The influence of filler load in 3D printing resin-based composites.

OBJECTIVE: To evaluate the influence of the barium glass (BG) filler in 3D printing resin-based composites for restorative structures. METHODS: Experimental 3D printing resin-based composites were formulated with UDMA 70%wt, Bis-EMA 20%wt, and TEGDMA 10%wt. Photoinitiators TPO and DFI (2%wt) were used. BG was incorporated at 40%wt and 50%wt. 0%wt BG was used as negative control and the VarseoSmile Crownplus (Bego) was used as a commercial control. Specimens were printed using a 3D printer. Subsequently, specimens were washed and submitted to post-curing with 405 nm at 60ºC for 2 × 20 min at FormCure (FormLabs). 3D printing resin-based composites were evaluated by flexural strength, degree of conversion, softening in solvent, radiopacity, and cytotoxicity against gingival fibroblasts. Data were statistically analyzed using one-way ANOVA (α = 0.05). RESULTS: No significant differences in flexural strength were showed between BG40% (90.5 ± 5,4 MPa), BG50% (102.0 ± 11.7 MPa) and VA (105.2 ± 11.7 MPa). Addition of 40% and 50% of BG showed no influence in the degree of conversion compared to VA (p > 0.05). All groups showed softening in solvent after immersion in ethanol (p < 0.05). All groups showed more than 1mmAl of radiopacity. BG50% showed significantly higher radiopacity (2.8 ± 0.3 mmAl) than other groups (p < 0,05). Cytotoxicity evaluation showed gingival cell viability higher than 80% for all groups. SIGNIFICANCE: Addition of up to 50%wt of barium glass in experimental 3D printing resin-based composites showed promising results for long-term restorative structures.

In vitro development and optimization of cell-laden injectable bioprinted gelatin methacryloyl (GelMA) microgels mineralized on the nanoscale.

Bone defects may occur in different sizes and shapes due to trauma, infections, and cancer resection. Autografts are still considered the primary treatment choice for bone regeneration. However, they are hard to source and often create donor-site morbidity. Injectable microgels have attracted much attention in tissue engineering and regenerative medicine due to their ability to replace inert implants with a minimally invasive delivery. Here, we developed novel cell-laden bioprinted gelatin methacrylate (GelMA) injectable microgels, with controllable shapes and sizes that can be controllably mineralized on the nanoscale, while stimulating the response of cells embedded within the matrix. The injectable microgels were mineralized using a calcium and phosphate-rich medium that resulted in nanoscale crystalline hydroxyapatite deposition and increased stiffness within the crosslinked matrix of bioprinted GelMA microparticles. Next, we studied the effect of mineralization in osteocytes, a key bone homeostasis regulator. Viability stains showed that osteocytes were maintained at 98 % viability after mineralization with elevated expression of sclerostin in mineralized compared to non-mineralized microgels, showing that mineralization can effectively enhances osteocyte maturation. Based on our findings, bioprinted mineralized GelMA microgels appear to be an efficient material to approximate the bone microarchitecture and composition with desirable control of sample injectability and polymerization. These bone-like bioprinted mineralized biomaterials are exciting platforms for potential minimally invasive translational methods in bone regenerative therapies.

Modulation of blood redox status by the progression of induced apical periodontitis in rats.

