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The development of the mouse molar periodontium.

The normal development of the tissues of attachment of mouse molar teeth was studied using standard histological techniques. Jaws were taken from mice on the day of birth and each subsequent day, up to and including thirty days after birth, and examined. At birth, the molar teeth were in the late shell stage of development and were enclosed in the dental sac. Subsequent growth of the crown was accompanied by minor changes in the dental sac and alveolar bone. The periodontal ligament began to develop when root formation began. Fibres were laid down in a superior-oblique orientation which was maintained throughout the prefunctional and functional phases of eruption although changes which gave rise to the cervical fibre groups took place in the latter part of the prefunctional phase. Changes in the alveolar bone and cementum were observed as the tooth became functional. It was concluded that the periodontal ligament was preadapted to function and changes in other tissues of attachment, occurring as the teeth attained functional occlusion, were designed to strengthen the attachment of the fibres to bone and tooth.