Eating disorders often begin with the selective eating of certain foods or following of specific diets, such as vegetarian diets, that seem easy to accept socially
[8]. The image of idealized figures created by social media can also lead to behaviors that promote eating disorders
[9]. A contributing factor is perfectionism, an ideal that is an important reference point for the individual
[10][11][12]. The following risk groups can be recognized: athletes— including more often female athletes, such as those in cycling, judo, gymnastics, and athletics—and people working in modeling, dance training, the military, catering, and show business
[13][14]. Biological backgrounds, e.g., disorders of the serotonergic system, are considered in genetic analysis or as correlations with metabolic and immunological features (including glycemic, lipid) and analysis of the fetal period
[7]. Meta-analyses indicate the potential importance of single-nucleotide polymorphisms (SNPs) including serotonin receptor gene and serotonin transporter gene (5-HTR2A, 5-HTT), catechol-O-methyltransferase (COMT) polymorphism (Val158Met), and brain-derived neurotrophic factor (BDNF) polymorphism (Val66Met)
[15][16]. The heritability in families with mono-dizygotic twins is estimated to be between 48–74%
[17]. Genome-wide association studies (GWASs) have identified a chromosome 12 (12q13.2) locus that is relevant to the inheritance of the disease
[18].
3. Oral Complications of Eating Disorders
3.1. Oral Hygiene
Until recently, studies have reported conflicting results regarding oral hygiene and periodontal health conditions in ED patients. On the one hand, the ED sufferer exhibits personality traits supposed to lead to overzealous toothbrushing. On the other hand, they suffer from depressive comorbidity with low interest in oral hygiene practices and a higher risk of periodontal diseases. Indeed, periodontal diseases include reversible and irreversible clinical forms of periodontal tissue destruction, known as plaque-induced gingivitis and periodontitis, respectively. The evidence-based pathogenesis of periodontal diseases emphasizes the role of malnutrition
[28][29], substance abuse in particular tobacco smoking and alcohol consumption
[30], and anxiety
[31]. Unbalanced diets with a high consumption of carbohydrates
[32][33] and deficiency in vitamins and minerals are frequent in EDs
[34]. In addition, mood and anxiety disorders are commonly associated with EDs
[35][36]. Hence, ED patients exhibit dietary habits and comorbidities at high risk of periodontal disease. According to the joint classification of the American Academy of Periodontology and the European Federation of Periodontology, plaque-induced gingivitis is an inflammatory response of the gingival tissues resulting from bacterial plaque accumulation located at and below the gingival margin
[37]. Managing gingivitis is a primary preventive strategy for periodontitis. Periodontitis is a chronic multifactorial inflammatory disease associated with dysbiotic plaque biofilms and characterized by the progressive destruction of the tooth-supporting apparatus
[38]. Its primary features include the loss of periodontal tissue support, manifested through clinical attachment loss (CAL) and radiographically assessed alveolar bone loss; the presence of periodontal pocketing; and gingival bleeding. Without treatment, periodontitis leads to tooth loss.
Case-control studies comparing oral health conditions in EDs with controls have evaluated plaque control with conflicting results. Two studies in the 1990s using the Plaque Index (PI) from Silness and Loe
[39], which is a partial recording system prone to bias, found no difference in plaque accumulation between ED and non-ED subjects
[40][41]. The oral hygiene level was better in ED outpatients than in non-ED controls in two studies again using non-full-mouth recorded data
[42][43]. Poorer plaque control in ED inpatients compared to non-ED controls was shown in two studies
[44][45]. In a study with a subgroup analysis, according to the ED diagnosis, plaque control was worse in patients with AN compared to patients with BN and controls with a Plaque Control Record (PCR), measured at 79%, 64%, and 53%,
p < 0.01, respectively
[44]. Hyposalivation induced by the disease and the psychotropic medications
[46] may make plaque control difficult and the lack of salivary mechanical and biological antimicrobial actions can favor plaque accumulation
[47][48]. However, in studies, the toothbrushing frequency in people with EDs was not different
[49] or even higher than in non-ED controls
[44][50].
