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PubMed1990

Changes in the pulpal vasculature during inflammation.

The reaction and vascular changes of pulpal vessels in experimentally induced acute and chronic pulpitis in dog teeth were investigated using corrosion resin casts and scanning electron microscopic examination. Following a cavity preparation without water cooling, increased permeability of blood vessels occurred in the primary stage of acute pulpitis. This was evidenced by the extravasation of resin in the vascular resin casts. This phenomenon was found initially in the venular network and in the post capillaries of the capillary network located under the dentin. In the resin casts of the vascular network underneath the cavity morphological change was minimal. This is in contrast to an expanded and tortuous granulomalike vascular network which was found around an abscess in chronic pulpitis.

Animals↗
PubMed2004

Effect of resin hydrophilicity and water storage on resin strength.

This study evaluated the change in the ultimate tensile strength (UTS) of five polymerised resin blends of increasing hydrophilicity, after ageing in distilled water or silicon oil. Resin blocks were prepared from each resin blend by dispensing the uncured resin into a flexible, embedding mould, containing multiple cavities. The resins were polymerised in the moulds under nitrogen at 551.6 kPa and light-activated at 125 degrees C for 10 min. After dry ageing for 24 h at 37 degrees C, the middle third of each resin specimen was trimmed into an 'I' shape. Fifteen control specimens were randomly selected from each resin blend for baseline UTS evaluation. The UTS of the experimental specimens were determined after 1, 3, 6 and 12 months of ageing in water or oil. The UTS of each group of resins at different storage periods in water or oil were analysed using the Friedman multiple ANOVA on ranks and Dunn's multiple comparison tests at 95% confidence level. Significant reduction (p < 0.01) in UTS was observed in Groups II-V resins after 12-month storage in water, while the most hydrophobic Group I resin showed no significant change (p > 0.05) in the same period. The percentage reduction in UTS increased with the hydrophilicity of the resin blends. Long-term water storage of hydrophilic resin blends such as those employed in dentine adhesives, resulted in a marked reduction in their mechanical strength that may compromise the durability of resin-dentine bonds.

Absorption↗
PubMed1979

[Autoradiographic study of the activity of odontoblasts and secretory ameloblasts in the rat incisor: changes induced by vinblastine].

An autoradiographic study conducted on the rat incisor showed the presence 4 hours after (3H) proline injection, of 25-30% of the grains on the secreting cells and 70 to 75% on the extracellular matrics. The simultaneous injection of vinblastine sulphate reversed these percentages to 75-80% on the cellular level and 25-25% on the matrics. The vinblastine therefore inhibited the secretory processes of these cell types. On the other hand, due to the alkaloid, the number of grains present increased over the ameloblasts and principally over the intercellular spaces. The effects of these secretion and permeability variations suggested that a flow of precursor rich material reached the epithelial layer whatever the state of ameloblast activity.

Ameloblasts↗
PubMed1992

Demineralization and remineralization evaluation techniques--added considerations.

Methods used for the analysis of tooth de- and remineralization include techniques with various degrees of sophistication and quantitative capabilities, ranging from direct measures of mineral gain/loss (e.g., microradiography) to indirect measures (e.g., iodide permeability) of changes in tooth mineral properties. In all instances, the capabilities of methods for accurate determination of changes in tooth mineral properties are affected by procedures used in the preparation of specimens for analysis, the magnitude of change taking place in the test (vs. the detection limits of the techniques), and protocols for specimen analysis. In specific instances, such as in the case of dentin, unique specimen-handling and analysis procedures must be used to prevent artifacts. The choice of techniques for the assessment of de- and remineralization depends strongly upon study protocols and laboratory capabilities; however, 'quantitative' measures of mineral gain and loss are possible only if direct chemical or radiographic techniques are used. Either radiographic, cross-sectioned microhardness or polarized light can be used for the determination of lesion depth. Porosity, light-scattering, and surface microhardness are indirect techniques which complement direct measures of mineral gain and loss. Whatever methods are used in the analysis of de- and remineralization, researchers must take care to differentiate accurately among the quantitative capabilities of techniques used in analysis.

Dental Enamel↗
PubMed1989

[Three dimensional study of the pulpal vascular changes during inflammation].

