Microfill Composite Resin Research Articles

Flexural Strength of Nanohybrid Composite Resin: An in-vitro Study

In the present study, the Flexural strength of nanohybrid composite was compared with conventional microfilled composite resin in vitro. Thirty nanohyrid and 30 conventional microfilled composite resins were subjected to Flexural strength measurement as follows; a teflon mold (4 mm in diameter and 6 mm in depth) was filled with materials, light cured through the glass slides for 40 sec top and bottom surfaces. Then the specimens were taken out from the mold, again light curing for 40 sec, stored in dry condition and placed into a Flexural strength tester and loaded until fracture of the sample. Student t-test was performed to assess the differences between two groups and a value of p >0.05 was considered as statistically significance. The results showed that the means ± SD Flexural strength of nanobybrid and conventional microfilled composite resin were 118.70 ± 3.90 Mpa and 77.43 ± 2.65 Mpa, respectively and the differences were statistically significant. It can be concluded that nanohybrid is superior to conventional microfilled composite resin in respect to Flexural strenth in class II restorations of permanent molar teeth.

Strengthening effect of different fiber placement designs on root canal treated and bleached premolars

To evaluate the strengthening effect of five different fibers with different placement designs in root canal treated and intracoronally bleached premolars. Seventy extracted single-rooted premolars were distributed into 7 groups (G1-G7). Group 1 (G1) included the intact (I) teeth as the negative control. Group 2 (G2) included root canal treated, intra-coronally bleached and composite (C) restored teeth as the positive control. In the other five test groups after root canal treatment the teeth were intra-coronally bleached and fiber materials were placed into standard MOD cavities in the following different designs: an intracanal rigid fiber/Reforpost (G3,RF), an intracanal flexible fiber/ Everstick (G4, FF), four intracanal flexible pin fibers/Dentapreg Pin (G5,PF), an intercuspal flexible fiber /Dentapreg SFU (G6, IF) or an intra-coronal horseshoe-shaped/ Dentapreg SFU (G7,CF). All cavities were filled with a microfilled resin composite. Fracture resistance was tested using a universal testing machine under a crosshead speed of 1mm/minute. One-way ANOVA and Duncan's Multiple Range tests were used for statistical analysis. Fracture types were recorded. The fracture resistance values in descending order were G1(I): 1190.97N > G6 (IF): 1138.78N > G5 (PF): 942.45N > G3 (RF): 737.40N > G4 (FF):694.29N > G2 (C): 611.83N > G7 (CF): 542.78N. There were statistically significant differences among the groups (p ≤ 0.05). In all groups, repairable coronal oblique fractures were mostly observed. Flexible fibers placed intercuspally exhibited a significantly better strengthening effect than those of the intracanal flexible and rigid fibers (p < 0.05).

Influence of Polishing Systems on Surface Roughness of Composite Resins: Polishability of Composite Resins.

The objective of this in vitro study was to compare, with a threshold value of 200 nm, the surface roughness obtained when using 12 different polishing systems on four different composite resins (microfill, nanofill, and two nanohybrids). A total of 384 convex specimens were made using Durafill VS, Filtek Supreme Ultra, Grandio SO, and Venus Pearl. After sandblasting and finishing with a medium-grit finishing disc, initial surface roughness was measured using a surface roughness tester. Specimens were polished using 12 different polishing systems: Astropol, HiLuster Plus, D♦Fine, Diacomp, ET Illustra, Sof-Lex Wheels, Sof-Lex XT discs, Super-Snap, Enhance/Pogo, Optrapol, OneGloss and ComposiPro Brush (n=8). The final surface roughness was measured, and data were analyzed using two-way analysis of variance. Pairwise comparisons were made using protected Fisher least significant difference. There were statistical differences in the final surface roughness between polishing systems and between composite resins (p<0.05). The highest surface roughness was observed for all composite resins polished with OneGloss and ComposiPro Brush. Enhance/Pogo and Sof-Lex Wheels produced a mean surface roughness greater than the 200-nm threshold on Filtek Supreme Ultra, Grandio SO, and Venus Pearl. Data showed that there was an interaction between the composite resins and the polishing systems. A single polishing system does not perform equally with all composite resins. Except for Optrapol, multi-step polishing systems performed generally better than one-step systems. Excluding Enhance/Pogo, diamond-impregnated polishers led to lower surface roughness. Durafill VS, a microfill composite resin, may be polished more predictably with different polishers.

