- Email: [email protected]
The efficacy of a fluoride chewing gum on salivary fluoride concentration and plaque pH in children
Journal of Dentistry (2004) 32, 471–477
www.intl.elsevierhealth.com/journals/jden
The efficacy of a fluoride chewing gum on salivary fluoride concentration and plaque pH in children ¨ ztas¸a,*, Haluk Bodura, Ays¸egu ¨ lmeza, ¨l O Nurhan O Aysel Berkkanb, Serpil Culac a
Department of Pediatric Dentistry, Gazi University, Biskek cad 82, Ankara 06510, Turkey Department of Analytic Chemistry of Pharmacy, Gazi University, Ankara, Turkey c School of Applied Sciences, Bas¸kent University, Ankara, Turkey b
Received 17 April 2003; received in revised form 6 January 2004; accepted 18 March 2004
KEYWORDS Chewing gum; Fluoride concentration; Plaque pH; Saliva
Summary Objectives. The purpose of this study was therefore to study the influence of different chewing times on the salivary F concentration and on the recovery of plaque pH directly after a sucrose rinse on both the chewing and the non-chewing side. Methods. For this purpose, one piece of sugar free chewing gum was chewed to 10 healthy subjects (aged 8–10 years, 5 male and 5 female children). Subjects refrained from toothbrushing for 3 days. On the fourth day, they rinsed for 1 min with 10 ml of a 10% sucrose solutions. After 8 min, chewing gum was given and started to chew for either 5, 10, 20, 30, 45 min or control (sucrose rinse). Thus, altogether six test sessions were repeated at one week intervals. Measurements of F concentration in saliva and pH of approximal plaque were carried out at two contralateral sites for up to 60 min. Results. Higher salivary F concentrations were found on the chewing side than on the non-chewing side (expressed as) ðp , 0:05Þ: But, the difference between the chewing and the non-chewing side was not obvious for the plaque pH (expressed as AUC) ðp . 0:05Þ: Therefore, this study showed that: (1) the F concentrations in saliva after chewing a F containing chewing gum had only small numerical differences among the various chewing times, with the exception for 5 min. All chewing time periods showed statistically significant differences between chewing and non-chewing side. (2) The prolonged chewing time increased the plaque pH recovery after a sucrose rinse ðp , 0:05Þ; but there was no statistically significant difference on both of the chewing and non-chewing side ðp . 0:05Þ: Conclusion. The results of this study indicated that a prolonged chewing time was favorable to the plaque pH recovery after a sucrose rinse and, to a certain extent, to the salivary fluoride concentration. Also it was shown that the F concentration in saliva was strongly dependent on which side the subject chewed on. q 2004 Elsevier Ltd. All rights reserved.
Introduction *Corresponding author. Tel.: þ 90-312-2126220/300; fax: þ 90-312-2239226. ¨ ztas¸). E-mail address: [email protected] (N. O
It is well known that dietary sugars play a vital role in the development of dental caries. The acid
0300-5712/$ - see front matter q 2004 Elsevier Ltd. All rights reserved. doi:10.1016/j.jdent.2004.03.002
¨ ztas¸ et al. N. O
472
produced from the fermentation of sugars results in a plaque pH drop, which initiates decalcification of the enamel.1 Chewing gum gained interest due to its ability to stimulate salivation and accelerate the clearance of fermentable carbohydrate still present from the dietary intake.2 However, chewing gums have the potential of being an effective vehicle for delivering therapeutic agents to dentition because they permit protracted contact of the agent to the teeth with minimal efforts on the part of the patient.3 The other studies evaluated the effectiveness of a number of potentially anticaries agents in chewing gum.4 – 6 The concept of remineralization of enamel lesions has been supported by clinical studies,7 the reversal of experimental caries,8 and the reversal of natural caries lesions in viva after use of topical fluorides.9 Additionally, low levels of fluoride (F) appear to facilitate the precipitation of mineral on the surface of enamel crystals,10 thereby improving the stability of the apatite and rendering it less susceptible to cariogenic challenges.11 The search for F delivery systems which provide prolonged elevation of salivary F levels has led to an interest in chewing gum as a logical vehicle for F administration. Fluoridated chewing gums allow for frequent, repetitive topical applications of a low level of F,12 and coincidentally stimulate salivary flow which facilitates the clearance of cariogenic substrate, raises salivary and plaque pH, and increases salivary calcium and phosphate concentrations and promotes enamel remineralization.13
Material and method Subject Ten children aged 8 – 10 years of both sexes (five male and five female children) were selected from Saray Social Rehabilitation Center in Ankara (Turkey) having the following criteria selection: 1. Having first permanent molar and primary second molar in the mouth with no restoration. 2. DFT/dft not more than two. 3. Normal occlusion in all subjects. 4. Same socio-economic status, having similar food habits. 5. Oral hygiene instructions were given utilizing tooth brushing without toothpaste. 6. Low fluoride concentration of the study area. The children were subjected to thorough oral prophylaxis and the plaque score of each child was
brought to zero/normal before the start of each experiment. They were instructed not to clean their teeth for 3 days prior to the test and to come to the laboratory on the fourth day without having eaten or drunk anything (except for water) during the last 3 h. In each individual, the chewing and nonchewing sides were carefully recorded during the chewing.
