Results of this study showed no correlation between the thickness or amount of reparative dentin deposited and the type of dental restorative material placed at either 5 or 8 weeks in controlled Class V cavity preparations in monkey teeth. Factors such as preparation trauma from the bur, operator hand instrumentation, and microleakage of bacterial toxins played a greater role in the stimulation of reparative dentin than did material irritation or toxicity. Some differences in the thickness of the reparative dentin deposited were noted when teeth were grouped according to the amount of remaining dentin.