MJOR REASONS FOR TOOTH LOSS ARE:

1. CONGENITAL

This type of tooth loss occurs due to a genetic condition or a developmental defect in the formation of teeth. There can be situations where a tooth or multiple teeth may be missing from the oral cavity. This condition is called Hypodontia which is referred to as the presence of less than the normal number of teeth in the oral cavity. Anodontia is a congenital condition where there is the absence of the entire complement of teeth with no signs of development of even a single tooth.

2. IMPACTION

Tooth impaction usually occurs when there is no space available for the tooth to erupt into the oral cavity. This  is commonly seen in relation to the third molars. A tooth impaction can also occur as a result of disruption in the formation of teeth. This can result in an abrupt cessation of the development of the root of the tooth, due to which the movement of the tooth towards the path of eruption gets prevented. Sometimes, during tooth development, an injury can cause the developing tooth to get encapsulated by a cyst either partially or fully, preventing it from erupting into the oral cavity. Even infections of the adjacent areas or the existing primary predecessor can cause a disruption in the eruption of its successor, permanent tooth. Ankylosis, which is the bony fusion of the alveolar bone to the tooth, can also cause the tooth to be impacted within the bone.

Tooth eruption involves a great deal of bone remodelling as well. This process allows the tooth to move within the bone until it erupts into the oral cavity. A disruption in the physiologic remodelling process can also prevent tooth eruption.

3. DENTAL CARIES

Dental caries, more commonly known as tooth decay, is one of the most common causes for tooth loss. Usually, dental caries starts off as a small niche that allows food particles to get stuck in the teeth. As the bacteria feed on these particles, they release acids that cause damage to the tooth. When spotted early, dental caries can be addressed easily and the tooth can be restored with minimal effort. Dental caries in advanced stages may require root canal intervention. 

4. PERIODONTAL DISEASES

Periodontal diseases (gum diseases) stands to be the most common cause of tooth loss. Various causes ranging from microbial to systemic conditions contribute to periodontitis. Periodontal diseases cannot infect the tooth by itself, but it can cause severe infection, inflammation, and destruction of the supporting structures of the teeth. Initial stages of Periodontitis can be managed successfully gets reduced. In very advanced stages, even surgical intervention will not help restore the affected tooth/teeth. In such situations, they may be required to be removed. Often the affected teeth will fall out from the oral cavity spontaneously.

5. TRAUMA

Another major reason for tooth loss is trauma or injury resulting in luxation of the tooth and even its dislodgement from the socket. Sometimes, the tooth can be placed back and splinted, while on certain occasions, it has to be removed entirely, depending on the severity of the injury. 

6. STRATEGIC EXTRACTION

There are situations where a tooth or teeth may have to be removed to facilitate certain treatment effectively. One of the commonest examples is the extraction of teeth (usually the 2nd premolars) from each quadrant to provide sufficient space for orthodontic correction of crowded teeth. Similarly planning the replacement of missing teeth may also require the extraction of one or more teeth to facilitate the successful placement of a more stable and ideal prosthesis.