Light-curing of restorative composite through milled and 3D-printed full-contour zirconia for adhesive luting.

Objectives: To evaluate the effect of different zirconia compositions and manufacturing processes on the light irradiance (LI), to measure the degree of conversion (DC) of solely light-curing restorative composite underneath these zirconia grades and to evaluate the respective zirconia microstructures.

Methods: Six dental zirconia grades (GC HT, GC UHT [GC]; Katana HT, Katana UTML [Kuraray Noritake]; Lava Esthetic, Lava Plus [3 M Oral Care]) were cut and sintered per manufacturer instructions. One 3D-printed zirconia grade (XJet [XJET]) was prepared according to previous research.

Cytotoxicity assessment of eluates from vacuum-forming thermoplastics.

Objectives: This study aimed to evaluate possible cytotoxic effects of thermoplastic materials commonly used for occlusal splints and orthodontic appliances.

Methods: Seven thermoplastics were included: three variants of the Essix sheets (C+, Plus, and Tray Rite; Dentsply Sirona), three thermoplastics (Bleach Heavy, Splint, and X-Heavy; Cavex Holland) and Invisalign (Align Technology). Cylindrical specimens (n = 24; 10 mm diameter) were incubated in cell culture medium for 24 h and 14 days.

Effect of printing layer orientation and polishing on the fatigue strength of 3D-printed dental zirconia.

Objective: The aim of the study was to evaluate the influence of surface polishing and printing layer orientation on the fatigue behaviour of 3 mol% yttria-stabilized zirconia (3Y-TZP) by stereolithography (SLA) in comparison with subtractive manufacturing.

Materials And Methods: 60 experimental zirconia bar-shaped specimens were 3D-printed (P) via SLA, and 30 specimens were milled (M) from commercial zirconia block (Lava™ Frame, 3 M ESPE AG). All specimens had the same dimensions (1 mm × 1 mm x 12 mm) after sintering.

3D printed zirconia dental implants with integrated directional surface pores combine mechanical strength with favorable osteoblast response.

Dental implants need to combine mechanical strength with promoted osseointegration. Currently used subtractive manufacturing techniques require a multi-step process to obtain a rough surface topography that stimulates osseointegration. Advantageously, additive manufacturing (AM) enables direct implant shaping with unique geometries and surface topographies.

Mechanical properties-translucency-microstructure relationships in commercial monolayer and multilayer monolithic zirconia ceramics.

Objectives: To evaluate the phase composition, microstructure, optical properties and mechanical properties of eight commercially available multilayer and monolayer monolithic dental zirconias.

Methods: Five commercial 3Y-TZP (GC ST, GC HT [GC, Tokyo Japan]; Katana ML, Katana HT [Kuraray Noritake] and Lava Plus [3M Oral Care]) and three Y-PSZ (Katana STML, Katana UTML [Kuraray Noritake]; GC UHT [GC, Tokyo Japan]) zirconia ceramic grades were cut in plate-shaped specimens, sintered according to the manufacturer's instructions and mirror polished. The zirconia chemical composition was determined using X-ray fluorescence (XRF), phase composition was characterized using X-ray diffraction (XRD), while the grain size was measured using scanning electron microscopy (SEM).

Mechanical properties, aging stability and translucency of speed-sintered zirconia for chairside restorations.

Objective: To evaluate the performance of zirconia ceramics sintered in a speed sintering induction furnace by comprehensive understanding of their optical and mechanical properties, microstructure, phase composition and aging stability, in comparison to ceramics sintered in a conventional furnace.

Methods: Speed sintered (SS) Katana STML (Kuraray Noritake) (total thermal cycle/sintering time/dwell temperature: 30min/16min/1560°C) and CEREC Zirconia (CEREC Zr) (Dentsply Sirona) (15min/2min/1578°C) were compared to conventionally sintered (CS) Katana STML (6.8h/2h/1550°C) and inCoris TZI (4h/2h/1510°C).

Filtration efficiency of surgical and FFP3 masks against composite dust.

The aim of this study was to investigate the protection efficiency of two types of face masks against composite dust and to characterize the particles that penetrated through the masks. Composite dust was created by grinding a commercial nano-filled composite in a plexiglass box without using water cooling or high vacuum evacuation, in order to obtain a worst-case exposure. Dust particles were collected using a personal inhalable aerosol sampler (IOM) fixed inside a custom-made phantom head.

Agglomeration of titanium dioxide nanoparticles increases toxicological responses in vitro and in vivo.

Background: The terms agglomerates and aggregates are frequently used in the regulatory definition(s) of nanomaterials (NMs) and hence attract attention in view of their potential influence on health effects. However, the influence of nanoparticle (NP) agglomeration and aggregation on toxicity is poorly understood although it is strongly believed that smaller the size of the NPs greater the toxicity. A toxicologically relevant definition of NMs is therefore not yet available, which affects not only the risk assessment process but also hinders the regulation of nano-products.

Cytotoxic and genotoxic potential of respirable fraction of composite dust on human bronchial cells.

