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At least 127 records · Page 7Linked to original sources

PubMed1983

Dentin permeability: effects of temperature on hydraulic conductance.

The rates of fluid movement across dentin discs, in vitro, were measured at 10, 20, 30, 40, and 50 degrees C in unetched and acid-etched dentin. Increasing the temperature 40 degrees (i.e., from 10 to 50 degrees C) resulted in a 1.8-fold increase in fluid flow in unetched dentin, which was of a magnitude similar to the decrease in viscosity that occurred over the same temperature range. In acid-etched dentin, the 40 degrees C temperature change produced more than a four-fold increase in fluid conductance, more than double that which could be accounted for by changes in viscosity. Analysis of the data suggests that this additional increment in hydraulic conductance is due to thermal expansion-induced increases in tubular diameter.

Acid Etching, Dental↗

PubMed2004

Dentine phosphoproteins in gingival crevicular fluid during root resorption.

External apical root resorption is a common, yet unexplained, phenomenon associated with orthodontic treatment. Available methods of clinical evaluation are radiographic. Biochemical assays offer the advantage of being non-invasive, as well as being diagnostic and potentially prognostic. The hypotheses are firstly that during the process of root resorption, organic matrix proteins are released into the gingival crevicular fluid (GCF) and, secondly, that there is a difference in the levels of these proteins between a group of patients with mild root resorption and a control group. GCF was collected from the permanent central incisors of untreated subjects (controls, n = 20), primary second molars with half of the root resorbed (primary group and positive controls, n = 20) and permanent central incisors with mild root resorption in patients undergoing active orthodontic treatment (orthodontic group, n = 20). Dentine phosphoproteins (DPP) were measured in the GCF using an enzyme-linked immunosorbent assay developed with DPP isolated from human first premolars and an antibody against rat incisor DPP. The primary group showed the highest levels of DPP in the GCF compared with the orthodontic (P = 0.296) and control (P = 0.001) groups. The orthodontic group showed elevated levels relative to the control group (P = 0.046). It is concluded that root resorption can be studied using a biochemical immunoassay and that this method can provide quantitative measurement of DPP in GCF.

Adolescent↗

PubMed1990

Evaporative water loss from human dentine in vitro.

The rate of spontaneous evaporation of water from dentine was measured in extracted human teeth in vitro. Spontaneous water loss was the same with or without a smear layer. When air was blown on the dentine, the rate of evaporation increased significantly. After removal of the smear layer, the air blast-induced evaporative loss was twice as great as before its removal. Thus, with a smear layer present, evaporation is the major route by which fluid is lost from dentine rather than by filtration of dentinal fluid. After smear layer removal, fluid filtration sometimes may exceed the spontaneous rate of fluid evaporation.

Body Water↗

PubMed1994

The neurophysiological basis and the role of inflammatory reactions in dentine hypersensitivity.

Recent studies indicate that intradental A-type nerve fibres are responsible for the sensitivity of dentine and are activated by fluid movements in dentinal tubules (hydrodynamic mechanism). The patency of the tubules affects dentine sensitivity to a great extent. Both A delta- and A beta-type nerve fibres respond to dentinal (hydrodynamic) stimulation in a similar way. Only a few studies have been made on the regional sensitivity of dentine or the receptive areas of intradental nerve fibres. The results indicate that the fibres innervating different parts of coronal dentine are equally sensitive to dentinal stimulation but those in the cervical area may be less responsive. Inflammation in the pulp can considerably alter dentine sensitivity. In dog teeth with chronically exposed dentine, nerve responses to hydrodynamic stimulation were reduced although other functional changes indicated nerve sensitization. This may be due to spontaneously occurring changes in the exposed dentine that block the tubules. In acute experiments on cat and dog teeth with open dentinal tubules, certain inflammatory mediators increase the sensitivity of the responding nerve fibres. It seems that intradental C-fibres do not respond to hydrodynamic stimulation of dentine. They are polymodal and activated when external stimuli reach the pulp proper. They could perhaps mediate the dull pain connected with pulpitis. However, they might also have an important modifying effect on dentine sensitivity because they can release neuropeptides, which function in the inflammatory reactions.

