Radiotherapy impairs adhesive bonding in permanent teeth.

OBJECTIVES: To evaluate the in vitro effects of radiotherapy (RT) on the morphological surface of the enamel and dentin and to determine the best adhesive system and most appropriate time to restore teeth in head and neck cancer patients. METHODS: Sixty third molars were cut into 120 enamel fragments and 120 dentin fragments and divided into four groups (n = 30): G1 (control): nonirradiated, only restorative procedure; G2: restorative procedure immediately before RT; G3: restorative procedure immediately after RT; and G4: restorative procedure 6 months after RT. Each group was divided into two subgroups: Adper™ Single Bond 2 (SB) and Clearfill SE Bond (CL) based on the material used. After RT and restorative procedures, the specimens were subjected to confocal microscopy and shear bond strength test. Data were analyzed using a two-way ANOVA followed by Tukey's test at a significance level of 5%. RESULTS: Morphological changes were observed in both substrates after a cumulative dose of 40 Gy, and after 60 Gy, the changes were more evident in both substrates. CL had the highest strength values in both substrates (p < 0.05), and G2 had the lowest strength values for the enamel and dentin (p < 0.05). CONCLUSIONS: Based on the in vitro study results, we can conclude that RT substantially changes the morphological surface of enamel and dentin and impairs the bond strength. The Clearfill system yielded better results than Adper Single Bond 2, and restoring teeth before RT resulted in the worst results in both substrates.

The effect of 1.5 T and 3 T magnetic resonance imaging on microleakage of amalgam restorations.

The aim of this article is to compare the effects of 1.5 T and 3 T MRI on microleakage of amalgam restorations. A total of 90 extracted molar teeth were used in this study. Amalgam was used to restore standard Class V preparations (5 × 3 × 2 mm). Following the restoration, the teeth were divided into three groups according to magnetic resonance imaging (MRI) protocol (Group I: Control, Group II: 1.5 T MRI, and Group III: 3 T MRI). A total of 6,000 thermal cycles at 5°C-55°C were applied on all samples. Microleakage values were measured in millimeters using the ImageJ program. Microleakage values were higher in the gingival region compared to the occlusal region in all groups and the differences were statistically significant (p < .05). Microleakage values were not statistically different among the groups in the occlusal region (p > .05), while there were statistically significant differences among the groups with respect to microleakage values in the gingival region (p < .01). The highest mean microleakage amount in the gingival region was measured in Group III (1.192 ± 0.941 mm). This was followed by Group II (0.519 ± 0.813 mm) and Group I (0.347 ± 0.726 mm), respectively. Within the limitations of this in vitro study, we observed that higher microleakage values in amalgam restored teeth in which were exposed to MRI procedure. We also found that the teeth exposed to the stronger magnetic field showed higher microleakage amount.

Influence of Er:YAG laser pulse duration on the long-term stability of organic matrix and resin-dentin interface.

The purpose of this study was to explore the influence of Er:YAG laser irradiation with different pulse durations on the organic matrix, micromorphology of the hybrid layer (HL), and bond strength over time. Sixty caries-free human molars were cut to obtain flat dentin surfaces which were randomly divided into 4 groups: control (not irradiated-G1) and laser groups (80 mJ/2 Hz) with pulse duration ranging between 50 (G2), 300 (G3), and 600 µs (G4). A self-etch adhesive system (Universal 3M ESPE) was applied on pre-treated dentin surfaces and cylinders of resin composite were built up and stressed in a universal testing machine (µSBS) at 24 h and after12 months (n = 12). In addition, 3 other dentin-bonded specimens were prepared as previously described for each group with the adhesive doped with 0.1 wt% Rhodamine B to analyze hybrid layer morphology under Confocal Laser Microscope Scanning (CLMS). Organic matrix and collagen fibrils were analyzed by second harmonic generation (SGH). Two-way ANOVA and Tukey's test detected significantly higher µSBS values for the control group, whereas the lower values were observed in all laser groups at 24 h (p < 0.05). Storage in artificial saliva did not reduce µSBS in all groups. The low signal emitted by SHG images below the irradiated area demonstrated thermal damage of the collagen matrix. CLMS images of laser groups exhibited thicker and irregular resin-dentin interfaces than the control group. Regardless of the pulse duration, Er:YAG laser pre-treatment altered the organic matrix and HL formation which resulted in low µSBS values at 24 h. The alterations on dentin's organic structure did not jeopardize the µSBS after 1 year of saliva storage.

