Comparative analysis of cytotoxicity effects of two denture hard lining materials on human gingival fibroblasts: an in vitro study.

Background: The objective of this study was to compare the cytotoxicity of TDV and Rebase II denture hard liners on human gingival fibroblasts, aiming to address issues associated with incomplete polymerization and free monomers that affect material properties. Methods: Seventy-two specimens (24 each of TDV, Rebase II, and controls) were prepared under aseptic conditions according to factory instructions. Cytotoxicity was determined using the MTT test with methyl tetrazolium salt added to the cell culture medium. A two-way ANOVA and a post-hoc Tukey test was used to evaluate the results of incubation before mitochondrial activity was measured using Multiscan spectrophotometry (570 nm). Results: There were significant differences in cell viability between the groups after 24 hours (P < 0.001), with TDV having higher viability than Rebase II. The difference between Rebase II and TDV, however, was not significant at 48 and 96 hours (P > 0.131). At 24 hours, Rebase II exhibited significantly lower viability than TDV liner, with a significant difference between the two groups (P = 0.001). Conclusion: Due to the maximum monomer release in the early hours of incubation, the amount of cytotoxicity decreased with increasing incubation time.

Effect of different storage conditions on dimensional accuracy of 3D-printed dental models.

PURPOSE: The objective was to determine the accuracy of 3D-printed dental models subjected to different storage conditions using six different material and printer combinations. MATERIALS AND METHODS: Three completely dentate models were designed using dental CAD software (3Shape Dental System). A horseshoe-shaped solid base with a posterior horizontal bar was used. The models were printed in a horizontal direction against the building platform without support. The models were printed using six printers with the corresponding recommended resin material: Carbon M2 (DPR10), HeyGears A2D4K (Model HP UV2.0), Stratasys J5 (MED610), Stratasys Origin One (DM200), Envision One (E-Model LightDLP), and Asiga Pro4K (VeriModel) with a standard layer thickness of 50 µm. All printed models underwent scanning using a laboratory scanner (Sirona inEOS X5) after printing. Subsequently, the models were randomly assigned into three groups of storage conditions, LT: cold environment (4 ± 1°C), HT: hot and dry environment (50 ± 2°C), and RT: room temperature (25 ± 2°C) serving as the control. Each group was kept under the designated condition and was scanned at 1, 2, 3, 4, and 8 weeks. The total number of models (N) was 72, with 6 printers producing 12 models per printer for 3 storage conditions, resulting in 4 models for each storage condition and each printer. The generated STL files were imported into a 3D inspection software for comparison with the original STL files. In-tolerance percentage, the deviation RMS, trueness, and precision were obtained and analyzed with least square mean linear regression using JMP Pro 15 to identify the significant effects (α = 0.05). RESULTS: The in-tolerance percentage as-printed was significantly different among different printers. Significant dimension deviations were observed after the first week of storage at HT and with subsequent weeks of storage. RT and LT did not show significant dimensional changes. Models printed with Carbon M2 showed the highest in-tolerance percentages compared to the other printers. CONCLUSIONS: The model deviations were affected by storage conditions and the printer used, with high-temperature storage showed least stability compared to low and room temperatures. No significant difference was observed between low and room temperature storage conditions. The Carbon M2 printer showed the highest accuracy among all printers tested. The region had a significant effect on the deviation measured, with the abutment body showing the least deviation. Among the 3D printers evaluated, A2D4K by HeyGears and Carbon M2 printers demonstrated the highest accuracy in terms of both precision and trueness.

Multifunctional Dental Adhesives Formulated with Silane-Coated Magnetic Fe3O4@m-SiO2 Core-Shell Particles to Counteract Adhesive Interfacial Breakdown.

