The Experts below are selected from a list of 1791 Experts worldwide ranked by ideXlab platform

Pekka K Vallittu - One of the best experts on this subject based on the ideXlab platform.

  • Bilayered composite restoration: the effect of layer thickness on fracture behavior
    Biomaterial investigations in dentistry, 2020
    Co-Authors: Lippo V.j. Lassila, Pekka K Vallittu, Eija Säilynoja, Roosa Prinssi, Sufyan Garoushi
    Abstract:

    Purpose: By combining the increased toughness of a resin composite reinforced with discontinuous fibers and the surface wear resistance of a Particulate Filler composite (PFC), a bilayered composit...

  • Fiber-Reinforced Composites for Implant Applications
    Current Oral Health Reports, 2018
    Co-Authors: Pekka K Vallittu
    Abstract:

    Purpose of Review Although metals, ceramics, and Particulate Filler resin composites have successfully been used as implant biomaterials for decades, devices made out of these materials do not meet all surgical requirements. This review describes the structure and mechanism of function of biostable glass fiber-reinforced composite (FRC) implants, which contain bioactive glass.

  • an overview of development and status of fiber reinforced composites as dental and medical biomaterials
    Acta biomaterialia odontologica Scandinavica, 2018
    Co-Authors: Pekka K Vallittu
    Abstract:

    AbstractFibr-reinforced composites (FRC) have been used successfully for decades in many fields of science and engineering applications. Benefits of FRCs relate to physical properties of FRCs and versatile production methods, which can be utilized. Conventional hand lamination of prefabricated FRC prepregs is utilized still most commonly in fabrication of dental FRC devices but CAD-CAM systems are to be come for use in certain production steps of dental constructions and medical FRC implants. Although metals, ceramics and Particulate Filler resin composites have successfully been used as dental and medical biomaterials for decades, devices made out of these materials do not meet all clinical requirements. Only little attention has been paid to FRCs as dental materials and majority of the research in dental field has been focusing on Particulate Filler resin composites and in medical biomaterial research to biodegradable polymers. This is paradoxical because FRCs can potentially resolve many of the problem...

  • Mechanical properties and fracture behavior of flowable fiber reinforced composite restorations.
    Dental materials : official publication of the Academy of Dental Materials, 2018
    Co-Authors: Lippo V.j. Lassila, Pekka K Vallittu, Filip Keulemans, Eija Säilynoja, Sufyan Garoushi
    Abstract:

    Abstract Objective The aim was to evaluate the effect of short glass-fiber/Filler particles proportion on fracture toughness (FT) and flexural strength (FS) of an experimental flowable fiber-reinforced composite (Exp-SFRC) with two methacrylate resin formulations. In addition, we wanted to investigate how the fracture-behavior of composite restorations affected by FT values of SFRC-substructure. Methods Exp-SFRC was prepared by mixing 50 wt% of dimethacrylate based resin matrix (bisGMA or UDMA based) to 50 wt% of various weight fractions of glass-fiber/Particulate Filler (0:50, 10:40, 20:30, 30:20, 40:10, 50:0 wt%, respectively). FT and FS were determined for each experimental material following standards. Specimens (n = 8) were dry stored (37 °C for 2 days) before they were tested. Four groups of posterior composite crowns (n = 6) composed of different Exp-SFRCs as substructure and surface layer of commercial Particulate Filler composite were fabricated. Crowns were statically loaded until fracture. Failure modes were visually examined. The results were statistically analysed using ANOVA followed by post hoc Tukey’s test. Results ANOVA revealed that ratio of glass-fiber/Particulate Filler had significant effect (p  Significance This study shows that short glass-fibers can significantly reinforce flowable composite resin and the FT value of SFRC-substructure has prior importance, as it influences the crack arresting mechanism.

