Intraindividual effect of daily supervised flossing on caries in schoolchildren* LARS-ERIC GRANATH', THORE MARTINSSON", LARS MATSSON', GOSTA NILSSON'', ULLA SCHRODER' AND BERIT SODERHOLM'^
^ Department oj Pedodontics, University oj Eund, School of Dentistry, Matmo, ^ Department of Orat Diagnosis, Karotinska Institutet, School of Dentistry, Huddinge, and •' Department of Preventive Dentistry, Public Dental Service, Malmg, Sweden
iW-^-
'
• -•
Granath, L.-E., Martinsson, T., Matsson, L., Nilsson, G., Schroder, U. & Soderholm, B.: Intraindividual effect of daily supervised flossing on caries in schoolchildren. Community Dent. Oral Epidemiol. 1979: 7: 147-150. Abstract - The aim was to study the effeet of flossing on proximal caries in children grouped according to different combinations of dietary and oral hygiene habits. 140 12-13-year-old children flossed the right or the left lateral region of the mouth once every school-day for 2 years by pulling a waxed floss once up and down through the proximal contacts. Proximal caries was recorded on bitewing films, taken at the baseline and at the 2-year registration. Diet history was obtained four times during the period. Oral hygiene was classified aeeording to the number of bleeding points registered with a feather-loaded probe at the final examination. Caries increments on the control side during the experimental period were calculated for groups with the same habits. A logical border with respect to the amount of new caries was then established between suitable and unsuitable dietary habits as well as between sufficient and insufficient oral hygiene. No statistically significant difference was found between the control and experimental subgroups in the different combinations of dietary and oral hygiene habits, neither with respect to the whole material nor comparable contralateral surfaces. The numerical differences were so small that the technique of flossing studied here cannot be recommended. Key words: dental earies; dental flossing. L.-E. Granath, Department of Pedodontics, University of Lund, School of Dentistry, S-214 21 Malmo, Sweden. Accepted for publieation 10 December 1978.
The area just below the proximal contact of teeth surrounded by a normally situated gingival margin is not accessible for cleaning with a toothbrush. However, dental flossing has been shown to be effective in removing proximal plaque (4,9,11), to such an extent that an improved gingival state can be obtained compared with the effect of toothbrushing (9) only. The caries-preventive effect of dental flossing
has been demonstrated by WRIGHT et al. (15) in a study on contralateral tooth surfaces in first-grade children. Research assistants did the flossing once a day for 20 months, with a 4-month break in the middle of the period. The frequency of new caries lesions in test surfaces was 6.7 % compared to 14.9 % in control surfaces, the difference being statistically significant at the 1 % level of probability. HOROWITZ et al. (10) and SILVERSTEIN et
* Read in abbreviated form at the 61st Annual Meeting of the Scandinivian Division of l.A.D.R. in Umea, June i6-J8, 1978. 0301-5661/79/030147-04 $02.50/0
©
1979
Munksgaard, Copenhagen
^
-
148
GRANATH et al.
al. (13) likewise found a slight reduction of the caries increment in treatment groups after 29-32 months, but the differences were not statistically significant. The latter studies concerned 5-8-grade children, who flossed themselves under supervision. When evaluating the effect of a caries-preventive measure it is important to know about the level of other factors in the caries process. Several studies (2,6-8) concerning children have shown that the effect of practicing one habit at the most favorable level is greatest when the others are most unfavorable. No such analyses were done in the abovementioned studies. The aim of the present investigation was to study the effect of flossing on proximal caries in schoolchildren who were grouped according to different combinations of dietary and oral hygiene habits. Such an approach should contribute to as correct conclusions as possible. Further, the purpose was to test a technique so simple that, if effective, it could be implemented as a suitable means in group prevention programs in schools.
