Micro-hardness evaluation of a micro-hybrid composite resin light cured with halogen light, light-emitting diode and argon ion laser

This in vitro study aimed to determine whether the micro-hardness of a composite resin is modified by the light units or by the thickness of the increment. Composite resin disks were divided into 15 groups (n = 5), according to the factors under study: composite resin thickness (0 mm, 1 mm, 2 mm , 3 mm and 4 mm) and light units. The light activation was performed with halogen light (HL) (40 s, 500 mW/cm(2)), argon ion laser (AL) (30 s, 600 mW/cm(2)) or light-emitting diode (LED) (30 s, 400 mW/cm(2)). Vickers micro-hardness tests were performed after 1 week and were carried out on the top surface (0 mm-control) and at different depths of the samples. Analysis of variance (ANOVA) and Tukey tests (P a parts per thousand currency signaEuro parts per thousand 0.05) revealed no statistically significant difference among the light units for the groups of 0 mm and 1 mm thickness. At 2 mm depth, the AL was not statistically different from the HL, but the latter showed higher micro-hardness values than the LED. In groups with 3 mm and 4 mm thickness, the HL also showed higher micro-hardness values than the groups activated by the AL and the LED. Only the HL presented satisfactory polymerization with 3 mm of thickness. With a 4 mm increment no light unit was able to promote satisfactory polymerization.

Influence of Cavity Preparation with Er:YAG Laser on Enamel Adjacent to Restorations Submitted to Cariogenic Challenge In Situ: A Polarized Light Microscopic Analysis

Background and Objectives: Er:YAG laser has been used for caries removal and cavity preparation, using ablative parameters. Its effect on the margins of restorations submitted to cariogenic challenge has not yet been sufficiently investigated. The aim of this study was to assess the enamel adjacent to restored Er:YAG laser-prepared cavities submitted to cariogenic challenge in situ, under polarized light microscopy. Study Design/Materials and Methods: Ninety-one enamel slabs were randomly assigned to seven groups (n = 13): I, II, III-Er:YAG laser with 250 mJ, 62.5 J/cm(2), combined with 2, 3, and 4 Hz, respectively; IV, V, VI-Er:YAG laser with 350 mJ, 87.5 J/cm(2), combined with 2, 3, and 4 Hz, respectively; VII-High-speed handpiece (control). Cavities were restored and the restorations were polished. The slabs were fixed to intra-oral appliances, worn by 13 volunteers for 14 days. Sucrose solution was applied to each slab six times per day. Samples were removed, cleaned, sectioned and ground to polarized light microscopic analysis. Demineralized area and inhibition zone width were quantitatively assessed. Presence or absence of cracks was also analyzed. Scores for demineralization and inhibition zone were determined. Results: No difference was found among the groups with regard to demineralized area, inhibition zone width, presence or absence of cracks, and demineralization score. Inhibition zone score showed difference among the groups. There was a correlation between the quantitative measures and the scores. Conclusion: Er:YAG laser was similar to high-speed handpiece, with regard to alterations in enamel adjacent to restorations submitted to cariogenic challenge in situ. The inhibition zone score might suggest less demineralization at the restoration margin of the irradiated substrates. Correlation between the quantitative measures and scores indicates that score was, in this case, a suitable complementary method for assessment of caries lesion around restorations, under polarized light microscopy. Lasers Surg. Med. 40:634-643, 2008. (c) 2008 Wiley-Liss, Inc.

Can the durability of one-step self-etch adhesives be improved by double application or by an extra layer of hydrophobic resin?

