bluuebunny/crossref_metadata_2025_split huggingface dataset:
Flexural properties of glass fibre reinforced acrylic resin polymers
Authors: Tacir IH , Kama JD , Zortuk M. , Eskimez S. 
Published: March 2008

Abstract Background: In recent years, glass fibres have been used to strengthen denture base resins. A major difficulty in using reinforcing fibres with multiphase acrylic resins, such as powder liquid resins, is inadequate impregnation of the fibres with the resin. Methods: This investigation examined the reinforcing effect of glass fibres on the fracture resistance and flexural strength of acrylic denture base resins. Eighty identical specimens were formed in specially designed moulds in accordance with the manufacturer's recommendations. The four experimental groups were prepared and these consisted of conventional acrylic resin and the same resin reinforced with glass fibres. Ten specimens were fabricated in a standardized fashion for each experimental group. Flexural strength was tested using a 3‐point universal testing machine. Results: In this study, statistically significant differences were found in the flexural strength of the specimens (P<0.05). The injection‐moulded, fibre‐reinforced group had significantly lower flexural strength than the injection‐moulded group (P<0.001), and the microwave‐moulded, fibre‐reinforced group had lower flexural strength than the microwave‐moulded group. The fracture resistance was significantly higher in the injection‐moulded, fibre‐reinforced group than in the injection‐moulded group (P<0.05), and the fracture resistance was significantly higher in the microwave‐moulded, fibre‐reinforced group than in the microwave‐moulded group. Conclusion: Within the limitations of this study, the flexural strength of heat‐polymerized PMMA denture resin was improved after reinforcement with glass fibres. It may be possible to apply these results to distal extension partial and complete denture bases.
The ability of thiourea to scavenge hydrogen peroxide and hydroxyl radicals during the intra‐coronal bleaching of bloodstained root‐filled teeth
Authors: Farmer DS , Burcham P. , Marin PD 
Published: March 2008

Abstract
Background
: Hydrogen peroxide, an agent used in the intra‐coronal bleaching of root‐filled teeth for over a century, has been shown to diffuse from the pulp chamber to the outer root surface. Furthermore, it has been demonstrated that destructive hydroxyl radicals, the by‐products of the bleaching process, have been detected on the external root surface. The control of such diffusion may be of importance in minimizing the risk of invasive cervical resorption (ICR) which has been linked to intra‐coronal bleaching of discoloured root‐filled teeth using hydrogen peroxide. The aims of the present in vitro study are to quantify the diffusion of hydrogen peroxide and hydroxyl radicals to the outer root surface following intra‐coronal bleaching, and to evaluate the ability of thiourea incorporated into the bleaching protocol to scavenge residual hydrogen peroxide and hydroxyl radicals.
Methods
: Thirty‐five single rooted premolar teeth with intact cementum at the cemento‐enamel junction were used in this project. Thirty teeth were stained with red blood cells and root‐filled with gutta‐percha and AH26. The five unstained teeth were root‐filled and constituted a negative control (Group 1). The stained teeth were divided equally into the following experimental groups and subjected to various intra‐coronal bleaching regimes: Group 2–‘walking bleach’ with 20μl 30 per cent w/w hydrogen peroxide; Group 3–20μl 30 per cent w/w hydrogen peroxide and thermocatalytically activated; Group 4–20μl acidified thiourea; Group 5–20μl acidified thiourea and 20μl 30 per cent w/w hydrogen peroxide; Group 6 –20μl acidified thiourea and 20μl one per cent sodium hypochlorite; Group 7 –20μl acidified thiourea, 20μl one per cent sodium hypochlorite and 20μl 30 per cent w/w hydrogen peroxide. The reaction products of the bleaching process were quantified at the outer root surface using high performance liquid chromatography and electrochemical detection (HPLC‐ECD).
Results
: Results showed that hydrogen peroxide used alone in Groups 2 and 3 was able to be detected at the outer root surface in 100 per cent of the samples, and that the presence of the hydroxyl radical generated in both groups was detected in equal amounts (P < 0.05). When thiourea was incorporated into the bleaching protocols in Groups 5–7, it was shown to scavenge both hydrogen peroxide and hydroxyl radicals to a significant degree (P < 0.05).
Conclusions
: Acidulated thiourea is an effective scavenger of residual hydrogen peroxide and hydroxyl radicals generated during the intra‐coronal bleaching of bloodstained root‐filled teeth.
Prevalence of percutaneous exposure incidents amongst dentists in Queensland
Authors: Leggat PA , Smith DR 
Published: March 2008

