Where does impaction collide?

In aerosol physics, impaction is the deposition of airborne particles when the air they ride turns sharply and their inertia carries them out of the streamline onto a surface, the principle used to size-sort particles in a cascade impactor. Marple and Willeke's 1976 Impactor design set out the fluid mechanics that determine which particle sizes an impactor collects. The referent is an inertial deposition process governed by particle size and flow, a physical mechanism unrelated to a stuck tooth or impacted stool beyond the shared root meaning of being driven against something.[1]

Unit

The particle size above which particles are captured by inertia (the cut-off diameter)

Recovery means

Not applicable

Measured by

Characterised by the collection-efficiency curve and cut-off diameter of an impactor

In dentistry, impaction is the failure of a tooth to erupt into its normal position because it is blocked by bone, another tooth, or soft tissue, most often seen with mandibular third molars (wisdom teeth). Santosh's 2015 review proposes a combined clinical and radiological classification of impacted mandibular third molars. The referent is a tooth lodged below or against an obstruction, classified by its angle and depth, and it is a distinct meaning from inertial particle impaction or bowel impaction.[2]

Unit

Position, angle, and depth of the unerupted, obstructed tooth

Recovery means

Not applicable

Measured by

Classified radiographically by angulation and depth (e.g., Winter's and Pell and Gregory's systems)

In medicine, faecal impaction is a large, hardened mass of stool that becomes stuck in the rectum or colon and cannot be passed, a common complication of chronic constipation, especially in older and immobile patients. Allu and colleagues' 2024 review surveys the causes, consequences, and management of faecal impaction in the elderly. The referent is immovable retained stool and the obstruction it creates, sharing the word with an impacted tooth and with aerosol impaction only through the meaning of being wedged in place.[3]

Unit

Presence and burden of immovable retained stool in the rectum or colon

Recovery means

Relieved by disimpaction and laxative or enema treatment; prevented by managing constipation

Measured by

Found by rectal examination and abdominal imaging