Year : 2008 | Volume
: 26 | Issue : 4 | Page : 149--152
Erosive effects of acidic center-filled chewing gum on primary and permanent enamel
M Bolan, MC Ferreira, RS Vieira
Department of Stomatology, Federal University of Santa Catarina, Brazil
Rua Delminda da Silveira, 235/101E - Agron˘mica, Florianˇpolis - SC, 88025500
Background: The higher incidence of dental erosion in children and teenagers possibly reflects a high intake of acidic food and beverages as well as a more frequent diagnosis on this condition. Aim: The aim of this study was to evaluate the erosive potential of acidic filling of chewing gum in primary and permanent enamel. Methods and Materials: Eighty enamel blocks (40 primary and 40 permanent teeth) were used and randomly distributed into eight groups. Groups were divided according to types of dental substrates (permanent or primary), frequency of exposure to the acidic substance (2X or 4X/day), and concentration (pure or diluted). Exposure time to the acidic content of the chewing gum was five minutes under agitation, during five days. Results: All groups showed a significant decrease in surface microhardness (P < 0.001). There was neither any significant difference in the frequency of exposure to the acidic content nor to the types of dental substrates. There was a statistically significant difference between D1 (pure, 2X/day) and D2 (diluted, 2X/day) (P = 0.002), D3 (pure, 4X/day) and D4 (diluted, 4X/day) (P = 0.009) regarding the concentration, then the diluted acid content was associated with a greater decrease in microhardness. Conclusion: It is concluded that the acidic filling of a chewing gum reduced the microhardness of primary and permanent enamel.
|How to cite this article:|
Bolan M, Ferreira M C, Vieira R S. Erosive effects of acidic center-filled chewing gum on primary and permanent enamel.J Indian Soc Pedod Prev Dent 2008;26:149-152
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Bolan M, Ferreira M C, Vieira R S. Erosive effects of acidic center-filled chewing gum on primary and permanent enamel. J Indian Soc Pedod Prev Dent [serial online] 2008 [cited 2020 May 27 ];26:149-152
Available from: http://www.jisppd.com/text.asp?2008/26/4/149/44029
A high intake of acidic food and beverages as well as a more frequent diagnosis of dental erosion reflect the higher incidence of this pathology in children and teenagers. Dental erosion is characterized by superficial mineral loss ensued by contact between teeth and acidic substances with no bacterial involvement.  Etiologic factors are established as intrinsic and extrinsic. Intrinsic are related to reflux, alcohol abuse, bulimia, and anorexia. Acidic food and ambiental acidics are extrinsic causes. ,,,,
Diet represents the most important external risk factor to the erosive process among children,  due to the high use of juices and soft drinks, ,,,,,,,,, some medicines, , acidic candies, , and more recently the acidic filling of some chewing gums.
Erosive potential is related to the food's pH, buffer capacity,  frequency of intake,  contact time,  amount,  and acid concentration.  But they are not predictive factors since saliva's content of calcium, phosphate, and fluoride,  salivary flow,  and dental composition affect the process. Dental erosion is not an isolated process and it can be associated with abrasion and attrition. ,
The effect of sucrose-based chewing gum upon dental caries is well established. , But there are no studies about the consumption and effects of the acidic filling of these gums, which are very popular among children due to their pleasant taste and their coloring effect in the mouth. The aim of this study was to evaluate in vitro the erosive effects of the acidic filling in the chewing gums on primary and permanent enamel.
Materials and Methods
This research was approved by UFSC's Human Being Ethic Committee. Primary and permanent molar teeth free of hypoplasia, hypocalcification, and cracks were used. Teeth were cleaned with slurry of pumice and stored in 10% formalin solution. Eighty enamel human blocks (3 x 3 mm) were obtained of 40 primary molars and 40 permanent molars using a No. 11.4253 diamond disk (Buehler« , Lake Bluff, IL, USA) in a cutting machine (Isomet 1000, Buehler« , Lake Bluff, IL, USA), under refrigeration.
Enamel blocks were embedded in polystyrenic resin and ground and polished. Microhardness tests were carried out with a knoop diamond indenter with a 50 g load for 10 seconds. Specimens with mean hardness between 272-440 KHN were selected and divided into eight experimental groups. Groups were divided according to types of dental substrates (permanent or primary), frequency of exposure to the acidic substance (2X or 4X/day), and concentration (pure or diluted) [Table 1].
In order to assess the dilution to be used, a previous experiment was carried out on a volunteer with normal stimulated salivary flow (>1 ml/min). The volunteer chewed the gum for five minutes and expectorated in a plastic recipient. 0.02 ml of chewing gum filling/1 ml saliva was used for the diluted groups. The pH of the gum's filling in concentrated/pure and diluted forms were 2.1 and 4.1, respectively.
