Self-Induced Vomiting and Dental Erosion -- A Clinical Study
In this study, dental erosions were found in 69.7% of the individuals having a history of self-induced vomiting (SIV). This is in the lower range of previously reported prevalence (47 – 93%) among bulimic patients. Although all the individuals included in the current study had a history of SIV, and thereby were at risk of developing dental erosions, 30.3% of the participants did not display any signs of erosion lesions. Previous studies have reported different findings. All patients with ED in the study by Robb et al. had significantly more abnormal tooth wear (erosion) than the healthy control group, this finding being most prominent in the SIV group. None of the 23 women with AN in the study by Shaughnessy et al. showed dental erosions, even though 26% of the participants reported a history of binge-eating/purging activity. Rytomaa et al. found that 13 of 35 bulimics did not suffer from dental erosions. The observation that not all bulimic patients show a pathological level of tooth wear has also been reported by Milosevic and Slade and Touyz et al.. Although vomiting has been related to the occurrence of erosive wear, the study by Robb et al. showed that those who suffered from AN, but did not vomit, also showed more erosions than the control population.
Dental erosions can be caused by acids from extrinsic (e.g. acidic foodstuff) as well as from intrinsic sources (gastric acid). In the present study, one of the inclusion criteria was self-induced vomiting, a challenge to the enamel due to exposure to gastric acid. Nearly half (n = 24) of the participants who completed the questionnaire also reported a high daily intake of acidic beverages. It is likely that individuals who induce vomiting up to several times per day have a higher risk of developing dental erosion than those who never, or more seldom, practice this behaviour. It is reasonable to assume that individuals who, in addition to exposing their teeth to gastric acids several times per day, often consume acidic beverages, have a greater risk of developing dental erosion than those who do not. However, in the present study, there were more erosions and more severe lesions in the group with low consumption of acidic beverages than in the group with high consumption. Bartlett and Coward compared the erosive potential of gastric juice and a carbonated beverage in vitro and found that gastric juice had greater potential to cause dental erosions in enamel and dentine than a carbonated drink. The authors pointed out that the result reflects the lower pH and titratable acidity of gastric juice. This could be a reason why more lesions were not found in those individuals who consumed large amounts of acidic beverages in addition to SIV.
For patients with ED it is difficult to evaluate the risk of various dietary factors, vomiting and/or unfavourable saliva factors. Information about the frequency and duration of SIV is associated with uncertainties, because ED often are associated with shame and denial. It is often a general finding that these individuals are well-educated and well-informed about the condition. Many of them normally choose healthy diets devoid of sweets and sugary soft drinks. In contrast, when they have episodes of binge-eating they select "junk food", which is high in fat, sugar, salt and calories.
The results from the present study showed that the participants who had been practicing SIV for more than 10 years showed more erosions and more severe lesions (with exposed dentine). Frequent acid exposures may have a detrimental effect on the teeth's hard tissue, and particularly if the exposures continue over a long period of time. This finding is in accordance with results from Johansson et al. and Altshuler et al., who found a significant association between the duration of the ED and the prevalence of dental erosions. In addition, Dynesen et al. showed that the duration of the ED had a significant influence on the severity grade of the erosive lesions. However, other studies did not find any association between frequency, duration of vomiting and dental erosion. In the present study nine individuals who had induced vomiting for more than 10 years showed surprisingly no signs of dental erosions, and in two individuals less than five teeth were affected.
The different results from the studies mentioned, and the fact that one third of the individuals in the present study did not show any erosive lesions despite regular vomiting, might be explained by individual differences in the susceptibility to erosion. It is still not clear what factors are relevant for the development and progression of erosion in these patients. Saliva factors, salivary flow rate, the pellicle and the composition of the enamel may be as important as the frequency of acid exposures.
