Q: Enamel is composed of ___ % minerals.
- Enamel: Hardest portion of the tooth comprising approximately 96% minerals (consists predominantly of apatite crystals containing calcium and phosphate). It is hardest at the biting edges or cusps.
- Dentin: Calcified tissue around the pulp under the enamel comprising approximately 70% minerals.
- The bulk of the crown is composed of dentin, which is also present in the crown and root portion.
Answer: (C). 95
Learn more for the dental hygiene boards
While we are discussing this topic, let’s review a little more about the dentin for the Dental Hygiene Board Exams (NBDHE, NDHCE).
There are different types of dentin:
- Dentin that forms when a tooth erupts is called primary
- Dentin that forms inside the primary dentin is called secondary Secondary dentin will continue to grow throughout the life of the tooth and can result in narrowing of the pulp canal.
- Tertiary dentin, also known as reparative or reactive dentin, forms as a response to irritation and trauma such as erosion and dental caries.
The topic of dentin links to dentinal hypersensitivity. Let’s dive further while our brain is awake! The exposed dentin (from a gingival recession and loss of enamel) is affected by external stimuli such as thermal (cold/heat), evaporative (blowing air), osmotic (sweet or sour/acid), tactile (toothbrushes, flossing, toothpick, dental instruments), and whitening solution. This is described with the hydrodynamic theory.
Hydrodynamic theory: When the fluid within the dentinal tubules (absent of a smear layer) is subjected to thermal, chemical, tactile or evaporative stimuli, movement and pressure occur. Movement of tubular fluids causes nerve endings at the pulp to be stimulated, inducing pain.
We have covered some information related to dentin and enamel today, but make sure you review the enamel and cementum as well! If you have a subscription to StudentRDH Dental Hygiene Board Exams Review, go to the chapter on Dental Anatomy, and find the section called “General Function and Structure of the Tooth”. You will see bullet points that summarize what you really need to know.
So far, we have provided a lot of review material through StudentRDH Weekly Vitamins. If you have suggestions or requests about other content for FREE mini-reviews, please email me at ClaireJ@StudentRDH.com. It is my responsibility to offer the content you need in order to become a successful hygienist! Have another amazing day!
Related post: Dentin formed from injury
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