A subjective study of dental diagnostic utility comparing xeroradiography and film radiography

A subjective study of dental diagnostic utility comparing xeroradiography and film radiography Barton M. Gratt, DDS,a Stuart C. White, DDS, PhD,” and Edward A. Sickles, MD,b Los Angeles and San Francisco, Calij UCLA DENTAL

RESEARCH

INSTITUTE

AND UCSF SCHOOL OF MEDICINE

This study determined the perceived strengths and weaknesses of xeroradiography, D-speed film, and E-speed film for intraoral radiography. Results indicated that xeroradiography was preferred for the imaging of structures useful in periodontics and endodontics whereas film demonstrated a low level of image artifacts and was judged to be better for the imaging requirements of routine restorative dentistry. D-speed film was rated higher than E-speed film. These subjective assessments are similar to previously reported pilot studies but differ from previously published objective studies, which showed no significant difference between the three imaging techniques. Although there are substantial subjective differences between xeroradiography, D-speed film radiography, and E-speed film radiography, all the techniques provide more than the threshold level of necessary diagnostic information and all techniques portray adequate information for evaluation of common abnormalities encountered in the oral cavity. (ORAL SURG ORAL MED ORAL PATHOL 1989;68:653-60)

X

eroradiography is a technique that uses a modified xerographic copying process to record images produced by diagnostic x rays. It is different from conventional silver halide film recording systems in that it involves neither chemical processing nor the use of a darkroom. Instead of film, xeroradiography usesa uniformly charged selenium-alloy plate held in a light-tight cassette. The charges on this plate are partially dissipated when exposed to x-irradiation, forming a latent electrostatic image; with the use of charged black particles called toner, the latent image is transferred into a real image by means of a tape transfer mechanism. This image is viewed by reflected light (room light) or by transillumination (viewbox light).’ Xeroradiographic images differ from film images

This study was funded in part from a grant from the National Institute of Dental Research #R 01 DE 06379-03, United States Department of Health and Human Services, United States Public Health Service, Bethesda, Md. %ection of Oral Radiology, UCLA Dental Research Institute, Los Angeles, Calif. bDepartment of Radiology, UCSF School of Medicine, San Francisco, Calif. 7/16/11631

by demonstrating a wide latitude of exposure, and by “edge enhancement,” a property by which small structures and areas of subtle tissue density differencesare made more visible. Edge enhancement occurs whenever differences in density are abrupt, and the magnitude of its effect is proportional to the amount of density difference present and its abruptness of change.2-3 Quantitative image analysis comparing resolution, noise, and contrast showed only minor differences between dental xeroradiographic images and those of conventional (D-speed) film radiography, but the much greater imaging latitude of xeroradiography along with its edge enhancement property permitted superior visualization of soft tissue structures, composite restorations, acrylic pontics, etc., as reported in pilot studies.4-5 Major disadvantages have also been reported for dental xeroradiograph. High-edge enhancement processorsettings (low back-bias) and/or high exposure settings (50% more than optimal) may create radiolucent shadows termed edge deletion artifacts.5 These radiolucent artifacts appear around sharply defined radiopacities (e.g., metal restorations, overlapping interproximal surfaces of enamel), giving a false indication of dental caries.6 Another disadvan653

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tage is the large number of additional image artifacts found on dental xeroradiographs; during testing of a prototype dental system approximately 30% of the images demonstrated artifacts, appearing as spots and lines.5 These were distracting, and if occurring in an anatomically important region of the image, may have resulted in a radiographic retake.7‘8 We have previously demonstrated in a pilot clinical trial that the new dental xeroradiographic technique offers a twofold reduction in radiation dosecompared to conventional intraoral film radiography.5 The images produced by dental xeroradiographic technique were subjectively judged to be superior for imaging (1) dental anatomy, (2) fine bony detail, (3) soft tissue details, (4) dental caries, and (5) calculus.5l 912 In addition, convenienceand economy studies of the dental xeroradiographic processhave been promising and make it seeman attractive alternative to conventional film radiography. 13 Three laboratory studies by White and coworkers evaluated specific diagnostic tasks (the detection of proximal dental caries,14detection of calculus,15 and detection of periapical diseaser’j),and in general indicated no significant differences between xeroradiography, D-speed film radiography, or E-speed film radiography. These objective studies employed receiver operating characteristics (ROC) analysis to minimize any biases that might be present in subjective comparisons of image quality. Several clinical studies also evaluated intraoral imaging as it relates to specific diagnostic tasks with the use of ROC analysis, the assessmentof approximal dental caries,17 the detection of recurrent caries,” and the detection of periapical disease.i9 In general, these objective studies indicated no significant differencesbetween xeroradiography, D-speed film radiography, or E-speed film radiography. These objectively derived findings suggest that one should question the results of the previously reported subjective xeroradiography studies5>9-‘2 as to study design or adequate sample size, or develop an explanation for the discrepant findings. Therefore, a largescale, detailed subjective study of diagnostic imaging was conducted in an attempt to resolve conflicting findings when a comparison is made of intraoral dental xeroradiography to D-speed (Ultra-speed) and Espeed (Ektaspeed) film technique. MATERIALS