Experimental procedures The sugar-free chewing gum used was DayGum Protex (Perfetti Gıda San. ve Tic. A.S¸, Turkey) containing 0.12 mg F/stick. Each subject was given 10 ml of 10% (w/v) sucrose solution and was asked to rinse for 1 min. The sucrose rinse was followed by an 8 min pause and a low plaque pH was recorded. Then chewing started with the following five times: 5, 10, 20, 30 and 45 min. Detailed chewing instructions were given before and during the chewing. A mouthrinse with sucrose without any chewing afterwards was carried out as a control. Thus, altogether six tests were carried out. No conversation was allowed during the test. The six test sessions were repeated at one-week intervals and the professional cleaning was repeated at the end of each experimental setting. The same subjects were then asked to brush their teeth and use normal oral hygiene regime for 4 days.
Salivary F concentration Saliva samples for F measurements were collected on eight occasions during and after chewing that is at 0, 10, 15, 20, 30, 40, 50 and 60 min. Two circular paper discs Millipore Corp., Bedford, USA) with a diameter of 13 mm each capable of absorbing approximately 80 ml. Of saliva were placed at two contralateral locations in the mouth (1) in the oral vestibule near the upper right primary second molar and (2) in the oral vestibule near the upper left primary second molar. The discs remained at the sampling site for approximately 15 s, and were then transferred to two test tubes, each containing 300 ml of redistilled water and 38 ml of Tisab III (Orion Research, Inc., Cambridge, USA). The F concentration was determined with an ion-sensitive electrode (96-09 Orion Res., Inc.) connected to an Orian SA-720 pH/ISE meter.
Plaque pH Plaque pH was measured parallel with saliva sampling on nine occasions, that is, at 0, 8, 10, 15, 20, 30, 40, 50 and 60 min using the microtouch method.14 An iridium touch microelectrode,
Chewing gum with fluoride
with a diameter of 0.1 mm (Beetrode, MEPH-1, WP Instruments, Inc., New Haven, USA) was inserted into the approximal plaque at two contralateral locations: (1) in the first molar and primary molar contact area of the right upper jaw; (2) in the first molar and primary molar contact area of the left upper jaw. The electrode was connected to an Orion 720 pH/ISE meter. A salt bridge was created in 3 M KCI between a reference electrode (MERE 1, WP Instruments, Inc., USA) and a finger of the subject. The electrode was calibrated using the buffers of 4.00 and pH 7.00 before the start of each test series and also after every plaque pH determination of all subjects. For cleaning after each test series, the electrodes were stored in 95% ethanol overnight after being rinsed with water.
Statistical analyses The mean values of F concentration and plaque pH at the different time points were calculated and plotted against time. The area under the curve (AUC) was estimated by computer, after which the mean values of the 10 individuals were calculated. For the F concentration, the AUC represents the area between the F curve and the time axis between 8 and 60 min, while for the plaque pH, the AUC represents the total area of pH 6.5. The significance levels between means of different groups at different time points were tested by means of repeated analysis of variance (ANOVA). Two-tailed paired t-test or Student’s t test for independent samples were applied to assess the significance levels between means of each group.
Results Salivary F concentration All 10 subjects instinctively preferred one chewing side (right side in eight individuals and left side in two individuals) and used this side for all five test series. Fig. 1 shows the mean salivary F concentrations for the chewing and the non-chewing side, presented both as absolute and logarithmic values. The F concentration reached the highest values on the first two sampling occasions, i.e. after chewing for 2 or 7 min corresponding to the 10 and 15 min value on the x-axis. After this, the concentration gradually decreased. The F concentrations were constantly higher on the chewing side than on
473
the non-chewing side for the first 40 min and then only numerical differences could be observed till the whole 60 min period. Fig. 2 shows the mean values of the AUC for the salivary F concentration. There were only small numerical differences among the various chewing times, with the exception for 5 min. In addition, all chewing time periods showed statistically significant differences between chewing and non-chewing side ðp , 0:05Þ:
Plaque pH Fig. 3 shows mean value results. The arrow in Fig. 3 shows the lowest pH after the rinse of sucrose solution. In the beginning of the chewing, a rise in the pH was immediately observed. After the long chewing times (20, 30, 45 min), the pH was nearly 6.5 throughout the whole 60 min registration period. Immediately, after the short chewing times (5 – 10 min), the pH rapidly dropped to lower values again. The mean values of AUC for the plaque pH are shown in Fig. 4. For all chewing times, statistically significant differences could not be observed between chewing and non-chewing side ðp . 0:05Þ: When comparing the five chewing times, statistically significant differences on the chewing side and non-chewing side for 5 vs 45 min ðp , 0:05Þ as well as for 10 vs 45 min ðp , 0:05Þ were found.
