Final answer:
The most common diseases of the mouth and teeth in the developed world are dental caries, gingivitis, and periodontal disease, which result from an overgrowth of oral bacteria due to insufficient dental hygiene.
Step-by-step explanation:
One of the most common diseases of the mouth and teeth in the developed world is dental caries, also known as cavities. Dental caries are microbial lesions caused by an overgrowth of oral bacteria, primarily Streptococcus and Actinomyces species, which result from insufficient dental hygiene. These bacteria feed on sugars in the mouth and release acids that lead to soft tissue inflammation and degradation of the calcium crystals of the enamel.
Gingivitis and periodontal disease are also prevalent issues that affect the gum and bone supporting the teeth. Gingivitis is an inflammation of the gums typically caused by the accumulation of plaque and can progress to more serious periodontal disease if not properly treated. This progression involves infection that leads to inflammation and damage of the tissues surrounding the teeth, but it is generally reversible and preventable with good oral hygiene practices.