Effect of sodium metabisulfite gel on the bond strength of dentin of bleached teeth.

OBJECTIVE: This study aimed to evaluate the effect of the application of sodium metabisulfite (SMB) on the bond strength of bleached teeth. MATERIALS AND METHODS: The study was divided into two parts. The first part evaluated the application of various concentrations of SMB for 1 h prior to the completion of bonding procedures. Fifty blocks were divided into five groups (n = 10): control; bleaching with 35% hydrogen peroxide (HP); HP + 5% SMB; HP + 12.5% SMB; and HP + 25% SMB. The second part evaluated the application of 25% gel SMB to either enamel or dentin, including the application time. Sixty blocks were divided into six groups (n = 10): control; bleaching with 35% HP; HP + 25% SMB for 1 h in enamel; HP + 25% SMB for 1 h in dentin; HP + 25% SMB for 10 min in enamel; and HP + 25% SMB for 10 min in dentin. STATISTICAL ANALYSIS: Following the completion of microshear bond testing, data were analyzed using one-way analysis of variance as well as Tukey's and Dunnett's tests. RESULTS: In part 1, data analysis revealed statistical differences (P < 0.0001) between HP and HP + 5% SMB. No statistical differences were found between the control and both HP + 12.5% SMB and HP + 25% SMB. Part 2 revealed a statistical difference (P = 0.001359) only between the bleached group and others. CONCLUSIONS: The use of 25% SMB gel immediately after bleaching was able to reverse the deleterious effect of bleaching on the bond strength of dental composites to dentin.

Tooth enamel properties and morphology after microabrasion: an in situ study.

AIM: This study evaluated the effect of saliva on enamel after microabrasion with different microabrasive compounds under in situ conditions. METHODS: Enamel/dentin blocks (16 mm2 ) from bovine incisors were divided into nine groups (n = 19): one control group (no treatment), four groups treated with microabrasion using 35% phosphoric acid (H3 PO4 ) + pumice, and the last four groups treated with microabrasion using 6.6% hydrochloric acid (HCl) + silica. The treated groups were subdivided according to the in situ regimen: without salivary exposure, 1 h, 24 h, or 7 days of saliva exposure. Surface microhardness (SMH) and cross-sectional microhardness (CSMH) were tested. Scanning electron microscopy (SEM) was used to evaluate enamel morphology. Microhardness data were tested by analysis of variance, and Tukey's and Dunnett's tests (α = 0.05). RESULTS: The SMH analysis revealed that all the microabrasion-treated groups presented significantly-reduced SMH values when compared to the control group (P < 0.05). Treatment with HCl + silica was more prone to the effect of saliva than H3 PO4 + pumice, even for CSMH analysis, once the superficial layers reached the same microhardness of that of the control group (P > 0.05). These results were confirmed by SEM, which demonstrated the mineral recovery effect over time. CONCLUSION: Saliva was effective in promoting the rehardening of enamel after microabrasion, mainly for the surfaces treated with HCl + silica.

Influence of Enamel Thickness on Bleaching Efficacy: An In-Depth Color Analysis.

This study evaluated the influence of different enamel thicknesses and bleaching agents on treatment efficacy in-depth by spectrophotometry color analysis. Eighty bovine dental fragments were previously stained in black tea solution and randomly assigned into eight groups (n=10), 1.75mm dentin thickness and different enamel thicknesses as follows: 0.5mm, 1.0mm planned, 1.0mm unplanned (aprismatic enamel), and absence of enamel. The 10% carbamide peroxide (CP) and 35% hydrogen peroxide (HP) bleaching gels were applied on the enamel surface following the manufacturer's recommendations. Color of underlying dentin was evaluated at four times: after staining with tea (baseline) and after each one of the three weeks of bleaching treatment, by CIE L*a*b* system using reflectance spectrophotometer (CM 700d, Konica Minolta). The ΔE, ΔL, Δa, and Δb values were recorded and subjected to repeated measures ANOVA and Tukey's test (α=0.05). The results showed an increase on lightness (L*), with decreased redness (a*) and yellowness (b*). At first and second week, bleaching with CP showed higher whitening effectiveness compared to bleaching with HP and the presence of aprismatic enamel significantly reduced ΔE for bleaching with CP. After three weeks of bleaching, few differences were observed between CP and HP groups, and outer enamel layer caused no influence on bleaching effectiveness. Overall, both at-home and in-office bleaching treatments were effective and the presence of aprismatic enamel did not interfere on the whitening efficacy.

