Optical and Mechanical Properties of the Multi-Transition Zones of a Translucent Zirconia.

Objective: To characterize the composition, flexure resistance, and optical properties of a multilayer translucent zirconia in relation to its multi-transition zones.

Materials And Methods: A multilayer zirconia (5Y/4Y) and a conventional 3 mol% yttria partially stabilized zirconia (3Y) were investigated. Bar-shaped specimens were obtained from the enamel and dentin layers, and the vertical cross-section of 5Y/4Y (N = 10).

Effect of elastic gradients on the fracture resistance of tri-layer restorative systems.

Objectives: To assess the impact of elastic gradients formed among restorative material, cement, and substrate on the fracture resistance of tri-layer restorative systems.

Methods: Four CAD/CAM materials were utilized, two glass-ceramics (IPS e.max CAD, Vita Suprinity) and two resin-ceramic hybrids (Vita Enamic, Lava Ultimate).

Stress distribution on teeth restored with veneers using various incisal preparation designs: A 3D finite element analysis study.

Statement Of Problem: The type of veneer preparation is often chosen according to the patient's tooth structure and occlusion. Taking biomechanics into account in this decision-making process provides the clinician with more technical information on how to improve the clinical longevity of restorations. However, biomechanical analyses of veneer preparation designs are sparse.

High-viscosity glass-ionomer cement or composite resin for restorations in posterior permanent teeth? A systematic review and meta-analyses.

Objectives: Answer the PICO question: Do class I and II posterior restorations in permanent teeth placed with high-viscosity glass-ionomer cement (HV-GIC) fail more than composite resin (CR) restorations?

Data: The study was registered in the PROSPERO database (CRD42020138290). Randomized and controlled clinical trials, comparing the performance of HV-GIC and CR in load bearing cavities of posterior permanent teeth were included. Cochrane risk of bias tool and GRADE were used to assess the quality and certainty of the evidence.

Relationship between battery level and irradiance of light-curing units and their effects on the hardness of a bulk-fill composite resin.

Objectives: This study evaluated the relationship between the battery charge level and irradiance of light-emitting diode (LED) light-curing units (LCUs) and how these variables influence the Vickers hardness number (VHN) of a bulk-fill resin.

Materials And Methods: Four LCUs were evaluated: Radii Plus (SDI), Radii-cal (SDI), Elipar Deep Cure (Filtek Bulk Fill, 3M Oral Care), and Poly Wireless (Kavo Kerr). Irradiance was measured using a radiometer every ten 20-second activations until the battery was discharged.

In-office dental bleaching with violet light emitting diode: bleaching efficacy and pulpal temperature rise.

Objectives: This study evaluated the bleaching efficacy of different in-office protocols associated with violet light emitting diode (V-LED), and measured the pulpal temperature rise caused by V-LED with or without gel application.

Materials And Methods: Bovine incisors were distributed in 4 groups ( = 10): VL - V-LED; HP - 35% hydrogen peroxide (control); HYB - hybrid protocol, V-LED applied without gel for 10 irradiation cycles followed by V-LED applied with gel for another 10 irradiation cycles; and HPVL - gel and V-LED applied for 20 irradiation cycles. Three bleaching sessions were performed with 7-day intervals.

Is the clinical performance of composite resin restorations in posterior teeth similar if restored with incremental or bulk-filling techniques? A systematic review and meta-analysis.

Objectives: A systematic review was performed to analyze the clinical performance of class I and II restorations in posterior teeth placed with the incremental or the bulk-filling techniques. The primary outcome was retention/fracture rate, and the secondary outcomes evaluated were anatomical form, surface texture, color match, marginal adaption, marginal discoloration, caries, and postoperative sensitivity.

Methods: Electronic and manual searches were performed for randomized clinical trials comparing the clinical performance of composite resin restorations in posterior teeth placed with the incremental or the bulk-filling techniques.

Extended glaze firings for porcelain-veneered zirconia: Effects on the mechanical and optical behavior.

Objective: This study evaluated the effect of dwell time (conventional or extended) and cooling protocol (fast or slow) of self-glaze firings on the mechanical (flexural strength and crack propagation) and optical (color and translucency) properties of a porcelain-veneered zirconia system.

Methods: Bilayer disc-shaped samples were prepared (Vita VM9 + In-Ceram YZ) and divided according to the final thermal treatment: glaze firing followed by slow cooling (furnace opening at 200 °C) (G-S) or fast cooling (furnace opening at 600 °C) (G-F, manufacturer-recommended protocol), extended glaze firing (15 min of dwell time) followed by slow cooling (EG-S) or fast cooling (EG-F), or no thermal treatment (CTRL). Porcelain roughness (Ra and Rz) was measured before and after glaze firings.

Flexural strength and crystalline stability of a monolithic translucent zirconia subjected to grinding, polishing and thermal challenges.

