1. Investigación

Objective: Remineralising composites with antibacterial properties may seal the cavity and prevent secondary caries. This study aimed at developing experimental flowable composites containing different concentrations of fluoride-doped calcium phosphate fillers and evaluating their remineralising and antibacterial properties. Methods: Experimental resin-based composites containing different concentrations (0–20 %) of fluoride-doped calcium phosphate fillers (VS10/VS20) were formulated. The release of calcium (Ca), phosphate (PO) and fluoride (F) ions was assessed for 30 days. Remineralisation properties were evaluated through ATR-FTIR and SEM/EDX after storage in simulated body fluid (SBF). The metabolic activity and viability of Streptococcus gordonii was also evaluated through ATP, CFU and live/dead confocal microscopy. The evaluation of specific monomer elution from the experimental composites was conducted using high-performance liquid chromatography (HPLC). Results: The composites containing VS10 showed the highest release of Ca, those containing VS20 released more F over time (p < 0.05), while there was no significant difference in terms of PO ions release between the groups (p > 0.05). A quick 7-day mineral precipitation was observed in the tested composites containing VS10 or VS20 at 10 %; these materials also showed the greatest antibacterial activity (p < 0.05). Moreover, the tested composites containing VS10 presented the lowest elution of monomers (p < 0.05). Conclusions: Innovative composites were developed with low monomers elution, evident antibacterial activity against S. gordonii and important remineralisation properties due to specific ions release. Clinical significance: Novel composites containing fluoride-doped calcium phosphates may be promising to modulate bacteria growth, promote remineralisation and reduce the risk of cytotoxicity related to monomers’ elution.

This study analyse the type of release kinetic of specific monomers from dental resin composites containing various fluoride-doped calcium phosphates. The release behavior of urethane dimethacrylate (UDMA), ethoxylated bisphenol-A dimethacrylate (bis-EMA) and 1.6-hexanediol ethoxylate diacrylate (HEDA) was evaluated over a period of 35 days. Two tailored calcium phosphates doped with different concentrations of fluoride salts (VS10% and VS20%) were prepared and incorporated in the dimethacrylate matrix at various concentrations to generate a range of experimental composites. The release kinetics were characterized using mathematical models such as zero-order, first-order, Peppas and Higuchi models. The results showed that the first-order model best described the release kinetics. UDMA and HEDA exhibited significant differences in release compared to bis-EMA from day 1, while no significant differences were observed between UDMA and HEDA, except on day 35, when UDMA exhibited a higher release rate than HEDA. When comparing the release of each monomer, VS20-R20% had the highest total release percentage, with 3.10 ± 0.25%, whereas the composite VS10-R5% showed the lowest release percentage, with a total of 1.66 ± 0.08%. The release kinetics were influenced by the composition of the resin composites and the presence of calcium fluoride and sodium fluoride in the calcium phosphate played a role in the maximum amounts of monomer released. In conclusion, the release of monomers from the tested resin composites followed a first-order kinetic behaviour, with an initial rapid release that decreased over time. The composition of the resin monomers and the presence of fluoride salts influenced the release kinetics. The VS10-R5% and VS10-R10% resin composites exhibited the lowest total monomer release, suggesting its potential favourable composition with reduced monomer elution. These findings contribute to understanding the release behavior of dental resin composites and provide insights for the development of resin-based bioactive dental materials.

Progesterone (PG) diminishes free radical damage and thus can afford protection against oxidative stress affecting the retina. The therapeutic use of PG is limited because it is a highly hydrophobic steroid hormone with very low solubility in water. This is the main drawback for the therapeutic application of PG at ocular level. The aims of this study were: (i) to analyze if PG causes ocular irritation (ii) to validate a HPLC method to determine PG in ex vivo studies and (iii) to evaluate PG permeation through cornea and sclera. A high performance liquid chromatographic method was developed and validated to detect PG incorporated to β-cyclodextrin using a Waters Sunfire C18 (150 × 4.6 mm) reverse-phase column packed with 5 μm silica particles using a mobile phase consisted of a mixture of acetonitrile (ACN) and pure water 80:20 (v/v), pH 7.4. The limit of detection and the limit of quantification for 50 μL injection of PG were found to be 0.42 and 1.26 μg/mL, respectively. The calibration curve showed excellent linearity over the concentration range (0.5 μg/mL to 100 μg/mL). As proof of concept, ex-vivo experiments to investigate PG permeation through cornea and sclera with vertical diffusion cells were carried out to quantify PG diffusion. Ex vivo experiments demonstrate its applicability to investigate permeation levels of PG from 6.57 ± 0.37 μg/cm2 at cornea and 8.13 ± 0.85 μg/cm2 sclera. In addition, at the end of diffusion studies the amount of PG retained in each tissue was also quantified, and it was 40.87 ± 9.84 μg/cm2 (mean ± SD; n = 6) in cornea and 56.11 ± 16.67 μg/cm2 (mean ± SD; n = 6) in sclera.

