Studies on the development of the articular part of the temporal bone with special reference to the postglenoid process.

The development and significance of the postglenoid process on the articular surface of the temporal bone were studied using 217 Indian skulls, which were divided by their level of tooth eruption into 6 developmental stages; preeruption period (Stage I), initial stage (m1 eruption) of the deciduous dentition period (Stage II), middle stage (m2 eruption) of the deciduous dentition period (Stage III), late state (eruption of 20 deciduous teeth) of the deciduous dentition period (Stage IV), mixed dentition period (Stage V), and permanent dentition period (Stage VI). Each skull was mounted on a Kraniophor in such a way that the auriculoorbital (Frankfurt) plane was positioned vertical to the horizontal plane and photographed at a focal distance of 40 cm. Using the Frankfurt plane as a base line, the vertical distances to the lowest point of the postglenoid process (a-A), to the deepest point of the mandibular fossa (b-B), and to the mid-point of the articular tubercle (c-C) were measured. The distances from various points of the mandibular fossa to the articular surface of the temporal bone were measured at the level of the Frankfurt plane. The results may be summarized as follows: The length of the postglenoid process as measured from the Frankfurt plane was 0.58 mm at Stage I and 0.75 mm at Stage II. It increased by 0.6-1.0 mm at each developmental stage. By Stage VI, it had increased to 3.85 mm (six- to seven-fold increase from the initial value). The anteroposterior width of the postglenoid process remained almost unchanged throughout the developmental stages. The growth of the articular structures of the temporal bone from the preeruption to deciduous dentition period increased 73% in the total anteroposterior dimension (5.22 mm) and 44% in the total vertical dimension (3.32 mm). The vertical dimension of the mandibular fossa began to rapidly increase following the eruption of the deciduous first molars.