It has often been speculated that differences in the composition of saliva could be responsible for the rapidly progressing erosive substance loss in patients with vomiting-associated ED. A lower salivary pH in ED patients than in healthy controls has been documented by Touyz et al., but in contrast Milosevic et al. did not find any differences between BN patients and controls. Schlueter et al. suggested that enhanced proteolytic activity in the saliva of bulimic patients might contribute to an altered buffering capacity of the saliva, as well as development and progression of dental erosion through degradation of dentine and the pellicle. Levels of amylase, immunoglobulin and electrolytes have also been investigated, but the findings differ substantially. Several studies have shown a significantly lower unstimulated salivary flow in bulimic patients than in controls. Many ED patients are prescribed antidepressants or other psychopharmaceutical medication, that are known to reduce salivary flow, and Dynesen et al. showed that xerogenic medication significantly lowered unstimulated flow rate in this patient group.
The assumption that dental erosions caused by vomiting or regurgitations are typically localized on the palatal surfaces of the upper front teeth, and that erosions caused by high consumption of acidic foods and drinks are found on buccal surfaces, has led to efforts to relate the location of erosive lesions to the etiology of the condition. From a clinical point of view, it is important to investigate whether it is possible to differentiate between erosions caused by SIV and erosions caused by consumption of acidic foodstuff. Hellstrom reported that while lingual erosions were a frequent finding in individuals experiencing SIV, such lesions did not appear in individuals without this behaviour. Lussi et al. found that chronic vomiting appeared to be the variable most indicative for lingual erosions. The present results showed that the majority of the lesions were found on the palatal surfaces and that the individuals with the longest duration of SIV had significantly more buccal and palatal lesions in the lateral segments than those with a shorter duration of the disorder. The more severe lesions (with exposed dentine) appeared most frequently on the occlusal surfaces of the lower first molars, followed by the palatal surfaces on the upper incisors. These results were consistent with work previously reported by Mulic et al. in a study of healthy adolescents, and can partly be explained by the position of these teeth in the mouth and partly by their early time of eruption. The lower first molars are the first permanent teeth to erupt, they have an important function concerning occlusion and chewing, and acidic liquids naturally gravitate towards the floor of the mouth. The upper incisors also erupt at an early age, and as the rough surface of the tongue serves as a short-time reservoir for acids from foodstuff and liquids, the movements of the tongue have the potential to cause both an abrasive and an erosive effect (perimylolysis) on the palatal surface of the upper front teeth. The rinsing effect of saliva is weaker on the upper teeth than on the lower, and the saliva clearance and buffer capacity are even lower in individuals with reduced saliva secretion.
Vigorously and frequent tooth brushing is a common habit in ED patients, and in combination with the repeated exposure to stomach acid, this could also contribute to the increased erosive tooth wear in this group. However, a study concerning oral hygiene habits did not ascertain why some of the vomiting bulimic patients suffered from severe erosions and others did not.
As expected, the prevalence of dental erosion in the individuals experiencing SIV was high. In addition, the duration of SIV seemed to influence the number of palatal and buccal lesions.
However, the present study does have some limitations: The proportion of male participants versus females was small. This, however, reflects the gender distribution shown in the study by Jaite et al., where as much as 92.7% of individuals with bulimia nervosa were female, and seems to reflect the population prevalence of ED. Information on e.g. the exact duration of disease, frequency of SIV, oral hygiene habits and eating habits is unfortunately difficult to obtain, as it is based exclusively on the participants' subjective memory and their willingness to share. One might consider using standardized questionnaires instead of interviews, but these have approximately the same limitations in this matter. Another possible limitation of this study is that the participants were all undergoing treatment at clinics for eating disorders. Thus, the study does not include individuals who do not receive treatment for their disease, and the results might have been different if corresponding information from such individuals was obtained. Saliva secretion was not measured in this study. Considering that one third of the participants with EDs in a study by Rytomaa et al. had decreased unstimulated saliva secretion, and hence decreased protection against dental erosion, this might have been an interesting addition to the study. However, Dynesen et al. found that although individuals with vomiting had a significantly lower unstimulated salivary flow rate compared to a control group, this did not significantly influence dental erosion.
