Sagittal growth trends of the craniofacial complex during formation of the secondary palate in mice

Normal C57BL and A/J mice and A/Js with spontaneous bilateral cleft lip and palate were obtained at 13–16 days of gestation and the heads were prepared for serial sectioning in the sagittal plane. The midsagittal sections were photographically enlarged and measurements made to assess the amount and rate of growth. The C57BL fetuses outgrew the A/Js. in all parameters. A mandibular growth spurt was not observed, but an increase in mandibular growth relative to that of the maxilla was found. Maxillary growth was less in malformed A/Js but the mandible was not micrognathic. The cranial base angle was not significantly different in normal and malformed A/J fetuses, but the vertical dimension was significantly greater in the former than the latter at days 15 and 16. The increase in the angle made by the mandible and the posterior cranial base before and during palatal closure appeared to have the greatest influence on the vertical dimension.