Objective To study the effect of remineralization procedures on surface morphology and Ca/P of bleached enamel. Methods Enamel samples of bovine teeth were prepared and bleached with bleaching gel, and then randomly divided into five groups for different remineralization procedures:deionized water (DW) group; 2% NaF group; 10% procyanidins (PC) group; casein phosphopeptide-amorphous calcium phosphate (CPP-ACP) group; PC+CPP-ACP group. Changes of color, surface morphology, elements and roughness were detected by chromometer, scanning electron microscopy, energy dispersive spectroscopy and atomic force microscopy before bleaching, immediately after bleaching and one week after remineralization, respectively. Results Significant differences in ΔE were not found among bleached groups (P>0.05). Mineral sediments of different degrees could be observed in all groups after remineralization procedures, especially in PC+CPP-ACP group. Energy dispersive spectroscopy showed that bleaching significantly reduced the Ca/P ratio (P<0.05). All remineralization treatment increased the Ca/P ratio. NaF and PC+CPP-ACP exhibited higher remineralization capacity in comparison to other groups (P<0.05). Atomic force microscopy showed that mineral sediments were observed and roughness was reduced in all groups after remineralization (P<0.05), and sediments were more obvious and roughness was much smaller in PC+CPP-ACP group (P<0.05). Conclusion PC and CPP-ACP could promote the remineralization on enamel surface after bleaching, and their combined effect was better. PC and CPP-ACP did not interfere with bleaching efficacy.

Objective To study the influence of different treatment methods on the shear strength of resin nano-ceramics (LAVA Ultimate) after bonding. Methods The LAVA Ultimate was cut into 80 samples with a size of about 6 mm×6 mm and a height of 2 mm. According to different sandblasting time and pressure, the samples were randomly divided into 4 groups with 10 specimens in each group. The fracture load was tested on the Universal testing machine after the 3M Single Bond Universal+3M RelyX Ultimate was bonded to the nano resin column, and the shear strength was calculated to select the highest group. Under the same blasting conditions, 40 samples were randomly divided into A (3M Single Bond Universal+3M+RelyX Ultimate), B (Porcelain Primer (Bisco)+All-bond Universal (Bisco) Relyx Ultimate (3M)) and nano resin columns for bonding. After bonding, they were divided into two subgroups, which were subjected to 5 000 cooling and heating cycles and a constant temperature water bath for 24 h, respectively. The breaking load was tested on a universal testing machine. The shear strength was calculated, and the data were statistically analyzed using one-way ANOVA. Results Results of one-way ANOVA showed that there were significant differences in shear strength between different sandblasting conditions (group 2 and group 4) (P=0.037). After hot and cold cycling, the shear strength of group A and group B decreased significantly (P=0.003, P<0.01). There was no significant difference in shear strength between groups A and B with different bonding modes (P=0.062). Conclusion The shear strength of resin nano porcelain and resin cement can be significantly improved by sandblasting at 0.2 MPa for 14s, and can be significantly reduced by cooling and heating cycles. The bonding mode has no obvious effect on the shear strength.

Objective To evaluate metal-bone interface and bone formation of Mg-2Zn-0.5Ca alloy/mineralized collagen in bone defect repair. Methods Forty Japanese rabbits were randomly divided into four groups: Mg-2Zn-0.5Ca alloy/mineralized collagen (group A), mineralized collagen (group B), Mg-2Zn-0.5Ca alloy (group C) and blank control group (group D). The cheek side of rabbit mandible was drilled with 10 mm×7 mm×2 mm defect, similar to the defect of bone window. Mg-2Zn-0.5Ca alloy/mineralized collagen was implanted in group A; mineralized collagen was implanted in group B; Mg-2Zn-0.5Ca alloy was implanted in group C; no materials were implanted in group D. They were evaluated in biocompatibility and osteogenesis through visual inspection, serological examination, X-ray, SEM and histology at the pre-set time point. Results There was no significant difference in serum magnesium ion concentration of group A, B, C and D; in group C, the concentration of magnesium ion in urine after operation was significantly higher than that before operation. At 12 weeks after operation, new bone tissue was found in group A and group B; cartilage-like tissue was found in group C, and trabecular bone structure was not found. X-ray showed that there were different degrees of degradation around the materials in group A and group C; there was more obvious shadow around group C than group A. SEM showed that the surface of group A became rough and the degradation was not obvious, and there was bone tissue attached to the surface; materials in group C showed obvious layered disintegration, and there was no tissue attached. Histological examination showed that there was bone trabeculaes and osteoblasts around group A and group B, cartilage-like tissue around group C. Conclusion The Mg-2Zn-0.5Ca alloy/mineralized collagen does not increase the content of magnesium in serum and can reduce the degradation rate. Mg-2Zn-0.5Ca alloy/mineralized collagen has good osteogenic performance.

