Tooth sensitivity prevention and treatment.
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Dentin Permeability↗
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Laboratory enamel solubility reduction and fluoride uptake from enamelon dentifrice.
The presence of calcium-releasing ingredients in toothpastes containing sodium fluoride is usually avoided to prevent loss of active fluoride due to the formation of the insoluble calcium salt. The purpose of this study was to determine the bio-availability of fluoride from Enamelon Toothpaste (E), which simultaneously supplies fluoride, calcium and phosphate salts from a dual dispensing package. Fluoride uptake into artificially lesioned enamel cores due to the use of the test dentifrice (E) diluted 1:3 in whole human saliva was compared to that from a clinically proven effective sodium fluoride/silica USP reference toothpaste (C) and a non-fluoride control (E-w/o F). Enamel solubility reduction due to the use of E, C and E-w/o F was measured by determining the quantity of phosphate released to lactic acid buffer before and after treatment of the crowns of molars with 1:3 slurries of the dentifrices in water. Fluoride uptakes and enamel solubility reductions were 5031 +/- 158 ppm and 21.6 +/- 2.2% for E, 1915 +/- 39 ppm and 13.6 +/- 2.0% for C, and -3 +/- 2 ppm and 0.8 +/- 1.7% for E-w/o F. The fluoride uptake and enamel solubility reductions from E were significantly greater than from C (p < 0.001, Fisher LSD), and both fluoride-containing dentifrices significantly outperformed E-w/o F (p < 0.001). The laboratory results indicate that the calcium and phosphate salts delivered by the remineralizing Enamelon dentifrice increase the bioavailability of fluoride to substantially exceed that of the clinically proven standard dentifrice.
Analysis of Variance↗
Remineralization by fluoride enhanced with calcium and phosphate ingredients.
The effectiveness of fluoride ions provided by toothpastes and mouthrinses in promoting remineralization can be limited by the low concentrations of calcium and phosphate ions in saliva. The purpose of this study was to determine whether improved remineralization can be obtained from toothpastes or mouthrinses that simultaneously deliver fluoride, calcium, and phosphate ions from dual-dispensing systems. Enamel specimens with artificial lesions between 60 and 90 microns deep were cycled 15 times through demineralization for 30 minutes, treated for 5 minutes with an experimental or control fluoride toothpaste or mouthrinse, and remineralized for 60 minutes. In the toothpaste study, surface hardness increased by 11.5 +/- 9.2 and 2.7 +/- 3.6 Vickers hardness units, and enamel fluoride content was 5984 +/- 521 ppm and 3971 +/- 531 ppm for the experimental and control fluoride toothpastes, respectively. Remineralization was confirmed by x-ray microradiography. In the mouthrinse study, surface hardness increased by 8.8 +/- 7.7 and 2.2 +/- 3.7 Vickers hardness units, and enamel fluoride content was 6111 +/- 1078 ppm and 3160 +/- 364 ppm for the experimental and control fluoride mouthrinses, respectively. Use of a non-fluoride control mouthrinse led to a decrease in surface hardness of 3.7 +/- 5.2 Vickers hardness units despite a fluoride content of 402 ppm. The results demonstrate that calcium and phosphate supplementation in a toothpaste or mouthrinse can improve remineralization and increase fluoride uptake.
Calcium Phosphates↗
[Diagnosis and treatment of dental caries at the white spot stage].
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Adolescent↗
Permeability of the apical third of the root to drugs used in endodontic therapy: an in vitro study.
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Cresols↗
Orthodontic tooth movement and bioelectricity.
Research in the field of orthodontics is now focused on the biology of tooth movement. Advanced molecular biology techniques has showed the researchers new avenue towards finding answers to the questions asked for the last few decades. Now it is possible for the researches to explore the lacunae in the field. One such field is, pharmaco-therapeutically or electrophysiologically enhancing the rate of tooth movement, improving the stability of the results, augmenting the anchorage. The voltage gated channels of cell membrane of connective tissue cells of the periodontal ligament can be modulated by electrophysiological ways. The application of an electric current may alter the electrolytic environment allowing changes in the type and rate of ions that move across the cell membranes. Changes of the flux of K+, Ca++, Na+, Mg+, and Cl. can act as a mediator for cellular changes. Micro-pulsed electrical stimulation could reach bone osteoblasts non-invasively and this current can result in an increase in the cAMP and cGMP. These cyclic nucleotides are a type of second messenger, which play a role in the efficient remodeling of alveolar bone and in including more tooth movement. This article discusses the role of electrical potential in orthodontic tooth movement, methodology of studying the electrophysiology of cell membrane and the recent advances in the field and its possible clinical application.
Animals↗
Dentin/enamel adhesives: review of the literature.
