Particulate Filler Composite Resin Research Articles

Cytotoxicity of Acrylic Resins, Particulate Filler Composite Resin and Thermoplastic Material in Artificial Saliva with and without Melatonin.

There is limited information on the effect of melatonin on the cytotoxicity of dental materials. The study evaluated the cytotoxic effects of heat- and auto-polymerized acrylic resin, particulate filler composite resin and a thermoplastic material on L-929 fibroblast cell viability at different incubation periods in artificial saliva without and with melatonin. Disk-shaped specimens were prepared according to each manufacturer’s instructions and divided into two groups to be stored either in artificial saliva (AS) and AS with melatonin (ASM). The measurements were performed using an MTT (3-(4,5)-dimethylthiazol-2-yl)-2,5-diphenyl tetrazoliumbromide) assay, in which the L-929 mouse fibroblasts cell culture was used. For the MTT test, extracts were examined at 1, 24, 72 h and 1 and 2 weeks. Data were analyzed using 3-way ANOVA and Tukey’s tests. No significant difference was found between groups AS and ASM (F = 0.796; p = 0.373). Incubation period significantly affected all materials tested (p < 0.001). Storing resin-based materials in artificial saliva with melatonin solution for 24 h may reduce cytotoxic effects on the fibroblast cells for which the highest effect was observed. Soaking resin prosthesis or orthodontic appliances in artificial saliva with melatonin at least 24 h before intraoral use or rinsing medium containing melatonin may be recommended for decreasing the cytotoxicity of dental resin materials.

Reinforcement effect of polyethylene fiber to composite cores of endodontically treated teeth

Statement of problem: Severely damaged teeth frequently require placement of a core before preparation to receive an indirect restoration. However, the choice of the core material may also influence the outcome although reliable research data are scare. Purpose: The purpose of this study was to evaluate the effect of short fiber-reinforced composite resin of endodontically treated teeth restored with and without root canal posts. Methods: Sixty human extracted maxillary incisors were sectioned at the cemento-enamel junction. The root canals were prepared and obturated with gutta percha. Three groups of direct complete crowns were fabricated (n = 20 per group); Group A: made from particulate filler composite resin (Corestore 2, Kerr, control), Group B: particulate filler composite resin with fiber post (Aestheti-Post; Bisco), Group C: made from particulate filler composite resin with fiber post and short polyethylene fibers substructure (Ribbond Inc.). After finishing and polishing, the specimens were stored in 100% humidity at 37°C for 24 hours before they were statically loaded with a cross-head speed of 0.5 mm/min until fracture. Data were analyzed with 1-way ANOVA followed by Ryan-Einot-Gabriel-Welsch multiple-range test (α=.05). Results: ANOVA revealed that restorations made from particulate filler composite resin with fiber post and short polyethylene fibers substructure had higher fracture resistance capacity (309 N) (p< 0.05) than restorations made from particulate filler composite resin with fiber post (258 N). Control group had significant lower fracture resistance (178 N) (P<0.05).Conclusion: Polyethylene fiber may be an effective and practical method for reinforcement of the composite core material of endodontically treated teeth.

Effects of Fiber-reinforced Composite Bases on Microleakage of Composite Restorations in Proximal Locations.

Objectives:The aim of this study was to evaluate the microleakage of direct restorative composite resin upon the addition of an intermediate glass fiber-reinforced composite (GFRC) layer of various fiber orientations between tooth and particulate filler composite resin (PFRC). Materials and Methods: Cavities were prepared both on the mesial and distal surfaces of sixty extracted human molars with one margin placed below and the other above the cementoenamel junction (CEJ). Teeth were assigned to five different groups. Four of the groups received a layer of semi-interpenetrating polymer network (semi-IPN) resin system impregnated E-glass GFRC at the bottom of the cavity: Group 1; unidirectional continuous GFRC (EVS) in buccolingual direction (EVS-BL), Group 2; EVS in mesiodistal direction (EVS-MD), Group 3; bidirectional woven GFRC (EVN), Group 4; multidirectional short GFRC (EXP-MLT), Group 5; PRFC only (control). After acid etching and priming of the cavities and insertion of GFRC layer with the adhesive resin (Scotchbond Multipurpose 3M-ESPE), the cavities were filled incrementally with PRFC (Filtek Z250, 3M-ESPE) and each layer was light cured for 20 s. After finishing and polishing, the restored teeth were water-stored for 24 h at 37 °C and then thermocycled for 6000 cycles between 5-55 °C, before immersion in 0.5 % basic fuchsin dye for 24 h. After sectioning by 3-5 sagittal cuts, each sequential section was imaged and digitally analyzed to determine the stain depth. Results: All GFRC groups in dentin revealed significantly lower microleakage compared to control (p<0.05). The orientation of FRC intermediate layer did not reveal significant differences in microleakage (p>0.05). The microleakeage in enamel was not different between the groups (p>0.05).Conclusion: Use of intermediate GFRC layer between tooth and PFRC could provide alternative method to minimize microleakage.Clinical Relevance: Use of GFRC intermediate layer underneath the particulate filler composite can be used to minimize the leakeage of the restorations.

