Effect of water glass treatment for zirconia and silane coupling on bond strength of resin cement.

OBJECTIVE: To evaluate the ability of the water glass treatment to penetrate zirconia and improve the bond strength of resin cement. MATERIAL AND METHODS: Water glass was applied to zirconia specimens, which were then sintered. The specimens were divided into water-glass-treated and untreated zirconia (control) groups. The surface properties of the water-glass-treated specimens were evaluated using surface roughness and electron probe micro-analyser (EPMA) analysis. A resin cement was used to evaluate the tensile bond strength, with2 and without a silane-containing primer. After 24 h in water storage at 37 °C and thermal cycling, the bond strengths were statistically evaluated with t-test, and the fracture surfaces were observed using SEM. RESULTS: The water glass treatment slightly increased the surface roughness of the zirconia specimens, and the EPMA analysis detected the water glass penetration to be 50 µm below the zirconia surface. The application of primer improved the tensile bond strength in all groups. After 24 h, the water-glass-treated zirconia exhibited a tensile strength of 24.8 ± 5.5 MPa, which was significantly higher than that of the control zirconia (17.6 ± 3.5 MPa) (p < 0.05). After thermal cycling, the water-glass-treated zirconia showed significantly higher tensile strength than the control zirconia. The fracture surface morphology was mainly an adhesive pattern, whereas resin cement residue was occasionally detected on the water-glass-treated zirconia surfaces. CONCLUSION: The water glass treatment resulted in the formation of a stable silica phase on the zirconia surface. This process enabled silane coupling to the zirconia and improved the adhesion of the resin cement.

Factors associated with viral RNA shedding and evaluation of potential viral infectivity at returning to school in influenza outpatients after treatment with baloxavir marboxil and neuraminidase inhibitors during 2013/2014-2019/2020 seasons in Japan: an observational study.

BACKGROUND: This study assessed the differences in daily virus reduction and the residual infectivity after the recommended home stay period in Japan in patients infected with influenza and treated with baloxavir (BA), laninamivir (LA), oseltamivir (OS), and zanamivir (ZA). METHODS: We conducted an observational study on children and adults at 13 outpatient clinics in 11 prefectures in Japan during seven influenza seasons from 2013/2014 to 2019/2020. Virus samples were collected twice from influenza rapid test-positive patients at the first and second visit 4-5 days after the start of treatment. The viral RNA shedding was quantified using quantitative RT-PCR. Neuraminidase (NA) and polymerase acidic (PA) variant viruses that reduce susceptibility to NA inhibitors and BA, respectively, were screened using RT-PCR and genetic sequencing. Daily estimated viral reduction was evaluated using univariate and multivariate analyses for the factors such as age, treatment, vaccination status, or the emergence of PA or NA variants. The potential infectivity of the viral RNA shedding at the second visit samples was determined using the Receiver Operator Curve based on the positivity of virus isolation. RESULTS: Among 518 patients, 465 (80.0%) and 116 (20.0%) were infected with influenza A (189 with BA, 58 with LA, 181 with OS, 37 with ZA) and influenza B (39 with BA, 10 with LA, 52 with OS, 15 with ZA). The emergence of 21 PA variants in influenza A was detected after BA treatment, but NA variants were not detected after NAIs treatment. Multiple linear regression analysis showed that the daily viral RNA shedding reduction in patients was slower in the two NAIs (OS and LA) than in BA, influenza B infection, aged 0-5 years, or the emergence of PA variants. The residual viral RNA shedding potentially infectious was detected in approximately 10-30% of the patients aged 6-18 years after five days of onset. CONCLUSIONS: Viral clearance differed by age, type of influenza, choice of treatment, and susceptibility to BA. Additionally, the recommended homestay period in Japan seemed insufficient, but reduced viral spread to some extent since most school-age patients became non-infectious after 5 days of onset.

The bleaching effect of office bleaching agents containing S-PRG filler evaluated by pH value and electron spin resonance.

