Acidic pH weakens the bonding effectiveness of silane contained in universal adhesives

Do all ceramic and composite CAD-CAM materials exhibit equal bonding properties to implant Ti-base materials? An Interfacial Fracture Toughness Study

OBJECTIVES

To compare the interfacial fracture toughness (IFT) with or without aging, of four different classes of CAD-CAM ceramic and composite materials bonded with self-adhesive resin cement to titanium alloy characteristic of implant abutments.

METHODS

High translucent zirconia (Katana; KAT), lithium disilicate-based glass-ceramic (IPS. emax.CAD; EMX), polymer-infiltrated ceramic network material (PICN) (Vita Enamic; ENA), and dispersed filler composite (Cerasmart 270; CER) were cut into equilateral triangular prisms and bonded to titanium prisms with identical dimensions using Panavia SA Cement Universal. The surfaces were pretreated following the manufacturers' recommendations and developed interfacial area ratio (Sdr) of the pretreated surfaces was measured. IFT was determined using the Notchless Triangular Prism test in a water bath at 36 °C before and after thermocycling (10,000 cycles) (n = 40 samples/material).

RESULTS

IFT of the materials ranged from 0.80 ± 0.25 to 1.10 ± 0.21 MPa.m1/2 before thermocycling and from 0.71 ± 0.24 to 1.02 ± 0.25 MPa.m1/2 after thermocycling. There was a statistical difference between IFT of CER and the two top performers in each scenario: KAT and EMX before aging, and KAT and ENA after aging. Thermocycling significantly decreased IFT of EMX. The Weibull modulus of IFT was similar for all materials and remained so after thermocycling. Sdr measurements revealed that ENA (7.60)>Ti (4.97)>CER (2.85)>KAT (1.09)=EMX (0.96).

SIGNIFICANCE

Dispersed filler CAD-CAM composite showed lower performance than the other materials. Aging only affected IFT of Li-Si glass-ceramic, whereas zirconia and PICN performed equally well, probably due to their chemical bonding potential and surface roughness respectively.

Is additional silane application necessary for a new silane-containing universal adhesive to bond to glass ceramics?

OBJECTIVE

To evaluate the in vitro influence of prior silane application on the microshear bond strength (μSBS) of Scotchbond Universal Plus to glass ceramic.

MATERIALS AND METHODS

Thirty blocks of lithium disilicate ceramic were etched with hydrofluoric acid for 20 s and distributed into Group 1 (no silane and no adhesive), Group 2 (adhesive), Group 3 (silane + adhesive). Three cylinders of resin cement were made on each ceramic block. Five blocks (n = 15 cylinders) were subjected to the μSBS test after 24 h, and the other five blocks (n = 15 cylinders) were tested after 6 months of water storage.

RESULTS

According to two-way ANOVA, followed by Tukey's test, the means of μSBS (MPa), denoted by different letters, show significant differences (p < 0.05): after 24 h-Group 1 (31.7)B, Group 2 (43.3)A, and Group 3 (31.3)B; after 6 months-Group 1 (14.8)B, Group 2 (33.6)A, and Group 3 (30.3)A. After 6 months of storage, there was a significant decrease in μSBS for Groups 1 and 2, along with an increase in adhesive failures across all groups.

CONCLUSIONS

Prior application of silane did not increase the μSBS between Scotchbond Universal Plus and ceramic, and there was degradation at the bond interface over time.

CLINICAL SIGNIFICANCE

Prior application of a silane agent is not necessary when using Scotchbond Universal Plus for bonding to glass ceramics. Regardless of the prior application of silane, there is degradation at the bond interface over time.

The effect of restorative material selection and cementation procedures on the durability of endocrowns in the anterior teeth: an in-vitro study

OBJECTIVE

To investigate the fracture resistance and failure modalities of anterior endocrown restorations fabricated employing diverse ceramic materials, and bonded using various cementation methodologies.

MATERIALS AND METHODS

Forty maxillary central incisors were divided into two main groups based on the ceramic materials used; GroupI (Zir): zirconia endocrwons (Zolid HT+, Ceramill, Amanngirrbach) and GroupII (E-Max): e-max endocrowns (IPS e.max CAD, Ivoclar Vivadent). Both groups were further split into two subgroups depending on the cementation protocols; subgroup IA "ZirMDP": endocowns cemented with MDP primer + MDP resin cement, subgroup IB (ZirNon-MDP): cemented with MDP primer + non-MDP resin cement, subgroup IIA (E-maxMDP): cemented with MDP primer + MDP resin cement, subgroup IIB (E-maxNon-MDP): cemented with MDP primer + non-MDP resin cement. (n = 10/subgroup). Endocrowns were manufactured using CAD/ CAM. Teeth were subjected to 10,000 thermal cycles. The fracture test was performed at 45o with a palatal force direction until the fracture occurred. Test results were recorded in Newton. The failure mode was examined using a stereomicroscope. A One-way ANOVA test was utilized to compare different groups regarding fracture strength values. Tukey`s Post Hoc was utilized for multiple comparisons.

RESULTS

The comparative analysis of fracture strength across the diverse groups yielded non-significant differences, as indicated by a p-value exceeding 0.05. Nonetheless, an observable trend emerged regarding the mode of failure. Specifically, a statistically significant prevalence was noted in fractures localized within the endocrown/tooth complex below the cementoenamel junction (CEJ) across all groups, except for Group IIB, "E-max Non-MDP," where fractures within the endocrown/tooth complex occurred above the CEJ.

CONCLUSIONS

Combining an MDP-based primer with an MDP-based resin cement did not result in a significant effect on the anterior endocrown fracture strength.

CLINICAL RELEVANCE

Regardless of the presence of the MDP monomer in its composition, adhesive resin cement achieved highly successful fracture strength when used with MDP-based ceramic primers. Additionally, ceramic materials exhibiting elastic moduli surpassing those of dentin are discouraged due to their propensity to induce catastrophic fractures within the tooth structure.

The Effect of Different Chemical Surface Treatments on the Bond Strength of Resin-Matrix Ceramic Repaired with Resin Composite

OBJECTIVE

 This study investigates the effect of different chemical surface treatment protocols with different functional monomers of universal adhesives on the shear bond strength between resin-matrix ceramic and resin composite.

MATERIALS AND METHODS

 Eighty resin-matrix ceramics (Shofu block HC) were built and designed into eight groups of ten specimens and surface treated with HC primer (HC) and/or three universal adhesives (single bond universal [SBU], Scotchbond universal plus [SBP], and Tetric N-bond universal [TNU]) assigning follows; group 1, nonsurface treated; group 2, HC; group 3, SBU; group 4, HC + SBU; group 5, SBP; group 6, HC + SBP; group 7, TNU; group 8, HC + TNU. A template was put on the specimen center, and then pushed packable resin composite. Mechanical testing machinery was used to examine the samples' shear bond strength (SBS) values. To examine failure patterns, the debonded specimen surfaces were examined by a stereomicroscope.

STATISTICAL ANALYSIS

 The one-way analysis of variance method was used to evaluate the data, and the Tukey's test was used to determine the significant level (p < 0.05).

RESULTS

 The highest SBS was obtained in group 6 (39.25 ± 1.65 MPa). Group 1 (4.15 ± 0.54 MPa) had the lowest SBS. Group 6 exhibited the highest percentage of cohesive failure patterns (70%). High SBS values were frequently correlated with the surface treatment groups and the cohesive failure patterns.

CONCLUSION

 The application of HC primer prior to the universal adhesive is an alternative protocol for enhancing the repair bond strength between resin-matrix ceramic and resin composite interfaces. Moreover, the application of HC primer prior to the SBP is the best strategy for resin-matrix ceramic and resin composite repairs.

Shear bond strength of orthodontic brackets bonded to high-translucent dental zirconia with different surface treatments: An in vitro study

PURPOSE

The objective of this study was to compare the shear bond strengths of orthodontic brackets bonded to translucent dental zirconia samples which are anatomically accurate and treated with various surface treatments.

