Adequate Bond Strength Research Articles

Evaluation of enamel loss by scanning electron microscopy after debonding brackets place with four different adhesives.

The clinically adequate shear bond strengths (SBS) should be from 2.8 to 10 MPa. The aim of this research is to observe tooth enamel loss through a scanning electron microscope (SEM) during the debonding of braces of four adhesive systems. Then, 100 premolars were used in 4 groups of 25 specimens each, for Transbond MIP (G1), Enlight (G2), Stylus (G3), and Transbond Plus SEP (G4). The research was done under the NOM ISO/TS 11405:2015. Gemini 3M were placed under the manufacturer's recommendations. The SBS test was done at 24 hr in an Instron electromechanical universal testing machine at 1 mm/1 min. Adhesive remnant index (ARI) was measured, all of the brackets where examined in the SEM. For the shear bonding strength G1 = 10.09 ± 2.73 MPa, G2 = 9.27 ± 3.99 MPa, G3 = 7.83 ± 4.46 MPa, and G4 = 6.40 ± 2.85 MPa statistically significant differences were found when comparing the four groups (p = .002). In the Tukey post hoc test, G1 versus G4 and G2 versus G4, statistically significant differences were found. For the ARI a value of 1 in 46%, followed by a value of 2 in 38%, a value of 3 in 13% and a value of 0 in 3% of the total samples, finding statistically significant differences (p < .001). In relation to the tooth enamel loss due to SBS, statistically significant differences were found (p = .326). G1 and G4 had not statistically significant differences. Even though our results concur with the appropriate clinical values, we observed tooth enamel loss with Transbond Plus SEP and Stylus.

Bonding of nano-modified concrete with steel under freezing temperatures using different protection methods

Concrete bond strength with steel re-bars depends on multiple factors including concrete-steel interface and mechanical properties of concrete. However, the hydration development of cementitious paste, and in turn the mechanical properties of concrete, are negatively affected by cold weather. This study aimed at exploring the concrete-steel bonding behavior in concrete cast and cured under freezing temperatures. Three concrete mixtures were cast and cured at -10 and -20oC. The mixtures were protected using conventional insulation blankets and a hybrid system consisting of insulation blankets and phase change materials. The mixtures comprised General Use cement, fly ash (20%), nano-silica (6%) and calcium nitrate-nitrite as a cold weather admixture system. The mixtures were tested in terms of internal temperature, compressive, tensile strengths, and modulus of elasticity. In addition, the bond strength between concrete and steel re-bars were evaluated by a pull-out test, while the quality of the interface between concrete and steel was assessed by thermal and microscopy studies. In addition, the internal heat evolution and force-slip relationship were modeled based on energy conservation and stress-strain relationships, respectively using three-dimensional (3D) finite-element software. The results showed the reliability of the proposed models to accurately predict concrete heat evolution as well as bond strength relative to experimental data. The hybrid protection system and nano-modified concrete mixtures produced good quality concrete-steel interface with adequate bond strength, without need for heating operations before casting and during curing under freezing temperatures down to -20oC.

Peel bond strength between 3D printing tray materials and elastomeric impression/adhesive systems: A laboratory study

ObjectivesThe present study aimed to evaluate the bonding between three 3D printed custom tray materials and three elastomeric impression/adhesive systems using the peel test. MethodsTest blocks were 3D printed by three different technologies using Dental LT, FREEPRINT tray, and polylactide (PLA) tray materials. The reference test blocks were conventionally fabricated with Zeta Tray LC, a light-curing resin. The surface topographies of the four tray materials were investigated by scanning electron microscopy (SEM) analyses and roughness measurements. The peel bond strength between the four tray materials and three impression/adhesive systems, vinylsiloxanether (VSXE), vinyl polysiloxane (VPS), and polyether (PE), was measured (n=12 per group). The peeling failure modes and rupture sites were identified microscopically. ResultsThe four tray materials featured different surface topographies. The peel bond strength was not significantly different with VSXE and PE, but PLA and the reference showed higher peel bond strength with VPS than the Dental LT and FREEPRINT tray (p<0.05). The rupture site of adhesive failure in all groups was partly at the adhesive-impression material interface and partly within the adhesive but never at the adhesive-tray material interface. SignificanceThe 3D printed tray materials can achieve satisfactory chemical compatibility with the adhesives of VSXE, VPS, and PE. Surface topographies generated by the 3D printing technologies may affect bonding. Generally, 3D printed tray materials can provide clinically adequate bond strength with the elastomeric impression/adhesive systems. PLA is recommended for bonding with VPS when severe impression removal resistance is detected.

