Fiber-reinforced Composite Substructure Research Articles

Digitally produced fiber-reinforced composite substructures for three-unit implant-supported fixed dental prostheses.

This study aimed to evaluate the probability of survival, Weibull modulus, characteristic strength, and failure modes of computer-aided design/computer-assisted manufacture (CAD/CAM) fiber-reinforced composite (FRC) substructures used for implant-supported fixed dental prostheses (ISFDPs). Three-unit ISFDPs (first molar pontic) fabricated as a monolithic composite piece or as composite veneered on a CAD/CAM FRC substructure with either a 12-mm² or 3-mm² connector area (n = 18 each) were subjected to step-stress accelerated life testing in water. Use-level probability Weibull curves and the probability of survival were calculated. Fractographic analysis was performed under polarized light and scanning electron microscopy. Fatigue did not accelerate the failure of any group, whereas prosthesis strength was the main factor in increased failure (β < 1). The probability Weibull contour plot showed no differences between the ISFDPs with 12 mm² and the monolithic composite ISFDP in characteristic strength (η = 643.5 N and 742.7 N, respectively) or Weibull modulus (6.7 and 5.8, respectively), whereas both were significantly higher than 3 mm² (444.91 N and 9.57). The probability of survival was not statistically different between groups at 100,000 mission cycles at 300 N. Differences were observed in fatigue failures above 800 N; monolithic composite ISFDPs failed catastrophically, whereas those with CAD/CAM FRC substructures presented veneer/composite cohesive or adhesive failures. Cracks evolved from the occlusal contact toward the margins of the cohesively failed composite, and in CAD/CAM FRC prostheses, competing failure modes of cracks developing at the connector area with those at the indentation contact were observed. The probability of survival did not differ between CAD/CAM FRC with either 3-mm² or 12-mm² connector areas, monolithic composite, or metal-ceramic ISFDPs previously tested under the same methodology. However, differences in failure modes were detected between groups.

Evaluation of the Load-bearing Capacity of Fractured Incisal Edge of Maxillary Permanent Central Incisors restored with a Glass Fiber-reinforced Nanocomposite: An in vitro Study.

ABSTRACTObjectives: The aim of this study was to evaluate and compare the load-bearing capacity of fractured incisal edge of maxillary permanent central incisors restored with a nanocomposite and a glass fiber-reinforced nanocomposite.Materials and methods: Thirty-six extracted sound maxillary central incisors randomly divided in three groups were used for the present study. Group I (control) contained untreated teeth. Samples in experimental groups II and III were prepared by cutting the incisal (one-third) part of the crown horizontally and subjected to enamel preparations and restored with a nanocomposite and a glass fiber-reinforced nanocomposite respectively. All restored teeth were stored in distilled water at room temperature for 24 hours. Fracture resistance was evaluated as peak load at failure (Newton) for samples tested in a cantilever-bending test using Hounsfield universal testing machine. Failure modes were microscopically examined.Results: Highest mean peak failure load (Newton) among experimental groups was observed in glass fiber-reinforced nano composite group (863.50 ± 76.12 N) followed by nanocomposite group (633.67 ± 40.14 N). One-way analysis of variance (ANOVA) revealed that the restoration technique significantly affected the load-bearing capacity (p < 0.001). Scheffe’s post-hoc comparison test (subset for α = 0.05) revealed that there was significant difference in the mean peak failure load values of nanocomposite and glass fiber-reinforced nanocomposite groups when considered together (p < 0.001). Experimental groups showed similar types of failure modes with majority occurring ascohesive and mixed type. Fifty-eight percent of the teeth in glass fiber-reinforced nanocomposite group fractured below the cementoenamel junction.Conclusion: By using fiber-reinforced composite substructure under conventional composites in the repair of fractured incisors, the load-bearing capacity of the restored incisal edge could be substantially increased.How to cite this article: Kumar PSP, Srilatha KT, Nandlal B, Dhull KS. Evaluation of the Load-bearing Capacity of Fractured Incisal Edge of Maxillary Permanent Central Incisors restored with a Glass Fiber-reinforced Nanocomposite: An in vitro Study. Int J Clin Pediatr Dent 2015;8(1):22-29.

