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 Table of Contents  
Year : 2012  |  Volume : 4  |  Issue : 6  |  Page : 285-289  

Direct digital radiography versus conventional radiography - assessment of visibility of file length placed in the root canal: An in vitro study

1 Department of Conservative Dentistry, Vivekanandha Dental College for Women, Tiruchengode, India
2 Private Practitioner, Tamil Nadu, India

Date of Submission01-Feb-2011
Date of Decision02-Jan-2012
Date of Acceptance26-Jan-2012
Date of Web Publication28-Aug-2012

Correspondence Address:
Vaiyapuri Ravi
Department of Conservative Dentistry, Vivekanandha Dental College for Women, Tiruchengode
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Source of Support: None, Conflict of Interest: None

DOI: 10.4103/0975-7406.100274

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Aim and Objective: To compare conventional and direct digital radiography (DDR) in working length measurement of the root canal and to assess the significance of the different enhancement modes provided by the software to visualize the file length. Materials and Methods: Access cavities were prepared in 30 extracted maxillary central incisors. Size 15 k-file was introduced into the canal till it was flush with the apical foramen. The working length was calculated as 0.5 mm less than the vernier caliper measured length of each file. The files were then sealed with resin at their respective lengths. Intraoral periapical radiographs and direct digital radiographs were taken. Vernier caliper was used to measure the file length in the periapical radiographs, and standard, positive conversion, and colorize modes were used with the CDR system. A multiple regression analysis was conducted to give an accurate analysis between the actual file length and the different groups. Results: There was no statistical significance between the different groups tested. The multiple regression analysis test showed that the positive and colorize modes more accurately corresponded to the actual file length. Conclusion: Both conventional radiography and DDR can be reliably used for working length determination. The positive and colorize modes enhancement features of DDR greatly improve the visual perception, leading to more accurate measurements.

Keywords: Colorize mode, conventional radiography, direct digital radiography, filmless radiography, positive mode

How to cite this article:
Ravi V, Lipee P, Rao CN, Lakshmikanthan L. Direct digital radiography versus conventional radiography - assessment of visibility of file length placed in the root canal: An in vitro study. J Pharm Bioall Sci 2012;4, Suppl S2:285-9

How to cite this URL:
Ravi V, Lipee P, Rao CN, Lakshmikanthan L. Direct digital radiography versus conventional radiography - assessment of visibility of file length placed in the root canal: An in vitro study. J Pharm Bioall Sci [serial online] 2012 [cited 2022 Aug 15];4, Suppl S2:285-9. Available from:

Endodontic therapy in recent times has become more exacting and sophisticated owing to developments in materials and techniques. A single critical factor in achieving success in endodontic therapy is the accurate determination of length of the tooth before radicular preparation. [1] The radiograph has been the most important aid for calculating root canal working length in addition to providing information [2] such as size, shape, and the number of root canals.

The current progress in this field is being channeled toward reducing the exposure time and obtaining immediate digital images. [3] Direct digital radiography (DDR), which was introduced in 1987 by Dr. Francis Mouyen, [4] has shown potential benefits in radiology. High-resolution computer monitor images are instantaneously produced with reduced radiographic exposure. The DDR systems provide the ability to electronically manipulate the digitized image stored in the computer. The operator can enhance the image by changing the contrast and brightness of the image without additional radiation exposure to the patient. The image may also be enlarged and color can be enhanced selectively improving the area of visual interest. The radiation dose [5],[6] has been reported to be 59-77% less than that of conventional radiographic techniques.

The DDR system consists of a conventional X-ray generating device that replaces the radiographic film and hence the term "filmless radiography." The capturing device is a charge-coupled device (CCD) connected directly to a computer by a cable, and once exposed, it produces an almost instantaneous image. The accompanying software allows manipulation of the radiographic image in the monitor. These include zoom facility, change of contrast, brightness, negative to positive conversion, coloring the image, double and multiple clicks in measuring the file length, and grid facility.

The aim of this in vitro study was to compare conventional radiography and DDR in visualizing the file length placed in the root canal. This study also aimed at assessing the significance of the different enhancement modes provided in the software to visualize the file length.

   Materials and Methods Top

The present study was conducted on an in vitro model using 30 maxillary central incisors which were recently extracted. The criteria for selection of the teeth were teeth with matured root apices and patent root canals. The extracted teeth were cleaned free of debris and standard access cavities were prepared using high-speed handpiece with diamond abrasive points. Pulp extirpation was done using a barbed broach. A size 15 k-file was then introduced into the canal until it was flush with the apical foramen. The length was measured using vernier calipers after which the working length was calculated as 0.5 mm less than the actual length. The actual working length was calculated using a vernier caliper [Figure 1]. All these procedures were done using an operating microscope under 8 × magnification (Carl-Zeiss Meditec, Jena- Germany). The file was then sealed in place with self-curing composite resin, with the stopper touching the incisal edge as the reference point. The teeth were then embedded in acrylic using a mold. These standardized acrylic blocks had a dimension of 1 × 1 × 2.5 cm [Figure 2].
Figure 1: Vernier caliper

