Physicochemical and mechanical characterization of a fiber-reinforced composite used as frameworks of implant-supported prostheses

ObjectivesTo characterize the physicochemical and mechanical properties of a milled fiber-reinforced composite (FRC) for implant-supported fixed dental prostheses (FDPs).MethodsFor FRC characterization, scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS), X-ray diffraction, Fourier-transformed infrared spectrometry, simultaneous thermogravimetric analysis and differential scanning calorimetry were performed. For fatigue testing, 3-unit FRC frameworks were fabricated with conventional (9 mm² connector area) and modified designs (12 mm² connector area and 2.5 mm-height lingual extension). A hybrid resin composite was veneered onto the frameworks. FDPs were subjected to step-stress accelerated-life fatigue testing until fracture or suspension. Use level probability Weibull curves at 300 N were plotted and the reliability for 100,000 cycles at 300, 600 and 800 N was calculated. Fractographic analysis was performed by stereomicroscope and SEM.ResultsThe FRC consisted of an epoxy resin (∼25%) matrix reinforced with inorganic particles and glass fibers (∼75%). Multi-layer continuous regular-geometry fibers were densely arranged in a parallel and bidirectional fashion in the resin matrix. Fatigue analysis demonstrated high probability of survival (99%) for FDPs at 300 N, irrespective of framework design. Conventional FDPs showed a progressive decrease in the reliability at 600 (84%) and 800 N (19%), whereas modified FDPs reliability significantly reduced only at 800 N (75%). The chief failure modes for FRC FDPs were cohesive fracture of the veneering composite on lower loads and adhesive fracture of the veneering composite at higher loads.SignificanceMilled epoxy resin matrix reinforced with glass fibers composite resulted in high probability of survival in the implant-supported prosthesis scenario.     

玻璃纤维预拉伸对增韧光固化树脂基桩力学性能的影响

目的 研究玻璃纤维预拉伸对自行研制的高强玻璃纤维增韧光固化树脂复合材料（FRC）桩力学性能的影响。方法 利用加载装置将高强玻璃纤维分别拉伸0%、0.5%、1.0%后,按60%体积比浸入自行配置的光固化树脂基质,采用压膜法制成玻璃纤维增韧树脂基齿科桩,三点弯曲测试各试样的弯曲模量、弯曲强度和弯曲载荷,测试结果进行统计学分析。使用扫描电子显微镜观察FRC桩横截面和断裂面的形态。结果 玻璃纤维拉伸率对FRC桩的力学性能影响有显著差异,其中拉伸率为1.0%的玻璃纤维制成的FRC桩综合性能最佳,弯曲模量(20.40±1.40) GPa,弯曲强度(573.38±29.45) MPa,弯曲载荷(180.42±5.88) N,与未预拉伸的玻璃纤维增韧的FRC桩有显著差异(P<0.05)。结论 玻璃纤维预拉伸对FRC桩有增韧效果。     

In vitro fracture resistance of fiber reinforced cusp-replacing composite restorations.

OBJECTIVES: To assess the fracture resistance and failure mode of fiber reinforced composite (FRC) cusp-replacing restorations in premolars. METHODS: Forty-five extracted sound upper premolars were randomly divided into three groups. Identical MOD cavities with simulated buccal cusp fracture and height reduction of the palatal cusp were prepared. In Group A two layers of resin impregnated woven continuous FRC (EverStick Net) were applied. In Group B one layer of unidirectional continuous FRC (EverStick) was used. In Group C no fibers were applied (control). Subsequently, all teeth were restored with resin composite (Clearfil Photo Posterior), subjected to thermocycling (6000 x 5-55 degrees C) and static load tests. Load until fracture was registered for each tooth. Simultaneously, fracture propagation was monitored using acoustic emission analysis (AE). Failure modes were visually assessed. RESULTS: Weibull analysis revealed a characteristic strength and Weibull modulus (m) at 2364.8 N for Group A (m=8.9), 2437.9 N for Group B (m=5.9) and 2160.3N for Group C (m=13.6). Fracture loads were not significantly different (ANOVA, p>0.05). Teeth with FRC showed less fractures below the cemento-enamel junction (CEJ) (38% and 23% for Groups A and B, respectively) than teeth without FRC (93%) (chi-square, p<0.05). The control group showed the least AE energy signals. SIGNIFICANCE: The results suggest that glass FRC does not increase fracture load of premolars with cusp-replacing restorations. However, FRC has a beneficial effect on the failure mode. Woven fibers give more consistent results than unidirectional fibers.     

