Effect of dental surface treatment with Nd:YAG and Er:YAG lasers on bond strength of resin composite to recently bleached enamel

The aim of this work is to evaluate the effect of surface treatment with Er:YAG and Nd:YAG lasers on resin composite bond strength to recently bleached enamel. In this study, 120 bovine incisors were distributed into two groups: group C: without bleaching treatment; group B: bleached with 35% hydrogen peroxide. Each group was divided into three subgroups: subgroup N: without laser treatment; subgroup Nd: irradiation with Nd:YAG laser; subgroup Er: irradiation with Er:YAG laser. The adhesive system (Adper Single Bond 2) was then applied and composite buildups were constructed with Filtek Supreme composite. The teeth were sectioned to obtain enamel-resin sticks (1 x 1 mm) and submitted to microtensile bond testing. The data were statistically analyzed by the ANOVA and Tukey tests. The bond strength values in the bleached control group (5.57 MPa) presented a significant difference in comparison to the group bleached and irradiated with Er:YAG laser (13.18 MPa) or Nd:YAG (25.67 MPa). The non-bleached control group presented mean values of 30.92 MPa, with statistical difference of all the others groups. The use of Nd:YAG and Er:YAG lasers on bleached specimens was able to improve the bond strengths of them.

Evaluation of the Cohesive Strength Between Resin Composite and Light-curing Characterizing Materials

Purpose: To evaluate the cohesive strength between composite and different light-curing characterizing materials (LCCM), which were prepared using the intrinsic technique.Materials and Methods: One hundred composite specimens were made by using a prefabricated Teflon device, and a layer of LCCM was applied at the interface. The specimens were divided into 5 groups (n = 20): group 1 (control), no LCCM was used; group 2: application of White Kolor Plus Pigment (Kerr) LCCM; group 3: White Tetric Color Pigment (Ivoclar/Vivadent) LCCM; group 4: Brown Kolor Plus Pigment (Kerr) LCCM; group 5: Black Tetric Color Pigment (Ivoclar/Vivadent) LCCM. All materials were used according to the manufacturers' instructions. Specimens were submitted to a tensile test in a universal testing machine (EMIC DL-200MF) to evaluate the cohesive strength at the composite interface. Data were subjected to one-way ANOVA and Tukey's test (alpha = 5%).Results: ANOVA showed a p-value = 0.0001, indicating that there were significant differences among the groups. The mean values in MPa (+/- standard deviation) obtained for the groups were: G1: 28.5 (+/-2.74)a; G2: 23.5 (+/-2.47)b; G3: 20.3 (+/-2.49)b; G4: 10.5 (+/-2.40)c; G5: 9.66 (+/-3.06)c. The groups with the same letters presented no significant differences. The control group presented statistically significantly higher cohesive strengths when compared to the other groups. The groups in which Brown Kolor Plus Pigment and Black Tetric Color Pigment LCCM were used showed significantly lower cohesive strengths when compared to the groups in which White Kolor Plus Pigment and White Tetric Color Pigment LCMM were used.Conclusion: The use of LCCM produced with the intrinsic technique reduced the cohesive strength of composite.

Polymerization shrinkage: effects of boundary conditions and filling technique of resin composite restorations

Objective: To evaluate the linear polymerization shrinkage (LPS) and the effect of polymerization shrinkage of a resin composite and resin-dentin bond strength under different boundary conditions and filling techniques.Methods: Two cavities (4 x 4 x 2 MM) were prepared in bovine incisors (n = 30). The teeth were divided into three groups, according to boundary conditions: In group TE, the total-etch technique was used. In group EE, only enamel was conditioned, and in group NE, none of the watts of the cavities were conditioned. A two-step adhesive system was applied to all cavities. The resin composite was inserted in one (B) or three increments (1), and tight-cured with 600 mW/cm(2) (80 s). The LPS (%) was measured in the top-bottom direction, by placing a probe in contact with resin composite during curing. Enamel and total mean gap widths were measured (400 x) in three slices obtained after sectioning the restorations. Then, the slices were sectioned again, either to obtain sticks from the adhesive interface from the bottom of the cavity or to obtain resin composite sticks (0.8 mm(2)) to be tested for tensile strength (Kratos machine, 0.5 mm/min). The data was subjected to a two-way repeated measures ANOVA and Tukey's test for comparison of the means (alpha = 0.05).Results: the highest percentage of LPS was found for the TE when bulk fitted, and the lowest percentage of LPS was found in the Hand NE when incrementally fitted. The resin dentin bond strength was higher and the total mean gap width was tower for TE group; no significant effect was detected for the main factor fitting techniques. No difference was detected for the tensile strength of resin composite among the experimental groups.Conclusions: the filling technique is not able to minimize effects of the polymerization shrinkage, and bonding to the cavity watts is necessary to assure reduced mean gap width and high bond strength values. (C) 2004 Elsevier Ltd. All rights reserved.

