Effect of Vinyl Acetate, Glass Fibers Contents, and Buffer Space on EVA's Mechanical Property and Shock Absorption Ability.

OBJECTIVES: The aim of the study was to evaluate the mechanical properties and impact absorption capacity of prototype materials comprising ethylene vinyl acetate (EVA) of different hardness reinforced using different amounts of glass fibers (GFs), considering a buffer space. MATERIALS AND METHODS: Six prototype materials were made by adding E-GFs (5 and 10 wt%) to EVA with vinyl acetate (VA) contents of 9.4 wt% ("hard" or HA) and 27.5 wt% ("soft" or SO). Durometer hardness and tensile strength tests were performed to evaluate the mechanical properties of the materials. Moreover, an impact test was conducted using a customized pendulum impact tester to assess the impact absorption capacity (with or without a buffer space) of the specimens. RESULTS: The mechanical properties of the prototypes, namely, durometer hardness, Young's modulus, and tensile strength, were significantly higher in the HA group than in the SO group, regardless of the presence or added amount of GFs. The addition of GFs, particularly in a large amount (10 wt%), significantly increased these values. In terms of the impact absorption capacity, the original hardness of the EVA material, that is, its VA content, had a more substantial effect than the presence or absence of GFs and the added amount of GFs. Interestingly, the HA specimens with the buffer space exhibited significantly higher impact absorption capacities than the SO specimens. Meanwhile, the SO specimens without the buffer space exhibited significantly higher impact absorption capacities than the HA specimens. Moreover, regardless of the sample material and impact distance, the buffer space significantly improved impact absorption. In particular, with the buffer space, the impact absorption capacity increased with the added amount of GFs. CONCLUSION: The basic mechanical properties, including durometer hardness, Young's modulus, and tensile strength, of the EVA prototype were significantly increased by reducing the amount of VA regardless of the presence or added amount of GFs. Adding GFs, particularly in large amounts, significantly increased the values of aforementioned mechanical properties. Impact absorption was significantly affected by the hardness of the original EVA material and enhanced by the addition of the buffer space. The HA specimen had a high shock absorption capacity with the buffer space, and the SO specimen had a high shock absorption capacity without the buffer space. With the buffer space, impact absorption improved with the amount of added GFs.

Assessing the Efficacy of Novel Fiber-Reinforced Dual-Cure Luting Resins.

Background: Dual-cure resin-based luting materials are increasingly favored in clinical applications due to their capacity to establish a strong bond with natural tooth structure and restorations. This study aimed to examine certain physical and handling characteristics of newly developed experimental dual-cure luting resins reinforced with short fibers (SFRCs) and compare them with commercially available dual-cure luting resins. Material and Methods: Seven dual-cure luting materials were tested (Relyx Ultimate, Duo-Link, eCEMENT, Variolink Esthetic, G-CEM LinkForce, experimental SFRC1, experimental SFRC2). Fourier transform infrared spectroscopy (FTIR) was utilized to determine the degree of monomer conversion (DC%) in the self and light-curing protocol. A rotating disk rheometer measured viscosity at room temperature (22°C) and simulated mouth temperature (35°C). Fracture toughness, flexural strength, and flexural modulus were evaluated using a 3-point bending test. Each luting resin was subjected to the examination of its surface microstructure using scanning electron microscopy (SEM). Analysis of variance (ANOVA) at a significance level of (p = 0.05) was conducted to analyze data. Results: It was revealed that DC% of the tested dual-cure resins was significantly (p< 0.05) affected by the curing mode, the dual-cure SFRC2 having the highest and Relyx having the lowest DC (64%, and 41% respectively). The viscosity of all tested materials decreased with increasing temperature. SFRC2 demonstrated the highest fracture toughness (2.3 MPa m1/2), while Relyx Ultimate, Duo-Link, and eCEMENT exhibited the lowest values (≈ 1 MPa m1/2)(p< 0.05). Both SFRCs and G-CEM link-force exhibited the highest flexural strength values, and SFRCs resulted in the highest flexural modulus values (p<0.05). Conclusions: The experimental fiber-reinforced dual-cure luting resins exhibited superior DC%, fracture toughness, and flexural properties, yet, SFRC2 showed the highest viscosity at elevated temperature. These results highlight the capability of short fiber reinforcement to enhance the mechanical properties of dual-cured resin-based luting materials without compromising handling characteristics. Key words:Dual-cure luting resin; short fibers; degree of conversion; viscosity; fracture toughness; flexural properties.

