"齿缝宽度" can be translated as "tooth gap width" or "interdental space width" in English.
"Tooth gap width" directly describes the width of the space between teeth.
"Interdental space width" is a more technical term, where "interdental" refers to the area between the teeth, and "space width" clearly indicates the measurement of that space.
Both expressions are accurate, and the choice between them may depend on the specific context or the level of technicality required.