Adequate Bond Strength Research Articles

Trustworthy machine learning-enhanced 3D concrete printing: Predicting bond strength and designing reinforcement embedment length

Three-dimensional concrete printing (3DCP) faces challenges in determining and ensuring adequate bond strength between reinforcement and printed concrete. Traditional methods for predicting bond performance are merely deterministic without considering potential uncertainty, which would lead to risks for structural safety. To address this issue, this paper develops a trustworthy machine learning based prediction model for bond strength in reinforced printed concrete (RPC) structures using Natural Gradient Boosting algorithm. This developed model provides both scalar bond strength predictions and corresponding standard deviations, and in the test, it achieved a 94.5% safety rate and outperformed empirical formulas and deterministic approaches. Instructive guidance can be offered for structural engineers and designers in determining reinforcement embedment lengths for 3D-printed concrete during constructions. This probabilistic prediction approach can further enhance the safety and efficiency of digitally fabricated concrete structures, potentially extending its application to other critical parameters in printed concrete.

Evaluation of Bond Strength of Concrete Repaired Using Polyurethane Grout Material under Static and Impact Loads Coupled with Statistical Analysis.

The effectiveness of repair work relies on whether the interface substrate can achieve sufficient bond strength when subjected to numerous stresses. This study investigated the bond properties of repaired normal concrete (NC-to-NC) elements, including cube, beam, and U-shaped specimens, after undergoing natural fracture due to flexural and tensile stresses. The specimens were repaired using a polyurethane (PU) matrix by gluing the two parts and applying compression, splitting, and drop-weight impact (DWI) tests to evaluate the bond strength properties. The results revealed that the PU matrix effectively repairs NC substrate with adequate bond strength, which exceeds the minimum allowable bond strength specified in the ASTM ACI 546-06 to rehabilitate damage concrete structures. The reference beams exhibit a peak applied load capacity of 15.6 kN with less deflection than the repaired samples. The compressive strength of the NC-to-NC repaired specimens loaded along and parallel to the interface plane revealed a decrease in compressive strength of 47.3% and 31.5% compared to the NC-R samples, respectively. The mean number of blows at the cracking stages appeared nearly equal for reference and repaired NC-to-NC specimens. The reference specimens exhibited an average number of 24 and 31 blows at the initial and failure stages, respectively, which were higher by 9.1% and 5.2% than the NC-to-NC repaired specimens. The PU binder showed promising results in achieving adequate interfacial bond strength under static and impact loads.

Enhancing the Opacity of Glass Ceramics by Applying Opaque Stains to the Intaglio Surface.

The aim of this study was to assess the effect of opaque stain application to the intaglio surface of lithium disilicate glass ceramics on the masking ability of discolored substrates and bond strength to a resin-based luting agent (depending on etching time); the stain film-thickness was also assessed. Ceramic specimens were produced with CAD-CAM blocks of lithium disilicate (IPS e.max CAD). Two opaque stains were tested at ceramic intaglio surface: opaque glassy stain for titanium frameworks (OP-ti) and low-fusion glassy stain for ceramic characterization (LFG-iv). Non-stained ceramic specimens served as controls. For optical and colorimetric analyses, A2-shaded ceramics of medium and low-translucencies were tested, in thicknesses of 1.0- and 1.5-mm (n = 10), with two coupling agents (non-shaded-glycerin and A2-shaded try-in paste). CIEDE2000 formula was used for calculation of translucency parameter (TP00) and color differences (ΔE00). Whiteness index for dentistry (WID) was also reported. ΔE00 were assessed over discolored substrates (tooth-shaded A2-reference, A4, C3, and C4; coppery metal, silvery metal, white zirconia, and PEEK). Microshear bond strength of stained and non-stained ceramic specimens to a resin-based luting agent was evaluated. Film-thickness of stains was assessed by scanning electron microscopy. The application of opaque stains to the intaglio surface of lithium disilicate ceramics resulted in significant reduction of TP00 (p < 0.001) and WID (p < 0.001) and differences in L*, C*, and ho color coordinates (especially with OP-ti) (p < 0.001). ΔE00 was significantly reduced in stained ceramic groups in comparison with the control, for all discolored substrates (p < 0.001). Acceptable color matching was obtained with stained ceramic specimens for all discolored substrates, depending on the type of stain, ceramic thickness, ceramic translucency, and coupling agent. The application of stains to the ceramic intaglio surface was not detrimental to bond strength to a resin-based luting agent, but depended on the time of hydrofluoric acid-etching (20 s for OP-ti and 60 s for LFG-iv) (p < 0.001). Film-thickness of stains presented mean values <70 μm. The application of opaque stains to the intaglio surface of lithium disilicate glass ceramics was effective to mask severely discolored substrates, presenting adequate bond strength to the luting agent and thin film-thicknesses. For indirect restorations over severely discolored substrates, the application of opaque stain to the intaglio surface of lithium disilicate glass ceramic ensures acceptable color matching, with adequate bond strength to resin-based luting agents and clinically acceptable stain film-thickness.

