A Narrative Review of the Histological and Histomorphometrical Evaluation of the Peri-Implant Bone in Loaded and Unloaded Dental Implants. A 30-Year Experience (1988-2018)

Animal Models for Investigating Osseointegration: An Overview of Implant Research over the Last Three Decades

Dental implants and bone augmentation are among dentistry's most prevalent surgical treatments; hence, many dental implant surfaces and bone grafts have been researched to improve bone response. Such new materials were radiologically, histologically, and histomorphometrically evaluated on animals before being used on humans. As a result, several studies used animals to evaluate novel implant technologies, biocompatibility, surgical techniques, and osseointegration strategies, as preclinical research on animal models is essential to evaluate bioactive principles (on cells, compounds, and implants) that can act through multiple mechanisms and to predict animal behavior, which is difficult to predict from in vitro studies alone. In this study, we critically reviewed all research on different animal models investigating the osseointegration degree of new implant surfaces, reporting different species used in the osseointegration research over the last 30 years. Moreover, this is the first study to summarize reviews on the main animal models used in the translational research of osseointegration, including the advantages and limitations of each model and determining the ideal location for investigating osseointegration in small and large animal models. Overall, each model has advantages and disadvantages; hence, animal selection should be based on the cost of acquisition, animal care, acceptability to society, availability, tolerance to captivity, and housing convenience. Among small animal models, rabbits are an ideal model for biological observations around implants, and it is worth noting that osseointegration was discovered in the rabbit model and successfully applied to humans.

The effect of porous compliance bushings in a dental implant on the distribution of occlusal loads

Porous dental implants are clinically used, but the mechanism of load distribution for stepped implant shaft surrounded by compliance bushings is still not known, especially for different bone conditions. The aim of the study was to assess the impact of the design of a dental implant with compliance bushings (CBs) on the occlusal load distribution during primary and secondary stability using finite element simulation (FEA), with a distinction between low and high quality cervical support under primary stability. The FEA of the oblique occlusal load transfer (250 N; 45°) was carried out for implants under variable bone conditions. The stepped shaft in the intermediate part of the dental implant was surrounded by CBs with an increasing modulus of elasticity of 2, 10 and 50 GPa. With a smaller Young's modulus of the bushings the increase of stress in the trabecular bone indicated that more bone tissue can be protected against disuse. The beneficial effect for the trabecular bone derived from the reduction of the stiffness of the bushings in relation to the loss of the implant's load bearing ability can be assessed using the FEM method.

The impact of immediate versus delayed mini-screw placement on alveolar bone preservation and bone density following tooth extraction: evidence from a canine model

The aim of this study was to evaluate the impact of mini-screw placement on the alveolar ridge using a split-mouth design. Twelve beagles underwent bilateral extraction of their lateral teeth. In the immediate group, a mini-screw was unilaterally placed approximately 3-4 mm below the alveolar crest of the extraction site on the experimental side. The delayed group received mini-screws six weeks after tooth extraction. On average, the dogs were sacrificed after 11 weeks, and the maxillary bones were excised and scanned using cone-beam computed tomography (CBCT). Histopathological examinations were conducted to assess inflammation and bone formation scores. The results showed that in the immediate group, bone height was significantly greater on the intervention side compared to the control side (p < 0.05), whereas there was no significant difference in the delayed group. In both groups, there was a significant increase in bone density around the mini-screws compared to the control sides (p < 0.05). Mini-screw insertion led to a significant enhancement of bone growth in both groups (p < 0.05), with no notable differences between the two groups. The mini-screws did not have any impact on bone inflammation or width. Overall, both immediate and delayed mini-screw placement in the extraction socket positively influenced bone dimensions, density, and histological properties. However, immediate insertion was more effective than delayed placement in preserving vertical bone height, despite delayed insertion resulting in higher bone density.

Comparison of mechanical stability of mini-screws with resorbable blasting media and micro-arc oxidation surface treatments under orthodontic forces: An in vitro biomechanical study

INTRODUCTION

The aim of this study was to compare the primary stability of mini-screws with different surface treatments such as resorbable blasting media (RBM) and micro-arc oxidation (MAO) under in vitro orthodontic forces.

MATERIAL AND METHODS

Thirty-six self-drilling TiAl6V4-ELI grade 23 titanium alloy 1.6×8mm mini-screws were inserted into polyurethane foam blocks and divided into three groups according to surface properties: machine surface (MS), RBM-treated, and MAO-treated. An orthodontic force of 150g was applied to the mini-screws using NiTi coils. Maximum insertion torque (MIT) and maximum removal torque (MRT) were measured with a digital torque screwdriver during insertion and removal. For each mini-screw, stability measurements were made with the Periotest M device at day 0 and weeks 1, 2, 4, 8, and 12.

