Level of BPA contamination in resin composites determines BPA release.

OBJECTIVES: Resin composites may release bisphenol A (BPA) due to impurities present in the monomers. However, there is a lack of knowledge regarding the leaching characteristics of BPA from resin composites. Therefore, experimental resin composites were prepared with known amounts of BPA. The objective of this study was (1) to determine which amount of BPA initially present in the material leaches out in the short term and, (2) how this release is influenced by the resin composition. METHODS: BPA (0, 0.001, 0.01, or 0.1 wt%) was added to experimental resin composites containing 60 mol% BisGMA, BisEMA(3), or UDMA, respectively, as base monomer and 40 mol% TEGDMA as diluent monomer. Polymerized samples (n = 5) were immersed at 37 °C for 7 days in 1 mL of water, which was collected and refreshed daily. BPA release was quantified with UPLC-MS/MS after derivatization with pyridine-3-sulfonyl chloride. RESULTS: Between 0.47 to 0.67 mol% of the originally added BPA eluted from the resin composites after 7 days. Similar elution trends were observed irrespective of the base monomer. Two-way ANOVA showed a significant effect of the base monomer on BPA release, but the differences were small and not consistent. SIGNIFICANCE: The released amount of BPA was directly proportional to the quantity of BPA present in the resin composite as an impurity. BPA release was mainly diffusion-based, while polymer composition seemed to play a minor role. Our results underscore the importance for manufacturers only to use monomers of the highest purity in dental resin composites to avoid unnecessary BPA exposure in patients.

Elution from direct composites for provisional restorations.

Purpose To assess elution from direct composite materials for provisional restorations and compare them with elution from direct restorative composites for permanent restorations.Methods Two dual-cure (Integrity Multi-Cure and Tempsmart DC) and two self-curing composites (Protemp 4 and Structur 3) were used, with Essentia serving as a reference. Cylindrical specimens (n=20) were cured according to the manufacturer's instructions; the dual-cure materials were prepared in both self- and dual-curing modes. Elution experiments were performed using water and absolute ethanol. The samples were incubated at 37 °C for either 24 h or four weeks; the extraction solvents were refreshed weekly. The eluted BisEMA (-3 / -6 / -10), BisGMA, CQ, UDMA, and TEGDMA were quantified using UHPLC-MS/MS.Results Monomer elution was detected in all provisional composites at 24 h and four weeks, but the amounts released did not exceed those released by the reference composite. When prepared in self-curing mode, Integrity Multi-Cure exhibited significantly higher elution of BisEMA-3, -6, and -10 in ethanol both after 24 h and cumulatively after four weeks. Self-cured Tempsmart DC released significantly more CQ, TEGDMA, and UDMA in both water and ethanol after immersion for 24 h and four weeks, along with significantly more BisGMA in ethanol both after 24 h and four weeks comparison to dual-cured Tempsmart DC (two-way ANOVA, post-hoc Tukey, P < 0.05).Conclusions Provisional composite materials did not elute higher amounts of monomers than a restorative composite. Dual-cured materials, prepared in the self-curing mode, show a trend towards higher monomer elution.

Degradation products of resin-based materials detected in saliva in vivo.

OBJECTIVES: Dental composites remain under scrutiny regarding their (long-term) safety. In spite of numerous studies on the release of monomers both in vitro and in vivo, only limited quantitative data exist on the in vivo leaching of degradation products from monomers and additives. The aim of this observational study was for the first time to quantitatively and qualitatively monitor the release of parent compounds and their degradation products in saliva from patients undergoing multiple restorations. MATERIALS AND METHODS: Five patients in need of multiple large composite restorations (minimally 5 up to 28 restorations) due to wear (attrition, abrasion, and erosion) were included in the study, and they received adhesive restorative treatment according to the standard procedures in the university clinic for Restorative Dentistry. Saliva was collected at different time points, starting before the restoration up until 24 h after the treatment with composite restorations. Saliva extracts were analyzed by liquid chromatography-mass spectrometry. RESULTS: Leaching of monomers and degradation products was highest within 30 min after the placement of the restorations. The highest median concentrations of monomers were recorded for UDMA, BisEMA-3, and TEGDMA; yet, besides BisEMA-3 and TEGDMA, no monomers could be detected after 24 h. Mono- and demethacrylated degradation products remained present up to 24 h and concentrations were generally higher than those of monomers. In patients with multiple restorations, degradation products were still present in the sample taken before the next operation, several weeks after the previous operation. CONCLUSIONS: Exposure to residual monomers and degradation products occurs in the first hours after restoration. Monomers are present in saliva shortly after restoration, but degradation products can be detected weeks after the restoration confirming a long-term release. CLINICAL SIGNIFICANCE: Future research should focus more on the release of degradation products from monomers and additives from resin-based materials given their prolonged presence in saliva after restoration.

