|Year : 2016 | Volume
| Issue : 1 | Page : 15-19
Effect of different levels of sharpness processing filter on the measurement accuracy of endodontic file length
Nastaran Farhadi1, Ali Shokraneh2, Masoud Saatchi3
1 Department of Oral and Maxillofacial Radiology, School of Dentistry, Physiology Research Center, Ahvaz Jundishapur University of Medical Sciences, Ahvaz, Iran
2 Department of Endodontics, Kashan University of Medical Sciences, Kashan, Iran
3 Torabinejad Dental Research Center, Department of Endodontics, Isfahan University of Medical Sciences, Isfahan, Iran
|Date of Web Publication||24-Feb-2016|
Department of Endodontics, Kashan University of Medical Sciences, Kashan - 8114787137
Source of Support: None, Conflict of Interest: None
Introduction: The present study was undertaken to evaluate the effect of different levels of sharpness processing filter on the accuracy of endodontic file length determination using digital periapical radiography. Materials and Methods: Forty human single-rooted permanent teeth were selected and International Organization for Standardization (ISO) #08 K-files were inserted into the root canals of the teeth. The file lengths were measured with a digital caliper as the gold standard. Digital periapical images were obtained using a phosphor storage plate as a detector. Three levels of sharpness tool of Scanora software program version 5.1 was used to produce enhanced images: Sharpen 1 (mild level), Sharpen 2 (moderate level), and Sharpen 3 (high level). Two radiologists and two endodontists measured file lengths on the original and enhanced images. The measurements were compared using repeated measures ANOVA and Bonferroni tests (α = 0.05). Results: There were no significant differences between the measurement accuracy of original images and that of the Sharpen 1 and Sharpen 2 enhanced images (P > 0.05). However, significant differences were found between the measurement accuracy of original and that of the Sharpen 3 enhanced images (P < 0.05). In addition, there were no significant differences among enhanced images processed by different levels of sharpness processing filter (P > 0.05). Conclusion: The application of mild and moderate levels of sharpness processing filter did not influence the accuracy of endodontic file length determination. However, high-level sharpness processing filter is not recommended due to its unfavorable effects on measurement accuracy.
Keywords: Digital radiography, endodontics, file, sharpness
|How to cite this article:|
Farhadi N, Shokraneh A, Saatchi M. Effect of different levels of sharpness processing filter on the measurement accuracy of endodontic file length. Dent Hypotheses 2016;7:15-9
|How to cite this URL:|
Farhadi N, Shokraneh A, Saatchi M. Effect of different levels of sharpness processing filter on the measurement accuracy of endodontic file length. Dent Hypotheses [serial online] 2016 [cited 2022 Aug 13];7:15-9. Available from: http://www.dentalhypotheses.com/text.asp?2016/7/1/15/177408
| Introduction|| |
Image processing is one of the main advantages of digital radiography. , Any procedure that changes the characteristics of digital images is called image processing. , The possibility of changing the image characteristics of conventional radiography is very limited. In contract, different types of image manipulations are possible in digital radiography. , Image processing is a computer-based procedure that changes the original electronic signal in order to suppress or enhance the specific details of images.  The basic aim of image processing is amplification of diagnostic signals and suppression of non-diagnostic signals. Unfortunately, some of the image data are lost during the processing. ,
Today, many image-processing techniques are available. Contrast inversion, noise reduction, magnification, edge enhancement, smoothing, and sharpening are some of the processing filters that are present in the majority of digital radiography software programs. ,, These filters are used in dentistry in order to facilitate image interpretation for diagnostic and treatment purposes. , The use of these filters is dependent on the demand, experience, and decision of the practitioner in different situations. ,, Although there is no standard method for use of image processing filters in certain diagnostic or treatment situations, task-specific use (for example, working length determination in endodontics) of processing filters is very important. 
