Do implants made of polyetheretherketone and its composites have reduced stress shielding effects compared to other dental implant materials? A systematic review.

PURPOSE: The present systematic review was executed to evaluate the stress shielding effect of PEEK and its composite dental implants as compared to other implant (titanium and zirconia) materials in peri-implant bone. MATERIALS AND METHOD: The comprehensive online literature search was conducted on PubMed, Google Scholar, and Web of Science from January 2011 to January 2023. A total of 43 in vitro studies were identified related to the raised question. In all, 34 studies were excluded as they included in vitro studies focusing on stress distribution in prosthesis framework, abutments, crown, and on biological properties such as cell adhesion, etc. Only eight studies after full-text screening were included in the present systematic review. RESULTS: The data extracted from included studies showed that PEEK and its composite materials, have a less stress shielding effect due to their low modulus of elasticity resulting in higher stress concentration and strain in the peri-implant bone as compared to titanium and zirconia implant materials. CONCLUSION: The PEEK and its composites can be used as an alternative material in the esthetic region and in those who have an allergy to metal implants. However, due to the low elastic modulus of PEEK, a homogenous stress distribution is not observed along the entire length of the implant. Further studies are required to improve the composition of PEEK material so that a homogenous reduction of stress shielding effect along the whole length of a dental implant can be achieved.

Biomechanical efficiency of different implant-abutment connection: a systematic review of studies using photoelastic stress analysis.

PURPOSE: The present review aimed to comparatively evaluate the biomechanical efficiency of different implant-abutment connections studied by photoelastic stress analysis. MATERIALS AND METHODS: A comprehensive online literature search was conducted on Medline (Pubmed), Web of Science, and Google Scholar from 2000(Jan) to 2023(Jan). Keywords used initially to carry out the search included implant-abutment connection & photoelastic stress analysis, and stress distribution in different implant-abutment connections. 34 photoelastic stress analysis studies were screened and 30 studies were excluded after the screening of the title, abstract and full article. Finally, 4 studies were included for complete review. RESULT: The result of this systematic review showed that the internal connection was more efficient then the external connection as there was less marginal bone loss and favorable distribution of stress in internal connection. CONCLUSION: Crestal bone loss is more in external connection when compared to internal connection. In Internal connection, there is more intimate contact between the abutment's outer surface and implant which renders a more stable interface, which favoring uniform stress distribution and protects the retention screw.

Comparison of Stress Distribution in Fixed Partial Prosthesis Restored with Different Combination of Support: A Finite Element Study.

AIM: This study was conducted to evaluate the distribution of stress in the bone around the natural tooth, endodontically treated tooth having post and core, and implant as an abutment in different combinations in fixed partial prosthesis using two-dimensional finite element analysis (FEA). MATERIALS AND METHODS: Six models were simulated using ANSYS Modeller19. All six models were divided into 12 zones and 4 lines, and stress values were calculated and compared. The study combinations were - tooth supported fixed partial prosthesis, fixed partial prosthesis having the combination of tooth and post- and core-treated tooth, fixed partial prosthesis with the combination of tooth and implant, fixed partial prosthesis having the combination of implant and post- and core-treated tooth, fixed partial prosthesis with the combination of post- and core-treated tooth on both sides, and fixed partial prosthesis having the combination of implant on both sides. RESULT: On comparing the stress values, the maximum stress value was observed in fixed partial prosthesis having the combination of implant on both sides (306.2434 MPa) followed by Model 4 (223.1255 MPa), Model 3 (154.3952 MPa), Model 5 (136.9041 MPa), Model 2 (116.2034 MPa), and least stress seen in Model 1 (99.6209 MPa), and minimum in tooth supported fixed partial prosthesis (99.6209 MPa). CONCLUSION: This study concluded that stress concentration in bone was maximum when the implant was used as an abutment in fixed partial prosthesis. The least stress was seen in bone around the natural tooth due to the dampening effect of the periodontal ligament. Further, the modulus of elasticity of a post acts as a vital parameter in the distribution of stress in post- and core-treated tooth. CLINICAL SIGNIFICANCE: The stress concentration in the bone around the abutments affects the longevity of the prosthesis, hence, the clinically appropriate combination of the abutments should be considered for a fixed partial prosthesis.

Multiple Wnts act synergistically to induce Chk1/Grapes expression and mediate G2 arrest in Drosophila tracheoblasts.

