A novel cutting machine supports dental students to study the histology of the tooth hard tissue.

BACKGROUND/PURPOSE: Ground section is the only way to study tooth enamel, and the conventional methods of making ground sections, grinding by hand or using a hard tissue microtome are either too time consuming or money costing. This study aimed to develop and assess a novel cutting machine in making ground sections and learning aid for dental students. MATERIALS AND METHODS: By using the novel cutting machine, the students cut the embedding teeth and got 50 µm ground sections efficiently. A series of fine/coarse combination stones were used for grinding the sections to uniform 20 µm thickness. Self-made ground sections were used in the lab class of tooth tissue. Questionnaires were designed to assess the participants' attitude towards the cutting machine and their knowledge of the tooth tissue before and after making the tooth ground sections. RESULTS: Our findings indicated that the novel cutting machine can act as an efficient tool to make tooth ground sections. Indeed, data indicated that making tooth ground section progress can assist students' understanding of the structure and function of tooth and their pathology knowledge had improved. From a qualitative point of view, the students described making tooth ground section progress improve their practical ability and study interest in oral pathology. CONCLUSION: Overall, these findings indicate that our novel cutting machine can act as an efficient tool to make tooth ground sections and support dental students to study the pathology of the tooth hard tissue in a simple and functional way.

Novel Calcium Phosphate Cement with Metformin-Loaded Chitosan for Odontogenic Differentiation of Human Dental Pulp Cells.

Metformin is an old and widely accepted first-line drug for treating type 2 diabetes. Our previous studies demonstrate that metformin can stimulate the osteo/odontogenic differentiation of human-induced pluripotent stem cell-derived mesenchymal stem cells and human dental pulp cells (DPCs). Due to the rapid dilution of metformin from the defect area, the aim of this study was to develop a drug delivery system with controlled release of metformin to promote cell viability and odontogenic differentiation of DPCs favoring dentin regeneration. Calcium phosphate cement (CPC) containing chitosan and metformin as a scaffold was synthesized. DPCs were seeded onto the scaffold, and the viability and proliferation were evaluated at several time points. For osteogenic differentiation analysis, alkaline phosphatase (ALP) activity was tested, cells were stained with Alizarin Red, and the expression of odontogenic markers was evaluated by real-time polymerase chain reaction. DPCs remained viable and attached well to the CPC-chitosan composite scaffold. Moreover, the addition of metformin to the CPC-chitosan composite did not adversely affect cell proliferation, compared to that of CPC control. Our data further revealed that the novel CPC-chitosan-metformin composite enhanced the odontogenic differentiation of DPCs, as evidenced by higher ALP activity, elevated expression of odontoblastic markers, and strong mineral deposition. These results suggest that the new CPC-chitosan-metformin composite is a highly promising scaffold with the potential for tissue engineering applications including dentin regeneration.

Alcohol Inhibits Odontogenic Differentiation of Human Dental Pulp Cells by Activating mTOR Signaling.

Long-term heavy alcohol consumption could result in a range of health, social, and behavioral problems. People who abuse alcohol are at high risks of seriously having osteopenia, periodontal disease, and compromised oral health. However, the role of ethanol (EtOH) in the biological functions of human dental pulp cells (DPCs) is unknown. Whether EtOH affects the odontoblastic differentiation of DPCs through the mechanistic target of rapamycin (mTOR) remains unexplored. The objective of this study was to investigate the effects of EtOH on DPC differentiation and mineralization. DPCs were isolated and purified from human dental pulps. The proliferation and odontoblastic differentiation of DPCs treated with EtOH were subsequently investigated. Different doses of EtOH were shown to be cytocompatible with DPCs. EtOH significantly activated the mTOR pathway in a dose-dependent manner. In addition, EtOH downregulated the alkaline phosphatase activity, attenuated the mineralized nodule formation, and suppressed the expression of odontoblastic markers including ALP, DSPP, DMP-1, Runx2, and OCN. Moreover, the pretreatment with rapamycin, a specific mTOR inhibitor, markedly reversed the EtOH-induced odontoblastic differentiation and cell mineralization. Our findings show for the first time that EtOH can suppress DPC differentiation and mineralization in a mTOR-dependent manner, indicating that EtOH may be involved in negatively regulating the dental pulp repair.

