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    ABSTRACT: Fine-grained, high strength, translucent leucite dental glass-ceramics are synthesized via controlled crystallization of finely milled glass powders. The objectives of this study were to utilize high speed planetary milling of an aluminosilicate glass for controlled surface crystallization of nano-scale leucite glass-ceramics and to test the biaxial flexural strength. An aluminosilicate glass was synthesized, attritor or planetary milled and heat-treated. Glasses and glass-ceramics were characterized using particle size analysis, X-ray diffraction and scanning electron microscopy. Experimental (fine and nanoscale) and commercial (Ceramco-3, IPS Empress Esthetic) leucite glass-ceramics were tested using the biaxial flexural strength (BFS) test. Gaussian and Weibull statistics were applied. Experimental planetary milled glass-ceramics showed an increased leucite crystal number and nano-scale median crystal sizes (0.048-0.055μm(2)) as a result of glass particle size reduction and heat treatments. Experimental materials had significantly (p<0.05) higher mean BFS and characteristic strength values than the commercial materials. Attritor milled and planetary milled (2h) materials showed no significant (p>0.05) strength difference. All other groups' mean BFS and characteristic strengths were found to be significantly different (p<0.05) to each other. The mean (SD) MPa strengths measured were: Attritor milled: 252.4 (38.7), Planetary milled: 225.4 (41.8) [4h milling] 255.0 (35.0) [2h milling], Ceramco-3: 75.7 (6.8) and IPS Empress: 165.5 (30.6). Planetary milling enabled synthesis of nano-scale leucite glass-ceramics with high flexural strength. These materials may help to reduce problems associated with brittle fracture of all-ceramic restorations and give reduced enamel wear.
    Dental materials: official publication of the Academy of Dental Materials 09/2013; DOI:10.1016/j.dental.2013.08.209
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    ABSTRACT: Dentine hypersensitivity (DHS) remains a worldwide under-reported and under-managed problem, despite making some dental treatments more stressful than necessary and having a negative impact on the patient's quality of life. This article is designed to build dental professionals' confidence and remove any confusion regarding the diagnosis, prevention and treatment of sensitive teeth caused by dentine hypersensitivity in those patients known to be at risk. There is a need for simple guidelines, which can be readily applied in general practice. However, it is also obvious that one strategy cannot suit all patients. This review describes a DHS management scheme for dental professionals that is linked to management strategies targeted at three different groups of patient. These patient groups are: 1) patients with gingival recession; 2) treatment patients with toothwear lesions; and 3) patients with periodontal disease and those receiving periodontal treatment. The authors also acknowledge the role of industry as well as dental professionals in a continuing role in educating the public on the topic of sensitive teeth. It is therefore important that educational activities and materials for both dental professionals and consumers use common terminology in order to reduce the possibility for confusion. This review article provides practical, evidence-based guidance on the management of dentine hypersensitivity for dental professionals covering diagnosis, prevention and treatment. Sensitivity associated with gingival recession, toothwear and periodontal disease and periodontal treatment are specifically addressed in the article.
    Dental update 09/2013; 40(7):514-6, 518-20, 523-4.
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    ABSTRACT: OBJECTIVES: Leucite glass-ceramics used to produce all-ceramic restorations can suffer from brittle fracture and wear the opposing teeth. High strength and fine crystal sized leucite glass-ceramics have recently been reported. The objective of this study is to investigate whether fine and nano-scale leucite glass-ceramics with minimal matrix microcracking are associated with a reduction in in vitro tooth wear. METHODS: Human molar cusps (n=12) were wear tested using a Bionix-858 testing machine (300,000 simulated masticatory cycles) against experimental fine crystal sized (FS), nano-scale crystal sized (NS) leucite glass-ceramics and a commercial leucite glass-ceramic (Ceramco-3, Dentsply, USA). Wear was imaged using Secondary Electron Imaging (SEI) and quantified using white-light profilometry. RESULTS: Both experimental groups were found to produce significantly (p<0.05) less volume and mean-height tooth loss compared to Ceramco-3. The NS group had significantly (p<0.05) less tooth mean-height loss and less combined (tooth and ceramic) loss than the FS group. Increased waviness and damage was observed on the wear surfaces of the Ceramco-3 glass-ceramic disc/tooth group in comparison to the experimental groups. This was also indicated by higher surface roughness values for the Ceramco-3 glass-ceramic disc/tooth group. CONCLUSIONS: Fine and nano-sized leucite glass-ceramics produced a reduction in in vitro tooth wear. The high strength low wear materials of this study may help address the many problems associated with tooth enamel wear and restoration failure.