Reinforcing effect of glass-fiber-reinforced composite on flexural strength at the proportional limit of denture base resin

OBJECTIVE: To evaluate the reinforcing effect of fiber-reinforced composite (FRC) on flexural strengths at the proportional limit (FS-PL) of a denture base resin. MATERIAL AND METHODS: Bar-shaped acrylic resin specimens and maxillary acrylic resin complete denture specimens were fabricated. The FS-PL of the reinforced bar-shaped specimens was tested. Novel FRC, FibreKor, Remanium, Palatal Bar Wire, and Clasp-Wire were used as reinforcing materials. Likewise, the compressive strength at the proportional limit (CS-PL) of the reinforced maxillary denture specimens was tested. RESULTS: The FS-PL of the bar-shaped specimens reinforced with the FRCs was significantly higher than that of the unreinforced specimens. The FS-PL of the bar-shaped specimens reinforced with the 1.0-mm-thick FRC was similar to the FS-PL of specimens reinforced with Remanium or Palatal Bar Wire. The FS-PL of specimens reinforced with the 1.5-mm-thick FRC was significantly higher than with the metal-reinforcing materials. The reinforcing efficiency of the 1.0-mm-thick FRC was 1.78-1.79 and of the 1.5-mm-thick FRC 3.14-3.27. The reinforcing effect of the FRC on the CS-PL of the maxillary denture specimen was similar to the effect on the FS-PL of the bar-shaped specimens. The reinforcing efficiency was 1.40 for the 1.0-mm-thick FRC and 1.67 for the 1.5-mm-thick FRC. CONCLUSION: The unidirectional glass-fiber-reinforced composite had a reinforcing effect on the flexural strength at the proportional limit of the denture base resin.     

Effects of mechanical properties of adhesive resin cements on stress distribution in fiber-reinforced composite adhesive fixed partial dentures

Using finite element analysis (FEA), this study investigated the effects of the mechanical properties of adhesive resin cements on stress distributions in fiber-reinforced resin composite (FRC) adhesive fixed partial dentures (AFPDs). Two adhesive resin cements were compared: Super-Bond C&B and Panavia Fluoro Cement. The AFPD consisted of a pontic to replace a maxillary right lateral incisor and retainers on a maxillary central incisor and canine. FRC framework was made of isotropic, continuous, unidirectional E-glass fibers. Maximum principal stresses were calculated using finite element method (FEM). Test results revealed that differences in the mechanical properties of adhesive resin cements led to different stress distributions at the cement interfaces between AFPD and abutment teeth. Clinical implication of these findings suggested that the safety and longevity of an AFPD depended on choosing an adhesive resin cement with the appropriate mechanical properties.     

Effect of location of glass fiber-reinforced composite reinforcement on the flexural properties of a maxillary complete denture in vitro

Objective. To evaluate the effect of the location of glass fiber-reinforced composite (FRC) reinforcement on the flexural load at the proportional limit (FL-PL) and the flexural deflection of a maxillary acrylic resin complete denture. Material and methods. Maxillary acrylic resin complete dentures strengthened with and without FRC reinforcement were tested. The polymerized FRC was embedded in the denture base resin in the doughy state and placed (1) under the ridge lap region, (2) in the anterior region, (3) in the middle region or (4) in the anterior and posterior regions. The FL-PL and flexural deflection value at the 100-N loading point of the reinforced maxillary denture specimens were tested. Results. All of the reinforced dentures had a higher FL-PL than the denture without reinforcement but the FL-PL values of all the dentures were not significantly different from each other. The efficiency of the FRC reinforcement compared to the unreinforced denture was 1.54-1.75 times greater. All of the reinforced dentures showed significantly lower deflection compared to the unreinforced denture, but the flexural deflections of all the dentures were not significantly different from each other. Conclusions. The location of the FRC reinforcement did not affect the fracture resistance of the maxillary acrylic resin complete denture. All of the reinforced dentures had higher FL-PL and lower flexural deflection than the denture without reinforcement.     