Registration of the gingival state was made on buccal, mesial and lingual surfaces of first molars and first and second premolars with the aid of a feather-loaded periodontal probe (1) and standardized load (0.27 N). T h e number of bleeding points on the control side was used as an expression of oral hygiene. Second molars were exeluded because they had not erupted in all children. The registration was done at the start of the trial and at the final examination. Unfortunately, the original values had to be discarded because of a mechanical defect in the probe. Proximal caries was registered on bitewing films, two on each side, taken before the study started and at the final examination, respectively. Orthoradial projection against the contact between the first and second premolars and between the second premolar and the first molar was used. Proximal enamel caries was defined as radiolucent areas that could not be related to normal anatomy or hypoplasia (5). All films were evaluated simultaneously by two examiners with the aid of a magnifying viewer (12), from the distal surface of the first premolar to the mesial surface of the second molar. A double determination of the baseline values of a random sample, covering about 1/5 of the total material, was done after 5 months. It showed a 96 % agreement with the primary registrations concerning caries — not caries. All registrations were done without knowing whether the films belonged to a eontrol or an experimental
MATERIAL AND METHODS
The children were grouped with respect to combinations of dietary and oral hygiene habits as follows. Total values of the caries increment on the control side during the experimental period were calculated for groups with the same frequency of high-sucrose consumptions and with the same number of bleeding points on that side, respectively. In this way a logical border with respect to the amount of new caries was established between suitable and unsuitable dietary habits as well as between sufficient and insufficient oral hygiene.
side. GROUPING OF THE SUBJECTS
A total of 140 children from six sehooklasses from one sehool in Malmo participated for 2 years during schooldays. May 1975-May 1977. The children were 12-13 years of age at the start of the study. This age was ehosen because a maximum of intact surfaces of newlyerupted premolars and second molars was available during the experimental period. The elasses were divided by lot into two halves. One half flossed on the left side and the other on the right. Thus, the effect of flossing could be studied intraindividually. Following information to and agreement with the parents, the study started with a training period, during which the children learned how to floss their teeth. A waxed floss was foreed up and down once through each proximal contact on the experhnental side, from the distal surface of the first premolar to the mesial surface of the seeond molar. The children flossed once every school-day, supervised by specially trained dental assistants. All the children brushed their teeth at least once a day with fluoride-containing toothpaste and participated in the preventive program run by the Public Dental Service, which included brushing the teeth every 6th week with a 0.2 % NaF-solution. A diet history was obtained four times during the period. The ehildren filled in a pretested questionnaire concerning regular meals and snacks. Each type of high-sucrose consumption was then given a weight corresponding to its regularity, and a mean value per day was calculated from the four diet histories per Individual.
STATISTICAL TREATMENT OF DATA The data were treated in two ways. First, all data were distributed among the four combinations of dietary and oral hygiene habits in control and experimental subgroups, respectively. In order to overcome the effect of variations in the number of erupted teeth, the values of caries increment were expressed as the percentage of surfaces that became earious during the experimental period out of the number of available surfaces at the end of the period minus those that had been carious and filled at the start. The difference between the subgroups in each combination was tested two-sidedly according to the t-test for percentage figures. Second, a separate study was performed on contralateral surfaces that were available and caries-free at the start of the trial and had identical contact relationship with the neighboring tooth. The t-test as above was applied. Differences at the 5 % level of probability were considered to be statistically significant. ; :•. , • . . ! :
Dental flossing in schoolchildren 149 Table 1. Distribution of the subjects with respect to habits
Table 3. Total caries increment in the subgroups related to comparable contralateral surfaces
Oral hygiene Oral hygiene Diet
Unsuitable Suitable
Insufficient
Sufficient
33 32
28 47
Insufficient Contr. Exp. Diet
Sufficient Contr. Exp.
Unsuitable 148
RESULTS The distribution of the subjects according to combinations of dietary and oral hygiene habits is presented in Table 1 and the total caries increment in the different control and experimental subgroups in Table 2. No statistically significant differences were found. Neither did the numerical differences exhibit the expected pattern, by which the effect should have been greatest for the most unfavorable and least for the most favorable combination. The total caries increment for all subjects was about 25 % for both the control side and the experimental side. Table 3 shows the total caries increment of comparable contralateral surfaces iti the different subgroups. The statistical tests revealed no significant differences. In the combination of unsuitable diet and sufficient oral hygiene, the experimental side developed more new caries than the control side. The percentage value of the experimental contralateral surfaces, 38 %, was higher than in atiy other subgroup.
DISCUSSION The results indicate that dental flossing as perTable 2. Total caries increment in the subgroups Oral hygiene Insufficient Conlr. Exp. Diet
Unsuitable n ci
Sufficient Contr. Exp.