In this study, the changes of canine pulpal vascular architecture, at various stage of growth when subjected so acute and chronic inflammation were examined through a scanning electron microscope using vascular corrosive resin casts. The following results were obtained. 1. The sites of leakage of MMA resin out of the blood vessels coincided with the site where microleakage occurred, thus suggesting that resin cast method is a useful technique to study the area where vascular permeability was increased. 2. In an acute inflammation, leakage of resin out of blood vessels was mainly observed at the sites of venular network (VN) and venous capillaries, and these could be discriminated by use of the casts method. This is in accordance with the result by Tsuchiya, Magino and Palade, where they showed that vascular permeability was preferentially observed in venule and venous capillaries. 3. In pulp with a lesser number of venules during the stage of late maturation, leakage of resin was observed from those surviving venules to the bundle of main blood vessels. 4. Leakage of resin was not observed in the terminal capillary network (TCN), but in the capillary network (CN) and VN, especially just beneath the dentin, where cavity preparation with a water spray was performed. Accordingly, the generation of heat during cavity preparation was thought to be the main reason for disturbance of the pulp. 5. Severe case of suppurative and chronic ulcerative pulpitis were generated within one week after cavity preparation. The vascular architecture was characterized by a dense granular capillary network facing the ulcerative surface. 6. One week after pulpal exposure, at the stage of early maturation of pulp, the granulated blood vessels located within the exposed pulp had a tendency to shift to a pulp polyp. And the granulated blood vessels after two months showed a pulp polyp. 7. At the late maturation stage of pulp, development the pulp chamber and dentin tubules were saturated by resin cast method, suggesting the possibility of leakage out of blood vessels and the death of some odontoblasts. The pulp at this stage shifted to a gangrous pulp. 8. In conclusion, the pulpal vascularity constantly undergoes morphologic changes incidential to various condition such as growth, maturation and inflammation. Basically, vascularity of dental pulp consists of three major layers, that is TCN, CN and VN. When it comes to the maturation stage, owing to the apposition of secondary dentin, the pulp cavity will become narrow and the vasculation within it will undergo a histologic change. As a result, most of the VN disappears.(ABSTRACT TRUNCATED AT 400 WORDS)

Dental Pulp↗
PubMed2002

Understanding and managing dentin hypersensitivity.

Dental hygienists frequently encounter clients who present with one or several sensitive teeth. These clients often rely on the dental hygienist to help determine the cause and to provide supportive treatment to relieve their discomfort. Therefore, it is essential for dental hygienists to fully understand the complexity of dentin sensitivity, be well informed about treatment approaches, and have an appreciation of the difficulties inherent in designing and conducting clinical hypersensitivity trials. Difficulties in designing hypersensitivity research have precluded a definitive answer concerning a best treatment approach. The purpose of this course is to present dental hygienists with current information about the pain of sensitive teeth and the associated differential diagnosis. The theory of pain transmission, etiology of dentin sensitivity, professional and self-care treatment modalities, and natural remission of tooth sensitivity will be discussed. Tooth and pulp biology will be reviewed as a means of explaining treatment and management approaches. At completion of this course, as measured by a post-test, participants with be prepared to apply the knowledge gained to their evidence-based practice to positively impact the oral health of their clients.

Dental Hygienists↗
PubMed1992

The colors of silver with silver nitrate staining in dental materials.

Silver nitrate has been used as a stain to study the permeability, degradation, and marginal integrity of dental composite restorations. The reagent results in various colors in the composite or marginal interface. So that the cause of these colors could be investigated, this study compared the appearances of the stained layers by light and electron microscopy. The results indicated that the colors could be explained by the distribution of silver particles ranging from minute colloidal particles (20 nm) in the composite or dentin, to clusters of large particles (0.1-1 micron) in marginal interfaces. The colors can be explained by the absorption and scattering of light by these particles. At elevated temperatures, fused concretions of silver formed in the composite subsurface, resulting in direct reflection of incident light. The colors which appear with silver nitrate staining may indicate the size and distribution of microporosity in the material.

Color↗
PubMed1989

Pulpal hemodynamics and interstitial fluid pressure: balance of transmicrovascular fluid transport.

The net rate of fluid movement across the microvascular endothelium is governed by hydrostatic and protein osmotic pressures operating on each side of the vessel wall. These basic forces regulating the pulpal transmicrovascular fluid exchange are the same as in other tissues. However, the pulp is special in regard to its enclosement between rigid dentin walls, implying low interstitial compliance. In addition, the pulp has a relatively low perfusion pressure. In the low compliant pulpal interstitium, even a modest rise in net filtration will favor a relatively large increase in interstitial fluid pressure (IFP) which opposes further filtration. This will result in a minimal increase in interstitial fluid volume and, theoretically, any dilution of interstitial protein concentration is not possible. Thus, an increase in vessels' permeability to protein in this low compliant system must be balanced by a further rise in IFP, unless a washout of proteins takes place by raised lymph flow. However, a significant increase in IFP may seriously impede pulpal blood flow both by raising venous vascular resistance and secondarily by reducing pulpal perfusion pressure. The most important edema-preventing mechanisms in tissues with low compliance, as the dental pulp, seems to be a rise in IFP which initiates increased lymph flow and washout of proteins.