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Figure 2: Teeth samples mounted in acrylic resin blocks

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The distance from the subject to the radiographic film/sensor was maintained at 0.5 cm. The distance of the X-ray tube head to the subject was maintained at 2.5 cm [Figure 3]. The intraoral periapical radiographic film used was Ekta speed plus films (Eastman Kodak, Rochester, NY, USA) [Figure 4].
Figure 3: Custom made direct digital radiograph sensor in position

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Figure 4: Direct digital radiograph sensor and radiographic film

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The DDR system used was Schick Technologies CDR System (Schick Technologies Inc., Long Island, NY, USA). This system consists of an intraoral sensor which is a CCD attached to the computer by means of a cable. The other components of the system are a computer monitor and a thermal printer. Computer requirement for the CDR system includes a Pentium-based PC, a minimum of 32 MB RAM, 1 GB of free hard disk space, and windows 98 software. The X-ray machine used was the Explor X-70 (Villa sistemi Medicalli, Buccinasco, Italy). The unit operates on 220 V AC and 4 A. The kVp is 70 and mA is 8.

The acrylic blocks were placed in the standardized model and the Ekta Plus film was exposed for 0.3 seconds at 70 kVp. Later, the intraoral sensor was placed in the model and exposed for 0.1 seconds at 70 kVp. Once the X-ray unit is activated, the digital radiographic image is displayed within 4 seconds on the computer monitor.

The exposed films were processed in an automatic processing unit (RR Periomat) using fresh chemicals according to manufacturer's instructions. The processed X-rays were viewed on an X-ray lobby and the length was measured using the vernier caliper from the rubber stopper to the file tip.

The CDR system has three different modes - standard, positive conversion, and colorize modes. In all these three modes, the brightness/contrast can be adjusted. Measurements were made for these three different modes separately. The brightness/contrast and color were adjusted so as to get maximum clarity of the file.

The groups formed were: Group 1 - radiographic working length [Figure 5]; Group 2 - DDR system, using standard image [Figure 6]; Group 3 - DDR system, using positive conversion [Figure 7]; and Group 4 - DDR system, using colorized image [Figure 8].
Figure 5: Conventional radiograph

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Figure 6: Standard mode-direct digital radiograph

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Figure 7: Positive mode- direct digital radiograph

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Figure 8: Colorised mode-direct digital radiograph

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   Results Top

[Table 1] shows the mean and standard deviation of the values obtained using different methods. The mean and standard deviation values of the groups showed minimum difference when compared with the actual length. A Student's t-test was performed comparing the different groups. It showed no statistical significance between the different groups tested.
Table 1: Mean and SD of the values obtained using different methods

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A multiple regression analysis was conducted taking the actual length as the dependable variable and the other groups were tested as independent variables and the results are shown in [Table 2]. The results of the multiple regression analysis show that the values of the positive and colorize modes were highly related to each other when compared to the other groups.
Table 2: Multiple regression analysis

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   Discussion Top

The success of an endodontic therapy depends on a good access cavity preparation, location of all the canals present, thorough cleaning and shaping, and a three-dimensional obturation. Determination of the accurate working length of the tooth is one of the most important procedures in root canal therapy.

The significance of these procedures is the following:

  1. The calculation determines how far into the canals the instruments are placed and worked.
  2. It will limit the depth to which the canal filling may be placed.
  3. It will affect the degree of pain and discomfort the patient will feel following the appointment.

Since the first dental radiograph was taken in 1896, radiographs [7] have become an essential part of dental practice. Though the sensitivity of radiographs has been increased over the years to a very high degree, silver halide based film emulsions have two major disadvantages - a fairly high radiation dose is needed and the film processing interrupts treatment.

In the late seventies, a new technology, the CCD, was developed for video applications. CCD detectors were proposed for radiographic imaging. Most investigations, however, used CCD detectors at photon energies below 20 kV. It was generally appreciated that the low quantum efficiency of CCD detectors at photon energies greater than 20 kV disqualified them from use as direct detectors of X-ray radiation. To circumvent this problem, a combination of CCD detectors with scintillators for energy conversion from X-ray radiation to light was suggested. In 1987, an intraoral radiographic imaging system, radiovisiography (RVG; Trophy Radiology, Toulouse, France), developed by Dr. Francis Mouyen, [8] was introduced in the international market. Since this was the first system introduced in the market, the term RVG became synonymous with the term DDR.

The image capturing devices are either of the following:

  1. A CCD connected directly to the computer by a cable, and once exposed to X-ray radiation, it produces an almost instantaneous image.
  2. A photo-stimulating phosphor image plate: After exposure, this is placed in a reader and scanned by a laser beam releasing the contained information to the computer for the creation of the image.

The main advantages of the system [9] include the following:

  1. Elimination of chemical processing and associated errors.
  2. Reduction in radiation dose.
  3. Computer storage and archiving of patient information.
  4. Transfer of images electronically.
  5. Image enhancement and manipulation.