OBJECTIVES: Surface reaction-type pre-reacted glass-ionomer (S-PRG) filler releases six types of ions with a neutralizing ability. This study evaluated the effect of S-PRG filler incorporation in an H2O2-based bleaching material on the bleaching efficacy, pH, and reaction state. MATERIALS AND METHODS: The experimental bleaching material was formulated by the addition of 5% or 10% S-PRG fillers to the powder part. The stained bovine teeth were treated with the prepared bleaching paste. Commission internationale de l'éclairage (CIE) L*a*b* color space values were recorded before and after bleaching, and the color difference (ΔE) and whiteness index (WID) were calculated. Moreover, the used bleaching formulations were assessed for their pH values and reaction state by evaluating the oxidation state of manganese (Mn+2) using electron spin resonance (ESR). RESULTS: The results of ΔE and WID showed that the addition of S-PRG filler increased the bleaching effect, but there was no significant difference between the groups with 5% and 10% S-PRG filler. A significant increase in pH in S-PRG filler groups (5% pH 6.7, 10% pH 6.8) was found compared to the 0% group (pH 4.8). ESR measurements showed that the signal emitted from Mn+2 decreased over time. The S-PRG filler groups showed a significantly higher reduction in Mn+2 compared to the 0% group, with no significant difference between the 5% and 10% S-PRG groups. CONCLUSIONS: S-PRG filler addition resulted in improved bleaching efficacy, higher reaction rate, and pH values that are close to neutral. CLINICAL RELEVANCE: S-PRG filler addition may be effective on the bleaching outcome of H2O2-based materials.

In vitro performance of an autocured universal adhesive system in bonding to dentin.

BACKGROUND: The successful integration of resin-based dental adhesives significantly impacts restorative dentistry, providing efficient and aesthetically pleasing caries treatments. Among various adhesives, one-step self-etching adhesives (1-SEAs) have gained popularity due to their simplicity and short application time. However, concerns have been raised regarding their bonding performance and marginal adaptation characteristics, which differ from two-step self-etching adhesives (2-SEAs) and three-step etch-and-rinse adhesives. Additionally, light-cured bonding materials may encounter challenges in deep cavities and inaccessible areas, necessitating extended light irradiation time. Autocured bonding materials are a potential solution, but limited comparative studies have been conducted on their performance. METHODS: In this in vitro study, we evaluated a new autocured universal bonding material (Bondmer Lightless 2) and compared the results with recent light-cured bonding materials. Microshear bond strength (µSBS) tests were performed on 25 human molars using five different combinations of adhesives and composite resins: Bondmer Lightless 2 with Estelite Bulk Fill Flow (BE group), Bondmer Lightless 2 with a prototype composite resin (BO group), Prime&Bond Universal with SDR flow + (PS group), Scotchbond Universal with Filtek Bulk Fill (SF group), and G-Premio Bond with Gracefil BulkFlo (GG group). The bond strengths and failure modes were assessed using a universal testing machine and scanning electron microscope (SEM), respectively. Marginal adaptation was evaluated using swept-source optical coherence tomography (SS-OCT) and confocal laser scanning microscopy (CLSM) on 40 sound bovine maxillary incisors. RESULTS: The µSBS test showed no significant differences in bond strength among the tested groups. Most failure modes were observed at the bond interface between the adhesive and the dentin. The autocured bonding material demonstrated significantly higher marginal adaptation (SI%) than PS, SF, and GG. The CLSM images corresponded with gaps observed in the SS-OCT images, indicating improved marginal sealing in the autocured group. CONCLUSIONS: The new autocured universal bonding material exhibited comparable bond strength to a conventional light-cured material while demonstrating a superior marginal adaptation level. This finding suggested that the autocured material could be a valuable alternative, especially when extended light irradiation would pose a challenge. Further clinical studies would be warranted to evaluate the performance of the autocured bonding material in actual restorative dental practice.

Optical Coherence Tomography for Patients with Developmental Disabilities: A Preliminary Study.

Dental radiographs are essential for diagnosis and treatment planning, but are sometimes difficult to acquire for patients with developmental disabilities (PDD). Optical Coherence Tomography (OCT) is a non-ionizing imaging modality that has the potential application as an alternative to dental radiographs for PDD. This study aimed to determine the feasibility of intraoral OCT imaging for PDD. Ten participants were recruited in the Dental Education in the Care of Persons with Disabilities (DECOD) Clinic to explore the utility of dental OCT. The prototype system (Yoshida Dental) creates in-depth and three-dimensional images of teeth. The participants indicated their degree of pain during imaging on the Wong-Baker FACES Pain Rating Scale, and the degree of discomfort after imaging on a visual analog scale. OCT can be used for patients with developmental disabilities with minimal levels of pain and discomfort, without ionizing radiation.