Animals↗
PubMedDate not supplied

Marginal permeability of self-etch and total-etch adhesive systems.

This study evaluated microleakage in vitro of self-etch and multi-step, total-etch adhesive systems. Ninety-six extracted non-carious human molars were randomly assigned to eight groups (n=12) and restored with different adhesive systems: Optibond Solo Plus, iBond, Adper Prompt L-Pop, Xeno III, Simplicity, Nano-Bond, Adper Scotchbond Multi-Purpose and Touch & Bond. Each group was treated following the manufacturer's instructions. Class V cavities were prepared on the facial or lingual surfaces of each tooth with coronal margins in enamel and apical margins in cementum (dentin). The teeth were restored with Z-100 resin composite. After polishing with Sof-Lex disks, the teeth were thermocycled for 1000 cycles and coated with nail varnish to within 1.0 mm of the restoration. The teeth were stained in 1% methylene blue dye for 24 hours and sectioned from the facial to lingual surface. Dye penetration (microleakage) was examined with a 20x binocular microscope. Enamel and dentin margin leakage was scored on a 0 to 3 ordinal scale. Data were analyzed using Kruskal-Wallis Analysis of Variance and Mann-Whitney U tests. Comparison of the adhesive groups at the enamel margin revealed: 1) Adper Scotchbond Multi-Purpose exhibited significantly less leakage than the other adhesive groups (except iBond); 2) among the self-etch adhesive groups, iBond exhibited significantly less leakage than Nano-Bond and 3) the other adhesive groups clustered intermediately. In contrast, there were no significant differences among the adhesive groups when the dentin margin was evaluated. A Wilcoxin signed rank test showed significantly less leakage at the enamel margins compared to the dentin margins of the eight adhesive systems tested. All data were submitted to statistical analysis at p<0.05 level of significance.

Acid Etching, Dental↗
PubMedDate not supplied

Fluoride in enamel lining pits and fissures of the occlusal groove-fossa system in human molar teeth.

The fluoride (F) distribution in enamel lining the occlusal fissures of human molars and premolars is difficult to investigate by normal microsampling techniques, yet this information is of importance as fissures are particularly susceptible to caries. We have used the proton probe to map the distribution of F and Ca in sections of 17 molar teeth collected from Danish and New Zealand populations. The caries status of the sectioned fissure was determined by microradiography or visually after drying. The probe scans were graphed as density images, surface plots and topographical plots. Sound enamel bordering grooves and fissures showed a high-F surface layer, in 1 sample approximately 60 microm wide near the fissure bottom but gradually widening to double this width near the fissure opening, and up to 200 microm wide in grooves, while underlying enamel had a low and almost constant F level. In this respect fissure and groove enamel resembled smooth surface enamel. The F concentration fluctuated along the surface layer, reaching maximum values ranging from 1,800 to 4,200 ppm in 5 non-carious fissures. Incipient caries in fissure enamel usually but not always resulted in an increase in F in the outer layer, the F maximum values in 5 such samples ranging from 1,900 to 7,200 ppm. F maximum values in outer enamel were higher in 7 samples showing advanced caries, 2, 700-10,000 ppm. The lesion subsurface body usually showed normal F values, as did carious dentine in the advanced lesions. The variable characteristics of the outer layer in sound fissure enamel are likely to be the result of a developmental process rather than environmental influences. The fact that we normally failed to find increased F concentrations in subsurface carious fissure enamel or in underlying carious dentine suggests that F does not diffuse into the deep part of fissure lesions, and probably has minimal effect on slowing the progress of such lesions, a suggestion in accord with clinical findings on the F effect on fissure caries.

Calcium↗
PubMed1993

Further NMR-spectroscopic studies of interaction of phospholipid liposomes with methacryloyloxydecyl dihydrogen phosphate (MDP) in dental adhesives.