Fourteen-year Clinical Performance of a HEMA-free One-step Self-etch Adhesive in Non-carious Cervical Lesions.

PURPOSE: This randomized controlled trial aimed to evaluate the 14-year clinical performance of a HEMA-free 1-step self-etch adhesive (1SEa) compared with that of a 3-step etch-and-rinse adhesive (3E&Ra). MATERIALS AND METHODS: 267 non-carious cervical lesions in 52 patients were restored with the microhybrid composite Gradia Direct (GC), bonded in random order either with the HEMA-free 1SEa G-Bond (GB; GC) or the 3E&Ra Optibond FL (OFL; Kerr), which is considered the gold-standard E&Ra (control). The restorations were followed over 14 years for retention, marginal adaptation and discoloration, and caries occurrence. Statistical analysis involved a logistic regression model with generalized estimating equations (2-way GEE model). RESULTS: The patient recall rate at 14 years was 63%. In total, 79 restorations (39 GB, 40 OFL) failed because of retention loss (GB: 19.4%, OFL: 19.6%), severe marginal defects, discoloration and/or caries (GB: 21.7%; OFL: 22.5%). The overall clinical success rate was 58.9% and 57.9% for GB and OFL, respectively. The number of restorations with an unacceptable marginal defect (GB: 14.5%; OFL: 19.2%) and deep marginal discoloration (GB: 18.2%; OFL: 13.2%) increased during the last 5 years. No significant difference in overall clinical performance was recorded between the two adhesives (p > 0.05). Changes in the medical health of some patients and recurrence of abrasion/erosion/abfraction increased the failure rate and retention rate. CONCLUSION: After 14 years, restorations bonded with the HEMA-free 1SEa performed as well as those bonded with the 3E&Ra gold standard. Unacceptable marginal deterioration was the main reason for failure, followed by loss of retention.

3D printing and milling accuracy influence full-contour zirconia crown adaptation.

OBJECTIVES: To correlate trueness and cement-space characteristics of crowns milled chairside and in the laboratory with those of inkjet 3D-printed crowns, and to assess whether 3D-printing accuracy meets the clinical standard. METHODS: Thirty crowns were either (1) milled using a chairside Cerec MCXL unit from Cerec Zirconia Mono L (Dentsply Sirona), (2) milled using a LX-O 5-axis (Matsuura Machinery) industrial machine from Initial Zirconia HT (GC), or (3) 3D-printed using an inkjet Carmel 1400 (Xjet) printer (n = 10). Crown trueness determined by comparing the original CAD with each visible-light digitized crown was correlated with the 3D cement-space characteristics recorded by micro-CT. Statistics involved Kruskal-Wallis testing and Spearman correlation. RESULTS: Crown trueness at the intaglio marginal area positively correlated with the marginal and axial cement-space characteristics. 3D-printing revealed data in-between those of the two milling systems with undercut values being not statistically different from those recorded for chairside milling and a low overcut level that was statistically similar to that obtained by laboratory milling. Laboratory milling revealed a significantly better marginal accuracy with a consequently lower cement-space thickness. A higher overcut level was recorded for the chairside-milled crowns in the marginal/occlusal thirds, resulting in the significantly highest occlusal cement-space thickness and cement-volume percentage with a cement thickness above 120 µm (limit considered as clinically acceptable). No statistical difference in trueness was found for the external crown dimensions. SIGNIFICANCE: The 3D-printed zirconia crowns provided sufficient manufacturing accuracy for clinical use. Accurate milling and printing of the crown's intaglio marginal area is primordial.

Dentin conditioned with a metal salt-based conditioner.

