The purpose of this in vitro study was to evaluate the influence of mechanical load cycling (MLC), which simulated mastication, alone or combined with thermal cycling (TC), on the resin shear bond ...strength (SBS) to zirconia. Two resin cements (Panavia F2.0 and RelyX U200) were bonded (bonding area: 2.38 mm) to air-abraded zirconia (Everest ZS-Ronde). The specimens were subjected to SBS test before and after TC (5000 cycles), MLC (5000 cycles in 37 °C water), TC/MLC, or MLC/TC aging (n = 15). Before SBS test, the mechanical and physical properties of the two resin cements were studied (n = 5). For both resins, unlike TC (p > 0.05), the three MLC-containing aging conditions significantly decreased the SBS values when compared to the non-aged condition (p < 0.05). In the case of MLC-only aging, RelyX U200, with significantly higher hydrophobicity (p = 0.004), showed a significantly higher SBS value than Panavia F2.0 (p = 0.035). The MLC aging-containing groups showed increased occurrence of mixed failure. The application of MLC combined with TC may more closely simulate intraoral conditions.
This study investigated the influence of curing mode (dual- or self-cure) on the surface energy and sorption/solubility of four self-adhesive resin cements (SARCs) and one conventional resin cement. ...The degree of conversion (DC) and surface energy parameters including degree of hydrophilicity (DH) were determined using Fourier transform infrared spectroscopy and contact angle measurements, respectively (
= 5). Sorption and solubility were assessed by mass gain or loss after storage in distilled water or lactic acid for 60 days (
= 5). A linear regression model was used to correlate between the results (%DC vs. DH and %DC/DH vs. sorption/solubility). For all materials, the dual-curing consistently produced significantly higher %DC values than the self-curing (
< 0.05). Significant negative linear regressions were established between the %DC and DH in both curing modes (
< 0.05). Overall, the SARCs showed higher sorption/solubility values, in particular when immersed in lactic acid, than the conventional resin cement. Linear regression revealed that %DC and DH were negatively and positively correlated with the sorption/solubility values, respectively. Dual-curing of SARCs seems to lower the sorption and/or solubility in comparison with self-curing by increased %DC and occasionally decreased hydrophilicity.
Although many techniques are available to assess enamel erosion in vitro, a simple, non-destructive method with sufficient sensitivity for quantifying dental erosion is required. This study ...characterized the bovine dental enamel erosion induced by various acidic beverages in vitro using attenuated total reflection Fourier transform infrared （ATR-FTIR） spectroscopy. Deionized water （control） and 10 acidic beverages were selected to study erosion, and the pH and neutralizable acidity were measured. Bovine anterior teeth （110） were polished with up to 1 200-grit silicon carbide paper to produce flat enamel surfaces, which were then immersed in 20 mL of the beverages for 30 min at 37 ℃. The degree of erosion was evaluated using ATR-FTIR spectroscopy and Vickers＇ microhardness measurements. The spectra obtained were interpreted in two ways that focused on the ~1, ~3 phosphate contour： the ratio of the height amplitude of ~3 P04 to that of/11 P04 （Method 1） and the shift of the v3 P04 peak to a higher wavenumber （Method 2）. The percentage changes in microhardness after the erosion treatments were primarily affected by the pH of the immersion media. Regression analyses revealed highly significant correlations between the surface hardness change and the degree of erosion, as detected by ATR-FTIR spectroscopy （P〈0.001）. Method 1 was the most sensitive to these changes, followed by surface hardness change measurements and Method 2. This study suggests that ATR- FTIR spectroscopy is potentially advantageous over the microhardness test as a simple, non-destructive, sensitive technique for the quantification of enamel erosion.
FUSE binding protein 1 (
), a regulator of the c-Myc transcription factor and a DNA/RNA-binding protein, plays important roles in the regulation of gene transcription and cellular physiology. In this ...study, to reveal the precise developmental function of
, we examined the detailed expression pattern and developmental function of
during tooth morphogenesis by RT-qPCR, in situ hybridization, and knock-down study using in vitro organ cultivation methods. In embryogenesis,
is obviously expressed in the enamel organ and condensed mesenchyme, known to be important for proper tooth formation. Knocking down
at E14 for two days, showed the altered expression patterns of tooth development related signalling molecules, including
and
. In addition, transient knock-down of
at E14 revealed changes in the localization patterns of c-Myc and cell proliferation in epithelium and mesenchyme, related with altered tooth morphogenesis. These results also showed the decreased amelogenin and dentin sialophosphoprotein expressions and disrupted enamel rod and interrod formation in one- and three-week renal transplanted teeth respectively. Thus, our results suggested that
plays a modulating role during dentinogenesis and amelogenesis by regulating the expression pattern of signalling molecules to achieve the proper structural formation of hard tissue matrices and crown morphogenesis in mice molar development.
Unlike vertebrates, the number of toothed taxa in invertebrates is very few, with leeches being the only tooth-bearing organisms in the phylum Annelida. Copious studies have been conducted regarding ...vertebrate teeth; however, studies regarding the structure and function of invertebrate teeth are limited. In this study, the tooth structure of leeches, specifically
and
, was revealed, which showed sharp and pointed teeth along the apex of three jaws. Understanding conserved signaling regulations among analogous organs is crucial for uncovering the underlying mechanisms during organogenesis. Therefore, to shed light on the evolutionary perspective of odontogenesis to some extent, we conducted de novo transcriptome analyses using embryonic mouse tooth germs,
teeth, and
proboscises to identify conserved signaling molecules involved in tooth development. The selection criteria were particularly based on the presence of tooth-related genes in mice,
teeth, and
proboscis, wherein 4113 genes were commonly expressed in all three specimens. Furthermore, the chemical nature of leech teeth was also examined via TEM-EDS to compare the chemical composition with vertebrate teeth. The examination of tissue-specific genetic information and chemical nature between leeches and mice revealed chemical similarities between leech and mice teeth, as well as conserved signaling molecules involved in tooth formation, including
,
, and
. Based on our findings, we propose that leech teeth express signaling molecules conserved in mice and these conserved tooth-specific signaling for dental hard tissue formation in mice would corresponds to the structural formation of the toothed jaw in leeches.