3.2. Periodontal Health
Several observational studies have assessed the periodontal status of ED patients, mostly those suffering from AN and BN. Gingivitis case definitions used were often heterogeneous among studies based on partial-mouth examination approaches with the Gingival Index (GI)
[51], leading to no difference
[41] and less gingival inflammation
[42][43] in ED patients. However, the two studies with full-mouth bleeding scores showed a higher occurrence of plaque-induced gingivitis in ED patients
[44][45]. In addition, two well-designed case-control studies found that ED patients present significantly fewer healthy (no gingival bleeding after probing) sextants, measured by the Community Periodontal Index and Treatment Needs (CPITN)
[52], compared with non-ED controls, but found no difference in the number of sextants with periodontitis (probing pocket depth > 3mm)
[45][53]. These results are in accordance with those of Pallier and collaborators, who observed a higher CAL, with significantly more sites exhibiting gingival recessions in the ED group in comparison with the control group, but no difference in the number of sites with probing pocket depth
[44]. To sum up, ED sufferers are not at risk of periodontitis but are at high risk of plaque-induced gingivitis and gingival recessions.
Gingival recession is defined as the apical shift of the gingival margin with respect to the cementoenamel junction; it is associated with attachment loss and with the exposure of the root surface to the oral environment
[54]. People with AN and BN have an increased prevalence of gingival recession compared to subjects without EDs of the same age
[44][45]. Gingival recessions have multiple maxillary and mandibular localizations. A whitish appearance of the free gingival margin of the recession is frequent as a sign of chemically induced tissue damage by intrinsic and extrinsic acidity. Atypical localizations such as the palatine surfaces of the upper molars are characteristic of ED patients
[55]. Toothbrushing frequency is one of the main risk factors for gingival recession along with improper toothbrushing duration and force
[54]. This could explain the more frequent generalized gingival recessions observed in ED patients.
Induced by both tooth wear and gingival recessions, dentinal hypersensitivity is also more frequently reported by patients suffering from EDs than controls
[40][50].
3.3. Oral Mucosal Health
Oral mucosal lesions are often observed in EDs. Factors such as malnutrition and associated deficiencies of vitamins or micro- and macronutrients, dehydration, or pathological behaviors such as provoking vomiting, overbiting, and other parafunctions predispose to their occurrence
[56]. Stress levels and addictions like smoking are also important
[49].
When analyzing the published results, it is important to pay attention to the profile of the study group. Some differences will exist due to the fact that previous authors analyzed subjects with varying proportions of AN, BN, and EDNOS cases; disease durations; and ages. Panico et al. (2018)
[57] and Lesar et al. (2022)
[58] observed oral lesions in up to 94% of patients. Their locations can be on the lips, which are dry in as many as 76.2%
[59], 93.2%
[49], or 69%
[42] of subjects. In addition, exfoliative cheilitis, angular cheilitis, and labial erythema are very frequently diagnosed
[1][49][50][57][58][60]. The mucosa is anemic, thin, and prone to injury. As a result, it is pale, and more often, ulcerations and hemorrhagic lesions appear on it, the occurrence of which are significantly influenced by the provocation of vomiting and the highly acidic content of vomit
[49][57][58][59][60].
Patients are more likely to report mouth irritation, diagnosed as Burning Mouth Syndrome (BMS)
[1][50][60]. This disease can be determined by the dentist on the basis of subjective symptoms reported by the patient as it is usually not accompanied by any objective local changes in the oral mucosa. Johansson et al. (2012)
[42] showed that the chance of experiencing episodes of burning mouth is 14.2 times higher in patients with eating disorders than in healthy individuals. This is suggested to be associated with mucosal atrophy, xerostomia, and the general disruption of oral homeostasis. Individuals with eating disorders have also been observed to have more common symptoms of cheek and lip biting, as well as impressions on the tongue and linea alba, associated with increased stress levels
[49][57][58][60]. A weakened immune system and dysbiosis resulting from a breach in tissue continuity will promote a variety of bacterial, viral, and fungal infections, with the typical clinical presentation of these pathogens
[61][62][63][64].
3.4. Dental Health
3.4.1. Dental Caries
Eating patterns in EDs that may affect the onset of dental caries include, on the one hand, avoiding entire food groups and certain macronutrients without a medical reason, participating in fad diets to lose weight, and intentionally skipping meals, which may result in nutritional deficiency
[65][66]. The low intake of nutrients such as proteins; vitamins A, C, and D; and minerals may enhance their susceptibility to demineralization in carious processes
[67]. On the other hand, alternative eating behaviors, such as slowing down the pace of eating, the consumption of large amounts of high-caloric and high-carbohydrate food during binge eating, and engaging in making yourself vomit to control body weight, may contribute to the retention of food debris, the formation of dental plaque on the tooth surface, the lowering of the pH of the oral cavity environment, and the promotion of demineralization, and thus favor dental caries
[65].