    Journal of dentistry 02/2013; DOI:10.1016/j.jdent.2013.02.006
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    ABSTRACT: OBJECTIVES: The aim of this overview is to consider the problems that may be associated with making a diagnosis of dentin hypersensitivity (DHS) and to provide a basis for clinicians to effectively diagnose and manage this troublesome clinical condition. MATERIALS AND METHODS: A PUBMED literature research was conducted by the author using the following MESH terms: ('diagnosis'[Subheading] OR 'diagnosis'[All Fields] OR 'diagnosis'[MeSH Terms]) AND ('therapy'[Subheading] OR 'therapy'[All Fields] OR 'treatment'[All Fields] OR 'therapeutics'[MeSH Terms] OR 'therapeutics'[All Fields]) AND ('dentin Sensitivity'[MeSH Terms] OR ('dentin'[All Fields] AND 'sensitivity'[All Fields]) OR 'dentin sensitivity'[All Fields]). Variations to the above MeSH terms using terms such as 'cervical', 'dentine' and 'hypersensitivity' as substitutes were also explored, but these searches failed to add any further information. RESULTS: The literature search provided only limited data on specific papers relating to the clinical diagnosis of DHS by dental professionals. Evidence from these published studies would therefore indicate that clinicians are not routinely examining their patients for DHS or eliminating other possible causes of dental pain (differential diagnosis) prior to subsequent management and may rely on their patients' self-reporting of the problem. Furthermore, the findings of the Canadian Consensus Document (2003) would also suggest that clinicians are not confident of successfully treating DHS. CONCLUSIONS: It is apparent from reviewing the published literature on the diagnosis of DHS that there are a number of outstanding issues that need to be resolved, for example, (1) is the condition under- or overestimated by dentists, (2) is the condition adequately diagnosed and successfully managed by dentists in daily practice, (3) is the impact of DHS on the quality of life of sufferers adequately diagnosed and treated and (4) is the condition adequately monitored by clinicians in daily practice. These and other questions arising from the workshop forum should be addressed in well-conducted epidemiological and clinical studies in order for clinicians to be confident in both identifying and diagnosing DHS and subsequent management that will either reduce or eliminate the impact of DHS on their patients' quality of life. CLINICAL RELEVANCE: Clinicians should be made aware not only of the importance of identifying patients with DHS but also of the relevance of a correct diagnosis that may exclude any confounding factors from other oro-facial pain conditions prior to the successful management of the condition.
    Clinical Oral Investigations 01/2013; 17(Suppl 1). DOI:10.1007/s00784-012-0911-1
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    ABSTRACT: The reported prevalence of dentine/root (hyper)sensitivity (DH/RS) in the published literature varies, and this may be due in part to a) the different study populations and (b) the different methodologies employed in evaluating the pain response. According to von Troil et al. (2002) there are limited data available in terms of the prevalence and intensity of DH/RS following periodontal therapy. Objectives. The aim of the present study was therefore to review the literature in order to identify all relevant studies for inclusion and to determine whether there was any evidence of DH/RS following periodontal procedures in the published literature up to 31st December 2009 using an agreed search protocol. Methods. 840 papers were identified, from searching both electronic databases (PUBMED) and hand searching of relevant written journals. Twelve papers were subsequently accepted for inclusion. Results. The results of the present study would indicate that the reported prevalence for DH/RS (following nonsurgical therapy) was between 62.5% and 90% one day after treatment decreasing to approximately 52.6% to 55% after one week. The prevalence of DH/RS following surgical therapy was between 76.8% and 80.4% one day after treatment subsequently decreasing over time to 36.8% after 1 week, 33.4% after 2 weeks, 29.6% after 4 weeks, and 21.7% after 8 weeks. Conclusions. It is evident from reviewing the included studies that patients may suffer from mild discomfort following periodontal procedures although both the prevalence and intensity of DH/RS may vary depending on the duration and the type of procedure involved. Most of the studies included in this paper would tend to suggest that DH/RS may be relatively mild/moderate in nature and transient in duration.
