Microhybrid Composite Resin Research Articles

Randomized controlled split-mouth clinical trial of direct laminate veneers with two micro-hybrid resin composites

ObjectivesThis randomized, split-mouth clinical study evaluated the survival rate of direct laminate veneers made of two resin-composite materials. MethodsA total of 23 patients (mean age: 52.4 years old) received 96 direct composite laminate veneers using two micro-hybrid composites in combination with two adhesive resins (Ena-Bond-Enamel HFO: n=48, Clearfil SE Bond-Miris2: n=48). Enamel was selectively etched with 38% H3PO4 for 30s, rinsed 30s and the corresponding adhesive resin was applied accordingly. Existing resin composite restorations in good conditions (small or big) were not removed but conditioned using silica coating (CoJet) and silanized (ESPE-Sil). Restorations were evaluated at baseline and thereafter every 6 months. Additional qualitative analysis was performed using modified USPHS criteria. ResultsMean observation period was 41.3 months. Altogether, 12 absolute failures were observed [survival rate: 87.5%] (Kaplan–Meier). The survival rates with the two resin composites did not show significant differences [Enamel HFO: 81.2%, Miris2: 93.8%] (p>0.05). The presence of existing composite restorations on the prepared teeth did not affect the survival rate significantly (intact teeth: 100%, small restorations: 90.6%, big restorations: 82.7%) (p>0.05). Surface roughness and marginal discolouration were the main qualitative deteriorations observed until the final recall. Secondary caries and endodontic complications did not occur in any of the teeth. ConclusionEarly findings of this clinical study with the two micro-hybrid composite laminate veneers showed similar survival rate and their clinical performance was not significantly influenced when bonded onto intact teeth or onto teeth with existing restorations with the protocol applied.

Degree of conversion of nanofilled and microhybrid composite resins photo-activated by different generations of LEDs

Objective This study aimed at evaluating the degree of conversion (DC) of four composite resins, being one nanofilled and 3 microhybrid resins, photo-activated with second- and third-generation light-emitting diodes (LEDs). Material and methods FiltekTM Z350 nanofilled composite resins and Amelogen® Plus, Vit-l-escenceTM and Opallis microhybrid resins were photo-activated with two second-generation LEDs (Radii-cal and Elipar Free LightTM 2) and one third-generation LED (Ultra-Lume LED 5) by continuous light mode, and a quartz halogen-tungsten bulb (QHT, control). After 24 h of storage, the samples were pulverized into fine powder and 5 mg of each material were mixed with 100 mg of potassium bromide (KBr). After homogenization, they were pressed, which resulted in a pellet that was evaluated using an infrared spectromer (Nexus 470, Thermo Nicolet) equipped with TGS detector using diffuse reflectance (32 scans, resolution of 4 cm-1) coupled to a computer. The percentage of unreacted carbon-carbon double bonds (% C=C) was determined from the ratio of absorbance intensities of aliphatic C=C (peak at 1637 cm-1) against internal standard before and after curing of the specimen: aromatic C-C (peak at 1610 cm-1). Results The ANOVA showed a significant effect on the interaction between the light-curing units (LCUs) and the composite resins (p<0.001). The Tukey's test showed that the nanofilled resin (FiltekTM Z350) and Opallis when photo-activated by the halogen lamp (QTH) had the lowest DC compared with the other microhybrid composite resins. The DC of the nanofilled resin (FiltekTM Z350) was also lower using LEDs. The highest degrees of conversion were obtained using the third-generation LED and one of second-generation LEDs (Elipar Free LightTM 2). Conclusions The nanofilled resin showed the lowest DC, and the Vit-l-escenceTM microhybrid composite resin showed the highest DC. Among the LCUs, it was not possible to establish an order, even though the second-generation LED Radii-cal provided the lowest DC.

