Adhesion to tooth structure: A critical review of “micro” bond strength test methods

Effect of cross-head speed on the bond strength of dental resin to tooth structure - A review and re-analysis

OBJECTIVE

To review the published evidence for the role of cross-head speed on the apparent mechanical properties and bond strength of filled resins to tooth structure in order to identify the causes of inconsistency and contradictory results.

METHOD

The data for all available mechanical test results for studies involving dental resins at more than one strain rate was collected from 22 papers. Statistical reanalysis using linear regression was used to test the hypothesis that cross-head speed was correlated with the outcome, with the implication of causality, in each case.

RESULTS

In many cases the expected trend was found, in others not. However, it was apparent that the quality of data was often less than can be achieved, and that known interferences have not been recognized.

SIGNIFICANCE

Experimental work for the effect of cross-head speed on bond strength and other properties for dental resin-based materials has often failed to reach the standard which is required for useful data and thus better comprehension of behaviour. Other relevant conditions, such as temperature and water saturation, are in need of attention in this context.

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.

Influence of additive and subtractive zirconia and lithium disilicate manufacturing on tensile bond strength and surface topography

STATEMENT OF PROBLEM

Although bonding is important for long-term clinical success, studies on the bonding of additively manufactured ceramics are sparse.

PURPOSE

The purpose of this in vitro study was to determine the influence of manufacturing methods, additive (LCM) versus subtractive (CAM). and ceramic materials, zirconia (ZrO2) and lithium disilicate (LiSi), on the tensile bond strength (TBS), failure mode, and surface roughness of ceramics.

MATERIAL AND METHODS

A total of 240 ceramic specimens (n=60/group; 2×2×10 mm) were prepared. Two additively manufactured (LCM-printed) ceramics, LiSi and ZrO2 (Lithoz), subtractively manufactured LiSi (IPS e.max CAD), and subtractively manufactured ZrO2 (KATANA Zirconia HTML PLUS) were evaluated. From each material, 40 specimens were bonded together (n=20 ceramic-ceramic specimens/group), and 20 specimens were bonded to equally sized human dentin specimens (n=20 ceramic-dentin specimens/group). The ZrO2 specimens were airborne-particle abraded (Al2O3, 50 µm, 0.1 MPa), and the LiSi specimens were etched with hydrofluoric acid. Then, a universal primer (Monobond Plus) was applied. After the dentin was coated with an etch-and-rinse adhesive (Syntac Classic), the specimens were bonded with luting composite resin (Variolink Esthetic DC), light polymerized for 40 seconds, thermally aged (10 000 cycles between 5 °C and 55 °C), tested for TBS, and statistically analyzed (1- and 3-way ANOVA and Weibull analysis). The ceramic surface was examined with scanning electron microscopy, and surface roughness was measured with digital microscopy before and after surface pretreatment.

RESULTS

TBS varied between 5.88 ±2.22 MPa and 6.34 ±2.26 MPa in the ceramic-dentin groups and 12.40 ±1.56 MPa and 18.82 ±5.92 MPa in the ceramic-ceramic groups. No significant difference was observed regarding the manufacturing method and material for different bonding conditions (P>.05). Additive and subtractive LiSi showed the highest reliability with m=18.27. The ceramic-ceramic specimens failed cohesively in the luting composite resin, whereas the ceramic-dentin specimens failed adhesively.

CONCLUSIONS

The manufacturing method and material used had little effect on bond strength values or surface properties. The recently introduced printed materials performed similarly to conventionally milled materials.

Light-curable urushiol enhanced bisphenol A glycidyl dimethacrylate dentin bonding agent

OBJECTIVES

The low durability of composite resin restorations can be attributed to the degradation of the resin dentin bonding interface. Owing to the presence of hydrophilic components in the adhesive, the integrity of the resin dentin bonding interface is easily compromised, which, in turn, leads to a reduction in bond strength. The hydrophilic nature of the adhesive leads to water sorption, phase separation, and leaching of the resin component. Therefore, hydrophobic adhesives could effectively be used to stabilize the integrity and durability of the resin dentin bonding interface.

METHODS

We synthesized a novel hydrophobic dentin adhesive by partially replacing bisphenol A glycidyl dimethacrylate (Bis-GMA) with a light-curable urushiol monomer. The properties of the produced adhesive, including the degree of conversion, viscosity, contact angle, water sorption/solubility, and mechanical strength, were comprehensively examined and compared to those of the commercially adhesive Adper Single Bond2 as a positive control. The adhesive properties were determined using microtensile bond strength measurements, laser confocal microscopy, scanning electron microscopy observations, and nanoleakage tests. Finally, the novel adhesive was subjected to biocompatibility testing to determine its potential cytotoxicity.

RESULTS

At a light-curable urushiol content of 20 %, the synthesized adhesive exhibited high degrees of conversion and hydrophobicity, low cytotoxicity, good mechanical properties, and outstanding adhesive strength.

CONCLUSIONS

The introduction of the light-curable urushiol into dentin adhesives can significantly enhance their hydrophobic, mechanical, and bonding properties, demonstrating potential to significantly improve restoration longevity.

CLINICAL SIGNIFICANCE

The integration of light-curable urushiol has endowed the experimental adhesives with several enhanced functionalities. These notable benefits underscore the suitability of this monomer for expanded applications in clinical practice.

Evaluation of polymerization shrinkage stress and cuspal strain in natural and typodont teeth

To evaluate the polymerization shrinkage stress and cuspal strain (CS) generated in an artificial (typodont) and in a natural tooth using different resin composites. Twenty artificial and 20 extracted natural molars were selected. Each tooth was prepared with a 4x4 mm MOD cavity. The natural and typodont teeth were divided into four experimental groups (n=10), according to the resin composite used: Filtek Z100 (3M Oral Care) and Beautifil II LS (Shofu Dental). The cavities were filled using two horizontal increments and the CS (µS) was measured by the strain gauge method. Samples were sectioned into stick-shaped specimens and the bond strength (BS) (MPa) was evaluated using a microtensile BS test. Shrinkage stress and CS were analyzed using 3D finite element analysis. No difference was found between the type of teeth for the CS as shown by the pooled averages: Natural tooth: 541.2 A; Typodont model: 591.4 A. Filtek Z100 CS values were higher than those obtained for Beautifil II LS, regardless of the type of teeth. No statistical difference was found for the BS data. Adhesive failures were more prevalent (79.9%). High shrinkage stress values were observed for Filtek Z100 resin, regardless of tooth type. The CS of typodont teeth showed a shrinkage stress effect, generated during restoration, equivalent to that of natural teeth.

Bond strength and marginal adaptation of resin composites and correlations with clinical results

OBJECTIVES

Due to innumerable confounding factors and a high number of types and brands of dental restorative materials, the clinical performance of restorative materials are sought predicted by various in vitro tests. However, only few such tests have been found to correlate well with clinical findings. Thus, the present study determined the in vitro dentin bond strength and marginal adaptation of Class II restorations and correlated the results to their clinical outcomes.

METHODS

Dentin bond strength (µTBS and µSBS) and marginal gap formation of Class II restorations (replica technique and SEM) were measured after 24 h and 6 m water storage using eight combinations of adhesive and resin composite. Clinical outcomes (mean survival time, Hazard Ratio, annual failure rate; n = 10.695) were gained from a data set of a retrospective multicenter study of direct restorations.

RESULTS

Significant differences were found for dentin bond strength and marginal gap formation between the restorative material groups, and negative effects of long-term storage were observed. µTBS correlated significantly with certain clinical outcomes of Class I restorations, while µSBS correlated with certain clinical outcomes of Class II, III, IV and V restorations. Marginal gap formation in enamel and number of paramarginal fractures correlated with certain clinical outcomes of Class II restorations.

SIGNIFICANCE

Using the same restorative materials in vitro as in vivo, gave significant, but weak correlations between in vitro bond strength or marginal adaptation and clinical outcomes, lending support to the use of in vitro tests in early stages of material selection.

Influence of airborne particle abrasion on dentin bonding effectiveness of a 2-step universal adhesive

OBJECTIVE

To determine the effect of airborne particle abrasion (APA) on micro-tensile bond strength (µTBS) to dentin using different air-abrasion/polishing powders.

METHODS

The bonding effectiveness of G2 Bond Universal (G2B), used in etch-and-rinse (E&R) and self-etch mode (SE), was tested on bur-cut dentin and dentin air abraded/polished using six different powders (aluminum oxide 29 µm (AO29) and 53 µm (AO53), aluminum trihydroxide (AT), sodium bicarbonate (SB), sodium bicarbonate soft (SBsoft) and bioactive glass (BG); Velopex). Adhesive-composite resin specimens were immersed in distilled water at 37 °C for one week and cut into microspecimens. Half of the specimens were subjected to 50,000 thermocycles (aged). Immediate and aged μTBS to dentin were measured. Statistical analysis was performed using linear mixed-effects (LME) modeling (p < 0.05).

RESULTS

Comparing the aged bond strengths to air-abraded/polished dentin with bur-cut dentin, pretreatment with SB and SBsoft in combination with G2B used in E&R mode, and BG air polishing in combination with both application modes (E&R, SE), resulted in a significantly higher bond strength. Dentin bond strength was only significantly lower when air abraded with AO29 and using G2B in SE mode. Aging did not significantly influence bond strength for both application modes (E&R, SE), except for AO29 and AT-treated dentin, where bond strengths decrea sed significantly using G2B in SE mode. In general, G2B reached significantly higher bond strengths on air-abraded/polished dentin in E&R mode than in SE mode.

