- Fusion: Two teeth joined together from the fusion of two separate adjacent germs. The radiographic appearance is enlarged crown and root with two root canals.
- Gemination: Two teeth arise from one tooth germ. The radiographic appearance is enlarged crown and root with one root canal.
* As in some cases fusion and gemination cannot be distinguished, both conditions can be named connation. - Concrescence: The two adjacent teeth are attached at cementum.
- Dens-in-dente (Dens Invaginatus): the outer surface of enamel is infolded in to the interior side.
Tooth shape

Features
Cases
Fusion and palatal bone loss.
Concrescence.
Talon cusp.
Fusion upper molars with periapical lesion.
Dens-in-dente (dens invaginatus) literally means “a tooth within a tooth”. It is a developmental anomaly. It is most frequently seen in maxillary lateral incisors. Caries and pulp necrosis is frequent in these teeth.
Different cases of dens-in-dente (dens invaginatus).
Different cases of dilaceration. It refers to an angulation, or a sharp bend or curve, in the root or crown of a formed tooth.