The effect of tensile strength on the clinical effectiveness and patient acceptance of dental floss
Philip J. Hanes', Norris L. O'Dell', Mark R. Baker\ James G. Keagle' and Harry C, Davis^ Department of Veriodontics, ^Oral Biology and ^Research Computing and Statistics, Medical College of Georgia, 1459 Laney Walker Boulevard, Augusta, Georgia 30912, USA
Hanes PJ, O'Dell NL, Baker MR, Keagle JG and Davis HC: The effect of tensile strength on the clinical effectiveness and patient acceptance of dental floss. J Clin Periodontol 1992; 19: 30-34. Abstract. This study compared the clinical effectiveness and subjective approval of 2 waxed dental flosses that differed significantly in tensile strength and wax content. At the initial appointment, subjects (20 lst-year dental students) were instructed to stop interproximal cleaning on 2 contralateral quadrants in order to allow plaque to accumulate on these surfaces for 1 week. 1 week later, subjects were instructed to begin flossing these 2 contralateral quadrants with 1 of the 2 types of floss for the next 1-week period, while withdrawing interproximal cleaning on the opposite 2 contralateral quadrants. After flossing these 2 quadrants for 1 week, the subjects began flossing the opposite 2 contralateral quadrants with the same floss. After 2 weeks of flossing contralateral quadrants, the 1st floss was withdrawn and replaced with the alternative floss for another similar 2-week trial period. At the end of each 2-week trial period, subjects completed subjective questionnaires concerning the floss they had used during the previous 2-week period. Pre- and post-flossing plaque indices were calculated for each week for both flosses, and compared statistically by a repeated measures analysis of variance. The results showed that both flosses significantly reduced interproximal plaque deposits, and had equal subjective approval. However, neither the greaterstrength nor the lower-wax content of the experimental floss was associated with an increase in clinical effectiveness or with a change in subjective approval.
The regular removal of dental plaque from interproximal tooth surfaces is an important component of any oral hygiene regimen that is designed to prevent or control dental caries and periodontal disease (Ash 1964, Mandel 1966, Loe et al. 1965, Lindhe & Koch 1967). Due to the relative ineffectiveness of toothbrushes in interproximal sites (Hansen & Gjermo 1971, Lindhe & Koch 1967, Sagnes et al. 1972), other devices such as floss (Bass 1948, Mohammed & Monserrate 1965, Hill et al. 1973), toothpicks (Schmid et al. 1976, Wolffe 1976, Bergenholtz & Brithon 1980) and interproximal brushes (Nayak & Wade 1977, Gjermo & Flotra 1970) are recommended as adjuncts to toothbrushing. Although toothpicks and interproximal brushes are considered easier to use than is floss (Kenney et al. 1976) and are usually preferred by patients over floss (Wolffe 1976), such devices can be prescribed only for patients with adequate embrasure space to accommodate their placement. Pa-
tients with intact gingival papillae which fill the interproximal spaces are usually required to use dental floss for proximal surface plaque removal. The optimum physical characteristics of dental floss were first proposed by Bass (1948). Other than a few comparisons of the clinical effectiveness of waxed and unwaxed flosses (Bergenholtz & Brithon 1980, Hill et al. 1973, Steven 1980, Lamberts et al. 1982, Wunderlich et al. 1982, Lobene et al. 1982), the relationship between various physical characteristics and the clinical effectiveness of dental floss is poorly understood. In addition, Httle attention is given to the control of physical properties in the manufacturing of dental floss. The bulk of dental floss marketed in the United Stated is purchased by dental product distributors as thread from various textile manufacturers. This thread is then waxed, colored or flavored and packaged as floss with no further effort to control or alter the physical properties ofthe floss. The pur-
Key words: dental floss; waxed dental floss; tensile strength; plaque; plaque index. Accepted for publication 25 October 1990
