Background: We investigated treatment outcomes and post-treatment stability in 10 patients with an anterior open bite and nonsurgical orthodontics. Methods: The patients underwent maxillary molar intrusion using temporary anchorage devices (TADs) to deepen the overbite due to mandibular autorotation. Lateral cephalograms and dental cast models were obtained before treatment (T0), immediately after it (T1), and >1 year after it (T2). Skeletal and dental cephalometric changes and three-dimensional movements of the maxillary dentitions were evaluated. Results: At T0, cephalometric analysis indicated that patients had skeletal class I with tendencies for a class II jaw relationship and a skeletal open bite. During active treatment (T0 to T1), the maxillary first molar intruded by 1.6 mm, the mandibular first molar extruded by 0.3 mm, the Frankfort-mandibular plane angle decreased by 1.1°, and the overbite increased by 4.1 mm. Statistically significant changes were observed in the amount of vertical movement of the maxillary first molar, Frankfort-mandibular plane angle, and overbite. Three-dimensional (3D) dental cast analysis revealed that the maxillary first and second molars intruded, whereas the anterior teeth extruded, with the second premolar as an infection point. In addition, the maxillary molar was tipped distally by 2.9° and rotated distally by 0.91°. Statistically significant changes were observed in the amount of vertical movement of the central incisor, lateral incisor, canine and first molar, and molar angulation. From T1 to T2, no significant changes in cephalometric measurements or the 3D position of the maxillary dentition were observed. The maxillary and mandibular dentitions did not significantly change during post-treatment follow-up. Conclusions: Maxillary molar intrusion using mini-screws is an effective treatment for open bite correction, with the achieved occlusion demonstrating 3D stability at least 1 year after treatment.

Cementum resorption, unlike bone resorption, is clinically known to occur only with limited pathological stimuli, such as trauma, orthodontic forces, and large apical periodontitis; however, the molecular mechanisms that control osteoclast formation on the cementum surface remain unclear. In this study, we focused on extracellular vesicles (EVs) secreted by cementoblasts and analyzed their effects on osteoclast differentiation. EVs were extracted from the conditioned medium (CM) of the mouse cementoblast cell line OCCM-30. Transmission electron microscopy (TEM) analysis confirmed the presence of EVs with a diameter of approximately 50–200 nm. The effect of the EVs on osteoclast differentiation was examined using the mouse osteoclast progenitor cell line RAW 264.7 with recombinant receptor activator of nuclear factor (NF)-κB ligand (rRANKL) stimulation. EVs enhanced the formation of tartrate-resistant acid phosphatase (TRAP) activity-positive cells upon rRANKL stimulation. EVs also enhanced the induction of osteoclast-associated gene and protein expression in this condition, as determined by real-time PCR and Western blotting, respectively. On the other hand, no enhancing effect of EVs was observed without rRANKL stimulation. A Western blot analysis revealed no expression of receptor activator of NF-κB ligand (RANKL) in EVs themselves. The effect on rRANKL-induced osteoclast differentiation was examined using the CM of cementoblasts in terms of TRAP activity-positive cell formation and osteoclast-associated gene expression. The conditioned medium partly inhibited rRANKL-induced osteoclast differentiation and almost completely suppressed its enhancing effect by EVs. These results indicate that cementoblasts secreted EVs, which enhanced RANKL-induced osteoclast differentiation, and simultaneously produced soluble factors that neutralized this enhancing effect of EVs, implicating this balance in the regulation of cementum absorption. A more detailed understanding of this crosstalk between cementoblasts and osteoclasts will contribute to the development of new therapies for pathological root resorption.

In orthodontic treatment, to achieve efficient tooth movement, it is important to reduce the frictional force between the wire and the bracket, especially the binding friction that occurs when the angle between the wire and the bracket is large. Electroless nickel–polytetrafluoroethylene (Ni-PTFE) coating is a coating technology used to deposit PTFE particles with a low coefficient of friction on the coating surface to provide a low-friction surface for metallic materials. The purpose of this study was to investigate the effect of Ni-PTFE-coated orthodontic wires on the frictional force between brackets. The surface morphology, surface roughness, and frictional properties of Ni-PTFE-coated stainless steel wires and Ni-Ti wires were evaluated. The results demonstrate that the Ni-PTFE coating reduced the frictional force between the orthodontic wires and brackets, despite the increased surface roughness. Even when the angle between the wire and bracket was increased, assuming binding friction, the frictional force was reduced by the Ni-PTFE coating. This suggests that the friction between the wire and the bracket was suppressed by the PTFE particles deposited on the wire surface in contact with the bracket.

Objectives: Malocclusion, particularly anterior crossbite and open bite, contributes to abnormal occlusal stress distribution, potentially leading to tooth loss. We examined the association between anterior malocclusions and tooth loss–related outcomes in a large-scale, community-based sample of Japanese adults. Materials and methods: This cross-sectional study targeted 17,349 participants aged ≥ 40 years from the Tohoku Medical Megabank Cohort Study (2013–2017). Based on overjet and overbite, participants were classified into normal occlusion ( n = 16,790), anterior open bite ( n = 177), anterior crossbite ( n = 348), and combined malocclusion ( n = 34). Outcomes included ≤ 19 remaining natural teeth and posterior tooth loss. Adjusted prevalence ratios (PRs) and 95% confidence intervals (CIs) were calculated using modified Poisson regression models. Results: The crossbite group demonstrated a higher prevalence of ≤ 19 remaining teeth (PR, 1.48; 95% CI, 1.04–2.10) and posterior tooth loss (PR, 1.14; 95% CI, 1.07–1.20) than the normal group; the open bite group exhibited a lower prevalence of posterior tooth loss (PR, 0.79; 95% CI, 0.69–0.90). Heatmap analysis revealed lower molar tooth retention in the crossbite group and higher retention in the open bite group. Conclusions: Anterior crossbite is associated with increased posterior tooth loss, whereas open bite shows a weaker association. These findings suggest that specific anterior malocclusions may be linked to reduced tooth retention. Clinical relevance: Identification of anterior malocclusion types, particularly anterior crossbite, may help identify individuals at higher risk for tooth loss. Orthodontic management of anterior crossbite might support posterior dentition preservation and long-term oral function.