In vitro study of the treatment of dentin hypersensitivity with gallic acid combined with sodium fluoride.

BACKGROUND: Dentin hypersensitivity (DH) is a common oral condition that is associated with severe dental pain. Pain relief is a key focus of the treatment of DH. The purpose of this study was to evaluate the blocking and antacid effects of gallic acid (GA) combined with sodium fluoride (NaF) on dentinal tubules in vitro. METHODS: Ninety dentin discs from human third molars were treated with 6% citric acid for 2 min. Then, the surface morphologies of ten dentin discs were observed by scanning electron microscopy (SEM). The remaining samples were randomly divided into four groups: the NaF group, which was treated with 1000 ppm NaF; the GA group, which was treated with 4000 ppm GA; the GA + NaF group, which was treated with 1000 ppm NaF + 4000 ppm GA; and the blank group, which was treated with deionized water. The dentin permeability of each sample was measured with a water-filled system before processing and after 7 days of treatment. Dentin morphology and surface deposits were observed by SEM. Then, samples from the NaF, GA + NaF and blank groups were subjected to an acid challenge by incubation with 0.02% citric acid for 2 min. SEM and a water-filled system were used to evaluate the blocking and antacid effects of NaF and GA + NaF. RESULTS: 1. NaF and GA + NaF significantly decreased dentin permeability. The effect of the GA + NaF treatment was more significant. After acid challenge, both groups still exhibited decreased dentin permeability compared with the initial assessment. 2. Compared with the NaF group, the GA + NaF group had more mineral deposits on the dentin surface and dentin tubules. After acid challenge, the deposits in the GA + NaF group were still clearly visible. CONCLUSION: The combined effect of GA and NaF on reducing dentin permeability by blocking open dentin tubules is better than that of NaF alone. After acid challenge, the GA + NaF treatment still had a better effect.

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.

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.

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)

Loss of mutual protection between human osteoclasts and chondrocytes in damaged joints initiates osteoclast-mediated cartilage degradation by MMPs.

Osteoclasts are multinucleated, bone-resorbing cells. However, they also digest cartilage during skeletal maintenance, development and in degradative conditions including osteoarthritis, rheumatoid arthritis and primary bone sarcoma. This study explores the mechanisms behind the osteoclast-cartilage interaction. Human osteoclasts differentiated on acellular human cartilage expressed osteoclast marker genes (e.g. CTSK, MMP9) and proteins (TRAP, VNR), visibly damaged the cartilage surface and released glycosaminoglycan in a contact-dependent manner. Direct co-culture with chondrocytes during differentiation increased large osteoclast formation (p < 0.0001) except when co-cultured on dentine, when osteoclast formation was inhibited (p = 0.0002). Osteoclasts cultured on dentine inhibited basal cartilage degradation (p = 0.012). RNA-seq identified MMP8 overexpression in osteoclasts differentiated on cartilage versus dentine (8.89-fold, p = 0.0133), while MMP9 was the most highly expressed MMP. Both MMP8 and MMP9 were produced by osteoclasts in osteosarcoma tissue. This study suggests that bone-resident osteoclasts and chondrocytes exert mutually protective effects on their 'native' tissue. However, when osteoclasts contact non-native cartilage they cause degradation via MMPs. Understanding the role of osteoclasts in cartilage maintenance and degradation might identify new therapeutic approaches for pathologies characterized by cartilage degeneration.

Application Modes Affect Two Universal Adhesive Systems' Nanoleakage Expression and Shear Bond Strength.

