Power output from 12 brands of contemporary LED light-curing units measured using 2 brands of radiometers.

BACKGROUND: Given the increasing use of photo-activated resins in dentistry, dentists and researchers need a user-friendly dental radiometer to measure the power output from dental light-curing units (LCUs). OBJECTIVE: Our goal was to measure the accuracy of two brands of dental radiometers in reporting the power (mW) from twelve brands of contemporary LCUs compared to a 'gold standard' (GS) reference value obtained from an integrating sphere attached to a fiberoptic spectroradiometer. METHODS: The power output was measured from two units of 12 brands of LCUs, five times on the ''GS" system, five times on two Bluephase Meter II dental radiometers, and five times on two Mini Gig hand-held spectroradiometers. The emission spectrum was also recorded using the 'GS' integrating sphere. The power values reported by each meter were subjected to t-tests to compare the two examples of each LCU, and 3-way ANOVA followed by Bonferroni's post-hoc tests. Regression analyses were also performed to determine the relationship between the data from the hand-held radiometers and the 'GS' integrating sphere. RESULTS: There was a large difference in the power values (mW) and the emission spectra from the 12 brands of LCUs on their standard-settings (p<0.001). Except for one LCU (Dental Spark @ 15.1%), the differences between the two LCUs of the same brand were less than 5.3% when measured using the 'GS' integrating sphere. Regression analyses showed a highly significant agreement between the power values reported from the two brands of radiometers and the 'GS' integrating sphere (R2 > 98%). CONCLUSION: We concluded that the power values reported from both brands of dental radiometers we tested were accurate, provided that the light source did not emit wavelengths of light that were beyond the radiometer's detection limit.

Kinetics of polymerization shrinkage of self-adhesive and conventional dual-polymerized resin luting agents inside the root canal.

STATEMENT OF PROBLEM: Information regarding the shrinkage kinetics and monomer conversion of dual-polymerized conventional and self-adhesive resin luting agents (RLA) in situ is lacking. PURPOSE: The purpose of this in vitro study was to evaluate the shrinkage strain and ratio of 1 conventional and 1 self-adhesive RLA by using fiber optic sensors based on Bragg gratings and Vickers hardness in the root canal. MATERIAL AND METHODS: The root canals of 34 single-rooted premolars were endodontically treated and assigned to 2 groups according to the RLA: RelyX ARC (ARC) and RelyX U200 (U200). Two Bragg grating sensors were attached to fiber posts (n=10), and both post and RLA were placed inside the root canal so that shrinkage strain and ratio values could be measured at the cervical and apical root thirds. For hardness analysis (n=7), two 1-mm-thick slices of each root-third (cervical and apical) were obtained, and 4 indentations were made on the RLA layer. The shrinkage strain and rate, as well as hardness data, were evaluated by using 2-way repeated-measures ANOVA followed by the Bonferroni post hoc test when a significant interaction between factors was detected (α=.05). RESULTS: The shrinkage strain and rate values of both RLAs were higher at the cervical third than those at the apical third. ARC showed higher shrinkage strain than U200 at the cervical third. The highest hardness values were observed at the cervical third, while ARC showed the lowest hardness values at the apical third. CONCLUSIONS: The shrinkage kinetics profile and hardness of self-adhesive RLA may differ from those of conventional RLA depending on the root third.

The effect of stainable drinks followed by simulated brushing on the roughness and stainability of acrylic resins polymerized with different cycles.

