Objective To compare the stress difference of the resin with different thicknesses in the screw access hole using three-dimensional finite element method. Methods A three-dimensional finite element model of the implant at the site of the mandibular first molar was established by computer aided design (CAD) software. A static load of 200 N was applied to the resin models with different thicknesses(1, 2, 3, 4, 5 mm) to analyze the effect of thickness on the von Mises stress and shear stress of the resin. Results In a certain range, the maximum von Mises stress and the maximum shear stress of the resin decreased with the increase of the thickness. At the thickness of 1mm, the maximum von Mises stress and shear stress of the resin were 23.85 MPa and 11.82 MPa, respectively. When the thickness was 2 mm, the maximum von Mises stress and shear stress of the resin were 18.75 MPa and 9.73 MPa respectively. At the thickness of 3 mm, the maximum von Mises stress and shear stress of the resin were 17.46 MPa and 9.04 MPa, respectively. When the thickness of the resin was more than 3 mm, the stress on it was in a stable level trend. When the thickness was 4 mm, the maximum von Mises stress and shear stress of the resin were 17.38 MPa and 9.04 MPa, respectively. When the thickness was 5 mm, the maximum von Mises stress and maximum shear stress of the resin were 17.18 MPa and 8.85 MPa, respectively. Conclusion When the resin reaches a certain thickness, the stress is small and stable. This study provides a new design strategy for reducing the complications after implant restoration caused by stress fatigue of the resin.

Objective To control the stepwise release of vascular endothelial growth factor A(VEGF-A) within the microcapsules, and to analyze the effects of the microcapsules on cellular angiogenic capability. Methods VEGF-A encapsulated poly(lactic-co-glycolic acid)(PLGA) microcapsules were prepared using a method combining dual-channel coaxial injection and continuous flow technology. The release and degradation performance of the microcapsules were characterized using a phosphate-buffered saline (PBS) soaking method. The biocompatibility of the microcapsules was assessed through the CCK-8 method and Calcein-AM/PI staining method. The impact of microcapsule extract on cellular angiogenesis ability was examined by conducting cell scratch assays and tubule formation experiments. Results The microcapsules were round in shape, with their particle diameter measuring in the range of hundreds of micrometers. Microcapsules with a molecular weight(Mw)-12 ku can release a large amount of VEGF-A in the initial phase, while Mw-30 ku ones had the capacity to provide a stable, long-term, low-dose release of VEGF-A. Microcapsules of Mw-12 ku exhibited outstanding potential for enhancing the healing of cell scratch wounds in the initial phase. Moreover, within the 0-12 day period, the two types of microcapsule extracts significantly enhanced the ability of cells to form tubules in vitro. Conclusion This study successfully regulated the release profile of VEGF-A by adjusting the molecular weight of PLGA, achieving an initial rapid and substantial release of VEGF-A followed by a sustained slow release over time, while maintaining its biological activity throughout the process.

Objective To evaluate the effect of Er: YAG(erbium-doped: yttrium aluminum garnet)laser combined with remineralizers on enamel acid resistance. Methods Healthy teeth that needed to be extracted due to orthodontic treatment were included, and 60 enamel blocks according to a unified standardwere prepared, and randomly divided into 6 groups(n=10). They were treated with deionized water(Group A), sodium fluoride(Group B), bioactive glass(Group C), Er: YAG laser(Group D), Er: YAG laser combined with sodium fluoride(Group E), and Er: YAG laser combined with bioactive glass(Group F)for 7 consecutive days before undergoing pH cycling demineralization. After the experiment, the surface morphology, calcium/phosphorus ratio, surface hardness, and surface roughness were measured in each group. Results ①Surface morphology: the enamel surfaces of groups A-F were all damaged to varying degrees, with groups E and F showing the least degree of damage, while group A had obvious concave defects. ②Calcium/phosphorus ratio: the calcium/phosphorus ratio on the enamel surface of groups B,C and D was significantly higher than that of group A(P<0.000 1), while there was no significant difference between groups B,C and D(P>0.05). The calcium/phosphorus ratio on the enamel surface of groups E and F was significantly higher than that of groups B,C and D(P<0.001). ③Surface hardness: after acid etching, the surface hardness of enamel in all groups decreased. The surface hardness loss of enamel in groups B,C and D was significantly lower than that in group A(P<0.000 1), while there was no significant difference between groups B,C and D(P>0.05). The surface hardness loss of enamel in groups E and F was significantly lower than that in groups B,C and D(P<0.001). ④Surface roughness: Compared with group A, the surface roughness of enamel in group D was reduced, but not statistically significant(P>0.05). Groups B and C showed a significant decrease(P<0.000 1), while there was no significant difference between groups B and C(P>0.05). The surface roughness of enamel in groups E and F was significantly lower than that in groups B,C and D(P<0.001). Conclusion The combined application of Er: YAG laser and remineralizers can enhance the acid resistance of enamel, providing a new reference for the treatment of dental erosion.