The process of bonding to dentin is complex and dynamic, greatly impacting the longevity of dental restorations. The tooth/dental material interface is degraded by bacterial acids, matrix metalloproteinases (MMPs), and hydrolysis. As a result, bonded dental restorations face reduced longevity due to adhesive interfacial breakdown, leading to leakage, tooth pain, recurrent caries, and costly restoration replacements. To address this issue, we synthesized and characterized a multifunctional magnetic platform, CHX@SiQuac@Fe3O4@m-SiO2, to provide several beneficial functions. The platform comprises Fe3O4 microparticles and chlorhexidine (CHX) encapsulated within mesoporous silica, which was silanized by an antibacterial quaternary ammonium silane (SiQuac). This platform simultaneously targets bacterial inhibition, stability of the hybrid layer, and enhanced filler infiltration by magnetic motion. Comprehensive experiments include X-ray diffraction, FT-IR, VSM, EDS, N2 adsorption-desorption (BET), transmission electron microscopy, scanning electron microscopy, thermogravimetric analysis, and UV-vis spectroscopy. Then, CHX@SiQuac@Fe3O4@m-SiO2 was incorporated into an experimental adhesive resin for dental bonding restorations, followed by immediate and long-term antibacterial assessment, cytotoxicity evaluation, and mechanical and bonding performance. The results confirmed the multifunctional nature of CHX@SiQuac@Fe3O4@m-SiO2. This work outlined a roadmap for (1) designing and tuning an adhesive formulation containing the new platform CHX@SiQuac@Fe3O4@m-SiO2; (2) assessing microtensile bond strength to dentin using a clinically relevant model of simulated hydrostatic pulpal pressure; and (3) investigating the antibacterial outcome performance of the particles when embedded into the formulated adhesives over time. The results showed that at 4 wt % of CHX@SiQuac@Fe3O4@m-SiO2-doped adhesive under the guided magnetic field, the bond strength increased by 28%. CHX@SiQuac@Fe3O4@m-SiO2 enhanced dentin adhesion in the magnetic guide bonding process without altering adhesive properties or causing cytotoxicity. This finding presents a promising method for strengthening the tooth/dental material interface's stability and extending the bonded restorations' lifespan.

Narrow diameter titanium-zirconium tissue-level implants supporting multi-unit FDPs in the anterior area: A 5-year prospective study.

BACKGROUND: Narrow diameter implants (NDIs) are used in cases of limited mesio-distal space, or if the alveolar ridge does not allow placement of a standard diameter implant. PURPOSE: The aim of this prospective case series study is to present the 5-year clinical-, radiological-, and patient-reported outcome measures (PROMs) of patients with partial edentulism in the anterior area of the jaws requiring the placement of two narrow diameter implants to support a 3- or 4-unit fixed partial denture (FPD). MATERIALS AND METHODS: Thirty partially edentulous patients missing 3 or 4 adjacent teeth in the anterior area of the jaws were included in the study. Two titanium-zirconium tissue-level NDIs were placed in each patient in healed anterior sites (60 implants). A conventional loading protocol was performed to provide a FPD. Implant survival, success, marginal bone-level changes (MBL), clinical parameters, buccal bone stability with CBCT, adverse events and PROMs were recorded. RESULTS: The survival and success rates for the implants were 100%. The mean MBL (±SD) after prosthesis delivery, and 5-year follow-up (mean 58.8 months; range: 36-60) was 0.12 ± 0.22 and 0.52 ± 0.46 mm, respectively. Decementation and screw loosening were the most frequent prosthetic complications, yielding a prosthetic survival and success rates of 100% and 80%, respectively. Patient satisfaction was high with a mean (±SD) score of 89.6 ± 15.1. CONCLUSIONS: The use of tissue-level titanium-zirconium NDIs supporting splinted multi-unit FPDs in the anterior area seems to be a safe and predictable treatment option after a 5-year follow-up period.

RoBDEMAT: A risk of bias tool and guideline to support reporting of pre-clinical dental materials research and assessment of systematic reviews.

OBJECTIVES: To develop a risk of bias tool for pre-clinical dental materials research studies that aims to support reporting of future investigations and improve assessment in systematic reviews. METHODS: A four-stage process following EQUATOR network recommendations was followed, which included project launch, literature review, Delphi process and the tool finalization. With the support of the European Federation of Conservative Dentistry (EFCD) and the Dental Materials Group of the International Association for Dental Research (DMG-IADR), a total of 26 expert stakeholders were included in the development and Delphi vote of the initial proposal. The proposal was built using data gathered from the literature review stage. During this stage, recent systematic reviews featuring dental materials research, and risk of bias tools found in the literature were comprehensively scanned for bias sources. The experts thus reached a consensus for the items, domains and judgement related to the tool, allowing a detailed guide for each item and corresponding signalling questions. RESULTS: The tool features nine items in total, spread between 4 domains, pertaining to the following types of bias: bias related to planning and allocation (D1), specimen preparation (D2), outcome assessment (D3) and data treatment and outcome reporting (D4). RoBDEMAT, as presented, features signalling questions and a guide that can be used for RoB judgement. Its use as a checklist is preferred over a final summary score. CONCLUSION: RoBDEMAT is the first risk of bias tool for pre-clinical dental materials research, supported and developed by a broad group of expert stakeholders in the field, validating its future use. CLINICAL SIGNIFICANCE: This new tool will contribute the study field by improving the scientific quality and rigour of dental materials research studies and their systematic reviews. Such studies are the foundation and support of future clinical research and evidence-based decisions.