pose ofthe present study was, therefore, to compare the clinical effectiveness of a widely-used dental floss with that of a newly developed dental floss of comparable size, but with greater tensile strength and more uniform incorporation of wax into the floss, and to determine whether or not these physical differences result in more effective removal of interproximal dental plaque and in a greater subjective acceptance ofthe floss by patients. iVIaterial and Methods Physical properties of experimental and control flosses
The experimental dental floss was a waxed, nylon thread floss, 1077 denier and 1196 dtex (dtex = g/10,000 m). The control floss selected for comparison was a commonly used waxed dental floss of similar size, 1183 dtex and 1065 denier (Johnson & Johnson). Both experimental and control flosses were packaged in identical dispensers and
Effectiveness of dental floss labe!!ed either "A" or "B". None of the clinica! investigators knew which fioss was the experimenta! or contro! fioss. !0 packages each of both A and B denta! fioss were se!ected at random from the 2 respective lots of denta! fioss used in the c!inica! study. Sing!e strands from these 20 fioss samples were subjected to tensi!e tests on an Instron Mode! TM1130 Tensile Testing Machine, having a jaw separation rate of 305 + / — 5 mm/ min. The strength of the fioss samples was expressed as the load (g) necessary to rupture the sample and the % elongation at rupture was calcu!ated for each fioss samp!e. The % of wax by weight in each samp!e of fioss was measured by weighting the samples of fioss, removing the wax from the fioss, and then reweighing the fioss sample. Specimens were boi!ed in petro!eum ether in a SoxMet apparatus for 4 h, oven dried for another 4 h and then placed in a dessicator for 1 h. The resu!ting dry, wax-free samples were then weighed, and the wax content of the original samp!e expressed as a percentage of tota! weight. The respective values for strength at rupture, % e!ongation and % wax content for the 2 types of fioss were compared using a two-tai!ed, /-test. A probabi!ity !eve! of less than 0.05 was considered to be statistica!ly significant. Subjects for clinical trial
20 1 st-year denta! students at the Medical Co!lege of Georgia Schoo! of Dentistry were se!ected who had at !east 24 natural teeth in occ!usion and in alignment, no probing depths greater than 3 mm, no orthodontic app!iances and no defective c!ass II ama!gam and/or fu!!crown restorations. The fina! experimental group included 8 fema!e and !2 male subjects with ati average age of approximate!y 22 years.
zonta!!y from the contct point, 1 mm on a!! proxima! surfaces mesia! to the canine tooth and 2 mm on al! proximal surfaces dista! to the canine. Plaque deposits were measured fo!lowing staining of the deposits with a disc!osing so!ution, using a modification (Tab!e !) of the plaque index of Quig!ey & Hein (Quigley & Hein 1962, Turesky et a!. !970). Plaque index scores were calibrated between examiners by a series of p!aque scoring sessions conducted prior to the commencement of the study, and immediately prior to each c!inica! examination session during the study. At the 1st appointment, subjects were given a prophy!axis and thorough instructions in denta! fiossing technique. P!aque was removed from the proxima! surfaces of a!l teeth in the upper right and !ower left quadrants (1 and 3). Subjects were instructed not to fioss the teeth in quadrants ! and 3 for ! week in order to a!!ow p!aque to accumulate on these teeth. Subjects were a!so asked to refrain from the use of any mouthwash, or "anti-p!aque" toothpaste for the duration of the study. No effort was made to a!ter the subjects' ora! hygiene regirnens in any other way. 1 week later, a pre-fiossin'g plaque index was recorded for the proximal surfaces of teeth in quadrants 1 and 3. At this time, 10 subjects were issued type A fioss and 10 subjects were issued type B fioss and asked to fioss the teeth in quadrants 1 and 3 for 1 week. In addition, p!aque was removed from the proxima! surfaces of the teeth in the remaining quadrants (2 and 4) and fiossing was suspended for these quadrants whi!e fiossing the teeth in quadrants 1 and 3. At the end of the !st week of fiossing, a post-fiossing p!aque index was determined for quadrants 1 and 3, and a pre-fiossitig p!aque index for the nonfiossed quadrants 2 and 4. Denta! p!aque was removed from quadrants !
