Effect of aging and curing mode on the compressive and indirect tensile strength of resin composite cements

Effect of the type of resin cement on the fracture resistance of chairside CAD-CAM materials after aging

PURPOSE

The study objective was to evaluate the influence of the type of resin cement on the flexural strength and load to fracture of two chairside CAD-CAM materials after aging.

MATERIALS AND METHODS

A polymer-infiltrated ceramic network (PICN) and a nanoceramic resin (RNC) were used to produce the specimens. Two types of dual-cure resin cements, a self-adhesive and a universal, were investigated. Bilayer specimens were produced (n = 10) and aged for 6 months in a humid environment before the biaxial flexural strength test (σ_f). Bonded specimens were subjected to a mechanical aging protocol (50 N, 2 Hz, 37℃ water, 500,000 cycles) before the compressive load test (L_f). σ_f and L_f data were analyzed using two-way ANOVA and Tukey tests (α = .05). Chi-square test was used to analyze the relationship between failure mode and experimental group (α = .05).

RESULTS

The type of resin cement and the interaction between factors had no effect on the σ_f and L_f of the specimens, while the type of restorative material was significant. RNC had higher σ_f and L_f than PICN. There was a significant association among the type of cracks identified for specimens tested in L_f and the restorative material.

CONCLUSION

The type of resin cement had no effect on the flexural strength and load to fracture of the two investigated CAD-CAM chairside materials after aging.

Influence of surface treatment and curing mode of resin composite cements on fibroblast behavior

BACKGROUND

Human gingival fibroblast (HGF-1) cells in the connective tissue provide an effective barrier between the alveolar bone and the oral environment. Cement margins of restorations with intrasulcular preparation or cemented implant restorations are in contact with HGF cells. However, it is unknown to what extend the cement surface finish affects the behavior of HGF cells. The purpose of this study was to compare the behavior of HGF-1 cells in contact with two different resin composite cements with three different surface treatments after light-curing and autopolymerization, respectively.

METHODS

Disks of one adhesive (Multilink Automix, Ivoclar Vivadent [MLA]) and one self-adhesive (RelyX Unicem 2 Automix, 3 M [RUN]) resin composite cement were either light-cured or autopolymerized. Specimen surfaces were prepared with the oxygen inhibition layer intact, polished with P2500-grit silicon carbide paper or treated with a scaler. Cells were cultivated on the specimens for 24 h. Viability assay was performed, and cell morphology was examined with scanning electron microscopy. Additionally, roughness parameters of the specimen were analyzed with a 3D laser scanning microscope. Three-way ANOVA was applied to determine the effect of cement material, curing mode and surface treatment (a = 0.05).

RESULTS

Overall, cement material (p = 0.031), curing mode (p = 0.001), and surface treatment (p < 0.001) significantly affected relative cell viability of HGF. The autopolymerized specimen with the oxygen inhibition layer left intact displayed the lowest relative cell viability (MLA 25.7%, RUN 46.6%). Removal of the oxygen inhibition layer with a scaler increased cell viability but also resulted in higher surface roughness values.

CONCLUSIONS

HGF cell viability is affected by the surface treatment and the curing mode. The oxygen inhibition layer is an inhibitory factor for the viability of HGF cells. Autopolymerization enhances the cytotoxic potential of the oxygen inhibition layer.

A comprehensive in vitro study on the performance of two different strategies to simplify adhesive bonding

Objective

The purpose of this study is to compare the bonding performance and mechanical properties of two different resin composite cements using simplified adhesive bonding strategies.

Materials and methods

Shear bond strength of two resin composite cements (an adhesive cement: Panavia V5 [PV5] and a self‐adhesive cement: RelyX Universal [RUV]) to human enamel, dentin, and a variety of restorative materials (microfilled composite, composite, polymer‐infiltrated ceramic, feldspar ceramic, lithium disilicate and zirconia) was measured. Thermocycle aging was performed with selected material combinations.

Results

For both cements, the highest shear bond strength to dentin was achieved when using a primer (PV5: 18.0 ± 4.2 MPa, RUV: 18.2 ± 3.3 MPa). Additional etching of dentin reduced bond strength for RUV (12.5 ± 4.9 MPa). On enamel, PV5 achieved the highest bond strength when the primer was used (18.0 ± 3.1 MPa), while for RUV etching of enamel and priming provided best results (21.2 ± 6.6 MPa). Shear bond strength of RUV to restorative materials was superior to PV5. Bonding to resin‐based materials was predominantly observed for RUV.

Conclusions

While use of RUV with the selective‐etch technique is slightly more labor intensive than PV5, RUV (with its universal primer) displayed a high‐bonding potential to all tested restorative materials, especially to resin.