Evaluation of Compressive Strength of Repaired Direct Composite Resin Restorations

The aim of the study was to evaluate and to compare the compressive parameters of repaired composite restoration when using different types of composite resins and a universal bonding agent as an intermediate layer. Aged micro-filled hybrid and nano-filled hybrid composite resins were chosen to simulate old restoration. The same micro-filled hybrid composite resin was used as a repair material. A universal bonding agent applied in etch-and-rinse and self etch strategies was used as an intermediate layer in restoration repair. Non-aged composite resins were considered as control. Compressive strength and compressive modulus were determined by evaluating the samples in a universal testing machine. Lower values of the tested parameters were recorded after aging both types of composite resin when compared to control. Higher values of compressive strength were recorded when nano-filled hybrid composite resin was repaired when compared to micro-filled hybrid composite resin. The strategy of universal bonding agent application as an intermediate layer did not influenced the compressive properties of repaired restoration.

In vitro analysis and comparison on depth of cure in newer bulk fill composite resin with conventional micro- and nano-hybrid composite resin using two different light sources quartz-tungsten-halogen and light emitting diode with three varying intensities

Aims: The current in vitro analysis evaluated the depth of cure in newer bulk fill composite resin which compared the traditionally used hybrid and microfill composite resin which used two different light sources quartz-tungsten-halogen (QTH) and light emitting diode (LED) unit with three varying intensities in conventional standard curing mode for 20 s. Materials and Methods: Three composite resins were selected for this study, namely, bulk fill (Smart Dentin Replacement, Dentsply), hybrid (Tetric N – Ceram, Ivoclar), and microfill (Te-Econom Plus, Ivoclar) with four different thickness 2, 4, 6, and 10 cured with varying intensities (625, 850, and 1025 mW/cm2) using two different light sources QTH (QHL 75, Dentsply) and LED (Ledition, Ivoclar and Valo, Ultradent). The depth of cure was determined using a scraping method based on ISO 4049:2000. Statistical Analysis Used: Data were analyzed using Kolmogorov–Smirnov test, Kruskal–Wallis test is applied followed by Bonferroni-corrected Mann–Whitney test. Results: Best depth of cure results were obtained with a bulk fill composite resin cured under 1025 mW/cm2 intensity using LED. Bulk fill showed the highest curing depth results in all varied intensities. Conclusions: Bulk fill composite resin was found to be more successful than hybrid and microfill composite resin with respect to the depth of cure.

Comparison of Wear Resistance Between Innovative Composites and Nano- and Microfilled Composite Resins

Background: One of the most common causes of failure in class 2 posterior composite restorations is occlusal and proximal wear. Estelite composites used supra-nano monodispersing spherical fillers and a new photoinitiator, and the manufacturer claimed that the wear of these composites is less than 1 mm3 volumetric wear. Objectives: Compare the wear resistance of new Estelite composites with that of other composites generations. Materials and Methods: Thirty-five specimens were evaluated in five groups: three kinds of Estelite composites (Estelite Sigma Quick, Estelite Flow Quick, and Estelite Flow Quick High Flow), Filtek Z350, and Filtek Z250. All specimens were prepared in 25 mm disks and cured with laboratory light for 120 seconds (60 s for each side). Then, they were polished by 600 grit sand paper and stored for one week in distilled water at room temperature. We used a two-body abrasion test and the pin-on-disk method with distilled water as medium. All specimens were worn under 15 N load, 0.05 m/seconds speed, 100 m distance, and steatite ceramic balls antagonists. After wearing, we measured wear volume by calculating the wear track cross-section area with a profilometer and analyzed the data with the one-way analysis of variance (ANOVA) test. Results: The wear amounts of the composites are as follows in order: Estelite sigma quick (1886.9 ± 518.5 µm 2 ), Estelite flow quick (2708.9 ± 578.1 µm 2 ), Estelite high flow (3206 ± 2445.1 µm 2 ), Filtek Z350 (3840 ± 1963.4 µm 2 ), and Filtek Z250 (4667.2 ± 2351.1 µm 2 ). No statistical difference was found among the groups (P value > 0.05). Conclusions: Estelite sigma quick composite had wear resistance similar to that of nano- and microfilled composites. Estelite flowable composites demonstrated similar wear resistance to that of a posterior composite.