  • An overview of development and status of fiber-reinforced composites as dental and medical biomaterials
    Taylor & Francis Group, 2018
    Co-Authors: Pekka K Vallittu
    Abstract:

    Fibr-reinforced composites (FRC) have been used successfully for decades in many fields of science and engineering applications. Benefits of FRCs relate to physical properties of FRCs and versatile production methods, which can be utilized. Conventional hand lamination of prefabricated FRC prepregs is utilized still most commonly in fabrication of dental FRC devices but CAD-CAM systems are to be come for use in certain production steps of dental constructions and medical FRC implants. Although metals, ceramics and Particulate Filler resin composites have successfully been used as dental and medical biomaterials for decades, devices made out of these materials do not meet all clinical requirements. Only little attention has been paid to FRCs as dental materials and majority of the research in dental field has been focusing on Particulate Filler resin composites and in medical biomaterial research to biodegradable polymers. This is paradoxical because FRCs can potentially resolve many of the problems related to traditional isotropic dental and medical materials. This overview reviews the rationale and status of using biostable glass FRC in applications from restorative and prosthetic dentistry to cranial surgery. The overview highlights also the critical material based factors and clinical requirement for the succesfull use of FRCs in dental reconstructions

Mutlu Ozcan - One of the best experts on this subject based on the ideXlab platform.

  • Comparison of Physicochemical Surface Conditioning Methods for Adhesion of bis-GMA Resin Cement to Particulate Filler Composite and Surface Characterization
    The Journal of Adhesion, 2014
    Co-Authors: Mutlu Ozcan, Silvia Masae De Araújo Michida, Cumhur Sipahi, Rodrigo Othávio De Assunção E Souza, Geraldo Henrique Leão Lombardo, Fernando Eidi Takahashi, P. Nascente
    Abstract:

    This study compared the effect of physicochemical surface conditioning methods on the adhesion of bis-GMA-based resin cement to Particulate Filler composite (PFC) used for indirect dental restorations. PFC blocks (N block = 54, n block = 9 per group) were polymerized and randomly subjected to one of the following surface conditioning methods: a) No conditioning (Control-C), b) Hydrofluoric acid (HF)etching for 60 s (AE60), c) HF for 90 s (AE90), d) HF for 120 s (AE120), e) HF for 180 s (AE180), and f) air-abrasion with 30 µm silica-coated alumina particles (AB). The conditioned surfaces were silanized with an MPS silane, and an adhesive resin was applied. Resin composite blocks were bonded to PFC using resin cement and photo-polymerized. PFC–cement–resin composite blocks were cut under coolant water to obtain bar specimens (1 mm × 0.8 mm). Microtensile bond strength test (μTBS)was performed in a universal testing machine (1 mm/min). After debonding, failure modes were classified using stereomicroscopy. Su...

  • load bearing capacity of indirect inlay retained fixed dental prostheses made of Particulate Filler composite alone or reinforced with e glass fibers impregnated with various monomers
    Journal of The Mechanical Behavior of Biomedical Materials, 2012
    Co-Authors: Mutlu Ozcan, Winand Koekoek, Gurel Pekkan
    Abstract:

    The load-bearing capacity and failure types of indirect inlay-retained fixed dental prostheses (FDP), made of Particulate Filler composite (PFC) (Estenia) alone or reinforced with E-glass fibers impregnated with various monomers were evaluated. Indirect inlay-retained FDPs were made between first premolars and first molars (N=30, 10/per group). The inlay parts of the specimens were silica coated and silanized and the specimens were cemented with dual-polymerized resin cement under ultrasonic vibrations. The experimental groups were as follows: Group 1: FRC1 (BR-100, UTMA) + PFC; Group 2: FRC2 (everStick CB Group 3: PFC only. The specimens were kept in distilled water at 37 °C for one month and then subjected to fracture strength test. No significant difference was found between the Group 1 and Group 2 FDPs (1357±301 N and 1213±316 N, respectively) (p>0.05) (ANOVA). Group 3 (856±299 N) showed significantly lower results than those of FRC reinforced groups (p<0.05). Failure analyses revealed no debonding of any of the FDPs from the inlay cavities. FDPs made of PFC only showed mainly catastrophic fracture of the pontic. In the FRC reinforced groups, predominantly delamination of the veneering was observed. The use of silica coating and silanization in combination with the dual-polymerized resin cement used; under ultrasonic cementation procedure provided sufficient adhesion to withstand static loading forces at the cementation interface, since the failures were predominantly delamination of the veneering in the FRC reinforced groups.

