A large-cohort study of 2971 cases of epulis: focusing on risk factors associated with recurrence

Epulis is a very common oral disease with a prevalence of varying from 5.6 to 20.6% [5, 9‐11]. The overgrowth of the gingival has multiple impacts including aesthetic problems, functional disorders, difficulty in chewing and speech, even serious psychological problems [12]. The present report is one of the largest series from single institute thus far. Focusing on the relative frequency distribution of various histological subtypes and analyzing the risk factors associated with recurrence of epulis, the present study provides a reference for in-depth study of the epulis.

In general, epulis had a predilection for female patients, and the results were consistent with Kfir, Buchner and Zhang, who analyzed 741, 1675 and 2439 cases, respectively [1, 3, 4]. Those three literatures reported the F/M ratio as 1.51, 1.49, and 1.40. The reason for this phenomenon was not entirely clear. Hormones, especially female hormones, might be partially contributed. It had been reported that estrogens and other sex hormones exaggerate inflammatory responses in gingival tissue, particularly in pregnancy [13]. The present study showed the average age was 45.55 years and the peak incidence was in the three and four decades of life, which was consistent with Zhang’s report (43.39 years) [4]. However, the average age was much younger in other studies, which showed the average age ranged from 30.0 to 37.7 years old [1, 5, 6]. The discrepancy might be caused by the number of the cases and the regional differences. In the present study, epulis in general were more frequent in the anterior region and maxilla, which was in agreement with those previously reported in most studies [1, 3]. The prevalence in anterior region might be due to the following reasons. Frequent teeth malposition often occurred in the anterior region, leading to the difficulty of oral hygiene maintenance and plaque control. The pooling of saliva provided a rich source of calcium and phosphate, which supersaturated dental plaque and resulted in calculus formation in this area [14, 15]. Though the lesions had a relatively large range of size, most lesions were small, allowing the patient to receive the complete excision in outpatient department.

FFH was the most common histological subtype, comprising 60.92% of all the lesions, followed by POF and PG. PGCG was the least common lesion in the present study, comprising 1.68% of all cases. The similar trend was observed in the previous studies [4, 16‐18]. By contrast, this differed from other studies where PG was reported as the most common lesion among all types of epulis [6, 19]. The differences might be attributed to the geographic or ethnic factors, as we found that the relative frequency of four types of epulis followed the same pattern with the previous Chinese investigation (FFH: 61.05%, POF: 17.67%, PG: 19.76%, PGCG: 1.52%) [4]. Other reasons, including unusual terminology and limited case number, might be also contributed [6, 19].

Analyzing sex distribution according to histological subtypes, an interesting finding was noted that all the four types of lesions were more common in female. The high prevalence in female could reflect the role of female hormones and more attention toward dental care. However, the differences presented in different histological subtypes. PG had the strongest predilection for female. Daley et al. concluded that the raised levels of serum progesterone and estrogen had a positive relationship with PG in pregnancies [20]. These hormones made the gingival tissues more susceptible to those chronic local irritants, leading to the development of PG [5, 6, 21]. The expression of estrogen receptors elevated in epulis tissues of pregnancy or non-pregnancy women, suggesting that the development of epulis was estrogen-dependent in a certain degree [22, 23].

POF showed the lowest average age of 39.21 years and the peak incidence was in the third decade. This was in accordance with reports from previous studies which indicated that POF was obviously biased towards younger age group [5, 17]. PG also mainly affected younger patients. By contrast, FFH occurred more frequently in older age groups. In the present study, PGCG and PG were more common in the posterior region, while POF was more commonly affected the anterior region (60.13%), which was consistent with the rate from Buchner et al. (58.3%) [1] and Zhang et al. (64.97%) [4], but higher than that from Kfir et al. (52.6%) [3]. PG had the largest mean size of all four subtypes of epulis, which was in general agreement with Kfir et al. [3].

The reported recurrence rate of epulis has varied widely among different studies. The recurrence rate of 11.28% recorded in the present study was similar to that reported by Babu (10.9%) [7] but lower than that reported in Austria (15.2%) [8]. Interestingly, in a previous study by Effiom et al. from Nigeria, the recurrence rate of epulis was much lower (2.9%) [5]. This discrepancy might be caused by the sample size. The present study had a large sample of 2971 cases and 1835 cases with recurrence information, while other studies consisted of less cases from 92 cases to 314 cases [5, 8]. Only few studies evaluated multiple recurrence of epulis. Of the 207 cases with recurrence in the present study, multiple recurrence occurred in 23 cases (11.11%), which was lower than that reported by Babu (16%) [7]. Multiple recurrence of epulis could be attributed to the failure to remove etiologic factors (e.g., continuous irritations and trauma) and gene regulation [24]. Performing the excision of adjacent periodontal membrane, periostium and alveolar bone, and the root planning could eliminate irritations and avoid the recurrence the epulis [25]. Other factors, including over-expression of anti-apoptotic genes in BCL-2 family and IAP family, could inhibit the apoptosis of gingival tissues, thus leading to epulis [26], and these genetic abnormalities might cause the multiple recurrence of epulis.

To the best of our knowledge, the present study is the largest series analyzing the risk factors associated with the recurrence of the epulis, allowing us to compare the recurrence rate between different histological subtypes for the first time. Different histological subtypes showed statistically significant recurrence rate. PG was the type with the highest recurrence rate of 17.18% and PGCG had the lowest recurrence rate (8.82%). PG frequently developed in pregnant women and the term “pregnancy tumor” had been used in these cases [1], which had high recurrence rate after treatment [27]. Another explanation was that PG were histologically highly vascular proliferative lesions and the vascular endothelial growth factor was related to the angiogenesis and rapid growth of PG [28]. Estrogen could enhance vascular endothelial growth factor production [29], therefore relating to the recurrence. The recurrence rate of PGCG was as low as 1.39% [30]. The low recurrence rate of PGCG might be partly explained by low capacity in neovascularization of granulation tissue. Another reason was that the mast cell count of PGCG was the lowest among all types of epulis [10, 31], while the mast cells were important sources of some proangiogenic and angiogenic factors [32]. Striking difference was reported in the results by Babu and Savage [7, 13], which demonstrated that PGCG had the highest recurrence rate among all types of epulis because the cells of PGCG show high proliferative potential. Further studies are required to reveal the mechanism of recurrence of different subtypes of epulis.

Regular supportive periodontal therapy including oral hygiene instruction, scaling and root planning could significantly reduce recurrence rate compared to the group of patients without it. There was evidence that poor oral hygiene was the main contributing factor leading to recurrence [7, 8]. Verma et al. suggested that the possibility of recurrence could be minimized with proper treatment strategies including standardized supportive periodontal therapy before treatment [33]. Personal oral hygiene status was a key factor in the preservation of periodontal support for a long term [34]. However, in the present study, there was no significant association between the other oral hygiene habits (the number of brushing times per day, the duration of brushing per time, dental floss and interdental brush usage) and recurrence of epulis. This might be explained by the fact that the treatment of dentists removes dental plaque more thoroughly, while the degree of plaque removal of other self-performed oral hygiene habits varies from person to person. Another risk factor for recurrence of epulis was the presence of periodontitis symptoms including swollen and bleeding gums, mastication weakness and tooth mobility. It could be explained that the patients with those symptoms constantly had local irritations.

The limitations of the present study should be noted. First, this was a retrospective study and the data was collected through patient interview, resulted in incomplete records and the information gaps between the researchers and patients. Second, this was a study conducted in a single tertiary hospital, further investigation should be carried out in multicenter to provide thorough conclusions.