This study aimed to investigate if apical periodontitis in different periods changes systemic levels of the antioxidant and pro-oxidant parameters in Wistar rats. Twenty-four rats were randomly allocated into healthy animals, apical periodontitis at 14 days (AP14) and apical periodontitis at 28 days (AP28). The first mandibular molars were accessed in the AP groups, and the pulp chamber was exposed to the oral environment, inducing the apical lesion. After 14 and 28 days, the animals were anesthetized, euthanized, and hemimandibles were collected for micro-computed tomography (micro-CT) analysis to measure lesion volume, bone volume (BV), percent of bone to total tissue volume (BV/TV), trabecular thickness (Tb.Th), trabecular number (Tb.N), and trabecular space (Tb.Sp). A histological examination of the remaining bone was also performed. Finally, blood samples were collected for oxidative biochemistry analysis, investigating glutathione (GSH), Trolox equivalent antioxidant capacity (TEAC), and lipid peroxidation (TBARS). The lesion volume was greater at 28 than at 14 days, as shown by micro-CT. AP14 and AP28 had decreased BV and Tb.Th, but only AP28 showed a reduction in BV/TV. Tb.N and Tb. Sp were increased in apical periodontitis at 28 days. In the histopathological analysis, AP14 had focal regions of moderate mononuclear inflammatory infiltrate, and AP28 had an intense inflammatory infiltrate with bacterial colonies. In the biochemical evaluation, GSH, TEAC, and TBARS were increased after 14 days. However, GSH returned to control levels, TEAC was similar to AP14, and TBARS increased significantly after 28 days. Therefore, the oxidative biochemistry response was modulated according to the progression of periapical damage. After 14 days, the organism could still react to the injury. However, at 28 days, the antioxidant response decreased, associated with an increase in TBARS.

Niobium-containing bioactive glasses modulate alkaline phosphatase activity during bone repair.

This study aimed to evaluate the pre-clinical behavior of niobium-containing bioactive glasses (BAGNb) by their ability to promote bone repair and regulate alkaline phosphatase (ALP) levels in an animal model. BAGNbs were produced as powders and as scaffolds and surgically implanted in the femur of male rats (Wistar lineage n = 10). Glasses without Nb (BAG) were produced and implanted as well. The Autogenous Bone (AB) was used as a control. After 15, 30, and 60 days of surgical implantation, blood serum samples were collected to quantify ALP activity, and femurs were removed to assess bone repair. Bone samples were histologically processed and stained with H&E to quantify the % new bone into defects. No postoperative complications were identified. Early-stage repair (15 days) resulted in increased ALP activity for all groups, with increased values ​​for powdered BAGNb. The maturation of the new bone led to a reduction in serum ALP levels. Histological sections showed the formation of immature bone tissue and vascularization with the progression of bone deposition to mature and functional tissue over time. BAG powder showed less new bone formation in 15 days, while the analysis at 30 and 60 days showed no difference between groups (p > .05). Niobium-containing bioactive glasses safely and successfully induced bone repair in vivo. The modulation of ALP activity may be a pathway to describe the ability of niobium-containing materials to contribute to new bone formation.

Antibacterial Effect of Triazine in Barrier Membranes with Therapeutic Activity for Guided Bone Regeneration.

Objective: This study aimed to develop polymer-based barrier membranes based on poly(butylene-adipate-co-terephthalate) (PBAT) with the addition of 1,3,5-triacriloilhexahydro-1,3,5-triazine (TAT). Materials and Methods: Polymeric solutions were used to produce membranes with 5 wt% and 10 wt% of TAT by solvent casting. Membranes without the addition of TAT were used as controls. The membranes were chemically characterized by Fourier transform infrared spectroscopy (FTIR) and thermogravimetry (TGA); surface properties were assessed by profilometry and contact angle; the mechanical behavior was evaluated by a tensile test, and the biological properties were assessed by direct−indirect cell viability and antibacterial activity by S. mutans and S. aureus colony-forming units. Results: TAT was detected in the FTIR and TGA analyses and modified the top surface of the membranes, increasing their roughness and wetness in both concentrations compared to the control group (p < 0.05). The addition of TAT, regardless of concentration, reduced the tensile strength and increased membrane stiffness (p < 0.05). The cell viability of 5 wt% TAT and 10 wt% TAT was 86.37% and 82.36%, respectively. All tested concentrations reduced the formation of biofilm on the membranes when compared to the control. Conclusion: The addition of TAT successfully resulted in the antimicrobial ability of PBAT-based barrier membranes, while it maintained acceptable levels of cell viability in membranes with adequate handling and surface properties.

Non-thermal plasma for surface treatment of inorganic fillers added to resin-based cements.

