In stomatology, root canal therapy is a commonly used and effective treatment for dental pulp diseases and periapical diseases. However, pain may occur during or after treatment and may severely affect patients. This article aimed to analyze the mechanism and cause of pain during root canal therapy, which may reduce or relieve pain.

Objective To construct a cell line of oral mucosa epithelial cells that stably express human telomerase reverse transcriptase (hTERT) by lentiviral vectors, approaches for the establishment of stable and efficient immortalized oral mucosa epithelial cell lines were explored. Methods Whole RNA was extracted from 293T cells. The hTERT gene was amplified by polymerase chain reaction (PCR) and cloned into the lentiviral vector as pLVX-puro-hTERT. The lentivirus particles were successfully packaged and used to infect primary oral epithelial cells. The positive cell clones were selected by puromycin. Finally, the expression of hTERT was examined by real-time fluorescent quantitative PCR (qRT-PCR) and Western blot analysis. Results The sequencing results confirmed the construction of the recombinant lentivirus pLVX-puro-hTERT. The morphology of infected cells was similar to that of normal oral mucosal epithelial cells, with a cobble stone-like appearance. The qRT-PCR and Western blot results showed that hTERT was overexpressed in infected cells compared with the normal group (P<0.05). Conclusion The oral epithelial cell line with stable expression of hTERT was successfully established by the lentivirus, which provides an experimental basis for the establishment of a highly efficient and stable oral epithelial immortalized cell line.

Objective  This study is to determine the common oral streptococcal adhesion forces by using composite resin and glass ionomer cement (GIC) with different degrees of surface roughness via atomic force microscopy (AFM) analysis. The influence of surface roughness on bacterial adhesion force is also discussed. Methods  Polishing and grinding were applied to obtain 300, 200, 100, and 10 nm surfaces of light-cured composite resin and GIC samples. Surface topography was assessed by AFM analysis. Initial colonizers (Streptococcus sanguinis and Streptococcus mitis) and cariogenic bacterial strains (Streptococcus mutans and Streptococcus sobrinus) were used to obtain bacteria-modified AFM probes. The force-distance curves were also measured by AFM analysis to determine the adhesion forces of bacteria on the surfaces of the composite resin and GIC. Material surface roughness was analyzed using ANOVA, and adhesion forces were subjected to nonparametric analysis (Kruskal-Wallis test). Comparison among groups was performed by Dunn’s test. Material surface roughness and bacterial adhesion forces were subjected to correlation analysis. Results  Bacterial adhesion forces increased with increasing material roughness. The adhesion forces of the four bacterial species reached the maximum on the material surface of 300 nm. The adhesion force of Streptococcus mutans increased from 0.578 nN to 2.876 nN on GIC surfaces with 10 and 300 nm roughness. The adhesion forces of the four species on the surface of the composite resin were stronger than that of GIC. The initial colonizers exhibited stronger adhesion forces to different materials than the cariogenic strains. Intergroup differences were evident on the 200 and 300 nm material surfaces. Conclusion  The surface roughness of the material significantly affected the bacterial adhesion forces, and a significant linear correlation existed between both factors. The bacterial adhesion forces of the GIC were lower than that of the composite resin. Furthermore, surface roughness exhibited less influence on the cariogenic strains than that on the initial colonizers.

Objective  This study explores the mechanism of cyclooxygenase-2 (COX-2) upregulation in oral cancers asso- ciated with macrophage by using molecular biology techniques and primary culture of murine macrophage. Methods  Murine macrophage was induced by macrophage colony-stimulating factor (M-CSF) and Cal27 conditional medium (CM). Purity of the macrophage was detected through CD68 immunofluorescence staining. Inhibitors of spleen tyrosine kinase (Syk) and nuclear factor κB (NFκB) were used to inhibit these pathways. In addition, real-time polymerase chain reaction and Western blot analysis were used to detect alterations in COX-2 and pathway-related proteins. Results  All of the induced cells specifically expressed CD68. Cal27 CM could significantly induce COX-2 expression (P<0.001). Moreover, inhibition of Syk pathway attenuated NFκB-P65 phosphorylation and reduced COX-2 expression (P<0.01), and inhibition of NFκB pathway exerted no effects on Syk phosphorylation but significantly inhibited COX-2 upregulation (P<0.01). Conclusion  Syk-NFκB is responsible for COX-2 overexpression in oral cancer associated with macrophages. Targeting this pathway is possibly a new approach to control oral cancer-related pain.

