Search Results (119)

Light-curing gingiva-colored composite resins (GCCs) are widely used for their esthetics and versatility, although they remain susceptible to discoloration. This in vitro study evaluated the effect of GCC thickness on color stability under different staining solutions and immersion times. Four hundred specimens were fabricated with a 3D-printed resin (P Pro; Institut Straumann AG), incorporating circular intaglio areas of varying thicknesses (0.2, 0.4, 0.6, 0.8, and 1.0 mm), into which paste (Nexco; Ivoclar AG) or flowable (Gradia Gum; GC Corp) GCCs were applied. After artificial aging in water at 55 °C for 5 days, specimens were immersed in coffee, black tea, red wine, or distilled water (control). Color differences (ΔE₀₀) were assessed using digital photocolorimetry (eLAB protocol) and the CIEDE2000 formula at 2.5, 5, and 7 days. Data for each consistency were analyzed with 3-way repeated measures ANOVA and Tukey HSD (α = 0.05). Thicker GCCs (0.6–1.0 mm) showed significantly greater discoloration (p < 0.05). Flowable GCCs were more prone to color changes induced by coffee (p < 0.05), whereas paste GCCs exhibited more discoloration with black tea (p < 0.05). Extended immersion time increased color change, particularly in flowable GCCs. Overall, GCC thickness, immersion duration, and material consistency influenced long-term color stability. Full article

Micron-sized near-spherical α-Al₂O₃ powders are widely used as thermal fillers due to their high thermal conductivity, high packing density, good flowability, and low cost. During the high-temperature calcination, the resulting α-Al₂O₃ powders often exhibit an aggregated worm-like morphology owing to limitations in solid-state mass transfer. Researchers have employed various mineralizers to regulate the morphology of α-Al₂O₃ powders; however, the preparation of micron-sized highly spherical α-Al₂O₃ powders via solid-state calcination is still a great challenge. In this work, micron-sized near-spherical α-Al₂O₃ powders were synthesized through high-temperature calcination using hydratable alumina (ρ-Al₂O₃) as precursor with water-soluble mineralizer ammonium fluoroborate (NH₄BF₄). ρ-Al₂O₃ can undergo a hydration reaction with water to form AlO(OH) and Al(OH)₃ intermediates, serving as an excellent precursor. With the addition of 0.1 wt% NH₄BF₄, the product exhibits an optimal near-spherical morphology. Excessive addition (>0.2 wt%), however, significantly promotes the transformation of α-Al₂O₃ from a near-spherical to a plate-like structure. Further studies reveal that the introduction of NH₄BF₄ not only modulates the crystal morphology but also effectively reduces the content of sodium impurities in the powder through a high-temperature volatilization mechanism, thereby enhancing the thermal conductivity of the powder. It is shown that the thermal conductivity of the micron-sized α-Al₂O₃/ epoxy resin composites reaches 1.329 ± 0.009 W/(m·K), which is 7.4 times that of pure epoxy resin. Full article

Background/Objectives: Composite resins are widely used in restorative dentistry due to their aesthetic properties and ease of handling. Preheating prior to light polymerization has been proposed to improve flowability, degree of conversion, and mechanical properties. This in vitro study aimed to evaluate the effect of preheating on the microhardness of three nanoparticulate composite resins—IPS Empress Direct (Ivoclar), Filtek Z350 XT (3M-ESPE), and Forma (Ultradent)—when cured with a high-power LED light. Methods: Sixty disc-shaped samples (n = 20 per material) were fabricated and divided into preheated and non-preheated groups. After polishing and 24 h storage in distilled water at 37 °C, samples were subjected to Knoop microhardness testing under a 300 g load for 15 s. Statistical analysis was conducted using R software. Results: Preheating produced a significant increase in surface microhardness for IPS Empress Direct (32.8%) and Filtek Z350 XT (5.8%) (p < 0.05 for both), whereas Forma showed no significant change. Conclusions: Under the conditions of this in vitro study, preheating can enhance the mechanical performance of specific composite resins by increasing microhardness; however, the effect is material-dependent. Full article