Animals↗

PubMed1987

The effects of burnishing NaF/kaolin/glycerin paste on dentin permeability.

The effects on dentin permeability of burnishing NaF, kaolin, or glycerin, alone and in various combinations, were determined using an in vitro system. The results indicate that the important variable was not any of the constituents of the paste but the burnishing process itself. Burnishing dentin creates a partial smear layer on the dentin surface, thereby occluding the orifices of dentinal tubules sufficiently to reduce fluid movement across dentin 50 to 80%.

Acid Etching, Dental↗

PubMed2003

Dentin deformation after scratching with clinically-relevant forces.

OBJECTIVE: In order to understand the mechanism of dentin sensitivity to tactile stimuli, the purpose of this study was to evaluate possible permanent deformation of dentin produced by scratching dentin surfaces with clinically-relevant forces. METHODS: Midcoronal dentin was prepared from twenty human teeth and polished to 4000-grit and ultrasonicated. The dentin surface of each specimen was scratched under forces ranging from 30 to 100 centi-Newtons (cN). The depth of the grooves were measured with a profilometer and the overall hardness of dentin in the vicinity of the grooves was measured. Additional dentin specimens were prepared for SEM evaluation. RESULTS: Dentin hardness was constant and no statistical difference was found among the specimens. Statistically significant differences in groove width and depth were found when increasing force was applied to the dental explorer tip. The depth of the groove ranged from 0.21+/-0.09 microm for the 30 cN group to 1.27+/-0.39 microm for the 100 cN group. The width of the groove ranged from 19.3+/-4.0 microm for the 30 cN group to 43.0 microm for the 10 0 cN group. CONCLUSIONS: (1). The threshold force necessary to create scratches in dentin with a dental explorer was 30 cN or a compressive stress of 1003 MPa. As this exceeds the crushing strength of dentin, this force produces plastic deformation of dentin; (2). Theoretical calculations indicated that even the highest scratching forces (100 cN) could not induce sufficient fluid flow to activate pulpal mechanoreceptors, although it could induce sufficient elastic deformation to theoretically shift dentinal fluid at a rate sufficient to activate mechanoreceptors; (3). The results of this work may lend support the hydrodynamic theory in that scratching of dentin surfaces causes both elastic and plastic deformation of dentin that may displace dentinal fluid toward the pulp where it could activate mechanoreceptors.

Dentin↗

PubMed1983

Intradental nerve activity induced by reduced pressure applied to exposed dentine in the cat.

In order to study the excitation of intradental nerves by fluid flow in dentinal tubules the following experiments were performed. The fluid flow was caused by reduced hydrostatic pressure applied to the exposed dentine surface of the canine teeth in the anesthetized cat. In one series of 7 cats the intradental nerve activity was recorded by means of electrodes inserted in dentinal cavities. Provided that the pressure was sufficiently reduced and applied to acid-etched dentine in preparations of sufficient depth, intradental nerve activity of different impulse amplitudes was recorded. The responding pressure sensitive units were found to be sensitized by a brief local application of veratrine and desensitized by potassium chloride. In the second series 26 single functional pulp nerve fibre units were dissected from the inferior alveolar nerve in 7 cats. Nerve impulses were recorded by means of platinum-iridium wire electrodes. The conduction velocities of the 9 fibres responding to reduced pressure varied from 8.3 to 43.0 m/s. Five of these fibres also responded to elevated pressure. None of the 9 fibres conducting impulses with a velocity below 2 m/s responded to a reduction in pressure. thus, the present data strongly suggest that intradental nerve endings with myelinated axons are activated by fluid flow in dentinal tubules. Our results support the hydrodynamic mechanism of dentine sensitivity.

Acid Etching, Dental↗

PubMed1993

Tooth sensitivity: mechanisms and management.

Tooth sensitivity is a common complaint encountered in clinical practice. Exposed superficial dentin is free of nerve endings, yet sensitive. Experimental evidence indicates that stimuli, such as probing the dentin surface and air blasts, induce fluid movements in the dentinal tubules and these fluid movements, in turn, activate the intradental nerves. The condition of the dentin surface is critically important in allowing this process. In addition, the internal environment of the pulp may influence nerve excitability. Therapies for tooth sensitivity include both agents that obstruct the dentinal tubules and agents that can decrease the excitability of the intradental nerves. The exact treatment used depends on the etiology of the individual's problem and the extent of dentinal tissue damage.

