Biomechanical aspects in dental replacements

This chapter deals with biomechanical aspects in dental replacements. The state of the art is critically reviewed taking into account the body of the literature results. The initial section is devoted to the mechanical properties of bone and to a description of the jaw geometry and of its loading and constraining. The following section presents a classifi cation of the various tooth replacement confi gurations and of the various materials adopted, where single and multiple replacements are considered. A specifi c section is devoted to the solid modelling of the jaw as input to numerical analyses, where the aid offered by reverse engineering and tomography is underlined. The fi nite element method as well as alternative numerical and experimental approaches are reviewed in a dedicated section. The stress analysis forecasts and measurements are biomechanically interpreted in the light of the current literature results. The chapter ends with a section devoted to biological aspects

Neural crest derived niche of human dental pulp stem cells promotes peripheral nerve regeneration and remyelination in animal model of critical sized sciatic nerve injury

ABSTRACT Peripheral nerve injuries are a commonly encountered clinical problem and often result in long-term functional defects. The use of stem cells, easily accessible, capable of rapid expansion in culture as well as fully integrate into the host tissue and capable to differentiate in myelinating cells of the peripheral nervous system, represent an attractive therapeutic approach for the treatment of nerve injuries. Farther, stem cells sources sharing the same embryological origin of Schwann cells, might be considered a suitable tool. The aim of this study was to demonstrate the ability of a neuroectodermal sub-population of STRO-1+/c-Kit+/CD34+ hDPSCs (1, 2), most of which being positive for neural crest (P75NTR) and neural progenitor cells (nestin) markers, to differentiate into Schwann cells-like cells in vitro and to promote axonal regeneration in vivo. As a matter of fact, following culture in appropriate induction medium, STRO-1+/c-Kit+/CD34+ hDPSCs were able to commit towards Schwann cells express- ing P75NTR, GFAP and S100b. After transplantation in animal model of sciatic nerve defect, hDPSCs promoted axonal regeneration from proximal to distal stumps, providing guidance to newly formed myelinated nerve fibers, which led to functional recovery as measured by sustained gait improvement. Particularly, transplanted hDP- SCs engrafted into critical sized sciatic nerve defect, as revealed by the positive stain- ing against human nuclei, showed the expression of typical Schwann cells markers, S100b and GFAP. In conclusion this study demonstrates that STRO-1+/c-Kit+/CD34+ hDPSCs, associated to neural crest derivation, represent a promising source of stem cells for the treatment of demyelinating disorders and might provide a valid alternative tool for future clinical applications to achieve functional recovery after injury or peripheral neuropathies besides minimizing ethical issues

Human dental pulp stem cells produce mineralized matrix in 2D and 3D cultures

The aim of this study was to characterize the in vitro osteogenic differentiation of dental pulp stem cells (DPSCs) in 2D cultures and 3D biomaterials. DPSCs, separated from dental pulp by enzymatic digestion, and isolated by magnetic cell sorting were differentiated toward osteogenic lineage on 2D surface by using an osteogenic medium. During differentiation process, DPSCs express specific bone proteins like Runx-2, Osx, OPN and OCN with a sequential expression, analogous to those occurring during osteoblast differentiation, and produce extracellular calcium deposits. In order to differentiate cells in a 3D space that mimes the physiological environment, DPSCs were cultured in two distinct bioscaffolds, Matrigel™ and Collagen sponge. With the addition of a third dimension, osteogenic differentiation and mineralized extracellular matrix production significantly improved. In particular, in Matrigel™ DPSCs differentiated with osteoblast/osteocyte characteristics and connected by gap junction, and therefore formed calcified nodules with a 3D intercellular network. Furthermore, DPSCs differentiated in collagen sponge actively secrete human type I collagen micro-fibrils and form calcified matrix containing trabecular-like structures. These neo-formed DPSCs-scaffold devices may be used in regenerative surgical applications in order to resolve pathologies and traumas characterized by critical size bone defects

Human dental pulp stem cells (hDPSCs): isolation, enrichment and comparative differentiation of two sub-populations

Human dental pulp represents a suitable alternative source of stem cells for the purpose of cell-based therapies in regenerative medicine, because it is relatively easy to obtain it, using low invasive procedures. This study characterized and compared two subpopulations of adult stem cells derived from human dental pulp (hDPSCs). Human DPSCs, formerly immune-selected for STRO-1 and c-Kit, were separated for negativity and positivity to CD34 expression respectively, and evaluated for cell proliferation, stemness maintenance, cell senescence and multipotency