Occlusal veneers and load-bearing capacity of a restored tooth.

PURPOSE: The aim of this study was to evaluate the influence of restoration bonding and type of preparation on load bearing capacity of a tooth restored with indirect glass ceramic or hybrid ceramic occlusal veneer restoration. MATERIALS AND METHODS: Occlusal surfaces of extracted human molar teeth were prepared for indirect occlusal veneers with or without circumferential chamfer. The occlusal veneers were milled either from CAD/CAM hybrid ceramic (HC) Cerasmart (GC), or lithium-disilicate glass ceramic (LDGC) IPS e.max CAD (Ivoclar Vivadent) blocks. Finalized veneers were bonded to teeth following manufacturers' instructions or according to the technique for the intended deteriorated bonding using n-hexane wax solution preconditioning on restorations (n=8/group). The ultimate fracture load was recorded, and fracture types were analyzed and classified visually. Statistical analysis was performed using one-way ANOVA. RESULTS: The highest fracture load was recorded in teeth with bonded LDGC veneer (p≤0.0007). The bonded HC veneers had only marginally higher fracture load compared to non-bonded veneers. In all groups with deteriorated bonding, veneers loosened without tooth fracture whereas in the bonded veneer groups tooth fractures were observed, especially in teeth restored with LDGC material. CONCLUSIONS: Bonded LDGC occlusal veneers have high load bearing capacity which exceeds the fracture resistance of tooth structure. Circumferential chamfer preparation for an occlusal veneer has no influence on fracture load of a restored tooth.

Mechanical Performance of Extensive Restorations Made with Short Fiber-Reinforced Composites without Coverage: A Systematic Review of In Vitro Studies.

In recent years, composite resin materials have been the most frequently used materials for direct restorations of posterior teeth. These materials have some clinically relevant limitations due to their lack of fracture toughness, especially when used in larger cavities with high volume factors or when utilized as direct or indirect overlays or crown restorations. Recently, short-fiber-reinforced composite materials have been used in bi-structure restorations as a dentine substituting material due to their superior mechanical properties; however, there is no scientific consensus as to whether they can be used as full restorations. The aim of our review was to examine the available literature and gather scientific evidence on this matter. Two independent authors performed a thorough literature search using PubMed and ScienceDirect up until December 2023. This study followed the PRISMA guidelines, and the risk of bias was assessed using the QUIN tool. The authors selected in vitro studies that used short-fiber-reinforced composite materials as complete restorations, with a conventional composite material as a comparison group. Out of 2079 potentially relevant articles, 16 met our inclusion criteria. All of the included studies reported that the usage of short-fiber-reinforced composites improved the restoration's load-bearing capacity. Fifteen of the included publications examined the fracture pattern, and thirteen of them reported a more favorable fracture outcome for the short-fiber-reinforced group. Only one article reported a more favorable fracture pattern for the control group; however, the difference between groups was not significant. Within the limitations of this review, the evidence suggests that short-fiber-reinforced composites can be used effectively as complete restorations to reinforce structurally compromised teeth.

Clinical evaluation of posterior flowable short fiber-reinforced composite restorations without proximal surface coverage.

The purpose of this clinical trail was to assess the clinical behavior of posterior composite restorations supported by a substantial foundation of flowable short fiber-reinforced composite SFRC (everX Flow, GC, Japan) used without proximal surface coverage with particulate filler resin composite (PFC). Seventy patients (20 males, 50 females; mean age: 30 ± 10 years) were randomly enrolled in this trial. Patients received direct restorations of either SFRC covered only on the occlusal surface (1-2 mm) by conventional PFC composite (G-ænial Posterior, GC), or plain conventional PFC composite without fiber-reinforcement, in Class II cavities in premolar and molar vital teeth. One operator made all restorations using one-step, self-etch bonding agent (G-ænial Bond, GC) according to manufacturers' recommendations. Two blinded trained operators evaluated the restorations at baseline, at 6, 12 and 18 months using modified USPHS criteria. Results indicated that, in both groups and at different follow-up intervals, according to evaluated criteria, restorations were rated mostly with best score (Alpha) (p > 0.05). For the marginal integrity after 6 months, a single case in the intervention [increased to 3 (8.8%) after 18 months] and 3 (9.7%) cases of the control group [increased to 4 (12.9%) after 18 months] had Bravo score but with no significant difference (p > 0.05). For color match measured after 6 and 18 months, three (8.8%) cases had Bravo score in the intervention group. The use of flowable SFRC composite without any PFC surface coverage proximally in Class II restorations demonstrated satisfactory clinical outcome throughout the 18-month follow-up.

