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BACKGROUND: Dental resin composites' performance is intricately linked to their polymerisation shrinkage characteristics. This study compares polymerisation shrinkage using advanced 3D micro-computed tomography (micro-CT) and traditional 2D linear assessments. It delves into the crucial role of filler content on shrinkage and the degree of conversion in dental resin composites, providing valuable insights for the field. METHODS: Five experimental dental composite materials were prepared with increasing filler contents (55-75 wt%) and analysed using either 3D micro-CT for volumetric shrinkage or a custom-designed linometer for 2D linear shrinkage. The degree of conversion was assessed using Optical Photothermal Infrared (O-PTIR) and Fourier-Transform Infrared (FTIR) spectroscopy. Light transmittance through a 2-mm layer was evaluated using a NIST-calibrated spectrometer. Scanning Electron Microscopy (SEM) and Energy-Dispersive X-ray Spectroscopy (EDX) examined surface morphology and elemental distribution. Correlation between the investigated parameters was determined using Spearman correlation analyses. RESULTS: The study found significant differences in polymerisation-related properties among different filler content categories, with volumetric shrinkage consistently demonstrating higher mean values than linear shrinkage across most groups. Volumetric shrinkage decreased with increasing curing depth, showing no direct correlation between filler content and shrinkage levels at different curing depths. The results highlighted a strong negative correlation between filler content and degree of conversion, volumetric and linear shrinkage, as well as maximum shrinkage rate. Light transmittance showed a moderate correlation with the filler content and a weak correlation with other tested parameters. CONCLUSIONS: This study underscores the importance of considering both volumetric and linear shrinkage in the design and analysis of dental composite materials. The findings advocate optimising filler content to minimise shrinkage and enhance material performance. Integrating micro-CT and O-PTIR techniques offers novel insights into dental composites' polymerisation behaviour, providing a foundation for future research to develop materials with improved clinical outcomes.

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BACKGROUND: This study presents a novel multi-technique approach that integrates micro-CT and optical photothermal infrared spectroscopy (O-PTIR) to evaluate polymerisation differences, so-called spatio-temporal polymerisation properties, between flowable and sculptable dental resin-based composites. METHODS: Ten commercially available dental composites were investigated, including flowable and sculptable counterparts from the same manufacturer. Eight parameters were evaluated: short-term polymerisation characteristics (degree of conversion after 5 min, maximum polymerisation rate, time to reach maximum polymerisation rate) was measured using ATR-FTIR with real-time monitoring; changes in the degree of conversion with depth were evaluated with O-PTIR, 3D visualisation of shrinkage patterns, overall volumetric shrinkage, depth-specific shrinkage, and porosity were measured using micro-CT; surface morphology with detailed measurements of elemental composition was characterised using SEM/EDX; light transmittance was analysed with a NIST-referenced spectrometer. RESULTS: The study found that the increase in filler weight and volume ratio reduced the degree of conversion and polymerisation shrinkage, while moderately influencing the maximum polymerisation rates. The time to reach maximum polymerisation rates and light transmittance were not dependent on the filler amount. O-PTIR assessed a depth-dependent decrease in the degree of conversion for both composite types, with flowable composites generally showing a greater decrease in the degree of conversion than sculptable composites, except for bulk-fill composites. Micro-CT scans showed significantly higher flowable shrinkage values than their sculptable counterparts, highlighting the performance differences between the two types of composites. CONCLUSIONS: The findings of this study have practical implications for the selection and use of dental composites. Flowable composites, despite their higher degrees of conversion and polymerisation rates, also exhibit higher volumetric shrinkage, which can be detrimental for clinical applications. The new measurement methods used in this study provide a comprehensive overview of the polymerisation behaviour of commercially available dental composites, offering valuable insights for material optimisation.

