Synthesis of polymerizable betulin maleic diester derivative for dental restorative resins with antibacterial activity.

OBJECTIVE: Bisphenol A glycidyl methacrylate (Bis-GMA) is of great importance for dental materials as the preferred monomer. However, the presence of bisphenol-A (BPA) core in Bis-GMA structure causes potential concerns since it is associated with endocrine diseases, developmental abnormalities, and cancer lesions. Therefore, it is desirable to develop an alternative replacement for Bis-GMA and explore the intrinsic relationship between monomer structure and resin properties. METHODS: Here, the betulin maleic diester derivative (MABet) was synthesized by a facile esterification reaction using plant-derived betulin and maleic anhydride as raw materials. Its chemical structure was confirmed by 1H and 13C NMR spectra, FT-IR spectra, and HR-MS, respectively. The as-synthesized MABet was then used as polymerizable comonomer to partially or completely substitute Bis-GMA in a 50:50 Bis-GMA: TEGDMA resin (5B5T) to formulate dental restorative resins. These were then determined for the viscosity behavior, light transmittance, real-time degree of conversion, residual monomers, mechanical performance, cytotoxicity, and antibacterial activity against Streptococcus mutans (S. mutans) in detail. RESULTS: Among all experimental resins, increasing the MABet concentration to 50 wt% made the resultant 5MABet5T resin have a maximum in viscosity and appear dark yellowish after polymerization. In contrast, the 1MABet4B5T resin with 10 wt% MABet possessed comparable shear viscosity and polymerization conversion (46.6 ± 1.0% in 60 s), higher flexural and compressive strength (89.7 ± 7.8 MPa; 345.5 ± 14.4 MPa) to those of the 5B5T control (48.5 ± 0.6%; 65.7 ± 6.7 MPa; 223.8 ± 57.1 MPa). This optimal resin also had significantly lower S. mutans colony counts (0.35 ×108 CFU/mL) than 5B5T (7.6 ×108 CFU/mL) without affecting cytocompatibility. SIGNIFICANCE: Introducing plant-derived polymerizable MABet monomer into dental restorative resins is an effective strategy for producing antibacterial dental materials with superior physicochemical property.

N-Acetyl Cysteine-Mediated Improvements in Dental Restorative Material Biocompatibility.

The fibroblast-rich gingival tissue is usually in contact with or adjacent to cytotoxic polymer-based dental restoration materials. The objective of this study was to determine whether the antioxidant amino acid, N-acetyl cysteine (NAC), reduces the toxicity of dental restorative materials. Human oral fibroblasts were cultured with bis-acrylic, flowable composite, bulk-fill composite, self-curing acrylic, and titanium alloy test specimens. Cellular behavior and function were analyzed on and around the materials. Impregnation of the bulk-fill composite and self-curing acrylic with NAC reduced their toxicity, improving the attachment, growth, and function of human oral fibroblasts on and around the materials. These mitigating effects were NAC dose dependent. However, NAC impregnation of the bis-acrylic and flowable composite was ineffective, with no cells attaching to nor around the materials. Although supplementing the culture medium with NAC also effectively improved fibroblast behaviors, direct impregnation of materials with NAC was more effective than supplementing the cultures. NAC-mediated improvements in fibroblast behavior were associated with reduced production of reactive oxygen species and oxidized glutathione together with increased glutathione reserves, indicating that NAC effectively directly scavenged ROS from materials and reinforced the cellular antioxidant defense system. These results establish a proof of concept of NAC-mediated improvements in biocompatibility in the selected dental restorative materials.

Effects of resin materials dedicated for additive manufacturing of temporary dental restorations on human gingival keratinocytes.