METHODS

This in vitro study included 156 samples from 3 brands of high-translucent zirconia split into a control group and 4 surface treatment groups: 9.6% hydrofluoric acid etching, 50-micron aluminium oxide particle air abrasion, and 30-micron tribochemical silica coating (TBS) particle air abrasion with and without silane application. After surface treatment, all groups were primed with a 10-MDP primer and bonded to metal orthodontic brackets. Shear bond strength (SBS) was tested and results were compared between all groups. Data analysis consisted of a balanced two-factor factorial ANOVA, a Shapiro-Wilks test, and a non-parametric permutation test. The significance level was set at 0.05.

RESULTS

Among all surface treatments, aluminium oxide particle abrasion produced significantly higher SBS (P≤0.002). Lava™ Plus zirconia samples had significantly higher SBS than Cercon® samples (P<0.0001). TBS surface treatment produced significantly higher SBS on Lava™ Plus samples than it did on the other zirconia brands (P=0.032).

CONCLUSIONS

This study indicated that mechanical abrasion using aluminium oxide in combination with a 10-MDP primer creates a higher SBS to high-translucent zirconia than the bond created by tribochemical silica coating. Also, there was no significant difference in ARI regardless of zirconia brand or surface preparation.

Effect of universal adhesives and self-etch ceramic primers on bond strength to glass-ceramics: A systematic review and meta-analysis of in vitro studies

STATEMENT OF PROBLEM

To simplify dental procedures, multicomponent products such as universal adhesives and self-etch ceramic primers have been recommended for glass-ceramic bonding; however, studies have shown a wide range of results.

PURPOSE

The purpose of this systematic review and meta-analysis was to analyze the in vitro bond strength promoted by hydrofluoric acid+silane-containing universal adhesives and a self-etch ceramic primer to glass-ceramics and compare it with that of conventional treatments.

MATERIAL AND METHODS

A systematic search was conducted in the PubMed/Medline, Scopus, LILACS, and ISI Web of Science databases up to April 2021. In vitro studies assessing the resin-mediated bond to glass-ceramics by using a self-etch ceramic primer and hydrofluoric acid+silane-containing universal adhesives and/or compared with traditional hydrofluoric acid+glass-ceramic primers were included. Selection of studies, data extraction, and risk-of-bias analysis were performed. Statistical analysis was performed by using a review management software program using a random effects model (α=.05).

RESULTS

A total of 33 studies were included in the qualitative analysis and 26 studies in the quantitative analysis. Bond strength to lithium disilicate ceramic was higher when a hydrofluoric acid+glass-ceramic primer was used than when using a hydrofluoric acid+silane-containing universal adhesive (P<.05), except when 9% to 10% acid concentration was used in combination with static aging (P=.100). A self-etch ceramic primer promoted bond strength values to lithium disilicate that were similar to those of the hydrofluoric acid+glass-ceramic primer (P>.100).

CONCLUSIONS

Hydrofluoric acid+silane-containing universal adhesive was not as effective as the hydrofluoric acid+glass-ceramic primer in promoting bond strength to glass-ceramic. Bond strength values generated by a self-etch ceramic primer to glass-ceramic were similar to those generated by the conventional treatment.

Bonding stability of universal adhesives to feldspathic ceramic with or without prior silane application

PURPOSE

This study aimed to assess the bonding stability of three universal adhesives to a CAD-CAM feldspathic ceramic with or without prior silane application.

MATERIALS AND METHODS

The universal adhesives tested were Ambar Universal (FGM), Single Bond Universal (3M), and Ybond Universal (Yller). Scotchbond Multipurpose Plus (3M) was used as a control. The silane used was RelyX Ceramic Primer (3M). Microtensile bond strength (μTBS) to Vitablocs Mark II was measured after 24 h or 6 months of water aging (n = 20). Failure modes were observed through scanning electron microscopy, and pH and degree of C=C conversion (DC) of the adhesives were measured (n = 3). Data were analyzed using one-, two-, and three-way ANOVA.

RESULTS

The pH values differed significantly among the adhesives (p < 0.001), while the DC was similar (p = 0.141). The universal adhesives showed significant differences in μTBS, with higher immediate results when using silane and lower results after aging. Notably, a significant decrease in μTBS was observed after 6 months when silane was applied. In contrast, the control adhesive exhibited consistent results between the 24-h and 6-month storage periods. The universal adhesives showed a decrease in μTBS ranging from 25.5% to 40.1% after prolonged storage. Adhesive failures were predominant in all groups. The presence or absence of silane in the adhesive composition did not affect the bonding performance.

CONCLUSIONS

The application of a separate silane coupling agent improved the immediate bond strength of universal adhesives to CAD-CAM feldspathic ceramic. However, this bond strength significantly decreased after 6 months of water aging. The bond strength remained stable for universal adhesives when applied without silane after 6 months of aging.

The Classification and Selection of Adhesive Agents; an Overview for the General Dentist

Adhesive agents are essential to most restorative procedures used in everyday practice. Depending on the clinical situation, the dentist will choose among a rapidly evolving variety of adhesive agents (bonding agents). Due to the availability of many adhesive agents, appropriate selection can take time and effort. Typically, a practitioner relies more on marketing and experience than in-depth material knowledge. The classification of adhesive agents may need to be clarified and easier to remember due to its lack of relevance to clinical procedures. This paper reviews the published literature retrieved from PubMed, Google Scholar, and Scopus by using specific keywords "adhesive agents", "classification", "dentin", "enamel", "universal", "self-etch", "etch-and-rinse", and "bonding". The titles and abstracts were screened, and the relevant literature was retrieved. The list of references from each identified article was examined to find other potentially relevant articles. Adhesive agents can be classified as etch-and-rinse, self-etch, or "multi-mode" according to their approach to interacting with the smear layer, and each approach can be further classified according to the number of clinical steps required during application. This article reviews the classification of current adhesive agents and discusses the properties that make a specific adhesive agent the optimal choice for a particular clinical indication. The review will assist the general dentist in understanding the various types of available adhesive agents and how they function. Overall, the review will facilitate decision-making and allow the selection of appropriate materials.

Effects of Different Primers on the Bond Strength to Properly and Excessively Etched Ceramic-coated Zirconia

PURPOSE

To determine the effects of various primers on the immediate and long-term bond strength of ceramic-coated ultratranslucent zirconia that is properly or excessively etched.

METHODS AND MATERIALS

Ceramic-coated zirconia plates were etched with 9.5% hydrofluoric acid (HF) for 2 or 5 minutes, after which the surface morphology and elemental composition were examined. The etched specimens were treated with different primers including methacryloyloxydecyl dihydrogen phosphate (MDP)-only containing primer, silane-only containing primer, MDP and silane-containing ceramic primer as well as MDP and silane-containing adhesive system. For surface contact angle and shear bond strength (SBS) data, the difference between groups was evaluated by one-way analysis of variance (ANOVA) and three-way ANOVA factorial analysis, respectively. The statistical significance level of 0.05 was set and the Tukey test and the Dunnett-T3 test were used for post-hoc multiple comparisons.

RESULTS

Excessive etching (9.5% HF for 5 minutes) led to overconsumption of the glass layer and exposure of zirconia substrate compared to proper etching (9.5% HF for 2 minutes). Among different primers, the surface contact angle of the silane-only containing primer group was the lowest. The silane-only containing primer and MDP and silane-containing ceramic primer produced higher shear bond strength of properly and excessively etched ceramic-coated zirconia, respectively, both before and after thermal aging.

CONCLUSIONS

The silane-only containing primer and MDP and silane-containing primer can obtain better immediate and long-term shear bond strength for properly and excessively etched ceramic-coated zirconia, respectively.

Push-out Bond Strength of Two Fiber Posts in Composite Resin Using Different Types of Silanization

OBJECTIVES

The aim of this study was to evaluate the effect of different surface treatments and thermocycling (TC) on the push-out bond strength of two brands of glass fiber posts (GFPs) to composite resin.