Repair bond strength of a resin composite to alumina-reinforced feldspathic ceramic

This study compared the microtensile bond strength of a repair resin to an alumina-reinforced feldspathic ceramic (Vitadur-alpha, Vita) after 3 surface conditioning methods: Group 1, etching with 9.6% hydrofluoric acid for 1 minute plus rinsing and drying, followed by application of silane for 5 minutes; group 2, airborne particle abrasion with 110-mm aluminum oxide using a chairside air-abrasion device followed by silane application for 5 minutes; group 3, chairside tribochemical silica coating with 30-mu m SiOx followed by silane application for 5 minutes (N = 30). Group 1 presented the highest mean bond strength (19.7 +/- 3.8 MPa), which was significantly higher than those of groups 2 (10 +/- 2.6 MPa) and 3 (10.4 +/- 4 MPa) (P <.01). Scanning electron microscope analysis of the failure modes demonstrated predominantly mixed types of failures, with adhesive and/or cohesive failures in all experimental groups.

Effect of surface conditioning methods on the microtensile bond strength of resin composite to composite after aging conditions

Objectives. This study evaluated the effect of two different surface conditioning methods on the repair bond strength of a bis-GMA-adduct/bis-EMA/TEGDMA based resin composite after three aging conditions.Methods. Thirty-six composite resin blocks (Esthet X, Dentsply) were prepared (5 mm x 6 mm x 6 mm) and randomly assigned into three groups for aging process: (a) immersion in citric acid (pH 3.0 at 37 degrees C, 1 week) (CA); (b) boiling in water for 8h (BW) and (c) thermocycling (x5000, 5-55 degrees C, dwell time: 30s) (TC). After aging, the blocks were assigned to one of the following surface conditioning methods: (1) silica coating (30 mu m SiOx) (CoJet, 3M ESPE) + silane (ESPE-Sil) (CJ), (2) phosphoric acid + adhesive resin (Single Bond, 3M ESPE) (PA). Resin composite (Esthet.X (R)) was bonded to the conditioned substrates incrementally and light polymerized. The experimental groups formed were as follows: Gr1:CA + PA; Gr2:CA + CJ Gr3:BW + PA; Gr4: BW + CJ; Gr5:TC + PA; Gr6: TC + CJ. The specimens were sectioned in two axes (x and y) with a diamond disc under coolant irrigation in order to obtain non-trimmed bar specimens (sticks, 10 mm x 1 mm x 1 mm) with 1 mm(2) of bonding area. The microtensile test was accomplished in a universal testing machine (crosshead speed: 0.5 mm min(-1)).Results. The means and standard deviations of bond strength (MPa +/- S.D.) per group were as follows: Gr1: 25.5 +/- 10.3; Gr2: 46.3 +/- 10.1; Gr3: 21.7 +/- 7.1; Gr4: 52.3 +/- 15.1; GrS: 16.1 +/- 5.1; Gr6, 49.6 +/- 13.5. The silica coated groups showed significantly higher mean bond values after all three aging conditions (p < 0.0001) (two-way ANOVA and Tukey tests, alpha = 0.05). The interaction effect revealed significant influence of TC aging on both silica coated and acid etched groups compared to the other aging methods (p < 0.032). Citric acid was the least aggressive aging medium.Significance. Chairside silica coating and silanization provided higher resin-resin bond strength values compared to acid etching with phosphoric acid followed by adhesive resin applications. Thermocycling the composite substrates resulted in the lowest repair bond strength compared to citric acid challenge or boiling in water. (C) 2006 Academy of Dental Materials. Published by Elsevier Ltd. All rights reserved.

