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Background: A major drawback of resin composites is their tendency to accumulate microbial biofilms that can lead to secondary caries. The objective of this study was to compare the mechanical properties and the degree of conversion of commercial resin-based composite materials containing a contact-killing antibacterial agent, dimethylaminohexadecyl methacrylate (DMAHDM), at different concentrations, with a fluoride-releasing composite material. Materials and methods: Four groups were tested: Tetric N Ceram composite material (G1), Tetric Evo Ceram (G2), and Tetric N Ceram with the addition of contact-killing antibacterial agent DMAHDM at concentrations of 3% (G3) and 5% (G4). The mechanical properties, including flexural strength, elastic modulus, and Vickers microhardness and the degree of conversion were investigated. Results: Adding 3 % and 5 % DMAHDM resulted in flexural strength values that were comparable to Tetric Evo Ceram. Tetric N Ceram was comparable to the group containing 3 % DMAHDM (p > 0.05). However, it was significantly greater when compared to Tetric Evo Ceram (93.3 ± 9.4) and 5 % DMAHDM (p 0.05). There was no statistically significant difference in the degree of conversion between the groups (p > 0.05). Conclusion: Adding 3% DMAHDM to Tetric N Ceram resulted in flexural strength values that were similar to those of Tetric N Ceram and Tetric Evo Ceram. DMAHDM did not affect the degree of conversion of Tetric N Ceram composite.

Purpose: To compare the nanoleakage between bulkfill and incremental-fill resin composites in class II slot preparations for primary and permanent teeth restored by the snowplow technique. Materials and Methods: Class II slots were prepared in 32 M (16 exfoliated/extracted primary and 16 permanent molars). Optibond All-InOne self-etching adhesive was applied and cured. A flowable composite, Premise, was then injected into the gingival seat without curing using the snowplow technique. Cavities were restored using Sonicfill/bulkfill or microhybrid Herculite composites. Energy dispersive X-ray spectrometry was used to assess nanoleakage as silver deposition percentages along the axial and cervical walls. Multivariate analysis of variance was used to assess the effect of tooth type (primary and permanent teeth) and placement technique (bulkfill and incremental techniques) on nanoleakage at the axial and cervical walls. Results: Bulkfill restorations had significantly greater nanoleakage than incremental restorations at the cervical walls in primary and permanent molars (mean = 1.21 vs 0.49 in primary molars and 0.76 vs 0.24 in permanent molars). Equivalent results were observed at the axial walls of the restorations (mean = 0.66 vs 0.14 in primary molars and 0.28 vs 0.08 in permanent molars, with a P value of

Given the convenience of using plastics, addressing the growing concerns about their hazardous health effects is imperative. Consequently, a comprehensive risk assessment is necessary to gauge the potential harm microplastics pose. With its urgent call to action, this study aimed to investigate the indoor source and abundance of microplastics in private dental units during routine professional activities. The current analyzed microplastic quantity variations based on morphological characteristics, seasonal fluctuations and polymer-types. The polymer hazard index (PHI) was calculated to evaluate the significant human health risks posed to dental professionals by inhalation of microplastics. Dust samples were collected using a clean brush and steel pan from various flat and horizontal surfaces within each dental unit. The study found that clinical dental units had fewer microplastics (587 ± 184.9 MPs/g/day) than teaching hospitals (1083.80 ± 133.7MPs/g/day), with comparatively more abundance in winter (31 %). ATR-FTIR analysis determined polyethylene terephthalate to be a more abundant polymer (39 %). This study also found an average inhalation microplastic intake risk of 20.23 MP/g/day and 5259.85 MP/g/year for clinical and 29.45 MP/g/day and 765.12 MP/g/year for teaching hospital dental units. Female dental professionals have 1.1 times more microplastic inhalation risks than male dental professionals. According to PHI findings, overall minor to medium polymer risk was determined. In conclusion, this evidence-based research underscores the urgent need for a shift towards more sustainable practices in the dental healthcare sector. Dental professionals should prioritize using non-plastic material protective equipment and a proper ventilation system to reduce exposure to these particles., Competing Interests: Declaration of Competing Interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 Elsevier B.V. All rights reserved.)

