The present invention discloses a teether capable of allowing a baby’s teeth freely moving from left to right, and up and down. A concave part 14a is formed on an edge of a protrusion part 14 of the teether 11, and the concave part 14a is arc-shaped by concaving toward the center of the teether. A maxillary dentition groove 20 is disposed on the surface of the protrusion part 14. When the baby bites the teether 11, the baby’s maxillary dentition is position-limited in the groove 20. A mandibular dentition groove 22 is disposed on another side of the protrusion part 14 for position-limiting the baby’s mandibular dentition.提供一種能讓嬰兒牙齒上下左右自由活動的固定牙齒器。該固定牙齒器11之突出部14的緣部為朝固定牙齒器11的中心側形成圓弧狀彎曲的凹部14a，且在突出部14表面形成有上顎齒列用溝20，當幼兒口中含著固定牙齒器11時，幼兒的上顎齒列會定位在該上顎齒列用溝20處，而在突出部14的背面形成有定位下顎齒列用的下顎齒列用溝22。
