Comparing Single Tooth Implant Placement With and Without Allogenic Soft Tissue Augmentation. A Randomized Clinical Trial

OBJECTIVE

To explore the effect of adding an allogenic soft tissue graft at time of single implant placement using a fully digital workflow for single implant placement and restoration without making either analog or digital impressions.

MATERIALS AND METHODS

A prospective randomized clinical study was performed enrolling thirtynine participants requiring single tooth implant randomized into (+ graft) group which received an allogenic dermal graft at the time of implant placement (n=19), or (- graft) group (n=20). A fully digital surgical and restorative protocol was implemented. Intraoral scans were taken before implant placement (T0), at time of final crown delivery (T1) and at one-year post placement (T2). Intraoral scans were aligned using Geomagic Control X 2020 software), linear and volumetric changes in buccal tissues were measured at T0, T1 and T2. Implant survival, probing depths, and complications were recorded. Participants were asked to complete an OHIP-14 survey at T0 and T2. Marginal bone levels were measured at T0 and T2 on peri-apical x-rays.

RESULTS

39 participants completed surgery and restoration in incisor, canine, premolar and molar positions. Two early failures were recorded in central incisor positions (95% survival). Crown delivery without complication from the digital workflow (impressionless) was achieved for 36/39 of cases (92%) with implant depth control being implicated as the chief challenge. Thirtyseven participants attended the one-year follow-up visit. Both groups showed gain in buccal tissues thickness without significant differences between the two groups for both linear and volumetric measurements (P>0.05). Soft tissue grafting was associated with minimal added morbidity. The interproximal marginal bone changes recorded were -0.16mm mesial and - 0.12mm distal for the graft group and -0.01mm mesial and -0.11mm distal for the non-graft group (p=0.07 for mesial and 0.83 for distal). OHIP score was significantly reduced at T2 compared to T0 (P=0.003) for the entire cohort.

CONCLUSIONS

The augmentation of alveolar mucosa on the buccal aspect of single tooth implants is associated with clinically favorable outcomes. A fully digital workflow has been validated to permit crown delivery on CAD/CAM abutments without implant impressions.

Evaluation of nanoscale versus hybrid micro/nano surface topographies for endosseous implants

We examined the effect of a nanoscale titanium surface topography (D) versus two hybrid micro/nanoscale topographies (B and OS) on adherent mesenchymal stem cells (MSCs) and bone marrow derived macrophages (BMMs) function in cell culture and in vivo. In the in vitro study, compared to OS and B surfaces, D surface induced earlier and greater cell spreading, and earlier and profound mRNA expression of RUNX2, Osterix and BMP2 in MSCs. D surface induced earlier and higher expression of RUNX2 and BMP2 and lower expression of inflammatory genes in implant adherent cells in vivo. Measurement of osteogenesis at implant surfaces showed greater bone-to-implant contact at D versus OS surfaces after 21 days. We explored the cell population on the D and OS implant surfaces 24 h after placement using single-cell RNA sequencing and identified distinct cell clusters including macrophages, neutrophils and B cells. D surface induced lower expression and earlier reduction of inflammatory genes expression in BMMs in vitro. BMMs on D, B and OS surfaces demonstrated a marked increase of BMP2 expression after 1 and 3 days, and this increase was significantly higher on D surface at day 3. Our data implicates a dynamic process that may be influenced by nanotopography at multiple stages of osseointegration including initial immunomodulation, recruitment of MSCs and later osteoblastic differentiation leading to bone matrix production and mineralization. The results suggest that a nanoscale topography (D) favorably modulates adherent macrophage polarization toward anti-inflammatory and regenerative phenotypes and promotes the osteoinductive phenotype of adherent mesenchymal stem cells. STATEMENT OF SIGNIFICANCE: Our manuscript contains original data developed to define effects of a novel nanotopography on the process of osseointegration at the cell and tissue level.  Few studies have compared the effects of a nanoscale surface versus the more typical hybrid micro/nano-scale surfaces used today. We have utilized single-cell RNA sequencing for the first time to identify earliest cell populations on implant surfaces in vivo. We provide data indicating that the nanoscale surface acts upon both osteoprogenitor and immune cell (macrophages) to alter the process of bone formation in a surface-specific manner. This work represents new observations regarding osseointegration and immunomodulation.

Comparative Osteogenesis of Three Clinical Bone Graft Materials: An In Vivo Study

PURPOSE

To investigate bone regeneration among three different bone graft materials in a rat calvarum model.

MATERIALS AND METHODS

A total of 24 rats had two 5-mm defects placed per calvarial. Rats were divided into four groups: bovine xenograft (XG), demineralized bone matrix (DBM), mineralized bone graft (MBG), and collagen membrane control (CC). Within each group, samples were collected at two time points: 4 weeks (T4) and 8 weeks (T8). Bone regeneration was assessed by microcomputed tomography (micro-CT) imaging and was analyzed using MATLAB software. Additionally, the fixed samples were subsequently demineralized for immunohistochemistry and histomorphometry. Slides were mounted and stained with hematoxylin and eosin (H&E) stain as well as bone morphogenetic protein 2 (BMP-2) and runt-related transcription factor 2 (RUNX2) markers. The numbers of positive cells/area were calculated for each group and analyzed.

RESULTS

At 4 weeks, DBM showed low mineral density (7.7%) compared to the control (25.2%), but increased dramatically at 8 weeks (DBM, T8 = 27.6%; CC, T8 = 27.2%). Xenograft material showed an increase in mineral desnity between T4 and T8 (XG, T4 = 25.0%; XG, T8 = 32.3%). MBG remained consistent over the 8-week trial period (MBG, T4 = 30.4%; MBG, T8 = 30.4%). BMP-2 expression was present in cells adherent to all graft materials. RUNX2 expression was also observed in cells adherent to all graft materials, indicating that during the 4- to 8-week healing period, all materials supported osteogenesis.

CONCLUSIONS

Compared to other materials, the DBM had high osteoinductive properties during the 4- to 8-week time period based on increased mineral content. All materials were associated with immunohistologic evidence of osteogenesis in the rat calvarial defect model.

Can patients detect peri‑implant mucosal inflammation? Results from a multicentre randomized trial

PURPOSE

The objective of this study was to compare patient-reported outcomes (PROs) of peri‑implant soft tissue inflammation and aesthetics around single-tooth implants in the anterior maxillary region with three different implant-abutment interface designs.

METHODS

Participants were randomized to one of three different types of implant-abutment interface designs [Conical (CI), flat-to-flat (FI), and Platform Switched (PS)]. Implants and provisional crowns with prefabricated titanium abutments were placed 5 months following extraction and/or ridge augmentation. Permanent ceramic crowns with zirconia abutments were placed after 12 weeks. To assess PROs, appearance and inflammation questionnaires were completed from provisional crown placement to the 3-year follow-up.

RESULTS

Tooth appearance at the 3-year follow-up revealed a difference amongst CI, FI and PS implants (p=0.049; Kruskal-Wallis test). PS was rated better than FI (p=0.047) at 1 year for appearance of soft-tissue and satisfaction with colour. There were no differences for self-consciousness, smile and pain/discomfort while eating/hard food items.

CONCLUSIONS

Although participants tended to rate the health of mucosa around PS implants as slighty better than the other two implant systems, the differences were minimal and inconsistent. Thus, patient satisfaction in terms self-perceived gingival health and esthetics was high for all 3 systems tested, suggesting that patients are unable to detect mucosal inflammation.

CLINICAL SIGNIFICANCE

Patients find it difficult to perceive mucosal inflammation; hence, it is recommended that patients attend implant follow-up visits, even if they do not perceive inflammation. The study suggests that there is a relationship between the PROs and the clinical outcomes of tested implants.

