The influence of neutral MDP-Na salt on dentin bond performance and remineralization potential of etch-&-rinse adhesive.

OBJECTIVES: To investigate the effect of neutral 10-methacryloyloxydecyl dihydrogen phosphate salt (MDP-Na) on the dentin bond strength and remineralization potential of etch-&-rinse adhesive. METHODS: Two experimental etch-&-rinse adhesives were formulated by incorporating 0 wt% (E0) or 20 wt% (E20) neutral MDP-Na into a basic primer. A commercial adhesive, Adper Single Bond 2 (SB, 3 M ESPE), served as the control. Sixty prepared teeth were randomly allocated into three groups (n = 20) and bonded using either one of the experimental adhesives or SB. Following 24 h of water storage, the bonded specimens were sectioned into resin-dentin sticks, with four resin-dentin sticks obtained from each tooth for microtensile bond strength (MTBS) test. Half of the sticks from each group were immediately subjected to tensile loading using a microtensile tester at a crosshead speed of 1 mm/min, while the other half underwent tensile loading after 6-month incubation in artificial saliva (AS). The degree of conversion (DC) of both the control and experimental adhesives (n = 6 in each group) and the adsorption properties of MDP-Na on the dentin organic matrix (n = 5 in each group) were determined using Fourier-transform infrared spectrometry. Furthermore, the effectiveness of neutral MDP-Na in promoting the mineralization of two-dimensional collagen fibrils and the adhesive-dentin interface was explored using transmission electron microscopy and selected-area electron diffraction. Two- and one-way ANOVA was employed to assess the impact of adhesive type and water storage on dentin bond strength and the DC (α = 0.05). RESULTS: The addition of MDP-Na into the primer increased both the short- and long-term MTBS of the experimental adhesives (p = 0.00). No difference was noted in the DC between the control, E0 and E20 groups (p = 0.366). The MDP-Na remained absorbed on the demineralized dentin even after thorough rinsing. The intra- and extra-fibrillar mineralization of the two-dimensional collagen fibril and dentin bond hybrid layer was confirmed by transmission electron microscopy and selected-area electron diffraction when the primer was added with MDP-Na. CONCLUSIONS: The use of neutral MDP-Na results in high-quality hybrid layer that increase the dentin bond strength of etch-&-rinse adhesive and provides the adhesive with remineralizing capability. This approach may represent a suitable bonding strategy for improving the dentin bond strength and durability of etch-&-rinse adhesive.

The effect of final irrigation with different solutions on smear layer removal and dentin erosion: A scanning electron microscope study.

AIM: This study aimed to compare the effectiveness of initial irrigation with sodium hypochlorite (NaOCl) and final irrigation with QMix, 40% citric acid, and 17% ethylenediaminetetraacetic acid (EDTA) on smear layer removal and dentin erosion. METHODOLOGY: Forty extracted human mandibular premolar teeth were randomly divided into four groups (n = 10) according to the type of final irrigants used: 17% EDTA, QMix, citric acid, and control (normal saline). Canals were mechanically prepared using ProTaper Next instruments to an apical size of X3. Subsequently, the roots were sectioned in a buccolingual direction. Scanning electron microscopy (SEM) was used to assess the presence of the smear layer and the amount of dentin erosion in the coronal, middle, and apical thirds of the root canals. RESULTS: In regards to smear layer removal, there was a significant difference between the control group and the other tested groups. Moreover, it was significantly higher in the coronal and middle thirds than in the apical third. However, there were no significant differences between the groups of EDTA, QMix, and citric acid. Concerning dentin erosion, citric acid produced significantly more dentin erosion than the other tested groups. CONCLUSION: Final irrigation with solutions had a higher ability to remove the smear layer in the coronal and middle thirds compared to the apical third. Of all the solutions tested, 40% citric acid had the most pronounced impact on dentin erosion, followed by 17% EDTA and QMix.

Effects of Propolis-Based Herbal Toothpaste on Dentine Hypersensitivity.

