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Dentomaxillofacial Radiology (2001) 30, 203 ± 208 ã 2001 Nature Publishing Group. All rights reserved 0250 ± 832X/01 $15.00 www.nature.com/dmfr

Experience of Norwegian general dental practitioners with solid state and storage phosphor detectors A Wenzel*,1 and A Mùystad2 1

Department of Oral Radiology, Royal Dental College, University of Aarhus, Denmark; 2Department of Maxillofacial Radiology, Faculty of Dentistry, University of Oslo, Norway

Objectives: To evaluate the opinions of Norwegian dental practitioners regarding the use of solid state sensor and storage phosphor (SP) detectors for intra-oral radiography. Methods: A questionnaire received from 2199 dentists 309 (219 male, 86 female, four unknown) con®rmed the use of digital radiography in their practices. Results: Sixty-one per cent of dentists used a SP and 35% a sensor system; four (1.3%) used both. Approximately 50% of dentists had experienced technical problems and 33% had needed repairs. Almost all dentists stored their images on the hard disk (497%) and 81% made a daily back-up. More sensor than SP users found diculty with the positioning holder. Two-thirds of dentists reported digital image quality was the same or better than ®lm. More Digora (Soredex, Helsinki, Finland) users reported better image quality than Denoptix (Gendex, Milan, Italy) or Digident (Digident, Nesher, Israel) users. Mean reduction in exposure time was 55% (range 2 ± 90%), although 17 dentists stated that no reduction was achieved. Approximately half of the sensor users also used ®lm and 38% of the SP users. Film was used more often for bitewing examination by the sensor users (27%) than by the SP users (4%). Mean time saved by the sensor users was 36 min/day (range 10 ± 120) and by the SP users 25 min/day (range 5 ± 120). Conclusions: The majority of dentists felt that digital image quality was the same or better than ®lm and exposure and examination times were reduced. However, technical problems and repairs were common. Keywords: radiography, dental; digital radiography, dental; dental oces

Introduction There are many matters to consider when implementing digital radiography in dental practice.1 Factors in¯uencing Norwegian general practitioners' choice of digital instead of ®lm radiography have been reported.2 In a Danish pilot study, it was found that two-thirds of dentists working with digital radiography had chosen a storage phosphor (SP) system, while the remainder used a sensor system based on either a charge-coupled device (CCD) or complex metal-oxide (CMOS).3 Such data has not been reported from large-scale studies of general dental practice and di€erences between the

*Correspondence to: A Wenzel, Department of Oral Radiology, Royal Dental College, Faculty of Health Sciences, University of Aarhus, Vennelyst Boulevard, DK 8000 Aarhus C, Denmark. Received 8 August 2000; accepted 16 April 2001

various digital systems in clinical use have never been assessed. Information is available on image quality, the use of image enhancement, image recording, and dose reduction in digital radiography. Image quality has been shown comparable with ®lm at a much wider exposure range for the Digora SP system,4,5 but with considerable variation among di€erent makes of SP systems.6,7 Image enhancement facilities can be used if density and contrast are not optimal,8 and enhancement may improve diagnostic accuracy.9 ± 11 The potential for digital image enhancement and the lack of chemical processing errors should result in fewer retakes with digital receptors, but more positioning errors may occur, leading to more retakes.12 In addition large dose reductions can be obtained with digital radiography.13 ± 15 The aim of this study was therefore to investigate how general dental practitioners perceive the advantages and disadvantages of digital radiography compared with ®lm and to

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204

determine the di€erences between the competing systems.

equipment. Due to the relatively small number of digital extra-oral systems, no further comparisons were made; all the results below refer to the intra-oral systems.

Material and Methods The questionnaire and analysis of the responses has been described in the preceding report.2 Three hundred and nine of the responding dentists (219 male, 86 female, four unknown) reported working with digital radiography. Di€erences between sensor and SP users and between di€erent makes of these systems are presented with descriptive statistics.

Technical problems Approximately half of the dentists had experienced technical problems, independent of the digital system used, and one-third had required repairs. The problems were almost equally distributed between hardware, software and networking problems or combinations of these. Half of the dentists reported the problems were solved within 3 months while the remainder took longer. Most repairs could be accomplished in the practice, but 30% of the dentists were without their system for some time.

Results Not all dentists had answered all questions, thus in the following text and tables, the total number of dentists may not equal 309.

