Mylar Strip Research Articles

The effect of three polishing systems on surface roughness of flowable, microhybrid, and packable resin composites.

Objectives:The aim of this study was to evaluate the effects of three different polishing systems on the surface roughness of three types of resin composite materials.Materials and Methods:Three types of resin composites (Heliomolar flow, TPH spectrum, and Tetric Ceram HB) and three polishing systems (Astropol, Enhance, and Soflex) were used. A total number of 40 samples were prepared from each one of the restorative materials and divided randomly into four groups (n = 10) according to the polishing procedure. The first group underwent no treatment and was used as a control group. Each one of the remaining groups was polished with one of the tested polishing systems. After completion of sample preparation, the mean surface roughness (Ra) value was measured using a surface profilometer. Data were analyzed using one-way analysis of variance (ANOVA).Results:The control group of each material recorded the lowest Ra value. Among the tested polishing systems, the groups finished with Soflex system exhibited the lowest Ra value. Among the resin composites, Heliomolar flow exhibited the lowest Ra value, regardless of the polishing system used.Conclusions:The smoothest surface of all types of resin composite was achieved under Mylar strip.

Comparative assessment of bond strengths of affected dentin, using two different remineralizing solutions with or without lasers: Results of an in vitro pilot study

Aims: Assessing remineralization and bond strengths of remineralizing agents with or without LASERS. Settings and Design: In vitro pilot study. Materials and Methods: Artificial caries-like lesion was created with 10% citric acid in 50 non carious extracted posterior teeth which were divided into six groups according to treatment: GC Tooth Mousse and Toothmin cream with or without LASER, positive and negative control. Remineralization was done for 5 min every day for 7 days. Microhardness test was repeated. Pulsed Nd:YAG Laser (1.064 cm wavelength) was used with a focused beam at 1W and 15 Hz for 10 s on exposed dentin surface. Samples were etched with etching gel for 15 s and rinsed with water for 30 s. Bonding composite restoration of 4 mm height was done with Mylar Strip. Tensile bond strength was calculated. Statistical Analysis: Student's paired t- test evaluated difference between mean values of microhardness. Student's unpaired t -test evaluated the difference between mean values of bond strengths between groups. Results: Significant difference in microhardness in HV (50 g load) was seen in all groups ( P P = 0.0021). Conclusions: Toothmin and GC Mousse with or without LASER were found to be effective in increasing mineralization. Bond strength of Toothmin with LASER treatment was higher compared to others.

Inibição da polimerização de resinas compostas por materiais usados como matrizes oclusais

ObjectiveTo study the effect of the curing method, of the presence of oxygen and of the removal of the oxygen inhibited layer on the microhardness of the resin composite cured through oclusal matrix. MethodsComposite disks (GrandioSO, VOCO) were cured with a LED through oclusal [two polyvinylsyloxanes: Memosil 2 (Heraeus Kulzer) e Registrado Clear, (Voco) and one polyethylene: Bite‐perf (Biteperf Dental Products)] (n=10). Control groups without matrix and with a mylar strip matrix were also created. The study had three steps. On the first step, the curing method was evaluated (40seconds through the matrix; 20seconds through the matrix + 20seconds without matrix). On the second step, specimens were prepared in different atmospheres (oxygen; nitrogen). On the third step, specimens prepared with polyvinylsyloxanes were polished with acetone or rubber cup. Knoop microhardness was tested 24h after curing. Data were treated with Kruskal‐Wallis e Mann‐Whitney (p =0.05). ResultsOnly with the Bite‐perf microhardness was similar (p >0.05) to the mylar matrix group. In nitrogen, specimens from the groups with Memosil, Registrado and without matrix yielded significantly higher microhardness than the same groups in oxygen atmosphere (p <0.05). After treatment of the superficial layer, microhardness was still lower than in the mylar matrix group (p <0.05). ConclusionsCuring through the Bite‐perf for 40seconds the composite microhardness was similar to the one obtain after 20seconds curing through the mylar matrix. Composite curing through the polyvinilsiloxanes lead to an inhibited oxygen layer that was not totally removed by the methods applied in this laboratory study.