Objective To identify the properties of nerve fibers of dogs by immunohistochemical staining method. Methods  Intact bone blocks above the inferior alveolar nerve canal were cut from the medial of the second premolar to the distal of the third premolar of healthy adult Beagle dogs of 18 months, embedded to make hard tissue sections, stained with S100 and neurofilament protein (NFP) antibodies, and finally observed the nerve distribution under the microscope. Results  The distribution of S100 positive tissue in the periodontal ligament of dogs showed the following patterns: bundles of densely gathered rings with different diameters, filaments accompanied by lumens, free endings and deep-dyeing oval lamellasome. The location of NFP positive tissue was similar to that of S100 positive tissue, but the distribution of these NFP positive filaments with various diameters showed largely as bundles, free ending and branches scattering in periodontal membrane. Conclusion  We may firstly distinguish the structure of the nerve fibers in periodontal ligament of nerve distribution, and then judge the categories of the nerve fibers by S100 immunohistochemistry furtherly according to comparison of the thickness of neural axon by NFP immunohistochemistry, and finally distinct the function and attribute of the nerve fibers in the periodontal ligament of dogs.

Objective  To study the biocompatibility of the polylactic acid (PLA)-absorbable root post film prepared by solvent evaporation film. Methods  The PLA post film-leaching liquor was prepared by the solvent evaporation of PLA root post films, and its biocompatibility was measured. Sources of human gingival fibroblasts (HGF) were cultivated in vitro and identified initially by the immunohistochemistry method. The toxicity reaction, survival rate, and morphological change of HGF incubated in PLA post film-leaching liquor were observed and tested by morphological observation, 3-(4,5-dimethylthiazolyl)-2,5-diphenyltetrazolium bromide (MTT) assay, and flow cytometry. The HGF were implanted on the PLA post film and observed by 4’,6-diamidino-2-phenylindole staining. After implanting the PLA post film, the surrounding subcutaneous tissue of SD rats and the implants were removed from the back of the rats in the 1st, 4th, 8th, and 12th weeks to observe the general condition of the incisions. The organization was given the hematoxylin-eosin (HE) stain to find the organization condition of local tissue inflammation and foreign body reaction through the infiltration degree of inflammatory fibroblasts. Results  The effects of the PLA post film-leaching liquor on the proliferation of HGF and fibroblast toxicity were insignificant. The living fibroblast rate was similar to the normal control group. The HGF were able to grow on the PLA film. The results of the organization general observation and HE staining of the rats were similar to the results for the control group, which met all the demands made by biological safety. Conclusion  The PLA-absorbable root post film prepared by the solvent evaporation film has good biocompatibility and can be used for further clinical research.

Objective  This study investigated the effects of salvianolic acid B (Sal B), a major bioactive component of the Chinese medicine salvia miltiorrhiza, on osteogenic differentiation of human periodontal ligament cells (hPDLCs). Methods Third passage PDLCs were used in this experiment. Methyl thiazolyl tetrazolium (MTT) method was employed to observe the effects of different Sal B concentrations on proliferation activity of hPDLCs. Alkaline phosphatase (ALP) activity and mineralization capability were measured, and mRNA expression of osteocalcin (OCN) was detected to investigate the effects of Sal B on osteogenesis of hPDLCs. Results  Sal B did not influence the viability of hPDLCs. The ALP activity and OCN mRNA expression levels of hPDLCs were both significantly improved (P<0.05) under treatment with different Sal B concentrations (0.5, 1, and 5 μmol·L⁻¹) compared with those in OIM group. Moreover, the number of mineralized nodules formed by hPDLCs were considerably higher under treatment with different Sal B concentrations (0.5, 1, and 5 μmol·L⁻¹) than that in the OIM group. Conclusion  Appropriate Sal B concentration can improve the osteogenic differentiation of hPDLCs.