Effects of light-curing time on the cytotoxicity of a restorative resin composite applied to an immortalized odontoblast-cell line

This in vitro study evaluated the cytotoxic effects of a restorative resin composite applied to an immortalized odontoblast-cell line (MDPC-23). Seventy-two round resin discs (2-mm thick and 4 mm in diameter) were light-cured for 20 or 40 seconds and rinsed, or not, with PBS and culture medium. The resin discs were divided into four experimental groups: Group 1: Z-100/20 seconds; Group 2: Z-100/20 seconds/rinsed; Group 3: Z100/40 seconds; Group 4: Z-100/40 seconds/rinsed. Circular filter paper was used as a control material (Group 5). The round resin discs and filter papers were placed in the bottom of wells of four 24-well dishes (18 wells for each experimental and control group). MDPC-23 cells (30,000 cells/cm(2)) were plated in the wells and allowed to incubate for 72 hours. The zone of inhibition around the resin discs was measured under inverted light microscopy; the MTT assay was carried out for mitochondrial respiration and cell morphology was measured under SEM. The scores obtained from inhibition zone and MTT assay were analyzed with the Kruskal-Wallis followed by Dunnett tests. In Groups 1, 2, 3 and 4, the thickness of the inhibition zone was 1,593 +/- 12.82 mum, 403 +/- 15.49 mum, 1,516 +/- 9.81 mum and 313 +/- 13.56 mum, respectively. There was statistically significant difference among the experimental and control groups at the 0.05 level of significance. The MTT assay demonstrated that the resin discs of the experimental groups 1, 2, 3 and 4 reduced the cell metabolism by 83%, 40.1%, 75.5% and 24.5%. Only between the Groups 2 and 4 was there no statistically significant difference for mitochondrial respiration. Close to the resin discs, the MDPC-23 cells exhibited rounded shapes, with only a few cellular processes keeping the cells attached to the substrate or, even disruption of plasma membrane. Adjacent to the inhibition zone, the cultured cells exhibited multiple fine cellular processes on the cytoplasmic membrane organized in epithelioid nodules, similar to the morphology observed to the control group. Based on the results, the authors may conclude that the Z-100 resin composite light cured for 20 seconds was more cytopathic to MDPC-23 cells than Z-100 light cured for 40 seconds. The cytotoxic effects of the resin discs decreased after rinsing them with PBS and culture medium. This was confirmed by MTT assay and upon evaluation of the inhibition zone, which was narrower following rinsing of the resin discs.

Resistance to maxillary premolar fractures after restoration of class II preparations with resin composite or ceromer.

OBJECTIVE: The aim of this study was to evaluate the resistance to fracture of intact and restored human maxillary premolars. METHOD AND MATERIALS: Thirty noncarious human maxillary premolars, divided into three groups of 10, were submitted to mechanical tests to evaluate their resistance to fracture. Group 1 consisted of intact teeth. Teeth in group 2 received mesio-occlusodistal cavity preparations and were restored with direct resin composite restorations. Teeth in group 3 received mesio-occlusodistal cavity preparations and were restored with ceromer inlays placed with the indirect technique. After restoration, teeth were stored at 37 degrees C for 24 hours and then thermocycled for 500 cycles at temperatures of 5 degrees C and 55 degrees C. RESULTS: Statistical analysis revealed that group 3 (178.765 kgf) had a significantly greater maximum rupture load than did group 1 (120.040 kgf). There was no statistically significant difference between groups 1 and 2 or between groups 2 and 3. CONCLUSION: Class II cavity preparations restored with indirect ceromer inlays offered greater resistance to fracture than did intact teeth. The fracture resistance of teeth restored with resin composite was not significantly different from that of either the ceromer or intact teeth.

Influence of cavity preparation and curing method on the marginal seal of resin composite restorations: an in vitro evaluation.