31
and 3 and subjects were asked to switch fiossed and non-fiossed quadrants for the following week. , ^ i; :-; At the end of the 2nd week of fiossing, post-fiossing plaque indices were determined for fiossed quadrants 2 and 4 and pre-fiossing plaque indices for non-fiossed quadrants 1 and 3. At this point, al! subjects turned in the fioss they had been using for the previous 2 weeks and were issued the alternative fioss. The subjects then fol!owed the same fiossing protoco! for the next 2 weeks using the a!ternative denta! fioss. The pre- and post-fiossing p!aque indices for each week were calculated for the both experimental and control fiosses. These measurements were subjected to a repeated measures analysis of variance using SPSS Release 2.01 Software on the University System of Georgia CYBER 180/850 computer. A probability level of less than 0.05 was considered to be statisticaHy significant. Subjective evaluation of flosses
At the end of each 2-week fiossing period, each subject comp!eted a standard questionnaire designed to provide a subjective appraisa! of the fioss used during that 2-week period. Subjects were asked to agree or disagree with each of a series of 12 statements using a standard Likert sca!e of 1 to 5 (see Table 4 for a listing of the subjective statements). The responses for the experimental and contro! fiosses were compared statistica!!y with a two-tai!ed, paired r-test, with a probabi!ity va!ue of !ess than 0,05 considered to be statistica!!y significant. Results Physical properties of experimental and control flosses
A!though the sizes and weights (dtex) of the 2 fiosses were simi!ar, the mean
Clinical trial methods
The 20 subjects were random!y divided into 4 groups of 5 subjects each, A sing!e investigator was assigned to each group and was responsib!e for determining the plaque scores for his group for the entire !ength of the study. P!aque scores were obtained for both the facial and ora! aspects of the mesial and dista! proximal surfaces of each tooth, excluding the central incisors and third molars. The facial or oral limits of the proximal surface were established by measuring hori-
Table 1. Interproximal plaque index Score
Criteria
0 1
no plaque on proximal surface separate flecks of plaque at the cervical margin or a solid band of plaque less than 1 mm in width on proximal surface continuous band of plaque at the cervical margin greater than or equal to 1 mm in width on proximal surface
The facial and oral limits of the interproximal tooth surfaces were established at a horizontal distance of 1 mm from the interproximal contact on anterior teeth and 2 mm from the interproximal contact on posterior teeth. Using the above criteria, the plaque scores for all the teeth were added together and divided by the total number of tooth surfaces scored in order to obtain a plaque index (i,e, either a pre-or post-flossing index), , . . ..
32
Hanes et al.
Table 2. Selected physical and chemical test data Mean + standard deviation
Dtex(gm/10,000 m) strength at rupture (g) elongation at rupture (%) wax content (% by weight)
control
experimental
P
1183 + 38 4730 + 264 16.93 ±1.79 27.47 + 3.36
1196 + 20 6461+291 15.81+0.98 22.51 ±1.70
0.291 0.0001* 0.099 0.0005*
Statistically significant at /'
Philip J. Hanes', Norris L. O'Dell', Mark R. Baker\ James G. Keagle' and Harry C, Davis^ Department of Veriodontics, ^Oral Biology and ^Research Computing and Statistics, Medical College of Georgia, 1459 Laney Walker Boulevard, Augusta, Georgia 30912, USA
Hanes PJ, O'Dell NL, Baker MR, Keagle JG and Davis HC: The effect of tensile strength on the clinical effectiveness and patient acceptance of dental floss. J Clin Periodontol 1992; 19: 30-34. Abstract. This study compared the clinical effectiveness and subjective approval of 2 waxed dental flosses that differed significantly in tensile strength and wax content. At the initial appointment, subjects (20 lst-year dental students) were instructed to stop interproximal cleaning on 2 contralateral quadrants in order to allow plaque to accumulate on these surfaces for 1 week. 1 week later, subjects were instructed to begin flossing these 2 contralateral quadrants with 1 of the 2 types of floss for the next 1-week period, while withdrawing interproximal cleaning on the opposite 2 contralateral quadrants. After flossing these 2 quadrants for 1 week, the subjects began flossing the opposite 2 contralateral quadrants with the same floss. After 2 weeks of flossing contralateral quadrants, the 1st floss was withdrawn and replaced with the alternative floss for another similar 2-week trial period. At the end of each 2-week trial period, subjects completed subjective questionnaires concerning the floss they had used during the previous 2-week period. Pre- and post-flossing plaque indices were calculated for each week for both flosses, and compared statistically by a repeated measures analysis of variance. The results showed that both flosses significantly reduced interproximal plaque deposits, and had equal subjective approval. However, neither the greaterstrength nor the lower-wax content of the experimental floss was associated with an increase in clinical effectiveness or with a change in subjective approval.