Animals↗

PubMed1992

Dentine hypersensitivity--the effect of toothbrushing and dietary compounds on dentine in vitro: an SEM study.

Dentine hypersensitivity occurs when dentinal tubules are open on the dentine surface and patent to a vital pulp. There has been limited interest in the aetiology of dentine hypersensitivity. In particular, little is known about agents that remove the dentine smear layer to expose tubules. Toothbrushing certainly may expose dentine, but whether a toothbrush per se has the effect of opening tubules has not been established. The aim of this study in vitro was to determine whether a toothbrush could remove or create a smear layer. In addition, the combined effects of toothbrushing with dietary fluids on dentine was assessed. Toothbrushing was observed, by scanning electron microscopy, both to remove and to recreate a smear layer on dentine specimens. However, the processes took a considerable time, and under conditions of normal toothbrushing it is unlikely that the latter plays a direct aetiological role in opening tubules. Indeed, together with toothpaste it is more likely that brushing has a therapeutic action by mechanically forming a smear layer. Conversely, and importantly, toothbrushing in the presence of dietary acids enhanced smear layer removal. This finding raises the question of whether the dental profession should be advising that teeth be brushed before meals rather than after, as is often the case.

Acid Etching, Dental↗

PubMed2005

Effect of desensitizing agents on the hydraulic conductance of human dentin subjected to different surface pre-treatments--an in vitro study.

OBJECTIVES: The aim of this study was to evaluate the variation of fluid filtration across dentin treated with different formulations of potassium oxalate gels and one gel of acidified sodium fluorophosphate, under five different pre-conditioned dentin surfaces. METHODS: The methodology used for the measurement of hydraulic conductance of dentin in the present study was based on the model suggested by Pashley, Stewart and Galloway [Arch Oral Biol 29 (1984)379]. Two hundred dentin discs 1 mm in thickness, obtained from human extracted third molars, were divided into 20 groups of ten specimens each. The groups corresponded to the following experimental materials: 3% potassium oxalate gel-pH 4; 6% potassium oxalate gel-pH 4; 3% potassium oxalate gel-pH 2.5 and 1.23% fluoride gel (APF gel)-pH 3.6-3.9, applied to dentin under the following surface conditions: air-dried, blot-dried, wet, EDTA air-dried; EDTA blot-dried. General MANOVA and post-hoc Duncan tests were performed on the data. RESULTS: Regardless of surface pre-treatment the 3% potassium oxalate gel-pH 2.5 produced the greatest reduction in dentinal filtration (p<0.05) even after citric acid challenge. In general, air-drying the dentin was the best surface pre-treatment (p<0.05). The interaction between the material and surface pre-treatment showed values of hydraulic conductance similar for most of the combinations, but the 3% potassium oxalate gel-pH 2.5 under wet conditions produced the largest reduction in hydraulic conductance. The APF gel produced the smallest reduction in hydraulic conductance when compared with the other materials, regardless of surface pre-treatment. SIGNIFICANCE: the potassium oxalate gels studied in this investigation have a great potential for tubule occlusion and, consequently, should be effective treatments of dentinal hypersensitivity, regardless of dentin wetness.

Acidulated Phosphate Fluoride↗

PubMed2006

Oxalate-containing phytocomplexes as dentine desensitisers: an in vitro study.

It is known that pulpal fluid movement through dentinal tubules causes dentinal hypersensitivity and that pain can be reduced by decreasing the fluid flow. The aim of this study was to evaluate dentinal permeability and morphology after a single exposure to experimental phytocomplex substances containing oxalates. The treatments tested were experimental pastes, gels and solutions of phytocomplexes (extracted from rhubarb, spinach and mint), an experimental paste containing 5% potassium oxalate, and two commercial toothpastes recommended for dentinal hypersensitivity (Elmex and Sensodyne). Dentine discs from human third molars were used in this study. Each sample was brushed for 3 min with each treatment in order to test reductions in dentinal permeability. Each treated sample was challenged with orthophosphoric acid for 90 s to determine changes in dentinal permeability and the sensitivity of treatments to acid challenge. Scanning electron microscopy was used to analyse the samples. This study found that spinach and rhubarb phytocomplex treatments reduced dentinal permeability by occluding dentinal tubules through formation of calcium oxalate crystals. These results indicate that phytocomplexes extracted from rhubarb and spinach, used in different formulations, should be effective for topical treatment of dentinal hypersensitivity.

