Evaluation of a photographic method for diagnosis of gingivitis and caries
D. Arnbjerg, S. Poulsen and J. Heidmann Department of Child Dental Health and Community Dentistry, Royal Dental College, Vennelyst Boulevard, Aarhus, Denmark
Arnbjerg D, Poulsen S, Heichnatin J: Evaluation of a photographic tnethod for diagnosis of gingivitis and caries. Scatid J Dent Res 1992; 100: 207-10.
The aitn of the present study was to determine the value of a photographic method when diagnosing gingivitis and caries. 78 patients participated in the investigation. The validity of the photographic method could not be established, since the reproducibility of the clinical diagnosis was not 100%. Instead, the value of the method was determined by comparing the reproducibility of the clinical and the photographic diagnosis. For gingivitis the intra- and interexaminer reproducibilities were best for the photographic readings. For caries the reproducibility of the clinical diagnosis was highest. The photographic method was not limited by method variation when diagnosing redness of the gingiva and caries. However, limitations due to variation were present when diagnosing gingival swelling. The paper also describes the bias reducing capacity of the photographic method.
The bias of the results of oral epidemiologic investigations has received relatively little attention until now. A recent review of dental epidemiologic studies (1) has revealed that the major sources of bias are: 1) changing diagnostic criteria during longitudinal studies and the use of different diagnostic criteria in cross-sectional studies, which are compared later on, 2) rneasurernent bias due to diagnostic suspicion bias (2), and 3) bias due to more than one exarniner diagnosing the condition. Bias will always be a threat to the validity of a study, and minimizing bias is therefore important. All three sources of bias can be reduced if the diagnosis is made on clinical photographs or radiographs, since these pictures can be evaluated under blind conditions. Furthermore, the use of the pictures will enable examination of all participants within a short period of time by one examiner, and the use of the same diagnostic criteria on all participants is therefore more likely. Ideally, the validity of a new diagnostic procedure should be determined. The validity is determined by comparing the result of the new diagnostic procedure with a final true diagnosis (3). For the purpose of the present study, the most obvious final true diagnosis would be the clinical diagnosis. However, previous studies have shown that the clinical diagnosis of gingivitis and caries is not in complete agreement with the histologic diagnosis of the same conditions (4-7). Caries studies have
Key words: bias; dental caries, gingivitis; photography Dorte Arnbjerg, Department of Child Dental Health and Community Dentistry, Royal Dental College, Vennelyst Boulevard, DK-8000 Aarhus C, Denmark Accepted for publication 31 August 1991
also shown that the clinical and the radiologic diagnosis are not in complete agreement (8). When the validity cannot be assessed, the reproducibility must be determined instead (3). The reproducibility is determined by comparing the results of repeated examinations of the same object, and the intraexaminer as well as the interexaminer reproducibility can be determined. The purpose of the present study is, therefore, to determine the reproducibility of the clinical diagnosis of gingivitis and caries, and compare this reproducibility to the reproducibility of a procedure using clinical photographs. Furtherrnore the aim is to assess the shortcomings of the photographic method. Subjects and methods
95 patients attending the Royal Dental College, Aarhus, on February 1st, 1990, were invited to participate in the investigation. 17 of these (18%) refused to participate. Eleven clinical photographs were taken in each individual. All photographs were taken with a Olympus OM-2 camera, and the same type of film (Kodak EPR 135 64) was used. Two occlusal, 3 facial and 6 lingual photographs were taken in a predetermined order. Further details on the method of photography are given elsewhere (1). Ten subjects were photographed twice.
208
Arnbjerg et al.
