Introduction to risk factors for periodontal diseases
There is strong evidence available today suggesting a multifactorial etiology of periodontal diseases. It has been demonstrated that the susceptibility of different individuals to periodontitis for the same amount of local factors is variable. Some individuals demonstrate less periodontal breakdown, whereas other demonstrate significantly more, for a similar amount of pathogenic microflora. A lot of research has been done in the last few decades to find out various risk factors responsible for periodontal disease progression. In the following sections, we shall study in brief about these risk factors with their details in the upcoming chapters.
Risk factors may be environmental, behavioral or biologic in nature that when present increases the likelihood of a disease. These include poor oral hygiene and pathogenic microflora, tobacco smoking, diabetes, and psychological stress.
Risk determinants are those risk factors that cannot be modified. These include genetic factors, host response, age, gender and socioeconomic status.
Risk indicators are probable or putative risk factors that have been identified in cross-sectional studies, but not confirmed through longitudinal studies. These include osteoporosis, HIV/AIDS, obesity, alcohol consumption, infrequent dental visits, drug intake associated periodontal disorders and iatrogenic factors.
A risk factor that can be used to predict the future course of the disease is known a risk marker. The risk markers for periodontal disease include the previous history of periodontal disease and bleeding on probing.
The risk factors for periodontal diseases can be classified broadly into two categories: modifiable risk factors and non-modifiable risk factors. Modifiable risk factors are usually environmental or behavioral in nature, whereas non-modifiable risk factors are usually intrinsic to the individual and therefore can not be easily changed. As already stated, the non-modifiable risk factors are also referred to as risk determinants. To establish a factor as a risk factor or determinant for periodontal disease, the evidence is gathered from longitudinal cohort studies, cross-sectional studies, case series, case-control study, and controlled clinical trials.
Modifiable risk factors
Poor oral hygiene and pathogenic microflora:
There is strong evidence in favor of the role of periodontal pathogenic microorganisms in the initiation and progression of periodontal diseases. Bacterial species, including Porphyromonas gingivalis 1, Aggregatibacter actinomycetemcomitans 2, 3, Bacteroides forsythus 4, Prevotella intermedia 5, Peptostreptococcus micros 6, Fusobacterium nucleatum 7 and spirochetes 8, 9 have been specifically found to contain the virulence factors responsible for evasion of host response and periodontal breakdown. The reduction of this pathogenic microflora has been found to be strongly associated with improvement in periodontal health 10-13. Thus, reduction in the microbial load around the teeth is the cornerstone of periodontal therapy.
The periodontal breakdown has been found to be more among smokers as compared to non-smokers 14, 15. This finding establishes tobacco smoking as an important risk factor for the development of periodontitis. Although, smokers have reduced clinical signs of periodontal inflammation as compared to non-smokers but they have an accelerated periodontal breakdown. The reduced signs of inflammation can be explained based on the fact that nicotine exerts local vasoconstriction, reducing blood flow, edema, and clinical signs of inflammation 16. Smoking cessation has been shown to improve periodontal health. In a 12 month study, it was demonstrated that patients who had continuously refrained from smoking for the entire study period had a significant reduction in probing depths as compared to smokers 17. Similarly, in another study, it was shown that subjects who had quit smoking during the entire study period had significantly reduced alveolar bone loss as compared to smokers 18. Thus, smoking can be considered as a modifiable risk factor for the development and progression of periodontal diseases. A detailed description of the effect of smoking on periodontitis has been given in “Smoking as a risk factor for periodontitis”.
The association between diabetes mellitus and periodontitis has been found to be bi-directional. The poor glycemic control worsens periodontal disease status and poor periodontal health has been shown to worsen the glycemic control. Many studies and reviews have been published which support a relationship between periodontitis and diabetes 19-23. There are multiple mechanisms by which hyperglycemic state worsens the periodontal status of the patient. The most well-established mechanism is, altered collagen metabolism in diabetic patients. Other mechanisms include altered monocyte-macrophage function, altered wound healing, increased oxidative stress and effects of the hyperglycemic state on cellular functions. On the other hand, periodontitis results in increased pro-inflammatory cytokines locally and then systemically. IL-6 and TNF-α are two main chemical mediators which relate periodontitis to diabetes. A detailed description of the relationship between diabetes and periodontitis has been given in “Diabetes and periodontitis: a bidirectional relationship”.
