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Methods of assessment of early dentine erosion: a review

Habib M, Chew HP

J Pak Med Assoc, 2019 Oct;69(10):1509-1513.
PMID: 31622307

Dentine erosion is an increasingly recognised problem, especially in aging population, and various methods have been utilised for its assessment. This narrative review was planned to summarise the methods for the assessment of the early stages of dentine erosion. Relevant original articles published in the English language from 2013 to 2017 were reviewed. Laboratory techniques and methods with in vivo potential were separately studied. It is evident that the assessment of early dentine erosion is complex and requires a combination of methods. For clinical evaluation, chemical analysis and optical methods show great potential but are in need of more validation.

Matched MeSH terms: Hardness Tests
Simvastatin-loaded lyophilized wafers as a potential dressing for chronic wounds

Rezvanian M, Tan CK, Ng SF

Drug Dev Ind Pharm, 2016 Dec;42(12):2055-2062.
PMID: 27237190

Wafers are an established drug delivery system for application to suppurating wounds. They can absorb wound exudates and are converted into a gel, offering a moist environment that is vital for wound healing. Simvastatin-loaded lyophilized wafers were developed using sodium carboxymethyl cellulose (CMC) and methyl cellulose (MC) and evaluated for their potential in the management of chronic wounds. Simvastatin (SIM) was chosen as the model drug since it is known to accelerate wound healing by promoting angiogenesis and lymphangiogenesis. Pre-formulation studies were carried out with CMC, MC, and a mixture of CMC and MC. Wafers obtained from aqueous gels of 3% CMC and blend of CMC-MC in the % weight ratio of 2:1 and 1.5:1.5 were selected for further analysis. The formulated wafers were characterized by microscopic examination, texture analysis, hydration test, rheological studies, FTIR spectroscopy, water vapor transmission and drug release test. Among the selected formulations, simvastatin-loaded CMC-MC (2:1) wafers exhibited the most desired characteristics for wound dressing application, such as good flexibility, hardness, sponginess, and viscosity. It showed a sustained drug release, which is desirable in wound healing, and was more appropriate for suppurating wounds. In conclusion, simvastatin-loaded CMC-MC (2:1) wafers showing potential for wound dressing applications were successfully developed.

Matched MeSH terms: Hardness
Development and Standardization of Moringa oleifera Leaves as a Natural Dietary Supplement

Ali MA, Yusof YA, Chin NL, Ibrahim MN, Muneer S

J Diet Suppl, 2019;16(1):66-85.
PMID: 29469600 DOI: 10.1080/19390211.2018.1429517

Moringa oleifera leaves were selected as a model due to their hundreds of health benefits. On the other hand, the powder of these leaves has exhibited poor flowability, low tensile strength, bitter taste, poor dissolution rate, and lack of information regarding dosage. These are the common hurdles and limitations in the adaptation of herbal-based medications. Therefore, a comprehensive study was planned to introduce herbal-based medicines into mainstream medicines by standardization according to the U.S. Food and Drug Administration (FDA) and international pharmaceutical standards. A Simplex Lattice Design (SLD) of Design Expert 8.0 software was used to formulate different concentrations of superdisintegrant, binder/diluent, and sweeteners. An Instron Universal Testing machine coupled with a 13 mm stainless cylindrical die was used to manufacture tablets by means of direct compression method at 20 kN applied force. Therefore, selection of excipients was made on the basis of their tensile strength, flowability, and taste-masking properties. Optimum formulation was tested on rabbits for toxicity and growth rate. All formulated tablets were evaluated on standard parameters for orally disintegrating tablets described by the Food and Drug Authority (U.S.). The optimum formulation fulfills all standard parameters such as hardness, disintegration time, friability, and dissolution rate. The present formulation showed no toxicity when tested on rabbits. The present study provides a fundamental understanding of the tableting characteristics of natural medicines. The present study provides information that will help to overcome the challenges.

