Patients with skeletal ClassⅡ hyperdivergent patterns often present with mandibular retrognathism, increased lower facial height, and excessive vertical dimension of occlusion, resulting in an unaesthetic facial profile and a higher incidence of temporomandibular disorder (TMD). Conventional treatments such as camouflage orthodontics with extraction or single-jaw surgery often struggle to achieve a balance between improving facial aesthetics and functional outcomes. In recent years, a treatment approach centered on counterclockwise rotation (CCR) of the mandible has gained attention. By adjusting the occlusal plane and mandibular position, this approach not only improves mandibular retrognathism and optimizes facial proportions but also helps reduce joint loading and alleviate TMD symptoms to some extent. This article systematically discusses the role of CCR in skeletal ClassⅡ hyperdivergent cases from perspectives such as biomechanical foundations, orthodontic and orthognathic treatment strategies, joint functional adaptation, and clinical applications, while also offering insights into its stability and future research directions.

Clear aligner treatment has evolved over the last 20 years. It has transformed from a simple tool for tooth alignment to an essential component of multidisciplinary oral treatment. It has shown significant advantages in the orthodontic treatment of periodontal disease, the orthodontic treatment of temporomandibular joint disorder (TMD), integrated approaches with dental implant restoration, and the combined treatment of orthodontics and orthognathic surgery. The objective of orthodontic treatment for periodontal disease is to enhance health and stability. Commencement of clear aligner treatment is advised after the management of periodontal inflammation. The principle of applying gentle and gradual force must be adhered to. The extent of tooth movement should be reduced. The coverage of the aligner should be minimized. The time between aligner replacements should be extended. The objective of orthodontic treatment for TMD is to achieve occlusal-joint coordination, eliminate occlusal trauma, stabilize joint function, align the teeth, and improve occlusion. Clear aligner intervention is only suitable for stable TMD. Emphasis is placed on collaborative multidisciplinary management. Informed consent for orthodontic treatment of patients with TMD is crucial. The goal of combined orthodontic and restorative treatment is to integrate space and aesthetics. The digital design of clear aligners can optimize spacing, expand the area for dental implants, intrude over-erupted opposing teeth, upright tilted abutment teeth, ensure optimal gingival distance and mesiodistal diameter for dental implants, and when combined with smile design, it can significantly improve the pink and white aesthetic score. Precise orthodontic-surgical coordination is achieved for the combined treatment of severe skeletal malocclusion via orthodontics and orthognathic surgery. The digital design of clear aligners facilitates the alignment of the upper and lower dental arches more effectively compared with fixed orthodontic treatment. It effectively reduces chairside operation time and significantly improves treatment efficiency. At present, the application of clear aligners in multidisciplinary fields remains limited, and high-quality studies are lacking. We anticipate further high-quality research in the future to enhance our understanding of clear aligner treatment. This will facilitate the exact and rapid completion of clear aligner therapy for patients, resulting in aesthetically pleasing smiles.

Clear aligner therapy (CAT) is increasingly used in orthodontic practice. However, the biomechanical effectiveness and predictability of tooth movement in complex cases should be further clarified and enhanced. This article provides a systematic review of the biomechanical mechanisms underlying four common complex treatment modalities in CAT, namely, molar distalization, arch expansion, vertical tooth movement, and extraction cases, and summarizes current clinical strategies, such as overcorrection design, attachment, mini-screw-assisted anchorage, and intra-/inter-arch elastic traction. The role of these strategies in improving tooth movement control and treatment efficacy is elucidated, and potential future developments is discussed. The findings can offer a theoretical basis and practical guidance for optimizing CAT and improving the control ability and predictability of treatment outcomes.

