Sci-Sat AM: Brachy - 10: Adaptation of the CVT algorithm for catheter optimization in high dose rate brachytherapy.

INTRODUCTION: In interstitial high dose rate (HDR) brachytherapy, the number and positions of the catheter are usually fixed by the use of a template, without considering tumor size and shape. In this work, we present a simple and fast method to optimize both the number and position of catheters, using a modified version of the Centroidal Voronoi Tessellations (CVT) algorithm. METHODS: 8 prostate HDR clinical cases were chosen randomly to test our method. The treatment plan was obtained from a research version of IPSA. Clinically relevant dosimetric parameters were computed to evaluate our method and help optimizing the CVT algorithm parameters. Plans were generated with a specified number of catheters ranging from 9 to 18 and compared to the clinical cases with 17 catheters. RESULTS: The computation time to optimize the positions of a specific number of catheters was 1.5 s. The prostate V100 was better than the clinical case up to 12 catheters. Plans with 9 or less catheters would not be clinically acceptable in terms of prostate V100 and D90. High conformity is achieved whether the number of catheters used. The V75 of the bladder seems slightly higher, but not significant clinically. All other dosimetric indices are as good as the clinical plan. CONCLUSION: We have devised a simple, fast and efficient method to optimize the number and position of catheters in HDR brachytherapy. Ultimately, this catheter optimization algorithm could be coupled with a 3D ultrasound system to allow real-time guidance and planning for any interstitial brachytherapy sites.

In vitro streptococcal adherence on prosthetic and implant materials. Interactions with physicochemical surface properties.

The aim of this study was to evaluate streptococcal adherence to eight currently used prosthetic and implant materials, and enamel samples, after a salivary coating and to investigate the influence of substrata surface free energy (SFE) and its polar and non-polar components, as well as bacterial surface characteristics, on bacterial adherence. Our results indicate a moderate hydrophobic character of saliva-coated surfaces and a pronounced basic character of the polar component of SFE values, except for one substrata. The lowest colonization was observed with enamel samples and the lowest values of adherent bacteria on the different substrata were observed with the hydrophilic bacterial strain. Both the nature of the substrata and the nature of the bacterial strains could have an effect on the extent of bacterial adhesion. When the interrelationship between the number of adherent bacteria and the surface properties of bacteria and substrata were analysed, bacterial adherence correlated with the non-polar component of substrata SFE (r = 0.8, P = 0.02) and with the adhesion to the solvents (r = 0.8, P < 0.0001). These results are consistent with the thermodynamic theory and underline the importance of acid-base characteristics of the cell surface when one is studying bacterial adherence on dental casting alloys and implant materials.

Clinical usefulness of microbiological diagnostic tools in the management of periodontal disease.

Periodontal diseases comprises a group of chronic inflammatory conditions affecting tooth supporting structures. It has been known for a long time that pathogenic oral bacteria colonizing the tooth surface are associated with the initiation of the disease process. However, to date, a dozen or so bacterial species have been implicated in the pathogenesis of periodontal disease and no one species by itself is synonymous with disease onset. This multibacterial etiology renders the diagnosis of active periodontal disease based on microbiological data difficult. Numerous studies have attempted to relate the usefulness of microbiological diagnostic aids such as microscopy, bacterial culture, immunological and enzymatic assays. Furthermore, recent technical advances have resulted in the use of nucleic acid probes and amplification techniques for the identification of genetic material belonging to potential periodontal pathogens. Despite the availability of a large number of microbiological testing protocols, identification of the microbial etiological agents remains hampered by the complexity of the microbial challenge during periodontal disease. This review discusses the clinical usefulness of these tests in detection and management of periodontal disease.

Effect of hydrophobicity on in vitro streptococcal adhesion to dental alloys.

