Noor Hayaty Abu Kasim

Abstract: This study aimed to compare the biomechanical behaviour of functionally graded structured posts (FGSPs) and homogenous-type posts in simulated models of a maxillary central incisor. Two models of FGSPs consisting of a multilayer xTi-yHA composite design, where zirconia and alumina was added as the first layer for models A and B respectively were compared to homogenous zirconia post (model C) and a titanium post (model D). The amount of Ti and HA in the FGSP models was varied in gradations. 3D-FEA was performed on all models and stress distributions were investigated along the dental post. In addition, interface stresses between the posts and their surrounding structures were investigated under vertical, oblique, and horizontal loadings. Strain distribution along the post-dentine interface was also investigated. The results showed that FGSPs models, A and B demonstrated better stress distribution than models C and D, indicating that dental posts with multilayered structure dissipate localized and interfacial stress and strain more efficiently than homogenous-type posts.

Abstract: A series of poly(urea-formaldehyde) (PUF) microcapsules filled with dicyclopentadiene (DCPD) was successfully prepared by in situ polymerization. The effect of diverse process parameters and ingredients on the morphology of the microcapsules was observed by SEM, optical microscopy (OM) and digital microscopy. Different techniques for the characterization of the chemical structure and the core content were considered such as FT-IR and (1)H-NMR as well as the characterization of thermal properties by DSC. High yields of free flowing powder of spherical microcapsules were produced. The synthesized microcapsules can be incorporated into another polymeric host material. In the event the host material cracks due to excessive stress or strong impact, the microcapsules would rupture to release the DCPD, which could polymerize to repair the crack.

Abstract: The post-natal dental pulp tissue contains a population of multipotent mesenchymal progenitor cells known as dental pulp stromal?stem cells (DPSCs), with high proliferative potential for self-renewal. In this investigation, we explored the potential of DPSCs to differentiate into pancreatic cell lineage resembling islet-like cell aggregates (ICAs). We isolated, propagated, and characterized DPSCs and demonstrated that these could be differentiated into adipogenic, chondrogenic, and osteogenic lineage upon exposure to an appropriate cocktail of differentiating agents. Using a three-step protocol reported previously by our group, we succeeded in obtaining ICAs from DPSCs. The identity of ICAs was confirmed as islets by dithiozone-positive staining, as well as by expression of C-peptide, Pdx-1, Pax4, Pax6, Ngn3, and Isl-1. There were several-fold up-regulations of these transcription factors proportional to days of differentiation as compared with undifferentiated DPSCs. Day 10 ICAs released insulin and C-peptide in a glucose-dependent manner, exhibiting in vitro functionality. Our results demonstrated for the first time that DPSCs could be differentiated into pancreatic cell lineage and offer an unconventional and non-controversial source of human tissue that could be used for autologous stem cell therapy in diabetes.

Abstract: A multilayered titanium (Ti)â??hydroxyapatite (HA) functionally graded material was produced via pressureless sintering at 1100�?C. The initial and final porosities were determined via shrinkage measurements. The final porosity verification was carried out by the Archimedes method. The experimental porosity measurements were compared with two proposed models. The macroscopic and microstructure features and the measured porosities confirmed that the volume fraction porosity was associated with both matrix and reinforcing particles in all cases. The percolation threshold was observed at x = 0�?75 in the xTi?(1â??x)HA mixture.

Abstract: Dental pulp stromal cells (DPSC) are considered to be a promising source of stem cells in the field of regenerative therapy. However, the usage of DPSC in transplantation requires large-scale expansion to cater for the need for clinical quantity without compromising current good manufacturing practice (cGMP). Existing protocols for cell culturing make use of fetal bovine serum (FBS) as a nutritional supplement. Unfortunately, FBS is an undesirable additive to cells because it carries the risk of transmitting viral and prion diseases. Therefore, the present study was undertaken to examine the efficacy of human platelet lysate (HPL) as a substitute for FBS in a large-scale set-up. Methods. We expanded the DPSC in Dulbecco�s modified Eagle�s medium-knock-out (DMEM-KO) with either 10% FBS or 10% HPL, and studied the characteristics of DPSC at pre- (T25 culture flask) and post- (5-STACK chamber) large-scale expansion in terms of their identity, quality, functionality, molecular signatures and cytogenetic stability. Results. In both pre- and post-large-scale expansion, DPSC expanded in HPL showed extensive proliferation of cells (c. 2-fold) compared with FBS; the purity, immune phenotype, colony-forming unit potential and differentiation were comparable. Furthermore, to understand the gene expression profiling, the transcriptomes and cytogenetics of DPSC expanded under HPL and FBS were compared, revealing similar expression profiles. Conclusions. We present a highly economized expansion of DPSC in HPL, yielding double the amount of cells while retaining their basic characteristics during a shorter time period under cGMP conditions, making it suitable for therapeutic applications.

Abstract: Urea-formaldehyde (UF) microcapsules filled with dicyclopentadiene (DCPD) show potential for making self-healing dental restorative materials. To enhance the physical properties of the capsules, the urea was partially replaced with 0-5% melamine. The microcapsules were analyzed by different microscopic techniques. DSC was used to examine the capsule shell, and the core content was confirmed by (1)H NMR spectroscopy. Capsules in the range of 50-300 mu m were then embedded in a dental composite matrix consisting of bisphenol-A-glycidyl dimethacrylate (Bis-GMA) and triethylene-glycol dimethacrylate (TEGDMA). Flexural strength, microhardness, and nanoindentation hardness measurements were performed on the light-cured specimens. Optical microscopy (OM) examination showed a random distribution of the microspheres throughout the host material. The incorporation of small amounts of the microcapsules did not affect the performance of the matrix material. Scanning electron microscopy (SEM) analysis revealed excellent bonding of the microcapsules to the host material which is a characteristic of utter importance for maintaining the very good mechanical properties of a dental composite with self-healing ability. (C) 2011 Wiley Periodicals, Inc. J Appl Polym Sci 122: 2557-2562, 2011

