Three-dimensional mapping of the enamel thickness on the labial surface of maxillary and mandibular incisors

Within-enamel preparation provides higher bond strength in minimally invasive esthetic treatment. However, determining the distribution of enamel thickness on the labial surface of human incisors remains difficult.

The purpose of this in vitro study was to reconstruct and map the labial enamel thickness of the maxillary and mandibular incisors.

Sixty human incisors, including 20 maxillary central incisors (MxCIs), 20 maxillary lateral incisors (MxLIs) and 20 mandibular incisors (MdIs), were scanned using microcomputed tomography. The labial enamel was reconstructed into 3-dimensional models and divided into 9 segments (mesial-cervical, central-cervical, distal-cervical, mesial-middle, central-middle, distal-middle, mesial-incisal, central-incisal, and distal-incisal segments). The enamel thicknesses of different segments of the labial enamel were measured and analyzed. Statistical analysis was performed using the paired t test and analysis of variance (α=.05).

The enamel thickness of MxCIs was 0.461 to 0.966 mm, the enamel thickness of MxLIs was 0.346 to 0.984 mm, and the enamel thickness of MdIs was 0.343 to 0.792 mm. The labial enamel thickness was significantly different between the maxillary and mandibular incisors (P<.05). In all incisors, the enamel was thickest in the incisal region and significantly thinner in the cervical region (P<.05). The distal enamel was significantly thicker than the mesial enamel in MxCIs (P<.01), whereas the central enamel was thicker than the mesial enamel in MdIs (P<.01).

The labial enamel thickness was significantly different between the maxillary and mandibular incisors (P<.05). Horizontally, the mesial enamel was thinner than the distal enamel in the MxCIs, whereas the central enamel was thicker than the mesial enamels in the MdIs. Vertically, the labial enamel thickness increased from the cervical region to the incisal region in all incisors.