Search Results (139)

Background: This study assessed the effect of solvent aging on Vickers microhardness (VHN) and fracture toughness (K_IC) of four resin composites: two high-strength flowable materials indicated for all cavity classes (GUF and CBF), a packable nanohybrid composite (XTE), and its flowable counterpart (XTEF). Methods: Disk specimens (n = 6 per group) were photocured and stored at 37 °C in distilled water or in a 75%/25% ethanol/water solution for 1 or 30 days. Vickers microhardness was recorded with a 300 g load applied for 15 s. Single-edge-notched beam (SENB) specimens (32 × 6 × 3 mm; n = 6 per group) were loaded in three-point bending for K_IC determination after 1 and 30 days of storage in water or ethanol/water. Data were analyzed by three-way ANOVA followed by Tukey’s post hoc test (α = 0.05). Results: At 1 day, the four composites separated into distinct VHN groups in the order XTE > GUF > CBF > XTEF (p ≤ 0.05). After 30 d, VHN decreased in all materials, with larger reductions in ethanol/water (17–30% relative to the 1 d water value) than in water alone (5–11%). At 1 day, K_IC values for XTE, GUF and CBF formed a single statistical group, all significantly higher than XTEF (p ≤ 0.05). Thirty-day water storage did not affect K_IC for any material (p > 0.05), whereas ethanol/water storage reduced K_IC by 21–26% in all four composites and produced four distinct material groups (p ≤ 0.05). Conclusions: The high-strength flowable composites showed greater hardness and toughness than a conventional flowable composite but did not match the mechanical performance of the highly filled packable composite. Ethanol/water aging markedly softened the composite surfaces and reduced fracture toughness, whereas prolonged water storage had a smaller effect on hardness and no measurable effect on K_IC. Full article

Deep margin elevation (DME) is a conservative technique used to relocate subgingival proximal margins to a more favorable supragingival position, facilitating adhesive procedures and impression taking. This in vitro study evaluated the influence of two DME materials—a universal flowable resin composite and a self-adhesive flowable resin composite—on the cervical interfacial sealing ability of lithium disilicate glass–ceramic CAD/CAM inlay restorations. Twenty extracted maxillary premolars were randomly allocated into two groups (n = 10). Group A received DME using a universal flowable resin composite (3M™ Filtek™ Z350 XT) preceded by a conventional adhesive system, while Group B received DME using a self-adhesive flowable resin composite (Vertise™ Flow). All teeth were restored with lithium disilicate CAD/CAM inlays (CEREC Tessera) cemented with a self-adhesive resin cement (Breeze^®). Specimens underwent thermocycling (10,000 cycles; 5–55 °C). Marginal gaps were assessed at the DME interface using high-resolution micro-computed tomography (micro-CT) in both coronal and sagittal cross-sections, before and after thermocycling. Statistically significant differences were found between groups in both sections before and after thermocycling (p < 0.05). The self-adhesive composite (Group B) demonstrated significantly lower gap values compared to the universal flowable composite (Group A) in both coronal and sagittal assessments. Thermocycling increased the gap in both groups; however, Group B maintained considerably lower leakage. The self-adhesive resin composite showed superior sealing ability at the DME interface compared to the universal flowable composite when used under lithium disilicate glass–ceramic inlay restorations. Further clinical studies are recommended to validate these findings. Full article

