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Abstract Background The fossil record has suggested that clade growth may differ in marine and terrestrial taxa, supporting equilibrial models in the former and expansionist models in the latter. However, incomplete sampling may bias findings based on fossil data alone. To attempt to correct for such bias, we assemble phylogenetic supertrees on one of the oldest clades of insects, the Odonatoidea (dragonflies, damselflies and their extinct relatives), using MRP and MRC. We use the trees to determine when, and in what clades, changes in taxonomic richness have occurred. We then test whether equilibrial or expansionist models are supported by fossil data alone, and whether findings differ when phylogenetic information is used to infer gaps in the fossil record. Results There is broad agreement in family-level relationships between both supertrees, though with some uncertainty along the backbone of the tree regarding dragonflies (Anisoptera). "Anisozygoptera" are shown to be paraphyletic when fossil information is taken into account. In both trees, decreases in net diversification are associated with species-poor extant families (Neopetaliidae, Hemiphlebiidae), and an upshift is associated with Calopterygidae + Polythoridae. When ghost ranges are inferred from the fossil record, many families are shown to have much earlier origination dates. In a phylogenetic context, the number of family-level lineages is shown to be up to twice as high as the fossil record alone suggests through the Cretaceous and Cenozoic, and a logistic increase in richness is detected in contrast to an exponential increase indicated by fossils alone. Conclusions Our analysis supports the notion that taxa, which appear to have diversified exponentially using fossil data, may in fact have diversified more logistically. This in turn suggests that one of the major apparent differences between the marine and terrestrial fossil record may simply be an artifact of incomplete sampling. Our results also support previous notions that adult colouration plays an important role in odonate radiation, and that Anisozygoptera should be grouped in a single inclusive taxon with Anisoptera, separate from Zygoptera.

Abstract Background The challenge of gene expression studies is to reliably quantify levels of transcripts, but this is hindered by a number of factors including sample availability, handling and storage. The PAXgene™ Blood RNA System includes a stabilizing additive in a plastic evacuated tube, but requires 2.5 mL blood, which makes routine implementation impractical for paediatric use. The aim of this study was to modify the PAXgene™ Blood RNA System kit protocol for application to small, sick chidren, without compromising RNA integrity, and subsequently to perform quantitative analysis of ICAM and interleukin-6 gene expression. Aliquots of 0.86 mL PAXgene™ reagent were put into microtubes and 0.3 mL whole blood added to maintain the same recommended proportions as in the PAXgene™ evacuated tube system. RNA quality was assessed using the Agilent BioAnalyser 2100 and an in-house TaqMan™ assay which measures GAPDH transcript integrity by determining 3' to 5' ratios. qPCR analysis was performed on an additional panel of 7 housekeeping genes. Three reference genes (HPRT1, YWHAZ and GAPDH) were identified using the GeNORM algorithm, which were subsequently used to normalising target gene expression levels. ICAM-1 and IL-6 gene expression were measured in 87 Malawian children with invasive pneumococcal disease. Results Total RNA yield was between 1,114 and 2,950 ng and the BioAnalyser 2100 demonstrated discernible 18s and 28s bands. The cycle threshold values obtained for the seven housekeeping genes were between 15 and 30 and showed good consistency. Median relative ICAM and IL-6 gene expression were significantly reduced in non-survivors compared to survivors (ICAM: 3.56 vs 4.41, p = 0.04, and IL-6: 2.16 vs 6.73, p = 0.02). Conclusion We have successfully modified the PAXgene™ blood collection system for use in small children and demonstrated preservation of RNA integrity and successful quantitative real-time PCR analysis.

Abstract Background Used alone, the MAS5.0 algorithm for generating expression summaries has been criticized for high False Positive rates resulting from exaggerated variance at low intensities. Results Here we show, with replicated cell line data, that, when used alongside detection calls, MAS5 can be both selective and sensitive. A set of differentially expressed transcripts were identified that were found to be changing by MAS5, but unchanging by RMA and GCRMA. Subsequent analysis by real time PCR confirmed these changes. In addition, with the Latin square datasets often used to assess expression summary algorithms, filtered MAS5.0 was found to have performance approaching that of its peers. Conclusion When used alongside detection calls, MAS5 is a sensitive and selective algorithm for identifying differentially expressed genes.

The effects of contaminant concentration on contaminant removal by Lemna minor were examined under elevated plant densities typical of full surface coverage. Uptake of 3-fluorophenol and 3-trifluoromethylphenol by L. minor was determined at concentrations from 10 to 1750 microM. Because standardized toxicity tests typically do not measure plant activity of L. minor at high plant densities, an oxygen production rate (OP) assessment was developed with consideration of experimental parameters that may inhibit OP by L. minor, including concentrations of carbonate and phosphate buffer in the media, time of assessment, and mass of L. minor. The OP by L. minor was inhibited by increasing media pH and mass of L. minor. The developed assessment used 0.5 g of L. minor per 60 ml of modified Standard Methods medium. A total of 30 h was needed to determine toxicity of fluorinated phenols, with an exposure period of 24 h, an incubation time of 6 h, and negligible analysis time. At concentrations from 10 to 1750 microM, 3-trifluoromethylphenol exhibited a sigmoidal toxicity response. However, 3-fluorophenol was neither toxic nor inhibitory at the experimental concentrations tested. Substantial decreases in uptake rate constants were observed for increasing concentrations of both contaminants, indicating that concentration may be a more important indicator of uptake by L. minor compared with decreasing plant activity because of toxicity.