STATEMENT OF PROBLEM: No information is available on roughness and stainability of acrylic resins polymerized by experimental microwave cycles after immersion in stainable liquids and simulated brushing. PURPOSE: The purpose of this in vitro study was to evaluate the effect of stainable drinks and brushing on roughness and stainability of acrylic resins (Vipi Cril [CA] and Vipi Wave [MA]) polymerized with different cycles. MATERIAL AND METHODS: CA and MA specimens (n=5; diameter, 20 mm; thickness, 3 mm) were made using 4 methods recommended by the manufacturer (water bath polymerization and microwave polymerization cycles) and experimental at 550 W or 650 W for 3 or 5 minutes (M550/3 and M650/5), respectively. After storage in distilled water at 37°C for 48 hours (T0), the specimens were stored in water, coffee, or red wine (37°C) for 36 days with simulated brushing (54 000 cycles, T1). Roughness (Ra) and stainability (ΔE/National Bureau of Standards) were measured at T0 and T1. Roughness and stainability data were analyzed by 3-way repeated measures and 2-way ANOVA, respectively, followed by the Bonferroni test (α=.05). RESULTS: After storing in coffee and brushing, CA showed the highest (M550/3=2.33 ±0.72 µm) and the lowest roughness (water bath polymerization=1.22 ±0.58 µm), whereas roughness of MA specimens processed by M650/5 increased (1.57 ±0.59 µm). Storing in wine and brushing increased roughness (1.75 ±0.32 µm) in the M550/3 group. No staining was observed on MA after brushing regardless of the polymerization cycle. All values were acceptable (ΔE≤3.3), except for MA (microwave polymerization), which showed National Bureau of Standards=4.49 (appreciable change) after storing in wine and brushing. CONCLUSIONS: A slight increase in material roughness was observed after staining and brushing. Only MA polymerized following manufacturer cycles showed relevant stainability after immersion in wine and brushing.

Effect of incorporating antifungals on the water sorption and solubility of interim resilient liners for denture base relining.

STATEMENT OF PROBLEM: Incorporating antifungals into interim denture resilient liners has been proposed to prolong their clinical longevity and to treat denture stomatitis. However, information is lacking on the effect of this addition on water sorption and solubility. PURPOSE: The purpose of this in vitro study was to evaluate the addition of minimum inhibitory concentrations (MICs) of antifungals for Candida albicans biofilm on the water sorption (WS) and solubility of interim denture resilient liners. MATERIAL AND METHODS: Disk-shaped specimens (n=10; 50×0.5 mm) of tissue conditioner (Softone) and resilient liner (Trusoft) were created either without (control) or with the incorporation of 1 of the 3 following drugs at MICs (g of drug per g of resilient material powder): nystatin (Ny, 0.032g/g), chlorhexidine diacetate (Chx, 0.064g/g), and ketoconazole (Ke, 0.128g/g). Specimens were dried; immersed in water for 24 hours and 7 or 14 days; weighed, dried, and weighed again. Data (µg/mm(3)) were analyzed by 3-way ANOVA followed by the Tukey-Kramer honest significant differences test (α=.05). RESULTS: At the 14-day interval, only the addition of Chx (483.0 ±61.0 µg/mm(3)) increased the WS of the tissue conditioner compared with the control group (244.0 ±42.0 µg/mm(3); P<.001). For all periods, the solubility of both materials increased with the addition of Chx (27.7 ±6.1 µg/mm(3)) and Ke (30.9 ±5.3 µg/mm(3)) compared with the control group (22.5 ±6.0 µg/mm(3); P<.001). CONCLUSIONS: After 14 days, the addition of Ny and Ke at MICs in both Softone and Trusoft and addition of Chx in Trusoft did not affect WS. The solubility of the 2 interim materials was not altered by the addition of Ny for up to 14 days.

Effect of storage times and mechanical load cycling on dentin bond strength of conventional and self-adhesive resin luting cements.

