RESUMEN
The use of cone beam computed tomography (CBCT) in the diagnosis and/or management of endodontic problems is increasing and is reflected in the exponential rise in publications on this topic in the last two decades. The aim of this paper is to: (i) Review current literature on the endodontic applications of CBCT; (ii) Based on current evidence make recommendations for the use of CBCT in Endodontics; (iii) Highlight the areas in which more research is required.
Asunto(s)
Endodoncia , Tomografía Computarizada de Haz CónicoRESUMEN
Proteomic analysis of histones has shown that they are subject to a superabundance of acylations, which extend far beyond acetylation, to include: crotonylation, propionylation, butyrylation, malonylation, succinylation, ß-hydroxybutyrylation and 2-hydroxyisobutyrylation. To date, much of the functional data has focussed on histone crotonylation which, similar to acetylation, has been associated with positive gene regulation and is added by the acyltransferase, p300. Although Sirtuins 1-3, along with HDAC3, have been shown to possess decrotonylase activity in vitro, there is relatively little known about the regulation of histone crotonylation in vivo. Here we show that Histone Deacetylase 1 and 2 (HDAC1/2), the catalytic core of numerous co-repressor complexes, are important histone decrotonylase enzymes. A ternary complex of HDAC1/CoREST1/LSD1 is able to hydrolyse both histone H3 Lys18-acetyl (H3K18ac) and H3 Lys18-crotonyl (H3K18cr) peptide substrates. Genetic deletion of HDAC1/2 in ES cells increases global levels of histone crotonylation and causes an 85% reduction in total decrotonylase activity. Furthermore, we mapped H3K18cr in cells using ChIP-seq, with and without HDAC1/2, and observed increased levels of crotonylation, which largely overlaps with H3K18ac in the vicinity of transcriptional start sites. Collectively, our data indicate that HDAC1/2 containing complexes are critical regulators of histone crotonylation in vivo.
Asunto(s)
Histona Desacetilasa 1/metabolismo , Histona Desacetilasa 2/metabolismo , Histonas/metabolismo , Complejos Multienzimáticos/metabolismo , Procesamiento Proteico-Postraduccional , Línea Celular , HumanosRESUMEN
AIM: To investigate how preparation of a simulated access cavity into ceramic materials suitable for the manufacture of dentine-bonded crowns (DBCs) impacted on biaxial flexural strength (BFS) determined as a monolithic structure and in a more clinically representative resin-cemented form. METHODOLOGY: One hundred and twenty feldspathic and 120 leucite-reinforced ceramic disc-shaped specimens were divided into eight groups (n = 30). All groups received 'fit' surface treatments representative of pre-cementation modifications and of cementation prior to preparation of a representative endodontic access cavity through the sample. BFS was determined for both 'intact' and the 'annular' disc-shaped specimens which had received simulated endodontic access. Newly reported analytical solutions were used to calculate BFS of the 'annular' specimens. Statistical analysis included two-way anovas (α = 0.05) and Weibull analysis. Fractographic examination provided insight into the fracture mechanisms. RESULTS: A two-way anova identified a significant impact of material (P < 0.01) and of resin coating (P < 0.01) on the mean BFS of intact specimens. For the annular ceramic specimens, the substrate material significantly impacted on mean BFS (P < 0.01), but the effect of resin coating was dependent on the substrate type (P < 0.01). CONCLUSIONS: Endodontic access cavity preparation modified the critical defect population of the all-ceramic restorative materials investigated. The strength of a predominantly glassy ceramic following endodontic access can be maintained if adhesive cementation was used; however, the beneficial effects of adhesive cementation on ceramic reinforcement were lost on leucite-reinforced ceramics following access cavity preparation. Replacement restoration for these materials would be recommended clinically following endodontic access as opposed to repair of the access cavity using a direct restorative material.
Asunto(s)
Coronas , Endodoncia/métodos , Cerámica , Dentina , Técnicas In VitroRESUMEN
AIMS: To investigate the approach of restorative dentists towards the assessment and treatment planning of oral cancer patients in the UK. MATERIAL AND METHODS: The survey was conducted at the annual meeting of the Association of Consultants in Restorative Dentistry (ACSRD) and Specialist Registrar in Restorative Dentistry group (SRRDG) in September 2011. Delegates were requested to fill in a two-section questionnaire; the first section included 16 questions, evaluating cancer service provision in their units, and the second included five questions based on a clinical scenario evaluating dental management of a patient undergoing pre-radiotherapy treatment. RESULTS: Ninety-four questionnaires were distributed; 65 (69.1%) were returned. Thirty (46.1%) respondents were consultants, 27 (41.5%) were specialist registrars and the remaining 8 (12.3%) were either specialist practitioners or trust grade dentists working in the speciality of restorative dentistry. Forty-eight (73%) of the respondents worked in NHS posts and the remaining 17 (27%) worked in academic posts. A total of 50 (77%) respondents carried out clinical work which regularly included the dental assessment or treatment of head and neck (H&N) oncology patients, before or post radiotherapy. Among the respondents who were involved in the dental assessment of oncology patients, 32% of them did not have a protocol for review appointments in their units. Ninety-one percent of respondents said that they used dental implants for rehabilitation post cancer surgery and 80% also used implants either always or sometimes in irradiated bone. Answers to scenario questions highlighted that all the respondents would extract very poorly prognostic tooth (that is, root stumps) before radiotherapy, irrespective of it being at the side of the planned radiotherapy field. Fifty-eight percent of respondents preferred to extract a non-functional, heavily restored, non-carious, distal maxillary molar tooth which was not in the area of radiotherapy beam and the majority (84%) chose to carry out root canal treatment (RCT) of a functional premolar tooth if considered non vital. CONCLUSION: This study highlights the variability in the approach of clinicians in dental and oral rehabilitation of patients undergoing radiotherapy treatment for oral cancer patients.
