Biomedical Ephemera, or: A Frog for Your Boils

Alveoli and Jaws Before the Appearance and After the Absorption of the Teeth

Fig 1. Alveoli of the adult upper jaw. Fig 2. Upper jaw of aged individual after the loss of alveoli. Fig 3. Alveoli of adult lower jaw. Fig 4. Aged lower jaw, alveoli absorbed. Fig 5 (center). Head of foetus, before appearance of alveoli.

Alveoli (trough, basin in Latin) in the skull are the hollows in which teeth sit. They’re surrounded by bony tissue, which grows the gums around the teeth.

When there are no teeth rooted in the jaws, the bony tissue recedes. When this happens due to injury, malformation, or old age, there is no anchor point for dental implants or bridges, so dentures or partial dentures must be used, instead.

The Anatomy, Physiology, and Pathology of the Human Teeth. Paul B. Goddard, aided by Joseph E. Parker, 1844.

Upper: Lateral view of the permanent teeth Lower: Lateral view of the deciduous teeth [also known as milk teeth or baby teeth]

The permanent teeth consist of 32 teeth of four different types. There are 16 teeth on each jaw, and each jaw has 4 incisors, 2 canines, 4 premolars, and 6 molars (this includes the wisdom teeth, which are shown here)

The smaller mouth of the child only accommodates 20 teeth of three different types. There are 10 teeth on each jaw, and each jaw has 4 incisors, 2 canines, and 4 primary molars. 

Atlas and Text-Book of Dentistry. Gustav Preiswerk, translated by George W. Warren, 1906

Fossil Reptiles and Fishes

Fig 1 (the jaw and partial skull) is from the cretaceous-era reptile Mosasaurus hoffmani.

The remainder of the figures (2-18) are "fossil teeth from various types of fishes, principally of the shark and ray families". The plate-like "teeth" with parallel striations are from the rays. The pointy teeth are from the sharks.

That big ol' tooth in the center is from Carcharius megalodon - the shark known as "megalodon". Literally translated from Greek, "megalodon" means "big tooth". Fitting, eh?

A Pictoral Atlas of Fossil Remains. Gideon Algernon Mandell, 1850.

Cross-section of a human tooth-germ

You can see all the layers of the developing tooth here. All the way to the right (i), you can see the tooth-sac that the developing tooth is surrounded by and nourished by. In the center (f), you can see the developing enamel (though it's still gelatinous at this point) - h signifies the outer epithelial cells of the enamel, which will comprise the outside of the tooth when it's fully formed. To the left, b signifies the odontoblasts (the cells that are precursors to the inner tooth structures), and a signifies the tooth-papilla, that the odontoblasts will expand into.

The tooth-germ starts like a cup, basically, and then expands both outward (to form enamel), and inward (to form the dentin and inner structures) at the same time. 

Atlas and Text-Book of Dentistry, Including Diseases of the Mouth. Gustav Preiswerk, 1906.

Cross-section of a young cuspid tooth

Illustrated from serial injected cross-sections. The arteries are colored red, and the veins are colored blue here. Note how vascular such a small structure is during development. If you look at the outside of the tooth, you can see a yellow periphery with lots of individual cells denoted - those are the odontoblasts. The odontoblasts form the layer between the dentin and the pulp, so we can tell that the enamel layer has been omitted from this illustration.

Atlas and Text-Book of Dentistry, Including Diseases of the Mouth. Gustav Preiswerk, 1906.

Position in extracting a tooth from the right upper jaw.

Fun with dentistry!

There are a LOT of different tools that are used for extraction. There was one tool that could do all the different teeth (the dental key), but it was not as effective as having forceps specialized for each area of the mouth.

Atlas and Text-Book of Dentistry Including Diseases of the Mouth. Gustav Preiswerk, 1906.

The horse, and how to tell its age by tooth wear.

The Animal Kingdom. Georges Cuvier, 1834.

Fig 1. Bicuspid with gangrene of pulp Fig 2. Molar with chronic hypertrophic sarcomatous pulpitis Fig 3. Incisor with chronic hypertrophic granulomatous pulpitis Fig 4. Incisor with chronic total purulent pulpitis - Yellow spots are abscess cavities within the destroyed parenchyma Fig 5. Bicuspid with ascending pulpitis Fig 6. Wisdom tooth with chronic parenchymatous pulpitis

Atlas and Textbook of Dentistry including Diseases of the Mouth. Dr. Gustav Preiswerk, 1906. Translated and edited by George W. Warren.