The effect of simplified adhesives on the bond strength to dentin of dual-cure resin cements

Influence of geometric dimensions on early failures of adhesively retained composite resin core build-ups

OBJECTIVE

To determine the influence of the geometric dimensions of core build-ups on early core build-up failure, that is, loss before definitive prosthesis cementation.

MATERIALS AND METHODS

Adhesive core build-ups of exclusively vital teeth in 114 participants were evaluated (n materials: 40 Rebilda DC, 38 Multicore Flow, 36 Clearfil DC Core; n teeth: 8 incisors, 54 premolars, 52 molars). Impressions of the abutment teeth were made (1) after removal of insufficient restorations/caries and (2) after core build-up and preparation for a fixed prosthesis. Digitized model surfaces of both situations were aligned (Geomagic Design X) and core build-up volume (V_CBU ), remaining hard tissue volume (V_Abut ), and size of the adhesive surface (A_adh ) were assessed. The derived measure d_CBU  = V_CBU /A_adh can be interpreted as mean arithmetic core build-up thickness. Associations between participant or core build-up design characteristics and the occurrence of early failures were statistically evaluated (SPSS v27, α = 0.05).

RESULTS

A total of six (5.3%) core build-up failures were registered. Higher participant age, greater core build-up volume V_CBU and greater arithmetic uniform thickness d_CBU were associated with a greater incidence of failure in bivariate and univariate, however, not in multivariate statistics.

CONCLUSIONS

Core build-up volume and thickness were associated with early success or failure.

CLINICAL SIGNIFICANCE

In the case of voluminous/thick core build-ups in relation to the adhesive surface, additional measures, such as the preparation of retentive elements to increase the bonding area, might be considered to reduce the risk of early core build-up failure.

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.

Repair Bond Strength of High-viscosity Glass-ionomer Cements Using Resin Composite Bonded with Light- and Self-cured Adhesive Systems

CLINICAL RELEVANCE

High-viscosity glass-ionomer cements (HVGICs) used with atraumatic restorative treatment can be repaired with light- or self-cured adhesive systems; however, the repair bond strength of two-step, self-etching and one-step adhesives in the light-cure mode surpass one-step self-cure adhesives. Working on a feasible self-cure approach in the absence of such in rural areas as well as in war zones is of prime importance.

SUMMARY

Color stability and degree of conversion of a novel dibenzoyl germanium derivative containing photo-polymerized resin luting cement

AIM

To compare the color stability and degree of conversion (DC) of a resin cement containing a dibenzoyl germanium derivative photo-initiator (Variolink Esthetic) to resin cements containing conventional luting agents.

MATERIALS AND METHOD

Spectrophotometry and Fourier transform infrared spectroscopy (FTIR) were used to compare the color stability and DC, respectively, of Variolink Esthetic compared to Calibra, Variolink-N, and NX3 resin cements. Ten specimens (1 × 2 mm²) of each resin cement were photo-polymerized and then subjected to color stability assessments. In addition, 30 samples of each of the four resin cements were prepared and then immersed in three staining solutions (tea, coffee, and distilled water) for two weeks. Changes in color for the immersed versus non-immersed specimens (control specimens) were determined by comparing ΔL (lightness), Δa, and Δb (color components), and an overall ΔE (color difference) obtained from spectrophotometry assays. One-way analysis of variance and a multiple comparison test (Tukey's test) were used to analyze color stability and DC data. NX3 and Variolink Esthetic resin cements exhibited significantly lower values compared to the dual cured resin cements (Variolink-N and Calibra).

RESULTS

The highest DC values were observed among the photo-polymerized samples of Variolink Esthetic (87.18 ± 2.90%), while the lowest DC values were observed among the Variolink-N samples (44.55 ± 4.33%).

CONCLUSION

The resin cement, Variolink Esthetic, containing a novel dibenzoyl germanium derivative photo-initiator exhibited superior color stability (p < 0.05) and a higher DC than other resin cements containing conventional luting agents in an in vitro setting.

