The oral cavity is the entrance to the digestive organs, and there are many microorganisms that colonize the oral cavity. In terms of oxygen concentration, there are both fairly high and anaerobic parts. There may be hundreds of microorganisms in the mouth, and it is not possible to cultivate and identify all of them, but only about 100 species have been mastered.
Streptococci were the most commonly detected, but the bacteria detected in areas with low oxygen concentrations, such as the gingival sulcus, were mostly gram-negative anaerobic bacilli. In the microecosystem of the oral cavity, a dynamic balance is always maintained between the oral microorganisms and between the oral microorganisms and the host, forming an interdependent and mutually restrictive system.
Under normal conditions, microorganisms do not exhibit pathogenic effects on the host, but when the microflora is out of balance, they cause disease. In recent years, with the gradual deepening of microecology research, the oral microecological environment has received more and more attention, especially the occurrence of many diseases is related to the change of oral microecological environment.
The basic theory of microecology holds that a microecosystem is a whole that interacts and interdepends on the host, microorganisms, and the environment. This whole is a three-dimensional intersecting network composed of different levels and different links, and the interaction of each chain and each point of the three-dimensional intersecting network is realized through the energy flow, material circulation and gene transmission in the micro-ecosystem.
The suitable temperature, humidity, nutrient source and complex ecological space characteristics in the oral ecological zone provide excellent conditions for the colonization and growth of bacteria. In the microecosystem of the oral cavity, a dynamic balance is always maintained between the oral microorganisms and between the oral microorganisms and the host, forming an interdependent and mutually restrictive system.
1. The main pathogenic bacteria in the oral cavity
1. Cies
The main pathogenic bacteria are Streptococcus mutans of the oral streptococcus genus, Streptococcus distal species, Staphylococcus epidermidis also known as Staphylococcus albicans, Lactobacillus orals, Oral Actinomycetes, Neisseria spp., Veronella, etc., these bacteria form plaque on the tooth surface, produce acid, cause tooth hard tissue demineralization, and eventually form caries. Streptococcus mutans is the bacterium that plays a key role in this.
2. Pulp and periapical disease
Mixed bacterial infection is the main bacteriological feature of pulp and apical perianim disease, and anaerobic bacteria are the main ones, accounting for more than two-thirds, followed by facultative anaerobic bacteria and aerobic bacteria. Melanogenesis is the dominant anaerobic bacterium that infects root canals, including Prevotella intermediates, Plasmosa puromonas, Plasma puromonas, Plasma gingivals, etc., as well as Fusobacterium, Eubacterium, and Streptococcus pepticus.
3. Subgingival flora
Different types of periodontal disease are caused by different specific bacterial infections, and the pathogenic bacteria may be different in different patients, different parts of the same patient, and different times in the same area. The main pathogenic bacteria of periodontal disease are gram-negative anaerobic bacilli, such as Yerinmonas sedentae, Prevotella intermediates, Pseudobacteroides forsysemi, Actinobacillus, etc.
4. Viruses and fungi associated with oral mucosal diseases
There are mainly simple scar virus, cytomegalovirus, virus, and other related fungal infections, mainly Candida albicans, etc.
5. Oral collar surgical infection
It is mainly odontogenic bacterial infection, the main bacteria are Staphylococcus aureus, Streptococcus haemolyticus, Actinomycetes, Pseudomonas aeruginosa, Streptococcus, etc., which are characterized by normal oral flora conditions pathogenic, mixed bacterial infection, and the main pathogenic bacteria are anaerobic bacteria.
6. Halitosis
The number of anaerobic bacteria and microaerophiles in the periodontal bag and dorsal tongue of patients with halitosis was significantly higher than that of the healthy control group, and the dominant bacteria in the periodontal bag were Larin gingivalis and Prevotella nigra, and the dominant bacteria on the dorsal tongue were Verona microflora and Prevotella nigra, and the distribution of dominant bacteria on the dorsum of the tongue and periodontal bag was also significantly higher than that of the healthy group, which proved that anaerobic pathogenic bacteria in the oral cavity played an important pathogenic role in the cause of halitosis.