Effect of diode laser irradiation on the bond strength of polymerized non-simplified adhesive systems after 12 months of water storage

Abstract Objectives: The aim of this in vitro study was to evaluate the bonding strength of non-simplified dentin bonding systems (DBS) to dentin irradiated with a diode laser (970 nm) immediately and after 12 months of water storage following either primer or bond application. Material and methods: The experimental design included three different factors: DBS type [AdperTM Scotchbond Multipurpose (MP) and Clearfil™ SE Bond (CSE)], irradiation [without irradiation - control (C), irradiation after primer application (AP), and irradiation after bond application (AB)], and time [initial (I) and after 12 months of water storage (12 m)]. Sixty sound human third molars (n = 10) were obtained, and their flat occlusal dentin areas were prepared and standardized. Laser irradiation was performed in the contact mode perpendicular to the dental surface over an automatically selected scanning area at a pulse energy of 0.8 W, frequency of 10 Hz, and energy density of 66.67 J/cm2. After 7 days of treatment, the specimens were cut, and half of them were subjected to microtensile testing (500 N/0.05 mm/min), whereas the remaining sticks were examined after 12 months of water storage. The obtained data were analyzed by three-way analysis of variance (ANOVA) followed by a Tukey test (p<0.05). The observed fracture modes were investigated using a portable digital microscope with a magnification of 40x. Results: Among the utilized DBS, MP generally exhibited higher bond strengths, but did not always differ from CSE under similar conditions. The irradiation factor was statistically significant only for the MP/AB groups. After 12 months of storage, all groups demonstrated a significant reduction in the bond strength, whereas the results of fracture analysis showed a predominance of the adhesive type. Conclusions: The laser treatment of non-simplified DBS was not able to stabilize their bonding characteristics after 12 months.

Effect of diode laser irradiation on the bond strength of polymerized non-simplified adhesive systems after 12 months of water storage.

OBJECTIVES: The aim of this in vitro study was to evaluate the bonding strength of non-simplified dentin bonding systems (DBS) to dentin irradiated with a diode laser (970 nm) immediately and after 12 months of water storage following either primer or bond application. MATERIAL AND METHODS: The experimental design included three different factors: DBS type [AdperTM Scotchbond Multipurpose (MP) and Clearfil™ SE Bond (CSE)], irradiation [without irradiation - control (C), irradiation after primer application (AP), and irradiation after bond application (AB)], and time [initial (I) and after 12 months of water storage (12 m)]. Sixty sound human third molars (n = 10) were obtained, and their flat occlusal dentin areas were prepared and standardized. Laser irradiation was performed in the contact mode perpendicular to the dental surface over an automatically selected scanning area at a pulse energy of 0.8 W, frequency of 10 Hz, and energy density of 66.67 J/cm2. After 7 days of treatment, the specimens were cut, and half of them were subjected to microtensile testing (500 N/0.05 mm/min), whereas the remaining sticks were examined after 12 months of water storage. The obtained data were analyzed by three-way analysis of variance (ANOVA) followed by a Tukey test (p<0.05). The observed fracture modes were investigated using a portable digital microscope with a magnification of 40x. RESULTS: Among the utilized DBS, MP generally exhibited higher bond strengths, but did not always differ from CSE under similar conditions. The irradiation factor was statistically significant only for the MP/AB groups. After 12 months of storage, all groups demonstrated a significant reduction in the bond strength, whereas the results of fracture analysis showed a predominance of the adhesive type. CONCLUSIONS: The laser treatment of non-simplified DBS was not able to stabilize their bonding characteristics after 12 months.

Effect of photodynamic therapy on the mechanical properties and bond strength of glass-fiber posts to endodontically treated intraradicular dentin.

