[Clinical factors affecting the prognosis of lower gingival squamous cell carcinoma].

OBJECTIVE: To define the clinical factors that influence local recurrence and survival in patients with lower gingival squamous cell carcinoma (LGSCC) and determine whether bone invasion is an independent prognostic factor for them. METHODS: A total of 104 patients with LGSCC hospitalized in Peking University Stomatology Hospital from June 2013 to December 2015 were enrolled in this retrospective study.All the patients were followed-up for more than 3 years.The degree of bone invasion was assessed using preoperative imaging data (CT and panoramic radiograph).The degree of bone invasion was divi-ded into four categories: no bone invasion, invasion of cortical bone, invasion of bone marrow cavity, and invasion of the mandibular canal.According to the central position of tumor, it was divided into two types: anterior mandibular invasion (anterior region of the mental foramen) and posterior mandibular invasion (posterior region of the mental foramen). RESULTS: of different invasion depth groups were compared using Mann-Whitney U test.P value < 0.05 was considered to be statistically significant.Kaplan-Meier survival analysis method was used to draw survival curve, and COX regression was used to explore the risk ratio (HR) and 95% confidence interval (CI) of prognostic factors of LGSCC. RESULTS: The follow-up results showed that the 1-, 3-, and 5-year survival rates of LGSCC in this group were 91%, 84%, 82%, respectively.32.7%(34/104) of patients had cervical lymph node metastasis.The cervical lymph node metastasis rate of the anterior segment of the mandible was 12.5%(2/16), and 36.4%(32/88) for the posterior segment of the mandible (P < 0.05).Univariate and multivariate COX analysis showed that the N stage and local recurrence were the prognostic factors of LGSCC patients (P < 0.05). CONCLUSION: As the degree of mandibular invasion increases, the prognosis of patients with mandibular gum cancer becomes worse.N stage and local recurrence are prognostic risk factors for LGSCC.The incidence of cervical lymph node metastasis for LGSCC is related to the primary tumor location.It is concluded that tumors located at the posterior of the mandible might be more prone to cervical lymph node metastasis than the anterior of the mandible.Thus various levels of cervical lymph node dissection strategies should be adopted for different sites of LGSCC.

[Research progress in multi-body system dynamics modeling in stomatology].

The stomatognathic system is an organic combination of bone, dentition, joints, masticatory muscles and innervation nerves. It is an organ system for the human body to perform mastication, speech, swallowing and other important functions. Due to the complex anatomical structure of stomatognathic system and ethical limitations, it is difficult to directly measure the movement and force by using the biomechanical experimental methods. Multi-body system dynamics is an important tool to study the kinetics and force of a multi-body system, which consists of several objects with relative motion. We can use the method of multi-body system dynamics simulation in engineering to study the movement, soft tissue deformation and force transfer of this complex stomatognathic system. This paper briefly introduces the history and application methods of multi-body system dynamics and the commonly used modeling methods. The application and research progress of multi-body system dynamics modeling methods in the field of stomatology was emphatically summarized, development prospects of current research and difficulties were put forward.

[A historical review of dental schools founded by dentist Situ Bo in modern time].

About 8 dental schools were founded by Chinese dentists during modern times (1909-1949) in China. Only one still worked after the founding of the People's Republic of China, which was one of the three dental schools founded by dentist Situ Bo. There were no systematic researches on Situ Bo's participation in dentistry education. This paper analyzes the founder's experience in dentistry and in the two schools he founded at the beginning, focusing on the background and process of the schools' construction, management, teaching, teachers and students training, etc. The results show that the establishment of the first two dental schools have laid important foundation for the establishment and development of Shanghai Dental College by the reserve of trained professional teachers and accumulated valuable experience in running schools. The systematic review of this history will help us better understand the establishment and development of Shanghai Dental College and the efforts in dentistry education made by dentists growed up in modern China, as well as the early development process of stomatology.

Neck management of pathological N1 oral squamous cell carcinoma: a retrospective study.

