Disclosed are embodiments of a dental prophylaxis angle. One dental prophylaxis angle includes a body having a neck that defines a first axial bore and a head that defines a second axial bore, the first and second axial bores communicating at an intersection and being angularly-offset from each other, a drive gear rotatably mounted in the first axial bore and having a drive gear head and a locking flange axially-offset from the drive gear head, an annular locking groove being defined between the drive gear head and the locking flange, a driven gear rotatably mounted in the second axial bore and operatively coupled to the drive gear, and a gear retainer having an annular body configured to extend about an outer surface of the head, a heel extending from the annular body, an arm extending from the heel, and a wedge extending from the arm.揭示一種牙科彎機的具體實施例。一牙科彎機包括：具有定義第一軸孔之一頸部以及定義第二軸孔之一頭部的一主體，該第一及該第二軸孔在一交叉點相通以及彼此具有角偏移，一驅動齒輪，其係可旋轉地裝在該第一軸孔中以及具有一驅動齒輪頭與軸向偏離該驅動齒輪頭的一鎖定凸緣，在該驅動齒輪頭與該鎖定凸緣之間定義一環狀鎖定槽，一從動齒輪，其係可旋轉地裝在該第二軸孔中以及可操作地耦合至該驅動齒輪，以及一齒輪保持器，其係具有：經組態成可在該頭部之外表面周圍延伸的一環狀主體、由該環狀主體伸出的一踵部、由該踵部伸出的一臂體、以及由該臂體伸出的一楔形物。
