Table 2 Caries Development Rate at the 6-, 12-, and 18-month Follow-ups Among 3 Groups
| Â | Group 1 Control | Group 2 5% NaF | Group 3 38% SDF | P Valuea |
|---|---|---|---|---|
Overall | n = 904 | n = 872 | n = 909 |  |
 6 months | 131 (14.5) | 61 (7.0) | 88 (9.7) | < 0.001 |
 12 months | 151 (16.7) | 107 (12.3) | 115 (12.7) | 0.011 |
 18 months | 218 (24.1) | 149 (17.1) | 247 (27.2) | < 0.001 |
Sound surface | n = 698 | n = 684 | n = 673 |  |
 6 months | 94 (13.5) | 37 (5.4) | 54 (8.0) | < 0.001 |
 12 months | 96 (13.8) | 61 (8.9) | 59 (8.8) | 0.003 |
 18 months | 142 (20.3) | 87 (12.7) | 151 (22.4) | < 0.001 |
Initial caries (RA1-2-3) | n = 206 | n = 188 | n = 236 |  |
 6 months | 37 (18.0) | 24 (12.8) | 34 (14.4) | 0.332 |
 12 months | 55 (26.7) | 46 (24.5) | 56 (23.7) | 0.760 |
 18 months | 76 (36.9) | 62 (33.0) | 96 (40.7) | 0.264 |