Noninvasive assessment of novel nanohybrid resin cement adaptation using cross-polarization optical coherence tomography

OBJECTIVES

Zein-coated magnesium oxide nanoparticles (zMgO NPs) can potentially improve cement adaptation to the tooth-restoration interface, which would aid in minimizing marginal leakage and secondary caries. The aim of this study was to assess the effect of incorporating zMgO NPs on the adaptation of self-adhesive resin cement using cross-polarization optical coherence tomography (CP-OCT) and scanning electron microscopy (SEM).

METHODS

Resin inlays were fabricated to be cemented in Class-I cavities of extracted human molars. All specimens were randomly divided into five groups (n = 10), and the resin inlays were cemented using self-adhesive resin cement with various concentrations of zMgO NPs (0% [control], 0.3%, 0.5%, 1%, 2%). Characterization was done by X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), and SEM. The specimens were examined for interfacial adaptation under CP-OCT. Floor and wall adaptation measurements were analyzed by software on 20 B-scans, and samples were sectioned for interfacial measurement by SEM.

RESULTS

Results for CP-OCT and SEM showed a statistically significant increase of adaptation in the floor and wall of resin cement filled with zMgO NPs compared to the control. The samples enhanced with 0.3% and 0.5% showed a statistically significantly better adaptation in floor and wall in CP-OCT and SEM. However, there was no significant difference between the 1%, 2%, and control groups for CP-OCT and SEM analysis.

SIGNIFICANCE

The incorporation of zMgO NPs in self-adhesive resin cement can enhance the cement's properties by significantly improving its wall and floor adaptation.

Long-Term Bonding Efficacy of CAD/CAM Hybrid Restorative Materials and Universal Adhesives

OBJECTIVES

In-office and lab milled prostheses are the staple for indirect restorations. It is therefore critical to determine their long-term bonding durability.

METHODS

CAD/ CAM blocks of two classes of restorative materials: 1) a nano-ceramic reinforced polymer matrix (NCPM) and, 2) a polymer-infiltrated ceramic network (PICN) were bonded using four different universal adhesives (UA) and silane systems. A lithium disilicate glassceramic (LDS) was used as a reference. The blocks were bisected and bonded with different UA/resin-cement pairs. Bonded blocks were then cut into 1.0x1.0x12.0 mm bar specimens for microtensile bond testing. Half the bars were subjected to bond strength testing immediately and the other half after aging by 50,000 thermal cycles between 5°C and 55°C. ANOVA and post-hoc tests were used to compare mean bond strength among groups.

RESULTS

NCPM presented consistently high bond strength regardless of bonding techniques, while the bond strength of PICN and LDS were lower when bonded with UA relative to traditional silanes. The more hydrophilic UA produced higher bond strengths.

DISCUSSION

Glass-ceramics exhibited lower bond strength with UA than the conventional etch-rinse-silane techniques. However, UAs preserved bonding interface in the long-term.

SIGNIFICANCE

NCPM displayed superior bond strength relative to PICN and LDS regardless of the type of adhesives and bonding techniques.

The Effect of Different Decontamination Methods on the Micro-Tensile Bond Strength of CAD/CAM Resin-Based Blocks to Resin Cement

INTRODUCTION

This study evaluates the impact of decontamination methods on Microtensile bond strength (μTBS) between resin cement and resin blocks.

METHODS

Twenty CAD/CAM resin blocks from two manufacturers were wet-polished, sandblasted, and ultrasonically cleaned. After blood and saliva contamination, blocks were divided into subgroups: control, water rinsing, acid etching, alkaline cleaning paste, or 10-MDP containing cleaner. Resin-based cement was then applied. After 24 hours, the blocks were sectioned to obtain bars for testing. Half of the specimens were tested immediately for μTBS, and the other half underwent artificial aging. The surfaces of the blocks were inspected with a scanning electron microscope (SEM). Three-way ANOVA was performed for μTBS values (α=0.05).

