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PubMed1991

Fluid and protein flux across the pulpodentine complex of the dog in vivo.

Dentinal fluid volume and protein concentrations were measured from cavities prepared in the dentine of dog molars. Fluid was collected under spontaneous conditions, during the application of negative pressures, and during a recovery period. The data allowed the calculation of dentine permeability as hydraulic conductances, fluid flux, protein flux, reflection coefficients and pulpal tissue pressures. In general, the protein concentration of dentinal fluid was about one-fifth that of plasma during spontaneous conditions and it fell when fluid flux was increased by the application of external negative pressures. The collection and analysis of dentinal fluid looks promising as a non-invasive method of assessing the state of the underlying pulp.

Animals↗
PubMed1992

The effect of dietary factors on intradentinal dye penetration in the rat.

Fluorescent dye injected systemically into rats penetrated the dentinal tubules of molar teeth in a dynamic fashion. The presence of dye was established using histological and fluorescence microscopy techniques. The rate of intradentinal dye penetration was dependent on dietary factors: it was high in rats chronically fed Purina rat chow and low in rats fed a cariogenic, high-sucrose diet. In addition, parotidectomized rats showed low levels of intradentinal dye penetration, even though they were maintained on Purina chow. One and 2 ml of plasma from Purina-fed rats were effective in stimulating the dye penetration in intact and parotidectomized rats, whereas 2 and 4 ml of plasma from rats fed a high-sucrose diet were ineffective when infused in either intact or parotidectomized animals. The results suggest that rats fed Purina chow have a significantly higher titre of a circulating, dye penetration stimulating factor than animals fed a high sucrose diet. This circulating factor could be the equivalent of the parotid hormone isolated from porcine tissue. It is suggested that dietary factors may affect secretion of a parotid hormone and thereby regulate the rate of dentinal fluid movement. There is therefore the prospect of a functional relationship between diet, the regulation of dentinal fluid flow by an endocrine system and dental health.

Acriflavine↗
PubMed1992

Dentin permeability and dentin sensitivity.

The hydrodynamic theory of dentin sensitivity is based on the premise that sensitive dentin is permeable throughout the length of the tubules. Such a condition may permit the diffusion of bacterial products across dentin to the pulp where they may cause irritation of pulpal soft tissues. However, the slow outward movement of dentinal fluid tends to flush the tubules free of exogenous substances. This balance between the inward diffusion of exogenous substances, whether bacterial or the active ingredients in desensitizing medicaments, and the cleansing action of dentinal fluid flow needs to be examined experimentally.

Dentin↗
PubMed1994

Effects of a supersaturated pulpal fluid on the formation of caries-like lesions on the roots of human teeth.

Root surfaces were exposed to demineralizing buffer in a continuous-flow system, with or without simultaneous perfusion of the pulp chamber with a supersaturated surrogate dentine fluid (SDF). Experimental lesions formed with perfusion of the pulp were significantly less deep than control lesions formed without perfusion, but the application of hydrostatic pressure to the SDF (15 or 30 cm water) did not produce significantly greater reductions. The lesion depth reduction was attributed to reduced undersaturation at the advancing lesion front through interdiffusion of the demineralizing buffer and the SDF. Translucent bands, resembling sclerotic dentine, were observed beneath 9 of 24 experimental lesions and 5 of 24 control lesions. Scanning electron microscopy showed that, in most of the bands beneath experimental lesions, dentinal tubules were either partly occluded by granular mineral deposits or were reduced in diameter. Thus, in vivo, dentine fluid may modify the rate of lesion progression and promote sclerosis in the underlying dentine.

Acetates↗
PubMed1990

[Effects of soft laser irradiation on dentinal pain].

The use of soft lasers in dental therapy has increased dramatically in recent years. However, there is a dearth of reports in the literature of controlled in vivo and in vitro studies of soft laser effectiveness with respect to dentinal pain. The purpose of this study was to assess the analgesic effects of soft laser treatment by the following five studies: (1) Clinical evaluation of soft laser irradiation of hypersensitive dentin. (2) Morphological study of dentinal surfaces following soft laser irradiation. (3) Study of the effect of soft laser irradiation on dentinal fluid movement. (4) Study of the effect of soft laser irradiation on the jaw opening reflex (JOR) in rats. (5) Study of thermal changes on the internal wall of pulp chamber with soft laser irradiation. After soft laser treatment of 3 min to hypersensitive dentin, patients experiences diminished sensitivity in 46 of 55 teeth (83.6%). In model experiment with extracted human teeth, the energy levels of this laser were too low to produce any morphological changes on the surface of exposed dentin, and dentinal fluid movements induced by air blasts for 15 sec to exposed dentin were not affected by laser irradiation to the dentin for 3 min. Moreover, there was an immediate 0.7 degree C increase in the temperature of the internal wall of the pulp chamber by laser irradiation to the tooth surface. In experimental rats, the digastric EMG induced by 1.3 x T (T: threshold value producing the JOR) was reduced by 3 min soft laser irradiation to teeth or Ho-ku points, but not at 2.0 x T. These results suggest that soft lasers have an analgesic effect, but the latter is affected by the degree of stimuli-elicited pain, and may be due in addition to descending inhibition in the central nervous system.

