Layer Technique Research Articles

The influence of suturing and or gluing of perforated Schneiderian membrane during sinuslift procedure on the outcome: a retrospective study

The sinus lift procedure has become the most common method for maxillary bone augmentation. The most frequently observed intraoperative complication is the perforation of the Schneiderian membrane. Various treatment options have been proposed for managing these perforations, including the use of resorbable membranes, centrifugated blood products as PRF, or PRGF, suturing, and fibrin glue application. While long-term studies exist for the use of resorbable membranes to close perforations, there is limited data on the long-term outcomes of suturing or gluing the perforated sinus membrane. The aim of this retrospective study is to evaluate the long-term outcomes of suturing and/or applying fibrin glue to repair perforated sinus mucosa during sinus floor elevation procedures. Between 2005 and 2009, a total of 692 patients underwent 923 sinus lift surgeries, and Schneiderian membrane perforation occurred in 202 sinus floor elevations (21.98%) across 168 patients. The main documented causes of perforations, which ranged from 2 to 10 mm in diameter, were the presence of septa, followed by thin and adherent membranes. Of the perforations, 100 (49.5%) were treated with microsurgical suturing combined with fibrin glue, 78 (38.6%) were treated with fibrin glue alone, and 24 (11.9%) were treated exclusively with suturing. Sinus grafting was performed using autogenous bone in combination with a biomaterial, following the layering technique. All surgeries resulted in primary healing without complications, enabling all patients to undergo restoration as planned. The long term clinical and radiological evaluations of 44 randomly selected patients who followed the recall program up to 10 years post operative confirmed the effectiveness of this treatment approach.

Explainable deep learning on multi-target time series forecasting: an air pollution use case

Urban air pollution represents a significant threat to public health and the environment, with nitrogen oxides, ozone, and particulate matter being among the most harmful pollutants. These contribute to respiratory and cardiovascular diseases, particularly in urban areas with high traffic and elevated temperatures. Machine learning, especially deep learning, shows promise in enhancing the prediction accuracy of prediction of pollutant's concentrations. However, the “black box” nature of these models often limits their interpretability, which is crucial for informed decision-making. Our study introduces a Temporal Selection Layer technique within deep learning models for time series forecasting to tackle this issue. This technique not only improves prediction accuracy by embedding feature selection directly into the neural network, but also enhances interpretability and reduces computational costs. In particular, we applied this method to hourly concentration data of pollutants, including particulate matter, ozone, and nitrogen oxides, from five urban monitoring sites in Graz, Austria. These concentrations were used as target variables to predict, while identifying the most relevant features and periods that affect prediction accuracy. Comparative analysis with other embedded feature selection methods showed that the Temporal Selection Layer significantly enhances both model effectiveness and transparency. Additionally, we applied explainable techniques to evaluate the impact of weather and time-related factors on air pollution, which also helped assess feature importance. The results show that our approach improves both prediction accuracy and model interpretability, leading finally to more effective pollution management strategies.

Radiofrequency sheath rectification on WEST: application of the sheath-equivalent dielectric layer technique in tokamak geometry*

Abstract Radiofrequency sheath rectification is a phenomenon relevant to the operation of Ion Cyclotron Range of Frequencies (ICRFs) actuators in tokamaks. Techniques to model the sheath rectification on 3D ICRF antenna geometries have only recently become available (Shiraiw et al 2023 Nucl. Fusion 63 026024; Beers et al 2021 Phys. Plasmas 28 093503). In this work, we apply the ‘sheath-equivalent dielectric layer’ technique, used previously only on linear devices (Beers et al 2021 Phys. Plasmas 28 103508), in tokamak geometry, computing rectified sheath potentials on the WEST ICRF antenna. Advancing the state of the art in sheath rectification modeling, we compute the sheath potentials not just on the limiters, but also on the Faraday Screen bars. The calculations show a peak rectified DC potential of 300 V on the limiters and 500 V on the Faraday screen. Assuming a typical sputtering yield curve, the RF sheath rectification increases the sputtering yield from the limiters by a factor of 2.6 w.r.t. the sputtering due to the non-rectified thermal sheath.