2. Microbial detection technology
1. Research on caries
At present, the etiology of caries is still in the observation stage of the phenomenon of the etiology of caries, although the observation methods continue to improve, but far from reaching the stage of rational understanding that people expect, and it is impossible to detect and diagnose caries before the cariogenic bacteria cause organic damage to the hard tissues of teeth.
The study of the cariogenic mechanism of Streptococcus mutans and the completion of genome sequencing have laid a foundation for the molecular diagnosis of caries. The molecular diagnosis of caries is based on the study of the etiology of caries, and the early diagnosis of caries is carried out in a substantive sense by applying molecular biology methods.
The main research focuses on how to quickly identify the bacteria in the plaque, calculate the proportion of cariogenic bacteria in the total number of plaque bacteria, distinguish the life state of cariogenic bacteria such as Streptococcus mutans, the growth quiescent period and the active growth period, and detect whether cariogenic virulence factors are expressed and their expression levels.
2. Subgingival microbial detection methods
(1) Bacterial culture method
Subgingival microbial isolation and culture techniques are the traditional and most commonly used methods for determining the subgingival microflora.
That is, the clinical specimens are dispersed and diluted and inoculated on the appropriate medium to obtain a pure culture of a single colony. A variety of microaerophilic or anaerobic bacteria can be isolated from the subgingival region, and different strains can be identified by phenotypic or genotypic characteristics.
The culture method is the only method that allows for later susceptibility experiments. When the amount of bacteria is small, it is difficult to obtain results in a short period of time by culture methods. The development of modern molecular biology has shown that the subgingiva contains a large number of bacteria that cannot be cultured or difficult to culture, and those who can be cultured only account for the left and right, and not all microorganisms can be cultured to survive, and false negatives can occur.
There are many types of subgingival bacteria, and various bacterial culture conditions are different, and some subgingival bacteria may not be isolated by conventional culture.
(2) Examination methods for bacterial enzymes
Periodontal bacteria produce many enzymes that destroy connective tissue, and these enzymes are important causes of periodontal destruction. The experiments developed from this can quickly detect bacteria at the chairside.
Because bacterial matrix proteases and bacterial proteolytic enzymes play an important role in the destruction of periodontal tissues, inhibitors of these enzymes can be used to develop reagents for the treatment of periodontitis, and the research on enzyme inhibitors is still in the discussion stage.
(3) Immunological examination techniques
Immunological techniques for the detection of pathogenic microorganisms are also an active field. Unlike bacterial culture, it does not require viable bacteria and has been reported to detect at least kernel cells, and is mainly used for screening experiments. Enzyme-linked immunosorbent assay (ELISA) showed that there was a significant difference in the total content of markers of immune activity of new chirp cells in saliva between patients with progressive periodontitis and control groups.
It shows that cellular immunity plays a crucial role in the immune pathogenesis of periodontitis, so the study of the content of new chatter in body fluids will have a profound impact on the diagnosis and prognosis of periodontal disease.
(4) Probe technology method
The pure cultured bacteria are first treated with enzymes to make their two strands free, and then labeled with radionuclide material for later use. During the test, the subocular specimen is treated with enzymes to degrade the bacteria into a single strand, and the spare nucleoxiic acid chain is added. According to the principle of base complementarity, if the same bacteria appear, the nucleoxiic acid chain is labeled to bind to it and is photosensitive on the film.
One of the most important scientific and technological inventions of more than a decade, polymerase chain reaction is a process that mimics natural replication in vitro, using primer-mediated enzymatic reactions to amplify fragments located between known sequences at two ends. The technical sensitivity is much higher than other methods, and it is quick and relatively simple.