CONCLUSION

Air-abrasion/polishing did not impair dentin bond strength using G2B, except when dentin was air abraded with AO29 and using G2B in SE mode. Air polishing positively influenced the bond strength to dentin in specific groups.

CLINICAL SIGNIFICANCE

APA is safe concerning bonding to dentin. The E&R application mode is preferred using G2B as adhesive on air-abraded/polished dentin. Air polishing with BG positively influenced dentin bond strength for both application methods.

Warm Air Delivery in Adhesive Application: Effect on Bonding Performance and Morphological Outcomes

Solvent evaporation within an adhesive layer is a crucial step during a bonding process. The aim of this current research was to test whether the use of different air temperatures (20 °C, 40 °C, and 60 °C) for solvent evaporation improves the performance of four adhesive systems to dentin. Sixty non-carious human molar teeth were randomly prepared for micro-tensile bond strength (μTBS) tests. Four different adhesive systems, Prime&Bond Universal (PBU), OptiBond Universal (OBU), OptiBond FL (OBFL), and Clearfil SE (CSE), were applied following the manufacturer's instructions. Three groups based on the air-drying temperature were used: solvent evaporation was performed with either of warm (40 °C), (60 °C), and cold air as control group (20 °C) for 10 s at a distance of 5 cm. In all bonded surfaces, three resin composite (Reflectys, Itena Clinical, Paris, France) layers of 2 mm thickness were built up. The resin-dentin samples were kept in distilled water at 37 °C for 24 h and 6 months, respectively, before μTBS testing. Failure analysis, scanning electron microscopy of resin-dentin bonded interface, and solvent evaporation rate were tested as secondary variables. All analyses were conducted using a significance level of α = 0.05. Bond strength (BS) values were similar among all the adhesive systems used (p > 0.05). Also, the aging factor did not affect the BS (p > 0.05). Only the factor of temperature used for solvent evaporation resulted in a statistically significant effect (p < 0.05), with the temperature of 60 °C being the highest value (p < 0.05). A failure mode evaluation revealed mostly adhesive or mixed modes of failures in all the different temperatures of air used for the solvent evaporation of each adhesive system. The thickness of the adhesive layer and the creation of resin tags varied amongst the temperatures evaluated. For all adhesive systems tested, the use of 40 °C or 60 °C air for solvent evaporation led to an increased mass loss. Warmer temperatures for solvent evaporation contributed positively to bonding performance, enhancing both the quality of the adhesive layer and its interaction with the dentin tissue. Optimizing solvent evaporation with warmer air temperatures (40 °C and 60 °C) significantly improved µTBS, offering a practical means to enhance the quality and longevity of adhesive restorations in esthetic dentistry.

Effects of dimethyl sulfoxide pretreatment on the bonding properties of fluorotic dentin of different severity: An in vitro study

STATEMENT OF PROBLEM

Bonding to fluorotic dentin is weaker than to sound dentin, but methods to improve bonding have not been well addressed.

PURPOSE

The purpose of this in vitro study was to investigate the effects of dimethyl sulfoxide (DMSO) pretreatment on the bond strength and resin-dentin surface of fluorotic dentin of different severity.

MATERIAL AND METHODS

Phosphoric acid-etched dentin specimens exhibiting mild fluorosis (ML-F), moderate fluorosis (MD-F), and severe fluorosis (SE-F) were randomly bonded with Single Bond 2 (SB2) pretreated with 50% DMSO (experimental groups) or deionized water (control groups). The bonded teeth were sectioned for microshear bond strength (μSBS) testing immediately or after aging, for micromorphology observation of the bonding interface under a scanning electron microscope, and for resin tags and microleakage evaluation under a confocal laser scanning microscope. The degree of conversion of the adhesive resin was calculated by Fourier transform infrared spectroscopy. According to varying bonding steps, the mineralized dentin powders of ML-F, MD-F, and SE-F were randomly divided into 4 subgroups (blank, PA, PA+SB2, and PA+DMSO+SB2) and incubated in artificial saliva to examine the level of enzymatic degradation product of type I collagen. Data were analyzed by using ANOVA and the Tukey test (α=.05).

RESULTS

Dental fluorosis and thermocycling had negative effects on μSBS (P<.001), while DMSO pretreatment preserved or even improved μSBS (P<.001). DMSO had no influence on the degree of conversion (P=.618). Significant effects were found for bonding steps (P<.001), but not that of dental fluorosis (P=.131) on the enzymatic degradation product of type I collagen. Images showed sparser and more expanded collagen fibril meshwork, deeper resin penetration, and less microleakage in the experimental groups.

CONCLUSIONS

DMSO pretreatment provided increased and durable dentin bonding to fluorotic dentin probably by dispersing collagen fibrils into a sparser network and inhibiting the degradation of type I collagen.

Reliability of an Innovative Slab Shear versus Microtensile Bond Strength Test: Mechanical and Finite Element Analysis

OBJECTIVE

 The aim of this study was to evaluate the efficiency of slab shear bond strength test (Slab_SBS) versus the microtensile in evaluation of the bond strength of different substrates.

MATERIALS AND METHODS

 Forty-eight extracted caries-free human third molars were utilized for teeth specimens' preparation. After flattening of all molars' occlusal table, the specimens were divided into two groups based on the type of utilized restorative material: nanohybrid resin composite and resin-modified glass ionomer (RMGI). Each group was further subdivided into three subgroups according to the subsequently applied bond strength test and specimen width; microtensile bond strength test (μTBS), Slab_SBS [2 mm] and Slab_SBS [3 mm]. Both testing methods were additionally applied on CAD/CAM specimens, nanohybrid resin composite blocks (composite-to-composite), and ceramic blocks (ceramic-to-ceramic). CAD/CAM specimens were prepared and cemented and then sectioned and subdivided as followed for teeth specimens' preparation. Pretest failures (PTF), bond strength, and failure mode of each specimen were recorded. Representative three-dimensional (3D) finite element analysis (FEA) models were developed to simulate μTBS and Slab_SBS specimens. Data were statistically analyzed using Shapiro-Wilk test and Weibull analysis.

RESULTS

 Pretest failures were only noted in the μTBS subgroups. Slab_SBS provided comparable bond strength to the μTBS of all substrates with adhesive mode of failure.

CONCLUSION

 Slab_SBS is easier to prepare with consistent and predictable outcome with no pretest failures during specimen preparation and better stress distribution.

To etch or not to etch, Part III: On the hydrophobic-rich content and fatigue strength of universal adhesives after long-term ageing

OBJECTIVES

To examine whether dentin-etching extension and/or the hydrophobic-rich content of hybrid layers would affect fatigue strengths of a mild universal adhesive after long-term aging.

METHODS

Twin-bonded resin-dentin interfaces were produced by etching sound midcoronal dentin beams with 32 % ortho-phosphoric acid for 15 s (OPA15s), 3 s (OPA3s) or 10 % meta-phosphoric acid for 15 s (MPA15s). Samples were bonded with a mild universal adhesive with or without additional coating using a solvent-free bisGMA-based bonding resin. Self-etch application served as control. Composite buildups were made with a nanofilled composite. Bar-shaped twin-bonded interfaces (0.9 × 0.9 × 12 mm) were aged for two years in artificial saliva at 37 ℃ and tested under 4-point flexure at quasi-static (n = 16) and cyclic loads (n = 35) until failure. The stress-life fatigue behavior was evaluated using the staircase method at 4 Hz. Crack initiation and fracture patterns were evaluated by SEM. Cyclic-loaded data was analyzed by Kruskal-Wallis on Ranks (α = 0.05).

RESULTS

Significantly higher fatigue life distributions and higher endurance limits were observed for less aggressive etch-and-rinse protocols (OPA3s and MPA15s) after long-term ageing. Hydrophobic-rich coating produced 20-32 % higher endurance limits, prevented micrometer-sized porosities at bonded interfaces, reduced etching-associated variability and lowered crack formation. Significance Long-term hydrolysis produces detrimental effects on the fatigue strength of resin-dentin interfaces. The bond-promotion effect of less aggressive etch-and-rinse protocols and the creation of hybrid layers with higher hydrophobic-rich content are critical to extend the durability of mild universal adhesives. Therefore, current oversimplification trends in adhesive dentistry may limit resin-dentin bonding performance.

Zirconia bond strength durability following artificial aging: A systematic review and meta-analysis of in vitro studies

The present study systematically reviewed the literature regarding the bond strength durability of zirconia ceramics to resin-based luting cements after application of different bonding protocols and aging conditions. Electronic searches in PubMed, Scopus, and Web of Science databases were performed for relevant literature published between January 1st 2015 and November 15th 2022. Ninety-three (93) English language in-vitro studies were included. The percentage of the mean bond strength change was recorded prior to and after artificial aging, and the weighted mean values and 95% confidence intervals were calculated. Bonding protocols were classified based on the combination of MDP/non-MDP containing cement/primer and surface pretreatment, as well as the level of artificial aging performed. Alumina sandblasting (SA) was identified as the most frequently used surface pre-treatment while an insufficient number of studies was identified for each category of alternative surface treatments. The combination of MDP cement with tribochemical silica coating (TSC) or SA yielded more durable results after aging, while the application of SA and TSC improved bond durability when a non-MDP cement and a non-MDP primer were used. TSC may lead to increased bond durability compared to SA, whereas MDP cements may act similarly when combined with SA or TSC.

