Bioinspired Catecholic Primers for Rigid and Ductile Dental Resin Composites.

In the construction of dental restorative polymer composite materials, surface priming on mineral fillers is essential to improve the mechanical performance of the composites. Here we present bioinspired catechol-functionalized primers for a tougher dental resin composite containing glass fillers. The catecholic primers with different polymerizable end groups were designed and then coated on glass surfaces using a simple drop-casting or dip-coating process. The surface binding ability and possible cross-linking (coupling or chemical bridging between the glass substrate and the dental resin) of the catecholic bifunctional primers were evaluated using atomic force microscopy, contact angle measurements, and the knife shear bonding test and compared to a state-of-the-art silane-based coupling agent. Various mechanical tests including shrinkage and compression tests of the dental resin composites were also conducted. Compression tests of the composites containing the catecholic primed fillers exhibited enhanced mechanical properties, owing to the bidentate hydrogen bonding of catechol moieties to the oxide mineral surface. Furthermore, the superior biocompatibility of the primed surface was confirmed via cell attachment assay, thus providing applicability of catecholic primers for practical dental and biomedical applications.

Significant Performance Enhancement of Polymer Resins by Bioinspired Dynamic Bonding.

Marine mussels use catechol-rich interfacial mussel foot proteins (mfps) as primers that attach to mineral surfaces via hydrogen, metal coordination, electrostatic, ionic, or hydrophobic bonds, creating a secondary surface that promotes bonding to the bulk mfps. Inspired by this biological adhesive primer, it is shown that a ≈1 nm thick catecholic single-molecule priming layer increases the adhesion strength of crosslinked polymethacrylate resin on mineral surfaces by up to an order of magnitude when compared with conventional primers such as noncatecholic silane- and phosphate-based grafts. Molecular dynamics simulations confirm that catechol groups anchor to a variety of mineral surfaces and shed light on the binding mode of each molecule. Here, a ≈50% toughness enhancement is achieved in a stiff load-bearing polymer network, demonstrating the utility of mussel-inspired bonding for processing a wide range of polymeric interfaces, including structural, load-bearing materials.

Influences of filler content and size on the color adjustment potential of nonlayered resin composites.

The blending effect (BE) plays an important role in esthetics of the composite resin. The objective of this study was to determine the extents to which filler size and content affect the BE. Three types of fillers (0.7, 1.0, and 1.5 µm) were mixed at weight contents of 60, 70, 75, and 80%. This study simulated clinical class 3 or 4 cavities and quantitatively measured the color diffusion of the objects next to the cavities based on the CIELab color space. For each filler size, there was a trend of increasing BE as the filler content was increased. The translucency parameter (TP) exhibited the opposite trend of decreasing (p<0.05) with increases in filler content. The filler size did not affect the BE, and the different filler sizes produced statistically non-significant results in this study. Increases in filler content elevated the opacity of the composite resin and significantly influenced the BE.

Fracture Strength After Fatigue Loading of Lithium Disilicate Pressed Zirconia Crowns.

PURPOSE: The aim of this study was to evaluate the fracture resistance of fatigued lithium disilicate pressed zirconia crowns versus other ceramic crowns. MATERIALS AND METHODS: Lithium disilicate pressed zirconia, fluorapatite pressed zirconia, monolithic lithium disilicate, and monolithic zirconia crowns were fabricated. Cyclic and static loadings were applied to the mesiobuccal cusp tip after thermocycling and fracture strengths were recorded. RESULTS: Fatigued lithium disilicate pressed zirconia crowns were found to have a fracture resistance of 9,117.81 ± 727.04 N, compared with 9,240.61 ± 887.21 N for monolithic zirconia crowns, 3,030.18 ± 1,505.83 N for fluorapatite pressed zirconia crowns, and 4,173.94 ± 877.46 N for monolithic lithium disilicate crowns (P = .001). CONCLUSION: This in vitro study shows that fatigued lithium disilicate pressed zirconia and monolithic zirconia crowns have better fracture resistance than fluorapatite pressed zirconia and monolithic lithium disilicate crowns.

Wear of primary teeth caused by opposed all-ceramic or stainless steel crowns.