Objective This study aimed to evaluate the clinical effect of extramedullary fixation combined with intramedullary fixation during the surgical reduction of sagittal mandibular condylar fractures. Methods  Twenty-four sagittal fractures of the mandibular condyle in18 patients were fixed by two appliances: intramedullary with one long-screw osteosynthesis or Kirschner wire and extramedullary with one micro-plate. The radiologically-recorded post-operative stability-associated complications included the screw/micro-plate loosening, micro-plate twisting, micro-plate fractures, and fragment rotation. The occluding relations, the maximalinter-incisal distances upon mouth opening, and the mandibular deflection upon mouth opening were evaluated based on follow-up clinical examination. Results  Postoperative panoramic X-ray and CT scans showed good repositioning of the fragment, with no redislocation or rotation, no screw/plate loosening, and no plate-twisting or fracture. Clinical examination showed that all patients regained normal mandibular movements, ideal occlusion, and normal maximal inter-incisal distances upon mouth opening. Conclusion  Extramedullary fixation combined with intramedullary fixation is highly recommended for sagittal condylar fractures because of the anti-rotation effect of the fragment and the reasonable placement of the fixation appliances.

Objective  This study aims to investigate the feasibility and clinical application value of a new method for primary donor-site closure of radial forearm flaps with the use of rotation and advancement of radial-based fasciocutaneous flaps. Methods  The forearm donor-site defects of 36 patients were primarily closed by rotation and advancement of radialbased fasciocutaneous flaps after radial flap harvest from November 2014 to May 2015. Patients included 28 males and 8 females aged 28 to 67 years (53.6 years old on average). Flap size ranged from 3.0 cm×5.0 cm to 4.0 cm×6.0 cm. Wound healing, scar hyperplasia, and forearm appearance were recorded and evaluated. Wrist flexion angle, dorsal extension angle, ulnar deviation angle, and radial deviation angle were measured three and six months after the operation. Wrist joint loss index was calculated and compared with the preoperative index to evaluate wrist function recovery. The results were subjected to comparative t test to perform statistical analysis with SPSS 19.0 statistical software package. Results  Forearm donor sites were successfully closed without skin grafting in all patients. Skin ischemia caused by excessive tension was observed at the incision edge in five cases, thereby leading to skin exfoliation and pigment loss without affecting wound healing. All patients were followed up at six and twelve months, and presented a satisfactory appearance. No scar hyperplasia was observed. No significant difference was observed in radial deviation, ulnar deviation, palmar flexion, dorsiflexion, radial deflection angle, or wrist joint loss index (P>0.05) after the operation. Conclusion Application of rotation and advancement of radial-based fasciocutaneous flaps can directly close small-to-medium radial forearm flap donor defects. Satisfactory postoperative appearance can be achieved with no loss in wrist joint function. The novel method prove worthy of promotion and application in clinical work.

Objective To investigate the clinical significance of cell blocks obtained by ultrasound-guided fine needle aspiration in diagnosing parotid gland masses. Methods Cell blocks were made in 285 parotid gland masses by ultrasound guided fine needle aspiration. Diagnosis was conducted using the cell blocks. Non-tumor masses were subjected to conservative treatment, and cysts and tumors were treated with surgery. The cell block sections from masses with the diagnosis of adenoid cystic carcinoma (ACC) and pleomorphic adenoma (PA) were applied to the detection of immunocytochemical staining forthe stem cell factor receptor CD117. Results  The satisfaction rate of the specimen was 95.1% (271/285). The accuracy rate of the diagnosis was 94.5% (256/271), the sensitivity was 87.0% (67/77), and the specificity was 98.1% (157/160). The positive rate of CD117 in ACC was 95.2% (20/21), whereas that in PA was 20.3% (25/123). The positive rate of CD117 in ACC was higher than that in PA (P<0.01). Conclusion  The use of cell blocks obtained from ultrasound-guided fine needle aspiration, together with molecular marker detection, has great significance in diagnosing parotid gland masses.

