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PubMedDate not supplied

Relationship between dentine hydraulic conductance and the cytotoxicity of four dentine bonding resins in vitro.

OBJECTIVES: Dentine modifies pulpward diffusion of monomers leaching from restorative materials. Thus, remaining dentine thickness must be taken into account during in vitro cytotoxicity tests. This in vitro study was designed to determine the influence of dentine permeability on the outcome of a cytotoxicity test. METHODS: Dentine slices were made from 36 human third permanent molar teeth. The 36 dentine slices were divided into two groups according to their hydraulic conductance: high or low hydraulic conductance. The cytotoxicity of four dentine bonding agents of similar cytotoxicity was tested on dentine slices from each group. Four dilutions of the experimental culture medium were tested: undiluted, 1:2, 1:10 and 1:100. An analysis of variance was used to compare the cytotoxicity of the dentine bonding agents tested on high versus low hydraulic conductance. RESULTS: The cytotoxicity of the high hydraulic conductance (Lp) group was higher than that of low Lp group when tested with the undiluted test culture medium (p = 0.001). No difference was obtained with the 1:2, 1:10, 1:100 dilutions. CONCLUSIONS: Under the conditions of the study, the dentine bonding resins were more cytotoxic when applied onto dentine slices of high hydraulic conductance.

Analysis of Variance↗
PubMed1992

In vitro permeability of furcation dentin in permanent teeth.

Extracted unerupted permanent third molars with the occlusal half of the crown and apical half of the roots removed were cemented to Plexiglas blocks. Using a positive pressure system in which the movement of fluid across the dental tubules could be measured, the permeability of furcation dentin was measured before and after alteration of the furcation thickness. Subsequently, measurements of reduction in thickness of cementum and dentin were performed. Furcation dentin permeability was found to increase as the cementum and dentin thickness was reduced and the smear layer removed. The permeability values obtained for the furcation dentin were similar to those found in radicular dentin in general, indicating that root dentin has a low permeability and that it has good barrier properties. The data would suggest that any bone resorption seen under the furcation region of permanent molars is more likely to be due to the presence of accessory canals than due to permeation directly through furcation hard tissues.

Adolescent↗
PubMed1995

Effects of fluoride on the calcium phosphate precipitation method for dentinal tubule occlusion.

Use of the calcium phosphate precipitation (CPP) method makes possible the occlusion of dentinal tubules to approximately 10 to 15 microns from the dentinal surface, and thus shows good potential for the treatment of dentin hypersensitivity. The precipitate formed in the dentinal tubules by the CPP method is, however, not apatite [HAP; Ca10(PO4)6(OH)2], a component of tooth and bone, but dicalcium phosphate dihydrate (DCPD; CaHPO4.2H2O). Since fluoride enhances the conversion of DCPD to HAP, we evaluated the effects of fluoride on the texture of the precipitate formed by the CPP method and on its capacity to occlude dentinal tubules in this in vitro study. CPP solution (1.0 mol/L CaHPO4.2H2O dissolved in 2.0 mol/L H3PO4) was applied to a dentin disk and was subsequently neutralized with a post-treatment solution (1 mol/L NaOH, from 0 to 0.1 mol/L NaF). Scanning electron microscopy revealed that the precipitate occluded dentinal tubules to a depth of approximately 10 to 15 microns from the dentinal surface, regardless of the NaF concentration (from 0 to 0.1 mol/L) in the post-treatment solution. Also, dentin permeability was reduced to 15% by the CPP treatment regardless of the NaF concentration. The Ca/P molar ratio of the precipitate, measured by x-ray micro-analysis, was higher (1.25 +/- 0.04) in the presence of NaF than in its absence (1.03 +/- 0.01). For further identification of the precipitate formed in the dentinal tubules, the same procedure was used in glass tubes (diameter, 1 mm), so that a larger amount of precipitate would be obtained.(ABSTRACT TRUNCATED AT 250 WORDS)

Calcium Phosphates↗
PubMed1997

The Dentin Disc surface: a plausible model for dentin physiology and dentin sensitivity evaluation.

