From: Clinical and radiographic performance of preformed zirconia crowns and stainless-steel crowns in permanent first molars: 18-month results of a prospective, randomized trial
Month
Simplified Oral Hygiene Index (OHI-S) Scores
Median (interquartile range)
Baseline
1.50(1.4–1.8)
1st month
1.25(1.1–1.8)
6th month
1.35(1.1–1.5)
12th month
1.30(1.1–1.6)
18th month
1.40(1.2–1.5)
p*
0.193