Efecto de fuentes de polimerización sobre el sellado marginal de restauraciones de resinas de incremento único / Effect of polymerization sources on the marginal sealing of single-increment resin restorations

Introducción: Las resinas de incremento único permiten una fotoactivación de 4 a 5 mm de profundidad, reduciendo el tiempo clínico de aplicación. No obstante, se deben considerar factores como la contracción que puede afectar el sellado marginal de la restauración. Objetivo: Evaluar el efecto de tres fuentes de polimerización sobre el sellado marginal de restauraciones Clase II, realizadas con tres sistemas de resina de incremento único. Métodos: Se realizó un estudio experimental in vitro. El cálculo de la cantidad de unidades de estudio se realizó con el software EPIDAT, para lo cual se tomaron las medias de dos estudios previos. Se realizaron nueve subgrupos según el material de restauración y la fuente de polimerización. En cada diente se confeccionaron dos restauraciones Clase II, que fueron realizadas según las instrucciones del fabricante. Los dientes fueron sometidos a inmersión pasiva en azul de metileno al 1 por ciento por 24 h. Los dientes fueron seccionados mesiodistalmente. Se realizaron fotografías con una cámara Canon y un lente macro 100 mm. La filtración marginal fue medida según una escala del 0 al 4. Los datos fueron analizados con las pruebas de Kruskal-Wallis para la comparación de los grupos. Se estableció un nivel de significancia ajustado al 5 por ciento. Resultados: La resina con menor nivel de filtración fue Filtek Bulkfill, con un 53,3 por ciento correspondiente a la escala 0, mientras que la resina con una mayor filtración fue Tetric N-Ceram Bulk Fill con un 76,7 por ciento (escala 4), similar a Sonicfill (70,0 por ciento). Conclusiones: Las diferentes fuentes de polimerización no influenciaron el nivel de filtración entre los tres sistemas de resinas de incremento único. Filtek Bulkfill presentó un mejor sellado marginal al compararlo con SonicFill y Tetric N-Ceram Bulk Fill(AU)

Introduction: Single-increment resins allow a photoactivation of 4 to 5 mm deep, reducing the clinical time of application. However, factors such as shrinkage that may affect the marginal sealing of the restoration should be considered. Objective: Evaluate the effect of three polymerization sources on the marginal sealing of Class II restorations, carried out with three single-increment resin systems. Methods: An in vitro experimental study was conducted. The calculation of the number of study units was carried out with the EPIDAT software, for which the means of two previous studies were taken. Nine subgroups were made according to the restoration material and the polymerization source. Two Class II restorations were made on each tooth, which were carried out according to the manufacturer's instructions. The teeth were subjected to passive immersion in 1 percent methylene blue for 24h. The teeth were sectioned mesiodistally. Photographs were taken with a Canon camera and a 100mm macro lens. Marginal filtration was measured on a scale of 0 to 4. Data were analyzed with Kruskal-Wallis tests for group comparison. A significance level adjusted to 5 percent was established. Results: The resin with the lowest filtration level was Filtek Bulkfill, with 53.3 percent corresponding to scale 0, while the resin with the highest filtration was Tetric N-Ceram Bulk Fill with 76.7 percent (scale 4), similar to Sonicfill (70.0 percent). Conclusions: The different polymerization sources did not influence the level of filtration between the three single-increment resin systems. Filtek Bulkfill presented a better marginal seal when compared to SonicFill and Tetric N-Ceram Bulk Fill(AU)

Application of bioactive glasses in various dental fields.

Bioactive glasses are a group of bioceramic materials that have extensive clinical applications. Their properties such as high biocompatibility, antimicrobial features, and bioactivity in the internal environment of the body have made them useful biomaterials in various fields of medicine and dentistry. There is a great variation in the main composition of these glasses and some of them whose medical usage has been approved by the US Food and Drug Administration (FDA) are called Bioglass. Bioactive glasses have appropriate biocompatibility with the body and they are similar to bone hydroxyapatite in terms of calcium and phosphate contents. Bioactive glasses are applied in different branches of dentistry like periodontics, orthodontics, endodontics, oral and maxillofacial surgery, esthetic and restorative dentistry. Also, some dental and oral care products have bioactive glasses in their compositions. Bioactive glasses have been used as dental implants in the human body in order to repair and replace damaged bones. Other applications of bioactive glasses in dentistry include their usage in periodontal disease, root canal treatments, maxillofacial surgeries, dental restorations, air abrasions, dental adhesives, enamel remineralization, and dentin hypersensitivity. Since the use of bioactive glasses in dentistry is widespread, there is a need to find methods and extensive resources to supply the required bioactive glasses. Various techniques have been identified for the production of bioactive glasses, and marine sponges have recently been considered as a rich source of it. Marine sponges are widely available and many species have been identified around the world, including the Persian Gulf. Marine sponges, as the simplest group of animals, produce different bioactive compounds that are used in a wide range of medical sciences. Numerous studies have shown the anti-tumor, anti-viral, anti-inflammatory, and antibiotic effects of these compounds. Furthermore, some species of marine sponges due to the mineral contents of their structural skeletons, which are made of biosilica, have been used for extracting bioactive glasses.