Abstract: Objective: The aim of this study was to investigate the cytotoxicity effect of polyurethane dimethacrylate monomer derived from palm oil polyol (PUDMA) and 2 experimental composite resins based on these monomer PUDMA- based composites) compared to an experimental Bis-GMA?TEGDMA-based composite and EsthetX flowable composite (Dentsply, Caulk, USA). Methods: The experimental composite resins were prepared by mixing 0.25 and 0.75 by weight camphorquinone and ethyl (4-dimethyl amino) benzoate with 60 filler for each of the following monomer systems; I) PUDMA monomer (PUDMA-based composite resin), II) Bis-GMA?TEGDMA at ratio of 75:25 by weight, III) PUDMA?BisGMA-TEGDMA at ratio of 50:50 by weight. Eight disk specimens of 2mm thick and 8mm in diater were prepared from the PUDMA monomer and each experimental composites and EsthetX. All specimens were cured for 40 seconds on both sides. Mouse fibroblast cell lines (L-929) and MTS assay were used to evaluate the cytotoxicity effect of all composites extraction according to ISO 10993-12:2002. Data was analysed using ANOVA and multiple comparison was carried out, P=.05 Results: The percentage of viable cells was lowest in the PUDMA monomer, P \ensuremath< .05. However, it was evident that the percentage of viable cells in the PUDMA?BisGMA-TEGDMA, Bis-GMA?TEGDMA and EsthetX flowable composite was high and no statistical difference were detected. Conclusion: PUDMA derived from palm oil polyol showed equally high percentage of viable cells compared to Bis-GMA?TEGDMA-based composites and EsthetX flowable composite. This study was supported by e-Sceince Fund, Ministry of Science and Innovation, Malaysia 03-01-03SF0190

Abstract: Metal Injection Molding (MIM) is a cost-effective technique for producing small, complex, precision parts in high volumes. MIM consists of four main processing steps: mixing, injection molding, debinding and sintering. In the mixing step, the powder titanium alloy (Ti6Al4V) medical grade is mixed with a binder system based on palm stearin to form a homogeneous feedstock. The rheological studies of the feedstock have been determined properly in order to success during injection into injection molding machine. After molding, the binder holds the particles in place. The binder systems then have to be removed completely through debinding step. Any contamination of the binder systems will affect the final properties of the parts. During debinding step, solvent extraction debinding has been used to remove partly of the binder systems. The debound part is then sintered at high temperature under control atmosphere furnace. The properties of the sintered craniofacial implants then was measured and compared. The sintered craniofacial implants also then were determined in term of in-vitro cytotoxicity study using mouse fibroblast lines L-929. The results show that the sintered craniofacial implants of titanium alloy produced by MIM fullfill the in-vitro cytotoxicity test.

Abstract: Objective: To evaluate the effect of viscosity and type of grooves on surface detail reproduction of elastomeric impression materials. Methods: Express putty?light-, Impregum medium- and heavy?light-bodied and Aquasil medium- and putty?light-bodied elastomeric impression materials were chosen for this study. Five impressions were made using a cylindrical aluminum reference block with U- and V- shaped grooves and to produce 35 master dies. Each master die was immersed in distilled water at 370 C for 5 minutes prior to the impression making on moist surfaces. Surface topography of the dies and impressions were captured using Alicona Imaging System. The mean difference in depth between the master dies and its corresponding impressions were analysed using two-way ANOVA, p=.01. Results: The lowest mean difference in depth for U- and V-shaped grooves was obtained from the Express putty?light group. The highest mean difference in depth for U- and V-shaped grooves was obtained from Impregum medium, Aquasil medium, Impregumâ??�? heavy?light and Impregum heavy?light groups respectively. Two-way ANOVA indicated that there was a significant difference in the effect of materials (p \ensuremath< .01) and grooves (p \ensuremath< .01). Conclusion: Express putty?light-bodied elastomeric material produced the best surface detail, and U-shaped groove showed better surface detail reproduction than V-shaped groove.

Abstract: Lately, several new stem cell sources and their effective isolation have been reported that claim to have potential for therapeutic applications. However, it is not yet clear which type of stem cell sources are most potent and best for targeted therapy. Lack of understanding of nature of these cells and their lineage-specific propensity might hinder their full potential. Therefore, understanding the gene expression profile that indicates their lineage-specific proclivity is fundamental to the development of successful cell-based therapies. Methods: We compared proliferation rate, gene expression profile, and lineage-specific propensity of stem cells derived from human deciduous (SCD) and permanent teeth (DPSCs) over 5 passages. Results: The proliferation rate of SCD was higher (cell number, 25 x 10(6) cells?mL; percent colony-forming units CFUs, 151.67 ??- 10.5; percent cells in S?G2 phase, 12.4 ??- 1.48) than that of DPSCs (cell number, 21 x 10(6) cells?mL; percent CFUs, 133 ??- 17.62; percent cells in S?G2 phase, 10.4 ??- 1.18). It was observed that fold expression of several pluripotent markers such as OCT4, SOX2, NANOG, and REX1 were higher ($$ensuremath\ensuremath>2) in SCD as compared with DPSCs. However, DPSCs showed higher expression of neuroectodermal markers PAX6, GBX2, and nestin (fold expression $$ensuremath\ensuremath>100). Similarly, higher neurosphere formation and neuronal marker expression (NF, GFAP) were found in the differentiated DPSCs into neuron-like cells as compared with SCD. Conclusions: This study thus demonstrates that both SCD and DPSCs exhibit specific gene expression profile, with clear-cut inclination of DPSCs toward neuronal lineage. (J Endod 2010;36:1504-1515)

Abstract: The case report, which has a long history in medicine, has seen its fortune wax and wane with time. We discuss the challenges facing the continued survival of the case report, including the inability of journals to cope with the increased load and increased cost of publication, ethical issues, the impact factor and the rise of evidence-based medicine. We highlight the important role that the case report will continue to play in medical research and education, as a means of sharing information and detecting novelty through observations. Most importantly, the case report serves as a stepping stone for young physicians and practitioners into the world of medical writing.

Abstract: Objective: To evaluate the demineralization potential of qat extracts at composite restoration interface. Methods: Class V cavities were prepared on the buccal surface of thirty extracted sound premolars and were restored with a nanohybrid composite (Grandio, VOCO, Germany). Specimens were subsequently coated with nail varnish exposing 2mm of enamel around the restoration margin. The specimens were divided into three equal groups of 10 and were then immersed in acid gel and qat extracts (10 and 20) for 4 weeks. All specimens were removed and washed using deionized water and later examined by direct vision and stereomicroscope prior to sectioning. Specimens were then immersed in distilled water for 24 hours, following which the sections were examined under polarized light microscope and demineralized area was measured as outer and wall lesion in the coronal and cervical part of restoration using image analyzer software (Image-Pro Version 4.5). Data were subjected to One-way MANOVA. Results: All specimens immersed in acid gel and qat extracts (10 and 20) exhibit demineralization at the restoration interface. The One-way MANOVA also indicated significant differences between the three groups on the different restoration interface (P\ensuremath<.05) and Tukey multiple comparison test was also performed as illustrated in the table below. Conclusion: 10 and 20 qat caused significantly lower demineralization at restoration interface compared to acid gel. This study was supported by a research grant from University of Malaya, P02182007a.

