The nature, significance, parameters, influencing factors and testing of implant primary stability were studied by a literature review. Primary stability is a kind of anchorage force at the interface between the implant and bone, and it is merely mechanical. The significance of primary stability is to keep the implant unmovable so that the new bone can grow undisturbed on the surface of the implant without interference from fibrous tissue. The implant is finally bound to the bone by osseointegration. The most common assessments of primary stability are insertion torque (IT), the implant stability quotient (ISQ) of the resonance frequency analysis (RFA) and Periotest. IT is more commonly used to directly imply initial stability. At present, no consensus has been reached regarding the concrete parameters of primary stability to predict osseointegration. Implant osseointegration could be developed through all phases of primary stability. However, the excessive primary stability would cause mini-bone fractures, followed by bone necrosis at the interface and the final failure of implantation. Primary stability is influenced by three factors: implant design, bone condition of alveolar bone, and surgical technique. Under the condition of a lack of primary stability and immediate implantation, there may be the possibility of successful osseointegration. Therefore, it is necessary to re-examine the accuracy of the current elaboration on the primary stability. It is related directly to whether the clinic can choose the appropriate implant treatment path.

Benign condylar hyperplasia is one of the causes of mandibular lateral deformity, it is easily to be misdiagnosed clinically and leads to the treatment failure. This article will elaborate the etiology and clinical features of benign condylar hyperplasia, as well as the diagnostic points and treatment progress, based on the literature and the clinical experience of our research group, to provide evidence-based medical evidence for the standardized clinical treatment of benign condylar hyperplasia. The etiology of benign condylar hypertrophy includes neurotrophic disorders, local circulatory disorders, traumatic injuries (especially condylar injuries that occur in childhood), unilateral mastication, temporomandibular arthritis, endocrine disorders, condylar osteoma, and heredity. Benign condylar hypertrophy is insidious, and occurs most frequently in individuals 10-30 years old, and the course of disease can last for many years. Its clinical characteristics are slow progressive facial asymmetry. Radionuclide bone scans have become the basis for the diagnosis and differential diagnosis of and treatment planning for benign condylar hypertrophy. Different treatment plans for active and inactive periods need to be developed, including close observation, proportional condylar resection and orthognathic surgery.

Objective To study the clinical manifestations and biological characteristics of Stafne bone cavity and to reduce misdiagnosis and excessive treatment. Methods Four cases of typical Stafne bone cavity, including clinical features and follow-up data, were retrospectively analyzed, and the results, combined with a review of the literature, were analyzed in terms of the etiology, clinical manifestations, diagnostic criteria and treatment of Stafne bone cavity. Results Stafne bone cavity is also known as static bone cavity, idiopathic bone cavity, latent bone cavity defects, aberrant salivary glands, heterotopic mandibular salivary glands, mandibular lingual bone cavity, mandibular lingual cortical bone defect, etc. The incidence of Stafne bone cavity is approximately 0.5%. This condition is easily misdiagnosed as a jaw or jaw cyst tumor and treated unnecessarily. Most scholars believe that the causes of Stafne bone cavity can be divided into two types: developmental and glandular. Stafne bone cavity is characterized by either no symptoms or occasional pain. This condition is observed mostly in 40-60-year-old male patients. The imaging diagnostic criteria for Stafne bone cavity are as follows: ① projecting round or ovoid mandible and uniform density with a distinct bone-cortical white line; ② clearly distinguishable from adjacent structures, such as teeth; ③ typical location in the mandibular angle and molar area, below the mandibular neural tube. Most Stafne bone cavities without advanced bone destruction do not require treatment, although individual cases may gradually progress. Conclusion Stafne bone cavity presents no symptoms or causes occasional pain and can be clearly diagnosed with CBCT. This condition does not require surgical treatment and should be followed up with observation.

Alveolar bone is an important anatomic basis for implant-supported denture restoration, and its different degrees of defects determine the choices of bone augmentation surgeries. Therefore, the reconstruction of alveolar bone defects is an important technology in the clinical practice of implant restoration. However, the final reconstructive effect of bone quality, bone quantity and bone morphology is affected by many factors. Clinicians need to master the standardized diagnosis and treatment principles and methods to improve the treatment effect and achieve the goal of both aesthetic and functional reconstruction of both jaws. Based on the current clinical experience of domestic experts and the relevant academic guidelines of foreign counterparts, this expert consensus systematically and comprehensively summarized the augmentation strategies of alveolar bone defects from two aspects: the classification of alveolar bone defects and the appropriate selection of bone augmentation surgeries. The following consensus are reached: alveolar bone defects can be divided into five types (Ⅰ-0, Ⅰ-Ⅰ, Ⅱ-0, Ⅱ-Ⅰ and Ⅱ-Ⅱ) according to the relationship between alveolar bone defects and the expected position of dental implants. A typeⅠ-0 bone defect is a bone defect on one side of the alveolar bone that does not exceed 50% of the expected implant length, and there is no obvious defect on the other side; guided bone regeneration with simultaneous implant implantation is preferred. Type Ⅰ-Ⅰ bone defects refer to bone defects on both sides of alveolar bone those do not exceed 50% of the expected implant length; the first choice is autologous bone block onlay grafting for bone increments with staged implant placement or transcrestal sinus floor elevation with simultaneous implant implantation. Type Ⅱ-0 bone defects show that the bone defect on one side of alveolar bone exceeds 50% of the expected implant length, and there’s no obvious defect on the other side; autologous bone block onlay grafting (thickness ≤ 4 mm) or alveolar ridge splitting (thickness > 4 mm) is preferred for bone augmentation with staged implant placement. Type Ⅱ-Ⅰ bone defects indicate that the bone plate defect on one side exceeds 50% of the expected implant length and the bone defect on the other side does not exceed 50% of the expected implant length; autologous bone block onlay grafting or tenting techniques is preferred for bone increments with staged implant implantation. Type Ⅱ-Ⅱ bone defects are bone plates on both sides of alveolar bone those exceed 50% of the expected implant length; guided bone regeneration with rigid mesh or maxillary sinus floor elevation or cortical autologous bone tenting is preferred for bone increments with staged implant implantation. This consensus will provide clinical physicians with appropriate augmentation strategies for alveolar bone defects.

