Narciso Garone-Netto

Effects of fluoride or nanohydroxiapatite on roughness and gloss of bleached teeth.

The aim of this study was to describe roughness and gloss alterations of enamel after treatment with 38% hydrogen peroxide (HP) and after polishing with 2% neutral sodium fluoride (SF) or a dental tooth paste containing nanohydroxiapatite particles (nHA) using power spectral density (PSD) description, roughness parameters (Ra, RMS, and Z range) and gloss analysis.

Effect of post translucency on bond strength of different resin luting agents to root dentin

STATEMENT OF PROBLEM Translucent fiber posts were developed to conduct light into the root canal more effectively, thereby contributing to the polymerization of dual-polymerized resin luting agents. However, there is no consensus in the literature regarding their effectiveness. PURPOSE The purpose of this study was to evaluate the tensile bond strength of fiber posts with different degrees of translucency to bovine dentin with 3 types of resin luting agents. MATERIAL AND METHODS Ninety bovine roots were endodontically treated and divided into 9 groups (n=10) according to the type of post (translucent, white, and black) and resin luting agent (dual-polymerized self-adhesive; dual-polymerized + etch-and-rinse adhesive system; and autopolymerized + etch-and-rinse adhesive system). Tensile tests were performed on a universal testing machine (0.5 mm/min). To determine tensile stress, the bond area of each specimen was calculated. Data were statistically analyzed with ANOVA, Kruskal-Wallis, and Mann-Whitney tests (α=.05). RESULTS Mean (standard deviation) tensile bond strength values (5.53 ± 2.29 MPa) were significantly lower for translucent posts than for white (9.51 ± 1.31 MPa) and black posts (10.12 ± 3.44 MPa) with a dual-polymerized luting agent in combination with an adhesive system (P=.012). For white (6.02 ± 1.88 MPa) and black posts (4.14 ± 0.6 MPa), the self-adhesive luting agent led to lower tensile bond strength than the dual-polymerized luting agent in combination with an adhesive system (P=.003). Irrespective of post type, the autopolymerized luting agent provided the lowest tensile bond strength (P<.001). Microscopic analysis revealed that resin luting agents adhered more to the post surface than to the root dentin. CONCLUSION Post translucency did not increase the tensile bond strength of dual-polymerized resin luting agents.

Microtensile bond strength of enamel after bleaching

OBJECTIVE To evaluate the bond strength of a composite resin to the bovine enamel bleached with 35% hydrogen peroxide. It was used an etching-and-rinse adhesive system employed immediately, 7 and 14 days after the bleaching. MATERIALS AND METHODS Twenty bovine teeth were randomly distributed into 4 groups (n = 5), 3 experimental and 1 control. G1: Unbleached + restoration 14 days after storage in artificial saliva (control); G2: Bleached + restoration immediately after bleaching; G3: Bleached + restoration 7 days after bleaching; G4: Bleached + restoration 14 days after bleaching. Their buccal enamel surfaces were flattened, and a 25 mm² (5 × 5 mm) area from each one of these regions was outlined so as to standardize the experimental region. Universal hybrid composite resin Filtek™Z350 was inserted into four layers of 1 mm each and photo-activated. The bond strength was quantitatively evaluated by a microtensile test (1.0 mm/min) 24 h after the restorative procedures. The failure mode was assessed through scanning electron microscopy (SEM). RESULTS There was a significant reduction in the bond strength of the restored teeth immediately after the bleaching (G2). There were no significant differences in enamel bond strength between groups G1, G3, and G4. There was a predominance of adhesive and mixed (cohesive + adhesive) failure in all groups. CONCLUSION The 7-day-period after the end of the bleaching with 35% hydrogen peroxide was enough to achieve the appropriate values of bond strength to the enamel.

A comparative leakage study on Er,Cr: YSGG laser- and bur- prepared Class V cavities restored with a low-shrinkage composite using different filling techniques

AIM: To evaluate the leakage on Er,Cr:YSGG laser- and bur- prepared Class V cavities restored with a silorane-based composite resin using different insertion techniques METHODS: 40 cavities were outlined according to: the type of instrument [Er,Cr:YSGG laser (3.0 W power, energy per pulse of 150 mJ, fluence of 53.57J/cm2, pulse duration of 140-200 ∝s, 20 Hz repetition rate and 55/65% air/water spray) or diamond bur]; and the type of filling technique (bulk increment or incremental). Four experimental groups were obtained (n=10): G1- diamond bur (DB) and incremental (I); G2- DB and bulk increment (BI); G3- Er,Cr:YSGG and I; and G4- Er,Cr:YSGG and BI. Specimens were restored with a silorane-based composite resin (Filtek P90, 3M/ESPE), subjected to 500 thermal cycles, sealed, infiltrated with 2% (w/v) methylene blue and sectioned in halves. Specimen analysis was scored based on a scale. Statistical analyses were done using the Kruskal-Wallis and Student Newman-Keuls tests (α=0.05). RESULTS: Statistically significant differences were observed between G2 and G4 (p=0.003) and between G1 and G2 (p=0.028). The filling technique did not influence the pattern of dye leakage in the cavity walls (p=0.151). CONCLUSIONS: Less leakage was observed when Er,Cr:YSGG cavities were restored with silorane-based composite resin, using the bulk increment technique. Nevertheless, cavities done using diamond bur have less leakage only when incrementally restored.

Is It Necessary to Prepare the Enamel before Dental Bleaching

The aim of this in vitro study was to assess the influence of distinct surface treatments on the microhardness and color of enamel that will be bleached. Surface treatments are tested, accordingly: G1, no treatment; G2, 2% sodium fluoride; G3, casein phosphopeptide paste; G4, 2% fluoride+Nd:YAG laser. Forty blocks from bovine teeth composed the sample that were tested in Knoop microhardness (n = 10) and in color change (n = 10). After 24 h, bleaching with 35% hydrogen peroxide was performed for 45 min. Microhardness and color changes (using parameters ΔE, ΔL, Δa, and Δb) were assessed before and after bleaching. The data were analyzed by two-way ANOVA and Tukeys test (p < 0.05). Despite all surface treatments, a reduction of enamel microhardness occurred immediately after bleaching in all groups, being greater in G1. Enamel color changed in all groups. Immediately after bleaching, there was a decrease on enamel microhardness. However, after 7 days, some of those specimens previously treated before bleaching significantly recovered their initial microhardness without influencing the esthetic results of bleaching.