OBJECTIVES: The aim of this study was to evaluate the shear bond strength and the nanoleakage expression of CLEARFIL Universal Bond Quick and Tetric N-Bond adhesive systems bonded to dentin. MATERIALS AND METHODS: 100 freshly extracted human premolar teeth were utilized. The teeth were sectioned to expose dentin. All dentin specimens were assigned into 4 experimental groups; 2 groups had Universal Bond Quick (Universalself group) and Tetric N-Bond (Tetricself group) applied in the self-etch mode, while 2 groups had Universal Bond Quick (Universaltotal group) and Tetric N-Bond (Tetrictotal group) applied in the total-etch mode. n = 15 for shear bond strength and n = 10 for nanoleakage experiment. One-way ANOVA and Kruskal-Wallis test were utilized to analyze the shear bond strength test and the nanoleakage expression, respectively. RESULTS: The highest significant bond strength value was recorded by the Tetricself specimens (p < 0.05) when compared to the remaining three groups. There were no statistically significant differences between the shear bond strength values recorded in the Tetrictotal, Universalself, and Universaltotal groups (p < 0.05). Both bonding systems applied in the self-etch mode (Universalself, Tetricself) had no silver nitrate deposits in the hybrid layer and the hybrid layer-adhesive interface (p < 0.001); however, both bonding systems applied in the total-etch mode (Universaltotal, Tetrictotal) had silver nitrate deposits in the hybrid layer, the hybrid layer-adhesive interface, and the bonding layer (p < 0.001). CONCLUSION: Applying the Universal Bond Quick and Tetric N-Bond in the self-etch mode exhibited better results in terms of nanoleakage expression. Universal Bond Quick showed the stability of the shear bond strength to dentin when applied using the total-etch or self-etch modes. Tetric N-Bond showed significant deterioration in bond strength when applied in the total-etch mode and exhibited the highest bond strength when applied in the self-etch mode.

Fluoride-Releasing Self-Etch Adhesives Create Thick ABRZ at the Interface.

A fluoride-releasing adhesive system is expected to promote mineralization of demineralized dentin/enamel around a composite restoration, thereby contributing to the longevity of the restoration. Scanning electron microscopic (SEM) and transmission electron microscopic (TEM) observations revealed the formation of an "acid-base resistant zone" (ABRZ) beneath the hybrid layer when dentin was treated with a self-etch adhesive system. A thicker ABRZ was formed from the upper slope to the end of the outer lesion, indicating greater resistance against an acid-base challenge, when a fluoride-releasing self-etch adhesive system was used. The slope formation of a fluoride-releasing adhesive is believed to be due to fluoride-release from the adhesive. Quantitative assessment of the acid resistance was performed at the interface using the region of interest (ROI) mode of a digital image analysis software package. The area of the ABRZ is influenced by the concentration of fluoride release from the adhesive resin. The threshold of fluoride concentration in the adhesive may exist to influence the morphology of the ABRZ. X-ray absorption fine structure (XAFS) analysis of the dentin treated with different concentrations of NaF-mouth rinses suggested that different fluoride concentrations result in the formation of different chemical compounds, such as fluorapatite and CaF2-like structures, on the dentin surface. This may explain the differences in µTBS values and morphological appearance of the ABRZ. NaF is effective in enhancing the enamel/dentin bond durability and also helps create a high quality of ARBZ to improve the clinical success of restorations.

Effect of Root Canal Filling Materials and Pretreatment with Solvents on the Shear Bond Strength of Composite Resin with Primary Tooth Dentin.

AIM: Root canal filling materials have the tendency to inhibit adhesion of resin-based composites. This study was aimed at evaluating the effect of root canal filling materials and their solvents on the shear bond strength (SBS) of resin composite with the primary tooth dentin. METHODS AND MATERIALS: Seventy-two intact anterior primary teeth were selected. Smooth dentinal surfaces were prepared to a minimum diameter of 3 mm and thickness of 1.5-2.0 mm. The samples were equally divided into six groups (n = 12). In group 1: control group, no root filling material; in group 2: Metapex, no solvent; in group 3: Metapex+ethanol solvent; in group 4: ZOE, no solvent; in group 5: ZOE+ethanol solvent; and in group 6: ZOE+orange oil solvent were applied. Then, dentin surfaces were etched, and composite restorations were placed and cured. The specimens were stored in distilled water at 37°C for 24 hours. SBS values were determined using a universal testing machine. RESULTS: The SBS values of composite to dentin in groups 2 and 4 were significantly lower than those in the control group (P < 0.001). Cleansing of the specimens with 96% ethanol after removal of Metapex significantly increased the composite-dentin bond (P < 0.001). Applying ZOE, only orange oil solvent significantly increased the SBS of the composite to the primary tooth dentin (P = 0.01). CONCLUSION: To reduce the negative effects of endodontic root filling materials on the SBS of composite and primary tooth dentin, ethanol is a suitable solvent when Metapex is used, while orange oil might be a better choice than ethanol when applying ZOE.

