Human Dentin Research Articles

Laser-fluorescence assessment of sodium hypochlorite quenching reversal agents on human dentine

BackgroundLaser-fluorescence diagnostic technology for real-time clinical assessment of residual bacteria could help assist in determining the endpoints for root canal debridement. Sodium hypochlorite (NaOCl) can however quench fluorescence and lead to false low reading. This study aims to evaluate various antioxidant for their ability to recover quenched fluorescence in dentine treated with NaOCl. MethodsHuman dentine fluorescence was measured using 655 nm laser at baseline and again after a 2 min application of 4% NaOCl. The putative recovery agents were then applied, and the fluorescence measured after 5, 10, 20, 30 and 60 min. Recovery from quenching was also assessed using laser confocal scanning microscopy (CLSM) with a bound tetracycline fluorophore using 488 nm excitation. ResultsA 5 min application of vitamin E oil or buffered 2% lignocaine solution (1:80,000 adrenaline) was effective in regaining quenched fluorescence within the following 5 mins. Distilled water, sodium thiosulfate, unbuffered 2% lignocaine with 1:80000 adrenaline and phosphate buffered saline were less effective, and of equal performance. Ascorbic acid and butylated hydroxyanisole were not effective and had deleterious effects on the levels of dentine fluorescence. CLSM provided confirmation of recovery from quenched fluorescence using vitamin E oil. ConclusionBased on these findings, reversal agents should be employed when assessing the fluorescence of dentine that has been exposed to NaOCl or other quenching agents.

Atomic force microscopy study on the effect of different irrigation regimens on the surface roughness of human root canal dentin.

Endodontic irrigants could alter the mechanical properties of root canal dentin, such as its roughness. To compare the effect of various irrigation protocols on root canal dentin roughness with respect to their application time, concentration, and additional ultrasonic activation. Forty single-rooted, non-endodontically treated upper incisors were decoronated and further sectioned longitudinally in a buccolingual direction. The surfaces of all eighty samples were polished and randomly segregated to eight equal groups (n = 10): Group A: 2% NaOCl/2 min followed by 17% EDTA/2 min; Group B: 2% NaOCl/5 min followed by 17% EDTA/5 min; Group C: 5.25% NaOCl/2 min followed by 17% EDTA/2 min; Group D: 5.25% NaOCl/5 min followed by 17% EDTA/5 min; Group E: 2% NaOCl solution, ultrasonically activated for 2 min; Group F: 5.25% NaOCl, ultrasonically activated for 2 min; Group G: 2% NaOCl/2 min followed by 17% EDTA/2 min, both ultrasonically activated; Group H: Control group (distilled water). All irrigation regimens increased root dentin surface roughness in comparison with the control group. The analysis of the values revealed significant differences between the arithmetical average roughness values (Ra) in the groups (p < 0.001). A statistically significant increase in the Ra parameter was observed in groups E, F, G, and D. The irrigation protocol in Group A showed a significantly smoother dentin surface than those with the ultrasonic activation. All tested irrigants increased root canal dentin roughness and the effect was time and concentration-dependent. The ultrasonic activation of the disinfection solutions roughened the root dentin surface significantly.

High-Performance Dental Composites Based on Hierarchical Reinforcements

Use of high-performance fibers such as poly(p-phenylene-2,6-benzobisoxazole) (PBO) improves the mechanical properties of dental fiber-reinforced composites (FRCs). However, the surfaces of high-performance fibers are relatively inert, and the interface with the resin matrix is poor. This has become a limitation restricting the performance of PBO FRCs in dentistry. Nanomaterials were introduced onto PBO fibers to construct various hierarchical reinforcements to obtain a dental FRC with higher flexural performance and optimized interface bonding. Four hierarchical reinforcements were constructed: PBO-ZnO nanoparticles (NPs), PBO-ZnO nanowires (NWs), PBO-ZnO NPs–cage silsesquioxane (POSS), and PBO-ZnO NWs-POSS. Performance following this optimized method was evaluated at macroscale and microscale levels, including measurement of the interfacial properties and mechanical properties of FRCs. The physicochemical characteristics of PBO fibers before and after modification were measured to determine the interfacial bonding mechanisms and to verify the connection between the microinterface and macromechanical properties. The cytotoxicity of the preferred PBO FRC was evaluated using the CCK8 assay. In comparison to other designs, the interfacial shear strength (IFSS) of PBO-ZnO NWs-POSS was the highest (29.31 ± 2.40 MPa). The corresponding FRC had the highest flexural strength under a static load (925.0 ± 39.2 MPa), the flexural modulus (39.39 ± 1.41 GPa) was equivalent to that of human dentin, and in vitro cytotoxicity was acceptable. The interfacial bonding mechanisms of PBO-ZnO NWs-POSS resulted from mechanical interlocking, chemical bonds, hydrogen bonds, and van der Waals forces. In summary, the PBO-ZnO NWs-POSS hierarchical reinforcement was introduced in dental FRCs and showed remarkable enhancement of the IFSS and flexural properties. We verified that the PBO-ZnO NWs-POSS hierarchical reinforcement was successful. This PBO FRC may be applied in dentistry as a new option for endodontic posts. Our study provides an interface design strategy for developing high-performance FRCs reinforced with high-performance fibers for dental applications.

