The e€ect of developer age on the detection of approximal caries ...

ã

Dentomaxillofacial Radiology (1999) 28, 208 ± 213 1999 Stockton Press All rights reserved 0250 ± 832X/99 $12.00 http://www.stockton-press.co.uk/dmfr

The e€ect of developer age on the detection of approximal caries using three dental ®lms K Syriopoulos*,1, XL Velders1, GCH Sanderink1, FC van Ginkel2, JP van Amerongen3 and PF van der Stelt1 1

Department of Oral Radiology, and 2Department of Information Technology, Academic Centre for Dentistry Amsterdam (ACTA), The Netherlands; 3Department of Cariology, Endodontology and Pedodontology, Academic Centre for Dentistry Amsterdam (ACTA), The Netherlands

Objectives: To compare the diagnostic accuracy for the detection of approximal caries of three dental X-ray ®lms using fresh and aged processing chemicals. Methods: Fifty-six extracted unrestored premolars were radiographed under standardized conditions using the new Dentus M2 (Agfa-Gevaert, Mortsel, Belgium), Ektaspeed Plus and Ultra-speed (Kodak Eastman Co, Rochester, USA) dental ®lms. The ®lms were processed manually using Agfa chemicals (Heraeus Kulzer, Dormagen, Germany). The procedure was repeated once a week until the complete exhaustion of the chemicals (6 weeks). Three independent observers assessed 210 radiographs using the following rating scale: 0=sound, 1=enamel lesion; 2=lesion reaching the ADJ; 3=dentinal lesion. True caries depth was determined by histological examination (14 sound surfaces, 11 enamel lesions, eight lesions reaching the ADJ and 23 dentinal lesions). True caries depth was subtracted from the values given by the observers and an analysis of variance was performed. The null hypothesis was rejected when P50.05. Results: No signi®cant di€erences were found in the diagnostic accuracy between the three ®lms when using chemicals of up to 3 weeks old (P=0.056). After the third week, Ultra-speed was signi®cantly better than the other two ®lms (P=0.012). On average caries depth was underestimated. Conclusion: A similar level of diagnostic accuracy for approximal caries is achieved when using the three ®lms. Dentus M2 and Ektaspeed Plus are at present the fastest available ®lms and they should therefore be recommended for clinical practice. Agfa chemicals should be renewed every 3 weeks. Fifty per cent reduction in average gradient is indicative of renewing processing chemicals. Keywords: dental caries; radiography, dental; X-ray ®lm

Introduction The detection of approximal caries lesions is an important task in dentistry. Approximal caries has traditionally been detected by a clinical examination supplemented by radiography. Numerous studies have demonstrated that the use of bitewing radiographs increases the number of lesions detected by

*Correspondence to: Kostas Syriopoulos, Department of Oral Radiology, Academic Centre for Dentistry, Amsterdam (ACTA), Louwesweg 1, 1066 EA Amsterdam, The Netherlands Received 23 October 1998; accepted 23 February 1999

clinical examination only.1 ± 4 However, there is concern about the e€ect of the frequency of bitewing examinations on the radiation risk for the patient. New developments in radiation protection are intended to minimize this risk.3,5 ± 7 One such method is to increase the speed of dental ®lms.8 Ektaspeed Plus (E-speed) results in a dose reduction of 40 ± 50% compared with Ultra-speed (D-speed)6 and numerous studies have concluded that both ®lms provide equivalent diagnostic performance.9 ± 13 Moreover, Ektaspeed Plus, in contrast to its predecessor Ektaspeed, is less sensitive to variations in processing conditions and in this respect is comparable with Ultra-speed.12,13

Developer ageing K Syriopoulos et al

Improper ®lm processing is one of the major causes of poor image quality in dental radiographs.14 ± 18 For this reason, it is very important to test dental ®lms under a variety of processing conditions.12,13,19,20 In 1997, Agfa introduced the new Dentus M2 Comfort dental ®lm. The speed of this ®lm is comparable with that of the Ektaspeed Plus when both ®lms are developed in automatic processing chemicals.21 Compared with the Ektaspeed Plus and Ultra-speed ®lms, Dentus M2 has been found to be more sensitive to under-processing caused by developer exhaustion.22 The implications of these ®ndings for the diagnostic quality of radiographs have not yet been examined. The aim of the present study was therefore to compare the diagnostic accuracy of the new Dentus M2 dental ®lm with that of Ektaspeed Plus and Ultra-speed for the detection of approximal caries in fresh as well as aged chemicals.

