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Made available in DSpace on 2022-04-29T08:39:18Z (GMT). No. of bitstreams: 0 Previous issue date: 2022-02-01 The dentin matrix is a collagenous scaffold structurally involved in anchoring resin-based materials to the tooth. Time-dependent degradation of this scaffold at the resin–dentin interface remains a core problem in adhesive dentistry, limiting the service life of dental fillings. This study explored the use of emergent materials termed metal–organic frameworks (MOFs)─formed by the self-assembly of metal ions and organic building blocks─to safeguard the collagen integrity in the functional dentin matrix. We demonstrate that collagen fibrils (from demineralized human dentin) can induce the biomimetic growth of MOF crystals as protective coatings to strengthen and stabilize the fibrils. Zeolitic imidazolate framework-8 (ZIF-8), a zinc-based microporous MOF, was used to fabricate the MOF composites via a “one-pot” reaction in water. The ZIF-modified dentin matrix presented superior mechanical strength and resistance to proteolysis, which can positively affect the longevity of collagen as an anchoring substrate. This work identifies a potential biomedical application of biomimetically synthesized MOFs in repairing dental tissues critical to restorative therapies. Department of General Dental Sciences School of Dentistry Marquette University Department of Physics School of Sciences São Paulo State University (UNESP) Department of Inorganic Chemistry Institute of Chemistry Sao Paulo State University (UNESP) Department of Physics School of Sciences São Paulo State University (UNESP) Department of Inorganic Chemistry Institute of Chemistry Sao Paulo State University (UNESP)

Made available in DSpace on 2020-12-12T02:22:14Z (GMT). No. of bitstreams: 0 Previous issue date: 2020-08-10 Plant-derived compounds incite applications virtually on every biomedical field due to the expedient antioxidant, anti-inflammatory and antimicrobial properties in conjunction with a natural character. Here, quercetin (QCT), a flavonoid with therapeutic potentials relevant to the oral environment, was encapsulated within metal-organic frameworks (MOFs) to address the concept of on-demand release of phytochemicals at the biointerface. We verified the applicability of a microporous MOF (ZIF-8) as a controlled-release system for QCT, as well as investigated the incorporation of QCT@ZIF-8 microparticles into a dental adhesive resin for desirable therapeutic capabilities at the tooth-restoration interface. QCT was encapsulated within the frameworks through a water-based, one-step synthetic process. The resulting QCT@ZIF-8 microparticles were characterized with respect to chemical composition, crystal structure, thermal behavior, micromorphology, and release profile under acidic and physiological conditions. A model dental adhesive formulation was enriched with the bioactive microparticles; both the degree of conversion (DC) of methacrylic double bonds and the polymer thermal behavior were accounted for. The results confirm that crystalline QCT@ZIF-8 microparticles with attractive loading capacities, submicron sizes, high thermal stability and responsiveness to environmental pH change were successfully manufactured. The concentration of QCT@ZIF-8 in the resin system was a key factor to maintain an optimal DC plateau and rate of polymerization. Essentially, one-step encapsulation of QCT in biocompatible ZIF-8 matrices can be easily achieved, and QCT@ZIF-8 microparticles proved as smart platforms to carry bioactive compounds with potential use to prevent microbial and enzymatic degradation of hard tissues and extracellular matrix components. Department of Physics School of Sciences São Paulo State University (UNESP) Department of Chemistry School of Sciences São Paulo State University (UNESP) Department of Restorative Dentistry College of Dentistry University of Illinois at Chicago (UIC) Dental Research Division Guarulhos University (UNG) Department of Inorganic Chemistry Institute of Chemistry São Paulo State University (UNESP) Department of Physics School of Sciences São Paulo State University (UNESP) Department of Chemistry School of Sciences São Paulo State University (UNESP) Department of Inorganic Chemistry Institute of Chemistry São Paulo State University (UNESP)

Made available in DSpace on 2021-06-25T10:22:27Z (GMT). No. of bitstreams: 0 Previous issue date: 2021-03-15 The use of polymer additives that stabilize fluidic amorphous calcium phosphate is key to obtaining intrafibrillar mineralization of collagen in vitro. On the other hand, this biomimetic approach inhibits the nucleation of mineral crystals in unconfined extrafibrillar spaces, that is, extrafibrillar mineralization. The extrafibrillar mineral content is a significant feature to replicate from hard connective tissues such as bone and dentin as it contributes to the final microarchitecture and mechanical stiffness of the biomineral composite. Herein, we report a straightforward route to produce densely mineralized collagenous composites via a surface-directed process devoid of the aid of polymer additives. Simulated body fluid (1×) is employed as a biomimetic crystallizing medium, following a preloading procedure on the collagen surface to quickly generate the amorphous precursor species required to initiate matrix mineralization. This approach consistently leads to the formation of extrafibrillar bioactive minerals in bulk collagen scaffolds, which may offer an advantage in the production of osteoconductive collagen-apatite materials for tissue engineering and repair purposes. Department of General Dental Sciences Marquette University School of Dentistry Department of Physics School of Sciences São Paulo State University (UNESP) Department of Restorative Dentistry School of Dentistry of Ribeirão Preto University of São Paulo (USP) Department of Physics School of Sciences São Paulo State University (UNESP)