Acidic Monetite Complex Paste with Bleaching Property for In-depth Occlusion of Dentinal Tubules.

BACKGROUND: Dentin hypersensitivity (DH) is a common dental clinical condition presented with a short and sharp pain in response to physical and chemical stimuli. Currently no treatment regimen demonstrates long-lasting efficacy in treating DH, and unesthetic yellow tooth color is a concern to many patients with DH. AIM: To develop a bi-functional material which can occlude dentinal tubules in-depth and remineralize dentin for long-lasting protection of the dentin-pulp complex from stimuli and bleach the tooth at the same time. METHODS: A mixture containing CaO, H3PO4, polyethylene glycol and H2O2 at a specific ratio was mechanically ground using a planetary ball. The mineralizing complex paste was characterized by X-ray diffraction (XRD) and scanning electron microscopy (SEM). Dentin was exposed to the synthesized paste for 8 h and 24 h in vitro. The mineralizing property was evaluated using SEM and microhardness tests. Red tea-stained tooth slices were exposed to the synthesized paste for 8 h and 24 h in vitro. The bleaching effect was characterized by a spectrophotometer. RESULTS: The complex paste had very a fine texture, was injectable, and had a gel-like property with 2.6 (mass/volume) % H2O2 concentration. The X-ray diffraction pattern showed that the inorganic phase was mainly monetite (CaHPO4). The mineralizing complex paste induced the growth of inorganic crystals on the dentin surface and in-depth occlusion of dentin tubules by up to 80 µm. The regenerated crystals were integrated into the dentin tissue on the dentin surface and the wall of dentinal tubules with a microhardness of up to 126 MPa (versus 137 Mpa for dentin). The paste also bleached the stained dental slices. CONCLUSION: The mineralizing complex paste is a promising innovative material for efficient DH management by remineralizing dentin and in-depth occlusion of dentin tubules, as well as tooth bleaching.

Shear bond strength of a self-adhesive resin cement to dentin surface treated with Nd:YAG and femtosecond lasers.

This study aims to evaluate the effect of Nd:YAG and femtosecond lasers irradiation on the shear bond strength (SBS) of a self-adhesive resin cement to the human dentin surface. One hundred extracted third molar teeth were randomly divided into 10 experimental groups according to dentin surface treatments; with and without the bonding agent, Nd:YAG 302 J/cm2 and 440 J/cm2, femtosecond 4 J/cm2 and 7 J/cm2, and control groups were prepared. After surface treatments, a self-adhesive resin cement was luted by using a bonding jig (Ultradent Products Inc.). The specimens were then subjected to shear test at a crosshead speed of 0.5 mm/min, and failure loads were recorded as megapascal (MPa). Two-way analysis of variance and Tukey HSD tests were performed (p Ë‚ 0.05). Representative specimens from each experimental subgroup were examined by means of SEM. The highest SBS values were obtained in Group 302 J/cm2 Nd:YAG with bonding agent, and there is no statistical difference between Group 440 J/cm2 Nd:YAG with bonding and Group 7 J/cm2 femtosecond with bonding (p > 0.05). The lowest SBS values were observed in Group control without bonding agent. Nd:YAG and femtosecond laser treatments improved the adhesion between the dentin surface and the self-adhesive resin cement.

Physiochemical characteristics: A robust tool to overcome teeth heterogeneity on predicting laser ablation profile.