Comparison of One-Step and Multistep Polishing Systems for the Surface Roughness of Resin Composites

Aim: This study analyzed the effect of different finishing and polishing systems on the surface roughness of a microfilled (Amaris), and a nanofilled resin composite (Clearfil Majesty Esthetic) using Scanning electron microscope (SEM) analysis and surface roughness tester. Materials and Methods: Thirty five specimens of each material were prepared in a plexiglass mold (10 mm in diameter and 2 mm in depth) and cured against a Mylar matrix strip to create a baseline surface. The average surface roughness was measured using a surface profilometer (Mahr Perthometer SP4, Germany) in three different positions on each sample before and after finishing with one of the seven finishing procedures: Procedure 1: Mylar strip (control), Procedure 2: Tungsten carbide burs, Procedure 3: Diamond burs, Procedure 4: Procedure 2 + one-step diamond micropolisher (PoGo), Procedure 5: Procedure 2 + multi-step discs (Super-snap), Procedure 6: Procedure 3 + one-step diamond micropolisher (PoGo), Procedure 7: Procedure 3 + multi-step discs (Supersnap). The obtained data were analyzed using two-way analysis of variance (ANOVA) and Duncan test at a p = 0.05 significance level. Results: Nanofilled composite showed significantly lower Ra values than microfilled composite in procedures 4, 6 and 7 (p 0.05). Conclusion: Nanofilled resin composite showed significantly lower Ra values than microfilled resin composite. Regardless of finishing methods, diamond micro-polisher produced smoother surfaces than polishing discs.

Effect of varying concentrations of home bleaching agents on hardness of a resin composite: An in vitro study

Aim: To evaluate the effect of 10%, 20% and 35% Carbamide Peroxide home bleaching agent on hardness of a microfilled resin composite. Materials and Methods: Forty specimens of micro filled resin composite(Z250, 3M ESPE) were prepared using moulds with dimensions of 4mm diameter x 2mm thickness and cured with a LED polymerization unit (LEDition - Ivoclar Vivadent). The specimens were polished with coarse, medium, fine and super fine polishing discs (Sof-lex, 3M ESPE) and were stored in distilled water at 37?C in an incubator for 24 hours. Specimens were then divided into four groups of 10 specimens each. One group was selected as the control group (not treated with bleaching agents) and was stored in artificial saliva for 7 days at 37?C. The other three groups were treated with 10%, 20% and 35% carbamide peroxide gels respectively (Opalesence PF 10%, Opalesence PF 20% and Opalesence PF 35%, Ultradent) as per the manufacturer’s instructions over a period of 7 days. The specimens were subjected to Shore Durometer for 15 seconds and checked for hardness. The results were analyzed using ANOVA and Post hoc Bonferroni tests. Results: There was no significant difference in the hardness of the specimens belonging to Group A, Group B or Group C when compared with the Control Group. Conclusion: It can be confirmed based on the results of this study that the hardness of the Micro filled Composite resin was not affected by10%, 20 % or 35% carbamide peroxide bleaching gels when used as per the manufacturer’s instructions. Restorations done using microfilled composite resins can be retained after bleaching procedures.