Discussion In the recent years, much research has focused on investigation into the effect of chewing gum use on dental caries. Much of this research has fallen into distinct approaches, each characterized by the nature of the mechanism by which the chewing gum is hypothesized to affect caries. First approach characterizes the mechanical and gustatory action of saliva stimulated by chewing of the gum itself as the primary factor in deriving an anti-caries benefit. Interest should be focused on the use of the product and chewing itself, and not on the presence or absence of any particular agent in the gum. The second approach is that chewing gum provides the delivery mechanism for a therapeutic, anti-caries agent, such as fluoride. The presence of the therapeutic agent is the key factor in providing an anti-caries benefit.6 Chewing gum is then suggested as a practical vehicle for caries prevention, because it allows fluoride to stay in the mouth long enough and requires only low dose.15 Previous F gum studies have demonstrated the elevation salivary F levels
474
¨ ztas¸ et al. N. O
Figure 1 Salivary F concentration on the chewing and the non-chewing side during and after 5, 10, 20, 30 and 45 min of chewing. The F concentration (mM) is given both as absolute and logarithmic (inserted) values. The arrow shows the chewing time. Mean values of 10 subjects.
for over 1 h12,16 to 4 h17 and the chewing of five sticks per day (after meals and at midmorning and mid afternoon) could potentially maintain elevated F levels during most of the waking hours and provide
prolonged protection against most cariogenic challenges. Also, it has been demonstrated that salivary F levels have remained above baseline values for over 1 h following the chewing of a stick of F
Chewing gum with fluoride
475
Figure 2 AUC for the salivary F concentration (mM) on the chewing side (a) and non-chewing side (b) during and after 5, 10, 20, 30 and 45 min of chewing. Degrees of significance between two sides and various chewing times are also shown (*p , 0:05). Mean values of 10 subjects.
chewing gum, with a minimal risk of systemic side effects due to F ingestion.16 – 18 Most of the studies emphasized the importance of frequent, repetitive use of low-potency selfapplied agents to provide prolonged elevated levels of salivary F.19 – 21 It has been suggested that elevated salivary F levels in the range of l – 10 ppm (0.053 – 0.53 mmol/l) are of clinical importance and appear sufficient to reduce enamel solubility and produce more rapid remineralization of early lesions.22 Because the salivary F concentration of this study between 1 and 10 ppm as informed above, it was advisable that repeated daily chewing of F chewing gums had an inhibitory effect on the acidogenecity of dental plaque in vivo. The results also indicated that chewing time of up to 45 min did not have any negative effect on the salivary F concentration. Considering all time points (10 – 60), the F concentrations were numerically higher for the 45 min chewing time compared to 5 min chewing time. This may be due to continuous
Figure 3 Plaque pH after a sucrose rinse on the chewing and non-chewing side during and after 5, 10, 20, 30 and 45 min of chewing and in a control, without chewing. The arrow shows the chewing-line. Mean values of 10 subjects.
release of F from the chewing gum during the longer chewing periods. In addition, Sjo ¨gren et al.23 suggested that some of the F released into saliva was transported back to gum base, resulting
¨ ztas¸ et al. N. O
476
side. This had strong influence on the salivary F level, resulting in concentration 2 –3 times higher on the chewing side compared to the non-chewing side. It has been shown in several studies26,27 that there was a limited migration of F from one side of the mouth to the other. The present investigation showed that the F concentration in saliva was strongly dependent on which side the subject chewed on. To conclude, the results from this study indicated that a prolong chewing time was favorable for the plaque pH recovery after a sucrose rinse and, to a certain extent, to the salivary F concentration. Present investigation also showed that F concentration in saliva was strongly dependent on which side the subject chewed on. So, the users should be informed about the importance of using both sides of the dentition when chewing in order to get an even F distribution in oral cavity.
Acknowledgements This study was supported by the research department of Gazi University. Figure 4 AUC for the plaque pH on the chewing side (a) non-chewing side (b) during and after 5, 10, 20, 30 and 45 min of chewing. Degrees of significance between two sides and various chewing times (*p , 0:05) are shown. Mean values of 10 subjects.
