{'fraction_non_alphanumeric': 0.00962962962962963, 'fraction_numerical': 0.0, 'mean_word_length': 5.526570048309178, 'pattern_counts': {'":': 0, '<': 0, '<?xml version=': 0, '>': 0, 'https://': 0, 'lorem ipsum': 0, 'www.': 0, 'xml': 0}, 'pii_count': 0, 'substrings_counts': 0, 'word_list_counts': {'cursed_substrings.json': 0, 'profanity_word_list.json': 0, 'sexual_word_list.json': 0, 'zh_pornsignals.json': 0}}
Role of physical forces in regulating the form and function of the periodontal ligament.

The periodontal ligament is a physically small but functionally important tissue in tooth support, proprioception and regulation of alveolar bone volume. There is a long-standing and widespread interest in the periodontal ligament as a model connective tissue because of its rapid matrix turnover and its ability to adapt to alterations of mechanical loading. These features are mediated in part by heterogeneous cell populations that enable the roots of teeth to maintain dynamic yet strong attachments to bone in spite of highly variable applied force levels. The remarkably precise maintenance of periodontal ligament width in spite of these force levels or the restoration of the ligament space after surgical ablation indicates the existence of highly effective regulatory systems for ‘‘measuring’’ tissue domains and for initiating localized matrix resorption and synthesis. Constitutive adaptation to applied forces is mediated in part by specific structural and regulatory proteins expressed by periodontal ligament cells. As an example of these adaptations we review recent evidence of how cytoskeletal proteins mediate protective responses to applied force and how these responses may enable the cells to survive in a mechanically active environment.