A preliminary study of a new endodontic irrigation system: Clean Jet Endo.

The purpose of the present study was to assess the irrigant penetration and cleaning ability of a new irrigation system, the Clean Jet Endo (Produits Dentaires SA, Switzerland) in comparison to conventional irrigation followed or not by sonic activation. Irrigant penetration was evaluated on resin blocks simulators by measuring the methylene blue absorbance thanks to a UV/visible spectrophotometer and cleaning ability was assessed in an ex vivo experiment according to the debris score in an artificial canal extension before and after the final irrigation protocol. A statistical analysis was carried out in order to highlight the significant differences between the irrigation techniques. Clean Jet Endo permitted to better eliminate the methylene blue into the simulated canals. A significant difference between the 2 techniques was observed in the middle third (p = 0.005) as well as in the apical third (p < 0.2). An additional microscope observation (16X) confirmed that Clean Jet Endo@ usage led to a better penetration of irrigant within the lateral canals of the simulators. Likewise, this irrigating system permitted to better eliminate the debris in the lateral groove than the other techniques. In conclusion, our findings implied the potential of this new irrigation system to enhance root canal debridement and disinfection.

Chemical & Nano-mechanical Study of Artificial Human Enamel Subsurface Lesions.

White lesions represent an early phase of caries formation. 20 human sound premolars were subjected to pH cycling procedure to induce subsurface lesions (SLs) in vitro. In addition, 2 teeth with naturally developed white spot lesions (WSLs) were used as references. All specimens characterized by confocal Raman microscopy being used for the first time in examining white & subsurface lesions and providing a high resolution chemical and morphological map based on phosphate peak intensity alterations at 960 cm-1. Nanoindentation technique was used to measure Hardness (H) and Young's modulus (E) of enamel. Phosphate map of examined samples exhibited presence of intact surface layer (ISL) followed by severe depletion in (PO43-) peak in the area corresponding to the body of the lesion. In all examined groups, the mechanical properties of enamel were decreased in lesion area and found to be inversely related to penetration depth of indenter owing to enamel hierarchical structure. By combining the above two techniques, we linked mechanical properties of enamel to its chemical composition and ensured that the two methods are highly sensitive to detect small changes in enamel composition. Further work is required to bring these two excellent tools to clinical application to perceive carious lesions at an early stage of development.

Laboratory Studies of Nonlinear Optical Signals for Caries Detection.

Multiphoton confocal microscopy and nonlinear spectroscopy are used to investigate the caries process in dentin. Although dentin is a major calcified tissue of the teeth, its organic phase comprises type I collagen fibers. Caries drive dentin demineralization and collagen denaturation. Multiphoton microscopy is a powerful imaging technique: the biological materials are transparent to infrared frequencies and can be excited to penetration depths inaccessible to 1-photon confocal microscopy. The laser excitation greatly reduces photodamage to the sole focal region, and the signal-to-noise ratio is improved significantly. The method has been used to follow pathologic processes involving collagen fibrosis or collagen destruction based on their 2-photon excited fluorescence (2PEF) emission and second harmonic generation (SHG). Combining multiphoton imaging with nonlinear spectroscopy, we demonstrate that both 2PEF and SHG intensity of human dentin are strongly modified during the tooth caries process, and we show that the ratio between SHG and 2PEF signals is a reliable parameter to follow dental caries. The ratio of the SHG/2PEF signals measured by nonlinear optical spectroscopy provides valuable information on the caries process, specifically on the degradation of the organic matrix of dentin. The goal is to bring these nonlinear optical signals to clinical application for caries diagnosis.

Bacterial leakage in endodontics: an improved method for quantification.

A new method for studying leakage of root fillings using the bacterium Pseudomonas fluorescens ATCC 13525 is described. The presence of the microorganism is detected by fluorimetry and can thus be used to measure the depth of penetration from the root apex toward the crown of the tooth. This system, applied to a number of methods of root canal filling, showed that procedures involving compaction of the gutta-percha gave a more effective seal than the use of a paste sealer with uncondensed gutta-percha. There was no statistically significant difference between the leakage results from the lateral, vertical, and thermomechanical condensed techniques.

In vitro fluoride release from restorative materials in water versus artificial saliva medium (SAGF).

OBJECTIVES: An extensive number of investigations have focused in recent years on the process of fluoride release by glass-ionomer cements. In order to compare the fluoride release of two recent resin-modified glass-ionomer cements (RMGICs) and one compomer, we investigated the initial and subsequent fluoride release in distilled water and in a mineral medium with composition similar to saliva (SAGF), as well as the renewal effect of the media on the release. METHOD: A preliminary thermodynamic study defined conditions under which the measurements by fluoride-selective electrode potentiometry were not affected by the presence of Ca2+ ions in SAGF. Disk-shaped samples (5 mm x 3 mm) for each material were placed in 5 ml of distilled water (n = 12) or 5 ml of SAGF (n = 12) and fluoride released was measured after 1, 2 and 7 days. For the investigation of medium renewal effect, RMGIC sample were dipped into distilled water for 5 days. Subsequently 12 samples of each material were placed for 7 days into water or SAGF, with or without daily renewal of the medium before fluoride-release measurements. The elements present on the surface of the RMGICs were analyzed by scanning electron microscopy. RESULTS: RMGICs released significantly more fluoride in water than in artificial saliva. The presence of CaF2 at the interface accounts for this phenomenon. The thickness of the CaF2 layer depends on the speed of its initial formation and renewal of the testing medium. A pattern of CaF2 formation was proposed.

