Enhancing Stability and Tooth Bleaching Activity of Carbamide Peroxide by Electrospun Nanofibrous Film

Structure and hydration of polyvinylpyrrolidone-hydrogen peroxide

The structure of the commercially important polyvinylpyrrolidone-hydrogen peroxide complex can be understood by reference to the co-crystal structure of a hydrogen peroxide complex and its mixed hydrates of a two-monomer unit model compound, bisVP·2H₂O₂. The mixed hydrates involve selective water substitution into one of the two independent hydrogen peroxide binding sites.

Compromised dental cells viability following teeth-whitening exposure

This study aimed to assess the viability of dental cells following time-dependent carbamide peroxide teeth-whitening treatments using an in-vitro dentin perfusion assay model. 30 teeth were exposed to 5% or 16% CP gel (4 h daily) for 2-weeks. The enamel organic content was measured with thermogravimetry. The time-dependent viability of human dental pulp stem cells (HDPSCs) and gingival fibroblast cells (HGFCs) following either indirect exposure to 3 commercially available concentrations of CP gel using an in-vitro dentin perfusion assay or direct exposure to 5% H₂O₂ were investigated by evaluating change in cell morphology and by hemocytometry. The 5% and 16% CP produced a significantly lower (p < 0.001) enamel protein content (by weight) when compared to the control. The organic content in enamel varied accordingly to the CP treatment: for the 16% and 5% CP treatment groups, a variation of 4.0% and 5.4%, respectively, was observed with no significant difference. The cell viability of HDPSCs decreased exponentially over time for all groups. Within the limitation of this in-vitro study, we conclude that even low concentrations of H₂O₂ and CP result in a deleterious change in enamel protein content and compromise the viability of HGFCs and HDPSCs. These effects should be observed in-vivo.

Biodegradable and Biocompatible 3D Constructs for Dental Applications: Manufacturing Options and Perspectives

Designing 3D constructs with appropriate materials and structural frameworks for complex dental restorative/regenerative procedures has always remained a multi-criteria optimization challenge. In this regard, 3D printing has long been known to be a potent tool for various tissue regenerative applications, however, the preparation of biocompatible, biodegradable, and stable inks is yet to be explored and revolutionized for overall performance improvisation. The review reports the currently employed manufacturing processes for the development of engineered self-supporting, easily processable, and cost-effective 3D constructs with target-specific tuneable mechanics, bioactivity, and degradability aspects in the oral cavity for their potential use in numerous dental applications ranging from soft pulp tissues to hard alveolar bone tissues. A hybrid synergistic approach, comprising of development of multi-layered, structurally stable, composite building blocks with desired physicomechanical performance and bioactivity presents an optimal solution to circumvent the major limitations and develop new-age advanced dental restorations and implants. Further, the review summarizes some manufacturing perspectives which may inspire the readers to design appropriate structures for clinical trials so as to pave the way for their routine applications in dentistry in the near future.

Stability and Influence of Storage Conditions on Nanofibrous Film Containing Tooth Whitening Agent

Carbamide peroxide (CP), a tooth whitening agent, is chemically unstable. The present study explores stability enhancement of CP by loading in a nanofibrous film (CP-F) composed of polyvinyl alcohol/polyvinylpyrrolidone/silica mixture, using an electrospinning technique. Kept at a temperature range of 60–80 °C for 6 h, CP in CP-F showed significantly higher stability than that in a polymer solution and in water, respectively. Degradation of CP in CP-F could be described by the first order kinetics with the predicted half-life by the Arrhenius equation of approximately 6.52 years. Physicochemical properties of CP-F after long-term storage for 12 months at different temperatures and relative humidity (RH) were investigated using scanning electron microscopy, X-ray diffractometry, differential scanning calorimetry, and Fourier transform infrared spectroscopy. It was found that high temperature and high humidity (45 °C/75% RH) could enhance water absorption and destruction of the nanofibrous structure of CP-F. Interestingly, kept at 25 °C/30% RH, the nanofibrous structure of CP-F was not damaged, and exhibited no water absorption. Moreover, the remaining CP, the mechanical properties, and the adhesive properties of CP-F were not significantly changed in this storage condition. It is concluded that the developed CP-F and a suitable storage condition can significantly improve CP stability.

Development of Controlled-Release Carbamide Peroxide Loaded Nanoemulgel for Tooth Bleaching: In Vitro and Ex Vivo Studies

Burst release of carbamide peroxide (CP) from traditional hydrogels causes severe inflammation to periodontal tissues. The present study explores the development of a novel CP nanoemulgel (CP-NG), an oil-in-water nanoemulsion-based gel in which CP was loaded with a view to controlling CP release. CP solid dispersions were prepared, using white soft paraffin or polyvinylpyrrolidone-white soft paraffin mixture as a carrier, prior to formulating nanoemulsions. It was found that carrier type and the ratio of CP to carrier affected drug crystallinity. Nanoemulsions formulated from the optimized CP solid dispersions were used to prepare CP-NG. It was found that the ratio of drug to carrier in CP solid dispersions affected the particle size and zeta potential of the nanoemulsions as well as drug release behavior and tooth bleaching efficacy of CP-NG. Drug release from CP-NG followed a first-order kinetic reaction and the release mechanism was an anomalous transport. Drug release rate decreased with an increase in solid dispersion carriers. CP-NG obtained from the solid dispersion with a 1:1 ratio of CP to the polymer mixture is suitable for sustaining drug release with high tooth bleaching efficacy and without reduction of enamel microhardness. The developed CP-NG is a promising potential tooth bleaching formulation.

Nonsolvent-induced phase separation of poly(3-hydroxybutyrate) and poly(hydroxybutyrate-co-hydroxyvalerate) blend as a facile platform to fabricate versatile nanofiber gels: Aero-, hydro-, and oleogels

We demonstrated a strategy to prepare different types of 3-D nanofibrous polymeric gels, including hydro-, aero-, and oleogels by nonsolvent-induced phase separation (NIPS). NIPS-derived gel monoliths of poly(3-hydroxybutyrate) (PHB) and poly(hydroxybutyrate-co-hydroxyvalerate) (PHBV) blends were converted into hydrogels and aerogels by solvent exchange and freeze-drying, respectively. The high hydrophobicity and porosity of the nanofibrous PHB/PHBV aerogels enabled them to absorb various oils and swell to 20-30 times their own weight. The pseudo-second-order model was successfully used to describe the oil absorption behavior, and the obtained absorption rate constant increased with increasing PHBV content. The oil-swollen aerogels were highly elastic, thereby indicating that NIPS-derived aerogels are an excellent template for the fabrication of oleogels. With an increase in the PHBV ratio, the gels exhibited reduced modulus and collapse strength but increased collapse strain, thereby revealing higher ductility by compression. The rapid separation and re-binding of the liquid phase entrapped in the nanofiber network resulted in the unique thixotropic properties of the hydro- and oleogels. Indomethacin, a hydrophobic model drug, was successfully incorporated into injectable self-healing oleogels containing soybean oil and aerogels. These gels exhibited excellent cytocompatibility, and a better sustained drug release was observed for the oleogels compared to the aerogels.