Favorable outcome of retreatment by direct-acting antivirals for hepatitis C patients with daclatasvir plus asunaprevir combination therapy failure.

AIM: In patients with hepatitis C virus, treatment failure of daclatasvir plus asunaprevir combination therapy (DCV + ASV) seems to become intractable due to the induction of resistance-associated substitutions. This study aimed to investigate the outcomes of retreatment with direct-acting antivirals (DAAs) in patients with DCV + ASV therapy failure, as well as changes in drug resistance mutations. METHODS: We retrospectively analyzed 44 patients re-treated with DAAs after DCV + ASV failure between December 2015 and April 2018. All patients were analyzed for amino acid substitutions, and additional treatment regimens were selected based on the results and current treatment guidelines. RESULTS: The sustained virological response rate with second-line treatment was 81.8% (36/44), and relapse occurred in five of 16 patients who received sofosbuvir/ledipasvir and three of seven patients who received DCV/ASV/beclabuvir. Third- and fourth-line treatments were also tried in relapsed cases, and the overall sustained virological response rates were 90.9% (40/44) and 93.2% (41/44), respectively. A high rate of viral clearance was eventually observed. Before second-line treatment, the prevalence of mutations in the NS5A and NS3/4A regions was 100% (44/44) and 86.4% (38/44), respectively. There was no significant increase in the number of amino acid substitutions in patients for whom second-line treatment failed. CONCLUSIONS: Amino acid substitutions were frequently observed in patients with DCV + ASV failure, but most patients achieved a sustained virological response after retreatment with DAAs. Although the spread of drug-resistant viruses due to unsuccessful DAA treatment was a matter of concern, most cases of DCV + ASV failure were overcome with additional treatment.

Analyses of objective response rate, progression-free survival, and adverse events in hepatocellular carcinoma patients treated with lenvatinib: A multicenter retrospective study.

AIM: The aim of this study was to investigate the predictive factors of objective response rate (ORR) and progression-free survival (PFS), and the correlation of albumin-bilirubin (ALBI) grade with decreased appetite and fatigue in hepatocellular carcinoma patients treated with lenvatinib. METHODS: From March 2018 to December 2018, a total of 94 patients was included in this retrospective multicenter study. RESULTS: The median age of all patients was 73 years (interquartile range 66-79.3 years), and approximately 78% patients were men. The ALBI grade was 1, 2, and 3 in 27 (28.7%), 64 (68.1%), and three patients (3.2%), respectively. The Barcelona Clinic Liver Cancer stage was early, intermediate, and advanced in one (1.1%), 22 (23.4%), and 71 patients (75.5%), respectively. Best radiological response was determined to complete response, partial response, stable disease, and progressive disease in 0 (0.0%), 24 (30.4%), 38 (48.1%), and 17 patients (21.5%), respectively, giving the ORR of 30.4%. The 3-, 6-, and 12-month PFS was calculated to be 78.7% (95% CI 70.3-87.1%), 46.7% (95% CI 36.1-57.3%), and 17.4% (95% CI 6.6-28.2%). Multivariate analysis showed that the Barcelona Clinic Liver Cancer intermediate stage was shown to be the only significant factor affecting the ORR (odds ratio 3.78, 95% CI 1.14-12.5, P = 0.030) and PFS (hazard ratio 0.49, 95% CI 0.26-0.94, P = 0.030). The incidence of all grades of decreased appetite and fatigue was significantly less in patients with ALBI grade 1 compared with ALBI grade 2 + 3. CONCLUSIONS: The Barcelona Clinic Liver Cancer intermediate stage was the predictive factor affecting the ORR and PFS, and ALBI grade was a good predictive factor affecting the incidence of fatigue and decreased appetite.

Diagnosis of Occlusal Tooth Wear Using 3D Imaging of Optical Coherence Tomography Ex Vivo.

