Maximum equivalent stress induced and the displacement of the developing permanent first molars after the premature loss of primary second molars: A finite element analysis

The use of a space maintainer during the deciduous dentition period at a proper time can prevent the consequences of the loss of the arch length in the future. There is controversy over the use of space maintainers. The aim of this study was to evaluate the magnitude of stresses exerted on immature permanent molar teeth, and the extent of displacement of these teeth when the adjacent teeth are missing, but after placing a space maintainer. Studies carried out to date have used clinical measurements, e.g., X-rays and dental casts. The finite element model (FEM) was used for modeling the maxillary and mandibular teeth and the bone structure. A space maintainer (band and loop) was also designed for modeling. Force was applied and a finite element analysis (FEA) was carried out in 6 states in the maxilla and in the mandible to evaluate the distribution of stresses and the amount of displacement of immature permanent first molar teeth in the presence or absence of deciduous second molar teeth and a space maintainer. During mastication, when the deciduous second molar tooth was absent, the maximum stress was transferred to incomplete roots. When there was a space maintainer, stress was transferred to the space maintainer itself and to the distal side of the deciduous first molar tooth. The displacement of permanent first molar teeth was minimal in the presence of all teeth; in the absence of the deciduous second molar tooth, this displacement increased 4-5-fold, which decreased again almost to the level of the 1st/4th state (intact arch) in the presence of the space maintainer. The results showed the importance of the use of space maintainers, as they significantly decrease the momentary displacement of the teeth as well as the stress exerted on the developing permanent first molar teeth.