Layered MXene Films via Self-Assembly.

MXene has attracted significant attention as a 2D material family due to its metallic conductivity and abundant surface functional groups and has been extensively studied and applied as bulk materials and microscale thin films. MXene possesses ionizable surfaces and edges, as well as high surface area. Its customizable dispersibility demonstrates unique advantages in self-assembly solution processing. Recent studies have demonstrated the application value of layered MXene films at the nanoscale thickness and the reliance of processing on self-assembly techniques. However, this field currently lacks sufficient attention. Here, the regulatory mechanisms are summarized for the preparation of layered MXene films through self-assembly techniques, as well as introduce their applications. Moreover, the future challenges of large-scale applications of MXene self-assembly techniques are proposed. It is believed that this review would provide a dynamic and promising path for the development of layered MXene self-assembly techniques.

Cost-Effective High Gain Wideband Antenna with Dual Partially Reflective Surface for 5G-mmWave Application

This research presents the performance improvement of the of rectangular patch microstrip antenna. The purpose is to increase gain and bandwidth with design on the PRS (Partially Reflective Surface) dual layer technique. There is a developing the low-cost substrate-based antennas suitable for 5G millimeter-wave. The prototype antenna achieves a maximum gain of 11.8 dBi at a frequency of 25.5 GHz. The gain increases by 6 dB throughout its operational frequency range, with an OBW (Overlap bandwidth) of 20.9%, covering frequencies from 24.0 GHz to 29.9 GHz. The performance achieved results indicate that the prototype antenna can be effectively utilized for 5G millimeter-wave communication applications in Thailand.

Clinical, radiographic and biochemical assessment of proximal cavities restored with composite resin using incremental vs. bulk packing techniques: One-year randomized clinical trial

BackgroundBulk-fill resin composites may suffer from recurrent caries around compound proximal restorations in posterior teeth, especially at the proximo-gingival interface.Over 12 months, will the bulk fill technique affect the caries recurrence rate at gingival margins when compared to the conventional incremental packing technique? How early will the first clinical, radiographical, and biochemical evidence of caries recurrence occur?MethodsAfter randomization, in 30 patients with two compound (OM or OD) supragingival lesions, one tooth was restored using the bulk fill technique on one side (group 1) (n = 15). In contrast, the other tooth on the other side was restored utilizing the incremental layering technique (group 2) (n = 15). Both teeth received restorative material (X-tra fil, Voco, Cuxhaven, Germany). The FDI criteria were used to evaluate restorations. As for the periodontal assessment, the gingival index, plaque index, papillary bleeding scoring index and periodontal pocket depth were evaluated. The gingival crevicular fluid (GCF) specimens were gathered, and MMP-9 was extracted and quantitated by ELISA. A customized radiographic template was designed, and 3D printed digital bitewing radiographs were taken. Assessments were done clinically, radiographically and biochemically at baseline (1 week) and after 3, 6 and 12 months. Data was statistically analyzed.ResultsThe null hypothesis was accepted clinically; no statistically significant differences appeared between bulk and incrementally filled posterior restorations. As for the radiographic assessment, the null hypothesis was accepted except for increased periodontal ligament width at 3 months. The null hypothesis for the biochemical evaluation was rejected as there were significant changes in levels of MMP-9 at different testing times.Conclusions1. With similar results but less sensitivity and significant time saving, the bulk fill technique can be considered an efficient alternative to the incremental fill technique in restoring proximal cavities. 2. Early evidence of caries recurrence can be correlated to an increase in the MMP-9 level in gingival crevicular fluid, followed by an increase in radiographic periodontal ligament width measurement.Trial registrationAn ethical approval from the Research Ethics Committee at the Faculty of Dentistry, October 6 University, (Approval No. RECO6U/5-2022). The study was registered at the Pan African Clinical Trials Registry on 24/07/2023 with an identification number (PACTR202307573531455).