Evalution of shear bond strength of brackets bonded using different hydrophobic and hydrophilic adhesives: An invitro study

A review of the long history of orthodontic bonding adhesives shows that many evolutional developments have occurred from the first chemically-cured composite resins to the most recently introduced light-cured color-change adhesives. An ideal orthodontic adhesive should have adequate bond strength while maintaining unblemished enamel after debonding. Therefore, researchers have been working hard to achieve the best quality and gentlest materials for bonding orthodontic brackets.To evaluate the shear bond strength of brackets bonded using four different adhesives in both dry and in moist environment.A total of 80 orthodontically extracted premolars will be selected. They are divided into 4 equal groups of different adhesives which are further sub-divided into 2 group each (dry and in presence of moisture). All the selected teeth will be cleaned and store in saline until it use. All teeth will be mounted on acrylic block. The shear bond strength will be measured by Lloyd’s Universal testing machine. The obtained data will be statistically evaluated using SPSS22 for Windows using ANOVA test at statistical significance.: The shear bond strength of the four groups were tested with Instron universal testing machine; breaking load at which bond failure occurred was recorded and bond strength was calculated. Data obtained was compiled on MS Office Excel Sheet (2007, Microsoft Redmond Campus, Redmond. Washington, United States.)Data was subjected to statistical package for social sciences (SPSS v 21).Statistically significant difference seen between the hydrophobic and hydrophilic adhesives. In the present study we did Tukey’s post hoc test for pairwise comparison of different hydrophobic and hydrophilic adhesives. It show highly significant values. : The greatest bond strength values were achieved with TransbondXT in both dry and saliva contamination condition. These values were significantly greater than those achieved with Greengloo, RMGIC and Aqualine LC. The overall study conclude that TransbondXT was considered the feasible adhesive material for orthodontic bonding followed by Aqualine LC.

Bond Strength Assessment of Normal Strength Concrete-Ultra-High-Performance Fiber Reinforced Concrete Using Repeated Drop-Weight Impact Test: Experimental and Machine Learning Technique.

Ultra-high-performance concrete (UHPC) has been used in building joints due to its increased strength, crack resistance, and durability, serving as a repair material. However, efficient repair depends on whether the interfacial substrate can provide adequate bond strength under various loading scenarios. The objective of this study is to investigate the bonding behavior of composite U-shaped normal strength concrete-ultra-high-performance fiber reinforced concrete (NSC-UHPFRC) specimens using multiple drop-weight impact testing techniques. The composite interface was treated using grooving (Gst), natural fracture (Nst), and smoothing (Sst) techniques. Ensemble machine learning (ML) algorithms comprising XGBoost and CatBoost, support vector machine (SVM), and generalized linear machine (GLM) were employed to train and test the simulation dataset to forecast the impact failure strength (N2) composite U-shaped NSC-UHPFRC specimen. The results indicate that the reference NSC samples had the highest impact strength and surface treatment played a substantial role in ensuring the adequate bond strength of NSC-UHPFRC. NSC-UHPFRC-Nst can provide sufficient bond strength at the interface, resulting in a monolithic structure that can resist repeated drop-weight impact loads. NSC-UHPFRC-Sst and NSC-UHPFRC-Gst exhibit significant reductions in impact strength properties. The ensemble ML correctly predicts the failure strength of the NSC-UHPFRC composite. The XGBoost ensemble model gave coefficient of determination (R2) values of approximately 0.99 and 0.9643 at the training and testing stages. The highest predictions were obtained using the GLM model, with an R2 value of 0.9805 at the testing stage.

