The present study was conducted with the objective of determining the relationship of OSA with the periodontal condition and its associated local and systemic risk factors.
When evaluating the association between patients who presented OSA with a periodontal condition, it was found that of those diagnosed with periodontitis, 66.66% presented with severe OSA, showing a tendency for patients with periodontitis to present with severe apnea, although the difference was not significant. The relationship between OSA and the periodontal condition has been reported in recent years, and Gunaratnam et al [11], in whose study the number of patients was quite similar to that of the present study (66 participants), reported that the prevalence of periodontitis in patients with OSA was four times higher. Likewise, Ahmad et al [18], in a case–control study with 154 patients (50 cases and 104 controls), reported that cases were 4.1 times more likely to have a high risk of OSA than controls. Similar to the results reported in the present study, Loke et al [19] found that the prevalence of periodontitis in the OSA group (96.4%) was significantly higher than that in the control group (75%) and that 48.2%% of patients with periodontitis had severe OSA. Consistently, Al-Jewair et al [20], Keller et al [21], Sanders et al [22] and Latorre et al [23] showed a positive association between OSA and periodontitis. However, there is controversy in this regard, and in contrast to the above, Kale et al [5], in a study with 260 patients, did not find significant differences between the OSA groups for the presence or absence of periodontitis.
Different hypotheses have been postulated to explain the mechanism by which periodontal disease causes OSA or vice versa. One of them is that the relationship between the two conditions is comorbid rather than causal, since both share common risk factors [11]. Another hypothesis is that periodontitis produces chronic inflammatory responses in susceptible hosts and acts as a mediator of systemic inflammation of OSA or vice versa[8,11,20,24]. It has also been reported that mouth breathing associated with OSA increases the expression of periodontitis, which may occur as a consequence of a greater accumulation of biofilm favoring the colonization of periodontopathogenic microorganisms caused by xerostomia[11,22,24]. Finally, it has been proposed that it may be due to oxidative stress that occurs in both pathologies [22,25].
When analyzing the periodontal variables in slightly more detail, it was reported that patients with periodontitis with and without OSA had a higher percentage of bleeding on probing, biofilm, greater depth of gingival sulcus, periodontal pockets and a greater loss of clinical attachment level, with statistically significant differences (p < 0.05). Scientific evidence repeatedly shows us that bleeding on probing, the percentage of biofilm, the depths of periodontal pockets and the greatest clinical attachment losses are the related parameters and are altered in the presence of periodontitis[7,17].
In the comparison of patients without periodontitis, the biofilm percentage was higher in patients with OSA. These results are similar to those of Gamsiz-Isik et al [13], who found that the biofilm index was higher in patients with OSA than in controls. This has been associated with the daytime sleepiness experienced by these patients, which leads to a lower frequency of daily brushing in patients with OSA[26]. It has also been associated with oral breathing during sleep since it favors the accumulation of biofilm on the surface of the teeth and the inability to eliminate it effectively due to the decrease in salivary flow[27].
The average age of the patients was 49.4 years, and that of patients in the OSA group with periodontitis was 53.2 years, similar to the results by Seo et al [28]. Indeed, there is scientific evidence that aging is positively related to an increase in the incidence of OSA [23,29]. In fact, a more recent study reported that due to aging, the number of obstruction sites and the pattern of collapse may vary due to changes in the pharyngeal anatomy, redistribution of body fat and greater laxity of the muscular and hypopharyngeal structures. In their results, they determined that the value of AHI increased with aging[30].
With respect to the systemic risk factors evaluated, it was found that one of the most frequent diseases was obesity, affecting 58.3% of the patients. The literature has suggested that obesity plays a role in the pathogenesis of OSA due to alterations in the structure and function of the upper respiratory tract. Obesity according to Ong et al [31] and Al-Qahtani et al [32] also induces an inflammatory state since adipose tissue is an abundant source of proinflammatory cytokines that are associated with defects in neuromuscular control of the respiratory tract that lead to higher susceptibility to and severity of OSA.
