Antimicrobial and Mechanical Effects of Zeolite Use in Dental Materials: A Systematic Review

Objective: Ion-incorporated zeolite is a widely used antimicrobial material studied for various dental applications. At present, there is no other systematic review that evaluates the effectiveness of zeolite in all dental materials. The purpose of this study was to review all available literature that analyzed the antimicrobial effects and/or mechanical properties of zeolite as a restorative material in dentistry. Material and methods: Following PRISMA guidelines, an exhaustive search of PubMed, Ovid Medline, Scopus, Embase, and the Dentistry & Oral Sciences Source was conducted. No language or time restrictions were used and the study was conducted from June 1, 2020 to August 17, 2020. Only full text articles were selected that pertained to the usage of zeolite in dental materials including composite resin, bonding agents, cements, restorative root material, cavity base material, prosthesis, implants, and endodontics. Results: At the beginning of the study, 1534 studies were identified, of which 687 duplicate records were excluded. After screening for the title, abstract, and full texts, 35 articles remained and were included in the qualitative synthesis. An Inter-Rater Reliability (IRR) test, which included a percent user agreement and reliability percent, was conducted for each of the 35 articles chosen. Conclusion: Although ion-incorporated zeolite may enhance the antimicrobial properties of dental materials, the mechanical properties of some materials, such as MTA and acrylic resin, may be compromised. Therefore, since the decrease in mechanical properties depends on zeolite concentration in the restorative material, it is generally recommended to add 0.2-2% zeolite by weight. © 2021 University of Zagreb. All rights reserved

Relationship Between Air-Blowing Duration and Bond Strengths of Three Adhesive Systems to Dentin After Thermal Aging

The purpose was to evaluate the effect of air-blowing duration of three different adhesive systems on immediate or thermal aged resin-dentin shear bond strength (SBS). Human dentin surfaces were bonded with: one-step (Bond Force, BF), two-step (FL-Bond II, FLB) and three-step (Scotch Bond Multi-Purpose, SBMP) adhesive systems. Bonded surfaces from each group were air-blown for 0, 5, or 10 s and cured. Composite cylinders were built on the treated surfaces and cured. Half of the specimens from each group were tested immediately and the other halves were tested after thermal aging. Statistical analysis showed signifcant decrease in SBS after thermal aging compared to immediate testing in all groups, except BF after 5 s air-blowing or FLB and SBMP with no air-blowing (p\u3e0.05). The results suggested that 5 s air-blowing is necessary to obtain a stable SBS for BF. However, extended airblowing duration of FLB and SBMP decreased the SBS significantly after thermal aging

Comparative Osteogenesis of Maxilla and Iliac Crest Human Bone Marrow Stromal Cells Attached to Oxidized Titanium - a Pilot Study

Objectives Severe alveolar bone loss affects dental implant placement. Bone augmentation by grafting iliac crest bone rich in osteoprogenitor cells like bone marrow stromal cells (BMSCs) requires a second surgical procedure in non-orofacial bone. Skeletal site-specific osteogenesis indicates maxilla and mandible BMSCs are highly proliferative and exhibit osteogenic properties superior to iliac crest BMSCs. Alveolar bone can be easily obtained during routine dental surgery, but it is unclear if titanium-attached alveolar BMSCs will retain their superior osteogenic properties. This study evaluated and compared in vitro osteogenic properties of titanium-attached maxilla and iliac crest BMSCs in same individuals. Materials and Methods Primary culture of maxilla and iliac crest BMSCs from four normal healthy volunteers were expanded in culture. In 24-well plates, first passage BMSCs were seeded directly (1 × 104 cells/well) on oxidized titanium discs (1.27cm diameter and 2mm thickness) or tissue culture plate. Each cell type was assessed for affinity for titanium, post-attachment survival and osteogenic differentiation based on alkaline phosphatase and osteopontin expressions. Results There was no difference in the affinity of maxilla and iliac crest BMSCs to titanium. However, titanium-attached maxilla BMSCs were apparently more osteogenically responsive than iliac crest cells based on calcium accumulation and gene expression of alkaline phosphatase and osteopontin. But these differences were not statistically significant in this small patient sample. Conclusion Maxilla and iliac crest BMSCs have similar attachment affinity for titanium. This pilot study indicate that titanium-attached maxilla BMSCs were more osteogenically responsive and may be a viable and more readily available donor graft material in implant dentistry