Oral lichen planus (OLP), a common and chronic disorder, has no effective treatment or cure because its etiology is complicated and has until now remained unclear. Therefore, effectively controlling the activity of the disease and preventing its recurrence are two primary purposes of clinical treatment for OLP. The available evidence supports the notion that topical steroids are the preferred drug for treating this disease. However, some cases have poor clinical curative responses to steroids or other medicines, mainly because of drug resistance and other factors. Therefore, scholars have explored new drugs and methods with the aim of achieving more effective and safe treatment effects. The current research evidence indicates that glucocorticoid remains the front-line drug for OLP treatment. Topical tacrolimus, pimecrolimus and retinoic acid combined with glucocorticoid can be used as alternative therapies, especially in cases with glucocorticoid drug resistance. The systemic application of glucocorticoid or immunosuppressive agents, such as methotrexate, mycophenolate mofetil, and sulfoxide, should be limited to extensive, refractory cases or those with lesions involving regions outside the oral cavity. Surgery and cryotherapy can be applied in a specific, limited range of lesions. Some previous randomized controlled clinical studies have had limitations, including a small sample size, short treatment and clinical follow-up periods, a lack of reliable questionnaires and differences in evaluation standards. Therefore, future studies should include the following: randomized controlled clinical studies with large sample sizes that offer reliable evidence of a curative effect; assessments of treatment outcomes should be extended as long as possible; the follow-up period should be long enough to assess the recurrence rate; and the methods and standards used to evaluate treatment effects should be standardized.

Cracked tooth is a common type of tooth fracture with diverse symptoms, different treatment principles and unpredictable prognosis. The available remedies for immediate, intermediate and definitive managements include occlusal adjustment, orthodontic band, bonded composite resin, onlay, full crown and so on. For teeth with localized crack and vital pulp, bonded composite resin and onlay with cuspal coverage are also protective remedies besides traditional full-crown restoration. Once pulpal infection occurs, root canal therapy and full-crown restoration is indicated. Clinical determination should be made with comprehensive consideration of the location and depth of the crack, risk of extension and pulpal condition. This review will focus on the traits and prognosis of various therapy options, so as to provide evidence-based treatment planning of cracked tooth.

Objective To study the changes in levels of interleukin (IL)-6, IL-10, tumor necrosis factor-alpha (TNF-α), and alkaline phosphatase (ALP) in the gingival crevicular fluid (GCF) of patients with severe chronic periodontitis before and after nonsurgical periodontal therapy and to explore the relationship among the levels of these four biomarkers in GCF, their periodontal status and their clinical significance to evaluate the effect of nonsurgical periodontal therapy and periodontitis activity. Methods In total, 30 patients with severe chronic periodontitis were enrolled in a 1-year longitudinal pilot study (Chinese Clinical Trial Registry: ChiCTR-OCH-13004679). At baseline and 1, 3, 6, and 12 months after nonsurgical therapy, the periodontal clinical indicators plaque index (PLI), probing depth (PD), clinical attachment loss (CAL), sulcus bleeding index (SBI) were recorded. Filter paper strips were used to collect two deep-pocket (probing depth ≥ 6 mm) and two shallow-pocket (probing depth ≤ 4 mm) periodontal sites for each patient and weighed. The levels of interleukin IL-6, IL-10, TNF-α, and ALP in GCF were assessed using enzyme-linked immunosorbent assay. Meanwhile, 30 healthy sites of 15 subjects with healthy periodontium were used as the baseline controls for patients with severe chronic periodontitis. Results At the baseline, the TNF-α, ALP and IL-6 levels in GCF of the disease sites of patients with periodontitis were significantly higher than those in healthy periodontal sites of the control group (P < 0.001), and the levels of IL-10 were significantly lower than those in the control group (P < 0.001). In patients with severe chronic periodontitis, the levels of TNF-α, ALP and IL-6 in GCF at deep-pocket sites were significantly higher than those at shallow-pocket sites (P <0.001), and the IL-10 levels were significantly lower than those at shallow-pocket sites (P < 0.001). 1, 3, 6, and 12 months after nonsurgical treatment, the levels of TNF-α and ALP in GCF at the shallow- and deep-pocket sites in patients with chronic periodontitis significantly decreased, the level of IL-10 significantly increased (P < 0.005), and the level of IL-6 in GCF at the deep-pocket sites significantly decreased (P < 0.005). However, there was no significant difference in IL-6 level at shallow-pocket sites (P > 0.05). 1, 3, 6, and 12 months after nonsurgical treatment, the periodontal clinical indicators were improved compared with the baseline. In addition, there was a significant correlation between the levels of these four biomarkers and the periodontal clinical parameters (P < 0.05). During the two follow-up visits after nonsurgical periodontal therapy, the sites with more than 2-mm increase in attachment loss had significant differences in the levels of the four biomarkers in the GCF compared with the previous visit time (P < 0.005). Conclusion The detection of the levels of these four biomarkers in GCF has strong clinical significance for assessing the severity of periodontitis and the efficacy of nonsurgical periodontal therapy. Increased levels of TNF-α, ALP, and IL-6 and decreased IL-10 levels in GCF may indicate periodontitis progression at this site.

Objective To explore the cause and preventive measures of floor-of-mouth hematoma after dental implant placement. Methods The prevention of hematoma of the floor of the mouth in a case of lower anterior teeth implant placement was analyzed, and the literature was reviewed. Results Four mandibular vascular canals were found on the lingual side of the anterior mandible before dental surgery in the reported case. Two of them were quite thick (1.4 mm and 1.0 mm, respectively) and were located adjacent to the crest of the alveolar bone and superior to the mental spine. These two thick endosseous branches from the sublingual artery were dissected and ligated , and there was no obvious hematoma in the patients immediately after the operation and at the postoperative 3 d review. The results of the literature review show that the incidence of endosseous branches from the lingual vascular canal of the mandible is 90%-100%. The distribution of the vessels on the lingual side of the mandible is highly variable and adjacent to the lingual cortical plate. Accidental injury of the lingual cortical plate during implant surgery would probably lead to bleeding or hematoma on the floor of the mouth. Conclusion Mastering the anatomy of blood vessels on the floor of the mouth, elaboratively examining preoperative three-dimensional radiographic imaging, and cautiously exploring the lower jaw bone morphology after flap elevation are preventive measures to avoid damage to the arterial supply on the lingual side of the anterior lower jaw and to prevent complications of hematoma in the floor of the mouth.

