Final answer:
A special type of retainer that can be placed from the lingual side is called a lingual retainer. Lingual retainers are often used in orthodontics.
Step-by-step explanation:
A special type of retainer that can be placed from the lingual side is called a lingual retainer. Lingual refers to the side of the teeth that faces the tongue. Lingual retainers are often used in orthodontics to maintain the position of the teeth after braces are removed.