Abstract: Objectives: This study is an attempt to enhance the properties of conventional PMMA denture material by incorporation of a polyfunctional polyol derived from palm oil by copolymerization with methyl methacrylate monomer to overcome the low fatigue resistance property of PMMA. Methods: A series of copolymerizations of palm oil polyol with MMA was performed in solution. The polyol was added from 40-20 , MMA from 20-40 , benzoyl peroxide as initiator was at 0.04 and toluene used as solvent was at 60 of the total weight. The copolymerization was carried out in a 500ml-round-bottom reaction flask, equipped with a magnetic stirrer, for 7.5 hour at 80�?C, in a water bath. The yield of each copolymerization obtained was recorded and the conversion was estimated gravimetrically. Later, the polymers acquired were analyzed by FTIR. Results: The copolymerizations have achieved conversions that ranged from 24 to 95, where the higher conversion was obtained when the reactant mixture contain higher amount of MMA. The reaction produced a clear color, light-weighted copolymer that has the potential to be developed as denture material. The evidence of incorporation of the polyol into PMMA was given by the FTIR measurements, by comparing the spectrum of the copolymer to the spectrum of PMMA and polyol. Evaluations of the mechanical properties were currently being carried out. Conclusion: The new copolymers have potential of being developed into new dental materials. The branching structure of the copolymer was expected to improve the impact strength of PMMA. In addition, the palm oil based polyol was made from natural sustainable material. This study was supported by E-Science fund, Grant No.: 03-0103-SF0190 and University of Malaya, Postgraduate Research Vote Grant No. : PS 079C? 2007C and National Science Fellowship (NSF 2007?2008).

Abstract: Objectives:Biocompatibility is an important desirable property for a dental polymer and it can be achieved by utilizing more materials from natural sources. The flexural strength of an experimental polymer prepared from MMA monomer modified with palm-oil polyol was compared to two commercial resins,namely the Lucitone 199�? (Dentsply Trubyte, USA) and Impact (Ivoclar Vivadent, Liechtenstein). Methods: The experimental polymer was prepared by copolymerizing MMA monomer and palm oil polyol. The resulting polymer was cast into a plate form and sectioned using a precision diamond saw (Buhler, Germany) to form 10 specimens of dimension, 65mm x 11mm x 5mm. These specimens were then polished to achieve a nominal dimension of 64mm x 10mm x 3.3mm. Another 10 specimens were prepared using Lucitone 199�? and Impact according to the manufacturers� instructions and were polished by the same procedure. Their flexural strengths were determined using a three point bend test on an Instron Universal Testing Machine (Anytown, Australia)according to the procedure of test method ISO 1567. Data obtained was analysed using Oneway ANOVA (SPSS 12.0) at 95 confidence interval. Results: The mean flexural strength of Lucitone 199�? was 127.39MPa (�$\pm$16.54), Impact was 177.57MPa (�$\pm$11.44) and experimental polymer was 51.62MPa (�$\pm$4.21). Although the experimental polymer has exhibited higher flexural strength than PMMA homopolymer, it has lower flexural strength when compared to Lucitone 199�? and Impact denture base resins, both of which were filler-reinforced materials. Conclusions:In this preliminary study, the experimental polymer contained a significant proportion of non-petroleum based materials derived from palm oil. Its lower flexural strength is expected to be enhanced and improved through the incorporation of reinforcing fillers or fibers in future work.

Abstract: Objectives: This study aim to evaluate the cutting efficiency of tungsten carbide burs (TC) and rotary diamond instruments by measuring their rake angle and visual examination of their cutting surfaces respectively, using scanning electron microscopy (SEM). Materials and Method: 60 short and long head pear-shaped TC and 18 round rotary diamond instruments that had been used to prepare \ensuremath< than 5, \ensuremath> than 5 and \ensuremath> than 10 cavities were selected from the 3rd & 4th year dental students, Dental Faculty, University of Malaya. 12 cylindrical and flame rotary diamond instruments were also selected from the 5th year students. The rake angle of TC was measured and surfaces of diamond instruments were evaluated using Field Emission Scanning Electron Microscope (FESEM). Each test group comprised of 10 samples and new burs constituted the control group. The data were analysed descriptively and statistically using Two-way ANOVA, SPSS version 12. Results: The rake angles of control, \ensuremath< than 5 and \ensuremath> than 5 groups were significantly higher compared to \ensuremath> than 10 groups, p\ensuremath< .05. Rotary diamond instruments used to prepare \ensuremath< than 5 cavities showed intact diamond particles with distinct cutting facets comparable to control group. Instruments used to prepare \ensuremath> than 10 teeth showed blunt and dislodged diamond particles. Conclusions: The rake angle of TC is significantly lower and diamond instruments showed blunt diamond particles after cutting \ensuremath> than 10 preparations.

Abstract: Objective: The aim of this study was to investigate the degree of conversion and cross-linking of polyurethane dimethacrylate (PUDMA), derived from palm oil polyol, for dental resin application. Methods: Polyurethane dimethacrylate was synthesized by reacting excess amount of Methylene diphenyl diisocyanate (MDI) with palm oil polyol. The resulting isocyanate polyurethane prepolymer was then acrylated using hydroxymethacrylate (HEMA). Fourier transform infrared spectroscopy was used to ascertain the formation of PUDMA, and to determine the degree of conversion (DC) of: I) PUDMA, II) Bis-GMA, III)Bis-EMA,IV) Bis-GMA?TEGDMA (3:1), V) Bis-GMA?TEGDMA(3:1)?Bis-EMA (3:1), VI) PUDMA?Bis-EMA (3:1), VII) Bis-GMA?TEGDMA(3:1)?PUDMA (1:1), and VIII) Bis-GMA?TEGDMA(3:1)?PUDMA?Bis-EMA (1-1-1). The photo initiator system Camphorquinone (CQ) and Ethyl-4-N,N-dimethylaminobenzoate (EDMAB) was used with ratio 0.25 and 0.75 by weight, respectively, for all monomers. The results were analyzed using one way ANOVA and Post Hoc Dunnett T3 for multiple comparisons. Results: The FTIR spectrum of PUDMA showed that the isocyanate peaks was absent and appearance of urethane peak. The results of degree of conversion showed that, the unreacted C=C in Bis-GMA is more than 50 , however, the DC of PUDMA is 63 with cross linking 0.4. The resin systems which contain PUDMA showed higher DC and cross-linking than that of other resin system. Conclusions: The degree of conversion of PUDMA monomer is highly significant than Bis-GMA, with more cross-linking. The PUDMA could improve the DC and cross-linking of resin system. Therefore, PUDMA may have promising mechanical properties and biocompatibility.