    International Journal of Dentistry 10/2012; 2012:407023. DOI:10.1155/2012/407023
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    ABSTRACT: A 49-year-old Black African male, originally of Nigerian origin, was referred by his dentist regarding a bad taste in the mouth. He was seen in a general restorative clinic at Barts and the London NHS Trust. Clinical examination did not reveal any relevant abnormalities. A panoramic tomography, however, showed the presence of multiple supernumerary teeth, which were located in the maxillary right and left premolar and molar regions, and the mandibular left premolar region. The family's history was non-contributory. The patient was unaware of the supernumerary teeth and, as far as he knew, there were no other members of his family with a similar problem. Clinical Relevance: A decision regarding the appropriate management of supernumerary teeth should be considered carefully since surgical removal of the teeth may cause damage to adjacent structures, including bone. In this respect, it is interesting and rare to find multiple supernumerary teeth in individuals with no other associated diseases or syndromes elucidated by clinical and historical enquiry.
    Dental update 10/2011; 38(8):569-70, 572.
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    ABSTRACT: Leucite glass-ceramics with fine-grained leucite crystals promote improved mechanical strength and increased translucency. The objectives of the study were to optimize the microstructure of a fine-grained leucite glass-ceramic in order to increase its flexural strength and reliability as measured by its Weibull modulus. Glass was prepared by a melt-derived method and ground into a powder (M1A). The glass crystallization kinetics were investigated using high temperature XRD and DSC. A series of two-step heat treatments with different nucleation/crystal growth temperatures and holds were carried out to establish the optimized crystallization heat treatment. Glass-ceramics were characterized using XRD, SEM and dilatometry. The glass-ceramic heat treated at the optimized crystallization parameters (M1A(opt)) was both sintered (SM1A(opt)) and heat extruded (EM1A(opt)) into discs and tested using the biaxial flexural strength (BFS) test. High temperature XRD suggested leucite and sanidine crystallization at different temperatures. Optimized crystallization resulted in an even distribution of fine leucite crystals (0.15 (0.09) μm(2)) in the glassy matrix, with no signs of microcracking. Glass-ceramic M1A(opt) showed BFS values of [mean (SD), MPa]: SM1A(opt)=252.4 (38.7); and EM1A(opt)=245.0 (24.3). Weibull results were: SM1A(opt); m=8.7 (C.I.=7.5-10.1) and EM1A(opt); m=11.9 (C.I.=9.3-15.1). Both experimental groups had a significantly higher BFS and characteristic strength than the IPS Empress Esthetic glass-ceramic, with a higher m value for the EM1A(opt) material (p<0.05). A processable fine-grained leucite glass-ceramic with high flexural strength and improved reliability was the outcome of this study.