Matched MeSH terms: Hardness
E-beam sterilizable thermoplastics elastomers for healthcare devices: Mechanical, morphology, and in vivo studies

Balaji AB, Ratnam CT, Khalid M, Walvekar R

J Biomater Appl, 2018 03;32(8):1049-1062.
PMID: 29298552 DOI: 10.1177/0885328217750476

The effect of electron beam radiation on ethylene-propylene diene terpolymer/polypropylene blends is studied as an attempt to develop radiation sterilizable polypropylene/ethylene-propylene diene terpolymer blends suitable for medical devices. The polypropylene/ethylene-propylene diene terpolymer blends with mixing ratios of 80/20, 50/50, 20/80 were prepared in an internal mixer at 165°C and a rotor speed of 50 rpm/min followed by compression molding. The blends and the individual components were radiated using 3.0 MeV electron beam accelerator at doses ranging from 0 to 100 kGy in air and room temperature. All the samples were tested for tensile strength, elongation at break, hardness, impact strength, and morphological properties. After exposing to 25 and 100 kGy radiation doses, 50% PP blend was selected for in vivo studies. Results revealed that radiation-induced crosslinking is dominating in EPDM dominant blends, while radiation-induced degradation is prevailing in PP dominant blends. The 20% PP blend was found to be most compatible for 20-60 kGy radiation sterilization. The retention in impact strength with enhanced tensile strength of 20% PP blend at 20-60 kGy believed to be associated with increased compatibility between PP and EPDM along with the radiation-induced crosslinking. The scanning electron micrographs of the fracture surfaces of the PP/EPDM blends showed evidences consistent with the above contentation. The in vivo studies provide an instinct that the radiated blends are safe to be used for healthcare devices.

Matched MeSH terms: Hardness
Characterization of nickel-doped biphasic calcium phosphate/graphene nanoplatelet composites for biomedical application

Baradaran S, Moghaddam E, Nasiri-Tabrizi B, Basirun WJ, Mehrali M, Sookhakian M, et al.

Mater Sci Eng C Mater Biol Appl, 2015 Apr;49:656-668.
PMID: 25686995 DOI: 10.1016/j.msec.2015.01.050

The effect of the addition of an ionic dopant to calcium phosphates for biomedical applications requires specific research due to the essential roles played in such processes. In the present study, the mechanical and biological properties of Ni-doped hydroxyapatite (HA) and Ni-doped HA mixed with graphene nanoplatelets (GNPs) were evaluated. Ni (3wt.% and 6wt.%)-doped HA was synthesized using a continuous precipitation method and calcined at 900°C for 1h. The GNP (0.5-2wt.%)-reinforced 6% Ni-doped HA (Ni6) composite was prepared using rotary ball milling for 15h. The sintering process was performed using hot isostatic pressing at processing conditions of 1150°C and 160MPa with a 1-h holding time. The results indicated that the phase compositions and structural features of the products were noticeably affected by the Ni and GNPs. The mechanical properties of Ni6 and 1.5Ni6 were increased by 55% and 75% in hardness, 59% and 163% in fracture toughness and 120% and 85% in elastic modulus compared with monolithic HA, respectively. The in-vitro biological behavior was investigated using h-FOB osteoblast cells in 1, 3 and 5days of culture. Based on the osteoblast results, the cytotoxicity of the products was indeed affected by the Ni doping. In addition, the effect of GNPs on the growth and proliferation of osteoblast cells was investigated in Ni6 composites containing different ratios of GNPs, where 1.5wt.% was the optimum value.

Matched MeSH terms: Hardness
Fabrication and mechanical properties of Al2O3/SiC/ZrO2 functionally graded material by electrophoretic deposition

Askari E, Mehrali M, Metselaar IH, Kadri NA, Rahman MM

J Mech Behav Biomed Mater, 2012 Aug;12:144-50.
PMID: 22732480 DOI: 10.1016/j.jmbbm.2012.02.029