Clear aligner therapy has become increasingly widespread in contemporary orthodontics, relying on composite resin attachments to enhance force transmission and improve the predictability of tooth movement. The physicochemical and mechanical properties of these biomaterials play a crucial role in attachment durability, dimensional stability, and esthetic performance during treatment. This systematic review aimed to evaluate how different composite resin types influence the mechanical, optical, and functional performances of orthodontic attachments used in clear aligner therapy. A systematic literature search was conducted in the PubMed, Scopus, and Cochrane databases for studies published between 2015 and 2025, following PRISMA guidelines. In vitro studies and clinical trials evaluating composite resins used for attachment fabrication were included. Fifteen studies met the eligibility criteria, including eleven laboratory investigations and four clinical studies. The evaluated outcomes comprised shear bond strength, wear resistance, surface roughness, microhardness, color stability, and accuracy of attachment reproduction. Overall, all evaluated composite resins demonstrated shear bond strength values within clinically acceptable ranges. However, significant differences were observed in the material performances depending on the resin composition and viscosity. Nanohybrid and high-viscosity composite resins were generally associated with improved mechanical resistance, reduced wear, and greater dimensional stability, although SBS outcomes should be interpreted in light of the bonding protocols used. In contrast, flowable composite resins showed improved handling and adaptation to attachment molds but presented higher susceptibility to surface degradation and discoloration. The findings suggest that the composition and properties of composite resins significantly influence the mechanical and optical behavior of orthodontic attachments. Optimizing material selection according to biomechanical demands and esthetic requirements may improve attachment longevity and treatment predictability in clear aligner therapy. Clinicians should prioritize nanohybrid or high-viscosity composite resins for high-load attachments and use flowable composite resins materials when adaptation and esthetics are critical. Full article

Clear aligner therapy (CAT) increasingly relies on composite-based attachments to improve force transmission and aligner retention, yet the role of flowable composite properties in clinical performance remains poorly understood. In this study, five commercially available flowable composites used for orthodontic attachments—Aligner FLOW LC, SIMPLY SHADE, SOFT ENA Flow, TETRIC EvoFlow, and VENUS Bulk Flow One—were comparatively investigated through physicochemical, morphological, optical, thermal, and rheological characterization. Scanning electron microscopy coupled with energy-dispersive X-ray analysis, thermogravimetric analysis, UV–Vis–NIR and ATR–FTIR spectroscopy, and rheological measurements before and after curing were employed to probe composition, filler content, viscoelastic behavior, and mechanical response. The results revealed marked differences among the investigated materials, with post-curing storage modulus spanning nearly two orders of magnitude, from 0.06 MPa for SOFT ENA Flow to approximately 5 MPa for SIMPLY SHADE. Similarly, the elastic modulus ranged from about 20 MPa to nearly 1000 MPa for the softest and stiffest resins, respectively. Interestingly, SOFT ENA Flow, the softest material after curing, also exhibited the highest pre-curing viscosity, nearly one order of magnitude greater than the least viscous resin, Aligner FLOW LC. These findings highlight an intrinsic trade-off between pre-cure processability and post-cure mechanical stability, providing a rational framework for material selection in orthodontic attachments and supporting more predictable and durable CAT outcomes. Full article

Background/Objectives: Provisional restorations are essential in prosthodontic treatment, and reliable intraoral repair is clinically important during extended interim use. This in vitro study evaluated the effects of organic solvent pretreatment on surface characteristics and shear bond strength (SBS) of CAD/CAM provisional restorative materials fabricated by milling, stereolithography (SLA), and digital light processing (DLP). Methods: Three materials were assigned to five surface treatment conditions: no solvent (control), isopropyl alcohol (IPA), tetrahydrofuran (THF), acetonitrile (ACN), and pyridine (PYR). After pretreatment, separate specimens were used for surface analysis and SBS testing. Surface roughness was measured by atomic force microscopy using arithmetic mean height (S_a) and root mean square height (S_q), and surface morphology was examined by scanning electron microscopy (SEM). For SBS testing, specimens were repaired using a universal adhesive and a flowable resin composite, followed by failure mode analysis. Data were analyzed using two-way ANOVA and Tukey’s post hoc test (α = 0.05). Results: Material type, solvent treatment, and their interaction significantly affected SBS, S_a, and S_q. The DLP material showed the highest SBS overall, with no significant differences among treatments. In the SLA material, ACN resulted in the lowest SBS, whereas PYR showed the highest mean value. In the milled material, THF, ACN, and PYR produced significantly higher SBS than the control and IPA groups. Conclusions: Within the limitations of this study, the effect of organic solvent pretreatment on repair performance was substrate-dependent. Full article