Abstract: 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 manufacturerâ??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 â??Vâ?? 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 37�?C. Eclipse�? baseplate resin showed the highest impact strength (2.73 kJ?m2�$\pm$0.54) followed by Meliodent�? Rapid Repair (2.50kJ?m2�$\pm$0.65), Meliodent�? Heat Cure (1.96kJ?m2�$\pm$0.42) and Experimental PU (1.04kJ?m2�$\pm$0.29). One-way ANOVA showed significant interaction between materials (p\ensuremath<.05) and Tukey HSD revealed that Experimental PU exhibited significantly lower impact strength compared to other materials. Meliodent�? Rapid Repair was not significantly different from Meliodent�? Heat Cure and Eclipse�? baseplate resin. It can be concluded that the Experimental PU exhibited the lowest impact strength while Eclipse�? baseplate resin the highest.

Abstract: In the implementation of criterion-based assessment some disparities in the interpretation of the assessment criteria have been observed.Therefore it is essential that a standardization exercise be carried out to ensure equitable and fair assessment. Objectives: The purpose of the study was to evaluate inter-examiner variability and examiners� internal consistency in applying a criterion-based assessment. Method: The subjects consisted of 9 full-time staff of the Department of Conservative Dentistry, University of Malaya, 4 part-time staff and 2 postgraduate students. One buccally-approached and one palatally-approached Class III cavity preparation were assessed according to a set of criteria developed by the department. Both preparations were cut by undergraduates in their preclinical year of study. Examiners rated each cavity on a 5-point scale (1=Redo, 2=Modification required, 3=Pass with minor mistakes, 4=Pass, and 5=Good). Ratings were analyzed based on the Many-facet Rasch model using its computer application, Facets, version 3.48.0. Results: Varying levels of examiner severity were found ranging from -1.99 logits to 0.18 logit. However, the majority of the examiners fall between -1.04 logits and -0.31 logit. The percentage of exact agreement was 45.5. Several examiners were found to be inconsistent in their ratings as indicated by the Infit and Outfit mean-square statistics. Results also revealed range restrictions amongst some examiners. With respect to the assessment criteria, some were misfitting; these include (1) shape of cavity outline, (2) bevel width, (3) bevel thickness, (4) preservation of contact point and (5) placement of labial wall. On the other hand, several criteria demonstrated high agreement amongst examiners. These were (1) 90o cavo-surface angle, (2) rounded internal line angle, and (3) contour of axial wall. Conclusions: This study has highlighted the need for standardization of assessment criteria intepretation and better staff training in the assessment of preclinical students� operative skills.

Abstract: Objectives: To identify the nature of multiple intelligences among dental students and investigate the relationship between these intelligences and performance in the various skill areas of dentistry. Methods: Sixty-one final year dental students at the Faculty of Dentistry, University of Malaya in Malaysia were administered a Multiple Intelligence Inventory (MII), David Larear, 1991) after their final written examinations. MII comprised 80 4-point likert items assessing eight types of multiple intelligences: Verbal?Linguistic, Visual Spatial, Logical Mathematical, Musical Rhythmic, Intra Personal, Body Kinesthetic, Inter Personal and Naturalist. These intelligences were correlated with six academic performance scores: Amalgam Class II, Composite, Crown & Bridge, Endodontic, Problem Based Learning and the Final Written Exam. The data were analysed by Pearson Product Moment Correlation and t-test. Results: Significant correlations were found between Intrapersonal intelligence and Composite (r = .32; p \ensuremath< .05) and between Body Kinesthetic and Composite scores (r = .26; p \ensuremath< .05). High Amalgam Class II scorers obtained significantly higher scores on Intrapersonal Intelligence than low scorers (t = 2.49; p \ensuremath< .05). High Composite scorers have significantly higher Body Kinesthetic intelligence than low scorers (t = .29; p \ensuremath< .05). Low endodontic scorers obtained significantly higher scores on Visual Spatial intelligence than high scorers (t = 2.06; p \ensuremath< .05). High PBL scorers obtained significantly higher Interpersonal (t = 2.06; p \ensuremath< .05) and Naturalist Intelligence (t = 3.57; p \ensuremath< .05) than low scorers. Conclusions: There appears to be no significant correlations between the various types of multiple intelligences and achievement in dentistry except for the correlations between Composite scores and Intrapersonal and Body Kinesthetic Intelligence. Generally, there were no significant multiple intelligence differences among high and low performers.

Abstract: Introduction: Owing to the variety of materials and methods employed, comparison of the results and findings from bonding studies is difficult. Until recently, several types of teeth have been used in published research papers as a substrate in orthodontic bonding research including bovine incisors, fresh and rebonded human premolars. Objectives: The purpose of this study was to compare the shear bond strength of an adhesive bonded to different tooth surfaces (human premolar, bovine incisor and rebonded human premolar). Methods: Two groups of thirty premolar teeth and one group of bovine incisors had brackets attached in a standardized manner using Transbond XT (3M Unitek). The adhesive was cured using conventional halogen light and a specially designed tool to standardize the distance between the light curing tip and the adhesive. The debonding force was measured using Instron universal testing machine. ANOVA and Post Hoc Dunnett C test were performed to determine any significant difference among groups (p\ensuremath<0.05). Results: The results of Post Hoc Dunnett C test indicated no statistical differences between the human premolar group and rebonded group. However, the differences existed in bond strength between bovine group versus human premolar group and bovine group versus human rebonded premolar group. Bovine group had the highest bond strength with mean values of 8.5 (S.D �$\pm$ 4.2) MPa. Human premolar and rebonded groups had mean bond strengths of 6.1(S.D �$\pm$ 4.5) and 4.9 (S.D �$\pm$ 2.7) MPa, respectively. Conclusions: This study revealed that bovine teeth produced higher bond strength compared to b o t h f r e s h a n d re b o n d e d h u m a n p r e m o l a r. Therefore, findings in any bond strength studies u s i n g b ovi n e t e e t h s h o u l d b e i n t e r p re t e d wi t h caution.

