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

OBJECTIVE: To evaluate the collection efficiency of water spray on the release of airborne composite particles during grinding of composite materials. MATERIALS AND METHODS: Composite sticks (L:35 mm × W:5.4 mm × H:1.6 mm) of seven commercial dental composites were ground with a rough diamond bur (grain size 100 µm, speed 200,000 rpm). All experiments were performed in an enclosed 1-m3 chamber with low particulate background (< 1,000 #/cm3), and airborne particles were evaluated based on their electrical mobility. The number size distribution was determined by scanning mobility particle sizer (SMPS). Particles were collected by an electrostatic precipitator (ESP), and were ultramorphologically and chemically analyzed by a transmission electron microscope equipped with energy-dispersive X-ray spectroscopy (TEM-EDS). RESULTS: SMPS measurements confirmed that both dry and wet grinding generated high concentrations of nanoparticles particles with the highest concentration recorded during the last minute of grinding (1.80 × 106 - 3.29 × 106#/cm3), after which a gradual decline in particle concentration took place. Nevertheless, grinding with water spray resulted in a significant reduction of the number of released particles (5.6 × 105 - 1.37 × 106#/cm3). The smallest particle diameter was recorded during the last minute of grinding followed by a continuous growth for every next measurement. TEM of composite dust revealed a high concentration of particles varying in both size and shape. CONCLUSIONS: Regardless of whether the water cooling spray system was used during bur manipulation of composite materials, predominately nanoparticles were released. However, the particle concentrations were significantly decreased with water spray. CLINICAL RELEVANCE: Since water spray might not be sufficient in nanoparticle collection, special care should be taken to prevent inhalation of composite dust.

Secondary caries: prevalence, characteristics, and approach.

OBJECTIVES: The objectives of this cross-sectional survey were to determine the prevalence of secondary caries (SC) in general population, to identify patient- and material-related factors which may affect the prevalence, and to describe some clinical characteristics of SC lesions. MATERIALS AND METHODS: A total of 4036 restorations in 450 patients, who visited the university dental clinic for a regular (half) yearly checkup, were examined clinically (and radiographically) for the presence of SC. Clinical characteristics of the detected SC lesions (size, activity, and location) and the planned treatment were recorded. In addition, patients' caries-risk status was assessed according to the modified "cariogram" model. RESULTS: In total, 146 restorations were diagnosed with SC, which gives an overall prevalence of 3.6%. Restorative material, restoration class, patient's caries risk, and smoking habits were shown to be important factors, as SC prevalence was significantly higher with composites, class II restorations, high-caries-risk patients, and smokers. Restorations' gingival margins were most frequently affected by SC. The largest number of restorations with SC (72%) was scheduled for the replacement. CONCLUSIONS: Prevalence of SC was higher with composite than with amalgam restorations, irrespective of the patient's caries-risk status. Gingival margins of class II, including MOD restorations, seem to be the place of less resistance to SC development. Management of SC seems to place a considerable burden on the health care workforce and expenditure. CLINICAL RELEVANCE: Secondary caries (SC) is considered to be the main cause of dental restoration failure and one of the biggest clinical challenges related to dental composites. Nevertheless, its prevalence in daily practice is still not clear, which impedes an accurate estimation of its impact on health care costs.

Extracting morphologies from third harmonic generation images of structurally normal human brain tissue.

MOTIVATION: The morphologies contained in 3D third harmonic generation (THG) images of human brain tissue can report on the pathological state of the tissue. However, the complexity of THG brain images makes the usage of modern image processing tools, especially those of image filtering, segmentation and validation, to extract this information challenging. RESULTS: We developed a salient edge-enhancing model of anisotropic diffusion for image filtering, based on higher order statistics. We split the intrinsic 3-phase segmentation problem into two 2-phase segmentation problems, each of which we solved with a dedicated model, active contour weighted by prior extreme. We applied the novel proposed algorithms to THG images of structurally normal ex-vivo human brain tissue, revealing key tissue components-brain cells, microvessels and neuropil, enabling statistical characterization of these components. Comprehensive comparison to manually delineated ground truth validated the proposed algorithms. Quantitative comparison to second harmonic generation/auto-fluorescence images, acquired simultaneously from the same tissue area, confirmed the correctness of the main THG features detected. AVAILABILITY AND IMPLEMENTATION: The software and test datasets are available from the authors. CONTACT: z.zhang@vu.nl. SUPPLEMENTARY INFORMATION: Supplementary data are available at Bioinformatics online.

