Influence of the Light Curing Tip Distance and Material Opacity on Selected Physical Properties of a Pit and Fissure Sealant

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)Purpose: The purpose of this study was to evaluate the influence of the light curing to distance and material opacity on hardness (KHN), degree of conversion (DC), and crosslink density (CLD) of a resin-based fissure sealant (Fluroshield). Methods: One-millimeter-thick white opaque and clear sealant specimens, photoactivated at 1-, 2-, and 3-mm distances, were fabricated (8 groups, N=5). KHN and DC were evaluated 24 hours after polymerization. Specimens were subjected to a new KHN reading after 24-hour immersion in absolute ethanol to indirectly assess the CLD. Results: Samples of clear sealant cured at longer distances presented lower KHN, although there were not differences between opacities at all distances. The mean DC of the opaque white material, however, was lower than that of the clear one at higher distances. There were no differences among CLD for all experimental conditions analyzed. Conclusions: KHN of the clear sealant was affected by increased distances. The clear sealant showed higher DC at increased distances, although CLD was not influenced by the factors under study. Since physical properties of sealing materials are directly related to their clinical efficacy, the clear sealant tested may present a better clinical performance than the opaque one. (Pediatr Dent 2011;33:505-9) Received April 20, 2070 vertical bar Last Revision July 4, 2010 vertical bar Accepted July 7, 2010337505509Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)FAPESP [07/02800-3

Effect of the application of a casein phosphopeptide-amorphous calcium phosphate (CPP-ACP) paste and adhesive systems on bond durability of a fissure sealant

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)This study aimed to evaluate the effect of the previous application of a casein phosphopeptide-amorphous calcium phosphate paste (MI Paste, MI) and adhesive systems on the bond durability of a fissure sealant. Ninety-eight enamel blocks were obtained from proximal surfaces of erupted third molars. Specimens were divided into 14 groups (n = 7) according to the previous application of MI (with and without) and the adhesive systems used (no adhesive system; hydrophobic resin of a three-step etch-and-rinse adhesive system; etch-and-rinse single-bottle adhesive system; all-in-one adhesive system; two-step self-etching adhesive system; additional phosphoric acid conditioning and all-in-one adhesive system; additional phosphoric acid conditioning and two-step self-etching adhesive system). A fissure sealant (Fluroshield) was applied and photoactivated for 20 s. Beams ( 0.7 mm(2)) were prepared for the microtensile bond strength test, which was executed after 24 h or 6 months of water storage. Fractured specimens were analyzed by scanning electronic microscopy. Data were analyzed by two-way ANOVA with repeated measures/Tukey's test (P < 0.05). Groups that received MI application and adhesive systems presented higher means than those groups where MI was not applied. Higher frequency of cohesive failures was observed for groups with MI. Applying a CPP-ACP containing paste on enamel before adhesive systems was an effective method to increase bond durability of the sealant tested.10115259Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)FAPESP [2009/17645-9

Thermo-mechanical degradation of composite restoration photoactivated by modulated methods-a SEM study of marginal and internal gap formation

Objective. To evaluate the influence of thermal-mechanical degradation on superficial and internal gap formation of composite restorations photoactivated using modulated methods. Materials and methods. An experimental composite was prepared using a resin matrix containing 65wt% Bis-GMA and 35wt% TEGDMA. Camphorquinone (0.5wt%) and dimethylaminoethyl-methacrylate (0.5wt%) were dissolved in the resin as a photo-initiator system and 65wt.% silanized glass fillers were added to the matrix. Ground buccal surfaces of bovine lower incisors were used to make 160 preparations (3 mm x 3 mm x 2 mm in depth). An adhesive system (Adper Single Bond 2) was applied and the specimens were assigned into 16 groups (n = 10), according to the photoactivation method [high intensity (HI), low intensity (LI), soft-start (SS) and pulse-delay (PD)] and the degradation protocol [(control/no degradation; thermal cycling (TC); mechanical loading (ML); thermo-mechanical loading (TC+ML)]. Marginal and internal interfaces of bonded restorations were replicated in epoxy resin and analyzed by SEM. Gaps were expressed as a percentage of the total length of the margins. Data were submitted to 2-way ANOVA and Tukey's test (alpha = 0.05). Results. For the control group no significance was noted among the photoactivation methods. TC had no effect in gap formation. ML and TC+ML increased the incidence of superficial gaps for both HI and SS groups as well as increased the internal gaps for all groups. Conclusion. Although photoactivation methods do not influence gap formation at first, composite restoration photoactivated by low intensity or modulated methods showed improved resistance to thermo-mechanical degradation. Mechanical loading is determinant for interfacial degradation of composite restorations, while thermal cycling has no effect on gap formation.7151341134

