This in vitro study evaluated the influence of radiant exposure and material shade on the degree of conversion (DC) and microhardness of a resin-based composite (RBC). Sixty-four RBC specimens in shades A1E (enamel) and A4D (dentin) were light cured at a calibrated exitance of 1000 mW/cm2 for 5, 10, 15, or 20 seconds, resulting in radiant exposure levels of 5, 10, 15, or 20 J/cm2. The DC was determined using Fourier-transform infrared spectroscopy (n = 3 per shade per exposure level). The Knoop hardness number (KHN) was measured on the top and bottom surfaces of each specimen (n = 5 per shade per exposure level). Data were analyzed using 2- and 3-way analyses of variance and post hoc Tukey tests (α = 0.05). The RBC shade did not affect the DC (P = 0.860), and the lowest DC values were achieved with an exposure level of 5 J/cm2 (P < 0.001). The shade did not affect the KHN on the top surface, but the radiant exposure level did, with the application of 5 J/cm2 resulting in significantly lower values (P < 0.05). For the bottom surface, shade A1E showed significantly higher KHN values than A4D (P < 0.001). An increase in the radiant exposure led to increased DC and KHN for both shades of RBC until reaching a saturation point of 10 J/cm2 for A1E and the top surface of A4D. The darker and more opaque shade was not adequately polymerized at a 2-mm depth, even when the highest radiant exposure level was applied.

OBJECTIVE: 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.
CONCLUSIONS: 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.

OBJECTIVE: The first aim of this study was to determine whether there is a difference in degree of conversion (DC) of touch-cure cements polymerized by self-curing with adhesive or dual-curing under reduced light. The second aim was to compare interfacial adaptation of zirconia restoration cemented using touch-cure cements self-cured or dual-cured by reduced light.
METHODS: The DC of touch-cure resin cements with adhesive was measured continuously using Fourier transform infrared spectrometry. Experimental groups differed depending on touch-cure cement. Each group had three subgroups of polymerization method. For subgroup 1, the DC was measured by self-curing. For subgroups 2 and 3, the DCs were measured by dual-curing with reduced light penetrating 3 mm and 1 mm zirconia blocks, respectively. For interfacial adaptation evaluation, Class I cavity was prepared on an extracted third molar, and zirconia restoration was fabricated. The restoration was cemented using the same cement. Groups and subgroups for interfacial adaptation were the same as those of the DC measurement. After thermo-cycling, interfacial adaptation at the tooth-restoration interface was evaluated using swept-source optical coherence tomography imaging.
RESULTS: The DC of touch-cure cement differed depending on the measurement time, resin cement, and polymerization method (p < 0.05). Interfacial adaptation was different depending on the resin cement and polymerization method (p < 0.05).
CONCLUSIONS: For touch-cure cement, light-curing with higher irradiance presented a higher DC and superior interfacial adaptation than light-curing with lower irradiance or self-curing.
CONCLUSIONS: Although some adhesives accelerate the self-curing of touch-cure cement, light-curing for touch-cure cement is necessary for zirconia cementation.

Aim: To prepare experimental adhesive (EA) with 1% and without chitosan nanoparticles on dentin conditioned with a conventional technique phosphoric acid (PA) compared with two different contemporary techniques: photodynamic therapy (PDT) and femtosecond laser (FSL). Method: The methodology consisted of synthesis of EA and 1% chitosan-modified adhesive (CMA). Scanning electron microscopy, dentin adhesive interface assessment, energy-dispersive spectroscopy, shear bond strength (SBS), degree of conversion (DC), and bond failure were assessed. Teeth were selected, disinfected, and mounted in acrylic up to the cementoenamel junction. Occlusal enamel was removed and teeth were randomly allocated into groups and conditioned. These included Group 1: samples treated with PA; Group 2: specimens conditioned with methylene blue photosensitizer (MBP) activated by PDT; and Group 3: samples conditioned with FSL. Following different conditioning regimes, specimens were bonded using 1% CMA and EA. The composite buildup was followed by SBS testing and a bond failure assessment. DC was assessed for both EA and CMA. Analysis of variance and Tukey\'s post hoc test were used to compare the mean and standard deviation of SBS and DC in different experimental groups, with a significance level of p < 0.05. Results: Dentin pretreated with etch and rinse demonstrated the highest bond strength with 1% CMA. Dentin conditioned with MBP activated by PDT and bonded to EA showed the lowest bond scores. Overall SBS values of 1% CMA were better than EA irrespective of the conditioning regime of dentin. The DC was higher in EA adhesive. This was followed by DC in 1% CMA. DC in EA was found to be comparable with 1% CMA. Conclusions: PA remains the gold standard for dentin conditioning. The incorporation of 1% chitosan in adhesive improves SBS and results in no change in DC. The use of FSL in dentin conditioning can be used as an alternative approach as it results in SBS within acceptable limits. The study was approved by the ethical board of King Saud University.