Bacterial Self-Healing Performance of Coated Expanded Clay in Concrete

Concrete crack healing by microbial calcium carbonate producers has been intensively studied for the last 10 years. To overcome the harsh environments of concrete, various carriers have been tested for their ability to protect the healing bacteria. Using expanded clay (EC) as a carrier is attractive because it provides adequate bond strength to the cement composites as well as protection to the bacteria from harsh environments. In this study, self-healing performance by EC was examined using styrene-acrylic emulsion coatings. First, the presence of bacteria (Lysinibacillus boronitolerans YS11) within EC was verified using electron microscopy after the bacteria were immobilized. Although coating has a negative effect on the preservation of bacterial density under normal conditions, the bacterial density was higher for coated EC [5.0×104 colony forming unit (CFU)/g of EC] than for uncoated EC (2.4×103 CFU/g of EC) when exposed to a harsh environment (60°C and pH 12) for 48 h. This suggests that coating the surface of EC was successful in protecting bacteria from the environmental stressors. Even though bacteria were within the EC, the bacterial survival rate quickly declined with time inside the mortar. However, the bacterial density was much higher for coated than for uncoated EC at day 28, suggesting that the coating provides the bacteria with excellent protection from the harsh environment within the mortar. The concrete healing rates were 70% for uncoated EC and 75% for coated EC, compared to the healing rate of 50% and 42% for plain mortar and mortar with empty EC, respectively. These results suggest that the healing rate has increased with EC containing bacteria.

Material and glass-fibre-reinforced polymer bond properties of geopolymer concrete

Geopolymers are recognised for their environmental benefits and excellent chloride and sulfate resistance. However, information on the material characteristics and bond behaviour of geopolymers based on fly ash (FA) and slag is still relatively scarce. This paper presents a comprehensive study on the integration of two modern construction materials – geopolymer concrete (GPC) based on FA and ground granulated blast-furnace slag and glass-fibre-reinforced polymer (GFRP) bars. The aim of the study was to assist concrete structural design by identifying the key preparation parameters such as hardening and bond behaviour. It was found that the hardening of the GPC was much faster than that of ordinary Portland cement (OPC) concrete at an early age and the stress–strain curves, elastic moduli and splitting tensile strengths of the GPC were accurately predicted by existing models developed for OPC concrete. The GFRP bars in the GPC outperformed those in the OPC concrete in terms of normalised bond strength. The GPC reinforced with both GFRP and steel rebars exhibited similar bond–slip curves to the OPC concrete. Overall, the behaviour of the GFRP-reinforced GPC was found to be analogous to that of the OPC concrete while providing adequate compressive, tensile and bond strength for the construction of foundations of low-rise buildings.

Orthodontic bonding to atypical tooth surfaces

Orthodontic bonding techniques continue to evolve with the ever-changing population. With the demand for orthodontic treatment increasing, the specialty is regularly presented with restored dentitions, anterior crowns, bleached teeth, as well as those presenting with developmental conditions, such as fluorosis and amelogenesis imperfecta. Reduced orthodontic bond strength can lead to failure of the appliance and in turn lead to prolonged treatment times and patient dissatisfaction. This article aims to summarize the recommended methods for bonding and give an updated review of optimizing techniques. CPD/Clinical Relevance: Adequate bracket bond strength is an essential part of orthodontic treatment, to prevent breakages and reduce treatment time and risk factors.

Performance of novel enamel-conditioning calcium-phosphate pastes for orthodontic bonding: An in vitro study.