Dentin sensitivity (DS) is a painful clinical condition which may affect 8-35% of the population. Various treatment modalities have claimed success in relieving DS, although at present there does not appear to be a universally accepted desensitizing agent. Current opinion based on Brännström's Hydrodynamic Theory would suggest that following exposure of the dentin surface (through attrition, abrasion, or erosion), the presence of open dentinal tubules, patent to the pulp, may be a prerequisite for DS. The concept of tubule occlusion as a method of dentin desensitization, therefore, is a logical conclusion from the hydrodynamic theory. The fact that many of the agents used clinically to desensitize dentin are also effective in reducing dentin permeability tends to support the hydrodynamic theory. This paper reviews the in vitro evaluation of desensitizing agents, the techniques used to characterize their effects on the prepared dentin surface, and the ability of these agents to reduce permeability through tubule occlusion, and presents recent findings from ongoing research based on the Pashley Dentin Disc model. It can be concluded that the use of this model to determine surface characteristics, and reductions in dentin permeability through tubule narrowing or occlusion, provides a useful screening method for evaluating potential desensitizing agents. Interpreting changes observed in vitro is difficult, and extrapolation to the clinical situation must be tempered with caution.

Animals↗
PubMed2004

Dentin evaluation after Nd:YAG laser irradiation using short and long pulses.

OBJECTIVE: Several reports have demonstrated the advantages of using the Nd:YAG laser to reduce dentin permeability by melting the dentin surface. A comparative study using different pulse durations can be useful to obtain further information about the laser-hard tissue interaction. MATERIALS AND METHODS: The present study pursues the evaluation of the morphological and chemical changes in human dentin surface resulting from Nd:YAG laser (lambda = 1064 nm) irradiation, with a total energy of 0.9 J distributed in 1, 2, 3, and 6 pulses with different pulse durations to promote surface melting and dentinal tubule occlusion. After irradiation, the samples were submitted to scanning electron microscopy (SEM) analysis for morphological study and energy-dispersive spectrometry (EDS) analysis for evaluation of the concentration of calcium and phosphorous in the melted layer. RESULTS: SEM analysis of the irradiated dentin surface showed surface structural changes due to laser irradiation, where the morphological changes are dependent on the laser pulse duration. EDS analysis showed an increase of calcium and phosphorous concentrations after Nd:YAG laser exposure, but no correlation with the number of pulses or pulse duration was found. CONCLUSION: Our results suggest that longer interaction times resulted in more evident effects with more melted substrate than shorter pulses, and in both cases the resultant melted layer contains a greater concentration of inorganic substances than non-irradiated dentin.

Calcium↗
PubMed1996

The density and branching of dentinal tubules in human teeth.

Detailed knowledge of dentine structure, and especially that of the dentinal tubules, is essential in order to understand dentine permeability and to interpret data from investigations on dentine adhesive materials. The aim here was to examine the density and branching of dentinal tubules in human teeth by light and scanning electron microscopy. Stained and unstained demineralized sections and undemineralized fractured specimens were studied. Statistically significant differences in the density of tubules were found depending on location. Differences in density of tubules between the peripheral and inner aspects were more marked in the crown than in root. The mean number of dentinal tubules in the middle part of the root was significantly lower than in the middle part of the crown. The density of the tubules in the outer dentine at the cusp location was also significantly different from that subjacent to the occlusal fissure. The number of branches of dentinal tubules was particularly abundant in locations where the density of tubules was low. The branching patterns revealed an intricate and profuse canalicular, anastomosing system, criss-crossing the intertubular dentine. Three types of branches, major, fine and microbranches, were identified on the basis of size, direction and location. Major branches, 0.5-1.0 micron dia., were the typical delta branchings found peripherally. Fine branches, 300-700 nm dia., forked off at 45 degrees and were abundant in areas such as in the root where the density of the tubules was relatively low. Microbranches, 25-200 nm dia., extended at right angles from the tubules in all parts of the dentine. The findings emphasize the need for detailed characterization of dentine substrates for adhesive testing and of samples used in permeability studies.