Evaluation of light curing distance and mylar strips color on surface hardness of two different dental composite resins.

Introduction: Hardness is one of the basic properties of dental materials, specially composite resins which is relevant to their polymerization. The aim of this study was to evaluate the effect of light curing distance and the color of clear Mylar strips on surface hardness of Silorane-based (SCR) and Methacrylate-based composite resins (MCR).Materials and methods: 40 samples of MCRs (Filtek Z250) and SCRs (Filtek P90) were prepared in size of 5 mm×2 mm (80 samples in total). The samples divided into 8 groups (10 samples in each one) based on the color of clear Mylar strips (white or blue) and distance from light curing source (0 mm or 2 mm). All the samples cured for 40 second and stored in incubator for 24 hours in 37°C temperature. Surface hardness test was done by Vickers test machine and the collected data were analyzed by one-way ANOVA and paired T-test by using SPSS software version 13 at significant level of 0.05.Results: MCRs cured with blue Mylar strips from 0 mm distance had the highest (114.5 kg/mm2) and SCRs cured with white Mylar strips from 2 mm distance had the lowest (42.2 kg/mm2) mean of surface hardness. Also, the results of comparison among SCRs and MCRs showed significant differences among all groups (all P values <0.01).Conclusion: The hardness decreased as the distance increased and the blue Mylar strips provided higher hardness than clear ones. Also, Filtek Z250 showed higher hardness compared to Filtek P90.

The influence of finishing/polishing time and cooling system on surface roughness and microhardness of two different types of composite resin restorations.

Objective:The aim of this study was to evaluate the effect of finishing time and polishing time on surface roughness and microhardness of nanofilled and hybrid resin composites.Materials and Methods:Hundred disk composite specimens from micro hybrid composite and nanohybrid composite were prepared, 50 for each type of composite. The specimens were divided into five groups according to the time of finishing and polishing (immediate, 15 min, 24 h and dry). Composite under the Mylar strip without finishing and polishing was taken as the control group. Surface roughness was measured with environmental scanning electronic microscope (ESEM) and microhardness was determined using Vickers Microhardness Tester. Data collected were statistically analyzed by t-test and one-way analysis of variance (ANOVA) followed by Turkey's post hoc test.Results:Smooth surface with low hardness was obtained for the group under Mylar strip without finishing and polishing. The highest roughness was recorded for delayed finishing and polishing for both composites. Immediate finishing and polishing increased the surface hardness more than that in the control group in both types of composites. Dry finishing reduced the hardness significantly for micro hybrid composite, but resulted in the highest surface hardness for nanofilled composite.Conclusion:Immediate finishing and polishing under coolant resulted in the best surface smoothness and hardness values in micro hybrid composite; however, immediate dry finishing and polishing gave the best smoothness and hardness values in nanohybrid composite.

Effects of different polishing systems on the surface roughness and microhardness of a silorane-based composite

The current study investigated the effects of different polishing systems on the surface roughness and microhardness of a silorane-based resin composite. Forty disks were fabricated (ø = 12 mm, h = 2.5 mm) of Filtek P90 (3 M ESPE, USA). The specimens were divided into four groups (n = 10), according to the polishing system: G1 - Mylar strip (control); G2 - Felt-disc + diamond paste, G3 - Sandpaper discs; G4 - Silicone tips. The specimens were stored in distilled water at 37°C for 24 h. The external surface roughness was determined through measuring the Ra of the specimens. The Vickers microhardness was measured using a microhardness tester. The values of surface roughness and microhardness of each specimen were statistically analyzed using one-way ANOVA, Games-Howell and Ryan-Einot-Gabriel-Welsch (REGW-Q), and setting the statistical significance at p ≤ 0.05. It was observed that G2 (0.42 μm) and G4 (0.43 μm) showed statistically significant differences when compared to groups G1 (0.25 μm) and G3 (0.19 μm) (p <0.05). There was no statistical difference between groups regarding microhardness (p > 0.05). The polishing systems altered the surface roughness of a silorane-based resin composite, but did not influence the microhardness values.

