Influence of soft tissue thickness on marginal bone level around dental implants: A systematic review with meta-analysis and trial-sequential analysis.

OBJECTIVES: The aim of the present review and meta-analysis was to evaluate the influence of soft tissue thickness on initial bone remodeling after implant installation. MATERIALS AND METHODS: A literature search was conducted by two independent reviewers on electronic databases up to May 2022. Randomized controlled trials (RCTs) and controlled clinical trials (CCTs) performed on human subjects were included. The risk of bias was evaluated using Cochrane Collaboration's tool. Meta-analysis and Trial Sequential Analysis (TSA) were performed on the selected articles. The primary outcome was marginal bone loss. RESULTS: After screening, 6 studies were included in the final analysis, with a total of 354 implants, and a follow-up from 10 to 14 months. 194 implants were placed in a ≥ 2 mm soft tissue thickness, while 160 had <2 mm soft tissue thickness before implant placement. The included studies had a high level of heterogeneity (I2  > 50%). The meta-analysis indicated a statistically significant difference between the two groups (0.54; p = .027) and the TSA analysis confirmed the results, despite the limited number of dental implants. Additional analysis showed that age and follow-up parameters were not statistically significant factors influencing the bone loss (p = .22 and p = .16, respectively). CONCLUSIONS: Based on the available RCTS and CCTs, initial soft tissue thickness seems to influence marginal bone loss after a short follow-up period. Based on TSA analysis, further studies are needed to assess the influence of the soft tissue thickness on marginal bone loss. PROSPERO registration number: CRD42021235324.

Reproducibility of Buccal Gingival Profile Using a Custom Pick-Up Impression Technique: A 2-Year Prospective Multicenter Study.

PURPOSE: The aim of this study was to transfer the provisional restoration emergence profile to the final implant-supported restoration and to buccal gingival margin (BGM) stability after 2 years of function. MATERIALS AND METHODS: A total of 33 patients were recruited for treatment of single gaps by means of 33 implant-supported restorations. Fixed provisional crowns were screwed to the fixture and adjusted until the complete peri-implant soft tissue maturation was achieved. After 12 weeks, a second fixture impression was taken by means of a pick-up customization technique in order to transfer the clinical aspect of the peri-implant soft tissues to the master cast. A definitive restoration was delivered. A standardized method from digital photographs was used to assess the gingival margin modification (BGM) from the provisional (P) to the definitive prosthesis installation at baseline (D0), and after 1 (D1) and 2 years (D2) of function. Also, marginal bone loss (MBL) was calculated after 1 (D1) and 2 years (D2) of definitive restoration function. RESULTS: The BGM index at the time of the final restoration installation (D0) was 0.12 ± 0.33 mm if compared with the BGM position of the provisional restoration (P); it was of 0.12 ± 0.46 mm after 1-year of follow-up (D1) and of 0.31 ± 0.21 after 2 years of function (D2). No significant difference was calculated between measurements in different follow-up visits (p > 0.05). No significant MBL was measured between the baseline (D0) and the 1-year follow-up (p = 0.816) with a mean MBL value of 0.2 ± 0.1 mm. Similar result was calculated after 2 years (p = 0.684) with a mean MBL value of 0.3 ± 0.2. CONCLUSION: A modified impression pick-up may be helpful to reproduce the gingival margin position from the provisional to the definitive restoration. Moreover, the gingival zenith position during the follow-up period seemed to be stable. CLINICAL SIGNIFICANCE: The modification of the standard impression pick-up technique may contribute to reproducing a natural emergence profile of esthetic implant prosthetic restorations (from the provisional to the definitive restoration.) With this technique, implant soft tissues stability around CAD-CAM (computer aided design-computer aided manufacturing) abutments can be easily obtained, and the customized abutment shape may better support the scalloped peri-implant soft tissues architecture, especially in anterior areas.

Managing the peri-implant mucosa: a clinically reliable method for optimizing soft tissue contours and emergence profile.