Additive effects of touch-activated polymerization and extended irradiation time on bonding of light-activated adhesives to root canal dentin

STATEMENT OF PROBLEM

The bonding of light-activated adhesives to root canal dentin with an additional touch-polymerization activator has been insufficiently examined.

PURPOSE

The purpose of this in vitro study was to investigate the effect of touch-polymerization activators and extended light-irradiation time on the microtensile bond strength (μTBS) of light-activated adhesives.

MATERIAL AND METHODS

Post cavities were prepared in 50 extracted mandibular premolars and bonded using Prime&Bond Universal (PBU); PBU+Self Cure Activator (SCA); Clearfil SE Bond 2 (SEB); SEB+Clearfil DC Activator (DCA); or Clearfil Universal Bond Quick ER (UBQ). After light-irradiation for 10 or 20 seconds, the post cavities were filled with dual-activated resin core materials. Eight beams were prepared per specimen and subjected to the μTBS test. The μTBS data were analyzed by using 3-way ANOVAs with the Bonferroni correction (α=.05).

RESULTS

The 3-way ANOVAs indicated that the use of touch-polymerization activators (SCA and DCA) significantly increased the μTBS of PBU and SEB in both the coronal (P=.015) and apical (P=.001) regions. The extension of light-irradiation time to 20 seconds significantly improved their μTBS in the apical region (P<.001), but not in the coronal region (P=.09). Light-irradiation for 20 seconds increased the μTBS of UBQ significantly in the coronal region (P=.014).

CONCLUSIONS

Touch-polymerization activators improved the bond strength of light-activated adhesives to root canal dentin, especially when combined with an extended light-irradiation time.

Dentin bond strength of bioactive cement in comparison to conventional resin cement when photosensitized with Er,Cr:YSGG Laser

Objective:

The purpose of the present study was to assess dentin shear bond strength (SBS) and mode of bond failure of bioactive cement (BA) in comparison to conventional resin cement when photosensitized by Er,Cr: YSGG Laser (ECL).

Methods:

The present in-vitro study was carried out from March 2019 to May 2019. Sixty permanent non-carious, intact, non-fractured molars were isolated and mounted vertically in acrylic resin. Buccal surface of each molar tooth was ground, polished and surface treated with ECL. Ketac conditioner was applied on the surface washed and air dried surface. Tetric -N-Bond adhesive was applied on forty-five samples and light cured. The specimens were allocated into four groups (n=15) according to the type of cement used i.e., Calibra (C), BA, Variolink II (V) and Maxcem-Elite (ME). For SBS testing was performed using the universal testing machine. Eight samples from each group were assessed for modes of failure. Means and standard deviations were compared using analysis of variance (ANOVA) and Tukey’s post hoc test at a significance level of p < 0.05.

Results:

The highest mean SBS was observed in group ECL-C (21.55±3.08). The lowest mean SBS was displayed in group ECL-ME (14.25±3.55). Mean SBS values for group ECL-C (21.55±3.08) and group ECL-V (20.74±4.15) were comparable (p <0.05). Similarly, SBS values of group ECL-BA (15.48±3.62) and group ECL-ME (14.25±3.55) were comparable (p <0.05).

Conclusion:

Dentin surface conditioned with Er,Cr: YSGG and bonded to C and V cements exhibit favourable bond strength values.

Effect of Different Adhesive Strategies and Time on Microtensile Bond Strength of a CAD/CAM Composite to Dentin

PURPOSE

The aim of this study was to evaluate the effect of adhesive strategy and time on the microtensile bond strength of a computer-aided design/computer-aided manufacturing (CAD/CAM) composite to dentin.

METHODS AND MATERIALS

Sixty CAD/CAM composite blocks were bonded to human dentin with simplified bonding agents using etch-and-rinse and self-etching approaches and amine-based and amine-free resin cements, with and without the application of a dual-cure activator (DCA; n=10): SBP-ARC (Adper Single Bond Plus + RelyX ARC), SBP-RXU (Adper Single Bond Plus + RelyX Ultimate), SBP-DCA-RXU (Adper Single Bond Plus + DCA + RelyX Ultimate), SBU-ARC (Scotchbond Universal + RelyX ARC), SBU-RXU (Scotchbond Universal + RelyX Ultimate), and SBU-DCA-ARC (Scotchbond Universal + DCA + RelyX ARC). Each specimen was light cured for 40 seconds under load and stored in distilled water at 37°C for seven days. Stick-shaped specimens (1.0 mm²) were obtained. Half of the specimens underwent microtensile bond strength testing, and the other half were subjected to the same tests after six months of storage. Failure mode was determined using an optical microscope (40×). The data were analyzed by a two-way analysis of variance followed by the Games-Howell test and Student t-test (preset alpha of 0.05).