The objective of this study is to investigate the magnitude of structural degradation of a monolithic translucent zirconia caused by clinically relevant grinding and polishing procedures, when associated or not with low temperature degradation (LTD), induced by accelerated hydrothermal aging using autoclave or thermocycling Ninety disks (Ø12 × 1 mm) were prepared from dental zirconia for monolithic restorations (Vipi Block Zirconn Translucent, Vipi). The specimens were divided into 3 groups (n = 30) according to surface treatment: As Sintered (untreated), Grind (diamond bur), Grind + Polish (diamond bur + polish); and then subdivided according to aging method (n = 10): Baseline (no aging), Autoclave (134°C, 2.2 kgf/cm pressure for 5 h), and Thermocycling (200,000 cycles, 5°C and 55°C, for 15 s each).

Novel speed sintered zirconia by microwave technology.

Objective: Continuous efforts have been made to hasten the zirconia densification process without compromising properties. This study evaluated the long-term structural durability of microwave speed-sintered zirconia (MWZ) relative to a conventionally sintered zirconia (CZ).

Methods: As-machined dental 3Y-TZP discs (Ø12 × 1.

Damage sensitivity of dental zirconias to simulated occlusal contact.

Objective: Mechanical damages can occur from dental restoration processing and fitting, or while it is in-service. This study evaluates the damage sensitivity of translucent zirconia (5Y-PSZ) relative to conventional 3Y-PSZ following mouth-motion simulations at various loads.

Methods: 5Y-PSZ and 3Y-PSZ discs were adhesively bonded to a dentin-like substrate and divided into groups according to the load (50 N or 200 N) and number of cycles (up to 10) used in the chewing simulation.

Wear behavior and microstructural characterization of translucent multilayer zirconia.

Objective: To characterize the composition, microstructure and wear properties of a multilayer translucent zirconia relative to the conventional 3Y-TZP.

Methods: Two types of ceramics were evaluated: a multilayer zirconia (MULTI, IPS e.max ZirCAD Multi, Ivoclar Vivadent) and a control 3Y-TZP (IPS e.

Non-silicate nanoparticles for improved nanohybrid resin composites.

Objective: Zirconia and alumina nanoparticles were coated with a silica-rich layer (ALSI and ZRSI) and used to prepare experimental nanohybrid resin composites, which were characterized and compared to a control commercial resin composite (Filtek Z350 XT).

Methods: Silica nanoparticles with sizes compatible to ALSI (Aerosil 150) and ZRSI (Aerosil OX 50) were tested as references. The volume of nanoparticles was equivalent across the composites, which also had consistent content of glass microparticles.

Cytotoxicity of contemporary resin-based dental materials in contact with dentin.

In this study, the cytotoxicity of different combinations of contemporary resin-based restoratives (adhesives, composites, luting agents) against human keratinocytes (HaCaT) was evaluated under two conditions, whether materials were applied to dentin or not. Adhesives (3-step etch-and-rinse/3ER: OptiBond FL; 2-step self-etch/2SE Clearfil SE Bond; Single Bond Universal/UNI), composites (conventional composite resin/CCR: Filtek Z350XT; flowable/FCR: Filtek Z350XT Flow; self-adhesive composite resin/SACR: Dyad Flow), and luting agents (conventional luting agent/CLA: Variolink-II; self-adhesive luting agent/SLA: RelyXU200) were combined according to their clinical use. Eluates from polymerized specimens applied to dentin were placed in contact with cells grown for 1 and 7 d.

Accurate and Efficient Thermal Stress Analyses of Functionally Graded Solids Using Incompatible Graded Finite Elements.

Functionally graded materials have found a wide usage in high temperature applications. The smooth transition from one material to another, in graded materials, may reduce thermal stresses, residual stresses and stress concentration factors as well as utilize properties of both materials. To perform accurate and efficient finite element analysis for heat transfer and transient thermal stress analyses in two-dimensional functionally graded materials, incompatible graded finite elements are developed and verified.

Probing the interfacial strength of novel multi-layer zirconias.

Objectives: The rapidly increasing use of zirconia-based CAD/CAM multi-layer structures in dentistry calls for a thorough evaluation of their mechanical integrity. This work examines the effect of the multi-layering architecture as well as variations in composition and inclusion of pigments among the layers on the flexural strength of multi-layer zirconias.

Methods: A modified 4-point bending test, aided by a Finite Element Analysis (FEA), was used to probe the interfacial strength of 3 classes of yttria-partially-stabilized zirconia: Ultra Translucent Multi-Layer (UTML-5Y-PSZ), Super Translucent Multi-Layer (STML-4Y-PSZ), Multi-Layer (ML-3Y-PSZ).

Radiofrequency therapy in esthetic dermatology: A review of clinical evidences.

