Micro-Computed Tomography Analysis of Resin and Calcium Silicate Based Sealers Removal in Mandibular Molars Curved Canals.

Objective: The removal of the root canal sealer is an important factor in nonsurgical retreatment. The aim of this study was to compare the removal of AH Plus, Well Root ST, and AH Plus Bioceramic Sealer using Protaper Universal retreatment files. Methods: The curved mesio-buccal canals of extracted mandibular molars were prepared with the Protaper Gold file system (up to F2). Specimens were randomly divided into 3 groups and filled with the single cone technique using AH Plus, Well-Root ST, and AH Plus Bioceramic Sealer, respectively. After two weeks, the root canal filling of all specimens was removed using Protaper Universal retreatment files. All specimens were scanned using micro-CT. The remaining volume of the root canal filling was recorded in total and the coronal, middle, and apical third of each specimen. Results: Well-Root ST and AH Plus Bioceramic Sealer groups had a higher percentage of total remaining filling material than the AH Plus group (P<0.05). Conclusion: This study has shown that the volume of remaining root canal filling was significantly higher in the samples filled with calcium silicate-based sealers.

Thickness Variations of Thermoformed and 3D-Printed Clear Aligners.

Objective: To assess thickness variations of thermoformed and 3D-printed clear aligners. Materials and Methods: Six different thermoplastic materials with different initial thicknesses were used for aligner thermoforming using Biostar® device (Biostar®, SCHEU-DENTAL GmbH, Iserlohn, Germany). Also, two different dental resins were used to create the printed aligners in three digitally designed thicknesses using IZZI Direct printer (3Dtech, Zagreb, Croatia). The aligners were measured using an electronic micrometer (ELECTRONIC UNIVERSAL MICROMETER, Schut Geometrical Metrology, Groningen, The Netherlands, accuracy: 0.001 mm) on a total of 20 points per aligner. Statistical analysis was performed using the JASP program (JASP, University of Amsterdam, Amsterdam, The Netherlands). Results: The difference between the thermoformed and printed groups was statistically significant. Significant differences between different thermoformed materials and between 3D-printed materials were found. The thickness of thermoformed aligners deviated more in the upper jaw, whereas the thickness of printed aligners deviated more in the lower jaw. Both differences were statistically significant. The greatest average deviation from the initial thickness was found in Duran 0.75; Erkodur 0.6; Erkoloc-Pro 1.0; IZZI 0.5; NextDent 0.6 and NextDent A 0.6. NextDent group had the lowest deviations for all teeth of both jaws, except for upper and lower first molar where NextDent A group was more accurate. Conclusions: Thermoformed aligners showed decreased values, while printed ones showed mostly increased values compared to the original material thickness. The highest mean deviation belonged to IZZI group, and the NextDent group had the lowest mean deviation. The thickness of both aligners was thinner at the edges compared to the thickness at cusps and fissures.

A Multidisciplinary Approach in Examining the Susceptibility to Microbial Attack of Polyacrylic and Polyurethane Resins Used in Art Restoration.

The synthetic polymers used to protect artworks from deterioration process can be colonized by the fungi and bacteria responsible for the biodeterioration process. In this study, the susceptibility of synthetic polyacrylics and polyurethane resins to microorganisms (Aspergillus niger ATCC 9642, Aureobasidium pullulans ATCC 15233, Chaetomium globosum ATCC 6205, Cladosporium cladosporioides ATCC 16022, Alternaria alternata BC01, Penicillium citrinum LS1 and Pseudomonas aeruginosa ATCC 9027) was investigated. The microbial attack was simulated alone and with a biocide and the related growth was observed up to 21 days for bacteria and 28 days for fungi. The polyacrylic and polyurethane resins were subjected to microbial attack, regardless of the biocide treatment, with a fungal growth from 60% to the complete coverage of the plate surface. Penicillium citrinum showed the greatest adaptation ability and was found in all the examined resins. P. aeruginosa was visible in all the different resins, regardless of the presence of biocide. An environmental scanning electron microscope (ESEM) revealed the presence of fungal conidia and hyphae in the inoculated resins and the Fourier transform IR spectroscopy (FTIR-ATR) indicated chemical transformations in the IR spectra, particularly the hydrolysis of esters, with some differences between the polyacrylic and polyurethane resins, which were probably due to their different chemical features. Overall, our data stress that the chemical, physical and biological deterioration caused by microorganisms capable of degrading synthetic polymers is still a problem in art restoration and that new strategies must be considered to counteract this phenomenon.

