The cells responsible for the formation and maintenance of dentin are odontoblasts.

Odontoblasts are specialized cells located in the dental pulp, at the periphery adjacent to the dentin. Their primary function is to synthesize and secrete the organic matrix of dentin, known as predentin, which subsequently mineralizes to form mature dentin. These cells remain vital throughout the life of the tooth, allowing for the continuous formation of secondary and tertiary dentin in response to stimuli such as trauma or decay.

In contrast, ameloblasts are responsible for the formation of enamel, the hard outer layer of the tooth crown. Cementoblasts form cementum, the mineralized layer covering the tooth root that aids in anchoring the tooth within the alveolar bone. Osteoblasts are bone-forming cells involved in the maintenance and remodeling of alveolar bone, not dentin.

Thus, the role of dentin formation and maintenance is uniquely attributed to odontoblasts.

Reference: Ten Cate's Oral Histology, Volume 1, Chapter 4 – Dentinogenesis, Page 85