OBJECTIVE: This study investigated the effect of eluates of conventional and 3D-printed resin materials for manufacturing temporary dental restorations on gingival keratinocytes. METHODS: Three-dimensional (3D)-printed resin materials: 3Delta temp (Deltamed), NextDent MFH (Nextdent), Freeprint temp (Detax), GC temp (GC), were compared to Grandio disc (Voco) and Luxatemp (DMG). Human gingival keratinocytes (IHGKs) were exposed to eluates of the materials and XTT assays were performed at 24 h, 48 h, 72 h, or 144 h. For quantification of the proinflammatory response, the protein amount of IL-6 and 8 was determined in the supernatants using ELISA. One-way ANOVA with post hoc analysis was used to compare differences in cell viability and IL-6 and IL-8 levels between groups. RESULTS: At 24 h, and more remarkably at 48 h, a significant decrease in cell viability occurred for the 3D-printed materials compared to the untreated IHGKs, but also compared to Grandio disc and Luxatemp. Except for the expression of IL-8 in presence of the eluate of Grandio disc at 24 and 48 h, all tested materials caused attenuation of IL-6 and 8 from IHGKs for any observation period. CONCLUSIONS: The materials for additive manufacturing affect cell proliferation differently than the subtractive manufactured material Grandio disc and the conventional material Luxatemp. CLINICAL SIGNIFICANCE: In comparison to conventional and subtractive manufactured restorations, 3D printed temporary restorations might induce more negative effects on the gingival and probably also on pulpal health since viability and the proinflammatory response of oral keratinocytes are more intensively affected by these materials.

Enamel matrix derivative (EMD) enhances the osteogenic differentiation of bone marrow mesenchymal stem cells (BMSCs).

To investigate the EMD's capacity in BMSCs osteogenic differentiation. In vivo and in vitro, BMSCs were treated with EMD, scanning electron microscopy, and Alizarin Red staining were used to detect the changes in the osteogenic ability of BMSCs, and the proliferation ability of BMSCs was evaluated by CCK8. In addition, by adding xav939, a typical inhibitor of Wnt/ß-catenin signaling pathway, the regulatory function of Wnt/ß-catenin signaling was clarified. The results showed that EMD promote cell proliferation and 25 µg/ml EMD had the most significant effect. Cells inducing osteogenesis for 2 and 3 even 4 weeks, the cell staining is deeper in EMD treated group than that of the control (P < 0.05) by alizarin Red staining, suggesting more mineralization of BMSCs. In vivo implanting the titanium plate wrapped with 25 µg/ml EMD treated-BMSC film into nude mice for 8 weeks, more nodules were formed on the surface of the titanium plate than that the control (P < 0.05). HE showed that there is a little blue-violet immature bone-like tissue block. Besides, the expression of RUNX Family Transcription Factor 2 (Runx2), Osterix, Osteocalcin (OCN), collagen I (COLI), alkaline phosphatase (ALP) and ß-catenin were inhibited in xav939 group (P < 0.05); Inversely, all were activated in EMD group (P < 0.05). In conclusion, EMD promoted the proliferation and osteogenic differentiation of BMSCs. EMD's function on BMSCs might be associated with the Wnt/ß-catenin signaling pathway.

Synthesis, characterization, and evaluation of curcumin-loaded endodontic reparative material.

Curcumin (CUR) is an ancient therapeutic agent with remarkable antimicrobial and anti-inflammatory properties. The purpose of the current study was to synthesize and evaluate a curcumin-based reparative endodontic material to reduce infection and inflammation besides the induction of mineralization during the healing of the dentin-pulp complex. Poly-ɛ-caprolactone (PCL)/gelatin (Gel)/CUR scaffold was synthesized and assessed by scanning electron microscopy, Fourier transform infrared spectroscopy, and thermo-gravimetric analysis (TGA). Agar diffusion test was performed against E. coli, A. baumannii, P. aeruginosa, S. aureus, E. faecalis, and S. mutans. Moreover, proliferative, antioxidative, anti-inflammatory, and calcification properties of these scaffolds on human dental pulp stem cells (hDPSCs) were evaluated. The results showed that PCL/Gel/CUR scaffold had antibacterial effects. Also, these CUR-based scaffolds had significant inhibitory effects on the expression of tumor necrosis factor α and DCF from inflamed hDPSCs (p < 0.05). Moreover, the induction of mineralization in hDPSCs significantly increased after seeding on CUR-based scaffolds (p < 0.05). Based on these findings, the investigated CUR-loaded material was fabricated successfully and provided an appropriate structure for the attachment and proliferation of hDPSCs. It was found that these scaffolds had antimicrobial, antioxidant, and anti-inflammatory characteristics and could induce mineralization in hDPSCs, which is essential for healing and repairing the injured dentin-pulp complex.