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NANOTECHNOLOGY: is the art and science of dealing with nanoscale particles. This has transformed contemporary dental practices through myriad contributions to biomaterial science. Titanium dioxide nanoparticles procured from Bacillus subtilis, an eco-friendly and biogenic source, can significantly magnify the physiochemical attributes of dental materials. However, postoperative sensitivity is a major drawback of composite restorations. The incorporation of these nanoparticles into dental adhesives can greatly benefit clinical dentistry by resolving this issue. This trial aimed to evaluate the effectiveness of a novel titanium dioxide nanofortified adhesive on the postoperative sensitivity of composite restorations. METHODS: This triple-blind, parallel-group randomized controlled trial was conducted at the Department of Operative Dentistry and Endodontics, School of Dentistry, Islamabad, from May 15, 2023, to November 25, 2023. Participants (n = 60) with Class I and II primary carious lesions with a minimum cavity depth of 3-5 mm were randomly assigned to two groups (n = 30). After obtaining informed consent, the restorative procedure was accomplished using a minimally invasive approach and etch-and-rinse adhesive strategy. In group A, a nanofortified adhesive was used for composite restoration, whereas in group B, an adhesive without nanoparticles was used. Postoperative sensitivity was evaluated using the Visual Analog Scale (VAS) score at follow-up periods: of one day, one week, two weeks and one month. A Chi-square test was used to compare postoperative sensitivity between the two groups. The level of significance was set at p < 0.05. RESULTS: A noteworthy association was observed between sensitivity and the group variable at all four evaluation periods: after one day (p = 0.002), 1 week (p = 0.002), 2 weeks (p = 0.007) and one month. In conclusion, participants who underwent restorative intervention using titanium dioxide nanoreinforced adhesives reported a notable reduction in sensitivity at all time intervals. Hence, the occurrence and severity of postoperative sensitivity are significantly reduced using Bacillus subtilis-procured nanofortified adhesives as compared to conventional adhesives without nanoparticles. TRIAL REGISTRATION: This trial was retrospectively registered at ClinicalTrials.gov (ID: NCT06242184) on 03/02/2024. All procedures involving human participants were performed in conformance with this protocol.

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Objectives: Previous in vitro studies determined the whitening effects of bleaching products on stained resin composite surfaces. This in vitro study aimed to verify the effectiveness of a whitening system on composite resin previously subjected to pigmentation, specifically examining the depth of whitening effectiveness within the material structure. Materials and Methods: A commercially available nano-filled composite resin was used. Specimens were stained using a coffee-based solution and a 10% carbamide peroxide-based gel was employed as the whitening agent. The pigment's penetration and the effect of the bleaching gel were evaluated by measuring color (CieLab values) from the outer edge to the inner part of the specimens. Color measurements were taken at 14 points, starting from 0.1 mm from the external perimeter up to 3.0 mm. Results: Analysis of variance tests showed a statistically significant difference between the Control Group (CG), Pigmentation Group, and Whitening Group. The whitening agent was effective up to 1.5 mm in depth, with Whiteness index (W) values not statistically different from those of CG up to 0.5 mm in depth. Conclusions: Whitening agents on nano-filled resin composite previously pigmented appear effective in restoring the W to values similar to the original, particularly in the superficial layers of the sample.

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Introdução:Na odontologia moderna, a estética vem ocupando um espaço cada vez mais expressivo, e o desejo por dentes mais brancos, a insatisfação com o alinhamento dos dentes e com a anatomia dentária, têm sido os motivos mais relevantes de procura dos pacientes nos consultórios odontológicos.Objetivo:O presente artigo tem como objetivo descrever, através de relato de caso clínico, uma abordagem terapêutica estética e conservadora para fechamento de múltiplos diastemas anterossuperiores com a utilização de facetas de resina composta.Relato de caso:Paciente do sexo masculino, 21 anos de idade, procurou atendimento queixando-se de insatisfação estética pelos diastemas apresentados. Por meio de um planejamento digital das facetas em resina, com mockup e modelo impresso em 3D, as restaurações foram feitas respeitando anatomia, forma, opacidade e cores dos dentes naturais do paciente. O resultado dos procedimentos adotados foi satisfatório, demonstrando que a técnica empregada foi eficaz, sendo capaz de devolver um sorriso estético e biológico ao paciente. A odontologia contemporânea tem ofertado cada vez mais materiais com capacidade de devolver estética e função em dentes de forma minimamente invasivas, além de passar total confiabilidade em tratamentos a longo prazo, agradando o paciente desde a apresentação digital do planejamento traçado pelo cirurgião dentista com previsibilidade dos resultados, até o momento final do tratamento.Conclusões:O recontorno estético com resina composta representa uma opção funcional e de baixo custo para o tratamento de pacientes que apresentam diastemas múltiplos, principalmente em pacientes jovens pela preservação daestrutura dentária e possibilidade de reparo, sendo considerado um procedimento reversível, rápido e de baixo custo (AU).