Effect of Preirradiation Fluoride Treatment on the Physical Properties of Dentin

Objective. To determine the effects of preirradiation fluoride treatments on the Knoop hardness of dentin. Materials and Methods. Human posterior teeth mounted into acrylic resin molds were polished with silicon carbide (SiC) abrasives and 3-micron diamond paste. The Knoop hardness of dentin was measured with a Leco hardness instrument. The teeth were divided into groups of ten teeth per group as follows: no treatment (control), treatment with silver diamine fluoride (SDF), MI varnish (MI), and cavity shield (CS). The teeth were exposed to 2 Gy of daily radiation for six weeks using an X-Rad 320ix biological irradiator. Hardness was measured weekly, before, during, and after irradiation. The teeth were stored in artificial saliva at 37oC between radiation treatments. Results. In preirradiation dentin, a Knoop hardness value of 58.8 (14.1) KHN was obtained. Treatment with SDF significantly increased KHN before irradiation. Immediately after radiation treatment, hardness was significantly reduced in all experimental groups. Postirradiation fluoride treatments increased the hardness of dentin to varying degrees. Conclusions. Preirradiation fluoride treatment does not provide protection from decreases in the hardness of dentin. Treatment of teeth with fluoride formulations after radiation progressively restores the hardness of dentin to different degrees. © 2022 Francis K. Mante et al

Antimikrobni i mehanički učinci upotrebe zeolita u dentalnim materijalima: sistematizirani pregledni rad

Objective: Ion-incorporated zeolite is a widely used antimicrobial material studied for various dental applications. At present, there is no other systematic review that evaluates the effectiveness of zeolite in all dental materials. The purpose of this study was to review all available literature that analyzed the antimicrobial effects and/or mechanical properties of zeolite as a restorative material in dentistry. Material and methods: Following PRISMA guidelines, an exhaustive search of PubMed, Ovid Medline, Scopus, Embase, and the Dentistry & Oral Sciences Source was conducted. No language or time restrictions were used and the study was conducted from June 1, 2020 to August 17, 2020. Only full text articles were selected that pertained to the usage of zeolite in dental materials including composite resin, bonding agents, cements, restorative root material, cavity base material, prosthesis, implants, and endodontics. Results: At the beginning of the study, 1534 studies were identified, of which 687 duplicate records were excluded. After screening for the title, abstract, and full texts, 35 articles remained and were included in the qualitative synthesis. An Inter-Rater Reliability (IRR) test, which included a percent user agreement and reliability percent, was conducted for each of the 35 articles chosen. Conclusion: Although ion-incorporated zeolite may enhance the antimicrobial properties of dental materials, the mechanical properties of some materials, such as MTA and acrylic resin, may be compromised. Therefore, since the decrease in mechanical properties depends on zeolite concentration in the restorative material, it is generally recommended to add 0.2-2% zeolite by weight.Svrha istraživanja: Zeolit s ugrađenim ionima često je korišten antimikrobni materijal koji se proučava za različite primjene u stomatologiji. Trenutačno ne postoji ni jedan drugi sistematizirani pregledni rad u kojemu bi se ocjenjivala učinkovitost zeolita u svim dentalnim materijalima. Svrha ovoga istraživanja bila je pregledati svu objavljenu literaturu u kojoj su analizirani antimikrobni učinci i/ ili mehanička svojstva zeolita kao restaurativnog materijala u stomatologiji. Materijal i metode: Slijedeći smjernice PRISMA-e, od 1. lipnja do 17. kolovoza 2020. provedeno je iscrpno pretraživanje baza Pubmed, Ovid Medline, Scopus, Embasa te Dentistry i Oral Sciences Source. Nisu korištena jezična ili vremenska ograničenja. Odabrani su samo cjeloviti članci kojima je tema bila upotreba zeolita u dentalnim materijalima, uključujući kompozitne materijale, adhezive, cemente, restaurativne intrakorijenske materijale, podloge te materijale u protetici, implantologiji i endodonciji. Rezultati: Na početku su pronađena 1534 istraživanja, od kojih je isključeno 687 duplih zapisa. Nakon pregleda naslova, sažetka i cjelovitih tekstova, ostalo je 35 radova koji su uključeni u kvalitativnu sintezu. Za svaki od njih proveden je test pouzdanosti među ocjenjivačima (IRR) koji je obuhvaćao postotak slaganja i postotak pouzdanosti. Zaključak: Iako zeolit s ugrađenim ionima može pojačati antimikrobna svojstva dentalnih materijala, mehanička svojstva nekih mogu biti ugrožena, poput MTA i akrilatne smole. Stoga, s obzirom na to da pogoršanje mehaničkih svojstava ovisi o koncentraciji zeolita u restaurativnom materijalu, općenito se preporučuje dodavanje 0,2 do 2 mas.% zeolita