This study systematically reviews the latest research advances in clear aligners across materials science, clinical treatment outcomes, and impacts on oral health. In materials science, research focuses on membrane biocompatibility, development of bio/smart composite aligners, and direct printing technology for clear aligners. Although mainstream materials are generally safe, some still harbor cytotoxic risks. Smart composite materials offer novel strategies for monitoring and preventing enamel demineralization and bacterial biofilm formation by integrating sensors or incorporating antimicrobial agents. Directly printed aligner technology demonstrates significant potential due to its customizability and high precision. Regarding clinical efficacy, evidence indicates that clear aligners achieve comparable results with fixed appliances for mild-to-moderate malocclusions, though their efficiency and effectiveness are slightly inferior in complex extraction cases. Regarding specific tooth movement control, arch expansion primarily relies on crown inclination, yielding results below design expectations; molar distalization achievement is also limited. Studies refute the notion that a specific “bite-ramp effect” causes mandibular counterclockwise rotation. For skeletal class Ⅱ malocclusions in children, clear aligners combined with functional orthodontic modules show promising applications, though evidence levels require further enhancement. Regarding oral health impacts, multiple studies confirm that clear aligners effectively reduce enamel demineralization risk, decrease plaque accumulation, and improve periodontal health compared with fixed appliances. In summary, clear aligner technology has advanced toward great precision, efficiency, and personalization. However, clinicians must recognize its tool-like nature. Successful treatment fundamentally relies on comprehensive diagnosis, appropriate treatment planning, and meticulous clinical execution.

The primary objectives of orthodontic treatment in adult patients with periodontal disease are to improve dental alignment and occlusal relationships, optimize oral hygiene conditions, restore masticatory function, and enhance aesthetic outcomes. During treatment, orthodontists should comprehensively and continuously evaluate the patient’s periodontal health status, adopt personalized biomechanical control strategies, enhance multidisciplinary collaboration, and implement targeted prevention and management measures for potential orthodontic risks. This article provides an overview of common clinical issues encountered in the orthodontic treatment of adult periodontal patients. Key areas addressed include the relationship between periodontal disease and the development of malocclusion, the formulation of treatment objectives, indications and contraindications, key aspects of treatment process control, the role of radiographic examination in treatment planning and monitoring, and post-orthodontic retention protocols.

Disc displacement (DD) is the primary type of temporomandibular disorder. Adolescence marks a period of high incidence for DD and is also a critical phase for dentofacial development. There is a strong correlation between DD and condyle size, ramus height, mandibular morphology and position. However, whether they are directly related, whether DD can cause or exacerbate dento-maxillofacial deformities, and the degree of association between different types of DD and adolescent craniofacial development remain inconclusive. This research reviews the abovementioned issues to deepen the understanding of the potential impact of DD on dento-maxillofacial development during adolescence. The aim is to offer comprehensive clinical recommendations for the etiological mechanisms, clinical diagnosis, and treatment planning of dento-maxillofacial deformities.

Objective This study comprehensively compares the differences between concealable traction hook spherical buccal tubes (concealable spherical tubes) and conventional rectangular buccal tubes in terms of patient comfort, incidence of buccal mucosal injury, periodontal health indices, and clinical bond failure rate to provide evidence for clinical application. Methods Thirty subjects were enrolled and treated using a split-mouth design, where the two sides of each patient’s oral cavity were randomly assigned to receive either conventional rectangular buccal tubes (group A) or concealable spherical buccal tubes (group B). During treatment, pain scores, ulcer occurrence, and bond failure of the first molar buccal tubes were recorded. Periodontal indices, including plaque index (PLI), gingival index (GI), and sulcus bleeding index (SBI) of the first molars, were assessed before treatment (T0) and 30 days after tube bonding (T1). Results The pain scores in group A were significantly higher than those in group B (Z=-5.231, P<0.001). Moderate or higher pain was reported by 86.7% of patients in group A, whereas 90.0% of patients in group B reported mild pain only. The incidence of ulcers in group A (76.7%) was significantly higher than that in group B (3.3%, Z=-4.508, P<0.001). After treatment, the periodontal indices in both groups increased significantly compared to pre-treatment levels (P<0.05); however, the increases in PLI, GI, and SBI were significantly greater in group A than in group B (P<0.001). The bond failure rate in group A (26.7%) was significantly higher than that in group B (8.3%, P<0.001). Conclusion The clinical performance of concealable spherical buccal tubes is significantly superior to that of conventional rectangular buccal tubes in improving patient comfort, reducing the incidence of mucosal injury and clinical bond failure, and maintaining periodontal health. This design offers patients a more comfortable and healthier orthodontic treatment experience.