Objective  To enhance the accuracy in diagnosis and management of submucous cleft palate via a thorough analysis of its anatomical and functional details. Methods  Two hundred seventy-six submucous cleft palate cases from 2008 to 2014 were retrospectively investigated. Subgroup analysis were performed on the basis of preoperative velopharyngeal function, palatal morphology, cleft lip concurrence, and patient motives for treatment. Results  Among the included cases, 96 (34.78%) were presented as velopharyngeal competence (VPC), 151 (54.71%) as velopharyngeal insufficiency (VPI), and 29 (10.51%) as marginal VPI (MVPI). Eighty cases (28.99%) also demonstrated cleft lip deformity, and 196 cases (71.01%) were merely submucous cleft palate. Compared with patients with submucous cleft palate only, those with cleft lips exhibited higher rates of complete velopharyngeal closure. The pathological spectrum of submucous cleft palate varied significantly. Only 103 (37.32%) cases met all the three diagnostic criteria proposed by Calnan. Conclusion Given that the velopharyngeal closure rate varies among the subgroups, the factors analyzed in this study should be considered in the personalized management of submucous cleft palate.

Objective This study was performed to investigate the electromyographic (EMG) activity of the masseter muscle and the anterior temporalis muscle, as well as the masticatory efficiency after insertion of the dentures in edentulous individuals whose maxillomandibular horizontal relationship records were obtained with three different methods. Methods  Ten edentulous individuals were enrolled in this study. Three types of complete dentures for these 10 edentulous patients were made according to their different maxillomandibular horizontal relationship records. The maxillomandibular horizontal relationship of complete dentures was recorded by three methods. In the first method (A), the maxillomandibular horizontal relationship was determined at the gothic arch tracing apex. In the second method (B), the relationship was 1 mm anterior to the tracing apex with the gothic arch. In the last method (C), the horizontal jaw relation was recorded by natural chewing. The muscular activities of the three complete dentures were examined by EMG. The masticatory efficiency was evaluated based on the absorbance. The differences among the dentures were statistically analyzed with SPSS 17.0. Results The muscular activities of dentures B and C were much higher than that of denture A during clenching in the center occlusion and during chewing (P<0.05). The highest asymmetry index was found indenture C, which was significantly higher than those of dentures A and B (P<0.05). A statistically significant increase in the absorbance was observed between dentures B and C (P<0.05); otherwise, no statistically significant differences were observed (P>0.05) between B and C. Conclusion  Given the limitations of this experimental design, in edentulous individuals the maxillomandibular horizontal relationship recorded at 1 mm anterior to the tracing apex with the gothic arch can improve the function of masticatory muscles and strengthen masticatory performance.

Objective  This study assessed the effects of two-phase treatment with Herbst appliance on the bony structure of the temporomandibular joint via cone beam computed tomography (CBCT) analysis. Methods  This study selected 15 patients exhibiting early permanent dentition and classⅡmalocclusion combined with mandibular retrusion treated by a two phase treatment (Herbst and fixed appliance). The CBCT scans of the patients were obtained at the following stages: 2 weeks before Herbst treatment (T1), at the start of treatment when the Herbst appliance was set in place (T2), immediately after removal of the Herbst appliance (T3), and immediately after removal of the edgewise appliance (T4). Three-dimensional reconstruction and related measurements were performed using InvivoDental software, and the acquired data were statistically analyzed. Results 1) CBCT showed a crescent-shaped hyperplasia at the posterior-superior border of the condyles that the outer edge was highly dense and the inner region was lowly dense in T3 in 14 patients (28 condyles). 2) In T3–T2 and T4–T1, the diameters of the anteroposterior condyles increased by 0.62 and 0.66 mm, respectively (P<0.01), and the condylar head height correspondingly increased by 0.54 and 0.53 mm (P<0.01). Conclusion  Condylar growth remodeling occurs during Herbst treatment.