This study was performed to compare the effects of neck dissection procedures on the prognosis of patients with pathological N1 (pN1) oral squamous cell carcinoma (OSCC), analyse factors affecting the prognosis, and provide a neck management strategy for clinical N1 (cN1) oral cancer. The study patients were divided into two groups according to the neck dissection: a selective neck dissection (SND) group (n = 85) and a radical or modified radical neck dissection (RND/MRND) group (n = 22). There was no statistically significant difference in recurrence rates at local, regional, and distant sites between the SND and RND/MRND groups. The 5-year overall survival was 68.3% for SND and 65.2% for RND/MRND patients (P = 0.590), while the 5-year disease-specific survival was 70.4% for SND and 75.7% for RND/MRND patients (P = 0.715). Histological grade and postoperative radiotherapy were independent predictors of the outcome for SND patients. For histological grade II/III cases, 5-year overall survival (P = 0.004) and disease-specific survival (P = 0.002) outcomes differed significantly between patients treated with and without postoperative radiotherapy, with worse survival for patients not treated with radiotherapy. Therefore, SND appears appropriate for cN1 OSCC patients, and postoperative radiotherapy is recommended for those with histological grade II or III tumours.

[Analysis of pathological characteristics of medication-related osteonecrosis of the jaw and discussion of clinical treatment strategies based on the pathological analysis results].

OBJECTIVE: To summarize the pathological characteristics of medication-related osteonecrosis of the jaw (MRONJ) specimens after jaw curettage or jaw osteotomy treatment and to comprehensively analyze the relationship between the different pathological features, treatment methods, and treatment effects to provide new ideas for effective treatment of MRONJ in clinical work. METHODS: The clinical and pathological data were collected from 23 patients with MRONJ who were treated with curettage (18 patients) and jaw osteotomy (5 patients) at the Department of Oral and Maxillofacial Surgery of Peking University Hospital of Stomatology between June 2014 and December 2015. The pathological characteristics of MRONJ were summarized and analyzed with treatment effects based on various surgical treatment methods. The diagnostic criteria and disease staging of MRONJ were determined according to the 2014 American Association of Oral and Maxillofacial Surgeon's Position Paper. RESULTS: In this study, 5 patients have treated with jaw segmental osteotomy, and all of them were in stage Ⅲ; the other 18 patients were treated with jaw curettage, including 5 patients in stage Ⅱ and 13 patients in stage Ⅲ. The pathological features of MRONJ in five cases of jaw segmental osteotomy were divided into three adjacent regions from shallow to deep: inflammation region (IR), sclerosis region (SR), and bone remodeling layer (BRL). Moreover, three types of pathological features of specimens from traditional curettage were defined as type 1 (IR), type 2 (IR + SR), and type 3 (IR + SR + BRL). The pathological features of the patients treated with jaw curettage were: type Ⅰ, 38.9% (7/18); type Ⅱ, 44.4% (8/18); type Ⅲ, 16.7% (3/18). Complete healing was achieved in 5 patients treated with jaw segmental osteo-tomy. Moreover, 2 cases with type Ⅰ, 1 case with type Ⅱ, and 1 with type Ⅲ completely healed after jaw curettage, while 5 cases with type Ⅰ, 7 cases with type Ⅱ, and 2 cases with type Ⅲ experienced recurrence after surgery. CONCLUSION: Pathological features of continuous regions of inflammation, sclerosis, and bone remodeling layer were identified from shallow to deep, based on the microscopic observation of jaw segmental osteotomy samples. Insufficient removal of the sclerotic region during jaw curettage that blocks the required blood, nutritional factors, and mesenchymal stem cells seems to be a common cause for failed treatment of MRONJ after curettage surgery.

[Preliminary measurement and analysis of the condylar movement envelope surface parameters in healthy adults].