Clinical significance

For a strong adhesion to the tooth substrate, PV5 (with its tooth primer) is to be preferred because etching with phosphoric acid is not required. However, when using a wide range of varying restorative materials, RUV with its universal primer seems to be an adequate option.

Effect of aging on color stability of amine-free resin cement through the ceramic laminate veneer

Background

This study aimed to assess the color change of two amine-free dual-cure resin cements following aging in comparison with a light-cure resin cement.

Materials and Methods

This in vitro, experimental study evaluated 6 groups (n = 10), including three groups of cements bonded to feldspathic porcelain and three groups of resin cements alone. Panavia V5 (Kuraray) and G-CEM LinkForce (GC) dual-cure resin cements and Choice 2 (Bisco) light-cure resin cements were bonded to porcelain according to the manufacturers' instructions. The color parameters of the groups were measured before and after 5000 thermal cycles by spectrophotometry. Data were analyzed using two-way ANOVA and Tukey's post hoc test (α =0.05).

Results

The color change (ΔE) of the cement groups alone was significantly greater than that of porcelain-bonded cements. The ΔE of G-CEM LinkForce cement group was significantly higher than that of Panavia V5 group (P = 0.020), and the ΔE of the latter group was significantly higher than that of Choice 2 cement group (P = 0.021).

Conclusion

Considering the color change of cements evaluated in this study, Choice 2 and Panavia V5 cements bonded to porcelain showed acceptable color change, which indicates that they are suitable for cementation of esthetic dental restorations. Ceramic laminates have become an ideal esthetic treatment for anterior restorations. The resin cement discoloration can affect final appearance of these restorations. Besides that, exposed resin cement line can lead to the esthetic problem over time.

Influence of the activation mode on long-term bond strength and endogenous enzymatic activity of dual-cure resin cements

Objective

To investigate the long-term microtensile bond strength (µTBS), interfacial nanoleakage expression (NL), and adhesive stability of dual-cure resin cements with/out light activation to dentin.

Materials and methods

Composite overlays (N = 20) were luted to deep dentin surfaces with RelyX Ultimate (RXU, 3M) or Variolink EstheticDC (VAR, Ivoclar-Vivadent). A universal adhesive was used for bonding procedures (iBond universal, Heraeus Kulzer). The resin cements were either self-cured (SC; 1 h at 37 °C) or dual-cured (DC; 20s light-cure followed by 15 min self-cure at 37 °C). Specimens were submitted to µTBS immediately (T₀) or after 1 year of laboratory storage (T₁₂). The fracture pattern was evaluated using scanning electron microscopy (SEM). Data were statistically analyzed with two-way ANOVA/Tukey test. Further, the NL was quantified and analyzed (chi-square test) and in situ zymography was performed to evaluate the endogenous enzymatic activity within the hybrid layer (HL) at T₀ and T₁₂ (Mann–Whitney test)_. The significance level for all statistical tests was set at p = 0.05.

Results

DC resulted in higher bond strength and decreased fluorescence at the adhesive interface, irrespective of the material and the storage period (p < 0.05). Significantly lower bonding performances (p < 0.05) and higher endogenous enzymatic activity (p < 0.05) were observed within the HL at T₁₂ compared to T₀ in all tested groups.

Conclusions

Light-curing the dual-cure resin cements, more than the cement materials, accounted for good bonding performances and higher HL stability over time when used with a universal adhesive.

Clinical significance

The curing condition influences the bonding performances of dual-cure resin cements to dentin when used with a universal adhesive.

Low-temperature flow-synthesis-assisted urethane-grafted zinc oxide-based dental composites: physical, mechanical, and antibacterial responses

A novel way was adopted to graft zinc oxide (ZnO) with urethane-modified dimethacrylate (UDMA) in order to utilize them as reinforcing agents in resin-based dental composites. Experimental novel composites were synthesized having UDMA-grafted and nongrafted ZnO, at a concentration of 0 wt.%, 5 wt.%, and 10 wt.%. The same concentrations of ZnO were also incorporated in Filtek Z250 XT (3 M ESPE, USA). The antibacterial behavior was evaluated against Streptococcus mutans by direct-contact test at one, three, and seven days of incubation. The compressive strength and Vickers microhardness were tested as per ISO 9917 and ISO/CD6507-1, respectively. For abrasive wear resistance, mass loss and roughness average after tooth-brushing cycles of 24,000 at custom-made tooth-brushing simulator were evaluated using noncontact profilometer. Data analysis was carried out using post hoc Tucky's test and nonparametric Kruskal-Wallis test. Direct contact test revealed that the antibacterial potential of novel and commercial composites was increased with an increase in the concentration of grafted ZnO as compared with nongrafted, whereby the potential was the highest at day seven. There was a significant decrease in compressive strength and Vickers hardness of commercial composites on addition of grafted ZnO while there was no significant difference in the strength of experimental novel composite. The abrasive wear of commercial and experimental composites was within clinical limits. Low-temperature flow-synthesis method was successfully employed to synthesize grafted and nongrafted ZnO. The UDMA-grafted ZnO can be incorporated into dental composites without decreasing their strength and these composites can be used to combat secondary caries.