RESULTS

Significant differences in MIT were observed between all groups in pairwise comparisons (P<0.001) with the highest value in the MAO-treated group and the lowest in the MS group. The mean MRT values differed in all three groups (P=0.001). In pairwise comparisons of MRT, only the difference between MS group and RBM-treated group was significant. The highest value was observed in the RBM-treated group, while the lowest value was observed in the MS group. Periotest values were significantly higher in the MAO-treated group than the RBM-treated group at weeks 8 and 12. A positive significant correlation was found between MIT and MRT in all groups. No significant correlation was found between MIT, MRT and Periotest values in all groups.

CONCLUSION

RBM-treated group was significantly higher than the MS group in MIT and MRT values. According to Periotest values, RBM-treated group was found to be significantly more stable than the MAO-treated group at weeks 8 and 12. Therefore, RBM surface treatment was found to be more favourable than other surfaces to increase success rate in clinical applications.

Numerical analysis of the mechanical response of novel swelling bone implants in polyurethane foams

In this study, a numerical framework was developed in order to analyze the swelling properties, mechanical response and fixation strength of swelling bone anchors. Using this framework, fully porous and solid implants, along with a novel hybrid design (consisting of a solid core and a porous sleeve), were modeled and studied. Free swelling experiments were conducted to investigate their swelling characteristics. The finite element model of swelling was validated using the conducted free swelling. Compared with the experimental data, results obtained from the finite element analysis proved the reliability of this frame-work. Afterwards, the swelling bone anchors were studied embedded in artificial bones with different densities with two different interface properties: considering frictional interface between the bone anchors and artificial bones (simulating the stages prior to osteointegration, when the bone and implant are not fully bonded and the surface of the implant can slide along the interface), and perfectly bonded (simulating the stages subsequent to osteointegration, when the bone and implant are fully bonded). It was observed that the swelling considerably decreases while the average radial stress on the lateral surface of the swelling bone anchor surges in the denser artificial bones. Ultimately, the pull-out experiments and simulations of the swelling bone anchors from the artificial bones were conducted to look into the fixation strength of the swelling bone anchors. It was found that the hybrid swelling bone anchor exhibits mechanical and swelling properties close to those of solid bone anchors, while also bone in-growth is expected to happen, which is an integral factor to these bone anchors.

Surface Coatings of Dental Implants: A Review

Replacement of missing teeth is possible using biocompatible devices such as endosseous implants. This study aims to analyze and recognize the best characteristics of different implant surfaces that ensure good peri-implant tissue healing and thus clinical success over time. The present review was performed on the recent literature concerning endosseous implants made of titanium, a material most frequently used because of its mechanical, physical, and chemical characteristics. Thanks to its low bioactivity, titanium exhibits slow osseointegration. Implant surfaces are treated so that cells do not reject the surface as a foreign material and accept it as fully biocompatible. Analysis of different types of implant surface coatings was performed in order to identify ideal surfaces that improve osseointegration, epithelial attachment to the implant site, and overall peri-implant health. This study shows that the implant surface, with different adhesion, proliferation, and spreading capabilities of osteoblastic and epithelial cells, influences the cells involved in anchorage. Implant surfaces must have antibacterial capabilities to prevent peri-implant disease. Research still needs to improve implant material to minimize clinical failure.

Peri-implant cell differentiation in delayed and immediately-loaded dental implant: A mechanobiological simulation

OBJECTIVE

This study aimed to investigate the effect of immediate versus delayed dental implant placement strategies on cell differentiation in a dental callus.

DESIGN

The implant was placed in the mandible with two nearby teeth using an idealized two-dimensional finite element model. Eight weeks after surgery, the mechanobiological modeling of healing was used to estimate cell differentiation. It was assumed that the callus was initially filled by mesenchymal cells. The model then transformed mechanical stimuli received by the callus from loadings in terms of distortional and dilatational strains into predictions of the cellular phenotypes, including fibroblasts, chondrocytes, and osteoblasts, or whether they would remain unchanged or die.

RESULTS

The results demonstrated that delayed loading led to greater bone formation than immediate loading. Osteoblast colonies were observed in the base of threads in the immediately-loaded implant, whereas the delayed loading caused distant bone formation from the surrounding bone side towards the implant. The osteoblasts were differentiated from both intramembranous and endochondral mechanisms of ossification. After eight weeks, approximately 61 % of the callus was ossified in the delayed placement model compared to 35 % in the immediate placement model, resulting in a greater amount of fibrocartilaginous tissue on the bone side of the callus.

CONCLUSIONS

Immediate and delayed loading models generated different results. In the delayed strategy, bone cells were supplied appropriately during the first few weeks following surgery, whereas the immediate loading caused fibrocartilaginous tissue differentiation. In the form of distant osseointegration, the secondary stability of the dental implant was higher and faster due to the delayed placement.