A retrospective clinical study on the resin infiltration of proximal caries lesions: the operator's effect.

PURPOSE: This retrospective university-based study investigated the effect of operators' training and previous experience on the success of resin infiltration (RI) in arresting proximal non-cavitated caries lesions in primary and permanent teeth. METHODS: Information was collected regarding RI of proximal non-cavitated caries lesions in primary and permanent teeth with a follow-up period up to 32 months. Factors investigated were: operators' clinical experience and training, patient's age, tooth, arch, mouth-side, surface treated, tooth separation, and baseline lesion depth. Kaplan-Meier survival and Cox regression analysis with shared frailty were used (α = 5%). RESULTS: A total of 130 proximal surfaces treated on 115 teeth of 43 children (11 ± 4.4 years) were evaluated. Survival of RI was 46% up to 32 months. Lesions treated by non-trained dentists were more likely-to-present progression than those performed by non-trained dental students under supervision (HR 2.41, 95% CI: 1.00-5.80); conversely, no difference was found between non-trained dental students under supervision and trained dentists (HR 0.52, 95% CI: 0.16-1.70). Additionally, dentin lesions were 59% more-likely-to-present progression than enamel lesions (HR 0.41, 95% CI: 0.17-0.99). CONCLUSION: The operator's experience and training could influence the success of RI on proximal non-cavitated caries lesions and it should be taken into consideration when choosing this treatment modality.

Shrinkage Stress and Temperature Variation in Resin Composites Cured via Different Photoactivation Methods: Insights for Standardisation of the Photopolymerisation.

The literature has shown that there is no consensus regarding the best resin composite photoactivation protocol. This study evaluated the efficiency of the conventional, soft-start, pulse-delay and exponential protocols for photoactivation of resin composites in reducing the shrinkage stress and temperature variation during the photopolymerisation. The photoactivation processes were performed using a photocuring unit and a smartphone app developed to control the irradiance according each photoactivation protocol. These photoactivation methods were evaluated applying photoactivation energies recommended by the resins manufactures. Three brands of resin composites were analysed: Z-250, Charisma and Ultrafill. The cure effectiveness was evaluated through depth of cure experiments. All results were statistically evaluated using one-way and multi-factor analysis of variance (ANOVA). The use of exponential and pulse-delay methods resulted in a significant reduction of the shrinkage stress for all evaluated resins; however, the pulse-delay method required too long a photoactivation time. The increases on the temperature were lower when the exponential photoactivation was applied; however, the temperature variation for all photoactivation protocols was not enough to cause damage in the restoration area. The evaluation of the depth of cure showed that all photoactivation protocols resulted in cured resins with equivalent hardness, indicating that the choice of an alternative photoactivation protocol did not harm the polymerisation. In this way, the results showed the exponential protocol as the best photoactivation technique for practical applications.

Infiltrantes para tratamiento estético de lesiones de manchas blancas por fluorosis: Reporte de caso / Infiltrants for Aesthetic Treatment of White Spots Lesions by Fluorosis: Case Report

Resumen La fluorosis dental es una anomalía en el desarrollo del esmalte debido a la excesiva ingesta de flúor durante la formación de los tejidos dentales, y se caracteriza principalmente por la hipomineralización y mayor porosidad de la estructura del esmalte. Muchas veces las manchas ocasionadas por la fluorosis dental pueden comprometer la estética del paciente y afectar su autoestima. En años recientes ha sido desarrollado una nueva generación de materiales odontológicos conocida como infiltrantes resinosos, que básicamente son resinas de baja viscosidad que infiltran y paralizan la progresión de las lesiones cariosas incipientes no cavitadas. Cuando infiltrantes resinosos han sido utilizados para detener las lesiones cariosas se ha verificado que también producen cambios en la apariencia de la mancha blanca, atenuándola o tornándola imperceptible. El presente artículo describe un reporte de caso del uso de infiltrantes resinosos para tratamiento estético de lesiones de manchas blancas ocasionadas por fluorosis.