in recirculation of F back and fort to saliva. Our study results support this theory. The plaque pH studies showed that an acid challenge could be rapidly reversed by chewing gum.1,24,25 This information was approved in the present study. All of the chewing times in this study raised the decline caused by sucrose challenged in plaque pH, but a gradually increase of the plaque pH recovery was found with increasing chewing time both on chewing side and non-chewing side. Another finding was that plaque pH dropped again rapidly after the shorter periods of chewing. This is in agreement with Sjo ¨gren et al.’s study,23 showing that prolonged chewing after a sucrose rinse resulted in elevated plaque pH. An interesting observation in the study was that the maximum pH recovery occurred at the same time point for the chewing and non-chewing side. A possible explanation for this is that pH recovery due to gum chewing is an effect of elevated salivary flow from all salivary glands in oral cavity leading to a systemic effect on plaque pH. All 10 subjects showed a distinct preference for one chewing
References 1. Gopinath VK, Tandon S, Shirwaikar A. The effect of chewing gums on acidogenicity of plaque after a sucrose challenge. Journal of Clinical Pediatric Dentistry 1997;22:77—81. 2. Itthagarun A, Wei SH. Chewing gum and saliva in oral health. Journal of Clinical Dentistry 1997;8:159—62. 3. Chow LC, Takagi S, Shern RJ, Chow TH, Takagi KK, Sieck BA. Effects on whole saliva of chewing gums containing calcium phosphates. Journal of Dental Research 1994;73:26—32. 4. Edgar WM, Geddes DMA. Chewing gum and dental health: a review. British Dental Journal 1990;24:173—6. 5. Isogangas P, Makinen KK, Tiekso J, Alanen P. Long term effect of xylitol chewing gum in the prevention of dental caries. A follow-up 5 years after termination of a prevention program. Caries Research 1993;27:495—8. 6. Szo ¨ke J, Banoczy J, Proskin HM. Effect of after-meal sucrosefree gum chewing on clinical caries. Journal of Dental Research 2001;80:1725—9. 7. Koulourides T, Cameron B. Enamel remineralization as a factor in the pathogenesis of dental caries. Journal of Oral Pathology 1980;9:255—69. 8. Von der Fehr FR, Lo ¨e H, Theilade E. Experimental caries in man. Caries Resaerch 1970;4:431—48. 9. Holmen L, Thylstrup A. Natural caries development and its arrestment. In: Leach SA, editor. Factor relating to demineralisation, remineralization of the teeth. Oxford: IRL Press; 1986. p. 139—52. 10. Ten Cate JM, Arends J. Remineralization of artificial enamel lesions in vitro. Caries Research 1977;11:277—86. 11. Lamp WJ, Corpron RE, More FG, Beltran ED, Strachan DS, Kowalski CJ. In situ remineralization of subsurface enamel
Chewing gum with fluoride
12.
13.
14.
15.
16.
17.
18.
lesion after the use of a fluoride chewing gum. Caries Research 1993;27:111—6. Hattab FN, Green RM, Pang GM, Mok YC. Effect of fluoridecontaining chewing gum on remineralisation of carious lesions and on fluoride uptake in man. Clinical Preventive Dentistry 1989;11:6—11. Leach SA, Lee GTR, Edgar WM. Remineralization of artificial caries-like lesions in human enamel in situ by chewing sorbitol gum. Journal of Dental Research 1989;68: 1064—8. Lingstro ¨m P, Imfeld T, Birkhed D. Comparison of three different methods for measurements of plaque pH humans after consumptions of soft bread and potato chips. Journal of Dental Research 1993;72:865—70. Honkala E, Rimpela A, Karvonen S, Rimpela M. Chewing of xylitol gum-a well adopted practice among Finnish adolescent. Caries Research 1996;30:34—9. Bruun C, Givskov H. Release of fluoride from fluoridecontaining chewing gum. Community Dentistry and Oral Epidemiology 1978;6:27—9. Oliveby A, Ekstrand J, Lagerlo ¨f F. Effect of a salivary flow rate on salivary fluoride clearance after use of a fluoride containing chewing gum. Caries Research 1987;21:393—401. Ekstrand J, Birkhed D, Lindgren LE, Oliveby A, Edwardsson S, Frostell G. Effect of repeated intake of sugar free fluoridecontaining chewing gum on acidogenicity and microbial composition of dental plaque. Scandinavian Journal of Dental Research 1985;93:309—14.
477
19. Melberg JR, Chomicki WG. FIuoride uptake by artificial caries lesions from fluoride dentifrice in vivo. Journal of Dental search 1983;62:540—2. 20. Ostrom CA, Koulourides T, Retief DH, Bradley EL. Enamel fluoride uptake and acid resistance in subjects with high and low experimental cariogenicity. Journal of Dental Research 1984;63:133—6. 21. Clark JW, Corpron RE, More FG, Easton JW, Merrill DF, Kowalski CJ. Comparison of the effects of two topical fluoride regimens on demineralised enamel in vivo. Journal of Dental Research 1988;67:954—8. 22. Heintze V, Petersson LG. Accumulation, clearance of fluoride in human mixed saliva after different topical fluoride agents. Sweden Dental Journal 1979;3:141—8. 23. Sjo ¨gren K, Lingstro ¨m P, Lundberg AB, Birkhed D. Salivary fluoride concentration and plaque pH after using fluoridecontaining chewing gum. Caries Research 1997;31:366—72. 24. Aguirre-Zero O, Zero DT, Proskin HM. Effect of chewing xylitol chewing gum on salivary flow rate and the acidogenic potential of dental plaque. Caries Research 1993;27:55—9. ˘rul F, Sabah E. Effect of chewing gum on 25. Koparal E, Ertug plaque acidogenicity. The Journal of Clinical Pediatric Dentistry 2000;24:129—32. 26. Weatherell JA, Robinson C, Ralph JP. Migration of fluoride in the mouth. Caries Research 1984;18:348—53. 27. Jenkins JN, Krebsbach PH. Experimental study of the migration of charcoal particles in the human mouth. Archives Oral Biology 1985;30:697—9.