291 30.6
300 29.0
231 28.1
239 31.8
269 26.4
274 26.3
438
432
17.8
18.1
Suitable n
ci
n, number of available surfaees during the trial. ci, caries increment in percent.
ci
33.1
Suitable n cl
31.3
166
27.7
29.5
29.3
22.4
38.0 255
147
18.0
n, number of surface pairs. ci, caries increment in percent.
formed in the present study is of limited, if aiiy, value as a group preventive measure for schoolchildren irrespective of dietary and oral hygiene conditions. The reason for the lack of effect is probably that the technique was insufficient to remove the bacterial plaque where the caries process starts. Concerning the supervision, the dental assistants may have had difficulty in checking that every child really followed the instructions, because they only had time to control that the class in question flossed the correct side of the mouth. Opinions in the literature diverge on whether schoolchildren are capable of learnitig how to floss their teeth effectively. TERHUNE (14) reported that 8-year-olds can be trained to do so, though it takes more time than for 11-year-olds. On the other hand, BRYN (3) found that teaching the use of dental floss to second-grade children is difficult and would take more time than is usually available in school. One of the goals of the present study was to test a technique so simple that everyone participating in the program shotild be able to follow the instructions. While we may have oversimplified the technique, a more advanced procedure would not have been realistic for the purpose. It is therefore concluded that implementation of dental floss program should be restricted to selected cases who are in particular need of such treatment and who can be expected to practice the measure in the recommended way, i. e. pulling the floss back and forth a number of times on the proximal area not accessible to toothbrushing.
150
GRANATH et al.
habits and chewing fluoride tablets in 4-year-old chil- ; dren. Caries Res. 1978: 12: 83-92 ^
REFERENCES 1. ASBOK-JORGENSEN, V., ATTSTROM, R . , LANG, N . P. &
8. GRANATH, L.-E. & SGHRODER, U . : Explanatory model
LoE, H.: Effect of chlorhexidine dressing on the healing after periodontal surgery. / . Periodontol. 1974: 45: 13-17
for the interaction of factors in the earies process. Aeta Odontol. Scand. 1978: 36: 253-256
2. BAWDEN, J . , GRANATH, L.-E., HOLST, K . , KOCH, G.,
KRASSE, P . & RooTZEN, H.: Effect of mouthrinsing with a sodium fluoride solution in. children with different caries activity. / . Dent. Res. 1978: 57: Spec. Issue A, Abstr. No. 810 3. BRYN, K . J.: A report on the feasibility of a plaque control program with the use of dental floss at a second grade level in a school setting. / . Indiana Dent. Assoc. 1973: 52: 437-441 4. GJERMO, P. & FLOTRA, L . : The effect
of
different
methods of interdental cleaning. / . Periodontal Res. 1970: 5; 230-236 5. GRANATH, L.-E., HOLST, K . & OMNELL, K . - A . : Effekten
av information i tandhalsovard i samband med halsokontroll av 4-aringar - (forts.). IV. Kariesforekomst. V. Sammanfattande diskussion. Swed. Dent. J. 1971: 64: 175-184 6. GRANATH, L.-E., ROOTZEN, H . , LILJEGREN, E . & HOLST,
K.: Variation in caries prevalence related to combinations of dietary and oral hygiene habits in 6-year-old children. Caries Res. 1976: 10: 308-317 7. GRANATH, L.-E., ROOTZEN, H . , LILJEGREN, E . , HOLST,
K. & KoHLER, L.: Variation in caries prevalence related to combinations of dietary and oral hygiene
9. HILL, H . C , LEVI, P. A. & GLICKMAN, I.: The effects •
of waxed and unwaxed dental floss on interdental plaque accumulation and interdental gingival health. / . Periodontol. 1973: 44: 411^13 • 10. HOROWITZ, A. M., SUOMI, J. D., PETERSON, J. K . &
LvM.AN, B. A.: Effect of supervised daily plaque re- , moval by children: Results after third and final year. .' / . Dent. Res. 1977: 56/ Spec. Issue A, Abstr. No. 170 ] 11. KELLER, S . E . & MANisON-HiNG, L. R.: Clearance studies of proximal tooth surfaees. Part I I I and IV: In vivo removal of interproximal plaque. Ala. J. Med. Sei. 1969: 6; 399-405 12. MATTSSON, O . : A magnifying viewer for photofluorographic films. Aeta Radiol. 1953: 39: 412-414 13. SILVERSTEIN, S., GOLD, S., HEILBRON, D . , NELMS, D . &
WYCOFF, S.: Effect of supervised deplaquing on dental caries, gingivitis, and plaque. / . Dent. Res. 1977: 57: , Spec. Issue A, Abstr. No. 169 ' 14. TERHUNE, J. A.: Predieting the readiness of elementary i school children to learn an effective dental flossing teehnique. / . Am. Dent. Assoc. 1973: 86: 1332-1336 15. WRIGHT, G . Z . , B.^NTING, D. W. & FEASBY, W . H . :
Effect of interdental flossing on the incidenee of proximal caries in children. / . Dent. Res. 1977: 56: 574-578
^ Department oj Pedodontics, University oj Eund, School of Dentistry, Matmo, ^ Department of Orat Diagnosis, Karotinska Institutet, School of Dentistry, Huddinge, and •' Department of Preventive Dentistry, Public Dental Service, Malmg, Sweden
iW-^-
'
• -•