This study aimed to develop remineralizing calcium-phosphate (CaP) etchant pastes for enamel conditioning before bracket bonding and evaluate the bonding performance, failure pattern, and enamel surface integrity post bracket debonding in comparison with the conventional phosphoric acid (PA) etchant gel. Micro-sized monocalcium phosphate monohydrate and hydroxyapatite (micro- and nano-sized) powders were mixed with various phosphoric and nitric acid concentrations to develop eight acidic CaP pastes. Ninety extracted human premolars were randomly assigned into eight experimental and one control group (n=10). The developed pastes and control (commercial 37% PA-gel) were applied onto the enamel using the etch-and-rinse protocol before bonding metal brackets. Shear bond strength and adhesive remnant index (ARI) scores were evaluated after 24 hours water storage (24 h) and post 5000 thermocycling (TC). Field emission scanning electron microscopy (FE-SEM) was used to evaluate enamel damage after bracket debonding. The developed CaP pastes, excepting MNA1 and MPA1, resulted in significantly lower SBS values and ARI scores than 37% PA gel. Etching with 37% PA yielded roughened, cracked enamel surfaces with excessive retention of adhesive residue. In contrast, enamel treatment with the experimental pastes exhibited smooth, unblemished surfaces, with obvious CaP re-precipitation induced by mHPA2 and nHPA2 pastes and to a lesser extent by MPA2 paste. Three newly developed CaP etchant pastes (MPA2, mHPA2, and nHPA2) can be promising alternative enamel conditioners that outperform conventional PA by generating adequate bracket bond strengths besides precipitating CaP crystals on the enamel. Moreover, these pastes maintained unblemished enamel surfaces with no or minimal adhesive residue after bracket removal. Key words:Enamel Conditioning, Calcium Phosphate, Bracket Bond Strength, Orthodontic Bonding, enamel damage.

Different bonding agents effect on adhesive bond strength: lithium disilicate glass ceramic

Abstract Introduction The silanization of the ceramic surface prior to applying the adhesive and/or resinous materials plays an important role in bond strength. Nowadays, a new family of adhesive systems has been introduced into the market, aiming to simplify the technique of adhesive procedures during cementation. Objective To investigate the effectiveness of different bonding agents containing silane and primer on Lithium Disilicate Glass Ceramic (LD) surface by shear bond strength tests. Material and method 130 LD ceramic blocks were included in acrylic resin, polished and washed in ultrasound for 10 minutes. The specimens were divided into 2 groups according to surface treatment: Polished Surface (PS); Hydrofluoric Acid 9.5% - 20s (HF). Each group was divided into 5 subgroups (n = 13) according to bonding agent type: metallic primer containing MDP (ZPrimePlus, Bisco Inc); two traditional silanes (MonobondPlus, IvoclarVivadent / Porcelain Prime, Bisco Inc.); mixture of silane and resin (Kerr Silane, Kerr); mixture of silane and universal adhesive (Single-bond Universal, 3M Espe). The specimens were mounted in a standard device for shear testing (UltradentBonding Assembly), cemented with dual resin cement (RelyX UltimateTM, 3M Espe.) and photo-polymerized for 20s. The samples were tested after 24 hours and 3 months of storage in distilled water at ±36 °C. The data were analyzed by 3-Way Anova and Tukey's test (α = 5%). Result Shear bond strength (SBS) was significantly influenced by surface treatment, bonding agent used and storage (p &lt;0.001). Conclusion Adequate adhesive bond strength to Lithium Disilicate Glass Ceramic can be obtained with traditional silanes, combined with HF acid pretreatment surface.

Repair strength and surface topography of lithium disilicate and hybrid resin ceramics with LLLT and photodynamic therapy in comparison to hydrofluoric acid.

