At what age is typical for a child to begin wearing a retainer, and what does one cost?

Orthodontic care ?: Each child is different as is their occlusion and their eruption pattern, bite, etc, so to give you a "typical" age is not appropriate. Many children are seen as early as 7 years old to be evaluated for bite problems, facial esthetics, and eruption patterns. In addition, a retainer is placed after orthodontic treatment has finished.. It is not an active appliance. Cost varies from office to office.