Fracture Resistance of Inlay-retained Fixed Partial Dentures Reinforced with Fiber-reinforced Composite

In-vitro performance of posterior fiber reinforced composite (FRC) bridge with different framework designs

This study aimed to investigate the effect of various framework designs on the failure of posterior fiber reinforced composite (FRC) bridges and assess the post crack performances of the repaired prostheses. Thirty samples were prepared into three different groups of framework designs: cuspal support (CS), anatomic features (AF) and circular reinforcement (CR). All specimens were subjected to static loading test and acoustic emission analysis. Significant differences were found in the load and time of initial failures among the three groups (p<0.001). CS was identified as the optimum framework design. Samples with composite delamination at the pontic site were selected and repaired with a clinically simplified protocol. Significant differences were also observed between the repaired and original FRC bridges (p=0.01). The performance of these prostheses was highly dependent on the framework design and the perspective of repairing FRC bridges may warrant future investigations.

Load bearing capacity and Weibull characteristics of inlay-retained resin-bonded fixed dental prosthesis made of all-ceramic, fiber-reinforced composite and metal-ceramic after cyclic loading

PURPOSE

The objectives of this study were to evaluate the load bearing capacity of RBFDPs made of different materials after cyclic loading, and classify the failure types after loading.

MATERIALS AND METHODS

Sound human mandibular first premolars and first molar pairs (N = 60 per tooth type, n = 10 per group) were randomly divided into six experimental groups to receive one of the following inlay-retained RBFDP types: RC: Resin composite only, DFRC: Direct E-glass fiber-reinforced composite (FRC), IFRC: Indirect E-glass FRC, LS: Lithium disilicate glass-ceramic, ZR: Yttria-stabilized tetragonal zirconia, MC: Metal-ceramic. Box preparations were made in abutment teeth using diamond burs followed by standardized ultrasonic burs. The teeth were conditioned employing an etch-and-rinse adhesive system and the indirect RBFDPs were cemented adhesively. The specimens were subjected to cyclic loading for x1.200.000 in distilled water alternating between 5 and 55 °C (Zurich Chewing Simulator). They were then loaded to failure from the occlusal surface in the Universal Testing Machine (cross-head speed: 1 mm/min). Failure types were classified as repairable or irreparable depending on the location and size. Data were analyzed using Welch and Tamhane's T2 post-hoc tests (α = 0.05). Weibull modulus for each group was calculated based on parametric distribution analysis of censored data for maximum fracture load.

RESULTS

Mean load bearing capacity (N) of Groups LS (1274 ± 270), ZR (1567 ± 363) and MC (1544 ± 787) were significantly higher than those of other groups (p < 0.05). RC, DFRC, IFRC (601 ± 130 - 819 ± 270) and MC did not show significant difference (p > 0.05). Weibull modulus (m) was the highest in Group LS (m = 5.3) followed by Group RC (m = 5.1). Other groups presented Weibull moduli ranging between 1.4 and 3.3. Only in Group ZR, 2 early debonding occurred during cyclic loading. While in this group predominantly irreparable failures (debonding with without tooth fracture) were observed (8 out of 10), all other groups presented mainly single or a combination of repairable failures (chipping in the veneering material). DFRC, IDRC and MC did not show any debonding from the abutment teeth.

CONCLUSION

Considering load bearing capacity, repairable failure types and Weibull moduli, lithium disilicate seem to be more durable than those of other material options for posterior inlay-retained RBFDPs. Due to early debondings and catastrophic irreparable failure types, zirconia RBFDPs should be indicated with caution in the posterior region.

Comparison of Load-Bearing Capacities of 3-Unit Fiber-Reinforced Composite Adhesive Bridges with Different Framework Designs

Background

The aim of this study was to investigate and compare the load-bearing capacities of three-unit direct resin-bonded fiber-reinforced composite fixed dental prosthesis with different framework designs.

Material/Methods

Sixty mandibular premolar and molar teeth without caries were collected and direct glass fiber-resin fixed FDPs were divided into 6 groups (n=10). Each group was restored via direct technique with different designs. In Group 1, the inlay-retained bridges formed 2 unidirectional FRC frameworks and pontic-reinforced transversal FRC. In Group 2, the inlay-retained bridges were supported by unidirectional lingual and occlusal FRC frameworks. Group 3, had buccal and lingual unidirectional FRC frameworks without the inlay cavities. Group 4 had reinforced inlay cavities and buccal-lingual FRC with unidirectional FRC frameworks. Group 5, had a circular form of fiber reinforcement around cusps in addition to buccal-lingual FRC frameworks. Group 6 had a circular form of fiber reinforcement around cusps with 2 bidirectional FRC frameworks into inlay cavities. All groups were loaded until final fracture using a universal testing machine at a crosshead speed of 1 mm/min.