Adolescent↗
PubMed1995

Effect of pulpal pressure on adhesion of resin composite to dentin: bovine serum versus saline.

The purpose of this study was to compare the tensile bond strengths of resin composite to dentin, mediated by two new bonding systems (Scotchbond Multi-Purpose and Clearfil Liner Bond II), under simulated pulpal pressure when diluted bovine serum or saline was used as the pulpal fluid. The bond strengths of the two bonding systems to dentin (under a pulpal pressure of 15 cm of water) obtained when bovine serum was used were statistically significantly higher than those obtained when saline was used. These data suggest that the primers of these bonding systems decreased the dentinal permeability when the bovine serum pulpal fluid was used through the precipitation of serum proteins by the primers in the dentinal tubules. This may have allowed better penetration of the bonding resin monomers into the conditioned dentinal structure, thus improving the bond strength. These findings support the idea that topical application of dentinal bonding systems may be an effective therapy for treating hypersensitive dentin.

Animals↗
PubMed1997

In vitro cytotoxicity of dental adhesive systems under simulated pulpal pressure.

OBJECTIVES: Most of the devices used to evaluate the cytotoxicity of resin-based composites in vitro use a dentin barrier test. However, it is difficult to obtain the number of freshly extracted teeth, all on the same day, that is necessary for powerful statistical analysis. Tooth cryopreservation provides a way to build up a supply of teeth. This in vitro study compared cryopreserved teeth and freshly extracted teeth in an evaluation of the cytotoxicity of resin-based composites. In addition, this study also evaluated the effects of pulsatile pressure and the importance of dentin permeability on the cytotoxic response to bonding resins. METHODS: Forty freshly extracted and forty cryopreserved third molars were used. A standardized Class I cavity was prepared within the dentin. The hydraulic conductance of each tooth was recorded. The cavities were filled either with Scotchbond Multi-Purpose Plus and Z 100 (3M Dental Products) or with Optibond and Herculite (Kerr). A plexiglas device was designed to permit 24 h long contact between culture medium and the roof of the pulp chamber while a pulsatile pulpal pressure was simulated. The viability of L 929 cells cultured with a control medium and evaluated by an MTT assay was compared to that of L 929 cells cultured with medium which remained for 24 h in contact with the pulp chamber of restored teeth. A three-way ANOVA was used to compare the cytotoxicity among the different groups. A simple least-squares linear regression was used to seek a relationship between the hydraulic conductance of dentin and the cytotoxicity of composite restorative materials. RESULTS: No significant differences in cytotoxicity were found between the freshly extracted teeth and the cryopreserved teeth (p = 0.53). The cytotoxicity of the resin adhesives was statistically higher when a pulsatile pulpal pressure was simulated (p = 0.04). A significant relationship was found between the hydraulic conductance of dentin and the cytotoxicity of resin-based composites (p = 0.02). SIGNIFICANCE: Cryopreserved teeth can be used for in vitro evaluation of the cytotoxicity of resin adhesives. Pulsatile pulpal pressure simulations increased the in vitro cytotoxicity of the tested materials.

Adult↗
PubMed1985

Dentin-predentin complex and its permeability: physiologic overview.

The major channels for solute diffusion across dentin are the dentinal tubules. Since dentin permeation is proportional to the product of tubule number and diameter, both of which increase as the tubules converge on the pulp, we find that dentin permeability increases rapidly as the pulp chamber is approached. The presence of a smear layer of cutting debris on top of cut dentin decreases dentin permeability, especially when permeability is measured by fluid filtration. Further, intratubular material--such as mineral deposits, collagen fibrils, proteoglycan linings, bacteria, etc.--can greatly reduce dentin permeability. Although the presence of irregular or irritation dentin has been thought to greatly reduce dentin permeability, recent in vivo experiments in dogs indicate that the dentin permeability of freshly cut cavities prepared in sound dentin falls very rapidly (i.e., 50-60% in the first six hours) before any histologic changes can be detected, either in the pulp or the dentin. When dogs were depleted of their plasma fibrinogen, this rapid decline in dentin permeability following cavity preparation failed to take place. The results implicate leakage of plasma proteins from the underlying pulpal vessels. The proteins subsequently permeate the tubules, where they are either adsorbed to the tubule walls or physically trapped in such a way as to reduce dentin permeability.

