Keep the direction and the viewpoint together

Comparison one: two directions in the same model

Overbite and overjet concern different directions: vertical overlap and forward projection, respectively.

Panels A and B repeat the same side-view shapes. Only the guide marks change. In A, follow the upright marker beside the front pair. In B, follow the horizontal marker between their front surfaces. The two markers ask different questions about the same fixed drawing.

The complete reading is: "A directs my attention up and down; B directs it forwards and backwards." Because the shapes have not moved, this is not a comparison of earlier and later treatment. Both directions can be discussed without turning either marker into a severity scale.

The glossary uses clinical terms for these relationships. This drawing teaches the directions; it does not classify the amount shown as excessive or tell you whether your own teeth need treatment.

Sources: AAO glossary

Comparison two: a space and a reversed front relationship

In an anterior open bite, front teeth do not touch while back teeth meet. In an anterior crossbite, upper front teeth sit behind lower front teeth.

C contains front and side views of the same model. The front shows a space; the side adds the back pair together. Read both to understand the label.

Panel D asks a different question. Its side view marks which front outline is further forwards. Follow the arrow labelled Front, then read the upper and lower labels. This is a reversed front relationship, not another name for the empty space in C.

A useful comparison says both things positively: "C shows a front space with the back pair together. D shows which front outline is ahead." Saying only that the drawings look unusual would lose the distinction this pair is designed to teach.

Sources: AAO glossary; AAO bite guide

Read the marker before drawing a conclusion

Start with the view, identify upper and lower, and follow the particular marker. You can then describe a direction or contact relationship instead of relying on the overall appearance of the drawing.

These models leave out roots, supporting structures and many other individual details. They cannot explain a person's cause, jaw relationship or treatment choice. The next lesson shows how to keep a useful positive explanation within what a set of views actually supplies.