Background/Objectives: Soft tissues are essential for maintaining the function and long-term success of dental implants. In many cases, implant placement necessitates soft tissue augmentation procedures such as free gingival grafts (FGGs) or connective tissue grafts (CTGs) to restore lost gingival architecture. Nevertheless, a significant challenge associated with FGG and CTG is postoperative pain, largely due to morbidity at the palatal donor site. To address this issue, various approaches have been proposed to reduce patient discomfort and promote improved wound healing at the donor site. This study aimed to compare the effectiveness of four different methods for protecting the palatal donor site following free gingival graft harvesting. Methods: A total of 76 patients undergoing implant therapy with an indication for free gingival grafting were selected and divided into four groups based on the method used to protect the palatal donor site: an absorbable gelatin sponge secured with sutures (GS); an absorbable gelatin sponge with sutures and cyanoacrylate tissue adhesive (GS+CTA); oxidized regenerated cellulose combined with cyanoacrylate tissue adhesive (ORC+CTA); and an absorbable gelatin sponge covered with a flowable resin composite and stabilized with sutures (GS+FRC). The effectiveness of each method was evaluated in terms of postoperative pain, bleeding, and wound healing. Results: Although the differences in pain intensity among the groups were not statistically significant throughout the observation period (p > 0.05), the GS+FRC group consistently exhibited the lowest mean pain scores. No statistically significant differences were observed between the groups regarding the incidence of secondary bleeding. The highest mean wound healing rate was recorded in the GS+FRC group (75.95 ± 18.75%), whereas the ORC+CTA group demonstrated the lowest rate (43.66 ± 25.74%). Conclusions: The use of an absorbable gelatin sponge covered with a flowable resin composite and secured with sutures, despite the presented limitations, appears to be a promising approach for palatal wound protection. While this group consistently demonstrated the lowest mean pain scores, differences in pain intensity among the groups were not statistically significant. Nonetheless, it achieved the most favorable outcomes in terms of wound epithelialization. Full article

Biomimetic restorative dentistry aims to preserve tooth structure and achieve optimal aesthetic harmony with surrounding dentition. The principles and protocols associated with biomimetic restorative dentistry are designed to enhance the longevity of the restoration. The use of flowable CRs is increasingly common; however, the effect of viscosity on the discoloration has not been clearly established. This in vitro study aimed to assess the color stability of flowable CRs with varying viscosities following immersion in common staining solutions and subsequent repolishing. A total of 250 disc-shaped specimens (8 mm × 2 mm) were prepared from five CRs with different viscosity profiles: high-viscosity (Spectra STHV, Dentsply, Milford, DE, USA), medium-viscosity (Estelite Universal Flow Medium, Tokuyama Dental Co., Tokyo, Japan), bulk-fill (Estelite Bulk-Fill Flow, Tokuyama Dental Co., Tokyo, Japan; SDR Plus, Dentsply, Milford, DE, USA), and packable (Estelite Posterior, Tokuyama Dental Co., Tokyo, Japan). After polymerization and baseline color measurements, specimens were immersed in coffee, tea, cola, red wine, or distilled water for 144 h. Color values were recorded before and after staining, and again following repolishing. Color changes (ΔE₁, ΔE₂, ΔE₃) were calculated using the CIE Lab system and statistically analyzed via two-way ANOVA and Tukey HSD (α = 0.05). Both the CR type and the staining solution substantially affected the color change. SDR Plus exhibited the highest ΔE values. Red wine caused the most discoloration. Repolishing enhanced color in selected groups. Full article