Affordable Oral Health Care: Dental Biofilm Disruption Using Chloroplast Made Enzymes with Chewing Gum Delivery

Current approaches for oral health care rely on procedures that are unaffordable to impoverished populations, whereas aerosolized droplets in the dental clinic and poor oral hygiene may contribute to spread of several infectious diseases including COVID-19, requiring new solutions for dental biofilm/plaque treatment at home. Plant cells have been used to produce monoclonal antibodies or antimicrobial peptides for topical applications to decrease colonization of pathogenic microbes on dental surface. Therefore, we investigated an affordable method for dental biofilm disruption by expressing lipase, dextranase or mutanase in plant cells via the chloroplast genome. Antibiotic resistance gene used to engineer foreign genes into the chloroplast genome were subsequently removed using direct repeats flanking the aadA gene and enzymes were successfully expressed in marker-free lettuce transplastomic lines. Equivalent enzyme units of plant-derived lipase performed better than purified commercial enzymes against biofilms, specifically targeting fungal hyphae formation. Combination of lipase with dextranase and mutanase suppressed biofilm development by degrading the biofilm matrix, with concomitant reduction of bacterial and fungal accumulation. In chewing gum tablets formulated with freeze-dried plant cells, expressed protein was stable up to 3 years at ambient temperature and was efficiently released in a time-dependent manner using a mechanical chewing simulator device. Development of edible plant cells expressing enzymes eliminates the need for purification and cold-chain transportation, providing a potential translatable therapeutic approach. Biofilm disruption through plant enzymes and chewing gum-based delivery offers an effective and affordable dental biofilm control at home particularly for populations with minimal oral care access. © 2021 The Authors. Plant Biotechnology Journal published by Society for Experimental Biology and The Association of Applied Biologists and John Wiley & Sons Ltd

SARS-CoV-2 Viral Shedding and Transmission Dynamics: Implications of WHO COVID-19 Discharge Guidelines

The evolving nature of the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) has necessitated periodic revisions of COVID-19 patient treatment and discharge guidelines. Since the identification of the first COVID-19 cases in November 2019, the World Health Organization (WHO) has played a crucial role in tackling the country-level pandemic preparedness and patient management protocols. Among others, the WHO provided a guideline on the clinical management of COVID-19 patients according to which patients can be released from isolation centers on the 10th day following clinical symptom manifestation, with a minimum of 72 additional hours following the resolution of symptoms. However, emerging direct evidence indicating the possibility of viral shedding 14 days after the onset of symptoms called for evaluation of the current WHO discharge recommendations. In this review article, we carried out comprehensive literature analysis of viral shedding with specific focus on the duration of viral shedding and infectivity in asymptomatic and symptomatic (mild, moderate, and severe forms) COVID-19 patients. Our literature search indicates that even though, there are specific instances where the current protocols may not be applicable ( such as in immune-compromised patients there is no strong evidence to contradict the current WHO discharge criteria

Fracture Toughness of Dental Ceramics

The plane strain fracture toughness (KIc) of two high-alumina core ceramics, Cerestore and Vitadur, was measured at room temperature by three methods. The single edge notch (SEN) specimen method was used to measure the fracture toughness of both ceramics in air, deionized water and artificial saliva. The short rod and indentation methods were used for Cerestore and Vitadur, respectively, in air. X-ray diffraction analysis and scanning electron microscopy were performed to identify the crystalline phases in the two ceramics and to examine the microstructural features of the fracture surfaces. The fracture toughness values obtained for Cerestore by the SEN method were 1.89 MPa.m 1/2 in air, 1.58 MPa.m 1/2 in deionized water and 1.63 MPa.m 1/2 in artificial saliva. There were no significant differences between fracture toughness values for the three different environments. The short rod method yielded a value of 1.91 MPa.m 1/2, in good agreement with the SEN method. For Vitadur fracture toughness values of 1.75 MPa.m 1/2 in air, 1.18 MPa.m 1/2 in deionized water and 1.54 MPa.m 1/2 in artificial saliva were obtained by the SEN method. The value of 1.18 MPa.m 1/2 obtained in deionized water was significantly different at the p\u3c 0.01 level from the values obtained in air and artificial saliva. A fracture toughness in air of 1.67 MPa.m 1/2 was provided by the indentation method. X-ray diffraction analysts showed the presence of Al 203 and Mg0 in the green Cerestore ceramic. After firing, the peaks corresponding to Mg0 were eliminated while peaks corresponding to magnesium aluminate spinel (MgA1204) were found; crystalline barium aluminum silicate was also present in minor amounts. Vitadur showed x-ray diffraction peaks corresponding principally to Al 203, and other peaks were attributed to possible ternary and higher order phases. Scanning electron micrographs indicated that fracture involved a combination of intergranular and transgranular modes for Cerestore. Substantial porosity, estimated at 5-10%, was present in this ceramic after firing. For Vitadur the fracture mode was predominantly transgranular, and considerably less porosity was evident compared to Cerestore. Optical photomicrographs showed that cracks emanating from indentations in Vitadur propagated indiscriminately through the matrix and alumina particles. In Cerestore cracks could not be measured at the tips of indentations due to their interaction with pores and other microstructural features