STATEMENT OF PROBLEM: The lack of long-term bond stability between resin cements and dentin may compromise the success of indirect restorations. PURPOSE: The purpose of this study was to evaluate the effects of long-term storage in artificial saliva and mechanical load cycling on the microtensile bond strength of conventional and self-adhesive resin cements to dentin. MATERIAL AND METHODS: The occlusal dentin surfaces of 128 human molars were exposed and flattened. The teeth were assigned to 16 groups (n=8) according to resin cement and in vitro aging strategy. Two self-adhesive resin cements (RelyX Unicem and Clearfil SA Cement) and 2 conventional cementing systems (RelyX ARC and Clearfil Esthetic Cement) were used. Resin cements were applied to prepolymerized indirect resin disks, which were bonded to the dentin surfaces and light polymerized. The control groups were represented by immediate microtensile bond strength (24 hours) and aging methods were performed with mechanical load cycling or storage in artificial saliva (1 year and 2 years). Bonded beams were tested in tension until failure. Data (MPa) were analyzed by Proc Mixed for repeated measures and the Tukey-Kramer test (α=.05). RESULTS: The self-adhesive resin cements exhibited higher microtensile bond strength than conventional cementing systems for all conditions studied. The microtensile bond strength of RelyX ARC and self-adhesive resin cements did not decrease after storage in artificial saliva and mechanical load cycling. The Clearfil Esthetic Cement showed the lowest microtensile bond strength and a significant reduction after 2 years of storage in artificial saliva. CONCLUSIONS: The storage times and mechanical load cycling did not affect the microtensile bond strength of self-adhesives and RelyX ARC resin cements. The highest microtensile bond strength was obtained for self-adhesive resin cements, with no significant difference between them.

Effects of a peripheral enamel margin on the long-term bond strength and nanoleakage of composite/dentin interfaces produced by self-adhesive and conventional resin cements.

PURPOSE: This study evaluated the effects of peripheral enamel margins on the long-term bond strength (µTBS) and nanoleakage in resin/dentin interfaces produced by self-adhesive and conventional resin cements. MATERIALS AND METHODS: Five self-adhesive [RelyX-Unicem (UN), RelyX-U100 (UC), GCem (GC), Maxcem (MC), Set (SET)] and 2 conventional resin cements [RelyX-ARC(RX), Panavia F(PF)] were used. An additional group included the use of a two-step self-etching adhesive (SE Bond) with Panavia F (PS). One hundred ninety-two molars were assigned to 8 groups according to luting material. Five-mm-thick composite disks were cemented and assigned to 3 subgroups according to water-exposure condition (n = 6): 24-h peripheral exposure (24h-PE-enamel margins), or 1 year of peripheral (1 yr-PE) or direct exposure (1 yr-DE-dentin margin). Restored teeth were sectioned into beams and tested in tension at 1 mm/min. Data were analyzed by two-way ANOVA and Tukey's test. Two additional specimens in each group were prepared for nanoleakage evaluation. Nanoleakage patterns were observed under SEM/TEM. RESULTS: Except for RX, no significant reduction in µTBS was observed between 24h-PE and 1 yr-PE. 1 yr-DE reduced µTBS for RX, PF, GC, MC, and SET. No significant reduction in µTBS was observed for PS, UC, and UN after 1 year. After 1 yr-DE, RX and PS presented the highest µTBS, and SET and MC the lowest. Nanoleakage was reduced when there was a peripheral enamel margin. SET and MC presented more silver deposition than other groups. CONCLUSION: The presence of a peripheral enamel margin reduced the degradation rate in resin/dentin interfaces for most materials. The µTBS values produced by the multi-step luting agents RX and PS were significantly higher than those observed for self-adhesive cement.

Effect of different concentrations of carbamide peroxide on microhardness of dental ceramics.

PURPOSE: To evaluate the effect of 10% and 16% carbamide peroxide bleaching agents on microhardness of dental ceramics after different periods of bleaching treatment. METHODS: 15 specimens with 5 x 3 x 1 mm3 were created with four dental ceramics following manufacturers' instructions: IPS Classic (Ivoclar-Vivadent); IPS d.Sign (Ivoclar-Vivadent); EX3 (Noritake); VMK-95 (Vita). A microhardness tester with a Knoop diamond with a 100 g load was used to evaluate the baseline microhardness values of all ceramics. Afterwards, the specimens were submitted to 6-hour daily bleaching treatments with 10% or 16% carbamide peroxide (Whiteness Perfect-FGM) for 21 days, while control groups from each ceramic system were maintained in artificial saliva. The microhardness of all groups was evaluated at 18, 42, 84, and 126 hours of bleaching treatment. The mean value of five indentations performed at each specimen in each time was obtained and all data were submitted to two-way repeated measures ANOVA and Tukey's post-hoc test (alpha = 0.05). RESULTS: No significant differences in ceramic microhardness were observed among either bleaching intervals or bleaching treatments. Ceramic restorations are not affected by carbamide peroxide 10% or 16% gel during bleaching treatment.

