André Luiz Fraga Briso

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.

The Number of Bleaching Sessions Influences Pulp Tissue Damage in Rat Teeth

INTRODUCTION Hydrogen peroxide tooth bleaching is claimed to cause alterations in dental tissue structures. This study investigated the influence of the number of bleaching sessions on pulp tissue in rats. METHODS Male Wistar rats were studied in 5 groups (groups 1S-5S) of 10 each, which differed by the number (1-5) of bleaching sessions. In each session, the animals were anesthetized, and 35% hydrogen peroxide gel was applied to 3 upper right molars. Two days after the experimental period, the animals were killed, and their jaws were processed for light microscope evaluation. Pulp tissue reactions were scored as follows: 1, no or few inflammatory cells and no reaction; 2, <25 cells and a mild reaction; 3, between 25 and 125 cells and a moderate reaction; and 4, 125 or more cells and a severe reaction. Results from each experimental group were compared between groups and within groups to the corresponding unbleached upper left molars and analyzed for significant differences using the Kruskal-Wallis test (P < .05). RESULTS All tissue sections showed significant bleaching-induced changes in the dental pulp. After 1 bleaching session, necrotic tissue in the pulp horns and underlying inflammatory changes were observed. The extent and intensity of these changes increased with the number of bleaching sessions. After 5 sessions, the changes included necrotic areas in the pulp tissue involving the second third of the radicular pulp and intense inflammation in the apical third. CONCLUSIONS The number of bleaching sessions directly influenced the extent of pulp damage.

Effect of Sodium Ascorbate on Tag Formation in Bleached Enamel

PURPOSE This study analyzed the influence of 10% sodium ascorbate (SA) on tag formation in bleached enamel. MATERIALS AND METHODS Five groups were tested: G1 - control; G2 - bleaching with 10% carbamide peroxide (CP) + restoration; G3 - CP + SA + restoration; G4 - bleaching with 35% hydrogen peroxide (HP) + restoration; and G5 - HP + SA + restoration. The teeth were sectioned and decalcified, and the resin tags were analyzed at 400X magnification using an optical light microscope and Axiovision software. RESULTS The resin tag lengths in µm for each group were as follows: G1 - 36.1A; G2 - 5.8C; G3 - 14.4B; G4 - 1.7D; G5 - 6.5C. Different letters indicate statistically significant differences. CONCLUSION Tooth bleaching with CP or HP impairs the formation of resin tags, and the utilization of sodium ascorbate increases tags length.

Clinical Comparison of At-Home and In-Office Dental Bleaching Procedures: A Randomized Trial of a Split-Mouth Design.

The objective of this split-mouth clinical study was to compare a combination of in-office and at-home dental bleaching with at-home bleaching alone. Two applications of in-office bleaching were performed, with one appointment per week, using 38% hydrogen peroxide. At-home bleaching was performed with or without in-office bleaching using 10% carbamide peroxide in a custom-made tray every night for 2 weeks. The factor studied was the bleaching technique on two levels: Technique 1 (in-office bleaching combined with home bleaching) and Technique 2 (home bleaching only). The response variables were color change, dental sensitivity, morphology, and surface roughness. The maxillary right and left hemiarches of the participants were submitted to in-office placebo treatment and in-office bleaching, respectively (Phase 1), and at-home bleaching (Phase 2) treatment was performed on both hemiarches, characterizing a split-mouth design. Enamel surface changes and roughness were analyzed with scanning electron microscopy and optical interferometry using epoxy replicas. No statistically significant differences were observed between the bleaching techniques for either the visual or the digital analyses. There was a significant difference in dental sensitivity when both dental bleaching techniques were used, with in-office bleaching producing the highest levels of dental sensitivity after the baseline. Microscopic analysis of the morphology and roughness of the enamel surface showed no significant changes between the bleaching techniques. The two techniques produced similar results in color change, and the combination technique produced the highest levels of sensitivity. Neither technique promoted changes in morphology or surface roughness of enamel.