Comparing Radiopacity of Nanohybrid Composite and Giomers: An In Vitro Study

Aim: The aim of this study was to evaluate and compare the radiopacity of three different composite resins; one nanohybrid and two giomers.&#x0D; Material and Methods:&#x0D; For evaluation of radiopacity of composites, ten specimens of each material [(3 groups) (total 30) (n=10] with thicknesses of 2 mm were prepared and radiographed alongside aluminum step wedge and human enamel and dentin. Occlusal radiograph was taken and mean gray values of the test materials were measured using Image J software. Then a conversion was performed to establish the radiopacity of the test materials, in millimeters of equivalent Aluminum (Al). Data were analyzed using one‑way analysis of variance and Scheffe’s Post Hoc tests (P &lt; 0.05).&#x0D; Results: &#x0D; The radiopacity values varied among the restorative materials (p &lt; 0.05) with the highest for Filtek followed by Beautifil Injectable, Beautifil 2, enamel and dentin.&#x0D; &#x0D; Conclusion: &#x0D; All materials tested had radiopacity values greater than dentin and had sufficient radiopacity to meet International Organization for Standardization 4049 standard.&#x0D; &#x0D; Key Words: Radiopacity, aluminum stepwedge, composites, opacifing-fillers.

Nanomechanical and Molecular Characterization of Aging in Dentinal Collagen

Methylglyoxal (MGO) is an important molecule derived from glucose metabolism with the capacity of attaching to collagen and generating advanced glycation end products (AGEs), which accumulate in tissues over time and are associated with aging and diseases. However, the accumulation of MGO-derived AGEs in dentin and their effect on the nanomechanical properties of dentinal collagen remain unknown. Thus, the aim of the present study was to quantify MGO-based AGEs in the organic matrix of human dentin as a function of age and associate these changes with alterations in the nanomechanical and ultrastructural properties of dentinal collagen. For this, 12 healthy teeth from <26-y-old and >50-y-old patients were collected and prepared to obtain crown and root dentin discs. Following demineralization, MGO-derived AGEs were quantified with a competitive ELISA. In addition, atomic force microscopy nanoindentation was utilized to measure changes in elastic modulus in peritubular and intertubular collagen fibrils. Finally, principal component analysis was carried out to determine aging profiles for crown and root dentin. Results showed an increased presence of MGO AGEs in the organic matrix of dentin in the >50-y-old specimens as compared with the <26-y-old specimens in crown and root. Furthermore, an increase in peritubular and intertubular collagen elasticity was observed in the >50-y-old group associated with ultrastructural changes in the organic matrix as determined by atomic force microscopy analysis. Furthermore, principal component analysis loading plots suggested different “aging profiles” in crown and root dentin, which could have important therapeutic implications in restorative and adhesive dentistry approaches. Overall, these results demonstrate that the organic matrix of human dentin undergoes aging-related changes due to MGO-derived AGEs with important changes in the nanomechanical behavior of collagen that may affect diagnostic and restorative procedures in older people.

Biomimetic remineralization of human dentine via a “bottom-up” approach inspired by nacre formation

Nacre exhibited noticeable similarities in fundamental material buildup and biological characteristics with tooth hard tissue, so the present study aims to achieve bionic dentine remineralization by duplicating nacre's “bottom-up” assembly concept. Inspired by nacre's mineralization mechanism, the present project starts to synthesize a “seawater-like” mineralizing precursor medium, then monitor its in vitro dentinal tubules occlusion effect, acid-resistant stability, the “fingerprint” dynamic components change in real time on in vitro sensitive tooth model as well as its in vitro cellular biological response towards human dental pulp stem cells. For the further exploration, a single-layer fibrillar collagen model was established to simulate the exposed collagen of demineralized dentine to appraise its intrafibrillar mineralization effect. The results demonstrated that the application of “seawater-like” mineralizing precursor medium effectively occluded dentinal tubules, reduced dentine permeability, increased surface microhardness, provided certain acid-resistant stability and possessed favorable in-vitro biocompatibility. In addition, the dynamic procedure of hierarchical intrafibrillar nanocrystalline assembly was observed, which offered a clue to uncover its remineralizing mechanism. It is attainable to realize the biomimetic remineralization of human dentine via the “bottom-up” concept inspired by nacre structure duplication, suggesting great potential for providing dentists a therapeutic strategy to counter dentine hypersensitivity in the future.

