharynx, retropalatal region, and retroglossal region. Intragroup and intergroup changes were evaluated for statistical significance at P < 0.05.

Results: Nasal lateral, nasal floor, external maxillary, palatal, and maxillary intermolar widths significantly increased in all groups. In MARPE, nasal cavity and nasopharynx volumes and minimum cross-sectional area increased significantly. Nasopharyngeal volume increased significantly in SARME-PD(-), whereas nasal cavity volume and minimum cross-sectional area decreased significantly in SARME-PD(+). MARPE group showed greater expansion in nasal lateral width than SARME-PD(-) and SARME-PD(+) groups. Mean changes in nasal cavity volume, minimum cross-sectional area, and nasopharyngeal volume were significantly greater in MARPE than in SARME-PD(+).

Conclusions: MARPE group showed greater increases in linear and volumetric measurements. However, differences were statistically insignificant compared to SARME-PD(-). Retropalatal and retroglossal parameters were unaffected in all groups. PD did not provide substantial advantage.

Objective: We investigated the potential association between intraoral metal alloys and the presence of Prevotella intermedia in patients with rheumatoid arthritis (RA).

Methods: A case-control study was conducted using bacteriological tests. The RA group included 80 patients, of whom 40 tested positive for Prevotella intermedia and 40 tested negative. The control group consisted of 81 subjects without RA, with 39 testing positive for Prevotella intermedia and 42 testing negative.

Results: Univariate analysis identified the presence of intraoral metal alloys (lingual fixed retainers or metal-ceramic crowns), male sex, and gingival inflammation as significant predictors of Prevotella Intermedia presence (P < 0.05). In multivariate analysis, intraoral metal alloys demonstrated the strongest association, with an odds ratio = 4.21 (P < 0.001). However, no significant difference in Prevotella intermedia positivity was observed between the RA and control groups.

Conclusions: These findings suggest that intraoral metal alloys are associated with an increased prevalence of Prevotella intermedia in subgingival pockets among adults, independent of RA status.

Objective: This study aimed to evaluate the accuracy of a three-dimensional (3D)-printed palatal auxiliary device (PAD) compared to computer-aided design (CAD) reference data.

Methods: Thirty patients who underwent orthodontic treatment using a PAD for maxillary protraction after palatal expansion were included in this study. Two groups of 15 patients were analyzed to compare the accuracy of the two PAD designs. Accuracy and adaptation were assessed through two sets of measurements: 1) deviations between the printed PAD and its CAD reference to determine printing accuracy, and 2) deviations in PAD positioning when clinically applied, simulated on a printed model. Sixteen measurement points (anterior, posterior, left, and right) were evaluated across the x-, y-, and z-axes and t tests were performed for comparison.

Results: The PAD-only measurements showed errors greater than 0.1 mm on all axes but within the marginal limits of 0.05 mm to 0.25 mm (P < 0.05). Similar results were observed with the PAD-adapted measurements. Significant differences were found across all axes in the PAD-only group and between the two designs. Tukey's post hoc analysis identified a specific ranking of errors in the combination-type PAD: left, anterior, posterior, and right. However, for PAD-adapted group, majority of comparisons showed no significant differences and those that did lacked consistency in pattern.

Conclusions: This study demonstrates that 3D-printed PADs maintain clinically acceptable accuracy and can be effectively integrated into existing intraoral devices. Although errors varied in certain areas, they did not significantly impact the final adaptation.

Objective: Effects of contemporary remineralization agents on the repair and regeneration of eroded enamel, specifically examining Vickers hardness (VH), shear bond strength (SBS), the calcium/phosphorus (Ca/P) ratio, and bracket-enamel interface.

Methods: Extracted maxillary premolars with intact enamel were selected. Sixteen samples with sound uneroded enamel (Group 1, control) and eighty artificially eroded samples were used. The eroded samples (n = 80) were etched with phosphoric acid and divided into five remineralization treatment groups (Groups 2, 3, 4, 5, and 6) based on the type of remineralization applied. VH and Ca/P ratios were assessed using energy dispersive X-ray spectroscopy. All samples were primed and bonded with orthodontic brackets. Two samples from each group were assessed under a scanning electron microscope to analyze the bracket-enamel interface. The remaining samples underwent SBS testing. The debonded surfaces were evaluated using the adhesive remnant index. Statistical analysis was conducted using ANOVA and post hoc multiple comparison tests (P < 0.05).

Results: The lowest SBS was recorded in Group 2, where brackets were bonded to eroded enamel. In contrast, the highest SBS was observed in sound enamel. Group 2 also exhibited the lowest Ca/P ratio, while sound enamel demonstrated the highest mean VH. Notably, eroded enamel treated with hydroxyapatite nanoparticles (HAnp), NR-5^TM, and Curodont^TM Repair exhibited VH comparable to sound enamel.

Conclusions: Eroded enamel remineralized with HAnp, NR-5^TM, and Curodont^TM Repair demonstrated improved VH and SBS when metallic brackets were bonded to the enamel surface, suggesting potential effectiveness in orthodontic applications.