In vitro Cell Proliferation Assay of Demineralized Dentin Material Membrane in Osteoblastic MC3T3-E1 Cells.

AIM: Demineralized dentin material membrane (DDMM) is a novel bioresorbable guided bone regeneration (GBR) which is derived from the demineralization process of bovine dentin. This material/process could be an alternative to resolve musculoskeletal dysfunction that harms the quality of human life. PURPOSE: To evaluate the cytotoxic effect of DDMM as GBR membrane on MC3T3-E1 osteoblast cell line. METHODS: Cytotoxic effect was evaluated using the 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay. Osteoblast MC3T3-E1 cell culture was used as a parameter of cell viability after reacting with GBR materials. The absorbance values were examined at each treatment to determine the percentage of cell viability. There were four groups created in the present study: two treatment groups and two control groups. The treatment groups consisted of a DDMM group and a bovine pericardium collagen membrane (BPCM) group. The control groups comprised a group containing cell culture medium as a negative control group and another positive control group that contained cell cultures. RESULTS: The results revealed no significant difference in MC3T3-E1 cell viability between the treatment and control groups (p < 0.05). Moreover, as observed in the DDMM group, there was an increase in the number of osteoblast cells. CONCLUSION: DDMM is a suitable alternative biomaterial for GBR as it is non-cytotoxic and could potentially increase the rate of repair of craniofacial defects.

Allergic Reactions in Orthodontic Patients: A Review

ABSTRACT: Allergic reactions are host immune responses to endogenous or exogenous antigens, which can result in local and systemic problems. Among the main allergens are the dental materials used in orthodontics, which faces some challenges with regard to biocompatibility with oral tissues.This study aimed to analyze in the literature which materials used in orthodontics are related to the appearance of oral and perioral allergic reactions, as well as to investigate the most prevalen t manifestations.An integrative review was carried out with articles published between 2010 and 2020 on the PubMed, Embase, and ScienceDirect on-line database. For this, MeSH descriptors and synonyms were used following two semantic fields: "Hypersensitivity" in association with "Orthodontic Appliances", the selection of studies counted with the stages of identifica tion, screening, eligibility and inclusion. Randomized clinical trials, cross-sectional or cohort clinical trials; Patients with alle rgic reactions affecting the oral or perioral region due to contact with orthodontic material, were included in the review.From a to tal of 549 articles only 04 were selected for the study. In accordance with what has been analyzed in the evidence of these studies, periodontal changes such as gingival inflammation as well as erythema, edema, papules and blisters were the main reactions described. Furthermore, in all articles there was an association with nickel and in only one with chromium. It is possible to i nfer that inflammatory lesions are frequent manifestations on the use of nickel in orthodontic patients.

RESUMEN: Las reacciones alérgicas son respuestas inmunes del huésped a antígenos endógenos o exógenos, los cuales pueden provocar problemas locales y sistémicos. Entre los principales alérgenos se encuentran los materiales dentales utilizados en la ortodoncia, la cual se enfrenta a algunos desafíos respecto a la biocompatibilidad de los tejidos orales. Este estudio tuvo como objetivo analizar en la literatura que materiales utilizados en ortodoncia están relacionados con la aparición de reacciones alérgicas orales y periorales, así como investigar las manifestaciones más prevalentes. Se llevó a cabo una revisión con artículos publicados entre 2010 y 2020 en las bases de datos PubMed, Embase y ScienceDirect. Para ello, se utilizaron descriptores y sinónimos de MeSH siguiendo dos campos semánticos: "Hipersensibilidad" en asociación con "Aparatos de Ortodoncia", la selección de estudios contó con las etapas de identificación, cribado, elegibilidad e inclusión. Ensayos clínicos aleatorizados, ensayos clínicos transversales o de cohortes; en la revisión se incluyeron pacientes con reacciones alérgicas que afectaron a la regiones oral o perioral debido al contacto con material de ortodoncia. De un total de 549 artículos sólo cuatro fueron seleccionados para el estudio. De acuerdo con lo que se analizó en la evidencia, las principales reacciones descritas fueron cambios periodontales, como inflamación gingival, eritema, edema, pápulas y ampollas. Además, en todos los artículos hubo una asociación con níquel y solamente en uno con cromo. Es posible inferir que las lesiones inflamatorias son manifestaciones frecuentes sobre el uso de níquel en pacientes de ortodoncia.