The effects of 45S5 bioactive glass and Er:YAG Laser on the microtensile bond strength of fluorosed teeth

This vitro study aimed to evaluate the effects of 45S5 bioactive glass (BAG) and Er:YAG laser as desensitization treatments on the microtensile bond strength (MTBS) of fluorosed teeth. The 120 noncarious fluorosis were to obtain superficial dentin, being classified into four groups according to the Thylstrup and Fejerskov Index (TFI). Specimens from each group were randomly divided into five subgroups. After fluorosed teeth hypersensitivity models were established, the following pretreatments were applied on dentine surface: Subgroup 1: deionized water (Control); Subgroup 2: BAG; Subgroup 3: Er:YAG laser; Subgroup 4: BAG + Er:YAG laser, and Subgroup 5: Er:YAG laser + BAG. One sample was randomly selected from each subgroup for scanning electron microscope (SEM). The remaining samples were bonded with composite resin by Adper Single Bond 2 adhesive. Then water bath at 37°C for 24 hr. After 5,000 thermocycling, MTBS was tested and fracture mode was analyzed. The difference of MTBS between BAG group and Control group was found statistically significant (p < .05) in fluorosis. The Er:YAG laser + BAG group showed lowest MTBS values in fluorosis. In conclusion, the pretreatment of BAG might be beneficial to the adhesive of fluorosed teeth. Er:YAG laser desensitization alone or using BAG first and then Er:YAG laser desensitization might not affect the adhesive of fluorosed teeth, while Er:YAG laser desensitization followed by the pretreatment of BAG would be not conducive to the adhesive of fluorosed teeth.

HF etching of CAD/CAM materials: influence of HF concentration and etching time on shear bond strength

Background

The required pretreatment of CAD/CAM ceramic materials before resin composite cement application varies among studies. The aim of the present study was to evaluate the effect of hydrofluoric acid concentration and etching time on the shear bond strength (SBS) of two adhesive and two self-adhesive resin composite cements to different CAD/CAM ceramic materials.

Methods

SBS of two adhesive (Panavia V5, Kuraray, [PV5]; Vita Adiva F-Cem, Vita Zahnfabrik, [VAF]) and two self-adhesive (RelyX Unicem 2 Automix, 3 M Espe, [RUN]; Vita Adiva S-Cem, Vita, [VAS]) cements to four different CAD/CAM materials (Vitablocs Mark II, Vita, [VM]; Vita Enamic, Vita, [VE]; e.max CAD, Ivoclar Vivadent, [EC]; Vita Suprinity PC, Vita, [VS]) was measured. The effect of the surface pretreatment by using two different hydrofluoric acid products (HF5% Vita Ceramics Etch, Vita and HF9% buffered, Ultradent Porcelain Etch, Ultradent Products) were assessed at etching times of 0 s, 5 s, 15 s, 30s and 60s for each cement and restorative material combination (n = 10 per group, total n = 1440).

Results

Significant effects were found for the etching time and cement for all materials with highest shear bond strength for etching times of 60s = 30s = 15 s ≥ 5 s > 0 s and for RUN>PV5 = VAF > VAS (p < 0.05). Etching with HF5% for 5 s to 15 s resulted in higher SBS values, while no differences were observed between HF5% and HF9% buffered when the substrates were etched for 30s to 60s (p < 0.05).

Conclusions

Within the limitations of this study the recommended surface pretreatment of silicate ceramics is HF etching with concentrations of 5% or 9% for 15 s to 60s to achieve highest shear bond strength while the glassy matrix is sufficiently dissolved. The tested resin composite cements can be applied with all tested materials and suggested for clinical application.