Mechanical properties of combined packable and high-filled flowable composite used for the fixed retainer: an in vitro study

BackgroundClinicians often utilize both flowable and packable composites concurrently in bonding fixed retainers. Thus, this study aimed to assess the synergistic effect of these composites in the bonding process.MethodsThis in vitro study divided specimens into three groups: flowable composite (nano-hybrid, Tetric N-Flow, Ivoclar Vivadent), packable composite (nano-hybrid, Tetric N-ceram, Ivoclar Vivadent), and combined use of flowable and packable composite. Shear bond strength (SBS), adhesive remnant index (ARI), and wire pull-out resistance were compared among the groups. Statistical analyses were conducted using ANOVA and Tukey tests to compare study groups. Additionally, Chi-square and Kruskal-Wallis tests were employed to analyze the ARI index among the groups.ResultsANOVA results indicated no statistically significant differences among test groups (P = 0.129) regarding SBS. However, a significant difference existed between flowable and packable composite groups (P = 0.01) regarding ARI scores. Among the study groups, flowable composite exhibited the highest frequencies of ARI scores of 1 and 2, whereas packable composite showed the highest frequency of ARI scores of 0. The combined group had higher frequencies of ARI scores of 0 and 1 compared to the flowable composite. The wire pull-out test revealed that the combined application of flowable and packable composite resulted in significantly lower detachments compared to the packable composite alone (P = 0.008). However, no significant differences were observed in the comparisons between the flowable-packable (P = 0.522) and combined-flowable (P = 0.128) groups.ConclusionThe combined use of flowable and packable composites for fixed retainers demonstrated adequate shear bond strength and ideal ARI scores, suggesting it as a suitable adhesive system for bonding orthodontic fixed retainers.

Predictive model for the interface bond strength of geosynthetic-reinforced asphalt layers

Innovation in the use of geosynthetics in roadway applications has resulted in the development of several different products, such as asphalt reinforcement geogrids and paving mats to minimize reflective cracks and limit moisture infiltration. For a proper performance of the reinforced asphalt systems, an adequate interface bond strength has proven to be crucial. However, the influence of the different paving interlayer characteristics, combined with tack coat types, and tack coat rates on the interface bond strength remains unclear. In this study, a comprehensive program of interface shear tests was conducted using Leutner shear device and laboratory-prepared reinforced asphalt specimens. The program involved eight geosynthetic types, two tack coat types, and three application rates. Results revealed that the geosynthetic type, tack coat type and rate, as well as the interactions among the parameters significantly affect interface bond strength. Multiple linear regression analysis indicated that geogrid aperture area, geosynthetic thickness, geotextile backing thickness, and the presence of bitumen coating are the most affecting parameters on bond strength. A predictive model for the bond strength based on geosynthetic parameters is presented. Based on literature results for specimens extracted from the field, the proposed predictive models were found to adequately predict interface bond strength.

Influence of overlay strength degradation on bond stresses of bridge deck system

This research paper intends to numerically investigate the impact of selected factors on the strength of the concrete overlay-bridge deck bond, directly and indirectly, using the nonlinear finite element analysis (NLFEA) method. Besides, the research introduces the guidelines necessary to attain adequate bond strength to eliminate the possibility of concrete detachment under the effect of different developed stresses. The NLFEA has been utilized in predicting and correlating the live applied loads and the induced shrinkage stresses at the interfacial region between the concrete overlay and the bridge deck. The developed stresses were related to the overlay's direct tensile bond strength. A total of 336 NLFEA models of overlay-bridge deck slab segments were designed and examined after being properly validated. The parameters of the study were as follows: the overlay degradation level (0 %, 19 %, 36 %, 51 %, 64 %, and 75 %); the ratio of the overlay's relative thickness-to-the bridge deck slab (toverlay/tslab); in addition to the age of the shrinkage induced stresses (early age (3 and 7 days) and moderate age (14 and 28 days)). The NLFEA live load and shrinkage stress values were validated using experimental results from the literature with difference percentages of less than 5 %. The numerical study results recommended that the thickness of the concrete's overlay should be within certain overlay thickness limits to be capable of handling the lower and higher stresses at the service and overloading conditions. The proposed guidelines enable the avoidance of unfavorable detachment between the interface parts under the effect of AASHTO HS-20 truck cyclic and impact loadings, as well as shrinkage loading.