Objective Alveolar bone height and thickness changes in the maxillary anterior region were assessed before treatment (T1), after treatment (T2), and during the retention phase (T3) in patients with maxillary protrusion treated with clear aligners combined with premolar extraction. The aim was to provide clinical insights for safely retracting anterior teeth with clear aligners. Methods This retrospective study included 15 patients (2 males and 13 females) with maxillary protrusion, who underwent bilateral maxillary first premolar extraction and anterior tooth retraction with clear aligners. Cone beam computed tomography images were collected at T1, T2, and T3 (≥18 mon-ths post-treatment) for the measurement of vertical alveolar bone height (labial, palatal, mesial, and distal aspects) and horizontal alveolar bone thickness (labial, palatal, and total). Statistical analysis was performed using SPSS 26.0, and changes across phases and correlations were assessed. Results After orthodontic treatment, the palatal and mesial alveolar bone height of the maxillary anterior teeth significantly decreased (P<0.05). Concurrently, the labial midroot and apical thickness of the maxillary central incisors showed a significant increase, whereas the palatal cervical alveolar bone of the maxillary lateral incisors and canines exhibited significant thinning (P<0.05). At T3, the labiopalatal alveolar bone height of the maxillary central incisors significantly increased (palatal height increase: 0.46 mm±0.57 mm; P<0.05). Although the palatal alveolar bone thickness of the maxillary lateral incisors and canines continued to decrease, the differences were not statistically significant (P>0.05). A negative correlation was observed between alveolar bone resorption during treatment and bone regeneration during retention (labial height of maxillary central incisors: r=-0.597, P<0.05). Conclusion After the retraction of maxillary anterior teeth with clear aligners, the alveolar bone height on the mesial and palatal sides of the upper anterior teeth showed considerable reduction. The palatal alveolar bone thickness at the cervical and middle root levels of the upper lateral incisors and canines decreased remarkably. By contrast, the labial alveolar bone thickness at the middle and apical root levels of the upper central incisors significantly increased. At T3-T2, the partial recovery of alveolar bone height and thickness was observed, but pretreatment levels were not reached. Notably, the degree of bone resorption during treatment may influence the remodeling potential at T3.

Tooth impaction is a prevalent dentofacial developmental anomaly, mostly observed in third molars, whereas second molar impaction occurs with lower frequency. This article presents a case of a male adolescent with mesially impacted second molars resulting in the external root resorption of multiple first molars. The patient received orthodontic and surgical treatments simultaneously, achieving dental alignment and enhanced occlusal function. The treatments mitigated the long-term adverse complications of external root resorption.

Digital and intelligent digital technologies can help optimize the clinical workflow of edentulous jaw implant restoration, significantly improving precision, predictability, and efficiency throughout all stages of treatment. In the preoperative phase, by acquiring the patient’s digital information model and integrating data with the assistance of an artificial intelligence-driven planning system, personalized design of implant positions and prosthesis morphologies can be achieved, thereby realizing accurate functional and aesthetic matching. During the surgical procedure, the adoption of static implant guides, dynamic navigation systems, or implant robotic systems can effectively enhance surgical precision and minimize patient trauma to the greatest extent. In the immediate and final restoration phases, digital impression technology based on intraoral and extraoral scanning systems enables accurate acquisition of information regarding implants, as well as hard and soft tissues related to edentulous jaw implantation. Among these technologies, the application of AI-assisted algorithms and modified intraoral scan bodies can further improve patient comfort and chairside work efficiency. When encountering metal restoration artifact interference, the use of artifact correction algorithms or methods to increase identifiable marker points can both enhance the fitting precision of virtual data, reduce the impact of metal artifacts on data matching, and provide more reliable data support for digital preoperative planning. For complex edentulous cases, such as pterygoid implant placement, implant robotic systems based on digital three-dimensional modeling enable high-precision implantation with intraoperative dynamic calibration, thereby improving prosthetic predictability. Although challenges remain in data interoperability and standardization of clinical protocols, the integration of unified data standards, comprehensive intelligent platforms, and standardized workflows may facilitate the standardized and intelligent application of digital technologies in edentulous implant rehabilitation. It is foreseeable that in the future, digital and intelligent digital technologies will continue to drive the development of the edentulous jaw implant restoration field, providing patients with more high-quality, efficient, and safe implant restoration solutions.

