Is Human Papilloma Virus Infection Linked to Periodontitis? A Narrative Review

Abstract

Purpose of Review

Research suggests that periodontal tissue might serve as a reservoir for oral human papillomavirus (HPV) infection, while another hypothesis is that chronic inflammation of the tissue might perpetuate an infection with oral HPV infection. In this narrative review, we summarize the evidence related to a potential association between oral HPV infection and periodontitis.

Recent Findings

Twelve articles were identified, and their key findings summarized. Studies vary in sample size, study population, study design, and methods for assessment of oral HPV and periodontitis. Although results are conflicting and still inconclusive, various studies have found an association between oral HPV infection and periodontitis, which is supported by biological plausibility.

Summary

Future longitudinal studies should further evaluate this association, using clinical definitions of oral HPV infection and periodontitis, and focusing on high-risk populations for oral HPV infection. Studying this association is important since periodontitis might help identify at-risk individuals for oral HPV infection and potentially HPV-related oropharyngeal cancers

Introduction

An increase in oropharyngeal cancers has been reported in the last decade (1) in the United States (U.S.), where oral and pharynx cancer incidence rates have risen, on average, 0.7% each year over the last decade (2). Approximately 70.1% of oropharyngeal cancer cases are attributable to human papillomavirus (HPV) infection, which is the most common sexually transmitted infection worldwide (3,4). Data from the National Health and Nutrition Examination Survey (NHANES) 2011–2014 showed that the prevalence of oral HPV infection in the U.S. was 7.3% among cancer free individuals aged 18–69 years old (5). This study also showed that men and non-Hispanic Blacks had a higher prevalence of oral HPV infection than women and other ethnic/racial groups (5). Documented risk factors for oral HPV infection include oral sex, male gender, older age, open mouthed kissing, increased number of sexual partners, human immunodeficiency virus (HIV) infection, tobacco use, and heavy alcohol intake (6●●,7). Some studies also suggest a possible association between periodontitis and oropharyngeal cancer (8–10).

Periodontitis is a chronic, inflammatory oral infection mainly caused by biofilm with Gram-negative anaerobic bacteria that affects the supporting structures around the teeth leading to soft (gingiva, periodontal ligament) and hard (alveolar bone) tissue destruction (11–13). Research has suggested that periodontitis is associated with increased risk of diabetes (14,15), cardiovascular disease (16,17), and adverse pregnancy outcomes (18,19). Chronic periodontitis has also been linked with other systemic conditions including rheumatoid arthritis, cancer, and respiratory diseases (13). Different pathogenic mechanisms have been proposed to support a relationship between periodontitis and systemic conditions. In advanced periodontitis, formation of periodontal pockets enables transportation of periodontal pathogens to the systemic circulation and disperse to different parts of the body (20). Support for this mechanism comes from studies indicating presence of periodontal bacteria in circulating leukocytes, liver, and placenta (20). Another mechanism proposed for this relationship has been the daily swallowing of oral bacteria in saliva to the gut (20), causing alterations in the gut microbiota, increased permeability of the gut epithelial layer, and ultimately onset of systemic inflammation (20). Data from NHANES 2009–2012 found that 46% of U.S. adults aged 30 years or more had periodontitis (12), being highest among Hispanics and men (12). Several risk factors have been established for chronic periodontitis. Modifiable risk factors include smoking, poor oral hygiene, stress, and hormonal changes in women (11,13,21), whereas non-modifiable risk factors include increasing age, genetics, and host response to periodontal pathogens (11,13,21). Some studies have suggested that periodontal tissues may serve as a reservoir for other viruses including herpes simplex virus (HSV) (22–24), Epstein-Barr virus (EBV) (25), and human cytomegalo virus (CMV) (26). Also, having these viruses may be associated with the pathogenesis and severity of periodontitis, since it has been proposed that as disease severity increases, it becomes more likely that viruses proliferate and remain in the tissues (27).