Effects of acids used in the microabrasion technique: Microhardness and confocal microscopy analysis.

BACKGROUND: This study evaluated the effects of the acids used in the microabrasion on enamel. MATERIAL AND METHODS: Seventy enamel/dentine blocks (25 mm2) of bovine incisors were divided into 7 groups (n=10). Experimental groups were treated by active/passive application of 35% H3PO4 (E1/E2) or 6.6% HCl (E3/E4). Control groups were treated by microabrasion with H3PO4+pumice (C5), HCl+silica (C6), or no treatment (C7). The superficial (SMH) and cross-sectional (CSMH; depths of 10, 25, 50, and 75 µm) microhardness of enamel were analyzed. Morphology was evaluated by confocal laser-scanning microscopy (CLSM). Data were analyzed by analysis of variance (Proc Mixed), Tukey, and Dunnet tests (α=5%). RESULTS: Active application (E1 and E3) resulted in higher microhardness than passive application (E2 and E4), with no difference between acids. For most groups, the CSMH decreased as the depth increased. All experimental groups and negative controls (C5 and C6) showed significantly reduced CSMH values compared to the control. A significantly higher mean CSMH result was obtained with the active application of H3PO4 (E1) compared to HCl (E3). Passive application did not result in CSMH differences between acids. CLSM revealed the conditioning pattern for each group. CONCLUSIONS: Although the acids displayed an erosive action, use of microabrasive mixture led to less damage to the enamel layers. KEY WORDS: Enamel microabrasion, enamel microhardness, confocal laser scanning microscopy.

Effects of Bleaching Agents Combined with Regular and Whitening Toothpastes on Surface Roughness and Mineral Content of Enamel.

OBJECTIVE: The purpose of this study was to evaluate surface roughness and changes in the composition of enamel submitted to different bleaching protocols and toothbrushing with regular and whitening toothpastes. BACKGROUND DATA: Bleaching treatment could promote morphological and chemical changes in enamel surface. METHODS: Enamel blocks were randomized into nine groups (n=10) according to the bleaching treatment (no bleaching, control group; 6% hydrogen peroxide, HP; or 10% carbamide peroxide, CP) and toothpaste used (placebo, PL; regular, R; or whitening dentifrice, W). Bleaching was performed according to manufacturers' instructions and all groups were submitted to 30,000 cycles of simulated toothbrushing with toothpaste (PL, R, or W). Mineral content evaluation and enamel roughness were evaluated initially (T1), after bleaching (T2), and after toothbrushing (T3), using an energy-dispersive micro X-ray fluorescence spectrometer and profilometry, respectively. Data were statistically analyzed with two way ANOVA, Tukey, and Dunnett tests (5%). RESULTS: Enamel surface roughness was influenced by bleaching and toothbrushing. Surface roughness increased for the groups that brushed with the placebo dentifrice (CP+PL, HP+PL, C+PL) and for the control group that brushed with whitening dentifrice (C+W). Enamel Ca/P ratio decreased after bleaching, but toothbrushing, regardless of the dentifrice used, did not reduce the enamel mineral content. CONCLUSIONS: The bleaching treatment resulted in a decrease of enamel mineral content, but the studied dentifrices did not contribute to surface mineral loss.

In vitro effects of hydrogen peroxide combined with different activators for the in-office bleaching technique on enamel.