INTRODUCTION: The objective of this in vitro study was to compare the effectiveness of a propolis-based herbal toothpaste with 5% sodium fluoride varnishin obstructing human dentinal tubules; Scanning electron microscopy was utilised to obtain quantitative and qulitative data on tubular obstruction. METHODS: Thirty-nine extracted human premolar teeth were collected. The cementum layer was removed using a water-cooled diamond bur and the smear layer using ethylenediaminetetraacetic acid (EDTA) 17%. Then, the samples were randomly divided into 3 groups (n = 13 each), as follows: group 1: dentin discs exposed to the propolis-based herbal toothpaste (Herbex); group 2: dentin discs exposed to 5% sodium fluoride varnish; and group 3: control. Then, all discs were observed and imaged in 4 non-overlapping fields by an electron microscope at 2000× magnification. The topography and number of open, closed, and semi-closed tubules were counted in all images. The data were analysed using Kruskal-Wallis test, Mann-Whitney U test, and Friedman test. The statistical analysis was performed with SPSS statistic 22.0 software, with a significance level of α = 0.05. RESULTS: In pairwise comparisons of the groups considering the percentage of open, closed, and semi-closed tubules, the difference was not statistically significant between the 5% sodium fluoride varnish and propolis groups in the closed and semi-closed tubules, but it was statistically significant with the control group. Additionally, the percentage of open tubules in the propolis-based herbal toothpaste group was significantly lower than in the 5% sodium fluoride varnish and control group. CONCLUSIONS: Both propolis-based herbal toothpaste and 5% sodium fluoride varnish is effective in blocking human dentin tubules to various extents.

Clinical implementation of comprehending dentin on a microscopic level

SUMMARY: The aim of the present in vitro study is to visualize dentin to get an in-depth knowledge of the nature of dentin that could provide useful information regarding conditioning dentinal substrate when treating dentinal lesions. Forty-nine extracted human third molars were obtained and prepared to produce artificial dentinal lesions through demineralizing with acetic acid for 7 and 14 days, or lactic acid for 7 days. The teeth were divided into groups and treated with either NaOCl, pepsin, trypsin, or phosphoric acid. To obtain information on the morphology of the treated dentinal surfaces, all samples were visualized under high resolution field emission scanning electron microscope. With high magnification reaching x50000 dentin was clearly visualized together with its constitutes. The effect of various demineralization approaches and various treatment protocols were demonstrated clearly. The relationship between the conditioning procedure steps and the subsequent bond strength was discussed. To our best knowledge, there is no previous clear highly magnified scanning electron microscope images for dentin, and dentinal components and constitutes with and without various treatments. The current in vitro study suggests the complexity nature of dentin as a substrate that should be treated carefully especially with technique sensitive procedures such as adhesive restorations.

El objetivo del presente estudio in vitro fue visualizar la dentina para obtener un conocimiento completo de la naturaleza de ella lo que podría proporcionar información útil sobre el acondicionamiento del sustrato dentinario en el tratamiento de lesiones dentinarias. Se obtuvieron 49 terceros molares humanos extraídos y se prepararon para producir lesiones dentinales artificiales mediante desmineralización con ácido acético por 7 y 14 días, o ácido láctico por 7 días. Los dientes se dividieron en grupos y se trataron con NaOCl, pepsina, tripsina o ácido fosfórico. Para obtener información sobre la morfología de las superficies dentinarias tratadas, todas las muestras se visualizaron bajo un microscopio electrónico de barrido de emisión de campo de alta resolución. Con un gran aumento que alcanzó x50000, la dentina se visualizó claramente junto con sus componentes. Se demostró el efecto de varios enfoques de desmineralización y varios protocolos de tratamiento. Se discutió la relación entre los pasos del procedimiento de acondicionamiento y la subsiguiente fuerza de unión. Hasta donde sabemos, no hay imágenes claras previas de microscopio electrónico de barrido altamente ampliadas para la dentina y los componentes y constituyentes de la dentina con y sin diferentes tratamientos. El estudio in vitro actual sugiere la naturaleza compleja de la dentina como sustrato que debe tratarse con cuidado, especialmente en los procedimientos sensibles a la técnica, tal como las restauraciones adhesivas.

Acrylamide monomers in universal adhesives.