Amines↗

PubMed1982

Responses of intradental nerve fibres to stimulation of dentine and pulp.

In the present work responses of intradental nerve fibres to stimuli that induce fluid flow in dentinal tubules as well as to direct mechanical irritation of the exposed pulp were studied on 9 young adult beagle dogs. Under pentobarbitone anesthesia 31 single functional intradental fibre units were dissected from the mandibular nerve. Stimuli were applied to the lower left canine tooth. Exposed dentine surface was irritated by scraping, air blasts and dry absorbent paper and the pulp mechanically with a von Frey hair. Ten fibre units responded to stimulation of dentine. Six of them were also tested with mechanical irritation of the pulp and were all responsive. Fifteen of twenty fibres responded to mechanical stimulation of the pulp. The mechanosensitive nerve fibres were all A-type according to conduction velocities (mean 25.6 +/- 8.1 (SD) m/s). It is concluded that there exist mechanosensitive intradental A-nerve fibres in the dog which are activated by stimuli that induce fluid flow in dentinal tubules. Nerve fibres of this type could be responsible for dentine sensitivity in man. Consequently, the present study gives support to the hydrodynamic hypothesis of dentine sensitivity. Moreover, mechanosensitive nerve fibres could also be responsible for the pain symptoms of pulpal inflammation, because pulpitis may also create suitable circumstances for their activation.

Animals↗

PubMed1991

The interfacial region of the tooth/glass ionomer restoration: a confocal optical microscope study.

The dynamic interactions between the tooth tissues and a glass ionomer cement were investigated, using fluorescent markers incorporated into components of glass ionomer restorations. A confocal optical microscope was used to examine the tooth/restoration interface. Samples were examined at specific intervals after restoration to determine the effect of maturation of the glass ionomer matrix. Loss of fluorescent dye from the glass ionomer restoration into the subjacent dentin indicated fluid movement across the interface during maturation. To determine the effect of shrinkage from water loss on the integrity of the tooth/restoration interface, restored teeth were maintained fully hydrated and then allowed to dry. Substantial cracking at the enamel margins after drying of the set restoration indicated the strength of the attachment to enamel and also cautioned against excessive clinical drying.

Dental Bonding↗

PubMed1976

The effect of veratrine and aconitine on the excitability of sensory units in the tooth of the cat.

Intradental sensory nerve impulse activity was recorded by means of electrodes inserted into dentinal cavities in the tooth of the cat. Impulses of different amplitudes was recorded. Local application of aconitine (10(-3) g/ml) and veratrine (10(-3) g/ml) induced nerve impulse activity. A rapid increase in the temperature of the tooth surface to 45-47 degrees C, which is known to induce fluid movements in the dentinal tubuli, did not induce any nerve impulse activity. However, after pretreatment of a tooth cavity with veratrine a rapid increase in the temperature of the tooth surface gave rise to nerve impulse activity. Steady state impulse activity induced by brief local application of aconitine was influenced by a rapid increase in the temperature of the tooth; during the increase in temperature impulses of low amplitude increased in frequency while impulses of high amplitude were blocked. Furthermore, reduced pressure applied to the exposed dentin, which also induces fluid movements in the dentin, gave rise to nerve impulse activity. Thus the sensory units in the tooth are stimulated by dentinal fluid movements and alkaloids known to excite mechanoreceptors increase their excitability. It is therefore suggested that the intradental sensory nerve endings are mechanosensitive structures.

Aconitine↗

PubMed2002

The effect of pulpward pressure on the response to 50% lidocaine (lignocaine) applied to exposed dentine in cats.