Biomimetic Growth of Metal-Organic Frameworks for the Stabilization of the Dentin Matrix and Control of Collagenolysis.

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.

Riboflavin and Its Effect on Dentin Bond Strength: Considerations for Clinical Applicability-An In Vitro Study.

Bioactive collagen crosslinkers propose to render the dentin hybrid layer less perceptive to hydrolytic challenge. This study aims to evaluate whether bond strength of dental resin composite to dentin benefits from riboflavin (RB)-sensitized crosslinking when used in a clinically applicable protocol. A total of 300 human dentin specimens were prepared consistent with the requirements for a macro-shear bond test. RB was applied on dentin, either incorporated in the primer (RBp) of a two-step self-etch adhesive or as an aqueous solution (RBs) before applying the adhesive, and blue light from a commercial polymerization device was used for RB photoactivation. Bonding protocol executed according to the manufacturer’s information served as control. Groups (n = 20) were tested after 1 week, 1 month, 3 months, 6 months or 1 year immersion times (37 °C, distilled water). The different application methods of RB significantly influenced bond strength (p < 0.001) with a medium impact (η2p = 0.119). After 1 year immersion, post hoc analysis identified a significant advantage for RB groups compared to RBp (p = 0.018), which is attributed to a pH-/solvent-dependent efficiency of RB-sensitized crosslinking, stressing the importance of formulation adjustments. We developed an application protocol for RB-sensitized crosslinking with emphasis on clinical applicability to test its performance against a gold-standard adhesive, and are confident that, with a few adjustments to the application solution, RB-sensitized crosslinking can improve the longevity of adhesive restorations in clinics.

Effect of Thermocycling on the Bond Strength of Self-Adhesive Resin Cements Used for Luting CAD/CAM Ceramics to Human Dentin.

The aim of the study was to evaluate the influence of thermocycling on the shear bond strength of self-adhesive, self-etching resin cements luted to human dentin and computer-aided design/computer-aided manufacturing (CAD/CAM) ceramics. Three modern self-adhesive dental cements (Maxcem Elite, RelyX U200, Panavia SA) were used to lute three CAD/CAM ceramics (IPS Empress CAD, IPS e.max CAD, IPS e.max ZirCAD) onto the dentin. One conventional cement (Panavia V5) served as a control. After preparation, the samples were subjected to thermocycling as a method of artificial aging of dental materials applied to simulate long-term use in oral conditions. Shear bond strength was evaluated according to PN-EN ISO 29022:2013-10 and failure modes were observed under a light microscope. Statistical analysis was performed. The study demonstrated that a combination of ceramics and cements directly impacts the bond strength. The highest bond strength was observed in Panavia V5, lower in Panavia SA and Maxcem Elite and the lowest–in RelyX U200. Adhesive failure between human dentin and cements was the most common failure mode. Moreover, thermocycling highly decreased bond strength of self-adhesive, self-etching cements.

Proanthocyanidin encapsulation for sustained bioactivity in dentin bioadhesion: A two-year study

ObjectivesTo determine the long-term effect on the stability of dentin-resin interfaces after the addition of polylactide (PLA) capsules containing proanthocyanidin (PAC) to adhesive resin. MethodsSub-micron (SM) and micron (M) size capsules containing PACs were produced using a combination of emulsification and solvent evaporation techniques and characterized. Human dentin surfaces (n = 8) were etched (35% glycolic acid) and primed (15% enriched Vitis vinifera extract solution - VVe), followed by the application of an experimental adhesive containing 0 (control), 1.5 wt% of SM or M PAC-filled PLA capsules light cured for 40 s. A crown was built using commercial composite. After 24 h-immersion (37 °C) in simulated body fluid, specimens were serially sectioned into resin-dentin beams. Microtensile bond strength (TBS), micro-permeability and fracture pattern were assessed immediately and after 1 and 2 years. Data were statistically analyzed using two-way ANOVA and post-hoc test (α = 0.05). ResultsPolydisperse capsules were manufactured with average diameter of 0.36 µm and 1.08 µm for SM and M, respectively. The addition of capsules did not affect TBS (p = 0.889). After 2 years, TBS significantly decreased in SM (p = 0.006), whereas M showed similar initial values (p = 0.291). Overall, less micro-permeability was found in M than the control and SM group (p < 0.001). After 2 years, fractured surfaces from capsule-containing groups failed within the adhesive layer while control fractured at the bottom of the hybrid layer. SignificanceThe addition of PAC-filled PLA microcapsules in a dental adhesive did not affect the bond strength while increased and sustained the protection against micro-permeability in the interface, likely due to release of PACs.