Disentangling Somatosensory Evoked Potentials of the Fingers: Limitations and Clinical Potential.

In searching for clinical biomarkers of the somatosensory function, we studied reproducibility of somatosensory potentials (SEP) evoked by finger stimulation in healthy subjects. SEPs induced by electrical stimulation and especially after median nerve stimulation is a method widely used in the literature. It is unclear, however, if the EEG recordings after finger stimulation are reproducible within the same subject. We tested in five healthy subjects the consistency and reproducibility of responses through bootstrapping as well as test-retest recordings. We further evaluated the possibility to discriminate activity of different fingers both at electrode and at source level. The lack of consistency and reproducibility suggest responses to finger stimulation to be unreliable, even with reasonably high signal-to-noise ratio and adequate number of trials. At sources level, somatotopic arrangement of the fingers representation was only found in one of the subjects. Although finding distinct locations of the different fingers activation was possible, our protocol did not allow for non-overlapping dipole representations of the fingers. We conclude that despite its theoretical advantages, we cannot recommend the use of somatosensory potentials evoked by finger stimulation to extract clinical biomarkers.

GPDM- and 10-MDP-based Self-etch Adhesives Bonded to Bur-cut and Uncut Enamel - "Immediate" and "Aged" µTBS.

PURPOSE: To determine the microtensile bond strength (µTBS) of two 2-step self-etch adhesives (SEAs) to bur-cut and uncut enamel. MATERIALS AND METHODS: The buccal and lingual enamel surfaces of 15 teeth were ground flat ("bur-cut" enamel), while the enamel surface of another set of 15 teeth was solely prophylactically cleaned ("uncut" enamel). Resin composite was bonded to the surfaces using the GPDM-based SEA OptiBond XTR (Kerr), the 10-MDP-based SEA Clearfil SE Bond (Kuraray Noritake), or the 3-step etch-and-rinse adhesive (E&RA) OptiBond FL (Kerr) that served as the gold-standard control. After 1-week water storage at 37°C, specimens were serially cut into 1-mm2 stick-shaped microspecimens, of which half per tooth were further subjected to 20,000 thermocycles (TC) prior to µTBS testing. Data were statistically analyzed using ANOVA and the post-hoc Tukey test. The interfacial ultrastructure of the GPDM-based SEA OptiBond XTR with uncut and bur-cut enamel was additionally characterized with transmission electron microscopy (TEM). RESULTS: After 1-week water storage and upon TC aging, both SEAs bonded significantly (p < 0.05) less effectively to both bur-cut and uncut enamel than did the control OptiBond FL, except when OptiBond XTR was bonded to bur-cut enamel; then a similarly high µTBS was recorded (p > 0.05). TEM interfacial characterization revealed a tight interaction of Optibond XTR with both bur-cut and uncut enamel. CONCLUSION: The best bonding efficacy to enamel is still achieved by etching with phosphoric acid, following an E&R approach, while the higher etching efficacy of the GPDM-based SEA may result in equally effective bonding, provided that the enamel is bur-roughened first.

Nine-year Clinical Performance of a HEMA-free One-step Self-etch Adhesive in Noncarious Cervical Lesions.

PURPOSE: One-step self-etch adhesives are among the most popular adhesives to directly bond composite to tooth tissue, mainly because of their perceived ease-of-use. The aim of this randomized controlled trial was to evaluate the clinical performance of a HEMA-free 1-step self-etch adhesive (1SEa), as compared with a 3-step etch-and-rinse adhesive (3E&Ra). MATERIALS AND METHODS: 267 non-carious cervical lesions in 52 patients were restored with a microhybrid composite Gradia Direct (GC), bonded in random order either with the HEMA-free 1SEa G-Bond (GB; GC) or the considered gold-standard 3E&Ra Optibond FL (OFL; Kerr). The restorations were evaluated after 6 months, 1, 2, 3, 5 and 9 years of clinical service for retention, marginal adaptation, marginal discoloration, caries occurrence and tooth sensitivity. Statistical analysis was done using a logistic regression model with generalized estimating equations (2-way GEE model). RESULTS: The patient recall rate at 9 years was 82.6%. The overall clinical success rate was 80.3% and 79.5% for GB and OFL, respectively. In total, 47 restorations (23 GB, 24 OFL) failed because of retention loss, severe marginal defects and/or discoloration and/or caries. A similar retention rate of 89.7% was recorded for both adhesives GB and OFL. Slight marginal defects and superficial marginal discoloration, though both still clinically acceptable, were significantly more observed at the incisal enamel side of GB (92.4% and 52.1%, respectively) than OFL (59.6%; 30.8%) restorations (p < 0.05). CONCLUSION: After 9 years of clinical service, class-V restorations bonded with the HEMA-free 1SEa performed clinically equally successful as those bonded with the 3E&Ra. However, more marginal deterioration, though still clinically acceptable, was recorded at the incisal enamel side for the 1SEa.