Carbon nanotubes functionalized with sodium hyaluronate: Sterilization, osteogenic capacity and renal function analysis.

AIM: This study determined the optimum gamma irradiation dosage to sterilize sodium hyaluronate (HY), single-walled carbon nanotubes (SWCNT), multi-walled carbon nanotubes (MWCNT) and CNT functionalized with HY (HY-SWCNT and HY-MWCNT), evaluated the structural integrity of the materials and assessed whether sterilized materials kept biological properties without affecting renal function. MAIN METHODS: Materials were submitted to dosages of 100 gγ to 30 Kgγ and plated onto agar mediums for colony forming units (CFUs) counting. Sterilized samples were inoculated with 107Bacillus clausii, submitted again to gamma irradiation, and plated in agar mediums for CFUs counting. Scanning electron microscope was used for structural evaluation of sterilized materials. Tooth sockets of rats were treated with sterilized materials for bone formation assessment and renal function of the animals was analyzed. KEY FINDINGS: The optimum gamma dosage for sterilization was 250 gγ for HY and 2.5 Kgγ for the other materials without meaningful structural changes. Sterilized materials significantly increased bone formation (p < 0.05) and they did not compromise renal function and structure. SIGNIFICANCE: Gamma irradiation efficiently sterilized HY, SWCNT, MWCNT, HY-SWCNT and HY-MWCNT without affecting structural aspects while maintaining their desirable biological properties.

Dental implant surfaces treated with phosphoric acid can modulate cytokine production by blood MN cells

Abstract: The study characterizes dental implant surfaces treated with phosphoric acid to assess the effects of acid treatment on blood cells and correlate them with cytokine levels. The implant surfaces examined were divided into untreated metal surface (US; n = 50), metal surface treated with phosphoric acid (ATS; n = 50) and cement surface (CS; n = 50) groups. The samples were characterized by scanning electron microscopy (SEM) and rheometry. The implants were incubated with human blood mononuclear cells for 24 h, with surface rinsing in the ATS treatment. Cell viability was determined by colorimetric methods and cytokines in the culture supernatant were quantified using flow cytometry. In the ATS group, the surface porosity and contact surface were increased and plaques were observed on the surface. The blood flow and viscosity curves were similar among the treatments, and the high cell viability rates indicate the biocompatibility of the materials used. An increase in the levels of IL-2, IL-4, IL-6, IL-10 and TNF-α was observed in the ATS and CS groups. There were positive correlations between IL-10 and IL-2 levels and between IL-10 and IL-4 levels in the culture supernatant of the ATS group. The results suggest that implant surface treatment with phosphoric acid activates the production of inflammatory cytokines. The increased cytokine levels can modulate the immune response, thereby improving biofunctional processes and promoting the success of dental implants.

Antibacterial, chemical and physical properties of sealants with polyhexamethylene guanidine hydrochloride

Abstract The aim of this study was to evaluate the influence of polyhexamethylene guanidine hydrochloride (PHMGH) in the physico-chemical properties and antibacterial activity of an experimental resin sealant. An experimental resin sealant was formulated with 60 wt.% of bisphenol A glycol dimethacrylate and 40 wt.% of triethylene glycol dimethacrylate with a photoinitiator/co-initiator system. PHMGH was added at 0.5 (G0.5%), 1 (G1%), and 2 (G2%) wt.% and one group remained without PHMGH, used as control (GCTRL). The resin sealants were analyzed for degree of conversion (DC), Knoop hardness (KHN), and softening in solvent (ΔKHN), ultimate tensile strength (UTS), contact angle (θ) with water or α-bromonaphthalene, surface free energy (SFE), and antibacterial activity against Streptococcus mutans for biofilm formation and planktonic bacteria. There was no significant difference for DC (p > 0.05). The initial Knoop hardness ranged from 17.30 (±0.50) to 19.50 (± 0.45), with lower value for GCTRL (p < 0.05). All groups presented lower KHN after immersion in solvent (p < 0.05). The ΔKHN ranged from 47.22 (± 4.30) to 57.22 (± 5.42)%, without significant difference (p > 0.05). The UTS ranged from 54.72 (± 11.05) MPa to 60.46 (± 6.50) MPa, with lower value for G2% (p < 0.05). PHMGH groups presented no significant difference compared to GCTRL in θ (p > 0.05). G2% showed no difference in SFE compared to GCTRL (p > 0.05). The groups with PHMGH presented antibacterial activity against biofilm and planktonic bacteria, with higher antibacterial activity for higher PHMGH incorporation (p < 0.05). PHMGH provided antibacterial activity for all resin sealant groups and the addition up to 1 wt.% showed reliable physico-chemical properties, maintaining the caries-protective effect of the resin sealant over time.

