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Objectives: This study aimed to evaluate how self-etching/universal dental adhesive systems (DASs) with differing compositions interact with sound (S), post-radiotherapy (irradiated; I), and artificially eroded (E) dentin in terms of bonding properties., Methods: The DASs tested were Adper Scotchbond Multipurpose (MP; control), Clearfil SE Bond (SE), FL Bond II (FL), Adper Single Bond Universal (SU) and BeautiBond Xtreme (BX). They were analyzed for initial and 6-month microtensile bond strength (µTBS, n = 12), mode of failure (40 x), scanning electron microscopy (SEM), surface wettability (W, n = 10), and degree of conversion (DC, n = 3) via Fourier-transform infrared spectroscopy (FTIR). Normal and homogeneous distribution of the data allowed their analyses through ANOVA and Tukey tests (p < 0.05)., Results: All DASs except BX exhibited higher µTBS for S decreasing for I and E. BX demonstrated the greatest stability among the altered substrates. FL showed the most hydrophobic properties, likely due to its bioactive components. Universal DASs achieved higher DC, regardless of composition., Conclusions: HEMA-free formulation combined with carboxylic and phosphoric acids in BX, achieved the most stable performance for altered substrates., Clinical Significance: Since radiotherapy and erosion affect dentin, their characteristics compromise adhesive performance and impair the achievement of durable and satisfactory restorations. The use of universal adhesives less dependent on calcium seems less susceptible to hydrolytic degradation and may be a promising option for maintaining adhesive stability over time., 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 Ltd. All rights reserved.)

Objectives: To systematically compile data on the degree of conversion (DC) for bulk-fill composites using a network meta-analysis., Methods: A systematic search for in vitro studies of DC of bulk-fill composites was performed in PubMed, Web of Science, Scopus, and Open Grey. Risk of bias within studies and due to missing evidence was assessed using the Joanna Briggs Institute scoring system and ROB-MEN tool, respectively. The primary outcome was the DC of bulk-fill composites. Surface Under the Cumulative Ranking curve (SUCRA) was used to rank relative performance. Inconsistencies in the model were investigated to ensure its validity and the level of confidence in the network meta-analysis (CINeMA) was assessed., Results: A total of 28 studies were included in the quantitative analysis. The average DC values (%) for 0-h/top, 0-h/bottom, 24-h/top, and 24-h/bottom were 59.09, 57.14, 66.73, and 63.87, respectively. According to their SUCRA ranking, the best-performing composites were: SonicFill, Venus Bulk Fill, and SDR (0-h/top), Reveal HD, i-Flow Bulk Fill, and Venus Bulk- Fill (0-h/bottom), Venus Bulk Fill, SDR, and QuiXfil (24-h/top), and Venus Bulk Fill, Aura Bulk Fill, and i-Flow Bulk Fill (24-h/bottom). Incoherence between direct and indirect evidence was identified as the most significant factor affecting confidence., Conclusions: DC values of bulk-fill composites were within the range commonly reported for previous generations of "conventional" composites, with flowable composites tending to perform better than sculptable composites. High variability in DC data was observed, which may be attributed to incompletely understood methodological differences., Clinical Significance: DC is a fundamental parameter that influences multiple mechanical and biological properties of resin composites and is particularly relevant for the group of bulk-fill composites that are designed for use in thick layers., 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 Ltd. All rights reserved.)

Objectives: The study aimed to introduce a novel two-step optical fiber-based photo-activation of dental resin-based composites (RBCs) for reducing polymerization shrinkage stress (PSS)., Methods: Proposed protocol design - in the first step, two flexible plastic optical fibers connected to a dental light curing unit (LCU), were used as light guides inserted into the filling to initiate low-irradiance polymerization from within; in the second step, fibers were extracted and remaining voids were filled with RBC, followed by conventional high-irradiance curing to finalize polymerization. Three bulk-fill RBCs were tested (Beautifil-Bulk Restorative, Filtek Bulk-fill Posterior, Tetric PowerFill) using tooth cavity models. Three non-invasive examination techniques were employed: Digital Holographic Interferometry, Infrared Thermography, and Raman spectroscopy for monitoring model deformation, RBC temperature change, and degree of conversion (DC), respectively. A control group (for each examined RBC) underwent conventional photo-activation., Results: The experimental protocol significantly reduced model deformation by 15 - 35 %, accompanied by an 18 - 54 % reduction in RBC temperature change, emphasizing the impact of thermal shrinkage on PSS. Real-time measurements of deformation and temperature provided indirect insights into reaction dynamics and illuminated potential mechanisms underlying PSS reduction. After a 24-hour dark-storage period, DC outcomes comparable to conventional curing were observed, affirming the clinical applicability of the method., Conclusions: Protocol involving the use of two 1.5 mm fibers in the first step (300 mW/cm 2 x 10 s), followed by a second conventional curing step (1000 mW/cm 2 x 10 s), is recommended to achieve the desired PSS reduction, while maintaining adequate DC and ensuring efficient clinical application., Clinical Significance: Obtained PSS reduction offers promise in potentially improving the performance of composite restorations. Additionally, leveraging the flexibility of optical fibers improves light guide approach for restorations on posterior teeth. Meanwhile, implementation in clinical practice is easily achievable by coupling the fibers with commercial dental LCUs using the provided plastic adapter., 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 Ltd. All rights reserved.)

Objectives: To evaluate the properties of novel hydrolytic resistant antibacterial monomers and to determine the properties of resin adhesives containing these monomers., Methods: Methacrylamide-based QAC (Quaternary Ammonium Compound) monomers, 1-(11-Methacryla-midoundecyl)pyridine-1-ium bromide (MAUPB) and 1-(12-Methacryl-amidododecyl)pyridine-1-ium bromide (MADPB), and their methacrylate-derivatives, N-(1-Methacryloylundecanyl)pyridinium bromide (MUPB) and N-(1-Methacryloyldodecanyl)pyridinium bromide (MDPB), were synthesized and characterized. The minimum inhibitory (MIC) and bactericidal (MBC) concentrations were determined against S.mutans and E.faecalis. Cytotoxicity of unpolymerized monomers were evaluated using L-929 and MDPC-23. Each monomer was incorporated into experimental resins (BisGMA/TEGDMA/CQ/EDMAB or BisGMA/HEMA/CQ/EDMAB) at 10wt%. FTIR Spectra were collected for degree of conversion (DC%) measurement. Bacterial attachment on resin disks were determined by fluorescent microscope. Mechanical properties of experimental resins were evaluated by flexural strength & modulus and shear bond strength testing., Results: The antibacterial activity of MDPB≥MUPB>MADPB>MAUPB. The TC 50 of MAUPB> MADPB>MUPB >MDPB. Incorporation of MAUPB in BisGMA/TEGDMA-based resin, had no significant effect on DC%, while significantly increase DC% in BisGMA/HEMA-based Resin. MUPB and MAUPB containing resins showed less viable bacterial attachment than pure resins. After 3-month storage, resins containing MAUPB illustrated higher flexural strength than their corresponding resins containing MUPB. BisGMA/HEMA-based resin containing MAUPB illustrated significantly higher resin-dentin shear bond strength than that of MUPB and pure resin., Conclusions: Methacrylamide monomer containing QAC, MAUPB, possessed antibacterial properties and superior physical and mechanical properties when incorporated in resin adhesives as compared to their corresponding methacrylate monomer, MUPB., Clinical Significance: Methacrylamide-based QAC monomers are potentially used to formulate antibacterial hydrolytic resistant resin adhesives and enhance resin-dentin bond strength., 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. The authors declare the following financial interests/personal relationships which may be considered as potential competing interests:, (Copyright © 2023 Elsevier Ltd. All rights reserved.)