Gingivitis was examined on 60 units in each subject. Separate diagnoses of redness and swelling evaluated visually and tactilly were made on each unit. Bleeding on pressure and probing pocket depth were assessed as well. Caries was diagnosed on 166 sites using 19 diagnostic categories. This classification enabled distinction of sound sites, different types of fillings, and sites with active and non-active caries. On 30 of the 78 participants both gingivitis and caries were diagnosed, and on the remaining 48 participants only caries was diagnosed. Investigator 1 (D.A.) examined all the subjects. Eight subjects were examined twice for gingivitis by investigator 1, and five subjects were examined by both investigators. Nine subjects were examined twice for caries status and investigator 2 (J.H.) examined eight subjects for caries. Calibration ofthe investigators was done while developing the classifications. The photographs were developed at a photographic laboratory, and then read in a dark room while projecting onto a screen (size 0.9 x 1.4 m). Before reading the photographs the data forms were coded for missing teeth. During the photographic readings as many sites as possible were diagnosed on each photograph. When a site had been read on one photograph, it was not diagnosed on the succeeding photographs. After having read all 11 photographs for one subject, the sites without any diagnosis were assigned the code "unreadable". On the photographs gingivitis was diagnosed by separate evaluation of redness and visual swelling. Five subjects were examined by both investigators, and one investigator (D.A.) examined eight subjects twice. For caries the same classification as for the clinical examination was used. The caries status of nine subjects was determined twice by one investigator, and seven subjects were diagnosed by both investigators. All the double readings were done without the investigator knowing that the photographs were being reread. The time spent on photographing and diagnosing 11 subjects was assessed. The data were analyzed using site by site crosstabulation. For gingivitis, redness and swelling were compared separately. The reproducibility was measured by Po and KAPPA. P^ was calculated as the proportion of sites on which the diagnosis were in agreement. KAPPA was calculated as the proportion of agreement after chance agreement was excluded (9). If chance agreement is denoted P^, then KAPPA is calculated as KAPPA = ^ ~ ^ 1-Pe The statistics were calculated for all sites and for readable sites. The variation due to the photo-
READABLE SITES
ALL SITES
0.8
0.6 -
0.2 - I
INTER
1 INTRA
REDNESS
INTER
INTRA
SWELLING
^ B KAPPA
INTER
INTRA
REDNESS
INTER
INTRA
SWELLING
^ ^ PO
Fig. 1. Reproducibility of clinical diagnosis of gingivitis.
graphic procedure was estimated by comparing the readings on two photographs taken ofthe same area during one session. Results
The 78 participants had on average 24 remaining teeth, and a mean age of 48 yr. 87% of the subjects had at least one site that bled on probing, 23% of the subjects had pockets with a probing depth larger than 5 mm. Calculated over all subjects 1% of all sites were affected by active caries and 30% of all sites were filled. On average 6 min were spent on photographing, 8.5 min were used for clinical examination and 14.7 min for the photographic readings on each participant. Figs. 1 and 2 show the reproducibility ofthe clinical and the photographic diagnosis of gingivitis. Both clinically and photographically the intraexALL SITES
0,8
H Mi
0,6
0,4
0,2
READABLE SITES
•
1
H INTER
1
••
1J1J J11 1
INTRA
REDNESS
INTER
INTRA
SWELLING
H I KAPPA
INTER
INTRA
REDNESS
INTER
INTRA
SWELLING
^ ^ PO
Fig. 2. Reproducibility of photographic readitig of gingivitis.
Photographic diagnosis of gingivitis and caries Table 1 Agreement between the clinieal and the photographie diagnosis of gingivitis Readable sites All sites Examiner 1 Examiner 2
Redness Swelling Redness Swelling
KAPPA 0.58 0.63 0.36 0.51
KAPPA 0.72 0.80 0.47 0.65
Po
0.69 0.74 0.53 0.67
Po
0.80 0.87 0.63 0.78
209
sites. For gingivitis the estimates were 0.84 (all sites) and 0.88 (readable sites) for redness and 0.70 (all sites) and 0.76 (readable sites) for swelling. Table 2 shows the distribution of unreadable sites. Most areas not included on the photographs were situated facially, and insufficient quality ofthe photograph was most frequent when diagnosing gingivitis. Discussion