The regular removal of dental plaque from interproximal tooth surfaces is an important component of any oral hygiene regimen that is designed to prevent or control dental caries and periodontal disease (Ash 1964, Mandel 1966, Loe et al. 1965, Lindhe & Koch 1967). Due to the relative ineffectiveness of toothbrushes in interproximal sites (Hansen & Gjermo 1971, Lindhe & Koch 1967, Sagnes et al. 1972), other devices such as floss (Bass 1948, Mohammed & Monserrate 1965, Hill et al. 1973), toothpicks (Schmid et al. 1976, Wolffe 1976, Bergenholtz & Brithon 1980) and interproximal brushes (Nayak & Wade 1977, Gjermo & Flotra 1970) are recommended as adjuncts to toothbrushing. Although toothpicks and interproximal brushes are considered easier to use than is floss (Kenney et al. 1976) and are usually preferred by patients over floss (Wolffe 1976), such devices can be prescribed only for patients with adequate embrasure space to accommodate their placement. Pa-
tients with intact gingival papillae which fill the interproximal spaces are usually required to use dental floss for proximal surface plaque removal. The optimum physical characteristics of dental floss were first proposed by Bass (1948). Other than a few comparisons of the clinical effectiveness of waxed and unwaxed flosses (Bergenholtz & Brithon 1980, Hill et al. 1973, Steven 1980, Lamberts et al. 1982, Wunderlich et al. 1982, Lobene et al. 1982), the relationship between various physical characteristics and the clinical effectiveness of dental floss is poorly understood. In addition, Httle attention is given to the control of physical properties in the manufacturing of dental floss. The bulk of dental floss marketed in the United Stated is purchased by dental product distributors as thread from various textile manufacturers. This thread is then waxed, colored or flavored and packaged as floss with no further effort to control or alter the physical properties ofthe floss. The pur-
Key words: dental floss; waxed dental floss; tensile strength; plaque; plaque index. Accepted for publication 25 October 1990
pose ofthe present study was, therefore, to compare the clinical effectiveness of a widely-used dental floss with that of a newly developed dental floss of comparable size, but with greater tensile strength and more uniform incorporation of wax into the floss, and to determine whether or not these physical differences result in more effective removal of interproximal dental plaque and in a greater subjective acceptance ofthe floss by patients. iVIaterial and Methods Physical properties of experimental and control flosses
The experimental dental floss was a waxed, nylon thread floss, 1077 denier and 1196 dtex (dtex = g/10,000 m). The control floss selected for comparison was a commonly used waxed dental floss of similar size, 1183 dtex and 1065 denier (Johnson & Johnson). Both experimental and control flosses were packaged in identical dispensers and
Effectiveness of dental floss labe!!ed either "A" or "B". None of the clinica! investigators knew which fioss was the experimenta! or contro! fioss. !0 packages each of both A and B denta! fioss were se!ected at random from the 2 respective lots of denta! fioss used in the c!inica! study. Sing!e strands from these 20 fioss samples were subjected to tensi!e tests on an Instron Mode! TM1130 Tensile Testing Machine, having a jaw separation rate of 305 + / — 5 mm/ min. The strength of the fioss samples was expressed as the load (g) necessary to rupture the sample and the % elongation at rupture was calcu!ated for each fioss samp!e. The % of wax by weight in each samp!e of fioss was measured by weighting the samples of fioss, removing the wax from the fioss, and then reweighing the fioss sample. Specimens were boi!ed in petro!eum ether in a SoxMet apparatus for 4 h, oven dried for another 4 h and then placed in a dessicator for 1 h. The resu!ting dry, wax-free samples were then weighed, and the wax content of the original samp!e expressed as a percentage of tota! weight. The respective values for strength at rupture, % e!ongation and % wax content for the 2 types of fioss were compared using a two-tai!ed, /-test. A probabi!ity !eve! of less than 0.05 was considered to be statistica!ly significant. Subjects for clinical trial
20 1 st-year denta! students at the Medical Co!lege of Georgia Schoo! of Dentistry were se!ected who had at !east 24 natural teeth in occ!usion and in alignment, no probing depths greater than 3 mm, no orthodontic app!iances and no defective c!ass II ama!gam and/or fu!!crown restorations. The fina! experimental group included 8 fema!e and !2 male subjects with ati average age of approximate!y 22 years.