STATEMENT OF PROBLEM: The use of photosensitizers in photodynamic therapy promotes intraradicular microbial reduction during nonsurgical endodontic therapy. However, studies are lacking on the consequences of the application of these agents on the mechanical properties of intraradicular dentin and on the bond strength of glass-fiber posts. PURPOSE: The purpose of this in vitro study was to evaluate the influence of photodynamic therapy on the bond strength of glass-fiber posts using a push-out test and, additionally, to measure the Martens hardness (MH) and elastic indentation modulus (Eit) of intraradicular dentin when different photosensitizers are used. MATERIAL AND METHODS: Eighty bovine teeth were used to simulate experimental endodontic treatments. Biomechanical instrumentation was performed for all root canals, and the teeth were distributed into 5 groups: control-deionized water; methylene blue 50 mg/L + red laser; methylene blue 100 mg/L + red laser; curcumin 500 mg/L + blue LED; and curcumin 1000 mg/L + blue LED. The MH and Eit of intraradicular dentin were measured using an ultramicrohardness tester under a load of 3 mN (n=8). The push-out bond strength of glass-fiber posts to dentin was measured using a universal testing machine (n=8). Mechanical properties and bond strength data were subjected to the Kruskal-Wallis test, ANOVA, and Fisher least significant difference test (α=.05). Images of representative specimens were obtained using a scanning electron microscope. RESULTS: The MH, Eit, and bond strength of intraradicular dentin were influenced by the photosensitizer used. In general, curcumin promoted lower mechanical properties values but higher bond strength values. CONCLUSIONS: Photosensitizers influenced the mechanical properties of intraradicular dentin and the bond strength of glass-fiber posts, and methylene blue at 50 mg/L had no marked effect on the mechanical properties of the dentin or the bond strength values.

Does laser diode irradiation improve the degree of conversion of simplified dentin bonding systems?

OBJECTIVE: This study aimed to investigate the effect of laser diode irradiation on the degree of conversion (DC), water sorption (WS), and water solubility (WSB) of these bonding systems in an attempt to improve their physico-mechanical resistance. MATERIAL AND METHODS: Two bonding agents were tested: a two-step total-etch system [Adper™ Single Bond 2, 3M ESPE (SB)] and a universal system [Adper™ Single Bond Universal, 3M ESPE (SU)]. Square-shaped specimens were prepared and assigned into 4 groups (n=5): SB and SU (control groups - no laser irradiation) and SB-L and SU-L [SB and SU laser (L) - irradiated groups]. DC was assessed using Fourier transform infrared spectroscopy with attenuated total reflectance. Additional uncured resin samples (≈3.0 µL, n=5) of each adhesive were also scanned for final DC calculation. For WS/WSB tests, similar specimens (n=10) were prepared and measured by monitoring the mass changes after dehydration/water storage cycles. For both tests, adhesive fluids were dropped into standardized Teflon molds (6.0×6.0×1.0 mm), irradiated with a 970-nm laser diode, and then polymerized with an LED-curing unit (1 W/cm2). RESULTS: Laser irradiation immediately before photopolymerization increased the DC (%) of the tested adhesives: SB-L>SB>SU-L>SU. For WS/WSB (µg/mm3), only the dentin bonding system (DBS) was a significant factor (p<0.05): SB>SU. CONCLUSION: Irradiation with a laser diode improved the degree of conversion of all tested simplified dentin bonding systems, with no impact on water sorption and solubility.

Does laser diode irradiation improve the degree of conversion of simplified dentin bonding systems?