Larval tracheae of Drosophila harbour progenitors of the adult tracheal system (tracheoblasts). Thoracic tracheoblasts are arrested in the G2 phase of the cell cycle in an ATR (mei-41)-Checkpoint Kinase1 (grapes, Chk1) dependent manner prior to mitotic re-entry. Here we investigate developmental regulation of Chk1 activation. We report that Wnt signaling is high in tracheoblasts and this is necessary for high levels of activated (phosphorylated) Chk1. We find that canonical Wnt signaling facilitates this by transcriptional upregulation of Chk1 expression in cells that have ATR kinase activity. Wnt signaling is dependent on four Wnts (Wg, Wnt5, 6,10) that are expressed at high levels in arrested tracheoblasts and are downregulated at mitotic re-entry. Interestingly, none of the Wnts are dispensable and act synergistically to induce Chk1. Finally, we show that downregulation of Wnt signaling and Chk1 expression leads to mitotic re-entry and the concomitant upregulation of Dpp signaling, driving tracheoblast proliferation.

Comparison of Diagnostic Accuracy of Non-fasting DIPSI and HbA1c with Fasting WHO Criteria for Diagnosis of Gestational Diabetes Mellitus.

BACKGROUND: To compare diagnostic accuracy of non-fasting DIPSI and HbA1c with fasting WHO 1999 as gold standard for diagnosis of gestational diabetes mellitus (GDM). METHODS: Pregnant women attending antenatal clinic underwent a 2-h 75-gm GCT in non-fasting state (DIPSI). HbA1c was also determined at the same sitting. A 2-h 75-gm GCT was repeated for all women after 72 h in a fasting state (WHO criteria). GDM was diagnosed if plasma glucose was ≥140 mg/dl by either test or if HbA1C ≥6%. RESULTS: Of the 800 women evaluated, 51 were diagnosed as GDM by WHO criteria, 63 by DIPSI, and 40 by HbA1c. The sensitivity of DIPSI test with respect to WHO 1999 was 98.04% and specificity 98.26%. The diagnostic accuracy was 98.25%. The area under the ROC curve for DIPSI was 0.988 (p < 0.001) (95% confidence interval: 0.960-1.000). The sensitivity of HbA1c with respect to WHO GTT was 47.06%, specificity 97.86%, and diagnostic accuracy 94.63%. The ROC curve between WHO GTT and HbA1c covered an area of 0.805 (p < 0.01) (95% confidence interval: 0.731-0.879). CONCLUSIONS: Non-fasting DIPSI criteria had high diagnostic accuracy compared to gold-standard WHO GTT and can be an effective and practical alternative to the latter. HbA1c had a low sensitivity although the specificity was good and therefore is not a suitable test for screening GDM.

Drosophila Malpighian Tubules: A Model for Understanding Kidney Development, Function, and Disease.

The Malpighian tubules of insects are structurally simple but functionally important organs, and their integrity is important for the normal excretory process. They are functional analogs of human kidneys which are important physiological organs as they maintain water and electrolyte balance in the blood and simultaneously help the body to get rid of waste and toxic products after various metabolic activities. In addition, it receives early indications of insults to the body such as immune challenge and other toxic components and is essential for sustaining life. According to National Vital Statistics Reports 2016, renal dysfunction has been ranked as the ninth most abundant cause of death in the USA. This chapter provides detailed descriptions of Drosophila Malpighian tubule development, physiology, immune function and also presents evidences that Malpighian tubules can be used as a model organ system to address the fundamental questions in developmental and functional disorders of the kidney.

A systematic review of strategies to recruit and retain primary care doctors.

BACKGROUND: There is a workforce crisis in primary care. Previous research has looked at the reasons underlying recruitment and retention problems, but little research has looked at what works to improve recruitment and retention. The aim of this systematic review is to evaluate interventions and strategies used to recruit and retain primary care doctors internationally. METHODS: A systematic review was undertaken. MEDLINE, EMBASE, CENTRAL and grey literature were searched from inception to January 2015. Articles assessing interventions aimed at recruiting or retaining doctors in high income countries, applicable to primary care doctors were included. No restrictions on language or year of publication. The first author screened all titles and abstracts and a second author screened 20%. Data extraction was carried out by one author and checked by a second. Meta-analysis was not possible due to heterogeneity. RESULTS: Fifty-one studies assessing 42 interventions were retrieved. Interventions were categorised into thirteen groups: financial incentives (n = 11), recruiting rural students (n = 6), international recruitment (n = 4), rural or primary care focused undergraduate placements (n = 3), rural or underserved postgraduate training (n = 3), well-being or peer support initiatives (n = 3), marketing (n = 2), mixed interventions (n = 5), support for professional development or research (n = 5), retainer schemes (n = 4), re-entry schemes (n = 1), specialised recruiters or case managers (n = 2) and delayed partnerships (n = 2). Studies were of low methodological quality with no RCTs and only 15 studies with a comparison group. Weak evidence supported the use of postgraduate placements in underserved areas, undergraduate rural placements and recruiting students to medical school from rural areas. There was mixed evidence about financial incentives. A marketing campaign was associated with lower recruitment. CONCLUSIONS: This is the first systematic review of interventions to improve recruitment and retention of primary care doctors. Although the evidence base for recruiting and care doctors is weak and more high quality research is needed, this review found evidence to support undergraduate and postgraduate placements in underserved areas, and selective recruitment of medical students. Other initiatives covered may have potential to improve recruitment and retention of primary care practitioners, but their effectiveness has not been established.