Dental restorative procedures remain a cornerstone of dental practice, and for many decades, dental amalgam was the most frequently employed material. However, its use is declining, mainly driven by its poor aesthetics and by the development of tooth-coloured adhesive materials. Furthermore, the Minamata Convention agreed on a phase-down on the use of dental amalgam. This concise review is based on a FDI Policy Statement which provides guidance on the selection of direct restorative materials as alternatives to amalgam. The Policy Statement was informed by current literature, identified mainly from PubMed and the internet. Ultimately, dental, oral, and patient factors should be considered when choosing the best material for each individual case. Dental factors include the dentition, tooth type, and cavity class and extension; oral aspects comprise caries risk profiles and related risk factors; and patient-related aspects include systemic risks/medical conditions such as allergies towards certain materials as well as compliance. Special protective measures (eg, a no-touch technique, blue light protection) are required when handling resin-based materials, and copious water spray is recommended when adjusting or removing restorative materials. Cost and reimbursement policies may need to be considered when amalgam alternatives are used, and the material recommendation requires the informed consent of the patient. There is no single material which can replace amalgam in all applications; different materials are needed for different situations. The policy statement recommends using a patient-centred rather than purely a material-centred approach. Further research is needed to improve overall material properties, the clinical performance, the impact on the environment, and cost-effectiveness of all alternative materials., Competing Interests: Conflict of interest F. Schwendicke is lecturing for GC, 3M, DMG, and Dentsply Sirona on various dental materials mentioned in this text. All other authors declare no conflict of interest., (Copyright © 2023 The Authors. Published by Elsevier Inc. All rights reserved.)

Background: The objective of this study was to evaluate the effect of bleaching techniques, including or not the use of violet light (405-410 nm), on resin-based composites' color, surface roughness, nanohardness, and elastic modulus., Methods: Ninety-six disk-shaped specimens (12 mm x 2 mm; n = 12) were prepared using Filtek Z350 XT (Z350) and IPS Empress Direct (ED) resin-based composites. After 24 h, specimens were stained in red wine for 28 days. After staining, specimens were divided into four experimental groups: 40 % Hydrogen Peroxide (HP); Violet Light (VL); 40 % Hydrogen Peroxide associated with Violet Light (HP+VL), and a control group - no treatment (NT). Specimens were evaluated at six experimental times: initial (24 h after light curing); after staining and after the 1st, 2nd, 3rd, and 4th bleaching sessions regarding the color change (ΔE 00 , L*, a*, b*, and WI D ); roughness (Ra), nanohardness and elastic modulus (GPa). Two-way analysis of variance for repeated measures was performed (α=0.05 %)., Results: There was a statistically significant difference between staining and the 1st bleaching session for all ED groups (p<0.05). After the last bleaching session, there were no differences between the experimental and the control groups of both resin-based composites. Bleaching using violet light did not change the roughness, nanohardness and elastic modulus of the tested resin-based composites (p>0.05)., Conclusions: Although hydrogen peroxide and violet light remove pigments from resin-based composites without affecting their surface roughness, nanohardness, and elastic modulus, the color change was similar to the one obtained by immersion in distilled water., Competing Interests: Conflict of interest None., (Copyright © 2023 Elsevier B.V. All rights reserved.)

The aim of the study was to investigate the retention behaviour (pull-off force include adhesive remnant index = ARI) as well as translucency of various temporary luting cements and use microstructure elucidation methods to formulate explanatory approaches to their mode of action. The retention force of the temporary luting cements Provicol QM Plus (P+), Provicol QM Aesthetic (Pae), Bifix Temp (BiT), and as a reference a glass ionomer cement Meron (M) with a direct (Structur 3/S3) or an indirect (Structure CAD/SCAD) resin-based composite restauration was investigated after accelerated aging (thermocycling). Additional investigation of the physical properties was performed regarding to translucency and surface free energy. The microstructure was evaluated by X-ray diffraction, thermogravimetric analysis, differential scanning calorimetry and micro X-ray computed tomography. All tested temporary luting cements showed different pull-off forces in the range between 3.0 and 16.8 N in combination with S3 or SCAD after thermocycling. Only BiT with S3 showed pull-off forces of 129.2 N and complete retention on the restoration (ARI = 0), which was significant (p < .001) to all other samples. High translucency (BiT > Pae > M > P+) was observed for materials with lower crystalline content and low residual mass (usally resulting from higher organic content). M showed the highest surface free energy with a predominantly polar fraction, while BiT had a predominantly dispersive fraction. The highest porosity was observed in the coronal region of the restoration. The results suggest that translucency of temporary luting cements can be increased with higher organic and lower cryristall content. All combinations of cements and temporary restorations (direct/indirect; with the exception of BiT/S3) showed pull-off forces below 17 N (equivalent to a weight force of ∼1.7 kg), which allows manual detachment of the restoration by the dentist., Competing Interests: Declaration of competing interest The authors declare the following financial interests/personal relationships which may be considered as potential competing interests: Andreas Koenig reports financial support was provided by VOCO GmbH., (Copyright © 2023 Elsevier Ltd. All rights reserved.)