Effect of Surface Treatment and Resin Cement on the Bond Strength of an Advanced Lithium Disilicate.

The aim of the study was to evaluate the effect of surface treatment and resin cement on the bond strength of conventional and advanced lithium disilicates (ALDs). Ceramic slices (2 × 13 × 15 mm) of conventional lithium disilicate (LD) (IPS e.max CAD) and ALD (CEREC Tessera) were sectioned, polished, and divided into 16 groups (n = 10) according to the factors: ceramic, surface treatment, and resin cement (Panavia V5 and Variolink Esthetic DC). Surface treatments consisted of hydrofluoric acid 4.9% etching for 20 seconds (Hf20) or 30 seconds (Hf30), self-etching ceramic primer (Se), and sandblasting (Sb). Then, a resin cement cylinder (Ø = 2.5 mm) was manufactured on each specimen's surface. The specimens were then submitted to a shear bond strength (SBS) test. Surface roughness was evaluated through a contact profilometer, and surface morphology was evaluated under scanning electron microscopy for qualitative analysis. Two-way analysis of variance (ANOVA) was used to analyze the data of SBS and surface roughness. For bond strength, the effects of surface treatment, resin cement, and the interaction were analyzed for each ceramic. For roughness, analyzed factors include ceramic and surface treatment. ANOVA revealed that ceramic (p = 0.047) and surface treatment (p < 0.001) factors affected the bond strength, while the cements performed similarly. Both materials showed adequate bond strength (ALD 19.1 ± 7.7 MPa; LD 17.1 ± 7.9 MPa). Sb protocol showed the lowest mean value (9.6 ± 2.9 MPa) compared with Hf20 (22.0 ± 7.1 MPa), Hf30 (21.7 ± 7.4 MPa), and Se (19.3 ± 6.0 MPa). For both ceramics, the highest performance was obtained after applying Se and Hf20 or Hf30. Therefore, longer etching time is unnecessary. Sb protocol must be avoided.

An in-situ method to evaluate the interlayer bond between hot-mix asphalt and portland cement concrete surface

Proper bonding between different layers of a composite pavement is a major factor in ensuring that the entire structure acts as a monolithic layer under load. This paper studies the bonding between hot mix asphalt (HMA) overlay and Portland cement concrete (PCC) pavement using tack coats. An in-situ pull-off test method was developed for use on project sites on a routine basis to screen and test the quality of bond between asphalt layer and concrete layer. This test replaces the arduous process of coring through often times very thick concrete layer with steel rebars, transporting the core to a lab, trimming the concrete side of the core to fit the shear jig, and finally conducting a shear test. Results show that the in-situ pull-off test method developed in this study is strongly correlated to the laboratory based direct shear test. Limits were also suggested to indicate an adequate bond strength in the PCC–HMA interlayer on the basis of laboratory and field testing. This study also evaluates the influence of various factors on the performance of the interlayer bond in laboratory. These factors include the type of tack coat, application rate, the texture of the concrete pavement surface, the surface cleanliness and the surface moisture. Results indicate that sandblasting and hydro-demolition textures offer the best interlayer bond strength, the influence of application rate is not significant on the interlayer bond strength and the influence of surface moisture and cleanliness are dependent on the type PCC surface texture.