Background/Objectives: Self-adhesive flowable resins (SAFR) entered the market, eliminating the adhesive system application due to their self-adhesive technology. Guided by the PICO framework (Population, Intervention, Comparison, Outcome), the aim was to conduct a systematic review of clinical studies to compare the clinical performance of Self Adhesive Flowable Resin (SAFRs) with conventional flowable resins used for direct restorations. Methods: The protocol of this systematic review was registered in the International Prospective Register of Systematic Reviews (CRD42023394297) and followed the Preferred Reporting Items for Systematic Reviews and Meta-Analyses guideline. Five databases (PubMed, Embase, Web of Science, Scopus, and Cochrane Library) were searched from inception to July 2025. Nine randomized clinical trials were included, totaling 493 restorations in 232 patients. Clinical performance was assessed using USPHS or FDI criteria, with follow-up periods ranging from 6 months to 5 years. Data were pooled using a random-effects meta-analysis to calculate risk differences (RD) and 95% confidence intervals (CI) for marginal adaptation, retention, marginal staining, post-operative sensitivity, color stability, surface roughness, secondary caries, and anatomical form. Results: Meta-analysis showed no significant differences between SAFRs and CFRCs for in terms of: marginal adaptation (RD = 0.01; 95% CI: −0.02 to 0.04; p = 0.53; I² = 0%), retention (RD = 0.00; 95% CI: −0.02 to 0.03; p = 0.81; I² = 0%), marginal staining (RD = 0.01; 95% CI: −0.01 to 0.02; p = 0.51; I² = 0%), and post-operative sensitivity (RD = −0.01; 95% CI: −0.03 to 0.02; p = 0.62; I² = 0%). The certainty of the evidence for all outcomes was rated as moderate to high according to the GRADE assessment. Conclusions: SAFR restorations demonstrated comparable clinical performance to conventional resins; however, heterogeneity in follow-up duration and the scarcity of long-term data (>5 years) warrant caution. Full article

Objectives: To study the effects of internal and marginal polymerization shrinkage stress and distribution in different resin composite class III dental restorations in relation to the restorative technique using numerical finite element analysis (FEA). Methods: A 3D model of a human hemi-maxilla with a sound maxillary central incisor were created. Four class III distal cavities were shaped and differently restored. Four groups of resin composite combinations were analyzed: group C (three increments of conventional composite); group B (two increments of bulk-fill composite); group FC (flowable base + three increments of conventional composite); and group FB (flowable bulk-fill base + two increments of conventional composite). The resulting four models were exported to FEA software for static structural analysis. Polymerization shrinkage was simulated using thermal analogy, and stress distribution was analyzed using the Maximum Principal Stress criterion at the marginal and internal cavity interfaces. Results: Group FC showed the highest stress at the level in the proximal region (9.05 MPa), while group FB showed the lowest (4.48 MPa). FB also exhibited the highest internal dentin stress, indicating potential risks for long-term bond degradation. In the cavo-surface incisal angle, the average peak stress across all groups was 3.76 MPa. At the cervical cavo-surface angle, stress values were 3.3 MPa (C), ~3.36 MPa (B), 3.41 MPa (FC), and 3.27 MPa (FB). Conclusions: Restorative technique did not significantly influence marginal stress distribution in class III composite restorations. However, the bevel area at the cervical margin showed the highest concentration of shrinkage stress. Full article

Background: Attachments are essential components in clear aligner therapy, enhancing retention and improving the predictability of tooth movements. Mechanical and wear properties of the composite resins used for attachment reproduction are critical to maintaining their integrity and shape over time. This study aimed to evaluate and compare the mechanical properties, thermal behavior, and wear performance of the hybrid composite Aligner Connect (AC) and the flowable resin (Connect Flow, CF). Methods: Twenty samples (ten AC and ten CF) were reproduced. All specimens underwent differential scanning calorimetry (DSC), combustion analysis, flat instrumented indentation, compression stress relaxation tests, and tribological analysis. A 3D wear profile reconstruction was performed to assess wear surfaces. Results: DSC and combustion analyses revealed distinct thermal transitions, with CF showing significantly lower Tg values (103.8 °C/81.4 °C) than AC (110.8 °C/89.6 °C) and lower residual mass after combustion (23% vs. 61%), reflecting reduced filler content and greater polymer mobility. AC exhibited superior mechanical properties, with higher maximum load (585.9 ± 22.36 N) and elastic modulus (231.5 ± 9.1 MPa) than CF (290.2 ± 5.52 N; 156 ± 10.5 MPa). Stress relaxation decrease was less pronounced in AC (18 ± 4%) than in CF (20 ± 4%). AC also showed a significantly higher friction coefficient (0.62 ± 0.060) than CF (0.55 ± 0.095), along with greater wear volume (0.012 ± 0.0055 mm³ vs. 0.0070 ± 0.0083 mm³) and maximum depth (36.88 ± 3.642 µm vs. 17.91 ± 3.387 µm). Surface roughness before wear was higher for AC (Ra, 0.577 ± 0.035 µm; Rt, 4.369 ± 0.521 µm) than for CF (Ra, 0.337 ± 0.070 µm; Rt, 2.862 ± 0.549 µm). After wear tests, roughness values converged (Ra, 0.247 ± 0.036 µm for AC; Ra, 0.236 ± 0.019 µm for CF) indicating smoothened and similar surfaces for both composites. Conclusions: The hybrid nanocomposite demonstrated greater properties in terms of stiffness, load-bearing capacity, and structural integrity when compared with flowable resin. Its use may ensure more durable attachment integrity and improved aligner–tooth interface performance over time. Full article