This study evaluated the effect of using two different pre-heating methods on the three resin-based composite (RBCs). Three paste viscosity bulk-fill RBCs (VisCalor Bulk [VC]; VOCO; x-tra fil Caps [XF], VOCO; Filtek One Bulk Fill [FO], 3 M) were pre-heated using either a VisCalor Dispenser (VOCO) to 65 °C, or the Caps Warmer (VOCO) to 37 °C, 54 °C, or 68 °C. The temperature inside the capsules and cavity was monitored before and after insertion into the matrix. Within 30 s of inserting the RBC, they were light-activated using a VALO (Ultradent) curing light for 20 s. The post-gel shrinkage (Shr - %), Flexural Strength (FS - MPa), Elastic Modulus (E - MPa), degree of conversion (DC - %), Knoop Hardness (KH - N/mm 2 ), diametral tensile strength (DTS - MPa), and compressive strength (CS - MPa) of the RBCs were measured (10 specimens per group). The shrinkage stress was calculated using three-dimensional finite element analysis. Data were analyzed using one-way, two-way ANOVA and Tukey's test (α = 0.05). The temperature fell rapidly after the RBC was inserted into the cavity. Pre-heating the RBCs did not affect the mechanical properties. FO had the lowest E, DC, and KH values, VC had intermediate values, and XF achieved the highest values. The DTS and CS values were not affected by the various pre-heating methods, the temperature, or RBC. Pre-heating methods at 37 °C produced higher shrinkage for all RBCs. VC pre-heated to 65 °C produced the lowest stress when measured at 10 min after light activation., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2022. Published by Elsevier Ltd.)

Objectives: This study: 1) measures the effect of sample thickness and high irradiance on the depth-dependent time delay before photopolymerization reaction onset; 2) determines if exposure reciprocity exists; 3) measures the conversion rate at four irradiance levels; 4) determines the time, t 0 , at which the maximum DC rate is reached for two bulk-fill and one conventional posterior resin-based composites (RBCs)., Methods: Tetric PowerFill IVA shade (Ivoclar Vivadent) and Aura bulk-fill ultra universal restorative (SDI), and one conventional posterior resin-based composite (RBC), Heliomolar A3 (Ivoclar Vivadent), that were either 0.2 mm, 2 mm, or 4 mm thick were photocured using a modified Bluephase G4 (Ivoclar Vivadent) light-curing unit (LCU) that delivered a single emission band (wavelength centered at 449 nm). The same radiant exposure of 24 J/cm 2 was delivered at irradiances ranging from 0.5 to 3 W/cm 2 by adjusting the exposure time. PowerFill was also photocured for 3 s or 6 s using a Bluephase PowerCure LCU (Ivoclar Vivadent) on the 3 s mode setting. The degree of conversion (DC) was measured in real-time at a high temporal resolution at 30 °C using Attenuated Total Reflection (ATR) FTIR spectroscopy with a sampling rate of 13 DC data points per second. The DC data were analyzed using a phenomenological autocatalytic model. The RBC viscosity was measured at 21 °C and 30 °C. Light transmission through the RBC samples at 22 °C was monitored with time to calculate the extinction coefficients of the RBCs., Results: The time delay before photopolymerization started increased as the RBC thickness increased and the irradiance decreased. An autocatalytic model described the DC data. The time t 0 was less than 77 ms for the 0.2 mm thick samples of PowerFill irradiated using the highest irradiance of 3 W/cm 2 . Among the three RBCs for each sample thickness and irradiance level, the PowerFill had the smallest time t 0 . There was a time delay of 0.59 s and 1.25 s before the DC started to increase at the bottom of 4 mm thick samples for the PowerFill and Aura, respectively, when an irradiance of 1 W/cm 2 was delivered. The time delay increased to 3.65 s for the Aura when an irradiance of 0.5 W/cm 2 was delivered. The extinction coefficients near 449 nm were 0.78 mm -1 , 0.76 mm -1 , and 1.55 mm -1 during the first 2 s after the start of photocuring of PowerFill, Aura, and Heliomolar, respectively. Only PowerFill followed exposure reciprocity. At T = 30 °C, the viscosity was 3400, 17000, and 5200 Paˑs for PowerFill, Aura, and Heliomolar, respectively., Significance: The time delay between when photopolymerization starts at the top and bottom of 2- or 4-mm thick RBC restorations may affect the structural integrity of the bond between the tooth and the bottom of the restoration. Only PowerFill followed exposure reciprocity between irradiance levels of 0.5 to 3 W/cm 2 . Exposure reciprocity did not occur for Aura or Heliomolar, neither of which are optimized for short light exposure or high irradiance conditions., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2022 Elsevier Ltd. All rights reserved.)

