THE EFFECT OF A SINGLE SCALING WITH OR WITHOUT ORAL HYGIENE INSTRUCTION ON GINGIVAL BLEEDING AND CALCULUS FORMATION

136 students of both sexes aged 14-18 years who were deprived of regul ar dental care participated in a 22-month longitudinal study. All stud ents underwent scaling of the assigned teeth in 2 quadrants according to a randomised split-mouth design on contralateral quadrants, 2 group s of students were formed, one group received oral hygiene instruction (OHI), Follow-up examinations on gingival bleeding and calculus were carried out 6, 12, and 22 months after the scaling session, The preval ence of calculus on assigned teeth at baseline was high with a mean sc ore of 1.10, At the end of the study, new calculus formation on scaled teeth reached a mean score of 0.58. Formation of calculus still conti nued on non-scaled teeth, but at a lower rate than on scaled teeth, Sc aling resulted in an approximately 20% reduction of the gingival bleed ing score which remained during the 22 months follow-up period, OHI ha d no significant effect on the calculus and bleeding scores, Since the effect of scaling alone on the gingival condition was small and the e ffect of a single OHI negligible, the practice of occasional scaling w ithout repeated OHI, which is commonly employed in developing countrie s, should be considered as clinically irrelevant and of little use in improving the standard of periodontal health.