OBJECTIVES: Universal adhesives (UAs) can optionally be applied in either an etch-and-rinse (E&R) or self-etch (SE) bonding mode. As the preferred bonding mode differs for enamel versus dentin, a universal conditioner for both enamel and dentin in replacement of the relatively aggressive phosphoric-acid etchant remains desirable. This study aimed to test if a metal salt-based etchant (ZrO(NO3)2) provides as durable bonding to dentin as a classic E&R or SE bonding mode METHODS: Before applying the UA Adhese Universal ('AdU'; Ivoclar Vivadent) to bur-cut dentin of 24 teeth (n = 8), dentin was conditioned with either (1) an experimental metal salt-based conditioner ('ZON'; Ivoclar Vivadent) or (2) 37% phosphoric acid (Total Etch gel, Ivoclar Vivadent), representing a classic 'E&R' mode; (3) a third experimental group involved AdU applied in SE mode. Bonding effectiveness was determined in terms of immediate ('1w') and aged ('50k' TC) micro-tensile bond strength (µTBS) to bur-cut dentin. Adhesive-conditioned dentin interfacial interactions were characterized by S/TEM. RESULTS: Linear mixed-effects modeling revealed significantly higher immediate µTBS to dentin of ZON_AdU than E&R_AdU, while ZON_AdU performed not significantly different from SE_AdU. No significant differences were found between the three experimental groups after 50k TC (aged µTBS). S/TEM disclosed less exposure of dentinal collagen fibrils when AdU was bonded upon ZON etching than when applied in E&R mode. Moreover, ZON resulted in more hydroxyapatite (HAp) crystals remaining at the bottom of the hybrid layer, while dentinal tubule orifices remained nearly fully closed, by which hardly any resin tags were formed. SIGNIFICANCE: The alternative metal salt-based conditioner revealed at dentin a more HAp-protected hybrid layer with less exposure of collagen fibrils, while a comparable bond strength was obtained to that with a phosphoric-acid E&R as well as with an SE (no conditioner) bonding mode. These findings confirm that the metal salt-based conditioner can be considered as a suitable alternative (enamel/)dentin conditioner to classic phosphoric acid employed in an E&R bonding mode.

Bisphenol A release from short-term degraded resin-based dental materials.

OBJECTIVES: There is still much debate about the release of bisphenol A (BPA) from resin-based dental materials. Therefore, this study aimed to quantify BPA present as an impurity and to evaluate whether their degradation by salivary, bacterial, and chemical challenges could increase its release. METHODS: BPA was determined in three different amounts (300, 400, and 500 µg) of eight unpolymerized resin-based materials (four composites, one fissure sealant, two adhesives and one root canal sealer). Next, polymerized samples (n = 5) of each material were immersed in 1 mL of whole human pooled saliva collected from adults, Streptococcus mutans (2 × 107 CFU/mL), and acidic (0.1 M HCl), alkaline (0.1 M NaOH), and control media, respectively. The amount of BPA was quantified using an UPLC-MS/MS method including derivatization of BPA by pyridine-3-sulfonyl chloride. RESULTS: Only the composites contained trace amounts of BPA above the limit of quantification (ranging from 301±32 pg PBA/mg to 1534±62 pg BPA/mg), most likely as impurity from the synthesis of the monomers. The amounts of BPA released from polymerized materials upon salivary and bacterial degradation were too low for accurate quantification, but in water, quantifiable amounts of BPA were released from all materials. In alkaline media, the BPA release from two composites was significantly decreased, while the release from one adhesive was significantly increased, compared to water. CONCLUSIONS: BPA already present in unpolymerized resin-based materials may account for the release of BPA after polymerization. There was no clear indication that short-term material degradation leads to increased release of BPA.

Identification of chemicals leaching from dental resin-based materials after in vitro chemical and salivary degradation.

OBJECTIVES: Only little is known about degradation of methacrylate monomers. Therefore, using in vitro chemical and saliva degradation this study aimed to identify the degradation products of organic compounds present in resin-based dental materials. METHODS: Ten dental monomers and nine polymerized dental resin-based materials were immersed for 24 h in chemical media (0.1 M HCl, 0.1 M NaOH) and human pooled saliva in order to identify leached monomers and degradation products from chemical and saliva degradation. Samples were analyzed using liquid chromatography coupled to high-resolution mass spectrometry to identify previously unknown degradation products. RESULTS: During in vitro chemical degradation, uncured monomers were rapidly hydrolyzed into mono- and demethacrylated degradation products. During chemical degradation in alkaline conditions of polymerized materials, considered the worst-case scenario, only degradation products could be detected. In acidic conditions, monomers and their degradation products were detected. In addition, different additives such as EDMAB, DMPA and HMBP were present in acidic degradation samples. Degradation in human pooled saliva for 24 h to mimic the in vivo situation, resulted in the identification of both monomers and their degradation products. CLINICAL SIGNIFICANCE: Using state-of-the-art high-resolution mass spectrometry previously unknown degradation products of commonly used monomers were identified for the first time. Results show that patients may be exposed to monomers and their degradation products in the first 24 h after restorative procedures. The results provide a base for further research on the degradation of resin-based dental composites in order to assess their safety using elution and toxicity studies.