The aim of the present laboratory study was to mechanically characterize the interface between two dental resin-based composite (RBC) increments, and to investigate if elevated temperatures have an influence on the quality of the interface mimicking clinical filling procedure. Four RBCs (CLEARFIL MAJESTY™ Posterior, Kuraray (CMP)/Filtek™ Supreme XTE, 3M (FSX)/Grandio®SO, VOCO (GSO)/VisCalor® bulk, VOCO (VCB)) were tested with a fracture toughness test using Chevron notched beams (K I,CNB ) at 23, 37 and 54 °C. K I,CNB specimens (3 × 4x25mm) with a V-shaped notch at the incremental interface were loaded until failure in a 4-point bending set-up. Failure modes were characterized using light microscopy, microstructural interface was analyzed using SEM. Statistical analysis was performed using Kolmogorov-Smirnoff test, two-way ANOVA and Tukey Post-Hoc test (p = 0.05). Mean K I,CNB ranged between 0.73 ±0.14 MPam 0.5 (VCB, 23 °C) and 1.11 ± 0.11 MPam 0.5 (FSX, 23 °C). The tested conventional highly filled RBCs presented fracture toughness at the incremental interface comparable to the cohesive strength of the bulk materials. VCB showed reduced interfacial fracture toughness at 23 and 37 °C, but performed well at elevated temperature of 54 °C., (Copyright © 2021 Elsevier Ltd. All rights reserved.)

Objective: This study correlates the mechanical and biological response of commercially available resin-based composites (RBCs) to clinically relevant light-curing conditions., Methods: Two RBCs (Venus and Venus Pearl; Kulzer) that use different monomer and photo-initiator systems, but have a similar filler volume and shade, were exposed to either just blue light, or violet and blue light from two different LCUs (Translux Wave and Translux 2Wave; Kulzer). Distance and exposure times were adjusted so that both LCUs delivered 5 similar levels of radiant exposures (RE) between 1.5 J/cm²-25 J/cm² in the blue wavelength range. Thus, the violet light was additional light. The top and bottom of 2-mm thick specimens were subjected to a depth-sensing indentation test (Martens hardness/HM, Vickers hardness/HV, indentation modulus/Y HU , mechanical work/W total , plastic deformation work/W plas , creep/Cr). The viability of human gingival fibroblasts was assessed after three days of exposure to RBC eluates. One and multiple-way analysis of variance (ANOVA), the Tukey honestly significant difference (HSD) post-hoc tests (α = 0.05), t-test and a Spearman correlation analysis were used., Results: As the RE increased, the mechanical properties increased at a greater rate at the top compared to the bottom of the RBCs. Values measured at the bottom of 2-mm increments approached the values measured at the top only when RE > 25 J/cm² of blue light was delivered. Toxicity decreased with RE and elution cycles and was lower for Venus Pearl. Within one RE level, addition of violet light resulted in significantly improved properties (in 131 out of 150 comparisons, p < 0.05). This effect was stronger for Venus Pearl. There was a good correlation between mechanical and biological parameters. This correlation decreased as the number of eluates increased., Clinical Significance: The mechanical and biological response to variation in RE is interrelated. The addition of violet light has a positive effect, particularly at low RE., (Copyright © 2021 Elsevier Ltd. All rights reserved.)

Objectives: Using standardized aluminum tooth models, this study: 1) measured the deflection along the cusp wall of models with a Class II cavity restored using either bulk filling or horizontal incremental filling techniques, and 2) calculated the cusp deflection and built-in stress within the restored tooth models for both filling techniques using a finite element (FE) model., Methods: Standardized tooth models with Class II cavities 4 mm deep, 4 mm high and 6 mm wide were machined out of aluminum. The models were restored using Filtek Posterior Restorative A2 shade resin-based composite (RBC). Both bulk filling and horizontal incremental filling techniques were used to restore the tooth models. After photocuring for 20 s from a single peak wavelength light-curing unit (LCU) with a radiant exitance of 1.25 W/cm 2 , the deflection of the cusp wall surface was measured using a profilometer. A FE model was used to predict the cuspal deflection and built-in stress of the restored tooth models., Results: The elastic modulus within the FE model was parameterized using cusp deflection data obtained on a bulk filled tooth model. An agreement was found between the measured and predicted cusp deflection only when considering partial stress relaxation within the first incremental layer for the two-layer incremental filling technique. The calculated built-in stress was significantly reduced within the RBC and along the cavity walls when the cavity was filled incrementally in a horizontal direction compared to when it was bulk filled, resulting in a significantly smaller cusp deflection., Significance: The FE model was first calibrated and then validated using measured cusp deflection data. Partial stress relaxation may play a significant role in the horizontal incremental filling technique. The model can be used to predict where the built-in stress within the tooth model occurs. This study explains why for a given RBC, a horizontal incremental filling and curing technique results in lower built-in stress within the restored tooth and lower cusp deflection compared to the bulk curing technique., (Copyright © 2020 Elsevier Ltd. All rights reserved.)