OBJECTIVES: This study aims to evaluate the effect of non-thermal plasma (NTP) surface treatment in two composite inorganic fillers and evaluate their impact on the chemical-mechanical properties and bond strength ability of experimental resin cements. MATERIALS AND METHODS: Ytterbium fluoride (YF) and barium silicate glass (BS) were characterized and submitted to different surface treatments: non-thermal plasma (NTP); non-thermal plasma and 3-(trimethoxysilyl) propyl methacrylate silanization; and 3-(trimethoxysilyl) propyl methacrylate silanization. Untreated fillers were used as a control. The fillers were incorporated at 65wt% concentration into light-cured experimental resin cements (50wt% BisGMA; 25wt% UDMA; 25wt% TEGDMA; 1mol% CQ). The degree of conversion, the flexural strength, and the microshear bond strength (µSBS) were evaluated to characterize developed composites. RESULTS: YF and BS were successfully cleaned with NTP treatment. Nor NTP neither the silanization affected the degree of conversion of resin cements. The NTP predicted an increase in YF-containing resin cements flexural strength, reducing the storage impact in these materials. NTP treatment did not affect the µSBS when applied to YF, while silanization was effective for BS-containing materials. CONCLUSION: NTP treatment of inorganic particles was possible and was shown to reduce the amount of organic contamination of the particle surface. YF surface treatment with NTP can be an alternative to improve the organic/inorganic interaction in resin composites to obtain materials with better mechanical properties. CLINICAL RELEVANCE: Surface cleaning with NTP may be an alternative for particle surface cleaning to enhance organic-inorganic interaction in dental composites resulting in improved mechanical strength of experimental resin cements.

Niobium silicate as a filler for an experimental photopolymerizable luting agent.

PURPOSE: To synthesize niobium silicate particles (SiNb) and incorporate into resin-based luting agents. METHODS: SiNb particles were synthesized and characterized by x-ray diffraction, FTIR spectroscopy, particle size, and specific surface area. Luting agents were formulated with 50 wt% BisGMA, 30 wt% TEGDMA and 20 wt% UDMA. BAPO was used as a photoinitiator in 1mol%. The SiNb particles were incorporated into the agents at concentrations of 50 wt% (SiNb50%) or 65% wt% (SiNb65%). Barium glass particles at the same concentrations were used as controls (SiBa50% and SiBa65%). Refractive index, degree of conversion (DC), polymerization kinetics, softening in solvent, radiopacity, film thickness, color stability, flexural strength (FS) and micro shear bond strength (µSBS) were evaluated. RESULTS: SiNb particles were successfully synthesized with an adequate structure to be applied as inorganic fillers. SiNb groups had higher DC, lower %ΔKHN, greater film thickness and greater radiopacity than the SiBa groups. Color stability was greater for SiNb50% and SiNb65% after six months of storage, as demonstrated by ΔE00. ΔWID values were lower for the SiBa groups. FS results decreased over time, and lower values were found for SiNb. In µSBS, the values of SiNb65% were higher at 24 h (45.22 MPa) and at six months (36.83 MPa), with statistically differences from values for the SiBa groups. CONCLUSIONS: SiNb particles were successfully synthesized using the sol-gel method, and their incorporation into luting agents at a concentration of up to 65% improved the physicomechanical characteristics and color stability of these agents.

Prolonged caffeine intake decreases alveolar bone damage induced by binge-like ethanol consumption in adolescent female rats.

Ethanol consumption has been reported to negatively impact on periodontal disease. In particular, oral cavity disorders occur upon ethanol exposure during adolescence, a life period associated with particular patterns of short and intense ('binge-like') ethanol consumption that is most deleterious to oral health. The hazardous central effects of ethanol have been linked to the overfunction of adenosine receptors, which are antagonized by caffeine, a bioactive substance present in numerous natural nutrients, which can also modify bone metabolism. The aim of this study was to investigate the effects of caffeine on alveolar bone damage induced by an ethanol binge drinking paradigm during adolescence. Female Wistar rats (35 days old; n = 30) were allocated to six groups: control (vehicle), ethanol (3 g/kg/day; 3 days On-4 days Off challenge), caffeine (10 mg/kg/day), caffeine plus ethanol, SCH58261 (0.1 mg/kg/day, an antagonist of A2A receptors), and SCH58261 plus ethanol. Bone micromorphology and vertical bone loss were analyzed by computed microtomography. Our data showed that ethanol binge drinking reduced alveolar bone quality, with repercussion on alveolar bone size. This ethanol-induced alveolar bone deterioration was abrogated upon treatment with caffeine, but not with SCH58261. This shows that caffeine prevented the periodontal disorder caused by ethanol binge drinking during adolescence, an effect that was not mediated by adenosine A2A receptor blockade.