Assessing the estrogenic activity of chemicals present in resin based dental composites and in leachates of commercially available composites using the ERα-CALUX bioassay.

OBJECTIVE: The biocompatibility of resin based dental composites has not yet been fully characterized even though certain monomers used in these composites are synthesized from Bisphenol A (BPA), a well-known estrogenic endocrine disruptor. As a result, they show structural relationship to BPA and can contain it as an impurity. Therefore, the estrogenic activity of 9 monomers, 2 photoinitiators, one photostabilizer and leachates of 4 commercially available composites was determined. METHODS: The ERα-CALUX bioassay was used to determine both agonistic and antagonistic estrogenic activities of the pure compounds (BPA, BisDMA, BisGMA, BisEMA(3), BisEMA(6), BisEMA(10), TEGDMA, TCD-DI-HEA, BADGE, UDMA, HMBP, DMPA, CQ) and the leachates of cured composite disks. The leachates of 4 commercially available composites (Solitaire 2, Ceram.x Spectra ST, G-ænial Posterior and Filtek Supreme XTE) in water and 0.1 M NaOH (pH = 13, 'worst-case scenario') were tested for estrogenic activity (pooled leachates from 10 cured composite disks). RESULTS: Agonistic estrogenic activity was found for the monomer BisDMA, the photostabilizer HMBP and photoinitiator DMPA. All leachates from the 4 tested composites showed significant agonistic estrogenic activity higher than the DMSO control, and the highest activity (potency and efficacy) was found for Solitaire 2, followed by Ceram.x Spectra ST. Furthermore, antagonistic estrogenic activity was found in the leachates from G-ænial Posterior. SIGNIFICANCE: These results show that significant estrogenic activity was found in all leachates of the cured composite disks, and that this estrogenicity is most likely due to a mixture effect of multiple estrogenic compounds (including BPA, HMBP and DMPA). This indicates that further research into the endocrine activity of all the compounds that are present in these composites (even at low quantities) and their possible mixture effect is warranted to guarantee their safe use.

Long-term elution of bisphenol A from dental composites.

OBJECTIVES: BPA release from composites on the short term has been reported in several in-vitro and in-vivo studies. However, it remains unclear whether these materials also leach BPA on the long term. Even though composites may release various (BPA-based) methacrylate monomers up to one year, quantitative data about BPA have not been reported due to the lack of a sensitive method to accurately quantify low levels of BPA. In this context, the aim of the study was to quantify the one-year release of BPA with an optimized analytical method. METHODS: Composite disks (n = 6, 6 mm diameter and 2 mm height) from four commercial materials (G-ӕnial Posterior, Venus, Ceram.x mono and Filtek Supreme XTE) were immersed in 1 mL of water or ethanol as extraction solvent and stored in the dark at 37 °C. The extraction solvent was renewed weekly for a period of 52 weeks. Samples were derivatized with pyridine-3-sulfonyl chloride before analysis with ultra-pressure liquid chromatography tandem mass spectrometry (UPLC-MS/MS). RESULTS: Derivatizing BPA increased the sensitivity of the analytical method and allowed accurate quantification of very low levels of BPA (i.e. 0.78 pmol BPA). BPA eluted continuously in ethanol from all four tested composites over a period of one year. BPA elution was clearly higher when ethanol was used as extraction solution. In water, BPA eluted could be detected up to one year, but levels could not be accurately quantified anymore after several weeks. SIGNIFICANCE: Composites can be considered as a potential long-term source of BPA, and thus should not be neglected when assessing the overall exposure to endocrine disrupting chemicals.

Experimental resin-modified calcium-silicate cement containing N-(2-hydroxyethyl) acrylamide monomer for pulp tissue engineering.

