CDCA North East Regional Board (NERB) Practice Exam

Tooth #9 refers to the maxillary right central incisor in the Universal Numbering System. The crown-to-root ratio is an important measurement that compares the length of the crown of the tooth (the visible part above the gum line) to the length of the root (the part of the tooth embedded in the jawbone). A favorable crown-to-root ratio usually indicates better stability and prognosis for a tooth, especially when considering restorations or periodontal health.

When examining tooth #9 specifically, it tends to have a shorter root in comparison to other teeth, especially when considering its position and common treatments that might involve it, such as extractions or restorations. Among the other choices, tooth #6 (maxillary right first premolar) and tooth #11 (maxillary left central incisor) typically have longer and more robust root structures, contributing to a more favorable crown-to-root ratio. Tooth #8 (maxillary left central incisor) is also likely to have a similar root length to tooth #9, but generally, both central incisors (teeth #8 and #9) would still have a shorter root compared to premolars or canines in the same arch.

When considering the overall context of anatomical structure and typical root