AND METHODS

Patient selection. We studied 300 consecutive patients requiring complete-mouth radiographic examination before their dental treatment. Informed written consent was obtained. Persons under 21 years of age and pregnant women were excluded from the study.

ORAL SURG ORAL MED ORAL PATHOL November 1989

X-ray equipment. The source of x-radiation for both film radiography and xeroradiography was a conventional dental x-ray unit (General Electric 1000 dental x-ray unit, General Electric Co., Milwaukee, Wisconsin), having a nominal focal spot size of 1.O mm and total filtration of 2.5 mm aluminum. All radiographs were taken with the useof a 17 inch (43 cm) target-film distance, 70 kVp, and 15 mA, with a beam 2% inches (7 cm) in diameter. Exposure time was varied from 10 impulses (l/6 second) to 60 impulses (1 second). Film. Conventional film images were recorded on Kodak Ultra-speed periapical film and Kodak Ektaspeed periapical film and processed with Kodak dental liquid x-ray developer and fixer according to the manufacturer’s manual processing recommendations. All films were mounted with the use of conventional film mounts (Ada Mounts, Inc., Milwaukee, Wisconsin). Xeroradiography. Dental xeroradiography used plastic intraoral cassettes43 X 33 X 3 mm and 43 X 24 X 3 mm in size. These cassettesheld and protected the selenium-alloy plates, which were stored, charged, developed, and reconditioned in a dental xeroradiography unit (Xerox 110 dental system, Xerox Medical Systems, Pasadena, California). All bitewing xeroradiographs were processedwith the use of the “lower contrast mode” whereas all periapical xeroradiographs used the conventional processing mode called “high contrast mode.” Machine and cassette maintenance was done according to the manufacturer’s recommendations. All xeroradiographs were mounted on Xerox complete-mouth x-ray mounts (Xerox Medical Systems, Pasadena, California). Both film packets and xeroradiography cassettes were positioned intraorally by means of conventional periapical positioning devices (Precision x-ray collimators, Masel Corp., Cleveland, Ohio, and Rinn XCP x-ray film holders, Rinn Corp., Elgin, Illinois). These positioning devices were adjusted to the greater thickness of the dental xeroradiography cassettes, when necessary. Posterior film bitewing radiographs were taken with the use of paper tabs (Green, Inc., Elgin, Illinois), whereas xeroradiography bitewing radiographs were taken with plastic bitewing holders (Xerox Medical Systems, Pasadena, California). Experimental design. Three hundred volunteer patients needing complete-mouth x-ray examination (21 projections) were examined by means of conventional film techniques. Double film packets were used so that one film from each exposure could be kept for study, Eleven radiographs of only one randomly selected side of each patient’s mouth were used; the selected side then was reexamined by xeroradiography (Fig. 1).

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Fig. 1. A, Half-complete-mouthsurvey(11 projections)of radiographstakenwith useof D-speedfilm radiography. B, Half-complete-mouthsurvey (11 projections)taken with xeroradiography.Note that the bitewingprojectionsare processed by meansof the “lower contrast mode” whereas the periapical projections

are all processedby means of the conventional (“high-contrast periapical”) mode.

