Effect of Additional Light Curing on Colour Stability of Composite Resins.

AIM: The objective of this study was to evaluate the effect of additional light curing on the colour stability of composite resins. MATERIALS AND METHODS: Four different composite resins-a nanofill, a nanohybrid, a microhybrid, and a bulk-fill composite resin-were tested. Eighty disc-shaped specimens were prepared from each material using either a quartz tungsten halogen or a light-emitting diode light source and were randomly divided into 2 groups according to the surface treatment: no polishing (nonpolished) or polishing with aluminum oxide discs (polished). Then additional light curing was applied to half of the specimens in each group. All specimens were immersed in coffee solution for 1 week. Colour was measured with a spectrophotometer at baseline and after 1 week of storage in coffee solution. RESULTS: Statistically significant differences in colour stability were observed in the restorative materials according to the composition of composite resin, the polishing protocol, and additional light curing, whilst there were no significant differences according to the light source. Additional light curing reduced discolouration in all groups tested. CONCLUSIONS: Additional light curing may be beneficial after finishing and polishing in order to maintain aesthetics and increase the resistance of composite resins to discolouration.

Evaluación clínica de acondicionamiento dentinario y presentaciones de ionómeros fotoactivados en odontopediatría / Clinical evaluation of dentin conditioning and different presentations of light cured glass ionomer in primary dentition

Objetivo: Comparar clínicamente el comportamiento, el tiempo operatorio requerido, el costo y la dificultad de diferentes técnicas de restauración en piezas primarias, empleando ionómero vítreo fotoactivado (IVF) polvo/líquido, con y sin uso de acondicionamiento dentinario, y en cápsulas, con acondicionamiento. Materiales y métodos: El diseño de este estudio fue experimental y comparativo. Se realizaron, en 18 pacientes de 7±2 años, 33 restauraciones con IVF de una o más piezas primarias vitales con lesiones amelodentinarias en 1 o 2 superficies. Según su día de concurrencia a la Cátedra de Odontología Integral Niños, se empleó: A) IVF polvo/líquido, con acondicionamiento (3M™ VitremerTM); B) IVF polvo/líquido, sin acondicionamiento (3M™ VitremerTM); y C) IVF en cápsulas, con acondicionamiento (Riva Light Cure). Las restauraciones fueron evaluadas clínicamente al inicio y a los 12 meses según los siguientes criterios: pérdida total, pérdida total con caries, requerimiento de reemplazo por pérdida parcial, requerimiento de reemplazo por caries, aceptable con deterioro, en condiciones. El grado de dificultad se analizó utilizando una planilla diseñada para tal fin. El tiempo operatorio requerido se midió sin considerar el tiempo de inserción. Resultados: El tiempo operatorio requerido fue de 2 minutos, 15 segundos en A; 1 minuto, 25 segundos en B; y 1 minuto, 10 segundos en C, sin considerar el tiempo de inserción. El costo fue 61,11% mayor para C. La dificultad fue de 3,2±0,6 para A y B, y de 1,5±0,7 para C (ANOVA; P<0,001). El comportamiento clínico no registró diferencias significativas entre los grupos (Fisher; P=0,339). Conclusión: Los ionómeros de restauración fotoactivados encapsulados utilizados en este estudio presentaron menor dificultad de manipulación, mayor costo y similar comportamiento clínico a un año que las presentaciones polvo-líquido, con o sin uso de acondicionamiento previo en piezas primarias (AU)

Aim: To assess the clinical performance, operative time required, cost and technical difficulties of different restorative techniques in primary teeth, using light cured glass ionomers (LCG), powder/liquid, with and without dentin conditioning and light cured glass ionomer in capsules with conditioning. Materials and methods: The design of this study was experimental and comparative. 33 restorations with LCG were performed in 18 patients, 7 ± 2-years-old, in one or more vital primary teeth with carious lesions involving one or more tooth surfaces. Patients were assigned to one of the three groups according to the day of the week in which they attended to the Pediatric Department of the Dental School: A) LCG powder/liquid, with conditioning (3M™ VitremerTM); B) LCG powder/liquid without conditioning (3M™ VitremerTM); and C) LCG in capsules with conditioning (Riva Light Cure). The restorations were clinically evaluated at baseline and after 12 months according to the following criteria: complete loss of the restoration, complete loss with caries, need of replacement because of partial loss, need of replacement because of caries, good condition with some wear and good condition. Technical difficulties were analyzed using a data sheet designed for that purpose. The operative time required was evaluated without considering the insertion time. Results: Time operative time required was 2 minutes 15 seconds in A, 1 minute 25 seconds in B and 1 minute 10 seconds in C. Cost was 61.11% higher for C. Difficulty was 3.2±0.6 for A and B and 1.5±0.7 for C (ANOVA; P<0.001). No significant differences were observed among the three groups in relation to the clinical performance (Fisher; P=0.339). Conclusions: In these 12 months, study in primary teeth, the light cured glass ionomers used dispensed in capsules showed to be the easiest to handle, had higher cost and similar clinical performance than the powder liquid presentations with and without dentin conditioner (AU)