The aim of this study was to assess the utility of 3D imaging of optical coherence tomography (OCT) for the diagnosis of occlusal tooth wear ex vivo. Sixty-three extracted human molars with or without visible tooth wear were collected to take digital intraoral radiography and 3D OCT images. The degree of tooth wear was evaluated by 12 examiners and scored using 4-rank scale: 1-slight enamel wear; 2-distinct enamel wear; 3-tooth wear with slight dentin exposure; 4-tooth wear with distinct involvement of dentin. The degree of tooth wear was validated by the histological view of confocal laser scanning microscopy (CLSM). The sensitivity, specificity, and area under the curve (AUC) of receiver operating characteristic analysis were calculated. Diagnostic accuracy was compared with the agreement with CLSM observation using weighted kappa. The results were statistically analyzed at a significance level of α = 0.05. Three-dimensional OCT showed significantly higher sensitivity (p < 0.05) for all the diagnostic thresholds of enamel wear and dentin exposure than digital radiography (0.82, 0.85, and 0.79 vs. 0.56, 0.52, and 0.57, respectively). Three-dimensional OCT showed higher AUC and kappa coefficients than digital radiography (p < 0.05), where mean AUC and Kappa values were 0.95 and 0.76 for OCT and 0.92 and 0.47 for radiography, respectively. No significant difference of specificity was observed (p > 0.05). Three-dimensional OCT could visualize and estimate the degree of tooth wear and detect the dentin exposure at the tooth wear surface accurately and reproducibly. Consequently, a new guideline for tooth wear assessment can be proposed using OCT.

Diagnosis of Occlusal Caries with Dynamic Slicing of 3D Optical Coherence Tomography Images.

Detecting the extent of occlusal caries is a clinically important but challenging task required for treatment decision making. The aim of this study was to assess the diagnostic power of 3D swept-source optical coherence tomography (OCT) for evaluation of occlusal caries in comparison with X-ray radiography. Extracted human molars not exhibiting American Dental Association (ADA) criteria advanced caries were mounted in a silicone block and digital dental radiographs were captured from the buccal side. Subsequently, occlusal surfaces were scanned with a prototype Yoshida Dental OCT. Thirteen examiners evaluated the presence and extent of caries on radiographs and dynamically sliced 3D OCT video images, using a 4 level scale-0: intact; 1: enamel demineralization without cavitation; 2: enamel caries with cavitation; 3: dentin caries with or without cavitation. Sensitivity, specificity and area under operating characteristic curves (Az) were statistically analyzed (α = 0.05). Reliability analysis showed an excellent agreement among the 13 examiners for both methods. The OCT presented a significantly higher sensitivity and Az value for the detection of caries compared to radiographs (p < 0.05). Radiography showed especially low sensitivity for dentin caries (0-2 versus 3). Dynamic slicing of 3D OCT volumes is a powerful adjunct tool to visual inspection to diagnose the dentin occlusal caries in vitro.

Effect of lights with various wavelengths on bleaching by 30% hydrogen peroxide.

The objective of this study was to evaluate the bleaching effect of light sources with various wavelengths using 30% hydrogen peroxide (HP) in vitro. The hematoporphyrin-stained paper was bleached with HP and irradiated for 10 min using LED light sources with 265, 310, 365, 405, or 450 nm respectively. In control group, HP was applied for 10 min without light irradiation. The bleaching procedure was repeated two times. The L*a*b* values of the samples before bleaching and after each bleaching step were measured using a colorimeter. Color changes of specimens were then calculated and statistically analyzed. There was an interaction between light sources and time of irradiation in the color change (p < 0.05). Time and light sources significantly affected ΔE and ΔL (p < 0.05). The light source of 256 nm showed the highest bleaching effect over time followed by that of 310 nm, which were statistically different from other groups (p < 0.001). The 365 nm, 450 nm groups, and control group showed low bleaching effect visually with no significant differences in ΔE and ΔL (p > 0.05). It was concluded that the wavelengths of the light sources affected the bleaching by HP. The 310-nm light can be a potential source for bleaching.

Effects of UVB and UVC irradiation on cariogenic bacteria in vitro.

