Indian Journal of Dental ResearchIndian Journal of Dental ResearchIndian Journal of Dental Research
HOME | ABOUT US | EDITORIAL BOARD | AHEAD OF PRINT | CURRENT ISSUE | ARCHIVES | INSTRUCTIONS | SUBSCRIBE | ADVERTISE | CONTACT
Indian Journal of Dental Research   Login   |  Users online: 3320

Home Bookmark this page Print this page Email this page Small font sizeDefault font size Increase font size         

 


 
Table of Contents   
ORIGINAL RESEARCH  
Year : 2014  |  Volume : 25  |  Issue : 2  |  Page : 214-219
Conventional and digital radiographic assessment of tooth enamel de-/remineralization processes: An experimental study


1 Department of Stomatology and Radiology, School of Dentistry Federal University of Bahia, Brazil
2 Substitute Professor at Department of Stomatology and Radiology, School of Dentistry Federal University of Bahia, Brazil
3 Department of Dental Practice, School of Dentistry Federal University of Bahia, Brazil
4 Department of Biochemistry, School of Dentistry Federal University of Bahia, Brazil

Click here for correspondence address and email

Date of Submission27-Feb-2013
Date of Decision02-Apr-2013
Date of Acceptance05-May-2014
Date of Web Publication4-Jul-2014
 

   Abstract 

Objective: This study aimed to compare digital techniques for evaluating dental enamel de-/remineralization.
Materials and Methods: Sixty extracted molars were subjected to a process of de- and remineralization. Radiographs were taken before and after each stage. These radiographs were evaluated by the conventional method and were then scanned and analyzed either with or without the use of image enhancement. Moreover, the gray levels (GLs) of the affected areas were measured.
Results: All methods exhibited low sensitivity and identical levels of specificity (99.4%). Analysis of the grayscale levels found statistically significant differences between the initial radiographs (P < 0.05). The mean GL of the carious group was significantly lower than that of the remineralized group. The GL did not differ significantly between the initial and final radiographs of the remineralized group, although the mean of the first group was lower than that of the second, which demonstrated that the remineralization process restored the normal density of the dental enamel.
Conclusion: Measurement of the mean GL was sufficiently sensitive to detect small alterations in the surface of the enamel.

Keywords: Caries, digital images, digital radiography, remineralization

How to cite this article:
Leite-Ribeiro P, de Oliveira TL, Mathias P, Campo Ed, Sarmento VA. Conventional and digital radiographic assessment of tooth enamel de-/remineralization processes: An experimental study. Indian J Dent Res 2014;25:214-9

How to cite this URL:
Leite-Ribeiro P, de Oliveira TL, Mathias P, Campo Ed, Sarmento VA. Conventional and digital radiographic assessment of tooth enamel de-/remineralization processes: An experimental study. Indian J Dent Res [serial online] 2014 [cited 2020 Jun 3];25:214-9. Available from: http://www.ijdr.in/text.asp?2014/25/2/214/135926
The use of radiographic examinations to complement clinical examination is becoming increasingly necessary. Digital radiographic systems allow images to be postprocessed during interpretation, making their evaluation a dynamic process relative to that of conventional radiographic images. Images treated in this way are of a higher quality and permit increased diagnostic precision. Furthermore, the possibility of making mathematical measurements on these images adds a quantitative dimension to their interpretation, making diagnosis less subjective. [1],[2]

Manipulation or postprocessing of images may be performed by specific digital system programs. Such programs are able to alter the image brightness and contrast, magnify and rotate images, invert the grayscale, and apply pseudocolors over different shades of gray. [3],[4],[5]

Radiography is the most efficient method for diagnosing proximal caries and has been shown to be more sensitive than clinical examination for this purpose. [1],[6]

The establishment of a diagnostic method capable of detecting small alterations in the mineralization of the proximal surfaces of teeth would be of great value to the clinical practice of dentistry, as it would permit early diagnosis of demineralization on these faces as well as enable such lesions to be treated noninvasively in a safe, efficient, and more cost-effective manner.