Effectiveness of Apigenin, Resveratrol, and Curcumin as Adjuvant Nutraceuticals for Calvarial Bone Defect Healing: An In Vitro and Histological Study on Rats

Bone healing is a major clinical issue, especially in bone defects of critical dimensions. Some studies have reported in vivo positive effects on bone healing by some bioactive compounds, such as the phenolic derivatives found in vegetables and plants, such as resveratrol, curcumin, and apigenin. The aim of this work was (1) to analyze in vitro in human dental pulp stem cells the effects of these three natural compounds on the gene expression of related genes downstream to RUNX2 and SMAD5, key factor transcriptions associated with osteoblast differentiation, in order to better understand the positive effects that can occur in vivo in bone healing, and (2) to evaluate in vivo the effects on bone healing of critical-size defects in the calvaria in rats of these three nutraceuticals tested in parallel and for the first time administered by the gastric route. Upregulation of the RUNX2, SMAD5, COLL1, COLL4, and COLL5 genes in the presence of apigenin, curcumin, and resveratrol was detected. In vivo, apigenin induced more consistent significant bone healing in critical-size defects in rat calvaria compared to the other study groups. The study findings encourage a possible therapeutic supplementation with nutraceuticals during the bone regeneration process.

Clinical and Radiological Evaluation of a Self-Condensing Bone Implant in One-Stage Sinus Augmentation: A 3-Year Follow-Up Retrospective Study

Stabilization of dental implants in the sinus region with a bone height below 4 mm gen-erally requires a two-stage sinus floor elevation surgery. To improve this aspect, the aim of this retrospective study was to demonstrate the feasibility of performing a one-stage maxillary sinus augmentation using an innovative self-condensing implant design, even in case of a bone height close to 2 mm. Clinical and radiological outcomes from 54 patients (26 females; 28 males; 69 total implants positioned) were analyzed 3 years post-surgery. The three-dimensional grafts change was evaluated by Cone-Beam Computed Tomography (CBCT) before surgery (T0), immediately after surgery (T1), and 1-year post-surgery (T2). The sinus floor levels measured at the medial (M-W), middle (MD-W), and lateral (L-W) walls reported: M-W of 1.9 ± 2.4 mm (T1) and 1.7 ± 2.6 mm (T2); MD-W of -0.1 ± 2.7 mm (T1) and 0.7 ± 2.4 mm (T2); L-W of 3.1 ± 3.0 mm (T1) and 3.1 ± 3.0 mm (T2); besides a bone crest height (C-F) of 4.6 ± 2.0 mm (T1) and 12.1 ± 1.4 mm (T2). Moreover, after 3 years only 1 implant was lost, and so an implant survival rate of 98.55% was recorded. In conclusion, these results suggest the efficacy of using this implant design for a one-stage sinus lift approach, not only in terms of increased implant survival rate and decreased marginal bone loss, but also for its potential applicability in case of reduced bone height.

Exploring the Importance of Corticalization Occurring in Alveolar Bone Surrounding a Dental Implant

Several measures describing the transformation of trabecular bone to cortical bone on the basis of analysis of intraoral radiographs are known (including bone index or corticalization index, CI). At the same time, it has been noted that after functional loading of dental implants such transformations occur in the bone directly adjacent to the fixture. Intuitively, it seems that this is a process conducive to the long-term maintenance of dental implants and certainly necessary when immediate loading is applied. The authors examined the relationship of implant design features to marginal bone loss (MBL) and the intensity of corticalization over a 10-year period of functional loading. This study is a general description of the phenomenon of peri-implant bone corticalization and an attempt to interpret this phenomenon to achieve success of implant treatment in the long term. Corticalization significantly increased over the first 5-year functional loading (CI from 200 ± 146 initially to 282 ± 182, p < 0.001) and maintained a high level (CI = 261 ± 168) in the 10-year study relative to the reference bone (149 ± 178). MBL significantly increased throughout the follow-up period—5 years: 0.83 ± 1.26 mm (p < 0.001), 10 years: 1.48 ± 2.01 mm (p < 0.001). MBL and radiographic bone structure (CI) were evaluated in relation to intraosseous implant design features and prosthetic work performed. In the scope of the study, it can be concluded that the phenomenon of peri-implant jawbone corticalization seems an unfavorable condition for the future fate of bone-anchored implants, but it requires further research to fully explain the significance of this phenomenon.

A Narrative Review on the Effectiveness of Bone Regeneration Procedures with OsteoBiol® Collagenated Porcine Grafts: The Translational Research Experience over 20 Years

Over the years, several bone regeneration procedures have been proposed using natural (autografts, allografts, and xenografts) and synthetic (i.e., metals, ceramics, and polymers) bone grafts. In particular, numerous in vitro and human and animal in vivo studies have been focused on the discovery of innovative and suitable biomaterials for oral and maxillofacial applications in the treatment of severely atrophied jaws. On this basis, the main objective of the present narrative review was to investigate the efficacy of innovative collagenated porcine bone grafts (OsteoBiol^®, Tecnoss^®, Giaveno, Italy), designed to be as similar as possible to the autologous bone, in several bone regeneration procedures. The scientific publications were screened by means of electronic databases, such as PubMed, Scopus, and Embase, finally selecting only papers that dealt with bone substitutes and scaffolds for bone and soft tissue regeneration. A total of 201 papers have been detected, including in vitro, in vivo, and clinical studies. The effectiveness of over 20 years of translational research demonstrated that these specific porcine bone substitutes are safe and able to improve the biological response and the predictability of the regenerative protocols for the treatment of alveolar and maxillofacial defects.