Materials and methods To examine the diagnostic accuracy for approximal caries detection 60 unrestored, extracted human premolars were selected. The teeth were mounted in plaster of Paris as close as possible to each other in groups of ®ve. Three teeth in the middle of each block were used in the study, the teeth at the either end serving to create natural contact points. In total 20 plaster blocks were constructed. For each radiograph two blocks were used simulating a bitewing radiograph (Figure 1). The radiographs were taken using Dentus M2 (Agfa-Gevaert, Mortsel, Belgium), Ektaspeed Plus (Eastman Kodak Co, NY, USA) and Ultra-speed (Eastman Kodak Co, NY, USA) dental X-ray ®lms. The ®lms of each manufacturer were from the same batch. The exposures were made by a Heliodent MD (Siemens, Bensheim, Germany) at 60 kVp and 7 mA

Figure 1 Radiographs of a set of tooth blocks exposed with Dentus M2 (a), Ektaspeed Plus (b), and Ultra-speed (c) over the 6 weeks of the study in Agfa manual processing chemicals

209

Developer ageing K Syriopoulos et al

210

with a ®ltration of 1.5 mm Al equivalent and a half value layer (HVL) of 1.9 mm Al. Measurements of the X-ray tube output showed a linear relationship between dose and exposure time. Reproducible radiographs were obtained by placing each plaster block in a specially designed holder mounted on the X-ray machine. The focus-®lm distance was 30 cm and the beam was collimated to 364 cm. A 12-mm thick soft tissue equivalent material was placed between the cone end and the tooth blocks. The exposure time of 0.5 s for Ultra-speed ®lms, and 0.32 s for Ektaspeed Plus and Dentus M2 ®lms was chosen so that the optical density of the dentine at the most prominent part of the approximal surface was as close as possible to 0.9 when fresh processing chemicals were used.20 The mean density of the dentine on all the teeth was found to be 0.92 (s.d. 0.07) for Ektaspeed Plus, 0.90 (s.d. 0.08) for Dentus M2 and 0.89 (s.d. 0.07) for Ultra-speed. Film densities were measured using a MacBeth TD-502 transmission densitometer (Newburg, NY, USA). In total 210 ®lms were processed manually with Agfa Dentus chemicals (Heraeus Kulzer, Dormagen, Germany). The volume of the developing tank was 1 liter and was placed in a thermostatically-controlled bath containing circulating water. The developing time was 5 min at 208C. The ®rst set of 30 ®lms (ten Ultraspeed, ten Ektaspeed Plus, and ten Dentus M2) was processed in fresh processing chemicals. The procedure was repeated once a week over a 6-week period at which time the Agfa Dentus chemicals would be completely exhausted.22 The processed radiographs were mounted in frames in such a way that the identi®cation of the three ®lm types was completely covered. Three dentists (observers A, B and C) from the Department of Oral Radiology examined all 210 radiographs in a random order, using a viewing box with constant light intensity and a 26magnifying viewer (X-Produkter, MalmoÈ, Sweden). No calibration of the observers was attempted before they read the radiographs. They were asked to detect caries in the approximal surfaces but were not informed about the number of lesions. Only one tooth surface was assessed, as measurements of disease from two surfaces in the same tooth may be dependent on each other.23 The following four-point scale was used: 0=no caries lesion; 1=lesion restricted to the enamel; 2=lesion reaching the amelodentinal junction (ADJ); 3=lesion extending into the dentine. The diagnostic performance of each observer with the three di€erent ®lm types was compared with the histological diagnosis. The histological examination was done with an 86-magnifying stereomicroscope (Wild 355110, Heerbrugg, Switzerland). It was performed by two observers (jointly) and served as the validation method for caries depth: no caries, caries in the enamel, caries reaching the ADJ and caries into the dentine.24 During sectioning four surfaces were damaged and these were therefore excluded from the study. The ®nal material consisted of 56 proximal surfaces: 14 sound, 11 with enamel lesions, eight

with lesions reaching dentinal lesions.