Heat generated during photopolymerization of resin-based composites from both the exothermic reaction of the material and the irradiance of light-curing units poses a risk to pulp vitality, especially in deep restorations. This study aimed to evaluate temperature variation (ΔT) during the photopolymerization of different resin composites, considering material type, shade, increment thickness, and light-curing unit output. An in vitro experimental study with a factorial design was conducted. Specimens were prepared using 2.0 mm and 4.0 mm increments from conventional (nanohybrid), bulk-fill, and flowable resin composites in different shades (BW, A1, A3, A4, and XB) and different light-curing unit output (100% and 50% battery charge). ΔT was measured using a type K thermocouple (Omega Engineering, Norwalk, CT, USA) positioned at the center of each increment. Data were analyzed using four-way analysis of variance (ANOVA) (α = 0.05). All groups demonstrated a statistically significant temperature increase (p < 0.05), with ΔT values ranging from 3.24 °C to 18.18 °C. Composite type significantly influenced ΔT (p < 0.001), with flowable composites showing the highest temperature rise, followed by bulk-fill and conventional composites. Increment thickness also had a significant effect (p = 0.008), with 4.0 mm increments producing greater temperature increases. Shade significantly affected ΔT (p < 0.001), with the XB shade exhibiting the highest values. Additionally, higher light-curing output (100%) resulted in significantly greater temperature increases compared to 50% output (p < 0.001). Photopolymerization temperature rise is influenced by multiple interacting factors. The combination of flowable composites, darker shades, thicker increments, and higher curing output may increase thermal risk. These findings should be considered when optimizing clinical protocols to minimize potential pulpal damage. Full article

Flowable composites improve adaptability at the gingival margin but may affect mechanical properties. This study tested the surface hardness of proximal restorations as indicator of depth-of-cure and mechanical properties. Typodont teeth with 4 mm deep disto-occlusal preparations were (a) restored with three flowable composites in 4 mm bulk, and (b) restored with a thin layer of a flowable at the gingival margin under a universal composite. For the latter, two techniques were tested: ‘pre-cure’ and ‘snowplow’. In the pre-cure technique, the flowables were cured separately; in the snowplow technique, they were cured together with the universal composite. The universal composite placed in two 2 mm increments was the control. After 24 h, the Vickers hardness of the proximal restorations was measured every 0.5 mm from occlusal to gingival. The results were statistically analyzed using ANOVA and post hoc tests (α = 0.05). The sample size was 10/group. Bulk-filled restorations having undergone 40 s of light curing were significantly harder than those cured for 20 s. The pre-cure technique decreased hardness at depths of 3 mm and greater. The snowplow technique also led to significantly lower hardness at 4 mm, but less reductions at the 3.0 and 3.5 mm depths. The fiber-reinforced flowable composite increased the overall hardness of the restorations. In conclusion, using a flowable composite in a thin layer at the gingival margin to improve adaptation affected the hardness of the restoration. The snowplow technique reduced the softening effect associated with flowable composites compared to the pre-cure technique. Full article

