Even though the majority of gingival diseases are caused by bacterial biofilms, it should also be borne in mind that numerous types of lesions with different etiological factors could also affect the gingival health, or even become life-threatening [12]. These lesions were not initially induced by dental pathogens; however, the outcomes of these lesions are also largely influenced by bacterial plaque. In this study, we carried out a single-institute retrospective study to analyze the frequency and distribution of NDPIGDs in a Chinese population over the past 20 years. We adjusted and compared the current results to the new classification of gingival health and gingival diseases/conditions established in 2018.
The biopsied NDPIGDs in this study consisted of 43 types according to their pathological diagnosis. We then categorized them into nine groups based on their pathological characteristics. From the most common lesions to the least common were hyperplastic lesion, malignant lesions, OPMDs, autoimmune disorders, benign neoplasms, genetic lesions, allergic reaction diseases, infectious diseases, and other diseases that could not be categorized into the former groups.
Previous studies regarding the classification of biopsied gingival lesions mainly divided them into three categories: non-neoplastic lesions, benign lesions, and malignant lesions [2, 7, 8], and the majority of biopsied samples were non-neoplastic lesions. Consistent with their reports, our statistical results also showed that the largest number of NDPIGDs were hyperplastic lesions, with 38.61% of all lesions. Among them, the most common diagnosis type was fibrous hyperplasia, which accounted for nearly 30% of all lesions. As important types of the epulis, pyogenic granuloma and peripheral giant cell granuloma also showed relatively high frequencies. In particular, females showed a higher prevalence of hyperplastic lesions compared with males, which were less frequently occurred in the mandible than in the maxilla. In our results, hyperplastic lesions widely ranged between and 20–59 years of age, with an incidence peak between and 30–39 years; however, this is not in complete agreement with previous studies. In a similar study, the highest frequency appeared in patients between and 60–69 years [2], while two other studies pointed out that the majority of biopsied samples were between 30–39 years and 20–29 years [6, 18]. We assumed that the inconsistency was possibly caused by different criteria as well as pathological diagnosis habits. Furthermore, one of these studies merged reactive hyperplastic lesions and other inflammatory diseases into one group.
The largest inconsistency of the biopsied NDPIGDs were the “malignant neoplasms” category. In past research, the proportion of malignancies on the gingiva was reported to be 1–8% [2, 6, 11]. However, malignant neoplastic lesions represented up to 33.14% of all gingival lesions in our study. This high incidence was significantly different from that in earlier reports. Among them, Layfield et al. [6] represented the most comprehensive biopsied gingival lesions research that collected a total of 30,056 samples over a period of 24 years. In their study, the frequency of malignant neoplasms was as low as 1.4%. Such a huge difference demonstrated the difference in prevalence between Easterners and Westerners. Notably, when considering the distribution of the malignancies, the most prevalent neoplasm reported in our research and previous studies was the same, OSCC [19, 20], which accounted for 30.53% of all samples.
The former category was then followed by “OPMDs”, “autoimmune disorders”, and “benign neoplasms”. The category “OPMD” was defined as a significant group of mucosal disorders that may precede the diagnosis of OSCC [21], which included oral leukoplakia, oral erythroplakia, oral lichen planus, and newly added oral lichenoid lesions. Depending on the presence or absence of epithelial dysplasia, oral leukoplakia was divided into epithelial hyperplasia/hyperkeratosis and epithelial dysplasia, with the frequencies of 6.36% and 6.95%, respectively. In this study, lichen planus and oral lichenoid lesions were placed under the OPMD category. In total, the total number of OPMDs reached 1214, accounting for 17.7% of all NDPIGD cases. This ratio was remarkably higher than those previously reported [11, 22].
The “autoimmune disorders” category was put forward for the first time in our work and pemphigoid and pemphigus were categorized under the group. In former studies, pemphigoid and pemphigus were not specifically mentioned, either due to the low frequency or they were classified into “mucocutaneous disorders” [11]. However, the two lesions in our work account for 5.6% of all samples, and we believed “mucocutaneous disorders” was ambiguous for describing the type, as many other diseases like oral leukoplakia might be confused. Benign neoplasms, on the other hand, are not commonly seen in the gingiva. Of all 6859 biopsied samples, only 197 cases of different diagnosis types were observed. While malignant neoplasms reached a peak incidence in those aged over 60 years, benign tumors were distributed separately.
Hereditary gingival fibromatosis is a frequently common genetic disease seen in the periodontal clinic. As the present research is mainly concentrated on biopsied cases, the frequency (0.58%) might be largely underestimated compared to the actual incidence in clinical settings. Hernández-Ríos’s team [11] classified papilloma into “infectious lesions” while we placed papilloma into benign neoplasms and tuberculosis was the only diagnosed type in the “infectious lesions” group. Plasma cell gingivitis was also found in two female patients.
Etiologies of gingival diseases were first introduced into the classification of periodontal diseases and conditions in 1999 [3]. This classification added gingival disease for the first time and divided them into two subcategories based on the initial factor, that is, dental plaque-induced gingival diseases and non-plaque-induced gingival diseases. Hernández-Ríos et al. [11] distributed the biopsied non-plaque-induced gingival lesions based on the 1999 classification of periodontal diseases and conditions. However, as they presented, over 90% of biopsied gingival lesions could not be categorized according to this classification, including the most prevalent groups (hyperplastic lesions and malignant neoplasms). To a large extent, these results reflect the shortcomings of this classification system.
To the best of our knowledge, the present study is the first report on the frequency and distribution of biopsied NDPIGDs in a Chinese population. This is also the first study to compare the pathological nature classification and the latest 2018 classification of gingival diseases. The epidemiology of the pathological diagnosis of NDPIGDs shared numerous similarities as well as certain differences with previous reports. Specifically, when categorizing pathologically diagnosed biopsied lesions with the pathological nature classification and the new classification of gingival diseases, there were some discrepancies. Lichen planus and lichenoid lesions were grouped under “OPMD”, however, lichen planus was grouped into “inflammatory and immune conditions” according to the new classification of gingival diseases, and lichenoid lesions were not specifically categorized. These results demonstrated the inconsistencies between the two classification systems, which may cloud clinicians’ judgments. It should be noted that the classification system may be helpful for clinicians in early diagnosis and subsequent treatments. A classification system with more specific categories that based on prevalence, specificity and mortality is highly recommended.
However, there are still some limitations for this study that require further investigation. First, our samples were all from the same hospital and the study is a single-center retrospective research. Second, we lack complete clinical and demographic information of many patients. In addition, our study only investigated the biopsied samples with definite pathological diagnosis; those gingival lesions that can be recognized through clinical performance without biopsy were not included into the research. Overall, the present research represented the first report of the distribution and frequency of biopsied NDPIGDs in a Chinese population as well as the first report to compare the prevalence using the 2018 classification of gingival diseases.