Impact of COVID-19 pandemic on retention in care of native and migrant people with HIV in the ICONA cohort

Background: COVID-19 pandemic challenged the UNAIDS 90-90-90 targets. How the COVID-19 pandemic affected HIV retention in care and whether it has disproportionally affected migrant people with HIV (PWH) remained to be investigated. Methods: PWH in ICONA Cohort in follow-up in each of the study periods were included: 01/09/2019-29/02/2020 (pandemic period) and 01/03/2018-31/08/2018 (historical period, as a control). Risk of temporary loss to follow-up (LTFU, defined as no data recorded for a person for one year) was analyzed by logistic regression, with migrant status as the main exposure variable. Difference in difference (DID) analysis was applied to evaluate the effect of COVID-19 pandemic in the different risk of LTFU between natives and migrants. Results: 8864 (17.1% migrants) and 8071 (16.8% migrants) PWH constituted the pandemic and the historical period population, respectively. Proportion of PWH defined as LTFU in the pandemic period was 10.5% in native and 19.6% in migrant PWH. After controlling for age, sex and geographical location of enrolling site, risk of temporary LTFU was higher for migrants than native PWH [adjusted odds ratio 1.85 (95%CI 1.54-2.22)] in pandemic period. In PWH contributing to both periods, LTFU was 9.0% (95% CI 8.3-9.8) in natives vs 17.0% (95% CI 14.7-19.4) in migrants during the pandemic. Instead, LTFU was 1.2% (95%CI 0.9, 1.5) in natives vs 2.2% (95% CI 1.3-3.1) in migrants during the historical period, with a resulting DID of 7.0% (95% CI 4.4-9.6). Conclusions: A greater proportion of LTFU in migrant PWH was observed in both periods, which remained unaltered over time. Interventions to reduce LTFU of migrants are necessary

Stem cells isolated from human dental pulp and amniotic fluid improve skeletal muscle histopathology in mdx/SCID mice

Introduction: Duchenne muscular dystrophy (DMD), caused by a lack of the functional structural protein dystrophin, leads to severe muscle degeneration where the patients are typically wheelchair-bound and die in their mid-twenties from cardiac or respiratory failure or both. The aim of this study was to investigate the potential of human dental pulp stem cells (hDPSCs) and human amniotic fluid stem cells (hAFSCs) to differentiate toward a skeletal myogenic lineage using several different protocols in order to determine the optimal conditions for achieving myogenic commitment and to subsequently evaluate their contribution in the improvement of the pathological features associated with dystrophic skeletal muscle when intramuscularly injected into mdx/SCID mice, an immune-compromised animal model of DMD. Methods: Human DPSCs and AFSCs were differentiated toward myogenic lineage in vitro through the direct co-culture with a myogenic cell line (C2C12 cells) and through a preliminary demethylation treatment with 5-Aza-2\u2032-deoxycytidine (5-Aza), respectively. The commitment and differentiation of both hDPSCs and hAFSCs were evaluated by immunofluorescence and Western blot analysis. Subsequently, hDPSCs and hAFSCs, preliminarily demethylated and pre-differentiated toward a myogenic lineage for 2 weeks, were injected into the dystrophic gastrocnemius muscles of mdx/SCID mice. After 1, 2, and 4 weeks, the gastrocnemius muscles were taken for immunofluorescence and histological analyses. Results: Both populations of cells engrafted within the host muscle of mdx/SCID mice and through a paracrine effect promoted angiogenesis and reduced fibrosis, which eventually led to an improvement of the histopathology of the dystrophic muscle. Conclusion: This study shows that hAFSCs and hDPSCs represent potential sources of stem cells for translational strategies to improve the histopathology and potentially alleviate the muscle weakness in patients with DMD

Impact of COVID-19 pandemic on retention in care of native and migrant people with HIV in the ICONA cohort