Abstract: Objective: To compare the surface microhardness of composites(Spectrum�?TPH, Filtekâ??Z350, Ceramâ??X mono and Ceramâ??X duo-enamel shade) before and after immersion in alcohol containing mouthrinses (Listerine), alcohol-free mouthrinses (Oral-B) and experimental herbal mouthrinses based on plant extract (mouthrinses X, Y and Z). Methods: 60 disc-shaped specimens of approximately 10mm x 2mm were perpared from various composites using perspex split mould and was cured for 40 seconds. The irradiated surface was polished using Sof-Lex pop-on polishing discs. The specimens were randomly divided to 6 groups. Microhardness was recorded before immersion (control group) using a load of 200g for 15 seconds using Vickers microhardness tester, (Shimadzu Corp, Kyoto, Japan). All specimens were then immersed in 20ml of Listerine,Oral B- Tooth and gum care alcohol-free mouth rinses, Experimental Mouth rinses X, Y and Z and distilled water for 24 hours at 37�? C, after which micro hardness value was measured again. Data collected was analyzed using one-way ANOVA ? Games-Howell post-hoc test for multiple comparisons between groups. Specimens were also subjected to surface analysis using AFM (Ambios Technology Universal Scanning Probe Microscopyâ??).Results: Filtek Z350 exhibited the highest Vickers microhardness number (VHN) and Ceram X Duo had the lowest VHN before immersion. All tested composite showed significant decreased in surface microhardness (VHN) compared to before immersion. Filtek Z350 showed the highest VHN and TPH Spectrum showed the lowest VHN after immersion. Ceram X Duo showed the roughest surface before immersion. The surface roughness of Ceram X Mono was high when immersed in experimental mouthrinses. Conclusions: Filtek Z350 exhibited significantly higher VHN compared to other composites tested. All composites showed significant decreased in VHN compared to before immersion. There was no significant different of VHN between mouthrinses, however it was material dependent. This study was supported by the Vot F:Grant no F0350?2005C, University of Malaya.

Abstract: Objective: This study evaluated the effect of an active oxygen based disinfectant, 2 Perform�? (Schulke & Mayr, Germany) on the dimensional accuracy of four alginates, Alginoplast (Heraeus Kulzer, Holland), Kromopan (LASCOD, Italy), Alginmax (MAJOR, Italy) and Duplast (Dentsply, China). Method: A cobalt chromium master model with four cylindrical studs representing 2 canines and 2 molars was constructed. A total of 40 impressions for each alginates were taken and treated in 4 different conditions, Immediate pour (control); 10 minutes immersion in distilled water; 10 minutes immersion in 2 Perform�? and 30 minutes in 2 Perform�?. The impressions were then poured in Type III stone. Dimensional changes between the master model and the resultant casts were measured using traveling microscope. The change at an antero-posterior dimension (C) and 3 different interarch dimensions (A,B and D) were noted. Results: Two way ANOVA showed significant interaction between alginates and treatment conditions except for dimension B and D. One-way ANOVA test and Student-Newman-Keuls indicated no significant difference (P\ensuremath> 0.05) in dimensional accuracy of impressions treated with Perform�? for 10 minutes compared to the control group except for Alginoplast (dimension A) and Duplast (dimension C and D). The maximum deviation in the dimension after 10 minutes Perform�? immersion was 0.552 for Duplast and 0.147 to 0.213 for other alginates. Immersion in Perform�? for 30 minutes produced maximum deviation of 0.591 for Duplast in dimension C whilst 0.223 to 0.235 for other alginates. Conclusion: Active oxygen based disinfectant has an effect on the dimensional accuracy of the resultant cast for the 4 alginates. Although some results indicated significant change, the magnitude of deviation was clinically negligible. Apart from Duplast, all the alginates indicated good stability in 2 Perform�? even up to 30 minutes of immersion time. (This study was supported by University of Malaya ; R&D FO200?2003D)

Abstract: Dental burs are a source of bacterial contamination due to its direct contact with carious teeth, saliva and blood. Objective: The aim of this study was to evaluate the disinfecting and cleaning ability of selected commercially available disinfectants on dental burs. Method: Size 5 round stainless steel burs were used to excavate caries from freshly extracted human molars. The burs were then immediately immersed in Grotanat Drill Bath (Sh�?lke & Mayr, Germany), Micro 10 (Unident, Swizerland), Gigasept FF (Sh�?lke & Mayr, Germany), Lysetol AF (Sh�?lke & Mayr, Germany) and 70 Isopropyl alcohol (J.Y. Baker, USA) according to the manufacturer�s instructions. Each test groups consisted of 10 burs. Positive and negative control groups (n=10) were also included in this study. The disinfecting ability of the disinfectants was evaluated using bacterial culture where presence and absence of bacterial colonies were noted. The cleaning ability was then assessed using scanning electron microscopy. Results: The results showed that the disinfecting ability of Grotanat Drill Bath was statistically significant when compared to all disinfectants evaluated, p\ensuremath<0.05. There was also a significant difference between the positive and negative groups. Examination of scanning electron micrographs showed that Grotanat Drill Bath exhibited the best cleaning ability compared to the other disinfectants evaluated. A positive correlation between bacterial growth and cleaning ability of disinfectants was also evident. Conclusion: It can be concluded that Grotanat Drill Bath is an effective disinfectant for the disinfection and cleaning of round stainless steel burs.

Abstract: Supervised practice in the dental clinic is one of the teaching tools in preparing a good dental practitioner. Teachers who are efficient in helping students learn in these settings improve this process. The ability to impart good feedback and carry out proper assessment is an important measure of effectiveness. Objective: The purpose of this study was to investigate the perception of students from the Faculty of Dentistry, University of Malaya towards effective clinical feedback and assessment from the staff of the Dept. of Conservative Dentistry. Method: A 4-point Likert-type scale questionnaire was formulated according to Myers, 1977 (J.Dent.Edu 41:68-76). Aspects of clinical feedback and assessment in the questionnaire include:- 1) the ability to be critical in assessing students� work, 2) the usage of criterion-based assessment and 3) the manner in which feedback are given to students. One hundred and sixty dental students from Year IV and V participated in this survey. Results: Generally, student responses showed that assessment and clinical feedback were carried out by staff. The data were subjected to two statistical procedures; exploratory factor analysis and Rasch rating scale analysis. Factor analysis indicated that all 3 constructs were clearly measured by the items in the questionnaire. Rasch rating scale analysis revealed logit values of -0.78 and -0.18 for the usage of criterion-based assessment when assessing students� clinical work. The highest logit value of 0.45, 0.37 and 0.34 were for the third construct; the students would like feedback be given privately and with a view to helping them improve their clinical performance. Conclusion: Students place great emphasis on the manner feedback is given and assessment is conducted of their clinical performance.

Abstract: The impaction of dental prostheses in either the airway or esophagus is an under-recognized problem which may result in severe morbidity or even mortality. The radio-opacity and the size of fixed and removable dental prostheses in an animal carcass was investigated. Prostheses were placed one at a time in the oro-laryngopharynx or in tho trachea and the esophagus. Lateral radiographs were taken for each prosthesis in site. The radio-opacity and size of the prostheses on the radiograph was graded. Most of the prostheses investigated were radio-opaque though the removable prostheses were more likely to be radiolucent and differ in size. In a symptomatic patient with a missing dental prosthesis, a negative chest or abdominal radiograph does not exclude impaction, inhalation or ingestion. Further evaluation with endoscopy or even computed tomography may be essential to reduce the possibility of severe morbidity or even mortality.

