Search Results (71)

Objective: This in vitro study quantitatively compared the time-dependent remineralization potential of three professional agents on artificially induced enamel lesions using Scanning Electron Microscopy (SEM) and energy-dispersive X-ray analysis (EDX). Methods: Sixty extracted sound molars were randomly assigned to three groups (number = 20): G_CPP-ACP, treated with casein phosphopeptide–amorphous calcium phosphate; G_Zn-HA, treated with zinc-hydroxyapatite; and G_F-ACP, treated with fluoridated amorphous calcium phosphate. The crown of each tooth was divided into three areas: one represented the control (CTRL, sound enamel), one underwent demineralization (DEMIN, demineralized enamel), and the third one was at first demineralized and then treated with a remineralizing agent, allowing intra-sample comparison. Artificial lesions were produced by immersion in 0.1 M lactic acid (72 h). Groups were subdivided according to remineralization time (7, 14, 21, and 28 days). Samples underwent daily treatment under a pH-cycling regimen. Surface morphology and Ca/P ratios were evaluated by SEM-EDX, and data were statistically analyzed (p < 0.05). Results: All agents promoted a progressive increase in Ca/P ratio over time, confirming a time-dependent remineralization effect. At day 7, G_Zn-HA showed higher Ca/P values, but from day 14 onward, G_F-ACP produced significantly greater mineral gain than the other groups (p < 0.05). By day 21, G_F-ACP reached Ca/P values approaching CTRL, while G_CPP-ACP and G_Zn-HA remained at lower levels, reaching a plateau respectively at 21 and 14 days. SEM observations supported these findings: G_CPP-ACP and G_Zn-HA showed partial surface recovery, whereas G_F-ACP exhibited a compact, homogeneous enamel-like structure at 28 days. Conclusions: All tested agents demonstrated time-dependent remineralization, enhanced with prolonged exposure, suggesting that the time of application represents a key factor for clinical success. Full article

Bamboo fiber is a prime green fiber due to its renewability, biodegradability, and high specific strength. Bamboo-fiber-reinforced epoxy (BFRE) composites have seen extensive use and shown great promise for natural biofiber-reinforced friction materials. Inspired by the decussated fiber alignment of bovine enamel, this study investigated how fiber orientation influences the tribological properties of BFRE composites. Specifically, the proportion of fibers oriented vertically to the surface was varied at seven levels: 0%, 25%, 33%, 50%, 67%, 75%, and 100%. The tribological performance was assessed through wear reciprocating testing and microscopic morphological characterization techniques. Results indicate that the bio-inspired fiber decussation can reduce the wear loss of the BFRE composites. Among all bio-inspired BFRE composites, BFRE composites with 67% vertical fibers achieve the best wear resistance. The vertical fibers in the BFRE composites can withstand pressure to provide a “compression–rebound” effect, while the parallel fibers can resist shear stress. The decussated structure inhibits crack initiation and propagation during wear and promotes transfer film formation, reducing wear loss. The findings expand understanding of the correlation between the bovine-tooth-like decussated structure and its tribological mechanisms, thereby offering essential guidance for the biomimetic design of high-performance BFRE composites for friction material application. Full article

Background: Adhesion to enamel is influenced by surface preparation, which affects the micromechanical retention of resin-based materials. Sodium hypochlorite (NaOCl) deproteinization has been proposed as a pretreatment to improve acid etching efficacy, but the optimal application time remains unclear. Methods: This in vitro study evaluated the effect of 5% NaOCl pretreatment at three exposure times (15, 30, and 60 s) on shear bond strength (SBS), the adhesive remnant index (ARI), and enamel etching patterns. Extracted human premolars (n = 140) were divided into four groups: the control (acid etching only) and three experimental groups. SBS was tested per ISO 11405, while ARI scores were assessed under stereomicroscopy, and surface morphology was examined by scanning electron microscopy (SEM). Results: The 30-s NaOCl group exhibited the highest SBS (20.9 MPa) compared with the control (15.9 MPa, p < 0.05) and 15-s (14.9 MPa, p < 0.05) groups. SEM analysis showed predominantly Type I–II etching patterns for the 30-s group, irregular Type III for 15 s, and overetched Type IV with loss of prism definition for 60 s, compromising the adhesive interface. ARI scores indicated 86.7% of samples in the 30-s group retained all adhesive on enamel (score 3). Conclusions: A 30-s 5% NaOCl pretreatment before acid etching improved enamel micromorphology and bonding performance compared to shorter or longer exposures. The intermediate duration provided effective deproteinization without structural damage, whereas prolonged exposure degraded the enamel microstructure. This protocol may offer a simple, cost-effective method to enhance clinical adhesive procedures, though prolonged exposure (60 s) should be avoided due to structural degradation of the enamel microstructure. Full article