RESULTS

After seven days, SBU-RXU presented the highest mean bond strength, statistically different from only SBU-ARC (p<0.05). Most of the groups exhibited a statistically significant reduction in bond strength after 6 months (p<0.05), except SBP-RXU and SBU-ARC (p>0.05).

CONCLUSION

The adhesive strategy, with different associations between adhesive systems and resin cements, as well as the use of a DCA, affected the bond strength of both amine-free and amine-based resin cements to a CAD/CAM composite.

Degree of conversion and depth of cure of Ivocerin containing photo-polymerized resin luting cement in comparison to conventional luting agents

OBJECTIVE

To evaluate the degree of conversion (DC) and depth (extent) of cure of four resin cements (Variolink E, Calibra, NX3 and Variolink N) using Fourier transform infrared (FTIR) and Vickers Micro hardness (MH).

METHODS

Ten disks (1mmx2mm) of each resin cement were light cured through a ceramic disk for 40 seconds prior to assessment. The ATR spectra of the uncured resin were collected in absorbance mode from 16 scans at 4 wave number resolutions. Degree of conversion was calculated by estimating the changes in peak height ratio of the absorbance intensities of aliphatic C=C peak at 1638 cm-1 and that of an internal standard peak of aromatic C=C at 1608 cm-1 during polymerization. For Vickers microhardness testing 10 disks of each cement specimen was exposed to 100 grams of load for 15 seconds. Three indentations were made 0.5mm apart and an average Vickers micro-hardness (MH) for each specimen. Two way ANOVA and multiple comparison tests were performed to assess data.

RESULTS

The highest degree of conversion by peak area was shown by Variolink-Esthetic [light-cure (87.18±2.90%)]; however the lowest was observed in samples of Variolink-N [Dual cure (44.55±4.33%)]. Similarly, Variolink-Esthetic and NX3 cement showed significantly higher MH as compared to other groups.

CONCLUSION

Ivocerin containing Variolink-E cement showed high degree of conversion and extent of polymerization when compared to conventional light and dual cure luting cements.

Influence of Infected Root Dentin on the Bond Strength of a Self-adhesive Resin Cement

AIM

The aim of this study was to determine the bond strength (BS) of a self-adhesive resin cement to the contaminated root dentin.

MATERIALS AND METHODS

The crown and apical third of twenty single-rooted teeth were removed. The root canals were flared and 1-mm-thick root sections were obtained. The sections were rinsed, dried, and sterilized. The control group (n=20) was composed of one section of each third, which remained immersed in sterile trypticase soy broth (TSB) for 2 months. The other sections comprised the experimental group (n = 40) and were immersed in a suspension of Enterococcus faecalis. The culture medium was changed at every 4 days for 2 months. The sections were rinsed with distilled water, dried, and the root canal space was filled with the self-adhesive resin cement RelyX™ U200. After 24 h, the push-out test was performed and the types of interface failure were observed on a stereo microscope.

STATISTICAL ANALYSIS

Data were statistically analyzed by the nonparametric Mann-Whitney test (α=5%).

RESULTS

A significant reduction was observed in the BS of resin cement to the contaminated dentin compared to the healthy dentin, for both thirds analyzed (P < 0.05). The BS was significantly greater at the cervical third compared to the middle third for specimens in the experimental group (P < 0.05). Adhesive and mixed failures were observed more frequently in specimens contaminated with E. faecalis.

CONCLUSION

Bacterial contamination negatively infl uenced the BS of the self-adhesive resin cement to the root dentin, and there was a predominance of adhesive and mixed failures.