Evaluation of the Physicochemical and Antibacterial Properties of Experimental Adhesives Doped with Lithium Niobate.

The aim of the present study was to formulate dental adhesives with different concentrations of LiNbO3 and to evaluate their physicochemical and antibacterial properties. A dental adhesive was formulated using methacrylate monomers and photoinitiators and used as a control filler-free group. Subsequently, three experimental adhesives doped with LiNbO3 at different concentrations (1 wt.%, 2 wt.%, and 5 wt.%) were also formulated. All the experimental adhesives were assessed to evaluate the degree of conversion (DC), softening in solvent, immediate and long-term microtensile bond-strength (µ-TBS), radiopacity, ultimate tensile strength, and antibacterial activity. The incorporation of 1 wt.% of LiNbO3 had no negative effect on the DC of the adhesive resin compared to the control group (p > 0.05). We observed a decrease in the percentage of softening in solvent in the group LiNbO3 at 1 wt.% (p < 0.05). The addition of LiNbO3 increased the radiopacity at a concentration above 2 wt.%, and there was also an increase in cohesive strength (p < 0.05). The immediate µ-TBS increased for LiNbO3 at 5 wt.% (p < 0.05), and there was no statistical difference for the other groups compared to the control (p > 0.05). After six months, the group with 5 wt.% still presented the highest µ-TBS (p < 0.05). The adhesives showed no antimicrobial activity (p > 0.05). LiNbO3 was successfully incorporated in dental adhesives, increasing the radiopacity and their resistance to degradation. Although LiNbO3 offered no antibacterial properties, the reliability of LiNbO3 incorporation in the adhesive encourages new tests to better investigate the antimicrobial action of LiNbO3 through temperature variation.

Quaternary ammonium compound as antimicrobial agent in resin-based sealants.

OBJECTIVES: The aim of this study was to evaluate the influence of [2-(methacryloyloxy)ethyl] trimethylammonium chloride (METAC) in the physico-chemical properties, antibacterial activity and cytotoxicity of an experimental resin-based sealant. MATERIALS AND METHODS: An experimental resin-based sealant was formulated with dimethacrylates and a photoinitiator system. METAC was added at 2.5 wt.% (G2.5%) and 5 wt.% (G5%) into the experimental resin-based sealant, and one group remained without METAC as control (GCTRL). The resin-based sealants were analysed for polymerization behaviour and degree of conversion (DC), Knoop hardness (KHN) and softening in solvent (ΔKHN), ultimate tensile strength (UTS), contact angle, surface free energy (SFE), immediate and long-term micro-shear bond strength (µ-SBS) and antibacterial activity and cytotoxicity against human keratinocytes. RESULTS: The experimental resin-based sealants presented different polymerization behaviours without significant differences in the DC (p > 0.05). There was no significant difference for initial KHN (p > 0.05). The ΔKHN ranged from 51.62 (±3.70)% to 62.40 (±4.14)%, with higher values for G5% (p < 0.05). G2.5% and G5% had decreased µ-SBS between immediate and long-term tests (p < 0.05) without significant differences among groups in the immediate and long-term analyses (p > 0.05). There were no significant differences for UTS, contact angle and SFE among groups (p > 0.05). G2.5% and G5% presented immediate and long-term antibacterial activity (p < 0.05) without cytotoxicity compared to GCTRL (p > 0.05). CONCLUSION: The addition of METAC provided antibacterial activity to the experimental resin-based sealant. CLINICAL RELEVANCE: METAC is an effective quaternary ammonium compound as an antibacterial agent for resin-based sealants without cytotoxic effects against human keratinocytes.

Boron Nitride Nanotubes as Filler for Resin-Based Dental Sealants.