Modeling based experimental investigation on polymerization shrinkage and micro-hardness of nano alumina filled resin based dental material.

This paper investigates the effect of %wt composition of BisGMA/TEGDMA, stirring time, bench time, curing time and filler loading on polymerization shrinkage and micro-hardness of resin based dental composites. The investigation was carried out in two stages. In first stage, samples were prepared with different %wt composition of BisGMA/TEGDMA, stirring time, bench time, and curing time to access the effect of different input parameters for minimum polymerization shrinkage and maximum micro-hardness using Taguchi methodology. Selecting optimum values of input factors from first stage, second stage optimization was performed to investigate the effects of different filler loading on different %wt composition of BisGMA/TEGDMA using full factorial design. Prediction model was developed using Design Expert software and analysis of effect of input parameters on output responses were carried out using 3D surface plots. ANOVA were performed to check the significance of prediction model. In first stage, optimum stirring time, bench time and curing time were found to be 4 h, 50 min and 30 s, respectively. In second stage, optimum polymerization shrinkage and micro-hardness of 3.54% and 310 Hv were predicted at 22.89% of TEGDMA content and 20% filler loading. Taguchi methodology and full factorial design were successfully implemented to access the effect of multi-input parameters on responses for resin based dental composites.

The effect of time between curing and tea immersion on composite resin discoloration.

One common cause for the replacement of a composite restoration is discoloration. This in vitro study evaluated the effect of tea solution on the discoloration of 3 types of composites at different timepoints after curing. For this study, 150 disc-shaped specimens of 3 types of composite resin-a nanohybrid (Filtek Z350), a microhybrid (Filtek Z250), and a microfilled material (Heliomolar)-were prepared. Specimens were randomly divided into 5 subgroups (n = 10) according to the type of composite and the time from curing to immersion in a tea solution (none [immersed immediately], 1 hour, 6 hours, 12 hours, or 24 hours postcuring). The color for all specimens was measured before and after immersion in tea. Color change (ΔE*) for all specimens was measured, and a ΔE* value of less than 3.3 was considered clinically acceptable. Analysis of variance and a post hoc Tukey test were used to analyze the data (α = 0.05). Immediately after curing, the levels of composite discoloration were deemed clinically acceptable (ΔE* < 3.3). In all composites, the greatest color change was found immediately after curing (P < 0.05). With each subsequent timepoint, the color stability increased. When the groups were immersed in tea 6 hours postcuring, the mean ΔE* value of the Filtek Z350 composite resin specimens was significantly greater than that of Heliomolar specimens (P < 0.05). The mean ΔE* value for specimens immersed 12 hours postcuring was also greater in the Filtek Z250 composite group than in the Heliomolar group (P < 0.05). The ΔE* values of Filtek Z350 and Filtek Z250 composites were not significantly different from each other (P > 0.05), except with 12-hour postcure immersion. The results suggest that patients should avoid the intake of staining foods or beverages for at least 12 hours after placement of a composite resin restoration, although this restriction may be reduced to 1 hour for microfilled composite resins.

Delayed Light Activation Improves Color Stability of Dual-Cured Resin Cements.