Research on the role of specific HPV genotypes in oral lesions and the mechanisms by which infection and subsequent lesions occur is limited (28). During the last decade, cumulative evidence suggests an association between oral HPV infection and periodontitis. One hypothesis is that periodontal tissue might serve as a reservoir for oral HPV infection (29●). Another hypothesis is that chronic inflammation of the tissue might perpetuate an infection with oral HPV (30,31). In this narrative review, the evidence related to a potential association between oral HPV infection and periodontitis is summarized. The link between these conditions could have implications for oropharyngeal cancer risk and prevention efforts (8–10).

Methods

Relevant studies were identified using the following search terms: periodontal disease, periodontitis, oral HPV infection, oral HPV, gum disease, and gingivitis. Articles published in the last 10 years were considered a priority, although some other articles were considered according to their relevance. A total of 12 articles were identified, and their key findings summarized. Studies vary in sample size, study population, study design, and methods for assessment of oral HPV and periodontitis (Table 1).

Table 1.

Summary of studies describing the association between periodontitis and oral HPV infection

Author (Year) [Reference]	Population	Sample size	Study design	Assessment		Major Findings
				Periodontitis	Oral HPV	Prevalence of periodontitis	Prevalence of oral HPV infection	Assessment of association
Madinier et al. (1992) [32]	French men and women aged 21–87 years with interproximal gingivitis	20	Cross-sectional study	Periodontitis was assessed with clinical and radiographical evidence in patients with poor dental health.	Biopsy analyzed by Southern Blot	─	25.0% HPV-6 10.0% HPV-11 15.0% HPV-16	─
Hormia et al. (2005) [29]	Finnish individuals with clinically diagnosed periodontal disease	38	Cross-sectional study	Having at least one tooth presenting 33% to 50% bone loss	Biopsy analyzed by PCR	─	26.0% HR-HPV	─
Horewicz et al. (2009) [27]	Brazilian men and women aged ≥ 21 years with and without chronic periodontitis	104 (56 cases with chronic periodontitis, 26 cases with gingivitis, and 22 controls)	Case-control study	Cases of chronic periodontitis defined as having ≥6 teeth, each with ≥1 site with PD and CAL ≥ 5 mm Cases of gingivitis defined as ≥20% of sites with plaque at the gingival margin, a change in gingival color and contour, and BOP Periodontal healthy controls did not have any site with PD and CAL <5 mm and showed <20% of sites exhibiting gingival bleeding or BOP	Biopsy from gingival tissue analyzed by PCR	─	HPV-16 was not detected in any of the 104 gingival samples evaluated	No association between HPV-16 and periodontal disease
Tezal et al. (2009) [33]	US patients newly diagnosed with primary base of tongue squamous cell carcinoma between 1999 and 2005	30	Case-control study	History of periodontitis was assessed quantitatively on the basis of alveolar bone loss from panoramic radiographs that were taken at admission before initiation of cancer treatment. No periodontitis defined as alveolar bone loss <2 mm Periodontitis defined as alveolar bone loss ≥2.74 mm	HPV DNA in tumor tissue analyzed by PCR	86% in HPV positive tumors 22% in HPV negative tumors	─	After adjustment for age at diagnosis, sex, race/ethnicity, alcohol use, smoking status, and number of missing teeth, each millimeter of ABL was associated with approximately 4-fold (95% CI: 1.18–13.36) increased risk of HPV-positive tongue tumor status.
Bui et al. (2013) [34]	US men and women aged 30–69 years selected from the general population	3,439	Cross-sectional study	Self-reported periodontal disease	Self-collected oral rinse analyzed by PCR	17.5%	7.5% any HPV	Higher prevalence of oral HPV infection was associated with gum disease: (PR 1.51, 95% CI: 1.13– 2.01).