Objectives: This study aimed to investigate the effects of hydrothermal aging, thermal cycling, and water storage on the mechanical properties of a machinable resin-based composite containing nano-zirconia fillers., Materials and Methods: A machinable resin-based composite containing nano-zirconia fillers (Lava Ultimate, LU) and a resin-based composite with a similar resin matrix-to-filler ratio but without zirconia fillers (Tetric N-Ceram, TNC) were prepared into bars and assigned into four groups based on the type of aging treatment (hydrothermal aging, thermal cycling, water storage, or no aging). The phase transformations of the zirconia fillers in LU after aging were evaluated by X-ray diffraction. The flexural strength, Weibull modulus, flexural modulus, and Vickers hardness of each group were investigated. The fracture surface morphologies of both resin-based composites before and after aging were observed by a scanning electron microscopy (SEM)., Results: Only Tetragonal zirconia was detected in the LU samples. Both before and after aging, the flexural strength, flexural modulus, and Vickers hardness values of LU were significantly higher than those of TNC (p < 0.05) with the exception of the flexural modulus of LU, which showed no difference with that of TNC after water storage (p = 0.68). Hydrothermal aging, thermal cycling, and water storage had no significant effects on the surface Vickers hardnesses of LU or TNC (p > 0.05). Hydrothermal aging significantly improved the flexural strength of LU (p = 0.00). Thermal cycling (p = 0.00) and water storage (p = 0.00) significantly decreased the flexural strength of LU. The flexural strength of TNC was not decreased by hydrothermal aging (p = 0.82) or water storage (p = 0.36), while it was decreased by thermal cycling (p = 0.00). The hydrothermal aging group of LU exhibited the highest Weibull modulus., Conclusions: The machinable resin-based composite containing nano-zirconia fillers provides superior flexural strength, flexural modulus, and Vickers hardness compared to the direct-filling resin-based composite with a similar resin matrix-to-filler ratio, although it fails to provide better aging resistance., Competing Interests: Declaration of competing interest None., (Copyright © 2019 Elsevier Ltd. All rights reserved.)

Objectives: Resin-based composites (RBCs) are commonly used in dental restorations. It is known that RBCs undergo volumetric shrinkage during photo-polymerization leading to a detrimental increased stress state at the RBC-tooth interface and potentially early restoration failure. The objectives of this in vitro study were: (1) to ascertain whether shrinkage strain could be measured using in-fibre Bragg grating (FBG) technology, without confounding effects of temperature; and (2) to ascertain whether FBGs can detect alteration in shrinkage strain with introduction of a surface condition change at the RBC-cavity analog interface., Methods: Aluminum cavity analogs with simulated cavity dimensions 3.5 mm height x 2 mm width x 8 mm length and 2 mm wall thickness were secured in a 3D printed experimental jig. Two FBGs were used in the RBC space, one that was covered with a polyimide tube and that measured only temperature, and another that was affected by both mechanical strain and temperature. Experiments to determine if the two FBG system could be used to compensate for thermal artefacts were contrived to verify that a tube-covered and bare FBG measure the same temperature effect (n = 5). In situ photo-polymerization experiments, which consisted of using controlled amounts of SureFil SDR Flow + RBC, were performed to study RBC shrinkage behavior. As-machined (n = 10) and micro-etched (n = 11) cavity analogs were used. Significant differences in FBG measurements, which could indicate the ability of FBGs to detect alterations in strain across surface preparations, were determined using one tail t-tests at 95% confidence. Finally, additional temperature experiments were conducted 5 h after initial light exposure using the same light irradiation regiment to investigate temperature effects within a cured RBC system (n = 3)., Results: For temperature measurement, the tubing-covered and bare FBGs measured temperature changes with time-lag of 3.7 ± 1.4 s (tubing-covered FBG relative to bare). For measurements in cured RBC, the bare FBG and tubing-covered FBG measured different strains, with the bare FBG measuring larger apparent strains because this FBG is affected by thermal volumetric expansion of the RBC and a temperature increase of the FBG itself. The tubing covered FBG, that is isolated from volumetric expansion effects, measured relatively less. The interpretation of these results is that thermally-compensated strain measures (in-situ) could require simultaneous use of two FBGs (one strain isolated). In situ measurements of the photo-polymerization procedure for as-machined analogs at two time-points, 500 and 1000 s, were determined to be -485.43 ± 131.06 μstrain and -524.96 ± 134.78 μstrain, respectively. For air-abraded surfaces measures were significantly lower at (p < 0.001) -211.36 ± 12.38 μstrain and -228.07 ± 49.08 μstrain, respectively., Conclusions: To measure shrinkage strain and compensate for associated thermal effects from photo-polymerization, systems employing two FBGs, one of them isolated from thermal volumetric expansion, may be required. The presented approach proved capable of detecting significant alteration in strain across two surface preparations., (Copyright © 2019 Elsevier Ltd. All rights reserved.)

