Average surface remodeling of the maxillary base and the orbital floor in female subjects from 8 to 25 years. An implant study.

The present study aimed to analyze the surface remodeling of the maxilla by the method of metallic implants. The sample comprised 14 series of lateral cephalometric films of girls, and was derived from the files of the implant study of Björk. Implants had been inserted below the anterior nasal spine and on the lower anterior surfaces of the zygomatic arches. Various types of malocclusion were represented in the sample, but records during periods of orthodontic treatment and retention were excluded from the analysis. No subjects with craniofacial anomalies were included. The final sample comprised 155 radiographs in the age range 8 to 25 years. In addition to the anatomically defined reference points, six fiducial points and two implant points in the maxilla were digitized from each film. Data were debugged by comprehensive numerical and graphical procedures. The average relocation of the reference point subspinale (ss, Down's A point) was about 4.5 mm down and 0.5 mm forward from 8 to 25 years, whereas the reference point spinal (sp, ANS) was relocated about 4.5 mm down and 1 mm forward. The reference point pterygomaxillare (pm, PNS) was relocated 6 mm backward and 1.5 mm down by surface remodeling. The relocation of the sp and pm points resulted in an angular remodeling of the palatal plane of 2.5 degrees (backward). At the same time the maxillary complex rotated -1.5 degrees (forward) in relation to the anterior cranial base, resulting in a 1 degrees increase in the inclination of the palatal plane to the anterior cranial base. The orbital floor showed an average relocation of about 2.5 mm up and 2 mm backward by surface apposition, partly masking both the downward and forward sutural translation and the average forward growth rotation of the maxilla. Because of the angular remodeling of the palatal plane and the surface apposition on the hard palate, it is recommended that great caution be exerted in the interpretation of clinical treatment analyses based on superimposition on lines or structures defined by the anatomy of the bony palate during the period of growth.