Early gene Broad complex plays a key role in regulating the immune response triggered by ecdysone in the Malpighian tubules of Drosophila melanogaster.

In insects, humoral response to injury is accomplished by the production of antimicrobial peptides (AMPs) which are secreted in the hemolymph to eliminate the pathogen. Drosophila Malpighian tubules (MTs), however, are unique immune organs that show constitutive expression of AMPs even in unchallenged conditions and the onset of immune response is developmental stage dependent. Earlier reports have shown ecdysone positively regulates immune response after pathogenic challenge however, a robust response requires prior potentiation by the hormone. Here we provide evidence to show that MTs do not require prior potentiation with ecdysone hormone for expression of AMPs and they respond to ecdysone very fast even without immune challenge, although the different AMPs Diptericin, Cecropin, Attacin, Drosocin show differential expression in response to ecdysone. We show that early gene Broad complex (BR-C) could be regulating the IMD pathway by activating Relish and physically interacting with it to activate AMPs expression. BR-C depletion from Malpighian tubules renders the flies susceptible to infection. We also show that in MTs ecdysone signaling is transduced by EcR-B1 and B2. In the absence of ecdysone signaling the IMD pathway associated genes are down regulated and activation and translocation of transcription factor Relish is also affected.

Ecdysone regulates morphogenesis and function of Malpighian tubules in Drosophila melanogaster through EcR-B2 isoform.

Malpighian tubules are the osmoregulatory and detoxifying organs of Drosophila and its proper development is critical for the survival of the organism. They are made up of two major cell types, the ectodermal principal cells and mesodermal stellate cells. The principal and stellate cells are structurally and physiologically distinct from each other, but coordinate together for production of isotonic fluid. Proper integration of these cells during the course of development is an important pre-requisite for the proper functioning of the tubules. We have conclusively determined an essential role of ecdysone hormone in the development and function of Malpighian tubules. Disruption of ecdysone signaling interferes with the organization of principal and stellate cells resulting in malformed tubules and early larval lethality. Abnormalities include reduction in the number of cells and the clustering of cells rather than their arrangement in characteristic wild type pattern. Organization of F-actin and ß-tubulin also show aberrant distribution pattern. Malformed tubules show reduced uric acid deposition and altered expression of Na(+)/K(+)-ATPase pump. B2 isoform of ecdysone receptor is critical for the development of Malpighian tubules and is expressed from early stages of its development.

Epithelial immune response in Drosophila malpighian tubules: interplay between Diap2 and ion channels.

Systemic immune response via the Immune deficiency pathway requires Drosophila inhibitor of apoptosis protein 2 to activate the NF-κB transcription factor Relish. Malpighian tubules (MTs), simple epithelial tissue, are the primary excretory organs, performing additional role in providing protection to Drosophila against pathogenic infections. MTs hold a strategic position in Drosophila as one of the larval tissues that are carried over to adults, unlike other larval tissues that are histolysed during pupation. In this paper we show that Diap2 is an important regulator of local epithelial immune response in MTs and depletion of Diap2 from MTs, increases susceptibility of flies to infection. In the absence of Diap2, activation and translocation of Relish to the nucleus is abolished and as a consequence the production of IMD pathway dependent AMPs are reduced. Ion channels, (Na(+)/K(+))-ATPase and V-ATPase, are important for the immune response of MTs and expression of AMPs and the IMD pathway genes are impaired on inhibition of transporters, and they restrict the translocation of Relish into the nucleus. We show that Diap2 could be regulating ion channels, as loss of Diap2 consequently reduces the expression of ion channels and affects the balance of ion concentrations which results in reduced uric acid deposition. Thus Diap2 seems to be a key regulator of epithelial immune response in MTs, perhaps by modulating ion channels.