Histological and Biological Response to Different Types of Biomaterials: A Narrative Single Research Center Experience over Three Decades

Background: In more than three decades of work of the Retrieval Bank of the Laboratory for Undemineralized Hard Tissue Histology of the University of Chieti-Pescara in Italy, many types of biomaterials were received and evaluated. The present retrospective review aimed to evaluate the histological and biological aspects of the evaluated bone substitute biomaterials. Methods: In the present study, the authors prepared a retrospective analysis after the screening of some databases (PubMed, Scopus, and EMBASE) to find papers published from the Retrieval Bank of the Laboratory for Undermineralized Hard Tissue Histology of the University of Chieti-Pescara analyzing only the papers dealing with bone substitute biomaterials and scaffolds, in the form of granules and block grafts, for bone regeneration procedures. Results: Fifty-two articles were found, including in vitro, in vivo, and clinical studies of different biomaterials. These articles were evaluated and organized in tables for a better understanding. Conclusions: Over three decades of studies have made it possible to assess the quality of many bone substitute biomaterials, helping to improve the physicochemical and biological properties of the biomaterials used in daily clinical practice.

What Does Bone Corticalization around Dental Implants Mean in Light of Ten Years of Follow-Up?

The phenomenon of peri-implant bone corticalization after functional loading does not yet have a definite clinical significance and impact on prognosis. An attempt was made to assess the clinical significance of this phenomenon. This prospective study included 554 patients. Standardized intraoral radiographs documenting the jawbone environment of 1556 implants were collected. The follow-up period was 10 years of functional loading. Marginal alveolar bone loss (MBL) and radiographic bone structure (bone index, BI) were evaluated in relation to intraosseous implant design features and prosthetic work performed. After five years, bone structure abnormalities expressed by a reduction of BI to 0.47 ± 0.21 and MBL = 0.88 ± 1.27 mm were observed. Both values had an inverse relationship with each other (p < 0.0001). Reference cancellous bone showed BI = 0.85 ± 0.18. The same relationship was observed after ten years of functional loading: BI = 0.48 ± 0.21, MBL = 1.49 ± 1.94 mm, and again an inverse relationship (p < 0.0001). Increasing corticalization (lower BI) is strongly associated with increasing marginal bone loss and increasing corticalization precedes future marginal bone loss. Marginal bone loss will increase as corticalization progresses.

Innovative Concepts and Recent Breakthrough for Engineered Graft and Constructs for Bone Regeneration: A Literature Systematic Review

Background: For decades, regenerative medicine and dentistry have been improved with new therapies and innovative clinical protocols. The aim of the present investigation was to evaluate through a critical review the recent innovations in the field of bone regeneration with a focus on the healing potentials and clinical protocols of bone substitutes combined with engineered constructs, growth factors and photobiomodulation applications. Methods: A Boolean systematic search was conducted by PubMed/Medline, PubMed/Central, Web of Science and Google scholar databases according to the PRISMA guidelines. Results: After the initial screening, a total of 304 papers were considered eligible for the qualitative synthesis. The articles included were categorized according to the main topics: alloplastic bone substitutes, autologous teeth derived substitutes, xenografts, platelet-derived concentrates, laser therapy, microbiota and bone metabolism and mesenchymal cells construct. Conclusions: The effectiveness of the present investigation showed that the use of biocompatible and bio-resorbable bone substitutes are related to the high-predictability of the bone regeneration protocols, while the oral microbiota and systemic health of the patient produce a clinical advantage for the long-term success of the regeneration procedures and implant-supported restorations. The use of growth factors is able to reduce the co-morbidity of the regenerative procedure ameliorating the post-operative healing phase. The LLLT is an adjuvant protocol to improve the soft and hard tissues response for bone regeneration treatment protocols.

Effects of masticatory loading on bone remodeling around teeth vs. implants: insights from a preclinical model

OBJECTIVES

Teeth connect to bone via a periodontal ligament whereas implants connect to bone directly. Consequently, masticatory loads are distributed differently to periodontal versus peri-implant bone. Our objective was to determine how masticatory loading of an implant versus a tooth affected peri-implant versus periodontal bone remodeling. Our hypothesis was that strains produced by functional loading of an implant would be elevated compared to the strains around teeth, and that this would stimulate a greater degree of bone turnover around implants versus in periodontal bone.

MATERIALS AND METHODS

Sixty skeletally mature mice were divided into two groups. In the Implant group, maxillary first molars (mxM1) were extracted, and after socket healing, titanium alloy implants were positioned sub-occlusally. After osseointegration, implants were exposed, resin crowns were placed, and masticatory loading was initiated. In a Control group the dentition was left intact. Responses of peri-implant and periodontal bone were measured using micro-CT, histology, bone remodeling assays, and quantitative histomorphometry while bone strains were estimated using finite element (FE) analyses.

CONCLUSIONS

When a submerged osseointegrated implant is exposed to masticatory forces peri-implant strains are elevated, and peri-implant bone undergoes significant remodeling that culminates in new bone accrual. The accumulation of new bone functions to reduce both peri-implant strains and bone remodeling activities, equivalent to those observed around the intact dentition.

