Search

Purpose: The aim of this study was to evaluate in vitro the influence of fiber reinforcement and luting cement on the static failure load (SFL) and dynamic failure load (DFL) of simulated two-unit cantilever resin-bonded fixed dental prostheses (RBFDPs). Materials and Methods: Forty-six particulate filler composite (PFC) beams and 76 fiber-reinforced composite (FRC) beams were prefabricated and subsequently luted (RelyX ARC or Panavia F2.0) onto flat ground bovine enamel. The SFL of the different specimen types was determined with a peel test and the DFL was determined with a rotating cantilever beam fatigue testing device. Results: The PFC specimens showed a significantly lower SFL than the FRC specimens. The luting cement showed a significant effect on the SFL of the PFC specimens, but not with FRC. The DFL of PFC specimens was significantly lower than for FRC specimens. The luting cement showed a significant effect on the DFL of the PFC specimens, but not so with FRC. With both the SFL and the DFL tests all PFC beams fractured, leaving the bonded part on the tooth surface, but FRC beams partially debonded from the tooth surface, leaving fibers connected to the enamel surface to a varying extent. Coincidentally, the uncured fibers turned out to be prone to aging, an effect which has been investigated. Conclusion: Within the limitations of this study, it can be concluded that PFC without fiber reinforcement is not suitable for the fabrication of two-unit cantilever RBFDPs, despite the significant effect of the luting cement, but FRC is suitable. [ABSTRACT FROM AUTHOR]

Purpose: To evaluate the clinical performance of direct Class II fiber-reinforced composite restorations on nonvital teeth. Materials and Methods: Thirty patients age 18 or older were included in this clinical trial restoring 35 molars. The inclusion criteria were: two- to four-surface restorations, replacement of composite and amalgam restorations necessary or unrestored teeth with decay reaching the pulp, teeth having homogeneous root canal fillings terminating 0 to 2 mm from the radiographic apex. Teeth with residual cavity walls less than 1 mm or with complete loss of the clinical crown were excluded. Teeth were restored using a combination of Ultra etch 35% phosphoric acid, PQ1 adhesive system, and Vit-l-escence microhybrid composite resin. The enamel peripheral shell of the restoration was built up first; a resin-impregnated piece of polyethylene ribbon fiber (Ribbond Triaxial) was covered with B1 Perma-Flo flowable composite, placed into a prepared canal, folded, and light cured; then, dentin and enamel occlusal surface stratification was completed. All 35 restorations were evaluated at 6 months and 1 year by two independent evaluators using modified USPHS criteria. Results: No failure was reported and alpha scores were recorded for all parameters. Before starting the treatment, 26 out of 35 teeth (74%) had apical periodontitis as diagnosed radiographically. At the 1-year recall, no signs of periapical lesions were detected and radiographs reported neither periodontal ligament widening nor periapical radiolucency. Conclusion: Direct fiber-reinforced composite resin restorations demonstrated excellent clinical performance at 1 year. [ABSTRACT FROM AUTHOR]

Purpose: The study evaluates the behavior of different adhesive systems and resin cements in fiber post placement, with the intent to clarify the possible role of unfilled resin as a luting material for fiber posts. Materials and Methods: Two luting agents (Dual-Link and Unfilled Resin) for cementing fiber posts into root canals were applied either with All-Bond 2 or One-Step Plus, or without an adhesive system, and challenged with the pushout test. Slices of roots restored with posts were loaded until post segment extrusion in the apical-coronal direction. Failure modes were analyzed under SEM. Results: Push-out strength was significantly influenced by the luting agent (p < 0.05), but not by the bonding strategy (p > 0.05). The best results were obtained in combination with Unfilled Resin with One-Step Plus. Dual-Link groups failed mainly cohesively within the cement, while Unfilled Resin demonstrated more adhesive fracture at the post interface. Conclusion: The results of this study support the hypothesis that adhesive unfilled resin application is essential for achieving high bond strength to radicular dentin. [ABSTRACT FROM AUTHOR]

Purpose: (1) To evaluate the interfacial strength between FRC Postec posts and three luting agents (Multilink, Variolink II, and MultiCore Flow) following different surface treatments, and (2) to observe the effect of sandblasting (Rocatec Pre) on the surface morphology of methacrylate-based fiber posts. Materials and Methods: The posts received one of the following surface treatments: (1) sandblasting, (2) sandblasting + silanization, (3) silanization or (4) no treatment. The three luting agents were bonded to the post and the post-cement bond strength was evaluated with the microtensile test. SEM observation of sandblasted and nontreated posts was performed. Post-cement interfaces were also evaluated. Data were statistically analyzed with two-Way ANOVA with post treatment and luting agent as factors. Tukey's test was applied for post-hoc comparisons. Results: Post treatment and the interaction between type of luting agent and type of post treatment were significant factors for bond strength (p < 0.001). The type of luting agent did not significantly influence bond strength (p = 0.07). Sandblasting + silanization performed better than sandblasting or no treatment (p < 0.001). Silanization resulted in significantly higher bond strengths than no treatment (p = 0.045). No differences were detected between sandblasting + silanization and silanization. SEM observation revealed an increased surface roughness and exposure of fibers in sandblasted posts. Conclusion: Silanization was confirmed to be a reliable method for improving the bond strength of resin luting agents to fiber posts. Bond strength of resin luting agents to fiber posts was not influenced by the type of luting agent. The sandblasting procedure modified the methacrylate-based post surface texture. [ABSTRACT FROM AUTHOR]