Complex Diagnostics of Silicon-on-Insulator Layers after Ion Implantation and Annealing

A technology was developed for activating ion-implanted dopants in silicon-on-insulator layers at a low annealing temperature (600°C) using the pre-amorphization technique of a silicon device layer. In the case of phosphorus implantation, silicon was amorphized directly by dopant ions. In the case of boron implantation for pre-amorphization, the layers were preliminary irradiated with argon or fluorine ions. Complex diagnostics of the implanted layers was carried out using secondary ion mass spectrometry, X-ray diffractometry and small-angle X-ray reflectometry. The combination of methods made it possible to characterize the impurity distribution, the degree of silicon crystallinity, the layer thicknesses, and the interface widths in structures. The results of diagnostics of the structure and composition correlate well with calculations in the SRIM software package and the electrophysical characteristics of the layers after annealing. It was shown that the use of argon for pre-amorphization of silicon interfered with the recrystallization process and did not make it possible to achieve acceptable electrical characteristics of the doped layer. Amorphization with phosphorus and pre-amorphization with fluorine during boron implantation allowed obtaining the required values of the resistance of the doped layers after annealing at a temperature of 600°C. The use of a complex approach made it possible to optimize the modes of amorphization, ion doping, and annealing of silicon-on-insulator structures at low temperatures, necessary for the creation of light-emitting device structures based on silicon-germanium nanoislands.

Double-Needle Bidirectional Barbed Wire Continuous Layered Suture Technique for Laparoscopic Stage I Common Bile Duct Surgery.

Background: Laparoscopic common bile duct exploration (LCBDE) proves a safe and effective treatment for choledochal stones. After LCBDE, preferred choledochal closure is favored for short- and long-term outcomes compared with t-tube drainage. However, there are no relevant studies on the technique of layered closure of the common bile duct with double-needle bidirectional barbed suture at home and abroad. Materials and Methods: A retrospective study of 37 patients who underwent laparoscopic choledochotomy from January 2021 to October 2023 in our hospital was performed. A continuous layered one-stage suture using two-needle bidirectional barb wire. The primary outcomes were stone clearance, operative time, blood loss, and complications. Secondary outcomes were complications, length of hospitalization, and time to drain removal. Results: During the study period, laparoscopic surgery was successful in all cases, and the initial stones were removed without complications. Conclusion: The treatment of choledocholithiasis with continuous layered one-stage suture with double-needle bidirectional barbed wire after LCBDE is a new convenient and effective treatment in selected patients.

An analysis of the high-homogeneity preparation, thermo-mechanical deformation and recrystallization behavior of a novel superalloy with γ′ content reaching 73%

A deformed superalloy with γ′ content reaching 73% has been designed by ourselves. In this work, the problems of preparation and deformation caused by the high γ′ phase content were solved by the electron beam smelting layered solidification technique (EBS-LST) and hot extrusion. Initially, the superalloy with low segregation and fine microstructure was prepared by EBS-LST, followed by conducting hot deformation experiments at different temperatures and strain rates. The compression curves are corrected, and the constitutive model, recrystallization models and thermo-mechanical processing maps were established based on the corrected curves, and the recrystallization mechanisms were analyzed by TEM and EBSD. Finally, the suitable hot extrusion parameters were obtained indirectly through the hot processing map, and the designed alloy was hot extruded. The microstructure of the extruded alloy is free of cracks and is characterized by fine equiaxed grains.