The shear adhesion strength between the FRC substructure and denture base resin: Effects of FRC architecture, adhesive composition and hydrolytic degradation

Abstract The adhesion strength between fiber reinforced composite (FRC) members and denture-base resin is pivotal for enhancing removable denture long lasting performance and patient comfort. FRC reinforcing rods based on glass fibers impregnated with light curing resin were used to model the FRC substructure. The influence of fiber architecture and adhesive layer composition on the shear adhesion strength, τ a , between the FRC and denture-base resin was investigated both dry and in moist environment to assess the stability of the adhesive bond in the oral cavity. The obtained results suggest that for a given fiber architecture, adhesive composition and test conditions, the wetting of the FRC surface was the primary variable affecting the τ a . In the case of good wetting and formation of adhesive bond between the substrates, interlaminar shear strength of the unidirectional FRC substrate was the limiting factor. In multidirectional FRC substrate, the shear strength of the outer resin rich layer was limiting factor for the maximum adhesion strength.

In vitro validation of a shape-optimized fiber-reinforced dental bridge

Objective To improve its mechanical performance, structural optimization had been used in a previous study to obtain an alternative design for a 3-unit inlay-retained fiber-reinforced composite (FRC) dental bridge. In that study, an optimized layout of the FRC substructure had been proposed to minimize stresses in the veneering composite and interfacial stresses between the composite and substructure. The current work aimed to validate in vitro the improved fracture resistance of the optimized design. Methods All samples for the 3-unit inlay-retained FRC dental bridge were made with glass-fibers (FibreKor) as the substructure, surrounded by a veneering composite (GC Gradia). Two different FRC substructure designs were prepared: a conventional ( n = 20) and an optimized design ( n = 21). The conventional design was a straight beam linking one proximal box to the other, while the optimized design was a curved beam following the lower outline of the pontic. All samples were loaded to 400 N on a universal test machine (MTS 810) with a loading speed of 0.2 mm/min. During loading, the force and displacement were recorded. Meanwhile, a two-channel acoustic emission (AE) system was used to monitor the development of cracks during loading. Results The load–displacement curves of the two groups displayed significant differences. For the conventional design, there were numerous drops in load corresponding to local damage of the sample. For the optimized design, the load curves were much smoother. Cracks were clearly visible on the surface of the conventional group only, and the directions of those cracks were perpendicular to those of the most tensile stresses. Results from the more sensitive AE measurement also showed that the optimized design had, on average, fewer cracking events: 38 versus 2969 in the conventional design. Significance The much lower number of AE events and smoother load–displacement curves indicated that the optimized FRC bridge design had a higher fracture resistance. It is expected that the optimized design will significantly improve the clinical performance of FRC bridges.

Marginal Adaptation and Microleakeage of Directly and Indirectly Made Fiber Reinforced Composite Inlays

Aim:This study evaluated in vitro microleakage of inlays made by direct or indirect techique with or without fiber reinforced composite (FRC) substructure. Materials and Methods: Standardized mesio-occlusal cavities were prepared and restored using direct-technique with composite resin only or FRC-composite resin, and indirect technique with laboratory composite only or FRC-laboratory composite resin. After thermocycling, teeth were immersed in basic fuchsin dye, sectioned and examined under a stereo-microscope (x40). Results:No differences of cement thickness and dye penetration were found in gingival area (p>0.05), whereas microleakage revealed statistical differences between groups (p=0.02) in occlusal area, where FRC-groups had lower microleakage than composite restorations. Thickness of cement layer did not show significant difference between groups with indirect technique (p>0.05). Conclusion: The present study suggests that insertion of FRC substructure to the inlay cavity by direct composite filling technique does not increase the marginal leakage compared to that of cementing indirectly made restotorations by composite resin luting cement.Clinical Significance: On the basis of the results of this in vitro study, the use of direct FRC technique might be an effective way to decrease the marginal leakage.