STATE OF THE PROBLEM: The proper representation of soft tissue contours for a natural aspect of the peri-implant mucosa and its mimesis with the adjacent teeth is a crucial aspect of the esthetic area restoration. PURPOSE: This paper describes a method for the easy transfer of the peri-implant tissue morphology onto impression material with a view to achieving an accurate, custom implant restoration. The procedure described is suitable both for single and multi-unit implant-supported prostheses. CLINICAL PROCEDURES: Once the peri-implant mucosa is sculpted by the provisional restoration, the emergence profile is duplicated. The implant analog is embedded into laboratory stone or plaster in a mixing cup and allowed to set. The provisional restoration is removed from the oral cavity and screwed to the implant analog; then, a polyether material is placed in the mixing cup so that the provisional restoration is put into impression material at the level of the prosthetic emergence profile. After the polyether polymerizing, the provisional prosthesis is unscrewed and replaced with the stock hexed transfer for the final impression. Next, cold self-curing resin is poured into this gap and left to set. A custom transfer for this single implant site is thus obtained. This modified transfer is then removed and screwed onto the implant in the oral cavity for the definitive impression. CONCLUSIONS: The technique described enables a faithful reproduction of the peri-implant soft tissues and emergence profile. CLINICAL SIGNIFICANCE: An emergence profile that mimics the natural tooth should be obtained by successful esthetic implant restoration. Moreover, it allows proper hygiene, which is fundamental for implant maintenance. The best way to achieve the correct emergence profile is to sculpture the peri-implant mucosa by means of a provisional prosthesis. Prefabricated provisional crowns cannot mimic the complexity and the variations of human soft tissue. Therefore, only a chair-side modification of the provisional restoration can accomplish the optimal result. Such a requirement can be satisfied by the clinical method described in the present report.

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.

Selection of Collagen Membranes for Bone Regeneration: A Literature Review.

Several treatment modalities have been proposed to regenerate bone, including guided bone regeneration (GBR) where barrier membranes play an important role by isolating soft tissue and allowing bone to grow. Not all membranes biologically behave the same way, as they differ from their origin and structure, with reflections on their mechanical properties and on their clinical performance. Collagen membranes have been widely used in medicine and dentistry, because of their high biocompatibility and capability of promoting wound healing. Recently, collagen membranes have been applied in guided bone regeneration with comparable outcomes to non-resorbable membranes. Aim of this work is to provide a review on the main features, application, outcomes, and clinical employment of the different types of collagen membranes. Comparisons with non-resorbable membranes are clarified, characteristics of cross-linked collagen versus native collagen, use of different grafting materials and need for membrane fixation are explored in order to gain awareness of the indications and limits and to be able to choose the right membrane required by the clinical condition.

The Use of Antibiotics in Implant Therapy: A Systematic Review and Meta-Analysis with Trial Sequential Analysis on Early Implant Failure.

PURPOSE: The aim of this systematic review was to estimate if an antibiotic prophylaxis regimen reduces implant failure and postoperative infection in healthy patients who are going to receive dental implants. MATERIALS AND METHODS: An electronic database search (MEDLINE/PubMed, Scopus, Web of Science, Cochrane Library) until June 30, 2019, for randomized controlled trials (RCTs) was performed. The Cochrane Handbook for Systematic Reviews of Interventions to assess the risk of bias in individual studies was used. Patient- and implant-level data were extracted for the analyzed outcomes. The risk ratio (RR) and the 95% confidence interval were calculated as meta-analytic effects. A fixed- or a random-effect model was employed on the basis of the presence/absence of heterogeneity (I2 > 50%). Differences between groups were analyzed using the inverse of variance test. The Higgins Index and chi-square test were used to assess the studies' heterogeneity. Additionally, in order to evaluate the power of evidence and to adjust the meta-analytic findings for type 1 and 2 errors, a trial sequential analysis (TSA) was performed. RESULTS: Nine studies including 1,984 patients and 3,588 implants were selected. Eight hundred eighty-five patients (1,617 implants) received no antibiotics or a placebo therapy before the implant surgery; 1,971 implants (1,099 patients) were treated with an antibiotic therapy. The meta-analysis at the patient level showed a statistically significant reduction in the rate of early implant failure associated with the use of antibiotics (I2 = 0%) (RR = 0.32 [0.20, 0.51], P > .001). Similar results were obtained after pooling the implant-level data with the fixed-effect model (RR = 0.33 [0.22, 0.51], P > .001). Such results were also confirmed by the TSA after adjusting for type 1 and 2 errors. CONCLUSION: The results of this systematic review with meta-analysis indicate that an antibiotic prophylaxis prevents early implant failures in the case of healthy patients. No information can be provided on peri-implant infections.