Background: Substituted hydroxyapatites (HAps) are widely used in oral-care formulations for enamel repair; however, head-to-head comparisons among commercial grades remain limited. Objective: To compare four commercial HAps: A (Kal-HAp), B (FL-HAp), C (FL-HAp-SC), and D (microRepair^®, a biomimetic Zn–carbonate-substituted HAp) and to evaluate their ability to form an enamel-like coating in vitro. Methods: We characterized the powders by X-ray diffraction (crystalline phase, Landi crystallinity index), FTIR-ATR (phosphate/carbonate bands), SEM/EDS (morphology, surface Ca/P), and DLS (particles size, ζ-potential). In vitro, human enamel sections were treated with 5% slurries in artificial saliva; surface coverage was quantified by image analysis on SEM. Results: All commercial materials analyzed in this work were composed of HAp. Differences were observed between HApin terms of crystallinity-range [2 Theta 8.0–60.0°], carbonate substitution (ATR [carbonate group evaluated −870 cm⁻¹]), and particle size (DLS [in a range 0.1–10,000 nm], Z-mean [mV]). On enamel, all samples form a hydroxyapatite layer; coverage differed between groups ([A] 28.83 ± 7.35% vs. [B] 31.11 ± 3.12% vs. [C] 57.20 ± 33.12% vs. [D] 99.90 ± 0.12%), with the biomimetic Zn–carbonate-substituted HAp showing the highest coverage, and the post-treatment Ca/P ratio approached values similar to those of dental enamel. Conclusions: Complementary physic-chemical signatures (crystallinity, carbonate substitution, and morphology) relate to enamel-surface coverage in vitro, providing evidence base for selecting HAp grades for enamel-repair formulations, which is a practical implication for product design. Full article

Background/Objectives: This in vitro study evaluated the effects of fluoride-free toothpaste, fluoride-containing toothpaste, and a color-correcting gel on the morphology, composition, and mechanical properties of demineralized human enamel. The hypothesis was that fluoride-containing formulations would better preserve enamel integrity compared to non-fluoride and cosmetic products. Methods: Extracted human teeth (n = 3 per group) were demineralized with 36% phosphoric acid and assigned to four groups: E0 (control), E1 (fluoride-free toothpaste), E2 (fluoride-containing toothpaste), and E3 (color-correcting gel). Brushing was performed manually twice daily for 7 days using standardized force. Surface morphology and elemental composition were assessed via SEM–EDX; chemical changes were analyzed by FTIR; mechanical properties were evaluated using the Vickers microhardness test. Results: E1 exhibited the highest microhardness (343.6 HV) but also the highest Ca/P ratio (2.37) and most pronounced surface roughness (p < 0.05 vs. control). E2 showed a balanced Ca/P ratio (2.07), smoother morphology, and detectable fluoride incorporation, despite a lower hardness value (214.5 HV). E3 presented moderate changes in both morphology and composition, with a Ca/P ratio similar to the control (2.06) but surface irregularities visible by SEM. The apparent paradox in E1—high hardness with structural damage—may be due to superficial mineral precipitation without true remineralization. Conclusions: Fluoride-containing toothpaste preserved enamel morphology and chemistry more effectively than the other formulations. Increased hardness in E1 does not necessarily indicate clinical benefit. In vivo studies with longer protocols and pH cycling are needed to confirm these findings. Full article