Introduction:Aesthetics have been occupying an increasingly significant role in modern dentistry, and the desire for whiter teeth, dissatisfaction with tooth alignment, and dental anatomy concerns have been the most relevant reasons for patients seeking dental care. Objective:This article aims to describe an aesthetic and conservative therapeutic approach for closing multiple anterior upper diastemas using composite resin veneers in a clinical case report. Case report:A 21-year-old male patient sought treatment, expressing dissatisfaction with the diastemas he had. The restorations were performed using digital planning of the resin veneers with a mockup and a 3D-printed model, while respecting the patient's natural tooth anatomy, shape, opacity, and colors. The results of the adopted procedures were satisfactory, demonstrating effectiveness of the employed technique in restoring an aesthetic and biologically harmonious smile to the patient. Contemporary dentistry has been offering increasingly more materials capable of providing aesthetics and function to teeth through minimally invasive approaches. This not only ensures long-term treatment reliability, but also pleases the patient with a digital presentation of the treatment plan outlined by the dentist, predicting the results up to the final stages of the treatment. Conclusions:Aesthetic contouring using composite resin presents a functional and cost-effective option for treating patients with multiple diastemas, especially among young patients due to its preservation of dental structure, repair potential, and being considered a reversible, fast, and low-cost procedure (AU).

Introducción: En la odontología moderna, la estética viene ocupando un espacio cada vez más destacado, y las ganas de tener dientes más blancos, la insatisfacción con el alineamiento de los dientes, y la anatomía dental son las razonesmás relevantes por las cuales los pacientes acuden a las consultas odontológicas. Objetivo:El presente artículo tiene como objetivo describir, a través de un relato de caso clínico, un abordaje terapéutico estético y conservador para el cierre de múltiples diastemas anterosuperiores mediante el uso de carillas de resina compuesta. Informe de caso:Paciente del sexo masculino, 21 años de edad, buscó atendimiento quejándose de insatisfacción estética debido a los diastemas presentados. A través de una planificación digital de las carillas en resina, con un mockup y un modelo impreso en 3D, las restauraciones fueron ejecutadas, respetándose la anatomía, forma, opacidad y colores de los dientes naturales del paciente. El resultado de los procedimientos adoptados fue satisfactorio y demostró que la técnica utilizada fue eficaz, siendo capaz de restituir una sonrisa estética y funcional al paciente. La odontología contemporánea viene ofreciendo cada vez más materiales con la capacidad de devolver estética y función a los dientes de maneras mínimamente invasivas, además de brindar total confiabilidad en tratamientos a largo plazo, satisfaciendo al paciente desde la presentación digital del plan trazado por el cirujano dentista con la previsibilidad de los resultados, hasta el momento final del tratamiento. Conclusiones:El recontorneado estético con resina compuesta representa una opción funcional y de bajo costo para el tratamiento de pacientes con múltiples diastemas, especialmente en pacientes jóvenes, debido a la preservación de la estructura dental y la posibilidad de reparación. Se considera, de este modo, que se trata de un procedimiento reversible, rápido y económico (AU).

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OBJECTIVE: The aim of this study was to evaluate the degree of conversion (%), flexural strength (MPa), elastic modulus (GPa), compressive strength (MPa), Knoop microhardness (KHN), post-gel shrinkage (%) and prediction of ideal concentration of cholesteryl methacrylate (CM) in experimental resins. METHODS: Four formulations were manipulated (F): F1, control group, (0 % CM); F2 (15 % CM); F3 (19.8 % CM) and F4 (30 % CM). Bis-GMA and CM percentages were determined using Statistica™ software. For the degree of conversion test, Raman spectroscopy was used. To testing flexural strength, elastic modulus and compressive strength, a universal testing machine was used. For the Knoop microhardness test five indentations were made in each sample. Post-gel shrinkage was determined using the strain gauge method. Statistica™ software processed all data obtained in this study. Results were submitted to one-way ANOVA and Tukey's post hoc tests (α = 0.05). RESULTS: Better performance was observed for F2 (15 % CM) and F3 (19,8 % CM) for degree of conversion, elastic modulus and post-gel shrinkage. For Knoop microhardness F2 (15 % CM), F3 (19,8 % CM) and F4 (30 % CM) showed higher values than F1 (0 % CM). For flexural strength F1 (0 % CM) and F3 (19,8 %) were similar and F4 showed the lowest values and for compressive strength F1 (0 % CM) showed the highest values. For mixture designs analysis data, concentrations ≤ 25 % of CM would provide better results. SIGNIFICANCE: Addition of CM at concentrations lower than 30 % contributed to a significant increase in the degree of conversion, microhardness values, elastic modulus and reduction of post-gel shrinkage.