OBJECTIVE: The main aim of the present study was to carry out a scoping review on the differences in degree of conversion of monomers regarding several types resin cements, indirect restorative materials, and light-curing procedures used in dentistry.
METHODS: A bibliographic review was performed on PubMed using the following search items: \"degree of conversion\" OR \"filler\" AND \"resin cement\" OR \"inorganic cement\" AND \"organic\" OR \"radiopacity\" OR \"refractive\" OR \"transmittance\" OR \"type\" AND \"resin composite.\" The search involved articles published in English language within the last thirteen years. A research question has been formulated following the PICO approach as follow: \"How different is the degree of conversion of monomers comparing several types of resin-matrix cements?\".
RESULTS: Within the 15 selected studies, 8 studies reported a high degree of conversion (DC) of the organic matrix ranging from 70 up to 90% while 7 studies showed lower DC values. Dual-cured resin-matrix cements revealed the highest mean values of DC, flexural strength, and hardness when compared with light- and self-polymerized ones. DC mean values of resin-matrix cements light-cured through a ceramic veneer with 0.4 mm thickness were higher (~ 83%) than those recorded for resin-matrix cements light-cured through a thicker ceramic layer of 1.5 mm (~ 77%).
CONCLUSIONS: The highest percentage of degree of conversion of monomers was reported for dual-cured resin-matrix cements and therefore both chemical and light-induced pathways promoted an enhanced polymerization of the material. Similar degree of conversion of the same resin-matrix cement were recorded when the prosthetic structure showed a low thickness. On thick prosthetic structures, translucent materials are required to allow the light transmission achieving the resin-matrix cement.
CONCLUSIONS: The chemical composition of resin-matrix cements and the light-curing mode can affect the polymerization of the organic matrix. Thus, physical properties of the materials can vary leading to early clinical failures at restorative interfaces. Thus, the analysis of the polymerization pathways of resin-matrix cements is significantly beneficial for the clinical performance of the restorative interfaces.

Although self-adhesive resin cements are convenient and less technique-sensitive materials for dental clinicians, they exhibit a lower degree of conversion due to acidic components in their composition. Supplementation of the initiator, accelerator, and activator in self-adhesive resin cements has been suggested to compensate for the lower degree of conversion. This study aimed to evaluate the effects of different combinations of self-curing initiators, self-curing activators, and accelerators on the degree of conversion (DC) of self-adhesive resin cements. A dual-cured self-adhesive resin was prepared using six combinations of initiators, activators, and accelerators. The change in the DC over time was evaluated with and without light curing. The film thickness, flow properties, and cytotoxicity of each formulation were assessed. The results showed that all supplemental components had an effect on increasing the DC, but a greater increase in the DC was observed in the following order: activator, accelerator, and initiator. The cytotoxicity of the resin cements was related to the DC values, as resin cements with lower DC values exhibited higher cytotoxicity. The film thickness met the ISO standards for all groups. The results suggest that utilizing an activator is the most effective approach to enhance the DC in self-adhesive resin cement and that cytotoxicity tended to increase with lower DC values, whereas film thickness and flow properties demonstrated no correlation with DC values.