Conventional radiographs and xeroradiographs were mounted, coded, and sorted in a random manner. Diagnostic evaluation was performed, in single-blind fashion, independently by eight dentists (including two oral radiologists) expert in radiographic interpretation. For each half-complete-mouth series, the visibility of 30 various anatomic parameters important in dental radiographic interpretation (Table I) was judged according to the following criteria: 4 = optimal, 3 = adequate, 2 = poor but diagnostic, or 1 = unacceptably poor and nondiagnostic. Study 1 compared xeroradiography to D-speedfilm and study 2 compared xeroradiography to E-speed film. In addition, each half-complete-mouth series of D-speed film, E-speed film, or xeroradiography was evaluated for overall diagnostic utility. Single-blind evaluation has been shown to be both accurate and clinically meaningful in the comparison of medical radiographic imaging systems.20 Independent of the random-order subjective evaluation previously described, all eight observers also participated in a paired subjective evaluation of xeroradiography versusD-speedfilm and xeroradiography versus E-speed film. These paired comparisons were scored on a scale ranging from 1 to 9. When xeroradiographs were judged superior to their counterparts, they received a rating of 4, 3, 2, or 1, with 1 being

markedly superior. If, on the other hand, film was higher rated, then a score of 6, 1, 8, or 9 was given (with 9 being markedly superior). If both paired images were judged to be equal in diagnostic utility, a rating of 5 was given. Data were then normalized by subtracting 5 from each score, resulting in positive and negative values. Positive scoresindicated a preference for film techniques, whereas negative scores indicated a preference for xeroradiography. The same 30 anatomic parameters, two image artifact criteria, and overall diagnostic utility were assessedfor each pair of half-complete-mouth series of images (Table II). In addition, an analysis was made relating the evaluation of D-speed film technique versus E-speed film technique. This analysis did not involve data collected from direct image-to-image comparison but instead assessedthe relative difference of D-speed film to xeroradiography and E-speed film to xeroradiography (Table III). RESULTS

The results of the random-order assessmentscomparing xeroradiography with D- and E-speedfilm are shown in Table I. In the assessmentof xeroradiography versus D-speed film, xeroradiography was rated higher in 16 of 33 categories whereas D-speed film

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ORAL SURG ORAL MED ORAL PATHOL November 1989

I. Random order subjective assessmentby eight dentists comparing xeroradiography with D-speed and E-speed film radiography on 600 patient half-complete-mouth surveys

Table

I

Study I *

Study 2*

I

Item of diagnostic interest

N

Xeroradiography Mean (SD)

D-speed film Mean (SD)

N

Xeroradiography Mean (SD)

E-speed jilm Mean (SD)

Enamel (normal nonoverlapped structures) Enamel (overlapped enamel structures) Enamel in proximity to metallic restorations Dentin (normal structures) Dentin in proximity to metallic restorations Cervical borders of teeth Pulp chambers and root canals (morphology) Pulp calcifications Root morphology Apical foramina of roots Metallic restorations (amalgam, gold, posts, pins, silver points) Composites/silicates/ acrylics/bonding agents Bases (e.g., calcium hydroxide) Porcelain crowns Gutta-percha and root canal sealers Bone trabeculae Maxillary sinus Mental foramen Tori Lamina dura Hypercementosis Interproximal alveolar bone Furcation bone/bone loss Periapical rarefying osteitis (PRO) Condensing/sclerosing osteitis Caries: interproximal Caries: occlusal Caries: recurrent Calculus Gingival outlines General frequency of artifacts Artifacts in areas of diagnostic interest Overall diagnostic utility

150

3.35 (0.25)$

3.21 (0.32)

150

3.03 (0.23)$

2.99 (0.27)

150

2.41 (0.30)

2.45 (0.29)

150

2.35 (0.25)

2.30 (0.27)

146

2.33 (0.44)

3.18 (0.33)$

135

2.29 (0.32)

3.06 (0.39)$

150 146

3.20 (0.28) 2.21 (0.46)

3.23 (0.24) 3.26 (0.30)$

146 136

3.17 (0.23)$ 2.10 (0.34)

3.08 (0.29) 3.15 (0.39)$

150 150

3.59 (0.21)-J 3.22 (.029)$

2.85 (0.40) 2.95 (0.25)

150 150

3.58 (0.18)f 3.21 (0.24)$

2.91 (0.31) 2.78 (0.23)

150 150 150 146

3.02 3.32 2.92 2.94

2.77 3.01 2.61 3.67

150 150 150 135

3.04 3.29 2.95 2.95

2.59 2.88 2.39 3.56

(0.39)$ (0.28)$ (0.32)$ (0.30)

(0.27) (0.32) (0.32) (0.18)$

(0.32)$ (0.22)$ (0.28)$ (0.24)

(0.31) (0.24) (0.32) (0.24)$

92

3.06 (0.33)$

2.83 (0.43)

86

3.00 (0.35)