Tara Gum as a Controlled Delivery System of Fluoride in Toothpaste: In Vitro Enamel Remineralization Study

ABSTRACT Objective: To evaluate the remineralizing potential of a hydrocolloid-based, controlled fluoride-releasing system added to dentifrice formulas. Material and Methods: Sixty-five human enamel blocks were prepared and the surface microhardness (SH0) values were determined. The artificial caries lesions were induced and the demineralization surface microhardness (SH1) was evaluated. The blocks were randomly allocated into five groups (n = 13): (1) 100-TGF (100% NaF with Tara gum added); (2) 50-TGF (50% free NaF + 50% NaF with Tara gum added); (3) 100% TG (100% Tara gum without fluoride); (4) 100% NaF (positive control); and (5) placebo (without Tara gum and NaF). The blocks were submitted to 7 days pH cycling and treated with dentifrice slurries twice a day. Finally, surface hardness (SH2) was assessed and the percentage of surface hardness recovery (%SMHR) was calculated. Analysis of variance (ANOVA) followed by Bonferroni test was used for statistical analysis. Results: A positive %SMHR was found in the 100% NaF (5.07) and 50-TGF (0.64) groups, while the 100-TGF (-1.38), 100% TG (-3.88) and placebo (-0.52) did not undergo remineralization. Statistically significant differences were observed between 100% NaF and all the groups except for 50-TGF (p<0.05). Conclusion: The presence of hydrocolloid (Tara gum) promoted minimal remineralization when associated with NaF. In the applied model, Tara gum may have compromised remineralization, preventing free fluoride from acting effectively in the carious lesion.

Synthesis, characterization, and incorporation of upconverting nanoparticles into a dental adhesive

Abstract: The purpose of this study was to describe the synthesis, characterization, and functionalization of b-NaYF4:30%Yb/0.5%Tm upconverting nanocrystals for use as nanofillers in a dental adhesive and microscopically evaluate the interface between the particles and a commercial adhesive. The upconverting nanoparticles were synthesized and purified by thermal decomposition, and their chemical composition determined by energy dispersive X-Ray spectroscopy. The crystalline structure was characterized using X-Ray diffraction and morphology and size were observed with scanning and transmission electron microscopy. Upconverting emission was evaluated by spectrophotometry irradiating the particles with a 975 nm diode laser. Particles were functionalized with polyacrylic acid and the success was confirmed by measurement of Zeta Potential and transmission electron microscopy. The results of X-ray diffraction found a pure hexagonal phase crystalline pattern. Scanning electron microscopy showed uniform dispersion of hexagonal-shaped particles of approximately 150 nm. Upconversion emission was observed in 344 nm, 361 nm, 450 nm, 474nm, 646 nm, 803 nm. Functionalization success was confirmed by formation of a stable aqueous colloid with a Zeta potential of −29.5mV and the absence of voids in the particle-adhesive interface on the transmission electron microscopy images. The reported synthesis and functionalization process produced upconverting nanoparticles emitting photons within the blue spectral region (450 nm and 474 nm).

The Role of Epigenetic Functionalization of Implants and Biomaterials in Osseointegration and Bone Regeneration-A Review.

The contribution of epigenetic mechanisms as a potential treatment model has been observed in cancer and autoimmune/inflammatory diseases. This review aims to put forward the epigenetic mechanisms as a promising strategy in implant surface functionalization and modification of biomaterials, to promote better osseointegration and bone regeneration, and could be applicable for alveolar bone regeneration and osseointegration in the future. Materials and Methods: Electronic and manual searches of the literature in PubMed, MEDLINE, and EMBASE were conducted, using a specific search strategy limited to publications in the last 5 years to identify preclinical studies in order to address the following focused questions: (i) Which, if any, are the epigenetic mechanisms used to functionalize implant surfaces to achieve better osseointegration? (ii) Which, if any, are the epigenetic mechanisms used to functionalize biomaterials to achieve better tissue regeneration? Findings from several studies have emphasized the role of miRNAs in functionalizing implants surfaces and biomaterials to promote osseointegration and bone regeneration, respectively. However, there are scarce data on the role of DNA methylation and histone modifications for these specific applications, despite being commonly applied in cancer research. Studies over the past few years have demonstrated that biomaterials are immunomodulatory rather than inert materials. In this context, epigenetics can act as next generation of advanced treatment tools for future regenerative techniques. Yet, there is a need to evaluate the efficacy/cost effectiveness of these techniques in comparison to current standards of care.