Objective: To measure and analyze parameters of the three-dimensional (3D) model of the condylar movement envelope surface (ES) and provide a reference for the design of the temporomandibular prosthesis. Methods: Thirty-four healthy adults aged (25.4±2.8) years were recruited from the Department of Oral and Maxillofacial Surgery, Peking University School and Hospital of Stomatology as subjects. There were 9 males and 25 females, most of them were university students and others outside the university have received undergraduate education or above. Condylar movement ES were obtained using the previous method on the 3D trajectory of condyle. The simulations of condylar movement were projected according to opening movements, protrusion movements, and lateral movements respectively. The total area of the ES and the area proportions of models formed by above different mandibular movements were measured and calculated. The adults' head and maxillofacial 3D models reconstructed by cone beam CT were registered with ES in Geomagic Studio. The inner and outer poles of the condyle, the corrective sagittal axis of the ES, and the median sagittal plane (MSP) were calibrated in registration models using Geomagic Studio, and the parameters were measured as follows: the anteroposterior and medialateral diameters of the condyle, the anteroposterior diameters and the transverse diameters (anterior, middle and posterior parts) of the ES, the angles between the corrective sagittal axis of the ES and MSP (ES-MSP). Pearson correlation analysis was performed by SPSS 24.0. Results: The total area of the ES was (760±133) mm2, the opening movement part accounted for (63.3±15.2)%, the protrusion movement part accounted for (14.9±9.6)%, the lateral movement part accounted for (21.8±13.3)%. Parameter measurements were as follows: mediolateral diameters of condyle was (19.8±2.3) mm; anteroposterior diameter of the ES was (21.2±3.1) mm, the transverse diameters (anterior, middle and posterior parts) of the ES were (20.6±2.4), (20.4±2.4), (22.0±2.6) mm, respectively; the transverse diameters of the ES were about 2 mm larger than that of the condyle. The angle between the corrective sagittal axis of ES and the MSP was 6.8°±6.2°. The coefficient of variation (CV) in these parameters showed: CV of the transverse diameters (anterior, middle and posterior parts) of the ES and mediolateral diameter of the condyle were 0.98, 0.99, 0.93, respectively (P<0.001). CV of aera of ES and mediolateral diameter of the condyle was 0.64 (P=0.002). CV of aera of ES and anteroposterior diameter of ES was 0.62 (P=0.004). Conclusions: The 3D envelope surface model formed by mandibular opening movements accounted for the largest proportion of the ES. The corrective sagittal axis of the ES was at an angle to the MSP, the transverse diameters (anterior, middle and posterior parts) of the ES were approximately 2 mm larger than the mediolateral diameter of the condyle, the transverse diameters (anterior, middle and posterior parts) of the ES were highly positively correlated with the mediolateral diameter of the condyle.

[Clinical analysis of selective tracheostomy necessary for patients undergoing head and neck surgery with free flap reconstruction].

OBJECTIVE: To discover the factors that may affect the use of selective tracheostomy among patients who have undergone head and neck surgeries with free flap reconstruction, so that the patients will not need tracheostomy nor receive the unnecessary treatment. METHODS: Five hundred and thirty-three patients who had undergone head and neck surgery with free flap reconstruction operated by the same team of surgery at Department of Oral and Maxillofacial Surgery at Peking University School of Stomatology from 2015 to 2016 were reviewed. Three hundred and twenty-one (60.2%) of these patients underwent selective tracheostomy. All the patients' demographic information, operation-related information, prior treatments, comorbidities and complications were recorded and analyzed. RESULTS: The patients with defects of the tongue, mouth floor, oropharynx and bilateral mandible, who underwent neck dissection and with previous radiotherapy and smoking habit were more likely to get selective tracheostomy. Usage of bulky soft tissue flap might also add to the risk of airway obstruction and the need of selective tracheostomy, while other factors were not significantly related to the risk of postoperative airway obstruction and the patients could be kept safe without selective tracheostomy. Most cases without tracheostomy were kept safe except one case, while 8.39% of the patients with tracheostomy suffered from tracheostomy related complications, mainly pneumonia and hemorrhage of the tracheostomy wound, yet none led to serious consequences or even death. CONCLUSION: Selective tracheostomy is not necessary for patients who have undergone head and neck surgeries with free flap reconstruction except that there are defects at the tongue, oropharynx and mandible. Neck dissection, bulky soft tissue flap reconstruction, previous radiotherapy and smoking habit may also add to the risk of postoperative airway obstruction, while a favorable decision would involve a combination of all the above factors to assure the safety of the postoperative airway for the patients undergone head and neck surgeries with free flap reconstruction.

[Analysis of M2 macrophage infiltration and its clinical significance in 44 patients with multiple primary cancers of the head and neck].