Biodentine is a bioactive dentin replacement material whose main component is high-purity tricalcium silicate without dicalcium silicate. It has a shorter cure time; although it has a higher solubility, it hardly affects the volume of the material. It has a low X-ray barrier property, low porosity, high bulk density, and high compressive strength and is not affected by moisture or a dry environment. It has strong acid corrosion resistance, can increase dentin resistance, and has biocompatibility due to the lack of cytotoxicity. It has antibacterial activity against various bacteria, with strong antibacterial activity against Streptococcus sanguis. Since 2010, Biodentine has been widely used in clinical treatments such as dental restoration, pulp capping, pulpectomy, et al. In clinical applications, Biodentine is primarily used as a permanent dentin substitute or as a temporary enamel substitute within 6 months. As a new dentin substitute material with a short clinical application time, the long-term efficacy of Biodentine requires further follow-up observation studies.

Oral submucous fibrosis (OSF) is a chronic disease that produces scars, tissue fibrosis, and precancerous lesions. Epidemiological studies have shown that chewing betel nut is the most significant risk factor for OSF. Many studies have also indicated that habits such as chewing and smoking tobacco and drinking alcohol increase the risk of OSF, which is widely recognized as an oral precancerous lesion or a potentially malignant oral disorder. Pathological characteristics include chronic inflammation, excessive collagen deposition in the connective tissues below the oral mucous epithelium and local inflammation in the lamina propria or deep connective tissues. OSF patients have a 7%~30% chance of developing oral cancer. Submucosal local injection of triamcinolone and tanshinone was mainly used for the treatment of oral submucosal fibrosis. This treatment improves mouth opening and alleviates the burning sensation in OSF, and the treatment efficacy was as high as 93%. The article will discuss the occurrence, development, diagnosis and treatment of oral submucous fibrosis for clinical management by the medical community.

The most common periodontal biotype in the Chinese population is thin, which obviously limits orthodontic tooth movement. Periodontally accelerated osteogenic orthodontics (PAOO) can not only accelerate tooth movement through corticotomy but also expand the range of orthodontic tooth movement by alveolar bone augmentation, which could reduce the periodontal complications of orthodontic therapy. The development of PAOO has gone through a long and tortuous historical process over more than 100 years: from osteotomy based on "bony block movement" at the beginning to cortical osteotomy based on "the regional acceleratory phenomenon" and then to PAOO based on "bone tissue engineering". Throughout its development history, the understanding of the biological basis determines the development of the clinical technology. Therefore, PAOO should be based on basic research. Both the present clinical practice and future surgical improvements should be based on the fundamentals of bone repair and regeneration. According to the current evidence, it is suggested that piezocision and laser-assisted flapless corticotomy should be chosen only for simple cortical osteotomy, and surgical navigation technology or 3D-printed surgical guides are recommended. When a large amount of bone augmentation is needed, PAOO with an intact flap is still the first choice. A stable and infection-free healing environment is the key to wound healing; therefore, in addition to infection control, the surgical area should also be protected from external forces. At present, there are few high-quality clinical studies on PAOO. Multicenter, large-sample, randomized controlled clinical trials are needed to evaluate the clinical efficacy of different PAOO techniques in the future. The present article introduces the development history, fundamentals and operation precautions of PAOO, and a new perspective is also proposed, which may provide a reference for clinical practice.

Guided bone regeneration technology applied in alveolar bone defect regeneration is based on the barrier function and space maintenance of the barrier membrane. Therefore, traditional development strategies for barrier membranes focus on their physical barrier function, degradation characteristics and biocompatibility to avoid immunogenicity. However, not only does the barrier membrane passively block connective tissue, it is recognized as a “foreign body”that triggers a persistent host immune response, known as a foreign body reaction. The theories of osteoimmunology reveal a close relationship between the immune system and bone system and emphasize the role of immune cells in bone tissue-related pathophysiological processes. Based on these findings, we propose a novel development strategy for barrier membranes based on immune microenvironment regulation: by manipulating mechanical properties, surface properties and physiochemical properties, barrier membranes are endowed with an improved immunomodulation ability, which helps to regulate immune cell reactions to induce a favorable local immune microenvironment, thus coordinating osteogenesis and osteoclastogenesis as well as barrier membrane degradation to increase the efficiency of barrier membranes in GBR applications. In this paper, we review the development of barrier membranes and their close relationship to the immune microenvironment concerning bone regeneration and membrane degradation. Additionally, the outcomes of research on barrier membranes based on the regulation of the immune microenvironment have been summarized to improve the osteogenesis efficiency of barrier membranes and solve the problem of the regeneration and repair of bone defects, especially alveolar bone defects.

With the arrival of the era of big data, increasing attention has been drawn to the application of artificial intelligence (AI) in the medical field. AI has many advantages, such as objectivity, accuracy, minimal invasiveness, time savings and high efficiency. Therefore, the combination of AI with dental diagnosis and treatment can help dentists improve work efficiency and save medical resources, offering potential significant benefits for dental application. At present, AI has been gradually integrated into prosthodontics, oral and maxillofacial surgery, orthodontics, endodontics and periodontics. The AI system can realize automatic tooth preparation, automatic tooth arrangement and implantology. Deep learning can be used to assist in diagnosing maxillary sinus inflammation, predicting the complications of tooth extraction and improving the accuracy of osteotomy. The AI system can also provide significant clues for the diagnosis, treatment and prognosis of oral and maxillofacial tumors. The breakthrough brought by AI in cephalometric and the assessment of facial attractiveness of patients has promoted the development of intelligent and personalized orthodontic treatment. Deep learning and analysis of medical images also promote the accuracy of root canal therapy as well as the diagnosis and treatment of periodontal diseases. AI technology has realized the leap from digitalization to automation and intelligence in oral diagnosis and treatment, and its application potential in the oral field should not be underestimated. Based on the concepts of AI, this paper will focus on the application of artificial intelligence in various oral clinical fields and briefly introduce its advantages, problems and future.

Objective To investigate the clinicopathological features, treatment and prognosis of oralmucosal malignant melanoma to provide a reference for clinical practice. Methods Data from 19 patients with oralmucosal malignant melanoma were collected, and their clinical manifestations, treatment methods and follow-up results were retrospectively analyzed. Results Among the 19 patients, 11 cases (58%) had lesions in the gingiva, 7 cases (37%) had lesions in the palate, and 1 case (5%) had lesions in the tongue, the difference was statistically significant (P<0.05). Eight patients had regional lymph node metastasis with a metastasis rate of 42%, of which 4 cases had multiple site metastasis, and the total number of regional lymph node metastasis sites was 15. Among the 19 patients, 3 cases received only surgery, 4 cases received cryotherapy, and 12 cases received combined surgery, cryotherapy and biological immunotherapy. Pathological examination showed malignant melanoma. The positive rates of S-100, HMB-45 and Melan-A were 95%, 89% and 84%, respectively. Kaplan-Meier survival analysis showed that patients with lesions less than 5 cm² had a higher survival rate (P < 0.05). Conclusions Oral malignant melanomas usually present as black lesions in the oral mucosa, which are prone to metastasis in early stage. The area of lesions may affect the prognosis of the disease. Therefore, the large range of black lesions or masses should be the alert for the clinicians. Oral malignant melanoma patients are usually treated with combined treatment with surgery, cryotherapy and biological immunotherapy.