Objective: To evaluate the curing profile of bulk-fill resin-based composites (RBC) using micro-Raman spectroscopy (µRaman). Methods: Four bulk-fill RBCs were compared to a conventional RBC. RBC blocks were lightcured using a polywave LED light-curing unit. The 24-h degree of conversion (DC) was mapped along a longitudinal cross-section using µRaman. Curing profiles were constructed and 'effective' (>90% of maximum DC) curing parameters were calculated. A statistical linear mixed effects model was constructed to analyze the relative effect of the different curing parameters. Results: Curing efficiency differed widely with the flowable bulk-fill RBCs presenting a significantly larger 'effective' curing area than the fibre-reinforced RBC, which on its turn revealed a significantly larger 'effective' curing area than the full-depth bulk-fill and conventional (control) RBC. A decrease in 'effective' curing depth within the light beam was found in the same order. Only the flowable bulk-fill RBCs were able to cure 'effectively' at a 4-mm depth for the whole specimen width (up to 4 mm outside the light beam). All curing parameters were found to statistically influence the statistical model and thus the curing profile, except for the beam inhomogeneity (regarding the position of the 410-nm versus that of 470-nm LEDs) that did not significantly affect the model for all RBCs tested. Conclusions: Most of the bulk-fill RBCs could be cured up to at least a 4-mm depth, thereby validating the respective manufacturer's recommendations. Clinical significance: According to the curing profiles, the orientation and position of the light guide is less critical for the bulk-fill RBCs than for the conventional RBC. [ABSTRACT FROM AUTHOR]

Objectives: To investigate the 24 h post-cure polymerization and the effect of temperature on the post-cure polymerization of one conventional and three bulk-fill composite materials. Methods: A conventional composite GrandioSO (GR) and three bulk-fill composites: Tetric EvoCeram Bulk Fill (TECBF), Quixfil (QF) and X-tra fil (XF) were investigated. The samples were cured for 20 s with irradiance of 1090 mW/cm². Composite samples were divided into two groups: the "room-temperature" group (RT, n = 5) and the "body-temperature" group (BT, n = 5) and they were stored in dark at 20°C and 37°C, respectively. Measurements of degree of conversion (DC) were made immediately after curing (0 h) and 24 h post-cure (24 h). To analyse the extent of post-cure DC increase, the DC values of 0 h-RT/24 h-RT and 0 h-BT/24 h-BT were compared. To analyse the difference in DC between RT and BT, the DC values of 0 h-RT/0 h-BT and 24 h-RT/24 h-BT were compared. Results: DC increase 24 h post-cure was significant for all composites and ranged between 6.3% and 8.2% in RT and between 12.5% and 15.7% in BT. All composites demonstrated a higher DC in 24 h-BT compared to 24 h-RT. The difference was statistically significant for GR, TECBF and QF. Conclusions: All composites demonstrated a significant post-cure effect after 24 h. Post-cure temperature increase from 20 °C to 37 °C yielded a higher post-cure DC increase. Clinical significance: Due to the temperature effect on the final DC, studies performed at composite samples at room temperature may record more inferior properties than these attained in the oral cavity. [ABSTRACT FROM AUTHOR]

Objectives: Bulk-fill composites have emerged, arguably, as a new "class" of resin-based composites, which are claimed to enable restoration in thick layers, up to 4 mm. The objective of this work was to compare, under optimal curing conditions, the physico-mechanical properties of most currently available bulk-fill composites to those of two conventional composite materials chosen as references, one highly filled and one flowable "nano-hybrid" composite. Methods: Tetric EvoCeram Bulk Fill (Ivoclar-Vivadent), Venus Bulk Fill (Heraeus-Kulzer), SDR (Dentsply), X-tra Fil (VOCO), X-tra Base (VOCO), Sonic Fill (Kerr), Filtek Bulk Fill (3M-Espe), Xenius (GC) were compared to the two reference materials. The materials were light-cured for 40 s in a 2 mm x 2 mm x 25 mm Teflon mould. Degree of conversion was measured by Raman spectroscopy, Elastic modulus and flexural strength were evaluated by three point bending, surface hardness using Vickers microindentation before and after 24 h ethanol storage, and filler weight content by thermogravimetric analysis. The ratio of surface hardness before and after ethanol storage was considered as an evaluation of polymer softening. Data were analyzed by one-way ANOVA and post hoc Tukey's test (p = 0.05). Results: The mechanical properties of the bulk-fill composites were mostly lower compared with the conventional high viscosity material, and, at best, comparable to the conventional flowable composite. Linear correlations of the mechanical properties investigated were poor with degree of conversion (0.09 < R < 0.41) and good with filler content (R > 0.8). Softening in ethanol revealed differences in polymer network density between material types. Conclusion: The reduction of time and improvement of convenience associated with bulk-fill materials is a clear advantage of this particular material class. However, a compromise with mechanical properties compared with more conventional commercially-available nanohybrid materials was demonstrated by the present work. [ABSTRACT FROM AUTHOR]

Objectives: To evaluate the effects of acidic functional monomers with different hydrophi- licity and spacer carbon chain length on the degree of conversion (DC), wettability (contact angle), water sorption (WS) and ultimate tensile strength (UTS) of experimental one-step self-etch adhesives (1-SEAs). Methods: A series of standard resin blends was prepared with each formulation containing 15 mol% of each acidic monomer. The structural variations of the acidic monomers were MEP (spacer chain with 2 carbons), MDP (10-carbons), MDDP (12-carbons), MTEP (more hydrophilic polyether spacer) and CAP-P (intermediate hydrophilicity ester spacer). Dumbbell- shaped and disc specimens were prepared and tested for UTS and WS, respectively. DC was assessed by FTIR, while the wettability of each 1-SEA was evaluated on glass slides and flat dentine surfaces. Results were analysed with one-way ANOVA and Tukey's test ( p < 0.05). Results: The outcomes showed lower UTS for CAP-P, control blend and MEP than MTEP, MDDP and MDP ( p < 0.05). The degree of conversion was statistically similar for all resins ( p = 0.122). On dentine, the wettability was higher (lower contact angle) with the most hydrophilic monomer MTEP. Higher WS was attained using MTEP. Different lengths of the spacer chains did not result in different wettability and WS ( p > 0.05). Conclusion: At similar molar percentage, different acidic functional monomers induced similar degree of conversion and different UTS when included in a 1-SEA. However, the inclusion of highly hydrophilic monomer may increase the wettability on dentine and the WS. [ABSTRACT FROM AUTHOR]

Objectives: To evaluate the effect of an additional hydrophobic resin coating (HE) on the resin-dentine microtensile bond strengths (mTBS), nanoleakage (NL), and in situ degree of conversion (DC) of three universal adhesives used in the etch-and-rinse (ER) and the selfetch (SE) modes. Methods: Sixty caries-free extracted third molars were divided into 12 groups according to the combination of the factors adhesive (All-Bond Universal [ABU]; G-Bond Plus [GBP] and Scotchbond Universal [SBU]), adhesive strategy (ER and SE), and the use of HE (Heliobond; yes or no). After restorations were constructed, specimens were stored in water (37 8C/24 h) and sectioned into resin-dentine beams (0.8 mm²) to be tested under tension (0.5 mm/min). Selected beams from each tooth were used for DC quantification and for NL evaluation. Data from each adhesive were analyzed with two-way ANOVA and Tukey's test (a = 0.05). Results: ABU and GBP resulted in higher mTBS in the ER mode. The use of HE increased the mTBS of ABU and GBP only in the SE mode. Lower NL was observed for SBU and ABU in the ER mode + HE, and for GBP in the SE mode + HE. SBU and GBP showed higher DC when used in the ER mode, which was increased with HE application. The DC of ABU was similar in all conditions. Conclusions: The conversion of 1-step SE to 2-step SE may increase the mTBS and DC of current universal adhesives. The reduction in the NL is more dependent on the adhesive composition than on the bonding strategy. [ABSTRACT FROM AUTHOR]

Objectives: To compare the degree of conversion (DC) of adhesives initiated by diphenyl(2,4,6- trimethylbenzoyl)phosphine oxide (TPO) or a camphorquinone/tertiary amine system (CQ/ Amine) as well as their 'immediate' micro-tensile bond strength (μTBS) to bur-cut dentine. Methods: DCofScotchbond Universal('SBU';3MESPE),its experimentalcounterpartcontaining TPO as photo-initiator system, an experimental G-aenial Bond ('Ga-B'; GC) adhesive formula- tion, and an experimental LUB-102 adhesive formulation ('LUB', Kuraray Noritake), containing as photo-initiatior system either 2 wt% CQ along with 2 wt% tertiary amine ('SBU_CQ/Amine'; 'Ga-B_CQ/Amine'; 'LUB_CQ/Amine'), or 2 wt% TPO ('SBU_TPO'; 'Ga-B_TPO'; 'LUB_TPO'), was determinedusingFourier-transforminfraredspectroscopy(FTIR),afterbeingcuredwithadual- wavelengthlight-curingunit(bluephase20i,IvoclarVivadent).Thesameadhesiveformulations were applied to bur-cut mid-coronal dentine of intact human molars, and subjected to a μTBS test after 1-week water storage. Besides being applied following a self-etch (SE) application mode, the adhesive formulations SBU_CQ/Amine and SBU_TPO were also applied following an etch-and-rinse (E&R) mode, this both for DS and μTBS measurement. Results: No significant difference in DC was found for any of the adhesive formulations, except for SBU_CQ/Amine_SE and SBU_TPO_SE. For both SBU formulations, a significantly higher DC was reached for the E&R than the SE approach. Regarding μTBS, no significant differences were recorded, except for the significantly higher μTBS measured for SBU_CQ/ Amine_E&R and SBU_TPO_E&R. Conclusions: In self-etch adhesives, the photo-initiator TPO may be used instead of CQ/ Amine. The curing and 'immediate' bonding efficiency depended on the application protocol (E&R versus SE), but not on the photo-initiator system. Clinical significance: The photo-initiator TPO may be used in self-etch adhesives instead of CQ/Amine with similar curing and 'immediate' bonding efficiency. [ABSTRACT FROM AUTHOR]