Tribute to Dianne Rekow-Dental "Imagineer"

Elizabeth Dianne Rekow, BSME, MSME, MBA, DDS, MS, Certificate in Orthodontics, and PhD (1944-2022), was a dental science futurist pursuing brave new paths during her career. She was one of the pivotal scientists who initiated the CAD/CAM movement in the 1980s and went on to focus on digital dentistry for the rest of her career. Her professional contributions involved seven patents, 92 peer-reviewed publications, 10 book contributions, 31 proceeding contributions, and well over 100 national and international presentations. She was an avid supporter of women in science. Her greatest contribution was her expansive imagination. She served as 35th president of the American Association for Dental, Oral, and Craniofacial Research in 2006-2007 and 88th president of the International Association for Dental Research in 2011-2012. The present article reviews key elements of her career and includes testimonies from friends about her special relationships.

Topography-mediated immunomodulation in osseointegration; Ally or Enemy

Osteoimmunology is at full display during endosseous implant osseointegration. Bone formation, maintenance and resorption at the implant surface is a result of bidirectional and dynamic reciprocal communication between the bone and immune cells that extends beyond the well-defined osteoblast-osteoclast signaling. Implant surface topography informs adherent progenitor and immune cell function and their cross-talk to modulate the process of bone accrual. Integrating titanium surface engineering with the principles of immunology is utilized to harness the power of immune system to improve osseointegration in healthy and diseased microenvironments. This review summarizes current information regarding immune cell-titanium implant surface interactions and places these events in the context of surface-mediated immunomodulation and bone regeneration. A mechanistic approach is directed in demonstrating the central role of osteoimmunology in the process of osseointegration and exploring how regulation of immune cell function at the implant-bone interface may be used in future control of clinical therapies. The process of peri-implant bone loss is also informed by immunomodulation at the implant surface. How surface topography is exploited to prevent osteoclastogenesis is considered herein with respect to peri-implant inflammation, osteoclastic precursor-surface interactions, and the upstream/downstream effects of surface topography on immune and progenitor cell function.

Biomaterials and Extracellular Vesicle Delivery: Current Status, Applications and Challenges

In this review, we will discuss the current status of extracellular vesicle (EV) delivery via biopolymeric scaffolds for therapeutic applications and the challenges associated with the development of these functionalized scaffolds. EVs are cell-derived membranous structures and are involved in many physiological processes. Naïve and engineered EVs have much therapeutic potential, but proper delivery systems are required to prevent non-specific and off-target effects. Targeted and site-specific delivery using polymeric scaffolds can address these limitations. EV delivery with scaffolds has shown improvements in tissue remodeling, wound healing, bone healing, immunomodulation, and vascular performance. Thus, EV delivery via biopolymeric scaffolds is becoming an increasingly popular approach to tissue engineering. Although there are many types of natural and synthetic biopolymers, the overarching goal for many tissue engineers is to utilize biopolymers to restore defects and function as well as support host regeneration. Functionalizing biopolymers by incorporating EVs works toward this goal. Throughout this review, we will characterize extracellular vesicles, examine various biopolymers as a vehicle for EV delivery for therapeutic purposes, potential mechanisms by which EVs exert their effects, EV delivery for tissue repair and immunomodulation, and the challenges associated with the use of EVs in scaffolds.

C5a complement receptor modulates odontogenic dental pulp stem cell differentiation under hypoxia

AIM

Alterations in the microenvironment change the phenotypes of dental pulp stem cells (DPSCs). The role of complement component C5a in the differentiation of DPSCs is unknown, especially under oxygen-deprived conditions. The aim of this study was to determine the effect of C5a on the odontogenic differentiation of DPSCs under normoxia and hypoxia.

MATERIAL AND METHODS

Human DPSCs were subjected to odontogenic differentiation in osteogenic media and treated with the C5a receptor antagonist-W54011 under normal and hypoxic conditions (2% oxygen). Immunochemistry, western blot, and PCR analysis for the various odontogenic differentiation genes/proteins were performed.

RESULTS

Our results demonstrated that C5a plays a positive role in the odontogenic differentiation of DPSCs. C5a receptor inhibition resulted in a significant decrease in odontogenic differentiation genes, such as DMP1, ON, RUNX2, DSPP compared with the control. This observation was further supported by the Western blot data for DSPP and DMP1 and immunohistochemical analysis. The hypoxic condition reversed this effect.

CONCLUSIONS

Our results demonstrate that C5a regulates the odontogenic DPSC differentiation under normoxia. Under hypoxia, C5a exerts a reversed function for DPSC differentiation. Taken together, we identified that C5a and oxygen levels are key initial signals during pulp inflammation to control the odontogenic differentiation of DPSCs, thereby, providing a mechanism for potential therapeutic interventions for dentin repair and vital tooth preservation.

Extracellular Vesicles From TNFα Preconditioned MSCs: Effects on Immunomodulation and Bone Regeneration

Mesenchymal stem cells show remarkable versatility and respond to extracellular and micro environmental cues by altering their phenotype and behavior. In this regard, the MSC’s immunomodulatory properties in tissue repair are well documented. The paracrine effects of MSCs in immunomodulation are, in part, attributable to their secreted extracellular vesicles (EVs). When MSCs migrate to the wound bed, they are exposed to a myriad of inflammatory signals. To understand their response to an inflammatory environment from an EV perspective, we sought to evaluate the effects of the inflammatory cytokine TNFα on MSC EV mediated immunomodulation. Our results indicate that while the physical characteristics of the EVs remain unchanged, the TNFα preconditioned MSC EVs possess enhanced immunomodulatory properties. In vitro experiments using polarized (M1 and M2) primary mouse macrophages indicated that the preconditioned MSC EVs suppressed pro-inflammatory (M1) markers such as IL-1β and iNOS and elevated reparatory (M2) markers such as Arg1 and CD206. When evaluated in vivo in a rat calvarial defect model, the TNFα preconditioned MSC EVs reduced inflammation at 1-, 3- and 7-days post wounding resulting in the subsequent enhanced bone formation at 4- and 8-weeks post wounding possibly by modulation of oncostatin M (OSM) expression. An analysis of EV miRNA composition revealed significant changes to anti-inflammatory miRNAs in the preconditioned MSC EVs hinting at a possible role for EV derived miRNA in the enhanced immunomodulatory activity. Overall, these results indicate that MSC exposure to inflammatory signals influence the MSC EV’s immunomodulatory function in the context of tissue repair. The specific function of TNFα preconditioned MSC EV miRNAs in immunomodulatory control of bone regeneration merits further investigation.

Ti-Ions and/or Particles in Saliva Potentially Aggravate Dental Implant Corrosion

The corrosive titanium products in peri-implant tissues are a potential risk factor for peri-implantitis. There is very limited information available on the effect of the corrosion and wear products on the dental implant corrosion. Therefore, we determined the influence of Ti-ions and Ti-particles on Ti corrosion. Eighteen commercially pure-Ti-grade-2 discs were polished to mirror-shine. Samples were divided into six groups (n = 3) as a function of electrolytes; (A) Artificial saliva (AS), (B) AS with Ti-ions (the electrolyte from group A, after corrosion), (C) AS with Ti-particles 10 ppm (D) AS with Ti-particles 20 ppm, (E) AS with Ti-ions 10 ppm, and (F) AS with Ti-ions 20 ppm. Using Tafel’s method, corrosion potential (E_corr) and current density (I_corr) were estimated from potentiodynamic curves. Electrochemical Impedance Spectroscopy (EIS) data were used to construct Nyquist and Bode plots, and an equivalent electrical circuit was used to assess the corrosion kinetics. The corroded surfaces were examined through a 3D-white-light microscope and scanning electronic microscopy. The data demonstrated that the concentration of Ti-ions and corrosion rate (I_corr) are strongly correlated (r = 0.997, p = 0.046). This study indicated that high Ti-ion concentration potentially aggravates corrosion. Under such a severe corrosion environment, there is a potential risk of increased implant associated adverse tissue reactions.

