Understanding the formation of maxillary sinus in Japanese human foetuses using cone beam CT

Abstract

The formation of the maxillary sinus (MS) is tied to the maturation of the craniofacial bones during development. The MS and surrounding bone matrices in Japanese foetal specimens were inspected using cone beam computed tomography relative to the nasal cavity (NC) and the surrounding bones, including the palatine bone, maxillary process, inferior nasal concha and lacrimal bone. The human foetuses analysed were 223.2 ± 25.9 mm in crown-rump length (CRL) and ranged in estimated age from 20 to 30 weeks of gestation. The amount of bone in the maxilla surrounding the MS increased gradually between 20 and 30 weeks of gestation. Various calcified structures that formed the bone matrix were found in the cortical bone of the maxilla, and these calcified structures specifically surrounded the deciduous tooth germs. By 30 weeks of gestation, the uncinate process of the ethmoid bone formed a border with the maxilla. The distance from the midline to the maximum lateral surface border of the MS combined with the width from the midline to the maximum lateral surface border of the inferior nasal concha showed a high positive correlation with CRL in Japanese foetuses. There appears to be a complex correlation between the MS and NC formation during development in the Japanese foetus. Examination of the surrounding bone indicated that MS formation influences maturation of the maxilla and the uncinate process of the ethmoid bone during craniofacial bone development.

Fig. 1

Frontal view showing the measurement points of the maxillary sinus in the maxilla on CBCT images. PP, defined by the anterior and posterior nasal spines and is perpendicular to the median sagittal plane; Dh, height of the first deciduous molar in the maxilla from the PP to the superior border of the dental sac; Dw, width of the first deciduous molar in the maxilla from the midline to the inner border of the dental sac; Eh, height of the second deciduous molar in the maxilla from the PP to the superior border of the dental sac; Ew, width of the second deciduous molar in the maxilla from the midline to the inner border of the dental sac; INMw, width from the midline to the lateral (outer) surface border of the inferior nasal concha; MSh, height to the inferior border of the maxillary sinus at a right angle from the PP; MSw, width from the midline to the lateral (outer) surface border of the maxillary sinus

Fig. 2

Regression lines (black lines) for the correlation between CRL and growth of facial length (Fig. 1). Pearson’s correlation coefficient was used to measure the strength of the association between the two variables. MSG (MSw, r = 0.861: INMw, r = 0.820); Ew (r = 0.600); MSh (r = 0.577); Eh (r = 0.682); Dh (r = 0.424); Dw (r = 0.423)

Fig. 3

Three-dimensional reconstruction of the nasal wall in the lower facial region at 20 weeks of gestation (CRL, 178 mm). a Frontal view of the maxillary sinus and nasal cavity. The locations of the cross-sectional axial slices that were taken through the area of interest are indicated (a1). Three-dimensional frontal view of the maxillary sinus and nasal cavity. A density indicating the presence of the uncinate process of the ethmoid cartilage appeared near the nasal side of the maxilla (a2). b Horizontal view of the maxillary sinus and nasal cavity. The locations of the cross-sectional axial slices that were taken through the area of interest are indicated (b1). Three-dimensional horizontal view of the maxillary sinus and nasal cavity (b2). Bar 2 cm, arrow maxillary sinus, arrowhead uncinate process

Fig. 4

Three-dimensional reconstruction of the nasal wall in the lower facial region at 24 weeks of gestation (CRL, 210 mm). a Frontal view of the maxillary sinus and nasal cavity. The locations of the cross-sectional axial slices that were taken through the area of interest are indicated (a1). Three-dimensional frontal view of the maxillary sinus and nasal cavity. The uncinate process of the ethmoid bone is located near the nasal side of the maxilla (a2). b Horizontal view of the maxillary sinus and nasal cavity. The locations of the cross-sectional axial slices taken through the area of interest are indicated (b1). Three-dimensional horizontal view of the maxillary sinus and nasal cavity (b2). Bar 2 cm, arrow maxillary sinus, arrowhead uncinate process

Fig. 5

Three-dimensional reconstruction of the nasal wall in the lower facial region at 30 weeks of gestation (CRL, 275 mm). a Frontal view of the maxillary sinus and nasal cavity. The locations of the cross-sectional axial slices that were taken through the area of interest are indicated (a1). Three-dimensional frontal view of the maxillary sinus and nasal cavity. The uncinate process of the ethmoid bone formed a border with the maxilla (a2). b Horizontal view of the maxillary sinus and nasal cavity. The locations of the cross-sectional axial slices that were taken through the area of interest are indicated (b1). Three-dimensional horizontal view of the maxillary sinus and nasal cavity (b2). Bar 2 cm, arrow maxillary sinus, arrowhead uncinate process

Fig. 6

Images of the maxilla and other craniofacial bones around the maxillary sinus during development from 20 to 30 weeks of gestation (CRL, 223.2 ± 25.9 mm). The uncinate process of the ethmoid bone extends to the maxillary sinus during development. Bar 1 cm, a 20 weeks, b 24 weeks, c 30 weeks of gestation, DC dental crypt, EB ethmoid bone, INC inferior nasal concha, MS maxillary sinus, NS nasal septum