Comparative Evaluation of Shear Bond Strength, Adhesive Remnant Index and Cytotoxicity of Different Orthodontic Adhesives: An In-vitro Study

Introduction: Orthodontic adhesives should possess adequate bond strength and biocompatibility. Inadequate bond strength may lead to bond failures, and if the adhesive is not biocompatible, it may result in allergic reactions. Therefore, it is of prime importance to study the cytotoxicity and Shear Bond Strength (SBS) of commercially available orthodontic materials. Aim: This study aimed to comparatively evaluate in-vitro cytotoxicity, the Adhesive Remnant Index (ARI), and SBS of various orthodontic adhesives. Materials and Methods: This in-vitro study was conducted in an institutional setting as a collaborative effort between the Department of Orthodontics and White Lab-Blue Lab at Saveetha Dental College and Hospital, Chennai, India, from July 2023 to August 2023. Forty extracted human premolar teeth were bonded with four different ARI adhesives (U Bond, Enlight, Transbond XT, Aqualine LC) (n=10/group) and mounted on acrylic blocks. They were evaluated for SBS using a Universal Testing Machine (UTM), ARI using Scanning Electron Microscopy (SEM), and cytotoxicity using the MTT {3-(4, 5-dimethylthiazolyl2)-2, 5-diphenyltetrazolium bromide} assay on Human Gingival Fibroblast Cells (HGFC). Statistical analysis was performed using One-way ANOVA, with a post-hoc test for pairwise comparison to evaluate the SBS values, and the Kruskal-Wallis Test to analyse ARI inter group scores and cytotoxicity levels. Statistical Package for the Social Sciences (SPSS) software (Version 23.0) was used to conduct the statistical tests. Results: Significant differences in SBS values (p=&lt;0.001) and ARI scores (p=&lt;0.001) were noted between the different adhesives. No significant difference (p-value=0.534) in cytotoxicity was observed among all adhesives, with all exhibiting acceptable levels of biocompatibility. Conclusion: Primer-based adhesive (Transbond XT) demonstrated the highest SBS and ARI scores among the various orthodontic adhesives, with acceptable levels of biocompatibility. No significant difference was found between the conventional primer-based adhesive (Transbond XT) and the Single Component Adhesive (SCA) (Aqualine LC). Therefore, this study advocates for the use of SCA in routine clinical practice.

The Effect of Preheating of Orthodontic Resin on The Shear Bond Strength of Convensional Orthodontic Bracket to Enamel Surface

Adequate bond strength between enamel and orthodontic bracket is crucial, several factors affect the bond strength including the adhesive temperature prior to bonding. The objective of the study was to investigate if there is any relationship between adhesive temperature prior to bonding and the Shear Bond Strength (SBS) of orthodontic bracket to the enamel surface. Method: In this in-vitro study, A total of 64 freshly extracted premolar teeth were used which were divided into four groups each one had different adhesive temperature prior to bonding (room temperature ,30°C, 50°C, and 70°C), and each group went through SBS test under Universal Instron machine and ARI score test using Stereomicroscope. R esults: All pre-heated groups had a higher mean value t han the room temperature group, while the mean value of SBS were highest in 70°C group but at 50°C there was a dr op down in the SBS values which had a mean less than 30°C and 70°C groups. ARI scores showed not statistically sign ificant different between the groups. Conclusion: Pre-heat ing orthodontic adhesive right before bonding to 70°C ca n significantly increase bracket SBS to enamel. While, preh eating to 30°C could have a greater SBS than pre-heating to 50° C.

Effect of Various Beverages on Adhesion of Repaired CAD/CAM Restorative Materials.

(1) Background: The purpose of this study was to determine the effect of commonly consumed beverages on the bond strength of three different computer-aided design-computer-aided manufacturing (CAD/CAM) resin-ceramic hybrid materials repaired with resin-based composite (RBC) materials. (2) Materials and Methods: Rectangular prism specimens (N = 138) measuring 6 mm × 5 mm × 2 mm were obtained from GC Cerasmart (GC), Lava Ultimate (LU), and Vita Enamic (VE) blocks. These blocks were polished and then subjected to thermal cycling (10,000 cycles, 5 °C to 55 °C). After the surface treatment was applied, the average surface roughness value was measured. All the surfaces were repaired with RBC. Thermal cycling was performed for the second time. Each group was then distributed into three subgroups according to the beverage used: tea (t), cola (c), and distilled water (0) (n = 15). The specimens were stored in these solutions for 28 days and then subjected to the shear bond strength (SBS) test. Statistical analysis was performed using a two-way ANOVA test with Bonferroni adjustment. (3) Results: The surface roughness of the materials presented no significant difference after different surface treatments (p > 0.05). No significant difference was observed among the materials (p > 0.05). Tea and cola presented similar SBS values (p > 0.05). Both were significantly lower than distilled water (p < 0.001, p < 0.001, respectively). (4) Conclusions: Consumption of beverages reduces the bond strength in surfaces repaired with RBC to CAD/CAM resin-ceramic hybrid materials. (5) Clinical Significance: Repairing damaged resin matrix dental restorations with RBC is advantageous in terms of time and cost by achieving adequate bond strengths. Frequently consumed beverages reduce the bond strength of repaired CAD/CAM resin-ceramic hybrid materials.