Effect of H2O2 Antiseptic on Dispersal of Cavitation-Induced Microdroplets

The persisting outbreak of SARS-CoV-2 has posed an enormous threat to global health. The sustained human-to-human transmission of SARS-CoV-2 via respiratory droplets makes the medical procedures around the perioral area vulnerable to the spread of the disease. Such procedures include the ultrasonic dental cleaning method, which occurs within the oral cavity and involves cavitation-induced sprays, thus increasing the risk of pathogen transmission via advection. To understand the associated health and safety risks for patients and clinicians, it is critical to understand the flow pattern of the spray cloud around the operating region, the size and velocity distribution of the emitted droplets, and the extent of fluid dispersion until ultimate deposit on surfaces or escape through air vents. In this work, the droplet size and velocity distributions of the spray emerging from the tip of a free-standing common ultrasonic dental cleaning device were characterized via high-speed imaging. Deionized water and 1.5% and 3% aqueous hydrogen peroxide (H₂O₂) solutions were used as working fluids, with the H₂O₂-an established oxidizing agent-intended to curb the survival of virus released in aerosols generated from dental procedures. The measurements reveal that the presence of H₂O₂ in the working fluid increases the mean droplet size and ejection velocity. Detailed computational fluid dynamic simulations with multiphase flow models reveal benefits of adding small amounts of H₂O₂ in the feed stream of the ultrasonic cleaner; this practice causes larger droplets with shorter residence times inside the clinic before settling down or escaping through air vents. The results suggest optimal benefits (in terms of fluid spread) of adding 1.5% H₂O₂ in the feed stream during dental procedures involving ultrasonic tools. The present findings are not specific to the COVID-19 pandemic but should also apply to future outbreaks caused by airborne droplet transmission.

Testing for COVID-19 in dental offices: Mechanism of action, application, and interpretation of laboratory and point-of-care screening tests

BACKGROUND

The dental office potentially possesses all transmission risk factors for severe acute respiratory syndrome coronavirus 2. Anticipating the future widespread use of COVID-19 testing in dental offices, the authors wrote this article as a proactive effort to provide dental health care providers with current and necessary information surrounding the topic.

METHODS

The authors consulted all relevant and current guidelines from the Centers for Disease Control and Prevention and the US Food and Drug Administration, as well as online resources and review articles.

RESULTS

Routine COVID-19 screening and triage protocols are unable to detect all infected people. With the advancements in diagnostic tools and techniques, COVID-19 testing at home or in the dental office may provide dentists with the ability to evaluate the disease status of their patients. At-home or point-of-care (POC) tests, providing results within minutes of being administered, would allow for appropriate measures and rapid decisions about dental patients' care process. In this review, the authors provide information about available laboratory and POC COVID-19 screening methods and identify and elaborate on the options available for use by dentists as well as the regulatory requirements of test administration.

CONCLUSIONS

Dentists need to be familiar with COVID-19 POC testing options. In addition to contributing to public health, such tests may deliver rapid, accurate, and actionable results to clinical and infection control teams to enhance the safe patient flow in dental practices.

PRACTICAL IMPLICATIONS

Oral health care must continue to offer safety in this or any future pandemics. Testing for severe acute respiratory syndrome coronavirus 2 at the POC offers a control mechanism contributing to and enhancing the real and perceived safety of care in the dental office setting.

The importance of cellular and exosomal miRNAs in mesenchymal stem cell osteoblastic differentiation

The differentiation of osteoblasts is under complex regulation that includes autocrine and paracrine signaling from MSCs. Exosomes are important components of the MSC secretome and their cargo contains numerous miRNAs. In this study, the importance of MSC miRNAs in modulation of osteoblastic differentiation was examined by global reduction of miRNA biosynthesis in Dicer knock down hMSCs. We additionally impaired hMSC responses to miRNAs by knockdown of Argonaute 2 expression. Knockdown of Dicer and Argonaute 2 both reduced osteoblastic differentiation of hMSCs. This was observed at the levels of hMSC culture mineralization and osteoblastic gene expression. The treatment of Dicer deficient hMSCs with wild type hMSC exosomes effectively recovered the impaired osteoblastic differentiation. Dicer knockdown reduced the quantity and diversity of miRNAs present in hMSC exosomes. miRSeq data and KEGG analysis implicated the miRNA-dependent effects on multiple osteoinductive pathways in Dicer deficient cells, including the Hippo signaling and TGF-beta signaling pathways. Treatment of hMSCs with mimics of miRNAs significantly downregulated in Dicer knockdown cells recovered functions of exosome-mediated signaling in hMSCs. These results indicate that hMSC exosomes exert miRNA-dependent control that contributes to osteoblastic differentiation.

Characteristics and Detection Rate of SARS-CoV-2 in Alternative Sites and Specimens Pertaining to Dental Practice: An Evidence Summary

Knowledge about the detection potential and detection rates of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) in various body fluids and sites is important for dentists since they, directly or indirectly, deal with many of these fluids/sites in their daily practices. In this study, we attempt to review the latest evidence and meta-analysis studies regarding the detection rate of SARS-CoV-2 in different body specimens and sites as well as the characteristics of these sample. The presence/detection of SARS-CoV-2 viral biomolecules (nucleic acid, antigens, antibody) in different clinical specimens depends greatly on the specimen type and timing of collection. These specimens/sites include nasopharynx, oropharynx, nose, saliva, sputum, bronchoalveolar lavage, stool, urine, ocular fluid, serum, plasma and whole blood. The relative detection rate of SARS-CoV-2 viral biomolecules in each of these specimens/sites is reviewed in detail within the text. The infectious potential of these specimens depends mainly on the time of specimen collection and the presence of live replicating viral particles.

Computer simulation of the SARS-CoV-2 contamination risk in a large dental clinic

COVID-19, caused by the SARS-CoV-2 (severe acute respiratory syndrome coronavirus 2) virus, has been rapidly spreading worldwide since December 2019, causing a public health crisis. Recent studies showed SARS-CoV-2's ability to infect humans via airborne routes. These motivated the study of aerosol and airborne droplet transmission in a variety of settings. This study performs a large-scale numerical simulation of a real-world dentistry clinic that contains aerosol-generating procedures. The simulation tracks the dispersion of evaporating droplets emitted during ultrasonic dental scaling procedures. The simulation considers 25 patient treatment cubicles in an open plan dentistry clinic. The droplets are modeled as having a volatile (evaporating) and nonvolatile fraction composed of virions, saliva, and impurities from the irrigant water supply. The simulated clinic's boundary and flow conditions are validated against experimental measurements of the real clinic. The results evaluate the behavior of large droplets and aerosols. We investigate droplet residence time and travel distance for different droplet diameters, surface contamination due to droplet settling and deposition, airborne aerosol mass concentration, and the quantity of droplets that escape through ventilation. The simulation results raise concerns due to the aerosols' long residence times (averaging up to 7.31 min) and travel distances (averaging up to 24.45 m) that exceed social distancing guidelines. Finally, the results show that contamination extends beyond the immediate patient treatment areas, requiring additional surface disinfection in the clinic. The results presented in this research may be used to establish safer dental clinic operating procedures, especially if paired with future supplementary material concerning the aerosol viral load generated by ultrasonic scaling and the viral load thresholds required to infect humans.

A 5-Year Esthetic RCT Assessment of Anterior Maxillary Single-Tooth Implants with Different Abutment Interfaces

PURPOSE

This study sought to define the tissue responses at different implant-abutment interfaces by studying bone and peri-implant mucosal changes using a 5-year prospective randomized clinical trial design study. The conus interface was compared with the flat-to-flat interface and platform-switched implant-abutment systems.

MATERIALS AND METHODS

One hundred forty-one subjects were recruited and randomized to the three treatment groups according to defined inclusion and exclusion criteria. Following implant placement and immediate provisionalization in healed alveolar ridges, clinical, photographic, and radiographic parameters were measured at 6 months and annually for 5 years. The calculated changes in marginal bone levels, peri-implant mucosal zenith location, papillae lengths, and peri-implant Plaque Index and bleeding on probing were statistically compared.