The aim of this study was to evaluate the influence of boron-nitride nanotubes (BNNTs) on the properties of resin-based light-curing dental sealants (RBSs) when incorporated at different concentration. RBSs were formulated using methacrylate monomers (90 wt.% TEGDMA, 10 wt.% Bis-GMA). BNNTs were added to the resin blend at 0.1 wt.% and 0.2 wt.%. A Control group without filler was also designed. Degree of conversion, ultimate tensile strength, contact angle, surface free energy, surface roughness and color of the RBSs were evaluated for the tested materials. Their cytotoxicity and mineral deposition ability (Bioactivity) were also assessed. A suitable degree of conversion, no effect in mechanical properties and no cytotoxic effect was observed for the experimental materials. Moreover, the surface free energy and the surface roughness decreased with the addition of BNNTs. While the color analysis showed no difference between specimens containing BNNTs and the control group. Mineral deposition occurred in all specimens containing BNNTs after 7d. In conclusion, the incorporation of BNNTs may provide bioactivity to resin-based dental sealants and reduce their surface free energy.

Ionic liquid as antibacterial agent for an experimental orthodontic adhesive.

OBJECTIVE: The aim of this study was to formulate and evaluate experimental orthodontic adhesives with different concentrations of 1-n-butyl-3-methylimidazoilium bis(trifluoromethanesulfonyl)imide (BMIM.NTf2). METHODS: The experimental orthodontic adhesives were formulated with methacrylate monomers, photoinitiators and silica colloidal. The ionic liquid BMIM.NTf2 was synthesized and characterized. BMIM.NTf2 was added at 5 (G5%), 10 (G10%) and 15 (G15%) wt.%. One group contained no BMIM.NTf2 to function as control (GCtrl). The adhesives were evaluated for polymerization kinetics, degree of conversion (DC), Knoop hardness and softening in solvent, ultimate tensile strength (UTS), shear bond strength (SBS), thermogravimetric analysis (TGA), antibacterial activity and cytotoxicity. RESULTS: BMI.NTf2 showed the characteristic chemical peaks. The polymerization kinetics were different among the groups. G10% and G15% showed higher DC (p < 0.05). G5% and GCtrl had no differences for softening in solvent (p > 0.05). There were no differences for UTS (p > 0.05) and SBS (p > 0.05). TGA showed one different peak for G15%. All groups with BMIM.NTf2 showed antibacterial activity compared to GCtrl (p < 0.05) without cytotoxicity (p > 0.05). SIGNIFICANCE: To reduce biofilm formation around brackets and to prevent demineralization at susceptible sites, materials have been developed with antibacterial properties. In this study, a new experimental orthodontic adhesive was formulated with an imidazolium ionic liquid (BMIM.NTf2) as antibacterial agent. The incorporation of 5 wt.% of ionic liquid decreased biofilm formation without affecting the physico-chemical properties and cytotoxicity of an experimental orthodontic resin.

Halloysite nanotubes loaded with alkyl trimethyl ammonium bromide as antibacterial agent for root canal sealers.

OBJECTIVE: This study aimed at evaluating the effects of experimental endodontic sealers containing halloysite nanotubes (HNT) doped with alkyl trimethyl ammonium bromide (ATAB). METHODS: An experimental dual-cure resin sealer was formulated and used as control material. This resin was also filled with ATAB and HNT at different ratios (GATAB:HNT 1:1; 1:2; 2:1) generate three experimental resin sealers. The ATAB:HNT filler was characterized through transmission electron microscopy (TEM). While, the experimental and control sealers were evaluated for degree of conversion, softening ration, radiopacity, flow, film thickness, antibacterial activity for biofilm and planktonic bacteria and cytotoxicity in human pulpal cells. RESULTS: GATAB:HNT (1:1) significantly increased the immediate DC (p < 0.05), although no difference was encountered between the groups after 24 h (p > 0.05). All the experimental cements (ATAB/HNT) showed relatively low initial Knoop hardness (p < 0.05), but with no significant reduction (p > 0.05) after storage in ethanol (softening ratio). The radiopacity of all groups achieved at least 3 mm of aluminum. All groups showed more than 17 mm of flow, with a film thickness lower than 50 µm (ISO 6876:2012). All the experimental ATAB:HNT cements showed antibacterial activity against E. faecalis; the higher the ATAB ratio, the greater the antibacterial activity (p < 0.05). Cell viability was higher than 70% with no significant difference between the groups (p > 0.05). SIGNIFICANCE: The incorporation of ATAB/HNT into the experimental resin sealers induced antibacterial activity against biofilm and planktonic E. faecalis without affecting the pulp cell viability or the chemo-mechanical properties.