Physical and chemical properties of an antimicrobial Bis-GMA free dental resin with quaternary ammonium dimethacrylate monomer.

The objective of this study was to evaluate the antibacterial activity, physicochemical properties of the quaternary ammonium dimethacrylate monomer N,N-bis[2-(3-(methacryloyloxy)propanamido)-ethyl]-N-methylhexadecyl ammonium bromide (IMQ-16) containing diurethane dimethacrylate (UDMA)/tricyclodecane dimethanol diacrylate (SR833s) resin system and compare with bisphenylglycidyl dimethacrylate (Bis-GMA)/triethylene glycol dimethacrylate (TEGDMA) resin system. It was hypothesized that the physical and chemical properties of the experimental polymers would be comparable with Bis-GMA/TEGDMA polymer and IMQ-16 monomer could endow the UDMA/SR833s resin with antibacterial activity. Double bond conversion (DC) was measured using Fourier transform infrared spectroscopy (FTIR). Mechanical properties including flexural strength (FS) and flexural modulus (FM) were measured by three-point bending test with bars of 2mm×2mm×25mm. Water sorption (WS) and solubility (WSL) were also investigated. Antibacterial activity of obtained polymers against Streptococcus mutans Ingbitt (S. mutans) was tested through direct contact test (DCT). The presence of antibacterial activity due to soluble components was also investigated by agar diffusion test (ADT). All of the polymers containing IMQ-16 exhibited improvements in WS and WSL, while maintaining equivalent DC and FS relative to the Bis-GMA/TEGDMA control system. Incorporation of 17% and 20% of IMQ-16 into UDMA/SR833s resin reduced the viable counts of S. mutans after incubation on the surface of the materials and produced no inhibition zones around the cured discs in ADT. UDMA/SR833s resin system is promising to formulate an antibacterial polymer with equivalent or even higher physicochemical properties relative to Bis-GMA/TEGDMA formulation. IMQ-16 is capable to endow UDMA/SR833s resin system with significant antibacterial activity when the mass ratio is 17% or 20%.

Two-year clinical evaluation of composite resins in non-carious cervical lesions.

OBJECTIVE: The purpose of this double-blind, randomised trial was to compare the clinical performance of a hybrid composite (Clearfil AP-X, Kuraray, Tokyo) and a nanocomposite (Filtek Z350, 3M ESPE, St. Paul, MN) over a period of 2 years in non-carious class V lesions using a modified US Public Health Service (USPHS) system. METHODS: Forty-six patients with at least one pair of equivalent non-carious cervical lesions under occlusion and a mean age of 44.1 years (range 27-66 years; median 45 years) were enrolled in this study. A total of 116 restorations (58 with each material) were placed according to manufacturer's instructions by two calibrated operators. The restorations were evaluated at baseline and at 6, 12 and 24 months after placement using the USPHS criteria for retention, colour match, marginal discolouration, marginal adaptation, anatomic form, surface texture and secondary caries. Statistical analysis was conducted using the Cochran and the McNemar tests at a significance level of 5% (P < 0.05). RESULTS: No surface texture changes or secondary caries were detected in association with any restorations. The retention rates for Clearfil AP-X (100%) and for Filtek Z350 (91.38%) did not differ significantly (P > 0.05). Two Z350 restorations were completely lost after 2 years. No significant differences were observed in the colour match, marginal discolouration, marginal adaptation or anatomic form. CONCLUSIONS: There were no significant differences in the clinical performances between the materials. CLINICAL RELEVANCE: Both restorative materials exhibited acceptable clinical performance in class V non-carious lesions 2 years post-restoration.

[Effects of muramyl dipeptide on the differentiation of human dental pulp cells].