www.intl.elsevierhealth.com/journals/jden
The efficacy of a fluoride chewing gum on salivary fluoride concentration and plaque pH in children ¨ ztas¸a,*, Haluk Bodura, Ays¸egu ¨ lmeza, ¨l O Nurhan O Aysel Berkkanb, Serpil Culac a
Department of Pediatric Dentistry, Gazi University, Biskek cad 82, Ankara 06510, Turkey Department of Analytic Chemistry of Pharmacy, Gazi University, Ankara, Turkey c School of Applied Sciences, Bas¸kent University, Ankara, Turkey b
Received 17 April 2003; received in revised form 6 January 2004; accepted 18 March 2004
KEYWORDS Chewing gum; Fluoride concentration; Plaque pH; Saliva
Summary Objectives. The purpose of this study was therefore to study the influence of different chewing times on the salivary F concentration and on the recovery of plaque pH directly after a sucrose rinse on both the chewing and the non-chewing side. Methods. For this purpose, one piece of sugar free chewing gum was chewed to 10 healthy subjects (aged 8–10 years, 5 male and 5 female children). Subjects refrained from toothbrushing for 3 days. On the fourth day, they rinsed for 1 min with 10 ml of a 10% sucrose solutions. After 8 min, chewing gum was given and started to chew for either 5, 10, 20, 30, 45 min or control (sucrose rinse). Thus, altogether six test sessions were repeated at one week intervals. Measurements of F concentration in saliva and pH of approximal plaque were carried out at two contralateral sites for up to 60 min. Results. Higher salivary F concentrations were found on the chewing side than on the non-chewing side (expressed as) ðp , 0:05Þ: But, the difference between the chewing and the non-chewing side was not obvious for the plaque pH (expressed as AUC) ðp . 0:05Þ: Therefore, this study showed that: (1) the F concentrations in saliva after chewing a F containing chewing gum had only small numerical differences among the various chewing times, with the exception for 5 min. All chewing time periods showed statistically significant differences between chewing and non-chewing side. (2) The prolonged chewing time increased the plaque pH recovery after a sucrose rinse ðp , 0:05Þ; but there was no statistically significant difference on both of the chewing and non-chewing side ðp . 0:05Þ: Conclusion. The results of this study indicated that a prolonged chewing time was favorable to the plaque pH recovery after a sucrose rinse and, to a certain extent, to the salivary fluoride concentration. Also it was shown that the F concentration in saliva was strongly dependent on which side the subject chewed on. q 2004 Elsevier Ltd. All rights reserved.
Introduction *Corresponding author. Tel.: þ 90-312-2126220/300; fax: þ 90-312-2239226. ¨ ztas¸). E-mail address: [email protected] (N. O
It is well known that dietary sugars play a vital role in the development of dental caries. The acid
0300-5712/$ - see front matter q 2004 Elsevier Ltd. All rights reserved. doi:10.1016/j.jdent.2004.03.002
¨ ztas¸ et al. N. O
472
produced from the fermentation of sugars results in a plaque pH drop, which initiates decalcification of the enamel.1 Chewing gum gained interest due to its ability to stimulate salivation and accelerate the clearance of fermentable carbohydrate still present from the dietary intake.2 However, chewing gums have the potential of being an effective vehicle for delivering therapeutic agents to dentition because they permit protracted contact of the agent to the teeth with minimal efforts on the part of the patient.3 The other studies evaluated the effectiveness of a number of potentially anticaries agents in chewing gum.4 – 6 The concept of remineralization of enamel lesions has been supported by clinical studies,7 the reversal of experimental caries,8 and the reversal of natural caries lesions in viva after use of topical fluorides.9 Additionally, low levels of fluoride (F) appear to facilitate the precipitation of mineral on the surface of enamel crystals,10 thereby improving the stability of the apatite and rendering it less susceptible to cariogenic challenges.11 The search for F delivery systems which provide prolonged elevation of salivary F levels has led to an interest in chewing gum as a logical vehicle for F administration. Fluoridated chewing gums allow for frequent, repetitive topical applications of a low level of F,12 and coincidentally stimulate salivary flow which facilitates the clearance of cariogenic substrate, raises salivary and plaque pH, and increases salivary calcium and phosphate concentrations and promotes enamel remineralization.13
Material and method Subject Ten children aged 8 – 10 years of both sexes (five male and five female children) were selected from Saray Social Rehabilitation Center in Ankara (Turkey) having the following criteria selection: 1. Having first permanent molar and primary second molar in the mouth with no restoration. 2. DFT/dft not more than two. 3. Normal occlusion in all subjects. 4. Same socio-economic status, having similar food habits. 5. Oral hygiene instructions were given utilizing tooth brushing without toothpaste. 6. Low fluoride concentration of the study area. The children were subjected to thorough oral prophylaxis and the plaque score of each child was
brought to zero/normal before the start of each experiment. They were instructed not to clean their teeth for 3 days prior to the test and to come to the laboratory on the fourth day without having eaten or drunk anything (except for water) during the last 3 h. In each individual, the chewing and nonchewing sides were carefully recorded during the chewing.
