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Evaluation of the reproducibility of two bitewing techniques by means of a microdensitometric recording method
Evaluation of the reproducibility of two bitewing techniques by means of a microdensitometric recording method Eva Margrete Beyer-Olsen and Svein Eggen, Oslo and Lillehammer, DEPARTMENT
OF ORAL
RADIOLOGY,
DENTAL
FACULTY,
UNIVERSITY
Norway
OF OSLO
collimator using principles suggested A new, simple, metal bitewing holder with a radiation dose-reducing by Eggen is presented and recommended. The reproducibility of the bitewing holder technique was compared with that of the conventional bitewing loop technique. The material consisted of twenty seven sets (fifty four pairs) of radiographs. A microdensitometric method was developed and used to assess the reproducibility of the radiographs, and 108 pairs of microdensitometric tracings were produced to evaluate the two techniques. The results showed that the metal bitewing holder was significantly superior to the bitewing loop for obtaining radiographs with high reproducibility. The suitability of the microdensitometric method is discussed.
T
he production of radiographs with high reproducibility is important for many clinical purposes and during scientific investigations. Considerable efforts have been made to standardize periapical radiographs, and mechanical aiding devices for this purpose have been developed.‘*2,4,5Some authors have also published methods for obtaining periodic “identical” bitewing radiographz?“; however, some of the devices are relatively complex and the methods are time consuming, requiring the storage of impressions of the occlusal surfaces. Moreover, methods for the evaluation of reproducibility vary in precision. The purpose of the present study was to compare the reproducibility of two bitewing techniques designed for everyday use, without using impressions, by means of a microdensitometric recording method. MATERIAL AND METHODS
The material consisted of twenty seven sets of bitewing radiographs of right and left premolarmolar regions. Each set contained two pairs obtained in the following way: Two radiographs of the same area were exposed,one with the new bitewing holder technique (E I) and the other with a paper loop technique (L I). After a time interval of 30 to 60 minutes the procedure was repeated to give a second set (E’II and L II) (Fig. 1, a and b). Radiographs of the patient’s right side were represented by fourteen sets and of the left side by thirteen. Some of the 0030-4220/83/010103
+
05$00.50/0@1983
The C.V.
Mosby Co.
exposureswere carried out by students and others by an experienced operator. The ages of the patients ranged from 40 to 60 years. Segments with teeth missing and with all teeth present were represented. Bitewing holder technique
The bitewing holder initially developed by Eggen is shown in Fig. 2. It is made of metal and equipped with an alignment rod and a collimator similar to the Eggen film holder for periapical radiographs.2*3The collimator slides easily along the rod and has a rectangular aperture corresponding to the dimension of the film, thereby reducing the radiation doseto the patierk8 The horizontal biting part of the filmholder may be covered with a disposable paper loop. The film holder, x-ray film, and collimator were positioned so that the mesial edge of the holder corresponded to the mesial surface of the mandibular canine (Fig. 3, a). The long cone was directed parallel to the rod, both horizontally and vertically, and was guided into contact with the collimator (Fig. 3, b), which also served as an additional positioning device (focus-film distance, 35 cm.). Bitewing
loop technique
When the bitewing loop (Rinn) was used the film was inserted parallel to the lingual surfaces and mesial to cover the distal aspect of the canine. The beam was directed parallel to the interproximal 103
104
Beyer-Olsen and Eggen
Oral Surg. January, I983
Fig. 1. a and b, Two setsof repeatedradiographs.ThoseletteredE are taken with the Eggenbitewing holder and the oneslettered L are taken with the paperloop.
Fig. 2. The Eggen bitewing holder with the collimator capable of sliding along the alignment rod (left and middle) and the paperloop (right).
surfaces of premolars and molars, and the vertical angulation was +lO degrees. The short cone was situated almost in contact with skin (focus-film distance, 24 cm.). Measuring technique
Fig, 3. a, The Eggen film hoIder with collimator in position; b, the cone in contact with the collimator ready for exposure.
Each of the four radiographs in a set was marked with a reference line through corresponding anatomic structures as parallel to the occlusal plane as possible (Fig. 1). Clearly visible corners of fillings were frequently used as primary reference points for lines drawn in both the maxillary and mandibular segments.