OBJECTIVE: To evaluate the influence of cavity design and photocuring method on the marginal seal of resin composite restorations. METHOD AND MATERIALS: Seventy-two bovine teeth were divided into 2 groups: group 1 received box-type cavity preparations, and group 2 received plate-type preparations. Each group was divided into 3 subgroups. After etching and bonding, Z250 resin composite (3M Espe) was applied in 2 equal increments and cured with 1 of 3 techniques: (1) conventional curing for 30 seconds at 650 mW/cm2; (2) 2-step photocuring, in which the first step was performed 14 mm from the restoration for 10 seconds at 180 mW/cm2 and the second step was performed in direct contact for 20 seconds at 650 mW/cm2; or (3) progressive curing using Jetlite 4000 (J. Morita) for 8 seconds at 125 mW/cm2 and then 22 seconds at 125 mW/cm2 up to 500 mW/cm2. The specimens were thermocycled for 500 cycles and then submitted to dye penetration with a 50% silver nitrate solution. Microleakage was assessed using a stereomicroscope. Data were analyzed using analysis of variance and Tukey test (5% level of significance). RESULTS: A statistically significant difference was found between groups when a double interaction between photocuring and cavity preparation was considered (P = .029). CONCLUSIONS: No one type of cavity preparation or photocuring method prevented micro-leakage. The plate-type preparation showed the worst dye penetration when conventional and progressive photocuring methods were used. The best results were found using the 2-step photocuring with the plate-type preparation.

Influence of resin composite insertion technique in preparations with a high C-factor

Objective: To evaluate the marginal microleakage in enamel and dentin/cementum walls in preparations with a high C-factor, using 3 resin composite insertion techniques. The null hypothesis was that there is no difference among the 3 resin composite insertion techniques. Method and Materials: Standardized Class 5 cavities were prepared in the lingual and buccal aspects of 30 caries-free, extracted third molars. The prepared teeth were randomly assigned to 3 groups: (1) oblique incremental placement technique, (2) horizontal incremental placement technique, and (3) bulk insertion (single increment). The preparations were restored with a 1-bottle adhesive (Single Bond, 3M ESPE) and microhybrid resin composite (Z100, 3M ESPE). Specimens were isolated with nail varnish except for a 2-mm-wide rim around the restoration and thermocycled (1,000 thermal cycles, 5°C/55°C; 30-second dwell time). The specimens were immersed in an aqueous solution of 50 wt% silver nitrate for 24 hours, followed by 8 hours in a photo-developing solution and evaluated for microleakage using an ordinal scale of 0 to 4. The microleakage scores obtained from occlusal and gingival walls were analyzed with Wilcoxon and Kruskal-Wallis nonparametric tests. Results: The null hypothesis was accepted. The horizontal incremental placement technique, the oblique incremental technique, and bulk insertion resulted in statistically similar enamel and dentin microleakage scores. Conclusion: Neither the incremental techniques nor the bulk placement technique were capable of eliminating the marginal microleakage in preparations with a high C-factor.

Effect of pre-heating resin composite and light-curing units on monomer conversion

The purpose of this study was to evaluate the effect of pre-heating resin composite photo-cured with light-curing units (LCU) by FT-IR. Twenty specimens were made in a metallic mold (4 mm diameter × 2 mm thick) from composite resin-Tetric Ceram® (Ivoclar/Vivadent) at room temperature (25°C) and pre-heated to 37, 54, and 60°C. The specimens were cured with halogen curing light (QTH) and light emitted by diodes (LED) during 40 s. Then, the specimens were pulverized, pressed with KBr and analyzed with FT-IR. The data were submitted to statistical analysis of variance and Kruskal-Wallis test. Study data showed no statistically significant difference to the degree of conversion for the different light curing units (QTH and LED) (p > 0.05). With the increase of temperature there was significant increase in the degree of conversion (p < 0.05). In this study were not found evidence that the light curing unit and temperature influenced the degree of conversion. © 2010 Pleiades Publishing, Ltd.

