Rubber dam, particularly for lower molars is a life saver. It keeps the tongue out of the way. Retracts the cheek. Keeps the field dry. Stops the patient from talking. However, sometimes, it just won’t sit right.
I find this commonly when there is a missing tooth or multiple missing teeth in an arch. The dam will sit up on the mesial and if that is where the cavity margin is, you want it out of the way.
There are a couple options
Punch Adequately Spaced Holes
For example, in this case the 36 is missing. You could place holes at 38, 37, leave space then 35, 34. This works well if you get the space right. Yet, I have repetitively found I misjudge and end up with a Borat Mankini like rubber dam attempt. The inevitable natural spring will well up and ruin your isolation efforts.
You could take it all off and start again. Or…
Use Another Clamp, Backwards
I find I more commonly reach for a second clamp, spin it around and hold the dam down by clamping the tooth mesial of the edentulous space. This allows the dam to stay tightly around the 37 and in my hands is simply quicker and more predictable.
If you find yourself in a situation where your rubber dam just isn’t sitting right, Consider a clamp on backwards before you start over, might be the tip that keeps you on time.