Schematic of thermocycling apparatus: (a) indicates soft drink tray; (b), artificial saliva tray; (c), tooth-carrying ball; (d), electric engine; (e), stop; (f), heater; (g), fuse switch; (h), main switch; (i), heater switch; (k), engine switch; (l), electric cable; (m), stop switch; (n), electric panel; (p), time-controlled handle; and (r), gear group