Objectives: This study measured the degree of conversion (DC), sorption, solubility and microhardness of methacrylate (Filtek Z250 and Filtek Z350XT) and silorane-based composites (Filtek P90). Methods: DC was measured using near infrared spectroscopy immediately and 24 h after the photoactivation. Sorption and solubility measurements were performed after 24 h, 4 weeks and 12 weeks of storage in water. Knoop microhardness was measured after 24 h and after thermal cycling. The data were statistically analyzed using ANOVA followed by Tukey's, Tamhane or paired t-tests (α = 0.05). Results: The DC for P90 (37.22 ± 1.46) was significantly lower than the Z250 (71.44 ± 1.66) and Z350 (71.76 ± 2.84). Water sorption was highest in the Z250 and lowest in the P90. All the tested composites exhibited similar values after 24 h of immersion, and no significant differences were observed. No significant differences were observed between the solubilities of the P90 composite (12 weeks) and the Z250 or Z350 composites (4 weeks). KHN values were less elevated for the P90 composite and similar for the Z250 and Z350 composites. An effect of thermal cycling on KHN values was observed for all the composites (p < 0.001). Conclusions: Silorane produced the lowest DC and KHN values and exhibited lower water sorption and solubility compared to methacrylate-based composites. These differences suggest that silorane composites exhibit better hydrolytic stability after 3 months of water immersion compared to conventional methacrylate-based composites. Clinical significance: Silorane had higher hydrolytic stability after 3 months of water immersion than the methacrylate-based resins, despite the lower values of DC and KHN recorded. [ABSTRACT FROM AUTHOR]

Objectives: To evaluate the dentine microtensile bond strength (mTBS), nanoleakage (NL), degree of conversion (DC) within the hybrid layer for etch-and-rinse and self-etch strategies of universal simplified adhesive systems. Methods: forty caries free extracted third molars were divided into 8 groups for μTBS (n = 5), according to the adhesive and etching strategy: Clearfil SE Bond [CSE] and Adper Single Bond 2 [SB], as controls; Peak Universal Adhesive System, self-etch [PkSe] and etch-and-rinse [PkEr]; Scotchbond Universal Adhesive, self-etch [ScSe] and etch-and-rinse [ScEr]; All Bond Universal, self-etch [AlSe] and etch-and-rinse [AlEr]. After restorations were constructed, specimens were stored in water (37 °C/24 h) and then resin-dentine sticks were prepared (0.8 mm²). The sticks were tested under tension at 0.5 mm/min. Some sticks from each tooth group were used for DC determination by micro-Raman spectroscopy or nanoleakage evaluation (NL). The pH for each solution was evaluated using a pH metre. Data were analyzed with one-way ANOVA and Tukey's test (α = 0.05). Results: For μTBS, only PkSe and PkEr were similar to the respective control groups ( p > 0.05). AlSe showed the lowest mTBS mean ( p < 0.05). For NL, ScEr, ScSe, AlSe, and AlEr showed the lowest NL similar to control groups ( p < 0.05). For DC, only ScSe showed lower DC than the other materials ( p < 0.05). Results: For μTBS, only PkSe and PkEr were similar to the respective control groups ( p > 0.05). AlSe showed the lowest mTBS mean ( p < 0.05). For NL, ScEr, ScSe, AlSe, and AlEr showed the lowest NL similar to control groups ( p < 0.05). For DC, only ScSe showed lower DC than the other materials ( p < 0.05). [ABSTRACT FROM AUTHOR]

Methods: The occlusal one-third of the crown was removed from un-erupted human third molars, followed by abrading with 600 grit SiC under water. Rectangular dentine slabs were prepared by sectioning the tooth specimens perpendicular to the abraded surfaces. The obtained dentine slabs were treated with one of the two one-step self-etch adhesives: Adper Easy Bond (AEB, pH ~ 2.5) and Adper Prompt L-Pop (APLP, pH ~ 0.8) with (15 s, active application) or without (15 s, inactive application) agitation. The dentine slabs were fractured and the exposed adhesive/dentine (A/D) interfaces were examined with micro-Raman spectroscopy and scanning electron microscopy (SEM). Results: The interfacial morphology, degree of dentine demineralization (DD) and degree of conversion (DC) of the strong self-etch adhesive APLP showed more significant dependence on the application mode than the mild AEB. APLP exhibited inferior bonding at the A/D interface if applied without agitation, evidenced by debonding from the dentine substrate. The DDs and DCs of the APLP with agitation were higher than those of without agitation in the interface, in contrast to the comparable DD and DC values of two AEB specimen groups with different application modes. Raman spectral analysis revealed the important role of chemical interaction between acid monomers of self-etch adhesives and dentine in the above observations. Conclusion: The chemical interaction with dentine is especially important for improving the DC of the strong self-etching adhesive at the A/D interface. Agitation could benefit polymerization efficacy of the strong self-etch adhesive through enhancing the chemical interaction with tooth substrate. [ABSTRACT FROM AUTHOR]

Objectives: To evaluate the effects of proanthocyanidins (PA) and photoinitiator type on the degree of conversion (DC) and polymerization rate (PR) of a model dental adhesive. Methods: Three types of photo-initiation systems were introduced into the Bis-GMA/HEMA co-monomer mixture, resulting in four resin formulations including CQ/A (0.5 wt% CQ and EDMAB), CQ/A/I-1 (0.5 wt% CQ, EDMAB and DPIHP), CQ/A/I-2 (1.0 wt% CQ, EDMAB and DPIHP), and TPO (2.1 wt% TPO). For each resin formulation, adhesives containing 0%, 2.5%, 5% and 10% of PA with respect to the weight of resin were produced after mixing the resin with various amount of PA/ethanol solution. When light-cured, the RP and DC of each adhesive was determined using ATR-FTIR spectroscopy. Results: Across and within the initiator groups, the DC followed the general trend of CQ/A < CQ/A/I-1 < CQ/A/I-2 < TPO and 0-PA > 2.5-PA > 5-PA > 10-PA, respectively. The change of PR with respect to photo-initiation systems and PA content was in a similar but less pronounced pattern. Conclusion: PA hampered the polymerization of all adhesives regardless of photoinitiators used. The initiator formulations CQ/A/I-2 and TPO are better fit for PA-containing adhesives, both leading to >65% DC in the presence of 5% PA. Clinical significance: The inclusion of PA in dental adhesives has been limited by its interference with the light-curing of adhesive resins. This study found photo-initiation formulations that could maintain a satisfactory degree of monomer conversion while a significant amount of PA is incorporated. [ABSTRACT FROM AUTHOR]

Abstract: Objectives: To evaluate the effect of prolonged exposure times on immediate and 6-month adhesive properties: degree of conversion (DC), nanoleakage (NL) and resin–dentine bond strength (μTBS) of three one-step self-etch adhesive systems (Adper Easy One [EO], Clearfil S3 Bond [CS3] and Go [GO]). Material and methods: The adhesives were applied on exposed dentine surfaces of 90 human molars according to manufacturers’ instructions and light polymerized for 10, 20, and 40s at 600mW/cm2. Bonded teeth were sectioned to obtain stick-shaped specimens (0.8mm2) and tested under tensile stress (0.5mm/min) immediately (IM) or after 6 months of water storage. Two bonded sticks from each tooth at each storage time interval were analysed by SEM for NL evaluation. The in situ DC was evaluated by micro-Raman spectroscopy. Data were analysed by appropriate ANOVA and Tukey''s test (α =0.05). Results: Prolonged exposure times significantly increased the DC (%) (10s [67.4±17.3]; 20s [85.9±8.9] and 40s [85.2±9.0]) and decreased the NL (%) (10s [24.8±13.2]; 20s [13.3±7.5] and 40s [13.5±9.3]) for all adhesives; however it did not increase the IM μTBS for two (EO, GO) out of the three adhesives. Furthermore, this technique did not minimize dentine bond degradation. Conclusion: Although longer exposure times than those recommended could not prevent degradation of dentine bonds, they could increase DC within the hybrid layer and reduced NL for all adhesives tested. [Copyright &y& Elsevier]