Animals↗
PubMed1993

Inhibition of serum albumin flux across exposed dentine following conditioning with GLUMA primer, glutaraldehyde or potassium oxalates.

A variety of medicaments used on dentine in various treatment procedures may cause a reduction in dentine permeability. By observing the flow of endogenous serum albumin across exposed dentine, agents known to promote dentine bonding of restorative resins or retard dentine sensitivity were assessed regarding their capacity to arrest dentinal fluid flow. Experiments were conducted in young adult macaque monkeys employing Class V cavity preparations in incisors and canines. A diffusion-in-gel-enzyme-linked-immunosorbent-assay (DIG-ELISA) was used to quantitate serum albumin in effluents from these cavities at various time periods following either no treatment or topical application with GLUMA primer, glutaraldehyde or potassium oxalates. While in untreated cavities serum albumin continued to flow even after a period of 1 week, a substantial reduction or complete cessation of serum albumin flux was seen following topical application of the agents tested, suggesting a durable effect on dentinal fluid flow. No difference between agents was observed. Further cutting of the cavity bottom a few tenths of a millimetre resulted in renewed flow of serum albumin. Data suggest that the solutions tested are capable of reducing dentinal fluid flow onto exposed dentine surfaces.

Acid Etching, Dental↗
PubMed1987

Regional variability in the permeability of human dentine.

This was measured qualitatively by using dyes and quantitatively by hydraulic conductance in dentine discs and crown segments in vitro. Both types of preparation demonstrated large regional differences in permeability, with the highest values at the periphery and the lowest in the centre of the disc or crown. As dentine permeability may vary 3-10-fold across a few millimetres, investigators should use as large a surface area as possible to compensate for these regional differences.

Dentin Permeability↗
PubMed1998

Biocompatibility of dentine-bonding agents. 2. Pulpal considerations.

The paper reviews the literature concerning the biocompatibility of dentine-bonding agents. The literature review indicates that two main hypotheses are presented to explain pulpal inflammation following the placement of materials such as dentine-bonding agents, namely material toxicity and bacterial infection. The paper discusses the role of such factors as microbial microleakage, remaining dentine thickness and the smear layer as factors in determining material toxicity and summarises the reported biocompatibility studies. From this it is concluded that most bonding agents contain constituents which have a potential irritant or toxic effect on the pulpo-dentinal complex. The irritant effect may be due to constituents of the bonding agents, or to poor or lost bonding, or to a combination of all these factors. The recently favoured total-etch technique may cause an increase in dentine permeability by removal of the smear layer and thereby increase the irritant effect of some materials.

Animals↗
PubMed2000

Evaluation of dentin root canal permeability after instrumentation and Er:YAG laser application.

BACKGROUND AND OBJECTIVES: Smear layer removal with EDTA from root canal walls allows greater cleaning and disinfection of root canals. However, because Er:YAG laser acts on the removal of the smear layer, the objective of investigation was to analyze in vitro the effect of Er:YAG laser on dentin root canal wall permeability after endodontic instrumentation and irrigation with water or sodium hypochlorite and Er:YAG laser application. STUDY DESIGN/MATERIALS AND METHODS: A total of 25 extracted human maxillary incisors were divided into five groups: Group I, instrumentation with deionized distilled water as the irrigating solution; Group II, instrumentation with 1% sodium hypochlorite as the irrigating solution; Group III, instrumentation with deionized distilled water as the irrigating solution and Er:YAG laser application; Group IV, instrumentation with 1% sodium hypochlorite solution as the irrigating solution and Er:YAG laser application; Group V, instrumentation only up to #20 file with deionized distilled water as the irrigating solution and Er:YAG laser irradiation. The laser parameters were 15 Hz, 140 mJ, total energy 42 J, 300 pulses (Kavo Key Laser). Copper sulfate (10%) was used to evaluate dentin permeability. The penetration of copper ions into the dentinal tubules was observed using 1% rubeanic acid, which reveals copper ions, forming a stained compound ranging in color from deep blue to black. Transverse sections (500-microm thick) were obtained with a diamond disk from the cervical, middle, and apical thirds. RESULTS: The instrumentation of the root canal that used water as the irrigating solution followed by Er:YAG laser irradiation promoted the greatest increase in dentin permeability. The use of Er:YAG laser, 1% sodium hypochlorite + Er:YAG, and 1% sodium hypochlorite used alone showed an intermediate capacity of increasing dentin permeability. The use of water as the irrigating solution without Er:YAG laser promoted the least dentin permeability. CONCLUSIONS: The use of water as the irrigating solution after instrumentation and Er:YAG laser irradiation was an effective procedure for increasing dentin permeability.