Fiber-reinforced composite in fixed prosthodontics

Fiber reinforced composite (FRC) is composed of resin matrix and fibers filler. Common types of fibers: polyethylene, carbon and glass. Fibers can be continuous and aligned, discontinuous and aligned, discontinuous and randomly oriented. The architecture of the fibers is unidirectional, woven or braided. The two main types are: dry fibers or impregnated. Inclusion of fibers to resin composite increased its average flexural strength in 100-200 MPa. FRC can be utilized by the dentist in direct approach (splinting, temporary winged bridge) or indirect approach (laboratory made fixed partial denture). Laboratory fixed partial denture (FPD) is made from FRC substructure and Hybrid/Microfill particulate composite veneer. Main indications: interim temporary FPD or FPD in cases of questionable abutment teeth, in aesthetic cases where All Ceram FPD is not feasible. Retention is attained by adhesive cementation to minimally prepared teeth or to conventionally prepared teeth; other options are inlay-onlay bridges or hybrid bridges. Contraindications are: poor hygiene, inability to control humidity, parafunction habits, and more than two pontics. Survival rate of FRC FPD over 5 years is 75%, lower compared to porcelain fused to metal FPD which is 95%. Main reasons for failure are: fracture of framework and delamination of the veneer. Part of the failures is repairable.     

Evaluation of some properties of two fiber-reinforced composite materials

OBJECTIVE: Water sorption, flexural properties, bonding properties, and elemental composition of photopolymerizable resin-impregnated fiber-reinforced composite (FRC) materials (everStick C&B and BR-100) (FPD) were evaluated in this study. MATERIAL AND METHODS: Bar-shaped specimens (2 x 2 x 25 mm) were prepared for water sorption and flexural strength testing. The specimens (n = 6) were polymerized either with a hand light-curing unit for 40 s or, additionally, in a light-curing oven for 20 min and stored in water for 30 days. Water sorption was measured during this time, followed by measurements of flexural strength and modulus. A shear bond strength test was performed to determine the bonding characteristics of polymerized FRC to composite resin luting cement (Panavia-F), (n = 15). The cement was bonded to the FRC substrate and the specimens were thermocycled 5000 times (5-55 degrees C) in water. SEM/EDS were analyzed to evaluate the elemental composition of the glass fibers and the fiber distribution in cross section. RESULTS: ANOVA showed significant differences in water sorption according to brand (p < 0.05). Water sorption of everStick C&B was 1.86 wt% (hand-unit polymerized) and 1.94 wt% (oven polymerized), whereas BR-100 was 1.07 wt% and 1.17 wt%, respectively. The flexural strength of everStick C&B after 30 days' water storage was 559 MPa (hand-unit polymerized) and 796 MPa (oven-polymerized); for BR-100, the values were 547 MPa and 689 MPa, respectively. Mean shear bond strength of composite resin cement to the FRC varied between 20.1 and 23.7 MPa, showing no statistical difference between the materials. SEM/EDS analysis revealed that fibers of both FRC materials consist of the same oxides (SiO2, CaO, and Al2O3) in ratios. The distribution of fibers in the cross section of specimens was more evenly distributed in everStick C&B than in BR-100. CONCLUSION: The results of this study suggest that there are some differences in the tested properties of the FRC materials.     

玻璃纤维的表面预处理对纤维增韧树脂基桩力学性能的影响

目的 研究不同表面预处理的高强玻璃纤维对纤维增强光固化树脂复合材料（FRC）桩的力学性能的影响。方法 将玻璃纤维分为4组分别进行以下表面处理：不预处理、450 ℃高温处理、450 ℃高温+10%HCl蚀刻1 h、450 ℃高温+10% HCl蚀刻3 h,然后将4组纤维经过硅烷偶联剂处理后按相同体积比浸入自行配制的光固化树脂基质中,用压挤法制成纤维增强树脂基桩。测试试样的弯曲模量、弯曲强度、弯曲载荷,扫描电子显微镜观察FRC截面和断裂面的形态。结果 不同表面预处理后的玻璃纤维对FRC桩的力学性能有显著差异,其中450℃+KH570组制成的FRC桩性能最佳,弯曲模量、弯曲强度、弯曲载荷分别为（37.70±1.46） GPa、（737.00±25.51） MPa、（196.53±6.80） N,与其余组有显著差异（P＜0.05）。结论 450 ℃高温+KH570处理玻璃纤维对FRC桩的增韧效果最佳。     

Direct restoration of severely damaged incisors using short fiber-reinforced composite resin

