Get to Know Your Teeth: Tooth Structure and Support

Introduction

Consider this post Teeth 101.  I’m not kidding myself; I know that this is a dull topic.  HOWEVER, it will provide the foundation for you to understand the other dental topics that you may actually be curious about.   

Let’s get started!

Tooth Structure

Teeth have 2 main structural components: CROWN and ROOT. 

The crown is the portion of the tooth that is visible in the mouth.  It’s the portion you chew with, show when you smile, and brush and floss so lovingly. 

The root is the anchorage.  More on this in a bit.

 

Tooth Layers

A tooth may also be broken down into deep and superficial layers.  At the core of a tooth is the PULP, which is the soft, vital tissue consisting of the tooth’s nerve, blood supply, and connective tissue.  Live cells reside here. 

Moving outward, 3 tooth “materials” form layers that protect the pulp: dentin, enamel, and cementum.  The diagram above is the easiest way to convey their relationships. 

Like glass, enamel is hard but brittle. In the same way that this glass would benefit from underlying support of a wood table top, enamel benefits from the support of dentin.

ENAMEL is the outermost layer of the crown and is composed primarily (96%, to be exact) of minerals in the form of hydroxyapatite crystals.  (Hydroxyapatite is a type of calcium phosphate that is also a primary mineral component in bone.)  Protein and water make up the remaining 4% of enamel. Because enamel is highly mineralized, it is hard but brittle.  It requires underlying support.  Think of a thick piece of glass.  It’s both hard and strong enough to serve as a table, but would still shatter if subjected to too much force.  It would be stronger if there were a slab of wood to provide underlying support for the glass. 

ends of cellular processes (arms) extending out of exposed dentin tubules

Image source: Goracci, G., Mori, G. & Baldi, M. Clinical Oral Investigations (1999) 3: 126. https://doi.org/10.1007/s007840050090

DENTIN is like the wood providing this underlying support for enamel and it continues from the crown down through the roots.  Because dentin is 70% mineral content and 30% protein and water, it is softer than enamel, but not brittle.  Structurally, dentin is made of microscopic tunnels, called tubules, through which processes of the live tooth cells in the pulp extend.  You can think of the processes as the cells’ arms.  This is why you may experience tooth sensitivity if dentin is exposed.  More on tooth sensitivity in a future post.

Last, CEMENTUM is the outermost layer that covers only the roots.  It is the layer that allows the tooth to attach to the bone via the periodontal ligament. 

Tooth Support

This is a great segway into the support structures of the tooth, referred to all together as the PERIODONTIUM, or periodontal support.  Periodontium consists of the periodontal ligament, alveolar bone, and gingiva (gums). 

The PERIODONTAL LIGAMENT (PDL) consists dense collagen fiber bundles that tether the cementum on the roots to the alveolar bone.  In addition to stabilizing the tooth, it also acts as a shock absorber as you chew.  It also has sensory nerve endings, giving your teeth the sense of pressure, pain, and proprioception.

The bone that supports the teeth is called ALVEOLAR BONE.  

The GINGIVA (gums) attach both to the bone and to the tooth.  Above where the gums attach to the tooth remains a little collar of tissue that forms the gingival sulcus or periodontal pocket.  Do you recall times when your dentist or hygienist called out numbers while walking an instrument around all of your teeth?  They were measuring the depth of this pocket!  We will go over the significance of these measurements in a separate post on periodontal disease. 

And there you have it.  More information than you ever wanted to know about tooth structure and its support.