Granath, L.-E., Martinsson, T., Matsson, L., Nilsson, G., Schroder, U. & Soderholm, B.: Intraindividual effect of daily supervised flossing on caries in schoolchildren. Community Dent. Oral Epidemiol. 1979: 7: 147-150. Abstract - The aim was to study the effeet of flossing on proximal caries in children grouped according to different combinations of dietary and oral hygiene habits. 140 12-13-year-old children flossed the right or the left lateral region of the mouth once every school-day for 2 years by pulling a waxed floss once up and down through the proximal contacts. Proximal caries was recorded on bitewing films, taken at the baseline and at the 2-year registration. Diet history was obtained four times during the period. Oral hygiene was classified aeeording to the number of bleeding points registered with a feather-loaded probe at the final examination. Caries increments on the control side during the experimental period were calculated for groups with the same habits. A logical border with respect to the amount of new caries was then established between suitable and unsuitable dietary habits as well as between sufficient and insufficient oral hygiene. No statistically significant difference was found between the control and experimental subgroups in the different combinations of dietary and oral hygiene habits, neither with respect to the whole material nor comparable contralateral surfaces. The numerical differences were so small that the technique of flossing studied here cannot be recommended. Key words: dental earies; dental flossing. L.-E. Granath, Department of Pedodontics, University of Lund, School of Dentistry, S-214 21 Malmo, Sweden. Accepted for publieation 10 December 1978.
The area just below the proximal contact of teeth surrounded by a normally situated gingival margin is not accessible for cleaning with a toothbrush. However, dental flossing has been shown to be effective in removing proximal plaque (4,9,11), to such an extent that an improved gingival state can be obtained compared with the effect of toothbrushing (9) only. The caries-preventive effect of dental flossing
has been demonstrated by WRIGHT et al. (15) in a study on contralateral tooth surfaces in first-grade children. Research assistants did the flossing once a day for 20 months, with a 4-month break in the middle of the period. The frequency of new caries lesions in test surfaces was 6.7 % compared to 14.9 % in control surfaces, the difference being statistically significant at the 1 % level of probability. HOROWITZ et al. (10) and SILVERSTEIN et
* Read in abbreviated form at the 61st Annual Meeting of the Scandinivian Division of l.A.D.R. in Umea, June i6-J8, 1978. 0301-5661/79/030147-04 $02.50/0
©
1979
Munksgaard, Copenhagen
^
-
148
GRANATH et al.
al. (13) likewise found a slight reduction of the caries increment in treatment groups after 29-32 months, but the differences were not statistically significant. The latter studies concerned 5-8-grade children, who flossed themselves under supervision. When evaluating the effect of a caries-preventive measure it is important to know about the level of other factors in the caries process. Several studies (2,6-8) concerning children have shown that the effect of practicing one habit at the most favorable level is greatest when the others are most unfavorable. No such analyses were done in the abovementioned studies. The aim of the present investigation was to study the effect of flossing on proximal caries in schoolchildren who were grouped according to different combinations of dietary and oral hygiene habits. Such an approach should contribute to as correct conclusions as possible. Further, the purpose was to test a technique so simple that, if effective, it could be implemented as a suitable means in group prevention programs in schools.
Registration of the gingival state was made on buccal, mesial and lingual surfaces of first molars and first and second premolars with the aid of a feather-loaded periodontal probe (1) and standardized load (0.27 N). T h e number of bleeding points on the control side was used as an expression of oral hygiene. Second molars were exeluded because they had not erupted in all children. The registration was done at the start of the trial and at the final examination. Unfortunately, the original values had to be discarded because of a mechanical defect in the probe. Proximal caries was registered on bitewing films, two on each side, taken before the study started and at the final examination, respectively. Orthoradial projection against the contact between the first and second premolars and between the second premolar and the first molar was used. Proximal enamel caries was defined as radiolucent areas that could not be related to normal anatomy or hypoplasia (5). All films were evaluated simultaneously by two examiners with the aid of a magnifying viewer (12), from the distal surface of the first premolar to the mesial surface of the second molar. A double determination of the baseline values of a random sample, covering about 1/5 of the total material, was done after 5 months. It showed a 96 % agreement with the primary registrations concerning caries — not caries. All registrations were done without knowing whether the films belonged to a eontrol or an experimental
MATERIAL AND METHODS
The children were grouped with respect to combinations of dietary and oral hygiene habits as follows. Total values of the caries increment on the control side during the experimental period were calculated for groups with the same frequency of high-sucrose consumptions and with the same number of bleeding points on that side, respectively. In this way a logical border with respect to the amount of new caries was established between suitable and unsuitable dietary habits as well as between sufficient and insufficient oral hygiene.