Objective To investigate the expression of Golgi membrane protein 1 (GOLM1) in oral squamous cell carcinoma (OSCC) and its effects on proliferation, migration, invasion, and epithelial-mesenchymal transition (EMT) in OSCC cells and the underlying mechanisms. Methods Bioinformatics analysis was performed using the data from The Cancer Genome Atlas and Genotype-Tissue Expression databases to evaluate the expression of GOLM1 in head and neck squamous cell carcinoma (HNSCC) and its prognostic significance. Immunohistochemistry was used to detect GOLM1 expression in OSCC tissues and adjacent tissues. The mRNA and protein levels of GOLM1 in human normal oral keratinocytes (HOK) and OSCC cell lines (HSC-3 and SCC-25, respectively) were measured via real-time quantitative polymerase chain reaction (qRT-PCR) and Western blot. For in vitro experiments, GOLM1 was silenced in HSC-3 and SCC-25 cells via lentiviral transfection, with the transfection efficiency validated through qRT-PCR and Western blot. Cell proliferation was assessed through Cell Counting Kit-8 (CCK-8) and colony formation assays. Cell migration and invasion were evaluated via wound healing and Transwell assays, respectively. Western blot was used to analyze EMT-related proteins (E-cadherin, N-cadherin, and Vimentin). Gene set enrichment analysis (GSEA) was conducted to identify potential signaling pathways associated with GOLM1, followed by validation through Western blot and rescue experiments. Results GOLM1 exhibited a high expression in HNSCC, correlation with poor prognosis, and significant upregulation in OSCC tissues. In addition, GOLM1 showed markedly elevated expression levels in OSCC cell lines HSC-3 and SCC-25 compared with those in HOK cells. Silencing of GOLM1 markedly suppressed OSCC cell proliferation, migration, and invasion, accompanied with an increased E-cadherin expression and decreased N-cadherin and Vimentin levels. GSEA revealed a strong association between GOLM1 and the transforming growth factor-beta (TGF-β) signaling pathway. Silencing of GOLM1 reduced the expressions of TGF-β1, Smad2, and phosphorylated Smad2. Exogenous recombinant human TGF-β1 protein rescued the inhibitory effects of GOLM1 knockdown on OSCC cell proliferation, migration, and invasion. Conclusion GOLM1 is overexpressed in OSCC tissues and cells, and silencing of this protein inhibits OSCC cell proliferation, migration, invasion, and EMT via the TGF-β1/Smad2 signaling pathway.

