Effects of MMP inhibitors incorporated within dental adhesives

Matrix metalloproteinase (MMP) inhibition has been shown to reduce adhesive bond degradation when applied as a pre-conditioner, adding to clinical steps in the placement of adhesives, but their incorporation within dental adhesives has not been fully explored. This study examined the effect of including 2 MMP inhibitors (BB94 and GM6001) within the primers of 3 commercially available adhesives. Fluorometric assay and zymography showed that adhesives with MMP inhibitors had high affinity toward both synthetic fluorogenic FRET peptides (95%) and dentin powder substrates, respectively. The immediate microtensile bond strength was enhanced for 2 types of adhesives following the addition of both inhibitors. However, no changes were detected between the control and the inhibitor groups following 3-month storage. The modified two-step etch-and-rinse and single-step systems showed less Rhodamine B penetration to the "hybrid layer" and to the "adhesive", respectively. The incorporation of BB94 and GM6001 within the primers resulted in the inhibition of dentin MMPs with improved initial bond strength and enhanced sealing ability.     

Effects of different photo-polymerization protocols on resin-dentine μTBS, mechanical properties and cross-link density of a nano-filled resin composite

Objectives

To evaluate the effects of four different light-curing protocols on the microtensile bond strength (μTBS), ultimate tensile strength (UTS), Knoop micro-hardness (KH) and cross-link density (CLD) of a nano-filled resin composite.

Methods

Filtek Supreme XT (3M-ESPE) was used for the entire experiments following four light-curing approaches: ST, standard irradiance; HI, high irradiance; PD, pulse delay; SS, soft start. The specimens were submitted to different storage periods (24 h or 6 months), cut into match-sticks and subsequently submitted to μTBS testing. Hourglass specimens were also prepared for UTS and KH. Cylindrical specimens were prepared for the CLD evaluation after absolute ethanol challenge. The results were statistically analyzed with a two-way ANOVA and Tukey's test (α = 0.05).

Results

For UTS and KH, continuous irradiance (PD and SS) induced statistically higher results (p < 0.05) both after 24 h and 6 months of water storage compared to ST and HI groups. However, a drop in UTS and KH was obtained after 6 months in all groups. The μTBS was not affected by the different light-curing approaches and, no statistical differences (p > 0.05) were observed between 24 h and 6 months storage. The CLD evaluation showed a statistical drop in KH after 24 h of ethanol storage for PD and SS (step-curing protocols) compared to those attained in continuous mode (ST and HI).

Conclusion

The soft-start mode may improve the UTS and KH of nano-filled resin composites without compromising the resin–dentine μTBS. However, both the step-curing protocols may reduce the cross-link density of the composite polymeric network.

Clinical significance

High irradiances photo-polymerization may be adequate for direct aesthetic restorations such as veneers and onlays. Meanwhile, the soft start protocol would seem more appropriate for the photo-polymerization of high c-factors class I and II restorations.     

Insight into motor adaptation to pain from between-leg compensation

Purpose

Although it appears obvious that we change movement behaviors to unload the painful region, non-systematic motor adaptations observed in simple experimental tasks with pain question this theory. We investigated the effect of unilateral pain on performance of a bilateral plantarflexion task. This experimental task clearly allowed for stress on painful tissue to be reduced by modification of load sharing between legs.

Methods

Fourteen participants performed a bilateral plantarflexion at 10, 30, 50 and 70 % of their MVC during 5 conditions (Baseline, Saline-1, Washout-1, Saline-2, Washout-2). For Saline-1 and -2, either isotonic saline (Iso) or hypertonic saline (Pain) was injected into the left soleus.

Results

The force produced by the painful leg was less during Pain than Baseline (range ?52.6 % at 10 % of MVC to ?20.1 % at 70 % of MVC; P < 0.003). This was compensated by more force produced by the non-painful leg (range 18.4 % at 70 % of MVC to 70.2 % at 10 % of MVC; P < 0.001). The reduction in plantarflexion force was not accompanied by a significant decrease in soleus electromyographic activity at 10 and 30 % of MVC. Further, no significant linear relationship was found between changes in soleus electromyographic activity and change in plantarflexion force for the painful leg (with the exception of a weak relationship at 10 % of MVC, i.e., R ² = 0.31).

Conclusion

These results show that when the nervous system is presented with an obvious solution to decrease stress on irritated tissue, this option is selected. However, this was not strongly related to a decrease in soleus (painful muscle) activity level.     

In Vitro Evaluation of Desensitizing Agents Containing Bioactive Scaffolds of Nanofibers on Dentin Remineralization

This study evaluated the effect of the incorporation of bioactive nanofibers in desensitizing agents on dentin permeability. Sixty disks of dentin were randomly distributed in four groups (n = 15). Distribution was based on the desensitizing agents, fluoride varnish and self-etching adhesive, and the presence of nanofibers: C (self-etching adhesive Clearfil SE Bond), CN (Clearfil SE Bond with 1% nanofiber), D (Duraphat varnish), and DN (Duraphat varnish with 1% nanofiber). Dentin permeability was determined using hydraulic conductivity. For a qualitative analysis, confocal laser microscopy and scanning electron microscopy were performed. The C group showed the lowest hydraulic conductance (Lp%) (89.33), while the DN group showed the highest Lp% (116.06). No statistical significance was observed in the Lp% values in all groups after the treatment and 6% citric acid challenge (p > 0.239). In the images, the CN group presented a higher superficial and intratubular deposition. In addition, this group presented a more homogeneous dentin surface and wide occlusion of dentinal tubules than the other treatments. Despite there being no statistical differences among the treatments employed, the images showed that the CN group presented a higher surface and intratubular deposition compared to the other treatments, even after the acid challenge.     