The aim was to compare the repair bond strength and surface topography of lithium disilicate ceramics (LDC) and hybrid resin ceramics (HRC) using different surface conditioning treatments [low level laser therapy (LLLT), photodynamic therapy (PDT), hydrofluoric acid (HF) with silane and air abrasion (AA) and silane]. Sixty specimens each of LDC and HRC were used. Discs were prepared for each group (6 × 2 mm), conditioned using different regimes. Specimens in group 1 and 5 were laser irradiated using Er,Cr:YSGG (ECYL), group 2 and 6 were conditioned using methylene blue photosensitizer (PDT), group 3 and 7 surface was treated with hydrofluoric acid and silane (HFA-S), group 4 and 8 conditioned with Al2O3 air abrasion and silane (AA-S). A Porcelain Repair Kit was used according to manufacturer recommendation in all samples. Peak universal bond adhesive was rubbed on ceramic surface and then bonded with composite resin. For shear bond strength testing the specimens were placed in a universal testing machine. A stereomicroscope at 40x magnification was used to analyse failure pattern. Five specimens in each group after surface treatment were evaluated for surface changes and topography using scanning electron microscopy. The mean repair bond strength was calculated using ANOVA and Tukey's post hoc test at a significance level of (p < 0.05). The highest repair bond strength was observed in group 3 (LDC) (20.57 ± 3.58 MPa) (HFA-S), whereas, the lowest score was displayed in Group 2 (LDC) using methylene blue photosensitizer (MBPS) (12.18 ± 1.08 MPa). Similarly, in HRC the highest repair SBS was presented in group 8 (AA-S) (20.52 ± 2.51 MPa) and the lowest SBS values were exhibited by PDT treated group 6 (13.22 ± 0.62 MPa). A combination of mechanical and chemical surface treatments should be used in order to achieve adequate repair bond strength between resin composites and ceramic interface of LDC and HRC.

Root dentin surface activation to improve bioceramic bonding: Ascanning electron microscopic study

Background. Bioceramics need to interact chemically with dentin to exhibit adequate bioactivity. Proper bonding of bioceramics with dentin is of considerable importance. This study aimed to evaluate the wettability and marginal adaptation of bioceramics after the use of surface-active agents on dentin: %0.5 cetrimide and %1 alkylbenzene sulfonate. Methods. Of ninety maxillary central incisors, 45 teeth were sectioned longitudinally with 45 root halves randomly assigned to three groups (n=15): group I: no pre-treatment; group II: %0.5 cetrimide; group III: %1 alkylbenzene sulfonate. Then, the samples were subdivided into three subgroups (n=5): subgroup I: MTA; subgroup II: Biodentine, and subgroup III: BioRoot. A controlled-volume droplet of bioceramic material was placed on each root half, which was positioned in a dynamic contact angle analyzer to record the static contact angle for wettability. The remaining 45 samples were decoronated; the root canals were prepared and randomly categorized, as mentioned above. The root canal surfaces were treated, filled with the bioceramic material, transversely sectioned, and then each middle section was analyzed microscopically for marginal adaptation. Statistical tests used included post hoc Tukey tests and one-way ANOVA. The level of statistical significance set at %95 (P<0.05). Results. The contact angle values and interfacial gap width values after surface pre-treatment were significantly lower when compared to no pre-treatment group (P<0.05). The values were significant for %0.5 cetrimide in the case of Biodentine and %1 alkylbenzene sulfonate in the case of BioRoot (P<0.05). Conclusion. The two surfactants yielded promising results for enhancing the wettability and marginal adaptation of materials to the root dentin, which is required for obtaining an adequate seal, penetration, and bond strength of bioceramics.

Resistance of bonded premolars to four artificial ageing models post enamel conditioning with a novel calcium-phosphate paste.

BackgroundThis in vitro study compares a novel calcium-phosphate etchant paste to conventional 37% phosphoric acid gel for bonding metal and ceramic brackets by evaluating the shear bond strength, remnant adhesive and enamel damage following water storage, acid challenge and fatigue loading. Material and MethodsMetal and ceramic brackets were bonded to 240 extracted human premolars using two enamel conditioning protocols: conventional 37% phosphoric acid (PA) gel (control), and an acidic calcium-phosphate (CaP) paste. The CaP paste was prepared from β-tricalcium phosphate and monocalcium phosphate monohydrate powders mixed with 37% phosphoric acid solution, and the resulting phase was confirmed using FTIR. The bonded premolars were exposed to four artificial ageing models to examine the shear bond strength (SBS), adhesive remnant index (ARI score), with stereomicroscopic evaluation of enamel damage. ResultsMetal and ceramic control subgroups yielded significantly higher (p < 0.05) SBS (17.1-31.8 MPa) than the CaP subgroups (11.4-23.8 MPa) post all artificial ageing protocols, coupled with higher ARI scores and evidence of enamel damage. In contrast, the CaP subgroups survived all artificial ageing tests by maintaining adequate SBS for clinical performance, with the advantages of leaving unblemished enamel surface and bracket failures at the enamel-adhesive interface. ConclusionsEnamel conditioning with acidic CaP pastes attained adequate bond strengths with no or minimal adhesive residue and enamel damage, suggesting a suitable alternative to the conventional PA gel for orthodontic bonding. Key words:Enamel etching, calcium phosphate, bracket bond strength, adhesive residue, enamel damage.