RESULTS

Forty-eight conus interface implants, 49 flat-to-flat interface implants, and 44 platform-switched implants were placed in 141 subjects. Six platform-switched interface and eight flatto- flat interface implants failed, most of them within 3 months. After 5 years, 33 conical interface, 28 flat-to-flat interface, and 27 platform-switched interface implants remained for evaluation. Calculation of marginal bone level change showed a mean marginal bone loss of -0.16 ± 0.45 (-1.55 to 0.65), -0.92 ± 0.70 (-2.90 to 0.20), and -0.81 ± 1.06 (-3.35 to 1.35) mm for conical interface, flat-to-flat interface, and platform-switched interface implants, respectively (P < .0005). The peri-implant mucosal zenith changes were minimal for all three interface designs (0.10 mm and +0.08 mm, P > .60). Only 16% to 19% of the surfaces had presence of bleeding on probing, with no significant differences (P > .81) between groups. Interproximal tissue changes were positive and similar among the implant interface designs.

CONCLUSION

Over 5 years, the immediate provisionalization protocol resulted in stable peri-implant mucosal responses for all three interfaces. Compared with the flat-to-flat and platform-switched interfaces, the conical interface implants demonstrated significantly less early marginal bone loss. The relationship of marginal bone responses and mucosal responses requires further experimental consideration.

Macrophage Control of Incipient Bone Formation in Diabetic Mice

Both soft and hard tissue wound healing are impaired in diabetes. Diabetes negatively impacts fracture healing, bone regeneration and osseointegration of endosseous implants. The complex physiological changes associated with diabetes often manifest in immunological responses to wounding and repair where macrophages play a prominent role in determining outcomes. We hypothesized that macrophages in diabetes contribute toward impaired osseous wound healing. To test this hypothesis, we compared osseous wound healing in the mouse calvaria defect model using macrophages from C57BL/6J and db/db mice to direct osseous repair in both mouse strains. Initial analyses revealed that db/db mice macrophages showed an inflamed phenotype in its resting state. Incipient bone regeneration evaluated by μCT indicated that bone regeneration was relatively impaired in the db/db mouse calvaria and in the calvaria of C57BL/6J mice supplemented with db/db macrophages. Furthermore, osteogenic differentiation of mouse mesenchymal stem cells was negatively impacted by conditioned medium from db/db mice compared to C57BL/6J mice. Moreover, miR-Seq analysis revealed an altered miRNA composition in db/db macrophages with up regulated pro-inflammatory miRNAs and down regulated anti-inflammatory miRNAs. Overall, this study represents a direct step toward understanding macrophage-mediated regulation of osseous bone regeneration and its impairment in type 2 diabetes mellitus.

A digital approach to robust and esthetic implant overdenture construction

OBJECTIVE

Overdenture therapy is an important option for implant rehabilitation. However, numerous reports suggest that mechanical/technical complications and failures can limit therapeutic success. The goal of this report is to illustrate a digital approach to design and construction of a robust overdenture with high-esthetic value.

MATERIALS AND METHODS

Beginning with new denture design to establish esthetic parameters, 3D modeling of a metal framework and the denture teeth are completed in a connected manner. This enables connection of rapidly printed, prototype dentition that is attached directly to the framework without intervening wax or acrylic components. Following evaluation of the dentition and required adjustments, the final dentition is milled from resin and processed to the selective laser sintered framework.

RESULTS

The advantages of the digital workflow include the control of dimensions and strength of the framework, the esthetic relationship of the framework to the dentition and the facilitation of esthetic try-in of the dentition.

CONCLUSION

Enhancing a robust overdenture can be readily achieved using a digital workflow.

CLINICAL SIGNIFICANCE

The use of digital technology enables the clinical team to plan and produce prostheses with dimensions and contours that support long-term function and esthetics. The clinical chair time can be potentially reduced by use of digital design that facilitates try-in and reduces major errors by improved communication between the patient, dentist, and technician.

Bone regeneration is mediated by macrophage extracellular vesicles

Multiple local and systemic factors including inflammation influence bone regeneration. Several lines of evidence demonstrate that macrophages contribute to the immunological regulation of MSC and osteoblast function during bone regeneration. Recent studies demonstrate that macrophage polarization influences this regulatory process. In this manuscript, we investigated the paracrine functional role of naïve (M0), M1 and M2 polarized macrophage derived EVs in bone repair. Treatment of rat calvaria defects with no EVs, M0 EVs, M1 EVs, or M2 EVs revealed polarization-specific control of bone regeneration by macrophage EVs at 3 and 6 weeks. M0 and M2 EVs promoted repair/regeneration and M1 EVs inhibited bone repair. Pathway-specific studies conducted in cell culture showed that M1 EVs negatively regulated the BMP signaling pathway, specifically BMP2 and BMP9. In parallel, miRNA sequencing studies showed similar miRNA cargo in M0 and M2 EVs and different miRNA cargo in M1 EVs. Functional examination of M1 macrophage EV-enriched miR-155 demonstrated that miR-155 mimic treatment reduced MSC osteogenic differentiation as measured by reduced BMP2, BMP9 and RUNX2 expression when compared to controls. Conversely, treatment of MSCs with the M2 macrophage EV-enriched miR-378a mimic increased MSC osteoinductive gene expression when compared to controls. These functional studies implicate polarized macrophage EV miRNAs in the positive or negative regulation of bone regeneration that was observed in vivo. Overall, the results presented in this study indicate that macrophage polarization influences EV cargo and related EV function in the paracrine regulation of bone regeneration.

Reopening dentistry after COVID-19: Complete suppression of aerosolization in dental procedures by viscoelastic Medusa Gorgo

The aerosol transmissibility of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) has impacted the delivery of health care and essentially stopped the provision of medical and dental therapies. Dentistry uses rotary, ultrasonic, and laser-based instruments that produce water-based aerosols in the daily, routine treatment of patients. Abundant aerosols are generated, which reach health care workers and other patients. Viruses, including SARS-CoV-2 virus and related coronavirus disease (COVID-19) pandemic, continued expansion throughout the USA and the world. The virus is spread by both droplet (visible drops) and aerosol (practically invisible drops) transmission. The generation of aerosols in dentistry-an unavoidable part of most dental treatments-creates a high-risk situation. The US Centers for Disease Control and The Occupational Safety and Health Administration consider dental procedures to be of "highest risk" in the potential spreading of SARS-CoV-2 and other respiratory viruses. There are several ways to reduce or eliminate the virus: (i) cease or postpone dentistry (public and personal health risk), (ii) screen patients immediately prior to dental treatment (by appropriate testing, if any), (iii) block/remove the virus containing aerosol by engineering controls together with stringent personal protective equipment use. The present work takes a novel, fourth approach. By altering the physical response of water to the rotary or ultrasonic forces that are used in dentistry, the generation of aerosol particles and the distance any aerosol may spread beyond the point of generation can be markedly suppressed or completely eliminated in comparison to water for both the ultrasonic scaler and dental handpiece.