Sr,Mg co-doping of calcium hydroxyapatite: Hydrothermal synthesis, processing, characterization and possible application as dentin substitutes

The aim of this study was to investigate the influence of binary Sr, Mg ion-doping compared to the single-ion doping effects on the phase composition and morphology of hydrothermally obtained calcium hydroxyapatite (HAP) powders and on the phase composition, microstructure, and mechanical properties of the sintered materials. Additionally, the focus of this study was to investigate the possible utilization of the binary doped Sr,Mg-HAP compacts as dentin substitutes in restorative dentistry by evaluating their bonding ability with commercially available restorative materials using the shear bond strength test (SBS). The hydrothermally obtained mono-doped Mg5 and Sr5 showed the monophasic apatite structure, while in all co-doped samples β-TCP phase was formed, resulting in biphasic calcium phosphate (BCP) powders. It was confirmed that co-doping with Sr and Mg ions led to the thermal stabilization of the β-TCP phase by suppressing the phase transition into α-TCP when sintered at 1200 °C. Moreover, the co-presence of Mg ions significantly improved the hardness of Sr-doped HAP from 3.74 to 5.02 GPa. Sr,Mg-HAP dental inserts were found to achieve sufficient bonding (13.53 MPa) through the micromechanical interlocking with Z250 dental composite and Single Bond Universal dental adhesive applied with a total etch approach. The SBS values obtained for the SrMg-HAP insert were similar to the literature data on bonding ability with human dentin, indicating that binary doped Sr,Mg-HAP ceramics present a promising material for application in restorative dentistry as dentin substitutes.

6 - Ceramic-Dentin Cement Thickness: Bond Strength and Residual Stress

This study aimed to test whether three different cement layer thicknesses (60, 120 and 180 μm) would provide the same bonding capacity between adhesively luted lithium disilicate and human dentin. Ceramic blocks were cut with a low-speed diamond saw with water cooling into 20 blocks, which were cemented to human flat dentin with adhesive protocol. The assembly was sectioned into 1 mm 2 cross-section beams composed of ceramic/cement/dentin. Cement layer thickness was measured, and three groups were formed. Half of the samples were submitted to aging simulation and the other half was immediately tested to evaluate the long-term bond strength. The microtensile test was performed in a universal testing machine. Bond strength (MPa) was calculated. The fractured specimens were examined under stereomicroscopy. Applying the finite element method, the residual stress of polymerization shrinkage according to cement layer thick-ness was also calculated using First Principal Stress as analysis criteria. ANOVA showed that the cement layer thickness factor significantly influenced the bond strength results for the aged samples (p=0.040) without difference between the groups for the immediately tested groups (p=0.772). The higher the cement layer thickness the higher the residual stress generated at the adhesive interface due to cement polymerization shrinkage. In conclusion, the cement layer thickness does not affect the immediate bond strength in lithium disilicate restorations; however, thinner cement layers are most stable in long-term showing constant bond strength and lower residual stress.

Assessment of Dental Age Estimation Using Aspartic Acid Racemization in Human Dentin in Single-Rooted Teeth

Assessment of Dental Age Estimation Using Aspartic Acid Racemization in Human Dentin in Single-Rooted Teeth

Influence of diode laser and warm air drying on the shear bond strength of Lithium di-silicate to Dentin. An in-vitro study