Experimental procedures The sugar-free chewing gum used was DayGum Protex (Perfetti Gıda San. ve Tic. A.S¸, Turkey) containing 0.12 mg F/stick. Each subject was given 10 ml of 10% (w/v) sucrose solution and was asked to rinse for 1 min. The sucrose rinse was followed by an 8 min pause and a low plaque pH was recorded. Then chewing started with the following five times: 5, 10, 20, 30 and 45 min. Detailed chewing instructions were given before and during the chewing. A mouthrinse with sucrose without any chewing afterwards was carried out as a control. Thus, altogether six tests were carried out. No conversation was allowed during the test. The six test sessions were repeated at one-week intervals and the professional cleaning was repeated at the end of each experimental setting. The same subjects were then asked to brush their teeth and use normal oral hygiene regime for 4 days.
Salivary F concentration Saliva samples for F measurements were collected on eight occasions during and after chewing that is at 0, 10, 15, 20, 30, 40, 50 and 60 min. Two circular paper discs Millipore Corp., Bedford, USA) with a diameter of 13 mm each capable of absorbing approximately 80 ml. Of saliva were placed at two contralateral locations in the mouth (1) in the oral vestibule near the upper right primary second molar and (2) in the oral vestibule near the upper left primary second molar. The discs remained at the sampling site for approximately 15 s, and were then transferred to two test tubes, each containing 300 ml of redistilled water and 38 ml of Tisab III (Orion Research, Inc., Cambridge, USA). The F concentration was determined with an ion-sensitive electrode (96-09 Orion Res., Inc.) connected to an Orian SA-720 pH/ISE meter.
Plaque pH Plaque pH was measured parallel with saliva sampling on nine occasions, that is, at 0, 8, 10, 15, 20, 30, 40, 50 and 60 min using the microtouch method.14 An iridium touch microelectrode,
Chewing gum with fluoride
with a diameter of 0.1 mm (Beetrode, MEPH-1, WP Instruments, Inc., New Haven, USA) was inserted into the approximal plaque at two contralateral locations: (1) in the first molar and primary molar contact area of the right upper jaw; (2) in the first molar and primary molar contact area of the left upper jaw. The electrode was connected to an Orion 720 pH/ISE meter. A salt bridge was created in 3 M KCI between a reference electrode (MERE 1, WP Instruments, Inc., USA) and a finger of the subject. The electrode was calibrated using the buffers of 4.00 and pH 7.00 before the start of each test series and also after every plaque pH determination of all subjects. For cleaning after each test series, the electrodes were stored in 95% ethanol overnight after being rinsed with water.
Statistical analyses The mean values of F concentration and plaque pH at the different time points were calculated and plotted against time. The area under the curve (AUC) was estimated by computer, after which the mean values of the 10 individuals were calculated. For the F concentration, the AUC represents the area between the F curve and the time axis between 8 and 60 min, while for the plaque pH, the AUC represents the total area of pH 6.5. The significance levels between means of different groups at different time points were tested by means of repeated analysis of variance (ANOVA). Two-tailed paired t-test or Student’s t test for independent samples were applied to assess the significance levels between means of each group.
Results Salivary F concentration All 10 subjects instinctively preferred one chewing side (right side in eight individuals and left side in two individuals) and used this side for all five test series. Fig. 1 shows the mean salivary F concentrations for the chewing and the non-chewing side, presented both as absolute and logarithmic values. The F concentration reached the highest values on the first two sampling occasions, i.e. after chewing for 2 or 7 min corresponding to the 10 and 15 min value on the x-axis. After this, the concentration gradually decreased. The F concentrations were constantly higher on the chewing side than on
473
the non-chewing side for the first 40 min and then only numerical differences could be observed till the whole 60 min period. Fig. 2 shows the mean values of the AUC for the salivary F concentration. There were only small numerical differences among the various chewing times, with the exception for 5 min. In addition, all chewing time periods showed statistically significant differences between chewing and non-chewing side ðp , 0:05Þ:
Plaque pH Fig. 3 shows mean value results. The arrow in Fig. 3 shows the lowest pH after the rinse of sucrose solution. In the beginning of the chewing, a rise in the pH was immediately observed. After the long chewing times (20, 30, 45 min), the pH was nearly 6.5 throughout the whole 60 min registration period. Immediately, after the short chewing times (5 – 10 min), the pH rapidly dropped to lower values again. The mean values of AUC for the plaque pH are shown in Fig. 4. For all chewing times, statistically significant differences could not be observed between chewing and non-chewing side ðp . 0:05Þ: When comparing the five chewing times, statistically significant differences on the chewing side and non-chewing side for 5 vs 45 min ðp , 0:05Þ as well as for 10 vs 45 min ðp , 0:05Þ were found.
