Why Are Teeth Different from Bones? Enamel vs. Collagen: A Textbook on the Definitive Differences Between Teeth and Bones

Using the latest article from Live Science, "Why don't teeth count as bones?" as a clue, we gently organize the fundamental reasons why teeth are different from bones. Additionally, we gather common reactions from social media to summarize the background of misunderstandings and key points useful in real life.Live Science

1. Fundamentally, "Teeth ≠ Bones" — Differences in Definition in Three Lines

• Function: Teeth are accessory organs of the digestive system, meant to "break down food." Bones "support, protect, and produce blood" as part of the skeletal system.Live Science

• Structure: The surface of teeth is enamel (the hardest substance in the human body). Inside, there is dentin→pulp. Bones consist of cortical bone→trabecular bone→bone marrow, with blood vessels and nerves running through all layers.Live Science

• Metabolism: Bones are living tissue that are constantly remodeling (most are replaced in about 10 years). Enamel is difficult to regenerate.Live Science
  
  

2. Details of "Similar but Different" Between Teeth and Bones

2-1. Differences in Material

• The outer layer of teethenamel is extremely hard due to densely packed hydroxyapatite crystals. It contains almost no collagen.Live Science

• Dentin is softer than enamel but harder than bone. It is approximately 70% inorganic, 20% organic, and 10% water.NCBI

• Bones are a composite of collagen × minerals, balancing flexibility and self-repairability. Blood cells are also produced in the bone marrow inside.Live Science

2-2. Differences in Construction and Function

• Teeth have a "sandwich structure" of enamel→dentin→pulp. While the pulp is living tissue, ameloblasts, which form enamel, disappear after formation, making it difficult to regenerate if chipped.Live Science

• Bones have osteoblasts (bone-forming) and osteoclasts (bone-resorbing) constantly working, allowing for a cycle of breaking down→building that heals fractures. The adult skeleton is replaced approximately every 10 years.Cleveland Clinic

2-3. To Which "System" Do They Belong?

• Teeth are accessory organs of the digestive system. They are placed here because digestion begins in the mouth.NCBI+1

• On the other hand, jawbones (maxilla and mandible) are part of the skeletal system. Teeth are merely "supported" by the jawbone through the periodontal ligament.Encyclopedia Britannica
  
  

3. What Did Live Science Emphasize? (Key Points)

• "Similar in Appearance but Different": The hardness derived from minerals like calcium is common, but the similarities end there. Function, structure, and metabolism are different.

• "A Member of the Digestive System": The main missions are chewing and speaking, not blood cell formation or body-wide defense like bones.

• "Bones Are Alive": Nerves and blood vessels run through all layers, allowing them to heal when broken. Teeth do not return if not cared for.Live Science
  
  

4. How It Is Discussed on Social Media (Snapshot of Reactions)

Surprise Type

"What, teeth aren't bones? I just learned they're part of the 'digestive system'" — a typical reaction on academic subreddits.Reddit

Meme Type

• Abroad, the joke "Outside bones" is widely circulated. Posts repeating the phrase from a Netflix drama are common.Reddit

Science Cluster Explanation Type

• "Bone = Collagen + Apatite, Teeth (Enamel) = Mostly Apatite. That's why their properties differ" — this materials science perspective explanation is highly rated.Reddit

News Dissemination

• Live Science's original post on X also saw dissemination, with the headline **"Similar but Different"** sparking discussions.X (formerly Twitter)

※The "voices" above are summaries of posts on each platform, with individual usernames omitted (quotes are limited to one sentence at most).

5. Why Is There a Common Misunderstanding?

1. Their appearance is white and hard (= bone-like)

2. The division of "dentistry" and "orthopedics (bones)" results in separate medical system channels

3. In educational illustrations, teeth are depicted in the "tooth row of the skull" and lined up in the same "bone picture"
   — such cognitive biases have reinforced the "teeth = bones" image. However, as defined above, they are biologically and functionally different.Live Science
   

6. Practical Tips: Teeth Are "Non-Renewable Assets," Bones Are "Renewable Assets"

• Enamel wears away: It is generally difficult to naturally regenerate once thinned by erosion or wear. Home care with fluoride and dental treatments can promote remineralization.Live Science

• Build materials through diet: Calcium is essential for the hydroxyapatite in teeth and