A growing class of multifunctional porous materials termed metal–organic frameworks (MOFs) has attracted attention for immobilization of biomolecules via self-assembly of inorganic and organic building blocks. Herein, we report the rapid formation of MOF shells surrounding collagen-degrading enzymes by using a biomimetic mineralization approach. Bacterial collagenase, which is functionally related to endogenous proteases in the human body, was used as a nucleating agent to induce the mineralization of zeolitic imidazolate framework-8 (ZIF-8) as a crystalline shell. This zinc-based MOF material was selected due to its remarkable stability under physiological conditions and good biocompatibility. The straightforward, water-based synthesis yielded microporous collagenase-embedded ZIF-8 particles. Once immobilized inside the biomimetically mineralized MOF, the protease presented limited catalytic activity, being ineffective in the proteolysis of a collagen-like peptide. In conclusion, biomimetic mineralization of ZIF-8 using collagenase not only provided immobilization of the enzyme, but also enabled the control of its activity. This synthetic approach provides a potentially useful concept in the prevention of proteolytic activity involved in the degradation of collagen matrices in living organisms.

Rhodamine B (RB) is commonly used to evaluate dental polymers, including dental bonding systems (DBS). For reliability assessments, its effect should not only allow visualization of the dentin-polymer interface but also must not interfere with the bonding of the DBS to dentin as measured by the microtensile bond strength and hardness tests.Flat human dentin surfaces were prepared and randomly distributed (n = 10) into six groups: Adper Scotchbond Multi-Purpose (MP) or Clearfil SE Bond (SE) in concentrations of none/control, 0.02 or 0.1 mg/mL. These combinations were prepared through ethanol dissolution to improve their penetration into the dentin. All specimens were fabricated with Filtek Z250 (n = 10) and prepared for a microtensile bond test (μTBS) (0.5 mm/min) after 7 days and 6 months. The failure modes were determined using a stereomicroscope (×40). For the hardness test, flat human dentin blocks were prepared and treated as previously described (n = 6). The specimens were stored at 37 °C/48 h and were tested (Knoop indenter - 25 gF/10 s). Data were analyzed with two-way ANOVA and Tukey tests for multiple comparisons (α = 0.05). The effect of time was evaluated using the Student t-test.For 7-day μTBS, both the DBS and RB concentrations were significant factors (p 0.01). After 6 months, only the RB concentration was significantly different. Adhesive failures were prevalent for all groups. Regarding hardness, the DBS differed only with the use of 0.10 mg/mL of RB.Ethanol-dissolved rhodamine B in concentrations of 0.02 and 0.10 mg/mL in non-simplified adhesives can affect the physical-mechanical properties of functional monomer-based systems rather more than those of BisGMA systems.

Simplified dentin-bonding systems are clinically employed for most adhesive procedures, and they are prone to hydrolytic degradation. Objective This study aimed to investigate the effect of laser diode irradiation on the degree of conversion (DC), water sorption (WS), and water solubility (WSB) of these bonding systems in an attempt to improve their physico-mechanical resistance. Material and Methods Two bonding agents were tested: a two-step total-etch system [Adper™ Single Bond 2, 3M ESPE (SB)] and a universal system [Adper™ Single Bond Universal, 3M ESPE (SU)]. Square-shaped specimens were prepared and assigned into 4 groups (n=5): SB and SU (control groups – no laser irradiation) and SB-L and SU-L [SB and SU laser (L) – irradiated groups]. DC was assessed using Fourier transform infrared spectroscopy with attenuated total reflectance. Additional uncured resin samples (≈3.0 µL, n=5) of each adhesive were also scanned for final DC calculation. For WS/WSB tests, similar specimens (n=10) were prepared and measured by monitoring the mass changes after dehydration/water storage cycles. For both tests, adhesive fluids were dropped into standardized Teflon molds (6.0×6.0×1.0 mm), irradiated with a 970-nm laser diode, and then polymerized with an LED-curing unit (1 W/cm2). Results Laser irradiation immediately before photopolymerization increased the DC (%) of the tested adhesives: SB-L>SB>SU-L>SU. For WS/WSB (μg/mm3), only the dentin bonding system (DBS) was a significant factor (pSU. Conclusion Irradiation with a laser diode improved the degree of conversion of all tested simplified dentin bonding systems, with no impact on water sorption and solubility.