The radiographs were measured by means of a double-beam automatic recording microdensitometer, MK III C, (Joyce, Loebl and Co., Ltd.). Each film was orientated with the reference line on the movable specimen table, and the light beam passing through the film registered the density of the struc-
Volume 55 Number I
Reproducibility
of two bitewing techniques
105
Fig. 4. Two graphs representing corresponding levels on a pair of radiographs as a method to compare the reproducibility of the radiographs. The graphs produced a 5X magnification of film dimensions in horizontal direction. X represents the mesial half of the radiograph and Y the distal half. X and Y are linear measurementscorresponding to film dimension giving x and y. The difference between distances x, and x2 and between y, and y, were calculated, giving Ax and Ay.
tures along a predetermined level parallel to the reference line. A recording table with graph paper and a writing pen was synchronized to this movement. The vertical fluctuation of the resulting graph (Fig. 4) reflected the varying density along the defined level of the radiograph. The horizontal direction of the graph indicated the distance; the recorder was adjusted to represent 1 mm. of the film as 5 mm. on the graph paper. To compare the repeated radiographs, corresponding levels on each pair were recorded on the same graph paper (Fig. 4). Differences in density between two films of a pair, produced graphs with different vertical positions. This did not affect the measurements, since they were carried out along the horizontal axis. The complete sample of recordings consisted of 108 pairs of graphs. The graphs were divided into a mesial part called X and a distal part called Y (Fig. 4). Three points easily recognizable on both graphs were chosen as references. The horizontal distance between these points were determined and recorded as X and Y values. The differences between the corresponding x values and y values of pairs of radiographs were calculated, giving Ax and Ay. All measurementswere made to the nearest 0.1 mm.; Ax and Ay were
I. Calculated differences between repeated exposures taken with bitewing holder and bitewing loop*
Table
L
(N=14)
(N=13)
(N=14)
(N=13)
0.26 0.57
0.19 0.68
0.53 0.59
0.23 0.43
0.34 0.57
0.21 0.31
0.27 0.94
0.38 0.19
Maxilla:
BW holder BW loop Mandible:
BW holder BW loop
*The measurements are divided, representing the mesial and the distal halves of the radiograph and the right and left sides of the patient.
used as a numerical measure of the reproducibility of the radiographic technique. The division of the graphs into a mesial and a distal part made it possible to evaluate whether the reproducibility was different in different parts of the bitewing image. The precision of the measuring technique was investigated by double-tracing ten films; each film was recorded twice on the same graph paper with a time interval between tracings to permit removal and
106
Beyer-Olsen and Eggen
Oral January,
Surg. 1983
Fig. 5. Two graphs showing the precision of the measuring technique by representing the same tracing level of one radiograph recorded with time interval between tracings to permit removal and replacement of the film on the recording table. Table II. Comparison of the variability of repeated
exposureswith bitewing holder and bitewing loop by means of variance ratio* B W holder (N = 108) SD.,
= 0.32
B W loop (N = 108) S.D.,
= 0.58
SD., *F == 3.26; p < 0.001 S.D.,z
replacement of the film on the recording table (Fig. 5). RESULTS Measuring technique
The microdensitometric measuring technique showed no discernible deviation from the first to the secondrecording of the samelevel of one radiograph, as illustrated in Fig. 5. The reproducibility techniques
of the two radiographic
The mean of x and y values turned out to be approximately 15 mm. in both techniques. The Ax and Ay of repeated radiographs appeared
to be randomly distributed in both techniques. Table I shows the standard deviations (S.D.) of Ax and Ay. There were no systematic differences in either of the two techniques between the mesial and distal parts of the radiographs, or the right and left sides of the patients, or between the maxillary and mandibular segments. Consequently, the S.D. values were pooled for each of the two techniques (Table II). The S.D. of the bitewing loop technique was almost twice the SD. of the bitewing holder technique; the difference was statistically highly significant (p < 0.001). DISCUSSION
Different devices for making bitewing exposures are available; metal, paper, and plastics are commonly used. In developing the metal bitewing holder, it was considered essential that (1) it should be simple to use, (2) it should be easily sterilizable, and (3) it should provide a high degree of reproducibility. The long-cone technique, as used with the bitewing holder and the collimator, ensuresminimal image distortion combined with a reduced radiation dose to the patient. Both the alignment rod and the collimator facilitate the positioning of the beam. Most periodic “identical” techniques described for
Reproducibility of two bitewing techniques 107
Volume 55 Number I
bitewing radiographs are time consuming. The film holders are rather complex, and the techniques usually rely on impressions for reproducibility. The present metal bitewing holder technique is easy to use and simple. In addition, the biting part can easily be covered with a paper loop and impression paste. To compare the identity of repeated radiographs, several methods have been described: the recording of tooth lengths by means of a slide gauge,5measuring the linear difference in distance between two selected points with a stereoautograph,’ the counting of well-depicted surfaces,6 variation in dental forms and dimensions, and richness of structural details.’ In the present study a microdensitometer was used for comparing repeated radiographs. This microdensitometric method entails registration of density differences of the films as reference points. The varying density along a predetermined level was transformed into graphs producing a 5~ linear magnification in a horizontal direction. Details of the radiograph were then clearly registered, and the method gave an objective and accurate basis for the comparisons. In many long-term scientific clinical studies the implementation of time-consuming procedures is a negative factor; the use of the Eggen bitewing holder technique produces radiographs with high reproducibility in a minimum amount of time.