Background and Objectives: Chairside bleaching can alter enamel morphology and mineral content. This in vitro study compared surface changes and elemental shifts after three in-office protocols using scanning electron microscopy (SEM) and energy-dispersive X-ray spectroscopy (EDS). Materials and Methods: Forty-two human premolars/molars were sectioned; matched halves served as control or received Opalescence Quick 45% carbamide peroxide (CP), Opalescence Boost 40% hydrogen peroxide (HP), or BlancOne Ultra+ 35% HP with light activation. Gels were applied per manufacturers’ instructions. SEM assessed topography (×500–×1100); EDS quantified atomic percent of O, Ca, P, C and trace elements. One-way ANOVA compared Ca and P between bleached groups (α = 0.05). Results: Controls showed compact surfaces with preserved Ca and P. After Quick, SEM revealed roughness, fissures and microcracks; Ca fell from 11.5 to 12.5 to 9.53–11.73 at% and P from 7.5 to 8.9 to 7.41–8.59 at%. Boost produced mild superficial restructuring and granular deposits with variable Ca 13.80–27.94 at% and P 7.32–14.65 at%. BlancOne Ultra+ caused diffuse erosion and loss of prismatic clarity with marked demineralization (Ca 1.42–7.85 at%, P 1.22–6.71 at%); C rose locally to 46.61 at%. Across bleached groups, Ca and P differed significantly (both p < 0.001). Oxygen remained dominant (~39–50 at%) in all spectra; occasional Al/Si/Cl/K likely reflected residues or preparation artifacts. Conclusions: All protocols produced surface and compositional alterations, with a severity gradient: BlancOne Ultra+ > Boost > Quick. High-concentration, light-activated HP yielded the largest Ca/P losses. Clinically, neutral-pH, non-activated or chemically activated regimens and immediate post-bleach remineralization should ideally be used when feasible, particularly before adhesive procedures. Full article

Background/Objectives: Within the minimum intervention oral care (MIOC) delivery framework, the management and improvement in the esthetics of enamel white spot lesions (WSLs) are recommended. This study evaluated the chemomechanical and morphological characteristics of WSLs treated by four therapeutic approaches using Raman spectroscopy, Knoop microhardness (KH), and field-emission scanning electron microscopy (FESEM). Methods: Sixty human enamel slabs were divided into six groups: non-treated (baseline), WSLs (8% methylcellulose gel with 0.1 M lactic acid, pH 4.6 at 37 °C for 21 days), and four treated groups, namely bovine collagen supplement (Nutravita Ltd., Maidenhead, Berkshire, UK), Regenerate system (NR-5, Bordeaux, France), Sylc air abrasion (AquaCare, Denfotex Research Ltd., Edinburgh, UK), and CO₂ laser (JHC1180, Jinan, China). Treatment lasted 28 days, followed by four weeks of storage in artificial saliva (pH = 7.0, 37 °C). Bovine collagen was analyzed using Fourier-Transform Infrared Spectroscopy (FTIR). The mineral content, including the phosphate peak intensities (PO₄ ν₁, ν₂, and ν₄) and carbonate (CO₃), as well as tissue microhardness, were assessed at varying depths (50–200 µm), followed by morphological assessment. Results: The FTIR spectrum of bovine collagen powder confirms the presence of amide I, II, and III. It produced a statistically significant enhancement in the phosphate content and KHN compared to WSLs of up to 150 µm in depth (p < 0.001). Regenerate-treated surfaces recorded the highest phosphate content among groups at the superficial layer. All treatment interventions enhanced the morphology of lesions by covering the exposed prisms and inter-prismatic structure. Conclusions: Bovine collagen supplements can enhance the phosphate content and surface properties of enamel white spot lesions (WSLs) and could be considered a potential modality comparable to other micro-invasive approaches for addressing incipient enamel lesions. This could significantly impact dental care management. Full article