Psychological stress is another risk factor for periodontal diseases 24. It has been observed that stressed, anxious, or depressed persons tend to neglect their oral hygiene. Furthermore, smokers have been observed to smoke more under stress which further deteriorates their periodontal status. A stressed individual often takes inadequate diet, which is responsible for the overall deterioration of his/her health. Stress has been shown to result in elevated levels of cortisols which further have been positively associated with the extent and severity of periodontitis 25. In a study, it was shown that salivary cortisol level was a significant predictor of the number of missing teeth and also of the number of teeth with clinical attachment loss of ≥5 mm 26. Stress management has been shown to improve the periodontal status of patients with periodontitis 27. Thus, stress can be considered as a modifiable risk factor that may influence the severity of periodontal diseases. A detailed description of stress as a risk factor for periodontitis has been given in chapter “Stress as a risk factor for periodontal diseases”.
Non-modifiable risk factors (Risk determinants)
Present data strongly suggest that genetic factors are important risk factors for periodontal disease progression. Family studies, twin studies, population studies and single nucleotide polymorphisms (SNP) have been done to find out the genetic basis of periodontal diseases. Gene poly-morphisms have been shown to have a positive correlation with increased severity of periodontal disease. IL-1 and TNF-α gene polymorphism have been studied extensively and a positive correlation has been demonstrated between periodontitis and these polymorphisms 28-31. A detailed description of the genetic basis of periodontal diseases has been given in “Role of genetics in pathogenesis of periodontal diseases”.
The present research on the etiopathogenesis of periodontal disease suggests that most of the tissue destruction caused by host-microbial interaction is primarily by host-derived chemical mediators. Further, it has been found that certain individuals mount an abnormal host response to the microbial challenge. The presence of hyperactive neutrophils and monocytes in individuals showing severe periodontal breakdown has been demonstrated in many studies 32-35. Matrix metalloproteinases (MMPs) are responsible for the remodeling of connective tissue. Studies have shown that individuals demonstrating aggressive periodontal breakdown have prolonged and excessive activation of the latent MMPs resulting in the enhanced degradation of collagen, which is a primary component of the periodontal matrix 36-38. Because these altered immune responses are genetically determined and cannot be altered with our present strategies, the altered host response can be considered as a non-modifiable risk factor.
Various studies have demonstrated that with increasing age the severity of periodontal diseases increases 10, 39-43. It is a general observation that periodontal attachment loss is more in elderly individuals than in younger individuals. Further-more, the advanced periodontal bone loss is less commonly observed in young individuals. However, it must be noted that the periodontal destruction observed in elderly individuals is a cumulative destruction over several years rather than a result of increased rates of destruction. Thus, aging cannot be considered as a risk factor per se 44.
In general, males have been shown to have more overall periodontal destruction as compared to females. Various studies done around the globe have highlighted this finding 44-47. The reason suggested for this finding is the ignorance of oral hygiene, which is usually observed among males. However, it should be noted that this association is not reliable as it entirely depends on the maintenance of oral hygiene and not on gender.
The individuals with low socioeconomic status have been shown to have more periodontal destruction as compared to those having average or high socioeconomic status. However, the relationship between socioeconomic status and periodontitis is less direct as compared to gingivitis 42, 48-50. The reason suggested for this difference is a better education level and more access to oral health care services by individuals with good socioeconomic status.
Osteoporosis is characterized by a decreased bone-mineral density throughout the skeletal system, including the jaws. This disorder has been shown to be positively associated with periodontal bone loss 51-55. Postmenopausal osteoporosis in females is an important risk factor associated with increased severity of periodontal diseases. A decreased estrogen production following menopause is associated with a decreased mineral density of bones 56. In a review, it was concluded that most of the studies done to find out any association between osteoporosis and periodontitis concluded that systemic …………… Contents available in the book…………. Contents available in the book…………. Contents available in the book…………. Contents available in the book…………
The HIV infection is associated with a compromised immune response which predisposes the individual to various infections. The periodontal problems which are associated with HIV infection include specific forms of gingivitis and necrotizing periodontal diseases, as well as with possible exacerbation of pre-existing periodontal disease 58, 59. However, it should be noted that the development of periodontal lesions vary among HIV-positive patients depending on the status of their immune system and maintenance of oral hygiene.