This study describes the synthesis of Al(2)O(3)/SiC/ZrO(2) functionally graded material (FGM) in bio-implants (artificial joints) by electrophoretic deposition (EPD). A suitable suspension that was based on 2-butanone was applied for the EPD of Al(2)O(3)/SiC/ZrO(2), and a pressureless sintering process was applied as a presintering. Hot isostatic pressing (HIP) was used to densify the deposit, with beneficial mechanical properties after 2 h at 1800 °C in Ar atmosphere. The maximum hardness in the outer layer (90 vol.% Al(2)O(3)+10 vol.% SiC) and maximum fracture toughness in the core layer (75 vol.% Al(2)O(3)+10 vol.% SiC + 15 vol.% ZrO(2)) composite were 20.8±0.3 GPa and 8±0.1 MPa m(1/2), respectively. The results, when compared with results from Al(2)O(3)/ZrO(2) FGM, showed that SiC increased the compressive stresses in the outer layers, while the inner layers were under a residual tensile stress.

Matched MeSH terms: Hardness
Fulltext Synthesis of Radiation Curable Palm Oil-Based Epoxy Acrylate: NMR and FTIR Spectroscopic Investigations

Salih AM, Ahmad MB, Ibrahim NA, Dahlan KZ, Tajau R, Mahmood MH, et al.

Molecules, 2015;20(8):14191-211.
PMID: 26248072 DOI: 10.3390/molecules200814191

Over the past few decades, there has been an increasing demand for bio-based polymers and resins in industrial applications, due to their potential lower cost and environmental impact compared with petroleum-based counterparts. The present research concerns the synthesis of epoxidized palm oil acrylate (EPOLA) from an epoxidized palm oil product (EPOP) as environmentally friendly material. EPOP was acrylated by acrylic acid via a ring opening reaction. The kinetics of the acrylation reaction were monitored throughout the reaction course and the acid value of the reaction mixture reached 10 mg KOH/g after 16 h, indicating the consumption of the acrylic acid. The obtained epoxy acrylate was investigated intensively by means of FTIR and NMR spectroscopy, and the results revealed that the ring opening reaction was completed successfully with an acrylation yield about 82%. The UV free radical polymerization of EPOLA was carried out using two types of photoinitiators. The radiation curing behavior was determined by following the conversion of the acrylate groups. The cross-linking density and the hardness of the cured EPOLA films were measured to evaluate the effect of the photoinitiator on the solid film characteristics, besides, the thermal and mechanical properties were also evaluated.

Matched MeSH terms: Hardness
Flexibility and hardness of dental stainless steel wrought wires used in Thailand

Benjakul P, Cheunarrom C, Ongthiemsak C

J Oral Sci, 2001 Mar;43(1):15-9.
PMID: 11383631

Stainless steel wrought wires used as clasp arms for removable partial dentures in Thailand were compared with those used in some other countries (in the as-received condition) in terms of flexibility, Vickers microhardness and composition. The results showed that there were significant differences (P< or =0.05) among the wires. A Japanese stainless steel wire (SK) was obviously different from the others. It had the lowest proportional limit and microhardness, but its flexibility was almost the same. The chemical composition of each wire was not greatly different. The wires were about 18-20 wt% chromium and 8-9 wt% nickel, except for the SK wire, which had about 12 wt% nickel.

Matched MeSH terms: Hardness
Fulltext Effect of sintering parameters on physical and mechanical properties of powder injection moulded stainless steel-hydroxyapatite composite

Ramli MI, Sulong AB, Muhamad N, Muchtar A, Arifin A, Mohd Foudzi F, et al.

PLoS One, 2018;13(10):e0206247.
PMID: 30359433 DOI: 10.1371/journal.pone.0206247

The combination of metallic bio-inert material, stainless-steel 316L (SS316L) and a bio-active material, hydroxyapatite (HA) can produce a composite which has superior properties for orthopaedic applications. The main objective of this study is to investigate the effects of sintering temperature and holding time on the physical and mechanical properties of the sintered part. 50wt.% SS316L and 50wt.% HA were mixed with a binder system of palm stearin (PS) and polyethylene (PE) at 61 vol.% powder loading. Rheological properties show a pseudo-plastic behaviour of the feedstock, where viscosity decreases with increasing shear rate. The feedstock was injection moulded into a tensile bar shape while thermal debinding was carried out at 320°C and 500°C. The brown parts were sintered at 1000, 1100, 1200 and 1300°C, with three different sintering times of 1, 3 and 5 hours in the furnace. It was found that the highest sintered density measured was 95.61% of the theoretical density. In addition, the highest hardness and Young's modulus measured were 150.45 HV and 52.61 GPa respectively, which are higher than those of human bone. The lowest percentage of carbon content was 0.022wt.% given by the sample sintered at 1300°C for 1 hour. Therefore, SS316L/HA composite with good mechanical and physical properties was successfully produced through the PIM process.