Objective: The current study aimed to evaluate the effect of diode laser irradiation (980 nm) and warm air drying(50°C) on shear bond strength between Lithium di-silicate (IPS e.max; Ivoclar) and human dentin using both(Etch &amp; Rinse) adhesive, Adper™ Single Bond 2 (3M ESPE) and (Self-etch) adhesive, Single Bond UniversalTM(3M ESPE) before adhesive polymerization. Material and Methods: 54 sound lower molars were sectioned toobtain flat dentinal surfaces. Specimens were divided into 2 equal groups (n=27): Group 1 (ER) and Group 2(SE) according to bonding approach. Each subgroup was subdivided according to dentin surface treatment into3 equal subgroups (n=9): Control (Co), Diode laser irradiation (L) and Warm air drying (W). All specimenswere adhesively cemented to IPS e.max® CAD discs using RelyX™ Ultimate Clicker™(3M ESPE) resin cement.Samples were then subjected to pre-loading in a thermodynamic manner. All samples were tested for shearbond strength using computer-controlled material testing machine. Data analysis was performed using two-way(ANOVA) (p&lt; 0.05) followed by pair-wise Tukey’s post-hoc tests. Results: In (SE) group, the subgroup (W) hadthe highest shear bond strength values followed by (Co) subgroup and the least was (L) subgroup with statisticallysignificant difference. As for (ER) group, the subgroup (W) had the highest shear bond strength values followedby (Co) subgroup and the least was (L) subgroup with no statistically significant difference. Conclusion: Warmair drying for (SE) bonding approach increased shear bond strength of Lithium di-silicate to human dentin andcan be introduced as a new effective protocol.KEYWORDSAdhesives; Diode laser; IPS e.max; Shear bond strength; Warm air drying.

Effect of SmearOFF and ethylenediaminetetraacetic acid on the surface roughness and microhardness of human root canal dentin – An ex vivo study

Effect of SmearOFF and ethylenediaminetetraacetic acid on the surface roughness and microhardness of human root canal dentin – An ex vivo study

Laser irradiation prevents root caries: Microhardness and scanning electron microscopy analysis.

A promising option for the prevention of dental caries is the use of laser irradiation. Evaluate the effects of Er:YAG, Nd:YAG, and CO2 laser irradiation, associated or not to 2% sodium fluoride (2% NaF), on root caries prevention. One hundred and four human root dentin samples were divided in eight groups (n = 13). A 9-mm2-area on each dentin sample was delimited and treated as follows: G1: no treatment (control); G2: 2% NaF; G3: Er:YAG; G4: 2% NaF + Er:YAG; G5: Nd:YAG; G6: 2% NaF + Nd:YAG; G7: CO2; G8: 2% NaF + CO2. When used, the 2% NaF was applied before irradiation for 4 min. The samples were subjected to a 2-week cariogenic challenge, consisted of daily immersion in de-remineralizing solutions for 6 h and 18 h, respectively. Knoop hardness (KHN) were evaluated (10 g and 20 s) at different depths from the dentin surface. The samples (n = 3) were prepared for scanning electron microscopy (SEM). Microhardness data were analysed by one-way analysis of variance (ANOVA) and Fisher's test (α = 5%). The Er:YAG laser group (KHN = 41.30) promoted an increase in acid resistance of the dentin (P < 0.05) when compared to all groups. There was no synergism between laser irradiation and 2% NaF application. Morphological changes were observed after irradiation with all lasers; carbonization and cracks were also observed, except when Er:YAG were used. Er:YAG laser irradiation can safely increase the acid resistance of the dentin surface of the root, since it promoted a significant increase in surface hardness. The application of 2% NaF did not result in a synergistic effect.

Structure and Deformation Behavior of Human Dentin

The relationship between structure and stress accommodation mechanisms (deformation and fracture) of human dentin on macro-, micro- and nano- scales is discussed. Dentin is the hard basis of human teeth with complicated hierarchically organized structure, which is attested as a natural composite consisted of a bioorganic matrix armed by collagen fibers and apatite crystallites. Dentin exhibits the unique strength properties. On the macroscopic level, under tensile load, it behaves like a brittle solid, and like a viscoelastic one in the case of compression. At the same time, on the microscopic scale cracks in dentin grow in a viscoelastic manner under tensile loading. Structure, mechanical properties and crack growth of human dentin on macro-, micro- and nano- scales, including TEM study, are considered in detail. It was shown that a brittle response under tension is the macroscopic feature of dentin caused by dentin channels, while viscoelasticity is its intrinsic property.