REFERENCES
4.
5. 6. I.
8.
9.
10.
Wege, William, R.: A Technique for Sequentially Reproducing Intraoral Film, ORAL SURG. 23: 454-458, 1967. Eggen, S.: Standardiserad intraoral riintgenteknik (English Summary), Sverig. Tandlak.-Wrb. Tidn. 61: 867-872, 1969. Beyer-Olsen, E. M.: En variant av Eggens filmholder til bruk i bakre molaromrader (English Summary), Nor. Tannlaegeforen. Tid. 89: 258-261, 1979. Silver, J. G., Catherall, D. M., Eastep, P. B., and Myall, R. W. T.: Sequential Reproduction of Intraoral radiographs, Can. Dent. Assoc. J. 40: 51-54, 1974. Refshauge, N., and Tolderlund, J.: Periodic Identical Intraoral Radiographs, ORAL SURG. 45: 311-316, 1978. Backer Dirks, O., van Amerongen, J., and Winkler, K. C.: A Reproducible Method for Caries Evaluation, J. Dent. Res. 30: 346-359, 1951. Baume, L. J., and Rordorf, A. P.: MCthode Standard pour radiographies interproximales (“Bite-Wing”), Can. Dent. Assoc. J. 27: 759-770, 1961. Henrikson, C. O., and Edward, S. : A Roentgenologic Method for Registering Dental Caries of Primary Molars in Preschool Children, Odontol. Revy 24: 235-244, 1973. Haugejorden, 0.: A Study of the Methods of Radiographic Diagnosis of Dental Caries in Epidemiological Investigations, Acta Odontol. Stand. 32: Supp. 65, p. 58, 1974. Kierkeeaard. E.. and Zeuner. P.: A Method for Obtaining Period; Identical Bitewing Radiographs, Stand. J. Den; Res. 82: 632-635, 1974.
Reprint requests Co: Dr. E. M. Beyer-Olsen Department of Oral Radiology Dental Faculty, University of Oslo Geitmyrsveien 7 1 Oslo 4, Norway
OF ORAL
RADIOLOGY,
DENTAL
FACULTY,
UNIVERSITY
Norway
OF OSLO
collimator using principles suggested A new, simple, metal bitewing holder with a radiation dose-reducing by Eggen is presented and recommended. The reproducibility of the bitewing holder technique was compared with that of the conventional bitewing loop technique. The material consisted of twenty seven sets (fifty four pairs) of radiographs. A microdensitometric method was developed and used to assess the reproducibility of the radiographs, and 108 pairs of microdensitometric tracings were produced to evaluate the two techniques. The results showed that the metal bitewing holder was significantly superior to the bitewing loop for obtaining radiographs with high reproducibility. The suitability of the microdensitometric method is discussed.
T
he production of radiographs with high reproducibility is important for many clinical purposes and during scientific investigations. Considerable efforts have been made to standardize periapical radiographs, and mechanical aiding devices for this purpose have been developed.‘*2,4,5Some authors have also published methods for obtaining periodic “identical” bitewing radiographz?“; however, some of the devices are relatively complex and the methods are time consuming, requiring the storage of impressions of the occlusal surfaces. Moreover, methods for the evaluation of reproducibility vary in precision. The purpose of the present study was to compare the reproducibility of two bitewing techniques designed for everyday use, without using impressions, by means of a microdensitometric recording method. MATERIAL AND METHODS
The material consisted of twenty seven sets of bitewing radiographs of right and left premolarmolar regions. Each set contained two pairs obtained in the following way: Two radiographs of the same area were exposed,one with the new bitewing holder technique (E I) and the other with a paper loop technique (L I). After a time interval of 30 to 60 minutes the procedure was repeated to give a second set (E’II and L II) (Fig. 1, a and b). Radiographs of the patient’s right side were represented by fourteen sets and of the left side by thirteen. Some of the 0030-4220/83/010103
+
05$00.50/0@1983
The C.V.