PURPOSE: To evaluate the color change caused by post-irradiation conversion (ΔE24h and ΔE8 days ) and artificial aging (ΔEAGING ) of resin cements light activated through ceramics of different opacities immediately and 6 minutes after manipulating the material. MATERIALS AND METHODS: Resin cement disks (Allcem and LuxaCore) were light activated through ceramics (without ceramic, e.max HT, LT, and MO) immediately and 6 minutes after the manipulation (n = 10). Spectrophotometry was used to evaluate ΔE24h and ΔE8 days after 37˚C-dry-dark-storage for 24 hours and 8 days, and ΔEAGING after 60˚C-water-storage for 24 hours. Data were analyzed with three-way ANOVA and Tukey's HSD (α = 0.05). RESULTS: Regarding the post-irradiation color change, significant differences were found between the cements (p < 0.0001), light activation protocols (p = 0.037), and ceramics (p < 0.001). The immediate activation (16.2 ± 0.1) showed lower ΔE values than the delayed activation (16.5 ± 0.1). Ceramics influenced the ΔE values as follows: MO (14.0 ± 1.2) < LT (14.9 ± 1.2) ≈ HT (15.4 ± 1.2) < control (21.2 ± 1.2). Regarding ΔEAGING , significant differences were found between cements (p < 0.001), light activation (p = 0.006), and ceramics (p < 0.001). The delayed activation (8.4 ± 0.1) showed lower values than the immediate activation (8.9 ± 0.1). Ceramic spacers influenced ΔEAGING as follows: control (5.6 ± 0.2) < MO (6.6 ± 0.2) < HT (11.0 ± 0.2) ≈ LT (11.5 ± 0.2). CONCLUSION: The delayed light activation resulted in increased color stability, while the ceramic interposition resulted in lower color stability.

Diagnóstico e tratamento restaurador com resina composta e matriz oclusal em molar com lesão de cárie oculta / Diagnosis and restorative treatment with composite resin and occlusal matrix on molar with occult caries lesion

Atualmente, o diagnóstico de cárie tem sido mais difícil em razão do aparecimento de pacientes com cáries ocultas nos dentes posteriores, sendo necessários métodos auxiliares capazes de proporcionar ao dentista segurança quanto à intervenção restauradora. Este trabalho teve como objetivo demonstrar, com um relato de caso clínico, a utilização do aparelho DIAGNOdent® (Kavo) como método auxiliar no diagnóstico de cárie oculta num primeiro molar inferior e a técnica restauradora direta com resina composta com auxílio de uma matriz oclusal em acrílico autopolimerizável (AU).

Currently the diagnosis of caries has been more difficult due to the presence of patients with occult caries in the posterior teeth, so ancillary methods are necessary to provide the dentist safety regarding restorative intervention. The objective of this study was to demonstrate through a clinical report, the use of the DIAGNOdent® (Kavo) device as an aid in the diagnosis of occult caries in a lower first molar and the direct restorative technique with a composite resin using an Acrylic self-curing occlusal matrix (AU).

Influencia de la presencia de barrillo en la profundidad de penetración dentinaria del agente fotosensible empleado en la terapia fotodinámica / Influence of the presence of semar layer in the depth of dentinal penetration of the phosotensitizing agent used in photodynamic therapy

La efectividad antimicrobiana de la terapia fotodinámica (TFD), como complemento a la preparación biomecánica, depende del íntimo contacto entre un agente fotosensible, una fuente de energía (LED) y los microorganismos presentes en el conducto. Objetivo. Evaluar si la eliminación del barrillo dentinario influye en la penetración del agente fotosensibilizante dentro de los túbulos dentinarios en la TFD. Metodología. 20 premolares con conductos tipo I fueron decoronados a 12 mm del ápicy preparados biomecánicamente con MTwo y NaOCL al 5,25%. La muestra se dividió aleatoriamente en dos grupos (ni = 10): I, se irrigó con EDTA 17% seguido de suero fisiológico; II, se irrigó sólo con suero fisiológico. Tras la aplicación de la TFD, los especímenes fueron seccionados, obteniéndose discos correspondientes a los tercios coronal, medio y apical. Las muestras fueron visualizadas con un microscopio óptico de reflexión y el software Canvas X16. Se evaluaron el porcentaje de área teñida (PAT) y la penetración intratubular media (PIM). Análisis estadístico: Tests U de Mann-Whitney y Wilcoxon con un nivel de significación de p<0,05. Resultados. Los resultados de PAT y PIM fueron mayores en el grupo I (11,1 ± 5,1/0,45 ± 0,18) que en el II (4,93 ± 4,1/0,26 ± 0,16). No hubo diferencias significativas de PIM en los tercios coronales de I vs. II. Ambos grupos presentaron diferencias de PAT y PIM entre sus tercios. Conclusión. La remoción del barrillo dentinario previa a la aplicación de la TFD mejora significativamente la penetración del agente fotosensible en los tres tercios de la raíz