  • Load-bearing capacity of indirect inlay-retained fixed dental prostheses made of Particulate Filler composite alone or reinforced with E-glass fibers impregnated with various monomers.
    Journal of the mechanical behavior of biomedical materials, 2012
    Co-Authors: Mutlu Ozcan, Winand Koekoek, Gurel Pekkan
    Abstract:

    The load-bearing capacity and failure types of indirect inlay-retained fixed dental prostheses (FDP), made of Particulate Filler composite (PFC) (Estenia) alone or reinforced with E-glass fibers impregnated with various monomers were evaluated. Indirect inlay-retained FDPs were made between first premolars and first molars (N=30, 10/per group). The inlay parts of the specimens were silica coated and silanized and the specimens were cemented with dual-polymerized resin cement under ultrasonic vibrations. The experimental groups were as follows: Group 1: FRC1 (BR-100, UTMA) + PFC; Group 2: FRC2 (everStick CB Group 3: PFC only. The specimens were kept in distilled water at 37 °C for one month and then subjected to fracture strength test. No significant difference was found between the Group 1 and Group 2 FDPs (1357±301 N and 1213±316 N, respectively) (p>0.05) (ANOVA). Group 3 (856±299 N) showed significantly lower results than those of FRC reinforced groups (p

  • fracture strength of direct surface retained fixed partial dentures effect of fiber reinforcement versus the use of Particulate Filler composites only
    Dental Materials Journal, 2008
    Co-Authors: Ovul Kumbuloglu, Mutlu Ozcan, Atilla User
    Abstract:

    This study compared the fracture strengths and analyzed the failure types of direct, surface-retained, anterior fixed-partial-dentures (FPD), reinforced with four types of fiber-reinforced composites (FRC) versus non-fiber-reinforced FPDs made of three Particulate Filler composites (PFC). To this end, surface-retained anterior FPDs (N=70, 10 per group) were prepared and divided into seven experimental groups, where Group 1: FRC1 (everStick)+PFC1 (Clearfil Photo Posterior); Group 2: FRC2 (BR 100)+PFC1; Group 3: FRC3 (Interling)+PFC1; Group 4: FRC4 (Ribbond)+PFC1; Group 5: PFC1 only; Group 6: PFC2 only (Sinfony); and Group 7: PFC3 only (Estenia). Fracture strength test was performed after water storage at 37°C for three days (universal testing machine, 1 mm/min). No significant differences were found among the four FRC types veneered with PFC1 (1490±548—1951±335 N) (p<0.05) (ANOVA, Tukey′s test). Among all the experimental groups, PFC1 presented a significantly higher mean value (2061±270 N) than PFC2 (1340±395 N) (p<0.05) and all the other FRC-reinforced groups (p<0.05). Complete pontic fracture was 100% and 70% for PFC2 and PFC3 respectively.

  • Fracture strength of direct surface-retained fixed partial dentures: effect of fiber reinforcement versus the use of Particulate Filler composites only.
    Dental materials journal, 2008
    Co-Authors: Ovul Kumbuloglu, Mutlu Ozcan, Atilla User
    Abstract:

    This study compared the fracture strengths and analyzed the failure types of direct, surface-retained, anterior fixed-partial-dentures (FPD), reinforced with four types of fiber-reinforced composites (FRC) versus non-fiber-reinforced FPDs made of three Particulate Filler composites (PFC). To this end, surface-retained anterior FPDs (N=70, 10 per group) were prepared and divided into seven experimental groups, where Group 1: FRC1 (everStick)+PFC1 (Clearfil Photo Posterior); Group 2: FRC2 (BR 100)+PFC1; Group 3: FRC3 (Interling)+PFC1; Group 4: FRC4 (Ribbond)+PFC1; Group 5: PFC1 only; Group 6: PFC2 only (Sinfony); and Group 7: PFC3 only (Estenia). Fracture strength test was performed after water storage at 37°C for three days (universal testing machine, 1 mm/min). No significant differences were found among the four FRC types veneered with PFC1 (1490±548—1951±335 N) (p

Lippo V.j. Lassila - One of the best experts on this subject based on the ideXlab platform.

  • Bilayered composite restoration: the effect of layer thickness on fracture behavior
    Biomaterial investigations in dentistry, 2020
    Co-Authors: Lippo V.j. Lassila, Pekka K Vallittu, Eija Säilynoja, Roosa Prinssi, Sufyan Garoushi
    Abstract:

    Purpose: By combining the increased toughness of a resin composite reinforced with discontinuous fibers and the surface wear resistance of a Particulate Filler composite (PFC), a bilayered composit...

