[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