Objectives: This study evaluated the immediate and 6-month resin-dentin mu-bond strength (mu TBS) of one-step self-etch systems (Adper Prompt L-Pop [AD] 3M ESPE; Xeno III [XE] Dentsply De Trey; iBond [iB] Heraeus Kulzer) under different application modes. Materials and methods: Dentin oclusal surfaces were exposed by grinding with 600-grit SiC paper. The adhesives were applied according to the manufacturer`s directions [MD], or with double application of the adhesive layer [DA] or following the manufacturer`s directions plus a hydrophobic resin layer coating [HL]. After applying the adhesive resins, composite crowns were built up incrementally. After 24-h water storage, the specimens were serially sectioned in ""x"" and ""y"" directions to obtain bonded sticks of about 0.8 mm 2 to be tested immediately [IM] or after 6 months of water storage [6M] at a crosshead speed of 0.5 mm/min. The data from each adhesive was analyzed by a two-way repeated measures ANOVA (mode of application vs. storage time) and Tukey`s test (alpha = 0.05). Results: The adhesives performed differently according to the application mode. The DA and HL either improved the immediate performance of the adhesive or did not differ from the MD. The resin-dentin bond strength values observed after 6 months were higher when a hydrophobic resin coat was used than compared to those values observed under the manufacturer`s directions. Conclusions: The double application of one-step self-etch system can be safety performed however the application of an additional hydrophobic resin layer can improve the immediate resin-dentin bonds and reduce the degradation of resin bonds over time. (c) 2008 Elsevier Ltd. All rights reserved.

Effect of prolonged application times on the durability of resin-dentin bonds

Objectives. To examine the effect of prolonged application time on the early and 3-year resin-dentin microtensile bond strength. Methods. Water/ethanol (Single Bond [SB]) and acetone-based systems (One Step [OS]) were employed. A flat superficial dentin surface was exposed in third human molars by wet abrasion. The adhesives were applied to a delimited area of 52 mm(2) on wet surfaces, for 40, 90, 150 and 300s. Four teeth were assigned for each experimental condition. Composite build-ups were constructed incrementally After water storage at 37 degrees C for 24 h, teeth were sectioned to obtain sticks with cross-sectional areas of 0.8 mm(2) to be tested in tension (0.5 mm/min) either immediately (IM) or after 3 years (3Y) of water storage. The microtensile bond strength (mu TBS) values were analyzed by two way repeated measures ANOVA and Tukey`s test (alpha = 0.05). Results. The 90- and 150-s groups achieved the highest IM mu TBS for OS (p < 0.01). For SB, the highest IM mu TBS values were observed after 300-s application (p < 0.01). Significant decreases in mu TBS were observed for OS in the 40- and 90-s groups after 3Y, except for the 150-s group. With regard to SB, after 3Y significant drops in mu TBS values were observed for the 40- and 150-s groups, except for the 300-s group. Significance. Prolonged application times can increase the immediate LTBS of two-step etch-and-rinse adhesive systems and make the adhesive layer more stable over time. (c) 2007 Academy of Dental Materials. Published by Elsevier Ltd. All rights reserved.

One-year stability of resin-dentin bonds created with a hydrophobic ethanol-wet bonding technique

Dentin bonding performed with hydrophobic resins using ethanol-wet bonding should be less susceptible to degradation but this hypothesis has never been validated. Objectives. This in vitro study evaluated stability of resin-dentin bonds created with an experimental three-step BisGMA/TEGDMA hydrophobic adhesive or a three-step hydrophilic adhesive after one year of accelerated aging in artificial saliva. Methods. Flat surfaces in mid-coronal dentin were obtained from 45 sound human molars and randomly divided into three groups (n = 15): an experimental three-step BisGMA/TEGDMA hydrophobic adhesive applied to ethanol (ethanol-wet bonding-GI) or water-saturated dentin (water-wet bonding-GII) and Adper Scotchbond Multi-Purpose [MP-GIII] applied, according to manufacturer instructions, to water-saturated dentin. Resin composite crowns were incrementally formed and light-cured to approximately 5 mm in height. Bonded specimens were stored in artificial saliva at 37 degrees C for 24h and sectioned into sticks. They were subjected to microtensile bond test and TEM analysis immediately and after one year. Data were analyzed with two-way ANOVA and Tukey tests. Results. MP exhibited significant reduction in microtensile bond strength after aging (24 h: 40.6 +/- 2.5(a); one year: 27.5 +/- 3.3(b); in MPa). Hybrid layer degradation was evident in all specimens examined by TEM. The hydrophobic adhesive with ethanol-wet bonding preserved bond strength (24 h: 43.7 +/- 7.4(a); one year: 39.8 +/- 2.7(a)) and hybrid layer integrity, with the latter demonstrating intact collagen fibrils and wide interfibrillar spaces. Significance. Coaxing hydrophobic resins into acid-etched dentin using ethanol-wet bonding preserves resin-dentin bond integrity without the adjunctive use of MMPs inhibitors and warrants further biocompatibility and patient safety`s studies and clinical testing. (C) 2009 Academy of Dental Materials. Published by Elsevier Ltd. All rights reserved.