A fiber-reinforced composite prosthesis restoring a lateral midfacial defect: A clinical report

This clinical report describes the use of a glass fiber-reinforced composite (FRC) substructure to reinforce the silicone elastomer of a large facial prosthesis. The FRC substructure was shaped into a framework and embedded into the silicone elastomer to form a reinforced facial prosthesis. The prosthesis is designed to overcome the disadvantages associated with traditionally fabricated prostheses; namely, delamination of the silicone of the acrylic base, poor marginal adaptation over time, and poor simulation of facial expressions.

Fracture resistance of short, randomly oriented, glass fiber-reinforced composite premolar crowns

The aim of this work was to determine the static load-bearing capacity of posterior composite crowns made of experimental composite resin (FC) with short fiber fillers and a semi-interpenetrating polymer network (IPN) matrix. In addition, we wanted to investigate how load-bearing capacity of surface composite resins was affected by substructures of fiber-reinforced composite (FRC) and FC, and by different curing systems. Five groups of crowns were fabricated ( n = 6). The crowns were either polymerized with a hand-light curing unit (LCU) or cured in a vacuum curing device (VLC) before they were statically loaded at a speed of 1 mm min −1 until fracture. Failure modes were visually examined. Data were analyzed using ANOVA. ANOVA revealed that crowns made from the FC had a statistically significant higher load-bearing capacity than the control PFC composite. Crowns with FRC substructure and PFC covering gave force values of 348 N (LCU) and 1199 N (VLC), respectively, which were lower than the values of FC composite. No statistically significant difference was found between crowns made from plain FC composite and those made from FC composite with a surface layer of PFC ( P = 0.892 and 1.00). Restorations made from short glass fiber-containing composite resin with IPN–polymer matrix showed better load bearing capacity than those made with either plain PFC or PFC reinforced with FRC substructure.

Static and fatigue compression test for particulate filler composite resin with fiber-reinforced composite substructure

Objectives The aim of this study was to determine static load-bearing capacity and compressive fatigue limits (CFL) of laboratory particulate filler composite resin (PFC) with three different types of fiber-reinforced composite (FRC) substructures. Methods A total of 420 test specimens were prepared having 1.0 mm of FRC layer as substructure (short random, continuous unidirectional and bidirectional fiber orientations), and a 2.0-mm thick surface layer of PFC. Control specimens were prepared from plain FRC or PFC. The specimens ( n = 15) were either dry stored or water stored (37 °C for 2 weeks) before they were loaded with a steel ball (Ø 3.0 mm) under static load until fracture and cyclic load with maximum controlled regimen following a staircase approach with maximum 10 3 cycles. The decrease in CFL compared to static load was calculated and data were analyzed using ANOVA and Weibull statistics. Results The highest static loads were registered for plain FRC specimens [short random 1842 N(205), continuous bidirectional 2258 N(233) and unidirectional fiber orientation 538 N(254)]. The specimens with FRC substructure and PFC coverage gave load values of 1517 N(249), 1670 N(241) and 677 N(240), respectively. The specimens made of PFC only, failed with 1047 N(230) load. The CFL for 10 3 cycles ranged between 19 and 39% of the static load values. ANOVA revealed that all factors significantly affected the load bearing capacity ( p < 0.001). Significance The results suggested that the material combination of continuous bidirectional or random FRC and PFC, gave higher CFL and static load-bearing capacity than that obtained with plain particulate filler composite resin

Fiber-reinforced Composite Substructure: Load-bearing Capacity of an Onlay Restoration and Flexural Properties of the Material

The aim of this study was to determine the static load-bearing capacity of composite resin onlay restorations made of particulate filler composite (PFC) with two different types of fiber-reinforced composite (FRC) substructures. In addition, flexural properties of the material combination and the effect of polymerization devices were tested. Specimens were prepared to simulate an onlay restoration, which consisted of 2 to 3 mm of FRC layer as a substructure (short random and continuous bidirectional fiber orientation) and a 1 mm surface layer of PFC. Control specimens were prepared from plain PFC. In Group A the specimens were incrementally polymerized only with a hand-light curing unit for 40 s, while in Group B the specimens were post-cured in a light-curing oven for 15 min before they were statically loaded with a steel ball. Bar-shaped test specimens were prepared to measure the flexural properties of material combination using a three-point bending test (ISO 10477). Analysis of variance (ANOVA) revealed all specimens with a FRC substructure have higher values of static load-bearing capacity and flexural properties than those obtained with plain PFC (p<0.001). The load-bearing capacity of all the specimens decreased after post-curing and water storage. Restorations made from a material combination of FRC and PFC showed better mechanical properties than those obtained with plain PFC.