OBJECTIVE: To investigate the nucleotide-binding oligomerization domain-2 (NOD-2) gene expression in deep caries and the effects of NOD-2 agonist muramyl dipeptide (MDP) on the differentiation of human dental pulp cells (hDPC). METHODS: NOD-2 gene level in deep caries and healthy pulp tissue was determined by real-time quantitative polymerase chain reaction (realtime-PCR). Realtime-PCR, Western blotting and immunofluorescence were performed to evaluate NOD-2 gene and protein expression. Dentin sialoprotein (DSP) protein level was assessed when hDPC were challenged by different concentrations of MDP for 24 hours, and sialophosphoprotein (DSPP), osteocalcin (OCN) mRNA and osteopontin (OPN) protein level were detected at different time points after incubation with 0.1 mg/L MDP. RESULTS: NOD-2 mRNA level was higher in pulp tissue of deep caries (0.2610 ± 0.0824) than that in healthy controls (0.0024 ± 0.0002), P < 0.05. The expression of NOD-2 gene and protein increased in a time denpendent manner upon stimulation with MDP. Immunofluorescence confirmed that NOD-2 protein was located in cytoplasm. Moreover, 0.1 mg/L MDP augmented DSP protein level. DSPP and OCN mRNA were elevated with time and reached the peak at 12 h and down-regulated. OPN protein level also increased with time. CONCLUSIONS: Dental pulp NOD-2 expression are up-regulated in pulp tissue of deep caries. MDP may be related to the differentiation of hDPC.

[Application and prospect on the resin-dentin adhesion in the root canal therapy].

The application of adhesive root canal filling materials is the tendency in root canal obturation. The orientation is to develop the adhesive core material and sealer making a whole structure. In this review, we summarized the researches on the resin-dentin adhesion in the root canal obturation.

Expression of nucleotide-binding oligomerization domain 2 in normal human dental pulp cells and dental pulp tissues.

INTRODUCTION: The nucleotide-binding oligomerization domain (NOD) proteins belong to a distinct family of proteins that are implicated in the intracellular recognition of bacterial components. NOD2 appears to be a sensor of bacterial peptidoglycans because it recognizes a minimal motif present in all peptidoglycans. The interaction of NOD2 with downstream signaling molecules ultimately results in the activation of NF-kappaB and production of inflammatory mediators in innate immunity. As such, NOD2 may play an important role in the detection of bacterial pathogens and the initiation of inflammation within the dental pulp. This study was designed to evaluate the expression of NOD2 in normal human dental pulp cells (HDPCs) and human pulp tissues. METHODS: Human pulp tissue samples were collected from freshly extracted human wisdom teeth, and HDPCs were prepared from the explants of normal human dental pulp tissues. Nested reverse-transcription polymerase chain reaction (Nested RT-PCR) and Western blotting were performed to detect the expression of NOD2 messenger RNA and protein, respectively. Immunohistochemical staining was used to determine the distribution of NOD2 in the pulp tissues. RESULTS: The NOD2 messenger RNA and protein were present in normal human dental pulp tissues, with most NOD2 protein expression being localized to odontoblasts and some pulp vascular endothelial cells. In contrast, HDPCs only showed a low level of NOD2 protein expression. CONCLUSIONS: Our results suggest that NOD2 protein expressed in HDPCs and pulp tissues may play an important role in dental immune defense.

[Clinical observation on the characteristics of occlusion and tooth abrasion in patients with cracked tooth].

OBJECTIVES: To investigate the occlusal characteristics and the condition of tooth abrasion in patients with cracked tooth and to discuss the etiology of the cracked tooth and the relationships between occlusal disorder, tooth abrasion and cracked tooth. METHODS: Twenty-seven patients with cracked tooth were selected. The occlusal courses were recorded by T-ScanIII system in intercuspal position, protrusive movement and lateral movement. Teeth with cracked tooth were regarded as the cracked tooth group, and the healthy adjacent teeth as the control group. The distribution of premature contact, occlusal interference, the center of occlusal force were examined. The abrasive conditions of the two groups were recorded according to the Smith tooth wear index and compared. RESULTS: There were more teeth with occlusal interference in cracked tooth group (20 teeth) than in the control group (6 teeth), which was significantly different (OR = 5.67, chi(2) = 8.45, P = 0.003). In 24 patients with single affected tooth, the center of occlusal force (COF) located in the inside and outside ellipse were 6 teeth (25%) and 18 teeth (75%) respectively, Z test showed that there were statistical differences between the cracked tooth group and normal people. In cracked tooth group, the proportion of the teeth with abrasion was higher in teeth with occlusal interference than those without occlusal interference (chi(2) = 4.79, P = 0.029). CONCLUSIONS: The formation of the cracked tooth was related to the occlusal disorder and associated with the tooth abrasion.