Bond Strength of Two Resin Cements with Leucite-reinforced Ceramic Using Different Bonding Agents

AIM

To compare the bond strength of two resin cements to leucite-reinforced ceramics using three different boding agents and evaluate the compatibility of bonding agents.

MATERIALS AND METHODS

Twenty extracted sound human molars were sectioned horizontally 2-3 mm above the cementoenamel junction (CEJ). CAD/CAM ceramic blocks for inLab were also sectioned to create 4 mm thick and bonded to the dentin. The adhesive groups assigned were divided into four adhesive groups: Group I: Variolink II dual-cure resin cement and Scotchbond Multi-Purpose Plus adhesive, group II: Multilink Automix dual-cure resin cement and Multilink primers, group III: Multilink Automix and Clearfil SE bond 2 (CSE2) adhesive, group IV: Multilink Automix and CSE2 with light curing after adhesive application. Five specimens of each group were sectioned perpendicular to obtain six microsticks of 1 × 1 mm width from each sample. Microtensile bond strength data were expressed in MPa. Fracture modes (FrMs) analyzed for the surfaces were divided into six patterns. Microtensile bond strength data were statistically analyzed with one-way ANOVA and Tukey post hoc tests (α = 0.05). T-test was performed at the 5% significance level to analyze groups III and IV with and without light curing.

RESULTS

Group I showed the highest μTBS average of 13.67 MPa, group IV showed 12.26 MPa, group III showed 12.15 MPa, and group II showed the lowest average of 10.84 MPa. No significant differences were found between the bonding agents. However, the six types of failure modes, although all observed, were characterized by the adhesive system: Type I: adhesive failure of laminated dentin and ceramic; type II: adhesive failure of laminated ceramic; type III: adhesive failure of laminated dentin; type IV: cohesive failure of luting agent; type V: cohesive failure of dentin, and type VI: mixed failure of adhesion and cohesion. As a result, the FrM most commonly observed was the adhesive failure at the luting cement-ceramic block interface.

CONCLUSION

The combination of resin cements and bonding agents did not significantly affect the bond strength of CAD/CAM ceramic restorations and dentin.

CLINICAL SIGNIFICANCE

Several universal bonding agents are currently available for direct and indirect bonding, and using the same bonding agent for direct and indirect restorations could simplify inventory and benefit routine clinical practice. How to cite this article: Aida N, Koi K, Amaya-Pajares SP, et al. Bond Strength of Two Resin Cements with Leucite-reinforced Ceramic Using Different Bonding Agents. J Contemp Dent Pract 2023;24(11):859-863.

Does extended air-drying time improve bond strength of universal adhesives to enamel?

OBJECTIVE

To investigate the effect of extended air-drying time on the microshear bond strength (MSBS) of universal adhesives to enamel.

MATERIALS AND METHODS

The distal and mesial specimens from third molars were wet-ground and randomly assigned to three groups according to adhesives tested (n = 60): Clearfil Bond Universal, Gluma Bond Universal, and G-Premio Bond. The adhesives were applied in etch-and-rinse or self-etch modes, followed by air-drying for 5, 15, or 25 s. Composite buildups were constructed and subjected to the MSBS test after 24-h or thermocycling. MSBS results were evaluated using a four-way ANOVA. The thickness of the adhesive layer and the degree of solvent evaporation were further evaluated.

RESULTS

At 24-h, MSBS of G-Premio Bond significantly improved with the 25 s air-drying in both of the etching modes when compared to the 5 s air-drying. After thermocycling, the extended air-drying did not produce a significant difference on the MSBS, regardless of the application strategy. Extended air-drying (25 s) evaporated almost all of the volatile part of Gluma Bond Universal and G-Premio Bond.

CONCLUSIONS

Extended air-drying times increased solvent evaporation but did not contribute to the bonding effectiveness of the adhesives, regardless of the etching mode.

CLINICAL SIGNIFICANCE

Air-drying applications for more than 5 s had no significant effect on enamel bonding performance of universal adhesives.

Bond Strength of Reline Materials to 3D-Printed Provisional Crown Resins

(1) Purpose: The aim of the present study was to compare the bond strength between two 3D-printed resins designed for long-term provisional crowns and three different reline materials. (2) Materials and Methods: Rectangular specimens were prepared from two 3D-printed resins (Envision Tech and NextDent C&B) and a conventional self-cure PMMA. Transparent tubes filled with three different reline materials including composite resin, Bis-acryl, and PMMA were bonded to the 3D-printed specimens (n = 11 per group, total of 6 study groups). Tubes filled with PMMA were bonded to the prepared PMMA specimens which served as the control group (n = 11, control group). The specimens were subjected to a shear bond strength (SBS) test, and mode of failure was recorded using light microscopy. Statistical analysis was performed using a one-way ANOVA and post hoc Tukey's tests (alpha = 0.05). (3) Results: The highest SBS value was achieved to both 3D-printed materials with the PMMA reline material. The bond to both 3D-printed materials was lower with Bis-acrylic or composite resin relines in comparison to that with PMMA (p-value < 0.05). No significant difference was found between the control PMMA group and either 3D-printed material when relined with PMMA (p-value > 0.05). (4) Conclusion: The tested 3D-printed resins achieved a clinically acceptable bond strength when relined with PMMA.

Effect of the Absence of HEMA on the Bonding Properties of Universal Adhesive Systems Containing 10-MDP: An In Vitro Study

OBJECTIVES

To evaluate the absence of 2-hydroxyethyl methacrylate (HEMA) on the adhesive properties with enamel and dentin of universal adhesive systems containing 10-methacryloyloxydecyl dihydrogen phosphate (MDP).

METHODS AND MATERIALS

One hundred and twelve caries-free third molars were used to test adhesion to dentin (n=64) and enamel (n=48). For each substrate, teeth were divided into eight experimental groups: four different adhesives each using two adhesive strategies. The adhesives used were: (1) Scotchbond Universal (SBU, 3M Oral Care, St Paul, MN, USA) as a HEMA-containing universal adhesive; (2) Gluma Bond Universal (GBU, Kulzer, Hanau, Germany); (3) Solare Universal Bond (SUB, GC, Tokyo, Japan); and (4) Zipbond Universal (ZIP, SDI, Victoria, Australia) as HEMA-free universal adhesives. The adhesive strategies used were etch-and-rinse (ER) and self-etch (SE). For dentin tests, the occlusal third of the crown of all teeth was removed and an adhesive protocol was applied. After completing the restoration, specimens were sectioned into bonded sticks (0.8 mm 2) and tested for microtensile bond strength (μTBS), in situ degree of conversion (DC), and nanoleakage (NL) by scanning electron microscopy. For enamel tests, teeth were sectioned into four parts (buccal, lingual, and proximal), and an adhesive protocol was applied. After completing the restoration, the specimens were tested for their microshear bond strength (μSBS). For in situ degree of conversion (DC) and nanoleakage (NL) evaluation of enamel, the specimens were sectioned in slices to be evaluated. The data for each substrate were subjected to two-way ANOVA and Tukey's test (α=0.05) for each property evaluated.

RESULTS

The SBU and ZIP adhesives showed the highest μSBS, and DC (dentin and enamel) and lower NL (dentin) values compared to GBU and SUB (p=0.001). However, SBU showed better results in terms of μTBS and μSBS (SE strategy), and DC (dentin and enamel) than ZIP. Strategy ER presented higher values of μTBS and μSBS when compared to strategy SE (p=0.001), except for SBU.

CONCLUSION

The effect of the absence of HEMA in commercial universal adhesive systems on enamel and dentin adhesive properties appears to be material-dependent.

Pushout Bond Strength in Coronal Dentin: A Standardization Approach in Comparison to Shear Bond Strength

To find an alternative that is closer to clinical reality in terms of cavity geometry and configuration factor, this study investigated the pushout test on in vitro adhesive testing to coronal dentin when compared to the established shear test, both in a standardized approach. For a feasible comparison between both tests, the pushout specimen was adjusted in thickness (1.03 ± 0.05 mm) and cavity diameter (1.42 ± 0.03 mm) to receive a bonding area (4.63 ± 0.26 mm2) that matches that of the shear test (4.57 ± 0.13 mm2). Though, the configuration factor between both tests differs largely (pushout 1.5 ± 0.08; shear bond 0.20 ± 0.01). The bond strength of five different adhesives (n = 20) was investigated for both tests. The pushout test registered a high number of invalid measurements (30%) due to concomitant dentin fracture during testing. In contrast to the shear test, the pushout test failed to discriminate between different adhesives (p = 0.367). Both tests differed largely from each other when comparing adhesive groups. When solely looking at the valid specimens, Weibull modulus reached higher values in the pushout approach. Conclusively, the pushout test in this specific setup does not distinguish as precisely as the shear bond test between different adhesives and needs adaption to be routinely applied in adhesive dentistry.

The comparison of the repair bond strength of the composite resin to direct and indirect composite restorations with different surface preparations

Background

Indirect restorations have been employed in restorative dentistry to solve some of the drawbacks of direct restorations. The aim of this study was to evaluate the effect of different modes of a universal adhesive resin on the repair capacity of two indirect resin composites and a direct resin composite.