Background and Clinical Significance: Traumatic dental injuries, particularly complicated crown fractures of permanent incisors, are common in adolescents, with maxillary central incisors most frequently affected due to their prominent position. These injuries, often resulting from sports or accidents, require prompt management to prevent complications such as pulp necrosis or infection, which can compromise long-term prognosis. Fragment reattachment offers a conservative, esthetically favorable approach when the fractured segment is intact, with outcomes comparable to composite restorations. This case report underscores the importance of timely intervention and advanced restorative techniques in pediatric dentistry. Case Presentation: A 16-year-old male presented with a complicated crown fracture of the upper left central incisor sustained during a soccer game. The fracture extended subgingivally with pulp exposure. The patient preserved the fragment in saline. Treatment involved fragment reattachment using a dentin bonding agent and flowable composite resin, followed by single-visit root canal therapy due to delayed presentation (48 h). A glass fiber post was placed to reinforce the restoration due to significant coronal loss. Three years of follow-up visits (1, 3, 6, 12, 24, and 36 months) revealed no clinical or radiographic complications, with the tooth remaining asymptomatic and functional. Conclusions: This case underscores the effectiveness of fragment reattachment when combined with meticulous technique and long-term monitoring. Full article

Reliable adaptation in Class II resin-based composite (RBC) restorations with margins on cementum remains challenging. This study compared the internal adaptation (IA) and closed porosity (CP) of three restorative strategies for such cavities, using either total-etch or self-etch adhesive approaches. Standardized box-only cavities were prepared on both proximal surfaces of 30 extracted molars, applying self-etch on mesial and total-etch on distal cavities. Group 1 used a layered microhybrid RBC; Group 2 used a flowable RBC base beneath a layered microhybrid RBC; and Group 3 used a thermoviscous RBC in a 4 mm bulk increment. Micro-computed tomography was employed to assess IA and CP. ANOVA, Tukey post hoc, and univariate analyses were used to evaluate group differences and the effects of adhesive/restorative strategies. Group 2 demonstrated the best adaptation (0.10%), whereas Group 3 exhibited the highest internal gap ratio (0.63%) and the lowest CP (p = 0.006). Total-etch adhesive significantly improved IA compared to self-etch (p < 0.001). These findings emphasize the impact of material selection and adhesive technique on the quality of restorations in cementum-located Class II cavities. Full article

The continuous need for simplified, minimally invasive restorative procedures with a high precision has led to the advancement of highly filled flowable resin-based materials. These materials present excellent initial outcomes in various clinical applications, including the injection molding technique. Given that several clinical reports present signs of wear and staining, this systematic review aims to investigate the mechanical and optical properties of highly filled flowable composite resins. A comprehensive literature research was conducted to identify relevant studies from the PubMed, the Cochrane Library, and Scopus databases. Data extraction and screening was performed by two independent evaluators. Both in vitro studies and clinical trials were included. A total of thirty-one studies were included in this review. A total of 27 in vitro studies investigated highly filled flowable composite resins independently, or in comparison with conventional composite resins, traditional flowable composites, bulk-fill flowable composites, glass ionomer cements, and compomers. Additionally, four randomized controlled clinical trials (RCTs) compared highly filled flowable composite resins with their conventional counterparts. Highly filled flowable composite resins exhibit adequate optical properties. Despite their significant improvements, their mechanical properties remain inferior to those of medium-viscosity composite resins. These materials demonstrate a favorable initial performance in the injection molding technique. Based on a limited number of RCTs, these materials demonstrate an adequate performance in class I and II restorations; however these findings should be interpreted with caution. The reported drawbacks in laboratory studies may contraindicate their clinical application in extensive cavities, load-bearing areas, and in cases of excessive tooth wear and parafunctional activity. A careful clinical case selection is strongly recommended. Full article

