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Dental Research Journal 2023An ever-increasing demand is seen for clear aligners and transparent vacuum-formed retainers. They are esthetic and convenient. However, the biomaterials used in these... (Review)
Review
A systematic review of biocompatibility and safety of orthodontic clear aligners and transparent vacuum-formed thermoplastic retainers: Bisphenol-A release, adverse effects, cytotoxicity, and estrogenic effects.
BACKGROUND
An ever-increasing demand is seen for clear aligners and transparent vacuum-formed retainers. They are esthetic and convenient. However, the biomaterials used in these appliances might pose biological safety and biocompatibility threats in terms of their bisphenol-A (BPA) release, cytotoxicity, adverse effects, and estrogenic effects. Due to the controversial results and the lack of any systematic reviews in this regard, we conducted this systematic review.
MATERIALS AND METHODS
Web of Science, PubMed, Cochrane, Scopus, and Google Scholar as well as references of the found articles were searched (independently by 3 researchers) up to December 22, 2021, to find studies relevant to the biocompatibility of clear aligners and thermoplastic retainers. The search keywords were a combination of the following (and more): Essix, vacuum-formed aligner, thermoplastic aligner, clear aligner, Invisalign, vacuum-formed retainer, BPA release, monomer release, cytotoxicity, estrogenicity, biocompatibility, chemical properties, and oral epithelial cell. As eligibility criteria, articles in all languages would be included as long as their text could be translated clearly using online translators or by professional translators; all types of publications (article, book, and thesis) would be included if containing relevant studies and information; they should have been on clear liners or thermoplastic retainers; and they should have been on biocompatibility, safety, cytotoxicity, or estrogenicity of clear aligners or thermoplastic retainers. There were no restrictions on the type of study (randomized clinical trials, experimental studies). Studies focusing merely on the mechanical properties of clear aligners or thermoplastic retainers (without examining their chemical properties) would be excluded. The risk of bias was assessed.
RESULTS
The risk of bias was rather low. However, the methodologies of the studies were quite different. Overall, 16 articles (1 randomized clinical trial and 15 studies) were identified. The data for BPA release were reported in four articles (1 clinical trial and 3 studies). Quantitatively speaking, the amount of released BPA reported by studies was very low, if not zero. However, the BPA level was very high in the only randomized clinical trial. Many adverse effects were linked to using clear aligners or transparent retainers, including pain and soft-tissue issues such as burning, tingling, sore tongue, lip swelling, blisters, ulceration, dry mouth, periodontal problems, and even systemic problems such as difficulty in breathing. Besides these biological adverse effects, oral dysfunctions and speech difficulties and tooth damage may be associated with clear aligners and should as well be taken into consideration.
CONCLUSION
Given the very high levels of BPA leach observed in the only clinical trial and considering other possible dangers of small traces of BPA (even at low doses) and also given the numerous adverse events linked to clear aligners or transparent retainers, it seems that safety of these appliances might be questionable and more clinical studies of biocompatibility are needed in this regard.
PubMed: 37180685
DOI: No ID Found -
Biomaterial Investigations in Dentistry 2023Flowable bulk-fill resin-based composites (BF-RBCs) represent a new and interesting alternative for the bulk-fill restorative techniques in the posterior region.... (Review)
Review
Flowable bulk-fill resin-based composites (BF-RBCs) represent a new and interesting alternative for the bulk-fill restorative techniques in the posterior region. However, they comprise a heterogeneous group of materials, with important differences in composition and design. Therefore, the aim of the present systematic review was to compare the main properties of flowable BF-RBCs, including their composition, degree of monomer conversion (DC), polymerization shrinkage and shrinkage stress, as well as flexural strength. The search was conducted following PRISMA guidelines in the Medline (PubMed), Scopus and Web of Science databases. articles reporting on the DC, polymerization shrinkage/shrinkage stress, and flexural strength of flowable BF-RBCs strength were included. The QUIN risk-of-bias (RoB) tool was used for assessing the study quality. From initially 684 found articles, 53 were included. Values for DC ranged between 19.41 and 93.71%, whereas polymerization shrinkage varied between 1.26 and 10.45%. Polymerization shrinkage stresses reported by most studies ranged between 2 and 3 MPa. Flexural strength was above 80 MPa for most materials. A moderate RoB was observed in most studies. Flowable BF-RBCs meet the requirements to be indicated for bulk fill restoration technique in the posterior region. However, important variations among composition and properties hinder extrapolation of the results to materials different from those reported here. Clinical studies are urgently required to assess their performance under a real working scenario.