The development of technology has opened up a new way of bacterial classification and identification, making bacterial classification and identification methods more objective and reasonable. Gene chip is a biotechnology technology that has developed rapidly in recent years, which can arrange a large number of probes on the support, and study thousands of genes simultaneously on a large scale and high throughput to obtain higher resolution.
3. Research status of oral antibacterial preparations
1. Application of antibiotics and synthetic drugs
The prevention of oral diseases such as caries has always been the focus of caries researchers, and many drug studies have been carried out in the past year. Although antibiotics have a certain anti-caries effect, long-term use can cause imbalance of white cavity and intestinal flora and lead to other diseases, and the abuse of antibiotics may also produce drug resistance, which is life-threatening.
Immune caries prevention is faced with the problem of enhancing immunogenicity and biological activity, while the problem of ecological impact on oral microbiota is still unsolved. Fluoride caries prevention is the most studied and widely recognized method, but its application still has many limitations, such as the stability of fluoride concentration, toxic side effects, and the generation of oral fluoride-resistant strains.
2. Antimicrobial peptide research
Antimicrobial peptides, also known as antimicrobial peptides or peptide antibiotics, are small molecule peptides with high-potency and broad-spectrum antimicrobial activity produced by the self-defense system of multicellular organisms. Different sources of antimicrobial peptides vary, but one antimicrobial peptide often originates from a specific tissue or cell.
Antimicrobial peptides are usually small molecule peptides, not antigenic, water-soluble and thermally stable, most of the antimicrobial peptides have a positive charge, the target is the bacterial cell membrane, it is difficult for bacteria to change their own membrane characteristics, and because the antimicrobial peptides lack bacterial protease epitopes, it is difficult for bacteria to develop drug resistance.
3. Natural medicine research
In recent years, many scholars at home and abroad have devoted themselves to the research of anti-caries drugs, some seeking from chemical and biological agents, and some isolating active ingredients from natural medicines. Natural medicines, including botanicals, animal medicines and mineral medicines, have a wide range of clinical applications, such as abundant sources, convenient materials, simple usage, significant efficacy and few side effects.
Tea polyphenols can inhibit the growth of Streptococcus mutans, Streptococcus distal and Actinomycetes, destroy the cell wall structure of bacteria, and inhibit the synthesis of dextran by glucosyltransferase, thereby inhibiting plaque formation.
Gallic can inhibit the sugar production and acid production ability of oral bacteria, inhibit the activity of glucosyltransferase, inhibit the erection of bacteria on the glass surface, inhibit the growth, acid production and aggregation of Streptococcus mutans, promote the remineralization of hard tissue on the root surface, and enhance the acid resistance. There is a need to establish extraction procedures, screening of active ingredients.
The active ingredient of propolis can inhibit bacterial acid production, extracellular polysaccharide production, inhibit bacterial early killing and other virulence factors, and has no obvious effect on tooth remineralization. Plants that are known to inhibit this bacterium, but whose active ingredients are not known are honeysuckle, bayberry, safflower, eleutherococcus, purple lily, chonglou, red peony, triangular and so on.
Scholars believe that the above-mentioned natural drugs can reduce the amount of plaque formation on the dental surface and reduce the amount of extracellular polysaccharides, thereby inhibiting the aggregation of bacteria and inhibiting the occurrence of caries and periodontal disease.
IV. Conclusion
At present, the traditional Chinese medicine in the study of caries prevention is not based on the diagnosis and interpretation of its medicinal properties by traditional Chinese medicine, but takes its effective ingredients for inhibiting the main cariogenic bacteria for ecological prevention and control. In recent years, with the gradual deepening of microecology research, the oral microecological environment has received more and more attention, and the occurrence of many diseases is related to the change of the oral microecological environment.
To control oral diseases, it is necessary to carefully select oral antibacterial drugs, and to prevent the occurrence and development of oral diseases from the perspective of reducing the virulence factors of microorganisms and maintaining the balance of microecology, which has become the consensus of scientists.
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