Background: Chronological skin aging causes the modification of genetic material through enzymes and proteins changes. The process reduces cellular proliferation, along with loss of tissue elasticity, reduced ability to regulate aqueous exchanges, and inefficient tissue replication. Appearance is negatively affected by cumulative changes in coloration, texture, and elasticity over time.

Zirconia-reinforced lithium silicate crowns: Effect of thickness on survival and failure mode.

Objective: To evaluate the reliability and failure mode of zirconia-reinforced lithium silicate (ZLS) molar crowns of different thicknesses.

Methods: Monolithic ZLS molar crowns (0.5mm, 1.

New multi-layered zirconias: Composition, microstructure and translucency.

Objectives: To fully realize the range of indication and clinical advantages of the new multi-layered zirconias, a comprehensive understanding of their chemical composition, microstructure, low temperature degradation (LTD) resistance, and translucency properties is paramount.

Methods: A zirconia system (Katana, Kuraray Noritake), including 3 distinct grades of multi-layered zirconias, was selected for study: Ultra Translucent Multi-layered zirconia (UTML), Super Translucent Multi-layered zirconia (STML), and Multi-layered zirconia (ML). For different materials and their individual layers, the chemical composition, zirconia phase fractions, and microstructure were determined by X-ray fluorescence (XRF), X-ray diffraction (XRD), and field emission scanning electron microscopy (FE-SEM).

Do thermal treatments affect the mechanical behavior of porcelain-veneered zirconia? A systematic review and meta-analysis.

Objectives: A systematic review of in vitro studies was conducted to assess the effect of thermal treatments on flexural strength or critical load to failure of porcelain-veneered zirconia (PVZ).

Sources: Literature searches were performed up to June 2018 in PubMed/MEDLINE, Scopus and Web of Science databases, with no publication year or language limits.

Data: From 393 relevant studies, 21 were selected for full-text analysis, from which 7 failed to meet the inclusion criteria.

The progressive wear and abrasiveness of novel graded glass/zirconia materials relative to their dental ceramic counterparts.

Objective: To investigate the wear behavior of novel graded glass/zirconia materials and their abrasiveness to the antagonist relative to homogeneous zirconias (polished or glazed) and a glass-ceramic.

Methods: Graded glass/zirconia specimens were prepared by sintering with concurrent glass-infiltration of pre-sintered zirconia (3Y-TZP) with a polished or as-machined surface. Monolithic zirconia samples were sintered and their surfaces were polished or glazed (as-machined).

Influence of light-cured luting agents and associated factors on the color of ceramic laminate veneers: A systematic review of in vitro studies.

Objective: The luting agent plays a significant role in the appearance of ceramic laminate veneers (CLV), allowing improved/stable shade matching with adjacent teeth. A systematic review was conducted to investigate the influence of light-cured luting agents and color-associated factors aiming to draw guidelines for stable shade matching of CLV. The paper has also given an overview of the compositional characteristics of all luting agents and ceramic systems whose performance was presented herein.

Load-bearing capacity of lithium disilicate and ultra-translucent zirconias.

Objective: The aim of this study was to evaluate the load-bearing capacity of monolithic lithium disilicate (LiDi - IPS e.max CAD) and novel ultra-translucent zirconia restorative systems of various compositions: 5Y-PSZ (5 mol% yttria-partially-stabilized zirconia) and 4Y-PSZ (4 mol% yttria-partially-stabilized zirconia); relative to a 3Y-TZP (3 mol% yttria-stabilized zirconia) control.

Materials And Methods: Experiments were carried out with 10 disc specimens (Ø12 ×1 mm) per ceramic material.

Viscoelastic finite element analysis of residual stresses in porcelain-veneered zirconia dental crowns.

The main problem of porcelain-veneered zirconia (PVZ) dental restorations is chipping and delamination of veneering porcelain owing to the development of deleterious residual stresses during the cooling phase of veneer firing. The aim of this study is to elucidate the effects of cooling rate, thermal contraction coefficient and elastic modulus on residual stresses developed in PVZ dental crowns using viscoelastic finite element methods (VFEM). A three-dimensional VFEM model has been developed to predict residual stresses in PVZ structures using ABAQUS finite element software and user subroutines.

Speed sintering translucent zirconia for chairside one-visit dental restorations: Optical, mechanical, and wear characteristics.

The fabrication of zirconia dental restorations is a time-consuming process due to traditional slow sintering schemes; zirconia (Y-TZP) produced by these conventional routes are predominantly opaque. Novel speed sintering protocols have been developed to meet the demand for time and cost effective chairside CAD/CAM-produced restorations, as well as to control ceramic microstructures for better translucency. Although the speed sintering protocols have already been used to densify dental Y-TZP, the wear properties of these restorations remain elusive.