Effect of Mechanical Loading on Bone Regeneration in HA/ß-TCP/SF Scaffolds Prepared by Low-Temperature 3D Printing In Vivo.

It has been well demonstrated that a dynamic culture environment improves tissue-engineered bone formation in vitro, but little is known about how cyclical mechanical loading induced bone formation in scaffolds in situ. To mimic the organic and inorganic components and multilevel structure of a bony microenvironment, hydroxyapatite/ß tricalcium phosphate/silk fibroin(HA/ß-TCP/SF) composite scaffolds with macro- and micropores were fabricated in this study. The mechanical properties and structure of the scaffolds were adjusted based on the ratio of organic and inorganic components and three-dimensional (3D) printing parameters. Dynamic sinusoidal loading with different frequencies was applied to the composite scaffold. Mouse bone precursor cells MC3T3-E1 were seeded on the scaffolds, and the cell compatibility of the scaffolds was investigated by MTT, SEM, and HE. The effect of the loading on bone formation in the scaffold in situ was investigated in a rabbit tibia defect model. The scaffold showed viscoelasticity and hysteresis under dynamic sinusoidal loading with different frequencies. With an increase in HA/ß-TCP, the stress and modulus of the scaffolds increased. MTT, SEM, and HE results showed that MC3T3-E1 cells could adhere and proliferate on the composite scaffolds. After loading in vivo, the quantity of newly formed bone and the bone volume fraction increased. Micro-CT, undecalcified Van Gieson (VG) staining, and fluorescent double-labeling results suggested that appropriate cyclical mechanical loading at frequencies of 1 and 10 Hz had positive effects on bone formation in situ and it may play a role in clinical bone defect repair.

Application of the ratio of the radiopaque calcified area to the dental follicle (RCA/DF) for dental age assessment on orthopantomograms.

OBJECTIVES: This study aimed at exploring a new tooth development evaluation method for age assessment and investigating the dynamic alteration and potential trend of tooth development by orthopantomograms (OPGs), in order to provide references for tooth development prediction and forensic purpose. MATERIALS AND METHODS: A total of 132 OPGs of children aged 3-8 years were collected. The developmental stages of the permanent mandibular second molar (M2)were evaluated by experienced examiners according to the Nolla method and Mimics software, respectively. Quantitative analysis of the ratio of the radiopaque calcified area to the dental follicle (RCA/DF) in different stages, ages, sexes and quadrants were evaluated and compared via descriptive statistics and Spearman's correlation coefficient analysis. RESULTS: There was a strong, positive correlation between the examiners' evaluation and mimics analysis results. With the age increased, the Nolla stage of M2 observed by OPGs increased, and the RCA/DF showed increased trends both in males and females. There were significant differences of the RCA/DF of the M2 at various ages. The tooth calcification development of female was 9.08% earlier than that of male between 3 and 8 years old. However, teeth of male seemed to develop faster than that of female during this period. There was no significant difference between left and right quadrant either according to the Nolla stage or RCA/DF. CONCLUSIONS: The RCA/DF value obtained from OPGs of the developmental mandibular second permanent molars could be used as a reliable indicator for tooth maturity and age estimation in children aged 3-8 years. CLINICAL RELEVANCE: Age assessment based on radiographs is considered as a reliable and efficient indicator for judging different types of malocclusion, making suitable orthodontic treatment plan, deciding the extraction time of retained deciduous teeth in clinic practice.

An amelogenin-based peptide hydrogel promoted the odontogenic differentiation of human dental pulp cells.

Amelogenin can induce odontogenic differentiation of human dental pulp cells (HDPCs), which has great potential and advantages in dentine-pulp complex regeneration. However, the unstability of amelogenin limits its further application. This study constructed amelogenin self-assembling peptide hydrogels (L-gel or D-gel) by heating-cooling technique, investigated the effects of these hydrogels on the odontogenic differentiation of HDPCs and explored the underneath mechanism. The critical aggregation concentration, conformation, morphology, mechanical property and biological stability of the hydrogels were characterized, respectively. The effects of the hydrogels on the odontogenic differentiation of HDPCs were evaluated via alkaline phosphatase activity measurement, quantitative reverse transcription polymerase chain reaction, western blot, Alizarin red staining and scanning electron microscope. The mechanism was explored via signaling pathway experiments. Results showed that both the L-gel and D-gel stimulated the odontogenic differentiation of HDPCs on both Day 7 and Day 14, while the D-gel showed the highest enhancement effects. Meanwhile, the D-gel promoted calcium accumulation and mineralized matrix deposition on Day 21. The D-gel activated MAPK-ERK1/2 pathways in HDPCs and induced the odontogenic differentiation via ERK1/2 and transforming growth factor/smad pathways. Overall, our study demonstrated that the amelogenin peptide hydrogel stimulated the odontogenic differentiation and enhanced mineralization, which held big potential in the dentine-pulp complex regeneration.

