Stefano Sivolella

Powder-based 3D printing for bone tissue engineering

Bone tissue engineered 3-D constructs customized to patient-specific needs are emerging as attractive biomimetic scaffolds to enhance bone cell and tissue growth and differentiation. The article outlines the features of the most common additive manufacturing technologies (3D printing, stereolithography, fused deposition modeling, and selective laser sintering) used to fabricate bone tissue engineering scaffolds. It concentrates, in particular, on the current state of knowledge concerning powder-based 3D printing, including a description of the properties of powders and binder solutions, the critical phases of scaffold manufacturing, and its applications in bone tissue engineering. Clinical aspects and future applications are also discussed.

Toward the Validation of Visual Analogue Scale for Anxiety

Anxiety is a relevant problem in dental practice. The Visual Analogue Scale for Anxiety (VAS-A), introduced in dentistry in 1988, has not yet been validated in large series. The aim of this study is to check VAS-A effectiveness in more than 1000 patients submitted to implantology. The VAS-A and the Dental Anxiety Scale (DAS) were administered preoperatively to 1114 patients (459 males and 655 females, age 54.7 ± 13.1 years). Statistical analysis was conducted with Pearson correlation coefficient, the receiver operating characteristic (ROC) curve, and McNemar tests. A close correlation between DAS and VAS-A was found (r  =  0.57, P < .0001); the VAS-A thresholds of dental anxiety and phobia were 5.1 and 7.0 cm, respectively. Despite a significant concordance of tests in 800 cases (72%), disagreement was found in the remaining 314 cases (28%), and low DAS was associated with high VAS-A (230 cases) or vice versa (84 cases). Our study confirms that VAS-A is a simple, sensitive, fast, and reliable tool in dental anxiety assessment. The rate of disagreement between VAS-A and DAS is probably due to different test sensitivities to different components of dental anxiety. VAS-A can be used effectively in the assessment of dental patients, using the values of 5.1 cm and 7.0 cm as cutoff values for anxiety and phobia, respectively.

Nanostructured Surfaces of Dental Implants

The structural and functional fusion of the surface of the dental implant with the surrounding bone (osseointegration) is crucial for the short and long term outcome of the device. In recent years, the enhancement of bone formation at the bone-implant interface has been achieved through the modulation of osteoblasts adhesion and spreading, induced by structural modifications of the implant surface, particularly at the nanoscale level. In this context, traditional chemical and physical processes find new applications to achieve the best dental implant technology. This review provides an overview of the most common manufacture techniques and the related cells-surface interactions and modulation. A Medline and a hand search were conducted to identify studies concerning nanostructuration of implant surface and their related biological interaction. In this paper, we stressed the importance of the modifications on dental implant surfaces at the nanometric level. Nowadays, there is still little evidence of the long-term benefits of nanofeatures, as the promising results achieved in vitro and in animals have still to be confirmed in humans. However, the increasing interest in nanotechnology is undoubted and more research is going to be published in the coming years.

Adipose Tissue Regeneration: A State of the Art

Adipose tissue pathologies and defects have always represented a reconstructive challenge for plastic surgeons. In more recent years, several allogenic and alloplastic materials have been developed and used as fillers for soft tissue defects. However, their clinical use has been limited by further documented complications, such as foreign-body reactions potentially affecting function, degradation over time, and the risk for immunogenicity. Tissue-engineering strategies are thus being investigated to develop methods for generating adipose tissue. This paper will discuss the current state of the art in adipose tissue engineering techniques, exploring the biomaterials used, stem cells application, culture strategies, and current regulatory framework that are in use are here described and discussed.

Donor Age-Related Biological Properties of Human Dental Pulp Stem Cells Change in Nanostructured Scaffolds

The aim of the present work is to study how biological properties, such as proliferation and commitment ability, of human adult dental pulp stem cells (DPSCs) relate to the age of the donor. Human dental pulps were extracted from molars of healthy adult subjects aged 16 to >66 years. DPSCs were isolated and cultured in the presence of osteogenic, neurogenic, or vasculogenic differentiation medium. Proliferation ability was evaluated by determining doubling time, and commitment ability was evaluated by gene expression and morphological analyses for tissue-specific markers. The results confirm a well-defined proliferative ability for each donor age group at an early in vitro passage (p2). DPSCs from younger donors (up to 35 years) maintain this ability in long-term cultures (p8). Stem cells of all age donor groups maintain their commitment ability during in vitro culture. In vivo tests on the critical size defect repair process confirmed that DPSCs of all donor ages are a potent tool for bone tissue regeneration when mixed with 3D nanostructured scaffolds.

In Vitro Concurrent Endothelial and Osteogenic Commitment of Adipose-Derived Stem Cells and Their Genomical Analyses Through Comparative Genomic Hybridization Array: Novel Strategies to Increase the Successful Engraftment of Tissue-Engineered Bone Grafts

In the field of tissue engineering, adult stem cells are increasingly recognized as an important tool for in vitro reconstructed tissue-engineered grafts. In the world of cell therapies, undoubtedly, mesenchymal stem cells from bone marrow or adipose tissue are the most promising progenitors for tissue engineering applications. In this setting, adipose-derived stem cells (ASCs) are generally similar to those derived from bone marrow and are most conveniently extracted from tissue removed by elective cosmetic liposuction procedures; they also show a great potential for endothelization. The aim of the present work was to investigate how the cocommitment into a vascular and bone phenotype of ASCs could be a useful tool for improving the in vitro and in vivo reconstruction of a vascularized bone graft. Human ASCs obtained from abdominoplasty procedures were loaded in a hydroxyapatite clinical-grade scaffold, codifferentiated, and tested for proliferation, cell distribution, and osteogenic and vasculogenic gene expression. The chromosomal stability of the cultures was investigated using the comparative genomic hybridization array for 3D cultures. ASC adhesion, distribution, proliferation, and gene expression not only demonstrated a full osteogenic and vasculogenic commitment in vitro and in vivo, but also showed that endothelization strongly improves their osteogenic commitment. In the end, genetic analyses confirmed that no genomical alteration in long-term in vitro culture of ASCs in 3D scaffolds occurs.