Functionally engineered extracellular vesicles improve bone regeneration

Lineage specific differentiation of host mesenchymal stem cells (MSCs) is a necessary step for bone repair/regeneration. Clinically, growth factors such as bone morphogenetic protein 2 (BMP2) are used to enhance/hasten this process to heal critical sized defects. However, the clinical application of such growth factors is fraught with dosage challenges as well as immunological and ectopic complications. The identification of extracellular vesicles (EVs) as active components of the MSC secretome suggest alternative approaches to enhancing bone regeneration. Based on our earlier studies on the properties of EVs from lineage specified MSCs, this study sought to engineer EVs to enhance osteogenic differentiation. To generate MSC EVs with enhanced osteoinductive abilities, genetically modified human bone marrow derived MSCs (HMSCs) were generated by constitutively expressing BMP2. We hypothesized that these cells would generate functionally engineered EVs (FEEs) with enhanced osteoinductive properties. Our results show that these FEEs maintained the general physical and biochemical characteristics of naïve HMSC EVs in the form of size distribution, EV marker expression and endocytic properties but show increased bone regenerative potential compared to MSC EVs in a rat calvarial defect model in vivo. Mechanistic studies revealed that although BMP2 was constitutively expressed in the parental cells, the corresponding EVs (FEEs) do not contain BMP2 protein as an EV constituent. Further investigations revealed that the FEEs potentiate the BMP2 signaling cascade possibly due to an altered miRNA composition. Collectively, these studies indicate that EVs' functionality may be engineered by genetic modification of the parental MSCs to induce osteoinduction and bone regeneration. SIGNIFICANCE STATEMENT: With mounting evidence for the potential of MSC EVs in treatment of diseases and regeneration of tissues, it is imperative to evaluate if they can be modified for application specificity. The results presented here indicate the possibility for generating Functionally Engineered EVs (FEEs) from MSC sources. As a proof of concept approach, we have shown that EVs derived from genetically modified MSCs (BMP2 overexpression) can be effective as biomimetic substitutes for growth factors for enhanced tissue-specific regeneration (bone regeneration) in vivo. Mechanistic studies highlight the role of EV miRNAs in inducing pathway-specific changes. We believe that this study will be useful to researchers evaluating EVs for regenerative medicine applications.

Engineering a Self-Assembling Leucine Zipper Hydrogel System with Function-Specific Motifs for Tissue Regeneration

Protein-based self-assembling hydrogels can exhibit remarkably tunable properties as a scaffold for regenerative medicine applications. In this study, we sought to develop a leucine zipper (LZ) based self-assembling hydrogel with function-specific motifs for tissue-specific regeneration. As a proof-of-concept approach, we incorporated (a) calcium-binding domains ESQES and QESQSEQS derived from dentin matrix protein 1 (DMP1) and (b) an heparin-binding domain adjacent preceded by an MMP2 (matrix metalloprotease 2) cleavage site to facilitate loading of heparin binding growth factors, such as BMP-2, VEGF, and TGF-β1, and their release in vivo by endogenous MMP2 proteolytic cleavage. These scaffolds were characterized and evaluated in vitro and in vivo. In vivo studies highlighted the potential of the engineered LZ hydrogel with respect to osteogenic differentiation of stem cells. The premineralized LZ scaffold loaded with HMSCs showed an enhanced osteoinductive property when compared with the control nonmineralized scaffold. The LZ backbone with heparin-binding domain containing an MMP2 cleavage site facilitated tethering of heparin-binding growth factors, such as VEGF, TGF-β1 and BMP2 and demonstrated controlled release of these active growth factor both in vitro and in vivo and demonstrated growth factor specific activity in vivo (BMP-2 and TGF-β1). Overall, we present a versatile protein based self-assembling system with tunable properties for tissue regeneration.

Comprehensive Rehabilitation for a Permanent Tooth Anodontia Patient Using an Integrated Digital Approach

Agenesis of the permanent dentition is rare. This report describes a 20-year-old woman with 19 deciduous teeth, a single permanent mandibular premolar, and other physical traits associated with ectodermal dysplasia. The patient demonstrated esthetic parameters associated with maxillomandibular alveolar insufficiency, and her chief complaints were directed toward esthetics and the potential impact of restorative choices on function. Three typical options for restoration include overdentures, removable partial dentures, or implant-supported prostheses replacing her natural dentition. This report illustrates a fully integrated digital approach to treatment planning, the fabrication of a computer-aided design/computer-assisted manufacture surgical guide and provisional restoration, guided implant placement, and definitive restoration using monolithic zirconia implant-supported fixed dental prostheses. The lifelong management of this rehabilitation is an acknowledged challenge.

Evaluating the Endocytosis and Lineage-Specification Properties of Mesenchymal Stem Cell Derived Extracellular Vesicles for Targeted Therapeutic Applications

Mesenchymal stem cells (MSCs) are multipotent cells with regenerative and immunomodulatory properties. Several aspects of MSC function have been attributed to the paracrine effects of MSC derived extracellular vesicles (EVs). Although MSC EVs show great promise for regenerative medicine applications, insights into their uptake mechanisms by different target cells and the ability to control MSC EV properties for defined function in vivo have remained elusive knowledge gaps. The primary goal of this study is to elucidate how the basic properties of MSC derived EVs can be exploited for function-specific activity in regenerative medicine. Our first important observation is that, MSC EVs possess a common mechanism of endocytosis across multiple cell types. Second, altering the MSC state by inducing differentiation into multiple lineages did not affect the exosomal properties or endocytosis but triggered the expression of lineage-specific genes and proteins in vitro and in vivo respectively. Overall, the results presented in this study show a common mechanism of endocytosis for MSC EVs across different cell types and the feasibility to generate functionally enhanced EVs by modifications to parental MSCs.

A Role for Exosomes in Craniofacial Tissue Engineering and Regeneration

Tissue engineering and regenerative medicine utilize mesenchymal stem cells (MSCs) and their secretome in efforts to create or induce functional tissue replacement. Exosomes are specific extracellular vesicles (EVs) secreted by MSCs and other cells that carry informative cargo from the MSC to targeted cells that influence fundamental cellular processes including apoptosis, proliferation, migration, and lineage-specific differentiation. In this report, we review the current knowledge regarding MSC exosome biogenesis, cargo and function. This review summarizes the use of MSC exosomes to control or induce bone, cartilage, dentin, mucosa, and pulp tissue formation. The next-step engineering of exosomes provides additional avenues to enhance oral and craniofacial tissue engineering and regeneration.

Are Nongrafting Solutions Viable for Dental Implant Treatment in Limited Bone Volume?

Dental implant therapies must be planned and executed to meet both the immediate and longer-term expectations of patients. The early developmental success of dental implants was dependent on the quality and quantity of a patient's bone. Implants were commonly placed into the parasymphyseal mandibular and anterior maxillary bone. Building on this success, bone grafting allowed patients lacking sufficient bone to obtain implant-supported prosthetic solutions for treatment of partial or complete edentulism. More recently, several nongrafting solutions for implant therapy, including pterygoid implants, zygomatic implants, tilted implants, and short implants, have reported success. This article will consider the rationale for graftless solutions in implant therapy as well as the data supporting the use of various graftless protocols as alternatives to grafting and conventional dental implant therapy. It will discuss factors concerning graftless versus grafted approaches to treatment of patients with limited bone volume and will describe the use of short dental implants as a graftless solution in the edentulous maxilla.

The Role of MicroRNAs in the Osseointegration Process

Regulation of cellular function is key to bone formation at endosseous implant surfaces. Osseointegration was "discovered" prior to the discovery of genetic regulation of osteoinduction or characterization of mesenchymal stem cells. Understanding osseointegration in cellular and molecular terms has benefited from genome-wide characterization of this healing process at endosseous implants in vivo. These in vivo studies also demonstrate a role for osteoprogenitor cells and cells involved in immune regulation and osteoclastogenesis. The identification of noncoding RNAs, including microRNAs, as key factors controlling cell function has highlighted the role of microRNAs in cell differentiation control. This review summarizes emerging in vitro and in vivo investigations emphasizing the role of microRNAs in the osseointegration process. Many microRNAs influence key osteoinductive pathways controlling Osterix, runt-related transcription factor 2 (RUNX2), and bone morphogenetic protein (BMP)/SMAD function. Others influence the monocyte/macrophage lineage. While significant progress has been made in elucidating the mechanisms associated with the regulation of surface modulation of osteoblast differentiation by microRNAs, knowledge gaps are evident in the identification and characterization of microRNAs linked to osseointegration. Given existing knowledge regarding the varied expression of microRNAs and their role in inflammation, it is important to understand how microRNA expression may influence the process of bone accrual at implant surfaces during osseointegration.

