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Ahmad R Mojdehi, Douglas P Holmes, David A Dillard
A generalized scaling law, based on the classical fracture mechanics approach, is developed to predict the bond strength of adhesive systems. The proposed scaling relationship depends on the rate of change of debond area with compliance, rather than the ratio of area to compliance. This distinction can have a profound impact on the expected bond strength of systems, particularly when the failure mechanism changes or the compliance of the load train increases. Based on the classical fracture mechanics approach for rate-independent materials, the load train compliance should not affect the force capacity of the adhesive system, whereas when the area to compliance ratio is used as the scaling parameter, it directly influences the bond strength, making it necessary to distinguish compliance contributions...
September 22, 2017: Soft Matter
Roya Naseh, Farnoosh Fallahzadeh, Mohammad Atai, Omid Mortezai, Raheleh Setayeshrad
BACKGROUND: The aim of study was to evaluate the application of casein phosphopeptide-amorphous calcium phosphate (CPP-ACP) and fluoride regarding their effect on the shear bond strength (SBS), bond failure pattern of brackets using the adhesive remnant index (ARI) and assessing the quality of enamel surface using the enamel damage index (EDI). MATERIAL AND METHODS: Sixty extracted premolar teeth were randomly divided into four groups regarding pretreatment application of CPP-ACP and fluoride...
August 2017: Journal of Clinical and Experimental Dentistry
Soghra Yassaei, Hossein Aghili, Azadeh Hosseinzadeh Firouzabadi, Hamidreza Meshkani
Introduction: This study was performed to determine the shear bond strength of rebonded mechanically retentive ceramic brackets after recycling with Erbium-Doped Yttrium Aluminum Garnet (Er:YAG) laser or sandblasting. Methods: Twenty-eight debonded ceramic brackets plus 14 intact new ceramic brackets were used in this study. Debonded brackets were randomly divided into 2 groups of 14. One group was treated by Er:YAG laser and the other with sandblasting. All the specimens were randomly bonded to 42 intact human upper premolars...
2017: Journal of Lasers in Medical Sciences
Valter O Arima, Mario Vedovello, Heloísa C Valdrighi, Adriana S Lucato, Milton Santamaria, Silvia A S Vedovello
Objective: To evaluate the shear bond strength of lingual orthodontic brackets with resin or metal pads, the location of bond failure and the adhesive remnant index (ARI). Methods: A total of 40 extracted upper premolars were randomly divided into two groups of 20 each: bonding with brackets having (1) pads with extended resin directly on the lingual surface of teeth, and (2) pads with metal custom base on the lingual surface of teeth. The debonding force was measured with an Instron universal testing machine...
July 2017: Dental Press Journal of Orthodontics
Laikuan Zhu, Yuping Li, Carola A Carrera, Yung-Chung Chen, Mingyu Li, Alex Fok
OBJECTIVE: To verify and calibrate a chemical model for simulating the degradation of the dentin-composite interface induced by multi-species oral biofilms in vitro. METHODS: Dentin-composite disks (5-mm dia.×2-mm thick) were made from bovine incisor roots and filled with either Z100™ (Z100) or Filtek™ LS (LS) composite. The disks, which were covered with nail varnish, but with one of the dentin-composite margins exposed, were immersed in lactic acid solution at pH 4...
September 8, 2017: Dental Materials: Official Publication of the Academy of Dental Materials
Go Yamako, Dennis Janssen, Shuji Hanada, Thomas Anijs, Kiyohide Ochiai, Koji Totoribe, Etsuo Chosa, Nico Verdonschot
Stress shielding-related bone loss occurs after total hip arthroplasty because the stiffness of metallic implants differs from that of the host femur. Although reducing stem stiffness can ameliorate the bone resorption, it increases stress at the bone-implant interface and can inhibit fixation. To overcome this complication, a novel cementless stem with a gradient in Young's modulus was developed using Ti-33.6Nb-4Sn (TNS) alloy. Local heat treatment applied at the neck region for increasing its strength resulted in a gradual decrease in Young's modulus from the proximal to the distal end, from 82...
August 24, 2017: Journal of Biomechanics
Sai Yu, Hailong Wang, Yong Ni, Linghui He, Mingyuan Huang, Yuan Lin, Jin Qian, Hongyuan Jiang
Many studies have demonstrated that the mechanical properties of the extracellular matrix can significantly influence the morphology, strength and lifetime of focal adhesions. However, how the morphology of the contact surface affects the pattern formation of the molecular bonds still remains largely unknown. Here, by simplifying the cell and extracellular matrix to two opposing elastic bodies and considering the lateral diffusion as well as the bonding/debonding of molecular bonds, we study the clustering behavior of receptor-ligand bonds between curved surfaces and the phase diagrams of cluster patterns...