CAD/CAM-generated resin-based composite crowns have been proposed as an inexpensive alternative to conventional crowns. However, concerns have been raised about crown loosening in clinical use. Therefore, the present in vitro study aimed to evaluate the influence of thermal and mechanical cycling (TC and MC) on retentive strength of CAD/CAM resin-based crowns in relation to microscale expansion and contraction caused by fatigue. Eighty standardized dies were produced using a resin-based composite material. Crowns were milled from resin-based composite (n = 40) and glass-ceramic blocks (n = 40; control) using a dental CAD/CAM system. The crowns bonded to the dies were subjected to TC (temperature: 5 and 55 °C, cycles: 50,000) and MC (load: 200 N, cycles: 1.2 million). After fatigue treatment, retentive strength of the crowns was evaluated by a crown pull-off test at a crosshead speed of 1 mm/min. Coefficient of thermal expansion (CTE) and modulus of elasticity (E-modulus) of each material were also analyzed to estimate the microscale expansion and contraction during TC and MC. TC and MC significantly reduced the retentive strength of the CAD/CAM resin-based crowns whereas that of the CAD/CAM ceramic crowns was only affected by TC. In addition, the resin-based crowns showed a higher number of crown loosening during TC than the ceramic crowns. Analyses of CTE and E-modulus indicated that the resin-based crowns would be more deformed during TC and MC than the ceramic crowns. The present study demonstrated that the resistance of crowns to microscale expansion and contraction caused by thermal and mechanical fatigue would play an important role in maintaining retentive strength., (Copyright © 2018 Elsevier Ltd. All rights reserved.)

Objective: To investigate the fundamental wear mechanisms of six resin-based composite (RBC) formulations during short-term in vitro wear testing., Materials: RBC materials were condensed into rectangular bar-shaped specimens and light irradiated using the ISO 4049 specimen manufacture and irradiation protocol. Wear testing (n=10 specimens for each RBC) was performed on a modified pin-on-plate wear test apparatus and wear facets were analysed for wear volume loss using a white light profilometer. The wear tested RBC specimens and their corresponding antagonists were analysed using scanning electron microscopy (SEM) and energy-dispersive X-ray spectroscopy (EDS), respectively to determine the wear mechanism., Results: Data generated using the profilometer showed variations in the mean total wear volume (mm 3 ) between the RBCs tested (p<0.05). Abrasive wear was evident in all RBCs investigated with varying degrees of damage. Material transfer/deposition of the filler particles on the corresponding antagonists was evident in two RBC materials (Filtek Supreme and Kalore) indicative of a further adhesive wear mechanism., Conclusion: It is proposed that the approach employed to use a combination of measurement and analytical techniques to quantify the wear facet volume (profilometry), wear trough (SEM) and material transfer (EDS) provides more useful information on the wear mechanism and the tribology of the system rather than relying on a simple wear ranking for the RBC materials as is routinely the case in dental research studies., (Copyright © 2017 Elsevier Ltd. All rights reserved.)

Objective: To investigate the use of a three-dimensional (3D) digital scanning method in determining the accuracy of the wear performance parameters of resin-based composites (RBCs) determined using a two-dimensional (2D) analogue methodology following in-vitro testing in an Academisch Centrum for Tandheelkunde Amsterdam (ACTA) wear machine., Methods: Specimens compatible with the compartments of the ACTA wear machine specimen wheel (n=10) were prepared from one commercial and four experimental RBCs. The RBC specimens were rotated against an antagonist wheel in a food-like slurry for 220,000 wear cycles. The mean wear depth was measured using the traditionally employed 2D and compared with the 3D profilometric (digital) techniques. Data were submitted to analyses of variance, Tukey's post hoc tests and Independent Samples Student's t-tests (where appropriate) at p<0.05., Results: The RBC rank achieved for mean wear depth calculations were similar whether the 2D or 3D techniques were employed. However, the mean wear depth values obtained from the 3D digital technique were significantly increased for two of the five RBC materials compared with the 2D methodology. The total volumetric wear data provided an assessment of the potential of the experimental RBC formulations for clinical usage., Conclusion: The 3D technique allowed for the assessment of mean maximum wear depth and mean total volumetric wear which enables tribological analyses of the wear facet and therefore the wear mechanisms operative. Employing the 2D profile technique ranks RBC materials in terms of in-vitro wear performance., Clinical Significance: Confidence in the wear volume measurements can only be achieved if the wear facet is analysed with sufficient resolution using a 3D digital measurement technique. However, the employment of 2D profilers is useful when screening potential new RBC formulations for the restoration of posterior dentition., (Copyright © 2015 Elsevier Ltd. All rights reserved.)

