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The fate of marginal bone around axial vs. tilted implants : a systematic review
No full textAims: The use of tilted implants has recently gained popularity as a feasible option for the treatment of edentulous jaws by means of implant-supported rehabilitations without recurring to grafting procedures. The aim of this review was to compare the crestal bone level change around axially placed vs. tilted implants supporting fixed prosthetic reconstructions for the rehabilitation of partially and fully edentulous jaws, after at least 1 year of function.
Materials and methods: An electronic search of databases plus a hand search on the most relevant journals up to January 2014 was performed. The articles were selected using specific inclusion criteria, independent of the study design. Data on marginal bone loss and implant survival were extracted from included articles and statistically analysed to investigate the effect of implant tilting, location, prosthesis type, loading mode and study design. The difference in crestal bone level change around axial vs. tilted implants was analysed using meta-analysis.
Results: The literature search yielded 758 articles. A first screening based on titles and abstracts identified 62 eligible studies. After a full-text review, 19 articles (14 prospective and five retrospective studies) were selected for analysis. A total of 670 patients have been rehabilitated with 716 prostheses (415 in the maxilla, 301 in the mandible), supported by a total of 1494 axial and 1338 tilted implants. Peri-implant crestal bone loss after 1 year of function ranged from 0.43 to 1.13 mm for axial implants and from 0.34 to 1.14 mm for tilted implants. In spite of a trend for a lower bone loss around axial implants with respect to tilted ones at 12 months, as well as after 3 or more years of function, no significant difference could be found (P = 0.09 and P = 0.30, respectively). The location (maxilla vs. mandible), the loading mode (immediate vs. delayed), the restoration type (full vs. partial prosthesis) and the study design (prospective vs. retrospective) had no significant effect on marginal bone loss. Forty-six implants (18 axial and 28 tilted) failed in 38 patients within the first year of function. All failures except five occurred in the maxilla. After 12 months of loading, the survival rate of implants placed in the maxilla (97.4%) was significantly lower as compared to the mandible (99.6%). No prosthesis failure was reported.
Conclusions: Tilting of the implants does not induce significant alteration in crestal bone level change as compared to conventional axial placement after 1 year of function. The trend seems to be unchanged over time even though the amount of long-term data is still scarce. The use of tilted implants to support fixed partial and full-arch prostheses for the rehabilitation of edentulous jaws can be considered a predictable technique, with an excellent prognosis in the short and mid-term. Further long-term trials, possibly randomised, are needed to determine the efficacy of this surgical approach and the remodelling pattern of marginal bone in the long term
PRODUCTION OF HUMAN RECOMBINANT DIFFERENTIATION FACTORS IN TRANSGENIC TOBACCO PLANTS
Get PDFResearch on bone regeneration began decades ago as a result of intensive studies on bone growth and healing. Bone has been recognised, among the many tissues in human body, as having the highest potential for regeneration, and it is the second most transplanted tissue following blood.
Due to both internal mediators and external mechanical demands, it possesses the intrinsic ability for regeneration and is constantly engaged in a cycle of resorption and renewal undergoing continual chemical exchange and structural remodelling throughout adult life as well as during repair process in response to injury. Despite these abilities, beyond a critical point clinical intervention measures are needed; there are different clinical conditions requiring a large quantity of bone regeneration, such as for skeletal reconstruction of large bone defects created by trauma, infection, or cases in which the regenerative process is compromised, including necrosis, atrophic non-unions and osteoporosis.
To describe the extent of this situation, it is estimated that annually more than 2.2 million patients receive bone defect repairs worldwide, with a cost greater than $2.5 billion just in the United States; this figure is expected to globally double by 2020 due to a variety of factors, including increased life expectancy. The board of the Bone and Joint Decade in 2009 has assessed that half of the people aged over 65, affected by chronic conditions, suffers of joint diseases and that the number of osteoporotic fractures has doubled in the previous 15 years. It should be also pointed out that the worldwide incidence of bone disorders and conditions is increasing in those societies where population ageing is combined with increased obesity and poor physical activity.
Shortcomings, limitations, and complications of current clinical treatments for bone repair and regeneration have been reported in different studies. A variety of graft materials are currently used to enhance bone healing, and the relative success of these materials depends on many factors, not only on the specific properties of the graft itself. In addition to its physical properties, to be effective, a grafting material is required to even provide osteoconductive and/or osteoinductive activities. Osteoconduction, the ability of promoting bone growth by allowing bone formation on material’s surface, may suffice in clinical condition of less severe defects, where sufficient quantities and margins of bone exist. Osteoinduction instead, is the capability of promoting de novo bone formation at soft or hard tissue sites, and offers needful advantages for biologic reconstruction of severe situations.
Among most commonly used materials there are allografts, cadaveric bone usually obtained from a bone bank, autologous grafts, bone harvested from the patient’s own body, or synthetic ones, often made of hydroxyapatite or other naturally and biocompatible substances.