Fiber-reinforced composite substructure: Load-bearing capacity of an onlay restoration

Objective. To determine the static load-bearing capacity of composite resin onlay restorations made of particulate filler composite (PFC) with two different types of fiber-reinforced composite (FRC) substructures. Material and Methods. Specimens were prepared to simulate an onlay restoration, composed of a 2 to 3 mm FRC layer as the substructure (short random and continuous bidirectional fiber orientation) and a 1 mm surface layer of PFC. Control specimens were prepared from plain PFC. The specimens were incrementally polymerized with a hand-light curing unit for 40 s and then post-cured in a light-curing oven for 15 min. The specimens were cemented on dentin substrate of extracted human molars using a standard adhesive resin cementation technique. The specimens (n=8/group) were water stored either for 24 h at room temperature or for 4 weeks at 37°C before they were statically loaded until fracture using a universal testing machine. Failure modes were visually examined. Results. ANOVA revealed that all specimens with FRC substructures had higher values of static load-bearing capacity than those obtained with plain PFC (p<0.001). The load-bearing capacity of all the specimens decreased after water storage (p<0.001). Conclusions. Restorations made from a combination of FRC and PFC showed better load-bearing capacity than those obtained with PFC alone.

Load bearing capacity of fibre-reinforced and particulate filler composite resin combination

Longevity of particulate filler resin (PFR) is controversial for large restorations with high occlusal-stresses. The aim of this study was to reinforce PFR with fiber reinforced composite (FRC) and to evaluate the effect of thickness of FRC substructure and thickness of overlaying PFR, on the static load-bearing capacity of the material combination. A total of 336 test specimens having a FRC substructure (short random or continuous bidirectional fibre orientation) and layer of restorative PFR were prepared for this study. In Group A, the specimens contained short random oriented fibres (length: 2-3mm) and in Group B, there were continuous bidirectionally oriented fibres. The specimens (n = 12/group) were polymerized with a hand light-curing unit and were either dry-stored or thermocycled before they were statically loaded with a steel ball until fracture, using a universal testing machine. Increase the volume fraction of the short random FRC versus the fraction of PFR, the load-bearing capacity of the specimen increased (p < 0.001). Short random FRC revealed significantly different behavior than the bidirectionally oriented FRC (p < 0.001). By combining the FRC layer of 0.5mm in thickness with a layer of 2.5mm of PFR gave load values of 1462N and 1196N, which were considerably higher than values for plain PFR of 3mm in thickness (782N and 729N). The results suggest that by adding a FRC substructure under the PFR, the load-bearing capacity of the material combination was increased.

Development and clinical applications of a light-polymerized fiber-reinforced composite

Statement of problem. After 30 years of intermittent reports in the literature, the use of fiber reinforcement is just now experiencing rapid expansion in dentistry. Purpose. This article describes the development and use of a continuous, unidirectional fiber-reinforced composite as a framework for the fabrication of fixed prostheses. Methods. By using various matrix materials and fibers, a number of fiber-reinforced composite formulations were evaluated with the goal of creating a system with optimized mechanical properties and handling characteristics. Fiber-reinforced composite based on a light-polymerized BIS-GMA matrix has been used clinically to make 2-phase prostheses comprised of an internal glass fiber-reinforced composite substructure covered by a particulate composite. The clinical and laboratory procedures required for the fabrication and use of reinforced composite fixed prostheses are described for laboratory-fabricated complete or partial coverage fixed prosthesis and chairside prosthesis. Results. Although additional clinical experience is needed, fiber-reinforced composite materials can be used to make metal-free prostheses with excellent esthetic qualities. (J Prosthet Dent 1998;80:311-8.)