Mechanical Behaviour and Primary Stability of a Self-Condensing Implant: A Laboratory Critical Simulation of a Severe Maxillary Atrophy on Polyurethane Lamina

Background: Posterior maxillary atrophies could emerge after the loss of teeth, trauma, infections, or lesions that often require regenerative approaches. In these critical conditions, the achievement of implant primary stability represents a clinical challenge in the operative practice. Therefore, a two-stage approach is often preferred with a delay of the rehabilitation time and a consistent increasing of the biological and the operative costs. The aim of this study was to evaluate the mechanical behaviour of a self-condenser implant compared to a standard implant in a critical simulation on different thicknesses and densities of polyurethane lamina. Materials and methods: A total of two implant models were tested: a self-condensing device (test) and a standard implant (control). The study evaluated the insertion torque and the pull-out strength values of the test and control implants inserted in different sizes (1, 2, and 3 mm) and density polyurethane lamina (10, 20, and 30 pcf) for a total of 320 experimental sites. Results: In total, 320 experimental sites were produced in the polyurethane samples. A statistically significant difference of insertion and pull-out torque values between the test and control Implants was found in the different bone densities (p < 0.05). The insertion and pull-out torque values were always higher for the test implants in all experimental conditions. In all bone densities, the insertion torque values were higher than the pull-out torque values. The self-condenser dental implant design evaluated in this in vitro study showed a high level of stability in all experimental conditions. Conclusions: The test implant could represent a useful tool for a one-stage surgical approach in the presence of limited residual native bone as an alternative to a delayed technique.

The response of bioactive titanium surfaces with different structure to UVC-irradiation to eliminate the negative effect on biological properties during aging time

The biological aging of titanium implants affects the service lifetime negatively in clinical applications, and UV irradiation is an applicable method to overcome the biological aging. This study investigated the changes in surface characteristics and biological properties of bioactive titanium surfaces with different structure and topography after UVC-irradiation. The bioactive titanium surfaces were prepared by anodizing (AO), sandblasting and acid-etching (SLA), acid-alkali etching (AA), alkali-heat etching (AH) methods. Samples were stored at dark for 7 weeks to simulate biological aging process and then irradiated by UVC for 2 hours. The results showed that the Ti-OH groups, which are crucial to enhance the biological properties, were easier to be generated on AO surfaces by UVC-irradiation, o owing to a mixture of anatase and rutile on surfaces. UVC-irradiation had the strongest effect on AO surfaces to enhance the bioactivity in bone-like apatite deposition and better biocompatibility in MSCs attachment and proliferation. Therefore, titanium surfaces with a mixture phase of anatase and rutile has the potential to effectively utilize the benefits of UVC-irradiation to overcome the negative effects of the biological aging and have a promising clinical application prospect.

An In Vitro Analysis on Polyurethane Foam Blocks of the Insertion Torque (IT) Values, Removal Torque Values (RTVs), and Resonance Frequency Analysis (RFA) Values in Tapered and Cylindrical Implants

Background: Several different dental implant microgeometries have been investigated in the literature for use in low-density bone sites. The polyurethane solid rigid blocks represent an optimal in vitro study model for dental implants, because their composition is characterized by symmetrical linear chains of monomers of hexa-methylene sequences producing a self-polymerization process. The aim of the present investigation was to evaluate the primary stability of cylindrical and tapered implants positioned into low-density polyurethane solid rigid blocks. Materials and Methods: Two different macrogeometries, cylindrical (4 mm diameter and 10 mm length) and tapered dental implants (4.20 mm diameter and 10 mm length), were investigated in the present study. The implants were inserted into 10 PCF and 20 PCF polyurethane blocks, with and without an additional cortical layer. The insertion torque (IT) values, the removal torque values (RTVs), and the resonance frequency analysis (RFA) values were measured and recorded. Results: A total of 80 sites were tested, and a significant increased primary stability (PS) was detected in favour of tapered dental implants when compared to cylindrical implants in all experimental conditions (p < 0.05). Higher IT, RT, and RFA values were measured in tapered implants in 10 and 20 PCF polyurethane blocks, both with and without the additional cortical layer. Conclusions: Both implants showed sufficient primary stability in poor density substrates, while, on the other hand, the tapered microgeometry showed characteristics that could also lead to clinical application in low-density posterior maxillary sites, even with a drastically decreased bone cortical component.

Factors Influencing Marginal Bone Loss around Dental Implants: A Narrative Review

Implant supported dental prostheses are increasingly used in dental practice. The aim of this narrative review is to present the influence of transmucosal surface of prosthetic abutment and implant on peri-implant tissue. The article describes causes of bone loss around the dental implant. Moreover, properties of different materials are compared and discussed. The advantages, disadvantages, and biomechanical concept of different implant-abutment connections are presented. The location of connections in relation to the bone level and the influence of microgap between the abutment and implant are described. Additionally, the implant abutments for cemented and screwed prosthetic restorations are compared. The influence of implant and abutment surface at the transmucosal level on peri-implant soft tissue is discussed. Finally, the biological aspect of abutment-implant connection is analyzed.