Abstract: A new method of producing and evaluating surface fatigue using a rolling-ball device has been developed. The method involves constraining a rolling ruby ball between the �v� groove of a rotor and the test specimen. The ball applies a compressive stress to the surface of the test material whilst it rolls in a circular pattern across the specimen surface. The fatigue life is defined as the time taken for surface degradation to begin to occur. The method is simple and reproducible and allows fatigue data to be gathered using a relatively small number of specimens. A series of model dental composites having varying filler fractions (23.7-66.4 vol%) were used to assess the potential of the method. The pattern of material loss as well as scanning electron microscopy examination of the damaged surfaces of test specimens confirmed that a fatigue mechanism was responsible for material loss. The fatigue life varied markedly with filler volume fraction being optimized at values in the range 30-50 vol%. Lower and higher volume fractions reduced the fatigue life. Filler silanation significantly improves fatigue life. The results suggest that the rolling ball device will prove useful in comparing the properties of different materials and in the development of improved products.

Abstract: Microleakage testing has been used to determine the possible clinical performance of a restorative material. Many microleakage testing materials have been developed and performed through the years. There has been no agreement as to which testing methodology would give the most accurate results. Attempts have been made to simulate the oral conditions and to give a more quantitative representation of micro leakage. The different micro leakage testing methodologies are presented in this paper.

Abstract: Objective: The main purpose of this paper is to present a new method of predicting clinical performance using mechanical loading in a ball mill. Methods: A series of four experiments (two involving a hybrid composite and one each on orthodontic brackets and bands) is described in which the ball mill was used to subject specimens to mechanical fatigue. Results: A reproducibility study using composite beam specimens showed no significant difference between the Mean Survival Time (MST) in all the three experimental runs (P = 0.42). When subjected to thermal cycling, the MST of the cycled group was 155.0 min compared to 247.0 min fur the control group (P \ensuremath< 0.01). The MST of untreated and sandblasted brackets was 7.9 h and 14 h respectively (P \ensuremath< 0.01). There is also a significant difference (P \ensuremath< 0.001) in the MST of sandblasted bands when compared to the untreated bands. Conclusions: The ball mill proved to be a convenient and reproducible means of producing mechanical fatigue and may be useful in predicting the clinical performance of dental materials.

Abstract: The effect of thermocycling on the fatigue behaviour of 2 microfilled composites; Silux Plus3 and Heliomolar2 and 3 hybrid composites; P502, Cleafil Photo Posterior3 (both light-activated) and Cleafil Posterior3 (chemically-activated) was investigated using a ball mill. Ninety specimens (2 x 2 x 25mm) of each material were used. The specimes were divided into 3 groups of 30 and were stored for 24 h in water at 37oC (Group A), subjected to 104 thermal cycle over 45 days (Group B) and stored in water at 37oC for 45 days (Group C). Ten specimens of each material were tested in a 0.5 litre capacity ceramic ball mill4 which was rotated at 100 rev?min. This procedure was repeated 3 times. The mill was charged with 470g steatite balls and 250m1 distilled water. At 30 minute intervals the number of fractured specimens was noted. All fractured and intact specimens were returned to the ball mill and the process repeated up to 5 hours. T�he mean survival time (mins) for P50 were \ensuremath>300(A), 85(B) and 130(C); Silux \ensuremath>300(A), 76(B) and 110(C); Heliomolar \ensuremath>300(A), 240(B) and \ensuremath>300(A); Clearfi Photo \ensuremath>300(A), \ensuremath>300(B), \ensuremath>300(C) and Cleafil Posterior \ensuremath>300(A), 165(B) and 160(C). Group A is significantly different (P\ensuremath< .05) from Groups B and C for all materials except Cearfil1 Photo Posterior. Howver, significant differences (P\ensuremath<.05) between Group B and C wan only observed in P50 and Silux. The fatigue behaviour of P50 and Silux is affected by thermocycling. 13M, St Paul,USA; 2Vivadent, Liechtenstein; 3Kuraray, Japan; 4Pascal Engineering, UK.

Abstract: SilverFil (Silverfildental Products, Malaysia) is another commercially available dental amalgam; however it is based on silver and mercury only. It is claimed that upon amalgamation, there is no excess mercury in SilverFil. Objectives: The objectives of this study were to determine the structural state and chemical composition of the starting materials and presence of mercury in the resulting amalgam. Methods: All the starting materials of SilverFil and the SilverFil amalgam specimens were characterize using Field Emission Scanning Electron Microscopy (FESEM-EDX), X-Ray Diffraction (XRD) and X-Ray Photoelectron Spectroscopy (XPS). Results: The FESEM images of the amalgam shows silver-mercury (Ag-Hg) clusters. The elemental mapping of SilverFilTM shows good distribution of Ag and Hg. The EDX analysis showed that all the chemical composition of the starting materials contain no and consist of only Ag and Hg. These results agreed concurred with the XRD analysis. The XRD analysis also revealed that the chemical composition of SilverFil is similar to naturally occuring mineral called â??Moschellandsbergiteâ??. The XPS analysis showed that there was no free mercury (Hg0) present in the starting material. When the resulting amalgam was analysed, the binding energy of Hg(4f) were 101.8eV and 100.6eV confirming the presence of bonded mercury to oxygen (HgO). Conclusion: It can be concluded that there was no free mercury present in SilverFil.

Abstract: Objective: To analyse thermo-mechanical stress in endodontically treated teeth restored with Multilayered Structured Dental Posts (MSDPs) under cold and hot conditions using Finite Element Analysis (FEM). Methods: Three MSDPs of multilayer design of xTi-yHA composition added to a zirconia layer (model A), an alumina layer (model B) and a titanium layer (model C) were compared with zirconia (model D) and titanium (model E) posts. The fractions of Ti and HA was varied gradually. Changes in temperature of an endodontically restored tooth model were calculated as a result of hot and cold response. The resulting thermo-mechanical stresses were analysed and compared using FEM in models A, B, C, D and E. Results: It was noted that Models A, B and C returned to near body temperature better than that Models of D and E. There was no evident difference in all MSDPs models. The smallest Von Mises thermal stresses were observed in MSDPs (models A, B and C) compared to models D and E. There were no also differences in Von Mises thermal stresses for all MSDPs. The magnitude of interface of stresses in models D and E with the surrounding tooth structures were greater than those in MSDPs especially in area close to middle third of the dental posts. The peak stress by thermal irritant for models D and E are approximately three times higher than models A, B and C. Conclusion: The findings of this study showed that pure zirconia and titanium posts produced greater thermal stresses than MSDPs.