Objective This study aims to explore the mechanism of carvacrol (CV) in regulating alveolar bone repair in periodontal disease. Methods A rat model of periodontal disease (P group) was created by ligating the first molar and injecting lipopolysaccharide (LPS). A control model (C group) was also created. The treatment models received low (L group), medium (M group), and high (H group) doses of CV hydrogel. Hematoxylin-eosin (HE) staining was used to observe the pathological changes in periodontal tissues. Immunohistochemical staining was employed to analyze the expression of collagen typeⅠ(COL1) and Runt-related transcription factor 2 (Runx2). In vitro, the rat osteoblast cells were divided into C, P, L, M, H, CV and CV+LY294002 (CV+LY) groups. Western blot analysis detected the phosphatidylinositol 3-kinase (PI3K)/protein kinase B (AKT)/glycogen synthase kinase 3 beta (GSK-3β) pathway-related and osteoblastic proteins. Quantitative reverse-transcription po-lymerase chain reaction was used to measure the expression of inflammatory factors and osteoblastic proteins. The alkaline phosphatase (ALP) colorimetric kit and alizarin red S staining kit were utilized to assess osteogenic ability. Immunofluorescence (IF) was used to detect COL1 expression in osteoblasts. Transmission electron microscopy was applied to detect cell apoptosis. Results CV hydrogel alleviated periodontal symptoms, upregulated PI3K/AKT/GSK-3β pathway-related and osteoblastic proteins, and increased the expression of ALP and the number of calcified nodules. However, it decreased cell apoptosis and inflammatory factors. LY294002 inhibited the PI3K/AKT pathway and decreased osteoblastic protein expression, ALP coloration, and calcified nodule quantity. Conclusion CV hydrogel promotes the proliferation and differentiation of alveolar bone osteoblasts by activating the PI3K pathway and inhibiting inflammation-induced bone resorption. This study emphasizes the potential of CV for the treatment of periodontal diseases.

Objective This study aims to design surface patterns using integrated programming software on zirconia posts fabricated through 3D printing. Methods A type 3 3M fiber post was built as a research model, and HyperMill 2021 software was applied to design linear overflow grooves extending from the apex to the base on the post surface. The design parameters included the number, depth, and width of the overflow grooves. Five groups of patterned microstructured zirconia posts were designed, with the 3M fiber post as the control group. Micro-push-out and three-point bending tests were used to measure the bon-ding and flexural strengths of the patterned microstructured zirconia posts. The failure mode of bonding was analyzed by using a stereomicroscope. Results The patterned microstructure significantly increased the bond strength of zirconia posts (P<0.05). Bonding strength ranged from 9.80 MPa±0.64 MPa to 26.49 MPa±0.94 MPa at the base of the root, from 9.26 MPa±1.08 MPa to 18.51 MPa±0.93 MPa at the center of the root, and from 6.74 MPa±0.31 MPa to 13.00 MPa±0.71 MPa at the apex of the root. The implementation of patterned microstructures reduced the flexural strength of the zirconia post (P<0.05), and flexural strength ranged from 378.3 MPa±24.18 MPa to 587.4 MPa±36.60 MPa. The failure mode of zirconia post adhesions treated with patterned microstructures was mainly mixed failure. Conclusion Patterned microstructured zirconia posts with improved flexural strength and adhesive properties could be produced by using 3D printing. The bonding and flexural strengths of the patterned zirconia posts can meet the clinical requirements for custom post-and-core design.

