Am I entitled to the 9 900 CHF ceiling for dental treatment in my first year of CHIS membership?

No. The carry-forward principle is based on an annual expenditure ceiling of 3 300 CHF. Any unused portion of this ceiling can be carried forward to the following year(s) until a maximum cumulated ceiling is reached after three calendar years. This means that the CHF 9 900 expenditure ceiling will apply only in the third year and only if you have not claimed for dental treatment in the previous two years.