Purpose: As polymerization shrinkage is compensated by flow of the composite, several attempts have been performed for relief of the contraction stresses. The aim of this in vitro study was to evaluate the effect of flowable composite or fiber use under composite restorations on microtensile bond strength of composite to dentin in Class I cavities or flat dentin surfaces. Materials and Methods: Twenty-four sound extracted human first or second mandibular molars were randomly assigned to two groups (Class I cavities with a high c-factor or flattened dentin surfaces with a low c-factor). The dentin surfaces were treated with adhesive resin and restored with resin composite using four different techniques (bulk; with flowable composite; with a glass fiber (everStick NET); with a polyethylene fiber [Ribbond]). After 24 h storage at 37°C in water, the specimens were thermocycled 600 times between 5 and 55°C. Microtensile test specimens with a 0.9 x 0.9 (± 0.1) mm2 cross-sectional area were produced, and bond strength tests were carried out at a crosshead speed of 1 mm/min. Mean bond strengths were analyzed using two-way ANOVA and Bonferroni's test at a 95% significance level. Results: Flowable composite decreased dentin bond strength in cavities with a high c-factor (p < 0.05). The group restored with everStick NET showed stable bond strengths regardless of the effect of c-factor. Ribbond THM used under composite restorations increased dentin bond strength in cavities with a high c-factor (p < 0.05). Conclusion: Flowable composite decreased dentin bond strength in cavities with a high c-factor; however, using a glass fiber in combination with flowable resin, stable bond strengths can be achieved in cavities with a high c-factor. Polyethylene fiber in combination with flowable resin increases the microtensile bond strength to the dentin floor in cavities with a high c-factor. [ABSTRACT FROM AUTHOR]

Purpose: The purpose of this study was to evaluate the clinical performance of surface-retained adhesive composite fixed partial dentures reinforced by an ultra-high molecular weight polyethylene (UHMWP) fiber (Ribbond THM). Materials and Methods: Twenty-three surface-retained fiber reinforced composite (FRC) fixed partial dentures (FPD) were placed by two operators in 23 patients, each with a single missing tooth. The restorations included prefabricated composite resin pontics, and no preparations were done on the lingual surfaces of the abutment teeth. The patients were recalled for examinations every year for up to 3 years. Restorations were evaluated directly using the modified Ryge criteria. The minimum observation period was 1 year and the maximum observation period was 3 years. Results: At baseline, 23 restorations were graded as Alpha for all parameters. At one year and two years (n = 21), three Bravos for wear resistance and surface texture/gingival inflammation and two Bravos for color match were observed. Twenty-one of 23 restorations were retained at the end of two years (91.3%) and 78.3% were retained after a maximum of 3 years. Conclusion: The results of this clinical study suggest that UHMWP FRC FPDs are quite acceptable at least for three years. However, further clinical investigations are still needed for improved long-term clinical performance. [ABSTRACT FROM AUTHOR]

This article describes the rationale and method of using glass fibers reinforced with resin composite as an external (framework to reuse a patient's own natural anterior tooth as a pontic, after extraction. (Quintessence Int 2004,35-549-553) [ABSTRACT FROM AUTHOR]

Purpose: The aim of this study was to measure the flexural strength and the elastic modulus of composite resin with and without reinforcing fibers and to evaluate the reinforcing effect of various fibers. Materials and Methods: A polyethylene fiber (Ribbond), a polyaramid fiber (Fibreflex), and three glass fibers (FibreKor, GlasSpan, Vectris) were used to reinforce composite resins. The flexural strength and elastic modulus of specimens in the three-point bending mode were measured using a universal testing machine at a cross-head speed of 1 mm/min after storage in water at 37°C for 24 hours. All tests were carried out in a water bath at 37°C. The data were analyzed using analysis of variance and the Sheffé test at P = 0.05. After testing, the fractured surface was evaluated using a scanning electron microscope at 50, 500, and 3,000 magnifications. Results: Yield flexural strengths of nonreinforced resins were 48 to 56 MPa, and those of reinforced resins were 56 to 134 MPa. Ultimate flexural strengths of nonreinforced specimens were 96 to 119 MPa, and those of reinforced ones were 203 to 386 MPa. Elastic modulus of nonreinforced resin was 6 to 9 GPa, and fiber reinforcing increased the value to 9 to 15 GPa, while it had no effect in Ribbond. Conclusion: Most of the fibers used in this study increased both yield and ultimate flexural strengths of composite resins, with the exception of the yield strength of Vectris. GlasSpan, Fibreflex, and FibreKor were effective in reinforcing elastic modulus, while Ribbond had no effect on it. Unidirectional glass fibers and polyaramid fiber were effective in reinforcing both flexural strength and elastic modulus of composite resin. [ABSTRACT FROM AUTHOR]