Abstract Simplified dentin-bonding systems are clinically employed for most adhesive procedures, and they are prone to hydrolytic degradation. Objective This study aimed to investigate the effect of laser diode irradiation on the degree of conversion (DC), water sorption (WS), and water solubility (WSB) of these bonding systems in an attempt to improve their physico-mechanical resistance. Material and Methods Two bonding agents were tested: a two-step total-etch system [Adper™ Single Bond 2, 3M ESPE (SB)] and a universal system [Adper™ Single Bond Universal, 3M ESPE (SU)]. Square-shaped specimens were prepared and assigned into 4 groups (n=5): SB and SU (control groups - no laser irradiation) and SB-L and SU-L [SB and SU laser (L) - irradiated groups]. DC was assessed using Fourier transform infrared spectroscopy with attenuated total reflectance. Additional uncured resin samples (≈3.0 µL, n=5) of each adhesive were also scanned for final DC calculation. For WS/WSB tests, similar specimens (n=10) were prepared and measured by monitoring the mass changes after dehydration/water storage cycles. For both tests, adhesive fluids were dropped into standardized Teflon molds (6.0×6.0×1.0 mm), irradiated with a 970-nm laser diode, and then polymerized with an LED-curing unit (1 W/cm2). Results Laser irradiation immediately before photopolymerization increased the DC (%) of the tested adhesives: SB-L>SB>SU-L>SU. For WS/WSB (μg/mm3), only the dentin bonding system (DBS) was a significant factor (p<0.05): SB>SU. Conclusion Irradiation with a laser diode improved the degree of conversion of all tested simplified dentin bonding systems, with no impact on water sorption and solubility.

The effect of Er:YAG laser irradiation on the bond stability of self-etch adhesives at different dentin depths.

The aim of this study was to evaluate the effect of Er:YAG laser irradiation on the micro-shear bond strength of self-etch adhesives to the superficial dentin and the deep dentin before and after thermocycling. Superficial dentin and deep dentin surfaces were prepared by flattening of the occlusal surfaces of extracted human third molars. The deep or superficial dentin specimens were randomized into three groups according to the following surface treatments: group I (control group), group II (Er:YAG laser; 1.2 W), and group III (Er:YAG laser; 0.5 W). Clearfil SE Bond or Clearfil S3 Bond was applied to each group's dentin surfaces. After construction of the composite blocks on the dentin surface, the micro-shear bond testing of each adhesive was performed at 24 h or after 15,000 thermal cycles. The data were analyzed using a univariate analysis of variance and Tukey's test (p < 0.05). Laser irradiation in superficial dentin did not significantly affect bond strength after thermocycling (p > 0.05). However, deep-dentin specimens irradiated with laser showed significantly higher bond strengths than did control specimens after thermocycling (p < 0.05). Thermocycling led to significant deterioration in the bond strengths of all deep-dentin groups. The stable bond strength after thermocycling was measured for all of the superficial-dentin groups. No significant difference was found between the 0.5 and 1.2 W output power settings. In conclusion, the effect of laser irradiation on the bond strength of self-etch adhesives may be altered by the dentin depth. Regardless of the applied surface treatment, deep dentin showed significant bond degradation.

Effect of different thermo-light polymerization on flexural strength of two glass ionomer cements and a glass carbomer cement.

STATEMENT OF PROBLEM: Whether polymerization lights can be used for heating glass ionomer cements (GICs) or glass carbomer (GCP) to improve their mechanical properties is not well established. PURPOSE: The purpose of this in vitro study was to assess the effect of thermo-light polymerization on the flexural strength (FS) of 2 GICs (Fuji IX GP Fast, Ketac Molar) and a GCP. MATERIAL AND METHODS: Specimens (n=10) were prepared in stainless steel molds (2×2×25 mm), compressed, exposed to 3 polymerization lights (500, 1000, 1200 mW/cm2) for 2 cycles of 40 seconds on each side, and stored in petroleum jelly (37°C, 24 hours). RESULTS: Significant FS differences were detected among groups after different thermo-light polymerization regimens (F=50.926, df=11, P<.001). GCP showed the highest mean FS (∼5 times, P<.001) after thermo-light polymerization with power outputs of 1000 (127.1 ±25.8 MPa) and 1200 mW/cm2 (117.4 ±18.5 MPa), with no significance difference between them (P=.98), compared with 500 mW/cm2 (24.1 ±1.7 MPa). For Ketac Molar, compared with autopolymerization setting (15.5 ±3.1 MPa), a significant increase in mean FS (∼2.5 times) was only observed in specimens treated with 1200 mW/cm2 polymerization light (P=.03). For Fuji IX GP Fast, only the light with 1000 mW/cm2 output significantly increased the FS (98.9 ±23.4 MPa, P<.001) compared with the autopolymerization setting (34.9 ±6.4 MPa). CONCLUSIONS: Thermo-light polymerization accelerated the development of FS in the tested GICs, potentially protecting against saliva contamination during the first 3 to 4 minutes after mixing GIC. Thermo-light polymerization of the glass carbomer with power outputs of 1000 and 1200 mW/cm2 also substantially increased FS. The clinical advantages of the findings should be validated by in vivo studies.