Image storage and communication Almost all dentists stored their images on a hard disk (497%). Eighty one per cent made a daily back-up and 13% a weekly; while 6% made no back-up). When transmission to other parties was needed, 5% used a ¯oppy disk or e-mail, 60% a laser paper printout, 16% a special thermal paper to increase image quality, while the rest used a combination of these. Eight per cent scanned their ®lm radiographs in addition to their digital acquisition.

Equipment Sixty-one per cent of the dentists used a storage phosphor (SP) system and 35% a CCD/CMOS sensor; four (1.3%) used both types of systems while seven gave no information. Table 1 lists the intra-oral digital systems used in Norway with the year of purchase; (32 dentists provided no data). There were nine makes, three SP and six sensor systems. One-third of the sensor users reported their sensor size; of these 2/3 were large (364 cm, `bitewing'). The number of sensors in a practice ranged from 1 ± 6; 70% had only one sensor. Table 2 gives the names, addresses and homepages of the relevant companies (see also: www.odont.aau.dk/rad/Digitalx/htm). Ten per cent altered their existing dental X-ray unit while 27% bought a new unit with their digital system. Fifty-three dentists used digital panoramic machines, 10 with sensors and 43 SPs: 16 had bought new panoramic equipment. Seventeen used a digital technique for cephalometry and other extra-oral examinations; ®ve were sensors and 12 SPs: six had bought new

Image recording More sensor than SP users found diculty with the holder (Table 3). The Schick holder scored better than the other sensors. The number of radiographs and retakes per examination was higher among the sensor than the SP users (Tables 4 and 5). Patient information The digital images were used much more frequently than ®lm for patient information: 85% stated this independent of their system. The dentists who used SP,

Table 1 Number, make and year purchased of digital intra-oral radiograph systems used in Norway Unidentified 1986 1988 1990 1991 1992 1994 1995 1996 1997 1998 1999 2000 Total

1 1 1 1 1 1 3 5 21 1 36

SP: storage phosphor Dentomaxillofacial Radiology

Denoptix Digident SP SP

Digora SP

Dixi sensor

MPDx sensor

Schick sensor

Sidexis sensor

Trophy sensor

Visualix sensor

SP and sensor

1 2 1 1

13 14 27

8 13 1 22

7 9 32 33 34 2 121

1 10 1 12

3 1 4

2 3 6 10 1 22

1 2 3

9 8 21 11 50

1 2

2 1

2

4

Total 2 1 2 1 2 1 17 21 60 79 110 7 303

Visualix

Gendex Dental Systems

Via Capelli 12 20126 Milano Italy

www. gendexdental.com

Trophy

Trophy Radiology S.A.

4, rue F. Pelloutier Croissy-Beaubourg 77437 Marne la Vallee, Cedex 2 France

www. trophyimaging.com

Sidexis

Sirona Dental Systems GmbH

Fabrikstrasse 31 D-64625 Bensheim Germany

Schick Technologies Inc.

31±00 47th Av. Long Island City NY 11101 USA

www. schicktech.com

6416 Variel Av Woodland Hills California 91367 USA

www. dmdcorp.com

Experience of digital systems A Wenzel and A Mùystad

Dental/Medical Diagnostic Systems Inc. Planmeca

Asentajankatu 6 00810 Helsinki Finland

www. planmeca.com

www. sirona.de

Schick MPDx

www. soredex.com www. digident.co.il Home page www. gendexdental.com

NilsiaÈnkatu 10±14 P.O. Box 79 00510 Helsinki Finland P.O. Box 465 Nesher 36603 Israel Via Capelli 12 20126 Milano Italy Address

Orion Corporation Soredex Digident Ltd. Gendex Dental Systems Company

Digora

Dixi

Works well Does not work well Total

Sensor

SP

43 (42) 59 (58) 102 (100)

121 (74) 42 (26) 163 (100)

205

Values in parentheses are per cent Table 4 film

Comparison of number of digital exposures compared with

Number of exposures Fewer Same More Total

Sensor 4 38 59 101

(4) (38) (58) (100)

SP 10 136 31 177

(6) (77) (17) (100)

Values in parentheses are per cent

Digident Denoptix

Manufacturers of the digital intra-oral receptor in Table 1

Name

Table 2

Table 3 Evaluation of receptor positioning and holding device

Table 5 Comparison of the number of retakes with digital receptors compared with film Number of retakes Fewer Same More Total