Polymerization Efficacy Affects the Long-term Mini-interfacial Fracture Toughness.

PURPOSE: To evaluate the effect of the type and concentration of photo-initiator on the long-term bonding efficacy to dentin in terms of mini-interfacial fracture toughness (mini-iFT). MATERIALS AND METHODS: The bonding efficacy of the one-step self-etch (SE) adhesive Clearfil S3 Bond Plus and four derivative experimental adhesives (Leuven University Bond [LUB]), which were similar in composition except for the (co)photo-initiators (all prepared by Kuraray Noritake), containing 2.0 wt% camphorquinone (CQ) and 2.0 wt% EDMAB (LUB-CQ/amine_high), 0.35 wt% CQ and 0.35 wt% EDMAB (LUB-CQ/amine_low ), 2.0 wt% TPO (LUB-TPO_high), and 0.35 wt% TPO (LUB-TPO_low), was measured using a mini-iFT approach after being aged for 6 months and 1 year by water storage at 37°C (control: 1 week mini-iFT). The mini-iFT specimens were loaded until failure in a 4-point bending device to determine the interfacial fracture toughness (KIc). All fractured specimens were evaluated using scanning electron microscopy (SEM). RESULTS: The mini-iFT of Clearfil S3 Bond Plus and the adhesives with high photo-initiator concentrations was not significantly different at 6 months, although it dropped significantly at 1 year. For each storage period, the mini-iFT of the adhesives with high photo-initiator concentrations was not significantly different from that of the commercial adhesive, in contrast to the significantly lower mini-iFT measured for adhesives with low concentrations of photo-initiator. SEM fracture analysis revealed that the adhesives with high concentrations of photo-initiator most frequently failed at the top of the hybrid layer at 1 week, while this failure pattern shifted to the bottom of the hybrid layer after aging. CONCLUSION: A one-step self-etch adhesive should contain photo-initiator in a sufficiently high concentration, as this directly improves its immediate and long-term bonding efficacy to dentin. While the mini-iFT remained stable up to 6 month of aging for both the commercial and the adhesive with a high concentration of photo-initiator, the mini-iFT was found to decrease after 1 year of aging.

Bulk-Fill Composites: A Review of the Current Literature.

PURPOSE: The aim of this article was to provide an overview of the literature on the currently available bulk-fill composites, and to describe the common trends as well as the wide variations. The findings may help the clinician to select the proper material with regard to its applicability in various clinical situations. METHODS: The literature up to October 2016 was reviewed based on a PubMed search (keywords: "bulk-fill OR bulkfill OR bulk fill" AND "composite OR composites"). RESULTS: This review revealed that bulk-fill composites differ most from conventional composites in their increased depth of cure, which could mainly be attributed to an increase in translucency. However, the literature is inconsistent regarding the determination of the depth of cure. Flowable "base" bulk-fill composites seem most suitable for narrow cavities deeper than 4 mm, in particular when a higher adaptation potential thanks to better flowability in less accessible cavity configurations is desirable. In more extensive cavities, "full-body" bulk-fill composites with a high filler load are preferable. Then, resistance against wear and fracture becomes increasingly important, while a thicker consistency might also help in obtaining a good contact point. Tests related to shrinkage stress induced by bulk-filling seem inconsistent and their clinical relevance is unclear. CONCLUSION: More clinical studies that specifically focus on bulk-filling deep and large restorations are definitely required to fully explore the clinical benefits of bulk-fill composites.

Mini-interfacial Fracture Toughness of a Multimode Adhesive Bonded to Plasma-treated Dentin.