Effect of thermo-mechanical cycling on the shear bond strength of porcelain to milled and cast cobalt-chromium alloys

Statement of problem: Most of the failures in metal-ceramic restorations occurs at the interface between the two materials. For long term clinical performance, these restorations should have adequate bond strength between metal and ceramic. Few data is available in regards to the metal-ceramic bond strength of Cobalt Chromium (Co-Cr) alloys fabricated by computer aided designing design/computer aided manufacturing CAD/CAM technology.Purpose of the study: The purpose of this in vitro study was to explore the influence of Co-Cr fabrication techniques on shear bond strength of porcelain to milled and cast Co-Cr alloys and to evaluate failure mode with & without thermo-mechanical cycling.Materials & Methods: A total of 20 disc samples (10 mm diameter x 4 mm thickness) were fabricated of Co-Cr alloy and divided into two groups (10 discs each) according to their fabrication technique: Group I: fabricated by CAD/CAM milling and Group II: fabricated by conventional casting. Then porcelain build up for all discs (10 mm diameter x 2mm thickness) was done using feldspathic porcelain. Each group was subdivided according to discs’ exposure to thermo-mechanical cycling into two sub-groups (5 discs each). Sub-group A : without thermo-mechanical cycling and Sub-group B: with thermo-mechanical cycling. All the disc samples were subjected to the shear bond strength (SBS) test and the failure mode was investigated under digital microscope at 40 X. Data were statistically analyzed using Independent sample t-test and Two-way ANOVA test (P ≤ 0.05).Results: The results showed that the fabrication techniques were statistically insignificantly affecting the SBS of both CAD/CAM milled and conventional casting groups. Regarding the thermo-mechanical cycling, the CAD/CAM milled and conventional casting groups without thermo-mechanical cycling showed a statistically significantly higher SBS than those with thermo-mechanical cycling. Failure mode was mixed type for all disc samples.Conclusions: Fabrication technique of Co-Cr alloy had no significant effect on SBS. Thermo-mechanical cycling of milled and cast Co-Cr samples significantly affecting SBS with the superiority of the non-thermo-mechanical cycled samples. All the tested samples showed SBS values within the clinically acceptable levels. CAD/ CAM fabricated Co -Cr may be considered a promising alternative to conventional cast Co-Cr for metal ceramic prosthesis in terms of SBS.

Shear Bond Strength of Orthodontic Brackets to Composite Restorations Using Universal Adhesive

Statement of the Problem: The dental adhesives may have the potential to increase the bond strength of orthodontic brackets to composite resin and it would be highly desirable if adequate bracket-composite bond strength could be yielded by using these adhesives without the need for surface roughening. Purpose:The purpose of this study was to measure the shear bond strength (SBS) of metal brackets to composite restorations by use of a universal adhesive compared with a conventional adhesive. Materials and Method: In this in vitro, experimental study, 45 composite discs measuring 6 mm in diameter and 4 mm in thickness were fabricated and assigned to three groups (n=15). In the group 1, discs were etched with 37% phosphoric acid for 15 seconds and Scotchbond Universal was then applied. Discs were roughened by diamond bur in the group 2 and were subjected to the application of Scotchbond Universal. In the group 3, conventional adhesive (Single Bond 2) was applied after roughening the discs by diamond bur. Metal brackets were then bonded to discs and after thermocycling, the SBS was measured by an Instron machine. The mode of failure and adhesive remnant index (ARI) score were determined using stereomicroscope. Data were analyzed by SPSS version 18, one-way ANOVA, and the Kruskal Wallis test. Results: The surface roughening plus universal adhesive group showed the highest SBS (11.90 MPa) but according to one-way ANOVA, the difference in this regard among the three groups was not statistically significant (p= 0.94). Most samples showed ARI score of 4. Conclusion:Universal adhesive can provide sufficient bond strength as high as that provided by conventional adhesives for orthodontic bracket bonding to composite restorations even in absence of surface roughening by bur.