Metabolic fate of xenobiotics in plant tissues has an important role in the ultimate fate of these compounds in natural and engineered systems. Chlorophenols are an important class of xenobiotics used in a variety of biocides and have been shown to be resistant to microbial degradation. Three chlorophenyl glycosides were extracted from tissues of Lemna minor exposed to 2,4-dichlorophenol (DCP). The products were identified as 2,4-dichlorophenyl-beta-D-glucopyranoside (DCPG), 2,4-dichlorophenyl-beta-D-(6-O-malonyl)-glucopyranoside (DCPMG) and 2,4-dichlorophenyl-beta-D-glucopyranosyl-(6 --> 1)-beta-D-apiofuranoside (DCPAG). Identification was based on reverse phase retention (C18), electrospray mass spectra collected in negative and positive mode (ESI-NEG and ESI-POS, respectively), and nuclear magnetic resonance (NMR) spectra comparisons to reference materials synthesized in the laboratory. Liquid chromatography-mass spectrometry (LC-MS) analysis of plants exposed to 2,4,5-trichlorophenol (TCP) formed analogous compounds: 2,4,5-trichlorophenyl-beta-D-glucopyranoside (TCPG), 2,4,5-trichlorophenyl-beta-D-(6-O-malonyl)-glucopyranoside (TCPMG) and 2,4,5-trichlorophenyl-beta-D-glucopyranosyl-(6 --> 1)-beta-D-apiofuranoside (TCPAG). Enzyme catalyzed hydrolysis with beta-glucosidase was ineffective in releasing the beta-glucosides with chemical modifications at C6. Presence of these glucoconjugates confirmed that L. minor was capable of xenobiotic uptake and transformation. Identification of these products suggested that chlorophenols were incorporated into vacuoles and cell walls of L. minor.

We used a novel digital autoradiographic technique that enabled, for the first time, simultaneous visualization and quantification of spatial and temporal changes in carbon allocation patterns in ectomycorrhizal mycelia. Mycorrhizal plants of Pinus sylvestris L. were grown in microcosms containing non-sterile peat. The time course and spatial distribution of carbon allocation by P. sylvestris to mycelia of its mycorrhizal partners, Paxillus involutus (Batsch) Fr. and Suillus bovinus (L.): Kuntze, were quantified following 14C pulse labeling of the plants. Litter patches were used to investigate the effects of nutrient resource quality on carbon allocation. The wood-decomposer fungus Phanerochaete velutina (D.C.: Pers.) Parmasto was introduced to evaluate competitive and territorial interactions between its mycelial cords and the mycelial system of S. bovinus. Growth of ectomycorrhizal mycelium was stimulated in the litter patches. Nearly 60% of the C transferred from host plant to external mycorrhizal mycelium (> 2 mm from root surfaces) was allocated to mycelium in the patches, which comprised only 12% of the soil area available for mycelial colonization. Mycelia in the litter patch most recently colonized by mycorrhizal mycelium received the largest investment of carbon, amounting to 27 to 50% of the total 14C in external mycorrhizal mycelium. The amount of C transfer to external mycelium of S. bovinus following pulse labeling was reduced from a maximum of 167 nmol in systems with no saprotroph to a maximum of 61 nmol in systems interacting with P. velutina. The 14C content of S. bovinus mycelium reached a maximum 24-36 h after labeling in control microcosms, but allocation did not reach a peak until 56 h after labeling, when S. bovinus interacted with mycelium of P. velutina. The mycelium of S. bovinus contained 9% of the total 14C in the plants (including mycorrhizae) at the end of the experiment, but this was reduced to 4% in the presence of P. velutina. The results demonstrate the dynamic manner in which mycorrhizal mycelia deploy C when foraging for nutrients. The inhibitory effect of the wood-decomposer fungus P. velutina on C allocation to external mycorrhizal mycelium has important implications for nutrient cycling in forest ecosystems.

Objective: To identify techniques commonly used in the management of periradicular disease by general dental practitioners and to ascertain views on continuing professional education in endodontics., Design: Data was collected via a postal questionnaire distributed to 617 general dental practitioners in Scotland (33% of practitioners registered with the Dental Practice Board)., Results: 417 (69%) questionnaires were completed and returned. Only 24.9% of respondents used rubber dam routinely. The majority of respondents used hand instruments for preparation with either sodium hypochlorite or local anaesthetic being used most frequently for irrigation. The mean time for treatment of a single rooted tooth was 71 minutes. The demand for continuing education courses was high with 340 and 197 respondents requesting endodontic and rubber dam courses, respectively., Conclusions: Traditional methods for preparing the root canal using hand instruments were favoured by most dentists. The major disincentive to the use of rotary instruments and new techniques for obturating with thermally softened gutta-percha was expense. The importance of rubber dam isolation requires reiteration and more continuing education courses are required to update clinical skills.