PURPOSE: To investigate the bonding efficacy of a multimode adhesive to plasma-treated and -untreated (control) dentin using a mini-interfacial fracture toughness (mini-iFT) test. MATERIALS AND METHODS: Twenty human molars were used in a split-tooth design (n = 10). The adhesive Scotchbond Universal (SBU; 3M ESPE) was applied in etch-and-rinse (E&R) and self-etch (SE) modes. Mid-coronal dentin was exposed and covered with a standardized smear layer ground to 320 grit. One half of each dentin surface received 15 s of non-thermal atmospheric plasma (NTAP), while the other half was covered with a metallic barrier and kept untreated. Following the E&R mode, dentin was plasma treated immediately after phosphoric acid etching. SBU and a resin-based composite were applied to dentin following the manufacturer's instructions. Six mini-iFT specimens were prepared per tooth (1.5 x 2.0 x 16 to 18 mm), and a single notch was prepared at the adhesive-dentin interface using a 150-µm diamond blade under water cooling. Half of the mini-iFT specimens were immediately loaded until failure in a 4-point bending test, while the other half were first stored in distilled water for 6 months. After testing, the exact dimensions of the notch were measured with a measuring optical microscope, from which ΚIc was determined. RESULTS: Three-way ANOVA revealed higher mini-iFT for SBU applied in E&R than SE mode for both storage times, irrespective of NTAP treatment. CONCLUSION: Overall, mini-iFT did not decrease for any of the experimental groups upon 6-month aging, while plasma treatment did not show a direct beneficial effect on mini-iFT of SBU applied in either E&R or SE mode.

Bonding Efficacy and Fracture Pattern of Adhesives Submitted to Mechanical Aging with the Rub&Roll Device.

PURPOSE: To evaluate the effect of water storage and cyclic loading on the microtensile bond strength (µTBS) and fracture pattern of adhesives to dentin. MATERIALS AND METHODS: Midcoronal dentin surfaces (n = 36) were prepared and composite restorations were built up using two adhesives (self-etch and etch-and-rinse). The specimens were randomly divided into 3 groups according to the aging conditions (n = 6): 1. CONTROL: storage in water for 24 h (CO); 2. water storage: storage in water for 6 months (WS); 3. mechanical loading: 750,000 mechanical cycles (ML) using the Rub&Roll loading device. Specimens were sections into beams and the µTBS was tested. Fracture patterns were analyzed using stereomicroscopy and fractographic analysis was performed using SEM. µTBS data (n = 53-72 specimens) were subjected to two-way ANOVA and Tukey's post-hoc test. The chi-squared test was used to compare the distribution of failure modes (p < 0.05). RESULTS: Aging conditions and adhesives significantly affected µTBS (p < 0.01). The CO group showed no difference between materials and had highest µTBS. After WS, the self-etch adhesive showed higher µTBS than did the etchand- rinse adhesive. ML resulted in lower µTBS for both adhesives. Materials (p < 0.01) and aging (p < 0.01) significantly influenced the distribution of failure modes. SEM analysis showed that specimens submitted to WS or ML showed features of degradation and fatigue at the fractured interface, depending on the adhesive. CONCLUSION: Mechanical loading had a negative effect on the bonding efficacy of both adhesives and influenced the fracture pattern, with specimens presenting a different fracture surface from that observed in water-stored specimens.

Curing characteristics of flowable and sculptable bulk-fill composites.

OBJECTIVES: The aim of this study was to determine and correlate the degree of conversion (DC) with Vickers hardness (VH) and translucency parameter (TP) with the depth of cure (DoC) of five bulk-fill composites. MATERIALS AND METHODS: Six specimens per group, consisting of Tetric EvoCeram Bulk Fill ("TEC Bulk," Ivoclar Vivadent), SonicFill (Kerr), SDR Smart Dentin Replacement ("SDR," Dentsply), Xenius base ("Xenius," StickTech; commercialized as EverX Posterior, GC), Filtek Bulk Fill flowable ("Filtek Bulk," 3M ESPE), and Tetric EvoCeram ("TEC," control), were prepared for DC and VH: two 2-mm-thick layers, each light-cured for 10 s; one 4-mm bulk-fill, light-cured for 10 or 20 s; and one 6-mm bulk-fill, cured for 20 s. DC was measured using a Fourier-transform infrared spectrometer, VH using a Vickers hardness tester. DoC and TP were measured using an acetone-shaking test and a spectrophotometer, respectively. Data were analyzed using ANOVA and Pearson's correlation (α = 0.05). RESULTS: DC and VH ranged between 40-70 % and 30-80 VHN, respectively. TEC Bulk, Xenius, and SonicFill, bulk-filled as 4-mm-thick specimens, showed bottom-to-top hardness ratios above 80 % after 20 s curing. A positive linear correlation was found for bottom DC and VH. An average DC ratio of 0.9 corresponded to a bottom-to-top VH ratio of 0.8. CONCLUSIONS: Sculptable bulk-fills require 20 s, whereas 10 s curing time was sufficient for flowable bulk-fills using a high-intensity LED unit. CLINICAL RELEVANCE: Clinicians should be aware that longer curing times may be required for sculptable than flowable bulk-fill composites in order to achieve optimal curing characteristics.