RESULTS

In one of the substrates, the positive control subgroup obtained the highest value (56,01 MPa, SD:6,96) followed by 10-MDP cleaner and universal cleaning paste, when immediately tested, with significant differences respect to the water rinsing (p⟨0.041) and acid etching (p⟨0.048) groups. After thermocycling, higher values were found in the 10-MDP cleaner (47,57 MPa, SD:8,15), but differences were not significant. In the other substrate group, the 10-MDP cleaner subgroup showed highest bond strengths (64,46 MPa SD: 10,92) at the initial test. After thermocycling, 10-MDP cleaner (58,66 MPa, SD: 9,93) gave the highest μTBS value. Significant differences between water rinsing group and the rest of subgroups (p⟨0.001), and between 10-MDP cleaner and the positive control group (p⟨0.006) were observed.

CONCLUSION

Cleaning after contamination improves bonding. 10-MDP containing cleaner can help to restore initial μTBS value and maintain it in the long-term.

Evaluating the Bond Strength of a Polymer Infiltrated Ceramic Network to Zirconia Using the Crossbeam Push-Off Method

Porcelains and glass-ceramics have been used to produce CAD-milled veneers and crowns for zirconia copings and implant-abutments. This study evaluated the bondstrength of a polymer-infiltrated-ceramic-network to zirconia using two adhesive cement systems: Panavia 21 and Multilink Automix. Lithium disilicate and feldspathic porcelain were also tested as reference CAD-On materials. Long beams (3x6x40 mm³) of zirconia and short beams (3x6x15 mm³) of the CAD-On materials were prepared. Zirconia and each CAD-On material were bonded in a crossbeam arrangement and subjected to a modified tensile bond-strength test. Half of the samples in each group (n=10) were tested 5 days after bonding (baseline) and the remaining (n=10) underwent aging (50,000 thermocycles at 5°C and 55°C) prior to bond-strength testing. The effects of material, cement, and aging on the tensile bond-strength were tested using a three-way ANOVA. The reference lithium disilicate/Multilink system showed no significant differences in bond strength compared to polymer-infiltrated-ceramic-network and porcelain. The long-term retention of polymer-infiltrated-ceramic-network was not statistically different compared to the baseline values and the two reference materials. With comparable bond strength between all materials, polymer-infiltrated-ceramic-network is the favorable choice for CAD-On to zirconia copings and implant-abutments due to its superior resistance to fatigue fracture relative to porcelain.

Effect of Tannic Acid and Quercetin Antioxidants on Bond Strength of Resin Cement to Dentin after Internal Bleaching

PURPOSE

To evaluate the influence of tannic acid and quercetin on the immediate microshear bond strength (μSBS) of two resin cements to dentin after internal bleaching.

MATERIALS AND METHODS

The access cavity in eighty extracted maxillary incisors was internally bleached except the control groups. The labial surfaces were ground to expose a flat dentin surface. The specimens were randomly divided into eight groups (n=10) as follows: 1) Control/Dou; Doulink without bleaching, 2) Bl/Dou; Bleaching+Doulink, 3) Bl+Ta/ Dou; Bleaching+Tannic acid+Doulink, 4) Bl+Qu/Dou;Bleaching+Quercetin+Doulink, 5) Control/ PSA; Panavia SA without bleaching, 6) Bl/PSA;Bleaching+Panavia SA, 7) Bl+Ta/ PSA; Bleaching+Tannic acid+Panavia SA, 8) Bl+Qu+PSA; Bleaching+Quercetin+Panavia SA. After 24 hours, the μSBS of the specimens was tested and the obtained data were analyzed with two-way ANOVA and Tamhane test (p⟨0.05).

RESULTS

The µSBS of Doulink groups were higher than the PSA groups (p⟨0.001). The μSBS of Bl+Ta/Dou and Bl+Qu/ Dou groups did not differ from Bl/Dou (p⟩0.05). The μSBS of Bl+Ta/PSA group was statistically significantly higher than the Bl/PSA group (p⟨0.001). There was no significant difference between µSBS of Bl+Qu/PSA and Bl/PSA groups (p=0.39).

CONCLUSIONS

TA partially reversed the negative influence of internal bleaching on the µSBS of Panavia SA while quercetin did not increase the bond strength of both resin cements.