Mesenchymal stem cells (MSCs) are capable of self-replication and multi-directional differentiation, which are very important for the development and reconstruction of mesenchymal tissue. Bone tissue damage repair involves the participation of various cells and molecules. The recovery of bone mass requires sufficiently many MSCs to migrate to the damaged site to perform the reconstruction function. The local inflammatory response at the injury site can recruit MSCs and promote new bone formation. Simultaneously, niche changes during the migration of MSCs will affect their biological performance and initiate the phase of directed differentiation. This article explores the relevant mechanisms that mediate the migration of MSCs in the process of bone injury repair, including the regulation of immune cells and chemotactic signaling molecules in the inflammatory response in the bone repair stage through signaling pathways such as BMP/Smads. Then, it summarizes the mechanism by which the high matrix stiffness upregulates the expression of the integrin and focal adhesions to promote the MSCs migration and osteogenic differentiation. Simultaneously, the migration ability of MSCs can be regulated through drugs or genetic modification to promote the bone injury repair. The improvement of MSCs migration ability can shorten the time of bone tissue damage repair and improve the bone quality. This article reviews the role of the MSCs migration ability in bone tissue injury repair to provide a reference for the application of MSCs with high migration ability in the fields of stem cell therapy for bone related diseases and bone tissue engineering.

Gingival recession (GR) is characterized by exposure of the root surface into oral environment due to apical migration of the marginal gingiva to the cementoenamel junction (CEJ). A high prevalence of GR has been reported in several representative population samples. GR may result in a certain degree of functional and aesthetic alterations if left untreated for long periods. In severe cases, root-dentin hypersensitivity, abrasion, abfraction and root caries may also be involved in GR, which increases the challenge of plaque control. The etiology of GR is multifactorial, including periodontal disease, local anatomical variation, tooth malposition, improper tooth brushing, mechanical trauma and iatrogenic factors, of which periodontal disease is the most common cause. The treatments of GR consist of nonsurgical and surgical therapy, and the latter generally involves mucogingival surgery to restore the aesthetics and function of the local gingival recession. However, over the past 50 years, the periodontal plastic surgical technique has evolved from the traditional free gingival graft method into a more advanced, minimally invasive tunnel technique. For this technique, sulcular incisions instead of vertical relieving incisions are provided through each recession area, and full thickness mucoperiosteal flaps are created and extended beyond the mucogingival junction to facilitate coronal displacement. Each pedicle adjacent to the recession is gently undermined to create a tunnel at recipient site, where either autograft or allograft can be used. A minimally invasive tunnel technique is a better method for root coverage and reduced postoperative patient discomfort. This technique is characterized by both practical and aesthetic features.

Chloroquine and hydroxychloroquine are both classic 4-aminoquinoline antimalarial drugs with similar chemical structures and mechanisms of action. As the toxicity and side effects of hydroxychloroquine are lower than those of chloroquine, hydroxychloroquine is the main clinical application at present, with good efficacy and safety. Chloroquine and hydroxychloroquine are widely used in the clinic because of their immunosuppressive, anti-inflammatory, antiviral, antitumor and photoprotective effects. The main mechanisms by which chloroquine/hydroxychloroquine inhibits immunity include inhibiting lysosome activity, autophagy, immune response signaling pathways production of proinflammatory cytokines. Chloroquine stabilizes the lysosomal membrane and reduces the release of lysosomal enzymes. As a prostaglandin antagonist, chloroquine can reduce the production of prostaglandins and leukotrienes, thus playing an anti-inflammatory role. Chloroquine/hydroxychloroquine can inhibit virus proliferation in the early stage of virus replication by inhibiting the glycosylation of the angiotensin converting enzyme 2 receptor. At present, hydroxychloroquine has been found to have significant efficacy in discoid lupus erythematosus, oral lichen planus, chronic cheilitis, pemphigus foliaceus, Sj?gren’s syndrome and other stomatological diseases. However, eye damage is the most important adverse reaction of hydroxychloroquine, and its occurrence is related to the cumulative dose of drugs.

The reconstruction effect of peri-implantitis bone defects depends on their morphological characteristics. This paper reviews the morphological classification and treatment of peri-implantitis bone defects. A literature review shows that the morphological classification of bone defects in peri-implantitis includes morphology classification and clinical classification. At present, the Renvert classification is more commonly used in the clinic and is divided into four-wall bone pockets, three-wall bone pockets, two-wall bone pockets, one-wall bone pocket and dehiscence according to the number of bone walls. This has guiding significance in the treatment plan of peri-implantitis. The treatment of peri-implantitis depends on the severity of peri-implant bone defects. Peri-implantitis with mild bone defects is treated by nonsurgical treatment, peri-implantitis with severe bone defects is recommended to remove the implant, and peri-implantitis with moderate bone defects is further judged according to the shape of the bone defects. Four-wall bone pockets, three-wall bone pockets and dehiscence are mostly treated by bone regenerative surgery. For shallow two-wall bone pockets, one-wall bone pockets and horizontal bone resorption, bone resection is often used. However, most peri-implantitis has a variety of bone defect forms at the same time, which need to be treated with bone regenerative surgery and bone resection surgery.

Radioactive jaw necrosis is a serious complication of head and neck radiotherapy. This complication's main characteristics are chronic necrosis and infection, and its clinical manifestations are local pain, mouth opening re'striction, speech disorder, dysphagia, exposure of dead bone, prolonged healing of facial and neck soft tissue fistula, and even pathological fracture, which brings great pain to the patient's body and mind. Radioactive jaw necrosis has become a clinical problem in the field of medicine, specifically for maxillofacial surgery of the external head and neck. The pathogenesis of radiation-induced jaw necrosis is still unclear, but high radiotherapy dose, extraction of teeth after radio-therapy and surgical trauma are recognized as high-risk factors. The diagnosis of radiation-induced jaw necrosis needs to be combined with the patient's radiotherapy history, clinical symptoms and imaging examination. Conservative or sur-gical treatment should be selected according to its clinical classification and stages, and the prevention of radiation-in- duced jaw necrosis should be emphasized. The key points are to remove dental caries, residual roots and crowns before radiotherapy; improve radiotherapy technology; and take preventive measures against high-risk factors. In recent years, the diagnosis and treatment of radiation-induced jaw necrosis has gradually become standardized and individualized.This article reviews the progress of treatment and research on radiation-induced jaw necrosis at home and abroad in terms of its definition, etiology, risk factors, diagnosis, treatment and prevention to provide reference for clinical treat-ment.

