Growth of human mandible angle during fetal period

Introduction: The angular part of the jaw develops in the stadium 19th of the embryonic period as a common primordium of the mandibular angle's cartilage and the masseter muscle. The consolidation of all skeletal jaw units takes place in 10th week of embryonic period. Getting to know the stadiums of jaw's development is extremely important, especially in orthodontic and prosthetic treatment. Objective: The objective of this research was the attempt for metrical definition of developmental changes of the mandible angle in the fetal period. Materials and Methods: The research was performed on 97 fetus's jaws (of 3-10 lunar months old); originated from University's of Adam Mickiewicz in Poznan Institute of Antropology's collection. The fetus's age was determined basing on total and crown-rump length. The particular points were marked on the jaws: Gonion (go), Kondylion laterale (kdl) and Gnathion (gn). Those marked points were connected with straight lines and the angle between them was measured with mandibulometer. The average of jaw's angle was calculated for the particular periods of embryonic periods. Results: The jaw's proportions in prenatal period change. The biggest overall growth of the jaw can be observed in 6th and 10th month of the fetus development. The values for the jaw angle also change. The observed average values for the angle in 3d month were 137,78° and then they gradually diminished to 136,00°, 136,44°, 135,05°, 131,79°, 132,91°, 131,00° the successive months to reach the value of 129,50° in 9th month. Conclusions: The small differences in values of jaw's angle connected with sex were noted. The jaw's angle development is similar at both sexes.