Matched MeSH terms: Hardness
Fulltext Formulation and in vitro, in vivo evaluation of effervescent floating sustained-release imatinib mesylate tablet

Kadivar A, Kamalidehghan B, Javar HA, Davoudi ET, Zaharuddin ND, Sabeti B, et al.

PLoS One, 2015;10(6):e0126874.
PMID: 26035710 DOI: 10.1371/journal.pone.0126874

Imatinib mesylate is an antineoplastic agent which has high absorption in the upper part of the gastrointestinal tract (GIT). Conventional imatinib mesylate (Gleevec) tablets produce rapid and relatively high peak blood levels and requires frequent administration to keep the plasma drug level at an effective range. This might cause side effects, reduced effectiveness and poor therapeutic management. Therefore, floating sustained-release Imatinib tablets were developed to allow the tablets to be released in the upper part of the GIT and overcome the inadequacy of conventional tablets.

Matched MeSH terms: Hardness
Effects of anodizing parameters and heat treatment on nanotopographical features, bioactivity, and cell culture response of additively manufactured porous titanium

Amin Yavari S, Chai YC, Böttger AJ, Wauthle R, Schrooten J, Weinans H, et al.

Mater Sci Eng C Mater Biol Appl, 2015 Jun;51:132-8.
PMID: 25842117 DOI: 10.1016/j.msec.2015.02.050

Anodizing could be used for bio-functionalization of the surfaces of titanium alloys. In this study, we use anodizing for creating nanotubes on the surface of porous titanium alloy bone substitutes manufactured using selective laser melting. Different sets of anodizing parameters (voltage: 10 or 20V anodizing time: 30min to 3h) are used for anodizing porous titanium structures that were later heat treated at 500°C. The nanotopographical features are examined using electron microscopy while the bioactivity of anodized surfaces is measured using immersion tests in the simulated body fluid (SBF). Moreover, the effects of anodizing and heat treatment on the performance of one representative anodized porous titanium structures are evaluated using in vitro cell culture assays using human periosteum-derived cells (hPDCs). It has been shown that while anodizing with different anodizing parameters results in very different nanotopographical features, i.e. nanotubes in the range of 20 to 55nm, anodized surfaces have limited apatite-forming ability regardless of the applied anodizing parameters. The results of in vitro cell culture show that both anodizing, and thus generation of regular nanotopographical feature, and heat treatment improve the cell culture response of porous titanium. In particular, cell proliferation measured using metabolic activity and DNA content was improved for anodized and heat treated as well as for anodized but not heat-treated specimens. Heat treatment additionally improved the cell attachment of porous titanium surfaces and upregulated expression of osteogenic markers. Anodized but not heat-treated specimens showed some limited signs of upregulated expression of osteogenic markers. In conclusion, while varying the anodizing parameters creates different nanotube structure, it does not improve apatite-forming ability of porous titanium. However, both anodizing and heat treatment at 500°C improve the cell culture response of porous titanium.

Matched MeSH terms: Hardness
Some mechanical properties of a highly cross-linked, microwave-polymerized, injection-molded denture base polymer