Methods

Indirect composite resins (Ceramage and Gradia Plus) and a direct composite resin (Filtek Z250) were prepared in a plastic mold with a height and diameter of 2-mm and 6-mm, respectively. Composite blocks were thermocycled (5000 cycles, 5°C-55°C). Then, according to their surface treatments, composite blocks were categorized into six-groups: Group 1: ER (etch&rinse), Group 2: SE (self-etch), Group 3: Bur+ER (bur+etch&rinse), Group 4: Bur+SE (bur+self-etch), Group 5: Bur+Silane+ER (bur+silane+etch&rinse), Group 6: Bur+Silane+SE (bur+silane+self-etch), respectively. After surface treatments and adhesive application for bonding with a direct resin composite, all groups were then thermocycled before performing shear-bond-strength-test. Failure modes were evaluated using a stereomicroscope. Data were analyzed by two-way-ANOVA and Bonferroni-test (P<0.05).

Results

The highest bond-strength values were obtained for Bur+Silane+SE groups, while the lowest values were obtained for the Bur+Silane+ER groups for all materials. Statistically significant differences were observed between the Bur+Silane+ER group and ER, Bur+ER and Bur+Silane+SE groups in Gradia Plus (P<0.05).

Conclusion

The self-etch-mode of the universal-adhesive and silane applications led to the increase in the repair-strength of the adhesive in the Filtek Z250 and Ceramage. The self-etch-mode of the universal-adhesive might be used to reduce adhesive-application-steps in the clinical repair procedures.

Effect of plasma surface treatment of three different CAD/CAM materials on the micro shear bond strength with resin cement (A comparative in vitro study)

Objectives

This study aimed to evaluate and compare the effect of plasma treatment versus conventional treatment on the micro shear bond strength (μSBS), surface roughness, and wettability of three different CAD/CAM materials.

Materials and methods

Sixty cylindrical specimens (5 mm diameter × 3 mm height) were prepared from three different CAD/CAM materials: Group A: Zirconia, Group B: Lithium disilicate, and Group C: Resin nano-ceramic. Each group was subdivided into two subgroups according to surface treatment used: Subgroup I: Conventional treatment, zirconia was sandblasted with Al₂O₃, while lithium disilicate and resin nano-ceramic were etched with hydrofluoric acid. Subgroup II: Plasma treatment, the surface of each material was treated with a plasma device (PiezoBrush® PZ3 Handheld Device, Relyon Plasma, Regensburg, Germany). G-Multi PRIMER was applied, then self-adhesive cement (G-CEM ONE) was applied using a split mold (1 mm diameter × 3 mm height), and μSBS was tested in a universal testing machine. The surface roughness was measured using a profilometer. Nine additional specimens of each material for wettability test using an optical tensiometer.

Statistical analysis

The data were analyzed using ANOVA and Bonferroni test at a level of significance of 0.05.

Results

The highest mean of μSBS was recorded by AII (27.3 MPa), while the lowest was recorded by AI (17.9 MPa). One-way ANOVA test revealed a significant difference among groups. Bonferroni test showed each two subgroups significant difference except subgroups AI, CI and BII, CII, where there was a non-significant difference. For all CAD/CAM materials, conventional treatment increased the surface roughness compared to plasma treatment, while the contact angle decreased after plasma treatment.

Conclusion

Plasma treatment increased the μSBS of resin cement to zirconia significantly while not significantly affecting the μSBS of resin nano-ceramic. Conventional treatment of lithium disilicate provided significantly higher μSBS than plasma treatment.

Phosphoric Acid Etch Partially Restores the Initial Bond Strength of Composite to Silver Diamine Fluoride-Treated Enamel Using Universal Adhesives

BACKGROUND

Restoring bonding composite to silver diamine fluoride (SDF)-treated enamel is challenging. This study investigates if phosphoric acid etch restores composite bond strength to SDF-treated enamel using universal adhesives.

METHODS

Twenty-four recently extracted permanent teeth were randomly divided into 4 (2 experimental (SDF) and 2 control (CTR)) groups: SDF+Water: SDF (1 min) then water rinse (15 mL); CTR+Water: no treatment and water rinse (15 mL); SDF+Etch+Water: SDF (1 min), 35% phosphoric acid (40 s) then water rinse (15 mL); CTR+Etch+Water no treatment, 35% phosphoric acid (40 s) then water rinse (15 mL). The enamel surface in all the groups was bonded (All-Bond Universal) to 4-5 mm composite blocks (Z-250). Each sample was sectioned, and 6-8 beams (1 mm × 1 mm) were selected. The micro-tensile bond strength was measured by dividing the micro-tensile force peak by the adhesive surface area. Univariate ANOVA and Chi-square were used for between-group comparisons with p < 0.05.

RESULTS

SDF+Water had significantly lower tensile strength compared to all the groups (p < 0.05). Although no difference was found in the tensile strength between the SDF+Etch+Water and the CTR+Etch+Water, the SDF+Etch+Water had significantly more adhesive failures compared to the CTR+Etch+Water (p = 0.047).

CONCLUSIONS

While phosphoric acid etch seems to restore the initial composite bond strength to SDF-treated enamel, the long-term success of composite restorations bonded to SDF-treated enamel may need further investigation.

A comparative evaluation of micro shear bond strength and microleakage between the resin-modified glass ionomer cement and residual dentin following excavation of carious dentin using Carie CareTM and conventional caries removal in primary teeth: an in vitro study

Background: The bond between the dentin and restorative material contributes to the success of the restoration. Structural changes associated with prepared dentin may influence the bonding of restorative materials. The present study evaluates the bond between the resin-modified glass ionomer cement (RMGIC) and residual dentin following excavation of carious dentin using Carie Care ^TM and conventional caries removal in primary teeth.

METHODS

52 primary teeth with dentinal caries were randomly grouped into group I, where caries removal was done using the conventional method, and group II which used Carie Care ^TM. All the teeth were restored using RMGIC. Micro shear bond strength between the residual dentin and the cement was tested using universal testing machine and the dye penetration method was used for microleakage testing. Independent t-test was performed for intergroup comparison. Pearson chi-square test was carried out to evaluate the microleakage patterns in the enamel and dentin.

RESULTS

The mean micro-shear bond strength of group I was 6.03±1.6 and that of group II was 8.54±2.92; this difference was statistically significant with a p-value of 0.012. Microleakage was higher in the test group (1.38±0.51) than the control group (0.77±0.6) and was significant with a p -value of .036.

CONCLUSIONS

Papain-based chemomechanical agent Carie Care ^TM can be used as an alternative method to conventional caries removal. However, further studies need to explore methods to improve the marginal sealing capacity of RMGIC to the residual dentin after chemomechanical caries removal.

Bond durability of a two-step adhesive with a universal-adhesive-derived primer in different etching modes under different degradation conditions

This study investigated the enamel and dentin bond durability of a two-step adhesive system, using a universal adhesive-derived primer (G2-Bond Universal [GU]), and compared it with the two conventional, two-step, self-etch adhesive systems (Clearfil SE Bond 2 [CS] and OptiBond XTR [OX]) under thermal cycling (TC) and long-term water storage (WS). The shear bond strengths to bovine enamel and dentin were determined using the etch-and-rinse and self-etch modes. Twelve specimens per test group were prepared and further divided into the following subgroups: 1) subjected to TC, 2) long-term WS, and 3) WS for 24 h (baseline). The enamel and dentin bond durability of GU was superior to those of CS and OX in different etching modes and under different degradation conditions. The latest two-step adhesive system, which utilizes universal adhesives' benefits in its primer, might offer durable clinical bonding performances and can be widely used in a clinical setting.

Effect of Different Application Modalities on the Bonding Performance of Adhesive Systems to Dentin: A Systematic Review and Meta-Analysis

Diverse types of dental adhesives exhibit different cytotoxic outcomes on cells in vitro. Currently, no standard adhesive application technique has so far been decisive for clinicians for better durability of resin-dentin bonds of adhesive systems. The purpose of this study was to systematically review the literature to evaluate the bonding performance of adhesive systems to dentin by using different application modalities. The systematic research strategy was conducted by two reviewers among multiple databases: PubMed, Scopus, Web of Science, Embase, and Scielo. In vitro studies reporting the effects of additional steps for the application of adhesive systems on the bond strength to dentin were selected. Meta-analysis was performed using Review Manager Software version 5.3.5 using the random effects model. The methodological quality of each in vitro study was assessed according to the parameters of a previous systematic review. The electronic research through different databases generated a total of 8318 references. After the examination of titles and abstracts, a total of 106 potentially relevant studies accessed the full-text evaluation phase. After full-text examination, 78 publications were included for the qualitative analysis, and 68 studies were included in the meta-analysis. Regarding the etch-and-rinse adhesive systems, the application modalities that improved the overall bond strength were the application of a hydrophobic resin layer (p = 0.005), an extended application time (p < 0.001), an application assisted by an electric current (p < 0.001), a double-layer application (p = 0.05), the agitation technique (p = 0.02), and the active application of the adhesive (p < 0.001). For self-etch adhesive systems, the techniques that improved the overall bond strength were the application of a hydrophobic resin layer (p < 0.001), an extended application time (p = 0.001), an application assisted by an electric current (p < 0.001), a double-layer application (p < 0.001), the agitation technique (p = 0.01), and the active application of the adhesive (p < 0.001). The in vitro evidence suggests that the application of adhesive systems using alternative techniques or additional strategies may be beneficial for improving their bond strength to dentin. The application modalities that favored the overall bond strength to dentin were an extended application time, a double-layer application, an application assisted by an electric current, the active application of the adhesive, and the application of a hydrophobic resin layer. Worth mentioning is that some techniques are intended to increase the degree of the conversion of the materials, and therefore, improvements in the biocompatibility of the materials can be expected.