This paper describes the development of dentin bonding systems, and describes the current strategies for bonding composite resin materials to dentin. Two main strategies are available--total-etch or self-etch--and each has unique advantages and disadvantages. For each category, simplified systems that reduce the number of application steps are available. Currently, the market is moving towards self-etching materials, largely because these are associated with less post-operative tooth sensitivity. However, the clinical performance of most of these materials is not yet proven.
Acid Etching, Dental↗
Ultrastructural study of tracer permeability through the cat and ferret enamel organ.
The access of exogenous materials to the developing enamel surface has been intensively studied in rodents, but not in other mammalian species. This ultrastructural study investigates the permeability of injected horseradish peroxidase (HRP) and lanthanum tracers in cat and ferret tooth buds. In cat enamel organs fixed by immersion, lanthanum did not escape the capillaries overlying secretory stage tooth buds, but it did permeate up to the distal junctions of ruffle-ended (RA) and the proximal junctions of smooth-ended (SA) ameloblasts. Perfusion fixation with lanthanum compromised junctional integrity of cat ameloblasts at all stages of development. Similarly, HRP rarely escaped the capillaries associated with cat secretory stage enamel organs. However, unlike lanthanum, HRP was mostly confined to the vasculature of maturation stage enamel organs in immersion fixed cats at all time intervals examined. In ferrets, HRP penetrated up to, but not beyond, the distal junctional complexes of secretory ameloblasts. In maturation stage enamel organs, HRP coated the papillary and RA cells, but did not penetrate the RA distal cell junctions. HRP did permeate the extracellular spaces of SA to reach the underlying enamel surface. Ameloblasts in transitional phases of SA and RA endocytosed HRP at the distal cell surface. This data leads to several conclusions. First, HRP localization in the ferret paralleled that observed in rodents. Second, the results of cat enamel organs substantiate previous studies showing perfusion fixation can increase vascular and intercellular permeability to lanthanum. However, in cats fixed by immersion, both lanthanum and HRP were restricted to capillaries associated with the secretory stage enamel organ, and only lanthanum escaped maturation stage capillaries. It is suggested that variations in the fenestrations and distribution of capillaries associated with the cat enamel organ may differentially retain some materials and permit other materials to escape with relative ease.
Ameloblasts↗
Penetration of the pulp chamber by carbamide peroxide bleaching agents.
Hydrogen peroxide readily penetrates the pulp chamber of freshly extracted teeth. This study was undertaken to determine whether carbamide peroxide also penetrates the pulp chamber. Freshly extracted teeth were sectioned 2 to 3 mm apical to the cementoenamel junction and the coronal pulpal tissue was removed. Acetate buffer was placed in the pulp chamber to absorb and stabilize any peroxide that might penetrate. The coronal portion of each tooth was immersed in either carbamide peroxide gel or gelled hydrogen peroxide at various concentrations for 15 min at 37 degrees C. The buffer was removed, leukocrystal violet was added, and the optical density of the resulting blue solution was determined spectrophotometrically. Amounts of peroxide found in the pulp chamber after 15 min ranged from 3.3 +/- 0.38 micrograms for the 10% sample to 40.4 +/- 3.51 micrograms for the 30% sample.
Carbamide Peroxide↗
Penetration of the pulp chamber by carbamide peroxide bleaching agents on teeth restored with a composite resin.
This in vitro study was performed to evaluate the effect of various concentrations of carbamide peroxide bleaching agents on the pulp chambers of teeth restored by a composite resin. Forty-nine human extracted anterior teeth were used. All the teeth were sectioned 3 mm apical of the cemento-enamel junction and the intracoronal tissue removed. The teeth were separated into the seven groups each containing seven teeth. Twenty-eight teeth were used as controls (groups I-IV), standardized cavities were prepared with the remaining 21 teeth (groups V, VI, VII), and restored with a hybrid composite resin (XR Herculite). Acetate buffer was placed in the pulp chamber to absorb and stabilize any peroxide that might penetrate. Group I was exposed only to distilled water. Groups II and V were applied with 10% CP (Contrast PM), groups III and VI were applied with 15% CP (Contrast PM), groups IV and VII were applied with 35% CP (Quik Start) and left for 30 min at 37 degrees C. Then, the acetate buffer solution in the pulp chamber of each tooth was removed and the chamber was then rinsed twice with 100 ml of distilled water. The contents then had leucocryctal violet and enzyme horseradish peroxidase added. The optical density of the resulting blue solution was determined spectrophotometrically, and was converted into microgram equivalents of hydrogen peroxide. A higher level of bleaching agent penetrated into the pulp chamber in the restored teeth than in the sound teeth.
Analysis of Variance↗
Time-dependent mechanical behaviour of the periodontal ligament.