2.83 (0.64)

137 46 41

2.62 (0.40) 3.09 (0.33) 3.51 (0.23)t

3.03 (0.34)$ 2.95 (0.43) 3.38 (0.30)

146 42 39

2.63 (0.35)$ 3.21 (0.12)$ 3.45 (0.23)f

2.82 (0.62)t 2.90 (0.32) 3.15 (0.34)

150 150 134 82 150 93 150

3.54 3.14 2.63 2.80 3.21 3.02 3.35

3.14 3.40 2.89 3.17 3.00 2.75 3.04

150 143 123 76 150 82 150

3.52 3.09 2.72 2.85 3.21 2.90 3.35

3.03 3.16 2.76 2.91 2.79 2.55 2.92

150 82

3.32 (0.21)$ 2.90 (0.61)

3.06 (0.26) 3.11 (0.53)

150 82

3.31 (0.20)$ 2.98 (0.44)f

2.96 (0.20) 2.73 (0.63)

98

2.82 (0.59)

3.11 (0.47)j

86

3.01 (0.45)

2.90 (0.53)

148 130 142 141 149 150

2.62 2.38 2.09 3.08 2.54 2.23

3.15 2.95 3.14 2.43 1.59 3.40

2.87 2.54 2.84 2.22 1.69 3.32

150 150

(0.23)$ (0.43)t (0.42) (0.51) (0.29)$ (0.27)$ (0.23)$

(0.19) (0.30)$ (0.47)$ (0.52)$ (0.24) (0.45) (0.26)

(0.23)$ (0.40)$ (0.45) (0.58) (0.28)$ (0.51)$ (0.24)$

(0.40)$ (0.52)$ (0.59)$ (0.43) (0.29) (0.45)$

141 124 132 141 150 150

2.68 2.30 1.97 3.07 2.54 2.67

2.27 (0.49)

3.46 (0.40)-j

150

2.33 (0.48)

3.41 (0.39)$

2.72 (0.29)

3.14 (0.29)$.

150

2.75 (0.23)

2.97 (0.27)$

(0.49) (0.65) (0.61) (0.33)$ (0.28)‘1 (0.47)

(0.49) (0.55) (0.49) (0.43)$ (0.31)$ (0.45)

(0.23) (0.48) (0.45) (0.43) (0.23) (0.46) (0.22)

(0.40)$ (0.60)$ (0.50)$ (0.54) (0.30) (0.42)$

*Mean value scale: 4 = optimal imaging, 3 = adequate imaging, 2 = poor, but diagnostic, and 1 = unacceptably poor. tStatistical significance tested with matched f test, p < 0.05, and indicates superiority. $Statistical significance tested with matched I test, p < 0.01, and indicates superiority.

was rated higher in 14 of the 33 categories. In the assessmentof xeroradiography versus E-speedfilm, xeroradiography was rated higher in 18 of 33 categories whereas E-speedfilm was rated higher in 10 of the 33

categories. In overall diagnostic utility, D- and Espeedfilm techniques were judged to be significantly better than xeroradiography. During conduct of the random-order assessments,

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Table II. Paired assessmentby eight dentists comparing xeroradiography with D-speed and E-speed film radiography on 600 patient half-complete-mouth surveys Xeroradiography versus D speedJilm* Item of diagnostic interest

Enamel (normal nonoverlapped structures) Enamel (overlapped enamel structures) Enamel in proximity to metallic restorations Dentin (normal structures) Dentin in proximity to metallic restorations Cervical borders of teeth Pulp chambers and root canals (morphology) Pulp calcifications Root morphology Apical foramina of roots Metallic restorations (amalgam, gold, posts, pins, silver points) Composites/silicates/acrylics/bonding agents Bases (e.g., calcium hydroxide) Porcelain crowns Gutta-percha and root canal sealers Bone trabeculae Maxillary sinus Mental foramen Tori Lamina dura Hypercementosis Interproximal alveolar bone Furcation bone/bone loss Periapical rarefying osteitis (PRO) Condensing/sclerosing osteitis Caries: interproximal Caries: occlusal Caries: recurrent Calculus Gingival outlines General frequency of artifacts Artifacts in areas of diagnostic interest Overall diagnostic utility

N

I

Mean (SD)

Xeroradiography versus E-speed film * I

N

I

Mean (SD)