Jacob et al. (2014) [35]	Indian men and women aged 15–70 years	102	Cross-sectional study	Periodontal pocket depth of ≥5 mm who required flap surgery.	Biopsy analyzed by PCR	65.7%	No HPV-16 detected	No association between HPV-16 and periodontitis disease
Fuster-Rossello et al. (2014) [30]	Argentinian women aged 18–50 years with gynecological HPV-related disease	30	Cross-sectional study	PI, PD, CAL, and BOP were recorded at 6 sites for all teeth No periodontitis: subjects that did not have PD or CAL >4 mm and <20% of sites showed BOP Gingivitis: having at least ≥20% of sites with plaque, gingival inflammation signs, and BOP where PD or CAL measurements were not >4 mm. Chronic periodontitis as having at least ≥6 teeth, each with ≥1 site with a PD and CAL ≥ 5mm	Oral swabs (30 from tongue60 from periodontal sites) analyzed using PCR and cytology	Gingivitis: 40.0% Periodontitis: 36.7%	67.0% HPV-16–30% from tongue tissues −13.3% from internal periodontal sites −16.7% from external periodontal sites.	No association.
Wiener et al. (2015) [36●●]	US men and women aged 30–69 years from the general population	6,004	Cross-sectional study	Mild: 1 site with PD≥ 5 mm or having at ≥2 interproximal periodontal sites with ≥3 mm CAL and ≥2 interproximal periodontal sites with ≥4 mm PD (not in the same tooth) Moderate: ≥2 interproximal sites with PD of ≥5 mm (not in the same tooth) or ≥2 interproximal sites not on the same tooth and CAL≥4 mm Severe: ≥1 interproximal site having PD≥5 mm with ≥2 interproximal sites on different teeth having CAL≥4 mm	Self-collected oral rinse analyzed with PCR	40.3% (mild, moderate or severe periodontitis)	7.5% any HPV	Periodontal diseases was not associated with oral HPV infection (OR 1.04, 95% CI: 0.63 –1.73) after adjusting for sex, race/ethnicity, education, age, income to poverty ratio, smoking, alcohol use and number of lifetime sexual partners.
Dayakar et al. (2016) [37]	Indian men and women aged 30– 70 years with chronic periodontitis	8	Cross-sectional study	CAL >5 mm clinically seen as pocket	Biopsy analyzed by hybridization and flow cytometry	─	50.0%	─
Shipilova et al. (2017) [38]	Indian men and women aged 21–70 years	60 (30 cases and 30 controls)	Case-control study	Cases of localized chronic periodontitis defined as CAL >5 mm involving less than 30% of total sites, clinically manifested as a periodontal pocket Controls were periodontally healthy subjects (no CAL)	Identification and estimation of E6/E7 mRNA of HPV using in situ hybridization and flow cytometry in pocket scrapings and gingival sulcus scrapings	─	Cases: 50% of pocket samples and 36.6% of sulcus samples showed presence of HR HPV E6/E7 mRNA. Controls: 40% of sulcus samples showed presence of HPV E6/E7 mRNA	─
Sun et al. (2017) [39]	Australian patients 18–90 years attending The University of Queensland School of Dentistry Clinic	223	Cross-sectional study	Periodontal screening (PSR), score 0–4 at six divided anatomical sextants in the mouth. Periodontal disease defined as having a score>3 in any of the six PSR No periodontal disease defined as none of the six PSR scores >2	Self-collected oral rinse and analyzed by PCR	40.5%	4.5% oral HPV-16	Periodontal disease was not associated with oral HPV-16 (OR 2.08, 95% CI: 0.52–8.27).
Ortiz et al. (2018) [6]	Puerto Rican overweight/obese men and women aged 40–65 years	740	Cross-sectional study	Mild periodontitis ≥2 interproximal sites with CAL ≥3 mm or ≥1 interproximal sites with PD ≥5 mm) Moderate periodontitis ≥2 interproximal sites with CAL ≥4 mm or ≥2 interproximal sites with PD ≥5 mm) Severe periodontitis (≥2 interproximal sites with CAL ≥6 mm and ≥1 interproximal sites with PD ≥5 mm)	Self-collected using the Gentra Puregene Buccal Cell Kit (QIAGEN) and analyzed by PCR using 38 type- specific probes.	Moderate periodontitis: 39.4% Severe periodontitis: 20.3%	5.7%	Participants with severe periodontitis had higher odds of oral HPV infection than those with none/mild disease. (OR=2.9, 95% CI: 1.0–8.4, p< 0.05).