Five-year prospective study on conometric retention for complete fixed prostheses.

PURPOSE: To evaluate the reliability of a conometric system for fixed retention of complete prostheses (CPs) on four implants after 5 years of function. MATERIALS AND METHODS: Twenty-five patients with a completely edentulous mandible received four implants supporting a CP. A total of 100 implants were immediately loaded with CPs on conometric abutments. A follow-up of 5 years was observed for each patient. Outcome measures were prosthesis and implant success, complications, probing pocket depth changes, marginal bleeding and plaque changes, and patient satisfaction. RESULTS: One patient dropped-out. In total, 96 implants supporting the 24 CPs completed the follow-up examination at 5 years. No implant failed. Two framework fractures occurred after 4 and 5 years of function. No loss of retention was recorded for the CPs. Mucositis was recorded for two implants after 1 year of prostheses function for two patients, for one implant after 3 years and for two implants after 4 years in different patients and successfully treated with interceptive supportive therapy. No significant differences were found between Plaque Index (PI) at baseline and after 2 years (P = 1.0); similar findings were calculated between PI at baseline and after 5 years (P = 0.6) of function. At baseline, after 2 and after 5 years, respectively, 69%, 64% and 56% of implants showed a PI of 0; 31%, 36% and 44% of implants showed a PI between 1 and 3. Modify Bleeding Index (MBI) was not significantly different both between baseline and after 2 years of function (P = 1.0) and between baseline and 5 years of function (P = 0.5). At baseline, after 2 and after 5 years, respectively, 69%, 65% and 61% of implants showed a MBI of 0; 27%, 28% and 29% of implants showed a MBI of 1; and 4%, 7% and 10% of implants showed a MBI of 2. The mean probing pocket depth was 1.2 ± 0.4 mm at baseline, 1.2 ± 0.4 mm after 2 years and 1.4 ± 0.5 mm after 5 years of function. The differences were not statistically significant between baseline and 2 years (P = 1.0) and between baseline and 5 years (P = 0.1). From the patient satisfaction questionnaire, 85% percent of patients were satisfied from both aesthetic and functional points of view after 5 years of conometric prostheses function. CONCLUSIONS: The present implant-supported conometric retention system can be used to give fixed retention to a CP supported by four implants. An adequate metal framework should be provided to the definitive restoration in order to avoid fractures in the long term.

Accuracy of 3D digital modeling of dental arches.

OBJECTIVE: The aim of the study was to verify and compare the accuracy of full-arch digital impressions obtained using two intraoral scanners and three scanning methodologies. METHODS: A resin model created with dental 3-D printing was scanned by a reference scanner (Zfx Evolution - Zimmer Biomet, Palm Beach Gardens, FL) in order to obtain a 3D reference; the same resin model was then scanned with two different intraoral scanners (Zfx IntraScan and Carestream 3600 - CS 3600®, Carestream, Rochester, NY, USA) using: Technique A (from tooth #27 up to tooth #17); Technique B (from tooth #11 up to tooth #17 and then from tooth #21 up to tooth #27) and Technique C (from tooth #22 up to tooth #17, and then from tooth #12 up to tooth #27 - the MeshLab software v. 1.3.3 was then used to match the two scans). The scans obtained were superimposed over the reference scan by means of a software, and the volumetric discrepancies were calculated. RESULTS: The mean results for the Zfx Intrascan scanner were: Technique A = 302.47 ± 37.42 µm; Technique B = 180.45 ± 29.86 µm; Technique C = 147.34 ± 28.23 µm. The mean results for the Carestream 3600 scanner were: Technique A = 303.59 ± 40.20 µm; Technique B = 181.53 ± 29.61 µm; Technique C = 142.28 ± 35.33 µm. Technique C, used by both scanners, produced less volumetric discrepancies compared to the other techniques. CONCLUSIONS: The scanning technique had a statistically significant effect on the quality of the scan (p< 0.0001), whereas the scanner did not present any significant influence (p= 0.91).

Effect on wound healing of a topical gel containing amino acid and sodium hyaluronate applied to the alveolar socket after mandibular third molar extraction: A double-blind randomized controlled trial.