Effect of finishing and polishing procedures on biofilm adhesion to composite surfaces: An ex vivo study

Introduction: Surface roughness allows plaque accumulation resulting in gingival inflammation, superficial staining and secondary caries. Proper surface finishing and polishing are critical clinical procedures which enhance esthetics and longevity of restorations. This study evaluated adhesion of Streptococcus mutans biofilm on the surface of composite resin discs (nanofilled, Filtek Z350, 3M ESPE, Salt Lake City, UT, USA) after finishing and polishing by different techniques. Methodology: Sixty samples of nanofilled composite resin were prepared in a circular shaped disc- 6 mm × 2 mm and divided randomly in three groups (n = 20) for surface treatments. Control group: composite resin surface in contact with Mylar matrix strips with no finishing or polishing performed, Sof-Lex aluminum oxide disc technique and 30-blade tungsten carbide burs and silicon carbide brushes, Astrobrush. The samples were subjected to biofilm adhesion by inoculation in suitable media. The response variable was the mean CFU/mL present in the Streptococcus mutans biofilms formed on the composite resin surface. Data was statistically analyzed by three-way analysis of variance (ANOVA). Results: The Mean adhesion found in Mylar matrix strip group at 10 dilution was 74.7 ± 3.5, in Sof-Lex group was 147.3 ± 7.0 and in Astrobrush group was 149.4 ± 8.1. This difference in the mean values between the groups was found to be statistically significant (p < 0.01). Conclusion: Mylar matrix strips promoted the least bacterial adhesion, polishing with Sof-Lex aluminium oxide discs provided a smoother surface than Astrobrush and hence less bacterial adhesion than Astrobrush system.

Effects of single-peak vs polywave light-emitting diode curing lights on the polymerization of resin cement.

This study examined the effect of selecting a single-peak blue vs a polywave blue/violet emission LED curing light on the degree of conversion (DC) and Knoop microhardness (KHN) of resin cements when light cured through a ceramic disk. Two shades (A1 and A4) of resin cement (Variolink II) were placed in a 0.5-mm-thick ring. The top surfaces were covered with a Mylar strip and further covered with a disk of 1-mm-thick Empress Esthetic ceramic, shade A2. The specimens were light cured by means of an Elipar-S10 (3M ESPE, single-peak blue LED) or BluePhase-G2 (Ivoclar Vivadent, polywave blue/violet LED) curing light, both for 20 s, directly on the surface of an attenuated total reflectance FT-IR plate at 30°C. The DC of the resin was calculated after 100 s. The specimens were removed, and the Knoop microhardness was tested immediately and again after 24-h storage in the dark at 37°C and 100% humidity. Five specimens were made in each group. The DC and Knoop microhardness results were analyzed with ANOVA and Fisher's PLSD at α = 0.05. The choice of curing light had no significant effect on the DC and only a small effect on the immediate and 24-h KHN values. Shade A4 of the resin cement was harder and had a higher DC than shade A1. When light cured for 20 s, Variolink II resin cement can be light cured with either the single-peak or the polywave curing light. Shade A4 of the cement was slightly harder than A1.

Influência de diferentes matrizes oclusais na fotopolimerização de uma resina composta: análise de microdureza Knoop

ObjectiveTo evaluate the influence of three occlusal matrix materials in the light curing effectiveness of a resin composite. Furthermore, we intend to determine if the application of these materials could prevent the oxygen-inhibited layer of the composite surface. MethodsOne-hundred composite (GrandioSO, VOCO) specimens, 2mm thick, were light-cured (20seconds) with a LED curing device (800 mW/cm2) through the study materials. The specimens were divided into ten groups (n=10) according to the placed material [no interposed material, mylar strip, Registrado Clear (VOCO), Memosil-2 (Heraeus Kulzer) e Bite-perf (BITEPERF Dental Products)] and thickness / light-cure tip distance (1 and 2mm). After 24hours, Knoop microhardness tests were performed at top and bottom surfaces. The data was analyzed with a two-way MANOVA followed by the Tukey post-hoc test. Statistical testing was performed at a 0.05 level of significance. ResultsThe light-cure tip distance did not show statistical differences (p≥0.05). The mylar strip groups showed the highest (p<0.05) microhardness values on top surface. The Bite-perf groups showed lower hardness values comparing to the mylar strip groups, but higher than the other groups (p<0.05). On the bottom surface, the Bite-perf group presented the lowest values (p<0.05). There were no statistically significant differences between the other groups (p≥0.05). ConclusionsThe Bite-perf was the only material that influenced the resin composite depth of cure and the only that seems to prevent the oxygen-inhibited layer.