[Morphological characteristics of the mandibular first premolars in people from Pearl River Delta region in Guangdong province].

OBJECTIVE: To investigate the morphological characteristics of the mandibular first premolars in people from Pearl River Delta region in Guangdong province using three techniques, including periapical radiographs, the radiographs with files inserted the canals and the clearing technique. METHODS: A total of 363 extracted mandibular first premolars were collected and numbered. Two preoperative radiographs were taken in buccolingual and mesiodistal directions respectively. After access opening, the files were placed in the canals and two other radiographs were taken. The mandibular first premolars with multi-canal system were selected and observed under dental operating microscope (DOM). The mandibular first premolars were made transparent and were categorized using the Vertucci's classification. RESULTS: There were different results among the three approaches. Periapical radiographs could be used to distinguish only between one and multiple canals systems. The incidence of multiple canals was 33.33% from the radiographs with file. The mandibular first premolars had a high frequency (34.44%) of multi-canal system by clearing method. The root canal morphology of the mandibular first premolars showed great variance. The canal orifices of the mandibular first premolars with one or two canal distributed in a buccolingual line. The floor of pulp chamber of the mandibular first premolars with three or four canals was a plat form. CONCLUSION: The mandibular first premolars have a high frequency multi-canal system and could be classified in many categories. Using DOM and radiographs with file is a useful way in judging the canal numbers and categories.

[Comparative study of sealing ability and fracture resistance of roots endodontically treated with bonded and unbonded filling materials].

OBJECTIVE: To compare the sealing ability and fracture resistance of roots endodontically treated with bonded and unbonded filling materials. METHODS: One hundred and fifteen straight mandibular premolar teeth with single canal were divided randomly into 6 experimental groups, with 15 samples each, and 3 control groups. The sealing ability was evaluated using a glucose quantitative microleakage mode and fracture resistance was tested by universal testing machine. RESULTS: The microleakage results showed that the bonded filling material had the lowest value while the unbonded filling material had the highest value in all groups. There were significant differences in microleakage value among the groups (P < 0.01), but no significant difference was noted in the fracture resistance among the testing groups (P = 0.7016). CONCLUSIONS: Bonded filling material enhanced the sealing ability but could not reinforce the fracture resistance of endodontically treated teeth.

An evaluation of the sealing ability of a polycaprolactone-based root canal filling material (Resilon) after retreatment.

OBJECTIVE: The aim of this study was to evaluate the sealing ability of Resilon after retreatment. STUDY DESIGN: Sixty-six single-rooted mandibular premolars were enlarged to apical size 45 and then obturated with Resilon. The roots were randomly divided into 3 groups (n = 22/group). In group 1 no further treatment was done. Groups 2 and 3 were reinstrumented to apical size 60 using K-files and ProFile, respectively. In each group, 4 samples were kept for environmental scanning electron microscopy (ESEM) analysis. The remaining roots from groups 2 and 3 were refilled with Resilon. Sixteen roots from each group were then evaluated for microleakage; two roots served as controls. Data were analyzed statistically by Kruskall-Wallis test. RESULTS: There were no significant differences between the experimental groups (P > .05). The ESEM showed new attachment of resin tags on the dentin surface of retreated roots. CONCLUSION: Resilon can be used for retreatment, but it still allowed microleakage.

Adenovirus-mediated recombinant human bone morphogenetic protein-7 expression promotes differentiation of human dental pulp cells.