aminer reproducibility was greater than the interexaminer reproducibility. The intra- as well as the interexaminer reproducibility were greater for readable sites compared to all sites. The diagnosis of redness was more reproducible than the diagnosis of swelling. The intraexaminer reproducibility for the clinical and the photographic method was almost the same, while the interexaminer reproducibility was greater for the photographic readings. Table 1 shows the estimates of agreement achieved when comparing the clinical and photographic diagnoses. For redness as well as swelling the agreement was weaker than the intraexaminer reproducibility. Examiner 2 showed the lowest agreement, and a tendency to diagnose more redness and swelling clinically. For caries Fig. 3 shows the reproducibility of the clinical and the photographic diagnoses. Both clinically and photographically the interexaminer reproducibility was greater than the interexaminer reproducibility. For the photographic readings the estimates were highest for readable sites, whereas the estimates are identical for the clinical diagnosis since all sites were readable. Comparison of readings of two photographs taken ofthe same area in the same session gave an agreement estimate (KAPPA) for caries of 0.89 for all sites and of 0.93 for readable
The clinical diagnosis of gingivitis and caries cannot be regarded as finally true diagnoses, since they are not fully reproducible. For gingivitis the intraexaminer reproducibility is comparable to earher findings (10), while the agreement betvi^een the two examiners is weaker than earlier reports (10, 11). However, in this study redness and swelling were diagnosed separately, since agreement in a combined classification can be true agreement as well as disagreement which is camouflaged. When analyzing the data with a dichotomous classification the reproducibility is enlarged, and the results become more comparable (10, 11). For caries the clinical reproducibility is comparable, especially when considering that the classification had 19 categories, while the compared classifications have a maximum of three categories (12, 13). The photographic readings are not fully reproducible either, but when the clinically and the photographie methods are compared on the basis of their reproducibility the clinical method is characterized as having "moderate" agreement, whereas the photographic method has "substantial" agreement when diagnosing gingivitis. For the diagnosis of caries, agreement for both methods is classified "substantial" or "almost perfect" (14). Basing the evaluation on the questionable comparison of the clinical and the photographic diagnosis the results are comparable to earlier findings (15, 16).
READABLE SITES
ALL SITES
Table 2 Distribution andfrequency of "unreadable" sites Not included Insufficient on the quality photograph Gingivitis Max. Facial 12.6% 3.6% Lingual 4.3% 6.3% Mand. Facial 11.3% 2.3% Lingual 7.0% 8.3% Region
INTER
INTRA
CUINIGAL
INTER
INTRA
PHOTOGRAPHIC
H H KAPPA
INTER
INTRA
OLINIOAL
INTER
INTRA
Caries Max.
PHOTOGRAPHIC
^ ^ PO
Fig. 3. Reproducibility of clinical and photographic diagnosis of caries.
Mand.
Molars Premolars Canines and incisors Molars Premolars Canines and incisors
8.1%
2.0%
0.3% 10.8%
0.5% 1.8%
1.3%
1.7%
210
Arnbjerg et al.
The method variation influences the value of the photographic method. For the diagnosis of redness and caries the method variation can be neglected, since it is weaker than the intraexaminer variation. However, when diagnosing swelling the method causes variation. This might be due to differences in dryness of the actual area when taking the photograph, or to the fact that different extent of mouth opening will influence the position of the mirrors. Furthermore, the value of the photographic method depends on areas being included on the photographs and on photographs of sufficient quality. The areas that were the most difficult to reproduce on the photographs were facially in the mandible, a fact that should be addressed when using the method. In conclusion, the relatively high reproducibility of the photographic reading of gingivitis and caries, and the bias reducing capacity of the photographic method, makes this method attractive when oral epidemiologic investigations are at high risk of bias. References 1. ARNBJERG D . Bias i odontologisk epidetniologi. Thesis, Aarhus Tandl8egeh0jskole, 1990. 2. SACKETT D L . Bias in analytical research. / Chron Dis 1979; 32:51-63. 3. GJ0Rtj p T. Klinisk vurderitig afdiagnostiske utulersogelsestnetoder. Thesis, Copenhagen; Lajgeforeningens Forlag, 1988. 4. OLIVER RC, HOLM-PEDERSEN P, LOE H . The correlation be-
tween clinical scoring, exudate measurements and micro-
5.
6.