September 13, 2017: Soft Matter
Nathan J Cochrane, Thomas W G Lo, Geoffrey G Adams, Paul M Schneider
INTRODUCTION: Iatrogenic damage to the tooth surface in the form of enamel tearouts can occur during removal of fixed orthodontic appliances. The aim of this study was to assess debonded metal and ceramic brackets attached with a variety of bonding materials to determine how frequently this type of damage occurs. METHODS: Eighty-one patients close to finishing fixed orthodontic treatment were recruited. They had metal brackets bonded with composite resin and a 2-step etch-and-bond technique or ceramic brackets bonded with composite resin and a 2-step etch-and- bond technique, and composite resin with a self-etching primer or resin-modified glass ionomer cement...
September 2017: American Journal of Orthodontics and Dentofacial Orthopedics
Qian Feng, Qingzhao Kong, Jian Jiang, Yabin Liang, Gangbing Song
Rubber-steel-layered structures are used in many engineering applications. Laminated rubber-steel bearing, as a type of seismic isolation device, is one of the most important applications of the rubber-steel-layered structures. Interfacial debonding in rubber-steel-layered structures is a typical failure mode, which can severely reduce their load-bearing capacity. In this paper, the authors developed a simple but effective active sensing approach using embedded piezoceramic transducers to provide an in-situ detection of the interfacial debonding between the rubber layers and steel plates...
September 1, 2017: Sensors
A Saad, G Inoue, T Nikaido, M Ikeda, M F Burrow, J Tagami
In this laboratory study, the microtensile bond strengths (μTBS) of resin-modified glass ionomer cement (RM-GIC) to sound and artificial caries-affected bovine root dentin (ACAD) using three different conditioning agents were evaluated after 24 hours and three months. The fractured interface was examined with a scanning electron microscope (SEM). Specimens were created on bovine root dentin that was embedded in epoxy resin. For the ACAD specimens, artificial carious lesions were created. The RM-GIC (Fuji II LC) was applied either directly (no treatment), after application of self conditioner, cavity conditioner, or 17% ethylenediamine tetraacetic acid (EDTA) applied for 60 seconds, on sound dentin and ACAD, then light cured...
August 31, 2017: Operative Dentistry
Sung-Hwan Choi, Jung-Yul Cha, Kee-Joon Lee, Hyung-Seog Yu, Chung-Ju Hwang
BACKGROUND: Assessing changes in patient's psychological health and oral health-related quality of life (OHRQoL) over time during orthodontic treatment may help clinicians to treat patients more carefully. OBJECTIVES: To evaluate changes in mental health, self-reported masticatory ability, and OHRQoL during orthodontic treatment in adults. METHODS: This prospective study included 66 adults (30 men, 36 women; mean age, 24.2 ± 5.2 years). Each patient completed the Korean versions of the State-Trait Anxiety Inventory, Zung Self-Rating Depression Scale, Rosenberg self-esteem scale, key subjective food intake ability (KFIA) test for five key foods, and Oral Health Impact Profile-14 (OHIP-14K) at baseline (T0), 12 months after treatment initiation (T1), and debonding (T2)...
August 29, 2017: Journal of Oral Rehabilitation
C W Extrand
In a recent article, Tadmor and co-workers (Tadmor, R., et al. Langmuir 2017, 33, 3594-3600) used a centrifugal adhesion balance (CAB) to detach liquid drops from solid surfaces. By orienting solid surfaces in their CAB such that normal and lateral surfaces were balanced, the debonding force acted perpendicularly to the surface and drops detached by the axisymmetric retraction of their contact line. The detachment force was used to estimate the work of adhesion. To match the work of adhesion values from CAB to those calculated from the Young-Dupré equation, relatively large contact angles were required...
August 28, 2017: Langmuir: the ACS Journal of Surfaces and Colloids
Ayca Tulga
STATEMENT OF PROBLEM: An annealing procedure is a heat treatment process to improve the mechanical properties of cobalt-chromium (Co-Cr) alloys. However, information is lacking about the effect of the annealing process on the bonding ability of ceramic to Co-Cr alloys fabricated by rapid prototyping. PURPOSE: The purpose of this in vitro study was to evaluate the effects of the fabrication techniques and the annealing procedure on the shear bond strength of ceramic to Co-Cr alloys fabricated by different techniques...
August 22, 2017: Journal of Prosthetic Dentistry
Dennis Pham, Prashanti Bollu, Kishore Chaudhry, Karthikeyan Subramani
BACKGROUND: The objective of this study was to evaluate the effect of orthodontic bracket base shape on shear bond strength and adhesive remnant index. MATERIAL AND METHODS: In this in vitro study using 140 bovine incisors, shear bond strength (SBS) of brackets with different base shapes (rectangle, flower, round, heart, diamond, star, and football) were measured with an Instron testing machine and tested until bond failure. Adhesive Remnant Index (ARI) scoring was evaluated after debonding to evaluate the location of bond failure...