PubMed: 37138762
DOI: 10.1080/26415275.2023.2175685 -
Chemosphere Feb 2023Much attention has been paid on polybrominated diphenyl ethers (PBDEs) in household dust due to their ubiquitous occurrences in the environment. Based on the data from... (Review)
Review
Much attention has been paid on polybrominated diphenyl ethers (PBDEs) in household dust due to their ubiquitous occurrences in the environment. Based on the data from 59 articles sampled from 2005 to 2020, we investigated the spatio-temporal distribution, sources, and health risk of 8 PBDE homologues in household dusts worldwide. BDE-209 is the predominant PBDE in household dusts, followed by BDE-99 and BDE-47. The total concentrations of PBDEs (∑PBDEs) are found to be high in household dusts sampled from 2005 to 2008 and show a significant decline trend from 2009 to 2016 (p < 0.05) and a little upward tendency from 2017 to 2020. The concentrations of PBDEs in household dusts vary greatly in different countries of the world. The use of penta-BDE is the main source of three to five bromo-biphenyl ether monomers contributing 17.4% of ∑PBDEs, while BDE-209 and BDE-183 are derived from the use of household appliances contributing 82.6% of ∑PBDEs. Ingestion is the main exposure route for adults and toddlers, followed by dermal contact. The values of hazard index (HI) exposed to PBDEs in household dusts are all less than 1 for both adults and toddlers, indicating a low non-cancer risk. The incremental lifetime cancer risks (ILCRs) of BDE-209 are less than 10 for both adults and toddlers, suggesting a negligible risk. However, the total carcinogenic risk of toddlers is higher than that of adults, indicating that much attention should be paid to toddlers exposed to BDE-209 in household dust.
Topics: Adult; Humans; Halogenated Diphenyl Ethers; Dust; Air Pollution, Indoor; Risk Assessment; Neoplasms; Environmental Monitoring; Environmental Exposure
PubMed: 36584828
DOI: 10.1016/j.chemosphere.2022.137641 -
Biomedicines Dec 2022This study aimed to assess whether degradation-resistant monomers included in experimental dental adhesives can improve long-term bond strength compared to conventional... (Review)
Review
This study aimed to assess whether degradation-resistant monomers included in experimental dental adhesives can improve long-term bond strength compared to conventional monomers. This study followed the latest PRISMA guidance (2020). The search for the systematic review was carried out in four electronic databases: PubMed/Medline, Scopus, SciELO and EMBASE, without restrictions on the year of publication and language. The last screening was conducted in July 2022. Interventions included were in vitro studies on experimental dental adhesives that tested short-term and long-term bond strength, but also water sorption and solubility data when available, in extracted human molars. Meta-analyses were performed using Rstudio v1.4.1106. A summary table analyzing the individual risk of bias was generated using the recent RoBDEMAT tool. Of the 177 potentially eligible studies, a total of 7 studies were included. Experimental monomers with acrylamides or methacrylamide−acrylamide hybrids in their composition showed better results of aged bond strength when compared to methacrylate controls (p < 0.05). The experimental monomers found better sorption and solubility compared to controls and were significantly different (p < 0.001). It is possible to achieve hydrolytically resistant formulations by adding novel experimental monomers, with chemical structures that bring benefit to degradation mechanisms.
PubMed: 36551861
DOI: 10.3390/biomedicines10123104 -
Molecular Aspects of Medicine Feb 2023This systematic review summarizes findings from human studies investigating the different routes of absorption, metabolism, distribution and excretion (ADME) of dietary... (Review)
Review
This systematic review summarizes findings from human studies investigating the different routes of absorption, metabolism, distribution and excretion (ADME) of dietary flavan-3-ols and their circulating metabolites in healthy subjects. Literature searches were performed in PubMed, Scopus and the Web of Science. Human intervention studies using single and/or multiple intake of flavan-3-ols from food, extracts, and pure compounds were included. Forty-nine human intervention studies met inclusion criteria. Up to 180 metabolites were quantified from blood and urine samples following intake of flavan-3-ols, mainly as phase 2 conjugates of microbial catabolites (n = 97), with phenyl-γ-valerolactones being the most representative ones (n = 34). Phase 2 conjugates of monomers and phenyl-γ-valerolactones, the main compounds in both plasma and urine, reached two peak plasma concentrations (C) of 260 and 88 nmol/L at 1.8 and 5.3 h (T) after flavan-3-ol intake. They contributed to the bioavailability of flavan-3-ols for over 20%. Mean bioavailability for flavan-3-ols was moderate (31 ± 23%, n bioavailability values = 20), and it seems to be scarcely affected by the amount of ingested compounds. While intra- and inter-source differences in flavan-3-ol bioavailability emerged, mean flavan-3-ol bioavailability was 82% (n = 1) and 63% (n = 2) after (-)-epicatechin and nut (hazelnuts, almonds) intake, respectively, followed by 25% after consumption of tea (n = 7), cocoa (n = 5), apples (n = 3) and grape (n = 2). This highlights the need to better clarify the metabolic yield with which monomer flavan-3-ols and proanthocyanidins are metabolized in humans. This work clarified in a comprehensive way for the first time the ADME of a (poly)phenol family, highlighting the pool of circulating compounds that might be determinants of the putative beneficial effects linked to flavan-3-ol intake. Lastly, methodological inputs for implementing well-designed human and experimental model studies were provided.
