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Journal of Dental Research Dec 2011Recent studies have reported collagen cross-linking after exposure to riboflavin followed by ultraviolet-A (UVA) exposure. This study is the first to investigate the...
Recent studies have reported collagen cross-linking after exposure to riboflavin followed by ultraviolet-A (UVA) exposure. This study is the first to investigate the effect of a riboflavin-containing primer on adhesive interface stability and dentinal matrix metalloproteinase activity. Human dentin was etched with 35% phosphoric acid, treated with 0.1% riboflavin, exposed to UVA for 2 min, and bonded with a two-step etch-and-rinse adhesive. Adhesive was applied to control specimens without riboflavin/UVA. Specimens were subjected to microtensile bond strength tests and pulled to failure after storage for 24 hrs, 6 mos, or 1 yr. Interfacial nanoleakage was evaluated by light and transmission electron microscopy. To investigate dentinal matrix metalloproteinase activity, we performed correlative zymographic assays on protein extracts obtained from phosphoric-acid-etched dentin powder with or without riboflavin/UVA treatment and XP Bond. Ultraviolet-activated riboflavin treatment increased the immediate bond strength to dentin at all aging intervals (p < 0.05 vs. control) and decreased interfacial nanoleakage in aged specimens (1 yr; p < 0.05). Zymograms revealed that riboflavin/UVA pre-treatment inhibited dentinal matrix metalloproteinase activity (especially MMP-9). In conclusion, dentinal collagen cross-linking induced by riboflavin/UVA increased immediate bond strength, stabilized the adhesive interface, and inhibited dentin matrix metalloproteinases, thereby increasing the durability of resin-dentin bonds.
Topics: Collagen Type I; Cross-Linking Reagents; Dental Bonding; Dental Leakage; Dental Stress Analysis; Dentin; Dentin-Bonding Agents; Electrophoresis, Polyacrylamide Gel; Humans; Matrix Metalloproteinase Inhibitors; Riboflavin; Tensile Strength; Time Factors; Ultraviolet Rays
PubMed: 21940521
DOI: 10.1177/0022034511423397 -
Journal of Endodontics Feb 2019Although the strength and toughness of dentin decrease with age, no study has explored if restorative treatments are a contributing factor.
INTRODUCTION
Although the strength and toughness of dentin decrease with age, no study has explored if restorative treatments are a contributing factor.
METHODS
Multiple extracted teeth were obtained from randomly selected donors and categorized according to donor age and prior root canal treatment. The microstructure and chemical composition of radicular dentin were evaluated using scanning electron microscopy and Raman spectroscopy, respectively, and the strength was evaluated in 4-point flexure to failure. Data were compared using the Student t test.
RESULTS
Dentin from the root canal-restored teeth exhibited significantly lower strength (P < .05) than tissue from age- and donor-matched unrestored tooth pairs. Although there was no significant difference in the mineral-to-collagen ratio between the 2 groups, dentin obtained from the root canal-treated teeth exhibited more extensive collagen cross-linking and lower tubule occlusion ratios than the unrestored tooth pairs.
CONCLUSIONS
There is a decrease in the strength of radicular dentin with aging, but prior root canal treatment increases the extent of degradation.
Topics: Aged; Aging; Collagen; Dental Stress Analysis; Dentin; Flexural Strength; Humans; Microscopy, Electron, Scanning; Middle Aged; Minerals; Root Canal Therapy; Shear Strength; Spectrum Analysis, Raman; Tooth Fractures
PubMed: 30711176
DOI: 10.1016/j.joen.2018.10.004 -
Calcified Tissue International Mar 2009The dentin-enamel junction (DEJ) plays an important role in preventing crack propagation from enamel into dentin. This function stems from its complex structure and...
The dentin-enamel junction (DEJ) plays an important role in preventing crack propagation from enamel into dentin. This function stems from its complex structure and materials properties that are different from either dentin or enamel. The molecular structural differences in both mineral and organic matrix across the DEJ zone were investigated by two-dimensional confocal Raman microspectroscopic mapping/imaging technique. The intensity ratios of 1450 (CH, matrix)/960 (P-O, mineral) decreased gradually to nearly zero across the DEJ. The width of this transition zone was dependent on the intratooth location, with 12.9 +/- 3.2 microm width at occlusal positions and 6.2 +/- 1.3 microm at cervical positions. The difference in width was significant (P < 0.001). Concurrently, spectral differences in both organic and inorganic matrices across the DEJ were also noted. For example, the ratios of 1243 (amide III)/1450 (CH) within the DEJ were lower than the values in dentin; however, the ratios of 1665 (amide I)/1450 (CH) within the DEJ were higher than those values in dentin. In addition, the ratios of 1070 (carbonate)/960 (phosphate) within the dentin were lower than the values in the DEJ. Raman images indicated that the distribution of the above ratios across the DEJ zone were also different at occlusal and cervical positions. The results suggest that the intratooth-location-dependent structure of the DEJ may be related to its function. Micro-Raman spectroscopic/imaging analysis of the DEJ provides a powerful means of identifying the functional width and molecular structural differences across the DEJ.