Photothermal effect of indocyanine green modified scaffold inhibits oral squamous cell carcinoma and promotes wound healing.

As the most prevalent malignant tumor of the oral and maxillofacial regions, squamous cell carcinoma (SCC) has relatively high recurrence and low survival rates. Currently, the most common treatment strategies are surgery and chemoradiotherapy. However, incomplete removal of the tumor can allow residual tumor cells to regrow and metastasis, resulting in treatment failure. Although postoperative adjuvant radiotherapy or chemotherapy can reduce recurrence, serious adverse reactions significantly compromise patients' quality of life. Large soft tissue defects after surgery are also difficult to heal. Therefore, therapies that eliminate residual tumor cells and promote tissue regeneration post-surgery are urgently needed. Indocyanine green (ICG) can convert absorbed light into heat to ablate tumor cells. Three-dimensional (3D) scaffolds are efficient drug carriers and support cell migration and proliferation. Here, we fabricated collagen/silk fibroin encapsulated ICG (I-CS) scaffolds by combining 3D printing with freeze-drying methods. The I-CS scaffolds delayed ICG decomposition and clearance, allowing the scaffolds to be used repeatedly for photothermal therapy (PTT). With the laser positioned at 4 cm from the 1.0 I-CS scaffold and irradiation for 10 min (1.0 W/cm2), temperatures above 50 °C were achieved, which effectively killed SCC-25 cells in vitro and suppressed tumor growth in vivo. Moreover, the I-CS scaffolds supported attachment and proliferation of rat buccal mucosa fibroblasts (RBMFs) and promoted the repair of buccal mucosal wounds in rats. These results suggested that I-CS scaffolds may be useful in preventing local recurrence and support regeneration of large soft tissue defects after oral SCC surgery.

Chemiluminescent polymeric nanoprobes for tumor diagnosis: A mini review.

Chemiluminescence (CL), a distinct luminescent process by taking advantage of chemical reactions rather than external light source, has recently attracted considerable research interests due to its high sensitivity and low background signal. The sensitivity and specificity of chemiluminescent signals in complex tumor microenvironment provide a sound basis for accurate detection of tumors. Various chemiluminescent nanoprobes with superior performance have been obtained by structural modification of chemiluminescent units or introduction of fluorescent dyes. In this review, we focused on the recent progress of chemiluminescent polymeric systems based on various chromophore substrates, including luminol, peroxyoxalates, 1, 2-dioxetanes and their derivatives for tumor detecting. And we also emphasized the design strategies, mechanisms and diagnostic applications of representative chemiluminescent polymeric nanoprobes. Finally, the critical challenges and perspectives of chemiluminescent systems usage in tumor diagnosis were also discussed.

Effect of acidic culture conditions on the proliferation, apoptosis, and migration ability of human tongue squamous cell carcinoma cells and its related mechanism.

OBJECTIVES: This study aims to explore the effect of acidic culture conditions on the proliferation, apoptosis, and migration ability of human tongue squamous cell carcinoma SCC15 and CAL27 cells and its potential molecular mechanism. METHODS: After acidic culture for different periods, methyl thiazolyl tetrazolium (MTT) method was adop-ted to detect the cell proliferation of SCC15 and CAL27. Flow cytometry was employed to detect the apoptosis level of SCC15 and CAL27 cells. The migration ability of SCC15 and CAL27 after acidic culture was detected by scratch hea-ling test. Real-time fluorescence quantitative polymerase chain reaction (FQ-PCR) was used to detect the mRNA expression of cyclooxygenase 2 (COX-2) and survivin in SCC15 and CAL27 cells after acidic culture. RESULTS: After culture for 24 h under acidic microenvironment, SCC15 and CAL27 cells grew rapidly and reached the stationary phase after adjustment for 3 days. The apoptosis levels of SCC15 and CAL27 cells decreased after acidic culture, but the most significant reduction occurred after 6 h of acidic culture. The scratch healing rates of SCC15 and CAL27 cells increased after acidic culture. The results of FQ-PCR showed that the mRNA expression levels of COX-2 and survivin in SCC15 and CAL27 cells increased after acidic culture. CONCLUSIONS: Extracellular acidic microenvironment can inhibit the apoptosis of tongue squamous carcinoma cells, promote their migration, and induce more adaptable and malignant tongue squamous carcinoma cells. The mechanism may be related to COX-2 and survivin and their signal pathways.