Degree of Conversion of Simplified Contemporary Adhesive Systems as Influenced by Extended Air-Activated or Passive Solvent Volatilization Modes

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)This study evaluated the effect of five methods of solvent volatilization on the degree of conversion (DC) of nine one-bottle adhesive systems using Fourier transform infrared/attenuated total reflectance (FTIR/ATR) analysis. Nine adhesives were tested: Adper Single Bond 2 (SB), Adper Easy One (EO), One Up Bond F Plus (OUP), One Coat Bond SL (OC), XP Bond (RP), Ambar (AM), Natural Bond (NB), GO, and Stae. The adhesive systems were applied to a zinc-selenide pellet and 1) cured without solvent volatilization, 2) left undisturbed for 10 seconds before curing, 3) left undisturbed for 60 seconds before curing, 4) air-dried with an air stream for 10 seconds before curing, and 5) air-dried with an air stream for 60 seconds before curing. FTIR/ATR spectra were obtained, and the DC was calculated by comparing the aliphatic bonds/reference peaks before and after light activation for 10 seconds (FlashLite 1401). The DC means of each material were analyzed by one-way analysis of variance and post hoc Tukey test (p<0.05). The DC of GO and Stae adhesive systems was not affected by the five evaporation conditions. Air-drying for 60 seconds before curing yielded the highest DC for SB, EO, and OC. Extended solvent volatilization time (60 seconds) either with or without air-drying before curing provided the highest DC for AM, NB, XP, and OUP. Thus, the monomer conversion of adhesive systems was material dependent. In general, the 60-second passive or active air-drying modes to volatilize solvents before curing enhanced the degree of conversion for the one-bottle simplified adhesive systems.373246252Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)FAPESP [07/02800-3

Effect of dentin pre-treatment with a casein phosphopeptide-amorphous calcium phosphate (CPP-ACP) paste on dentin bond strength in tridimensional cavities

Objective. This study aimed to evaluate the push-out bond strength of dimethacrylate (Clearfil SE Bond/Filtek Z250; and Adper SE Plus/Filtek Z250) and silorane-based (Filtek P90 adhesive system/Filtek P90 composite resin) restorative systems following selective dentin pre-treatment with a CPP-ACP-containing paste (MI Paste). Materials and methods. Sixty bovine incisors were utilized. The buccal surface was wet-ground to obtain a flat dentin area. Standardized conical cavities were then prepared. Adhesive systems were applied according to manufacturers' directions and the composites were bulk-inserted into the cavity. The push-out bond strength test was performed at a universal testing machine (0.5 mm/min) until failure; failure modes were analyzed by scanning electron microscopy. Data were analyzed by two-way ANOVA and Tukey post-hoc test (p < 0.05). Results. For Clearfil SE Bond/Filtek Z250 and Filtek P90 adhesive system/Filtek P90 composite resin, the dentin pre-treatment did not influence bond strength means. For Adper SE Plus/Filtek Z250, dentin samples treated with MI Paste had statistically higher bond strength means than non-treated specimens. Adhesive failures were more frequent. Conclusion. Dentin pre-treatment with the CPP-ACP containing paste did not negatively affect bond strength for Clearfil SE Bond/Filtek Z250 and Filtek P90 adhesive system/Filtek P90 composite resin restorative systems and improved bond strength for the Adper SE Plus/Filtek Z250 restorative system.71127127

Effect of irradiation times on the polymerization depth of contemporary fissure sealants with different opacities