side. GROUPING OF THE SUBJECTS
A total of 140 children from six sehooklasses from one sehool in Malmo participated for 2 years during schooldays. May 1975-May 1977. The children were 12-13 years of age at the start of the study. This age was ehosen because a maximum of intact surfaces of newlyerupted premolars and second molars was available during the experimental period. The elasses were divided by lot into two halves. One half flossed on the left side and the other on the right. Thus, the effect of flossing could be studied intraindividually. Following information to and agreement with the parents, the study started with a training period, during which the children learned how to floss their teeth. A waxed floss was foreed up and down once through each proximal contact on the experhnental side, from the distal surface of the first premolar to the mesial surface of the seeond molar. The children flossed once every school-day, supervised by specially trained dental assistants. All the children brushed their teeth at least once a day with fluoride-containing toothpaste and participated in the preventive program run by the Public Dental Service, which included brushing the teeth every 6th week with a 0.2 % NaF-solution. A diet history was obtained four times during the period. The ehildren filled in a pretested questionnaire concerning regular meals and snacks. Each type of high-sucrose consumption was then given a weight corresponding to its regularity, and a mean value per day was calculated from the four diet histories per Individual.
STATISTICAL TREATMENT OF DATA The data were treated in two ways. First, all data were distributed among the four combinations of dietary and oral hygiene habits in control and experimental subgroups, respectively. In order to overcome the effect of variations in the number of erupted teeth, the values of caries increment were expressed as the percentage of surfaces that became earious during the experimental period out of the number of available surfaces at the end of the period minus those that had been carious and filled at the start. The difference between the subgroups in each combination was tested two-sidedly according to the t-test for percentage figures. Second, a separate study was performed on contralateral surfaces that were available and caries-free at the start of the trial and had identical contact relationship with the neighboring tooth. The t-test as above was applied. Differences at the 5 % level of probability were considered to be statistically significant. ; :•. , • . . ! :
Dental flossing in schoolchildren 149 Table 1. Distribution of the subjects with respect to habits
Table 3. Total caries increment in the subgroups related to comparable contralateral surfaces
Oral hygiene Oral hygiene Diet
Unsuitable Suitable
Insufficient
Sufficient
33 32
28 47
Insufficient Contr. Exp. Diet
Sufficient Contr. Exp.
Unsuitable 148
RESULTS The distribution of the subjects according to combinations of dietary and oral hygiene habits is presented in Table 1 and the total caries increment in the different control and experimental subgroups in Table 2. No statistically significant differences were found. Neither did the numerical differences exhibit the expected pattern, by which the effect should have been greatest for the most unfavorable and least for the most favorable combination. The total caries increment for all subjects was about 25 % for both the control side and the experimental side. Table 3 shows the total caries increment of comparable contralateral surfaces iti the different subgroups. The statistical tests revealed no significant differences. In the combination of unsuitable diet and sufficient oral hygiene, the experimental side developed more new caries than the control side. The percentage value of the experimental contralateral surfaces, 38 %, was higher than in atiy other subgroup.
DISCUSSION The results indicate that dental flossing as perTable 2. Total caries increment in the subgroups Oral hygiene Insufficient Conlr. Exp. Diet
Unsuitable n ci
Sufficient Contr. Exp.
