Noor Hayaty Abu Kasim - Profile on Academia.edu (original) (raw)

Papers by Noor Hayaty Abu Kasim

Effects of different implant–abutment connections on micromotion and stress distribution: Prediction of microgap formation

OBJECTIVES: The aim of this study was to analyse micromotion and stress distribution at the conne... more OBJECTIVES: The aim of this study was to analyse micromotion and stress distribution at the connections of implants and four types of abutments: internal hexagonal, internal octagonal, internal conical and trilobe. METHODS: A three dimensional (3D) model of the left posterior mandible was reconstructed from medical datasets. Four dental implant systems were designed and analysed independently in a virtual simulation of a first molar replacement.

Induced pluripotent stem cell-based therapy for treating genetic disorders has become an interest... more Induced pluripotent stem cell-based therapy for treating genetic disorders has become an interesting field of research in recent years. However, there is a paucity of information regarding the applicability of induced pluripotent stem cells in dental research. Recent advances in the use of induced pluripotent stem cells have the potential for developing disease-specific iPSC lines in vitro from patients.

ABSTRACT The aim of this study was to assess the wear of tungsten carbide burs and round rotary d... more ABSTRACT The aim of this study was to assess the wear of tungsten carbide burs and round rotary diamond instruments through measurements of rake angle and visual observations respectively under a field emission scanning electron microscope. Sixty short and long head pear-shaped tungsten carbide burs and 18 round rotary diamond instruments that had been used to complete< 5,> 5 and> 10 cavity preparations (n= 10/group) were selected from the 3rd and 4th year dental students, Faculty of Dentistry, University of Malaya.

ABSTRACT The main objective of this study was to assess knowledge on tooth bleaching among patien... more ABSTRACT The main objective of this study was to assess knowledge on tooth bleaching among patients visiting dental health care centres in Klang Valley. A total of 200 patients were conveniently selected and interviewed using structured questionnaires. Among the 200 respondents, 75.5% knew about bleaching.

Abstract: Eleven compounds: goniomicin A (1), goniomicin B (2), goniomicin C (3), goniomicin D (4... more Abstract: Eleven compounds: goniomicin A (1), goniomicin B (2), goniomicin C (3), goniomicin D (4), tapisoidin (5), goniothalamin (6), 9-deoxygoniopypyrone (7), pterodondiol (8), liriodenine (9), benzamide (10) and cinnamic acid (11), were isolated from the stem bark of Goniothalamus tapisoides. All compounds were identified by spectroscopic analysis and, for known compounds, by comparison with published data.

The purpose of this study was to validate the use of digital dental study casts obtained from Con... more 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>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.

Objective: To analyse thermo-mechanical stress in endodontically treated teeth restored with Mult... more 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.

Objective: This study evaluated the effect of an active oxygen based disinfectant, 2% Perform® (S... more 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> 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)

Objectives: To identify the nature of multiple intelligences among dental students and investigat... more 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 < .05) and between Body Kinesthetic and Composite scores (r = .26; p < .05). High Amalgam Class II scorers obtained significantly higher scores on Intrapersonal Intelligence than low scorers (t = 2.49; p < .05). High Composite scorers have significantly higher Body Kinesthetic intelligence than low scorers (t = .29; p < .05). Low endodontic scorers obtained significantly higher scores on Visual Spatial intelligence than high scorers (t = 2.06; p < .05). High PBL scorers obtained significantly higher Interpersonal (t = 2.06; p < .05) and Naturalist Intelligence (t = 3.57; p < .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.

Objective: To compare the surface microhardness of composites(Spectrum®TPH, Filtek™Z350, Ceram•X ... more Objective: To compare the surface microhardness of composites(Spectrum®TPH, Filtek™Z350, Ceram•X mono and Ceram•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 37º 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 Microscopy™).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.

Objective: The aim of this study was to investigate the degree of conversion and cross-linking of... more 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.

Objectives:Biocompatibility is an important desirable property for a dental polymer and it can be... more 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 (±16.54), Impact was 177.57MPa (±11.44) and experimental polymer was 51.62MPa (±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.

Objective: To evaluate the demineralization potential of qat extracts at composite restoration in... more 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<.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, P0218_2007a.

Objective: The aim of this study was to investigate the cytotoxicity effect of polyurethane dimet... more 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 < .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

Objective: To evaluate the effect of viscosity and type of grooves on surface detail reproduction... more 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, Impregum„· heavy/light and Impregum heavy/light groups respectively. Two-way ANOVA indicated that there was a significant difference in the effect of materials (p < .01) and grooves (p < .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.

Ideally, dental post should have stiffness that is similar to the crown at the coronal part and s... more 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.

The impact strength of a newly developed experimental polyurethane-based polymer which is derived... more 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 manufacturer’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 impact strength (2.73 kJ/m2±0.54) followed by Meliodent® Rapid Repair (2.50kJ/m2±0.65), Meliodent® Heat Cure (1.96kJ/m2±0.42) and Experimental PU (1.04kJ/m2±0.29). One-way ANOVA showed significant interaction between materials (p<.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.

Fracture toughness has been recognised to be one of the most important mechanical property for re... more 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<.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.

The effect of thermocycling on the fatigue behaviour of 5 commercially available dental composite... more 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<.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.

