ABSTRACT
Objective@#To study the relation between the upper first molar root tips and the maxillary sinus floor in patients with different vertical facial patterns using cone-beam computed tomography (CBCT) and to explore the reference data for safe clinical orthodontic treatments.@*Methods@#Three-dimensional images were reconstructed from CBCT data. The CBCT data from 120 adolescents and adults were divided into three groups (low-angle group, average-angle group, high-angle group) based on vertical facial type. For each subject, the distance from the maxillary sinus floor to the upper first molar root tips was measured, and the types of contacts were classified. ANOVA and LSD t tests were used for statistical comparisons and performed using SPSS 19.0.@*Results@#Of the 120 samples, only 27% of the upper first molar root tips lost their contacts with the maxillary sinus floor, and the other 73% of the root tips contacted the sinus to different extents. Significant differences in the distances from the maxillary sinus floor to the upper first molar root tips were found for different vertical facial types (P < 0.05). The high-angle group had the lowest sinus floor, relative to the root tips, of the three adult groups (P < 0.05). In the adult group with a low angle, the measured value for the palatal root tips was the lowest and was significantly different from those in the other groups (P < 0.05).@*Conclusion@#Seventy-three percent of the upper first molar root tips contacted the maxillary sinus floor. The maxillary sinus floor tended to be lower relative to the first molar root tips in patients with a high-angle facial pattern than in others. The roots protruded into the sinus to a greater extent.