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Otimização dos parâmetros de fotoativação: efeitos do tempo e dose de energia em uma resina composta nanohíbrida

2026-07-16T06:27:14Z

Title: Otimização dos parâmetros de fotoativação: efeitos do tempo e dose de energia em uma resina composta nanohíbrida Abstract: The evolution of composite resins over the past decades represents one of the most significant advances in modern dentistry, offering superior aesthetic, functional, and biocompatibility benefits compared to traditional restorative materials. In this context, photoactivation has allowed for better control of clinical working time and improved the physicomechanical properties of these materials, with the light energy dose — directly dependent on the photoactivation time — being a critical factor for the formation of an adequate three-dimensional polymer network. Inadequate polymerization, whether due to insufficient or excessive energy dosage, can lead to failure and increased degradation. Therefore, optimizing polymerization requires a balance between the applied light energy and the material's characteristics. This study aimed to evaluate the influence of different energy doses (11,5 J/cm²; 23,0 J/cm²; 46,0 J/cm²; 69,0 J/cm²; and 138,0 J/cm²) by varying photoactivation times (10, 20, 40, 60, and 120 seconds), on the physicomechanical properties of a nanohybrid composite resin (Aura, shade DC2, SDI, Australia), including Knoop microhardness, elastic modulus, degree of conversion, diametral tensile strength, sorption and solubility, three-point flexural strength, and interlayer adhesion. Data were subjected to statistical analysis, including normality tests (Shapiro–Wilk) and homogeneity of variance (Levene). Two-way repeated measures ANOVA and Tukey’s HSD post-hoc test were used for microhardness, elastic modulus, degree of conversion, and flexural strength. Student’s t-test was applied for diametral tensile strength, and the Kruskal–Wallis test followed by Tukey was used for sorption, solubility, and interlayer adhesion. All analyses were conducted with a 95% confidence level (α=0.05). The results showed that shorter photoactivation times, such as 10 seconds, resulted in significantly lower mechanical properties (P<0.001), such as microhardness (top: 51.41 ± 5.57 KHN; bottom: 43.88 ± 3.97 KHN), elastic modulus (top: 9.93 ± 2.70 GPa; bottom: 8.76 ± 2.92 GPa), and flexural strength (54.85 ± 6.95 MPa). Additionally, a lower degree of conversion was observed at the bottom surface (23.16% at 10s; P<0.001), along with higher sorption (30.38 ± 4.55 µg/mm³; P<0.001) and solubility (13.15 ± 3.36 µg/mm³; P<0.001), and reduced interlayer adhesion (5.99 ± 0.17 MPa; P<0.001). Although the top surfaces reached an acceptable degree of conversion starting at 20s of activation (64.60%; p=0.159), the bottom regions required longer photoactivation times to achieve satisfactory performance. Diametral tensile strength was not significantly affected by activation time (P=0.442). It was observed that activation times between 40 and 60 seconds resulted in the optimization of most evaluated properties, while 120 seconds did not bring additional benefits and even led to a reduction in flexural strength (95.77 ± 4.91 MPa for 120s; P<0.001), possibly due to higher internal stresses. It is concluded that photoactivation time and energy dose are critical factors influencing the physicomechanical properties of composite resins. Photoactivation time and energy dose influenced the physico-mechanical properties of composite resins. Short exposure (10s) resulted in inferior performance, while optimized photoactivation occurred between 40 and 60 seconds. Excessive exposure (120s) provided no additional benefits and were, sometimes, detrimental. Thus, the delivered light energy dose defines the quality of polymerization, which is essential for the clinical success of resin-based restorations.

Transmissão de luz emitida por fotopolimerizador multi-picos através de braquetes cerâmicos mono e policristalinos