Maxillary sinus membrane lesions have been broadly detected before implant surgery in the posterior maxilla region, resulting in uncertainty regarding maxillary sinus floor elevation surgery. In this context, we composed this commentary article based on the current literature and the clinical experience of our department. We discuss the common lesion types shown by CBCT including membrane pathological thickening, polyps/cystic lesions and air-liquid level in the sinus. Maxillary sinus floor elevation surgery can be conducted in patients with membrane thickening of 2-5 mm or with polyps/cysts of less than half of the sinus height (because the above symptoms have little influence on the outcome of surgery). Membrane thickening of more than 5 mm with ostium obstruction, antrochoanalpolyps, mucoceles and cysts of more than half of the sinus height should be carefully treated. Different treatments can be performed such as conducting elevation surgery while retaining the cyst, removing the cyst before surgery or removing the cyst during surgery based on the cyst type and size, inflammation, patency of the ostium, etc. Antibiotics-anti-inflammatory-aspiration, surgical debridement and oral lesions eliminations are generally used for treating post-operative sinusitis. Presurgical radiographic evaluation is the key to diagnosing and treating these membrane lesions. We highly advocate collaboration between our dentists and otolaryngologists on this issue.

牙龈卟啉单胞菌(Porphyromonas gingivalis,P.gingivalis)是牙周感染最重要的致病菌,与慢性牙周炎的发生发展密切相关。其致病性归因于一系列毒力因子如菌毛、荚膜、脂多糖、牙龈蛋白酶等。相关毒力因子的致病机制引起了国内外学者的广泛关注和重视。本文就牙龈卟啉单胞菌表面结构菌毛、荚膜及菌体分泌脂多糖、牙龈蛋白酶等重要致病因子的致病机制研究进展做一综述,以期为牙周炎的防治提供新的靶点和思路。

The facial submental artery island flap (FSAIF) is a fasciocutaneous flap supplied by the facial submental artery. It is in close proximity with many oral and maxillofacial regions, and its tex ture and color are similar to those of the head and face. The flap has a constant and sufficient blood supply, and it is easy to prepare and has high survival rates and few complications. According to the tissue carried, FSAIF can be divided into fasciocutaneous flaps, myocutaneous flaps and simple flaps. The flap can also be made into an osteofasciocutaneous (myocutaneous) flap with a mandible to repair maxillary defects. Because this flap is a pedicled flap, it can greatly shorten the operation time, bed rest time and hospitalization time and has been widely used in repairing medium-sized defects of the oral and maxillofacial region. The indications for FSAIF in repairing maxillofacial defects should be strictly controlled. It can be safely used for benign or malignant tumors without cervical lymph node metastasis. For malignant tumors with cervical lymph node metastasis but without extranodal extension, the flap can be used on the premise of thorough neck dissection. The contraindication is cervical lymph node metastasis and extranodal extension of malignant tumors; therefore, other flaps should be selected for repair.

Accurate positioning of brackets is a necessary condition for ideal orthodontic treatment. Traditional bracket bonding technology has certain limitations, such as long operation time and poor accuracy. Indirect bonding technology is a method that bonding brackets on the model through intraoral impression or scanning, and then the brackets are accurately bonded to the tooth crowns using a transfer tray. In this article, the progression of transfer trays and adhesive agents, the application of digital technology in indirect bonding technology, indirect bonding for invisible appliances, and the prospect of this technology are reviewed. The literature review results show that indirect bonding technology can locate the bracket accurately, the operation is simple, the patient’s experience is comfortable, and the clinical efficiency can be significantly improved, the photocurable adhesive is an ideal adhesive for indirect bonding technology. With the development of digital technology, indirect bonding technology will be able to locate the brackets with increasing accuracy, thus achieving the "digital precision movement" of the teeth. The bonding technology of invisible appliance accessories is essentially a type of indirect bonding technology, It requires indirect bonding technology and digital technology to highly fit the needs of computer design accessories for the visual tooth movement and the use of indirect bonding technology to accurately bond accessories, ultimately achieving the desired tooth movement. Indirect bonding technology will play an increasingly important role with the development of digital technology and invisible correction technology.

Hemangiomas and vascular malformations are common clinical diseases. According to their clinical and imaging characterizations, the International Society for the Study of Vascular Anomalies (ISSVA) has systematically classified infantile hemangioma and vascular malformations, and the classification has been widely recognized and applied. To date, most vascular malformations involve the following important signaling pathways: PI3K/Akt/mTOR and RAS/MAPK/ERK. This discovery has major impacts on the diagnosis and treatment of vascular malformations including the following: the understanding of the biology of vascular malformations has been increased; the understanding of vascular malformations based on genotype has been refined; and the development of targeted drugs for the treatment of vascular malformations has been promoted. Despite facing many challenges, with the development of gene sequencing, molecular biology and imaging technology, the relevance of vascular malformation classification and the accuracy of diagnosis are improving, and this is accompanied by innovations in surgical treatment and sclerotherapy, interventional embolization, and continuous progress in targeted therapy. At present, investigations on vascular malformations are mostly retrospective clinical studies or low-level clinical trials. The purpose of this paper is to review the literature on the treatment of infantile hemangioma, lymphatic malformation, venous malformation and arteriovenous malformation and to review the research progress in evidence-based treatment of infantile hemangioma and vascular malformation.

Root canal isthmus(RCI) is defined as a narrow, ribbon-shaped communication between two root canals that contains pulp or tissue derived from pulp. Any root that contains two or more root canals has the potential to contain an isthmus. The incidence of RCI from different tooth positions varies, with the highest RCI incidences usually found in the mesial root of the mandibular first molar and the mesiobuccal root of the maxillary first molar. The presence of RCI increases the difficulty of root canal therapy and introduces uncertainty regarding the prognosis for dental treatment. It is recommended to use CBCT and dental microscopy to identify teeth with suspected RCI in clinical practice. At the same time, for treatment of teeth with RCI, appropriate instruments should be selected, and enhanced root canal irrigation assisted by ultrasound should be considered to improve the success rate of root canal treatment and endodontic root-end surgery. The current technology still has some limitations regarding the cleaning and filling of RCI and additional research and development. Improvement of the corresponding technology and equipment is a current research hotspot and a future research direction.