Efeito da irradiação com laser de diodo sobre adesivos dentinários: estudo in vitro / Effect of diode laser irradiation on dentin-bonding agents

A irradiação de sistemas adesivos com laser tem obtido resultados promissores, no entanto, seu mecanismo de ação, bem como a longevidade da camada híbrida obtida após a irradiação com laser ainda não estão bem estabelecidos na literatura. A presente tese teve como objetivo: avaliar a absorvância do laser de Diodo por diferentes sistemas adesivos por meio de espectroscopia no infravermelho próximo; avaliar a evaporação de água e solventes proporcionada pelo laser por meio da variação da massa analisada em balança de precisão; avaliar a resistência de união por meio de teste de microtração após envelhecimento de 12 meses. Os dados obtidos foram analisados por modelos de ANOVA, seguidos de teste Tukey (p<0,05) e os resultados demonstraram que: a irradiação no infravermelho próximo, área do espectro eletromagnético que compreende o laser de Diodo, não apresenta interação com os sistemas adesivos testados; o laser de Diodo é capaz de proporcionar maior alteração de massa, mesmo após contínua evaporação dos solventes com jatos de ar por 60s; sistemas adesivos simplificados apresentaram valores de resistência de união imediato semelhantes aos valores obtidos após 12 meses de envelhecimento. Os dados obtidos neste estudo sugerem que a irradiação com laser de Diodo pode contribuir favoravelmente para a adesão em dentina com sistemas adesivos simplificados após 1 ano.(AU)

The laser irradiation of adhesive systems has obtained promising results, however, its mechanism of action, as well as the longevity of the hybrid layer obtained after laser irradiation are still not yet well established in the literature. This thesis aimed to: assess the diode laser interaction with different adhesive systems by means of near infrared spectroscopy; evaluate the evaporation of solvents and water provided by the laser through the mass variation analyzed at a precision balance; evaluate the bond strength through microtensile bond strength test after 12 months of aging. The data was analyzed through ANOVA models, followed by Tukey test (p<0.05), and the results demonstrated that: in the near-infrared irradiation area, the electromagnetic spectrum comprising the diode laser, shows no interaction with the adhesive systems tested; the diode laser was able to provide greater mass variation, even after continual evaporation of solvents with air jets for 60s; simplified adhesive systems presented immediate bond strength values similar to the ones verified after 12 months of aging. The data obtained in this study suggest that the Diode laser irradiation can contribute favorably for the adhesion between dentin and simplified adhesive systems after 1 year.(AU)

Influence of light intensity on surface-free energy and dentin bond strength of single-step self-etch adhesives.

In this study, we investigated the influence of light intensity on the surface-free energy and dentin bond strength of single-step selfetch adhesives. The adhesives were applied to the dentin surfaces of bovine mandibular incisors and cured with light intensities of 0 (no irradiation), 200, 400, and 600 mW/cm(2). Surface-free energies were determined by measuring the contact angles of three test liquids placed on the cured adhesives. Dentin bond strengths of the specimens were also measured. Polymerization with a higher light intensity resulted in a lower surface-free energy of the cured adhesives. The greatest bond strength was achieved when a light intensity of 400 mW/cm(2) or greater was used. Our data suggest that the surface-free energy and dentin bond strength of single-step self-etch adhesives are affected by light intensity of the curing unit.

Effect of Nd:YAG laser on the solvent evaporation of adhesive systems.