AIM: Our study aimed to measure (1) the flexural strength, (2) shear bond strength to dentin, (3) pH, and (4) calcium (Ca) release of a series of innovative resin-modified calcium-silicate pulp-capping cements (Rm-CSCs). Using an ex-vivo human vital tooth-culture model, we additionally assessed (5) their pulp-healing initiation when brought in direct contact with human dental pulp tissue. METHODOLOGY: Three experimental Rm-CSCs, being referred to 'Exp_HEAA', 'Exp_GDM' and 'Exp_HEAA/GDM', contained either 20 wt% N-(2-hydroxyethyl) acrylamide (HEAA), 20 wt% glycerol dimethacrylate (GDM) or 10 wt% HEAA plus 10 wt% GDM, added to a common base composition consisting of 25 wt% urethane dimethacrylate (UDMA), 10 wt% 4-methacryloxyethyl trimellitate anhydride (4-MET), and 5 wt% N,N'-{[(2-acrylamido-2-[(3-acrylamidopropoxy)methyl] propane-1,3-diyl)bis(oxy)]bis-(propane-1,3-diyl)}diacrylamide (FAM-401). As Ca source and radiopacifier, 37 wt% tricalcium silicate powder (TCS) and 3 wt% zirconium oxide (ZrO 2) were respectively added. RESULTS: All three experimental Rm-CSCs revealed a significantly higher flexural strength and shear bond strength to dentin (p < 0.05) than the commercial reference Rm-CSC TheraCal LC (Bisco). Exp_HEAA presented with a significantly higher Ca release and pH at 24 h compared with the other Rm-CSCs (p < 0.05). At 1 week, the Ca release and pH of Exp_HEAA and Exp_HEAA/GDM was significantly higher than those of Exp_GDM and TheraCal LC (p < 0.05). Using the ex-vivo human vital tooth culture model, Exp_HEAA revealed pulp-healing initiation capacity as documented by nestin and collagen-I expression. CONCLUSIONS: Depending on the formulation, the innovative Rm-CSCs performed favorably for primary properties of relevance regarding pulp capping, this more specifically in terms of flexural strength, bond strength to dentin, as well as alkaline pH and Ca release. However, only Exp_HEAA revealed pulp-healing initiation in direct contact with human dental pulp tissue in the ex-vivo human vital tooth-culture model. This promising outcome for Exp_HEAA should be attributed to the combined use of (1) a novel hydrophilic acrylamide monomer, enabling sufficient polymerization while maintaining adequate hydrophilicity, with (2) the functional monomer 4-MET, possessing chemical bonding potential to dentin, and (3) tricalcium silicate powder to achieve an alkaline pH and to release Ca in a sufficient and controlled way.

Bisphenol A as degradation product of monomers used in resin-based dental materials.

OBJECTIVE: There is still much debate about the release of bisphenol-A (BPA) from dental materials. Therefore, this study aimed to quantify BPA present as an impurity in both BPA-based and non-BPA-based monomers and to evaluate whether these monomers may degrade to BPA upon salivary, bacterial, and chemical challenges. METHODS: BPA was determined in three different amounts (1, 2, and 3 µmol) of each monomer (TEGDMA, UDMA, mUDMA, BisGMA, BisEMA-3, -6, -10, -30, BisPMA, EBPADMA urethane, BADGE, and BisDMA). Next, the monomers (3 µmol) were immersed in whole human pooled saliva collected from adults, Streptococcus mutans (2 × 107 CFU/mL), and acidic (0.1 M HCl), alkaline (0.1 M NaOH), and control media. The amount of BPA was quantified using a specific and highly sensitive UPLC-MS/MS method including derivatization of BPA by pyridine-3-sulfonyl chloride. RESULTS: The monomers BisGMA and BisEMA-3 contained trace amounts (0.0006% and 0.0025%, respectively) of BPA as impurities of their synthesis process. BPA concentrations increased when the monomers BisGMA, BisEMA-3, BisEMA-6, BisEMA-10, BisPMA and BADGE were exposed to saliva and S. mutans, indicating degradation of a small amount of monomer into BPA. In addition, BisPMA and BADGE degraded into BPA under alkaline conditions. The conversion rate of the monomers into BPA ranged between 0.0003% and 0.0025%. SIGNIFICANCE: Impurities and degradation of BPA-based monomers may account for the release of BPA from resin-based dental materials. Even though the detected amounts of BPA due to monomer impurity were small, manufacturers of dental materials can reduce the BPA content by using only monomers of the highest purity. Considering the overall current trend towards BPA-free materials, it may be recommendable to investigate whether non-BPA based monomers can be used in dental resin-based materials.

Optimizing glass-ceramic bonding incorporating new silane technology in an experimental universal adhesive formulation.