Objective: To investigate and analyze the characteristics of M2 macrophage infiltration and the clinical significance in patients with multiple primary cancers (MPCs) of head and neck in order to explore its role in the diagnosis and prognosis for patients with MPCs. Methods: RNA-seq data were downloaded from the Genomic Data Commons data portal (TCGA) and the R software v4.0.3 was used to statistically analyze the differences. A retrospective analysis was conducted by screening the clinical data of 44 patients (17 males and 27 females) with MPCs in head and neck from July 1998 to February 2016 in the Department of Oral and Maxillofacial Surgery, Peking University School and Hospital of Stomatology. Clinical data from a batch of 41 patients (28 males and 13 females) with gingival cancer and without MPCs from August 2013 to December 2015 were collected and analyzed. The number of CD163 positive cells and the expression patterns in immunohistochemically panoramic slices were observed under high magnification. Chi-square test and Spearman correlation analysis were used to compare the difference and correlation between the CD163 positive counts and/or depths of invasion and the number of incidences. The descriptive statistics on the clinical features was performed by SPSS 25.0. Results: TCGA database analysis showed that the infiltration of macrophage in patients with squamous cell carcinoma of head and neck (HNSCC) was increased compared to the para-cancer sites. A total of 142 tissue samples from 44 patients with MPCs were selected in the present single-center retrospective research. The number of CD163-positive cells in MPCs patients [90.9% (40/44)] was significantly increased compared to single gingival cancer patients [61.0%(25/41)] (r=0.353, P=0.001), which was related to the number of occurrence (r=0.368, P=0.001). The ratio of the CD163 counts in primary tumor to the depths of invasion was positively correlated with the number of onsets (r=0.331, P=0.03). In terms of clinical features, the 44 patients with MPCs were mainly female, non-smoking, no alcohol addiction, no systemic history, Tis-T2 stage and N0 stage squamous cell carcinoma. The number of incidences ranged from two to eight. The incidence of cancer relative to synchronous cancer increased with the increased occurrence of MPCs. The primary cancer mainly occurred in tongue, gingiva and buccal sites, while the proportion of onset sites in gingiva, buccal and palate areas increased with the increased occurrence. Conclusions: M2 type macrophage counts and/or ratio to depth of infiltration were associated with the occurrence of MPCs, which could be used as a clinical indicator to distinguish single and MPCs in HNSCC. For early stage of HNSCC, patients with clinical characters of women, non-smoking, no alcohol addiction, no systemic medical history and sites of tongue, gingiva, and buccal should be paid more attention on their follow-up plan. The findings in the present study was also helpful to explore new treatment methods for the patients with MPCs.

[Application of iodine staining technique for tumor identification in Micro-CT of mouse model with skull base-infratemporal fossa tumor].

OBJECTIVE: To establish an animal model with malignant tumor in the skull base-infratemporal region, and to explore the role of iodine staining technique in identifying tumor tissues with Micro-CT data. METHODS: Sedation anesthesia was carried out on 12 BABL/c nude mice using inhaled isoflurane, and then WSU-HN6 cells that cultured and immortalized from human tongue squamous cell carcinoma were injected into the right infratemporal fossa via the submandibular area. The procedure was carried out under ultrasonographic guidance. The nude mice were sacrificed after 3 weeks observation. The head specimens were fixed and scanned by Micro-CT, and repeated scans were performed after staining with 3.75% compound iodine solution. Following decalcification in 20% EDTA for 2-4 weeks, the head specimens were embedded and sectioned. Hematoxylin and eosin staining and Pan-Keratin immunohistochemical staining were carried out. Bright-field microscopy and stereomicroscopy were used to visualize. The Micro-CT data were analyzed using iPlan software (Brainlab). RESULTS: Non-traumatic ultrasonography was used to guide HN-6 cells injection and confirm skull-base tumor formation in all the animals. Ultrasonographic guidance reduced the risk of cervical vessel injury when transferring tumor cells into the skull base space. An obvious asymmetrical appearance was detected via ultrasonography 3 weeks after tumor cell injection. The Micro-CT analysis showed that the bone was obviously damaged on the right side of the skull base, but the soft tissue image was unrecognizable. After four days staining with compound iodine solution, the morphology of the tumor and surrounding soft tissue could be clearly identified. Hematoxylin and eosin staining showed the tumor formation of the right infratemporal fossa region accompanied by bone destruction. Human keratin immunohistochemical staining showed that the tumor tissue originated from human squamous cell carcinoma, and the polynuclear osteoclasts could be seen at the margin of the skull base bone resorption. CONCLUSION: The animal model with malignant tumor in the skull base-infratemporal region could be successfully established via submandibular injection under ultrasound-guidance. Bone changes of the skull were easily observed on Micro-CT, but the tumor counter was not able to be distinguished from surrounding soft tissue. The 3.75% compound iodine staining of the head specimen could help discern the tumor and surrounding soft tissue in more details.