Abstract: Objectives: DC of three commercial two-step etch-and-rinse adhesives across the dentine–adhesive interface was investigated using micro-Raman spectroscopy. The hypothesis tested was that no difference in DC would exist among the adhesives tested. Methods: Adper Scotchbond 1XT (3M ESPE), Prime&Bond NT (Dentsply DeTrey), and Ambar (FGM) were applied on human dentine disks (n =9). Composite increments of 2mm were then applied on the adhesive surface. Raman spectra were collected along the dentine–adhesive interface. The relative intensities of the peaks associated with the mineral (PO4 3− at 960cm−1) and the adhesive (Ccm−1; phenyl Ccm−1) were used to identify the adhesive within the hybrid layer and calculate its DC. Results: Adper Scotchbond 1XT and Ambar showed similar DC (79±7% and 77±7%, respectively), while a lower DC was found for Prime&Bond NT (70±7%; p <0.05). Conclusions: The hypothesis tested was rejected because differences were found among the adhesives tested. The difference in DC among the three adhesive systems can be attributed to different monomer compositions and solvents. Further studies are needed to correlate DC with other mechanical properties of these adhesives. Clinical significance: Insufficient polymerization of an adhesive can result in a weak hybrid layer, and the presence of unreacted monomers may result in degradation of the polymeric network, decreasing the strength and longevity of the bond. In the present study, Adper Scotchbond 1XT and Ambar performed significantly better than Prime&Bond NT. [Copyright &y& Elsevier]

Abstract: Objective: To understand the correlation of the acidic monomer/hydroxyapatite (HAp) reaction with the photopolymerization behaviour of self-etching adhesives with different aggressiveness. Methods: Two commercial self-etching adhesives the strong Adper Prompt L-Pop (APLP, pH∼0.8) and the mild Adper Easy Bond (AEB, pH∼2.5) were used. HAp powders were incorporated into both adhesives to acquire solutions with concentrations of 0, 1, 3, 5, 7wt%. The attenuated total reflectance Fourier transform infrared (ATR/FT-IR) technique was employed to collect the in situ spectra during light-curing, from which the degree of conversion (DC) and polymerization rate (PR) were calculated. The pH of each tested solution was also measured. Results: Without HAp incorporation, the DC and PR of the strong APLP (7.8% and 0.12%/s, respectively) were much lower than those of the mild AEB (85.5% and 5.7%/s, respectively). The DC and PR of APLP displayed an apparent increasing trend with the HAp content. For example, the DC increased from 7.8% to 58.4% and the PR increased from 0.12 to 3.8%/s when the HAp content increased from 0 to 7wt%. In contrast, the DC and PR of AEB were much less affected by the HAp content. The observations were correlated well with the spectral and pH changes, which indicated that APLP underwent a higher extent of chemical reaction with HAp than AEB. Conclusions: The results disclosed the important role of the acidic monomer/HAp chemical reaction in improving the photopolymerization of the strong (low-pH) self-etching adhesives such as APLP. The phenomenon of polymerization improvement strongly depended on the adhesive aggressiveness. [Copyright &y& Elsevier]

Abstract: Objectives: Because fibre post restorations are influenced by multiple factors such as the types of bonding materials, the dentine region and the time under moist exposure, this study sought to determine the bond strength of endodontic restorations and its relation to the degree of conversion of the cement layer and the molecular structure of the dentine-bonded joints. Methods: The performance of 2 etch-and-rinse (All-Bond 2 and One-Step Plus) and 2 self-etch (Clearfil SE Bond and Xeno III) adhesives at post spaces regions, after 7d or 4m, was evaluated. FRC Postec Plus posts were cemented to the root canal with a dual-cure resin cement (Duo-Link). Transverse sections of the tooth were subjected to push-out testing, to degree-of-conversion measurements and to hybrid layer evaluation through μ-Raman spectroscopy. Results: Coronal bonding was higher than cervical and middle bonding. The hybrid layer was thicker for the etch-and-rinse systems, with thicknesses decreasing towards the middle region. The degree of conversion measured for the 3-step etch-and-rinse group after 4m was significantly higher than that for the self-etching groups. Conclusions: Although not totally stable at the adhesive–dentine interface, the 3-step etch-and-rinse adhesive in the coronal dentine provided the best bond strength, degree of conversion of the cement and hybrid layer thickness in post restorations, in both short- and long-term analyses. [Copyright &y& Elsevier]

Abstract: Objectives: To determine the degree of conversion (DC) over 48h post-curing of resin mixtures containing trimethylbenzoyl-diphenylphosphine oxide (TPO) initiator cured by a polywave or a monowave LED light-curing unit (LCU). Methods: In resin mixtures based on equal weight percent (wt%) of BisGMA and TEGDMA the following initiators were added: 0.2wt% camphorquinone (CQ)+0.8wt% ethyl-4-dimethylaminobenzoate (EDMAB) (Group 1); 1wt% TPO (Group 2) and 0.1wt% CQ+0.4wt% EDMAB+0.5wt% TPO (Group 3). Half of the samples in each group (n =5) were cured using a polywave (bluephase® G2, Ivoclar Vivadent) or a monowave LED LCU (bluephase®, Ivoclar Vivadent). The DC was measured using micro-Raman spectroscopy within 5min and then 1, 3, 6, 24 and 48h post-irradiation. The data were analysed using general linear model and two-way ANOVA for the factors ‘time’, ‘material’, ‘surface’ and ‘LCU’ at α =0.05. Results: The initial DC values obtained upon light curing remained similar over a 48h period. bluephase® G2 produced the highest DC in Group 2 followed by Group 3, and Group 1. bluephase® resulted in the highest DC in Group 1, followed by Group 2 and Group 3 (p <0.05). Conclusions: Unfilled resin materials containing both TPO– and CQ–amine initiators are effectively cured using bluephase® G2. Resin mixture with the same wt% of initiators is better cured when TPO is the only initiator, compared to CQ–amine only or combined TPO and CQ–amine system. After initial light cure, no additional conversion of uncured monomers was detected in an unfilled resin material over 48h at 37°C. [Copyright &y& Elsevier]

Abstract: Objective: To investigate the correlation of the chemical interaction between model self-etching adhesives and dentine with the degree of conversion (DC) of the adhesives. Methods: The model self-etching adhesives contained bis[2-methacryloyloxy)ethyl] phosphate (2MP) and 2-hydroxyethyl methacrylate (HEMA) with a mass ratio of 1/1, and 0–40% water contents, respectively. The adhesives were applied either onto the prepared dentine surface or unreactive substrates (such as glass slides), agitated for 15s, then light-cured for 40s. The DCs of the adhesives were determined using micro-Raman spectral and mapping analysis. Results: The DCs of the adhesives cured on the dentine substrate were found to be significantly higher than those on the unreactive glass substrate. Moreover, the DCs of the adhesives displayed a decreasing trend as the distance from the dentine surface became greater. The chemical interaction of the acidic 2MP/HEMA adhesives with the mineral apatite in dentine was proposed to play a significant role for the observations. The chemical interaction could be validated by the spectral comparison in the phosphate regions of 1100cm−1 and 960cm−1 in the Raman spectra. The results also revealed a notable influence of water content on the DC of adhesives. The DCs of the adhesive at 10% water content exhibited the highest DC level for both substrates. Conclusions: Interaction with dentine dramatically improved the degree of conversion of self-etching adhesives. Our ability to chemically characterise the a/d interface including in situ detection of the DC distribution is very important in understanding self-etching adhesive bonding under in vivo conditions. [Copyright &y& Elsevier]

