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Water activity effect on lipase immobilized onto different compositions of poly(HEMA-MMA)

Esa NM, Yunus WM, Ahmad MB, Basri M, Razak CN, Salleh AB

Ann N Y Acad Sci, 1998 Dec 13;864:489-92.
PMID: 9928130
Matched MeSH terms: Methylmethacrylates*
Proton conducting polymer electrolytes based on PVDF-HFP and PVDF-HFP/PEMA blend

Rudhziah S, Muda N, Ibrahim S, Rahman A, Mohamed N

Sains Malaysiana, 2011;40:1179-1186.

In the present work, polymer electrolytes of poly(vinylidene fluoride co-hexafluoroproplyne) (PVDF-HFP) and PVDF-HFP/poly(ethyl methacrylate) (PVDF-HFP/PEMA) blend complexed with different concentrations of ammonium triflate (NH4CF3SO3) were prepared and characterized. The structural and thermal properties of the electrolytes were studied by XRD and DSC while the electrical properties were investigated by impedance spectroscopy. Ionic transference number measurements were done by D.C polarization technique. The results of these study showed that the PVDF-HFP/PEMA based electrolytes exhibit higher ionic conductivity as compared to PVDF-HFP based electrolytes. This could be attributed to the higher degree of amorphicity in the PVDF-HFP/PEMA based electrolytes. The results of ionic transference number measurements showed that the charge transport in these electrolytes was mainly due to ions and only negligible contribution comes from electrons.

Matched MeSH terms: Methylmethacrylates
Ionic conductivity of PEMA-LiClO4 polymer electrolytes

Amir S, Othman R, Subban R, Mohamed N

Sains Malaysiana, 2011;40:1179-1186.

Solid polymer electrolytes comprised of various weight percent ratios of poly(ethyl methacrylate) (PEMA) and lithium perchlorate (LiClO4) salt were prepared via solution casting technique using N,N-dimethylformamide (DMF) as the solvent. The conductivity values of the electrolytes were determined via impedance spectroscopy. The conductivity of the PEMA-LiClO4 electrolytes increased with increasing salt concentration and the highest conductivity obtained was in the order of 10-6 S cm-1 at salt concentration of 20 wt%. The conductivity decreased for higher salt concentration. In order to understand the conductivity behavior, XRD and dielectric studies were done. The results showed that the conductivity was influenced by the fraction of amorphous region and number of charge carriers in the system. The transference number measurement was also performed on the highest conducting electrolyte systems. The result of the measurement indicated that the systems were ionic conductors.

Matched MeSH terms: Methylmethacrylates
Fulltext Impact strength of an experimental polyurethane- based polymer

Zamri Radzi, Noor Hayaty Abu Kasim, Yahya, N.A., Gan, S.N., Daud, N.M., Saffai, L., et al.

Ann Dent, 2007;14(1):46-51.
MyJurnal

The impact strength of a newly developed experimental polyurethane-based polymer which is derived from palm oil (Experimental PU) was compared with denture polymers; heat-cured and self cured polymethyl methacrylate (PMMA) and ® Eclipse , light-activated urethane dimethacrylate prosthetic resin system. Ten specimens were ® prepared using heat-cured PMMA (Meliodent Heat Cure, Heraeus Kulzer, Germany), self cured PMMA ® (Meliodent Rapid Repair, Heraeus Kulzer, ® Germany), Eclipse baseplate resin (Dentsply, USA) and Experimental PU material. Specimens were prepared following manu- facturer’s instructions except for the Experimental PU material where it was prepared in bulk and sectioned to the desired dimension, 64 x 6 x 4 mm. A ‘V’ notch of approximately 0.8mm in depth was machine cut across the 6mm width. Prior to the Charpy type impact test, specimens were soaked in a water bath for 50 hours at 37ºC. ® Eclipse baseplate resin showed the highest 2 impact strength (2.73 kJ/m ±0.54) followed by ® 2 Meliodent Rapid Repair (2.50kJ/m ±0.65), ® 2 Meliodent Heat Cure (1.96kJ/m ±0.42) and 2 Experimental PU (1.04kJ/m ±0.29). One-way ANOVA showed significant interaction between materials (p