14.5 145 141 145 142 145 145 143 145 145 141

-0.62 +0.06 +0.98 -0.19 +1.42 -0.84 -0.84 -0.70 -0.74 -0.79 +0.83

(0.46)s (0.29)t (OSl)$ (0.45)$ (0.48)$ (0.40)$ (0.39)$ (0.46)$ (0.44)$ (0.33)$ (0.36)$

150 150 143 150 150 150 150 149 150 150 137

-0.85 -0.04 +0.90 -0.43 +I .36 -1.03 -1.03 -0.83 -0.07 -0.92 +0.80

94 129 48 39 145 142 130 117 145 89 145 145 91 105 139 127 136 143 145 145 145 145

-0.26 +0.38 -0.28 -0.37 -1.05 +0.16 +0.56 +0.94 -0.76 -0.70 -0.90 -0.74 0.00 +a.07 +0.30 +0.36 +1.18 -1.07 -1.26 +1.46 +1.16 +oso

(0.64)$ (0.63)$ (0.60)f (0.54)$ (0.30)$ (OSl)$ (0.61)t. (0.73)t. (0.32)$: (0.46)$ (0.42)$ (Q.36)$ (0.86) (1.OO) (0.74)$ (0.76)$ (0.73)$ (0.45)$ (0.45)$ (0.68)$ (0.62)$ (0.54)$

98 120 42 42 150 149 136 119 150 102 150 150 85 100 145 128 132 148 150 150 150 150

-0.41 (0.57)$ +0.22 (0.52)f -0.29 (0.49)$ -0.69 (0.53)$ -1.21 (0.30)$ -0.13 (0.54)$ +O.ll (0.81) +0.88 (0.92)$ -0.90 (0.32)$ -0.71 (0.59)$ -0.96 (0.38)$ -0.81 (0.31)$ -0.22 (0.77)? +0.05 (0.95) +0.06 (0.71) +0.35 (0.89)f +1.04 (0.80)$ -1.08 (0.51)$ -1.11 (0.46)$ +1.28 (0.73)$ + 1.OO(0.69)$ +0.27 (0.56)$

(0.48)$ (0.29) (0.55)$ (0.47)$ (0.49)$ (0.34)$ (0.39)$ (0.45)$ (0.33)$ (0.42)$ (0.34)f

*Value scale:0 = both techniquesequal,positivevaIues(+) = fitm superior,and negativevalues (-) = xeroradiographysuperior. tlndicates statisticalsignificancetestedwith t test,p < 0.05,and indicatessuperiority. $Indicatesstatisticalsignificancetested with f test, p < 0.01, and indicates superiority.

xeroradiography produced several unacceptably poor images in the following categories: enamel near metal restorations, dentin near metal restorations, proximal caries, occlusal caries, and especially recurrent caries. In addition, xeroradiography was rated very poor in the general frequency of image artifacts and of disturbing artifacts in the area of diagnostic interest. Film techniques (either D- or E-speed), on the other hand, produced unacceptable images only for calculus detection and in the imaging of gingival outlines. Results of the paired evaluations of xeroradiography versus D- and E-speed film (Table II) are strikingly similar to those shown in the random-order evaluations (Table I). Xeroradiography was rated superior to D-speedfilm radiography (negative scores) in 17 of 33 categories, whereas D-speedfilm was rated superior (positive scores) in 14 of the 33 categories.

Xeroradiography was rated superior to E-speed film radiography in 19 of 33 categories, whereas E-speed film was rated superior in 10 of the 33 categories evaluated. Indirect comparisons of D-speed and E-speed film radiography were made by comparing absolute rating scores in the random-order evaluations. These are shown in Table III. Overall, D-speed film was rated better than E-speed film in 24 of 33 categories. E-speedfilm was rated better in only one category: the imaging of gingival outlines. In overall diagnostic utility, D-speed film was rated significantly better than E-speed film. DISCUSSION

The results of this subjective clinical study indicated that xeroradiography was preferred for certain

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III. Subjective assessmentby eight dentists relating D-speed and E-speed film radiography on 320 patient half-complete-mouth surveys