Objective: To identify factors influencing the diagnosis and management of periradicular disease by general dental practitioners., Design: The study was conducted in two stages. 1. Analysis of recent returns to the Scottish Dental Practice Board. 2. Data collection via a postal questionnaire distributed to 617 general dental practitioners in Scotland (33% of practitioners registered with the Dental Practice Board)., Results: 417 (69%) questionnaires were completed and returned. The majority of respondents undertook root canal treatment and the number of cases treated had increased in the last five years. The vast majority of the respondents (89.3%) were confident in their diagnosis of periradicular disease and 77.1% were confident of their treatment of the disease. A referral system for treatment was used by 31% of respondents of whom the majority used a specialist in a hospital. Over 50% of the respondents undertook surgical root canal treatment. Only 40% of respondents followed up their completed cases for longer than six months. Constraints on the provision of treatment included the time available and the low level of fees., Conclusions: Current arrangements for the treatment of periradicular disease in general dental practice are less than optimal. The fiscal arrangements for the provision of these treatments must be developed to encourage a high standard of treatment to be performed thereby maximising the likelihood of success. In addition, efforts to inform patients of the benefits of the treatment of periradicular disease should be increased.

The aim of this study was to compose in vitro coronal leakage of a super EBA root-end filling material after two root-end cavity preparation techniques. A mixed anaerobic microbial marker was used. Forty-five extracted human teeth with straight, single root canals were prepared chemo-mechanically to a size 40 master apical file. The teeth were divided into experimental groups (35 teeth) and control groups (10 teeth). Forty teeth (35 experimental teeth and five negative control teeth) were obturated by lateral condensation of cold gutta-percha with Tubliseal EWT sealer. The remaining five teeth were not obturated and served as positive controls. These teeth were stored for 6 months in artificial saliva. The apical 3-4 mm of each root was resected perpendicular to the long axis of the root and a root-end cavity prepared to a depth of 3 mm using either a size 008 rosehead burr or an ultrasonic retroprep tip. Freshly mixed EBA cement was placed into the root-end cavity. The entire root surface of each tooth, except the cutting surface of the apical end, was sealed with nail varnish. The coronal part of each root canal was sealed with the cut end of a tube and placed in a bottle containing sterile Brain Heart Infusion Broth (BHIB). A marker consisting of Anaerobic streptococci and Fusobacterium nucleatum in BHIB was placed in each coronal chamber at 7-day intervals and daily observations were made for bacterial growth in the apical chamber for 60 days. All positive control teeth exhibited bacterial leakage within 48 h, whilst the apical chamber of negative control teeth remained uncontaminated throughout the test period. Fifty-nine percent (n = 10) of the specimens prepared with a burr showed leakage after 90 days, whilst only 22% (n = 4) of the ultrasonically prepared group showed leakage after the same time. The group prepared with ultrasonic tips showed statistically significant less specimens with leakage (P < 0.05) than the group prepared with burrs.

This in vitro study investigated the effect of a resin-reinforced glass ionomer lining material on the coronal leakage of a mixed obligate microbial marker in maxillary molars obturated with lateral condensation of cold gutta-percha and Tubliseal sealer, after 2 years' storage. Forty maxillary first molars were prepared chemomechanically to a size 30-40 master apical file. The teeth were divided into an experimental group (30 teeth) and control group (10 teeth). In the experimental group, the floor of pulp chamber and the root-canal opening of 15 teeth were covered with Vitrebond as a lining; the remaining 15 teeth received no lining. These teeth were tested for leakage using a microbiological marker consisting of anaerobic streptococci and Fusobacterium nucleatum. The teeth were checked daily for bacterial leakage for 60 days. All positive control teeth leaked within 48 h, while the negative control teeth remained uncontaminated throughout the test period. The teeth restored with Vitrebond liner showed no leakage whilst 60% of the specimens with no Vitrebond liner showed leakage after 60 days.

Heavily restored teeth which become pulpally involved are now often root canal treated rather than extracted. While this is laudable it has a significant impact on the practice of endodontics today. The curved calcified canal can prove very difficult to prepare to its natural shape by conventional techniques and there is always the likelihood of iatrogenic damage. To compensate for this many clinicians tend to under-prepare these canals, perhaps leaving them inadequately cleaned and certainly remarkably difficult to fill to length. The purpose of this article is to outline the stages of and the rationale behind a hand instrumentation preparation method which uses the balanced force method of movement of files from canal entrance to apical constriction. In the authors' experience this technique has gone a long way towards solving the problem of cleaning and shaping the fine curved canal. With some practice, but no extra expense, the technique described will not only speed up canal preparation but will also make it more predictable.