Polymerization shrinkage of contemporary dental resin composites: Comparison of three measurement methods with correlation analysis.

The aim of this study was to evaluate a novel approach for measuring the polymerization shrinkage of dental resin composites - measurement of sample depth variation. This new method was compared with two testing methodologies used for assessing the polymerization shrinkage (buoyancy and strain gauge methods). Eleven commercial resin composites were investigated (EverX Posterior; EverX Flow Bulk & Dentin; G-aenial Anterior, Posterior, A'chord & Universal Injectable; Filtek One Bulk Fill & Universal Restorative; SDR + Flow and Aura Bulk Fill). In addition, filler content (wt. %), flexural modulus, and the degree of conversion were evaluated. Shrinkage values, obtained by the buoyancy method, are greater than shrinkage evaluated by the strain gauge. There are significant differences in polymerization shrinkage among the tested resin composite materials. There is a strong correlation between the newly proposed method of shrinkage measurement and the buoyancy method (r2 = 0.8; p < 0.01). There is no correlation between volumetric shrinkage measurement (depth changes and buoyancy method) and linear strain measurement. Volumetric filler amount correlates with shrinkage values evaluated by all three methods. The degree of conversion for the tested resin composites ranges from 36 % to 52 %. There are some differences (around 10 %) between the filler content (wt. %) measured by the ashing-in-air method and the data given by the manufacturers. The highest flexural modulus is 14.8 GPa and the lowest 6.6 GPa. New formulations may introduce unknown relationships between the fundamental properties of dental resin composites.

Effect of low-temperature degradation and sintering protocols on the color of monolithic zirconia crowns with different yttria contents.

This study investigated the effects of low-temperature degradation (LTD) on the L*, a*, and b* values of highly translucent zirconia crowns. Four types of zirconia disks with different yttria contents (IPS e.max ZirCAD LT, IPS e.max ZirCAD MT, IPS e.max ZirCAD MT Multi, IPS e.max ZirCAD Prime, Ivoclar) and two shades (A2 and BL) were used. A crown was manufactured using four types of zirconia and LTD treated. Color measurements were performed, and the color difference (ΔE00) before and after LTD was calculated. The microstructure was determined through X-ray fluorescence and X-ray diffractometry. Highly translucent zirconia crowns showed greater changes in the a* and b* values than in the L* value after LTD, regardless of the shade. The Multi2 crowns exhibited a discernible color change due to the LTD treatment. The X-ray fluorescence results did not reveal any apparent change in the microstructure between sintering programs for all zirconia specimens.

Polymerization shrinkage stress of contemporary dental composites: Comparison of two measurement methods.

The aim of this study was to compare two testing methodologies employed for assessing the polymerization shrinkage stress of dental resin composites. Ten commercial resin composites were investigated (EverX Posterior & Flow; G-ænial Anterior, Posterior, A'CHORD & Universal Injectable; Filtek One Bulk Fill & Universal Restorative; SDR flow+ and Aura Bulk Fill). Photoelastic and contraction forces measurement methods were performed. The slope of the linear trendline and C-factor of specimens were calculated. The shrinkage stress values (range between: 6.4-13.4 MPa) obtained by the photoelastic method were higher for all resin composites than the values obtained by contraction forces measurements (range between 1.2-4.8 MPa). However, there was a strong linear correlation between these methods (r=0.8). The use of both investigated methods revealed important information about the shrinkage behavior of the restorative resin composites.

Osteoblast Attachment on Bioactive Glass Air Particle Abrasion-Induced Calcium Phosphate Coating.