METHODS

White Post DC (WP) (FGM Dental Group International, Joinville, Santa Catarina, BR) and Exacto (EC) (Angelus, Clinical Research Dental, Londrina, PR, Brazil). GFPs were cleaned with 70% alcohol and divided into five groups, according to the surface treatment (n=15): control (C), without treatment; prehydrolyzed silane (S-pre) (Prosil, FGM Dental Group International); 37% phosphoric acid + prehydrolyzed silane AcS-pre); Scotchbond Universal Adhesive System (AdU), 3M Oral Care; two-bottle silane (S2B) (Dentsply Sirona Inc). The composite resin was inserted around the posts by using a split matrix. The samples were cut into 1-mm slices. Half of the samples were subjected to the push-out test immediately, and the other half underwent TC before the test. After failure analysis, the data were submitted to three-way analysis of variance (ANOVA) (α=0.05).

RESULTS

EC achieved higher bond strength than WP, regardless of TC (p<0.05). Regarding WP, surface treatments (p<0.001) and TC (p<0.001) influenced bonding strength. As for EC without TC, the highest bond strength (p<0.05) was found for C, then AcSpre, S-pre, AdU, and S2B. Application of TC resulted in a statistically higher bond strength values for the EC AcS-pre group (p<0.05), followed by S2B, S-pre, C, and AdU. The WP failures were predominantly cohesive, similar to the EC AdU and EC S2B groups. The other EC groups showed mostly mixed failures.

CONCLUSIONS

Surface treatment and TC affected the bond strength to composite resin, depending on which post was used. It is important for dentists to understand the effects of different types of silanization on their chosen post.

Increasing Acid Concentration, Time and Using a Two-Part Silane Potentiates Bond Strength of Lithium Disilicate-Reinforced Glass Ceramic to Resin Composite: An Exploratory Laboratory Study

There is still a lack of consensus concerning the recommended etching concentration, application time and type of silane when bonding lithium disilicate-reinforced glass ceramics manufactured by CAD/CAM. The purpose of this study was thus to conduct an in vitro study which investigates the influence of hydrofluoric acid (HF) concentration, etching time and silane type on the microtensile bond strength (μTBS) of lithium disilicate to resin composites. Thirty-nine IPS e.max CAD blocks were randomly divided between thirteen groups (n = 3). The variables were HF concentration (9.5 or 4.9%), etching time (20 or 60 s) and silane type (Bis-Silane, Monobond Plus and ESPE Sil Silane). The blocks were cut into beams, aged for 10,000 cycles in a thermocycler and submitted to tensile stress to determine μTBS. A control group featuring the Monobond Etch & Prime (MEP) agent that combines etching/silanisation into a simultaneous process was also added. This group was discarded from the analysis due to only having pre-test failures. The data were analysed using a three-way ANOVA (α = 0.05). The HF concentration, etching time and silane type significantly influenced μTBS (p < 0.001). Significant interactions between time and silane type (p = 0.004), HF concentration and silane type (p < 0.001) and among the three factors (p < 0.001) were noted. Etching lithium disilicate with 9.5% HF (60 s), followed by the application of Bis-Silane, resulted in the highest μTBS (16.6 ± 9.0 MPa). The highest concentration and etching time under study, combined with a two-part silane, resulted in the highest bond strength, while the application of MEP showed a complete pre-test failure.

Dentin contamination during repair procedures: A threat to universal adhesives?

Objective

This study examined the influence of surface contamination during repair procedures with hydrofluoric acid, silane, or ammonium polyfluoride on the bond strength of universal adhesives to dentin using different etching modes before and after thermocycling.

Materials and Methods

Dentin surfaces of human molars were contaminated in different ways (silane, hydrofluoric acid, ammonium polyfluoride, and no pretreatment as control) followed by application of a universal adhesive (etch & rinse or self‐etch mode). After a composite build‐up was placed onto each tooth, sticks for the microtensile bond strength (MTBS) test were sectioned. Half of the sticks were tested after water storage for 24 h, the other half after thermocycling (15,000 cycles, 5/55°C). The MTBS data were analyzed statistically by using the Kolmogorov–Smirnov test, one‐way analysis of variance, and Tukey HSD test (p < 0.05). The fracture patterns of all specimens were evaluated and analyzed using a χ² test.

Results

Dentin contamination with a multifunctional silane does not influence microtensile bond strength irrespective of aging. Contamination with hydrofluoric acid or an ammonium polyfluoride primer leads to a significantly lower bond strength after aging, irrespective of the etch mode.

Conclusion

Dentin contamination with hydrofluoric acid or ammonium polyfluorides during repair procedures should be avoided, as they appear to decrease the bond strength of universal adhesives.

In Vitro Performance of Different Universal Adhesive Systems on Several CAD/CAM Restorative Materials After Thermal Aging

OBJECTIVE

To evaluate the microshear bond strength (mSBS) of 10 universal adhesive systems applied on five different CAD/CAM restorative materials, immediately and after thermal aging.

METHODS AND MATERIALS

Five CAD/CAM materials were selected: 1) feldspathic glass ceramic (FeCe); 2) pre-polymerized reinforced resin composite (ReRC); 3) leucite-reinforced glass ceramic (LeGC); 4) lithium disilicate (LiDi); and 5) yttrium-stabilized zirconium dioxide (ZiDi). For each material, 15 blocks were cut into four rectangular sections (6 × 6 × 6 mm; n=60 per group) and processed as recommended by the respective manufacturer. For each indirect material, the following adhesive systems were applied according to the respective manufacturer's instructions: 1) AdheSE Universal [ADU]; 2) All-Bond Universal [ABU]; 3) Ambar Universal [AMB]; 4) Clearfil Universal Bond [CFU]; 5) Futurabond U [FBU]; 6) One Coat 7 Universal [OCU]; 7) Peak Universal Bond [PUB]; 8) Prime&Bond Elect [PBE]; 9) Scotchbond Universal Adhesive [SBU]; 10) Xeno Select [XEN, negative control]. After the application of the adhesive system, cylinder-shaped transparent matrices were filled with a dual-curing resin cement (NX3) and light cured. Specimens were tested in shear mode at 1.0 mm/ min (mSBS), after 24 hours and 10,000 thermal cycles (TC). All data were submitted to statistical analysis (α=0.05).

RESULTS

For FeCe, there was no significant decrease in mean mSBS for AMB, FBU, and SBU after TC when compared at 24 hours. For ReRC, AMB and SBU showed higher mean mSBS when compared to CFU and XEN, after 24 hours and TC. For LiDi, FBU and OCU showed higher mean mSBS when compared to CFU and XEN, after 24 hours and TC. For LeGC, AMB and PUB showed higher mean mSBS when compared to XEN, after 24 hours and TC. For ZiDi, OCU and SBU showed higher mean mSBS when compared to XEN, after 24 hours and TC. In addition, PBE and XEN showed the lowest mean mSBS after TC with higher percentage of bond strength reduction.

CONCLUSIONS

The mean mSBS among the different universal adhesives varied widely for each CAD/ CAM material used. In addition, most universal adhesives underwent a statistically significant bond strength reduction after TC.

MDP Salts: A New Bonding Strategy for Zirconia

Durable resin-ceramic adhesion may influence the clinical success of ceramic restorations, which has been one of the challenging issues in dentistry. The present study assessed the bond strength and chemical interaction of 10-methacryloxydecyl dihydrogen phosphate (MDP), MDP+silane, and MDP-salt primers to alumina-blasted zirconia ceramic by tensile bond strength test, surface elemental composition with x-ray photoelectron spectroscopy analysis, contact angle measurement, surface morphology with scanning electron microscopy, and surface topography with 3-dimensional confocal laser scanning microscope analyses. MDP-salt showed the highest tensile bond strength before and after thermocycling when compared with MDP and MDP+silane (P < 0.05). The measured contact angle values differed significantly (P < 0.001) in the order of MDP-salt > control (no chemical pretreatment) > MDP+silane > MDP. There was no difference in surface roughness (P = 0.317) and surface topography among all tested groups. Zirconia treated with MDP-salt showed phosphorus peaks in addition to zirconia and alumina peaks. MDP-salt has zirconia priming properties, which improves bonding performance to resin cement.