Results

Mean values of the groups were determined with ANOVA and Tukey HSD. When all data were evaluated, Group 6 had the highest load-bearing capacities and revealed significant differences from Group 3 and Group 4. Group 6 had the highest strain (p>0.05). When the fracture patterns were investigated, Group 6 had the durability to sustain fracture propagation within the restoration.

Conclusions

The efficiency of fiber reinforcement of the restorations alters not only the amount of fiber, but also the design of the restoration with fibers.

Load-bearing capacity of novel resin-based fixed dental prosthesis materials

To evaluate the influence of different materials on the load-bearing-capacity of inlay-retained fixed-dental-prosthesis (FDP). Ten types of FDPs were evaluated (n=7/group): Group PEEK: CAD-CAM polyetheretherketone (PEEK-TechnoMed), Group RC, made of discontinuous-fiber-composite (EverX Posterior); Group FRC1, made of discontinuous-fiber-composite (EverX Posterior) with two-bundles of continuous-unidirectional fiber-reinforced-composite (FRC) (Everstick C&B); Group FRC2, made of discontinuous-fiber-composite (EverX Posterior) with two-bundles of continuous-unidirectional-FRC (Everstick C&B) covered by two-pieces of short-unidirectional-FRC (Everstick C&B) placed perpendicular to the main-framework; Group FB, CAD-CAM fiber-block (Fibra-Composite Bio-C); Group PMMA, CAD-CAM polymethyl methacrylate block (Temp basic); Group RP, resin-paste; Group FRP1, made of resin-paste (G-Fix) with two-bundles of continuous-unidirectional-FRC (Everstick C&B); Group FRP2, made of resin-paste (G-Fix) two-bundles of continuous-unidirectional-FRC covered by two-pieces of short unidirectional-FRC placed perpendicular to the main-framework and Group exp-FRC, experimental CAD-CAM FRC. The bridges were statically-loaded until fracture. Fracture modes were visually examined. ANOVA revealed that significant differences were observed between FDP-materials (p<0.05). In addition, fiber addition to the framework significantly affected load-bearing-capacity (p<0.05).

Fracture behavior of single-structure fiber-reinforced composite restorations

Objective: The applications of single-structure fiber-reinforced composite (FRC) in restorative dentistry have not been well reported. This study aimed to clarify the static mechanical properties of anterior crown restorations prepared using two types of single-structure FRC. Materials and methods: An experimental crown restoration was designed for an upper anterior incisor. The restorations were made from IPS Empress CAD for CEREC (Emp), IPS e.max^® CAD (eMx), experimental single-structure all-FRC (a-FRC), Filtek™ Supreme XTE (XTE), and commercially available single-structure short-FRC (everX Posterior™) (n = 8 for each material) (s-FRC). The a-FRC restorations were prepared from an experimental FRC blank using a computer-aided design and manufacturing (CAD/CAM) device. A fracture test was performed to assess the fracture load, toughness, and failure mode. The fracture loads were vertically applied on the restorations. The surface micromorphology of the FRC restorations was observed by scanning electron microscopy (SEM). The data were analyzed by analysis of variance (p = .05) followed by Tukey's test. Results: s-FRC showed the highest mean fracture load (1145.0 ± 89.6 N) and toughness (26.2 ± 5.8 Ncm) among all the groups tested. With regard to the micromorphology of the prosthetic surface, local crushing of the fiberglass was observed in s-FRC, whereas chopped fiberglass was observed in a-FRC. Conclusions: The restorations made of short-FRC showed a higher load-bearing capacity than those made of the experimental all-FRC blanks for CAD/CAM. The brittle-like fractures were exhibited in the recent dental esthetic materials, while local crushing fractures were shown for single-structure FRC restorations.

