[A study of developmental changes of Indian mandibles concerning development of weight, height, thickness and length of the mandible].

A total of 230 mandibles were classified into 7 groups 8 stages according to eruption phase, observing developmental changes from unerupted stage (Group A) to permanent dentition (Group G) 1. Development from Group A to deciduous dentition completion stage (Group C) was classified into 3 types. 1) Regarding height of mandibular ramus, height and weight of mandibular body, the increase from Group B where the deciduous central incisor erupts to Group C is greater that from Group A-B (type a). 2) As to coronoid process height, length of mandibular body, mandibular length and mandibular ramus width, equal increases were seen between Group A-B and B-C (type b). 3) Chin height and thickness of the mandibular body developed suddenly with the eruption of the deciduous central incisors. The increase is greater in Group A-B (type c). 2. They are classified according to size proportion in unerupted stage as compared to entire size. The classification are: 42%-33% (smaller), 50%-45% (medium), 70%-50% (bigger). 1) Type a is small at Group A and developed steadily after Group C. Development is greater, about 2.3-3 times. 3) Type b at Group A is larger than type a. It continuously developed after Group C. The developmental rate is about 2 times except the coronoid process height. 3) Type c is large at Group A. No development occurred after D1 stage when first molars erupt. Developmental rate is 1.4-1.85 times and smallest of the 3 types. 3. Developmental quantity: 1) Regarding total increase; The height of the mandibular ramus, the height of the mandibular ramus and coronoid process showed about 28-32 mm increase Group C accounted for 55%, Group C-D2 14%-17%, Group D2-G 30%-27% of the developmental increase. The mandibular ramus width showed increases of 14.43mm (74% at D1 stage) and subsequent increase was 7% between each group, showing equal increases. 2) Chin and mandibular ramus height showed increases of 14 mm. At Group C, development in chin height accounted for 67%. The mandibular body width increased 4.0mm-6.0mm at the foramen in m2/m2 and 6/6 portions. It reached 82%-100% in D1 stage. 3) An increase in mandibular body length and mandibular length was 50mm and 32mm, reaching 73% of the entire developmental amount by D1 stage.