Effect on Adhesion to Tooth Structure for some Experimental Dental Adhesive System

The present study was conducted with the aim of evaluating and comparing the microleakage at the dentin and enamel/composite interfaces of two adhesive systems. The adhesives are: a new-developed experimental adhesive systems and OptiBond FL (Kerr Corp.) The new adhesive system was prepared for the composite material as three steps adhesive (etchant, primer and bonding). The bonding resin contains the base monomer that was present in the corresponding composite material, HEMA and TEGDMA as diluents. Twenty box-type Class V standardized cavities were prepared on the facial and oral surfaces of each tooth, with coronal margins in enamel and apical margins in cementum (dentin). The preparations were restored with two restorative materials a new experimental microfilled resin composites based on Bis-GMA analogue and hybrid resin composite Herculite XRV Ultra (Kerr Corp.). The teeth were thermocycled and immersed in 2% methyl blue solution for 24 hours. The specimens were sectioned buccolingually into 3 slices and the resulted sections were examined using a stereomicroscope under 40x magnification. The extent of dye penetration was measured in a quantitative manner. This measurement was converted into percentage using the formula described by Sano et al.I=p/Lx100. These percentage values were submitted to variance analyses (ANOVA) andttest at a p&lt;0.05 level of significance. Scanning electron microscopy was used in order to see the interface between tooth and composite restoration. Significantly less microleakage was associated with the use of OptiBond FL adhesive system at the enamel surface. Between the enamel and the dentin margins no significantly statistical differences were found just for the experimental adhesive system. This adhesive containing water and ethanol as solvent performed significantly better at the dentin margins.

Evaluation and comparison of the effect of enamel preparation designs on fracture resistance of micro-filled and nano-filled composite resin: Anin vitrostudy

Background and Objectives: The main objective of this study was to compare and evaluate the effect of enamel preparation designs; bevel and stair step chamfer, on fracture resistance of composite resins (micro-filled and nano-filled) using incremental technique. Materials and Methods: The sample group consisted of 60 non-carious maxillary permanent central incisors. They were divided into four groups of 15 teeth each. According to the group, the teeth were prepared and restored with corresponding design and material. The teeth were subjected to compression bending test under instron testing machine then were examined under stereomicroscope. The results were subjected to statistical analysis. Results: Mean peak failure load (Newton) of among experimental groups was observed in the order; Group I (Bevel with micro-filled material) was 255.6 ± 65.0 N and Group II (bevel with nano-filled material) l was 282.1 ± 67.7 N. Group III (Stair-step chamfer with micro-filled material) was 249.8 ± 78.0 N. and Group IV (Stair-step chamfer with nano-filled material) was 283.3 ± 52.0 N. Results of the analysis of variance revealed there was no significant difference in the mean peak failure load values of the four different groups. Failure mode evaluation revealed, majority of the failures occurred as cohesive and mixed type for all the experimental groups. Adhesive type failure was observed maximum (47%) in the bevel group. Stair-step chamfer preparation showed the greatest potential for application, but also involved sacrificing less amount of tooth structure adjacent to fractured edge. Conclusion: This study concludes that both the preparations, bevel as well as stair-step chamfer are equally good to resist fracture when restored either with micro-filled or nano-filled composite resins.

Evaluation of the wear resistance of new nanocomposite resin restorative materials

The use of composite resins for the restoration of posterior teeth is popular because of the improved performance and appearance of these materials. Wear resistance continues to be of particular importance when restoring large occlusal areas in posterior teeth. The purpose of this study was to evaluate the relative wear characteristics of 2 recently introduced nanofiller-based composite resins (Filtek Supreme, Premise) and compare them to the more traditional microhybrid (Point 4) and microfill (Heliomolar RO) materials that have been used for many years. Six specimens (2 mm thick and 15 mm in diameter) of each material were subjected to 3-body wear tests using the Oregon Health Sciences University Oral Wear Simulator to produce abrasive wear and attrition for all specimens using human enamel as the opposing cusp. Profilometric tracings of the worn surfaces were used to determine the relative abrasive wear, attrition wear, and roughness (Ra) of the composite resin substrate. The mean diameter of the antagonist enamel wear facets was determined under a measuring microscope. Qualitative SEM analysis was also used to assess the surface appearance of the resulting enamel and composite resin wear facets. The data were analyzed by 1-way ANOVA and Tukey's multiple range post hoc test (alpha=.05). The results indicated that the composite resin type did not significantly affect the amount of measured attrition (P=.15) but did significantly affect abrasive wear (P=.02). The conventional microfill composite resin (Heliomolar RO) exhibited significantly less abrasive wear than the nanohybrid material (Premise). There was no significant difference in the average size of the opposing enamel wear facet generated by the different composite resin materials. Heliomolar RO resulted in a significantly rougher surface within the wear track than either nanohybrid composite resin (Premise) or microhybrid composite resin (Point 4) but was not significantly different than nanofilled composite resin (Filtek Supreme). The incorporation of nanofillers in 2 of the composite resin materials tested did not significantly improve their wear resistance or the amount of opposing cusp wear when compared to the traditional materials tested.