The precise measurement of working length in endodontics can influence the final verification of the outcome of root-canal treatment, and consequently, enhance the potential of successful treatment. , In our previous studies, we evaluated the effect of some processing filters on the accuracy of endodontic file length in digital radiography. ,, We found that contrast inversion enhancement decreases the accuracy of endodontic file length determination in digital radiography, whereas noise reduction and magnification enhancements do not influence the accuracy of endodontic file length determination. ,, The aim of the present study was to evaluate the effect of different levels of sharpness processing filter on the measurement accuracy of endodontic file length in digital periapical radiography.
| Materials and Methods|| |
Following obtaining approval from the Ethics Committee of the Isfahan University of Medial Sciences (no. 391284), 40 extracted human single-rooted permanent teeth were used in this ex vivo study. The inclusion criteria consisted of intact crown and root and single-rooted and single-canal teeth, measuring 20-24 mm in length. Exclusion criteria were canal calcification, severe root curvature, root resorption, and other root malformations.
The teeth were prepared and radiographic images were obtained similar to our previous studies. ,, After tooth disinfection, the anatomic access cavity was prepared, and an International Organization for Standardization (ISO) #08 K-file was inserted into the root canal until the tip of the file was just visible at the apical foramen. The file length was measured with a digital caliper (Guilin Guanglu Measuring Instrument Co., Ltd., Guilin, China), and the file was shortened by 0.5 mm, which was set as the standard value for the endodontic file length. Only teeth with a length of 20-24 mm were included. After the insertion of the file into the root canal and fixation of it with Tetric Flow (Ivoclar Vivadent AG, Schaan, Liechtenstein), the tooth was placed in dental sockets of anterior region of a dry human lower jaw. For elimination of radiographic magnification, a 10-mm round orthodontic wire was placed in the adjacent dental socket and it was fixed with wax. A film holder was used to ensure that the teeth were radiographed at the same geometric situation. The standard geometric configuration was fixed at 30-cm source-to-object distance. Radiographic images of each sample were obtained with Digora storage phosphor plates (Soredex Corporation, Helsinki, Finland) and its special scanner, Digora Optime (Soredex Corporation), using a Prostyle dental x-ray unit (Planmeca OY, Helsinki, Finland) operating at 63 kVp, 8 mA, and 1.5-mm Al-equivalent filtration for 0.03 s. The digital images were numbered by the Scanora software program version 5.1 (Soredex Corporation, Helsinki, Finland) in a dimly lit room and saved in the Digital Imaging and Communications in Medicine (DICOM) format for further processing and analysis. The Sharpen 1 (mild level), Sharpen 2 (moderate level), and Sharpen 3 (high level) options of software program were used for each image and the resultant image was saved again in the same format [Figure 1]. Therefore, 120 enhanced images were obtained. Then, two experienced oral and maxillofacial radiologists and two experienced endodontists determined the endodontic file tip and the most apical portion of the rubber stop of each file in the original and enhanced digital images. They also determined the most coronal and apical points of the orthodontic wire in the adjacent dental socket. The fifth observer measured the endodontic file and orthodontic wire lengths by using the measurement tool of the software program. The magnification coefficient of each image was determined using real and radiographic orthodontic wire lengths measured by the digital caliper and software linear measurement tool, respectively. To eliminate the magnification effect of radiography, the obtained endodontic file length for each image was divided by the magnification coefficient. Then, the means of values determined by the radiologists and endodontists were taken as data.
|Figure 1: Example of (a) original, (b) Sharpen 1, (c) Sharpen 2, and (d) Sharpen 3 enhanced images|
Click here to view
Repeated measures ANOVA and the Bonferroni test were used to compare the standard value and radiographic file length with and without sharpness enhancement. SPSS software (SPSS Inc. Released 2007. SPSS for Windows, Version 16.0. Chicago, SPSS Inc.) was used for the analysis. The level of significance was set at 0.05. In addition, Cohen's kappa statistic was used to assess interobserver reliability.
| Results|| |
Repeated measures ANOVA indicated significant differences between the five groups (gold standard, original and enhanced images) (P < 0.05). Post hoc Bonferroni test showed statistically significant differences between the gold standard and each radiographic measurement group (original and enhanced images) (P < 0.05). There was a tendency to overestimate endodontic file length in all sets of digital images. Also, significant differences were found between Sharpen 3 enhanced and original images (P < 0.05). There were no significant differences between the original image and the other enhanced images (Sharpen 1 and Sharpen 2) (P > 0.05). In addition, there were no significant differences between images processed by different levels of sharpness filter (P > 0.05). Enhanced images exhibited longer measurements compared to original images. The results were summarized in [Table 1]. Interobserver reliability assessment using Cohen's kappa revealed a kappa value of 0.81. No significant differences existed between measurements made by endodontists and radiologists (P > 0.05).