OBJECTIVE: The study aimed to assess the effect of topical applications of an amino acid and sodium hyaluronate gel after mandibular third molar extraction. METHOD AND MATERIALS: 136 patients requiring mandibular third molar extraction were enrolled. An amino acid and sodium hyaluronate gel was applied to the sockets of patients in the test group immediately following the extraction. The sockets of controls were simply flushed with a sterile saline solution. Patients' outcomes and postoperative complications were assessed 7 and 14 days after surgery. The cumulative incidence of dehiscence and secondary outcome measures were analyzed using a chi-square test. RESULTS: Concerning the primary outcome, the incidence of dehiscence was 27.4% after 7 days in the treatment group and 36.4% in the controls (P = .28), and at 14 days it was 21.4% and 36.0%, respectively (P = .10). No statistically significant differences emerged in other variables (mouth opening range, appearance of soft tissue, presence of pus, pain on palpation of the alveolar socket, alveolitis, local lymphadenopathy, and adverse reactions). Pain perception was always lower in the treatment group during the first 7 days after surgery. CONCLUSION: Topical applications of an amino acid and sodium hyaluronate gel after mandibular third molar extraction made no statistically significant difference to the variables examined in the test and control groups. CLINICAL RELEVANCE: This trial focused on postoperative complications after surgical third molar extraction. The use of a gel containing amino acid and sodium hyaluronate was investigated for the management of postoperative pain, edema, alveolitis, wound dehiscence and swelling.

Graphene-Based Nanomaterials for Tissue Engineering in the Dental Field.

The world of dentistry is approaching graphene-based nanomaterials as substitutes for tissue engineering. Apart from its exceptional mechanical strength, electrical conductivity and thermal stability, graphene and its derivatives can be functionalized with several bioactive molecules. They can also be incorporated into different scaffolds used in regenerative dentistry, generating nanocomposites with improved characteristics. This review presents the state of the art of graphene-based nanomaterial applications in the dental field. We first discuss the interactions between cells and graphene, summarizing the available in vitro and in vivo studies concerning graphene biocompatibility and cytotoxicity. We then highlight the role of graphene-based nanomaterials in stem cell control, in terms of adhesion, proliferation and differentiation. Particular attention will be given to stem cells of dental origin, such as those isolated from dental pulp, periodontal ligament or dental follicle. The review then discusses the interactions between graphene-based nanomaterials with cells of the immune system; we also focus on the antibacterial activity of graphene nanomaterials. In the last section, we offer our perspectives on the various opportunities facing the use of graphene and its derivatives in associations with titanium dental implants, membranes for bone regeneration, resins, cements and adhesives as well as for tooth-whitening procedures.

Medication-Related Osteonecrosis of the Jaw and Dental Implants Failures: A Systematic Review.

No well-established evidence supporting safe use of bisphosphonates (BPs) or other antiresorptive agents prior, during, or after dentoalveolar surgery, are currently available; moreover, the real risk of osteonecrosis of the jaw (ONJ) development is still unknown. The aim of the present systematic review was to assess the scientific literature concerning the implants placement in antiresorptive agent users and the related risk of implants failure and ONJ development. English papers published from January 2003 until December 2014 were identified on the MEDLINE database. Titles and abstracts retrieved form electronic search were screened separately by 2 examiners; thus, original studies dealing with dental implants placement during or before bone antiresorptive agent therapy and the relative risk of implant failure or development of osteonecrosis were evaluated. Due to the heterogeneity of the included studies and the high risk of bias, there is no evidence of the safe use of oral antiresorptive agents prior or after dental implant surgery. Indeed, implant failure and ONJ development can occur and represent a devastating side effect that should be considered during treatment. Within the limitation of the present systematic review, high quality studies are needed to provide an adequate level of evidence regarding the safety of dentoalveolar surgery during or before bone resorption inhibition therapy and the increase predisposition to osteonecrosis of the jaw (ONJ) development. Therefore, antiresorptive agent therapy should be considered a risk factor until further evidence is prospectively obtained.

Evaluation of root coverage with and without connective tissue graft for the treatment of single maxillary gingival recession using an image analysis system: a randomized controlled clinical trial.

