Application of the foramina of the trigeminal nerve as landmarks for analysis of craniofacial morphology

Abstract

Objective: The objective of this study was to develop new parameters based on the foramina of the trigeminal nerve and to compare them with the conventional cephalometric parameters in different facial skeletal types.

Methods: Cone-beam computed tomography (CBCT) scans and cephalograms from 147 adult patients (57 males and 90 females; mean age, 26.1 years) were categorized as Class I (1° < ANB < 3°), Class II (ANB > 5°), and Class III (ANB < -1°). Seven foramina in the craniofacial area-foramen rotundum (Rot), foramen ovale (Ov), infraorbital foramen, greater palatine foramen, incisive foramen (IF), mandibular foramen (MDF), and mental foramen (MTF)-were identified in the CBCT images. Various linear, angular, and ratio parameters were compared between the groups by using the foramina, and the relationship between the new parameters and the conventional cephalometric parameters was assessed.

Results: The distances between the foramina in the cranial base did not differ among the three groups. However, the Rot-IF length was shorter in female Class III patients, while the Ov-MTF length, MDF-MTF length, and Ov-MDF length were shorter in Class II patients than in Class III patients of both sexes. The MDF-MTF/FH plane angle was larger in Class II patients than in Class III patients of both sexes. Most parameters showed moderate to high correlations, but the Ov-MDF-MTF angle showed a relatively low correlation with the gonial angle.

Conclusions: The foramina of the trigeminal nerve can be used to supplement assessments based on the conventional skeletal landmarks on CBCT images.

Keywords: Anatomy; Computed tomography; Foramen; Trigeminal nerve.

Figure 1. Three-dimensional reconstruction and orientation of the cone-beam computed tomography image with three reference planes and three axes. The origin was set at the sella.

Figure 2. Description of landmarks in cone-beam computed tomography images. The images in each column have the same orientation as the corresponding images in the first row.

Rot, Foramen rotundum; Ov, foramen ovale; IOF, infraorbital foramen; GPF, greater palatine foramen; IF, incisive foramen; MDF, mandibular foramen; MTF, mental foramen.

Figure 3. Linear (A) and angular (B) parameters in cone-beam computed tomography (CBCT) images. Identification of the landmark and measurements were performed three-dimensionally. To visualize the location of the landmarks and measurement parameters, they were simply drawn in the lateral maximum projection image of CBCT.

FH, Frankfort horizontal plane. See Table 2 for definition of each landmark.

Figure 4. Spearman correlation analysis between conventional cephalometric parameters and the new cone-beam computed tomography parameters using foramina in maxillomandibular analysis.

See Tables 2 and 3 for definitions of each landmark or measurement.

Figure 5. The locations of landmarks and measurements were visualized in the lateral maximum projection image of cone-beam computed tomography. Values of linear and angular parameters as measured in a 22-year-old male patient with skeletal Class II malocclusion (A), and a 23-year-old male patient with skeletal Class III malocclusion (B).

FH, Frankfort horizontal plane. See Table 2 for definition of each landmark.