Morphological Characteristics of Nasomaxillary Complex and Cranial Base in Maxillary Retrognathism

Abstract

Background and aim: The cranial base is considered to be related to the growth and development of the maxillofacial structures morphologically, and is regarded as one of the factors in malocclusion. The purpose of this study was to extract morphological characteristics of maxillary retrognathism to analyze relationships among the cranial base,maxilla, and ethmoid and vomer bones constituting the nasal septum.

Materials and methods: Materials were the lateral cephalograms and computed tomography(CT)images of 26 pre-treatment mandibular prognathism patients(Japanese males, 24.8±8.4 years). Subjects were divided into two groups based on the position of point A: a posterior group(n = 10)and an anterior group(n = 16). The posterior group was thought to correspond to maxillary retrognathism. Angular and linear measurements were made on lateral cephalograms and median sagittal plane CT images.

Results: Compared with the anterior group, the posterior group displayed a short anterior cranial base(S-N), a more posteriorly positioned posterior nasal spine, and counterclockwise inclination of the cranial base on cephalometric measurements. The posterior space of the vomer was smaller, and mid-facial height was smaller on CT measurements. No difference between groups was seen in shape of the cranial base or anteroposterior length of the hard palate(ANS-PNS).

Conclusion: The cranial base is inclined counterclockwise due to insufficient growth of the nasal septum, especially the posterior part of the vomer. These morphological factors are suggested to contribute to maxillary retrognathism.