Reduced Dentin Permeability Research Articles

Effects of high-speed cutting on dentin permeability and bonding

The effects of high-speed cutting by use of a diamond bur with or without water coolant or sanding by 80-grit SiC paper on dentin permeability, before and after surface treatment, and dentin bonding of adhesive resins were compared. Three different bonding systems were used: Scotchbond DC, which requires no removal of smear layers, and two others, Clearfil Photobond and Superbond C&B, both of which remove smear layers (phosphoric acid gel or 10% citric acid containing 3% ferric chloride, respectively). Creation of smear layers by bur cutting or sanding reduced dentin permeability to levels that were only 1-3% of the maximum permeability values. Scotchbond DC gave low but consistent bond strengths (3.7–6.1 MPa) to dentin covered with smear layers. Clearfil Photobond also produced consistent bond strengths (8.6–9.4 MPa). The increase in the permeability of dentin after phosphoric acid treatment was higher when the SiC paper was used (146%) than when the high-speed bur was used (87–90%). The smear layer and smear plugs produced by the diamond bur were more resistant to 10-3 treatment than were the SiC-created smear layers. The bond strengths of Superbond showed the highest bond strengths to the conditioned dentin when the high-speed cutting was used with water coolant (16.3 MPa), compared with the other two groups (12.2–12.5 MPa).

Dentin permeability: Effects of endodontic procedures on root slabs

The permeability of human radicular dentin was measured as a hydraulic conductance before and after treatment with K files and before and after subsequent treatment of the endodontic smear layer with NaOCl, 50% citric acid, or 3% monopotassium-monohydrogen oxalate. Filing reduced dentin permeability 25 to 49%, respectively, depending upon whether outer or inner root dentin was filed. The permeability of these smear layers was unaffected by 5% NaOCl but increased many times after treatment with 50% citric acid for 2 min. Oxalate treatment lowered root dentin permeability to levels below that produced by creation of smear layers due to the production of a crystalline precipitate.

A Review of Current Approaches to In-Office Management of Tooth Hypersensitivity

In-office treatment of dentinal hypersensitivity should be capable of providing the patient with immediate and lasting relief of pain. Regardless of the type of treatment employed, 20 to 40 per cent of hypersensitive teeth usually improve over a period of 4 to 8 weeks. Partial obturation of open tubules is the most widely practiced treatment, with other forms of therapy being recommended as a backup for patients in whom this approach fails. Obturation can be achieved with topical application of agents that form insoluble precipitates within the orifices of the tubules. Burnishing the exposed root surface produces a smear layer, which in itself can significantly reduce dentin permeability. At times, the use of a restorative resin or dentin bonding agent can be successful in reducing sensitivity when other forms of therapy have failed. Proper patient management should stress dietary counseling when dietary acids are an important etiologic factor. The importance of proper tooth brushing and plaque control must be stressed. At the present time, the use of oxalates for the obturation of tubules shows promise as a future in-office clinical agent; however, further clinical studies are required to evaluate and compare their efficacy with other currently effective methods and agents.

Clinical considerations of microleakage

Most dental materials permit the microleakage of bacteria and bacterial products from oral fluids to reach dentin. Thus, an understanding of the clinical consequences of microleakage demands that we analyze the permeability characteristics of dentin. The more dentin surface that is exposed during tooth preparation, the greater the potential for microleakage. Thicker dentin is less permeable than thin dentin. Dentin over pulp horns is more permeable than central dentin. Similarly, the dentin making up axial walls is more permeable than dentin forming the pulpal floor of cavities. Coronal dentin is much more permeable than root dentin. In addition to the number of tubules per unit area, tubule diameter, and the location of the dentin in a tooth, another extremely important variable is the presence or absence of a smear layer. When smear layers are created, grinding debris are forced into each tubule to form a smear plug. Smear plugs are usually 1- to 2-microns long but may be 10-microns long. They are much longer than the smear layer thickness and they reduce dentin permeability more than the overlying smear layer. Smear layers constitute a natural cavity liner that reduces the permeability of dentin far more than any cavity varnish. However, its presence limits the strength of dentin bonding agents because of the relatively low cohesive forces holding the smear layer together and to dentin. If it is removed, the bond strengths of dentin adhesive resins increases, but removal also increases the potential liability for pulpal inflammation if the bond is not uniformly perfect.(ABSTRACT TRUNCATED AT 250 WORDS)

