IN-VIVO EFFECTS OF FLUORIDE, CHLORHEXIDINE AND ZINC IONS ON ACID FORMATION BY DENTAL PLAQUE AND SALIVARY MUTANS STREPTOCOCCUS COUNTS IN PATIENTS WITH IRRADIATION-INDUCED XEROSTOMIA

Irradiation therapy including major salivary glands may result in xero stomia and enhanced susceptibility to dental caries. The present aim w as to assess the ability of mouthrinses with F-, Zn2+, and chlorhexidi ne (CH), in various combinations, to reduce acidogenic potential of de ntal plaque and salivary mutans streptococcus counts (SMSC) in 7 patie nts with xerostomia secondary to irradiation. The patients rinsed twic e daily for 3 weeks with the following test solutions: (1) 12 mmol/l N aF (F; control), (2) NaF+20 mmol/l ZnCl2 (F-Zn), and (3) NaF+1.1 mmol/ l CH (F-CH). Resting periods (F) of varying lengths were incorporated. Acid formation by dental plaque was monitored as plaque pH response t o a sucrose mouthrinse, at the end of each test period, 4h after mouth rinsing with test solution. Plaque pH was measured repeatedly at 2-8 s ites in each patient before, and up to 60 min after the sucrose mouthr inse using touch microelectrodes. SMSC were determined using Dentocult SM-Strip mutans. Compared with F, F-CH significantly (P less than or equal to 0.02) reduced acid formation by plaque and SMSC, whereas F-Zn did not affect acid formation or SMSC significantly. Pilot experiment s in 4 patients showed mouthrinses with NaF+0.55 mmol/l CH+10 mmol/l Z n2+ to be ineffective, whereas' NaF+2.2 mmol/l CH was highly effective , but no better than F-CH. Twice daily mouthrinses with 12 mmol/l NaF in combination with 1.1 mmol/l CH may be an effective regimen to preve nt postirradiation caries.