OBJECTIVES: The aim of this in vitro study was to evaluate the static load-bearing capacity and the failure mode of endodontically treated maxillary incisors restored with complete crowns made of experimental composite resin (FC) with short fiber fillers, with and without root canal posts. Further aim was to evaluate the effect of fiber-reinforced composite resin (FRC) on the failure mode of the restoration. MATERIAL AND METHODS: The experimental composite resin (FC) was prepared by mixing 22.5 wt.% of short E-glass fibers (3mm in length) and 22.5 wt.% of semi-interpenetrating polymer network (IPN) resin with 55 wt.% of silane treated silica fillers. The clinical crowns of 30 human extracted maxillary incisors were sectioned at the cemento-enamel junction. Five groups of direct complete crowns were fabricated (n=6); Group A: made from particulate filler composite resin (PFC) (Grandio Caps, VOCO, control), Group B: PFC with fiber post (everStick, StickTeck), Group C: made from PFC with everStick fiber post and FRC-substructure, Group D: made from FC, Group E: made from FC with FRC-substructure. The root canals were prepared and posts were cemented with resin cement (ParaCem Universal). All restored teeth were stored in water at room temperature for 24h before they were statically loaded with speed of 1.0 mm/min until fracture. Data were analyzed using ANOVA (p=0.05). Failure modes were visually examined. RESULTS: ANOVA revealed that restorations made from experimental fiber composite resin had higher load-bearing capacity (349N) (p<0.05) than the control restorations (173N). No significant difference was found in load-bearing capacity between restorations reinforced with FRC-substructure and those without (p>0.05). CONCLUSIONS: 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 fiber post.     

Three-dimensional finite element analysis of posterior fiber-reinforced composite fixed partial denture Part 2: influence of fiber reinforcement on mesial and distal connectors

The aim of this study was to evaluate the influence of connectors under two different loading conditions on displacement and stress distribution generated in isotropic hybrid composite fixed partial denture (C-FPD) and partially anisotropic fiber-reinforced hybrid composite fixed partial denture (FRC-FPD). To this end, two three-dimensional finite element (FE) models of three-unit FPD from mandibular second premolar to mandibular second molar - intended to replace the mandibular first molar - were developed. The two loading conditions employed were a vertical load of 629 N (applied to eight points on the occlusal surface) and a lateral load of 250 N (applied to three points of the pontic). The results suggested that the reinforcing fibers in FRC framework significantly improved the rigidity of the connectors against any twisting and bending moments induced by loading. Consequently, maximum principal stress and displacement generated in the connectors of FRC-FPD were significantly reduced because stresses generated by vertical and lateral loading were transferred to the reinforcing fibers.     

Direct composite resin restoration of an anterior tooth: effect of fiber-reinforced composite substructure

The aim of the study was to determine the static load-bearing capacity of fractured incisal teeth restored with the conventional adhesive-composite technique or by using fiber reinforced composites (FRC). Upper incisal teeth were prepared by cutting the incisal part of the crown horizontally. Restorations were made by three techniques. Group A (control group) was restored by reattaching the original incisal edge to the tooth. Group B was restored using composite resin. Group C was restored with composite and FRC. Restored teeth were statically loaded until fracture. Results suggest that an incisally fractured tooth restored with a combination of composite resin and FRC-structure provide the highest load bearing capacity.     

Finite element analysis of fiber-reinforced fixed partial dentures

Two-dimensional finite element models were created for a three-unit posterior fixed partial denture. An experimental resin-impregnated glass fiber was used as the fiber-reinforced composite (FRC) for the framework. The FRC was evaluated using varying combinations of position and thickness, alongside with two types of veneering composite. A load of 50 N simulating bite force was applied at the pontic in a vertical direction. Tensile stress was examined using a finite element analysis program. Model without FRC showed tensile stress concentrations within the veneering composite on the cervical side of the pontic--from the connector area to the bottom of the pontic. Model with FRC at the top of the pontic had almost the same stress distribution as the model without FRC. Models with 0.4-0.8 mm thick FRC positioned at the bottom of the pontic showed maximum tensile stresses reduced by 4-19% within the veneering composite.     

