Abstract
Ectopic eruption of the permanent molar may absorb the distal root of the primary second molar and may result in a decreased arch length or delayed eruption of the permanent tooth, requiring timely treatment. Therefore, we devised an effective and convenient method to unlock the entrapped tooth using a novel device called a "piston-elastic". This case report aims to explain the design and clinical application of this piston-elastic and to describe successful cases. Three patients (aged 6, 13, and 16 years) with ectopically erupted maxillary and mandibular molars, respectively, were treated with a piston-elastic. It was bound to the locked molar to improve the eruption path. After a certain time period, the repulsive force pushed the surface of the adjacent tooth, improving the eruption path of the entrapped tooth. The piston-elastic is a novel device that simply and effectively changes the direction of eruption of ectopically entrapped molars. As it can be manufactured and attached to the chair side, impression acquisition on a model cast and laboratory procedures are unnecessary. Compared to existing methods, the piston-elastic can be easily produced and delivered, causes little irritation, and is inexpensive.