Topics: Dental Enamel; Dentin; Humans; Microscopy, Confocal; Molecular Structure; Spectrum Analysis, Raman; Tooth
PubMed: 19152060
DOI: 10.1007/s00223-008-9212-8 -
Proceedings of the Finnish Dental... 1992Smear layers are created on hard tissues whenever they are cut with hand or rotary instruments. This thin (1-2 microns) layer of denatured cutting debris is very... (Review)
Review
Smear layers are created on hard tissues whenever they are cut with hand or rotary instruments. This thin (1-2 microns) layer of denatured cutting debris is very tenacious and, in fact, is often the surface to which restorative materials are luted. The solubility characteristics, chemical reactivity and the structure-function relationships of this layer have not yet been well-defined. During creation of the smear layer, cutting debris is forced variable distances into dentinal tubules. These so-called smear plugs, together with the smear layer decrease dentin permeability, dentin sensitivity and surface wetness. Bonding adhesive resins to smear layers appears to limit the theoretical bond strength unless the smear layers are loosened or partially removed. Future research in this area will include the use of surface analytical techniques such as Auger electron spectroscopy and ESCA. These techniques are required because of the thinness of the smear layer. It is clear that the nature of this critical interface between dental materials and cut hard tissues remains largely unknown. This field will provide fertile ground for future research.
Topics: Animals; Dentin; Humans; Smear Layer
PubMed: 1508877
DOI: No ID Found -
Minerva Stomatologica Sep 1995Samples of dentine of healthy teeth were analysed in this study with at the scanning electron microscope. In order to see the morphological changes in the structure of... (Review)
Review
Samples of dentine of healthy teeth were analysed in this study with at the scanning electron microscope. In order to see the morphological changes in the structure of both the dentine and the dentinary tubules, the dentine was observed at different levels according to the distance from the pulp. After the removal of the odontoblasts the predentine appears to be composed only by collagen fibres and is about 15 microns thick. At this level, the dentinary tubules can reach a diameter of 4 microns. This measure decreases progressively in proportion to the distance from the pulp, reaching about 2 microns at a distance of 1 mm, and 1 micron at 2 mm from the pulp. A decrease in the tubular lumina is observed when the peritubular dentine changes from 0.8 to 1 in thickness. The internal surface of the tubules appears smooth and shows the confluence of very thin lateral canaliculi. The dentinary tubules end forming forks which spread out until they enter into contact with the enamel.
Topics: Dental Pulp; Dentin; Humans; In Vitro Techniques; Microscopy, Electron, Scanning; Ultrasonography
PubMed: 8668111
DOI: No ID Found -
Human & Experimental Toxicology Sep 2014The effect of dentin contacting materials on three-dimensional cultures of pulp-derived cells was evaluated in a dentin barrier test device using erbium-doped yttrium,...
OBJECTIVES
The effect of dentin contacting materials on three-dimensional cultures of pulp-derived cells was evaluated in a dentin barrier test device using erbium-doped yttrium, aluminum, and garnet (Er:YAG) laser-treated dentin.
METHODS
The test materials (iBond(®), G-Bond™, and Vitrebond™) were applied on laser-treated or untreated dentin discs. After 24 h of exposure with perfusion of the test chamber, cell survival was evaluated by enzyme activity and related to a nontoxic control material. The mean values of control tissues were set to represent 100% viability. Data were analyzed using Kruskal-Wallis and Mann-Whitney U test.
RESULTS
Vitrebond was the most toxic material for both laser-treated and untreated dentin. On untreated dentin, G-bond was cytotoxic to the pulp-derived cells (p < 0.05), and iBond was similar to the negative control group (p > 0.05). However, G-Bond and iBond were not cytotoxic when they were applied to Er:YAG laser-treated dentin (p > 0.05).
CONCLUSION
Er:YAG laser treatment of dentin may protect the pulp cells from toxic substances of dentin contacting restorative materials; however, this effect is material related. Taking into consideration the limitations of this in vitro study, the Er:YAG laser treatment of dentin before restoration might be an option for decreasing the cytotoxic effects of the dental materials. Further research is required for clinical applications.