Non-specific interactions such as electrostatic interactions, and surface free energy are of importance in bacterial adhesion to dental surfaces as they determine whether or not bacteria are attracted to the surface. The relationship between adherence of Streptococcus mitis, S. mutans, S. oralis and S. sanguinis on precious and non-precious dental alloys, and the bacterial and alloy surface hydrophobicities (a measure of the surface free energy) was studied. The number of adhering bacteria was determined by fluorescence microscopy counts. The hydrophobicity of the bacteria and alloy surfaces were evaluated by adhesion to hexadecane and water contact angles, respectively. Our results showed that (i) the surfaces of the tested alloys were hydrophobic, (ii) S. sanguinis, S. mutans and S. oralis were hydrophobic, and (iii) S. mitis was hydrophilic. S. oralis, the more hydrophobic strain, demonstrated the highest adherence on the tested materials, whereas S. mitis adhered least on the hydrophobic surfaces. For the tested alloys, bacterial adherence was highest for the high gold content alloy, and lowest for the non-precious alloy. Our results showed that for the tested bacterial strains, there was a significant correlation between bacterial adhesion and substratum hydrophobicity: hydrophobic metal surfaces favor adhesion of hydrophobic bacteria.

Automatic enumeration of adherent streptococci or actinomyces on dental alloy by fluorescence image analysis.

The aim of the present study was to develop an automated image analysis method to quantify adherence of Streptococcus sanguinis or Actinomyces viscosus on surfaces of a currently used dental alloy. Counting such bacterial strains was difficult because of their arrangement, thus S. sanguinis being a coccus arranged in chains or pairs, and A. viscosus a long complexly arranged polymorph rod. Direct counting of fluorescently stained adherent bacteria was done visually and with image analysis methods. To differentiate these two morphotypes, two programs were developed: (i) for streptococci, thresholding and selection of the object maxima, and (ii) for actinomyces, two step thresholding and processing of the characteristic points of the object skeletons. The triplicate enumerations for each bacterial strain were not significantly different (p > 0.005) and correlations between visual counting and automated counting were significant (r = 0.91 for S. sanguinis and r = 0.99 for A. viscosus, p <00.0001). These rapid and reproducible methods, allowed us to count either cocci or rods, adherent on an inert substratum, in high density conditions.

Interactions between non-immune host cells and the immune system during periodontal disease: role of the gingival keratinocyte.

Periodontal disease and inflammatory dermatoses, such as psoriasis, are characterized by the accumulation of dense inflammatory infiltrates immediately beneath the epithelial cell layer of the gingiva and skin, respectively. Dermatologists are increasingly aware that the epidermal keratinocyte probably contributes to inflammatory disease progression by secreting a number of pro-inflammatory cytokines and expressing various adhesion molecules. In psoriatic lesions, it is now believed that epidermal keratinocytes may also act as antigen-presenting cells and participate directly in the superantigenic activation of T-cell clones, some of which may initiate, contribute to, or maintain the disease process. Although the role of the host response in periodontal disease has been extensively studied over the years, very little is known about the contribution of the gingival keratinocyte to the inflammatory response. The available published information is discussed in this review, and we suggest that, like its epidermal counterpart, the gingival keratinocyte may participate actively in the pathogenesis of periodontal disease.

Antimicrobial activity of amalgams, alloys and their elements and phases.

