[Resistance to B-lactamines of bacteria responsible for endodontic root canal infections]. / Résistance aux beta-lactamines des bactéries responsables des infections canalaires endodontiques.

Samples were taken under strictly anaerobic conditions from the root canals of 22 patients having a tooth in which necrotic pulp was associated with an inflammatory peri-apical lesion an optical periodontitis. In the majority of cases (85%), these lesions were chronic and the pulp chamber was closed. One hundred and two strains were isolated, 71.7% of the bacteria being obligate anaerobes and 49.8% being Gram-negative bacilli. Their ability to produce beta-lactamases was tested and 8.8% gave a positive reaction in a cefinase test. These cefinase positive strains were nevertheless susceptible to 3rd-generation cephalosporins (cefoxitin) and to amoxicillin-clavulanate, with the exception of M. Morganii.

Root canal shaping using rotary nickel-titanium files in preclinical teaching.

AIMS: This study set out to evaluate the prevalence of iatrogenic events during preclinical teaching of endodontics, comparing manual stainless steel versus nickel-titanium (Ni-Ti) rotary techniques for shaping natural root canals. METHOD: Two groups of 13 inexperienced dental students were randomly made up and asked to shape 104 canals in natural teeth. Group R used Ni-Ti rotary files for shaping while Group M used a sequence of five manual stainless steel files. Occurrence of file breakage, loss of work length, and iatrogenic instrumentation on apical foramina were evaluated. RESULTS: Overall occurrence of adverse events during shaping did not differ between the groups, being 58% in Group R and 51% in Group M. Inter-group distribution of type of event differed significantly, however. File breakage (7.7%) and loss of working length of > 2 mm (6.7%) occurred only in Group R. Iatrogenic shaping on apical foramina showed the same frequency in each group. CONCLUSION: Manual instrumentation is safer than rotary instrumentation in the hands of inexperienced students. Acquiring skill in the use of Ni-Ti rotary instrumentation requires specific preclinical training to avert file breakage. These findings argue for the rethinking of theoretical and practical coursework in endodontics teaching, especially in dentistry schools where students are required to treat patients during their training.

Determination of the bactericidal activity of different calcium hydroxide presentations on a dentin model.

Calcium hydroxide placed as a temporary dressing in the root canal helps sterilize infected canals. Hycal and Roeko calcium hydroxide points are two delayed-action medications containing Ca(OH)2 recommended for root canal treatment. The purpose of this study was to test their bactericidal activity in comparison with that of C-PMCP on Streptococcus sanguins strain NCTC 7823. Artificially infected 4-mm high blocks of dentin obtained from bovine incisors were used as an experimental model (n = 192). After three days of treatment with the two antiseptics, intracanal dentin powder was collected by serial drillings and used to inoculate a culture broth. The turbidity of this broth after 24 hours showed if the bacteria were eliminated or not and was used as criterion of antiseptic efficacy. No bacterial growth was observed in the samples treated with C-PMCP. Hycal had a considerable bactericidal activity with 94% of negative cultures whereas first-generation Roeko points had no activity on the strain of S. sanguis tested.

[Diffusion of hydroxyl ions from calcium hydroxide in the dentinal tubules]. / Etude de la diffusion des ions OH- de l'hydroxyde de calcium dans les tubuli dentinaires.

The aim of this study was to compare hydroxyl ions diffusion from various calcium hydroxide forms: Hycal (1), Roeko points (2) and aqueous suspension placed in the pulpar chamber (3) or in the root canal (4). These experiments were conducted with bovine incisors in order to obtain quantitative evaluation. 540 lateral cavities, deep and superficial, were created in root dentin to measure the hydroxyl ions diffusion with a color indicator, the Blue epsilon With Hycal and aqueous suspension the diffusion of the OH- is obtained in the superficial cavities situated in the coronal part at 14 days (1 = 72%; 3 = 44%; 4 = 100%, (n=18)). In the apical part of the canal this phenomenon is never complete at 21 days (1 = 17%; 3 = 22%; 4 = 17%, (n=18)). No diffusion was observed with the Roeko points (the first generation).

[Dental consultations at a university hospital in Toulouse: the role for conservative treatments in oral health]. / Consultations dentaires au CHU de Toulouse: place des soins conservateurs.

A retrospective study was carried out looking at the files of 481 patients who were seen for their first consultation at a university hospital dental school clinic. Their needs for conservative treatment were evaluated and the data from their files were analysed, including the following elements: demography, general health status, the expressed reason for the consultation, and the initially planned treatment. The descriptive analysis reveals a relatively young population group with an average age of 43.8 years, for whom 32% of them had existing or past medical conditions which necessitated that certain precautions be taken when prescribing conservative treatment. The most frequently given reasons for the consultation were the need for an annual dental check-up (41%) and pain (20%). 74% of the patients were in need of conservative treatments, and a priority for an initial treatment was cited for 48.4% of them.

[Composite-bonded bridges reinforced with Ribbond THM ribbon: an alternative of choice to other temporary prosthetic methods]. / Les bridges collés en composite renforcés avec l'attelle Ribbond THM: une alternative de choix aux autres moyens transitoires prothétiques.