Education Technology in Orthodontics and Paediatric Dentistry during the COVID-19 Pandemic: A Systematic Review

Over the last decade, medical education changed from traditional teaching methods to telematic and networking scholar and e-learning approach. The objective of the present systematic review was to evaluate the effectiveness and teachers/student's acceptability of e-learning applied to the field of orthodontics and paediatric dentistry. A database search of the literature was conducted on PubMed and Embase databases from January 2005 to May 2021. A total of 172 articles were identified by the electronic search, while a total of 32 papers were selected for qualitative analysis. Overall, 19 articles investigated the effectiveness of e-learning, and no difference of acceptability was reported between e-learning and traditional methods for a wide part of the articles selected. A total of 25 papers provided a satisfaction questionnaire for learners and all were positive in their attitude towards e-learning. The results showed that e-learning is an effective method of instruction, complementing the traditional teaching methods, and learners had a positive attitude and perception. The evidence of the present study reported a high level of acceptability and knowledge level of e-learning techniques, compared to frontal lecture methods, in the fields of orthodontics and paediatric dentistry.

The 15-Months Clinical Experience of SARS-CoV-2: A Literature Review of Therapies and Adjuvants

BACKGROUND

Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) is the virus responsible for the coronavirus disease of 2019 (COVID-19) that emerged in December 2019 in Wuhan, China, and rapidly spread worldwide, with a daily increase in confirmed cases and infection-related deaths. The World Health Organization declared a pandemic on the 11th of March 2020. COVID-19 presents flu-like symptoms that become severe in high-risk medically compromised subjects. The aim of this study was to perform an updated overview of the treatments and adjuvant protocols for COVID-19.

METHODS

A systematic literature search of databases was performed (MEDLINE PubMed, Google Scholar, UpToDate, Embase, and Web of Science) using the keywords: "COVID-19", "2019-nCoV", "coronavirus" and "SARS-CoV-2" (date range: 1 January 2019 to 31st October 2020), focused on clinical features and treatments.

RESULTS

The main treatments retrieved were antivirals, antimalarials, convalescent plasma, immunomodulators, corticosteroids, anticoagulants, and mesenchymal stem cells. Most of the described treatments may provide benefits to COVID-19 subjects, but no one protocol has definitively proven its efficacy.

CONCLUSIONS

While many efforts are being spent worldwide in research aimed at identifying early diagnostic methods and evidence-based effective treatments, mass vaccination is thought to be the best option against this disease in the near future.

The Influence of the Implant Macrogeometry on Insertion Torque, Removal Torque, and Periotest Implant Primary Stability: A Mechanical Simulation on High-Density Artificial Bone

Background: The primary stability is a determinant clinical condition for the success of different dental implants macro-design in different bone density using a validated and repeatable in vitro technique employing solid rigid polyurethane blocks. Materials and Methods: Five implants 3.8 × 13 mm2 for each macro-design (i.e., IK—tapered; IC—cylindric; and IA—active blade shape) were positioned into 20- and 30- pounds per cubic foot (PCF) polyurethane blocks. Bucco-lingual (BL) and mesial-distal (MD) implant stability quotient score (ISQ) was assessed by resonance frequency analysis while, insertion/removal torques were evaluated by dynamometric ratchet. Results: IC implants shown better primary stability in terms of ISQ compared to IA and IK in lower density block (20 PCF), while IK was superior to IA in higher density (30 PCF). IC shown higher removal torque in 30-PCF compared to IA and IC. Conclusions: The study effectiveness on polyurethane artificial bone with isotropic symmetry structure showed that the implants macro-design might represent a key factor on primary stability, in particular on low-density alveolar bone. Clinicians should consider patients features and implant geometry during low-density jaws rehabilitation. Further investigations are needed to generalize these findings.

Survival Rate of Zygomatic Implants for Fixed Oral Maxillary Rehabilitations: A Systematic Review and Meta-Analysis Comparing Outcomes between Zygomatic and Regular Implants

Background: Zygomatic implants have been proposed alone or in combination with premaxillary conventional implants for severe resorbed maxillary atrophy rehabilitation. The aim of the present investigation was to evaluate through a qualitative systematic review and meta-analysis the survival rate of zygomatic implants in conjunction with regular fixtures for maxillary rehabilitation. Methods: The article screening was conducted on the PubMed/Medline and EMBASE electronic databases according to the “Preferred Reporting Items for Systematic Reviews and Meta-Analyses” (PRISMA) guidelines. The scientific papers were included for qualitative analysis and risk-of-bias evaluation. Only the papers that included rehabilitation with zygomatic implants in combination with regular implants were considered for the meta-analysis comparative evaluation of the implant survival rate. Results: The paper search screened a total of 137 papers. After the initial screening, a total of 32 articles were considered for the qualitative analysis. There was a similar implant survival rate between zygomatic and premaxilla regular implants (p = 0.02; Z: 2.26). Conclusions: Zygomatic and conventional implants showed a high long-term survival rate for fixed maxillary rehabilitations, but few included studies reported the marginal bone loss after loading. Further studies are necessary to evaluate the pattern of marginal bone loss between zygomatic and conventional implants after long-term functional loading.

