The physiologic process resulting in the elimination of deciduous dentition is called exfoliation or shedding.
This shedding or exfoliation is due to progressive resorption of the roots of the deciduous teeth and their supporting tissue, the periodontal ligament.
In general, the pressure generated by the growing and erupting permanent tooth dictates the pattern of deciduous tooth resorption.
The first sign of root resorption is seen in the deciduous medial incisors and the first Molars by the age of 4-5 years.
Resorption of the incisors begins primarily on the lingual side with horizontal resorption of the apical parts commencing at a later stage.
Root resorption in the deciduous molars starts from the inner surfaces of the developing permanent tooth germ.
Resorption of the deciduous incisors takes place more rapidly (lasting 1.5 -2 years on average) than that of the canines and molars (2.5 -5.7 years).
The permanent successor may be visible immediately after exfoliation of a deciduous tooth, or there may be a latent period of 0.1 to 0.5 years before the permanent successor erupts.
The resorption process is not continuous, but is interrupted by periods of rest and periods of repair. This intermittent resorption and repair explains the variation in mobility of the deciduous teeth prior to exfoliation.
Premature loss of deciduous tooth has been found to accelerate the clinical eruption of the subsequent permanent tooth if the deciduous tooth is lost shortly before normal tooth exfoliation time i.e., 1-2 years before, whereas there is evidence both for and against a retarding effect in the case of very early tooth loss i.e., 2-5 years before exfoliation.
The explanation for this is that the dense fibrous connective tissue which forms in place of the extracted deciduous may hinder the eruption of its permanent successor.