Bond strength between temporary 3D printable resin and conventional resin composite: influence of cleaning methods and air-abrasion parameters

OBJECTIVES

The influence of different cleaning methods, air-abrasion parameters, and aging on shear bond strength (SBS) and tensile bond strength (TBS) of 3D resin luted to composite resin.

MATERIALS AND METHODS

Nine hundred resin substrates were 3D printed (D20II, Rapid Shape) and cleaned with either isopropanol (ISO), butyldiglycol-based solution (BUT), or centrifugation (CEN). After 24-h storage in 37 °C water, specimens were air-abraded (mean particle size 50 µm; n = 60) with either alumina at 0.1 MPa (AL0.1) or 0.4 MPa (AL0.4) and glass pearls at 0.1 MPa (GP0.1) and 0.4 MPa (GP0.4) or conditioned with visio.link (control) and luted with PanaviaV5. Initially (24 h, 37 °C water storage) or after aging (10,000 thermal cycles), SBS and TBS were measured, and fracture types were examined. Surface free energy (SFE) and roughness (Ra) were determined after air-abrasion. Kolmogorov-Smirnov, Kruskal-Wallis H, Mann-Whitney U, chi-square, and partial eta-squared were computed.

RESULTS

SBS measurements presented higher values than TBS (p < 0.001-0.033). Within the pretreatment groups, CEN showed the highest SBS and TBS values compared to cleaning with ISO or BUT (p < 0.001-0.040). Pretreatment with GP0.1 displayed the lowest bond strength values (p < 0.001-0.049), and mostly adhesive fractures occurred. The highest Ra values (p < 0.001) were observed for AL0.4 pretreatment.

CONCLUSIONS

Pretreatment with AL0.4 and the control group mainly presented the highest bond strength values. Thermocycling had a positive effect on the bond strength.

CLINICAL RELEVANCE

According to this study, 3D-printed restorations should be pretreated with AL0.4 or with visio.link before adhesive luting, regardless of their cleaning.

Development of Proanthocyanidin-Loaded Mesoporous Silica Nanoparticles for Improving Dental Adhesion

Dentin biomodification is a promising approach to enhance dental tissue biomechanics and biostability for restorative and reparative therapies. One of the most active dentin tissue biomodifiers is proanthocyanidin (PAC)-rich natural extracts, which are used in the dental bonding procedure in combination with resin-based adhesives (RBAs). This study aimed to investigate the use of mesoporous silica nanoparticles (MSNs) for the sustained delivery of PACs for dentin biomodification as a novel drug-delivery system for dental applications. The effects of the incorporation of MSN functionalized with 3-aminopropyltriethoxysilane (APTES) and loaded with PAC into an experimental RBA were assessed by characterizing the material mechanical properties. In addition, the immediate and long-term bonding performance of an experimental resin-based primer (RBP) containing MSN-APTES loaded with PAC was also evaluated. For that, different formulations of RBA and RBP were prepared containing 20% w/v MSN-APTES loaded with PAC before or after functionalization (MSN-PAC-APTES and MSN-APTES-PAC, respectively). The incorporation of MSN-APTES-PAC did not negatively impact the degree of conversion or the overall mechanical properties of the RBA. However, adding MSN-PAC-APTES resulted in inferior mechanical properties of the experimental RBA. In the adhesion studies, APTES-functionalized MSN was successfully added to an experimental RBP for drug-delivery purposes without compromising the bond strength to the dentin or the failure mode. Interestingly, the sequence of surface functionalization with APTES resulted in differences in the bonding performance, with better long-term results for RBP containing MSN loaded with PAC after functionalization.

Phase Formation, Mechanical Strength, and Bioactive Properties of Lithium Disilicate Glass-Ceramics with Different Al2O3 Contents

Owing to its excellent mechanical properties and aesthetic tooth-like appearance, lithium disilicate glass-ceramic is more attractive as a crown for dental restorations. In this study, lithium disilicate glass-ceramics were prepared from SiO2-Li2O-K2O-P2O5-CeO2 glass systems with various Al2O3 contents. The mixed glass was then heat-treated at 600 °C and 800 °C for 2 h to form glass-ceramic samples. Phase formation, microstructure, mechanical properties and bioactivity were investigated. The phase formation analysis confirmed the presence of Li2Si2O5 in all the samples. The glass-ceramic sample with an Al2O3 content of 1 wt% showed rod-like Li2Si2O5 crystals that could contribute to the delay in crack propagation and demonstrated the highest mechanical properties. Surface treatment with hydrofluoric acid followed by a silane-coupling agent provided the highest micro-shear bond strength for all ceramic conditions, with no significant difference between ceramic samples. The biocompatibility tests of the material showed that Al2O3-added lithium disilicate glass-ceramic sample was bioactive, thus activating protein production and stimulating the alkaline phosphatase (ALP) activity of osteoblast-like cells.

Evaluation of Bond Durability, Surface Morphology, and Remineralization at the Adhesive Interface with Dentin Bonding Agents Modified with Silica-doped Nanohydroxyapatite

Objectives

To compare and evaluate the bond durability, surface morphology, and remineralization of the adhesive layer with newer adhesive systems modified with novel bioactive nanoparticles.

Methodology

Bonding agents evaluated in this study include (a) Conventional dentin bonding agent (CN-DBA) (b) Nanohydroxyapatite (nanoHAP) incorporated dentin bonding agent (NH DBA); (c) Silica doped nanohydroxyapatite (Si nanoHAP) incorporated dentin bonding agent (Si NH DBA). A total of 104 human dentin discs (5 mm × 5 mm × 2 mm) were sectioned. Elemental analysis (Ca/P ratio) and surface morphology of the adhesive layer with different dentin adhesives were evaluated under scanning electron microscopy with energy-dispersive X-ray analysis after speculated storage time of 1 day and 6 months. Microshear bond strength of adhesive restorations with different dentin adhesives was evaluated under universal testing machine and fractographic analysis under scanning electron microscope after speculated storage time of 1 day and 6 months. The results were analyzed using analysis of variance and post hoc analysis.

Results

Si-NH-DBA showed highest mean microshear bond strength for both 1 day and 6 months, which was significantly higher compared to conventional nanofilled dentin bonding agent (CN-DBA) and NH-DBA. Si-NH-DBA group showed only 10% reduction in bond strength after 6 months, which was less compared to that of other groups. Similarly, Si-NH-DBA showed higher remineralization with stellate-shaped crystals at the adhesive layer after 6 months with hydrolytic resistant hybrid layer, compared to CN-DBA and NH-DBA.

Conclusion

Silica-doped nanohydroxyapatite proved its efficiency on bond stability, remineralization, and hydrolytic resistance when incorporated into dentin bonding agents because of its bioactivity and carbonate-containing apatite-forming ability.

Effect of quercetin pretreatment on the immediate and aged bond strength of bleached dentin

This in vitro study aimed to investigate the effect of quercetin pretreatment on the bond strength of bleached dentin. Human dentin blocks (2 × 2 × 1 mm) were prepared and randomly divided into 5 groups (n = 16): deionized water pretreatment + no bleaching treatment (DNB); deionized water pretreatment + bleaching treatment (DYB); 75 μg/mL quercetin pretreatment + bleaching (Q75B); 150 μg/mL quercetin pretreatment + bleaching (Q150B); and 300 μg/mL quercetin pretreatment + bleaching (Q300B). The surfaces of superficial dentin (bonding surfaces) were treated with the respective solutions for 2 min, and then the surfaces opposite to the bonding surfaces (near pulp, bleaching surfaces) were subjected to bleaching treatment with 40% hydrogen peroxide (Ultradent, USA) for two 15-min sessions (groups DYB, Q75B, Q150B, and Q300B). After the bleaching procedure, the bonding surfaces were bonded with resin cements (Panavia V5, Kuraray, Japan). The bonded specimens were then divided into 2 subgroups (n = 8): the aging group (subgroup T), which was subjected to 10,000 thermocycles, and the nonaging group (subgroup N), which was not subjected to thermocycling. The microshear bond strength (μSBS) was obtained using a universal testing machine (AGS-X, Shimadzu, Tokyo, Japan). Additional dentin blocks (5 × 5 × 1 mm) were prepared and treated the same as the groups DYB, Q75B, Q150B, and Q300B (n = 8) to evaluate the color change, defined as groups CC_DYB, CC_Q75B, CC_Q150B, and CC_Q300B, respectively. Color evaluation was performed using a spectrophotometer (Vita Easyshade Advance 4.0, Vident, USA) to obtain a baseline and again at the end of the bleaching treatment. The data were analyzed via two-way analysis of variance (ANOVA) and Tukey's post-hoc test (α = 0.05). For the immediate bond strength, the specimens in the groups Q75B, Q150B, and Q300B showed significantly higher μSBS values than those in the group DYB (all P < 0.05). No significant differences in the μSBS values were found among the groups Q75B, Q150B, Q300B, and DNB, respectively (all P > 0.05). For the aged bond strength, both the groups Q150B and Q300B exhibited significantly higher μSBS values than groups DYB and DNB (all P < 0.05), whereas no significance differences were found between groups Q150B and Q300B (P = 1.00) or between the groups DYB and DNB (P = 1.00). No significant differences were observed in the △E values among all the groups tested (P = 0.80). Therefore, the application of quercetin for 2 min prior to the bleaching procedure preserved the immediate bond strength and improved the aged bond strength of bleached dentin while maintaining the effectiveness of bleaching.