Abstract Dental fluorosis is an abnormality in the development of enamel due to the excessive intake of fluoride during formation of dental tissues, mainly characterized by hypomineralization and increased porosity of the enamel structure. Oftenly the spots caused by dental fluorosis can compromise the aesthetics of the patient and affect their self-esteem. In recent years a new generation of dental materials has been developed, known as resin infiltrants, which are basically low viscosity resins that infiltrate and paralyze the progression of incipient non cavitated carious lesions. When resin infiltrants have been used to stop carious lesions it has been verified that they also produce changes in the appearance of white spots, masking or making them imperceptible. The present article describes a case report of the use of resin infiltrants for aesthetic treatment of white spot lesions caused by fluorosis.

Direct resin composite restoration of endodontically-treated permanent molars in adolescents: bite force and patient-specific finite element analysis

Abstract Objective To evaluate the influence of three levels of dental structure loss on stress distribution and bite load in root canal-treated young molar teeth that were filled with bulk-fill resin composite, using finite element analysis (FEA) to predict clinical failure. Methodology Three first mandibular molars with extensive caries lesions were selected in teenager patients. The habitual occlusion bite force was measured using gnathodynamometer before and after endodontic/restoration procedures. The recorded bite forces were used as input for patient-specific FEA models, generated from cone-beam computed tomographic (CT) scans of the teeth before and after treatment. Loads were simulated using the contact loading of the antagonist molars selected based on the CT scans and clinical evaluation. Pre and post treatment bite forces (N) in the 3 patients were 30.1/136.6, 34.3/133.4, and 47.9/124.1. Results Bite force increased 260% (from 36.7±11.6 to 131.9±17.8 N) after endodontic and direct restoration. Before endodontic intervention, the stress concentration was located in coronal tooth structure; after rehabilitation, the stresses were located in root dentin, regardless of the level of tooth structure loss. The bite force used on molar teeth after pulp removal during endodontic treatment resulted in high stress concentrations in weakened tooth areas and at the furcation. Conclusion Extensive caries negatively affected the bite force. After pulp removal and endodontic treatment, stress and strain concentrations were higher in the weakened dental structure. Root canal treatment associated with direct resin composite restorative procedure could restore the stress-strain conditions in permanent young molar teeth.

Validation Study of Selected Ion Flow Tube-Mass Spectrometry (SIFT-MS) in Heritage Science: Characterization of Natural and Synthetic Paint Varnishes by Portable Mass Spectrometry.

The identification at molecular level of organic materials in heritage objects as paintings requires in most cases the collection of micro-samples followed by micro-destructive analysis. In this study, we explore the possibility to characterize natural and synthetic resins used as paint varnishes by mean of non-invasive analysis of released volatile organic compounds (VOCs) through selected ion flow tube-mass spectrometry (SIFT-MS). SIFT-MS is a portable direct mass spectrometric technique that achieves the analysis of VOCs at trace levels in real time, by controlled ultra-soft chemical ionization using eight different chemical ionization agents. We tested the portable instrumentation on different reference resins used as paint varnishes, both natural (mastic, dammar, and colophony) and synthetic (Paraloid B67, MS2A, Regalrez 1094, and polyvinyl acetate), to evaluate the possibility to acquire qualitative data for the identification of these materials in heritage objects avoiding any sampling. This new analytical approach was validated by comparison with the traditional approach for VOCs analysis based on solid phase micro extraction-gas chromatography/mass spectrometry (SPME-GC/MS) analysis. The results demonstrate the use of SIFT-MS as an in situ non-invasive and non-destructive mass spectrometric technique to identify organic materials, such as paint varnishes.

Analysis of the Mechanical Behavior and Surface Rugosity of Different Dental Die Materials.