Sensor 14 34 51 99

(14) (34) (52) (100)

SP 54 93 28 175

(31) (53) (16) (100)

Values in parentheses are per cent

in particular the Digora, stated that their patients complained more about sharp edges than did the sensor users. Subjective image quality One-third of dentists said image quality was worse than ®lm, independent of the type of system used, while the majority said it was the same or better. However, there were signi®cant di€erences between the three SP systems; in order of satisfaction Digora was best, followed by Denoptix and then Digident (Table 6). More than 90% of the dentists used at least two of the image enhancement functions: 89% used contrast, 81% density, 78% zooming, 66% distance measurements, 48% inversion, 22% density measurements and 19% pseudocolour. Dose reduction Almost all dentists achieved dose reductions by lowering the exposure time. Exposure time was reduced to about half that used for ®lm (mean=55%, range 5 ± 90%). However, seventeen dentists stated that no dose reduction was achieved. Sensor users obtained a bigger reduction than the SP users (Table 7). Seventy-eight dentists had bought a new X-ray unit or changed some of the parameters of their existing unit; in this way 17 had achieved a smaller radiation ®eld, 14 had changed to a longer cone, 15 had installed an electronic timer and the rest had combinations of these changes. Dentomaxillofacial Radiology

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Table 6 Evaluation of image quality reported by the SP users Image quality

Denoptix

Digident

Worse Same Better Total

13 10 3 26

15 5 2 22

(50) (38) (12) (100)

(68) (23) (9) (100)

Digora 28 46 44 118

(24) (39) (37) (100)

Table 8 Dentists' responses to the statement: `my expectations have been fulfilled', ranked on a six-point scale (0=totally disagree, 5=totally agree) Ranking

Sensor

Table 7 Reported exposure reduction with digital receptors compared with film

0 1 2 3 4 5 Total

Reduction (per cent)

Values in parentheses are per cent

Values in parentheses are per cent

5±25 26±50 51±75 476 Total

Sensor 3 25 35 26 89

(3) (28) (39) (29) (100)

SP 13 75 41 22 151

(9) (50) (27) (14) (100)

Values in parentheses are per cent

Film use Approximately half of the sensor users still used ®lm in their practice but only 38% of the SP users. Film was used more for bitewing examination by the sensor (27%) than the SP users (4%). The same pattern was seen for recording a full-mouth survey and for single exposures of mandibular wisdom teeth. Availability of a large sensor resulted in less use of ®lm for a bitewing examination (13%) compared with small sensors (53%). Moreover, 36% of those who exposed sensor bitewings, exposed 2 ± 4 images on each side of the mouth while the majority (90%) of SP users exposed only one image. SP users let their dental assistant perform the radiography more often than sensor users. Time saved Seventy-nine per cent stated they saved time although 52 dentists said they did not. The mean time saved by sensor users was 36 min/day (range 10 ± 120) and by the SP users 25 min/day (range 5 ± 120).

3 2 7 13 38 27 90

SP

(3) (2) (8) (15) (42) (30) (100)

0 6 13 31 53 54 157

(0) (4) (8) (20) (34) (34) (100)

Table 9 Percentage of dentists who gave additional critical comments on five aspects of their digital system System Denoptix (27) Digident (21) Digora (121) Schick (22) Trophy (50)

Receptor Recording 30 27 15 23 21

0 0 1 14 29

Image quality

Software/ hardware

Vendor

29 28 2 0 6

11 14 9 9 2

11 18 3 18 37

Values in parentheses are numbers of respondents

systems. Only sensor users complained that their receptor was dicult to position. Users of two of the SP systems complained that the contrast was bad and enhancement sub-optimal. Overall, Digora users were less critical. Seventeen dentists reported using digital radiography for approximately 6 months (range 2 ± 40 months) and then returned to ®lm. Three gave no reason, four had changed jobs while two Digident and two Sens-A-Ray users said it was because of poor image quality. Two Trophy users stated the sensors were dicult to handle and one that the Denoptix/Visualix system did not ful®l his expectations, while three said that the sensor gave inferior image quality, but did not give the make. Discussion

Costs and expectations Most dentists had not calculated the time to recover their costs but 51 had estimated the average time was 3 years. Eighty eight per cent gave a score of above 2 (0=not at all, 5=fully) that their system had reached their expectations (Table 8).

