Response to alkaline stress by root canal bacteria in biofilms

AIM: To determine whether bacteria isolated from infected root canals survive alkaline shifts better in biofilms than in planktonic cultures. METHODOLOGY: Clinical isolates of Enterococcus faecalis, Lactobacillus paracasei, Olsenella uli, Streptococcus anginosus, S. gordonii, S. oralis and Fusobacterium nucleatum in biofilm and planktonic cultures were stressed at pH 10.5 for 4 h, and cell viability determined using the fluorescent staining LIVE/DEAD BacLight bacterial viability kit. In addition, proteins released into extracellular culture fluids were identified by Western blotting. RESULTS: Enterococcus faecalis, L. paracasei, O. uli and S. gordonii survived in high numbers in both planktonic cultures and in biofilms after alkaline challenge. S. anginosus, S. oralis and F. nucleatum showed increased viability in biofilms compared with planktonic cultures. Alkaline exposure caused all planktonic cultures to aggregate into clusters and resulted in a greater extrusion of cellular proteins compared with cells in biofilms. Increased levels of DnaK, HPr and fructose-1,6-bisphosphate aldolase were observed in culture fluids, especially amongst streptococci. CONCLUSIONS: In general, bacteria isolated from infected roots canals resisted alkaline stress better in biofilms than in planktonic cultures, however, planktonic cells appeared to use aggregation and the extracellular transport of specific proteins as survival mechanisms.     

INFLUENCE OF THERMAL STRESS ON MARGINAL INTEGRITY OF RESTORATIVE MATERIALS

The aim of this study was to evaluate the influence of thermal stress on the marginal integrity of restorative materials with different adhesive and thermal properties. Three hundred and sixty Class V cavities were prepared in buccal and lingual surfaces of 180 bovine incisors. Cervical and incisal walls were located in dentin and enamel, respectively. Specimens were restored with resin composite (RC); glass ionomer (GI) or amalgam (AM), and randomly assigned to 18 groups (n=20) according to the material, number of cycles (500 or 1,000 cycles) and dwell time (30 s or 60 s). Dry and wet specimens served as controls Specimens were immersed in 1% basic fuchsine solution (24 h), sectioned, and microleakage was evaluated under x40 magnification. Data were analyzed by Kruskal-Wallis and Mann-Whitney tests: Thermal cycling regimens increased leakage in all AM restorations (p<0.05) and its effect on RC and GI restorations was only significant when a 60-s dwell time was used (p<0.05). Marginal integrity was more affected in AM restorations under thermal cycling stress, whereas RC and GI ionomer restoration margins were only significantly affected only under longer dwell times.     

Five-year study of Class II restorations in permanent teeth using amalgam, glass polyalkenoate (ionomer) cermet and resin-based composite materials

The aim of this study was to compare the clinical performance of an amalgam, a glass polyalkenoate (ionomer) cermet material and a resin-based composite material used in small Class II cavities in permanent teeth. All restorations were inserted under rubber dam. They were examined yearly for 3 years. One clinician continued the study up to 5 years. The clinical examination focused on two criteria: clinically acceptable and failure. In addition, impressions were taken of the prepared cavities immediately before restoration and at each clinical examination using an elastomeric material. The study comprised 274 Class II restorations (88 amalgams, 95 cermets and 91 resin composites) placed in 142 adolescent patients. One hundred and sixty-seven restorations were in molar and 107 in premolar teeth. Patient dropout after 5 years resulted in the loss of 161 restorations, evenly distributed for restorative material and type of tooth involved. Four amalgam restorations, 22 glass ionomer cermet and nine resin composite restorations failed. The glass ionomer cermet and amalgam restorations failed primarily due to bulk fractures, while the resin composite restorations failed due to secondary caries and bulk fractures.     

The effect of hygiene instruments on dentin surfaces: scanning electron microscopic observations.

The present study consists of two separate parts. The first section is an in vitro evaluation of the relative abrasiveness of some hygiene instrumentations commonly used during maintenance therapy. In the second section, one of the instruments, a recently developed plastic tip for use on a sonic scaler, was examined for its ability to remove dental plaque from root surface specimens instead for 5 weeks in the oral cavities of dogs. The in vitro study was performed on recently obtained dentin specimens where a ridge had been machined parallel to the long axis of the tooth. The sonic scaler fitted with the plastic tip gave considerably less removal of dentin and a smoother dentin surface than the curet, the rubber cup with polishing paste, or the sonic scaler with an ordinary metal tip. These findings further demonstrated that the plastic tip was able to efficiently remove 5-week old dental plaque from experimental root surface areas within a time frame of 5 seconds. The new plastic tip may be valuable in maintenance therapy giving less risks for iatrogenic effects on the root surfaces than other debridement methods.     

Results with multi-band appliances in the treatment of class II]

Corrections of Angle's Class II malocclusions constitute nearly 1/4 of the treatments performed by the orthodontist. The author studied the results achieved with treatment methods applicable to these malocclusions and compared them with those obtained by means of multiband appliances. On the basis of 2,110 cases, he establishes the indications for the use of multiband appliances in the framework of social dental treatment.     

Results of a 3-year oral hygiene programme, including amine fluoride products, in patients treated with fixed orthodontic appliances

This paper reports the results of a 3-year study on children treated with fixed orthodontic appliances. They were all regularly instructed in oral hygiene maintenance and used a standardized fluoride-free toothpaste during the course of the study. The patients were divided into three groups. Groups one and two, respectively, had a fluoride gel and fluoride fluid (Elmex amine fluoride products, GABA International Ltd, Basle, Switzerland) applied. Group three used only the toothpaste supplied, had oral hygiene instruction, but not topical applications. Caries increments were lowest and gingival health best in the two groups using amine fluorides, especially the gel group.     