Antimicrobial efectiveness of the photodynamic therapy (PDT), in addition to chemicomechanical preparation, depends on the contact between a photosensitizer, a light source (LED) and root canal microorganisms. Aim. To evaluate if the removal of smear layer influences the penetration of the photosensitizer into dentinal tubules in the PDT. Methodology. 20 premolars with Type I canals were sectioned at 12 mm from apex and conformed with MTwo and 5.25% NaOCl. Were randomized divided in two groups (ni = 10): group I was irrigated with 17% EDTA and 0.9% NaCl; group II was irrigated with 0.9% NaOCl. For the PDT 0.01% of TBO (Fotosan® ,CMS) as photosensitizer was applied into the canal and activated for 30 sec with a LED red light source (Foto-san630®, CMS). After this, all specimens were sectioned in order to obtain dentin discs of coronal, medium and apical third. Samples were evaluated with an optical microscope at 20x and the software Canvas X16, measuring the percentage of stained area (PAT) and Intratubular media penetration (PIM). Statistical analysis: Test U de Mann-Whitney y Wilcoxon with a significance level of p < 0.05. Results. The results of PAT and PIM were higher in Group I (11,1 ± 5,1/0,45 ± 0,18) than Group II (4,93 ± 4,1/0,26 ± 0,16). No significant differences of PIM were founded between coronal thirds of I vs II. Both groups presented differences of PAT and PIM between their thirds. Conclusion. The removal of smear layer before the TFD application improves the penetration of the photosensitizer in the three root thirds

Clinical evaluation of composite restorations in Er:YAG laser-prepared cavities re-wetting with chlorhexidine.

OBJECTIVES: The objective of this study was to evaluate longitudinally the composite restorations, performed in cavities prepared by Er:YAG or conventional bur, and dentin re-wetting with water or chlorhexidine. MATERIALS AND METHODS: Twenty individuals with four active caries with cavitation reaching the dentin located on the occlusal surface of molars counterparts are selected. The teeth of each individual were randomly assigned into four groups: (I) Er:YAG laser (260 mJ/4 Hz) re-wetting with chlorhexidine, (II) Er:YAG laser (260 mJ/4 Hz) re-wetting with deionized water, (III) conventional method re-wetting with chlorhexidine, and (IV) conventional method re-wetting with deionized water. The teeth were isolated, prepared cavities, phosphoric acid etching, and re-wetting according to previously assigned method. Restoration was performed employing the Single Bond 2 and Z350XT resin. Clinical follow-up was held after the polishing of the restoration (baseline) and 6 and 12 months of the making of the restoration using the modified USPHS criteria. The restorations were qualitatively analyzed by means of photographs. In the evaluation period, replicas of the restorations were analyzed by SEM. Data were analyzed by statistics using chi-square test (p < 0.05). RESULTS: After 12 months of clinical evaluation, groups prepared with laser and re-wetting with chlorhexidine and water showed the lowest marginal staining value. There was no statistical difference between the groups for other factors. SEM analysis revealed that a non-expressive amount of restorations showed gaps and irregularities of tooth-restoration interface after 6 and 12 months compared to the baseline. CONCLUSION: The restorations performed in laser-prepared cavities, regardless of the re-wetting, presented the best clinical performance over the evaluated period. CLINICAL RELEVANCE: Laser-prepared teeth, regardless of re-wetting, showed greater resistance to marginal discoloration.

Accelerated Fatigue Resistance of Thick CAD/CAM Composite Resin Overlays Bonded with Light- and Dual-polymerizing Luting Resins.