Effect of Listerine Mouthwash with Green Tea on the Inhibition of Streptococcus Mutans: A Microbiologic Study

Abstract Objective: To evaluate in vitro the antimicrobial effect of Listerine-green tea mouthwash on Streptococcus mutans (SM) in comparison with 0.12% Chlorhexidine (CHX) and Listerine-Zero. Material and Methods: The sensitivity and growth inhibition of SM bacterial species were evaluated and compared between Listerine-green tea, 0.12% CHX and Listerine-Zero mouthwashes. Sixty plates containing SM colonies were prepared in three groups (n=20), and growth inhibition zones were measured using the disk diffusion agar test in mm. Data were analyzed with SPSS 21. One-way ANOVA was used to compare the efficacy of the three mouthwashes tested. Post hoc Tukey tests were used for two-by-two comparisons. Statistical significance was defined at P<0.05. Results: Analysis of data showed significant differences between the three groups (p<0.001); 0.12% CHX was the most effective mouthwash, and Listerine-Zero exhibited the least effect on the growth inhibition of SM (p<0.004). Conclusion: All three mouthwashes were significantly effective in inhibiting the growth of SM. The effect of Listerine-green tea mouthwash was higher than that of Listerine-Zero and less than that of 0.12% CHX.

Influence of activation mode, fatigue, and ceramic interposition on resin cements' diametral tensile strength

Abstract This study evaluated the influence of activation modes, on Diametral Tensile Strength (DTS) of dual cured resin cements subjected to a Mechanical Fatigue test (MF). Four dual-cured resin cements (RelyX UNICEM [U], RelyX ARC [A], ENFORCE [E] and Nexus 2 [N]) were activated by three different curing modes as follows: Self-Curing (SC), Dual Cure activation with photoactivation executed directly (DC) and Dual Cure activation with Photoactivation Through Porcelain (DCTP). After 24 hours, half of the sample was subjected to 30.000 fatigue cycles at 1 Hz frequency and 12 N load. Then, all specimens were subjected to DTS test in Instron Universal Testing Machine and data were analyzed by three-way ANOVA and Tukey's Test (5%). The results of DTS test means (MPa) and standard deviation, for each cement factor activated by SC, DC and DCTP was respectively: U (28.12 ± 5.29; 37.44 ± 6.49 and 40.10 ± 4.39), A (49.68 ± 8.42; 55.12 ± 5.16 and 63.43 ± 6.92), E (49.12 ± 3.89; 56.42 ± 8.88 and 56.96 ± 6.45) and N (61.89 ± 11.21; 59.26 ± 9.47 and 62.56 ± 10.93). Turkey's test indicated that DC is related to the highest DTS values; Nexus 2 DTS remained the same independently of activation mode and that the Porcelain disk interposition enhanced DTS only for RelyX ARC the ANOVA statistical test indicated that MF didn't alter the DTS values for all experimental groups. MF results clinical implication is that all cements tested exhibited, in an immediate loading, good cross linked bonds quality.

Biomechanical Behavior of an Implant System Using Polyether Ether Ketone Bar: Finite Element Analysis.

AIM AND OBJECTIVES: This study assessed, through finite element analysis, the biomechanical behavior of an implant system using the All-on-Four® technique with nickel-chromium (M1) and polyether ether ketone (PEEK) bars (M2). MATERIALS AND METHODS: Implants and components were represented in three-dimensional (3D) geometric models and submitted to three types of load: axial, oblique, and load on all teeth. The 3D models were exported to a computer-aided design-like software such as Solidworks 2016 (Dassault Systemes, Solidworks Corps, USA) for editing and Nonuniform Rational Basis Splines parametrization. RESULTS: Data were analyzed according to system's areas of action: peri-implant bone, implant, intermediates, intermediates' screws, prostheses' screws, and bars. Largest peak stress was shown in M2. CONCLUSION: PEEK is a promising material for use in dentistry; however, further studies are necessary to evaluate its performance.

Accuracy of various imaging methods for detecting misfit at the tooth-restoration interface in posterior teeth.