Purpose: The aim of the present study was to investigate the influence of different filling materials and methods on marginal integrity in Black Class I fillings. Materials and Methods: Standardized occlusal cavities were prepared in SO extracted human molars The preparations were filled with composite resin (1), with composite resin using the incremental technique (2), an experimental glass-fiber-reinforced (3) and polyester-reinforced (4) composite resin, a direct composite inlay (5), a ceramic insert (6), a Cerafil inlay (7), and with an experimental direct filling using Dyract AP compomer (8). Allocation of the teeth to the test groups was randomized; further processing was done on a blind basis. After the preparation of replicas, the teeth were subjected to a thermomechanical cycling process of 2,000 temperature cycles (5°C/55°C) and 50,000 stress cycles (50 N). This was followed by production of a second set of replicas and quantitative margin analysis by SEM (200X). A dye penetration test was then performed on the mesiodistal section. Results: Groups 1, 2, 5, 6 and 7 displayed a good primary marginal quality, with the proportion of continuous margins reaching more than 85%. Significantly poorer results were recorded for the experimental glass-fiber-reinforced composite resins and Dyract compomer. where the proportion of perfect margins was only between 36% and 73%. In groups 1, 2, 5, 6 and 7, marginal integrity remained stable after the thermomechanical stress cycles, with the Cerafil inlays recording the best values: 89% perfect margins and 3% marginal gaps. In contrast, the experimental composite resins and the compomer underwent a significant (p < 0.05) increase in the proportion of marginal gaps and a significant (p < 0.05) reduction in the proportion of continuous margin. Conclusion: The results of This study show that neither Dyract compomer nor the glass-fiber-reinforced composite resins tested can be recommended for use in the occlusally stressed posterior region, whereas the other filling materials and methods were sufficiently stress resistant. [ABSTRACT FROM AUTHOR]

Objective: This study was intended to quantify the marginal leakage of three glass-ionomer-resin composite hybrid materials and compare it with the leakage exhibited by a glass-ionomer cement and a bonded resin composite system. Method and materials: Standardized Class V cavities were prepared on root surfaces of 105 extracted human teeth, randomly assigned to five groups of 21 each, and restored with either Ketac-Fil Aplicap, ZWO/Scotchbond Multi-Purpose Plus, Vitremer, Photac-Fil Aplicap, or Dyract. The teeth were thermally stressed tor 500 cycles and stained with methylene blue. The microleakage was quantified spectropholometrically, and the data were statistically analyzed with Friedman's test. Results: There were no significant differences in microleakage among the live groups. Restorations of all tested materials showed some marginal leakage in Class V cavities. Conclusion: The microleakage performance of glass-ionomer-resin composite hybrid materials was similar to those of a conventional glass-ionomer and a bonded resin composite system (Quintessence Int 1999;30:117-121) [ABSTRACT FROM AUTHOR]

The article presents information on the observations made on the intraenamel veneers of processed composite resin used for the esthetic restoration of generalized facial stains or defects. It was found that the physical properties of these veneers are superior to chairside microfilled resins and are less technique-sensitive to operator ability. It sates that the bond strength of indirect resin veneers are not as great as that of etched porcelain veneers, because they are fabricated indirectly. However, the minimal cost, simplicity of fabrication and esthetic qualities of indirect resin veneers make them a viable alternative to other veneering systems.

Introduction: Treatment of mechanical exposure of the pulp during caries excavation presents a clinical challenge. In this case series of 15 patients, with a follow-up period of over a year, the outcome of direct pulp capping with Biodentine (septodont) after mechanical pulp exposure was assessed.Aim Of Study: The aim of this study is to evaluate the outcome of direct pulp capping with Biodentine in deeply carious teeth when pulp was mechanically exposed during caries excavation and cavity preparation. Vital pulps exposed during caries excavation in molar teeth were treated with 3% sodium hypochlorite for 2 min. If adequate hemostasis was achieved, the pulp tissue was capped with Biodentine, which covered the entire pulpal floor. This was followed by the placement of a layer of resin-modified glass ionomer cement and a final layer of composite resin (Filtek Z350-3M) to complete the restoration. The patients were recalled periodically and evaluated for any evidence of pulpal/periapical pathology.Results: In the follow-up period that ranged from 12 to 24 months, all teeth were asymptomatic.Conclusion: Biodentine appears to be a suitable material for direct pulp capping under clinical conditions. However, long-term follow-up studies and controlled trials involving a large sample size are warranted. [ABSTRACT FROM AUTHOR]