This study evaluated the accuracy of marginal and internal fit between the all-ceramic crowns manufactured by a conventional double-layer computer-aided design/computer-aided manufacturing (CAD/CAM) ...system and a single-layer system. Ten standardized crowns were fabricated from each of these two systems: conventional double-layer CAD/CAM system (Procera) and a single-layer system (Cerec 3D). The copings and completed crowns were seated on the abutments by a special device that facilitated uniform loading, and the marginal discrepancies were measured. Internal gaps were also measured using a low-viscosity silicone material. Marginal discrepancies of Procera copings were significantly smaller than those of Procera crowns and Cerec 3D crowns (p<0.05), but Procera crowns and Cerec 3D crowns did not differ significantly from each other (p>0.05). On internal gaps, Cerec 3D crowns showed significantly larger internal gaps than Procera copings and crowns (p<0.05). Within the limitations of this study, the single-layer system demonstrated acceptable marginal and internal fit.
To test the hypothesis that there are no differences in mutans streptococci (MS) adhesion between esthetic and metallic orthodontic arch wires based on their surface characteristics.
Surface ...roughness (Ra) and apparent surface free energy (SFE) were measured for six wires-four esthetic, one nickel-titanium (NiTi), and one stainless-steel (SS)-using profilometry and dynamic contact angle analysis, respectively. The amount of MS (Streptococcus mutans and Streptococcus sobrinus) adhering to the wires was quantified using the colony-counting method. The surfaces, coating layers, and MS adhesion were also observed by scanning electron microscopy. Statistical significance was set at P < .05.
The Ra values of the esthetic wires were significantly different from one another depending on the coating method (P < .05). The NiTi wire showed the highest SFE, followed by the SS wire and then the four esthetic wires. The NiTi wires produced a significantly higher MS adhesion than did the SS wires (P < .05). The esthetic wires showed significantly lower MS adhesions than did the NiTi wire (P < .05). Pearson correlation analyses found moderate significant positive correlations between the SFE and the S mutans and S sobrinus adhesions (r = .636/.427, P < .001/P = .001, respectively).
The hypothesis is rejected. This study indicates that some esthetic coatings on NiTi alloy might reduce MS adhesion in vitro in the short term.
Against a general consensus regarding the high toxicity and low biocompatibility of cast nickel–chromium (Ni–Cr) alloys, the in vitro biocompatibility of selective laser melting (SLM)-fabricated ...Ni–Cr alloys was investigated and compared with that of cast alloy. Using a single Ni–Cr alloy powder, two SLM alloys with high (SLM_a) and low (SML_b) porosity were prepared by adjusting the laser process parameters in addition to a cast alloy. The alloys were studied in terms of their microstructure, metal ion release, and cell response. All three alloys were composed of only the γ (face-centered cubic) phase. However, both SLM alloys showed more homogeneous dispersion of Ni, Cr, and molybdenum elements and finer grain formation than the cast alloy. Immersion test results indicated that both SLM alloys (in particular, SML_b) exhibited a significantly lower Ni ion release than the cast alloy (P<0.001). A water-soluble tetrazolium salt-8 assay also showed that the viability of L929 mouse fibroblasts was significantly higher for both SLM groups (in particular, SML_b) than for the cast alloy group (P<0.001). Thus, the combined results of this in vitro study suggest that the SLM-processed Ni–Cr alloys exhibited greatly enhanced biocompatibility in comparison with the cast alloy.
Cellular responses such as adhesion, spreading, growth and proliferation can be altered by macro and micro pores as well as surface patterns on its surface. In this study, the scaffold was prepared ...with interconnected macro pores by the polymeric sponge method and with interconnected micro pores by BCP slurry coating with different particle sizes on sintered porous body and necking sintering process. Two particle sizes for micro pores, 200–400nm and 600–800nm, were coated on a pre-sintered porous body. A combined macro and micro pore structure of the BCP scaffold can improve osteoblast cellular activity. In vitro study of MG63 cells suggest that the modified scaffolds improved cell response such as cell spreading, proliferation and differentiation. The scaffold that has a uniform distribution of micro pores ranging 1~5µm in diameter on its surface yields the highest rate of cellular response.
This study compared the microstructures and mechanical properties of nickel–chromium–molybdenum (Ni–Cr–Mo) alloys prepared from a single alloy with an identical composition using two new digital ...processes (selective laser melting (SLM) and soft metal milling (SMM)) and conventional lost-wax casting (LWC). Disc specimens were used to study the microstructures via various analytical methods, while dumbbell-shaped specimens were subjected to tension to determine the mechanical properties (n = 6). The SLM and SMM alloys showed a higher number of large and small pores, respectively, than the LWC alloy. A face-centered cubic (γ)-phased matrix was indexed for all three resultant alloys. The SLM and SMM alloys also showed more homogeneously distributed elements and finer grains (in particular, ultrafine grains in the SLM alloy) when compared to the LWC alloy. Meanwhile, the LWC alloy showed a statistically higher yield strength than the other two alloys (p < 0.001). Notwithstanding, all three resultant Ni–Cr–Mo alloys satisfied the ISO 22674 standard criteria for type 5 materials (yield strength: >500 MPa; percentage elongation: >2%; and elastic modulus: >150 GPa).
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