Objective To investigate the effect of miR-129-1-3p on the osteogenic differentiation of human bone marrow mesenchymal stem cells (hBMSCs) and its potential mechanism. Methods Negative control group, the miR-129-1-3p mimic group, the miR-129-1-3p inhibitor group and the corresponding negative control were constructed and transfected into hBMSCs. The formation of calcium-mineralized nodules was observed by alkaline phosphatase staining and alizarin red S staining. The expression levels of miR-129-1-3p and osteogenic differentiation markers were detected by qRT-PCR. Western blot detected the protein expressions of bone morphogenetic protein 2 (BMP2), SMAD1 and p-SMAD1. Results After transfection, the expression level of miR-129-1-3p in mimic group was significantly increased (P<0.05), the number of mineralized nodules was significantly decreased, and the expression levels of BMP2, Runt-related transcription factor 2 (RUNX2), osteocalcin (OCN) mRNA were significantly down-regulated (P<0.05). BMP2 and p-SMAD1 protein were also significantly down-regulated (P<0.05) compared with Mimic-NC group. The expression levels of BMP2, RUNX2, OCN mRNA were significantly up-regulated in inhibitor group (P<0.05) compared with Inhibitor-NC group. BMP2 and p-SMAD1 protein were significantly up-regulated in inhibitor group (P<0.05). Conclusion miR-129-1-3p can inhibit the osteogenic differentiation of human bone marrow mesenchymal stem cells by suppressing BMP2/SMAD1 signaling pathway.

Objective To investigate the differences of condylar position in patients with temporomandibular disorders(TMD), and to further explore the effects of condylar position displacement and malocclusion factors on TMD. Methods According to the inclusion criteria, normal occlusion subjects without TMD(group A, n=10), normal occlusion subjects with TMD(group B, n=8), malocclusion subjects without TMD(group C, n=9) and malocclusion subjects with TMD(group D, n=20) were collected. Condylar position measurement(CPM) and Cadiax Ⅳ were used to locate the position of condyle in RP and ICP, and the displacement and direction of condyle in three-dimensional direction from RP to ICP were measured by vernier caliper. All the data were averaged three times and analyzed by SPSS26.0 statistical software. Results In the sagittal direction, the condylar displacement of group A and group B, group C and group D, and group A and group D had statistical differences(P<0.01). The displacement of the right condyle in the vertical direction of group D was greater than that of group A, and the difference was statistically significant(P<0.05). The difference among other groups was not statistically significant. There was no significant difference in the lateral displacement of condyle between the four groups. In group A and group D, the largest proportion of condyle deviation was anterior up, while in group B and group C, the largest proportion of condyle deviation was posterior up. Conclusion RP-ICP condylar sagittal displacement is common in people with TMD. The condyle displacement of RP-ICP in malocclusion patients without TMD is not significantly different from that in normal occlusion patients without TMD. Patients with TMD malocclusion are more likely to have condylar displacement in sagittal direction and vertical direction than normal occlusion without TMD.