Mineral trioxide aggregate enriched with iron disulfide nanostructures: an evaluation of their physical and biological properties.

The purpose of this study was to characterize mineral trioxide aggregates (MTA) enriched with iron disulfide (FeS2 ) nanostructures at different concentrations, and to investigate their storage modulus, radiopacity, setting time, pH, cytotoxicity, and antimicrobial activity. Iron disulfide nanostructures [with particle size of 0.357 ± 0.156 µm (mean ± SD)] at weight ratios of 0.2, 0.4, 0.6, 0.8, and 1.0 wt% were added to white MTA (wMTA). The radiopacity, rheological properties, setting time, and pH, as well as the cytotoxicity (assessed using the MTT assay) and antibacterial activity (assessed using the broth microdilution test) were determined for MTA/FeS2 nanostructures. The nanostructures did not modify the radiopacity values of wMTA (~6 mm of aluminium); however, they reduced the setting time from 18.2 ± 3.20 min to 13.7 ± 1.8 min, and the storage modulus was indicative of a good stiffness. Whereas the wMTA/FeS2 nanostructures did not induce cytotoxicity when in contact with human pulp cells (HPCs) and human gingival fibroblasts (HGFs), they showed bacteriostatic activity against Staphylococcus aureus, Escherichia coli, and Enterococcus faecalis. Adding FeS2 nanostructures to MTA might be an option for improving the root canal sealing and antibacterial effects of wMTA in endodontic treatments.

Biomaterials in temporomandibular joint replacement: current status and future perspectives-a narrative review.

The alloplastic total temporomandibular joint (TMJ) prosthesis has a long history, with many different materials and designs used. While several of these materials have proven valuable over time, many others have not been suitable for implantation, resulting in failure and the need for explantation of the implant. Because of the failure of several of these systems, the use of alloplastic prostheses has reduced dramatically, despite their advantages over autogenous restoration. The aim of this narrative review is to discuss the criteria that must be met by a biomaterial in order for it to be considered suitable for implantation, as well as the common complications that can occur. Currently used materials are highlighted, as well as potential future materials that might prove better suitable for implantation. Several surface modification techniques are proposed as an alternative to the materials used in current TMJ prosthesis systems.

Bioactivity of NANOZR Induced by Alkali Treatment.

In recent years, zirconia has been a recognized implant material in clinical dentistry. In the present study, we investigated the performance of an alkali-modified ceria-stabilized tetragonal ZrO2 polycrystalline ceramic-based nanostructured zirconia/alumina composite (NANOZR) implant by assessing surface morphology and composition, wettability, bovine serum albumin adsorption rate, rat bone marrow (RBM) cell attachment, and capacity for inducing bone differentiation. NANOZR surfaces without and with alkali treatment served as the control and test groups, respectively. RBM cells were seeded in a microplate with the implant and cultured in osteogenic differentiation medium, and their differentiation was evaluated by measuring alkaline phosphatase (ALP) activity, osteocalcin (OCN) production, calcium deposition, and osteogenic gene expression. The alkali-treated NANOZR surface increased ALP activity, OCN production, calcium deposition, and osteogenesis-related gene expression in attached RBM cells. These data suggest that alkali treatment enhances the osteogenesis-inducing capacity of NANOZR implants and may therefore improve their biointegration into alveolar bone.

Evaluation of candida albicans biofilm formation on various dental restorative material surfaces.