The main disadvantages [10],[11] include:

  1. Cost,
  2. Reduced resolution,
  3. Quality of hard copy prints,
  4. Image storage,
  5. Image security,
  6. Limited size of sensor available,
  7. Lack of sensor flexibility, and
  8. Lack of training at both undergraduate and postgraduate levels.

Walton and Torabinejad in 1989 suggested that an ISO size 10 file or less is not adequate for working length determination because the file tip appears to fade out and is usually not visible on radiographs. Other influencing factors that can affect the clarity of the file at the root tip are selection of optimal exposure time, the effects of scattered radiation, superimposition of trabecular bone pattern, bone processes, roots, and differences in bone density. A system which will overcome these potential problems and allow for visualization of small endodontic file tips would be of great advantage. The purpose of this study was to compare DDR and conventional radiography in visualizing the file length.

The results from the conventional radiographs and DDR modes show that there is a minimal increase in the file length (<0.5 mm). According to Vajrabhaya, [12] the working length measurements in the range of -1 to +0.5 mm were considered to be clinically acceptable. In this study, it was noted that the values of the positive and the colorize modes were the best owing to the enhancement features present. In these modes, the file and the surrounding structure are presented in different colors which enhance the visual perception unlike the standard mode where they are nearly of the same color.

The singular purpose of radiographic capturing device, whether it is the DDR sensor or the conventional film, is to capture the X-ray photon density pattern as it emerges from the subject tissues. The photon dispersion pattern that emerges from the tissues is a function of the tissues and the radiation source. Since the X-ray photons cannot be focused into a sharp image as light can be focused through a camera lens, the image captured by a conventional film or the DDR sensors will never have a crisp, in-focus appearance like a photograph focused through a lens. Radiographic images will always be subject to a certain degree of geometric unsharpness, thereby limiting the resolution of the image that can be captured.

An area that can be improved is the ability to capture the emerging photon pattern accurately. This is a function of the size of the sensor's capture units. Smaller capture units add more resolution, and hence more detail to the image. The capture units of the conventional and the radiographic emulsion films are essentially the grain size of the film. Faster films have larger grain size that results in loss of image sharpness. This is one of the main reasons where DDR systems stand a step ahead of the conventional radiography systems.

   Conclusion Top

In endodontic practice, for working length determination, both conventional radiography and DDR can be reliably used, provided the ISO file size used in case of conventional radiography is size 15 or greater. The enhancement feature of DDR greatly improves the visual perception, leading to more accurate measurements. The positive and colorize enhancement modes were found to be more closely associated with the actual file length than the other groups.

   References Top

1.Ingle J, Barkland: Ingle's Endodontics. 3 rd ed:BC Decker: Hamilton, Ontario, Canada; 2002.  Back to cited text no. 1
2.Weine FS; Endodontic Therapy. 3 rd ed. Mosby, St. Louis, Missouri; 1982.  Back to cited text no. 2
3.Nelvig P, Wing K, Welander U. Sens-A-Ray: A new system for direct digital intra-oral radiography. Oral Surg Oral Med Oral Pathol 1992;74:818-23.  Back to cited text no. 3
4.Horner K, Shearer AC. Radiovisiography, an initial evaluation. Br Dent J 1990;168:244-8.  Back to cited text no. 4
5.Whaites E, Brown J. An update on dental imaging. Br Dent J 1998;185:166-72.  Back to cited text no. 5
6.Mouyen F, Benz C, Sonnabend E, Lodter JP. Presentation and physical evaluation of radiovisiography. Oral Surg Oral Med Oral Pathol 1989;68:238-42.  Back to cited text no. 6
7.Benz C, Mouyen M. Evaluation of the new radiovisiography system image quality. Oral Surg Oral Med Oral Pathol 1991;72:627-31.  Back to cited text no. 7
8.Horner K, Brettle DS, Rushton VE. The potential medico - legal implications of computed radiography. Br Dent J 1996;180:271-3.  Back to cited text no. 8
9.Bruder GA, Casale J, Goren A, Friedman S. Alteration of computer dental radiography images. J Endod 1999;25:275-6.  Back to cited text no. 9
10.Vajrabhaya L, Tepmongkal P. Accuracy of apex locators. Endod Dent Traumatol 1997;13:180-2.  Back to cited text no. 10
11.Shearer AC, Horner K, Wilson NH. Radiovisiography for length estimation in root canal treatment: An in vitro comparision with conventional radiography. Int Endod J 1991;24:233-9.  Back to cited text no. 11
12.Burger CL, Mork TO, Hutter JW, Nicoll B. Direct digital radiography versus conventional radiography for estimation of canal length in curved canals. J Endod 1999;125:260-3.  Back to cited text no. 12


  [Figure 1], [Figure 2], [Figure 3], [Figure 4], [Figure 5], [Figure 6], [Figure 7], [Figure 8]

  [Table 1], [Table 2]

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