Effectiveness of Dental and Maxillary Transverse Changes in Tooth-Borne, Bone-Borne, and Hybrid Palatal Expansion through Cone-Beam Tomography: A Systematic Review of the Literature

Background and Objectives: Palatal expansion is a common orthodontic technique able to increase the transverse changes for subjects with constricted maxillary arches. The aim of the present investigation was to evaluate through a systematic review the tomography effectiveness of different palatal expander approaches. Materials and Methods: The database used to perform the screening and determine the eligibility of the clinical papers was PubMed (Medline). Results: The database search included a total of 284 results, while 271 articles were excluded. A total of 14 articles were included for the qualitative assessment. Conclusions: The effectiveness of the present studies reported that skeletal expansion was a useful approach to increase the transverse changes for subjects with constricted maxillary arches.

Histological and Histomorphometric Effectiveness of the Barrier Membranes for Jawbone Regeneration: An Overview of More Than 30 Years’ Experience of Research Results of the Italian Implant Retrieval Center (1988–2020)

With the advent of implant dentistry, height and width of the bone site are fundamental to perform implant placements. There are several techniques to restore the amount of bone loss and one of them is guided bone regeneration, which is based on the employment of a membrane in order to bypass non-osteogenic cell invasion in the bone healing area, dispersing every interference with bone regeneration. Two expert reviewers performed a retrospective evaluation of all scientific papers published by the Implant Retrieval Center Laboratory of University “G. D’Annunzio” of Chieti-Pescara in the last three decades, and they implemented it by also similar conducting research on the main scientific databases, i.e., PubMed, Scopus, and EMBASE. The search was conducted up to December 2020, and a total of 843 articles published by the Implant Retrieval Center Laboratory of University “G.D’Annunzio” of Chieti-Pescara were identified and evaluated. After the application of inclusion and exclusion criteria, a total of 27 manuscripts were included for the qualitative synthesis: 8 animal studies, 17 human studies, and 2 in vitro articles. The present overview shows the importance of translational research for barrier membranes for bone regeneration, and additionally, the need for experts in different fields and research centers to produce high quality data in future research.

The Effectiveness of Osseodensification Drilling Protocol for Implant Site Osteotomy: A Systematic Review of the Literature and Meta-Analysis

Many different osteotomy procedures has been proposed in the literature for dental implant site preparation. The osseodensification is a drilling technique that has been proposed to improve the local bone quality and implant stability in poor density alveolar ridges. This technique determines an expansion of the implant site by increasing the density of the adjacent bone. The aim of the present investigation was to evaluate the effectiveness of the osseodensification technique for implant site preparation through a literature review and meta-analysis. The database electronic research was performed on PubMed (Medline) database for the screening of the scientific papers. A total of 16 articles have been identified suitable for the review and qualitative analysis—11 clinical studies (eight on animals, three on human subjects), four literature reviews, and one case report. The meta-analysis was performed to compare the bone-to-implant contact % (BIC), bone area fraction occupied % (BAFO), and insertion torque of clockwise and counter-clockwise osseodensification procedure in animal studies. The included articles reported a significant increase in the insertion torque of the implants positioned through the osseodensification protocol compared to the conventional drilling technique. Advantages of this new technique are important above all when the patient has a strong missing and/or low quantity of bone tissue. The data collected until the drafting of this paper detect an improvement when the osseodensification has been adopted if compared to the conventional technique. A significant difference in BIC and insertion torque between the clockwise and counter-clockwise osseodensification procedure was reported, with no difference in BAFO measurements between the two approaches. The effectiveness of the present study demonstrated that the osseodensification drilling protocol is a useful technique to obtain increased implant insertion torque and bone to implant contact (BIC) in vivo. Further randomized clinical studies are required to confirm these pieces of evidence in human studies.

Influence of the dental implant macrogeometry and threads design on primary stability: an in vitro simulation on artificial bone blocks

The implant macrogeometry and thread profile represent one of the most important factors for a successful achievement of primary stability during the positioning procedure. The aim of the present investigation was to evaluate the insertion torque (IT), removal torque (RT) and Implant stability Quotient (ISQ) of two different implant macrogeometry and thread profile on solid rigid polyurethane model. Two different implants macrogeometries were tested: K2 (Group I) with 11° angle, 1.17 mm pitch and self-cutting V thread profile and K3 (Group II) implants with 30° angle, 0.71 mm pitch and spyral thread profile. A total of 120 specimens (n = 60 for each group) were positioned into different conditions of solid rigid polyurethane blocks. The insertion torque (IT), removal torque (RT) and ISQ were measured for each specimen. All specimens achieved the positioning into solid rigid polyurethane blocks for both of groups with no loss of stability. A significantly higher IT, RT and ISQ were detected in Group II (p < 0.05). In both groups the mean values for IT, RT and ISQ appeared promising from a clinical point of view. In spite of different macrogeometry and thread profile, both implant types achieved high primary stability on solid rigid polyurethane block to support the functional loading for a clinical application.

