| Type of plaque | Frequency | Percent (%) |
| I | 00 | 0.0 |
| II | 00 | 0.0 |
| III | 00 | 0.0 |
| IV | 26 | 32.5 |
| V | 43 | 53.8 |
| VI | 11 | 13.8 |
| Total | 80 | 100.0 |