On the other hand, in the analysis of obesity according to study group, it was found that in the group of patients with apnea and periodontitis, the percentage of patients (34%) with obesity was higher. This finding has been previously reported in the literature, where Martinez-Herrera et al [33] related obesity with periodontitis. Likewise, in a systematic review, Keller et al [34] determined that overweight, obesity, weight gain and increased waist circumference can be risk factors for the development of periodontitis and even increased disease severity. It has been shown that obesity is higher in patients with periodontal disease than in periodontally healthy patients[21].
In the evaluation of BMI in the general population, an average of 26.12 kg/m2 was found, being higher in patients in the apnea group with periodontitis (28.04 kg/m2). Although no significant differences were found among groups, there was a trend showing that patients with OSA tend to have a higher BMI. These results are similar to those reported by Cuervo et al [35]. Additionally, Martinez-Herrera et al [33] revealed that both BMI> 35 kg/m2 and neck circumference> 40 cm were risk factors for OSA, but after adjustments were made for all other variables, the difference was not significant for BMI but was significant for neck circumference. This may be because BMI is an indicator of total adiposity, but it does not evaluate the distribution of body mass. Therefore, it does not provide specific information related to localized fat deposition around the neck, which can be an accurate predictor of OSA.
Arterial hypertension (AHT) was another of the most common systemic conditions since 28.33% of patients had AHT. Likewise, it was evident that in the group of patients with severe OSA, there were a greater number of patients with HTN. The relationship between OSA and AHT has been reported previously, and in accordance with the results, González-Pliego et al [36] reported the coexistence between OSA and AHT, relating OSA as one of the most common causes of secondary HT. Likewise, Latorre et al [23] and Rimoldi et al [37] reported an association between HT and OSA. It is evident then that the vast majority of studies indicate that OSA and hypertension coexist and are common.
The present investigation found that patients without periodontitis had more AHT than patients with periodontitis, with a statistically significant difference (p = 0.038). These results are contrary to those reported by Latorre et al [23] who found a significant association between OSA and chronic periodontitis or AHT, as well as an association with hypertensive cardiomyopathy, in a much larger sample of 190 patients.
Hypothyroidism was the third most common systemic pathology reported since 16.6% of the general population had it. Kuczyński et al [38] and Thavaraputta et al [39] also reported an association between OSA and hypothyroidism. In contrast to these results, in a study conducted by Bielicki et al [40] in 813 patients diagnosed with OSA, 4.7% had hypothyroidism, but there was no significant relationship between these two pathologies.
In the analysis of the associated local factors, a statistically significant association was found between severe OSA and removable partial dentures. This relationship has been studied since the report that edentulism can generate a loss of vertical dimension, reduction of the height of the lower face and rotation of the mandible, which leads to disharmony of the occlusion causing an alteration of the upper airways[41,42]. Additionally, it has been found that the tongue could be positioned in a manner that obstructs the airway during sleep [32]. One of the first to explain this association was Bucca et al [43], who reported that removing the removable prosthesis at night significantly decreases the retropharyngeal space and that sleeping without it is associated with a significant increase in the severity of OSA and a decrease in oxygen saturation.
In the evaluation of the relationship between decayed, lost and filled teeth in the present study, it was shown that the average number of missing teeth was 6.7, and the percentages of patients with caries and filled teeth were 15% and 79.9%, respectively. A significant association among severe OSA, periodontitis and maladaptive resins was evident. Additionally, data have shown an association between periodontitis and maladaptive restorations, whether interproximal or cervical, since they are bacterial niches that trigger inflammation and destruction of periodontal tissues[44,45].
Continuing with local factors, in the analysis of malocclusion, open bite and edge-to-edge bite were evaluated. However, no significant association with OSA was found in this study. These results are consistent with those reported by Alqahtani et al [46] and Gudipaneni et al [47] in adult patients. In contrast, associations between anterior open bite, posterior crossbite, lip incompetence and OSA symptoms have been reported in adolescent patients[47,48].
When evaluating the facets of dental wear, it was found that 41.67% of the population had them, and despite this high prevalence, there was no significant association with OSA or periodontitis. In contrast, a study conducted by Durán-Cantolla et al [49] reported a statistically significant correlation between tooth wear and OSA severity and indicated that the prevalence of OSA in patients with tooth wear was three times higher than that in patients in the general population. In the literature, it has been reported that nocturnal bruxism could be a factor associated with tooth wear[50].