Effect of Plasma and Fiber Position on Flexural Properties of a Polyethylene Fiber-Reinforced Composite

The aim of this study was to evaluate the effect of plasma treatment using argon and oxygen gases, combined with fiber position on flexural properties of a fiber-reinforced composite. Eleven groups were evaluated, a non-reinforced control group and 10 groups reinforced with InFibra, a woven polyethylene fiber, varying according to the plasma treatment and fiber position. The samples were prepared using a stainless steel two-piece matrix. The three point bending test was performed in an EMIC testing machine. Flexural strength (FS) and flexural deflection (FD) were calculated from initial (IF) and final (FF) failure. Data were evaluated statistically using Kruskal-Wallis and Mann-Whitney tests (p<0.05). For IF, in all groups with fibers placed on the base, the FS and FD values were significantly higher than those positioned away from the base. The highest value of FS was obtained in the group treated with O 3 min (296.2 MPa) and the highest value of FD was obtained in the group treated with 1 min (0.109 mm). For FF the FS and FD values obtained for the groups with fibers positioned away from the base were similar or higher than those placed on the base. The highest FS value was obtained in the group treated with 1 min (317.5 MPa) and the highest FD value was obtained in the group treated with O 3 min (0.177 mm). Plasma treatment influenced FS and FD. Fiber position and plasma treatment affected the flexural properties of a fiber-reinforced composite.

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.

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.

Model system for measuring the effects of position and curvature of fiber reinforcement within a dental composite

PURPOSE

The aim of this study was to compare the effect of fiber curvature and position on flexural strength (FS), toughness, and elastic modulus in a dental flowable composite test specimen.

METHODS AND MATERIALS

Test specimens made of composite resin (Denfil Flow) were reinforced with preimpregnated glass fibers (Interlig). Control specimens (group A) did not contain fiber reinforcement. Fibers were placed with different positions and orientations into the test specimens (2 mm x 2 mm x 25 mm) (groups B, C, D). The test specimens (n = 10) were stored in distilled water for 3 days at 37 degrees C before testing in a three-point loading test (ISO 10477) at a crosshead speed of 1 mm/min to determine FS, flexural modulus (FM), and toughness. Data were analyzed with 1-way analysis of variance and Tukey HSD (sigma= 0.05).

RESULTS

The FM varied from 4.7 +/- 0.5 to 6.7 +/- 0.5 GPa. The lowest flexural strength and toughness values in reinforced specimens resulted from compression side fiber reinforcement (132 +/- 12 MPa, 21 +/- 4 MJ) and the highest from curved fiber reinforcement (174 +/- 8 MPa, 83 +/- 28 MJ), though this was not statistically significant from tension-side reinforcement. Although the toughness of the curved reinforced group was significantly higher than other groups, the flexural strength of curved reinforcement was not significantly higher than tension-side reinforcement.

CONCLUSION

Position and fiber orientation influenced the flexural strength, FM, and toughness. The most effective in increasing toughness was curved placement of fibers.

Effect of fiber-premixed indirect resin composite substructure on fracture resistance of MOD composite inlays adhered with two different adhesive resin cements

This study evaluated the effect of a fiber-premixed indirect resin composite (FMC) substructure on the fracture resistance of mesialocclusal-distal (MOD) indirect composite restorations adhered to extracted human upper premolars. The teeth received a standardized MOD cavity preparation, and indirect composite inlays were fabricated with or without using the FMC. Inlays were cemented into the cavity preparations using either Super-Bond C&B or Panavia F2.0. A total of 28 specimens, namely seven specimens for four groups, were thus fabricated. Failure load and failure energy were determined after thermocycling (4-60 degrees C for 5,000 cycles). In terms of failure load, no significant differences were found among the four groups. In terms of failure energy, FMC substructure exerted a significantly favorable effect on Super-Bond C&B-bonded group but a negative one on Panavia F2.0-bonded group. In conclusion, the failure energy of the group using FMC substructure and which was adhered using Super-Bond C&B was significantly higher than the other groups.

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 1mm 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 348N (LCU) and 1199N (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.

Optimum Design for Fixed Partial Dentures Made of Hybrid Resin with Glass Fiber Reinforcement by Finite Element Analysis: Effect of Vertical Reinforced Thickness on Fiber Frame

By means of finite element analysis, the optimal thickness of fiber framework placed in a fiber-reinforced composite bridge replacing the mandibular first molar was obtained. Test results demonstrated that more than 30% maximum principal stress was reduced by reinforcing with fiber framework in a thickness of up to 0.6 mm for 1.5-mm occlusal clearance. Indeed, maximum principal stress generated in lower embrasure of connectors was reduced from 107 MPa to 70 MPa by maximizing reinforcement effect.