Background/Objectives: This study aimed to evaluate the efficacy of a 445 nm diode laser in enhancing enamel resistance to acid-induced demineralization and to investigate the associated compositional and structural modifications using scanning electron microscopy (SEM), electron spectroscopy for chemical analysis (ESCA), and X-ray diffraction (XRD) crystallographic analysis. Methods: A total of 126 extracted human teeth were used. A total of 135 (n = 135) enamel discs (4 × 4 mm) from 90 teeth were assigned to either a laser-irradiated group or an untreated control group for SEM, ESCA, and XRD analyses. Additionally, 24 mono-rooted teeth were used to measure pulp temperature changes during laser application. Laser irradiation was performed using a 445 nm diode laser with a pulse width of 200 ms, a repetition rate of 1 Hz, power of 1.25 W, an energy density of 800 J/cm², a power density of 3980 W/cm², and a 200 µm activated fiber. Following acid etching, SEM was conducted to assess microstructural and ionic alterations. The ESCA was used to evaluate the Ca/P ratio, and XRD analyses were performed on enamel powders to determine changes in phase composition and crystal lattice parameters. Results: The laser protocol demonstrated thermal safety, with minimal pulp chamber temperature elevation (0.05667 ± 0.04131 °C). SEM showed that laser-treated enamel had a smoother surface morphology and reduced acid-induced erosion compared with controls. Results of the ESCA revealed no significant difference in the Ca/P ratio between groups. XRD confirmed the presence of hydroxyapatite structure in laser-treated enamel and detected an additional diffraction peak corresponding to a pyrophosphate phase, potentially enhancing acid resistance. Results of the spectral analysis showed the absence of α-TCP and β-TCP phases and a reduction in the carbonate content in the laser group. Furthermore, a significant decrease in the a-axis lattice parameter suggested lattice compaction in laser-treated enamel. Conclusions: Irradiation with a 445 nm diode laser effectively enhances enamel resistance to acid demineralization. This improvement may be attributed to chemical modifications, particularly pyrophosphate phase formation, and structural changes including prism-less enamel formation, surface fusion, and decreased permeability. These findings provide novel insights into the mechanisms of laser-induced enhancement of acid resistance in enamel. Full article

This study evaluated the physicochemical and morphological properties of tooth enamel in patients with caries-predisposing SNPs (rs4694075 in AMBN and rs2337359 in TUFT1 genes), based on the DMFT index. We included 40 of 120 individuals (aged 19–43), collecting stimulated saliva and 58 healthy teeth extracted for orthodontic/surgical reasons. Saliva DNA was genotyped. Enamel properties were assessed using Vickers microhardness, deposition thickness, and calcium content. Genotype and allele frequencies aligned with the literature. The TUFT1C/C genotype subgroup showed a significantly higher DMFT index (p = 0.03) compared to the T/T genotype, while AMBN showed no such correlation. Calcium content, microhardness, and enamel thickness were similar across all polymorphic variants of both genes. A statistically significant correlation (p = 0.003) was found between reduced enamel calcium content and a higher DMFT index. Despite existing literature on the subject, the studied SNPs did not reflect any correlation with morphological or physicochemical changes in enamel. The above results suggest that genetic variability identifies patients classified by dentists as being at higher risk of caries, even though these patients follow a non-cariogenic diet and adhere to a hygiene regime. As no structural or physicochemical changes in the enamel of this group were observed, the potential cause may be disturbances in the remineralisation mechanisms or enamel surface properties that promote biofilm adhesion in polymorphic patients. Intensive tooth calcification control algorithms using LIF and RVG, as well as remineralisation cycles to increase hydroxyapatite saturation with calcium phosphates and bioadhesive fluoride delivery systems for long-term biofilm control, are used to more effectively prevent or slow down the progression of caries. Full article