Influence of Photoactivation Protocol and Light Guide Distance on Conversion and Microleakage of Composite Restorations

Purpose: To evaluate the effect of light guide distance and the different photoactivation methods on the degree of conversion (DC) and microleakage of a composite. Methods and Materials: Three photoactivation protocols (600mW/cm(2) x 40 seconds; 400 mW/cm(2) x 60 seconds or 200 mW/cm(2) x 20 seconds, followed by 500 mW/cm(2) X 40 seconds) and three distances from the light source (0, 3 or 7 mm) were tested. Cylindrical specimens (5 nun diameter; 2 mm tall; n=3) were prepared for the DC test (FT-Raman). Class V cavities were made in 90 bovine incisors to conduct the microleakage test. The specimens were conditioned for 15 seconds with phosphoric acid (37%), followed by application of the adhesive system Prime & Bond NT (Dentsply/Caulk). The preparations were restored in bulk. The specimens were stored for 24 hours in distilled water (37 degrees C) before being submitted to the silvernitrate microleakage protocol. The restorations were sectioned and analyzed under 25x magnification. Results: Statistical analyses (two-way ANOVAs and Tukey test, alpha=0.05) found significance only for the factor distance (p=0.015) at the top of the composite for the DC test. Conversion was statistically lower for the 7 mm groups compared to the 0 and 3 mm groups, which were equivalent to each other. At the bottom of the specimens, none of the factors or interactions was significant (p<0.05). The Kruskal-Wallis test showed that, in general, the soft-start method led to lower microleakage scores when compared to the continuous modes, mainly when associated with a distancing of 7 mm (p<0.01). With the exception of specimens irradiated with 400mW/cm(2) that did not demonstrate variations on scores for the distances tested, higher microleakage was observed for shorter distances from the light source. Conclusions: Soft-start methods may reduce microleakage when the light guide distancing provides a low level of irradiance, which also causes a discrete reduction in the DC.

Durability of Enamel Bonding Using One-step Self-etch Systems on Ground and Unground Enamel

Objective: To examine the morphological, early and long-term microtensile bond strengths (mu TBS) of one-step self-etch systems to unground and ground enamel. Materials and Methods: Resin composite (Filtek Z250) buildups were bonded to the buccal and lingual enamel surfaces (unground, bur-cut or SiC-roughened enamel) of third molars after adhesive application using the following adhesives: Clearfil S(3) Bond (CS3); Adper Prompt L-Pop (ADP); iBond (iB) and, as the control, Clearfil SE Bond (CSE). Six tooth halves were assigned for each condition. After storage in water (24 hours/37 degrees C), the bonded specimens were sectioned into beams (0.8 mm(2)) and subjected to pTBS (0.5 mm/min) either immediately (IM) or after six (6M) or 12 months (12M) of water storage. The data were analyzed by three-way repeated measures ANOVA and Tukey`s test (alpha=0.05). Surface conditioning was observed under scanning electron microscopy (SEM). Results: The mu TBS in the Si-C paper and diamond bur groups were similar and higher than the unground group. No significant difference was observed among the different storage periods, except for CS3, which showed an increase in the pTBS after 12M. The etching pattern was more retentive on ground enamel. Conclusions: One-step self-etch adhesives showed higher bond strengths on ground enamel and no reductions in resin-enamel bonds were observed after 12M of water storage.