Recombinant human bone morphogenetic protein-7 (BMP-7) has been shown to stimulate new reparative dentin formation in animal models. However, little is known about whether BMP-7 could promote the odontoblast-like differentiation and the formation of mineralized nodules in human dental pulp cells. Here, we reported that the infection with adenovirus-BMP-7 (Ad-BMP-7), a BMP-7-expressing adenoviral vector, induced the expression of BMP-7 in primarily cultured human dental pulp cells in the long term with little effect on their proliferation and viability. Importantly, BMP-7 expression significantly increased alkaline phosphatase activity and induced the dentin sialophosphoprotein expression in a dose- and time-dependent manner, suggesting that BMP-7 promoted the odontoblast differentiation. Furthermore, BMP-7 expression stimulated the formation of many mineralized dentin-like calcified nodules. Our data suggest that Ad-BMP-7-mediated BMP-7 expression can promote the differentiation of human pulp cells into odontoblast-like cells and mineralization in vitro, which may provide insight for the design of new gene therapy for the pulp capping in the clinic.

[Preparation and stability assessment of a new resin root canal filling material].

OBJECTIVE: To synthesize a new resin root canal filling material (NRCFM) and evaluate its stability in water and artificial saliva. METHODS: The new root canal filling material was made of thermoplastic elastomer (TPE), ethylene vinyl acetate (EVA) and activity fillers. The NRCFM's stability in water and artificial saliva with different pH values was assessed using gravimetric analysis, ICP and FE-SEM. RESULTS: NRCFM1 and NRCFM2 were successfully made. Gravimetric evaluation showed that the changes in mass over 30 days different solution medium for NRCFM1 and NRCFM2 were comparable to that of GP (P > 0.05) and significantly different from Resilon (P < 0.001). ICP showed slight changes in Si concentration for NRCFM1 and NRCFM2, Zn for GP, Na and Si for Resilon in the alkaline artificial saliva (pH 9.5). GP and Resilon showed release of Zn and Na respectively in distilled water whereas NRCFM1 and NRCFM2 were stable. FE-SEM micrographs showed that there were slight changes on the surface topography of NRCFM1 and NRCFM2. CONCLUSIONS: The new resin root canal filling material NRCFM1 and NRCFM2 had good stability in different experimental solutions.

[Effects of adenovirus-mediated human bone morphogenetic protein-7 on proliferation and differentiation of human dental pulp cells].

OBJECTIVE: To investigate the effect of adenovirus expressing human bone morphogenetic protein-7 (hBMP-7) on proliferation and differentiation of human dental pulp cells. METHODS: The replication-deficient adenoviral vector encoding hBMP-7 gene was constructed by using homologous recombinant modality. The efficiency of transfection was evaluated by fluorescent microscopy and flow cytometry. The expression of hBMP-7 protein in adenovirus-infected dental pulp cells was determined by Western blot. The proliferation of cells was tested by MTT method, the activity of alkaline phosphatase was assayed, von Kossa staining was used to detect mineralized nodule formation, and the expression of DSPPmRNA in cells was detected using semi-quantitative RT-PCR. RESULTS: Green fluorescent protein was visible under fluorescent microscopy. Higher transfection efficiency (91.1 +/- 1.0)% could be obtained at MOI of 75. Western blot from dental pulp cells infected with Ad-hBMP-7 for 48h detected protein expression of a hBMP-7 gene. The activity of alkaline phosphatase in cells was significantly higher than those of the control groups (P < 0.05). The cells infected with Ad-hBMP-7 had the ability of mineralization. DSPP mRNA expression of cells was in a time- and dose- dependent manner. CONCLUSIONS: Ad-hBMP-7 can induce human pulp cells into odontoblasts, but has no obvious effect on their proliferation.

Synthesis and characterization of dimethacrylate monomer with high molecular weight for root canal filling materials.

A new dimethacrylate monomer 9,9'-bis[4-(2'-hydroxy-3'-methacryloyloxy-propoxy)phenyl] fluorene (3) with a molecular weight of 634 was synthesized in 51.4% yield by addition of a glycidyl ether group to 9,9'-bis(4-hydroxyphenyl) fluorene (1) by the reaction of compound 1 with epichlorohydrin, and then introducing the methacrylate moiety by the reaction of the epoxy group with methacrylic acid. The structure of monomer 3 was confirmed by FT-IR, (1)H-NMR, mass spectra and elemental analysis.