The Application of a Case-Based Social Media-Assisted Teaching Method in Cariology Education：Comparative Study.

BACKGROUND: Current cariology education based on the traditional teaching method faces a lot of challenges. Meanwhile, the COVID-19 pandemic caused an unprecedented disruption in medical education and health care systems worldwide. Innovation in the teaching mode of cariology education is required to change the situation. OBJECTIVE: The goal of the research was to evaluate the application effects of a case-based social media-assisted teaching method in cariology education. METHODS: Dental students of class 2019 were enrolled into the experimental group, while students of class 2018 served as control. A case-based social media-assisted teaching method was used in the experimental group, which included preclass activity via social media, additional discussion and practice process record in class, and questions and answers on the platform after class. The traditional teaching method, which consisted of conventional preparation before class, traditional lectures and demonstrations followed by students practice in class, and questions and answers step after class, was used in the control group. The teaching materials were the same in both groups. At the end of the program, students from both groups took cavity preparation skill evaluation tests. Questionnaires were tested on the case-based social media-assisted teaching group students anonymously. All data were analyzed using SPSS statistical software (version 22.0, IBM Corp). RESULTS: The mean student cavity preparation skill evaluation scores was 82.51 (SD 6.82) in the experimental group and 77.19 (SD 5.98) in the control group (P<.05). The questionnaire response rate was 100%. Of those, 94.3% (100/106) of the students recommended the case-based social media-assisted teaching method in cariology education. The majority of the participants agreed that it helped them memorize the theoretical knowledge of cariology, facilitated in-depth discussion, improved their enthusiasm and initiative in learning, and enhanced the relationship between teachers and students (104/106, 98.1%). They also recognized that the classroom atmosphere was active (94/106, 88.7%). CONCLUSIONS: The case-based social media-assisted teaching method was beneficial in terms of learning, as demonstrated by the statistically significant improvement of the cavity preparation skill evaluation scores and satisfaction from attending students. This method could be used to supplement the teaching of cariology.

Effects of different aperture-sized type I collagen/silk fibroin scaffolds on the proliferation and differentiation of human dental pulp cells.

This study aimed at evaluate the effects of different aperture-sized type I collagen/silk fibroin (CSF) scaffolds on the proliferation and differentiation of human dental pulp cells (HDPCs). The CSF scaffolds were designed with 3D mapping software Solidworks. Three different aperture-sized scaffolds (CSF1-CSF3) were prepared by low-temperature deposition 3D printing technology. The morphology was observed by scanning electron microscope (SEM) and optical coherence tomography. The porosity, hydrophilicity and mechanical capacity of the scaffold were detected, respectively. HDPCs (third passage, 1 × 105 cells) were seeded into each scaffold and investigated by SEM, CCK-8, alkaline phosphatase (ALP) activity and HE staining. The CSF scaffolds had porous structures with macropores and micropores. The macropore size of CSF1 to CSF3 was 421 ± 27 µm, 579 ± 36 µm and 707 ± 43 µm, respectively. The porosity was 69.8 ± 2.2%, 80.1 ± 2.8% and 86.5 ± 3.3%, respectively. All these scaffolds enhanced the adhesion and proliferation of HDPCs. The ALP activity in the CSF1 group was higher than that in the CSF3 groups (P < 0.01). HE staining showed HDPCs grew in multilayer within the scaffolds. CSF scaffolds significantly improved the adhesion and ALP activity of HDPCs. CSF scaffolds were promising candidates in dentine-pulp complex regeneration.

CCR7-CCL21 axis promotes the cervical lymph node metastasis of tongue squamous cell carcinoma by up-regulating MUC1.