Retrospective cohort analysis of maxillary overdentures retained by unsplinted implants

STATEMENT OF PROBLEM

Implant therapy involving an unsplinted 2-implant-retained overdenture is well defined as a successful treatment for a patient with an edentulous mandible. However, a similar unsplinted implant therapy supporting a maxillary overdenture is not well characterized.

PURPOSE

The purpose of this retrospective study was to evaluate maxillary overdentures retained by 4 unsplinted implants measuring implant survival, overdenture survival, and patient-reported outcomes.

MATERIAL AND METHODS

Participants who had received an unsplinted implant-retained maxillary overdenture were included in the study. Participants presented for one denture recall appointment, during which comprehensive examination, including radiographs, was performed and clinical findings were recorded. Participants also completed the Oral Health Impact Profile-49 (OHIP-49) and a 20-item visual analog scale (VAS) satisfaction questionnaire. Nonparametric statistical tests were used to compare OHIP-49 and VAS scores across age, sex, time since overdenture insertion, mandibular dental status, smoking status, maxillary mucosal health, and overdenture hygiene.

RESULTS

For the 44 participants, 3 of 4 implants failed in 1 individual. The cumulative implant survival rate was 98% (97.7% patient level). No prosthetic failures (that is, overdenture replacement) occurred, indicating a 100% prosthesis survival rate. The mean ±standard deviation OHIP-49 severity score was 23.6 ±26.0, and the mean ±standard deviation total VAS score was 179.2 ±29.4. Increased age was associated with lower OHIP-49 severity score (P=.036), and participants with unhealthy oral mucosa or denture stomatitis demonstrated significantly higher OHIP-49 severity scores (P=.003).

CONCLUSIONS

In this retrospective evaluation, unsplinted implant-retained maxillary overdenture therapy was associated with high implant and prosthetic survival, as well as high patient satisfaction and quality of life. Age, sex, maxillary mucosal health, and mandibular dental status resulted in significant differences with respect to oral health-related quality of life and patient satisfaction, indicating that this treatment option may be ideal for certain patients.

Management of Implant/Prosthodontic Complications

Dental implants continue to grow in popularity because they are a predictable treatment to replace missing teeth. They have a high success rate; however, they are still associated with some clinical complications. This article discusses a diverse range of complications related to the restorative and mechanical aspects of dental implants and the management of such complications, as well as potential factors contributing to them.

Prosthodontic Management of Implant Therapy: Esthetic Complications

The essential promise of implant dentistry is the ability to imperceptibly replace missing teeth. To achieve this, careful planning, execution, and maintenance is required by the dentist and patient to maintain a long-term esthetic and functional result. Unfortunately, as a result of biological, prosthetic, and iatrogenic factors, unesthetic results can occur. This article explores the potential causes for the unesthetic dental implant and the possible solutions that may improve the clinical situation. Whereas relatively simple errors may be corrected through prosthetic means, greater complications may require surgical intervention to achieve the desired result.

C5L2 Regulates DMP1 Expression during Odontoblastic Differentiation

The presence of stem cells within the dental-pulp tissue as well as their differentiation into a new generation of functional odontoblast-like cells constitutes an important step of the dentin-pulp regeneration. Recent investigations demonstrated that the complement system activation participates in 2 critical steps of dentin-pulp regeneration: pulp progenitor's recruitment and pulp nerve sprouting. Surprisingly, its implication in odontoblastic differentiation has not been addressed yet. Since the complement receptor C5a receptor-like 2 (C5L2) is expressed by different stem cells, the aim of this study is to investigate if the dental pulp stem cells express C5L2 and if this receptor participates in odontoblastic differentiation. Immunohistochemistry performed on human third molar pulp sections showed a perivascular co-localization of the mesenchymal stem cell markers STRO1 and C5L2. In vitro immunofluorescent staining confirmed that hDPSCs express C5L2. Furthermore, we determined by real-time polymerase chain reaction that the expression of C5L2 is highly modulated in human dental pulp stem cells (hDPSCs) undergoing odontoblastic differentiation. Moreover, we showed that this odontogenesis-regulated expression of C5L2 is specifically potentiated by the proinflammatory cytokine TNFα. Using a C5L2-siRNA silencing strategy, we provide direct evidence that C5L2 constitutes a negative regulator of the dentinogenic marker DMP1 (dentin matrix protein 1) expression by hDPSCs. Our findings suggest a direct correlation between the odontoblastic differentiation and the level of C5L2 expression in hDPSCs and identify C5L2 as a negative regulator of DMP1 expression by hDPSCs during the odontoblastic differentiation and inflammation processes. This work is the first to demonstrate the involvement of C5L2 in the biological function of stem cells, provides an important knowledge in understanding odontoblastic differentiation of dental pulp stem cells, and may be useful in future dentin-pulp engineering strategies.

C5L2 Silencing in Human Pulp Fibroblasts Enhances Nerve Outgrowth Under Lipoteichoic Acid Stimulation

INTRODUCTION

We recently reported that caries-associated C5a receptor (C5aR) expression and activation result in up-regulation of brain-derived neurotropic factor secretion by pulp fibroblasts inducing prominent neurite outgrowth toward the carious site. Our data further showed a negative regulation of this brain-derived neurotropic factor secretion by C5L2, another C5aR. C5L2 was considered a nonfunctional receptor and thus has received much less attention than C5aR. The aim of this study was to identify the role of C5L2 in pulp fibroblast-mediated neurite outgrowth.

METHODS

In this study, lipoteichoic acid (LTA) was used to mimic dental caries-like inflammation. To evaluate the role of C5L2 in pulp neurite outgrowth, human pulp fibroblasts were C5L2 small interfering RNA silenced and cocultured with human neurons in a nerve growth assay system.

RESULTS

C5L2 silencing drastically increased the neurite outgrowth toward the LTA-stimulated pulp fibroblasts. The number of neurites detected was increased in the LTA-treated pulp fibroblasts.

CONCLUSIONS

Our results show that C5L2 constitutes a negative regulator of the neurite outgrowth under LTA stimulation. Of the events occurring during dentin-pulp regeneration, nerve regeneration is the key factor for maintaining tooth viability after infection or injury. Our study provides a foundation for creating therapeutic tools that target pulp fibroblasts during pulp/nerve regeneration.

Immediate provisionalization of dental implants in grafted alveolar ridges in the esthetic zone: a 5-year evaluation

This clinical study assessed at 5 years both implant survival and peri-implant tissue architecture of immediately provisionalized implants placed 4 to 6 months following augmentation with demineralized bovine bone allograft and collagen membrane. Of 23 implants in 19 patients, one implant failed prior to loading (95.6% survival). Implant tissue relationships were stable following implant placement; marginal bone level changes from implant placement to 5 years (mean ± SD: -0.18 ± 0.79 mm, range: -1.6 to 1.4 mm, P = .51), the mesial and distal papilla length changes (mesial mean ± SD: 1.14 ± 0.92 mm, P < .001; distal mean ± SD: 0.74 ± 1.46 mm, P = .04), and the unchanged mucosal zenith location (mean ± SD: 0.24 ± 0.93 mm, P = .15) were recorded. There were no major surgical complications during the 5-year period. When augmentation is required, subsequent dental implant placement in the anterior maxilla may be achieved using immediate placement and provisionalization protocol to attain osseointegration success and stable peri-implant tissue responses.

Fracture rate of monolithic zirconia restorations up to 5 years: A dental laboratory survey

STATEMENT OF PROBLEM

The demand for ceramic restorations has increased over the past years because of their esthetic properties and the high cost of noble metals. However, the lack of long-term clinical studies and the difficulty of interpreting in vitro studies have placed the durability of ceramic restorations in doubt.

PURPOSE

The purpose of this study was to determine the failure rate of monolithic zirconia restorations due to fracture up to 5 years of clinical performance.