The aim of this study was to evaluate the bactericidal effect of ultraviolet (UV) light at 265-nm (UVC) and 310-nm (UVB) wavelengths from a newly developed UV light-emitting diode (LED) device against cariogenic bacteria in vitro. Suspensions of Streptococcus mutans (S. mutans) and Streptococcus sobrinus were directly irradiated by UVB or UVC for 2.5 min or 5 min. Numbers of colonies were counted and calculated as colony forming units (CFU) per milliliter. Fluorescence microscopy (FM) and optical density measurements at 490 nm (OD490) were also taken after irradiation. In addition, the bactericidal effects of irradiation against S. mutans under 0.5 mm-thick dentin were compared using culture tests and OD490 measurements. Direct UV-LED irradiation with both UVB and UVC showed strong bactericidal effects. UVB showed superior bactericidal effect through 0.5-mm-thick dentin than did UVC, especially after demineralization. These results suggest that UVB irradiation could be utilized for the prevention and management of dental caries.

Remineralization capacity of carious and non-carious white spot lesions: clinical evaluation using ICDAS and SS-OCT.

OBJECTIVES: To assess the remineralization capacity of carious, non-carious, and combined white spot lesions (WSLs) using the ICDAS and SS-OCT. MATERIALS AND METHODS: This clinical trial was based on a quasi-experimental design. Forty-two healthy subjects (median age 26.6 years), who visited university hospital and had at least one WSL with an ICDAS score of 2 or 1, were recruited. The subjects chewed a non-blind sugar-free gum containing bioavailable calcium and fluoride for 3 months. The remineralization capacities of carious and non-carious 121 WSLs were assessed using ICDAS by two calibrated non-blind examiners and optical boundary depth (BD) by SS-OCT at a monthly recall. The outcome variables, transitions of ICDAS score, mean BD, and mean BD recovery rate (RR%), were statistically analyzed using the chi-square test, two way-repeated measures ANOVA, and Wilcoxon rank sum test, respectively (alpha = 0.05). RESULTS: Based on the visual inspection, OCT images at the baseline, 72 WSLs were purely carious, 20 were non-carious (developmental) lesions, while 29 were combined (carious-developmental). The responses of WSLs over time showed to be highly variable. There was a significant difference in transitions of ICDAS scores after 3 months between carious and non-carious WSLs (p < 0.05) and non-carious and combined WSLs (p < 0.05). Carious and combined WSLs underwent significant changes in the mean BD between baseline (161.8 ± 56.8 µm) and 2 months (130.7 ± 57.4 µm) or 3 months (119.1 ± 57.5 µm) (p < 0.05), while there was no significant difference between baseline (132.2 ± 26.2 µm) and 2 months (122.8 ± 24.1 µm) or 3 months (119.8 ± 22.6 µm) in non-carious WSLs (p > 0.05). There was a significant difference in mean RR% after 2 and 3 months between carious and non-carious WSLs (p < 0.05). CONCLUSIONS: The remineralization capacity of WSL was variable among the cases and subjects, and depended on the WSLs history, etiology (carious, non-carious, or combined lesion) and structure (histological pattern). CLINICAL RELEVANCE: Carious WSLs showed the highest remineralization potential.

Dental cements: Bioactivity, bond strength and demineralization progression around restorations.

PURPOSE: To evaluate demineralization progression around indirect restorations placed with various cements using swept-source optical coherence tomography (OCT) and microshear bond strength (MSBS) to enamel and dentin. METHODS: Resin inlays in cervical preparations (4×2 mm) were luted with two glass ionomer luting cements, Fuji I (FI) and RelyX Luting Cement (RL) and two adhesive cements, Adshield RM (AD) and RelyX Unicem 2 (UC). After 7-day artificial saliva incubation and 10,000 thermal cycles, specimens were demineralized (pH 4.5). Lesion progression at enamel and dentin margins was measured on OCT images after 1, 3 and 5 weeks demineralization (n= 8). RESULTS: Repeated-measures ANOVA showed that demineralization period, cement type, and their interaction had a significant effect on lesion size in both substrates (P< 0.001). Enamel lesion progression was slower in RL, FI and AD, and was significantly different from UC and control (P< 0.001). RL dentin lesions were significantly different from FI and AD lesions (P< 0.05), which in turn were significantly different than UC and control lesions (P< 0.001). MSBS means of AD and UC were significantly higher than those of FI and RL (P< 0.001). CLINICAL SIGNIFICANCE: A bioactive cement combining bioavailable calcium, functional monomer and glass-ionomer formulations showed better lesion progression inhibition around restorations than the adhesive resin cement, and higher bond strength than the resin-modified and conventional glass-ionomer cements.