Effect of Different Polishing Systems and Drinks on the Color Stability of Resin Composite

The purpose of this study was to evaluate the color stability of resin composit using different finishing systems and drinks. Composit disks (5 mm diameter, 2 mm thickness) were prepared for each nanofilled composite using a brass mold. The specimens were divided into 5 finishing system groups Mylar strip (Mylar, DuPont, Wilmington, Del., USA), Soft Lex (3M(™) ESPE(™) St. Paul, MN, USA), Enhance (Dentsply-DeTrey GmbHD Konstanz, Germany), Hiluster (KerrHawe, Bioggio, Switzerland), Opti Disc (KerrHawe, Bioggio, Switzerland) and each group was divided into 10 subgroups (n = 10) and stored for 24 hours at 37°C in different drinks water coffee, coffee with sugar, tea, tea with sugar, diet coke, coke, light sour cherry juice or sour cherry juice. Color of all specimens was measured before and after exposure with a spectrophotometer using CIE L*a*b* relative, and color changes (ΔE*) were then calculated. The data were analyzed with a twoway analysis of variance (ANOVA), and mean values were compared by the Tukey HSD test (p = 0.05). For the drinks, the lowest ΔE* values were observed in the water and highest ΔE* values were observed in sour cherry juice. When drinks with and without sugar were compared, all groups with sugar demonstrated a higher color difference than without sugar. For the different finishing systems, Mylar strip group demonstrated significantly highest color change; Enhance groups demonstrated significantly lowest color change. Finishing treatments and storage solutions significantly affect the color stability of resin composite. The presence of sugar in drinks increased the color difference compared to drinks without composit. Polishing techniques and drinking drinks with sugar may affect the color of esthetic restorations.

Profilometric study to compare the effectiveness of various finishing and polishing techniques on different restorative glass ionomer cements

Objective: The aim of the present study was to evaluate the effect of various finishing and polishing techniques on the surface roughness of different types of glass ionomer (GI) restorative cements. Materials and Methods: Surface roughness of conventional, resin modified and nano-ionomer cements was evaluated after different polishing regimens. Totally 20 specimens of 12 mm thick and 10 mm diameter were prepared using Teflon mold. Prepared specimens were subjected to polishing (n = 5) by Sof-Lex discs, diamond finishing points and 30-fluted carbide burs. Control specimens did not receive any polishing treatment, but mylar trip was used as matrix. Average surface roughness (Ra) in micrometers was measured using Surtronic 3 + profilometer. Results were analyzed using Kruskal-Wallis and Mann-Whitney test. Results: Control specimens (mylar strip) showed least Ra values followed by Sof-Lex disc, carbide finishing burs and diamond finishing points with all types of glass ionomer cements used in the study. Among the GIs tested, Nano-ionomer showed least Ra followed by resin-modified GI and conventional GI. Conclusion: Mylar strip produced the smoothest surface on all the GIs tested. Nano-Ionomer showed the best polish ability with least Ra values.Clinical Relevance to Interdisciplinary DentistryGlass ionomer cements (GIC) is one of the most commonly used direct restorative material used in non-stress bearing areas especially to restore cervical lesion at tooth gingival interfacePolished GIC surface reduces plaque accumulation and thus decreases the incidence of gingival inflammation and thereby prevents periodontal problemsFinishing and polishing of the GIC enhances the longevity and color stability of the restoration.