OBJECTIVES: The mono-functional monomer 2-hydroxyethyl methacrylate (HEMA) is often added to universal adhesives (UAs) to improve surface wetting and prevent phase separation. Nevertheless, HEMA promotes water sorption and hydrolysis at adhesive interfaces, hereby affecting long-term bonding to dentin. This study investigated if two acrylamide monomers could replace HEMA in an UA formulation applied in etch-and-rinse (2E&R) and self-etch (1SE) bonding mode. METHODS: Four experimental UAs were bonded to bur-cut dentin. In addition to 12 wt% 10-MDP, 25 wt% Bis-GMA and 10 wt% TEGDMA as common monomer composition, 20 %wt ethanol and 15 %wt water as solvent, and 3 wt% polymerization-related additives, the four formulations solely differed for either the acrylamide cross-linker monomer 'FAM-201' as TEGDMA alternative and HEMA replacement, the hydroxyethyl acrylamide monomer 'HEAA' as HEMA alternative, HEMA ('HEMA+'), or extra TEGDMA in a HEMA-free control ('HEMA-'), all added in a 15 wt% concentration. The split-tooth study design involved application in 2E&R mode on one tooth half versus 1SE mode on the corresponding half. Micro-tensile bond strength of half of the micro-specimens was measured upon 1-week distilled water storage ('immediate' 1w µTBS), with the other half measured after additional 6-month storage ('aged' 6 m µTBS). Statistics involved linear mixed-effects (LME) modelling (p < .05). Additionally, interfacial TEM characterization, thin-film (TF) XRD surface analysis, LogP determination, and a cytotoxicity assay were carried out. RESULTS: FAM-201 revealed significantly higher µTBS than HEMA+ at 1w and 6 m when applied both in E&R and SE bonding modes. HEAA's µTBS was significantly lower than that of HEMA+ at 1w when applied in SE mode. TF-XRD and TEM revealed similar chemical and ultrastructural interfacial characterization, including stable 10-MDP_Ca salt nano-layering. FAM-201 was least cytotoxic and presented with an intermediary LogP, while HEAA presented with the highest LogP, indicating high hydrophilicity and water-sorption sensitivity. SIGNIFICANCE: The acrylamide co-monomer FAM-201 could replace HEMA in an UA formulation, while HEAA not.

Bonding of universal adhesives to bur-cut dentin: Effect of double application and dentin moisture level.

This study investigated how the double application of adhesives and dentin moisture level influence the microtensile bond strength (µTBS) of universal adhesives containing different hydrophilic monomers to bur-cut dentin. Four universal adhesives (Scotchbond Universal, Clearfil Universal Bond Quick, Prime&Bond Universal, BeautiBond Universal) were applied to wet and dry bur-cut dentin either in one or two layers. The µTBS test was performed after 25,000 thermal cycles, and scanning electron microscopy was used for the analysis of failure mode and interfacial ultrastructure. Double application significantly improved µTBS on wet dentin (p<0.001), but the effect was not significant on dry dentin (p>0.050). Double application also enhanced the formation of resin tags and limited voids within the adhesive layer of BeautiBond Universal. Dentin moisture had a significant effect on µTBS only if the adhesives were applied in a single layer (p=0.007). Except for Prime&Bond Universal, the tested universal adhesives performed better on dry dentin.

X-RAY SPECTRAL ANALYSIS OF DENTAL HARD TISSUE TRACE ELEMENTS (ELECTRON-MICROSCOPIC EXAMINATION).

The role of trace elements (microelements) in maintaining oral health has not been fully investigated and still remains the subject of research and discussion. Some trace elements contribute to the development of caries, while others, on the contrary, prevent formation of this process and accelerate the restoration of dental hard tissues. Penetration of trace elements into human dental structures via saliva, food, water and other routes contributes to the formation of carious diseases, or, conversely, its cessation and/or regression. Analyzing the studies allowed us to conclude that there is very scarce information available in the literature about the layered, zonal distribution of "vital" trace elements in healthy (intact) teeth dentin and enamel. However, to study the distribution of caries-static elements (Ca, F, P) on the enamel surface as well as in para-pulpal dentin is of great importance as well. It was aimed to identify trace elements in human teeth structures (enamel, dentin and cementum), as well as to determine their localization and concentration. To reach this objective, X-ray spectral analysis on 6 intact, extracted teeth has been performed by Scanning Electron Microscopy (SEM). Identification of trace elements was performed on the 6 sites/locations of these teeth: enamel surface layer, enamel thickness, enamel-dentin border, parapulpal dentin, root dentin, and cementum. As a result, it has been found that the distribution of essential trace elements in dental hard tissues is uneven, while such an important element in maintaining healthy teeth as Fluorine has been found in only minimal concentrations in hard tissues.

Influence of dual rinse irrigation on dentinal penetration of a bioceramic root canal sealer: A Conofocal microscopic Analysis.