To determine how MDP interacts with liposomes, the chemical shifts of dipalmitoylphosphatidylcholine (DPPC)/MDP and dilauroylphosphatidylethanolamine (DLEA)/cholesterol (CS)/MDP liposomes were studied by NMR spectroscopy using a D2O buffer solution at pH 7.0 as a model for biological membranes. Proton chemical shifts of MDP enhanced shielding in DPPC liposomes together with an increase in the mobility of DPPC. However, MDP signals were not observed in DLEA/CS liposomes due to saturation. It is known that an ionized chemical does not lead to increased permeability of cell membranes composed of a lipid bilayer. However, MDP, which is ionized at pH 7.0, had a large interaction with the liposome systems. This appeared to arise from hydrophobic interaction between deca methylene groups of MDP and acyl chains of phospholipid.

1,2-Dipalmitoylphosphatidylcholine↗
PubMed1996

Correlation of clinical pain symptoms with histopathological changes of the dental pulp: a review.

Pulpalgia is strong and often throbbing and it can start and stop spontaneously. When evoked, pain in pulpitis outlasts the stimulus. The pain is difficult to localise and often radiates to other parts of the face. But the pain symptoms vary. There are cases of severe pulpitis progressing to abscess formation and even necrosis without any symptoms (silent pulpitis). In some cases slight pulpal inflammatory changes will cause severe pain. It seems that correlation between clinical symptoms and histopathological condition of the pulp is not clear. Pulpal inflammatory changes may cause hypersensitivity of the intradental nerves. Vasodilation, increased vascular permeability and extravasation will cause increased intrapulpal pressure. This could spontaneously activate the pulpal nerves. The increased pressure will selectively activate the C-fibres while blocking the A-fibres which are more vulnerable to hypoxia. This would explain the change in pain symptoms during progress of pulpitis to dull type of pain. Some of the inflammatory mediators can excite the pulpal nerves while others even have an analgesic effect. Some of the exogenous compounds (bacterial metabolites and substances released during the breakdown of dentine) induce nerve activity in the pulp while others have a depressing effect. The net effect will probably depend on the relative proportions and concentrations of these substances in the pulp. This would also explain the variability of pain symptoms in pulpitis. Also the condition of dentine with blocked or patent dentinal tubules is important. If the substances with depressive effect are predominantly in greater proportions and concentrations, and if the dentinal tubules are blocked, this could be the case of "silent pulpitis".

Dentin↗
PubMed1999

Experimental intra-oral caries models in fluoride research.

The use of experimental intra-oral caries models has increased in fluoride research. This paper focuses on the pre-clinical intra-oral models, the in situ and in vivo models, the various types, their benefits and disadvantages. Both preparation and sterilization of the hard tissue substrates can affect the substrates and therefore the results. Care needs to be taken that dentine samples are not exposed to drying and consequently shrinking during preparation and evaluation. Sterilization by gamma-radiation is at present the least tissue-damaging method. The most realistic experimental model is the in vivo model, followed by the in situ model using specimens with natural surfaces. The most accurate and direct evaluation technique for demineralization and remineralization studies is quantitative transversal microradiography, whereas confocal laser scanning microscopy (CLSM) is the most sensitive qualitative evaluation technique. Other evaluation techniques discussed are microhardness testing and the iodine permeability test. In light of the present skewed caries situation in western countries we suggest that fluoride research focuses on experimental caries models that can mimic severe cariogenic challenge. Testing of fluoride combinations and dosages that can prevent lesion development rather than promote remineralization would then be a practical consequence.

Animals↗
PubMed2005

Immunocytochemical localization of the neurokinin 1 receptor in rat dental pulp.

The dentin-pulp complex is a peripheral end-organ supplied by dense sensory nerve fibers. Substance P, a representative neuropeptide widely distributed in the dental pulp, has been reported to play roles in pain transmission and the amplification of inflammation. We analyzed here the expression of the neurokinin 1 (NK1) receptor, preferentially activated by substance P, using immunocytochemistry in rat dental pulp at both the light and electron microscopic levels. Conspicuous NK1 receptor immunoreactivity was found in the odontoblasts; immunolabelings were present at their plasma membrane and endosomal structures, especially in their cytoplasmic processes. Immunoreactions for NK1 receptor were also detectable in a part of the nerve terminals associated with the cytoplasmic processes of the odontoblasts. Furthermore, the endothelial cells of capillaries and post-capillary venules and the fibroblasts were labeled with the NK1 receptor in the subodontoblast layer. These findings suggest that pulpal cells and nerve fibers are targets for substance P that mediate multiple functions, including a vasoactive function and the regulation of vascular permeability as well as the modulation of pain transmission.