This study aimed to compare conventional radiography and digital imaging for the assessment of the de- and remineralization of proximal tooth enamel in terms of the sensitivity, specificity, and positive and negative predictive values of these methods. The mean and the coefficient of variance (CV) of the gray levels (GLs) of the proximal faces of healthy teeth before and after artificial demineralization (producing caries lesions) and remineralization were also determined.


   Materials and methods Top


Sixty unerupted third molars with completely formed crowns that had been indicated for extraction were randomly selected. Unerupted teeth were used so that the posteruptive maturation process would not interfere with the de- and remineralization processes. [7]

The teeth were cleaned with periodontal curettes, washed with distilled deionized water, and mounted in blocks of three with proximal contacts. To maintain their positions throughout the following stages, the teeth were placed into partial molds containing condensation silicone [Figure 1]. Next, they were made fully impermeable by the application of three layers of nail polish except for unprotected windows measuring 3 mm 2 on their proximal surfaces and were then subjected to pH cycling to simulate highly cariogenic challenge conditions. To induce artificial caries-like lesions, the blocks were subjected to a previously published dynamic demineralization and remineralization cycling model. [8] The test specimens were subjected to 15 pH cycles. Each cycle consists of immersion in demineralizing solution (latic acid: 0.1 mol/L; dehydroxyphosphate methane: 0.2 mmol/L; pH: 5.0) for six hours, rinse in deionized distilled water, and immersion in remineralizing solution (acidulated phosphate fluoride) for 18 hours at 37 o C. At the end of the induction period of the artificial caries, the caries-like lesions appeared as very opaque white-stained lesions but did not exhibit cavitation. Next, each tooth was washed, dried, and mounted on the silicone support with the previous positioning maintained. At this time, 10 blocks (30 teeth) were randomly selected to be set aside and were not subjected to the remineralization process.
Figure 1: Teeth mounted in blocks

Click here to view


The remaining 30 teeth exhibiting caries-like lesions were subjected to the remineralization process. The samples were exposed to acidulated phosphate fluoride in gel (1.23%) for four minutes and then immersed in the remineralizing solution. This process was carried out daily for five consecutive days, and the remineralizing solution was changed daily. After this period, the teeth were washed, dried, and positioned in their respective blocks.

Radiographs were taken of all of the teeth before the demineralization process, after the artificial induction of caries, and after remineralization. In total, 30 radiographs and 30 corresponding digitized images were assessed.

An acrylic box filled with water (4 cm 3 ) was placed in front of the teeth to be radiographed to simulate the presence of soft tissues [9] [Figure 2].
Figure 2: Radiographs taken of all the teeth in standardized conditions

Click here to view


Each radiograph was digitized in a scanner with a transparency reader in the grayscale mode, with a spatial resolution of 600 dpi, at the original size (100%), and in eight bits. The teeth were radiographed in a standardized manner in the same radiographic appliance. The film was placed parallel to the support of the teeth, and the appliance locater was positioned so that the X-ray beams intersected both the teeth and the film perpendicularly, thus ensuring parallelism. A 10 mA, 70 Kv apparatus was used with a focal distance of 20 cm and an exposure time of 0.4 seconds [Figure 2].

The brightness of the radiographs was corrected according to a previously published method, [10] with the aim of standardizing the appearance of the images. The radiographs obtained in each of the three stages of the treatment were corrected using the Photoshop software using the first degree of gray (most radiopaque) from the penetrometer of the initial radiograph as a reference. This process aimed to reduce the effect of any variability in the grayscales of the radiographs resulting from distortion while obtaining or digitizing the radiographs. It should be noted that such alterations were restricted to a few images and that the level of alteration was no more than 5 GLs for those images for which it was required. This indicates that the precautions taken to standardize the methodology were efficient and ensured that very little distortion was incorporated into the images.

For conventional radiographic analysis using a light box, the radiographs of all of the experimental stages were mounted in film holders in random order and deidentified so that the examiner would not know their identity. The radiographs were interpreted by a single experienced examiner who recorded the presence or absence of any proximal caries-like lesions.

