Table 3.
Average tooth-level FRI scores [count (%) of teeth].
| Tooth Type (Gamma, p-value)* | Average Tooth-Level FRI Score Category | Age 9 (n = 3,269) (Permanent Teeth Only) | Age 13 (n = 3,269) | Age 17 (n = 3,269) | Age 23 (n = 3,269) |
|---|---|---|---|---|---|
| Early-Erupting Teeth (−0.31, < 0.0001) | 0 | 2,249 (68.8) | 2,577 (78.8) | 2,791 (85.4) | 2,847 (87.1) |
| 0.01–0.50 | 428 (13.1) | 338 (10.3) | 252 (7.7) | 239 (7.3) | |
| 0.51–1.00 | 323 (9.9) | 220 (6.7) | 152 (4.7) | 133 (4.1) | |
| 1.01–3.00 | 269 (8.2) | 134 (4.1) | 74 (2.3) | 50 (1.5) | |
| Late-Erupting Teeth (−0.28, < 0.0001) | (n = 4,251) | (n = 4,251) | (n = 4,251) | ||
| 0 | – | 2,871 (67.5) | 3,368 (79.2) | 3,543 (83.4) | |
| 0.01–0.50 | – | 798 (18.8) | 608 (14.3) | 501 (11.8) | |
| 0.51–1.00 | – | 402 (9.5) | 160 (3.8) | 131 (3.1) | |
| 1.01–3.00 | – | 180 (4.2) | 115 (2.7) | 76 (1.8) | |
| Maxillary Incisors (−0.32, < 0.0001) | (n = 1,068) (Permanent Teeth Only) | (n = 1,068) | (n = 1,068) | (n = 1,068) | |
| 0 | 547 (51.2) | 683 (64.0) | 792 (74.2) | 831 (77.8) | |
| 0.01–0.50 | 216 (20.2) | 201 (18.8) | 151 (14.1) | 143 (13.4) | |
| 0.51–1.00 | 179 (16.8) | 121 (11.3) | 98 (9.2) | 75 (7.0) | |
| 1.01–3.00 | 126 (11.8) | 63 (5.9) | 27 (2.5) | 19 (1.8) |
*
Gamma statistic for association between age and fluorosis severity. p-value was calculated using a permutation test method to account for clustering of teeth within participants. In addition, p-value was calculated under the assumption that the sample size was sufficiently large for (gamma statistic/asymptotic standard error) to approximately follow a standard normal distribution.