Danielle Cristine Messias

Effect of light-activation with different light-curing units and time intervals on resin cement bond strength to intraradicular dentin

The aim of this study was to assess the bond strength of a resin cement to intraradicular dentin varying the light-curing unit and the moment at which the light was applied. Post spaces of endodontically treated canines were prepared. The roots were distributed into 6 groups (n=10) according to the light-curing unit and the moment of light exposure: I) Quartz tungsten halogen-600 mW/cm² (QTH) + immediate light activation (t0); II) QTH + light activation after 10 min (t10); III) Light-emitting diodes (LED)-800 mW/cm² (LED-800)+ t0; IV) LED-800 + t10; V) LED-1,500 mW/cm² (LED-1500)+ t0; VI) LED-1500 + t10. After post cementation, slices from coronal, middle and apical post/root regions were submitted to the push-out test and failure evaluation. It was verified that LED-800 (4.40 ± 3.00 MPa) and LED-1500 (4.67 ± 3.04 MPa) provided bond strength statistically superior to QTH (3.13 ± 1.76 MPa) (p<0.05), and did not differ from each other (p>0.05). There was no significant difference between t0 and t10 (p>0.05). Coronal post/root region (4.75 ± 3.10 MPa) presented significantly higher bond strength than the apical (3.32 ± 2.30 MPa) (p<0.05) and middle regions (4.14 ± 2.99 MPa) showed intermediate values. Adhesive failures were predominant when using QTH. Adhesive and mixed failures occurred more frequently in the apical region. Higher adhesion of the resin cement to intraradicular dentin was observed in the coronal region with LED light-activation, regardless of the moment of light exposure.

Influence of Sealer and Light-Curing Units on Push-Out Bond Strength Of Composite Resin to Weakened Roots

The aim of this study was to assess the influence of sealer and light-curing unit on regional bond strength of resin composite to the weakened roots. Ninety roots of incisors were experimentally weakened, subjected to biomechanical preparation and filled with either Endofill, AH Plus or MTA Fillapex The roots were desobturated e reinforced with resin composite and fiber post light-activated with one of the light sources: halogen at 600 mW/ cm2 (QTH-600), LED at 800 mW/ cm2 (LED-800) and LED at 1500 mW/ cm2 (LED-1500). The roots were sectioned in slices from cervical, middle and apical root-reinforcement regions and analyzed by push out test, scanning electron microscopy (SEM) and confocal laser scanning microscopy (CLSM). Bond strength data were analyzed using three-way ANOVA and Tukey´s test (α=0.05). Specimens filled with AH Plus had higher bond strength, followed by MTA Fillapex and Endofill (p<0.05). For light-curing unit, LED-1500 presented superior bond strength than LED-800, which was higher than QTH-600 (p<0.05). The cervical region had the greatest mean values (p<0.05) while apical part showed the lowest bond strength (p<0.05). CLMS revealed remaining filling material in the dentinal tubules for all groups. The eugenol-containing sealer (Endofill) compromised the push-out bond strength of composite resin to the root dentin. Bond strength was favored in the cervical region, and when LED-1500 was used.

Impact of Intracoronal Dentin Treatment Prior to Bleaching on Bond Strength of Restorative Materials

Surface treatment of dentin before the bleaching procedure may affect its permeability and influence the bond strength of restorative materials. This study evaluated the influence of surface treatment before the bleaching on shear bond strength (SBT) of restorative materials to intracoronal dentin. Dentin slabs were subjected to surface treatment: no bleaching (control - CON), no surface treatment + bleaching (HP), 37% phosphoric acid + bleaching (PA) and Er:YAG laser + bleaching (L). After the bleaching procedure, specimens (n=10) were restored with: microhybrid composite resin (MH), flowable composite resin (F), and resin-modified glass-ionomer cement (RMGIC). The shear test was carried out. ANOVA and Tukeys test (α=0.05) showed significant difference for surface treatment and restorative materials (p<0.05). CON presented higher STB and was statistically different from HP (p<0.05). PA and L showed intermediate values and were statistically similar to CON and HP (p>0.05). STB for MH and F were higher than RMGIC (p<0.05), and did not differ from each other (p>0.05). The surface treatments with phosphoric acid and Er:YAG laser before the bleaching procedure provided shear bond strength at the same level of unbleached dentin and the composite resins presented superior bond strength to the intracoronal dentin.

Tensile Strength of Glass Fiber Posts Submitted to Different Surface Treatments

The aim of this in vitro study was to evaluate the tensile strength of glass fiber posts submitted to different surface treatments. Forty-eight maxillary canines had their crowns sectioned and root canals endodontically treated. The roots were embedded in acrylic resin and distributed into 3 groups according to the surface treatment: Group I: the posts were treated with silane agent for 30 s and adhesive; Group II: the posts were cleaned with alcohol before treatment with silane agent and adhesive; Group III: the posts were submitted to conditioning with 37% phosphoric acid for 30 s before treatment with silane agent and adhesive. Each group was divided into 2 subgroups for adhesive polymerization or not before insertion into the canal: A - adhesive was not light cured and B - adhesive was light cured. All posts were cemented with Panavia F and the samples were subjected to tensile strength test in a universal testing machine at crosshead speed of 1 mm/min. Data were submitted to one-way ANOVA and Tukeys test at 5% significance level. There was statistically significant difference (p<0.01) only between group GIII-B and groups GI-A and GI-B. No significant difference was found among the other groups (p>0.05). It was concluded that the products used for cleaning the posts influenced the retention regardless of adhesive light curing.

