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SBL 4 on Dental Fluorosis
Medicine (A100)
Queen Mary University of London
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Table of Contents
- Introduction:..........................................................................................................................................
- Eruption + Shedding times of deciduous teeth:.....................................................................................
- Eruption of permanent teeth:...............................................................................................................
- How tooth shape relates to function:....................................................................................................
- Process of normal tooth formation:......................................................................................................
- How fluoride affects normal enamel formation:...................................................................................
- Enamel Strengthening and Skeletal Fluorosis:.......................................................................................
- Dietary sources of Fluoride:.................................................................................................................
- Cosmetic treatments available:...........................................................................................................
- Conclusion:..........................................................................................................................................
- Bibliography:........................................................................................................................................
Introduction:..........................................................................................................................................
The scenario found on the previous page suggests that one of my relatives as a child was diagnosed with dental fluorosis, but since then has undergone dental treatment that has made their teeth more "aesthetically pleasing". However, now that they are older they are complaining of joint pain, has osteosclerosis of the spine and has also recently broken a bone. My scientific report will be explaining the process of normal tooth formation and their different eruption times, identify different sources of fluoride and how it affects the process of enamel formation to cause fluorosis. I will then outline how fluoride may be involved in the causation of skeletal problems similar to those faced by my relative. Lastly, I shall discuss the different cosmetic methods available, with one perhaps being the option my relative had used, that may improve the appearance of teeth.
Eruption + Shedding times of deciduous teeth:.....................................................................................
Humans are diphyodont mammals, meaning they have two successive set of teeth. Initially it is the deciduous set, followed by the permanent set (Liversidge, 2020a). The deciduous set consists of 5 teeth in each of the four quadrants of the mouth giving a total number of 20, which includes; 1 Central Incisor, 1 Lateral Incisor, 1 Canine and 2 Molars per quadrant. The permanent set on the other hand, consists of 8 teeth in each of the quadrants, this includes; 1 Central Incisor, 1 Lateral Incisor, 1 Canine, 2 Pre molars and 3 Molars (Liversidge, 2020b). I will firstly provide a brief overview of when the deciduous dentition (Primary Teeth) begin to erupt and then shed, as well as that also describe the eruption sequence of the permanent dentition. In the later stages of the report I will try to explain normal tooth formation in a lot more detail.
Tooth eruption is one of the most important aspect of the normal development of the rest of the dentition and also the face as a whole. Children usually begin their tooth eruption around the age of 6-8 months, possibly lasting until the age of 3 years for the majority. Normally, the anterior teeth (both the upper and lower) are the first to be seen, followed by the other teeth moving in the posterior direction, towards the back of both jaws. However there is an exception that needs to be noted, which is that the first molars in normal circumstances erupt before the canines. The first teeth that erupt are the lower and upper central incisors at the age of 6-8 months. The next teeth to erupt, unsurprisingly are the lateral incisors, upper followed by the lower around the age 9-13months. The eruption then moves onto the first molars, upper then lower, around the age of 13-14 months. Next, the Canines (Cuspids) erupt from around the 16th month, with uppers erupting before the lowers. Lastly, the second molars begin to erupt around the age of 26 months with the lowers erupting before the uppers (Dr Munroe's Dental Centre (Quinn Dental Inc), 2020). Figure 1 below clearly shows the order and timings for the eruption of the deciduous teeth.
Figure 1 - Eruption and shedding timings of the different deciduous teeth (Dental Health Foundation, 2020)
Deciduous teeth are not able to withstand the growth of the jaw and also the increase in force of mastication, from when a child becomes an adult. Hence is the reason why a larger set of teeth must replace this set allowing the mouth to function as usual. The timings of the deciduous shedding varies greatly as well. Children would normally begin shedding their teeth at the age of 6, starting from the central incisors followed very closely about a year later by the lateral incisors. With the same trend continuing, the first molars are shed next at ages 9-11, with the canines also shedding closely with regards to time ( at around age 10). The upper canines and all the second molars are shed last at around 10-12 years of age. Refer to Figure 1 to show outline of timings of shedding as well.