Objective This study aimed to investigate the clinical and cone beam computed tomography (CBCT) characteristics of root fractures in endodontically versus nonendodontically treated posterior teeth. Methods A total of 340 posterior teeth from 305 patients were retrospectively collected. The fractured teeth were divided into endodontically treated (ET) teeth and nonendodontically treated (NET) teeth. The clinical information (age and gender of patients) was recorded. The type of fractured tooth, fractured root, orientation of fracture lines (vertical, horizontal, oblique, and irregular), direction of vertical fracture lines, location of horizontal root fractures, and bone resorption around fractured roots were evaluated and recorded based on CBCT images. Results 1) The distribution of teeth was significantly different between NET and ET teeth (P=0.028). Root fractures predominantly occurred in mandibular and maxillary molars. However, the proportion of premolars was significantly higher in ET teeth (27.2%) than in NET teeth (14.2%). 2) We observed a significant difference in root distribution between NET roots and ET roots (P=0.037). The mesial roots of mandibular molars were the most common fractured roots in NET and ET roots (36.4% in NET roots and 32.2% in ET roots); however, the second most common roots were the palatal roots of maxillary molars in NET roots (23.0%) and the maxillary premolar roots in ET roots (20.3%). 3) A statistically significant difference in the orientation of root fractures was observed between the two groups (P<0.001). Vertical root fractures accounted for only 43.6% of all root fractures in NET root fractures, whereas they accounted for 75.6% in ET root fractures. 4) For vertical root fractures, the direction of fracture lines between NET and ET root fractures was not significantly different (P=0.58), with both types predominantly presenting as buccal-palatal fractures (86.0% and 84.1%). 5) No significant difference was observed in the location of horizontal fractures between NET and ET root fractures (P=0.132), and the most common site was the cervical third of roots. 6) Bone loss around fractured lines significantly differed between NET and ET root fractures (P<0.001). Around 59% exhibited obvious bone loss around fractured roots in NET root fractures, whereas 91.8% of fractured roots presented bone loss in ET root fractures. Conclusion The NET root fractured teeth and ET root fractured teeth presented quite different clinical and CBCT characteristics. The complex and diverse traits of NET root fractured teeth indicate the influence of multifaceted occlusal factors in their occurrence. By contrast, ET root fractured teeth demonstrate high uniformity, indicating that their occurrence may be related to the structural changes caused by endodontic treatment.

Objective To evaluate the clinical efficacy of the simple taper-retained external connection narrow-diameter implant JUST J1 MINI (J1 implant) applied in the narrow alveolar ridge of the premolar region for 5-8 years. Methods Sixty-six patients who attended the Department of Stomatology of the Fourth Affiliated Hospital of Nanchang University for implant restoration in the premolar region from January 2017 to March 2020 were selected. A total of 87 simple taper-retained external connection narrow-diameter implants were implanted into the narrow alveolar ridge of the premolar region in the immediate postoperative period after implantation without any bone augmentation surgery. CBCT and surface tomography films were taken after the completion of final crown restoration and at the time of final follow-up. With a mean follow-up of 78.9±9.0 months, the survival rate of the J1 implants, rate of abutment loosening and shedding, amount of bone resorption at peri-implant margins, and changes in the bone width and height of the implants were observed. Results At the final follow-up of 5-8 years, two implants failed when they loosened at three and four months after surgery, and the implant survival rate was 97.7%. The bone resorption values of the distal and mesial margins were 0.719 mm±0.495 mm and 0.722 mm± 0.604 mm, respectively. The bone height and width resorption of the implants were 0.581 mm±0.346 mm, 0.209 mm±0.118 mm. Conclusion The results of long-term follow-up after 5-8 years showed that J1 implants in the narrow alveolar ridge of premolar teeth without bone augmentation can reduce surgical trauma, simplify implant surgery, and satisfy a certain degree of aesthetics and masticatory function in patients. Therefore, J1 implants have good long-term clinical results and expand the indications for implant restorations in the narrow alveolar ridge.

Objective A community intervention mo-del was used to investigate the preventive effects and cost-effectiveness of I-ReHealth^® and Duraphat^® in early childhood caries. Methods Children from Yizhou District, Hechi City, were enrolled and randomly assigned into two groups: the I-ReHealth^® group and the Duraphat^® group. Each group received topical fluoride varnish applications and dental health education every 6 months. After 1.5 years, the incidence of caries and associated costs were compared between the two groups before and after the intervention. Cost minimization analysis was employed to evaluate economic efficiency, and sensitivity analysis was performed to assess the influence of variations in key parameters on result stability and to quantify the probabilistic differences in cost benefits between the two fluoride varnishes under equivalent caries-preventive effects. Results Prior to the intervention, we found no statistically significant differences in caries prevalence or mean dmft scores between the two groups (P>0.05). After 1.5 years of treatment, both groups still showed no statistically significant differences in caries prevalence (P>0.05), mean dmft scores (P>0.05), caries incidence rate (P>0.05), or increment in mean dmft (P>0.05). The one-sided 97.5% confidence interval for the difference in mean dmft increment was below the non-inferiority threshold, confirming non-inferiority (P<0.025). Cost minimization analysis revealed lower total costs in the I-ReHealth^® group (¥25 411.44) than in the Duraphat^® group (¥26 692.98). One-way sensitivity analysis identified material price as the most influential parameter affecting total costs. Monte Carlo simulation with 1 000 iterations demonstrated a 73.1% probability that the I-ReHealth^® group will yield cost savings compared with the Duraphat^® group. Conclusion I-ReHealth^® is non-inferior to Duraphat® in caries-preventive efficacy but superior in cost-effectiveness in reducing patient expenses.

