How is secondary dentine formed?

Secondary dentine is formed as the tooth ages after eruption. This process occurs continuously throughout the life of a tooth, primarily in response to stimuli that can cause the pulp to react. As the tooth matures and ages, odontoblasts, which are the cells responsible for dentine formation, continue to lay down layers of secondary dentine. This gradual increase in dentine deposition helps to protect the pulp and can serve to respond to certain stimuli, such as wear or stress on the tooth.

The notion that secondary dentine forms only before tooth eruption or exclusively during the first year of life is inaccurate, as secondary dentine formation is an ongoing process that begins after the primary dentine has been formed and the tooth has erupted into the oral cavity. Moreover, it is not limited to external injuries; while trauma can stimulate additional secondary dentine production, it is also part of the natural aging process of the tooth.