MAXILLARY INCISORS

* U1 to SN (Max. Incisor to SN): 103 +/- 6
Reference Line: Sella – Nasion
This angular measurement determines the inclination of the central incisor relative to the anterior cranial base.
• A greater than average angle indicates proclination (labioversion) of incisors as often seen in Class II division 1 cases.
• A smaller than average angle indicates upright or retroclined (lingually inclined) incisors as often seen in Class II division 2 cases.
* U1 to NA (Max. Incisor to NA): Angular: 22 +/- 6, Linear: 3 +/- 2 mm
Reference Line: Nasion – A point
The relationship of the maxillary central incisor to the N-A reference line is used to establish the position of maxillary incisors relative to the maxillary apical base.
Both the inclination of the long axis of the incisor to the line and the distance that the labial surface of the incisor in front of the line are measured. Both angular and linear measurements indicates the amount of maxillary dental protrusion.
• Labially proclined incisors will have a greater than average angular and linear measurement (Class II division 1 cases)
• Upright or retroclined (lingually inclined) incisors will have a smaller than average angular and linear measurement (Class II division 2 cases).
• Positive values are recorded if the labial surface of the incisor is anterior to the NA line, negative values if it is posterior.