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Effect of root canal treatments on dentin permeability.

Calcium hydroxide has been used to slow or reverse external root resorption subsequent to trauma. In this study, an experimental model was established to study the diffusion of calcium ions from the canal to the root periphery after various intracanal treatments. Analyses of calcium ion concentrations from extraradicular samples revealed that dentin specimens varied in their rates of diffusion of calcium and that treatment of the canals with various agents affected the amounts of calcium recovered.

Analysis of Variance↗

The effects of acid etching on the in-vivo permeability of dentine in the dog.

Cavities were cut in both lower molars of 11 anaesthetized dogs. Dentine permeability was quantitated in these teeth using a filtration technique before and after acid etching to remove the smear layer. Acid-etching increased 5-fold the ease with which fluid could flow across dentine. Under conditions of high fluid filtration, an opening into the pulp chamber from the opposite side of the tooth produced only slight increases in filtration rate, indicating that the rate-limiting step is filtration of fluid across dentine, rather than removal of the fluid by the pulp circulation.

Acid Etching, Dental↗

Comparison of two methods to measure permeability of dentin.

Dentin permeability was measured alternatively with two methods: a 10-microl capillary method with visual evaluation (PC) and a motorized automatic measuring device (Flodec, FD), both interposed in a simulated perfusion system. Eight human third molar coronal fragments were connected to systems, and their permeability to distilled water measured at 0, 5, 10, 15, 20, 25, and 29 cm H(2)O pressure. Resultant permeabilities (in microl/s) for both techniques were interrelated with the use of the Passing and Bablok nonparametric method, which gives information about the range of constant and proportional errors and their 95% confidence intervals (95CI). The relationship between the methods is described by the regression formula: FD = -0.0003 + 0.945.PC, with 95CI for constant (-0.0015-0.0009) and for slope (0.738-1.168), indicating that both methods are interchangeable, although not identical.

Dentin↗

An update on the physiology of the dentine-pulp complex.

The properties of dentine and pulp are closely related and from a functional standpoint these tissues are often referred to as the dentine-pulp complex. In recent years there has been considerable progress in our understanding of the physiology of the dentine-pulp complex. This review describes some of the advances that are relevant to clinical dentistry, including dentine permeability, dentine bonding, dentine sensitivity, the properties of pulpal nerves and blood vessels and the reactions of the dentine-pulp complex to operative dental procedures.

Dental Bonding↗

[Cervical wedge-shaped lacunae and dentin hypersensitivity--a histological and SEM study].

The purpose of this study was to establish a correlation between dentinal hypersensitivity and tissular modifications of the pulp-dentinal complex at the level of cervical abrasions. 65 freshly extracted human teeth (from patients aged 20 to 80 years) presenting cervical abrasions without carious lesions were prepared in order to be examined histologically (31 teeth) and by scanning electron microscopy (34 teeth). Open tubules were present on the abraded surfaces in 83.3% of the specimens with presence of cytoplasmic processes in 78.46% of the cases without any correlation with tooth age and depth of the abrasions. The sensitivity could be partially explained by the persistence of cervical dentinal permeability. This permeable dentin seems to be susceptible to mechanical, chemical and bacterial irritations, no matter how thick the reactional dentin is. In the absence of any reliable and biological product capable to seal efficiently the open tubules, only nonabrasive hygiene methods can preserve the integrity of cervical dental tissues.

Adult↗

[The influence of dentin conditioning on permeability of dentin].

In this study the influence of four different pretreatments showed significant differences on the permeability of cut dentin. On the average the application of 25% polyacrylic acid increased the permeability by approximately 10 percent, the application of 34% polyacrylic acid by 30 percent. The treatment with 0.1% chlorhexidin-digluconate produced no change of permeability. Calciumhydroxide suspension reduced the permeability by 15 percent and diminished the increase caused by phosphoric acid significantly.

Acid Etching, Dental↗

Correlation among dentin depth, permeability, and bond strength of adhesive resins.

Correlations among dentin permeability, dentin depth, and dentin bonding of Scotchbond, Clearfil New Bond, and Superbond C&B were studied in bovine incisor crown segments. Since the dentin surface was prepared on deeper dentin, the permeability of the dentin increased both in the presence of, and especially after removal of, the smear layer. In general, the deeper the dentin, the lower the bond strengths of Scotchbond, Clearfil New Bond, and Superbond C&B. The higher the dentin permeability, the lower the bond strength of Superbond C&B, but there was no simple relationship in the case of either Scotchbond or Clearfil New Bond. The bond strength of Superbond C&B was much higher than those of Scotchbond or Clearfil New Bond at any depth of dentin. Superbond C&B should be considered as both an enamel- and dentin-bonding agent.