Influence of curing mode and time on degree of conversion of one conventional and two self-adhesive resin cements.

This study evaluated the effect of curing mode (auto- and dual-polymerizing mode) and time interval (5, 10 and 15 minutes) on the degree of conversion of resin cements. One conventional dual-cured resin cement (Panavia F 2.0 [Kuraray Medical Inc]) and two self-adhesive cements (RelyX Unicem [3M ESPE] and BisCem [BISCO, Inc]) were evaluated. The products (n = 5) were manipulated according to the manufacturer's instructions and applied to the surface of a horizontal attenuated reflectance unit attached to an infrared spectrometer. The materials were either light-cured for 40 seconds (dual-polymerizing mode) or allowed to auto-polymerize. The degree of conversion was calculated according to changes in the aliphatic-to-aromatic peak ratios prior to and 5, 10 and 15 minutes after light-activation or after mixing when the specimens were allowed to auto-polymerize. Data (%) were analyzed by two-way repeated measure ANOVA (curing mode and time interval) and Tukey's post-hoc test (alpha = 0.05%). The light-activating mode led to a higher degree of conversion values than the self-curing mode in self-adhesive cements (RelyX Unicem and BisCem), while there was no difference in the degree of conversion between the self- and light-cured groups of Panavia F 2.0 resin cement. All products showed a higher degree of conversion at 15 minutes postcuring than any other evaluation interval. The self-adhesive cements provide a higher degree of conversion values when light-activated. After 15 minutes of polymerization initiation, the degree of conversion was higher in all resin cements, regardless of the curing mode.

Microtensile bond strength of new self-adhesive luting agents and conventional multistep systems.

STATEMENT OF PROBLEM: Several self-adhesive luting agents have recently been introduced on the market. It is crucial to know the effectiveness of such luting agents prior to their clinical application. PURPOSE: The purpose of this study was to evaluate the microtensile bond strengths (microTBS) produced by different self-adhesive cements and compare them with conventional luting agents. MATERIAL AND METHODS: Six self-adhesive cements (RelyX Unicem (UN), RelyX U100 (UC), SmartCem 2 (SC), G-Cem (GC), Maxcem (MC), and SeT (SET), and 2 conventional luting agents, one that uses a 2-step etch-and-rinse adhesive (RelyX ARC (RX)), and one that uses a 1-step self-etching adhesive (Panavia F (PF)), were used in this study. An additional group included the use of a 2-step self-etching primer adhesive system (Clearfil SE Bond) prior to the application of Panavia F (PS). Fifty-four human molars were abraded to expose occlusal surfaces and were assigned to 9 groups according to the luting material (n=6). Five composite resin (Filtek Z250) discs (12 mm in diameter, 5 mm thick) were cemented on the teeth according to manufacturers' instructions. After 24 hours of water storage, restored teeth were serially sectioned into beams with a cross-sectional area of approximately 1 mm2 at the bonded interface and were tested in tension with a crosshead speed of 1 mm/min. Failure mode was determined using scanning electron microscopy. Data were statistically analyzed by 1-way ANOVA and Tukey's studentized range HSD test (alpha =.05). RESULTS: Mean bond strengths (SD) in MPa were: RX, 69.6 (16.6)A; PS, 49.2 (9.7)A; PF, 33.7 (13.9)AB; GC, 16.9 (10.3)BC; UC, 15.3 (3.4)BC; UN, 12.5 (2.4)C; MC 11.5 (6.8)CD; SC, 8.5 (4.9)CD; SET, 4.6 (0.5)D. Groups with different uppercase letters were significantly different from each other (P<.05). The predominant failure mode of the self-adhesive cements was adhesive between the resin cement and dentin. CONCLUSIONS: The bond strengths produced by the multistep luting agents were significantly higher than those observed for most self-adhesive cements.

Micromorphology of resin/dentin interfaces using 4th and 5th generation dual-curing adhesive/cement systems: a confocal laser scanning microscope analysis.