Abstract
Background
: Percutaneous exposure incidents (PEI) represent an important occupational health issue in dentistry, and one that can incur severe consequences from blood‐borne infections. Given the importance of this topic, we considered it necessary to investigate the distribution and cause of PEI among Queensland dentists.
Methods
: In 2004, a self‐reporting questionnaire was mailed to a random sample of 400 dentists on the register of the Queensland Branch of the Australian Dental Association.
Results
: A total of 285 questionnaires (73.1 per cent) were completed and returned. Of the respondents, 73.3 per cent were male and 26.7 per cent female, with a mean age of 45.2 years (SD = 11.9 years). Most were general dentists (89.1 per cent) with the remainder being specialists (10.9 per cent). More than three‐quarters (78.5 per cent) reported damaging their gloves at least once during a clinical procedure in the previous 12‐month period. Roughly one‐quarter (27.7 per cent) had experienced at least one ‘sharps’ or needlestick injury in the previous 12 months, 16.1 per cent of which involved a contaminated instrument that had been previously used on a patient. The most common devices to cause ‘sharps’ injury in the previous 12 months were needles (14.4 per cent) and burs (10.2 per cent).
Conclusions
: Although PEI clearly remains a major occupational health problem for Queensland dentists, the prevalence of needlestick injuries appears to be lower than other studies from developed countries. The identification of needle‐stick injuries as a common cause of PEI again stresses the importance of preventive strategies with respect to potential blood‐borne infections. Further research is now needed to more carefully identify effective measures for reducing PEI among dental personnel.
Bond strengths between composite resin and auto cure glass ionomer cement using the co‐cure technique
Authors: Knight GM , McIntyre JM , Mulyani  
Published: March 2008

Abstract
Background
: The clinical technique for sandwich restorations prescribes etching initially set auto cure glass ionomer cement (GIC) prior to placing a layer of resin bond to develop a weak mechanical bond between composite resin and GIC. Co‐curing a resin modified glass ionomer cement (RMGIC) bond and composite resin to GIC may create a chemical bond and improve the bond strengths between these two materials.
Methods
: A total of 48 specimens were prepared, 12 in each of four categories. Capsulated GIC was placed into a mould and allowed to set for four minutes, etched for five seconds followed by placement of a resin bond and photo cured for five seconds over which a composite resin was puddled onto the resin bond and photo cured for 10 seconds. Capsulated GIC was placed into a mould and allowed to set for four minutes after which a sample of RMGIC (Riva LC) was prepared using twice the liquid powder ratio and painted over the surface of the set GIC using a micro brush. An increment of composite resin was added over the RMGIC and both materials were photo co‐cured for 10 seconds. Capsulated GIC was placed into a mould and RMGIC (Riva LC) that had been prepared using twice the liquid powder was brushed over the GIC (prior to initial set) followed by the placement of a layer of composite resin and photo co‐cured for 10 seconds. Capsulated GIC was placed into a mould and RMGIC (Fuji II LC) that had been prepared using twice the liquid powder was brushed over the GIC (prior to initial set) followed by the placement of a layer of composite resin and photo co‐cured for 10 seconds. Shear testing of each of the samples was carried out and specimens were examined to determine the nature of the fracture. Selected samples were prepared for SEM investigation to observe the interfaces between the GIC and composite resin.
Results
: There were significantly lower bond strengths (P < 0.05) amongst samples that had been etched and bonded (2.42MPa) compared to the other samples that had been co‐cure bonded with RMGIC (6.48–7.05MPa). There were no significant differences amongst the bond strengths of the samples co‐cure bonded with RMGIC. Specimens prepared by the ‘etch and bond’ technique failed adhesively and co‐cured specimens failed cohesively within the GIC. SEM investigation showed chemical bonds between RMGIC bond and GIC and composite resin.
Conclusions
: The co‐cured RMGIC bonding system eliminates several placement steps and produces a significantly stronger chemical bond between GIC and composite resin than the ‘etch and bond’ technique. RMGIC bond and composite resin may be co‐cured to GIC either before or after initial set has occurred.
The mandibular ramus donor site
Authors: Brener D. 
Published: March 2008