Composite Resins↗

Effect of cutting instruments on permeability and morphology of the dentin surface.

There are major differences in morphological detail after cutting the dentin surface among the methods commonly used to prepare dental cavities. The purpose of this study was to compare dentin permeability and the morphology of the dentin surfaces prepared with diamond and carbide steel burs after etching with 6% citric acid. Twenty-four freshly extracted human third molars were sectioned, mounted on plexiglass, and connected to the dentin-permeability measuring apparatus. The permeability of dentin was measured by fluid filtration and expressed as hydraulic conductance. There were two study groups of 12 teeth. Each tooth had one occlusal cavity preparation prepared but utilized three depths: the original was prepared just into the dentin, the second 0.5 mm deeper than the first, and the third 0.5 mm deeper than the second. One group had the first cavity prepared with a diamond, the second deepened using a steel bur, then the third depth was made by use of the diamond. The other group had the first cavity preparation prepared with a steel bur, deepened 0.5 mm again using a diamond, then deepened again using a steel bur. Dentin permeability was measured after cavity preparation, then after 2 minutes of acid etching. Analysis of variance and Duncan's multiple range test were used to establish whether differences were significant at the 0.05 confidence level. Prepared and acid-etched surfaces were characterized using a scanning electron microscope to identify any differences between the two groups. After acid etching with 6% citric acid, the permeability of dentin cavities prepared with diamond burs was significantly less than the permeability of cavities prepared with carbide steel burs. After etching, there were differences in the appearance of the dentin surfaces prepared with diamonds and steel burs. Dentin bonding agents may have their effectiveness reduced when placed following cavity preparation by use of a diamond.

Dental Bonding↗

Permeability changes of dentine treated with titanium tetrafluoride.

OBJECTIVES: The aim of this research was to evaluate the effect of titanium tetrafluoride on dentine permeability in comparison with sodium fluoride and acidulated phosphate fluoride to determine their contribution to acid resistance of dentine. METHODS: Thirty-two dentine discs were prepared from extracted mandibular molars. The hydraulic conductance of all discs was measured before and after the formation of smear layer. The discs were then randomly divided into five experimental and one-control groups. Coronal surfaces of dentine discs were treated with either fluoride solutions of NaF, APF, 1% TiF4, 0.5% TiF4 and 0.1% TiF4 or de-ionised water. Following the measurement of hydraulic conductance, treated surfaces were subjected to 25% citric acid application. Then, final permeability measurements were made. The data were statistically analysed using ANOVA and Tukey's HSD multiple comparisons. RESULTS: While smear layer formation considerably reduced dentinal permeability of dentine discs, fluoride or de-ionised water application to smeared surfaces did not cause any significant change in hydraulic conductance (p > 0.05). After citric acid application, control and NaF groups showed higher permeability values than 1%, 0.5% and 0.1% TiF4 and APF groups (p < 0.01). CONCLUSION: Clinical use of acidic solutions of titanium tetrafluoride in dentine cavities may be considered since smeared dentine surfaces are modified to a stabile and acid-resistant state.

Acidulated Phosphate Fluoride↗

Smear layer: overview of structure and function.

Smear layers are created on hard tissues whenever they are cut with hand or rotary instruments. This thin (1-2 microns) layer of denatured cutting debris is very tenacious and, in fact, is often the surface to which restorative materials are luted. The solubility characteristics, chemical reactivity and the structure-function relationships of this layer have not yet been well-defined. During creation of the smear layer, cutting debris is forced variable distances into dentinal tubules. These so-called smear plugs, together with the smear layer decrease dentin permeability, dentin sensitivity and surface wetness. Bonding adhesive resins to smear layers appears to limit the theoretical bond strength unless the smear layers are loosened or partially removed. Future research in this area will include the use of surface analytical techniques such as Auger electron spectroscopy and ESCA. These techniques are required because of the thinness of the smear layer. It is clear that the nature of this critical interface between dental materials and cut hard tissues remains largely unknown. This field will provide fertile ground for future research.

Animals↗

Permeability effects of two dentin adhesive systems.

This in vitro study evaluated the effects of two dentin adhesive systems on dentin permeability. The XR-Bonding System modifies the smear layer but does not open dentinal tubules. The Kanca or "total-etch" technique (phosphoric acid, Tenure A and B, Scotchbond 2 Adhesive) removes the smear layer and opens dentinal tubules. Despite these differences, both systems reduced dentin permeability in a similar manner. XR-Bond decreased permeability to 52% of the smear layer value, while total etching reduced permeability to 66% of that value.

Acid Etching, Dental↗