Anderson Catelan

COLOR STABILITY of SEALED COMPOSITE RESIN RESTORATIVE MATERIALS AFTER ULTRAVIOLET ARTIFICIAL AGING and IMMERSION IN STAINING SOLUTIONS

STATEMENT OF PROBLEM The color alteration of resin-based materials is one of the most common reasons to replace esthetic dental restorations. PURPOSE 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. MATERIAL AND METHODS 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 Fishers test (α=.05). RESULTS 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. CONCLUSIONS All composite resins showed some color alteration after the aging methods. The surface sealant did not alter the color stability of the tested materials.

Effect of artificial aging on the roughness and microhardness of sealed composites.

STATEMENT OF THE PROBLEM   The application of surface sealant could improve the surface quality and success of composite restorations; however, it is important to assess the behavior of this material when subjected to aging procedures. PURPOSE   To evaluate the effect of artificial aging on the surface roughness and microhardness of sealed microhybrids and nanofilled composites. MATERIALS AND METHODS   One hundred disc-shaped specimens were made for each composite. After 24 hours, all samples were polished and surface sealant was applied to 50 specimens of each composite. Surface roughness (Ra) was determined with a profilometer and Knoop microhardness was assessed with a 50-g load for 15 seconds. Ten specimens of each group were aged during 252 hours in a UV-accelerated aging chamber or immersed for 28 days in cola soft drink, orange juice, red wine staining solutions, or distilled water. Data were analyzed by two-way analysis of variance and Fischers test (α=0.05). RESULTS   Artificial aging decreased microhardness values for all materials, with the exceptions of Vit-l-escence (Ultradent Products Inc., South Jordan UT, USA) and Supreme XT (3M ESPE, St. Paul, MN, USA) sealed composites; surface roughness values were not altered. Water storage had less effect on microhardness, compared with the other aging processes. The sealed materials presented lower roughness and microhardness values, when compared with unsealed composites. CONCLUSIONS   Aging methods decreased the microhardness values of a number of composites, with the exception of some sealed composites, but did not alter the surface roughness of the materials. CLINICAL SIGNIFICANCE The long-term maintenance of the surface quality of materials is fundamental to improving the longevity of esthetic restorations. In this manner, the use of surface sealants could be an important step in the restorative procedure using resin-based materials.

In Vitro Evaluation of Surface Roughness and Microhardness of Restorative Materials Submitted to Erosive Challenges

The aim of this study was to evaluate the effect of different acidic solutions on the microhardness and surface roughness of restorative materials. The 120 specimens of restorative materials (Fuji II LC, Vitremer, Supreme XT, and Supreme XT + Biscover LV) were randomly divided into three groups according to the immersion media: hydrochloric acid, soft drink, or distilled water. Over a period of five weeks, the groups were immersed in the solutions, which were changed weekly. Data were tested using analysis of variance and the Fisher protected least significant difference test (p<0.05). The results showed that the glass ionomer materials showed the highest surface roughness values (Fuji II LC: 0.111 ± 0.014 μm before and 0.139 ± 0.016 μm after immersion; Vitremer: 0.177 ± 0.012 μm before and 0.084 ± 0.012 μm after immersion), whereas the lowest values were found for the resin sealed with Biscover LV before (0.047 ± 0.011 μm) and after exposure in distilled water (0.043 ± 0.007 μm), soft drink (0.040 ± 0.005 μm), and hydrochloric acid (0.045 ± 0.005 μm). The Supreme XT showed the highest microhardness values before (44.96 ± 2.51 KHN) and after the aging process (41.26 ± 1.22 KHN in water, 35.96 ± 0.81 KHN in soft drink, and 34.74 ± 0.97 KHN in HCl), with significant differences from the other materials (p<0.0001). The lowest microhardness values were found for glass ionomer materials. The solutions used in this study decreased the microhardness of all studied materials, whereas the sealed surface suffered minor changes in microhardness and surface roughness after exposure to acidic solutions.