Investigations of silane-MDP interaction in universal adhesives: A ToF-SIMS analysis

OBJECTIVES

The purposes of this study were to investigate whether the presence of silane in universal adhesives affects the functions of 10-methacryloyloxydecyl dihydrogen phosphate (MDP) and adhesion to zirconia.

METHODS

Two silane-containing universal adhesives (Scotchbond Universal (SBU) and Clearfil Universal-Bond (CUB)) and two silane-free adhesives (All-Bond Universal (ABU) and SE-Bond primer (SE)) were individually applied on zirconia disks. Time-of-flight secondary-ion-mass-spectrometry (ToF-SIMS) examined the distributions of MDP- and silane-related ions, as well as evidence of zirconium phosphate (ZrP) compounds, on the surface and interfacial regions using a depth profiling mode. The hydrophilicity and resin wettability of the treated zirconia were examined using a contact angle test. For the shear bond strength (SBS) test, the zirconia disks were air-blasted, treated with the assigned adhesives, and bonded with pre-cured composite cylinders using a resin cement. These resin-zirconia assemblies received a bond test after 24-h storage.

RESULTS

Both SBU and CUB exhibited silane-related ions and ZrO₂(OH)^-, but fewer PO^- ions in the interfacial regions. CUB had more siloxane-related ions. SE-treated zirconia had abundant PO^- ions and particularly high PO₃^-- and ZrP- related ions in the interfacial regions. The silane-free adhesives exhibited a higher affinity to both water and adhesive liquids. SE showed significantly higher SBSs compared to ABU, while SBU and CUB were not statistically different.

SIGNIFICANCE

The silane content may cause hydroxylation of zirconia and affect MDP adsorption. An acidic pH accelerated the condensation of silanol. The bond performance of the MDP-based adhesive could be influenced by the silane content and other components.

The effects of different silicatization and silanization protocols on the bond durability of resin cements to new high-translucent zirconia

OBJECTIVE

The aim of this study was to assess the influence of different silicatization protocols with various silane treatment methods on the bond performance to high-translucent zirconia.

MATERIALS AND METHODS

High-translucent zirconia specimens were assigned to five groups according to mechanical surface pretreatment: as-sintered (Con), 0.2 MPa alumina sandblasting (AB2), tribochemical silica coating (TSC), 0.2 and 0.4 MPa glass bead air abrasion (GB2) and (GB4). Each group was subjected to 4 different cementation protocols: Panavia SA Universal (SAU), Panavia SA plus (SAP), silane + SAP (S-SAP), and Universal adhesive + SAP (U-SAP). Tensile bond strength (TBS) was measured after 24 h and 10,000 thermocycling (TC). Surface topography, surface energy, and elemental composition of the abraded zirconia surface analyses were completed. TBS data was analyzed using the Weibull analysis method. Surface roughness and surface energy were compared by one-way ANOVA analysis of variance (α = 0.05).

RESULTS

After 24 h, higher TBS was achieved with all cementation protocols in AB2 and TSC, also, in GB2 with all protocols except U-SAP, and in GB4 with SAU and S-SAP. After aging, GB4/S-SAP, GB2/S-SAP, AB2/U-SAP, and TSC/S-SAP showed the highest bond strength. GB groups showed the lowest surface roughness and highest surface energy.

CONCLUSION

Glass bead abrasion achieved the durable bond strength to high-translucent zirconia using a separate silane coupling agent while altered surface chemistry, surface energy, and roughness without effect on morphology.

CLINICAL RELEVANCE

Glass bead air abrasion is an alternative to alumina sandblasting and tribochemical silica coating and improves bond strength to high translucent zirconia.

The effect of silane and universal adhesives on the micro-shear bond strength of current resin-matrix ceramics

PURPOSE

The aim of this in vitro study was to evaluate the effect of silane and universal adhesive applications on the micro-shear bond strength (µSBS) of different resin-matrix ceramics (RMCs).

MATERIALS AND METHODS

A total of 120 slides (14 × 12 × 1 mm) were produced from 5 different RMC materials (GC Cerasmart [GC]; Brilliant Crios [BC]; Grandio blocs [GB]; Katana Avencia [KA]; and KZR-CAD HR 2 [KZR]) and sandblasted using 50 µm Al₂O₃ particles. Each RMC material was divided into six groups according to the surface conditioning (SC) method as follows: control (G1), silane primer (G2), silane-free universal adhesive (G3), silane-containing universal adhesive (G4), silane primer and silane-free universal adhesive (G5), and silane primer and silane-containing universal adhesive (G6). Three cylindric specimens made from resin cement (Bifix QM) were polymerized over the treated surface of each slide (n = 12). After thermal cycling (10000 cycles, 5 – 55℃), µSBS test was performed and failure types were evaluated using a stereomicroscope. Data were analyzed using 2-way ANOVA and Tukey tests (α = .05).

RESULTS

µSBS values of specimens were significantly affected by the RMC type and SC protocols (P < .001) except the interaction (P = .119). Except for G2, all SC protocols showed a significant increase in µSBS values (P < .05). For all RMCs, the highest µSBS values were obtained in G4 and G6 groups.

CONCLUSION

Only silane application did not affect the µSBS values regardless of the RMC type. Moreover, the application of a separate silane in addition to the universal adhesives did not improve the µSBS values. Silane-containing universal adhesive was found to be the best conditioning method for RMCs.

Bonding ability of resin cements to different types of CAD/CAM composite blocks

This study investigated the bonding performance of two different types of resin cements to computer-aided design/computer-aided manufacturing (CAD/CAM) composite blocks based on the shear bond strength (SBS) test. A silane-containing self-adhesive resin cement (Panavia SA Cement Universal) and resin luting cement (Block HC Cem) with a primer, were used. Specimens were fabricated from three different types of CAD/CAM composite blocks, and their surfaces were blasted with alumina. Resin cements were bonded to the specimens, and their SBSs were measured after 15 min, 24 h, and after being subjected to thermal cycling for 10,000 and 30,000 cycles. Three-way ANOVA for bond strength revealed that CAD/CAM composite block, resin cement and storage time significantly influenced the SBS values, and the three-way interactions between the evaluated factors, and all the interactions were significant. It was concluded that the bonding performance of resin cements to CAD/CAM composite blocks were material and storage period dependent.

Predictable bonding of adhesive indirect restorations: factors for success

Adhesive indirect restorations are a popular restorative treatment option. This article discusses the many factors that contribute to their successful adhesive cementation, including a review of how to surface treat and manage contaminants across the wide range of indirect materials available.

Critiques the current various adhesive strategies used by resin cements at the tooth tissue interface.

Describes how to prepare the fitting surface of a wide range of restorative materials for adhesive cementation.

Discusses how to mitigate against contaminants during the adhesive cementation process.

Effect of Silane-Containing Universal Adhesives on the Bonding Strength of Lithium Disilicate

The purpose of this study was to investigate the effect of silane-containing universal adhesives on the bonding strength of lithium disilicate. Two-hundred-and-forty lithium disilicate blocks were divided into 16 groups according to the following surface treatments: hydrofluoric acid (HF)-treated or not, silane-treated or not, and the type of universal adhesive used (All-Bond Universal (ABU); Prime & bond (PB); Clearfil Universal Bond (CU); Single bond Universal (SBU)). After surface treatment, resin discs were bonded to each lithium disilicate using dual-cure resin cement. Bonded specimens were stored in distilled water for 24 h and then subjected to microtensile bond strength (μTBS) test. Failure modes were examined under stereomicroscope. Microscopic observation of bonded interfaces was analyzed using scanning electron microscopy. The μTBS data were statistically analyzed. Regardless of silane treatment, all groups treated with HF showed higher bonding strengths compared to those that were not treated with HF (p < 0.05). In groups treated with HF, the bonding strength increased after silane application (p < 0.05) except PB and CU (p > 0.05). Adhesive failures were dominant in all groups, but some mixed failures were observed in ABU treated with HF and silane. While most of the specimens that were not treated with silane after HF application only showed loose bonding between the ceramic and resin cement due to partial gaps, the specimens treated with silane application after HF showed a tight ceramic–resin interface. In conclusion, the silane in universal adhesives did not effectively improve the bonding strength between lithium disilicate and resin cement.