Allografts, mineralized or demineralized, are histocompatible, available in various forms including demineralized bone matrix and cortical grafts and whole-bone segments, depending on the host-site requirements, and provide an osteoconductive environment; however, their osteoinductive capacity is highly variable depending on the processing method and sourcing, and may be present in inadequate amounts for any bone-inductive effect.
To date, autografts serve as the gold standard for bone grafts because they are histocompatible, non-immunogenic, and they offer all of the properties required. Specifically, this material provides an osteoconductive environment (i.e., three-dimensional scaffolds and porous matrix) coupled with cells (i.e., osteoprogenitor cells) as well as growth and differentiation factors(i.e., growth factors) that can result in osteoinduction Nevertheless, autogenous grafting is sometimes an expensive procedure that has a number of shortcomings, including the need for secondary surgery to harvest the graft, donor site morbidity, irregular resorption of transplanted tissue, and limited availability of donor bone. Furthermore autograft may be a useless or inadequate treatment option in cases where the defect site requires larger amounts of bone than is available.
Other commonly used bone repair techniques involve synthetic materials and fillers, and growth and differentiation factors, but, although all these clinical interventions have been shown to improve bone repair, none of them possess all of the necessary characteristics: high osteoinductive and angiogenic potentials, biological safety, low patient morbidity, ready access to surgeons, no size restrictions, long shelf life and reasonable cost; all these limitations have led to an extensive research for alternatives.
The discovery and subsequent production of the osteoinductive agents in bone, the Bone Morphogenetic Proteins (BMPs), have provided the possibility of reducing or avoiding the need for autograft, through a tissue-engineering product.
Clinically, BMPs have demonstrated the potential to replace the use of autogenous bone in many applications so that costs and complications related to harvesting autograft can be prevented; in addition, the ability to control quality, activity and dose of the osteoinductive agent may provide greater assurance of bone induction and repair. Despite this, a widespread therapeutic use of BMPs has been hindered by difficulties in obtaining large amounts of pure, biologically active protein at a cost-effective price.
Thus, the aim of this study was to develop a plant based system for cost-effective production of active recombinant BMPs. This introduction provides a review of the relevant literature pertaining to BMPs (especially to BMP-2) synthesis, processing and recombinant production process
Effect of platelet concentrate on quality of life after periradicular surgery : a randomized clinical study
No full textIntroduction: Control of postoperative discomfort might enhance the patient's quality of life and treatment acceptance. The aim of the present randomized single-blind study was to evaluate whether the use of platelet concentrate during endodontic surgery might have a favorable impact on pain and other factors related to patient's quality of life during the first week after surgery. Methods: Eighteen patients with periapical lesion were treated with modern endodontic surgical procedure (control group). In another 18 patients, in adjunct to surgical procedure, platelet concentrate was applied on the root end in liquid form, within the bone defect in clot form, and over the suture in liquid form (test group). All patients completed a questionnaire for evaluation of main symptoms and daily activities during the first week after surgery. The outcomes of the questionnaires of the 2 groups were statistically compared. Results: The test group showed significantly less pain and swelling, fewer analgesics taken, and improved functional activities as compared with the control group. Conclusions: The adjunct of platelet concentrate to the endodontic surgical procedure produced significant beneficial effect to patients' quality of life during the early postoperative stage
Going Beyond Counting First Authors in Author Co-citation Analysis
Get PDFThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Variations on the Author
Get PDF“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
Appropriate Similarity Measures for Author Cocitation Analysis
Get PDFWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
Dispelling the Myths Behind First-author Citation Counts
Get PDFWe conducted a full-scale evaluative citation analysis study of scholars in the XML research field to explore just how different from each other author rankings resulting from different citation counting methods actually are, and to demonstrate the capability of emerging data and tools on the Web in supporting more realistic citation counting methods. Our results contest some common arguments for the continued
use of first-author citation counts in the evaluation of scholars, such as high correlations between author rankings by first-author citation counts and other citation
counting methods, and high costs of using more realistic citation counting methods that are not well-supported by the ISI databases. It is argued that increasingly available digital full text research papers make it possible for citation analysis studies to go beyond what the ISI databases have directly supported and to employ more
sophisticated methods
koamabayili/VECTRON-author-checklist: VECTRON author checklist
No full textWe have done our best to complete the author checklist relating to the use of animals in the hut study. Note that the objective for the hut study was to evaluate the IRS treatment applications for residual efficacy against Anopheles mosquitoes, including the local An. coluzzii mosquito population. Cows were only used to attract mosquitoes into the huts and no tests were carried out directly on the cows. The author checklist is intended for use with studies where experiments are carried out on animals, which is why we have had such difficulty in completing this for the hut study, as many of the questions do not relate to how the cows were used
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