Background: Glass fiber-reinforced composites (FRCs) have been adapted for routine clinical use in various dental restorations and are presently also used in cranial implants. The aim of this study was to measure the load-bearing capacity and failure type of glass FRC implants during static loading with and without interconnective bars and with different fixation modes. Methods: Load-bearing capacities of 2 types of FRC implants with 4 different fixation modes were experimentally tested. The sandwich-like FRC implants were made of 2 sheets of woven FRC fabric, which consisted of silanized, woven E-glass fiber fabrics impregnated in BisGMA-TEGDMA monomer resin matrix. The space between the outer and inner surfaces was filled with glass particles. All FRC implants were tested up to a 10-mm deflection with load-bearing capacity determined at 6-mm deflection. The experimental groups were compared using non-parametric Kruskal-Wallis analysis with Steel-Dwass post hoc test. Results: FRC implants underwent elastic and plastic deformation until 6-mm deflection. The loading test did not demonstrate any protrusions of glass fibers or cut fiber even at 10-mm deflection. An elastic and plastic deformation of the implant occurred until the FRC sheets were separated from each other. In the cases of the free-standing setup (no fixation) and the fixation with 6 screws, the FRC implants with 2 interconnective bars showed a significantly higher load-bearing capacity compared with the implant without interconnective bars. Conclusions: FRC implants used in this study showed a load-bearing capacity which may provide protection for the brain after cranial bone defect reconstruction. [ABSTRACT FROM AUTHOR]

Objectives: The aim of this study was to assess the effect of artificial accelerated aging (AAA) on color change of direct and indirect fiber-reinforced composite (FRC) restorations. Materials and Methods: Direct (Z250) and indirect (Gradia) composite resins were reinforced with glass (GF) and polyethylene fibers (PF) based on the manufacturers' instructions. Forty samples were fabricated and divided into eight groups (n=5). Four groups served as experimental groups and the remaining four served as controls. Color change (ΔE) and color parameters (ΔL*, Δa*, Δb*) were read at baseline and after AAA based on the CIELAB system. Three-way ANOVA and Tukey's test were used for statistical analysis. Results: Significant differences were found in ΔE, ΔL*, Δa* and Δb* among the groups after AAA (P<0.05). Most of the studied samples demonstrated an increase in lightness and a red-yellow shift after AAA. Conclusions: The obtained ΔE values were unacceptable after AAA (ΔE≥ 3.3). All indirect samples showed a green-blue shift with a reduction in lightness except for Gradia/PF+ NuliteF. [ABSTRACT FROM AUTHOR]

Objectives: To evaluate the influence of irradiation time on degree of conversion (DC) and microhardness of high-viscosity bulk-fill resin composites in depths up to 6 mm. Materials and methods: Four bulk-fill materials (Tetric EvoCeram Bulk Fill-TECBF; x-tra fil-XF; QuixFil-QF; SonicFill-SF) and one conventional nano-hybrid resin composite (Tetric EvoCeram-TEC) were irradiated for 10, 20, or 30 s at 1,170 mW/cm. DC and Knoop microhardness (KHN) were recorded after 24-h dark storage at five depths: 0.1, 2, 4, 5, and 6 mm. Data were statistically analyzed using ANOVA and Bonferroni's post-hoc test ( α = 0.05). Results: With increasing bulk thickness, DC and KHN significantly decreased for TEC. TECBF and SF showed a significant decrease in DC and KHN at 4-mm depth after 10-s irradiation, but no decrease in DC after 30-s irradiation ( p > 0.05). XF and QF demonstrated no significant DC decrease at depths up to 6 mm after irradiation of at least 20 s. At 4-mm depth, all materials tested achieved at least 80 % of their maximum DC value, irrespective of irradiation time. However, at the same depth (4 mm), only XF and QF irradiated for 30 s achieved at least 80 % of their maximum KHN value. Conclusions: Regarding DC, the tested bulk-fill resin composites can be safely used up to at least 4-mm incremental thickness. However, with respect to hardness, only XF and QF achieved acceptable results at 4-mm depth with 30 s of irradiation. Clinical relevance: Minimum irradiation times stated by the manufacturers cannot be recommended for placement of high-viscosity bulk-fill materials in 4-mm increments. [ABSTRACT FROM AUTHOR]