Fracture toughness comparison of six resin composites

Objectives This study investigated the Mode I and II fracture toughness values of resin composites used for the restorations of anterior teeth by the Brazilian disk test method. Methods The Brazilian disk test was performed on six commercially available dental resin composites, VenusTM (hybrid resin composite), Durafill ® (micro-filled resin composite), GradiaTM (micro-filled/hybrid resin composite), Point 4TM (hybrid resin composite), SupremeTM (nano-particle resin composite) and Filtek Z250™ (resin composite with zirconia particles). Five resin composite disks of 25 mm in diameter and 2 mm in thickness with chevron notches were prepared for each fracture mode per material. The specimens were stored in distilled water for 24 h at 37 °C, and then tested by a Zwick testing machine under compression mode with a constant crosshead speed of 0.25 mm/min at room temperature. The stress intensity factors under combined Modes I and II fracture toughness were calculated by the formula presented by Atkinson et al. The fracture patterns of two specimens randomly selected from each test group were examined using a scanning electron microscope. A one-way analysis of variance (ANOVA) was performed for the statistical evaluations followed by the post-hoc Tukey's Student Range (HSD) test. Results The highest mean Mode I and II fracture toughness values were found in Filtek Z250™ and Filtek™ Supreme and they were significantly higher than other materials (comparisons significant at the 0.05 level). The intermediate group consisted of Point4TM, VenusTM and GradiaTM ANTERIOR, whereas Durafill ®, statistically, had the lowest mean value for fracture toughness. Significance Fracture toughness values of hybrid and nano-particle resin composites are significantly higher than those of micro-filled resin composites. This suggests that the latter should be used for non-stress bearing areas.

Coronally Positioned Flap for Treatment of Restored Root Surfaces: A 6‐Month Clinical Evaluation

The aim of this study was to evaluate clinically the treatment of gingival recession associated with non-carious cervical lesions (NCCLs) by resin modified glass ionomer cement (RMGI) or microfilled resin composite (MRC) and coronally positioned flap (CPF) at 6 months following surgery. Fifty-nine patients were assigned to one of three treatments: root exposure without NCCL treated with CPF (group 1); root exposure with NCCL treated with RMGI restoration plus CPF (group 2); or root exposure with NCCL treated with MRC restoration plus CPF (group 3). Clinical measurements that were assessed at baseline and at 3 and 6 months after surgery included plaque index (PI), bleeding on probing (BOP); probing depth (PD), recession reduction (RR), clinical attachment level gain (CALG), keratinized tissue height (KTH), keratinized tissue thickness (KTT), percentage of root coverage (RC), and percentage of restored root coverage (RRC). Intra- and intergroup analyses demonstrated no significant differences in PI, BOP, PD, RR, CALG, KTH, or KTT (P >0.05) among the groups at any time. At 6 months, the mean RC was 80.83% +/- 21.08% for group 1; the mean RRCs were 71.99% +/- 18.69% and 74.18% +/- 15.02% for groups 2 and 3, respectively. There were no statistically significant differences in RRC between groups 2 and 3. All treatments showed root coverage improvement without damage to periodontal tissues, supporting the use of CPF for treatment of root surfaces restored with RMGI or MRC as being effective over the 6-month period.