PURPOSE: This study evaluated the differential composition of resin/dentin interfaces of indirect restorations created by the application of 4th and 5th generation dual-curing luting systems (bonding agents/resin cements), when each material was either light cured or allowed to self-cure. MATERIALS AND METHODS: Occlusal flat dentin surfaces of 60 human third molars were assigned into 12 groups (n = 5) according to curing mode and dual-curing cementing system: 4th generation All Bond2 (AB2)/Duolink (Bisco) and 5th generation (B1) Bond1/Lute-it (Pentron). Fluorescein-labeled dextran (FDx) was mixed with the bonding agents, while rhodamine-labeled dextran (RhDx) was incorporated into resin cements and Pre-Bond resin from AB2. Resin cements were applied to 2-mm-thick, precured resin composite disks (Z250, 3M ESPE), which were fixed to dentin surfaces containing adhesive resin in either cured (light cured; LC) or uncured (self-cured; SC) states. The restored teeth were light activated (XL3000, 3M ESPE) according to the manufacturers' instructions (LRC) or allowed to self-cure (SRC), were stored for 24 h, and then vertically, serially sectioned into l-mm-thick slabs, which were analyzed using confocal laser scanning microscopy. Fluorescent additives indicated where individual components of the bonding/cement systems were located. Additional specimens were prepared and analyzed using a conventional scanning electron microscope. RESULTS: AB2/LC and B1/LC exhibited nonuniform primer/adhesive layer thickness. AB2/SC showed adhesive resin penetration within the primed dentin, and resin cement penetration at the entrance of the dentin tubules. B1/SC/LRC demonstrated resin cement penetration within the hybrid layer and into the dentin tubules. More resin cement penetration was observed in B1/SC/SRC groups than in its LRC equivalent. CONCLUSION: The morphological features and component interactions among materials at resin/dentin interfaces are related to the activation modes of the primer/adhesive layer and of the resin cement used.

Effect of sodium sulfinate salts on the polymerization characteristics of dual-cured resin cement systems exposed to attenuated light-activation.

OBJECTIVES: To evaluate the effectiveness of sodium sulfinate salt co-initiators on the degree of conversion (DC) of dual-cured cementing systems [combination of bonding agent (BA) and resin cement (RC)] when the activating light is attenuated or not available. METHODS: Two 5th generation products [Prime&Bond NT Dual-Cure/Calibra (Dentsply), and Excite DSC/Variolink II (Ivoclar/Vivadent)] were applied, either with or without co-initiators (sodium sulfinate salts) added to the bonding agents, to the surface of a horizontal attenuated-total-reflectance unit, and were polymerized using one of four conditions: self-cure (SC), or direct light exposure (DLE/XL3000/3M) through a glass slide or through pre-cured resin discs (shades A2 or A4/2mm-thick) (Z250/3M-ESPE). Real-time infrared spectra were obtained after placing components (uncured) and during 10 min (cured) (16 scans at 2 cm(-1), FTS-40/Digilab/Bio-Rad) to obtain polymerization kinetics. DC and maximum rate of polymerization (Rpmax) were calculated using standard techniques of observing changes in aliphatic-to-aromatic peak ratios pre- and post-curing. Data (n=5) were analyzed by two-way ANOVA and Tukey's test (p=0.05). RESULTS: The addition of co-initiators increased the DC in most of the groups. No significant difference in DC was observed between Prime Bond NT Dual-Cure/Calibra and its version without co-initiator using the DLE curing mode. All DLE groups exhibited the highest DC after 10 min. No significant difference in DC was observed between A2 and A4 pre-cured overlay groups. The SC groups exhibited lower DC than the light-activated groups regardless of the presence of co-initiator. Use of co-initiators increased the Rpmax only in the SC groups. The A2 and A4 groups exhibited lower Rpmax than DLE groups, regardless of the presence of co-initiator. CONCLUSION: The detrimental effects of light attenuation on the DC were not avoided by inclusion of sodium sulfinate salts, despite their ability to eliminate the chemical incompatibility between acidic monomers and self-curing components.

Kinetic analysis of monomer conversion in auto- and dual-polymerizing modes of commercial resin luting cements.