Objective To construct a three-dimensional finite element model based on digital removable partial denture framework, to analyze the effects of different modeling strategies on framework and oral soft and hard tissues, and to explore the optimal design method of digital framework. Methods One adult volunteer with complete dentition and healthy periodontal tissues was selected. On the basis of cone beam computed tomography (CBCT)and extraoral plaster model scanning, the removable partial denture was designed by 3Shape Dental System software. The maxillary Kennedy Class Ⅱ dentition defect model and removable partial denture model were established by Mimics, Geomagic Studio and HyperMesh software, and three-dimensional finite element models of the simplified group and control group (including teeth and periodontal ligament)were constructed respectively. The finite element analysis software Abaqus/CAE was used to analyze the force put on two groups of models under vertical and oblique 45° load. Results The stress distribution of framework in the simplified group was basically the same as that in the control group, and there was no significant difference in stress value between two groups. Under the vertical load, stress concentration appeared at the minor connector of the framework in both groups; distal end of the framework sank; the maximum stress was 44.39 MPa and 51.05 MPa, and the maximum displacement was 49.05 μm and 38.29 μm, respectively. Under oblique load, the major connector of the framework had a high stress zone; the stress concentration at the right angle of the Ⅰ bar was concentrated; the maximum stress was 324.58 MPa and 303.11 MPa, and the maximum displacement was 291.86 μm and 298.02 μm, respectively. Conclusion Properly simplified model can improve the modeling efficiency, and calculation results have good credibility, which can provide reference for the optimal design of clinical digital removable partial denture framework.

Objective To develop a protocol of fixed occlusal rehabilitation for severely worn permanent dentition. Methods Severely worn permanent dentition with no sign of tension/pain of temporomandibular joint and muscles when loading was included. On the pathway of hinge movement at centric relation position, the minimal thickness required by restoration materials was used to determine the vertical dimension of occlusion and construct intercuspal occulusion. The occlusion contact was designed by the principle of aesthetic prosthodontics and the simplified therapeutic occlusion. Results Ten patients with fixed prosthesis followed up for 1 to 5 years were satisfied with its aesthetics and function. The occlusion was stable with no occlusal interference. There were no signs of tension/pain of temporomandibular joint and muscles. The stomatognathic system was healthy and comfortable. Conclusion The easy-controlled protocol of full-dentition rehabilitation may achieve the coordination in stomatognathic system.

Objective To observe and evaluate the clinical effect of Trausim bone level implant system on dental defect with a 4-year follow-up research. Methods A multi-centric, prospective, single-group target-value clinical trial design was used in this study. Three 3A hospitals in Shanghai were selected as the research center. One Hundred and twenty patients with dental defects were treated with implant therapy. The success rate was evaluated, and indexes such as postoperative healing, bone loss, soft tissue health around implants and implant stability were recorded. Results The results showed the implant success rate was 97.5% after 4 years of occlusal loading. X-ray examination showed that there was no transparent area around the implant and cervical bone resorption was less than 1 mm. The soft tissue around implants was healthy and the occlusal relation was functionally reconstructed. Conclusion Trausim bone level implant system is effective in the treatment of dental loss, with high success rate and low complication, which could be used in clinical practice.

Objective To analyze the expression and clinical significance of ubiquitin like with PHD and ring finger domain 1(UHRF1)in oral squamous cell carcinoma. Methods Patients with primary oral squamous cell carcinoma who underwent surgery at the department of oral and maxillofacial surgery, The First Affiliated Hospital of USTC from 2008 to 2016 were collected. The expression of UHRF1 in tumor tissues, adjacent normal tissues and invasion front were evaluated by immunofluorescence staining to explore the difference in UHRF1 expression. The patients were divided into high expression group and low expression group according to the value of immunoreactivity intensity distribution index(IRIDI). Relationship between the expression level of UHRF1 and clinicopathological characteristics of patients was analyzed. The correlation between the relative expression of UHRF1 in oral squamous cell carcinoma and survival rate was analyzed by Kaplan Meier method, and the relevant risk factors affecting the survival rate of patients with oral squamous cell carcinoma were analyzed by Cox risk regression model. Results Compared with the tumor invasion front and adjacent normal tissues, UHRF1 was highly expressed in oral squamous cell carcinoma(P<0.01). The expression level of UHRF1 in oral squamous cell carcinoma was correlated with gender, tumor size and depth of invasion(P<0.05). There were significant differences in tumor recurrence, cervical lymph node metastasis, occult lymph node metastasis and survival rate between low expression group and high expression group(P<0.05). Cox risk regression model showed that the expression level of UHRF1 was a risk factor for the prognosis of patients with oral squamous cell carcinoma(P=0.002). Conclusion UHRF1 is highly expressed in oral squamous cell carcinoma, and its expression level is closely related to the clinical prognosis of patients with oral squamous cell carcinoma. It can be used as a valuable prognostic index of oral squamous cell carcinoma.