OBJECTIVES: This in vitro study aimed to evaluate the antibacterial effect of amalgams, alloys, elements and phases against two cariogenic bacteria, Actinomyces viscosus and Streptococcus mutans. METHODS: Test materials comprised: (i) commercial amalgams comprising Amalcap (Vivadent), Cavex Avalloy LC and DP (Cavex), Cupromuc (Merz), Fluoralloy and Synalloy (Dentoria); (ii) Ag-Cu alloy; (iii) gamma, gamma 1, gamma 2 and Cu6Sn5 phases; (iv) pure metal samples and chloride solutions of copper, mercury, tin and zinc; and (v) aqueous sodium fluoride. Bacterial suspensions of each of the two bacteria were grown in the presence of the test materials for 24 h. Antimicrobial effectiveness was assessed by measuring reduction in optical density at 640 nm using a visible spectrophotometer. RESULTS: Cupromuc/Fluoralloy, non gamma 2 amalgams and Amalcap displayed high, moderate and no antibacterial activity, respectively. Antibacterial effectiveness was not related to copper content. Whereas mercury, copper, Ag-Cu alloy, fluoride and zinc showed antibacterial activity (Hg > Cu > F > Zn), tin, gamma phases and Cu6Sn5 showed no such activity. SIGNIFICANCE: Although the fluoride and copper solutions were most effective at 50 micrograms ml-1 concentration, their antibacterial action was still significant, albeit reduced, at 10 micrograms ml-1 concentration. This was not the case for mercury chloride which was just as effective at both concentrations. Our results show that although mercury and copper contribute significantly to the antibacterial properties of amalgams, a high copper content does not necessarily relate to high antibacterial effectiveness. These elements could be useful in conferring antibacterial properties to amalgam although their effects on host cells must be investigated.

In vitro evaluation of the antibacterial effects of intracanal micro plasma system treatment.

Forty freshly extracted single-rooted teeth were prepared to a size 25 master apical file, autoclaved, and inoculated with a known quantity of Actinomyces naeslundii. The teeth were divided into four groups (n = 10), including an untreated control group. The three treatment groups were exposed to Micro Plasma System (MPS), 0.5% NaOCl and 0.5% NaOCl + MPS respectively. The content of each root canal was absorbed by sterile paper points, diluted in 2 ml Schaedler Broth Medium, and incubated on blood agar. The number of CFU was determined. Data analysis, using an analysis of variance and Scheffe's test at the 1% level (Statview II software), indicated a significant reduction in CFU count for the three treatment groups compared to the control group. For the three treatment groups, no significant intergroup differences were observed.

Antibacterial action of dental cements: an in vitro study.

The antibacterial activity of seven commercially available dental cements (Eugespad, Dentical, Dycal, Expaliner, PR. Scell, PR. Base Cement, PR. Lining Cement) against 1) bacterial species implicated in carious lesions or in dental plaque (Actinomyces israelii ATCC 10048, Actinomyces viscosus ATCC 19246, Streptococcus mutans ATCC 25175, Streptococcus sanguis ATCC 10557) and 2) bacterial samples of stimulated saliva was studied, in vitro, using a modification of the method of McComb and Ericson (1987). Dycal and Expaliner did not affect bacteria whereas the other dental cements displayed some antibacterial properties. Eugespad was the most active followed by PR. Base Cement + PR. Scell + Dentical and by PR. Lining Cement. Associated with mechanical and biocompatibility properties, these differences could be taken into account when choosing a dental cement for clinical use.

[The measurement of the tooth-restoration material gap: the value of SEM]. / Mesure du hiatus dent-matériau de restauration: intérêt du MEB.

The purpose of this article was to describe a method of measuring the interface between cavity walls and restorative materials and to evaluate it by comparing the interface of amalgam, composite restorations and cavity walls. With the different restorative materials the interface could be measured. Its value was dependent of the type of restoration. This methodology is available for all restorative biomaterials. It could be of interest in clinical evaluation of restorative materials.

rRNA gene restriction patterns as possible taxonomic tools for the genus actinomyces.

Species delineation in the genus Actinomyces remains unclear, particularly regarding the two taxa, A. naeslundii and A. viscosus. The ribotyping patterns of 64 strains of Actinomyces, representing 8 species and comprising different serotypes, were studied as possible taxonomic tools, using an acetyl-aminofluorene (AAF)-labelled E. coli 16S + 23S rRNA probe. Similarities between patterns were assessed using Jaccard's coefficient and clustering achieved using the unweighted pair-group method with average linkage (UPGMA) on a Macintosh II (Apple, Cupertino, USA) computer. The dendrogram obtained from the ribotypes gave results which were in reasonable agreement with many previous reports: A. bovis, A. gerensceriae, A. israelii, A. meyerii, A. odontolyticus and A. pyogenes were found to be distinct species but the two taxa A. naeslundii and A. viscosus remained unclear. Further investigations, using a larger number of A. naeslundii and A. viscosus strains and other endonucleases, need to be carried out to provide more information concerning the relatedness of these two taxa. Nevertheless, these preliminary results suggested that the Actinomyces chromosome contains multiple rRNA operons which may be used as an epidemiological and taxonomical tool.