    Dental materials: official publication of the Academy of Dental Materials 09/2011; 27(11):1153-61. DOI:10.1016/j.dental.2011.08.009
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    ABSTRACT: The aims of the study were to develop and test multi-phase glaze coatings for zirconia restorations, so that the surface could be etched and adhesively bonded. Zirconia disc specimens (n=125, 16 mm x 1 mm) were cut from cylinders of Y-TZP (yttria-stabilized tetragonal zirconia polycrystals) ZS-Blanks (Kavo, Everest) and sintered overnight. Specimens were subjected to the recommended firing cycles, and next sandblasted. The specimens were divided into 5 groups of 25, with Group 1 as the sandblasted control. Groups 2-5 were coated with overglaze materials (P25 and IPS e.max Ceram glazes) containing secondary phases. Group 2 was (wt%): 10% hydroxyapatite (HA)/P25 glaze, Group 3: 20% IPS Empress 2 glass-ceramic/glaze, Group 4: 20% IPS Empress 2 glass/glaze and Group 5: 30% IPS Empress 2 glass/glaze. After sintering and etching, Monobond-S and composite resin cylinders (Variolink II, Ivoclar-Vivadent) were applied and light cured on the test surfaces. Specimens were water stored for 7 days. Groups were tested using the shear bond strength (SBS) test at a crosshead speed of 0.5 mm/min. Overglazed and the fractured specimen surfaces were viewed using secondary electron microscopy. Room and high temperature XRD and DSC were carried out to characterize the materials. The mean (SD) SBS (MPa) of the test groups were: Group 1: 7.7 (3.2); Group 2: 5.6 (1.7); Group 3: 11.0 (3.0); Group 4: 8.8 (2.6) and Group 5: 9.1 (2.6). Group 3 was significantly different to the control Group 1 (p<0.05). There was no significant difference in the mean SBS values between Group 1 and Groups 2, 4 and 5 (p>0.05). Group 2 showed statistically lower SBS than Groups 3-5 (p<0.05). Lithium disilicate fibres were present in Groups 3-5 and fine scale fibres were grown in the glaze following a porcelain firing cycle (Groups 4 and 5). XRD indicated a lithium disilicate/minor lithium orthophosphate phase (Group 3), and a tetragonal zirconia phase for the sintered Y-TZP ZS-Blanks. DSC and high temperature XRD confirmed the crystallization temperatures and phases for the IPS Empress 2 glass. The application of a novel glass-ceramic/glaze material containing a major lithium disilicate phase might be a step in improving the bond strength of a zirconia substrate to a resin cement.
    Journal of dentistry 10/2010; 38(10):773-81. DOI:10.1016/j.jdent.2010.06.008
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    ABSTRACT: Manufacturing of leucite glass-ceramics often leads to materials with inhomogeneous microstructures. Crystal-glass thermal mismatches which produce microcracking around larger crystals-agglomerates are associated with reduced mechanical properties. The hypotheses were that fine (< 1 µm) crystal size and uniform microstructure in a thermally matched glass would increase the biaxial flexural strength (BFS). Glass was synthesized, attritor-milled, and heat-treated. Glasses and glass-ceramics were characterized by XRD, SEM, and Dilatometry. Experimental (A, M1A and M2A) and commercial glass-ceramics were tested by the BFS test. Experimental glass-ceramics showed an increased leucite crystal number and decreased crystal size with glass particle size reduction. Leucite glass-ceramics (< 1 µm) showed minimal matrix microcracking and BFS values of [mean (SD) MPa]: M1A = 253.8 (53.3); and M2A = 219.5 (54.1). Glass-ceramics M1A and M2A had higher mean BFS and characteristic strength than the IPS Empress Esthetic glass-ceramic (p < 0.05). Fine-grained, translucent leucite glass-ceramics were synthesized and produced high mean BFS.
    Journal of dental research 10/2010; 89(12):1510-6. DOI:10.1177/0022034510377795
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    ABSTRACT: Previous studies have suggested that the mandible may be more influenced by mechanical loading than by circulating hormone levels. We tested the hypothesis that hypofunction has a greater influence than ovariectomy on mandibular bone. Two-month-old rats were ovariectomized (OVX) or had maxillary molars removed from one side to induce unilateral mandibular hypofunction. Control animals remained untreated. After 5 months, animals were killed, and bones were assessed by micro-tomography (muCT), quantitative back-scattered electron analysis in an SEM (qBSE-SEM), and light microscopy. Mineralization density was reduced in calvarial, maxillary, and mandibular alveolar bone following OVX, yet was increased in lingual mandibular alveolar bone of the hypo-function animals compared with controls. OVX caused a reduction in osteocyte density in alveolar bone, while hypofunction showed an increase compared with controls. Hypofunction led to alveolar bone becoming more highly mineralized and more cellular, while ovariectomy caused a reduction in both mineralization density and osteocyte numbers.
    Journal of dental research 08/2009; 88(7):615-20. DOI:10.1177/0022034509340132
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