Topics: Animals; Biocompatible Materials; Cattle; Dental Pulp; Dentin; Lasers, Solid-State; Materials Testing; Microscopy, Electron, Scanning
PubMed: 24275641
DOI: 10.1177/0960327113511476 -
Journal of Endodontics Feb 2012The objectives of this study were to evaluate and compare the time-dependent chemical and ultramorphologic effects of ethylenediaminetetraacetic acid (EDTA) and sodium... (Comparative Study)
Comparative Study
OBJECTIVES
The objectives of this study were to evaluate and compare the time-dependent chemical and ultramorphologic effects of ethylenediaminetetraacetic acid (EDTA) and sodium hypochlorite (NaOCl) in young and old dentin.
METHODS
Sixty-four teeth scheduled for extraction were collected from young (<30 years) and old (>60 years) patients. In 48 teeth, the dentin was reduced to a powder state and treated with EDTA or EDTA + NaOCl for 1 and 10 minutes, respectively. X-ray diffraction analysis was used to determine the changes in the composition of dentin through dissolution of hydroxyapatite (HAp). In the remaining teeth (n = 16), the root canals were prepared, bisected, and subjected to the same time-dependent treatment regimens. The changes in the number and area of dentinal tubules were calculated by image analysis. The data were analyzed statistically by paired t test and one-way analysis of variance, followed by Tukey honestly significant difference test at P = .05.
RESULTS
In both young and old dentin, EDTA significantly decreased the HAp intensity at 1 and 10 minutes, whereas EDTA + NaOCl only decreased that of old dentin at 10 minutes. Pair-wise comparisons revealed that in old dentin, the reduction in HAp intensity after treatment with EDTA and EDTA + NaOCl was significantly greater at 10 minutes than at 1 minute, whereas in young dentin, a significant decrease was only observed in the EDTA/10-minute subgroup. Compared with their 1-minute counterparts, 10-minute treatment with EDTA + NaOCl significantly increased the tubular diameter and tubular area of old dentin. In young dentin, the tubular area and diameter values were not affected by treatment time (P > .05).
CONCLUSIONS
In young root dentin, 10-minute treatment with EDTA + NaOCl does not significantly alter the chemical and ultramorphologic structure and thus appears to be unnecessary. In old dentin, extended treatment time with EDTA + NaOCl should be avoided owing to excessive demineralization and erosion. In both types of dentin, EDTA was not effective in complete removal of the smear layer.
Topics: Adult; Age Factors; Chelating Agents; Dental Pulp Cavity; Dentin; Durapatite; Edetic Acid; Humans; Image Processing, Computer-Assisted; Microscopy, Electron, Scanning; Middle Aged; Root Canal Irrigants; Smear Layer; Sodium Hypochlorite; Time Factors; X-Ray Diffraction
PubMed: 22244637
DOI: 10.1016/j.joen.2011.10.024 -
Journal of Dentistry May 2016To determine the effects of intrinsic wetness on the formation of dentin bonding interfaces of four resin cement systems bonded to dentin under different pulpal...
OBJECTIVES
To determine the effects of intrinsic wetness on the formation of dentin bonding interfaces of four resin cement systems bonded to dentin under different pulpal pressures.
METHODS
Thirty-six freshly extracted third molars were selected and processed for dentin μTBS. The teeth were randomly assigned into 12 experimental groups, according to the adhesive luting system [Adper Single Bond Plus (3M ESPE) combined with two luting agents RelyX ARC (3M ESPE) and heated Filtek Z250 Universal Restorative (3M ESPE), Clearfil CD Bond (Kuraray) combined with Clearfil Esthetic Cement (Kuraray), and RelyX Unicem 2 Automix (3M ESPE)] and pulpal pressure (0, 5, and 20 cm of simulated pulpal pressure). Leucite-reinforced glass-ceramic slabs (IPS Empress CAD, Ivoclar Vivadent) of 3mm thickness were bonded to dentin. The samples were stored in distilled water for 24h and then sectioned in X/Y directions across the adhesive interface to obtain specimens with a cross section of 0.8 ± 0.2mm(2). All sticks were fractured by tension at a crosshead speed of 1.0mm/min and the data were submitted to Kruskal-Wallis and Mann-Whitney Tests (α=0.05). Ultrastructural analysis of the interfaces was performed using Confocal Laser Scanning Microscopy (CLSM) and Scanning Electron Microscopy (SEM).