In vitro evaluation of the effect of two finishing and polishing systems on four esthetic restorative materials

Aim:To determine the surface roughness of esthetic restorative materials after finishing and polishing.Materials and Methods:All 60 specimens were divided into four groups. Group I: Nanocomposite, Z 350 XT (3M ESPE, USA); Group II: Microhybrid composite, Z 250 (3M ESPE, USA); Group III: Compomer, Dyract XP (LD Caulk/Dentsply, USA); and Group IV: Resin modified glass ionomer cement (GIC), Fuji II LC (GC, Japan). Each group was again divided into three subgroups. Subgroup A: Sof-Lex (3M ESPE); Subgroup B: Super-Snap Rainbow finishing and polishing kit (Shofu INC, Japan); and Subgroup C: Control Mylar strip. Surface roughness was determined by Perthen Perthometer S6P profilometer.Result:Filtek Z350 XT showed minimum surface roughness followed by Filtek Z250, Dyract XT and Fuji II LC. Super-Snap exhibited less surface roughness than Sof-Lex polishing systems.Statistical Analysis:One-way analysis of variance (ANOVA) followed by multiple post hoc comparisons using least square difference method and unpaired t-test was used.Conclusion:Filtek Z350 XT with Mylar strip exhibited least surface roughness.

Effect of one-step polishing system on the color stability of nanocomposites

ObjectivesThis study was to compare the effect of three different one-step polishing systems on the color stability of three different types of nanocomposites after immersion in coffee for one day and seven days and determine which nanocomposite material has the best color stability following polishing with each of the one-step polishing system. MethodsThe nanocomposites tested were Tetric EvoCeram, Grandio and Herculite Précis. A total of 120 discs (40/nanocomposite, 8mm×2mm) were fabricated. Ten specimens for each nanocomposite cured under Mylar strips served as the control. The other specimens were polished with OptraPol, OneGloss and Occlubrush immersed in coffee (Nescafé) up to seven days. Color measurements were made with a spectrophotometer at baseline and after one and seven days. Two way repeated measure ANOVA, two way ANOVA and Bonferroni tests were used for statistical analyses (P<0.05). ResultsThe immersion time was a significant factor in the discoloration of the nanocomposites. The effect of three one-step polishing systems on the color stability was also significant. The color change values of the materials cured against Mylar strips were the greatest. The lowest mean color change values were from the Occlubrush polished groups. The effect of the three different types of nanocomposite on the color change was significant. The highest color change values were with Tetric EvoCeram groups. The lowest color change values were with Herculite Précis groups. ConclusionThe color change of nanocomposite resins is affected by the type of composite, polishing procedure and the period of immersion in the staining agent.

Influence of surface properties of resin‐based composites on in vitro Streptococcus mutans biofilm development

The aim of this in vitro study was to evaluate the influence of physicochemical surface properties of resin-based composites on Streptococcus mutans biofilm formation. Specimens were prepared from each of four resin-based composites by polymerization against Mylar strips. Half of the number of specimens received no further surface treatment, whereas the other half were subjected to a polishing treatment. Surface roughness (SR) and topography were assessed using profilometry and atomic force microscopy. Surface free-energy (SFE) was determined, and the chemical surface composition was analysed by X-ray photoelectron spectroscopy (XPS). S. mutans biofilms were formed on the surface of the resin-based composite specimens for either 48 or 96 h using an artificial mouth system (AMS). Polishing caused a significant decrease in SFE, and XPS analysis indicated an increase of surface silicon and a decrease of surface carbon. Only for Grandio was a significant increase in SR identified after polishing, which was probably related to the higher concentration of filler particles on its surface. Significantly less S. mutans biofilm formation was observed on polished resin-based composites than on unpolished resin-based composites. These results indicate that the proportions of resin matrix and filler particles on the surface of resin-based composites strongly influence S. mutans biofilm formation in vitro, suggesting that minimization of resin matrix exposure might be useful to reduce biofilm formation on the surface of resin-based composites.

The effects of finishing and polishing techniques on surface roughness and color stability of nanocomposites