OBJECTIVE: This study evaluated the influence of Nd:YAG laser on the evaporation degree (ED) of the solvent components in total-etch and self-etch adhesives. MATERIALS AND METHODS: The ED of Gluma Comfort Bond (Heraeus-Kulzer) one-step self-etch adhesive, and Adper Single Bond 2 (3M ESPE), and XP Bond (Dentsply) total-etch adhesives was determined by weight alterations using two techniques: Control--spontaneous evaporation of the solvent for 5 min; Experimental--Nd:YAG laser irradiation for 1 min, followed by spontaneous evaporation for 4 min. The weight loss due to evaporation of the volatile components was measured at baseline and after 10 s, 20 s, 30 s, 40 s, 50 s, 60 s, 70 s, 80 s, 90 s, 100 s, 110 s, 2 min, 3 min, 4 min, and 5 min. RESULTS: Evaporation of solvent components significantly increased with Nd:YAG laser irradiation for all adhesives investigated. Gluma Comfort Bond showed significantly higher evaporation of solvent components than Adper Single Bond 2 and XP Bond. All the adhesives lost weight quickly during the first min of Nd:YAG laser irradiation. CONCLUSION: The application of Nd:YAG laser on adhesives before light curing had a significant effect on the evaporation of the solvent components, and the ED of Gluma Comfort Bond one-step self-etch adhesive was significantly higher than with Adper Single Bond 2 and XP Bond total-etch adhesives. CLINICAL RELEVANCE: The use of the Nd:YAG laser on the uncured adhesive technique can promote a greater ED of solvents, optimizing the longevity of the adhesive restorations.

Influence of light intensity on surface free energy and dentin bond strength of core build-up resins.

OBJECTIVE: We examined the influence of light intensity on surface free energy characteristics and dentin bond strength of dual-cure direct core build-up resin systems. METHODS: Two commercially available dual-cure direct core build-up resin systems, Clearfil DC Core Automix with Clearfil Bond SE One and UniFil Core EM with Self-Etching Bond, were studied. Bovine mandibular incisors were mounted in acrylic resin and the facial dentin surfaces were wet ground on 600-grit silicon carbide paper. Adhesives were applied to dentin surfaces and cured with light intensities of 0 (no irradiation), 200, 400, and 600 mW/cm(2). The surface free energy of the adhesives (five samples per group) was determined by measuring the contact angles of three test liquids placed on the cured adhesives. To determine the strength of the dentin bond, the core build-up resin pastes were condensed into the mold on the adhesive-treated dentin surfaces according to the methods described for the surface free energy measurement. The resin pastes were cured with the same light intensities as those used for the adhesives. Ten specimens per group were stored in water maintained at 37°C for 24 hours, after which they were shear tested at a crosshead speed of 1.0 mm/minute in a universal testing machine. Two-way analysis of variance (ANOVA) and a Tukey-Kramer test were performed, with the significance level set at 0.05. RESULTS: The surface free energies of the adhesive-treated dentin surfaces decreased with an increase in the light intensity of the curing unit. Two-way ANOVA revealed that the type of core build-up system and the light intensity significantly influence the bond strength, although there was no significant interaction between the two factors. The highest bond strengths were achieved when the resin pastes were cured with the strongest light intensity for all the core build-up systems. When polymerized with a light intensity of 200 mW/cm(2) or less, significantly lower bond strengths were observed. CONClUSIONS: The data suggest that the dentin bond strength of core build-up systems are still affected by the light intensity of the curing unit, which is based on the surface free energy of the adhesives. On the basis of the results and limitations of the test conditions used in this study, it appears that a light intensity of >400 mW/cm(2) may be required for achieving the optimal dentin bond strength.

Influence of photopolymerization parameters on the mechanical properties of polymer-ceramic composites applied in the conservative dentistry.

In this paper, the results of study of mechanical properties for four commercial polymer-ceramic composites applied in the conservative dentistry are presented, including one new silorane based composite and three standard composites based on methacrylate compounds. Influence of the type of light of diode and halogen polymerization lamps on the microhardness, flexural strength and elasticity were studied. Both exposed and unexposed specimens were taken into account. An exposure time was also differentiated (40 sec and 60 sec). Basic statistics of the analysed material parameters were determined. A post hoc test (Newman-Keuls) was performed in order to evaluate differences between microhardness of the materials studied, as well as Kruskal-Wallis test to evaluate differences in flexural strength and elasticity modulus of the material. It has been indicated that there is an impact of the type of lamp on the microhardness and flexural strength of composites with methacrylate matrix and lack of such impact in the case of composites containing siloranes. Additionally, it has been found that an increase of photopolymerization time has a significantly different impact on the mechanical properties depending on the type of irradiated material.