Influence of extended light exposure time on the degree of conversion and plasticization of materials used as pit and fissure sealants

AIM To evaluate the conversion and plasticization of fissure sealer materials, as influenced by extended curing time. METHODS Twenty specimens (n=5) of a pit and fissure sealant and a flowable composite at two curing times (20 and 60 sec) were photocured with the Bluephase 16i light-emitting diode. The conversion was determined by Fourier transform infrared/attenuated total reflection spectroscopy 24 h after polymerization. Hardness was measured, and samples were stored in absolute ethanol for 24 h. A second hardness measurement was executed after storage to assess plasticization by the percentage of hardness decrease. Data were analyzed by analysis of variance and Pearsons correlation (α=0.05). RESULTS The pit and fissure sealant showed lower degree of conversion than the flowable composite. The 60-sec curing time increased the conversion only for the flowable composite. Plasticization was lower for the flowable composite than for the pit and fissure sealant. The 60-sec light exposure time showed a similar percentage of hardness decrease of 20 sec. A low correlation between the conversion and plasticization was found. CONCLUSION Extended curing time improved the conversion only for the flowable composite. The pit and fissure sealant presented lower conversion and higher plasticization than the flowable composite.

Microtensile bond strength of resin cements to caries-affected dentin

STATEMENT OF PROBLEM The bonding of resin materials to caries-affected dentin, especially self-adhesive cements, remains a challenge in dentistry. PURPOSE The purpose of this study was to evaluate the bond strength of different resin cements to sound or caries-affected dentin at 24 hours and 6 months after the bonding procedure. MATERIAL AND METHODS Thirty-six human molars were used, 18 sound and 18 affected by caries. Indirect composite resin blocks (Tescera) were bonded to dentin by using 3 different resin cements: RelyX ARC, Panavia F, and RelyX Unicem. A universal testing machine was used to measure the microtensile bond strength 24 hours and 6 months after the bonding procedure. Representative specimens were analyzed with a scanning electron microscopy. The results were submitted to 3-way analysis of variance and the Fisher test (α=.05). RESULTS The highest values of microtensile bond strength were found with RelyX ARC for both tooth conditions (P<.001). There was no difference between RelyX Unicem and Panavia F (P>.05). There was no difference between caries-affected and sound dentin (P=.89). CONCLUSIONS Caries did not influence the bonding strength of resin cements to dentin.

Effect of light curing modes on mechanical properties of direct and indirect composites

Abstract Objective. To evaluate the degree of conversion (DC), flexural strength (FS) and Knoop microhardness (KHN) of direct and indirect composite resins polymerized with different curing systems. Materials and methods. Specimens of direct (Z250, 3M/Espe) and indirect (Sinfony, 3M/Espe) restorative materials were made and polymerized using two light curing units: XL2500 (3M/Espe) and Visio system (3M/Espe). Absorption spectra of both composites were obtained on a FTIR spectrometer in order to calculate the DC. FS was evaluated in a universal testing machine and surface microhardness was performed in a microhardness tester (50gf/15s). DC, FS and KHN data were submitted to two-way ANOVA and Tukeys test (α = 0.05). Results. Z250 showed higher DC, FS and KHN compared with Sinfony when the polymerization was carried out with XL2500 (p < 0.05). However, there is no statistical difference in DC between the materials when Visio was used (p > 0.05). Visio showed higher DC and KHN for Z250 and Sinfony than the values obtained using XL2500 light curing (p < 0.05). For FS, no significant difference between curing units was found (p > 0.05). Conclusion. Even though the Visio system could increase DC and KHN for some direct and indirect composites, compared with the conventional halogen curing unit, a high number of monomers did not undergo conversion during the polymerization.