This study aims at investigating the potential role of MUC1 in CCR7-CCL21 axis-induced metastasis of tongue squamous cell carcinoma (TSCC). TSCC patients were selected for epidemiologic trends. The expression of CCR7 and MUC1 was detected via immunohistochemistry. SCC15 and CAL27 cells were induced by CCL21 and specific antibody to CCR7. Gene and protein expression was detected using qRT-PCR and western blotting. Migration and invasion capacities of TSCC cells were determined using wound healing and Transwell invasion assays. The male:female ratio of 78 patients was 1.6:1. Metastasis rate of cervical lymph nodes (CLNs) was 42.3%. CLN metastasis significantly correlated with T staging (P = 0.026), clinical staging (P = 0.024), and depth of invasion (DOI, P = 0.001). DOI significantly influenced CLN metastasis (P = 0.033, OR = 10.919) of TSCC, as did CCR7 (P = 0.041) and MUC1 (P = 0.026). The consistency of CCR7 and MUC1 expression was fairly good (Kappa = 0.683, P < 0.001). Reduced survival was significantly associated with higher expression of CCR7 (P = 0.039) and MUC1 (P = 0.030). CCL21 up-regulated MUC1 in SCC15 cells, which was inhibited when CCR7 was blocked. MUC1 positively correlated with TSCC cell migration and invasion. CCR7-CCL21 axis might promote CLN metastasis of TSCC by up-regulating MUC1. CCR7 and MUC1 show promise as potential biomarkers for TSCC treatment.

Cyclic mechanical stimulation inhibits rheumatoid arthritis fibroblast-like synoviocytes proliferation via cell cycle arrest.

The imbalance between proliferation and apoptosis of fibroblast-like synoviocytes (FLSs) has been the main cause of rheumatoid arthritis (RA) synovial hyperplasia. Our previous study confirmed that the cyclic mechanical stimulation (CMS) inhibited the proliferation of RA FLSs, but the underlying mechanisms are still unclear. This study aimed to investigate these underlying mechanisms. The in vitro cultured human RA FLSs were subjected to CMS (6%, 1.0 Hz). Cell cycle was detected by flow cytometry. The expression of cyclin D1, cyclin E1, CDK-2 and p27 was detected by reverse transcription-polymerase chain reaction (RT-PCR). MTS assay was used to detect cell viability. Cyclooxygenase-2 (COX-2) and prostaglandin E2 (PGE2) levels in RA FLSs were detected by western blotting and enzyme-linked immunosorbent assay (ELISA), respectively. The results showed that CMS significantly inhibited the cell cycle transformation of RA FLSs from G1 phase to S phase, which significantly decreased the cell proliferation index. Meanwhile, both cyclin E1 and CDK-2 gene expressions were significantly decreased, p27 gene expression was increased, and no significant change was observed in the expression of cyclin D1. The inhibition of COX-2/PGE2 pathway in RA FLSs by celecoxib treatment showed no effect on the inhibition of RA FLSs proliferation by CMS. In conclusion, CMS inhibited the proliferation of RA FLSs by modulating the expression of cell cycle-related molecules such as cyclin E1, CDK2 and p27 to arrest cell cycle transformation, which is independent of COX-2/PGE2 signaling pathway.

Downregulation of caveolin-1 promotes murine breast cancer cell line progression by highly glycosylated CD147.

Caveolin-1 (CAV-1) can extensively regulate lipid transportation, cell growth and cell death. In the present study, we revealed a novel function of CAV-1 in inhibiting glycosylation of other molecules in murine breast cancer cell line. After the silencing of CAV-1, we found that the mRNA and protein expressions of cluster of differentiation 147 (CD147) and its related molecules (MCT4, matrix metalloproteinase MMP2 and MMP9) increased in the breast cancer cells. Meanwhile, the migration and invasion of the breast cancer cells were significantly enhanced assessed by cell wound healing experiment and transwell assays. Further, the gelatin zymography and lactate assay in the cells also showed the strengthened enzyme activity of MMP9 and the increased extracellular lactate concentration, respectively, after the silencing of CAV-1. Notably, the glycosylation level of CD147 overtly increased after the inhibition of CAV-1 detected by Western Blot analysis, whereas upregulation of CAV-1 did the opposite. Therefore, the findings suggest that the downregulation of CAV-1 can promote breast cancer cell progression probably by highly glycosylated CD147.