Aims: To compare the clinical efficacy of two space maintainers namely, conventional band and loop and Fiber Reinforced Composite Resin (FRCR) space maintainers. Subjects and Methods: Thirty healthy children, aged 5 to 8 years were selected having at least two deciduous molars in different quadrants indicated for extraction or lost previously. FRCR space maintainer was placed in one quadrant and in the other quadrant band and loop space maintainer was cemented. All the patients were recalled at 1st, 3rd, and 6th months for evaluation of both types of space maintainer. Patient acceptability, time taken, and clinical efficacy was recorded. Statistical analysis used: The observations thus obtained were subjected to statistical analysis using Chi- square test and Mann-Whitney U test. Results: Patient acceptability was greater in Group I (FRCR) in comparison to Group II (band and loop space maintainer). The time taken by Group I was significantly lower as compared to that of Group II. In Group I, debonding of enamel, composite was the most common complication leading to failure followed by debonding of fi ber composite. In Group II, cement loss was the most common complication leading to failure followed by slippage of band and fracture of loop. The success rates of Groups I and Group II weares 63.3% and 36.7%, respectively. Conclusion: The study concluded that FRCRFiber Reinforced Composite Resin (Ribbond) space maintainers can be considered as viable alternative to the conventional band and loop space maintainers. [ABSTRACT FROM AUTHOR]

The aim of this study was to determine the retentive forces of fiber-reinforced composite (FRC) posts luted with different core build-up composite resins, and resin cements. Extracted single-rooted teeth were restored using FRC posts luted with the core build-up composites Build-It, Culmat, Flow White, Luxacore, Multi-Core Flow, Rebilda DC and luted with the resin cements Calibra, Cement-It, Multilink, and RelyX Unicem (control group, no separate etching, priming or bonding steps). The Rebilda DC was used with both the light-polymerizing Solobond and the dual-polymerizing AdheSE. Following water storage (37°C, 24 h) and thermal cycling (5000 cycles, 5-55°C, 30 s) tensile strength testing was performed and fracture modes were assessed. Statistical analysis of the data was done by one-way ANOVA, Bonferroni/Dunn correction, and unpaired t-test with α = 0.05. Except for Multilink (319 N, SD 50 N) and Cement-It (331 N, SD 85 N) significantly higher retentive forces were obtained for the core build-up composite Build-It (422 N, SD 43 N) and for the resin cements Calibra (408 N, SD 50 N) and RelyX Unicem (405 N, SD 64 N) compared to the other materials (p < 0.001). The lowest retentive forces were found for the core build-up composites Luxacore (145 N, SD 36 N) and Rebilda DC/Solobond (148 N, SD 39 N) (p < 0.001). Fracture modes were mainly interfacial. The use of core build-up composites did not improve the retentive forces of FRC posts compared to resin cements. Except for Culmat, core build-up composites as well as resin cements in combination with dual-polymerizing bonding materials were superior to composites with light-polymerizing bonding materials. [ABSTRACT FROM AUTHOR]

Background/purpose: A fiber-reinforced composite (FRC) resin system was introduced as an alternative for implant-retained fixed dental prostheses (FDPs); however, the stress distribution in the bone around the implants which support the FRC-FDP has so far not been reported. The aim of this study was to investigate the biomechanical behavior of FRCFDPs supported by implants with different collar geometries. Materials and methods: A 3-dimensional finite element analysis method was selected to evaluate the stress distribution. FRC-FDPs were supported by 2 different dental implant systems with 2 distinct collar geometries: a microthread collar structure (MCS) and a non-MCS (NMCS). In separate load cases, 300-N vertical, 150-N oblique, and 60-N horizontal forces were simulated. Tensile and compressive stress values in the cortical and cancellous bone and von Mises stresses in the fixture-abutment complex, the framework, and veneer material were calculated. Results: The MCS model revealed higher compression stresses at the cortical bone than did the NMCS model under all 3 load conditions. Moreover, higher tensile stresses under the oblique loads at the cortical bone were shown with the MCS model. In each model, stresses were much higher in the implant-abutment complex than in the cortical bone, and they were very low in the cancellous bone. Conclusion: Although additional experimental and clinical studies are needed, FRC-FDPs can be considered a suitable and alternative treatment choice for an implant-supported prosthesis. The implant design and geometry affect the load-transmission mechanisms, Implants with an MCS that supports FRC-FDPs were shown to be superior in terms of the stress distribution in the bone around the implant compared to implants with an NMCS. [ABSTRACT FROM AUTHOR]

The article discusses the effectiveness of resin-based, bulk fill composites for dental restorations. It describes technique in dealing with polymerization shrinkage and composite placement during restoration. It cites a case study of a 42-year-old male who was scheduled for teeth 18 and 19 Class II posterior direct composite restorations.

The article presents a case study of a 34-year-old male who was admitted for routine direct restorative dentistry in the mandibular right quadrant. His tooth number 29 has a decay on the distal surface associated with minor marginal ridge fracture. A small occlusal direct composite with marginal recurrent decay was also observed in tooth number 30. The article also discusses the efficacy of flowable resins in dental restoration which claimed it make good cavity liners.