PURPOSE: To evaluate the accelerated fatigue resistance of thick CAD/CAM composite resin overlays luted with three different bonding methods. MATERIALS AND METHODS: Forty-five sound human second mandibular molars were organized and distributed into three experimental groups. All teeth were restored with a 5-mm-thick CAD/CAM composite resin overlay. Group A: immediate dentin sealing (IDS) with Optibond FL and luted with light-polymerizing composite (Herculite XRV). Group B: IDS with Optibond FL and luted with dual-polymerizing composite (Nexus 3). Group C: direct luting with Optibond FL and dual-polymerizing composite (Nexus 3). Masticatory forces at a frequency of 5 Hz were simulated using closed-loop servo-hydraulics and forces starting with a load of 200 N for 5000 cycles, followed by steps of 400, 600, 800, 1000, 1200 and 1400 N for a maximum of 30,000 cycles. Each step was applied through a flat steel cylinder at a 45-degree angle under submerged conditions. RESULTS: The fatigue test generated one failure in group A, three failures in group B, and no failures in group C. The survival table analysis for the fatigue test did not demonstrate any significant difference between the groups (p = 0.154). The specimens that survived the fatigue test were set up for the load-to-failure test with a limit of 4600 N. The survival table analysis for the load-to-failure test demonstrates an average failure load of 3495.20 N with survival of four specimens in group A, an average failure load of 4103.60 N with survival of six specimens in group B, and an average failure load of 4075.33 N with survival of nine specimens in group C. Pairwise comparisons revealed no significant differences (p < 0.016 after Bonferroni correction). CONCLUSION: Within the limitations of this in vitro study, it can be concluded that although the dual-polymerizing luting material seems to provide better results under extreme conditions, light-polymerizing luting composites in combination with IDS are not contraindicated with thick restorations.

Microtensile Bond Strength of Resin-bonded Hightranslucency Zirconia Using Different Surface Treatments.

PURPOSE: To evaluate the effect of a novel surface treatment intended to improve bond strength to high-translucency zirconia. MATERIALS AND METHODS: Fully sintered high-translucency zirconia disks (Incoris TZI) were divided into four groups according to the surface treatment received: modified fusion sputtering technique, selective infiltration etching, low pressure particle abrasion using 30-µm alumina particles, while 50-µm particle abrasion served as control. Surface roughness was evaluated quantitatively using a contact profilometer. The disks were bonded to pre-aged composite resin disks using a light-polymerized adhesive resin (RelyX ultimate). The bilayered disks were sectioned into microbars and zirconia-resin bond strength was evaluated using the microtensile bond strength test (MTBS). The test was repeated after 3 months of water storage (37°C). Scanning electron microscopic examination of the zirconia resin interface was performed at different magnifications. A repeated measures ANOVA and Bonferroni post-hoc test were used to analyze the data (n = 20, α = 0.05). RESULTS: One-way ANOVA revealed significant differences in average surface roughness (Ra) between the tested groups (p < 0.001). The highest Ra value was recorded for fusion sputtering (12.23 ± 0.11 µm), followed by 50-µm particle abrasion (6.400 ± 0.887), then low pressure 30-µm particle abrasion (2.4 ± 0.15 µm), while the lowest surface roughness was recorded for the selective infiltration group (0.368 ± 0.04 µm). Modified fusion sputtering and selective infiltration etching produced significantly higher MTBS values at each of the tested intervals (p < 0.001) compared to particle abrasion using different particle sizes. Water storage resulted in reduction in the bond strength of 30-µm abraded specimens, which was attributed to structural defects observed at the zirconia/ resin interface. Scanning electron microscopic examination revealed a nanoporous surface characteristic of selective etching surface treatment, and modified fusion sputtering resulted in the creation of surface-fused microbeads. CONCLUSION: Within the limitations of this study, selective infiltration etching and modified fusion sputtering techniques established a strong, stable, durable bond to high-translucency zirconia.

Different Strategies to Bond Bis-GMA-based Resin Cement to Zirconia.