An in vitro evaluation of wear and surface roughness of particulate filler composite resin after tooth brushing

Objective. To evaluate the influence of tooth brushing on wear and surface roughness of four different particulate filler composite resins. Materials and methods. Six specimens (2 mm thick and 8 mm in diameter) of each tested material (Filtek Z250-Microhybrid, SpectrumTPH3-Submicron hybrid, Filtek Z350XT Nanofiller and Filtek P90- Microhybrid) were prepared according to the manufacturer’s directions. A brushing sequence of 5000, 10 000 and 20 000 cycles was performed for all the samples. A non-contact profilometer was used to determine average surface roughness (Ra) and wear of the material assessed using an analytic electronic balance at baseline and each cycle interval. The data obtained were analyzed using one-way ANOVAs and post-hoc multiple comparison tests. Paired t-test was used for comparisons between cycle intervals for each material. Analyses with scanning electron microscopy (SEM) were also performed. Results. The resin composite Filtek P 90 presented an increase in percentage weight loss after final toothbrushing cycles over the rest of the materials. Brushing significantly increased roughness (Ra) for all composites. Filtek Z250, after brushing, was significantly rougher than the other resins followed by Filtek P 90, Spectrum TPH 3 and Filtek Z350 XT. However, SEM images indicated severe change in surface topography of ‘sub-micron hybrid’ specimen compared to each other after tooth brushing. Conclusions. Wear and surface roughness increased with each cycle interval for all the materials and one composite resin demonstrated a higher increase in surface roughness than the other three tested brands of composite resins. Not much difference was observed in the weight loss between tested samples.

The Effect of Surface Roughness on Repair Bond Strength of Light-Curing Composite Resin to Polymer Composite Substrate

Objective:The purpose of this study was to analyze the shear bond strength of a new composite resin to polymer-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 (Ra) 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.

Influence of intermediate resin on the bond strength of light-curing composite resin to polymer substrate

Objectives. The aim of this study was to examine the effect of intermediate resin (IMR) of different monomer compositions and viscosities on the shear bond strength between polymer substrate and light-curing composite. Methods. The substrate used in the study was an autopolymerizing polymethyl methacrylate (PMMA) based polymer. The substrate was treated with the IMR for 3 min before application of light polymerizable particulate filler composite resin. The monomers of the IMR were either bisphenol-A-glycidyl dimethacrylate (BisGMA) and triethyleneglycol dimethacrylate (TEGDMA) or BisGMA and methyl methacrylate (MMA). The shear bond strength of the IMR treated substrate to the particulate filler composite was evaluated after storing the specimens dry and after thermocycling the specimens in water. Light microscope examination was accomplished to determine the swelled layer of the substrate. Results. Significant differences were found between the shear bond strength values of the IMRs (p < 0.001). The bond strengths were generally higher in the BisGMA-MMA groups than in the BisGMA-TEGDMA groups. Two-way ANOVA revealed significant effects of type of IMR (p < 0.001) and thermocycling (p = 0.017) on the shear bond strength. No interaction was found between these variables (p > 0.05). Conclusions. The results suggest that the monomer composition and ratio of the IMRs used in the study influence the shear bond strength of the polymer substrate to the new resin.

Effect of Short Fiber Fillers on the Optical Properties of Composite Resins

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<0.05) on the translucency and color change values of the short fiber composite resin. Translucency values at various thicknesses of short fiber composite was significantly lower than particulate filler composite with same total fillers weight fractions.Significance: Inclusion of short glass fiber fillers reduced the translucency values of the composite resins. Thus, the masking ability of short fiber composite resin at various thicknesses was better than particulate filler composite. Color change was also altered with an increase of fractions of fiber fillers.

Preliminary Clinical Evaluation of Short Fiber-Reinforced Composite Resin in Posterior Teeth: 12-Months Report

This preliminary clinical trial evaluated 12 month clinical performance of novel filling composite resin system which combines short fiber-reinforced composite resin and conventional particulate filler composite resin in high stress bearing applications. A total of 37 class I and II restorations (compound and complex type) were placed in 6 premolars and 31 molars. The restorations were reviewed clinically at 6 months (baseline) and 12 months using modified USPHS codes change criteria for marginal adaptation, post-operative sensitivity, pulpal pain and secondary caries criteria. Photographs and x-rays were obtained for restorative analysis. Results of 12 months evaluation showed 5 restorations having little marginal leakage (B score) and 1 patient had minor pulpal symptom and post-operative sensitivity (B score). No secondary caries or bulk fracture was detected. The majority of restorations exhibited A scores of the evaluated criteria. After 12 months, restorations combining base of short fiber reinforced composite resin as substructure and surface layer of hybrid composite resin displayed promising performance in high load bearing areas.