For digital analysis, the image identifications were changed so that the examiner did not know their identities. The same experienced examiner indicated whether each proximal face exhibited any caries-like lesions. This analysis was performed using the Image Tool program (University of Texas Health Science Center, San Antonio, Texas, USA).

To compare the accuracy of the diagnosis with and without image processing, in the first phase of the visual digital analysis, the examiner was unable to use the program tools to alter the appearance of the image. In the second visual digital analysis, the examiner was permitted to alter the appearance of the image in the following ways: Alteration of brightness and contrast, inversion, and enlargement of the image.

To determine the means and standard deviations (SDs) of the GLs of the selected areas, a rectangle containing approximately 400 pixels was traced on the external side of the enamel at the point of contact of the proximal surfaces. Measurements of GLs were obtained using the histogram tool [Figure 3] and [Figure 4]. The mean of the GLs was taken to represent the degree of mineralization of the tissue in the caries-like lesions.
Figure 3: Gray level analysis of radiograph 10 before the demineralization process (GL =141)

Click here to view
Figure 4: Gray level analysis of radiograph 10 after the demineralization process (GL =136)

Click here to view


Next, all of the teeth were sectioned in the mesiodistal plane at the locations of the lesions on their proximal faces using a diamond disk, and the sections were assessed under a stereomicroscopic lens.

For statistical analysis, the Student's t-test for paired samples was used with an α value of 0.05. The diagnostic tests (sensitivity, specificity, and positive and negative predictive values) were also calculated. The 95% confidence intervals (CIs) were used to determine whether these measures differed between the radiographic methods.


   Results Top


The sensitivity of the methods was: 3.5% for conventional radiography, 7.89% for visual evaluation of digitized radiographs without postprocessing, and 9.65% for the evaluation of digitized images using additional resources.

The positive predictive values of the digital methods with and without image postprocessing showed 91.66 and 90%, respectively. These values were not significantly different. The positive predictive value of conventional radiographic analysis was 80%. No statistically significant differences were noted among the negative predictive values of the three methods (61.85% for the digital method with postprocessing, 61.39% for digitized radiographs without image enhancement, and 60.28% for the conventional radiographic method) [Table 1].
Table 1: Accuracy of methods studied for the detection of caries-like lesions and remineralization


Click here to view


Comparison of the GL means among the groups before and after demineralization revealed that the mean of the first group was significantly higher than that of the second (145.06 vs. 141.52, P < 0.001) [Table 2].
Table 2: Means of gray level (GL)


Click here to view


Comparison of the GL means of images taken after demineralization and after remineralization showed that the mean of the first caries-like lesions group was significantly lower than that of the second group (143.56 vs. 146.76, P < 0.048) [Table 2].

Comparison of the GL means of the remineralized teeth before demineralization and after remineralization showed a small but nonsignificant increase after the de- and remineralization process (145.02 vs. 146.76, P < 0.129) [Table 2].

CV of each group was calculated from SD using the formula: CV = SD/mean × 100. The CV was 8.02 for the initial radiographs and 7.54 for the carious group; these values were not significantly different (P = 0.131). The CVs of the carious and remineralization groups were also not significantly different at 7.30 and 7.63, respectively (P = 0.089). CVs of 7.52 and 7.59 were obtained for the initial and remineralization groups, respectively, and these values were not significantly different (P = 0.39).


   Discussion Top


This study assessed 120 proximal faces of 60 teeth. The number chosen was based on the literature, which includes innumerable studies with similar sample sizes. [11],[12] The literature also contains several remineralization studies that incorporate the use of fluorides. [13],[14],[15] The proven convenience and efficacy of this methodology made it a logical choice for the present study.

