Application

The shrinkage of PTC-rings corresponds to the furnace temperature. They indicate the actual furnace temperature and highlight deviations from the programmed temperature. PTC-rings type MTH work in the temperature range of 1340 – 1520 °C and are well suited for dental sintering of Zirconia.

Why is the correct sintering temperature important? Only a 20 - 30 °C deviation from the recommended sintering temperature will affect translucence and colour negatively. Lower temperatures will make the restorations appear “milky” (= lower translucence), and higher temperatures will affect the colour, especially yellow colouring will begin to fade. If the deviation exceeds 20 – 30 °C considerably, mechanical properties start to deteriorate. Hence, it is of utmost importance that the recommended sintering temperature of 1450 °C (priti® standard sintering programme) or 1500 °C (priti® fast sintering programme) is reached.

Application of PTC-rings type MTH

1. Just place the PTC-ring into the sinter tray along with the restorations.
2. Carry out the sintering process as usual.
3. After sintering, measure the diameter of the ring with a measuring gauge. Find the diameter on the enclosed reference temperature table “Temperature Table for PTCR” (included in the PTC-ring set) and look at the corresponding temperature. Does it fall into the recommended interval?
4. Recommended temperature intervals:
5. priti® standard sintering programme (2 h @ 1450 °C): 1450 - 1470 °C (*)
6. priti® fast sintering programme (1 h @ 1500 °C): 1480 – 1500 °C (*)
7. If the ring indicates a temperature outside these ranges, the furnace needs adjustment. Increase or decrease the temperature by the difference indicated by the ring. E.g.: The ring shows a temperature of 1420 °C. Increase the temperature by at least 30 °C in order to fall within the recommended interval.
8. Check the corrected temperature with a PTC-ring (steps 1-4). If necessary, correct the temperature again until the recommended interval is reached.

(*) Explanation: As the shrinkage of the rings does not exclusively depend on temperature, but to a far lesser degree also on holding time, the recommended temperature interval does not scatter evenly around 1450 °C (standard sintering programme; holding time 2 h) and 1500 °C (fast sintering programme; holding time 0.5 h).