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Schematic drawing of theoretic mechanism of dentin sensitivity. Fluid movement as proposed in hydrodynamic theory.
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... mechanism of eliciting pain in this case is due to fluid flow through the dentinal tubules "hydrodynamic hypothesis."; this disturbance results in the activation of nociceptors in the inner dentin and peripheral pulp ( Figure 6) [37]. If the thickness of the residual dental tissue is thin, it may also cause enamel fracture (Figure 7) when this latter is not sufficiently supported by the dentin [38]. ...
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... The protocol validation was performed by the analysis of reference sample by GFAAS and FAAS (three replicates were realized). The comparison of the values determined with the methodology applied with the certified values of reference samples showed low standard deviations and good accuracy [13]. The application of t-student test shows that the null hypothesis H0 in all cases can be accepted since calculated t is lower than the critical t and measured values are similar to certified values. ...
Fish are an important human food with increasing consumption in
recent decades. Diet is the main route of exposure to heavy metals for
human health. For this reason, many studies have been performed on
the pollution by heavy metals in different species of fish. Our main
objective was to evaluate the pollution by trace metals (Zn, Cu, Pb,
and Cd) in sardine muscles collected from the bay of Boumerdés
(Algeria). Flame atomic absorption spectroscopy (AAS) was used for
the quantification of Cu and Zn. The quantification of Cd and Pb was
achieved by graphite furnace (GF) AAS. The analysis revealed the
presence of metal trace elements in the muscles of species at
concentrations below the thresholds established by national and
international regulations.
... However, after gelation this flow ceases and cannot compensate for stresses created at the tooth-restoration interface. If this stress does not surpass the bond strength of the adhesive, it is manifested clinically as cuspal deflection, which is a commonly occurring biomechanical phenomenon with resin composite restorations [2, 13,14]. ...
... Moreover, the resultant stresses could affect the tooth-restoration interface resulting in debonding or enamel microcracks at the cavity margins; both would result in microleakage with its sequelae of postoperative sensitivity, pulpal irritation and recurrent decay [6,13,15]. ...
Objective: This study was conducted to investigate the efficacy of insert application on the cuspal deflection and microleakage of maxillary bicuspids restored with resin composite restoration. Methods: Sixty sound upper human premolars were selected and divided equally into two groups for cuspal deflection measurement and microleakage assessment. Standardized mesio-occluso-distal (MOD) cavities were prepared. Each group was subdivided according to the type of insert used into equally three subgroups (n = 10); the first group (A0), no insert was applied (resin composite only) (3M Filtek TM Z250 XT), while in the second group (A1); partially polymerized glass fiber post insert (everstick post) was used, while in the third group (A2); fully polymerized glass fiber post insert (rely X TM fiber post) was applied. Cuspal deflection measured at 5 minutes, 60 minutes and after thermocycling and cyclic loading, using universal measuring microscope at 5 x magnification. The microleakage assessed gingivally and occlusally after thermocycling and cyclic loading. Cavities were restored and the inserts were applied between the composite increments. The results were recorded, tabulated and statistically analyzed. Results: The insert application in resin composite restoration produced a statistically significant decrease in cuspal deflection and microleakage both gingivally and occlusally. Conclusion: The problem of cuspal deflection and microleakage in complex cavities prepared in premolars can be greatly controlled by utilizing inserts.
The development of composite materials is subject to the desire to overcome polymerization shrinkage and generated polymerization stress. An indicator characterizing the properties of restorative materials, with specific importance for preventing secondary caries, is the integrity and durability of marginal sealing. It is a reflection of the effects of polymerization shrinkage and generated stress. The present study aimed to evaluate and correlate marginal integrity and micropermeability in second-class cavities restored with three different types of composites, representing different strategies to reduce polymerization shrinkage and stress: nanocomposite, silorane, and bulk-fill composite after a ten-month ageing period. Thirty standardized class ΙΙ cavities were prepared on extracted human molars. Gingival margins were 1 mm apical to the cementoenamel junction. Cavities were randomly divided into three groups, based on the composites used: FiltekUltimate-nanocomposite; Filtek Silorane LS-silorane; SonicFill-bulk-fill composite. All specimens were subjected to thermal cycles after that, dipped in saline for 10-mounds. After ageing, samples were immersed in a 2% methylene blue. Thus prepared, they were covered directly with gold and analyzed on SEM for assessment of marginal seal. When the SEM analysis was completed, the teeth were included into epoxy blocks and cut longitudinally on three slices for each cavity. An assessment of microleakage on stereomicroscope followed. Results were statistically analyzed. For marginal seal evaluation: F.Ultimate and F.Silorane differ statistically with more excellent results than SonicFill for marginal adaptation to the gingival margin, located entirely in the dentin. For microleakage evaluation: F.Ultimate and F.Silorane differ statistically with less microleakage than SonicFill. Based on the results obtained: a strong correlation is found between excellent results for marginal adaptation to the marginal gingival ridge and micropermeability at the direction to the axial wall. We observe a more significant influence of time at the gingival margin of the cavities. There is a significant increase in the presence of marginal fissures (p = 0.001). A significant impact of time (p < 0.000) and of the material (p < 0.000) was found in the analysis of the microleakage.