Air particle abrasion (APA) using bioactive glass (BG) effectively decontaminates titanium (Ti) surface biofilms and the retained glass particles on the abraded surfaces impart potent antibacterial properties against various clinically significant pathogens. The objective of this study was to investigate the effect of BG APA and simulated body fluid (SBF) immersion of sandblasted and acid-etched (SA) Ti surfaces on osteoblast cell viability. Another goal was to study the antibacterial effect against Streptococcus mutans. Square-shaped 10 mm diameter Ti substrates (n = 136) were SA by grit blasting with aluminum oxide particles, then acid-etching in an HCl-H2SO4 mixture. The SA substrates (n = 68) were used as non-coated controls (NC-SA). The test group (n = 68) was further subjected to APA using experimental zinc-containing BG (Zn4) and then mineralized in SBF for 14 d (Zn4-CaP). Surface roughness, contact angle, and surface free energy (SFE) were calculated on test and control surfaces. In addition, the topography and chemistry of substrate surfaces were also characterized. Osteoblastic cell viability and focal adhesion were also evaluated and compared to glass slides as an additional control. The antibacterial effect of Zn4-CaP was also assessed against S. mutans. After immersion in SBF, a mineralized zinc-containing Ca-P coating was formed on the SA substrates. The Zn4-CaP coating resulted in a significantly lower Ra surface roughness value (2.565 µm; p < 0.001), higher wettability (13.35°; p < 0.001), and higher total SFE (71.13; p < 0.001) compared to 3.695 µm, 77.19° and 40.43 for the NC-SA, respectively. APA using Zn4 can produce a zinc-containing calcium phosphate coating that demonstrates osteoblast cell viability and focal adhesion comparable to that on NC-SA or glass slides. Nevertheless, the coating had no antibacterial effect against S. mutans.

Effect of ethylene oxide unit number in bis-EMA on the physical properties of additive-manufactured occlusal splint material.

PURPOSE: To investigate the effects of the number of ethylene oxide units in bis-EMA on the physical properties of additively manufactured occlusal splints. METHODS: Seven experimental materials containing bis-EMAs with three and 10 ethylene oxide units (BE3 and BE10, respectively) were prepared at different BE10 content rates (BE10-0%, -20%, -30%, -40%, -50%, -60%, and -80%). Half the specimens of each material were aged in boiling water. Flexural strength (FS), flexural modulus (FM), fracture toughness (FT), microwear depth (MD), degree of conversion (DC), water sorption (WSP), water solubility (WSL), color difference between non-aged and aged series (ΔE), and translucency (TP) were evaluated. All the evaluated properties other than FS and MD were analyzed by 1-way ANOVA and Tukey's post hoc analysis, while FS and MD were analyzed by Kruskal-Wallis's test and Bonferroni correction (α=0.05). RESULTS: BE10-80% revealed the lowest FS (P < 0.01 for BE10-0%, -20%, and -30%) and FM (P < 0.01, for all), while revealing the highest DC, WSP, WSL (P < 0.01 for all) and TP (P < 0.01 for all other than BE10-60%). BE10-50% showed the highest FT (P < 0.01 for all). BE10-50%, -60%, and -80% revealed significantly lower ΔE than others (P < 0.01) and lower MD than BE10-0% (P < 0.05). Regardless of the BE10 content, FS, FM, and FT decreased with aging. CONCLUSIONS: The number of ethylene oxide units affects the physical properties of additively manufactured occlusal splints. The higher number of ethylene oxide units in bis-EMA enhanced the microwear resistance, DC, WSP, WSL, color stability, and translucency, whereas it deteriorated the FS and FM.

Effect of different surface treatments on shear bond strength of autopolymerizing repair resin to denture base materials processed with different technologies.

PURPOSE: To evaluate the effect of chemical, mechanical, and combination surface treatments on the shear bond strength (SBS) of autopolymerizing repair resins to conventional heat-cured, computer aided design (CAD)-computer aided manufacturing (CAM) milled, and three-dimensionally (3D) printed denture base materials. METHODS: Specimens were fabricated and divided according to the surface treatment as follows: no surface treatment (control group), monomer treatment (monomer group), resin remover treatment (resin remover group), roughening with 180 FEPA grit abrasive paper followed by monomer treatment (180-grit plus monomer group), and air particle abrasion (air abrasion group). Autopolymerizing resin cylinders were attached before accelerated aging of the specimens in water at 100 °C for 16 h. The SBS was tested using a universal testing machine. Surface roughness was evaluated using a 3D optical profilometer. Scanning electron microscopy (SEM) and stereomicroscopy were used for surface analysis. Data was collected and analyzed using analysis of variance (ANOVA) and Kruskall-Wallis tests (α = 0.05). RESULTS: The denture base material and surface treatment significantly affected the SBS. The milled Temp Basic Tissue demonstrated the highest SBS values across all surface treatments, whereas the two 3D-printed denture base materials exhibited the lowest SBS values. CONCLUSIONS: The bond strength of CAD-CAM-milled denture base resins to autopolymerizing repair resins is comparable to that of heat-cured resins. Surface roughening using air particle abrasion or 180-grit carbide paper can enhance the bond strength of the autopolymerizing repair resin to 3D-printed denture base materials.