Discussion In the recent years, much research has focused on investigation into the effect of chewing gum use on dental caries. Much of this research has fallen into distinct approaches, each characterized by the nature of the mechanism by which the chewing gum is hypothesized to affect caries. First approach characterizes the mechanical and gustatory action of saliva stimulated by chewing of the gum itself as the primary factor in deriving an anti-caries benefit. Interest should be focused on the use of the product and chewing itself, and not on the presence or absence of any particular agent in the gum. The second approach is that chewing gum provides the delivery mechanism for a therapeutic, anti-caries agent, such as fluoride. The presence of the therapeutic agent is the key factor in providing an anti-caries benefit.6 Chewing gum is then suggested as a practical vehicle for caries prevention, because it allows fluoride to stay in the mouth long enough and requires only low dose.15 Previous F gum studies have demonstrated the elevation salivary F levels
474
¨ ztas¸ et al. N. O
Figure 1 Salivary F concentration on the chewing and the non-chewing side during and after 5, 10, 20, 30 and 45 min of chewing. The F concentration (mM) is given both as absolute and logarithmic (inserted) values. The arrow shows the chewing time. Mean values of 10 subjects.
for over 1 h12,16 to 4 h17 and the chewing of five sticks per day (after meals and at midmorning and mid afternoon) could potentially maintain elevated F levels during most of the waking hours and provide
prolonged protection against most cariogenic challenges. Also, it has been demonstrated that salivary F levels have remained above baseline values for over 1 h following the chewing of a stick of F
Chewing gum with fluoride
475
Figure 2 AUC for the salivary F concentration (mM) on the chewing side (a) and non-chewing side (b) during and after 5, 10, 20, 30 and 45 min of chewing. Degrees of significance between two sides and various chewing times are also shown (*p , 0:05). Mean values of 10 subjects.
chewing gum, with a minimal risk of systemic side effects due to F ingestion.16 – 18 Most of the studies emphasized the importance of frequent, repetitive use of low-potency selfapplied agents to provide prolonged elevated levels of salivary F.19 – 21 It has been suggested that elevated salivary F levels in the range of l – 10 ppm (0.053 – 0.53 mmol/l) are of clinical importance and appear sufficient to reduce enamel solubility and produce more rapid remineralization of early lesions.22 Because the salivary F concentration of this study between 1 and 10 ppm as informed above, it was advisable that repeated daily chewing of F chewing gums had an inhibitory effect on the acidogenecity of dental plaque in vivo. The results also indicated that chewing time of up to 45 min did not have any negative effect on the salivary F concentration. Considering all time points (10 – 60), the F concentrations were numerically higher for the 45 min chewing time compared to 5 min chewing time. This may be due to continuous
Figure 3 Plaque pH after a sucrose rinse on the chewing and non-chewing side during and after 5, 10, 20, 30 and 45 min of chewing and in a control, without chewing. The arrow shows the chewing-line. Mean values of 10 subjects.
release of F from the chewing gum during the longer chewing periods. In addition, Sjo ¨gren et al.23 suggested that some of the F released into saliva was transported back to gum base, resulting
¨ ztas¸ et al. N. O
476
side. This had strong influence on the salivary F level, resulting in concentration 2 –3 times higher on the chewing side compared to the non-chewing side. It has been shown in several studies26,27 that there was a limited migration of F from one side of the mouth to the other. The present investigation showed that the F concentration in saliva was strongly dependent on which side the subject chewed on. To conclude, the results from this study indicated that a prolong chewing time was favorable for the plaque pH recovery after a sucrose rinse and, to a certain extent, to the salivary F concentration. Present investigation also showed that F concentration in saliva was strongly dependent on which side the subject chewed on. So, the users should be informed about the importance of using both sides of the dentition when chewing in order to get an even F distribution in oral cavity.
Acknowledgements This study was supported by the research department of Gazi University. Figure 4 AUC for the plaque pH on the chewing side (a) non-chewing side (b) during and after 5, 10, 20, 30 and 45 min of chewing. Degrees of significance between two sides and various chewing times (*p , 0:05) are shown. Mean values of 10 subjects.