STATEMENT OF PROBLEM: Lack of knowledge regarding the kinetics of the setting reaction of dual- and autopolymerizing resin luting agents (RLA) leads the clinician to underestimate the care required during occlusal adjustments of indirect restorations. PURPOSE: The purpose of this study was to evaluate the degree of conversion (DC), maximum rate of polymerization (R(p)(max)), and potential of cure (ratio of conversions in autopolymerized relative to dual-polymerized modes; PC(A/D)) of 5 dual-polymerizable RLAs at 5 and 10 minutes, after mixing RLA components using infrared (IR) spectroscopy. MATERIAL AND METHODS: The RLAs evaluated included Calibra, Duo-Link, Lute-It, Nexus 2, and RelyX ARC. The RLAs were manipulated and applied to the horizontal diamond element in the optical bench of an IR spectrometer. The materials were either light activated for 40 seconds (dual-polymerizing mode) or were allowed to autopolymerize (autopolymerizing mode). The DC, R(p)(max), and PC(A/D) were calculated using standard techniques of observing changes in aliphatic-to-aromatic peak ratios before and after polymerization. Data (n=5) were analyzed by 2-way repeated measures ANOVA and Tukey's post hoc test (alpha=.05). RESULTS: All autopolymerizing groups exhibited lower DC and R(p)(max) values than the dual-polymerizing groups (P<.001), and higher DC values at 10 minutes than at 5 minutes, only in the autopolymerizing mode. Duo-Link exhibited the highest R(p)(max) values among dual-polymerizing groups, while Lute-It and Calibra showed the lowest R(p)(max) values and the highest PC(A/D) values. Within autopolymerizing groups, Nexus 2 and Lute-It exhibited the highest R(p)(max) values, while RelyX ARC demonstrated the lowest R(p)(max) as well as the lowest PC(A/D) values. CONCLUSIONS: The DC values of all autopolymerized groups of RLAs were lower than those of the dual-polymerized RLAs, but the differences in R(p)(max) and PC(A/D) were product dependent. The DC of all products was higher at the 10-minute interval than at the 5-minute interval, only in the autopolymerizing mode.

Effect of curing mode on the polymerization characteristics of dual-cured resin cement systems.

OBJECTIVES: To evaluate the effects of different curing conditions on the degree of conversion (DC) of dual-cured cementing systems [combination of bonding agent (BA) and resin cement (RC)] using infrared spectroscopy. METHODS: Four fourth generation products [Scotchbond Multipurpose Plus/RelyX (3M ESPE), Optibond/Nexus 2 (Kerr), All Bond2/Duolink (Bisco), and Bond-It!/Lute-It! (Pentron)], and three fifth generation materials [Bond1/Lute-It! (Pentron), Prime&Bond NT Dual-Cure/Calibra (Dentsply), and Optibond Solo Dual Cure/Nexus 2 (Kerr)] were applied to the surface of a horizontal attenuated-total-reflectance unit, and were polymerized using one of four conditions: self-cure (SC), direct light exposure through glass slide (DLE, XL3000/3M ESPE) or through pre-cured resin discs (shades A2;A4/2mm thick/Z250/3M ESPE). Infrared spectra of the uncured cementing systems were recorded immediately after application to the ATR, after the system was light-cured or left to self-cure, and spectra were obtained 5 and 10 min later. DC was calculated using standard techniques of observing changes in aliphatic-to-aromatic peak ratios pre- and post-curing. Data (n=5) were analyzed by two-way repeated measures ANOVA and Tukey's test (p=0.05). RESULTS: Changes in aliphatic-to-aromatic peak ratios before and after placing RC onto the BA demonstrated that a combined layer was created. All groups exhibited higher DC after 10 min than after 5 min, except the DLE group of Bond-it!/Lute-it!. No significant differences in DC were observed among light-activated groups regardless of the resin disc shade in three of the four fourth generation cementing systems. The SC groups exhibited lower DC than the DLE groups for both fourth and fifth generation products either after 5 or 10 min. CONCLUSION: The chemistry of the bonding interface changed when RCs were applied to uncured BAs. The presence of an indirect restoration can decrease the DC of some cementing systems and the self-curing mode leads to lower DC than the light-activating one.