PURPOSE: The present study aimed to evaluate which of the following imaging methods best assessed misfit at the tooth-restoration interface: (1) bitewing radiographs, both conventional and digital, performed using a photostimulable phosphor plate (PSP) and a charge-coupled device (CCD) system; (2) panoramic radiographs, both conventional and digital; and (3) cone-beam computed tomography (CBCT). MATERIALS AND METHODS: Forty healthy human molars with class I cavities were selected and divided into 4 groups according to the restoration that was applied: composite resin, composite resin with liner material to simulate misfit, dental amalgam, and dental amalgam with liner material to simulate misfit. Radiography and tomography were performed using the various imaging methods, and the resulting images were analyzed by 2 calibrated radiologists. The true presence or absence of misfit corresponding to an area of radiolucency in regions subjacent to the esthetic and metal restorations was validated with microscopy. The data were analyzed using a receiver operating characteristic (ROC) curve, and the scores were compared using the Cohen kappa coefficient. RESULTS: For bitewing images, the digital systems (CCD and PSP) showed a higher area under the ROC curve (AUROC) for the evaluation of resin restorations, while the conventional images exhibited a larger AUROC for the evaluation of amalgam restorations. Conventional and digital panoramic radiographs did not yield good results for the evaluation of resin and amalgam restorations (P<.05). CBCT images exhibited good results for resin restorations (P>.05), but showed no discriminatory ability for amalgam restorations (P<.05). CONCLUSION: Bitewing radiographs (conventional or digital) should be the method of choice when assessing dental restoration misfit.

Photopolymerization of cell-laden gelatin methacryloyl hydrogels using a dental curing light for regenerative dentistry.

Photopolymerized hydrogels, such as gelatin methacryloyl (GelMA), have desirable biological and mechanical characteristics for a range of tissue engineering applications. OBJECTIVE: This study aimed to optimize a new method to photopolymerize GelMA using a dental curing light (DL). METHODS: Lithium acylphosphinate photo-initiator (LAP, 0.05, 0.067, 0.1% w/v) was evaluated for its ability to polymerize GelMA hydrogel precursors (10% w/v) encapsulated with odontoblast-like cells (OD21). Different irradiances (1650, 2300 and 3700mW/cm2) and photo-curing times (5-20s) were tested, and compared against the parameters typically used in UV light photopolymerization (45mW/cm2, 0.1% w/v Irgacure 2959 as photoinitiator). Physical and mechanical properties of the photopolymerized GelMA hydrogels were determined. Cell viability was assessed using a live and dead assay kit. RESULTS: Comparing DL and UV polymerization methods, the DL method photopolymerized GelMA precursor faster and presented larger pore size than the UV polymerization method. The live and dead assay showed more than 80% of cells were viable when hydrogels were photopolymerized with the different DL irradiances. However, the cell viability decreased when the exposure time was increased to 20s using the 1650mW/cm2 intensity, and when the LAP concentration was increased from 0.05 to 0.1%. Both DL and UV photocrosslinked hydrogels supported a high percentage of cell viability and enabled fabrication of micropatterns using a photolithography microfabrication technique. SIGNIFICANCE: The proposed method to photopolymerize GelMA cell-laden hydrogels using a dental curing light is effective and represents an important step towards the establishment of chair-side procedures in regenerative dentistry.

Can low-fusing glass application affect the marginal misfit and bond strength of Y-TZP crowns?

Abstract To evaluate the effect of different surface treatments on the marginal misfit and retentive strength between Y-TZP crowns and an epoxy resin. Forty (40) epoxy resin (G10) abutments (height: 5mm, conicity: 60, finish line: large chamfer) with equal dimensions were milled and included in polyurethane to simulate the periodontal ligament. Next, 40 Y-TZP crowns (thickness: 1mm) were milled (Cerec in Lab) and randomly divided into four groups (n=10) according to the surface treatment: GS(glaze spray), GP(glaze powder/liquid), P(zirconia primer) and RS(tribochemical silica coating). The conditioned surfaces were cemented with dual self-adhesive cement, light cured and submitted to thermomechanical cycling (2x106, 100N, 4Hz, 5°/55°C). Marginal misfit was analyzed by a stereomicroscope and SEM. Retentive strength test was performed (1mm/min) until crown debonding. Glaze layer thickness was also performed to GS and GP groups. Marginal misfit data were analyzed by Kruskal Wallis and Dunn tests; one-way ANOVA and Tukey (5%) analyzed the tensile strength data. The marginal misfit of the GS (48.6±19.9μm) and GP (65.4±42.5μm) were statistically lower than the RS (96±62.9μm) and P (156±113.3μm) (p=0.001). The retentive strength of the GP (470.5±104.1N) and GS (416.8±170.2N) were similar to the P (342.1±109.7N), but statistically higher than those of the RS (208.9±110N). The GS and GP glaze layer was 11.64μm and 9.73μm respectively. Thus, glaze application promoted lower marginal discrepancy and higher retentive strength values than conventional techniques.