It has been stated that no method for diagnosing caries-like lesions is sufficiently accurate to be used as a gold standard in clinical studies. [13] Wenzel et al. considered that whenever possible, new diagnostic methods should be tested in vitro before being applied clinically. [14],[16] In vitro assessment permits the determination of the accuracy of the method, which for this purpose should be assessed in comparison with the real diagnosis. To measure the true extent of demineralization, it is necessary to section the teeth in the area in which the artificially produced caries-like lesions are located. Stereomicroscopy, microradiography, and radiographic film are some of the various methods for establishing the presence and extent of caries-like lesions that have been proposed. Stereomicroscopy has proven to be the most reliable method of validation. [17] Therefore, stereomicroscopy has been recommended as the method of choice for validating diagnoses of caries-like lesions. [18] In considering these recommendations, the present study used stereomicroscopy to assess the extent of caries-like lesions.

Digital radiography enables image enhancement and the detection, by means of specific tools, of alterations that are not seen by the human eye. [1],[16],[19] However, all radiographic methods tested for detection of the experimental lesions displayed low sensitivity, as follows: 3.5% for conventional radiography, 7.89% for visual evaluation of digitized radiographs without postprocessing, and 9.65% for evaluation of digitized images using additional resources. From these results, it is possible to conclude that both conventional and digital radiographic methods were only minimally efficient in detecting artificially produced active white-stained lesions in enamel. This analysis showed that conventional radiography was significantly less sensitive than the digital methods for identifying the experimental caries-like lesions; these results are similar to Haiter-Neto et al. (2005). [20] Sensitivity was evaluated relative to the results of stereomicroscopy as the established gold standard for in vitro studies.

Carneiro et al. (2009) [19] showed the quantitative analysis that mean pixel gray values can be used for monitoring remineralization of caries, revealing status of the lesion. Quantitative values correlated with status of the lesion in subjective analysis. Greater values were observed for remineralized lesions and lower values for demineralized lesions, whereas intermediary values (near 128 gray value) were consistent with stabilized lesions.

The results of the positive predictive values in this study are in disagreement with a previous study that showed that the performance of digital radiography was similar to that of conventional film despite the available postprocessing methods, such as optimization of density and contrast. [14] In the present study, digitized radiography showed a small but statistically significant advantage in sensitivity. Studies showed no statistically significant difference between the conventional and digital methods for the diagnosis of proximal caries. [14],[16],[18]

Analysis of the results of another study [21] showed that the assessment of images after postprocessing improved the detection of lesions located in the external half of the enamel but that the methods did not differ significantly for detection of lesions located beyond this point. For lesions in the external half of the enamel, the rate of false-positive diagnoses was higher for the digital images than for conventional radiographs.

Comparison of the GL means among the groups before and after demineralization revealed that the mean of the first group was significantly higher than that of the second, indicating that mineral loss had occurred [Table 2]. This result for the GL mean indicates that digitized radiographs are even more valuable when dealing with incipient caries in enamel, as the traditional methods are not capable of detecting the disease at its onset. It is at precisely this stage that it is possible to intervene preventively in an efficient manner.

Comparison of the GL means of images taken after demineralization and after remineralization indicated that the enamel density of the areas assessed increased after the remineralization process [Table 2].

Finally, comparison of the GL means of the remineralized teeth before demineralization and after remineralization demonstrates that the remineralization process seemed to restore the normal density of the tooth enamel [Table 2]. Carneiro et al. (2009) [19] observed greater values for remineralized lesions.

The results of the evaluation of the SD (and, consequently, the CV, as they are directly proportional values) were unexpected. The SD of the GL mean obtained from the area subjected to de- and remineralization of the enamel indicates the distribution of the GLs of that specific area. Heterogeneous areas produce greater variation in the GLs of the pixels that constitute them. The compact homogeneous periapical bone tissue of healthy teeth should produce pixels of the same intensity of gray and, thus, a smaller SD [Table 3].
Table 3: Standard deviation (SD) of the mean in relation to the group assessed


Click here to view


Given this premise, it was expected that both the SD and the CV of the areas submitted to the demineralization process would be greater than those of the initial images and that the CV of the carious group would be greater than that of the remineralization group for the same reasons. However, this did not occur, as no significant differences were observed between the groups. The results conformed to expectations only between the initial and remineralization groups. These findings are not easy to explain. It is possible that the indirectly digitized images were not sufficiently of high quality to show small alterations in the distributions of the GLs or that the induced caries were very superficial and their GL distributions impossible to visualize.