Asunto(s)
Restauración Dental Permanente , Neoplasias de la Boca/terapia , Planificación de Atención al Paciente , Humanos , Especialidades Odontológicas , Medicina Estatal , Encuestas y Cuestionarios , Reino UnidoRESUMEN
OBJECTIVES: To report analytic solutions capable of identifying failure stresses from the biaxial flexure testing of geometries representative of endodontic access cavities prepared through dental restorative materials. METHODS: The ring-on-ring biaxial flexure strength of annular discs with a central circular hole supported peripherally by a knife-edge support and loaded evenly at the upper edge of the central hole were solved using general expressions of deformations, moments and shears for flat plates of a constant thickness. To validate the solutions, finite element analyses were performed. A three-dimensional one-quarter model of the test was generated using a linear P-code FEA software and the boundary conditions represented the experimental test configuration whereby symmetry planes defined the full model. To enable comparison of the maximum principal stresses with experimental derived data, three groups of nominally identical feldspathic ceramic disks (n=30) were fabricated. Specimens from Group A received a 4mm diameter representative endodontic access cavity and were tested in ring-on-ring. Group B and C specimens remained intact and were tested in ring-on-ring and ball-on-ring, respectively, to give insight into strength scaling effects. Fractography was used to confirm failure origins, and statistical analysis of fracture strength data was performed using one-way ANOVAs (P<0.05) and a Weibull approach. RESULTS: The developed analytical solutions were demonstrated to deviate <1% from the finite element prediction in the configuration studied. Fractography confirmed the failure origin of tested samples to coincide with the predicted stress maxima and the area where fracture is observed to originate clinically. Specimens from the three experimental groups A-C exhibited different strengths which correlated with the volume scaling effects on measured strength. SIGNIFICANCE: The solutions provided will enable geometric and materials variables to be systematically studied and remove the need for load-to-failure 'crunch the crown' testing.
Asunto(s)
Cerámica , Restauración Dental Permanente , Ensayo de Materiales , Tratamiento del Conducto Radicular , Análisis de Elementos FinitosRESUMEN
It is now over a decade since the birth, in 1996, of Dolly the first animal to be produced by nuclear transfer using an adult derived somatic cell as nuclear donor. Since this time similar techniques have been successfully applied to a range of species producing live offspring and allowing the development of transgenic technologies for agricultural, biotechnological and medical uses. However, though applicable to a range of species, overall, the efficiencies of development of healthy offspring remain low. The low frequency of successful development has been attributed to incomplete or inappropriate reprogramming of the transferred nuclear genome. Many studies have demonstrated that such reprogramming occurs by epigenetic mechanisms not involving alterations in DNA sequence, however, at present the molecular mechanisms underlying reprogramming are poorly defined. Since the birth of Dolly many studies have attempted to improve the frequency of development, this review will discuss the process of animal production by nuclear transfer and in particular changes in the methodology which have increased development and survival, simplified or increased robustness of the technique. Although much of the discussion is applicable across species, for simplicity we will concentrate primarily on published data for cattle, sheep, pigs and mice.
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Técnicas de Transferencia Nuclear/tendencias , Algoritmos , Animales , Técnicas de Cultivo de Embriones , Fertilización In Vitro/veterinaria , Humanos , Técnicas de Transferencia Nuclear/veterinaria , Oocitos/citología , Oocitos/fisiología , Donantes de TejidosRESUMEN
While the biophysics of anemophilous pollen dispersal is understood in principle, empirical studies for testing such principles are rare, particularly in native ecosystems. This paper describes mechanisms underlying the dispersal of Artemisia pollen in a Wyoming sagebrush steppe. The relationships between meteorological variables and pollen flux were defined during the 1999 Artemisia flowering season, and detailed processes at the individual plant level were experimentally tested in the field in 2000. Results indicated that Artemisia pollen presentation is continuous but with early morning maxima. Atmospheric pollen concentrations and potential dispersal rates are controlled at diurnal time scales by individual flower development together with characteristic changes in temperature/humidity and wind speeds, at multi-day scales by frontal weather patterns, and at week-long scales by flowering phenology.
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Artemisia/fisiología , Polen/fisiología , Atmósfera , Evolución Biológica , Fenómenos Biofísicos , Biofisica , Ritmo Circadiano , Ecosistema , Conceptos Meteorológicos , Modelos Biológicos , WyomingRESUMEN
It is now 8 years since the birth of Dolly, the first animal produced by nuclear transfer using a donor cell population established from an adult animal. During this time, the technique of nuclear transfer has been successfully applied to a range of mammalian species for the production of offspring using a plethora of donor cell types derived from both foetal and adult tissues. In addition, when coupled with genetic manipulation of the donor cells, transgenic offspring have been produced with a range of genetic modifications including gene knockouts and gene knockings. Despite the apparent successes of the technology, the efficiency of development to live offspring has remained low and developmental abnormalities still occur. The objectives of this paper are to review some of the successes and failures of the nuclear transfer procedure since the production of Dolly. In particular, we will review the major steps in the procedure and discuss studies from our laboratory and others which have modified the procedure in ways which may impact on development.