Background/Objectives: The introduction of composite attachments has greatly improved orthodontic aligner therapy, through better force delivery, more predictable movements, and enhanced retention. This in vitro study aims to present and investigate an innovative digital protocol for aligner attachment fabrication incorporating the latest 3D technology used in dentistry. Methods: A virtual attachment measuring 2.5 × 2 × 2 mm was designed using computer-aided design (CAD) software (Meshmixer, Autodesk Inc., San Francisco, CA, USA) and exported as an individual STL file. The attachments were fabricated using a digital light processing (DLP) 3D printer (model: Elegoo 4 DLP, Shenzhen, China) and a dental-grade biocompatible resin. A custom 3D-printed placement guide was used to ensure precise positioning of the attachments on the printed maxillary dental models. A flowable resin was applied to secure the attachments in place. Following attachment placement, the models were scanned using a laboratory desktop scanner (Optical 3D Smart Big, Open Technologies, Milano, Italy) and three intraoral scanners: iTero Element (Align Technology, Tempe, AZ, USA), Aoral 2, and Aoral 3 (Shining 3D, Hangzhou, China). Results: Upon comparison, the scans revealed that the iTero Element exhibited the highest precision, particularly in the attachment, with an RMSE of 0.022 mm and 95.04% of measurements falling within a ±100 µm tolerance. The Aoral 2 scanner showed greater variability, with the highest RMSE (0.041 mm) in the incisor area and wider deviation margins. Despite this, all scanners produced results within clinically acceptable limits. Conclusions: In the future, custom attachments made by 3D printing could be a valid alternative to the traditional composite attachments when it comes to improving aligner attachment production. While these preliminary findings support the potential applicability of such workflows, further in vivo research is necessary to confirm clinical usability. Full article

Background/Objectives: A material incompatibility has been established between self-etching adhesives and amine-containing dual-cure resin composite materials used for core buildups. This study aims to compare the dentin bond strength of several amine-containing and amine-free core materials using self-etching adhesives with different pHs. Methods: Extracted human molars were mounted in acrylic and ground flat with 320-grit silicon carbide paper. Next, 520 specimens (n = 10/group) were assigned to a dual-cure core buildup material group (10 amine-containing, 2 amine-free, and 1 reference light-cure only bulk fill flowable composite) and assigned to a self-etching adhesive subgroup (pH levels of approximately 1.0, 3.0, and 4.0). Within 4 h of surface preparation, the adhesive corresponding to the specimen’s subgroup was applied and light-cured. Composite buttons for the assigned dual-cure core material of each group were placed using a bonding clamp apparatus, allowed to self-cure for 2 h at 37 °C, and then unclamped. An additional group with one adhesive (pH = 3.0) was prepared in which the dual-cure core materials were light-cured. The bonded specimens were stored in water at 37 °C for 24 h. The specimens were mounted on a testing clamp and de-bonded in a universal testing machine with a load applied to a circular notched-edge blade at a crosshead speed of 1 mm/min until bond failure. The maximum load divided by the area of the button was recorded as the shear bond strength. The data was analyzed via 2-way ANOVA. Results: The analysis of bond strength via 2-way ANOVA determined statistically significant differences between the adhesives, the core materials, and their interaction (p < 0.01). There was a general trend in shear bond strength for the adhesives, where pH 4.0 > 3.0 > 1.0. The amine-free core materials consistently demonstrated higher shear bond strengths as compared to the other core materials when chemically cured only. Light-curing improved bond strength for some materials with perceived incompatibility. Conclusions: The results of this study suggest that an incompatibility can exist between self-etching adhesives and dual-cure resin composite core materials. A decrease in the pH of the utilized adhesive corresponded to a decrease in the bond strength of dual-cure core materials when self-curing. This incompatibility may be minimized with the use of core materials formulated with amine-free chemistry. Alternatively, the dual-cure core materials may be light-cured. Full article