The effect of surface treatment and bonding procedures on the bond strength of silorane composite repairs

Abstract Objective. The aim of this study was to evaluate the effect of surface treatments and adhesive protocols on the microtensile bond strength of a low-shrinkage composite repair. Materials and methods. Ninety-six blocks of composite resin Filtek LS were prepared using a half-hourglass-shaped silicone matrix. The specimens were storage for 24 h in distilled water and were randomly divided into the experimental (6) and negative control (2) groups (n = 12) according to the surface treatment (diamond bur and aluminum oxide sandblasting) and adhesive protocol (none; Filtek LS adhesive; phosphoric acid + Filtek LS adhesive; and phosphoric acid + silane + Filtek LS adhesive). After the adhesive procedure, the specimens were fixed in an hourglass-shaped silicone matrix and the other half of the specimen was restored. Hourglass shaped specimens (n = 12) were used as positive control (cohesive strength of the resin). The microtensile bonding test was performed at a crosshead speed of 0.5 mm/min. The data were analyzed using ANOVA, Tukeys and Dunnetts tests (α = 0.05). Results. The bond strength values were similar for all experimental groups, except the groups without adhesive application. None of the experimental groups presented results similar to the positive control group. Conclusions. The repair of silorane restorations is viable; nevertheless, the different bonding procedures tested were incapable to produce bond strengths similar to the cohesive strength of the material.

Effect of light curing protocol on degree of conversion of composites

Abstract Objective. To evaluate the degree of conversion (DC) of two light-cured composites with different protocols of light curing. Materials and methods. One hundred and ninety two specimens (n = 8) were prepared (5 mm × 2 mm) according to experimental groups: two composite resins (Filtek Supreme and four seasons); three light curing protocols [20 s with the tip of the light curing unit (LCU) device touching composite surface (C); 20 s with the tip of the LCU at 8 mm distant from composite surface (D); and tip of the LCU at 8 mm distant from composite surface and polymerization time required to obtain a radiant exposure of 16 J/cm2 (DS)]. Four LCUs (Bluephase 16i, Ultralume LED 5, XL 3000 and Optilux 501C) were used. DC of the bottom and top surface of specimens were measured using a FTIR spectrometer. Data were statistically analyzed by 3-way split splot ANOVA and Tukey’s test (alpha = 0.05). Results. The results showed that DC of the top surface was higher than the bottom at all experimental conditions (p < 0.0001). Overall, the curing at 8 mm of distance did not affect conversion rate on the top surface (p > 0.05), but bottom surfaces showed DC reduction (p < 0.05). The highest monomer conversion values were observed for C and DS situations. Conclusion. The distance between the LCU and material surface and radiant exposure can affect the DC. Polymerization at distance should be performed with curing units with higher light power and/or extended exposure time.

Impact of the distance of light curing on the degree of conversion and microhardness of a composite resin

Abstract Objective. This study evaluated the impact of the distance between the light guide tip of the curing unit and material surface on the degree of conversion and Knoop microhardness of a composite resin. Materials and methods. Circular samples were carried out of a methacrylate micro-hybrid resin-based composite and light cured at 0, 2 and 4 mm distance. Monomer conversion rate was measured using a Fourier-transform Raman spectrometer and Knoop hardness number was obtained using a microhardness tester on the top and bottom surfaces. Data were statistically analyzed by analysis of variance and Tukey’s test (α = 0.05). Results. Overall, the increase of curing distance reduced the microhardness (p ≤ 0.05), but did not influence the carbon double bond conversion rate (p > 0.05) of the composite resin tested; and the top surface showed better properties compared to the bottom (p ≤ 0.05). Conclusions. The light curing at distance can reduce mechanical properties and could affect long-term durability of the composite restorations. Thus, the use of a curing device with high irradiance is recommended.

Effect of thermocycling on roughness of nanofill, microfill and microhybrid composites

Abstract Objective. This study aimed to investigate the surface roughness of composite resins subjected to thermal cycles procedure. Materials and methods. Two microfill, four microhybrid and four nanofill composites were used. The surface roughness (Ra) was initially measured in a profilometer using a cut-off 0f 0.25 mm, after 3000 and 10,000 thermal cycles. Data were subjected to ANOVA and Fischer’s test (α = 0.05). Results. Overall, 3000 thermal cycles increased the surface roughness values for all materials and there was a trend in all groups to decrease the roughness after 10,000 thermal cycles. Conclusions. The composition of material, including the type of organic matrix, could be more relevant to roughness maintenance over time than the general behavior of composites based on particles fillers. The maintenance of smooth surface in resin-based composite restorations is totally dependent of organic composition of the material.