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.     

Alkali‐resistant bacteria in root canal systems

The aim of this study was to isolate and identify alkali‐resistant bacteria from the dentin of infected root canals. Bacteria from homogenized dentin powder made up from infected root canal walls from human teeth were cultured on buffer‐enriched Brain Heart Infusion agar supplemented with 4% sheep blood (BHI‐blood agar), adjusted to pH 7.0, 9.0 or 10.0. Incubation took place for 7 days at 37°C in an anaerobic glove box. Bacterial strains selected according to colony and morphology were subcultured in buffer‐enriched BHI broth adjusted to pH 9.0, 10.0 or 11.0 to confirm their growth as alkali‐resistant bacteria. Polymerase chain reaction amplification using specific primer sets and 16S rDNA sequence analysis was performed for identification of alkali‐resistant isolates. In the present study, 37 teeth extracted from 37 patients were used for preparation of the dentin powder samples. Bacteria were detected in 25 samples when standard BHI‐blood agars (pH 7.0) were used. Of these, 29 strains from 15 samples were alkali resistant, 25 strains growing at pH 9.0 and 4 at pH 10.0. The alkali‐resistant strains included Enterococcus faecium (10 strains) and Enterococcus faecalis (2 strains), Enterobacter cancerogenus (1 strains), Fusobacterium nucleatum (1 strains), Klebsiella ornithinolytica (2 strains), Lactobacillus rhamnosus (2 strains), Streptococcus anginosus (2 strains), Streptococcus constellatus (3 strains), and Streptococcus mitis (2 strains). Three strains were also identified as bacteria of genus Firmicutes or Staphylococcus at the genus level. The present study showed that many bacterial species in infected root canal dentin were alkali‐resistant at pH 9.0 and/or pH 10.0, and belonged mainly to the genus Enterococcus.     

Removable partial denture abutments restored with all-ceramic surveyed crowns.

All-ceramic crowns are used as alternatives to conventional metal-ceramic crowns for the restoration of single teeth. Traditionally all-ceramic restorations possessed physical properties that contraindicated their use in many treatment situations. The strength that zirconia ceramics exhibit seems to support the hypothesis that, in specific situations, an all-ceramic crown may be used to restore removable partial denture (RPD) abutments in areas previously reserved for metal or metal-ceramic restorations. Abutments for RPDs may now be fabricated with Procera AllZirkon with the classically prepared guide planes and rest seats. This article provides an overview of a technique for the fabrication of a zirconia-based crown to be used in conjunction with removable partial dentures using the Procera CAD/CAM technology.     

Biodegradable porous calcium polyphosphate scaffolds for the three-dimensional culture of dental pulp cells

AIM: To develop a three-dimensional culture model of human dental pulp cells (DPCs) with biodegradable porous calcium polyphosphate (CPP) scaffolds. METHODOLOGY: Human DPCs were isolated from three donors. The 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl tetrazolium bromide (MTT) assay was used to evaluate the cytotoxicity of CPP compared with hydroxyapatite (HA) and beta-tricalcium phosphate (beta-TCP). Values were analysed using unpaired t-tests. Cells were seeded onto porous CPP scaffolds with pore sizes in the range of 200-300 microm. The nature of cellular adaptation in the three-dimensional culture model was then evaluated visually by scanning electronic microscopy (SEM) and confocal laser scanning microscopy (CLSM). The apoptotic property of cells on the scaffolds was also assessed by DNA staining with CLSM. RESULTS: The cytotoxicity assay indicated that there was no significant difference between CPP and HA for each donor's original cells (P>0.05). Calcium polyphosphate had no cytotoxic effect on DPCs, whilst SEMs showed that cells successfully adhered to CPP scaffolds and spread amongst pores. On the cell surface, fine processes and matrix secretory granules were found. Confocal laser scanning microscopy showed that cells took on a three-dimensional structure with signs of vitality. CONCLUSION: Porous CPP scaffolds are promising for the establishment of a three-dimensional culture model of DPCs.     

Consideration of biomechanical stress in treatment with dental implants

The most common implant complications, whether associated with the implant or prosthetic restoration, occur as a result of biomechanical stress. These complications include early implant failure, fracture of the prosthesis, abutment or prosthetic screw loosening, implant crestal bone loss, and problems with overdenture attachments. An engineering approach to resolve biomechanical problems involves determining the nature of complications and then designing an approach to eliminate their underlying causes. Treatment planning should incorporate methods to reduce stress and minimize its initial and long-term effects. The treatment plan is altered when forces are greater or bone is less dense than usual to minimize the negative impact of stress on the implant, bone, and restoration. Several parameters under the clinician's control can improve the transosteal environment relative to managing stress on the implant-restoration complex. The goal is to decrease the amount of force, or increase the implant-bone surface area, to decrease the chance of implant-restoration complications.+     

Asaccharolytic anaerobic gram‐negative coccobacilli (AAGNC) isolated from infected root canals and periodontal pockets

Background/aims: Culture‐difficult bacteria, including asaccharolytic anaerobic gram‐negative coccobacilli (AAGNC), may constitute a predominant group of organisms in oral sites. This study aimed to characterize phylogenetically 10 AAGNC isolated from endodontic lesions and periodontal pockets. Methods: 16S rDNA sequence and G + C content were determined. Strains sharing more than 98% sequence similarities and similar G + C content were considered the same bacterial species. Results: One isolate resembled Dialister pneumosintes (the type species of the genus Dialister) with 35 mol% G+C content and 97% sequence similarity. Of eight isolates having 45–47 mol% G+C content, seven were identified as D. invisus and one resembled Dialister invisus with 97% sequence similarity. However the 16S rDNA sequence similarities with D. pneumosintes were relatively low, indicating the strains may belong to a new genus. The last isolate revealed 35 mol% G+C content, but had higher 16S rDNA sequence similarity with D. invisus than with D. pneumosintes. Conclusion: The group of oral AAGNC isolates need to be reclassified.     

