Review of the biological aspects in the periodontal ligament and alveolar bone associated with compression

Background: Tissue remodeling requires protein degradation through a process directly dependent on metalloproteinases — enzymes capable of degrading the majority of proteins in this system. This process is regulated by some enzyme inhibitors, and balance between enzyme and inhibitor activity is fundamental to tissue integrity and health. Bone resorption and formation, and the molecules involved in these processes, raise questions on possible differences in tissue behavior in the system. Histological studies of tissues surrounding teeth that have been subjected to such forces show the presence of tension (associated with bone formation) and compression, which induce bone resorption. The duration of load application is an important parameterin osteoclastogenesis. The present study aimed to analyze the biological aspects associated with in vitro compression of the PL and alveolar bone. To this end, we reviewed articles describing the biological events that occur in the PL and alveolar bone during load application on this system and the possible influence of culture medium on the expression of molecules involved in response to such an event. Methods: This literature review included articles published between March 2008 and January 2018 describing in vitro laboratory tests and data on load application and its associated biological events in the human PL and alveolar bone, including studies on molecular-expression events and pathways involved in the process. Conclusions: Intermittent compressive forces stimulate bone resorption in orthodontic treatment, while cyclical forces induce cellular apoptosis at lighter loads than do compressive forces. Both 2D and 3D cell-culture systems seem to reproduce the physiology of evaluated tissues and are reliable analytical models for research purposes.