Recent updates to European Union directives on drinking water have extended safety limits to hot water, increasing the need to assess materials commonly used in water storage systems, such as porcelain enamel. This study investigates the interaction between enameled surfaces and aqueous environments, focusing on element release and microstructural alterations. The mass loss and chemical stability of the enamel were evaluated through a combination of surface characterization and Inductively Coupled Plasma (ICP) analysis. Time-resolved quantification of selected elements confirmed that all concentrations remained within EU regulatory thresholds. Additionally, the enamel was subjected to acidic and alkaline environments to explore the influence of pH on degradation mechanisms. Scanning electron microscopy (SEM) revealed that while the enamel undergoes surface-level modifications, the bulk structure remains intact. Notably, alkaline exposure had the strongest impact, dissolving needle-like calcium-rich structures and altering the surface more significantly than water or acid alone. These structures appear to facilitate localized corrosion once degraded. The correlation between surface morphology and elemental release dynamics highlights the critical role of microstructural features in determining long-term chemical resistance. Overall, the results underscore the importance of optimizing both the composition and structure of enamel coatings for applications involving prolonged contact with potable water. Full article

The junctional epithelium, which lines the inner gingival surface, seals the gingival sulcus to block the infiltration of food debris and pathogens. The junctional epithelium is derived from the reduced enamel epithelium, consisting of late developmental stage ameloblasts and accessory cells. No prior studies have investigated whether defective ameloblast differentiation or enamel matrix formation affects junctional epithelium anatomy or function. Here, we examined the junctional epithelium in mice exhibiting amelogenesis imperfecta due to loss-of-function mutations in the major enamel matrix protein amelogenin (Amelx^−/−) or the critical enamel matrix protease KLK4 (Klk4^−/−). Histological analyses demonstrated altered morphology and cell layer thickness of the junctional epithelium in Amelx^−/− and Klk4^−/− mice as compared to wt. Immunohistochemistry revealed reduced ODAM, laminin 5, and integrin α6, all of which are critical for the adhesion of the junctional epithelium to the enamel in Amelx^−/− and Klk4^−/− mice. Furthermore, we observed altered cell–cell adhesion and increased permeability of Dextran-GFP through the mutants’ junctional epithelium, indicating defective barrier function. Reduced β-catenin and Ki67 at the base of the junctional epithelium in mutants suggest impaired mitotic activity and reduced capacity to replenish continuously desquamated epithelium. These findings highlight the essential role of normal amelogenesis in maintaining junctional epithelium homeostasis. Full article

Tooth bleaching is a widely used esthetic treatment; however, bleaching agents can temporarily alter the surface morphology of enamel, increasing surface roughness and porosity, which may lead to increased susceptibility to discoloration. This in vitro study investigated the effectiveness of fluoride varnish in preventing immediate discoloration of bovine incisors after bleaching. Specimens were bleached with 35% hydrogen peroxide and treated with either Clinpro White Varnish (CW) or Enamelast Fluoride Varnish (EN), whereas control specimens received no treatment after bleaching. The samples were immersed in coffee for 24 h, and the color difference (ΔE₀₀) was calculated using the CIEDE2000 formula. The surface morphology of enamel was examined using SEM. The fluoride varnish groups showed significantly lower color difference values than the control group (p < 0.05), with ΔE₀₀ reduced by approximately two-thirds in both the CW and EN groups. SEM observations showed that the enamel surfaces in the varnish-treated groups exhibited reduced surface irregularities compared to the untreated group, suggesting remineralization. These results suggest that the immediate application of fluoride varnish after bleaching can effectively reduce short-term discoloration by providing physical protection and promoting remineralization. Fluoride varnish may serve as a simple and effective strategy to maintain whitening outcomes and minimize early discoloration. Full article