Memon MS, Yunus N, Razak AA

Int J Prosthodont, 2001 May-Jun;14(3):214-8.
PMID: 11484567

PURPOSE: The impact strength and the flexural properties of denture base materials are of importance in predicting their clinical performance upon sudden loading. This study compares the impact and transverse strengths and the flexural modulus of three denture base polymers.
MATERIALS AND METHODS: The investigation included a relatively new microwave-polymerized polyurethane-based denture material processed by an injection-molding technique, a conventional microwave-polymerized denture material, and a heat-polymerized compression-molded poly(methyl methacrylate) (PMMA) denture material. Impact strength was determined using a Charpy-type impact tester. The transverse strength and the flexural modulus were assessed with a three-point bending test. The results were subjected to statistical analysis using a one-way analysis of variance and the Scheffé test for comparison.
RESULTS: The impact strength of the microwave-polymerized injection-molded polymer was 6.3 kl/m2, while its flexural strength was 66.2 MPa. These values were lower than those shown by the two compression-molded PMMA-based polymers. The differences were statistically significant. The flexural modulus of the new denture material was 2,832 MPa, which was higher than the conventional heat-polymerized polymer but was comparable to the other microwave-polymerized PMMA-based polymer. The difference in the flexural modulus was statistically significant.
CONCLUSION: In terms of the impact and flexural strengths, the new microwave-polymerized, injection-molded, polyurethane-based polymer offered no advantage over the existing heat- and microwave-polymerized PMMA-based denture base polymers. However, it has a rigidity comparable to that of the microwave-polymerized PMMA polymer.

Matched MeSH terms: Hardness
Cellular and Molecular Interaction of Human Dermal Fibroblasts with Bacterial Nanocellulose Composite Hydrogel for Tissue Regeneration

Xi Loh EY, Fauzi MB, Ng MH, Ng PY, Ng SF, Ariffin H, et al.

ACS Appl Mater Interfaces, 2018 Nov 21;10(46):39532-39543.
PMID: 30372014 DOI: 10.1021/acsami.8b16645

The evaluation of the interaction of cells with biomaterials is fundamental to establish the suitability of the biomaterial for a specific application. In this study, the properties of bacterial nanocellulose/acrylic acid (BNC/AA) hydrogels fabricated with varying BNC to AA ratios and electron-beam irradiation doses were determined. The manner these hydrogel properties influence the behavior of human dermal fibroblasts (HDFs) at the cellular and molecular levels was also investigated, relating it to its application both as a cell carrier and wound dressing material. Swelling, hardness, adhesive force (wet), porosity, and hydrophilicity (dry) of the hydrogels were dependent on the degree of cross-linking and the amount of AA incorporated in the hydrogels. However, water vapor transmission rate, pore size, hydrophilicity (semidry), and topography were similar between all formulations, leading to a similar cell attachment and proliferation profile. At the cellular level, the hydrogel demonstrated rapid cell adhesion, maintained HDFs viability and morphology, restricted cellular migration, and facilitated fast transfer of cells. At the molecular level, the hydrogel affected nine wound-healing genes (IL6, IL10, MMP2, CTSK, FGF7, GM-CSF, TGFB1, COX2, and F3). The findings indicate that the BNC/AA hydrogel is a potential biomaterial that can be employed as a wound-dressing material to incorporate HDFs for the acceleration of wound healing.

Matched MeSH terms: Hardness
Measuring initial enamel erosion with quantitative light-induced fluorescence and optical coherence tomography: an in vitro validation study

Chew HP, Zakian CM, Pretty IA, Ellwood RP

Caries Res, 2014;48(3):254-62.
PMID: 24481141 DOI: 10.1159/000354411

BACKGROUND: Measurement of initial enamel erosion is currently limited to in vitro methods. Optical coherence tomography (OCT) and quantitative light-induced fluorescence (QLF) have been used clinically to study advanced erosion. Little is known about their potential on initial enamel erosion.
OBJECTIVES: To evaluate the sensitivity of QLF and OCT in detecting initial dental erosion in vitro.
METHODS: 12 human incisors were embedded in resin except for a window on the buccal surface. Bonding agent was applied to half of the window, creating an exposed and non-exposed area. Baseline measurements were taken with QLF, OCT and surface microhardness. Samples were immersed in orange juice for 60 min and measurements taken stepwise every 10 min. QLF was used to compare the loss of fluorescence between the two areas. The OCT system, OCS1300SS (Thorlabs Ltd.), was used to record the intensity of backscattered light of both areas. Multiple linear regression and paired t test were used to compare the change of the outcome measures.
RESULTS: All 3 instruments demonstrated significant dose responses with the erosive challenge interval (p < 0.05) and a detection threshold of 10 min from baseline. Thereafter, surface microhardness demonstrated significant changes after every 10 min of erosion, QLF at 4 erosive intervals (20, 40, 50 and 60 min) while OCT at only 2 (50 and 60 min).
CONCLUSION: It can be concluded that OCT and QLF were able to detect demineralization after 10 min of erosive challenge and could be used to monitor the progression of demineralization of initial enamel erosion in vitro.