Progesterone (PG) affords neuroprotection in degenerative diseases associated to oxidative stress, such as cataracts, age-related macular degeneration, glaucoma, diabetic retinopathy and retinitis pigmentosa. The aim of this project was to develop ocular inserts for delivery of PG to the eye. Different inserts with PG in its composition were formulated and the insert with the best characteristics (59% polyvinyl alcohol, 39% polyvinylpyrrolidone K30 and 2% propylene glycol) was selected for ex vivo studies. Physical characteristics and drug release patterns of the insert were analysed. In vitro diffusion studies revealed a controlled diffusion of progesterone. Ex vivo experiments demonstrated similar trans-corneal and trans-scleral PG diffusion (corneal apparent permeability coefficient 6.46 ± 0.38 × 10-7 cm/s and scleral apparent permeability coefficient 5.87 ± 1.18 × 10- 7 cm/s; mean ± SD; n = 5). However, the amount of PG accumulated in scleras was statistically higher than in corneas (30.07 ± 9.09 μg/cm2 and 15.56 ± 4.36 μg/cm2 respectively). The PG-loaded inserts (55.6 μg/cm2) were thin, translucent, showed no irritancy (HET-CAM test) and were elastic and robust, all suitable properties for its potential use in the treatment of several ocular diseases.

Retinitis pigmentosa (RP) is an inherited eye disorder which triggers a cascade of retinal disorders leading to photoreceptor cell death and for which there is currently no effective treatment. The purpose of this research was to study whether ocular administration of a solution of progesterone (PG) in -cyclodextrins (CD) could delay photoreceptor cell death and counteract the gliosis process in an animal model of RP (rds mice). The possible effect of PG reaching the contralateral eye through the circulatory system was also evaluated. Finally, this research discusses and evaluates the diffusion of the drug from possible topical formulations for ocular administration of PG. A group of rds mice received one drop of a solution of PG in CD every 12 h for 10 days to the left eye, while the right eye was left untreated. Another group of rds mice (control) received the drug vehicle (PBS) on the left eye and, again, the right eye was left untreated. Once the treatment was finished on postnatal day 21, the animals were euthanized and histological immunofluorescence studies (TUNEL, GFAP, and DAPI staining) were carried out. Our results showed that the administration of a solution of PG in CD (CD-PG) as drops significantly decreased cell death and inflammation in the retina of the PG-treated eyes of rds mice. No effect was seen in the contralateral eye from PG that may have entered systemic circulation. In conclusion, CD-PG applied topically as drops to the eye decreases photoreceptor cell death in the early stages of RP, delaying vision loss and decreasing gliosis.

Objective: The study aimed to quantitatively evaluate the elution of methylmethacrylate from CAD-CAM manufactured removable complete dentures (RCDs) using high performance liquid chromatography (HPLC). Methods: Thirty-two RCDs were manufactured following either the CNC-milling (Milled: n=8) or the 3D-printing (n=24) protocols. The 3D-printed dentures were further categorized into three groups based on their postproduction rinsing cycles [Extended wash cycle (EWC), Standard wash cycle (SWC), and SWC with an additional Dur´econ coating (SWC2)]. HPLC was used to evaluate the methylmethacrylate concentrations (MMCs) eluted from the dentures in each group for different time periods (1, 2, 4, 8, and 24 hours). Mean and standard deviations were calculated for the MMCs; data was verified for normal distribution, ANOVA and post hoc tests were applied for statistical analyses (⍺=0.05). Results: The HPLC revealed that all the denture groups recorded some amounts of MMCs, with significant differences [F (3, 31) = 23.646, p<0.0001]. The milled denture group had the highest MMCs at 24 hours when compared to the EWC (p<0.0001), SWC (p=0.001), and SWC2 (p<0.0001) denture groups. SWC had a higher MMC than EWC (p=0.032) and SWC2 (p=0.015). No differences were found in MMCs when comparing EWC and SWC2 (p=0.989). Conclusion: Methylmethacrylate concentrations were significantly lower in 3D-printed RCDs than in milled RCDs when using the resins employed in this study. Furthermore, the MMCs can be further decreased in 3D-printed RCDs when coated with an additional thin protective layer (Dur´econ) by following the manufacturerrecommended rinsing protocol or when an extended isopropanol wash cycle is adopted.