Discussion
In this study, dental erosions were found in 69.7% of the individuals having a history of self-induced vomiting (SIV). This is in the lower range of previously reported prevalence (47 – 93%) among bulimic patients. Although all the individuals included in the current study had a history of SIV, and thereby were at risk of developing dental erosions, 30.3% of the participants did not display any signs of erosion lesions. Previous studies have reported different findings. All patients with ED in the study by Robb et al. had significantly more abnormal tooth wear (erosion) than the healthy control group, this finding being most prominent in the SIV group. None of the 23 women with AN in the study by Shaughnessy et al. showed dental erosions, even though 26% of the participants reported a history of binge-eating/purging activity. Rytomaa et al. found that 13 of 35 bulimics did not suffer from dental erosions. The observation that not all bulimic patients show a pathological level of tooth wear has also been reported by Milosevic and Slade and Touyz et al.. Although vomiting has been related to the occurrence of erosive wear, the study by Robb et al. showed that those who suffered from AN, but did not vomit, also showed more erosions than the control population.
Dental erosions can be caused by acids from extrinsic (e.g. acidic foodstuff) as well as from intrinsic sources (gastric acid). In the present study, one of the inclusion criteria was self-induced vomiting, a challenge to the enamel due to exposure to gastric acid. Nearly half (n = 24) of the participants who completed the questionnaire also reported a high daily intake of acidic beverages. It is likely that individuals who induce vomiting up to several times per day have a higher risk of developing dental erosion than those who never, or more seldom, practice this behaviour. It is reasonable to assume that individuals who, in addition to exposing their teeth to gastric acids several times per day, often consume acidic beverages, have a greater risk of developing dental erosion than those who do not. However, in the present study, there were more erosions and more severe lesions in the group with low consumption of acidic beverages than in the group with high consumption. Bartlett and Coward compared the erosive potential of gastric juice and a carbonated beverage in vitro and found that gastric juice had greater potential to cause dental erosions in enamel and dentine than a carbonated drink. The authors pointed out that the result reflects the lower pH and titratable acidity of gastric juice. This could be a reason why more lesions were not found in those individuals who consumed large amounts of acidic beverages in addition to SIV.
For patients with ED it is difficult to evaluate the risk of various dietary factors, vomiting and/or unfavourable saliva factors. Information about the frequency and duration of SIV is associated with uncertainties, because ED often are associated with shame and denial. It is often a general finding that these individuals are well-educated and well-informed about the condition. Many of them normally choose healthy diets devoid of sweets and sugary soft drinks. In contrast, when they have episodes of binge-eating they select "junk food", which is high in fat, sugar, salt and calories.
The results from the present study showed that the participants who had been practicing SIV for more than 10 years showed more erosions and more severe lesions (with exposed dentine). Frequent acid exposures may have a detrimental effect on the teeth's hard tissue, and particularly if the exposures continue over a long period of time. This finding is in accordance with results from Johansson et al. and Altshuler et al., who found a significant association between the duration of the ED and the prevalence of dental erosions. In addition, Dynesen et al. showed that the duration of the ED had a significant influence on the severity grade of the erosive lesions. However, other studies did not find any association between frequency, duration of vomiting and dental erosion. In the present study nine individuals who had induced vomiting for more than 10 years showed surprisingly no signs of dental erosions, and in two individuals less than five teeth were affected.
The different results from the studies mentioned, and the fact that one third of the individuals in the present study did not show any erosive lesions despite regular vomiting, might be explained by individual differences in the susceptibility to erosion. It is still not clear what factors are relevant for the development and progression of erosion in these patients. Saliva factors, salivary flow rate, the pellicle and the composition of the enamel may be as important as the frequency of acid exposures.