To evaluate the sealer penetration after applying dual rinse irrigant in comparison with sodium hypochlorite and 17% EDTA. Mandibular premolars were prepared by ProTaper Next and irrigated with NaOCl, NaOCl/Dual Rinse or NaOCl/EDTA and then obturated with a single-cone technique and bioceramic-based. Samples were observed using confocal laser microscopy, and the maximum depth of penetration was measured, as well as the percentage of sealer coating the canal wall and the penetration area of the sealer. One-way anova was used, followed by Tukey post hoc test. Sealer penetration area displayed a statistically significant difference between the tested groups (P < 0.05), and the highest percentage of sealer coating the canal wall and the greatest depth of sealer penetration were found in Group (NaOCl/Dual Rinse). Group (NaOCl/Dual Rinse) displayed better sealer penetration inside the dentinal tubules than Group (NaOCl/EDTA), while Group (NaOCl) showed the lowest sealer penetration.

Adhesión a dentina parte I: características del sustrato y sistemas adhesivos / Dentin bonding part I: substrate characteristics and bonding systems

La Odontología Restauradora contemporánea no puede concebirse sin la adhesión de los materiales restauradores a las estructuras dentarias. En mu-chos procedimientos restauradores, no sólo el esmal-te sino también la dentina se encuentra involucrada, por lo tanto, la adhesión a esta última juega un rol cla-ve en el éxito clínico. No obstante, todavía supone un gran desafío lograr una adhesión estable y predeci-ble en el tiempo. El propósito del presente artículo es analizar las características principales de la dentina como sustrato adhesivo y describir los sistemas ad-hesivos actuales y sus mecanismos de acción (AU)

Contemporary Restorative Dentistry cannot be conceived without the adhesion of restorative materials to dental structures. In many restorative procedures not only the enamel, but also the dentin is involved, therefore dentin bonding plays a key role in their success. However, it is still a great challenge to achieve stable and predictable dentin bonding over time. The aim of this article is to analyze the main characteristics of dentin as an adhesive substrate and to describe current adhesive systems and their bonding mechanisms (AU)

Caracterización microscópica de la dentina de dientes temporales / Microscopic characterization of the dentin of temporary teeth

La dentina se compone de un mineral de fosfato de calcio identificado como dahllita, que se dispone en pequeños cristales de hidroxiapatita carbonatada con dimensiones de 36 × 25 × 4 nm, y por una fase orgánica cuyo principal componente es el colágeno tipo 1 en 90%, que se orienta en forma de malla. Esta conformación corresponde a los dientes permanentes. Dentro de las estructuras, encontramos túbulos dentinarios que miden, aproximadamente, entre 0.5-1 µm de diámetro en la periferia y hasta 3-5 µm cerca de la pulpa. En el presente estudio, realizado en dentina de dientes temporales, el lumen de dichos túbulos es más grande cuando se encuentra cerca de la pulpa dental. Asimismo, se encontraron cambios elementales importantes de acuerdo con las diferentes profundidades en las que se observó, encontrando un aumento en el peso porcentual de carbono cuando se encuentra a mayor profundidad, lo que indica una composición orgánica mayor en la dentina pulpar. En estudios de dientes permanentes esta composición es disminuida y con mayor concentración en la dentina cercana a la unión amelodentinaria. En dentina de dientes temporales se encontraron diferencias en el recuento de túbulos dentinarios por mm2, comparado a la dentina de dientes permanentes, donde el número de túbulos no varía mucho (AU)

Dentin is composed of a calcium phosphate mineral identified as dahllite, which is arranged in small crystals of carbonated hydroxyapatite with dimensions of 36 × 25 × 4 nm, and by an organic phase whose main component is type l collagen in 90%, which is oriented in the form of a mesh. This conformation corresponds to permanent teeth. Within the structures, we find dentin tubules that measure approximately 0.5-1 µm in diameter at the periphery and up to 3-5 µm near the pulp. In the present study, carried out in dentin of primary teeth, the lumen of these tubules is larger when it is close to the dental pulp. Likewise, important elemental changes were found according to the different depths in which it was observed, finding an increase in the percentage weight of carbon when it is at a greater depth, indicating a greater organic composition in the pulp dentin. In studies of permanent teeth, this composition is decreased and with a higher concentration in the dentin near the amelodentinal junction. In dentin of primary teeth, differences were found in the count of dentin tubules per mm2, compared to dentin of permanent teeth, where the number of tubules did not vary much (AU)