Clinical Evaluation of Stress-reducing Direct Composite Restorations in Structurally Compromised Molars: A 2-year Report

To evaluate the clinical performance of class II large-size direct composite restorations. Fifty (50) patients 18 years or older were included in this clinical trial restoring 75 vital molar teeth with large-size cavities. Occlusal extension greater than two-thirds the intercuspal distance and proximal extension greater than half the distance between line angles. Teeth with residual cavity walls less than 1 mm and with one or more cusps involved were excluded. Teeth were randomly divided in three groups. Group 1: Opti-Bond FL; group 2: Scotchbond 1 XT; group 3: PQ1. Total-etching was performed using 35% phosphoric acid followed by the application of 2% chlorhexidine gluconate in the three groups. All teeth were restored using Vit-l-escence microhybrid composite resin. The proximal surface was built up first, followed by dentin and enamel occlusal surface stratification; wedge-shaped increments of composite resin were placed and cured using the UltraLume V curing light through a combination of pulse and progressive curing techniques. Restorations were evaluated at six-month intervals during the two-year period using a modified US Public Health Service criteria by two independent evaluators precalibrated at 85% reliability. No failures were reported and α scores were recorded for all parameters. Statistical analysis was performed using a χ(2) test and the Fisher exact test (χ(2)=10.6; p=0.001). No teeth exhibited sensitivity in the three groups both at the two-week recall and two-year follow-up.

Surface discoloration of composite resins: Effects of staining and bleaching

The purpose of this in vitro study was to evaluate surface discoloration of three microhybrid composite resins (Esthet•X HD, Clearfil AP-X, Gradia Direct) and five nanohybrid composite resins (Ceram•X, GC Kalore, G-aenial, Grandio, GrandioSO), after staining and bleaching procedures. The composite resins were polymerized with a curing light (Celalux II, Voco, Cuxhaven, Germany) into 160 silicon molds (6,4 mm in diameter and 2 mm in thickness) to obtain identical specimens. Twenty samples for each composite resin were prepared. The specimens were polished using an automated polishing machine with the sequence of 600-, 800-, 1000-grit abrasive paper under water irrigation. The specimens were immersed in tea and distilled water: the specimens were dipped for 20 min, once a day (every 24 h), for 14 days into the drinks. The specimens were then bleached with carbamide peroxide at 17% (Perfect Bleach-Voco). The color of specimens was measured with a spectrophotometer according to the CIE L(*)a(*)b(*) system after light-polymerization of composite resin specimens, after 7 days, after 14 days, and after bleaching. The color difference h index (DEab(*)) between each measurement was calculated. Statistical analysis was made using analysis of variance (ANOVA). All specimens showed a significant increase in staining with a similar trend and no significant differences between microhybrid and nanohybrid composite resins. After whitening procedures, materials tested showed both significant and unsignificant differences of the h index. Microhybrid and nanohybrid composite resins had similar in vitro surface discoloration in tea. After bleaching, discoloration was removed from some composite resins tested.

Evaluation of Microleakage in Class V Composite Restoration using Different Techniques of Polymerization

ABSTRACT Aims The purpose of this study was to evaluate the effect of light intensity and curing cycle of quartz tungsten halogen (QTH) and plasma arc curing (PAC) lights on the microleakage of class V composite restorations. Materials and methods A total of 60 freshly extracted human maxillary premolars were used for this study. Standardized class V cavities were prepared and restored with microhybrid resin composite. According to the curing protocol, the teeth were then divided into three groups (n = 20): QTH curing (standard and soft start mode) and PAC high intensity irradiation. The microleakage was evaluated by immersion of the samples in 50% silver nitrate solution. The samples were then sectioned, evaluated under a stereomicroscope and scored for microleakage. Statistical analysis used Dye leakage scores were obtained, and analysis was done using Student's t-test. Results Light curing with QTH light in the soft start mode, showed the least leakage in the composite restoration, which was highly significant when compared with the other groups (p &lt; 0.01). Light curing with QTH light in the standard mode, showed moderate microleakage, which was statistically significant (p &lt; 0.05), when compared with the PAC high intensity curing. Curing with PAC light in high intensity mode resulted in severe microleakage along the cavity margins. Conclusion Within the limitations of the study, it may be concluded that: 1. The high intensity PAC light resulted in maximum leakage, when compared to the other groups in the study. 2. The soft start polymerization mode offers a distinctive advantage over the standard curing protocol, in terms of microleakage, for the QTH curing lights. Clinical significance In the clinical scenario, soft start curing regimen offers a distinctive advantage over the conventional mode of the QTH curing and the high intensity rapid curing offered by the PAC light. How to cite this article Chandurkar AM, Metgud SS, Yakub SS, Kalburge VJ. Evaluation of Microleakage in Class V Composite Restoration using Different Techniques of Polymerization. Int J Prosthodont Restor Dent 2012;2(1): 10-15.