Assessment of Self-Adhesive Resin Composites: Nondestructive Imaging of Resin-Dentin Interfacial Adaptation and Shear Bond Strength.

Shear bond strength (SBS) and the interfacial adaptation (IA) of self-adhesive resin (SAR) composites to dentin were evaluated. Two SARs [Vertise Flow (VTF) and Fusio Liquid Dentin (FLD)] were evaluated and compared with a conventional restorative system [adhesive: OptiBond FL and composite: Herculite Précis (OBF/HP)]. Human third molars were used for SBS testing and IA imaging (n=7) using optical coherence tomography (OCT). Flattened dentin disks were prepared and the composites were applied into molds (2.4 mm diameter) that were positioned on dentin. Samples were subjected to SBS testing and OCT analysis, which considered an increase in signal intensity at the bonded interface as evidence of internal gaps. SBS data were analyzed by one-way analysis of variance and Tukey's test and IA data (% distribution of high brightness values) by Kruskal-Wallis and Dunn's test (p≤0.05). No statistically significant difference in SBS was observed between VTF (13.9±3.6 MPa) and FLD (11.3±3.2 MPa), whereas OBF/HP showed higher average strength (27.3±6.1 MPa). However, there was a statistically significant difference in IA when VTF (33.3%) was compared with FLD (1.2%) and OBF/HP (1.5%). The conventional restorative system exhibited superior SBS performance compared with SARs. However, the IA of FLD to dentin had values that were not significantly different from OBF/HP.

Characterization of transparent dentin in attrited teeth using optical coherence tomography.

Attrition and wear of tooth surface occur with aging and result in loss of enamel, with exposure and histological changes in dentin. Dealing with attrited teeth and restoration of the lost tissue are clinically challenging. The main objective of this study is to characterize the exposed transparent dentin in the occlusal surface of attrited teeth by optical coherence tomography (OCT). Naturally attrited, extracted human teeth with occlusal-transparent dentin were investigated in comparison to sound and carious teeth. The teeth were subjected to OCT imaging and then cross-sectioned and polished. OCT B-scans were compared to light microscopy images of the same cross section. In OCT images, some changes were evident at the transparent dentin in attrited teeth. An OCT attenuation coefficient parameter (µ t) was derived based on the Beer-Lambert law as a function of backscatter signal slope. The mean values of µ t were 1.05 ± 0.3, 2.23 ± 0.4, and 0.61 ± 0.27 mm(-1) for sound, carious, and transparent dentins, respectively. One-way ANOVA with Tukey's post-hoc showed a significant difference between groups (p < 0.05). Physiological changes in transparent dentin that involve deposition of mineral casts in the dentinal tubules lead to lower attenuation of OCT signal. OCT has a potential role to detect transparent dentin on the surface of attrited teeth and can be used in the future as a clinical adjunct tool.

Interfacial Adaptation of Composite Restorations Before and After Light Curing: Effects of Adhesive and Filling Technique.

PURPOSE: To investigate the effects of placement technique and adhesive material on adaptation of composites before and after light curing. MATERIALS AND METHODS: Cylindrical cavities (3 mm diameter, 1.7 mm depth) in extracted human molars were restored in 6 groups (n=5) using 2 adhesives--two-step self-etching Clearfil SE Bond 2 (SE2) and all-in-one Clearfil Tri-S Bond Plus (TSP) (Kuraray Noritake Dental)--and 2 composites--Estelite Sigma Quick (ESQ) and Estelite Flow Quick (FLQ) (Tokuyama Dental)--placed with three different techniques: ESQ bulk placed, FLQ lining followed by ESQ and FLQ bulk placed. Specimens were scanned twice using swept-source optical coherence tomography (SS-OCT) before and after photopolymerization of the composite. Gap formation during polymerization or the difference in floor interface (DFI%) and final unsealed interface (USI%) were measured by image coregistration and subtraction on 6 diametrical planes across each scan. RESULTS: Two-way ANOVA suggested that both factors (adhesive and filling technique) and their interaction were significant (p<0.001). SE2 showed significantly lower DFI% than did TSP when the composites were placed in bulk, but no difference was found when flowable lining was applied (p<0.05). Within TSP, all filling techniques were significantly different and the lining group showed the lowest values, followed by ESQ-bulk. Overall, SE2 always showed lower UFI% than did TSP, while there was no difference among different techniques within SE2. CONCLUSION: SS-OCT is a unique method to observe the pre-existing interfacial defects and gaps developed during polymerization, which were found to depend on both placement technique and applied adhesive.