Objective To study the morphological differences of condyles in different genders, positions, normal healthy people and temporomandibular disorders(TMD)patients by using Mimics software. Methods Forty subjects were enrolled in our study from the Department of Stomatology, Taizhou Central Hospital(Taizhou University Hospital). Twenty patients with TMD and 20 volunteers without temporomandibular joint(TMJ)disorders were included. All subjects received CBCT examination of the TMJ. Three-dimensional reconstruction of the condyle was conducted by Mimics 19.0 software and condylar volume, surface area and morphological index(MI) were measured and statistically analyzed. Results The condylar volume, surface area and MI of TMD patients were lower than those of normal population(P<0.05).The condylar volume, surface area and MI of males were higher than those of females(P<0.05), and there were no significant differences between left and right sides in the condylar volume, surface area and MI(P>0.05). Conclusion Patients with TMD have smaller condylar volume and surface area than normal population. Mimics can effectively measure condylar volume and surface area, and provide assistance for establishing reference values of condylar volume and surface area in normal population and patients with TMD.

Objective To summarize clinical manifestations and treatment results of parotid lipoma. Methods The medical history, clinical manifestations, imaging examination, treatment and prognosis of 17 patients with parotid lipoma were retrospectively analyzed. Results All 17 cases of parotid lipoma were located in the superficial lobe and presented as a painless mass. There were 6 females and 11 males, aging from 33 to 76, with an average age of 50.7. Ultrasound examination showed a clear and hypoechoic mass within the parotid gland, and CT examination showed a clear boundary, intact capsule, and low-density mass. Partial parotidectomy with preservation of the facial nerve was performed, and there was no symptom of facial nerve paralysis and no recurrence after operation. Conclusion Parotid lipoma is more common in men, manifested as a painless and gradually enlarged mass in parotid gland. The tumor is completely removed in the normal parotid gland with partial parotidectomy, and the prognosis is good.

Objective To compare and analyze differences in clinical failure rate of removable partial dentures (RPD) Cobalt-Chromium (Co-Cr) frameworks made by conventional methods and digital printing methods. Methods From 2020 to 2021,1 020 RPD Co-Cr frameworks made by conventional methods and digital printing methods (selective laser melting, SLM) were analyzed retrospectively, and clinical failure rate and factors affecting the failure were analyzed. Results Clinical failure rate of conventional casting Co-Cr frameworks was slightly higher than that of SLM frameworks. The main reason for the failure of casting frameworks was poor precision with an incidence of 3.42%, and followed by the fracture rate, accounting for 0.22%. The main reasons for the failure of SLM frameworks were fracture and poor precision with an incidence of 1.75% and 0.88%, respectively. There was a statistical difference in the fracture rate of large junction between the two frameworks, and there was no statistical difference in other failure factors. Conclusion The clinical failure rate of conventional Co-Cr frameworks is slightly higher than that of SLM frameworks. The main reason for failure of casting framework is poor precision, while the main reason for SLM framework failure is fracture.

Osseointegration of implants is a dynamic process involving multi-cell and multi-factor. Traditional research has been focusing on bone formation and absorption in osseointegration. With the development of osteoimmunology, studies find that the immune microenvironment of bone plays an important role in the establishment and long-term maintenance of osseointegration. Immune cells regulate bone repair around implants by chemokines and cytokines. Ideal immune microenvironment could promote tissue healing and regeneration to achieve better bone-implant contact. More attention has been given to the regulation of osseointegration and treatment of peri-implantitis via bone immunomodulation. In this article, the immune response process around dental implants was summarized by reviewing relevant literature. At present, there are more studies on macrophages, but few on other immune response cells. There are still many questions about the mechanism of immune response between immune cells and implants remaining to be explained.