PURPOSE: To evaluate the effect of different bonding strategies on short- and long-term bis-GMA-based resin cement bond strengths to zirconia. MATERIALS AND METHODS: One hundred twenty samples of fully-sintered zirconia (Prettau Zirconia) were sandblasted and randomly distributed into 5 groups (n = 24): UA: Scotchbond Universal Adhesive; SZP: Signum Zirconia Bond I + II; ZPP: Z-Prime Plus; EXP: MZ experimental primer; CO: no primer application (control). After performing these surface treatments, translucent tubes (0.8 mm diameter and 1.0 mm height) were placed on the zirconia specimens, and bis-GMA-based cement (Duo-Link) was injected into them and light cured. Specimens were tested for microshear bond strength either 24 h or 6 months (m) after water storage (37°C) and surfaces were characterized by SEM and EDX. Two-way ANOVA and Tukey's post-hoc test (p < 0.05) were used to evaluate bond strength results. RESULTS: The mean bond strengths (MPa ± SD) were: UA=14.6 ± 4.7a (24 h); 16.0 ± 4.8a (6 m); SZP = 14.0 ± 5.4ab (24 h); 11.9 ± 2.6ab (6 m); ZPP=8.0 ± 1.8b (24 h); 8.6 ± 3.3b (6 m); EXP = 1.2 ± 0.5c (24 h); 0.6 ± 0.7c (6 m); CO=1.0 ± 1.2c (24 h); 1.3 ± 1.2c (6 m). Bonding strategy significantly influenced bond strength (p = 0.0001), but storage time did not (p = 0.841). Groups UA and SZP showed a homogeneous layer covering the zirconia surface. In these groups, EDX demonstrated the presence of phosphorus. Group ZPP resulted in a nonhomogeneous layer, exposing the zirconia substrate underneath. EXP application resulted in an undetectable layer. CONCLUSION: Water storage did not affect resin cement bond strengths to zirconia irrespective of the surface treatment. Bis-GMA-based resin cement bond strengths to zirconia are affected by specific bonding strategies.

Influence of Surface Conditioning Protocols on Reparability of CAD/CAM Zirconia-reinforced Lithium Silicate Ceramic.

PURPOSE: To test the effect of surface conditioning protocols on the reparability of CAD/CAM zirconia-reinforced lithium silicate ceramic compared to lithium-disilicate glass ceramic. MATERIALS AND METHODS: Zirconia-reinforced lithium silicate ceramic (Vita Suprinity) and lithium disilicate glass-ceramic blocks (IPS e.max CAD) were categorized into four groups based on the surface conditioning protocol used. Group C: no treatment (control); group HF: 5% hydrofluoric acid etching for 60 s, silane (Monobond-S) application for 60 s, air drying; group HF-H: 5% HF acid etching for 60 s, application of silane for 60 s, air drying, application of Heliobond, light curing for 20 s; group CO: sandblasting with CoJet sand followed by silanization. Composite resin (Tetric EvoCeram) was built up into 4 x 6 x 3 mm blocks using teflon molds. All specimens were subjected to thermocycling (5000x, 5°C to 55°C). The microtensile bond strength test was employed at a crosshead speed of 1 mm/min. SEM was employed for evaluation of all the debonded microbars, the failure type was categorized as either adhesive (failure at adhesive layer), cohesive (failure at ceramic or composite resin), or mixed (failure between adhesive layer and substrate). Two-way ANOVA and the Tukey's HSD post-hoc test were applied to test for significant differences in bond strength values in relation to different materials and surface pretreatment (p < 0.05). RESULTS: The highest microtensile repair bond strength for Vita Suprinity was reported in group CO (33.1 ± 2.4 MPa) and the lowest in group HF (27.4 ± 4.4 MPa). Regarding IPS e.max CAD, group CO showed the highest (30.5 ± 4.9 MPa) and HF the lowest microtensile bond strength (22.4 ± 5.7 MPa). Groups HF, HF-H, and CO showed statistically significant differences in terms of all ceramic types used (p < 0.05). The control group showed exclusively adhesive failures, while in HF, HF-H, and CO groups, mixed failures were predominant. CONCLUSIONS: Repair bond strength to zirconia-reinforced lithium silicate ceramics and lithium-disilicate glass ceramic could be improved when ceramic surfaces are sandblasted with CoJet sand followed by silanization.

Influence of Light Irradiation Through Zirconia on the Degree of Conversion of Composite Cements.

PURPOSE: To assess the light irradiance (LI) delivered by two light-curing units and to measure the degree of conversion (DC) of three composite cements and one flowable composite when cured through zirconia or ceramic-veneered zirconia plates with different thicknesses. MATERIALS AND METHODS: Three dual-curing composite cements (Clearfil Esthetic Cement, Panavia F2.0, G-CEM LinkAce) and one light-curing flowable composite (G-aenial Universal Flo) were investigated. Nine different kinds of zirconia plates were prepared from three zirconia grades (YSZ: Aadva and KATANA; Ce-TZP/Al2O3: NANOZR) in three different thicknesses (0.5- and 1.5-mm-thick zirconia, and 0.5-mm-thick zirconia veneered with a 1.0-mm-thick veneering ceramic). Portions of the mixed composite cements and the flowable composite were placed on a light spectrometer to measure LI while being light cured through the zirconia plates for 40 s using two light-curing units (n = 5). After light curing, micro-Raman spectra of the composite films were acquired to determine DC at 5 and 10 min, 1 and 24 h, and at 1 week. RESULTS: The zirconia grade and the thickness of the zirconia/veneered zirconia plates significantly decreased LI. Increased LI did not increase DC. Only the Ce-TZP/Al2O3 (NANOZR) zirconia was too opaque to allow sufficient light transmission and resulted in significantly lower DC. CONCLUSION: Although zirconia-based restorations attenuate the LI of light-curing units, the composite cements and the flowable composite could be light cured through the YSZ zirconia. LI is too low through Ce-TZP/Al2O3 zirconia, necessitating the use of self-/dual-curing composite cements.