  • Mechanical properties and fracture behavior of flowable fiber reinforced composite restorations.
    Dental materials : official publication of the Academy of Dental Materials, 2018
    Co-Authors: Lippo V.j. Lassila, Pekka K Vallittu, Filip Keulemans, Eija Säilynoja, Sufyan Garoushi
    Abstract:

    Abstract Objective The aim was to evaluate the effect of short glass-fiber/Filler particles proportion on fracture toughness (FT) and flexural strength (FS) of an experimental flowable fiber-reinforced composite (Exp-SFRC) with two methacrylate resin formulations. In addition, we wanted to investigate how the fracture-behavior of composite restorations affected by FT values of SFRC-substructure. Methods Exp-SFRC was prepared by mixing 50 wt% of dimethacrylate based resin matrix (bisGMA or UDMA based) to 50 wt% of various weight fractions of glass-fiber/Particulate Filler (0:50, 10:40, 20:30, 30:20, 40:10, 50:0 wt%, respectively). FT and FS were determined for each experimental material following standards. Specimens (n = 8) were dry stored (37 °C for 2 days) before they were tested. Four groups of posterior composite crowns (n = 6) composed of different Exp-SFRCs as substructure and surface layer of commercial Particulate Filler composite were fabricated. Crowns were statically loaded until fracture. Failure modes were visually examined. The results were statistically analysed using ANOVA followed by post hoc Tukey’s test. Results ANOVA revealed that ratio of glass-fiber/Particulate Filler had significant effect (p  Significance This study shows that short glass-fibers can significantly reinforce flowable composite resin and the FT value of SFRC-substructure has prior importance, as it influences the crack arresting mechanism.

  • Bioactive glass Particulate Filler composite: Effect of coupling of Fillers and Filler loading on some physical properties
    Dental materials : official publication of the Academy of Dental Materials, 2014
    Co-Authors: Onur Oral, Lippo V.j. Lassila, Ovul Kumbuloglu, Pekka K Vallittu
    Abstract:

    Abstract Objectives The aim of this study was to investigate the effect of silanization of biostable and bioactive glass Fillers in a polymer matrix on some of the physical properties of the composite. Methods The water absorption, solubility, flexural strength, flexural modulus and toughness of different Particulate Filler composite resins were studied in vitro. Five different specimen groups were analyzed: A glass-free control, a non-silanized bioactive glass, a silanized bioactive glass, a non-silanized biostable glass and a silanized biostable glass groups. All of these five groups were further divided into sub-groups of dry and water-stored materials, both of them containing groups with 3 wt%, 6 wt%, 9 wt% or 12 wt% of glass particles (n = 8 per group). The silanization of the glass particles was carried out with 2% of gamma-3-methacryloxyproyltrimethoxysilane (MPS). For the water absorption and solubility tests, the test specimens were stored in water for 60 days, and the percentages of weight change were statistically analyzed. Flexural strength, flexural modulus and toughness values were tested with a three-point bending test and statistically analyzed. Results Higher solubility values were observed in non-silanized glass in proportion to the percentage of glass particles. Silanization, on the other hand, decreased the solubility values of both types of glass particles and polymer. While 12 wt% non-silanized bioactive glass specimens showed −0.98 wt% solubility, 12 wt% silanized biostable glass specimens were observed to have only −0.34 wt% solubility. The three-point bending results of the dry specimens showed that flexural strength, toughness and flexural modulus decreased in proportion to the increase of glass Fillers. The control group presented the highest results (106.6 MPa for flexural strength, 335.7 kPA for toughness, 3.23 GPa for flexural modulus), whereas for flexural strength and toughness, 12 wt% of non-silanized biostable glass Filler groups presented the lowest (70.3 MPa for flexural strength, 111.5 kPa for toughness). For flexural modulus on the other hand, 12 wt% of silanized biostable glass Filler group gave the lowest results (2.57 GPa). Significance The silanization of glass Fillers improved the properties of the glass as well as the properties of the composite. Silanization of bioactive glass may protect the glass from leaching at early stage of water storage.