the

ADJ

and

23

with

Data analysis Data were analysed using the Statistical Package for the Social Sciences (SPSS 7.5 for Windows). The main statistical test was analysis of variance. The values of caries depth, which were determined by means of the histological examination, were subtracted from the values estimated by the three observers. Observers' estimations yielded an amount of under- (negative values) and overestimation (positive values). For instance, if the histological examination revealed a sound surface (score 0) and the diagnosis of the observer was enamel lesion (score 1), the subtraction resulted in an estimation error score of +1 (overestimation). In a similar manner, the observer's diagnosis of an actual dentinal lesion (score 3) as an enamel lesion (score 1) yielded an estimation error score of 72 (underestimation). Estimation error score 0 indicated that the observers' diagnosis was the same as the outcome of the histological examination. The analysis of variance was performed with these estimation error scores (73, 72, 71, 0, +1, +2, or +3) as the `dependent variable'. The lesion depth scores (0, 1, 2, or 3) derived from the histological examination were entered as a `between subject factor'. Observer (A, B, or C), type of ®lm (Dentus M2, Ektaspeed Plus, or Ultra-speed) and age of the processing chemicals (0, 1, 2, 3, 4, 5, or 6 weeks) were entered as `within subject factors'. The null hypothesis was rejected when P50.05. Results The results of the statistical analysis over the whole study period (from week 0 up to week 6) are summarized in Table 1. The e€ects of ®lm type, age of chemicals and observer were signi®cant. A number of interaction e€ects were also signi®cant. It is important to distinguish between the radiographic images of teeth with caries and teeth with sound surfaces. The radiographic examination of

Table 1 P-values for factors affecting caries diagnosis using three film types (Ultra-speed, Ektaspeed Plus and Dentus M2) processed in the same Agfa manual processing chemicals during a 6 week period Effect

Week 0±6

Week 0±3

Film type Age of chemicals Film type/Lesion depth Film type/Age of chemicals Histological depth/Age of chemicals Film type/Age of chemicals/Lesion depth Observer Observer/Lesion depth Observer/Age of chemicals Observer/Age of chemicals/Lesion depth

0.000 0.000 0.002 0.000 0.000 0.037 0.000 0.006 0.001 0.028

0.056 0.199 0.422 0.215 0.099 0.984 0.000 0.000 0.381 0.642

Developer ageing K Syriopoulos et al

enamel lesions and lesions reaching the ADJ could result in underestimating (negative values) or overestimating (positive values) the actual depth of the lesion. The radiographic examination of dentinal lesions could only yield underestimation, since there were no deeper lesions. On the other hand, the radiographic examination of sound surfaces could only yield overestimation, since the only possible error is diagnosing a sound surface as a carious one. Figure 2 shows that the number of sound surfaces on average was overestimated, while the depth of the carious lesions was underestimated. The degree of underestimation increased in the last 2 weeks of the study period. Figure 3 shows the average estimation error for both sound and carious surfaces using the three ®lm types.

Figure 2 Observer estimation error per lesion depth level per week using the three ®lm types. Average estimation error is the sum of the estimation error per tooth surface divided by 56. An explanation of the estimation error is given in the text (positive values indicate overestimation, negative values indicate under-estimation). & D0: no lesion; ~ D1: enamel lesion; * D2: lesion reaching the DEJ; * D3: dentin lesion

Figure 3 Average observer estimation error per ®lm type per week. The error is averaged over the di€erent caries depth levels. & Dentus M2; * Ektaspeed Plus; ~ Ultraspeed