Effects of prolonged light exposure times on water sorption, solubility and cross-linking density of simplified etch-and-rinse adhesives.

PURPOSE: This study evaluated the effects of light exposure times on water sorption, solubility, and polymer cross-linking density of simplified etch-and-rinse adhesives. MATERIALS AND METHODS: Four commercial adhesives (XP Bond, Adper Single Bond 2, Tetric N-Bond, and Ambar) were selected, and resin disks 5 mm in diameter and 1.0 mm thick were prepared and light cured for 20, 40, or 80 s using an LED light-curing unit at 1200 mW/cm2. Water sorption and solubility were evaluated over a 28-day period. For polymer cross-linking density, additional specimens were prepared and their Knoop hardness measured before and after immersion in 100% ethanol. The data from each test were evaluated using a two-way ANOVA and Tukey's test (α = 0.05). RESULTS: The XP Bond adhesive showed higher water sorption (similar to Adper Single Bond 2) and solubility (p < 0.05) than did the other materials. Prolonged exposure times did not reduce the water sorption but did reduce the solubility of all tested materials (p < 0.05). For Ambar, the increase in the exposure time resulted in a significantly lower percent reduction in hardness. CONCLUSION: Water sorption, solubility, and cross-linking density of the materials selected in this study seem to be mainly influenced by the adhesive composition. Prolonged light exposure times reduced the solubility of the materials.

Influence of ceramic thickness and type on micromechanical properties of light-cured adhesive bonding agents.

OBJECTIVE: The aim of this study was to evaluate the micromechanical properties of different adhesive bonding agents when polymerized through ceramics. MATERIALS AND METHODS: Sixty sound extracted human third molars were selected and the crowns were sectioned perpendicular to the long axis in order to obtain dentin slices to be bonded with one of the following adhesives: Syntac/Heliobond (Ivoclar-Vivadent) or Adper-Scotchbond-1XT (3M-ESPE). The adhesives were cured by using a LED-unit (Bluephase®, Ivoclar Vivadent) with three different curing times (10 s, 20 s and 30 s) under two ceramics (IPS-e.max-Press, Ivoclar-Vivadent; IPS-Empress®CAD, Ivoclar-Vivadent) of different thicknesses (0 mm, 0.75 mm, 2 mm). Thirty groups were included, each containing 60 measurements. Micromechanical properties (Hardness, HV; indentation modulus, E; and creep, Cr) of the adhesives were measured with an automatic microhardness indenter (Fisherscope H100C, Germany). Data were statistically analyzed by using one-way ANOVA and Tukey's post-hoc test, as well as a multivariate analysis to test the influence of the study parameters (SPSS 18.0). RESULTS: Significant differences were observed between the micromechanical properties of the adhesives (p < 0.05). The ceramic type showed the highest effect on HV (Partial-eta squared (η(2)) = 0.109) of the tested adhesives, while E (η(2) = 0.275) and Cr (η(2) = 0.194) were stronger influenced by the adhesive type. Ceramic thickness showed no effect on the E and Cr of the adhesives. CONCLUSIONS: The adhesive bonding agents used in this study performed well by curing through different thicknesses of ceramics. The micromechanical properties of the adhesives were determined by the adhesive type and were less influenced by ceramic type and curing time.

Effects of plasma-emulating light-emitting diode (LED) versus conventional LED on cytotoxic effects and polymerization capacity of orthodontic composites.