Eruption of permanent teeth:...............................................................................................................
Permanent teeth start to erupt around the age of 6 years old. Deciduous teeth would gradually fall out by wobbling. All the deciduous teeth will be replaced before children turn 12-13 years old. The period in between these 2 sets is known as the mixed dentition stage of a child. The eruption ages of each of the permanent teeth can be seen clearly below in the figure.
Figure 2 - Eruption timings of the different permanent teeth (Dental Health Foundation, 2020)
difference being the permanent set complete it after the deciduous to replace them. Odontogenesis is fundamentally divided into 4 separate stages, the formation of dental lamina, bud, cap and bell stage.
Initially, the stomatodeum is lined by stratified squamous epithelium cell bundles known as the oral ectoderm. Underlying this layer is another layer of cells called the endoderm which the oral ectoderm makes contact with through a membrane layer known as the bucco- pharyngeal membrane. On the 27th day of pregnancy, the bucco-pharyngeal membrane will begin to rupture, which will allow the ectoderm to come into direct contact with the endoderm. This contact point allows the basal cells of the oral ectoderm to proliferate much more than the other cells to then form the primary epithelial band. This band then divides into 2 processes; one named the Dental lamina and the other named the Vestibular lamina.
Next, during the bud stage, cells named the dental epithelium start to bud from the thick layer of the dental lamina formed inside both the jaws. The dental epithelium then eventually become and evolve into the tooth germ, which contains a mixture of all the soft tissues needed for efficient and healthy teeth to erupt (Colgate, 2018).
Following that, comes the cap stage, in which the cells start to mould and shape themselves to form the outer parts of the tooth, forming a structure that resembles a cap that sits on the rest of the bud. This cap is called the enamel organ, due to the fact that it will soon differentiate into cells called ameloblasts that are involved in the process of amelogenesis (Enamel Formation). The bud, known more commonly as the dental papilla would make up the 2 underlying layers of the enamel; the dentin and the pulp. Another group of cells called the dental follicle surrounds the entire enamel organ, as well as the dental papilla. The dental follicle is the where many blood vessels and nerves innervate (Simmer and Hu, 2001). Figure 2 below shows these different features during the cap stage.
The final stage known as the bell stage, plays a huge role in odontogenesis as it is when both amelogenesis (the formation of enamel) and dentinogenesis (the formation of dentin) takes place simultaneously and alongside one another, a famous concept known as reciprocal induction, whereby both processes are required for each other to initiate effectively (Nanci, 2014). This stage can usually be subdivided into two; an early stage where there has been no formation of dentine and a late stage where the layer of dentine has been formed fully. The bell stage is also when the enamel organ that has formed, grows into a bell- like shape and it's cells then begin to
Figure 3 - A diagram showing the cap stage of odontogenesis (Nanci et. al, 2014)
differentiate and change functions to allow amelogenesis to happen. The figure below clearly shows how the bell stage of odontogenesis looks: (Lodish, 2016).
How fluoride affects normal enamel formation:...................................................................................
formation:
The scenario states that my relative has had excessive exposure to fluoride, which led to the fluorosis diagnosis and also the skeletal problems they are currently facing as an adult. Fluoride (F-) is an inorganic anion of the element fluorine, and compounds containing it are used in the prevention of tooth decay. E of these are water fluoridation and also oral hygiene products. We have seen that excessive intake of fluoride can lead to an array of conditions such as dental fluorosis as well as skeletal problems. So that we can understand how fluoride may affect enamel, it is necessary to give an overview of amelogenesis.