The questionnaire16 and the appropriateness of the sample has been discussed previously.2 It is not known whether the systems in use in Norway are equally represented in our sample. This would be dicult to determine even with manufacturers' sales data which may be unreliable. We do not however believe that there was a systematic bias in the users' reports to any particular make of system.

Qualitative critical remarks In the section of the questionnaire entitled `I am/was not satis®ed with the following' the dentists were invited to give their opinions on ®ve aspects of their system: receptor, recording process, software/hardware, image quality and service/manufacturer support. Table 9 summarises these system-related criticisms. Complaints about sensors related to thickness and for SPs to sharpness of their edges. Problems were reported using the scanners for the Denoptix and Digident

Equipment During the last 3 years, sales of digital systems in Norway have increased with the emergence of new sensor and SP models. Trophy was the ®rst CCD system on the market in 1986, while the Digora SP system became available in 1994. The four dentists in Table 1 currently using Digora but reporting the use of digital radiography before 1994, must have changed systems, possibly from the early Trophy equipment.

Dentomaxillofacial Radiology

Experience of digital systems A Wenzel and A Mùystad

Technical problems Purchasers of digital systems should expect technical problems on the basis of our ®ndings. About half of the users reported diculties in the initial phase and one-third needed repairs. This is consistent with the study of Danish dentists.3 Image storage and communication Dentists in this study stored their images on a hard disk which was electronically backed-up once a day. Occasionally, dentists need to send radiographs to other parties and most respondents reported using paper images from a laser printer. However, paper images do not have the same diagnostic quality as electronic images17 and a recent study suggested graphic printers produced better images.18 Some dentists used a special printer for their hard copies while only a few sent their images electronically. Image recording Some of the newer sensors have a higher resolution and are thinner than the older versions. The thickness of the sensors is a disadvantage reported with the early systems and some of our respondents had diculty in using the holders. This may explain the increased number of retakes using sensors due to periapical positioning errors compared with ®lm.12 In the present study more sensor than SP users had retakes compared with ®lm. It may be that sensor positioning is more dicult than ®lm or SP receptors. Early sensors were small, equivalent to size 0 ®lm, and not suitable for bitewing views. Recently larger size 2 sensors have become available although they are sti€er and thicker than ®lm. Bitewing examinations are also dicult due to the sensor cord preventing closure of the mouth. In some patients, they are not possible even with the large sensor.19 Unfortunately, only onethird of respondents reported their sensor size although recently larger sensors (approx. 364 cm) have been purchased leading to more bitewing exposures. There are no published studies on the ease of bitewing examinations with sensors. SP systems vary in their scanner and post-processing techniques: Denoptix and Digident use drum scanners for intra- and extraoral imaging whereas Digora has a separate scanner for extra-oral radiography. The Digora requires less time for intra-oral scanning of a single plate compared with the other two systems, but longer for multiple plates. Time is also needed to mount the light-sensitive plates in the drum scanners, which should take place in a dark or darkened room. Unlike the other two SP makes, the Denoptix image plate has to be light-erased outside the scanner which takes several minutes.20 More SP than sensor users said the examination was uncomfortable for the patient. In contrast, in a previous study, patients reported greater discomfort during bitewing examinations with a sensor than a SP.19

Subjective image quality Overall, 34% of sensor and SP users stated that image quality was poorer than ®lm. However, more Denoptix (50%) and Digident (71%) users were dissatis®ed than Digora users. Fewer Digora users (24%) rated their image quality as worse than ®lm. In contrast, there were no di€erences among the sensor users. Recent studies of intraoral6 and panoramic7 SP images gave similar results, with the Digident having a lower contrast subjectively. Wide exposure latitudes have been reported for Digora4,5,21 and Denoptix imaging,21 while some sensor systems showed higher or lower image quality.21 The poor image quality reported by Denoptix users may be due to exposure to light when inserting the image receptor in the drum, a problem not always emphasized by the manufacturers. All dentists used image enhancement, but SP users altered the contrast and density in particular more than the sensor users and conversely for pseudocolour manipulation. This may be explained by ease of access to di€erent software functions. Both SP and sensor images may be improved by image enhancement,9 ± 11 which are used when available.8 Zooming was also used by almost all dentists.22,23