Matched MeSH terms: Methylmethacrylates
Shear bond strength of two chemically different denture base polymers to reline materials

Ahmad F, Dent M, Yunus N

J Prosthodont, 2009 Oct;18(7):596-602.
PMID: 19515166 DOI: 10.1111/j.1532-849X.2009.00481.x

This study evaluated the shear bond strengths of light-polymerized urethane dimethacrylate (Eclipse) and heat-polymerized polymethylmethacrylate (Meliodent) denture base polymers to intraoral and laboratory-processed reline materials.

Matched MeSH terms: Methylmethacrylates/chemistry
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: Methylmethacrylates/radiation effects; Methylmethacrylates/chemistry
Fulltext 13-year-old exposed interlocking nail: a case report

Chua, Y.C.J., Lim, L.A., Hudzairy, A.

Malays Orthop J, 2009;3(1):91-94.
MyJurnal

We are reporting a case of post-traumatic chronic osteomyelitis of the tibia with an open wound exposing an intra medullar nail implant for 13 years. The patient presented with fresh ipsilateral tibia plateau fracture. He was treated by removal of the implant, debridement and local placement of Gentamicin-impregnated PMMA beads according to guidelines of two-stage Belfast technique . After five months of wound treatment, the exposed bone was covered by healthy granulation tissue and the patient was able to fully bear weight.

Matched MeSH terms: Methylmethacrylates
Effect of heparin-surface-modified poly(methyl methacrylate) intraocular lenses on the postoperative inflammation in an Asian population

Lai YK, Fan RF

J Cataract Refract Surg, 1996;22 Suppl 1:830-4.
PMID: 9279680

PURPOSE: To compare the efficacy of heparin-surface-modified (HSM), poly(methyl methacrylate) (PMMA) posterior chamber intraocular lenses (IOLs) with that of unmodified PMMA IOLs in reducing postoperative complications caused by inflammatory reactions after extracapsular cataract extraction in an Asian population.
SETTING: Departments of Ophthalmology, University of Malaya, Kuala Lumpur, Malaysia, and Tan Tock Seng Hospital, Singapore.
METHODS: In a randomized, double-blind study performed at two centers, 51 patients received an HSM PMMA lens and 48, an unmodified PMMA IOL. Cell and pigment deposits were evaluated by slitlamp at 1 to 6 days, 2 to 3 weeks, and 3 to 6 months postoperatively.
RESULTS: Significantly more eyes with unmodified IOLs had inflammatory cell deposits than those with HSM IOLs at 3 to 6 months (P < .001) and 12 to 14 months (P = .018) postoperatively. The HSM group also had significantly fewer cell deposits per patient at these two follow-ups. Significantly more eyes in the non-HSM group had pigment deposits 3 to 6 months after surgery (P = .049). One year postoperatively, about 85% of patients in both groups had a best corrected visual acuity of 0.5 or better.
CONCLUSION: Heparin surface modification significantly reduced the inflammatory response to PMMA IOLs in an Asian population for at least 12 to 14 months.

Matched MeSH terms: Methylmethacrylates*
Hardness, flexural strength, and flexural modulus comparisons of three differently cured denture base systems

Ali IL, Yunus N, Abu-Hassan MI

J Prosthodont, 2008 Oct;17(7):545-9.
PMID: 18761582 DOI: 10.1111/j.1532-849X.2008.00357.x

This study compared the surface hardness, flexural strength, and flexural modulus of a light- and heat-cured urethane dimethacrylate (UDMA) to two conventional polymethyl methacrylate (PMMA) denture base resins. The effect of less-than-optimal processing condition on the hardness of internal and external surfaces of UDMA specimens was also investigated.

