Hierarchy of pulp capping and repair activities responsible for dentin bridge formation

PURPOSE: The importance of pulp capping variables which mediate pulp repair activities and dentin bridge formation following pulp exposure are not well understood. Consequently, the aim of this study was to investigate the effects of pulp capping variables on tertiary dentin bridge formation. MATERIALS AND METHODS: Calcium hydroxide [Ca(OH)2], resin-modified glass-ionomer (RMGI) and resin-based composite (RBC) were used to restore pulp exposures prepared in 161 nonhuman primate teeth, according to ISO usage guidelines. Teeth were collected from between 7 and 720 days to observe the pulp repair activities leading to dentin bridge formation. Bacteria were detected using McKays stain. Pulp activity was categorized histomorphometrically using ISO standards, and analyzed statistically using ANOVA statistics. RESULTS: The pulp capping variables in order of their relationship to dentin bridge area, from the most important to the least important were: time elapsed since pulp capping (P = 0.0009), pulp capping materials (P = 0.0252), bacterial microleakage (P = 0.0358) and area of operative debris in the dentin bridge (0.0362). A further 10 pulp capping variables were found to be less important. Relationships between pulp capping materials, operative debris, tunnel defects, bacterial microleakage, inflammation and dentin bridge formation were observed. Bacteria contaminated 18.6% of RBC, 22.2% of RMGI and 47.0% of Ca(OH)2 capped pulps.