PURPOSE: This study was conducted to evaluate the effects of full-coverage all-ceramic zirconia, lithium disilicate glass-ceramic, leucite glass-ceramic, or stainless steel crowns on antagonistic primary tooth wear. MATERIALS AND METHODS: There were four study groups: the stainless steel (Steel) group, the leucite glass-ceramic (Leucite) group, the lithium disilicate glass-ceramic (Lithium) group, and the monolithic zirconia (Zirconia) group. Ten flat crown specimens were prepared per group; opposing teeth were prepared using primary canines. A wear test was conducted over 100,000 chewing cycles using a dual-axis chewing simulator and a 50 N masticating force, and wear losses of antagonistic teeth and restorative materials were calculated using a three-dimensional profiling system and an electronic scale, respectively. Statistical significance was determined using One-way ANOVA and Tukey's test (P<.05). RESULTS: The Leucite group (2.670±1.471 mm(3)) showed the greatest amount of antagonist tooth wear, followed by in decreasing order by the Lithium (2.042±0.696 mm(3)), Zirconia (1.426±0.477 mm(3)), and Steel groups (0.397±0.192 mm(3)). Mean volume losses in the Leucite and Lithium groups were significantly greater than in the Steel group (P<.05). No significant difference was observed between mean volume losses in the Zirconia and Steel groups (P>.05). CONCLUSION: Leucite glass-ceramic and lithium disilicate glass-ceramic cause more primary tooth wear than stainless steel or zirconia.

Tunicate-Inspired Gallic Acid/Metal Ion Complex for Instant and Efficient Treatment of Dentin Hypersensitivity.

Dentin hypersensitivity is sharp and unpleasant pains caused by exposed dentinal tubules when enamel outside of the tooth wears away. The occlusion of dentinal tubules via in situ remineralization of hydroxyapatite is the best method to alleviate the symptoms caused by dentin hypersensitivity. Commercially available dental desensitizers are generally effective only on a specific area and are relatively toxic, and their performance usually depends on the skill of the clinician. Here, a facile and efficient dentin hypersensitivity treatment with remarkable aesthetic improvement inspired by the tunicate-self-healing process is reported. As pyrogallol groups in tunicate proteins conjugate with metal ions to heal the torn body armor of a tunicate, the ingenious mechanism by introducing gallic acid (GA) as a cheap, abundant, and edible alternative to the pyrogallol groups of the tunicate combined with a varied daily intake of metal ion sources is mimicked. In particular, the GA/Fe(3+) complex exhibits the most promising results, to the instant ≈52% blockage in tubules within 4 min and ≈87% after 7 d of immersion in artificial saliva. Overall, the GA/metal ion complex-mediated coating is facile, instant, and effective, and is suggested as an aesthetic solution for treating dentin hypersensitivity.

A rapid, efficient, and facile solution for dental hypersensitivity: The tannin-iron complex.

Dental hypersensitivity due to exposure of dentinal tubules under the enamel layer to saliva is a very popular and highly elusive technology priority in dentistry. Blocking water flow within exposed dentinal tubules is a key principle for curing dental hypersensitivity. Some salts used in "at home" solutions remineralize the tubules inside by concentrating saliva ingredients. An "in-office" option of applying dense resin sealants on the tubule entrance has only localized effects on well-defined sore spots. We report a self-assembled film that was formed by facile, rapid (4 min), and efficient (approximately 0.5 g/L concentration) dip-coating of teeth in an aqueous solution containing a tannic acid-iron(III) complex. It quickly and effectively occluded the dentinal tubules of human teeth. It withstood intense tooth brushing and induced hydroxyapatite remineralisation within the dentinal tubules. This strategy holds great promise for future applications as an effective and user-friendly desensitizer for managing dental hypersensitivity.

Cytotoxicity of four denture adhesives on human gingival fibroblast cells.

OBJECTIVE: The purpose of this study was to compare the cytotoxicity of four denture adhesives on human gingival fibroblast cells. MATERIALS AND METHODS: Immortalized human gingival fibroblasts were cultured with one of four different denture adhesives, Polident, Protefix, Staydent or Denfix-A, which was placed in insert dishes (10% w/v concentration) for 48 h. The MTT [3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide] assay and flow cytometric apoptosis assay were used to evaluate cell viability and apoptosis rates. The fibroblasts were also examined under a scanning electron microscope. RESULTS: The MTT assay showed that all denture adhesives resulted in a significantly lower cell viability compared to the control cells propagated in normal culture medium (p < 0.05), with Staydent demonstrating the lowest cell viability. According to the flow cytometric apoptosis assay, Staydent and Protefix showed significantly higher apoptosis rates than the control group (p < 0.05), whereas Polident and Denfix-A did not demonstrate any significant differences (p > 0.05). Staydent showed the highest apoptosis rate. Scanning electron microscopy showed that the cells of the Staydent group underwent cytoplasmic membrane shrinkage, with cell free areas containing residual fragments of the membrane of dead cells. CONCLUSIONS: The four denture adhesives evaluated in this study imparted cytotoxic effects on human gingival fibroblast cells. Staydent showed the highest toxicity.