Abstract: Objectives: The aim of this work was to investigate the effect of high irradiance curing on resultant degree of conversion of ‘flowable’ resin composites and their counterpart higher viscosity paste materials. Methods: Five commercial flowable materials (Venus; Heraeus Kulzer, Synergy D6; Coltene, Premise; Kerr, Grandio; Voco and Gradia; GC Corp) and their counterpart higher viscosity restorative versions were tested. Specimens were cured with a halogen Swiss Master Light (EMS, Switzerland) using five different curing protocols with similar radiant exposure (18J/cm2): 400mW/cm2 for 45s, 900mW/cm2 for 20s, 1500mW/cm2 for 12s, 2000mW/cm2 for 9s and 3000mW/cm2 for 6s. Degree of conversion (DC) was measured in real time by Fourier transform near infrared spectroscopy (FT-NIRS). Results: Three- and subsequent two way ANOVA testing revealed significant differences (p ≤0.02) with respect to “composite type” and “cure protocol” for DC for all 5 product comparisons. Supplementary one-way ANOVA also revealed significant differences between curing protocols (p <0.05). The majority of higher viscosity resin composite paste materials exhibited similar DC regardless of curing protocol. However, a significant decrease in DC for specimens cured at 3000mW/cm2 for 6s compared with 400mW/cm2 for 45s was observed for the flowable materials, Grandio (41±0.36 and 62±1.15%, respectively) and Venus (44±0.44 and 67±0.44%, respectively). Conversely, other flowable materials exhibited little or no significant differences between curing modes. Generally, a higher degree of conversion was observed for flowables compared with their more viscous counterpart, except at high irradiance for those materials where a reciprocal relationship with exposure time was not observed. Conclusions: The validity of exposure reciprocity law and final degree of conversion depends on several factors, amongst which resin viscosity and filler content were important. Practitioners should be aware of the importance of resin composite constituents and irradiation protocols. Information on material composition and appropriate radiation sources by manufacturers may assist practitioners with the selection of appropriate curing protocols for specific material/light curing unit combinations with the aim of reducing the incidence of under-cured restorations and the clinical impact thereof. [Copyright &y& Elsevier]

Abstract: Objectives: To evaluate the effect of the filler content in the cohesive strength (σ), Weibull modulus (m) and degree of conversion (DC) of an experimental adhesive system. Methods: A HEMA/Bis-GMA/TEGDMA-based adhesive was formulated and filled with silica nanofillers in the following weight percentages (wt%): R0=0%; R1=1%; R3=3%; R5=5% and R10=10%. The adhesive of Adper Scotchbond Multi-Purpose (SBMP) system was used as a commercial reference. Twenty dumbbell-shaped specimens with cross-sectional area of 0.5mm2 were made per group and tensile tested with a crosshead speed of 0.5mm/min until fracture. The cohesive strength was calculated in MPa. DC was obtained through FTIR after light curing for 25s. Data were submitted to one-way ANOVA and Tukey''s test (α =0.05) and to Weibull analysis. Results: Mean σ results were: R0=65.4±8.4; R1=73.2±8.8; R3=72.0±8.4; R5=73.1±9.7; R10=85.5±13.1 and SBMP=79.0±11.0MPa. R10 presented the highest σ, while R0 showed the lowest. R5 and SBMP did not differ significantly (p <0.05). Weibull analysis revealed no significant difference in structural reliability between groups. The experimental adhesives presented similar results of DC, which, in turn, were significantly higher than the SBMP. Conclusions: The addition of 10% filler in weight improves the cohesive strength of the adhesive, not interfering in the structural reliability or the degree of conversion. [Copyright &y& Elsevier]

Abstract: Objectives: To quantify monomer elution from different adhesive systems using reverse-phase high-performance liquid chromatography (HPLC) and correlate this elution with the ratio of carbon–carbon double bonds from monomer to polymer (RDB) obtained using micro-Raman spectroscopy. Methods: Thirty dentine discs were cut from 30 human, intact, third molars and randomly allocated to five groups according to the adhesive applied: total-etch, Excite (Ivoclar Vivadent), two-bottle self-etch, Clearfil SE (Kuraray), one-bottle self-etch, Clearfil 3S (Kuraray), ormocer-based, Admira (Voco) and Filtek Silorane adhesive system (FS) (3M ESPE). Monomer elution was studied 1h, 6h, 24h, 96h and 7 days after immersion in 75% ethanol/water. The RDB was calculated immediately after light-curing and thereafter at 24h and 7 days. The data were statistically analysed using one-way ANOVA and Pearson''s correlation coefficient (p <0.05). Results: More than 90% of the whole elution occurred during the first 1h, except for BisGMA in FS, with the highest absolute amount from Clearfil SE and the highest wt% from Admira. Initial RDB was in the ascending order FS

Abstract: Objectives: To evaluate the effectiveness of sodium sulfinate salt co-initiators on the degree of conversion (DC) of dual-cured cementing systems [combination of bonding agent (BA) and resin cement (RC)] when the activating light is attenuated or not available. Methods: Two 5th generation products [Prime&Bond NT Dual-Cure/Calibra (Dentsply), and Excite DSC/Variolink II (Ivoclar/Vivadent)] were applied, either with or without co-initiators (sodium sulfinate salts) added to the bonding agents, to the surface of a horizontal attenuated-total-reflectance unit, and were polymerized using one of four conditions: self-cure (SC), or direct light exposure (DLE/XL3000/3M) through a glass slide or through pre-cured resin discs (shades A2 or A4/2mm-thick) (Z250/3M-ESPE). Real-time infrared spectra were obtained after placing components (uncured) and during 10min (cured) (16 scans at 2cm−1, FTS-40/Digilab/Bio-Rad) to obtain polymerization kinetics. DC and maximum rate of polymerization (Rpmax) were calculated using standard techniques of observing changes in aliphatic-to-aromatic peak ratios pre- and post-curing. Data (n =5) were analyzed by two-way ANOVA and Tukey''s test (p =0.05). Results: The addition of co-initiators increased the DC in most of the groups. No significant difference in DC was observed between Prime Bond NT Dual-Cure/Calibra and its version without co-initiator using the DLE curing mode. All DLE groups exhibited the highest DC after 10min. No significant difference in DC was observed between A2 and A4 pre-cured overlay groups. The SC groups exhibited lower DC than the light-activated groups regardless of the presence of co-initiator. Use of co-initiators increased the Rpmax only in the SC groups. The A2 and A4 groups exhibited lower Rpmax than DLE groups, regardless of the presence of co-initiator. Conclusion: The detrimental effects of light attenuation on the DC were not avoided by inclusion of sodium sulfinate salts, despite their ability to eliminate the chemical incompatibility between acidic monomers and self-curing components. [Copyright &y& Elsevier]

Summary: Objectives: This study evaluated the effect of a warm or cold air-dry stream for solvent evaporation on the microtensile resin–dentin bond strength (μTBS), nanoleakage pattern (SEM), degree of conversion (DC) and solvent evaporation rates (SE) of an ethanol/water- (Adper Single Bond, [SB] 3MESPE) and an acetone-based (Prime & Bond 2.1, [PB] Dentsply), two-step etch-and-rinse adhesive system. Materials and methods: Adhesives were applied on demineralized dentin surfaces. For SE, a warm or cold air-dry stream (10s) was applied prior to light-activation (10s). Bonded sticks (0.8mm2) were tested in tension (0.5mm/min). Two bonded sticks from each tooth were immersed in a 50% (w/v) solution of silver nitrate (24h), photodeveloped (8h) and analyzed by SEM. The DC and solvent evaporation rate of the adhesives were evaluated under FTIR and analytical balance, respectively. Data were analyzed by two-way ANOVA and Tukey test (α =0.05). Results: Higher μTBS and lower nanoleakage were observed when the SE step was performed with warm air-dry stream. However, the DC of the adhesives was not altered by the use of a warm air-dry. Conclusions: The use of a warm air-dry stream seems to be a clinical tool to improve the bond strength and the quality of the hybrid layer (less nanoleakage infiltration), since it might reduce the number of pores within the adhesive layer. [Copyright &y& Elsevier]

