Edoardo Stellini

Silver nanoparticles in alveolar bone surgery devices

Silver (Ag) ions have well-known antimicrobial properties and have been applied as nanostrategies in many medical and surgical fields, including dentistry. The use of silver nanoparticles (Ag NPs) may be an option for reducing bacterial adhesion to dental implant surfaces and preventing biofilm formation, containing the risk of peri-implant infections. Modifying the structure or surface of bone grafts and membranes with Ag NPs may also prevent the risk of contamination and infection that are common when alveolar bone augmentation techniques are used. On the other hand, Ag NPs have revealed some toxic effects on cells in vitro and in vivo in animal studies. In this setting, the aim of the present paper is to summarize the principle behind Ag NP-based devices and their clinical applications in alveolar bone and dental implant surgery.

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.

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.

Magnesium-enriched hydroxyapatite at immediate implants: a histomorphometric study in dogs

AIM To evaluate the influence of magnesium-enriched hydroxyapatite (MHA) (SintLife(®)) on bone contour preservation and osseointegration at implants placed immediately into extraction sockets. MATERIAL AND METHODS In the mandibular pre-molar region, implants were installed immediately into extraction sockets of six Labrador dogs. MHA was placed at test sites, while the control sites did not receive augmentation materials. Implants were intended to heal in a submerged mode. After 4 months of healing, the animals were sacrificed, and ground sections were obtained for histomorphometric evaluation. RESULTS After 4 months of healing, one control implant was not integrated leaving n=5 test and control implants for evaluation. Both at the test and the control sites, bone resorption occurred. While the most coronal bone-to-implant contact was similar between test and control sites, the alveolar bony crest outline was maintained to a higher degree at the buccal aspect of the test sites (loss: 0.7 mm) compared with the control sites (loss: 1.2 mm), even though this difference did not reach statistical significance. CONCLUSIONS The use of MHA to fill the defect around implants placed into the alveolus immediately after tooth extraction did not contribute significantly to the maintenance of the contours of the buccal alveolar bone crest.

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.

The precision of fit of cast and milled full-arch implant-supported restorations.

PURPOSE The purpose of this study was to investigate the marginal precision of computer numeric control-milled frameworks fabricated of grade 4 commercially pure titanium or cobalt-chrome alloy through digital technology and to compare them with conventional cast frameworks. MATERIAL AND METHODS A titanium cast of a mandibular arch with six implant analogs was used as a master. The master cast was measured with a coordinate measuring machine. Fifteen rigid anatomic frameworks were created on the master cast in cast gold alloy and milled in titanium or cobalt-chrome material. The fifteen anatomic frameworks were measured in the same manner as the master cast. While the milled frameworks were measured once, at the end of the milling process, the cast anatomic frameworks were measured twice: immediately after the casting and divesting procedures and again after a technical adaptation procedure. Each anatomic framework was weighed. To compare the measurements obtained from each group of frameworks, descriptive statistics were calculated and one-way analysis of variance was performed, with values considered statistically significant at P < .05. RESULTS The mean weight of the cast frameworks was 33.41 g, the cobalt-chrome frameworks weighed 18.12 g on average, and the titanium frameworks averaged 8.7 g. The mean values for three-dimensional deviation of the center point position for each group of frameworks were 261 μm (cast frameworks before adaptation), 49 μm (cast frameworks after adaptation), 26 μm (milled frameworks in cobalt-chrome), and 26 μm (milled frameworks in titanium). CONCLUSIONS Within the limitations of this in vitro study, absolute passive fit cannot be achieved, regardless of material and fabrication technique. Anatomic milled frameworks fabricated in titanium or cobalt-chrome presented reduced center point deviation compared to cast frameworks. Titanium frameworks weighed less than cobalt-chrome and cast gold alloy frameworks.

Coronally Advanced Flap Combined With a Subepithelial Connective Tissue Graft Using Full- or Partial-Thickness Flap Reflection

BACKGROUND Although the use of a subepithelial connective tissue graft (SCTG) in conjunction with a coronally advanced flap (CAF) is a widely performed periodontal procedure, the creation of a partial-thickness flap can incur a risk of perforation or overthinning of the flap itself. Therefore, the aim of the present trial is to compare the efficacies of partial- and full-thickness flap reflections combined with an SCTG. METHODS Twenty patients with Miller Class I or II defects (52 teeth) were selected, and teeth with defects were randomly assigned to the test group (25 teeth) for a CAF and SCTG using a full-thickness flap reflection or to the control group (27 teeth) for a CAF associated with an SCTG and partial-thickness flap reflection. The probing depth (PD), gingival recession (GR), and width of the keratinized tissue (KT) were assessed at baseline and 6 months after surgery. RESULTS The mean root coverage was 97% in the test group (mean reduction in GR: 2.27 ± 1.15 mm) and 95% in the control group (mean reduction in GR: 1.68 ± 0.74 mm). The gain in KT was 0.46 ± 1.47 mm in the test group and 0.49 ± 1.3 mm in the control group, the PD ranged from 1.33 to 1.55 mm in the test group and from 1.31 to 1.64 mm in the control group; no statistically significant difference was found between the two groups for all of these parameters (P >0.05). CONCLUSIONS The elevation of a full- or partial-thickness flap did not appear to influence the amount of KT or the percentage of root coverage achieved post-surgically. More expanded studies are needed to confirm the present findings.

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.

In vitro comparison of the flexibility of different splint systems used in dental traumatology.

AIM The aim of the study was to evaluate the flexibility of five different splint systems [polyethylene fibre-reinforced splint (Ribbond THM, Ribbond Inc., Seattle, WA, USA), resin splint (RS), wire-composite splint (WCS), button-bracket splint (BS) and titanium trauma splint (TTS)] commonly used in clinical practice for the treatment of dental traumatic injuries involving the periodontal supporting tissues. MATERIALS AND METHODS For the experimental study, a resin cast of the upper arch was manufactured, where teeth 11, 12 and 21 (used for the stress analysis) were inserted in a non-rigid fashion so as to allow for replacement, whereas the other teeth were permanently fixed to the corresponding sockets. Two different test sessions were performed for each splint: (i) stress analysis with increasing intensity ranging between 0 and 50 N directed along the tooths longitudinal axis; (ii) stress analysis with 45 degrees of oblique force of increasing intensity ranging between 0 and 30 N. For each loading direction, five recordings were conducted without a splint, followed by five with the splint applied. The energy required to modify the position of the teeth was calculated for both the splinted and un-splinted teeth and the difference between the two values was determined. Energy variation was assessed for the testing of both axial (DeltaE(a)) and oblique force (DeltaE(o)). DeltaE represents the rigidity index of the analysed contention devices: high DeltaE values correspond to high rigidity materials. RESULTS The RS showed the highest DeltaE value for the axial stress analysis, whereas the highest DeltaE value at a 45 degrees was recorded for the WCS and RS. For both tests, the lowest DeltaE values were recorded for the TTS and Ribbond THM splints. CONCLUSIONS The data show that the contention devices with the highest flexibility are the TTS and the Ribbond THM as they exhibit a lower energy variation needed for splint deformation compared with the other materials that were examined.