Dental Health Component of Index of Orthodontic Treatment needs (DHC of IOTN)

 # From a public health perspective, the Dental Health Component (DHC) grade 4 of the IOTN classifies conditions where the adverse consequences are severe enough to require treatment for health reasons. Which Grade 4 sub-criterion is most directly linked to the risk of dental trauma?

A. 4a: Increased overjet 6 mm to 9 mm with incompetent lips

B. 4h: Extensive hypodontia requiring restorative dentistry

C. 4i: Submerged deciduous teeth

D. 4e: Severe skeletal discrepancy requiring surgery

The correct answer is A. 4a: Increased overjet 6 mm to 9 mm with incompetent lips

In the IOTN DHC, grade 4a specifically addresses increased overjet of 6–9 mm, which significantly elevates the risk of traumatic dental injuries to the maxillary incisors (relative risk ~2.8–4.0 compared to normal overjet <3 mm), as proclined incisors are more protrusive and vulnerable to impacts. Incompetent lips exacerbate this by failing to provide protective coverage, further increasing exposure—though standard IOTN 4a criteria focus on overjet magnitude alone, with lip incompetence noted in grade 3a for moderate cases. Public health guidelines prioritize this sub-criterion for early intervention due to its direct link to injury incidence (e.g., 20–30% higher in affected children), unlike hypodontia (B, 4g/4h: restorative needs without trauma risk), submerged teeth (C, typically 5s: ankylosis-related eruption issues), or severe skeletal discrepancies (D, often 4p or 5a: functional/surgical needs but indirect trauma association via secondary malocclusions).