Objective To compare the effects of three nickel-titanium file systems, ProTaper Next, TruNatomy, and VDW. ROTATE, on the morphology of the Danger Zone of the mesial buccal root of mandibular first molar after root canal preparation using Micro-CT and 3D printing technology. Methods 3D-printed mandibular first molars were selected and designed for purpose. They were randomly divided into three groups according to the used NiTi files(n=20). Micro-CT was used to scan the cross-sectional images of the Danger Zone 2 mm below the furcation of the mesial buccal root before and after root canal preparation. The changes in the root canal wall thickness, root canal volume, surface area, cross-sectional area, and root canal transportation in the Danger Zone were observed. Statistical analysis was performed using one-way ANOVA(P<0.05). Results Statistically significant differences were observed before and after root canal preparation in the Danger Zone among the three groups(P<0.05). Among the three groups, the PTN files caused the largest change before and after preparation, followed by VDW files, and the TRU files had the smallest change. Conclusion The study highlights TruNatomy’s conservative shaping capacity, advocating its use in minimally invasive endodontics, whereas ProTaper Next may be reserved for cases requiring aggressive canal preparation.

Objective To study the relationship between the mandibular bone arch and the dental arch in patients with skeletal Class Ⅱmalocclusion and compare it with the Class Imalocclusion by establishing a 3D digital model. Methods A total of 25 cases with skeletal Class Ⅱ malocclusion and 25 cases with skeletal Class Ⅰ normal occlusion were selected. The mandibular model was scanned and a three-dimensional digital model was set up. After the determination of the WALA ridge and the FA point, the reference plane and coordinate system was established. Four degree polynomial curve fitting was performed with WALA ridge and FA point coordinates to represent the corresponding basal and dental arch curves. The width difference between the basal arch curve and the dental arch curve was measured and calculated at 3 mm, 10 mm, and 18 mm away from the horizontal axis of the coordinate. The differences of basal bone and dental arch width between skeletal Class Ⅱ and skeletal Class Ⅰ malocclusion was compared. Results The width differences between the arch and the dental arch in the anterior, middle and posterior mandibular segments of skeletal Class Ⅱ patients were -1.58 mm, 1.80 mm and 3.80 mm, respectively. The width differences between the arch and the dental arch in the anterior, middle and posterior mandibular segments of skeletal Class Ⅰ patients were 2.08 mm, 2.92 mm and 4.24 mm, respectively. There was a significant difference between skeletal Class Ⅱ and skeletal Class Ⅰ in the anterior and middle segments(P<0.05), but no significant difference in the posterior segment(P>0.05). Conclusion In skeletal Class Ⅰ patients, the width of the basal bone is larger than that of the dental arch, and the dental arch was located medial to the basal bone. In skeletal Class Ⅱ patients, the width of the anterior arch is larger than the width of the basal bone, that is, the dental arch is located outside the basal bone. The width difference of the basal arch in skeletal Class Ⅱ is smaller than that in skeletal Class Ⅰ.

Objective To evaluate the impact of different methods of harvesting palatal connective tissue on patients’ postoperative pain at the palatal donor site. Methods A total of 30 patients were included. The control group was de-epithelialized free gingival graft technique group, and the experimental group was the single-incision technique group. The keratinized gingival width of the recipient site, number of vertical incisions, number of teeth, donor site mucosa thickness, graft width, graft length, graft thickness, operation time and amount of anesthetic were recorded. The postoperative quality of life rating scale and visual analog scale were completed and statistical analysiswas performedon the results by SPSS 26.0. Results The postoperative quality of life score of the experimental group was significantly lower than that of the control group, and there was no significant difference in the total VAS score of the donor site. In terms of the total postoperative pain level after mucogingival surgery,the number of vertical incisions and graft thickness were positively correlated with the pain. Palate mucosal thickness was negatively correlated with postoperative pain levels. Conclusion In mucogingival surgery, the degree of postoperative pain in the donor palatal region of the patient is independent of the choice of de-epithelialized free gingival graft technique or single-incision technique to obtain subepithelial connective tissue. The surgeon should also give comprehensive considerationsto the anatomical factors of the patient’s donor site, surgical technical level and experience, and aesthetic requirements when selecting the surgical method.