The process of tooth displacement in response to orthodontic forces is thought to be induced by the stresses and strains in the periodontium. The mechanical force on the tooth is transmitted to the alveolar bone through a layer of soft connective tissue, the periodontal ligament. Stress and/or strain distribution in this layer must be derived from mathematical models, such as the finite element method, because it cannot be measured directly in a non-destructive way. The material behaviour of the constituent tissues is required as an input for such a model. The purpose of this study was to determine the time-dependent mechanical behaviour of the periodontal ligament due to orthodontic loading of a tooth. Therefore, in vivo experiments were performed on beagle dogs. The experimental configuration was simulated in a finite element model to estimate the poroelastic material properties for the periodontal ligament. The experiments showed a two-step response: an instantaneous displacement of 14.10 +/- 3.21 microns within 4 s and a more gradual (creep) displacement reaching a maximum of 60.00 +/- 9.92 microns after 5 h. This response fitted excellently in the finite element model when 21 per cent of the ligament volume was assigned a permeability of 1.0 x 10(-14) m4/N s, the remaining 97 per cent was assigned a permeability of 2.5 x 10(-17) m4/N s. A tissue elastic modulus of 0.015 +/- 0.001 MPa was estimated. Our results indicate that fluid compartments within the periodontal ligament play an important role in the transmission and damping of forces acting on teeth.
Animals↗
Biological characteristics of the junctional epithelium.
This review summarizes the biological properties of the junctional epithelium, focusing on its developmental aspects, wide intercellular spaces and desmosomes, dense granules, permeability barrier, phagocytotic activity, adhesive structures and nerve terminals. It also discusses the morphology and functions of long junctional epithelium and peri-implant epithelium. Junctional epithelium is derived from the reduced enamel epithelium during tooth development. Apoptosis occurs in the border between oral and reduced enamel epithelia during tooth eruption. Junctional epithelium expresses a cytokeratin-19 immunoreaction, suggesting that this protein is a consistent differentiation marker. Wide intercellular spaces, which contain neutrophils and nerve endings, are formed as there are fewer desmosomes than in the oral epithelium. Dense, membrane-bound granules in the epithelium might correspond with membrane-coating granules, as revealed by their shape, components and freeze-fracture images. Junctional epithelium with high permeability contains exogenously expressed alpha-defensins, while stratified epithelia contain endogenously expressed beta-defensins. The phagocytotic activity in this epithelium remains unclear. Integrin-alpha6beta4 and laminin-5 form a complex in the tooth surface internal basal lamina. Long junctional epithelium created experimentally attaches to the cementum surface by hemidesmosomes and basal lamina. The peri-implant epithelium differs in proliferation and in adhesive structure from the normal junctional epithelium. In conclusion, wide intercellular spaces and poorly developed desmosomes are closely correlated with a permeable nature. There is still uncertainty over the phagocytotic activity of the epithelium. Integrin-alpha6beta4 and laminin-5 form a significant complex in the internal basal lamina. Junctional epithelium receives a rich sensory nerve and has a high rate of cell turnover. Long junctional epithelium can be produced rapidly during wound healing, due to high proliferative activity. Peri-implant epithelium might be a poorly adhered and permeable epithelium.
Animals↗
[Use of the CO2 laser in enamel-dentin bonding procedures: experimental findings].
The objective of this study is to verify if laser (CO2) preparation of dental tissues has an effect on the quality of the seal of composite fillings. Forty-eight cavities were filled with the Scotchprep/Scotchbond 2 system, using P 50 (3M) as filling material, following the clinical protocol of the system; 40 cavities had previously been treated with a CO2 laser Sharplan 1020 (SBM). The teeth were thermocycled (240 cycles 4 degrees C/55 degrees C), then placed in a 0.5% basic fuschine solution for 48 hours after isolation of the root dentin. After inclusion and section, the penetration of the coloring agent was examined at the interface tooth-filling. This was followed by examination of the interface composite-tooth with the Scan Electronic Microscope. In order to visualize a possible alteration of the dentinal seal, 4 cavities treated with laser were placed in a 0.5% basic fuschine solution for 48 hours after isolation of the root dentin. Four reference cavities were cut with a diamond bur on a high speed handpiece. The following results were obtained: 1) the dentinal permeability of the laser-treated samples increases markedly in comparison with the reference group. 2) the filling-tooth junction of the laser-treated samples were never dye-tight (contrary to the reference samples). 3) fissures were created in the enamel and the dentin. The Scan Electron Microscopy confirms these results.
Carbon Dioxide↗
The permeability of human dentine in vitro and in vivo.