zonta!!y from the contct point, 1 mm on a!! proxima! surfaces mesia! to the canine tooth and 2 mm on al! proximal surfaces dista! to the canine. Plaque deposits were measured fo!lowing staining of the deposits with a disc!osing so!ution, using a modification (Tab!e !) of the plaque index of Quig!ey & Hein (Quigley & Hein 1962, Turesky et a!. !970). Plaque index scores were calibrated between examiners by a series of p!aque scoring sessions conducted prior to the commencement of the study, and immediately prior to each c!inica! examination session during the study. At the 1st appointment, subjects were given a prophy!axis and thorough instructions in denta! fiossing technique. P!aque was removed from the proxima! surfaces of a!l teeth in the upper right and !ower left quadrants (1 and 3). Subjects were instructed not to fioss the teeth in quadrants ! and 3 for ! week in order to a!!ow p!aque to accumulate on these teeth. Subjects were a!so asked to refrain from the use of any mouthwash, or "anti-p!aque" toothpaste for the duration of the study. No effort was made to a!ter the subjects' ora! hygiene regirnens in any other way. 1 week later, a pre-fiossin'g plaque index was recorded for the proximal surfaces of teeth in quadrants 1 and 3. At this time, 10 subjects were issued type A fioss and 10 subjects were issued type B fioss and asked to fioss the teeth in quadrants 1 and 3 for 1 week. In addition, p!aque was removed from the proxima! surfaces of the teeth in the remaining quadrants (2 and 4) and fiossing was suspended for these quadrants whi!e fiossing the teeth in quadrants 1 and 3. At the end of the !st week of fiossing, a post-fiossing p!aque index was determined for quadrants 1 and 3, and a pre-fiossitig p!aque index for the nonfiossed quadrants 2 and 4. Denta! p!aque was removed from quadrants !
31
and 3 and subjects were asked to switch fiossed and non-fiossed quadrants for the following week. , ^ i; :-; At the end of the 2nd week of fiossing, post-fiossing plaque indices were determined for fiossed quadrants 2 and 4 and pre-fiossing plaque indices for non-fiossed quadrants 1 and 3. At this point, al! subjects turned in the fioss they had been using for the previous 2 weeks and were issued the alternative fioss. The subjects then fol!owed the same fiossing protoco! for the next 2 weeks using the a!ternative denta! fioss. The pre- and post-fiossing p!aque indices for each week were calculated for the both experimental and control fiosses. These measurements were subjected to a repeated measures analysis of variance using SPSS Release 2.01 Software on the University System of Georgia CYBER 180/850 computer. A probability level of less than 0.05 was considered to be statisticaHy significant. Subjective evaluation of flosses
At the end of each 2-week fiossing period, each subject comp!eted a standard questionnaire designed to provide a subjective appraisa! of the fioss used during that 2-week period. Subjects were asked to agree or disagree with each of a series of 12 statements using a standard Likert sca!e of 1 to 5 (see Table 4 for a listing of the subjective statements). The responses for the experimental and contro! fiosses were compared statistica!!y with a two-tai!ed, paired r-test, with a probabi!ity va!ue of !ess than 0,05 considered to be statistica!!y significant. Results Physical properties of experimental and control flosses
A!though the sizes and weights (dtex) of the 2 fiosses were simi!ar, the mean
Clinical trial methods
The 20 subjects were random!y divided into 4 groups of 5 subjects each, A sing!e investigator was assigned to each group and was responsib!e for determining the plaque scores for his group for the entire !ength of the study. P!aque scores were obtained for both the facial and ora! aspects of the mesial and dista! proximal surfaces of each tooth, excluding the central incisors and third molars. The facial or oral limits of the proximal surface were established by measuring hori-
Table 1. Interproximal plaque index Score
Criteria
0 1
no plaque on proximal surface separate flecks of plaque at the cervical margin or a solid band of plaque less than 1 mm in width on proximal surface continuous band of plaque at the cervical margin greater than or equal to 1 mm in width on proximal surface
The facial and oral limits of the interproximal tooth surfaces were established at a horizontal distance of 1 mm from the interproximal contact on anterior teeth and 2 mm from the interproximal contact on posterior teeth. Using the above criteria, the plaque scores for all the teeth were added together and divided by the total number of tooth surfaces scored in order to obtain a plaque index (i,e, either a pre-or post-flossing index), , . . ..
32
Hanes et al.
Table 2. Selected physical and chemical test data Mean + standard deviation
Dtex(gm/10,000 m) strength at rupture (g) elongation at rupture (%) wax content (% by weight)
control
experimental
P
1183 + 38 4730 + 264 16.93 ±1.79 27.47 + 3.36
1196 + 20 6461+291 15.81+0.98 22.51 ±1.70
0.291 0.0001* 0.099 0.0005*
Statistically significant at /'