The influence of a continuous increase in thickness of opaque-shade composite resin on masking ability and translucency.

OBJECTIVES: This study was conducted to determine the minimum thickness of opaque-shade composite resin required to mask discolored tooth structures or darkness of the oral cavity and to determine the effect of the brand and shade of composite resins on masking ability and translucency. MATERIALS AND METHODS: Discs and beveled specimens were manufactured using six opaque-shade light-curing composite resins (Charisma, Heraeus Kulzer; Estelite Sigma Quick, Tokuyama; Gradia Direct Anterior, GC). The discolored tooth structures and darkness of the oral cavity were reproduced using background tiles. The disc specimen colors were measured using a spectroradiometer by increasing the thickness of the beveled specimens on the backing by 0.05 mm in series, and color difference (ΔE*(ab)) and translucency parameter (TP) were calculated. RESULTS: The thicknesses of opaque-shade composite resins that masked the C4 shade and black backings were 0.80-1.45 and 1.85-2.00 mm, respectively. Overall, the ΔE*(ab) and TP values decreased as the thickness of the opaque-shade composite resins increased. When the shades of the composite resins were identical, the TP decreased in the order of Charisma, Estelite Sigma Quick and Gradia Direct Anterior. When the brand was fixed, the TP was higher in the OA3 shade than in the OA2 shade. A significant correlation was seen between ΔE*(ab) and TP (p < 0.05). CONCLUSIONS: The brands and shades of the composite resins were shown to have a clear effect on TP, but an inconsistent tendency for ΔE*(ab).

Wear evaluation of the human enamel opposing different Y-TZP dental ceramics and other porcelains.

PURPOSE: This study examined the wear resistance of human enamel and feldspathic porcelain after simulated mastication against 3 zirconia ceramics, heat-pressed ceramic and conventional feldspathic porcelain. MATERIALS AND METHODS: Human teeth and feldspathic porcelain cusp were tested against ceramic discs. 5 brands were tested - 3 monolithic zirconia, Prettau, Lava, and Rainbow, one lithium disilicate, IPS e.max Press, and one feldspathic porcelain, Vita-Omega 900. The surface was polished using a 600 grit and 1200 grit SiC paper. Each group was loaded for 300,000 cycles in a chewing simulator. The wear resistance was analyzed by measuring the volume of substance lost. The wear surfaces were observed by scanning electron microscopy to determine the wear characteristics. RESULTS: Vita-Omega 900 led to the greatest amount of enamel wears followed by IPS e.max Press, Prettau, Lava and Rainbow. There was a significant difference between Vita-Omega 900 and IPS e.max Press (p<0.05). The wear values for human enamel were significantly greater than those for feldspathic porcelain, regardless of the surface roughness of the ceramic specimens (p<0.05). CONCLUSION: The wear behaviour of human enamel and feldspathic porcelain varies according to the type of substrate materials. On the other hand, 3 zirconia ceramics caused less wear in the abrader than the conventional ceramic. CLINICAL SIGNIFICANCE: Dental professionals should be aware of the wear effect of dental restorations on the opposing teeth or restorations. The amount of enamel wear was highest in feldspathic porcelains whereas zirconia ceramics caused less wear on the opposing teeth.

Influence of dentin porcelain thickness on layered all-ceramic restoration color.

OBJECTIVES: Final aesthetic performance of all-ceramic restorations is influenced by the thickness ratio of core and porcelain ceramics. This study aimed to identify and quantify the effect of increased dentin porcelain thickness on the color and color coordinates of all-ceramic specimens. METHODS: Lava and IPS e.max Press all-ceramic systems were investigated. A1, A2 and A3.5 shades of layered specimens were made with 2-mm ceramic cores and 0-2mm bevelled dentin porcelain. Color was measured at 0.05mm dentin porcelain thickness intervals with a spectroradiometer. The effect of ceramic brand, shade and dentin porcelain thickness on color change was analyzed by 3-way ANOVA. RESULTS: Color changes of layered ceramics varied by ceramic brand, shade and dentin porcelain thickness. For most ceramics, CIE a* and b* values gradually increased as the thickness of the dentin porcelain increased. Conversely, such increases in dentin porcelain thickness were correlated with decreasing CIE L* values. When compared with the IPS e.max Press ceramics, Lava ceramics showed smaller color changes in response to increases in dentin porcelain thickness. CONCLUSIONS: The final appearance of ceramic restorations can be manipulated by varying the dentin porcelain thickness; however, the color of the layered ceramics varied by ceramic brand, shade and dentin porcelain thickness.