[Thoughts on the prevention, clinical diagnosis and treatment of osteonecrosis of the jaw and future research directions].

With the progress and development of society, osteonecrosis of the jaw has appeared some new features and new problems in oral clinical work. The prevention, early diagnosis, and early treatments of osteonecrosis of the jaw are of great significance. This article describes the current clinical diagnosis and treatment status of osteoradionecrosis of the jaw and medication-related osteonecrosis of the jaw, and puts forward some thoughts on the prevention, clinical diagnosis and treatment and future research direction of osteonecrosis of the jaw.

[Evaluation of the preliminary clinical effect of flap-raising combined with cortical-perforation technique in tooth extraction cases of patients with potential risk of medication-related osteonecrosis of the jaw].

Objective: To evaluate the preliminary clinical effect of flap-raising and cortical-perforation based extraction method in patients with potential risk of medication-related osteonecrosis of the jaw (MRONJ). Methods: Eighteen patients, who needed teeth extraction in the Department of Oral and Maxillofacial Surgery, Peking University School and Hospital of Stomatology from February 2016 to November 2020, with a history of using anti-resorption/anti-angiogenesis medication were included in this retrospective study. According to the characteristics of the patient's medication history, patients were stratified into three categories, low-dose anti-resorption drug group, high-dose anti-resorption drug group, and high-dose anti-resorption combined with anti-angiogenesis targeted drug group. There were 15 females and 3 males, the average age was 62.4 years (range from 27 to 87 years) old. A total of 31 teeth were indicated for extraction due to chronic infection. The flap-raising and cortical-perforation techniques were used to extract the affected teeth, and the patients were followed up closely. By observing the healing status and swelling degree of the mucosa of tooth extraction sites, whether there was a fistula, pus and bone exposure of jaw bone,the healing of the tooth extraction sites were evaluated. Results: Among the 18 patients, there were 9 cases of osteoporosis and 9 cases of malignant tumors. Classified by medication-using history, 10 cases were treated with low-dose anti-resorption drugs, 5 cases were high-dose anti-resorption drugs, and 3 cases were high-dose anti-resorption drugs combined with anti-angiogenesis drugs. A total of 31 teeth of the patients were extracted by flap-raising and cortical-perforation based extraction method. Thirteen patients completed treatment underwent local anesthesia and five cases were performed under general anesthesia. The shortest follow-up period was 3 months with an average of 13.2 months. Seventeen patients recovered well after the tooth extraction. One patient had the mandible exposed at one extraction site one month after the surgery, resulting in MRONJ. Conclusions: In patients with potential risks of MRONJ, the application of flap-raising and cortical-perforation based teeth extraction method could safely and effectively alleviate the dental inflammation in the oral cavity.

[Expert consensus on the treatment of oral and maxillofacial space infections].

Oral and maxillofacial space infections (OMSI) are common diseases of the facial region involving fascial spaces. Recently, OMSI shows trends of multi drug-resistance, severe symptoms, and increased mortality. OMSI treatment principles need to be updated to improve the cure rate. Based on the clinical experiences of Chinese experts and with the incorporation of international counterparts' expertise, the principles of preoperative checklist, interpretation of examination results, empirical medication principles, surgical treatment principles, postoperative drainage principles, prevention strategies of wisdom teeth pericoronitis-related OMSI, blood glucose management, physiotherapy principles, Ludwig's angina treatment and perioperative care were systematically summarized and an expert consensus on the diagnosis and treatment of OMSI was reached. The consensus aims to provide criteria for the diagnosis and treatment of OMSI in China so as to improve the level of OMSI treatment.

Surgical resection of clinically benign tumours in the maxillomandibular deep lobe of the parotid gland via sternocleidomastoid muscle-parotid space approach.