Table

Item of diagnostic interest Enamel (normal nonoverlapped structures) Enamel (overIapped enamel structures) Enamel in proximity to metallic restorations Dentin (normal structures) Dentin in proximity to metallic restorations Cervical borders of teeth Pulp chambers and root canals (morphology) Pulp calcifications Root morphology Apical foramina of roots Metallic restorations (amalgam, gold, posts, pins, silver points) Composites/silicates/acrylics/bonding agents Bases (e.g., calcium hydroxide) Porcelain crowns Gutta-percha and root canal sealers Bone trabeculae Maxillary sinus Mental foramen Tori Lamina dura Hypercementosis Interproximal alveolar bone Furcation bone/bone loss Periapical rarefying osteitis (PRO) Condensing/sclerosing osteitis Caries: interproximal Caries: occlusal. Caries: recurrent Calculus Gingival outlines General frequency of artifacts Artifacts in areas of diagnostic interest Overall diagnostic utility

I

D-speed film radiography

I

N

I

*

/

E-speed film radiography*

Mean (SD)

I

N

79 79 77 79 77 79 79 79 79 79 71

3.20 2.43 3.11 3.22 3.24 2.86 2.92 2.75 2.99 2.59 3.63

(0.31)$ (0.30) (0.35)t (0.25)$ (0.33)$ (0.39) (0.29)'1 (0.30)$ (0.34)$ (0.32)$ (0.25)$

51 72 21 24 79 19 17 66 19 50 79 19 57 63 78 70 77 76 78 79 79 79

2.87 2.97 2.94 3.32 3.14 3.37 2.88 3.12 2.96 2.75 3.03 3.05 3.00 3.05 3.14 2.89 3.13 2.43 1.60 3.39 3.43 3.13

(0.44) (0.40)$ (0.41) (0.31)

(0.19)t (0.34)$ (0.46)t (0.53)$ (0.28)# (0.45)$ (0.26)t (0.26) (0.57)f (0.44)? (0.42)$ (0.61)$ (O.SO)$ (0.43)$ (0.29) (0.45) (0.43) (0.29)$

81 81 77

81 77 81 81

81 81 81 15 53 70 19 22 81 80 77 56 81 52 81 81 50 59

19 69 74 76 81 81 81 81

I

Mean (SD/ 2.99 2.30 3.04 3.04 3.06 2.92 2.75 2.57 2.86 2.39 3.47

(0.25) (0.29) (0.41) (0.30) (0.48) (0.32) (0.27) (0.32) (0.27) (0.32) (0.35)

2.83 (0.59) 2.14 (0.65) 3.16 (1.46) 3.43 (1.30) 3.05 (0.27) 3.12 (0.48) 2.72 (0.50) 2.85 (0.46) 2.76 (0.26) 2.51 (0.47) 2.94 (0.25) 2.97 (0.23) 2.69 (0.60) 2.83 (0.54) 2.83 (0.45) 2.54 (0.58) 2.76 (0.55) 2.23 (0.56) 1.75 (0.38)t 3.25 (0.41) 3.31 (0.49) 2.97 (0.25)

‘Mean value scale: 4 = optimal imaging, 3 = adequate imaging, 2 = poor, but diagnostic, and 1 = unacceptably poor. frndicates statistical significance tested with matched t test, p < 0.05, and indicates superiority. Slndicates statistical significance tested with matched t test, p < 0.01. and indicates superiority.

particular tasks when subjectively compared to film radiography. Using the paired image assessment,independent observers (dentists) judged xeroradiography to be better than either D- or E-speed film radiography in the imaging of gingiva (mean score, 1.19), bone trabeculae (mean score, 1.13), calculus (mean score, I.OS>, and interproximal bone (mean score, 0.93). These anatomic structures are important iti the evaluation of periodontal conditions and for assessing the extent of periodontal disease. Xeroradiography also was rated highly in the imaging of pulp morphology (mean score, 0.94), root apex (mean score, 0.86), root morphology (mean score, 0.86), cervical burnout (mean score, 0.84), lamina dura (mean score, 0.83), furcation bone (mean score, 0.78), and pulp calcifications (mean score, 0.77). These anatomic structures are important in the evaluation of root end

diseasesthat require endodontic diagnosis and treatment. We believe the perceived imaging advantage of xeroradiography for these applications to be due to edge enhancement occurring around fine bone structures (allowing them to be more easily seen), improved delineation of all structural boundaries (allowing them also to be more easily defined), and increasedimaging latitude, permitting the full range of intraoral structures to be more easily seen (as if optimally exposed). Film was shown to have major advantages, as well, since it was preferred for imaging dentin near metallic restorations (mean score, 1.39), recurrent caries (mean score, 1.1l), enamel near metallic restorations (mean score, 0.94), and metal restorations themselves (mean score, 0.82). These items are important in assessingthe possibility of recurrent caries and in a pa-

