A model for clinical evaluation of the effect of antimicrobial agents on carious dentin

Purpose: To evaluate, longitudinally, the effect of a chlorhexidine varnish on the proteolytic activity of dentin caries in vivo. Materials and Method s: 20 permanent molars and 8 primary molars with carious lesions in dentin were studied in subjects 18-35 yrs old (n=20), and 5-6 yrs old (n=8) respec tively. These lesions were clinically evaluated according to texture and co lor. Carious dentin specimens were obtained by means of biopsies performed with a #4 carbide bur at the initial visit (T0) before application of a 10% chlorhexidine varnish and 2, 4, 8, and 12 wks thereafter. The dentin biops ies were immersed in Sorensen's buffer, vortexed for 30 s, and mixed with a 1.67 mM solution of n-benzoyl-DL-arginine-naphthylamide (BANA), a substrat e for proteolytic enzymes. Samples were incubated overnight at 37 degreesC and color was developed with 0.1% fast garnet. The optical density (OD) of reaction mixtures was recorded photometrically. All teeth were grouped for analysis, as Mann-Whitney tests revealed no statistically significant diffe rences between median values for OD for both age groups. ANOVA was used to compare progressive inhibition of proteolytic activity in dentin caries sam ples over time. Results: The average proteolytic activity at the dentin sub strates (OD) at TO and 2, 4, 8 and 12 wks thereafter were 0.794 +/- 0.089, 0.741 +/- 0.071, 0.676 +/- 0.087, 0.600 +/- 0.094, and 0.508 +/- 0.108 resp ectively. The chlorhexidine varnish mediated a significant inhibition of th e proteolytic activity present in dentin caries after 12 wks (P < 0.0001). At T0, 100% of the carious lesions examined were characterized as soft upon exploration. After 12 wks, 54% (15/28) of the lesions were partially harde ned and 46% (13/28) hardened/non-progressing. The dentin color was yellow/l ight brown in 100% of the lesions at baseline, and dark brown/black in 86% (24/28) after 12 wks.