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Lesson Plan - Oral Microbiology
7
Oral Microbiology
By: Adam Renaud (105011277)
References
Booth S. 2019. How to stop bad bacteria in your mouth from migrating to your brain [online]. Available from https://www.healthline.com/health-news/bacteria-in-your-mouth-can-find-its-way-to-your-brain [accessed April 2 2022].
Bostanci N., and Belibasakis, G. N. 2012. Porphyromonas gingivalis: An invasive and evasive opportunistic oral pathogen. FEMS Microbiol. Lett. 333(1): 1–9. https://doi.org/10.1111/j.1574-6968.2012.02579.x
Bradley N. 2018. Oral microflora: what you need to know [online]. Available from https://www.colgatetalks.com/oral-microflora/ [accessed April 2 2022].
Brookes Z., Bescos R., Belfield L.A., Ali K., and Roberts A. 2020. Current uses of chlorhexidine for management of oral disease: a narrative review. J. Dent. 103: 103497. https://doi.org/10.1016/j.jdent.2020.103497
Cafasso J. 2019. What is fluoride, and is it safe [online]. Available from https://www.healthline.com/health/what-is-fluoride [accessed April 2 2022].
CT Kids Dentist. 2015. Do oral appliances increase the risk of cavities? [online]. Available from http://www.ctkidsdentist.com/do-oral-appliances-increase-the-risk-of-cavities/ [accessed April 2 2022].
Dashper S.G., and Reynolds E.C. 1996. Lactic acid excretion by Streptococcus mutans. Microbiol. 142(1): 33–39. https://doi.org/10.1099/13500872-142-1-33
Dominy S.S., Lynch C., Ermini F., Benedyk M., Marczyk A., Konradi A., et al. 2019. Porphyromonas gingivalis in Alzheimer’s disease brains: evidence for disease causation and treatment with small-molecule inhibitors. Sci. Adv. 5(1). https://doi.org/10.1126/sciadv.aau333
Enaia M., Bock N., and Ruf S. 2011. White-spot lesions during multibracket appliance treatment: A challenge for clinical excellence. Am. J. Orthod Dentofacial Orthop. 140(1): 17–24. https://doi.org/10.1016/j.ajodo.2010.12.016
FDA. 2021. Dental amalgam fillings [online]. Available from https://www.fda.gov/medical-devices/dental-devices/dental-amalgam-fillings [accessed April 2 2022].
Health Canada. 2010. Canadian health measures survey (CHMS) [online]. Available from https://www.canada.ca/en/health-canada/services/healthy-living/reports-publications/oral-health/canadian-health-measures-survey.html [accessed April 2 2022].
Hussain M., Stover C. M., and Dupont A. 2015. P. gingivalis in periodontal disease and atherosclerosis - scenes of action for antimicrobial peptides and complement. Front. immunol. 10(6): 20-30. https://doi.org/10.3389/fimmu.2015.00045
Kim S.J., Kim K., Choi S., Chang J., Min S., Min S., et al. 2019. Chronic periodontitis and community-acquired pneumonia: a population-based cohort study. BMC Pulm. Med. 19(268). https://doi.org/10.1186/s12890-019-1017-1
Lamont R.J., Koo H., and Hajishengallis G. 2018. The oral microbiota: dynamic communities and host interactions. Nat Rev Microbiol. 16(12): 745–759. https://doi.org/10.1038/s41579-018-0089-x
Mayo Clinic. 2022. Cavities/tooth decay [online]. Available from https://www.mayoclinic.org/diseases-conditions/cavitie
Learning Outcomes
After the presentation, students will be able to:
- Define the oral microflora.
- Highlight the differences between aerobic and anaerobic bacteria.
- Define biofilm and name harmful bacteria that may reside in the oral cavity.
- Describe the mechanism of cavity formation.
- Understand different treatments for cavities and ways to prevent them.
Learning Outcomes
My Personal Interests
I have gone to the dentist on a regular basis throughout the past few years to get my teeth cleaned, fill in cavities, and tighten my braces. This sparked my curiosity to learn more about oral microbiology. I think it is important for everyone to learn about the microbes that live inside our mouths because they contribute to many teeth problems that many of us have encountered, such as cavities. This is especially critical for teenagers, who are more likely to have poor dental hygiene and cavities. I created this lesson plan to help adolescents learn more about oral microbiology, so that they can be more cautious and develop good oral hygiene habits.
(https://www.pngitem.com/middle/ixJhoTR_stuff-can-grow-on-your-toothbrush-toothbrush-clipart/)
What is The Oral Microflora?