  • Short fiber reinforced composite: a new alternative for direct onlay restorations.
    The open dentistry journal, 2013
    Co-Authors: Sufyan Garoushi, Enas Mangoush, Mangoush Vallittu, Lippo V.j. Lassila
    Abstract:

    To determine the static load-bearing capacity of direct composite onlay restorations made of novel filling composite resin system which combines short fiber-reinforced composite resin (FC) and conventional Particulate Filler composite resin (PFC). Three groups of onlay restorations were fabricated (n = 8/group); Group A: made from conventional Particulate Filler composite resin (Z250, 3M-ESPE, USA, control), Group B: made from short fiber-reinforced composite resin (EverX posterior, StickTeck Ltd, member of GC group, Turku, Finland) as substructure with 1 mm surface layer of PFC, Group C: made from FC composite resin. The specimens were incrementally polymerized with a hand-light curing unit for 80 s before they were statically loaded with two different sizes (3 & 6 mm) of steel ball until fracture. Failure modes were visually examined. Data were analyzed using ANOVA (p = 0.05). ANOVA revealed that onlay restorations made from FC composite resin had statistically significantly higher load-bearing capacity (1733 N) ( p < 0.05) than the control PFC composite resin (1081 N). Onlays made of FC composite resin with a surface layer of PFC gave force values of 1405 N which was statistically higher than control group ( p < 0.05). No statistically significant difference was found in the load-bearing capacity between groups loaded by different ball sizes. Onlay restorations combining base of short fiber reinforced composite resin as substructure and surface layer of conventional composite resin displayed promising performance in high load bearing areas.

  • The Effect of Surface Roughness on Repair Bond Strength of Light-Curing Composite Resin to Polymer Composite Substrate
    The open dentistry journal, 2013
    Co-Authors: Timo Kallio, Lippo V.j. Lassila, Arzu Tezvergil-mutluay, Pekka K Vallittu
    Abstract:

    Objective: The purpose of this study was to analyze the shear bond strength of a new composite resin to poly- mer-based composite substrates using various surface roughnesses and two kinds of polymer matrices. Materials and methods: Particulate Filler composite resin with cross-linked polymer matrix and fiber-reinforced composite with semi-interpenetrating polymer matrix were used as bonding substrates after being ground to different roughnesses. Substrates were aged in water for one week before bonding to new resin composites. Twelve specimens in the substrate groups were ground with grinding papers of four grits; 320, 800, 1200 and 2400. Results: Corresponding values of surface roughness (R a ) varied from 0.09 to 0.40 for the Particulate Filler composite resin and 0.07 to 0.96 for the fiber-reinforced composite resin. Characteristic shear bond strength between the new resin and Particulate Filler composite resin was highest (27.8 MPa) with the roughest surface (Weibull modulus: 2.085). Fiber- reinforced composite showed the highest bond strength (20.8 MPa) with the smoothest surface (Weibull modulus: 4.713). Conclusions: We concluded that surface roughness did not increase the bonding of new resin to the substrate of IPN based fiber-reinforced composite, whereas the roughness contributed to bonding the new resin to the Particulate Filler composite resin with a cross-linked polymer matrix. Keyword: Bond strength, composite, repair, adhesion, bonding.

U. S. Tewari - One of the best experts on this subject based on the ideXlab platform.

  • The Effect of Fibre Reinforcement and Solid Lubricants on Abrasive Wear Behavior of Polyetheretherketone Composites
    Journal of Reinforced Plastics and Composites, 2003
    Co-Authors: A. P. Harsha, U. S. Tewari
    Abstract:

    The tribo performance evaluations were carried out for various composites of polyetheretherketone (PEEK) filled with short glass, carbon fibre, and solid lubricants in abrasive wear situation. Abrasive wear studies were carried out under single pass condition against SiC abrasive paper by using pin-on-disc machine. The influence of variables such as sliding distance, load and abrasive grit size has been investigated. It was observed that fibre reinforcement deteriorated the abrasive wear resistance of neat PEEK matrix. Combination of fibre and Particulate Filler is more detrimental to abrasive wear performance. Efforts were made to correlate the abrasive wear performance with the appropriate mechanical properties. Ratner-Lancaster plot showed linear correlation. SEM was used to analyse the worn surfaces of the samples.