The aim of this study was to evaluate the depth of curing of 10 contemporary blue light-activated dental flowable materials at several opacities, influenced by different irradiation times using FT-IR spectroscopy. Fifty-five specimens (n = 5) with a 5-mm diameter and 1-mm thickness of translucent (Opallis Flow T), yellowed (Master Flow A2; Opallis Flow A2; Natural Flow A2; Fluroshield Yellowed), and opaque materials (Master Flow OA2; Natural Flow O; Opallis Flow OA3.5; Opal lis Flow OP; Fluroshield White) were obtained at six curing times (10s, 20s, 30s, 40s, 50s, and 60s) using a high-intensity LED (Coltolux, Coltene/Whaledent). The degree of conversion (DC) (%) was obtained using the Nexus 470 FTIR Spectrometer (Nicolet Instruments, USA). The FTIR-ATR spectra for uncured and cured samples were analyzed using a ZnSe crystal. The top and bottom surfaces of the cured specimens were analyzed to obtain the depth of curing. Two-way ANOVA was used to analyze the data. The highest curing depth was obtained by Natural Flow OA2, while the lowest was shown by Master Flow OA2. The shortest curing time generated similar depths of cure in comparison with the most extensive for Opallis Flow A2 and Fluroshield Yellowed. Therefore, depth of curing, influenced by the irradiation time, was dependent on the materials. Using the Natural Flow OA2 opaque sealant and the 10-s curing time for Opallis Flow A2 and Fluroshield Yellowed may represent alternative approaches to sealing tooth fissures.25213514

Influence of the preheating of bonding agents on the degree of conversion and bond durability in tridimensional dentin cavities

Objectives: The aim of this study was to evaluate the degree of conversion (DC) of dental bonding agents at different temperatures and the bond durability of restorations bonded with preheated dental bonding agents. Materials and methods: Three multistep adhesive systems, including one 3-step etch-and-rinse (Adper Scotchbond Multipurpose Plus) and two 2-step self-etching systems (Clearfil SE Bond; Filtek Low-Shrinkage Adhesive System), were evaluated. Dental bonding agents were preheated at 25, 37, and 60 degrees C. Bar-shaped specimens (n=5) were prepared for DC analysis. Fourier Transform Infrared/Attenuated Total Fluorescence spectra were obtained, and the DC was calculated by comparing the aliphatic bonds/reference peaks of nonpolymerized and polymerized materials. For bond durability analysis, tridimensional dentin cavities were prepared in 180 bovine incisors, which were then restored. Samples were stored in water for 24h, and half of them were subjected to additional degradation with 10% NaOCl for 5h. The push-out bond strength test was performed in a universal testing machine until failure. Failure modes were analyzed by scanning electron microscopy. Data were analyzed by analysis of variance (ANOVA) and Tukey's tests (p<0.05). Results: Dental bonding agents preheated at 60 degrees C showed higher DC values than those preheated at 25 and 37 degrees C. The temperature of the dental bonding agent did not influence the bond durability, although fewer adhesive failures were observed in restorations bonded with dental bonding agents at 60 degrees C. Conclusion: Although the preheating of dental bonding agents can increase the DC, it may not improve the bond durability of dentin restorations.27111226123

Dual-Cured Etch-and-Rinse Adhesive Systems Increase the Bond Durability of Direct Corona! Dentin Restorations

This study aimed to evaluate the bond durability of dentin restorations bonded with lightor dual-cured etch-and-rinse adhesive systems. A three-step adhesive system (Scotchbond Multipurpose Plus), an acetone-based two-step adhesive system (Prime & Bond 2.1), and an ethanol-based two-step adhesive system (Excite) were tested. Both the light- and the dualcured versions were evaluated. High C-factor dentin cavities were prepared on 120 bovine incisors, which were then restored with resin composite (n=10). The samples were stored in water for 24 hours, and half of them were subjected to additional degradation with 10% NaOCl for five hours. The push-out bond strength test was performed in a universal testing machine until failure. Failure modes were evaluated by scanning electron microscopy. Data were analyzed by three-way analysis of variance and Tukey tests (p<0.05). The dual-cured adhesive system presented a higher immediate bond strength and durability than those that were light cured. The three-step adhesive system produced the highest values, whereas the acetone-based adhesive system produced the lowest result. Therefore, the use of dual-cured etch-and-rinse adhesive systems can induce increased bond durability to direct coronol dentin restorations.38551251