The clinical performances of a compomer (Dyract AP") is combination with a non-rinse conditioner ... more 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.

Effects of different implant–abutment connections on micromotion and stress distribution: Prediction of microgap formation

OBJECTIVES: The aim of this study was to analyse micromotion and stress distribution at the conne... more OBJECTIVES: The aim of this study was to analyse micromotion and stress distribution at the connections of implants and four types of abutments: internal hexagonal, internal octagonal, internal conical and trilobe. METHODS: A three dimensional (3D) model of the left posterior mandible was reconstructed from medical datasets. Four dental implant systems were designed and analysed independently in a virtual simulation of a first molar replacement.

Induced pluripotent stem cell-based therapy for treating genetic disorders has become an interest... more Induced pluripotent stem cell-based therapy for treating genetic disorders has become an interesting field of research in recent years. However, there is a paucity of information regarding the applicability of induced pluripotent stem cells in dental research. Recent advances in the use of induced pluripotent stem cells have the potential for developing disease-specific iPSC lines in vitro from patients.

ABSTRACT The aim of this study was to assess the wear of tungsten carbide burs and round rotary d... more ABSTRACT The aim of this study was to assess the wear of tungsten carbide burs and round rotary diamond instruments through measurements of rake angle and visual observations respectively under a field emission scanning electron microscope. Sixty short and long head pear-shaped tungsten carbide burs and 18 round rotary diamond instruments that had been used to complete< 5,> 5 and> 10 cavity preparations (n= 10/group) were selected from the 3rd and 4th year dental students, Faculty of Dentistry, University of Malaya.

ABSTRACT The main objective of this study was to assess knowledge on tooth bleaching among patien... more ABSTRACT The main objective of this study was to assess knowledge on tooth bleaching among patients visiting dental health care centres in Klang Valley. A total of 200 patients were conveniently selected and interviewed using structured questionnaires. Among the 200 respondents, 75.5% knew about bleaching.

Abstract: Eleven compounds: goniomicin A (1), goniomicin B (2), goniomicin C (3), goniomicin D (4... more Abstract: Eleven compounds: goniomicin A (1), goniomicin B (2), goniomicin C (3), goniomicin D (4), tapisoidin (5), goniothalamin (6), 9-deoxygoniopypyrone (7), pterodondiol (8), liriodenine (9), benzamide (10) and cinnamic acid (11), were isolated from the stem bark of Goniothalamus tapisoides. All compounds were identified by spectroscopic analysis and, for known compounds, by comparison with published data.

The purpose of this study was to validate the use of digital dental study casts obtained from Con... more 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>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.

Objective: To analyse thermo-mechanical stress in endodontically treated teeth restored with Mult... more 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.

Objective: This study evaluated the effect of an active oxygen based disinfectant, 2% Perform® (S... more 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> 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)

Objectives: To identify the nature of multiple intelligences among dental students and investigat... more 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 < .05) and between Body Kinesthetic and Composite scores (r = .26; p < .05). High Amalgam Class II scorers obtained significantly higher scores on Intrapersonal Intelligence than low scorers (t = 2.49; p < .05). High Composite scorers have significantly higher Body Kinesthetic intelligence than low scorers (t = .29; p < .05). Low endodontic scorers obtained significantly higher scores on Visual Spatial intelligence than high scorers (t = 2.06; p < .05). High PBL scorers obtained significantly higher Interpersonal (t = 2.06; p < .05) and Naturalist Intelligence (t = 3.57; p < .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.

Objective: To compare the surface microhardness of composites(Spectrum®TPH, Filtek™Z350, Ceram•X ... more Objective: To compare the surface microhardness of composites(Spectrum®TPH, Filtek™Z350, Ceram•X mono and Ceram•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 37º 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 Microscopy™).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.

Objective: The aim of this study was to investigate the degree of conversion and cross-linking of... more 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.

Objectives:Biocompatibility is an important desirable property for a dental polymer and it can be... more 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 (±16.54), Impact was 177.57MPa (±11.44) and experimental polymer was 51.62MPa (±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.

Objective: To evaluate the demineralization potential of qat extracts at composite restoration in... more 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<.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, P0218_2007a.

Objective: The aim of this study was to investigate the cytotoxicity effect of polyurethane dimet... more 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 < .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

Objective: To evaluate the effect of viscosity and type of grooves on surface detail reproduction... more 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, Impregum„· heavy/light and Impregum heavy/light groups respectively. Two-way ANOVA indicated that there was a significant difference in the effect of materials (p < .01) and grooves (p < .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.

Ideally, dental post should have stiffness that is similar to the crown at the coronal part and s... more 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.

The impact strength of a newly developed experimental polyurethane-based polymer which is derived... more 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 manufacturer’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 impact strength (2.73 kJ/m2±0.54) followed by Meliodent® Rapid Repair (2.50kJ/m2±0.65), Meliodent® Heat Cure (1.96kJ/m2±0.42) and Experimental PU (1.04kJ/m2±0.29). One-way ANOVA showed significant interaction between materials (p<.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.

Fracture toughness has been recognised to be one of the most important mechanical property for re... more 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<.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.

The effect of thermocycling on the fatigue behaviour of 5 commercially available dental composite... more 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<.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.

The clinical performances of a compomer (Dyract AP") is combination with a non-rinse conditioner ... more 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.