Modeling of visco-electro-elastic responses of PZT-based functionally graded beam benders

The modeling of the visco-electro-elastic behavior of functionally graded beam benders with PZT constituents is accomplished via a hierarchical framework that is based on the homogenization technique for composite layers and the laminate theory for a composite laminate. The representation of a bulk PZT constituent is based on linear visco-electro-elastic constitutive equations. The resulting bending displacements of PZT-graded bimorph and multimorph are obtained under the assumption of the Euler–Bernoulli beam. The experimental data of the bending displacements versus applied voltage are compared with the predictions for a bimorph and a multimorph, resulting in a good agreement. The responses of a bender to a complete cycle of applied voltage are shown in order to reveal the critical hysteretic actuation due to the presence of a visco-electro-elastic PZT material in a functionally graded piezoelectric beam bender which is made by functionally graded piezoelectric materials.

Introducing a novel approach to dental color reproduction using AI technology.

This article aims to describe a systematic method for tooth color reproduction with ceramics restorations employing artificial intelligence (AI) software named Matisse. It provides a comprehensive analysis of the entire process, beginning with shade-taking and extending to ceramic application in a complex clinical case in the anterior region-specifically, a single central restoration supported by an implant. The clinical case presented highlights the potential of Matisse software for generating ceramic (inSync-Jensen Dental, USA) and staining (Miyo-Jensen Dental, USA) recipes over a zirconia abutment (Katana-Noritake Dental, Japan). This approach achieves an optimal single central restoration utilizing CAD-CAM and layering techniques. The systematic method employing the Matisse software achieved accurate color reproduction for a single central restoration supported by an implant. This result was achieved by the dental ceramist within the first attempt and without seeing the patient in the entire process. The Matisse AI-assisted protocol offers a systematic and scientifically grounded method for color reproduction in dentistry for indirect restorations.

Alternatives for Enhancing Mechanical Properties of Recycled Rubber Seismic Isolators.

Base isolators, traditionally made from natural rubber reinforced with steel sheets (SERIs), mitigate energy during seismic events, but their use in developing countries has been limited due to high cost and weight. To make them more accessible, lighter, cost-effective reinforcement fibers have been utilized. Additionally, the increasing use of natural rubber has caused waste storage and disposal issues, contributing to environmental pollution and disease spread. Exploring recycled rubber matrices as alternatives, this study improves seismic isolators' mechanical properties through modified reinforcements and layer adhesion. Eight reinforcement materials and eight adhesives, which may be activated with or without heat application, are systematically evaluated. Employing the chosen reinforcements and adhesives, prototypes are tested mechanically to examine their vertical and horizontal performance through cyclic compression and cyclic shear testing. Two innovative devices using recycled rubber matrices were developed, one using a layering technique and another through a monolithic approach shaped with heat and pressure. Both integrate a fiberglass mesh reinforced with epoxy resin; one employs a heat-activated hybrid adhesive, while the other uses a cold bonding adhesive. These prototypes exhibit potential in advancing seismic isolation technology for low-rise buildings in developing countries, highlighting the viability of recycled materials in critical structural applications.

Enhancing PEMFC Performance: Optimization of Hot-Pressed Decal Transfer Conditions for MEA Fabrication

Proton exchange membrane fuel cells (PEMFCs) hold significant promise in curbing greenhouse gas emissions within the transportation sector. While historically more expensive than conventional internal combustion engines, the cost per kW is poised to significantly drop as production volumes increase and the adoption of fuel cell electric vehicles progresses [1]. In heavy-duty vehicle applications, predictions suggest that hydrogen fuel cells will achieve a cost equivalence with diesel, potentially becoming the most cost-effective option when evaluating the total ownership expenses [2]. Membrane-electrode-assemblies (MEAs) serve as the core of fuel cells, where all reactions—proton and electron generation, distribution, and consumption occur. Their efficiency dictates both cell performance and lifespan. Various methods for fabricating MEAs have been developed, including decal transfer, catalyst-coated membrane (CCM), and catalyst-coated gas diffusion layer (CCG) techniques. Among these, the decal transfer method is widely regarded as the most appropriate for large-scale production of MEAs [3]. This study delves into an examination of diverse hot-pressed decal transfer conditions for the preparation of MEAs tailored for PEMFC application. Our investigation involves fabricating MEAs through hot-press decal transfer at temperatures spanning 115°C to 145°C and pressures ranging from 200 psi to 400 psi, each held for a 5-minute duration. Electrochemical characterizations were performed within a single-cell setup to assess MEA performance. Moreover, an accelerated stress test (AST) was carried out to scrutinize the stability of the fabricated MEAs concerning their decal transfer conditions and morphological variations. Our study extensively explored catalyst layers transferred under diverse hot-pressed decal transfer conditions, focusing on their fuel cell performance and transport properties. To comprehensively understand the influence of morphological alterations on electrochemical characteristics, additional morphological characterizations, including white light interferometer (WLI) imaging, field emission scanning electron microscopy (FESEM), Brunauer-Emmett-Teller (BET) surface area analysis, and nano-computed tomography (Nano-CT) were employed for MEA evaluation. Our findings indicate that the MEA produced at 145°C and 200 psi exhibited superior performance in both pre- and post-AST testing. Comprehensive experimental results and insights will be elaborated upon during the conference presentation.