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OBJECTIVE: This study aimed to investigate the effects of adding cholesteryl methacrylate (CM) monomer to experimental composite resins and evaluate its impact on polymerization shrinkage force (PSF), Knoop microhardness (KHN), sorption and solubility (SS), vulnerability to spontaneous oxidation (VOE), porosity (BES), viscosity (V), and cross-link density (CLD). CM was synthesized, mixed with varying proportions of Bis-GMA, 70 wt% filler particles, and 40 % TEGDMA. The groups tested were: CM0 (60 % Bis-GMA), CM6 (54 % Bis-GMA/6 % CM), CM12 (48 % Bis-GMA/12 % CM), CM18 (42 % Bis-GMA/18 % CM) and CM24 (36 % Bis-GMA/24 % CM). The PSF was evaluated using a universal testing machine. KHN was measured with a 50 g load for 30 s. SS was determined according to ISO 4049:2009. VOE was measured with a three-electrode system in an electrochemical cell. BES images were obtained using an electron microscope to assess porosity. Viscosity was measured through rheological analysis. CLD was estimated from hardness readings before and after ethanol storage. RESULTS: CM6 (0.34 N) and CM12 (0.34 N) exhibited the lowest PSF values compared to CM0 (0.91 N). For KHN, CM6 (32.03) and CM12 (31.03) had higher values than CM0 (25.83) and were similar to CM18 (29.39) and CM24 (28.64). SS showed no significant differences among the groups. VOE indicated low vulnerability across all groups. CM12 had greater porosity compared to CM0 in BES images. CM0 had the lowest viscosity among the groups. No differences in CLD were observed among CM0, CM12, CM18, and CM24 regarding softening effects. SIGNIFICANCE: Adding CM to Bis-GMA/TEGDMA composite resins can reduce polymerization shrinkage force and increase the initial Knoop microhardness without affecting the other properties studied.

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Objectives: The use of fiber posts in endodontically treated primary maxillary central incisors improves the retention of composite resin restorations. The purpose of this study was to evaluate the effect of 4 different luting cements on fracture resistance of primary maxillary central incisors with fiber posts. Materials and Methods: In this in vitro study, 40 primary maxillary central incisors were endodontically treated and obturated with Metapex. They were then randomly divided into four groups (n=10) for cementation of fiber posts with GC Fuji I glass ionomer luting cement, Panavia F2.0 dual-cure luting cement, Panavia SA Luting Plus cement (self-adhesive), and TotalCem self-adhesive cement. After 1000 thermal cycles, the fracture resistance was measured. Data were statistically analyzed using ANOVA (alpha=0.05). Results: The mean fracture resistance was 267.07±130.01N in TotalCem, 257.27±102.56N in Panavia F2.0 dual-cure cement, 227.82±110.40N in Panavia SA Luting Plus self-adhesive cement, and 220.89±59.96N in GC Fuji I glass ionomer group. There was no statistically significant difference in fracture resistance among the four groups (P=0.714). Conclusion: Type of luting cement had no significant effect on fracture resistance of primary maxillary central incisors with fiber posts. Nonetheless, TotalCem yielded the highest fracture resistance. Considering its self-adhesive property and easy workability, it can be a good option for cementation of fiber posts in endodontically treated primary central incisors.

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Objectives: This study aimed to investigate the effect of different reinforcement techniques on the push-out bond strength of fiber posts to over-flared root canals. Materials and Methods: Forty-eight extracted human single-canal premolars were endodontically treated, over-flared, and randomly divided into four groups (N=12) including SARC: luting with self-adhesive resin cement, DCC: luting with dual-cure core build-up resin composite, CRR: relining root canal walls with bulk-fill resin composite, and DAP: relining fiber post with bulk-fill resin composite. After 24 hours, the roots were sectioned to obtain three cervical, middle, and apical 3mm slices. The push-out test was performed and failure pattern was examined. Kruskal-Wallis and post-hoc Dunn-Bonferroni tests were used for statistical analysis (P<0.05). Results: In all three regions, the lowest and highest bond strength was found in the SARC and DAP groups, respectively. In the middle region, there was a statistically significant difference between the bond strength of the SARC group and that of the DCC (P=0.044), CRR (P=0.021), and DAP (P<0.001) groups. There was no significant difference in the apical region. The lowest bond strength was observed in the apical region, and the highest was related to the cervical region. Adhesive failure was the most common failure pattern in all groups. Conclusion: Based on our results DCC, CRR and DAP methods increased bond strength in the middle and cervical sections of over-flared root regions. Considering that DCC is the easiest and most practical method, we propose that CRR and DAP can be replaced with this method in clinical procedures.

