[Biomechanical study of different kinds of internal fixation for the typeâ Hangman fracture, type â ¡ odontoid fracture and the C(2/3) disc injury: a finite-element analysis].

Objectives: To analyze the biomechanical stability of four kinds of internal fixation for the type Ⅰ Hangman fracture, type Ⅱ odontoid fracture and the C(2/3) disc injury by finite element (FE) analysis. Methods: Thin-section spiral computed tomography (0.5 mm) was performed on C(1) to C(3) region of cervical vertebra in healthy male volunteers.A three-dimensional hexahedral FE model of upper cervical spine was established by software (Mimics, GEOMAGICS, Pro/E and Ansys). Then the weakening of the strength of grid was performed to simulate the FE model of the type Ⅰ Hangman fracture, type Ⅱ odontoid fracture and the C(2/3) disc injury (FE/Fracture), the four internal fixation models: anterior cervical plate+ odontoid screw+ cage (FE/ACP+ OS+ cage), affixing rods from pedicle screws in C(2) to lateral mass screws in C(3)+ odontoid screw + cage (FE/C(2)PS+ C(3)LMS+ OS+ cage), affixing rods from pedicle screws in C(1) to pedicle screws in C(2) and lateral mass screws in C(3) (FE/C(1)PS+ C(2)PS+ C(3)LMS), anterior odontoid screw plate fixation system (FE/AOSP) were simulated on the FE/Fracture model.Flexion, extension, lateral bending and axial rotation were imposed on the FE/Intact, FE/Fracture and the four fixation models respectively. Results: The intact model of upper cervical spine (C(1)-C(3)) was established successfully, consisting of 259 641 nodes and 403 674 units.There was no significant difference among the FE/ACP+ OS+ cage, the FE/ C(2)PS+ C(3)LMS+ OS+ cage and the FE/AOSP of ROMC(1/2).During flexion, extension, left axial rotation and right axial rotation of ROMC(2)-C(3), the FE/AOSP decreased 70.7%, 74.4%, 38.9%, 41.1% respectively compared with the FE/C(1)PS+ C(2)PS+ C(3)LMS.The ROMC(2)-C(3) during flexion, extension, left lateral bending, right lateral bending, left axial rotation and right axial rotation in the FE/AOSP decreased for 82.2%, 82.8%, 73.2%, 64.8%, 72.2%, 81.5% respectively when compared with those in FE/ACP+ OS+ cage.The ROMC(2)-C(3) during flexion, extension, left lateral bending, right lateral bending, left axial rotation and right axial rotation in the FE/AOSP decreased 88.2%, 81.2%, 47.6%, 41.2%, 38.9%, 39.0% respectively when compared with those in FE/C(2)PS+ C(3)LMS+ OS+ cage.The stress concentrated on the connection between plate and screw in the FE/ACP+ OS+ cage, the FE/C(2)PS+ C(3)LMS+ OS+ cage and the FE/C(1)PS+ C(2)PS+ C(3)LMS, while it distributed evenly in the FE/AOSP. Conclusion: Anterior odontoid screw plate fixation system can be used to treat the type Ⅰ Hangman fracture, type Ⅱ odontoid fracture, and the C(2/3) disc injury and can reserve the function of atlanto-axial joint.

[A biomechanical evaluation of odontoid screw plate fixation system].

