The two main types of dental abscesses are periodontal and periapical abscesses. A periodontal abscess is caused by an infection of the gap between a tooth and the gum while a periapical abscess occurs inside a tooth and affects the tip of its roots, notes the Colgate Oral Care Centre. A dental abscess that only affects gum tissue and not the tooth or the periodontal ligament is categorized as a gingival abscess, according to Medical News Today.
A combination of small food particles, saliva and bacteria form a sticky film in the mouth known as plaque, says NHS Choices. Periodontal abscesses occur when plaque bacteria infect the gum and cause the periodontal ligament, which is the tissue that surrounds the tooth root, to peel away from the tooth. The infection occurs when food gets trapped in the gap formed between the root and the gum. Periodontal pockets that are formed accidentally during dental procedures can also cause abscesses.
Plaque bacteria release acids, which cause caries and tooth decay if left to accumulate as a result of lack of brushing or practicing other forms of dental hygiene, notes NHS Choices. Periapical abscesses form when bacteria enter the tooth through caries formed on the enamel and infect the soft inner pulp. The bacteria then progress down to the alveolar bone that surrounds the tooth and cause the abscess to be formed.