Abstract: Objectives: This investigation evaluated the flexural properties of two composite resins, and the influence of unidirectional glass fiber reinforcements, with and without pre-tensioning. Methods: Two composite resins (Q: Quixfil and A: Adoro) were used to fabricate 2mm×2mm×25mm beams (N =10), reinforced with two fiber bundles along the long axis of the beam and pre-tensioned under a load equivalent to 73.5% of its tensile strength (groups QPF and APF). In two other experimental groups, the bundles were similarly positioned but without pre-tension (groups QF and AF). Two more groups were included without fiber reinforcement (control groups Q and A). After 24h storage, specimens were subjected to a three-point flexural bending test to establish the flexural module, the deflection at initial failure and the flexural strength. Data were analyzed using a two-way analysis of variance (composite resin system and fiber reinforcement type) and the Tukey HSD post hoc tests (α =.05). Results: The results showed that prestressing increased the flexural module of Adoro specimens (p <.001) but not Quixfil (p =.17). Prestressed beams reached greater deflection at initial failure than those conventionally reinforced (p <.001), namely .85–1.35mm for Adoro and .66–.90mm for Quixfil. Prestressing also significantly increased the flexural strength of beams (p <.001) in both Adoro and Quixfil groups, from 443.46 to 569.15MPa and from 425.47 to 568.00MPa, respectively. Significance: Pre-tensioning of unidirectional glass fibers increased both deflection until initial failure and flexural strength of Quixfil and Adoro composite resins, however, with limited effects on the flexural modulus. [Copyright &y& Elsevier]

The aim of this study was to evaluate the effects of plasma treatment on adhesion between fiber-reinforced posts and a composite core material. Two types of posts, methacrylate-based (FRC Postec) and epoxy resin-based (DT Light-Post), were treated with oxygen plasma (O2), argon plasma (Ar), nitrogen plasma (N2), or helium mixed with nitrogen plasma (He+N2) using a radio-frequency generator before bonding to a methacrylate-based composite. Pull-out tests were performed using a universal testing machine. Surface roughness of each group was evaluated using a profilometer. On tensile-shear bond strength, statistical analysis revealed that the type of post, type of plasma treatment, and their interaction significantly influenced the results (pc0.05). Tukey's test revealed significant differences in tensile-shear bond strength between the control and other plasma treatment groups (p<0.05). On surface roughness, Tukey's test revealed significant differences between the control group and the Ar group (p<0.05) with DT Light Post. Plasma treatment appeared to increase the tensile-shear bond strength between post and composite. [ABSTRACT FROM AUTHOR]

Abstract: Objectives: To compare polymerization efficiency of resin composite basing materials when light-cured through resin composite and fiber reinforced composite (FRC) by testing microhardness. Methods: Simulated indirect restorations were prepared by application of resin composite (Clearfil AP-X) or FRC (EverStick) to nylon rings with 1.5mm thickness and 8mm diameter, followed by light-curing. Resin composite basing material (Clearfil Majesty Flow or Clearfil AP-X) was applied to identical rings and light-cured through the simulated indirect restorations with exposure times of 20, 40, or 60s. Light-curing though a ring without resin material (=no indirect restoration) served as control. For each combination of basing material and indirect restoration 10 specimens were prepared for each exposure time. Top and bottom surface Vickers microhardness numbers (VHNs) of basing materials were recorded after 24h. Results: After 60s exposure time, VHNs with indirect FRC were not different from control VHNs, while VHNs with indirect resin composite were significantly lower (p <0.001). Linear regression analysis revealed that resin composite basing material used had the greatest effect on top and bottom VHNs (p <0.001). The presence of an indirect restoration resulted in decreased VHNs (p <0.001), with resin composite resulting in lower VHNs when compared to FRC. Moreover, a longer exposure time resulted in increased VHNs (p <0.001). Significance: Results suggest that polymerization of resin composite basing materials is more effective when light-curing through an FRC than through a resin composite indirect restoration. Prolonging of exposure time, however, is necessary when compared to light-curing without presence of indirect restoration material. [Copyright &y& Elsevier]

Abstract: Objectives: Fractured coronal fragments of incisors can be adhered to the remaining tooth with resin composite, but are prone to failure. This study explores whether mini fibre-reinforced composite (FRC) anchors increase fracture resistance of reattached fragments. Methods: Forty-five extracted incisors were randomly divided into three groups. In Groups A and B coronal fragments were reattached to the remaining tooth, with additionally two anchors placed in Group B. In Group C resin composite buildups were made. Specimens were statically loaded until failure occurred. Failure modes were characterized as intact remaining tooth substrate (adhesive or cohesive failure of coronal fragment) or fractured remaining tooth substrate (fracture limited to enamel or extending into dentin). Results: Mean fracture loads were 255N (SD=108N) for Group A, 599N (SD=465N) for Group B and 786N (SD=197N) for Group C (values significantly different, all p values <0.05). Group A showed purely adhesive failures, while Groups B and C showed 73 and 53% fractures of remaining tooth substrate (p <0.05). Conclusions: Mini FRC anchors increase fracture resistance of reattached coronal fragments, but induce more remaining tooth substrate fractures. [Copyright &y& Elsevier]