Reattachment of Fractured Anterior Teeth—Determining Fracture Strength using Different Techniques: An in vitro Study

The aim of this in vitro study was to evaluate and compare the shear bond strength of teeth reattached with sixth generation dentin bonding agent: Xeno III and microhybrid resin composite: Esthet-X, using three different techniques: (1) Simple reattachment, (2) overcontour and (3) internal dentinal groove. A total of 70 human maxillary central incisors were selected and divided into four groups as follows. Group I: Control group comprised of 10 samples. Group II: Simple reattachment, group III: Overcontour and group IV: Internal dentinal groove. Groups II, III and IV comprised of 20 samples each. The teeth in three study groups were sectioned using a diamond disk and the fragment was reattached with Esthet-X and Xeno III using three different techniques. Specimens were stored in tap water for 24 hours and shear bond strength was determined using universal testing machine using a knife edge chisel (0.5 mm in cross-section) at a crosshead speed of 1 mm/minute. The results of this study showed following mean value of fracture strength in Kgf: Group I: Control-27.71; group II: Simple reattachment-9.78; group III: Overcontour-24.41; group IV: Internal dentinal groove-23.83. The overcontour technique had the highest strength recovery while the simple reattachment had the lowest. The overcontour technique provided strength recovery almost similar to intact teeth emphasizing that tooth preparation influenced fracture resistance.

The filler content of the dental composite resins and their influence on different properties

The purpose of this study was to compare the inorganic content and morphology of one nanofilled and one nanohybrid composite with one universal microhybrid composite. The Vickers hardness, degree of conversion and scanning electron microscope of the materials light-cured using LED unit were also investigated. One nanofilled (Filtek™ Supreme XT), one nanohybrid (TPH®(3)) and one universal microhybrid (Filtek™ Z-250) composite resins at color A(2) were used in this study. The samples were made in a metallic mould (4 mm in diameter and 2 mm in thickness). Their filler weight content was measured by thermogravimetric analysis (TG). The morphology of the filler particles was determined using scanning electron microscope equipped with a field emission gun (SEM-FEG). Vickers hardness and degree of conversion using FT-IR spectroscopy were measured. Filtek™ Z-250 (microhybrid) composite resin shows higher degree of conversion and hardness than those of Filtek™ Supreme XT (nanofilled) and TPH®(3) (nanohybrid) composites, respectively. The TPH(3)® (nanohybrid) composite exhibits by far the lowest mechanical property. Nanofilled composite resins show mechanical properties at least as good as those of universal hybrids and could thus be used for the same clinical indications as well as for anterior restorations due to their high aesthetic properties.

Effect of static and cyclic loading on ceramic laminate veneers adhered to teeth with and without aged composite restorations.