Physical and mechanical properties of dual functional cements-an in vitro study.

OBJECTIVES: The aim of this study was to evaluate the physical and mechanical properties of different dual functional cements. MATERIALS AND METHODS: Three dual functional cements (Allcem Core (FGM), Rebilda DC (VOCO), and LuxaCore Z (DMG)), a luting resin cement (Rely X ARC (3 M ESPE)), and a Core Buildup composite resin GrandioSo (VOCO) were used. Flexural strength (n = 10) and film thickness (n = 6) were evaluated according to ISO 4049:2009. Flow (n = 6) was evaluated according to ISO 6876:2001. Degree of conversion (DC) was assessed immediately and 24 h after polymerization (n = 5). For resistance to dislodgment (RD) analysis, bovine teeth were prepared to receive fiber glass posts, and a push-out test (n = 12) was used. RESULTS: Luxacore Z presented lower flexural strength when compared to GrandioSo (p < 0.001). No statistical difference was found between cements for film thickness (p = 0.66). Reduced flow values were found for Allcem Core (p = 0.006). No statistical difference was found for immediate DC for different cements (p > 0.05). After 24 h, DC increased for all groups, except for Luxacore Z (p = 0.054). The RD did not differ from the control Rely X ARC, regardless of the root third (p > 0.05). Luxacore Z showed lower mean values in the apical third compared to the coronal third (p = 0.046). CONCLUSIONS: The dual functional cements (Allcem Core and Rebilda DC) possessed similar physical and mechanical properties of luting resin cement (RelyX ARC) and Core Buildup composite resin (GrandioSo). Hence, they could be used for one-stage post and core buildup restorations. CLINICAL RELEVANCE: The dual functional cements could be used for one-stage post and core buildup restorations since they possess similar physical and mechanical properties of luting resin cements and Core Buildup composite resin.

Influence of the addition of microsphere load amoxicillin in the physical, chemical and biological properties of an experimental endodontic sealer.

AIM: To develop an endodontic sealer with amoxicillin-loaded microsphere and to evaluate its properties. METHODS: Experimental sealer was obtained by mixing 70wt% UDMA, 15wt% GDMA and 15wt% BISEMA. In addition, CQ, DHEPT and PB were incorporated at 1 mol% and 0.01wt% BHT and 10wt% YbF3. Microspheres were produced by drying in spray dryer. Two experimental groups (10 and 15wt% of microspheres) and one control group (without microspheres) were formulated. The sealers were evaluated for the degree of conversion (n=3), degradation in solvent (n=3), drug release profile (n=3), antimicrobial activity (n=3), flow (n=3), film thickness (n=3) and cytotoxicity (n=3). Data were analyzed by ANOVA and Tukey with significance level of 5%. RESULTS: Microespheres presented a mean size of 2.664µm. Immediate degree of conversion ranged from 51.73% to 55.13% and the 24h degree of conversion ranged from 60.79% to 73.80%. Upon solvent degradation 54.44% and 56.21% reduction in hardness were observed for 10% and 15% concentrations respectivelly. The drug release profile showed an average release of 73.76% of the drug in 96h. Significant reduction in antimicrobial activity was observed for 10% concentration after 24h, 48h and 96h compared to control. The flow and film thickness showed values in accordance to the ISO 6876. Cytotoxicity showed high cellular viability. CONCLUSION: The addition of up to 10% of microspheres containing amoxicillin presented antimicrobial activity and did not alter the properties of the experimental endodontic cement. CLINICAL SIGNIFICANCE: Amoxicillin microspheres with its antimicrobial activity in root canal sealers could reduce reintervations in endodontics when persistent bacteria or reinfection takes place in root canal system.