Competition for Tooth Surface—Microbial Olympics

We share the world we live in with millions of microbial species, some of them having no interest in harming various parts of our body, while others discover new ways of harnessing resources from human cells and tissues, for which newer and more powerful antibiotics must be developed and prescribed to people in need. Intriguingly, up to 15% of all antibiotic prescriptions worldwide are made by dentists, with a relevant proportion of these prescriptions having a prophylactic aim [1].

There are more than 700 bacteria types in oral microbiota, [2]. with habitats ranging from hard tissues (natural: tooth surface—enamel/cementum, or artificial—various dental materials), to soft tissues (tongue, but also lips/cheeks/palate) and of course, saliva. Some authors even place this number in the range of thousands [3]. Oral microorganisms organize in biofilms [4], following a complex milieu of signaling, physical and chemical and immune interactions. Since in saliva succession cannot occur for a longer period due to swallowing, the colonization mostly take place on the cells/materials surface. Most available surfaces in the oral cavity are represented by soft tissues, however since the surface cells detach and are also mostly swallowed, only non- pathogenic monolayer form on mucosal surfaces [3]. Intriguingly, oral microbiota may be also used as a non-invasive diagnostic tool, for local and systemic disease [5]. As regards the hard surfaces, these are first covered by pellicle and then colonized by bacteria, in several steps, from initial adhesion to maturation and in the end, dispersion [6]. The best characterized type of oral biofilm is the supragingival and subgingival plaque. Here, many different bacterial species aggregate to form polymicrobial biofilms [7]. On the other hand, biofilms are able protect constituent bacteria from host defense mechanisms as well as from some applied antibiotics [6]. A number of oral bacteria have been linked to carcinogenesis—i.e., Fusobacterium nucleatum, Porphyromonas gingivalis [8]. Some species are increased in patients with dental caries or various degrees of periodontitis—i.e., Streptococcus mutans or Porphyromonas gingivalis. Other periodontal pathogens include Aggregatibacter actinomycetemcomitans, Tannerella forsythia, Prevotela intermedia, some of which are Gram positive, other Gram negative; some anaerobic, other aerobic, hence yielding a large variety of response to a spectrum of prescribed antibiotics. Moreover, an increase in antibiotic prescriptions during and after the COVID-19 pandemic was recently reported [9].

Prescribing oral antibiotics in dentistry should be reserved for specific pathologies, mostly with systemic involvement. Eliminating the cause of infection should be the primary concern, and in some situations this can be achieved by operative intervention associated or not with local-delivered antibiotics. For example, reduced blood flow (for pulp infections) would impede the efficiency of systemic antibiotics [10]. In case where general symptoms are associated, or risk of spreading is imminent, use of oral antibiotics is, of course, reccommended. Oral antibiotics effective for odontogenic infections include penicillin, clindamycin, erythromycin, cefadroxil, etronidazole, and tetracyclines [10,11]. Undoubtly, one of the most prescribed antibiotic in dentistry is amoxicillin, as well as its association with clavulanic acid [12,13]. Prophylactic administration of amoxicillin before impacted wisdom tooth extraction yielded a lower incidence of surgical site infections [14], as did lead to a low early implant failure rate [15], however a consensus is yet to be reached.

Last, but not least, antimicrobial effects of commensal oral species should not be neglected. Bacterial antagonism is species specific and depends on environmental conditions [16]. Prophylactic oral antibiotics should be restricted to specific situations, as should therapeutic doses be prescribed taking into account on one hand commensal species that are sensitive to the prescribed dosage, and on the other hand the possibility of direct operative procedures or local antibiotic solution.