Effect of Er:YAG Laser Application and Sandblasting on Shear Bond Strength of Veneering Ceramic to Zirconia Core.

Objectives: Porcelain chipping and delamination are among the shortcomings of all-ceramic restorations. This study aimed to assess the effect of laser irradiation and sandblasting on shear bond strength (SBS) of zirconia to veneering porcelain. Materials and Methods: In this in vitro, experimental study, 60 zirconia blocks were randomly divided into three groups (n=20) for surface treatment with Er:YAG laser, sandblasting, and no surface treatment (control). Each group was randomly divided into two subgroups (n=10) for porcelain application by the layering or the pressing technique. The surface roughness, SBS, and failure mode were determined and analyzed using two-way ANOVA, Tukey's HSD test, Chi-square test, and Pearson's correlation test (alpha=0.05). Results: The mean SBS was 8.16±3.66 MPa, 9.32±2.7 MPa, and 11.85±3.06 MPa in the control, laser, and sandblasting groups, respectively. The SBS was significantly different among the three groups (P=0.002). The failure mode of the three groups was not significantly different (P>0.05). The sandblasted group showed significantly higher surface roughness than the control and laser groups (P<0.001). Conclusion: Sandblasting yielded higher SBS particularly when the porcelain was applied by the layering technique. Although laser irradiation increased the SBS, the difference with the control group was not statistically significant.

Creation of Contemporary Batik with Brush Stroke Motifs Using Layering Technique

Creation of Contemporary Batik with Brush Stroke Motifs Using Layering Technique

Prussian blue pigment: Bridging the historical palette to modern innovations

This comprehensive review explores the multifaceted realm of Prussian Blue, a pigment with a rich history and varied applications tracing its origins, artistic applications, and chemical properties. Beginning with its origins as a laboratory creation, the paper traces its evolution into a revered pigment in the artistic world. The review explores the electronic transitions responsible for Prussian Blue's deep blue hue, shedding light on the intricate chemistry behind its vivid coloration. Additionally, the pivotal role of iron ions in determining the pigment's properties is examined in detail, highlighting the importance of precise composition in achieving desired color characteristics. Challenges in the reintegration of Prussian Blue into conservation and restoration projects are also explored, emphasizing the importance of careful preservation techniques to maintain the pigment's integrity and vibrancy. The review discusses the pigment's lightfastness and stability, addressing common issues such as fading and discoloration over time. A notable phenomenon of bronzing particularly associated with Chinese Blue has been characterized by the appearance of yellow or brown hues on the surface of the pigment, that has puzzled artists and conservators for centuries. The review delves into the underlying causes of bronzing, examining factors such as environmental conditions, pigment composition, and application techniques. The review explores the pigment's interactions with other blues and whites, offering insights into the spectrum of shades achievable through careful color mixing and layering techniques. The paper revisits the perennial debate surrounding the permanence of Prussian Blue. While some argue for its enduring stability and longevity, others point to instances of fading and discoloration observed in historical artworks. The manuscript navigates these conflicting perspectives, providing an understanding of Prussian Blue's permanence in different contexts. Prussian Blue stands as a testament to the symbiotic relationship between science and art, where its molecular structure and vibrant shades continue to inspire both chemists in laboratories and artists in studios. The Prussian Blue emerges as a captivating convergence of art and chemistry that has left an indelible mark on laboratory benches and artists' canvases. The unique interplay of ferric and ferrous ions, not only renders a deep blue color but also makes it sensitive to the variation of its environment. The interplay of its refractive index, bronzing tendencies, and tinting strength shapes its artistic applications, influencing the vibrant hues it contributes to diverse palettes. The permanence paradox surrounding Prussian Blue underscores the importance of precision in its preparation. As artists mix and blend, the pigment unveils its versatility, playing a pivotal role in color harmonies and shade variations. Beyond its role in art, Prussian Blue finds diverse applications in medicinal and industrial contexts. From its use as an antidote for heavy metal poisoning to its incorporation into high-performance materials such as batteries and sensors, Prussian Blue continues to demonstrate its versatility and utility in modern society. The review highlights these varied applications, showcasing Prussian Blue's enduring relevance and evolution beyond its historical roots.