Assessment of the antimicrobial, micro tensile bond strength (μTBS), and degree of conversion (DC) of fifth-generation adhesive modified using photoactivated 0.5% rose bengal (RB) and photoactivated RB-doped titanium dioxide nanoparticles (TiO2NPs) in different concentrations (2% and 5%) as compared with the unmodified adhesive bonded to the carious affected dentin (CAD). Forty mandibular molars with caries progression up to the middle third of the dentin, as per the International Caries Detection and Assessment System (ICDAS) score of 4 and 5 were included. Specimens were divided into four groups based on etch and rinse adhesive (ERA) modification group 1: unmodified ERA, group 2: photoactivated 0.5% RB photosensitizer (PS) modified ERA, group 3: photoactivated RB-doped 2 wt% TiO2NPs adhesive, group 4: photoactivated RB-doped 5 wt% TiO2NPs adhesive. Followed by adhesive and composite restoration on the CAD surface. All the specimens were thermocycled and an assessment of μTBS and failure pattern analysis was performed. The antibacterial potency of RB and RB-doped TiO2NPs (2% and 5%) followed by their activation using visible light against Streptococcus mutans (S.mutans) were tested. The survival rate of S.mutans was assessed using the Kruskal-Wallis test. The analysis of μTBS involved the use of ANOVA, followed by a post-hoc Tukey honestly significant difference (HSD) multiple comparisons test. Group 1 (Unmodified ERA) (0.52 ± 0.31 CFU/mL) treated samples unveiled the highest means of bacterial survival and lowest μTBS (11.32 ± 0.63 MPa). Nevertheless, group 4: photoactivated RB-doped 5 wt% TiO2NPs adhesive displayed the lowest outcomes of S.mutans survival (0.11 ± 0.02 CFU/mL) and highest bond strength (18.76 ± 1.45 MPa). The photoactivated RB-doped 2 wt% TiO2NPs in adhesive demonstrated promising enhancements in both μTBS and antibacterial efficacy against S.mutans. However, it is noteworthy that this modification led to a decrease in the DC of the adhesive. RESEARCH HIGHLIGHTS: Unmodified ERA-treated samples unveiled the highest bacterial survival and the lowest μTBS. Photoactivated RB-doped 5 wt% TiO2NPs adhesive displayed the lowest S.mutans survival rate and highest bond strength. DC decreased with an increase in concentration of TiO2.

With the purpose of further reducing surface free energy to achieve better anti-bacterial adhesion effect of fluorinated dimethacrylate (FDMA)/tricyclo (5.2.1.0) decanedimethanol diacrylate (SR833s) based dental resin composites (DS), 1H,1H-heptafluorobutyl methacrylate (FBMA) was used to partially replace SR933s as reactive diluent. According to the degree of substitution, the obtained resin composites were marked as DSF-1 (20 wt.% of SR833s was replaced by FBMA), DSF-2 (40 wt.% of SR833s was replaced by FBMA), and DSF-3 (60 wt.% of SR833s was replaced by FBMA). Bisphenol A glycidyl dimethacrylate (Bis-GMA)/triethylene glycol dimethacrylate (TEGDMA) based resin composite (BT) was used as control. The influence of FBMA concentration on double bond conversion (DC), contact angle, surface free energy, anti-bacterial adhesion effect against Streptococcus mutans (S. mutans), volumetric shrinkage (VS) and shrinkage stress (SS), flexural strength (FS) and modulus (FM), water sorption (WS) and solubility (SL) were investigated. The results showed that FBMA addition could reduce surface free energy from 44.6 mN/m for DS to 32.9 mN/m for DSF-3, and lead to better anti-bacterial adhesion effect (the amounts of adherent bacteria decreased from 2.03 × 105 CFU/mm2 for DS to 6.44 × 104 CFU/mm2 for DSF-3). The FBMA had no negative effects on DC, VS, SS, WS, and SL. Too high a concentration of FBMA reduced FS and FM before water immersion, but the values were still higher than those of BT.

