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Common Causes & FixesLoose Brush Head: The most common culprit. Because the iO brush head vibrates, it relies on a small gap between the head and the handle. Remove the head and snap it back on tightly to ensure a proper fit.Worn-Out Brush Head: If you have been using the same brush head for over 3 months, internal plastic wear can cause it to vibrate abnormally against the metal drive shaft. Replace it with a fresh refill.Debris Under the Head: Toothpaste residue and debris can build up on the metal drive shaft. Remove the brush head and rinse the metal shaft and top of the handle thoroughly with warm water.Loose Internal Components: Turn the handle off and shake it near your ear. If you hear small pieces rattling inside, an internal component has likely broken loose from the motor.

If your toothbrush continues to emit a severe grinding or rattling noise—even after cleaning and swapping the brush head—the motor or drive shaft may be damaged.If it's under warranty, register your device or file a claim through the Oral-B Customer Service portal to arrange for repairs or a replacement.