AbstractWith the increased awareness of the population about dental implants, more patients are presenting after losing a number of teeth and requesting fixed solutions to their dilemmas. Often they have lost width of alveolus which does not allow implant placement without its augmentation. The mandibular ramus is one intra‐oral site that can supply excellent quality and often quantity of autologous bone for use in augmenting alveolar ridge deficiencies. This article describes the general surgical principles in harvesting the mandibular ramus.
Ion uptake into demineralized dentine from glass ionomer cement following pretreatment with silver fluoride and potassium iodide
Authors: Knight GM , Mclntyre JM , Craig GG , Mulyani  
Published: March 2008

Background: Diamine silver fluoride (Ag(NH3)2F), referred to as AgF, has been shown to provide a pronounced antimicrobial action against caries. The clinical application of this material has been limited by the staining associated with both teeth and tooth coloured restorative materials. The application of potassium iodide (KI) after AgF eliminates stain formation. The purpose of this study was to determine if a prior application of silver fluoride and potassium iodine to demineralized dentine affected the uptake of strontium and fluoride from a glass ionomer cement restoration. Method: Three cavities were prepared in each of five recently extracted human third molars. The cavities were demineralized and treated as follows. In each tooth, one cavity was left as a control, one cavity was restored with glass ionomer cement and one cavity was treated with 1.8M AgF and a saturated KI solution and then restored with glass ionomer cement. The penetration of the various elements into demineralized dentine was measured by their relative percentage weights using electron probe microanalysis (EPMA). Results: Fluoride uptake was significantly higher in the AgF and KI treated samples compared to the other two samples and significantly higher in the glass ionomer restored sample compared to the control. The application of AgF and KI did not significantly interfere with the transfer of strontium from glass ionomer cement into dentine. Silver and iodine deposits were present in the demineralized dentine treated with AgF and KI. Conclusions: The application of AgF and KI onto dentine prior to the placement of glass ionomer cement did not significantly affect the strontium uptake into the subjacent demineralized dentine and the fluoride levels in this zone were significantly increased.
Clinical, radiographic and histological analysis of the effects of mineral trioxide aggregate used in direct pulp capping and pulpotomies of primary teeth
Authors: Caicedo R. , Abbott PV , Alongi DJ , Alarcon MY 
Published: March 2008

Abstract Background: Primary teeth pulp exposures have traditionally been treated with formocresol or ferric sulphate pulpotomies or calcium hydroxide pulp capping. The aim of this study was to observe the tissue response when mineral trioxide aggregate (MTA) was used. Methods: Ten primary teeth had direct pulp caps and 11 had a pulpotomy with MTA. The teeth were restored and then clinically reviewed monthly for five months and before extraction. Radiographs were taken prior to treatment, after one month and prior to extraction. After extraction, the teeth were examined histologically and the responses to treatment were assessed. Results: One pulpotomy and two pulp capping cases had postoperative pain and signs of pulp degeneration. Radiographs showed no root resorption, no periodontal pockets and no furcation radiolucencies. No cases had draining sinuses or increased mobility. Most pulps responded favourably from a clinical perspective although a variety of responses were noted Histologicallyormal odontoblasts, irregular odontoblasts, intrapulpal calcifications, dentinal bridges, cementum formation, internal resorption, inflammatory infiltrate and pulp necrosis. Conclusions: The responses of pulps in primary teeth to MTA pulpotomies and pulp caps were favourable from clinical and radiographic perspectives although a variety of histological responses were noted. MTA may be a favourable material for pulp capping and pulpotomies in primary teeth.
Problem‐based learning in dental education: what's the evidence for and against … and is it worth the effort?
Authors: Winning T. , Townsend G. 
Published: March 2008