Water uptake of bonding systems applied on root dentin surfaces: a SEM and confocal microscopic study.

OBJECTIVES: Dentin adhesives have been proposed as desensitizing agents to seal exposed root dentin surfaces. Simplified 'one-step' dentin adhesives are highly permeable to water. The authors hypothesized that a lactic acid challenge may increase permeability of simplified adhesives and may induce fast degradation of bonding. This phenomenon adversely affects their durability as long term desensitizing agents. The aim of this in vitro study was to evaluate the ability of four dentin adhesives to seal root dentin surfaces that were exposed to water and lactic acid challenges. METHODS: Four commercially-available dentin adhesives were applied with a small sponge to the root dentin of extracted human molars as de-sensitizing agents. Impression replicas of the adhesive-covered root dentin were fabricated after water immersion, as a control, and after lactic acid challenge. The replicas were examined with SEM for quantitative comparison of fluid droplet formation on the surfaces. The bonded specimens were also examined using reflected light confocal microscopy. RESULTS: Replicas of water droplets were observed on the adhesive surfaces, by SEM which corresponded with direct confocal observation of blisters and voids from the surface of the bonded specimens. There were significantly more water droplets from samples that were subjected to lactic acid challenge than water only immersion. SIGNIFICANCE: Although the dentin adhesives examined were able to cover exposed root dentin, they all exhibited fluid transudation through the polymerized adhesives. Dentin adhesives were also susceptible to surface degradation after lactic acid challenge. As simplified self-etch adhesives were highly water permeable and exhibited the most extensive surface damage, they may not be the best adhesives to be used for long-term dentin desensitization. These preliminary in vitro findings warrant validation in vivo.     

Adenosine deaminase inhibitors: Structure-activity relationships in 1-deazaadenosine and erythro-9-(2-hydroxy-3-nonyl)adenine analogues

Adenosine deaminase (ADA) is the enzyme which catalyzes the irreversible deamination of adenosine and deoxyadenosine to inosine and deoxyinosine, respectively. It is widely distributed in vertebrate tissues and is thought to be essential for proper functioning of mammalian cells. ADA inhibitors may have several clinical applications (i.e., in the chemotherapy of lymphoproliferative disorders, in the immunosuppresive therapy, in adenosine level modulation). Modification of the purine moiety of adenosine led to ADA inhibitors. In particular, 1-deazaadenosine ( 1 , Ki = 0.66 μM) and its 2′-deoxy derivative ( 21 , Ki = 0.19 μM) are the most potent in the series. Substitutions on the N⁶ amino group did not produce a decrease in activity only when small groups, as hydroxyl or methyl, were introduced. The presence of a chlorine atom in position 2 produced a decrease in ADA inhibitory activity. All these findings are in agreement with a direct interaction of the 1-deazapurine moiety with the catalytic site of ADA. Erythro-9-(2-hydroxy-3-nonyl)adenine ( 12 , EHNA) and 3-deazaEHNA ( 14 ) are potent ADA inhibitors with Ki in the nanomolar range. Opening the pyrimidine ring of EHNA led to a series of erythro-1-(2-hydroxy-3-nonyl)imidazole derivatives which are still ADA inhibitors. In order to introduce additional simplification and to investigate the role of nitrogen atoms in the azole structure, a series of di-, tri-, and tetrazoles bearing the 2-hydroxy-3-nonyl chain have been synthesized and tested. The results indicated that the presence of N-3 in the azole ring is critical for the inhibitory activity and that the introduction of additional nitrogens led to compounds whose potency range accounts for a direct interaction with an inhibitory site of ADA. © 1993 Wiley-Liss, Inc.     

The Stress and Migraine Interaction

There are several ways in which stress may interact with migraine in those predisposed to migraine attacks. These interactions may result from biochemical changes related to the physiological stress response, as, for example, the release of corticotrophin releasing hormone, or from changes induced by the psychological response to stressors. Stress is the factor listed most often by migraine sufferers as a trigger for their attacks, but in addition there is evidence that stress can help initiate migraine in those predisposed to the disorder, and may also contribute to migraine chronification. Migraine attacks themselves can act as a stressor, thereby potentially leading to a vicious circle of increasing migraine frequency. Since the important factor in the stress–migraine interaction is likely the individual's responses to stressors, rather than the stressors themselves, the acquisition of effective stress management skills has the potential to reduce the impact of stressors on those with migraine.     

Prospective Merger Between Car-Parrinello and Lattice Boltzmann Methods for Quantum Many-Body Simulations

Formal analogies between the Car-Parrinello (CP) ab-initio molecular dynamics for quantum many-body systems, and the Lattice Boltzmann (LB) method for classical and quantum fluids, are pointed out. A theoretical scenario, whereby the quantum LB would be coupled to the CP framework to speed-up many-body quantum simulations, is also discussed, together with accompanying considerations on the computational efficiency of the prospective CP-LB scheme.