Abbreviations: Plaque index (PI); periodontal probing depth (PD); clinical attachment level (CAL); bleeding on probing (BOP); alveolar bone loss (ABL); polymerase chain reaction (PCR); Centers for Disease and Control Prevention (CDC); American Academy of Periodontology (AAP); High-risk human papillomavirus (HR-HPV)

Classification of Periodontitis

Diagnosis of periodontitis depends on the number of teeth and sites examined and severity of the disease, which is affected by the magnitude of pocket depth (PD), clinical attachment loss (CAL), and alveolar bone loss (ABL) (11,13). While different methodologies and indices have been designed to assess and define periodontitis, ABL, PD, and CAL have been described as the most practical measures; indices developed include the periodontal index, the extent and severity index, the National Institute of Dental and Craniofacial Research (NIDCR) periodontal disease index, and a periodontal disease index based on a self-reported questionnaire (21). Meanwhile, the World Health Organization (WHO) has a global oral data bank that uses the community periodontal index (CPI), a score that range from 0–4 indicating the healthy condition and 4 the deep periodontal pocket (40). For the classification of periodontal disease, the definition of the American Association of Periodontology (AAP) was the most widely used in the studies included in this review. This definition classifies periodontal disease into seven categories: gingivitis, chronic periodontitis, aggressive periodontitis, periodontitis as a manifestation of systemic diseases, necrotizing periodontal disease, abscesses of periodontium, and periodontitis associated with endodontic lesions (41, 42). In the U.S., periodontal disease is assessed using the NHANES protocol, where clinical measures of PD and CAL at six sites per tooth for all teeth present (except for the third molars) are performed (43, 44). For periodontitis severity the definition of the Centers for Disease Control and Prevention and the American Association of Periodontology (CDC/AAP) of 2013 is used, which utilizes four categories: no periodontitis, mild periodontitis, moderate periodontitis, and severe periodontitis (43). In this definition, mild periodontitis is defined as having one periodontal site with a PD ≥ 5mm or having at least two interproximal sites with CAL ≥3 mm and at least two interproximal sites with PD ≥4 mm (not in the same tooth); moderate as having at least two interproximal sites with PD ≥5 mm (not on the same tooth) or at least two interproximal sites which are not on the same tooth and which have a CAL ≥4 mm, and severe periodontitis as having at least one interproximal site with PD ≥5 mm and at least two interproximal sites on different teeth with CAL ≥4 mm (35).

Classification of Oral HPV infection

A standard diagnostic protocol has not been established for oral HPV infection (45). The majority of the studies assess oral HPV infection in tissue biopsies (27, 29●, 32●, 33, 37) and the most widely used technique used is polymerase chain reaction (PCR) (6●●, 27, 29●, 30, 33–35, 36●●, 39). The use of tissue biopsy is recommended when oral lesions are present, in order to obtain a site-specific diagnosis (45). The disadvantage of this method is that a negative result does not exclude the presence of the virus in other epithelial sites (45). More recently, self-collected oral rinse has been used (6●●, 34, 36●●). This method is widely used today, as it is a noninvasive sampling method that yields high-quality DNA (46). It is important to mention that HPV detection rate is related to the analytical testing method of HPV (31), and that PCR is the most widely used technique due to its low cost and highly accurate results (31,47).

Results

Evidence to support the association between periodontitis and HPV infection

Eight studies support an association between periodontitis and oral HPV infection. The first published cross-sectional study that suggested a possible association between periodontal tissues and oral HPV infection was conducted in France among men and women with interproximal gingivitis (n=20) (32●). Results showed a prevalence of 15.0% for HPV-16, 10.0% for HPV-11, and 25.0% for HPV-6, supporting that periodontal tissues may act as a reservoir for HPV infection in the oral cavity. Similar results were observed in a cross-sectional study in Finland which took biopsies from the gingival tissue of 38 patients clinically diagnosed with periodontal disease and assessed the presence of oral HPV DNA (29●). This descriptive study was also among the first studies to propose that periodontitis might serve as a reservoir for oral HPV infection in the oral mucosa and to establish a possible link between the two diseases. Periodontal disease was defined as having at least one tooth presenting 33% to 50% bone loss (29●). HPV prevalence was 26.0% in the gingival tissues of patients. Similarly, a small pilot study in India (n=8) among patients with chronic periodontitis found a prevalence of 50% of oral HPV infection in the marginal periodontium of these individuals (37). Only persons with periodontitis were evaluated in these studies, and thus the association between these variables could not be assessed. Nonetheless, the high prevalence of HPV detected suggests a possible link between HPV infection and periodontitis.