Objective  Finite elemental analysis of the mechanical characteristics of a first mandibular implant molar under different mandibular plane angles determines the load conditions on the implant, thereby providing guidance for clinical application. Methods  CT data of three mandibular plane angles (low, average, high) were collected. A finite elemental combination model of a dental implant was constructed. The orthogonal experimental research was designed. Results followed data collection and analysis. Results The optimal combination was a low angle, 4.8 mm, and type Ⅱ bone. The relations among diameter of the implant, angle of mandibular bone, and bone density were determined. Conclusion  Mandibular plane angle influences the stability of a dental implant. Under constant biting force, dental implants bear the stress proportional to the angle, high angles cause high stress, average angles cause average stress, and low angles cause the least stress.

Objective  To compare the stripping length obtained through the model of 0.012 and 0.014 of the nickel-titanium dual-stage maxillary sinus mucosa stripper, and the umbrella detacher. Methods  Twenty-four goats (1.5-2 years old) were chosen, randomly divided into A, B, C groups, each group of eight. Group A was 0.012 model group, group B was 0.014 model group, group C was umbrella detacher group. Animal model was established, and maxillary sinus mucosa was stripped to the left and right sides of the bottom of the sinus in three groups. The data was measured when stripping to the limit or being perforated. Results  The average length of group A was 12.41 mm±4.35 mm, two cases perforated. The average length of group B was 23.38 mm±4.84 mm, one case perforated. The average length of group C was 2.61 mm±0.30 mm. The population mean of stripping length in three groups was not all the same calculated by analysis of variance (P<0.01). There were significant differences in the stripping length of the three groups by the SNK test (P<0.05). Conclusion  The nickel-titanium dualstage maxillary sinus mucosa stripper can achieve a larger mucosal stripping range. The stripper with a model of 0.014 has a moderate flexibility and safety, and it can strip a large area of sinus mucosa.

A new clinic conception, healthy cosmetic management (HCM), was innovated introduced into diagnose and treatment of patients with high caries risk. The priority of HCM should be given to aesthetic restoration of teeth, taking consideration of the conserving of tissue and pulp of teeth and the balance between health and aesthetics, which may reach to the goal of the individual clinic treatment. HCM includes five steps: 1) caries risk assessment; 2) detection of initial caries; 3) digital aesthetic design; 4) minimally invasive therapy; 5) behavior management of caries and doctor-patient communication pattern. In this article, HCM is introduced into two aspects: process management and clinical protocols, followed by the combination of the clinical practice.

Objective Microstructural changes in dentin carious lesions were investigated using a 3D laser scanning microscope, which has a morphological theoretical foundation in the further study of clinical caries disease prevention and treatments. Methods  Six fresh extracted caries molars were prepared into cross-section specimens. The sections were examined by 3D and laser measuring morphology. Results  Zones were identified in the lesions on the basis of their optical appearance. Two zones were identified in the lesions on the basis of their laser appearance. The microstructure showed that the tubular was partly closed in transparent dentin; peritubular and intertubular dentin were reduced in the zone of demineralization; peritubular and intertubular dentin were damaged and fused; a beaded sample and oval lesions formed in the zone of bacterial invasion; and abnormal dentin structure was present in the zone of destruction on the basis of their laser appearance. Four zones were identified in the lesions according to their colors, as determined from their 3D appearance. Conclusion  3D laser scanning micros- cope may be a powerful, accessible, and non-destructive technique, as it identified the lesion and tubular zones, as well as peritubular and intertubular dentin in the four zones’ lesions. The microstructure of dentin caries lesions may have significant merit in the evaluation of clinical prevention and treatment.