Specimens from all groups were exposed to the acidic substance (gum filling, Adams« , Brasil), at room temperature, under vibration (speed of 7200 vpm) , and for five minutes during five days [Figure 1],[Figure 2],[Figure 3]. Specimens from groups D1 and P1 were exposed to one drop of the acidic substance twice a day (9:00 am and 3:00 pm). Specimens from groups D2 and P2 were exposed to the acidic substance diluted in 10 ml of artificial saliva twice a day (9:00 am and 3:00 pm). Groups D3 and P3 were exposed to one drop of the acidic substance four times a day (9:00 am; 11:00 am; 1:00 pm; and 3:00 pm). Groups D4 and P4 were exposed to the acidic substance diluted in 10 ml of artificial saliva four times a day. After the acidic procedures, specimens were washed in distilled water for 20 seconds, individually immersed in 10 ml of artificial saliva (methyl-p-hydroxybenzoate, 2.00 g/L; sodium carboxymethyl cellulose, 10.0 g/L; KCl, 0.625 g/L; MgCl 2 .6H 2 O, 0.059 g/L; CaCl 2 .2H 2 0, 0.166 g/L; K 2 HPO 4 , 0.804 g/L; KH 2 PO 4 , 0.326 g/L; and fluoride, 0.022 ppm; pH adjusted to 6.75), and stored at 37 ║C until the next experimental step. At the end of the last step, specimens were stored in artificial saliva until the next day. In all groups, artificial saliva was changed daily.
At the end of the experimental period, specimens were submitted to microhardness tests. Indentations were located at 100 Ám from those already made and with a 100 Ám distance between them. Results were submitted to homogenized variance tests (Levene's test) and normally test (Shapiro-Wilk). Changes on superficial microhardness were used as primary measure in order to evaluate differences between primary and permanent teeth, frequency of exposure, and concentration of the erosive substance. Paired t test was used to measure the difference between the means of superficial hardness (initial and final) and the nonpaired t test was applied to measure alterations in the superficial microhardness between the groups.
All experimental groups presented a significant reduction of the superficial hardness ( P P = 0.002), and D3 and D4 ( P = 0.009) related to the concentration of the acidic substance. The diluted acidic substance caused a greater decrease in microhardness in the primary enamel than the concentrated/pure form. There was no difference between primary and permanent enamel [Table 3].
Chewing gums with a liquid stuffing were first introduced in the market around 1977 and since then they are widely used by children and teens. Recently, gums with acidic liquid stuffing with pH around 2.0 were marketed. Additionally, sucrose-based chewing gums with acidic stuffing provide a higher concentration of lactic acid in saliva from metabolization of sucrose by plaque bacteria.  They can promote dental erosion.
Our results as well as other studies ,,,,,,,,,,,, have shown that there is a significant reduction in primary and permanent enamel's microhardness under acidic stuffing challenge.
In general, wear of dental enamel is a multifactorial process. The erosive action caused by the acidic stuffing occurs simultaneously to the abrasion produced by the gum itself on dental surface and to the dental attrition that occurs during mastication. Chewing activates the stuffing/saliva mixture to flow over enamel  promoting a faster elimination of mineral ions dissolved at the subsurface zone of the enamel, reducing or even eliminating remineralization. 
Besides the role of high consumption of acidic products over erosion lesions, factors such as lower buffer capacity can contribute to the erosive process.  Yet, chewing gums with or without sucrose produce the same salivary flow, the saliva produced with a sucrose gum contains lower amounts of bicarbonate, the saliva's most important buffer system. It is suggested that lower values are due to the reaction between bicarbonate and the acid produced by the bacterial sucrose metabolism. 
Some studies have shown that primary enamel is more prone to erosion than the permanent enamel, , Hunter et al.  have shown significant difference between primary and permanent enamel only after 15 days of acidic action. Our results also did not show significant difference between the two types of enamel for a 5-day period.
In this study, the mean hardness decrease was 29% for both tissues, in agreement with Lussi et al.  that found 27% for primary enamel and 26% for permanent.
There was no difference in the loss of dental tissue between twice or four times a day of acidic exposure. Hunter et al. , found that differences in frequency of enamel acidic exposure increases as the time of experiment is increased. It is expected that as the period of experiment is increased significant differences would appear.
The pH value is a significant variable in the erosion process, but it is not necessarily the most important factor.  The substance concentration is also an important factor in the erosive process. West et al.  and Hughes et al.  have shown that acidic concentration is as influent as pH, exposure time, temperature, and type of acid on the erosive power of acidic substances. It would be expected that the acidic stuffing in its pure state, that is, more concentrated and with lower pH, could promote higher erosion of the enamel surface. But this did not occur maybe because the stuffing is viscous creating a higher surface tension and a higher contact angle with the enamel surface, presenting a lower flow.
A higher change in enamel's superficial hardness when the diluted substance was used is due to a lower surface tension which promotes a higher flow and consequently a lower contact angle with the enamel's surface.  Besides, other factors could be contributed with the results as the components of the artificial saliva which could have restrained a subsurface partial remineralization. This can be attributed to the presence of sodium carboxylmethyl cellulose (CMC) which enhances the saliva's viscosity, lowering saliva's diffusion. Besides that, CMC forms complexes with calcium and/or phosphate ions turning those unavailable for remineralization of the lesions. 
The difference between the diluted and pure substances in promoting demineralization could be explained by shaking done during the acidic exposure. It is probably that shaking factors a higher loss of enamel's ions contrary to what occurs during a static bath. , Even under agitation, the flow of the pure substance over the enamel tends to be lower than the diluted substance. According to Ireland et al.  when a substance is ingested, a certain agitation occurs, which favors the substance's capacity to cause erosion. The authors state that this occurs because of the higher thermodynamic work of adhesion. It could be observed that the gum's acidic stuffing can significantly compromise or affect the dental structure. It is presumed that in vivo this could be more severe, with abrasion and attrition occurring simultaneously resulting in dental erosion.
It is concluded that the acidic filling of a chewing gum, pure or diluted, promotes a significant alteration on the microhardness of primary and permanent enamel and when the substance is diluted in artificial saliva the enamel's demineralization is higher.
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