The effects of 2-hydroxyethyl methacrylate on matrix metalloproteinases 2 and 9 in human pulp cells and odontoblast-like cells in vitro.

AIM: To assess the effects of 2-hydroxyethyl methacrylate (HEMA) on proliferation and migration of human pulp cells, as well as on matrix metalloproteinase (MMP-2 and MMP-9) expression in human odontoblast-like cells, contributing to the goal of determining the relationship between resin materials and MMP activity in pulp-dentine complexes. METHODOLOGY: Dental pulp cell cultures were established from pulp tissue of human teeth extracted for orthodontic purposes. Pulp cell differentiation was characterized in the presence of dentine sialophosphoprotein, bone sialoprotein and alkaline phosphatase by reverse transcription polymerase chain reaction. MMP activity was assessed by gelatine zymography with media containing HEMA. Cell viability was evaluated using methyl thiazolyl tetrazolium assay for 24-72 h. Cell migration was tested using Transwell migration assay. Western blotting was used to visualize MMP expression with the nontoxic HEMA concentrations (0-400 µg mL-1 ) for 48 h. RESULTS: Pulp cell proliferation decreased with HEMA exposure in a time- and concentration-dependent manner. HEMA concentrations ≤400 µg mL-1 did not induce changes in cell viability at 48 h (P < 0.05). Pulp cells were induced to differentiate into odontoblast-like cells in media containing 5 mg mL-1 ascorbic acid and 10 mmol L-1 ß-sodium glycerophosphate for 3-4 weeks. After incubation with HEMA, dose-dependent inhibition was observed; HEMA had a strong inhibitory effect on MMP activity. Compared with the control group, cell migration and MMP expression were inhibited significantly with increasing HEMA concentration at noncytotoxic doses (P < 0.05). CONCLUSIONS: Cell viability was not affected at HEMA concentrations ≤400 µg mL-1 . Within this range, HEMA inhibited MMP-2 and MMP-9 expression and activity, which may protect against type I collagen degradation effectively during dentine adhesive procedures.

The antibacterial effect and physical performance of pit and fissure sealants based on an antibacterial core-shell nanocomposite.

The application of pit and fissure sealants is a well-established method to prevent and treat early childhood caries. Resin-based sealants with antibacterial properties provide additional benefits for caries prevention in a cariogenic oral environment. The objective of this study was to evaluate the effect of an antibacterial core-shell AgBr/cationic polymer nanocomposite (AgBr/BHPVP) on the properties of a resin-based pit and fissure sealant. A commercialized pit and fissure sealant without fluoride, Concise (3M, ESPE, USA), was used as the parent material and negative control. Experimental antibacterial sealants were formulated by the addition of AgBr/BHPVP nanoparticles at mass fractions of 0.5, 1.0, and 1.5 wt% to the parent material. A fluoride-releasing sealant, Clinpro (3M, ESPE), was used as the positive control. Bacterial colony-forming unit (CFU) counts, metabolic activity tests, field emission-scanning electron microscopy (FE-SEM), and confocal laser scanning microscopy (CLSM) observations were used to evaluate the antibacterial properties of AgBr/BHPVP-modified sealants against Streptococcus mutans before and after five months of aging. The Vickers microhardness, degree of conversion, and microleakage level of the sealants were also investigated. According to the results of CFU counts and metabolic tests, sealants containing AgBr/BHPVP showed better contact-killing bactericidal activity against S. mutans than the two commercial sealants, irrespective of aging conditions (both P < 0.05). The AgBr/BHPVP-modified sealants also showed a significant inhibitory effect on the planktonic S. mutans around the cured sealant surfaces. In addition, the Vickers microhardness, degree of conversion, and microleakage level of the parent material were not damaged by modification with AgBr/BHPVP (P > 0.05). AgBr/BHPVP-modified pit and fissure sealant with a dual bactericidal mechanism is a promising option for the prevention of pit and fissure caries.

A novel dentin bonding scheme based on extrafibrillar demineralization combined with covalent adhesion using a dry-bonding technique.

Dentin bonding is a dynamic process that involves the penetration of adhesive resin monomers into the extrafibrillar and intrafibrillar demineralized collagen matrix using a wet-bonding technique. However, adhesive resin monomers lack the capacity to infiltrate the intrafibrillar space, and the excess water that is introduced by the wet-bonding technique remains at the bonding interface. This imperfectly bonded interface is inclined to hydrolytic degradation, severely jeopardizing the longevity of bonded clinical restorations. The present study introduces a dentin bonding scheme based on a dry-bonding technique, combined with the use of extrafibrillar demineralization and a collagen-reactive monomer (CRM)-based adhesive (CBA). Selective extrafibrillar demineralization was achieved using 1-wt% high-molecular weight (MW) carboxymethyl chitosan (CMCS) within a clinically acceptable timeframe to create a less aggressive bonding substance for dentin bonding due to its selectively extrafibrillar demineralization capacity. CMCS demineralization decreased the activation of in situ collagenase, improved the shrinking resistance of demineralized collagen, and thus provided stronger and more durable bonding than traditional phosphoric acid etching. The new dentin bonding scheme that contained CMCS and CBA and used a dry-bonding technique achieved an encouraging dentin bonding strength and durability with low technical sensitivity. This bonding scheme can be used to improve the stability of the resin-dentin interface and foster the longevity of bonded clinical restorations.

[Modification of the composite resin with the hyperbranched polyester and evaluation of the mechanical properties of the modified composite resin].