The oral microflora refers to the group of microorganisms that live inside our mouths, which includes many different species of bacteria, viruses, fungi, protozoa, etc. The number of species in the oral microflora varies as a person ages and accumulates microbes. It also depends on how often a person brushes their teeth and their diet. On average, there are over 700 species of bacteria contained within the oral microflora. Most of these bacteria help protect your mouth against harmful bacteria that may be found in food (Bradley 2018).
Quiz
Oral Microflora
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Analogy: Beehive
The oral microflora is analogous to a hive of bees, where each bee serves a specific function in the colony's survival. Some bees, for example, create honey, while others are in charge of reproduction. Similarly, bacteria in the oral microflora each serve a unique function in assisting one other's survival and reproduction.
Analogy
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QUIZ
At any given time, how many bacteria are present in the average human mouth?
a. 2 million
b. 20 billion
c. 6 million
d. 1 trillion
Answer: c. It is estimated that there are 6 million bacteria in our mouths at any given time (Booth 2019).
What is Biofilm?
In a healthy mouth, the good bacteria form an invisible layer that protects our teeth from harmful bacteria. However, when there are a lot of harmful bacteria, they can form communities known as oral biofilm (also known as plaque). In oral biofilm, the microbes are fixed to dental surfaces and surrounded by an extracellular matrix that is made up of proteins, polysaccharides, and environmental DNA (Lamont et al. 2018). Oral biofilm helps harmful bacteria survive and reproduce. It provides harmful bacteria with important nutrients and forms a physical barrier that protects them from antimicrobial agents and good bacteria. This can be observed as a thick and slimy film that has a bad odour (think of morning breath).
Biofilm
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What Harmful Bacteria Live Inside Our Mouths?
Quiz
Most of the good bacteria in the oral microflora are aerobic, meaning, they rely on oxygen to grow and survive. However, most of the bad bacteria are anaerobic or facultatively anaerobic, meaning they grow in the absence of oxygen or can grow with or without it. Here are three of the most common harmful bacteria that can live inside our mouths:
Harmful Bacteria
- Porphyromonas gingivalis,
- Streptococcus pneumoniae, and
- Streptococcus mutans.
P. gingivalis
P. gingivalis is a rod-shaped anaerobic bacteria that causes periodontitis, an inflammatory gum disease that causes the destruction of supportive tissues for the tooth. P. gingivalis erodes the tissue surrounding the tooth, which creates pockets around teeth that hold plaque and harmful bacteria that can further damage the connection of the tooth to the socket. If left untreated, it can cause tooth loss (Bostanci and Belibasakis 2012).
Porphyromonas gingivalis
https://www.google.com/url?sa=i&url=https%3A%2F%2Fwww.dentistrytoday.com%2Fp-gingivalis-borrows-growth-molecules-from-v-parvula-to-cause-gum-disease%2F&psig=AOvVaw0y4pJ3iu3OpzacNzwpf6FJ&ust=1649387013024000&source=images&cd=vfe&ved=0CAsQjhxqFwoTCJCKks37gPcCFQAAAAAdAAAAABAD
QUIZ
P. gingivalis has been linked to which other diseases?
a. Alzheimer's disease
b. Atherosclerosis
c. Rheumatoid arthritis
d. All of the above
Answer: d. P. gingivalis has been linked to Alzheimer's disease, atherosclerosis, and rheumatoid arthritis (Dominy et al. 2019; Hussain et al. 2015; Perricone et al. 2019).
S. pneumoniae
S. pneumoniae is a lancet shaped anaerobic bacteria that causes pneumonia, a severe lung infection where the lungs fill up with fluid and swell, contributing to difficulty breathing . S. pneumoniae can be spread through the air when a person with the bacteria coughs or sneezes. It can also be spread through surfaces. S. pneumoniae is commonly found in the mouth and nose, however, it is not always invasive. It can take advantage of certain diseases like periodontitis to invade into the blood vessels and eventually enter the lungs (Kim et al. 2019).
Streptococcus pneumoniae
https://www.google.com/url?sa=i&url=https%3A%2F%2Fwww.cdc.gov%2Fpneumococcal%2Fclinicians%2Fstreptococcus-pneumoniae.html&psig=AOvVaw0qOAggJxn0lbMcbrNTq3MW&ust=1649387621267000&source=images&cd=vfe&ved=0CAsQjhxqFwoTCLCH1ez9gPcCFQAAAAAdAAAAABAD
S. mutans
S. mutans is a spherical (cocci) shaped facultative anaerobe bacteria that is a known contributor to cavities, otherwise known as dental caries. S. mutans live on our tooth surface inside dental plaque. S. mutans feed off of the leftover food particles in our mouths. They can metabolize different types of sugars and carbohydrates and the by-product of this reaction is lactic acid. Acids like lactic acid can degrade the minerals on the outer layer of the tooth (enamel). Thankfully, our saliva has minerals such as calcium and phosphate that help to remineralize damaged enamel (Dashper and Reynolds 1996).