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.

Microabrasion in tooth enamel discoloration defects: three cases with long-term follow-ups

Superficial irregularities and certain intrinsic stains on the dental enamel surfaces can be resolved by enamel microabrasion, however, treatment for such defects need to be confined to the outermost regions of the enamel surface. Dental bleaching and resin-based composite repair are also often useful for certain situations for tooth color corrections. This article presented and discussed the indications and limitations of enamel microabrasion treatment. Three case reports treated by enamel microabrasion were also presented after 11, 20 and 23 years of follow-ups.

Effect of fluid resins on the surface roughness and topography of resin composite restorations analyzed by atomic force microscope

The aim of the study was to verify the influence of surface sealants on the surface roughness of resin composite restorations before and after mechanical toothbrushing, and evaluate the superficial topography using atomic force microscope. Five surface sealers were used: Single Bond, Opti Bond Solo Plus, Fortify, Fortify Plus and control, without any sealer agent. The lowest values of surface roughness were obtained for control, Single Bond and Fortify groups before toothbrushing. Fortify and Fortify Plus were the sealer agents that support the abrasive action caused by the toothbrushing although Fortify Plus group remained with high values of surface roughness. The application of specific surface sealants could be a useful clinical procedure to maintain the quality of resin-based composite restorations.

Longitudinal photographic observation of the occurrence of bubbles in pit and fissure sealants

The purpose of this study was to employ photographic evaluation to observe the presence or absence of bubbles in pit and fissure sealants Concise and Prisma Shield, at 7 days, 18 months, 36 months and 11 years after accomplishment of treatment. Methods: A hematoxylin-based staining solution was applied to the occlusal surface at the study periods, which allowed assessment of the sealing material on the surface. All occlusal surfaces were photographed and the photographs corresponding to each period were subjected to photographic evaluation. Results: There was statistically significant difference only at 18 months, with a significantly higher number of specimens with bubbles for the Prisma Shield sealant compared to the Concise, whereas the groups were similar at all other study periods. On the other hand, separate analysis of subsequent periods of the sealants did not reveal any significant difference. Conclusions: According to the results of the present longitudinal investigation, it may be concluded that the sealing materials showed that bubbles came into and went out with time. However, this fact did not interfere with its clinical purpose, provided the remaining material covers the expected region of pits and fissures.

Hydrogen peroxide induces cell proliferation and apoptosis in pulp of rats after dental bleaching in vivo: Effects of the dental bleaching in pulp

OBJECTIVE This study provides an in vivo evaluation of the inflammatory response, levels of cell proliferation and apoptosis, and the presence of necrosis after dental bleaching with two concentrations of hydrogen peroxide (H2O2). DESIGN Wistar rats were divided into Control (placebo gel), BLUE (20% H2O2, 1×50min), and MAXX (35% H2O2, 3×15min) groups. At 2 and 30days, the rats were killed (n=10). The jaws were processed for histology analysis and PCNA and Caspase-3-cleaved immunohistochemistry, and data were submitted to the Mann-Whitney or ANOVA test (P<0.05). RESULTS At 2days, the MAXX group showed necrosis and the BLUE group revealed moderate inflammation on the occlusal third of the crown (P<0.05). At 30days, tertiary dentin had formed and there was an absence of inflammation. The level of cell proliferation was higher in the middle third of the BLUE group (P<0.05), and cervical of MAXX at 2days (P<0.05), decreasing at 30days. The apoptosis was present at 2days, particularly in the cervical third of the crown in the bleached groups (P<0.05), with a decrease only at 30days in the BLUE group (P<0.05). CONCLUSIONS The concentration of H2O2 influences effects on the pulp tissue, where a higher concentration of H2O2 can cause necrosis in the pulp and a prolonged effect within the apoptotic process; lower concentrations of H2O2 provide moderate inflammation, cell proliferation and apoptosis with a reduction of these processes over time.