Recent research has demonstrated a positive association between obesity and periodontitis and obesity can be considered as a risk factor for periodontal disease 60, 61. Various mechanisms have been suggested to explain the effects of obesity on the severity of periodontal disease 62-64. The dietary habits of young and adolescents are different from that of older individuals. In a study, it was observed that adolescents (11-18 years old) have a reduced intake of raw fruits and non-potato vegetables, which are sources of vitamin C. Furthermore, an increased intake of soft drinks and non-citrus juices were observed in this age group. Calcium intake was also found to be reduced in this age group. Thus, a low dietary intake of vitamin-C and calcium can adversely affect the periodontal status of the individual 65.
Alcohol intake has been associated with an increased severity of clinical attachment loss in a dose-dependent manner. In a study 66 on data obtained from NHANES III from 13,198 individuals which employed 20 years and older adults, it was observed that a linear relationship existed between a number of alcoholic drinks per week and log clinical attachment loss (P= 0.0001). However, more clinical research is required to establish alcohol consumption as a risk factor for periodontal diseases.
Infrequent dental visits:
Adhering strictly to the periodontal maintenance protocol has been shown to have a beneficial effect on the overall dentition and periodontium of the patients. Various longitudinal studies done on non-surgical and surgical periodontal therapy have demonstrated that patients who regularly visit the dental office for periodontal maintenance have a better periodontal status as compared to those who infrequently visit the dental office (more details in “Periodontal maintenance”).
Drug intake associated periodontal disorders:
Certain drugs have been shown to be associated with decreased salivary flow. These include anti-hypertensive drugs, narcotic analgesics, some tranquilizers and sedatives, antihistamines, and antimetabolites. A decreased salivary flow is associated with a decreased flushing effect of saliva in the oral cavity, which may contribute to the increased periodontal disease activity. Certain drugs which are in a chewable form, commonly have sugar as one of their constituents. It may alter the pH of the oral cavity, thus affecting plaque composition 67. Gingival overgrowth has been shown to be associated with the intake of drugs such as anticonvulsants, calcium channel blocking agents, and cyclosporine. The gingival overgrowth is also associated with increased accumulation of local factors, thus, facilitating the progression of periodontal disease.
The presence of faulty restorations and overhanging margins of crowns facilitate the accumulation of food particles and debris at the tooth-soft tissue interface. These areas become inaccessible for cleaning by the patient and promote the formation of a periodontal pocket. Furthermore, the position of the margin of restoration is also related to the gingival health. Subgingival margins of the restorations have been shown to have a positive correlation with the presence of gingival inflammation 68-70. Rough …………… Contents available in the book…………. Contents available in the book…………. Contents available in the book…………. Contents available in the book…………
Previous history of periodontal disease:
A previous history of periodontitis is a good predictor of future risk of periodontal disease. Patients having existing severe attachment loss are at a higher risk for future attachment loss. On the other hand, individuals with minimum periodontal loss of attachment have less risk for future periodontal breakdown.
Bleeding on probing:
Bleeding on probing is one of the earliest indicators of gingival inflammation. However, it must be remembered that bleeding on probing does not indicate the severity of periodontal breakdown. This is because bleeding on probing indicates the presence of inflammation but not the severity of periodontal attachment loss. However, it has been demonstrated that absence of bleeding on probing is a good indicator of periodontal health 71, 72.
Periodontal risk assessment
Periodontal risk assessment is the overall evaluation of the patient to assess the risk for the development of periodontitis. The risk assessment is done based on the patient’s demographic data, medical history, dental history, and clinical examination. The patient may have a single or multiple risk factors or determinants. The treatment planning of the patient should be done taking into consideration the overall risk. For example, if the patient is a smoker, the smoking cessation protocol should be included in the treatment plan.
An overall assessment of risk factors is an integral part of the periodontal maintenance program. The maintenance visits should be planned depending on the periodontal status of the patient and the presence of risk factors. In other words, it can be said that periodontal risk assessment involves identifying elements that either may predispose a patient to develop periodontal disease or may influence the progression of the disease that already exists.
It can be concluded from the above discussion that risk factors play an important role in the etiopathogenesis of periodontal diseases, as well as they affect the overall treatment plan designed for the patient. A reduction or elimination of risk factor(s) should be included in the treatment protocol designed for a particular patient. The periodontal maintenance program should be planned, taking into consideration all the risk factors and determinants for a particular patient. In the upcoming articles, we shall read in detail various risk factors and determinants associated with periodontal diseases and the mechanisms of their association.
References are available in the hard-copy of the website.