Nowadays, orthodontic treatment has become increasingly popular. However, the biological mechanisms of orthodontic tooth movement (OTM) have not been fully elucidated. We were aiming to summarize the evidences regarding the mechanisms of OTM. Firstly, we introduced the research models as a basis for further discussion of mechanisms. Secondly, we proposed a new hypothesis regarding the primary roles of periodontal ligament cells (PDLCs) and osteocytes involved in OTM mechanisms and summarized the biomechanical and biological responses of the periodontium in OTM through four steps, basically in OTM temporal sequences, as follows: (1) Extracellular mechanobiology of periodontium: biological, mechanical, and material changes of acellular components in periodontium under orthodontic forces were introduced. (2) Cell strain: the sensing, transduction, and regulation of mechanical stimuli in PDLCs and osteocytes. (3) Cell activation and differentiation: the activation and differentiation mechanisms of osteoblast and osteoclast, the force-induced sterile inflammation, and the communication networks consisting of sensors and effectors. (4) Tissue remodeling: the remodeling of bone and periodontal ligament (PDL) in the compression side and tension side responding to mechanical stimuli and root resorption. Lastly, we talked about the clinical implications of the updated OTM mechanisms, regarding optimal orthodontic force (OOF), acceleration of OTM, and prevention of root resorption.

Objective: To compare the diagnostic accuracy of cone-beam computed tomography (CBCT) and periapical radiographs (PR) for the detection of external root resorption (ERR). Material and Methods: An electronic search in databases, including the Cochrane Central Register of Controlled Trials, PubMed, Embase, the China National Knowledge Infrastructure, and System for Information on Grey Literature in Europe (SIGLE), was performed until August 2016. A manual search of relevant journals and reference lists of enrolled studies was conducted. The studies investigating the diagnostic accuracy of CBCT or PR for ERR, with simulated ERR as the reference test, were considered eligible. The diagnostic accuracy of CBCT and PR was statistically pooled using a bivariate model. Meta-regression and subgroup analysis were performed to explore the sources of heterogeneity. Sensitivity analysis was used to test the stability of the overall results in the meta-analysis. Results: A total of 15 studies were included in this systematic review. The pooled results showed that CBCT had significantly higher sensitivity (0.89; 95% confidence interval [CI]: 0.77-0.96) and area under curve (0.96; 95% CI: 0.77-0.96) than PR (sensitivity: 0.68; 95% CI: 0.56-0.78; area under curve: 0.88; 95% CI: 0.85-0.90). No difference in sensitivity, specificity, and area under the curve between conventional and digital PR was observed. Conclusions: Currently available evidence suggests that CBCT could be reliable to detect the presence of ERR in clinical practice and has a higher diagnostic efficacy than PR. (Angle Orthod. 2017;87:328-337)

Background and objective Periodontitis in diabetic patients is characterized by enhanced inflammation and aggravated tissue damage in comparison with that in non‐diabetic counterparts. The progression of periodontal damage under diabetic condition can be partly ascribed to hyperglycemia‐induced disturbance between immune activation and inflammation resolution, where macrophages are capable of participating given their plasticity in response to different stimuli. Herein, we aimed to investigate the changes of macrophage polarization in periodontitis under diabetic condition and the underlying mechanism. Materials and Methods Type‐1 diabetes was induced by the injection of streptozotocin (STZ, 60 mg/kg) in Sprague‐Dawley rats. Rats in N‐acetyl cysteine (NAC)‐treated groups received NAC dissolved in drinking water (200 mg/kg/day). Experimental periodontitis was induced by ligating 3–0 silk around left maxillary second molars for 4 weeks. Alveolar bone destruction was tested by micro‐computed tomography and tartrate‐resistant acid phosphatase (TRAP) staining. M1/M2 macrophage polarization in periodontal tissue was detected by immunohistochemistry staining. RAW264.7 were cultured in normal glucose (5.5 mM) or high glucose environment (25 mM) with or without NAC (8 mmol/L). LPS (100 ng/ml) and IL‐4 (20 ng/ml) were used to induce M1 macrophages and M2 macrophages, respectively. M1/M2 macrophage polarization was detected by qRT‐PCR, immunofluorescent staining, and flow cytometry. Reactive oxygen species (ROS) accumulation was detected by fluorogenic probes. RANKL (100 ng/ml) were applied to induce osteoclastogenic differentiation of RAW264.7, and osteoclast formation was examined by TRAP staining. Results Rats with diabetes displayed enhanced macrophages infiltration and M1 macrophage polarization in periodontal lesions compared with vehicle‐treated rats. Under LPS or IL‐4 stimulation, high glucose culture of RAW264.7 elevated ROS level and increased the expression of M1 macrophage markers (iNOS, TNF‐α, and IL‐6) whereas decreased the expression of M2 macrophage markers (Arg‐1 and CD206). Supernatants of high glucose‐treated M1/M2 macrophages enhanced osteoclast formation compared to normal glucose‐cultured cells. Decreasing ROS level via NAC partially reversed the effect of high glucose on M1/M2 macrophage polarization. Meanwhile, daily intake of NAC in rodent models inhibited M1 macrophage polarization, which subsequently ameliorated alveolar bone loss and decreased osteoclast numbers in periodontitis in diabetic rats. Conclusion These findings demonstrated that hyperglycemia could polarize macrophage toward M1 macrophages via overproducing ROS under inflammatory condition, which might take responsibility for aggravated periodontal damage in periodontitis under diabetic condition. Inhibiting M1 macrophages and restoring M2 macrophages by ROS scavenger is hopefully a potential adjunct treatment strategy for diabetic periodontitis.

Based on currently available information, weak evidence supports that piezocision is a safe adjunct to accelerate orthodontic tooth movement, at least in the short term. More high-quality clinical trials to determine the long-term effects and optimal protocol for piezocision are needed to draw more reliable conclusions.

ObjectiveTo determine how early musculoskeletal disorders (MSDs) develop in dental professionals and to explore the potential differences among distinct dental specialties.Material and Methods271 dental postgraduates majoring in five dental specialties were recruited, i.e., orthodontics, prosthodontics, endodontics, periodontics and alveolar surgery. 254 age-matched non-dental postgraduates served as the control. The standardized Nordic questionnaire on MSDs and a self-report questionnaire regarding correlative factors (only for dental postgraduates) were answered through emails. Reliability of responses was assessed applying test-retest method.ResultsThe intraclass correlation coefficient of participants' answers ranged from 0.89 to 0.96. Dental postgraduates had significantly higher prevalence of MSDs than the control group, especially at neck, upper back and lower back. In all dental specialties included, high prevalence of MSDs was reported at neck (47.5%-69.8%), shoulders (50.8%-65.1%), lower back (27.1%-51.2%) and upper back (25.6%-46.5%), with lower prevalence at elbows (5.1%-18.6%), hips (3.4%-16.3%) and ankles (5.1%-11.6%). Periodontics students reported the worst MSDs in most body regions except wrists and knees, which were more prevalent for prosthodontic and alveolar surgery students, respectively. Furthermore, year of clinical work, clinical hours per week and desk hours per week were found as risk factors for MSDs, whereas physical exercise and rest between patients as protective factors. ConclusionsHigh and specialty-related MSDs afflict dental professionals even since very early stage of careers. Prevention aimed at the specialty-related characteristics and the risk/protective factors revealed in this study should be introduced to dental personnel as early as possible.