The responses of intradental nerves can be blocked by 50% lidocaine applied to exposed, etched dentine. The aim here was to analyse electrophysiologically the contribution of pulpward pressure to the anaesthetic effect of lidocaine applied to exposed dentine. In 17 adult cats with intact lower canines, approximately 1mm of the coronal tip of the canine was removed and the exposed dentine acid-etched. Pulpward pressure was applied to the exposed dentine through a chamber fixed to the tip of the tooth. Cervical and coronal electrodes of silver wire and Ag/AgCl mixture were placed, the cervical 2mm from the gingival margin of the canine and the coronal into the coronal pulp chamber. The inferior alveolar nerve was surgically exposed and single pulpal nerve fibres responding to electrical stimulation of the canine were identified. The chamber was filled with 50% lidocaine solution, and 0 (atmospheric pressure), 1.3, 5.0 or 10.0 kPa pressure was applied to the chamber for 20 min. Orthodromic and antidromic action potentials were compared before and after the lidocaine application. When lidocaine was applied at 0, 1.3 or 5.0 kPa (n=5 each) for 20 min, all the orthodromic responses to cathodal electrical stimulation with the coronal electrode were blocked. Almost all orthodromic responses (12/15) remained unblocked when the cathodal electrical stimulation was applied with the cervical electrode. Applying 10.0 kPa pressure to the lidocaine solution blocked all the pulpal nerve responses (n=5) to both stimulation modes. The amplitude of the antidromic compound action potential was significantly decreased when the applied pressure was increased. These results suggest that increased pulpward pressure may effectively force anaesthetic solution more rapidly through the dentinal tubules into the pulp.

Action Potentials↗

PubMedDate not supplied

Effects of pulsatile versus non-pulsatile pulpal pressure simulations on diffusional transport across human dentine in vitro.

The influence of a simulated pulsatile pulpal pressure on the diffusion of NaCl through slices of human dentine (n = 12) was evaluated in vitro. The average hydraulic conductance of the slices of dentine was 0.0131 +/- 0.0031 microliter/cm2 per min per cmH2O(x +/- SD). A 1 mol/l NaCl solution was placed on one side of the slices of dentine and deionized water on the other side. The time needed to reach a steady state and the quantity of NaCl that diffused through the slice were successively measured on the same slice of dentine, under three conditions: without pressure simulation, with a static pressure of 1.5 kPa, and with a pulsatile pressure varying from 1.2 to 1.8 kPa. The pressure was applied to the deionized water. When a static pressure was applied, the time required to reach a steady state increased from 24 to 30 h. When a pulsatile pressure was applied the time required to reach a steady state decreased from 24 to 12 h. No statistically significant difference was found between the quantity of NaCl that had diffused when the steady state was reached.

Analysis of Variance↗

PubMed1997

The effect of pressure on a maximum incisal bite force in man.

The maximum bite force an individual can exert on an upper central incisor when the force is transmitted through a point on the incisal edge (no cover) was compared with maximum bite force when distributed over a full acrylic cap (full cover). Eighteen participants rapidly produced a maximum bite force three times each under no-cover and full-cover conditions. The magnitude and direction of the maximum bite force were monitored by a transducer placed between upper and lower incisors. There was no significant change in the direction of the bite force under the two conditions. The average maximum bite force was significantly larger (mean-4.9%, SD-4.6%, p < 0.001) in the full-cover condition. The increase in maximum bite force was attributed to the reduced pressure on the crown under the full-cover condition when compared with the no-cover condition. This implies the existence of mechanoreceptors within the pulp of a tooth because periodontal mechanoreceptors can affect feedback only by monitoring differences in the force on a tooth, not differences in pressure on the crown.

Adult↗

PubMed2002

The effects of dentin permeability on restorative dentistry.

The permeability properties of dentin determine its sensitivity and the degree of pulpal response to restorative procedure materials and microleakage. Most pulpal reactions are due to bacteria or bacterial products that permeate across dentin. These reactions can be prevented if dentin is sealed with resins as soon as it is exposed. In the future, restorative dentists may employ topical application of biologic growth factors to permeate across dentin to modify the formation of reactionary or reparative dentin, thereby lowering dentin permeability and protecting the pulp.

Dental Leakage↗