Patients are increasingly wishing to undergo conventional endodontic treatment rather than to risk the loss of a tooth. Endodontic treatment in teeth that have been previously restored with extensive intracoronal or extracoronal restorations are often difficult to treat. The orientation of the root canals to the crown of the tooth may be lost, and this may often be compounded by the deposition of reparative dentin in the pulp chamber. The operating microscope allows better visualization of the working field, ensuring that the anatomy of the tooth is more readily inspected. This greatly enhances the clinician's ability to locate extra root canals and therefore increase the likelihood of a successful outcome. It should not be forgotten that the operating microscope also has a place in other fields of dentistry, especially restorative dentistry, and is an asset to both the specialist and the generalist.

Objective: To examine the periapical status, technical standard and frequency of root canal treatment in an adult population in Scotland., Design: Examination of full-mouth periapical radiographs from 340 consecutive adult patients (8420 teeth) attending Glasgow and Dundee Dental Hospitals for clinical examination., Methods: Position and quality of the root fillings were assessed together with signs of periradicular radiolucencies. The influence of the type of coronal restoration was also assessed., Main Outcome Measures: Pathologies associated with impacted third molars and outcomes following surgical removal of third molars., Results: 54% of the patient sample had root filled teeth. 5.6% of the teeth examined radiographically had root fillings, and of these, 58.1% had radiographic signs of periapical disease. 41% of the patients had at least one non-root canal treated tooth with periapical disease. 77% of teeth with post-retained crowns had evidence of periapical pathology., Conclusions: Root fillings judged to be adequate radiographically had a reduced incidence of radiolucencies. Teeth obturated beyond the apex had more radiolucencies than those obturated flush with or within 2 mm of the radiographic apex. A high proportion of post-retained crowns were associated with periapical pathology. There is a substantial future need both for root canal treatment and for standardised treatment methods.

The effect of five root canal sealers and two root canal dressing materials on the growth of three anaerobic bacteria associated with endodontic infections was determined using the agar diffusion inhibitory test. Samples of the following endodontic sealers (Apexit, Ketac-Endo, Roth Sealer, Sealapex and Tubliseal) and root canal dressing materials (Pulpdent and Root-cal) were incubated for 48 h with the following anaerobic bacteria: Capnocytophaga ochracea, Porphyromonas gingivalis and Peptostreptococcus micros. Statistically significant zones of bacterial growth inhibition for all the bacteria tested were observed in descending order of antimicrobial activity: Roth Sealer, Ketac-Endo, Tubliseal, Apexit and Sealapex. Root-cal and Pulpdent also showed statistically significant antimicrobial activity, but only to Capnocytophaga ochracea, not to the other two bacteria tested, with Pulpdent being the least active.

Purpose: To assess the microleakage of Class V preparations restored with three bonding agents using wet and dry bonding., Materials and Methods: Cavities were prepared in the buccal and lingual surfaces of extracted human premolar teeth and restored with resin composite after application of the dentin bonding agents, using a wet or dry bonding technique. The teeth were stored for 2 weeks at 37 degrees C, thermocycled, and the restorations examined for leakage using buffered methylene blue as the marker. The teeth were sectioned bucco-lingually through the restorations and the degree of microleakage assessed microscopically., Results: All groups showed leakage at both the dentin and enamel margins. There was no significant difference in leakage at the enamel margins between groups (p > 0.05) and no significant differences in leakage between the wet bonding (P > 0.05) or dry bonding (P > 0.05) procedures. However, when comparing the effects of wet and dry bonding, there was less leakage at the gingival margin in the groups where the bonding agent was acetone-based and wet bonding was used (P < 0.03). There was no significant difference in leakage for Scotchbond Multi-Purpose Plus when either maleic acid or phosphoric acid was used as the etchant (P > 0.05).

The purpose of this study was to assess long-term coronal leakage in root fillings achieved by 2 gutta-percha techniques using 2 calcium hydroxide-containing sealers. The root canals of 90 single-rooted teeth with mature apices were prepared chemomechanically. The teeth were placed randomly into four experimental groups (n = 20) and obturated with either lateral condensation of cold gutta-percha or a thermo-plasticized gutta-percha delivery system, JS Quickfill, using Sealapex or Apexit as the sealer. A further five teeth were placed in each of negative or positive control groups. After root filling the teeth were sectioned at the cementoenamel junction and stored in saline solution at 37 degrees for 1 yr. Coronal leakage was then determined with an India ink tracer (using a reduced pressure model) and a clearing technique. The extent of coronal leakage was measured at x6 magnification. Non-parametric analysis showed that there was significantly more leakage with the thermally softened gutta-percha technique than with lateral condensation (p < 0.05). There was no significant difference in leakage between the groups obturated with lateral condensation (p > 0.005) but, with the thermoplasticized technique, there was more leakage with the sealer Sealapex (p < 0.05).