Experiments in cats have shown that Evans blue dye diffuses at a greater rate into dentine in recently extracted teeth than in vivo. These experiments have now been repeated in man and similar results were obtained except that, after applications in vivo, visible concentrations of the dye were present in the dentine, and in a few cases, even in the pulp. It is concluded that, as in the cat, the diffusion in vivo was impaired by outward flow of fluid in the dentinal tubules but the mean velocity of flow in the human dentine was less than that in the cat.
Acid Etching, Dental↗
Density of dentinal tubules affects the tensile strength of root dentin.
OBJECTIVES: The aim of this study is to count the dentinal tubules in the coronal and middle-apical third of root dentin of teeth extracted due to the progression of periodontal disease, and to compare the Ultimate Tensile Strength (UTS) of the same areas. The research hypothesis was that root dentin areas with different densities of dentinal tubules would also show different UTS values. METHODS: From 10 caries free maxillary central, lateral incisors and canines, extracted for periodontal reasons from three patients, cylindrical specimens approximately 10 mm long were prepared parallel to the long axis of the root and then divided into two parts using a low speed diamond saw one from the coronal third of the root, (Group 1) and one from the middle-apical third of the root (Group 2). The density of the dentinal tubules of the specimens of the two groups was measured by means of a scanning electron microscope and the UTS of the specimens was measured by a microtensile test. One way ANOVA was used to assess the effect of specimen location (coronal specimens vs. middle-apical specimens) on UTS. The differences in the density of dentinal tubules between coronal and middle-apical specimens were also subjected to statistical analysis using one-way ANOVA. RESULTS: UTS values of middle-apical specimens were found to be significantly (p < 0.05) higher than those of coronal specimens. The results of the one-way analysis of variance showed that the number of dentinal tubules of the samples from the coronal part of the root groups was significantly higher than that of samples from the middle-apical part (p < 0.05). SIGNIFICANCE: These results suggest that high values of tensile strength of the dentin are associated with low densities of dentinal tubules and that apical areas of root dentin are more resistant to tension than coronal ones.
Analysis of Variance↗
Vascular changes during the development of the rat gingiva.
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Animals↗
An in vitro model for assessment of fluoride uptake from glass-ionomer cements by dentin and its effect on acid resistance.
This investigation presents an experimental model for studying interactions of glass-ionomer cements (GICs) with bovine dentin slabs. Fluoride incorporation was studied with five serial abrasion biopsies, each being approximately 10 microns thick. The time of interaction was a very important parameter, indicating continuous fluoride release from the GIC and diffusion into dentin over a 30-day period. Expressed in mass per volume (mg F/cm3), the fluoride incorporation reached 12.0 mg at the first and 2.5 mg at the fifth layer, several times greater than the baseline of 0.27 mg/cm3 in bovine dentin. A subsequent test of acid resistance in a lactic acid buffer (pH 4.0), followed by microradiography of lesions, showed a characteristic 40-microns-wide acid-resistant zone on surfaces exposed to the GICs. In contrast, the untreated control surfaces had lesions demineralized evenly from the surface to the intact tissue, without the higher-density zone at the surface of the lesion. The model seems promising for screening fluoride incorporation into dentin from fluoride-releasing dental materials.
Animals↗
Invasion of dentinal tubules by oral bacteria.
Bacterial invasion of dentinal tubules commonly occurs when dentin is exposed following a breach in the integrity of the overlying enamel or cementum. Bacterial products diffuse through the dentinal tubule toward the pulp and evoke inflammatory changes in the pulpo-dentin complex. These may eliminate the bacterial insult and block the route of infection. Unchecked, invasion results in pulpitis and pulp necrosis, infection of the root canal system, and periapical disease. While several hundred bacterial species are known to inhabit the oral cavity, a relatively small and select group of bacteria is involved in the invasion of dentinal tubules and subsequent infection of the root canal space. Gram-positive organisms dominate the tubule microflora in both carious and non-carious dentin. The relatively high numbers of obligate anaerobes present-such as Eubacterium spp., Propionibacterium spp., Bifidobacterium spp., Peptostreptococcus micros, and Veillonella spp.-suggest that the environment favors growth of these bacteria. Gram-negative obligate anaerobic rods, e.g., Porphyromonas spp., are less frequently recovered. Streptococci are among the most commonly identified bacteria that invade dentin. Recent evidence suggests that streptococci may recognize components present within dentinal tubules, such as collagen type I, which stimulate bacterial adhesion and intra-tubular growth. Specific interactions of other oral bacteria with invading streptococci may then facilitate the invasion of dentin by select bacterial groupings. An understanding the mechanisms involved in dentinal tubule invasion by bacteria should allow for the development of new control strategies, such as inhibitory compounds incorporated into oral health care products or dental materials, which would assist in the practice of endodontics.
Animals↗