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 »  Home  »  Endodontic Articles 7  »  In vitro comparison of root-canal measurements with conventional and digital radiology
In vitro comparison of root-canal measurements with conventional and digital radiology
Materials and methods.



A total of 70 teeth extracted for orthodontic and periodontal reasons and obtained from different sources with or without caries were studied. The teeth were kept in 37% aqueous formaldehyde solution with 10% methanol. There were five teeth corresponding to each tooth type from both jaws: central and lateral incisors, canines, fifirst and second premolars, and fifirst and second molars. A digital CCX 70 kVp and 8 mA  X-ray generator (Trophy Radiologie, Vincennes, France) with DF58 radiographic film (Eastman Kodak Company, Rochester, NY, USA) was used. Two digital radiological systems were also selected.( a) Radiovisiography (RVG 4,Trophy), consisting of a computer, monitor and software (Trophy 97) under MS Windows 95 to visualize, modify and store the image obtained, and a sensor (HDS, with a resolution of 12 pixels mm_1). The corresponding image appeared on screen in manual format and could be modified in terms of contrast brightness and magnification.(b ) PSP system (Digora, Soredex, Orion Corporation, Helsinki, Finland), consisting of a computer, monitor and software (Digora1.51) under MS Windows 95, with a scanner and reusable imaging plate. The standard plate was used with a resolution of 6 pixels mm_1.The corresponding image appeared on screen and could be modified in terms of contrast, brightness and magnification.
An apparatus with tooth-positioning and angle-measurement functions was used that was similar to a device assessed previously (Forsberg1987). The teeth were positioned in a geo metrically standardized support incorporating a horizontal goniometer. A s a result, it was not necessary to rotate the X-ray tube; rather, the tooth supporting post was turned, and the appropriate horizontal grading of the X-ray beam with respect to each tooth was selected directly.
Anautomatic Periomat developer (Durr Dental GmbH & Co., Bietigheim-Bissingen, Germany) was used to ensure uniform development of the conventional fifilms.
Access cavity preparation was carried out using a round diamond bur 801/014 (Komet, Lemgo, Germany) and the canals were located with a probe. K-Flexofifile Colorinox instruments (sizes 08,10 and15; Dentsply Maillefer, Ballaigues, Switzerland) were used. The root-canal lengths were assessed by placing each file size inside the canal; the working length was recorded when the tip of the file was seen at the apical foramen. Conventional radiography, RVG and PSP systems were used in turn with the teeth positioned on the supporting post. In order to ensure reproducible and centred tooth positioning,  marks were made in the centre of the buccal and proximal surfaces of the teeth, coinciding with marks on the supporting post. The X-ray cone was in turn placed on a support to allow exact parallel alignment with the dental support both horizontally and vertically. In order to keep the film perpendicular to the beam at all times, an XCP radiographic support (Rinn Corporation, Elgin, IL, USA) was used fifixed to the X-ray tube. The PSP system plate was positioned in the same way, whilst the RVG sensor was fifixed with elastic bands. Two projections were used for each tooth (08 and 208 mesial). The horizontal angle was modified by turning the goniometer and hence also the supporting post; the vertical angle was directly selected from the X-ray tube (908). In all cases a distance of 5 cm was established between the X-ray source and the specimen, with 1 cm between the latter and the fifilm or sensor.
The distance from the file tip to the radiographic apex was measured, recording the values as positive, zero or negative (i.e. beyond the apex, at the apex, and short of the apex). In the case of the conventional film images the measurements were made directly on the film when assessed on a X-ray viewer and under 6_magnification using a Diastar 200 slide viewer (Osram, Austria). In the case of the digital systems, measurement was carried out by calibrating the apparatus for each projection by placing a wire of known length alongside the specimen support post. The RVG measurements were made of the original image and also of the 100% magnified image. The same approach was used with the Digora system by using a maximum magnification of 200%. All the measurements were made by a trained observer.
The percentage of concordance and the Cohen’s kappa test of the grading system (through, at, short of apex) were used to determine agreement between two different techniques, eliminating the coincidences attributable to chance. Intra observer error was assessed by re-reading a random sample of10% of the teeth. The percentage of concordance between the two group of measurements was evaluated in order to determine the reproducibility of the results.