A case-control study in the US among tongue cancer patients (n=30) found a positive association between ABL and oral HPV-positive tumor status (OR 3.96, 95% CI: 1.18– 13.36) (33). Meanwhile, another case-control study in India (n=60) found that the periodontium could serve as a reservoir for high-risk HPV (38). Cases (n= 30) were defined as patients with chronic periodontitis and controls (n=30) were patients with no CAL. A total of 90 samples - 2 samples from each case (periodontal pocket and gingival sulcus scrapings) and one for each control (gingival sulcus scrapings) - were obtained; of those, 38 (42.3%) samples were positive to oral HPV in the form of E6/E7 mRNA (38). Finally, two cross-sectional studies with larger sample sizes support an association between oral HPV infection and periodontitis. A recent cross-sectional study among Hispanic adults in Puerto Rico (n=740) found an association between severe periodontitis and oral HPV infection (6●●). In this study, periodontitis was assessed using NHANES methodology and was classified as none/mild, moderate, and severe, following CDC/AAP definition (6●●). Adults with severe periodontitis had higher odds of oral HPV infection (OR 2.0, 95% CI: 1.0–8.4, p<0.05) than those with no/mild periodontal disease (17). Meanwhile, a study that used data from the NHANES 2009–2010 (n=3,439) found a higher prevalence of oral HPV infection (from self-collected oral rinse) in individuals who self-reported that they might have gum disease (PR 1.51, 95% CI: 1.13– 2.01) in comparison with their counterparts (34). Nonetheless, this last study did not consider clinical diagnosis of periodontal disease.

Evidence to support the lack of association between periodontitis and HPV infection

Five research studies have not supported an association between periodontitis and oral HPV infection. The largest cross-sectional study to evaluate this association was performed using data from NHANES 2009–2012 (n= 6004). Periodontitis was diagnosed using the CDC/AAP definition. Meanwhile oral HPV infection was diagnosed through self-collected oral rinse using NHANES methodology (36●●). This study did not find an association between periodontitis and oral HPV infection (OR 1.04, 95% CI: 0.63– 1.73) (36●●), although this analysis did not consider periodontitis severity. Null results regarding the association between periodontitis and oral HPV infection were seen in a pilot study in Australia (n=223) among patients from a University dental clinic (OR 2.08, 95% CI: 0.52 – 8.27). In this study, periodontitis was defined using a score between 0 and 4 at anatomical sextants in the mouth and self-collected salivary oral rinse was used for oral HPV infection (39). Another cross-sectional study in India with a smaller sample (n=102) did not detected HPV-16 infection in gingival tissues, concluding that the marginal periodontium does not act as a reservoir for HPV-16 (35). They defined periodontitis in participants who had PD ≥ 5 mm and required flap surgery (35.). Similarly, a study in Argentina (n=30) found a high prevalence of oral HPV-16 (67.0%) infection and periodontitis (36.7%) among women with gynecological HPV-related disease, although they could not link oral HPV infection with periodontal status. In this study, periodontitis was defined according to the 1999 AAP definition, and oral HPV infection was diagnosed through oral swabs from the tongue and periodontal sites (30). Also, a case-control study in Brazil (n=104) did not detect HPV-16 in cases with gingivitis or chronic periodontitis or in controls with healthy periodontium, concluding no association between HPV-16 and these conditions (27). In this study periodontal disease was classified as chronic periodontitis, gingivitis, and no periodontal disease following the 1999 AAP methodology (27).