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Fig. 2. A, Xeroradiograph demonstrating edge-deletion artifact. Arrow indicates the radiolucent zone, which could be misinterpreted as recurrent caries. B, Same patient examined with D-speed film radiography. Note there is no radiolucent zone near edge of metal restoration.

periodic general dental examination. We believe that film technique’s perceived imaging advantage versus xeroradiography is due to three features. The first is that of excessiveedge enhancement on xeroradiographs. Excessive edge enhancement occurs when an average edge-enhancement setting (useful for bone) is chosen to image a metallic restoration. The resultant image (near the edge of the metallic restoration) demonstrates excessive edge enhancement, which results in a radiolucent band around metal restorations (termed an edge-deletion artifact, Fig. 2). These edge-deletion artifacts can be misinterpreted as recurrent caries6 and are a major reason for observers preferring film techniques when assessing enamel or dentin near metal restorations. Also of importance as an imaging characteristic is the difference in broad-area contrast (not to be confused with edgecontrast) between film technique and xeroradiography. Xeroradiography has wide imaging latitude, which results in low broad-area contrast compared to film techniques. Previous investigators have shown that observers prefer high-contrast imageswhen assessingcaries.21It may well be that the broad-area contrast differences between film and xeroradiography account for observers preferring film techniques for caries detection. In addition, film has a relatively low frequency of tient’s

image artifacts compared to xeroradiography. The low artifact level is indicative of a system that is good for overall general dental diagnosis, being one that requires fewer exposure retakes. It may well be that the difference in artifact level also was important in film receiving an overall higher rating for diagnostic utility. The results of the subjective assessmentscomparing D-speed to E-speed film technique indicated a strong preference for D-speed film. This probably is related to the fact that D-speed film has more pleasing image qualities, less grain, slightly greater contrast, and a lower base plus fog density.22*23 Other subjective studies of dentists comparing D- and E-speed film techniques have produced similar results.24 Contrary to these subjective findings and contrary to previously published subjective reports,5*7-8,lo objective tests of the detection of interproximal dental caries, recurrent caries, and periapical diseasesindicated that xeroradiography and both film techniques performed equally well. These clinical findings are in agreement with laboratory studies by White and associatesindicating no objective differences among the three imaging systems tested. In these reported studies, greater differences were found between observers than between imaging systems.14-16

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What do these apparently conflicting subjective and objective results indicate? Our subjective evaluations suggest that xeroradiography is preferred for the evaluation of fine mineralized structures (such as those used in the evaluation of root-end diseases) compared with D- or E-speedfilm techniques, whereas our objective ROC analysis of the presenceor absence of periapical disease demonstrates no difference between film and xeroradiography techniques. Similarly, our subjective results indicate that film is preferred for the imaging of structures important in the diagnosis of recurrent caries (enamel and dentin near metal restorations) whereasobjective (ROC) study of the presence or absenceof recurrent caries indicates no significant overall differences between film techniques and xeroradiography. We interpret these apparently discrepant findings to mean that one imaging system probably doescontain more detail than the other, but that the additional detail is not clinically useful. Therefore, when one compares imaging techniques subjectively, the one that portrays the most detail will be rated higher. However, when objective analysis is performed, if both systemscontain an adequate amount of information for solving the task at hand (even though one may contain more detail), both systems are found to perform equally well. Xeroradiography and both film techniques portray different amounts of radiographic detail in imaging specific dental structures, but all three techniques display adequate amounts of information for the conduct of common dental tasks. In summary, xeroradiography in a subjective assessmentby eight dentists has been shown to be preferred over film for the evaluation of periodontal conditions and for the evaluation of periapical changes useful in endodontic therapy and treatment. However, xeroradiography has also been shown to have a high artifact level and to be undesirable at imaging metal restorations near either dentin or enamel structures. Therefore, it appearsthat film radiography may be best suited for evaluation in commonplace restorative dentistry. We thank Ms. Rhona Littman, Research Associate, for conducting the intraoral radiography; the Faculty of the Section of Oral Radiology, UCLA School of Dentistry, for image evaluation; and Professor Agnar Halse, Bergen, Norway, for his critical review of the manuscript. REFERENCES

1. Jeromin LS, Geddes GF, White SC, Gratt BM. Xeroradiography for intraoral dental radiology: A process description. ORAL SURGORAL MED ORAL PATHOL 1980;49:178-83. 2. Wolfe JN, Dooley RP, Harkins LE. Xeroradiography of the breast: a comparative study with conventional film mammography. Cancer 1971;28:1569-74. 3. Wolfe JN. Xeroradiography of the breast. Springfield, Illinois: Charles C Thomas Publisher, 1972172.