Nanotechnology to drive stem cell commitment

Stem cells (SCs) are undifferentiated cells responsible for the growth, homeostasis and repair of many tissues. The maintenance and survival of SCs is strongly influenced by several stimuli from the local microenvironment. The majority of signaling molecules interact with SCs at the nanoscale level. Therefore, scaffolds with surface nanostructures have potential applications for SCs and in the field of regenerative medicine. Although some strategies have already reached the field of cell biology, strategies based on modification at nanoscale level are new players in the fields of SCs and tissue regeneration. The introduction of the possibility to perform such modifications to these fields is probably due to increasing improvements in nanomaterials for biomedical applications, as well as new insights into SC biology. The aim of the present review is to exhibit the most recent applications of nanostructured materials that drive the commitment of adult SCs for potential clinical applications.

Implant‐supported mandibular overdentures: a cross‐sectional study

OBJECTIVE The aim of this cross-sectional study was to determine the clinical outcome and patient satisfaction in subjects treated with mandibular overdentures supported by two implants. MATERIAL AND METHODS One hundred and fifty-nine patients, who received restorative therapy in the edentulous mandible consisting of a bar-retained overdenture supported by two osseointegrated implants in a private clinic in Italy, were recalled for a clinical and radiographic examination. One hundred and forty-one subjects with 280 implants attended the examination. The average follow-up time was 3.9 years. The radiographic examination included assessments of the distance between the implant margin and the most coronal position of bone-to-implant contact at the mesial and distal aspects of each implant. A questionnaire regarding comfort, satisfaction with the treatment, aesthetics, speaking capacity and efficiency in chewing was obtained from each subject. Biological and technical complications were recorded and the number of visits due to complications between the delivery of the prostheses and the re-examination was determined. RESULTS The results from the examination revealed that the number of lost implants was small and the average marginal bone level around the implants was 0.67 mm apical of the implant margin. The most frequently observed complication was hyperplasia of the mucosal tissue under the bar construction. Few patients experienced loosening of retention. The vast majority of patients reported to be satisfied in relation to the restorative therapy from both functional and aesthetic points of view. CONCLUSION Patients with edentulous mandibles may be successfully rehabilitated by means of two implants supporting a bar-retained overdenture.

Extraoral endodontic treatment, odontotomy and intentional replantation of a double maxillary lateral permanent incisor: case report and 6‐year follow‐up

AIM To describe combined endodontic, surgical and orthodontic treatment of a maxillary lateral incisor fused with a supernumerary. SUMMARY Double tooth is a dental irregularity consequent to fusion of two or more teeth or dental gemination. The teeth most commonly involved are deciduous, but in 0.1% of cases permanent teeth are affected, in which case aesthetic, functional and periodontal problems can result. This paper reports a clinical case of a double tooth in the position of the maxillary right lateral permanent incisor. Combined orthodontic, endodontic and surgical treatment (intentional replantation) allowed the tooth to be retained without periodontal compromise and with a positive orthodontic result both immediately and 6 years following intervention. *A conservative approach that addresses periodontal, pulpal and tooth tissues, can result in the retention of a double tooth. *Maintenance of the root and alveolar bone in young adults at least until full skeletal maturation should be the main treatment objective.

Mechanisms underlying the attachment and spreading of human osteoblasts: from transient interactions to focal adhesions on vitronectin-grafted bioactive surfaces.

The features of implant devices and the reactions of bone-derived cells to foreign surfaces determine implant success during osseointegration. In an attempt to better understand the mechanisms underlying osteoblasts attachment and spreading, in this study adhesive peptides containing the fibronectin sequence motif for integrin binding (Arg-Gly-Asp, RGD) or mapping the human vitronectin protein (HVP) were grafted on glass and titanium surfaces with or without chemically induced controlled immobilization. As shown by total internal reflection fluorescence microscopy, human osteoblasts develop adhesion patches only on specifically immobilized peptides. Indeed, cells quickly develop focal adhesions on RGD-grafted surfaces, while HVP peptide promotes filopodia, structures involved in cellular spreading. As indicated by immunocytochemistry and quantitative polymerase chain reaction, focal adhesions kinase activation is delayed on HVP peptides with respect to RGD while an osteogenic phenotypic response appears within 24h on osteoblasts cultured on both peptides. Cellular pathways underlying osteoblasts attachment are, however, different. As demonstrated by adhesion blocking assays, integrins are mainly involved in osteoblast adhesion to RGD peptide, while HVP selects osteoblasts for attachment through proteoglycan-mediated interactions. Thus an interfacial layer of an endosseous device grafted with specifically immobilized HVP peptide not only selects the attachment and supports differentiation of osteoblasts but also promotes cellular migration.