Existing composite restorations on teeth are often remade prior to the cementation of fixed dental prostheses. The aim of this study was to evaluate the effect of static and cyclic loading on ceramic laminate veneers adhered to aged resin composite restorations. Eighty sound maxillary incisors were collected and randomly divided into four groups: group 1: control group, no restorations; group 2: two Class III restorations; group 3: two Class IV restorations; group 4: complete composite substrate. Standard composite restorations were made using a microhybrid resin composite (Anterior Shine). Restored teeth were subjected to thermocycling (6000 cycles). Window preparations were made on the labial surface of the teeth for ceramic laminate fabrication (Empress II). Teeth were conditioned using an etch-and-rinse system. Existing composite restorations representing the aged composites were silica coated (CoJet) and silanized (ESPE-Sil). Ceramic laminates were cemented using a bis-GMA-based cement (Variolink Veneer). The specimens were randomly divided into two groups and were subjected to either static (groups 1a, 2a, 3a, 4a) or cyclic loading (groups 1b, 2b, 3b, 4b). Failure type and location after loading were classified. Data were analyzed using one-way ANOVA and Tukey's test. Significantly higher fracture strength was obtained in group 4 (330 ± 81 N) compared to the controls in group 1 (179 ± 120 N) (one-way ANOVA, p < 0.05). Group 1b survived a lower mean number of cyclic loads (672,820 cycles) than teeth of groups 2b to 4b (846x103 to 873x103 cycles). Failure type evaluation after the fracture test showed predominantly adhesive failures between dentin and cement, but after cyclic loading, more cohesive fractures in the ceramic were seen. Ceramic laminate veneers bonded to conditioned aged composite restorations provided favorable results. Surface conditioning of existing restorations may eliminate the necessity of removing aged composite restorations.

Effect of thermocycling on the bond strength of composite resin to bur and laser treated composite resin

The objective of this study was to investigate the effect of two different surface treatments (Er:YAG laser and bur) and three different numbers of thermal cycling (no aging, 1,000, 5,000, and 10,000 cycles) on the micro-shear bond strength of repaired composite resin. Ninety-six composite blocks (4 mm × 4 mm × 1 mm) obtained with a micromatrix hybrid composite were prepared. The composite blocks were then randomly divided into four groups (n = 24), according to the thermal cycling procedure: (1) stored in distilled water at 37°C for 24 h (control group), (2) 1,000 cycles, (3) 5,000 cycles, and (4) 10,000 cycles. After aging, the blocks were further subdivided into two subgroups (n = 12), according to surface treatment. Bur and laser-treated composite surfaces were treated with an etch&rinse adhesive system. In addition, a microhybrid composite resin was bonded to the surfaces via polyethylene tubing. Specimens were subjected to micro-shear bond strength test by a universal testing machine with a crosshead speed of 0 and 5 mm/min. The data were analyzed using one-way analysis of variance and Tukey tests (α = 0.05) for micro-shear bond strengths. After conducting a bond strength test, it was found that the laser and bur-treated specimens had similar results. Aging with 10,000 thermocycles significantly affected the repair bond strength of composite resins.

Infiltração Marginal de Resinas Compostas Associadas a Sistemas Adesivos com e sem Carga

The objective of this research was to verify the degree of marginal infiltration in class-V, vestibular, and lingual cavities in 30 recently-extracted human premolar teeth, divided into four groups, which, after the thermal cycle at 5oC/55oC, and stained with 2% methylene blue, were assessed in two ways: 1 - types of dentin bonding: self-etching adhesive (no load) and restored with micro-hybrid composite resin, one-bottle adhesive (with load), on which acid attack was conducted, and which was restored with micro-hybrid composite resin, and 2 - location of the cavity wall ( enamel occlusal wall and cement gingival wall). The data were measured through scores of 0 to 4 and statistically analyzed by nonparametric Kruskal-Wallis test to demonstrate the most effective dentin adhesive and determine which cavity wall that allowed less dye leakage.

Effect of light curing sources on microhardness of different composite resins

This study evaluated the influence of light-curing units (LCUs) on Knoop microhardness (KHN) of different composite resins formulations. Four LCUs, one Quartz-Tungsten-Halogen (QTH) for 20 s, one Argon-Ion-Laser (AL) for 10 s, one Plasma-Arc-Curing (PAC) for 9 s, and one Light-Emitting-Diode (LED) for 20 s, and three composite resins, nanofill and easy cure (Filtek™ Supreme), microhybrid and medium cure (Herculite XRV), and microfill and difficult cure (Heliomolar) were used. Discs (4 × 2 mm2) of each composite resin were divided in 12 Groups and KHN was measured at the top (T) and bottom (B) surfaces. Data were analyzed using two-way ANOVA and Tukey’s test (p < 0.05). Top presented significantly higher KHN than bottom surface for all composite resins and LCUs tested. Statistical significant differences were observed among the LCUs. At the bottom surface QTH and LED presented higher KHN than PAC and LA. However, at the top surface PAC and LA presented similar results than QTH for nanofill and microhybrid composite resins. Different LCUs play an important effect on Knoop microhardness and the composite resin formulations were significant factor on the photosensitivity.