It has often been speculated that differences in the composition of saliva could be responsible for the rapidly progressing erosive substance loss in patients with vomiting-associated ED. A lower salivary pH in ED patients than in healthy controls has been documented by Touyz et al., but in contrast Milosevic et al. did not find any differences between BN patients and controls. Schlueter et al. suggested that enhanced proteolytic activity in the saliva of bulimic patients might contribute to an altered buffering capacity of the saliva, as well as development and progression of dental erosion through degradation of dentine and the pellicle. Levels of amylase, immunoglobulin and electrolytes have also been investigated, but the findings differ substantially. Several studies have shown a significantly lower unstimulated salivary flow in bulimic patients than in controls. Many ED patients are prescribed antidepressants or other psychopharmaceutical medication, that are known to reduce salivary flow, and Dynesen et al. showed that xerogenic medication significantly lowered unstimulated flow rate in this patient group.
The assumption that dental erosions caused by vomiting or regurgitations are typically localized on the palatal surfaces of the upper front teeth, and that erosions caused by high consumption of acidic foods and drinks are found on buccal surfaces, has led to efforts to relate the location of erosive lesions to the etiology of the condition. From a clinical point of view, it is important to investigate whether it is possible to differentiate between erosions caused by SIV and erosions caused by consumption of acidic foodstuff. Hellstrom reported that while lingual erosions were a frequent finding in individuals experiencing SIV, such lesions did not appear in individuals without this behaviour. Lussi et al. found that chronic vomiting appeared to be the variable most indicative for lingual erosions. The present results showed that the majority of the lesions were found on the palatal surfaces and that the individuals with the longest duration of SIV had significantly more buccal and palatal lesions in the lateral segments than those with a shorter duration of the disorder. The more severe lesions (with exposed dentine) appeared most frequently on the occlusal surfaces of the lower first molars, followed by the palatal surfaces on the upper incisors. These results were consistent with work previously reported by Mulic et al. in a study of healthy adolescents, and can partly be explained by the position of these teeth in the mouth and partly by their early time of eruption. The lower first molars are the first permanent teeth to erupt, they have an important function concerning occlusion and chewing, and acidic liquids naturally gravitate towards the floor of the mouth. The upper incisors also erupt at an early age, and as the rough surface of the tongue serves as a short-time reservoir for acids from foodstuff and liquids, the movements of the tongue have the potential to cause both an abrasive and an erosive effect (perimylolysis) on the palatal surface of the upper front teeth. The rinsing effect of saliva is weaker on the upper teeth than on the lower, and the saliva clearance and buffer capacity are even lower in individuals with reduced saliva secretion.
Vigorously and frequent tooth brushing is a common habit in ED patients, and in combination with the repeated exposure to stomach acid, this could also contribute to the increased erosive tooth wear in this group. However, a study concerning oral hygiene habits did not ascertain why some of the vomiting bulimic patients suffered from severe erosions and others did not.
As expected, the prevalence of dental erosion in the individuals experiencing SIV was high. In addition, the duration of SIV seemed to influence the number of palatal and buccal lesions.
However, the present study does have some limitations: The proportion of male participants versus females was small. This, however, reflects the gender distribution shown in the study by Jaite et al., where as much as 92.7% of individuals with bulimia nervosa were female, and seems to reflect the population prevalence of ED. Information on e.g. the exact duration of disease, frequency of SIV, oral hygiene habits and eating habits is unfortunately difficult to obtain, as it is based exclusively on the participants' subjective memory and their willingness to share. One might consider using standardized questionnaires instead of interviews, but these have approximately the same limitations in this matter. Another possible limitation of this study is that the participants were all undergoing treatment at clinics for eating disorders. Thus, the study does not include individuals who do not receive treatment for their disease, and the results might have been different if corresponding information from such individuals was obtained. Saliva secretion was not measured in this study. Considering that one third of the participants with EDs in a study by Rytomaa et al. had decreased unstimulated saliva secretion, and hence decreased protection against dental erosion, this might have been an interesting addition to the study. However, Dynesen et al. found that although individuals with vomiting had a significantly lower unstimulated salivary flow rate compared to a control group, this did not significantly influence dental erosion.
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