Exosomes are phospholipid bilayer vesicles secreted by living cells that can carry a variety of signaling molecules, such as RNA, DNA, protein, and lipids. Exosomes play a role in the transmission of signaling molecules between cells, thus regulating many physiological and pathological processes. The methods of extracting exosomes include differential centrifugation, density gradient centrifugation, exclusion chromatography, ultrafiltration, coprecipitation, polymer immune affinity, microfluidic separation technology, etc. Each of these extraction technologies has advantages and disadvantages; however, there is no unified international standard. In addition, the expression of specific proteins and genetic material of exosomes from different cell sources are different; thus, their expression characteristics and functions are also distinctive. Based on this situation, research on exosomes is limited to preclinical studies, and difficulties and challenges still exist in clinical application. This paper summarizes the progress of research in the field of exosomes, to understand the characteristics, modification and application of exosomes from different cell sources, and to summarize their advantages and disadvantages as well as challenges, which can help researchers better understand and master the performance of exosomes. Furthermore, improvement of standard procedures in the extraction and manufacturing of exosomes is important, as it will provide a reference for researchers to carry out exosome-related translational clinical research.

Ectopic eruption of the first permanent molar is a common malocclusion in the early stage of mixed dentition. The incidence among children aged 6-10 years is 0.83%-8.7%, with an increasing trend. The main manifestation is mesial impaction of the first permanent molar during eruption, which is accompanied by the loss of root resorption and space loss of the second primary molar. Ectopic eruption of the first permanent molars can lead to underdevelopment of the dental arch and severe crowding of the posterior dentition. Prevention and early intervention are very important. The ectopic eruption of the first permanent molar is related to the disruption of the differential growth and developmental balance among the teeth, alveolar bone and jaw. In clinical practice, the diagnosis can be made according to the patient's medical history and clinical and imaging examinations, and the treatment can be performed by dividing the teeth, dividing the distal slices of the second primary molars, and distally moving the first permanent molars. This paper reviews the incidence, etiology, clinical manifestations, risks of ectopic eruption of the first permanent molar, diagnostic methods, and common treatment options to provide references for clinical treatment.

Objective To analyze the different fabrication methods and surface structure of treated dentin matrix (TDM) and demineralized dentin matrix (DDM) and their diverse function on promoting the proliferation and osteogenic differential capability of human periodontal ligament cells (hPDLCs). This study provides a preliminary basis for the treatment of periodontal bone defects with bone substitutes from teeth.Methods TDM was made from human dentin matrices and demineralized incompletely by soaking in different concentrations of ethylene diamine tetra-acetic while DDM was made of human dentin matrices and demineralized completely by soaking in a hydrochloric acid solution followed by observation via SEM. The liquid extracts of TDM and DDM were collected according to the protocol of the International Standardization Organization (ISO 10993). Then, hPDLCs were divided into the following three groups: the TDM group (liquid extracts of TDM), the DDM group (liquid extracts of DDM), the control group (a-modified eagle medium with 10% fetal bovine serum), hPDLCs were cultured with liquid extracts of TDM or DDM, or a-modified eagle medium with 10% FBS). hPDLC proliferation was detected by a Cell Counting Kit-8 (CCK-8). The alkaline phosphatase (ALP) expression and calcified nodules of hPDLCs were tested.Results TDM obtained a preferable surface structure compared to DDM due to more sufficiently exposed dentinal tubules and looser fiber bundles of the intertubular and peritubular dentin. Both TDM and DDM promoted the proliferation of hPDLCs compared with the control group, and the proliferation of hPDLCs was significantly greater in the TDM group compared to the DDM group (F = 36.480, P < 0.05). The ALP activity of hPDLCs in the TDM group was higher than the DDM group. After a 14-day osteogenic induction, Alizarin red staining mineral nodes were observed in both groups; however, the TDM group displayed more calcified nodules than the DDM group.Conclusion The advantages of TDM including the surface structure, proliferation and osteogenic differentiation of hPDLCs, are more prominent than those of DDM, suggesting that TDM is a potential promising bone graft substitute in periodontal regeneration.

Objective To investigate the effects of type Ⅱa histone deacetylase inhibitor LMK-235 during early osteoblast/odontoblast differentiation in hPDLCs.Methods hPDLCs were obtained by the collagenase digestion method. hPDLCs at the 3 ^rd passage were treated with medium containing 10% fetal bovine serum mixed with different concentrations of LMK-235 (0, 50, 100, 250, 500 nmol/L), respectively. Proliferative capability of hPDLCs was tested by MTT and qRT-PCR was used to detect mRNA expression levels of Runx2, ALP and DMP-1 3 d later. Results MTT assay showed that cell proliferation in hPDLCs treated with 100 nmol/L LMK-235 was increased significantly compared with the control group (P<0.05). The expression of Runx2 mRNA in the 100 nmol/L group was 1.77 times of the control groups (P<0.05). The expressions of ALP mRNA in all the experimental groups were significantly higher than that in control groups (P<0.05), and the expression in the 100 nmol/L groups was the highest. The expressions of DMP-1 mRNA in the 50 and 100 nmol/L groups were higher than the control groups (P<0.05). Conclusion Type Ⅱa histone deacetylase inhibitor LMK-235 could accelerate cell proliferation in hPDLCs at the concentration of 100 nmol/L, and regulate early osteoblast/odontoblast differentiation by upregulating the mRNA expressions of Runx2, ALP and DMP-1.

Objective To explore the method of apically positioned flap technique (APFT) on buccal keratinized gingiva reconstruction around dental implants and evaluate its clinical outcomes and technical characters. Methods 13 patients, who were insufficient of buccal keratinized gingiva around dental implants but sufficient with alveolar ridge crest tissue or palatal tissue at posterior maxillar, were enrolled in this study. APFT was operated during the phase Ⅱ surgery, by which some tissues were transferred from the alveolar ridge crest or palatal side to the original site of keratinized gingiva. Before APFT surgery and 1, 6 and 12 months after crown restoration, the width and thickness of transferred tissues were measured, gingival index (GI) and bleeding on probing (BOP) were also detected. The results were applied to comparative t-test statistical analysis. Results Transferred tissues by APFT showed healthy one month after crown restoration and exhibited characters of keratinized gingiva compared with the adjacent teeth at 6 and 12 months after restoration. Mean value of width of transferred tissue were respectively (3.25 ± 0.40) mm, (3.04 ± 0.34) mm and (2.97 ± 0.32) mm, meanwhile the thickness were respectively (2.05 ± 0.20) mm, (1.91 ± 0.23) mm and (1.84 ± 0.25) mm. The value of width and thickness of the adjacent teeth gingiva were (3.19 ± 0.42) mm and (1.96 ± 0.23) mm respectively. No significant differences were found between transferred tissue and adjacent teeth gingiva on width and thickness (P>0.05). Observation results of GI and positive rate of BOP of transferred tissue were also similar to which of gingiva of the adjacent teeth. Conclusion Technique of apically positioned flap is an effective measure on buccal keratinized gingiva reconstruction.

