[GROUP 1: Components of the Periodontium] - Gingiva - Periodontal ligament (PDL) - Cementum - Alveolar bone proper - Distinct in location, architecture, and biochemical properties

[GROUP 2: Function of the Periodontium] - Supports teeth during function - Maintains teeth in the maxillary and mandibular bones - Provides necessary support for teeth - Allows teeth to respond to forces - Functions as a single unit

[GROUP 3: External Forces and the Periodontium] - Constant state of balance between periodontal structures and external forces - Alveolar bone undergoes remodeling in response to occlusal forces - Osteoblasts and osteoclasts line areas of tension and compression - Trabeculae align in the path of stresses to resist occlusal forces - Increased forces lead to increased trabeculae and bone thickness

[GROUP 4: Stimulation and Adaptation of the Periodontium] - Periodontal ligament depends on stimulation from function - PDL can accommodate increased function by increasing its width - Excessive forces cause injury known as trauma from occlusion - Reduced occlusal forces result in PDL atrophy - Disuse atrophy can occur in the periodontium

[GROUP 5: References] - Kumar GS, ed. (2011). Orbans Oral Histology and Embryology - Newman MG, Takei H, Klokkevold PR, Carranza FA, eds. (2012). Carranzas Clinical Periodontology - Mitsiadis TA, Pagella P, Cantù C (2017). Early Determination of the Periodontal Domain by the Wnt-Antagonist Frzb/Sfrp3. - Tanne K, Sakuda M, Burstone CJ (December 1987). Three-dimensional finite element analysis for stress in the periodontal tissue by orthodontic forces. - Capnocytophaga sp., Preston D. Miller, Willoughby D. Miller, Carl E. Misch, John Mankey Riggs, Jay Seibert, Jørgen Slots, Paul Roscoe Stillman, Dennis P. Tarnow