In the presence of anterior unitary tooth loss, the therapeutical arsenal of the practitioner remains the implant solution. But, at the young patients who have not completed their growth, it's necessary to pass by a transitional stage. The bonded bridges reinforced by a polyethylene fibbers splint such as Ribbond THM constitute an alternative of choice to solve the aesthetic damage in the short and medium term while waiting for the prosthesis with implant. It's a similar case that is reported through this article.

[Computer-assisted preoperative planning of knee replacement arthroplasty]. / Planification préopératoire assistée par ordinateur pour la pose des prothèses totales de genou.

UNLABELLED: The general configuration of replaced knee is difficult to anticipate because of the large number of geometrical parameters related to morphology, prosthetic implants and pre-operative choices (such as ligament release). This article features the studies achieved in order to create a decision aiding computer tool dedicated to total knee prosthesis. METHOD AND MODEL: We have built a geometrical modelling of the physiological knee and prosthesis elements association. A numerical processing through biomechanical laws permitted to simulate the geometrical and mechanical behaviour of the whole for different flexing angle. RESULTS: A first validation of the model, comparing the numerical simulation results and the measuring of the 30 implanted knee X-rays, showed a valid matching (86 p.cent of the total cases) between model and real configuration. DISCUSSION: This tool allows to realise simulations and optimizations with regard to the following issues: decreased risks of the unsealing of the patellar component through contact centering with the trochlea, increased mechanical efficiency of the force transmission from the quadriceps to the tibia, increased maximum flexing angle considering the extension of the quadriceps. CONCLUSION: The orthopedic surgeon should be greatly assisted in the future preoperative planning by these initial findings.

Disinfection of the Optical Fibre of a Nd-YAP Laser Used in Dental Care.

In order to set up a disinfection protocol, the tip of the optical fibre of an Nd-YAP laser, λ=1.34 µm, was contaminated in vitro with: Mycobacterium smegmatis (CIP 7326), Candida albicans (ATCC 2091), Bacillus stearothermophilus (ATCC 7953) or Streptococcus sanguis (ATCC 10556). It was then treated with various biocidal solutions, Septinol(®) V, glutaraldehyde 2%, ethanol 95° and NaOCl 6%, using one of two protocols: 10 s of contact, or 5 s of contact followed by 5 s of wiping. The latter technique proved to be the most effective. Whatever the biocidal solution used, all the bacteria adhering to the fibre were eliminated. The protocol was checked in vivo in the canals of 10 teeth presenting root canal infections. No bacteria withstood the treatment with Septinol(®) V. This treatment does not alter the qualities and performance of the fibre as far as light transmission is concerned.

In vitro adhesion of two strains of Prevotella nigrescens to the dentin of the root canal: the part played by different irrigation solutions.

Blocks of bovine incisor dentin, on the root canal surface of which a smear layer had been formed, were inoculated in vitro with two strains of Prevotella nigrescens, a wild sampled strain and a reference one (NCTC 9336). Half the blocks were pretreated with irrigating solutions: 6% citric acid for 5 min + 6.25% sodium hypochlorite for 10 min. They were compared with the other blocks simply rinsed in distilled water (i.e. the control samples). The bacteria adhering to the dentin surface after an incubation time of 3 h were counted by direct examination using a scanning electron microscope. The adhesion of P. nigrescens was less marked on all of the samples treated with irrigating solutions. Adherence was particularly significant in the case of the wild strain (F = 10.22). The latter was far more active than the reference strain (F = 35.82). The use of a chelating agent at the end of root canal preparation served to remove the smear layer and limited the attachment of P. nigrescens to the dentin.

Evaluation of the Bactericidal Activity on Oral Organisms of the Nd-YAP Laser In Vitro.

The bactericidal activity of a pulsed fibre-optic Nd-YAP laser on various strains of oral bacteria: Prevotella nigrescens, Streptococcus sanguis, Actinomyces viscosus (i), Fusobacterium nucleatum, Actinobacillus actinomycetemcomitans and Peptostreptococcus micros (i) was evaluated. A 200-µm optical fibre was placed in Eppendorf tubes containing the different bacterial suspensions. At an energy of 170 mJ/30 Hz, 351 pulses of 150 µs were sufficient to kill the most resistant bacteria (i). The exposure time was 28 s. The temperature rise caused by the shots were measured in vitro at the surface of the roots of two groups of 10 single-rooted teeth. One group received 350 pulses; for the other the preparation time was fixed at 28 s. The temperature rose by 25.66°C for the first group and 25.25°C for the second.

Effect of dentin treatment on in vitro root tubule bacterial invasion.

