Dental Materials最新文献

Dentinogenesis Imperfecta (DI) is a rare genetic disorder characterized by dentin hypomineralisation. While DI is known to impair dentin's mechanical properties of the tissue and cause multiple tooth fractures, the microstructural origins of dentin fragility remain poorly understood. To address this gap,we conducted a pilot study comparing primary healthy dentin (n=4 - four incisors) and dentin affected by DI associated with a COL1A2 variant (DI type I, n=4 - two canines and two molars) using thermogravimetry and backscattered electron scanning microscopy to quantify mineralization at macroscale and microscale. We further assessed mechanical properties using nanoindentation to evaluate the effect of mineralization changes. Unlike prior studies, we found that our DI group exhibits 8% higher mineralization of the bulk of the tissue; however shows a 34% reduction in effective nanohardness. At the microscale, the DI group displays profound mineralization heterogeneities with hypermineralized zones exhibiting twice the nanohardness of hypomineralized zones. Our findings show that cracks predominantly propagate in these hypermineralized zones in DI samples, particularly beneath the dentin-enamel junction, where cracks can cause enamel detachment. These findings suggest that, for the DI group with the COL1A2 variant studied, mineralization heterogeneities, rather than bulk mineral content, is the key determinant of fragility. They provide preliminary results to investigate the mechanistic origins of crack propagation of this DI phenotype, that could be further supported by broadening the sample size and ensuring tooth-type consistency.

Objectives: Resin infiltration is a micro-invasive treatment option to manage enamel opacities, arresting lesion progression and improving esthetics. As restorative interventions may be required during or after infiltration treatment, this study evaluated the bond strength of composite resin to infiltrated bovine enamel, focusing on the effect of enamel priming.

Methods: Bovine sound incisors (n = 120) were used and demineralized lesions were created in half of the specimens. Prior to resin infiltration (Icon, DMG, Hamburg, Germany), the etched enamel surface was dried with either Icon Dry or Icon Prime (DMG), the later containing 10-Methacryloyloxydecyl dihydrogen phosphate (10-MDP). A resin composite (Ecosite Elements, DMG) was placed without any adhesive and half of the specimens in each group underwent ageing using thermocycling (5°C/55°C, 5000 cycles); the other half served as non-aged controls. Notched-edge shear bond strength (SBS) was measured after storage of the specimens in water at 37°C for 24 h. A three-way ANOVA (α = 0.05) was used to analyze the effects of enamel priming (Icon Dry/Icon Prime), enamel type (sound/demineralized) and aging condition (aged/non-aged). Failure mode analysis was performed by SEM.

Results: Enamel priming with Icon Prime significantly increased SBS compared to Icon Dry (p = 0.012). No significant main effects were observed for enamel type (p = 0.671) or aging condition (p = 0.794). Adhesive failure predominated at the enamel-infiltrant interface; no interfacial degradation was observed after thermocycling in Icon Prime-pretreated specimens.

Significance: Bond strength between composite resin and infiltrated enamel can be clinically sufficient without an adhesive if the oxygen inhibition layer is preserved, enabling simplified workflows. Long-term bond durability depends on the aging resistance of the infiltrant layer itself, making enamel priming a key determinant.

Objective: To compare the success and survival rates of metal-ceramic crowns and direct composite resin restorations retained with glass fiber posts, and to identify causes of failure during extended follow-up.

Material and methods: A prospective randomized controlled trial (NCT01461239) with parallel groups was conducted. Eighty-three teeth from 68 patients were initially randomized; however, six did not receive the assigned treatment. Thus, 77 teeth from 62 patients (42 composite resin, 35 metal-ceramic crown) with a glass fiber post and at least one remaining wall were analyzed. Standardized procedures were used, with annual follow-ups for up to 14 years. Failures were classified as repairable or non-repairable. Cox regression with shared frailty and Kaplan-Meier curves were used for statistical analysis.