Single-molecule multiplexed profiling of protein-DNA complexes using magnetic tweezers.

Epigenetics, such as the dynamic interplay between DNA methylation and demethylation, play diverse roles in critical cellular events. Enzymatic activity at CpG sites, where cytosines are methylated or demethylated, is known to be influenced by the density of CpGs, methylation states, and the flanking sequences of a CpG site. However, how the relevant enzymes are recruited to and recognize their target DNA is less clear. Moreover, although DNA-binding epigenetic enzymes are ideal targets for therapeutic intervention, these targets have been rarely exploited. Single-molecule techniques offer excellent capabilities to probe site-specific protein-DNA interactions and unravel the dynamics. Here, we develop a single-molecule approach that allows multiplexed profiling of protein-DNA complexes using magnetic tweezers. When a DNA hairpin with multiple binding sites is unzipping, strand separation pauses at the positions bound by a protein. We can thus measure site-specific binding probabilities and dissociation time directly. Taking the TET1 CXXC domain as an example, we show that TET1 CXXC binds multiple CpG motifs with various flanking nucleotides or different methylation patterns in an AT-rich DNA. We are able to establish for the first time, at nanometer resolution, that TET1 CXXC prefers G/C flanked CpG motif over C/G, A/T, or T/A flanked ones. CpG methylation strengthens TET1 CXXC recruitment but has little effect on dissociation time. Finally, we demonstrate that TET1 CXXC can distinguish five CpG clusters in a CpG island with crowded binding motifs. We anticipate that the feasibility of single-molecule multiplexed profiling assays will contribute to the understanding of protein-DNA interactions.

Mapping the amelogenin protein expression during porcine molar crown development.

INTRODUCTION: Amelogenin (AMEL) plays critical roles during enamel and dentin matrix deposition and mineralization. Most studies focused on the expression patterns of AMEL through the bud, cap, and bell stages. The spatial-temporal expression of AMEL protein during different mineralization stages, especially from presence of crypts to crown completed stages, remains unknown. Thus, the distribution pattern of AMEL in tooth crown formation from Nolla Stage 1 to 6 was investigated. METHODS: Porcine mandibular molar tooth germs from Nolla Stage 1 to 6 were obtained. The dynamic morphologic changes of tooth germs were examined by X-ray and surgical operating microscope. The AMEL protein expression was evaluated immunohistochemically, then analyzed semi-quantitatively, and further visualized via heat map. RESULTS: Tooth germs continuously increased in size from Nolla Stage 1 to 6. AMEL expression in the newly formed enamel kept negative, but presented intensively positive in the previously formed enamel from Stage 1 to 3. The adjacent enamel-dentin junction (EDJ) was strongly positive during the whole process. In predentin, AMEL was weakly seen at Stage 1 and then dramatically up-regulated from Stage 2 to Stage 3, then down-regulated but was still apparently seen in the whole process. AMEL expression in dentin was decreased during dentin matrix secretion and mineralization. CONCLUSIONS: This study identified the dynamic distribution of AMEL during porcine tooth crown formation. Semi-quantitative analysis and heat map emerged as reliable indicators in demonstrating AMEL distribution pattern.

Comparison of actual porcine tooth crown development stages and computer image analysis.

Tooth developmental stage evaluation is important in dental and chronological age estimation, and it is important for accurate diagnoses and appropriate treatment in dental practice. It is routinely assessed by clinical observations and radiographic techniques. This study aimed at ascertaining tooth developmental stage judgments made by examiners and Mimics software according to the Nolla method with radiographs. Meanwhile, the true tooth developmental stages would be explored with histological analysis. Twenty freshly slaughtered porcine heads were collected and hemisected, and both the left and right mandibular samples were numbered. The developmental stages of the second and third permanent molars (M2 and M3) were evaluated by examiners and Mimics software analysis. The ratio of the radiopaque calcified area to the dental follicle (RCA/DF) at different stages was calculated. Both non-decalcified and decalcified samples were processed for histologic observation. The results showed significant differences between RCA/DF ratios from different developmental stages. There was a high positive correlation between the examiners' evaluation results and Mimics analysis results. Radiograph judgments and histology observation results were consistent from Stages 2-6. However, radiograph images of Stage 1 samples showed only crypts present, while under a surgical operating microscope, a bell-shaped tooth germ was observed. This was also confirmed by normal and hard tissue histology. In conclusion, radiograph judgments made by either examiners or Mimics software were both reliable. Mimics analysis can be a useful tool in evaluating tooth developmental stages. However, judgments need to be made cautiously in early developmental stages.