Long-term microtensile bond strength of self-etch adhesives and influence of 7-s phosphoric acid etching on adhesion of a 3-step etch-and-rinse adhesive to the dentine of primary teeth

BACKGROUND

The immediate microtensile bond strength (µTBS) of self-etch (SE) adhesives to primary dentine is promising, but evidence about the durability is scarce.

AIM

To assess the long-term µTBS of SE adhesives to primary dentine and to examine the effect of 7-s etching on µTBS of a 3-step etch-and-rinse (ER) adhesive.

DESIGN

The enamel of 115 caries-free human primary teeth was ground flat, and bonding was performed according to group assignment: G-aenial™ Bond/GC [GB], Clearfil™ SE Bond/Kuraray [CS], OptiBond™ XTR/Kerr [OX], Scotchbond™ Universal/3M™ [SU], Prime&Bond^® NT™/Dentsply [PB], and OptiBond™ FL/Kerr [OF]. After storage (24 h, 6 mos., 12 mos.), 1,762 beams were cut for µTBS testing. Fracture analysis was performed using light/fluorescence microscopy. Resin-dentine interfaces were exemplarily analyzed using SEM.

RESULTS

After 24 h, OX and SU showed significantly higher estimated mean µTBS than GB, which exhibited the lowest µTBS at all stages (p < .05). μTBS within each adhesive group showed slight variations over time (p > .05). OF_SE produced acceptable µTBS. Etching increased the mean immediate µTBS for OF (p > .05) and the percentage of cohesive fractures.

CONCLUSIONS

SE adhesives achieved durable μTBS to primary dentine. 7-s etching may improve the immediate µTBS of a 3-step ER adhesive.

Does adding accelerators to Mineral Trioxide Aggregate affect the shear bond strength?

Amaç: Bu çalışmada, farklı hızlandırıcı ilave edilen Mineral Trioksit Agregat’ın (MTA) kompozite farklı sertleşme sürelerinde makaslama bağlanma dayanımının (MBD) değerlendirilmesi amaçlanmıştır. Gereç ve Yöntemler: Merkezi boşluklara sahip 120 adet akrilik blok 4 ana gruba ayrıldı. 1. grup (kontrol); sadece MTA, 2, 3 ve 4. grup ise sırasıyla %10 kalsiyum klorür (CaCl2), %23,1 kalsiyum laktat glokonat (CLG) ve %15 disodyum hidrojen fosfat (Na2HPO4) ile karıştırılmış MTA içermektedir. Her grup 2 saat 45 dakika , 24 saat ve 96 saat sertleşme süresine göre 3 alt gruba ayrıldı. Bekleme süreleri tamamlandıktan sonra adeziv sistem (Clearfil SE Bond, Kuraray) ve kompozit rezin (Clearfil Majesty, Kuraray) işlemleri tamamlanan örneklere evrensel test cihazında MBD testi uygulandı. Elde edilen verilerinin karşılaştırmasında, tek yönlü varyans analizi (ANOVA) ve Tukey HSD testleri kullanıldı. Bulgular: Hızlandırıcısız MTA en yüksek ortalama MBD değeri sergiledi. Hızlandırıcısız MTA, hızlandırıcı olarak CLG ve Na2HPO4 eklenen MTA ile kıyaslandığında aralarındaki fark anlamlı bulundu (p&lt;0.0001). Başlangıç sertleşme süresinde alt gruplar arasında istatistiksel olarak anlamlı farklılık gözlenmedi (p&gt;0,05), diğer sertleşme sürelerinde fark anlamlı bulundu (p&lt;0,05). MTA’ya hızlandırıcı olarak CLG ve Na2HPO4 ilavesinin tüm sürelerde MBD değerlerini azalttığı, CaCl2 ilavesinin ise 96 saatin ardından MBD değerini anlamlı olarak yükselttiği gözlendi. Sonuç: MTA içerisine hızlandırıcı eklemek MBD değerini düşürmektedir. Ancak MTA’ya hızlandırıcı olarak %10 CaCl2 eklemek 96 saatin ardından yapılacak restoratif işlemlerde pozitif bağlantı sonuçları ortaya çıkarabilir.

Influence of mechanical and chemical pre-treatments on the repair of a hybrid ceramic

OBJECTIVES

This study aimed to investigate the influence of the respective mechanical and chemical pre-treatments on the composite repair of a CAD/CAM hybrid ceramic using a microtensile bond strength test (μTBS).

METHODS

15 CAD/CAM Blocks of Vita Enamic (VE) were randomly sectioned into three mechanical pre-treatments: (1.) Diamond bur (D), (2.) Airborne abrasion (A), (3.) Tribochemical silica coating (T) and subsequently five chemical pre-treatments: (1.) Clearfil SE Bond Bond (B; negative control), (2.) ESPE Sil (S), (3.) Clearfil Ceramic Primer Plus (CPP), (4.) Clearfil Repair (CR) and (5.) Scotchbond Universal (SCB). Per block, n = 20 specimens were sawn. Half of the specimens were randomly selected and subjected to an immediate bond strength test, while the other half was subjected to artificial aging for 6 months 180 days at 37 °C and subsequent thermocycling of 5000 cycles. A μTBS was performed and data (MPa) were compared in one-way and two-way ANOVA and Tukey's HSD. Paired-t-test was used for artificial aging (α = 0.05). Debonded specimens were analyzed of for failure modes with a stereomicroscope (SEM).

RESULTS

The results of one-way ANOVA for the fifteen fastening procedures after aging indicated significant differences according to SCB-A and CPP-T. Two-way ANOVA after aging observed inferior bond strength for SCB. No differences were observed for mechanical pre-treatments. Artificial aging showed a significant reduction in bond strength on most of the fastening procedures.

SIGNIFICANCE

SCB showed the lowest bond strength values besides B, S, CPP, and CR. MDP and silane are both suitable for the repair of VE.

Evaluation of the Effect of the Loading Time on the Microtensile Bond Strength of Various Restorative Materials Bonded to Silver Diamine Fluoride-Treated Demineralized Dentin

The aim of this study was to evaluate the effect of immediate versus delayed loading times on the microtensile bond strength (μTBS) of restorative materials, including resin-based composite (RBC), resin-modified glass ionomer cement (RMGIC) and glass ionomer cement (GIC), that were bonded to silver diamine fluoride (SDF)-treated demineralized dentin. Ninety caries-free extracted premolar teeth were assigned to three groups (n = 30) loaded with RBC, RMGIC and GIC restorative materials. Each group was further divided into three subgroups (n = 10): subgroup A (control specimens), immediate loading of the restorative material on sound dentin; subgroup B, demineralized dentin, SDF treatment and immediate loading of the restorative material; and subgroup C, demineralized dentin, SDF treatment and restorative material loading a week later. One-way ANOVA and Tukey’s post-hoc tests were performed to compare the μTBS values. The RBC exhibited the highest µTBS, followed by RMGIC and GIC. Multiple comparisons showed an increase in the µTBS in the delayed loading groups irrespective of the restorative material used. The majority of the failure modes were adhesive. Delayed loading of RMGIC for 1 week after SDF application showed significantly higher µTBS than that of immediate loading.

Effect of mold enclosure and chisel design on fatigue bond strength of dental adhesive systems

To examine the effect of mold enclosure and chisel design on macro shear fatigue bond strengths of dental adhesive systems. The fatigue bond strength testing was conducted with two commercially available dental adhesive systems, (1) OptiBond eXTRa and (2) Scotchbond Universal, for bonding a resin composite (Filtek Supreme Ultra) to both enamel and dentin using a mold enclosure and a non‐mold enclosure with a knife‐edge and two sized notched‐edge chisel assemblies for loading. As a loading reference for the fatigue testing, macro shear bond strengths of the adhesive systems to enamel and dentin were conducted using a mold enclosure and a knife‐edge chisel assembly. The shear bond strengths with the mold enclosure using knife‐edge chisel assembly did not exhibit a significant difference between the adhesive systems for either enamel or dentin. The fatigue bond strengths of bonded specimens demonstrated significant differences when comparing the mold enclosure and non‐mold enclosure, but not between knife‐edge and notched‐edge chisel assemblies. The fatigue bond strengths of dental adhesive systems demonstrated significantly higher values when using mold‐enclosed bonded specimens than a non‐mold enclosure, regardless of type of chisel assembly.

Effect of Different Mouthwashing Regimens on Adhesion of a Universal Adhesive:A Microshear Bond Strength and Scaning Electron Microscopy Evaluation

Objective: To evaluate the effect of probiotic or chlorhexidine-based mouthwashes and coconut oil pulling therapy on microshear bond strength of a universal adhesive, used with two application modes. Method: Ninety-six enamel specimens were prepared using bovine incisors and the surfaces were grounded. Then the specimens were randomly divided into 4groups and each group were subjected to a mouth washing regimen with one of three agents-chlorhexidine mouthwash, probiotic-based mouthwash, coconut oil pulling – or stored in artificial saliva(control) for 7 days(n=24). After the procedure, all groups were divided into 2 subgroups, and a universal adhesive was applied with etch-and-rinse or self-etch mode(n=12). Composite micro-cylinders were bonded to the enamel surfaces and micro-shear-bond strength was measured after 24hours water storage. Failure modes were determined using a stereomicroscope and SEM analysis was also performed. The data were analyzed using Mann-Whitney-U and Kruskal-Wallis tests. Results: No significant differences were observed between the different mouthwash groups, regardless of application modes(p> .05). There were no significant differences in microshear-bond strength, within the same mouthwash groups, between self-etch or etch-and-rinse modes, except for oil pulling group. Etch-and-rinse group showed higher bond strength than self-etch group in specimens subjected to oil pulling(p< .05). Conclusion: Etch-and-rinse mode might be preferable on patients who practice oil pulling.