Objectives: To assess the cuspal deflection and cervical microleakage scores of standardised large mesio-occlusal-distal (MOD) cavities filled with different restoration protocols: (1) conventional resin restoratives, (2) bulk fill flowable base materials 'capped' with a conventional dimethacrylate resin-based composite (RBC) or (3) bulk fill resin restorative materials., Methods: Standardised MOD cavities were prepared in sixty-four sound maxillary premolar teeth and randomly allocated to eight groups. Restorations were placed in conjunction with a universal bonding system and resin restorative materials were irradiated with a quartz-tungsten-halogen light-curing-unit. Restoration protocol (eight oblique increments of conventional resin restorative, bulk fill flowable base and two occlusal 'capping' RBC increments (three increments in total) or bulk fill resin restorative (two increments)) was the dependent variable. A twin channel deflection measuring gauge measured the buccal and palatal cuspal deflections. Teeth were thermally fatigued, immersed in a 0.2% basic fuchsin dye for 24h, sectioned and examined for cervical microleakage score., Results: Post hoc Tukey's tests highlighted significant differences in the mean total cuspal deflection values between resin restoratives (p < 0.0001) and restoration protocol (p < 0.005). In general (albeit product dependently), an increase in mean total cuspal deflection and concomitant decrease in cervical microleakage score was evident for bulk fill flowable base materials with occlusal 'capping' RBC increments (restoration protocol 2) compared with bulk fill resin restoratives (restoration protocol 3)., Conclusions: Not all bulk fill flowable materials or bulk fill resin restoratives behave in a similar fashion when used to restore standardised MOD cavities in maxillary premolar teeth and material selection is vital in the absence of clinical data., Clinical Significance: Poorly performing bulk fill flowable materials or bulk fill restoratives can be identified using the cuspal deflection and cervical microleakage protocol which could save the complications encountered clinically when restoring Class II restorations., (Copyright © 2015 Elsevier Ltd. All rights reserved.)

Objectives: To assess the adhesive performance of three universal bonding systems (self-etch and total-etch protocols) with cuspal deflection and cervical microleakage score., Methods: Fifty-six standardised sound maxillary premolar teeth with uniform mesio-occlusal-distal (MOD) cavities were randomly allocated to six groups. Restoration with resin-based composite (RBC) was performed in conjunction with a universal bonding system facilitated by a quartz-tungsten-halogen light-curing-unit. The dependent variable was the universal bonding protocol (self-etch or total-etch). Buccal and palatal cuspal deflections were recorded at 0, 30, 60 and 180s post-irradiation using a twin channel deflection measuring gauge. Following restoration, the teeth subjected to 500 thermocycles, immersed in a 0.2% basic fuchsin dye for 24h, sectioned and examined for cervical microleakage., Results: Comparing between bonding protocol (self-etch or total-etch), a decrease in total cuspal deflection and a concomitant increase in cervical microleakage were evident when employing the total-etch compared with the self-etch protocol for two of the three universal dental adhesives., Conclusions: The 'Adhesion-Decalcification concept' suggests a trend towards 'mild self-etch' adhesives. Differences in adhesive performance (cuspal deflection and cervical microleakage) between the teeth restored using the self-etch or total-etch protocols is suggested to be a result of the pH of the self-etch solutions. 'Mild self-etch' (pH∼2.0) adhesives out-performed ultra-mild (pH>2.5) or strong (pH<1.5) self-etch solutions., Clinical Significance: Poorly performing adhesives could be identified using the cuspal deflection and cervical microleakage protocol reported which could save the complications encountered clinically with Class II RBC restorations., (Copyright © 2014 Elsevier Ltd. All rights reserved.)

Objectives: To investigate if resin-cementation of a soda lime glass dental analogue could elucidate information regarding the pattern of resin-reinforcement when coated in an environment actively scavenged of moisture., Methods: 192 soda lime disc-shaped specimens (alumina particle air abraded, hydrofluoric acid-etched and silane coated) were randomly assigned to eight groups (n=24 per group) prior to resin-coating at seating loads of 5 N (Groups A-D) and 30 N (Groups E-H) in an environment where moisture was actively scavenged and maintained below 15 ppm. Following one week storage the discs were tested in biaxial flexure at crosshead rates of 0.01, 0.1, 1 and 10mm/min. Analysis of group means was performed utilising a general linear model univariate analysis and post hoc all paired Tukey tests (P<0.05)., Results: The general linear model univariate analysis identified the mean biaxial flexure strength (BFS) was significantly influenced by the factors resin-cementation seating load (P<0.001) and crosshead speed of the applied load (P<0.001) with a significant interaction (P=0.008) between both factors. The linear logarithmic regression curves fitted to the group mean BFS data plotted against the crosshead speed highlighted significant differences between the pattern of resin-strengthening for the cementation loads and testing conditions., Conclusions: The decrease in resin-penetration expected within the 'resin-ceramic hybrid layer' following removal of the 30 N seating load was proposed as the modifying resin-strengthening parameter. These observations are supported by the viscoelastic and creep behaviour of resins at slow testing rates which becomes the dominant or determining phenomenon., (Copyright © 2013 Elsevier Ltd. All rights reserved.)