AbstractAll Australian dental schools have introduced problem‐based learning (PBL) approaches to their programmes over the past decade, although the nature of the innovations has varied from school to school. Before one can ask whether PBL is better than the conventional style of education, one needs to consider three key issues. Firstly, we need to agree on what is meant by the term PBL; secondly, we need to decide what “better” means when comparing educational approaches; and thirdly, we must look carefully at how PBL is implemented in given situations. It is argued that PBL fulfils, at least in theory, some important principles relating to the development of new knowledge. It also represents a change in focus from teachers and teaching in conventional programmes to learners and learning. Generally, students enjoy PBL programmes more than conventional programmes and feel they are more nurturing. There is also some evidence of an improvement in clinical and diagnostic reasoning ability associated with PBL curricula. The main negative points raised about PBL are the costs involved and mixed reports of insufficient grounding of students in the basic sciences. Financial restraints will probably preclude the introduction of pure or fully integrated PBL programmes in Australian dental schools. However, our research and experience, as well as other published literature, indicate that well‐planned hybrid PBL programmes, with matching methods of assessment, can foster development of the types of knowledge, skills and attributes that oral health professionals will need in the future.
Comparative uptake of fluoride ion into enamel from various topical fluorides in vitro
Authors: Pai N. , McIntyre J. , Tadic N. , Laparidis C. 
Published: March 2008

Abstract Background: There are many forms of topical fluoride available today, making the decision as to which is most effective to manage the immediate caries risk problem at hand, very difficult. The objective of this project was to determine the concentration and pattern of fluoride ion uptake into enamel from a variety of categories of topical fluoride recently available in Australia. Methods: Extracted, intact molar teeth were sectioned to provide six plates of smooth surface enamel. Windows of enamel 2 times 6mm were exposed to a variety of topical fluorides for periods simulating those used in vivo. Following drying, the slates of enamel were exposed to 2ml of 0.1M HCl as a chemical biopsy agent for incremental periods of time. The concentrations of fluoride ion in the biopsy solutions for both test and background (control) slates of enamel were determined directly using a fluoride combination selective electrode in conjunction with a high impedance pH meter. Cumulative amounts of fluoride were determined for each topical fluoride agent. Results: The concentrations of fluoride ion taken up into enamel were generally proportional to those present in each agent. However, those from APF gel greatly exceeded the amounts taken up from NaF gel. Also, the concentrations taken up from some of the highly concentrated metal fluorides were surprisingly low. Prior etching of enamel increased uptake and prolonged application of APF gel provided no extra benefit. Conclusions: Some topical fluorides, e.g., APF gel, provided a greatly increased uptake and to a greater depth than other self‐application products. However, the frequency of its use should be considered with caution where patients have glass‐based restorations.
Different bone loading patterns due to fixation of three‐unit and five‐unit implant prostheses
Authors: Karl M. , Winter W. , Dickinson AJ , Wichmann MG , Heckmann SM 
Published: March 2008