This article reports the surgical resection of clinically benign tumours in the maxillomandibular deep lobe of the parotid gland via sternocleidomastoid muscle-parotid space (SPS) approach. The use of maxillary-mandibular planes to subdivide the deep lobe of the parotid gland in order to establish the tumour location and accessibility is introduced. This approach, which does not raise a skin flap, may preserve the superficial lobe. Ten patients with clinically benign tumours in the maxillomandibular deep lobe of the parotid gland were treated via the SPS approach. The patients were followed up for 3-5 years and the surgical outcomes were analysed. All tumours were completely enucleated via the SPS approach with an optimal aesthetic outcome. No permanent facial weakness or tumour recurrence was identified during the 3-5 years of follow-up. The SPS approach to surgical resection is an ideal option for clinically benign tumours in the maxillomandibular deep lobe of the parotid gland and demonstrates good results.

Navigation-guided core needle biopsy for skull base and parapharyngeal lesions: a five-year experience.

The aim of this study was to evaluate the diagnostic accuracy of navigation-guided core needle biopsy for skull base and parapharyngeal lesions. Twenty patients with skull base and parapharyngeal lesions were included in this study. The preoperative design and intraoperative real-time image guiding was done using an optical navigation system. A spring-loaded semi-automatic biopsy gun and biopsy needle were used for specimen harvesting. Accuracy was established on the basis of the postoperative pathology. All patients underwent needle biopsy successfully without any immediate or delayed complications. The subzygomatic approach was adopted in all cases. The number of passes ranged from three to five. The diagnostic accuracy was 90% (18/20). Navigation-guided core needle biopsy offers an easy approach for the diagnosis of skull base and parapharyngeal lesions, with a high yield of specimens and good patient tolerance.

Three-dimensional assessment of root migration and rotation patterns after coronectomy: bone-embedded roots versus soft tissue-covered roots.

In this study, a three-dimensional evaluation was performed to explore differences between bone-embedded and soft tissue-covered roots after mandibular third molar (M3M) coronectomy. Patients were recruited according to the results of cone-beam computed tomography, 6 months after coronectomy. Completely bone-embedded M3Ms were assigned to group B, while completely soft tissue-covered M3Ms were assigned to group S. Data were recorded using digital software. A total of 213 M3Ms in 181 patients were investigated, of which 170 were assigned to the two study groups. Age was the primary factor influencing root migration (P<0.001). The smaller the degree of angulation of the M3M, the more likely was the root complex to rotate distally (r=-0.37, P<0.001). The depth of the impacted M3M contributed to the regeneration of new bone (P≤0.008). The length of the root complex (odds ratio 0.82, P=0.048) and distance from the root to the alveolar crest (odds ratio 1.23, P=0.026) were two critical factors influencing whether the root complex was bone-embedded. Ensuring that the length of the root complex is <7.6mm and the distance between the root and alveolar crest is ≥5mm were both found to be critical to the remaining root being completely bone-embedded and thus preventing eruption and the need for secondary surgery.

[Three-dimensional imaging study on the anatomical morphology of trabecular bone of the condyle based on the distribution of volume of interests].