Abstract: Objectives: To evaluate the effects of different curing conditions on the degree of conversion (DC) of dual-cured cementing systems [combination of bonding agent (BA) and resin cement (RC)] using infrared spectroscopy. Methods: Four fourth generation products [Scotchbond Multipurpose Plus/RelyX (3M ESPE), Optibond/Nexus 2 (Kerr), All Bond2/Duolink (Bisco), and Bond-It!/Lute-It! (Pentron)], and three fifth generation materials [Bond1/Lute-It! (Pentron), Prime&Bond NT Dual-Cure/Calibra (Dentsply), and Optibond Solo Dual Cure/Nexus 2 (Kerr)] were applied to the surface of a horizontal attenuated-total-reflectance unit, and were polymerized using one of four conditions: self-cure (SC), direct light exposure through glass slide (DLE, XL3000/3M ESPE) or through pre-cured resin discs (shades A2;A4/2mm thick/Z250/3M ESPE). Infrared spectra of the uncured cementing systems were recorded immediately after application to the ATR, after the system was light-cured or left to self-cure, and spectra were obtained 5 and 10min later. DC was calculated using standard techniques of observing changes in aliphatic-to-aromatic peak ratios pre- and post-curing. Data (n =5) were analyzed by two-way repeated measures ANOVA and Tukey''s test (p =0.05). Results: Changes in aliphatic-to-aromatic peak ratios before and after placing RC onto the BA demonstrated that a combined layer was created. All groups exhibited higher DC after 10min than after 5min, except the DLE group of Bond-it!/Lute-it!. No significant differences in DC were observed among light-activated groups regardless of the resin disc shade in three of the four fourth generation cementing systems. The SC groups exhibited lower DC than the DLE groups for both fourth and fifth generation products either after 5 or 10min. Conclusion: The chemistry of the bonding interface changed when RCs were applied to uncured BAs. The presence of an indirect restoration can decrease the DC of some cementing systems and the self-curing mode leads to lower DC than the light-activating one. [Copyright &y& Elsevier]

Abstract: Objectives: To evaluate the shrinkage-strain, degree of conversion (DC) and percent filler of a range of flowable resin-composites. Methods: Several commercially available flowable resin-composites were selected. The bonded-disk technique was used to measure shrinkage-strain kinetics. Measurements were obtained continuously for 60min by irradiation for 40s at 750mW/cm2 at two initial temperatures of 23 and 37°C. Three repetitions (n =3) were made at each temperature per material. The DC was measured by FTIR spectroscopy immediately post-cure. The percent filler was determined by combustion of specimens for 1h at 400°C. Results: The final values of shrinkage-strain ranged from 2.61 to 6.25% at 23°C and from 3.88 to 6.56% at 37°C. Statistically significant differences (p <0.05) were found in shrinkage-strain between the flowable resin-composites at both temperatures 23 and 37°C. Significantly higher values were obtained at 37°C (p <0.05). A strong inverse correlation was found between the percent filler and the shrinkage-strain at 37 and 23°C (r 2 =0.94 and 0.87, respectively). No correlation was found between shrinkage-strain and DC (p >0.05). Conclusions: Flowable resin-composites vary widely in shrinkage-strain magnitude and the inverse relationship between filler percent and shrinkage-strain is explained by the corresponding decrease in volume fraction of monomers present to undergo polymerisation. [Copyright &y& Elsevier]

Abstract: Objectives: To investigate the effect of reduced light exposure times on Vickers hardness (VH) of class II composite resin restorations. Methods: Class II restorations were made in vitro in three 2mm thick increments in a human molar. Two composite resins (Clearfil AP-X; Esthet-X) were polymerized with four light-curing units (Halogen; Astralis 10, LED; The Cure, L.E.Demetron I, Smartlite) following four curing protocols. Three protocols with exposure times of 10s, 20s or 40s (control) per layer. In the fourth protocol, 10s irradiation per layer was combined with additional lateral curing for 10s from buccal and palatal after removal of the metal matrix. VH of the axial surface was determined at top and bottom layers directly after light-curing and after 7 days storage. Linear regression analysis was performed to analyze the effect of protocol variables. Results: Directly after light-curing VH of both composite resins was significantly influenced by curing protocols. After 7 days, curing protocols had no significant effect on VH of Clearfil AP-X, except for the Smartlite. VH of Esthet-X was still influenced by curing protocol, but differences were smaller than directly after light-curing. Conclusions: With high intensity light-curing units, exposure times of 10s/2mm increment can be sufficient to obtain under in vitro conditions a high degree of conversion, depending on materials and curing protocols. With additional lateral curing of a class II composite resin restoration a higher degree of cure can be obtained in less time. [Copyright &y& Elsevier]

Summary: Objectives: To investigate the influence of photoactivation method on degree of conversion (DC), flexural strength (FS), flexural modulus (FM) and Knoop hardness (KHN) of a composite and an unfilled resin (Filtek Z250 and Scotchbond multi-purpose plus, 3M ESPE) after storage in water or ethanol, and on composite contraction stress (CS). Methods: Specimens 1×2×10mm were prepared for FS test, photoactivated by 600mW/cm2×40s (A), 200mW/cm2×120s (B), or 600mW/cm2×1s +3min delay +600mW/cm2×39s (C), and tested after 24h in water or ethanol. Load and displacement values were used to calculate FM. Specimen fragments were used to measure KHN. DC was determined by FT-Raman spectroscopy. CS was determined by mechanical testing. Data were submitted to ANOVA/Tukey''s test (α=0.05). Results: Composite DC was not affected by photoactivation (A: 65±1.8%; B: 66±3.4%; C: 65±2.9%). Unfilled resin DC was statistically higher using method A (79±0.3%) than B (74±1.0%) and C (73±0.9%). Photoactivation did not influence composite properties, regardless of the storage medium (p>0.05). After ethanol storage, FS of the unfilled resin was lower for specimens irradiated by method B (p<0.001). Pulse-delay curing (C) significantly reduced CS (7.7±1.3MPa), compared to A (10.7±1.2MPa) and B (10.1±1.3MPa). Significance: Photoactivation method did not affect composite properties or susceptibility to ethanol degradation. For the unfilled resin, DC was lower with the use of low intensity and pulse-curing, while FS after ethanol storage was reduced by low intensity curing. Pulse-delay curing significantly reduced CS. [Copyright &y& Elsevier]

Objectives. To quantify the monomer conversion and flexural strength of an experimental oxirane-based composite material (EXL596) compared with two, commercially available, dimethacrylate based restoratives (Z250 and Z100).Methods. Fourier-transform infra-red spectroscopy (FTIR) was utilised to evaluate the degree of conversion (DC) (n=5) and biaxial flexure strength (BFS) testing (n=20) was used to analyse flexural strength and associated Weibull moduli (m) of each material following 0.1, 0.5, 1, 4, 24 and 48 h immersion in a lightproof waterbath maintained at 37±1 °C.Results. The DC of Z250 and Z100 following 0.1, 0.5 and 1 h post-irradiation was significantly greater than the DC of EXL596 for the same immersion periods. This was manifested as a significant decrease in BFS and associated m of EXL596 compared with Z250 and Z100 for the 0.1, 0.5 and 1 h post-irradiation periods. The DC and BFS of EXL596 were significantly greater than Z250 and Z100 following 24 h immersion.Conclusions. Assessment of FTIR spectra, BFS and associated m has provided a useful method in the quantitative analysis of resin-based composite conversion. Identification of the decreased DC of EXL596 compared with Z250 and Z100 was achieved using FTIR. However, decreased conversion rates within the first hour following irradiation of EXL596 may compromise flexural strength properties (associated with a decrease in BFS and m) which may be inadequate under masticatory loading. [Copyright &y& Elsevier]

Objective. The hypothesis that low light intensity and long but sufficient curing time can produce composites with volumetric shrinkage, degree of conversion (DC%) and Young''s modulus (E-modulus) comparable to those of high light intensity cured composite was tested, when the contraction strain and heat generation were lower with low light intensity curing.Methods. Dental composites (Z100 and Z250, 3M ESPE) were investigated. Specimens were cured with light intensities of 200, 450 and 800 mW/cm2 for 140, 60 and 35 s from a distance of 7 mm. Strain-gages were used for contraction strain measurements. DC% was measured at the top and the bottom of 4 mm thick samples using FT-Raman spectroscopy. Volumetric polymerization shrinkage was determined using a water displacement method. E-modulus was determined in tension on composite specimens.Results. The results were analyzed using ANOVA and Duncan''s multiple range tests and regular t-test. Polymerization stress level decreased significantly (p<0.05) when cured with 200 mW/cm2 rather than with 800 mW/cm2. Temperature rises were significantly different (p<0.05) for different composites and light intensity values. Reduction in light intensity did not decrease the DC% values significantly at the top surfaces. The most dramatic differences existed between top and bottom surfaces (p<0.05) rather than among curing groups. Measured E-modulus and volumetric shrinkage values were not significantly different (p>0.05) between different light intensity groups.Conclusion. DC%, E-modulus and the volumetric shrinkage values in cured composites were not affected by low light intensity, however, the contraction strain and polymerization''s exotherm were decreased. Thus our results support the proposed hypothesis. [Copyright &y& Elsevier]

