Dalam makalah ini, masalah aliran genangan dalam bendalir mikrokutub terhadap permukaan mencancang yang telap dengan fluks haba boleh ubah dipertimbangkan. Dengan menggunakan penjelmaan keserupaan, persamaan asas yang menakluk aliran bendalir dan pemindahan haba dijelmakan kepada satu set persamaan perbezaan biasa. Persamaan yang dijelmakan tertakluk kepada syarat-syarat sempadan yang berkaitan kemudiannya diselesaikan secara berangka menggunakan kaedah tembakan. Kesan parameter sedutan/semburan fw ke atas profil halaju dan suhu serta pekali geseran kulit dan nombor Nusselt setempat diperoleh dan dibincangkan. Keputusan berangka menunjukkan bahawa penyelesaian dual wujud dalam kedua-dua aliran membantu dan aliran menentang.
BACKGROUND: The clinical success of relining depends on the ability of reline resin to bond to denture base. Surface preparations may influence reline bond strength of urethane-based dimethacrylate denture base resin.
AIM: To investigate the effect of bur preparation on the surface roughness (R a ) of eclipse denture base resin and its shear bond strength (SBS) to an intra-oral self-curing reline material. The mode of reline bonding failure was also examined.
MATERIALS AND METHODS: Twenty-four cylindrical Eclipse™ specimens were prepared and separated into three groups of eight specimens each. Two groups were subjected to mechanical preparation using standard and fine tungsten carbide (TC) burs and the third group (control) was left unprepared. The R a of all specimens was measured using a contact stylus profilometer. Subsequently, relining was done on the prepared surface and SBS testing was carried out a day later using a universal testing machine.
RESULTS: One-way ANOVA revealed significant differences (P<0.05) in R a and SBS values for all the groups. Post-hoc Tukey's HSD test showed significant differences (P<0.05) between all the groups in the R a values. For SBS also there were significant differences (P<0.05), except between standard bur and control.
CONCLUSIONS: 1) There was a statistically significant difference in the R a of Eclipse™ specimens prepared using different carbide burs (P<0.05). 2) There was a statistically significant difference in the relined SBS (P<0.05) when prepared using different burs, but the difference between the standard bur and the control group was not statistically significant.
Amelogenesis imperfecta represents a group of dental developmental conditions that are genomic in origin. Hypoplastic AI, hypomineralised AI or both in combination were the most common types seen clinically. This paper describes oral rehabilitation of a 9-year-old Malay girl with inherited hypoplastic AI using transparent thermoforming templates. The defective surface areas were reconstructed to their original dimensions on stone cast models of the upper and lower arches using composite, and transparent thermoform templates were fabricated on the models. The templates were used as crown formers to reconstruct the defective teeth clinically using esthetically matching composite. The usage of the templates allowed direct light curing of the composite, accurate reproducibility of the anatomic contours of the defective teeth, reduced chair-side time and easy contouring and placement of homogenous thickness of composite in otherwise inaccessible sites of the affected teeth.
Some restorative materials are susceptible to erosion but whether it also causes microleakage is still questionable. The aim of this study was to assess the microleakage of few restorative materials after immersion in acidic solution. Standardized ‘U’ shaped cavity of 4mm diameter and 2mm depth were prepared on buccal or lingual surface of 52 human premolar and molar teeth. The teeth were divided into 4 groups which contains 13 samples and 3 controls for each and were restored either with Filtek Z250 (Group 1), Fuji IX (Group 2), Fuji II LC (Group 3), or Silverfill amalgam (Group 4).
All surfaces were painted with nail varnish leaving only 2mm of tooth structure surrounding the restoration before the study samples were immersed in acidic solution, lemon juice (pH 2.74) and control samples in deionised distilled water for 24 hours. Surface photos for erosion were taken before immersion in methylene blue for 7 days. After sectioning, the assessment of dye penetration was done using Leica Imaging System DMLM (Germany). Photos showed that Fuji IX demonstrated severe erosion but no obvious changes were seen on other materials. Kruskal-Wallis test indicated that microleakage between all four groups were statistically significant. The most significant difference was between Filtek Z250 and Fuji IX (p
Evaluation of the mechanical behaviour of restoration dental materials is essential to understand their performance under different load conditions and to estimate their durability under clinical oral function. Restorative materials and dental tissues like other materials by having specific mechanical properties, such as static strength (i.e. compressive strength, tensile strength, flexural strength) and dynamic strength (i.e. fatigue strength). The selection of proper mechanical test type depends on the goals that the study claims to define. On such basis, the mechanical test can be chosen correctly. Laboratory studies should be designed as replications of the clinical oral circumstances to measure the mechanical and physical properties of a material and any arbitrary choices in the design of the study may result in large variations of data.