Abstract: The purpose of this study was to investigate the effect of light curing tip angulations on the shear bond strength of an orthodontic adhesive. Three groups of thirty premolar teeth had brackets attached in a standardized manner using Transbond XT. The orthodontic adhesive were cured with a Blue LED light curing unit for 40 seconds using three different angulations 0 degrees, 45 degrees and 9 degrees at a standardized 3 mm distance. The debonding force was measured using an Instron Universal Testing Machine. Data were computed and analysed using SPSS version 12.0. Kruskal-Wallis test was employed to compare the shear bond strength of all groups. The study found that there was no significant difference on the shear bond strengths of orthodontic adhesive when cured at the angulations of light curing tip of 0 degrees, 45 degrees and 90 degrees.

Abstract: An Automated Rapid Maxillary Expander (ARME), is a specially designed orthodontic appliance to overcome the shortcomings imposed by the traditional butterfly expansion appliance. It operates by automatically widening the maxilla (upper jaw) by expanding the midpalatal suture 1. This procedure is not feasible after late teenage years due to more rigid facial skeleton features. According to the study by Cozzani 2, the activation of the device could produce 0.25 mm of expansion per day. Over the period of 2 weeks, the expansion produced is up to 7 mm in total 1. For this study, we explored the mechanism involved in the ARME appliance by using Finite Element Modeling method.

Abstract: The purpose of this study was to validate the use of digital dental study casts obtained from Cone beam CT Scan (CBCT) against gold standard; that is traditional dental study cast measured with digital caliper. Thirty-four study casts of Malaysian Aborigines were selected from Centre of Malaysian Pribumi Studies Databank. Palatal depth of each study casts were measured using Mitutoyo digital caliper. Subsequently, all the study models were scanned using i-CAT CBCT and the palatal depth were measured using i-CAT software. Data were analysed using SPSS version 12.0 where Intraclass correlation and paired T-test were employed. There was no significant difference in palatal depth between CBCT and Mitutoyo digital caliper (p\ensuremath>0.05). Average measures for Intraclass Correlation is 0.753 indicate that it is consistently good. Within the limitation of this study palatal depth measurement produced by CBCT was as accurate as the digital caliper. However, more samples and parameters should be added to further substantiate the result of this study.

Abstract: The objective of this study was to investigate the effect of various luting agents on bond strength of fibre-reinforced posts to root canal dentine. 40 extracted single rooted sound premolar teeth were root filled, decoronated and randomly divided into four groups. Fibre posts, Aestheti-Plus (TM) (Bisco,Inc. Schaumburg, IL, USA) were cemented using four luting agents: Group A (control): Elite 1000 Zinc phosphate (GC Corp, Japan), Group B: Calibra (TM) Esthetic Resin Cement (Dentsply Caulk, USA), Group C: RelyX ARC Adhesive Resin (3M ESPE), Group D: RelyX Unicem Aplicap (3M ESPE). Each roots were sliced into 2 discs representing the coronal and middle portions of the root canal giving rise to 20 specimens per group. Bond strength was determined using push-out tests and data were analyzed using SPSS version 14.0. The mean bond strength of Group A to Aestheti-Plus (TM) post was 7.71 MPa (??- 2.51) and Group B was 5.69 MPa (??- 3.23). Group C exhibited the lowest mean bond strength, 4.29 MPa (??- 3.53) while the highest bond strength was obtained from Group D, 7.98 MPa (??- 2.61). One way ANOVA showed significant interaction between all groups (p=.001). Post-hoc Bonferroni test revealed that bond strength of Group C was significantly lower compared to Group A (p=.008) and D (p=.004). In conclusion, the mean bond strength of Aestheti-Plus (TM) post to root canal dentine was highest when cemented with RelyX Unicem followed by Elite 100, Calibra and RelyX ARC. However, the bond strengths of Calibra and RelyX Unicem were not significantly different from Elite 100 (R).

Abstract: The purpose of the study is to model and provide a better understanding of maxilla bone involved in the treatment for rapid maxillary expander (RME) for dento-facial applications. The treatment is recommended for patients presented with an arch width deficiency named cross bites. Cross bites often cause abnormal physical forces that disrupt the balance of the occlusal relationship. More commonly, the maxilla or the upper jaw appears to be narrow and contributes to significant degree of crowding in the mouth. Early investigators 1-4 discovered that rapid maxillary expansion resulted in a splitting of the median palatal suture. The expansion is possible with the process of bone resorption and new bone deposition thus maintaining the expansion achieved 10. This preliminary study shows that the FE model has the potential to be a valuable tool for further analysis of dental simulation and the understanding of orthodontic treatment.

Abstract: This paper focuses on the usage of a novel binder system base on palm oil product to produce sintered parts of stainless steel 316L produced by vertical injection molding technique for biomedical application. The stainless steel 316L powder was mixed using z-blade mixer with the thermoplastic binder system comprising of polyethylene, paraffin wax, stearic acid and palm stearin which was derived from palm oil at different volume percent (%). The feedstock then was studied in term of viscosity and shear rate using capillary rheometer. The feedstock was molded using vertical injection molding machine. After molding, the green molded part was immersed into the solvent to extract part of the binder system followed by sintering under vacuum atmosphere at the temperature of 1360 degrees C. The physical and mechanical properties of the sintered part such as density, hardness, shrinkage, ultimate tensile strength and elongation were measured. Biocompatibility study of in vitro test using cell osteosarcoma MG-63 was observed and discussed.

Abstract: This article focuses on the physical characterization of Silverfil (R) amalgam. Analysis of the amalgamated material semi-quantitatively showed that Silverfil (R) comprised of approximately two thirds mercury and one third silver. No other elements were detected. Examination of the amalgamated material by x ray mapping and metallographically showed no evidence of free mercury present. Silverfil (R) has strong affinity towards the mercury ion. X-ray Diffraction analysis showed that the amalgamated Silverfil (R) is similar to a mineral in nature called "Moschellandsbergite". The advantages of Silverfil (R) over conventional amalgam were highlighted.

Abstract: Fracture toughness has been recognised to be one of the most important mechanical property for retorative materials. It is the aim of this study to investigate the effect of thermocycling an fracture toughness of a range of dental composites; P50(P)1 , Silux Plus(S)2, Heliomolar(H)3, Clearfil Photo Posterior-light activated(CLA)4 and Clearfil Posterior-chemically activated(CC)3. 110 rectangular pre-notched specimens was prepared for each material utilising a stainless steel mould. The specimens were divided into 11 groups of 10 each. Test groups 1-6 were subjected to 0, 250, 500, 750, 1000 and 10,000 thermal cycles respectively. All specimens were subjected to a 3 point bend test and loaded at a crosshead speed of 1mm?min-1 on an Instron Testing Machine. The fracture toughess of all materials decreases with the number of thermal cycles and length of water storage except for CC where the fracture toughness increases during the earlier stages of thermocycling and water storage. However the lowest fracture toughness values were for groups 6 and 11. One way analysis of variance showed that Group 1 was significantly different from groups 6 and 11 (P\ensuremath<.05), the thermally cyled and the water storage groups were not different from each other for al materials. The decrease in fracture toughness exhibited by all light activated composites could be explained by interfacial stress formation and resin-filler debonding while the increase in fracture toughness during the earlier stages of thermocycling and water storage of chemically-activated composite be explained by continued polymerisation. Thermocycling did not cause any significant in fracture toughness composites over and above by water storage.