Dental Pulp Cavity↗
PubMedDate not supplied

Comparison of the in vitro permeability of human dentine according to the dentinal region and the composition of the simulated dentinal fluid.

OBJECTIVE: To compare the permeability of the occlusal and the cervical dentinal regions within the same tooth, which represent the bottom of Class I and V cavities, respectively, with two different compositions of perfusion fluid, in vitro. METHODS: An occlusal and a buccal disc were cut from each extracted third molar at a level close to the pulp chamber. The convective permeability of the discs was measured in a fluid transport model using de-ionised water or 1:3 diluted bovine serum and the hydraulic conductance was determined. RESULTS: The mean hydraulic conductance values of the occlusal and the buccal cervical human dentine to water were 0.069 and 0.047 microl min(-1) cm(-2) cm H(2)O(-1), respectively. When diluted bovine serum was used, the corresponding values were 0.036 and 0.012 microl min(-1) cm(-2) cm H(2)O(-1), respectively. Statistical analysis revealed no significant difference between the permeability of these two regions. The composition of the perfusion fluid significantly influenced the permeability of dentine. CONCLUSIONS: The occlusal and the buccal cervical regions of human dentine have similar permeability characteristics in vitro. There is a strong reverse correlation between the viscosity of the perfusion fluid and the perfusion through the dentine.

Animals↗
PubMed1997

The use of extracted teeth for in vitro bonding studies: a review of infection control considerations.

OBJECTIVE: Infection control concerns regarding the handling of teeth for research purposes have prompted investigators to evaluate the effects of disinfection/sterilization on extracted teeth. The objectives of this literature review were to assess the reported findings of the effect of disinfection or sterilization on teeth used for in vitro bonding studies and make recommendations on their use. METHODS: A search of the literature was performed to obtain background information on infection control guidelines and current findings regarding disinfection or sterilization of extracted teeth. Published articles addressing the effects of different disinfection and sterilizing procedures on the tooth, such as structural changes of dentin and dentin permeability or effect on bond strengths, were examined and compared for agreement or disagreement of findings. The review was organized by the type of disinfection or sterilization method utilized by the investigators. These methods were evaluated in an attempt to address whether disinfection/sterilization of extracted teeth can be recommended or if the procedure simply produces another variable. RESULTS: Formalin, chemical heat sterilization (Chemiclave), autoclave, ethylene oxide and gamma radiation methods of disinfection/sterilization have been investigated for their effects on extracted teeth. When the effect of formalin storage on dentin bond strengths was examined, investigator results were extremely varied. Autoclave and chemical sterilization were found to produce comparable dentin bond results when compared to controls. Gamma radiation did not produce structural changes in the dentin but it currently has not been investigated for its effect on dentin bond strength. And while ethylene oxide produced similar dentin bond strength results when compared to controls, its use as a sterilant was determined to be ineffective. SIGNIFICANCE: Investigators have found formalin storage to be effective for infection control purposes. It cannot, however, be recommended as a storage medium for dentin bonding studies due to the variability in dentin bond strengths resulting from its use. Ethylene oxide is also not recommended due to its inability to effectively sterilize teeth. Chemical heat and autoclave sterilization methods are recommended for preventing cross-contamination during in vitro dentin bonding research. This recommendation is based on current research findings which examined the effect of these sterilization methods on dentin and dentin bond strengths.