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OBJECTIVE: To evaluate the fracture behavior of human molars with extensive MOD restorations using short-fiber-reinforced resin composite of varying viscosities. MATERIALS AND METHODS: Human molars were randomly divided into seven groups (n = 12): intact teeth (control); restoration using conventional high-viscosity resin composite without (Filtek Z350XT, 3M) or with fibers (everX Posterior, GC); conventional low-viscosity resin composite without (Filtek Supreme Flowable, 3M) or with fibers (everX Flow Dentin Shade, GC); bulk-fill low-viscosity resin composite (Filtek Bulk Fill Flow, 3M) or with fibers (everX Flow Bulk Shade, GC). Restorations were performed on extensive MOD preparations, following the manufacturers' recommendations for each material. Specimens underwent fracture strength testing (N) and fracture pattern (%) categorized as repairable, possibly repairable, or non-repairable. Results were analyzed using a generalized linear model (N) and Fisher's exact test (%), with α = 0.05. RESULTS: Restorations performed with high-viscosity materials showed fracture strength values similar to the control and higher than those of restorations using low-viscosity resin composites (p < 0.0001), except for the bulk-fill low-viscosity resin composite with fibers (p > 0.05). Teeth restored using low-viscosity resin composite with fibers showed a higher % of repairable and possibly repairable fractures than the control (p = 0.0091). CONCLUSIONS: The viscosity of materials mediated the fracture strength, with restorations using high-viscosity resin composites promoting values similar to the intact tooth; however, the presence of fibers influenced the fracture pattern. CLINICAL SIGNIFICANCE: Teeth with MOD cavities restored with high-viscosity resin composites showed similar fracture strength to intact teeth. Fiber-reinforced low-viscosity resin composite for the base of restoration resulted in a more repairable/possibly repairable fracture pattern.

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The aim of this study was to evaluate the influence of different mouthwash solutions on the color stability of a nanohybrid composite resin. Forty discs of Luna nanohybrid composite resin were prepared and randomly assigned to 4 experimental groups (n = 10), determined by the type of immersion solution: distilled water (DW); Oral-B Pro-Health mouthwash (OBPH); Listerine Total Care mouthwash (LTC); or Colgate Plax Infinity mouthwash (CPI). The discs were immersed in solution for 30 minutes a day and stored at 37°C for 24 hours. Digital photographs of each specimen were taken at each timepoint and transferred to a computer program for color analysis. The International Commission on Illumination L*a*b* system was used to analyze the color of the specimens at baseline and the overall color change (ΔE*) at baseline, 30 days, 60 days, and 90 days. Two-way analysis of variance was used to evaluate the influence of solution and time on ΔE* values (α = 0.05). The t test was used as a post hoc test to compare the mean values between groups (α = 0.05). After 30 days, all groups showed small color change values compared with baseline (ΔE*1 < 1.0). However, after 60 days, the LTC and CPI groups showed greater color change (ΔE*2) than the other groups, and the difference was statistically significant (P < 0.05). After 90 days, all groups differed significantly compared with the control group (P < 0.05), and all mouthwash groups presented color change values that are considered clinically unacceptable (ΔE*3 > 3.0). The results of this in vitro study indicate that mouthwash solutions do not cause significant color changes in nanohybrid composite resin for a period of up to 30 days; however, longer periods (90 days) of exposure could make the restorative material esthetically unacceptable.