OBJECTIVE: To evaluate the biomechanical stability of anterior odontoid screw plate (AOSP). METHODS: Eight fresh-frozen cadaveric cervical spine specimens were subjected to stepwise destabilization of the C1-C3 complex, simulating a type Ⅰ Hangman fracture, type Ⅱ odontoid fracture, and the C2-3 disc injury. Intact specimens, fractured specimens, and fractured specimens with posterior, anterior fixation techniques were divided into six groups: control group (intact), injury group of type Ⅱ odontoid fracture and type Ⅰ Hangman fracture combined with C2-3 disk injury, after anterior cervical plate+ odontoid screw+ cage (ACP+ OS+ cage) group, after anterior odontoid screw plate (AOSP) fixation system group, after affixing rods from pedicle screws in C2 to lateral mass screws in C3+ odontoid screw (C2PS+ C3LMS+ OS) group, after affixing rods from pedicle screws in C1 to pedicle screws in C2 and lateral mass screws in C3 (C1PS+ C2PS+ C3LMS) group. The range of motion (ROM) and neutral zone of C1-C2 and C2-C3 segment was tested. RESULTS: There was statistically significant difference between the C1PS+ C2PS+ C3LMS fixation group and the AOSP fixation group of ROMC1-C2(P<0.05). During all loading modes, AOSP+ Bone graft fixation significantly outperformed the ACP+ OS+ cage fixation in limiting ROMC2-C3. During flexion and extension, AOSP fixation significantly outperformed the C1PS+ C2PS+ C3LMS fixation and C2PS+ C3LMS+ OS fixation in limiting ROMC2-C3. CONCLUSION: The AOSP fixation system has excellent biomechanical performance when dealing with type Ⅰ Hangman fracture, type Ⅱ odontoid fracture, and the C2-3 disc injury, and appear to be a safe and effective technique for dealing with the combined injury.

Complex relation among Health Belief Model components in TB prevention and care.

OBJECTIVES: This study aims to explore the relationships among components of the Health Belief Model, tuberculosis (TB) preventive behavior, and intention of seeking TB care. STUDY DESIGN: Cross section study. METHODS: Using convenience sampling, 1154 rural-to-urban migrant workers were selected between the ages of 18-50 years in six urban areas of three provinces in China. The survey was conducted by individual, face-to-face interviews with a standardized questionnaire. Lisrel 8.7 was used to conduct path analysis. RESULTS: The knowledge and benefits components of the Health Belief Model predicted preventive behaviors: cover nose/mouth when coughing or sneezing (ß = 0.24, 0.33 respectively), evade others' coughs (ß = 0.13, 0.25) and also predicted seeking TB care (ß = 0.27, 0.19). Susceptibility and severity also predicted seeking TB care (ß = 0.12, 0.16). There were also important relationships among model components. Knowledge of TB predicted both susceptibility (ß = 0.32-0.60) and severity (ß = 0.41-0.45). Further, each of susceptibility (ß = 0.30) and severity (ß = 0.41) predicted perceived benefits of preventive care. CONCLUSION: Thus, a path from knowledge, through severity and susceptibility, and then through benefits predicted prevention and TB care seeking behaviors.

[Clinical effect evaluation of anodized and sandblasted, large-grit, acid-etched implants within 10 years: a meta-analysis].

Objective: To systematically evaluate the clinical effect of anodized implants and sandblasted, large-grit, acid-etched (SLA) implants in the recent 10 years, so as to provide a reference for the selection and evaluation of implants. Methods: The data from Pubmed, Cochrane Library, Embase, CNKI, and Wanfang Data database from January 2010 to April 2020 were searched, to find clinical studies on anodized and SLA implants. According to the inclusion and exclusion criteria, literature was strictly screened, and data was extracted. Included studies were evaluated by using the methodological index for non-randomized studies (MINORS) and were analyzed by Stata14.0. The outcome of interest was cumulative survival rate (CSR) and marginal bone loss (MBL). Heterogeneity and publication bias among included literature was evaluated comprehensively. Results: A total of 22 articles, including 6 276 anodized implants, were collected for the analysis of anodized implants. Meta-analysis of proportions showed that anodized implants CSR were 98% (95%CI: 97%-98%, P<0.05) in total, at 5 years were 98% (95%CI: 98%-99%, P<0.05), and at 10 years were 97% (95%CI: 96%-98%, P<0.05). MBL change was 1.02 mm (95%CI: 0.69-1.34, P<0.05) in total. A total of 17 articles, including 4 567 SLA implants, were collected for the analysis of SLA implants. Meta-analysis of proportions showed that SLA implants CSR were 99% (95%CI: 98%-100%, P<0.05) in total, 99% at 5 years (95%CI: 98%-100%, P<0.05), and 99% at 10 years (95%CI: 97%-100%, P<0.05). MBL change was 0.69 mm (95%CI: 0.44-0.95, P<0.05) in total. The results of the above two studies were tested for bias (P>0.05), indicating no significant publication bias. Conclusions: Meta-analysis suggested that SLA implants have higher CSR and lower MBL than anodized implants.

