Orthodontic tooth movement is a complex physiological process based on periodontal tissue remodeling. Numerous factors, such as the anatomical characteristics of oral and maxillofacial complications, occlusal interference, mechanical factors and systematic factors, may play critical roles in orthodontic tooth movement, leading to tooth movement difficulty. In recent years, many scholars have focused on factors related to tooth movement difficulty, but current research mostly involves animal experiments and retrospective studies. Clinical trials of high-quality and evidence-based medicine studies are required. Although no sound theory system is available that is universally recognized and the mechanism of many factors remains debatable, alveolar bone defects, the maxillary sinus, the gingiva, tooth ankylosis, bone islands and friction may cause orthodontic tooth movement. Understanding the factors related to the difficulty of orthodontic tooth movement is advantageous to develop a more comprehensive personalized treatment plan for patients and achieve more efficient and safer tooth movement. In this paper, the current factors related to orthodontic tooth movement are reviewed to provide references for clinical orthodontic treatment.

Deep bite is a common clinical malocclusion that has a great impact on patients' facial aesthetics and oral function. Bite opening is the key step in the treatment of deep bite, playing a decisive role in the development of mandible and the progress of orthodontic treatment. Torque and tip control during the correction of deep bites is a hot topic in orthodontics. The three-dimensional finite element method can accurately simulate clinical processes and conduct dynamic stress analysis, which provides the basis of the biomechanical mechanism. This paper reviewed the finite element analysis of various orthodontic systems for bite opening to provide a reference for clinical application. The emergence of mini-implants provided a new idea for anchorage control in bite opening. Finite element studies found that high-positioned mini-implants are beneficial for bodily tooth intrusion and proposed the ideal position for force application. For the finite element simulation of the reverse curve archwire, it was found that the intrusion and inclination of the anterior teeth increased with the curve depth of the archwire. The application of clear aligners has also been flourishing, but these forces are still difficult to effectively control. Finite element studies on their attachment design and corresponding tooth movement may be helpful to open the bite quickly and effectively. However, the existing studies still have modeling limitations. The structural simplification, linearization and nonstandard parameter definition of the model reduce model accuracy. Additionally, the existing research mostly focused on initial tooth movement, and studies on long-term tooth movement after bone remodeling are lacking. These studies are needed in the future.

Antimicrobial photodynamic therapy uses photosensitizers to produce reactive oxygen species under light exposure to inhibit pathogenic bacteria. Although its application in the management of oral infectious diseases has increased over recent years, it is limited by inadequate tissue and biofilm penetration and suboptimal bioavailability exhibited by individual photosensitizers. These challenges can potentially be surmounted through the integration of nanomaterials, such as polymers, metals and metal oxides, metal – organic frameworks, and carbon and silicon nanomaterials. Polymers allow the controlled release of photosensitizers through structural adjustments but have low stability, while metals and metal oxides possess strong antibacterial properties but can be potentially toxic. Meanwhile, metal–organic frameworks have flexible structures and multifunctionality but have low stability and potential toxicity.Moreover, carbon and silicon nanomaterials, despite exhibiting excellent antibacterial properties and biocompatibility, have limited application due to high production costs. Materials with inherent antibacterial properties, such as chitosan and graphene oxide, have broader application prospects, as they can form multimodal antibacterial platforms with photosensitizers, enhancing the antibacterial effects and eliminating infections. Future research could incorporate other functional materials, such as anti-inflammatory agents and immunomodulatory materials, to construct comprehensive therapeutic nanoplatforms for the treatment of oral infectious diseases.

N6-methyladenosine (m⁶A) is the most prevalent modification in the eukaryotic transcriptome and has a wide range of functions in coding and noncoding RNAs. It affects the fate of the modified RNA, including its stability, splicing, and translation, and plays an important role in post-transcriptional regulation. Bones play a key role in supporting and protecting muscles and other organs, facilitating the movement of the organism, ensuring blood production, etc. Bone diseases such as osteoarthritis, osteoporosis, and bone tumors are serious public health problems. The processes of bone development and osteogenic differentiation require the precise regulation of gene expression through epigenetic mechanisms including histone, DNA, and RNA modifications. As a reversible dynamic epigenetic mark, m⁶A modifications affect nearly every important biological process, cellular component, and molecular function, including skeletal development and homeostasis. In recent years, studies have shown that m⁶A modification is involved in osteogenesis and bone-related diseases. In this review, we summarized the proteins involved in RNA m⁶A modification and the latest progress in elucidating the regulatory role of m⁶A modification in bone formation and stem cell directional differentiation. We also discussed the pathological roles and potential molecular mechanisms of m⁶A modification in bone-related diseases like osteoporosis and osteosarcoma and suggested potential areas for new strategies that could be used to prevent or treat bone defects and bone diseases.

Human adipose-derived stem cells (hASCs) are a promising cell type for bone tissue regeneration. Circular RNAs (circRNAs) have been shown to play a critical role in regulating various cell differentiation and involve in mesenchymal stem cell osteogenesis. However, how circRNAs regulate hASCs in osteogenesis is still unclear. Herein, we found circ_0003204 was significantly downregulated during osteogenic differentiation of hASCs. Knockdown of circ_0003204 by siRNA or overexpression by lentivirus confirmed circ_0003204 could negatively regulate the osteogenic differentiation of hASCs. We performed dual-luciferase reporting assay and rescue experiments to verify circ_0003204 regulated osteogenic differentiation via sponging miR-370-3p. We predicted and confirmed that miR-370-3p had targets in the 3′-UTR of HDAC4 mRNA. The following rescue experiments indicated that circ_0003204 regulated the osteogenic differentiation of hASCs via miR-370-3p/HDAC4 axis. Subsequent in vivo experiments showed the silencing of circ_0003204 increased the bone formation and promoted the expression of osteogenic-related proteins in a mouse bone defect model, while overexpression of circ_0003204 inhibited bone defect repair. Our findings indicated that circ_0003204 might be a promising target to promote the efficacy of hASCs in repairing bone defects.