AIMS: Candida adhesion to any oral substrata is the first and essential stage in forming a pathogenic fungal biofilm. In general, yeast cells have remarkable potential to adhere to host surfaces, such as teeth or mucosa, and to artificial, nonbiological surfaces, such as restorative dental materials. This study compared the susceptibility of six dental restorative materials to Candida albicans adhesion. MATERIALS AND METHODS: Cylindrical samples of each material were made according to the manufacturersa instructions. The antifungal effect of the samples on C. albicans was determined with the disc-diffusion method. The samples were put in plates with sterile Mueller Hinton and Sabouraud dextrose agar previously seeded with C. albicans. After the incubation period, the inhibition zone around each sample was evaluated. To evaluate the biofilm formation, the XTT technique and scanning electron microscopy (SEM) were used. RESULTS: No inhibition zone was observed around the samples. According to the XTT assays, the amalgam samples revealed the lowest quantity of biofilm formation (P > 0.001). The highest median XTT values, significantly higher than the other materials (P < 0.001), were found for the composite and the compomer samples. Within the SEM examination, the amount of candidal growth was significantly lower on the resin-modified glass ionomer and glass-ionomer cement samples. The compomer and the composite samples showed more candidal adhesion. CONCLUSION: This finding emphasizes the use of glass ionomer restorative cements and amalgam to reduce C. albicans adhesion to dental restorative materials especially in people with weakened immune systems, neutropenia, and cancer.

General Toxicity and Antifungal Activity of a New Dental Gel with Essential Oil from Abies Sibirica L.

BACKGROUND The aim of this study was to analyze the antifungal activity and the general toxicity of a new dental gel containing essential oil from the tree Abies sibirica L., which grows in the Republic of Kazakhstan. MATERIAL AND METHODS The essential oil from Abies sibirica L. was obtained by microwave heating method using the STARTE Microwave Extraction System. Adjutants used to prepare the oil were carbomer 974P, glycerin, polysorbate 80, xylitol, triethanolamine, and purified water, all allowed for medical usage. The antifungal activity of the essential oil was assessed by monitoring the optical density of Candida albicans in a microplate reader. The safety was determined by analyzing the acute and subacute toxicity. RESULTS The essential oil obtained by the microwave heating method revealed a higher antifungal activity in comparison with the essential oil obtained by the steam distillation method. No obvious changes were detected in guinea pigs following cutaneous application of the gel. Enteral administration of the essential oil caused minimal functional and histological changes in mice after 4 weeks. The new harmless dental gel containing pine oil from Abies sibirica L. was provided for the purposes of this particular clinical research. CONCLUSIONS The high antifungal activity of the gel is the basis for more in-depth studies on its safety and pharmacological activity.

Peri-implant soft tissue analyses comparing Ti and ZrO2 abutments: an animal study on beagle dogs.

OBJECTIVE: The aim of this study was to evaluate the soft tissue histomorphometric composition around implant abutments comparing two different materials, titanium (Ti) and zirconia (ZrO2 ). MATERIAL AND METHODS: Twelve implants were placed at bone level in the mandible of six beagle dogs (one in each side). At the same day of surgery one titanium abutment was screwed to the implant in one side (control group) and a zirconia abutment was screwed in the contralateral side. Nine months after implant/abutments placement, animals were sacrificed for histological analysis. Descriptive analysis was calculated for each variable and Wilcoxon test was applied to evaluate histomorphometric variables. RESULTS: At the end of the study the soft tissue dimension at Ti and ZrO2 were similar in all counterparts: biological width, the length of the barrier epithelium, length of the connective tissue, and the percentage of collagen fibers density. However, the percentage of blood vessels was higher for the Ti in comparison to ZrO2 (5.11% ± 1.70 and 2.23% ± 0.98, respectively [P = 0.016]). CONCLUSIONS: Peri-implant soft tissue histomorphology composition was similar in implant abutments made of ZrO2 and titanium after 9 months of healing.

Synthesis, characterization, biocompatibility of hydroxyapatite-natural polymers nanocomposites for dentistry applications.

Hydroxyapatite (HA), the main mineral component of bones and teeth, was synthesized by using the reaction between calcium nitrate tetrahydrate Ca(NO3)2∙4H2O and diammonium hydrogen phosphate (NH4)2HPO4 (DAHP) with a chemical precipitation method. The objective of this study is to utilize novel inorganic-organic nanocomposites for biomedical applications. HA is an inorganic component (75% w) and chitosan, alginate and albumin (Egg white) are organic components of nanocomposites (25% w). Nanocomposites were prepared in deionized water solutions, at room temperature, using a mechanical and magnetic stirrer for 48 h. The microstructure and morphology of sintered n-HAP were tested at different preheating temperature and laser sintering speed with scanning electron microscopy (SEM), X-ray diffraction (XRD) and Fourier transform infrared spectroscopy (FT-IR).

