'satisfactory smile' with a restorative approach - Indian Dental ...

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IMAGE 2010-11 ISSN: 2229-5658 Vol No: 11 ISSUE No: 4 39 question is how reliable and accurate these methods are in calibrating the exact WL. In view of the possible variation between the radiographic apex, anatomical apex and apical foramen, this in vitro study was done to evaluate the accuracy of Raypex5 (VDW, Munich, Germany) electronic apex locator (EAL) in determining the RCL in comparison to conventional radiography and RVG. Materials and Methods Forty single rooted anterior teeth exhibiting normal and mature root condition were used in this study. For RCL measurement by conventional radiography the specimens were directly positioned on a geometrically standardized support equipped with a horizontal goniometer (Fig. 1). As a result, it was not necessary to rotate the X-ray tube since the tooth could be turned to directly select the horizontal position of the X-ray beam with respect to the specimen. X-ray cone position was standardized with the use of XCP Rinn fixed to the X-ray tube so that the X-ray film was perpendicular to the beam at all times (Fig. 1). In order to ensure centered and reproducible positioning of the teeth, a coronal reference point was marked by making ditch cut on labial surface (2x5x2 mm) and filled it with amalgam. All the specimens were kept at a constant distance of 10 mm from the X-ray film and 50mm from the X-ray cone (Fig. 1). Tooth localization was always referenced to calibrated graph paper, to allow Xray cone positioning parallel to the paper lines. After all these standardization, preoperative Xray images with size zero intraoral periapical film (Kodak, Rochester, NY, USA) were obtained and developed with an automatic Periomat device (D¸rr Dental GmbH & Co. KG, Bietigheim-Bissingen, Germany). Preoperative digitized X-ray images were also taken in the same approach but by replacing a size zero IOPA film with a same size sensor (eva with proimage Æ , DENT.X, Elmsford, NY, USA). On the sensor, 10mm premeasured metal wire was fixed with the help of cello tape for giving precaliberation measurements of digitized images. Digital vernier caliper (Sankin, Mitutoyo Co., Kanagawa, Japan) with accuracy to the nearest 0.01mm was in turn used to obtain measurements of each specimen from all the preoperative X-ray images by viewing them on viewerís box. RVG provided calibrated measurements between different points in a given image and the maximum radiovisiographic length of each sample was recorded by calibrating the device for each projection. Maximum preoperative root length of both conventional and digitized images was recorded by measuring the distance between the incisal edge and the radiographic apex. Standard access preparation was carried out and the root canals were located. Measurement of actual root canal length (ARCL) was calculated by inserting a size 15 Kfile into the canal until the tip of the file was just visible at the level of apical foramen under 2.5x-420 magnifying loupes (Galilean loupes Æ , Lifecare Medical Equipments Co., Ltd., Zhejiang, China). A rubber stopper was then carefully adjusted to the reference level, file was removed and the distance between the rubber stopper and the file tip was measured and recorded with a digital vernier caliper to the nearest 0.01mm. Electronic measurement of RCL was calculated for each specimen using Raypex5 apex locator by four blinded observers. In order to reproduce clinical conditions involved in the electronic measurement of root canal length, each specimen was mounted in alginate 6 . The relative stiffness of the alginate mould prevented fluid movement inside the canal that is responsible for premature electronic reading registered with previous models 7,8 . All measurements were made within 2 hours of the model being prepared in order to ensure the alginate was kept sufficiently humid 9 . The labial clip of the Apit device was in contact with the alginate at all times (Fig. 2). Each canal was irrigated with 3% sodium hypochlorite and size 15 K-file attached to the instrumental clip was inserted into the root canal till the red mark was visible on the screen of apex locator. The red mark indicated the position of the apical foramen. Point at which red mark was seen the rubber stopper was adjusted to the reference level, file was taken out and its length was Visit: http://image.idakunnamkulam.com/ The International Journal of Indian Dental Association, Kunnamkulam Branch. Indexed in Journals Master List of IC TM
IMAGE 2010-11 ISSN: 2229-5658 Vol No: 11 ISSUE No: 4 40 measured with the help of digital vernier caliper. The tooth was demounted and file was reinserted with rubber stopper adjusted at the measured electronic length. The tooth was again mounted on the adjustable jig and radiographic images with file were taken by conventional radiograph and RVG. Now the position of the file at its tip was noted and recorded similarly as done before. If it was at the apex it was recorded as ì*î, if file tip is 0.5 mm beyond the apex it was designated as ì+îand if it was 0.5mm short of apex it was designated as ì-î.Measurements within ± 0.5 mm of the apical foramen were considered acceptable 7,19 . Statistical analysis Data were analysed using the one-way analysis of variance (ANOVA) and Cronbachís alpha-reliability analysis to compare between different blinded observers. Student pair t-test was used for comparison between different groups. Statistical significance was considered to be P ≤ 0.05. The statistical analysis was carried out with SPSS version 11.5 software (SPSS Inc., Chicago, USA). Results In this study, RCL obtained by conventional radiography and RVG when compared to ARCL using Student pair t-test, significant difference (P=0.00) was observed (Table 1). Mean of the RCL obtained from four different blinded observers with Raypex5 apex locator, when compared with ARCL no significant difference was found (P= 0.719) (Table 1). Also no significant difference was seen when comparison was done within four different observers (P=1.00). The reliability coefficient among them was found to be 0.9929, which indicates very good agreement among them (Table 2). Evaluation of the position of file with respect to the apical foramen was based on the distance from file tip to apical foramen. Measurement was regarded as correct or incorrect when this distance was under or over 0.5 mm in absolute terms (Table 3). From the data obtained, conventional radiograph showed accuracy in 72.5% of cases (i.e. within ± 0.5 mm of the apical foramen), 25% fell short of ñ0.5 mm, and 2.5% exceeded +0.5 mm. With respect to RVG, 85% of cases showed to be within the acceptable range (i.e. within ± 0.5 mm of the apical foramen), 10% fell short of ñ0.5 mm, and 5% exceeded +0.5 mm. In turn, Raypex5 EAL provided good measurements in 90% of cases (i.e. within ± 0.5 mm of the apical foramen), 2.5% fell short of ñ0.5 mm, and 7.5% exceeded +0.5 mm. Discussion Based on the two possible points for terminating instrumentation, i.e. the CDJ and the apical foramen, it should be taken into account that systematic working to the apical constriction entails the risk of leaving tissue remains within the apical region; as this tissue may be diseased, treatment may fail. In contrast, over-obturation can result using the radiographic apex as reference. Most experts agree that the WL should terminate at the CDJ which is usually found about 0.5-1mm short of the radiographic apex 2,10 . However CDJ is a histological term and microscope is needed to find it. Clinically this is not practical. In this sense, we considered the apical foramen to be an appropriate reference and moreover no welldefined apical constriction has been clearly confirmed in all root canals. Different studies that have compared digital and conventional radiography and has considered the reliability of the former technique in measuring working length to be equal or even superior to that of conventional radiography 1,11,12,13 . Similarly, experience accumulated over the years clearly confirms the reliability of EALs. Various studies 14,15,16,17,18,19 have reported the accuracy of EALs to be between 80 to 95% , whereas some have even found radiographic better than EAL 20 . This large variation is due different type of EALs. According to the manufacturer, Raypex5 apex locator is based on the principle that impedance measurement not only differs between two electrodes depending on the frequencies used, but also differs greatly Visit: http://image.idakunnamkulam.com/ The International Journal of Indian Dental Association, Kunnamkulam Branch. Indexed in Journals Master List of IC TM
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