Matched MeSH terms: Methylmethacrylates
Fulltext Students perception and satisfactory level in preclinical fixed prosthodontic teaching: post and core

Marlynda Ahmad, Natasya Ahmad Tarib

Malaysian Dental Journal, 2008;29(2):128-134.
MyJurnal

Introduction: Preclinical teaching using simulation is very beneficial in training dental graduates. The use of laboratory simulation for its undergraduate training during the preclinical years has been used in dental education. Purpose: The aim of this study was to evaluate student’s perception, self evaluation and satisfactory level in preparing duralay burn-out post and core in preclinical fixed prosthodontics sessions.

Materials and Methods: The participants comprised of 104 fourth year dental undergraduates in the Faculty of Dentistry Universiti Kebangsaan Malaysia. The students had undergone preclinical session for endodontics during the 3rd year and had already completed root canal treatment on single rooted tooth. The same tooth was used for preclinical post and core preparation. The gutta percha was partially removed and the root canal was prepared. They then proceeded with the preparation of duralay build-up/pattern based on the lecture, video demonstration and manual given. Once completed and satisfied with their work, students were asked to answer the questionnaires in the simulation manual.

Results: Student response rate was 88.46% (92/104). Majority of the students were satisfied with their canal preparation, with about 5mm gutta percha left apically, appropriately shaped canal with sufficient retention and resistance form. They also thought that the surface of the duralay was good with no voids. With regards to the coronal preparation, majority of them incorporated ferrule effect and prepared preliminary crown preparation. More than half of the students claimed the level of difficulty of this procedure was moderate. Furthermore, majority of them said that the lecture and the preclinical manual were sufficient and helpful. The help from the supervisors was also benefit in preparing duralay burnout post and core.

Conclusions: From this study, majority of fourth year dental students could perform appropriate canal preparation as well as duralay pattern post and core. Only one student did not feel competent and confident in doing canal preparation and duralay pattern post and core. Our teaching methods and aids were proven to help them in preparing these tasks.

Matched MeSH terms: Methylmethacrylates
Intracanal bisphosphonate does not inhibit replacement resorption associated with delayed replantation of monkey incisors

Thong YL, Messer HH, Zain RB, Saw LH, Yoong LT

Dent Traumatol, 2009 Aug;25(4):386-93.
PMID: 19459923 DOI: 10.1111/j.1600-9657.2008.00631.x

Progressive replacement resorption following delayed replantation of avulsed teeth has proved to be an intractable clinical problem. A wide variety of therapeutic approaches have failed to result in the predictable arrest of resorption, with a good long-term prognosis for tooth survival. Bisphosphonates are used in the medical management of a range of bone disorders and topically applied bisphosphonate has been reported to inhibit root resorption in dogs. This study evaluated the effectiveness of a bisphosphonate (etidronate disodium) as an intracanal medicament in the root canals of avulsed monkey teeth, placed before replantation after 1 h of extraoral dry storage. Incisors of six Macaca fascicularis monkeys were extracted and stored dry for 1 h. Teeth were then replanted after canal contamination with dental plaque (negative control) or after root canal debridement and placement of etidronate sealed in the canal space. A positive control of calcium hydroxide placed 8-9 days after replantation was also included. All monkeys were sacrificed 8 weeks later and block sections were prepared for histomorphometric assessment of root resorption and periodontal ligament status. Untreated teeth showed the greatest extent of root resorption (46% of the root surface), which was predominantly inflammatory in nature. Calcium hydroxide treated teeth showed the lowest overall level of resorption (<30% of the root surface), while the bisphosphonate-treated group was intermediate (39%). Ankylosis, defined as the extent of the root surface demonstrating direct bony union to both intact and resorbed root surface, was the lowest in the untreated control group (15% of the root surface), intermediate in the calcium hydroxide group (27%) and the highest in the bisphosphonate group (41%). Bony attachment to the tooth root was divided approximately equally between attachment to intact cementum and to previously resorbed dentin. Overall, bisphosphonate resulted in a worse outcome than calcium hydroxide in terms of both root resorption and ankylosis.

Matched MeSH terms: Methylmethacrylates/therapeutic use