“…Of these, 102 studies were considered for TDI prevalence to permanent teeth 1,7,9, (Unpublished Material 2), 46 for TDI prevalence to primary teeth 9,36,45, (Unpublished Material 3), 42 for TDI prevalence among 12-year-old c h i l d r e n 3 1-3 4 , 4 8 -5 3 , 55 , 5 6 , 61 , 6 3 , 6 4 , 7 2 , 7 7-7 9, 8 1 , 8 3 -8 5 , 8 9,9 1 ,9 3 -95 ,9 9, 106,107,109,111,112,116,118,121-123,125,126 All the included studies yielded modified NOS ranging between 3 and 5. Indeed, the items "Case definition," "Reliability of diagnosis," and "Response rate" were always satisfied; the item "Sample size" was satisfied by all studies excluding seven; 47,64,117,120,122,134,160 some studies also satisfied the item "Sample selection" (Unpublished Material 2-6). Several diagnostic classification systems were adopted (Table 1), and the most frequent was Andreasen's/WHO classification (49.3%) followed by O'Brien's classification (24.3%).…”