The effect of three methods of root-end preparation, following apical resection, on the apical seal of root-end fillings, was studied in vitro. Root canals of 116 single-rooted teeth with mature apices were prepared chemomechanically and obturated with gutta-percha and sealer. The root ends were resected with a diamond bur under water coolant and were prepared as follows: group I a size 010 round bur was used to prepare an apical cavity 2-3 mm down the long axis of the root; group II treatment as per group 1 followed by a 60-s rinse with a solution of 10:3 (10% citric acid: 3% Fe2Cl3); and group III an ultrasonic retrotip was used to prepare a 2-3 mm deep apical cavity. The root end was restored with an EBA cement. Apical leakage was determined using India ink after 7 days and 7 months. The teeth were demineralized, rendered transparent and linear dye penetration was recorded. Results showed that there was no significant difference in leakage between the groups at each time interval (P > 0.05) but there was increased leakage after 7 months (P < 0.01). Cracking of the root surface was seen most often with the ultrasonically prepared roots (P < 0.001).

Preparations of apical cavities in resected root ends using rotary burs, with and without citric acid rinse, and ultrasonic tips were compared based on the presence or absence of superficial debris and smear layer. Three groups of 20 extracted teeth each were prepared as follows; I, a size 010 round bur was used to prepare an apical cavity 2-3 mm down the long axis of the root; II, treatment as per group I followed by a 60-s rinse with a solution of 10:3 (10% citric acid, 3% Fe2Cl3); and III, an ultrasonic retrotip was used to prepare a 2-3 mm deep apical cavity. Roots were grooved longitudinally, split and prepared for SEM analysis at x100 and x780 magnification. Examiners were calibrated to a standardized grading system. Extensive statistical analyses indicated statistically significant differences within and among the groups (P < 0.05). Root-end preparation with a bur created a heavy smear layer at all levels of the preparation. This layer was partially removed during ultrasonic preparation in the apical two-thirds. A greater removal of the smear layer was achieved with the citric acid rinse (P < 0.05). Coronally, root-end preparations were contaminated with moderate to heavy amounts of debris with all techniques.

Fifty-one extracted intact human first molar teeth with mature root apices were radiographed in a standardized way; their root curvature was determined and they were divided into three groups. One root canal in the mesial root of the mandibular molars, or the major mesiobuccal root in maxillary molars, was prepared with the modified double-flared technique, in one of three ways. The modified double-flared technique involves coronal flaring followed by working length determination and apical preparation. In group 1, unmodified tipped instruments (Flexofile) were manipulated with a balanced force technique. In groups 2 and 3, Flexogates files and Canal Master U files were operated in the manner recommended by the manufacturers. After preparation, the teeth were radiographed. The processed images of the root canals were traced using an image analysis computer software package. Comparisons were made between the preoperative and postoperative shapes of each root canal. A low viscosity polyvinyl siloxane was injected into the prepared root canals and the specimens were demineralized, dehydrated, and cleared. The preparation was evaluated subjectively according to desirable or undesirable criteria. The overall quality of preparation was rated. Statistical analysis showed that there was no significant difference in the overall change of area between the three groups (p = 0.994). There was a significant proportional increase in mesiodistal width in the coronal part of the canals in the Canal Master U group and more of the instruments in this group fractured.(ABSTRACT TRUNCATED AT 250 WORDS)

The effect on coronal leakage of the use of either a single gutta-percha cone or cold lateral condensation of gutta-percha, with a glass ionomer sealer cement was studied. In addition, the effect of the removal of the smear layer was also determined. Eighty-eight single-rooted teeth were prepared chemomechanically using hand files, with the balanced force technique. Lubrication was provided by either Hibiscrub (maintaining the smear layer) or an EDTA-containing paste (to remove the smear layer). Copious irrigation was carried out with 2.2% sodium hypochlorite. The teeth were allocated randomly to four groups of 20 teeth each, the remaining eight teeth served as controls. Two groups of teeth, one with and one without smear layer, were obturated with either a single gutta-percha cone or cold laterally condensed gutta-percha, with Ketac Endo as the sealer. The teeth were stored for 6 weeks, thermocycled, and the extent of coronal leakage determined for each group after immersion in India ink for 90 h. The teeth were demineralized, dehydrated and immersed in methyl salicylate, which rendered them transparent. Linear measurement of maximum dye penetration was recorded. The mean depth (+SD) of leakage for the groups in which the smear layer was left intact was 1.68 mm (+0.38) for the single cone (A1) and 2.29 mm (+1.58) for lateral condensation (B1). When the smear layer was removed the mean depth of leakage for the single cone group (A2) was 2.04 mm (+0.73) and 2.37 mm (+1.70) for the laterally condensed group (B2). There was no significant difference in coronal leakage between the groups (P > 0.05).

This paper reviews the evidence that coronal leakage of root canals may lead to failure of root-canal therapy. The causes of coronal leakage and methods by which this leakage may be prevented are described.

Recent interest in amalgam as a restorative material has been directed toward the development of the bonded amalgam restoration. The literature regarding the theoretical and clinical aspects of this technique is reviewed. Four cases of successful treatment of cracked-tooth syndrome with the bonded amalgam restoration are presented.

