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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.

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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.

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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.

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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.

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OBJECTIVE: To examine the periradicular status of crowned teeth in an adult population in Scotland. DESIGN: Examination of full-mouth periapical radiographs from 319 consecutive adult patients (7596 teeth) attending Glasgow and Dundee Dental Hospitals for clinical examination. METHODS: The periradicular status of teeth with a crown present was assessed to determine the presence of a radiolucency which may indicate pulpal disease. RESULTS: 63.3% (n = 202) of patients had at least one tooth that was crowned. The total number of crowns assessed was 802, of which 458 (57.1%) were vital preparations, and 87 (19.0%) of these had radiographic signs of periradicular disease. The majority of the teeth (62.0%) had distinct widening of the periodontal membrane space which is considered to be an early sign of periapical disease. 42.9% (n = 344) of the crowned teeth had previous root canal treatment of which 50.8% (175) had evidence of a periradicular radiolucency. CONCLUSIONS: Pulpal damage may occur during procedures to provide a crown which may require subsequent root canal treatment. Radiographic follow-up of crowned teeth should be undertaken routinely.

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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.

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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.

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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.

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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.

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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.

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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).

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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).

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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.

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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).

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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)

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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).

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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.

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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.

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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).

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