To avoid excessive tissue removal and collateral damage, the high-power density laser is apt for dental surgery also need to have high precision. For high-precision dental surgery with minimal tissue damage, the present work frames a method to predict laser ablation profile based on surface morphology and chemical composition of dentin. The surface morphology and chemical composition were studied on different dentin samples using scanning electron microscope (SEM) and Energy Dispersive X-ray Analysis (EDAX), respectively. The key laser ablation parameters (ω0 , Deff , and Fth ) were determined by laser irradiation study using 800 nm, Ti:Sapphire femtosecond laser at processing condition of 100 fs, 10 kHz and 10 mm/s. The dentin samples show a strong linear correlation between physiochemical characteristics and laser ablation parameters. The surface morphology exhibits a negative linear correlation with threshold fluence, whereas the converse is true for chemical composition. The laser ablation parameters of a random dentin sample are derived from the knowledge of linearity data. From the obtained laser ablation parameters, the complete theoretical ablation profile is constructed and validated with experimental ablation profile. Even though the surface morphology of dentin shows high linearity, the concentration of Ca and P can be used as the most feasible probe in clinical settings. Furthermore, the laser ablation rate and ablation efficiency are predicted by the method to optimize the laser processing condition for any specific teeth. The versatility of the method overcomes the problem of heterogeneity on various teeth and simplifies the method of finding optimal laser processing condition for immaculate laser surgery.

Evaluation of bond strength of resin cement to Er:YAG laser-etched enamel and dentin after cementation of ceramic discs.

The purpose of this study was to investigate the shear bond strength (SBS) of ceramic discs luted to differently etched enamel and dentin surfaces. Occlusal surfaces of 64 carious-free human molars and vestibule surfaces of 64 first maxillary incisors were ground to get flat superficial dentin and flattened enamel respectively. After generating 4 groups according to the surface etching method (37% orthophosphoric acid, Er:YAG laser-contact handpiece/scanning handpiece (1 or 2 times of scanning)), ceramic discs were luted to the surfaces with adhesive resin cement (Variolink N, Vivadent Ets., Schaan/Liechtenstein). After etching and cementation, thermocycling of 5000 cycles (Sd Mechatronik Gmbh, Feldkirchen-Westerham, Germany) and SBS test (Servopulser EHFFD1; Shimadzu, Kyoto, Japan) were performed respectively. The surface morphologies of 2 specimens, etched enamel and dentin, prepared for each group were examined with SEM analysis. Failure modes were determined under a USB digital microscope. Data were analyzed with one-way analysis of variance (ANOVA) and Tukey HSD test (α = 0.05). SBS values in dentin surfaces showed statistically significant differences (p < 0.05) among tested groups. The highest SBS among dentin groups was determined in the group which had 2 times etching by Er:YAG laser (11.42 MPa) by a scanning handpiece. No statistical differences were observed in the other dentin or enamel groups. Laser etching seems to be a viable alternative to acid etching on both enamel and dentin surfaces while double etching of dentin with a scanning handpiece can improve the adhesion.

Effect of silver diamine fluoride and proanthocyanidin on resistance of carious dentin to acid challenges.

The aim of this study was to evaluate the effect of silver diamine fluoride and grape seed extract on the microstructure and mechanical properties of carious dentin following exposure to acidic challenge. Ninety-eight molars with occlusal caries were used. In the control group the specimens were kept in distilled water. In the GSE group, the specimens were immersed in 6.5% grape seed extract solution for 30 minutes. In the SDF group, the specimens were immersed in 30% SDF solution for 4 minutes. In the GSE+SDF group, the specimens were immersed in 6.5% grape seed extract solution for 30 minutes and then exposed to 30% SDF solution for 4 minutes. All the groups underwent pH cycling model for 8 days. Microhardness measurements were taken at the baseline before surface treatments and after pH cycling. Elastic modulus was measured, after pH cycling. In the control group, the final hardness was significantly lower than the initial hardness (P = 0.001). In the SDF group, the final hardness was significantly higher than the initial hardness (P < 0.001). There was no significant difference between the initial and final hardness values in the GSE and GSE + SDF groups (p = 0.92, p = 0.07). The H1-H0 in the SDF group was significantly higher than the other groups (P<0.05). Moreover, elastic modulus of the experimental groups except GSE+SDF group was significantly higher than control. The highest mean elastic modulus was detected in the SDF group (P<0.001). The use of SDF and GSE prior to the acid challenge improved mechanical properties. Microstructural investigation, using scanning electron microscope showed dentin structure protection against acid challenges with SDF treatment and collagen matrix stabilization with GSE treatment. However combined use of these agents was not beneficious.