An in vitro investigation of the fracture strength of root-filled - posterior teeth restored with polymer full-coverage crowns

Objectives: To investigate, by an in vitro study, the fracture strength of root-filled teeth restored with polyetheretherketone (PEEK) full-coverage crowns.Materials and Methods: Two single-rooted maxillary second premolar Typodont teeth were prepared according to the standardized preparation guidelines for two different full-coverage crown restorations: computer-aided design/computer-aided manufacturing monolithic lithium disilicate crowns (E.max) for the control samples and machine pressed monolithic PEEK crowns for the test samples. Teeth were duplicated in a polyurethane-based resin, with properties analogous to human dentin; n = 5 for each category. Replicas were embedded in polyurethane-based resin material using a retaining copper ring, with a simulated 200-μ periodontal ligament. Subsequently, all samples received orthograde root canal treatment using standardized preparation and obturation techniques. Crowns were cemented with resin-modified glass ionomer cement using a standardized cementation force. All teeth were subjected to a monotonic, axial static load of 2500 N to the point of fracture.Results: All control group samples displayed failure as a combined crown/tooth fracture. The crowns in the test group samples (PEEK) did not fracture under the experimental loads. Under the maximum loads, the crowns exhibited plastic deformation visible as an indentation created on the occlusal surface. Subsurface cohesive damage of the interface cement was noted. T-test showed that the resistance to fracture of the test group compared to the control group was highly significant (P < 0.001).Conclusions: Within the limitations of this study, PEEK crowns help preserve the remaining tooth structure and provide more predictable protection when compared to E.max crowns. They demonstrate failure by surface deformation and subsurface cohesive damage to the interface cement layer. It is unknown if this failure mode would occur under normal masticatory loads.

COMPARATIVE EVALUATION OF THE SHEAR BOND STRENGTH OF TWO RESIN CEMENTS WITH THAT OF ZIRCON-BASED CROWNS – AN IN-VITRO STUDY

Introduction: Because of ceramics' exceptional esthetical qualities, the range of materials for implicitly rebuilding missing tooth structures has already grown substantially in recent years. One of the earliest ceramics, silica-based ceramics, needs an adhesive attachment to the tooth structures to keep them from breaking. Previous studies looked at the relationship between the properties of human dentine and the shear bond strength of adhesive on a polished, flat tooth structure surface. For the cementation of inlays, Onlays, crowns, posts, and veneers, resin-based adhesive luting substances are often utilized. the self-adhesive qualities are based on phosphoric-acid methacrylates, which demineralize and penetrate the tooth substrate to provide micromechanical retention.&#x0D; Methodology: This study was undertaken to investigate the shear bond strength between zirconia and two resin-luting types of cement. One is a conventionally used dual-cure resin cement and the other is a new universal self-adhesive self-cure resin cement. Methods: The two self-adhesive self-cured resin cement utilized in the current study, Panavia-F 2.0 and Rely X U 100 were two of these relatively novel products.&#x0D; Result: The number of adhesive and cohesive fractures was calculated for both groups .chi-square test was applied to compare the two parameters in both groups. it was found that 60% of Group RelyX–U100 showed cohesive fractures and 13.33% of group Panavia–F2.0 showed cohesive fractures. There was a highly significant difference found in the type of fractures shown by each group.&#x0D; Conclusion: It is thus concluded from the above study that to bond the zirconia restorations to dentin a better shear bond strength can be observed with respect to self-adhesive self-cure cement rather than the conventional dual resin cement where the application of primer &amp; etchants is required for the bonding process.

Cross-Linking of Apatite-Gelatin Nanocomposites as the Basis for Dentine Replacement Materials.

A novel approach for the production of a bioinspired dentine replacement material is introduced. An apatite-gelatin nanocomposite material was cross-linked with various cross-linkers. These nanocomposites have a high resemblance to mammalian dentine regarding its composition and properties. A precipitation reaction was used to produce apatite-gelatin nanocomposites as starting materials. Cross-linking of the gelatin has to be performed to produce dentine-like and thus tough and robust apatite-gelatin nanocomposites. Therefore, the efficacy of various protein cross-linkers was tested, and the resulting materials were characterized by scanning electron microscopy, transmission electron microscopy, powder X-ray diffraction, and EXAFS as well as CHNS analysis and tested for their mechanical performance using Vickers hardness measurements as well as for their dissolution stability in EDTA. Especially glutaraldehyde, proanthocyanidins, and transglutaminase gave promising results with hardness values of up to 63 HV0.2. To further improve the material properties, we combined the effective cross-linker transglutaminase with casein, which led to an improved interconnection between the single nanocomposite platelets. By doing so, a cross-linked composite was obtained, which shows even higher hardness values than does human dentine, at 76 HV0.2. The combination of apatite-gelatin nanocomposites with an effective cross-linker resulted in a bioinspired material with composition and properties close to those of human dentine.