Background/Objectives: Tooth bleaching is a widely requested aesthetic procedure in modern dentistry. However, the structural effects of high-concentration peroxide-based bleaching agents on enamel remain insufficiently understood. This study aims to evaluate and compare the effects of three in-office bleaching agents—Opalescence Boost (40% hydrogen peroxide [HP]), Opalescence Quick (45% carbamide peroxide [CP]), and BlancOne Ultra + (35% hydrogen peroxide [HP])—on enamel surface characteristics and color change using confocal laser scanning microscopy (CLSM) and spectrophotometric analysis. Methods: Forty-two extracted human teeth were sectioned and divided into experimental and control halves. Each experimental specimen underwent bleaching according to the manufacturer’s protocol. Color measurements were conducted at baseline, immediately post-treatment, at 3 days, 7 days, and 6 months following treatment using the Vita Easyshade^® spectrophotometer. Color differences were calculated using the CIEDE2000 (ΔE₀₀) formula. Enamel surface morphology was assessed by CLSM. Data were analyzed using Wilcoxon and Kruskal–Wallis tests (p < 0.05), performed with SPSS v23. Results: All bleaching agents produced clinically perceptible color changes (ΔE₀₀ > 3.3). Opalescence Boost achieved the highest and most consistent whitening effect (mean ΔE₀₀ > 11), while Opalescence Quick showed moderate efficacy (ΔE₀₀ ~6–8), and BlancOne Ultra+ induced milder changes (ΔE₀₀ ~4–5). CLSM imaging revealed surface alterations in all bleached samples, with more pronounced changes observed in specimens treated with higher peroxide concentrations. Conclusions: All three bleaching systems were effective in improving enamel color, with Opalescence Boost delivering the most substantial and durable effect. CLSM analysis confirmed morphological changes in enamel without evidence of severe damage. These results underscore the importance of selecting bleaching protocols that balance efficacy with enamel safety. Further in vivo studies are recommended to validate long-term structural effects and support clinical decision-making. Full article

Background/Objectives: Sandblasting build-ups before applying the acid and adhesive significantly improves the bond strength. The aim of this study is to evaluate, for the first time, the effectiveness of an Er:YAG laser used in QSP mode to treat the surface of build-ups before the adhesive cementation sequence. Methods: This ex vivo study was conducted on 12 intact, undecayed extracted teeth kept hydrated in NaCl 0.9% solution. A cavity was created in the center and reconstructed with composite resin (build-up). Then, samples were prepared with burs and divided into three groups: control group G1, prepared only with burs; group G2, in which surfaces were treated with a sandblaster (2.5 bar, 10 mm from composite surface, aluminum oxide, 10 s); and group G3, treated using an Er:YAG laser (QSP modality, 1 W, 10 Hz, 100 mJ). The surface roughness of the build-ups was measured using a CCI MP-L digital optical profiler (Taylor Hobson, Leicester, UK), and surface morphology was studied using the Quanta™ 250 FEG (FEI, Hillsboro, OR, USA) ESEM instrument. Results: Regarding enamel, mean surface roughness in G1 vs. G2 was not statistically significant (p = 0.968); meanwhile, differences between the Er:YAG laser group (G3) and G1 or G2 were significant (G3 vs. G1 p < 0.001; G3 vs. G2 p < 0.001). Regarding dentin, G1 vs. G2 was significant (p = 0.021); differences between G3 and G1 or G2 were extremely significant (G3 vs. G1 p < 0.001; G3 vs. G2 p < 0.001). The same trend was detected for resin. Conclusions: An Er:YAG laser in QSP mode used on the build-up surface for indirect adhesive restorations is innovative and should be investigated with further studies. However, it seems extremely effective with increased roughness, the absence of a smear layer and characteristics potentially favorable for good adhesion for all substrates (enamel, dentin, resin). Full article

The actin cytoskeleton plays an important role in morphological changes of ameloblasts during the formation of enamel, which is indispensable for teeth to withstand wear, fracture and caries progression. This study reveals that the actin nucleator Cobl is expressed in ameloblasts of mandibular molars during amelogenesis. Cobl expression was particularly pronounced during the secretory phase of the enamel-forming cells. Cobl colocalized with actin filaments at the cell cortex. Importantly, our analyses show an influence of Cobl on both ameloblast morphology and cytoskeletal organization as well as on enamel composition. At P0, Cobl knock-out causes an increased height of ameloblasts and an increased F-actin content at the apical membrane. During the maturation phase, the F-actin density at the apical membrane was instead significantly reduced when compared to WT mice. At the same time, Cobl-deficient mice showed an increased carbon content of the enamel and an increased enamel surface of mandibular molars. These findings demonstrate a decisive influence of the actin nucleator Cobl on the actin cytoskeleton and the morphology of ameloblasts during amelogenesis. Our work thus expands the understanding of the regulation of the actin cytoskeleton during amelogenesis and helps to further elucidate the complex processes of enamel formation during tooth development. Full article