OBJECTIVE: Incorporating silane-coupling agent into universal adhesives (UAs) to simplify adhesive luting of glass-ceramic restorations appeared ineffective due to silane's instability in an acidic aqueous solution. This study aimed to evaluate new silane technology added to an experimental UA to be bonded to glass ceramics without separate prior silanization. METHODS: Combined silane technology, consisting of 3-(aminopropyl)triethoxysilane (APTES) and γ-methacryloxypropyltriethoxysilane (γMPTES), was incorporated into an experimental UA formulation, being referred to as ADH-XTE (3M Oral Care). Immediate and aged shear bond strength (SBS) of ADH-XTE onto as-milled ('AM'), tribochemical silica-coated ('TSC'), HF-etched ('HF'), and mirror-polished ('MP') glass-ceramic CAD/CAM blocks (IPS e.max CAD) with/without separate silanization was measured (n = 10/group). The control adhesives included Scotchbond Universal ('SBU') and Scotchbond 1 XT ('SB1-XT'). The glass-ceramic surface topography and the fractography of the SBS-debonded specimens were observed by SEM. RESULTS: Without separate prior silanization, the experimental UA ADH-XTE, containing combined APTES/γMPTES silane technology, significantly outperformed the glass-ceramic bonding efficiency of its silane-containing SBU precursor, while it performed equally effective as SBU applied with prior silanization. Upon aging, significant reduction in SBS was recorded when ADH-XTE was bonded to TSC glass-ceramic surfaces (p < 0.05), while not to HF ones. Notably, the lowest SBS was obtained when the UAs were bonded to AM and MP glass-ceramic surfaces, in particular when applied without separate prior silanization (p < 0.05). SIGNIFICANCE: The glass-ceramic bonding capacity of the new combined APTES/γMPTES silane-containing UA ADH-XTE surpassed that of its SBU precursor. HF etching remains needed to durably bond to glass-ceramics.

Extra Bonding Layer Compensates Universal Adhesive's Thin Film Thickness.

PURPOSE: Universal adhesives (UAs) are applied in 2-step etch-and-rinse (2-E&R) or 1-step self-etch (1-SE) mode. This study investigated whether three UAs could benefit from a highly filled extra bonding layer (EBL), turning them into 3-E&R and 2-SE UAs, respectively, thus also compensating for the commonly thin film thickness of UAs. MATERIALS AND METHODS: Microtensile bond strength (µTBS) to bur-cut dentin of Clearfil Universal Bond Quick (C-UBq, Kuraray Noritake), G-Premio Bond (G-PrB, GC) and Prime&Bond Active (P&Ba, Dentsply Sirona), applied in E&R and SE mode without/with the adhesive resin (EBL) of OptiBond FL (Opti-FL_ar, Kerr), was compared to that of the 3-E&Ra OptiBond FL (Opti-FL; Kerr), which was also employed in 2-SE mode. As a cross reference, the SE primer of Clearfil SE Bond 2 (Kuraray Noritake) was combined with Opti-FL_ar (C-SE2/Opti-FL) and again applied in 2-SE and 3-E&R mode. µTBS was measured after 1 month of water storage (37°C) and additional 25,000 and 50,000 thermocycles (TC). All µTBS were statistically analyzed using three different linear mixed-effects models with specific contrasts (p < 0.05). RESULTS: Overall, the four parameters (adhesive, bonding mode, aging, EBL) significantly influenced µTBS. G-PrB and P&Ba benefited from EBL when applied in both E&R and SE bonding modes. In E&R mode, P&Ba generally revealed the highest µTBS; C-UBq presented an intermediate and G-PrB the lowest µTBS. No significant differences were found between different bonding modes. C-SE2/Opti-FL outperformed Opti-FL in 3-E&R and 2-SE_1 month/25k. CONCLUSION: The overall benefit of EBL on the 1-month and TC-aged bonding efficacy differed for the different UAs tested.

Preclinical effectiveness of an experimental tricalcium silicate cement on pulpal repair.