Topics: Humans; Biological Availability; Catechin; Proanthocyanidins; Diet
PubMed: 36207170
DOI: 10.1016/j.mam.2022.101146 -
The International Journal of... 2022To systematically review all clinical studies focusing on the clinical outcomes of zirconia restorations bonded to different types of tooth or implant abutments and to...
PURPOSE
To systematically review all clinical studies focusing on the clinical outcomes of zirconia restorations bonded to different types of tooth or implant abutments and to provide practical clinical guidelines.
MATERIALS AND METHODS
A search was performed for English-language articles in dental journals published up to September 2020 using a combination of free-text words and MeSH terms. Studies were identified for review according to certain inclusion and exclusion criteria.
RESULTS
A total of 2,856 studies were identified, and 24 studies were finally included. The included studies featured different types of surface pretreatment methods, primers, resin cements, tooth and implant abutments, zirconia restorations, and designs. The relatively limited number of identified studies and the heterogeneity of the extracted data did not allow for meta-analysis.
CONCLUSION
Airborne-particle abrasion (APA) and tribochemical silica (TBS) APA surface pretreatment methods yielded positive clinical outcomes on zirconia/resin bonding to all types of tooth surfaces identified. Chemically activating the APA and the TBS APA zirconia surfaces with an MDP monomer-based primer, along with an MDP monomer or phosphoric ester monomer-based resin cement, seems to be a durable bonding protocol for all types of tooth surfaces identified. Skipping the surface pretreatment method step in the bonding protocol did not affect the clinical outcomes of certain types of zirconia restorations on most types of tooth or implant abutment surfaces identified. Type of resin cement seems to be a less influential factor.
Topics: Dental Bonding; Dental Implants; Esters; Humans; Materials Testing; Resin Cements; Silicon Dioxide; Zirconium
PubMed: 36125875
DOI: 10.11607/ijp.6871 -
Thrombosis Research Sep 2022Ranging from bleeding to thrombosis, the clinical features of congenital fibrinogen qualitative disorders, including dysfibrinogenemia and hypodysfibrinogenemia, are... (Review)
Review
Ranging from bleeding to thrombosis, the clinical features of congenital fibrinogen qualitative disorders, including dysfibrinogenemia and hypodysfibrinogenemia, are highly heterogeneous. Although the associations between some specific fibrinogen mutations and the thrombotic phenotypes have been well elucidated, the underlying mechanism between fibrinogen variants and bleeding events remains underestimated. After systematically reviewing the literature of (hypo-)dysfibrinogenemia patients with bleeding phenotypes, we identified several well-characterized bleeding-related fibrinogen variants in those patients. Several possible pathomechanisms are proposed to explain the genotype-phenotype associations: 1, mutations in the NH-terminal portion of the Aα chain hamper fibrinogen fitting into the active site cleft of thrombin and drastically slow the conversion of fibrinogen into monomeric fibrin; 2, mutations adding new N-linked glycosylation sites introduce bulky and negatively charged carbohydrate side chains and undermine the alignment of fibrin monomers during polymerization; 3, mutations generating unpaired cysteine form extra disulfide bonds between the abnormal fibrinogen chains and produce highly branched and fragile fibrin networks; 4, truncation mutations in the fibrinogen αC regions impair the lateral fibril aggregation, as well as factor XIII crosslinking, endothelial cell and platelet binding. These established relationships between specific variants and the bleeding tendency will help manage (hypo-)dysfibrinogenemia patients to avoid adverse bleeding outcomes.