Background: The objectives of this randomized comparative effectiveness study conducted by members of the Practitioners Engaged in Applied Research and Learning (PEARL) Network were to determine whether using a resin-modified glass ionomer (RMGI) liner reduces postoperative hypersensitivity (POH) in dentin-bonded Class I and Class II resin-based composite (RBC) restorations, as well as to identify other factors (putative risk factors) associated with increased POH., Methods: PEARL Network practitioner-investigators (P-Is) (n = 28) were trained to assess sensitivity determination, enamel and dentin caries activity rankings, evaluation for sleep bruxism, and materials and techniques used. The P-Is enrolled 341 participants who had hypersensitive posterior lesions. Participants were randomly assigned to receive an RBC restoration with or without an RMGI liner before P-Is applied a one-step, self-etching bonding agent. P-Is conducted sensitivity evaluations at baseline, at one and four weeks after treatment, and at all visits according to patient-reported outcomes., Results: P-Is collected complete data regarding 347 restorations (339 participants) at baseline, with 341 (98 percent) (333 participants) recalled at four weeks. Treatment groups were balanced across baseline characteristics and measures. RBC restorations with or without an RMGI liner had the same one-week and four-week POH outcomes, as measured clinically (by means of cold or air stimulation) and according to patient-reported outcomes., Conclusions: Use of an RMGI liner did not reduce clinically measured or patient-reported POH in moderate-depth Class I and Class II restorations. Cold and air clinical stimulation findings were similar between groups. Practical Implications. The time, effort and expense involved in placing an RMGI liner in these moderate-depth RBC restorations may be unnecessary, as the representative liner used did not improve hypersensitivity outcomes.

Background: Knowing which factors influence restoration longevity can help clinicians make sound treatment decisions. The authors analyzed data from The National Dental Practice-Based Research Network to identify predictors of early failures of amalgam and resin-based composite (RBC) restorations., Methods: In this prospective cohort study, the authors gathered information from clinicians and offices participating in the network. Clinicians completed a baseline data collection form at the time of restoration placement and annually thereafter. Data collected included patient factors, practice factors and dentist factors, and the authors analyzed them by using mixed-model logistic regression., Results: A total of 226 practitioners followed up 6,218 direct restorations in 3,855 patients; 386 restorations failed (6.2 percent) during the mean (standard deviation) follow-up of 23.7 (8.8) months. The number of tooth surfaces restored at baseline helped predict subsequent restoration failure; restorations with four or more restored surfaces were more than four times more likely to fail. Restorative material was not associated significantly with longevity; neither was tooth type. Older patient age was associated highly with failure (P < .001). The failure rate for children was 4 percent, compared with 10 percent for people 65 years or older. Dentist's sex and practice workload were associated significantly with restoration longevity., Conclusions: In this prospective cohort study, these factors were significantly predictive of failure for amalgam and RBC restorations: patient's age, a higher number of surfaces restored at baseline, the dentist's sex and the practice workload. Material choice was not significantly predictive in these early results. Practical Implications. If clinicians can recognize and identify the risk factors associated with early restoration failure, more effective treatment plans may be offered to the patient.

Background: The Practitioners Engaged in Applied Research and Learning (PEARL) Network conducted a three-armed randomized clinical study to determine the comparative effectiveness of three treatments for hypersensitive noncarious cervical lesions (NCCLs): use of a potassium nitrate dentifrice for treatment of hypersensitivity, placement of a resin-based composite restoration and placement of a sealant., Methods: Seventeen trained practitioner-investigators (P-Is) in the PEARL Network enrolled participants (N = 304) with hypersensitive posterior NCCLs who met enrollment criteria. Participants were assigned to treatments randomly. Evaluations were conducted at baseline and at one, three and six months thereafter. Primary outcomes were the reduction or elimination of hypersensitivity as measured clinically and by means of patient-reported outcomes., Results: Lesion depth and pretreatment sensitivity (mean, 5.3 on a 0- to 10-point scale) were balanced across treatments, as was sleep bruxism (present in 42.2 percent of participants). The six-month participant recall rate was 99 percent. Treatments significantly reduced mean sensitivity (P < .01), with the sealant and restoration groups displaying a significantly higher reduction (P < .01) than did the dentifrice group. The dentifrice group's mean (standard deviation) sensitivity at six months was 2.1 (2.1); those of the sealant and restoration groups were 1.0 (1.6) and 0.8 (1.4), respectively. Patient-reported sensitivity (to cold being most pronounced) paralleled clinical measurements at each evaluation., Conclusions: Sealing and restoration treatments were effective overall in reducing NCCL hypersensitivity. The potassium nitrate dentifrice reduced sensitivity with increasing effectiveness through six months but not to the degree offered by the other treatments. Practical Implications. Sealant or restoration placement is an effective method of immediately reducing NCCL sensitivity. Although a potassium nitrate dentifrice did reduce sensitivity slowly across six months, at no time was the reduction commensurate with that of sealants or restorations.