Short-segment posterior instrumentation combined with calcium sulfate cement vertebroplasty for thoracolumbar compression fractures: radiographic outcomes including nonunion and other complications.

OBJECTIVE: To evaluate the radiographic outcomes of short-segment posterior instrumentation plus vertebroplasty using injectable calcium sulfate cement (CSC) for thoracolumbar compression fractures. MATERIALS AND METHODS: Twenty-eight patients with a single-level thoracolumbar compression fracture, who underwent short-segment pedicle screw fixation and CSC vertebroplasty, were included in the study. The anterior vertebral body height ratio, local kyphosis angle, and the height of the intervertebral disc adjacent to the fractured vertebra were used to evaluate the radiographic results. Complications including bone nonunion, instrument failure, cement leakage, and disc vacuum formation were also assessed. RESULTS: The patients were followed up for an average of 24.20±5.40 months. The relative preoperative anterior body height was 55.71±15.29%, which improved to 94.93±5.39% immediately after surgery (P<0.001), and at final follow-up showed a 6.50±3.89% loss of height correction (P<0.001). The mean preoperative local kyphosis angle was 22.23±5.65°, which corrected to 2.67±4.43° immediately after surgery (P<0.001), but reverted to 6.71±4.95° at final follow-up, showing a 4.04±1.91° loss of correction (P<0.001). The mean height of the intervertebral disc proximal to the fractured vertebra was 9.87±0.91 mm before surgery, 12.53±0.98 mm after operation (P<0.001), and the loss of correction at final follow-up was 2.35±1.15 mm with a significant difference compared to immediate postoperative values (P<0.001). Bone nonunion occurred in 7 patients, 2 patients had hardware failure, 9 patients had cement leakage, and 10 patients had disc vacuum phenomenon adjacent to the fractured vertebra. CONCLUSIONS: The patients who underwent this procedure had a loss of correction of vertebral height and local kyphosis. Complications such as bone nonunion, instrument failure, cement leakage, and disc vacuum may occur. Rapid CSC resorption accounts for these radiographic outcomes and complications. LEVEL OF EVIDENCE: Level IV, retrospective study.

Effective dentin restorative material based on phosphate-terminated dendrimer as artificial protein.

In clinic, it calls for effective and simple materials to repair etched dentin. Bioinspired by the natural mineralization process guided by noncollagenous proteins (NCPs), in this work, we synthesized the fourth generation phosphate-terminated polyamidoamine dendrimer (G4-PO3H2) by one-step modification. We used FT-IR and 1H NMR to characterize the structure of G4-PO3H2, and MTT assay to prove its biocompatibility. It was applied as the analog of dentin phosphophoryn (DPP: a type of NCPs) to repair dentin, due to its similar dimensional scale, topological architecture and peripheral functionalities to that of DPP. By the characterization of SEM and XRD, the effective regeneration of human dentin induced by G4-PO3H2 is characterized and illustrated both in vitro (artificial saliva) and in vivo (oral cavity of rats). It is noted that the thickness of the regenerated mineral layers are more than 10 µm both in vitro and in vivo. The design strategy of G4-PO3H2 may be valuable for researchers in the fields of material science, stomatology and medicine to prepare various promising restorative nano-materials for biomineralized hard tissues such as bone and teeth.

Resin monomers act as adjuvants in Ni-induced allergic dermatitis in vivo.