No evidence for the growth-stimulating effect of monomers on cariogenic Streptococci.

BACKGROUND: In spite of contradicting results, the high susceptibility of composites for secondary caries is still often associated with the bacterial growth-stimulating effect of released methacrylate monomers. However, most studies that showed this effect were performed with techniques having inherent limitations (spectrophotometry). OBJECTIVES: Therefore, our objective was to determine the effect of four methacrylate monomers (2-Hydroxyethyl methacrylate (HEMA), triethylene glycol dimethacrylate (TEGDMA), ethylene glycol dimethacrylate (EGDMA), diethylene glycol dimethacrylate (DEGDMA)) on the growth of two caries-associated bacteria, Streptococcus mutans and sobrinus, and one non-cariogenic species, Streptococcus sanguinis, using TaqMan quantitative polymerase chain reaction (qPCR) to quantify bacterial DNA. MATERIALS AND METHODS: Cultures were exposed to monomer solutions selected after spectrophotometric growth measurements. At baseline and predetermined time intervals, bacterial DNA was extracted and quantified with TaqMan qPCR. Biofilms grown in the presence of monomers were analyzed with scanning electron microscopy (SEM). RESULTS: Spectrophotometry indeed showed increased growth rates of all three strains with 5 mM TEGDMA, EGDMA, and DEGDMA and increased total biomass of S. sanguinis with 5 mM TEGDMA. However, qPCR failed to show any growth-stimulating effect of these monomers on S. mutans and S. sobrinus. In contrast, some monomers exhibited a growth-inhibiting effect on S. sanguinis. SEM revealed extracellular matter in S. sobrinus and S. sanguinis biofilms, which might be attributed to polymer formation. CONCLUSIONS: Techniques which quantify bacterial DNA are more appropriate to evaluate bacterial growth in the presence of monomers than spectrophotometry. CLINICAL RELEVANCE: Even though methacrylate monomers did not affect the growth of cariogenic species, growth inhibition of S. sanguinis, a non-cariogenic antagonistic species, may lead to ecological shifts towards higher cariogenicity.

Modified tricalcium silicate cement formulations with added zirconium oxide.

OBJECTIVES: This study aims to investigate the effect of modifying tricalcium silicate (TCS) cements on three key properties by adding ZrO2. MATERIALS AND METHODS: TCS powders were prepared by adding ZrO2 at six different concentrations. The powders were mixed with 1 M CaCl2 solution at a 3:1 weight ratio. Biodentine (contains 5 wt.% ZrO2) served as control. To evaluate the potential effect on mechanical properties, the mini-fracture toughness (mini-FT) was measured. Regarding bioactivity, Ca release was assessed using ICP-AES. The component distribution within the cement matrix was evaluated by Feg-SEM/EPMA. Cytotoxicity was assessed using an XTT assay. RESULTS: Adding ZrO2 to TCS did not alter the mini-FT (p = 0.52), which remained in range of that of Biodentine (p = 0.31). Ca release from TSC cements was slightly lower than that from Biodentine at 1 day (p > 0.05). After 1 week, Ca release from TCS 30 and TCS 50 increased to a level that was significantly higher than that from Biodentine (p < 0.05). After 1 month, Ca release all decreased (p < 0.05), yet TCS 0 and TCS 50 released comparable amounts of Ca as at 1 day (p > 0.05). EPMA revealed a more even distribution of ZrO2 within the TCS cements. Particles with an un-reacted core were surrounded by a hydration zone. The 24-, 48-, and 72-h extracts of TCS 50 were the least cytotoxic. CONCLUSIONS: ZrO2 can be added to TCS without affecting the mini-FT; Ca release was reduced initially, to reach a prolonged release thereafter; adding ZrO2 made TCS cements more biocompatible. CLINICAL RELEVANCE: TCS 50 is a promising cement formulation to serve as a biocompatible hydraulic calcium silicate cement.

