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Front-surface mirror (vs. plane mirror)
Also called: first-surface mirror, plane mirror, flat mirror, concave mirror
A mirror whose shiny coating is on the front, so it shows one sharp image with no ghost.
Mouth mirrors come in three kinds. A front-surface mirror has its reflecting layer on the top of the glass, so the picture is sharp with no double image. A plane (flat) mirror has the coating behind the glass, so you may see a faint second "ghost" image, but it is more durable. A concave mirror makes things look bigger but bends the picture a little.
How to spot it
- Touch the glass with an instrument tip: on a front-surface mirror the tip and its reflection seem to meet; on a plane mirror you see a small gap.
- A plane mirror can show a faint double outline of whatever it reflects.
- A concave mirror makes the tooth look larger than it is.
What it is used for
- Front-surface mirrors are preferred for detailed work such as checking margins and restorations.
- Plane mirrors are fine for routine exams and retraction.
Safety and care
- Semicritical item (it touches the inside of the mouth): clean it, package it and heat-sterilize it after every patient.
- The front coating scratches more easily, so handle and clean these heads gently.
Related
Sources: Dental Update. Technique tips: a reflection on mouth mirrors, types, usage and modifications