MATERIAL AND METHODS

Data were collected over 5 years from 2 commercial dental laboratories. Restorations that were returned to the laboratory for remake because of catastrophic failure (fracture) were identified and included. Restorations were categorized as anterior or posterior. Each category was further divided into complete-coverage single crowns (SCs) and multiple-unit fixed dental prostheses (FDPs). Fracture rates were compared and analyzed using a chi-square test (α=.05).

RESULTS

A total of 39827 restoration records were reviewed and included 3731 anterior restorations (1952 SC; 1799 FDP) and 36096 posterior restorations (29808 SC; 6288 FDP). The overall fracture rate of up to 5 years for all restorations (anterior and posterior) was 1.09%. Fracture rates were 2.06% for all anterior restorations and 0.99% for all posterior restorations. Fracture rates were 0.97% for anterior SCs and 0.69% for posterior SCs, and the combined fracture rate (anterior and posterior) was 0.71%. For FDPs, 3.26% restorations fractured anteriorly and 2.42% fractured posteriorly, and the combined fracture rate (anterior and posterior) was 2.60%.

CONCLUSION

Within the relative short-term evaluation of 5 years, restorations fabricated from monolithic zirconia material displayed relatively low fracture rates. Anterior restorations fractured at a slightly higher rate than posterior restorations, and FDPs fractured at a rate double that of SCs.

A Digital Approach to Improved Overdentures for the Adolescent Oligodontia Patient

OBJECTIVE

The use of overdentures for treatment of oligodontia in adolescent patients using conventional techniques has described limitations. The aim of the case report is to demonstrate the use of CAD (Computer Aided Design) CAM (Computer Aided Manufacture) technology to produce an esthetic monolithic polymethylmethacrylate prosthesis that is retentive and stable on insertion.

CLINICAL CONSIDERATIONS

Adolescent oligodontia patients are typically not suitable candidates for dental implant therapy. Overdentures provide interim or definitive restorative advantages. Given the important esthetic, psychological, and social functions of the prosthesis, an important therapeutic goal for the overdenture prosthesis is esthetics. A CAD-CAM approach to overdenture manufacture can provide a highly esthetic, strong, and retentive prosthesis.

CONCLUSIONS

CAD-CAM manufacture of monolithic acrylic overdentures offer several advantages that include (1) improved planning and clinical communication, (2) high fidelity manufacture, (3) improved flexural strength, impact strength, and porosity, (4) improved prosthesis integrity and durability (due to the monolithic design), (5) CNC control of occlusal contacts, (6) high esthetic potential due to quality of bulk material and iterative design, and (7) archival nature of the digital prosthesis. CAD-CAM manufacture of monolithic overdentures is a viable approach to completing high value esthetic management of the adolescent oligodontia patient.

CLINICAL SIGNIFICANCE

This case report identifies a new way to utilize CAD CAM technology to produce an improved overdenture for the oligodontia patient. It will be of interest to many and underscores the fundamental principles of smile design transfer to the digital environment. (J Esthet Restor Dent, 2016).

RhoA-Mediated Functions in C3H10T1/2 Osteoprogenitors Are Substrate Topography Dependent

Surface topography broadly influences cellular responses. Adherent cell activities are regulated, in part, by RhoA, a member of the Rho-family of GTPases. In this study, we evaluated the influence of surface topography on RhoA activity and associated cellular functions. The murine mesenchymal stem cell line C3H10T1/2 cells (osteoprogenitor cells) were cultured on titanium substrates with smooth topography (S), microtopography (M), and nanotopography (N) to evaluate the effect of surface topography on RhoA-mediated functions (cell spreading, adhesion, migration, and osteogenic differentiation). The influence of RhoA activity in the context of surface topography was also elucidated using RhoA pharmacologic inhibitor. Following adhesion, M and N adherent cells developed multiple projections, while S adherent cells had flattened and widespread morphology. RhoA inhibitor induced remarkable longer and thinner cytoplasmic projections on all surfaces. Cell adhesion and osteogenic differentiation was topography dependent with S < M and N surfaces. RhoA inhibition increased adhesion on S and M surfaces, but not N surfaces. Cell migration in a wound healing assay was greater on S versus M versus N surfaces and RhoA inhibitor increased S adherent cell migration, but not N adherent cell migration. RhoA inhibitor enhanced osteogenic differentiation in S adherent cells, but not M or N adherent cells. RhoA activity was surface topography roughness dependent (S < M, N). RhoA activity and -mediated functions are influenced by surface topography. Smooth surface adherent cells appear highly sensitive to RhoA function, while nano-scale topography adherent cell may utilize alternative cellular signaling pathway(s) to influence adherent cellular functions regardless of RhoA activity.

Complete-arch implant-supported monolithic zirconia fixed dental prostheses: A systematic review

STATEMENT OF PROBLEM

Monolithic zirconia prostheses are emerging as a promising option in the implant-based rehabilitations of edentulous patients, yet their clinical performance is not fully documented.

PURPOSE

The purpose of this systematic review was to assess the clinical performance of complete-arch implant-supported monolithic zirconia fixed dental prostheses.

MATERIAL AND METHODS

The electronic databases PubMed, Science Direct, and Cochrane Library were searched for clinical studies on complete-arch implant-supported monolithic zirconia fixed dental prostheses. Human studies with a mean follow-up of at least 1 year and published in an English-language peer-reviewed journal up to June 2015 were included. Two independent examiners conducted the search and the review process.

RESULTS

The search generated 903 titles. Eighteen qualifying studies were retrieved for full-text evaluation. Nine studies were included on the basis of preestablished criteria. Eight studies reported satisfactory clinical and esthetic outcomes. One study demonstrated prosthesis failure. Clinical studies are lacking on the long-term outcome of complete-arch implant-supported monolithic zirconia prostheses.

CONCLUSIONS

Complete-arch dental implant restoration with monolithic zirconia is associated with high short-term success. Despite the many advantages and short-term favorable reports, studies of longer duration are necessary to validate the broad application of this therapy.

Titanium nanotubes induce osteogenic differentiation through the FAK/RhoA/YAP cascade

TNT topography restricts cell spreading, impairs the FAK recruitment in FAs, and thereby attenuates RhoA activity as well as cytoskeleton formation, which in turn expels YAP from that cell nucleus to the cytoplasm and initiates osteodifferentiation.

Gene Expression Profiles of Early Implant Adherent Cells in Smokers and Nonsmokers

The objective of this study was to evaluate the impact of smoking on the early molecular events involved in peri-implant healing at either a micro-roughened or a micro-roughened with superimposed nanofeatures surface implant in humans. Twenty-one subjects, 10 smokers and 11 nonsmokers received 4 mini-implants (2.2 × 5.0 mm; 2 of each surface). After 3 and 7 days, paired mini-implants were retrieved by reverse threading and RNA isolated from implant adherent cells. Whole genome microarrays were used interrogate the gene expression profiles. The study failed to identify differences in the gene expression profiles of implant adherent cells at this early stage of osseointegration (up to day 7) comparing smoker and nonsmoker individuals.

Topography Influences Adherent Cell Regulation of Osteoclastogenesis

The importance of osteoclast-mediated bone resorption in the process of osseointegration has not been widely considered. In this study, cell culture was used to investigate the hypothesis that the function of implant-adherent bone marrow stromal cells (BMSCs) in osteoclastogenesis is influenced by surface topography. BMSCs isolated from femur and tibia of Sprague-Dawley rats were seeded onto 3 types of titanium surfaces (smooth, micro, and nano) and a control surface (tissue culture plastic) with or without osteogenic supplements. After 3 to 14 d, conditioned medium (CM) was collected. Subsequently, rat bone marrow-derived macrophages (BMMs) were cultured in media supplemented with soluble receptor activator of NF-κB ligand (RANKL) and macrophage colony-stimulating factor (M-CSF) as well as BMSC CM from each of the 4 surfaces. Gene expression levels of soluble RANKL, osteoprotegerin, tumor necrosis factor α, and M-CSF in cultured BMSCs at different time points were measured by real-time polymerase chain reaction. The number of differentiated osteoclastic cells was determined after tartrate-resistant acid phosphatase staining. Analysis of variance and t test were used for statistical analysis. The expression of prominent osteoclast-promoting factors tumor necrosis factor α and M-CSF was increased by BMSCs cultured on both micro- and nanoscale titanium topographies (P < 0.01). BMSC CM contained a heat-labile factor that increased BMMs osteoclastogenesis. CM from both micro- and nanoscale surface-adherent BMSCs increased the osteoclast number (P < 0.01). Difference in surface topography altered BMSC phenotype and influenced BMM osteoclastogenesis. Local signaling by implant-adherent cells at the implant-bone interface may indirectly control osteoclastogenesis and bone accrual around endosseous implants.