Objective. This article is a brief review about in vitro proposals to overcome the low bond strength values to bleached dental surfaces through a one-year follow-up case report of the immediate replacement of composite resin restorations after enamel bleaching. Clinical considerations. The presence of residual oxygen after bleaching may be responsible for inhibiting the polymerization of the monomers present in the adhesive systems, leading to the failure of the restorative procedure. The use of antioxidants, especially the 10% sodium bicarbonate solution (SB), could be a fast and practical alternative to improve the bond strength of these restorations. In office bleaching with hydrogen peroxide 35% (Lase Peroxide Sense, DMC, Ribeirão Preto, SP, BRA) was performed followed by the removal of the unsatisfactory restorations. Then, the BS was applied and the new adhesive restorations were placed. After one year, the clinical performance of the restorations were successful, showing no signs of failure nor infiltration. Conclusions. The use of the 10% sodium bicarbonate in bleached enamel seems to be a viable alternative for clinical practice.

The technique of enamel microabrasion is considered an aesthetic alternative conservative and effective for stain removal or surface irregularities of the enamel and different materials or pastes can be used for this purpose Objetives: The objective of this study was to compare the efficiency of the technique of enamel microabrasion using two different pastes at removing hypoplastic stains by fluorosis. Methods: The female patient, 18 years, was submitted to enamel microabrasion, and in the right half of the maxilla was manipulated in the proportion of 1:1 by volume a paste of pumice (SSWhite) and 37% phosphoric acid (Etch Alpha, DFL), and in the left half of the maxilla used paste based on hydrochloric acid and 6.6% silicon carbide (Micropol, DMC Equipment Ltd.). In both hemi-arches was performed the same clinical protocol and repeated three times, by the application of 1.0 mm thickness of paste and realized the enamel microabrasion through mechanical friction with rubber cup at low speed for 10 seconds. Then, the teeth were polished with felt disc and diamond paste, and topical fluoride APF 1.23% for 3 minutes was applied. Results: The clinical outcome was similar for both hemi-arches, regardless of the used technique. The success in removing stains on tooth enamel is directly related to a correct diagnosis and accurate indication of microabrasion technique. Conclusions: It can be concluded that the two pastes used in the enamel microabrasion were effective for removing intrinsic stains from fluorosis, with similar results and with the re-establishment of aesthetics of the teeth involved.

Water contributes to the setting reaction of self-adhesive luting cements, however, it can also accelerate their degradation. Objectives: The aim of this study was to compare a self-adhesive resin luting cement to other resin-based and glass-ionomer luting materials with regards to water sorption (WS) and solubility (WSB). The tested null hypothesis was that there is no difference in respect to these properties among the materials. Material and methods: Eight specimens from each group (15 mm x 0.5 mm) were prepared from self-adhesive luting cements Biscem (BC) and RelyX Unicem (R), dual-cure cements Bifix (BF), Allcem (A) and Enforce (E), chemical-cure cements C&B (CB) and Cement Post (CP) and a glass-ionomer luting cement Meron C (M) as the control group. The dual-cure products were light-cured beneath an IPS Empress Esthetic ceramic disk (20 mm x 1.5 mm) and for the chemical reaction materials, a 15 min-interval was respected for removal from the mould. The WS and WSB were respectively calculated as (m2-m3/V) and (m1-m3/V). Mass values of m1, m2 and m3 were determined by cycles of desiccation, water-immersion and a new desiccation. For each property, the data was analyzed by one-criteria ANOVA and Tukey tests (p < 0.05). Results: The glass-ionomer cement presented the highest WS, followed by the self-adhesive luting cements. Other resin cements were less susceptible to WS. No materials differed from each other when the WSB was considered, except for the M, which presented the lowest WSB. Conclusions: Self-adhesive luting cements were more prone to WS since water is essential to their setting reaction. However, their WSB was similar to the other resin-based cements.