Longevity of Bond Strength of an Indirect Composite Resin to Dentin Using Conventional or Self-Adhesive Resin Cementation: Influence of Dentin Pretreatment with TiF₄

The purpose was to evaluate the influence of dentin pretreatment with titanium tetrafluoride (TiF₄) on the longevity of bond strength (BS) of an indirect composite to dentin, using conventional resin cementation strategy or a self-adhesive resin cement. Forty third human molars with exposed dentin surfaces were used. The teeth were divided into groups (n = 10), according to the cementation strategy and the presence or absence of pretreatment with TiF₄. Microtensile strength testing and failure mode analysis were performed after 24 hours, 180 and 360 days of storage in water. Split-plot ANOVA and Tukey's test showed that BS was significantly higher when the conventional strategy was used, regardless of the time period, and of the application or no application of pretreatment with TiF₄ (p ⟨0.0001). When TiF₄ was used for both cementing strategies, BS was lower after 360 days (p = 0.0019). Both cementing strategies led to the formation of a shallow hybrid layer, regardless of the presence of TiF₄. BS was higher when the conventional cementation strategy was used, regardless of TiF₄ pretreatment. TiF₄ used as a pretreatment agent associated with different types of resin cementation was unable to maintain adhesive bond strength in the long term.

Effect of Resin Cement Color on the Final Color of Lithium Disilicate All-Ceramic Restorations

OBJECTIVES

Obtaining an adequate ceramic thickness to mask the substructure color is not always feasible, and appropriate use of a cement may be the only solution. This study aimed to evaluate the effect of the color of Variolink II resin cement on the final color of lithium disilicate glass ceramic restorations.

MATERIALS AND METHODS

In this in-vitro study, 90 discs of IPS e.max Press ceramic were evaluated. The ceramic discs were cemented to composite and amalgam blocks. The effect of the cement color and substructure on the final color of ceramic was analyzed by calculating the color change (ΔE) value using a spectrophotometer. Data were analyzed via three-way analysis of variance (ANOVA) and Tukey's test.

RESULTS

The cement color had a statistically significant effect on the final color of ceramic (P≤0.001). The white, yellow, and translucent cements caused the highest color change (ΔE=4.558, 3.308, and 2.649, respectively). The effect of composite substructure and the yellow cement on the final color was less prominent compared to other combinations of cement and substructure (ΔE=2.043). The white cement over amalgam substructure showed the greatest effect on the final color (ΔE=4.890). The ΔE in HO group was less than that of other combinations (P<0.05), and the greatest ΔE was reported in MO group with the white cement (ΔE=6.255).

CONCLUSIONS

The final color of the restoration is influenced by the cement color. Therefore, when IPS e.max Press is used over a metal core, it is recommended to use a cement with an HO ceramic.

The Effect of BC Sealer, AH-Plus and Dorifill on Push-out Bond Strength of Fiber Post

Introduction:

Dentinal canal walls are in direct contact with endodontic sealers prior to post space preparation and luting cements after post space preparation. This direct contact may affect the bond strength of intraradicular posts to root dentin. This study aimed to assess the effect of three different sealers on the bond strength of fiber posts to root dentin.

Methods and Materials:

The canals of 56 extracted single-rooted human premolars after selection and decoronation were prepared. For obturation of the canals, specimens were randomly divided into four groups (n=14) according to the type of sealer used in conjunction with gutta-percha: group 1 (control) without any sealer; group 2 with AH-Plus sealer (resin based); group 3 with Dorifill sealer (ZOE-based); and group 4 with BC Sealer (calcium silicate-based). Nine mm-deep post space was prepared in the canal of each specimen. Intraradicular fiber posts were cemented using dual-cure resin cement (Panavia F2.0). Sections of 1 mm thickness were made at the coronal, middle and apical thirds of the post space of each specimen. The push-out bond strength of post to root dentin was measured in a universal testing machine. The data were analyzed using one-way ANOVA and post-hoc Tukey’s test.

Results:

The mean push-out bond strength in the coronal third was significantly lower in Dorifill group compared to AH-Plus (P=0.004). This value was significantly lower in BC Sealer group than AH-Plus (P=0.000) and control group (P=0.03). In middle and apical thirds, the mean push-out bond strength was not significantly different among the four groups (P=0.407, P=0.065, respectively). The mean push-out bond strength was significantly lower in apical than coronal third in AH-Plus group (P=0.001).

Conclusion:

Application of BC Sealer and Dorifill decreased the mean push-out bond strength of intracanal post to root dentin in the coronal third in comparison to AH-Plus.

Mutans on Lithium Disilicate Reinforced Glass-Ceramics, Monolithic Zirconia and Dual Cure Resin Cement

OBJECTIVE

Monolithic zirconia and glass ceramics are increasingly used in implant crowns. Limited data is available on bacterial adhesion and early biofilm formation on these materials.