Effect of cyclical lateral forces on microleakage of cervical resin composite restorations

The purpose of this in-vitro study was to compare the amount of microleakage occurring in cervical restorations in groups of extracted teeth restored with four different types of resin composite materials, representing four basic categories widely used by restorative dentists today. This comparison was made, both with and without the application of cyclic lateral forces. A testing instrument developed specifically to reproduce cyclic lateral forces was utilized. The amount of microleakage that occurred was compared, both with and without the application of the forces. Within the limitations of the study, we found that the packable and the hybrid resin composite material exhibited significantly more leakage than either the flowable or the microfilled resin composite. This was observed in both the fatigued and the non-fatigued specimens. This finding supported the theory that the lower modulus of elasticity of flowable and microfilled resin composites allows more flexure of the restoration during the flexure of the tooth, that results from its reciprocal movements. The non-fatigued specimens restored with flowable and microfilled resin composite material had less microleakage than did those restored with the hybrid resin composite material. The findings in the study supported the possibility that lower modulus of elasticity of the microfilled and flowable resin composite materials may have some beneficial effects in reducing the stress placed on the adhesive bond at the resin tooth interface during the polymerization phase.

Dynamic and static elastic moduli of packable and flowable composite resins and their development after initial photo curing

The purpose of this study was to evaluate the dynamic (storage) shear modulus and the static shear modulus of elasticity of packable and flowable composite resins and to investigate their development after initial photo-curing. Three pairs of a packable versus a flowable composite and a microfill composite resin were tested (Alert/Flow It, Filtek P60/Filtek Flow, Admira/Admira Flow, A 110). Cylindrical specimens (0.85 mm x 18 mm) were made for each material. All specimens were conditioned and tested dry at 21 degrees C. The specimens were tested at 30 min, 24h and 1 week after the end of photo curing. Storage shear modulus and loss tangent were determined by conducting dynamic torsional loading in the frequency range from 1 to 150 Hz. Static shear modulus measurements were made by applying a constant load (below the proportional limit of the materials) for 10s and recording the angular deformation of the specimens. Data were analyzed by ANOVA and Duncan's Post hoc test (alpha=0.05). Storage shear moduli (at 1 week measurement) ranged from 3.39 to 9.67 GPa, and loss tangents from 0.0735 to 0.0235; static shear moduli ranged between 2.66 and 9.80 GPa. High values of elastic moduli and low tandelta values were obtained with packable composites, while low moduli values were obtained with flowable composites. Statistically significant (alpha=0.05) differences were recorded between materials of the same category. Storage time, 24h and 1 week after initial polymerization, resulted in significant increases in both moduli of elasticity. Dynamic shear storage moduli were highly correlated to the static ones (r(2)=0.92; P<0.05). The results of the aging studies showed that the rigidity of these materials increases significantly even 1 week after the clinician turns off the curing unit.

Effects of filler composition on flexibility of microfilled resin composite

The effects of the filler composition on physical and mechanical properties of microfilled composites was investigated by measuring water absorption, solubility, compressive, flexural, and impact strength. A series of experimental composites, consisting of UDMA/TEGDMA comonomer matrix and prepolymerized fillers, was fabricated. The prepolymerized fillers were composed of hydrophobic colloidal silica and two monomers in varying ratios, trimethylolpropanetrimethacrylate (TMPT), and polyesterdiacrylate (PEDA). TMPT/PEDA ratios were 100:0, 64:36, 46:54, 18:82, and 0:100%. There were no significant differences in water sorption and solubility, regardless of the amount of PEDA monomer. Young's modulus and modulus of resilience increased with decreasing PEDA ratio. Fracture energy exhibited drastic changes (30.1 x 10(-5) J to 93.4 x 10(-5) J). The highest value of flexural strength (96.0 +/- 3.5 MPa) was obtained when the TMPT-PEDA filler was 46:54. The impact strengths of composites fabricated with TMPT-PEDA filler of 46:54 (11.2 +/- 1.4 kJ/m(2)), 18:82 (10.6 +/- 3.2 kJ/m(2)), and 0:100 (13.1 +/- 3.8 kJ/m(2)) were significantly higher than those with 100:0 (6.0 +/- 1.8 kJ/m(2)) or 64:36 (7.1 +/- 2.4 kJ/m(2)). Based upon the results, it was concluded that the mechanical properties of microfilled composites were improved by the modification of prepolymerized filler composition.

