Final answer:
Periodontal disease is caused by bacterial colonization in the gingival space, leading to inflammation and gum damage.
Step-by-step explanation:
Periodontal disease is caused by the colonization of bacteria in the gingival space, resulting in inflammation and damage to the gums. The bacteria involved in periodontal disease include Porphyromonas, Streptococcus, and Actinomyces species. The bacterial products released during the colonization process cause inflammation and gum damage.