METHODS

Four different materials were investigated: (1) Lithium disilicate glass-ceramics (LDS), (2) Fully stabilized zirconia (FSZ), (3) Partially stabilized zirconia (PSZ), and (4) Dual curing cement (DCC). The materials' surfaces were characterized with spinning disc confocal microscopy and by water contact angle and surface free energy (SFE) measurements. For the adhesion tests the materials were rolled in suspensions of Streptococcus mutans. Early biofilm formation was studied on the materials and allowing the biofilms to form for 24 h. S. mutans cell counts were determined by plate culturing. ANOVA and post-hoc Tukey's tests (p⟨0.05) were used for statistical evaluation.

RESULTS

The LDS surfaces were clearly hydrophilic with the highest SFE value (p⟨0.001). For S. mutans adhesion, the ranking of the materials from lowest to highest was: LDS = FSZ ⟨ DCC ⟨ PSZ (p⟨0.05). No significant differences among the materials were noticed in biofilm formation.

CONCLUSIONS

LDS has lower S.mutans adhesion than other materials examined in this study, but the difference was not reflected in early biofilm formation.

The Effect of Lithium Disilicate Opacity on Polymerization of a Dual-Cured Resin Cement

The aim of this study was to evaluate the influence of different levels of opacity of the lithium disilicate framework upon polymerization of dual-cured resin cement. Four ceramic discs were used, one for each opacity framework covered by their respective ceramic veneering, and a cement group without a ceramic cover. The degree of conversion for each resin cement was estimated using the Knoop microhardness test. The group with the highest opacity showed the lowest hardness score at baseline. The study concluded that the opacity level of lithium disilicate framework could influence the degree of polymerization of a dual-cured resin cement.

Effect of Self-Adhesive and Separate Etch Adhesive Dual Cure Resin Cements on the Bond Strength of Fiber Post to Dentin at Different Parts of the Root

OBJECTIVES

Bonding of fiber posts to intracanal dentin is challenging in the clinical setting. This study aimed to compare the effect of self-adhesive and separate etch adhesive dual cure resin cements on the bond strength of fiber post to dentin at different parts of the root.

MATERIALS AND METHODS

This in-vitro experimental study was conducted on 20 single-rooted premolars. The teeth were decoronated at 1mm coronal to the cementoenamel junction (CEJ), and the roots underwent root canal treatment. Post space was prepared in the roots. Afterwards, the samples were randomly divided into two groups. In group 1, the fiber posts were cemented using Rely X Unicem cement, while in group 2, the fiber posts were cemented using Duo-Link cement, according to the manufacturer's instructions. The intracanal post in each root was sectioned into three segments of coronal, middle, and apical, and each cross-section was subjected to push-out bond strength test at a crosshead speed of 1mm/minute until failure. Push-out bond strength data were analyzed using independent t-test and repeated measures ANOVA.

RESULTS

The bond strength at the middle and coronal segments in separate etch adhesive cement group was higher than that in self-adhesive cement group. However, the bond strength at the apical segment was higher in self-adhesive cement group compared to that in the other group. Overall, the bond strength in separate etch adhesive cement group was significantly higher than that in self-adhesive cement group (P<0.001).

CONCLUSIONS

Bond strength of fiber post to intracanal dentin is higher after the use of separate etch adhesive cement compared to self-adhesive cement.

Can Cleansing Regimens Effectively Eliminate Saliva Contamination from Lithium Disilicate Ceramic Surface?

This study evaluated the effect of cleaning protocols on the bond strength of resin cement to glass-ceramic. Ceramic specimens (N=120, n=12 per group) were etched with hydrofluoric acid and rinsed with water. After saliva contamination, specimens were cleaned as follows: water, 37% H3PO4, cleaning-paste (Ivoclean), or isopropanol. Non-contaminated specimens acted as the control. Resin cement was bonded to the specimens, and tested either after 24 h or x5000 thermocycling. Both the cleaning method (p=0.001) and the storage conditions (p=0.005) significantly affected the bond strength results. In dry conditions, the groups PA and IV showed no significant difference, being also similar to the non-saliva contaminated control group (p⟩0.05). In dry conditions, no significant difference was observed between the mean DW and IS being significantly lower than those of other groups (p⟨0.05). Except for the group IV, thermocycling decreased the results significantly in all groups (p⟨0.05). Predominantly mixed failure type was observed in both dry and aged conditions. SEM micrographs of ceramic surfaces after cleaning agents showed no major differences but on the specimens from the IV group, small, rounded-zirconia particles were observed. In case of saliva contamination of acid-etched glass-ceramics, mechanical cleaning can restore adhesion to the baseline situation.