Animals↗
PubMed1991

[The hydrodynamic behavior of dentinal tubule fluid under occlusal loading].

In an in-vitro study, the fluid movements were quantitatively recorded in natural teeth incorporated rigidly in a closed measuring system and exposed to an occlusal load of 122.6 N. Fluid movements under load are the result of elastic deformations of the tooth. Occlusal loads which were repeated within a short period of time caused a reversible plastic deformation. In comparison to the unfilled tooth the placement of an MOD restoration combined with a glass ionomer cement base caused the following alterations in fluid movements: composite inlay -24.7%, ceramic inlay +34.7%, MOD amalgam -3.1%; the placement of the base per se induced a reduction of -12.7%. In this in-vitro study, the physical properties of the restorative materials governed the magnitude of the fluid movements under load. The results are in contradiction to clinical findings and favor the pulpitis-related genesis of postoperative sensitivity. The intratubular and intrapulpal fluid movements under occlusal load simply seem to trigger the pain sensation.

Biomechanical Phenomena↗
PubMed1989

Biological and chemical evidence for the existence of a porcine hypothalamic parotid hormone-releasing factor.

Methodology has been developed to achieve partial purification of a parotid hormone-releasing peptide from porcine hypothalamus-thalamus tissue using an in vivo parotid hormone stimulation test in pigs and a dentinal fluid transport stimulation test in rats. The purification steps include: acetone-water extraction of the tissue at pH 5.2, ultrafiltration through Amicon PM10 membrane, size exclusion chromatography on Bio-Gel P2, and open-column reversed-phase chromatography on Lichroprep RP8. A 100-fold increase in specific activity was attained. Intravenous infusion of porcine hypothalamus-thalamus extract stimulates a dentinal fluid transport mechanism in teeth of intact anesthetized rats, and the release of plasma immunoreactive parotid hormone in conscious catheterized pigs. Parotidectomy in both species suppresses the response, suggesting that the expression of parotid hormone-releasing activity requires the integrity of a putative hypothalamus-parotid gland endocrine axis.

Animals↗
PubMed1992

Microleakage related to restorative procedures.

A current Med-line search from 1966 to present cited over 344 juried publications employing the term microleakage. Dentistry recognizes microleakage as a multifaceted biological phenomenon. Brännström et al. (1967), Trowbridge (1982), Närhi (1983), and others have reported the sensory component of microleakage as a consequence of hydrodynamic fluid movement within the dentinal tubule complex. This movement of dentinal fluid has been demonstrated to displace nociceptive receptors which stimulate the nerves of the Group A fibers which run and terminate within the odontoblastic layer (see Matthews 1992). Penetration of oral fluids, bacteria and their toxic products within the preparation-material interface following material insertion accounts for the pathological component of microleakage (Browne and Tobias 1986). Continued microleakage of bacterial infiltrates eventually present as an inflammatory process which may initially signal the dentin complex to respond by deposition of a hypermineralized or sclerotic dentin. The pulp-dentin interface will repair with a specialized zone of reparative dentin. An overwhelming carious lesion often results in pulp infection and eventual necrosis. Vital dentin is an extension of the pulp, presenting the first line of defense to the consequences of microleakage. Recent publications have demonstrated that microleakage of dental materials in non-exposed and exposed pulps is a function of controlling bacterial infection. In an exposed mature dental pulp, the mesenchymal tissue permits the reorganization of pulp tissue and regeneration of a new dentin bridge in the presence of a biological seal. New odontoblastoid cells appear to regenerate from deeper pulpoblasts in the presence of various dental materials, apparently without an epithelial stimulating factor (Yamamura 1985). This inherent healing of the dental pulp and regeneration of a new dentin bridge is expressed in the presence of various dental materials, but only in the absence of bacterial infection. Data which evaluates the biological deposition of reparative and dentin bridges as either repair or regeneration are presented as a basis for considering the clinical selections of dental materials. Recent data demonstrate that dentin and pulp healing are ensured when a proper biological seal is provided to control and prevent microleakage.

Animals↗
PubMed1994

Effect of food and oral simulating fluids on dentine bond and composite strength.