Surface Modifications on Aesthetically Restored Teeth following Home Bleaching with 16% Peroxide Carbamide

This clinical study evaluated the effects of a highly concentrated home-bleaching agent on the surface morphology of aesthetically restored teeth. Specimens of human enamel and micro-hybrid composite resin were randomly adhered to the buccal side of right premolar and molar teeth of ten volunteers, who underwent a routine home-bleaching procedure with 16% carbamide peroxide on the upper jaw for 8 days. The mandibular unbleached specimens served as paired controls (n=10). Ultra-structural assessment of the sample was carried out by scanning electron microscopy, and the resulting images were blindly evaluated for topographical alterations. The differences between groups were calculated with the Mann-Whitney test adjusted at the 95% confidence interval. The bleached enamel presented significantly more morphological changes than the control group. The aspect of resin composite exposed to the whitening substance was statistically similar to that observed in the corresponding control group (P<.05). The occurrence of surface topography changes during home bleaching of aesthetically restored teeth with 16% carbamide peroxide was restricted to enamel.

Color stability of sealed composite resin restorative materials after ultraviolet artificial aging and immersion in staining solutions

The color alteration of resin-based materials is one of the most common reasons to replace esthetic dental restorations. This study assessed the influence of surface sealant (Biscover) on the color stability of nanofilled (Supreme XT) and microhybrid (Vit-l-escence and Opallis) composite resins after artificial aging. One hundred disc-shaped (6 × 1.5 mm) specimens were made for each composite resin. After 24 hours, all specimens were polished and sealant was applied to 50 specimens of each material. Baseline color was measured according to the CIE L*a*b* system using a reflection spectrophotometer. Ten specimens of each group were aged for 252 h in an ultraviolet (UV)-accelerated aging chamber or immersed for 4 weeks in cola soft drink, orange juice, red wine staining solutions or distilled water as control. Color difference (ΔE) after aging was calculated based on the color coordinates before (baseline) and after aging/staining treatment. Data were analyzed with 2-way ANOVA and Fisher's test (α=.05). The results showed significant changes in color after artificial aging in all the groups (P<.05). Independent of the material studied, red wine resulted in the highest level of discoloration. Intermediate values were found for orange juice, UV accelerated aging, and the cola soft drink. The lowest values of ΔE were found for specimens stored in distilled water. All composite resins showed some color alteration after the aging methods. The surface sealant did not alter the color stability of the tested materials.

Effects of curing units and staining solutions on the color susceptibility of a microhybrid composite resin

Background/purpose To examine the effect of different light-curing units and staining solutions on a microhybrid composite resin. Materials and methods Two shades (A3 and B3) of a light-activated composite (Ecusit resin) were cured in polytetrafluoroethylene disk rings (45 each) using 3 different light-curing units: 1) a quartz–tungsten–halogen (QTH) unit, 2) a light-emitting diode (LED) unit, and 3) a plasma-arc curing (PAC) unit. Two beverages (coffee and tea) were used as staining solutions, and distilled water was used as a control. Evaluations were made after 1, 7, 15, and 30 days by means of reflectance spectrophotometry. Results Data were statistically analyzed using one-way analysis of variance, and post-hoc comparisons were made using Tukey’s test with a significance level of 5%. A Kruskal–Wallis multiple-comparison test was performed to evaluate ΔE ∗ values among water, tea, and coffee immersion with 2 shades of the composite. Statistically significant color changes were observed between water and coffee, and tea and coffee for different time periods; whereas no difference was seen between water and tea in LED-cured A3 Ecusit resin specimens after either 1 or 15 days of immersion, those cured by PAC after 15 days of immersion, or in LED-cured B3 Ecusit resin specimens after 7 days. Conclusions PAC-cured Ecusit resin specimens showed significantly higher discoloration than the other specimens. The staining solutions produced discoloration, while water caused the least changes.