Survei keberintangan geoelektrik ini telah dijalankan di kawasan Bukit Tenggek, Setiu, Terengganu untuk mengesan kemungkinan wujudnya terowong lama yang dipercayai berada di kawasan berkenaan. Kaedah keberintangan geoelektrik ini bukanlah asing dan didapati amat berkesan di dalam eksplorasi mencari bahan arkeologi dan struktur terkambus di bawah tanah (terowong dan bahan artifak). Survei keberintangan geoelektrik ini dijalankan dengan menggunakan peralatan ABEM Terrameter SAS1000 dan susun atur elektrod jenis Wenner. Kawasan kajian terletak di kawasan lembah yang lembap dan terdapat anak sungai yang merentasi kawasan tersebut. Imej keberintangan 2-D menunjukkan wujudnya beberapa kawasan beranomali yang boleh dikaitkan dengan struktur yang dicari. Nilai keberintangan yang rendah mewakili kawasan yang dianggarkan wujudnya terowong lama. Manakala anomali yang menunjukkan bentuk gugusan dianggarkan berasosiasi dengan lokasi tong/bahan artifak. Profil keberintangan 3-D menunjukkan anomali yang mungkin disebabkan oleh wujudnya satu terowong mendatar dan dua terowong menegak. Namun, kerja galicari perlu dilakukan bagi menentukan punca sebenar anomali tersebut.
The purpose of this in vitro study was to determine if packable resin composite with/without flowable resin composite has the ability to prevent coronal leakage in restored endodontic access openings following aging.
Objectives: To evaluate the marginal microleakage of Class II cavities restored with various types of composite resins.
Materials and Methods: Standard Class II slot cavities were prepared at the proximal surfaces of 40 intact premolars which were divided into 4 groups. Four types of composite resins (Esthet-X-Denstply, USA, FiltekTMZ350- 3M ESPE, USA, Beautifil- Shofu, Japan and Solare P-GC, Japan) were used to restore the slot cavities. All the specimens were thermocycled and immersed in 0.5% basic fuschin dye for 24 hours. The specimens were then sectioned in mesio-distal direction. The marginal microleakage at the occlusal and cervical margin was scored using the ISO microleakage scoring system. Data was entered using SPSS Version 12.0 and analyzed using STATA software programme.
Results and discussion: All composite resins exhibited worse microleakage at the cervical margin compared to occlusal margin. Esthet-X showed significantly better microleakage score at the occlusal margin compared to Beautifil and Solare P. FiltekTMZ350 and Beautifil showed mainly microleakage into enamel only at the occlusal margin. Solare P demostrated better resistance against microleakage at the cervical margin compared to other composite resin tested. Esthet-X, Filtek Z350 and Beautiful is not significantly different from each other in terms of microleakage at the cervical margin.
Conclusion: This study showed that none of the materials used in this study is able to eliminate microleakage. Composite resin restorations exhibited worse micorleakage at cervical margin in comparison to occlusal margin.
The widespread use of aesthetic fillings has highlighted their advantages and disadvantages. One
of the most troublesome features of earlier aesthetic materials was the difficulty of finishing the restoration surface to decrease adherence of food debris. The rougher the finished surface, the greater the possibility of bacterial accumulation and discolouration of restoration along the restoration margin with secondary caries formation. Aside from these clinical implications, patients are highly discerning and could detect roughness of 0.30 μm with their tongue. The aesthetic restoration should mimic the appearance of natural dentition and should have an enamel-like appearance. An increased demand for superior aesthetics from composite resin has increased the
demand for more eff icient and simple polishing techniques. The development of nanocomposites has given a new perspective to the polishing of composite resins. Nanocomposites claim the advantage of improved gloss, optical characteristics and reduced wear. To date, results of in vitro studies have been equivocal regarding the most efficient and effective polishing system. There is variation in the effects of different finishing and polishing instruments on the surface roughness due to great diversity in size, shape, composition and distribution of the filler particles of composite resins, type of resin and a wide variety of finishing and polishing instruments. This paper will
review the different factors that affect polishing techniques used in achieving the desired polish on
composite resin restorations.