Effect of bioactive glass particles on mechanical and adhesion properties of resin cements.

PURPOSE: The aim of this study is to evaluate the mechanical and adhesive properties of three different resin cements with bioactive glass (BAG) incorporated in two different ratios. METHODS: BAG was added to different resin cements (3M Rely-X Ultimate, GC Link Ace, and GC Link Force) in different ratios (5% and 10% by weight). The three-point flexural strength, microhardness, and bond strength properties were evaluated. The fracture types of the groups were then analyzed using a stereo microscope. The data were analyzed using a multifactorial analysis of variance and Tukey's post-hoc tests (α < 0.05). RESULTS: The addition of BAG reduced the flexural strength of the resin cements (P < 0.05).The effect of BAG addition on the Vickers microhardness value was significantly different for each cement group (P < 0.05). In addition, with the exception of the GC link force group (10% BAG addition), the BAG addition decreased the bond strength of cements to dentin in all the groups (P = 0.171). CONCLUSIONS: The results of this study confirmed that different resin cements comprising different ratios of BAG exhibited different flexural strength, hardness, and bond-strength properties. Since the bond strength values increased with the addition of 10% BAG in the GC Link Force cement group, the effects of different BAG compositions could be worth investigating in future studies.

Bioactive glasses promote rapid pre-osteoblastic cell migration in contrast to hydroxyapatite, while carbonated apatite shows migration inhibiting properties.

Different biomaterials have been clinically used as bone filling materials, although the mechanisms behind the biological effects are incompletely understood. To address this, we compared the effects of five different biomaterials: two bioactive glasses (45S5 and S53P4), hydroxyapatite (HAP), carbonated apatite (CAP), and alumina on the in vitro migration and viability of pre-osteoblastic cells. In addition, we studied the effects of biomaterials' calcium release on cell migration, viability and differentiation. We found differences between the materials as the bioactive glasses promoted rapid pre-osteoblastic cell migration. In contrast, CAP decreased cell migration, which was also associated with lower activity of migration related kinases. Bioactive glasses released significant amounts of calcium into the media, while CAP decreased the calcium concentration. The response of cells to calcium was mechanistically studied by blocking calcium sensing receptor (CaSR) and ATP-gated ion channel P2X7, but this had no effect on cell migration. Surprisingly, HAP and CAP initially decreased cell viability. In summary, bioactive glasses 45S5 and S53P4 had significant and long-lasting effects on the pre-osteoblastic cell migration, which could be related to the observed calcium dissolution. Additionally, bioactive glasses had no negative effects on cell viability, which was observed with HAP and CAP.

The effect of low-temperature degradation and building directions on the mechanical properties of additive-manufactured zirconia.

This study aimed to investigate the effect of low-temperature degradation (LTD) on the mechanical properties of additive-manufactured zirconia. In addition, the mechanical properties of additive-manufactured were compared with those before aging under similar experimental conditions. This study prepared stereolithography apparatus fabricated zirconia specimens with flexural strength, modulus of elasticity, Vickers hardness, and fracture toughness. The specimen position data were set as parallel (0°), diagonal (45°), and perpendicular (90°) to the direction of the building. The LTD condition was 5 h under 134ºC and 0.2 MPa in an autoclave. It was found that the 0° direction differed significantly from all other conditions before and after aging, and the highest flexural strength was obtained when the additive specimen was manufactured perpendicular to the building direction. However, the results indicate that there is a negligible effect of aging on the mechanical properties of additive-manufactured zirconia.

Repair bond strength of bulk-fill composites: influence of different primers and direction of debonding stress.