Streptococcus mutans
https://www.google.com/url?sa=i&url=https%3A%2F%2Fwww.sciencedirect.com%2Ftopics%2Fmedicine-and-dentistry%2Fstreptococcus-mutans&psig=AOvVaw1xqrdwXnXJVFQQYvTCRaHU&ust=1649387968065000&source=images&cd=vfe&ved=0CAsQjhxqFwoTCJCDy5P_gPcCFQAAAAAdAAAAABAJ
Quiz
S. mutans and
cavity formation
Consuming too much sugar or carbohydrates as well as not practicing proper oral hygiene causes the accumulation of plaque on the tooth. This plaque can harden into tartar, which makes it even more difficult to remove and helps to protect harmful bacteria like S. mutans. As harmful bacteria and acid build up, the enamel degrades faster than the saliva can repair it. The degradation of the enamel creates holes that allow S. mutans and the acid it creates to attack the inner layers of the tooth. The first layer that they reach is the dentin layer, which is softer and less resistant to acid. After dentin is degraded, S. mutans and the acid can reach the pulp layer, causing the painful swelling of blood vessels and nerves (Mayo Clinic 2022).
Quiz
Cavity Formation
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QUIZ
Approximately what percentage of Canadian adolescents (12-19) have or have had a cavity?
a. 59%
b. 40%
c. 73%
d. 25%
Quiz
Answer: a. 59% of adolescents and 96% of Canadian adults have or had cavities during their lives (Health Canada 2010).
Addressing common concerns: Cavities and dental appliances
One common concern about dental appliances, such as braces, is that they may increase the likelihood of developing cavities. This is backed by studies that report 60.9% of people that have braces for around 2 years develop white spot lesions, which are spots where the teeth have lost minerals (Enaia et al. 2011). One of the reasons for this is because they make it harder to clear certain parts of your teeth to remove plaque and food particles, allowing harmful bacteria like S. mutans to thrive. Dental appliances may also shield parts of your teeth from saliva, which prevents the remineralization of the enamel (CT Kids Dentist 2015). Studies have found that patients with dental appliances had higher levels of S. mutans in their mouths (Rosenbloom and Tinanoff 1991).
Cavities and dental appliances
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QUIZ
True or False. Patients with dental appliances have higher numbers of S. mutans long-term after active treatment.
Answer: False. Studies have found that there are no long-term effects of dental appliances on the accumulation of harmful bacteria (Rosenbloom and Tinanoff 1991).
Cavity Treatment
Treatment for cavities depends on the stage of the tooth decay. If S. mutans and the acid has only partly damaged the enamel, fluoride treatment can be used to lower acid buildup and repair the enamel (Cafasso 2019). However, if the enamel has been completely destroyed, there is no way to repair it. In this case, dentists will fill the tooth with dental amalgam made up of metals, such as mercury, silver, tin, and copper (FDA 2021). This replaces the enamel to prevent further damage to the inner layers of the tooth. If the damage has extended to the pulp layer, a root canal may be required, which involves removing the decayed pulp and cleaning out the inside of the tooth to get rid of the bacteria and acid. Afterwards, the tooth is filled with dental amalgam. If there is too much pulp decay, the damage may be irreparable and the damaged tooth is taken out (Mayo Clinic 2022).
Cavity Treatment and Prevention
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Cavity Prevention (1/2)
The key to preventing cavities is to reduce the growth of S. mutans, which can be done by:
1. Brushing teeth after meals
Brushing your teeth immediately after meals will help to get rid of plaque accumulation and food particles that help S. mutans survive and reproduce.
2. Using antibacterial mouthwash
Using antiseptic mouthwashes that have chlorhexidine gluconate help to eliminate S. mutans (Brookes et al. 2020).
Cavity prevention (2/2)
Cavity Prevention (2/2)
3. Limiting the consumption of sugary foods
The metabolic process used by S. mutans relies on the conversion of sugars and carbohydrates to lactic acid, so limiting the consumption of sugary foods will help to reduce acid buildup.
4. Flossing twice a day
Flossing helps to get the areas in between your teeth that may be missed when brushing. These areas are prone to having food particles and accumulating plaque that help S. mutans grow.
Quiz
Approximately what proportion of Canadians brush their teeth twice a day and floss a minimum of once per day?
⅓
a. 1/3
b. 1/2
c. 2/3
d. 3/4
Answer: a. 1/3, specifically 37.5% (Statistics Canada 2018).