Mosby Co.
exposureswere carried out by students and others by an experienced operator. The ages of the patients ranged from 40 to 60 years. Segments with teeth missing and with all teeth present were represented. Bitewing holder technique
The bitewing holder initially developed by Eggen is shown in Fig. 2. It is made of metal and equipped with an alignment rod and a collimator similar to the Eggen film holder for periapical radiographs.2*3The collimator slides easily along the rod and has a rectangular aperture corresponding to the dimension of the film, thereby reducing the radiation doseto the patierk8 The horizontal biting part of the filmholder may be covered with a disposable paper loop. The film holder, x-ray film, and collimator were positioned so that the mesial edge of the holder corresponded to the mesial surface of the mandibular canine (Fig. 3, a). The long cone was directed parallel to the rod, both horizontally and vertically, and was guided into contact with the collimator (Fig. 3, b), which also served as an additional positioning device (focus-film distance, 35 cm.). Bitewing
loop technique
When the bitewing loop (Rinn) was used the film was inserted parallel to the lingual surfaces and mesial to cover the distal aspect of the canine. The beam was directed parallel to the interproximal 103
104
Beyer-Olsen and Eggen
Oral Surg. January, I983
Fig. 1. a and b, Two setsof repeatedradiographs.ThoseletteredE are taken with the Eggenbitewing holder and the oneslettered L are taken with the paperloop.
Fig. 2. The Eggen bitewing holder with the collimator capable of sliding along the alignment rod (left and middle) and the paperloop (right).
surfaces of premolars and molars, and the vertical angulation was +lO degrees. The short cone was situated almost in contact with skin (focus-film distance, 24 cm.). Measuring technique
Fig, 3. a, The Eggen film hoIder with collimator in position; b, the cone in contact with the collimator ready for exposure.
Each of the four radiographs in a set was marked with a reference line through corresponding anatomic structures as parallel to the occlusal plane as possible (Fig. 1). Clearly visible corners of fillings were frequently used as primary reference points for lines drawn in both the maxillary and mandibular segments.
The radiographs were measured by means of a double-beam automatic recording microdensitometer, MK III C, (Joyce, Loebl and Co., Ltd.). Each film was orientated with the reference line on the movable specimen table, and the light beam passing through the film registered the density of the struc-
Volume 55 Number I
Reproducibility
of two bitewing techniques
105
Fig. 4. Two graphs representing corresponding levels on a pair of radiographs as a method to compare the reproducibility of the radiographs. The graphs produced a 5X magnification of film dimensions in horizontal direction. X represents the mesial half of the radiograph and Y the distal half. X and Y are linear measurementscorresponding to film dimension giving x and y. The difference between distances x, and x2 and between y, and y, were calculated, giving Ax and Ay.
tures along a predetermined level parallel to the reference line. A recording table with graph paper and a writing pen was synchronized to this movement. The vertical fluctuation of the resulting graph (Fig. 4) reflected the varying density along the defined level of the radiograph. The horizontal direction of the graph indicated the distance; the recorder was adjusted to represent 1 mm. of the film as 5 mm. on the graph paper. To compare the repeated radiographs, corresponding levels on each pair were recorded on the same graph paper (Fig. 4). Differences in density between two films of a pair, produced graphs with different vertical positions. This did not affect the measurements, since they were carried out along the horizontal axis. The complete sample of recordings consisted of 108 pairs of graphs. The graphs were divided into a mesial part called X and a distal part called Y (Fig. 4). Three points easily recognizable on both graphs were chosen as references. The horizontal distance between these points were determined and recorded as X and Y values. The differences between the corresponding x values and y values of pairs of radiographs were calculated, giving Ax and Ay. All measurementswere made to the nearest 0.1 mm.; Ax and Ay were
I. Calculated differences between repeated exposures taken with bitewing holder and bitewing loop*
Table
L
(N=14)
(N=13)
(N=14)
(N=13)
0.26 0.57
0.19 0.68
0.53 0.59
0.23 0.43
0.34 0.57
0.21 0.31
0.27 0.94
0.38 0.19
Maxilla:
BW holder BW loop Mandible:
BW holder BW loop
*The measurements are divided, representing the mesial and the distal halves of the radiograph and the right and left sides of the patient.