Chemical interaction between 10-methacryloyloxydecyl dihydrogen phosphate and methacryloxypropyltrimethoxysilane in one-bottle dental primer and its effect on dentine bonding

In the present study, we investigated the chemical interaction between 10-methacryloyloxydecyl dihydrogen phosphate (10-MDP) and methacryloxypropyltrimethoxysilane (gamma-MPS) in one-bottle primer solutions and its effect on dentine bonding performance. Solutions containing 10 wt% 10-MDP and/or gamma-MPS at 0, 1, 5, 10, or 15 wt% were prepared, providing 10 experimental groups (labeled MDP/MPSxx or MPSxx, where MDP indicates the presence of 10 wt% MDP and xx is the wt% of gamma-MPS in the solution). Phosphoric-acid-etched dentine blocks were prepared from human molars and conditioned in the solutions before being used to build resin-dentine-bonded specimens, which were subsequently subjected to microtensile bond strength (μTBS) testing after 24-h or six-months water storage. Interfacial nanoleakage was evaluated by SEM observation. All the primer-conditioned samples showed significantly higher initial μTBS values than that of the control group, and six-months water storage significantly lowered the μTBS for all the groups; however, the decreases for MDP/MPS10 and MDP/MPS15 were significantly greater than those for MDP/MPS1 and the control solution. Furthermore, MDP/MPS10 and MDP/MPS15 groups also showed more serious nanoleakage. Fourier-transform infrared spectroscopy, X-ray photoelectron spectroscopy, and X-ray diffraction analyses were used to investigate the chemical affinity between 10-MDP and hydroxyapatite (HAp). In XRD analysis, the intensities of peaks assigned to 10-MDP-calcium salts were lower for the solutions containing gamma-MPS. Overall, the results indicate that the copresence of gamma-MPS (above 10 wt%) and 10-MDP in one-bottle primer solutions inhibit the formation of 10-MDP-calcium salts, leading to increased long-term nanoleakage and decreased bonding durability.

Clinical performance of two different adhesive strategies for metal-ceramic cracks repairing and related in vitro study

To evaluate the bonding reliability of a universal adhesive compared to a commercial ceramic repair system for metal-ceramic cracks. In vitro part: sixty specimens with porcelain, metal and porcelain-metal substrate were fabricated. Half specimens were bonded by Singlebond Universal adhesive and Filtek Z350 resin composite. The other were processed by Ceramic Repair N. Shear bond strength was tested. In vivo part: forty patients with sixty ceramic fractured porcelain-fused-metal restorations were involved. Half were repaired by Singlebond Universal and Filtek Z350. The other were restored by Ceramic Repair N. The mean observation period was 65 weeks. Results showed the bond strength ranged from 13.97 MPa to 15.85 MPa using two different repair system on different substrate with no statistical difference. There was no statistical difference between the two adhesive system in survival rate according to Kaplan-Meier analysis. The universal adhesive had a similar repair performance compared to commercial ceramic repair system.

Optimizing glass-ceramic bonding incorporating new silane technology in an experimental universal adhesive formulation

OBJECTIVE

Incorporating silane-coupling agent into universal adhesives (UAs) to simplify adhesive luting of glass-ceramic restorations appeared ineffective due to silane's instability in an acidic aqueous solution. This study aimed to evaluate new silane technology added to an experimental UA to be bonded to glass ceramics without separate prior silanization.

METHODS

Combined silane technology, consisting of 3-(aminopropyl)triethoxysilane (APTES) and γ-methacryloxypropyltriethoxysilane (γMPTES), was incorporated into an experimental UA formulation, being referred to as ADH-XTE (3M Oral Care). Immediate and aged shear bond strength (SBS) of ADH-XTE onto as-milled ('AM'), tribochemical silica-coated ('TSC'), HF-etched ('HF'), and mirror-polished ('MP') glass-ceramic CAD/CAM blocks (IPS e.max CAD) with/without separate silanization was measured (n = 10/group). The control adhesives included Scotchbond Universal ('SBU') and Scotchbond 1 XT ('SB1-XT'). The glass-ceramic surface topography and the fractography of the SBS-debonded specimens were observed by SEM.

RESULTS

Without separate prior silanization, the experimental UA ADH-XTE, containing combined APTES/γMPTES silane technology, significantly outperformed the glass-ceramic bonding efficiency of its silane-containing SBU precursor, while it performed equally effective as SBU applied with prior silanization. Upon aging, significant reduction in SBS was recorded when ADH-XTE was bonded to TSC glass-ceramic surfaces (p < 0.05), while not to HF ones. Notably, the lowest SBS was obtained when the UAs were bonded to AM and MP glass-ceramic surfaces, in particular when applied without separate prior silanization (p < 0.05).

SIGNIFICANCE

The glass-ceramic bonding capacity of the new combined APTES/γMPTES silane-containing UA ADH-XTE surpassed that of its SBU precursor. HF etching remains needed to durably bond to glass-ceramics.

Adhesive dentistry: Current concepts and clinical considerations

OBJECTIVES

To address contemporary concepts in adhesive dental materials with emphasis on the evidence behind their clinical use.

OVERVIEW

Adhesive dentistry has undergone major transformations within the last 20 years. New dental adhesives and composite resins have been launched with special focus on their user-friendliness by reducing the number of components and/or clinical steps. The latest examples are universal adhesives and universal composite resins. While clinicians prefer multipurpose materials with shorter application times, the simplification of clinical procedures does not always result in the best clinical outcomes. This review summarizes the current evidence on adhesive restorative materials with focus on universal adhesives and universal composite resins.

CONCLUSIONS

(a) Although the clinical behavior of universal adhesives has exceeded expectations, dentists still need to etch enamel to achieve durable restorations; (b) there is no clinical evidence to back some of the popular adjunct techniques used with dental adhesives, including glutaraldehyde-based desensitizers and matrix metalloproteinase inhibitors; and (c) the color adaptation potential of new universal composite resins has simplified their clinical application by combining multiple shades without using different translucencies of the same shade.

CLINICAL SIGNIFICANCE

New adhesive restorative materials are easier to use than their predecessors, while providing excellent clinical outcomes without compromising the esthetic quality of the restorations.

Bond strengths of three-step etch-and-rinse adhesives to silane contaminated dentin

This study aimed to evaluate the effect of silane coupling agent contamination on the microtensile bond strength (µTBS) of 3-step etch-and-rinse adhesives on dentin. Flat occlusal dentin surfaces were prepared and randomly divided into 8 groups (n=20) based on the tested adhesives; Scotchbond Multi-purpose or Optibond FL, with contamination of an experimental silane (2 vol% of 3-m ethacryloxypropyltrimethoxysilane at pH 4.5) before acid-etching, after-etching or after-priming; while the groups without silane contamination served as controls. µTBS data were analyzed by two-way ANOVA and Tukey's HSD tests at a significance level of 0.05. Additional specimens of contaminated dentin were used to analyze changes in the organic molecules by Fourier transform infrared spectroscopy (FTIR). Silane contamination before acid-etching did not significantly change µTBS (p>0.05), but contamination after-etching and after-priming significantly decreased µTBS of both adhesives (p<0.05). Silane contamination had an adverse effect on the dentin bond strength of 3-step etch-and-rinse adhesives especially after-priming.

