Frequency and Profile of Severe Periodontitis in Kinshasa Dental Hospitals, DR Congo

Purpose: Severe periodontitis (SP) is the sixth most prevalent disease world-wide. Prevalence and incidence are poorly reported in DR Congo. The aim of this study was to assess the prevalence of SP and to compare its profile with that of mild to moderate periodontitis (MMP). Materials and Methods: Four hundred and four patients from four hospitals of Kinshasa City Capital participated in this study. Probing pocket depth (PPD) at six sites per tooth, bleeding on probing (BoP) and plaque index (PIl) were the main clinical parameters assessed. Results: Out of 404 patients examined in this study, 92 (22.8%) had severe periodontitis and 276 (68.3%) had mild to moderate periodontitis. Among patients with SP, 48 (52%) were female, 44 (48%) were male and 63% of them had a PPD of 6 mm. SP was significantly different from MMP according to patients age, 47.3 ± 18.6 versus 32.87 ± 14.40 years old, p < 0.001; plaque index, 1.153 ± 0.39 versus 0.90 ± 0.39, p < 0.001; BoP, 26.65 versus 17.04, p < 0.001. Conclusion: The Frequency of SP is relatively high in patients attending dental services in Kinshasa City and SP is significantly different from MMP.

Periodontitis causes microulceration of the investing sulcular and pocket lining epithelium. The estimated surface area of this ulcerated epithelium approximates 40 cm 2 in severe periodontitis. The prevalence of SP varies worldwide. In the USA it's 8.9% [8], 20% in East Germany [9] and 11.9% as study reported result from Australia [10]. While mild to moderate periodontitis affects the majority of adults, severe periodontitis (SP) affects 5% to 20% of any population [11] [12].
In a systematic review and meta-regression analysis by Kassenbaum et al. [13], SP was found to affect 748 millions of people worldwide and is the sixth most prevalent condition. The loss of productivity due to SP amounted to US$54 billion yearly worldwide [14].
To the best of our knowledge, the prevalence or incidence of SP is poorly reported in DR Congo and also no study has yet compared subjects with severe periodontitis and those with mild to moderate periodontitis. The objective of the present study was to determine the frequency of SP and to compare its profile with that of MMP.

Materials and Methods
This cross-sectional study took place in four hospitals selected randomly in the province of Kinshasa from October 2012 to April 2013. These centers were Ngaliema clinic, Boyambi clinic, Saint Joseph hospital and affiliated clinic of Kinshasa University.
The study was approved by the local ethic committee, school of public health of the University of Kinshasa, approval number ESP/015/2012. An informed consent was obtained from each participant and pertinent information concerning the study was explained to all of them.
The study assessed 404 subjects aged between 12 and 81 years who consulted the dental services of mentioned above hospitals. Their mean age was 35.26 ± 16.94 with a median of 30 years, a sex ratio of 1.49:1 and the most represented age group between 20 and 29 years old ( Table 1).
The data were collected by interview and a clinical exam. The subject comfortably seated on a dental chair was first interviewed and then a periodontal clinical examination was performed by the same trained and calibrated examiner (E.K.K). The parameters of interest were socio-demographic data and anamnestic informations on the interview. On clinical examination, the plaque index (PlI), bleeding on probing (BoP), and probing pocket depth (PPD) were assessed. The PlI was calculated as the sum of scores of all surfaces examined divided by the total number of surfaces examined. BoP was calculated as the sum E. K. Kalala et al. of the surfaces that bled after probing divided by the number of the surfaces examined. The bleeding was assessed 20 seconds after the passage of a periodontal probe into the sulcus.
The examination started on the disto-buccal surface of the maxillary right second molar, and continued anteriorly to the disto-buccal surface of the maxillary left second molar. Then, the disto-lingual surface of the maxillary right second molar was examined to the disto-lingual surface of the maxillary left second molar. The mandibular teeth were then examined in the same manner, starting on the disto-buccal surface of the mandibular right second molar.
All fully erupted permanent teeth were examined, excluding the third molars. Erupting teeth, supernumerary and partially impacted teeth were excluded. The measurements were assessed at six sites per tooth (mesiobuccal, midbuccal, distobuccal, mesiolingual, midlingual and distaolingual). The PPD was defined as the distance between the free gingival margin to the bottom of the pocket/sulcus. The periodontal probe (Hu-Friedy, PCP 11.5, CHICAGO, Illinois) was used for probing depth measurements and bleeding on probing.
In this study, we defined subject with periodontitis as the patient with a probing pocket depth of at least 3.5 mm on at least one tooth. The patient with SP was defined as the one with a PPD of at least 6 mm on at least one tooth. The data collected were entered into the computer using Excel 2007 software. The SPSS software version 20.0 was used for descriptive statistics. The Student's T-test and Analyze of Variance (ANOVA) were used to compare the means. The significance level was set at 0.05%.
Among SP patients, forty-eight were female (52%) and forty-four (48%) were male. The mean age of SP patients was 47.3 (SD ± 18.60) years and a median of 46 years old.
The proportion of subjects with PPD = 6 mm was 63% and those with a PPD =