Additional factors that may promote dental caries in ED patients are alterations in the composition of saliva
[68]; a decrease in saliva’s buffer capacity and secretion rate
[49][50][69][70], which may be associated with the structural changes in the salivary glands
[42][71]; self-induced vomiting or starvation; and the side effects of psychotropic drugs (i.e., antidepressants, appetite suppressants), diuretics or laxatives
[46]. Undoubtedly, poor oral hygiene in patients with eating disorders, presumably also resulting from psychological reasons, may be a contributing factor to dental caries
[44][72].
Numerous studies have examined the association between dental caries and EDs, applying commonly used caries assessment measures such as caries prevalence or caries severity based on the clinical or (less often) radiographic recordings and expressed by the sum of decayed (D), missing (M), and filled (F) teeth (DMFT index) or tooth surfaces (DMFS index)
[42][44][49][50][71][72][73][74][75] or the International Caries Detection and Assessment System (ICDAS-II) system)
[76]. However, the results obtained are contradictory and vary between 37% and 80% depending on the type of ED and the qualification criteria adopted for diagnosis
[71][72][75][76][77][78]. Some authors demonstrated significantly higher values in terms of the DMFT index and its D and M components in comparison with control groups
[44][50][72].
Relationships between the caries index and vomiting frequency are also inconsistent although it is clear that gastric acid along with high-carbohydrate food or beverages may initiate the carious process
[79].
It is important to emphasize that there is no single ED-associated factor, but rather, all the above-discussed contributing risk factors may have inputs in ED. The following factors should be considered: cariogenic diet, oral hygiene level, remineralization exposure, and taking certain types of medication
[78].
3.4.2. Erosive Tooth Wear
Erosive tooth wear (dental erosion), the irreversible loss of tooth structure due to chemical dissolution by acids not of bacterial origin, is one of the major oral complications of eating disorders
[80]. Erosive tooth wear (ETW) is caused by the frequent contact of teeth with acid from either the stomach (gastric acid) or drinking and eating acidic drinks and foods, particularly outside meal times
[81]. EDs, particularly BN, can potentially increase the risk for ETW since they may be associated with bingeing on acidic foods and/or drinks followed by vomiting after every meal
[42][82][83][84][85]. Some of these patients use these beverages both in the place of normal meals as well as during intense exercise to lose calories
[84]. These characteristics are associated with the frequent contact of the teeth with gastric or dietary acids over an extended period of time, with the consequent wearing away of the dental hard tissue through acid demineralization, initially affecting the enamel, and with the progression to an advanced stage, dentin is exposed (
Figure 2 and
Figure 3). The exposure of dentin may result in dentin hypersensitivity in response to external stimuli of a cold, hot, tactile, or osmotic nature. The acid of gastric juice brought up due to vomiting, the pH of which can be as low as 1, causes the wear of the palatal surfaces of upper incisors (
Figure 2), and with lesion progression, the lingual surfaces of premolars and molars become affected, and in more advanced stages, the process extends to the occlusal surfaces of molars and to the facial surfaces of all teeth
[85][86]. Erosion due to dietary acid, with pH ranging from 2.7 to 3.8, has no specific distribution pattern, but depends on factors such as the method of application. Thus, EDs in combination with vomiting are associated with an increased occurrence, severity, and risk of dental erosion
[85]. The reported prevalence of ETW among eating disorder patients, particularly those with BN, varies among countries and ranges from 42 to 98%
[85].
Figure 2. Palatal surfaces of maxillary teeth affected by erosive tooth wear (Courtsey Amaechi BT, UTHSA, San Antonio, TX, USA).
Figure 3. Occlusal surfaces of mandibular teeth affected by erosive teeth wear (Courtsey Amaechi BT, UTHSA, San Antonio, TX, USA).
Main ED’s symptoms and oral effects are presented in Figure 4.
Figure 4. EDs’ main symptoms (in yellow) and oral effects (in blue and purple). The following factors may influence any oral complications: subtype of AN, BN, and EDNOS according to nutritional behaviors; vomiting frequency; disease duration; age and sex of the patient; general health status; pharmacotherapy and their side effects to salivation; and psychosocial profile; as well as cariogenic/acidic diet, individual oral hygiene, and remineralization exposure. Abbreviations: ↑↓ means the ED symptoms increase the oral effect/decrease the oral effect.