Objective: To determine the most suitable core build-up materials based on their mechanical and physical properties, different resin based materials were evaluated for flexural strength (FS), flexural modulus (E), modulus of resilience (R), water sorption (WS), and solubility (SO). Materials and Methods: Three dual-cure resins (CosmeCore DC Automix, CCC; Clearfil DC Core Plus, CCP; MultiCore Flow, CMC) and two bulk fill composites (Filtek One Bulk Fill Restorative, BFO; Filtek Bulk Fill Flowable, BFF) were tested, with Filtek Supreme Ultra (FSU) as the control. All tests followed ISO 4049. Beam specimens (25 × 2 × 2 mm, n = 12) were used to determine FS and E after 24 h storage in 37 °C deionized water, using a three-point bending test. Disc specimens (15 × 1 mm, n = 5) were used for WS and SO by measuring mass changes before and after water storage. Data were analysed using one way ANOVA and Tukey post hoc tests (p < 0.05). Results: CCC exhibited the highest FS and lowest WS. BFF showed the lowest E, while BFO exhibited the highest R. FSU demonstrated the lowest FS and R, along with the highest WS. No significant differences in SO were observed among groups. Conclusions: The evaluated materials showed considerable variation in mechanical and physical properties. CCC and BFO demonstrated the most favourable performance, suggesting they are the most suitable candidates for core build up procedures among the materials tested. Full article

Background: This study evaluated the void volume percentage and compressive strength of restorations prepared with different resin composite materials and techniques. Methods: There were five experimental groups: (1) ZS (Filtek™ Z350XT, single layer); (2) ZH (Filtek™ Z350XT, horizontal increment); (3) ZO (Filtek™ Z350XT, oblique increment); (4) BS (Filtek™ One Bulk Fill, single layer); (5) BF (Filtek™ One Bulk Fill and Filtek™ Z350XT Flowable Composite). Specimen dimensions were 4 mm high and 5 mm in diameter. Internal void evaluation was done by micro-CT, followed by a compressive strength test. Data were analyzed using one-way analysis of variance (ANOVA) followed by Tukey’s post hoc test (p = 0.05) and Pearson’s correlation analysis. Results: Group BF had the largest void volume percentage (0.5501 ± 0.2031%), and groups ZS and BS had the smallest (0.0366 ± 0.0279% and 0.1991 ± 0.1463%, respectively). Groups ZH and ZS showed significantly higher compressive strength values (200.18 ± 16.32 MPa, 192.18 ± 17.23 MPa, respectively) than groups BS and BF. Pearson’s correlation analysis revealed no statistically significant correlation. Conclusions: The multilayer filling technique created significantly more voids than the single-layer technique. Some materials also contain inherent voids. However, these voids may not directly affect the strength of the restoration. Full article

Effects of gastric acid and antiacid medications on the surface and optical properties of resin-based restorative materials were evaluated. A hybrid-CAD/CAM block, a 3D-printed resin, a paste-type composite, and a flowable composite were investigated (n = 9). Samples were prepared (1 mm thickness) and polished. All samples were exposed to gastric acid for 6 days, followed by a second exposure to distilled water, antiacid medication, or gastric acid for 56 min. Surface roughness, translucency, and fluorescence were assessed at baseline (T₀), after gastric acid exposure (T₁), and after the second exposure (T₂). Surface morphology was examined by scanning electron microscopy. Data were analyzed with a significance level of p < 0.05. Gastric acid exposure caused a significant increase in surface roughness and a significant reduction in translucency in all materials (p < 0.05). CAD/CAM and paste-type composites exhibited significantly higher roughness values than the 3D-printed and flowable composites (p < 0.001). Fluorescence changes were observed in all groups, but the highest ΔE₀₀ values were observed in the 3D-printed and flowable composites (p < 0.001). Gastric acid adversely affected the surface and optical properties of resin-based restorative materials, while antiacid medication showed limited, material-dependent protective effects. Full article

