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The aim of the present study is to propose a classification of calcium hydroxide pastes on the basis of the vehicle that retains the calcium hydroxide. The vehicle determines the working characteristics of the calcium hydroxide: viscous and only vehicles prolong the action of the calcium hydroxide as compared with water-soluble substances. Physicochemical properties of the vehicle may limit the effectiveness in disinfecting the entire root canal system. As calcium hydroxide is not effective against all bacterial species found in root canal infections, associations with other medicaments have been proposed to enhance the efficacy of the intracanal medication.

Glass ionomer cements are currently used in endodontic therapy for sealing root canals (orthogradely and retrogradely), for sealing and restoring the pulp chamber, for repairing perforations and root resorption defects, and, rarely, for treating vertically fractured teeth. The successful use of these cements is the result of their particular characteristics: a chemical bond to dentin, which enhances the seal of the root canal and the reinforcement of the tooth; a good biocompatibility in the periradicular area and a fluoride release without loss of strength of the material. The fluoride release imparts an antimicrobial effect to combat root canal infection and attributes to bone mineralization after surgery. The present paper reviews the literature regarding the various applications of glass ionomer cements in present-day endodontics.

The smear layer is a direct consequence of instrumentation of the root canal wall. Hand instrumentation as well as ultrasonic instrumentation produce a smear layer on the canal wall. This smear layer is composed of dentine, remnants of pulp tissue and odontoblastic processes and bacteria in an infected canal. Removal of the smear layer is accomplished by the irrigation of root canals with EDTA (17%) followed by NaOCl (5.25%). Permeability of the dentine is increased by the removal of smear layer. In this way the bacteria within the infected tubuli can be more easily destroyed by an intracanal dressing. Whether the removal of smear layer decreases the apical leakage is uncertain. To establish the clinical consequences from removal or preservation of the smear layer, further research is needed.

The present paper reviews the literature and gives the evidence that apical and coronal leakage of the root canals may lead to failures of the root-canal therapy. It becomes clear that none of the present-day root canal sealers may hermetically seal "the root canal wall--gutta-percha filling interface". In this respect the importance of perfectly sealing coronal restorations (both temporary and permanent) is emphasized.

The long term success of any bonded prosthesis mainly depends on the quality of the marginal adaptation. Its degradation has been noted both at the clinical and the experimental levels. It may be due to biological, chemico-physical, mechanical and clinical factors. Improving the marginal gap closure is based on some principles: the type of preparations on which depends the stabilisation and the good positioning of the restorations; the quality of the clinical isolation which will avoid any humidity on the bonded surfaces (saliva, blood, gingival fluids); the chemical and physical type of the bonding polymer and the quality of its polymerisation; the finishing and final surface condition directly related to the kind of finishing burs used. The understanding and application of these few clinical principles enable the practitioner to expect a better clinical result as regards the bonding of aesthetic restorations.

The daily use of composite resins, the rapid evolution in their composition and that of adhesives, as well as the defects in their dimensional stability on setting, led us to carry out this study on the sealing ability of modern bonded aesthetic fillings by measurement of the thickness of the dentine-filling hiatus. In vitro, category V dental fillings are made then sectioned, polished, dyed and observed under optic microscopy. Penetration of the dyeing agent unto the outer two-thirds of the fillings proves the lack of tightness. Enamel-composite limits are almost always acceptable. The dentine-composite hiatus measures between 4 and 8 micrometers on average with the use of new adhesives (from 1 to 10 micrometers maximum). This represents a substantial improvement in comparison to the old generation of adhesives which allowed hiatuses of 10 to 50 micrometers to show. No particular product of the new generation showed to be better in this study.

Dye penetration following obturation of standardized access cavities with three different ready to use temporary cements was compared (Cavit G, Dentorit and Ciprospad). Leakage and dye penetration of the materials were simultaneously evaluated. Ciprospad appears to be the most adapted material.

The objective of this study is to verify if laser (CO2) preparation of dental tissues has an effect on the quality of the seal of composite fillings. Forty-eight cavities were filled with the Scotchprep/Scotchbond 2 system, using P 50 (3M) as filling material, following the clinical protocol of the system; 40 cavities had previously been treated with a CO2 laser Sharplan 1020 (SBM). The teeth were thermocycled (240 cycles 4 degrees C/55 degrees C), then placed in a 0.5% basic fuschine solution for 48 hours after isolation of the root dentin. After inclusion and section, the penetration of the coloring agent was examined at the interface tooth-filling. This was followed by examination of the interface composite-tooth with the Scan Electronic Microscope. In order to visualize a possible alteration of the dentinal seal, 4 cavities treated with laser were placed in a 0.5% basic fuschine solution for 48 hours after isolation of the root dentin. Four reference cavities were cut with a diamond bur on a high speed handpiece. The following results were obtained: 1) the dentinal permeability of the laser-treated samples increases markedly in comparison with the reference group. 2) the filling-tooth junction of the laser-treated samples were never dye-tight (contrary to the reference samples). 3) fissures were created in the enamel and the dentin. The Scan Electron Microscopy confirms these results.

Marginal staining is the major cause of failure of composite resin restorations. The following reasons were incriminated: The nonrespect of the integrity of the cavity limits during cavity obturation, as for instance, when a simple bevel is made. The appearance of fractures or composite bond strength failures during polishing procedures. This phenomenon can be enhanced by the use of composite finishing knives (KOMET) and by overfilling the cavity.

In this article, the authors deal with the problem of marginal fit for posterior composites, where direct class-II aesthetic restoration is involved. For different materials, they analyse and discuss the influence of their physicochemical properties, the contour of preparations, and composite handling. Three types of clinical cases are described: preparation using the tunneling technique, adhesive preparation, conventional preparation.

The aim of this paper is to assess filling biomaterials according to specification criteria, the foremost of which is the respective ability of each to form a tight seal along cavity walls. Their direct or indirect (cementing or bonding) adhesive potential is the determining factor in their durability and the biocompatibility of the restoration achieved. Gold inlay alloys and amalgams appear as yet to be the most reliable and well-tolerated biomaterials for posterior restorations. For filling small cavities in the anterior sector, microfilled composites are clearly indicated; bonded porcelain, while not yet validated over time, would seem to be a good alternative for more extensive restorations.

The objectives of tooth preparation for porcelain crowns are emphasized in this article. The forms of contour described by Gonon, LE Huche, Poggioli and Leibowitch are reviewed in the first part. In the second part, the profile of the cervical limits and their evolution are described, according to the materials used. The importance of the marginal fit, in relation to microleakage and esthetics, is related in the third part.

Preparation of the cavo-surface margin for fillings with "composites resins" is an important operative step. The good peripheral fit of the restoration and the stability of the bond between tooth and material depend on that preparation. How should the "bevel" be shaped? Scan electron microscopy of long bevels and rounded bevels show that the former seem more favorable to the fit of the filling. The section of enamel prisms is clean. The aprismatic surface area disappears. This enables to etch the cristallites in a more favorable axis as opposed to the rounded bevel.