Effect of borate, fluoride and strontium ions on biomimetic nucleation of calcium phosphate studied using solid-state nuclear magnetic resonance and X-ray diffraction.

OBJECTIVES: Apatite minerals can have various anions and cations in their crystal structure in addition to phosphate ion (PO4³â») and calcium ion (Ca2+). The aim of this study is to investigate effects of the borate, fluoride and strontium ions on biomimetic nucleation of calcium phosphate. METHODS: Nano-crystalline hydroxyapatite (H-Ap) was obtained from a supersaturated buffered solution containing 4.12 mM HPO42- and 5.88 mM Ca2+ (H-Ap). Four additives were used in solid solution methods: (i) 0.588 mM F- (F-Ap), (ii) 5.88 mM Sr2+ (Sr-Ap), (iii) 4.12 mM BO33- (BO3-Ap), and (iv) a surface pre-reacted glass ionomer (S-PRG) filler eluate that contained 0.17 mM Sr2+, 0.588 mM F-, 11.1 mM BO33-- (SPRG-Ap). Apatite crystallization was investigated using a solid-state magic-angle spinning NMR spectroscopy and X-ray diffraction (XRD) with the Rietveld analysis. RESULTS: A 2D 1H-31P heteronuclear-correlation NMR showed F- ion incorporation in the apatite structure of the F-Ap and SPRG-Ap. The peaks on the 31P axis of the F-Ap, Sr-Ap, and BO3-Ap were different from that of the H-Ap, and the full width at half maximum increased in the following order: H-Ap∼F-Ap∼BO3-Ap< SPRG-Ap< Sr-Ap, suggesting the incorporation of the F-, Sr2+ and BO33-. The incorporation of F and BO3 was further confirmed by 19F and 11B NMR. The XRD revealed that Sr2+ was preferentially incorporated into the CaII site. SIGNIFICANCE: The F-, Sr2+ and BO33-ions might be involved in modifying the crystallization of apatite precipitation, producing a variety of apatite. S-PRG filler that release these ions may have an effect on remineralization, i.e., the reformation of apatite lost due to caries.

Influence of surface pre-reacted glass-ionomer (S-PRG) filler eluate on collagen morphology, remineralization, and ultimate tensile strength of demineralized dentin.

OBJECTIVE: To evaluate the effect of ions released from surface pre-reacted glass-ionomer (S-PRG) filler on collagen morphology, remineralization, and ultimate tensile strength (UTS) of demineralized dentin. MATERIALS AND METHODS: Bovine incisor root dentins were demineralized with EDTA and divided into three treatment groups: 1) water (control); 2) S-PRG filler eluate; 3) 125 ppm sodium fluoride (NaF). After a 3-min treatment, the specimens were stored in simulated body fluid (SBF) for 3 months. Collagen morphology and remineralization were assessed using transmission electron microscopy (TEM), scanning electron microscopy (SEM), and Fourier-transform infrared spectroscopy (FTIR). Additionally, ultimate tensile strength (UTS) was measured. RESULTS: TEM and SEM demonstrated that S-PRG induced more effective remineralization compared to NaF, while the control group exhibited faint mineral deposition with collagen degradation. S-PRG displayed the most homogenous mineral deposition in collagen fibrils, along with closure of interfibrillar spaces. Extensive mineral precipitation was observed within dentinal tubules in the S-PRG group. In addition, S-PRG filler eluate demonstrated significantly higher phosphate-to-amide ratio and UTS compared to NaF and control groups (p < 0.05). CONCLUSIONS: Ion released from S-PRG filler positively influenced collagen morphology, remineralization, and ultimate tensile strength of demineralized dentin. CLINICAL SIGNIFICANCE: S-PRG filler enhances remineralization and improve the biomechanics of demineralized dentin.