A Three Long Noncoding RNA-Based Signature for Oral Squamous Cell Carcinoma Prognosis Prediction.

Oral squamous cell carcinoma (OSCC) is one of the most common malignancies worldwide. Despite relative high 5-year survival rate, delayed diagnosis still hampers its prognosis improvement. Long noncoding RNA (lncRNA) has recently been demonstrated to involve in development of various cancers. This study aimed to identify a lncRNA-based signature by which we could accurately predict OSCC prognosis. We first downloaded the RNA sequencing datasets for OSCC from The Cancer Genome Atlas (TCGA) and divided samples into training set and validation set. Associations between lncRNAs' expression and OSCC overall survival (OS) were evaluated in training set. Further screening through Random Survival Forest (RSF) method identified a prognostic signature composed of three lncRNAs, including AC013268.5, RP11.65 L3.4, and RP11.15A1.7, and by which OSCC samples in training set could be divided into high-risk and low-risk group with significantly different OS (p < 0.001, hazard ratio [HR] = 1.873). Besides, reliability of the prognostic signature was confirmed in the validation set (p < 0.01, HR = 2.14). Receiver operating characteristic curve analysis showed the superiority of the signature in OSCC prognosis prediction than other clinical characteristics. Gene set enrichment analysis indicated that high-risk score was closely associated with metabolism and spliceosome related pathways. Our findings suggest that lncRNA should be an important biomarker for prognosis of OSCC patients.

An integrated methylation and gene expression microarray analysis reveals significant prognostic biomarkers in oral squamous cell carcinoma.

Oral squamous cell carcinoma (OSCC) is a life­threatening disease with a poor prognosis. Although previous studies have reported that the methylation of certain genes is associated with the pathogenesis of OSCC, the methylation of genes that have relevance to OSCC progression is not clearly documented. The present study aimed to gain insights into the mechanisms underlying DNA methylation regulation associated with OSCC progression and to identify potential prognostic markers for OSCC treatment. DNA methylation dataset GSE41114 and gene expression dataset GSE74530 were downloaded from the Gene Expression Omnibus database. The global methylation status of OSCC tumor samples and normal control samples was determined, and differentially methylated genes (DMGs) in OSCC samples compared with control samples were identified. The mRNA expression data were then integrated to identify differentially expressed genes (DEGs) in OSCC samples compared with control samples. Overlapping genes between DEGs and DMGs were identified, and functional enrichment analysis was performed. In addition, survival analysis of the overlapping genes was performed to screen genes with prognostic significance in OSCC. A total of 40,115 differential methylation CpG sites spanning 3,360 DMGs were identified; CpG sites in the promoter, gene body and intergenic regions were generally highly hypermethylated or hypomethylated. Additionally, 508 DEGs in OSCC samples were identified, including 332 upregulated and 176 downregulated genes. A total of 82 overlapping genes between DEGs and DMGs were found, which were mainly involved in protein metabolism, regulation of the metabolic process and the immune system. Additionally, differential methylation or expression of several genes, including fibroblast activation protein α (FAP), interferon α inducible protein 27 (IFI27), laminin subunit Î³2 (LAMC2), matrix metallopeptidase 1 (MMP1), serine peptidase inhibitor Kazal­type 5 (SPINK5) and zinc finger protein 662 (ZNF662), was significantly associated with the survival of OSCC patients, and their differential expression in OSCC patients was further confirmed by reverse transcription­quantitative polymerase chain reaction in OSCC and normal oral cell lines. Overall, FAP, IFI27, LAMC2, MMP1, SPINK5 and ZNF662 genes caused by epigenetic changes via DNA methylation may be associated with the development and progression of OSCC, and should be valuable OSCC therapeutic biomarkers.

Investigation of Human Dental Pulp Cells on a Potential Injectable Poly(lactic-co-glycolic acid) Microsphere Scaffold.