AIM: This work evaluated the mechanical and surface behavior of different die materials. The studied materials are polyurethane resin Exakto-Form (Bredent), Gypsum type IV, Fuji Rock EP (Gc), and Durone (Dentsply). MATERIALS AND METHODS: Two metallic matrices molded in polyvinyl siloxane provided 30 cylindrical test specimens for the diametral compression test and 30 hemispherical test specimens for the surface rugosity test. The cylindrical test specimens were submitted to tests of diametral compression strength using a DL2000 universal assay machine, with a load cell of 2000 Kgf and constant speed of 1 mm/min connected to the software. Kruskal-Wallis and Dunn's nonparametric tests were used to analyze the results. The hemispheres were submitted to the surface rugosity assay using a SJ201-P rugosimeter with a sensitivity of 300 µm, speed of 0.5 mm/s, and cut-off of 0.8 mm, and the readings were taken on the convex surface of the test specimens and metallic matrix. Results were analyzed using with Fisher's least significant differences test (LSD) and Dunnett's test. RESULTS: Kruskal-Wallis test showed significant difference between die materials for diametral compression strength (P = 0.002). Dunn's test showed significantly higher values for modified polyurethane resin (Exakto-Form). The gypsum type IV, which did not significantly differ regarding diametral compression strength, showed 34.0% (Durone) and 42.7% (Fuji Rock) lower values in comparison to Exakto-Form. CONCLUSION: Within the parameters adopted in this study, it is possible to conclude that Exakto-Form polyurethane resin showed higher resistance to compression and was closer to the metallic matrix rugosity, and, along with the gypsum type IV Durone, showed better reproducibility of details relative to the Fuji Rock.

Scaling up a virginiamycin production by a high-yield Streptomyces virginiae VKM Ac-2738D strain using adsorbing resin addition and fed-batch fermentation under controlled conditions.

Virginiamycin produced by Streptomyces virginiae as a natural mix of macrocyclic peptidolactones M and S is widely used in the industrial production of ethanol fuel and as an antibiotic feed additive for cattle and poultry. Its main antimicrobial components, M1 and S1 factors, act synergistically if the M1:S1 ratio in the final product is 70-75:25-30. This fact significantly complicates the development of stable high-yield strains suitable for industrial application. In the previous work, authors obtained a mutant S. virginiae VKM Ac-2738D strain, characterized by a high productivity in flasks and the optimum M1:S1 ratio (75:25) in the final product. In this study, the scale-up of the virginiamycin production by VKM AC-2738D from shake flasks to a pilot-scale (100 L) stirred fermentor was carried out and the possibility of the in situ use of synthetic adsorbing resins to remove virginiamycin from culture broth was assessed. After the optimization of pH and dissolved oxygen concentration (6.8-7.0 and 50%, respectively), the fed-batch fermentation of VKM Ac-2738D with continuous addition of 50% sucrose solution (5 g/L/day starting from 48 h of fermentation) resulted in a final virginiamycin titer of 4.9 g/L. Among four tested resins, Diaion® HP21 added to fermentation medium prior to sterilization absorbed 98.5% of the total virginiamycin that simplifies its further recovery procedure and increased its total titer to 5.6 g/L at the M1:S1 ratio of 74:26. The developed technology has several important advantages, which include (1) the optimum M1:S1 ratio in the final product, (2) the possibility to use sucrose as a carbon source instead of traditionally used and more expensive glucose or D-maltose, and (3) selective binding of up to 98.5% of produced virginiamycin on the adsorbing resin.

Efeito do tratamento de superfície e condição de armazenamento sobre a resistência de união resina-cerâmica / Effect of surface treatment and storage condition on the ceramic-resin bond strength

Uma superfície de cada um de quatro blocos foi polida e submetida aos seguintes tratamentos de superfície: bloco A (HF+S) - microjateamento com Al2O3 de 50 μm (15 s), condicionamento com ácido HF a 9,5% (20 s) e aplicação de silano (3 min); bloco B (HF) - microjateamento e condicionamento com ácido HF; bloco C (S) - microjateamento e silano; e bloco D (CJ) - microjateamento com CoJet Sand e aplicação de silano. O adesivo Scotchbond Multi-Purpose Plus foi aplicado sobre a superfície dos blocos A, B e C, e o adesivo Visio-Bond do sistema CoJet, no D, todos polimerizados, e resina composta (Filtek Z250) foi adicionada em quatro incrementos de 1 mm e fotopolimerizada. Os blocos de resina-cerâmica foram, então, seccionados em dois eixos perpendiculares, produzindo cada um aproximadamente 40 corpos de prova, divididos em dois grupos: grupo “Imediato”, dividido em quatro subgrupos: HF+S/I (n = 19), HF/I (n = 19), S/I (n = 20) e CJ/I (n = 16), armazenados por 24 h em água destilada; e grupo “12m+Tc”, dividido em quatro subgrupos: HF+S/12m (n = 20), HF/12m (n = 20), S/12m (n = 20) e CJ/12m (n = 17), armazenados por 12 meses em saliva artificial, seguidos por termociclagem (800 ciclos). Os valores médios obtidos (HF+S/I = 56,85±16,52(a), HF/I = 51,69±11,34(ab), S/I = 50,73±12,37(ab), CJ/I = 40,13±9,27(bc), HF+S/12m = 42,29±17,34(b), HF/12m = 21,03±7,02(d), S/12m = 13,72±6,24(d), CJ/12m = 26,77±21,07(cd)) foram analisados estatisticamente (ANOVA 2). Observou-se interação entre tratamento de superfície e condição de armazenamento. Condicionamento da superfície cerâmica com ácido HF combinado com silanização propiciou maior μ-TBS à resina após 12 meses de armazenamento em saliva artificial e termociclagem...