In recent years, the use of 3D printing technologies in orthopedic surgery has markedly increased, as they offer the possibility of printing personalized prostheses. The work presented in this article is a preliminary study of a research project which aims to manufacture customized spacers containing antibiotics for use in joint replacement surgery. The objective of this work was to design and print different 3D constructs to evaluate the use of different materials, their properties after the process of 3D printing, such as resistance, and the release kinetics of drugs from the constructs. Different designs and different materials were analyzed to obtain a 3D construct with suitable properties. Our design takes advantage of the micropores created between the layers of the 3D printed filaments to release the contained drug. Using polylactic acid (PLA) we were able to print cylindrical structures with interconnected micropores and a hollow chamber capable of releasing methylene blue, which was selected as a model drug. The final PLA 3D construct was printed with a 10% infill. The physical and technological characteristics, morphological changes at body temperature and interaction with water were considered to be acceptable. The PLA 3D printed constructs were found to have sufficient strength to withstand a force of 500 kg. The results obtained allow to continue research in this project, with the aim of manufacturing prostheses containing a reservoir of antibiotics or other drugs in their interior for their subsequent controlled release.

Progesterone (PG) may provide protection to the retina during retinitis pigmentosa, but its topical ocular supply is hampered by PG poor aqueous solubility and low ocular bioavailability. The development of e cient topical ocular forms must face up to two relevant challenges: Protective barriers of the eyes and lack of validated ex vivo tests to predict drug permeability. The aims of this study were: (i) To design micelles using Pluronic F68 and Soluplus copolymers to overcome PG solubility and permeability; and (ii) to compare drug di usion through the cornea and sclera of three animal species (rabbit, porcine, and bovine) to investigate interspecies di erences. Micelles of Pluronic F68 (3–4 nm) and Soluplus (52–59 nm) increased PG solubility by one and two orders of magnitude, respectively and exhibited nearly a 100% encapsulation e ciency. Soluplus systems showed in situ gelling capability in contrast to the low viscosity Pluronic F68 micelles. The formulations successfully passed the hen’s egg-chorioallantoic membrane test (HET-CAM) test. PG penetration through rabbit cornea and sclera was faster than through porcine or bovine cornea, although the di erences were also formulation-dependent. Porcine tissues showed intermediate permeability between rabbit and bovine. Soluplus micelles allowed greater PG accumulation in cornea and sclera whereas Pluronic F68 promoted a faster penetration of lower PG doses.

Exposure to sunlight and contact with atmospheric oxygen makes the eye particularly susceptible to oxidative stress, which can potentially produce cellular damage. In physiological conditions, there are several antioxidant defense mechanisms within the eye. Glutathione (GSH) is the most important antioxidant in the eye; GSH deficit has been linked to several ocular pathologies. The aim of this study was to explore the potential for newly developed formulations allowing controlled delivery of antioxidants such as GSH and vitamin C (Vit C) directly to the eye. We have investigated the stability of antioxidants in aqueous solution and assessed ex-vivo the di usion of GSH through two ocular membranes, namely cornea and sclera, either in solution or included in a semisolid insert. We have also carried out the hen’s egg-chlorioallantoic membrane test (HET-CAM) to evaluate the ocular irritancy of the di erent antioxidant solutions. Our results showed that GSH is stable for up to 30 days at 4 C in darkness and it is not an irritant to the eye. The di usion studies revealed that the manufactured formulation, a semisolid insert containing GSH, could deliver this tripeptide directly to the eye in a sustained manner.