Durability of enamel bonding using two-step self-etch systems on ground and unground enamel

This study examined the early and long-term microtensile bond strengths (mu TBS) and interfacial enamel gap formation (IGW) of two-step selfetch systems to unground and ground enamel. Resin composite (Filtek Z250) buildups were bonded to proximal enamel surfaces (unground, bur-cut or SiC-treated enamel) of third molars after the application of four self-etch adhesives: a mild (Clearfil SE Bond [SE]), two moderate (Optibond Solo Plus Self-Etch Primer [SO] and AdheSE [AD]) and a strong adhesive (Tyrian Self Priming Etchant + One Step Plus [TY]) and two etch-and-rinse adhesive systems (Single Bond [SB] and Scotchbond Multi-Purpose Plus [SBMP]). Ten tooth halves were assigned for each adhesive. After storage in water (24 hours/37 degrees C), the bonded specimens were sectioned into beams (0.9 mm(2)) and subjected to mu TBS (0.5 mm/minute) or interfacial gap width measurement (stereomicroscope at 400x) either immediately (IM) or after 12 months (12M) of water storage. The data were analyzed by three-way repeated measures ANOVA and Tukey`s test (alpha=0.05). No gap formation was observed in any experimental condition. The mu TBS in the Si-C paper and diamond bur groups were similar and greater than the unground group only for the moderate self-etch systems (SO and AD). No reductions in bond strength values were observed after 12 months of water storage, regardless of the adhesive evaluated.

Light cola drink is less erosive than the regular one: An in situ/ex vivo study

Objective: This in situ/ex vivo study assessed the erosive potential of a light cola drink when compared to a regular one. Methods: During 2 experimental 14-days crossover phases, eight volunteers wore palatal devices with 2 human enamel blocks. The groups under study were: group light, erosive challenge with light cola drink and group regular, erosive challenge with regular cola drink. During 14 days, erosive challenges were performed extraorally 3X/day. In each challenge, the device was immersed in 150 ml of light cola (group light) or regular cola (group regular) for 5 min. Erosion was analysed by surface profilometry (mu m) and surface microhardness change (%SMH). The data were statistically analyzed using paired t test (p<0.05). Results: Group light (0.6 +/- 0.2 mu m) showed significantly lesser wear than group regular (3.1 +/- 1.0 mu m). There was no significant difference between the groups for the %SMH (group light -63.9 +/- 13.9 and group regular -78.5 +/- 12.7). Conclusions: The data suggest that the light cola drink is less erosive than the regular one. (C) 2008 Elsevier Ltd. All rights reserved.

An in situ/ex vivo comparison of the ability of regular and light colas to induce enamel wear when erosion is combined with abrasion

Objective: To evaluate whether the type of cola drink (regular or diet) could influence the wear of enamel subjected to erosion followed by brushing abrasion, Method and !Materials: Ten volunteers wore intraoral devices that each had eight bovine enamel blocks divided into four groups; ER, erosion with regular cola; EAR, erosion with regular cola plus abrasion; EL, erosion with light cola; and EAL, erosion with light cola plus abrasion, Each day for 1 week, half of each device was immersed in regular cola for 5 minutes, Then, two blocks were brushed using a fluoridated toothpaste and electric toothbrush for 30 seconds four times daily, Immediately after, the other half of the device was subjected to the same procedure using a light cola, The pH, calcium, phosphorus, and fluoride concentrations of the colas were analyzed using standard procedures, Enamel alterations were measured by profilometry. Data were tested using two-way ANOVA and Bonferroni test (P < .05), Results: Regarding chemical characteristics, light cola presented pH 3.0, 13.7 mg Ca/L, 15.5 mg P/L, and 0.31 mg F/L, while regular cola had pH 2.6, 32.1 mg Ca/L, 1:8.1 mg P/L, and 0.26 mg F/L, The light cola promoted less enamel loss (EL, 0.36 pm; EAL, 0.39 pm) than its regular counterpart (ER, 0.72 pm; EAR, 0.95 pm) for both conditions, There was not a significant difference (P > .05) between erosion and erosion plus abrasion for light cola, However, for regular cola, erosion plus abrasion resulted in higher enamel loss than erosion alone,.nclusion: The data suggest that light cola promoted less enamel wear even when erosion was followed by brushing abrasion, (Quintessence Int 2011;42:xxx-xx)()