Flowable bulk-fill versus layering restorative material on Class II restorations: A randomized clinical trial

ObjectiveThis study evaluated the clinical performance of Class II restorations made with flowable bulk-fill base versus conventional layering ORMOCER-based restorative material in a split-mouth randomized clinical trial. MethodsThirty patients received two class II restorations (n = 60) performed with different strategies. All preparations received the application of the universal self-etching adhesive system according to the manufacturer's recommendation, followed by the placement of a sectional matrix, wooden wedge, and separation ring. The first restoration was performed using 4 mm of flowable bulk-fill material covered by 2 mm of conventional viscosity restorative material (Bulk-fill technique). The second restoration was performed only with the conventional viscosity material, with a maximum of 2 mm thick increments, up to fill the cavity (Layering technique). After occlusal adjustment, the same polishing system was used for all restorations. Evaluations using the FDI criteria were conducted after 7 days, 12, and 24 months. Data were analyzed with the Fisher's Exact test (α=0.05). ResultsFrom 30 participants, 24 attended the 24-month recall, and 48 restorations were evaluated. All restorations received acceptable overall scores for esthetic and biological properties after this period, while only 6.66 % of the restorations exhibited unacceptable overall scores for the functional properties in both groups. No significant differences between the tested restorative materials and techniques were found for each FDI criterion assessed. The success rate after 2 years was 93.33 % for both groups. ConclusionBoth restorative materials exhibited good clinical performance for the parameters analyzed with no differences between them after 24-month follow-up. Clinical relevanceFlowable bulk-fill ORMOCER-based material is a suitable alternative for direct Class II restorations, providing good clinical outcomes and simplifying the restorative procedure. Clinical trial registration numberRBR-6mvp9w

Deep learning model using classification for diabetic retinopathy detection: an overview

Early detection of diabetic retinopathy is a serious disease for diabetics to minimize their sightlessness risks. The different approaches take a much longer time for a very large training dataset. In classifying to better the accuracy of diabetic retinopathy, a novel technique called MAP Concordance Regressive Camargo’s Index-Based Deep Multilayer Perceptive Learning Classification (MAPCRCI-DMPLC) has been introduced with minimum time consumption. The novel model of MAPCRCI-DMPLC comprises the input layer, hidden layers, and output layer for detecting diabetic retinopathy at an early stage through high accuracy and less moment consumption. The proposed MAPCRCI-DMPLC model collected the retinal fundus images from the dataset as input. After that, we carried out image preprocessing using the MAP-estimated local region filtering-based preprocessing technique in the first hidden layer. In the second hidden layer, Camargo’s index-based ROI extraction is performed to identify the infected region. Then, Concordance Correlative Regression is applied for texture feature extraction. Then the color feature is extracted, beginning the image. The features extracted to the output layer to classify the different levels of DR using the swish activation function through higher accuracy. An investigational assessment using a retinal image dataset on factors such as peak signal-to-noise ratio (PSNR), disease detection accuracy (DDA), false-positive rate (FPR), and disease detection time (DDT), regarding the quantity of retinal fundus images and image dimension. The quantitative and qualitatively analyzed outcome shows a better presentation of our proposed MAPCRCI-DMPLC technique when compared through the five state-of-the-art approaches.