ObjectivesThe aim of this in vitro study was to evaluate the effects of different finishing and polishing techniques on the surface roughness and color stability of nanocomposites. MethodsTwo nanohybrid (Grandio, Aelite Aesthetic Enamel), two nanofill (Filtek Supreme XT Dentin and Translucent), and a microhybrid (Filtek Z250) composites were used. Two hundred and eighty disc-shaped specimens were cured under a mylar strip. Seven specimens of each resin composite were randomly assigned to one of the seven polishing systems. A profilometer was used for assessing surface roughness. ΔE was calculated with a colorimeter at baseline and 48h after storage in a coffee solution. The results were analysed by two-way ANOVA and Tukey's HSD test (α=0.05). Regression analysis was used to examine the correlation between surface roughness and color stability (α=0.01). ResultsThere was no significant difference in Ra values between mylar strips and Sof-Lex polishing discs (p>0.05). The highest ΔE and Ra values were obtained from Grandio (p<0.05), and Aelite Aesthetic Enamel had the lowest ΔE values (p<0.05). The Enhance system showed the lowest color differences among all the finishing systems. The highest ΔE values were found in the composite resin groups under mylar strips and finished with diamond burs (p<0.05). ConclusionsWhile the Sof-Lex discs provided the lowest surface roughness, the Enhance Polishing system provided the most stain-resistant groups. Grandio presented the highest surface roughness and staining susceptibility after storage in coffee solution. Aelite Aesthetic Enamel, which did not include TEGDMA in its composition, showed the least discoloration. Clinical significanceThe composites with smaller filler size did not necessarily show low surface roughness and discoloration. Staining of composite resins was dependent on monomer structure, as well as surface irregularities.

Effects of polishing systems on the surface roughness of tooth-colored materials

Background/purposePolishing systems may affect the surface characteristics of the tooth-colored restorative materials. In this in vitro study, we evaluated the surface roughness of various tooth-colored restorative materials after polishing them with three different polishing systems. Materials and methodsThe tooth-colored restorative materials evaluated were conventional glass–ionomer cement, compomer, microhybrid, and nanofil composite. In total, 112 specimens (10 mm in diameter and 2 mm thick) were prepared in a metal mold using four different tooth-colored restorative materials. After the light curing and setting cycle, seven specimens from each group which received no polishing treatment were used as controls. Specimens were randomly polished with Sof-Lex disks, Poli-pro disks, and the HilusterPlus systems for 30 seconds. The mean surface roughness of each polished specimen was determined with a profilometer and examined using scanning electron microscopy. Data were analyzed using a two-way analysis of variance and Bonferroni's post-hoc multiple-comparison test, with a probability level of 0.05. ResultsAccording to the two-way analysis of variance, the type of tooth-colored materials, polishing technique, and their interactions were statistically significant (P < 0.001). The smoothest surfaces of all materials were obtained with the Mylar strip. Glass–ionomer cement demonstrated statistically significantly higher Ra values (1.36 ± 0.77) than the other restorative materials tested (P < 0.05). Compomer (0.65 ± 0.28) produced the smoothest surface and did not significantly differ from the microhybrid composite (0.78 ± 0.39; P > 0.05). No significant difference was observed between the microhybrid and nanofil composites (1.08 ± 0.83; P > 0.05). According to the scanning electron microscopy observations, the surface irregularities of the materials were consistent with the surface roughness profilometric findings. ConclusionThe effectiveness of a polishing system on the surface roughness depends on both the polishing system and restorative material.

Effects of Food-simulating Liquids on Surface Properties of Giomer Restoratives

This study examined the effects of food-simulating liquid (FSL) on the hardness and roughness of giomer restoratives based on pre-reacted glass ionomer (PRG) technology. The materials investigated included a regular (Beautifil II [BT]) and a recently introduced injectable (Beautifil Flow Plus F00 [BF]) hybrid PRG composite. A direct hybrid composite (Filtek Z250 [ZT]) and an indirect hybrid composite (Ceramage [CM]) were used for comparison. The materials were placed into customized square molds (5 mm × 5 mm × 2.5 mm), covered with Mylar strips, and cured according to manufacturers' instructions. The materials were then conditioned in air (control), distilled water, 50% ethanol solution, and 0.02 N citric acid at 37°C for seven days. Specimens (n=6) were then subjected to hardness testing (Knoop) and surface profilometry. Data were analyzed using one-way analysis of variance and post hoc Scheffe test (p<0.05). Mean Knoop hardness values for the control group (air) ranged from 53.4 ± 3.4 (BF) to 89.5 ± 5.2 (ZT), while mean surface roughness values values ranged from 0.014 ± 0.002 (ZT) to 0.032 ± 0.001 (BT). All materials were significantly softened by FSL. The degree of softening by the different FSLs was material dependent. The hardness of giomers was most affected by citric acid and ethanol. The smoothest surface was generally observed with the control group. Giomer restoratives were significantly roughened by citric acid.