2026-04-09T06:17:29Z

Title: Transmissão de luz emitida por fotopolimerizador multi-picos através de braquetes cerâmicos mono e policristalinos Abstract: Objective: To evaluate light transmission through monocrystalline and polycrystalline ceramic brackets using a multi-peak light-curing unit (LCU). Materials and Methods: In vitro study with seventeen ceramic brackets: five monocrystalline (IceramS, InspireIce, Luminous, Radiance, Safira) and twelve polycrystalline (CeramicSLI, ClarityAdvancedCeramic, DamonClear, Iceclear, Iceram, Iceram, In-OvationC, In-Vu, Inflexion, OvationC, PolySafira, and Translux). LCU power and emission spectrum in normal and ortho modes were measured at zero mm from the integrating sphere aperture and transmitted through each bracket using an integrating sphere connected to a spectrometer. Irradiance and transmitted energy were calculated. Beam profiles were obtained via laser beam profiler. Data were analyzed by two-way ANOVA and Tukey's test (α = 0.05). Results: All brackets significantly reduced radiant power, irradiance, and energy compared to the light emitted by the LCU (P < 0.001). PolySafira and IceramP showed higher light transmission, while CeramicSLI and In-Vu showed the lowest values. Light transmission was not influenced by the crystalline structure. The ortho mode increased radiant power and irradiance but reduced total energy compared to the standard mode (P < 0.001). Conclusion: Light transmission depends on bracket design and optical properties, rather than crystalline structure. The activation mode modifies light emission; the ortho mode increases irradiance but reduces total energy, which is lower than required for light-activation of orthodontic resins, a factor that should be considered when selecting polymerization protocols. Keywords: Orthodontic Brackets; Ceramics; Curing Lights Dental; Photopolymerization.

Lipoxina A4 e Resolvina D1 preservam a capacidade de indução neural de células-tronco da polpa dentária cultivadas sob condições inflamatórias

2026-02-27T06:21:15Z

Title: Lipoxina A4 e Resolvina D1 preservam a capacidade de indução neural de células-tronco da polpa dentária cultivadas sob condições inflamatórias Abstract: Human dental pulp stem cells (DPSCs) exhibit neurogenic differentiation potential; however, inflammatory conditions may impair this process. This study investigated the impact of tumor necrosis factor-alpha (TNF-α) on DPSC neurodifferentiation and the modulatory role of the pro-resolving lipid mediators lipoxin A4 (LXA4) and resolvin D1 (RvD1). DPSCs were isolated and subjected to neuronal differentiation for 21 days. The optimal TNF-α concentration was determined in a pilot study using real-time PCR. The expression of OCT3/4, doublecortin, and β-III-tubulin was analyzed by MTT assay, flow cytometry, and immunofluorescence. The effects of LXA4 (10 or 100 nM) and RvD1 (10 or 100 nM) were assessed by flow cytometry. Data were analyzed using the Kruskal–Wallis test followed by the Mann–Whitney test (p<0.05) and one-way ANOVA with Tukey’s post hoc test. TNF-α at a concentration of 25 ng/mL was shown to induce inflammation without causing cytotoxicity. The high production of doublecortin indicated the neuronal differentiation potential of DPSCs, whereas reduced β-III-tubulin expression demonstrated that TNF-α inhibits the progression of neuronal differentiation. Conversely, increased β-III-tubulin expression in the presence of LXA4 (10 and 100 nM; p=0.02 and p=0.03, respectively) and RvD1 (100 nM; p=0.02) indicate that these mediators attenuate the inhibitory effects of TNF-α. These findings suggest that anti-inflammatory therapy combined with DPSCs may enhance motor recovery following neurotrauma.

Impacto da pandemia de COVID-19 nos intervalos de tempo da trajetória diagnóstica e terapêutica de pacientes com câncer da cavidade bucal

2026-02-24T06:20:32Z

Title: Impacto da pandemia de COVID-19 nos intervalos de tempo da trajetória diagnóstica e terapêutica de pacientes com câncer da cavidade bucal Abstract: This study aimed to evaluate the potential impact of the COVID-19 pandemic on the diagnostic and therapeutic trajectory of patients with oral cavity cancer. A retrospective, cross-sectional study was conducted using secondary data from patients diagnosed with oral cancer between 2017 and 2023, who were treated at a regional reference center for oncological diagnosis and treatment in the state of Minas Gerais, Brazil. The cases were categorized into three groups according to the year of diagnosis: pre-pandemic (2017–2019), pandemic (2020–2021), and post-pandemic (2022–2023). Demographic, clinical, pathological, and therapeutic information was collected for sample characterization and comparative analyses to identify significant variations. A shorter delay in seeking care for the initial diagnosis was observed during the pandemic, whereas in the post-pandemic period a longer interval between histopathological diagnosis and the first oncological consultation was observed. Overall survival did not show a statistically significant difference between the groups. These findings indicate that the pandemic impacted essential stages of the oral cancer care, particularly access to oncology services. This underscores the need for screening strategies and strengthening the referral networks to ensure early diagnosis and appropriate treatment, especially in the context of public health crises.