291 30.6
300 29.0
231 28.1
239 31.8
269 26.4
274 26.3
438
432
17.8
18.1
Suitable n
ci
n, number of available surfaees during the trial. ci, caries increment in percent.
ci
33.1
Suitable n cl
31.3
166
27.7
29.5
29.3
22.4
38.0 255
147
18.0
n, number of surface pairs. ci, caries increment in percent.
formed in the present study is of limited, if aiiy, value as a group preventive measure for schoolchildren irrespective of dietary and oral hygiene conditions. The reason for the lack of effect is probably that the technique was insufficient to remove the bacterial plaque where the caries process starts. Concerning the supervision, the dental assistants may have had difficulty in checking that every child really followed the instructions, because they only had time to control that the class in question flossed the correct side of the mouth. Opinions in the literature diverge on whether schoolchildren are capable of learnitig how to floss their teeth effectively. TERHUNE (14) reported that 8-year-olds can be trained to do so, though it takes more time than for 11-year-olds. On the other hand, BRYN (3) found that teaching the use of dental floss to second-grade children is difficult and would take more time than is usually available in school. One of the goals of the present study was to test a technique so simple that everyone participating in the program shotild be able to follow the instructions. While we may have oversimplified the technique, a more advanced procedure would not have been realistic for the purpose. It is therefore concluded that implementation of dental floss program should be restricted to selected cases who are in particular need of such treatment and who can be expected to practice the measure in the recommended way, i. e. pulling the floss back and forth a number of times on the proximal area not accessible to toothbrushing.
150
GRANATH et al.
habits and chewing fluoride tablets in 4-year-old chil- ; dren. Caries Res. 1978: 12: 83-92 ^
REFERENCES 1. ASBOK-JORGENSEN, V., ATTSTROM, R . , LANG, N . P. &
8. GRANATH, L.-E. & SGHRODER, U . : Explanatory model
LoE, H.: Effect of chlorhexidine dressing on the healing after periodontal surgery. / . Periodontol. 1974: 45: 13-17
for the interaction of factors in the earies process. Aeta Odontol. Scand. 1978: 36: 253-256
2. BAWDEN, J . , GRANATH, L.-E., HOLST, K . , KOCH, G.,
KRASSE, P . & RooTZEN, H.: Effect of mouthrinsing with a sodium fluoride solution in. children with different caries activity. / . Dent. Res. 1978: 57: Spec. Issue A, Abstr. No. 810 3. BRYN, K . J.: A report on the feasibility of a plaque control program with the use of dental floss at a second grade level in a school setting. / . Indiana Dent. Assoc. 1973: 52: 437-441 4. GJERMO, P. & FLOTRA, L . : The effect
of
different
methods of interdental cleaning. / . Periodontal Res. 1970: 5; 230-236 5. GRANATH, L.-E., HOLST, K . & OMNELL, K . - A . : Effekten
av information i tandhalsovard i samband med halsokontroll av 4-aringar - (forts.). IV. Kariesforekomst. V. Sammanfattande diskussion. Swed. Dent. J. 1971: 64: 175-184 6. GRANATH, L.-E., ROOTZEN, H . , LILJEGREN, E . & HOLST,
K.: Variation in caries prevalence related to combinations of dietary and oral hygiene habits in 6-year-old children. Caries Res. 1976: 10: 308-317 7. GRANATH, L.-E., ROOTZEN, H . , LILJEGREN, E . , HOLST,
K. & KoHLER, L.: Variation in caries prevalence related to combinations of dietary and oral hygiene
9. HILL, H . C , LEVI, P. A. & GLICKMAN, I.: The effects •
of waxed and unwaxed dental floss on interdental plaque accumulation and interdental gingival health. / . Periodontol. 1973: 44: 411^13 • 10. HOROWITZ, A. M., SUOMI, J. D., PETERSON, J. K . &
LvM.AN, B. A.: Effect of supervised daily plaque re- , moval by children: Results after third and final year. .' / . Dent. Res. 1977: 56/ Spec. Issue A, Abstr. No. 170 ] 11. KELLER, S . E . & MANisON-HiNG, L. R.: Clearance studies of proximal tooth surfaees. Part I I I and IV: In vivo removal of interproximal plaque. Ala. J. Med. Sei. 1969: 6; 399-405 12. MATTSSON, O . : A magnifying viewer for photofluorographic films. Aeta Radiol. 1953: 39: 412-414 13. SILVERSTEIN, S., GOLD, S., HEILBRON, D . , NELMS, D . &
WYCOFF, S.: Effect of supervised deplaquing on dental caries, gingivitis, and plaque. / . Dent. Res. 1977: 57: , Spec. Issue A, Abstr. No. 169 ' 14. TERHUNE, J. A.: Predieting the readiness of elementary i school children to learn an effective dental flossing teehnique. / . Am. Dent. Assoc. 1973: 86: 1332-1336 15. WRIGHT, G . Z . , B.^NTING, D. W. & FEASBY, W . H . :
Effect of interdental flossing on the incidenee of proximal caries in children. / . Dent. Res. 1977: 56: 574-578