Background: The purpose of this in vitro study was to evaluate the effect of different adhesion primers on the repair bond strength of bulk-fill resin composite and short-term hydrolytic stability of the repair interface before and after accelerated aging. In addition, direction of debonding stress was examined. Materials and methods: Bulk-fill substrates were aged in water for 14 days at 37 °C. Smooth resin composite surfaces were prepared for the substrates with a superfine grinding paper (FEPA #500, #1200, #2000). Test specimens were produced by attaching bulk-fill composite to the substrate surfaces, using three different primer/bonding systems. Specimens were aged 24 h at 37 °C in water, or thermal cycled (5-55 °C/5,000 cycles). Subsequently, shear bond strength and micro-tensile bond strength were evaluated. In total there were 60 specimens for the shear bond strength and 60 specimens for the micro-tensile bond strength measurements (30 stored in water 24 h, 30 thermal cycled, n = 10 in each primer/bonding mode). Results: The mean shear bond strength was 9.1-13.1 MPa after 24 h water storage and 6.9-10.7 MPa after thermal cycling. The mean micro-tensile bond strength was 28.7-45.8 MPa after 24 h water storage and 22.7-37.9 MPa after thermal cycling. Conclusion: The Ceramic primer (silane containing) seems to perform better than the three-step etch and rinse adhesive or the Composite primer. Shear-type stress had an adverse effect on the repair bond strength of bulk-fill resin composites.

Evaluation of flexible three-dimensionally printed occlusal splint materials: An in vitro study.

OBJECTIVE: To evaluate and compare the mechanical properties, water sorption, water solubility, and degree of double bond conversion of three different commercially available three-dimensional (3D) printing resins used for the fabrication of flexible occlusal splints. METHODS: A digital printer was used to generate specimens from the evaluated splint materials (KeySplint Soft, IMPRIMO LC Splint flex, and V-Print splint comfort). The specimens were equally divided and tested either dry or after water storage at 37 °C for 30 days. A three-point bending test was used to assess flexural strength, elastic modulus, and fracture toughness. A two-body wear test was performed using a dual-axis chewing simulator. Water sorption and water solubility were measured after 30 days. The degree of double bond conversion was determined by FTIR-spectrometry. All data for the evaluated properties were collected and statistically analyzed. RESULTS: Both material and storage conditions had a significant effect on the flexural strength (P < 0.001), elastic modulus (P < 0.001), fracture toughness (P < 0.001), and wear (P < 0.001). The highest water sorption was noticed with IMPRIMO LC Splint flex (1.9 ± 0.0 %), while V-Print splint comfort displayed the lowest water solubility (0.2 ± 0.0 %). For the degree of conversion, it was statistically non-significant among the different materials (P = 0.087). SIGNIFICANCE: Different flexible 3D-printed splints available in the market displayed variations in the evaluated properties and clinicians should consider these differences when choosing occlusal device materials. Among the tested flexible splint materials, KeySplint Soft had the greatest flexural strength, elastic modulus, fracture toughness, wear resistance, and degree of conversion. It also showed the lowest water sorption.

Particulate Filler and Discontinuous Fiber Filler Resin Composite's Adaptation and Bonding to Intra-Radicular Dentin.

The aim of this study was to assess adaptation and bonding to root canal dentin of discontinuous (short) glass fiber-reinforced composite to intra-radicular dentin (DSGFRC). METHODS: Seventy virgin human teeth were extracted and then endodontically treated; then samples were randomly divided into 7 groups (n = 10), based on the materials' combinations as follows: Group 1, a two-bottle universal adhesive + DSGFRC; Group 2, a single-component universal adhesive + DSGFRC; Groups 3 and 4, the same materials of Goups 1 and 2 were used but after cleaning of the canal walls with 17% EDTA and final irrigation with 5.25% NaOCl Ultrasound Activated (UA); Group 5, traditional prefabricated fiber posts were luted after being silanized with G-Multi Primer; Groups 6 and 7, like Group 5 but after ultrasonic irrigation (UA). All sample roots were cut 1 mm thick (n = 10) to be evaluated regarding root canal adaptation using a light microscope and scanning electron microscope (SEM) and push-out bond strength. These results were statistically analyzed by Kruskal-Wallis analysis of variance by ranks. The level of significance was set at p < 0.05. RESULTS: Bond strength forces varied between 6.66 and 8.37 MPa and no statistically significant differences were recorded among the groups. By microscopic examination, it was noted that ultrasonic irrigation increased the adaptation of the materials to the dentin surface. CONCLUSIONS: Within the limitations of this in vitro study, it may be concluded that when DSGFRC was used for intracanal anchorage in the post-endodontic reconstruction, similar push-out retentive force and strength to those of traditional fiber posts cemented with particulate filler resin composite cements were achieved.