Traumatic temporomandibular joint ankylosis refers to fibrous or bony fusion between the condyle and the glenoid fossa. It can cause problems with mouth-opening limitations, mastication difficulties, obstructive sleep apnea and hypopnea syndrome. When traumatic temporomandibular joint ankylosis occurs during childhood, it can cause facial asymmetry, micrognathia, and malocclusion, which significantly affect the physical and mental health. Once temporomandibular joint ankylosis occurs, it will be refractory and recurrent. The pathogenesis of temporomandibular joint ankylosis has not been completely elucidated and has always been a research hotspot in the oral and maxillofacial fields. In this paper, worldwide research was conducted, and the pathogenesis of traumatic temporomandibular joint ankylosis was clarified, such as “damage of condyle”,“disc displacement or rupture”,“damage to the glenoid fossa” and “lateral pterygoid muscle distraction”. The relative pathogenesis hypotheses were summarized, such as “hematoma organization” and “lateral pterygoid muscle distraction osteogenesis”. The related pathogenesis of traumatic temporomandibular joint ankylosis was discussed based on the latest cytology and molecular biology research.

Interleukin-33(IL-33) is a new member of the interleukin-1 (IL-1) cytokine superfamily. It can activate mast cells, lymphocytes and macrophages to produce Th2 cytokines and plays a very important role in inflammation, infection, and autoimmune disease. The classical signal pathway of IL-33 includes the isotrimer of ST2 and interleukin-1 receptor accessory protein (IL-1 RAcP), which transduces signals into cells. The IL-33/ST2 signaling pathway affects bone metabolism by activating T and B lymphocytes. This article reviews the role of the IL-33/ST2 signaling pathway in bone metabolism. The results of a literature review showed that at present, scholars at home and abroad still dispute the role of IL-33 in bone metabolism. Some scholars believe that IL-33 can inhibit osteoclast formation, and IL-33 has been recently implicated in physiological bone remodeling. However, other scholars believe that IL-33 can promote osteoclast formation and differentiation, which leads to bone absorption. IL-33 and its signaling pathway are involved in bone metabolism of alveolar bone in periodontitis and periapical periodontitis. The specific mechanism remains unclear, and further studies are warranted.

Impacted teeth are a kind of complex malocclusion, and their incidence differs among different races, sexes and dental positions. The causes of impacted teeth include systemic factors and local factors, such as endocrine disorders, malnutrition, and acute and chronic infectious diseases. Local factors can cause abnormal tooth development or eruption during the process from tooth development to tooth eruption, such as damaged permanent tooth embryos caused by local inflammation or trauma, insufficient eruption space caused by premature loss of deciduous teeth, and eruption disorders caused by local lesions for example hyperplasia or odontoma. The clinical manifestation of impacted teeth is the absence of a permanent tooth in a normal position. We can use cone beam CT (CBCT) to locate the impacted teeth. Comprehensive orthodontic treatment includes surgical-assisted eruption, extraction of retained deciduous teeth or supernumerary teeth, removal of lesions such as odontomas and cysts, and expansion of the orthodontic space. When the dysfunctional local soft and hard tissues are removed during a surgical operation, the tooth still cannot sprout smoothly, and it needs to be assisted by orthodontic traction-guided eruption or extracted and autotransplantation. A clear diagnosis, evaluation of the difficulty of treatment and appropriate treatment are the keys to improving the success rate of treatment. In this paper, the epidemiology, etiology, diagnosis and corresponding treatment methods of impacted teeth will be reviewed, and the orthodontic treatment of impacted teeth will be comprehensively described to provide a reference for clinicians about the treatment of impacted teeth.

Benign tumors of the parotid gland are common tumors of the head and neck. Surgical resection is considered the main treatment. For the treatment of benign parotid tumors, different surgical approaches can be applied based on many factors, such as tumor type, size, location, depth of tumor and patient requirements, such as improved periauricular incision and improved facial wrinkle removal incision, to achieve the best therapeutic effect. In parotidectomy, the facial nerve, great auricular nerve and parotid duct should be protected as much as possible to preserve the function of the nerve and gland and reduce postoperative complications. In addition, complications after parotidectomy, such as facial nerve injury, salivary fistula, Frey syndrome, postoperative facial depression, abnormal ear sensation and recurrence, should be actively prevented and treated early after the operation, consequently minimizing the impact on patients' postoperative life and improving patients' satisfaction with the operation.

Objective To study the effect of tetrandrine (TET) on oral squamous cell carcinoma cell line Tca8113 and its influence against the expression of β-catenin.Methods CCK-8 method was used to detect the effect of TET on Tca8113 by different dose and time. Western blot assay was used to detect the expression of β-catenin after treatment by TET meanwhile the distribution of the β-catenin treated by TET was detected by the immunofluorescence method.Results With the increasing dose of TET, the inhibition rate against Tca8113 was raising (P < 0.05). The half maximal inhibitory concentration (IC₅₀) value of TET against Tca8113 was 64 μmol/L. With this concentration, the inhibition rate against Tca8113 exhibited a time-dependent manner. The results of western blot revealed that the expression of β-catenin was significantly inhibited after treatment by TET (P < 0.05). The results of immunofluorescence method showed that the β-catenin protein mainly located at nucleus in Tca8113, while after treatment by TET, the β-catenin protein mainly located at cellular membrane and cytoplasm in a diffused distribution manner.Conclusion Our data suggest that TET can inhibit the cell growth of oral squamous cell carcinoma, and influence the cellular distribution of β-catenin protein in tumor cells.