July 2017: Journal of Clinical and Experimental Dentistry
Blerim Mehmeti, Bleron Azizi, Jeta Kelmendi, Donika Iljazi-Shahiqi, Željko Alar, Sandra Anić-Milošević
BACKGROUND: An increasing demand for esthetic restorations has resulted in an increased use of all-ceramic restorations, such as zirconium. However, one of the challenges the orthodontist must be willing to face is how to increase bond strength between the brackets and various ceramic restorations.Bond strength can beaffected bybracket type, by the material that bracketsaremade of, and their base surface design or retention mode. ​: Aim: of this study was to perform a comparative analysis of the shear bond strength (SBS) of metallic and ceramic orthodontic brackets bonded to all-zirconium ceramic surfaces used for prosthetic restorations, and also to evaluate the fracture mode of these two types of orthodontic brackets...
June 2017: Acta Stomatologica Croatica
Douxing Pan, Chao Wang, Tzu-Chiang Wang, Yugui Yao
Because of the combined advantages of both porous materials and two-dimensional (2D) graphene sheets, superior mechanical properties of three-dimensional (3D) graphene foams have received much attention from material scientists and energy engineers. Here, a 2D mesoscopic graphene model (Modell. Simul. Mater. Sci. Eng. 2011, 19, 054003), was expanded into a 3D bonded graphene foam system by utilizing physical cross-links and van der Waals forces acting among different mesoscopic graphene flakes by considering the debonding behavior, to evaluate the uniaxial tension behavior and fracture mode based on in situ SEM tensile testing (Carbon 2015, 85, 299)...
August 25, 2017: ACS Nano
Pengwu Xu, Qingtao Zeng, Ying Cao, Piming Ma, Weifu Dong, Mingqing Chen
The interfacial adhesion between polyhydroxyalkanoates (PHAs) and native starch is poor. To improve the interfacial adhesion, PHAs were in-situ grafted onto starch using dicumyl peroxide (DCP) as a free radical initiator. The grafting reaction was carefully characterized and confirmed by gel analysis and Fourier transform infrared spectroscopy (FT-IR). The gel yield of the PHAs/starch/DCP blend increased with the DCP concentration up to 2wt%. Meanwhile, obvious plastic deformation (stretched fibrils) was observed at the interface in the PHAs/starch/DCP blend in comparison with complete interfacial debonding in the PHAs/starch physical blend...
October 15, 2017: Carbohydrate Polymers
Maryam Tamaddon, Sorousheh Samizadeh, Ling Wang, Gordon Blunn, Chaozong Liu
Large bone defects and nonunions are serious complications that are caused by extensive trauma or tumour. As traditional therapies fail to repair these critical-sized defects, tissue engineering scaffolds can be used to regenerate the damaged tissue. Highly porous titanium scaffolds, produced by selective laser sintering with mechanical properties in range of trabecular bone (compressive strength 35 MPa and modulus 73 MPa), can be used in these orthopaedic applications, if a stable mechanical fixation is provided...
2017: International Journal of Biomaterials
Zhaokun Li, Shixin Song, Xuanchen Zhao, Xue Lv, Shulin Sun
In order to overcome the brittleness of polylactide (PLA), reactive core-shell particles (RCS) with polybutadiene as core and methyl methacrylate-co-styrene-co-glycidyl methacrylate as shell were prepared to toughen PLA. Tert-dodecyl mercaptan (TDDM) was used as chain transfer agent to modify the grafting properties (such as grafting degree, shell thickness, internal and external grafting) of the core-shell particles. The introduction of TDDM decreased the grafting degree, shell thickness and the Tg of the core phase...
August 16, 2017: Materials
Hua Jin, Songhe Meng, Weihua Xie, Chenghai Xu, Jiahong Niu
ZrB₂-based nanocomposites with and without carbon nanotubes (CNTs) as reinforcement were prepared at 1600 °C by spark plasma sintering. The effects of CNTs on the microstructure and mechanical properties of nano-ZrB₂ matrix composites were studied. The results indicated that adding CNTs can inhibit the abnormal grain growth of ZrB₂ grains and improve the fracture toughness of the composites. The toughness mechanisms were crack deflection, crack bridging, debonding, and pull-out of CNTs. The experimental results of the nanograined ZrB₂-CNTs composites were compared with those of the micro-grained ZrB₂-CNTs composites...
November 29, 2016: Materials
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