Fiber post has the advantages of beautiful appearance and excellent biosafety, which is widely used in clinical practice. However, it has limitations and failure rate, manifested as shortcomings like fiber post loosening, falling off, breaking, core damage and non-degradability. With the sustainable development of ecology, plant fibers have been widely used, such as coconut shell and bamboo fiber. Bamboo fiber has been paid close attention to by scholars due to its advantages including good mechanical properties, low cost, degradability, non-toxicity, anti-bacteria and good biocompatibility. Based on existing research, the mechanical and physical properties of bamboo fiber basically meet the requirements of dental post and core system. However, such studies are mostly non-medical experiments, and little research at home and abroad focuses on dental post and core system. This paper will further explore the application potential of bamboo fiber in dental post and core system in terms of mechanical and physical properties, anti-bacteria, cytotoxicity and biocompatibility of bamboo fiber. Moreover, related problems limiting application of bamboo fiber and possible improvement methods are proposed. It provides clinical guidance for the development of dental post and core system.

The type Ⅸ secretion system(T9SS) consists of at least 16 potential structural proteins and 4 transcription regulators. Porphyromonas gingivalis utilizes T9SS to transport many virulence factors, such as gingipain, across the outer membrane and attach them to the cell surface. This review focusses on the recent advances made in structural proteins and transcription regulators on the T9SS of Porphyromonas gingivalis and to provide further insight into the composition and function of T9SS translocon.

Previous studies indicated that low-level therapy (LLLT) may accelerate tooth movement. We review literature to summarize the clinical effect of LLLT on accelerating tooth movement and its biological mechanism. A majority of the studies believed that LLLT could accelerate orthodontic tooth movement. However, some studies believed that LLLT had no effect on the acceleration of orthodontic tooth movement. LLLT is characterized by low dose stimulation and high dose inhibition. Therefore, the difference may be related to parameters in its application. LLLT promotes the reconstruction of alveolar bone by photobiomodulation. Results of recent research have showed that the number of bone cells, local collagen content and the expression of inflammatory factors in periodontal tissues of the patients treated with LLLT were regulated, but the biological mechanism remains to be discovered by further research.

Antimicrobial peptides have strong antibacterial effects and are considered as a potential alternative to traditional antibiotics due to their unique bactericidal mechanism. Compared with natural antimicrobial peptides, synthetic antimicrobial peptides have better antibacterial activity and stability, and can be used for dental caries prevention and treatment in terms of inhibiting major cariogenic bacteria, reducing the formation of dental plaque biofilm, and promoting remineralization. This paper will review these synthetic antimicrobial peptides and their mechanisms, and provide a reference for further study on synthetic antimicrobial peptides in caries prevention and treatment.

The stable aesthetic outcome and functional restoration in the long run become the focus of recent studies on implant in the aesthetic area. Concentrated growth factor (CGF), as a third-generation platelet concentrate product, has been effective in promoting the natural processes of tissue regeneration with simple preparation method, higher multitude of growth factors contained, and no need of any additives. The article will introduce the preparation method, performance characteristics of CGF, and summarize the progress of research on its ability and underlying machanism to promote tissue regeneration and clinical application in implant restoration in aesthetic areas.

Platelet-rich plasma(PRP), a platelet concentrate derived from autologous blood, is rich in cytokines and growth factors.Among these factors, platelet-derived growth factor(PDGF), transforming growth factor β(TGF-β)and vascular endothelial growth factor(VEGF)mainly affect the activity of osteoblasts and osteoclasts, thus promoting the process of bone reconstruction. The efficiency of orthodontic teeth movement is influenced by bone reconstruction, so local injection of PRP will be a new direction to accelerate the efficiency of orthodontic teeth movement. This paper mainly reviews the application of PRP in orthodontic treatment to accelerate the efficiency of orthodontic teeth movement and relevant research, which will help further explore the feasibility of PRP in clinical treatment to accelerate the efficiency of orthodontic teeth movement.

Alternate rapid maxillary expansions and constrictions (Alt-RAMEC) is a new method of expansion proposed by Liou in 2005, which expands sutures around maxilla more effectively and leads to greater amount of maxillary protraction. Compared with rapid maxillary expansion and facemask, it can obtain better skeletal effects and correct maxillary deficiency more efficiently. This paper reviews characteristics of the conventional Alt-RAMEC device, clinical outcomes, long-term stability, airway changes and periodontal complications in order to provide reference for promoting clinical application.

Root development will continue after immature permanent tooth eruption. However, during this period if the pulp is inflamed or necrosed due to caries, dental trauma or teeth dysplasia, root formation will be interrupted, which results in an open apex and thin root canal wall. It has been reported that apical development of immature permanent teeth is independent of main root canal, which is a special type of root development. In this paper, we reviewed literature and analyzed possible causes for the separated root tip formation of immature permanent tooth, which could provide some suggestions for clinicians to make correct preventive and therapeutic decisions.