| Discussion|| |
Working length determination is a vital step in root-canal treatment. , The accuracy of working length determination can influence the outcome of the root-canal treatment. , Several methods are used to measure it accurately, including digital radiography.  One of the main advantages of digital radiography is the manipulation of images with a processing filter, such as sharpness, to facilitate image interpretation. , Sharpness processing filter improves the image clarity by making the edges more clear and distinct. ,, On the other hand, the use of this filter may increase the noise level on the image and consequently compromise radiographic diagnostic quality.  Wenzel et al.  demonstrated that observers preferred the sharpness processing filter rather than other filters for evaluation of dental disease. In addition, Raitz et al.  showed that the most frequently used processing filter among experienced and nonexperienced observers is sharpness. In the present study, the effect of different levels of sharpness processing filter on the accuracy of working length determination was evaluated.
The results of the present study showed no significant differences between enhanced images with Sharpen 1 and Sharpen 2 processing filters and original images. This is in accordance with the results of a study performed by Kal et al.  They showed that the processing of the image obtained by Digora photostimulable phosphor plate (Soredex, Helsinki, Finland) with sharpness filter of Scanora software did not influence the working length determination of #08, #10, and #15 K-files inserted into teeth mounted in acrylic blocks. Moreover, they reported that the enhanced images tend to underestimate the endodontic file length, in contrast with the results of the present study, in which the enhanced images overestimated the file lengths. This inconsistency might be due to the use of different versions of software programs and tooth mounting procedures. Moreover, the results of the present study showed significant differences between the images enhanced with Sharpen 3 processing filter and original images. This might be due to the fact that the sharpness processing filter may increase the noise level on the image, and higher noise level may interfere with diagnostic quality of digital radiographs.
There are several studies using sharpness processing filter for diagnostic purposes in dentistry. ,,, Choi et al.  reported that the application of sharpness filter did not influence the detectability of tip of endodontic file in digital periapical radiographies. Dabbaghi et al. , showed that original and low-level sharpened images were more accurate than the intermediate and high-level sharpened images in the diagnosis of primary and recurrent caries. In contrast, Wenzel et al.  and Shrout et al.  showed that sharpness processing filter enhanced the accuracy of interproximal caries detection. However, Belem et al.  revealed that there were no significant differences between original and sharpened digital images in detection of interproximal enamel subsurface demineralization. Moreover, Kositbowornchai et al.  and Wenzel et al.  demonstrated that sharpness did not influence the accuracy of occlusal caries diagnosis. In addition, Kamburoglu et al.  evaluated the effects of digital sharpening on detectability of vertical root fractures of the tooth. They reported that there were no differences between original and enhanced images in the detection of vertical root fracture. In contrast, Nascimento et al.  showed that the sharpness filter improved the radiographic detection of vertical root fracture.
It is well known that #08 files are not good choices for determining the working length because there are some complications in radiographic detection of the tip of these small files. , Nevertheless, there is no other choice in some clinical situations such as small or calcified canals.  Also, it has been reported that the effect of processing filters on measurement accuracy of endodontic file decreases with an increase in file size.  Therefore, we used ISO #08 K-files in the present study similar to our previous studies. ,, However, it is recommended other file sizes be used for further task-specific investigations.
There were some limitations in the present study: First, in the present study the ex vivo model was used. This model could not represent the conditions during endodontic treatment; second, endodontists usually prefer solid-state detector rather than storage phosphor plate system for working length determination during endodontic treatment because of instantaneous image capture and consequently, faster image acquisition  ; third, in the present study, the soft tissue that could alter the visual characteristics of the digital radiograph was not reproduced. 
| Conclusion|| |
In conclusion, considering the results of this ex vivo study, the application of mild (Sharpen 1) and moderate (Sharpen 2) levels of sharpness filter does not influence the accurate determination of endodontic file length. However, high-level sharpness filter (Sharpen 3) is not recommended for use in clinical situations due to its negative effect on the accuracy of endodontic file length measurement.
Financial support and sponsorship
This study was financially supported by Isfahan University of Medical Sciences (no. 391284).
Conflicts of interest
There are no conflicts of interest.
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