Effect of Different Endodontic Sealers on the Push-out Bond Strength of Fiber Posts

Introduction:

The aim of this in vitro study was to evaluate the effect of MTA-based sealer (MTA Fillapex), eugenol-based sealer (Dorifill) and an epoxy resin sealer (AH Plus) on the bond strength of fiber posts cemented with a self-etch adhesive.

Materials and Methods:

The root canals of 72 maxillary incisors were prepared using the step-back technique after removing/cutting off the crowns. The samples were randomly divided to 4 groups (n=18). In group 1 (the controls) gutta-percha was used without sealer. In groups 2, 3 and 4, the canals were filled with gutta-percha using AH Plus, Dorifill and MTA Fillapex sealers, respectively, by cold lateral compaction technique. After post space preparation, the fiber posts were cemented in the root canals using self-etch adhesive. Then 1-mm-thick disks were prepared from the coronal thirds of all the root canals and subjected to a push-out test. Data were analyzed using the one-way ANOVA and post hoc Tukey’s tests.

Results:

The maximum (4.45±0.09 MPa) and minimum (1.02±0.03 MPa) bond strength values were recorded in the control and Dorifill groups, respectively. The mean push-out bond strength values were similar for MTA Fillapex and AH Plus sealers (P>0.05). However these values were significantly higher than that of the Dorifill sealer (P<0.05).

Conclusion:

Sealer type affected the bond strength of the fiber posts and MTA Fillapex decreased the dislodgment resistant of the fiber post.

Cytotoxicity Comparison of Harvard Zinc Phosphate Cement Versus Panavia F2 and Rely X Plus Resin Cements on Rat L929-fibroblasts

OBJECTIVE

Resin cements, regardless of their biocompatibility, have been widely used in restorative dentistry during the recent years. These cements contain hydroxy ethyl methacrylate (HEMA) molecules which are claimed to penetrate into dentinal tubules and may affect dental pulp. Since tooth preparation for metal ceramic restorations involves a large surface of the tooth, cytotoxicity of these cements would be more important in fixed prosthodontic treatments. The purpose of this study was to compare the cytotoxicity of two resin cements (Panavia F2 and Rely X Plus) versus zinc phosphate cement (Harvard) using rat L929-fibroblasts in vitro.

MATERIALS AND METHODS

In this experimental study, ninety hollow glass cylinders (internal diameter 5-mm, height 2-mm) were made and divided into three groups. Each group was filled with one of three experimental cements; Harvard Zinc Phosphate cement, Panavia F2 resin cement and Rely X Plus resin cement. L929- Fibroblast were passaged and subsequently cultured in 6-well plates of 5×10(5) cells each. The culture medium was RPMI_ 1640. All samples were incubated in CO2. Using enzyme-linked immune-sorbent assay (ELISA) and (3-(4,5-dimethylthiazol-2-yl)-2, 5-diphenyltetrazolium bromide) (MTT) assay, the cytotoxicity of the cements was investigated at 1 hour, 24 hours and one week post exposure. Statistical analyses were performed via two-way ANOVA and honestly significant difference (HSD) Tukey tests.

RESULTS

This study revealed significant differences between the three cements at the different time intervals. Harvard cement displayed the greatest cytotoxicity at all three intervals. After 1 hour Panavia F2 showed the next greatest cytotoxicity, but after 24-hours and oneweek intervals Rely X Plus showed the next greatest cytotoxicity. The results further showed that cytotoxicity decreased significantly in the Panavia F2 group with time (p<0.005), cytotoxicity increased significantly in the Rely X Plus group with time (p<0.001), and the Harvard cement group failed to showed no noticeable change in cytotoxicity with time.

CONCLUSION

Although this study has limitations, it provides evidence that Harvard zinc phosphate cement is the most cytotoxic product and Panavia F2 appears to be the least cytotoxic cement over time.