OBJECTIVES: To investigate the pulpal repair potential of an experimental zirconium-oxide containing tricalcium-silicate cement, referred to as 'TCS 50'. MATERIALS AND METHODS: The effect of TCS 50 on viability, proliferation, migration, and odontoblastic differentiation of human dental pulp cells (HDPCs) was assessed using XTT assay, in-vitro wound healing assay and RT-PCR, respectively. Additionally, the pulp-capping potential was evaluated using a vital human tooth model. Statistical analysis was performed using non-parametric Kruskal-Wallis test and post-hoc test (Mann-Whitney U test). The tests were performed at a significance level of α = 0.05. RESULTS: The effect of TCS 50 towards HDPCs was dose dependent. Undiluted TCS 50 extract showed no immediate adverse impact on cell viability (p > .05); however, it significantly inhibited proliferation and migration of HDPCs (p < .05). A 25% diluted TCS 50 extract showed no significant effect on cell viability, proliferation or migration (p > .05), and it significantly enhanced odontoblastic differentiation of HDPCs (p < .05). In pulps capped with TCS 50 for both 2 and 4 weeks, H&E staining revealed a normal morphology of pulp tissue; mineralized foci with cellular components entrapped in the matrix were formed underneath the exposure site. Collagen I expression was weak within the matrix of mineralized foci, while the expression of nestin was positive for entrapped cellular components within the mineralized foci, indicating that the formed mineralized foci corresponded to an initial form of reparative dentin formation. CONCLUSION: TCS 50 is capable of generating an early pulp-healing reaction and therefore could serve as a promising pulp-capping agent.

Monomer release from direct and indirect adhesive restorations: A comparative in vitro study.

OBJECTIVES: Indirect dental restorations produced by computer-aided design and computer-aided manufacturing (CAD/CAM) are relatively new in daily dental practice. The aim of the present study was to compare the monomer release between direct composite restorations and indirect CAD/CAM produced restorations (composite, ceramic and hybrid). METHODS: Identical crown restorations were prepared from three indirect materials (Cerasmart, Vitablocs Mark II and Vita Enamic) and one composite material (Clearfil AP-X). For each restoration, eight crown restorations were luted onto tooth samples and immersed into 2.5mL of an aqueous extraction solvent. Additionally, three nonluted crowns of each restoration type were also immersed in the extraction solvent, and served as controls. Every week, the extraction solvent was collected and refreshed, during a period of 8 weeks. The released monomers were quantified using ultra-performance liquid chromatography-tandem mass spectrometry. RESULTS: Indirect restorations release significantly lower quantities of residual monomers than direct restorations, and the monomers released by the luted indirect restorations are mainly derived from the composite material used for cementation. The quantity of monomers released by direct restorations greatly depended on the time of light polymerization. SIGNIFICANCE: In terms of monomer release, indirect restorations are a good alternative to direct restorations to limit patient exposure to residual monomers. It is important to ideally design the fit of indirect restoration so that the cement layer is as thin as possible and the monomer release from this cement layer remains as low as possible.

Human phase I in vitro liver metabolism of two bisphenolic diglycidyl ethers BADGE and BFDGE.

Root canal sealers are commonly used to endodontically treat teeth with periapical infections. Some root canal sealers based on epoxy resin contain bisphenol A diglycidyl ether (BADGE) and bisphenol F diglycidyl ether (BFDGE). The presence of these chemicals is of concern due to the close contact to the blood stream at the apex and the long setting times of up to 24 h. These chemicals, or any of their degradation products or metabolites, can then exert their toxic effects before being excreted. This study aimed to identify the phase I in vitro biotransformation products of BADGE and BFDGE using human liver microsomes. During incubation with microsomal fractions, the epoxides were rapidly hydrolysed in a NADPH independent manner resulting in the formation of BADGE.2H2O and BFDGE.2H2O. Further, oxidative reactions, such as hydroxylation and carboxylation, generated other BADGE metabolites, such as BADGE.2H2O-OH and BADGE.H2O.COOH, respectively. For BFDGE, further oxidation of BFDGE.2H2O led to the newly reported carboxylic acid, BFDGE.H2O.COOH. In total, three specific metabolites have been identified which can serve in future human biomonitoring studies of BADGE and BFDGE.

Zinc-Calcium-Fluoride Bioglass-Based Innovative Multifunctional Dental Adhesive with Thick Adhesive Resin Film Thickness.