Proliferation of preosteoblasts on TiO2 nanotubes is FAK/RhoA related

Topographies promote surface-dependent behaviors which may positively influence peri-implant bone healing. In this study the topological effects of TiO2 nanotubes (TNTs) on aspects of preosteoblast behavior was investigated. Specifically, we hypothesize that TNTs can influence cell proliferation of preosteoblasts through cell adhesion and related modulation of FAK and RhoA. By culturing MC3T3-E1 cells on TNTs with different diameters (40nm and 150nm diameters), topography-dependent modulation in cell morphology and cell growth were observed. The average spreading area of the cell on Flat Ti, 40nm TNTs and 150nm TNTs were respectively 2176.05 μm2, 1510.44 μm2 and 800.72 μm2. Proliferation increased among cells cultured on the 150nm TNTs (28.6%) compared with on Flat Ti (17.06%). The expression of FAK was 86.2% down regulated superimposition of TNTs topography. RhoA expression only slightly decreased (45.9%). Increasing TNT diameter enhanced initial adherent cell growth, which was relevant to the increased RhoA-to-FAK ratio in the cell. Increased TNT diameter was associated with higher ratio and greater proliferation in the first 24 hours. These findings not only support our hypothesis, but suggest that RhoA might be critically involved in TNTs mediated cell proliferation. Future investigation using functional gain and loss of RhoA may further reveal its mechanism.

Electromyographic evaluation of masticatory muscles in dentate patients versus conventional and implant-supported fixed and removable denture wearers- a preliminary report comparing model foods

PURPOSE

To evaluate differences in masticatory muscle function during chewing of model foods designed to differ in fracture strength between dentate subjects (n = 5, ages 59 to 68 years) versus patients treated with a maxillary conventional complete denture opposing natural dentition or one of the following types of mandibular complete dentures: conventional, implant-supported overdenture, implant-supported fixed denture (n = 20, ages 45 to 83 years). The authors hypothesized that denture wearers would differ in duration of chewing, frequency of chewing, and masticatory muscle activity while preparing a bolus for swallowing.

MATERIALS AND METHODS

Surface electromyography was recorded bilaterally from the masseter, anterior temporalis, and anterior digastric. Masticatory muscle activity was evaluated using scaled values of the area under the electromyographic curve, while subjects chewed agar-based model foods with different fracture strengths. Chewing duration and frequency also were calculated from electromyographic recordings. Mixed model analysis of variance with "subject" as a random factor was used during statistical analysis. Logarithmic transformation was required to achieve normalization of residuals for the duration of chewing and the relative masticatory muscles activity, but not for the chewing frequency.

RESULTS

Relative masticatory muscle activity was 2.57 times higher for the denture wearers than for the dentate subjects during chewing of model foods (P < .0001). The reduction in masticatory muscle activity from the 1st to the 10th chewing cycle was proportionally less in magnitude and occurred more gradually for denture wearers compared to dentate subjects. While chewing sequence duration increased with food fracture strength, it did not differ significantly in treatment versus dentate groups. Chewing cycle frequency did not differ between groups or with food fracture strength.

CONCLUSIONS

The observed increases in relative masticatory muscle activity for denture wearers compared to the dentate subjects during oral food processing likely reflect supplemental mechanical efforts to accommodate the use of dentures for preparing a bolus for swallowing.

Esthetic outcomes in relation to implant-abutment interface design following a standardized treatment protocol in a multicenter randomized controlled trial--a cohort of 12 cases at 1-year follow-up

The design of an implant-abutment interface may have an impact on the peri-implant soft tissue esthetics. In an ongoing randomized controlled trial (RCT) with 141 participants, the authors evaluated the peri-implant tissue responses around three different implant-abutment interface designs used to replace single teeth in the esthetic zone. The aim of this report is to describe the treatment protocol utilized in this ongoing RCT by (1) demonstrating in detail a clinical case treated under this protocol and (2) reporting peri-implant soft tissue responses in a cohort of 12 representative cases from the RCT at 1-year follow-up. Male and female adults requiring single implants in the anterior maxilla were enrolled in the RCT according to the study protocol. Five months following any required extraction and/or socket bone grafting/ridge augmentation, one of the following three implant-abutment interfaces was placed and immediately provisionalized: (1) conical interface (CI; OsseoSpeed, Dentsply Implants), n = 4; (2) flat-to-flat interface (FI; NobelSpeedy Replace, Nobel Biocare), n = 4; or (3) platform-switch interface (PS; NanoTite Certain Prevail, Biomet 3i), n = 4. Twelve weeks later, definitive crowns were delivered. Throughout the treatment, peri-implant buccal gingival zenith height and mesial/distal papilla height were measured on stereotactic device photographs, and pink esthetic scores (PES) were determined. The demographics of the participants in each of the three implant-abutment interface groups were very similar. All 12 study sites had ideal ridge form with a minimum width of 5.5 mm following implant site development performed according to the described treatment protocol. Using this treatment protocol for single-tooth replacement in the anterior maxilla, the clinicians were able to obtain esthetic peri-implant soft tissue outcomes with all three types of implant-abutment interface designs at 1-year follow-up as shown by the Canfield data and PES. The proposed treatment protocol for single-tooth replacement in the esthetic zone provides a reliable method to obtain and assess the esthetic outcome as a function of implant-abutment interface design and is now in its fifth year of follow-up.

Immediate provisionalization of dental implants placed in healed alveolar ridges and extraction sockets: a 5-year prospective evaluation

PURPOSE

This 5-year prospective multicenter study compared implant survival and success, peri-implant health and soft tissue responses, crestal bone level stability, and complication rates following immediate loading of single OsseoSpeed implants placed in anterior maxillary healed ridges or extraction sockets.

MATERIALS AND METHODS

Individuals requiring anterior tooth replacement with single implants were treated and immediately provisionalized. Definitive all-ceramic crowns were placed at 12 weeks. Implant survival, bone levels, soft tissue levels, and peri-implant health were monitored for 5 years.

RESULTS

One hundred thirteen patients received implants in fresh sockets (55) and healed ridges (58). After 5 years, 45 and 49 patients remained for evaluation, respectively. During the first year, three implants failed in the extraction socket group (94.6% survival) and one implant failed in the healed ridge group (98.3% survival); this difference was not significant. No further implant failures were recorded. After 5 years, the interproximal crestal bone levels were located a mean of 0.43 ± 0.63 mm and 0.38 ± 0.62 mm from the reference points of implants in sockets and healed ridges (not a significant difference). In both groups, papillae increased over time and peri-implant mucosal zenith positions were stable from the time of definitive crown placement in sockets and healed ridges. Compared to flap surgery for implants in healed ridges, flapless surgery resulted in increased peri-implant mucosal tissue dimension (average, 0.78 ± 1.34 mm vs 0.19 ± 0.79 mm).

CONCLUSION

After 5 years, the bone and soft tissue parameters that characterize implant success and contribute to dental implant esthetics were similar following the immediate provisionalization of implants in sockets and healed ridges. The overall tissue responses and reported implant survival support the immediate provisionalization of dental implants in situations involving healed ridges and, under ideal circumstances, extraction sockets.