The effect that two methods of root canal obturation, combined with removal of the smear layer, had on coronal leakage was studied in vitro. Single-rooted teeth with mature apices were prepared chemomechanically and divided into two groups of 72 teeth each. One of the groups was treated with 40% citric acid and 2% sodium hypochlorite to remove the smear layer. The teeth were then subdivided and obturated using the glass ionomer sealer, Ketac Endo and either lateral condensation or Thermafil. After storage for 7 days or 4 months, the specimens were evaluated for coronal leakage using Indian ink. After 90 h, each root was split longitudinally and the maximum extent of leakage was measured using a stereomicroscope at x6 magnification. After 7 days, there was significantly less leakage in those teeth obturated with Thermafil without smear layer compared with the other groups (p < 0.05). After 4 months, there was no significant difference in leakage between the groups (p > 0.05).

The effect of post space preparation on the apical seal of teeth roots treated with the plastic-cored Thermafil was studied in vitro. Single rooted teeth with mature apices were prepared chemomechanically and obturated with alpha-phase gutta-percha, Thermafil, on plastic core-carriers and sealer, Sealapex. The teeth were divided randomly into four groups of 18 teeth each. In two of the groups post space was prepared by hand using a Parapost drill (diam. 1.25 mm) after gutta-percha removal with Peeso reamers in a slow-speed handpiece, one group immediately after canal obturation and the other after storage in 100% relative humidity at 37 degrees C for 1 week; 5 mm of root filling was left intact. The time taken to remove the gutta-percha was recorded. Post space was not prepared in the control groups. Apical leakage was determined using black India ink. The teeth were demineralized, rendered transparent, and linear measurement of dye penetration was recorded. Results showed that there were no significant differences in leakage between any of the groups (P > 0.05). There was no statistically significant difference in the time required to remove the gutta-percha from the root canals in both groups (P < 0.05). It is concluded that under the conditions of this study post space preparation immediately after obturation, or after a delay of 1 week, does not affect the apical seal of Thermafil with plastic core-carriers.

Adaptation and placement of alpha-phase gutta-percha delivered with a plastic core-carrier, Thermafil, was compared to the lateral condensation of gutta-percha in a specific tooth model. Fifty-one mandibular molar roots with separate canals, patent canal orifices and curvatures greater than 15 degrees were cleaned and shaped with K-files and 2.5% sodium hypochlorite to a size 30 at the apex, and flared with Hedstrom files to create a continuously tapering funnel preparation. Canals were randomly obturated with Sealapex root canal sealer and either alpha-phase gutta-percha on a plastic Thermafil carrier, or standard beta-phase gutta-percha with lateral condensation. Roots were radiographed from the proximal and evaluated by three examiners, based on established criteria for overall material adaptation, apical adaptation, and filling material extrusion. Thermafil provided a statistically significant better overall canal obturation (P < 0.001), while, in the apical third, both techniques were not significantly different (P > 0.05). When the apical orifice was patent there was a significant propensity for the extrusion of filling materials beyond the apex (P < 0.001) with the Thermafil technique.

The short- and long-term apical seal of root canals obturated with softened alpha-phase gutta-percha on plastic core-carriers, Thermafil, was compared to that of laterally condensed, cold gutta-percha. Fifty-one roots from mandibular molars with separate canals, patent canal orifices and curvatures greater than 15 degrees were cleaned and shaped with K-files and 2.5% sodium hypochlorite to a size 30 at the apex, and flared with Hedstrom files to create a continuously tapering funnel preparation. Canals were randomly obturated with Sealapex root canal sealer and either alpha-phase gutta-percha on a plastic Thermafil carrier, or standard beta-phase gutta-percha with lateral condensation. Teeth were separated into three groups of 17 each and placed in black India ink for 24 h, 7 days or after 5 months storage in water. The teeth were demineralized, rendered transparent, and apical microleakage determined by the linear measurement of dye penetration. Significant differences in microleakage were noted between the 24 h and 5-month Thermafil groups (P < 0.05), 24-h and 7-day lateral condensation groups (P < 0.05), and 24-h and 5-month lateral condensation groups (P < 0.05). There were no significant differences between the two techniques at each time interval. It was concluded that both techniques demonstrated a significant increase in apical microleakage over a 5-month period.