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The objective was to compare the color match and color stability behavior of single- and multi-shade resin-based composites (RBCs) used for direct restorations. This review was conducted according to the Preferred Reporting Items for Systematic Reviews and Meta-Analyses guidelines. Randomized clinical trials evaluating the shade performance of single-shade RBCs in direct restorations were included. A search of the scientific literature was performed in five databases (April 2024). The meta-analysis was performed using RevMan 5.4, calculating the risk difference (RD) and 95% confidence interval (CI) of the dichotomous outcome using a random effects model. Bias was assessed using the RoB 2.0 tool, and certainty of evidence was assessed using the GRADEpro tool. Four studies were selected, with 263 restorations analyzed. The results showed comparable performance between single-shade RBCs and multi-shade RBCs in terms of color match and color stability over 12 months. Three studies had a low risk of bias with all expected results, and one study had some concerns. The certainty of evidence for color stability was considered low for all follow-up periods due to the small number of events and sample size. According to the United States Public Health Service Evaluation (USPHS) and the World Dental Federation (FDI), there is comparable clinical color performance between single-shade and multi-shade RBCs over 12 months.

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Objective: To evaluate the clinical efficacy of novel titania-nanoparticle reinforced bonding agent on post-restorative sensitivity in patients. Methods: This triple-blinded, randomized clinical trial included participants (n = 60) having Class- I and II cavitations with a minimum cavity depth of 3mm at Department of Operative Dentistry & Endodontics, School of Dentistry, Shaheed Zulfiqar Ali Bhutto Medical University, Islamabad from January 5, 2023, to June 20, 2023. They were randomly assigned into two groups A and B (n = 30). After informed consent, restorative intervention was accomplished using an etch-and-rinse adhesive strategy. In Group-A, titania-nanoparticle-incorporated bonding agent was used for composite restoration, while in Group-B, bonding agent without nanoparticles was used. The primary outcome was assessed using Visual Analogue Scale mean score. Participants were instructed to rate their sensitivity status at follow-ups: 24 hours, one week, and one month. Mann-Whitney U test was employed to compare sensitivity between the two groups. Results: According to results of this trial, a significant difference was observed between two groups after 24 hours (p = 0.004) and one week (p = 0.002). However, no discernible difference was observed after one month (p = 0.643). Conclusion: Post-restorative sensitivity in patients with composite restorations was reduced using titania-reinforced bonding agents as compared to bonding agents without nanoparticles. This shows that inclusion of titania nanoparticles into adhesive dentistry could be beneficial in resolving post-restorative sensitivity occurring with composite restorations.

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This study evaluated the changes in surface properties of three resin-based restorative materials after two laser-assisted, in-office tooth bleaching protocols using erbium, chromium: yttrium-scandium-gallium-garnet (Er,Cr:YSGG) or diode (980 nm) lasers. A nanohybrid composite (Enamel Plus HRi), a Bis-GMA-free composite (Enamel Plus HRi Bio Function), and a resin-matrix CAD-CAM ceramic (Shofu Block HC) were tested. Forty specimens for each material were prepared and divided into four groups (n = 10/group). The control specimens did not undergo any bleaching treatment, whereas group 2 received bleaching with 40% hydrogen peroxide (H2O2), while groups 3 and 4 underwent the same bleaching procedure with the use of diode (980 nm) or Er,Cr:YSGG lasers, respectively. Surface microhardness and roughness measurements were conducted using a Vickers tester and an optical profilometer. Microhardness was lower in bleached specimens, with the nanohybrid composite exhibiting the largest difference from the no bleaching group. For the Bis-GMA-free composite the microhardness difference between no bleaching and laser-assisted bleaching were smaller than seen for the conventional bleaching technique. Surface roughness was higher in bleached specimens, with nanohybrid composite showing the largest differences from the control specimens. The examined laser-assisted tooth bleaching protocols were found not to impact surface microhardness and roughness of the tested resin-based specimens and they are deemed suitable for clinical use.

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Background: The main disadvantage of silver diamine fluoride (SDF) is its persistent dark coloring. The aim of this study was to cover this discoloration on affected primary tooth dentin with different materials and subsequently measure their shear bond strength (SBS). Materials and Methods: In this in vitro study total of 60 primary teeth were demineralized and randomly divided into five groups (n = 12). The tooth surfaces were treated with 38% SDF, and restorative cylinders were built on the dentin as follows: (1) phosphoric acid etching + GLUMA Universal Adhesive (GUA; etch-and-rinse mode) + composite resin (CR); (2) GUA (self-etch mode) + CR; (3) resin-modified glass ionomer (RMGI; Fuji II); (4) Surefil One (self-adhesive CR); and (5) TheraCem (self-adhesive resin cement) + CR. After restoration, the specimens were tested for SBS. Failure mode was determined by digital analysis and scanning electron microscopy. Data were analyzed by one-way analysis of variance and Tukey's honest significant difference post hoc test. P <0.05 indicated statistical significance. Results: Group 1 had significantly higher mean SBS (P < 0.05) compared to Groups 2-5, while Group 5 had the least SBS (P < 0.001). Mean SBS differences between Groups 2 and 3 were not significant (P = 0.328). Group 4 had lower mean SBS than Groups 1 (P < 0.001) and 2 (P = 0.17). Most groups showed adhesive failure. Conclusion: CR associated with the universal adhesive in etch-and-rinse mode had much higher SBS than the other groups; therefore, we recommend it to cover the dark discoloration generated by SDF.