Effectiveness of Porcelain Polishing Methods on the Roughness and Color Stability of CAD-CAM Ceramics after Orthodontic Bracket Debonding.

Increased utilization of all ceramic restorations for aesthetic consideration in combination with routine adult orthodontic practice has led to numerous clinical challenges. Obtaining adequate bond strength between the orthodontic bracket and all-ceramic restoration and damage to the ceramic surface during the bracket debonding procedure needs to be better understood. This study analyzed the surface texture and color change of glazed and bracket-debonded ceramic CAD-CAM materials and the efficiency of porcelain polishing systems in restoring surface morphology and color. A total of 30 rectangular test specimens from each lithium disilicate CAD (LD-CAD), polymer-infiltrated ceramic (PICN), zirconia-reinforced lithium silicate glass ceramic (ZLS), and 5YTZP zirconia (5YZP) were prepared. The ceramic samples were embedded within acrylic resin, and baseline surface roughness and color were recorded using an optical profilometer and a reflected color spectrophotometer. The porcelain samples were bonded with lower incisor ceramic brackets. The samples were thermocycled 2000 times between 5 and 55 °C. Afterward, the brackets were peeled with bracket-removing pliers. The resin adhesive from the debonded surface was eliminated with tungsten carbide bur, and samples were randomly divided into three subgroups of (n = 10) to be polished with Diapol-twist (DT), a Keramik-Politur 4313B Komet polishing kit (KK), and a Horico diamond polisher (HDP). The polished surface roughness and color were recorded. The data were statistically analyzed using a two-way analysis of variance at p < 0.05. The debonded porcelain surfaces across the groups displayed significantly higher mean surface roughness (Ra) compared to glazed surfaces. The debonded 5YZP showed the least Ra at 0.661 (0.09), while the highest Ra was recorded by PICN at 4.057 (0.82). All of the polishing systems evaluated in the study significantly reduced the surface roughness. However, they were unsuccessful in regaining the surface topography of the glazed surface. The flexible discs (DT) produced the smoothest surface, followed by the diamond-impregnated rubber points (KK). Unpolished porcelain surfaces had a discernable mean color difference from glazed surfaces. Polished surfaces from the different polishing systems among the all-ceramic groups achieved a clinically acceptable mean color difference. Polishing debonded rough porcelain surfaces is imperative, and flexible discs performed better in all of the tested CAD-CAM ceramic materials.

Comparative Evaluation Of The Shear Bond Strength Of Two Different Orthodontic Bonding Agents On Artificial Crown Surfaces: An Invitro Study

