Cartilage and bone

Why this matters

Two of the three hard tissues a dentist works on are bone, and the only joint you will ever treat is covered by the one cartilage that is not hyaline. Every clinical fact you will meet later sits on this lesson: why an extraction socket fills with woven bone and the ridge still shrinks, why orthodontic force moves a tooth at all, why a patient on denosumab must not simply be told to stop it before an extraction, why a child with unerupted permanent teeth and hypoplastic clavicles is a genetics referral, and why a flattened condyle in a 70-year-old is usually normal remodelling and not arthritis.

The big picture

Cartilage is a tissue that put everything into its matrix and kept almost no cells, so it cannot repair. Bone made the opposite bet: it buried a cell in the matrix, wired it to every neighbour, and gave it command of both demolition and construction. Everything else in this lesson follows from those two decisions.

The 15 cards in this lesson

1. 01Almost nothing you are looking at in cartilage is cell
2. 02Three cartilages, and the question that separates them
3. 03The halo around a chondrocyte is mostly the fixative's work
4. 04Elastic cartilage is a stain result — and the nasal septum is not on the list
5. 05Fibrocartilage is the cartilage a dentist actually meets
6. 06The mandible grew up beside Meckel's cartilage, not out of it
7. 07Two routes to bone, and the jaws take the membrane route
8. 08The osteoblast lays down osteoid and may end up buried in it
9. 09A ground section is where bone admits it has been rebuilt
10. 10The osteocyte cannot reach the surface, and it gives the orders anyway
11. 11The osteoclast seals a chamber and dissolves bone inside it
12. 12Remodelling is a coupled cycle at one site; modelling is not
13. 13Clinical alert — in the lesson
14. 14Fracture repair replays both routes to bone — and the socket is the version you will watch
15. 15Six bone numbers everyone quotes, and what each one actually rests on

You have got it when

You can: (1) name the three cartilage types, what dominates each matrix, whether each has a perichondrium and where each sits in the head and neck; (2) identify osteoblast, osteoid seam, osteocyte, lining cell and osteoclast and say what each does; (3) read an osteon, its lamellae and its cement line in a ground section; (4) separate modelling from remodelling and name the five stages of a BMU cycle; and (5)…