Tooth loss is accompanied by alveolar bone absorption or defect, resulting in insufficient bone and soft tissue. In addition to restoring the masticatory function of missing teeth, implant treatment should also needs to restore the contour and shape of the dental arch. Guided bone regeneration is a common means of bone increase. Xenogeneic granular bone substitute materials are widely used in the field of clinical bone augmentation due to their advantages of long degradation time and low immunogenicity, but other problems, such as inconvenient operation and low osteogenic activity, remain. Plasmatrix can effectively improve the effect of oral tissue regeneration and reduce the occurrence of postoperative complications, and its application in oral tissue regeneration is gradually increasing. This article first introduces the main application forms of plasmatrix in horizontal bone augmentation (mainly solid plasmatrix membrane and plasmatrix bone block), and reclassifies horizontal bone defects according to commonly used decision-making schemes in clinical bone augmentation, in other words, whether the implant can be placed in the ideal position and whether there is bone dehiscence after implantation. Type Ⅰ defects refers to the situation where the bone at the implant site can allow the insertion of an implant with ideal size, and there is no bone dehiscence around the implant, but the alveolar bone contour is not ideal; type Ⅱ defects refers to the situation that when an ideal size implant is placed at the implant site determined by the future prosthesis position, there will be bones on three sides of the implant, but there is bone dehiscence in the buccal bone wall (the length of bone dehiscence is less than 50% of the implant length); type Ⅲ defects refers to the situation where the bone volume at the implant site is not enough to for the placement of the ideal size implant at the ideal position, and bone grafting is required to restore the bone volume before the implant placement. The application of plasmatrix in different types of bone defects is then described. In type Ⅰ bone defects, the solid plasmatrix membrane is used instead of the collagen membrane; in type Ⅱ bone defects, the bone defect around the implant is filled by plasmatrix bone block and then covered with collagen membrane and solid plasmatrix membrane; and in type Ⅲ bone defects, plasmatrix bone block is used to replace autogenous bone block to fill the defect area, and titanium screws are used for fixation. The defect is then covered with a collagen membrane and a solid plasmatrix membrane. This article aims to provide oral clinicians with a comprehensive understanding of plasmatrix and simplify the guidelines for bone regeneration operations.

Objective To investigate the effect of pure titanium surface of large diameter TiO₂ nanotubes modified by RGD peptide on the adhesion and proliferation of MG63 osteoblasts. to provide theoretical proof for developing titanium implants.Methods Commercially pure titanium discs were divided into four groups and treated with SLA to obtain a microrough surface (SLA group). Then, nanotubes were imposed on this microrough surface by anodization (SLA+80 group). The surface was then modified by dopamine (DOPA) (DOPA Group), after which bioactive RGD peptide layers were generated on the TiO₂ nanotube surfaces via electrochemical and molecular self-assembly techniques (RGD group). The titanium surface morphology and elemental composition of each group were characterized by field emission scanning electron microscopy (FE-SEM) and X-ray photoelectron spectroscopy (XPS). MG63 cells were cultured in vitro to evaluate biological activities of titanium before and after treatment, including the evaluation of early-stage cell adhesion capacity by fluorescence microscopy, proliferation capacity by MTS assay, and mRNA expression of the cell osteoblast-related genes alkaline phosphatase (ALP) and osteocalcin (OCN) by qRT-PCR.Results FE-SEM and XPS showed that hierarchical micro/nanosurfaces decorated with TiO₂ nanotubes were produced on titanium using sandblasting and large grit etching combined with anodization, dopamine was then self-polymerized to form a polydopamine film on the TiO₂ nanotube surfaces, and RGD peptides were then conjugated to the polydopamine film, finally forming RGD peptide-modified bioactive layers. In vitro experiments showed that compared with the other three materials, the RGD-modified material was more conducive to cell adhesion and proliferation (P < 0.05). The expression levels of ALP and OCN mRNA in the RGD group were significantly higher than those in the SLA group and DOPA group (P < 0.05).Conclusion Hierarchical micro/nanosurfaces decorated with TiO₂ nanotubes functionally modified with RGD peptides have good biocompatibility and could be used for developing titanium implants and further improving early osseointegration.

In recent years, artificial intelligence technology has developed rapidly and has been gradually applied to the fields of clinical image data processing, auxiliary diagnosis and prognosis evaluation. Research has shown that it can simplify doctors’ clinical tasks, quickly provide analysis and processing results, and has high accuracy. In terms of orthodontic diagnosis and treatment, artificial intelligence can assist in the rapid fixation of two-dimensional and three-dimensional cephalometric measurements. In addition, it is also widely used in the efficient processing and analysis of three-dimensional dental molds data, and shows considerable advantages in determining deciding whether orthodontic treatment needs tooth extraction, thus assisting in judging the stage of growth and development, orthodontic prognosis and aesthetic evaluation. Although the application of artificial intelligence technology is limited by the quantity and quality of training data, combining it with orthodontic clinical diagnosis and treatment can provide faster and more effective analysis and diagnosis and support more accurate diagnosis and treatment decisions. This paper reviews the current application of artificial intelligence technology in orthodontic diagnosis and treatment in the hope that orthodontists can rationally treat and use artificial intelligence technology in the clinic, and make artificial intelligence better serve orthodontic clinical diagnosis and treatment, so as to promote the further development of intelligent orthodontic diagnosis and treatment processes.

Bisphosphonate-related osteonecrosis of the jaw (BRONJ) is a class of disease due to complications of long-term use of bisphosphonates drugs such as zoledronic acid, phosphoric acid, etc. It is mainly manifested in the mouth as a result of tooth extraction or appearing spontaneously mandibular long-term healing wounds, sequestrum exposure, local soft tissue swelling with pain and pus, etc. The X-ray showed irregular bone destruction and bone sclerosis as the lesions progress. At present, the diagnosis and treatment of the disease has not reached agreement. In this paper, clinical diagnosis and treatment on BRONJ in recent years were reviewed.

The crown-root ratio (C/R) theory of natural teeth has been widely recognized in the field of stomatology,and has important clinical significance in predicting and assessing the prognosis?of natural teeth as well as for abutment selection during denture restoration. In the past few decades, scholars have advocated for the implantation of implants as long in length as possible to improve the success rate according to the theory of crown-root ratio of natural teeth. However, with the application of short implants, our philosophy of implantation has changed, and the relationship between the crown-implant (C/I) ratio and complications has become one of the current research hotspots. In this paper, the concept of the crown-implant ratio, the research progress of the C/I ratio, the implant survival rate and clinical complications of implant?restoration were reviewed and summarized, and the following suggestions were put forward: although most studies have shown no significant correlation between the C/I ratio and implant survival or marginal bone loss, this relationship may increase the risk of mechanical complications. A C/I < 3 and a crown length < 15 mm are recommended in implant restoration; when ultra-short implants are applied, the implant system can increase the bone-to-implant contact area, and splint prostheses such as crown or bridge are recommended.