Accuracy of various imaging methods for detecting misfit at the tooth-restoration interface in posterior teeth

PURPOSE: The present study aimed to evaluate which of the following imaging methods best assessed misfit at the tooth-restoration interface: (1) bitewing radiographs, both conventional and digital, performed using a photostimulable phosphor plate (PSP) and a charge-coupled device (CCD) system; (2) panoramic radiographs, both conventional and digital; and (3) cone-beam computed tomography (CBCT). MATERIALS AND METHODS: Forty healthy human molars with class I cavities were selected and divided into 4 groups according to the restoration that was applied: composite resin, composite resin with liner material to simulate misfit, dental amalgam, and dental amalgam with liner material to simulate misfit. Radiography and tomography were performed using the various imaging methods, and the resulting images were analyzed by 2 calibrated radiologists. The true presence or absence of misfit corresponding to an area of radiolucency in regions subjacent to the esthetic and metal restorations was validated with microscopy. The data were analyzed using a receiver operating characteristic (ROC) curve, and the scores were compared using the Cohen kappa coefficient. RESULTS: For bitewing images, the digital systems (CCD and PSP) showed a higher area under the ROC curve (AUROC) for the evaluation of resin restorations, while the conventional images exhibited a larger AUROC for the evaluation of amalgam restorations. Conventional and digital panoramic radiographs did not yield good results for the evaluation of resin and amalgam restorations (P .05), but showed no discriminatory ability for amalgam restorations (P < .05). CONCLUSION: Bitewing radiographs (conventional or digital) should be the method of choice when assessing dental restoration misfit.

Avaliação da redução das forças geradas por elásticos ortodônticos em cadeia / Evaluation of the forces reduction delivered by orthodontic elastomeric chain

A movimentação dentária é obtida através de recursos capazes de gerar forças e o ortodontista dispõe de uma série de dispositivos mecânicos responsáveis por realizar essa movimentação, incluindo os elásticos em cadeia, que além de serem de fácil aplicação, são também bem tolerados pela maioria dos pacientes. Porém, apesar dos avanços obtidos no desenvolvimento destes materiais, ainda existem dúvidas em relação a influência de diversos fatores que podem afetar a liberação de forças destes. O objetivo deste trabalho é avaliar a redução dos valores das forças geradas por elásticos ortodônticos em cadeia em relação a intensidade de estiramento, tempo e configuração. Foram utilizados 432 segmentos de cadeias elásticas, divididos em 3 grupos de acordo com as configurações curta, média e longa. Os segmentos de cadeia foram distendidos em 25%, 50%, 75% e 100% do comprimento original e mantidos estirados em placas de acrílicos confeccionadas especialmente para esse fim, em água destilada, a temperatura constante de 37°C durante os períodos de 24 horas, 1, 2, 3 e 4 semanas. Os dados foram avaliados através do teste de Análise de Variância (ANOVA) seguido do teste de Tukey. Todos os fatores mostraram significância estatística na diminuição das forças geradas. Quanto maior a intensidade de estiramento e tempo, maior a redução dos valores das forças geradas, entretanto os estiramentos 75% e 100% quando comparados entre si não apresentaram significância estatística. As cadeias elásticas do tipo curto foram capazes de promover a menor redução dos valores das forças geradas.

The aim of this study is to evaluate the reduction in the values of the forces generated by orthodontic chain regarding the intensity of stretching, time and configuration. Were used 432 segments of elastic chains, divided into 3 groups according to following configurations: short, medium and long. The chain segments were stretched at 25%, 50%, 75% and 100% and kept stretched in acrylic plates confectioned specially for this purpose, in distilled water, at constant temperature of 37°C, during periods of 0h, 24h, 1, 2, 3 and 4 weeks. The data were evaluated by analysis of variance (ANOVA) followed by Tukey test. All factors showed statistical significance in the reduction of forces delivered. The higher the stretching intensity and the time, the greater the reduction of the forces generated values. However the stretches of 75% and 100% when compared to each other were not statistically significant. The short elastomeric chain were able to promote the smallest reduction of the values of forces generated