The effect of curing mode of dual-cure resin cements on bonding performance of universal adhesives to enamel, dentin and various restorative materials

The effect of curing mode of dual-cure resin cements on the tensile bond strength (TBS) of universal adhesives to enamel, dentin, zirconia, lithium disilicate ceramics (LDS), feldspathic porcelain (FP), and a Pd-Au alloy was evaluated. The substrates were bonded using Tokuyama Universal Bond (TUB) or Scotchbond Universal Adhesive (SBU), followed by luting with Estecem II (ECII) or Rely-X Ultimate (RXU), respectively, which were used either in light-curing or self-curing mode. The TBS test was performed after 24 h or 5,000 thermal cycles. Light-curing significantly improved the 24-h TBS of TUB/ECII to enamel, dentin and FP, as well as the TBS of SBU/RXU to all substrates except LDS. After thermal cycling, light-curing significantly increased the TBS of both adhesives/cements to dentin, but significant differences between curing modes were seldom observed for other substrates. This suggested that light-curing is essential for the hydrophilic dentin, but self-curing might be sufficient for other substrates.

Phosphate group adsorption capacity of inorganic elements affects bond strength between CAD/CAM composite block and luting agent

This study aimed to investigate whether inorganic elements of polymer-infiltrated ceramic (PIC) and microfilled resin (MFR) for CAD/CAM would affect initial bond strength to luting agent. Inorganic elements of PIC and MFR were different with shape and ingredient observed by SEM, STEM and EDS. Microtensile bond strengths (µTBS) value of PIC was increased by 10-methacryloyloxydecyl dihydrogen phosphate (MDP) and acetic acid (AA)- or MDP-activated silane treatment, and further increased by succeeding heat treatment (HT). The µTBS of MFR was increased by MDP and MDP-activated silane, but decreased by AA-activated silane without HT. The HT improved the µTBS of MFR with AA-activated silane, but conversely for MDP-activated silane. Only in MFR, phosphoric acid (PA) application before each surface treatment dramatically decreased the µTBS of AA-activated silane. FTIR peaks in MFR shifted according to phosphate group's peak. MFR would possess high phosphate group adsorption capacity, with MDP effectively improving its bonding capability.

Current perspectives on dental adhesion: (1) Dentin adhesion - not there yet

The essential goal of any adhesive restoration is to achieve a tight and long-lasting adaptation of the restorative material to enamel and dentin. The key challenge for new dental adhesives is to be simultaneously effective on two dental substrates of conflicting nature. Some barriers must be overcome to accomplish this objective. While bonding to enamel by micromechanical interlocking of resin tags within the array of microporosities in acid-etched enamel can be reliably achieved and can effectively seal the restoration margins against leakage, bonding effectively and durably to organic and humid dentin is the most puzzling task in adhesive dentistry.

Much of the research and development of dental adhesives has focused on making the clinical procedure more user-friendly by reducing the number of bottles and/or steps. Although clinicians certainly prefer less complicated and more versatile adhesive materials, there is a trade-off between simplification of dental adhesives and clinical outcomes. Likewise, new materials are launched with claims of being novel and having special properties without much supporting evidence.

This review article discusses dental adhesion acknowledging pioneer work in the field, highlights the substrate as a major challenge to obtain durable adhesive restorations, as well as analyzes the three adhesion strategies and their shortcomings. It also reviews the potential of chemical/ionic dental adhesion, discusses the issue of extensively published laboratory research that does not translate to clinical relevance, and leaves a few thoughts in regard to recent research that may have implications for future adhesive materials.

Primer-Treated Ceramic Bracket Increases Shear Bond Strength on Dental Zirconia Surface

The purpose of this study is to evaluate the shear bond strength (SBS) of a primer-treated ceramic bracket on dental zirconia and to compare it with conventional ceramic bracket bonding on surface-treated zirconia. Sintered and finished dental zirconia was sandblasted. Samples were divided according to the treated surfaces: no treatment (X), ceramic primer on zirconia (Z), ceramic primer on bracket base (B), and ceramic primer on both zirconia and bracket base (ZB). The ceramic bracket was bonded on zirconia and SBS was measured before (T₀) and after 10,000 cycles of thermocycling (T_f). The failed surfaces were examined under field emission scanning electron microscope (FE-SEM), and adhesive remnant index (ARI) was evaluated. SBS was significantly higher in ZB and significantly lower in X in both T₀ and T_f. There was no significant difference between Z and B. In X and B, adhesive failure occurred while ZB showed mixed failures. There was no apparent change in the zirconia surface except for the existence of some adhesive and resin remnants. The application of ceramic primer on the bracket base increased the bonding strength to the level of conventional bonding with fewer adhesive remnants. The highest bonding strength was obtained when the primer-treated bracket was bonded on the primer-treated zirconia.

Effect of Tribochemical Coating on Composite Repair Strength

Clinical Relevance

Tribochemical treatment of existing composite surfaces is highly effective for composite repair. When repairing an old composite restoration, the clinician should try to use the same composite originally used for the restoration. If the information about the original restoration is not known, a composite with strong mechanical properties should be used for the repair restoration.

SUMMARY

This study evaluated the effect of tribochemical coating on composite-to-composite repair interfacial fracture toughness (iFT). Sixty beam-shaped specimens (21×4×3 ± 0.2 mm) were prepared with a nanofill composite (Filtek Supreme Ultra [FSU]) and a nanohybrid composite (Clearfil Majesty ES-2 [CME]) and aged for 50,000 thermocycles (5°C-55°C, 20-second dwell time) and then sectioned in half. The resulting 120 hemispecimens (60 for each composite) were randomly assigned to different repair methods (n=10): universal adhesive (Clearfil Universal Bond Quick [CUB]), sand-blasting followed by CUB, or tribochemical coating (CoJet, CoJet sand, Espe-Sil, and Visio-Bond). The repair surface was prepared with a diamond bur (Midwest #471271), rinsed, and dried. Each aged composite brand (FSU, CME) was repaired with either the same composite or the opposite composite. All adhesives and composites were light cured with a high-irradiance LED curing light (Elipar DeepCure-S). After postrepair storage in 100% humidity and at 37°C for 24 hours, iFT was measured as KIc (MPa m½). Data were analyzed for statistical significance using two-way analysis of variance (ANOVA) and the Tukey honest significant difference post hoc test (α=0.05). Regardless of the substrate composite, ANOVA showed significant differences for surface treatment (p&lt;0.0001) and repair composite (p&lt;0.0001). Mean iFT values (SD) ranged from 0.91 (0.10) MPa·m½ to 2.68 (0.12) MPa·m½. Repairs made with FSU after CoJet resulted in significantly higher iFT (FSU: 2.68 MPa·m½; CME: 2.21 MPa·m½) when compared to the other experimental groups. The repair iFT was higher with CoJet treatment and when the nanofill composite FSU was used as the repair composite.

Silane-coupling effect of a silane-containing self-adhesive composite cement

OBJECTIVE

Hydrofluoric-acid etching followed by silanization is a routine clinical protocol for durable bonding to glass ceramics. Simplifying ceramic-bonding procedures, new technological developments involve the inclusion of a silane coupling agent in a self-adhesive composite cement. To investigate the effectiveness of the incorporated silane coupling agent, shear bond strength (SB) to ceramic and dentin, contact angle of water (CA), transmission electron microscopy (TEM), X-ray diffraction (XRD) and ²⁹Si nuclear magnetic resonance (NMR) assessments were correlatively conducted.

MATERIALS AND METHODS

SB to glass ceramic was measured without ('immediate') and with ('aged') 50K thermocycles upon application of (1) the silane-containing self-adhesive composite cement Panavia SA Cement Universal ('SAU'), being light-cured: 'SAU_light', (2) 'SAU_chem': chemically cured SAU, (3) 'SAP_light': light-cured Panavia SA Cement Plus ('SAP'), and (4) 'SAP_CP': SAP light-cured after separate silanization using Clearfil Ceramic Primer Plus ('CP'). CA was also measured on glass ceramic. The cement pastes before and upon mixing were characterized using ²⁹Si NMR. SB of SAU or SAP onto dentin was measured. Finally, the cement-dentin interface was characterized by TEM and XRD.