OBJECTIVE: The aim of this study was to evaluate the alteration of human enamel bleached with high concentrations of hydrogen peroxide associated with different activators. MATERIALS AND METHODS: Fifty enamel/dentin blocks (4 × 4 mm) were obtained from human third molars and randomized divided according to the bleaching procedure (n = 10): G1 = 35% hydrogen peroxide (HP - Whiteness HP Maxx); G2 = HP + Halogen lamp (HL); G3 = HP + 7% sodium bicarbonate (SB); G4 = HP + 20% sodium hydroxide (SH); and G5 = 38% hydrogen peroxide (OXB - Opalescence Xtra Boost). The bleaching treatments were performed in three sessions with a 7-day interval between them. The enamel content, before (baseline) and after bleaching, was determined using an FT-Raman spectrometer and was based on the concentration of phosphate, carbonate, and organic matrix. Statistical analysis was performed using two-way ANOVA for repeated measures and Tukey's test. RESULTS: The results showed no significant differences between time of analysis (p = 0.5175) for most treatments and peak areas analyzed; and among bleaching treatments (p = 0.4184). The comparisons during and after bleaching revealed a significant difference in the HP group for the peak areas of carbonate and organic matrix, and for the organic matrix in OXB and HP+SH groups. Tukey's analysis determined that the difference, peak areas, and the interaction among treatment, time and peak was statistically significant (p < 0.05). CONCLUSION: The association of activators with hydrogen peroxide was effective in the alteration of enamel, mainly with regards to the organic matrix.

Enamel microabrasion: An overview of clinical and scientific considerations.

Superficial stains and irregularities of the enamel are generally what prompt patients to seek dental intervention to improve their smile. These stains or defects may be due to hypoplasia, amelogenesis imperfecta, mineralized white spots, or fluorosis, for which enamel microabrasion is primarily indicated. Enamel microabrasion involves the use of acidic and abrasive agents, such as with 37% phosphoric acid and pumice or 6% hydrochloric acid and silica, applied to the altered enamel surface with mechanical pressure from a rubber cup coupled to a rotatory mandrel of a low-rotation micromotor. If necessary, this treatment can be safely combined with bleaching for better esthetic results. Recent studies show that microabrasion is a conservative treatment when the enamel wear is minimal and clinically imperceptible. The most important factor contributing to the success of enamel microabrasion is the depth of the defect, as deeper, opaque stains, such as those resulting from hypoplasia, cannot be resolved with microabrasion, and require a restorative approach. Surface enamel alterations that result from microabrasion, such as roughness and microhardness, are easily restored by saliva. Clinical studies support the efficacy and longevity of this safe and minimally invasive treatment. The present article presents the clinical and scientific aspects concerning the microabrasion technique, and discusses the indications for and effects of the treatment, including recent works describing microscopic and clinical evaluations.

In situ assessment of the saliva effect on enamel morphology after microabrasion technique

AIM: This study evaluated saliva effects on enamel morphology surface after microabrasion technique. METHODS: Enamel blocks (16 mm2) obtained from bovine incisors were divided into 9 groups as follows: one control group (no treatment), four groups with microabrasion treatment using 35% phosphoric acid and pumice (H3PO4+Pum) and other four groups treated with 6.6% hydrochloric acid and silica (HCl+Sil). One group of each treatment was submitted to 4 frames of saliva exposure: without exposure, 1-h exposure, 24-h exposure, and 7-days exposure on in situ regimen. Nineteen volunteers (n=19), considered as statistical blocks, used an intraoral appliance containing the specimens, for 7 days. Enamel roughness (Ra) was tested before and after treatment, and after saliva exposure. Confocal laser scanning microscopy (CLSM) was used to evaluate qualitatively the enamel morphology. RESULTS: All groups exhibited increased Ra after microabrasion. With regards to saliva exposure, the treatment with HCl+Sil presented more susceptibility to the saliva action, but no period of time was efficient in re-establishing this characteristic compared with the control group. CLSM analysis showed reduction of the micro-abrasive damages during the experimental times. CONCLUSIONS: Seven days of saliva exposure were not sufficient for the treated enamel to reach its normal characteristics compared with the control group...

Effect of light polymerization time, mode, and thermal and mechanical load cycling on microleakage in resin composite restorations.