Impact of Irradiation on the Adhesive Performance of Resin-Based Dental Biomaterials: A Systematic Review of Laboratory Studies

Head and neck cancers are a significant global health burden, with radiation therapy being a frequently utilized treatment. The aim of this systematic review was to provide a critical appraisal of laboratory studies that assessed the effect of irradiation on the adhesive performance of resin-based biomaterials. The analysis included 23 laboratory studies obtained from five databases, with most studies using human enamel, dentin, or both, and bonding procedures involving the fabrication of direct restorations, standardized specimens, bonding of orthodontic brackets, and luting of endodontic fiber posts. The protocols used for irradiation varied, with most studies exposing specimens made from extracted teeth to irradiation using cabinet irradiators to simulate treatment of head and neck cancer. The findings indicate that irradiation reduces the bond strength of dental adhesives and resin-based composites on flat, ground enamel and dentin specimens, with different adhesives and timing of irradiation having a significant impact on adhesive performance. Irradiation also increased microleakage in most studies. The effect of irradiation on marginal adaptation of direct resin-based composite restorations was inconclusive. This systematic review indicates that irradiation has detrimental effects on the adhesive performance of resin-based biomaterials and highlights the need for further clinical and laboratory studies evaluating the performance of adhesive materials and approaches to improve it

Bond Strength of Different Self-Adhesive Resin Cements to Zirconia

Objectives: The purpose of the study was to compare the shear bond strength of five self-adhesive resin cements used to bond zirconia. Methods: Seventy-two KATANA Zirconia STML (n=12) specimens were sectioned and sintered in an induction furnace (CEREC SpeedFire, Dentsply Sirona, Germany). Specimen surfaces were ground finished with 800 grit silicon carbide abrasive with cooling water and cleaned with ultrasonication in alcohol. Specimens were air-particle abraded with 50 μm aluminum oxide at 2.8 bar pressure. Cylindrical composite resin specimens (2.1 mm in diameter, 3 mm in height) were bonded to the zirconia samples with self-adhesive resin cements Panavia SA Universal (PSA), TheraCem (TCM), SpeedCem 2.0 (SCM), RelyX Unicem 2 (RCM), PermaCem 2.0 (PCM) and dual-cure multi-step composite resin cement Panavia V5 (control, PV5, after application of ceramic primer) following manufacturers’ instructions. A load of 1000 g was applied to the composite cylinders during bonding in an alignment apparatus, then light cured for 80 s. Samples were stored in distilled water at 37° C for 24 h, then subjected to 10,000 thermal cycles. Shear bond strength was determined using a universal testing machine at a crosshead speed of 0.5 mm/min expressed in MPa. The fractured surfaces of specimens were inspected with a stereo microscope and classified as 8 adhesive, cohesive, or mixed failures. One-way ANOVA test and Tukey test were applied for statistical analysis. Results: Shear bond strength values [MPa] were for PSA 8.64 (1.78 SD), TCM 9.05 (2.64 SD), SCM 8.54 (1.92 SD), RCM 7.60 (1.26 SD), PMC 7.59 (1.10 SD) and PV5 9.59 (1.55 SD). One-way ANOVA test revealed no statistically significant differences in shear bond strength between the resin cements tested (p\u3e0.05). Pair wise comparison using Tukey test revealed that the shear bond strength using RCM was statistically lower than that using PV5 (p\u3c0.05). Conclusions: According to the results of this in vitro study, self-adhesive resin cements can achieve shear bond strengths to zirconia that are comparable multi-step resin cements. In routine clinical application, self-adhesive resin cements can be a user- friendly, less technique sensitive alternative for bonding Zirconia restorations following the APC concept