The effect of up to 30 days' immersion in 75% ethanol solution and in an artificial saliva (Moi-Stir) on the dentine shear bond strength (SBS) of three adhesive/composite systems (Tenure/Marathon One, Scotchbond Multi-Purpose/Z100 and Optibond/Herculite XRV) was evaluated. Two control series were stored either in 100% humidity or in air. Diametral tensile specimens (DTS) of the composites studied were stored in 75% ethanol for up to 30 days. The fracture mode and morphology of the failure interface were examined by scanning electron microscopy (SEM). Data were analysed using ANOVA and the Tukey LSD test. The SBS for all systems stored in Moi-Stir (24.8 +/- 3.0 MPa) and air (28.3 +/- 3.0 MPa) was not influenced by length of storage. Microscopic (SEM) examination of the debonded air, and Moi-Stir stored specimens showed that failure had primarily occurred through the dentine. Significant decreases (30-50%) in the SBS of all systems occurred after immersion in 75% ethanol. There was no significant difference among brands. The DTS of the composites showed significant decreases as a function of ethanol exposure. Marathon One and Herculite XRV showed significantly lower DTS after 14 days' storage while Z100 showed no reduction in DTS until after 30 days. The decrease in both SBS and DTS after storage in ethanol was a function of the square root of time (P < 0.001) and followed Fick's laws of diffusion. Ethanol diffusivity was approximated as 1.8 x 10(-6) cm2 s-1 for both SBS and DTS specimens, suggesting that alcohol attack in SBS specimens occurred primarily in the composite system.(ABSTRACT TRUNCATED AT 250 WORDS)

Composite Resins↗
PubMed1990

[Effect of phenolic resin fluid on the dentin resistance].

SEM observation was made in the experiment to analyze the ultrastructure of resinified dentin. Phenolic resin fluid permeates in to the dentinal-tubule and set in it. The permeability of this agent was also able to permeate into intercellular substance and changed the appearance of inter-weaved fibril to the condition of agent had set. According to the Fracture Mechanics, it was not beneficial to resist the fracture progress if the microspace had been fulfilled by the agent. The tensile stress of resinified dentin was 387 kg/cm2, which was 30 kg/cm2 lower than that of unresinified-dentin.

Dentin↗
PubMed1993

Dentine hypersensitivity: the measurement in vitro of streaming potentials with fluid flow across dentine and hydroxyapatite.

Stimulus transmission across dentine, in conditions such as dentine hypersensitivity, is considered to occur via a hydrodynamic mechanism. This fluid flow in dentine may then induce a mechanoreceptor response in pulpal nerves. However, when fluid flows through a porous structure electrical potentials are also generated. The aim of this study was to develop a reproducible model system to measure streaming potential across dentine and hydroxyapatite and determine the influence of pressure. Using an acrylic cell, with silver electrodes, streaming potentials were recorded across dimensionally standardized dentine and hydroxyapatite specimens, over a pressure range of 1-6 atmospheres. Streaming potentials were found to be directly proportional to pressure and dependent on the electrical conductivity of the saline used in the cell. The results confirm the limited existing data on streaming potentials across dentine and indicate that at these low pressures excitation of pulpal nerves would not occur. However, if, as may be the case, stimuli applied to dentine create very high pressures, the resultant potentials generated could indeed evoke a neural response. The model system is worthy of further use to study this phenomenon and the factors which may influence it.

Dentin↗
PubMed2005

In vivo fluid movement through dentin adhesives in endodontically treated teeth.

Fluid transudation through simplified dentin adhesives can occur in bonded vital crown dentin, since these adhesives behave as permeable membranes after polymerization. The effect of adhesive permeability in endodontically treated teeth is unknown. This study examined the hypothesis that in vivo fluid movement through simplified adhesives occurs when they are applied to root canals. Dowel spaces were prepared in endodontically treated teeth with single root canals. Six adhesives were applied to the intra-radicular dentin of canal walls. Impressions were obtained with polyvinyl siloxane, and replicas were fabricated with the use of polyether impression material. Replica hemisections were gold-coated for SEM examination. Fluid transudation was evident on the adhesive surfaces of all simplified total-etch and self-etch adhesives. Conversely, most of the specimens bonded with the control three-step total-etch adhesive were devoid of fluid droplets. Permeability of simplified adhesives results in water movement, even in root-treated dentin. This may adversely affect the coupling of auto-/dual-cured resin cements.

Acid Etching, Dental↗
PubMed1990

[Characterizing the smear layer].

The smear layer was first described as a debris layer which is left on all cavity walls following tooth preparation. It is composed of an outer contiguous layer of amorphous instrumentation matrix which covers all cavity walls, and a deeper zone of matrix plugs which obturate the cut tubules. Recent scanning electron microscopic (SEM) studies have characterized the smear layer as mineralized collagen fibers appearing as globules dispersed within an amorphous cutting matrix. Removal of smear plugs increases the outward hydraulic conductance (Lp) of dentinal fluid flow which may lead to dentinal hyperalgesia, bacterial infection and pulp pathosis if left untreated.