Topics: Afibrinogenemia; Blood Coagulation Tests; Fibrin; Fibrinogen; Fibrinogens, Abnormal; Hemorrhage; Humans; Thrombosis
PubMed: 35853369
DOI: 10.1016/j.thromres.2022.07.005 -
Journal of Hazardous Materials Sep 2022Microplastic (MP) pollution in global sediment has been intensely studied and recognized as the ultimate sink for residual MPs in terrestrial and aquatic ecosystems.... (Review)
Review
Microplastic (MP) pollution in global sediment has been intensely studied and recognized as the ultimate sink for residual MPs in terrestrial and aquatic ecosystems. During MP long-term retention in sediments, plastic-degrading bacteria (i.e., Flavobacteriaceae, Bacillus, Rhodobacteraceae, and Desulfobacteraceae) can utilize those MPs as their carbon and energy sources through enzyme (hydrolase and oxidoreductase) reactions, which further alter or transform high molecular weight MP polymers into lower molecular weight biodegradation byproducts (i.e., monomers and oligomers) and release toxic additives. In other words, MPs can act as durable substrates for plastic-degrading bacteria in sediments. However, to date, the biodegradation rates of MPs in sediment environments are still poorly understood due to their limited degradation efficiency. Herein, we review the enzyme-induced biodegradation processes of MPs in sediment environments, which is important for accessing the alteration of MP properties and their potential ecological risks after undergoing long-term weathering processes. In addition, the factors associated with the MP properties (polymer type, molecular weight, crystallinity, and hydrophobicity) and sediment conditions (sediment type, temperature, pH, salinity, and oxygen content) that influence plastic degradation processes are also reviewed. The mechanisms may relate to the MP properties and sediment conditions that can influence microbial abundance, enzyme concentrations, and enzyme activities, thus altering MP biodegradation ratios. We anticipate that the observations reviewed in this study will pose a new issue to better understand the formation process, fate, and potential ecological risks associated with aged MPs in sediment environments.
Topics: Biodegradation, Environmental; Ecosystem; Environmental Monitoring; Geologic Sediments; Microplastics; Plastics; Water Pollutants, Chemical
PubMed: 35714544
DOI: 10.1016/j.jhazmat.2022.129287 -
International Journal of Molecular... May 2022Amidst growing technological advancements, newer denture base materials and polymerization methods have been introduced. During fabrication, certain mechanical... (Review)
Review
Amidst growing technological advancements, newer denture base materials and polymerization methods have been introduced. During fabrication, certain mechanical properties are vital for the clinical longevity of the denture base. This systematic review aimed to explore the effect of newer denture base materials and/or polymerization methods on the mechanical properties of the denture base. An electronic database search of English peer-reviewed published papers was conducted using related keywords from 1 January 2011, up until 31 December 2021. This systematic review was based on guidelines proposed by the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA). The search identified 579 papers. However, the inclusion criteria recognized 22 papers for eligibility. The risk of bias was moderate in all studies except in two where it was observed as low. Heat cure polymethyl methacrylate (PMMA) and compression moulding using a water bath is still a widely used base material and polymerization technique, respectively. However, chemically modified PMMA using monomers, oligomers, copolymers and cross-linking agents may have a promising result. Although chemically modified PMMA resin might enhance the mechanical properties of denture base material, no clear inferences can be drawn about the superiority of any polymerization method other than the conventional compression moulding technique.
Topics: Denture Bases; Materials Testing; Polymerization; Polymers; Polymethyl Methacrylate
PubMed: 35628546
DOI: 10.3390/ijms23105737 -
Advanced Materials (Deerfield Beach,... Sep 2022Globally, liver cancer, which is one of the major cancers worldwide, has attracted the growing attention of technological researchers for its high mortality and limited... (Review)
Review
Globally, liver cancer, which is one of the major cancers worldwide, has attracted the growing attention of technological researchers for its high mortality and limited treatment options. Hydrogels are soft 3D network materials containing a large number of hydrophilic monomers. By adding moieties such as nitrobenzyl groups to the network structure of a cross-linked nanocomposite hydrogel, the click reaction improves drug-release efficiency in vivo, which improves the survival rate and prolongs the survival time of liver cancer patients. The application of a nanocomposite hydrogel drug delivery system can not only enrich the drug concentration at the tumor site for a long time but also effectively prevents the distant metastasis of residual tumor cells. At present, a large number of researches have been working toward the construction of responsive nanocomposite hydrogel drug delivery systems, but there are few comprehensive articles to systematically summarize these discoveries. Here, this systematic review summarizes the synthesis methods and related applications of nanocomposite responsive hydrogels with actions to external or internal physiological stimuli. With different physical or chemical stimuli, the structural unit rearrangement and the controlled release of drugs can be used for responsive drug delivery in different states.
Topics: Delayed-Action Preparations; Drug Delivery Systems; Humans; Hydrogels; Liver Neoplasms; Nanogels
PubMed: 35583434
DOI: 10.1002/adma.202201651