Resin monomers (RMs) are inflammatory agents and are thought to cause allergic contact dermatitis (ACD). However, mouse models are lacking, possibly because of the weak antigenicities of RMs. We previously reported that inflammatory substances can promote the allergic dermatitis (AD) induced by intradermally injected nickel (Ni-AD) in mice. Here, we examined the effects of RMs on Ni-AD. To sensitize mice to Ni, a mixture containing non-toxic concentrations of NiCl2 and an RM [either methyl methacrylate (MMA) or 2-hydroxyethyl methacrylate (HEMA)] was injected intraperitoneally or into ear-pinnae intradermally. Ten days later, a mixture containing various concentrations of NiCl2 and/or an RM was intradermally injected into ear-pinnae, and ear-swelling was measured. In adoptive transfer experiments, spleen cells from sensitized mice were transferred intravenously into non-sensitized recipients, and 24 h later NiCl2 was challenged to ear-pinnae. Whether injected intraperitoneally or intradermally, RM plus NiCl2 mixtures were effective in sensitizing mice to Ni. AD-inducing Ni concentrations were greatly reduced in the presence of MMA or HEMA (at the sensitization step from 10 mM to 5 or 50 µM, respectively, and at the elicitation step from 10 µM to 10 or 100 nM, respectively). These effects of RMs were weaker in IL-1-knockout mice and in macrophage-depleted mice. Cell-transfer experiments in IL-1-knockout mice indicated that both the sensitization and elicitation steps depended on IL-1. Challenge with an RM alone did not induce allergic ear-swelling in mice given the same RM + NiCl2 10 days before the challenge. These results suggest that RMs act as adjuvants, not as antigens, to promote Ni-AD by reducing the AD-inducing concentration of Ni, and that IL-1 and macrophages are critically important for the adjuvant effects. We speculate that what were previously thought of as "RM-ACD" might include ACD caused by antigens other than RMs that have undergone promotion by the adjuvant effects of RMs.

Experimental titanium alloys for dental applications.

STATEMENT OF PROBLEM: Although the use of titanium has increased, casting difficulties limit routine use. PURPOSE: The purpose of the present study was to compare the mechanical properties and biocompatibility of the experimental titanium alloys titanium-5-zirconium, titanium-5-tantalum, and titanium-5-tantalum-5-zirconium (in wt%) with those of commercially pure titanium. MATERIAL AND METHODS: Specimens of titanium alloys and commercially pure titanium were cast by using plasma. Their modulus of elasticity and ultimate tensile strength were determined in a universal testing machine. Biocompatibility was evaluated with SCC9 cells. In periods of 1, 4, 7, 10, and 14 days, cell proliferation was evaluated by the (3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide) tetrazolium reduction assay, and cell viability was evaluated in the 7-day period. Cell morphology was evaluated at 2, 12, and 24 hours. Modulus of elasticity, ultimate tensile strength, and cell viability were analyzed by 1-way ANOVA and the Bonferroni test; cell proliferation data were compared by 2-way ANOVA (alloy versus time) and by the Bonferroni test; and the cell morphology data were analyzed by split-plot design. All statistical tests were performed at the 95% confidence level (P<.05). RESULTS: Titanium-5-tantalum presented the lowest modulus of elasticity and ultimate tensile strength, whereas titanium-5-zirconium and titanium-5-tantalum-5-zirconium were statistically similar to commercially pure titanium. Cell proliferation and viability were not affected by any alloy being similar to those observed for commercially pure titanium. No noticeably differences were found in the morphology of cells cultured on any alloy and commercially pure titanium. CONCLUSION: Experimental alloys, especially titanium-5-zirconium and titanium-5-tantalum-5-zirconium, presented promising mechanical results for future studies and clinical applications. In addition, these alloys, evaluated by cell proliferation, viability, and morphology, were found to be biocompatible in vitro.

Telechelic poly(2-oxazoline)s with a biocidal and a polymerizable terminal as collagenase inhibiting additive for long-term active antimicrobial dental materials.

Dental repair materials face the problem that the dentin below the composite fillings is actively decomposed by secondary caries and extracellular proteases. To address this problem, poly(2-methyloxazoline) with a biocidal and a polymerizable terminal was explored as additive for a commercial dental adhesive. 2.5 wt% of the additive rendered the adhesive contact-active against Streptococcus mutans and washing with water for 101 d did not diminish this effect. The adhesive with 5 wt% additive kills S. mutans cells in the tubuli of bovine dentin. Further, the additive inhibits bacterial collagenase at 0.5 wt% and reduces activity of MMP-9. Human MMPs bound to dentin are inhibited by 96% in a medium with 5 wt% additive. Moreover, no adverse effect on the enamel/dentine shear bond strength was detected.