Objective: To analyze the anatomical morphological characteristics of the trabecular bone of human mandibular condyle by observing the distribution of volume of interests (VOI). Methods: The micro-CT images of a right condyle specimen of a 61-year-old adult male was analyzed in this study. The cylindrical VOI with both diameter and height of 2 mm were arranged, according to a certain pattern, as many as possible at various levels within the trabecular bone of the condyle. Each VOI had no intersection area. The selected VOI were divided into 5 parts: medial part, middle part, lateral part, anterior part and posterior part, with 6 layers from top to bottom. And the distribution of the overall anatomical morphological characteristics of three-dimensional (3D) images of the trabecular bone of the condyle was analyzed by using seven morphological parameters of each VOI, i.e. bone mineral density (BMD), bone volume/total volume (BV/TV), bone surface area/bone volume (BS/BV), trabecular thickness (Tb.Th), trabecular bone number (Tb.N), trabecular spacing (Tb.Sp) and trabecular bone pattern factor (Tb.Pf). Results: In the present study, totally 34 VOI were selected from the condyle specimen.The morphological distribution of the VOI was uneven in the 3D structure of the trabecular bone of the human condyle. BMD, BV/TV, Tb.N and Tb.Th were much higher at the middle part, while showed the smallest at the medial part. The anterior part demonstrated much higher parameters than the posterior part at the first, second, fifth and sixth layers, respectively, however, the posterior part showed much higher parameters than the anterior part at the third and fourth layers, respectively. The BMD was much higher at the first [(332.66±97.11) mg/cm3] and sixth [(255.79±45.68) mg/cm3] layers, while the lowest at the second layer [(255.79±41.06) mg/cm3]. The BV/TV and Tb.N were much higher at the first layer, with the lowest at the fifth layer. The Tb.Th at the first layer [(0.11±0.03) mm] was much higher than the others, which were similarly lower. The BS/BV, Tb.Sp and Tb.Pf were lower at the first layer and much higher at the medial and lateral parts, while were lower at the middle and anterior parts. The posterior part demonstrated much higher BS/BV, Tb.Sp and Tb.Pf than the anterior part at the first, fifth and sixth layers, respectively. However, the anterior part showed much higher scores than the posterior part at the third and fourth layers, respectively. The ANOVA results showed that the 7 morphological parameters of VOI were not statistically significant amongst the 6 layers (P>0.05). However, the 6 out of the 7 parameters, i.e. BV/TV, BS/BV, Tb.Th, Tb.N, Tb.Sp and Tb.Pf, were statistically significant amongst the five parts (P<0.05), while the only parameter of BMD was not statistically significant (P>0.05). Conclusions: The anatomical distribution characteristics of the trabecular bone of condyle were analyzed by using 3D imaging measurement based on the VOI. The results showed uneven distributions and indicated that the method of dividing the trabecular bone of mandibular condyle into VOI sets, which accorded with its specific anatomical characteristics, was feasible for further reference.

Computer-aided three-dimensional assessment of periodontal healing distal to the mandibular second molar after coronectomy of the mandibular third molar: a prospective study.

BACKGROUND: The periodontal healing distal to the mandibular second molar (M2M) after coronectomy of the M3M has shown controversial results. We aimed to combine a digital method with cone-beam computed tomography (CBCT) and estimate periodontal healing of M2M after M3M coronectomy. An accurate and stable indicator in three dimensions was also explored tentatively. METHODS: Patients with a M3M in contact with the inferior alveolar canal were included. CBCT was applied immediately after coronectomy (baseline) and 6-months later. Data were investigated with digital software for registration. Previously reported and coronectomy-related factors were included for univariate and multivariate analyses. RESULTS: A total of 181 patients (213 M3Ms) completed 6-month follow-up. Significant reduction in the distal intra-bony defect (DBD) depth of the M2M was shown (1.28 ± 1.24 mm, P < 0.001). DBD depth of the M2M at baseline was the most influential factor (r = 0.59), followed by preoperative M3M condition, age, rotation and migration of the root complex. Remaining enamel (OR = 6.93) and small retromolar space (0.67) contributed to re-contact of the root complex and M2M. Bone volume regenerated in the distal 2 mm was associated significantly with DBD-depth reduction (r = 0.74, P < 0.001). CONCLUSIONS: Bone volume regenerated in the distal 2 mm of the M2M denoted stability of distal periodontal healing of the M2M. DBD depth at baseline was the most influential factor for healing of a DBD of the M2M after M3M coronectomy. The remaining enamel and a small retromolar space could contribute to re-contact of the root complex and the M2M. TRIAL REGISTRATION: China Clinical Trial Center, ChiCTR1800014862 . Registered 10 February 2018.

Does the Brown classification of maxillectomy defects have prognostic prediction for patients with oral cavity squamous cell carcinoma involving the maxilla?