Endodontically treated teeth are generally weaker than sound teeth. The study objective was to compare the fracture resistance of endodontically treated teeth restored with different restorative techniques. Fifty extracted human maxillary central incisors of similar size were divided into five groups of 10 teeth. Group 1 was left intact as the control group. Other groups (Groups 2, 3, 4 and 5) were all endodontically treated followed by restorations using different restorative techniques; light cured composite resin (CR), CR and crown, post and CR, and post-CR core and crown respectively. The specimens were loaded in a universal testing machine with a static force at a crosshead speed of 0.5mm/min at 135 ° to the long axis of the root until failure. The means and the standard deviations of the maximum load at failure for groups 1, 2, 3, 4 and 5 were 1259.11N (379.12N), 578.63N (196.70N), 667.13N (298.72N), 1247.65N (294.48N) and 623.60N (193.75N) respectively. The results of one-way ANOVA showed statistically significant differences existed among the groups tested (p
Penggunaan formulasi tablet pelepasan tertahan untuk dadah anti-inflamatori bukan steroid (DAIBS) seperti aspirin berupaya melindungi lapisan perut dari kesan buruk jus asid tubuh. Kajian ini dilakukan untuk menilai keberkesanan formulasi tablet matriks pelepasan tertahan dengan kepelbagaian kepekatan polimer bersama ketoprofen sebagai model. Tablet dibangunkan dengan menggunakan kaedah granulasi basah yang terdiri daripada polimer hidrofilik (hidroksipropil metilselulosa), polimer hidrifobik bersandar pada pH (Eudragit L100-55) dan polimer tak bersandar pada pH (Eudragit R100) sebagai bahan asas pembentukan matriks pada kepekatan 10, 20 dan 30%b/b. Semua formulasi dimampatkan dengan menggunakan mesin pentabletan yang mempunyai penebuk berbentuk cembung bersaiz 10 mm. Tablet yang terhasil diuji daripada segi keseragaman berat, kekerasan, kerapuhan, ketebalan, peratus kandungan dadah dan kajian pelepasan in vitro menggunakan kaedah BP 2007. Hasil menunjukkan kadar pelepasan dadah dikawal oleh jenis dan kepekatan polimer di dalam formulasi matriks. Secara umumnya peningkatan kepekatan kandungan polimer di dalam tablet matriks didapati mengurangkan kadar pelepasan dadah. Perbandingan polimer melalui kepekatan yang sama menggunakan t50%, pula mendapati terdapat perbezaan statistik bermakna (p<0.05) pada kadar pelepasan dadah. Berdasarkan kepada pelepasan dadah dalam kajian in vitro, polimer hidrofobik bersandar pada pH (Eudragit L100-55) menunjukkan profil pelepasan dadah secara tertib sifar yang terbaik berbanding polimer yang lain.
Fire-retarding polyurethane (PU) composite was produced by adding 2,4-ditert-butylphenyl phosphite (FR) to palm-based monoester resin with loading percentage of 0, 2, 4, and 6 wt%. The Shore D hardness index increased marginally with increasing FR content. However, the impact and flexural strengths decreased with increasing FR loading attributed to the weak interfacial bonding between FR and PU matrix. The fire test indicated lowering of burning rate (from 5.30 mm.s-1 to 2.80 mm.s-1) as the loading percentage of FR increased. The combustion enthalpy of the composites also decreased with higher loading percentage of FR.
Teknik reka bentuk untuk meningkatkan gandaan bagi menambah baik prestasi antena tompok mikrojalur konvensional dibincangkan. Kaedah suapan prob tersongsang jalur lebar bagi antena tompok mikrojalur berbilang lubang alur bertindan dicadangkan. Reka bentuk tersebut menggabungkan beberapa teknik kontemporari iaitu kaedah suapan prob, struktur tompok tersongsang dan tompok berbilang lubang alur bertindan. Kesan komposit daripada penyatuan pelbagai teknik ini dan dengan memperkenalkan bentuk elemen tompok yang baru, memberikan profil yang rendah, jalur lebar yang lebih luas, gandaan tinggi dan elemen antena yang padat. Keputusan menunjukkan peningkatan gandaan di mana gandaan maksimum adalah 11.42 dBi. Reka bentuk ini sesuai untuk aplikasi tata susunan terutama untuk stesen tapak.