The effects of a multi-step dentin bonding system on dentin permeability

Composite resin was bonded to dentin of crown segments using the multi-step Bowen bonding method. The permeability of the crown segments was measured before and after each step of the procedure to determine their effects on dentin permeability. Treatment of dentin smear layers with ferric oxalate alone reduced dentin permeability by 65%. The use of NTG-GMA or PMDM alone had much less effect on dentin permeability. The combined use of NTG-GMA and PMDM increased dentin permeability. The use of these agents following ferric oxalate treatment reduced permeability. The combined use of these agents followed by composite bonding led to a decrease in dentin permeability, which remained low after breaking the bond for 3 months, the longest time period studied. The ability of a dentin bonding system to seal dentinal tubules and decrease dentin permeability should be an important characteristic of dentin bonding agents.

The efficacy of resin-compatible cavity varnishes in reducing dentin permeability to free monomer

The effectiveness of three resin-compatible cavity varnishes in reducing the dentin permeability to free monomer liquid was evaluated by means of a dentin disk mounted within a pressurized split-chamber diffusion device filled with low-viscosity aliphatic dimethacrylate. Substantial reduction in dentin permeability was obtained with all of the products tested (Microjoin, Cavi-Line, and Universal). This study suggests their likely effectiveness as a protective barrier against permeation of free monomer into the dental pulp.

The effects of calcium hydroxide on dentin permeability.

Calcium hydroxide paste was applied to human dentin in vitro to determine its effects on dentin permeability. Discs of dentin were acid-etched on both sides to permit determination of their maximum permeability. Smear layers were then applied to the enamel sides of the discs, thereby reducing dentin permeability 99%. Topical application of Ca(OH)2 paste to the smear layer reduced dentin permeability further, to levels 48% below that of untreated smear layers. When the Ca(OH)2-treated smear layers were exposed to 6% citric acid for two min, dentin permeability returned to the initial acid-etched value, demonstrating that Ca(OH)2 offers little protection to acid challenge. Treatment of acid-etched dentin with Ca(OH)2 produced a similar reduction in dentin permeability, which was restored to normal following acid challenge. Thus, Ca(OH)2 is effective at reducing the permeability of both the smear layer and of acid-etched dentin, in vitro.

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.

Dentin permeability: Effects of cavity varnishes and bases

C avity lining materials are used to protect the pulp from possible injurious effects after restorative procedures. They are intended to provide a barrier against substances liberated from restorative materials, acidic components of cements, or the dehydrating effects of some restorative materials.‘-3 Lining materials should also prevent penetration of cavity margins and dentinal tubules by bacteria and their products, which are currently thought to cause most of the pulpal inflammation seen under restorative materials.4-6 Many techniques and procedures have been used to evaluate the permeability of cavity lining materials. Histologic examination of the pulps of teeth treated with various materials has been used for many years.‘, * Dies, silver nitrate, and autoradiographic studies have been widely used.2~9-‘9 Unfortunately, most of the previous work has been qualitative or semiquantitative at best. Several reports described quantitative techniques that can accurately determine the efficacy of lining materials to reduce marginal leakage and/or dentin permeability.20-23 As part of a systematic study of the permeability characteristics of dentin, two quantitative techniques have been developed to accurately measure dentin permeability. This report describes the use of these techniques in evaluating the ability of several cavity varnishes and bases to reduce dentin permeability.

Effects of fibrinogen in vivo on dentine permeability in the dog

Dentine permeability measurements were made each hour for 6 h in tooth cavities prepared in control dogs or dogs which had been pretreated with a purified fraction of snake venom to deplete their plasma of fibrinogen. The control dogs exhibited a progressive fall in dentine permeability (~ 50 per cent reduction in 6 h); the permeability in the fibrinogen-depleted dogs only fell 15 per cent in 6 h. The results implicate plasma proteins, particularly high molecular-weight proteins such as fibrinogen, as agents which reduce dentine permeability in vivo.

Human coronal dentine: Structure and reactions

The present survey of the structure and reactions of human coronal dentine demonstrates the need for a thorough knowledge of this tissue if one is to understand the biology of the pulp. Particular attention is paid to conditions which result in increased mineralization of the primary dentine, for these conditions may reduce dentine permeability and thus probably modify the pulp reactions which may occur. In order to prevent damage to the pulp, it is possible that treatment should be aimed toward a reduction in the permeability of the dentine rather than toward an attempt to stimulate irregular secondary dentine formation.