The micro-shear bond strength of resin cements to aged laser bleached enamel after using different desensitizing agents

OBJECTIVES

To evaluate the micro-shear bond strength of two resin cements to aged laser bleached enamel after the application of three different desensitizing agents.

MATERIALS AND METHODS

Forty extracted human central and lateral incisors were prepared and bleached using laser activation bleaching protocol. The teeth were assigned randomly into four groups for desensitization; G1: No post-bleaching treatment, G2: GC MI Paste Plus, G3: Hydroxyapatite nanoparticles (n-HAP) and G4: Flor-Opal. Specimens were subjected to aging for 6 months. All groups were subdivided into two subgroups according to the resin cements used (dual-curing resin cement and light-curing resin cement).

RESULTS

Flor-Opal groups showed the highest statistically significant micro-shear bond strength (MSBS), followed by GC MI Paste Plus and n-HAP groups with no statistically significant difference between them. The light-curing resin cement had statistically higher MSBS than dual-curing resin cement in case of no-post bleaching treatment and n-HAP groups, and no statistical difference in case of GC MI Paste Plus and Flor-Opal groups.

CONCLUSION

Usage of desensitizing agents containing, CPP-ACP, n-HAP or fluoride after laser bleaching can enhance the bond strength of the resin cements to enamel.

CLINICAL SIGNIFICANCE

The composition of the desensitizing agents applied after laser bleaching could interfere in bond strength values.

Composite repair: On the fatigue strength of universal adhesives

OBJECTIVES

To determine whether the composition of universal adhesives and the use of silane coupling agents could affect the fatigue strength of composite repair.

METHODS

Composite samples were aged in water at 37 °C for 90 days and bonded to fresh composite to produce twin-bonded bar-shaped composite specimens (2 × 2 × 12 mm). Five universal adhesives, a multistep composite repair system and a hydrophobic solvent-free resin associated to a separate silane coupling agent application were used for bonding. Composite samples were tested under 4-pointflexure initially at quasi-static loading (n = 12) followed by cyclic loading (n = 25). The stress-life fatigue behavior was evaluated following the staircase method at 4 Hz. The unfractured side of cyclic loaded beams were evaluated under SEM to determine crack initiation sites. Fatigue data was analyzed by ANOVA and Tukey test and Wilcoxon Rank Sum Test (α = 0.05).

RESULTS

Bonding protocols were unable to restore the cohesive strength of the nanofilled composite (p < 0.05). Fatigue testing was more discriminative to reveal discrepancies in composite repair than conventional quasi-static loading. While the composition of universal adhesives affected composite repair potential, the highest endurance limits occurred for the separate silane coupling agent application. Crack propagation sites were mostly located on the aged composite surface.

SIGNIFICANCE

Although a trend for simplification invariably overruns current adhesive dentistry, composite repair using solely universal adhesives may result in inferior repair potential. The additonal use of silane coupling agents remains as an important procedure in composite repairs.

Effect of saliva contamination on the bond strength of single-step and three-step adhesive systems

The aim of this study was to evaluate the effect of saliva contamination on bond strength to dentin with an etch-and-rinse and a self-etch adhesive system. For each of these adhesive systems, the dentin surface of 24 human molars were allocated to one of four groups representing different saliva contamination scenarios. Saliva was applied at different stages in the bonding process, and was investigated to be remedied by water rinsing and/or air drying. Uncontaminated tooth surfaces were used as controls. Bonding procedures were performed according to the manufacturer's instructions, and a polymer-based composite was placed. The bond strength was measured by a micro-tensile test. Except for the etch-and-rinse approach having contamination with saliva after etching, followed by air drying, all salivary contamination regimens resulted in a substantial number of specimens not surviving the test, and the bond strength value of these was therefore set to 0 MPa for the purposes of the statistical analysis. Water rinsing after etching and salivary contamination did significantly reduce the bond strength. Contamination after priming showed the lowest bond strength. For the self-etch approach, saliva contamination before the adhesive procedure, followed by air drying, significantly reduced the bond strength, while contamination followed by water rinsing or air drying did not statistically significantly reduce the strength.

Bonding properties of third-generation zirconia CAD-CAM blocks for monolithic restorations to composite and resin-modified glass-ionomer cements

PURPOSE

To compare the interfacial fracture toughness (IFT) of two MDP-based composite cements and a resin-modified glass-ionomer cement (RMGIC) with third-generation zirconia CAD-CAM restorations using two different airborne-particle abrasion (AB) pressures.

METHODS

Blocks were cut into prisms (n=60), split and sintered to the desired equilateral half prisms. Half-prisms were divided into two groups for AB at 0.5 or 2.5 bar with 50 µm Al₂O₃ particles. Each group was then further divided into 3 subgroups, and half-prisms were bonded to their counterparts with Panavia V5 (V5), Panavia Self Adhesive Cement Plus (SA), or RMGIC Fuji Plus (n=10/group). The IFT was determined using the Notchless Triangular Prism test in a water bath at 36°C after thermocycling (10,000 cycles). Surface roughness and SEM analyses were performed for representative zirconia samples after AB, and composite cements were tested for flexural strength and wettability.

RESULTS

SA (2.5 bar) showed a significantly higher IFT. The 3 other groups with SA and V5 showed no significant difference in their IFT values regardless of the AB pressure (1-way ANOVA). Weibull analysis of SA was higher than V5. All RMGIC samples debonded while thermocycling, and were, therefore, not included in the statistical analysis. Surface roughness increased with increasing AB pressure, and both cements showed similar flexural strength values and good wettability.

CONCLUSION

Contrary to RMGIC, composite cements show high performance with zirconia after AB. Increasing AB pressure enhances the micromechanical retention of composite cement. Future perspectives should include study of the effect of AB pressure on zirconia surface properties.

Effects of application method on shrinkage vectors and volumetric shrinkage of bulk-fill composites in class-II restorations

OBJECTIVES

Upon initial proximal wall construction, the favorable C-factor of class-II cavities may become unfavorable. This study investigated the application method on bulk-fill resin composite polymerization shrinkage.

METHODS

Occluso-proximal class-II cavities were prepared in 40 molars and bonded with a self-etch adhesive (Adhese Universal). The study groups varied according to the resin composite application: group-1: bulk application, Tetric EvoCeram Bulk Fill (TBF); group-2: proximal wall construction (TBF) and occlusal cavity filling (TBF); group-3: thin flowable liner layer, Tetric EvoFlow Bulk Fill (TEF) and bulk filling (TBF); group-4: flowable liner (TEF), proximal wall (TBF), occlusal cavity (TBF); and group-5: bulk application, SDR (3 mm) and capping layer (TBF, 1 mm). Each resin composite increment was scanned twice using micro-CT (uncured, cured 40 s) at a resolution of 16 µm. Shrinkage vectors and volumetric polymerization shrinkage were evaluated and statistically analyzed (one-way ANOVA). SEM images were used to investigate the tooth-restoration interface.

RESULTS

Shrinkage vectors differed significantly among the groups and were greatest in gp5-fl/SDR (47.6 µm), followed by gp1-TBF (23.8 µm) and least in gp5-fl/SDR+TBF (11.1 µm). Volumetric shrinkage varied significantly with the use of SDR (gp5-fl/SDR: 2.6%) and TEF (gp4-fl/TEF: 2.5%) to TBF (gp4-fl/TEF+wl/TBF: 0.6%) in the incremental application.

SIGNIFICANCE

Building a proximal resin composite wall yielded smaller shrinkage vectors than the bulk application. Applying a thin flowable liner decreased the shrinkage vectors, even more when building a proximal wall. A thin flowable liner is recommended when building a proximal resin composite wall.

Using bonding agent prior to pits and fissure sealant application enhances the microtensile bond strength and the interface morphology

Background

A pits and fissures sealant is an effective method for preventing dental caries. Using a bonding agent before applying the sealant may increase its retention. This study aimed to compare the microtensile strength (µTBS) of a fissure sealant with and without a bonding agent and to characterize the enamel-sealant interface using confocal laser scanning microscopy (CLSM). The null hypothesis was that the use of a bonding agent before fissure sealant application would not change the microtensile strength or the enamel-sealant interface.

Materials and methods

Twenty caries-free premolars were used. Each tooth was divided into four parts. The first two parts were assigned to the bonded group, where a bonding system was used before sealant application. The remaining two parts were treated only with a fissure sealant (i.e., the nonbonded group). In each group, the µTBS was examined after 24 h (n = 20) and after a 3-month aging period (n = 20). Five other caries-free extracted premolars were used to assess the enamel-sealant interface using CLSM. Two-way analysis of variance (ANOVA) and Pearson chi-square statistical analysis tests were used to analyze the µTBS and the enamel-sealant interface, respectively.

Results

The mean µTBS for the bonded group was significantly higher (p = 0.001) in the immediate group (36.87 ± 14.95 MPa) and the aged group (31.08 ± 15.88 MPa) than in the respective nonbonded groups (19.77 ± 9.67 MPa and 19.52 ± 14.14 MPa). The µTBS was not significantly different in either group after aging (p = 0.46 [bonded group] and p = 0.98 [nonbonded group]). In addition, using a dental adhesive, before applying a fissure sealant resulted in a significantly higher (53%) resin penetration into the enamel with the continuous integrity of the resin.