Discussion
The objective of this study was to assess the prevalence of SP among patients attending hospitals in Kinshasa and to compare its profile with that of MMP.
The present study showed a high prevalence of SP. In Norwegian circumpolar communities, the SP prevalence of 9.1% was found [15]. But a study of large population in West Pomerania in the former East Germany found 20% of SP [9] whereas NHANES 2009-2012 estimated that about 8.9% of the US adult population aged 30 years and older had SP [8]. A meta-analysis study by Kassenbaum et al. [13] has concluded that SP affected 5% to 20% of people worldwide, indeed, the majority of adult population had MMP. In this study, 22.8% of subjects have SP whereas 68.3% has MMP indicating that the proportion of SP is high but fewer than that of MMP. This is in agreement with others studies where the proportion of MMP was greater than that of SP and MMP was common and affected the majority of adults [11] [12]. Proportions of periodontitis can vary according to the methodologies and diagnostic criteria used [16] [17]. It should be noted that, the criteria used in this study defined MMP as the presence of a PPD of at least 3.5 mm on at least one tooth and SP as the presence of a PPD of 6 mm E. K. Kalala et al. or over on at least one tooth. The majority of patients had PPD of 6 mm.
The mean age of SP patients was higher than that of MMP patients with significant difference. SP seems to be more prevalent in older age and this was consistent with the literature showing that periodontitis prevalence and severity of disease are associated with increasing age [8] [11] [18]. Age is considered as an aggravating factor in the fact that the cumulative effect of the disease during the life of the individual is measured [3] [19].
The plaque index expresses the level of dental plaque. It can be used to qualify whether the individual has or not a poor oral hygiene. There is pronounced relationship between poor oral hygiene and increased accumulation of dental plaque, high prevalence and increased severity of periodontal disease [20]. Dental plaque can set a stage for inflammatory changes in periodontal tissues [21]. In the etiology of periodontal diseases, dental plaque as dental biofilm is considered as the primary factor that initiates the inflammation. According to the host response, this inflammation can lead to the tissues breakdown. Also other factors, such as environmental, genetics or systemic may play an important role. In a prospective study of 15 years duration, Axelsson et al. found no further deterioration of periodontal structure among the subjects who maintained proper oral hygiene and took routine professional dental care [22]. In this study, the PlI of SP patients was significantly greater than that of MMP patients.
Bleeding on probing was demonstrated to be a sign of inflammation of gingival tissue or a proxy for gingival inflammation [23]. The presence of BoP may be considered as a predictor for the progression of periodontal disease [24], whereas its absence is a reliable predictor for the maintenance of periodontal health [25]. BoP is at present a clinical sign of periimplant disease. In this study, BoP of patients with SP was significantly higher than that of MMP patients. Inflammation by means of BoP is greater in patients with SP. The presence of deep pockets may influence the accumulation of dental plaque and the microorganisms within the biofilm may act in maintaining the inflammation.
This study has some limitations; it was carried out in patients attending hospitals and therefore is prone to selection bias. The prevalence found here is the prevalence of patients consulting the dental services of Kinshasa in DR Congo.
Future studies involving randomly sample selected in population are needed.
Within the limitations of this study, it provides information on the frequency