Comparison of different finishing/polishing systems on surface roughness and gloss of resin composites

Objectives The aim of this study was to compare four finishing/polishing systems (F/P) on surface roughness and gloss of different resin composites. Methods A total of 40 disc samples (15 mm × 3 mm) were prepared from a nanofill – Filtek Supreme Plus (FS) and a micro-hybrid resin composite – Esthet-X (EX). Following 24 h storage in 37 °C water, the top surfaces of each sample were roughened using 120-grit sandpaper. Baseline measurements of surface roughness (Ra, μm) and gloss were recorded. Each composite group was divided into four F/P disk groups: Astropol[AP], Enhance/PoGo[EP], Sof-Lex[SL], and an experimental disk system, EXL-695[EXL] ( n = 5). The same operator finished/polished all samples. One sample from each group was evaluated under SEM. Another blinded-operator conducted postoperative measurements. Results were analysed by two-way ANOVA, two interactive MANOVA and Tukey's t-test ( p < 0.05). Results In surface roughness, the baseline of two composites differed significantly from each other whereas postoperatively there was no significance. The Sof-Lex F/P system provided the smoothest surface although there were no statistical significance differences between F/P systems ( p > 0.01). In gloss, FS composite with the EXL-695 system provided a significantly higher gloss ( p < 0.01). EX treated by Soflex revealed the least gloss ( p < 0.05). SEM images revealed comparable results for F/P systems but EX surfaces included more air pockets. Conclusions Four different finishing/polishing systems provided comparable surface smoothness for both composites, whereas EXL with FS provided significantly higher gloss. SEM evaluations revealed that the EX surface contained more air pockets but F/P systems were compatible.

Effect of endodontic irrigating solutions on the adhesive bond strength to dentin

PURPOSE: To evaluate the bond strength of a total-etching adhesive system to dentin irrigated with 1% sodium hypochlorite (NaOCl) and ethylenediaminetetraacetic acid 17% (EDTA). METHODS: Thirty human molars were sectioned 3mm below the oclusal surface and were randomly divided into 3 groups (n=10): G1, no treatment (control); G2, 1% NaOCl; G3, NaOCl followed by EDTA. The specimens received the total-etching adhesive system, restored with microhybrid composite resin, sectioned and trimmed to create 4 hourglass-shaped slabs of each tooth. The slabs were tested in microtensile bond strength in a universal testing machine (Emic DL 2000) at a crosshead speed of 0.5 mm/min until fracture. The results were analyzed statistically by ANOVA and Newman-Keuls test. G2 samples were not submitted to the test because they fractured just before testing, and its values were considered zero to the statistical analysis. RESULTS: The means and standard deviations (MPa) were: G1, 8.41 (±3.51); G2, 0.0 (±0.00); G3, 8.47 (±3.53). CONCLUSION: It was concluded that the application of the NaOCl irrigating solution significantly decreased the bond strength values. The use of NaOCl followed by EDTA resulted in bond strength values not statistically different from control group.

Relationship between filler content and selected mechanical properties of six microhybrid composites

PURPOSE: The purpose of this study was to evaluate the influence of filler weight content on selected mechanical properties of six microhybrid composite resins. METHODS: Compressive strength, elastic modulus, Vickers microhardness (VHN), and weight filler content were evaluated in the following dental composites: Admira (AD), Charisma (CH), InTen-S (IN), Tetric Ceram (TC), Point 4 (P4), and Z250 (Z2). RESULTS: Mean values for compressive strength (MPa) ranged from P4 76.60 to Z2 222.33. The elastic moduli (GPa) ranged from IN 2.56 to Z2 4.59. Microhardness VHN ranged from P4 50.53 to Z2 87.88. Filler weight content (Wt %) ranged from IN 72.51 to TC 79.56. Significant differences were found between the composites (ANOVA/Tukey's, P<0.05). CONCLUSION: Z2 had the highest compressive strength; Z2 and TC showed the highest elastic modulus, VHN and filler weight content. Weight filler content had a strong influence on mechanical properties (0.78<R2<0.98, P<0.01).