INTRODUCTION: Poly(lactic-co-glycolic acid) (PLGA) has been extensively explored in the tissue engineering field with good biocompatibility and biodegradability. PLGA microspheres' injectable potency makes it highly desirable in dentin-pulp complex regeneration. Therefore, we investigated the cell adhesion, proliferation, odontogenic differentiation, and matrix mineralization of human dental pulp cells (HDPCs) on a PLGA microsphere scaffold. We hypothesized that this scaffold might be suitable for dentin-pulp complex regeneration. METHODS: PLGA microsphere scaffolds were fabricated using the double-emulsion solvent extraction technique with or without type I collagen surface modification. HDPCs were isolated from freshly extracted premolar or third molar teeth with patients' informed consent and ethical approval. Fourth-passage HDPCs (1 × 105 cells/ml) were seeded onto surface-modified or -unmodified PLGA microspheres and cultured in vitro. Cell adhesion, proliferation, and alkaline phosphatase activity were evaluated at different time points. Odontogenic-related gene expression (DMP1, DSPP, COL1, OPN, and OCN) were analyzed using quantitative real-time polymerase chain reaction. After 8 weeks of culture, samples were observed under scanning electron microscopy. RESULTS: Surface modification using type I collagen significantly enhanced HDPC attachment to the PLGA microspheres and promoted cell spreading. Alkaline phosphatase activity and odontogenic-related gene expression of HDPCs cultured with PLGA microsphere scaffolds were enhanced significantly compared with HDPCs cultured without PLGA microsphere scaffolds. After 8 weeks of culture, HDPCs combined with PLGA microspheres formed 3-dimensional structures. Partial degradation of the scaffolds and matrix mineralization were also observed. CONCLUSIONS: HDPCs can adhere to the PLGA microspheres, proliferate and differentiate into odontoblastlike cells, and form a 3-dimensional complex with matrix mineralization. This study may provide insight into the clinical dentin-pulp complex restoration with HDPCs and PLGA microsphere constructs.

Frequency and Influencing Factors of Rubber Dam Usage in Tianjin: A Questionnaire Survey.

Objective. To investigate the frequency and influencing factors of rubber dam usage for endodontic procedures among general dentistry practitioners and specialized practitioners (endodontist) in Tianjin. Methods. Three hundred questionnaires were distributed among practitioners from 3 different types of medical institutions in Tianjin. Data were collected and analysed using Chi-square tests. Results. There were 63.3% of respondents who have used rubber dam (response rate 82.7%, valid response rate 76.3%). However, only 0.4% and 3.1% of them recognized using rubber dam "every time" during caries direct restoration and root canal therapy, respectively. There was no significant difference in rubber dam usage between male and female practitioners. Among the respondents, practitioners with working experience between 5 and 10 years showed the highest usage rate (76.3%), while practitioners working more than 20 years showed the lowest (53.2%). The endodontists gained the highest and the most frequent usage rate and the best rubber dam technique mastering skills. Practitioners working in those stomatological departments of general hospitals showed the lowest rubber dam usage rate. Conclusions. The prevalence of rubber dam usage in Tianjin city is still low. The practitioner's gender, years of professional experience, general or specialized field, and the type of dental setting they work for are the factors that need to be considered during making policy and executing training.

A Cavity Preparation Evaluation System in the Skill Assessment of Dental Students.

The aim of this study was to compare a computerized, laser-scanning Cavity Preparation Skill Evaluation System (CPSES) with conventional teachers' eye-hand grading assessment of dental students' Class I cavity preparation evaluations. Thirty-eight cavity preparations of lower left first molars made by junior dental students at a dental school in China were tested from September 2013 to November 2014. The outline and retention form, smoothness, depth, wall angulation, and cavity margin index of the preparations were evaluated by CPSES and then by teachers' eye-hand grading. The mean difference in scores for each method was considered, as was the variability of scores within each method. Compared with the teachers' eye-hand grading method, CPSES provided objective evaluation results that had statistically significant differences (p<0.05). A questionnaire was also designed and distributed to the students; the response rate was 100%. The results indicated that most of the students recognized CPSES effects in the preclinical teaching; 92.1% perceived that CPSES provided high simulation and appropriate practice guidance for them; and 94.7% reported that the evaluation results provided by CPSES gave targeted and objective recommendations. These findings suggest that CPSES can consistently and reliably scan a student's tooth preparation, compare it to a theoretically ideal preparation, and provide objective feedback. The application of CPSES in preclinical operative training can help students better understand the desired parameters for occlusal cavity preparation skills and encourage students in their self-paced learning and independent practice.