The use of a resin-based glass ionomer as an endodontic sealer was studied in vitro. The root canals of extracted single-rooted human teeth with mature apices were prepared using a stepback technique. Subsequently, the smear layer was removed with 40% citric acid and the canals obturated using lateral condensation of cold gutta-percha and a resin-based glass ionomer as the sealer. The relationship between the sealer and the wall of the root canal was studied using scanning electron microscopy. The shear bond strength of gutta-percha to this glass ionomer was also determined. Finally, the uptake of fluoride into the wall of the root canal was studied using scanning electron microprobe analysis after storage for 2 weeks, 1 month and 3 months following root filling with gutta-percha and glass ionomer cement. The results showed that removal of the smear layer allowed the sealer to enter some of the dentinal tubules. This was observed most frequently in the middle third of the root canal, where there was good adaptation of the sealer. The shear bond strength of gutta-percha to the glass ionomer sealer was not significantly different from that obtained between gutta-percha and a proprietary zinc oxide-eugenol endodontic sealer. The concentration of fluoride in the dentine in the coronal part of the root canal increased after obturation with gutta-percha and the glass ionomer sealer at every time interval. The increase in fluoride concentration varied widely between teeth. It is concluded that a resin-based glass ionomer cement may have potential as a root canal sealer.

The effect of the removal of the smear layer on coronal leakage of root fillings was studied using two sealer cements. Sixty single-rooted teeth with mature apices were prepared chemomechanically using a modified double-flared technique with non-cutting tipped files and copious irrigation with 2% sodium hypochlorite. The teeth were randomly allocated to four groups of 15 teeth each. Two groups were treated with 40% citric acid to remove the smear layer. Two groups of teeth, one with and one without smear layer, were filled by lateral condensation of gutta-percha with either Tubliseal or a resin-based glass ionomer, Vitrebond. The teeth were stored for 1 week, thermocycled, and the extent of coronal leakage determined for each group after immersion in Indian ink for 90 h. The teeth were demineralized, dehydrated and immersed in methyl salicylate which rendered them transparent. Linear measurement of dye penetration was recorded. The mean depth (+/- SD) of leakage for the groups in which the smear layer was left intact was 4.26 +/- 1.53 mm and 6.83 +/- 1.65 mm for the Vitrebond and Tubliseal, respectively. When the smear layer had been removed, the mean depth of leakage for the Vitrebond group was 1.13 +/- 0.29 mm, and 3.72 +/- 1.23 mm for the Tubliseal group. There was a statistically significant difference in leakage between the groups (P < 0.001). With both sealers, those teeth in which the smear layer had been removed showed less leakage than the specimens in which the smear layer was left intact (P < 0.001).(ABSTRACT TRUNCATED AT 250 WORDS)

Fifty-one extracted human first molar teeth with intact crowns and mature root apices were divided into three groups. Root curvature was determined. One of the root canals in the mesial root of lower molars, or the mesiobuccal root in maxillary molars, was prepared in one of three ways. In group 1 the root canals were instrumented using a modified double-flared technique with noncutting tipped files (Flex R); in group 2 the same files were used with a step-back technique. Group 3 was prepared with conventionally tipped files (K-Flex) using the step-back technique. A low viscosity polyvinyl siloxane impression material was injected into the prepared root canals and the specimens were decalcified, dehydrated, and cleared. The preparation was evaluated subjectively according to various desirable or undesirable criteria. A rating for overall quality of preparation was given. Statistical analysis showed that the teeth in group 1 had better overall preparation than those in group 3 (p < 0.05). There were no other statistically significant differences between the groups. The mean time required for each preparation technique was not statistically significantly different (p > 0.1). The use of a modified double-flared technique with non-cutting tipped files was shown to be an effective method for the preparation of curved root canals.

Considerable preparation, planning and detailed organization are necessary if endodontic 'hands-on' courses are to be stimulating and worthwhile for participant and teacher alike. Projection facilities, lighting, seating and working surface requirements must be checked immediately on arrival at the venue. The format, although flexible enough to allow for the wide range of knowledge and practical ability found within any one group, must adhere to and stress the current fundamentals in endodontic teaching. Not only can information and skill in diagnosis, root canal preparation and obturation be taught in a 'hands-on' format, but rubber dam isolation techniques can also be practised very successfully. Tutors must be prepared to demonstrate personally their clinical ability and experience of principles and techniques taught during the course. Post-course feedback can be an extremely useful means of ensuring that 'hands-on' courses are relevant, with the appropriate practical emphasis required by the general dental practitioner, as well as the necessary stress on endodontic principles.

The effect on the apical seal of root filling teeth with two sealer cements that reacted chemically with tooth structure was studied in vitro. In addition, apical leakage of teeth obturated with these materials and subsequently prepared to accept a post was tested. Ninety single-rooted teeth with mature apices were prepared chemomechanically by the stepback technique using files and copious irrigation with 2.5 per cent sodium hypochlorite. The teeth were then randomly allocated to six groups of 15 teeth each. Two groups were root filled by lateral condensation of gutta-percha and one of three sealer cements: Tubliseal, a radiopaque glass ionomer luting cement, Ketac Cem, and a chemically active composite resin, Panavia Ex. Thirty minutes later, in one group for each material, a post space was prepared leaving 4-5 mm of root filling at the apex. The extent of apical leakage in each group was determined after immersion in Indian ink for 14 days. The teeth were demineralized, dehydrated and immersed in methyl salicylate, which rendered them transparent, and a linear measurement of dye penetration was recorded. No statistically significant difference in the extent of leakage was found between the sealers in those groups which were filled by lateral condensation and left intact. However, the degree of leakage increased after post space preparation with the glass ionomer and Tubliseal groups, but was reduced in the Panavia Ex group.