Background/Objectives: Bulk-fill (BF) resin-based composites (RBCs) have become increasingly popular due to their efficient placement. However, there is a lack of comprehensive performance comparisons among commercially available BF RBCs. In standardized curing conditions, this study aimed to compare the mechanical performance, water sorption and solubility, surface roughness, and color stability of commercially available BF RBCs with different consistencies (flowable and packable). Methods: Ten BF RBCs, along with a conventional RBC (control), were evaluated. Flexural strength and elastic modulus were measured using a three-point bending test. Water sorption and solubility were assessed after 28-day water storage. Color (ΔE₀₀) and surface roughness (ΔRa) changes were measured after 28-day immersion in water, Pepsi, or coffee. One-way ANOVA and Tukey’s tests analyzed the data. Results: 3M Flow, Shofu Bulk, and Ivoclar Flow revealed lower strength (p < 0.001) compared to 3M Bulk (132.17 ± 12.54 MPa) and the control (124.56 ± 15.60 MPa). Shofu Bulk (24.68 ± 12.55 µg/mm³) and Ivoclar Flow (27.11 ± 6.27 µg/mm³) were the least affected by water sorption. While Shofu Bulk (13.98 ± 11.39 µg/mm³), Ivoclar Flow (20.28 ± 6.64 µg/mm³), and SDR (20.84 ± 9.74 µg/mm³) exhibited the lowest solubility (p < 0.01). After water and Pepsi immersion, FGM Bulk showed a significant color change compared to 3M Bulk and Ivoclar Bulk (p < 0.05). Following coffee immersion, Shofu Bulk (17.38 ± 1.82) revealed significant color changes (p < 0.001). Increased surface roughness was observed in 3M Bulk and Ivoclar Bulk after water immersion, Shofu Bulk after Pepsi immersion, and FGM Bulk after coffee immersion. Conclusions: BF RBCs exhibit notable variability in their intrinsic properties. 3M Bulk and Control showed the highest strength, while Shofu Bulk had significant color changes. Full article

This study aimed to evaluate the effect of preheating on the push-out bond strength (PBS) and microhardness (HV) of fiber-reinforced flowable and injectable composites and to compare them with dual-cure resin–cement for post cementation. Fifty premolars were endodontically treated, and post spaces were prepared. Specimens were divided into five groups (n = 10) based on the resin luting material. After adhesive application, fiber posts were luted with dual-cure resin–cement (LinkForce), fiber-reinforced flowable composites (EverX Flow; non-heated/preheated), and injectable composites (G-aenial Universal Injectable; non-heated/preheated). After 24 h, roots were sectioned (coronal, middle, apical) for PBS testing (Instron). For HV, 10 specimens per resin luting material were prepared, and top/bottom microhardness was measured to assess the depth of cure. Data were analyzed with two-way ANOVA and post hoc Tukey tests (p < 0.05). Both types of resin luting material and preheating significantly affected PBS and HV (p = 0.0001). Preheated EverX Flow showed significantly higher PBS and HV than LinkForce, while G-aenial Injectable exhibited the lowest values (p < 0.05). Within each resin luting material, PBS significantly decreased from the coronal to the apical region (p = 0.0001). Preheated fiber-reinforced flowable composites demonstrate improved microhardness and adhesion, offering a reliable alternative to the dual-cure resin–cements for fiber post cementation. Full article

Background/Objectives: This article presents a novel approach that combines the Palatal Silicone Key and Injection Molding techniques as a viable alternative for complex anterior cases with high esthetic demands, where layering multiple shades is essential to achieve a natural appearance, rather than using a single monochromatic composite. Methods: The Palatal Silicone Key technique utilizes a silicone index to transfer palatal and incisal anatomy from a diagnostic wax-up, allowing freehand layering of proximal and buccal surfaces with multiple composite shades. The Injection Molding technique provides a simpler and more predictable workflow by using a transparent silicone index to replicate the wax-up. However, the original injection technique relies on a single-shade composite, limiting the esthetic outcomes. In the presented case canines and first premolars were reshaped to replace congenitally missing lateral incisors. Palatal surfaces were built with medium-viscosity enamel shade composite using the silicone key, and dentin anatomy was sculpted freehand with dentin shade composite. Buccal anatomy was restored by injecting enamel shade flowable composite into the transparent index. Results: This combined protocol facilitated the precise transfer of the wax-up, minimizing adjustments, while the use of multiple composite shades reproduced the natural translucency of adjacent teeth, resulting in highly esthetic restorations. Conclusions: Handling traditional composites in complex anterior cases can be time-consuming and technique-sensitive. The presented combination of techniques, while requiring a high level of skill and precision, integrates the strengths of both approaches, enabling a minimally invasive, additive workflow with reduced clinical time and more predictable esthetic outcomes. Full article