Development of a novel digital subtraction technique for detecting subtle changes in jawbone density

The objective of this paper is to develop a novel digital subtraction technique for serial intra-oral radiography, which would allow the detection of subtle variations in grey values. Digital images of the maxilla of a dried human skull and of a fresh pig mandible were acquired using intra-oral photostimulable phosphor plates (Digora FMX, Soredex, Helsinki) with an aluminium calibration stepwedge incorporated in the filmholder. Exposures were made with an X-ray tube for intra-oral radiography (Prostyle Intra, Planmeca, Helsinki). During pilot testing, parameter settings were adapted to reach an optimal contrast. Exposures were repeated within a 1-week interval to determine the test-retest reliability of the development. After in vitro and in vivo testing, the exposure technique and software development were used to evaluate its applicability in a pilot clinical case. Although parameter settings remained stable during the in vitro studies, the clinical exposures yielded non-linear digital images, thus, not readily suitable for data acquisition and comparison of the regions of interest. To allow further analysis, image processing was carried out using self-developed software for semi-automated linearisation and optimised contrast normalisation. This processing significantly increased the precise quantisation of jawbone density and the assessment of subtle bone density changes in arbitrarily selected regions of interest of in vivo exposures. The clinical applicability of the technique is demonstrated in a pilot case. It was demonstrated that minute densitometric deviations could be detected. The present technique and image processing may allow the quantification of jawbone density.     

A new checkerboard panel for testing bacterial markers in periodontal disease

BACKGROUND/AIMS: Various microbiological methods have been used for testing bacterial markers for periodontitis and periodontal disease progression. Most studies have used only a limited number of well recognized bacterial species. The purpose of the present study was to evaluate the association of 13 more recently identified bacterial species in a new panel in comparison with 12 previously more recognized periodontotopathogens ('old panel') using the 'checkerboard' DNA-DNA hybridization method. METHODS: Fifty individuals were chosen who showed at least one site with a probing pocket depth of 6 mm or more (disease) and bleeding on probing and at least one site with a probing pocket depth of 3 mm and without bleeding on probing (health). One diseased and one healthy site on each individual were sampled with the paperpoint technique and the samples were processed in the checkerboard technique against deoxigenin-labeled whole genomic probes to 25 subgingival species representing 12 well recognized and 13 newly identified periodontitis associated species. RESULTS: Twenty-four (out of 25) species were detected more frequently in the subgingival plaque of diseased than healthy sites both at score 1 (> 10(4)) and score 3 (> 10(5)). A significant difference at the higher score (score 3) was noticed for all species of the old panel except for three (Streptococcus intermedius, Selenomonas noxia, and Eikenella corrodens). Of the species in the new panel only Prevotella tannerae, Filifactor alocis, and Porphyromonas endodontalis showed a statistical significant difference between diseased and healthy sites. CONCLUSION: It was concluded that P. tannerae, F. alocis, and P. endodontalis should be added to the 12 species used for routine diagnostics of periodontitis-associated bacterial flora.     

Immunolocalization of a human cementoblastoma-conditioned medium-derived protein

Little is known about the molecular mechanisms that regulate the cementogenesis process, because specific cementum markers are not yet available. To investigate whether a cementoblastoma-conditioned medium-derived protein (CP) could be useful as a cementum biological marker, we studied its expression and distribution in human periodontal tissues, human periodontal ligament, alveolar bone, and cementoblastoma-derived cells. In human periodontal tissues, immunoreactivity to anti-CP was observed throughout the cementoid phase of acellular and cellular cementum, cementoblasts, cementocytes, cells located in the endosteal spaces of human alveolar bone, and in cells in the periodontal ligament located near the blood vessels. Immunopurified CP promoted cell attachment on human periodontal ligament, alveolar bone-derived cells, and gingival fibroblasts. A monoclonal antibody against bovine cementum attachment protein (CAP) cross-reacted with CP. These findings indicate that CP identifies potential cementoblast progenitor cells, is immunologically related to CAP species, and serves as a biological marker for cementum.     

Gram-positive rods prevailing in teeth with apical periodontitis undergoing root canal treatment

AIMS: To identify Gram-positive rods from root canals of teeth with apical periodontitis and to examine their associations with other species. METHODOLOGY: Consecutive root canal samples (RCSs) from 139 teeth undergoing root canal treatment were analyzed prospectively for cultivable microbes. Gram-positive rods in the first RCS submitted after chemo-mechanical preparation were categorised to genus level by selective media and gas-liquid chromatography (GLC), and identified to species level by sodium dodecyl sulphate-polyacrylamide gel electrophoresis (SDS-PAGE). Associations between organisms were measured by odds ratios (OR). RESULTS: In the first samples submitted a total of 158 Gram-positive rods, 115 Gram-positive cocci, 26 Gram-negative rods and 9 Gram-negative cocci, were identified. At genus levels Gram-positive rods were classified into: Lactobacillus spp. (38%), Olsenella spp. (18%), Propionibacterium spp. (13%), Actinomyces spp. (12%), Bifidobacterium spp. (13%) and Eubacterium spp. (6%). The most frequent species were Olsenella uli, Lactobacillus paracasei and Propionibacterium propionicum. In subsequent samples taken during treatment, Gram-positive rods were also identified, although the number of strains was considerably reduced. Positive associations were observed between members of the genus lactobacilli and Gram-positive cocci (OR>2). CONCLUSIONS: Olsenella uli and Lactobacillus spp. predominated over other Gram-positive rods. A possible association exists between Lactobacillus spp. and Gram-positive cocci in root canals of teeth with apical periodontitis receiving treatment.