Abstract: The purpose of this study was to investigate the light intensity of selected light curing unit with varying distance and angulation of the light curing tip and lightmeter. Four types of light units; Spectrum 800 (Dentsply), Coltulux 3 (Coltene), Elipar FreeLight 2 (3M Espe) and Starlight Pro (Mectron) were evaluated for light intensity at various distance between the light curing tip and the lightometer Cure Rite Denstply (0, 1, 3, 5, 10 and 15 mm). The light curing units were angulated at 45 degrees, 60 degrees and 90 degrees at a standardized 5 mm distance. The intensity of light curing is affected by the distance between the light curing tip and the lightmeter. However, the decrease in light intensity of the light curing unit was found not to obey the inverse square law for the distances 0 to 15 Mm. The study found that there was no significant difference between 45 degrees and 600 angulation between the light curing tip and the lightmeter. However, the decrease in light intensity is significant when compared to the light tip is placed perpendicular (90 degrees) to the aperture of the light meter.

Abstract: Ideally, dental post should have stiffness that is similar to the crown at the coronal part and stiffness similar to the dentine at the apical part. This will reduce stress concentration at either coronal or the apical parts of the dentine and minimize the chance of interfacial loosening and enhance the reliability of post. Objective: To investigate the biomechanical behaviour of Multilayered Structured Dental Posts (MSDPs) using finite element analysis (FEA). Methods: Two models of MSDPs consist of multilayer design of xTi-yHA composition added to a zirconia layer (model A) and the same compositions added to alumina layer (model B) was compared with pure zirconia (model C) and pure titanium (model D) posts. The fractions of Ti and HA was varied layer by layer, gradually. FEA of models A, B, C and D were compared. Stress distributions due to 100 N vertical, oblique, and horizontal loads were investigated. Results: The highest stress regions were observed at area of the applied force and at the apical part of the dentine when vertical load was applied. Models C and D showed a considerable stress at the middle and apical region of the posts compared to models A and B. Oblique load showed high stresses around the loading area, then at the outer surface of the dentine for all the models. While in models C and D the stress highly propagated into the inner part of the canal compared to A and B. Horizontal load showed a similar stress distribution as the oblique load, but it demonstrated higher propagation of stress into the centre of the canal. Conclusions: The results showed that models A and B demonstrated advantages compared with models C and D. Therefore, it is recommended that dental post have multilayered structure to function efficiently at coronal and apical parts.

Abstract: The clinical performances of a compomer (Dyract AP") is combination with a non-rinse conditioner (K-0100�) and self-priming adhesive (K-0 I07�) were compared with a hybrid composite resin (Spectrum TPH�) in combination with a 36% phosphoric acid conditioner (DeTrey Conditioner�) and self-priming adhesive (K-0107�) in a randomized controlled split-mouth model. 23 patients with bilateral occlusal and/or interproximal caries had their teeth restored with Dyract AP in one quadrant and Spectrum TPH in the opposite quadrant by either one of the 2 evaluators. Removal of tooth structure was as dictated by caries and access. All non-caries fissures were sealed with either a compomer pit and fissure sealant (K-0093�) for compomer restorations or an opaque resin sealant (Delton DDS�). All enamel and dentin were treated with conditioner prior to application of 1 layer of self-priming adhesive. A total of 42 compomer restorations (12 with fissure sealants and 18 complex) and 35 composite resin restorations (13 with fissure sealants and 15 complex) were evaluated at baseline, 6 months and 1 year using the USPHS criteria for retention , colour match,marginal discolouration and integrity, secondary caries, anatomical form, occlusal and proximal contacts, surface texture and hypersensitivity. Two evaluators compared the epoxy resin casts of the restorations with models of the Leinfelder clinical wear standards. All clinical parameters were rated alpha except for fissure sealant with 2 bravo and 1 charlie for compomer restorations and 1 bravo for composite restorations at 6 months and 1 year. Two Class 1 restorations (1 Dyract AP and 1 Spectrum TPH) from same patient were rated bravo for marginal integrity and one large Class II compomer restoration was bravo for hypersensitivity. No detectable wear was observed except for 1 compomer and 2 composite restorations that exhibited wear of 25µm. There was no significant difference in all parameters measured between compomer and composite restorations (Fisher Exact Test p<0.01). The clinical results indicate that compomer (Dyract AP) in combination with a non-rinse conditioner and self-priming adhesive can be used for restoring posterior teeth with good clinical response at 1year. This study was supported by DENTSPLY DeTrey, Germany with �materials supplied by the same company.

Abstract: The effect of thermocycling on the fatigue behaviour of 5 commercially available dental composites; P50(P)1, Silux Plus(S)2, Heliomolar(H)3, Clearfil Photo Posterior-light activated(CLA)4 and Clearfil Posterior-chemically activated(CC)5 was investigated. One hundred and ten rectangular bar specimens were prepared for each materil and divided into 11 groups of 10 each. Test groups 1-6 were subjected to 0, 250, 500, 750, 1000 and 1000 thermal cycles respectively. Each thermal cycle consisted of 1 minute immersion time of 50 seconds per change. The control groups 7-11 were stored in distilled water at 370c for the equivalent time to complete 250, 500, 750, 1000 and 10000 thermal cycles respectively. All specimens were subjected to a 3 point bend test and loaded at a crosshead speed of 1mm?min on a an Inston Testing Machine. The flexural strength of all materials decreases with the number of cycles and length of water storage except for CC where the flexural strength increases during the earlier stages of thermocycling and water storage. The lowest flexural strength was observed in groups 6 and 11. One way analysis of varience showed that Group 1 was significantly different from groups 6 and 11 (P\ensuremath<.05), however the thermally cycled and water storage groups were not different from each other for all materials tested. The decrease in flexural strength of all materials in the water storage groups (7-11) when compared to the 24 hour group (1) is related to weakening of resin-filler interface bu hydrolysis. While the decrease of the thermally cycled groups can be attributed to debongding of matrix-filler due to variation in coefficient of thermal expansion. It can be concluded that thermal changes does not reduce the flerxural strength of composites.