Intraindividual Variation and Personal Specificity of Salivary Microbiota.

Salivary microbiota is a typical habitat of the human microbiome. This study intended to use salivary microbiota as a model aiming to systematically address the influence of collection methods and temporal dynamics on the human microbiota compared to personal specificity. We carried out a supervised short-term longitudinal study to evaluate the influence of the change of collection methods and sampling time point on salivary microbiota in 10 systemically and orally healthy individuals with certain confounding factors (sex, oral and general health state, medication history, physical exercise, diet, and oral hygiene behavior) controlled before and during the sampling period. The microbial profiles were analyzed by 16S rDNA V3 to V4 hypervariable region amplicon sequencing. The taxonomic structure represented by the dominant species and the weighted UniFrac distance algorithm were used to demonstrate the individual specificity and the intraindividual variation introduced by the change of collection method and sampling time point. The findings suggested individual specificity existed in salivary microbiota from individuals with similar oral and general health status. The intraindividual variation brought by the change of collection method or sampling time point might introduce remarkable perturbation with the personal specificity. Insights into the intraindividual variation and personal specificity of salivary microbiota will enhance our understanding in salivary microbiota-related research. We recommend keeping collection conditions consistent within a study to avoid interference brought by the sampling. The strategy of repeated sampling at multiple time points as representative samples, as well as thorough interpretation of the complex relationships and causality between microbiome composition and disease without the interference of temporal dynamics, is optimal for research exploring the relationship between the salivary microbiome and disease.

[Pattern of sugar-sweetened beverages consumption-based on group-based trajectory modeling and its association with childhood periodontal health].

Objective: To explore the prospective association between consumption pattern of sugar-sweetened beverages and childhood periodontal health. Methods: This study was based on a 4-year longitudinal cohort of children from Bengbu, Anhui province. Pattern of sugar-sweetened beverages was determined by group-based trajectory modeling (GBTM) through annual child-reported questionnaire. Association between sugar-sweetened beverages pattern with plague index and gingivitis was explored through multivariate linear and logistic regression. Results: A total of 997 children including 418 boys and 579 girls were included in this study, with an average age of (11.00±0.70) years at the final wave. Four consumption patterns on sugar-sweetened beverages were identified by GBTM: persistent low group (80.70%), gradually decreasing group (12.40%), decreasing after increasing group (2.20%) and gradually increasing group (4.70%). Compared with the persistent low group (1.08±0.70), the Plague index among gradually increasing group (1.73±0.80) was significantly higher (t=4.00, P<0.001). The prevalence of gingivitis was significantly higher among children in the gradually increasing group (12.80%) than that in the persistent low group (3.00%) (χ(2)=12.40, P<0.001). After controlling for related confounders, results suggested that Plague index increased by 0.58 (95%CI: 0.27-0.89) and 0.38 (95%CI: 0.03-0.73) in the gradually increasing group and "decreasing follow the increase" group, respectively when compared with the persistent low group. The risk for gingivitis was 4.42 times (95%CI: 1.65-12.20, P=0.003) higher in the gradually increasing group. Conclusion: Our data suggested that children with higher sugar-sweetened beverages consumption during the transition period from childhood to adolescence were under higher risk for periodontal diseases.

[Pre- and post-treatment changes of gingvitis-associated peptidomic profiles in the saliva and gingival crevicular fluid by mass spectrometry].