  • Three-body abrasive wear behaviour of polyaryletherketone composites
    Wear, 2003
    Co-Authors: A. P. Harsha, U. S. Tewari, B. Venkatraman
    Abstract:

    Abstract An experimental investigation was carried out to study the effect of reinforcement fibres, solid lubricants, mass of abrasives and load in three-body abrasive wear situations on various polyaryletherketone (PAEK) matrix. Three-body abrasive wear studies were carried out using a rubber wheel abrasion test (RWAT) rig. In the present investigation, angular silica sand particles of size ranging between 150 and 300 μm were used as dry and loose abrasives. The ketone/ether ratios among the selected PAEKs have shown significant influence on three-body abrasive wear behaviour at higher load. It was observed that fibre reinforcement is detrimental to the abrasive wear resistance of neat PAEK matrix. A combination of fibre and Particulate Filler is more detrimental to abrasive wear performance. Efforts were made to correlate the abrasive wear performance of the composites with appropriate mechanical properties. The Ratner–Lancaster plot showed a linear correlation. Scanning electron microscopy was used to observe the worn surfaces and to understand the mechanisms involved in the removal of the material.

  • Studies on abrasive wear of carbon fibre (short) reinforced polyamide composites
    Tribology International, 1992
    Co-Authors: U. S. Tewari, Jayashree Bijwe, J. N. Mathur, Indu Sharma
    Abstract:

    This paper reports the results of the abrasive wear investigations of various composites of polyamide (nylon 6,6) reinforced with increasing amounts of carbon fibre against various abrasive papers under dry conditions. The object was to study the influence of parameters such as: amount of fibre, its orientation, effect of solid lubricant (PTFE), and other experimental parameters eg load and abrading particle size. It was observed that wear rates increased rapidly with increasing fibre concentration. A combination of Particulate Filler (PTFE) and carbon fibre proved to be very detrimental to abrasive wear resistance. Load, abrading particle size and fibre orientation were observed to be important factors in these studies. Efforts are made to correlate wear behaviour with appropriate mechanical properties. Ratner/Lancaster plots did not show linearity. Instead, a proportional rise in wear was noticed with an increase in e−1, where e is ultimate elongation, with the exception of one composite. Worn surfaces were studied with a SEM to give a greater insight into the wear mechanisms.

Sufyan Garoushi - One of the best experts on this subject based on the ideXlab platform.

  • Bilayered composite restoration: the effect of layer thickness on fracture behavior
    Biomaterial investigations in dentistry, 2020
    Co-Authors: Lippo V.j. Lassila, Pekka K Vallittu, Eija Säilynoja, Roosa Prinssi, Sufyan Garoushi
    Abstract:

    Purpose: By combining the increased toughness of a resin composite reinforced with discontinuous fibers and the surface wear resistance of a Particulate Filler composite (PFC), a bilayered composit...

  • Mechanical properties and fracture behavior of flowable fiber reinforced composite restorations.
    Dental materials : official publication of the Academy of Dental Materials, 2018
    Co-Authors: Lippo V.j. Lassila, Pekka K Vallittu, Filip Keulemans, Eija Säilynoja, Sufyan Garoushi
    Abstract:

    Abstract Objective The aim was to evaluate the effect of short glass-fiber/Filler particles proportion on fracture toughness (FT) and flexural strength (FS) of an experimental flowable fiber-reinforced composite (Exp-SFRC) with two methacrylate resin formulations. In addition, we wanted to investigate how the fracture-behavior of composite restorations affected by FT values of SFRC-substructure. Methods Exp-SFRC was prepared by mixing 50 wt% of dimethacrylate based resin matrix (bisGMA or UDMA based) to 50 wt% of various weight fractions of glass-fiber/Particulate Filler (0:50, 10:40, 20:30, 30:20, 40:10, 50:0 wt%, respectively). FT and FS were determined for each experimental material following standards. Specimens (n = 8) were dry stored (37 °C for 2 days) before they were tested. Four groups of posterior composite crowns (n = 6) composed of different Exp-SFRCs as substructure and surface layer of commercial Particulate Filler composite were fabricated. Crowns were statically loaded until fracture. Failure modes were visually examined. The results were statistically analysed using ANOVA followed by post hoc Tukey’s test. Results ANOVA revealed that ratio of glass-fiber/Particulate Filler had significant effect (p  Significance This study shows that short glass-fibers can significantly reinforce flowable composite resin and the FT value of SFRC-substructure has prior importance, as it influences the crack arresting mechanism.