In general, Ultra-speed appeared to perform better than the two other ®lms. Although the ®lm type e€ect was signi®cant (P=0.000), it should not be concluded that a particular ®lm type should be recommended for clinical use. This is because the diagnostic accuracy of each type of ®lm was signi®cantly a€ected by the age of the chemicals and by the depth of the carious lesion (®lm type, age of chemicals and depth of lesion showed a signi®cant interaction e€ect, P=0.037). This is shown in the Figures 4 ± 6 where the e€ect of the age of chemicals is demonstrated for each depth of carious lesion for the three ®lm types. From week 4, Ultraspeed ®lm performed better especially for carious lesions reaching the ADJ. Figures 3 ± 6 suggest that the signi®cance of the ®lm main e€ect could have been due to divergences occurring in the last 2 weeks of the study. If a shorter study period were to have been selected, the signi®cance of the ®lm type and age of chemicals interaction e€ect or even the ®lm type e€ect might have disappeared. That was indeed the case when the study period was limited to 3 weeks (Table 1). The

Figure 4 Observer estimation error per ®lm type per week for caries restricted to enamel. & Dentus M2; * Ektaspeed Plus; ~ Ultraspeed

Figure 5 Observer estimation error per ®lm type per week for caries reaching the amelodentinal junction (ADJ). & Dentus M2; * Ektaspeed Plus; ~ Ultraspeed

211

Developer ageing K Syriopoulos et al

212

Figure 6 Observer estimation error per ®lm type per week for caries extending into the dentine. & Dentus M2; * Ektaspeed Plus; ~ Ultraspeed

three ®lms no longer showed statistically signi®cant di€erences (P=0.056). Only after the third week Ultra-speed was signi®cantly better than the other two ®lm types (P=0.012). Ektaspeed Plus was signi®cantly better than Dentus M2 in the last 2 weeks of the study (weeks 5 and 6) (P=0.025). When using Ultra-speed a signi®cant decrease in the diagnostic accuracy was found only in the last study week (week 6) (P=0.015). When the two columns of the results in Table 1 are compared, it is apparent that only two e€ects were statistically signi®cant throughout the study period. These e€ects were the observer main e€ect and the interaction e€ect between observer and histological caries depth (P=0.00). Contrast computation showed that two observers (B and C) were not signi®cantly di€erent (P=0.097), whereas the di€erence between the third observer (A) and the average of the other two observers (B+C) was signi®cant (P=0.000). The main di€erence occurred in only one category (lesions reaching the ADJ) which caused the overall significance of the interaction e€ect. Two of the observers showed almost the same degree of underestimation whereas the third observer slightly overestimated on the average. Discussion A signi®cant di€erence in diagnostic accuracy using the three ®lm types was found after the third week of the study. From week 4, the diagnostic performance using Ultra-speed ®lm was signi®cantly better than when using the other two ®lm types. During the last 2 weeks (weeks 5 and 6) the lowest accuracy resulted from Dentus M2 ®lm. These ®ndings are consistent with a previous study where the sensitometric properties of the three ®lms were examined.22 That study revealed that Ultra-speed was the least sensitive and Dentus M2 the most sensitive ®lm to the exhaustion of the developer.

