1. Anodontia: This is the complete absence of teeth. It is a rare condition where an individual fails to develop any teeth.
2. Oligodontia: This term is used when an individual has fewer teeth than the typical dental formula, which is six incisors, two canines, two premolars, and six molars in the permanent dentition (excluding the third molars or wisdom teeth). The term "hypodontia" is often used synonymously with oligodontia, but hypodontia can also refer to a broader range of conditions characterized by the congenital absence of one or more teeth, whereas oligodontia is more specifically the absence of six or more teeth.
3. Microdontia: This condition involves teeth that are smaller than normal. It can affect either the primary or permanent dentition and may involve one tooth or multiple teeth.
4. Dens in dente: This is a rare developmental anomaly where a tooth forms within the dental crown of another tooth, typically in the form of a small tooth-like structure. It is not a condition of tooth number but rather an abnormality of tooth structure.

Talon cusp (TC) and dens in dente (DiD) are both developmental anomalies of the teeth, but they differ in their formation and appearance. A talon cusp arises from the palatal or lingual aspect of an incisor tooth, typically in the maxillary central or lateral incisors. It is composed of enamel and dentin, and its shape can vary from a mild bulge to a fully formed cusp that extends to the incisal edge of the tooth. It can be mistaken for a supernumerary tooth on radiographs due to its pointed projection and density.

In contrast, dens in dente is a condition where a tooth has an invagination in its crown that contains a smaller tooth-like structure, known as the "dental lamina," which is enclosed within it. This invagination is usually filled with pulp tissue and dentin, and the internal structure resembles a tooth within a tooth. The smaller structure within the affected tooth can mimic a supernumerary tooth on radiographs, but it is not a separate tooth.

Acetic acid is a key ingredient in the fixing solution used in radiography. It acts as a stop bath, neutralizing the developer and maintaining the acidic environment necessary for proper fixation. Hydroquinone and elon are developer agents, while sodium bisulfate is not typically part of the fixing process.

To determine the anterior-posterior extent of ameloblastoma in the mandibular molar area, the projection used is distal oblique.

For maintaining parallelism between the object and film, the film is placed at a distance to avoid distortion by increasing the target to object distance.