Effect of nanofiller fractions and temperature on polymerization shrinkage on glass fiber reinforced filling material

Objectives The aim was to evaluate the effect of different nanofiller fractions and temperature on polymerization shrinkage strain and degree of monomer conversion of short glass fibers reinforced semi-interpenetrating polymer network (semi-IPN)-polymer matrix composite resin. Methods Experimental composite resin was prepared by mixing 22.5 wt% of short E-glass fibers (3 mm in length) to the 22.5 wt% of resin matrix with various weight fractions of nanofillers (0, 10, 20, 30, 40, 50 wt%) and then 55 wt% of silane treated silica filler were added gradually using high speed mixing machine. Another study group contained composite resin prepared by mixing 22.5 wt% of resin matrix (without nanofillers) to 77.5 wt% of filler particles (without fiber fillers). As control material, commercial particulate filler composite resin was used. The shrinkage strain of the specimens was measured using the bonded-disk technique at 26 and 37 °C with respect to time. Degree of conversion of the experimental composites containing different nanofiller fractions was measured using FTIR spectroscopy. Results ANOVA revealed that fraction of nanofillers and polymerization temperature had significant effect ( p < 0.05) on the shrinkage strain and degree of conversion of the composite resin. Shrinkage strain correlated with nanofiller fraction and polymerization temperature ( r 2 = 0.96 and 0.95). Significance The use of high nanofiller fraction with short fiber fillers and IPN-polymer matrix yielded improved rate of shrinkage strain.

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 (3 mm 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 24 h 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 (349 N) ( p < 0.05) than the control restorations (173 N). 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.

Polymerization shrinkage of experimental short glass fiber-reinforced composite with semi-inter penetrating polymer network matrix

Objectives The aim of this study was to determine the magnitude of short fiber-reinforced composite resin, with a semi-IPN-polymer matrix, on polymerization resin shrinkage-strain, shrinkage stress and marginal microleakage of the restoration. Materials and methods Experimental composite FC resin was prepared by mixing 22.5 wt.% of short E-glass fibers, 22.5 wt.% of IPN-resin and 55 wt.% of silane treated silica fillers using a high speed mixing machine. As control material, commercial particulate filler composite resin (PFC) was used. Polymerization shrinkage-strain and stress of the specimens ( n = 5) were measured using the bonded-disc technique and tensilometer, respectively with respect to time. FC composite and PFC were placed incrementally in class II cavities sized 4 mm × 4 mm × 6 mm ( n = 8/group) using total-etch adhesive system according to manufacturer's instructions. After the class II restorations were completed, the specimens were finished and polished, thermocycled, stained, sectioned, and viewed under a stereo-microscope for leakage at occlusal/enamel and gingival/dentin margins. The data were analyzed using ANOVA. Results ANOVA revealed that restorations made from experimental FC composite had a significantly lower shrinkage stress and microleakage than those made from PFC ( p < 0.05). The data show that gingival margins had higher microleakage than that obtained from occlusal margins of restorations ( p < 0.05). Conclusions The use of short fiber filler with semi-IPN polymer matrix reduced polymerization shrinkage stress and microleakage compared to a conventional restorative composite.

Effect of short-term water storage on the elastic properties of some dental restorative materials—A resonant ultrasound spectroscopy study

Objectives This study was aimed to determine if short-term water storage would change elastic properties of dental composite materials. Methods Particulate filler composite resin and continuous unidirectional E-glass FRC materials were photopolymerized and additionally post-polymerized by heat for testing elastic properties with the Resonance Ultrasound Spectroscopy method as a function of time in water storage. The test specimens were stored in 37 °C water for up to 30 days. Results About 1% weight increase due to water sorption was observed in both materials with both polymerization methods. Water sorption did not change the resonance frequencies towards lower values, indicating no significant decrease in elastic properties in these materials. Because of high damping of the polymer composite materials leading to wide resonance peaks and low number of the recorded peaks, accurate determination of the elastic properties was not possible. Significance Results suggest that the most likely explanation for the previously observed decrease in bending stiffness of FRC materials is the decreased yield limit of the hydrated polymer matrix. It is important to recognize that water sorption has the effect on mechanical properties of dental composite materials by changing the yield limit of the matrix rather than by changing the elastic properties of the material.