BACKGROUND: COVID-19 pandemic challenged the UNAIDS 90-90-90 targets. How the COVID-19 pandemic affected HIV retention in care and whether it has disproportionally affected migrant people with HIV (PWH) remained to be investigated. METHODS: PWH in ICONA Cohort in follow-up in each of the study periods were included: 01/09/2019-29/02/2020 (pandemic period) and 01/03/2018-31/08/2018 (historical period, as a control). Risk of temporary loss to follow-up (LTFU, defined as no data recorded for a person for one year) was analyzed by logistic regression, with migrant status as the main exposure variable. Difference in difference (DID) analysis was applied to evaluate the effect of COVID-19 pandemic in the different risk of LTFU between natives and migrants. RESULTS: 8864 (17.1% migrants) and 8071 (16.8% migrants) PWH constituted the pandemic and the historical period population, respectively. Proportion of PWH defined as LTFU in the pandemic period was 10.5% in native and 19.6% in migrant PWH. After controlling for age, sex and geographical location of enrolling site, risk of temporary LTFU was higher for migrants than native PWH [adjusted odds ratio 1.85 (95%CI 1.54-2.22)] in pandemic period. In PWH contributing to both periods, LTFU was 9.0% (95% CI 8.3-9.8) in natives vs 17.0% (95% CI 14.7-19.4) in migrants during the pandemic. Instead, LTFU was 1.2% (95%CI 0.9, 1.5) in natives vs 2.2% (95% CI 1.3-3.1) in migrants during the historical period, with a resulting DID of 7.0% (95% CI 4.4-9.6). CONCLUSIONS: A greater proportion of LTFU in migrant PWH was observed in both periods, which remained unaltered over time. Interventions to reduce LTFU of migrants are necessary

Solution behavior, circular dichroism and 220 MHz PMR studies of the bovine myelin basic protein

Bovine myelin basic protein has been investigated with regard to its solution behavior, circular dichroism and 220 MHz PMR spectral properties.At pH 4.8 [gamma]/2 = 0.1 acetate buffer, light scattering yielded a Mr of 17 700 and a virial coefficient of 1.0[middle dot]10-4 mol[middle dot]ml/g2. Above pH 7.0 the protein was found to aggregate to higher mol. wt species.Sedimentation experiments at pH 4.8 yielded s[deg]20,w of 1.27 S at [gamma]/2 = 0.1 and 1.46 S at [gamma]/2 = 0.35. The diffusion coefficient determined from ultracentrifugal experiments was 7.25[middle dot]10-7 cm2/s at [gamma]/2 = 0.1 and 0.35. The value of [function of (italic small f)]/[function of (italic small f)]0 from diffusion at pH 4.8 and [gamma]/2 = 0.35 was 1.64, corresponding to an axial ratio of 11 to 1. The radius of gyration was calculated as 4.28 nm and the root mean square end to end distance was 10.5 nm. At pH 9.0, [gamma]/2 = 0.1, s[deg]20,w was 1.71 S and D[deg]20,w was estimated at 7.4[middle dot]10-7 cm2/s. The behavior at pH 9.0 reverted to the behavior at pH 4.8 when the pH was readjusted. The E1cm1% = 5.64 at 276.4 nm and 225 at 196 nm.Titration of the protein with trifluoroethanol elicited three distinct regions of conformational stability having increasing helical content as the mol fraction of trifluoroethanol increased.The results of the present study have permitted some comparison of analogous properties and conformational behavior with the basic membrane protein cytochrome c.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/21990/1/0000400.pd

High Risk of Secondary Infections Following Thrombotic Complications in Patients With COVID-19

Background. This study’s primary aim was to evaluate the impact of thrombotic complications on the development of secondary infections. The secondary aim was to compare the etiology of secondary infections in patients with and without thrombotic complications. Methods. This was a cohort study (NCT04318366) of coronavirus disease 2019 (COVID-19) patients hospitalized at IRCCS San Raffaele Hospital between February 25 and June 30, 2020. Incidence rates (IRs) were calculated by univariable Poisson regression as the number of cases per 1000 person-days of follow-up (PDFU) with 95% confidence intervals. The cumulative incidence functions of secondary infections according to thrombotic complications were compared with Gray’s method accounting for competing risk of death. A multivariable Fine-Gray model was applied to assess factors associated with risk of secondary infections. Results. Overall, 109/904 patients had 176 secondary infections (IR, 10.0; 95% CI, 8.8–11.5; per 1000-PDFU). The IRs of secondary infections among patients with or without thrombotic complications were 15.0 (95% CI, 10.7–21.0) and 9.3 (95% CI, 7.9–11.0) per 1000-PDFU, respectively (P = .017). At multivariable analysis, thrombotic complications were associated with the development of secondary infections (subdistribution hazard ratio, 1.788; 95% CI, 1.018–3.140; P = .043). The etiology of secondary infections was similar in patients with and without thrombotic complications. Conclusions. In patients with COVID-19, thrombotic complications were associated with a high risk of secondary infections