Objective This study aimed to evaluate the efficacy of different treatment methods on local plaque lesions of incisors and the sealing of pits and fissures in first permanent molars in patients with mild molar-incisor hypomineralization (MIH). Methods Patients clinically diagnosed with mild MIH were selected as research subjects for a prospective clinical comparative study on the treatment of local plaque lesions in incisors and the pits and fissures of first permanent molars. Infiltrative resin and fluoride varnish were used to treat local plaque lesions on incisors. The area of local plaque lesions on incisors and lightness (L), red-green hue (a), and yellow-blue hue (b) of the lesion area were measured before treatment and at 1, 3, and 6 months after treatment. The color difference value (ΔE) and tooth whiteness index (WI_D) were then calculated. Two methods, phosphoric acid etching pit and fissure sealing and self-etching pit and fissure sealing, were used for the treatment of pits and fissures of first permanent molars. The incidence rate of caries, sealant retention rate, and success rate of pit and fissure sealing for the two methods were calculated at 1, 3, and 6 months after treatment. Results In patients with mild MIH, local plaque lesions on incisors exhibited a significant reduction in area at 1, 3, and 6 months post-treatment in the infiltrative resin group (P<0.05), whereas no significant change was observed in the fluoride application group (P>0.05). After infiltrative resin treatment, the L value and ΔE value showed a decreasing trend (P<0.05), whereas the L value in the fluoride application group did not change significantly (P>0.05). In patients with first permanent molars, the phosphoric acid etching pit and fissure sealing group exhibited superior success and retention rates at 6 months post-treatment compared with the self-etching pit and fissure sealing group (P<0.05) and a lower loss rate than the self-etching pit and fissure sealing group (P<0.05). Conclusion Infiltrative resin treatment can reduce the L value and ΔE value of local plaque lesions on incisors in patients with mild MIH. It demonstrates a significant improvement in plaque lesion area, with relatively stable effects within 6 months. Phosphoric acid etching is recommended for the pit and fissure sealing of first permanent molars in patients with mild MIH.

Objective The incidence and clinical characteristics of bi-rooted primary canines were investigated by performing oral panoramic radiographs. Methods A total of 100 976 oral panoramic radiograph of subjects aged 3-9 years old were collected, and the incidence and distribution of bi-rooted primary canines were observed and recorded. The obtained data were analyzed using SPSS 25.0 statistical software, and the literature on bi-rooted primary canine was reviewed to record patient’s data. Results The incidence of bi-rooted primary canines was 0.37‰ (37/100 976), of which 0.59‰ (32/54 276) occurred in males and 0.12‰ (5/46 700) in females. Statistically significant difference was observed between males and females (χ² =15.955, P=0.000). The number of bi-rooted primary canine in 37 children was mainly 1-2. Among them, 11 subjects (29.73%) had one bi-rooted primary canine, and 18 subjects (48.65%) had two bi-rooted primary canines. The tooth position distribution of 76 bi-rooted primary canines showed no significant difference between the left and right sides (χ² =1.316, P=0.251). However, significant difference was found between the upper and lower jaws (χ² =15.213, P=0.000) and between the unilateral and bilateral sides (χ² =6.083, P=0.014). Conclusion Bi-rooted primary canines are rare, mostly occur in 1-2 teeth, and are more common in males than females, in the upper jaw than in the lower jaw, and on both sides than on one side.