ORAL SURGORAL MED ORAL PATHOL November 1989 4. Gratt BM, Sickles EA, Parks CR. Xeroradiography of dental

structures. II. Image analysis. ORAL SURGORAL MED ORAL PATHOL1978;45:156-65. 5. Gratt BM. Xeroradiography of dental structures. III. Pilot clinical studies. ORAL SURGORAL MED ORAL PATHOL1979; 48:276-80. 6. Gratt BM, Gerloczy PJ. An introduction to the interpretation

of dental caries using xeroradiography. Calif Dent Assoc J 1986;14:36-45. 7. Gratt BM, Sickies EA, Littman RI. Comparison of dental xeroradiography and conventional film techniques for the frequency and significance of image artifacts. ORAL SURGORAL MED ORAL PATHOL1985;60:546-52. 8. Gratt BM, Sickles EA, Littman RI. Frequency of artifacts with xeroradiography using artifact reduction techniques. ORAL SURGORAL MED ORAL PATHOL1986;62:589-94. 9. Gratt BM, Sickles EA, Nguyen NT. Dental xeroradiography for endodontics: a rapid x-ray system producing high quality images. J Endod 1979;5:266-70. 10. Gratt BM, Sickles EA, Armitage GC. Use of dental xeroradiography in periodontics: comparison with conventional radiographs. J Periodontol 1980;51:1-4. 11. Gratt BM, Sickles EA, Lacy AM. Dental xeroradiography for imaging biomaterials: a comparison with conventional radiography. J Prosthet Dent 1980;44:567-72. 12. White SC, Gratt BM. Intraoral dental xeroradiography: clinical trials. J Am Dent Assoc 1979;99:810-6. 13. Gratt BM, Sickles EA. A cost analysis comparing xeroradiography to film techniques for intraoral radiography. J Public Health Dent 1986;46:96-105. 14. White SC, Hollender L, Gratt BM. Comparison of xeroradiographs and film for detection of proximal surface caries. J Am Dent Assoc 1984;108:755-9. 15. White SC, Gratt BM, Hollender L. Comparison of xeroradiographs and film for detection of calculus. J Dentomaxiliofac Radio1 1984;13:39-43. 16. White SC, Hollender L, Gratt BM. Comparisons of xeroradiographs and film for detection of periapical lesions. J Dent Res 1984;63:910-3. 17. White SC, Gratt BM, Bauer JG. A clinical comparison of xeroradiography and film radiography for the detection of interproximal dental caries. ORAL SIJRGORAL MED ORALPATHOL 19883653242-7. 18. Gratt BM, White SC, Bauer JB. A clinical comparison of xeroradiography and film radiography for the detection of recurrent dental caries. ORAL SURG ORAL MED ORAL PATHOL 1988;65:483-9. 19. Gratt BM, White SC, Lucatorto FS, Sapp SP, Kalfe I. A clinical comparison of xeroradiography and film for the interpretation of neriauical structures. J Endod 1986:12:346-51. 20. Sickles Ek, G&ant JK, Doi K. Comparison of laboratory and clinical evaluation of mammographic screen-film systems. In: Application of optical instrumentation in medicine IV. New York: Society Photo-Optical Instrument Engineers 1978; 127:144-9. 21. Price C. The effects of beam quality and optical density on image quality in dental radiography. ORAL SURCORAL MED ORAL PATHOL1986;62:580-8. 22. Havukainen R, Servomaa A. Characteristic curves of dental x-ray film. ORALSURGORALMEDORALPATHOL1986,62:1079. 23. Horton PS, Sippy FH, Kohout FJ, Nelson JF, Kienzle GC. A

clinical comparison of speedgroup D and E dental x-ray films. ORAL SURGORAL MED ORAL PATHOL1984;58:104-8. 24. Kleir DJ, Benner SJ, Averbach RE. Two dental x-ray films compared for rater preference using endodontic views. ORAL SURGORAL MED ORAL PATHOL1985;59:201-5. Reprint requests to:

Barton M. Gratt, DDS UCLA School of Dentistry Los Angeles, CA 90024-1668