An in vivo investigation is described and a histological evaluation made of the effect of canal obturation by thermomechanical compaction of gutta-percha and sealer on the cementum on the lateral surface of the root and adjacent periodontal membrane and alveolar bone of the ferret canine after time intervals of 24 hours, 20 days and 40 days. These tissue reactions were compared with those in the roots of control teeth filled by lateral condensation of cold gutta-percha and sealer. Iatrogenic damage was apparent in a minority of the experimental specimens 20 and 40 days after obturation.

Temperature elevations of 10 degrees C above body temperature, of duration greater than 1 minute, may be sufficient to cause bone tissue injury. Temperature rises on the root surface in excess of 10 degrees C have been shown in studies in vitro of thermoplasticized gutta-percha root filling techniques. To determine whether results in vitro at room temperature could be extrapolated to conditions in vivo, temperature elevations were recorded at the mid-point on the root surface of the canine tooth in the ferret during thermomechanical compaction of gutta-percha. The time taken for the temperature to return to normal was also measured. There was no statistically significant difference between temperature elevations recorded in vitro and those measured in vivo. A linear extrapolation may therefore be made from results recorded at room temperature. Temperature elevations dissipated more rapidly in vivo than in vitro; this may be due to the cooling effect of the microvasculature of the periodontal membrane.

From the many types of laser that are available commercially, the CO2 laser is presently thought to have the greatest potential for use in dentistry. An outline of the generation of emitted radiation from such a laser is given together with a review of work previously carried out and reported in the literature regarding application to the teeth. The main points of interest are the effects of radiation on the enamel and dentine, but concern is felt towards the possible iatrogenic damage of thermal origin that may occur within the pulp following irradiation of the dental tissues.

An investigation is described that attempts to establish, in vitro, the characteristics of heat transference following laser irradiation of bovine dentinal tissue and the relationship with the periodicity of radiation. The results of this study appear to indicate that at depths of overlying dentine of up to 3 mm, laser-induced thermal injury to the pulp is a definite possibility. Fail-safe facilities to prevent build up of heat must be incorporated into the design of dental lasers to allow their beneficial effects to be utilized without the risk of iatrogenic damage.

The leakage associated with restorative materials placed within the pulp chamber of maxillary and mandibular molars was studied in vitro. The root canals and pulp chambers of 69 extracted teeth were prepared chemomechanically and sealed with gutta-percha and Tubliseal using cold lateral condensation. The teeth were divided into five groups. Gutta-percha was removed from the pulp chambers of three of the groups of 15 teeth and filled with one of three materials, a glass ionomer cement, a cermet cement or an amalgam. The gutta-percha was removed from the pulp chamber in the fourth group of nine teeth, which were left unfilled. The gutta-percha in the pulp chambers of the fifth group of teeth was left intact. The teeth were suspended in Indian ink, thermocycled for 24 hours and stored for a further 48 hours at 37 degrees C. They were then demineralized and cleared and the degree of coronal leakage was assessed. Those teeth with no filling in the pulp chamber showed extensive leakage. The gutta-percha-filled group demonstrated greater leakage than did the groups in which other restorative materials had been employed (P less than 0.01). No significant differences in leakage occurred between the other groups (P less than 0.05). It is recommended that the pulp chamber of molars should be restored with a filling material following root canal treatment.

The purpose of the present study was to assess the effect of compactor design, alterations in rotational speed and modification to the basic technique of thermomechanical compaction on the quality of the apical seal produced by gutta-percha and sealer cement. The integrity of the apical seal achieved using two different configurations of compactor, rotational speeds of 8000 and 16,000 rev/minute and a hybrid technique which combined thermomechanical compaction with lateral condensation were compared with conventional lateral condensation. The same brand of gutta-percha and type of sealer were used throughout the investigation. A cleared tooth technique that allowed the three-dimensional assessment of Indian ink leakage was employed. Instrument fracture, a problem experienced in some other investigations, did not occur with either design of compactor used. Apical dye leakage was found to be a relatively frequent occurrence with each variation in obturation technique studied, including that of lateral condensation of cold gutta-percha and sealer. The results showed no significant difference in the mean degree of leakage for each of the groups or in the proportion of specimens that showed leakage (P greater than 0.1). The advantages of the hybrid method of root canal obturation were discussed.

The heat generated on the external root surface of human premolar teeth during post space preparation was measured in vitro. The rise in temperature was recorded at a point 6 mm from the apex of the tooth using a thermocouple attached to a chart recorder. The temperature rise was greatest when the removal of gutta-percha was combined with post channel preparation. Temperature rises of up to 31 degrees C were recorded. Instruments that only removed gutta-percha did not generate the same amount of heat. The results from this study suggest that the use of engine-driven drills to prepare post channels in teeth may generate temperature rises that may cause periradicular tissue damage, and caution should be exercised during their use.