Resin composite characterizations following a simplified protocol of accelerated aging as a function of the expiration date

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Adhesive bonding of resin composite to various titanium surfaces using diferente metal conditioners and a surface modification system

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Effect of Surface Conditioning Modalities on the Repair Bond Strength of Resin Composite to the Zirconia Core / Veneering Ceramic Complex

Purpose: This study evaluated the effect of different surface conditioning protocols on the repair strength of resin composite to the zirconia core / veneering ceramic complex, simulating the clinical chipping phenomenon.Materials and Methods: Forty disk-shaped zirconia core (Lava Zirconia, 3M ESPE) (diameter: 3 mm) specimens were veneered circumferentially with a feldspathic veneering ceramic (VM7, Vita Zahnfabrik) (thickness: 2 mm) using a split metal mold. They were then embedded in autopolymerizing acrylic with the bonding surfaces exposed. Specimens were randomly assigned to one of the following surface conditioning protocols (n = 10 per group): group 1, veneer: 4% hydrofluoric acid (HF) (Porcelain Etch) + core: aluminum trioxide (50-mu m Al2O3) + core + veneer: silane (ESPE-Sil); group 2: core: Al2O3 (50 mu m) + veneer: HF + core + veneer: silane; group 3: veneer: HF + core: 30 mu m aluminum trioxide particles coated with silica (30 mu m SiO2) + core + veneer: silane; group 4: core: 30 mu m SiO2 + veneer: HF + core + veneer: silane. Core and veneer ceramic were conditioned individually but no attempt was made to avoid cross contamination of conditioning, simulating the clinical intraoral repair situation. Adhesive resin (VisioBond) was applied to both the core and the veneer ceramic, and resin composite (Quadrant Posterior) was bonded onto both substrates using polyethylene molds and photopolymerized. After thermocycling (6000 cycles, 5 degrees C-55 degrees C), the specimens were subjected to shear bond testing using a universal testing machine (1 mm/min). Failure modes were identified using an optical microscope, and scanning electron microscope images were obtained. Bond strength data (MPa) were analyzed statistically using the non-parametric Kruskal-Wallis test followed by the Wilcoxon rank-sum test and the Bonferroni Holm correction (alpha = 0.05).Results: Group 3 demonstrated significantly higher values (MPa) (8.6 +/- 2.7) than those of the other groups (3.2 +/- 3.1, 3.2 +/- 3, and 3.1 +/- 3.5 for groups 1, 2, and 4, respectively) (p < 0.001). All groups showed exclusively adhesive failure between the repair resin and the core zirconia. The incidence of cohesive failure in the ceramic was highest in group 3 (8 out of 10) compared to the other groups (0/10, 2/10, and 2/10, in groups 1, 2, and 4, respectively). SEM images showed that air abrasion on the zirconia core only also impinged on the veneering ceramic where the etching pattern was affected.Conclusion: Etching the veneer ceramic with HF gel and silica coating of the zirconia core followed by silanization of both substrates could be advised for the repair of the zirconia core / veneering ceramic complex.

Impact of Quantity of Resin, C-factor, and Geometry on Resin Composite Polymerization Shrinkage Stress in Class V Restorations

Objective: This study evaluated the effect of quantity of resin composite, C-factor, and geometry in Class V restorations on shrinkage stress after bulk fill insertion of resin using two-dimensional finite element analysis.Methods: An image of a buccolingual longitudinal plane in the middle of an upper first premolar and supporting tissues was used for modeling 10 groups: cylindrical cavity, erosion, and abfraction lesions with the same C-factor (1.57), a second cylindrical cavity and abfraction lesion with the same quantity of resin (QR) as the erosion lesion, and then all repeated with a bevel on the occlusal cavosurface angle. The 10 groups were imported into Ansys 13.0 for two-dimensional finite element analysis. The mesh was built with 30,000 triangle and square elements of 0.1 mm in length for all the models. All materials were considered isotropic, homogeneous, elastic, and linear, and the resin composite shrinkage was simulated by thermal analogy. The maximum principal (MPS) and von Mises stresses (VMS) were analyzed for comparing the behavior of the groups.Results: Different values of angles for the cavosurface margin in enamel and dentin were obtained for all groups and the higher the angle, the lower the stress concentration. When the groups with the same C-factor and QR were compared, the erosion shape cavity showed the highest MPS and VMS values, and abfraction shape, the lowest. A cavosurface bevel decreased the stress values on the occlusal margin. The geometry factor overcame the effects of C-factor and QR in some situations.Conclusion: Within the limitations of the current methodology, it is possible to conclude that the combination of all variables studied influences the stress, but the geometry is the most important factor to be considered by the operator.