Resin Composite Restorations of Permanent Incisors with Crown Fractures: A Case Report with a Six-year Follow-up

Using resin composite for the restoration of permanent incisors that have crown fractures is a conservative, timely and economical treatment option. Presented in this case report is a 41-year old female patient with resin composite restorations of anterior teeth that had crown fractures. This manuscript presents the clinical success of these resin composite restorations of permanent incisors after six-years.

Comparative evaluation of marginal adaptation between nanocomposites and microhybrid composites exposed to two light cure units

Recent advances in resin adhesives and restorative materials, as well as an increased demand for esthetics, have lead to the introduction of newer resin-based composites like nanocomposites and light-curing units like light emitting diodes (LEDs). The present study was conducted to evaluate the effect of conventional quartz tungsten halogen (QTH) curing unit and blue LED on marginal adaptation of microhybrid composite (Filtek Z250) and nanocomposite (Filtek Z350) resins. Eighty Class V cavities were prepared on, extracted human premolars and were divided into four groups of 20 each. The four groups were designed according to the restorative resin and light cure unit used microhybrid/QTH, nanocomposites/QTH, microhybrid/LED and nanocomposites/LED. After thermocycling and immersion in 2% Basic Fuschin dye solution, the teeth were sectioned and dye penetration was observed under a stereomicroscope at 20X magnification. All the samples were scored and results were analyzed using the "Kruskal Wallis and Mann Whitney tests" with "Wilcoxone correction." The results revealed least microleakage in microhybrid composites exposed to QTH and maximum in nanocomposites exposed to LED. Microhybrid composites exhibited lesser microleakage than nanocomposite resins.

Effect of three different acidic beverages on surface characteristics of composite resin restorative materials

The purpose of this study was to compare the effects of different beverages upon the surface hardness, roughness and micromorphology of light cured composite resins. One microhybrid (Artemis), one nanohybrid (Grandio), one microfil (Tescera) and Filtek Silorane composite resin materials were selected for this study. Sixty-four disc shaped specimens (8 × 2 mm) of each resin composite were prepared according to manufacturers' instructions. After light curing, the specimens were polished with flexible aluminium oxide discs (Sof-Lex; 3M ESPE) under water spray and immersed in 37°C distilled water for 24 h. Sixteen specimens (half for hardness and half for roughness) were set aside to measure the initial hardness and roughness of four different composites. Baseline surface roughness Ra (in μm) measurements were taken by a surface profilometer (Mitutoyo Surfcorder/SE-40D; Kosaka Laboratory Ltd, Japan) on the top of the specimens. Baseline Vickers hardness measurements were made on the surface of eight specimens for each composite group with a Vickers hardness testing machine (Buehler OmniMet MHT1600-4980T). The remaining specimens were exposed to a dynamic pH cyclus in three different beverages (orange juice, spring water and Coca Cola) over 7 days. After a 7-day storage, samples were taken from the beverages. Specimens were subjected to post-immersion surface roughness and microhardness testing. Samples of SEM images were recorded before and after storage. Data were analysed using two-way ANOVA and Duncan's test at a significance level of 0·05. The results of this study showed that acidic drinks did not reduce the surface hardness of composite restoratives. However, for all resin composites, surface roughness measurements showed a statistically significant increase (p<0.05) after the seven days' storage. Micromorphological changes were noticed in a situation of acid challenge. This study evaluated the effect of three acidic beverages under ph cycling conditions on four composite resins after seven days' storage protocol. Microhardness and surface roughness were measured to evaluate mechanical surface properties. Surface degradation and changes were evaluated using SEM. The one-week period of storage in different beverages presented no significant deleterious alteration or softening effect on the surface of the composites, although it did have a significant effect on the surface roughness of composites. Surface degradation was observed in specimens immersed in different beverages.