This study evaluated the three-year clinical performance of Class V restorations made of a polyacid-modified resin composite, Dyract. Ninety-two Class V carious lesions in 28 patients were restored with Dyract. Restorations were clinically evaluated at baseline, first, second, and third year recall visits, according to the modified Ryge criteria by two experienced, calibrated examiners. Retention rate after three years it. Class V carious restorations was 92.4%, with only seven failed restorations. Color change and marginal discoloration in restorations were found to be statistically significant (p=0.013 and p<0.001, respectively) at the end of third year, but none of the affected restorations required replacement. The results of this study revealed that at the end of three years, Dyract exhibited good clinical success rate but significant color change and marginal discoloration in Class V carious lesions. [ABSTRACT FROM AUTHOR]

To investigate the pre-clinical relevancy of a machinable composite, its physical properties were evaluated and compared with a machinable ceramic and two indirect composites. A machinable resin composite (GN-I composite, CO), a machinable ceramic (GN-I ceramic, CE), and two resin composites (Artglass dentin, AG; Estenia dentin. ST) were used. Compressive strength, diametral tensile strength, flexural strength, elastic modulus, and fracture load of standardized, premolar crown- shaped specimens were determined. In terms of compressive strength, diametral tensile strength, and flexural strength, AG showed significantly lower values than the other three materials In terms of fracture load, specimens with 15 mm thick wall showed a higher value than those with 10 mm thick wall and the value decreased in the order of ST, CE, CO, and AG Marginal tipping was also observed in ET and CE. Within the limits of the current study, CO showed physical properties favorable for constructing esthetic restorations [ABSTRACT FROM AUTHOR]

PURPOSE: To (1) review the literature and analyze the longevity and reasons for failure of direct resin-based composite (RBC), amalgam, and glass-ionomer cement (GIC) restorations in stress-bearing posterior cavities and (2) to assess new material developments and treatment techniques to restore these cavities. MATERIALS AND METHODS: This work reviewed the dental literature predominately of the last decade for longitudinal, controlled clinical studies and retrospective cross-sectional studies. Only studies investigating the clinical performance of restorations in permanent teeth were included. Annual failure rates of direct resin-based composite, amalgam, and GIC restorations were determined and failure reasons were discussed. RESULTS: Annual failure rates in posterior stress-bearing cavities were determined to be: 0-9% for direct RBC restorations, 0-7% for amalgam restorations, and 1.9-14.4% for GIC restorations. The median annual failure rate of longitudinal studies for amalgam was calculated with 1.1%, for RBCs 2.1% and for GICs 7.7%. GIC is significantly worse compared with amalgam and RBC. Main reasons for failure were secondary caries, marginal deficiencies, fracture, and wear. Longitudinal studies showed a strong trend towards a higher longevity compared with cross-sectional investigations. [ABSTRACT FROM AUTHOR]

Focused ion beam (FIB) has been available for over 10 yrs but until recently its usage has been confined to the semiconductor industry. It has been developed as an important tool in defect analysis, circuit modification and recently transmission electron microscope sample preparation. This paper introduces FIB and demonstrates its application in dental research. Its ion and electron imaging modes complement the SEM while its ability to prepare TEM samples from a wide range of material will allow the study of new types of adhesive interface. As an example, its use is described in the characterization of the interface of resin to a tribochemically treated surface of an experimental fiber-reinforced resin-based composite. As with all new techniques, the initial learning curve was difficult to manage. This new instrument offers opportunities to expand research in dental materials to areas not possible before. [ABSTRACT FROM AUTHOR]

The objective of this study was to test the hypothesis that a degraded subsurface layer containing microcracks is produced in dental composites as a result of finishing procedures. Various composites in the form of rectangular bars were finished with a 12-fluted carbide bur or a fine diamond within minutes of light-curing, and were subsequently stained with silver nitrate. Microscopic evaluation revealed that significant penetration of stain occurred in the unfinished as well as in the finished surfaces. The extent of dye penetration that could be directly attributed to a damaged layer produced by the finishing procedure was less than 10 µm, being greatest for a microfill (Silux Plus) and a hybrid (P-S0) composite. There was no difference between the effects of the finishing instruments. SEM analysis of the subsurface showed an absence of any cracks for the composites. However, occasional disruption of the interface between the pre-polymerized resin fillers and the matrix was apparent for the microfill material. The results showed that only a very limited subsurface damage may be created in certain composites during the initial contouring of a restoration. [ABSTRACT FROM AUTHOR]