   Conclusions Top


Assessment of the reliability of conventional and digital radiographic methods with and without image postprocessing showed that both conventional and digital radiographic methods were minimally effective at detecting caries-like active white-stained lesions in enamel.

The assessment of the GL means was sensitive for detecting small alterations in the surface of the enamel, as demonstrated by the fact that the mean was lower for the images of teeth subjected to demineralization than for the images of healthy or remineralized teeth. The GL means were sufficiently sensitive that no differences were detected even between the demineralized and remineralized groups.

The results for the GL means indicate that digitized radiographs are even more valuable when dealing with incipient caries in enamel, as the traditional methods are not capable of detecting the disease at its onset. It is at precisely this stage that it is possible to provide efficient preventive intervention.

 
   References Top

1.Xavier CR, Araujo-Pires AC, Poleti ML, Rubira-Bullen IR, Ferreira O Jr, Capelozza AL. Evaluation of proximal caries in images resulting from different modes of radiographic digitalization. Dentomaxillofac Radiol 2011;40:338-43.  Back to cited text no. 1
    
2.Ohki M, Okano T, Nakamura T. Factors determining the diagnostic accuracy of digitized conventional intraoral radiographs. Dentomaxillofac Radiol 1994;23:77-82.  Back to cited text no. 2
    
3.Haak R, Wicht MJ. Grey-scale reversed radiographic display in the detection of approximal caries. J Dent 2005;33:65-71.  Back to cited text no. 3
    
4.Hintze H. Diagnostic accuracy of two software modalities for detection of caries lesions in digital radiographs from four dental systems. Dentomaxillofac Radiol 2006;35:78-82.  Back to cited text no. 4
[PUBMED]    
5.Guneri P, Lomcali G, Boyacioglu H, Kendir S. The effects of incremental brightness and contrast adjustments on radiographic data: A quantitative study. Dentomaxillofac Radiol 2005;34:20-7. Kimmes NS, Saini TS, Carroll LR. Comparison of clinician agreement during visualization of conventional and digitized bitewing radiographs. Gen Dent 2006;54:182-5.  Back to cited text no. 5
    
6.Woltgens JH, Bervoets TJ, de Blieck-Hogervorst JM, Driessens FC. Remineralization in human premolars of different posteruptive age. J Biol Buccale 1983;11:35-40.  Back to cited text no. 6
    
7.Serra MC, Cury JA. The in vitro effect of glass-ionomer cement restoration on enamel subjected to a demineralization and remineralization model. Quintessence Int 1992;23:143-7.  Back to cited text no. 7
    
8.Svanaes DB, Moystad A, Risnes S, Larheim TA, Grondahl HG. Intraoral storage phosphor radiography for approximal caries detection and effect of image magnification: Comparison with conventional radiography. Oral Surg Oral Med Oral Pathol Oral Radiol Endod 1996;82:94-100.  Back to cited text no. 8
    
9.Shrout MK, Hall JM, Hildebolt CE. Differentiation of periapical granulomas and radicular cysts by digital radiometric analysis. Oral Surg Oral Med Oral Pathol 1993;76:356-61.  Back to cited text no. 9
    
10.Li G, Yoshiura K, Welander U, Shi XQ, McDavid WD. Detection of approximal caries in digital radiographs before and after correction for attenuation and visual response. An in vitro study. Dentomaxillofac Radiol 2002;31:113-6.  Back to cited text no. 10
    
11.Welande U, Yoshiura K, Li G, Sallstrom P, McDavid WD. Correction for attenuation and visual response in digital radiography. Dentomaxillofac Radiol 2002;31:117-25.  Back to cited text no. 11
    