An investigation into the use of restriction endonuclease analysis for the study of transmission of Actinomyces.

DNA fingerprints of 28 reference strains of Actinomyces, comprising representatives of different species and serotypes, and 19 isolates recovered from 16 periodontal patients was performed. The aim was to determine the potential of the method for detecting strain differences in terms of discriminatory power and to evaluate its usefulness in the typing of Actinomyces strains for eco-epidemiological studies. Among the 17 restriction endonucleases tested, Bst EII, Pvu II and Sma I proved to be the most suitable for the genus Actinomyces restriction digest analysis. Visual comparisons of Bst EII, Pvu II and Sma I digest patterns of chromosomal DNA revealed clear differences within species but also within serotypes of Actinomyces that are otherwise identical. The method offers the qualities for use as an epidemiological tool for identifying sources and tracing routes of transmission of Actinomyces: stability, reproducibility, ease of preparation and interpretation and enough sensitivity for detection of differences between morphologically and serologically similar strains of Actinomyces.

[Evaluation of an immediate cleaning and decontamination device]. / Evaluation d'un appareillage de nettoyage et de décontamination extemporanés.

A new technical approach for immediate cleansing and decontamination was studied. Control of cleansing was observed using macroscopic and microscopic (S.E.M.) examinations on different instruments currently used in dentistry. Antiseptic solution was tested regarding four bacterial strains representative of the normal oral flora. The synergistic action of the combined solution plus pressure was effective for removal of debris before they dry. Antiseptic solution was bacteriostatic and at concentration level recommended by the manufacturer, viable colonies were not detected.

[Secretary IgA and the oral cavity: general review]. / IgA sécrétoire et cavité buccale: revue générale.

The authors present a synthesis of the knowledge concerning the nature and origin of secretory IGA as well as its main components (J chain and secretory component) in the oral cavity. This IgA is the main mediator of humoral immunity and is the most frequently identified immunoglobulin in saliva. Its role in the protection of mucosae as well as in the anti-caries immunity is presented.

Antibacterial properties of five dental amalgams: an in vitro study.

The antibacterial activity of five commercially available amalgams (Cupromuc, Dispersalloy, Fluoralloy, Predalloy, and Synalloy) against two bacterial species frequently isolated from dental plaque and caries (Actinomyces viscosus and Streptococcus mutans) was studied by use of a modification of the method of Orstavik (1985). All amalgams displayed some antibacterial properties. This antibacterial activity was amalgam- and bacteria-dependent. Cupromuc and Fluoralloy were the most active, and the non-gamma 2 amalgams showed intermediate activity. Combined with mechanical and biological properties, these differences should be taken into account when one is choosing an amalgam for clinical use.

[Initial colonization of composite resins by Streptococcus mutans: the influence of polishing]. / Colonisation initiale de résines composites par Streptococcus mutans: influence du polissage.

The purpose of the present investigation was to compare the in vitro initial colonization of Streptococcus mutans on three composite materials (HERCULITE, FILLISPAD and SILIFILL) regarding the polishing procedure (SOFT-LEX, 3M). Surface roughness and bacterial deposit were analyzed by SEM and the deposit was estimated using a modified method of SKJORLAND. Results indicated that surface roughness was reduced by the polishing procedure, but this roughness was more important at the periphery of restorations. Bacterial deposit was strongly reduced on the polished materials but bacteria not adhered in the same number on the composites with a comparable surface roughness: the accumulation of bacteria was less important on FILLISPAD materials. It is concluded that the initial colonization of resin composites was not only dependent of surface roughness.