Mechanical stability of adhesives under water storage

Objectives. To evaluate the effects of storage condition (wet or dry) and storage time (24 h and 3 months) on the ultimate tensile strength (UTS) of Single Bond (SB), 3M-ESPE; Opti Bond Solo Plus (OB), Kerr; One Step (OS), Bisco, and Prime & Bond NT (PB), Dentsply adhesive resins. Methods. Hourglass-shaped specimens were obtained from a metallic matrix. Each adhesive was dispensed to fill the molds completely and left undisturbed in a dark chamber for 4 min at 37 degrees C for solvent evaporation. They were individually light-cured for 80 s at 500 mW/cm(2) and randomly divided into three groups: 24 h of water storage; 3 months of water storage; 3 months of dry storage. The specimens were tested in tension at 0.5 mm/min using the microtensile method and data were analyzed by two-way ANOVA and SNK tests for each material. Results. Water storage for 3 months did not cause significant changes in the UTS of any of the adhesives (p-value). Values for water storage ranged from 25.9 MPa for Single Bond at 24 h to 32.7 MPa for Prime & Bond NT after 3 months. Dry storage for 3 months yielded significantly higher UTS for most adhesives, which ranged from approximately 20% for Opti Bond to 160% higher values for Single Bond compared to their 3 months wet storage values. Conclusion. The effects of storage condition and time on the UTS of adhesives were material-dependent. (C) 2009 Academy of Dental Materials. Published by Elsevier Ltd. All rights reserved.

Cytotoxicity of resin-based light-cured liners

Purpose: To evaluate the cytotoxic effects of resin-based light-cured liners on culture of pulp cells. Methods: Discs measuring 4 mill in diameter and 2 mm thick were fabricated from TheraCal (TCMTA), Vitrebond (VIT), and Ultrablend Plus (UBP). These specimens were immersed in serum-free culture medium (DMEM) for 24 hours or 7 days to produce the extracts. After incubating the pulp cells for 72 hours, the extracts were applied on the cells and the cytotoxic effects were determined based on the cell metabolism (MTT), total protein expression and cell morphology (SEM). In the control group, fresh DMEM was used. Data from MTT analysis and protein expression were submitted to Kruskal-Wallis and Mann-Whitney tests at the preset level of significance of 5%. Results: When in contact with the 24-hour extract, TCMTA, VIT, and UBP decreased the cell metabolism by 31.5%, 73.5% and 71.0%, respectively. The total protein expressed by the cells in contact with VIT and UBP was lower than TCMTA and DMEM (Mann-Whitney, P< 0.05). When in contact with the 7-day extract, TCMTA, VIT, and UBP decreased the metabolic activity by 45.9%, 77.1% and 64.4%, respectively. All the liners expressed statistically lower amounts of proteins when compared to the control. A reduction in the number of cells was observed for all liners. The remaining cells from TCMTA group resembled those from the control group while for VIT and UBP the cells presented significant morphological alterations. (Ani J Dent 2009;22:137-142).