This study evaluated the effect of polymerization mode and time and thermal and mechanical loading cycling (TMC) on microleakage in composite resin restorations. One hundred and eighty cavities were prepared and randomly divided according to the light curing time (20, 40, or 60 s), modes (quartz-tungsten-halogen (QTH)-420 mW/cm(2), LED 2 (2nd degree generation)-1,100 mW/cm(2), or LED 3 (3rd degree generation)-700 mW/cm(2)), and TMC. Following standard restorative procedures, the samples were prepared for analysis in an absorbance spectrophotometer. All results were statistically analyzed using the three-way ANOVA and Tukey test (p ≤ 0.05). The results revealed that the groups QTH and LED 3 submitted to TMC showed higher microleakage than those that were not submitted to TMC. Only for LED 3, 60 s showed higher microleakage than 20 s. For LED 2 and QTH, there were no differences between the times. QTH showed lower microleakage means than LED 2, when photoactivated for 20 s, without TMC. When photoactivated for 60 s, QTH showed lower microleakage means than LED 3, for the groups with or without TMC. It was concluded that TMC, the increase in polymerization time, and the irradiance were factors that may increase the marginal microleakage of class II cavities.

Effect of curing light distance and different mouthwashes on the sorption and solubility of a nanofilled composite.

The aim of this in vitro study was to evaluate the sorption (Sp) and solubility (Sl) of a nanofilled composite (Filtek™ Z350) light-activated from the top in three curing light distances (0 mm, 3 mm and 6 mm) and immersed in three different mouthwashes (Plax Fresh Mint, Plax Alcohol Free, and Plax Whitening). Specimens (6 mm Ø and 1 mm height) were prepared (n = 5) and initially the degree of conversion (DC%) of discs was obtained by using a fourier transform infrared spectrometer. Then, the specimens were placed in a desiccator at 37°C and were weighed until a constant mass (m1) was obtained. The discs were immersed in the mouthwashes for 30 days. Twice a day, the samples were immersed in 2 ml of the mouthwashes (12 hr intervals). After the 30-day period, the discs were reweighed (m2). The reconditioning in the desiccator was done until a constant mass (m3) was obtained. The data of DC% were analyzed by analysis of variance (ANOVA) in split plots and the results showed statistical difference when photoactivated to 6 mm from the tip of the curing unit. The sorption data were submitted to two-way ANOVA and Tukey's Test at a 5% level of significance and it was observed that a statistical difference (P < 0.05) was only cured when the distance was 6 mm, but there was no difference in sorption between mouthwashes. The solubility data were analyzed by Kruskal-Wallis's Test (P = 0.05) and Dunn's Test, since a non-normal data distribution was observed. The values were negative, which means that there was a mass gain, masking the real solubility.

Influence of coffee and red wine on tooth color during and after bleaching.

OBJECTIVE: The aim of this study was to evaluate the influence of coffee and red wine staining on tooth color during and after bleaching. MATERIALS AND METHODS: Blocks obtained from human molars were divided into 11 groups (n = 5) in accordance with the bleaching treatment-peroxide carbamide 10%, 15% or 20%-and in accordance with the stain therapy-coffee, wine or without staining (control). Color change analysis was performed by photo-reflectance using a spectrophotometer, during (3-times/week) and after (7, 15 and 30 days) the bleaching treatment. During the experiment, the samples were stored in artificial saliva. The results were submitted to statistical analysis with the Dunnet and Tukey tests (p < 0.05). RESULTS: The concentrations of carbamide peroxide (10%, 15% and 20%) did not differ significantly from the control group during bleaching (up to the 22nd day), with (Tukey, p > 0.05) or without storage in pigment solution. After the bleaching, there were statistically significant differences between the groups treated with coffee (30th day) and wine (7th and 30th days) relative to the control, which was treated with whitening agents. CONCLUSION: During bleaching, remineralization of the enamel with artificial saliva and the subsequent bleaching session were effective in preventing enamel staining. After the whitening procedures, both stain therapies-coffee and wine-caused enamel color changes; however, the wine led to greater staining than did coffee.