The aim of this study was to investigate the correlation between the maxillectomy defect, T stage, and prognosis of patients with maxillary squamous cell carcinoma (SCC). The Brown classification system was used to appraise the maxillectomy defects due to maxillary SCC. The clinical data of 137 patients with maxillary SCC during the period 2000-2010 were reviewed; 105 patients were followed up. Preoperative T stage and postoperative maxillectomy class were recorded. The relationship between the maxillectomy defect class and T stage of maxillary SCC was analysed. Correlations between the maxillectomy defect class, local recurrence rate, and survival rate were assessed using IBM SPSS Statistics v19.0. The most common maxillectomy defect class was IIb (54.7%, 75/137). The maxillectomy defect class was significantly associated with the T stage (P < 0.001). Both T stage and the maxillectomy defect class were significantly associated with the survival rate of patients with maxillary SCC (both P< 0.001). In conclusion, the class of the maxillectomy defect was found to be associated with the T stage. Both of these were prognostic factors for patients with maxillary SCC. The class of the maxillectomy defect is suitable for clinical application in predicting the prognosis compared with T stage.

Clinical and immunohistochemical analysis of diffuse tenosynovial giant cell tumour of the temporomandibular joint.

The objective of this study was to summarize diagnostic points and treatment strategies for diffuse tenosynovial giant cell tumours (D-TSGCTs) of the temporomandibular joint (TMJ), and to evaluate the expression of proteins related to bone destruction and recurrence. The clinical and histopathological characteristics of 24 cases were analysed retrospectively. TRAP staining and immunohistochemical staining for MMP-9, MMP-13, and Ki-67 were performed. The median age of the patients was 45.5 years; the female to male ratio was 1.7:1. In 11 cases (45.8%), skull base destruction seen on computed tomography was confirmed by surgery. Computer-assisted navigation was performed in six cases. Four patients received adjuvant radiotherapy after first surgery. Five patients had recurrent lesions. Multinucleated giant cells were positive for TRAP, MMP-9, and MMP-13. The average Ki-67 index of the recurrent cases was significantly higher than that of the non-recurrent ones (P<0.05). This study demonstrates the aggressive and recurrent nature of D-TSGCT occurring in the TMJ. Computer-assisted navigation is helpful to protect vital structures and determine margins. Adjuvant postoperative radiotherapy is recommended for local control of residual or recurrent tumour. In conclusion, MMP-9 and MMP-13 may play a role in bone destruction of D-TSGCT, and the Ki-67 index has predictive significance for recurrence.

[Expression of cartilage oligomeric matrix protein in the synovial chondromatosis of the temporomandibular joint].

OBJECTIVE: To detect the expression of cartilage oligomeric matrix protein (COMP) in the synovial chondromatosis of the temporomandibular joint (TMJSC), and to discuss the possible interactions between COMP, transforming growth factor (TGF)-ß3, TGF-ß1 and bone morphogenetic protein-2 (BMP-2) in the development of this neoplastic disease. METHODS: Patients in Peking University School and Hospital of Stomatology from January 2011 to February 2020 were selected, who had complete medical records, TMJSC was verified histologically after operation. The expressions of COMP, TGF-ß3, TGF-ß1 and BMP-2 in the TMJSC of the temporomandibular joint were detected by immunohistochemistry and quantitative real-time PCR (RT-PCR) at the protein level and mRNA level respectively, compared with the normal synovial tissue of temporomandibular joint. The histological morphology, protein expression and distribution of TMJSC tissues were observed microscopically, and the positive staining proteins were counted and scored. SPSS 22.0 statistical software was used to analyze the expression differences between the related proteins in TMJSC tissue and the normal synovial tissue of temporomandibular joint and to compare their differences. P < 0.05 indicated that the difference was statistically significant. RESULTS: Immunohistochemical results showed that the positive expression of COMP in TMJSC tissues was mostly found in synovial tissues and chondrocytes adjacent to synovial tissues, and the difference was statistically significant, compared with the normal temporomandibular joint synovial tissues. The positive expression of COMP was significantly different between recurrent TMJSC and non-recurrent ones. The positive expressions of TGF-ß3, TGF-ß1 and BMP-2 were higher than the normal synovial tissue, and were also mostly found in the synovial cells and adjacent chondrocytes, which was further confirmed by Western blot. According to the RT-PCR results, the expressions of COMP, TGF-ß3, TGF-ß1 and BMP-2 in TMJSC were higher than those in the normal synovial tissue. CONCLUSION: The expression of COMP in TMJSC of temporomandibular joint increased significantly, compared with the normal synovial tissue. There may be interactions between COMP and cytokines related to the proliferation and differentiation, like TGF-ß3, TGF-ß1 and BMP-2, which may play a potential role in the pathogenesis of TMJSC.