[21].
The erosive damage to the dental hard tissues occurs after exposure to acidic substances and does not include the effects of bacteria or their products. The process involves an initial softening of the tooth surface, which is followed by a permanent loss of tooth substance. The degree of saturation of Ca2+, PO43–, OH– and F– ions in the fluid that exists in the vicinity of the hydroxyapatite crystals, together with the critical pH for equilibrium and the erosive potential/chelating ability of the acid, are some factors that influence whether the minerals will dissolve or form deposits on the enamel surfaces [22]. To counteract the erosive processes, a satisfactory saliva secretion rate, composition and buffering capacity together with the formation of a protective dental biofilm shield, are considered to be influential protective biological parameters [23, 24].
Future
In the future, studies aiming to bring about the remineralisation of the affected dental tissues are needed. Increased awareness in the public and dental communities, early detection, change of behaviours associated with erosive tooth wear, applied preventive measures and continued targeted research are other plausible avenues to limit the expansion of dental erosion.
Periodontal Diseases
Introduction and Prevalence
Periodontal diseases comprise chronic, biofilm-initiated, inflammatory conditions including gingivitis and periodontitis [25]. They affect the tooth-supporting structures and may lead to masticatory dysfunction. Together with dental caries, they are the main cause of tooth loss. In its early stages, the disease may be restricted to the gingiva and be seen clinically as an inflammation indicated by bleeding upon probing. At this stage, it is possible for the gum tissues to return to a state of health, without the irreversible loss of tooth attachment, once the cause is removed. Further progression from gingivitis to periodontitis is manifested by attachment loss, clinically taking the form of deep periodontal pockets and gingival recession. Although periodontal disease may be identified in younger individuals, an increase in prevalence is seen with increasing age [26]. Even if signs of disease can be found in prehistoric samples, it is more common in the modern population. A substantial increase in periodontal health has taken place during the last 50 years. A reduction in gingivitis in Swedish individuals aged ≥20 years, from 40% in 1973 to 15% in 2013, has been seen [27]. A reduction in the frequency of individuals with a probing pocket depth of >4 mm, an increase in the number of individuals with no marginal bone loss and a reduction in the number of subjects with moderate alveolar bone loss have also been observed [27]. The peak incidence of severe periodontitis occurs between the age of 30 and 50 years, with the prevalence remaining basically the same afterwards [28, 29].
Aetiology and Pathogenesis
Like dental caries, periodontal diseases are complex and of a multifactorial nature, including both inherited and acquired risk factors. A subgingival biofilm is required for the development of periodontitis, where the presence of proteolytic and anaerobic bacterial species plays a key role [30]. Differences in host response may determine disease onset, progression and severity, and several conditions may influence the interaction between the host and the bacterial biofilm. It has long been known that genetics contribute to periodontal diseases, with a likely risk estimated at up to 50%, and several different genes associated with chronic periodontitis have been identified [31]. A gender difference for periodontal diseases can be seen, but this is instead related to variations in lifestyle and is not genetically determined [32]. There is extensive support for smoking as a risk factor for periodontal disease where smoking, nicotine and its metabolites may have a negative effect on subgingival microflora, periodontal tissue and host response [33, 34]. Other risk factors for periodontal disease are diabetes, obesity, and other metabolic disorders; however, lifestyle factors such as alcohol and stress are also included [32, 34].
Destructive inflammatory processes occurring around osseointegrated dental implants have been described by the term “peri-implantitis.” The disease process is very similar to that found in association with periodontal disease. In severe cases, peri-implantitis can lead to the disintegration and loss of implants and their supported prostheses.
Disease Prevention
Preventive strategies and maintenance focus on mechanisms, which directly or indirectly may have an impact on the amount and composition of the subgingival biofilm. This includes regular oral hygiene on a daily basis, as well as the professional mechanical removal of biofilm and calculus. A significant reduction in pathological bacteria in periodontal pockets may permit repopulation by non-pathogenic microbes. It is important to remember that disease susceptibility varies widely among individuals and periodontal maintenance must therefore be individualised for each patient. Recent data also indicate a link between periodontal and general health, where heart disease, diabetes, stroke and respiratory disease all involve an increased risk. For this reason, periodontal patients should also be regarded as risk patients from a systemic health angle.
Oral Cancer
Introduction and Prevalence
Oral cancer, which includes cancer of the lips, tongue and oral cavity, is a highly complex condition and can be life threatening if not diagnosed and treated at an early stage. It represents the eighth most commonly found form of cancer worldwide, but it has an uneven distribution where low-income countries bear the greatest burden [35, 36]. In these countries, oral cancer is twice as prevalent as it is in high-income countries. Head and neck cancer are also known to be more common among males compared to females, as well as being found more frequently in individuals of higher age. It was estimated that around 50,000 individuals would develop oral/oropharyngeal cancers in the USA in 2017 [37]. The oral cavity is made up of cells of different types and cancer can develop from each cell type, including the bone and salivary glands. The tumours can be (i) of benign or non-cancerous nature, (ii) pre-cancerous conditions or (iii) cancerous tumours, which may grow into the tissue and spread to other body parts. A total of >90% of oral cancers are oral squamous cell carcinoma with a higher incidence in Melanesian and South Asian countries [38].
Aetiology and Pathogenesis
Lifestyle plays a major role in oral cancer, and its incidence is particularly high in relation to risk factors such as tobacco smoking, excessive alcohol consumption, oral tobacco products, and frequent exposure