Objective To build an automatic segmentation model of temporomandibular joint(TMJ) based on magnetic resonance imaging(MRI) using deep learning method. Methods The MRI data of TMJ of 104 subjects were collected, with the articular disc, condyle and glenoid fossa marked. The adaptive U-Net framework(nnU-Net) was used to construct a segmentation model, which was subjected to both quantitative and qualitative assessments. Results The segmentation model demonstrated excellent accuracy in segmentation. In the segmentation of different joint structures, the model achieved Dice of 0.77 for the articular disc, 0.85 for the condyle, and 0.66 for the glenoid fossa. The model showed similar segmentation performance when processing MRI images in both open-mouth and closed-mouth states. Conclusion This study developed an automatic segmentation model for TMJ MRI based on deep learning, which can assist clinicians in diagnosing anterior displacement of the TMJ disc.

Maxillary first molar teeth usually have 4 cusps, a few teeth have stuck cusps on the lingual side of the mesial tongue tip, while the presence of additional cusp on the buccal side of the mesial buccal tip is rarely reported, and it is even more rare for the cusp to connect with the dentin, cementum and pulp cavity of the main crown and fuse together to form C-shaped roots. A case of the buccal supernumerary cusp of the right maxillary first molar with C-shaped root canal was reported.

Bonding technology has made tremendous progress over the past 50 years, but there are still some unresolved issues regarding the durability of the bonding interface. In order to improve the durability and stability of dentin bonding, researchers have been trying to develop adhesives with more biological functions, such as promoting dentin remineralisation, inhibiting enzyme activity at the bonding interface, and enhancing collagen cross-linking. Based on the above starting point, this paper evaluates adhesive system monomers with multiple functions through a review of scientific papers published in recent years, in the hope of improving the development of new adhesive systems and reducing the degradation of the bonding interface.

Early diagnosis and therapy of the periodontitis are crucial for the prognosis. Although the latest international classification of periodontal diseases and peri-implant diseases in 2018 can improve the accuracy of diagnosis and reduce the misdiagnosis and missed diagnoses, it is extremely complex in practice. At present, the application of artificial intelligence in the field of dentistry is becoming more and more extensive, which has good performance in detecting tooth types and periodontal bone loss. The use of artificial intelligence to detect periodontal lesions and calculate periodontitis staging and grading, and guide clinical personalized and precise treatment has become a hot topic of current research. This paper summarizes and analyzes the current research status of artificial intelligence in periodontal radiographic diagnosis, and provides ideas for further research.

Oral squamous cell carcinoma is a common malignant tumor of the head and neck. Early surgery can achieve good results, but most patients have cervical lymph node metastasis at the time of initial diagnosis. Although surgery combined with radiotherapy or chemotherapy can delay the progression of the disease, the overall prognosis is still not ideal. Especially in patients at stage Ⅲ / Ⅳ, the long-term survival rate has not improved. As a key microbubble in intercellular communication, exosomes contain a large number of biological molecules such as nucleic acids, proteins and lipids. Tumor-derived exosomes play a key role in regulating the tumor microenvironment. This article reviews the effects of tumor-derived exosomes on tumor proliferation, metastasis, immune regulation, diagnosis and treatment in oral squamous cell carcinoma, in order to provide new ideas for early diagnosis and treatment of oral cancer.

The wide application of digital scanning technology in the field of dentistry has made medicine more modern and convenient. It has become popular to obtain digital face models through facial scanning systems. In order to reproduce the perfect maxillofacial shape and proportion, accurate facial scanning equipment is indispensable. For all kinds of facial scanners on the market, their working principles and scanning characteristics are not the same. This article will summarize the development of digital facial scanning technology, introduce different technical principles and discuss the clinical application, and look into the application prospect of this technology in the medical field. The limitations of this technology are proposed, in order that the digital facial scanning technology can be better applied in clinical practice.

As oral implant technology advances, implant prostheses have become an important option for restoring missing teeth. The surface properties of implants, which are a crucial component of implant prostheses, have a significant influence on implant success rate. As a result, surface modification of implants to improve their biological characteristics has emerged as a research hotspot in the field of oral implants. Due to their excellent biocompatibility, high porosity and drug loading, adjustable structure and pore size, metal-organic framework materials have drawn increased attention as promising implant surface coating materials. This paper reviews the research on metal-organic framework materials in implant surface coatings in recent years, and provides a reference for their further application in implantology.