Penyelesaian berangka bagi masalah aliran lapisan sempadan olakan bebas mantap terhadap silinder bulat mengufuk yang dijanakan oleh pemanasan Newtonan, iaitu pemindahan haba dari permukaan berkadar langsung dengan suhu permukaan setempat, dipertimbangkan. Persamaan lapisan sempadan terjelma diselesaikan secara berangka dengan suatu skim berangka beza terhingga tersirat yang dikenali sebagai kaedah kotak Keller. Penyelesaian berangka diperoleh bagi pekali geseran kulit, pekali pemindahan haba setempat, suhu dinding serta profil halaju dan suhu. Ciri-ciri aliran dan pemindahan haba bagi suatu julat nilai nombor Prandtl yang besar dianalisis dan dibincangkan.
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.
Phenolic resin-silica nanocomposites samples in pellet shape have been successfully prepared by intercalation of polymer solution through the hot pressing method. The phenolic resin is modified with organic elastomers of silica nanoparticles, which is about 20 nanometer in diameter. The change of density and porosity was studied based on the addition of silica content in the phenolic resin composites. The densities of composites increased with the addition of the silica content from 10 wt.% to 40 wt.%. On the other hand, the porosity percentage was decreased with increasing of silica contents. The mechanical properties (Young’s modulus, energy to break and time to failure) of the nanocomposites samples were identified using the Universal Testing Material Machine (UTM). The results of Young’s modulus, energy to break and time to failure of the phenolic resin composites were found to be slightly increased with silica content from 10 wt.% to 30 wt.%. The X-Ray Microtomogaphy (XRM) topographies have shown that the porosity exists on fracture structure for each nanocomposite. The nanocomposites surface structure has been analyzed using Scanning Electron Microscope (SEM). The observation shows that the fracture surface of the pure phenolic resin is relatively smooth and glassy, which is typical for a brittle material, but the phenolic resin- silica composites fracture surface is not smooth at all. The observations indicate the pure phenolic resin is brittle than phenolic resin-silica nanocomposites. Consequently, the physical properties of the phenolic resin-silica nanocomposites were improved with the addition of 10 wt.% to 30 wt.% silica contents, as compared to that of the pure phenolic resin.
Composite resins Amaris is claimed to have hydrophobic effect which minimizes the staining intake. This study is to investigate the colour stability of Amaris compared to Filtek Z250 in coffee solution. Sixty discs of composite resins Filtek Z250 (3M ESPE) and Amaris (Voco) with diameter of 5mm and depth of 2mm were fabricated by packing in a drinking straw and sectioned with hard tissue cutter (Exakt, Japan). The surfaces of the specimens were polished with Sof-Lex disc before each group of the samples is immersed in coffee solution. They were kept in the solution for 4 days at 370C and assessed at the period of 2 hours, 1 day, 2 days, 3 days, and 4 days. The staining was assessed visually and recorded using Lobene (1968) Stain Index and score was given accordingly. The colour changes of both groups were not statistically significant (p
Kajian ini dijalankan untuk mencirikan kepelbagaian kelakuan cuaca dalam lapisan bawah dan atas atmosfera, terutama kebergantungannya kepada keadaan di dalam troposfera dan ionosfera pada enam stesen yang berbeza di UKM Bangi, Selangor. Pengukuran adalah berasaskan pemonitoran jangka pendek wap air bolehmendak (PWV) dalam troposfera dan jumlah kandungan elektron (TEC) dalam ionosfera menggunakan penerima GPS Bumi. Data PWV, TEC dan pengukuran meteorologi permukaan adalah dicerap bermula 12 November sehingga 7 Disember 2007. Hasil pemonitoran menunjukkan bahawa kedua-dua profil kebolehubahan PWV dan TEC memperlihatkan kitaran harian. Purata harian PWV dan TEC adalah tinggi, masing-masing dengan nilai ~42 mm dan ~35 TECU. Perubahan kedua-duanya didapati dipengaruhi aktiviti Matahari.