Objectives: This study investigated the effects of the surface conditioning of nano-zirconia fillers with 10-methacryloyloxydecyl dihydrogen phosphate (MDP) and dipentaerythritol penta-acrylate phosphate (PENTA) on the degree of conversion and mechanical properties of Bis-GMA- and UDMA-based resin composites containing the fillers., Methods: MDP or PENTA conditioned nano-zirconia fillers were characterized by Fourier transform infrared spectroscopy (FTIR) and X-ray photoelectron spectroscopy (XPS). The conditioned nano-zirconia fillers were then used to prepare Bis-GMA- and UDMA-based resin composites. The bending strength and elastic modulus of the prepared composites were evaluated, and Weibull analysis was adopted to evaluate the reliability of the bending tests. Degree of conversion (DC) was measured by FTIR., Results: FTIR and XPS analysis confirmed formation of ZrOP bonds in the MDP-conditioned and PENTA-conditioned zirconia fillers. MDP-conditioning and PENTA-conditioning increased bending strength of Bis-GMA-based composites (100.70 ± 7.15 MPa, 98.65 ± 4.76 Mpa) and UDMA-based composites (99.02 ± 4.45 MPa, 99.92 ± 5.78 MPa) compared to the groups with untreated nano-zirconia fillers (Bis-GMA-based, 84.98 ± 5.13 MPa; UDMA-based, 88.24 ± 4.61 MPa). The same trend was observed for the Weibull modulus (m) and elastic modulus. The MDP/PENTA conditioning did not affect the DC of the composites., Conclusion: MDP or PENTA conditioning of nano-zirconia fillers improved the mechanical properties of the composite compared to the composites containing untreated nano-zirconia fillers; however, it did not affect DC., Clinical Significance: Mixing MDP- or PENTA-conditioned nano-zirconia fillers directly with gamma-MPS-conditioned silica to the resin composite has the potential to improve the composite's mechanical properties., 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 © 2020 Elsevier Ltd. All rights reserved.)

Objectives: To investigate the polymerization kinetics and the degree of conversion (DC) of experimental resin composites with varying amount of bioactive glass 45S5 (BG)., Methods: Experimental resin composites based on a photo-curable Bis-GMA/TEGDMA resin system were prepared. The composite series contained 0, 5, 10, 20, and 40 wt% of BG and reinforcing fillers up to the total filler amount of 70 wt%. Composite specimens were light cured with 1219 mW/cm 2 for 20 or 40 s and their DC was monitored during 5 min at the data collection rate of 2 s -1 using attenuated total reflectance Fourier transform infrared spectroscopy (ATR-FTIR)., Results: The 5-min DC values for experimental composites were in the range of 42.4-55.9% and 47.3-57.9% for curing times of 20 and 40 s, respectively. The differences in the 5-min DC between curing times of 20 s or 40 s became more pronounced in materials with higher BG amount. Within both curing times, a decreasing trend of the 5-min DC values was observed with the increasing percentage of BG fillers. The maximum polymerization rate also decreased consistently with the increasing BG amount., Conclusions: Unsilanized BG fillers showed a dose-dependent inhibitory effect on polymerization rate and the DC. Extending the curing time from 20 to 40 s showed a limited potential to improve the DC of composites with higher BG amount., Significance: The observed inhibitory effect of BG fillers on the polymerization of resin composites may have a negative influence on mechanical properties and biocompatibility., (Copyright © 2018 Elsevier Ltd. All rights reserved.)

Objectives: The aim of this work was to investigate the curing potential of an experimental resin composite series with the systematically varying amount of bioactive glass 45S5 by evaluating the degree of conversion, light transmittance and depth of cure., Methods: Resin composites based on a Bis-GMA/TEGDMA resin with a total filler load of 70 wt% and a variable amount of bioactive glass (0-40 wt%) were prepared. The photoinitiator system was camphorquinone and ethyl-4-(dimethylamino) benzoate. The degree of conversion and light transmittance were measured by Raman spectroscopy and UV-vis spectroscopy, respectively. The depth of cure was evaluated according to the classical ISO 4049 test., Results: The initial introduction of bioactive glass into the experimental series diminished the light transmittance while the further increase in the bioactive glass amount up to 40 wt% caused minor variations with no clear trend. The curing potential of the experimental composites was similar to or better than that of commercial resin composites. However, unsilanized bioactive glass fillers demonstrated the tendency to diminish both the maximum attainable conversion and the curing efficiency at depth., Conclusions: Experimental composite materials containing bioactive glass showed a clinically acceptable degree of conversion and depth of cure. The degree of conversion and depth of cure were diminished by bioactive glass fillers in a dose-dependent manner, although light transmittance was similar among all of the experimental composites containing 5-40 wt% of bioactive glass., Clinical Significance: Reduced curing potential caused by the bioactive glass has possible consequences on mechanical properties and biocompatibility., (Copyright © 2018 Elsevier Ltd. All rights reserved.)

Objectives: To evaluate the effect of addition of copper nanoparticles at different concentrations into an etch-and-rinse adhesive (ER) on antimicrobial activity, Knoop microhardness (KHN), in vitro and in situ degree of conversion (DC), as well as the immediate (IM) and 2-year (2Y) resin-dentine bond strength (μTBS) and nanoleakage (NL)., Methods: Seven experimental ER adhesives were formulated according to the amount of copper nanoparticles incorporated into the adhesives (0 [control], 0.0075 to 1wt.%). We tested the antimicrobial activity of adhesives against Streptococcus mutans using agar diffusion assay after IM and 2Y. The Knoop microhardness and in vitro DC were tested after IM and 2Y. The adhesives were applied to flat occlusal dentine surfaces after acid etching. After resin build-ups, specimens were longitudinally sectioned to obtain beam-like resin-dentine specimens (0.8mm 2 ), which were used for evaluation of μTBS and nanoleakage at the IM and 2Y periods. In situ DC was evaluated at the IM period in these beam-like specimens. Data were submitted to appropriate statistical analyses (α=0.05)., Results: The addition of copper nanoparticles provided antimicrobial activity to the adhesives only in the IM evaluation and slightly reduced the KHN, the in vitro and in situ DC (copper concentrations of 1wt.%). However, KHN increase for all concentrations after 2Y. After 2Y, no significant reductions of μTBS (0.06 to 1% wt.%) and increases of nanoleakage were observed for copper containing adhesives compared to the control group., Conclusion: Copper nanoparticles addition up to 0.5wt.% may provide antimicrobial properties to ER adhesives and prevent the degradation of the adhesive interface, without reducing the mechanical properties of the formulations., (Copyright © 2017 Elsevier Ltd. All rights reserved.)

Objectives: This study aims at evaluating and comparing mechanical, chemical, and cytotoxicological parameters of a commercial brand name composite material against two 'own brand label' (OBL) composites., Methods: Parameters included depth of cure, flexural strength, degree of conversion, polymerization shrinkage, filler particle morphology and elemental analyzes, Vickers hardness, surface roughness parameters after abrasion, monomer elution, and cytotoxicity., Results: The conventional composite outperformed the OBLS in terms of depth of cure (p<0.001), degree of cure at the first and last time intervals (p<0.001), hardness (p<0.001), and post-abrasion roughness (p<0.05). The polymerization volumetric shrinkage ranged from 2.86% to 4.13%, with the highest shrinkage seen among the OBLs. Both Monomer elution from the OBLs was statistically significantly higher (p<0.001). Statistically significantly higher cytotoxicity combined with altered morphology and loss of confluence was detected in the cells exposed to extracts from the OBLs., Conclusions: The OBLs were in general outdone by the conventional composite., Clinical Significance: OBLs restorative materials have become pervasive in the dental market. Manufacturers often promise equal or better characteristics than existing brand-name composites, but at a lower price. Dentists are highly recommended to reconsider utilization of OBLs lacking sound scientific scrutiny, and our findings underscore this recommendation., (Copyright © 2016 Elsevier Ltd. All rights reserved.)