UNASSIGNED: Recently, a group of universal single-shade resin-based composites (RBCs) has been developed to simplify the process of shade selection. Excellent mechanical and physical properties are crucial for the ultimate success and clinical longevity of restorations. Therefore, evaluating the properties of the single-shaded RBCs is imperative. This study aimed to determine the flexural strength (FS) and degree of conversion (DC) of universal single-shade RBCs.
UNASSIGNED: In this study, four commercial RBCs were used; three universal single-shade RBCs; Omnichroma (OC), Charisma® Diamond ONE (CD), and Vittra APS Unique (VU), and a conventional nanohybrid composite Filtek™ Z250 XT (FT) which was used as a control. Sixty composite beams and 40 composite discs were used for FS and DC, respectively. A universal test machine with a three-point bending test was used to measure the FS, whereas the DC was measured using a Fourier-transform infrared spectrometer (FTIR). Three fractured specimens from each resin composite group were qualitatively analyzed using scanning electron microscopy.
UNASSIGNED: ANOVA was used to compare the mean values of FS and DC among the four RBCs (OC, CD, VU, and FT). Highly significant differences were observed in the mean FS and DC values (F = 673.043, p < 0.001 and F (=782.4, p < 0.0001), respectively. The highest FS was observed in the CD group, followed by FT and VU groups; the lowest value was observed in the OC group. In addition, a statistically significant difference was identified in DC values. The highest DC value was observed in VU, followed by OC and CD, and the lowest DC value was observed in FT.
UNASSIGNED: Universal single-shade RBCs demonstrated a good FS, except for OC, which exhibited a significantly low FS. The DC of the universal single-shade RBCs was higher than that of the conventional nanohybrid composite restorative material.

OBJECTIVE: This study investigated the influence of photoinitiator types on degree of conversion (DC), rate of polymerization (RP), flexural strength (FS), flexural modulus (FM), and light transmittance (LT) of filled and unfilled light-curable resin cements through different thicknesses and shades of lithium disilicate ceramics.
METHODS: Lithium disilicate ceramic discs (IPS Emax Press, background [0.0], 0.5, 1.0, 2.0, 3.0, and 4.0 mm, shades A1 and BL3) were prepared. Experimental resin-based cements [TEGDMA/BisGMA (50/50 mass%)] were prepared using either camphorquinone (CQ)/amine (0.44/1.85 mol%) or TPO (0.44 mol%)], and a micro and nanofiller loads of nil (unfilled); 40/10 mass%; and 50/10 mass%). Resin cements (0.2 mm thick) were placed on the lower surface of the ceramic specimens and light-activated for 30 s from the upper surface using a Bluephase Style curing light (exitance at tip: 1236 mW/cm2 ± 1.20). LT and distribution of irradiance through the ceramics were measured using a UV-vis spectrometer and a beam profile camera, respectively (n = 3). The DC and RP were measured in real-time using mid infrared spectroscopy in attenuated total reflectance (ATR) mode (n = 3). FS and FM were measured using a universal testing machine (n = 5). Statistical analyses were performed on LT, DC, RP, FS, and FM data using a general linear model, and supplementary ANOVA and post hoc Tukey multiple comparison test were also performed (α = .05).
RESULTS: Thicknesses, shades, photoinitiator type, and fillers load significantly influenced the optical and mechanical characteristics of the resin-based materials (p < 0.05). The BL3 shade ceramic provided higher values of DC, RP, FS, FM, and LT compared with the A1 shade (p < 0.05). Increasing ceramic thickness decreased the properties of the resin-based materials (p < 0.05). Generally, TPO improved mechanical properties of the resin cement compared with CQ (p < 0.05).
CONCLUSIONS: The luting process of indirect restorations may be improved by using high molar absorptivity, more reactive, and more efficient photoinitiators such as TPO, as opposed to conventional CQ. The use of such initiator may allow the placement of thicker and more opaque indirect restorations.