7. 8. 9. 10.
scopic evaluation of inflammation in the gingiva. J Periodontol 1969; 40: 201-9. HARA K , TAKAHASHt T, NoHARA H, KotiAYASHt S. A Correlation between microscopic numerical evaluation on clinical scoring on total collagen content in inflamed gingivae. / Periodontol \915\ 46; 455-64. KoNiG KG. Findings in serially sectioned teeth showing early fissure lesions. In; JAMES, KONIG K , HELD A. Advances inflttoride research and caries prevention. 1966; 4; 73-9. DOWNER M C . Validation of methods used in dental caries diagnosis, bit Dent J \9S9\ 39; 241-6. EsPELtD I. Radiographic diagnosis and treattnent decisions on approximal caries. Thesis. Bergen, 1987. COHEN J. A coefficient of agreement for nominal scales. Educ Psycliol Meas 1960; 20; 3 7 ^ 6 . FELDMAN RS, DOUGLASS C W , LOFTUS E R , KAPLER K K ,
CHAUNCEY HH. Interexaminer agreement in the measurement of periodontal disease. J/'(?f/oc/o«/ Res 1982; 17; 80-9. 11. MARKKANEN H , PAUNIO K , PAUNIO I, RAJALA M . Reproduc-
ibility of a clinical screening method for assessing gingival infiammation, pockets and plaque retentions. Cotntmtnity Dent Oral Epidemiol \9%S; 13; 33-6. 12. NORDBLAD A, LoRMAS M. Cades and fillings in the permatient dentition of cohorts at schoolchildren in Espoo, Finland, during a 3-year period. Cotnmunltv Dent Oral Epidemiol 19H6; \4: 126-7. 13. ALANEN P, TtEKSO J, PAUNIO 1. Effect of war-time dietary changes on dental health of Finns 40 years later. Cotntntmity Dent Oral Epidetniol 1985; 13; 281-4. 14. LANDIS J R , KOCH G G . The measurement of observer agreement for categorial data. Biometrics 1977; 33; 59-74. 15. JOHNSON RH, ROZANISJ, SCHOFIELD IDF, HAQ MS. A com-
parison of a clinical and photographic assessment of plaque and gingivitis. Can Dent As.soc J1977; 43; 476-81. 16.
DUNNE SM, DAY C R , ALEXANDER A G . Evaluation of the use
of colour transparencies for scoring gingivitis. Comtmtttity Dent Orcd Epidemiol 19&0: 8; 110-3.
D. Arnbjerg, S. Poulsen and J. Heidmann Department of Child Dental Health and Community Dentistry, Royal Dental College, Vennelyst Boulevard, Aarhus, Denmark
Arnbjerg D, Poulsen S, Heichnatin J: Evaluation of a photographic tnethod for diagnosis of gingivitis and caries. Scatid J Dent Res 1992; 100: 207-10.
The aitn of the present study was to determine the value of a photographic method when diagnosing gingivitis and caries. 78 patients participated in the investigation. The validity of the photographic method could not be established, since the reproducibility of the clinical diagnosis was not 100%. Instead, the value of the method was determined by comparing the reproducibility of the clinical and the photographic diagnosis. For gingivitis the intra- and interexaminer reproducibilities were best for the photographic readings. For caries the reproducibility of the clinical diagnosis was highest. The photographic method was not limited by method variation when diagnosing redness of the gingiva and caries. However, limitations due to variation were present when diagnosing gingival swelling. The paper also describes the bias reducing capacity of the photographic method.