Determination of head conductivity frequency response in vivo with optimized EIT-EEG.

Electroencephalography (EEG) benefits from accurate head models. Dipole source modelling errors can be reduced from over 1cm to a few millimetres by replacing generic head geometry and conductivity with tailored ones. When adequate head geometry is available, electrical impedance tomography (EIT) can be used to infer the conductivities of head tissues. In this study, the boundary element method (BEM) is applied with three-compartment (scalp, skull and brain) subject-specific head models. The optimal injection of small currents to the head with a modular EIT current injector, and voltage measurement by an EEG amplifier is first sought by simulations. The measurement with a 64-electrode EEG layout is studied with respect to three noise sources affecting EIT: background EEG, deviations from the fitting assumption of equal scalp and brain conductivities, and smooth model geometry deviations from the true head geometry. The noise source effects were investigated depending on the positioning of the injection and extraction electrode and the number of their combinations used sequentially. The deviation from equal scalp and brain conductivities produces rather deterministic errors in the three conductivities irrespective of the current injection locations. With a realistic measurement of around 2 min and around 8 distant distinct current injection pairs, the error from the other noise sources is reduced to around 10% or less in the skull conductivity. The analysis of subsequent real measurements, however, suggests that there could be subject-specific local thinnings in the skull, which could amplify the conductivity fitting errors. With proper analysis of multiplexed sinusoidal EIT current injections, the measurements on average yielded conductivities of 340 mS/m (scalp and brain) and 6.6 mS/m (skull) at 2 Hz. From 11 to 127 Hz, the conductivities increased by 1.6% (scalp and brain) and 6.7% (skull) on the average. The proper analysis was ensured by using recombination of the current injections into virtual ones, avoiding problems in location-specific skull morphology variations. The observed large intersubject variations support the need for in vivo measurement of skull conductivity, resulting in calibrated subject-specific head models.

Alzheimer Disease and Behavioral Variant Frontotemporal Dementia: Automatic Classification Based on Cortical Atrophy for Single-Subject Diagnosis.

Purpose To investigate the diagnostic accuracy of an image-based classifier to distinguish between Alzheimer disease (AD) and behavioral variant frontotemporal dementia (bvFTD) in individual patients by using gray matter (GM) density maps computed from standard T1-weighted structural images obtained with multiple imagers and with independent training and prediction data. Materials and Methods The local institutional review board approved the study. Eighty-four patients with AD, 51 patients with bvFTD, and 94 control subjects were divided into independent training (n = 115) and prediction (n = 114) sets with identical diagnosis and imager type distributions. Training of a support vector machine (SVM) classifier used diagnostic status and GM density maps and produced voxelwise discrimination maps. Discriminant function analysis was used to estimate suitability of the extracted weights for single-subject classification in the prediction set. Receiver operating characteristic (ROC) curves and area under the ROC curve (AUC) were calculated for image-based classifiers and neuropsychological z scores. Results Training accuracy of the SVM was 85% for patients with AD versus control subjects, 72% for patients with bvFTD versus control subjects, and 79% for patients with AD versus patients with bvFTD (P ≤ .029). Single-subject diagnosis in the prediction set when using the discrimination maps yielded accuracies of 88% for patients with AD versus control subjects, 85% for patients with bvFTD versus control subjects, and 82% for patients with AD versus patients with bvFTD, with a good to excellent AUC (range, 0.81-0.95; P ≤ .001). Machine learning-based categorization of AD versus bvFTD based on GM density maps outperforms classification based on neuropsychological test results. Conclusion The SVM can be used in single-subject discrimination and can help the clinician arrive at a diagnosis. The SVM can be used to distinguish disease-specific GM patterns in patients with AD and those with bvFTD as compared with normal aging by using common T1-weighted structural MR imaging. (©) RSNA, 2015.

Effect of Bulk-filling on the Bonding Efficacy in Occlusal Class I Cavities.