Apart from producing high bond strength to tooth enamel and dentin, a dental adhesive with biotherapeutic potential is clinically desirable, aiming to further improve tooth restoration longevity. In this laboratory study, an experimental two-step universal adhesive, referred to as Exp_2UA, applicable in both the etch-and-rinse (E&R) and self-etch (SE) modes and combining a primer, containing 10-methacryloyloxydecyldihydrogen phosphate as a functional monomer with chemical binding potential to hydroxyapatite, with a bioglass-containing hydrophobic adhesive resin, was multifactorially investigated. In addition to primary property assessment, including measurement of bond strength, water sorption, solubility, and polymerization efficiency, the resultant adhesive-dentin interface was characterized by transmission electron microscopy (TEM), the filler composition was analyzed by energy-dispersive X-ray spectroscopy, and the bioactive potential of the adhesive was estimated by measuring the long-term ion release and assessing its antienzymatic and antibacterial potential. Four representative commercial adhesives were used as reference/controls. Application in both the E&R and SE modes resulted in a durable bonding performance to dentin, as evidenced by favorable 1 year aged bond strength data and a tight interfacial ultrastructure that, as examined by TEM, remained ultramorphologically unaltered upon 1 year of water storage aging. TEM revealed a 20 µm thick hydrophobic adhesive layer with a homogeneous bioglass filler distribution. Adequate polymerization conversion resulted in extremely low water sorption and solubility. In situ zymography revealed reduced endogenous proteolytic activity, while Streptococcus mutans biofilm formation was inhibited. In conclusion, the three-/two-step E&R/SE Exp_2UA combines the high bonding potential and bond degradation resistance with long-term ion release, rendering the adhesive antienzymatic and antibacterial potential.

Filtration efficiency of surgical and FFP3 masks against composite dust.

The aim of this study was to investigate the protection efficiency of two types of face masks against composite dust and to characterize the particles that penetrated through the masks. Composite dust was created by grinding a commercial nano-filled composite in a plexiglass box without using water cooling or high vacuum evacuation, in order to obtain a worst-case exposure. Dust particles were collected using a personal inhalable aerosol sampler (IOM) fixed inside a custom-made phantom head. Surgical and filtering facepiece (FFP3) masks were tested, and the situation without a mask served as control. The IOM sampler contained a cassette with two filters to collect large inhalable (4-100 µm) and respirable dust particles (<4 µm). The amount of particles was determined gravimetrically by weighing filters before and after composite grinding, and further characterized by electron microscopy. Particle collection for both inhalable and respirable dust was the highest when no mask was used, and the lowest with the use of a FFP3 mask. Different sizes and shapes of particles were observed, with the largest particles (>1 µm) being seen when no mask was applied, whereas only nanoparticles could be detected when either type of face mask was applied. Even though FFP3 masks showed a higher filtration efficacy than surgical masks of the inhalable dust fraction, penetration of a small respirable particle fraction was inevitable for both masks.

Agglomeration of titanium dioxide nanoparticles increases toxicological responses in vitro and in vivo.

BACKGROUND: The terms agglomerates and aggregates are frequently used in the regulatory definition(s) of nanomaterials (NMs) and hence attract attention in view of their potential influence on health effects. However, the influence of nanoparticle (NP) agglomeration and aggregation on toxicity is poorly understood although it is strongly believed that smaller the size of the NPs greater the toxicity. A toxicologically relevant definition of NMs is therefore not yet available, which affects not only the risk assessment process but also hinders the regulation of nano-products. In this study, we assessed the influence of NP agglomeration on their toxicity/biological responses in vitro and in vivo. RESULTS: We tested two TiO2 NPs with different primary sizes (17 and 117 nm) and prepared ad-hoc suspensions composed of small or large agglomerates with similar dispersion medium composition. For in vitro testing, human bronchial epithelial (HBE), colon epithelial (Caco2) and monocytic (THP-1) cell lines were exposed to these suspensions for 24 h and endpoints such as cytotoxicity, total glutathione, epithelial barrier integrity, inflammatory mediators and DNA damage were measured. Large agglomerates of 17 nm TiO2 induced stronger responses than small agglomerates for glutathione depletion, IL-8 and IL-1ß increase, and DNA damage in THP-1, while no effect of agglomeration was observed with 117 nm TiO2. In vivo, C57BL/6JRj mice were exposed via oropharyngeal aspiration or oral gavage to TiO2 suspensions and, after 3 days, biological parameters including cytotoxicity, inflammatory cell recruitment, DNA damage and biopersistence were measured. Mainly, we observed that large agglomerates of 117 nm TiO2 induced higher pulmonary responses in aspirated mice and blood DNA damage in gavaged mice compared to small agglomerates. CONCLUSION: Agglomeration of TiO2 NPs influences their toxicity/biological responses and, large agglomerates do not appear less active than small agglomerates. This study provides a deeper insight on the toxicological relevance of NP agglomerates and contributes to the establishment of a toxicologically relevant definition for NMs.