Influence of repair procedure on composite-to-composite microtensile bond strength.

PURPOSE: To investigate the effect of different repair procedures and storage time on microtensile bond strength (µTBS) of a resin composite to an older one from a simulated previous restoration. METHODS: Composite disks were made by layering 2 mm-thick increments of a nanohybrid composite (Grandio) shade A1 in a Teflon mold (4 x 8 mm). Afterwards, they were light-cured and stored (37 degrees C/7 days) in a saline solution. Specimens were randomly divided into groups according to the surface treatment applied: (1) Composite surface was roughened with a bur (Cimara) and Solobond Plus adhesive was applied; (2) Sandblasting with 27 µm aluminum oxide particles (KaVo Rondoflex), and adhesive application; (3) Air-abrasion with 30 µm alumina particles coated with silica (CoJet Sand), silane (Monobond-S) and adhesive application; (4) Negative control group with only adhesive application. Afterwards, Grandio composite (shade A3.5) was packed incrementally on the treated surface obtaining another disk (4 x 8 mm). Repaired blocks were stored (24 hours or 6 months) and afterwards µTBS test was performed and failure mode was evaluated. Also, beams obtained from 8 mm-high composite blocks without any surface treatment were immediately submitted to µTBS test to determine Grandio composite cohesive bond strength (positive control group). Data were analyzed using ANOVA and Tukey's test (P < 0.05). RESULTS: The repair procedure affected µTBS values (P < 0.001) while neither storage time nor interactions did (P > 0.05). All repair procedures achieved bond strength values higher than the negative control group but they did not reach the composite's cohesive bond strength. The overall conclusion was that an increased superficial roughness by means of a bur, silica coating or alumina sandblasting improved µTBS of the repaired composite and bond strength remained stable after 6 months.

Shear bond strength between alumina substrate and prosthodontic resin composites with various adhesive resin systems.

BACKGROUND: With the increase in demand for cosmetics and esthetics, resin composite restorations and all-ceramic restorations have become an important treatment alternative. Taking into consideration the large number of prosthodontic and adhesive resins currently available, the strength and durability of these materials needs to be evaluated. This laboratory study presents the shear bond strengths of a range of veneering resin composites bonded to all-ceramic core material using different adhesive resins. METHODS: Alumina ceramic specimens (Techceram Ltd, Shipley, UK) were assigned to three groups. Three types of commercially available prosthodontic resin composites [BelleGlass®, (BG, Kerr, CA, USA), Sinfony® (SF, 3 M ESPE, Dental Products, Germany), and GC Gradia® (GCG, GC Corp, Tokyo, Japan)] were bonded to the alumina substrate using four different adhesive resins. Half the specimens per group (N = 40) were stored dry for 24 hours, the remaining were stored for 30 days in water. The bonding strength, so-called shear bond strengths between composite resin and alumina substrate were measured. Data were analysed statistically and variations in bond strength within each group were additionally evaluated by calculating the Weibull modulus. RESULTS: Bond strengths were influenced by the brand of prosthodontic resin composites. Shear bond strengths of material combinations varied from 24.17 ± 3.72-10.15 ± 3.69 MPa and 21.20 ± 4.64-7.50 ± 4.22 at 24 h and 30 days, respectively. BG resin composite compared with the other resin composites provided the strongest bond with alumina substrate (p < 0.01). SF resin composite was found to have a lower bond strength than the other composites. The Weibull moduli were highest for BG, which was bonded by using Optibond Solo Plus adhesive resin at 24 h and 30 days. There was no effect of storage time and adhesive brand on bond strength. CONCLUSION: Within the limitations of this study, the shear bond strengths of composite resins to alumina substrate are related to the composite resins.