12.Wakoh M, Kuroyanagi K. Digital imaging modalities for dental practice. Bull Tokyo Dent Coll 2001;42:1-14.  Back to cited text no. 12
    
13.Wenzel A. Digital imaging for dental caries. Dent Clin North Am 2000;44:319-38.  Back to cited text no. 13
[PUBMED]    
14.Lippert F, Hara AT. Fluoride dose-response of human and bovine enamel caries lesions under remineralizing conditions. Am J Dent 2012;25:205-9.  Back to cited text no. 14
    
15.Wenzel A, Hintze H, Kold LM, Kold S. Accuracy of computer-automated caries detection in digital radiographs compared with human observers. Eur J Oral Sci 2002;110:199-203.  Back to cited text no. 15
    
16.Hintze H, Wenzel A, Larsen MJ. Stereomicroscopy, film radiography, microradiography and naked-eye inspection of tooth sections as validation for occlusal caries diagnosis. Caries Res 1995;29:359-63.  Back to cited text no. 16
    
17.Hintze H, Frydenberg M, Wenzel A. Influence of number of surfaces and observers on statistical power in a multiobserver ROC radiographic caries detection study. Caries Res 2003;37:200-5. Carneiro LS, Nunes CA, Silva MA, Leles CR, Mendonca EF. In vivo study of pixel grey-measurement in digital subtraction radiography for monitoring caries remineralization. Dentomaxillofac Radiol 2009;38:73-8.  Back to cited text no. 17
    
18.Haiter-Neto F, Ferreira RI, Tabchoury CP, Boscolo FN. Linear and logarithmic subtraction for detecting enamel subsurface demineralization. Dentomaxillofac Radiol 2005;34:133-9.  Back to cited text no. 18
    
19.Svanaes DB, Moystad A, Larheim TA. Approximal caries depth assessment with storage phosphor versus film radiography. Evaluation of the caries-specific Oslo enhancement procedure. Caries Res 2000;34:448-53.  Back to cited text no. 19
    
20.Haiter-Neto F, Ferreira RI, Tabchoury CP, Boscolo FN. Linear and logarithmic subtraction for detecting enamel subsurface demineralization. Dentomaxillofac Radiol 2005;34:133-9.  Back to cited text no. 20
    
21.Svanaes DB, Moystad A, Larheim TA. Approximal caries depth assessment with storage phosphor versus film radiography. Evaluation of the caries-specific Oslo enhancement procedure. Caries Res 2000;34:448-53.  Back to cited text no. 21
    

Top
Correspondence Address:
Patrícia Leite-Ribeiro
Department of Stomatology and Radiology, School of Dentistry Federal University of Bahia
Brazil
Login to access the Email id

Source of Support: None, Conflict of Interest: None


DOI: 10.4103/0970-9290.135926

Rights and Permissions


    Figures

  [Figure 1], [Figure 2], [Figure 3], [Figure 4]
 
 
    Tables

  [Table 1], [Table 2], [Table 3]

This article has been cited by
1 Detecting demineralization of enamel and cementum after gamma irradiation using radiographic densitometry
Rowida Abdalla,Amr Omar,Kareem Eid
Radiation and Environmental Biophysics. 2018; 57(3): 293
[Pubmed] | [DOI]
2 Detecting demineralization of enamel and cementum after gamma irradiation using radiographic densitometry
Rowida Abdalla,Amr Omar,Kareem Eid
Radiation and Environmental Biophysics. 2018; 57(3): 293
[Pubmed] | [DOI]



 

Top
 
 
 
  Search
 
    Similar in PUBMED
   Search Pubmed for
   Search in Google Scholar for
 Related articles
    Email Alert *
    Add to My List *
* Registration required (free)  
 


    Abstract
    Materials and me...
   Results
   Discussion
   Conclusions
    References
    Article Figures
    Article Tables

 Article Access Statistics
    Viewed1985    
    Printed41    
    Emailed0    
    PDF Downloaded94    
    Comments [Add]    
    Cited by others 2    

Recommend this journal