Effect of thermal cycling and filling technique on leakage of composite resin restorations

The objective of this study was to evaluate in vitro the effect on leakage of two incremental filling techniques and two composite resins with different elastic modulus and similar polymerization shrinkage. Eighty Class V cavities (4x4x2mm) were prepared in bovine incisors and were randomly restored with Z-250 (Z) or Durafill VS (D) + Single Bond in axial (a) or oblique (o) increments. The restorations were divided into two groups: Not Aged - N (4-hour-storage in water at 37ºC) and Aged - A (1-week storage in water at 37ºC + 1000 x - 5º-55ºC / 1-min dwell time). The specimens were covered with 2 coats of nail varnish so that only the restoration margins were exposed to silver nitrate 50% (2h) and developed under fluorescent light (8h). After they were sectioned twice in buccal-lingual direction, the four exposed surfaces were digitized (Vidcap) and the silver nitrate penetration was measured (ImageLab) at the incisal and gingival walls. Data were analyzed by a 3-way ANOVA (Resin, Filling Technique and Aging) separately for incisal and gingival walls (alpha=0.05). Resin and Aging were statistically significant either for the incisal and the gingival walls. The microfill composite resin infiltrated more than the hybrid composite. The thermal cycling caused an overall increase in silver nitrate penetration. The filling technique affected leakage depending on the composite resin and aging regimen.

Effect of microfiller fraction and silane treatment on resin composite properties.

A series of microfilled resin composites were formulated by incrementally mixing either agglomerated 20 nm or unagglomerated 50 nm silica microfillers into monomers composed of diphenyloxymethacrylate and TEGDMA. The microfiller particles were prepared with and without a gamma-methacryloxypropyl-trimethoxy silane coupling agent. Following polymerization, five material properties were tested: uniaxial tensile strength, Young's modulus in slow compression, Knoop hardness, water sorption, and toothbrush abrasion resistance. Results from these tests indicated that microfiller content clearly was the most influential parameter affecting material property performance. Composites containing 20 nm particles demonstrated greater water sorption, higher Knoop hardness, and better resistance to toothbrush wear. Surprisingly, the application of silane to microfiller surfaces did not greatly improve composite performance for most of the material properties tested in this study. However, water sorption behavior over a 3-year period was observed to be more stable for materials possessing silane-treated particles. Future evaluation of coupling agents should include long-term water storage prior to conducting mechanical tests.

Effect of microfiller fraction and silane treatment on resin composite properties

A series of microfilled resin composites were formulated by incrementally mixing either agglomerated 20 nm or unagglomerated 50 nm silica microfillers into monomers composed of diphenyloxymethacrylate and TEGDMA. The microfiller particles were prepared with and without a γ-methacryloxypropyl-trimethoxy silane coupling agent. Following polymerization, five material properties were tested: uniaxial tensile strength, Young's modulus in slow compression, Knoop hardness, water sorption, and toothbrush abrasion resistance. Results from these tests indicated that microfiller content clearly was the most influential parameter affecting material property performance. Composites containing 20 nm particles demonstrated greater water sorption, higher Knoop hardness, and better resistance to toothbrush wear. Surprisingly, the application of silane to microfiller surfaces did not greatly improve composite performance for most of the material properties tested in this study. However, water sorption behavior over a 3-year period was observed to be more stable for materials possessing silane-treated particles. Future evaluation of coupling agents should include long-term water storage prior to conducting mechanical tests. © 1998 John Wiley & Sons, Inc. J Biomed Mater Res, 40,12–23, 1998.

Evaluating a Microfill Posterior Composite Resin a Five-Year Study

This study evaluates a pre-polymerized microfill composite resin. Results show this particular resin is resistant to generalized wear in conservative restorations.