Contorno cosmético: estética sem restauração / Cosmetic contour: esthetic without restoration

O desgaste irregular dos dentes, especialmente dos anteriores, além de uma diversidade de formatos anatômicos, pode acarretar em desarranjos estéticos do sorriso. Dessa forma, o contorno cosmético é um procedimento estético que implica em desgaste irreversível da estrutura dentária com pontas diamantadas e discos de acabamento, visando corrigir os parâmetros de estética e reflexão da luz dos dentes anteriores e pré-molares. Nesse sentido, todos os passos para a realização do contorno cosmético são críticos e de extrema importância. O objetivo desse artigo é apresentar, através do relato de um caso clínico, a confecção de uma remodelação cosmética do sorriso guiada por princípios de ilusão de óptica baseados em mínimos desgastes em esmalte dentário, garantindo uma previsibilidade estética do sorriso

Irregular dental wear, especially from the anterior teeth, and the various anatomic shapes can lead to an esthetic breakdown of the smile. So, cosmetic contouring is an esthetic approach which implies irreversible dental abrasion by diamond burs and fnishing disks in order to correct the esthetic parameters and light reflection of anterior teeth and pre-molars. In this sense, all steps for the cosmetic contouring procedure are critical and very important. The aim of this work was to present a case report that shows the cosmetic smile remodeling guided by principles of optical illusion based on minimal dental abrasion, ensuring a predictable esthetic smile.

Evaluation of ultrasound and light sources as bleaching catalysts - an in vitro study.

PURPOSE: To evaluate the efficacy of tooth bleaching with high concentration agents, varying the catalyst sources and exposure times. MATERIALS AND METHODS: Stained human third molar fragments were randomized and placed into 8 groups (n = 5). G1: Whiteness HP Maxx (FGM, Joinville, SC, Brazil) 35% (HP)/5 min on enamel surface without external catalyst source; G2: HP/15 min without external catalyst association; G3: HP/5 min with Quartz Tungstein Halogen (QTH: Optilux 501C, Demetron/Kerr, Danbury, CT, USA) as a catalyst; G4: HP/15 min with QTH as a catalyst; G5: HP/5 min with LED/laser as a catalyst; G6: HP/15 min with LED/ laser as a catalyst; G7: HP/5 min with ultrasound as a catalyst; G8: HP/15 min with ultrasound as a catalyst. The efficacy of bleaching was measured using a spectrophotometer (initial fotoreflectance analysis, after artificial staining with black tea, and after each of the bleaching sessions). Three bleaching sessions were performed. Data were submitted to Analysis of Variance and Tukey-Kramer tests (P < 0.05). RESULTS: No significant differences were found between the catalyst sources as related to the factor of exposure time and within each evaluation time. For the 15 min exposure, the best result was achieved in the second bleaching session, except for the LED/laser group. For the 5 min exposure, the best result was achieved in the third session, except for ultrasound. The 15 min of exposure time showed higher reflectance than 5 min for LED/laser and ultrasound in all bleaching sessions and for halogen in the second bleaching session. CONCLUSION: Light sources did not increase the catalytic efficiency of bleaching, and allowing a longer time for gel exposure on the enamel achieves faster results.

Influence of previous acid etching on interface morphology and bond strength of self-etching adhesive to cavosurface enamel.

OBJECTIVES: The aim of this study was to evaluate the (1) bond strength of a etch-and-rinse and self-etching adhesive systems to cavosurface enamel, (2) influence of the previous acid etching with phosphoric acid 35% to the self-etching adhesive application on bond strength values, and (3) analysis of the cavosurface enamel morphology submitted to different types of conditioning, with the use of a scanning electronic microscope (SEM). METHODS: Twenty four human third molars were sectioned on mesio-distal direction, resulting in two slices. The specimens were ground flat with 600-grit aluminum oxide papers, and were randomly divided into three groups: Group 1 (etch-and-rinse adhesive system (control group)), Group 2 (self-etching adhesive), and Group 3 (self-etching adhesive with previous 35% phosphoric acid-etching for 15 s). Four cylinders (0.75 mm of diameter, 1 mm height) were confectioned prior to the microshear test. Four samples for each group were prepared according the cavosurface enamel treatment and were analyzed in an SEM. RESULTS: Group 3 had the highest values on bond strength to cavosurface enamel compared to the other two groups, which presented statistically similar values. The performance of acid etching before the application of the self-etching adhesive results in an etching pattern that is different than the other groups, favoring the adhesion to the cavosurface enamel. CONCLUSIONS: Acid etching increases the bond strength values of the self-etching adhesive to cavosurface enamel, promoting a conditioning pattern that favors the adhesion to this substrate.