In the present study there was deterioration in image quality due to the exhaustion of the developer. However, there was no corresponding decrease in caries detection using Ektaspeed Plus or Dentus M2 ®lms during the ®rst 3 weeks of the study. Detection levels using Ultra-speed only declined after 5 weeks. By that time the average gradient of the characteristic curve is 50% lower on average than the values obtained in fresh chemicals.22 Other studies have also demonstrated that a loss in density and contrast due to underdevelopment has no e€ect on diagnostic accuracy.20,25 An average gradient of less than 50% indicates a clinically unacceptable diagnostic performance level for approximal caries detection. Since various processing chemicals di€er markedly in the exhaustion rate,22 the 50% threshold level can be used to determine the appropriate interval to renew each type of processing chemicals. In the present study, di€erences in diagnostic accuracy among the observers where found. This is consistent with most caries observation studies.12,26 ± 28 The main di€erence occurred in assessing carious lesions reaching the ADJ. Two of the observers displayed almost the same degree of underestimation whereas the third observer slightly overestimated lesion depth. A comprehensive examination of observer characteristics was, however, beyond the aims of the present study. To do that a large number of observers would be necessary. This study clearly demonstrates the potential e€ects of under-developed ®lms on the performance of observers who are familiar with the radiographic diagnosis of caries. A degree of underestimation of lesion depth was present, although it did not increase with lesion depth or with developer age during the ®rst 3 weeks. These ®ndings support those of other investigations which have demonstrated the tendency for radiographic diagnosis to underestimate the severity of approximal caries.2,7,10,29 After the third week of the study, a number of e€ects became signi®cant. Subsequently the in¯uence of developer exhaustion (age of chemicals) became unpredictable since other parameters, such as the ®lm type and the depth of the carious lesion, also in¯uenced the diagnostic accuracy. We conclude that as far as the diagnosis of approximal caries is concerned, the Agfa manual processing chemicals should not be used for longer than 3 weeks, if Espeed ®lms are developed. In a previous study the same three ®lms were exposed without interposing a soft tissue equivalent material.21 Under those conditions Ektaspeed Plus was the fastest ®lm in chemicals for manual processing, whereas Ektaspeed Plus and Dentus M2 had similar speed in chemicals used for automatic processing. In the present study, where clinical conditions were simulated, we found that both Ektaspeed Plus and Dentus M2 required identical exposure time to produce almost the same dentine density. The Dentus M2 ®lm is therefore, an alternative to Ektaspeed Plus as far as radiation exposure and diagnostic accuracy are concerned.

Developer ageing K Syriopoulos et al

In conclusion, an average gradient of the characteristic curve of less than 50% indicates a clinically unacceptable level of diagnostic performance for detecting approximal caries. In the present study, this level was reached after the third week for the Ektaspeed Plus and Dentus M2 ®lms and after the ®fth week for Ultra-speed. It may therefore be

concluded that all three ®lms will perform equally well for diagnosing approximal caries as long as the Agfa manual processing chemicals are not more than 3 weeks old. Ektaspeed Plus and Dentus M2 need a lower exposure than Ultra-speed ®lm and are therefore recommended for clinical practice.

References 1. Kidd EAM, Pitts NB. A reappraisal of the value of the bitewing radiograph in the diagnosis of posterior approximal caries. Br Dent J 1990; 169: 195 ± 200. 2. de Vries HCB, Ruiken HMHM, KoÈnig KG, Van `t Hof MA. Radiographic versus clinical diagnosis of approximal carious lesions. Caries Res 1990; 24: 364 ± 370. 3. Wenzel A, Pitts N, Verdonschot EH, Kalsbeek H. Developments in radiographic caries diagnosis. J Dent 1993; 21: 131 ± 140. 4. Pitts NB. Diagnostic methods for caries: what is appropriate when? J Dent 1991; 19: 377 ± 382. 5. Pitts NB, Kidd EAM. Some of the factors to be considered in the prescription and timing of bitewing radiography in diagnosis and management of dental caries. J Dent 1991; 20: 74 ± 84. 6. NRPB. Guidelines on Radiology Standards for Primary Dental Care. Report by the Royal College of Radiologists and the National Radiological Protection Board. Doc NRBP 1994; 5 (3). 7. Hintze H, Wenzel A. Clinically undetected dental caries assessed by bitewing screening in children with little caries experience. Dentomaxillofac Radiol 1994; 23: 19 ± 23. 8. Horner K. Radiation protection in dental practice. Review article. Br J Radiol 1994; 67: 1041 ± 1049. 9. Svenson B, Welander U, Shi X-Q, Stamatakis H, Tronje G. A sensitometric comparison of four dental X-ray ®lms and their diagnostic accuracy. Dentomaxillofac Radiol 1997; 26: 230 ± 235. 10. Hintze H, Christo€ersen L, Wenzel A. In vitro comparison of Kodak Ultra-speed, Ektaspeed, and Ektaspeed Plus, and Agfa M2 Comfort dental X-ray ®lms for the detection of caries. Oral Surg Oral Med Oral Pathol Oral Radiol Endod 1996; 81: 240 ± 244. 11. Conover G, Hildebolt CF, Anthony D. A comparison of six intra-oral X-ray ®lms. Dentomaxillofac Radiol 1995; 24: 169 ± 172. 12. Ludlow JB, Platin E, Delano EO, Clifton L. The ecacy of caries detection using three intraoral ®lms under di€erent processing conditions. JADA 1997; 128: 1401 ± 1408. 13. Thunthy KH, Weinberg R. E€ects of developer exhaustion on Kodak Ektaspeed Plus, Ektaspeed, and Ultra-speed dental ®lms. Oral Surg Oral Med Oral Pathol Oral Radiol Endod 1995; 79: 117 ± 121. 14. Chadwick BL, Dummer PHM. Factors a€ecting the diagnostic quality of bitewing radiographs: a review. Br Dent J 1998; 184: 80 ± 84. 15. Eliasson S, Lavstedt S, Wouters F, OÈstlin L. Quality of intraoral radiographs sent by private dental practitioners for therapy evaluation by the Social Insurance Oce. Swed Dent J 1990; 14: 81 ± 89. 16. Syriopoulos K, Velders XL, Van der Stelt PF, Van Ginkel FC, Tsiklakis K. Mail survey of dental radiographic techniques and radiation doses in Greece. Dentomaxillofac Radiol 1998; 27: 321 ± 328.