The aim of this prospective randomized clinical study was to evaluate, by means of an image analysis system, the efficacy of two different surgical procedures for the treatment of Miller Class I and II maxillary gingival recession. Patients treated for maxillary gingival recession were recruited and randomly divided into two groups: patients who received a coronally advanced flap with connective tissue graft (CAF + CTG) or CAF alone. Outcome parameters included complete root coverage, recession reduction, and keratinized tissue amount. Twenty-five patients completed the 12-month follow-up period. Patients in the CAF + CTG group showed a better primary outcome- gingival recession at 12 months-than CAF patients (P = .0001). Gingival recession at 12 months had a median of 0.5 (interquartile range [IQR] 0.5 to 0.6) in the CAF + CTG group and a median of 1.0 (IQR 0.9 to 1.1) in the CAF group. CAF + CTG and CAF groups had similar complete root coverage at 6 and 12 months. Recession and keratinized tissue width significantly decreased over time (P < .0001), with no effect of treatment or of treatment over time. Buccal probing depth had similar values over time (P = .28) and in the two groups (P = .52). Buccal clinical attachment level had similar values in the two groups (P = .87); moreover, mesial and distal clinical attachment levels did not show any variation over time (P = .88 and P = .68, respectively). By means of a computerized image analysis system better outcomes in terms of recession reduction after 12 months of follow-up were measured for maxillary gingival recessions treated with CAF and CTG. Adjunctive application of a CTG under a CAF increased the probability of achieving complete root coverage in maxillary Miller Class I and II defects (61.5% versus 83.3%; P = .38). Both treatments were equally effective in providing a consistent reduction of the baseline recession.

Adipose-Derived Stem Cells as a Tool for Dental Implant Osseointegration: an Experimental Study in the Dog.

The biological interaction between the jaw bones and dental implant is fundamental for the long-term success of dental implant placement. Nevertheless, the insufficient bone volume remains a major clinical problem, especially in case of immediate dental implant. Using a canine model, the present study proves the regenerative potential of adipose- derived stem cells (ADSCs) to repair peri-implant bone defects occurring in immediate dental implant placement. In six labradors, all mandibular premolars and the first molars were extracted bilaterally and three months later dental implants were installed with a marginal gap. The marginal defects were filled with hydroxyapatite (HA)-based scaffolds previously seeded with ADSCs. After one month of healing, specimens were prepared for histological and histomorphometric evaluations. Histological analyses of ground sections show that ADSCs significantly increase bone regeneration. Several new vessels, osteoblasts and new bone matrix were detected. By contrast, no inflammatory cells have been revealed. ADSCs could be used to accelerate bone healing in peri- implant defects in case of immediate dental implant placement.

Decellularization and Delipidation Protocols of Bovine Bone and Pericardium for Bone Grafting and Guided Bone Regeneration Procedures.

The combination of bone grafting materials with guided bone regeneration (GBR) membranes seems to provide promising results to restore bone defects in dental clinical practice. In the first part of this work, a novel protocol for decellularization and delipidation of bovine bone, based on multiple steps of thermal shock, washes with detergent and dehydration with alcohol, is described. This protocol is more effective in removal of cellular materials, and shows superior biocompatibility compared to other three methods tested in this study. Furthermore, histological and morphological analyses confirm the maintenance of an intact bone extracellular matrix (ECM). In vitro and in vivo experiments evidence osteoinductive and osteoconductive properties of the produced scaffold, respectively. In the second part of this study, two methods of bovine pericardium decellularization are compared. The osmotic shock-based protocol gives better results in terms of removal of cell components, biocompatibility, maintenance of native ECM structure, and host tissue reaction, in respect to the freeze/thaw method. Overall, the results of this study demonstrate the characterization of a novel protocol for the decellularization of bovine bone to be used as bone graft, and the acquisition of a method to produce a pericardium membrane suitable for GBR applications.