Abstract Background: It has been considered that implant prostheses ought to display passive fit. The objective of this finite element analysis (FEA) was to simulate the bone loading resulting from the fixation of implant‐supported three and five‐unit fixed partial dentures (FPDs). Methods: Based on a patient case, six different FPD‐groups were fabricated using either two or three implants for support. Strain gauges on the pontics of the prostheses were used for in vivo measurements. Based on the values obtained, bone loading models were simulated using three‐dimensional finite element analysis and the results obtained were represented as von Mises equivalent stress. Results: The mean strain (e) values ranged from 15μe to 170μe for the three‐unit FPDs and from 32μe to 302μe for the five‐unit FPDs. FEA revealed von Mises stresses up to 30MPa in the cortical area, while in trabecular bone values up to 5MPa were observed. Static implant loading of similar magnitude can be provoked through 200N axial load. Conclusions: Although the in vivo measured strain levels (e) were of higher magnitude for the five‐unit prostheses, FEA revealed bone loading of comparable magnitude for both three‐and five‐unit FPDs. Multi‐unit prostheses may demonstrate greater inaccuracies compared with single implant restorations, but due to the absence of moment loading the multi‐implant configuration appears to compensate for the higher strain development.
Laser‐activated fluoride treatment of enamel as prevention against erosion
Authors: Vlacic J. , Meyers IA , Walsh LJ 
Published: March 2008

Abstract Background: Erosion is the loss of dental hard tissues from an acidic challenge, often resulting in exposure of dentinal tubules and hypersensitivity to environmental stimuli. Laser‐activated fluoride (LAF) therapy with 488nm laser energy has been shown previously to increase the resistance of human enamel and dentine to acid dissolution. The aims of this study were to investigate the action spectrum of LAF in protecting tooth enamel from softening in response to an erosive challenge, and to examine for any temperature change with the treatment. Materials and Methods: Buccal and lingual surfaces of extracted sound molar and premolar teeth were used to prepare matched pairs of enamel slabs (N=10 per group). After application of 1.23% neutral sodium fluoride gel (12 300ppm F ion), slab surfaces were lased with 488, 514.5, 532, 633, 670, 830 or 1064nm wavelength (energy density 15J/cm2; spot size 5mm), then exposed to an erosive challenge (1.0M HCl for five minutes). The Vicker's hardness number (VHN) was recorded before fluoride gel application and again following the acid challenge. Negative controls did not receive laser exposure. Results: All wavelengths of laser light examined provided a protective LAF effect against softening, compared with the negative control surfaces. Conclusion: From these findings, we conclude that the action spectrum of the LAF effect extends across the visible spectrum, providing protection to dental enamel from an erosive challenge.
An in vitro investigation of marginal dentine caries abutting composite resin and glass ionomer cement restorations
Authors: Knight GM , McIntyre JM , Craig GG , Mulyani  , Zilm PS , Gully NJ 
Published: March 2008

Abstract Background: There are a number of studies citing the primary reason for replacing auto cure glass ionomer cements was due to recurrent caries. The purpose of this study was to use an in vitro model to measure caries at the dentine restoration interface of bonded composite resin and auto cure glass ionomer cement restorations and to measure the amount of surface degradation occurring in the restorative materials. Methods: Specimens of auto cure glass ionomer cements (Riva Fast, Fuji IX Fast, Ketac Molar Quick and Fuji VII) and bonded composite resin restorations (Ice, SDI) were placed separately at the dentino‐enamel junction of 10 recently extracted human third molar teeth, disinfected and placed into the overflow from a continuous culture of S. mutans for two weeks. Restorations were sectioned and prepared for scanning electron microscopy (SEM) and electron probe microanalysis (EPMA). Restoration tooth interfaces were photographed and the distance from the surface of the teeth to the surface of the restorations measured. EPMA of percentage weights of calcium, phosphorous and fluoride were made outwards from the restoration surface 130μm at a depth of 10μm below the surface of the dentine. Results: There were significant differences between the surface heights of composite resin, auto cure glass ionomer cements compared to teeth surfaces. Percentage weights of calcium and phosphorus levels were similar to non‐demineralized dentine in the auto cure glass ionomer cement samples but there were significant reductions in mineral content of dentine adjacent to bonded composite resin restorations. Fluoride levels were mixed. Conclusions: This study shows that placing a bonded composite resin restoration into dentine affords little protection to the surrounding tooth from caries attack although insignificant degradation of the restorative surface occurs. Placing a glass ionomer cement restoration into dentine protects the surrounding tooth from caries but degradation of the restoration surface occurs.