Stability of wet versus dry bonding with different solvent-based adhesives

Objective. To evaluate the effects of surface moisture (wet or dry) and storage (24h or 3 months) on the microtensile bond strength (BS) of resin/dentin bonds mediated by two water/ethanol based adhesives Single Bond, 3M-ESPE, (SB) and Opti Bond Solo Plus, Kerr, (OB), and two acetone-based adhesives, One Step, Bisco, (OS) and Prime&Bond NT, Caulk/Dentsply, (PB). Materials and methods. Flat dentin surfaces were polished with 600-grit SiC paper, etched with 35% phosphoric acid for 15 s and rinsed for 20 s. Half the surface was maintained moist and the other half was air-dried for 30 s. Each adhesive was applied simultaneously to both halves, left undisturbed for 30 s and light-cured. Four-mm resin build-ups were constructed incrementally. After storage in water at 37 degrees C for 24h, slabs were produced by transversal sectioning and trimmed to an hourglass shape (0.8 mm 2). Half of the specimens were tested in tension at 0.6 mm/min immediately after trimming and the other half after 3 months of water storage. Data were analyzed by two-way ANOVA and SNK for each material. Results. Both moisture and storage affected BS to dentin, and was material- dependent. Dry, bonding affected mostly the acetone-based adhesives. Larger reductions in bond strength were associated with dry bonding after 3 months of water storage. Significance. Wet bonding resulted in more stable bonds over 3 months of water storage for most of the materials tested. (C) 2007 Academy of Dental Materials. Published by Elsevier Ltd. All rights reserved.

Influence of curing protocol on selected properties of light-curing polymers: Degree of conversion, volume contraction, elastic modulus, and glass transition temperature

Objectives. The purpose of this study was to investigate the effect of light-curing protocol on degree of conversion (DC), volume contraction (C), elastic modulus (E), and glass transition temperature (T(g)) as measured on a model polymer. It was a further aim to correlate the measured values with each other. Methods. Different light-curing protocols were used in order to investigate the influence of energy density (ED), power density (PD), and mode of cure on the properties. The modes of cure were continuous, pulse-delay, and stepped irradiation. DC was measured by Raman micro-spectroscopy. C was determined by pycnometry and a density column. E was measured by a dynamic mechanical analyzer (DMA), and T(g) was measured by differential scanning calorimetry (DSC). Data were submitted to two-and three-way ANOVA, and linear regression analyses. Results. ED, PD, and mode of cure influenced DC, C, E, and T(g) of the polymer. A significant positive correlation was found between ED and DC (r = 0.58), ED and E (r = 0.51), and ED and T(g) (r = 0.44). Taken together, ED and PD were significantly related to DC and E. The regression coefficient was positive for ED and negative for PD. Significant positive correlations were detected between DC and C (r = 0.54), DC and E (r = 0.61), and DC and T(g) (r = 0.53). Comparisons between continuous and pulse-delay modes of cure showed significant influence of mode of cure: pulse-delay curing resulted in decreased DC, decreased C, and decreased T(g). Influence of mode of cure, when comparing continuous and step modes of cure, was more ambiguous. A complex relationship exists between curing protocol, microstructure of the resin and the investigated properties. The overall performance of a composite is thus indirectly affected by the curing protocol adopted, and the desired reduction of C may be in fact a consequence of the decrease in DC. (C) 2009 Academy of Dental Materials. Published by Elsevier Ltd. All rights reserved.

Bond Strength of Fiber Posts to Weakened Roots After Resin Restoration With Different Light-Curing Times

Introduction: This study evaluated the bond strength of translucent fiber posts to experimentally weakened radicular dentin restored with composite resin and polymerized with different light-exposure time. Methods: Roots of 60 maxillary incisors were used. Twenty-four hours after obturation, the filling materials of root canals were removed to a depth of 12 mm, and 4 groups were randomly formed. In 3 groups, root dentin was flared to produce a space between fiber post and canal walls. In the control group, the roots were not experimentally weakened. The flared roots were bulk restored with composite resin, which was light-activated through the translucent post for 40, 80, or 120 seconds. Posts were cemented, and after 24 hours, all roots were sectioned transversely in the coronal, middle, and apical regions, producing 1-mm-thick slices. Push-out test was performed, and failure modes were observed. Results The quantitative analysis showed significant statistical difference only among groups (P <.001). Comparing the weakened/restored groups, composite light-exposure time did not influence the results. Overall, adhesive failures occurred more frequently than other types of failures. Cohesive failures occurred only in the weakened/restored roots. Conclusions Intracanal root restoration with composite resin and translucent fiber posts provided similar or higher bond strength to dentin than the control group, regardless of the light-exposure time used for polymerization. (J Endod 2009;35:1034-1039)