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AIM: This study compared the effectiveness of several techniques in restoring compromised bonding to recently bleached enamel. METHODS: Seventy-five healthy bovine incisors were divided into five groups (n = 15). Fifteen teeth (Group 1) remained intact, whereas 60 (Groups 2 to 5) underwent at-home bleaching with 16% carbamide peroxide. The bonding procedures were as follows: Group 1: Bonding of resin composite to unbleached enamel; Group 2: Bonding immediately after bleaching; Group 3: Application of a 10% sodium ascorbate solution for 10 min before bonding; Group 4: Enamel removal to the depth of 0.5 mm; and Group 5: Increased curing time of the bonding agent to 80 instead of 20 s. After 24 h, the specimens were subjected to micro-shear testing, and the failure mode was determined. RESULTS: ANOVA revealed a significant difference in bond strength among the groups (P < 0.001). The mean bond strength was significantly lower in group 2 than in other groups (P < 0.05), which showed comparable bond strength to each other (P > 0.05). Adhesive failure was the most predominant failure type in all groups. The mixed failure occurred with a frequency of 26.7% in groups 3 and 5. The Fisher's exact test revealed a significant difference in failure modes among the groups (P = 0.047). CONCLUSIONS: The three experimental procedures used in this study, including the application of 10% sodium ascorbate before bonding, enamel removal to the depth of 0.5 mm, and increasing the curing time of the bonding agent to 80 s, were effective in restoring the compromised bonding to recently bleached enamel.

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OBJECTIVES: To assess the impact of elastic gradients formed among restorative material, cement, and substrate on the fracture resistance of tri-layer restorative systems. METHODS: Four CAD/CAM materials were utilized, two glass-ceramics (IPS e.max CAD, Vita Suprinity) and two resin-ceramic hybrids (Vita Enamic, Lava Ultimate). Their fracture resistance was examined by biaxial flexure (n = 8) and Hertzian indentation (n = 10) tests. Statistical analysis was conducted using ANOVA and Tukey tests (p = 5 %). Finite element analysis (FEA) was employed to simulate the Hertzian indentation test and elucidate the stress-fields formed on the intaglio surface below the loading area. RESULTS: The biaxial flexural strength (MPa) of glass-ceramics exceeded the hybrid materials (e.max 417a, Suprinity 230b, Enamic 138c, and Lava Ultimate 183bc). Conversely, the load-bearing capacity (N) of the materials bonded to dentin analog demonstrated the opposite trend, with the hybrid materials achieving superior results (e.max 830 C, Suprinity 660D, Enamic 1822B, and Lava Ultimate 2593 A). The stress-fields observed by FEA were coherent with the experimental results for Hertzian flexural stresses (MPa): e.max 501 A, Suprinity 342 C, Enamic 406B, whereas no tensile stress was observed at the intaglio surface of Lava Ultimate. SIGNIFICANCE: Detailed analysis of the fracture resistance of the tri-layer restorative systems showed that the elastic gradients play a more significant role than the flexural strength of the restorative materials. The coherence of the elastic moduli between the restorative material and supporting structures results in reduced tensile stress concentration at the intaglio surface beneath the loading area and enhances the ability to withstand load.