Results: The median follow-up was 8.1 years for success and 10.58 years for survival. Overall, 10-year cumulative success and survival rates were 57.7% and 72.2%, respectively. Crowns had higher success (75.2%) and survival (79.4%) rates than composite resin (40.0% and 57.6%). Composite resin showed a significantly higher failure risk (HR = 3.53; p < 0.001), although survival did not differ statistically (p = 0.753). Most failures in composite resins were repairable (70%), while crown failures were mostly non-repairable (70%). At the final follow-up, 13 teeth were lost to follow-up in each group.

Conclusions: Metal-ceramic crowns demonstrated superior long-term success and required fewer repairs than composite resin restorations.

Clinical significance: For endodontically treated teeth, material selection influences outcomes. Metal-ceramic crowns provide longevity, while composite resin restorations offer the advantage of repairability.

Objective: Photocatalytic materials have shown great potential in oral care for caries prevention. However, challenges remain in promoting enamel remineralization while ensuring biosafety, as photocatalytic agents are applied directly to the tooth surface and may contact oral tissues or be swallowed. This study aimed to design a multifunctional photocatalytic material that integrates antibacterial, and remineralizing properties with high biosafety.

Methods: A hydroxyapatite-zinc oxide (ZnO-HAP) composite was synthesized via a hydrothermal method and characterized by XRD, SEM, and EDS. Photocatalytic activity under blue light (455 nm) was evaluated through hydroxyl radical (·OH) generation and dye degradation. Antibacterial, and remineralization performances were evaluated using standard plate counting method, and Vickers method. Biosafety was examined through cell viability assays and in vivo tests in mice.

Results: The ZnO-HAP composite exhibited strong photocatalytic activity and generated abundant hydroxyl radicals under blue light irradiation. ZnO-HAP treatment under light irradiation resulted in superior antibacterial efficacy and minimal enamel damage. The Ca/P ratio on the enamel surface increased from 1.52 to 1.86 after treatment, indicating effective mineral restoration. Moreover, the ZnO-HAP composite demonstrated excellent cytocompatibility, suggesting good biosafety.

Significance: The ZnO-HAP composite combines antibacterial activity, and remineralization capability in a biocompatible platform. Its biomimetic composition and light-activated functionality offer a safe and effective strategy for comprehensive oral care and enamel regeneration.

Objective: To develop a machine learning framework using Gaussian Process Regression (GPR) and Bayesian Optimization (BO) to predict and optimize the viscosity of resin composites at two shear rates (0.0106 and 74.4 s^-1).

Methods: Fifty-four experimental resin composite formulations were prepared using two types of main fillers and one type of fumed silica filler under controlled conditions. Viscosity was measured using a rotational rheometer at 25 °C, and log-transformed values at 0.0106 and 74.4 s^-1 were used as targets. The GPR models were trained with multiple kernel functions selected via 10-fold cross-validation (CV). Shapley Additive Explanations (SHAP) analysis was applied to interpret the feature contributions. BO with the Probability of Improvement acquisition function identified optimal formulations from 67,140 candidates.

Results: The predicted viscosity values at both shear rates were significantly correlated with the corresponding experimental data (p < 0.001, Pearson's correlation test). SHAP analysis revealed that fumed silica content had the greatest impact on viscosity at low shear rates, whereas main filler particle size and surface treatment were most influential at high shear rates. BO efficiently navigated the formulation space, achieving simultaneous optimization of V1 (0.0106 s^-1) within the target range and reducing V2 (74.4 s^-1) to the lowest quartile within only seven experimental iterations.

Significance: This study demonstrates the potential of GPR and BO for the data-driven design of dental resin composites. This approach enables rational optimization of handling properties, supporting clinical requirements for sculptability and extrudability. Future studies should expand the dataset and incorporate multi-objective optimization to balance viscosity with other critical properties such as mechanical strength and polymerization shrinkage.