Upcycling spent Ni–Cd battery for selective synthesis of nanoparticles to harness into electro-conductive thin films: An eco-friendly approach for e-waste management

Inspired by Sustainable Development Goal-12 (responsible consumption and production) to reduce e-waste, an environment friendly extraction of Cd, Ni and Co from Ni–Cd spent batteries have been reported here using ammonium chloride as a chlorinating agent for the first time. Multiple parameters i.e. dose of chlorinating agent, roasting time, and temperature has been optimized that resulted in extraction of 99.93 % Cd, 90.1 % Ni and 84.81 % Co. Metal enriched leachate was then subjected to unique precipitation steps that resulted in synthesis of Cd nanoparticles, Co3O4·NiO composite nanoparticles, and NiO nanoparticles, characterized through XRD and FESEM-EDX. Synthesized nanoparticles were further employed in the fabrication of electro-conductive nano thin films via Layer by Layer (LbL) technique. Film buildup of six novel architectures was monitored using an Ellipsometer. Homogenous film growth was tailored by optimizing ratio, concentration and dipping time of nanoparticles and polymer solutions. Conductivity studies revealed that imbedding synthesized nanoparticles impart significant conductive behavior in thin films with maximum conductivity of 1.8 × 10−4 S/cm, in addition to exhibiting appreciable resistance against 0.1 M HCl, 0.1 M NaOH and acetone. Contact angle and AFM images revealed that the films were slightly wettable and homogenous respectively. Conclusively not only Cd, Ni and Co were successfully recycled from Ni–Cd spent batteries employing greener technique but were also harnessed into robust nano-thin films with focus towards electro-conductivity based applications.

New Perspectives in Overcoming Bulk-Fill Composite Polymerization Shrinkage: The Impact of Curing Mode and Layering.

The purpose of this study was to investigate the effect of different light curing modes on the polymerization shrinkage of a bulk-fill composite and to evaluate the impact of two layering techniques on the cuspal deflection. Nine different light curing modes were tested on bulk-fill composite samples in aluminum MOD cavities. Intensity, duration, and illumination distance were the factors that changed during the different curing modes. The digital image correlation method was used to visually represent the displacement of carbon particles on the materials' surface caused by shrinkage along both the horizontal and vertical axes. For simulating cuspal deflection, a separate protocol was used, with a bulk and horizontal layering technique. The results showed that the largest horizontal displacements were present in the soft start group (6.00 ± 0.82 µm) and in the X-tra power group (5.67 ± 1.21 µm). The smallest horizontal displacements were detected in normal curing modes (4.00 ± 1.58 µm; 4.00 ± 2.68 µm). The largest vertical displacements, at the bottom layer, were present in the normal curing mode group with a 20 s curing time (5.22 ± 1.56 µm), while the smallest vertical displacements were shown in the X-tra power group (2.89 ± 0.60 µm). The observed particle displacements showing the shrinkage of the composite were correlated with the curing mode. The bulk-fill group showed less cuspal deflection than the horizontal layering group did, but the difference was not statistically significant (p = 0.575). Within the limitations of this in vitro study, it can be concluded that lower intensities of curing lights (1200 mW/cm2) may perform better from the point of view of material shrinkage than high and extreme light intensities do. The pulse delay mode might be recommended in the case of bulk-fill materials. The number of layers did not significantly affect the cuspal deflection in the case of the studied composite.