Yes teeth grinding can be a sign of sleep apnea.
Not all cases of teeth grinding mean that you have sleep apnea but people who do have sleep apnea tend to grind their teeth.
So you could have sleep apnea when you start grinding your teeth but not always.
Teeth Grinding during the night may also be caused nervousness and also stress so it's not always a case of sleep apnea when you do grind your teeth.
You can use a teeth guard at night to prevent teeth grinding which helps prevent damage to your teeth because teeth grinding can cause teeth problems.
Some signs of sleep apnea are excessive daytime sleepiness, insomnia, nightmares, sleep deprivation, or snoring, episodes of no breathing, breathing through the mouth, or loud breathing, depression, dry mouth, dry throat, fatigue, headache, irritability, mood swings, or weight gain.
Morning headaches can also be a sign of sleep apnea.
If you think you have sleep apnea then you should see a doctor about it.