Objectives: To evaluate the effect of photoinitiators and reducing agents on cure efficiency and color stability of resin-based composites using different LED wavelengths., Methods: Model resin-based composites were associated with diphenyl(2,4,6-trimethylbenzoyl) phosphine oxide (TPO), phenylbis(2,4,6-trimethylbenzoyl) phosphine oxide (BAPO) or camphorquinone (CQ) associated with 2-(dimethylamino) ethyl methacrylate (DMAEMA), ethyl 4-(dimethyamino) benzoate (EDMAB) or 4-(N,N-dimethylamino) phenethyl alcohol (DMPOH). A narrow (Smartlite, Dentisply) and a broad spectrum (Bluephase G2, Ivoclar Vivadent) LEDs were used for photo-activation (20 J/cm(2)). Fourier transform infrared spectroscopy (FT-IR) was used to evaluate the cure efficiency for each composite, and CIELab parameters to evaluated color stability (ΔE00) after aging. The UV-vis absorption spectrophotometric analysis of each photoinitiator and reducing agent was determined. Data were analyzed using two-way ANOVA and Tukey's test for multiple comparisons (α=0.05)., Results: Higher cure efficiency was found for type-I photoinitiators photo-activated with a broad spectrum light, and for CQ-systems with a narrow band spectrum light, except when combined with an aliphatic amine (DMAEMA). Also, when combined with aromatic amines (EDMAB and DMPOH), similar cure efficiency with both wavelength LEDs was found. TPO had no cure efficiency when light-cured exclusively with a blue narrowband spectrum. CQ-systems presented higher color stability than type-I photoinitiators, especially when combined with DMPOH., Conclusions: After aging, CQ-based composites became more yellow and BAPO and TPO lighter and less yellow. However, CQ-systems presented higher color stability than type-I photoinitiators, as BAPO- and TPO-, despite their higher cure efficiency when photo-activated with corresponding wavelength range., Clinical Significance: Color matching is initially important, but color change over time will be one of the major reasons for replacing esthetic restorations; despite the less yellowing of these alternative photoinitiators, camphorquinone presented higher color stability., (Copyright © 2015 Elsevier Ltd. All rights reserved.)

Objectives: To evaluate the degree of conversion (DC%), water sorption (WS), solubility (SO) and the resin-dentin bonding stability (μTBS) of experimental (EXP) etch-and-rinse adhesive systems containing MMP-inhibitors: Galardin-GAL, Batimastat-BAT, GM1489-GM1 and chlorhexidine diacetate-CHX., Methods: DC% was measured using FT-IR spectroscopy, while WS and SO were calculated based on ISO4049. Thirty-six human molars were wet ground until the occlusal dentin was exposed. The adhesive systems were applied and resin composite buildups were incrementally constructed. After 24 h immersion in distilled water at 37 °C, the specimens were cut into resin-dentin beams with a cross-sectional area of 1 mm(2). The μTBS was evaluated after 24 h, 6 months and 12 months of water storage at 37 °C. Adper Single Bond 2 (SB2) was used as a commercial control. The data were analyzed using ANOVA and Tukey's HSD test., Results: SB2 presented the highest DC% (p<0.05). CHX presented the lowest WS (p<0.05). GM1, GAL and BAT presented similar WS when compared with SB2 (p>0.05). SO was found to be not significant (p>0.05). All adhesive systems maintained μTBS stability after 6 months of water storage. Only BAT, GM1 and CHX maintained μTBs stability after 12 months of water storage., Conclusions: The experimental adhesive systems with GM1489 and chlorhexidine diacetate presented the best physicochemical properties and preserved resin-dentin bonding stability after 12 months of water storage., Clinical Significance: GM1489 could be suitable for inclusion as an MMP-inhibitor in etch-and-rinse adhesive systems to maintain resin-dentin bonding stability over time., (Copyright © 2015. Published by Elsevier Ltd.)

Objectives: The aim of this study was to determine the degree of conversion (DC) and the monomer release of three composite types when employed following a layer- and bulk-filling technique., Methods: The release of monomers from a 'conventional paste-like' (Filtek Z250), a 'conventional flowable' (Filtek Supreme XTE Flowable) and a 'bulk-fill' flowable composite (Filtek Bulk Fill Flowable) from the same manufacturer (3M ESPE, Seefeld, Germany) was determined. Ten cylindrical specimens per composite were built, either in two 2-mm layers or in one 4-mm bulk. DC was measured at the specimen top and bottom surface using micro-Raman spectroscopy, after which the specimens were immersed in 2 ml absolute ethanol for 24 h at 37 °C. This solution was refreshed weekly during six weeks and the concentration of BisGMA, BisEMA(6), BisPMA, UDMA, TEGDMA and BPA was determined by liquid chromatography/mass spectroscopy., Results: DC at the specimen top and bottom was similar except for the bulk-fill technique, which resulted in significantly lower DC at the specimen bottom. The release of BisGMA and TEGDMA was initially very high, but rapidly dropped in the second week. In contrast, the release of BisPMA and UDMA increased initially, but then declined towards the sixth week. BisEMA(6) release was relatively steady over time. All composites released small amounts of BPA. The total monomer release was significantly lower for the layer- than the bulk-filling technique., Conclusions: The slightly reduced degree of conversion at 4-mm depth resulted in a higher monomer elution when the composite was applied following a bulk-fill application method., Clinical Significance: Applying a flowable and a bulk-fill composite following a bulk-fill application method resulted in a significantly reduced degree of conversion at the bottom of polymerized composite specimens when compared to a layer-application method. This reduced polymerization degree was reflected in significantly increased monomer release., (Copyright © 2015 Elsevier Ltd. All rights reserved.)

Objectives: To evaluate the effect of adhesion strategy on the enamel microshear bond strengths (μSBS), etching pattern, and in situ degree of conversion (DC) of seven universal adhesives., Methods: 84 extracted third molars were sectioned in four parts (buccal, lingual, proximal) and divided into 21 groups, according to the combination of the main factors adhesive (AdheSE Universal [ADU], All-Bond Universal [ABU], Clearfil Universal [CFU], Futurabond U [FBU], G-Bond Plus [GBP], Prime&Bond Elect (PBE), and Scotchbond Universal Adhesive [SBU]), and adhesion strategy (etch-and-rinse, active self-etch, and passive self-etch). Specimens were stored in water (37°C/24h) and tested at 1.0mm/min (μSBS). Enamel-resin interfaces were evaluated for DC using micro-Raman spectroscopy. The enamel-etching pattern was evaluated under a field-emission scanning electron microscope (direct and replica techniques). Data were analyzed with two-way ANOVA and Tukey's test (α=0.05)., Results: Active self-etch application increased μSBS and DC for five out of the seven universal adhesives when compared to passive application (p<0.001). A deeper enamel-etching pattern was observed for all universal adhesives in the etch-and-rinse strategy. A slight improvement in etching ability was observed in active self-etch application compared to that of passive self-etch application. Replicas of GBP and PBE applied in active self-etch mode displayed morphological features compatible with water droplets. The DC of GBP and PBE were not affected by the application/strategy mode., Conclusions: In light of the improved performance of universal adhesives when applied actively in SE mode, selective enamel etching with phosphoric acid may not be crucial for their adhesion to enamel., Clinical Significance: The active application of universal adhesives in self-etch mode may be a practical alternative to enamel etching in specific clinical situations., (Copyright © 2015 Elsevier Ltd. All rights reserved.)

Abstract: Objectives: To assess color stability and opacity associated with the degree of conversion of a pre-heated nanohybrid composite (Tetric N-Ceram, Ivoclar/Vivadent, Schaan, Liechtenstein). Methods: Twenty-seven specimens were prepared (n =9) using a Teflon matrix following storage of compules containing the composite at temperatures of 8°C, 25°C or 60°C. After photoactivation and polishing, baseline readings of six specimens were taken regarding their color and opacity (Spectrophotometer PCB 6807, Byk Gardner, Geretsried, Germany). Then, the specimens were submitted to artificial ageing for 384h (C-UV, Adexim Comexim, São Paulo, SP, Brazil), after which the final readings were taken. Three specimens for each temperature were submitted to analysis of degree of conversion (Nicolet 380, Thermo Scientific, Waltham, MA, USA). The results were analysed by 1-way ANOVA/Tukey (p <0.05). Results: There was no significant difference in color stability and opacity variation amongst the temperatures evaluated. The composite pre-heated at 60°C had a higher degree of conversion (65.13%), with statistically significant difference compared to the other temperatures (p <0.05). Conclusions: Composite pre-heating does not promote changes in the optical properties, despite the increase in the degree of conversion. [Copyright &y& Elsevier]