PURPOSE: To evaluate the effect of bulk filling Class I posterior cavities on bonding to cavity-bottom dentin. MATERIALS AND METHODS: Two flowable "base" bulk-fill composites (Filtek Bulk Fill Flowable, SDR), one paste-like "full-body" bulk-fill composite (Tetric EvoCeram Bulk Fill) and one conventional paste-like composite (Filtek Z100) were bonded (G-ænial Bond) to either a flat surface (3.5 x 3.5 x 4 mm; C-factor: 0.18) or a Class I cavity (3.5 x 3.5 x 4 mm; C-factor: 5.8). After 1-week water storage, the restorations were sectioned to obtain 4 rectangular microspecimens that were subjected to microtensile bond strength (µTBS) testing. RESULTS: No significant differences in µTBS were recorded between all composites when bonded onto a flat surface (p > 0.05). When bonded into a Class I cavity, the µTBS of all composites except SDR significantly decreased (p < 0.001). CONCLUSION: Both the configuration factor and the type of bulk-fill composite were found to have a great impact on bonding to cavity-bottom dentin.

Bonding Effectiveness of Luting Composites to Different CAD/CAM Materials.

PURPOSE: To evaluate the influence of different surface treatments of six novel CAD/CAM materials on the bonding effectiveness of two luting composites. MATERIALS AND METHODS: Six different CAD/CAM materials were tested: four ceramics - Vita Mark II; IPS Empress CAD and IPS e.max CAD; Celtra Duo - one hybrid ceramic, Vita Enamic, and one composite CAD/CAM block, Lava Ultimate. A total of 60 blocks (10 per material) received various mechanical surface treatments: 1. 600-grit SiC paper; 2. sandblasting with 30-µm Al2O3; 3. tribochemical silica coating (CoJet). Subsequent chemical surface treatments involved either no further treatment (control), HF acid etching (HF), silanization (S, or HF acid etching followed by silanization (HF+S). Two specimens with the same surface treatment were bonded together using two dual-curing luting composites: Clearfil Esthetic Cement (self-etching) or Panavia SA Cement (self-adhesive). After 1 week of water storage, the microtensile bond strength of the sectioned microspecimens was measured and the failure mode was evaluated. RESULTS: The bonding performance of the six CAD/CAM materials was significantly influenced by surface treatment (linear mixed models, p < 0.05). The luting cement had a significant influence on bond strength for Celtra Duo and Lava Ultimate (linear mixed models, p < 0.05). Mechanical surface treatment significantly influenced the bond strength for Celtra Duo (p = 0.0117), IPS e.max CAD (p = 0.0115), and Lava Ultimate (p < 0.0001). Different chemical surface treatments resulted in the highest bond strengths for the six CAD/CAM materials: Vita Mark II and IPS Empress CAD: S, HF+S; Celtra Duo: HF, HF+S; IPS e.max CAD: HF+S; Vita Enamic: HF+S, S. For Lava Ultimate, the highest bond strengths were obtained with HF, S, HF+S. Failure analysis showed a relation between bond strength and failure type: more mixed failures were observed with higher bond strengths. Mainly adhesive failures were noticed if no further surface treatment was done. The percentage of adhesive failures was higher for CAD/CAM materials with higher flexural strength (Celtra Duo, IPS e.max CAD, and Lava Ultimate). CONCLUSION: The bond strength of luting composites to novel CAD/CAM materials is influenced by surface treatment. For each luting composite, an adhesive cementation protocol can be specified in order to obtain the highest bond to the individual CAD/CAM materials.

Influence of Light Irradiation Through Zirconia on the Degree of Conversion of Composite Cements.

PURPOSE: To assess the light irradiance (LI) delivered by two light-curing units and to measure the degree of conversion (DC) of three composite cements and one flowable composite when cured through zirconia or ceramic-veneered zirconia plates with different thicknesses. MATERIALS AND METHODS: Three dual-curing composite cements (Clearfil Esthetic Cement, Panavia F2.0, G-CEM LinkAce) and one light-curing flowable composite (G-aenial Universal Flo) were investigated. Nine different kinds of zirconia plates were prepared from three zirconia grades (YSZ: Aadva and KATANA; Ce-TZP/Al2O3: NANOZR) in three different thicknesses (0.5- and 1.5-mm-thick zirconia, and 0.5-mm-thick zirconia veneered with a 1.0-mm-thick veneering ceramic). Portions of the mixed composite cements and the flowable composite were placed on a light spectrometer to measure LI while being light cured through the zirconia plates for 40 s using two light-curing units (n = 5). After light curing, micro-Raman spectra of the composite films were acquired to determine DC at 5 and 10 min, 1 and 24 h, and at 1 week. RESULTS: The zirconia grade and the thickness of the zirconia/veneered zirconia plates significantly decreased LI. Increased LI did not increase DC. Only the Ce-TZP/Al2O3 (NANOZR) zirconia was too opaque to allow sufficient light transmission and resulted in significantly lower DC. CONCLUSION: Although zirconia-based restorations attenuate the LI of light-curing units, the composite cements and the flowable composite could be light cured through the YSZ zirconia. LI is too low through Ce-TZP/Al2O3 zirconia, necessitating the use of self-/dual-curing composite cements.