The bias of the results of oral epidemiologic investigations has received relatively little attention until now. A recent review of dental epidemiologic studies (1) has revealed that the major sources of bias are: 1) changing diagnostic criteria during longitudinal studies and the use of different diagnostic criteria in cross-sectional studies, which are compared later on, 2) rneasurernent bias due to diagnostic suspicion bias (2), and 3) bias due to more than one exarniner diagnosing the condition. Bias will always be a threat to the validity of a study, and minimizing bias is therefore important. All three sources of bias can be reduced if the diagnosis is made on clinical photographs or radiographs, since these pictures can be evaluated under blind conditions. Furthermore, the use of the pictures will enable examination of all participants within a short period of time by one examiner, and the use of the same diagnostic criteria on all participants is therefore more likely. Ideally, the validity of a new diagnostic procedure should be determined. The validity is determined by comparing the result of the new diagnostic procedure with a final true diagnosis (3). For the purpose of the present study, the most obvious final true diagnosis would be the clinical diagnosis. However, previous studies have shown that the clinical diagnosis of gingivitis and caries is not in complete agreement with the histologic diagnosis of the same conditions (4-7). Caries studies have
Key words: bias; dental caries, gingivitis; photography Dorte Arnbjerg, Department of Child Dental Health and Community Dentistry, Royal Dental College, Vennelyst Boulevard, DK-8000 Aarhus C, Denmark Accepted for publication 31 August 1991
also shown that the clinical and the radiologic diagnosis are not in complete agreement (8). When the validity cannot be assessed, the reproducibility must be determined instead (3). The reproducibility is determined by comparing the results of repeated examinations of the same object, and the intraexaminer as well as the interexaminer reproducibility can be determined. The purpose of the present study is, therefore, to determine the reproducibility of the clinical diagnosis of gingivitis and caries, and compare this reproducibility to the reproducibility of a procedure using clinical photographs. Furtherrnore the aim is to assess the shortcomings of the photographic method. Subjects and methods
95 patients attending the Royal Dental College, Aarhus, on February 1st, 1990, were invited to participate in the investigation. 17 of these (18%) refused to participate. Eleven clinical photographs were taken in each individual. All photographs were taken with a Olympus OM-2 camera, and the same type of film (Kodak EPR 135 64) was used. Two occlusal, 3 facial and 6 lingual photographs were taken in a predetermined order. Further details on the method of photography are given elsewhere (1). Ten subjects were photographed twice.
208
Arnbjerg et al.
Gingivitis was examined on 60 units in each subject. Separate diagnoses of redness and swelling evaluated visually and tactilly were made on each unit. Bleeding on pressure and probing pocket depth were assessed as well. Caries was diagnosed on 166 sites using 19 diagnostic categories. This classification enabled distinction of sound sites, different types of fillings, and sites with active and non-active caries. On 30 of the 78 participants both gingivitis and caries were diagnosed, and on the remaining 48 participants only caries was diagnosed. Investigator 1 (D.A.) examined all the subjects. Eight subjects were examined twice for gingivitis by investigator 1, and five subjects were examined by both investigators. Nine subjects were examined twice for caries status and investigator 2 (J.H.) examined eight subjects for caries. Calibration ofthe investigators was done while developing the classifications. The photographs were developed at a photographic laboratory, and then read in a dark room while projecting onto a screen (size 0.9 x 1.4 m). Before reading the photographs the data forms were coded for missing teeth. During the photographic readings as many sites as possible were diagnosed on each photograph. When a site had been read on one photograph, it was not diagnosed on the succeeding photographs. After having read all 11 photographs for one subject, the sites without any diagnosis were assigned the code "unreadable". On the photographs gingivitis was diagnosed by separate evaluation of redness and visual swelling. Five subjects were examined by both investigators, and one investigator (D.A.) examined eight subjects twice. For caries the same classification as for the clinical examination was used. The caries status of nine subjects was determined twice by one investigator, and seven subjects were diagnosed by both investigators. All the double readings were done without the investigator knowing that the photographs were being reread. The time spent on photographing and diagnosing 11 subjects was assessed. The data were analyzed using site by site crosstabulation. For gingivitis, redness and swelling were compared separately. The reproducibility was measured by Po and KAPPA. P^ was calculated as the proportion of sites on which the diagnosis were in agreement. KAPPA was calculated as the proportion of agreement after chance agreement was excluded (9). If chance agreement is denoted P^, then KAPPA is calculated as KAPPA = ^ ~ ^ 1-Pe The statistics were calculated for all sites and for readable sites. The variation due to the photo-
READABLE SITES
ALL SITES
0.8
0.6 -
0.2 - I
INTER
1 INTRA
REDNESS
INTER
INTRA
SWELLING
^ B KAPPA
INTER
INTRA
REDNESS
INTER
INTRA
SWELLING
^ ^ PO
Fig. 1. Reproducibility of clinical diagnosis of gingivitis.