Biological plausibility of the association between periodontitis and oral HPV infection

Studies have found a relationship between a variety of benign lesions in the epithelial tissue of the oral mucosa and oral HPV infection (29●). HPV has been reported in various parts of the body, but they are typically found in the anogenital mucosa and oral mucosa (27,48). In the genital mucosa, it has been found that HPV exclusively infects the basal cells of the epithelium, where it can remain latent (29●). The manner in which HPV affects this tissue, is by micro-lesions or by exposures of parabasal cells of the uterine-cervix (29●). The periodontal pocket is the only place of oral mucosa where the basal cells are exposed. Evidence has been found that HPV can also infect gingival tissue suggesting that oral tissue, and sulcular and junctional epithelium, can act as a reservoir for HPV infection (27, 29●). Research suggests that chronic oral inflammation may facilitate HPV acquisition and persistence and may be involved in the etiology of certain head and neck cancers by facilitating HPV infection (6, 30). Studies have explained that HPV only affects the basal cells of the epithelium (49). The infection usually gains access by micro-injuries, while the proliferation of basal cells favors the replication and persistence of HPV infection (49).

Use of various definitions to determine Periodontitis and Oral HPV infection

Periodontitis.

Through the years periodontitis diagnosis has not been standardized in epidemiological studies, making comparisons between studies difficult (13,21). This fact can explain the variability in the prevalence of periodontitis (11–13) and potentially conflicting evidence regarding the association between periodontitis and oral HPV infection. Five studies used the 1999 AAP methodology as the assessment method (27, 30, 37, 38). Meanwhile, only two of the studies included in this review used the CDC/AAP definition of disease severity (6●●, 36●●). Of the two studies that defined periodontal disease using NHANES methodology, one study assessed the association between oral HPV infection and periodontitis severity and suggested that the periodontal pocket could be a reservoir for oral HPV infection (6●●, 29●, 30). The discrepancy in findings between the study by Bui et al. (34) with a positive association and the null association by Wiener et al. (36●●) using the same NHANES data might be explained by the differences in the periodontal case definition. The study by Bui et al. used self-reports of people who think they have gum disease and this might have led to an overestimation. On the other hand, the prevalence of periodontal disease by Wiener et al. might have been underestimated as the study did not distinguish the severe form of periodontitis as explained above. Nonetheless, apart from issues related to different methodologies in defining periodontal disease, the prevalence of periodontitis depends also on the study population. For instance, both the study by Ortiz et al. (6●●) and Wiener et al. (36●●) used a the same definition of periodontal disease, but the former used a Hispanic overweight or obese adult population (aged 40–65 years) with a higher prevalence of periodontitis, and the latter used a general U.S. population aged 30–69 years. Future longitudinal studies should use standardized definitions for disease assessment, including the most recent CDC/AAP definition, to facilitate comparison of study findings in the future.

Oral HPV infection.

The use of the self-collected oral rinse method to detect oral HPV infection, has been recommended as the gold standard for sample collection (45). As described above, the prevalence of oral HPV infection in the studies was low (4.5% to 7.5%), with greater prevalence seen in the studies with low sample size (25.0% - 70.0%). Future studies may focus on high-risk populations, where the prevalence of oral HPV infection is expected to be higher, in order to strengthen the statistical power of such studies to evaluate the association of oral HPV infection with periodontitis.

Limitations

Most studies that have evaluated the association between oral HPV infection and periodontitis have used small sample sizes, with the exception of Bui et al. (34), Wiener et al. (36●●), and Ortiz et al. (6●●). Thus, some may have had limited power to detect the associations of interest. Also, the majority of the studies had a low prevalence of oral HPV infection (4.5%– 7.5%) within the studied populations, consistent with the observation that the prevalence of this infection in the general population is low (5, 50). Moreover, there were differences in the methodology used to assess periodontitis and oral HPV infection, potentially having an impact on the differences in results observed in studies described. Finally, most studies were cross-sectional in nature, and none assessed the longitudinal association between the two conditions.

Conclusions

Although the study results are still conflicting and inconclusive, various studies suggest an association between oral HPV infection and periodontitis, which is supported by biological plausibility. Future longitudinal studies should further evaluate this association, using clinical definitions of oral HPV infection and periodontitis. Longitudinal studies should include high-risk populations for oral HPV infection, such as HIV-infected people and individuals who attend sexually transmitted infections (STI) clinics, since the prevalence of this infection in general population before is low. Studying this association is important since periodontitis might help to identify at-risk individuals for oral HPV infection and also potential HPV-related oropharyngeal cancers.