used as a numerical measure of the reproducibility of the radiographic technique. The division of the graphs into a mesial and a distal part made it possible to evaluate whether the reproducibility was different in different parts of the bitewing image. The precision of the measuring technique was investigated by double-tracing ten films; each film was recorded twice on the same graph paper with a time interval between tracings to permit removal and
106
Beyer-Olsen and Eggen
Oral January,
Surg. 1983
Fig. 5. Two graphs showing the precision of the measuring technique by representing the same tracing level of one radiograph recorded with time interval between tracings to permit removal and replacement of the film on the recording table. Table II. Comparison of the variability of repeated
exposureswith bitewing holder and bitewing loop by means of variance ratio* B W holder (N = 108) SD.,
= 0.32
B W loop (N = 108) S.D.,
= 0.58
SD., *F == 3.26; p < 0.001 S.D.,z
replacement of the film on the recording table (Fig. 5). RESULTS Measuring technique
The microdensitometric measuring technique showed no discernible deviation from the first to the secondrecording of the samelevel of one radiograph, as illustrated in Fig. 5. The reproducibility techniques
of the two radiographic
The mean of x and y values turned out to be approximately 15 mm. in both techniques. The Ax and Ay of repeated radiographs appeared
to be randomly distributed in both techniques. Table I shows the standard deviations (S.D.) of Ax and Ay. There were no systematic differences in either of the two techniques between the mesial and distal parts of the radiographs, or the right and left sides of the patients, or between the maxillary and mandibular segments. Consequently, the S.D. values were pooled for each of the two techniques (Table II). The S.D. of the bitewing loop technique was almost twice the SD. of the bitewing holder technique; the difference was statistically highly significant (p < 0.001). DISCUSSION
Different devices for making bitewing exposures are available; metal, paper, and plastics are commonly used. In developing the metal bitewing holder, it was considered essential that (1) it should be simple to use, (2) it should be easily sterilizable, and (3) it should provide a high degree of reproducibility. The long-cone technique, as used with the bitewing holder and the collimator, ensuresminimal image distortion combined with a reduced radiation dose to the patient. Both the alignment rod and the collimator facilitate the positioning of the beam. Most periodic “identical” techniques described for
Reproducibility of two bitewing techniques 107
Volume 55 Number I
bitewing radiographs are time consuming. The film holders are rather complex, and the techniques usually rely on impressions for reproducibility. The present metal bitewing holder technique is easy to use and simple. In addition, the biting part can easily be covered with a paper loop and impression paste. To compare the identity of repeated radiographs, several methods have been described: the recording of tooth lengths by means of a slide gauge,5measuring the linear difference in distance between two selected points with a stereoautograph,’ the counting of well-depicted surfaces,6 variation in dental forms and dimensions, and richness of structural details.’ In the present study a microdensitometer was used for comparing repeated radiographs. This microdensitometric method entails registration of density differences of the films as reference points. The varying density along a predetermined level was transformed into graphs producing a 5~ linear magnification in a horizontal direction. Details of the radiograph were then clearly registered, and the method gave an objective and accurate basis for the comparisons. In many long-term scientific clinical studies the implementation of time-consuming procedures is a negative factor; the use of the Eggen bitewing holder technique produces radiographs with high reproducibility in a minimum amount of time.
REFERENCES
4.
5. 6. I.
8.
9.
10.
Wege, William, R.: A Technique for Sequentially Reproducing Intraoral Film, ORAL SURG. 23: 454-458, 1967. Eggen, S.: Standardiserad intraoral riintgenteknik (English Summary), Sverig. Tandlak.-Wrb. Tidn. 61: 867-872, 1969. Beyer-Olsen, E. M.: En variant av Eggens filmholder til bruk i bakre molaromrader (English Summary), Nor. Tannlaegeforen. Tid. 89: 258-261, 1979. Silver, J. G., Catherall, D. M., Eastep, P. B., and Myall, R. W. T.: Sequential Reproduction of Intraoral radiographs, Can. Dent. Assoc. J. 40: 51-54, 1974. Refshauge, N., and Tolderlund, J.: Periodic Identical Intraoral Radiographs, ORAL SURG. 45: 311-316, 1978. Backer Dirks, O., van Amerongen, J., and Winkler, K. C.: A Reproducible Method for Caries Evaluation, J. Dent. Res. 30: 346-359, 1951. Baume, L. J., and Rordorf, A. P.: MCthode Standard pour radiographies interproximales (“Bite-Wing”), Can. Dent. Assoc. J. 27: 759-770, 1961. Henrikson, C. O., and Edward, S. : A Roentgenologic Method for Registering Dental Caries of Primary Molars in Preschool Children, Odontol. Revy 24: 235-244, 1973. Haugejorden, 0.: A Study of the Methods of Radiographic Diagnosis of Dental Caries in Epidemiological Investigations, Acta Odontol. Stand. 32: Supp. 65, p. 58, 1974. Kierkeeaard. E.. and Zeuner. P.: A Method for Obtaining Period; Identical Bitewing Radiographs, Stand. J. Den; Res. 82: 632-635, 1974.
Reprint requests Co: Dr. E. M. Beyer-Olsen Department of Oral Radiology Dental Faculty, University of Oslo Geitmyrsveien 7 1 Oslo 4, Norway