Matched MeSH terms: Hardness
Investigation on the effect of polymer and starch on the tablet properties of lyophilized orally disintegrating tablet

Liew KB, Peh KK

Arch Pharm Res, 2021 Aug;44(8):1-10.
PMID: 25579848 DOI: 10.1007/s12272-014-0542-y

Orally disintegrating tablet (ODT) is a user friendly and convenient dosage form. The study aimed to investigate the effect of polymers and wheat starch on the tablet properties of lyophilized ODT, with dapoxetine as model drug. Three polymers (hydroxypropylmethyl cellulose, carbopol 934P and Eudragit® EPO) and wheat starch were used as matrix forming materials in preparation of lyophilized ODT. The polymeric dispersion was casted into a mould and kept in a freezer at -20 °C for 4 h before freeze dried for 12 h. It was found that increasing in HPMC and Carbopol 934P concentrations produced tablets with higher hardness and longer disintegration time. In contrast, Eudragit® EPO was unable to form tablet with sufficient hardness at various concentrations. Moreover, HPMC seems to have a stronger effect on tablet hardness compared to Carbopol 934P at the same concentration level. ODT of less friable was obtained. Wheat starch acted as binder which strengthen the hardness of ODTs and prolonged the disintegration time. ODT comprising of HPMC and wheat starch at ratio of 2:1 was found to be optimum based upon the tablet properties. The optimum formulation was palatable and 80 % of the drug was released within 30 min in the dissolution study.

Matched MeSH terms: Hardness
Development of a bone substitute material based on alpha-tricalcium phosphate scaffold coated with carbonate apatite/poly-epsilon-caprolactone

Bang LT, Ramesh S, Purbolaksono J, Long BD, Chandran H, Ramesh S, et al.

Biomed Mater, 2015 Aug;10(4):045011.
PMID: 26225725 DOI: 10.1088/1748-6041/10/4/045011

Interconnected porous tricalcium phosphate ceramics are considered to be potential bone substitutes. However, insufficient mechanical properties when using tricalcium phosphate powders remain a challenge. To mitigate these issues, we have developed a new approach to produce an interconnected alpha-tricalcium phosphate (α-TCP) scaffold and to perform surface modification on the scaffold with a composite layer, which consists of hybrid carbonate apatite / poly-epsilon-caprolactone (CO3Ap/PCL) with enhanced mechanical properties and biological performance. Different CO3Ap combinations were tested to evaluate the optimal mechanical strength and in vitro cell response of the scaffold. The α-TCP scaffold coated with CO3Ap/PCL maintained a fully interconnected structure with a porosity of 80% to 86% and achieved an improved compressive strength mimicking that of cancellous bone. The addition of CO3Ap coupled with the fully interconnected microstructure of the α-TCP scaffolds coated with CO3Ap/PCL increased cell attachment, accelerated proliferation and resulted in greater alkaline phosphatase (ALP) activity. Hence, our bone substitute exhibited promising potential for applications in cancellous bone-type replacement.

Matched MeSH terms: Hardness
Taste-masked and affordable donepezil hydrochloride orally disintegrating tablet as promising solution for non-compliance in Alzheimer's disease patients

Liew KB, Tan YT, Peh KK

Drug Dev Ind Pharm, 2015 Apr;41(4):583-93.
PMID: 24495273 DOI: 10.3109/03639045.2014.884130

Manufacturing process and superdisintegrants used in orally disintegrating tablet (ODT) formulation are often time discussed. However, the effect of suitable filler for ODT formulation is not explored thoroughly.

Matched MeSH terms: Hardness

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