Dental Bonding↗
PubMed1999

A fluid filtration and clearing technique to assess microleakage associated with three dentine bonding systems.

OBJECTIVES: The aims of this in vitro study were to (a) measure fluid flow through teeth restored with one of three dentine bonding systems and a resin composite restoration; (b) measure the distribution of a silver tracer through the same teeth, and make a comparison with fluid flow; and (c) investigate the effect of thermocycling on both measurement types. METHODS: Coronal segments of 30 premolars, randomly allocated to three equal groups, were assessed by fluid filtration. Each group was restored with a resin composite restoration in conjunction with Fuji Bond LC (FBLC), Scotchbond Multi-Purpose Plus (SMP+) or Prime&Bond 2.1 (P&B2.1). Fluid filtration rates were measured in the intact crown and then after cavity preparation, conditioning, dentine bonding, restoration and at 2 and 24 h, 1 week and 1 month following restoration. Six specimens from each group were thermocycled at 1 week. After final filtration measurements the specimens were perfused with silver nitrate and cleared before scoring tracer penetration. RESULTS: No significant differences (P > 0.05) in fluid filtration rates were found amongst the different bonding systems or at any restoration stage. Thermocycling was not associated with any significant (P > 0.05) increase in fluid filtration. Final fluid filtration and tracer distribution showed a weak and not statistically significant correlation (P > 0.05). The penetration of silver stain indicated a failure of the restorations to seal the cavity and demonstrated a possible pathway by which in vivo post-operative sensitivity could occur. CONCLUSIONS: Although not statistically significant, conditioning of the cavity increased the dentinal permeability but this effect was variable. Thermocycling had no statistically significant effect on microleakage.

Analysis of Variance↗
PubMed1993

Structural and functional changes in root dentin following exposure to KTP/532 laser.

The use of a new, modified Nd:YAG laser called the KTP/532 laser was evaluated within root canals to determine whether it would modify dentin permeability or alter the scanning electron microscopic appearance of canal dentin. Energies and exposure times were chosen which did not permit periodontal temperatures to increase above 5 degrees C (1 W x 1 s-5 W x 0.5 s). Half of the root canals were covered with smear layer and half were treated with EDTA/NaOCI to remove the smear layer. The results showed that this laser did not change the permeability of the smear layer-covered dentin, although scanning electron microscopic examination revealed modifications to the surface of smear layer. Lasing of etched dentin produced modest increases in root permeability which were associated with enlargement and cracking of tubule orifices.

Dental Pulp Cavity↗
PubMed2003

Evaluation of the permeability of the furcation area of deciduous molars conditioned with Er:YAG laser and cyanoacrylate.

The purpose of this study was to evaluate in vitro the dentin permeability of the deciduous pulp chamber floor after employing 2-octyl cyanoacrylate and Er:YAG laser. Twenty four deciduous molars were used, divided into four groups. After chemical-surgical preparation each group received a different treatment: Group 1 - control, without treatment; Group 2 - the floor of the pulp chamber was covered with a fine layer of 2-octyl cyanoacrylate; Group 3 - the floor of the pulp chamber was irradiated with Er:YAG laser (250 mJ, 10 Hz for 30 seconds, 80 J of energy and 320 pulses), and covered with a fine layer of 2-octyl cyanoacrylate; and Group 4 - the floor of the pulp chamber was irradiated with Er:YAG laser set at the parameters already described. After that the specimens received application of 0.5% methylene blue, for 15 minutes. The teeth were cut, photographed, and the digitalized images were analyzed using the ImageLab program. The results obtained were submitted to statistical analysis. Group 4 (Er:YAG) presented the largest averages in percentage of dye penetration area (19.5%), followed by Group 1 (11.1%), Group 3 (1.4%) and Group 2 (0.2%). The experimental model allowed to conclude that the specimens conditioned with 2-octyl cyanoacrylate (Group 2) and Er:YAG laser associated to 2-octyl cyanoacrylate (Group 3) presented a decrease in permeability, and the specimens treated with Er:YAG laser (Group 4) presented an increase in permeability of the analyzed area.

Cyanoacrylates↗