INTRODUCTION: Bonding of buccal tubes to the tooth is an essential procedure in orthodontic treatment. With the increase in the number of adult patients seeking fixed orthodontic treatment, there is a need to find a more reliable procedure to bond the artificial crown surface. Successful orthodontic treatment requires sufficiently high and durable bond between buccal tubes and ceramic/zirconia surfaces. There is a need for a bonding agent which can provide maximum bond strength to all surfaces. This study aimed to assess and compare the shear bond strength and adhesive remnants of orthodontic buccal tubes to natural teeth, ceramic crowns and zirconia crowns using two different bonding systems. METHODS: In this in vitro study, 60 extracted human molar teeth were randomly assigned to three groups (n=20) and then divided into two subgroups(n=10). Bonding of buccal tubes to enamel, ceramic and zirconia surfaces was done using Assure plus universal bonding resin and Enhance LC. The shear bond strength of buccal tubes to the enamel, ceramic and zirconia surfaces were determined by universal testing machine. The SBSs and ARI scores were statistically analysed with and Kruskal Wallis test. RESULTS: The mean shear bond strength of buccal tubes to enamel, ceramic and zirconia surfaces bonded with Assure plus and Enhance LC was highest for enamel followed by zirconia surfaces respectively. Non-parametric Kruskal-Walli’s test found significant differences regarding the shear bond strength and adhesive remnant index (ARI). CONCLUSION: Bonding of buccal tubes to enamel, zirconia, and ceramic surfaces with Assure universal bonding resin and Enhance LC provided adequate bond strength. Thus, it may be used for bonding of orthodontic buccal tubes to the artificial crown surfaces in the clinical setting.

Bonding durability and remineralizing efficiency of orthodontic adhesive containing titanium tetrafluoride: an invitro study

BackgroundTitanium tetrafluoride has been shown to protect tooth enamel from demineralization. This study investigated the effect of incorporating different concentrations of TiF4 (1, 2 and 3 Wt.%) into an orthodontic primer on the shear bond strength of orthodontic brackets and the enamel microhardness after cariogenic challenges.MethodsThree different TiF4 concentrations (1, 2 and 3 Wt.%) were prepared and added to the etch and rinse orthodontic primer. Ninety freshly extracted premolars were randomly divided into five groups according to the experimental primers and ageing conditions: TF0, TF0C, TF1C, TF2C, and TF3C. The TF0C group had no TiF4 in the primer, while TF1C, TF2C, and TF3C had 1, 2 and 3 Wt.% TiF4 in the primer, respectively. In the TF0 group, specimens were immersed in deionized water for 24 h as a control group, while all other groups were immersed in a demineralizing solution for 28 days. Each of the five groups was divided into two subgroups: The first group was subjected to shear bond strength and adhesive remnant index testing (N = 50 teeth, 10/group), while the second group was subjected to enamel surface microhardness testing (N = 25 teeth, 50 tooth halves, 10 tooth halves/group). Fifteen teeth (N = 15 teeth, n = 3/group) representing the five groups were subjected to SEM and microelemental analysis (EDX). SBS, ARI, microhardness, and Ca/P ratio were measured, and the data were analyzed using ANOVA and Tukey's tests.ResultsThe TF2C group had the highest SBS value (9.93 ± 1.23), while the TF0C (5.24 ± 0.65) and TF3C (5.13 ± 0.55) had the lowest SBS values. The enamel microhardness in the TF0C group was significantly reduced (p < .001). Enamel microhardness values were significantly (p < .001) higher in groups TF1C, TF2C, and TF3C than in TF0C. The highest Ca/P ratio was significantly recorded for the TF2C group (2.65 ± 0.02).ConclusionsIncorporation of 1 and 2 Wt.% TiF4 into the orthodontic primers showed adequate bond strength and better remineralization effect. However, 1 Wt.% TiF4 showed lower ARI values than 2 Wt.% TiF4.

Bond-slip performance of seawater sea sand concrete filled filament wound FRP tubes under cyclic and static loads

Adequate bond strength of concrete filled tubes is required to ensure full composite action and prevent premature bond failure before ultimate bending capacity is reached. This study investigates the bond strength and bond slip mechanisms of FRP tubes filled with seawater sea sand concrete (SWSSC) under static and cyclic axial loads using a push-out test. Glass and carbon fibre reinforced polymer (FRP) and two different diameters (100 mm and 165 mm) were tested to investigate the effect of changing parameters on the bond strength. Each group of specimen was tested under static load (SL) and various different cyclic loading (CL) regimes. An ANSYS FE model was created to simulate a static pushout test for FRP SWSSC composites under varying parameters to quantify the induced tube and confinement stress. Confinement and accumulated damage were found to be the two main factors determining the change in bond strength between cyclic and static load conditions. The high active confinement of the smaller diameter GFRP tubes resulted in a slight increase in bond strength for most samples under CL. The larger diameter CFRP tubes generally exhibited a slight drop in bond strength under CL due to the more pronounced effects of accumulated interface damage.