Streptococcus mutans Biofilm Adhesion on Composite Resin Surfaces After Different Finishing and Polishing Techniques

This study evaluated Streptococcus mutans biofilm adhesion on the surface of three composite resins (nanofilled, Filtek Z350, 3M ESPE, Salt Lake City, UT, USA; nanohybrid, Vit-1-escence, Ultradent Products, South Jordan, UT, USA; and microhybrid, Esthet X, Dentsply, Milford, DE, USA) following different finishing and polishing techniques. Sixty standardized samples (6 × 3 mm) of each composite were produced and randomly divided into three finishing and polishing treatments (n=20): 1) control group: composite resin surface in contact with Mylar matrix strips with no finishing or polishing performed, 2) Sof-Lex aluminum oxide disc technique (3M ESPE, and 3) carbide bur finishing and Astrobrush polishing technique (Ultradent). Half the samples of each group were incubated in human saliva for 1 hour, and all the samples were subjected to S mutans (ATCC 35688) biofilm development. The mean log of CFU/mL present in the S mutans biofilm was calculated, and data were statistically analyzed by three-way analysis of variance and the Tukey test (p<0.05). Human saliva incubation promoted a significant increase of bacterial adherence on all three of the composites' surfaces, regardless of the polishing treatment performed (p<0.05). Of the three, the nanofilled composite (Filtek Z350) had the lowest bacterial adherence with each of the finishing and polishing techniques despite the presence or absence of human saliva (p<0.05). Mylar matrix strips (control group) promoted the lowest bacterial adhesion on the surface of the microhybrid and nanofilled composites in the absence of human saliva.

Flexural strength of dual cured composite resin cements polymerized with different light sources

Aim: To determine the flexural strength of dual cured composite resin cements polymerized with LED light and Quartz-tungsten halogen light and to determine the effect of curing and storage time on the flexural strength. Materials and Methods: feldspathic porcelain (IPS InLine) used to produce uniform disc-shaped specimens (10mm diameter and 1.5mm thickness ). An electronic caliper was used to confirm precise specimen dimensions. Vita shade 2A was selected. One commercial dual-polymerizing composite resin cement was used (Variolink II; Ivoclar Vivadent ). The resin cement was placed in brass molds 8 ×6× 2 mm in size that lined with a teflon used to prepared the specimens to determine flexural strength. After insertion of the resin cements a glass slab was pressed over the mold and removed any expressed materials around the margins of the mold. A mylar strip (0.07 mm) was used to prevent adhesion of the resin cement to ceramic disk. Two types of light source were used: Quartz-tungsten halogen light and LED. The specimens divided into 8 groups (10 specimens for each). For each light source the curing time done for 20 and 60 sec. and the specimens either tested 15min. after curing or after 24hrs. Measurements for the 3-point flexural strength test were performed at a constant crosshead speed of 1 mm/min. Statistical data analysis was performed by three-way ANOVA and Duncan Multiple Range Tests to determine the significant group. Results: three- way ANOVA indicated there is no statistical significant differences between the two light sources (p>0.05), were as there is statistically significance between the flexural strength of specimen cured for 60 sec. and tested after 24hrs more than other groups (p<0.05). Conclusions: adequate curing time with 60sec. and instruction for the patient not to use of the restoration until at least 24hrs after the insertion of the restoration is advocated.

Diastema closure with direct composite: architectural gingival contouring

One of the most challenging task in closing anterior diastema is avoiding “black triangle”between the teeth. This paper reports a case that the closure of diastema in anterior teeth could be successfully accomplished using direct adhesive restorations and gingival recontouring. The traditional technique using Mylar strip was modified to increase the emergence profile with natural contours at the gingival-tooth interface. Mylar strip was extended out of the sulcus by approximately 1 mm high from the gingival margin, and a small cotton pellet was used to provide the emergence contour. This modified approach is acceptable for the clinical situation. [J Kor Acad Cons Dent 2011;36(6):515-520.]