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Dose reduction We found an approximate 50% decrease in exposure time, less than in the previous Danish study.3 For a single examination, the dose reduction was higher for sensor than SP users, but the amount depended on the make of sensor.24 For some diagnostic tasks the dose with SP can be much lower than for ®lm,13 ± 15 because of the very large dynamic range.4,5 It might be expected that users with small size sensors would collimate their radiation ®eld but very few did. Since sensor users performed many more radiographs and retakes than ®lm users, the actual dose reduction in general practice may have been overestimated. Film use Film was used for bitewings more frequently by sensor than SP users with a few dentists making 2 ± 4 small sensor exposures for both sides of the mouth. The small Trophy sensor size available to early users may explain why more images were made compared with the other sensor users. Since 37% of the dentists had bought their systems recently (since 1999), it is too early to predict the rate and completeness of transition from ®lm to digital imaging. Time saved Mean time saved per day was approximately half an hour. The di€erence between sensor and SP users was less than expected and suggests that this factor may have little impact on clinical practice. The di€erence was similar to a study of bitewing examinations made Dentomaxillofacial Radiology

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with a sensor and an SP system (Wenzel A, Frandsen E and Hintze H, unpublished data). Qualitative opinions The additional opinions of their systems reported by dentists were consistent with replies to the questionnaire.2 In conclusion, from a self-reported questionnaire, the majority of dentists felt that digital image quality was

the same or better than ®lm and exposure and examination times were reduced. However, technical problems and repairs were common. Acknowledgements We wish to thank Professor Jostein Grytten for constructive advice in connection with the development of the questionnaire. We also wish to thank all the dentists who took the time to ®ll in and return the questionnaire.

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13. Huysmans M-CDNJM, Hintze H, Wenzel A. E€ect of exposure time on in vitro caries diagnosis using the Digora1 system. Eur J Oral Sci 1997; 105: 15 ± 20. 14. Borg E, Grondahl H-G. Endodontic measurements in digital radiographs acquired by a photostimulable, storage phosphor system. Endod Dent Traumatol 1996; 12: 20 ± 24. 15. Velders XL, Sanderink GCH, van der Stelt PF. Dose reduction of two digital sensor systems measuring ®le length. Oral Surg Oral Med Oral Pathol Oral Radiol Endod 1996; 81: 607 ± 612. 16. Brislin RW, Lonner WJ, Thorndike RM. Questionnaire wording and translation. In: Cross-cultural research methods. New York: John Wiley, 1973, pp 32 ± 58. 17. Russell M, Pitts NB. Radiovisiographic diagnosis of dental caries: initial comparison of basic mode videoprints with bitewing radiography. Caries Res 1993; 27: 65 ± 70. 18. Nishikawa K, Wakoh M, Kuroyanagi K. Suitability of the general-purpose printer as an image output device for digital dental x-ray images. Oral Surg Oral Med Oral Pathol Radiol Endod 2000; 89: 382 ± 387. 19. Wenzel A, Frandsen E, Hintze H. Patient discomfort and crossinfection control in bitewing examination with a storage phosphor plate and a CCD-based sensor. J Dent 1999; 27: 243 ± 246. 20. GroÈndahl H-G, Wenzel A, Borg E, Tammisalo E. An image plate system for intra-oral radiography. Dent Update 1996; 23: 334 ± 337. 21. Borg E, Attaelmanan A, GroÈndahl H-G. Subjective image quality of solid-state and photostimulable phosphor systems for digital intra-oral radiography. Dentomaxillofac Radiol 2000; 29: 70 ± 75. 22. Mùystad A Svanaes DB, Larheim TA, GroÈndahl H-G. E€ect of image magni®cation of digitized bitewing radiographs on approximal caries detection: an in vitro study. Dentomaxillofac Radiol 1995; 24: 255 ± 259. 23. Svanaes DB, Mùystad A, Risnes S, Larheim T, GroÈndahl H-G. Intraoral storage phosphor radiography for approximal caries detection and e€ect of image magni®cation ± comparison with conventional radiography. Oral Surg Oral Med Oral Pathol Oral Radiol Endo 1996; 82: 94 ± 100. 24. Hayakawa Y, Shibuya H, Ota Y, Kuroyanagi K. Radiation dosage reduction in general dental practice using digital intraoral radiographic systems. Bull Tokyo Dent Coll 1997; 38: 21 ± 25.