Correlative micro-Raman/EPMA analysis of the hydraulic calcium silicate cement interface with dentin.

OBJECTIVES: This study aims to characterize the chemical interplay of hydraulic calcium silicate cements at dentin. MATERIALS AND METHODS: Class I cavities were prepared in non-carious human third molars and filled with Biodentine (Septodont) or ProRoot MTA (Dentsply). After 1-day, 1-week, and 1-month Dulbecco's phosphate-buffered saline (DPBS) storage, the specimens were cross-sectioned perpendicular to the cement-dentin interface. The interfaces were evaluated using micro-Raman (µRaman) spectroscopy and at a higher spatial resolution using field emission gun electron probe microanalysis (Feg-SEM/EPMA). RESULTS: µRaman spectroscopy revealed the formation of a transition zone at the interface of both Biodentine (Septodont) and ProRoot MTA (Dentsply) with dentin, having an average thickness of, respectively, 7.5 ± 4.2 and 6.2 ± 5.4 µm, which however was not statistically different. No difference in interfacial ultrastructure and chemistry was found using µRaman spectroscopy between 1 day, 1 week, and 1 month DPBS-stored specimens. The observation of a transition zone at the cement-dentin interfaces contrasts with the EPMA data that revealed a sharper transition from cement to dentin. Again, no difference in interfacial ultrastructure and chemistry was found for different storage periods, with the exception of one 1 month DPBS-stored specimen prepared using Biodentine (Septodont). More specifically, EPMA revealed a gap of about 10-µm wide in the latter specimen that was filled up with newly formed calcium phosphate depositions. CONCLUSIONS: Up to 1 month, the interaction of hydraulic calcium silicate cements investigated did not reveal ultrastructural or chemical changes at unaffected dentin with the exception of a calcium phosphate gap-filling property. CLINICAL RELEVANCE: Hydraulic calcium silicate cements were found to fill gaps by calcium phosphate deposition, however, without conducting chemical changes to the adjacent dentin.

Short fibre-reinforced composite for extensive direct restorations: a laboratory and computational assessment.

OBJECTIVES: The objective of the study was to evaluate the effectiveness of a short fibre-reinforced composite (FRC) applied in combination with a conventional filler composite (CFC) on the fatigue resistance, fracture strength, failure mode and stress distribution, for restorations of premolars under two loading angles. MATERIAL AND METHODS: Thirty-two inferior premolars received extensive cavities with removal of the lingual cusp. Teeth were restored directly using 'FRC (EverX Posterior, GC) + CFC (G-aenial, GC)' or 'CFC only' and received two fatigue/fracture loadings at two different angles (0°/45°) (n = 8). Data were submitted to two-way ANOVA (α = 5 %) and Tukey test. Failure mode was analysed using SEM. Four 3D finite element (FE) models were constructed and static, linear and elastic analyses were performed. Maximum principal and von Mises stresses were evaluated. RESULTS: All specimens survived the mechanical fatigue simulation. No statistical difference in fracture resistance was recorded between FRC + CFC and CFC only, considering both loading angles (p = 0.115). However, the 0° loading showed a statistical significant higher strength than the 45° loading (p = 0.000). Failure mode analysis revealed more repairable fractures upon 0° loading, versus more root fractures (unrepairable) upon 45° loading. FE revealed a higher amount of stress upon 45° loading, with tensile stress being imposed to the lingual cervical area. CONCLUSION: The fracture strength was not increased using the FRC. Loading at a 45° decreased significantly the fracture resistance. CLINICAL RELEVANCE: The restoration of extensive cavities in posterior tooth is a challenge for the clinicians and the choice of the material that increases the fracture strength of tooth-restoration complex is required.