Enhancement of mineral density and mechanical properties in root caries treated with silver diammine fluoride and glass ionomer cement, with emphasis on silver ion distribution.

OBJECTIVES: This study aimed to measure the distribution of silver ion (Ag+), mineral recovery, and nanohardness in carious lesions and comprehensively evaluate the degree of dentin restoration. METHODS: Sixty human teeth with root caries were randomly assigned to the control, silver diammine fluoride (SDF) [Safo], and SDF+Glass ionomer cement (GIC) treatment [Safo+Fuji] groups. Micro-computed tomography (micro-CT) was performed at five time points for each sample before/after treatment to evaluate mineral density within and around carious lesions. Three months following treatment, 12 samples were selected for synchrotron radiation X-ray fluorescence analysis to evaluate Ag+ distribution, while 15 samples were selected for nanoindentation. Data were analyzed using Dunnett's T3 test for micro-CT and Wilcoxon rank sum test with Bonferroni correction (p = 0.017) for nanoindentation. The correlation between hardness and mineral change was analyzed using the Spearman rank correlation coefficient. RESULTS: The Safo and Safo+Fuji groups showed significantly higher mineral recovery rates than did the control group (p < 0.001). In the Safo group, Ag+ accumulated in the deeper layers rather than the superficial layer of caries. In the Safo+Fuji group, Ag+ was found evenly distributed throughout caries, with only a few Ag+ detected in the GIC layer. Hardness in the Safo+Fuji group was significantly higher compared with the Safo group at depths in the range of 10-50 µm. CONCLUSION: In the presence of GICs, SDF exhibited high remineralization capacity when diffusing throughout carious lesions over time. Combined treatment with SDF and GIC could strengthen root dentin even in the presence of caries. CLINICAL SIGNIFICANCE: We found that combination treatment with SDF and GIC could increase mineral density in caries and improve the hardness of the tooth structure compared with fluoride-based agents alone. These findings might pave the way for future clinical trials to determine the therapeutic potential of nanotechnology-based restorative materials.

Analysis of cariogenic biofilms by using a swept-source optical coherence tomography in vitro.

OBJECTIVE: The objective was to measure the thickness of Streptococcus mutans (S. mutans) biofilms forming in an oral biofilm reactor (OBR) by using a noninvasive swept-source optical coherence tomography (SS-OCT) system at every 4 h time interval until 20 h and analyze the correlations with the amounts of biofilms. METHODS: S. mutans biofilms were formed on square-shaped bovine enamel blocks inside an OBR. Biofilms were analyzed at every 4 h stage (4 h, 8 h, 12 h, 16 h and 20 h) using a SS-OCT system and a laser scanning confocal microscope (LSCM). The amounts of biofilms were measured at each stage by separating the water insoluble glucan (WIG) and bacterial cells. Co-relationships between the SS-OCT measured biofilm thickness and the amounts of adhered biofilms were analyzed. RESULTS: The thickness of biofilms detected on SS-OCT images at 4 h stage was 0.059 ± 0.029 (Av ± SD) mm which increased time-dependently in a linear fashion after 8 h stage and reached to 0.435 ± 0.159 mm at 20 h stage and the correlation coefficient was about 0.89. The amounts of biofilms; bacterial optical density (OD) and WIG concentration increased time-dependently were 0.035 ± 0.008 / mm2 and 10.328 ± 2.492 µg/ mm2 respectively at 20 h stage. Correlation coefficients of 0.66 between 'the amounts of bacteria' and 'biofilm thickness on OCT' and 0.67 between 'the amounts of WIG' and 'biofilm thickness on OCT' were obtained, suggesting that there was a relatively positive correlation between them. CONCLUSION: The SS-OCT can be a useful tool to measure time-dependent growth of biofilms. Further studies are needed in order to assess biofilms using SS-OCT more accurately.