Immune response and anti-microbial peptides expression in Malpighian tubules of Drosophila melanogaster is under developmental regulation.

Malpighian tubules (MT) of Drosophila melanogaster are osmoregulatory organs that maintain the ionic balance and remove toxic substances from the body. Additionally they act as autonomous immune sensing organs, which secrete antimicrobial peptides in response to invading microbial pathogens. We show that the antimicrobial peptides (AMP) diptericin, cecropinA, drosocin and attacinA are constitutively expressed and are regulated in developmental stage specific manner. Their developmental expression begins from 3(rd) instar larval stage and an immune challenge increases the expression several folds. Spatial variations in the level of expression along the MT tissue are observed. The mortality of 3(rd) instar larvae fed on bacterial food is much less than that of the earlier larval stages, coinciding with the onset of innate immunity response in MT. Ectopic expression of AMP imparts better resistance to infection while, loss of function of one of the AMP through directed RNAi reduces host survival after immune challenge. The AMP secreted from the MT exhibit bactericidal activity. Expression of the NF-κB transcription factor, Relish, also coincides with activation of immune responsive genes in MT, demonstrating that immune regulation in MT is under developmental control and is governed by the Imd pathway.

Synthesis and evaluation of indole-based new scaffolds for antimicrobial activities--identification of promising candidates.

Search for new antimicrobial agents led to the synthesis of series of N-1, C-3 and C-5 substituted bis-indoles. Their evaluation for antifungal and antibacterial activities resulted in the optimization of pyrrolidine/morpholine/N-benzyl moiety at the C-3 end and propane/butane/xylidine groups as linkers between two indoles for significant inhibition of microbial growth. Preliminary investigations have identified three highly potent antimicrobial agents. Dockings of these molecules in the active sites of lanosterol demethylase, dihydrofolate reductase and topoisomerase II indicate their strong interactions with these enzymes.

Research productivity among recipients of AAFP foundation grants.

PURPOSE: This study examines research productivity generated by the American Academy of Family Physicians (AAFP) Foundation and the AAFP Joint Grant Awards Program (JGAP) based upon projects funded during the period 1990 through 2000. METHODS: A structured questionnaire was mailed to all JGAP applicants who were funded between 1990 and 2000 (N = 95). The cross-sectional questionnaire included items reflective of research productivity: (1) numbers of publications, (2) numbers of presentations, and (3) numbers and types of subsequent grants. An additional comparison examined publication productivity among a subset of funded (n = 17) and nonfunded applicants (n = 36). RESULTS: The 69 funded respondents reported 91 publications and 129 presentations deriving from JGAP-supported research; 26 subsequent grants were funded ($9.6 million total costs). Funded and nonfunded applicants showed a significant increase in the overall number of publications during the 5-year period after their application when compared with the 5-year period before their application. Funded applicants had a greater number of publications during both the 5 years before and the 5 years after their JGAP grant submission. CONCLUSION: Projects supported by the JGAP have generated a considerable body of publications and presentations, as well as subsequent grant activity. This program appears to be important in supporting the early career development of family medicine researchers.

Mortality experiences among 15+ year survivors of childhood and adolescent cancers.

BACKGROUND: Studies of childhood and adolescent cancer survivorship have tended to focus on limited survival intervals (e.g., 5 and 10 years). Our report evaluates gender-specific overall mortality, as well as mortality by age group, and by cause, among 15+ year survivors of cancer diagnosed during childhood or adolescence. PROCEDURE: This was a retrospective cohort study of 565 15+ year childhood cancer survivors from Roswell Park Cancer Institute's Long-Term Follow-Up Project. Sex- and age-specific person-years at risk were accumulated and applied to age-specific mortality rates for New York State, excluding New York City. Standardized mortality ratios (SMRs), and 95% confidence intervals, were calculated and compared to mortality risks of the general population. RESULTS: Second malignancy was the leading cause of death among male and female survivors (15/38 deaths, 39%). Excess overall mortality was noted among both males (SMR = 284) and females (SMR = 371). Significant mortality excesses were seen in both genders for deaths due to primary malignant neoplasms and secondary malignancies, as well as cardiac deaths among males. Excess mortality was noted across most age strata. In the scenario of no cancer relapse, overall mortality in both genders did not differ significantly from the general population. CONCLUSIONS: Long-term survivors of childhood and adolescent cancers continue to demonstrate significant excess mortality. However, overall mortality among 15+ year survivors without a relapse appears to be comparable to the general population. The leading cause of death among 15+ year survivors is second malignancy in this study, which represents a novel and important finding in terms of long-term follow-up.