Amino Acid Sequence↗
PubMed1990

[An experimental study on healing process of replanted mature permanent teeth. Changes of periodontal vascular network].

This study was conducted to clarify both changes of periodontal vascular architecture and concomitant remodelling phenomena associated with hard tissues in the healing process of replanted teeth of first premolar. Utilizing both vascular corrosive resin casts method, scanning electron microscopy, and histological examinations, 45 matured mongrel dogs were used for this study. The results were as follows: 1. 4 days after operation: Newly formed vascular networks with a exceedingly irregular course were observed on lower two thirds of the alveolar wall. They derived from comparatively less damaged periodontal vascular components. No vascular networks were observed surrounding in the crevicular area of the replanted tooth where the periodontal membrane tissue was thoroughly damaged when tooth was extracted. 2. 1 week after operation: Newly formed periodontal vascular networks with a slightly irregular course were observed over the entire alveolar bone surface. 3. 2 weeks after operation: Formation of Sharpey's fibers occurred. The surrounding alveolar bone was remodelled and rearrangement of periodontal vascular architecture was observed. Also, several Howship's lacunae were observed on the root surface where characteristic capillary loops with glomerular-like appearance penetrated into these lacunae. 4. 3 weeks after operation: Root resorption was advanced and capillary loops with glomerular-like appearance were extensively distributed in association with each lacunae. On the other hand, the less space where periodontal membrane vasculature occupied, the more space was occupied by osteoid tissue. 5. 4 weeks after operation: Blood vessels within the periodontal space were reduced in number and the osteoid tissue showed bony fusion adjacent to the extensively resorbing surface of dentin. 6. 12 weeks after operation: Functional arrangement of Sharpey's fibers was completed. Restoration of Howship's lacunae on the root surface and two layered arrangements of vascular network within the periodontal space were observed. Newly formed periodontal vascular architecture showed a fine meshwork pattern, which was somewhat different from that of the control (noreplantation) group. 7. 20 weeks after operation: Increased number of capillary loops was observed with leakage of methacrylate resin through the weakened endothelial linings of capillaries in one case. It is supposed that this leakage through capillaries is correlated with the inflammatory root resorption that occurs clinically in marginal periodontitis. Also in some cases, periodontal capillary network showed secondary occlusal traumatic changes. Above results indicated that periodontal vascular architecture varied depending upon the reactions of periodontium following tooth replantation and the prognosis of replanted tooth was deeply associated with repair of periodontal vascular network.

Alveolar Process↗
PubMed2006

Cytokine signalling in rat pulp interstitial fluid and transcapillary fluid exchange during lipopolysaccharide-induced acute inflammation.

The dental pulp consists of loose connective tissue encased in rigid dentinal walls. Because of its topography the tissue has low interstitial compliance and limited capacity to expand during fluid volume changes. Due to limitations regarding access to interstitial fluid, basic knowledge on transcapillary fluid transport parameters is lacking for this organ. The scope of this project was dual: first we aimed at establishing a method for isolation of pulp interstitial fluid (IF), and second we applied the method in rats subjected to lipopolysaccharide (LPS)-induced endotoxaemia. The aim was to measure colloid osmotic pressure (COP) and pro-inflammatory cytokines in the pulp IF during acute inflammation. Fluid volumes and pulpal blood flow (PBF) were measured to obtain more information about microcirculatory changes that take place in this pulpitis model. By centrifugation of incisor pulp at 239 g we were able to extract fluid representative for IF. Pulp IF had a relative high control COP (approximately 83% of plasma COP) and was similar to plasma COP 3 h after LPS challenge. The pulp exhibited a high content of IF (0.60 +/- 0.03 ml (g wet weight)(-1)) and a vascular volume of 0.03 +/- 0.01 ml (g w.w.)(-1) No differences were observed in the distribution of fluid volumes after 1.5 and 3 h LPS exposure. PBF and systemic blood pressure dropped significantly after LPS administration. PBF remained low whereas systemic blood pressure was re-established during the 3-h period, implying organ dysfunction. There was a differential pattern of cytokine expression in pulp IF and serum with cytokines such as IL-1alpha, IL-1beta and TNF-alpha locally produced, whereas others such as IFN-gamma and IL-6 were produced systemically and probably spilled over to the pulp IF after LPS exposure. Our findings show that pulp IF can be isolated by centrifugation and that this method is useful when studying fluid balance and extracellular signalling mechanisms in the dental pulp in normal and pathological conditions.

Acute Disease↗