Use of new minimum intervention dentistry technologies in caries management.

Preservation of natural tooth structure requires early detection of the carious lesion and is associated with comprehensive patient dental care. Processes aiming to detect carious lesions in the initial stage with optimum efficiency employ a variety of technologies such as magnifying loupes, transillumination, light and laser fluorescence (QLF® and DIAGNOdent® ) and autofluorescence (Soprolife® and VistaCam®), electric current/impedance (CarieScan(®) ), tomographic imaging and image processing. Most fluorescent caries detection tools can discriminate between healthy and carious dental tissue, demonstrating different levels of sensitivity and specificity. Based on the fluorescence principle, an LED camera (Soprolife® ) was developed (Sopro-Acteon, La Ciotat, France) which combined magnification, fluorescence, picture acquisition and an innovative therapeutic concept called light-induced fluorescence evaluator for diagnosis and treatment (LIFEDT). This article is rounded off by a Soprolife® illustration about minimally or even non-invasive dental techniques, distinguishing those that preserve or reinforce the enamel and enamel-dentine structures without any preparation (MIT1- minimally invasive therapy 1) from those that require minimum preparation of the dental tissues (MIT2 - minimally invasive therapy 2) using several clinical cases as examples. MIT1 encompasses all the dental techniques aimed at disinfection, remineralizing, reversing and sealing the caries process and MIT2 involves a series of specific tools, including microburs, air abrasion devices, sonic and ultrasonic inserts and photo-activated disinfection to achieve minimal preparation of the tooth. With respect to minimally invasive treatment and prevention, the use of lasers is discussed. Furthermore, while most practices operate under a surgical model, Caries Management by Risk Assessment (CaMBRA) encourages a medical model of disease prevention and management to control the manifestation of the disease, or keep the oral environment in a state of balance between pathological and preventive factors. Early detection and diagnosis and prediction of lesion activity are of great interest and may change traditional operative procedures substantially. Fluorescence tools with high levels of magnification and observational capacity should guide clinicians towards a more preventive and minimally invasive treatment strategy.

[Evaluation of four methods of preparing curved canals]. / Evaluation de quatre modes de préparation des canaux courbes.

The authors used the protocol provided by Bramante, Berbert and Borges, to evaluate the respect of the canal position during the curved canal preparation. They compared four preparation types, two hand preparation and two engine driven ones: the step back technique, the anticurvature filing technique, the contact shaping technique, the canal finder. A statistic analysis of the results shows that the preparation is done to the detriment of the furcation wall and that only the step back technique is not suitable for the curved canal preparation.

["Endo-prosthetic" preparation of curved roots]. / Préparation "endo-prothétique" des racines courbes.

During the tooth preparation for root posts, all must be attempted to avoid weakening of the root. This "must" is rather easy for straight roots, but the same is not true of curved roots. The authors have used the method described by BRAMANTE et al. to study the effects of various techniques of instrumental sequences of endodontic preparation, and of two instrumental sequences of root post preparation. From this studies, it results that: --the respect of the canal path during the endodontic phase conditions the respect of the internal wall of the curvature, during drilling. --among the four endodontic techniques studied: MM 3000, Step-Back, Anti Curvature Filling and Canal Finder System, the last two seem to allow more respect of the canal path. --the instrumental sequence using Largo drills to prepare a canal, presents two types of drawbacks: * Excessive abrasion of the convex (internal) wall of the canal system. It seems that the blunt point rests against the concave portion of the canal and pushes the drill toward the internal wall, therefore weakening it. * Inadequate match between the size of the drill and that of the prepared canal. --the Parapost drills, on the contrary, respect the endodontic path, and may even be used beyond the curvature (2 mm). Besides, the diameter of the prepared canal is similar to that of the instrument used. These two factors permit to obtain a better retention of the post as well as a lesser weakening of the root.

Relationship between file size and stiffness of nickel titanium instruments.

The purpose of this study was to evaluate the relationship existing between file size and stiffness for 3 endodontic files made of nickel titanium. Three groups of instruments with different cross-sections were tested: a triangular cross-section, a square cross-section and a modified triangular cross-section. The instruments were tested from size 15 to size 40 or 60 according to ANSI/ADA specification no. 28 for binding moment evaluation. There was a statistically significant difference between the 3 groups: the square cross-section K files presented a larger bending moment than the triangular cross-section K files, which presented a larger bending moment than the modified cross-section K files. Like the stainless steel instruments, there was an exponential relationship between file size and bending moment for triangular and square cross-section K files, but a linear relationship between file size and bending moment for the files with a modified triangular cross-section.