Accuracy of 3D digital modeling of dental arches

ABSTRACT Objective: The aim of the study was to verify and compare the accuracy of full-arch digital impressions obtained using two intraoral scanners and three scanning methodologies. Methods: A resin model created with dental 3-D printing was scanned by a reference scanner (Zfx Evolution - Zimmer Biomet, Palm Beach Gardens, FL) in order to obtain a 3D reference; the same resin model was then scanned with two different intraoral scanners (Zfx IntraScan and Carestream 3600 - CS 3600®, Carestream, Rochester, NY, USA) using: Technique A (from tooth #27 up to tooth #17); Technique B (from tooth #11 up to tooth #17 and then from tooth #21 up to tooth #27) and Technique C (from tooth #22 up to tooth #17, and then from tooth #12 up to tooth #27 - the MeshLab software v. 1.3.3 was then used to match the two scans). The scans obtained were superimposed over the reference scan by means of a software, and the volumetric discrepancies were calculated. Results: The mean results for the Zfx Intrascan scanner were: Technique A = 302.47 ± 37.42 µm; Technique B = 180.45 ± 29.86 µm; Technique C = 147.34 ± 28.23 µm. The mean results for the Carestream 3600 scanner were: Technique A = 303.59 ± 40.20 µm; Technique B = 181.53 ± 29.61 µm; Technique C = 142.28 ± 35.33 µm. Technique C, used by both scanners, produced less volumetric discrepancies compared to the other techniques. Conclusions: The scanning technique had a statistically significant effect on the quality of the scan (p< 0.0001), whereas the scanner did not present any significant influence (p= 0.91).

RESUMO Objetivo: o objetivo do presente estudo foi verificar e comparar a precisão de modelos digitais de uma arcada dentária completa obtidos utilizando-se dois tipos de scanners e três metodologias de digitalização. Métodos: um modelo de resina feito com impressão 3D foi digitalizado em um scanner de referência (Zfx Evolution - Zimmer Biomet, Palm Beach Gardens, FL) para se obter uma referência em 3D; o mesmo modelo de resina foi, então, digitalizado com dois scanners intrabucais diferentes (Zfx IntraScan e Carestream 3600 - CS 3600®, Carestream, Rochester, NY, EUA) utilizando: Técnica A (do dente #27 ao dente #17); Técnica B (do dente #11 ao dente #17 e, em seguida, do dente #21 ao dente #27); e Técnica C (do dente #22 ao dente #17 e, em seguida, do dente #12 ao dente #27 - osoftware MeshLab v. 1.3.3 foi, então, usado para mesclar as duas leituras). Em seguida, as imagens digitalizadas foram sobrepostas à imagem de referência, utilizando-se um software, e as discrepâncias volumétricas foram calculadas. Resultados: a média dos resultados para o scanner Zfx Intrascan foram: Técnica A = 302,47 ± 37,42 µm; Técnica B = 180,45 ± 29,86 µm; Técnica C = 147,34 ± 28,23 µm. A média dos resultados para o scanner Carestream 3600 foram: Técnica A= 303,59 ± 40,20 µm; Técnica B = 181,53 ± 29,61 µm; Técnica C = 142,28 ± 35,33 µm. A Técnica C, utilizada em ambos os scanners, produziu as menores discrepâncias volumétricas, quando comparada às outras técnicas. Conclusões: a técnica de digitalização teve um efeito estatisticamente significativo sobre a qualidade do modelo digital (p< 0,0001), enquanto o tipo de scanner usado não apresentou qualquer influência significativa (p= 0,91).

Platform switching on wide-diameter external hex implants: a finite element analysis.

OBJECTIVES: The objective of this work was to use finite element analysis to compare the effect of forces coming to bear on abutments 4.1 or 5.0 mm in diameter connected to a 5.0 mm implant (i.e. with or without platform switching). STUDY DESIGN: A 3D CAD model of a 5 x 11.5 mm external hex implant was developed, complete with a connection screw and either of two abutments, one 4.1 and the other 5 mm in diameter, to assess the influence of two loading conditions, i.e. 200 N loaded either axially or off center on the top of the abutment. RESULTS AND CONCLUSIONS: In the symmetrically loaded models, greater stresses were transmitted to the bone in the area below the neck of the implant in the case of the wider-diameter abutment. When the narrower abutment was considered, the stress lines remained confined to the metal and were transferred to the bone in a more distal position. When the stresses in the bone where compared under non-symmetrical loading of the larger- and smaller-diameter abutments, the stresses reached lower values in the latter case. These findings indicate that platform switching (i.e. coupling a 4.1 mm abutment with a 5 mm implant) achieves a better, more even distribution of the peri-implant stresses deriving from simulated occlusal loads on the bone margins. Key words:Platform switching, finite element analysis, implant.

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.