Objective  This study aims to evaluate the effects of Pinus massoniana needle extract (PMNE) on inhibiting demineralization of root dentin. Methods  Root dentin blocks were randomly divided into distilled deionized water (DDW) group, fluoride sodium (NaF) group, and 4%, 8% and 12% PMNE groups according to the experimental solution used in the process of pH cycling in each group. All specimens in each group experienced pH cycling for 8 d. The dentin mineral density (DMD) of the normal dentin and demineralized dentin and their D-value (ΔDMD) were determined using micro computed tomography. The morphology of dentin surface after pH cycling was also observed using a scanning electron microscope. Results The ΔDMD values in all PMNE groups and the NaF group were considerably lower than the ΔDMD in the DDW group (P<0.05). The ΔDMD values of the 8% and 12% PMNE groups had no difference (P>0.05), both of which were lower than the ΔDMD in the 4% PMNE group and higher than that in the NaF group (P<0.05). The dentin tubules were partly opened in the PMNE groups. The opening degrees of the dentin tubule in PMNE groups were significantly less and smaller than the opening degree in the DDW group and were larger than that in the NaF group. Conclusion  PMNE can inhibit the demineralization of root dentin and can slow down the reduction in DMD. PMNE has the potential to prevent caries, and 8% PMNE can effectively inhibit dentin demineralization.

DNA methylation and demethylation are two important mechanisms of epigenetics, which is important in the study of cell differentiation, proliferation, and senescence. During osteogenic differentiation of stem cells, the expression of osteogenic specific genes and demethylated promoters is upregulated, whereas the expression of pluripotent genes and hyper- methylated promoters is downregulated. The dynamic changes and balance between DNA methylation and demethylation are important for the coordination of gene expression and the inhibition of improper phenotypes. Abnormal changes in the methylation modification mechanism in osteogenic differentiation not only affect the normal function of stem cells but are also associated with the occurrence and development of many common skeletal diseases. This paper reviews the new progress of DNA methylation and demethylation in regulating osteogenic differentiation. The possible skeletal diseases caused by ab- normal DNA methylation are also presented.

Zygomaticomaxillary complex (ZMC) fracture is a common type of maxillofacial fracture. In addition to facial depression and diplopia, paresthesia of the lower eyelid, malar regions, nose skin, upper lip skin, and mucous membranes occurs because of infraorbital nerve injury. This article reviewed the anatomy, diagnosis, assessment, treatment, and prognosis of ZMC fracture-related infraorbital nerve injury.

Traditional craniomaxillofacial surgery significantly affects aesthetic appreciation. In contrast to traditional methods, robot-assisted surgery has been extensively investigated because it is microinvasive, precise, and safe. With robot- assisted surgery, operational vision and manipulation space become extended. As a result, operational quality and patient’s postoperative life are improved. This article reviewed the development of surgical robot systems and their applications in craniomaxillofacial surgery.

The root and canal anatomy of maxillary first molar is very complicated. The incidence of having two canals in the mesiobuccal root of maxillary first molar is higher than that in its distobuccal root. This article described a maxillary first molar with five root canals, including two canals in mesiobuccal and distobuccal roots.

Ectopic tooth is a common problem reported in clinics. Ectopic tooth generally occurs around its primary posi- tion, and long-distance displacement is rare. A case of ectopic maxillary premolar in palatal suture with a supernumerary tooth in the mentum region was reported in this study, and the relevant literature is presented in this paper.

Peer instruction is one of the best recognized teaching methods in the world. In this study, we aim to discuss the necessity and feasibility of applying peer instruction to the current dental school education with respect to the specialty features of stomatology in China. We also propose a new paradigm of teaching based on peer instruction for the development of a more effective system to train elite dentists and meet the increasing needs of the society for oral health.