Adhesive Systems Used in Indirect Restorations Cementation: Review of the Literature

New technologies are changing the therapeutical options to do indirect restorations and new adhesive systems are continuously introduced to be used by clinicians. Different interactions between restorations, adhesive systems components, enamel and dentin require having criteria based on the selection of the adhesive system, ensuring the longevity of the restorations and the preservation of the biological remnant. The adhesion force to the dental tissue is one of the indicatives of the behavior of the adhesive systems and influences the behavior of the treatments with direct and indirect restorations. The objective of this search was to find the adhesive systems with the best results in terms of the adhesion strength of indirect restorations on the dental tissues. The search was conducted in two MEDLINE digital databases (PubMed), and the Cochrane Library with a search strategy based on the combination of MeSH (Medical Subject Headings) keywords. This systematic review used the PRISMA guide (Preferred Reporting Items for Systematic Reviews and Meta-Analysis). According to this review, the 3-step adhesive systems were the best performing and still are the gold standard for the cementing of indirect restorations. In addition, it can be concluded that self-etched adhesive systems reduce the time spent in clinical practice, however at the interface level they behave as permeable membranes more susceptible to degradation.

Resistência à compressão, flexão e tração diametral de cimentos resinosos em tempos diferentes de armazenamento

Objetivos: O objetivo desse estudo foi avaliar a resistência à compressão, tração diametral e flexão de dois cimentos resinosos de presa dual. Métodos: foi utilizado o cimento autoadesivo RelyX U200 (3M ESPE) e o cimento convencional Variolink II (Ivoclar Vivadent). Foram confeccionados corpos de prova cilíndricos com 4mm de diâmetro x 6mm de altura para o teste de compressão, 6mm de diâmetro x 2mm de altura para o teste de tração diametral (ISO 9917-1:2007) e em forma de barra com 25mm de comprimento x 2mm de altura e largura para o teste de flexão três pontos (ISO 4049:2009). As amostras foram armazenadas por 24h (n = 10) e 45 dias (n = 10) em água destilada a 37ºC. Os testes foram realizados em uma máquina universal de ensaios EMIC (DL 2000) com uma célula de carga de 2000 Kgf para o teste de compressão e 200 Kgf para os testes de tração diametral e flexão, à uma velocidade de 0,5 mm/min. Os dados foram submetidos à análise de variância dois critérios (ANOVA) e as médias comparadas pelo teste de Tukey (5%). Resultados: os resultados mostraram valores estatisticamente similares para todas as propriedades mecânicas avaliadas entre todos os cimentos e tempos de armazenamento estudados. Conclusões: A composição química dos cimentos resinosos e o armazenamento em água por 45 dias não foram suficientes para ocasionar alterações nas propriedades mecânicas avaliadas nesse estudo.

The Effect of Expiration Date on Mechanical Properties of Resin Composites

Objective

The aim of this in vitro study is to evaluate the effect of expiration date on some mechanical properties of resin composites after controlled storage of syringes and compules in a refrigerator at 4°C.

Materials and Methods

Specimens were tested at 7 days after storage in distilled water at room temperature. The investigated properties are the static modulus of elasticity, the flexural strength, and the Vickers microhardness. Same batches of restorative materials were examined at baseline (at least 1 year before their expiration date) and 1 year after they expired.

Results

Paired t-test is used to compare the results between the two groups using StatView software (version 5.0) SAS Campus Drive Cary, North Carolina, USA. Except for the flexural strength, no statistical differences were found between the mechanical properties of the expired and the unexpired group.

Conclusion

The 1-year expiry date did not seem to affect the investigated mechanical properties.

Effect of a filled adhesive as the desensitizer on bond strength of "Self-Adhesive Cements To" differently severity of fluorosed dentin

The objectives were to evaluate the efficacy of a filled adhesive named Prime & Bond NT (P&B NT) as the dentin desensitizer in occluding fluorosis dentinal tubules and compare the shear bond strength (SBS) of RelyX U200 self-adhesive resin cement (RXU) and RelyX Luting self-adhesive resin-modified glass ionomer cement (RMGIC) before and after P&B NT pretreatment. 176 non-carious fluorosis were classified into four subgroups by the Thylstrup and Fejerskov index (TFI): normal group (TFI = 0), mild group (TFI = 1-3), moderate group (TFI = 4-5), severe group (TFI = 6-9). 160 composite cylinders (4 × 5 mm) were fabricated, then every severity of fluorosed dentin was subjected to four treatments: P&B NT + RXU (n = 40), RXU (n = 40), P&B NT + RMGIC (n = 40), RMGIC (n = 40). The specimens were immersed in water at 37°C for 24 hr first and half of them underwent 5,000 thermocycling before shear bond strength test. A factorial design (factorial 4 × 2 × 2 × 2) was developed to make statistical analysis. Scanning electron microscope (SEM) analysis (n = 16) in cross section and longitudinal section view characterized the occlusion situation of dentinal tubules. P&B NT might occlude dentinal tubules as the dentin desensitizer for normal teeth and mild-moderate fluorosis. P&B NT significantly increased the SBS of RXU (p < .05) but had no statistical significance on the SBS of RMGIC (p > .05). RXU could benefit from P&B NT desensitization to achieve a better quality of adhesion.