Shear Bond Strength of different resin-based materials Processed on Poly-ether-ether ketone frameworks (IN VITRO STUDY)

INTRODUCTION: Removable partial dentures (RPDs) are fabricated to replace the lost teeth of a partially edentulous individual. The serviceability of an RPD is dependent on the bond strength at the resin–framework interface. The esthetically unacceptable display of metal clasps, the increased weight of the prosthesis, the potential for metallic taste, and allergic reactions to metals led to the introduction of a number of thermoplastic materials in clinical practice such as nylon and acetal resins. An alternative restoration material (poly-ether-etherketone [PEEK]) has been successfully used over the last years. OBJECTIVES: to evaluate the shear bond strength and the effect of aging on bond strength of two different resin based materials to polyether-ether-ketone [PEEK]. MATERIALS AND METHODS: Fifty two PEEK cylinders was prepared. Specimens was randomly assigned into two parallel groups, 26 specimens each according to the resin materials used. The bond strength and aging of resin material to poly-ether-ether-ketone [PEEK] was evaluated. RESULTS: the initial shear bond strength of PMMA to PEEK was significantly higher than that of composite resin to PEEK. However, after aging process the shear bond strength of PMMA to PEEK decreased while that of composite resin to PEEK remained unchanged. There was no significant difference between the shear bond strength of both PMMA and composite resin to PEEK after aging. CONCLUSIONS: PMMA can be used as a veneering material with PEEK with comparable results to traditionally used composite resin. Moreover, owing to the adequate bond strength between PEEK and PMMA, PEEK frameworks could be relined in the traditional method similar to metal frameworks

Bond strength of orthodontic adhesives to dry and saliva-moistened enamel – a comparative in vitro study

salivamoistened enamel. Design/methodology/approach: One hundred twenty stainless steel brackets were bonded to human mandibular third molars with six materials: Enlight LC® (Ormco Corp), Grengloo® (Ormco Corp), Light Bond® (Reliance Orthodontic Products), Charisma® (Heraeus Kulzer), SmartBond® (Gestenco), and Transbond XT® with MIP® primer (3M Unitek). One half of the specimens in each group (n=10) was bonded to dry enamel, while the other half to saliva-moistened enamel. Bond strength testing was performed with a wire loop loading technique after 30-min incubation in artificial saliva. Failure mode was evaluated using adhesive remaining index (ARI). Findings: No significant differences in bond strength to dry enamel were noted for all composite materials (p&gt;0.05). SmartBond exhibited significantly greater bond strength to moistened enamel (7.10 ± 1.47 MPa) and comparable with other composite materials to dry enamel. Composite materials demonstrated significantly reduced bond strength to saliva-moistened enamel (p&lt;0.001), except for Transbond MIP, whose bond strength was not significantly decreased by saliva contamination (p=0.089). There was not statistically significant difference between bond strength of SmartBond and Transbond to saliva contaminated enamel. A higher incidence of cohesive failures was noted for all materials. Research limitations/implications: Composite light-cured materials provide adequate bond strength to dry enamel. Cyanoacrylate adhesive provides sufficient bond strength only under moist conditions. Transbond XT+MIP has sufficient bond strength to either dry or saliva-moistened enamel. Practical implications: The study evaluated the bonding strength of orthodontic brackets, which is a critical parameter in orthodontics, especially in situations that do not allow for proper isolation from saliva, such as bonding to impacted teeth following surgical exposure. Originality/value: Bond strengths evaluated with loop loading technique in different study environments would help the orthodontist to choose the most effective adhesive for the specific clinical situation.