RESULTS

The immediate and aged SB to glass ceramic of SAU did not significantly differ from those of SAP_CP, while they were significantly higher than those of SAP. CA of SAU did not significantly differ from that of SAP_CP, but it was significantly higher than CA of SAP. ²⁹Si NMR revealed siloxane bonds after mixture. SB of SAU and SAP to dentin did not show any significant difference. SEM, TEM and XRD confirmed tight and chemical interaction, respectively.

SIGNIFICANCE

Incorporating silane in a 10-MDP-based self-adhesive composite cement combined efficient silane-coupling ability at the ceramic surface with effective bonding ability at dentin.

Adhesion procedures for CAD/CAM indirect resin composite block: A new resin primer versus a conventional silanizing agent

PURPOSE

The purpose of this study was to evaluate the effectiveness of both a resin primer containing methyl methacrylate (MMA) and a silanizing agent on bonding to indirect resin composite blocks, using two types of build-up hybrid resin composites.

METHODS

SHOFU BLOCK HC (Shofu) specimens were blasted with alumina, after which one of two surface treatments was applied: CERA RESIN BOND (Shofu, the Silane group) or HC primer (Shofu, the MMA group). Resin composites made using either Solidex Hardura (SDH, Shofu) or Ceramage Duo (CMD, Shofu) were built up and micro-tensile bond strength (μTBS) values were measured after storage in water for either 24h or 6 months (n=24 per group). The fracture surfaces after μTBS measurements and the resin block/build-up resin interfaces were observed by scanning electron microscopy (SEM).

RESULTS

The bond strength of the Silane/SDH group significantly decreased after 6 months (p<0.001), whereas in the MMA group there was no significant loss after 24h or 6 months (p=0.99). In the CMD group, the bond strength after 6 months was significantly lowered in both the Silane group (p<0.001) and the MMA group (p<0.001), but the latter still showed greater adhesion. SEM images demonstrated that the matrix resin was partially destroyed at the fracture surfaces of the MMA group and fracture surface unevenness was observed.

CONCLUSIONS

A primer containing MMA produced stronger bonding to CAD/CAM resin even after long-term aging compared to a silane treatment.

Which materials would account for a better mechanical behavior for direct endocrown restorations?

PURPOSE

To investigate the mechanical performance and fracture behavior of endocrown restorations prepared using different composite materials and following a direct technique.

METHODS

Sound molars were cut at 2 mm above the cementoenamel junction, endodontically treated, and allocated according to the type of restoration (n = 7): without post (endocrowns) or with post (post-retained restorations). Endocrowns were fabricated with conventional composite (Filtek Z350); bulk fill composite (Filtek Bulk Fill); conventional composite modeled using resin adhesives (SBMP: Scotchbond Multipurpose Adhesive; or SBU: Scotchbond Universal Adhesive); and lithium disilicate ceramic (E.max; Positive control). The post-retained restorations were fabricated with glass-fiber post combined with conventional or bulk fill composites. All restorations were bonded following an etch-and-rise adhesive approach or self-adhesive resin cement. The teeth were submitted to fatigue (Byocycle) and compression (EMIC DL500) testing at a crosshead speed of 1 mm/min. Data were analyzed with ANOVA and Tukey (p < 0.05) and Weibull analysis was carried out in order to evaluate the reliability of restorations.

RESULTS

The bulk-fill-based endocrown showed a stronger performance than the control. The presence of SBMP or the use of bulk-fill composite resulted in the occurrence of less aggressive fractures than the other restorative systems. Endocrowns bonded directly to the tooth seemed to produce similar fracture strength properties as compared to endocrowns bonded using self-adhesive resin cementation. The bulk-fill-based endocrown showed the greatest reliability of study.

CONCLUSION

Resin-based restorative materials seem to be interesting alternative options to fabricate large dental restorations in lieu of the more traditionally used glass ceramics or root canal post systems.

Self-Etch Silane Primer: Reactivity and Bonding with a Lithium Disilicate Ceramic

The aim of the study was to evaluate the stability, reactivity, and bond strength with a lithium disilicate ceramic of a self-etch silane primer (Monobond Etch and Prime/MEP). The stability was evaluated by ¹H-,³¹P-NMR spectroscopy (before/after aging), and the reactivity by micro MIR-FTIR spectroscopy on Ge surfaces (0, 1, 24 h) using a prehydrolyzed silane primer (Calibra Silane Coupling Agent/CLB), as a control. The effect of MEP vs. 5% HF-etching on ceramic roughness was assessed by optical profilometry. The shear bond strength (SBS) of a resin composite bonded to polished ceramic surfaces treated with MEP, HF without silane (HF+NS), HF+CLB, and HF+MEP (n = 20) was evaluated after storage in water (A: 37 °C/1 week, B: 5000×/5–55 °C and C: 100 °C/24 h). Aging did not affect the silanol groups of MEP, but only the phosphate co-monomer. Silanols were reactive forming siloxanes, but exhibited lower consumption rate than CLB. HF-etching induced significantly higher values than MEP, in all the roughness parameters tested (Sa, Sz, Sdr, Sc, Sv), with the greatest differences found in Sdr and Sv. For SBS, MEP was inferior to all treatments/storage conditions, except of HF+NS in A, where the values were similar. However, on a HF-etched substrate, MEP provided highest strength and reliability.

[Effects of universal adhesives and resin cement on the shear bond strength of zirconia]

OBJECTIVE

To study the effects of universal adhesives and resin cement on the shear bond strength and durability of zirconia ceramics.

METHODS

Zirconia ceramics were sintered into 20 mm×10 mm×10 mm and 10 mm×10 mm×10 mm specimens. The experiment was divided into 12 groups. The two types of specimens were bonded using two variants of resin cement (RelyX Ultimate and Clearfil SAC self-adhesive resin cement), universal adhesives (non-adhesive, Scotchbond uni-versal adhesive, and Clearfil SE One adhesive), and storage conditions (water bath and water bath-thermal cycling). The shear bond strengths were tested, and the fracture morphologies were analyzed.

RESULTS

The cement (F=8.41, P<0.01) and adhesive (F=30.34, P<0.01) exerted a significant effect on the shear bond strength of zirconia, whereas storage condition showed no significant effect on this property (F=1.83, P=0.18). The lowest shear bond strength (14.02 MPa±6.86 MPa) was exhibited by the group treated with RelyX Ultimate resin cement, non-adhesive, and water bath-thermal cycling, whereas the highest shear bond strength (54.12 MPa±8.37 MPa) was displayed by the group treated with RelyX Ultimate resin cement, Scotchbond universal adhesive, and water bath-thermal cycling.

CONCLUSIONS

Universal adhesives can improve the durability of the bonding of resin cement to zirconia. If non-self-adhesive resin cement is used without a universal adhe-sive, the durability of the bond will be greatly reduced.

Silane reactivity and resin bond strength to lithium disilicate ceramic surfaces

OBJECTIVE

To evaluate the silane status in commercially available products and their bonding capacity with polished glass-ceramic surfaces before and after hydrofluoric (HF) acid-etching.

METHODS

The products tested were Calibra Silane Coupling Agent/CS, G-Multi Primer/GM, Kerr Silane Primer/KS, Monobond Plus/MB and Scotchbond Universal Adhesive/SB. The silane status was studied by ¹³C nuclear magnetic resonance spectroscopy (¹³C-NMR). The roughness parameters of polished (group A) and HF acid-etched (group B) lithium disilicate glass-ceramic surfaces were measured by optical profilometry (n = 5/group). The interaction of the products with group A and B ceramic surfaces was examined by attenuated total reflection Fourier transform infrared spectroscopy (ATR-FTIR). The shear strength (SBS) of a flowable composite bonded to the ceramic surfaces (groups A, B) was assessed before (NS) and after silane treatment (n = 20/group, product).