The objectives of this study were to determine the cytotoxic concentrations of 11 components of resin composites on monolayers of cultured Balb/c 3T3 fibroblasts, to study the inhibitory effects of these components on DNA synthesis, total protein content, and protein synthesis, and to determine whether effects were reversible when the components were withdrawn from the medium. These data were reported as concentrations which inhibited 10%(ID10) and 50%(ID50) of a particular metabolic process as well as the range of concentrations over which cell metabolism was irreversibly inhibited. For any individual component, the ID60 values for all three metabolic parameters were of the same magnitude. The same was true for the ranges of irreversibility. Ethoxylated Bis-phenol A dimethacrylate (E-BPA) was the most toxic molecule of the group (ID50 being between 1 and 10 µmol/L). The ID50 concentrations for three of the components, including Bis-GMA, UDMA, TEGDMA, and Bis-phenol A, ranged between 10 and 100 µmol/L, while the ID50 values of three components (N,N dihydroxyethyl-p-toluidine, camphoroquinone, and N,N dimethylaminoethyl methacrylate) were above 100 µmol/L. The concentrations to which the cells and tissues are exposed in vivo are not known. This study should help to identify the concentrations of organic composite components which pose clinical cytotoxic hazards. [ABSTRACT FROM AUTHOR]

The monomer systems of conventional composites and smooth-surface microfilled composites were studied by means of nuclear magnetic resonance spectroscopy. The monomer composition varied from brand to brand. Obviously, this will result in different physical properties and clinical behavior. Transmission electron microscopy revealed the presence of a free submicron fraction in the monomer system of some restorative resins. [ABSTRACT FROM AUTHOR]

Abstract: Introduction: This study investigated and compared the root reinforcement potential of 3 different intraorifice barriers (mineral trioxide aggregate [MTA], resin-modified glass ionomer cement [Vitremer], and fiber-reinforced composite [FRC]) placed over root canals obturated with gutta-percha or Resilon. Methods: Crowns of 80 extracted human mandibular premolars were sectioned off to obtain 14-mm-long root specimens. After preparation of root canals with nickel-titanium rotary files, the roots were obturated with either the Resilon/Epiphany system or gutta-percha + AH Plus sealer. In both obturation groups, specimens were further subgrouped with respect to the intraorifice barrier material placed after removal of 3-mm coronal portion of the root fillings: (1) MTA, (2) Vitremer, and (3) FRC. The specimens were loaded vertically at 1 mm/min crosshead speed until vertical root fracture occurred. Results were evaluated statistically with two-way analysis of variance and Tukey tests. Results: Fracture resistance of roots was significantly affected by the type of intraorifice barrier (P < .05), but not by the type of obturation system used (P > .05). Conclusions: The use of Vitremer and FRC significantly improved the fracture resistance, whereas MTA did not exhibit any reinforcing effect as an intraorifice barrier. [Copyright &y& Elsevier]

PURPOSE: This article focuses on the polymerization shrinkage of current dental composites as their major disadvantage and to find new routes for a solution. MATERIALS AND METHODS: A brief introduction describes selected methods for the shrinkage determination as well as some principal solutions to overcome the shrinkage problem. RESULTS: Siloranes, a new class of ring opening monomers, are presented as a promising resin matrix for dental composites. The synthesis of these monomers, and further consequences of the new chemistry for the formulation are discussed. Two selected silorane composites are presented with their mechanical data and their volume shrinkage. [ABSTRACT FROM AUTHOR]

The purpose of this in vitro study was to determine the metameric color difference between resin composites and dentin. Changes in lightness, chroma, hue, and hue angle under the 3 standard illuminants were also evaluated. Spectral reflectance of 5 selected shades (n = 5 of each shade) of 1 brand of resin composites (2 mm thickness and 10 mm in diameter) and actual dentin (n = 10) were measured to obtain CIELAB values relative to standard illuminants: daylight (D65), incandescent lamp (A), and fluorescent lamp (F2). Spectral curves of resin composites and 2 average dentin specimens were compared. Color difference and their ratios of color difference (modification of metamerism index) by illuminant were compared. The ratio of change in hue angle between resin composites and dentin relative to the illuminant (A/D65 and F/D65) were also calculated. The difference in value depending on shade was analyzed by analysis of variance and Scheffe multiple range test. Three of the 5 composite shades made 3 crossing points with dentin, indicating a metameric effect. Color differences between resin composite and dentin changed when the illuminant changed. Their ratio ranged from 0.74 to 0.98. Differences in hue angle were found: (1) A and D65: resin (-10.1 to -7.2) and dentin (-13.8 to -14.0); (2) F and D65: resin (2.6 to 5.2) and dentine (-3.9 to -2.8). Changes in optical properties of resin composites relative to different illuminants that varied from those of dentin may reveal potential problems of metamerism of resin composites over dentin clinically. Bonding different shades of resin composite to dentin and then comparing to actual dentin/enamel samples under different lighting may improve secondary validity of this line of research. [ABSTRACT FROM AUTHOR]