What effect does bad teeth have on the body?

Many things: Bad teeth is an infection of the teeth causing cavities or of the gums causing periodontal disease. When untreated abscesses occur which leads to other health problems, the extreme of which is death.

Many Systemic Effect: There are clear connections that bad teeth and gums are associated with increased risks of heart disease, stroke and diabetes complications. Do a pubmed or internet search and you can find the scholarly research on this topic.

Many effects: If you can't chew your food properly, that can lead to digestive problems. Gum problems (periodontitis) have been linked to heart and respiratory disease, diabetes, stroke, pancriatic cncer and low birth weight babies.