Repair bond strength of restorative resin composite applied to fiber‐reinforced composite substrate

Delamination or fracture of composite veneers can occur as a result of improper design of the fiber‐reinforced composite (FRC) framework. This in vitro study tested the repair bond strength of restorative composite to aged FRC. The substrate was multiphase polymer matrix FRC (everStick) aged by boiling for 8 h and storing at 37°C in water for 6 weeks. The aged substrate surfaces were wet‐ground flat with 1200‐grit silicon carbide paper and subjected randomly to 5 different surface treatments: 1) An adhesion primer (Composite Activator) and resin (CA), 2) Silane (EspeSil) and resin (SIL‐MP), 3) Silane, adhesive primer, and resin (Clearfil Repair) (CF), 4) Air particle‐abrading (CoJet), silane, and resin (CJ‐SIL‐MP), 5) Resin (Scotchbond Multipurpose Resin) only as control (MP). Restorative composite resin (Z250) was added to the substrate in 2 mm layer increments and light‐cured. Subsequently, every surface treatment group was divided into 2 subgroups of 12 specimens each. The specimens were either 48 h water‐stored or thermocycled (6000 x 5–55°C). The shear bond strengths of composite resin to FRC were measured at a crosshead speed of 1.0 mm/min. The data were analyzed by ANOVA for factors ‘treatment type’ and ‘storage condition’; Tukey's post‐hoc tests and Weibull analysis were performed. ANOVA showed a significant difference as a function of surface treatment (P<0.05) and storage condition (P<0.05). The CJ‐SIL‐MP group showed highest bond strength and Weibull modulus after thermocycling. Repair of multiphase polymer matrix FRC may show reliable bond strength when silane treatment is used along with air‐particle abrading.     

Use of short fiber-reinforced composite with semi-interpenetrating polymer network matrix in fixed partial dentures

OBJECTIVES: The aim of this study was to determine the static load-bearing capacity of fixed partial dentures (FPDs) made of experimental composite resin (FC) with short fiber fillers and interpenetrating polymer network (IPN) polymer matrix. MATERIALS AND METHODS: Experimental composite FC resin was prepared by mixing short E-glass fibers (3mm in length) of 22.5wt% and IPN-resin 22.5wt% with silane treated silica fillers 55wt%. Four groups of FPDs (3-unit) were fabricated (n=6); Group A: made from commercial composite resin (Sinfony dentin, 3M-ESPE, control), Group B: Sinfony and fiber-reinforced composite (FRC) substructure, Group C: made from FC, Group D: made from FC with 1mm surface layer of Sinfony. The bridges were polymerized with a hand-light curing unit for 40s then post-cured in vacuum curing device (Visio Beta) for 15min before they were statically loaded with speed of 1mm/min until fracture. Failure modes were visually examined. Data were analyzed using ANOVA (p=0.05). RESULTS: ANOVA revealed that bridges made from experimental fiber composite had statistically significantly higher load-bearing capacity (2171N) (p<0.05) than the control restorations (1482N). SIGNIFICANCE: Restorations made from short glass fiber containing composite resin with IPN-polymer matrix showed better load bearing capacity than in those made with conventional composites resin and similar with those reinforced with FRC-substructure.     

含固位型填料光固化复合树脂的流变特性

目的　探讨含固位型填料 (retentivefiller,RF)复合树脂的流变性及其与普通填料复合树脂的差异。方法　采用动态应力流变仪DSR 2 0 0 ,在室温 (2 5℃ )时测试含固位型填料复合树脂和普通填料复合树脂的流变性 ,包括黏度、剪切应力和柔量。结果　含固位型填料复合树脂的黏度大于普通填料复合树脂 (P <0 0 1)。随剪切应力的增大 ,前者的黏度开始基本保持不变 ,而后者会降低 ;当剪切应力大于 2 0 3 18Pa时 ,两者的黏度随剪切应力的增大而增加 ;含固位型填料复合树脂的柔量明显小于普通填料复合树脂者 (P <0 0 1)。结论　两种复合树脂的流变性有较大差异 ,因而其临床应用特性也有所不同。     

The effect of veneering materials on stress distribution in implant-supported fixed prosthetic restorations

In this study, the effect of various materials used in fabricating superstructures for implant-retained fixed partial dentures on stress distribution around implant tissues was investigated. Five different mathematical models consisting of 11,361 nodes and 54,598 elements were constructed to study porcelain, gold alloy, composite resin, reinforced composite resin, and acrylic resin veneering materials using the 3-dimensional finite element analysis method. MARC K7.2/Mentat 3.2 software was used for the analysis. Reference points were determined on the cortical bone, where perpendicular, oblique, and horizontal forces were applied. Stress values created by oblique and horizontal forces appeared to be higher than those created by vertical forces. Stress seemed to be concentrated at the cortical bone around the cervical region of the implant. Gold alloy and porcelain produced the highest stress values in this region. Stresses created by acrylic resin and reinforced composite resin were 25% and 15% less, respectively, than porcelain or gold alloy. Porcelain and gold alloy produced stress values at the lingual implant sites that reached the ultimate strength values of the cortical bone.     