Objective: To determine the cytotoxic and genotoxic potential of the respirable fraction of composite dust (<4 μm) on human bronchial epithelial cells.

Methods: Composite sticks of three commercial dental composites (Filtek Supreme XTE, Grandio, Transbond XT) were ground in an enclosed plexiglass chamber with a rough dental bur (grain-size 100 μm) and the generated airborne respirable dust was collected in a personal cyclone on a teflon filter (pore size 5 μm). Immediately after particle collection, the dust was quantified gravimetrically and the particles were suspended in cell culturing medium.

The effect of water spray on the release of composite nano-dust.

Objective: To evaluate the collection efficiency of water spray on the release of airborne composite particles during grinding of composite materials.

Materials And Methods: Composite sticks (L:35 mm × W:5.4 mm × H:1.

Long-term elution of monomers from resin-based dental composites.

Objective: To bridge the gap between the current alarming literature on resin-based dental materials and the limited clinical observations, more precise knowledge on the actual quantity of released compounds should be acquired. The objective of this study was to quantify the long-term elution of various compounds from resin-based dental composites during one year.

Methods: Eight materials were investigated: G-aenial Anterior, G-aenial Posterior, Venus, Venus Pearl, Venus Diamond, Ceram X mono, Dyract and Filtek Supreme XTE.

Freshly-mixed and setting calcium-silicate cements stimulate human dental pulp cells.

Objectives: To evaluate the effect of the eluates from 3 freshly-mixed and setting hydraulic calcium-silicate cements (hCSCs) on human dental pulp cells (HDPCs) and to examine the effect of a newly developed hCSC containing phosphopullulan (PPL) on HDPCs.

Methods: Human dental pulp cells, previously characterized as mesenchymal stem cells, were used. To collect the eluates, disks occupying the whole surface of a 12-well plate were prepared using an experimental hCSC containing phosphopullulan (GC), Nex-Cem MTA (GC), Biodentine (Septodont) or a zinc-oxide (ZnO) eugenol cement (material-related negative control).

Saturation reduces in-vitro leakage of monomers from composites.

Objective: Accurate knowledge of the quantity of released monomers from composites is important. To evaluate the elution of monomers, polymerized composites are typically immersed in an extraction solvent. The objective was to determine whether the volume of extraction solvent and the immersion time influences monomer leachability from dental composite materials.

Silica nanoparticles inhibit the cation channel TRPV4 in airway epithelial cells.

Background: Silica nanoparticles (SiNPs) have numerous beneficial properties and are extensively used in cosmetics and food industries as anti-caking, densifying and hydrophobic agents. However, the increasing exposure levels experienced by the general population and the ability of SiNPs to penetrate cells and tissues have raised concerns about possible toxic effects of this material. Although SiNPs are known to affect the function of the airway epithelium, the molecular targets of these particles remain largely unknown.

Cyto-genotoxic and DNA methylation changes induced by different crystal phases of TiO-np in bronchial epithelial (16-HBE) cells.

With the increase in use of TiO-np, a better understanding of their safety is important. In the present study the effect of different crystal phases of TiO-np (anatase, rutile and anatase: rutile mixture; 20-26nm) were studied for cyto-genotoxicity and global DNA methylation and hydroxymethylation. Cytotoxic response was observed at a concentration of 25μg/ml for the particles tested.

Simultaneous analysis of bisphenol A based compounds and other monomers leaching from resin-based dental materials by UHPLC-MS/MS.

Resin-based dental materials have raised debates concerning their safety and biocompatibility, resulting in a growing necessity of profound knowledge on the quantity of released compounds into the oral cavity. In this context, the aim of this study was to develop a comprehensive and reliable procedure based on liquid chromatography with mass spectrometry for the simultaneous analysis of various leached compounds (including bisphenol A based compounds) in samples from in vitro experiments. Different experiments were performed to determine the optimal analytical parameters, comprising mass spectrometry parameters, chromatographic separation conditions, and sample preparation.

Epigenetic effects of carbon nanotubes in human monocytic cells.

Carbon nanotubes (CNTs) are fibrous carbon-based nanomaterials with a potential to cause carcinogenesis in humans. Alterations in DNA methylation on cytosine-phosphate-guanidine (CpG) sites are potential markers of exposure-induced carcinogenesis. This study examined cytotoxicity, genotoxicity and DNA methylation alterations on human monocytic cells (THP-1) after incubation with single-walled CNTs (SWCNTs) and multi-walled CNTs (MWCNTs).

Cytotoxic effects of composite dust on human bronchial epithelial cells.

Introduction: Previous research revealed that during routine abrasive procedures like polishing, shaping or removing of composites, high amounts of respirable dust particles (<5μm) including nano-sized particles (<100nm) may be released.

Objective: To determine the cytotoxic potential of composite dust particles on bronchial epithelium cells.

Methods: Composite dust of five commercial composites (one nano-composite, two nano-hybrid and two hybrid composites) was generated following a clinically relevant protocol.