One surface of each out of four blocks was polished and subjected to the following surface treatments: A: (HF + S) – sandblasting with AL2O3 50 μm (15 s), etching with 9.5% HF (20 s) and silane application (3 min); B:(HF) - sandblasting and etching with HF; C: (S) – sandblasting and silane; D: (CJ) – sandblasting with CoJet Sand and silane application. A three-step total-etch adhesive was applied (ScotchBond Multi-Purpose Plus) on the surface of the blocks A, B, and C, and the light-cured bonding material, proprietary of the CoJet system (Visio-Bond) on block D, light-cured, and composite resin (Filtek Z250) was added in four 1 mm increments and light cured. The ceramic-resin blocks were then sectioned into two perpendicular axes, each producing approximately 40 specimens, divided into two groups: “immediate” group divided into four subgroups: HF + s / i (n = 19) , HF / i (n = 19), S / I (n = 20) and cj / i (n = 16), stored for 24 h in distilled water; and group “12m + tc”, divided into four subgroups: s/12m + HF (n = 20) HF/12m (n = 20) s/12m (n = 20) and CJ/12m (n = 17) stored for 12 months in artificial saliva followed by thermocycling (800 cycles). The obtained average values (HF + s / i = 56.85 ± 16.52 (a) HF / i = 51.69 ± 11.34 (ab) s / i = 50.73 ± 12.37 (ab), CJ/ i = 40.13 ± 9.27 (bc) + HF s/12m = 42.29 ± 17.34 (b), HF/12m = 21.03 ± 7.02 (d), s / 12m = 13.72 ± 6.24 (d), 26.77 ± 21.07 CJ/12m = (cd)) were statistically analyzed (2-way ANOVA). Interaction between surface treatment and storage conditions were observed. Conditioning of the ceramic surface with HF associated with silanization provided greater μ-TBS values to resin after 12 months of storage in artificial saliva and thermocycling...

Defluoridation of water using chitosan assisted ethylenediamine functionalized synthetic polymeric blends.

In this paper, a new kind of approach undertakes for the synthesis of novel chitosan (CS) blended with ethylenediamine (ED) functionalized synthetic polymers viz., acrylonitrile/divinylbenzene/vinylbenzyl chloride (CS@AN/DVB/VBC-ED) and styrene/divinylbenzene/vinylbenzyl chloride (CS@ST/DVB/VBC-ED) for defluoridation of water. Under batch mode, various influencing parameters like shaking time, pH, competitor ions and temperature were optimized. The fluoride removal was reasonably explained using Freundlich, Langmuir and D-R isotherms. The thermodynamic parameters viz., ΔG°, ΔH° and ΔS° indicates the nature of the fluoride sorption with the sorbents. The FT-IR, XRD and SEM with EDAX analysis were used to study the fluoride adsorption of CS@AN/DVB/VBC-ED and CS@ST/DVB/VBC-ED blends. The thermal stability of both the sorbents was tested using TGA/DSC analysis. Studies were also conducted to test the potential application of the prepared polymeric blends for fluoride removal from field water collected from the nearby fluoride endemic area.

A Case of Radiolucent Foreign Body (Temporary Resin Bridge) Aspiration Accompanied by Inflammatory Polyps / 결핵및호흡기질환

This case demonstrates the rare occurrence of a radiolucent temporary resin bridge aspiration in adults while they are in a conscious and awaken state and the resultant formation of inflammatory polyps. Although no unique findings were noted in a chest x-ray, careful history taking accompanied by physical examinations can lead to clinical suspicion of foreign body aspiration in an earlier stage. Moreover, flexible bronchoscopy is a tool useful not only for the evaluation process but also for managing the aspirated foreign material.