Bond strength of Gradia veneering composite to fibre-reinforced composite

This study investigated the shear bond strength of light-curing veneering composite resin to glass fibre-reinforced composite (FRC). Polymer pre-impregnated FRC reinforcement was further impregnated with dimethacrylate monomer resin. The light polymerized FRC substrate was ground and dimethacrylate intermediate resin was applied on the surface before the light-curing veneering composite. Adhesional behaviour of veneering composite to the initially light polymerized FRC substrate was compared with well-polymerized FRC substrate. The treatment time of FRC substrate by the intermediate resin for 5 s and 5 min were also compared. Shear bond strength of veneering composite to FRC was determined for dry and thermocycled specimens (n = 6). The analysis of variance (anova) revealed significant differences (P = 0.042) between the shear bond strengths when 5 s and 5 min intermediate resin treatment times were compared. The highest shear bond strength (21.0 MPa) for FRC substrates was achieved when the well-polymerized FRC substrate was treated for 5 min with the intermediate resin and stored dry before tests. Thermocycling reduced the shear bond strengths. The results of this study suggest that applying the intermediate resin increased the shear bond strength values of veneering composite to FRC with multiphase polymer matrix. It was also concluded, that the use of multiphase polymer matrix FRC can be polymerized to high degree of conversion without deferiorating the shear bond strength of veneering composite to the FRC.     

五种黏固剂下纤维/树脂复合材料桩钉固位力的研究

目的 比较纤维/树脂复合材料(FRC)桩钉在5种黏固剂下的固位力。方法 将FRC桩钉用5种黏固剂(磷酸锌水门汀、玻璃离子水门汀、聚羧酸水门汀、EB复合树脂、AB组份复合树脂)分别黏固于新鲜离体上前牙牙根内,在电子力学试验机上测试其固位力。结果 FRC桩钉在不同黏固剂下与根管的固位力由大到小的顺序是:AB组份复合树脂>玻璃离子水门汀>EB复合树脂>聚羧酸锌水门汀>磷酸锌水门汀。AB组份复合树脂的固位力最大,为(418.14±23.40)N。结论 新研制的FRC桩钉的固位力可以满足临床需要。     

Fracture strength of fiber-reinforced surface-retained anterior cantilever restorations

PURPOSE: This study compared the fracture strength of direct anterior cantilever fiber-reinforced composite (FRC) fixed partial dentures (FPD) reinforced with 3 types of E-glass fibers preimpregnated with either urethane tetramethacrylate, bisphenol glycidylmethacrylate/polymethyl methacrylate, or bisphenol glycidylmethacrylate monomers and 1 ultrahigh molecular weight polyethylene fiber. Failure types were also evaluated. MATERIALS AND METHODS: A total of 40 caries-free, human maxillary central incisors (n = 10 per group) received surface-retained direct cantilever restoration (1 pontic) after etching and application of bonding agent. Four FRC materials were used (FRC1 = EverStick; FRC2 = BR-100; FRC3 = Interling; FRC4 = Ribbond), and pontics were built up using 1 particulate filler composite (Clearfil Photo Posterior). After the fracture test, failure types were analyzed. RESULTS: No significant difference was found between the 4 FRC types veneered with particulate filler composite (893 +/- 459 N to 1326 +/- 391 N) (P = .1278). Complete pontic fracture at the connector area was most prominent for FRC4 (90%), followed by FRC3 (70%). Only FRC2 (10%) showed some fiber fractures, with half of the fiber remaining attached on the enamel surface of the abutment. CONCLUSION: The fracture strengths of cantilever FPDs made of 4 FRC materials with different monomer matrices and architectures, veneered with particulate filler composite, did not show significant differences. However, failure behavior varied between groups.