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Objective: Compare the surface roughness of two composite resins after immersion in carbonated beverages. Materials and methods: 160 resin discs (6 x 2 mm) were divided into 8 groups (n=20 per group) according to type of resin (Filtek™ Z350 XT® and Palfique LX5®) and type of immersion in beverages (distilled water, Coca Cola®, Inca Kola® and Kola Escocesa®. The immersions were carried out under a structured cycle: 4 immersions a day for 5 days, intermediate storage in distilled water and overnight incubation for 8 h at 37°C. The measurements with the roughness meter were evaluated in three times: baseline, 7 and 14 days. The three-way Anova test was used at P<0.05. Results: Roughness showed differences only for the individual factors of time (P<0.000) and resin (P=0.000), and for the interaction time*drink (P=0.000) and resin*drink (P=0.003). Roughness was higher with Filtek Z350 XT® immersed with Inca Kola® (0.85 ± 0.37) than 14 days compared to other times (P=0.035) and with Palfique LX5 immersed in Coca Cola® at 7 days (1.61 ± 0.42) and in Inca Kola® at 14 days (1.66 ± 0.56) compared to distilled water (P<0,05). Conclusion: Surface roughness was affected by the type of resin, the type of soft drink and the immersion time. The roughness was greater with the Palfique LX5® nanohybrid resin, the Inca Kola® drink and after 14 days of immersion.

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Resin composites have become the preferred choice for chairside provisional dental restorations. However, these materials may undergo discoloration, changes in surface roughness, and mechanical properties with aging in the oral cavity, compromising the aesthetics, functionality, and success of dental restorations. To investigate the color and mechanical stability of chairside provisional composite resins, this study evaluated the optical, surface, and mechanical properties of four temporary restoration resin materials before and after aging, stimulated by thermal cycling in double-distilled water. Measurements, including CIE LAB color analysis, three-point bending test, nanoindentation, scanning electron microscopy (SEM), and atomic force microscopy (AFM), were conducted (n = 15). Results showed significant differences among the materials in terms of optical, surface, and mechanical properties. Revotek LC (urethane dimethacrylate) demonstrated excellent color stability (ΔE00 = 0.53-Black/0.32-White), while Artificial Teeth Resin (polymethyl methacrylate) exhibited increased mechanical strength with aging (p < 0.05, FS = 68.40 MPa-non aging/87.21 MPa-aging). Structur 2 SC (Bis-acrylic) and Luxatemp automix plus (methyl methacrylate bis-acrylate) demonstrated moderate stability in optical and mechanical properties (Structur 2 SC: ΔE00 = 1.97-Black/1.38-White FS = 63.20 MPa-non aging/50.07 MPa-aging) (Luxatemp automix plus: ΔE00 = 2.49-Black/1.77-White FS = 87.72 MPa-non aging/83.93 MPa-aging). These results provide important practical guidance for clinical practitioners, as well as significant theoretical and experimental bases for the selection of restorative composite resins.

RESUMEN

OBJECTIVE: Sodium hypochlorite solution (NaOCl) is an effective canal irrigant but interferes with the mechanical features of dentin and the bonding capability of adhesives when restoring endodontically treated teeth. This study evaluated whether access cavity resin sealing before using canal irrigant would augment the resistance of endodontically treated anterior teeth against fracture. METHODS: Sixty maxillary incisors underwent endodontic treatment in five groups (n = 12). Irrigation with 5.25% NaOCl and 17% ethylenediaminetetraacetic acid (EDTA) was performed in all groups except for Group 5. After root canal obturation, in Group 1, the access cavity was kept unrestored. In Group 2, immediate restoration after obturation was achieved. For Group 3, delayed restoration after 1 week was provided. In Group 4 (pre-sealed), before canal irrigation, the dentin surface of access cavities was sealed using self-adhesive composite resin (Vertise Flow) and then restored after obturation. In Group 5, which was saline irrigated, immediate restoration was performed. After storage and thermal cycling for 5000 cycles at 5°C-55°C with a dwell time of 15 s and a transfer time of 5 s, teeth were statically loaded by a universal testing machine until a fracture occurred. Data were collected as the fracture resistance (FR) and analyzed using the one-way analysis of variance and Tukey's tests. RESULTS: FR significantly differed between all groups (p < 0.001). The lowest FR was recorded in the unrestored group (284 ± 86 N), which was not statistically different from the immediately restored group (p = 0.065). The pre-sealed group exhibited the highest FR value (810 ± 127 N, p ≤ 0.02 vs. other groups). The FR of the saline-irrigated and delayed restored groups was almost similar (p = 0.13). CONCLUSIONS: NaOCl/EDTA irrigation resulted in an adverse effect on FR. Delayed restoration could reduce this adverse effect. Access cavity pre-sealing with flowable composites led to a higher FR than conventional methods and may be considered an effective step during treatment procedures.

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