OBJECTIVE: To study the effect of hyperbranched polyester(HBP)on mechanical properties of the conventional resin matrix. METHODS: Two hyperbranched monomers(HBP2-X and HBP2-Y)were synthesized and incorporated at 40%(by mass)into a 2∶1(by mass)bisphenol-A diglycidyl methacrylate(Bis-GMA): triethylene glycol dimethacrylate(TEGDMA)resin. Bis-GMA/TEGDMA without the incorporation of hyperbranched polyester was used as control(n=8 per group). The mechanical properties of the modified neat resin, including polymerization volumetric shrinkage, Vickers hardness, water absorption and dissolution rate, as well as the flexural strength, compressive strength and diametral tensile strength of the composite resin with different content of filler(0%, 30%, 50%, 70%)were measured. Mechanical properties of the composite resin were measured by universal testing machine. The results were analyzed by the ANOVA and LSD-t-test. RESULTS: The resin with HBP greatly decreased the polymerization shrinkage of the composite resin, and the value of group X was(6.32±0.49)%, and that of group Y was(6.31±0.68)%, whereas that of the control group was(8.14 ± 0.53)%. The value of volumetric shrinkage of the modified groups were significantly lower than that of the control group(P<0.05). By adding HBP, the hardness value of group X([198 ± 5]MPa)and group Y([177 ± 4]MPa)were significantly lower than that of the control group([214±6]MPa)(P<0.05). The HBP significantly influenced the water sorption and solubility of the neat resin(P<0.05). For the composite materials, with 70% inorganic filler, there were no significant difference in the value of flexural strength among the groups(P>0.05). There was no significant difference in the value of compressive strength, between group X([244 ± 13]MPa)and the standard group([234 ± 17]MPa)(P>0.05). However, they were significantly higher than that in group Y([204 ± 24]MPa)(P<0.05). For the value of diametral tensile strength, there was no significant difference between group Y([36.4 ± 2.1]MPa)and the control group([34.4 ± 2.9]MPa)(P>0.05), but both were significantly lower than that in group X([41.1 ± 3.0]MPa)(P<0.05). CONCLUSIONS: Although there were certain effect on the mechanical properties of the resin that was modified with the HBP, we should make further analysis and study based on the property of low volumetric shrinkage, to strive for the development of low volumetric shrinkage of HBP, without affecting its mechanical properties.

[Three dimensional reconstruction measurement study of palatal contour changes in different bone ages after rapid maxillary expansion].

Objective: To compare dental and skeletal changes after rapid maxillary expansion in patients with different bone ages. Methods: Thirty-seven patients in different growth period were divided into three groups according to cervical vertebral maturation (CVM). There were 13 patients in the growth acceleration group, 13 patients in growth peak group, and 11 patients in growth deceleration group. Cone-beam computed tomography (CBCT) images were segmented and reconstructed using Mimics image processing software to assess the change of palatal morphology before and after treatment. Statistical analysis was carried out using SPSS 17.0 software. Results: After the expansion the posterior teeth and alveolar bone were tilted and the mid-palatal suture was opened in all three groups. The first molar angle in the three groups decreased by 2.66°±1.04°, 3.53°±0.81° and 12.32°±1.64°, respectively and no significant difference was found between the acceleration group and the peak group (P >0.05), but the changes in the acceleration group and the peak groups were significantly less than that in the deceleration group (P<0.05). The palatal angle in the three groups increased by 6.01° ± 2.06°, 4.79° ± 1.31° and 6.73° ± 1.71°, respectively and no significant difference was found between the acceleration group and the deceleration group (P>0.05), but the changes in the acceleration group and the deceleration group were significantly greater than that in the peak group (P<0.05). The palatal cemento-enamel junction (CEJ) width, the middle palate width and the mid-palatal suture width in the three groups increased by (7.37 ± 1.31), (6.68 ± 0.72) and (5.13 ± 1.42) mm; (5.72±1.68), (4.82±1.66) and (3.42±1.15) mm; (3.14±0.45), (2.98±0.51) and (0.96±0.83) mm, respectively and no significant difference was found between the acceleration group and the peak group (P >0.05), but the changes in the acceleration group and the peak group were significantly greater than that in the deceleration group (P <0.05). Conclusions: The mid-palatal suture could be opened in patients in different CVM period. More skeletal and less dental effects were found in patients in the growth acceleration and peek group than in those in the growth deceleration group and the inclination of the alveolar bone could be avoided to a greater degree in patients in the growth peek group.

Tetrapod-like zinc oxide whisker enhancement of resin composite.

There is an increasing demand for composite resins with both strong antibacterial activity and satisfactory mechanical properties. This study tested the hypothesis that the new antibacterial agent tetrapod-like zinc oxide whisker (T-ZnOw) could simultaneously enhance the antibacterial activity and mechanical properties of a two-component composite resin. The antibacterial activities of the materials were assessed by the broth dilution test and direct contact test. Optical microscopy, scanning electron microscopy, and measurements of the flexural strength, compressive strength, and diametral tensile strength were carried out for mechanical characterization. The results revealed that T-ZnOw provided the resin with strong antibacterial activity and improved mechanical properties in all tested groups. However, the antibacterial activity of the resin with 10% T-ZnOw in the powder component significantly decreased after aging treatment. The incorporation of 5% T-ZnOw into the resin powder was optimal to give appropriate antibacterial activity, long-term antibacterial effectiveness, and mechanical properties.