graphic procedure was estimated by comparing the readings on two photographs taken ofthe same area during one session. Results
The 78 participants had on average 24 remaining teeth, and a mean age of 48 yr. 87% of the subjects had at least one site that bled on probing, 23% of the subjects had pockets with a probing depth larger than 5 mm. Calculated over all subjects 1% of all sites were affected by active caries and 30% of all sites were filled. On average 6 min were spent on photographing, 8.5 min were used for clinical examination and 14.7 min for the photographic readings on each participant. Figs. 1 and 2 show the reproducibility ofthe clinical and the photographic diagnosis of gingivitis. Both clinically and photographically the intraexALL SITES
0,8
H Mi
0,6
0,4
0,2
READABLE SITES
•
1
H INTER
1
••
1J1J J11 1
INTRA
REDNESS
INTER
INTRA
SWELLING
H I KAPPA
INTER
INTRA
REDNESS
INTER
INTRA
SWELLING
^ ^ PO
Fig. 2. Reproducibility of photographic readitig of gingivitis.
Photographic diagnosis of gingivitis and caries Table 1 Agreement between the clinieal and the photographie diagnosis of gingivitis Readable sites All sites Examiner 1 Examiner 2
Redness Swelling Redness Swelling
KAPPA 0.58 0.63 0.36 0.51
KAPPA 0.72 0.80 0.47 0.65
Po
0.69 0.74 0.53 0.67
Po
0.80 0.87 0.63 0.78
209
sites. For gingivitis the estimates were 0.84 (all sites) and 0.88 (readable sites) for redness and 0.70 (all sites) and 0.76 (readable sites) for swelling. Table 2 shows the distribution of unreadable sites. Most areas not included on the photographs were situated facially, and insufficient quality ofthe photograph was most frequent when diagnosing gingivitis. Discussion
aminer reproducibility was greater than the interexaminer reproducibility. The intra- as well as the interexaminer reproducibility were greater for readable sites compared to all sites. The diagnosis of redness was more reproducible than the diagnosis of swelling. The intraexaminer reproducibility for the clinical and the photographic method was almost the same, while the interexaminer reproducibility was greater for the photographic readings. Table 1 shows the estimates of agreement achieved when comparing the clinical and photographic diagnoses. For redness as well as swelling the agreement was weaker than the intraexaminer reproducibility. Examiner 2 showed the lowest agreement, and a tendency to diagnose more redness and swelling clinically. For caries Fig. 3 shows the reproducibility of the clinical and the photographic diagnoses. Both clinically and photographically the interexaminer reproducibility was greater than the interexaminer reproducibility. For the photographic readings the estimates were highest for readable sites, whereas the estimates are identical for the clinical diagnosis since all sites were readable. Comparison of readings of two photographs taken ofthe same area in the same session gave an agreement estimate (KAPPA) for caries of 0.89 for all sites and of 0.93 for readable
The clinical diagnosis of gingivitis and caries cannot be regarded as finally true diagnoses, since they are not fully reproducible. For gingivitis the intraexaminer reproducibility is comparable to earher findings (10), while the agreement betvi^een the two examiners is weaker than earlier reports (10, 11). However, in this study redness and swelling were diagnosed separately, since agreement in a combined classification can be true agreement as well as disagreement which is camouflaged. When analyzing the data with a dichotomous classification the reproducibility is enlarged, and the results become more comparable (10, 11). For caries the clinical reproducibility is comparable, especially when considering that the classification had 19 categories, while the compared classifications have a maximum of three categories (12, 13). The photographic readings are not fully reproducible either, but when the clinically and the photographie methods are compared on the basis of their reproducibility the clinical method is characterized as having "moderate" agreement, whereas the photographic method has "substantial" agreement when diagnosing gingivitis. For the diagnosis of caries, agreement for both methods is classified "substantial" or "almost perfect" (14). Basing the evaluation on the questionable comparison of the clinical and the photographic diagnosis the results are comparable to earlier findings (15, 16).
READABLE SITES
ALL SITES
Table 2 Distribution andfrequency of "unreadable" sites Not included Insufficient on the quality photograph Gingivitis Max. Facial 12.6% 3.6% Lingual 4.3% 6.3% Mand. Facial 11.3% 2.3% Lingual 7.0% 8.3% Region
INTER
INTRA
CUINIGAL
INTER
INTRA
PHOTOGRAPHIC
H H KAPPA
INTER
INTRA
OLINIOAL
INTER
INTRA
Caries Max.