Conclusion

The use of a bonding agent before the application of fissure sealant resulted in superior microtensile bond strength immediately and after aging. In addition, the enamel-sealant interface characteristics were improved.

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.

[Laboratory methods for measuring adhesive bond strength between restoration materials and hard tooth tissues]

THE AIM OF THE STUDY

Was to review laboratory methods measuring the bond strength of adhesive dental materials to hard tooth tissues. The paper points out the impact of test conditions on the measured strength of adhesive bond to dentine and enamel. Various in vitro studies are discussed, including the analyses of fracture surfaces and test-induced stresses. These studies are found to be helpful to identify particularities, advantages, and limitations of each approach. We present a systematic picture of available bond-strength data aimed at revealing general trends in adhesive performance. No clear superiority of any particular method for determining the bond strength between restoration materials and tooth tissues can be identified on the basis of reviewed literature. Therefore, no single universal approach can be at present proposed for determining the strength of adhesive bond.

Does Simulated Porcelain Firing Influence Corrosion Properties of Casted and Sintered CoCr Alloys?

The aim of the study was to evaluate how heat processing used for dental porcelain firing influences the surface properties of sintered and casted CoCr alloy. Two CoCr alloys, Soft Metal LHK (milling in soft material and sintering) and MoguCera C (casting), were used for the study. The samples were examined using SEM-EDS before and after heat treatment. Next, corrosion examinations (E_corr, j_corr, polarization curve, E_br) were performed. Finally, the samples were evaluated under SEM. Based on the results, the following conclusions might be drawn: 1. Thermal treatment (porcelain firing) did not cause chemical impurities formation on the surface of CoCr alloy; 2. The sintered metal exhibited significantly higher corrosion resistance than the casted one due to its homogeneity of structure and chemical composition; 3. Heat treatment (porcelain firing) decreased the resistance of casted and sintered CoCr alloy to electrochemical corrosion. The reduction in corrosion resistance was significantly higher for the casted alloy than for the sintered alloy; 4. The corrosion resistance decrease might be due to an increased thickness and heterogeneity of oxide layers on the surface (especially for the casted alloy). The development of corrosion process started in the low-density areas of the oxide layers; 5. The sintered metal seems to be a favourable framework material for porcelain fused to metal crowns.

Effect of Die Spacer Thickness on the Microshear Bond Strength of CAD/CAM Lithium Disilicate Veneers

Aim

The aim of this study was to compare the microshear bond strength of ceramic veneers with digital die spacer settings at 20, 40, and 100 µm.

Materials and Methods

Eighteen milled lithium disilicate microdiscs (IPS e.max CAD, Ivoclar Vivadent) were divided into three groups (n = 6) according to their digital die spacer settings: group A = 20 µm, group B = 40 µm, and group C = 100 µm. Six randomly selected sound maxillary premolars received three microdiscs each. Each microdisc was 1 mm in diameter and 1 mm in height. The buccal surfaces of the premolars were prepared with a 0.5 mm depth in enamel. After cementation, the specimens were thermocycled for 2,500 cycles between 5 and 55°C. Microshear bond strength testing was performed using a universal testing machine until bonding failure. Failure modes were evaluated using a stereomicroscope. Statistical analyses included one-way ANOVA, Tukey's post hoc test, and chi-square test with a 5% alpha error and 80% study power.

Results

The mean microshear bond strength values were calculated in MPa for group A = 31.91 ± 12.41, group B = 29.58 ± 5.03, and group C = 13.85 ± 4.12. One-way ANOVA (p ≤ 0.05) showed a statistically significant difference in microshear bond strength among the three groups. Tukey's post hoc test showed significant differences between groups A and C (p=0.004) and between groups B and C (p=0.011). The failure modes were presented as cohesive, adhesive, and mixed failures. Chi-square test indicated that the failure mode distribution was not significantly different among the three groups (p=0.970).

Conclusion

Higher digital die spacer settings decrease the microshear bond strength of CAD/CAM lithium disilicate veneers.

Influence of reduced application time on bonding durability of universal adhesives to demineralized enamel

OBJECTIVES

This study aimed to assess the effect of application time on the microshear bond strength (μSBS) of three universal adhesives in demineralized and sound enamel before and after aging.

MATERIALS AND METHODS

Bovine teeth (192) were prepared where buccal surfaces were ground and divided into two groups (sound enamel and demineralized enamel). The specimens in each group were divided into 12 subgroups by combining 3 adhesive agents (All-Bond Universal, Scotchbond Universal, and Tokuyama Universal Bond) × 4 adhesion strategy. Each adhesive was applied with either prolonged (PA) or reduced (RA) application time in etch-and-rinse or self-etch mode. Bonded composites were subjected to μSBS testing after 24-h or 2-year water storage. The results were evaluated using four-way ANOVA and Tukey's post-hoc test (α = 0.05).

RESULTS

The μSBS of adhesives to sound enamel in both etching modes was mostly similar to demineralized enamel, regardless of application time and aging time. At 24-h, all adhesives with PA in self-etch mode showed higher μSBS when compared with RA, except Tokuyama Universal Bond, but after 2-year aging, no significant difference was found in μSBS between RA and PA. The μSBS of adhesives with PA in etch-and-rinse mode depended on used adhesive and enamel condition compared to RA, regardless of μSBS testing time.

CONCLUSIONS

PA of adhesives did not reveal a significant difference in μSBS to enamel, regardless of substrate type and etching mode.

CLINICAL RELEVANCE

After 2-year aging, the bond strength of universal adhesives presented no significant difference between PA and RA treatments.

Probing the mineralized tissue-adhesive interface for tensile nature and bond strength

The mechanical performance of the dentin-adhesive interface contributes significantly to the failure of dental composite restorations. Rational material design can lead to enhanced mechanical performance, but this requires accurate characterization of the mechanical behavior at the dentin-adhesive interface. The mechanical performance of the interface is typically characterized using bond strength tests, such as the micro-tensile test. These tests are plagued by multiple limitations including large variations in the test results. The challenges associated with conventional tensile tests limit our ability to unravel the complex relationships that affect mechanical behavior at the dentin-adhesive interface. This study used the diametral compression test to overcome the challenges inherent in conventional bond strength tests. The bovine femur cortical bone tissue was considered as a surrogate material (the mineralized tissue) for human dentin. Two different adhesive formulations, which differed by means of their self-strengthening properties, were studied. The tensile behavior of the mineralized tissue, the adhesive polymer, and the bond strength of the mineralized tissue - adhesive interface was determined using the diametral compression test. The diametral compression test improved the repeatability for both the tensile and bond strength tests. The rate dependent mechanical behavior was observed for both single material and interfacial material systems. The tensile strength and bond strength of the mineralized tissue-adhesive interface was greater for the self-strengthening formulation as compared to the control.

Adhesion between zirconia and resin cement: A critical evaluation of testing methodologies

This study aimed to analyze different methodologies (tensile, microtensile, shear, microshear, and interfacial toughness) for evaluation of the bond strength between zirconia (Y-TZP) and resin cement. Zirconia ceramic blocks (VITA in-Ceram® YZ, VITA Zahnfabrik, Germany) were obtained, substrate surfaces were air-abraded with aluminum oxide (50 μm) for 10 s (2 bar pressure, distance: 10 mm, angle: 90°). Then, the specimens were washed with distilled water, dried, and coated with Clearfil Ceramic Primer that was actively applied with a microbrush for 20 s. The specimens were then cemented with resin cement under a load of 750 g, followed by photo-polymerization (40 s on each surface). After cementation, the specimens were aged in thermocycling (8000 cycles, 5-55 °C, 30 s for each bath) and subjected to tensile, microtensile, shear, microshear or interfacial toughness tests. All specimens were inspected for failure modes. The microtensile test showed the highest bond value (18.29 N/mm²). The microshear tests showed the highest coefficient of variation (0.59) and highest number of pre-test failures. The interfacial energy to fracture test showed that as the shear stress increased its interaction in the adhesive interface, the coefficient of variation also increased. The bond strength of Y-TZP showed different results according to the methodology, as well as its interfacial energy to fracture varied according to the angulation/type of stress specimen was submitted. The lower the shear stress at the adhesive interface of the mixed tests (interfacial energy to fracture), the lower was the variability of the test.

The Influence of Blade Type and Feeding Force during Resin Bonded Dentin Specimen Preparation on the Microtensile Bond Strength Test

This paper presents the effect of blade type and feeding force during resin-bonded dentin specimen preparation on the microtensile bond strength (μTBS) test. Forty resin-bonded flat middle dentin specimens were divided into four groups. The specimens of each group were sectioned according to type of blade and feeding force as follows: fine grit/20 N, fine grit/40 N, medium grit/20 N, and medium grit/40 N to obtain resin-dentin sticks with a cross-sectional area of 1.0 mm². Four sticks from the center of each tooth were subjected to the μTBS test. Five remaining sticks of each group were selected for surface topography observation under a scanning electron microscope (SEM). As a result, the bond strength of the medium-grit group was higher than that of the fine-grit group (p < 0.001), whereas the feeding force had no influence on bond strength values (p = 0.648). From the SEM, sticks prepared with the fine-grit blade showed a smoother surface integrity and fewer defects on the specimen edges in comparison with the sticks prepared with the medium-grit blade. The grit type of the blade is one of the considerable factors that may affect the bond strength and the surface integrity of resin-dentin specimens for microtensile testing.