This study aimed to evaluate the nanomechanical surface properties and water uptake of a flowable short-fiber-reinforced composite (SFRC) using various restorative techniques in order to assess its potential as a standalone restorative material. Nanoindentation and compressive creep testing were employed to characterize material performance. Three resin composites were examined: a flowable SFRC (everX Flow), a bulk-fill particulate filler composite (PFC), and a conventional PFC. Five experimental groups were established based on the restorative technique: layered PFC, layered SFRC, bulk SFRC, bulk PFC, and a bi-structure combining SFRC and PFC. Ninety standardized specimens (n = 18/group) were fabricated. Static and creep nanoindentation tests were conducted to assess surface properties, and water uptake was measured over a 30-day period. Data were analyzed using one-way ANOVA and Bonferroni post hoc tests. Nanoindentation revealed significant differences in hardness, with bulk PFC exhibiting the lowest values (p < 0.001). Creep testing indicated changes in modulus and viscosity following water storage. Notably, bulk SFRC showed the lowest water absorption (p < 0.001). Overall, bulk-applied SFRC demonstrated favorable nanomechanical properties and reduced water uptake, demonstrating its suitability as a standalone restorative material. Further clinical investigations are recommended to validate its long-term performance. Full article

Objectives: Trauma to maxillary incisors is frequent, and requires timely, conservative management for optimal prognosis. This in vitro study evaluated the fracture resistance (FR) and orthodontic bracket bond strength (BS) of incisors following incisal fragment reattachment using various restorative techniques. Materials and Methods: Two independent tests—FR testing (Newtons) and BS testing (megapascals)—were conducted. Eighty intact human maxillary central incisors (n = 40/test), standardized in size and shape using a digital caliper (Mitutoyo, ±0.01 mm), were embedded in acrylic resin and numbered. An uncomplicated crown fracture was induced in 64 teeth (n = 32/test), and the teeth were randomly assigned (simple randomization using Excel’s RAND function) to five groups (n = 8/group/test): (1) intact teeth (negative control, NC); (2) nanohybrid composite buildup using Filtek Z250 and Single Bond 2 (positive control, CB); (3) fragment reattachment using flowable composite (Filtek Supreme, FL); (4) reattachment with a palatal veneer using a nanohybrid composite (PV); and (5) reattachment reinforced with a polyethylene fiber band (Ribbond Inc., RB). In BS testing groups, stainless steel orthodontic brackets (PINNACLE) were bonded using Transbond XT, centered over the fracture line. Light curing was performed using an LED unit (Mini LED Standard, Acteon, 1250 mW/cm², 20 s/bond, 40 s/composite, 2 mm curing tip distance). Specimens were stored in distilled water at room temperature for 24 h before reattachment. FR and BS were evaluated using a universal testing machine (Instron) until failure. Failure modes were analyzed, and data were statistically evaluated using one-way ANOVA, Tukey’s post hoc test, and Pearson’s correlation analysis. Results: Significant differences were observed among groups for both FR and BS (p < 0.05). The NC group exhibited the highest FR (514.4 N) and BS (17.6 MPa). The RB group recorded the second-highest FR (324.6), followed by the PV (234.6), CB (224.9), and FL (203.7) groups. The CB group demonstrated the second-best BS (16.6), followed by the RB (15.2), FL (13.4), and PV (6.5) groups. FR and BS were negatively correlated. Mixed failures predominated in the reattachment groups, except for the PV group, which showed mainly adhesive failures. In BS testing, mixed failures dominated in the NC and CB groups, while adhesive failures predominated in the PV and FL groups. Conclusions: Ribbond reinforcement improves the mechanical performance of reattached incisal fragments, and composite buildup may provide more reliable bracket bonding than fragment reattachment. Clinical Relevance: In cases where biomimetic, minimally invasive reattachment is indicated, Ribbond fiber reinforcement appears to offer a reliable restorative solution. Full article