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

The effect of fiber orientation on the polymerization shrinkage strain of fiber-reinforced composites

The aim of this study was to characterize the linear polymerization shrinkage strain of glass fiber-reinforced composite (FRC) according to the fiber orientation. Test specimens (n=5) (10.0 x 10.0 x 1.5mm) were prepared from different brands of photopolymerizable resin-preimpregnated FRC; unidirectional continuous FRC, experimental random-oriented FRC, and bidirectional continuous FRC. As control materials, particulate filler composite resin and unfilled dimethacrylate monomer resin were used. Two uniaxial strain gages (gage length 2mm) were used to measure shrinkage strains in two directions: longitudinally and transversally to the fiber direction. The uncured composite or resin was placed on top of the strain gages, covered with a separating sheet and a glass plate, and irradiated for 40s with a light-curing unit. The shrinkage strain was monitored for 300 s. ANOVA and Tukey's posthoc test were used at a significance level of 0.05. ANOVA revealed that orientation of fiber and brand of material had a significant effect (P<0.05) on shrinkage strain. The unidirectional FRC revealed no shrinkage longitudinally to the fiber direction, whereas the shrinkage occurred transversally to the fiber direction. Particulate filler composite resin and unfilled resin revealed equal shrinkage strain in both of the measured directions. Anisotropic nature of FRC exists with regard to polymerization shrinkage strain. The variation of polymerization shrinkage strains of FRC compared to those of particulate filler composites and unfilled resin might be important for future clinical applications.

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.

The shear bond strength of bidirectional and random-oriented fibre-reinforced composite to tooth structure

The objective of this study was to evaluate the bond strength and fracture pattern of fibre-reinforced composite (FRC) with two different fibre orientations and matrix compositions to dentine and enamel. Extracted human molars were used as substrates (enamel and dentine) with a standard acid-etch technique. Light-polymerizable FRC with two different interpenetrating polymer network matrices and random or bidirectional fibre orientations was applied to the substrate, together with the adhesive resin. As a control, particulate filler composite resin was bonded to the substrates. The substrate-composite specimens (n=10) were either stored in water for 24h or additionally thermocycled for 6000 cycles. The shear bond strength of composite to substrate was measured and the fracture surfaces were evaluated visually and with SEM. Three-way factorial analysis of variance highlighted significant differences according to the substrate type, storage condition and composite material (p<0.05). Dentine specimens showed a significantly lower range of bond strength values (8.8-15.0 MPa), compared with enamel specimens (14.0-23.0 MPa). The highest mean bond strength in dentine was 15.0 MPa obtained with bidirectional FRC, whereas the highest bond strength in enamel was 23.0 MPa obtained with random-oriented FRC. Thermocycling did not identify a significant effect on the dentine bond strength, but did identify a significant decrease in enamel bond strength values (p<0.05). Several cohesive failures were observed in the tooth structure with the control material, whereas no cohesive bulk fracture of the tooth was observed when a thin layer of FRC was placed at the interface. The addition of bidirectional or random continuous fibres did not show any significant improvement in bond strength values compared to control of particulate filler. However, the difference in the fracture patterns observed may have implications for clinical applications.

The degree of conversion of fiber-reinforced composites polymerized using different light-curing sources

Fiber-reinforced composites (FRC) with different polymer matrix compositions are available on the market. The aim of this study was to compare the degree of monomer conversion of FRC that contained either dimethacrylate resin matrix or semi-IPN resin matrix. In addition, the effect of different types of light-curing units and durations of light irradiation on the degree of conversion was evaluated. Continuous unidirectional fibers impregnated with dimethacrylate or semi-IPN resin were compared. As control materials, a particulate filler composite resin and an unfilled resin were used. The materials were photopolymerized using various irradiation times and different types of light-curing units (quartz-tungsten-halogen with standard or turbo tip, light-emitting diode and plasma-arc). Degree of monomer conversion (DC%) was determined by FT-IR spectrometry. The infrared spectra were recorded at seven different time points after polymerization. ANOVA showed significant differences between the materials tested, and the curing units (P<0.05). The DC% of semi-IPN and dimethacrylate matrix FRC was not statistically different (P>0.05) compared to that of unfilled resin. Conventional quartz-tungsten halogen with turbo tip showed the highest DC% (69-72.3%), whereas the plasma-arc curing unit showed the lowest degree of conversion (47-62%). Within the limitations of this study, it can be concluded that semi-IPN matrix of FRC did not show a difference in the degree of conversion compared to dimethacrylate resin FRC when quartz-tungsten or a light-emitting diode polymerization unit was used. The plasma-arc light-curing unit showed a lower degree of conversion with all materials compared to the light-emitting diode and quartz-tungsten-halogen lamps.