The aim was to evaluate the shear-bond strength (SBS) of experimental short fiber-reinforced CAD/CAM composites (SFRC-CAD) and commercial CAD/CAM composites (Cerasmart 270) to different luting resin composites before and after hydrothermal aging. Discs (2 mm) obtained from SFRC-CAD and Cerasmart 270 were air-particle abraded and treated with a primer (G-CEM One Enhancing Primer) with or without universal adhesive (G2 Bond). A fiber-reinforced flowable composite (everX Flow) and a self-adhesive resin cement (G-CEM One) were used as luting materials under direct or indirect curing conditions. Thirty-two experimental groups were determined based on restorative material, bonding protocol, luting resin, curing technique, and aging procedure (n = 8/group). SBS was measured after 24 h of water storage or following hydrothermal aging. Data were analyzed using nonparametric statistical tests (p < 0.05). No statistically significant differences in SBS were observed between everX Flow and G-CEM One regardless of the bond application (p > 0.05). SFRC-CAD bonded with everX Flow and universal adhesive demonstrated significantly higher SBS than the corresponding Cerasmart groups (p < 0.05), whereas no significant differences were observed between comparable groups when G-CEM One was used. Failure mode analysis showed predominantly adhesive and mixed failures, with no cohesive failures within SFRC-CAD. Overall, the everX Flow proved to be an effective luting material, indicating that this material may be suitable for luting CAD/CAM indirect restorations. Full article

The existing scientific literature indicates that flowable short fiber-reinforced composites (SFRCs) can be used for direct restoration due to their favorable mechanical properties. However, there is a lack of data on the mechanical properties of SFRCs designed specifically for indirect CAD/CAM restorations. This study aims to fabricate a novel experimental SFRC CAD/CAM block and evaluate its fracture toughness and polishability as an indirect restoration in comparison with different conventional resin-based CAD/CAM blocks with different compositions. Fourier-transform infrared spectroscopy (FTIR) was employed to analyze the chemical structure of the Experimental SFRC group, while the microstructure of specimens from each group was examined using scanning electron microscopy (SEM). Then, this study divided the specimens into three groups—Group 1 (Grandio blocks), Group 2 (Cerasmart 270), and Group 3 (Experimental SFRC)—with 30 specimens in each group. Each group was then subdivided into sub-groups for the fracture toughness test, which evaluated resistance to crack propagation, and the surface roughness test, which assessed surface topography. FTIR analysis showed that the experimental SFRC exhibited distinct spectral changes after polymerization, confirming successful chemical reactions and network formation. SEM analysis showed that the Experimental SFRC block had a polymeric matrix with randomly oriented, well-dispersed short fibers. Grandio blocs exhibited a dense nanohybrid structure with irregular fillers, while Cerasmart 270 displayed a more uniform microstructure with evenly dispersed nano-sized spherical fillers. The Experimental SFRC showed the highest fracture toughness (2.758 MPa·√m), surpassing the other groups (p < 0.05) and highlighting its superior resistance to crack propagation. Regarding surface roughness Ra, the novel Experimental SFRC group (0.182) presented a significant difference compared to other groups (p < 0.05) but within clinical acceptance, and they can be well polished for clinical use after milling. The Cerasmart 270 block showed the lowest surface roughness Ra (0.135) among the groups, which is attributed to its filler size, geometry, and composition, resulting in a smoother surface. The higher fracture toughness of the Experimental SFRC among the groups suggests superior resistance to crack propagation, attributed to the incorporation of short fibers that enhance energy absorption and reduce brittleness, thereby supporting its suitability for high-stress-bearing clinical applications. Full article