Objective: To explore peptidomic changes of peptides in saliva and gingival crevicular fluid (GCF) before and after treatment of gingivitis. Methods: From January 2017 to September 2017, seventeen participants at the age of 24-62 (6 males and 11 females) at Department of Preventive Dentistry, Peking University School and Hospital of Stomatology with gingivitis were recruited in the present study. Their clinical parameters were measured and recorded. Saliva and GCF samples were collected from each of the participants at the baseline and 7 days after ultrasonic supragingival scaling, respectively. Matrix-assisted laser desorption-ionization time-of-flight mass spectrometry (MALDI-TOF MS) was employed to detect the changes of peptidomic profiles, while ano-liquid chromatography-electrospray ionization-tandem mass spectrometry (nano-LC/ESI-MS/MS) was performed to identify the possible proteins from which the peptides might derive. Results: Initially, four peptide peaks [mass-to-charge ratio (m/z) values: 1 030.6, 1 043.4, 1 053.4 and 1 064.6] were screened out exhibiting a decreasing trend after treatment (P<0.05). Besides, five peptide peaks from gingival crevicular fluid (P<0.05) exhibited differential expression, among which 1 055.5 and 1 168.3 demonstrating a decrease after treatment, while 3 363.7, 3 480.9 and 3 489.5 increased overtime. Certain positive correlations were detected between some peptides and clinical parameters. Principle component analysis using the above mentioned peptide peaks showed a distinct distribution before and after treatment and peptides from GCF showed a slightly better capacity to discriminate patients before and after treatment. The peptides with m/z values of 1 055.5 in GCF and 1 064.6 in saliva were identified to be segments of serum albumin and complement C3, respectively. Conclusions: Several differentially expressed peptides were detected in saliva and GCF by MALDI-TOF MS, exhibiting the potentiality to act as biomarkers in gingivitis patients.

RUNX2 Mutation Impairs 1α,25-Dihydroxyvitamin D3 mediated Osteoclastogenesis in Dental Follicle Cells.

Cleidocranial dysplasia (CCD), a skeletal disorder characterized by delayed permanent tooth eruption and other dental abnormalities, is caused by heterozygous RUNX2 mutations. As an osteoblast-specific transcription factor, RUNX2 plays a role in bone remodeling, tooth formation and tooth eruption. To investigate the crosstalk between RUNX2 and 1α,25-dihydroxyvitamin D3 (1α,25-(OH)2D3) in human dental follicle cells (hDFCs) during osteoclast formation, we established a co-culture system of hDFCs from CCD patient and healthy donors with peripheral blood mononuclear cells (PBMCs). Expression of the osteoclast-associated genes and the number of TRAP(+) cells were reduced in CCD hDFCs, indicating its suppressed osteoclast-inductive ability, which was reflected by the downregulated RANKL/OPG ratio. In addition, 1α,25-(OH)2D3-stimulation elevated the expression of osteoclast-related genes, as well as RANKL mRNA levels and RANKL/OPG ratios in control hDFCs. Conversely, RUNX2 mutation abolished this 1α,25-(OH)2D3-induced RANKL gene activation and osteoclast formation in CCD hDFCs. Therefore, RUNX2 haploinsufficiency impairs dental follicle-induced osteoclast formation capacity through RANKL/OPG signaling, which may be partially responsible for delayed permanent tooth eruption in CCD patients. Furthermore, this abnormality was not rescued by 1α,25-(OH)2D3 application because 1α,25-(OH)2D3-induced RANKL activation in hDFCs is mediated principally via the RUNX2-dependent pathway.

Abnormal differentiation of dental pulp cells in cleidocranial dysplasia.

Cleidocranial dysplasia (CCD) is a skeletal dysplasia caused by heterozygous mutations of RUNX2, a gene that is essential for the mineralization of bone and tooth. We isolated primary dental pulp cells from a 10-y-old patient and tested their proliferative capacity, alkaline phosphatase activity, and ability to form mineralized nodules, in comparison with those from 7 healthy children. All these measures were reduced in primary dental pulp cells from the CCD patient. The expression of the osteoblast/odontoblast-associated genes RUNX2, ALP, OCN, and DSPP was also found to be significantly decreased in the primary dental pulp cells of the CCD patient. The osteoclast-related markers TRAP, CTSK, CTR, and MMP9 were decreased in primary dental pulp cells cocultured with human peripheral blood mononuclear cells. Moreover, the expression of RANKL and the ratio of RANKL/OPG were both reduced in the cells from the CCD patient, indicating that the RUNX2 mutation interfered with the bone-remodeling pathway and decreased the capacity of primary dental pulp cells to support osteoclast differentiation. These effects may be partly responsible for the defects in tooth development and the retention of primary teeth that is typical of CCD.