Comparison of Shear Bond Strength of Orthodontic Metal Brackets Adhered to Composite Restorations Pretreated with Er;Cr:YSGG and CO2 Lasers and Phosphoric Acid

Background &amp;amp; Aim. The aim of this study was to compare the bond strength of the orthodontic brackets bonded to the composite restorations following preparations by CO2 and Er;Cr:YSGG lasers and conventional phosphoric acid etching adult orthodontic treatment. Materials &amp;amp; Methods. Class V cavities were prepared on the buccal surfaces of 60 acrylic teeth and restored by composite after etching by 37% acid-etch gel. The specimens&amp;rsquo; surfaces were prepared randomly by 37% phosphoric acid etching or Er;Cr:YSGG or CO2 lasers. Central metal brackets were installed on the teeth&amp;#39;s surfaces. The shear bond strength of the brackets to composite surfaces was measured by the crosshead speed of 1mm/min. The scores of the remaining adhesive on the surfaces were calculated by ARI index in 5 scales. The shear bond strength values and the ARI scores were analyzed by one-way ANOVA and Chi-square tests respectively. Results. There were no significant differences among the surface preparation methods regarding bond strength between composite surfaces and the brackets. Most specimens showed ARI index of 3 in the acid phosphoric etching. In CO2 laser application, ARI index of 2 and 3 were more frequent. In Er;Cr:YSGG laser, ARI index of 3 was predominant. No significant differences existed among 3 modalities regarding scores of ARI index. Conclusion. Irradiation of CO2 and Er;Cr:YSGG lasers is recommended for clinical applications due to adequate bond strength created between the brackets and composite surfaces as well as advantages such as lower chair time and no damage to the gingival tissues.

Evaluation of Different Pretreatment Efficacy with Fluoride-releasing Material on Shear Bond Strength of Orthodontic Bracket: An In Vitro Study

The aim of this study was to assess the efficacy of different pretreatments with fluoride-releasing material on shear bond strength (SBS) of orthodontic bracket. A total of 60 human mandibular premolars were taken in this study. These samples were stored in periodically changed distilled water at room temperature so as to stop bacterial growth. All samples were randomized to three pretreatment groups: group I, acid etching; group II, fluoride varnish; group III, casein phosphopeptide-amorphous calcium phosphate (CPP-ACP) paste. Later, Transbond XT was applied on brackets made of stainless steel and brackets were centered buccally and then light-cured. The INSTRON universal machine was used to measure SBS. Based on the values, the adhesive remnant index (ARI) was estimated. The maximum SBS was seen in group III (18.84 μ 1.04), followed by group II (14.18 μ 0.23), and the minimum bond strength was found in group I (13.90 μ 1.22). The one-way analysis of variance (ANOVA) showed high statistically significant difference within the pretreatment groups. The pretreatment group comparisons showed statistically significant difference between group I vs group III and group II vs group III. Score 0 was more in group III [8 (40%)] followed by group II [4 (20%)] and group I [2 (10%)]. The lowest number of score 3 was found in CPP-ACP paste group. After comparing the ARI scores within the groups, the Chi-square test showed a probability of 0.001 which was statistically significant. Our study established that the CPP-ACP paste pretreatment improves the SBS of orthodontic bracket significantly followed by fluoride varnish and acid etching. The bond strength of orthodontic brackets that were bonded should be adequate to resist orthodontic forces applied during treatment. The effect of the adhesive material to improve the adequate bond strength depends on the efficient pretreatment methods.

EVALUATION OF SHEAR BOND STRENGTH OF HIGH-PERFORMANCE POLYMERS TO ITS RESIN VENEERING AND TO DENTIN (IN VITRO STUDY)