RESULTS

The NMR analysis showed the presence of silanol monomers only in CS. Methoxylated-siloxane adducts were found in GM, silanol-siloxane adducts in MB, SB, and siloxane polymers in KS. Acid-etching greatly increased Sa, Sz, Sdr, Sc and Sv parameters (p < 0.001) and ATR-FTIR analysis demonstrated evidence of bonding with the substrate in CS. Weibull analysis of SBS revealed the following rankings in characteristic life (p < 0.05): CS > SB,KS,MB > GM > NS (group A) and CS > GM > SB,KS,MB,NS (group B). The most reliable treatment in both groups was CS. For the same silane treatment, the SBS of group B were significantly higher from group A. Failures were mainly of adhesive type, except of several partial resin cohesive failures found in group B.

SIGNIFICANCE

The chemical bonding capacity of the silanes was highest in products with silanol monomers. Acid-etching increased bond strength to a level that neutralized the silane contribution in products with silanol-siloxane adducts and siloxane polymers, providing thus bond strength values similar to silane-free treatments.

Physicochemical and morphological characterization of a glass ceramic treated with different ceramic primers and post-silanization protocols

OBJECTIVE

Evaluate the effect of different ceramic primers and post-silanization protocols on physicochemical and morphological characteristics of a lithium disilicate glass ceramic.

METHODS

Lithium disilicate ceramic (IPS e-max CAD) plaques (6 × 10 × 2 mm) were divided into 3 groups according to the ceramic primer used: (1) Silane (RelyX Ceramic Primer-RL); (2) Silane + MDP (Clearfil Ceramic Primer Plus-CP); (3) Self-etching ceramic primer (Monobond Etch and Prime-MB). Specimens from each group were distributed into 5 sub-groups according to post-silanization protocols: (a) Treated as recommended by the manufacturer (MR), (b) MR + Additional drying with air at room temperature for 30 s (RTA), (c) MR + additional drying with hot air for 30 s (HT), (d) MR + Surface rinsing with water at room temperature for 10 s and drying with air at room temperature for 30 s (WT), and (e) Specimens were not silanized (NS). Surface free energy (SFE) was determined using static contact angles measurements with water and diiodomethane. SFE data were submitted to Friedman followed by Wilcoxon post-hoc test (α = 0.05). Morphology was analyzed using scanning electron microscopy. Elemental composition and chemical interactions were determined with X-ray photoelectron spectroscopy analysis.

RESULTS

RL presented the highest SFE (62.4 mN/m) followed by CP (59.7 mN/m). Post-silanization protocols resulted in similar SFE, but WT and HT induced the highest water contact angles when using CP and RL. CP modified ceramics' surface morphology compared to the etched and RL treated groups. The presence of water was identified on CP treated specimen. All analyzed primers formed siloxane bonds with ceramic surface.

SIGNIFICANCE

Ceramic primers resulted in different surface free energy and morphology, but siloxane bonds were identified for all tested solutions. HT and WT protocols should be used with RL and CP primers. MB was not influenced by the different silanization protocols.

Adhesion behavior of conventional and high-translucent zirconia: Effect of surface conditioning methods and aging using an experimental methodology

OBJECTIVE

Evaluate the adhesive behavior of conventional and high-translucent zirconia after surface conditioning and hydrothermal aging.

MATERIALS AND METHODS

Conventional (ZrC) and high-translucent zirconia (ZrT) specimens were divided into six groups: without surface treatment (ZrC and ZrT), air-borne particle abrasion with 50-μm Al₂ O₃ sized particles (ZrC-AO and ZrT-AO), and tribochemical treatment with 30-μm silica modified Al₂ O₃ sized particles (ZrC-T and ZrT-T). Zirconia specimens were treated using an MDP-containing universal adhesive and bonded to two resins blocks with an adhesive luting cement. Microbar specimens with cross-sectioned areas of 1 mm² were achieved. Half of the microbars were subjected to hydrothermal aging. Bond strength was evaluated by microtensile bond strength test and statistically evaluated by the Weibull analysis.

RESULTS

Roughness of the ZrC-AO and ZrT-AO groups were statistically higher. Bond strength analysis revealed higher bond strength for ZrC-AO and ZrC-T groups compared to ZrT-AO and ZrT-T, respectively. Mixed failure was the most frequent for the mechanically treated groups, while no cohesive failures were obtained.

CONCLUSION

Lower values of bond strength were obtained for the mechanically treated high-translucent zirconia groups when compared to their conventional zirconia counterparts. Mechanical surface treatment significantly improved the bond strength to conventional and high-translucent zirconia.

CLINICAL SIGNIFICANCE

Mechanical surface treatment (air-borne particle abrasion or tribochemical treatment) associated with the use of universal adhesives containing MDP could provide a durable bonding to conventional and high-translucent zirconia.

Silanediol versus chlorosilanol: hydrolyses and hydrogen-bonding catalyses with fenchole-based silanes

Biphenyl-2,2'-bisfenchyloxydichlorosilane (7, BIFOXSiCl2) is synthesized and employed as precursor for the new silanols biphenyl-2,2'-bisfenchyloxychlorosilanol (8, BIFOXSiCl(OH)) and biphenyl-2,2'-bisfenchyloxysilanediol (9, BIFOXSi(OH)2). BIFOXSiCl2 (7) shows a remarkable stability against hydrolysis, yielding silanediol 9 under enforced conditions. A kinetic study for the hydrolysis of dichlorosilane 7 shows a 263 times slower reaction compared to reference bis-(2,4,6-tri-tert-butylphenoxy)dichlorosilane (14), known for its low hydrolytic reactivity. Computational analyses explain the slow hydrolyses of BIFOXSiCl2 (7) to BIFOXSiCl(OH) (8, E a = 32.6 kcal mol-1) and BIFOXSiCl(OH) (8) to BIFOXSi(OH)2 (9, E a = 31.4 kcal mol-1) with high activation barriers, enforced by endo fenchone units. Crystal structure analyses of silanediol 9 with acetone show shorter hydrogen bonds between the Si-OH groups and the oxygen of the bound acetone (OH···O 1.88(3)-2.05(2) Å) than with chlorosilanol 8 (OH···2.16(0) Å). Due to its two hydroxy units, the silanediol 9 shows higher catalytic activity as hydrogen bond donor than chlorosilanol 8, e.g., C-C coupling N-acyl Mannich reaction of silyl ketene acetals 11 with N-acylisoquinolinium ions (up to 85% yield and 12% ee), reaction of 1-chloroisochroman (18) and silyl ketene acetals 11 (up to 85% yield and 5% ee), reaction of chromen-4-one (20) and silyl ketene acetals 11 (up to 98% yield and 4% ee).

Universal dental adhesives: Current status, laboratory testing, and clinical performance

Increasing demand for simplified and user-friendly adhesive systems has led to the development of a new class of adhesives termed as Universal Adhesives (UAs). The term "Universal" reflects manufacturers' claims that these adhesives can be applied with any adhesion strategy and offer the versatility of use with a variety of direct and indirect restorative materials. The aim of this review was to synthesize the literature regarding the current status of UAs, their adhesion potential to various substrates and their performance in different restorative situations. In vitro studies, clinical trials and systematic reviews were identified utilizing controlled vocabulary and keyword searches in Medline and EMBASE databases. About 282 studies (272 in vitro studies; 11 clinical studies) were included. Available laboratory and clinical evidence does not support the claim that UAs can be used with any adhesive strategy. Although, they can chemically bond to various tooth and direct/indirect restorative substrates, the stability of this bond is material-dependent and subject to hydrolytic degradation. Hence, additional measures are still needed to ensure long-term durability. which undermines the versatility of UAs. The lack of long-term data regarding the clinical performance of UAs further complicates clinical decision-making. © 2019 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater 107B: 2121-2131, 2019.