ABO Growth and Development Flashcards

Which is the LAST permanent tooth to erupt in the normal sequence?

Answer: Third molar (wisdom tooth)

Third molars (wisdom teeth) are the last permanent teeth to erupt, typically appearing between ages 17 and 25, if they erupt at all.

The soft tissue profile change after orthodontic retraction of protruding teeth is best described by which ratio?

Answer: Lip-to-tooth movement ratio (approximately 0.6–0.8 mm lip movement per 1 mm tooth retraction)

Research shows that upper lip retraction averages about 0.6–0.8 mm for every 1 mm of upper incisor retraction, though this varies by individual.

During the transition from primary to permanent dentition, the permanent incisors tend to erupt:

Answer: More labially than the primary incisors (especially upper centrals)

Permanent incisors, especially the upper centrals, erupt labial to the primary predecessors because the roots of primaries resorb and the permanent tooth follows a slightly more labial path.

In Angle's classification, a Class II Division 2 malocclusion is characterized by:

Answer: Upper central incisors retroclined with a deep overbite and a Class II molar relationship

Class II Division 2 features retroclined upper central incisors (often with flared laterals), a deep overbite, and Class II molar and canine relationships.

The nasolabial angle is measured between which two lines?

Answer: The columella of the nose and the upper lip

The nasolabial angle is formed between the columella (bottom of the nose) and the upper lip, with a normal range of approximately 90–110 degrees.

The Frankel classification of arch form (type I–IV) is based on:

Answer: The shape of the dental arch when viewed from the occlusal plane (tapered, ovoid, square, etc.)

Arch form classifications describe the geometric shape of the dental arch from the occlusal view, ranging from narrow and tapered to broad and square.