Collagen↗
PubMedDate not supplied

The effect of pulpal fluid flow on tensile bond strength of a glass-ionomer cement: an in vivo and in vitro comparison.

Previous studies of the bonding capabilities of glass-ionomer cements have concentrated on the use of in vitro testing conditions. Since early moisture contamination appears to have adverse effects on the physical properties of glass-ionomer cements, and with the probability of pulpally derived dentinal fluid being present under in vivo conditions, the objective of this study was to compare in vivo tensile bond strength with in vitro tensile bond strength of a glass-ionomer cement to dentin utilizing the same teeth under similar test conditions. A glass-ionomer lining cement was placed on freshly exposed labial dentin of the maxillary incisor on 10 Rhesus monkeys. Immediately following placement, an orthodontic button was placed over the cement and left undisturbed for 1 hour. The teeth were then extracted and stored in 100% relative humidity for 23 hours. An Instron testing machine was used to register in kilograms the force required to cause tensile bond failure of the cement. Identical methodology was then used on the same teeth for in vitro testing. The concluding results indicate that a statistically significant difference (P < or = 0.05) exists between in vivo and in vitro tensile bond strengths of the glass-ionomer lining cement and that the bond failure was cohesive in character for all cases both in vivo and in vitro. These findings suggest that clinically, tensile bond strengths of glass-ionomer cements to cut dentin can be expected to be weaker in vital teeth than in devital teeth.

Animals↗
PubMed2000

[Electroanalgesia: operating principles].

We are faced every day with the problem of dental pain arising from the concomitant action of the nerve fibres, the odontoblasts and the dentinal fluid. Its propagation is due to the triggering of the action potential from the resting potential. It can be reduced thanks to a reversible process of anelectrotonus in electro-analgesia.

Action Potentials↗
PubMed2004

The use of the replica technique to record fluid emerging from exposed dentine.

The effect of pulpal cavity pressure on structures present on etched and unetched dentine was determined in 24 human premolars in vitro. The dentine was exposed in vivo. After extraction, the pulp was removed and the crown stored in 2.5 N sodium hydroxide for 3 days to remove the odontoblasts. The pulp cavity was filled with Ringer's solution at atmospheric pressure, +30 or -5 mmHg. After 30s-5 min a silicone-rubber impression was taken of the cavity floor and a resin cast prepared and examined in a SEM. The replicas reproduced the dentine surface accurately when there was no outward flow through dentine. With a pressure of + 30 mmHg in the pulp cavity, but not at the lower pressures, droplets were present on unetched dentine after 30s. Droplets accumulated less rapidly on etched dentine, indicating that it may act as a sponge.

Acid Etching, Dental↗
PubMed1991

In vitro simulations of in vivo bonding conditions.

Most in vitro bonding studies have been performed on extracted teeth of unknown age, stored in a wide variety of solutions, embedded in substances that encourage dehydration, and polished flat with abrasive paper. In vivo, teeth are vital and maintained moist by dentin fluid that exudes from pulpal blood vessels to dentin surfaces prepared with burs. In vivo conditions can be simulated in vitro by filling the pulp chamber of extracted teeth with physiologic solutions maintained under a positive pressure. Dentin bonding surfaces can be prepared flat using burs. More attention should be focused on the effects of dentin depth (superficial versus deep) and position (occlusal, proximal, etc.) on the bond strengths of materials during screening experiments. Alternatively, bonding of adhesives can be performed in vivo using various animals such as monkeys, goats and dogs. Although the bond strengths of adhesives are low in animals, this may represent species and tooth-type differences rather than unique in vivo conditions. The methods in these studies could be used in human teeth scheduled for extractions. Many of these models could be used before the introduction of new dentin bonding systems.

Animals↗
PubMed2003

Patterns of fluoro-gold entry into rat molar enamel, dentin, and pulp.

Permeabilities of enamel and dentin are not fully understood despite their importance for caries, restorative materials, and pulp-dentin-enamel interactions. We have found that Fluoro-Gold is useful for examining tooth permeability, and we designed studies to test the effects of aging, injury, neural function, and dentinal repair on its influx into vital rat teeth. We used fluorescence microscopy and immunocytochemistry to show that Fluoro-Gold rapidly penetrates enamel, the dentin-enamel junction, and outer dentinal acellular tubules, and then concentrates in odontoblasts, where it remains for weeks. As predicted, influx was greatest in immature teeth, and formation of reparative dentin impeded it. We expected that denervation would disrupt influx, because of neural regulation of dentinal fluid movement, but it did not. Damage to odontoblasts under injured dentin caused increased influx and efflux of Fluoro-Gold. Analysis of our data suggests that permeabilities of enamel and dentin to Fluoro-Gold are age-related, inter-dependent, and regulated by odontoblasts.

Aging↗