Load-bearing capacity and wear characteristics of short fiber-reinforced composite and glass ceramic fixed partial dentures.

The aim of this study was to evaluate load-bearing capacity and wear performance of experimental short fiber-reinforced composite (SFRC) and conventional lithium-disilicate CAD/CAM fabricated fixed partial dentures (FPDs). Two groups (n = 12/group) of three-unit CAD/CAM fabricated posterior FPDs were made. The first group used experimental SFRC blocks, and the second group fabricated from lithium-disilicate (IPS e.max CAD). All FPDs were luted on a zirconia testing jig with dual-curing resin cement. Half of FPDs per group were quasi-statically loaded until fracture. The other half experienced cyclic fatigue aging (100.000 cycles, Fmax = 500 N) before loading quasi-statically until fracture. Fracture mode was examined using SEM. Wear test was performed using 15,000 loading cycles. Both material type and aging had a significant effect on the load-bearing capacity of FPDs. Experimental SFRC CAD without fatigue aging had significantly the highest load-bearing capacity (2096 ± 149N). Cyclic fatigue aging decreased the load-bearing capacity of the SFRC group (1709 ± 188N) but increased it for the lithium-disilicate group (1546 ± 155N). Wear depth values of SFRC CAD (29.3µm) were significantly lower compared to lithium-disilicate (54.2µm). Experimental SFRC CAD demonstrated the highest load-bearing capacity before and after cyclic fatigue aging, and superior wear behavior compared to the control material.

Zirconia implants interfere with the evaluation of peri-implant bone defects in cone beam computed tomography (CBCT) images even with artifact reduction, a pilot study.

OBJECTIVES: Three-dimensional cone beam computed tomography (CBCT) imaging can be considered, especially in patients with complicated peri-implantitis (PI). Artifacts induced by dense materials are the drawback of CBCT imaging and the peri-implant bone condition may not be assessed reliably because the artifacts are present in the same area. This pilot study investigates the performance of the artifact reduction algorithm (ARA) of the Planmeca Viso G7 CBCT device (Planmeca, Helsinki, Finland) with three different implant materials and imaging parameters. METHODS: Three pairs of dental implants consisting of titanium, zirconia, and fiber reinforced composite (FRC) were set into a pig mandible. A vertical defect simulating peri-implantitis bone loss was made on the buccal side of one of each implant. The defect was identified and measured by two observers and compared to the actual dimensions. In addition, the bone structure and the marginal cortex visibility between the implants were estimated visually. RESULTS: The bone defect and its dimensions with the zirconia implant could not be identified in any image with or without the metal artifact reduction algorithm. The bone defect of titanium and FRC implants were identified with all three imaging parameters or even without ARA. The interobserver agreement between the two observers was almost perfect for all categories analyzed. CONCLUSION: Peri-implantitis defect of the zirconia implant and the peri-implant bone structure of the zirconia implants cannot be recognized reliably with any ARA levels, or any imaging parameters used with the Planmeca Viso G7. The need for ARA when imaging the peri-implant bone condition of the titanium and FRC implants may be unnecessary.

Retrospective Analysis of Artifacts in Cone Beam Computed Tomography Images Used to Diagnose Chronic Rhinosinusitis.

BACKGROUND: Cone beam computed tomography (CBCT) is frequently used to corroborate the signs and symptoms of chronic rhinosinusitis (CRS). However, artifacts induced by dental restorations might complicate the diagnosis of CRS. Here, we assessed the frequency and location of artifacts in CBCT images taken to confirm the CRS. METHODS: All CBCT images of the patients referred to the Emergency Radiology unit, Turku University Hospital, with an indication of CRS in 2017 were re-examined. The prevalence of the artifacts was analyzed in three cross-sectional views and three horizontal levels delimited by anatomical landmarks. RESULTS: In total, 214 CBCT images of patients with CRS were evaluated. The diagnosis of apical periodontitis (AP) was impaired by artifacts present in 150/214 images (70%). The diagnosis of CRS was impaired in 5 of the 214 images (2.3%). The main origins of the artifacts were large dental fillings or crowns, and endodontic fillings were present in 95% (203/214) and 52% (111/214) of the images, respectively. CONCLUSIONS: AP as an etiology of CRS is possible to miss because of artifacts originating from dental and endodontic fillings in the CBCT images of the paranasal sinuses.