Surface and interfacial analysis of sandblasted and acid-etched enamel for bonding orthodontic adhesives.

INTRODUCTION: The purposes of this study were to characterize enamel surfaces treated with sandblasting, acid etching, or sandblasting followed by acid etching for bonding of orthodontic adhesives and to evaluate the enamel-adhesive interfaces. METHODS: Buccal premolar surfaces were sandblasted, acid etched, sandblasted and subsequently acid etched, or left intact. For 2 treatments (acid etching and sandblasting plus acid etching), orthodontic brackets were bonded for resin infiltration assessment. Surface roughness and enamel loss were evaluated by optical profilometry, and surface morphology and elemental composition were examined by low-vacuum scanning electron microscope/energy dispersive x-ray analysis, whereas interfacial resin infiltration was assessed by high-vacuum scanning electron microscopy. Differences were statistically analyzed by 1-way analysis of variance and Tukey-Kramer multiple comparison tests or t tests (α = 0.05). RESULTS: The sandblasted and sandblasted-plus-acid-etched groups showed higher surface roughness values than the acid-etched group. Sandblasting plus acid etching removed more enamel than did sandblasting or acid etching alone. Sandblasting plus acid etching demonstrated a more uniform type I etching pattern, without alumina particles implanted in the enamel, unlike sandblasting. No difference was found in the extent of resin infiltration between the bonded acid-etched and sandblasted-plus-acid-etched groups, although the latter showed improved infiltration characteristics. CONCLUSIONS: Sandblasting-plus-acid-etching treatment creates a rough enamel surface, typical of type I etching, with the greatest extent of enamel loss, free of alumina interferences, demonstrating the same extent of resin infiltration as acid etching, but exhibiting improved infiltration quality.

In-vivo evaluation of the surface roughness and morphology of enamel after bracket removal and polishing by different techniques.

INTRODUCTION: The aim of this study was to evaluate the surface roughness and morphology of enamel with a surface roughness tester and scanning electron microscopy after the removal of metal brackets and polishing. METHODS: Ten orthodontic patients were selected for the study. At the conclusion of orthodontic treatment, their metal brackets were removed. For each patient, teeth on one side of the mouth were randomly chosen for finishing and polishing with aluminum oxide discs (n = 10). Teeth on the other side were finished with multilaminated carbide burs (n = 10). Dental replicas (before and after tooth polishing) were obtained with epoxy resin. Three surface roughness measurements were made in different directions with an angle of 120° among them, and a mean for each dental replica was calculated. The roughness data were statistically evaluated by repeated-measurements analysis of variance. Three specimens from each group were also used for scanning electron microscopy analysis. RESULTS: After resin removal, the average roughness in the carbide bur group (0.31 µm) was significantly greater than that in the aluminum oxide disc group (0.25 µm). CONCLUSIONS: The aluminum oxide disc polishing system resulted in less enamel roughness than did the multilaminated carbide bur system.

Effect of different surface treatments for ceramic bracket base on bond strength of rebonded brackets.

The aim of this study was to evaluate the shear bond strength of rebonded ceramic brackets after subjecting the bracket base to different treatments. Seventy-five premolars were selected and randomly distributed into five groups (n=15), according to the type of the bracket surface treatment: I, no treatment, first bonding (control); II, sandblasting with aluminum oxide; III, sandblasting + silane; IV, silica coating + silane; and V, silicatization performed in a laboratory (Rocatec system). The brackets were fixed on an enamel surface with Transbond XT resin without acid etching. The brackets were then removed and their bases were subjected to different treatments. Thereafter, the brackets were fixed again to the enamel surface and the specimens were subjected to shear bond strength (SBS) test. The adhesive remnant index (ARI) was then evaluated for each specimen. Data were subjected to ANOVA and Tukey's tests (α=0.05). A statistically significant difference was observed only between Rocatec and the other groups; the Rocatec group showed the lowest SBS values. The highest SBS values were observed for group 1, without any significant difference from the values for groups II, III and IV. Most groups had a higher percentage of failures at the enamel-resin interface (score 1). It was concluded that the surface treatments of rebonded ceramic brackets were effective, with SBS values similar to that of the control group, except Rocatec group.