Made available in DSpace on 2018-11-26T17:20:50Z (GMT). No. of bitstreams: 0 Previous issue date: 2017-02-01 Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP) Fluorescent dyes like Rhodamine B (RB) have been used to identify the spatial distribution of adhesive restorative materials in the tooth/restoration interface. Potential effects of the addition of RB to dental adhesives were addressed in the past, but no further information is available on how to determine suitable concentrations of RB in these bonding agents for imaging in the confocal laser scanning microscope. This study provides systematical strategies for adding RB to viscous dental adhesive resins, focusing on the determination of the lowest range of dye concentrations necessary to achieve an acceptable image of the dentin/adhesive interface. It was demonstrated that optimized images of the resin distribution in dentin can be produced with 0.1-0.02 mg/mL of RB in the (tested) adhesives. Our approaches took into account aspects related to the dye concentration, photophysical parameters in different host media, specimen composition and morphology to develop a rational use of the fluorescent agent with the resin-based materials. Information gained from this work can help optimize labeling methods using dispersions of low-molecular-weight dyes in different monomer blend systems. Univ Sao Paulo, Bauru Sch Dent, Dept Operat Dent Endodont & Dent Mat, BR-17012901 Bauru, SP, Brazil Univ Estadual Paulista, Inst Chem, Dept Inorgan Chem, BR-14800060 Araraquara, SP, Brazil Univ Sao Paulo, Bauru Sch Dent, Dept Prosthodont, BR-17012901 Bauru, SP, Brazil Univ Sao Paulo, Sch Dent, Dept Operat Dent, BR-05508000 Sao Paulo, SP, Brazil Univ Estadual Paulista, Inst Chem, Dept Inorgan Chem, BR-14800060 Araraquara, SP, Brazil FAPESP: 2011/14971-2 FAPESP: 2012/13160-3 FAPESP: 2013/13161-2

Objective This study investigated the effect of the fluorescent dye rhodamine B (RB) for interfacial micromorphology analysis of dental composite restorations on water sorption/solubility (WS/WSL) and microtensile bond strength to dentin (µTBS) of a 3-step total etch and a 2-step self-etch adhesive system. Material and Methods The adhesives Adper Scotchbond Multi-Purpose (MP) and Clearfil SE Bond (SE) were mixed with 0.1 mg/mL of RB. For the WS/WSL tests, cured resin disks (5.0 mm in diameter x 0.8 mm thick) were prepared and assigned into four groups (n=10): MP, MP-RB, SE, and SE-RB. For µTBS assessment, extracted human third molars (n=40) had the flat occlusal dentin prepared and assigned into the same experimental groups (n=10). After the bonding and restoration procedures, specimens were sectioned in rectangular beams, stored in water and tested after seven days or after 12 months. The failure mode of fractured specimens was qualitatively evaluated under optical microscope (x40). Data from WS/WSL and µTBS were assessed by one-way and three-way ANOVA, respectively, and Tukey’s test (α=5%). Results RB increased the WSL of MP and SE. On the other hand, WS of both MP and SE was not affected by the addition of RB. No significance in µTBS between MP and MP-RB for seven days or one year was observed, whereas for SE a decrease in the µTBS means occurred in both storage times. Conclusions RB should be incorporated into non-simplified DBSs with caution, as it can interfere with their physical-mechanical properties, leading to a possible misinterpretation of bonded interface.

This study evaluated the influence of 2% chlorhexidine digluconate (CHX) on the bond strength (BS) of a glass-fibre post to the root canal, regarding the cements (dual-cured resin or resin-modified glass-ionomer cement), the root thirds and the time of storage.Eighty bovine roots were selected and endodontically treated, before being randomly assigned to the following groups according to the luting protocol: ARC (RelyX ARC); ARC+CHX; RL (RelyX Luting 2); and RL+CHX. After 24 h of luting, the roots were sliced to obtain 1 mm-thick slices. Half of each group was submitted to either 7-day or 6-month storage in artificial saliva (n=10). The specimens were subjected to push-out tests with a crosshead speed of 0.5 mm/min. The data were analysed with four-way ANOVA and Tukey's test (P≤0.05). The failure modes were analysed with a digital microscope (50× and 200×).ARC yielded a significantly higher BS compared to RL (P0.001). Despite CHX exerted a significant effect; it depends on the interaction with the luting cement and time (P0.001). Thus, CHX decreased the values of BS to those of ARC after 6 months (P0.001). On the 7th day of storage, the ARC+CHX presented higher BS to the cervical and middle thirds compared to RL+CHX (P=0.012). Time solely was not a significant factor (P=0.081). Adhesive cement-dentine type and mixed failures were predominant modes for the ARC groups. For the RL groups, the main failures were adhesive cement-post and mixed modes.Glass-fibre posts luted with RelyX ARC dual-cure resin cement exhibited higher BS than those luted with RelyX Luting 2 resin-modified glass-ionomer cement. Furthermore, CHX was not effective to improve the BS and negatively affected the BS of RelyX ARC after 6 months of storage.The use of chlorhexidine solution seems not to improve the bond strength of fibre posts to root canals, disregarding the composition of the luting cement.