RESULTS
The statistical analyses showed that pulpal pressure decreased μTBS for all groups. Significantly higher μTBS values were obtained in heated Z250 group restored without any pulpal pressure. CLSM showed that the uptake of water through the dentin tubuli and their anastomosis of lateral branches during the adhesive luting procedures prevented adequate formation of the dentin bonding interfaces. SEM showed that the luting film created is material- dependent and all adhesive failure occurred at the resin-dentin interface.
CONCLUSION
The constant intrinsic wetness replenishment prevents adequate formation of the hybrid layer.
CLINICAL SIGNIFICANCE
Intrinsic moisture during adhesive luting procedures significantly affects the interaction between luting materials and dentin subtract and decreases the quality and bonding strength of the resin-dentin bond.
Topics: Acid Etching, Dental; Bisphenol A-Glycidyl Methacrylate; Dental Bonding; Dental Cements; Dental Stress Analysis; Dentin; Dentin Permeability; Dentin-Bonding Agents; Humans; Materials Testing; Molar, Third; Resin Cements; Water
PubMed: 26976554
DOI: 10.1016/j.jdent.2016.03.005 -
Journal of Structural Biology Aug 2013Dentin is a mineralized collagen tissue with robust mechanical performance. Understanding the mechanical behavior of dentin and its relations to the dentinal structure...
Dentin is a mineralized collagen tissue with robust mechanical performance. Understanding the mechanical behavior of dentin and its relations to the dentinal structure can provides insight into the design strategies to achieve tooth functions. This study focuses on the inelastic deformation of human dentin and its underlying mechanisms. By combining four-point bending tests with fluorescent staining and laser scanning confocal microscopy, it was found that human dentin, especially root dentin, exhibited significant inelastic deformation and developed extensive microdamage in the form of microcracks prior to fracture. Dense and wavy microcracks spread uniformly across the tensile surface of root dentin, while compressive microcracks formed cross-hatched patterns. The presence of peritubular dentin in coronal dentin dramatically decreased the extent of microcracking, reducing inelasticity. Dentinal tubules were found to be initiation sites of both tensile and compressive microcracks. A unique crack propagation process was observed in root dentin under tension: numerous ring-shaped cracks formed at each dentinal tubule ahead of a growing crack tip. The advance of the tensile microcracks occurred by the merging of those ring-shaped cracks. The current findings on the microcracking process associated with inelastic deformation helps to understand the nature of strength and toughness in dentin, as well as the mechanical significance for structural variations across the whole tooth.
Topics: Biomechanical Phenomena; Collagen; Dentin; Elasticity; Humans; Stress, Mechanical; Tensile Strength; Tooth Fractures; Tooth Root
PubMed: 23583703
DOI: 10.1016/j.jsb.2013.04.002 -
Journal of Oral Science Mar 2010This study was done to assess the influence of the topical application of two different desensitizing agents on dentin permeability and dentinal tubule occlusion....
This study was done to assess the influence of the topical application of two different desensitizing agents on dentin permeability and dentinal tubule occlusion. Twenty-one rats provided 84 teeth: 36 for the in vitro and 48 for the in vivo investigation. The following agents were tested: Group 1, 2% potassium nitrate plus 2% sodium fluoride gel; Group 2, 5% sodium fluoride varnish; Group 3, 3% hydroxyethylcellulose gel (control). Cervical cavities were prepared and EDTA was applied to expose the dentinal tubules. After each treatment, Evans blue dye was applied to the teeth. Dentin permeability, scanning electron microscope (SEM) sections, and energy dispersive X-ray (EDX) were analyzed. One-way ANOVA was used to compare the data. There were significant differences (P < 0.05) among groups for dentin permeability, number of tubules/mm(2), tubule area and tubular diameter. Groups 1 and 2 (both in vitro and in vivo) showed open and partially occluded tubules. Group 3 had the most open tubules. EDX revealed similar composition for both experimental conditions. Within the limits of the study, 2% nitrate potassium plus 2% sodium fluoride gel and 5% fluoride varnish decreased the dentin permeability, resulting in partial tubular occlusion.
Topics: Animals; Dentin; Dentin Desensitizing Agents; Dentin Permeability; Drug Combinations; Fluorides, Topical; Male; Microscopy, Electron, Scanning; Nitrates; Potassium Compounds; Random Allocation; Rats; Rats, Wistar; Reproducibility of Results; Sodium Fluoride; Spectrometry, X-Ray Emission
PubMed: 20339229
DOI: 10.2334/josnusd.52.23