in recirculation of F back and fort to saliva. Our study results support this theory. The plaque pH studies showed that an acid challenge could be rapidly reversed by chewing gum.1,24,25 This information was approved in the present study. All of the chewing times in this study raised the decline caused by sucrose challenged in plaque pH, but a gradually increase of the plaque pH recovery was found with increasing chewing time both on chewing side and non-chewing side. Another finding was that plaque pH dropped again rapidly after the shorter periods of chewing. This is in agreement with Sjo ¨gren et al.’s study,23 showing that prolonged chewing after a sucrose rinse resulted in elevated plaque pH. An interesting observation in the study was that the maximum pH recovery occurred at the same time point for the chewing and non-chewing side. A possible explanation for this is that pH recovery due to gum chewing is an effect of elevated salivary flow from all salivary glands in oral cavity leading to a systemic effect on plaque pH. All 10 subjects showed a distinct preference for one chewing
References 1. Gopinath VK, Tandon S, Shirwaikar A. The effect of chewing gums on acidogenicity of plaque after a sucrose challenge. Journal of Clinical Pediatric Dentistry 1997;22:77—81. 2. Itthagarun A, Wei SH. Chewing gum and saliva in oral health. Journal of Clinical Dentistry 1997;8:159—62. 3. Chow LC, Takagi S, Shern RJ, Chow TH, Takagi KK, Sieck BA. Effects on whole saliva of chewing gums containing calcium phosphates. Journal of Dental Research 1994;73:26—32. 4. Edgar WM, Geddes DMA. Chewing gum and dental health: a review. British Dental Journal 1990;24:173—6. 5. Isogangas P, Makinen KK, Tiekso J, Alanen P. Long term effect of xylitol chewing gum in the prevention of dental caries. A follow-up 5 years after termination of a prevention program. Caries Research 1993;27:495—8. 6. Szo ¨ke J, Banoczy J, Proskin HM. Effect of after-meal sucrosefree gum chewing on clinical caries. Journal of Dental Research 2001;80:1725—9. 7. Koulourides T, Cameron B. Enamel remineralization as a factor in the pathogenesis of dental caries. Journal of Oral Pathology 1980;9:255—69. 8. Von der Fehr FR, Lo ¨e H, Theilade E. Experimental caries in man. Caries Resaerch 1970;4:431—48. 9. Holmen L, Thylstrup A. Natural caries development and its arrestment. In: Leach SA, editor. Factor relating to demineralisation, remineralization of the teeth. Oxford: IRL Press; 1986. p. 139—52. 10. Ten Cate JM, Arends J. Remineralization of artificial enamel lesions in vitro. Caries Research 1977;11:277—86. 11. Lamp WJ, Corpron RE, More FG, Beltran ED, Strachan DS, Kowalski CJ. In situ remineralization of subsurface enamel
Chewing gum with fluoride
12.
13.
14.
15.
16.
17.
18.
lesion after the use of a fluoride chewing gum. Caries Research 1993;27:111—6. Hattab FN, Green RM, Pang GM, Mok YC. Effect of fluoridecontaining chewing gum on remineralisation of carious lesions and on fluoride uptake in man. Clinical Preventive Dentistry 1989;11:6—11. Leach SA, Lee GTR, Edgar WM. Remineralization of artificial caries-like lesions in human enamel in situ by chewing sorbitol gum. Journal of Dental Research 1989;68: 1064—8. Lingstro ¨m P, Imfeld T, Birkhed D. Comparison of three different methods for measurements of plaque pH humans after consumptions of soft bread and potato chips. Journal of Dental Research 1993;72:865—70. Honkala E, Rimpela A, Karvonen S, Rimpela M. Chewing of xylitol gum-a well adopted practice among Finnish adolescent. Caries Research 1996;30:34—9. Bruun C, Givskov H. Release of fluoride from fluoridecontaining chewing gum. Community Dentistry and Oral Epidemiology 1978;6:27—9. Oliveby A, Ekstrand J, Lagerlo ¨f F. Effect of a salivary flow rate on salivary fluoride clearance after use of a fluoride containing chewing gum. Caries Research 1987;21:393—401. Ekstrand J, Birkhed D, Lindgren LE, Oliveby A, Edwardsson S, Frostell G. Effect of repeated intake of sugar free fluoridecontaining chewing gum on acidogenicity and microbial composition of dental plaque. Scandinavian Journal of Dental Research 1985;93:309—14.
477
19. Melberg JR, Chomicki WG. FIuoride uptake by artificial caries lesions from fluoride dentifrice in vivo. Journal of Dental search 1983;62:540—2. 20. Ostrom CA, Koulourides T, Retief DH, Bradley EL. Enamel fluoride uptake and acid resistance in subjects with high and low experimental cariogenicity. Journal of Dental Research 1984;63:133—6. 21. Clark JW, Corpron RE, More FG, Easton JW, Merrill DF, Kowalski CJ. Comparison of the effects of two topical fluoride regimens on demineralised enamel in vivo. Journal of Dental Research 1988;67:954—8. 22. Heintze V, Petersson LG. Accumulation, clearance of fluoride in human mixed saliva after different topical fluoride agents. Sweden Dental Journal 1979;3:141—8. 23. Sjo ¨gren K, Lingstro ¨m P, Lundberg AB, Birkhed D. Salivary fluoride concentration and plaque pH after using fluoridecontaining chewing gum. Caries Research 1997;31:366—72. 24. Aguirre-Zero O, Zero DT, Proskin HM. Effect of chewing xylitol chewing gum on salivary flow rate and the acidogenic potential of dental plaque. Caries Research 1993;27:55—9. ˘rul F, Sabah E. Effect of chewing gum on 25. Koparal E, Ertug plaque acidogenicity. The Journal of Clinical Pediatric Dentistry 2000;24:129—32. 26. Weatherell JA, Robinson C, Ralph JP. Migration of fluoride in the mouth. Caries Research 1984;18:348—53. 27. Jenkins JN, Krebsbach PH. Experimental study of the migration of charcoal particles in the human mouth. Archives Oral Biology 1985;30:697—9.