Changes in condylar path inclination during maximum protrusion between the ages of 6 and 12 years.

The purpose of this study is to quantify the changes in sagittal condylar path inclination during mandibular protrusion between the ages of 6 and 12 years. A total of 172 children (82 males and 90 females) ranging in age from 6.5 to 12.9 years were divided according to their chronological age into five subgroups with mean ages of 7.1, 8, 9, 10 and 11.4 years respectively. The control group consisted of 41 adults with a mean age of 28 years. All subjects had a normal temporomandibular joint function and neutral occlusion. Five maximum protrusion-retrusion movements were recorded with six degrees of freedom in each subject using an ultrasound (JMA) jaw-tracking system. Initially, condylar path inclination angle (CPIA) was calculated stepwise for each millimetre distance, for the first 10 mm of protrusive tracing path on both sides. A single mean value was then assigned for the entire protrusive path. One-way analysis of variance proved to be significant among the five subgroups of children. Linear regression analysis showed that condylar path had a tendency to become steeper with age, although it was statistically weak. The data indicated that the mean CPIA is 43 degrees -44 degrees at the age of seven, increases annually by 1.2 degrees -1.3 degrees and reaches an average of 49 degrees -50 degrees by the age of 12 at which time it attains around 83-85% of its adult level. In subgroup V, the female population had significantly steeper condylar path on the left-hand side than the male population. Condylar path inclinations indicated a symmetrical growth pattern of the articular eminence.