OBJECTIVES: The aim of this study was to evaluate, the cytotoxicity of orthodontic composites in vitro as a function of degree of conversion (DC) and the light curing units (LCU) employed on mouse fibroblast (L929). MATERIALS AND METHODS: Cured samples of the composites Light bond (Reliance Orthodontic Products, Itasca, Illinois, USA), Ortho bracket paste (Bisco, Schaumburg, Illinois, USA), Opal bond MV (OPAL, South Jordan, Utah, USA), and Transbond XT (3M, Monrovia, California, USA) were prepared. Polymerization was performed with two LCUs: VALO Ortho (Ultradent, South Jordan, Utah, USA) is a third-generation LCU and Elipar S10 (3M, USA) is a second-generation LCU. Four samples were immersed in cell culture medium to obtain composite extracts. After incubation of L929 cell cultures with the extracts obtained, cytotoxicity was determined using the methyl tetrazolium test. Fourier transform infrared spectroscopy (FTIR) was used to evaluate DC for five samples. A multivariate analysis of variance (ANOVA), two-way ANOVA, and Tukey's honestly significant difference test were utilized for statistical analyses. RESULTS: Cytotoxicity and DC of all tested composites (p < 0.001) and the interaction between composites and LCUs (p < 0.01) were significantly different. LCUs had no significant influence on the cytotoxicity and DC of composite materials (p > 0.05). The correlations between cell viability and DC were positive for three composites but statistically insignificant. CONCLUSION: Composites and LCUs must be matched with one another to result in satisfactory maximal biocompatibility and DC. Opal Bond plasma light-emitting diode combination was a better choice for cell viability. Three composites showed a positive correlation between cytotoxicity and DC. Therefore high-intensity LCUs can be said to efficiently affect polymerization, and so, higher DC rates may achieve higher cell viability rates.

The effect of photoactivation time and light tip distance on the degree of conversion of light and dual-cured dentin adhesives.

BACKGROUND: The degree of conversion of dental adhesive is an important parameter since poor mechanical properties are related to low percentage of monomer-to-polymer conversion within resin-based materials. OBJECTIVES: To evaluate the influence of polymerization time and light guide distance on the degree of conversion (DC) of three contemporary dental adhesives. MATERIALS AND METHODS: The spectral data of ExciTE DSC, Single Bond ® , and Adper ® Prompt L-Pop were analyzed using FTIR spectroscopy after 20 s, 40 s, and 60 s of photoactivation times. Light tip distances were kept at 1, 3, and 6 mm during the exposures. STATISTICS: Data were analyzed using ANOVA and Tukey's test (α = 0.05). RESULTS: Within groups, greater DC values were found using a tip distance of 1 mm or a 60-s curing time for Single Bond ® (59%) and Adper ® Prompt L-Pop (65%). No statistically significant difference (P > 0.05) was found using either 1 mm or 3 mm tip distances after 20 s, 40 s, and 60 s of light curing time for Single Bond ® . ExciTE ® DSC showed the greatest DC values with light tip distances of 1 mm (90%) and 3 mm (89%), using 60 s of light curing. CONCLUSION: The self-etch adhesive Adper ® Prompt L-Pop could be applied in shallow cavity preparations and must be light cured for at least 40 s. The light-cured total-etch adhesive ExciTE ® DSC could be applied in every restorative scenario if the curing time is extended up to 60 s or if the tip distance is extended up to 3 mm.

Temperature changes in the pulpal chamber and the sealing performance of various methods of direct pulp capping of primary teeth.

AIM: To compare changes in pulpal chamber temperature during the visible-light curing of direct pulp capping compounds and various modes of diode laser irradiation without prior placement of a pulp capping compound and the resultant seals. MATERIALS AND METHODS: Pulp exposure holes were made in 100 extracted human primary first molars, which were randomly assigned to ten equal groups. The holes were sealed by (a= Group 1, 2, 3, 4, 5, 6 and 7) different pulp capping compounds which were cured using various types of visible-light curing units or (b=Group 8, 9 and 10) diode laser irradiation without prior application of a pulp capping compound. Pulpal chamber temperatures were recorded during the procedure, and the resultant seals were examined under a scanning electron microscope. RESULTS: Visible-light curing of the pulp capping compounds and diode laser irradiation at a 0.7 W output power can cause non-injurious temperature rises in the pulpal chamber. At higher output powers of the diode laser, the temperature rises are sufficient to cause thermal injury. The seals were complete when pulp capping compounds were used for direct pulp capping, but were incomplete when laser irradiation without prior placement of a pulp capping compound was used for the identical purpose. CONCLUSION: The visible-light curing of pulp capping compounds is not harmful to vital pulp, and provides an effective seal of the pulp exposure hole. Laser irradiation is not an effective sealant, and can cause thermal injury to vital pulp at high output powers.