Amelogenesis is the process that produces enamel in the early bell stage. The process is divided into 4 different stages; 1) Presecretory 2) Secretory 3) Transition 4) Maturation. The presecretory stage is when the IEE cells differentiate into Preameloblasts cells that then produce the first layer of enamel through the secretion of different proteins. Following this stage, these cells then further differentiate into secretory ameloblasts which then release enamel matrix proteins such as ameloblastin and enamelin forming the aprismatic enamel till it reaches fullness. The transition phase is when the ameloblasts begin to lower in number as they begin to undergo apoptosis and dont secrete enamel anymore. Lastly, the maturation stage is when the ameloblasts have one of two phases; either ruffled or smooth ended. The smooth ended ones are involved in the mineralisation, however the ruffle ended ones resorb all the matrix proteins, which allows the enamel to grow whilst the teeth erupt. ( Summarised from SBL 2).
Now having covered amelogenesis we can now discuss how fluoride affects the whole process to cause fluorosis. Fluorosis is an irreversible disease and only takes place during enamel formation. The severity of it is determined not only by the intake but also age, exposure levels and many more. The mild version of fluorosis is when small white lesions are found on the surface of the teeth. On the other hand severe fluorosis is when the teeth begin to have discolouration and greater number of lesions (Dean et al., 2016). Fluoride being a very electronegative ion, can interact with cells during amelogenesis. Studies have shown multiple ways by which high levels of fluoride can affect the process of enamel formation:
Figure 4 - Image of the enamel organ during the bell stage of development (Nanci, 2014)
Dietary sources of Fluoride:.................................................................................................................
Other than the fluoridation of water supplies in certain areas of the world with the aim to reduce caries, the addition of fluoride has spread and increased to be part of many different dental products in the market today, as well as food items and also chemicals. The table below clearly indicates the main sources that contain the most levels of fluoride in them. These foods and drinks need to be taken in moderation to prevent excessive accumulation of fluoride which may cause fluorosis and even skeletal problems going ahead in the future (Medlineplus, 2017).
Figure 5 - Foods/Drinks with most fluoride (Myfooddata, n.)
Cosmetic treatments available:...........................................................................................................
There are an array of different treatments available to improve the appearance of an individual with fluorosis and can differ depending on the severity of the tooth condition. With cases that involve mild fluorosis, it would be recommended that patients avoid any sort of treatment. However for harsher cases, there are different options available (Animated- teeth, n.).
1) Dental Veneers – Veneers are fundamentally shells of ceramic that bind to the labial surface of the tooth. They greatly improve aesthetics. They are best used when the majority of the side has been affected (Animated-teeth, n.).
2) Composites - Mainly used where a small portion on each tooth are affected with the condition, it is better to use composites (bonding) to correct these spots. Composites also mimics the colour of enamel and provides better aesthetics (Animated-teeth, n.)
3) Dental Crowns – This is a cap like structure that covers the whole tooth space and functions in exactly the same way. Unlike the other methods, these can be used even when the fluorosis has severely affected the whole tooth as it acts as a replacement (Animated- teeth, n.).
4) Microabrasion – This is a process where the stained surface of the tooth is broken off using a acid paste. Mostly useful when the spots of fluorosis are bound to a small layer of the enamel as this would mean less of the enamel will be lost. If they are deeper it could damage the enamel layers (Animated-teeth, n.).
5) Teeth Whitening – In this, the teeth are bleached to make the colour and shade lighter so that the staining caused by fluorosis can be hidden (Animated-teeth, n.).
Figure 6 - A before and after from Teeth whitening (Animated-teeth, n.)
Conclusion:
Fluoride is a great method to reduce tooth decay and also caries, yet also not cause the harmful effects, as long as it is consumed in the correct way. However excess consumption as we have seen can be very detrimental for your health. Throughout this report I have discussed, how important it is to monitor our fluoride intake, in particular for children up to 6 years old and also to brush effectively, as the major cause of fluorosis still remains to be the inappropriate usage of oral hygiene products such as toothpaste and also mouthwash that contain fluoride. My relative's discrepancy on the reason why fluoride is used in dental
SBL 4 on Dental Fluorosis
Module: Medicine (A100)
University: Queen Mary University of London
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