Traumatic intrusion of permanent teeth. Part 3. A clinical study of the effect of treatment variables such as treatment delay,method of repositioning,type of splint,length of splinting and antibiotics on 140 teeth

Abstract – A prospective study of 140 intruded permanent teeth was examined for the following healing complications: pulp necrosis (PN), root resorption (RR; surface, inflammatory and replacement resorption), and defects in marginal periodontal bone healing (MA). The occurrence of these healing complications was related to various treatment factors such as treatment delay, method of repositioning (i.e. expecting re‐eruption, orthodontic reposition and surgical reposition), type of splint (rigid, semirigid and flexible), length of splinting (days) and the use of antibiotics. Treatment delay, i.e. before and after 24 h, had no effect upon healing. Active repositioning in individuals with incomplete root formation (surgical or orthodontic) had a negative effect upon the three healing parameters compared with spontaneous eruption. In teeth with complete root formation and an age of 12–17 no repositioning was still the best treatment in regard to MA. In individuals older than 17 years of age, cases were not anticipated to spontaneously erupt and in these cases, the general choice of treatment was either active orthodontic or surgical repositioning. The former procedure appeared in this treatment scenario to slightly reduce the risk of MA complications. However, this treatment procedure was also found to be more time demanding (an average of 22 consultations for orthodontic repositioning compared with 17 consultations for surgical repositioning). If a surgical repositioning was performed, the type of splint (i.e. flexible, semirigid or rigid) appeared to have no significant effect on the type of healing. The same applied to the length of splinting time (shorter or longer than 6 weeks). No effect of dentin covering procedures for associated crown fractures (enamel–dentin fractures) could be demonstrated. Likewise, antibiotics had no apparent effect upon healing. In conclusion, in patients with intruded teeth with incomplete root formation, spontaneous eruption should be expected. In patients with completed root formation and with an age of 12–17 spontaneous eruption can still occur, but must be monitored very carefully. In older patients (i.e. >17 years) with completed root formation, either surgical or orthodontic extrusion should be attempted. The latter procedure appeared to lead to a slight reduction (not significant) in the risk of MA complications. The extent and direction of the intrusion may however favour surgical repositioning.     

Changes in the masticatory jaw movement following orthodontic traction of an impacted and transposed upper canine and occlusal adjustment

In a 10-year-old female with an impacted and completely transposed upper left canine, posterior temporal muscle activity and jaw movement during mastication were examined before and after orthodontic traction of the canine, alignment of teeth, and occlusal adjustment of the canine. After the orthodontic treatment, but before the occlusal adjustment, esthetic improvement in the static occlusion was achieved. The posterior temporal muscle on the non-chewing side exhibited earlier bursts in the electromyography. Jaw movement trajectory of the jaw-closing phase at a level close to the maximum intercuspation position was more to the medial side on the frontal view, and the jaw-closing velocity in the lateral direction was slower during left-sided chewing. Following occlusal adjustment of the transposed canine, however, the muscle activity and jaw movement patterns were improved to normal patterns. We suggest that it might be advisable to perform occlusal adjustment at an early stage during the retention period in such cases.     

A mixture of Ca(OH)2 paste and ZnO powder as a root canal filling material for primary teeth: a preliminary study

The present pilot study was conducted on five primary mandibular second molars requiring endodontic treatment to evaluate the clinical and radiographic success of root canal filling material which was a mixture of calcium hydroxide paste (1 cm), Zinc oxide powder (15 gms) and distilled water using hand operated lentulo spirals. All the five cases on clinical evaluation after 2,4,6,9, and 12 months were found to be asymptomatic with no history of pain, tenderness or abnormal mobility. Immediate post-operative radiographic evaluation revealed adequate root canal filling in all cases. The obturated material remained upto the apex of root canals till the beginning of physiologic root resorption. The roots of the primary teeth as well as the filling material mentioned above were seen to resorb at the same rate in one case.     

Inactivation of local root canal medicaments by dentine: an in vitro study

AIMS: The aim of the study was to investigate the inactivation by dentine of the antibacterial activity of various commonly used local root canal medicaments. METHODOLOGY: The medicaments tested were saturated calcium hydroxide solution, 1% sodium hypochlorite, 0.5% and 0.05% chlorhexidine acetate, and 2/4% and 0.2/0.4% iodine potassium iodide. Dentine was sterilized by autoclaving and crushed into powder with a particle size of 0.2-20 microns. Aliquots of dentine suspension were incubated with the medicaments in sealed test tubes at 37 degrees C for 24 h or 1 h before adding the bacteria. In some experiments bacteria were added simultaneously with dentine powder and the medicament. Enterococcus faecalis A197A was used as a test organism. Samples for bacterial culturing were taken from the suspensions at 5 min, 1 h and 24 h after adding the bacteria. RESULTS: Dentine powder had an inhibitory effect on all medicaments tested. The effect was dependent on the concentration of the medicament as well as on the length of the time the medicament was preincubated with dentine powder before adding the bacteria. The effect of calcium hydroxide on E. faecalis was totally abolished by the presence of dentine powder. Similarly, 0.2/0.4% iodine potassium iodide lost its effect after preincubation for 1 h with dentine before adding the bacteria. The effect of 0.05% chlorhexidine and 1% sodium hypochlorite on E. faecalis was reduced but not totally eliminated by the presence of dentine. No inhibition could be measured when full strength solutions of chlorhexidine and iodine potassium iodide were used in killing E. faecalis. CONCLUSIONS: The dentine powder model appears to be an efficient tool for the study of interactions between local endodontic medicaments, dentine, and microbes.