Xenograft bone substitutes are obtained from different species and prepared by various procedures including heat treatment, hydrazine, and chemical and hydrothermal methods. These grafts are utilized widely because of similar structure and properties to human bone, proper bone formation, and biocompatibility. The aim of this systematic review was to evaluate different xenografts from structural and chemical aspects. In vitro studies published in English language, which assessed xenografts’ features, met the inclusion criteria. Electronic search of four databases including PubMed, Google Scholar, Scopus, and Web of Science and a hand search until September 2020 were performed. The irrelevant studies were the ones which focused on cell adhesion and effect of growth factors. Finally, 25 studies were included in the review. Nineteen studies used bovine xenografts, and 12 studies applied heat treatment as their preparation method. Particles showed various morphologies, and their largest size was observed at 5 mm. From 18 studies, it is found that the smallest pore size was 1.3 µm and the highest pore size was 1000 µm. There is large heterogeneity of porosity, crystallinity, Ca/P ratio, and osteogenesis based on the preparation method. Proper porosity and the connection between pores affect bone regeneration. Therefore, biomaterial selection and outcomes evaluation should be interpreted separately.

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Combining different procedures to reduce the number of surgical sessions and patient discomfort in implant placement and sinus floor elevation has been recommended, and evidence supports good outcomes. The aim of this study was to review the results of clinical studies on sinus floor elevation through extraction sockets and simultaneous immediate posterior implant placement. An electronic search was carried out in PubMed, Scopus, and Web of Science to find English articles published in or before August 2020. A manual search was also performed. Titles, abstracts, and the full-text of the retrieved articles were studied. Thirteen studies met our eligibility criteria: 6 retrospective case series, 3 case reports, 2 prospective cohort caseseries, 1 prospective case series, and 1 randomized controlled trial. Overall, 306 implants were placed; 2 studies reported implant survival rates of 91.7% and 98.57%. The others either did not report the survival rate or reported 100% survival. Sinus floor elevation through a fresh extraction socket and simultaneous immediate implant placement appears to be a predictable modality with a high success rate. However, proper case selection and the expertise of the clinician play fundamental roles in the success of such complex procedures.

Dental implants are popular for dental rehabilitation after tooth loss. The goal of this systematic review was to assess bone changes around bone-level and tissue-level implants and the possible causes. Electronic searches of PubMed, Google Scholar, Scopus, and Web of Science, and a hand search limited to English language clinical trials were performed according to PRISMA (Preferred Reporting Items for Systematic Reviews and Meta-Analysis) guidelines up to September 2020. Studies that stated the type of implants used, and that reported bone-level changes after insertion met the inclusion criteria. The risk of bias was also evaluated. A total of 38 studies were included. Eighteen studies only used bone-level implants, 10 utilized tissuelevel designs and 10 observed bone-level changes in both types of implants. Based on bias assessments, evaluating the risk of bias was not applicable in most studies. There are vast differences in methodologies, follow-ups, and multifactorial characteristics of bone loss around implants, which makes direct comparison impossible. Therefore, further well-structured studies are needed.

Introduction: SARS-CoV-2 is a novel coronavirus that causes an infectious disease named COVID-19. Respiratory distress syndrome and multiple organ failure are the common outcomes of COVID-19 that may finally lead to death. During COVID-19, cytokine storm takes place that is known by the release of notable amounts of pro-inflammatory cytokines including IL-1, IL-6, and TNF-α. The Hypothesis: Periodontal disease are a group of inflammatory diseases in which elevated levels of some cytokine such as IL-1, IL-2, IL-5, IL-6, IL-10, and TNF-α are observed in patients’ serums. Due to the similarity of cytokine expressions in these two diseases, there might be a possible association between COVID-19 and periodontitis, especially the chronic type. Also, genotype polymorphisms of IL-1, IL-6, IL-10, and TNF-α have been proposed to be in association with chronic periodontitis susceptibility. Evaluation of the Hypothesis: assessment of these polymorphisms may also play a significant role in detection of these diseases.