  • Short fiber reinforced composite: a new alternative for direct onlay restorations.
    The open dentistry journal, 2013
    Co-Authors: Sufyan Garoushi, Enas Mangoush, Mangoush Vallittu, Lippo V.j. Lassila
    Abstract:

    To determine the static load-bearing capacity of direct composite onlay restorations made of novel filling composite resin system which combines short fiber-reinforced composite resin (FC) and conventional Particulate Filler composite resin (PFC). Three groups of onlay restorations were fabricated (n = 8/group); Group A: made from conventional Particulate Filler composite resin (Z250, 3M-ESPE, USA, control), Group B: made from short fiber-reinforced composite resin (EverX posterior, StickTeck Ltd, member of GC group, Turku, Finland) as substructure with 1 mm surface layer of PFC, Group C: made from FC composite resin. The specimens were incrementally polymerized with a hand-light curing unit for 80 s before they were statically loaded with two different sizes (3 & 6 mm) of steel ball until fracture. Failure modes were visually examined. Data were analyzed using ANOVA (p = 0.05). ANOVA revealed that onlay restorations made from FC composite resin had statistically significantly higher load-bearing capacity (1733 N) ( p < 0.05) than the control PFC composite resin (1081 N). Onlays made of FC composite resin with a surface layer of PFC gave force values of 1405 N which was statistically higher than control group ( p < 0.05). No statistically significant difference was found in the load-bearing capacity between groups loaded by different ball sizes. Onlay restorations combining base of short fiber reinforced composite resin as substructure and surface layer of conventional composite resin displayed promising performance in high load bearing areas.

  • Effect of Short Fiber Fillers on the Optical Properties of Composite Resins
    Journal of Materials Science Research, 2012
    Co-Authors: Sufyan Garoushi, Pekka K Vallittu, Lippo V.j. Lassila
    Abstract:

    Objectives: The aim was to evaluate the effect of different fractions of fiber Fillers on the translucency and color change of short fiber composite with various thicknesses. Methods: Fiber composite resin was prepared by mixing resin matrix with various weight fractions of short (3 mm in length)  E-glass fiber Fillers (0, 11.7, 21.0, 28.5, 34.7 wt%) and then silane treated Particulate silica Fillers were gradually added by using high speed mixing machine. Particulate Filler composite resin without fibers was used as control. Composite resins disks of 10 mm in diameter and with various thicknesses (1.0, 2.0, 3.0, 4.0, and 5.0 mm) of each group were prepared (n=3). Translucency parameter (TP) and color change (?E) were calculated over a white and black background using spectrophotometer to determine the CIELAB values of each specimen. Data were statistically analyzed with analysis of variance (ANOVA). Results: ANOVA revealed that fraction of fiber Fillers had a significant effect (P

  • Influence of nanometer scale Particulate Fillers on some properties of microfilled composite resin
    Journal of Materials Science: Materials in Medicine, 2011
    Co-Authors: Sufyan Garoushi, Lippo Veli Juhana Lassila, Pekka Kalevi Vallittu
    Abstract:

    The aim of this study was to evaluate the effect of different weight fractions of nanometer sized Particulate Filler on properties of microfilled composite resin. Composite resin was prepared by mixing 33 wt% of resin matrix to the 67 wt% of silane treated microfine silica Particulate Fillers with various fractions of nanometer sized Fillers (0, 10, 15, 20, 30 wt%) using a high speed mixing machine. Test specimens made of the composites were tested with a three-point bending test with a speed of 1.0 mm/min until fracture. Surface microhardess (Vicker’s microhardness) was also determined. The volumetric shrinkage in percent was calculated as a buoyancy change in distilled water by means of the Archimedes principle. The degree of monomer conversion (DC%) of the experimental composites containing different nanoFiller fractions was measured using FTIR spectroscopy. Surface roughness (Ra) was determined using a surface profilometer. Nanowear measurements were carried out using a nanoindentation device. The water uptake of specimens was also measured. Parameters were statistically analysed by ANOVA ( P