Esthetic and functional rehabilitation via reattachment of dental fragments.

Anterior teeth fractures are frequently encountered in clinical practice. The reattachment of dental fragments, if possible, is a conservative and effective technique, which is utilized in this case. This case presentation concerns an 18-year-old male patient with a root-crown fracture of the left maxillary central incisor, which involves the periodontal biologic space. The treatment was the reattachment of the dental fragment with a composite resin and adhesive, in association with periodontal surgery. The reattachment technique described in this case report is simple, but it provides long-lasting esthetics and improved function via a very conservative approach.

Advances in dental veneers: materials, applications, and techniques.

Laminate veneers are a conservative treatment of unaesthetic anterior teeth. The continued development of dental ceramics offers clinicians many options for creating highly aesthetic and functional porcelain veneers. This evolution of materials, ceramics, and adhesive systems permits improvement of the aesthetic of the smile and the self-esteem of the patient. Clinicians should understand the latest ceramic materials in order to be able to recommend them and their applications and techniques, and to ensure the success of the clinical case. The current literature was reviewed to search for the most important parameters determining the long-term success, correct application, and clinical limitations of porcelain veneers.

Microhardness of nanofilled composite resin light-cured by LED or QTH units with different times

Aim: To evaluate the influence of light-curing units and light-curing time on the microhardness of a nanofilled composite resin. Methods: Forty-five composite resin (Z350 - 3M) specimens were randomly prepared using Teflon ring molds (4.0 mm internal diameter and 2 mm depth) and divided into nine experimental groups (n=5): three polymerization units (conventional - 450 mW/ cm2; 2nd generation LED - 1100 mW/cm2; and 3rd generation LED - 700 mW/cm2) and three lightcuring times (20 s, 40 s, and 60 s). All specimens were polymerized with the light-curing tip positioned 8 mm far from the top surface of the specimen. After 24 h, Knoop microhardness measurements were made on the top and bottom surfaces of the specimen, with a load of 10 g for 10 s. Five indentations were made on each surface. All results were analyzed statistically by subdivided parcel ANOVA (Split-Plot) and Tukey's tests (p<0.05). Results: There were no statistically significant differences for the polymerization unit and light-curing time factors in either top or bottom surface. For all experimental conditions, the top surfaces showed greater hardness than the bottom surfaces (p<0.0001). Conclusions: The mode of polymerization and the lightcuring time did not affect the hardness of the nanofilled composite resin, and increasing the lightcuring time did not improve the hardness of the bottom surface of the composite resin.

Effect of surface sealants on microleakage of Class II restorations after thermocycling and long-term water storage.

PURPOSE: To evaluate interface degradation leading to marginal microleakeage in Class II restorations that had received an application of surface sealant at the tooth/restoration interface or not. MATERIALS AND METHODS: Eighty bovine incisors were used, and the teeth were split obliquely, 10 mm from the amelodentinal proximal junction, and finished with water abrasive papers to obtain a smooth, flat incisal surface. Cavities were made to simulate Class II preparations (8 mm high, 4 mm wide and 1.5 mm deep), and the restorations were performed with a composite resin. Teeth were then randomly allocated into 8 groups according to the surface sealant (none, Fortify, Single Bond 2, or Scothbond MP Plus) and aging process (none or thermocycling and storage for 6 months). Microleakage was then evaluated using a dye penetration method immediately after the restoration or after aging. The samples were triturated and assessed by spectrophotometer. RESULTS: Microleakage was statistically similar in all groups when assessed immediately after the restorative procedure. After aging, teeth sealed with Fortify presented better results than the other groups. CONCLUSION: Aging causes interface degradation and increased microleakage. Surface sealant can reduce these effects and decrease microleakage in Class II restorations.