In light of the in vitro S. sanguis bacterial migration observed deep into root dentin, an in vitro system was developed to determine the viability of these bacteria at the end of migration. Also of interest is whether the smear layer formed during root canal instrumentation modifies migration into root dentinal tubules. Forty-eight bovine root dentin samples were randomly split into two groups. Group 1 dentin blocks were not instrumented and were treated with 17% ethylenediamine tetraacetic acid and 2.5% sodium hypochlorite for 4 minutes in an ultrasonic bath Group 2 root canals were conventionally instrumented. The smear layer formed was not removed. Dentin blocks were inoculated with a S. sanguis National Collection of Type Culture 7863 suspension. Each sample was immersed in a receiver broth, incubated at 37 degrees C, and checked daily for 14 days. After a 14-day incubation period, group 1 S. sanguis cells remained viable and capable of inoculating the receiver medium after migration through the tubules. Group 2 cells, where the smear layer was intact, revealed an absence of S. sanguis migration in 88% of the cases. It is therefore plausible that smear layer on canal walls limits S. sanguis penetration of dentinal tubules in vitro.

In vitro attachment of Streptococcus sanguis to the dentin of the root canal.

The adhesion of a strain of Streptococcus sanguis (NCTC 7863) to the root canal dentin of bovine incisors was evaluated. Samples (104) were prepared and smear layer was created on the root canal surface with a tungsten carbide bur. The samples were divided into four groups, one of them serving as a control sample and the other three each receiving a different treatment: 6% citric acid for 2 min (group 3), 6% citric acid for 2 min + 6.25% sodium hypochlorite for 1 min (group 2), 6% citric acid for 10 min (group 4). After sterilization, they were incubated, and adhesion was assessed by direct examination using a scanning electron microscope. The use of irrigation solutions significantly reduced the adhesion in the latter two groups only, with a reduction of 15% (group 2) and 18.7% (group 4) in the number of bacteria.

[Incidence and elimination of parietal smear layer in endodontics]. / Incidence et élimination de l'enduit pariétal en endodontie.

During canal preparation, the repeated passage of instruments provokes the formation of smear on the surface of the dentin. It is advisable to eliminate that, so as to increase antisepsis and filling impermeability. This is obtained by means of an irrigation, using a chelate compound of 6% citric acid for 60 seconds, at the end of the preparation.

In vitro study of the penetration of three bacterial strains into root dentine.

The purpose of this study was to assess in vitro migration of the following three bacterial species into dentinal tubules: Streptococcus sanguis, Actinomyces naeslundii and Prevotella intermedia. Twenty-seven bovine incisors were randomly divided into three groups. Only the root dentin was used for the experiment. Within each group, the nine incisors were sectioned into 36 dentin blocks that were incubated with one of the tested bacterial suspensions. Twelve samples were taken after 10, 20, and 28 days. Half the samples were observed with scanning electron microscopy and the others with light microscopy after standard histologic procedures, and the depth of bacterial penetration was measured. Analysis of the examinations showed that whatever the technique used, only one strain on this experimental model migrated into dentinal tubules. S. sanguis was observed at a depth of 792 microns, but no migration was observed for either A.naeslundii or P.intermedia. The differences in migration of the bacteria tested appear to be related to their morphologic factors and cellular arrangement.

Migration of a Streptococcus sanguis strain through the root dentinal tubules.

The persistent presence of bacteria in the root canal system often leads to the failure of treatment. The aim of this study was to study the in vitro penetration of root dentinal tubules by bacteria. Bovine dentin was inoculated with a strain of Streptococcus sanguis, NCTC 7863; samples were taken at 10, 20, and 28 days, and bacterial penetration of the tubules was demonstrated using two techniques, scanning electron microscopy and light microscopy after Brown and Brenn staining. The results showed that S. sanguis can penetrate deep inside the tubules (792 microns). The maturity of the dentin blocks seems to be a major factor in tubule penetration.

Apical root canal anatomy in the dog.

240 permanent teeth from 8 different dogs aged 1, 3, 8, 10, 15 years, were used for an anatomic study. The teeth were cleaned, their root canal system was stained with dye, then the teeth were decalcified and cleared to determine the root canal anatomy. The apical root canal anatomy in dogs can be described as a "sprinkler-rose" anatomy: at the tip of the pulpal canal, the canal is divided in numerous narrow channels radiating peripherally through the dentin and the cementum and ending in numerous apical foramina on the cementum surface. This architecture constitutes a very complex apical delta.

[Interpretation of S.E.M. images using a treatment system and image analysis: preliminary study]. / Interprétation des images de M.E.B. à l'aide d'un système de traitement et d'analyse d'images: étude préliminaire.

The scanning electron microscope has multiple applications in the research of endodontics, but there are not standard methods for the evaluation of the results. The use of the computerized processing and analysing systems for the images reduces the sources of error due to the subjectivity of the operator. This first part, after the introduction of the principles of processing and analysis, puts in view two methods of computerized analysis used in the study of the films of dentinal walls in the scanning electron microscope.

[The use of ultrasonic files in canal preparation]. / Empleo de las limas ultrasónicas en la preparación de conductos.

The continuous high volume of irrigating solution delivered by the ultrasonic system facilitates the root canal debridement. An excellent cleaning of dentin wall is obtained even on surfaces unreached by the mechanical instrumentation. In order to obtain an efficacious preparation, the use of ultrasonic files were combined with instrumentation. This new technique is described in this article.