Synthetic Scaffold/Dental Pulp Stem Cell (DPSC) Tissue Engineering Constructs for Bone Defect Treatment: An Animal Studies Literature Review

Background: Recently a greater interest in tissue engineering for the treatment of large bone defect has been reported. The aim of the present systematic review and meta-analysis was to investigate the effectiveness of dental pulp stem cells and synthetic block complexes for bone defect treatment in preclinical in vivo articles. Methods: The electronic database and manual search was conducted on Pubmed, Scopus, and EMBASE. The papers identified were submitted for risk-of-bias assessment and classified according to new bone formation, bone graft characteristics, dental pulp stem cells (DPSCs) culture passages and amount of experimental data. The meta-analysis assessment was conducted to assess new bone formation in test sites with DPSCs/synthetic blocks vs. synthetic block alone. Results: The database search identified a total of 348 papers. After the initial screening, 30 studies were included, according to the different animal models: 19 papers on rats, 3 articles on rabbits, 2 manuscripts on sheep and 4 papers on swine. The meta-analysis evaluation showed a significantly increase in new bone formation in favor of DPSCs/synthetic scaffold complexes, if compared to the control at 4 weeks (Mean Diff: 17.09%, 95% CI: 15.16–18.91%, p < 0.01) and at 8 weeks (Mean Diff: 14.86%, 95% CI: 1.82–27.91%, p < 0.01) in rats calvaria bone defects. Conclusion: The synthetic scaffolds in association of DPSCs used for the treatment of bone defects showed encouraging results of early new bone formation in preclinical animal studies and could represent a useful resource for regenerative bone augmentation procedures

An in vitro evaluation on polyurethane foam sheets of the insertion torque, removal torque values, and resonance frequency analysis (RFA) of a self-tapping threads and round apex implant

The dental implant primary stability and micromovement absence represent critical factor for dental implant osseointegration. The aim of the present in vitro investigation was to simulate the bone response on different polyurethane densities the effect of self-tapping threads and round apex implant geometry. A total of 40 implants were positioned in D1, D2, D3 and D4 polyurethane block densities following a calibrated drilling protocol. The Insertion, removal Torque and resonance frequency analysis (RFA) means were calculated. All experimental conditions showed insertion torque values >30 Ncm. A significant higher insertion torque, removal and RFA was present in D1 polyurethane. Similar evidences were evidenced for D3 and D4. The effectiveness of the present study suggested a valuable clinical advantage for self-tapping threads and round apex implant using, such as in case of reduced bone density in the posterior maxilla

Implant primary stability with an osteocondensation drilling protocol in different density polyurethane blocks

The implant primary stability is a fundamental condition for avoiding implant micro-motions that might result in fibrous encapsulation; its achievement is facilitated by macro- and micro-geometry of the implant, and by the bone density and architecture at the intended implant site. The aim was to evaluate an osteocondensing drilling protocol for dental implant positioning compared to standard protocol on polyurethane block. A total of 40 implants, 20 for each osteocondensing group (Test) and 20 for standard drilling group (Control), were positioned. Insertion torque (IT), removal torque (RT), and Periotest were measured. A IT, RT, and Periotest significant difference was present in favor of the implant osteocondensing protocol. The results suggested that osteocondensing protocol represents a useful technique for implant placement in poor density bone.

Osseodensification Drilling vs. Standard Protocol of Implant Site Preparation: An In Vitro Study on Polyurethane Foam Sheets

(1) Background: The aim of the present in vitro investigation was to evaluate, on polyurethane sheets, two different drilling techniques for dental implant positioning using osteocondensing burs compared to a standard type protocol. (2) Methods: Three different implant designs (Implacil De Bortoli UN III 4 × 10 mm, Restore RBM 4 (HEX) × 10 mm; Implacil De Bortoli UN II 4 × 10 mm) were evaluated (test implant (osteocondensing drills) and control implant (standard drills)). The insertion torque (IT), the removal torque (RT) and the resonance frequency analysis (RFA) values of test and control implants inserted in different size and different density polyurethane foam models were compared for 120 experimental sites. Accordingly, 120 experimental holes were produced in different PCF polyurethane foams: 60 sites were produced in 10 PCF sheets and 60 sites in 10 PCF sheets with an additional 1 mm layer of 30 PCF. (3) Results: The IT, removal torque and RFA values were significantly higher for both of the evaluated implants, in the sites prepared with the osteocondenser drills when compared to sites prepared with standard drills (p < 0.05). The UNII and UN III showed significantly higher stability compared to the HEX implant; these differences increased drastically in the 10 PCF Polyurethane Block with the additional 1 mm cortical layer (p < 0.05). (4) Conclusions: The outcome of this investigation suggested a possible clinical application of osteocondensing burs in case of reduced bone quality and quantity in the posterior maxilla.