Effects of mouthwashes on Knoop hardness and surface roughness of dental composites after different immersion times.

The aim of this in vitro study was to evaluate the effect of different mouthwashes on superficial roughness and Knoop hardness of two resin composites. Eighty specimens (6 mm Ø and 2 mm height) were prepared and divided into eight experimental groups (n = 10) according to the resin composites (4 Seasons and Esthet X), and storage solutions (G1 - Distilled water; G2 - Colgate Plax Overnight; G3 - Colgate Plax Alcohol Free; and G4 - Colgate Plax Whitening). The initial hardness and roughness readings (T1) were measured and then the specimens were stored in 2 mL of mouthwash for 12 h (T2) and 24 h (T3). The data were analyzed with repeat-measures two-way ANOVA and Tukey's test (α = 5%). Regardless of the type of solution and time of exposure, there was no statistical difference for roughness between the resins (p = 0.44). G4 and G8 presented higher roughness means than G1, G3, G5 and G7, after 12 and 24 hours of immersion. For Knoop microhardness analysis, there was a significant reduction for all groups after 12 hours and 24 hours. We conclude that the mouthwashes containing hydrogen peroxide and/or alcohol decrease the microhardness of the resins tested; however, the mouthwash containing hydrogen peroxide had a higher deleterious effect on roughness.

Effect of different light-curing modes on degree of conversion, staining susceptibility and stain's retention using different beverages in a nanofilled composite resin.

STATEMENT OF PROBLEM: It is unknown whether the staining pigment concentration would affect the color of composite resin and whether the absorption of the staining pigment is related to the degree of conversion (DC). PURPOSE: The purpose of this study was to evaluate the effect of light-curing units (LCUs) on DC, superficial staining (ΔE), and pigment concentration (PC) in a nanofilled composite resin (Z350, 3M ESPE) using different beverages. MATERIALS AND METHODS: Specimens were polymerized for 20 seconds using four LCUs (N=50): quartz-tungsten-halogen (QTH)--450 mW/cm(2); laser (LAS)--300 mW/cm(2); second-generation light-emitting diode (LED)-1100 mW/cm(2); and third generation LED--700 mW/cm(2). DC (%) was measured using Fourier transform infrared spectroscopy. Specimens concerning each group (N=10) were then immersed in one of the solutions (distilled water, red wine, whisky, coffee, and cola--40 min/day, for 40 days). Specimen's color was measured before and after exposure to solutions using a colorimeter (Commission Internacionale de I'Eclairaga L*a*b* color scale), and ΔE was calculated. Specimens were then prepared for the spectrophotometric analysis to measure PC. Data were submitted to two-way analysis of variance and Tukey's test (p=0.05). RESULTS: DC: QTH presented the lowest DC, with statistical differences for LAS, LED 2, and LED 3. Whisky and wine showed lower PC mean values than cola and coffee. No statistical difference was observed for LCUs regarding PC and all staining solutions, except cola. Whisky showed the highest values for ΔE regarding all LCUs. Wine showed statistically lower ΔE than whisky, with water presenting the lowest ΔE. LAS and QTH showed higher values than LED 2 concerning ΔE. CONCLUSION: LCUs interfered with DC and altered the PC and ΔE of the composite resin submitted to different staining solutions. There was no correlation among DC, PC, and ΔE. CLINICAL SIGNIFICANCE: Light-curing modes might interfere with staining susceptibility, stain's retention, and DC of a composite resin, compromising the clinical performance. The highest pigment absorption was not associated with the highest superficial staining of the composite resin. Alcoholic drinks lead to greater superficial staining and non-alcoholic solutions lead to a higher pigment concentration.