Slavoljub Zivkovic

Smear layer in endodontics

Modern methods of root canal cleaning and filing are causing formation of the smear layer on treated surfaces. The aim of this paper was to review clinical aspect of smear layer in endodontics. Smear layer is the consequence of instrumentation of root canal walls and is consisted of organic and inorganic particles of cut dentine, necrotic and/or vital pulp fragments, microorganisms and their products. Existence of smear layer is affecting permeability of the radicular dentine, thus decreasing effects of canal medicaments and impairing adhesion of obturation materials in root canal. Removal of the smear layer from canal walls is possible with use of various chemical agents, ultrasonic or laser techniques. Regardless to contradictory attitudes and opinions, removing the smear layer is required for possible bacterial contamination, compromised effects of root canal medication and in order to obtain better obturation of canals system. .

Smear layer on dentin in restorative dentistry

Adhesion to enamel has become a routine technique in restorative dentistry. Adhesion to dentin, however, is still under investigation. Except structural elements of the dentin, smear layer has been one of the reasons that the interaction between the adhesive system and this tissue is difficult. The smear layer tissue created by cutting a tooth. It varies in thickness, roughness, density and degree of attachment andoccludes tubules and reduces the dental permeabilita. Dentin adhesivesystems can react with intertubular and peritubular dentin only when this smear layer is removed or when the adhesive system is capable of diffusion through layer of debris. As part of restorative procedures required by adhesive dentistry, the smear layer must be removed, modified or impregnated by the resin to allow for bonding between the tooth and the restorative material. For remove and dissolve of smear layer acid conditioners on total etch and self-etching primers were used. Self-etching primer systems are undergoing rapid evolution; their results are not yet sufficiently predictable overall, but some systems have achieved positive results in both enamel and dentin bonding. Further studies are necessary to confirm the long-term efficiency of these self-etching primers.

Smear layer removal with citric acid solution

The aim of this study was to evaluate efficacy in smear layer removal of 17% EDTA and 10% citric acid, using SEM. Material and method: Twenty human, extracted teeth with a single root canal were examined. Whilst instrumentation with step-back technique and manual K files, root canals were irrigated with 2 ml of 2.5% NaOCl, between each file size. After instrumentatio n, specimens were divided into two groups. The first group was irrigated with a final flush of 17% EDTA, during one minute, and the second group was irrigated with a 10% citric acid. Results: Irrigation with 17% EDTA and 10% citric acid removed smear layer from the root canals walls. There was not statistically significant differences (p>0.05) in cleaning ability between EDTA and citric acid groups.

[Root canal preparation techniques using nickel-titanium rotary instruments].

INTRODUCTION The main purpose of endodontic treatment is to clean the root canal system, eliminate the infected and toxic contents, and shape it in order to get a tridimensional obturation. The aim of this paper is to inform dental practitioners about crown-down technques for root canal preparation using nickel-titanium rotary instruments. ROOT CANAL PREPARATION Today most endodontists believe that root canal preparation is more efficious, cleaning and shaping are better, if pre-enlargement of coronal two thirds is performed first, and shaping of the apical part later. Machine driven rotary instruments provide much quicker and better root canal preparation. CONCLUSION Contemporary endodontic rotary files vary in regard to their taper, cutting blades, guiding tip and material they are made of. The usage of rotary nickel-titanium files adds a new quality to root canal preparation.

Polymerization quality testing of composite resins cured by led light source

The quality of interface between composite resin materials and hard dental tissues is highly dependent on the polymerization light source. Newly developed blue light- emitting diode units for light polymerization of dental restorative materials are the most innovative light source technology in dentistry nowadays. The aim of this work was to estimate the depth of cure of five different light-activating composite resins exposed to different irradiation times (5s, 10s, 20s and 40s) when the experimental LED light source was used. The tested materials were: Tetric Ceram (Vivadent), Point 4 (Kerr), Admira (VOCO), Filtek Z250 (3M) and Diamond Lite (DRM Lab., Inc). The depth of cure testing was determined using a penetrometer. Results after 40s curing time were as following: the deepest depth of cure was achieved after application of Filtek Z 250, Diamond Lite Point 4 and Tetric Ceram. For the restorative material Admira was found the lowest depth of cure for the light exposure of 40s. An experimental LED light source achieved a sufficient depth of cure (over 2 mm) for all tested materials after curing time of 10s. The polymerization light source spectral distribution should be considered in addition to irradiance as a depth of cure indicator.