17. Kaugars GE, Broga DW, Collet WK. Dental radiographic survey of Virginia and Florida. Oral Surg Oral Med Oral Pathol 1985; 60: 225 ± 229. 18. Platin E, Janhom A, Tyndall D. A quantitative analysis of dental radiography quality assurance practices among North Carolina dentists. Oral Surg Oral Med Oral Pathol Oral Radiol Endod 1998; 86: 115 ± 120. 19. Ka€e I, Littner MM, Tamse A, Kuspet ME. Densitometric evaluation of three X-ray ®lms with ®ve di€erent developing chemicals. Oral Surg Oral Med Oral Pathol 1984; 57: 207 ± 211. 20. Svenson B, Petersson A. In¯uence of di€erent developing chemicals and developing times on radiographic caries diagnosis. Dentomaxillofac Radiol 1990; 19: 157 ± 160. 21. Syriopoulos K, Velders XL, Sanderink GCH, Van Ginkel FC, Van der Stelt PF. Sensitometric evaluation of four dental X-ray ®lms using ®ve processing chemicals. Dentomaxillofac Radiol 1999; 28: 73 ± 79. 22. Syriopoulos K, Velders XL, Sanderink GCH, Van Ginkel FC, Van der Stelt PF. E€ects of developer exhaustion on the sensitometric properties of four dental ®lms. Dentomaxillofac Radiol 1999; 28: 80 ± 88. 23. Wenzel A, Verdonschot EH. Some considerations in the evaluation of diagnostic tests in dentistry. Dentomaxillofac Radiol 1994; 23: 179 ± 182. 24. Thylstrup A, Fejerskov O. Clinical and pathological features of dental caries. In: Thylstrup A, Fejerskov O (eds). Textbook of clinical cariology. Munksgaard: Copenhagen, 1994, pp 111 ± 157. 25. Svenson B, GroÈndahl H-G, Lindvall A-M. In¯uence of ®lm fog on radiographic caries diagnosis. Dentomaxillofac Radiol 1990; 19: 105 ± 108. 26. Arnold LV. The radiographic detection of initial carious lesions on the proximal surfaces of teeth. Part I: The in¯uence of exposure conditions. Oral Surg Oral Med Oral Pathol 1987; 64: 221 ± 231. 27. Firestone AR, Lussi A, Weems RA, Heaven TJ. The e€ects of experience and training on the diagnosis of approximal coronal caries from bitewing radiographs. Schweiz Monatsschr Zahnmed 1994; 104: 719 ± 723. 28. GroÈndahl H-G. The in¯uence of observer performance in radiographic caries diagnosis. Swed Dent J 1979; 3: 101 ± 107. 29. Douglass CW, Valachovic RW, Wijesinha A, Chauncey HH, Kapur KK, McNeil BJ. Clinical ecacy of dental radiography in the detection of dental caries and periodontal diseases. Oral Surg Oral Med Oral Pathol 1986; 62: 330 ± 339.

213