In vitro assessment of bracket adhesion post enamel conditioning with a novel etchant paste

Background: 37% phosphoric acid (PA) is the traditional enamel etching technique prior to bracket ‎adhesion, yet it has been implicated in numerous enamel injuries. The purpose of the current study was to create a calcium phosphate (CaP) etching paste in a ‎‎simplified capsule ‎formula that can underpin clinically ‎adequate bracket bond strength ‎without jeopardizing the ‎integrity of enamel upon ‎the debracketing procedure. Materials and Methods: micro-sized hydroxyapatite (HA) powder was mixed with 40% PA solution to prepare ‎experimental acidic CaP paste. Sixty human premolars were ‎assigned into two groups of 30 each. ‎Enamel conditioning was accomplished using 37% PA-gel‎ for control group and CaP paste for experimental group. Each group was further divided into two subgroups regarding the water storage (WS) period (24 h and 30 days). Shear bond strength (SBS) test conducted with examination of debonded surfaces for adhesive remnants and enamel damage using a digital microscope. Results: CaP paste produced significantly lower SBS values than PA (p &lt; 0.01), yet sufficient for clinical use. PA etching caused often cracked enamel surfaces with excessive ‎retention of adhesive remnants (mainly ARI scores 2 and 3). Contrarily, enamel treated with the experimental CaP paste exhibited smooth, ‎unblemished surfaces mostly clean of adhesives residues (scores 0 and 1). Conclusion: a newly developed CaP paste in a capsule formula fosters ‎clinically adequate bracket ‎adhesion with a sustained bonding performance, allows a harmless bracket removal with ‎minimal or no adhesive residues on debonded surfaces; thus, it can be introduced as a suitable ‎alternative to PA‎.

In Vitro Study on the Bond Strength Between 3D-Printed Resin and Resin Cement for Pediatric Crown Restoration

A 3D-printed resin crown is a novel option for esthetic crown restoration for primary teeth, which are typically bonded with resin cement. The purpose of this study was to evaluate the bonding ability of a 3D printing resin and compare it with other indirect resin materials for crown fabrication. The shear bond strengths of two 3D printing resin materials, Graphy (GP) and NextDent (NXT), and two indirect resin materials, VIPI Block (VIPI) and MAZIC Duro (MZ), were compared in the study. For all materials, the shear bond strength at the interface between the surface of the resin material and resin cement was measured. The mean shear bond strength values of GP, NXT, MZ, and VIPI were 23.29 ± 3.88, 26.14 ± 4.67, 25.41 ± 4.03, and 18.79 ± 4.26 MPa, respectively. There was no significant difference among the SBSs of GP, NXT and MZ except for VIPI. The result of this study indicates that the 3D printing resin meets the essential requirement for clinical use by showing clinically adequate bond strength.

Bond Strength and Adhesion Mechanisms of Novel Bone Adhesives.

Bone adhesives offer distinct advantages over the use of screws to attached internal fixation plates (IFPs). As the chemical composition of bone is similar to dentine, it is possible that the types of monomers used to make dentine adhesives could be utilised to affix IFPs to bone. The ability to attach a bio-resorbable IFP to porcine bone was assessed for the monomer 10-methacryloyloxydecyl dihydrogen phosphate (MDP), used either as a homopolymer or a copolymer with urethane dimethacrylate (MDP + U). Additionally, the addition of a priming step (MDP + U + P) was evaluated. The chemical interactions of the monomers with bone were assessed using XRD and imaged using TEM, revealing the formation of nano-layered structures with the MDP primer, something we believe has not been reported on bone. In a 6-week artificial aging study both MDP + U and MDP + U + P demonstrated adequate shear bond strength to affix bio-resorbable IFPs. The cytotoxicity profiles of the adhesive formulations were determined using indirect and direct contact with MC3T3 cells, with indirect conditions suggesting the MDP + U + P is as cytocompatible as the resorbable IFP. The findings of this study suggest our newly developed adhesive has the potential to be used as a bone adhesive to affix bioresorbable IFPs.