PHOTOGRAPHIC
^ ^ PO
Fig. 3. Reproducibility of clinical and photographic diagnosis of caries.
Mand.
Molars Premolars Canines and incisors Molars Premolars Canines and incisors
8.1%
2.0%
0.3% 10.8%
0.5% 1.8%
1.3%
1.7%
210
Arnbjerg et al.
The method variation influences the value of the photographic method. For the diagnosis of redness and caries the method variation can be neglected, since it is weaker than the intraexaminer variation. However, when diagnosing swelling the method causes variation. This might be due to differences in dryness of the actual area when taking the photograph, or to the fact that different extent of mouth opening will influence the position of the mirrors. Furthermore, the value of the photographic method depends on areas being included on the photographs and on photographs of sufficient quality. The areas that were the most difficult to reproduce on the photographs were facially in the mandible, a fact that should be addressed when using the method. In conclusion, the relatively high reproducibility of the photographic reading of gingivitis and caries, and the bias reducing capacity of the photographic method, makes this method attractive when oral epidemiologic investigations are at high risk of bias. References 1. ARNBJERG D . Bias i odontologisk epidetniologi. Thesis, Aarhus Tandl8egeh0jskole, 1990. 2. SACKETT D L . Bias in analytical research. / Chron Dis 1979; 32:51-63. 3. GJ0Rtj p T. Klinisk vurderitig afdiagnostiske utulersogelsestnetoder. Thesis, Copenhagen; Lajgeforeningens Forlag, 1988. 4. OLIVER RC, HOLM-PEDERSEN P, LOE H . The correlation be-
tween clinical scoring, exudate measurements and micro-
5.
6.
7. 8. 9. 10.
scopic evaluation of inflammation in the gingiva. J Periodontol 1969; 40: 201-9. HARA K , TAKAHASHt T, NoHARA H, KotiAYASHt S. A Correlation between microscopic numerical evaluation on clinical scoring on total collagen content in inflamed gingivae. / Periodontol \915\ 46; 455-64. KoNiG KG. Findings in serially sectioned teeth showing early fissure lesions. In; JAMES, KONIG K , HELD A. Advances inflttoride research and caries prevention. 1966; 4; 73-9. DOWNER M C . Validation of methods used in dental caries diagnosis, bit Dent J \9S9\ 39; 241-6. EsPELtD I. Radiographic diagnosis and treattnent decisions on approximal caries. Thesis. Bergen, 1987. COHEN J. A coefficient of agreement for nominal scales. Educ Psycliol Meas 1960; 20; 3 7 ^ 6 . FELDMAN RS, DOUGLASS C W , LOFTUS E R , KAPLER K K ,
CHAUNCEY HH. Interexaminer agreement in the measurement of periodontal disease. J/'(?f/oc/o«/ Res 1982; 17; 80-9. 11. MARKKANEN H , PAUNIO K , PAUNIO I, RAJALA M . Reproduc-
ibility of a clinical screening method for assessing gingival infiammation, pockets and plaque retentions. Cotntmtnity Dent Oral Epidemiol \9%S; 13; 33-6. 12. NORDBLAD A, LoRMAS M. Cades and fillings in the permatient dentition of cohorts at schoolchildren in Espoo, Finland, during a 3-year period. Cotnmunltv Dent Oral Epidemiol 19H6; \4: 126-7. 13. ALANEN P, TtEKSO J, PAUNIO 1. Effect of war-time dietary changes on dental health of Finns 40 years later. Cotntntmity Dent Oral Epidetniol 1985; 13; 281-4. 14. LANDIS J R , KOCH G G . The measurement of observer agreement for categorial data. Biometrics 1977; 33; 59-74. 15. JOHNSON RH, ROZANISJ, SCHOFIELD IDF, HAQ MS. A com-
parison of a clinical and photographic assessment of plaque and gingivitis. Can Dent As.soc J1977; 43; 476-81. 16.
DUNNE SM, DAY C R , ALEXANDER A G . Evaluation of the use
of colour transparencies for scoring gingivitis. Comtmtttity Dent Orcd Epidemiol 19&0: 8; 110-3.