Effect of Light Sources on the Bond Strength of Resin Material to Thin-walled Roots

The aim of this study was to evaluate the bond strength to the dentin of an adhesive material used for root reinforcement light activated with different sources. Roots were divided into 4 groups (n=15) according to the light source used to activate the resin reinforcement: GI, non-weakened roots (control); GII, halogen light (H) 600 mW/cm²; GIII, LED 800 mW/cm² and GIV, LED 1500 mW/cm². The reinforcement was done with adhesive, composite resin and fiberglass posts. After 24 h, the specimens were sectioned and the first slice of each post region was used in the push out test in a universal testing machine with a crosshead speed of 0.5 mm/min. Failure modes of the debonded specimens were examined. Data (MPa) were analyzed by ANOVA and Holm-Sidak test (α=0.05). The second slice from each region was analyzed by scanning electron microscopy (SEM). LED-1500 (4.69 ± 1.74) provided bond strength similar to the control group (5.05 ± 2.63) and statistically different from H-600 (1.96 ± 0.94) and LED-800 (2.75 ± 1.90), which were similar to each other (p<0.05). Cervical (4.16 ± 2.32) and middle (4.43 ± 2.32) regions showed higher bond strength than the apical (2.25 ± 1.50) (p<0.05). There was a prevalence of adhesive failures in H-600 and LED-800 and cohesive failures in LED-1500. SEM showed the formation of long, numerous and fine tags. It was concluded that LED-1500 provided higher bond strength of resin reinforcement to the dentin.

Effect of a 12-methacryloyloxy-dodecyl-pyridinium-bromide–containing adhesive with different post types on the long-term bond strength to dentin

The use of matrix metalloproteinase (MMPs) inhibitors, such as 12-methacryloyloxy-dodecyl-pyridinium-bromide (MDPB), might improve the adhesion of glass-fiber (GF) and polyfiber (PF) posts to root dentine. This study assessed the effect of an MDPB-containing adhesive on the long-term bond strength of GF or PF posts to bovine dentine. Bovine endodontically treated roots were randomly divided into six groups, according to the post type and adhesive system used, as follows: GF serrated post + MDBP-free adhesive; GF serrated post + MDPB-containing adhesive; GF smooth post + MDBP-free adhesive; GF smooth post + MDPB-containing adhesive; PF post + MDBP-free adhesive; PF post + MDPB-containing adhesive. Specimens were stored in water for 6 months, thermocycled (500 cycles wk-1 ), and submitted to the pull-out test and failure pattern analysis. The cement-dentin interface was evaluated using scanning electron microscopy. The pull-out data were analyzed using anova and Tukeys test (α = 0.05). No significant interaction between the type of post and the adhesive system was found. Polyfiber posts showed lower bond strength than GF posts, whether serrated or smooth, and the bond strength of the serrated and smooth GF posts was not significantly different. Adhesive failures were predominant in all groups. The type of retainer influenced the bond strength, and MDPB-containing adhesive did not improve the long-term bond strength of posts to dentine.

Rehabilitation of weakened premolars with a new polyfiber post and adhesive materials

BACKGROUND Polyfiber posts used inside the root canal can help to restore the fracture resistance of weakened premolars. AIM To assess the fracture resistance of endodontically treated premolars restored with different techniques, including the new polyfiber post (Spirapost). MATERIALS AND METHODS One hundred superior premolars were distributed into 10 groups (n = 10): Sound teeth (G1-positive control) and experimental (G2 to G10), which received MODP cavities and canal treatment. Groups were restored as follows: G2 - unrestored (negative control); G3 - microhybrid resin (MR); G4 - flowable resin (FR) + (MR); G5 - glass fiber post (Reforpost) + MR; G6 - Reforpost + FR + MR; G7 - polyethylene fiber (Ribbond) + MR; G8 - Ribbond + FR + MR; G9 - polyfiber post (Spirapost) + MR and G10 - Spirapost + FR + MR. After 24 h, the specimens were loaded until fracture. Data were analyzed by ANOVA and Tukeys test (P < 0.05). RESULTS Premolars restored with Spirapost (G9 and G10) provided the highest fracture strength (P < 0.05), similar to sound teeth (G1), regardless of the composite resin. Intermediate values were achieved by G3, G4, G5, G6, G7, and G8, which were similar (P > 0.05) and different from the others (P < 0.05). Inferior values were found in G2 (P < 0.05). CONCLUSION Fracture resistance of premolars with MODP cavities and endodontic access was recovered with the direct rehabilitation with Spirapost, regardless of the type of composite resin.