US Patent 7785106 Sponge prophy

A dental prophy chip with a hollow core of different shapes such as canopy, cylinder, cup and inverted cone, is covered by hydrophilic grindstone sponge containing a polishing agent and its edge is either pressed fixed or folded into the interior of the core with a latch plate. A shaft is fixed to the latch plate to avoid resonance at bottom surface, during rotation. The device maintains polishing efficiency by avoiding transverse oscillation in polishing barrel-shaped tooth clearance and reducing frictional heat.