INTRODUCTION: : Looking through the wide range of prosthetic options High-performance polymers properties. Needs over layering resin veneer, bonded by a special adhesive, this adds an additional challenge to achieve adequate bond strength, also its bonding to tooth structure remains difficult. OBJECTIVES: To evaluate shear bond strength of CAD/CAM High-performance polymers (BioHPP) with its CAD/CAM veneering composite using two different adhesives, as well as to dentin using two types of cements. MATERIALS AND METHODS: This in vitro study, for Group I, twenty BioHPP discs with their CAD/CAM veneering composite, were milled and divided randomly into two subgroups (n =10) according to the adhesive system used. Subgroup IA: using DTK adhesive (dualhardening adhesive). Subgroup IB: using Combo.lign (dual-hardening adhesive). For Group II, twenty CAD/CAM High-performance polymers (BioHPP) discs were milled and divided into two subgroups according to the different cements used to lute to dentin surface. Subgroup IIA: using: RelyX Unicem resin cement, subgroup IIB: using Fuji Plus GI cement. After water storage, thermocycling (1200 cycles, 5°C/55°C) corresponding to one year of clinical service, all the specimens were subjected to shear force until failure and the results in the various groups were compared and statistically analyzed. Modes of failure were assessed. RESULTS: Mean SBS were as follows: subgroup IA (DTK adhesive 6.238), subgroup IB (combo.lign2.42), subgroup IIA (RelyX Unicem 2.07) and subgroup IIB (Fuji Plus 3.77). Mann-Whitney test demonstrated significant differences between the two subgroups in groups I and II (U= 2.0, P=.001) (U=17, P=.013) respectively. Stereomicroscope revealed that mixed and adhesive failure were the most dominant mode of failure. CONCLUSIONS MDP-Containing Self-adhesive Resin (DTK adhesive) is recommended as efficient adhesive to increase the shear bond strength of the veneering composite to BioHPP. Also Fuji Plus showed better bond strength than RelyX Unicem with BioHPP and dentin.

Use of Fiber-Reinforced Self-Consolidating Concrete to Enhance Serviceability Performance of Damaged Beams

The use of fiber-reinforced self-consolidating concrete (FR-SCC) in repairing damaged concrete beams has been evaluated. An experimental program was conducted to design and test key fresh and hardened properties of SCC and FR-SCC mixtures. The designed FR-SCC mixtures included two types of supplementary cementitious materials (silica fume (SF) and slag (SL)) and two types of fibers (steel fiber (STF) and polypropylene fiber (PPF)) were used. To ensure good workability to repair congested areas, the optimized volume fractions of the STF were 0.25% and 0.50% compared with 0.10%, 0.15%, and 0.20% for the PPF. In addition, the flexural behavior of 10 beam specimens was investigated. The main reinforcement for the control beams consisted of #5 reinforcing bars, while the main reinforcement for the repaired beams was either #4 or #3 reinforcing bars that were introduced to simulate 35% and 65% reduction of the bar areas, respectively, due to corrosion. The results demonstrate that the optimized FR-SCC mixtures are effective repair materials and can develop adequate bond strength to existing concrete. The flexural test results showed that the repair mixtures were able to increase the cracking load for the repaired beams compared with the control beams. Such an increase is expected to contribute to extending the life of the damaged member or structure at the service load level. This paper also presents a comparison of the predicted values for the first-crack load strength using the ACI 544 code equation with the experimental data. Results showed that the code equation provides safe prediction.

Effect of ZrO2 sol-gel coating on the Ti 99.2 – Porcelain bond strength investigated with mechanical testing and Raman spectroscopy

Titanium in dental prosthetics is used for making prosthetic appliances permanently faced with low melting porcelain. This process is difficult due to the differences in chemical bonds characterizing both materials. The nature of the bonds varies sharply from metallic to ion-covalent metal on the metal-ceramic border. Improving the properties of the titanium-ceramic combination is a widely explored topic in the field of material engineering. The article presents the results of titanium 99.2 – bioceramics system interface bond strength investigated with mechanical tests and Raman spectroscopy. Titanium substrate was prepared with sandblasting (Al2O3) combined with ZrO2 sol-gel layer and finally covered with low fusing porcelain (Duceratin, GC Initial). In order to investigate the effects of metal-ceramics interface bond strength, mechanical testing (three point bending) microscopic (SEM/EDX), spectroscopic (RS) were performed. Applied technique of substrate preparation made it possible to improve the effects of porcelain adhesion to Ti 99.2 which was confirmed by bond strength improvement in the area of titanium/bioceramic interface. Furthermore, the Raman spectroscopy showed results of phase distribution change along the interface which proved the different character of metallic and ceramic chemical bonding, which has changed slightly from metallic to ionic and covalent nature. Adequate interface bond strength and phase composition of titanium/sol-gel – bioceramics system is essential to the durability improvement of the dental implants and also influences in substrate functional properties enhancement.