Microtensile bond strength of dual-polymerizing cementing systems to dentin using different polymerizing modes.

STATEMENT OF THE PROBLEM: The effectiveness of bond strength using dual-polymerizing cementing systems ([DCSs] defined as the combination of dual-polymerizing bonding agents and resin cements) used with indirect restorations has not been evaluated when used solely with the autopolymerizing mode. PURPOSE: This study evaluated the in vitro microtensile bond strength (MTBS) of fourth- and fifth-generation DCSs with indirect composite restorations either light polymerized or autopolymerized. MATERIAL AND METHODS: Occlusal dentin surfaces of 48 human third molars were exposed and flattened. Teeth were assigned to 8 groups (n=6) according to the DCS and polymerizing modes: All-Bond2/Duolink (AB2), Optibond/Nexus2 (OPT), Bond1/Lute-it (B1), and Optibond Solo Dual Cure/Nexus2 (SOLO). Bonding agents were applied to dentin surfaces and left in the unpolymerized state. Resin cements were applied to prepolymerized resin discs (2 mm thick/Z250), which were subsequently bonded to the dentin surfaces. The restored teeth were light polymerized according to manufacturers' instructions (PP/XL 3000) or allowed to autopolymerize (AP). Restored teeth were stored in water at 37 degrees C for 24 hours and were both mesio-distally and bucco-lingually sectioned to obtain multiple bonded beams (1.2 mm2 of cross-sectional area). Each specimen was tested in tension at a crosshead speed of 0.6 mm/min until failure. Data (MPa) were analyzed by 2-way analysis of variance and the Tukey post hoc test (alpha=.05). Failure patterns of tested specimens were analyzed using scanning electron microscopy. RESULTS: The mean (SD) MTBS values (MPa) were: AB2/PP: 36.9 (6.5); AB2/AP: 32.7 (7.3); B1/PP: 38.2 (7.0); B1/AP: 13.0 (4.2); SOLO/PP: 33.2 (7.2); SOLO/AP: 23.4 (3.4); OPT/PP: 30.8 (7.5); OPT/AP: 13.1 (5.8). The AP groups showed significantly lower MTBS than the PP groups (P<.0001), except for AB2, which showed no difference between polymerization modes (P=.2608). CONCLUSION: The autopolymerizing mode of some dual-polymerizing cement systems may not be effective in promoting bond strength.

Ultramorphological analysis of resin-dentin interfaces produced with water-based single-step and two-step adhesives: nanoleakage expression.

This study evaluated the nanoleakage patterns in bonded interfaces using two single-step, self-etching adhesives (Adper Prompt-AD, and One-up Bond F-OB), two two-step, self-etching primers (Clearfil SE Bond-CF, and Unifil Bond-UB), and one two-step, total-etch adhesive (Single Bond-SB). Dentin surfaces were bonded with the adhesive systems and stored in water at 37 degrees C for 1 week and 6 months. After storage periods, teeth were sectioned into 0.8 mm-thick slabs, coated with nail varnish except for the bonded interfaces, and immersed in ammoniacal AgNO(3) for 24 h. After immersion in photodeveloping solution, bonded sections were prepared and observed under a SEM using the backscattered electron mode. Undemineralized, unstained, epoxy resin-embedded sections were prepared for TEM. Nanoleakage patterns were qualitatively compared between periods. Nanoleakage was observed in all bonded specimens at both periods. CF and UB presented silver deposits predominantly restricted to the thin (0.5 microm) hybrid layer (HL) at both periods. Although no evident differences were observed in the nanoleakage pattern of UB at 7 days and 6 months, CF presented enlarged areas of silver impregnation after 6 months. SB presented accumulation of silver particles mostly within the HL at 7 days, which was intensified after 6 months. AD and OB presented massive silver accumulation within the HL and the overlying adhesive layer. No evident differences were noticed between storage periods. Silver impregnation increased for all adhesive systems from 7 days to 6 months, except for UB.